Will Zeolite‐Based Catalysis be as Relevant in Future Biorefineries as in Crude Oil Refineries?

Transition from petroleum‐ to biomass‐based fuel economy will require new conversion strategies. In a petroleum refinery, particular hydrocarbon fractions from crude oil are catalytically converted into high‐grade fuels. Certain zeolite catalysts are performing exceptionally well. Unlike petroleum fractions, biomass‐derived compounds have a high oxygen content requiring low‐temperature catalytic aqueous phase processes for selective conversion and stability of zeolite catalysts in hot liquid water. It will be shown that recent developments in zeolite synthesis and modification allow adapting zeolite properties to achieve selective conversion of biomass compounds/fractions as well.     

Maximizing the Number of Interfacial Sites in Single‐Atom Catalysts for the Highly Selective,Solvent‐Free Oxidation of Primary Alcohols

The solvent‐free selective oxidation of alcohols to aldehydes with molecular oxygen is highly attractive yet challenging. Interfacial sites between a metal and an oxide support are crucial in determining the activity and selectivity of such heterogeneous catalysts. Herein, we demonstrate that the use of supported single‐atom catalysts (SACs) leads to high activity and selectivity in this reaction. The significantly increased number of interfacial sites, resulting from the presence of individually dispersed metal atoms on the support, renders SACs one or two orders of magnitude more active than the corresponding nanoparticle (NP) catalysts. Lattice oxygen atoms activated at interfacial sites were found to be more selective than O₂ activated on metal NPs in oxidizing the alcohol substrate. This work demonstrates for the first time that the number of interfacial sites is maximized in SACs, providing a new avenue for improving catalytic performance by developing appropriate SACs for alcohol oxidation and other reactions occurring at metal–support interfacial sites.     

Maximizing the Number of Interfacial Sites in Single‐Atom Catalysts for the Highly Selective,Solvent‐Free Oxidation of Primary Alcohols

The solvent‐free selective oxidation of alcohols to aldehydes with molecular oxygen is highly attractive yet challenging. Interfacial sites between a metal and an oxide support are crucial in determining the activity and selectivity of such heterogeneous catalysts. Herein, we demonstrate that the use of supported single‐atom catalysts (SACs) leads to high activity and selectivity in this reaction. The significantly increased number of interfacial sites, resulting from the presence of individually dispersed metal atoms on the support, renders SACs one or two orders of magnitude more active than the corresponding nanoparticle (NP) catalysts. Lattice oxygen atoms activated at interfacial sites were found to be more selective than O₂ activated on metal NPs in oxidizing the alcohol substrate. This work demonstrates for the first time that the number of interfacial sites is maximized in SACs, providing a new avenue for improving catalytic performance by developing appropriate SACs for alcohol oxidation and other reactions occurring at metal–support interfacial sites.     

Synthesis of MoVNbTe(Sb)O(x) composite oxide catalysts via reduction of polyoxometalates in an aqueous medium

The synthesis of MoVNbTe(Sb)O(x)() composite oxide catalysts based on the self-organization of polyoxometalates (POMs) was investigated. The catalysts which were synthesized via reduction of POMs by using reducing agents under mild conditions and/followed by calcination in an O(2)-excluded atmosphere which superior performance for propane (amm)oxidation. It was suggested that the metastable phase formed at an elevated temperature with a specific oxidation state corresponds to the catalytic activity.     

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.     

Effect of pretreatment methods on the performance of Cu-Zr-Ce-O catalyst for CO selective oxidation

The Cu-Zr-Ce-O catalysts prepared using the coprecipitation method exhibited better catalytic performance for CO selective oxidation. The Cu-Zr-Ce-O catalysts pretreated with different methods were studied by CO-TPR and XPS techniques. The results showed that the Cu-Zr-Ce-O catalyst pretreated with oxygen exhibited the best catalytic performance and had the widest operating temperature window, with CO conversion above 99% from 160 to 200 ℃. The O2 pretreatment caused an enrichment of the oxygen storaged on the Cu active species and promoted the conversion of adsorbed oxygen into surface lattice oxygen. It also improved the amount of Cu＋/Cu^2＋ ionic pair, and then facilitated the formation of CuO active species on the catalyst for selective CO oxidation.     

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。     

掺杂多孔碳材料催化醇选择性氧化研究进展

羰基化合物是重要的有机中间体,醇类化合物的选择性氧化是合成羰基化合物的一类重要反应.在这类反应中,掺杂多孔碳材料因其独特的性能可直接作为催化剂或者催化剂载体.我们综述了单一掺杂多孔碳材料、共掺杂多孔碳材料和负载型掺杂多孔碳材料的制备方法,可能存在的活性位点和催化机理.最后,讨论了掺杂多孔碳材料目前需要解决的问题,指出设计绿色高效的负载非贵金属的掺杂多孔碳材料是未来的一个重要发展方向.     

