巴豆醛选择性加氢制巴豆醇催化剂的研究进展

从催化剂活性组分、载体、助剂、催化剂前驱体和选择性加氢机理等多方面综述了巴豆醛选择性加氢制备巴豆醇催化剂的研究，指出了巴豆醛选择性加氢催化剂的研究应着重在以下几个方面：纳米金属族催化剂的研制及其催化机理；在分子筛和纳米碳管上的择形加氢规律；用作催化剂助剂稀土元素的系统研究；应用原位红外光谱研究择形加氢机理；研究价廉易得的非贵金属加氢催化剂及常压固定床连续加氢工艺。     

贵金属催化剂理性设计在选择性加氢反应中的研究进展

从多相催化的特征出发,综述了多相催化理性设计中典型调控理论和方法的研究进展。同时,以芳香硝基化合物及不饱和醛/酮选择性加氢反应为特征反应,从多相催化剂表面的电子效应、几何效应、界面效应和协同效应等角度进行了全面综述。指出了筛选合适的载体、合成特定尺寸形貌的活性中心、调控金属-载体强相互作用是开发更高效的多相选择性加氢催化剂的重要方向,调控金属-载体强相互作用,优化活性中心的电子效应、空间效应和界面效应,微调N=O及C=O不饱和键的吸附与活化,是实现高效选择性加氢催化体系的理论设计的重要手段。进一步优化氢气的活化裂解方式、活性氢的稳定与迁移,可抑制选择性加氢的副反应。     

Diffusion effects in the hydrogenation of 3-methyl crotonaldehyde over zeolite-supported Ru

The activity and selectivity in gas-phase hydrogenation of the unsaturated aldehyde 3-methyl crotonaldehyde (UAL) over zeolite-supported Ru was found to depend markedly on the partial pressures of the two reactants in the gas phase, with the rate increasing as the ratio decreased. Anomalously low apparent activation energies were found compared to the same reaction over Ru/SiO₂, and secondary reactions to produce the totally hydrogenated product occurred much more readily in the zeolite-supported Ru. These observations led to the suggestion that these reactions were under diffusion control.     

Preparation and investigation of Pd doped Cu catalysts for selective hydrogenation of acetylene

A series of PdCu bimetallic catalysts with low Cu and Pd loadings and different Cu: Pd atomic ratios were prepared by conventionally sequential impregnation (CSI) and modified sequential impregnation (MSI) of Cu and Pd for selective hydrogenation of acetylene. Characterization indicates that the supported copper (II) nitrate in the PdCu bimetallic catalysts prepared by MSI can be directly reduced to Cu metal particles due to the hydrogen spillover from Pd to Cu(NO₃)₂ crystals. In addition, for the catalysts prepared by MSI, Pd atoms can form PdCu alloy on the surface of metal particles, however, for the catalysts prepared by CSI, Pd tends to migrate and exist below the surface layer of Cu. Reaction results indicate that compared with CSI, the MSI method enables samples to possess preferable stability as well as comparable reaction activity. This should be due to the MSI method in favor of the formation of PdCu alloy on the surface of metal particles. Moreover, even Pd loading is super low, <0.045 wt-% in this study, by through adjusting Cu loading to an appropriate value, attractive reactivity and selectivity still can be achieved.     

大颗粒SiO_2载体负载Ir/FeO_x催化剂的巴豆醛加氢性能

选择粒径(1~3)mm的Si O2为载体,采用浸渍法制备Ir/Fe Ox/Si O2催化剂,考察Fe含量对催化剂气相巴豆醛选择加氢反应性能的影响,采用X射线粉末衍射、拉曼光谱及光电子能谱等对催化剂进行表征。结果表明,随着Fe添加量的增加,反应1 h时巴豆醛转化率和反应10 h时巴豆醇选择性呈现先提高后下降趋势,n(Fe)∶n(Ir)=1.0时,反应1 h时巴豆醛转化率最高(达67%);n(Fe)∶n(Ir)=0.3时,反应1 h时巴豆醛转化率和反应10 h时巴豆醇选择性分别达88%和95%,反应过程中催化剂表面积炭是导致巴豆醛转化率降低的主要原因。对于同种催化剂,反应后电子结合能往低结合能方向偏移可能是导致选择性提高的原因。     

