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Study on ultrasound-assisted oxidative desulfurization for crude oil
Journal Pre-proofs Study on ultrasound-assisted oxidative desulfurization for crude Oil Yinhe Lin, Li Feng, Xuhao Li, Yuning Chen, Guoliang Yin, Wen Zhou PII: DOI: Reference:
S1350-4177(19)31437-3 https://doi.org/10.1016/j.ultsonch.2019.104946 ULTSON 104946
To appear in:
Ultrasonics Sonochemistry
Received Date: Revised Date: Accepted Date:
11 September 2019 18 December 2019 24 December 2019
Please cite this article as: Y. Lin, L. Feng, X. Li, Y. Chen, G. Yin, W. Zhou, Study on ultrasound-assisted oxidative desulfurization for crude Oil, Ultrasonics Sonochemistry (2019), doi: https://doi.org/10.1016/j.ultsonch. 2019.104946
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Study on ultrasound-assisted oxidative desulfurization for crude Oil Yinhe Lina,b,
Li Fengd,*, Xuhao Lid,
Yuning Chend, Guoliang Yine, Wen Zhouc,*
a Institute
of Chemical Engineering, Yangtze Normal University, Chongqing, 408100, China and Environment Engineering Institute, Nanchang Institute of Technology, Nanchang, 330000, China c The Second Clinical College of Guangzhou University of Chinese Medicine (Guangdong Provincial Academy of Chinese Medical Sciences), 55 Neihuanxi Road, Guangzhou 510006, China d School of Civil and Transportation Engineering, Guangdong University of Technology, No100, Waihuan Xi Road, Guangzhou, Higher Education Mega Center, Panyu District, Guangzhou 510006, Guangdong, China e Chemistry and chemical engineering college, Yinbin University, Yibin, 644007, China b Energy
*Corresponding
author. E-mail address: [email protected] (Li Feng) and [email protected] (Wen Zhou)
Abstract: The existence of sulfur compounds in crude oil will bring many problems such as corrosion, catalyst poisoning and pollution to the petroleum processing process. Therefore, how to reduce the sulfur content as much as possible in the process of crude oil processing has become an important research topic in the petroleum processing industry. In this paper, ultrasonic-oxidative desulfurization is studied. The effects of reaction temperature, reaction time, amount of oxidant and demulsifier on desulfurization rate are investigated. And the effect of oxidative desulfurization and single oxidative desulfurization under ultrasonic treatment are compared. It is found that the addition of ultrasonic treatment can enhance the desulfurization effect of desulfurizer, the desulfurization efficiency can be increased by about 10% under ultrasonic treatment (100W, 70kHz); ultrasonic wave plays an auxiliary role in the system, it can promote heterogeneous reactions, improve the activity of oxidants, and promote the degradation of macromolecular compounds. Finally, physical desulfurization, chemical desulfurization and biological desulfurization technologies are compared. Keywords: ultrasound; crude oil; desulfurization 1.Introduction The sulfides in crude oil can be divided into two categories according to their properties: active sulfur and inactive sulfur. Active sulfur mainly includes elemental sulfur, hydrogen sulfide, etc. Its active nature can react directly with metal substances, which is the main cause of equipment corrosion. Inactive sulfur mainly includes sulfides, disulfides, thiophene and so on. Generally, it does not react with metal substances, but its thermal stability is poor and it is easy to decompose to produce hydrogen sulfide when heated [1-3]. Crude oil desulfurization is mainly to remove active sulfur. Generally, sulfur is a rare element in crude oil. H2S is the main sulfide that causes harm in the process of exploitation, storage, transportation and processing of crude oil. these H2S will be produced in every link of oil and gas exploration, exploitation, processing and postprocessing [4]. Hydrogen sulfide poisoning will occur if the staff members are careless in the process of operation. Therefore, in order to ensure production safety, it is
necessary to reduce the harm of hydrogen sulfide to employees and production equipment [5]. At present, the application of crude oil desulfurization technology can be divided into three categories: physical desulfurization, chemical desulfurization and biological desulfurization [6]. Pre-desulfurization prior to crude oil processing can reduce hydrogen consumption in subsequent processes, as well as damage and corrosion to catalysts and equipment. At present, there are few studies on pre-desulfurization for crude oil, and the main desulfurization methods are all non-hydrodesulfurization. This is mainly because the cost of hydrodesulfurization is too high. It can be seen from the above discussion that at this stage, the crude oil pre-desulfurization technology has the disadvantages of low desulfurization rate, high cost, and low oil yield. The main problems faced by the oxidation process are as follows: First, it is necessary to select a catalyst with strong specificity, otherwise the crude oil is easily over-oxidized and its properties are deteriorated; Second, oxidative desulfurization causes hydrocarbon loss. Therefore, it is necessary to develop a technology for processing and utilizing the sulfone material that has been removed to make it feasible for industrialization. Physical desulfurization is based on the theory of vapor-liquid equilibrium of crude oil to use corresponding physical equipment to remove hydrogen sulfide from crude oil. For example, vacuum flash evaporation, multi-stage separation, fractionation and gas extraction method. Vacuum flash evaporation is based on the principle of reducing separation pressure to remove H2S from crude oil. Its working principle can be divided into two cases. One is to increase the original saturation temperature under certain pressure [7]. The second is to reduce the pressure of saturated crude oil at a certain temperature. Both of these operations can vaporize part of the crude oil, allowing the crude oil state point to enter the gas-liquid two-phase zone, and finally achieve crude oil desulfurization. Multi-stage separation is a commonly used crude oil degassing process [8]. As the crude oil flows along the fixed pipe, the pressure inside the pipe is continuously reduced. When the pressure reaches a certain critical value, the low pressure environment will force a part of the gas inside the crude oil to be discharged. At this time, the crude oil and gas in the pipeline are in a state of mutual contact. Under these conditions, the gas is also discharged out of the pipeline. After the above cycle, the desulfurization effect of crude oil is finally achieved. Fractionation is also one of the common technologies for desulfurization of crude oil. It is clearly based on the principle of rectification to desulfurize crude oil [9]. The desulfurization process is essentially a constant balance between gasification and condensation. Special attention should be paid to the separation of gas and liquid from crude oil when desulfurizing crude oil by this method. On this basis, some of the lighter components are separated, and the hydrogen sulfide in the crude oil is the most volatile part. Physical desulfurization is a combination of stripping process and mechanical stirring. This method is based on the principle of phase equilibrium to reduce the vapor partial pressure in the crude oil pipeline. After the pressure reaches a certain value, the light component of the crude oil will be gasified, so as to desulfurize the crude oil. After comprehensive comparison of four physical hydrogen sulfide removal processes, the stripping process has the best effect on H2S removal of heavy oil, and the H2S content can meet the requirement of less than 60mg/kg at the operating temperature of 90℃ [10-13]. Chemical desulfurization technology for crude oil refers to injecting desulfurizer into the proper position of crude oil production system to achieve the purpose of desulfurization. The key of this technology is to develop and select proper desulfurizer. Using water-soluble hydrogen sulfide desulfurizer is a very effective desulfurization
method. Since the dehydration rate of crude oil is required to be lower than 0.5%, if the actual dehydration rate is lower than this value, such as 0.2%~0.3%, there will be a dissolution space of 0.2%~0.3%. Existing desulfurizers can only fix hydrogen sulfide through chemical reactions, but cannot remove it from crude oil, and such reactions are often reversible [14]. It is difficult to achieve the expected effect when hydrogen sulfide is regenerated under appropriate temperature and pressure, and the addition of desulfurizer also increases the burden of subsequent crude oil processing. Therefore, the chemical desulfurization process needs to be improved [15]. Based on the immobilization of H2S by the chemical reaction of desulfurizer with H2S in crude oil, the immobilized sulfide is migrated to the water phase, and can be separated from crude oil by a simple separation process, so that it does not affect the processing of subsequent crude oil. Water-soluble desulfurizer can solve this problem better. The desulfurizer can dissolve well in the water phase in crude oil, and with the aid of good solubilization and mutual solubility, the reaction can proceed quickly [16-19]. The reaction products can also be removed by dehydration and desalination process of crude oil without affecting the processing of petroleum and the quality of petroleum products [20]. Biological hydrogen desulfurization technology can inhibit the formation of hydrogen sulfide by killing sulfate reducing bacteria. The technology has been successfully applied in Gullfaks, Foinaven and Skjold oilfields [21]. Ultrasonic oxidative desulfurization for crude oil is an environmentally friendly method. Fully utilizing the cavitation, mechanical action and thermal action of ultrasound can realize the original desulfurization. On the one hand, it saves solvent, saves time and energy, and reduces waste generation. It is conducive to environmental protection, no pollution and belongs to green engineering. Meanwhile, oxidative desulfurization has the advantages of simple technological process, low reaction temperature, low equipment investment and low operating cost [22-25]. The combination of ultrasound and oxidation can not only achieve a certain desulfurization effect, but also is a new technology with broad prospects for development. It fundamentally solves the problem of desulfurization of petroleum products and is conducive to the production of clean fuels. In this paper, the existing problems of desulfurization technology are briefly analyzed, and the corresponding optimal design scheme is put forward to select a better and more suitable formula for field experiments, which has important guiding significance for solving the removal of hydrogen sulfide in oil and gas reservoir exploitation 2. Principle of ultrasonic oxidation desulfurization In the oxidation desulfurization process, it is difficult to mix the water phase and the oil phase fully with general mechanical agitation. The mechanical action, cavitation and heat generated by the ultrasonic wave can form a microemulsion between the water phase and the oil phase, thereby improving the mutual contact between the molecules, forming a local high temperature and high pressure, and simultaneously generating free radicals and activated oxygen. This not only rapidly oxidizes the sulfide, improves the oxidizing ability of the oxidant, improves the selectivity of the reaction, and significantly shortens the oxidation reaction time, but also changes the way and direction of the reaction, so that the oxidation reaction can be carried out more thoroughly. In the extraction stage, ultrasonic intervention can effectively mix the extractant and partial oxidized diesel oil, and promotes sufficient contact between the oxidized sulfide molecules and the extractant to effectively release the sulfone.
3. Ultrasonic oxidation desulfurization for crude oil 3.1 Instruments, materials and experimental methods The instruments and materials used in the experiment were as follows: DS-3510DTH type ultrasonic reactor (frequency is 40 kHz); TSN-2000 type fluorescent sulfur nitrogen analyzer. Crude oil sample; oxidant; demulsifier. Experimental steps: duplicate the crude oil sample (i.e. the process of mixing crude oil, oxidant, demulsifier and water). Take a certain amount of crude oil in a conical flask, add a certain proportion of oxidant, demulsifier and first-grade water, mix it relatively evenly, and then put it into an ultrasonic reactor that has been heated to a specified temperature and set a certain reaction time to start the reaction. After the reaction, the reaction liquid is separated, washed and separated (contrast experiment: single oxidation desulfurization experiment is carried out on a digital constant temperature magnetic stirrer). The sulfur content of the reaction oil sample is determined by fluorescence sulfur nitrogen meter. 3.2 Results and discussion 3.2.1 Comparison between ultrasonic oxidation desulfurization and single oxidation desulfurization The desulfurization effects of ultrasonic oxidation desulfurization and single oxidation desulfurization are investigated under different temperature and reaction time. It can be seen from Figure 1, 2 that the ultrasonic oxidation desulfurization rate is higher than the single oxidation desulfurization rate. Therefore, the desulfurization efficiency of crude oil can be significantly improved under the action of ultrasonic wave.
