Maya crude hydrodemetallization and hydrodesulfurization catalysts: An effect of TiO2 incorporation in Al2O3

Hydrotreating of Maya heavy crude oil over high specific surface area CoMo/TiO₂–Al₂O₃ oxide supported catalysts was studied in an integral reactor close to industrial practice. Activity studies were carried out with Maya crude hydrodesulfurization (HDS), hydrodemetallization (HDM), hydrodenitrogenation (HDN), and hydrodeasphaltenization (HDAs) reactions. The effect of support composition, the method of TiO₂ incorporation, and the catalyst deactivation are examined. Supported catalysts are characterized by BET specific surface area (SSA), pore volume (PV), pore size distribution (PSD), and atomic absorption. It has been found that sulfided catalysts showed a wide range of activity variation with TiO₂ incorporation into the alumina, which confirmed that molybdenum sulfided active phases strongly depend on the nature of support. The pore diameter and nature of the active site for HDS, HDM, HDN, and HDAs account for the influence of the large reactant molecules restricted diffusion into the pore, and/or the decrease in the number of active sites due to the MoS₂ phases buried with time-on-stream. The textural properties and hysteresis loop area of supported and spent catalysts indicated that catalysts were deactivated at the pore mouth due to the metal and carbon depositions. The atomic absorption results agreed well regarding the textural properties of spent catalysts. Thus, incorporation of TiO₂ with γ-Al₂O₃ alters the nature of active metal interaction with support, which may facilitate the dispersion of active phases on the support surface. Therefore, the TiO₂ counterpart plays a promoting role to HDS activity due to the favorable morphology of MoS₂ phases and metal support interaction.     

Support Effects on Thiophene Hydrodesulfurization over Co-Mo-Ni/Al2O3 and Co-Mo-Ni/TiO2-Al2O3 Catalysts

A carbon-based sulfonated catalyst was prepared by direct sulfonation and carbonization （in moderate conditions：200 ＆#176;C, 12 h） of red liquor solids, a by-product of paper-making process. The prepared sulfonated cata-lyst （SC） had aromatic structure, composed of carbon enriched inner core, and oxygen-containing （SO3H, COOH, OH） groups enriched surface. The SO3H, COOH, OH groups amounted to 0.74 mmol·g^-1, 0.78 mmol·g^-1, 2.18 mmol·g^-1, respectively. The fresh SC showed much higher catalytic activity than that of the traditional solid acid catalysts （strong-acid 732 cation exchange resin, hydrogen type zeolite socony mobile-five （HZSM-5）, sulfated zir-conia） in esterification of oleic acid. SC was deactivated during the reactions, through the mechanisms of leaching of sulfonated species and formation of sulfonate esters. Two regeneration methods were developed, and the catalytic activity can be mostly regenerated by regeneration Method 1 and be fully regenerated by regeneration Method 2, respectively.     

Effect of Zr-SBA-15 support on catalytic functionalities of Mo, CoMo, NiMo hydrotreating catalysts

SBA-15 and ZrO₂ (10–50 wt.%) containing SBA-15 mesoporous materials were prepared by direct and post-synthesis methods. Characterization using low angle XRD, pore size distribution, CO₂ chemisorption indicate that hexagonal mesoporous structure is retained even after ZrO₂ addition (25 wt.%). Mo, CoMo and NiMo catalysts prepared using these supports were examined by XRD, oxygen chemisorption, temperature programmed reduction (TPR). The catalysts were tested for hydrodesulfurization (HDS) of thiophene and hydrogenation (HYD) of cyclohexene. HDS of thiophene for 8%Mo, 3%Co8%Mo, and 3%Ni8%Mo increases with increasing ZrO₂ loading in SBA-15 up to 25 wt.%. Oxygen chemisorption and TPR hydrogen consumption indicated that the molybdenum dispersion and anion vacancies, and catalytic activities are significantly influenced by ZrO₂ content in Zr-SBA-15. A comparison indicated that TiO₂-SBA-15, ZrO₂-SBA-15 supported CoMo catalysts show higher activities for hydrodesulfurization.     

