Ultra-deep hydrodesulfurization of feedstock containing cracked gasoil

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Ultra-deep hydrodesulfurization of feedstock containing cracked gasoil through NiMo/#-Al2O3 catalyst pore size optimization Amir Atabak Asadi, Seyed Mahdi Alavi, Sayed Javid Royaee, and Mansour Bazmi Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.7b03461 • Publication Date (Web): 09 Jan 2018 Downloaded from http://pubs.acs.org on January 10, 2018

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Ultra-deep hydrodesulfurization of feedstock containing cracked gasoil through NiMo/γ-Al2O3 catalyst pore size optimization Amir Atabak Asadi, a, b Seyed Mahdi Alavi, *a Sayed Javid Royaee, b and Mansour Bazmi c a. School of Chemical Engineering, Iran University of Science and Technology (IUST), Narmak, Tehran, 16846-13114, Iran b. Petroleum Refining Technology Development Division, Research Institute of Petroleum Industry (RIPI), Tehran, 14857-33111, Iran c. Deputy of Technology and International Affairs, Research Institute of Petroleum Industry (RIPI), Tehran, 1485733111, Iran Corresponding author email address: [email protected]

KEYWORDS: Hydrodesulfurization, Cracked gasoil, Catalyst support, NiMo/γ-Al2O3 catalyst, Pore diameter ABSTRACT: The importance of ultra-deep hydrodesulfurization (HDS) of the cracked and straight run gasoil blend necessitate an extensive study on HDS catalyst optimization. Herein, we report a CO2 assisted neutralization of NaAlO2 aqueous solution conducted in a semi-batch membrane dispersion microstructured reactor, as a novel method to synthesize pseudoboehmite powders with different textural properties. A number of γ-Al2O3 catalyst supports as well as NiMo catalysts with the average pore sizes of 6.3 (5.2) to 21.5 (18.6) nm and 5.0 (3.7) to 20.3 (17.2) nm are prepared using the as synthesized pseudoboehmite powders. XRD analysis shows the sizes of all pseudoboehmite and γ-Al2O3 supports crystalline are in the nanoscale range. NH3 TPD results reveal that about half of the total NH3 (1.76 mmol NH3/g) is adsorbed on the surface of γ-Al2O3 support due to presence of strong acidic cites. FTIR spectrometer confirms formation of MoO4−2 species. The effects of catalyst pore size on HDS performance of the straight run gasoil and its blend with cracked gasoil are also investigated according which, the most sulfur removal from both feedstocks using catalysts with the average pore size of 8.0 (5.9) and 9.1 (7.2) nm, respectively, emphasizing the significant role of the pore size on the catalyst activity and HDS process efficiency. However, effects of textural and physico-chemical properties of the catalyst and its support cannot be neglected. The obtained results confirm the proposed synthesis route would be an efficient alternative method to prepare mesoporous γAl2O3 supports with precisely controlled average pore size in a wide range of a few up to 20 nanometers.

INTRODUCTION One of the most significant current discussions in fossil fuels processing and their environmental impacts is elimination of heteroatoms including sulfur, nitrogen, oxygen and metals. To control and reduce the environmental impacts of fossil fuels consumption, strict regulations have been developed worldwide. In this regard, Euro V standard has been implemented in which diesel sulfur content is restricted to be less than 10 ppm 1, 2. Therefore, it is becoming increasingly difficult to ignore the importance of ultra-deep hydrodesulfurization (HDS) in providing clean transportation fuels. Besides, considering increasing necessity to process petroleum fractions which are more sour, the need for novel and more efficient HDS catalysts has heightened 3-5. γ-Al2O3 is the most common support for HDS catalysts which can be due to the outstanding textural, chemo physical and mechanical properties. All these characteristics are tunable by demand of the reaction carried out inside the reactor, processed petroleum fraction and the product’s targeted specifications 8.