Fig.1. Effect of ultrasonic oxidation and single oxidation desulfurization at different temperature
Fig.2. Effect of ultrasonic oxidation and single oxidation desulfurization at different temperature within different reaction time.
3.2.2 Influence of reaction temperature and time on desulfurization rate of crude oil As can be seen from Figure 3, desulfurization first increases with the increase of reaction temperature, reaches the maximum when the reaction temperature reaches 65℃, and then decreases with the increase of temperature. Because the oxidation of sulfide to sulfoxide and sulfoxide is endothermic. Increasing the reaction temperature shifts the equilibrium in the positive direction, and at the same time makes the lowboiling substances in the crude oil more volatile, and the peroxide is unstable and decomposes at higher temperatures [7]. Therefore, the selected reaction temperature is 65℃.
Fig.3.Influence of reaction temperature on desulfurization rate of crude oil
It can be seen from Figure 4 that the desulfurization rate increases with the extension of the reaction time. The maximum is reached when the reaction time is 10 min, and when the reaction time exceeds 10 min, the desulfurization rate decreases. As
the reaction time prolongs, the peroxide is unstable, and the oxidation reaction almost reaches equilibrium, which is not conducive to the oxidation reaction. Therefore, the reaction time is chosen to be 10 min.
Fig.4.Influence of reaction time on desulfurization rate of crude oil
3.3 Influence of catalyst volume fraction on ultrasonic desulfurization As can be seen from Figure 5, the catalyst volume fraction is proportional to the desulfurization rate of the oil [49]. When the volume fraction of catalyst is less than 2%, the removal rate of sulfide in diesel increases with the increase of catalyst volume fraction. However, with the increase of catalyst volume fraction, the removal rate of sulfide in diesel tends to be gently.
Fig.5. Influence of catalyst volume fraction on ultrasonic desulfurization
3.4 Effect of oxidant volume fraction on ultrasonic desulfurization
It can be seen from Figure 6 that the volume fraction of oxidant is proportional to the removal rate of sulfide in diesel oil [49]. When the volume fraction of oxidant is less than 9%, the desulfurization rate of diesel increases with the increase of the volume fraction of oxidant. However, when the volume fraction of oxidant is more than 9%, the desulfurization rate of diesel tends to be stable with the increase of the volume fraction of oxidant.
Fig.6. Effect of oxidant volume fraction on ultrasonic desulfurization
3.5 Influence of oxidant and demulsifier dosage on desulfurization rate of crude oil As can be seen from Figure 7, when the dosage of oxidant increased from 50×10-6 (ppm) to 200×10-6 (ppm), the desulfurization rate significantly increased. After that, with the increase of oxidant dosage, the desulfurization rate was not obvious. Considering the desulfurization effect, the properties of desulfurized oil and economic benefits, the oxidant dosage is chosen to be 200×10-6 (ppm).
Fig.7. Effect of oxidant dosage on desulfurization rate of crude oil
It can be seen from Figure 8 that the desulfurization rate increases obviously when the demulsifier dosage increases from 15×10-6 (ppm) to 60×10-6 (ppm). Thereafter, with the increase of demulsifier dosage, the desulfurization rate does not change significantly. Demulsifier helps to separate oil from water, and enables sulfur compounds in crude oil emulsion to transfer smoothly from oil phase to water phase under the action of ultrasonic wave and peroxide. Therefore, considering the desulfurization effect, the properties of desulfurized oil and economic benefits, the demulsifier dosage is 60×10-6 (ppm).
Fig.8. Effect of demulsifier dosage on desulfurization rate of crude oil
In short, ultrasound oxidation desulfurization has obvious advantages over single oxidation desulfurization. The desulfurization efficiency of crude oil is the best when the reaction temperature is 65℃, reaction time is 10 min, oxidant dosage is 200×10-6 (ppm) and demulsifier dosage is 60×10-6 (ppm). The desulfurization rate can reach 65.28 (m)%. The best match for the study is only relative to the chosen factor. However, due to the difference of crude oil properties, the conditions of oxidative desulfurization
test under the action of ultrasound will change [51]. More systematic experiments are needed to investigate the desulfurization effect of this method. The oil parameters before and after ultrasonic desulfurization are shown in Table 1 [49]. It can be seen from Table 1 that the properties of the oil after ultrasonic desulfurization are significantly improved, the density of the oil is reduced, and the sulfur mass fraction is reduced from 2133 μg·g-1 to 363 μg·g-1. Tab.1. Oil parameters before and after ultrasonic desulfurization Before ultrasonic After ultrasonic Parameters desulfurization desulfurization ρ(20℃)/g·mL-1 0.9156 0.8581 -1 ω(sulfur)/μg·g 2133 363 Freezing point (℃) -7 -3 Kinematic Viscosity 4.2 3.4 (20℃) (mm2·s-1) Cetane number 31 45 Oxidation stability 1.76 10% carbon residue on 1.14 <0.3 residuum/%
In addition, Chan Sheng [50] studied ultrasonic assisted oxidation desulfurization for crude oil. The crude oil desulfurization test device is shown in Figure 9. Three flasks with reactants are placed in the water bath box 2. Water bath box 2 is connected with ultrasonic generator 1, where the mechanical mixing of reactants is realized by the electronic agitator. Full-digital ultrasonic generator has the function of transmitting ultrasonic wave and constant temperature heating. When you need to investigate the effect of ultrasonic on the reaction, turn it on and set the ultrasonic parameters. When ultrasonication is not required, only the function of heating the thermostat can be used.
Fig.9. Schematic diagram of crude oil desulfurization test device. 1-ultrasonic generator; 2-water bath; 3-three-port flask; 4-stirring rod; 5-motor; 6electronic stirring regulator
The comparison results of desulfurization effects before and after ultrasonic action are shown in Table 2. It can be seen from Tab.2 that the desulfurization rate of A-
phosphotungstic acid system without ultrasonic wave is only 12.0%, while that of Aphosphotungstic acid system with ultrasonic wave increases to 13.3%. The desulfurization rate of A-Sb2O5 system increased from 5.8% to 7.8% after ultrasonic action. The desulfurization rate of A-active Ni system increases from 10.6% to 12.4% after ultrasonic action. It indicates that ultrasound assistance can promote the desulfurization agent system to varying degrees [50]. Tab.2. Ultrasound-oxidation desulfurization test for crude oil Mass fraction of sulfur after Desulfurization Experimental scheme treatment/(mg·kg-1) rate/% 0.5%A+0.05% 6016 12.0 Phosphotungstic acid 0.5%A+0.05% 5931 13.3 Phosphotungstic acid+UL 0.5%A+0.05% Sb2O5 6444 5.8 0.5%A+0.05% Sb2O5+UL 6304 7.8 0.5%A+0.05% Active Ni 6116 10.6 0.5%A+0.05% Active Ni+UL 5988 12.4
For A-phosphotungstic acid system, the desulfurization rate is low before ultrasonic treatment. It has been proved that transition metal catalysts (usually transition metal complexes, such as phosphotungstic acid and phosphomolybdic acid) can activate the catalytic activity of peroxides [50]. The catalyst forms a highly selective oxidantperoxide-metal complex with peroxide, which plays an important role in oxidising sulfide. Even weakly nucleophilic organic sulfides, such as dibenzothiophene, can be oxidized to sulfoxide or sulfone in high yield under mild conditions. However, in crude oil system, the oxidation of organic sulfides mainly occurs at the oil-water interface due to the two-phase oxidation of desulfurizer and crude oil. The interfacial resistance between catalyst solution and organic phase hinders the catalytic reaction. Due to the small effective contact area, the addition of ultrasonic wave rapidly formed a very fine emulsion in the two phases, which greatly increased the specific surface area of the reaction and greatly promoted the oxidation reaction of organic sulfide molecules. From the perspective of the oxidation system, the local high temperature and high pressure formed by the ultrasonic field promotes the activation of reactive oxygen species and improves the oxidation activity. From the perspective of ultrasonic degradation, the high temperature generated by ultrasonic can break the carbon-carbon bond and carbonsulfur bond, making some high-molecular sulfur compounds smaller and simpler. The oxidant is easier to react with it, and the sulfones produced by the reaction are more easily extracted by methanol. For A-Sb2O5 and A-active Ni systems, the desulfurization rate increased by about 2 percentage points with the addition of ultrasound. The main reason is that ultrasound promotes oil-water two-phase mechanical mixing and thermal action. It can be seen that the addition of ultrasound is helpful to enhance the desulfurization effect of desulfurizer. By introducing 400 W and 70 Hz ultrasonic wave, the desulfurization efficiency can be increased by about 10%. Ultrasound assists the system, promotes heterogeneous reaction, enhances the activity of oxidants and promotes the degradation of macromolecular compounds. In a word, the research shows that different types of desulfurizers have different
