Effect of operating conditions on HDS of CGO blended middle distillate

Journal Pre-proof Effect of operating conditions on HDS of CGO blended middle distillate A. Marafi, A. Al-Barood, H. AlBazzaz, Mohan S. Rana

PII:

S0920-5861(19)30589-9

DOI:

https://doi.org/10.1016/j.cattod.2019.10.029

Reference:

CATTOD 12534

To appear in:

Catalysis Today

Received Date:

15 April 2019

Revised Date:

20 September 2019

Accepted Date:

18 October 2019

Please cite this article as: Marafi A, Al-Barood A, AlBazzaz H, Rana MS, Effect of operating conditions on HDS of CGO blended middle distillate, Catalysis Today (2019), doi: https://doi.org/10.1016/j.cattod.2019.10.029

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier.

Effect of operating conditions on HDS of CGO blended middle distillate A. Marafi,* A. Al-Barood, H. AlBazzaz, Mohan S. Rana

Petroleum Research Center, Kuwait Institute for Scientific Research, PO Box: 24885, Safat 13109 Ahmadi, Kuwait; Fax:+965 23980445. *E-mail: [email protected]

Graphic Abstract

LHSV-2.6

re

LHSV-2.6 → Temperature

lP

Temperature, C

100

150

Jo

0

300

390

+15 C, 5.2 LHSV, h-1

ur na

Sulfur in Product, wppm

LHSV-5.2

1000

400

-p

10000

450

600

380 +7 C, 2.6 LHSV,

h-1

370

450 ppmS in product

Temperature, C

ro of

*Corresponding author: Dr. Mohan S Rana, Petroleum Research Center, Kuwait Institute for Scientific Research, P.O. Box 24885, 13109-Safat, Phone: +965 24956890, Fax: +965 23980445, Kuwait, E-mail: [email protected] Dr. A. Marafi ([email protected])

360 350 340

750

900

1050

1200

1350

330 1500

TOS, h

Role of temperature, LHSV, and TOS on achieving 450 ppmS in the hydrotreated product Highlights 

CGO and SRGO blend HDT and its operating condition to achieve 450ppmS in product

1



After sulfur, cetane number is the key diesel fuel properties



PM strongly depends on the low cetane index



Aromatic content acts as incompetent diesel fuel

Abstract The utilization of heavier stream of petroleum hydrocarbon such as coker gas oil (CGO) via diluting with straight run gas oil (SRGO) (blended feed: SRGO and CGO; 30/70) in order to enhance the middle distillate pool of fuel (heating oil, diesel fuel, jet fuel, and kerosene). Usu-

ro of

ally, CGO fraction has a propensity of refractory sulfur, followed by nitrogen and finally aromatics compounds. The former two elements are mainly associated with the aromatic sulfur and nitrogen compound (i.e., refractory). Hence, a systematic study was conducted with the

variation of hydrotreating operating conditions to convert sulfur, nitrogen, and aromatic com-

-p

pounds. The performance was carried out in a fixed bed bench-scale reactor unit, using a

re

commercial CoMo/Al2O3 (catalyst X) catalyst after sulfidation. The CGO has a significantly higher amount of nitrogen, aromatic, and refractory sulfur compounds than that of SRGO,

lP

which makes this blend more challenging. Hence, the operating conditions have been investigated to remove sulfur and nitrogen compounds and improve the cetane index during the hy-

ur na

droprocessing. The variation in operating conditions is to achieve 450 ppmS in the hydrotreated product using CGO and SRGO blend as a feedstock. The conversion of sulfur and nitrogen compounds indicated that hydrodesulfurization (HDS) is selectively higher than hydrodenitrogenation (HDN) where hydrogenation played a crucial role in their selectivities

Jo

at high conversion. The hydrogenation function also relates to the cetane index that decreases with increasing aromatic content. The degree of inhibition (HDS and cetane index) depends on the feed composition (nitrogen and aromatics) that consumes a large amount of hydrogen. Conclusively, beyond 90% of HDS conversion, most of the sulfur compounds are refractory, which requires a stronger hydrogenation function to remove steric-hindrance from the refractory molecule. 2

Keywords: HDS, HDN, SRGO, CGO, blending, aromatics, cetane index

1. Introduction The global scenario for petroleum products is changing from light to heavy crude oil. The heavy crudes are not only having a high amount of contaminants but also its fractions are heavier in nature, which could have a tremendous effect on refining operation [1,2]. Recently

ro of

the acceptable limits of sulfur content in diesel fuel (gasoline) have been reduced up to 50 ppmw (to be <10 ppm in the near future) in several countries mainly due to environmental

regulations [3,4]. A significant amount of attention has been focused on the deep desulfuriza-