6, 7

HDS catalysts structure–function relationships have been thoroughly investigated over the last few years in order to improve organosulfur molecules removal from transport fuels 9-13. Activity of catalysts in HDS of feedstock containing 4,6-DMDBT can be improved by enhancing hydrogenation and isomerization reactions through optimizing the catalyst support characteristics 14 which can be performed by increasing the catalyst support acidity 15-18 or using a chelating agent such as EDTA, CyDTA, citric acid and glycol in the catalyst preparation step 19. Total active phase loading and the ratio of the loaded promoter to the active phase are other parameters which significantly affect the catalyst activity 20. Among all chemo-physical and textural properties, pore size could be announced as the most important one due to its well-known impacts on diffusion of different species which could affect and limit the HDS overall reaction rate 21 . However, due to tortious pore structure of γ-alumina and its broad pore size distribution, it is impossible to determine whether pore diffusion is the rate determining step or not 22. In this regard, by increasing average molecular weight of the processed petroleum fraction, intrinsic

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diffusivity decreases significantly. Reaction rate of various sulfur containing compounds are different which could be ascribed to the dimensions of the molecule and spatial steric hindrance of these species 23, 24. It is not that easy to determine the optimum pore diameter and consequently the optimum catalyst support for processing a petroleum fraction which contains variety of organosulfur molecules. Hence, studying the effects of support structural characteristics on performance of the corresponding HDS catalyst is of great importance and is also a key for developing a highly active HDS catalyst 25-29. Mesoporous γ-alumina, can be nominated for the best HDS catalyst support due to thermal stability, adjustable textural properties and moderate Lewis acidity 30, 31 only if right preparation procedures are applied 32. For instance, the Alumina supported catalysts exhibit undesirable strong metal-support interaction which can be overcome using EDTA as chelating agent. Not only EDTA and its derivatives favour formation of NiMoS type II active phases rather than less active NiMoS type I in HDS reaction, but also reduce the metal support interactions 33. γalumina transition phase could be synthesis through precipitation and hydrolyzing of the precursors in presence of surfactants or co-polymers such as sodium dodecyl sulfate 34, 35, stearic acid 36, dibenzoyl-L-tartaric acid 37 and polyethylene oxide and polypropylene oxide 38, 39 as structure directing agents. It’s worth underlying that, Tergitol 15-S-7 40, 1-butyl-3-methylimidazolium tetrafluoroborate 41 , Pluronic P-123 42, Pluronic F-127 43 were also used as structure directing agent. Addition of a porogen, triblock copolymer P123, during the peptization step was proposed as a simple post-modification to produce alumina supports with high surface areas and high pore volumes 44. It is worth mentioning that in addition to conventional methods of catalyst support preparation, there are some other methods such as paste processing 45 through which catalysts were prepared by the reaction of α-boehmite with metal sources in an aqueous paste. Even in methods which are developed to synthesize composite supports such as mechanochemical route for preparation of CeO2Al2O3 support 46, NH4HCO3 was used as an additive. It could be concluded that structure directing agents are commonly used in synthesis of mesoporous γ-alumina while aluminum nitrate or alkoxides were used as precursors. These chemicals are all expensive and more importantly, removal of these structure directing agents after synthesis may result in mesostructure collapse which could be related to the strong interaction between the surfactant and alumina framework 34, 47. In our previous work, we introduced NaAlO2 solution neutralization using CO2 gas as a simple, one-pot and solvent-deficient synthesis method to prepare pseudoboehmite 48. Through this synthesis route, textural properties of the resulting γ-alumina, including pore size, pore volume and surface area, could be tuned. Besides, mesostructure formation is under the effects of in-situ synthesized Na2CO3 molecules which plays the role of structure directing agent. It worth mentioning that Na2CO3 could be removed during washing step and thus

