Zn取代的磷钨酸季铵盐无溶剂氧化苯甲醇合成苯甲醛

合成了一系列过渡金属Zn取代的Keggin型磷钨杂多酸的季铵盐,采用傅里叶变换红外光谱(FTIR)、X射线衍射(XRD)等方法表征了杂多化合物的结构.并将其用于苯甲醇无溶剂氧化合成苯甲醛的反应,考察了催化剂种类、反应条件对苯甲醇氧化的影响.实验结果表明,在无任何溶剂的情况下,Zn取代的Keggin型磷钨四丁基铵盐具有最佳的催化活性,反应时间仅为30 min,苯甲醇的转化率可以达到95.6%,苯甲醛的选择性达到了96.4%.在对杂多酸季铵盐结构的研究基础上,对可能的反应机理进行了初步探讨.     

Oxidation of benzyl alcohol by K<Subscript>2</Subscript>FeO<Subscript>4</Subscript> to benzaldehyde over zeolites

A novel and green procedure for benzaldehyde synthesis by potassium ferrate oxidation of benzyl alcohol employing zeolite catalysts was studied. The prepared oxidant was characterized by SEM and XRD. The catalytic activity of various solid catalysts was studied using benzyl alcohol as a model compound. USY was found to be a very efficient catalyst for this particular oxidation process. Benzaldehyde yields up to 96.0% could be obtained at the following optimal conditions: 0.2 mL of benzyl alcohol, 4 mmol of K₂FeO₄, 0.5 g of USY zeolite; 20 mL of cyclohexene, 0.3 mL of acetic acid (36 wt %), 30°C temperature, 4 h reaction time.     

Ag/SBA-15低温气相选择性催化氧化苯甲醇合成苯甲醛

以SBA-15为载体,采用浸渍法制备了不同Ag含量的Ag/SBA-15,通过N₂吸附-脱附、X射线衍射、扫描电子显微镜、高分辨透射电子显微镜、X射线光电子能谱和电感耦合等离子体质谱对催化剂进行了表征。将Ag/SBA-15用于苯甲醇气相选择性催化氧化合成苯甲醛,研究了反应条件对转化率和选择性的影响。结果表明,Ag/SBA-15具有均一的一维孔道结构、较厚的孔壁（3-5 nm）及较大的比表面积（411-541 m²/g）,其规整纳米空间的限域作用使一定负载量的Ag以纳米尺寸均匀分散于介孔SBA-15孔道内,增加了活性组分的比表面积。亲核性氧物种从Ag到SBA-15表面的氧溢流,提高了低温下Ag/SBA-15对苯甲醇气相选择性氧化合成苯甲醛的催化性能。5.3% Ag/SBA-15中的Ag粒径为5-6 nm,且均匀分散于载体孔道中,反应温度为220℃时,苯甲醇转化率为87%,苯甲醛选择性为95%;240℃时,苯甲醇转化率和苯甲醛选择性分别高达94%和97%;并在240-300℃范围内,其催化活性和选择性保持不变,表现出了良好的温度耐受能力。催化剂经活化再生可以连续使用40 h,选择性基本保持不变。     

Selective alcohol oxidation to aldehydes and ketones over base-promoted gold–palladium clusters as recyclable quasihomogeneous and heterogeneous metal catalysts

Bimetallic gold–palladium clusters, with an average size of 1.9 nm and composed of 80 mol% gold, proved to be highly active and selective metal catalysts for the organic phase oxidation with O₂ of aliphatic, allylic and benzylic alcohols to the corresponding carbonyl products. Polyvinylpyrrolidone stabilized gold–palladium clusters dispersed in N,N-dimethylformamide emerged as promising quasihomogeneous metal catalysts for the oxidation of benzyl alcohol to benzaldehyde with full selectivity; they could be efficiently recycled with unaffected catalytic performance by solvent-resistant nanofiltration. Highly active and durable heterogeneous catalysts for the amide phase or solvent-free alcohol oxidation were prepared by the quantitative immobilization of the optimized gold–palladium clusters on the high surface area basic BaAl₂O₄ spinel support with preservation of the bimetallic clusters’ nanodispersion.     