-p

tion of light gas oil (LGO) and CGO fraction mainly due to the increasing the middle distillate pool. However, LGO and light cycle oil (LCO) are highly aromatic and contains a large

re

amount of sulfur, nitrogen, and aromatics in compare to diesel. The demand for low-sulfur

lP

diesel continues to grow in the international market, which has to be supplied adequately by the refinery. Thus, considering the future demand, an option is to blend SRGO with coker fraction. However, cocker stream has a higher amount of hereto-atoms and more in aromatic

ur na

[5,6,7]. Cracked distillates stream such as LCO and CGO are poor quality, which streams should be utilized via the clean diesel fuel processes [8,9,10]. In recent studies, the blending of various refinery streams and their impact on fuel properties have been reported for middle

Jo

distillates including SRGO, CGO, and LCO [11-14]. Diesel fuel feedstocks mainly consist of middle distillates in the boiling range at 220-360 °C with plus or minus some front or back ends. Depending on refinery complexity, the deep HDS unit feed components may comprise a variety of distillate sources including SRGO, CGO thermally cracked distillates, fluid catalytic cracking (FCC), and light cycle oil (LCO). Most refiners process a wide variety of crudes and routinely adjust the operating conditions of ma-

3

jor processing units according to the changing feeds and overall product needs. Additionally, the types and volume of streams feeding into the diesel pool may change due to seasonal swing in the product demand and changes in upstream operations. These changes in upstream operations, as well as the blending of CGO and LCO with SRGO, will cause the type and concentrations of sulfur, nitrogen and aromatic compounds and their distributions in the diesel feedstock to vary. Moreover, such type of feedstock is prone to catalyst stability and usually lead to rapid deactivation, shorter cycle lengths, and reduced throughput [3].

ro of

In general, CGO is more complex feed in compare to SRGO. The CGO dilution with lighter fraction (SRGO) improves its processing flexibility such as lower viscosity, aromatic content and the lower heteroatoms. The CGO has a significantly higher amount of nitrogen, aromatic,

-p

and refractory sulfur compounds than that of SRGO [14], which makes this blend more

challenging. Hence, the operating conditions have been investigated to improve the cetane

re

index during the hydroprocessing. Al-Barood et al. [15] compared the degree of desulfuriza-

lP

tion of CGO, SRGO and their blends under identical reaction conditions, indicating that SRGO desulfurization is easier than CGO, which removes a significant amount of heteroatoms and improve cetane number. The CGO has a low cetane index (CI) and a very high con-

ur na

centration of nitrogen and aromatics, making it less reactive and a more pollutant fuel than SRGO. The cetane index can be improved via reducing the aromatic content resulting in having more efficient burning that releases less particulate matter (PM) and aromatics [16,17,18].

Jo

Hence diesel combustion parameters and its engine performance are highly dependent on CI of the fuel.

The worldwide thrust towards clean transportation fuels relative to not only sulfur content but also polynuclear aromatic hydrocarbon (PNA) content, has a strong impact on NOx and particulate matter (PM) emissions [19,20]. The CGO is rich in nitrogen and aromatic content; thus, the specific focus has been given to the cetane index. In the middle distillate fraction,

4

the presence of PNAs lowers the CI, which in turn determines the ignition quality of the fuel [21-24]. In recent years, many countries imposing threshold limit for sulfur in diesel had to be regulated from < 500 wppm to 10 ppm in near future [3]; however, other specifications such as aromatic and PM may not be implemented. Hence health-wise, it is therefore extremely desirable to meet these stricter regulations. The most decisive fuel properties are known to be sulfur, nitrogen, and aromatic contents, which are responsible for SOx, NOx, and PM, respectively. On the other hand, there have been significant studies on the effects of die-

ro of

sel fuel regarding cetane index (CI), aromatic content, the boiling temperature of diesel fraction on the engine combustion and exhaust emissions [25,26]. Besides, changes in one type

of desired property may not be favorable to others such as increasing temperature may favor

-p

sulfur and nitrogen removal, but it may not improve the cetane index.

Hence the main objective of this study was to enhance diesel pool by adding CGO as a

re

blend to SRGO with a ratio of 70 to 30 wt% from a local refinery. An effect of hydrotreating

lP

operating conditions has been investigated to conserve hydrotreated product sulfur 450 ppm using CGO and SRGO blend as a feedstock. During the hydrotreating process, along with low sulfur and nitrogen, a significant reduction in polyaromatic compound could be

ur na

essentially carried out via hydrogenation as well as ring-opening reactions.

