The influence of MSI (metal–support interactions) on activity and selectivity in the hydrogenation of aldehydes and ketones

The vapor–phase hydrogenation of a group of aldehydes and ketones which contain unsaturated C=C bonds has been studied over a family of supported Pt catalysts. Turnover frequencies, activation energies and reaction orders for crotonaldehyde, benzaldehyde, phenylacetaldehyde and acetophenone are provided and compared to those for butyraldehyde, benzyl alcohol, 1–phenylethanol, acetylcyclohexane and acetone. Metal–support interactions (MSI) induced in Pt/TiO₂ not only enhance specific activity but also markedly shift selectivity because hydrogenation of the carbonyl bond is favored. The retention of high selectivity to the intermediate unsaturated alcohols shows that adsorption properties, as well as kinetic parameters, are altered. A model is discussed which describes the sites responsible for this behavior. This revised version was published online in June 2006 with corrections to the Cover Date.     

磁性纳米钌催化剂制备及其催化甲苯氢化反应性能

采用共沉淀法制备Fe₃O₄粒子,用SiO₂对Fe₃O₄纳米粒子进行表面包覆,用改性聚乙烯吡咯烷酮对所得磁性粒子进行表面修饰,制备磁性纳米粒子负载钌催化剂Ru/PVP-DB-171/SiO₂/Fe₃O₄。红外光谱、X射线衍射、扫描电子显微镜及透射电子显微镜分析表明,所得粒子结构是面心尖晶石结构,Fe₃O₄为核,无定形SiO₂为壳,纳米钌吸附在磁性载体表面。该粒子具有高分散性,可用磁分离实现固液分离。以甲苯液相催化加氢反应为模型,评价磁性负载钌催化剂的催化性能,计算出甲苯氢化的活化能为16.6 kJ·mol^-1,在433 K和4.0 MPa条件下,反应转换数达30 262 mol·(mol-Ru）^-1,Ru催化剂可循环使用8次,添加助剂的种类和数量影响催化剂活性。     

Homogeneous catalytic hydrogenation of poly(styrene-co-butadiene) using a ruthenium based Wilkinson catalyst

Summary Poly(Styrene-co-butadiene) can be quantitatively hydrogenated using tris(triphenyl phosphine) ruthenium(II) chloride, RuCl₂(PPh₃)₃ as catalyst. The effect of temperature, pressure and catalyst concentration on both the rate and degree of hydrogenation have been studied. The hydrogenated elastomers have been characterized by IR, ¹H NMR and TGA.Ref. 1     

Activity of ruthenium hydrogenation catalysts in copper(II) formate decomposition

Charcoal-, silica-, alumina- and titanium(IV) oxide-supported ruthenium catalysts, prepared by conventional impregnation and incipient wetness methods from a ruthenium(III) oxide precursor were tested in copper(II) formate decomposition in aqueous solution. Such a reaction was found to be an efficient and simple activity test of charcoal-supported catalysts. The application of this reaction for a bimetallic ruthenium–copper catalyst preparation was also suggested. Experimental results were compared with those obtained using commercial catalysts and ruthenium black.     

Arene ruthenium(II) p-chloroacetophenone phenylthiosemicarbazone complex mediated transfer hydrogenation of ketones

A series of cationic half-sandwich arene ruthenium(II) complexes of general formula [Ru(η⁶-p-cymene)Cl(L)]Cl have been synthesized from the reaction of [Ru(η⁶-p-cymene)Cl₂]₂ with thiosemicarbazone derivatives (L). Characterization of the complexes were accomplished by analytical and spectral (FT-IR, UV–Vis, ¹H NMR) methods. Single crystal structure determination reveals the presence of a pseudooctahedral three-legged piano stool conformation. All the complexes exhibit a quasi-reversible one electron reduction in the range from ?0.75 to ?0.85 V. Further, the catalytic activity of the titled complex has been investigated in the transfer hydrogenation of ketones in the presence of isopropanol/NaOH.     

Asymmetric transfer hydrogenation of ketones by N,N-containing quinazoline-based ruthenium(II) complexes

The novel set of quinazoline-based chiral ligands was synthesized starting from optically pure amino acids. Coordination with RuCl₂(PPh₃)dppb gave ruthenium(II) N-heterocyclic complexes 4b–d. The structure of complex 4b was fully illuminated by X-ray crystallography. The steric environment of these chiral ruthenium complexes 4b–d was evaluated in asymmetric transfer hydrogenation (ATH) of prochiral ketones in the presence of NaOⁱPr by using 2-propanol as the hydrogen source and solvent. The resultant catalytic system can achieve very good enantioselectivities (up to 91%) and high yields (up to 99%).     

