Development of new catalysts for deep hydrodesulfurization of gas oil

TiO₂–Al₂O₃ composite supports have been prepared by chemical vapor deposition (CVD) over γ-Al₂O₃ substrate, using TiCl₄ as the precursor. High dispersion of TiO₂ overlayer on the surface of Al₂O₃ has been obtained, and no cluster formation has been detected. The catalytic behavior of Mo supported on Al₂O₃, TiO₂ and TiO₂–Al₂O₃ composite has been investigated for the hydrodesulfurization (HDS) of dibenzothiophene (DBT) and methyl-substituted DBT derivatives. The conversion over the Mo catalysts supported on TiO₂–Al₂O₃ composite, in particular for the HDS of 4,6-dimethyldibenzothiophene (4,6-DMDBT) is much higher than that of conversion obtained over Mo catalyst supported on Al₂O₃. The ratio of the corresponding cyclohexylbenzenes/biphenyls is increased over Mo catalyst supported on TiO₂–Al₂O₃ composite support. This means that the reaction rate of prehydrogenation of an aromatic ring rather than the rate of hydrogenolysis of C–S bond cleavage is accelerated for the HDS of DBT derivatives. The Mo/TiO₂–Al₂O₃ catalyst leads to higher catalytic performance for deep HDS of gas oil.     

Mesoporous molecular sieve MCM-41 supported Co–Mo catalyst for hydrodesulfurization of petroleum resids

In this work, we explored the potential of mesoporous zeolite-supported Co–Mo catalyst for hydrodesulfurization of petroleum resids, atmospheric and vacuum resids at 350–450°C under 6.9 MPa of H₂ pressure. A mesoporous molecular sieve of MCM-41 type was synthesized; which has SiO₂/Al₂O₃ ratio of about 41. MCM-41 supported Co–Mo catalyst was prepared by co-impregnation of Co(NO₃)₂·6H₂O and (NH₄)₆Mo₇O₂₄ followed by calcination and sulfidation. Commercial Al₂O₃ supported Co–Mo (criterion 344TL) and dispersed ammonium tetrathiomolybdate (ATTM) were also tested for comparison purposes. The results indicated that Co–Mo/MCM-41(H) is active for HDS, but is not as good as commercial Co–Mo/Al₂O₃ for desulfurization of petroleum resids. It appears that the pore size of the synthesized MCM-41 (28 Å) is not large enough to convert large-sized molecules such as asphaltene present in the petroleum resids. Removing asphaltene from the resid prior to HDS has been found to improve the catalytic activity of Co–Mo/MCM-41(H). The use of ATTM is not as effective as that of Co–Mo catalysts, but is better for conversions of >540°C fraction as compared to noncatalytic runs at 400–450°C.     

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.     

TPD study and carbazole hydrodenitrogenation activity of nitrided molybdena–alumina

The relationship between the activity and surface molybdenum species of nitrided 12.5% MoO₃/Al₂O₃ was studied in the hydrodenitrogenation (HDN) of carbazole at 573 K and 10.1 MPa total pressure. The surface molybdenum species were determined by the desorption of nitrogen gas during TPD. The surface area of NH₃-cooled Mo/Al₂O₃ nitrided at 773 and 1173 K was decreased by 8% and 61% from 245 m² g⁻¹ of the fresh MoO₃/Al₂O₃, respectively. The NH₃-cooled Mo/Al₂O₃ catalysts had slightly higher surface area than the He-cooled catalysts. The HDN rate increased with increasing nitriding temperature in the HDN of carbazole on the nitride catalysts. The NH₃-cooled Mo/Al₂O₃ catalysts nitrided at 1173 K were the most active in carbazole HDN and the He-cooled catalyst nitrided at 773 K was the least.     