Efficient and selective oxidation of alcohols with <Emphasis Type="Italic">tert</Emphasis>-BuOOH catalyzed by a dioxomolybdenum(VI) Schiff base complex under organic solvent-free conditions

The catalytic activity of dioxidobis{2-[(E)-p-tolyliminomethyl]phenolato}molybdenum(VI) complex was studied, for the first time, in the selective oxidation of various primary and secondary alcohols using tert-BuOOH as oxidant under organic solvent-free conditions at room temperature. The effect of different solvents was studied in the oxidation of benzyl alcohol in this catalytic system. It was found that, under organic solvent-free conditions, the catalyst oxidized various primary and secondary alcohols to their corresponding aldehyde or ketone derivatives with high yield. The effects of other parameters such as oxidant and amount of catalyst were also investigated. Among different oxidants such as H₂O₂, NaIO₄, tert-BuOOH, and H₂O₂/urea, tert-BuOOH was selected as oxygen donor in the oxidation of benzyl alcohol. Also, it was found that oxidation of benzyl alcohol required 0.02 mmol catalyst for completion. Dioxomolybdenum(VI) Schiff base complex exhibited good catalytic activity in the oxidation of alcohols with tert-BuOOH under mild conditions. In this catalytic system, different primary alcohols gave the corresponding aldehydes in good yields without further oxidation to carboxylic acids.     

Mn-Al和Cu-Mn-Al复合氧化物催化苯甲醇选择氧化反应

用溶胶-凝胶法制备了不同组成的Mn-Al和Cu-Mn-Al复合氧化物两组催化剂,用于苯甲醇选择氧化反应.用X射线衍射(XRD)、N2物理吸附(BET)、扫描电镜(SEM)、H_2程序升温还原(H_2-TPR)、O_2程序升温脱附(O_2-TPD)和X射线光电子能谱(XPS)技术对催化剂进行了结构表征,考察了催化剂组成对催化活性的影响.结果表明:以甲苯为溶剂,O_2为氧化剂,353 K反应5 h,Mn_2Al和Cu_(0.3)Mn_(0.7)Al_2催化剂上的苯甲醇转化率分别为36.6%和40.9%,苯甲醛选择性均为100%.进一步研究表明:催化剂活性与其H2还原性和O_2吸附性有关,高活性的催化剂吸附氧多,生成的活性氧易参与反应.     

Bimetallic Au/Pd catalyzed aerobic oxidation of alcohols in the poly(ethylene glycol)/CO2 system

Bimetallic Au/Pd nanoparticles were prepared and used to catalyze oxidation of alcohols in the poly(ethylene glycol) (PEG)/CO₂ biphasic system using O₂ as the oxidant without adding any base. The catalytic activity of Au/Pd bimetal with different mole ratios was studied using benzyl alcohol as the substrate. It was found that bimetallic Au/Pd nanoparticles with Au:Pd=1:3.5 had higher catalytic activity than monometallic Au, Pd and the bimetallic Au/Pd nanoparticles with other molar ratios. The effect of CO₂ pressure on the oxidation of benzyl alcohol and 1-phenylethanol in PEG/CO₂ was investigated. It was demonstrated that CO₂ pressure could be used to tune the conversion and selectivity of the reactions effectively. α,β,-Unsaturated alcohols were also studied and found to be more reactive than benzyl alcohol and 1-phenylethanol. Recycling experiments showed that the Au/Pd/PEG/CO₂ catalytic system could be recycled at least four times without reducing the activity. In addition, the catalytic system is clean and the products can be separated easily.     

