Preparation, characterization, and catalytic activity of CoMo/gamma-Al2O3 catalysts prepared by equilibrium deposition filtration and conventional impregnation techniques

A CoMo/gamma-Al(2)O(3) catalyst, prepared by depositing on the Al(2)O(3) carrier first the Mo species via equilibrium deposition filtration (EDF) and then the Co species by dry impregnation, was compared to three CoMo/gamma-Al(2)O(3) samples prepared using various conventional impregnation methods. All samples had the same composition, corresponding to an atomic ratio Co/(Co+Mo) equal to 0.3. The above samples were characterized using various physicochemical techniques (AAS, BET, DRS, LRS, XPS, TPR, and NO chemisorption), and their catalytic activity was determined using the hydrodesulfurization (HDS) of thiophene as a probe reaction. The EDF-prepared catalyst was about 30-43% more active in HDS than those prepared with the conventional impregnation techniques at all reaction temperatures studied. In contrast, the EDF catalyst exhibited the lowest hydrogenation activity. The higher HDS activity of the EDF sample is attributed to the higher number of active HDS sites formed on its surface. It is concluded that the increased number of active sites is due to the fact that the deposition of the Mo species by EDF results to a higher coverage of the support surface by supported molybdenum phase, which in turn, inhibits the formation of the catalytically inactive CoAl(2)O(4) and favors the dispersion of octahedral cobalt on its surface.     

Unsupported Molybdenum and Cobalt-Molybdenum Nitrides for Thiophene Hydrodesulfurization

The catalytic activity and the structure of unsupported Mo and CoMo nitrided catalysts were investigated. It was found that the structure and catalytic activity of the nitrided catalysts are influenced by the conditions of nitridation. Molybdenum oxynitrides are more active in hydrodesulfurization (HDS) of thiophene than MoS₂. The addition of cobalt to nitrided Mo improves its HDS activity, however, sulfided CoMo catalyst is still more active than the nitrided one. Synergy between Co and Mo for the nitrided unsupported CoMo catalyst exists at lower degree than for the sulfided form of CoMo.     

Development of Highly Active Co(Ni)Mo Catalysts for the Hydrodesulfurization of Dibenzothiophene Compounds

Co- or Ni-promoted Mo sulfide catalysts were prepared by combining three methods, sonochemical synthesis of Mo sulfides, promoter addition by chemical vapor deposition (CVD), and fluorination of alumina support, to improve their performance in the hydrodesulfurization (HDS) process. Sonochemically synthesized Mo sulfides exhibited higher HDS activity, particularly for the hydrogenation (HYD) of dibenzothiophene (DBT) compounds, than in the case of the catalysts prepared by impregnation due to the improved dispersion of the Mo species. The addition of Co or Ni to the catalyst by a CVD method allowed the selective decoration of the Mo-sulfide surface with the promoter and accordingly produced greater amounts of the Co–Mo–S and Ni–Mo–S phases, which are known to be active sites for HDS. The performance of catalysts prepared by combining sonochemical and CVD methods was further improved by the addition of fluorine, which generated Brönsted acid sites that were responsible for the HYD route and also for the migration of methyl groups in 4,6-dimethyldibenzothiophene (4,6-DMDBT).     

Increased promotion by deposition of Co acetylacetonate over sulphided Mo/TiO2 hydrodesulphurization catalyst

CoMo/TiO₂ catalysts prepared by deposition of Co acetylacetonate on presulphided Mo/TiO₂ catalyst in methanol exhibited higher promotion of hydrodesulphurization activity than catalysts prepared by conventional impregnation of Mo/TiO₂ by a solution of Co nitrate.     

CO吸附原位红外光谱结合分子模拟计算研究FCC汽油加氢脱硫催化剂的选择性

以脱硫选择性不同的2组催化裂化汽油加氢脱硫催化剂为研究对象, 采用CO吸附原位红外光谱表征了2组催化剂的活性相特征, 并通过分子模拟计算方法比较了助剂Co加入前后噻吩和1-己烯在催化剂表面的电荷分布、吸附能及其加氢反应的活化能等, 探讨了助剂Co的加入对选择性加氢脱硫催化剂脱硫选择性的作用机理. 结果表明, 加氢脱硫催化剂CoMoS活性相的增加有利于提高催化剂的加氢脱硫/加氢降烯烃(HDS/HYD)选择性. 与1-己烯加氢位相比, Co的加入显著提高了噻吩分子加氢位的缺电子性, 噻吩在催化剂表面的吸附度增强, 显著降低噻吩加氢反应的能垒, 从而使噻吩加氢反应更易进行. 这也表明CoMoS为高HDS活性、高HDS/HYD选择性的活性相.     

