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Fractionation of tire pyrolysis oil into a light fuel fraction by steam distillation
Fuel 241 (2019) 558–563
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Full Length Article
Fractionation of tire pyrolysis oil into a light fuel fraction by steam distillation Guilherme Anchieta Costa, Ronaldo Gonçalves dos Santos
T
⁎
Chemical Engineering Department, Centro Universitário FEI, São Bernardo do Campo, SP 09850-901, Brazil
A R T I C LE I N FO
A B S T R A C T
Keywords: Tire waste Pyrolysis oil Fuel Petrol Steam distillation
Pyrolysis has been identified as a possible process for producing alternative fuels from thermal degradation of residue materials. In this work, a steam distillation process was applied to extract a light fuel fraction from tire pyrolysis oil. The light fuel fraction (LFF) was a light yellow, translucent liquid with a specific gravity of 0.76 g·cm−3 and dynamic viscosity of 0.4 mPa.s at 20 °C. LFF was mainly composed of volatile organic components of the tire pyrolysis oil. GC-MS analysis shows the light fraction composed mostly of benzene-substituted compounds (62.06%), mainly ethylbenzenes (14.84%) and methylbenzenes (13.02%) derivatives. Saturates were mainly branched alkanes containing eight carbon atoms (21.94%) and cycloalkanes in minor amount (1.35%). Olefins were essentially alkyl-branched cyclohexenes (14.66%), highlighting limonene (8.2%). The standard mid-infrared spectroscopy revealed the light fuel fraction resembles very closely the petroleum-derived gasoline. In addition, typical distillation properties (such as T50, T90, and driveability index) and octane number (Motor Octane Number and Research Octane Number) for the light fuel fraction matched to the gasoline properties. The results point out to the feasibility to replace conventional gasoline by the light fraction obtained from tire-derived oil by means of steam distillation.
1. Introduction Tire waste has been an environmental concern because the severe potential damage that can be caused by the inappropriate disposal in dumps and landfills, resulting in contamination of groundwater and watercourses. In addition, scrap tire improper discarding and handling must lead to the emission risk of harmful pollutants, such as sulfur dioxide (SO2), nitrogen oxides (NOx) and volatile organic compounds (VOCs). Retreading, incineration and grinding represent traditional methods for reusing scrap tires; however, they have shown serious limitations [1]. Furthermore, these tire residues are practically immune to chemical and biological treatments. Waste thermal degradation is a potential method to degrade scrap tire and obtaining unconventional fuels, converting long molecular structures into smaller molecules [1,2]. Pyrolysis is a thermal degradation process that operates under an inert atmosphere at moderate to high temperatures (usually 400–900 °C) to cleave molecules, producing a liquid phase containing an organic mixture [3]. The organic mixture composition depends on the operating conditions, mainly the feedstock composition, temperature, pressure and residence time [4–8].
According to the process arrangement, the oil derived from pyrolysis may be a suitable substitute for petrol-derived fuels [4–6,9]. The pyrolytic oil properties depend especially on the feedstock composition [10,11]. Biomass residues are composed essentially by lignocellulose constituents and they constitute the most abundant and the more studied supplies for pyrolysis processing. Typically, pyrolysis oils obtained from lignocellulosic materials are composed mainly of aldehydes, furans, ketones, esters, and carboxylic acids, as well as ethers, alcohols and hydrocarbons in minor quantities [11,12]. Besides, a large set of studies has addressed the scrap tire conversion into fuels and chemical by means pyrolysis process [1,2,13,14]. The tire-derived oil composition has been typically characterized as a mixture of 7–14 carbon hydrocarbons, containing single ring alkylbenzenes and polycyclic aromatics, such as indene and naphthalene derivatives, and terpenes, as limonene (1-methyl-4-prop-1-en-2-yl-cyclohexene) and cymene (1-methyl-4-(1-methylethyl) benzene) [15]. Fatty acid and nitrogen compounds with high added value have also been identified in pyrolysis oils [16]. Besides the irregular composition, the pyrolysis-derived oil has strong potential to replace conventional fuels in several industrial application, including combustion engine, boilers, and furnaces [17].
⁎ Corresponding author at: Chemical Engineering Department, Centro Universitário FEI, Avenida Humberto de Alencar Castelo Branco 3972, São Bernardo do Campo, SP 09850-901, Brazil. E-mail address: [email protected] (R.G.d. Santos).
https://doi.org/10.1016/j.fuel.2018.12.075 Received 30 August 2018; Received in revised form 12 December 2018; Accepted 13 December 2018 0016-2361/ © 2018 Elsevier Ltd. All rights reserved.
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fraction, high-purity syringol (1,3-Dimethoxy-2-hydroxybenzene) was obtained from wood-derived pyrolysis oil using steam distillation [42]. In addition, a combination of solvent extraction and steam distillation was used to obtaining aroma components extracted from waste tobacco leaves. The combined method was effective to recovering flavor compounds, such as β-damascone, β-damascenone, β-ionone, dihydroactinidiolide, neophytadiene, cembrene and safranal, which are prone to be degraded at high temperatures [43]. The purpose of this work was to obtain a light fuel fraction extracted from a tire-derived pyrolytic oil to be used as an alternative to the gasoline. The pyrolytic oil was produced from tire waste in a pilotscaled pyrolysis reactor operated at 450 °C. The fuel fraction was separated from the tire pyrolysis oil by means of steam distillation (water vapor injection). The main properties of the fuel fraction, including specific gravity, dynamic viscosity, chemical composition, and fuel ignition properties, were found to have a very close resemblance to the petroleum-derived gasoline.