Effect of phosphorus on activity of hydrotreating catalyst of Maya heavy crude

The effect of phosphorus on physical properties of the catalyst and on activity of hydrotreating of Maya crude was studied in this work. Catalysts were prepared by the co-impregnation method. Alumina-titania binary oxide was used as a support material. The presence of phosphorus in the catalyst decreases the percentage of micropores, and it results in a decrease of specific surface area. Temperature program reduction (TPR) shows that phosphates reduce metal support interaction. It leads to the formation of polymolybdate phases in expense of strongly bonded tetrahedral molybdates. At higher P loading, polymolybdates may be present with quasi crystalline MoO₃. However, the TPR experiment is not sufficiently sensitive to distinguish several phases present on the catalysts used by the authors. A slight increment of HDM activity is observed, but HDS activity is lower in the P containing catalyst compared with the P free catalyst. The changes of physical properties of the spent catalysts are mainly due to the coke formation on the catalyst. The presence of phosphorus on hydrotreating catalysts inhibits coke formation during the hydrotreating reaction.     

Effect of preparation methods and content of phosphorus on hydrotreating activity

The effect of phosphorus content and preparation methods is studied in this present investigation. Three different methods are employed for preparation of catalysts. The catalysts are characterized by pore size distribution, X-ray diffractogram and temperature programmed reduction. Thiophene hydrodesulfurization (HDS), cumene hydrocracking (HC), gas oil HDS and Maya heavy crude HDS and hydrodemetallization (HDM) activities are performed. It is found that specific surface area gradually decreases with P loading. The addition of phosphorus increases the formation of polymolybdate species which are more active for hydrotreating reaction. It is also observed that reducibility of these species also increases with P loading. However, at higher P loading the crystalline MoO₃ is formed at the expense of these multilayer polymeric molybdates. The increment in the activity is more in the catalyst prepared by co-impregnation method. The activity increases with P loading up to 1 wt% P content. At higher loading the activity decreases. It is also noted that P inhibits coke formation on the catalyst during hydrotreating of heavy crude oil. Phosphorus can also modify the Brønsted acidity of the catalyst and hence cumene hydrocracking activity slightly increases.     

Preparation and characterization of nano-sized CoMo/Al2O3 catalyst for hydrodesulfurization

CoMo on Al₂O₃ catalyst prepared by spray pyrolysis method was found in the form of spheres of 0.5–1.2 μm, which consisted of tiny primary particles of ca. 10–20 nm diameter. The materials shows comparable activity to those of commercial catalysts in HDS of straight run gas oil, in particular, refractory 4,6-dimethyldibenzothiophene (4,6-DMDBT). Weaker interactions between CoMo and Al₂O₃ are suggested by temperature-programmed reduction (TPR), Raman spectroscopy, to give more active species than those over the impregnated catalysts. This accounts for its comparable activity in spite of its smaller surface area.     

水滑石法制备渣油加氢催化剂

用离子交换法合成钼酸盐阴离子柱撑镍铝水滑石,并进一步合成了渣油加氢催化剂（MoO₃-NiO/Al₂O₃）。通过XPS检测发现MoO₃以单分子层存在于催化剂孔道中,其饱和分散容量为4.69μmol/m²。通过XRD分析显示中间产物水滑石结构晶形完好,且置换后晶粒尺寸有所增大。采用低温氮气吸附法研究了不同阶段产物的比表面积、孔容和孔体积的变化规律。采用固定床反应器以沙轻常压混合渣油为原料进行催化剂评价,发现水滑石法制备的催化剂较浸渍法制备的催化剂在金属脱除率、脱硫率、脱氮率和脱残炭率等方面初活性有明显提高,但活性衰减较快,寿命相对较短。     

