Cu/SiO2催化剂在草酸二乙酯加氢过程中失活研究

草酸酯加氢合成乙二醇过程中负载量为20％的Cu催化剂可以获得较高的乙二醇(EG)收率,但是该催化剂寿命过短的问题限制了其工业应用.本实验主要研究造成该催化剂失活的原因.使用蒸氨法将铜负载在SiO2上,制成用于草酸二乙酯(DEO)加氢的催化剂.运用X射线衍射(XRD)、程序升温还原(TPR)和高分辨率透射电镜(HRTWE...     

载体性质对Pd催化剂加氢脱硫性能的影响

以Si O2、全硅MCM-41(Si-MCM-41)、通过机械混合Si-MCM-41与ZSM-5得到的Z-MCM-41-M以及通过在ZSM-5外部包覆MCM-41制备得到的Z-MCM-41四种材料为载体,制备了四种负载型Pd催化剂。采用XRD、HRTEM、N2吸附-脱附、NH3-TPD手段对Pd催化剂进行了表征;以二苯并噻吩(DBT)为模型化合物,在固定床反应器上对四种催化剂的加氢脱硫(HDS)活性、加氢路径选择性和加氢裂化活性进行了考察,研究了不同类型载体对Pd催化剂加氢脱硫性能的影响。结果表明,载体的性质会显著影响负载型Pd催化剂的加氢脱硫性能。载体的比表面积对负载型Pd催化剂加氢脱硫活性影响不大,但是HYD路径的选择性与载体的孔道结构有关;具有介孔孔道结构有利于加氢路径选择性的提高。酸性载体负载的Pd催化剂表现出较好加氢脱硫活性和加氢选择性,这与氢溢流有关。介孔材料的孔道结构与微孔沸石的酸性有机结合,所得到的Z-M CM-41复合材料是是潜在的贵金属Pd加氢脱硫催化剂优良载体,可有效提升其加氢脱硫活性。     

Preparation of rhodium–phyllosilicate catalysts without leaching in liquid-phase 1-hexene hydrogenation

Rhodium catalysts have been prepared on palygorskite and montmorillonite (clay) supports by reduction with hydrogen (1 atmosphere) at room temperature of a cationic organometallic rhodium compound anchored to the support. The activity of these catalysts for the hydrogenation of liquid-phase 1-hexene remains constant with increase of prehydrogenation time and with re-use for several runs. No rhodium leaching is observed.     

Pd/CexZr1-xO2/SiO2催化剂的制备及其甲烷催化燃烧性能的研究

采用浸渍法制备了Pd质量分数为0.1%~1.0%的Pd/SiO2和Pd/5%CexZr1-xO2/SiO2（x0.0~1.0）系列催化剂,在微型固定床反应器上对催化剂的甲烷催化燃烧性能进行了评价,用XRD、H2-TPR等分析测试技术对催化剂的结构进行了表征。结果表明,Pd/SiO2和Pd/CexZr1-xO2/SiO2催化剂都具有较好的甲烷催化燃烧活性,CexZr1-xO2可以明显提高催化剂的催化活性,并且Ce和Zr的比值对催化剂催化活性也有显著的影响。XRD和TPR显示,Pd/CexZr1-xO2/SiO2催化剂中的CexZr1-xO2对PdO的分散性和还原性有较好的促进作用。     

Pd/C modified with Sn catalyst for liquid-phase selective hydrogenation of maleic anhydride to gamma-butyrolactone

Pd catalysts suffered from poor selectivity and stability for liquid-phase hydrogenation of maleic anhydride (MA) to gamma-butyrolactone (GBL). Thus, Pd/C catalysts modified with different Sn loadings were synthesized, and characterized by XRD, XPS, TEM and elemental mapping. The types of alloy phase and the amounts of the surface Pd-SnOx sites altered along with Sn/Pd mass ratios from 0-1.0 synthesized in the process of preparation. The maximum reaction rate was 0.57 mol-GBL/(mol-Pd min) and selectivity was 95.94% when the Sn/Pd mass ratio was 0.6. It might be attributed to the formation of Pd₂Sn alloy and less amounts of Pd-SnOx sites.     

Palladium catalysts supported on oligomeric aramides in the liquid-phase hydrogenation of phenylacetylene

The catalytic behaviour of palladium supported on oligomeric aramides has been investigated in the liquid phase selective hydrogenation of phenylacetylene to styrene, by comparison with conventional Pd-supported systems, such as Pd/carbon. Pd/Al₂O₃ and Pd/SiO₂. The influences of the reduction temperature and metal loading on the activity/selectivity behaviour of the title reaction are explained in terms of different reducibility patterns of the catalysts, as well as in the light of a peculiar support effect of the organic matrix on Pd particles.     

