Nickel and cobalt promoted tungsten and molybdenum sulfide mesoporous catalysts for hydrodesulfurization

High-performance hydrodesulfurization (HDS) catalysts were prepared by incipient wetness impregnation of Ni-Mo(W) and Co-Mo(W) species over siliceous MCM-41 doped with zirconium. Catalysts with W and Mo loadings of 20 and 11 wt%, respectively, and with a Ni or Co loading of 5 wt%, were prepared. As a reference, a nickel-tungsten catalyst supported on a commercial γ-Al₂O₃ with a 5 and 20 wt% metal loadings, respectively has also been prepared. HDS reaction of dibenzothiophene (DBT) under 3.0 MPa of total pressure and with hourly space velocity (WHSV) of 28 h⁻¹ was used to evaluate the activity of these sulfided catalysts. All the catalysts displayed a very good performance in the temperature range of 300-340 °C, with conversions between 49.0% and 92.6%. The Ni promoted catalysts displayed better performances than those of Co promoted catalysts in the HDS of DBT. On the other hand they show different selectivity to hydrogenation, thus, in Ni promoted catalysts, the hydrogenation (HYD) reaction contributes more to the conversion of DBT than Co promoted catalysts where the direct desulfurization (DDS) reaction is more important. The performance of this set of catalysts is similar to that observed with a Ni5W20-Al₂O₃ catalyst in the same range of temperature (300-340 °C). However, the selectivity to the HYD product, CHB, observed with nickel promoted catalysts (Ni5-Mo11 and Ni5-W20) is higher than that found for Ni5W20-Al₂O₃ catalyst probably due to a higher superficial area of the MCM-support and to the presence on the surface of zirconium species, which leading to a better dispersion and lower stacking of the active phases.     

加氢脱硫催化剂载体的研究进展

综述了加氢脱硫催化剂载体的研究现状及其发展趋势,分别从单组分载体、复合氧化物载体、分子筛和改性载体4个方面论述了加氢脱硫催化剂载体各自的优缺点。单组分载体重点介绍了A12O3、TiO2、炭载体;复合氧化物载体主要对铝基、钛基二元复合氧化物以及三元复合氧化物载体进行了综述;并且对以MCM-41、SBA-15和KIT为代表的介孔分子筛做了介绍;还描述了近年来以改性MCM-41、SBA-15、活性炭为主要研究对象的改性的分子筛。最后指出改性载体尤其是改性分子筛将是未来研究的焦点。     

Synthesis of alumina-nitrogen-doped carbon support for CoMo catalysts in hydrodesulfurization process

More stringent environmental legislation imposes severe requirements to reduce the sulfur content in diesel to ultra-low levels with high efficient catalysts.In this paper,a series of CoMo/NDC@alumina cat-alysts were synthesized by combination of the chemical vapor deposition of nitrogen-doped carbon(NDC) using 1,10-phenanthroline and co-impregnation of Mo and Co active components.The optimal cat-alyst with additive of 25％ 1,10-phenanthroline was screened by a series of property characterization and the hydrodesulfrization (HDS) active test.The amount of "CoMoS" active phase of the optimal CoMo/C3 catalyst increased 5.3％ as compared with the CoMo/γ-Al2O3.The introduction of NDC improved the sul-fidation degree of Mo by 21.8％ as compared to the CoMo/γ-Al2O3 catalyst,which was beneficial to form more active sites.The HDS conversion of the NDC supported catalysts are higher than CoMo/γ-Al2O3 whether for the dibenzothiophene (DBT) or 4,6-dimethyl dibenzothiophene (4,6-DMDBT).Further hydroprocessing evaluation with Dagang diesel revealed that the CoMo/C3 catalyst possessed higher HDS property and the removal rate of DBTs in the diesel increased by 4％-11％ as compared to the CoMo/γ-Al2O3 catalyst.     

Preparation of CoMoS catalysts for hydrodesulfurization using methylacetoacetate as a chelating agent