2. Experimental

Jo

The blending of CGO and SRGO feed was obtained from KNPC's refineries. The CGO was obtained from delayed coker while SRGO was reserved from atmospheric distillation units, which were mixed in a 70/30 ratio (CGO/SRGO). Hydrotreating experiments were conducted in a fixed bed reactor unit using a commercial catalyst (Catalyst X). About 30 ml of the oxide catalyst diluted with an equal volume of carborundum was charged in a tubular reactor keep-

5

ing the catalyst section in the middle of the reactor. In order to avoid channeling the coarse carborundum and inert alumina balls were loaded above and below the catalyst bed. Before catalyst performance, the catalyst was presulfided using a CS2 in SRGO, which was introduced into the reactor with hydrogen at 150°C for 5 hrs and 230°C for 12 hrs. Subsequently, the heating rate (15°C/h) was increased to 345°C, 50 bar, and stabilized for 8 hrs. After sulfidation, the feed was switched to the test blended feed (SRGO and CGO; 30/70), and the operating conditions were adjusted accordingly (LHSV 2.6 to 5.5 h-1; tem-

ro of

perature 320 to 375 °C, pressure 50 bar, and H2/HC = 200 Nl/L). The test run was carried out about 1500 hrs (63 d) under various operating conditions. The detailed reactor design with various steps of feed and product handling is shown schematically in Fig. 1.

-p

A typical bench-scale flow-reactor unit was used for the blended feed hydrotreating where the feed was treated with hydrogen at elevated temperature and space velocities. The operating

re

conditions were varied in order to achieve 450 ppmS in the hydrotreated products. The

lP

blended (SRGO/CGO 30/70) feed physicochemical properties are given in Table 1. The total sulfur and nitrogen contents of feed and product samples were determined using a sulfur chemiluminescent detector (SCD). Total aromatics and polynuclear aromatics contents in feed

ur na

and products were determined with a Supercritical Fluid Chromatography (SFC) aromatic analyzer. Cetane index is used as a substitute for cetane number. Cetane number [27] is an empirical index that characterizes the autoignition behaviour of diesel fuel while the cetane

Jo

index is based on the densities and the distillation using ASTM D86 method.

3. Results and discussion In the refinery, hydrotreating processes are the most common, which are mainly used to reduce the heteroatom and increase the efficiency of fuel for the various fraction of hydrocarbon. The catalytic activities were studied for catalyst X in the micro-flow reactor (Fig. 1) us-

6

ing blended feedstocks (Table 1). The composition of the feedstock such as sulfur, nitrogen, and aromatics are relatively very high in blended feed compare to diesel. The operating conditions were varied in order to achieve 450 ppmS in the product (i.e., constant conversion) with the variation of operating conditions as reported in Fig. 2. The sulfur content in hydrotreated product was kept constant at each stage by changing temperature and LHSV. The test run was conducted in about 63 d (1512 hrs; TOS). The results indicated that the operating parameter required significant changes. However, the role of the sulfur removal is not only to

ro of

the operating conditions but also other components of feedstock. In general, sulfur removal is the key parameters, but how other conversions reflect on targeting specific values must be established during the testing. The overall concept and specific

-p

refinery stream (30/70, SRGO/CGO) with commercial catalyst X to obtained marketable

product (450 wppmS) with a variety of processing steps (space velocity, temperature, and

re

conversion), have made this as a case study. Hence the study illustrated the importance of

lP

operating parameter not only on sulfur removal but also on HDN, aromatic, and CI changes. Apart from the specified 450 ppmS, the other properties such as flash point, cloud point, pour

ur na

point, cold filter plug-in point, CI, etc. must comply with the market standard.

Effect of Space Velocity and Temperature on HDS Conversion: The effect of space velocity on sulfur removal was studied between 2.6 and 5.2 h-1 as a function of temperature to

Jo

obtained 450 ppmS in the hydrotreated product. The HDS conversion increased progressively with an increase in the reactor temperature. Fig. 3 indicated that with increasing LHSV from 2.6 to 5.2 the conversion dropped to 5%, of which 15°C higher temperature is required in order to uphold the target sulfur. Figure 3 indicating the temperature required to compensate variation in LHSVs (i.e., 2.5 h-1 and 5.2 h-1). Although, the catalyst showed good stability at both LHSVs particularly at the end of the run, where same LHSV (i.e., 2.6 h-1) required about

