Selective hydrogenation of cinnamaldehyde over carbon nanotube supported pd-ru catalyst

Summary Carbon nanotube supported Pd, Ru and Pd-Ru catalysts have been prepared and tested with the hydrogenation of cinnamaldehyde as a probe reaction. It has been found that the cinnamaldehyde conversion and the selectivity towards the hydrogenation of C=O bond over Pd-Ru/PCNT catalyst could reach 56.6% and 79.1%, respectively, at 120^oC and 5.0 MPa, which is better than Pd/PCNT and Ru/PCNT catalysts under the same reaction conditions. It is assumed that the better performance of Pd-Ru/PCNT catalyst for cinnamaldehyde hydrogenation may be due to the synergic effect of Pd and Ru metals or the promoting effect of Ru metal.     

Ruthenium-tin sol-gel catalysts: effect of the preparation and tin precursor influence

The influence of the synthesis route and the chemical nature of tin precursors on the catalytic properties of supported sol-gel Ru-Sn/SiO₂ catalysts were studied. It was demonstrated that introduction of tin afforded better selectivities than a monometallic sol-gel catalyst in the liquid-phase hydrogenation of cinnamaldehyde; however, the chemical nature of the tin precursor did not influence the catalyst performance. Sol-gel catalyst properties depended significantly upon the preparation method used and on the activation temperature. The selectivity to unsaturated alcohol increased with conversion, which is indicative of the in-situ creation of active sites selective in the carbonyl bond hydrogenation.     

Hydrogenation of crotonaldehyde and cinnamaldehyde catalyzed by water-soluble palladium complex

The selective hydrogenations of crotonaldehyde and cinnamaldehyde in the aqueous-benzene biphasic system were investigated using water-soluble palladium complex PdCl₂(TPPTS)₂ as catalyst. The hydrogenation rate of crotonaldehyde was higher than that of cinnamaldehyde under similar reaction conditions. The palladium complex selectively catalyzed the hydrogenation of CC bond in crotonaldehyde to form butanal (100%). On the contrary, hydrogenation of both CC and CO bonds in cinnamaldehyde occurred simultaneously, with the amount of phenylpropanal only slightly higher than that of phenylpropanol. However, the reduction of CO bond of cinnamaldehyde could be inhibited by the addition of Na₂CO₃ solution. Therefore, high selectivity to form phenylpropanal (91%) could be obtained by using Na₂CO₃ solution at pH 12.2. Other factors affecting the hydrogenation conversion and selectivity of crotonaldehyde and cinnamaldehyde were also discussed.     

Cyclohexene Reactivity Using Catalysts Containing Pt,Re and PtRe Supported on Na‐ and H‐Mordenite

The reactivity of cyclohexene (CHE) over catalysts containing 0.3 wt% Pt, 0.3 wt% Re or 0.3 wt% Pt + 0.3 wt% Re supported on Na‐ and H‐mordenite has been studied in an atmospheric flow‐type reactor at a temperature range of 100–400 °C, using a flow of hydrogen (20 cm³/min). The catalysts were characterized for acid sites strength‐distribution, using desorption of ammonia in DSC. The acidity of H‐mordenite (HM) is attributed to strong acid sites, whereas the acidity of Na‐mordenite (NaM) is due to weak acid sites which are not involved in the catalytic reaction under study. The catalysts containing HM enhance the reactivity of CHE for isomorization reactions. However, the reactivity of CHE on NaM catalysts enhances only the hydrogenation and dehydrogenation reactions. Pt/HM is the most selective catalyst for isomerization of CHE, whereas Pt/NaM and PtRe/NaM catalysts are the most selective for hydrogenation and dehydrogenation reactions, respectively. The hydroisomorization of CHE seems to depend only on the acidity of the catalysts, whereas both hydrogenation and dehydrogenation reactions were controlled by metallic function of the catalysts.     

Effect of transition metals (Cr, Mn, Fe, Co, Ni and Cu) on selective hydrogenation of cinnamaldehyde over Pt/CNTs catalyst

Summary The effect of transition metals (Cr, Mn, Fe, Co, Ni and Cu) on the selective hydrogenation of cinnamaldehyde (CMA) to the corresponding semi-hydrogenated product over Pt/CNTs catalyst has been studied in ethanol at 343 K under 2.0 MPa H₂ pressure. PtNi/CNTs catalyst shows good catalytic activity and selectivity of C=C bond hydrogenation, 68.4% for conversion of CMA and 97.0% for selectivity of hydrocinnamaldehyde (HCMA). PtCo/CNTs catalyst shows good catalytic activity and selectivity of C=O bond hydrogenation, 91.3% for conversion of CMA and 88.2% for selectivity of cinnamylalcohol (CMO).     