CoMoS/Al₂O₃ catalyst, which was prepared using Co(MeAA)₂·2H₂O as a new Co precursor, showed activity for hydrodesulfurization (HDS) higher than that of conventional catalysts, which were prepared using Co(NO₃)·6H₂O as a Co precursor and/or by adding ethylene-di-amine-tetra-acetic acid (EDTA) as a chelating agent. Catalyst of a similar activity was also obtained simply by impregnating a conventional CoMo/Al₂O₃ catalyst with an aqueous solution of methylacetoacetate (MeAA) followed by drying and sulfidation. The added MeAA reacted with Co to produce Co(MeAA)₂·2H₂O on the catalyst surface during impregnation step, such that the resulting catalyst became similar to one prepared by direct impregnation with Co(MeAA)₂·2H₂O. The in-situ synthesis of Co(MeAA)₂·2H₂O on the catalyst surface was advantageous over the method of directly adding the Co precursor to the impregnation solution because the former method did not use a basic material, which was required for the synthesis of the Co precursor. Furthermore, MeAA was soluble in water, whereas Co(MeAA)₂·2H₂O had to be dissolved in an organic solvent, e.g., 1,4-dioxane. The Co species in the MeAA-added catalysts were sulfided at temperatures higher than those of conventional catalysts, and consequently the former catalysts contained greater amounts of the HDS-active CoMoS phase than the latter.     

Graphitic mesoporous carbon as a support of promoted Rh catalysts for hydrogenation of carbon monoxide to ethanol

Graphitic mesoporous carbon (GMC), prepared through high-temperature graphitization of soft-templated amorphous mesoporous carbon (AMC), was used as the support for Mn, Li, and Fe triple-promoted Rh catalysts for CO hydrogenation to ethanol. The use of GMC results in C₂H₅OH selectivity and formation rate comparable to nonporous SiO₂ support along with a significant inhibition on the formation of undesired CH₄ and light hydrocarbons at the expense of appreciable amounts of CO₂ produced. The better catalytic performance of promoted-Rh/GMC than those supported on other carbon allotropes (AMC and non-porous graphitic carbon black) seems to be associated with the specific graphitic structure and mesoporosity of GMC. The surface modification of GMC by wet oxidation leads to considerable increases in C₂H₅OH selectivity and formation rate. The modified GMC as a support shows substantially greater CO₂-free selectivity for C₂H₅OH than the SiO₂.     

Dispersion measurement of heteropoly acid supported on KIT-1 mesoporous material

Heteropoly acid (HPA) catalysts supported on KIT-1 mesoporous material were prepared with different loadings and characterized using XRD, UV–VIS and N₂ adsorption. Supported HPA was dispersed mainly on the inner surface of pores, resulting in the disappearance of XRD peaks. The diffraction peaks of HPA from the KIT-1 mesoporous material loaded with HPA of 41 wt% was very weak compared to those of physical mixtures of HPA and mesoporous material. The remaining adsorption amount of 1-butene on the supported HPA catalysts revealed the exposed amount of HPA molecules, which is useful in determining the HPA dispersion. HPA dispersion of supported HPA catalysts was useful to interpret their catalytic activity in the skeletal isomerization of 1-butene.     

Carbon as a support for catalysts—III glassy carbon as a support for iron

As described in the Hucke patent, glassy carbons containing not only open pores of molecular size but also pores in the transitional or macropore range can be produced from appropriate formulations. The formulation always consists of a carbon-yielding monomer, an organic to yield larger pores upon its removal once the monomer has been partially polymerized, and a polymerization catalyst. It may contain a dispersing agent, depending upon the size of the larger pores which is desired. In this study, furfuryl alcohol was the monomer. Great flexibility is shown to exist in the total surface areas of the carbons which can be produced, degree of carbon molecular sieving in the super micropores, and pore volume and pore size in the larger pores following polymerization and carbonization steps. Different ways of adding iron into the mix are explored which also can have pronounced effects on the nature of the porosity in the final carbons. Further modification is shown upon addition of potassium or boron into the mix. Carbons produced are expected to have potential as catalyst supports.     

Mixed oxides as a support for new CoMo catalysts

Interest in bifunctional catalysts, active in reactions such as hydrodesulphurisation (HDS) of hydrocarbon fractions, is growing in the last years. An improvement of CoMo/Al₂O₃ materials can be obtained by the introduction of other oxides during the sol–gel synthesis. This heavily affects the acid–base characteristics of the catalysts, while textural properties are less influenced. The catalytic performances change as well: a relationship between the density of acid sites and HDS activity has been found.     