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mesostructure would be protected from collapse during calcination. In this paper, γ-alumina supports were prepared through this novel synthesis route and effects of mesoporous γ-alumina pore size on performance of the corresponding HDS catalyst were discussed. In petroleum refineries with visbreaker unit, cracked gasoil is produced and considering environmental regulations, it should be desulfurized. Due to the limits of HDS process, this stream could not be processed solely and should be mixed with atmospheric gasoil for desulfurization. It is worth mentioning that there are very few studies on HDS of this hydrocarbon blend and hence there is a knowledge gap in this field of research. To fill this knowledge gap, a typical blend of visbreaker cracked gasoil with atmospheric gasoil was used as feedstock. The main concern addressed in this article is to tune structural characteristics of γ-alumina support, prepared through NaAlO2 solution neutralization using CO2 gas with the aim of maximization of the HDS catalyst performance. Prepared pseudoboehmite, γ-alumina support and HDS catalyst were characterized using X-ray diffraction, field emission scanning electron microscope, nitrogen adsorption-desorption analysis, fourier transform infrared spectroscopy and NH3 temperature programmed desorption and the HDS catalyst performance was studied. This paper has been divided into two parts. The first part deals with synthesis and characterization of pseudoboehmite, γ-alumina support and HDS catalysts. The second part focuses on studying the effects of mesoporous γ-alumina pore size on HDS catalyst performance in a bench scale reactor under a typical industrial conditions.

1. EXPERIMENTAL 1.1. Materials Carbon dioxide, nitrogen and helium gases were supplied by Tarkib Gas Alvand company and were all above 0.99995 g/g in purity. Sodium aluminate (NaAlO2, 0.9995 g/g in purity) was used as received from SIGMAALDRICH. EDTA (> 0.994 g/g in purity), ammonium hydroxide, (NH4OH, 0.25 g/g), ammonium heptamolybdate tetrahydrate ((NH4)6Mo7O24·4H2O, > 0.994 g/g in purity) and nickel nitrate hexahydrate (Ni(NO3)2.6H2O, for analysis grade) were used as received from Merck KGaA. 1.2. Syntheses 1.2.1. Mesoporous support A CO2 containing gas mixture, prepared using two SLA5850 BROOKS INSTRUMENT mass flow controllers (MFC), entered a semi-batch membrane dispersion microreactor after passing through a stainless steel coil which was used to ensure accurate temperature control. The semi-batch membrane dispersion microreactor was equipped with a porous glass membrane of 35 mm diameter and 16–40 μm nominal max pore size. By passing gas mixture through the reaction zone, NaAlO2 solution was neutralized. Pseudoboehmite was obtained after aging, filtering, washing and drying the obtained suspension from neutralization step. Synthesis route steps were discussed in detail in our previous work 48.


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Table 1. Pseudoboehmite synthesis parameters Parameters

Ageing time

CO2 gas concentration

Gas mixture flow rate

h

Vol.%

SCCM

25

-

0.1

Final pH of the solution

80

°C

He

Synthesis temperature

°C

-

Unit PB1

NaAlO2 solution molarity molar

Ageing temperature

Inert gas Type

Sample ID

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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8.5

100

40

2

PB2

N2

80

0.1

10

9

100

40

2

PB3

N2

90

0.1

10

8.5

100

40

2

PB4

N2

90

0.1

10

8

100

50

2

PB5

He

90

0.1

40

10

100

50

2

PB6

N2

90

0.25

10

10

100

60

2

PB7

N2

90

0.3

40

10

100

60

2

properties of the synthesized pseudoboehmite, γ-Al2O3 supports and the prepared catalysts. Surface area was obtained using the Brunauer-Emmett-Teller (BET) method. Average pore size and pore size distribution were calculated from desorption branch of the isotherm through BET and Barrett-Joyner-Halenda (BJH) methods, respectively. To remove adsorbed gasses, prior to the test, alumina and catalyst samples were degassed at 300 °C for 3 h and the adsorption-desorption analysis were carried out at -196 °C. FTIR spectrometer (VERTEX 70, Bruker, USA) was used to obtain the ATR-FTIR spectra in the wavenumber range of 400–4,000 cm–1. The characteristics of catalyst acid sites were studied using TPD/TPR analyzer (TPD/TPR 2900, Micromeritics Instrument Corporation, USA) with a thermal conductivity detector.

1.3.1. Hydrodesulfurization activity Catalysts performance were studied in a microreactor, flow scheme of which is shown in Figure 1.