Influence of chlorine poisoning of copper/alumina catalyst on the selective hydrogenation of crotonaldehyde

The effect of the presence of chlorine on the activity and selectivity of a Cu/Al₂O₃ catalyst has been examined for the selective hydrogenation of an unsaturated aldehyde, crotonaldehyde. Cu/Al₂O₃ in the absence of chlorine poisons produced 1-butanol almost exclusively, whereas catalysts pre-dosed with a suitable amount of chlorine compound (CCl₄, CHCl₃ and CH₂Cl₂) shifted the product distribution towards formation of butanal. The poisoning effectiveness increased in the order CCl₄32Cl₂CH₃Cl and methyl chloride was found to totally deactivate the catalyst. The most significant enhancement in butanal selectivity was observed with CCl₄ and CH₂Cl₂. The effect of chlorine as a poison is in contrast to the effect of sulphur which enhances formation of crotyl alcohol and the origins of these effects are discussed.     

Correlation between metal oxidation state and catalytic activity: hydrogenation of crotonaldehyde over Rh catalysts

The effects of the rhodium (oxidation) state on the activity and selectivity for the crotonaldehyde hydrogenation reaction over Rh/Al₂O₃ and Rh/SiO₂ catalysts were examined using the techniques of temperature-programmed reduction, hydrogen chemisorption and X-ray absorption near-edge structure (XANES). In the alumina-supported system, the active phase-support interaction is shown to affect the chemical behavior of rhodium under the influence of a reductive atmosphere by stabilizing Rh³⁺ species. This behavior is not observed (as expected) for Rh/SiO₂ catalysts. The structural and electronic bases of the active phase-support interaction and the effect of the latter phenomenon on the hydrogenation of crotonaldehyde are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Activity and selectivity of PtNi/TiO2 catalysts for hydrogenation of crotonaldehyde

The hydrogenation of crotonaldehyde over a series of titania supported PtNi catalysts was investigated. Pt/TiO₂ had the highest activity to hydrogenate the bond of crotonaldehyde. With the addition of Ni to Pt the activity for carbonyl group hydrogenation decreased, while that for the bond hydrogenation increased. Two different types of sites were established to be active for bond hydrogenation, located at (i) the Pt-TiO₂ interface and (ii) the PtNi bimetallic phase. For the Pt-TiO₂ interface the presence of accessible Ti ^x+ cations in close distance to Pt and for the PtNi phase a slightly positively charged Ni on the surface of these alloy particles were concluded to be responsible for the enhanced selectivity to crotylalcohol. The hydrogenation of the bond occurs mainly on the clean metal surfaces of Ni and Pt.     

Reactant induced restructuring and corrosion of germanium-palladium catalysts during hydrogenation reactions

An anomalous rate enhancement with increasing conversion has been observed during the liquid phase hydrogenation of nitrobenzene and crotonaldehyde over Ge/Pd/C catalysts at ambient temperature and atmospheric pressure. Inductive coupled plasma atomic emission spectroscopy and electrochemical measurement of the oxidation state of catalysts during reaction revealed that the bimetallic particles were partially oxidized by the reactants, which resulted in Ge-dissolution and increased exposure of Pd on the surface. It is proposed that the surface and bulk composition of Ge/Pd catalysts are a function of their oxidation state. This behaviour is due to the unusually high mobility of Ge in the Pd lattice and to the good solubility of GeO₂ in polar solvents. The influence of hydrogen transport on the corrosion process and the stability of other X/Pd type bimetallic catalysts during liquid phase hydrogenation are also discussed.     