富氮空心蠕虫状碳材料的合成及其苯甲醇非金属选择性催化氧化的高活性

Carbon materials have become one of the research hotspots in the field of catalysis as a typical representative of non-metallic catalytic materials. Herein, a facile synthetic strategy is developed to fabricate a series of hollow carbon nanoworms (h-NCNWs) that contain nitrogen up to 9.83 wt% by employing graphitic carbon nitride (g-C₃N₄) as the sacrificing template and solid nitrogen source. The h-NCNWs catalysts were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscope (HR-TEM), N₂ adsorption-desorption, Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric (TG), Raman spectra, and X-ray photoelectron spectroscopies (XPS). The catalytic activities of the h-NCNWs catalysts for selective oxidation of benzyl alcohol with O₂ were also evaluated. The characterization results revealed that the h-NCNWs catalysts displayed a unique hollow worm-like nanostructure with turbostratic carbon shells. The nitrogen content and shell thickness can be tuned by varying the relative ratio of resorcinol to g-C₃N₄ during the preparation process. Furthermore, nitrogen is incorporated to the carbon network in the form of graphite (predominantly) and pyridine, which is critical for the enhancement of the catalytic activity of carbon catalysts for the selective oxidation of benzyl alcohol. At a reaction temperature of 120 ℃, a 24.9% conversion of benzyl alcohol with > 99% selectivity to benzaldehyde can be achieved on the h-NCNWs catalyst prepared with a mass ratio of resorcinol to g-C₃N₄ of 0.5. However, the catalytic activities of the h-NCNWs catalysts were dependent on the amount of N dopants, in particular graphitic nitrogen species. The conversion of benzyl alcohol markedly decreased to 13.1% on the h-NCNWs catalyst prepared with a mass ratio of resorcinol to g-C₃N₄ of 1.5. Moreover, the h-NCNWs catalyst showed excellent stability during the reaction process. The conversion of benzyl alcohol and the high selectivity to aldehyde can be kept within five catalytic runs over the h-NCNWs0.5 catalyst. These results indicate that rationally designed carbon materials have great potential as highly efficient heterogeneous catalysts for oxidation reactions.     

Cover Feature: Oxidation of Benzyl Alcohol Using Cobalt Oxide Supported Inside and Outside Hollow Carbon Spheres (ChemistryOpen 6/2021)

The Cover Feature shows the cobalt oxide nanoparticles supported both inside and outside hollow carbon spheres (HCSs), which serve as a catalyst for benzyl alcohol oxidation. A metal oxidation step prior to the reaction enhanced the catalytic activity of benzyl alcohol which was used as a model reaction for the catalysts. Both catalysts showed similar activity and selectivity (to benzaldehyde) whether placed inside or outside the HCSs (70% selectivity at 50% conversion). No poisoning was observed due to product build up in the HCSs. More information can be found in the Full Paper by Pumza Mente et al.     

Cu-superconductors in organic catalysis, II. The conversion of benzyl alcohol on various Cu-catalysts

The catalytic conversion of benzyl alcohol to toluene and benzaldehyde was performed on YBa₂Cu₃O_7–x (Y–Ba–Cu–O) in the presence of hydrogen at 250–400°C. The catalytic characteristics of Y–Ba–Cu–O were compared with those of CuO, Cu/SiO₂ and Y₂BaCuO₅. The structural changes in the catalysts during the reaction were measured by means of XRD and SEM. It was found that the oxidation state of the copper in Y–Ba–Cu–O was a considerable factor in the conversion of benzyl alcohol.Part I:React. Kinet. Catal. Lett. 51, 61 (1993).     

超临界二氧化碳中功能化聚乙二醇稳定的钯纳米粒子催化醇的选择氧化反应

 以超临界二氧化碳 (scCO2)/聚乙二醇 (PEG) 两相为反应介质, 双齿氮配体功能化聚乙二醇稳定的 Pd 纳米颗粒作为催化剂, 进行了醇的需氧氧化反应. 系统研究了催化剂制备条件和反应条件对苯甲醇需氧氧化反应的影响. 结果表明, 以氢气为还原剂制备的 Pd 纳米粒子的催化活性最高. 反应结束后, 可以利用 scCO2 直接进行原位萃取得到产物, 实现了催化剂与产物的有效分离和催化剂的循环使用. 反应中没有检测到钯的流失. 催化剂经过 5 次循环利用后转化率仍可达 98%.     