Nevertheless, the pyrolytic oil is scarcely prone to be directly used in combustion engines. Instead, the use of the pyrolysis-derived oil as an alternative automotive fuel requires a supplementary upgrading stage to reach the entire technical and law requirements. Other exploitation methods include blending the oil with conventional fuels and the oil fractionation to obtaining fuel fractions and specific chemical grades [18]. Pyrolysis oil properties can be improved by means of an upgrading process. Oil upgrading must reduce the oil viscosity, the oxygen content and the corrosivity, as well as the oil thermal instability. Hydrogenation and hydrodeoxygenation, a catalytic pyrolysis carried out under a hydrogen atmosphere, are the main methods for oil upgrading [19]. Other promisor upgrading methods include catalytic cracking, steam reforming, molecular distillation, and, more recently, supercritical phase reaction [20–24]. Many works have dedicated efforts to blend the pyrolysis oil with petroleum diesel to reduce the fossil fuel consumption [15,25–27]. The results of these works have shown successful performance for pyrolysis oil-diesel blends in indirect injection multi-cylinder engines, as well as appropriate physicochemical and fuel properties. The pyrolysis oil fractionation is an essential stage for the installation perspective of alternative energy platforms based on the biorefinery concept. The biorefinery concept was originally developed to manner biomass as a feedstock, but it can be extended to the waste dealing out. The fundamental aim is to provide options to replace fossil fuels with alternative fuels that lead to greenhouse gas saving and sustainable energy growth [28,29]. The more common methods for pyrolysis oil fractionation have been solvent extraction, chromatography, and distillation [30]. Solvent extraction (or partitioning) method is based on the relative chemical affinity of a given compound with two immiscible solvents. Solvent (liquid–liquid) extraction has been applied to recovery glycolaldehyde and acetic acid from the aqueous phase produced by wood pyrolysis using tri-n-octylamine/2-ethyl-1-hexanol as a solvent [31]. Phenolic fractions have also been removed from the pyrolysis bio-oil different solvents. Methyl isobutyl ketone (MIBK) was found to be a more selective solvent than ethyl acetate to isolate phenol, p-cresol, creosol, guaiacols and eugenols [32]. The solvent – Anti-solvent (SAS) extraction has also been applied to obtain a phenol-rich organic phase using dichloromethane as solvent and water as anti-solvent [33]. SAS extraction produced organic fractions containing high phenol concentrations and low contents sugars and water, allowing the organic phase to be blended with diesel. Supercritical fluids have a large potential as economically feasible and green technology to fractionating crude bio-oil and recovering of value-added chemicals. Carbon dioxide has commonly been the preferred fluid to be applied in supercritical extraction because relatively low critical temperature and pressure required. Acids and esters fractions were extracted by means of sc-CO2 fractionation from the pyrolysis oil produced from the palm kernel shell [34]. A large amount of furanoids, pyranoids and benezoids has been identified in the pyrolysisoil acid fraction [35]. Value-added chemical fractions such as acids, aldehydes, ketones, furans and aromatics have been found in the biomass-derived fraction from sc-CO2 extraction [36,37]. Distillation processes are based on the relative volatility of the mixture components and they can be applied for the separation of a wide range of volatile organic compounds (VOCs) from the pyrolysis oil. The steam injection heats the oil, increase the total vapor pressure and decrease its boiling point [30,38]. The steam addition allows the organic-water mixture boils at temperatures below than 100 °C, avoiding the degradation of thermally-sensitive compounds [30]. Steam distillation can be applied to separate important components from an oil type variety, comprising essential oils [39] and crude oils [40]. Steam distillation has also been successfully used to obtain valuable substances from pyrolysis oils. Eucalyptol (1,8-cineole) was extracted from Mallee biomass using steam extraction [41]. Chemically-stable
2. Experimental methodology 2.1. Materials The waste tire was obtained from passenger vehicles tires. The end of life tires were shredded into pieces with 2–5 cm long. A 1 wt% of residual steel was found in the shredded material. The shredded waste tire was pyrolyzed in a stainless-steel reactor with 15 kg capacity at 1 bar under N2 inert environment. The pyrolysis process was carried out in a semi batch process for 30 min at 450 °C. An early description of the tire-derived oil properties was presented [15]. 3. Methods 3.1. Fractionation of the tire-derived oil The pyrolytic oil fractionation was carried out by steam distillation. Steam distillation represents an indirect distillation process using liquid vaporization. Briefly, water vapor was yielded from deionized water in an electric boiler. The steam was bubbled by differential pressure into the 500 mL of pyrolytic oil enclosed in a distillation vessel. The water vapor injection promoted a raising up of the total vapor pressure enough to boiling the pyrolytic oil, volatilizing the oil light cuts. Subsequently, the gaseous mixture containing water vapor and light cuts was converted into liquid in a condenser operated at −7°C using ethanol as refrigerant fluid. Finally, the organic liquid fraction was separated from the aqueous phase and labelled as light fuel fraction (LFF). Fig. 1 illustrates the steam distillation process. 3.2. Composition and fuel properties 3.2.1. GC-MS chemical composition A gas chromatographer coupled with an Ion Trap mass spectrometer (model Saturn 2100D, Varian, USA) was used in the quantitative chemical analysis of the tire pyrolysis oil and its light fuel fraction. A HP5MS capillary column (30 m × 0.25 mm × 0.25 μm) containing 5% biphenyl and 95% di-methyl polysilane was used. High purity helium (99.9999%) was used as carrier gas at a flow rate of 1.0 mL·min−1. The injector temperature was 240 °C. The injector was operated in split mode at a 1:20 ratio. Elemental composition was determinate using a Perkin Elmer (USA) elemental analysis model CHN 2400 Series II, using a thermal conductivity detector. 3.2.2. Standard fuel properties The compositional analysis and the main fuel properties were performed by mid-infrared (Mid-IR) spectrometry using a Gas Sensor Portable Process Analyzer (GS-PPA-I, model GS1000 plus VOC), supplied from PAC (USA). The Mid-IR analysis evaluated the multiple 559
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Fig. 1. Steam distillation process to fractionate the tire-derived oil into a light cut.
to replace fossil fuels.
chemical and physical properties, including standard resolution of olefin, aromatic and saturate fractions. Motor Octane Number (MON) by ASTM D2700 Method, Research Octane Number (RON) by ASTM D2699 Method, and anti-knock index (AKI) were also assessed. The High Heat Value (HHV) was determined by a Basic C2000 combustion calorimeter (IKA, Germany). Specific gravity and dynamic viscosity were simultaneously assessed by means of a Stabinger SVM 3000 viscometer (Anton Paar, Germany), according to ASTM D7042. The Stabinger operation is based on the harmonic oscillation law in a U-tube filled with the test sample to perform dynamic viscosity and density measurements.
4.2. Fractionation of the tire-derived oil A light fraction was extracted from the TPO by means of a vaporinjection distillation process, such as illustrated in Fig. 1. The steam distillation process was chosen because the high-temperature requirement to flash the liquid TPO by means of the traditional distillation methods. Besides, steam distillation is very useful fractionation process for resolving fuel mixtures containing low-molecular weight components. The water vapor injection rises up the total vapor pressure in the flask, allowing the liquid mixture to boiling at a temperature below than its normal boiling point. The TPO boiling point was reduced to 94 ± 1 °C, which is entirely feasible to be reached in typical distillation facilities. The vapor mixture leaving the flask was composed of water (from the vapor injected) and light hydrocarbons (from the TPO). The vapor mixture condensation led to a two-phase liquid system containing 33 vol% of oily fraction and 67 vol% of aqueous phase, which contains some water-soluble oil components. The oily fraction was carefully separated from the aqueous phase in a static separator and labelled as light fuel fraction (LFF).