Effect of the support on the selective hydrogenation of benzeneover ruthenium catalysts. 1. Al2O3 and SiO2

The effect of the support on the liquid phase selective hydrogenation of benzene to cyclohexene over Ru catalysts was studied. Catalysts were prepared using RuCl₃ as precursor and characterized by hydrogen chemisorption, XPS and TPR. The reaction was carried out at 373 K and 2 MPa using a stirred tank reactor. It was found that the catalytic activity is not influenced by the Ru dispersion. More electron-deficient Ru species are present on Al₂O₃ than on SiO₂. The electronic state of Ru affects the selectivity to cyclohexene.     

The selective hydrogenation of acetonitrile on supported nickel catalysts

The catalytic behavior of several supported nickel catalysts in the hydrogenation of acetonitrile was studied. It was established that the selectivity of this process is greatly influenced by the nature of the support used. Catalysts consisting of nickel supported on acidic supports catalyzed the formation of condensation products, diethyl- and triethylamine. Nickel supported on basic supports was highly selective with respect to the formation of the primary amine, ethylamine. It was shown that modification of the intrinsic acidity of alumina-based supports by the application of alkaline additives has a large impact on the selectivity of the resulting catalyst. Based on the results obtained from measurements on a basic catalyst diluted with either an acidic or a basic support, a dual-function mechanism is suggested. The mechanism implies that the hydrogenation function of the catalyst is located on the metal, while the acid function, responsible for the condensation reactions, is located on the support. A mechanism, accounting for the occurrence of the acid-catalyzed condensation reactions, is proposed.     

加氢催化剂的器外再生

介绍了国内外再生技术的发展状况，对比器内和器外再生技术的优缺点以及催化剂活性恢复率的差异，说明器外再生技术是催化剂再生的发展方向。     

肉桂醛选择性加氢Co-Fe/硅藻土催化剂稳定性考察

通过肉桂醛在高压微反固定床上24 h的催化加氢反应,考察了肉桂醛选择加氢的催化剂Co-Fe/硅藻土稳定性。结果表明,肉桂醛选择加氢催化剂Co-Fe/硅藻土在反应初期存在反应的诱导期,诱导期后,肉桂醛转化率70%,肉桂醇选择性80%,肉桂醇收率可达60%以上,且催化性能趋于平稳,表现出良好的催化性能和稳定性。利用XRD、SEM、TG-DSC对反应前后催化剂结构进行表征,发现催化剂经24 h反应,结构不变,表面颗粒分布更细化,无积炭迹象。     

烯烃选择性加氢脱炔催化剂SMT-342的研究及工业应用

针对聚烯烃生产过程中烯烃聚合前的脱炔烃净化,大连凯特利催化工程技术有限公司开发了加氢脱炔催化剂SMT-342。考察床层高径比、空速、压力等因素对SMT-342脱炔催化剂性能的影响。结果表明,在高径比2.56、反应压力0.5 MPa、空速5 000 h^(-1)条件下,出口反应气中乙炔体积分数小于1×10^(-6)。1 056 h稳定性测试表明该催化剂可以稳定、有效脱除烯烃中的炔烃,满足烯烃聚合工艺指标。SMT-342脱炔催化剂已在多种工业化装置上使用,现场运行数据表明该催化剂完全满足乙烯精馏分离前乙炔脱除要求。     

Recent advances in selective acetylene hydrogenation using palladium containing catalysts