desulfurization effects. Although the desulfurization efficiency of crude oil increases with the increase of desulfurizer dosage, excessive desulfurizer will cause excessive oxidation and destroy crude oil components. The results of catalytic oxidation test show that phosphotungstic acid is the best catalyst for desulfurization, followed by active Ni. The catalytic mechanism of the two is different in crude oil. The main role of phosphotungstic acid is to improve the oxidation activity of the system and its strong oxidation, while the main role of active Ni is to react with sulfides as a reactant to reduce sulfides, which then react with desulfurizers. Ultrasound assisted desulfurization can enhance the desulfurization effect, and the desulfurization efficiency can be increased by about 10%. Ultrasound plays an auxiliary role in the system, promoting the full mixing of heterogeneous reactions, improving the activity of oxidants and degrading macromolecular compounds. 4.Comparison of physical desulfurization, chemical desulfurization and biological desulfurization 4.1 Physical Desulfurization The basic principle of physical desulfurization is to remove hydrogen sulfide from crude oil by means of corresponding technical methods and equipment according to the theory of gas-liquid equilibrium. It is a semi-desulfurization method. Strictly speaking, hydrogen sulfide is extracted from crude oil by simple physical methods, and some technical methods are needed to remove hydrogen sulfide completely in the later stage. 4.1.1 Crude oil stabilization method The crude oil stabilization methods mainly include multistage separation, vacuum flash evaporation and fractionation. Hydrogen sulfide is a gaseous phase at room temperature, so it can be separated from the gas phase and liquid phase of crude oil by multistage separation, so as to remove hydrogen sulfide from crude oil. This method can only remove hydrogen sulfide in gas phase, while hydrogen sulfide dissolved in crude oil and water cannot be completely removed [26-29]. Vacuum flash evaporation refers to the method of reducing external pressure and heating oil body to analyze the dissolved hydrogen sulfide in crude oil and water and remove it to achieve deep desulfurization. Usually, the removal rate of hydrogen sulfide can reach more than 95% by combining the two methods. The method is simple in equipment and low in energy consumption, and is suitable for treating low-sulfur crude oil. Fractionation can be used for the removal of hydrogen sulfide from high sulfur crude oil, which has high recovery and deep desulfurization. But Moins [43] pointed out that when the fractionation process is used to treat heavy crude oil, the temperature at the bottom of the fractionator is too high, the energy consumption is too high and the cost is too high to be adopted. 4.1.2 Gas extraction method Pure stripping gas (mainly natural gas without sulfur or with low sulfur content) is introduced from the bottom of the gas stripping tower to reverse contact with the crude oil flowing from the top of the tower, and hydrogen sulfide in the crude oil is taken away by stripping gas, so as to remove hydrogen sulfide from the crude oil [30]. The boiling point of hydrogen sulfide at atmospheric pressure is - 60.3 ℃, which is between
C2 ~ C3. In the process of gas stripping, hydrogen sulfide will be separated from the crude oil and some of the low hydrocarbon components will be carried away, resulting in a certain loss of crude oil. There are two main factors affecting the desulfurization efficiency of gas extraction [44]: feed temperature and gas lift. The desulfurization efficiency can be improved by increasing atmospheric volume and feed temperature, and the desulfurization efficiency is higher when the operating pressure is lower or the vacuum is higher. Beijing university of chemical technology [45] has invented a method to remove hydrogen sulfide from crude oil by using supergravity technology. It does not need to add chemical agents and is safe and environmentally friendly. Physical desulfurization equipment is simple, low operating cost, large processing capacity, will not have adverse impact on downstream crude oil processing, is suitable for crude oil easy to centralized processing blocks, and is now the main means of crude oil desulfurization. 4.2 Chemical desulfurization Chemical desulfurization of crude oil refers to reducting sulfur content in crude oil by adding certain chemical agents (i.e. desulfurizers) in the suitable position in the process of crude oil production, transportation and processing [31]. The research and development of high efficiency desulfurizer is the key to chemical desulfurization. The existing desulfurizers for crude oil mainly include amino desulfurizer, inorganic basic desulfurizer, strong oxidizing desulfurizer and other types of desulfurizer [32]. 4.2.1 Amine desulfurizer Amine desulfurizers are widely used because of their high hydrogen sulfide absorption capacity. Amine desulfurizers mostly use alkanolamines or their derivatives as main absorbents, adding a small amount of defoamers, fungicides and other additives, to improve their performance [33]. The main alcoholic amines are ethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), N-methyl diethanolamine (MDEA), monoisopropanolamine (MIPA), etc. Tianjin Yilike Energy Technology Development Co., Ltd. [46] developed a watersoluble desulfurizer for crude oil. Its composition is: 10%-15% formaldehyde, 6%-22% methyl diethanolamine, 32%-34% diethanolamine and 5%-7% sodium nitrite. The desulfurizer has the advantages of simple preparation method, easy availability of raw materials and rapid desulfurization. The volume content of hydrogen sulfide in crude oil can be reduced from 5000 mg/m3 to 8 mg/m3 in 30 minutes to meet the transportation standard [34-36]. Most amine-based desulfurizers can only remove hydrogen sulfide from crude oil, but can not remove other sulfur-containing organic compounds from crude oil. The Institute of Process Engineering of Chinese Academy of Sciences [47] invented an oil desulfurizer based on ionic liquids. It is composed of ionic liquids mixed with alcoholic amines or alcoholic amines derivatives in a certain proportion. It can remove organic sulfur or inorganic sulfur from oil products at the same time. The desulfurization efficiency can reach more than 50%. There is still a problem when amine-based desulfurizer is used as crude oil desulfurizer. Amino desulfurizer has poor thermal stability in salt formed by absorbing hydrogen sulfide. When heated, reversed reaction will occur to re-release hydrogen sulfide. At the same time, amine desulfurizers can be recycled [37]. If directly injected into crude oil, it is difficult to recover, which will increase the difficulty of downstream crude oil processing, resulting in waste and greater economic investment.
4.2.2 Hydroxide desulfurizer Hydroxide desulfurizers are mostly inorganic hydroxides. It is based on the principle of acid-base neutralization to remove hydrogen sulfide. NaOH, KOH and ammonia water are commonly used as hydrogen sulfide removal agents for hydroxide crude oil. Their basic desulfurization principles are as follows: 𝐍𝐚𝐎𝐇 + 𝐇 𝟐 𝐒→𝐍𝐚𝐇𝐒 + 𝐇 𝟐 𝐎 𝐊𝐎𝐇 + 𝐇 𝟐 𝐒→𝐊𝐇𝐒 + 𝐇 𝟐 𝐎 𝐍𝐇 𝟒 𝐎𝐇 + 𝐇 𝟐 𝐒→𝐍𝐇 𝟒 𝐇𝐒 + 𝐇 𝟐 𝐎 The solution of NaOH and KOH is still alkaline after absorbing hydrogen sulfide, and it is easy to form stable oil-water emulsion at this time, thus increasing the difficulty of dehydration of downstream crude oil. When ammonia water is used as desulfurizer, the ammonium salt produced is easy to be removed, the ammonia water is volatile, the loss is large, and the heat stability of the ammonium salt is poor. When the temperature rises, a reverse reaction will occur to release hydrogen sulfide again, and at the same time, it will cause corrosion of equipment and environmental pollution, so this kind of desulfurizer has been rarely used [48]. 4.2.3 Strong oxidizing desulfurizer Commonly used strong oxidizing desulfurizers are H2O2 and KMnO4. It is possible to oxidize the sulfur in the hydrogen sulfide to a low-valent -2 value to a stable highvalence state SO24 ― . Strong oxidizing desulfurizer has certain risks when used. H2O2 is easy to decompose into H2O and O2 and generate a lot of heat. KMnO4 also produces O2 and a lot of heat when heated or acidic. O2 is prone to explosion when mixed with low hydrocarbons in the gas phase of crude oil. Therefore, the amount of desulfurizer should be strictly controlled when it is used, and the operation should be very careful to avoid danger [38]. 4.3 Bio-desulfurization (BDS) In recent years, BDS has developed rapidly. Through screening special strains with high digestibility of sulfur-containing organic matter in petroleum, sulfur-containing organic compounds are converted into water-soluble substances ( SO24 ― ) by bacteria or enzymes, and then eluted from crude oil. When used for desulfurization of crude oil, BDS technology can reduce the total sulfur content of crude oil, and longer residence time of crude oil is also conducive to biological desulfurization process. However, the large amount of crude oil treatment, the variety of sulfides, the single strain can not be completed, and the short life of the strain, which seriously affect its desulfurization effect and application. However, due to the large amount of crude oil treatment and the variety of sulfur compounds, the desulfurization can not be completed by a single strain and the short life of the strain, all of which seriously affect the desulfurization effect and application. The key of BDS technology is the selection of effective strains, and the problem of strain life-span should be solved in industrial application. Table 3 shows some internationally recognized desulfurization strains. BDS, as a new and environmentally friendly biotechnology, is still in the stage of development, but it develops rapidly and has broad application prospects [39-42].
Tab.3. Some internationally recognized desulfurization strains
The type of bacteria
Stroma
Pseudomonas sp
Dibenzothiophene (DBT)
Desulfovibrio escambium Lac 10
Dibenzothiophene (DBT)
Rhodococcus erythropolis H-2
Dibenzothiophene (DBT)
Rhodococcus rhodochrous Acineobater sp
Dibenzothiophene (DBT), Petroleum, Coal Dibenzothiophene (DBT), Thiophene
Corynebacterium sp
Dibenzothiophene (DBT)
Pseudomonas delafieldii
Dibenzothiophene (DBT)
Corynebacteriu sp.SY1
Dibenzothiophene (DBT),DBTO2, Dimethyl sulfoxide（DMSO）
5.Conclusion In this paper, ultrasonic-oxidative desulfurization is studied. The effects of reaction temperature, reaction time, amount of oxidant and demulsifier on desulfurization rate are investigated. And the effect of oxidative desulfurization and single oxidative desulfurization under ultrasonic treatment are compared. The results show that: (1) ultrasound-assisted oxidative desulfurization has obvious advantages over single oxidative desulfurization; (2) when the reaction temperature is 65℃, the reaction time is 10 min, the dosage of oxidant is 200×10-6 (PPM), and the dosage of demulsifier is 60×10-6 (PPM), the ultrasound-assisted oxidative method can achieve the best desulfurization effect, and the desulfurization rate can reach up to 65.28 (m) %; (3) ultrasonic wave plays an auxiliary role in the system, it can promote heterogeneous reactions, improve the activity of oxidants, and promote the degradation of macromolecular compounds. Finally, physical desulfurization, chemical desulfurization and biological desulfurization technologies are compared. Physical desulphurization is the main desulphurization method for crude oil nowadays because of its simple equipment and large capacity, but it will produce a lot of acid gas due to its large initial investment. The chemical desulfurization effect is affected by many factors, and different types of desulfurizing agents should be selected according to the application conditions. Biological desulfurization, as a new type of crude oil desulfurization technology, is still in the research and development stage with broad prospects. Acknowledgments This work is supported by the financial support provided by National Natural Science Foundation of China (Grant No. U1960101), Major Science and Technology Projects of Sichuan Province (No. 2019YFSY0029), Key Laboratory of Photovoltaic and Energy Conservation Materials, CAS (PECL2019KF003), Sichuan Key Laboratory of Vanadium and Titanium Resources Comprehensive Utilization (No. 2018FTSZ37) and The Specific Research Fund for TCM Science and Technology of Guangdong Provincial Hospital of Chinese Medicine (No. YN2016QJ08 and No. YN2019MJ17).
