Effect of pore size on bitumen hydrocracking over Al2O3-AlPO4 supported Ni-Mo catalysts

A study of co-precipitated aluminum oxide-aluminum phosphate (AAP) materials as supports of Ni-Mo heavy oil upgrading catalysts has been completed. Results of both short duration (8 h) and longer duration (up to 200 h) experiments at conditions relevant to the commercial H-Oil process are reported and compared with a commercial NiMo/Al₂O₃ catalyst. The initial activity of the Ni-Mo/AAP catalysts correlates with the catalyst average pore diameter which is determined by the P content of the AAP support. An optimum pore diameter of about 20 run exists for HDM whereas for HDS a pore diameter < 10 nm is desirable. After 100 h operation the HDM conversion of the best Ni-Mo/AAP catalyst was approximately 10 percentage points greater than for the commercial catalyst. The HDS and CCR conversions were comparable over the two catalysts. The difference in performance between the catalysts is attributed primarily to the smaller pore size of the Al₂O₃ support compared to the AAP support. The amount of coke deposited on the Ni-Mo/AAP catalyst was less than that on the commercial catalyst, presumably due to differences in pitch conversion levels.     

乙烯环氧化反应中银催化剂助剂的研究进展

介绍了乙烯直接氧化制环氧乙烷工艺中银催化剂助剂的研究进展,以元素周期表为序,总结和分析了碱金属、碱土金属、过渡金属及其他主族元素作为催化助剂的研究和应用情况,并对主要助剂的作用机理进行了探讨。     

Effect of triethylamine treatment of titanium silicalite-1 on propylene epoxidation

Titanium silicalite-1(TS-1) treated with triethylamine (TEA) solution under different conditions was characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectrum (FTIR), ultraviolet-visible diffuse reflectance spectrum (UV-Vis), nitrogen physical adsorption and desorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The characterization results show that many irregular hollows are generated in the TS-1 crystals due to the random dissolution of framework silicon and the volume of the hollow cavities increase with increasing the TEA concentration, and the treatment temperature and time. The modified TS-1 samples improved in varying degrees the catalyst life for the epoxidation of propylene in a fixed-bed reactor probably due to the generation of the hollows to make it easy for the reactants and products to diffuse out of the channels.     

钼基催化剂在烯烃液相环氧化反应中的应用研究进展

介绍了钼络合物催化剂、固载化的钼络合物催化剂及MoO₃基的固体钼催化剂在烯烃液相环氧化反应中的应用。以有机过氧化物为氧化剂时,不同的钼基催化剂均表现出很好的催化性能,其中络合物中的配体对其催化性能有很大影响,并且可以通过引入手性配体实现对烯烃的不对称环氧化,而固体钼催化剂的性能则与载体上钼物种的种类密切相关。但绝大多数钼催化剂对H₂O₂参与的环氧化反应没有活性,开发对H₂O₂有催化活性的钼基催化剂是一个重要的研究方向。     

环己烯液相环氧化催化剂的研究进展

烯烃环氧化是一类重要的有机合成反应 ,其中环己烯经催化环氧化制得的环氧环己烷可广泛用作合成精细化学品的原料。阐述了Mo(Ⅵ )、V(Ⅴ )、Ti(Ⅳ )络合物、过渡金属卟啉络合物等环氧化用催化剂以及无机过氧酸盐、过氧化氢、分子氧、有机过氧酸及烷基过氧化氢等常用氧化剂在环己烯液相环氧化中的应用研究进展。还介绍了无机固体负载催化剂和高分子负载催化剂的负载化方法。最后展望了烯烃环氧化的研究开发趋势。     

Preparation of silica-immobilized titanium-containing silsesquioxane catalysts and activity for the epoxidation of alkenes

Silsesquioxanes containing tetrapodal titanium species and alkenylsilyl groups were immobilized onto dimethylsilyl-functionalized silica having mesopores by chemical tethering via hydrosilylative reaction in the presence of a Pt catalyst. The immobilized catalysts showed higher activity than their corresponding homogeneous catalyst towards the epoxidation of cyclooctene by tert-butylhydroperoxide, probably because of the improvement of the micro-environment around the titanium center. The reaction was found to be truly heterogeneous, since no further reaction proceeded after the separation of the catalyst by filtration. These catalysts also showed excellent catalytic activity for the epoxidation using hydrogen peroxide as an oxidant, while the parent homogeneous catalysts did not show any activity at all.     

Dendrimeric silanes for formation of metallosilicates: new heterogeneous catalysts for the epoxidation of alkenes with tert-butylhydroperoxide

New metallosilicate catalysts were prepared by reacting a silanol capped dendrimer, Si[CH₂CH₂Si(CH₃)₂OH]₄ with MCp₂Cl₂ (M = Ti^IV, Mo^VI, W^VI and V^V). The resulting Si[CH₂CH₂>Si(CH₃)₂OMCp₂Cl]₄compounds were incorporated in a silica matrix by the sol–gel method. The catalytic activity of the metallosilicates after calcination revealed excellent activity and selectivity towards epoxidation of alkenes with tert-butylhydroperoxide. Maximum activity was observed with molybdenum-containing materials. Analysis of the catalytic activity revealed that the catalysts were truly heterogeneous.     