ZrO_2负载Pt催化巴豆醛选择性加氢

以高比表面积ZrO2为载体,采用浸渍法制备了负载型Pt催化剂,应用于常压下气相巴豆醛加氢反应,考察了Pt负载量和H2还原温度等对巴豆醛选择性加氢性能的影响.实验结果表明,Pt负载量(质量分数)为3%的3Pt/ZrO2催化剂经500℃还原后,具有较高的巴豆醛选择性加氢性能:巴豆醛转化率为27%,巴豆醇的选择性为55%.X射线粉末衍射(XRD)分析,CO化学吸附,NH3程序升温脱附(NH3-TPD)表征结果表明Pt/ZrO2催化剂上Lewis强酸中心和适宜的Pt颗粒(约为8nm)有利于巴豆醛选择性加氢生成巴豆醇.     

H+−H− Pairs in Partially Oxidized MAX Phases for Bifunctional Catalytic Conversion of Furfurals into Linear Ketones

Currently, less favorable C=O hydrogenation and weak concerted acid catalysis cause unsatisfactory catalytic performance in the upgrading of biomass-derived furfurals (i.e., furfural, 5-methyl furfural, and 5-hydroxymethyl furfural) to ketones (i.e., cyclopentanone, 2,5-hexanedione, and 1-hydroxyl-2,5-hexanedione). A series of partially oxidized MAX phase (i.e., Ti₃AlC₂, Ti₂AlC, Ti₃SiC₂) supporting Pd catalysts were fabricated, which showed high catalytic activity; Pd/Ti₃AlC₂ in particular displayed high performance for conversion of furfurals into targeted ketones. Detailed studies of the catalytic mechanism confirm that in situ hydrogen spillover generates Frustrated Lewis H⁺−H⁻ pairs, which not only act as the hydrogenation sites for selective C=O hydrogenation but also provide acid sites for ring opening. The close intimate hydrogenation and acid sites promote bifunctional catalytic reactions, substantially reducing the reported minimum reaction temperature of various furfurals by at least 30–60 °C.     

Selective Electrochemical Hydrogenation of Phenol with Earth-abundant Ni−MoO2 Heterostructured Catalysts: Effect of Oxygen Vacancy on Product Selectivity

Herein, we report highly efficient carbon supported Ni−MoO₂ heterostructured catalysts for the electrochemical hydrogenation (ECH) of phenol in 0.10 M aqueous sulfuric acid (pH 0.7) at 60 °C. Highest yields for cyclohexanol and cyclohexanone of 95 % and 86 % with faradaic efficiencies of ∼50 % are obtained with catalysts bearing high and low densities of oxygen vacancy (O_v) sites, respectively. In situ diffuse reflectance infrared spectroscopy and density functional theory calculations reveal that the enhanced phenol adsorption strength is responsible for the superior catalytic efficiency. Furthermore, 1-cyclohexene-1-ol is an important intermediate. Its hydrogenation route and hence the final product are affected by the O_v density. This work opens a promising avenue to the rational design of advanced electrocatalysts for the upgrading of phenolic compounds.     

Activity of palladium sulfide catalysts in the reaction of gas-phase hydrogenation of 2-methylthiophene

In the interaction of hydrogen with 2-methylthiophene in the gas phase over palladium sulfide catalysts at 180–260?C and 0.1–0.8 MPa, the saturation of the thiophene ring resulting in 2-methylthiolane and the hydrogenolysis of 2-methylthiophene occurs. When the conversion is lower than 60%, these reactions occur independently; at higher conversions, methylthiolane also undergoes hydrogenolysis. The specific catalytic activity of PdS supported on γ-Al₂O₃, TiO₂, and carbon and without support is much lower in the hydrogenation of 2-methylthiophene than the activity of PdS supported on SiO₂, aluminosilicate, and zeolite HNaY having strong Brönsted acid surface sites.     