4. Results and discussion 4.1. Properties of the tire-derived oil Tire waste pyrolysis was carried out by a semi batch process. A water-cooled condenser was attached to the top of the heated closedreactor to collect the condensable gas leaving the vessel. Non-condensable gases were blown out since they were composed essentially of water vapor and N2 (together with a minor amount of CO, CO2 and short chain hydrocarbons). In the end of the reaction time, the solidliquid system inside the pyrolysis reactor was separated by filtration using a bottom valve. The resolved liquid phase was blended with the liquid collected in the top condenser, constituting a liquid–liquid twophase system. The aqueous and organic phase were separated in a gravitational separator and the water-free organic phase was signed as pyrolysis oil. The pyrolysis process yields 44 wt% of solid phase (carbon black along with a minor amount of metallic residue) and 45 wt% of liquid phase (pyrolysis oil). The quantity of non-condensed gases was determined by mass balance, achieving 11 wt% of the whole tire waste fed in the reactor. The waste tire pyrolysis produced a dark brown oil, labelled tire pyrolysis oil (TPO). TPO was characterized as a complex mixture composed principally of a wide assortment of hydrocarbon compounds. Hydrocarbons were composed of 7–14 carbon atom compounds. The aromatic fraction was composed of cyclic and polycyclic compounds, mainly indene and naphthalene. Terpenes represented approximately 50% of the total TPO chemical composition. A detailed description of the TPO chemical composition and properties was previously presented by Umeki et al. (2016) [15]. The authors state that the TPO properties were not enough satisfactory to able it to the immediate application in combustion engines since they are out of the fuel standard specifications. Nevertheless, the data show the TPO must be very valuable to be fired into heating processes and blended with conventional fuels. An alternative way for the pyrolysis oil recovery is the fractionation into burnable fractions with appropriated properties
4.3. Characterization of the light fuel fraction The light cut was extracted from the tire-derived oil by steam distillation aiming to replace petroleum fuel fractions. Properties of the light fuel fraction are displayed in Table 1. The light fuel fraction was a light yellow, translucent liquid, displaying specific gravity of 0.76 g·cm−3 and apparent viscosity of 0.40 mPa.s (equivalent to 0.53 cSt), both evaluated at 20 °C. Specific gravity and apparent viscosity for representative gasoline has been reported respectively in the ranges of 0.72–0.78 g·cm−3 and 0.37–0.44 cSt (at 20 °C) [44,45]. The specific gravity of local-gathered petrol has been reported as 0.75 g·cm−3 [15]. Specific gravity and viscosity are important physicochemical parameters to define engine fuels. Then, the Fig. 2 displays the temperature effects on the specific gravity and dynamic viscosity for the light cut obtained by vapor injection distillation. The specific gravity of the light fuel fraction decreased linearly along with the temperature increasing. LFF viscosity curve follows a smooth exponential decaying with the increasing temperature. LFF viscosity was reduced from 0.47 to 0.25 mPa.s for a temperature rising from 30 to 60 °C. A specific gravity reduction from 0.75 to 0.71 mPa.s was achieved for a temperature variation from 10 to 60 °C. Previously published data show the specific gravity and dynamic viscosity disclose an analogous behavior to the PDG [15]. Table 1 also displays the results from the fuel standard 560
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local government regulates the addition of 27 ± 1 vol% of ethanol into the gasoline to the use in automotive engines. This fact explains the discrepancy between the ethanol content in the fuel composition. The ethanol addition is also responsible for the high amount of the oxygen compound fraction in petroleum gasoline. The anti-knock engine performance was assessed by Octane number measurements, which evaluate the fuel relative ability to resist to the knocking during the burning inside the combustion chamber. The main procedures to assess the octane number (the most important properties for fuel application in Otto cycle engines) are Motor Octane Number (MON), Research Octane Number (RON), antiknock index (AKI). RON is the most useful octane rating and it is achieved under a variable compression rate and low speed, whereas MON is obtained under full load engine at high speed. Table 1 summarizes the results of octane number measurements for LFF. Again, the light fraction obtained from steam distillation displays properties similar to the petroleum-derived gasoline data reported in the literature [15,45]. The difference between the RON and MON designates the gasoline sensitivity to the changes in engine operating conditions. Large RON-MON differences indicate a more sensitive gasoline, therefore the octane numbers for LFF and gasoline are found equivalent. The light fuel fraction has a High Heat Value slightly lower than the tire-pyrolysis oils and slightly higher than the petrol-derived gasoline [15,44,45]. In addition, LFF anti-nock index is in-between that of PDG and TPO [15]. The chemical composition of the light fuel fraction is shown in Table 2, according to the gas chromatography analysis. In many cases, the chemical compound grade was displayed instead of individual molecules because the complicated mixture composition grows into unfeasible the resolving of very similar components. GC-MS measurements show the light fraction composed mostly of benzene-substituted compounds (62.06%), most of them were derivate compounds from ethylbenzenes (14.84%) and methylbenzenes (13.02%). Saturates were mainly branched alkanes containing eight carbon atoms (21.94%).
Table 1 Properties of the light fuel fraction extracted from tire pyrolysis oil by steam distillation. Property
Value
Specific gravity (g.cmcm−3 ) at 20 °C Dynamic viscosity (mPa.s) à 20 °C High Heat Value (kJ.g−1)
0.76
–
0.40 40.5
– –
Composition from Mid-IR (Vol.%) MTBE ETOH TAME ETBE MEOH DIPE Aromatics Benzene Olefins Saturates Toluene Xylene Oxygen (in mass percentage)
0.3 0.6 0.0 1.1 0.0 0.2 18.5 0.43 12.7 65.9 4.0 3.6 0.77
For PDGa 0.3 26.2 0.3 0.9 0.7 0.8 18.4 1.16 16.8 35.8 1.50 6.00 11.06
Octane number MON RON AKI
84.5 94.5 89.6
– – –
From [15] for comparison.
0.6
0.76
(g.cm-3)
0.75
0.5
0.74
0.4 0.73
0.3 0.72
μ (mPa.s)
a
Table 2 Chemical composition of oil fraction extracted from the fresh tire-derived oil determined by GC-MS.
0.2
0.71 0.70 0
10
20
30
40
50
60
70
Retention time (min)
Chemical compound
Normalized peak area (%)
3.165 3.453 3.542 3.665 3.82 4.142 4.365 4.576 4.842 5.242 5.509 5.653 6.386 6.664 7.409 7.82 8.816 8.731 9.608 9.93 10.064
Dimethyl Hexane Methyl Heptane Trimethyl Pentane Dimethyl Hexane Toluene Trimethyl Hexane Cyclo-octane Dimethyl Heptane Dimethyl Bicyclo Hexane Dimethyl Cyclohexene Ethenyl Cyclohexene Methyl Ethyl Cyclopentene Ethylbenzene Xylene Styrene Nonane Methyl Propyl Furan Methyl Ethyl Benzene Propenyl Benzene Propyl benzene 1-Methyl-4-methylethenylcyclohexene (Limonene) Ethyl Methyl Benzene Methyl Styrene Trimethyl Benzene Cymene Indane Butyl Benzene Phenyl Butene Cyclopentyl Benzene Total
0.80 7.49 7.69 3.21 13.02 1.20 0.48 0.62 0.87 0.53 1.31 0.52 14.84 5.98 4.09 0.92 0.48 5.41 1.56 3.27 8.20
0.1
Temperature (oC) Fig. 2. Specific gravity (ρ) and dynamic viscosity (μ) as a function of temperature for the distillation light cut obtained from the tire-derived oil by steam distillation.