TiO2-coated on Al2O3 support prepared by the CVD method for HDS catalysts

Mo---Co or Mo---Ni catalysts supported on alumina (Al₂O₃) have been widely used for hydrodesulfurization (HDS) of heavy petroleum fractions. In order to enhance the catalytic activities for HDS, a composite type support (TiO₂-Al₂O₃) prepared by the chemical vapor deposition (CVD) method has been studied. We found that Mo catalyst supported on TiO₂-Al₂O₃ showed much higher catalytic activity for HDS of dibenzothiophene derivatives than the catalysts supported on Al₂O₃.     

Hydrodesulfurization of dibenzothiophenes over molybdenum catalyst supported on TiO2–Al2O3

Composite types of TiO₂–Al₂O₃ supports, which are γ-aluminas coated by titania, have been prepared by chemical vapor deposition (CVD), using TiCl₄ as a precursor. Then supported molybdenum catalysts have been prepared by an impregnation method. As supports, we employed γ-alumina, anatase types of titania, and composite types of TiO₂–Al₂O₃ with different loadings of TiO₂. We studied the conversion of Mo from oxidic to sulfidic state through sulfurization by X-ray photoelectron spectroscopy (XPS). The obtained spectra unambiguously revealed the higher reducibility from oxidic to sulfidic molybdenum species on the TiO₂ and TiO₂–Al₂O₃ supports compared to that on the Al₂O₃ support. Higher TiO₂ loadings of the TiO₂–Al₂O₃ composite support led to higher reducibility for molybdenum species. Furthermore, the catalytic behavior of supported molybdenum catalysts has been investigated for hydrodesulfurization (HDS) of dibenzothiophene (DBT) and methyl-substituted DBT derivatives. The conversion over the TiO₂–Al₂O₃ supported Mo catalysts, in particular for the 4,6-dimethyl-DBT, is much higher than that obtained over Al₂O₃ supported Mo catalyst. The ratio of the corresponding cyclohexylbenzene (CHB)/biphenyl (BP) derivatives is increased over the Mo/TiO₂–Al₂O₃. This indicates that the prehydrogenation of an aromatic ring plays an important role in the HDS of DBT derivatives over TiO₂–Al₂O₃ supported catalysts.     

Deactivation patterns of Mo/Al2O3, Ni–Mo/Al2O3 and Ni–MoP/Al2O3 catalysts in atmospheric residue hydrodesulphurization

In the present work, a comparative study on the deactivation behavior of three types of industrial hydrotreating catalysts, namely, Mo/Al₂O₃, Ni–Mo/Al₂O₃ and Ni–MoP/Al₂O₃, that are used to promote primarily hydrodemetallization (HDM), hydrodesulphurization (HDS) and hydrodesulphurization + hydrodenitrogenation (HDS/HDN) reactions, respectively, in the first, second and third reactor of commercial atmospheric residue desulfurization (ARDS) units was carried out. The main objective of the study was to contribute to a better understanding of the relationship between catalyst type and catalyst deactivation patterns. The used catalysts from these experiments were fully characterized to determine the extent and the cause of deactivation. Special emphasis was paid to understanding the nature of the coke and metal deposition on the used catalysts by applying chemical analysis and various advanced analytical techniques, such as solid-state carbon-13 nuclear magnetic resonance spectroscopy (¹³C NMR), temperature-programmed oxidation (TPO), electron probe micro-analysis (EPMA), and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. The results are discussed scientifically based on the physico–chemical properties of the three catalysts.     

Alumina-supported cobalt-molybdenum catalyst for slurry phase Fischer–Tropsch synthesis