β-Mo2N0.78/γ-Al2O3催化剂的制备及其噻吩加氢脱硫活性的研究

以γ-Al2O3为载体，钼酸铵为氧化钼前驱体，采用在N2-H2气氛下的程序升温还原氮化反应，制备β-Mo2N0.78/γ-Al2O3催化剂，以噻吩为模型化合物，考察了该催化剂的加氢脱硫反应性能，以及反应温度、氢还原预处理和钴、镍助剂的引入等因素对催化剂活性的影响。结果表明，在320 ℃～400 ℃之间，随着反应温度的升高，催化剂的活性逐渐增加；预还原则降低了催化剂的活性；添加钴、镍均在一定负载量范围内可以改善β-Mo2N0.78/γ-Al2O3催化剂的加氢脱硫活性，但镍对催化剂活性的影响要小于钴。     

Effect of cobalt and its adding sequence on the catalytic performance of MoO3/Al2O3 toward sulfur-resistant methanation

The effect of promoter cobalt and the sequences of adding cobalt and molybdenum precursors on the performance of sulfur-resistant methanation were investigated. All these samples were prepared by impregnation method and characterized by N₂-adsorption, X-ray diffraction (XRD), temperature-programmed reduction (TPR) and laser Raman spectroscopy (LRS). The conversions of CO for Mo-Co/Al, Co-Mo/Al and CoMo/Al catalysts were 59.7%, 54.3% and 53.9%, respectively. Among these catalysts, the Mo-Co/Al catalyst prepared stepwisely by impregnating Mo precursor firstly showed the best catalytic performance. Meanwhile, the conversions of CO were 48.9% for Mo/Al catalyst and 10.5% for Co/Al catalyst. The addition of cobalt species could improve the catalytic activity of Mo/Al catalyst. The N₂-adsorption results showed that Co-Mo/Al catalyst had the smallest specific surface area among these catalysts. CoMoO₄ species in CoMo/Al catalyst were detected with XRD, TPR and LRS. Moreover, crystal MoS₂ which was reported to be less active than amorphous MoS₂ was found in both Co-Mo/Al and CoMo/Al catalysts. Mo-Co/Al catalyst showed the best catalytic performance as it had an appropriate surface structure, i.e., no crystal MoS₂ and very little CoMoO₄ species.     

Highly active CoMo HDS catalyst for the production of clean diesel fuels

HY–Al₂O₃-supported CoMo catalysts with a chelating agent and phosphorus for the hydrodesulfurization (HDS) of diesel fractions were prepared. The activity measurements with the prepared catalysts were carried out with straight-run light gas oil feedstocks in a pilot plant under industrial hydrotreating conditions. As a result, Cosmo Oil Co., Ltd. developed a new CoMoP/HY–Al₂O₃ catalyst, C-606A, which had three times higher HDS activity than the conventional CoMoP/Al₂O₃ catalyst. Commercial operations to produce ultra-low sulfur diesel (ULSD) with C-606A have successfully demonstrated its high performance and high stability. This catalyst has an extremely high activity, which enables to achieve <10-ppm sulfur in products in diesel hydrotreater designed to produce 500-ppm sulfur diesel fuels. Mo K-edge EXAFS, TEM and FT-IR of adsorbed NO were performed to investigate the nature of the active sites on the developed catalysts. The results showed that the new catalyst has multiple layers of MoS₂ slabs and the edges of MoS₂ are mainly occupied by Co–Mo–S phases. XPS and FT-IR were used to investigate the sulfiding behavior of Co and Mo in the formation process of the active sites during sulfidation. The results showed that addition of carboxylic acid to the impregnation solution postponed the sulfidation of Co at low temperatures, thereby increasing formation of the Co–Mo–S phase.     