characterization, performed by means of mid-infrared spectrometry. Mid-IR data in Table 1 show the composition of the light cut comprising almost of 30% of the total amount of aromatic (18.5%) and olefin (12.7%) fractions contained in the original pyrolytic oil. The benzene and xylene content in LFF was almost 50% of the whole content in TPO; however, the toluene content was hugely greater in LFF. The light fuel fraction presents a high toluene content (4.0%), while it was 1.43% in TPO. The saturate content in the light cut was found surprisingly high (65.9%), despite the fact the saturate fraction does not be find in TPO. Since the Mid-IR assesses the compound content by means of infrared spectra database, the absence (zero content) of saturate fraction in TPO means that the spectra of TPO individual compounds does not match to the single hydrocarbons present in the database. Instead, TPO presents more complex chemical structures containing branched and multifunctional groups. The petroleum-derived gasoline composition obtained by Mid-IR measurements is also presented in Table 1 for contrast. The main differences between PDG and LFF composition are on the content of ethanol, saturates, benzene, toluene, xylene e oxygen compounds. The
10.275 11.175 11.652 13.097 13.486 14.552 15.885 22.251
561
5.32 1.08 1.89 5.35 1.12 1.17 0.86 0.73 100.00
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Cycloalkanes were found in a minor amount (1.35%). Olefins were essentially alkyl-branched cyclohexenes (14.66%), highlighting limonene (8.2%). Terpenes with an extensive range of industrial application, such as limonene and cymene, were also extracted by steam distillation and they substantially accounted into the light fuel fraction. Mid-IR data (Table 1) and GC-MS data (Table 2) are in agreement for the olefin content, but they differ themselves extensively with regard to the aromatic and saturate determination. Gas chromatography is an analytical method based on the differential interaction of a given substance with the stationary and mobile phases, while the Mid-IR is based on chemical functionality. As a common aspect of the Mid-IR measurements, some compounds containing both aromatic and saturate chains were not resolved accurately into a specific chemical group by Mid-IR, resulting in total percentages upper than 100%. Despite the similar values for viscosity and specific gravity, the whole LFF chemical composition obtained from GC-MS differs of the conventional gasoline composition. A typical composition of gasoline includes 4–8% alkanes, 2–5% alkenes, 25–40% isoalkanes, 3–7% cycloalkanes, l-4% cycloalkenes, and 20–50% total aromatics [46]. It can be seen that the aromatic and olefin contents in the fuel fraction are notably greater than in petroleum gasoline. Nevertheless, it must be stressed that some components of the LFF aromatic and olefin fractions enclose branched alkyl-chains, which are not individually accounted. Even with the somewhat dissimilar composition, the light fuel fraction obtained from scrap tire pyrolysis exhibits physicochemical properties strictly comparable to the petroleum gasoline. The boiling properties of the tire-derived oil, its light cut from steam injection distillation, and petroleum gasoline are displayed in Table 3. Data show the temperature to vaporizing 50% of sample (T50), the temperature to vaporizing 90% of sample (T90) and the Driveability Index (DI, which is given by Eq. (1)) for light fuel fraction and petroleum-derived gasoline have essentially the same values.
Table 4 Chemical composition of oil fraction extracted from aged tire-derived oil determined by GC-MS.
TFF
PDG
T50 (°C) T90 (°C) DI E200 (Vol.%) E300 (Vol.%) VOC (mg/mi) VOC Reduction (%)
215.3 209.3 2324.0 37.0 33.2 2601.4 77.4
134.7 157.0 1462.7 35.9 84.2 – –
132.0 157.0 1460.0 50.1 76.4 1799.2 22.7
Normalized peak area (%)
3.154 3.454 3.542 3.82 4.142 4.365 4.842 5.242 5.498 5.653 6.386 6.653 7.409 7.82 8.731 9.608 9.93 10.064
Dimethyl Hexane Methyl Heptane Trimethyl Pentane Toluene Trimethyl Hexane Cyclo-octane Dimethyl Bicyclo Hexane Dimethyl Cyclohexene Ethenyl Cyclohexene Methyl Ethyl Cyclopentene Ethylbenzene Xylene Styrene Nonane Methyl Ethyl Benzene Propenyl Benzene Propyl benzene 1-Methyl-4methylethenylcyclohexene (Limonene) Ethyl Methyl Benzene Methyl Styrene Trimethyl Benzene Methyl Propyl Benzene Cymene Indane Butyl Benzene Phenyl Butene Total
C8H18 C8H18 C8H18 C7H8 C9H20 C8H16 C6H10 C8H14 C8H12 C8H14 C8H10 C8H10 C8H12 C9H20 C9H12 C9H10 C9H12 C10H16
4.45 8.24 8.82 13.76 1.23 0.55 1.03 0.63 1.69 0.61 15.40 5.71 3.70 0.95 4.64 1.59 3.02 6.97
C9H12 C9H10 C9H12 C10H14 C10H14 C9H10 C10H14 C10H12
4.93 1.33 1.87 1.06 4.44 1.13 1.39 0.88 100.00
5. Conclusions A light fuel fraction extracted from tire pyrolysis oil by steam distillation was found to be a feasible alternative fuel. The light cut was composed mainly of volatile organic components. Physicochemistry properties of light fuel fraction resemble very closely the petroleumderived gasoline properties, include typical distillation properties (such as T50, T90, and driveability index) and octane number (MON, RON and AKI). The evaluation of the fuel extracted by means of steam distillation has shown the feasibility to replace petroleum gasoline by the light fraction obtained from tire-derived oil by means of steam distillation.
Table 3 Distillation properties for conventional and tire derived fuels. TDO
Chemical Structure
obtained from the aged oil is presented in Table 4. The comparison between the light cut obtained from fresh (Table 2) and aged (Table 4) tire-derived oil revealed a slight change in the fuel fraction composition. Light fuel fraction obtained from the aged oil exhibits an increment of 1.90% on the aromatic fraction, and of 1.74% on the saturate fraction. The TPO ageing promoted an increase of the cycloalkane composition from 1.35% to 1.58%. On another hand, the olefin content, including cyclo-olefins, was decreased by 3.87%. However, even aged tire-derived oil is able to produce a light cut with properties similar to the petroleum gasoline. Summarizing, the light fraction extracted from the tire pyrolysis oil by means of steam distillation is nearly comparable to the gasoline cut derivate from petroleum distillation. The investigation illustrates a route from the residue processing by pyrolysis up to the fuel production, pointing out to the feasibility to achieve the application of a residue-derived fuel into combustion engines.
In Eq. (1), DI represents the driveability index, which has been constituted by the temperatures for the evaporated percentages of 10 percent (T10), 50 percent (T50) and 90 percent (T90), and by ethanol content (xEtOH). The distillation temperatures for the petrol gasoline were comparable to the values reported in other studies [44,45,47]. Driveability index refers to the engine performance, which comprises start-up, warm-up, and running performance. T50, T90 and DI values for tire pyrolysis oil are significantly greater than for LFF and PDG. However, the amount of fuel evaporated at 200 °C (E200) for the gasoline is greater than other fuels in Table 3. On another hand, the amount of fuel evaporated at 300 °C (E300) for the gasoline is lower than for LFF. The DI depends on the gasoline grade. However, low DI values usually produce more suitable cold-start and warm-up performance. As a final point, a closing set of experiments was carried out to evaluate the effects of the ageing of the tire-derived oil on the composition of the fuel fraction extracted using steam distillation. The tire pyrolysis oil was kept to age at rest for six months in a sealed flask protected from the light. After the ageing time, the oil was distilled by steam injection, such as described early. The GC-MS analysis of the fuel
Property
Chemical compound
10.275 11.175 11.652 12.441 13.097 13.486 14.552 15.885
(1)
DI = 1.5∙T 10 + 3.0∙T 50 + T 90 + 1.33∙xEtOH
Retention time (min)
Acknowledgements The authors gratefully acknowledge support from the Brazilian agency CNPq to this project through an undergraduate scholarship to 562
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G.A.C.