Preparation of heavy oil hydrotreating catalyst from spent residue hydroprocessing catalysts

In recent years, increasing emphasis has been placed on recycling spent hydroprocessing catalysts due to environmental regulations which list them as hazardous waste materials. In the present work, the recycling of spent residue hydroprocessing catalysts that contained high levels of vanadium was investigated by using them in the preparation of active new hydrotreating catalyst after subjecting them to different treatments such as decoking, acid-leaching and hydrothermal treatment. Catalyst extrudates containing different levels of V, Mo and Ni on Al₂O₃ were prepared by mixing the spent catalyst powder with boehmite in different proportions followed by peptization, kneading and extrusion. The prepared catalyst extrudates were characterized by chemical analysis and surface area and porosity measurements. The HDS and HDM activities of the catalysts were tested using Kuwait atmospheric residue as feed and compared with that of a reference HDM catalyst. Partial leaching of vanadium from the spent catalyst opened up the pores, and the catalyst prepared by mixing the metal-leached spent catalyst (MLSC) with boehmite had higher surface area and pore volume and showed higher hydrotreating activity than that prepared from unleached spent catalyst. Hydrothermal treatment of the spent catalyst increased its porosity and surface area. Catalysts prepared from hydrothermally treated spent catalyst (HTSC) had higher surface area and pore volume and showed higher HDM and HDS activities than that prepared from the spent catalyst without hydrothermal treatment. The catalysts prepared from the treated spent catalysts also exhibited substantially higher HDM and HDS activities than the reference commercial HDM catalyst. The results indicate that spent catalysts containing high levels of vanadium together with Mo and Ni on Al₂O₃ can be used in the preparation of active HDM/HDS catalysts, and thereby, their environmental problem can be reduced.     

Deep HDS over NiMo/Zr-SBA-15 catalysts with varying MoO3 loading

In the present work, with the aim of searching for new, highly effective catalysts for deep HDS, a series of NiMo catalysts with different MoO₃ loadings (6–30 wt.%) was prepared using SBA-15 material covered with ZrO₂-monolayer as a support. Prepared catalysts were characterized by N₂ physisorption, small- and wide-angle XRD, UV–vis diffuse reflectance spectroscopy, temperature-programmed reduction, SEM-EDX and HRTEM, and their catalytic activity was evaluated in the 4,6-dimethyldibenzothiophene hydrodesulfurization (HDS). It was observed that ZrO₂ incorporation on the SBA-15 surface improves the dispersion of the Ni-promoted oxidic and sulfided Mo species, which were found to be highly dispersed, up to 18 wt.% of MoO₃ loading. Further increase in metal charge resulted in the formation of MoO₃ crystalline phase and an increase in the stacking degree of the MoS₂ particles. All NiMo catalysts supported on ZrO₂-modified SBA-15 material showed high activity in HDS of 4,6-DMDBT. The best catalyst having 18 wt.% MoO₃ and 4.5 wt.% NiO was almost twice more active than the reference NiMo/γ-Al₂O₃ catalyst. High activity of NiMo/Zr-SBA-15 catalysts and its evolution with metal loading was related to the morphological characteristics of the MoS₂ active phase determined by HRTEM.     

Synthesis,characterization and hydrotreating performance of supported tungsten phosphide catalysts