Highly Active Supported Pt Nanocatalysts Synthesized by Alcohol Reduction towards Hydrogenation of Cinnamaldehyde: Synergy of Metal Valence and Hydroxyl Groups

The hydrogenation of α,β‐unsaturated aldehydes to allylic alcohols or saturated aldehydes provides a typical example to study the catalytic effect on structure‐sensitive reactions. In this work, supported platinum nanocatalysts over hydrotalcite were synthesized by an alcohol reduction method. The Pt catalyst prepared by the reduction with a polyol (ethylene glycol) outperforms those prepared with ethanol and methanol in the hydrogenation of cinnamaldehyde. The selectivity towards the C=O bond is the highest over the former, although its mean size of Pt particles is the smallest. The hydroxyl groups on hydrotalcite could act as an internally accessible promoter to enhance the selectivity towards the C=O bond. The optimal Pt catalyst showed a high activity with an initial turnover frequency (TOF) of 2.314 s^?1. This work unveils the synergic effect of metal valence and in situ promoter on the chemoselective hydrogenation, which could open up a new direction in designing hydrogenation catalysts.     

Hybrid Pd-Nanoparticles within Polymeric Network in Selective Hydrogenation of Alkynols: Influence of Support Porosity

This work is addressing the selective hydrogenation of alkynols over hybrid catalysts containing Pd-nanoparticles, within newly synthesized hyper-cross-linked polystyrenes (HPS). Alkynols containing C₅, C₁₀, and C₂₀ with a terminal triple bond, which are structural analogues or direct semi-products of fragrant substances and fat-soluble vitamins, have been studied. Selective hydrogenation was carried out in a batch mode (ambient hydrogen pressure, at 90 °C, in toluene solvent), using hybrid Pd catalysts with low metal content (less than 0.2 wt.%). The microporous and mesoporous HPS were both synthesized and used as supports in order to address the influence of porosity. Synthesized catalysts were shown to be active and selective: in the case of C₅, hydrogenation selectivity to the target product was more than 95%, at close to complete alkynol conversion. Mesoporous catalysts have shown some advantages in hydrogenation of long-chain alkynols.     

Ir nanoclusters confined within hollow MIL-101(Fe) for selective hydrogenation of α,β-unsaturated aldehyde

Although the selective hydrogenation of α,β-unsaturated aldehyde to unsaturated alcohol(UOL) is an extremely important transformation, it is still a great challenge to achieve high selectivity to UOL due to thermodynamic favoring of the C=C hydrogenation over the C=O hydrogenation. Herein, we report that iridium nanoclusters(Ir NCs) confined within hollow MIL-101(Fe) expresses satisfied reaction activity(93.9%) and high selectivity(96.2%) for the hydrogenation of cinnamaldehyde(CAL) to cinnamyl ...     

Development of High Performance Heterogeneous Catalysts for Selective Cleavage of C−O and C−C Bonds of Biomass‐Derived Oxygenates

The environmental impact of CO₂ emissions via the use of fossil resources as chemical feedstock and fuels has stimulated research to utilize renewable biomass feedstock. The biogenic compounds such as polyols are highly oxygenated and their valorization requires the new methods to control the oxygen to carbon ratio of the chemicals. The catalytic cleavage of C?O bonds and C?C bonds is promising methods, but the conventional catalyst systems encounter the difficulty to obtain the high yields of the desired products. This review describes our recent development of the high performance heterogeneous catalysts for the valorization of the biogenic chemicals such as glycerol, furfural, and levulinic acid via selective cleavage of C?O bonds and C?C bonds in the liquid‐phase. Selective C?O bond cleavage by hydrogenolysis enables production of various diols useful as engineering plastics, antifreeze, and cosmetics in high yields. The success of the selective C?C bond scission of levulinic acid can be applied to a wide range of the biogenic oxygenates such as carboxylic acids, esters, lactones, and primary alcohols, in which the selective C?C bond scission at adjacent to the oxygen functional groups are achieved. Furthermore, valorization of glycerol by selective acetylation and acetalization, and of levulinic acid by hydrogenation is described. Our catalysts show excellent performance compared to the reported catalysts in the aforementioned valorization.     

可循环磁性Pt/Fe_3O_4-MCNT催化剂上的肉桂醛选择性加氢反应

采用多步法依次将制备的Fe3O4纳米颗粒和Pt纳米颗粒负载到多壁碳纳米管(MCNT)上得到Pt/Fe3O4-MCNT磁性催化剂,以X射线衍射(XRD)、透射电镜(TEM)、超导量子干涉磁强计(SQUID)和热重-差热分析(TG-DTA)对Pt/Fe3O4-MCNT磁性催化剂的结构和磁性质进行了表征。研究发现预制备的Fe3O4纳米颗粒与Pt纳米颗粒均匀地分散于MCNT上,新制备以及多次使用后的Pt/Fe3O4-MCNT室温下都具有良好的超顺磁性。研究了Pt/Fe3O4-MCNT磁性催化剂上的肉桂醛选择性加氢反应,结果显示催化剂具有良好的C=O加氢活性,肉桂醛转化率在50%左右时,肉桂醇选择性可达96%以上。尺寸均一的Pt粒子均匀的分散在催化剂上可能是催化剂具有良好的C=O加氢选择性的重要原因。在外加磁场作用下催化剂可以高效地从液相反应体系中分离,经多次循环使用后仍具有良好的催化性能。     