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Full Length Article
Fractionation of tire pyrolysis oil into a light fuel fraction by steam distillation Guilherme Anchieta Costa, Ronaldo Gonçalves dos Santos
T
⁎
Chemical Engineering Department, Centro Universitário FEI, São Bernardo do Campo, SP 09850-901, Brazil
A R T I C LE I N FO
A B S T R A C T
Keywords: Tire waste Pyrolysis oil Fuel Petrol Steam distillation
Pyrolysis has been identified as a possible process for producing alternative fuels from thermal degradation of residue materials. In this work, a steam distillation process was applied to extract a light fuel fraction from tire pyrolysis oil. The light fuel fraction (LFF) was a light yellow, translucent liquid with a specific gravity of 0.76 g·cm−3 and dynamic viscosity of 0.4 mPa.s at 20 °C. LFF was mainly composed of volatile organic components of the tire pyrolysis oil. GC-MS analysis shows the light fraction composed mostly of benzene-substituted compounds (62.06%), mainly ethylbenzenes (14.84%) and methylbenzenes (13.02%) derivatives. Saturates were mainly branched alkanes containing eight carbon atoms (21.94%) and cycloalkanes in minor amount (1.35%). Olefins were essentially alkyl-branched cyclohexenes (14.66%), highlighting limonene (8.2%). The standard mid-infrared spectroscopy revealed the light fuel fraction resembles very closely the petroleum-derived gasoline. In addition, typical distillation properties (such as T50, T90, and driveability index) and octane number (Motor Octane Number and Research Octane Number) for the light fuel fraction matched to the gasoline properties. The results point out to the feasibility to replace conventional gasoline by the light fraction obtained from tire-derived oil by means of steam distillation.
1. Introduction Tire waste has been an environmental concern because the severe potential damage that can be caused by the inappropriate disposal in dumps and landfills, resulting in contamination of groundwater and watercourses. In addition, scrap tire improper discarding and handling must lead to the emission risk of harmful pollutants, such as sulfur dioxide (SO2), nitrogen oxides (NOx) and volatile organic compounds (VOCs). Retreading, incineration and grinding represent traditional methods for reusing scrap tires; however, they have shown serious limitations [1]. Furthermore, these tire residues are practically immune to chemical and biological treatments. Waste thermal degradation is a potential method to degrade scrap tire and obtaining unconventional fuels, converting long molecular structures into smaller molecules [1,2]. Pyrolysis is a thermal degradation process that operates under an inert atmosphere at moderate to high temperatures (usually 400–900 °C) to cleave molecules, producing a liquid phase containing an organic mixture [3]. The organic mixture composition depends on the operating conditions, mainly the feedstock composition, temperature, pressure and residence time [4–8].
According to the process arrangement, the oil derived from pyrolysis may be a suitable substitute for petrol-derived fuels [4–6,9]. The pyrolytic oil properties depend especially on the feedstock composition [10,11]. Biomass residues are composed essentially by lignocellulose constituents and they constitute the most abundant and the more studied supplies for pyrolysis processing. Typically, pyrolysis oils obtained from lignocellulosic materials are composed mainly of aldehydes, furans, ketones, esters, and carboxylic acids, as well as ethers, alcohols and hydrocarbons in minor quantities [11,12]. Besides, a large set of studies has addressed the scrap tire conversion into fuels and chemical by means pyrolysis process [1,2,13,14]. The tire-derived oil composition has been typically characterized as a mixture of 7–14 carbon hydrocarbons, containing single ring alkylbenzenes and polycyclic aromatics, such as indene and naphthalene derivatives, and terpenes, as limonene (1-methyl-4-prop-1-en-2-yl-cyclohexene) and cymene (1-methyl-4-(1-methylethyl) benzene) [15]. Fatty acid and nitrogen compounds with high added value have also been identified in pyrolysis oils [16]. Besides the irregular composition, the pyrolysis-derived oil has strong potential to replace conventional fuels in several industrial application, including combustion engine, boilers, and furnaces [17].
⁎ Corresponding author at: Chemical Engineering Department, Centro Universitário FEI, Avenida Humberto de Alencar Castelo Branco 3972, São Bernardo do Campo, SP 09850-901, Brazil. E-mail address: [email protected] (R.G.d. Santos).
https://doi.org/10.1016/j.fuel.2018.12.075 Received 30 August 2018; Received in revised form 12 December 2018; Accepted 13 December 2018 0016-2361/ © 2018 Elsevier Ltd. All rights reserved.
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fraction, high-purity syringol (1,3-Dimethoxy-2-hydroxybenzene) was obtained from wood-derived pyrolysis oil using steam distillation [42]. In addition, a combination of solvent extraction and steam distillation was used to obtaining aroma components extracted from waste tobacco leaves. The combined method was effective to recovering flavor compounds, such as β-damascone, β-damascenone, β-ionone, dihydroactinidiolide, neophytadiene, cembrene and safranal, which are prone to be degraded at high temperatures [43]. The purpose of this work was to obtain a light fuel fraction extracted from a tire-derived pyrolytic oil to be used as an alternative to the gasoline. The pyrolytic oil was produced from tire waste in a pilotscaled pyrolysis reactor operated at 450 °C. The fuel fraction was separated from the tire pyrolysis oil by means of steam distillation (water vapor injection). The main properties of the fuel fraction, including specific gravity, dynamic viscosity, chemical composition, and fuel ignition properties, were found to have a very close resemblance to the petroleum-derived gasoline.