Table 1 summarizes the synthesis parameters values in each sample preparation. Mesoporous γ-alumina supports were prepared by calcination of the obtained pseudoboehmite powders for 4 h at 550 ˚C in air.

1.2.2. Catalyst Porefilling method was used to prepare NiMo catalysts 49 . Total metal loading (NiO+MoO3) and NiO/(NiO+MoO3) ratio were 0.24 g/g. and 0.125, respectively. The synthesis process was started by dissolving 1.544 g of EDTA in 14 cc of ammonium hydroxide aqueous solution at pH ∼ 10. Molar ratio of EDTA/NiO was adjusted to 1. This chemical was used as chelating agent 50. Afterward, 3.389 g of ((NH4)6Mo7O24·4H2O was added to the solution. By complete dissolution of MoO3 source, pH decreased slightly. Then 1.537 g of Ni(NO3)2.6H2O was dissolved in the obtained solution. The pH value of the impregnation solution was adjusted to 9. 10 g of γalumina with water uptake capacity of 1.66 cc/g was used for metal loading. The volume of impregnation solution was increased to 16 cc and used for incipient wetness impregnation. It is worth mentioning that the isoelectric point of the synthesized γ-Al2O3 support is measured to be 7.58. The impregnated γ-alumina supports were dried overnight at 120 ˚C and calcined for 4 h at 550 ˚C. The described procedure was used to prepare 13.158 g of NiMo/γ-Al2O3 catalyst. 1.3. Characterization Philips 1840 X-ray diffraction apparatus at 40 kV using Co Kα radiation with 2θ varying from 10 to 90°, scan rate of 1°/min, and 2θ intervals of 0.02° was used to study the phase structure of the samples. TESCAN Mira 3-XMU FESEM apparatus was used to examine morphology of the prepared powders. Surface area analyzer (TriStar-II-Series, Micromeritics Instrument Corporation, USA) was used to obtain textural

Figure 1. Flow scheme of the catalyst performance evaluation system, F: Filter, MFC: Mass flow controller, CHV: Check valve, FP: Feed pump, CF: Coolant flow, SFV: Sulfiding feed vessel, MFV: Main feed vessel, PSV: Pressure safety valve, R: Reactor, PH: Preheater zone, CR: Catalytic reaction zone, AH: After heater zone, HS: Hot separator, CS: Cold separator HTG: Hydrotreated gasoil, BPC: Back pressure controller, RCS: Readout and controller system, FCS: Furnace controller system, CST: Caustic sulfur trap, GC: Gas chromatograph

Liquid hydrocarbon and hydrogen gas were fed into the catalyst evaluation system with a high pressure pump (Eldex Optos Series, 1SMP) and through a SLA5850 BROOKS INSTRUMENT mass flow controller, respectively. At the reactor inlet, hydrogen gas was mixed with hydrocarbon feed and entered the preheating zone in which the mixture was heated to the temperature sufficient for the reaction zone in which the catalyst was placed. Reactor effluent was entered into the vessels where gas phase was separated from the liquid phase. Pressure of the system was controlled using a SLA5820 BROOKS INSTRUMENT back pressure controller. Both the MFCs and the back pressure controller were governed by 0254


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four-channel power supply, readout and set-point controller. The gas was vented after passing through H2S and other acidic gas caustic trap. Gas and liquid hydrocarbon samples were collected through sampling valves throughout the catalyst evaluation cycle. Performance of all the synthesized catalysts were evaluated in hydrodesulfurization of two feedstock which are atmospheric gasoil (AGO) and a blend of 0.05 g/g visbreaker gasoil (VisGO) into atmospheric gasoil. Catalysts activities were determined in terms of remained sulfur in the treated hydrocarbon. The hydrodesulfurization tests were performed in similar conditions for all the catalysts. Prior to each test, the catalyst was activated during presulfiding process using initial ultra-low sulfur gasoil (ULSG) containing 0.02 g/g dimethyl disulfide (DMDS) as the sulfiding agent. Boiling range of the initial gasoil was 150 to 350 °C, sulfur and nitrogen contents were lower than 100 ppmw. Conditions under which HDS and presulfiding were performed are summarized in table 2. Table 2. HDS and presulfiding conditions