References [1] H. Zhao, G.A. Baker, Q. Zhang, Design rules of ionic liquids tasked for highly efficient fuel desulfurization by mild oxidative extraction, Fuel 189 (2017) 334–339. [2] A. Afzalinia, A. Mirzaie, A. Nikseresht, T. Musabeygi, Ultrasound-assisted oxidative desulfurization process of liquid fuel by phosphotungstic acid encapsulated in a interpenetrating amine-functionalized Zn(II)-based MOF as catalyst, Ultrason. Sonochem. 34 (2017) 713–720. [3] W.N.W. Abdullah, W.A.W.A. Bakar, R. Ali, W.N.A.W. Mokhtar, M.F.Omar, Catalytic oxidative desulfurization technology of supported ceria based catalyst: physicochemical and mechanistic studies, J. Cleaner Prod. 162 (2017) 1455–1464. [4] T.L. Skafte, P. Blennow, J. Hjelm, C. Graves, Carbon deposition and sulfur poisoning during CO2 electrolysis in nickel-based solid oxide cell electrodes, J. Power Sources 373 (2018) 54–60. [5] B.K. Saikia, A.C. Dalmora, R. Choudhury, T. Das, S.R. Taffarel, L.F. Silva, Effective removal of sulfur components from Brazilian power-coals by ultrasonication (40 kHz) in presence of H2O2, Ultrason. Sonochem. 32 (2016) 147–157. [6] M.R. Jalali, M.A. Sobati, Intensification of oxidative desulfurization of gas oil by ultrasound irradiation: optimization using Box-Behnken design (BBD), Appl. Therm. Eng. 111 (2017) 1158–1170. [7] B. Khodaei, M.A. Sobati, S. Shahhosseini, Rapid oxidation of dibenzothiophene in model fuel under ultrasound irradiation, Monatshefte für Chemie-Chemical Monthly 148 (2017) 387–396. [8] M.D.G. de Luna, C.M. Futalan, R.A. Dayrit, A.E.S. Choi, M.-W. Wan, Evaluation of continuously mixed reactor configurations in the oxidative-adsorptive desulfurization of diesel fuel: optimization and parametric studies, J. Cleaner Prod. 203 (2018) 664–673. [9] J.B. Bhasarkar, S. Chakma, V.S. Moholkar, Investigations in physical mechanism of the oxidative desulfurization process assisted simultaneously by phase transfer agent and ultrasound, Ultrason. Sonochem. 24 (2015) 98–106. [10] B. Khodaei, M.A. Sobati, S. Shahhosseini, Optimization of ultrasound-assisted oxidative desulfurization of high sulfur kerosene using response surface methodology (RSM), Clean Technol. Environ. Policy 18 (2016) 2677–2689. [11] B. Khodaei, M. Rahimi, M.A. Sobati, S. Shahhosseini, M.R. Jalali, Effect of operating pressure on the performance of ultrasound-assisted oxidative desulfurization (UAOD) using a horn type sonicator: Experimental investigation and CFD simulation, Chem. Eng. Process. Process Intensification 132 (2018) 75–88. [12] E.C. Gaudino, D. Carnaroglio, L. Boffa, G. Cravotto, E.M. Moreira, M.A. Nunes, V.L. Dressler, E.M. Flores, Efficient H2O2/CH3COOH oxidative desulfurization/ denitrification of liquid fuels in sonochemical flow-reactors, Ultrason. Sonochem. 21 (2014) 283–288. [13] N.S. More, P.R. Gogate, Intensified approach for desulfurization of simulated fuel containing thiophene based on ultrasonic flow cell and oxidizing agents, Ultrason.
Sonochem. 51 (2019) 58–68. [14] M. Rahimi, S. Shahhosseini, S. Movahedirad, Continuous-flow ultrasound assisted oxidative desulfurization (UAOD) process: an efficient diesel treatment by injection of the aqueous phase, Ultrason. Sonochem. 39 (2017) 611–622. [15] M. Rahimi, S. Movahedirad, S. Shahhosseini, CFD study of the flow pattern in an ultrasonic horn reactor: introducing a realistic vibrating boundary condition, Ultrason. Sonochem. 35 (2017) 359–374. [16] A. Žnidarčič, R. Mettin, M. Dular, Modeling cavitation in a rapidly changing pressure field – application to a small ultrasonic horn, Ultrason. Sonochem. 22 (2015) 482–492. [17] S. Mottyll, R. Skoda, Numerical 3D flow simulation of ultrasonic horns with attached cavitation structures and assessment of flow aggressiveness and cavitation erosion sensitive wall zones, Ultrason. Sonochem. 31 (2016) 570–589. [18] M. Rahimi, S. Shahhosseini, S. Movahedirad, Hydrodynamic and mass transfer investigation of oxidative desulfurization of a model fuel using an ultrasound horn reactor, Ultrason. Sonochem. (2018). [19] J.B. Bhasarkar, M. Singh, V.S. Moholkar, Mechanistic insight into phase transfer agent assisted ultrasonic desulfurization, RSC Adv. 5 (2015) 102953–102964. [20] N.S. More, P.R. Gogate, Intensified approach for desulfurization of simulated fuel containing thiophene based on ultrasonicflow cell and oxidizing agents, Ultrason.– Sonochem. 51 (2019) 58–68. [21] J. Bhasarkar, A. Jyoti, P. Goswami, V.S. Moholkar, Bioresource Technology Mechanistic analysis of ultrasound assisted enzymatic desulfurization of liquid fuels using horseradish peroxidase, Bioresour. Technol. 196 (2015) 88–98. [22] F. Tian, Z. Fu, H. Zhang, J. Zhang, Y. Chen, C. Jia, Thiophene adsorption onto metal-organic framework HKUST-1 in the presence of toluene and cyclohexene, Fuel. 158 (2015) 200–206. [23] K.X. Lee, J.A. Valla, Investigation of metal-exchanged mesoporous Y zeolites for the adsorptive desulfurization of liquid fuels, Appl. Catal. B Environ. 201 (2017) 359– 369. [24] T.A. Saleh, K.O. Sulaiman, S.A. AL-Hammadi, H. Dafalla, G.I. Danmaliki, Adsorptive desulfurization of thiophene, benzothiophene and dibenzothiophene over activated carbon manganese oxide nanocomposite: with column system evaluation, J. Clean. Prod. 154 (2017) 401–412. [25] Y. Zhang, G. Li, L. Kong, H. Lu, Deep oxidative desulfurization catalyzed by Tibased metal-organic frameworks, Fuel. 219 (2018) 103–110. [26] H. Liu, S. Bao, Z. Cai, T. Xu, N. Li, L. Wang, H. Chen, W. Lu, W. Chen, A novel method for ultra-deep desulfurization of liquid fuels at room temperature, Chem. Eng. J. 317 (2017) 1092–1098. [27] L. Hao, L. Sun, T. Su, D. Hao, W. Liao, C. Deng, Polyoxometalate-based ionic liquid catalyst with unprecedented activity and selectivity for oxidative desulfurization of diesel in [Omim] BF4, Chem. Eng. J. 358 (2019) 419–426. [28] H. Haji, A. Akbari, M. Omidkhah, High efficient and selective oxidative desulfurization of diesel fuel using dual-function [Omim]FeCl4 as catalyst / extractant,
Fuel Process. Technol. 185 (2019) 8–17. [29] A. Coletti, F. Sabuzi, B. Floris, P. Galloni, V. Conte, Efficient and sustainable Vcatalyzed oxidative desulfurization of fuels assisted by ionic liquids, J. Fuel Chem. Technol. 46 (2018) 1121–1129. [30] D. Margeta, K. Sertić-Bionda, L. Foglar, Ultrasound assisted oxidative desulfurization of model diesel fuel, Appl. Acoust. 103 (2016) 202–206. [31] Zhenjun Wang. Advances in ultrasonic production units for enhanced oil recovery in China, Ultrasonics Sonochemistry, Volume 60, January 2020, 104791. 6. [32] M. Toghyani, A. Rahimi, UV-irradiation effect on desulfurization of hydrocarbon fuels through an advanced oxidation-extraction process in presence of acid catalyst, Chem. Eng. Process. Process Intensif. 133 (2018) 303–311. [33] M. Shi, D. Zhang, X. Yu, Y. Li, X. Wang, W. Yang, Deep oxidative desulfurization catalyzed by (NH4)5H6PV8Mo4O40 using molecular oxygen as an oxidant, Fuel Process. Technol. 160 (2017) 136–142. [34] X. Zeng, X. Xiao, Y. Li, J. Chen, H. Wang, Deep desulfurization of liquid fuels with molecular oxygen through graphene photocatalytic oxidation, Appl. Catal. B, Environ. 209 (2017) 98–109. [35] H. Fatimah, M. Zaid, F. Kait, M. Ibrahim, A. Mutalib, Photooxidative – extractive deep desulfurization of diesel using Cu–Fe/TiO2 and eutectic ionic liquid, Fuel 156 (2015) 54–62. [36] M. Zarrabi, M.H. Entezari, Modification of C/TiO2@MCM-41 with nickel nanoparticles for photocatalytic desulfurization enhancement of a diesel fuel model under visible light, J. Colloid Interface Sci. 457 (2015) 353–359. [37] J. Behin, N. Farhadian, Multi-objective optimization of oxidative desulfurization in a sono-photochemical airlift reactor, Ultrason. – Sonochem. 38 (2017) 50–61. [38] X. Li, et al., Development of Bi2W1ÀxMoxO6/Montmorillonite nanocomposite as efficient catalyst for photocatalytic desulfurization, J. Alloy. Compd. J. 709 (2017) 285–292. [39] M. Mafi, B. Mokhtarani, M.R. Dehghani, Removal of thiophene from model diesel oil with nitrate based ionic liquids at several temperatures, J. Mol. Liq. 221 (2016) 1104–1110. [40] K.R. Balinge, A.G. Khiratkar, M. Krishnamurthy, D.S. Patle, K.K. Cheralathan, P.R. Bhagat, Deep-desulfurization of the petroleum diesel using the heterogeneous carboxyl functionalized poly-ionic liquid, Resour. Technol. 2 (2016) S105–S113. [41] J. Wang, L. Zhang, Y. Sun, B. Jiang, Y. Chen, X. Gao, H. Yang, Deep catalytic oxidative desulfurization of fuels by novel Lewis acidic ionic liquids, Fuel Process. Technol. 177 (2018) 81–88. [42] L. Rivoira, J. Juárez, H. Falcón, M.G. Costa, O. Anunziata, A. Beltramone, Vanadium and titanium oxide supported on mesoporous CMK-3 as new catalysts for oxidative desulfurization, Catal. Today. 282 (2017) 123–132. [43] Feng Shuchu, Guo Yingchang. Oil and gas gathering and transportation and field processing [M]. Dongying: China University of Petroleum Press, 2006:350-357. [44] Clanton G W, Gipson R E. Sweetening of sour crude using gas string process [C]. SPE2599, 1969.
[45] Zhao Hong, Liu Haitao, Chen Jianfeng. A method for removing hydrogen sulfide from crude oil [P].CN105018132, 2015. [46] Feng Yu. A water-soluble desulfurizer for crude oil and its preparation method [P]. CN 104263404, 2015. [47] Zhang Suojiang, Dong Haifeng, Liu Kunfeng. An oil desulfurization method based on ionic liquids [P]. CN 101063046, 2010. [48] Wang Hong, Zhang Junsheng, Tian Yonghong. Research and application status of chemical desulfurizers for crude oil [J]. Oilfield Chemistry, 2015, 32(2): 313-316. [49] Sun Zhenbo, Cao Zubin, Han Dongyun, Zhao Rongxiang. Exploratory Study on Ultrasonic Oxidation Desulfurization of Catalytic Cracking Diesel Oil. JOURNAL OF LIAO NING SHIHUA UNIVERSITY, Vol. 36 No. 5 Oct. 2016, 10-13. [50] Chan Sheng. Exploratory Research on Crude Oil Desulfurization Technique, Technology & Economics in Petrochemicals, Volume 30, No. 2 April 2014, 16-19. [51] LIU Lin, Lv Hong, XING Jinjuan. Study on Oxidative Desulfurization of Crude Oil Under Ultrasound Irradiation, Science Technology and Engineering, 1671-1815 (2011) 1-0148-03.