An evaluative investigation of the Fischer–Tropsch performance of two catalysts (20%Co/Al₂O₃ and 10%Co:10%Mo/Al₂O₃) has been carried out in a slurry reactor at 2 MPa and 220–260 °C. The addition of Mo to the Co-catalyst significantly increased the acid-site strength suggesting strong electron withdrawing character in the Co-Mo catalyst. Analysis of steady-state rate data however, indicates that the FT reaction proceeds via a similar mechanism on both catalysts (carbide mechanism with hydrogenation of surface precursors as the rate-determining step). Although chain growth, , on both catalysts were comparable (  0.6), stronger CH₂ adsorption on the Co-Mo catalyst and lower surface concentration of hydrogen adatoms as a result of increased acid-site strength was responsible for the lower individual hydrocarbons production rate compared to the Co catalyst. The activation energy, E, for Co (96.6 kJ mol⁻¹), is also smaller than the estimate for the Co-Mo catalyst (112 kJ mol⁻¹). Transient hydrocarbon rate profiles on each catalyst are indicative of first-order processes, however the associated surface time constants are higher for alkanes than alkenes on individual catalysts. Even so, for each homologous class, surface time constants for paraffins are greater for Co-Mo than Co, indicative that the adsorption of CH₂ species on the Co-Mo surface is stronger than on the monometallic Co catalyst.     

A model catalyst approach to the effects of the support on Co–Mo hydrodesulfurization catalysts

Co–Mo model sulfide catalysts, in which CoMoS phases are selectively formed, were prepared by means of a CVD technique using Co(CO)₃NO as a precursor of Co. It is shown by means of XPS, FTIR and NO adsorption that CoMoS phases form selectively when the Mo content exceeds monolayer loading. A single exposure of MoS₂/Al₂O₃ to a vapor of Co(CO)₃NO at room temperature fills the edge sites of the MoS₂ particles. It is suggested that the maximum potential HDS activity of MoS₂/Al₂O₃ and Co–Mo/Al₂O₃ catalysts can be predicted by means of Co(CO)₃NO as a “probe” molecule. An attempt was made to determine the fate of Co(CO)₃NO adsorbed on MoS₂/Al₂O₃. The effects of the support on Co–Mo sulfide catalysts in HDS and HYD were investigated by use of CVD-Co/MoS₂/support catalysts. XPS and NO adsorption showed that model catalysts can also be prepared for SiO₂-, TiO₂- and ZrO₂-supported catalysts by means of the CVD technique. The thiophene HDS activity of CVD-Co/MoS₂/Al₂O₃, CVD-Co/MoS₂/TiO₂ and CVD-Co/MoS₂/Al₂O₃ is proportional to the amount of Co species interacting with the edge sites of MoS₂ particles or CoMoS phases. It is concluded that the support does not influence the HDS reactivity of CoMoS phases supported on TiO₂, ZrO₂ and Al₂O₃. In contrast, CoMoS phases on SiO₂ show catalytic features characteristic of CoMoS Type II. With the hydrogenation of butadiene, on the other hand, the Co species on MoS₂/TiO₂, ZrO₂ and SiO₂ have the same activity, while the Co species on MoS₂/Al₂O₃ have a higher activity.     

Tailoring of alumina surfaces as supports for NiMo sulfide catalysts in the ultra deep hydrodesulfurization of gas oil: case study of TiO2-coated alumina prepared by chemical vapor deposition technique

The present paper gives a detailed review of the different studies under investigation in our laboratory concerning the use of TiO₂ and TiO₂–Al₂O₃ composites prepared by chemical vapor deposition (CVD) as support for sulfide catalysts in the HDS of dibenzothiophene (DBT) derivatives. The supports investigated here are: TiO₂ (from Degussa, 50 m²/g), Al₂O₃ (Nikki, 186 m²/g) and TiO₂–Al₂O₃ supports prepared by CVD of TiCl₄ on alumina. Using several characterization techniques, we have demonstrated that the support composite presents a high dispersion of TiO₂ over γ-Al₂O₃ without forming precipitates up to ca. 11 wt.% loading. Moreover, the textural properties of the support composite are comparable to those of alumina. XPS investigations of Mo and NiMo catalysts supported on the different carriers show that Mo-oxide species exhibit a higher degree of sulfidation on the surface of TiO₂ and TiO₂–Al₂O₃ than on alumina. The HDS tests of 4,6-DMDBT under mild operating conditions (573 K, 3 MPa) show that sulfide catalysts supported on the composite support (ca. 11 wt.%) are more active than those supported on to TiO₂ or Al₂O₃. This higher HDS catalytic activity is attributed to the promotion of the hydrodesulfurization pathway, whereby the pre-hydrogenation of one of the aromatic rings adjacent to the thiophenic one may reduce the steric hindrance caused by the two methyl groups adjacent to the sulfur atom during the C–S bond cleavage.     