含Ni介孔分子筛的合成及其对苯加氢催化性能

采用水热法合成出不含镍和含镍的硅基介孔分子筛.利用XRD、FT-IR、TPR、TEM和比表面孔径测定等手段对样品进行了表征.结果表明：合成出有序性好的介孔分子筛（MCM-41）,550 ℃焙烧可以将模板剂有效去除,所合成介孔分子筛负载Pt后介孔有序性降低,但是介孔结构仍然存在.苯催化加氢反应研究表明：不含Ni的介孔分子筛不具有加氢活性,当将其负载Pt后具有苯加氢催化活性;含Ni介孔分子筛本身具有苯加氢活性,含Ni介孔分子筛负载Pt后苯加氢催化活性有较大的提高,所有样品的环己烷选择性都接近100 %,说明含Ni介孔分子筛可以直接作为苯加氢反应的催化剂或作为苯加氢催化剂良好的载体.     

The effect of pH on the hydrogenation of benzene in an aqueous biphase using a ruthenium catalyst

There is currently much controversy surrounding homogeneous arene hydrogenation catalysis since it has been suggested that the active catalysts are actually heterogeneous. Since many of the proposed homogeneous catalysts operate in water under biphasic conditions we have studied the effect of pH on a mononuclear ruthenium catalyst precursor. As the pH increases, turnover frequency also increases, which corresponds to an increase in nanoparticle formation. The method could be used as a screen to help assess homogeneous versus heterogeneous catalysis.     

Synthesis of Ru(II) pyridoxal thiosemicarbazone complex and its catalytic application to one-pot conversion of aldehydes to primary amides

A convenient method for the synthesis of Ru(II) pyridoxal thiosemicarbazone complex has been described. Elemental analysis, spectral methods and single crystal X-ray diffraction analysis were used to confirm the composition of the complex. The synthesized complex could act as an efficient, reusable homogeneous catalyst for transformation of aldehydes to the corresponding primary amides in the presence of NH₂OH·HCl. The effect of solvent, base, temperature, time, catalyst loading and recyclability was also investigated.     

A study on the catalytic hydrogenation of aldehydes using mayenite as active support for palladium

Selective benzaldehyde reduction to benzyl alcohol was accomplished using a new catalyst based on Pd dispersed on mayenite (Ca₁₂Al₁₄O₃₃) support. In this work, mayenite has been doped in its nanocages with H⁻ ions to investigate its role in the reduction of aldehydes. Benzaldehyde reduction was observed in H₂ atmosphere (120 °C, 8 atm). Catalytic performances compared to commercial Pd/C catalyst are superior in terms of selectivity and comparable as activity.     

General scheme of adsorption,electroreduction and catalytic hydrogenation of nitro-compounds on platinum—II. Mechanism of electroreduction and catalytic hydrogenation

The effect of basic kinetic parameters (potential, the nature and concentration of nitro-compounds solution pH, coverage of the surface with organic particles and hydrogen) on electroreduction and catalytic hydrogenation of nitro-compounds on platinum has been investigated. Direct comparison of kinetic and adsorption data obtained under the same conditions enabled the mechanism of these processes to be clarified.Kinetics of electroreduction of preliminarily chemisorbed semireduced nitro-compounds particles and kinetics of their hydrogenation by molecular and atomic hydrogen diffused through a palladium membrane have been investigated. Kinetics of interaction of hydrogen preliminaryly adsorbed on platinum with nitro-compounds has also been investigated.One and the same stage of interaction between a semireduced chemisorbed particle, formed in the preceding rapid stages of nitro-compound chemisorption, and adsorbed atomic hydrogen, formed in the preceding rapid electrochemical stage

or in the preceding rapid stage of molecular hydrogen adsorption

has been shown to represent the slow stage of electroreduction and catalytic liquid-phase hydrogenation of nitro-compounds on platinum.     

Syntheses, structures and catalytic activities of ruthenium (II) carbonyl iodide complexes with CNC-pincer bis (carbene) ligand

Two new pincer bis (carbene) ligands and corresponding ruthenium (II) carbonyl iodide complexes have been synthesized and characterized. The structures of complexes 3 and 4 have been determined by X-ray crystallography. Complexes 3 and 4 have been proved to be efficient catalysts in the transfer hydrogenation of acetophenone.     

Electropolymerization and characterization of terpyridinyl iron (II) and ruthenium (II) complexes

Electroactive 2,2′: 6,2″-terpyridinyl ligands ( 3, 5, 6 ) and their iron(II) ( 7a–9a ) and ruthenium(II) complexes ( 7b–9b ) were synthesized. Bis[3-(aminophenyl)-2,2′ :6,2″-terpyridinyl]metal(II) complexes ( 7a, 7b ) and bis[2-(hydroxyphenyl)-2,2′ :6,2″-terpyridinyl]metal(II) complexes ( 8a, 8b ) were electropolymerized on to the surface of Pt or In-SnO₂ (ITO) electrodes in acetonitrile containing Bu₄NCIO₄ by scanning the potential between O and + 1.6V (for 7a and 7b ), and ?0.8 and +1.6V (for 8a and 8b ) versus saturated calomel electrode. The electrodes obtained by electropolymerization exhibited reversible electrochromism based on Fe(II)/Fe(III) or Ru(II)/Ru(III) redox couple. Photoresponses to visible light were found in the modified electrode obtained by electropolymerization of ruthenium complex 7b in an aqueous LiClO₄ solution containing methylviologen (cation MV²⁺) under an O₂ atmosphere. The mechanism for the photoresponded cathodic current was explained in terms of an excitation of bis(terpyridinyl)ruthenium(II) complex [Ru(terpy)²₂⁺] by visible light, an electron transfer from the excited state [Ru(terpy)^2+*₂] to MV²⁺, reduction of Ru(terpy)³⁺₂ at an electrode, and oxidation of MV^+* with O₂.     