Catalytic hydrogenation by recyclable supported Pd(II)-amino acid complex

L-phenyl alanine was anchored to P(S-DVB) resin and its complex with PdCl₂ was prepared. The newly synthesized catalyst was found to be a versatile and recyclable catalyst for the hydrogenation of 1-octene and acetophenone. This chiral catalyst induced moderate enantioselectivity during the asymmetric reduction of acetophenone. This revised version was published online in June 2006 with corrections to the Cover Date.     

Catalytic behavior of supported Pd catalysts in the selective hydrogenation of campholenic aldehyde to naturanol

Selective catalytic reduction of campholenic aldehyde to naturanol was investigated over Sn-and Fe-doped SiO₂, and Fe₂O₃-supported Pd catalysts. On Pd/SiO₂ and Pd-Sn/SiO₂ only saturated campholenic aldehyde is formed. Addition of Fe increases the C=O hydrogenation rate producing the corresponding unsaturated alcohol with a good selectivity. Also Fe₂O₃-supported catalysts were found to be more selective towards carbonyl hydrogenation. Addition of tin to Pd/Fe₂O₃ contributes to a further selectivity enhancement towards naturanol.     

Dehydrogenation of n-butane over vanadia catalysts supported on silica gel

VOx/SiO2 catalysts prepared by impregnation method were used for catalytic dehydrogenation of n-butane to butenes and characterized by X-ray diffraction,FT-IR,UV-vis,Raman,and BET measurements.The effects of VOx loading and the reaction temperature on the VOx/SiO2 catalysts and their catalytic performances for the dehydrogenation of n-butane were studied.When the VOx loading was 12% g/gcat and reaction temperature was between 590 ℃ and 600 ℃,n-butane conversion and butenes yields reached the highest value under H2 flux of 10 ml/min and n-butane flux of 10 ml/min.Product distribution,such as the ratio of 2-butene to 1-butene and the ratio of cis-2-butene to trans-2-butene,was mainly influenced by the reaction temperature.     

Pd/MCM-41催化碘苯Ullmann偶合制备联苯

联苯是一种重要的有机合成中间体,广泛应用于超分子、高性能染料和药物活性剂以及有机导体和半导体的生产中。目前,联苯的合成方法主要有Ullmann偶合反应、Stille反应、Heek反应、Suzuk反应和Sonogashira反应等。其中,Ullmann偶合反应由于成本低且简单易操作而倍受青睐。最早采用Cu-基催化剂,但需要在高温下进行,反应条件相当苛刻。采用Pd-基均相催化剂可大大降低反应温度,     

High enantioselectivity in the asymmetric hydrogenation of ketones by a supported Pt nanocatalyst on a mesoporous modified MCM-41 support

Catalysts containing metal nanotubes were prepared by the adsorption of platinum metal nano‐tubes onto functionalized and modified silica surfaces (MCM‐41 and fumed silica). (3‐Chloropro‐pyl)trimethoxysilane and cinchonidine were used for functionalization and modification, respec‐tively. Potassium chloroplatinate was used as the metal precursor to impregnate platinum metal nanotubes on the pretreated functionalized and modified silica surfaces. The solid catalysts were characterized by ESEM, TEM, EDAX, and XPS. The MCM‐41 supported platinum nanotube catalyst showed>98%to~100%enantioselectivity towards the hydrogenation of a range of pharmaceuti‐cally important chemicals such as methyl pyruvate, ethyl pyruvate, and acetophenone with nearly full conversion.     

超细Pd—B／SiO2非晶态合金加氢反应的催化活性

采用浸渍法并通过ＫＢＨ４还原制备超细Ｐｄ－Ｂ／ＳｉＯ２非晶态合金催化剂,以硝基苯加氢生成苯胺为目标反应,考察了上述催化剂的活性和选择性及热稳定性,并与晶态Ｐｄ－Ｂ／ＳｉＯ２和Ｐｄ／ＳｉＯ２催化剂及非负载型Ｐｄ－Ｂ非晶态合金催化剂进行了比较。     

胶原纤维接枝多酚负载纳米钯的制备及其对硝基苯加氢的催化特性

以胶原纤维(CF)接枝表棓儿茶素棓酸脂(EGCG)为载体,制备了新型非均相钯(Pd)纳米催化剂(CF-EGCG-Pd).EGCG作为"桥分子"不仅对Pd纳米颗粒具有锚定作用,而且能控制Pd纳米颗粒的大小及分布.通过SEM、TEM、XRD、XPS对该催化剂的形貌和物理特性能进行了表征,发现该催化剂具有规整的纤维结构,在胶原纤维的外表面形成了高分散的平均粒径在3.8 nm的Pd纳米颗粒.将该催化剂用于硝基苯液相催化加氢反应,结果表明在308 K和1.0 MPa氢压下,硝基苯转化速率(TOF)达到34.13 mol·mol-1·min-1,苯胺选择性为100%,催化剂重复使用3次其催化活性基本不变.     