Effect of phosphorus addition on the hydrotreating activity of NiMo/Al2O3 carbide catalyst

A series of phosphorus promoted γ-Al₂O₃ supported NiMo carbide catalysts with 0–4.5 wt.% P, 13 wt.% Mo and 2.5 wt.% Ni were synthesized and characterized by elemental analysis, pulsed CO chemisorption, BET surface area measurement, X-ray diffraction, near-edge X-ray absorption fine structure, DRIFT spectroscopy of CO adsorption and H₂ temperature programmed reduction. X-ray diffraction patterns and CO uptake showed the P addition to NiMo/γ-Al₂O₃ carbide, increased the dispersion of β-Mo₂C particles. DRIFT spectra of adsorbed CO revealed that P addition to NiMo/γ-Al₂O₃ carbide catalyst not only increases the dispersion of Ni-Mo carbide phase, but also changes the nature of surface active sites. The hydrodenitrogenation (HDN) and hydrodesulfurization (HDS) activities of these P promoted NiMo/γ-Al₂O₃ carbide catalysts were performed in trickle bed reactor using light gas oil (LGO) derived from Athabasca bitumen and model feed containing quinoline and dibenzothiophene at industrial conditions. The P added NiMo/γ-Al₂O₃ carbide catalysts showed enhanced HDN activity compared to the NiMo/γ-Al₂O₃ catalysts with both the feed stocks. The P had almost no influence on the HDS activity of NiMo/γ-Al₂O₃ carbide with LGO and dibenzothiophene. P addition to NiMo/γ-Al₂O₃ carbide accelerated CN bond breaking and thus increased the HDN activity.     

Hydrodesulfurization over supported monometallic, bimetallic and promoted carbide and nitride catalysts

The preparation of alumina-supported β-Mo₂C, MoC_1−x (x≈0.5), γ-Mo₂N, Co–Mo₂C, Ni₂Mo₃N, Co₃Mo₃N and Co₃Mo₃C catalysts is described and their hydrodesulfurization (HDS) catalytic properties are compared to conventional sulfide catalysts having similar metal loadings. Alumina-supported β-Mo₂C and γ-Mo₂N catalysts (Mo₂C/Al₂O₃ and Mo₂N/Al₂O₃, respectively) are significantly more active than sulfided MoO₃/Al₂O₃ catalysts, and X-ray diffraction, pulsed chemisorption and flow reactor studies of the Mo₂C/Al₂O₃ catalysts indicate that they exhibit strong resistance to deep sulfidation. A model is presented for the active surface of Mo₂C/Al₂O₃ and Mo₂N/Al₂O₃ catalysts in which a thin layer of sulfided Mo exposing a high density of sites forms at the surface of the alumina-supported β-Mo₂C and γ-Mo₂N particles under HDS conditions. Cobalt promoted catalysts, Co–Mo₂C/Al₂O₃, have been found to be substantially more active than conventional sulfided Co–MoO₃/Al₂O₃ catalysts, while requiring less Co to achieve optimal HDS activity than is observed for the sulfide catalysts. Alumina-supported bimetallic nitride and carbide catalysts (Ni₂Mo₃N/Al₂O₃, Co₃Mo₃N/Al₂O₃, Co₃Mo₃C/Al₂O₃), while significantly more active for thiophene HDS than unpromoted Mo nitride and carbide catalysts, are less active than conventional sulfided Ni–Mo and Co–Mo catalysts prepared from the same oxidic precursors.     