7

7°C higher temperature to obtained same sulfur content in the product. However, recurrence of experiments after 1000 h TOS, the catalyst showed slight deactivation, which was compensated by increasing the temperature to 3°C. On the other hand, about 7°C increase in the reactor temperature was found necessary to maintain the sulfur level 450 ppm in the product during the two months of operation (i.e., 3.5°C/month). Similarly, the conversion of blended feed was also studied for the HDN conversion. Fig. 4 shows results indicating that about 1.2 % drop in conversion with a variation of LHSV 2.6 to

ro of

5.2 h-1 corresponding to the 15°C of the increase in the reactor temperature. Compared to HDS the HDN reaction appeared to have been less affected by the increasing 15°C temperature increase, which is responsible for the lower difference (between two LHSV), because the

1

-p

temperature is more effective to mitigate the inhibition effect [28]. The repeated LHSV (2.6 h) results further implied the negligible catalyst deactivation or the stable performance of the

re

catalyst.

lP

Usually, CGO contains a large amount of nitrogen compounds [14,29,30], which is not only inhibit HDS reaction but also overpower the hydrogenation function of the catalyst [3,12,28,31,32]. Nitrogen compounds are known for their detrimental role in hydrotreating,

ur na

catalyst deactivation and product stability [33,34]. Therefore, nitrogen compounds (basic as well as non-basic) play a significant role in inhibiting catalytic sites, particularly when lowering sulfur content below 500 ppm [3]. Indeed, the diesel sulfur content is likely to level off 10

Jo

to 5 ppm across the globe [35] but using 70% CGO may not be immediately easy to achieve required sulfur level mainly it has a high concentration of aromatic and nitrogen. Fig. 5, presents the selectivity between HDS and HDN where HDS reaction was more selective up to 95% conversion subsequently reaction has selectively turned to HDN. The catalytic site mainly depends on the adoption of sulfur and nitrogen, where nitrogen compounds are expected to be adsorbed more strongly [36].

8

In addition, C-N bond cleavage of aromatic ring compounds is more complex and required hydrogenation of the ring [4,37]. The propagation of nitrogen compound reaction via hydrogenation is expected to consume nascent hydrogen (i.e., heterolytically dissociated of H2 into H+ and H-) favourably, which further inhibits HDS reaction pathway particularly hydrogenation reaction route of refractory sulfur compounds [38,39]. Usually, the hydrogenation function eliminates steric hinderance and access sulfur adsorption of Mo site (CUS, coordinative unsaturated site) and ease hydrogenolysis of C-S bond. Hence, the inhibition effect of nitro-

ro of

gen compounds is more on refractory sulfur compounds. The saturation in HDS selectivity after 90% conversion in the presence of nitrogen is mainly due to the stronger mandate of hy-

-p

drogenation to the nitrogen containing ring and subsequent C-N bond breakage.

Role of Aromatics on Cetane index: Apart from the nitrogen, coker blended feed is very

re

rich in aromatic content particularly polynuclear aromatics (PNA) is very high. The aromatic

lP

compounds in the blended feed have a significant negative impact on the rate of reaction of refractory sulfur by the hydrogenation route is similar to the nitrogen compounds, and H2S displayed a poisoning effect on HDS rate for supported catalysts [3,40,41,42]. The high ce-

ur na

tane is needed to regulate unburned hydrocarbon resulting from low cetane index that produces PM and soot [19], which vary in their size and densities. The fuel with low CI has poor ignition properties, which leads to engine knocking, noise, and PM emission. Aromatic

Jo

content has very low cetane index (i.e., low efficiency of fuel) and usually responsible for producing unburnt hydrocarbon or the PM. Fig. 6 shows that the total aromatics and PNA content are lower and cetane index is higher for the diesel produced at low LHSV and lower temperature operation compare to that produced by high LHSV and high-temperature conditions. The catalyst has a significant impact on the degree of cetane number uplift during the hydroprocessing. The sulfide catalyst mainly enhances cetane number with hydrogenation

9

and ring-opening (cracking) functions, which is being provided by metallic phases and support acidity, respectively. Hence high hydrogenation and acidic catalyst usually deliver higher cetane uplift. The operating conditions typically regulate catalyst performance such as low sulfur, low nitrogen, low aromatic, and high cetane products, which is particularly imperative to heavier feed like CGO. Recently Calemma et al. [43] reported that due to the hydrocracking reaction at higher temperature the CI decreases. It means that hydrogenation (HYD) of aromatics rings occurred parallel to HDS where after the ring-opening further cracking may

ro of

occur at a higher temperature, thereby, likely causing a decrease in CI. Similar to the nitrogen, aromatics also compete for HYD sites with refractory sulfur compounds, thus affecting the HYD route more than that of the direct HDS route [3].