Influence of electronic state and dispersion of platinum particles on the conversion and selectivity of hydrogenation of an α,β-unsaturated aldehyde in supercritical carbon dioxide

The selective hydrogenation of cinnamaldehyde (CAL) was investigated using silica supported platinum catalysts in supercritical carbon dioxide. Selectivity to cinnamyl alcohol (COL) is enhanced as Pt⁰/Pt²⁺ ratio increases; namely, zero-valent metallic surface is beneficial to the formation of COL compared with less reduced surface. The influence of Pt⁰/Pt²⁺ ratio is more significant on the selectivity than on the total conversion. For the catalyst with small Pt⁰/Pt²⁺ value, the selectivity also depends on the degree of platinum dispersion. The selectivity to COL is higher for higher degree of platinum dispersion. The CO₂ pressure did not affect the conversion and selectivity so much.     

Hydrogenation of cinnamaldehyde over platinum catalysts: influence of addition of metal chlorides

The effect of addition of metal chlorides to platinum-supported catalysts has been studied in the hydrogenation of cinnamaldehyde in the liquid phase. FeCl₃, SnCl₄ and GeCl₄ were found to be the most effective promoters for the selective synthesis of cinnamyl alcohol. The rate of reaction increased by addition of small amounts of metal chlorides and then decreased at higher contents. Selectivity to cinnamyl alcohol was slightly dependent on the concentration of the additives and on the level of conversion.A reaction mechanism for the hydrogenation of cinnamaldehyde over promoted platinum is suggested.     

Selective hydrogenation of α,β-unsaturated aldehydes over Pt supported on cerium–zirconium mixed oxide of different composition

Cerium–zirconium mixed oxides with different Ce/Zr ratio were prepared and used as supports for Pt-containing catalysts. The study of the catalysts in the cinnamaldehyde hydrogenation reaction has shown that cinnamaldehyde conversion and cinnamyl alcohol selectivity strongly depend on the CeO₂ content in the support. The highest cinnamyl alcohol yield of 81% was obtained in 105 min at room temperature and atmospheric pressure over the 1%Pt/CeO₂–ZrO₂ catalyst with Ce : Zr atomic ratio equal to 4 : 1.     

Characterization and application of supported metal catalysts with well-tailored pore systems and metal dispersions

Silica supported silver catalysts were prepared by sol-gel techniques and characterized by physisorption, in-situ ESCA measurements and transmission electron microscopy. Compared to conventional supported group VIII metal catalysts, these Ag/SiO₂ catalysts exhibited a superior performance for the selective hydrogenation of α,β-unsaturated aldehydes to allylic alcohols.     

温控聚乙二醇两相体系中纳米钯催化肉桂醛选择性加氢反应

将具有“高温混溶、室温分相”功能的聚乙二醇4000(PEG₄₀₀₀)与甲苯-正庚烷组成的两相体系用于纳米钯催化的肉桂醛选择性加氢反应中.在优化的反应条件下,肉桂醛转化率和氢化肉桂醛选择性分别为99%和98%.钯纳米催化剂经简单分相即可与产物分离,且循环使用8次,其活性和选择性基本保持不变.     

Synergism of Pt nanoparticles and iron oxide support for chemoselective hydrogenation of nitroarenes under mild conditions

An efficient and low-cost supported Pt catalyst for hydrogenation of niroarenes was prepared with colloid Pt precursors and α-Fe₂O₃ as a support. The catalyst with Pt content as low as 0.2 wt% exhibits high activities, chemoselectivities and stability in the hydrogenation of nitrobenzene and a variety of niroarenes. The conversion of nitrobenzene can reach 3170 mol_conv h^?1 mol_Pt^?1 under mild conditions (30 °C, 5 bar), which is much higher than that of commercial Pt/C catalyst and many reported catalysts under similar reaction conditions. The spatial separation of the active sites for H₂ dissociation and hydrogenation should be responsible for the high chemoselectivity, which decreases the contact possibility between the reducible groups of nitroarenes and Pt nanoparticles. The unique surface properties of α-Fe₂O₃ play an important role in the reaction process. It provides active sites for hydrogen spillover and reactant adsorption, and ultimately completes the hydrogenation of the nitro group on the catalyst surface.