Mono and Bifunctional Catalysts for Styrene Oxide Isomerization or Hydrogenation

Abstract  

Styrene oxide can be effectively isomerized to phenyl-acetaldehyde (98%) over amorphous silica alumina catalysts under very mild liquid phase conditions. On the other hand, a copper catalyst prepared using a silica zirconia support gave up to 80% yield in the hydrogenation of styrene oxide to 2-phenyl-ethanol.     

Screening of Soluble Rhodium Nanoparticles as Precursor for Highly Active Hydrogenation Catalysts: The Effect of the Stabilizing Agents

We report the preparation of rhodium nanoparticles (NPs) stabilized by 1-octadecanethiol (ODT), polyvinyl alcohol (PVA), and tetraoctylammonium bromide (TOAB), and their application for hydrogenation catalysis. The three metal–ligand systems correspond to different mechanism of NPs stabilization via strong covalent linkage, chemisorbed atoms and electrostatic interactions, respectively. We found a strong effect of the interaction between the stabilizer and the surface of the metal nanoparticle on the catalytic activity. The Rh NPs were studied as soluble nanoparticle catalysts and as precursors for the synthesis of supported catalysts. All catalysts were tested in the hydrogenation of cyclohexene under similar conditions as a model reaction. Generally, Rh–ODT NPs were inactive, Rh–PVA NPs exhibited distinct activities in solution (aqueous biphasic catalysis) and as a supported catalyst, and Rh–TOAB NPs exhibited similar activities in solution and after immobilization. This last result opens the opportunity for the preparation of highly active Rh NP catalysts both in solution and as a heterogeneous catalyst. Additionally, the stability of the nanoparticles depends on the choice of ligand and on the functionalization of the support surface before immobilization. By optimizing the catalyst synthesis and reaction conditions, turnover frequencies as high as 700,000 h^?1 where observed for stable and recyclable catalyst.     

Nano-Ni-MOFs: High Active Catalysts on the Cascade Hydrogenation of Quinolines

Catalysis Letters - The reduction of nitrogen-containing heterocyclic compounds in aqueous medium under mild condition is quite challenging. In view of metal–organic frameworks (MOFs) possess...     

茂类金属催化剂用于苯乙烯聚合

概述了茂类金属催化剂用于苯乙烯均聚及共聚合的现状。     

Highly Active Carbon‐supported PdSn Catalysts for Formic Acid Electrooxidation

PdSn/C catalysts with different atomic ratios of Pd to Sn were synthesised by a NaBH₄ reduction method. Electrochemical tests show that the alloy catalysts exhibit significantly higher catalytic activity and stability for formic acid electrooxidation (FAEO) than the Pd/C catalyst prepared with the same method. XRD and TEM indicate that a particle‐size effect is not the main cause for the high performance. XPS confirms that Pd is modified by Sn through an electronic effect which can decrease the adsorption strength of poisonous intermediates on Pd and thus promote the FAEO greatly.     

新型高效催化剂气相聚合制备聚乙烯

综合报道了新型乙烯气相聚合ＭＧ型催化剂的制备及其聚合反应性能。研究了采用浸渍反应法制备含ＴｉＣｌ４／ＭｇＣｌ２／ＺｎＣｌ２／ＳｉＯ２醇／Ａｌ（ｉ－Ｂｕ）３的ＭＧ－４型高效催化剂。在压力１．０ＭＰａ下,乙烯聚合催化效率高达４４５￣８８４ｋｇＰＥ／ｇＴｉ,制得了表观密度≥ｇ／０．３７／ｃｍ＾３、重均颗粒分布（２０￣２００目）≥９７．７％、颗粒状态良好的聚乙烯。用ＤＳＣ、ＳＥＭ、ＷＡＸＤ对聚合产物进行了     

Highly Active Dinuclear Copper Catalysts for Homogeneous Azide–Alkyne Cycloadditions

The main feature of the herein presented class of molecularly defined catalysts for the copper‐catalyzed azide–alkyne cycloaddition reaction is the presence of two copper centres in one catalyst molecule. We report the facile three‐step synthesis of two representative bis‐NHC‐dicopper complexes as well as their catalytic performance in the azide–alkyne cycloaddition. A screening with one of these complexes has proved its wide applicability and excellent performance as homogeneous catalyst in various organic solvents and with different alkyne and azide substrates.     

高活性骨架镍温和条件下催化间苯二甲腈加氢制备间苯二甲胺

将骤冷法制备的非晶态NiAl合金薄条,经粉碎、碱活化后,制备出高活性的骨架镍,发现其对于间苯二甲腈催化加氢制备间苯二甲胺具有极高的活性和选择性。研究了溶剂、催化剂用量、原料初始浓度、温度、压力等因素对间苯二甲胺收率和选择性的影响。结果表明,在以甲醇作为溶剂、原料初始浓度1.5 mol/L、催化剂质量为原料质量的3%~6%、80℃、1.5~2.0 MPa,并添加适量碱性助剂的条件下反应150 min,间苯二甲腈转化率可达99.9%,间苯二甲胺的摩尔收率可达96.0%。     

油脂在镍基催化剂上氢化性能的研究

研究由共沉淀方法制备的镍基催化剂上大豆色拉油加氢活性,测定氢化反应温度180℃,反应压力0．8MPa,反应时间120min,催化剂用量4％g／mL、搅拌转速360r／min条件下氢化油脂的碘值、折光指数、熔点数据,考察改变镍铝比、添加助剂铜铁镧等对催化剂在油脂氢化过程中活性的影响,镍基催化剂有较好的加氢活性。     

New Catalysts for the Hydrogenation of Glucose to Sorbitol

Nickel catalysts supported on ZrO₂, TiO₂ and ZrO₂/TiO₂ mixtures performed more active, selective and stable than Ni/SiO₂ catalysts in the hydrogenation of glucose to sorbitol. This was shown by catalytic testing as well as by determination of Ni crystallite size before and after the test. The reason for the better performance was assumed to be metal‐support interaction in the Ni/ZrO₂, Ni/TiO₂ and Ni/ZrO₂/TiO₂ catalysts.     