A high-throughput experimentation study of the epoxidation of alkenes with transition-metal-free heterogeneous catalysts

A set of transition-metal-free heterogeneous catalysts for the epoxidation of alkenes with hydrogen peroxide was studied by means of high-throughput experimentation. The catalysts were tested with a range of substrates. Gallium oxide displayed the highest epoxidation activity with all tested alkenes, followed by Ga-MCM-41. The reaction conditions were optimised by investigating the effect of the solvent in which the epoxidation takes place. Considerable improvements in the epoxide yields were obtained in the processes catalysed by Al-MCM-41, Ga-MCM-41 and zeolite USY_(2.6). This work confirms the versatility of HTE for studying catalytic systems.     

Novel homogeneous Salen Mn(III) catalysts synthesized from dialdehyde or diketone with o-aminophenol for catalyzing epoxidation of alkenes

A series of novel non-salicylaldehyde based Salen ligands have been synthesized from the condensation of dialdehyde or diketone with o-aminophenol and the corresponding manganese(III) complexes prepared by further coordination of them with . FT-IR, UV–Vis spectra, chemical analysis and the structure optimized by Hartree-Fork/3-21G+ all indicated that the qualities of these novel Mn complexes were relative to their molecular structures. More specifically, glyoxal based Mn complex 2c, which was similar to the traditional Mn(III)-salicylethylenediamine, had a short carbon chain and non geometrical constraint of the aliphatic bridge in the two o-aminophenol, and its quality was the best when compared to glutaraldehyde, 2,4-pentanedione and 1,3-cyclohexanedione based Salen Mn(III) complexes (3c, 4c and 5c). And it was also the excellent catalyst for the epoxidations of several non-functionalized alkenes with molecular oxygen/sacrificial-isobutyaldehyde, PhI(OAc)₂ or H₂O₂ as oxidant.     

FCC催化剂酸性与孔结构对焦炭选择性的影响

分别制备酸性和孔体积不同的催化剂,并通过红外光谱、N₂吸附和ACE评价等方法,考察B酸与L酸的调变以及催化剂孔体积的变化对焦炭选择性的影响。结果表明,催化剂B酸量增加,L酸量在一定范围适度减少,均有利于焦炭选择性的提高;催化剂孔体积低于0.39 mL·g^-1时,随着孔体积增加,生焦因子呈降低趋势;孔体积高于0.39 mL·g^-1时,由孔体积增加带来焦炭选择性的优势便无法体现。     

Analysis of products distribution and selectivity in maleic acid epoxidation by hydrogen peroxide in catalytic systems

This paper discusses the results of the analysis of products distribution and selectivity in hydrogen peroxide (H₂O₂) epoxidation of maleic acid (MA) in the presence of sodium tungstate as catalyst in the native form and also immobilized on polymer resin support. A specially designed experimental procedure afforded accurate monitoring of the oxygen released during epoxidation occasioned by H₂O₂ decomposition and also enabled selectivity to be reliably estimated. Irrespective of the catalytic system employed, it was observed that between 10 and 15% of the H₂O₂ initially present in the reaction is lost via decomposition which, presumably, is induced by the action of the metallic catalytic species. Consequently, selectivity was observed to drop gradually in the course of the reaction, but more rapidly in the case of the homogeneous catalysis. ©1997 SCI     

Propylene epoxidation in a microreactor with electric heating

Gas phase propylene epoxidation on gold catalysts has attracted wide attention from industry and academia due to its high selectivity. However, it suffers from low propylene conversion and rapid catalyst deactivation. Experiments showed that propylene conversion could be increased by raising H₂, O₂, or C₃H₆ concentration in the feed, but the feed compositions were within the explosion limit. It was also shown that the activity of the used catalyst could be fully recovered, but the regeneration temperature was 280 °C, much higher than that for reaction. Therefore a microchannel reactor was devised to suppress explosion and was constructed with Fecralloy, to raise the temperature rapidly for catalyst regeneration by electric heating. In two minutes the temperature of the reactor could be raised from 50 to 300 °C. Catalysts were coated on the alloy belt by dip coating, and the performance of the reactor was evaluated under different operating conditions. Results showed that in the microreactor the overall reaction rate was controlled mainly by the intrinsic reaction rate, and also influenced by film diffusion to a certain extent. The deactivated catalyst was regenerated in the microchannel reactor and the activity was fully recovered.     