The effects of picolinic acid and pH on the adsorption of Cu(II) by activated carbon fibers

The adsorption characteristics of Cu(II) on activated carbon fibers (ACFs) from simulated wastewater was investigated in the picolinic acid concentration range from 0.15 to 15 mM by varying pH from 2 to 8. When pH is below 4, the removal fraction of Cu(II) ions decreased with the decrease of pH. The removal fraction of Cu(II) ions is almost constant above pH 4. The removal efficiency of Cu(II) ions increased as the molar ratio of picolinic acid to Cu(II), specific surface area of ACFs and pH of the solution increased. In the case of [Pic]/[Cu(II)]=10, complete adsorption of Cu(II) was performed on ACF, even at pH 2.     

Hydroxyl group effect in novel NNN type pyridine based ruthenium (II) complex for the transfer hydrogenation of ketones

The new NNN type pyridine ligands were prepared by using low cost and readily available starting materials and metalated with RuCl₂(PPh₃)₃ to obtain ruthenium(II) complexes. All structures were illuminated by NMR, HRMS, and FT-IR spectroscopy. The complexes exhibited good catalytic activity in transfer hydrogen reaction of ketones and it was found that a hydroxyl group on β-position of the pyridine ring had a dramatic effect on the catalyst efficiency.     

Kinetic study of hydrogen transfer from benzyl alcohol to aliphatic aldehydes catalysed by heterogenised ruthenium(II) catalysts

Aliphatic aldehydes were reduced to corresponding alcohols by transfer hydrogenation in the presence of Ru(II) complexes bound to swellable polymer matrices. Benzyl alcohol was used as hydrogen donor because of its strong hydrogen donor ability. The kinetics of the reaction has been measured between 100 and 140°C. The results showed that reaction rate depended on the structure of aldehydes and concentrations of aldehyde. Also reaction rate depended on the concentration of hydrogen donor, and on the amount of catalyst. The reaction proceeded efficiently in halogenated hydrocarbon solvents. The metal leaching was different for different catalytic runs and it was most pronounced in the first catalytic run. The observed activation energy, E_a = 18 ± 1 kcal/mol was obtained, suggested that process in predominantly chemically controlled reaction. A general reaction mechanism and rate equation have been proposed.     

三齿吡啶基钌配合物的对位取代基对氢转移催化活性的影响

Three stable 4-substituted pyridine-based ruthenium(II)complexes[RuCl2(PPh3)L](L=4-R-2,6-bis (diethylaminomethylene)pyridine,R=Br,H or allyloxy)were synthesized.The catalytic activities of the complexes toward transfer hydrogenation from alcohols to ketones were investigated.The electronic effects of the para-substituent in the pyridyl ring were probed and we found that the electron-donating group increased the catalytic activity.The result suggests that an electron-donating group is probably preferential for linking the catalytic ruthenium complex and the chemically inert supporting molecules such as a carbosilane dendrimer.     

浸渍液pH对镍物种存在状态及催化剂加氢催化性能的影响

以HZSM-5为载体,硝酸调节浸渍液的pH,采用等体积浸渍法制备含Ni质量分数0.5%的Ni/HZSM-5催化剂,结合XRD、TEM、BET、NH3-TPD及H2-TPR等表征手段,考察浸渍液pH对Ni物种存在状态及催化剂加氢催化性能的影响.结果表明,pH为2.5时,Ni物种以3种形式存在,载体外表面较大颗粒(8 nm...     

铬形态及使用条件对糠醛催化加氢反应产物分布的影响

采用共沉淀法制备系列Cu-Cr糠醛加氢催化剂,考察不同铬形态对催化剂反应性能的影响。采用管式连续流动固定床积分反应器, 研究糠醛在Cu-Cr催化剂上的气-液相加氢反应规律。结果表明,制备催化剂时的铬原料不同,将极大地影响催化剂的加氢活性和产物选择性,以硝酸铬形式加入制备的催化剂对糠醇的生成较为有利,而以醋酸铬形式加入制备的催化剂对甲基呋喃的形成有利;在(70～110) ℃,随着温度升高,糠醛转化率和糠醇选择性增加,2-甲基呋喃选择性降低;糠醛流速为(0.01～0.06) mL·min^-1时,随着流速的增加,糠醛转化率下降,0.03 mL·min^-1时糠醇选择性出现极大值,而副产物2-甲基呋喃和呋喃类则在此处出现极小值。副产物戊二醇和四氢康醇的选择性则随着糠醛流速的增大上升。