煤焦油加氢脱硫催化剂的研究进展

随着石油资源的日趋减少,煤焦油加工技术受到关注。汽车尾气中含有的硫化物严重污染环境,如何高效脱除煤焦油中含硫化合物的硫原子是开发煤焦油加氢脱硫催化剂的研究重点。简述煤焦油中含硫化合物的分布状况及其特点,并分别从贵金属、非贵金属、过渡金属磷化物、氮化物、碳化物及金基双金属催化剂方面综述煤焦油加氢脱硫催化剂的研究现状,针对煤焦油中含硫组分复杂多样的特性,提出研发高效和高活性煤焦油加氢脱硫催化剂的新方向。     

以KIT-6为模板制备有序介孔氧化铈催化剂

为了制备介孔氧化铈,并研究其对CO的催化氧化活性,本文以介孔氧化硅(KIT-6)为模板,采用硬模板法制备了有序介孔氧化铈。利用X-射线衍射、透射电镜、氮气吸脱附、傅里叶红外光谱、拉曼光谱和X-射线荧光光谱等技术对介孔氧化铈催化剂的结构进行了表征,并考察了该催化剂催化氧化CO的性能。实验结果表明:所制备的催化剂为萤石结构的有序介孔氧化铈,平均孔径约为3.4 nm,比表面积高达123.9 m2/g,平均晶粒尺寸为8.2 nm,表面存在质量分数3.3%的氧化硅。介孔氧化铈对CO的催化氧化实验表明,CO转化率达到50%时的温度即t50为284℃,明显优于沉淀法制备的普通氧化铈的催化性能(t50为320℃)。     

Lewis acidic mesoporous Fe-TUD-1 as catalysts for synthesis of Hantzsch 1,4-dihydropyridine derivatives

Lewis acidic mesoporous material (TUD-1) containing Fe was investigated as stable and reusable catalyst for the synthesis of Hantzsch 1,4-dihydropyridine (DHP) derivatives. Yields between 76 and 91 % of DHP derivatives were obtained in shorter reaction times of 3 h depending on the nature of substituents in benzaldehyde.     

Cobalt oxide species supported on SBA-15, KIT-5 and KIT-6 mesoporous silicas for ethyl acetate total oxidation

Cobalt oxide modified SBA-15, KIT-5 and KIT-6 mesoporous silicas with different pore size/pore entrances have been synthesized by a conventional wet impregnation method using cobalt nitrate as the precursor. The modified materials were characterized by N₂-physisorption, XRD, TEM-EDX, XPS, FT-IR, UV–vis and TPR-TG with hydrogen. Their catalytic activities in total oxidation of ethyl acetate were evaluated. A good correlation was observed between the catalytic activity, and the presence of spinel-type Co₃O₄ in the materials. Supports with larger mesopores facilitated the formation of such easily reducible spinel particles. However, the interconnectivity of the mesopores and the uniformity of the channel dimensions also had an influence on the catalytic activity, implying that mass-transfer effects, especially in the case of supports with cage-like mesopores.     

焦炉煤气加氢脱硫催化剂器外预硫化

探讨了焦炉煤气加氢脱硫催化剂器外预硫化的方法,研究了硫化剂加入量以及预硫化浸渍温度、浸渍时间、浸渍压力等硫化条件对催化剂活性的影响,同时对预硫化催化剂的稳定性能进行考察。结果表明,以单质硫和有机多硫化物的混合物溶于馏分油中制成的混合硫化物作为硫化剂,在温度140℃和压力1. 0 MPa的条件下,将焦炉煤气加氢脱硫催化剂浸渍2 h所制备的器外预硫化型催化剂活性优于传统的器内预硫化的催化剂,且催化剂性能稳定。     

MFI zeolite as a support for automotive catalysts with reduced Pt sintering

The noble metals used as catalysts in automotive exhaust systems are subject to sintering at extreme temperatures, leading to deterioration of catalytic activity. Zeolite with the MFI (ZSM5) structure is examined as a support for Pt particulate catalysts. The MFI structure is composed of agglomerates of single-crystal zeolite with interstitial mesoporosity. Pt fixed within these mesopores is shown through high-temperature aging tests in air to be highly resistant to sintering due to the mechanical constraints on particle size imparted by the mesoporous structure. The deterioration of catalytic activity after aging is significantly lower than that for comparable γ-alumina supported catalyst.     

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.     

Miniemulsion polymers as solid support for transition metal catalysts

A pentadentate salen-type ligand was immobilized in a poly[(styrene)]-co-(butyl acrylate)] matrix by miniemulsion polymerization. The obtained polymer beads revealed a particle size of 50 nm in the dry state by transmission electron microscopy. Dynamic light scattering experiments in methanol and water showed a solvent-dependent average particle size with a mean particle diameter of up to 233 nm in methanol. These results provide valuable insights for the optimization of macromolecular oxidation catalysts and their future use as enzyme-like entities in aqueous media. The particle stability was demonstrated over a wide pH range (3-11) by gel permeation chromatography, and initial results for the metal ion binding ability were obtained.