磷添加方式对NiMo/Al2O3催化剂加氢脱硫性能的影响

采用分步浸渍法制备了不同磷添加方式改性的NiMo/Al₂O₃催化剂,在固定床微反装置上考察了该系列催化剂对焦炉煤气中噻吩加氢脱硫（HDS）性能的影响,采用BET、X射线衍射（XRD）、H₂程序升温还原（H₂-TPR）、NH₃程序升温脱附（NH₃-TPD）、C₄H₄S(H₂)程序升温脱附[C₄H₄S(H₂)-TPD]、X射线光电子能谱（XPS）、高清透射电镜（HRTEM）和拉曼（Raman）等分析手段对催化剂进行表征。结果表明,不同磷添加方式制备NiMo/Al₂O₃催化剂的HDS性能存在较大差异。其中,催化剂PNi-Mo/Al和PMo-Ni/Al表面弱吸附解离活性位增强,对焦炉煤气中噻吩有较好的低温加氢脱硫活性,以含292.5mg/m³噻吩的模拟焦炉煤气为原料时,PNi-Mo/Al在250℃下对噻吩的脱硫率达61%。对于PNi-Mo/Al和PMo-Ni/Al催化剂,先浸渍P、Ni或者P、Mo时,P优先和载体Al₂O₃作用,减弱了活性金属组分Ni、Mo与载体间的相互作用,而又防止Ni或者Mo与载体间相互作用过低而聚集,提高了Ni、Mo在载体表面的均匀分散,生成能够促进硫化形成Ⅱ型活性相Ni-Mo-S的NiMoO₄物种。NiMoO₄和MoO₃之间的协同作用提高了催化剂的硫化度,使HDS活性得以提高。     

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.     

一种新γ相氧化铝负载的铁铝双金属催化剂用于反向水煤气转化反应(英文)

In reverse water gas shift (RWGS) reaction CO₂ is converted to CO which in turn can be used to produce beneficial chemicals such as methanol. In the present study, Mo/Al₂O₃, Fe/Al₂O₃ and Fe-Mo/Al₂O₃ catalysts were synthesised using impregnation method. The structures of catalysts were studied using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) method, inductively coupled plasma atomic emission spectrometer (ICP-AES), temperature programmed reduction (H₂-TPR), CO chemisorption, energy dispersive X-ray (EDX) and scanning electron microscopy (SEM) techniques. Kinetic properties of all catalysts were investigated in a batch reactor for RWGS reaction. The results indicated that Mo existence in structure of Fe-Mo/Al₂O₃ catalyst enhances its activity as compared to Fe/Al₂O₃. This enhancement is probably due to better Fe dispersion and smaller particle size of Fe species. Stability test of Fe-Mo/Al₂O₃ catalyst was carried out in a fixed bed reactor and a high CO yield for 60 h of time on stream was demonstrated. Fe₂(MoO₄)₃ phase was found in the structures of fresh and used catalysts. TPR results also indicate that Fe₂(MoO₄)₃ phase has low reducibility, therefore the Fe₂(MoO₄)₃ phase signifificantly inhibits the reduction of the remaining Fe oxides in the catalyst, resulted in high stability of Fe-Mo/Al₂O₃ catalyst. Overall, this study introduces Fe-Mo/Al₂O₃ as a novel catalyst with high CO yield, almost no by-products and fairly stable for RWGS reaction.     

Supported MoO3 catalysts: preparation by the new “slurry impregnation” method and activity in hydrodesulphurization

A new preparation of supported MoO₃ is described. Slurry MoO₃/water is used instead of the solution (NH₄)₆Mo₇O₂₄. Preparation and HDS activity are illustrated for MoO₃ supported over Al₂O₃, active carbon and ZrO₂. Another application of the new principle is the preparation of high surface area MoO₃/MgO by the reaction of MgO with slurry (NH₄)₆Mo₇O₂₄/methanol. Texture of MgO that is deteriorated in aqueous solution of (NH₄)₆Mo₇O₂₄ is stable in that slurry. “Slurry impregnation” is a special case of equilibrium adsorption impregnation. It is simple and it provides monolayer dispersion of molybdena.     