Highlights
Ultrasonic waves can improve the activity of oxidants Ultrasonic waves can promote heterogeneous reactions Ultrasonic waves can promote the degradation of macromolecular compounds
Conflict of Interest We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the position presented in, or the review of the manuscript.
S1350-4177(19)31437-3 https://doi.org/10.1016/j.ultsonch.2019.104946 ULTSON 104946
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Ultrasonics Sonochemistry
Received Date: Revised Date: Accepted Date:
11 September 2019 18 December 2019 24 December 2019
Please cite this article as: Y. Lin, L. Feng, X. Li, Y. Chen, G. Yin, W. Zhou, Study on ultrasound-assisted oxidative desulfurization for crude Oil, Ultrasonics Sonochemistry (2019), doi: https://doi.org/10.1016/j.ultsonch. 2019.104946
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Study on ultrasound-assisted oxidative desulfurization for crude Oil Yinhe Lina,b,
Li Fengd,*, Xuhao Lid,
Yuning Chend, Guoliang Yine, Wen Zhouc,*
a Institute
of Chemical Engineering, Yangtze Normal University, Chongqing, 408100, China and Environment Engineering Institute, Nanchang Institute of Technology, Nanchang, 330000, China c The Second Clinical College of Guangzhou University of Chinese Medicine (Guangdong Provincial Academy of Chinese Medical Sciences), 55 Neihuanxi Road, Guangzhou 510006, China d School of Civil and Transportation Engineering, Guangdong University of Technology, No100, Waihuan Xi Road, Guangzhou, Higher Education Mega Center, Panyu District, Guangzhou 510006, Guangdong, China e Chemistry and chemical engineering college, Yinbin University, Yibin, 644007, China b Energy
*Corresponding
author. E-mail address: [email protected] (Li Feng) and [email protected] (Wen Zhou)
Abstract: The existence of sulfur compounds in crude oil will bring many problems such as corrosion, catalyst poisoning and pollution to the petroleum processing process. Therefore, how to reduce the sulfur content as much as possible in the process of crude oil processing has become an important research topic in the petroleum processing industry. In this paper, ultrasonic-oxidative desulfurization is studied. The effects of reaction temperature, reaction time, amount of oxidant and demulsifier on desulfurization rate are investigated. And the effect of oxidative desulfurization and single oxidative desulfurization under ultrasonic treatment are compared. It is found that the addition of ultrasonic treatment can enhance the desulfurization effect of desulfurizer, the desulfurization efficiency can be increased by about 10% under ultrasonic treatment (100W, 70kHz); ultrasonic wave plays an auxiliary role in the system, it can promote heterogeneous reactions, improve the activity of oxidants, and promote the degradation of macromolecular compounds. Finally, physical desulfurization, chemical desulfurization and biological desulfurization technologies are compared. Keywords: ultrasound; crude oil; desulfurization 1.Introduction The sulfides in crude oil can be divided into two categories according to their properties: active sulfur and inactive sulfur. Active sulfur mainly includes elemental sulfur, hydrogen sulfide, etc. Its active nature can react directly with metal substances, which is the main cause of equipment corrosion. Inactive sulfur mainly includes sulfides, disulfides, thiophene and so on. Generally, it does not react with metal substances, but its thermal stability is poor and it is easy to decompose to produce hydrogen sulfide when heated [1-3]. Crude oil desulfurization is mainly to remove active sulfur. Generally, sulfur is a rare element in crude oil. H2S is the main sulfide that causes harm in the process of exploitation, storage, transportation and processing of crude oil. these H2S will be produced in every link of oil and gas exploration, exploitation, processing and postprocessing [4]. Hydrogen sulfide poisoning will occur if the staff members are careless in the process of operation. Therefore, in order to ensure production safety, it is
necessary to reduce the harm of hydrogen sulfide to employees and production equipment [5]. At present, the application of crude oil desulfurization technology can be divided into three categories: physical desulfurization, chemical desulfurization and biological desulfurization [6]. Pre-desulfurization prior to crude oil processing can reduce hydrogen consumption in subsequent processes, as well as damage and corrosion to catalysts and equipment. At present, there are few studies on pre-desulfurization for crude oil, and the main desulfurization methods are all non-hydrodesulfurization. This is mainly because the cost of hydrodesulfurization is too high. It can be seen from the above discussion that at this stage, the crude oil pre-desulfurization technology has the disadvantages of low desulfurization rate, high cost, and low oil yield. The main problems faced by the oxidation process are as follows: First, it is necessary to select a catalyst with strong specificity, otherwise the crude oil is easily over-oxidized and its properties are deteriorated; Second, oxidative desulfurization causes hydrocarbon loss. Therefore, it is necessary to develop a technology for processing and utilizing the sulfone material that has been removed to make it feasible for industrialization. Physical desulfurization is based on the theory of vapor-liquid equilibrium of crude oil to use corresponding physical equipment to remove hydrogen sulfide from crude oil. For example, vacuum flash evaporation, multi-stage separation, fractionation and gas extraction method. Vacuum flash evaporation is based on the principle of reducing separation pressure to remove H2S from crude oil. Its working principle can be divided into two cases. One is to increase the original saturation temperature under certain pressure [7]. The second is to reduce the pressure of saturated crude oil at a certain temperature. Both of these operations can vaporize part of the crude oil, allowing the crude oil state point to enter the gas-liquid two-phase zone, and finally achieve crude oil desulfurization. Multi-stage separation is a commonly used crude oil degassing process [8]. As the crude oil flows along the fixed pipe, the pressure inside the pipe is continuously reduced. When the pressure reaches a certain critical value, the low pressure environment will force a part of the gas inside the crude oil to be discharged. At this time, the crude oil and gas in the pipeline are in a state of mutual contact. Under these conditions, the gas is also discharged out of the pipeline. After the above cycle, the desulfurization effect of crude oil is finally achieved. Fractionation is also one of the common technologies for desulfurization of crude oil. It is clearly based on the principle of rectification to desulfurize crude oil [9]. The desulfurization process is essentially a constant balance between gasification and condensation. Special attention should be paid to the separation of gas and liquid from crude oil when desulfurizing crude oil by this method. On this basis, some of the lighter components are separated, and the hydrogen sulfide in the crude oil is the most volatile part. Physical desulfurization is a combination of stripping process and mechanical stirring. This method is based on the principle of phase equilibrium to reduce the vapor partial pressure in the crude oil pipeline. After the pressure reaches a certain value, the light component of the crude oil will be gasified, so as to desulfurize the crude oil. After comprehensive comparison of four physical hydrogen sulfide removal processes, the stripping process has the best effect on H2S removal of heavy oil, and the H2S content can meet the requirement of less than 60mg/kg at the operating temperature of 90℃ [10-13]. Chemical desulfurization technology for crude oil refers to injecting desulfurizer into the proper position of crude oil production system to achieve the purpose of desulfurization. The key of this technology is to develop and select proper desulfurizer. Using water-soluble hydrogen sulfide desulfurizer is a very effective desulfurization
method. Since the dehydration rate of crude oil is required to be lower than 0.5%, if the actual dehydration rate is lower than this value, such as 0.2%~0.3%, there will be a dissolution space of 0.2%~0.3%. Existing desulfurizers can only fix hydrogen sulfide through chemical reactions, but cannot remove it from crude oil, and such reactions are often reversible [14]. It is difficult to achieve the expected effect when hydrogen sulfide is regenerated under appropriate temperature and pressure, and the addition of desulfurizer also increases the burden of subsequent crude oil processing. Therefore, the chemical desulfurization process needs to be improved [15]. Based on the immobilization of H2S by the chemical reaction of desulfurizer with H2S in crude oil, the immobilized sulfide is migrated to the water phase, and can be separated from crude oil by a simple separation process, so that it does not affect the processing of subsequent crude oil. Water-soluble desulfurizer can solve this problem better. The desulfurizer can dissolve well in the water phase in crude oil, and with the aid of good solubilization and mutual solubility, the reaction can proceed quickly [16-19]. The reaction products can also be removed by dehydration and desalination process of crude oil without affecting the processing of petroleum and the quality of petroleum products [20]. Biological hydrogen desulfurization technology can inhibit the formation of hydrogen sulfide by killing sulfate reducing bacteria. The technology has been successfully applied in Gullfaks, Foinaven and Skjold oilfields [21]. Ultrasonic oxidative desulfurization for crude oil is an environmentally friendly method. Fully utilizing the cavitation, mechanical action and thermal action of ultrasound can realize the original desulfurization. On the one hand, it saves solvent, saves time and energy, and reduces waste generation. It is conducive to environmental protection, no pollution and belongs to green engineering. Meanwhile, oxidative desulfurization has the advantages of simple technological process, low reaction temperature, low equipment investment and low operating cost [22-25]. The combination of ultrasound and oxidation can not only achieve a certain desulfurization effect, but also is a new technology with broad prospects for development. It fundamentally solves the problem of desulfurization of petroleum products and is conducive to the production of clean fuels. In this paper, the existing problems of desulfurization technology are briefly analyzed, and the corresponding optimal design scheme is put forward to select a better and more suitable formula for field experiments, which has important guiding significance for solving the removal of hydrogen sulfide in oil and gas reservoir exploitation 2. Principle of ultrasonic oxidation desulfurization In the oxidation desulfurization process, it is difficult to mix the water phase and the oil phase fully with general mechanical agitation. The mechanical action, cavitation and heat generated by the ultrasonic wave can form a microemulsion between the water phase and the oil phase, thereby improving the mutual contact between the molecules, forming a local high temperature and high pressure, and simultaneously generating free radicals and activated oxygen. This not only rapidly oxidizes the sulfide, improves the oxidizing ability of the oxidant, improves the selectivity of the reaction, and significantly shortens the oxidation reaction time, but also changes the way and direction of the reaction, so that the oxidation reaction can be carried out more thoroughly. In the extraction stage, ultrasonic intervention can effectively mix the extractant and partial oxidized diesel oil, and promotes sufficient contact between the oxidized sulfide molecules and the extractant to effectively release the sulfone.
3. Ultrasonic oxidation desulfurization for crude oil 3.1 Instruments, materials and experimental methods The instruments and materials used in the experiment were as follows: DS-3510DTH type ultrasonic reactor (frequency is 40 kHz); TSN-2000 type fluorescent sulfur nitrogen analyzer. Crude oil sample; oxidant; demulsifier. Experimental steps: duplicate the crude oil sample (i.e. the process of mixing crude oil, oxidant, demulsifier and water). Take a certain amount of crude oil in a conical flask, add a certain proportion of oxidant, demulsifier and first-grade water, mix it relatively evenly, and then put it into an ultrasonic reactor that has been heated to a specified temperature and set a certain reaction time to start the reaction. After the reaction, the reaction liquid is separated, washed and separated (contrast experiment: single oxidation desulfurization experiment is carried out on a digital constant temperature magnetic stirrer). The sulfur content of the reaction oil sample is determined by fluorescence sulfur nitrogen meter. 3.2 Results and discussion 3.2.1 Comparison between ultrasonic oxidation desulfurization and single oxidation desulfurization The desulfurization effects of ultrasonic oxidation desulfurization and single oxidation desulfurization are investigated under different temperature and reaction time. It can be seen from Figure 1, 2 that the ultrasonic oxidation desulfurization rate is higher than the single oxidation desulfurization rate. Therefore, the desulfurization efficiency of crude oil can be significantly improved under the action of ultrasonic wave.