镍钼杂多酸制备NiMo/γ-Al2O3催化剂及硼、钴或镍改性氧化铝的影响（英文）

A hydrotreating NiMo/γ-Al2O3 catalyst(12 wt% Mo and 1.1 wt% Ni) was prepared by impregnation of the support with the Anderson-type heteropolyoxomolybdate(NH4)4Ni(OH)6Mo6O18.Before impregnation of the support,it was modified with an aqueous solution of H3BO3,Co(NO3)2,or Ni(NO3)2.The catalysts were investigated using N2 adsorption,O2 chemisorption,X-ray diffraction,UV-Vis spectroscopy,Fourier transform infrared spectroscopy,temperature-programmed reduction,temperature-programmed desorption,and X-ray photoelectron spectroscopy.The addition of Co,Ni,or B influenced the Al2O3 phase composition and gave increased catalytic activity for 1-benzothiophene hydrodesulfurization(HDS).X-ray photoelectron spectroscopy confirmed that the prior loading of Ni,Co or B increased the degree of sulfidation of the NiMo/γ-Al2O3 catalysts.The highest HDS activity was observed with the NiMo/γ-Al2O3 catalyst with prior loaded Ni.     

XPS Characterization of Carbon Nanotube Supported CoMo Hydrodesulfurization Catalysts

In this paper, the effect of catalytic support and sulfiding method on the chemical state of supported Co-Mo catalysts is studied by XPS. After sulfidation with in-situ method, the majority of molybdenum in CNT supported CoMo catalyst is transferred to a species with a formal chemical state Mo(Ⅳ) in MoS2 phase, and the rest to Mo(Ⅴ) which consists of Mo coordinated both to O and S, such as MoO2S2^2- and MoO3S^2-. In case of CoMo/γ-Al2O3 catalyst sulfided with in-situ method, a fraction of molybdenum is transferred to formal state Mo(Ⅳ) in the form of MoS2, but there is still a mount of unreduced Mo(VI) phase which is difficult to be sulfided. In CoMo/CNT catalyric system sulfided with ex-situ method, Mo(IV) in the form of MoS2 is detected along with a portion of unreduced Mo(VI) phase, suggesting that not all the Mo phases are reduced and sulfided by ex-situ method. As for CoMo/γ-Al2O3, a portion of molybdenum is sulfided to intermediate reduced state Mo(V) which consists of Mo coordinated both to O and S, such as MoO2S2^2- and MoO3S^2-, in addition, there is still a fraction of unreduced Mo(Ⅵ)phase. XPS analyses results suggest that CNT support facilitates the reduction and sulfidation of active species to a large extent, and that alumina support strongly interacts with active species, hereby producing a fraction of phase which resists complete sulfiding. Catalytic measurements of catalysts in the HDS of dibenzothiophene (DBT) show that CoMo/CNT catalysts are of higher HDS activity and selectivity than CoMo/γ-Al2O3 catalyst, which is in good relation with the sulfiding behavior of the corresponding catalyst.     

Approach to the prediction of some surface characteristics of carbon-supported CoMo- catalysts from the adsorption/desorption technique

Carbon-supported CoMo- catalyst samples have been prepared through the impregnation (in solution) method using two different Co/Mo loads of 2/10 and 4/20 wt%. The catalytic activities of these catalysts for hydrodesulfurization of dibenzothiophene at 2.9 MPa H(2) and 340 degrees C have been investigated and measured in a sampler microautoclave reactor. Adsorption of dibenzothiophene from decane solution over both carbon and catalysts was studied. The consecutive desorption of adsorbates was followed by the thermal gravimetric technique. Pore volumes and surface areas of carbon and catalysts based on dibenzothiophene desorption data have been estimated. Catalysts exhibit almost the same hydrodesulfurization activity. CoMo catalyst of 4/20 wt% load is speculated to have a tendency to form clusters larger than 2/10 catalyst ratio. Models for catalyst dispersion and agglomeration are suggested.     

Comparing the hydrodesulfurization reaction of thiophene on γ-Al2O3 supported CoMo, NiMo and NiW sulfide catalysts

The thiophene hydrodesulfurization (HDS) reaction on γ-Al₂O₃ supported CoMo, NiMo and NiW sulfide catalysts was compared in order to gain insight into the promoter effect on direct desulfurization (DDS) and hydrogenation (HYD) pathways. Ni-promoted Mo (or W) sulfide catalysts favor the hydrogen transfer reactions relative to CoMo sulfide catalyst, which facilitates the direct route instead. This different performance and also the dependence of the apparent Arrhenius parameters with the catalyst formulation were attributed to the major participation of Mo (or W) edge for the Ni-containing catalysts and S edge for CoMo sulfide catalyst upon the thiophene-HDS reaction.     