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fraction and fourier transform infrared spectroscopy. All obtained results are reported as follows. Table 3. Feedstock properties Property

Unit

AGO

VisGO

Specific gravity @ 15.6°C

-

0.826

0.850

TBP Cut points

°C

170-370

170-390

Sulfur Content

g/g

0.0103

0.035

Total nitrogen

wt. ppm

(4) > (5) > (2) > (6) > (1) = (7), while in AGO/VisGO blend hydrodesulfurization reaction they were ranked based on their activity as (4) > (3) > (5) > (6) > (7) > (2) > (1). Results are in good agreement with the fact that VisGO contains heavier and larger sulfur containing species and thus average pore size of the optimum catalyst with the highest HDS performance in AGO/VisGO blend processing should be bigger compared with that of the optimum catalyst in HDS of pure AGO. Results revealed that the most active catalysts in HDS of AGO and AGO/VisGO blend had BJH adsorption (desorption) average pore width of 8.0 (5.9) and 9.1 (7.2) nm, respectively. Sulfur content of the hydrotreated AGO samples were in range of 16 to 25 ppmw. All the synthesized catalysts exhibited high activities in HDS reaction of AGO which could be ascribed to good active phase dispersion due to mesoporous structure of the catalyst supports. However, using AGO/VisGO blend as feed results in a noticeable difference between catalysts performance which could be attributed to the nature of VisGO. Visbreaker gasoil has sulfur containing species which are more complex compared with molecules present in AGO. The HDS reaction rate in AGO/VisGO blend processing was affected by diffusivity and spatial steric hindrance of these species. By increasing the average pore size of the synthesized catalyst to that of Catalyst (4), catalyst performance was enhanced significantly, which could be ascribed to enhancement in diffusion of big sulfur containing molecules with significant spatial steric hindrance. However, more


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increase in average pore size adversely affects catalyst activity, though it was expected that it could enhance the catalyst performance. In conclusion, pore diameter is not the only factor which governs the catalyst activity and this fact highlights the importance of physico-chemical properties, mesoporosity, surface area and pore volume of the catalyst and its support 60, 61. The rational model was fitted to the experimental data and the relevant equation is shown in eq. 1. S . ( ppm) =

p1 × PDav 3 + p2 × PDav 2 + p3 × PDav + p4 PDav 2 + q1 × PDav + q2

eq. 1

where PDav is the average pore diameter of the catalyst in Å. p1, p2, p3, p4, q1 and q2 are calculated coefficients and sulfur content of the processed hydrocarbon is calculated in ppm. The values of coefficients are calculated and summarized in the table 4. Table 4. Coefficients of sulfur prediction correlations Coefficients

Gasoil (1)

Gasoil (2)

p1

-0.039003119

-0.25126661

p2

44.23383911

167.7391528

P3

-6697.815931

-23278.94137

P4

302357.3465

1057573.534

q1

-153.2871953

-118.6174628

q2

7528.902317

6012.4096

Experimentally obtained sulfur contents of the processed gasoils using different catalysts and the predicted values obtained via the developed correlations are showed against the catalyst average pore size in Figure 12.

Figure 12. Experimental and calculated sulfur contents of the processed gasoils vs. the catalyst average pore size

2.3. The Privileged Catalyst Characterization 2.3.1. X-ray diffraction Phase structure of Catalyst (4) which exhibited the highest catalytic activity in HDS of AGO/VisGO blend was studied and X-ray diffraction pattern is depicted in Figure 13.

Figure 13. XRD patterns of Catalyst (4)

Comparing the XRD pattern showed in Figure 13 with patterns presented in Figure 5, revealed that in X-ray diffraction pattern of Catalyst (4) there is just peaks corresponding to the dhlk (311), (400) and (440) planes and there are no additional peaks. Based on these results, it could be inferred that the synthesized catalyst maintained its cubic γ-Al2O3 structure 52. Besides, as peaks which are corresponding to nickel and molybdenum oxides are not present in the catalyst XRD pattern, it could be concluded that active metal loading was performed successfully and there is a fine active phase dispersion on the catalyst support surface 60.