Hydrodesulfurization of dibenzothiophene over alumina-supported nickel molybdenum phosphide catalysts

The activity of nickel molybdenum phosphide catalysts was studied for the hydrodesulfurization of dibenzothiophene at 573 K and total pressure of 2.0 MPa. The Al₂O₃-supported NiMo phosphide catalysts were prepared by successive and simultaneous methods. The effect of the reduction temperature on the catalyst activity was also studied. The simultaneous preparation was determined to be the best method for the preparation of the active supported catalyst for dibenzothiophene HDS. The 623 K-reduced catalyst had the highest HDS rate of the catalysts. Nickel migrated from the inside to the surface during the reaction and promoted the HDS activity. The active species in the dibenzothiophene HDS and the oxidation states of Mo, Ni and P in the catalyst before and after reaction and of S after the reaction were studied on the basis of an XPS analysis.     

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.     

A study on the preparation of supported metal oxide catalysts using JRC-reference catalysts. I. Preparation of a molybdena–alumina catalyst. Part 4. Preparation parameters and impact index

The effects of the volume and pH of the impregnation solution and of the calcination conditions were examined on the physicochemical and catalytic properties of a 13 wt% MoO₃/Al₂O₃ extrudate catalyst. The Al₂O₃ support and drying procedures (static conditions without flowing air) were fixed in the preparations. In the present series of catalysts, the amount of crystalline MoO₃ was marginally small. It was found that the dispersion of Mo oxide species increased as the volume of the impregnation solution increased, gradually approaching a maximum value. The increase in pH (2–8) of the impregnation solution was found to reduce the dispersion of Mo oxide species. The Mo dispersion increased slightly for the impregnation catalysts as the calcination temperature increased (673–873 K), whereas it decreased for the equilibrium adsorption catalysts. The effects of the calcination atmosphere (with or without flowing air, or with flowing humid air) were very small on the dispersion of Mo oxide species under the present preparation conditions. On the other hand, the methanol oxidation activity of MoO₃/Al₂O₃ was sensitive to the preparation parameters examined here. It was demonstrated by means of EPMA and XPS that a considerable migration of Mo took place during the calcination.

In the present study on the preparation of a 13 wt% MoO₃/Al₂O₃ catalyst, an impact index is proposed to measure the magnitude of the effects of the respective parameter(s) on the physicochemical and catalytic properties. With the Mo dispersion, the effects of the preparation parameter decreased in the order, surface area of the support >> drying process > volume of the impregnation solution > pH, calcination temperature and atmosphere. The size of the impact index for the dispersion of Mo sulfide species is 70–75% of that for the Mo oxide species. The HDS activity of the catalyst was less affected by the preparation parameters than the Mo sulfide dispersion. The preparation parameters affected the segregation of Mo on the outer surface of extrudates in a decreasing order: drying process > volume of the impregnation solution > pH, calcination conditions. It was found that the oxidation of methanol was affected most intensely by the drying procedures. The volume of the impregnation solution, calcination conditions and pH of the impregnation solution also strongly affected the oxidation activity. The impact index suggests that the sensitivity to the preparation variables of the physicochemical and catalytic properties of MoO₃/Al₂O₃ decreases in the order, methanol oxidation activity > surface Mo segregation > Mo oxide dispersion > Mo sulfide dispersion > HDS activity.     

Accelerated deactivation of hydrotreating catalysts: comparison to long-term deactivation in a commercial plant

Accelerated deactivation tests of a laboratory prepared Co–Mo/Al₂O₃ catalyst were performed using three kinds of petroleum feedstocks. A high reaction temperature employed in the accelerated aging resulted in large amounts of carbonaceous deposition with high aromaticity, which were found to be the major deactivation cause. However, the effect of carbonaceous deposition during accelerated deactivation tests might have been overestimated compared with that during practical hydrotreating. When the catalysts were aged in a H₂S/H₂ stream without petroleum under the same reaction conditions, the crystal growth of MoS₂ layered structures was significant, but this rather resulted in an increase of both k (HDS) and k (HY). It was also suggested that the crystal growth during a commercial hydrotreating run was unlikely to be the major cause of catalyst deactivation.     