MCM-41分子筛负载钼钴系催化剂的噻吩HDS研究

通过氧吸附量、噻吩吸附热及反应速率常数的测定，研究了MoO3/MCM-41、MoO3-CoO(NiO)/MCM-41系列催化剂，发现，对于MoO3/MCM-41催化剂，当MoO3的质量分数（以MCM－41为底数，即MCM－41＝1g时，MoO3含量为0．15g，下同）从15％增加到20％时，其噻吩的加氢硫（HDS）活性增大，至25％时活性下降，所对应的氧吸附量（mL/g催化剂）也是先增大后减少，并且两者有很好的线性对应关系，而且噻吩吸附热则基本保持不变，采用不同的MoO3-CoO(NiO)浸渍顺序制备的MoO3-CoO(NiO)/MCM-41催化剂中，先浸渍CoO(NiO）再浸渍MoO3的催化剂，其噻吩HDS活性明显优于对其它浸渍顺序制备的催化剂，同时催化剂的氧吸附量和噻吩吸附热也最大。     

Kinetics of thiophene hydrodesulfurization over a supported Mo–Co–Ni catalyst

In this study, the kinetics of thiophene (TH) hydrodesulfurization (HDS) over the Mo–Co–Ni-supported catalyst was investigated. Trimetallic catalyst was synthesized by pore volume impregnation and the metal loadings were 11.5 wt % Mo, 2 wt % Co, and 2 wt % Ni. A large surface area of 243 m²/g and a relatively large pore volume of 0.34 cm³/g for the fresh Mo–Co–Ni-supported catalyst indicate a good accessibility to the catalytic centers for the HDS reaction. The acid strength distribution of the fresh and spent catalysts, as well as for the support, was determined by thermal desorption of diethylamine (DEA) with increase in temperature from 20 to 600 °C. The weak acid centers are obtained within a temperature range between 160 and 300 °C, followed by medium acid sites up to 440 °C. The strong acid centers are revealed above 440 °C. We found a higher content of weak acid centers for fresh and spent catalysts as well as alumina as compared to medium and strong acid sites. The catalyst stability in terms of conversion as a function of time on stream in a fixed bed flow reactor was examined and almost no loss in the catalyst activity was observed. Consequently, this fact demonstrated superior activity of the Mo–Co–Ni-based catalyst for TH HDS. The activity tests by varying the temperature from 200 to 275 °C and pressure from 30 to 60 bar with various space velocities of 1–4 h^?1 were investigated. A Langmuir–Hinshelwood model was used to analyze the kinetic data and to derive activation energy and adsorption parameters for TH HDS. The effect of temperature, pressure, and liquid hourly space velocity on the TH HDS activity was studied.     

配合物的配位基团性质对CoMo/γ-Al_2O_3催化剂加氢脱硫性能的影响

选择四种不同配位基团的双齿配位分子乙二胺(EN)、乙醇胺(EA)、乙二醇(EG)和丙二酸(MA)对CoMo/γ-Al_2O_3催化剂改性,比较了它们对二苯并噻吩HDS性能的影响。结果表明,其活性顺序为CoMo(EN)CoMo(EA)CoMo(EG)≈CoMo(MA)CoMo,反应以直接脱硫路径为主,随反应温度升高,加氢路径的占比增加,加入配合物后可以促进加氢路径脱硫,CoMo(EN)催化剂具有最高的加氢活性。采用UV-vis、EA、XPS和HRTEM等手段对催化剂进行表征,结果表明,-NH_2与Co~(2+)有强络合作用,-COOH主要是静电作用,而-OH与钴离子没有相互作用。配位基团和Co~(2+)的相互作用,与HDS活性直接相关。配合物与Co~(2+)的结合可以有效生成Co-Mo-S活性相,且配合物碳化减弱载体与活性相的相互作用,有利于生成有更高本征活性的II型活性相。     

WP/γ-Al2O3催化剂负载方式对噻吩加氢脱硫性能的影响

以γ-Al2O3为载体，分别采用机械混合法、共浸渍法、分步浸渍法和程序升温、高纯氢气还原无定型磷钨酸盐的方法，制备了活性组分为磷化钨，负载量为20%的WP/γ-Al2O3催化剂。考察了不同方法制备的催化剂对噻吩加氢脱硫（HDS）反应的催化活性。结果表明：不同负载方式对催化剂结构有一定影响，对噻吩加氢脱硫性能的影响在低温时较明显。采用机械混合方式，先混合后还原方法制备的催化剂其HDS活性比先还原后混合方法制备的催化剂高；采用共浸渍和分步浸渍方式，通过焙烧所形成的催化剂其HDS活性分别比不经焙烧所形成的催化剂高或接近；浸渍焙烧所形成的催化剂其HDS活性远远高于机械混合法制备的催化剂。     