2.3.2. Fourier transform infrared spectroscopy The FTIR spectra of Catalyst (4) is shown in Figure 14. Peaks which were appeared in the region of 400–1050 cm−1 are corresponding to MoO3 IR bands 60.

Figure 14. FTIR spectrometer for Catalyst (4)

Catalyst (4) exhibited peaks in the range of 850–930 cm−1 which is corresponding to MoO vibrations in tetrahedral species MoO4−2 62. There is no vibration bands in range of 950–980 cm−1 which could be ascribed to the absence of polymolybdates phase 60.

2.3.3. NH3 temperature programmed desorption The results of ammonia-TPD are depicted in Figure 15.


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3. CONCLUSIONS

Figure 15. Ammonia-TPD profile for Catalyst (4)

As clearly seen, in the TPD profile three peaks were indicated which are located at 257.5, 455.3 and 691.3 °C. The corresponding amount of NH3 per grams of catalyst for each peak were 0.99, 0.34 and 0.43 mmol NH3/g respectively and the total adsorbed NH3 was 1.76 mmol NH3/g. Acid sites were classified into weak (peaks 350 °C) based on the desorption peak location. Considering the peek location and amount of desorbed NH3, 0.56 g/g of the acid sites are from moderate type and 0.44 g/g of them are of strong type.

2.3.4. Distillation Curve The AGO/VisGO blend and the product stream which was hydrotreated using the most active catalyst tagged as catalyst (4) were also studied in order to determine the distillation curve. The distillation curves were found using the True Boiling Point (TBP) method and results are demonstrated at Figure 16. Results revealed that along with the hydrodesulfurization process, hydrocracking was also occurred, which results in production of a lighter hydrocarbon cut.

Figure 16. True boiling point curves of the fresh and hydrotreated AGO/VisGO blend

This paper has argued that the novel synthesis method which was developed to prepare pseudoboehmite powder with specified textural properties and thereafter, mesoporous γ-Al2O3 catalyst support with controllable hierarchical structure can be considered as an alternative route for synthesis of these crucial materials for petrochemical and refining usages. The nitrogen adsorption-desorption analysis revealed that all synthesized catalyst supports had mesoporous structure and can be classified as Type IV adsorption-desorption isotherms. By increasing the average pore size, the hysteresis of the isotherm patterns changes from type H1 to H3, which signifies samples with smallest average pore sizes, γ-Al2O3 (1) and γ-Al2O3 (2) had narrow pore sized distribution; while samples with larger pore sizes, γ-Al2O3 (4), γ-Al2O3 (5), γ-Al2O3 (6) and γ-Al2O3 (7) had board pore size distributions. BJH adsorption (desorption) average pore width, pore volume and BET surface area of synthesized mesoporous γ-Al2O3 supports were in range of 6.3 (5.2) to 21.5 (18.6) nm, 0.47 to 1.17 cm3/g and 249 to 290 m2/g, respectively. FESEM micrographs revealed that pseudoboehmite, mesoporous γAl2O3 supports and NiMo catalysts had hierarchical structure consist of macro and mesopores. It was inferred from broadened XRD peaks that all synthesized powders had nanoscale crystallite size, poor crystallinity and high water content. FTIR spectra confirmed XRD results regarding presence of γ-Al2O3 phase. Through porefilling method, NiMo active phase was loaded on the synthesized mesoporous γ-Al2O3 supports. The absence of XRD peaks corresponding to molybdenum oxide in the obtained pattern for NiMo/γ-Al2O3 catalyst revealed that the active phase is finely dispersed and loaded on the support. Catalysts with different textural properties were synthesized and used in hydrodesulfurization of atmospheric gasoil (AGO) and a blend of 0.05 g/g visbreaker gasoil (VisGO) into atmospheric gasoil. Sulfur content of the hydrotreated AGO and AGO/VisGO blend were in range of 16 to 25 and 37 to 77 ppmw. The narrow and low sulfur content range of the hydrotreated AGO revealed that textural properties of all the synthesized catalysts and consequently, catalyst supports are promising regarding hydrodesulfurization process performance. In contrast, considering the noticeable difference between catalysts performance in hydrodesulfurization of AGO/VisGO blend and larger difference between remained sulfur in treated samples with catalyst (1) and catalyst (2) having the smallest average pore sizes amongst all samples, it is revealed that this feedstock contains sulfur compounds which are bigger and have more spatial steric hindrance compared to AGO. Clearly, it could be inferred that, the source of these species are VisGO. Catalysts could be sorted based on their activities in AGO and AGO/VisGO blend hydrodesulfurization as (3) > (4) > (5) > (2) > (6) > (1) = (7) and (4) > (3) > (5) > (6) > (7) > (2) > (1), respectively. Taken together, these findings suggest that neutralization of NaAlO2 aqueous solution with CO2 gas in semibatch membrane dispersion microstructured reactor can