Studies on the roles of vanadyl sulfate and sodium nitrite in catalytic oxidation of benzyl alcohol with molecular oxygen

An efficient catalytic system consisting of vanadyl sulfate/sodium nitrite was disclosed previously for the oxidation of benzylic alcohols into aldehydes with molecular oxygen.However,the roles of catalyst components were not investigated.In this paper,we examined catalytic oxidation of benzyl alcohol as a model reaction,especially by infrared spectroscopy.The role of each component is discussed including nitrite,vanadyl,sulphate,and water.Sodium nitrite could be converted into nitrate and nitric acid.The vanadium(IV)could be smoothly oxidized into vanadium(V)under mild and acidic conditions without any organic ligands.The transformation of sulfate and bisulfate,the cessation of an induction period,and the oxidation of benzyl alcohol were closely interrelated.The multiple roles of water are discussed,including reduction of the induction period,participation in redox cycles of nitric compounds,deactivation of vanadium,and as a byproduct of oxidation.This study contributes to further development of aerobic oxidation using vanadium based catalysts.     

Selective liquid-phase oxidation of toluene over heterogeneous Mn@ZIF-8 derived catalyst with molecular oxygen in the solvent-free conditions

In this work, liquid-phase catalytic oxidation of toluene was carried out under solvent-free conditions, and highly selective synthesis of benzaldehyde (BAL) and benzyl alcohol (BOL) and benzoic acid (BAC) in the presence of Mn@ZIF-8 calcined material as catalyst with oxygen molecules. As a heterogeneous catalyst, the zeolitic imidazolate framework Mn@ZIF-8 derived material exhibited reasonable substrate-product selectivity (70.3% of selectivity to BAL and BOL, 95.1 % of selectivity to BAL, BOL and BAC) and conversion (6.5%) under optimum reaction conditions. The catalysts were characterized by BET-specific surface area determination, XRD, XPS, FT-IR, TG-DTG and SEM-EDS-Mapping. The results demonstrated that the catalytic capacity of the catalysts was enhanced by the good dispersion of amorphous Mn species in ZIF-8 derivatives and high specific surface area. The possible reaction pathway for the catalytic oxidation of toluene was also suggested. Maybe this method employing Mn@ZIF-8 as efficient catalyst affords a new and environmentally friendly route for the synthesis of BOL and BAL from the selective oxidation of toluene.     

Enhanced Catalytic Aryl Alkene Oxidation by Constructing Hierarchical Polyoxometalate-Based Metal-Organic Framework

Achieving highly selective oxidation of aryl alkenes to aldehydes is of great significance in chemical industry. Herein, the performance of catalytic aryl alkene oxidation is enhanced via constructing a hierarchical fractal polyoxometalate-based metal–organic framework (POM@MOF) containing hierarchical pores and layered surface structure, which improve the mass transfer efficiency of substrates and increase the accessibility to active POMs clusters. Accordingly, the activity of fractal POM@MOF is increased by 4.8 times compared with microporous counterpart in 4-tert-butylstyrene oxidation to aldehyde product. This work paves a way for designing efficient catalysts for selective oxidation of aryl alkenes via increasing the accessibility of active sites and broadening the diffusion channels by hierarchical construction.     

Hybrid polyoxotungstates as second-generation POM-based catalysts for microwave-assisted H2O2 activation

[structure: see text] Organic-inorganic hybrids synthesized from lacunary polyoxotungstates (POMs) have been screened as oxidation catalysts with H2O2 under MW irradiation. Yields up to 99% have been obtained in 25-50 min depending both on the POM structure and on the organic moiety. The reaction scope, optimized with the best performing catalyst [gamma-SiW10O36(PhPO)2]4-, includes epoxidation of terminal and internal double bonds, alcohol oxidation, and sulfoxidation, as well as oxygen transfer to electron-deficient substrates as chalcone, ketones, and sulfoxides.     

Cu(II) 2-quinoxalinol salen catalyzed oxidation of propargylic,benzylic, and allylic alcohols using tert-butyl hydroperoxide in aqueous solutions

The synthesis of carbonyl compounds by oxidation of alcohols is a key reaction in organic synthesis. Such oxidations are typically conducted using catalysts featuring toxic metals and hazardous organic solvents. Considering green and sustainable chemistry, a copper(II) complex of sulfonated 2-quinoxalinol salen (sulfosalqu) has been characterized as an efficient catalyst for the selective oxidation of propargylic, benzylic, and allylic alcohols to the corresponding carbonyl compounds in water when in combination with the oxidant tert-butyl hydroperoxide. The reactions proceed under mild conditions (70 °C in water) to produce yields up to 99% with only 1 mol % of catalyst loading. This reaction constitutes of a rare example of propargylic alcohol oxidation in water, and it makes this process greener by eliminating the use of hazardous organic solvents. Excellent selectivity was achieved with this catalytic protocol for the oxidation of propargylic, benzylic, and allylic alcohols over aliphatic alcohols. The alcohol oxidation is thought to go through a radical pathway.     