乙烯环氧化制环氧乙烷银催化剂研究进展

主要从载体、制备方法和助催化剂的改进等几个方面入手，对乙烯环氧化制环氧乙烷的银催化剂的进展情况进行了综述，并简述了我国环氧乙烷生产发展概况。     

高性能钛硅分子筛可控合成及其催化丙烯气相环氧化研究进展

随着绿色化工发展战略的推进,钛硅分子筛凭借其独特的选择性环氧化能力而引起广泛关注,合理调控钛硅分子筛的结构是提升烯烃环氧化反应效果的关键。本文分别对钛硅分子筛的结构类型、硅钛原子比、表面疏水性、颗粒传质性能的调控方法进行了介绍,系统总结了高活性钛硅分子筛的合成策略,并概述了TS-1钛硅分子筛工业生产技术的进展。以负载金属的钛硅分子筛催化剂为例,着重讨论了基于该催化剂的丙烯直接临氢气相环氧化反应的性能与机理,肯定了催化剂中包括载体钛位点和负载金属位点的双位点在环氧化反应中的重要性,并从金基催化剂的电子性质、空间分布、尺寸效应三个方面总结了高效金属位点的调控策略。此外,基于丙烯气相临氢环氧化当前存在的问题与挑战,进一步提出其潜在的解决方案与未来的发展方向。     

Effect of pore size on the performance of mesoporous material supported chiral Mn(III) salen complex for the epoxidation of unfunctionalized olefins

A series of mesoporous MCM-41 and MCM-48 materials with different pore sizes were synthesized and used as supports to immobilize chiral Mn(III) salen complex. The heterogeneous catalysts were characterized by XRD, FT-IR, DR UV–vis, and N₂ sorption, and the results indicated the successful immobilization of chiral Mn(III) salen complex. The confinement effect of pore size on the catalytic performance of the heterogeneous catalysts was studied for the asymmetric epoxidation of unfunctionalized olefins with m-chloroperoxybenzoic acid as an oxidant. It was found that the conversions and enantiomeric excess (ee) values were closely correlated with the pore sizes of parent supports. The catalysts immobilized on the large-pore mesoporous supports exhibited higher conversions, and for the catalysts immobilized on MCM-41 materials, the ee values improved with increasing pore size. However, for the MCM-48 material-supported catalysts, the compatible pore size of the support with the substrate was beneficial for obtaining higher enantioselectivity in olefin epoxidation.     

TS-1催化氯丙烯环氧化反应过程中的溶剂效应

研究了具有不同官能团的溶剂对TS-1催化氯丙烯环氧化反应性能的影响,发现与无溶剂的反应结果相比,含羟基的溶剂和丙酮对反应有明显的促进作用,在含氰基的乙腈溶剂中,环氧化反应效果变差。试验中还发现,溶剂分子的空间结构影响环氧化的反应速率,并且部分溶剂会与氯丙烯发生竞争性氧化,降低H2O2的有效利用率。在甲醇或丙酮溶剂中混入一定比例的乙腈可提高产物的选择性,但对提高催化剂稳定性效果不显著。     

Fischer-Tropsch synthesis by reduced graphene oxide nanosheets supported cobalt catalysts: role of support and metal nanoparticle size on catalyst activity and products selectivity

In this paper,a series of cobalt catalysts supported on reduced graphene oxide(rGO)nanosheets with the loading of 5,15 and 30 wt-%were provided by the impregnation method.The activity of the prepared catalysts is evaluated in the Fischer-Tropsch synthesis(FTS).The prepared catalysts were carefully characterized by nitrogen adsorption-desorption,hydrogen chemisorption,X-ray diffraction,Fourier transform infrared spectroscopy,Raman spectroscopy,temperature programmed reduction,transmission electron microscopy,and field emission scanning electron microscopy techniques to confirm that cobalt particles were greatly dispersed on the rGO nanosheets.The results showed that with increasing the cobalt loading on the rGO support,the carbon defects are increased and as a consequence,the reduction of cobalt is decreased.The FTS activity results showed that the cobalt-time yield and turnover frequency passed from a maximum for catalyst with the Co0 average particle size of 15 nm due to the synergetic effect of cobalt reducibility and particle size.The products selectivity results indicated that the methane selectivity decreases,whereas the C5+selectivity raises with the increasing of the cobalt particle size,which can be explained by chain propagation in the primary chain growth reactions.     

Effects of acid strength and micro pore size on -caprolactam selectivity and catalyst deactivation in vapor phase Beckmann rearrangement over acid solid catalysts

The vapor phase Beckmann rearrangement of cyclohexanone oxime (CHO) over solid acid catalysts including zeolites was carried out to elucidate the effects of the acid strength and the micropore size of the catalysts on the selectivity of -caprolactam (CL) and the catalyst deactivation rate. It was found that the catalyst deactivation rate was strongly dependent on the acid strength of the acid catalysts. The improvement of catalyst life was achieved by using MFI-type metallosilicates having weak acid sites. The CL selectivity decreased over the acid catalysts with micropores larger than those of the MFI zeolites. Furthermore, using methanol and carbon dioxide as the diluent solvent and diluent gas improved CL selectivity and catalyst life, respectively.     

负载钛催化丁二烯-异戊二烯共聚合反应动力学的研究

研究了TiCl4 /MgCl2 负载型高效催化剂催化丁二烯 -异戊二烯共聚合的动力学特征 ,并对影响聚合速率的因素进行了考察。首先通过计算排除了扩散控制对反应总聚合速率的影响 ,测定了单体浓度和催化剂浓度的反应级数和表观活化能 (2 2 .8kJ/mol) ,建立的聚合速率方程为 :R =kp·f·[Ti]·[M]。