Supported tungsten phosphide catalysts were prepared by temperature-programmed reduction of their precursors (supported phospho-tungstate catalysts) in H₂ and characterized by X-ray diffraction (XRD), BET, temperature-programmed desorption of ammonia (NH₃-TPD) and X-ray photoelectron spectroscopy (XPS). The reduction-phosphiding processes of the precursors were investigated by thermogravimetry and differential thermal analysis (TG-DTA) and the suitable phosphiding temperatures were defined. The hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) activities of the catalysts were tested by using thiophene, pyridine, dibenzothiophene, carbazole and diesel oil as the feedstock. The TiO₂, ?-Al₂O₃ supports and the Ni, Co promoters could remarkably increase and stabilize active W species on the catalyst surface. A suitable amount of Ni (3%–5%), Co (5%–7%) and V (1%–3%) could increase dispersivity of the W species and the BET surface area of the WP/?-Al₂O₃ catalyst. The WP/?-Al₂O₃ catalyst possesses much higher thiophene HDS and carbazole HDN activities and the WP/TiO₂ catalyst has much higher dibenzothiophene (DBT) HDS and pyridine HDN activities. The Ni, Co and V can obviously promote the HDS activity and inhibit the HDN activity of the WP/?-Al₂O₃ catalyst. The G-Ni5 catalyst possesses a much higher diesel oil HDS activity than the sulphided industrial NiW/?-Al₂O₃ catalyst. In general, a support or promoter in the WP/?-Al₂O₃ catalyst which can increase the amount and dispersivity of the active W species can promote its HDS and HDN activities.     

Analysis of the hydrotreatment of Maya heavy crude with NiMo catalysts supported on TiO2-Al2O3 binary oxides: Effect of the incorporation method of Ti

Heavy Maya crude has been hydrotreated with NiMo/alumina-titania catalysts in which titania was incorporated by two different methods. Titania added to boehmite followed by calcination in order to promote formation of Ti–O–Al bonds, and Ti added to alumina in order to promote the formation of TiO₂ structures on the surface. The reaction results indicate that hydrodesulfurization (HDS), hydrodemetallization (HDM) and hydrodenitrogenation (HDN) activities are improved by the incorporation of Ti to the catalyst. In all cases, catalysts prepared by the method leading to the formation of surface TiO₂ structures show superior performance in the three functionalities (HDS, HDM and HDN). Raman analysis of the supports gives clear evidence of the differences in Ti oxide structures on the surface. The characterization of the catalysts indicates that Ti-modified catalysts have increased surface acidity (evaluated by pyridine adsorption) and greater number of coordinatively unsaturated sites (titrated by NO adsorption). Ti-containing catalysts seem to be also more stable with time-on-stream.     

Catalytic activities of Co(Ni)Mo/TiO2–Al2O3 catalysts in gasoil and thiophene HDS and pyridine HDN: effect of the TiO2–Al2O3 composition

The effect of the TiO₂–Al₂O₃ mixed oxide support composition on the hydrodesulfurization (HDS) of gasoil and the simultaneous HDS and hydrodenitrogenation (HDN) of gasoil+pyridine was studied over two series of CoMo and NiMo catalysts. The intrinsic activities for gasoil HDS and pyridine HDN were significantly increased by increasing the amount of TiO₂ into the support, and particularly over rich- and pure-TiO₂-based catalysts. It is suggested that the increase in activity be due to an improvement in reducing and sulfiding of molybdena over TiO₂. The inhibiting effect of pyridine on gasoil HDS was found to be similar for all the catalysts, i.e., was independent of the support composition. The ranking of the catalysts for the gasoil HDS test differed from that obtained for the thiophene test at different hydrogen pressures. In the case of gasoil HDS, the activity increases with TiO₂ content and large differences are observed between the catalysts supported on pure Al₂O₃ and pure TiO₂. In contrast, in the case of the thiophene test, the pure Al₂O₃-based catalyst appeared relatively more active than the catalysts supported on mixed oxides. Also, in the thiophene test the difference in intrinsic activity between the pure Al₂O₃-based catalyst appeared relatively more active than the catalysts supported on mixed oxides. Also in the thiophene test, the difference in intrinsic activity between the pure Al₂O₃- and pure TiO₂-based catalysts is relatively small and dependent on the H₂ pressure used. Such differences in activity trend among the gasoil and the thiophene tests are due to a different sensitivity of the catalysts (by different support or promoter) to the experimental conditions used. The results of the effect of the H₂ partial pressure on the thiophene HDS, and on the effect of H₂S concentration on gasoil HDS demonstrate the importance of these parameters, in addition to the nature of the reactant, to perform an adequate catalyst ranking.     