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.     

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.     

Silica–alumina-supported transition metal sulphide catalysts for deep hydrodesulphurization

Deep hydrodesulphurization (HDS) of dibenzothiophene (DBT) and gas-oil has been carried out on amorphous-silica–alumina (ASA)-supported transition metal sulphides (TMS) under conditions which approach industrial practice. The activity and selectivity of the binary Ni-, Ru- and Pd-promoted Mo catalysts were compared with the monometallic ones (Ru, Ir, Pd, Ni, Mo on ASA). For both HDS of DBT and gas-oil, the observed activity trends were similar; thus, all catalysts were more active with model feed than with gas-oil, and less active than commercial CoMo/Al₂O₃. The binary catalysts showed larger activity than monometallic ones, with Ni–Mo catalyst being more effective than Ru–Mo or Pd–Mo. For Ni–Mo sample, the X-ray photoelectron and temperature-programmed reduction techniques confirmed that incorporation of Mo minimises metal–support interaction, although the formation of nickel hydrosilicate was not prevented. The consecutive impregnation of calcined Mo/ASA catalyst with precursor solution followed by calcination enhances molybdenum surface exposure in binary samples. As a consequence, the temperature of reduction of MoO₃ to molybdenum suboxides is decreased.     

CoMo/MgO–Al2O3 supported catalysts: An alternative approach to prepare HDS catalysts

Three different supports were prepared with distinct magnesia–alumina ratio x = MgO/(MgO + Al₂O₃) = 0.01, 0.1 and 0.5. Synthesized supports were impregnated with Co and Mo salts by the incipient wetness method along with 1,2-cyclohexanediamine-N,N,N′,N′-tetraacetic acid (CyDTA) as chelating agent. Catalysts were characterized by BET surface area, Raman spectroscopy, SEM-EDX and HRTEM (STEM) spectroscopy techniques. The catalysts were evaluated for the thiophene hydrodesulfurization reaction and its activity results are discussed in terms of using chelating agent during the preparation of catalyst. A comparison of the activity between uncalcined and calcined catalysts was made and a higher activity was obtained with calcined MgO–Al₂O₃ supported catalysts. Two different MgO containing calcined catalysts were tested at micro-plant with industrial feedstocks of heavy Maya crude oil. The effect of support composition was observed for hydrodesulfurization (HDS), hydrodemetallization (HDM), hydrodeasphaltenization (HDAs) and hydrodenitrogenation (HDN) reactions, which were reported at temperature of 380 °C, pressure of 7 MPa and space-velocity of 1.0 h⁻¹ during 204 h of time-on-stream (TOS).     

The role of molybdenum in Mo-doped V–Mg–O catalysts during the oxidative dehydrogenation of n-butane

A detailed study on the influence of the addition of molybdenum ions on the catalytic behaviour of a selective vanadium–magnesium mixed oxide catalyst in the oxidation of n-butane has been performed. The catalysts have been prepared by impregnation of a calcined V–Mg–O mixed oxides (23.8 wt% of V₂O₅) with an aqueous solution of ammonium heptamolybdate, and then calcined, and further characterised by several physico-chemical techniques, i.e. S_BET, XRD, FTIR, FT-Raman, XPS, H₂-TPR. MgMoO₄, in addition to Mg₃V₂O₈ and MgO, have been detected in all the Mo-doped samples. The incorporation of molybdenum modifies not only the number of V⁵⁺-species on the catalyst surface and the reducibility of selective sites but also the catalytic performance of V–Mg–O catalysts. The incorporation of MoO₃ favours a selectivity and a yield to oxydehydrogenation products (especially butadiene) higher than undoped sample. In this way, the best catalyst was obtained with a Mo-loading of 17.3 wt% of MoO₃ and a bulk Mo/V atomic ratio of 0.6. From the comparison between the catalytic properties and the catalyst characterisation of undoped and Mo-doped V–Mg–O catalysts, the nature of selective sites in the oxidative dehydrogenation of n-butane is also discussed.     