Nevertheless, the pyrolytic oil is scarcely prone to be directly used in combustion engines. Instead, the use of the pyrolysis-derived oil as an alternative automotive fuel requires a supplementary upgrading stage to reach the entire technical and law requirements. Other exploitation methods include blending the oil with conventional fuels and the oil fractionation to obtaining fuel fractions and specific chemical grades [18]. Pyrolysis oil properties can be improved by means of an upgrading process. Oil upgrading must reduce the oil viscosity, the oxygen content and the corrosivity, as well as the oil thermal instability. Hydrogenation and hydrodeoxygenation, a catalytic pyrolysis carried out under a hydrogen atmosphere, are the main methods for oil upgrading [19]. Other promisor upgrading methods include catalytic cracking, steam reforming, molecular distillation, and, more recently, supercritical phase reaction [20–24]. Many works have dedicated efforts to blend the pyrolysis oil with petroleum diesel to reduce the fossil fuel consumption [15,25–27]. The results of these works have shown successful performance for pyrolysis oil-diesel blends in indirect injection multi-cylinder engines, as well as appropriate physicochemical and fuel properties. The pyrolysis oil fractionation is an essential stage for the installation perspective of alternative energy platforms based on the biorefinery concept. The biorefinery concept was originally developed to manner biomass as a feedstock, but it can be extended to the waste dealing out. The fundamental aim is to provide options to replace fossil fuels with alternative fuels that lead to greenhouse gas saving and sustainable energy growth [28,29]. The more common methods for pyrolysis oil fractionation have been solvent extraction, chromatography, and distillation [30]. Solvent extraction (or partitioning) method is based on the relative chemical affinity of a given compound with two immiscible solvents. Solvent (liquid–liquid) extraction has been applied to recovery glycolaldehyde and acetic acid from the aqueous phase produced by wood pyrolysis using tri-n-octylamine/2-ethyl-1-hexanol as a solvent [31]. Phenolic fractions have also been removed from the pyrolysis bio-oil different solvents. Methyl isobutyl ketone (MIBK) was found to be a more selective solvent than ethyl acetate to isolate phenol, p-cresol, creosol, guaiacols and eugenols [32]. The solvent – Anti-solvent (SAS) extraction has also been applied to obtain a phenol-rich organic phase using dichloromethane as solvent and water as anti-solvent [33]. SAS extraction produced organic fractions containing high phenol concentrations and low contents sugars and water, allowing the organic phase to be blended with diesel. Supercritical fluids have a large potential as economically feasible and green technology to fractionating crude bio-oil and recovering of value-added chemicals. Carbon dioxide has commonly been the preferred fluid to be applied in supercritical extraction because relatively low critical temperature and pressure required. Acids and esters fractions were extracted by means of sc-CO2 fractionation from the pyrolysis oil produced from the palm kernel shell [34]. A large amount of furanoids, pyranoids and benezoids has been identified in the pyrolysisoil acid fraction [35]. Value-added chemical fractions such as acids, aldehydes, ketones, furans and aromatics have been found in the biomass-derived fraction from sc-CO2 extraction [36,37]. Distillation processes are based on the relative volatility of the mixture components and they can be applied for the separation of a wide range of volatile organic compounds (VOCs) from the pyrolysis oil. The steam injection heats the oil, increase the total vapor pressure and decrease its boiling point [30,38]. The steam addition allows the organic-water mixture boils at temperatures below than 100 °C, avoiding the degradation of thermally-sensitive compounds [30]. Steam distillation can be applied to separate important components from an oil type variety, comprising essential oils [39] and crude oils [40]. Steam distillation has also been successfully used to obtain valuable substances from pyrolysis oils. Eucalyptol (1,8-cineole) was extracted from Mallee biomass using steam extraction [41]. Chemically-stable
2. Experimental methodology 2.1. Materials The waste tire was obtained from passenger vehicles tires. The end of life tires were shredded into pieces with 2–5 cm long. A 1 wt% of residual steel was found in the shredded material. The shredded waste tire was pyrolyzed in a stainless-steel reactor with 15 kg capacity at 1 bar under N2 inert environment. The pyrolysis process was carried out in a semi batch process for 30 min at 450 °C. An early description of the tire-derived oil properties was presented [15]. 3. Methods 3.1. Fractionation of the tire-derived oil The pyrolytic oil fractionation was carried out by steam distillation. Steam distillation represents an indirect distillation process using liquid vaporization. Briefly, water vapor was yielded from deionized water in an electric boiler. The steam was bubbled by differential pressure into the 500 mL of pyrolytic oil enclosed in a distillation vessel. The water vapor injection promoted a raising up of the total vapor pressure enough to boiling the pyrolytic oil, volatilizing the oil light cuts. Subsequently, the gaseous mixture containing water vapor and light cuts was converted into liquid in a condenser operated at −7°C using ethanol as refrigerant fluid. Finally, the organic liquid fraction was separated from the aqueous phase and labelled as light fuel fraction (LFF). Fig. 1 illustrates the steam distillation process. 3.2. Composition and fuel properties 3.2.1. GC-MS chemical composition A gas chromatographer coupled with an Ion Trap mass spectrometer (model Saturn 2100D, Varian, USA) was used in the quantitative chemical analysis of the tire pyrolysis oil and its light fuel fraction. A HP5MS capillary column (30 m × 0.25 mm × 0.25 μm) containing 5% biphenyl and 95% di-methyl polysilane was used. High purity helium (99.9999%) was used as carrier gas at a flow rate of 1.0 mL·min−1. The injector temperature was 240 °C. The injector was operated in split mode at a 1:20 ratio. Elemental composition was determinate using a Perkin Elmer (USA) elemental analysis model CHN 2400 Series II, using a thermal conductivity detector. 3.2.2. Standard fuel properties The compositional analysis and the main fuel properties were performed by mid-infrared (Mid-IR) spectrometry using a Gas Sensor Portable Process Analyzer (GS-PPA-I, model GS1000 plus VOC), supplied from PAC (USA). The Mid-IR analysis evaluated the multiple 559
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Fig. 1. Steam distillation process to fractionate the tire-derived oil into a light cut.
to replace fossil fuels.
chemical and physical properties, including standard resolution of olefin, aromatic and saturate fractions. Motor Octane Number (MON) by ASTM D2700 Method, Research Octane Number (RON) by ASTM D2699 Method, and anti-knock index (AKI) were also assessed. The High Heat Value (HHV) was determined by a Basic C2000 combustion calorimeter (IKA, Germany). Specific gravity and dynamic viscosity were simultaneously assessed by means of a Stabinger SVM 3000 viscometer (Anton Paar, Germany), according to ASTM D7042. The Stabinger operation is based on the harmonic oscillation law in a U-tube filled with the test sample to perform dynamic viscosity and density measurements.
4.2. Fractionation of the tire-derived oil A light fraction was extracted from the TPO by means of a vaporinjection distillation process, such as illustrated in Fig. 1. The steam distillation process was chosen because the high-temperature requirement to flash the liquid TPO by means of the traditional distillation methods. Besides, steam distillation is very useful fractionation process for resolving fuel mixtures containing low-molecular weight components. The water vapor injection rises up the total vapor pressure in the flask, allowing the liquid mixture to boiling at a temperature below than its normal boiling point. The TPO boiling point was reduced to 94 ± 1 °C, which is entirely feasible to be reached in typical distillation facilities. The vapor mixture leaving the flask was composed of water (from the vapor injected) and light hydrocarbons (from the TPO). The vapor mixture condensation led to a two-phase liquid system containing 33 vol% of oily fraction and 67 vol% of aqueous phase, which contains some water-soluble oil components. The oily fraction was carefully separated from the aqueous phase in a static separator and labelled as light fuel fraction (LFF).