Catalytic oxidation of methane over hexaaluminates and hexaaluminate-supported Pd catalysts

An aqueous (NH₄)₂CO₃ coprecipitation method, based on that of Groppi et al. [Appl. Catal. A 104 (1993) 101–108] was used to synthesize Sr_1−xLa_xMnAl₁₁O₁₉₋ hexaaluminates. These materials were first synthesized by alkoxide hydrolysis. This synthesis route requires special handling of the starting materials and is not likely to be commercially practical. The materials prepared by (NH₄)₂CO₃ coprecipitation have similar surface areas as those prepared by the alkoxide hydrolysis method. Their CH₄ oxidation activity, measured as the temperature needed for 10% conversion of methane, is higher than those prepared by alkoxide hydrolysis. The La-substantiated material, LaMnAl₁₁O₁₉₋, shows high surface area with 19.3 m²/g after calcination at 1400°C for 2 h. It is active for CH₄ oxidation with T_10% at 450°C using 1% CH₄ in air and 70 000 cm³/h g space velocity. The stability and activity of LaMnAl₁₁O₁₉₋ prepared by (NH₄)₂CO₃ coprecipitation method is a simple and important step forward for the application of CH₄ catalytic combustion for gas turbines.     

钼酸铵与LaHY固相反应机理

采用TG-DSC技术研究了钼酸铵和LaHY在空气气氛中的失重行为,考察了钼酸铵与LaHY的固相反应机理,用XRD、BET和NH₃-TPD对其物相结构、比表面积和表面酸性进行了表征。结果表明,（NH₄）₆Mo₇O₂₄·4H₂O分解产生的表相Mo物种借助固相反应以金属-氧簇定位在LaHY分子筛体相笼中形成nMoO_x·LaHY单相复合体,引起分子筛的晶胞收缩,晶胞参数a₀减小,比表面积下降。制备的nMoO_x·LaHY较相应LaHY分子筛的弱酸中心变化较小,中强酸中心增加,强酸中心略有减少,总酸量增加。以质量分数为0.6%的二苯并噻吩/正癸烷溶液为模型反应物,评价了制备的nMoO_x·LaHY催化剂的加氢脱硫性能。负载Mo质量分数为5.0%制得的nMoO_x·LaHY催化剂在反应压力4.0 MPa,反应液时空速20 h^-1,H₂/原料液体积比500:1的实验条件下,290℃和310℃的二苯并噻吩加氢脱硫转化率达到了56.38%和88.79%,较相应负载Mo质量分数为20.0%制备的MoO₃/Al₂O₃催化剂分别提高了约12个百分点和28个百分点,表现出了较高的二苯并噻吩加氢脱硫反应活性。     

Reactivity of olefins in the hydrodesulfurization of FCC gasoline over CoMo sulfide catalyst

To achieve selective hydrodesulfurization (HDS) of fluid catalytic-cracked (FCC) gasoline for producing sulfur-free gasoline (S < 10 ppm), the reactivity of various olefins contained in FCC gasoline on CoMoP/Al₂O₃ sulfide catalysts was investigated. Isomerization of the CC double bond from the terminal position to an internal position was observed. The steric hindrance around the CC double bond suppresses the reactivity of olefin hydrogenation. The sulfidation temperature of the catalyst has a major influence on olefin hydrogenation active sites. Addition of the appropriate amount of cobalt (Co/Mo ratio approximately 0.6) contributes to the suppression of olefin hydrogenation at high reaction temperature (260 °C). From the comparison of catalytic performance and characterization of our CoMoP/Al₂O₃ catalyst with an analogous commercial catalyst, it is suggested that the hydrogenation of olefins depends not only on the state of the Mo CUS but also on the steric effects of both olefin structure and MoS₂ crystalline structure.