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.     

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.     

Ni and Mo interaction with Al-containing MCM-41 support and its effect on the catalytic behavior in DBT hydrodesulfurization

A series of Mo and NiMo catalysts supported on Al-containing MCM-41 was prepared and characterized by N₂ physisorption, XRD, ammonia TPD, temperature programmed reduction (TPR), UV-Vis diffuse reflectance spectroscopy (DRS) and ²⁷Al MAS-NMR. It was shown that the incorporation of Al atoms into the siliceous MCM-41 framework causes a deterioration of the textural characteristics and some loss in the periodicity of the MCM-41 pore structure. However, the acidity of the Al-containing MCM-41 is substantially higher. The dispersion of Mo and Ni oxidic species increases with the incorporation of aluminum in the MCM-41 support due to the strong interaction of Mo and Ni oxidic species with aluminum atoms of the support. However, the strong interaction of metal species with the Al-containing MCM-41 supports, up to the formation of Al₂(MoO₄)₃ in the case of unpromoted Mo catalysts, produces an increase in the proportion of Ni and Mo species difficult to reduce. When Ni and Mo are impregnated simultaneously the formation of Al₂(MoO₄)₃ is prevented because of the competitive interaction of both, Ni and Mo species, with Al atoms of the support. For both, Mo and NiMo catalysts, maximum catalytic activity in dibenzothiophene (DBT) hydrodesulfurization is observed for the catalysts supported on Al-MCM-41 with SiO₂/Al₂O₃ molar ratio of 30. When Al-containing MCM-41 is used as a support for NiMo catalyst, some cracking of the main reaction products (biphenyl (BiP), cyclohexylbenzene (CHB) and dicyclohexyl (DCH)) is observed.     

Selective catalytic hydrogenation of naphthalene to tetralin over a NiMo/Al2O3 catalyst

The selective catalytic hydrogenation of naphthalene to high-value tetralin was systematically investigated. A series of Al₂O₃ catalysts containing different active metals (Co, Mo, Ni, W) were prepared by incipient wetness impregnation. The effects of different active metals forms (oxidation, reduction, sulfuration) and reaction conditions on naphthalene hydrogenation were investigated and the catalysts were characterized by XRD, XPS, BET, NH₃- TPD and SEM. Especially, Ni-Mo/Al₂O₃ was first used in this reactive system. The results show that the oxidative 4%NiO-20%MoO₃/Al₂O₃ is the best catalyst for the preparation of tetralin. The conversion of naphthalene and the selectivity of tetralin can reach 95.62% and 99.75% respectively at 200 ℃, 8 h and 6 MPa. Compared with reduced and sulfureted 4%NiO-20%MoO₃/Al₂O₃ catalysts, oxidative 4%NiO-20%MoO₃/Al₂O₃ has a well dispersed and uniform monolayer of the active metals, larger pore volume and size, and larger total acidity. NiO-MoO₃/Al₂O₃ has a synergistic effect between NiO activity and MoO₃ selectivity.     

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.     

A comparative study of supported MoO3 catalysts prepared by the new “slurry” impregnation method and by the conventional method: their activity in transesterification of dimethyl oxalate and phenol

A new preparation method for supported MoO₃ catalyst, slurry impregnation, has been described and compared with the conventional impregnation method. Slurry MoO₃/water is used instead of the solution ammonium heptamolybdate, AHM [(NH₄)₆Mo₇O₂₄]. The MoO₃/γ-alumina, MoO₃/active carbon, and MoO₃/silica catalysts with different Mo loadings were prepared by slurry and by conventional method. The low solubility of MoO₃ was sufficient to transport molybdenum species from solid MoO₃ to the adsorbed phase. The equilibrium was achieved after several hours at 95 °C based on the loading amount of molybdenum. Only the process of drying was needed; calcination was not necessary and was left out. This is an important advantage for active carbon support because oxidative degradation of active carbon impregnated by molybdena starts at a relatively low temperature of about 250 °C during calcination on air. The activity was tested in the transesterification of dimethyl oxalate (DMO) and phenol at 180 °C. The dependences of catalytic activity on Mo loadings for the slurry prepared catalysts were similar to the dependences for the samples prepared by the conventional impregnation method with AHM. The activities of the slurry impregnation MoO₃/γ-Al₂O₃ catalysts were almost the same as those of catalysts prepared conventionally. Although the performances of slurry impregnation MoO₃/SiO₂ catalysts for transesterification of DMO were slightly better than those of the corresponding catalysts prepared by conventional impregnation, no waste solution and no calcining nitrogenous gases were produced. Therefore, we conclude that the new slurry impregnation method for preparation of supported molybdenum catalysts is an environmentally friendly process and a simple, clean alternative to the conventional preparation using solutions of (NH₄)₆Mo₇O₂₄. The present work will lead to a remarkable improvement in the catalyst preparation for the transesterification reaction.     