Fig.1. Effect of ultrasonic oxidation and single oxidation desulfurization at different temperature
Fig.2. Effect of ultrasonic oxidation and single oxidation desulfurization at different temperature within different reaction time.
3.2.2 Influence of reaction temperature and time on desulfurization rate of crude oil As can be seen from Figure 3, desulfurization first increases with the increase of reaction temperature, reaches the maximum when the reaction temperature reaches 65℃, and then decreases with the increase of temperature. Because the oxidation of sulfide to sulfoxide and sulfoxide is endothermic. Increasing the reaction temperature shifts the equilibrium in the positive direction, and at the same time makes the lowboiling substances in the crude oil more volatile, and the peroxide is unstable and decomposes at higher temperatures [7]. Therefore, the selected reaction temperature is 65℃.
Fig.3.Influence of reaction temperature on desulfurization rate of crude oil
It can be seen from Figure 4 that the desulfurization rate increases with the extension of the reaction time. The maximum is reached when the reaction time is 10 min, and when the reaction time exceeds 10 min, the desulfurization rate decreases. As
the reaction time prolongs, the peroxide is unstable, and the oxidation reaction almost reaches equilibrium, which is not conducive to the oxidation reaction. Therefore, the reaction time is chosen to be 10 min.
Fig.4.Influence of reaction time on desulfurization rate of crude oil
3.3 Influence of catalyst volume fraction on ultrasonic desulfurization As can be seen from Figure 5, the catalyst volume fraction is proportional to the desulfurization rate of the oil [49]. When the volume fraction of catalyst is less than 2%, the removal rate of sulfide in diesel increases with the increase of catalyst volume fraction. However, with the increase of catalyst volume fraction, the removal rate of sulfide in diesel tends to be gently.
Fig.5. Influence of catalyst volume fraction on ultrasonic desulfurization
3.4 Effect of oxidant volume fraction on ultrasonic desulfurization
It can be seen from Figure 6 that the volume fraction of oxidant is proportional to the removal rate of sulfide in diesel oil [49]. When the volume fraction of oxidant is less than 9%, the desulfurization rate of diesel increases with the increase of the volume fraction of oxidant. However, when the volume fraction of oxidant is more than 9%, the desulfurization rate of diesel tends to be stable with the increase of the volume fraction of oxidant.
Fig.6. Effect of oxidant volume fraction on ultrasonic desulfurization
3.5 Influence of oxidant and demulsifier dosage on desulfurization rate of crude oil As can be seen from Figure 7, when the dosage of oxidant increased from 50×10-6 (ppm) to 200×10-6 (ppm), the desulfurization rate significantly increased. After that, with the increase of oxidant dosage, the desulfurization rate was not obvious. Considering the desulfurization effect, the properties of desulfurized oil and economic benefits, the oxidant dosage is chosen to be 200×10-6 (ppm).
Fig.7. Effect of oxidant dosage on desulfurization rate of crude oil
It can be seen from Figure 8 that the desulfurization rate increases obviously when the demulsifier dosage increases from 15×10-6 (ppm) to 60×10-6 (ppm). Thereafter, with the increase of demulsifier dosage, the desulfurization rate does not change significantly. Demulsifier helps to separate oil from water, and enables sulfur compounds in crude oil emulsion to transfer smoothly from oil phase to water phase under the action of ultrasonic wave and peroxide. Therefore, considering the desulfurization effect, the properties of desulfurized oil and economic benefits, the demulsifier dosage is 60×10-6 (ppm).
Fig.8. Effect of demulsifier dosage on desulfurization rate of crude oil
In short, ultrasound oxidation desulfurization has obvious advantages over single oxidation desulfurization. The desulfurization efficiency of crude oil is the best when the reaction temperature is 65℃, reaction time is 10 min, oxidant dosage is 200×10-6 (ppm) and demulsifier dosage is 60×10-6 (ppm). The desulfurization rate can reach 65.28 (m)%. The best match for the study is only relative to the chosen factor. However, due to the difference of crude oil properties, the conditions of oxidative desulfurization
test under the action of ultrasound will change [51]. More systematic experiments are needed to investigate the desulfurization effect of this method. The oil parameters before and after ultrasonic desulfurization are shown in Table 1 [49]. It can be seen from Table 1 that the properties of the oil after ultrasonic desulfurization are significantly improved, the density of the oil is reduced, and the sulfur mass fraction is reduced from 2133 μg·g-1 to 363 μg·g-1. Tab.1. Oil parameters before and after ultrasonic desulfurization Before ultrasonic After ultrasonic Parameters desulfurization desulfurization ρ(20℃)/g·mL-1 0.9156 0.8581 -1 ω(sulfur)/μg·g 2133 363 Freezing point (℃) -7 -3 Kinematic Viscosity 4.2 3.4 (20℃) (mm2·s-1) Cetane number 31 45 Oxidation stability 1.76 10% carbon residue on 1.14 <0.3 residuum/%
In addition, Chan Sheng [50] studied ultrasonic assisted oxidation desulfurization for crude oil. The crude oil desulfurization test device is shown in Figure 9. Three flasks with reactants are placed in the water bath box 2. Water bath box 2 is connected with ultrasonic generator 1, where the mechanical mixing of reactants is realized by the electronic agitator. Full-digital ultrasonic generator has the function of transmitting ultrasonic wave and constant temperature heating. When you need to investigate the effect of ultrasonic on the reaction, turn it on and set the ultrasonic parameters. When ultrasonication is not required, only the function of heating the thermostat can be used.
Fig.9. Schematic diagram of crude oil desulfurization test device. 1-ultrasonic generator; 2-water bath; 3-three-port flask; 4-stirring rod; 5-motor; 6electronic stirring regulator
The comparison results of desulfurization effects before and after ultrasonic action are shown in Table 2. It can be seen from Tab.2 that the desulfurization rate of A-
phosphotungstic acid system without ultrasonic wave is only 12.0%, while that of Aphosphotungstic acid system with ultrasonic wave increases to 13.3%. The desulfurization rate of A-Sb2O5 system increased from 5.8% to 7.8% after ultrasonic action. The desulfurization rate of A-active Ni system increases from 10.6% to 12.4% after ultrasonic action. It indicates that ultrasound assistance can promote the desulfurization agent system to varying degrees [50]. Tab.2. Ultrasound-oxidation desulfurization test for crude oil Mass fraction of sulfur after Desulfurization Experimental scheme treatment/(mg·kg-1) rate/% 0.5%A+0.05% 6016 12.0 Phosphotungstic acid 0.5%A+0.05% 5931 13.3 Phosphotungstic acid+UL 0.5%A+0.05% Sb2O5 6444 5.8 0.5%A+0.05% Sb2O5+UL 6304 7.8 0.5%A+0.05% Active Ni 6116 10.6 0.5%A+0.05% Active Ni+UL 5988 12.4
For A-phosphotungstic acid system, the desulfurization rate is low before ultrasonic treatment. It has been proved that transition metal catalysts (usually transition metal complexes, such as phosphotungstic acid and phosphomolybdic acid) can activate the catalytic activity of peroxides [50]. The catalyst forms a highly selective oxidantperoxide-metal complex with peroxide, which plays an important role in oxidising sulfide. Even weakly nucleophilic organic sulfides, such as dibenzothiophene, can be oxidized to sulfoxide or sulfone in high yield under mild conditions. However, in crude oil system, the oxidation of organic sulfides mainly occurs at the oil-water interface due to the two-phase oxidation of desulfurizer and crude oil. The interfacial resistance between catalyst solution and organic phase hinders the catalytic reaction. Due to the small effective contact area, the addition of ultrasonic wave rapidly formed a very fine emulsion in the two phases, which greatly increased the specific surface area of the reaction and greatly promoted the oxidation reaction of organic sulfide molecules. From the perspective of the oxidation system, the local high temperature and high pressure formed by the ultrasonic field promotes the activation of reactive oxygen species and improves the oxidation activity. From the perspective of ultrasonic degradation, the high temperature generated by ultrasonic can break the carbon-carbon bond and carbonsulfur bond, making some high-molecular sulfur compounds smaller and simpler. The oxidant is easier to react with it, and the sulfones produced by the reaction are more easily extracted by methanol. For A-Sb2O5 and A-active Ni systems, the desulfurization rate increased by about 2 percentage points with the addition of ultrasound. The main reason is that ultrasound promotes oil-water two-phase mechanical mixing and thermal action. It can be seen that the addition of ultrasound is helpful to enhance the desulfurization effect of desulfurizer. By introducing 400 W and 70 Hz ultrasonic wave, the desulfurization efficiency can be increased by about 10%. Ultrasound assists the system, promotes heterogeneous reaction, enhances the activity of oxidants and promotes the degradation of macromolecular compounds. In a word, the research shows that different types of desulfurizers have different