-p

Indeed, the aromatic contents are more of a pollutant than sulfur and nitrogen mainly because of their carcinogenicity and relatively less focused issue. High aromatic contents are respon-

re

sible for lowing CI as shown in Fig. 7. It is clearly seen that in order to convert aromatic

lP

molecule to high CI complete hydrogenation of an aromatic ring is needed before the ring opening to straight carbon chain (paraffin) without hydrocracking. On the other hand, the practical consequence of this fact is to enhance hydrogen content of products in the form of

ur na

paraffinic hydrocarbon. An utmost effect of hydrogen content on the aromatic and cetane index indicated that with an increase in hydrogen, there would follow a decrease in aromatic; but with an increase in CI. The low density of the hydrotreated product has high H2 content

Jo

that is expected to have greater CI and better diesel fuel properties with lower PM formation. Diesel fuel is a commercial product, which requires several analysis or multiple quality pa-

rameters to meet the fuel specifications before it can be sold in the market. These parameters include CI, sulfur content, flash point, density, and cold filter plugging point or boiling points (T95). Usually, aromatic content is responsible for most of the aforementioned properties showing a negative relationship with CI (Fig. 7) while exhibiting a positive relationship with

10

density. The hydrotreated products range for density lies between 0.8575 and 0.8675, which is significantly affected by the total aromatic as well as PNA content as shown in Fig. 8. The density (API gravity) and aniline point are related to aromatic/paraffinic content to some extent the degree of branched molecules. The CI and lower density are a function of the hydrogen content, with a corresponding increase in the CI, but with a decreasing density. In other words, hydrogen is a parameter for better fuel efficiency [1]. The aromatics contents are mainly responsible for the efficiency of fuel (i.e., CI) and that effects on the engine exhaust

ro of

emissions of unburnt hydrocarbon (HC) and PM [20,23,25]. During the hydrotreating, an enhancement in the cetane index was observed. It is a generic concept of HDT catalyst that

aromatics compounds assume to hydrogenation, which subsequently can be hydrogenolysis

-p

(C-C ring opening) during the desulfurization of the blend (SRGO+CGO) feeds. However,

with a variety of operational conditions, the aromatics hydrogenation is not appreciably influ-

re

enced particularly mono-aromatic remain almost same while CI improved marginally. In gen-

lP

eral, the aromatic compounds are being hydrogenated in presence of hydrogen into the naphthenic and subsequently to the saturated products via ring opening reaction. A significant conversion of PNA compounds to mono and diaromatic was observed at low space velocity,

ur na

which decreases with increasing contact time. Hence, a limited saturation was observed for mono-aromatic compounds, which is a relatively slow process and its rate enhances with decreasing LHSV. These results indicated that PNA saturation ensues readily under typical hy-

Jo

drotreating conditions, but the saturation of mono rings aromatics is much more difficult and required more severe operating conditions as well as a more active catalyst with hydrogenation and acidic functions [44,45]. This can be described by the high aromatics content of CGO feeds and their lower reactivity. On the other hand, higher operating temperatures also do not enhance aromatics saturation significantly, which is probably due to thermodynamic limitations on aromatics hydrogenation reactions. Low temperatures and high pressure usually

11

favour aromatics hydrogenation reactions [3]. However, at a higher temperature, the cracking activity promoted along with higher coke formation, which makes them unsuitable for deep HDS at high temperature [46]. The blended feed was hydrotreated to produce ultralow-sulfur and to enhance fuel efficiency by improving the CI using a commercial catalyst. The content and type of sulfur, nitrogen and poly-nuclear aromatic (PNA) compound’s nature strongly influence the degree of HDS during hydrotreating. Therefore, the composition of feed is one of the important factors particularly

ro of

nitrogen compounds are known for the detrimental role [1,3]. An effect of nitrogen removal also showed that removal of nitrogen adversely affects HDS conversion, which is mainly due to the limitation of hydrogenation or the inhibition effect generated via the nitrogen species

-p

[31]. Abundant refractory sulfur compounds are available (alkyl-substituted dibenzothio-

phenes) in CGO that also coexist with nitrogen compound. The deep HDS trend would be-

re

come even more critical if the feed also contains nitrogen compound, which not only requires

lP

hydrogen in its hydrogenation but also would produce inhibition effect on hydrogenolysis by adsorbing it is intermediate or by-products on the catalytic sites. The aromatic compounds are known to lower the CI, competitively adsorbing on catalytic sites and inhibiting these sites.

ur na

There are significant studies [24,25] that reported the effect of fuel properties such as CI, distillation characteristics, aromatic content, etc., The aromatic content is known to have a significant effect on NOx and PM emissions. The authors investigated the effects of various

Jo

cetane index along with different aromatic content on the emissions. The investigation of the engine emissions as a function aromatic and CI is to be the subject of a further later study by using blend feedstock.