4. Results and discussion 4.1. Properties of the tire-derived oil Tire waste pyrolysis was carried out by a semi batch process. A water-cooled condenser was attached to the top of the heated closedreactor to collect the condensable gas leaving the vessel. Non-condensable gases were blown out since they were composed essentially of water vapor and N2 (together with a minor amount of CO, CO2 and short chain hydrocarbons). In the end of the reaction time, the solidliquid system inside the pyrolysis reactor was separated by filtration using a bottom valve. The resolved liquid phase was blended with the liquid collected in the top condenser, constituting a liquid–liquid twophase system. The aqueous and organic phase were separated in a gravitational separator and the water-free organic phase was signed as pyrolysis oil. The pyrolysis process yields 44 wt% of solid phase (carbon black along with a minor amount of metallic residue) and 45 wt% of liquid phase (pyrolysis oil). The quantity of non-condensed gases was determined by mass balance, achieving 11 wt% of the whole tire waste fed in the reactor. The waste tire pyrolysis produced a dark brown oil, labelled tire pyrolysis oil (TPO). TPO was characterized as a complex mixture composed principally of a wide assortment of hydrocarbon compounds. Hydrocarbons were composed of 7–14 carbon atom compounds. The aromatic fraction was composed of cyclic and polycyclic compounds, mainly indene and naphthalene. Terpenes represented approximately 50% of the total TPO chemical composition. A detailed description of the TPO chemical composition and properties was previously presented by Umeki et al. (2016) [15]. The authors state that the TPO properties were not enough satisfactory to able it to the immediate application in combustion engines since they are out of the fuel standard specifications. Nevertheless, the data show the TPO must be very valuable to be fired into heating processes and blended with conventional fuels. An alternative way for the pyrolysis oil recovery is the fractionation into burnable fractions with appropriated properties
4.3. Characterization of the light fuel fraction The light cut was extracted from the tire-derived oil by steam distillation aiming to replace petroleum fuel fractions. Properties of the light fuel fraction are displayed in Table 1. The light fuel fraction was a light yellow, translucent liquid, displaying specific gravity of 0.76 g·cm−3 and apparent viscosity of 0.40 mPa.s (equivalent to 0.53 cSt), both evaluated at 20 °C. Specific gravity and apparent viscosity for representative gasoline has been reported respectively in the ranges of 0.72–0.78 g·cm−3 and 0.37–0.44 cSt (at 20 °C) [44,45]. The specific gravity of local-gathered petrol has been reported as 0.75 g·cm−3 [15]. Specific gravity and viscosity are important physicochemical parameters to define engine fuels. Then, the Fig. 2 displays the temperature effects on the specific gravity and dynamic viscosity for the light cut obtained by vapor injection distillation. The specific gravity of the light fuel fraction decreased linearly along with the temperature increasing. LFF viscosity curve follows a smooth exponential decaying with the increasing temperature. LFF viscosity was reduced from 0.47 to 0.25 mPa.s for a temperature rising from 30 to 60 °C. A specific gravity reduction from 0.75 to 0.71 mPa.s was achieved for a temperature variation from 10 to 60 °C. Previously published data show the specific gravity and dynamic viscosity disclose an analogous behavior to the PDG [15]. Table 1 also displays the results from the fuel standard 560
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local government regulates the addition of 27 ± 1 vol% of ethanol into the gasoline to the use in automotive engines. This fact explains the discrepancy between the ethanol content in the fuel composition. The ethanol addition is also responsible for the high amount of the oxygen compound fraction in petroleum gasoline. The anti-knock engine performance was assessed by Octane number measurements, which evaluate the fuel relative ability to resist to the knocking during the burning inside the combustion chamber. The main procedures to assess the octane number (the most important properties for fuel application in Otto cycle engines) are Motor Octane Number (MON), Research Octane Number (RON), antiknock index (AKI). RON is the most useful octane rating and it is achieved under a variable compression rate and low speed, whereas MON is obtained under full load engine at high speed. Table 1 summarizes the results of octane number measurements for LFF. Again, the light fraction obtained from steam distillation displays properties similar to the petroleum-derived gasoline data reported in the literature [15,45]. The difference between the RON and MON designates the gasoline sensitivity to the changes in engine operating conditions. Large RON-MON differences indicate a more sensitive gasoline, therefore the octane numbers for LFF and gasoline are found equivalent. The light fuel fraction has a High Heat Value slightly lower than the tire-pyrolysis oils and slightly higher than the petrol-derived gasoline [15,44,45]. In addition, LFF anti-nock index is in-between that of PDG and TPO [15]. The chemical composition of the light fuel fraction is shown in Table 2, according to the gas chromatography analysis. In many cases, the chemical compound grade was displayed instead of individual molecules because the complicated mixture composition grows into unfeasible the resolving of very similar components. GC-MS measurements show the light fraction composed mostly of benzene-substituted compounds (62.06%), most of them were derivate compounds from ethylbenzenes (14.84%) and methylbenzenes (13.02%). Saturates were mainly branched alkanes containing eight carbon atoms (21.94%).
Table 1 Properties of the light fuel fraction extracted from tire pyrolysis oil by steam distillation. Property
Value
Specific gravity (g.cmcm−3 ) at 20 °C Dynamic viscosity (mPa.s) à 20 °C High Heat Value (kJ.g−1)
0.76
–
0.40 40.5
– –
Composition from Mid-IR (Vol.%) MTBE ETOH TAME ETBE MEOH DIPE Aromatics Benzene Olefins Saturates Toluene Xylene Oxygen (in mass percentage)
0.3 0.6 0.0 1.1 0.0 0.2 18.5 0.43 12.7 65.9 4.0 3.6 0.77
For PDGa 0.3 26.2 0.3 0.9 0.7 0.8 18.4 1.16 16.8 35.8 1.50 6.00 11.06
Octane number MON RON AKI
84.5 94.5 89.6
– – –
From [15] for comparison.
0.6
0.76
(g.cm-3)
0.75
0.5
0.74
0.4 0.73
0.3 0.72
μ (mPa.s)
a
Table 2 Chemical composition of oil fraction extracted from the fresh tire-derived oil determined by GC-MS.
0.2
0.71 0.70 0
10
20
30
40
50
60
70
Retention time (min)
Chemical compound
Normalized peak area (%)
3.165 3.453 3.542 3.665 3.82 4.142 4.365 4.576 4.842 5.242 5.509 5.653 6.386 6.664 7.409 7.82 8.816 8.731 9.608 9.93 10.064
Dimethyl Hexane Methyl Heptane Trimethyl Pentane Dimethyl Hexane Toluene Trimethyl Hexane Cyclo-octane Dimethyl Heptane Dimethyl Bicyclo Hexane Dimethyl Cyclohexene Ethenyl Cyclohexene Methyl Ethyl Cyclopentene Ethylbenzene Xylene Styrene Nonane Methyl Propyl Furan Methyl Ethyl Benzene Propenyl Benzene Propyl benzene 1-Methyl-4-methylethenylcyclohexene (Limonene) Ethyl Methyl Benzene Methyl Styrene Trimethyl Benzene Cymene Indane Butyl Benzene Phenyl Butene Cyclopentyl Benzene Total
0.80 7.49 7.69 3.21 13.02 1.20 0.48 0.62 0.87 0.53 1.31 0.52 14.84 5.98 4.09 0.92 0.48 5.41 1.56 3.27 8.20
0.1
Temperature (oC) Fig. 2. Specific gravity (ρ) and dynamic viscosity (μ) as a function of temperature for the distillation light cut obtained from the tire-derived oil by steam distillation.