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be considered as a novel, simple, one-pot and solventdeficient method to synthesize mesoporous γ-Al2O3 supports with controllable hierarchical structure. The results of this study indicate that supports with specified textural characteristics, specially controlled average pore width, can be prepared through this synthesis route which makes the neutralization of NaAlO2 solution with CO2 an alternative method to prepare catalyst supports with the aim of hydroprocessing a variety of feedstock.

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Figure 1. Flow scheme of the catalyst performance evaluation system, F: Filter, MFC: Mass flow controller, CHV: Check valve, FP: Feed pump, CF: Coolant flow, SFV: Sulfiding feed vessel, MFV: Main feed vessel, PSV: Pressure safety valve, R: Reactor, PH: Preheater zone, CR: Catalytic reaction zone, AH: After heater zone, HS: Hot separator, CS: Cold separator HTG: Hydrotreated gasoil, BPC: Back pressure controller, RCS: Readout and controller system, FCS: Furnace controller system, CST: Caustic sulfur trap, GC: Gas chromatograph 69x48mm (300 x 300 DPI)


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Figure 2. XRD patterns of the synthesized PB powders 70x49mm (300 x 300 DPI)


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Figure 3. XRD patterns of the synthesized γ-alumina supports 70x49mm (300 x 300 DPI)


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Figure 4. Nitrogen adsorption-desorption isotherms of the synthesized γ-Al2O3 supports 70x49mm (300 x 300 DPI)


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Figure 5. Average pore size (nm) of the synthesized PB powders, γ-Al2O3 supports and NiMo catalysts 70x49mm (300 x 300 DPI)


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Figure 6. Pore volume (cm3/g) of the synthesized PB powders, γ-Al2O3 supports and NiMo catalysts 70x49mm (300 x 300 DPI)


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Figure 7. Pore size distribution of γ-Al2O3 supports 70x49mm (300 x 300 DPI)


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Figure 8. BET surface area (m2/g) of the synthesized PB powders, γ-Al2O3 supports and NiMo catalysts 70x49mm (300 x 300 DPI)


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Figure 9. FESEM micrograph of PB (4) 109x120mm (300 x 300 DPI)


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Figure 10. FESEM micrograph of γ-Al2O3 (4) 54x29mm (300 x 300 DPI)


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Figure 11. Sulfur content of the hydrotreated gasoil samples 70x49mm (300 x 300 DPI)


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Figure 12. Experimental and calculated sulfur contents of the processed gasoils vs. the catalyst average pore size 70x49mm (300 x 300 DPI)


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Figure 13. XRD patterns of Catalyst (4) 70x49mm (300 x 300 DPI)


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Figure 14. FTIR spectrometer for Catalyst (4) 62x39mm (300 x 300 DPI)


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Figure 15. Ammonia-TPD profile for Catalyst (4) 70x49mm (300 x 300 DPI)


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Figure 16. True boiling point curves of the fresh and hydrotreated AGO/VisGO blend 70x49mm (300 x 300 DPI)


Ultra-deep hydrodesulfurization of feedstock containing cracked gasoil

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