4. Conclusions

12

The conversion of sulfur and nitrogen compounds indicated that HDS is selectively higher than HDN where hydrogenation plays an essential role in their reaction route and conversion. It is expected that beyond 90% of HDS conversion, most of the sulfur compounds are refractory, which would require a stronger hydrogenation function to remove steric-hindrance from the refractory molecule. The target objective 450 ppmS was achieved using various operating conditions such as space velocity on sulfur and temperature from a feed whereby the blend contains SRGO and CGO in the ratio of 30:70. The low sulfur (450ppm) diesel produced by

ro of

hydrotreating at low LHSV and the low temperature showed better in quality with higher cetane index and lower concentration of aromatics, nitrogen, and PNA compared to that produced at high LHSV and high temperature conditions. As an effect of operating condition

-p

one type of desired property may not be favorable to others, such as increasing temperature requiring conversion of HDS and HDN being achieved; but, at the same time, CI was

re

decreased. The hydrogenation function also was seen to be critical to the cetane index, which

lP

decreased with increasing aromatic content. The catalyst used in the study did not show rapid deactivation although the feed contained 70% CGO. The deactivation rate of the catalyst was

ur na

found to be 3.5oC/month at an LHSV of 2.6 h-1.

Statement of Interest Recent years, due to the environmental legislation the sulfur specification for diesel fuel has been tightened exponentially. However, fuel quality is expected to become heavier and more complex. An essential question then is whether the goal of reaching such ultra-low sulfur re-

Jo

gime is expected exponentially in difficulty. Therefore, the key problem in deep HDS is the low reactivity of DBTs with an alkyl group substitution at the 4- and 6-position (i.e., refractory sulfur) which make up the significant amount when the sulfur content brought down to concentration below 500 ppm. The coker gas oil (CGO) has a large amount of refractory sulfur, nitrogen, and poly-nuclear aromatics while it has a very low cetane number (i.e., low fuel efficiency). Thus, the sulfur content in fuel is not the only issue to investigate HDS but also to improve the efficiency of fuel. The fuel efficiency is mainly affected by high PNA or low

13

cetane number. So, treating feedstocks that contain CGO will become more challenging and entirely different from SRGO (diesel). The investigation was carried out on the demand of local refinery (KNPC) to mimic the existing refinery operating condition for poor quality blended feedstock and produce low sulfur along with required other properties. The refinery point of view is to utilize the CGO stream and convert into valuable products. Moreover, there are many countries in Asia and the Middle East without fuel sulfur limits where they are still using 500 to 1,500 ppmS in diesel. So, it is likely that refineries are looking market for such a low-value stream. Therefore, operating conditions were varied in order to achieve 450 ppmS in the HDT product using 70 volume %

ro of

CGO and 30 % SRGO blend as a feedstock. The role of aromatic and nitrogen compounds have been studied, and their effect on HDS, HDN, and aromatic conversion are reported.

References

A. Marafi, H. Albazzaz, M. S. Rana, Catal. Today 329 (2019) 125-134.

[2]

J. Weitkamp, ChemCatChem 4 (2012) 292-306

[3]

A. Stanislaus, A. Marafi, M. S. Rana, Catal. Today 153(1–2) (2010) 1-68.

[4]

M.S. Rana, M. Vinoba, F.S. AlHumaidan, Current Sustainable/Renewable Energy Re-

lP

re

-p

[1]

ports 4(4) (2017) 232–244.

Y. Choi, J. Lee, J. Shin, S. Lee, D. Kim, J.K. Lee, Appl. Catal. A 492 (2015) 140-150.

[6]

G.C. Laredo, P. Perez-Romo, J. Escobar, J.L. Garcia-Gutierrez, P.M. Vega-Merino, Ind.

ur na

[5]

Eng. Chem. Res. 56 (2017) 10939-10948. [7]

G.C. Laredo, P.M.V. Merino, P.S. Hernandez, Ind. Eng. Chem. Res. 57 (2018) 7315-

Jo

7321. [8]

A. Galadima, O. Muraza, Fuel 181 (2016) 618-629.

[9]

J. Shin, Y. Oh, Y. Choi, J. Lee, J.K. Lee, Appl. Catal. A 547 (2017) 12-21.

[10] Y.S. Kim, K.S. Cho, Y.K. Lee, J. Catal. 351 (2017) 67-78. [11] S. Torrisi, P.M. Gunter, NPRA Annual Meeting March 21-23, 2004, San Antonio, TX, AM-04-27.