Hydrotreating of gas oil on SBA-15 supported NiMo catalysts

The siliceous and the metal substituted (B or Al)-SBA-15 molecular sieves were used as a support for NiMo hydrotreating catalysts (12 wt.% Mo and 2.4 wt.% Ni). The supports were characterized by X-ray diffraction (XRD), scanning electron microscopy and N₂ adsorption–desorption isotherms. The SBA-15 supported NiMo catalysts in oxide state were characterized by BET surface area analysis and XRD. The sulfided NiMo/SBA-15 catalysts were examined by DRIFT of CO adsorption and TPD of NH₃. The HDN and HDS activities with bitumen derived light gas oil at industrial conditions showed that Al substituted SBA-15 (Al-SBA-15) is the best among the supports studied for NiMo catalyst. A series of NiMo catalysts containing 7–22 wt.% Mo with Ni/Mo weight ratio of 0.2 was prepared using Al-SBA-15 support and characterized by BET surface area analysis, XRD and temperature programmed reduction and DRIFT spectroscopy of adsorbed CO. The DRIFT spectra of adsorbed CO showed the presence of both unpromoted and Ni promoted MoS₂ sites in all the catalysts, and maximum “NiMoS” sites concentration with 17 wt.% of Mo loading. The HDN and HDS activities of NiMo/Al-SBA-15 catalysts were studied using light gas oil at temperature, pressure and WHSV of 370 °C, 1300 psig and 4.5 h⁻¹, respectively. The NiMo/Al-SBA-15 catalyst with 17 wt.% Mo and 3.4 wt.% of Ni is found to be the best catalyst. The HDN and HDS activities of this catalyst are comparable with the conventional Al₂O₃ supported NiMo catalyst in real feed at industrial conditions.     

Studies on recycling and utilization of spent catalysts: Preparation of active hydrodemetallization catalyst compositions from spent residue hydroprocessing catalysts

Spent catalysts form a major source of solid wastes in the petroleum refining industries. Due to environmental concerns, increasing emphasis has been placed on the development of recycling processes for the waste catalyst materials as much as possible. In the present study the potential reuse of spent catalysts in the preparation of active new catalysts for residual oil hydrotreating was examined. A series of catalysts were prepared by mixing and extruding spent residue hydroprocessing catalysts that contained C, V, Mo, Ni and Al₂O₃ with boehmite in different proportions. All prepared catalysts were characterized by chemical analysis and by surface area, pore volume, pore size and crushing strength measurements. The hydrodesulfurization (HDS) and hydrodemetallization (HDM) activities of the catalysts were evaluated by testing in a high pressure fixed-bed microreactor unit using Kuwait atmospheric residue as feed. A commercial HDM catalyst was also tested under similar operating conditions and their HDS and HDM activities were compared with that of the prepared catalysts. The results revealed that catalyst prepared with addition of up to 40 wt% spent catalyst to boehmite had fairly high surface area and pore volume together with large pores. The catalyst prepared by mixing and extruding about 40 wt% spent catalyst with boehmite was relatively more active for promoting HDM and HDS reactions than a reference commercial HDM catalyst. The formation of some kind of new active sites from the metals (V, Mo and Ni) present in the spent catalyst is suggested to be responsible for the high HDM activity of the prepared catalyst.     