characterization, performed by means of mid-infrared spectrometry. Mid-IR data in Table 1 show the composition of the light cut comprising almost of 30% of the total amount of aromatic (18.5%) and olefin (12.7%) fractions contained in the original pyrolytic oil. The benzene and xylene content in LFF was almost 50% of the whole content in TPO; however, the toluene content was hugely greater in LFF. The light fuel fraction presents a high toluene content (4.0%), while it was 1.43% in TPO. The saturate content in the light cut was found surprisingly high (65.9%), despite the fact the saturate fraction does not be find in TPO. Since the Mid-IR assesses the compound content by means of infrared spectra database, the absence (zero content) of saturate fraction in TPO means that the spectra of TPO individual compounds does not match to the single hydrocarbons present in the database. Instead, TPO presents more complex chemical structures containing branched and multifunctional groups. The petroleum-derived gasoline composition obtained by Mid-IR measurements is also presented in Table 1 for contrast. The main differences between PDG and LFF composition are on the content of ethanol, saturates, benzene, toluene, xylene e oxygen compounds. The
10.275 11.175 11.652 13.097 13.486 14.552 15.885 22.251
561
5.32 1.08 1.89 5.35 1.12 1.17 0.86 0.73 100.00
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Cycloalkanes were found in a minor amount (1.35%). Olefins were essentially alkyl-branched cyclohexenes (14.66%), highlighting limonene (8.2%). Terpenes with an extensive range of industrial application, such as limonene and cymene, were also extracted by steam distillation and they substantially accounted into the light fuel fraction. Mid-IR data (Table 1) and GC-MS data (Table 2) are in agreement for the olefin content, but they differ themselves extensively with regard to the aromatic and saturate determination. Gas chromatography is an analytical method based on the differential interaction of a given substance with the stationary and mobile phases, while the Mid-IR is based on chemical functionality. As a common aspect of the Mid-IR measurements, some compounds containing both aromatic and saturate chains were not resolved accurately into a specific chemical group by Mid-IR, resulting in total percentages upper than 100%. Despite the similar values for viscosity and specific gravity, the whole LFF chemical composition obtained from GC-MS differs of the conventional gasoline composition. A typical composition of gasoline includes 4–8% alkanes, 2–5% alkenes, 25–40% isoalkanes, 3–7% cycloalkanes, l-4% cycloalkenes, and 20–50% total aromatics [46]. It can be seen that the aromatic and olefin contents in the fuel fraction are notably greater than in petroleum gasoline. Nevertheless, it must be stressed that some components of the LFF aromatic and olefin fractions enclose branched alkyl-chains, which are not individually accounted. Even with the somewhat dissimilar composition, the light fuel fraction obtained from scrap tire pyrolysis exhibits physicochemical properties strictly comparable to the petroleum gasoline. The boiling properties of the tire-derived oil, its light cut from steam injection distillation, and petroleum gasoline are displayed in Table 3. Data show the temperature to vaporizing 50% of sample (T50), the temperature to vaporizing 90% of sample (T90) and the Driveability Index (DI, which is given by Eq. (1)) for light fuel fraction and petroleum-derived gasoline have essentially the same values.
Table 4 Chemical composition of oil fraction extracted from aged tire-derived oil determined by GC-MS.
TFF
PDG
T50 (°C) T90 (°C) DI E200 (Vol.%) E300 (Vol.%) VOC (mg/mi) VOC Reduction (%)
215.3 209.3 2324.0 37.0 33.2 2601.4 77.4
134.7 157.0 1462.7 35.9 84.2 – –
132.0 157.0 1460.0 50.1 76.4 1799.2 22.7
Normalized peak area (%)
3.154 3.454 3.542 3.82 4.142 4.365 4.842 5.242 5.498 5.653 6.386 6.653 7.409 7.82 8.731 9.608 9.93 10.064
Dimethyl Hexane Methyl Heptane Trimethyl Pentane Toluene Trimethyl Hexane Cyclo-octane Dimethyl Bicyclo Hexane Dimethyl Cyclohexene Ethenyl Cyclohexene Methyl Ethyl Cyclopentene Ethylbenzene Xylene Styrene Nonane Methyl Ethyl Benzene Propenyl Benzene Propyl benzene 1-Methyl-4methylethenylcyclohexene (Limonene) Ethyl Methyl Benzene Methyl Styrene Trimethyl Benzene Methyl Propyl Benzene Cymene Indane Butyl Benzene Phenyl Butene Total
C8H18 C8H18 C8H18 C7H8 C9H20 C8H16 C6H10 C8H14 C8H12 C8H14 C8H10 C8H10 C8H12 C9H20 C9H12 C9H10 C9H12 C10H16
4.45 8.24 8.82 13.76 1.23 0.55 1.03 0.63 1.69 0.61 15.40 5.71 3.70 0.95 4.64 1.59 3.02 6.97
C9H12 C9H10 C9H12 C10H14 C10H14 C9H10 C10H14 C10H12
4.93 1.33 1.87 1.06 4.44 1.13 1.39 0.88 100.00
5. Conclusions A light fuel fraction extracted from tire pyrolysis oil by steam distillation was found to be a feasible alternative fuel. The light cut was composed mainly of volatile organic components. Physicochemistry properties of light fuel fraction resemble very closely the petroleumderived gasoline properties, include typical distillation properties (such as T50, T90, and driveability index) and octane number (MON, RON and AKI). The evaluation of the fuel extracted by means of steam distillation has shown the feasibility to replace petroleum gasoline by the light fraction obtained from tire-derived oil by means of steam distillation.
Table 3 Distillation properties for conventional and tire derived fuels. TDO
Chemical Structure
obtained from the aged oil is presented in Table 4. The comparison between the light cut obtained from fresh (Table 2) and aged (Table 4) tire-derived oil revealed a slight change in the fuel fraction composition. Light fuel fraction obtained from the aged oil exhibits an increment of 1.90% on the aromatic fraction, and of 1.74% on the saturate fraction. The TPO ageing promoted an increase of the cycloalkane composition from 1.35% to 1.58%. On another hand, the olefin content, including cyclo-olefins, was decreased by 3.87%. However, even aged tire-derived oil is able to produce a light cut with properties similar to the petroleum gasoline. Summarizing, the light fraction extracted from the tire pyrolysis oil by means of steam distillation is nearly comparable to the gasoline cut derivate from petroleum distillation. The investigation illustrates a route from the residue processing by pyrolysis up to the fuel production, pointing out to the feasibility to achieve the application of a residue-derived fuel into combustion engines.
In Eq. (1), DI represents the driveability index, which has been constituted by the temperatures for the evaporated percentages of 10 percent (T10), 50 percent (T50) and 90 percent (T90), and by ethanol content (xEtOH). The distillation temperatures for the petrol gasoline were comparable to the values reported in other studies [44,45,47]. Driveability index refers to the engine performance, which comprises start-up, warm-up, and running performance. T50, T90 and DI values for tire pyrolysis oil are significantly greater than for LFF and PDG. However, the amount of fuel evaporated at 200 °C (E200) for the gasoline is greater than other fuels in Table 3. On another hand, the amount of fuel evaporated at 300 °C (E300) for the gasoline is lower than for LFF. The DI depends on the gasoline grade. However, low DI values usually produce more suitable cold-start and warm-up performance. As a final point, a closing set of experiments was carried out to evaluate the effects of the ageing of the tire-derived oil on the composition of the fuel fraction extracted using steam distillation. The tire pyrolysis oil was kept to age at rest for six months in a sealed flask protected from the light. After the ageing time, the oil was distilled by steam injection, such as described early. The GC-MS analysis of the fuel
Property
Chemical compound
10.275 11.175 11.652 12.441 13.097 13.486 14.552 15.885
(1)
DI = 1.5∙T 10 + 3.0∙T 50 + T 90 + 1.33∙xEtOH
Retention time (min)
Acknowledgements The authors gratefully acknowledge support from the Brazilian agency CNPq to this project through an undergraduate scholarship to 562
Fuel 241 (2019) 558–563
G.A. Costa, R.G.d. Santos
G.A.C.
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