14

[12] T.C. Ho, Appl. Catal. A: Gen. 244 (2003) 115-128. [13] A. Stanislaus, A. Al-Barood, and H. Qabazard, Prepr. Am. Chem. Div. Fuel Chem. 48 (2003) 655-656. [14] A. Al-Barood, A. Stanislaus, Fuel Processing Technology 88 (2007) 309-315. [15] A. Al-Barood, A. Stanislaus, Petrol Sci and Tech 23 (2005) 749-760. [16] G. Escalona, A. Rai, P. Betancourt, A. K. Sinha, Fuel 219 (2018) 270-278. [17] N. Catherin, E. Blanco, L. Piccolo, D. Laurenti, F. Simonet, C. Lorentz, E. Leclerc, V.

ro of

Calemma, C. Geantet, Catal. Today 323 (2019) 105-111. [18] Y. Oh, J. Shin, H. Noh, C. Kim, Y.-S. Kim, Y.-K. Lee, J.K. Leea, Applied Catal. A: Gen. 577 (2019) 86-98.

-p

[19] P.T.M. Do, S. Crossley, M. Santikunaporn, D.E. Resasco, Catalysis 20 (2007) 33-64. [20] M. Han, Fuel 109 (2013) 512–519.

re

[21] A. Stanislaus, B.H. Cooper, Catal. Rev. Sci. & Eng., 36(1), (1994), 75–123.

lP

[22] B. H. Cooper, B.B.L. Donnis, Appl Catal A: Gen., 137(2) (1996) 203–223. [23] J. Reijnders, M. Boot, P. Goey, Fuel 186 (2016) 24-34. [24] Y. Kidoguchi, C. Yang, R. Kato, K. Miwa, JSAE Rev, 21(4) (2000) 469-475.

ur na

[25] S.S. Kee, A. Mohammadi, Y. Kidoguchi, K. Miwa, J. Fuels & Lubricants 114 (2005), 765-772. (SAE Paper 2005-01-2086; 2005). [26] M.L. McMillan, R. Halsall, SAE Paper No. 881650; 1988

Jo

(https://doi.org/10.4271/881650.)

[27] C. Guan, J. Zhai, D. Han, Fuel 249 (2019) 1-7. [28] T. Ho, J. Catal., 219(2) (2003) 442–451. [29] G. Marroquin, J. Ancheyta, Appl. Catal. A: Gen. 207 (2001) 407-420. [30] J. Ancheyta, R.E. Aguilar, S.D. Salazar, G.R. Betancourt, M.L. Nuncio, Appl. Catal. A: Gen., 180 (1-2), (1999) 195–205.

15

[31] M.S. Rana, A. Al-Barood, R Bouresli, A.W. Al-Hendi, N. Mustafa, Fuel Processing Technology 177 (2018) 170-178. [32] G.C. Laredo, R.S. Martin, M.C. Martinez, J. Castillo, J.L. Cano, Fuel 83 (2004) 13811389. [33] J.W. Bauserman, G.W. Mushrush, D.R. Hardy, H.D. Willauer, M. Laskoski, T.M. Keller, Petrol. Sci. and Tech. 32 (2014) 638–645. [34] A. Niquille-R, R. Prins, Catal. Today 305 (2018) 28–39.

ro of

[35] N. Chandak A. George, A. Hamadi, M Dakhan, A. Chaudhry, G. Singaravel, S. Morin Catalysis Today 329 (2019) 116-124.

[36] A. Logadottir, P.G. Moses, B. Hinnemann, N. Topsøe, K.G. Knudsen, H. Topsøe, J.K.

-p

Nørskov, Catal. Today 111 (2006) 44–51.

[37] S. Eijsbouts, V.H.J. Debeer, R. Prins, J. Catal. 127 (1991) 619–625.

lP

Kwart, J. Catal. 61 (1980) 523-527.

re

[38] M. Houalla, D.H. Broderick, A.V. Sapre, N. K. Nag, V. H. J. de Beer, B. C. Gates, H.

[39] B. C. Gates, H. Topsøe, Polyhedron 16(18), (1997) 3213–3217. [40] M.S. Rana, R. Navarro, J. Leglise, Catal. Today 98(1-2), (2004), 67-74.

ur na

[41] M. Nagai, T. Sato, A. Aiba, J. Catal. 97 (1986) 52-58. [42] P. Zeuthen, K.G. Knudsen, D.D. Whitehurst, Catal. Today. 65 (2001) 307-314. [43] V. Calemma, R. Giardino, M. Ferrari, Fuel Processing Technology 91(7) (2010) 770–

Jo

776.

[44] G. Wan, A. Duan, Z. Zhao, G. Jiang, D. Zhang, R. Li, T. Dou, K.H. Chung, Energy & Fuels 23 (2009) 81-85.