Hydrodesulfurization activity of CoMo and NiMo supported on Al2O3–TiO2 for some model compounds and gas oils

Catalytic activities of Al₂O₃–TiO₂ supporting CoMo and NiMo sulfides (CoMoS and NiMoS) catalysts were examined in the transalkylation of isopropylbenzene and hydrogenation of naphthalene as well as the hydrodesulfurization (HDS) of model sulfur compounds, conventional gas oil (GO), and light cycle oil (LCO). Al₂O₃–TiO₂ supporting catalysts exhibited higher activities for these reactions except for the HDS of the gas oil than a reference Al₂O₃ supporting catalyst, indicating the correlation of these activities. Generally, more content of TiO₂ promoted the activities. Inferior activity of the catalyst for HDS of the gas oil is ascribed to its inferior activity for HDS of dibenzothiophene (DBT) in gas oil as well as in model solvent decane, while the refractory 4,6-dimethyldibenzothiophene (4,6-DMDBT) in gas oil as well as in decane was more desulfurized on the catalyst. Characteristic features of Al₂O₃–TiO₂ catalyst are discussed based on the paper results.     

MgO-supported Mo, CoMo and NiMo sulfide hydrotreating catalysts

The most common preparation of high surface area MgO (100–500 m² g⁻¹) is calcination of Mg(OH)₂ obtained either by precipitation or MgO hydration or sol–gel method. Preparation of MoO₃/MgO catalyst is complicated by the high reactivity of MgO to H₂O and MoO₃. During conventional aqueous impregnation, MgO is transformed to Mg(OH)₂, and well soluble MgMoO₄ is easily formed. Alternative methods, that do not impair the starting MgO so strongly, are non-aqueous slurry impregnation and thermal spreading of MoO₃. Mo species of MoO₃/MgO catalyst are dissolved as MgMoO₄ during deposition of Co(Ni) by conventional aqueous impregnation. This can be avoided by using non-aqueous impregnation. Co(Ni)Mo/MgO catalysts must be calcined only at low temperature because Co(Ni)O and MgO easily form a solid solution. Literature data on hydrodesulfurization (HDS) activity of MgO-supported catalysts are often contradictory and do not reproduced well. However, some results suggest that very highly active HDS sites can be obtained using this support. Co(Ni)Mo/MgO catalysts prepared by non-aqueous impregnation and calcined at low temperature exhibited strong synergism in HDS activity. Co(Ni)Mo/MgO catalysts are much less deactivated by coking than their Al₂O₃-supported counterparts. Hydrodenitrogenation (HDN) activity of Mo/MgO catalyst is similar to the activity of Mo/Al₂O₃. However, the promotion effect of Co(Ni) in HDN on Co(Ni)Mo/MgO is lower than that on Co(Ni)Mo/Al₂O₃.     

Simultaneous hydrodesulfurization of thiophene and hydrogenation of cyclohexene over dimolybdenum nitride catalysts

A series of unsupported dimolybdenum nitride (γ-Mo₂N) catalysts differing in surface area were prepared by temperature programmed reduction of MoO₃ with a mixture of NH₃:N₂ (90:10). Characterization of catalysts by BET, XRD, TPR and XPS techniques was carried out. The samples were used as catalysts in hydrotreating reactions (simultaneous hydrodesulfurization of thiophene and hydrogenation of cyclohexene). Low surface area γ-Mo₂N materials show much higher specific conversions than those with higher surface area. These results indicate that HDS and HYD reactions over γ-Mo₂N seem to be structure-sensitive. The relative exposure extent of crystalline planes (1 1 1) and (2 0 0) over the different catalysts can be associated with their hydrogen adsorption capacities and with their catalytic performances. The catalytic activities are significantly affected by the catalyst pretreatment conditions.     

A series of NiMo/Al2O3 catalysts containing boron and phosphorus: Part II. Hydrodenitrogenation and hydrodesulfurization using heavy gas oil derived from Athabasca bitumen