基于能带理论研究非贵过渡金属对Pd基催化剂的影响

采用乙二醇为溶剂和还原剂、谷氨酸为螯合剂、非贵过渡金属为助剂、XC-72为载体的一步溶剂热法制备了3种Pd基催化剂：PdCr/XC-72,PdMn/XC-72和PdHg_3.5/XC-72.实验结果表明,Cr、Mn、Hg 3种非贵过渡金属元素的加入会影响催化剂中活性金属颗粒的粒径和分散度.其中,PdCr/XC-72催化剂具有金属粒径小、分散均匀的特点,其在无溶剂条件下对DL-sec-苯乙醇的转化率为91%,远远高于PdMn/XC-72（53%）和PdHg_3.5/XC-72（32%）.同时,利用基于密度泛函理论的第一性原理,从能带理论和d带空穴的角度出发,进一步从理论上分析了PdCr/XC-72催化剂催化活性较好的原因.     

Selective Production of Secondary Amine by the Photocatalytic Cascade Reaction Between Nitrobenzene and Benzyl Alcohol over Nanostructured Bi2MoO6 and Pd Nanoparticles Decorated with Bi2MoO6

The synthesis of secondary amine by the photoalkylation of nitrobenzene with benzyl alcohol using a simple light source and sunlight is a challenging task. Herein, a one-pot cascade protocol is employed to synthesize secondary amine by the reaction between nitrobenzene and benzyl alcohol. The one-pot cascade protocol involves four reactions: (a) photocatalytic reduction of nitrobenzene to aniline, (b) photocatalytic oxidation of benzyl alcohol to benzaldehyde, (c) reaction between aniline and benzaldehyde to form imine, and (d) photocatalytic reduction of imine to a secondary amine. The cascade protocol to synthesize secondary amine is accomplished using Bi₂MoO₆ and Pd nanoparticles decorated Bi₂MoO₆ catalysts. The surface characteristics, oxidation states, and elemental compositions of the materials are characterized by several physicochemical characterization techniques. Optoelectronic and photoelectrochemical measurements are carried out to determine the bandgap, band edge potentials, photocurrents, charge carrier's separation, etc. An excellent yield of secondary amine is achieved with simple household white LED bulbs. The catalyst also exhibits similar or even better activity in sunlight. The structure-activity relationship is established using catalytic activity data, control reactions, physicochemical, optoelectronic characteristics, and scavenging studies. Bi₂MoO₆ and Pd nanoparticles decorated Bi₂MoO₆ exhibit excellent photostability and recyclability. The simple catalyst design with a sustainable and economical light source for the synthesis of useful secondary amine from the nitrobenzene and benzyl alcohol would attract the researchers to develop similar catalytic protocols for other industrially important chemicals.     

Oxidation of Benzyl Alcohol Using Cobalt Oxide Supported Inside and Outside Hollow Carbon Spheres

Cobalt oxide nanoparticles (6 nm) supported both inside and outside of hollow carbon spheres (HCSs) were synthesized by using two different polymer templates. The oxidation of benzyl alcohol was used as a model reaction to evaluate the catalysts. PXRD studies indicated that the Co oxidation state varied for the different catalysts due to reduction of the Co by the carbon, and a metal oxidation step prior to the benzyl alcohol oxidation enhanced the catalytic activity. The metal loading influenced the catalytic efficiency, and the activity decreased with increasing metal loading, possibly due to pore filling effects. The catalysts showed similar activity and selectivity (to benzaldehyde) whether placed inside or outside the HCS (63 % selectivity at 50 % conversion). No poisoning was observed due to product build up in the HCS.     