Effects of small MoO3 additions on the properties of nickel catalysts for the steam reforming of hydrocarbons III. Reduction of Ni-Mo/Al2O3 catalysts

Ni/Al₂O₃ catalyst modified by small amounts of Mo show unusual properties in the steam reforming of hydrocarbons. There are no data about the effect of small amounts of molybdenum on reduction of the Ni-Mo supported catalysts. The properties of these very complex systems depend on the conditions of successive preparation stages (calcination, reduction) or the process conditions.

A series of Ni/Al₂O₃ catalysts modified by Mo were prepared in order to investigate the influence of promoter amounts and preparation sequence on their properties. Temperature programmed reduction (TPR) has been employed to study the reducibility of Ni-Mo/Al₂O₃ catalysts. Catalysts were further characterized by BET area, H₂ chemisorption and X-ray diffraction measurements.

The TPR curves of Ni-Mo/Al₂O₃ catalysts are very complex. Mo addition leads to the decrease of catalysts reducibility. However, complete reduction of NiO and MoO₃ can be achieved at 800 °C. The reduction course depends on the sequence of nickel and molybdenum addition into the support. Precise measurements of Ni peaks positions in the XRD pattern of Ni/Al₂O₃ and Ni-Mo/Al₂O₃ samples show the possibility of Ni-Mo solid solution formation.     

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.     

Effect of a promoter on the methanation activity of a Mo-based sulfur-resistant catalyst

The effect of adding Co, Ni or La on the methanation activity of a Mo-based sulfur-resistant catalyst was investigated. As promoters, Co, Ni and La all improved the methanation activity of a 15% MoO₃/Al₂O₃ catalyst but to different extents. Similar improvements were also found when Co, Ni or La was added to a 15% MoO₃/25%-CeO₂-Al₂O₃ catalyst. The promotion effects of Co and Ni were better than that of La. However, the catalytic methanation activity deteriorated the most with time for the Ni-promoted catalyst. The used catalysts were analyzed by nitrogen adsorption measurement, X-ray diffraction and X-ray photoelectron spectroscopy.     

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.     

HDS and HDN activity of molybdenum and nickel–molybdenum catalysts supported on alumina–titania carriers

Alumina–titania supports containing 5–50 wt.% of TiO₂ were prepared by coprecipitation method using inorganic precursors (sodium aluminate and titanium chloride). DTA-TGA, XRD, SEM, TPD_NH3, and IR spectroscopy were used to characterise these materials. The study shows that the promoting effect of nickel on the HDS activity of molybdenum catalysts supported on Al₂O₃TiO₂ is significantly lower than that for molybdenum catalyst supported on Al₂O₃, and depends on the TiO₂ content. The SEM results show that in the case of rich Al support (20 wt.% of TiO₂) molybdenum was aggregated on the external surface of the catalyst, whereas it was uniformly dispersed on the external surface of alumina. Results also show that molybdenum is preferably supported on aluminum oxide. Application of Al₂O₃TiO₂ oxides enhances the HDN activity of nickel–molybdenum catalysts. The highest HDN efficiency was obtained for the NiMo/Al₂O₃TiO₂ catalyst containing 50 wt.% of TiO₂. HDN activity was found to depend on protonic acidity and anatase content.