Enantioselective hydrogenation of isophorone over Pd catalysts in the presence of(−)-dihydroapovincaminic acid ethyl ester: The effect of reduction method of Pd blacks on the enantiomeric excess

The enantioselective heterogeneous catalytic hydrogenation of isophorone in the presence of apovincaminic acid ethyl ester was investigated. Various Pd black catalysts differing in their preparation method were studied. The catalysts were characterized by different methods such as physical adsorption and chemisorption, SEM and XPS. An explanation was created for the different enantioselectivity of the catalysts being precipitated by different reducing agents.     

Pd/TiN nanocomposite catalysts for selective hydrogenation of phenol and its derivatives

Pd/TiN nanocomposite catalysts were fabricated for one-step selective hydrogenation of phenol to cyclohexanone successfully. High conversion of phenol (99%) and selectivity of cyclohexanone (98%) were obtained at 30℃ and 0.2 MPa H₂ for 12 h in the mixed solvents of H₂O and CH₂Cl₂. The Pd nanoparticles were stable in the reaction, and no aggregation was detected after four successive runs. The catalytic activity and selectivity depended on slightly the Pd particle sizes. The generality of the catalysts for this reaction was demonstrated by the selective hydrogenation of phenol derivatives, which showed that the catalyst was selective for the formation of cyclohexanone.     

Pd supported on graphene modified g-C3N4 hybrid: a highly efficient catalyst for hydrogenation of nitroarenes

Graphitic carbon nitride (g-C₃N₄) and graphene (GO) have been greatly utilized as supports in the field of heterogeneous catalysis. In this work, layered C₃N₄ polymer/graphene hybrid (CNNS/rGO₂₀) with heterostructure was fabricated by a hydrothermal method followed by loading Pd nanoparticles on the hybrid. The palladium was well dispersed uniformly (1.31 nm) owing to the layered and porous heterostructure of CNNS/rGO₂₀. The obtained catalyst was used for the transfer hydrogenation of a series of nitro-compounds to give the corresponding aromatic amines with outstanding activity by employing formic acid as hydrogen donor under mild conditions. The catalytic activity of the heterogeneous catalyst showed no significant loss after five continuous use.     

Preparation of Pd/C catalysts via deposition of palladium hydroxide onto Sibunit carbon and their application to partial hydrogenation of rapeseed oil

Pd/Sibunit catalysts were prepared by deposition of palladium hydroxide onto the support surface in an alkaline medium. It was found that the palladium distribution throughout the catalyst grain, and the dispersion of Pd particles depend on (i) the order of the addition of H₂PdCl₄ and Na₂CO₃ to carbon suspension, (ii) Na₂CO₃ to H₂PdCl₄ ratio, and (iii) aging time of the mixture H₂PdCl₄ + Na₂CO₃ before its addition to the carbon. The catalysts were tested in the hydrogenation of cyclohexene and rapeseed oil under static conditions. The yield of trans-isomers as products of partial hydrogenation of rapeseed oil was found to decrease with decreasing the Pd particle size in the catalysts, as well as with increasing the Pd concentration on the periphery of the support grains.     

Stereoselective hydrogenation of 11-hexadecyne-l-ol on supported copper catalysts

Hydrogenation of 11-hexadecyne-l-ol on 5–30 % copper catalysts supported on -A1₂O₃ and MgCO₃ results incis-11-hexadecyne-1-ol in 100 % yield. Hydrogenation does not occur on 5–30 % Cu/ZnO catalysts. The difference in behavior of the catalysts is connected with the valent state of copper on the surface and different hydrogen chemisorption.Positive conclusion on the application No. 930071.1 of 16.06.93 for the Kazakhstan preliminary Patent (A. M. Pak, O. 1. Kartonozhkina, and G. T. lzdebskaya).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1147–1150, May, 1996.     

不同硅源的Cu/SiO2催化糠醛加氢制2-甲基呋喃

以硅溶胶和气相二氧化硅为载体,采用氨蒸法制备了Cu/SiO₂-sol和Cu/SiO₂-aer两种催化剂,采用N₂吸附脱附、X射线衍射（XRD）、傅里叶红外光谱（FT-IR）、透射电子显微镜（TEM）、N₂O-H₂滴定、氢气程序升温还原（H₂-TPR）、氨程序升温脱附（NH₃-TPD）及X射线光电子能谱（XPS）对样品进行表征,在固定床反应器中考察两种催化剂对糠醛气相加氢制2-甲基呋喃的催化性能。结果表明,Cu/SiO₂-sol催化剂具有更好的催化活性,在150 h反应时间内,糠醛转化率为100%,2-MF选择性在91%以上。这主要归因于以硅溶胶为硅源可以生成更多页硅酸铜,还原后催化剂表面Cu的分散性更高、弱酸位更多,有利于提高糠醛的转化率与2-甲基呋喃的选择性。同时Cu/SiO₂-sol具有较大的孔容孔径,有利于降低反应过程中积炭,延长催化剂寿命。