硝基苯加氢合成对氨基苯酚的催化剂研究进展

对氨基苯酚是一种重要的医药、农药、染料中间体。以硝基苯为原料直接一步催化加氢合成对氨基苯酚具有成本低、收率高、三废排放少等优点,是一条绿色的合成路线。详细综述了硝基苯加氢生成羟基苯胺及羟基苯胺Bamberger重排生成对氨基苯酚的反应机理,加氢及重排催化剂研究等方面的研究进展,介绍了表面活性剂助剂对对氨基苯酚选择性及收率的影响。     

Magnetically Recoverable Nanoparticles: Highly Efficient Catalysts for Asymmetric Transfer Hydrogenation of Aromatic Ketones in Aqueous Medium

Two magnetic chiral iridium and rhodium catalysts were prepared via directly postgrafting 1,2‐diphenylethylenediamine‐derived organic silica or 1,2‐cyclohexanediamine‐derived organic silica onto the silica‐coated iron oxide nanoparticles followed by complexation with iridium(III) or rhodium(III) complexes. During the asymmetric transfer hydrogenation of aromatic ketones in aqueous medium, the magnetic chiral catalysts exhibited high catalytic activities (up to 99% conversion) and enantioselectivities (up to 92% ee). Both catalysts could be recovered easily by magnetic separation and be reused ten times without significantly affecting their catalytic activities and enantioselectivities.     

Palladium Decorated N-Doped Carbon Foam as a Highly Active and Selective Catalyst for Nitrobenzene Hydrogenation

Carbon foam was synthesized by the carbonization of 4-nitroaniline. The reaction is an alternative of the well-known “carbon snake” (or sugar snake) demonstration experiment, which leads to the formation of nitrogen-doped carbon foils due to its nitrogen content. The synthesized carbon foils were grinded to achieve an efficient catalyst support. Palladium nanoparticles were deposited onto the surface of the support, which showed continuous distribution. The prepared Pd nanoparticle decorated carbon foils showed high catalytic activity in nitrobenzene hydrogenation. By applying the designed catalyst, total nitrobenzene conversion, a 99.1 n/n% aniline yield, and an exceptionally high selectivity (99.8 n/n%) were reached. Furthermore, the catalyst remained active during the reuse tests (four cycles) even without regeneration.     

AgRu双金属催化剂在乙二醇选择加氢中的研究

乙醇是化工生产中重要的有机溶剂和生产原料。通过氨蒸法制备新型的AgRu双金属负载Si O2催化剂,采用XRD、BET和TEM等对催化剂进行表征,考察Ru的加入对Ag/Si O2催化剂在乙二醇加氢中催化性能的影响。当在反应温度175℃,压力2 MPa条件下,Ru的加入,对反应活性起到抑制作用,但可促进C-C键的选择加氢。产生这个结果的主要原因可能是由于当Ru的加入,改变了Ag纳米颗粒对C-O键的活化能力。     

Highly Active Silica Gel‐Supported Metathesis (Pre)Catalysts

Highly active Hoveyda–Grubbs and Hoveyda–Blechert type (pre)catalysts, immobilized on silica gel, are presented. These (pre)catalysts are synthesized in a few steps from readily available precursors and demonstrate high activity in a number of test metathesis reactions. The catalyst is easily separated by simple filtration of the non‐swelling material.     

A Phosphite‐Pyridine/Iridium Complex Library as Highly Selective Catalysts for the Hydrogenation of Minimally Functionalized Olefins

A modular library of readily available phosphite‐pyridine ligands has been successfully applied for the first time in the iridium‐catalyzed asymmetric hydrogenation of a broad range of minimally functionalized olefins. The modular ligand design has been shown to be crucial in finding highly selective catalytic systems for each substrate. Excellent enantioselectivities (ees up to 99%) have therefore been obtained in a wide range of E‐ and Z‐trisubstituted alkenes, including more demanding triaryl‐substituted olefins and dihydronaphthalenes. This good performance extends to the very challenging class of terminal disubstituted olefins, and to olefins containing neighbouring polar groups (ees up to 99%). Both enantiomers of the reduction product can be obtained in excellent enantioselectivities by simply changing the configuration of the carbon next to the phosphite moiety. The hydrogenations were also performed using propylene carbonate as solvent, which allowed the iridium catalyst to be reused and maintained the excellent enantioselectivities.

     

Alkynes Hydrogenation over Pd-Supported Catalysts

The liquid-phase stereoselective hydrogenation of phenyl alkyl acetylenics at 298 K and atmospheric pressure on Pd-supported catalysts has been studied. The catalysts were prepared by impregnation of Pd(acac)₂ precursor (1 wt% of Pd) on different siliceous substrates such as amorphous SiO₂, mesoporous MCM-41 and silylated MCM-41. The poisoning effect of lead incorporation on the supported palladium was also studied. All the catalysts displayed high selectivity to cis-alkene isomer, with Pd/MCM-41 being the most active catalyst. Deliberately adding lead to the base, palladium catalysts underwent changes in the selectivity to cis-alkene isomer and a significant drop in the activity. All the solids were characterized by nitrogen adsorption–desorption isotherms at 77 K, TGA, TPR, H₂ and CO chemisorption, XRD, XPS, and TEM.