Study of Carbon Nanotube Supported Co-Mo Selective Hydrodesulphurization Catalysts for Fluid Catalytic Cracking Gasoline

In this paper, carbon nanotube supported Co-Mo catalysts for selective hydrodesulphurization （HDS） of fluid catalytic cracking （FCC） gasoline were studied, using di-isobutylene, cyclohexene, 1-octene and thiophene as model compounds to simulate FCC gasoline. The results show that the Co-Mo/CNT has very high HDS activity and HDS/hydrogenation selectivity comparing with the Co-Mo/γ-Al2O3 and Co-Mo/AC catalyst systems. The saturation ratio of cyclohexene was lower than 50%, and the saturation ratio of 1,3-di-isobutylene lower than 60% for the Co-Mo/CNT catalysts. Co/Mo atomic ratio was found to be one of the most important key factors in influencing the hydrogenation selectivity and HDS activity, and the most suitable Co/Mo atomic ratio was 0.4. Co/CNT and Mo/CNT mono-metallic catalysts showed lower HDS activity and selectivity than the Co-Mo/CNT bi-metallic catalysts.     

Genesis and activity of mo-based hydrotreating catalysts prepared by a sol-gel method

Molybdenum oxide-alumina catalysts used in hydrodesulfurization (HDS) with a wide range of Mo loadings (1–25% Mo) were prepared by the sol-gel process. Two different methods of adding the molybdenum oxide precursor to the support were used.In the first route, alumina is prepared by hydrolysis of aluminium tri sec-butylate in butanol and butanediol, and molybdenum is deposited by a classical dry impregnation with ammonium heptamolybdate (AHM). In the second route, the molybdenum oxospecies are dispersed in butanediol and added to the aluminium alkoxide before hydrolysis. The solids were calcined to obtain the oxide precursors which are then sulfided to give the active phase in hydrodesulfurization.The effect of preparation on the structural properties of alumina as well as on the state and dispersion of molybdenum in the dried, calcined and sulfided form was studied by various characterization techniques (XRD, XPS, Raman spectroscopy). Molybdenum appears to be present as well dispersed oxomolybdenum species in the oxide form even at high loadings. This good dispersion of molybdenum is preserved after sulfidation which induces the formation of MoS₂ crystallites whose morphology has been determined by HREM.The catalyst activities were evaluated in thiophene hydrodesulfurization and compared with that of catalysts prepared by dry impregnation of a commercial alumina. The observed performances are in agreement with the good dispersion of molybdenum at high loadings we were able to obtain owing to the sol-gel process.     

Improvement of HDS catalysts through the modification of the oxidic precursor with 1,5-pentanediol: Gas phase sulfidation and thiophene conversion

The performance, in thiophene HDS, of a CoMo/Al₂O₃ catalyst was successfully improved through chemical modification of its oxidic precursor by impregnation with 1,5-pentanediol solution. The gas phase activation with a H₂/H₂S mixture was followed by thermogravimetric analysis coupled with a rapid chromatograph; the catalysts were characterized at different steps of the activation using X-ray photoelectron spectroscopy (XPS). It appeared that the addition of the organic agent retards the sulfidation of the supported metals, leading to a simultaneous sulfidation of Co and Mo atoms. This induces the formation of smaller MoS₂ slabs and thus an increase in the number of active CoMoS sites, directly correlated with the better HDS performance of the modified solid. The role of 1,5-pentanediol is likely to inhibit, at low temperature, the adsorption of H₂S on the solid and thus the sulfidation of the supported metals.     

硫代硫酸铵预硫化的Mo/AC催化剂加氢脱硫性能的研究

采用等体积浸渍法将硫代硫酸铵(ATS)负载在Mo/AC催化剂上,制备了器外预硫化的Mo/AC-ATS催化剂;以噻吩加氢脱硫(HDS)为探针反应,考察了活化温度和活化时间对预硫化催化剂加氢脱硫活性的影响。研究发现,300 ℃下活化0.5 h所得到的预硫化催化剂具有最好的加氢脱硫活性。与传统硫化剂CS₂和DMDS硫化的催化剂相比,采用Mo/AC-ATS催化剂,在最佳活化条件下,噻吩转化率分别提高了34%和42%。XPS、TPR-MS和TEM等表征结果显示,预硫化的Mo/AC-ATS催化剂中Mo⁴⁺含量较高,这是其具有较高加氢脱硫活性的主要原因。