Influence of Periodic Nitrogen Functionality on the Selective Oxidation of Alcohols

An enhancement in catalytic alcohol oxidation activity is attributed to the presence of nitrogen heteroatoms on the external surface of a support material. The same Pd particles (3.1–3.2 nm) were supported on polymeric carbon–nitrogen supports and used as catalysts to selectively oxidize benzyl alcohol. The polymeric carbon–nitrogen materials include covalent triazine frameworks (CTF) and carbon nitride (C₃N₄) materials with nitrogen content varying from 9 to 58 atomic percent. With comparable metal exposure, estimated by X‐ray photoelectron spectroscopy, the activity of these catalysts correlates with the concentration of nitrogen species on the surface. Because the catalysts showed comparable acidic/basic properties, this enhancement cannot be ascribed to the Lewis basicity but most probably to the nature of N‐containing groups that govern the adsorption sites of the Pd nanoparticles.     

纳米孔炭负载 MnOx 催化剂上苯甲醇氧化反应性能

 以纳米孔炭 (NC) 为载体, 采用浸渍法制备了一系列 MnOx/NC 催化剂, 并用于以空气为氧源的苯甲醇液相氧化反应. 通过 X 射线衍射、X 射线光电子能谱、N2 吸附-脱附和 H2-程序升温还原等手段对催化剂进行了表征, 考察了催化剂中 Mn 负载量和焙烧温度, 以及反应条件等对反应性能的影响. 结果表明, 10%MnOx/NC 催化剂的活性较高, 反应 4 h 后苯甲醇转化率可达 80.4%; 明显高于活性炭负载的 MnOx 催化剂. 这主要归因于其表面存在大量高分散、且易于还原的 Mn 物种.     

Influence Type and Temperature of Activation on the Catalytic Activity of Derived Form of Au 101 Nanocatalysts

Recently, gold nanoparticles attracted an increased attention due to unusual and somewhat unexpected catalytic properties especially pronounced in the oxidation of some organic compounds. Gold nanoparticles, which was immobilized on powder Norit® activated carbon as a support (1.0 wt % Au101/AC) exhibited high activity and selectivity for benzyl alcohol oxidation particularly with the gold catalysts subjected to a specific type of activation and temperature. The interaction between Au101 particles and its support was studied by measuring the catalytic activity and selectivity as a function of activation procedure. The first method included washing with a solvent (i.e., toluene) at elevated temperature, and/or followed by heat treatments at mild temperatures (i.e., 100 and 200°C for 3 h). The highest catalytic activity of benzyl alcohol oxidation was however obtained when gold catalysts were pre-washed with hot toluene at 100°C for 2 h followed by thermal treatment under vacuum. In these cases, the gold core diameters was ∼3.5 nm. In a number of experiments, the reaction time was 3 h, whereas in other runs it was extended to 24 h. The conversion level of benzyl alcohol oxidation was affected by the type of activation and its temperature related to the gold particles size.     

Controlling the duality of the mechanism in liquid-phase oxidation of benzyl alcohol catalysed by supported Au-Pd nanoparticles

In the solvent-free oxidation of benzyl alcohol to benzaldehyde using supported gold-palladium nanoparticles as catalysts, two pathways have been identified as the sources of the principal product, benzaldehyde. One is the direct catalytic oxidation of benzyl alcohol to benzaldehyde by O(2), whereas the second is the disproportionation of two molecules of benzyl alcohol to give equal amounts of benzaldehyde and toluene. Herein we report that by changing the metal oxide used to support the metal-nanoparticles catalyst from titania or niobium oxide to magnesium oxide or zinc oxide, it is possible to switch off the disproportionation reaction and thereby completely stop the toluene formation. It has been observed that the presence of O(2) increases the turnover number of this disproportionation reaction as compared to reactions in a helium atmosphere, implying that there are two catalytic pathways leading to toluene.     

Effective platinum catalysts for low-temperature oxidation of CO

A number of platinum-based catalysts bonded on carbon fiber karbopon were prepared using alcohol solutions of H₂PtCl₆. The catalytic activity of the samples was determined in the low-temperature oxidation of carbon monoxide by oxygen. The effect of the solvent nature of the precursor on the activity of the catalysts was determined. The best results were obtained in the presence of 1.5% Pt/karbopon catalyst prepared using isobutyl alcohol; 100% CO conversion was achieved in respiratory treatment (12000 h^?1, room temperature).