Recent advances with Pd containing catalysts for the selective hydrogenation of acetylene are described. The overview classifies enhancement of catalytic properties for monometallic and bimetallic Pd catalysts. Activity/selectivity of Pd catalysts can be modified by controlling particle shape/morphology or immobilisation on a support which interacts strongly with Pd particles. In both cases enhanced ethylene selectivity is generally associated with modifying ethylene adsorption strength and/or changes to hydride formation. Inorganic and organic selectivity modifiers (i.e., species adsorbed onto Pd particle surface) have also been shown to enhance ethylene selectivity. Inorganic modifiers such as TiO₂ change Pd ensemble size and modify ethylene adsorption strength whereas organic modifiers such as diphenylsulfide are thought to create a surface template effect which favours acetylene adsorption with respect to ethylene. A number of metals and synthetic approaches have been explored to prepare Pd bimetallic catalysts. Examples where enhanced selectivity is observed are generally associated with decreased Pd ensemble size and/or hindering of the ease with which an unselective hydride phase is formed for Pd. A final class of bimetallic catalysts are discussed where Pd is not thought to be the primary reaction site but merely acts as a site where hydrogen dissociation and spillover occurs onto a second metal (Cu or Au) where the reaction takes place more selectively.

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Cyclic extrusion synthesis of mesoporous carbon-supported metal catalysts for selective hydrogenation

The mesoporous carbon-supported metal catalysts are important materials in heterogeneous catalysis. From the standpoint of process intensification, the current synthesis methods still suffer from several issues, such as the excessive use of toxic solvents, the time-consuming self-assembly process, and the difficulty of continuous production. Herein, we report a solvent-free and continuous route to synthesize mesoporous carbon-supported metal catalysts. Interestingly, the use of cyclic extrusion could promote mixing, coordination, and assembly of catalyst precursors (tannin-metal salts-additives) by shearing and squeeze force. The as-made mesoporous carbon-supported nickel materials showed high surface areas (up to 512 m² g⁻¹), narrow pore size distribution (~10 nm), and good performance in the selective hydrogenation of nitrobenzene to aniline (Conv. >99%; Sel. >99%). In addition, the fluid property of catalyst precursors and the geometry of the twin-screw extrusion channel were studied, and the essence of this cyclic extrusion process is also discussed.     

Structure and catalytic properties of Cu-Ni bimetallic catalysts for hydrogenation

The dependence of catalytic activity and selectivity of Cu-Ni bimetallic catalysts for oil hydrogenation on CuNi ratios have been investigated while they were reduced at low temperature (230 °C). Two maxima occurred at Cu₂Ni₁ and Cu₁Ni₃ in the activity-CuNi curve. Cu riched catalysts have higher selectivity than Ni riched ones, and may cause dehydrogenation and isomerization of linoleate at the beginning of the reaction. The structures of the catalysts reduced at different temperatures have been studied by means of XRD, XPS, EXAFS and FMR et al. The structure of the catalysts reduced at 230 °C can be described as an aggregate of Cu particles inlaid with Ni atoms and unreduced NiO, and the easily reduced Cu always segregates on the surface, while homogeneous solid solution particles can be formed in the case 400 °C being used as reduction temperature.     

草酸二甲酯气相选择性加氢铜基催化剂研究进展

乙二醇是重要的化工原料,广泛应用于各种行业。煤经草酸二甲酯加氢制乙二醇符合我国"富煤少油"能源特点,具有良好的发展前景。对于草酸二甲酯气相选择性加氢合成乙二醇反应中催化剂的开发是实现该路线工业化的关键。重点介绍Cu基催化剂非均相气相加氢的研究进展,包括Cu基催化剂的活性中心、载体以及助剂,展望草酸二甲酯加氢Cu基催化剂的研究方向。     

催化裂解汽油加氢催化剂及工艺研究

根据催化裂解汽油组成特点,开发了“切C5-脱砷-切C9-两段加氢”工艺技术路线及配套的一、二段加氢催化剂.采用该工艺技术路线,利用自制催化剂对催化裂解汽油进行加氢处理,500 h稳定性评价结果表明,开发的工艺技术路线合理、可靠,催化剂性能稳定,产品溴价小于1.0 g Br/100 g,硫含量小于1.0 μg/g,满足芳烃抽提要求.