The hydrodenitrogenation (HDN) and hydrodesulfurization (HDS) activity of a series of NiMo/Al₂O₃ catalyst containing boron (B) and phosphorus (P) were tested in a trickle bed reactor using heavy gas oil derived from Athabasca bitumen. Detailed characterization of these catalysts is given in Part I of this paper. Addition of B and P caused the formation of extremely strong acid sites on the catalyst and enhanced its HDN activity. The total (TN), basic (BN) and non-basic nitrogen (NBN) conversions increased from 61.9 to 78.0 wt.%, from 78.9 to 93.0 wt.% and from 52.8 to 70.0 wt.%, respectively, with the increase in B concentration from 0 to 1.7 wt.% to NiMo/Al₂O₃ catalyst. Similarly, TN, BN and NBN conversions increased from 61.9 to 78.4 wt.%, from 78.9 to 91.0 wt.%, and from 52.8 to 71.6 wt.% with the addition of 2.7 wt.% P. Though the addition of B and P to NiMo/Al₂O₃ catalyst did not show any significant effect on S conversion, the HDN and HDS activities of the catalyst containing 1.7 wt.% B and the one containing 2.7 wt.% P are comparable to those of a commercial catalyst. The activity over extended period indicated that catalysts L and K were more stable (lower deactivation rate) in terms of nitrogen removal activity than catalyst B (reference catalyst). On the other hand, the stability for sulfur removal was comparable with catalyst B. Selected catalysts after use were characterized using BET surface area, TPR, TPD and SEM techniques which were correlated further with their activities.     

A comparative study for heavy oil hydroprocessing catalysts at micro-flow and bench-scale reactors

CoMo and NiMo catalysts were prepared and the catalytic activities were evaluated in fixed bed micro-flow and bench-scale reactors with different feed composition. Experiments were conducted at conditions close to those that exist in the industrial practice. Due to the different nature of the feeds, the conditions were varied with respect to both evaluation scales. The fresh and spent catalysts were characterized. Spent catalyst textural properties indicated that catalysts were deactivated and the surface area and pore volume dropped by 20–60%. The adsorption–desorption hysteresis of spent catalysts indicated that cylindrical pores are deactivated at the pore mouth and played an important role in modification by either closing one end of the pore or forming a narrow neck pore, which is indicative of the formation of “ink-bottle” type pores. Thus, the deposition of metal and carbon takes place preferentially at the pore entrance, which causes pore mouth plugging. These results are also supported by the SEM–EDAX analysis, where metal and carbon depositions are evident and taking place at the superficial region of a catalyst particle. The increase in absolute area of hysteresis is based on the catalyst's average pore diameter: the higher the average pore diameter, the lower the area of the spent catalyst. The activity and deactivation of the catalyst are discussed on the basis of catalyst porosity and deposited metal characterization. The composition of catalysts varies, considering two applications in a multi-reactor system: a CoMo catalyst for the first reactor, and a NiMo in the second reactor; the former is supported on γ-Al₂O₃ and the latter on TiO₂/Al₂O₃. As a comparison, the CoMo catalyst exhibited better hydrogenolysis while the NiMo catalyst showed better hydrogenation activity in both micro-flow and bench-scale reactors. It appears that there is a moderate effect of TiO₂ content in support on Ni and V hydrodemetallization (HDM) while hydrodeasphaltenization (HDAs) and hydrodesulfurization (HDS) activities were slightly improved when a partially hydrotreated feed, which contains more refractory compounds than virgin feedstock, was employed.     

Effect of catalyst composition on the hydrodesulphurization and hydrodemetallization of atmospheric residual oil

A series of CoMo/Al₂O₃ catalysts containing a third additive, a Si, Ti, or P compound, were prepared using a consecutive impregnation method. The activities for the hydrodesulphurization (HDS), hydrodemetallization (HDM) and Conradson carbon residue (CCR) reduction of atmospheric residual oil were tested in a semi-batch basket type reactor. Cycle-aging tests were carried out for comparison of catalyst stability. The intrinsic rate constants of HDS from a semi-empirical calculation were used to test the coke tolerance of the catalysts. The CoMo/Al₂O₃ catalyst with a titanium compound added exhibited the highest activity enhancement for HDS and HDM reactions. It was also found that the surface activity maintenance can be effectively improved by the addition of an appropriate amount of titanium compound. The activity and stability of CoMo and NiMo catalysts for the HDS and HDM reactions were also compared.