desulfurization effects. Although the desulfurization efficiency of crude oil increases with the increase of desulfurizer dosage, excessive desulfurizer will cause excessive oxidation and destroy crude oil components. The results of catalytic oxidation test show that phosphotungstic acid is the best catalyst for desulfurization, followed by active Ni. The catalytic mechanism of the two is different in crude oil. The main role of phosphotungstic acid is to improve the oxidation activity of the system and its strong oxidation, while the main role of active Ni is to react with sulfides as a reactant to reduce sulfides, which then react with desulfurizers. Ultrasound assisted desulfurization can enhance the desulfurization effect, and the desulfurization efficiency can be increased by about 10%. Ultrasound plays an auxiliary role in the system, promoting the full mixing of heterogeneous reactions, improving the activity of oxidants and degrading macromolecular compounds. 4.Comparison of physical desulfurization, chemical desulfurization and biological desulfurization 4.1 Physical Desulfurization The basic principle of physical desulfurization is to remove hydrogen sulfide from crude oil by means of corresponding technical methods and equipment according to the theory of gas-liquid equilibrium. It is a semi-desulfurization method. Strictly speaking, hydrogen sulfide is extracted from crude oil by simple physical methods, and some technical methods are needed to remove hydrogen sulfide completely in the later stage. 4.1.1 Crude oil stabilization method The crude oil stabilization methods mainly include multistage separation, vacuum flash evaporation and fractionation. Hydrogen sulfide is a gaseous phase at room temperature, so it can be separated from the gas phase and liquid phase of crude oil by multistage separation, so as to remove hydrogen sulfide from crude oil. This method can only remove hydrogen sulfide in gas phase, while hydrogen sulfide dissolved in crude oil and water cannot be completely removed [26-29]. Vacuum flash evaporation refers to the method of reducing external pressure and heating oil body to analyze the dissolved hydrogen sulfide in crude oil and water and remove it to achieve deep desulfurization. Usually, the removal rate of hydrogen sulfide can reach more than 95% by combining the two methods. The method is simple in equipment and low in energy consumption, and is suitable for treating low-sulfur crude oil. Fractionation can be used for the removal of hydrogen sulfide from high sulfur crude oil, which has high recovery and deep desulfurization. But Moins [43] pointed out that when the fractionation process is used to treat heavy crude oil, the temperature at the bottom of the fractionator is too high, the energy consumption is too high and the cost is too high to be adopted. 4.1.2 Gas extraction method Pure stripping gas (mainly natural gas without sulfur or with low sulfur content) is introduced from the bottom of the gas stripping tower to reverse contact with the crude oil flowing from the top of the tower, and hydrogen sulfide in the crude oil is taken away by stripping gas, so as to remove hydrogen sulfide from the crude oil [30]. The boiling point of hydrogen sulfide at atmospheric pressure is - 60.3 ℃, which is between
C2 ~ C3. In the process of gas stripping, hydrogen sulfide will be separated from the crude oil and some of the low hydrocarbon components will be carried away, resulting in a certain loss of crude oil. There are two main factors affecting the desulfurization efficiency of gas extraction [44]: feed temperature and gas lift. The desulfurization efficiency can be improved by increasing atmospheric volume and feed temperature, and the desulfurization efficiency is higher when the operating pressure is lower or the vacuum is higher. Beijing university of chemical technology [45] has invented a method to remove hydrogen sulfide from crude oil by using supergravity technology. It does not need to add chemical agents and is safe and environmentally friendly. Physical desulfurization equipment is simple, low operating cost, large processing capacity, will not have adverse impact on downstream crude oil processing, is suitable for crude oil easy to centralized processing blocks, and is now the main means of crude oil desulfurization. 4.2 Chemical desulfurization Chemical desulfurization of crude oil refers to reducting sulfur content in crude oil by adding certain chemical agents (i.e. desulfurizers) in the suitable position in the process of crude oil production, transportation and processing [31]. The research and development of high efficiency desulfurizer is the key to chemical desulfurization. The existing desulfurizers for crude oil mainly include amino desulfurizer, inorganic basic desulfurizer, strong oxidizing desulfurizer and other types of desulfurizer [32]. 4.2.1 Amine desulfurizer Amine desulfurizers are widely used because of their high hydrogen sulfide absorption capacity. Amine desulfurizers mostly use alkanolamines or their derivatives as main absorbents, adding a small amount of defoamers, fungicides and other additives, to improve their performance [33]. The main alcoholic amines are ethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), N-methyl diethanolamine (MDEA), monoisopropanolamine (MIPA), etc. Tianjin Yilike Energy Technology Development Co., Ltd. [46] developed a watersoluble desulfurizer for crude oil. Its composition is: 10%-15% formaldehyde, 6%-22% methyl diethanolamine, 32%-34% diethanolamine and 5%-7% sodium nitrite. The desulfurizer has the advantages of simple preparation method, easy availability of raw materials and rapid desulfurization. The volume content of hydrogen sulfide in crude oil can be reduced from 5000 mg/m3 to 8 mg/m3 in 30 minutes to meet the transportation standard [34-36]. Most amine-based desulfurizers can only remove hydrogen sulfide from crude oil, but can not remove other sulfur-containing organic compounds from crude oil. The Institute of Process Engineering of Chinese Academy of Sciences [47] invented an oil desulfurizer based on ionic liquids. It is composed of ionic liquids mixed with alcoholic amines or alcoholic amines derivatives in a certain proportion. It can remove organic sulfur or inorganic sulfur from oil products at the same time. The desulfurization efficiency can reach more than 50%. There is still a problem when amine-based desulfurizer is used as crude oil desulfurizer. Amino desulfurizer has poor thermal stability in salt formed by absorbing hydrogen sulfide. When heated, reversed reaction will occur to re-release hydrogen sulfide. At the same time, amine desulfurizers can be recycled [37]. If directly injected into crude oil, it is difficult to recover, which will increase the difficulty of downstream crude oil processing, resulting in waste and greater economic investment.
4.2.2 Hydroxide desulfurizer Hydroxide desulfurizers are mostly inorganic hydroxides. It is based on the principle of acid-base neutralization to remove hydrogen sulfide. NaOH, KOH and ammonia water are commonly used as hydrogen sulfide removal agents for hydroxide crude oil. Their basic desulfurization principles are as follows: 𝐍𝐚𝐎𝐇 + 𝐇 𝟐 𝐒→𝐍𝐚𝐇𝐒 + 𝐇 𝟐 𝐎 𝐊𝐎𝐇 + 𝐇 𝟐 𝐒→𝐊𝐇𝐒 + 𝐇 𝟐 𝐎 𝐍𝐇 𝟒 𝐎𝐇 + 𝐇 𝟐 𝐒→𝐍𝐇 𝟒 𝐇𝐒 + 𝐇 𝟐 𝐎 The solution of NaOH and KOH is still alkaline after absorbing hydrogen sulfide, and it is easy to form stable oil-water emulsion at this time, thus increasing the difficulty of dehydration of downstream crude oil. When ammonia water is used as desulfurizer, the ammonium salt produced is easy to be removed, the ammonia water is volatile, the loss is large, and the heat stability of the ammonium salt is poor. When the temperature rises, a reverse reaction will occur to release hydrogen sulfide again, and at the same time, it will cause corrosion of equipment and environmental pollution, so this kind of desulfurizer has been rarely used [48]. 4.2.3 Strong oxidizing desulfurizer Commonly used strong oxidizing desulfurizers are H2O2 and KMnO4. It is possible to oxidize the sulfur in the hydrogen sulfide to a low-valent -2 value to a stable highvalence state SO24 ― . Strong oxidizing desulfurizer has certain risks when used. H2O2 is easy to decompose into H2O and O2 and generate a lot of heat. KMnO4 also produces O2 and a lot of heat when heated or acidic. O2 is prone to explosion when mixed with low hydrocarbons in the gas phase of crude oil. Therefore, the amount of desulfurizer should be strictly controlled when it is used, and the operation should be very careful to avoid danger [38]. 4.3 Bio-desulfurization (BDS) In recent years, BDS has developed rapidly. Through screening special strains with high digestibility of sulfur-containing organic matter in petroleum, sulfur-containing organic compounds are converted into water-soluble substances ( SO24 ― ) by bacteria or enzymes, and then eluted from crude oil. When used for desulfurization of crude oil, BDS technology can reduce the total sulfur content of crude oil, and longer residence time of crude oil is also conducive to biological desulfurization process. However, the large amount of crude oil treatment, the variety of sulfides, the single strain can not be completed, and the short life of the strain, which seriously affect its desulfurization effect and application. However, due to the large amount of crude oil treatment and the variety of sulfur compounds, the desulfurization can not be completed by a single strain and the short life of the strain, all of which seriously affect the desulfurization effect and application. The key of BDS technology is the selection of effective strains, and the problem of strain life-span should be solved in industrial application. Table 3 shows some internationally recognized desulfurization strains. BDS, as a new and environmentally friendly biotechnology, is still in the stage of development, but it develops rapidly and has broad application prospects [39-42].
Tab.3. Some internationally recognized desulfurization strains
The type of bacteria
Stroma
Pseudomonas sp
Dibenzothiophene (DBT)
Desulfovibrio escambium Lac 10
Dibenzothiophene (DBT)
Rhodococcus erythropolis H-2
Dibenzothiophene (DBT)
Rhodococcus rhodochrous Acineobater sp
Dibenzothiophene (DBT), Petroleum, Coal Dibenzothiophene (DBT), Thiophene
Corynebacterium sp
Dibenzothiophene (DBT)
Pseudomonas delafieldii
Dibenzothiophene (DBT)
Corynebacteriu sp.SY1
Dibenzothiophene (DBT),DBTO2, Dimethyl sulfoxide（DMSO）
5.Conclusion In this paper, ultrasonic-oxidative desulfurization is studied. The effects of reaction temperature, reaction time, amount of oxidant and demulsifier on desulfurization rate are investigated. And the effect of oxidative desulfurization and single oxidative desulfurization under ultrasonic treatment are compared. The results show that: (1) ultrasound-assisted oxidative desulfurization has obvious advantages over single oxidative desulfurization; (2) when the reaction temperature is 65℃, the reaction time is 10 min, the dosage of oxidant is 200×10-6 (PPM), and the dosage of demulsifier is 60×10-6 (PPM), the ultrasound-assisted oxidative method can achieve the best desulfurization effect, and the desulfurization rate can reach up to 65.28 (m) %; (3) ultrasonic wave plays an auxiliary role in the system, it can promote heterogeneous reactions, improve the activity of oxidants, and promote the degradation of macromolecular compounds. Finally, physical desulfurization, chemical desulfurization and biological desulfurization technologies are compared. Physical desulphurization is the main desulphurization method for crude oil nowadays because of its simple equipment and large capacity, but it will produce a lot of acid gas due to its large initial investment. The chemical desulfurization effect is affected by many factors, and different types of desulfurizing agents should be selected according to the application conditions. Biological desulfurization, as a new type of crude oil desulfurization technology, is still in the research and development stage with broad prospects. Acknowledgments This work is supported by the financial support provided by National Natural Science Foundation of China (Grant No. U1960101), Major Science and Technology Projects of Sichuan Province (No. 2019YFSY0029), Key Laboratory of Photovoltaic and Energy Conservation Materials, CAS (PECL2019KF003), Sichuan Key Laboratory of Vanadium and Titanium Resources Comprehensive Utilization (No. 2018FTSZ37) and The Specific Research Fund for TCM Science and Technology of Guangdong Provincial Hospital of Chinese Medicine (No. YN2016QJ08 and No. YN2019MJ17).