Holey Lamellar High-Entropy Oxide as an Ultra-High-Activity Heterogeneous Catalyst for Solvent-free Aerobic Oxidation of Benzyl Alcohol

The development of noble-metal-free heterogeneous catalysts is promising for selective oxidation of aromatic alcohols; however, the relatively low conversion of non-noble metal catalysts under solvent-free atmospheric conditions hinders their industrial application. Now, a holey lamellar high entropy oxide (HEO) Co_0.2Ni_0.2Cu_0.2Mg_0.2Zn_0.2O material with mesoporous structure is prepared by an anchoring and merging process. The HEO has ultra-high catalytic activity for the solvent-free aerobic oxidation of benzyl alcohol. Up to 98 % conversion can be achieved in only 2 h, to our knowledge, the highest conversion of benzyl alcohol by oxidation to date. By regulating the catalytic reaction parameters, benzoic acid or benzaldehyde can be selectively optimized as the main product. Analytical characterizations and calculations provide a deeper insight into the catalysis mechanism, revealing abundant oxygen vacancies and holey lamellar framework contribute to the ultra-high catalytic activity.     

Oxidation of Water to Molecular Oxygen by One-Electron Oxidants on Transition Metal Hydroxides

Surveyed in this review are the most important achievements in the research and development of catalysts based on Mn, Fe, Co, and Cu hydroxides for the oxidation of water to molecular oxygen by chemical oxidizing agents obtained, for the most part, at Boreskov Institute of Catalysis, Siberian Branch of the Russian Academy of Sciences. An analysis of the results of kinetic studies on water oxidation in the presence of the above-menthioned catalysts together with data obtained by quantum chemistry methods allowed us to make a conclusion on the general nature and process mechanism both in the presence of artificial catalytic systems based on metal hydroxides and the natural enzyme photosystem II of green plants. The most important properties of hydroxo compounds responsible for catalytic activity in the oxidation of water by one-electron oxidants are discussed, and a possible reaction mechanism is considered.     

苯直接羟基化制苯酚研究进展*

综述了苯直接羟基化制苯酚的几种催化反应,包括阳极氧化法、N₂O氧化法、H₂O₂氧化法、O₂直接氧化法,这些反应均具有良好的原子经济性和环境效益.同时重点介绍了相关的催化剂及其活性中心,探讨了这些新型方法的工业应用前景.     

多酸在电催化析氢反应中的应用研究进展

电催化水裂解是一种可持续用于生产可再生氢能源的技术。然而,开发高效稳定、低成本的析氢电催化剂仍是一项具有挑战性的任务。多金属氧酸盐(多酸)是一种离散的金属氧簇合物,通常由氧配体和高价的钒(V)、钼(VI)、钨(VI)金属构成。由于多酸含有丰富的氧化还原活性金属中心,因此,近几年来,多酸在水裂解应用研究方面备受关注。本综述将聚焦于多酸在电催化水裂解析氢的应用研究进展。本文还突出强调了电催化析氢目前面临的主要问题,以及对多酸基催化剂及作为催化剂前体在电催化析氢方面的应用及发展前景做了展望。     

金属卟啉/MgAl水滑石催化醇选择性氧化制备羰基化合物

将MgAl水滑石引入到金属四苯基卟啉(MTPPs,M=Co,Fe,Mn,Ni)催化氧化体系中,实现了醇的选择性氧化。 结果表明,在分子氧/异丁醛体系中,CoTPP在苯甲醇氧化制苯甲醛反应中表现出优异的催化活性,MgAl水滑石添加剂可有效地提高醛的选择性。 在苯甲醇1 mmol、乙腈2 mL、CoTPP 5 mg、MgAl水滑石18 mg、异丁醛5 mmol、反应温度60 ℃、氧气气氛下反应2 h,苯甲醇的转化率和苯甲醛的选择性分别达到94%和92%。 另外,此催化体系在其它醇类化合物的氧化反应中也具有较好催化活性。     

多孔材料负载金催化剂的制备与应用*

本文综述了微孔材料和介孔材料负载型金催化剂的制备、表征与应用研究的最新进展,从多孔载体的选择（氧化物、微孔分子筛、介孔氧化物、介孔分子筛和介孔碳材料）、金的最新负载方法（沉积-沉淀法、溶胶-凝胶法、原位法/一步法和化学气相沉积法）与表征及其催化性能（一氧化碳低温氧化、氢气/氧气直接合成过氧化氢、直接合成环氧丙烷和有机物的选择性氧化）等方面详尽地评述了微孔材料和介孔材料负载型金催化剂研究概况。同时,提出了多孔材料负载金催化剂存在的一些问题,并展望了其研究和发展的方向。     

过渡金属催化醇氧化反应的研究进展

氧化醇为相应的羰基化合物在有机化学基础研究及其工业应用中占有非常重要的地位.在众多关于醇氧化反应的研究中,如何使用对环境友好的氧化剂替代传统的氧化剂,选择具有高性能、廉价、清洁、可回收的催化剂,一直是化学工作者研究的一个热点.综述了近年来该研究领域中的一些重要过渡金属催化体系,并简要介绍了各类催化氧化体系的催化效果.