[45] J. Escobar, M.C. Barrera, V. Santes, J.E. Terrazas, Catal. Today 296 (2017) 197-204. [46] N. Azizi, S. A. Ali, K. Alhooshani, T. Kim, Y. Lee, J.-I. Park, J. Miyawaki, S.-Ho Yoon, I. Mochida, Fuel Processing Technology 109 (2013) 172–178.

16

Table 1. Physicochemical characteristics of the coker gas oil/gas oil (70/30) feedstock

SRGO

Coker

Density @15˚C, g/ml

0.8509

0.9312

Coker and SRGO blend 0.8713

API, ˚

34.8

20.5

30.85

Total Sulfur, wt%

1.406

0.855

0.896

Kinematics Viscosity at 50oC, cSt

4.32

19.41

5.63

Non Aromatic, vol%

77.9

54.0

60.5

Total aromatic, vol%

22.09

45.99

39.5

Mono, vol%

16.64

21.89

21.2

Poly (Di & Tri ), vol%

5.45

24.1

18.3

Nitrogen, ppmw

40

Cetane Index

50.82

-p

ro of

Properties

691

21.4

48.2

165

232

212

256

317

273

267

339

302

312

417

360

90 %

342

448

371

95 %

357

450

388

456

389

Distillation (ASTM D-86)

5% 10 %

ur na

50 %

lP

IBP, oC

Jo

FBP, oC

re

837

17

H2

VENT

Reactor

FC

T -4

N2

FC

TK 7

TK 8

NaOH

NaOH`

TO DRAIN

T -3 CW

C -2

ro of

TO STRIPPER

C –1

SAMPLER

TK 1

TK 2

TK 3

FEED TANK

WASHING

PRESULF

-p

N2

TANK IDING

T–6

PRODUCT TANK

PRODUCT TANK

ur na

lP

re

TANK

T–5

Jo

Fig. 1. Simplified flow diagram of a micro-reactor pilot plant (Unit 07 at PRC) used for a catalyst evaluation test

18

10000

400 LHSV-2.6 LHSV-5.2

390

LHSV-2.6 → Temperature

Temperature, C

ro of

370 1000

360

450 ppmS

-p

350

100 0

150

300

450

600

re

Sulfur in product, wppm

380

750

900

1050

1200

340

1350

330 1500

ur na

lP

TOS, h

Jo

Fig 2. Effect of operating conditions on target sulfur (450 ppmS) in hydrotreated product

19

100

90

ro of

HDS conversion, %

95

85

-p

LHSV (2.6 h-1 ; TOS: 0 - 602 hrs)  LHSV (5.2 h-1 ; TOS: 602 - 1111 hrs) ∆ LHSV (2.6 h-1 ; TOS: 1111 - 1471 hrs)

re

80

330

340

lP

75 350

360

370

380

390

400

ur na

Temperature, C

Jo

Fig. 3. Effect of temperature and space velocities on the HDS of blended feedstock

20

83

79

ro of

HDN conversion, %

81

LHSV 2.6 h-1 (TOS: 0-602 hrs) 77

LHSV 5.2 h-1 (TOS: 602-1111 hrs)

75 340

350

360

370

380

390

400

re

330

-p

LHSV 2.6 h-1 (TOS: 1111-1471 hrs)

lP

Temperature, C

Jo

ur na

Fig 4. Effect of temperature and space velocities on the HDN of blended feedstock

21

100

90

ro of

HDS, %

95

85

75 79

80

81

82

re

78

-p

80

lP

HDN, wt%

Jo

ur na

Fig. 5. Effect of nitrogen conversion on deep HDS

22

58

54

ro of

Cetane index

56

LHSV 2.6 h-1 (TOS: 0-602 hrs)

52

LHSV 2.6 h-1 (TOS: 1111-1471 hrs) 50 340

350

360

370

re

330

-p

LHSV 5.2 h-1 (TOS: 602-1111 hrs)

380

390

400

lP

Temperature, C

Jo

ur na

Fig 6. Effect of temperature and space velocities on the HDN of blended feedstock

23

60

56

ro of

Cetane Index

58

54

-p

52

36.5

37 37.5 38 Total Aromatic, wt%

38.5

39

ur na

lP

36

re

50

Jo

Fig. 7. Role of aromatic content in cetane improvement

24

40

15 Total Aromatic

38

13

37

12

11

0.858

0.8585

0.859

-p

36

35 0.8575

PNA, wt%

14

PNA

ro of

Aromatic total, wt%

39

0.8595

0.86

0.8605

10 0.861

lP

re

Density @ 15 C, g/ml

Jo

ur na

Fig. 8. Aromatic (total aromatic and PNA) content in the hydrotreated product with the variation of density

25