References [1] H. Zhao, G.A. Baker, Q. Zhang, Design rules of ionic liquids tasked for highly efficient fuel desulfurization by mild oxidative extraction, Fuel 189 (2017) 334–339. [2] A. Afzalinia, A. Mirzaie, A. Nikseresht, T. Musabeygi, Ultrasound-assisted oxidative desulfurization process of liquid fuel by phosphotungstic acid encapsulated in a interpenetrating amine-functionalized Zn(II)-based MOF as catalyst, Ultrason. Sonochem. 34 (2017) 713–720. [3] W.N.W. Abdullah, W.A.W.A. Bakar, R. Ali, W.N.A.W. Mokhtar, M.F.Omar, Catalytic oxidative desulfurization technology of supported ceria based catalyst: physicochemical and mechanistic studies, J. Cleaner Prod. 162 (2017) 1455–1464. [4] T.L. Skafte, P. Blennow, J. Hjelm, C. Graves, Carbon deposition and sulfur poisoning during CO2 electrolysis in nickel-based solid oxide cell electrodes, J. Power Sources 373 (2018) 54–60. [5] B.K. Saikia, A.C. Dalmora, R. Choudhury, T. Das, S.R. Taffarel, L.F. Silva, Effective removal of sulfur components from Brazilian power-coals by ultrasonication (40 kHz) in presence of H2O2, Ultrason. Sonochem. 32 (2016) 147–157. [6] M.R. Jalali, M.A. Sobati, Intensification of oxidative desulfurization of gas oil by ultrasound irradiation: optimization using Box-Behnken design (BBD), Appl. Therm. Eng. 111 (2017) 1158–1170. [7] B. Khodaei, M.A. Sobati, S. Shahhosseini, Rapid oxidation of dibenzothiophene in model fuel under ultrasound irradiation, Monatshefte für Chemie-Chemical Monthly 148 (2017) 387–396. [8] M.D.G. de Luna, C.M. Futalan, R.A. Dayrit, A.E.S. Choi, M.-W. Wan, Evaluation of continuously mixed reactor configurations in the oxidative-adsorptive desulfurization of diesel fuel: optimization and parametric studies, J. Cleaner Prod. 203 (2018) 664–673. [9] J.B. Bhasarkar, S. Chakma, V.S. Moholkar, Investigations in physical mechanism of the oxidative desulfurization process assisted simultaneously by phase transfer agent and ultrasound, Ultrason. Sonochem. 24 (2015) 98–106. [10] B. Khodaei, M.A. Sobati, S. Shahhosseini, Optimization of ultrasound-assisted oxidative desulfurization of high sulfur kerosene using response surface methodology (RSM), Clean Technol. Environ. Policy 18 (2016) 2677–2689. [11] B. Khodaei, M. Rahimi, M.A. Sobati, S. Shahhosseini, M.R. Jalali, Effect of operating pressure on the performance of ultrasound-assisted oxidative desulfurization (UAOD) using a horn type sonicator: Experimental investigation and CFD simulation, Chem. Eng. Process. Process Intensification 132 (2018) 75–88. [12] E.C. Gaudino, D. Carnaroglio, L. Boffa, G. Cravotto, E.M. Moreira, M.A. Nunes, V.L. Dressler, E.M. Flores, Efficient H2O2/CH3COOH oxidative desulfurization/ denitrification of liquid fuels in sonochemical flow-reactors, Ultrason. Sonochem. 21 (2014) 283–288. [13] N.S. More, P.R. Gogate, Intensified approach for desulfurization of simulated fuel containing thiophene based on ultrasonic flow cell and oxidizing agents, Ultrason.
Sonochem. 51 (2019) 58–68. [14] M. Rahimi, S. Shahhosseini, S. Movahedirad, Continuous-flow ultrasound assisted oxidative desulfurization (UAOD) process: an efficient diesel treatment by injection of the aqueous phase, Ultrason. Sonochem. 39 (2017) 611–622. [15] M. Rahimi, S. Movahedirad, S. Shahhosseini, CFD study of the flow pattern in an ultrasonic horn reactor: introducing a realistic vibrating boundary condition, Ultrason. Sonochem. 35 (2017) 359–374. [16] A. Žnidarčič, R. Mettin, M. Dular, Modeling cavitation in a rapidly changing pressure field – application to a small ultrasonic horn, Ultrason. Sonochem. 22 (2015) 482–492. [17] S. Mottyll, R. Skoda, Numerical 3D flow simulation of ultrasonic horns with attached cavitation structures and assessment of flow aggressiveness and cavitation erosion sensitive wall zones, Ultrason. Sonochem. 31 (2016) 570–589. [18] M. Rahimi, S. Shahhosseini, S. Movahedirad, Hydrodynamic and mass transfer investigation of oxidative desulfurization of a model fuel using an ultrasound horn reactor, Ultrason. Sonochem. (2018). [19] J.B. Bhasarkar, M. Singh, V.S. Moholkar, Mechanistic insight into phase transfer agent assisted ultrasonic desulfurization, RSC Adv. 5 (2015) 102953–102964. [20] N.S. More, P.R. Gogate, Intensified approach for desulfurization of simulated fuel containing thiophene based on ultrasonicflow cell and oxidizing agents, Ultrason.– Sonochem. 51 (2019) 58–68. [21] J. Bhasarkar, A. Jyoti, P. Goswami, V.S. Moholkar, Bioresource Technology Mechanistic analysis of ultrasound assisted enzymatic desulfurization of liquid fuels using horseradish peroxidase, Bioresour. Technol. 196 (2015) 88–98. [22] F. Tian, Z. Fu, H. Zhang, J. Zhang, Y. Chen, C. Jia, Thiophene adsorption onto metal-organic framework HKUST-1 in the presence of toluene and cyclohexene, Fuel. 158 (2015) 200–206. [23] K.X. Lee, J.A. Valla, Investigation of metal-exchanged mesoporous Y zeolites for the adsorptive desulfurization of liquid fuels, Appl. Catal. B Environ. 201 (2017) 359– 369. [24] T.A. Saleh, K.O. Sulaiman, S.A. AL-Hammadi, H. Dafalla, G.I. Danmaliki, Adsorptive desulfurization of thiophene, benzothiophene and dibenzothiophene over activated carbon manganese oxide nanocomposite: with column system evaluation, J. Clean. Prod. 154 (2017) 401–412. [25] Y. Zhang, G. Li, L. Kong, H. Lu, Deep oxidative desulfurization catalyzed by Tibased metal-organic frameworks, Fuel. 219 (2018) 103–110. [26] H. Liu, S. Bao, Z. Cai, T. Xu, N. Li, L. Wang, H. Chen, W. Lu, W. Chen, A novel method for ultra-deep desulfurization of liquid fuels at room temperature, Chem. Eng. J. 317 (2017) 1092–1098. [27] L. Hao, L. Sun, T. Su, D. Hao, W. Liao, C. Deng, Polyoxometalate-based ionic liquid catalyst with unprecedented activity and selectivity for oxidative desulfurization of diesel in [Omim] BF4, Chem. Eng. J. 358 (2019) 419–426. [28] H. Haji, A. Akbari, M. Omidkhah, High efficient and selective oxidative desulfurization of diesel fuel using dual-function [Omim]FeCl4 as catalyst / extractant,
Fuel Process. Technol. 185 (2019) 8–17. [29] A. Coletti, F. Sabuzi, B. Floris, P. Galloni, V. Conte, Efficient and sustainable Vcatalyzed oxidative desulfurization of fuels assisted by ionic liquids, J. Fuel Chem. Technol. 46 (2018) 1121–1129. [30] D. Margeta, K. Sertić-Bionda, L. Foglar, Ultrasound assisted oxidative desulfurization of model diesel fuel, Appl. Acoust. 103 (2016) 202–206. [31] Zhenjun Wang. Advances in ultrasonic production units for enhanced oil recovery in China, Ultrasonics Sonochemistry, Volume 60, January 2020, 104791. 6. [32] M. Toghyani, A. Rahimi, UV-irradiation effect on desulfurization of hydrocarbon fuels through an advanced oxidation-extraction process in presence of acid catalyst, Chem. Eng. Process. Process Intensif. 133 (2018) 303–311. [33] M. Shi, D. Zhang, X. Yu, Y. Li, X. Wang, W. Yang, Deep oxidative desulfurization catalyzed by (NH4)5H6PV8Mo4O40 using molecular oxygen as an oxidant, Fuel Process. Technol. 160 (2017) 136–142. [34] X. Zeng, X. Xiao, Y. Li, J. Chen, H. Wang, Deep desulfurization of liquid fuels with molecular oxygen through graphene photocatalytic oxidation, Appl. Catal. B, Environ. 209 (2017) 98–109. [35] H. Fatimah, M. Zaid, F. Kait, M. Ibrahim, A. Mutalib, Photooxidative – extractive deep desulfurization of diesel using Cu–Fe/TiO2 and eutectic ionic liquid, Fuel 156 (2015) 54–62. [36] M. Zarrabi, M.H. Entezari, Modification of C/TiO2@MCM-41 with nickel nanoparticles for photocatalytic desulfurization enhancement of a diesel fuel model under visible light, J. Colloid Interface Sci. 457 (2015) 353–359. [37] J. Behin, N. Farhadian, Multi-objective optimization of oxidative desulfurization in a sono-photochemical airlift reactor, Ultrason. – Sonochem. 38 (2017) 50–61. [38] X. Li, et al., Development of Bi2W1ÀxMoxO6/Montmorillonite nanocomposite as efficient catalyst for photocatalytic desulfurization, J. Alloy. Compd. J. 709 (2017) 285–292. [39] M. Mafi, B. Mokhtarani, M.R. Dehghani, Removal of thiophene from model diesel oil with nitrate based ionic liquids at several temperatures, J. Mol. Liq. 221 (2016) 1104–1110. [40] K.R. Balinge, A.G. Khiratkar, M. Krishnamurthy, D.S. Patle, K.K. Cheralathan, P.R. Bhagat, Deep-desulfurization of the petroleum diesel using the heterogeneous carboxyl functionalized poly-ionic liquid, Resour. Technol. 2 (2016) S105–S113. [41] J. Wang, L. Zhang, Y. Sun, B. Jiang, Y. Chen, X. Gao, H. Yang, Deep catalytic oxidative desulfurization of fuels by novel Lewis acidic ionic liquids, Fuel Process. Technol. 177 (2018) 81–88. [42] L. Rivoira, J. Juárez, H. Falcón, M.G. Costa, O. Anunziata, A. Beltramone, Vanadium and titanium oxide supported on mesoporous CMK-3 as new catalysts for oxidative desulfurization, Catal. Today. 282 (2017) 123–132. [43] Feng Shuchu, Guo Yingchang. Oil and gas gathering and transportation and field processing [M]. Dongying: China University of Petroleum Press, 2006:350-357. [44] Clanton G W, Gipson R E. Sweetening of sour crude using gas string process [C]. SPE2599, 1969.
[45] Zhao Hong, Liu Haitao, Chen Jianfeng. A method for removing hydrogen sulfide from crude oil [P].CN105018132, 2015. [46] Feng Yu. A water-soluble desulfurizer for crude oil and its preparation method [P]. CN 104263404, 2015. [47] Zhang Suojiang, Dong Haifeng, Liu Kunfeng. An oil desulfurization method based on ionic liquids [P]. CN 101063046, 2010. [48] Wang Hong, Zhang Junsheng, Tian Yonghong. Research and application status of chemical desulfurizers for crude oil [J]. Oilfield Chemistry, 2015, 32(2): 313-316. [49] Sun Zhenbo, Cao Zubin, Han Dongyun, Zhao Rongxiang. Exploratory Study on Ultrasonic Oxidation Desulfurization of Catalytic Cracking Diesel Oil. JOURNAL OF LIAO NING SHIHUA UNIVERSITY, Vol. 36 No. 5 Oct. 2016, 10-13. [50] Chan Sheng. Exploratory Research on Crude Oil Desulfurization Technique, Technology & Economics in Petrochemicals, Volume 30, No. 2 April 2014, 16-19. [51] LIU Lin, Lv Hong, XING Jinjuan. Study on Oxidative Desulfurization of Crude Oil Under Ultrasound Irradiation, Science Technology and Engineering, 1671-1815 (2011) 1-0148-03.
Highlights
Ultrasonic waves can improve the activity of oxidants Ultrasonic waves can promote heterogeneous reactions Ultrasonic waves can promote the degradation of macromolecular compounds
Conflict of Interest We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the position presented in, or the review of the manuscript.