固载TEMPO应用于醇选择性氧化的研究进展

有机小分子催化剂2,2,6,6-四甲基哌啶-N-氧自由基(TEMPO)催化醇的氧化反应是在温和条件下醇选择氧化的一个重要方法,但是TEMPO价格偏高,反应结束后难以分离和回收使用,限制了该反应的广泛应用。将TEMPO接枝在载体上,完成TEMPO多相化,可以实现催化剂的回收再用,成为TEMPO催化研究的一个新领域。因此本文综述了固载TEMPO催化醇氧化反应的最新研究进展。     

2,2,6,6-四甲基哌啶-1-氧自由基在醇氧化研究中的应用

2,2,6,6-四甲基哌啶-1-氧自由基（TEMPO）作为有机小分子,形成的催化醇氧化反应体系相对传统醇氧化具有高效性、高选择性、反应条件温和等优点,可以解决传统醇氧化工艺中反应条件苛刻、成本高以及产生大量污染物的问题,是目前最具前景的醇氧化技术之一。本文综述了近年来关于TEMPO体系在催化醇氧化方面的相关研究进展,重点介绍了均相环境下过渡金属（铜、铁、钌等）参与和无过渡金属参与的TEMPO催化醇氧化,以及多相环境下的固载型TEMPO催化醇氧化,并根据催化反应效率、氧化成本、实际应用性等因素比较总结了均相催化和非均相催化两种类型催化氧化体系的优缺点。指出离子液体与TEMPO的耦合体系、廉价过渡金属掺杂的TEMPO体系和高稳定性碳基材料负载型TEMPO体系是该类型催化剂优化调控的目标与方向。     

固载化的TEMPO催化醇的氧化研究

醇被氧化为相应的醛或酮是有机合成中重要的官能团转化之一。有机小分子催化剂2,2,6,6-四甲基哌啶-1-氧自由基(TEMPO)催化醇的氧化反应是温和条件下选择性氧化醇的一个重要方法,在实验室和工业生产中得到了广泛应用。将TEMPO通过共价键嫁接在载体上,以实现催化剂的回收再用,一直是TEMPO催化研究的一个领域。文章综述了近年来固载化的TEMPO催化醇氧化反应的发展和最新研究进展。     

温控两相聚合型离子液体-纳米金催化苯乙烯环氧化反应

针对环氧苯乙烷制备过程中存在催化剂回收困难、催化剂活性低等缺陷,本文利用温控两相离子液体的"高温均相反应、低温两相分离"的特点及聚合物大分子在反应体系中性能稳定、不易流失的优点,结合过渡金属的高效催化能力设计合成出一种具有温控两相功能、催化活性高、流失量小、易回收的聚合型离子液体-纳米金催化剂。其催化苯乙烯环氧化反应结果显示:聚合离子液体-纳米金催化剂具有催化活性高、流失量小、回收方便的优点,苯乙烯的转化率为97.8%,环氧苯乙烷的选择性为81.9%。     

配体与氮氧自由基TEMP O结合氧化醇的研究进展

醇选择性的氧化成相应的醛或酮是有机化学中十分重要的反应之一。以分子氧作为氧化剂催化氧化醇成为相应的羰基化合物反应中,高性能的催化剂的研究具有重要的意义。作为有机小分子催化剂TEMPO(2,2,6,6-四甲基哌啶-1-氧自由基)应用到醇的催化氧化体系中得到了广泛的关注。研究发现,在含有TEMPO催化氧化醇的反应体系中,一些配体的加入使反应效果更加理想。本文描述了近年来TEMPO与不同的配体形成的催化体系在醇的氧化研究中的应用进展。     

福建物构所可溶性多孔配位聚合物复合催化材料研究获进展

正与均相催化剂相比,异相催化剂可以回收再循环使用,但其活性通常较低,而将其均相化能有效地结合均相和异相催化的优点,因此是解决异相催化剂活性低这一短板的有效途径之一。近年来,金属—有机框架(MOFs)化合物,也称作多孔配位聚合物,因其具有高比表面积、可调的孔道,是优良的纳米催化剂载体之一。将金属纳米颗粒负载于MOFs上可实现异相催化性能,但     

醇类选择性催化氧化的研究进展

醇类选择性氧化制备相应羰基（醛或酮）化合物是有机合成中的重要反应。综述醇类选择性催化氧化的研究现状,主要有液均相氧化、液多相氧化和水/有机两相催化氧化,对所用催化剂发展状况和反应机理分别进行阐述。均相催化氧化催化剂难于从反应体系分离,造成成本过高,而且污染环境。大部分多相催化剂来自均相催化剂的负载,活性中心分布不均匀,结构不明确,存在活性组分易从载体上脱落和流失的现象,导致催化剂活性下降。以水作溶剂,不仅清洁无污染,且产物和催化剂容易分离,催化剂可以循环使用,从经济和环保角度值得大力推广,但该体系价格昂贵,反应条件不够温和,还需进一步改进。因此,多相催化氧化和水/有机两相催化氧化相对于均相催化剂有更广阔的发展和应用空间,是今后的研究方向。     

二氧化铈载金催化剂催化CO氧化的研究进展

将金纳米颗粒负载在二氧化铈上,形成负载型催化剂,能应用于多种反应体系,表现出良好的催化活性,有着广阔的发展前景。综述了二氧化铈载金催化剂在一氧化碳催化氧化中的应用研究进展,介绍了二氧化铈载金催化剂中金的结构、价态和纳米尺寸,载体二氧化铈的形貌、结构、尺寸和氧空位以及金和载体二氧化铈两者之间的相互作用对一氧化碳催化氧化性能的影响。     

TEMPO催化醇氧化反应进展

选择性催化氧化醇类化合物为相应的醛或酮是一类重要的官能团转化反应。四甲基哌啶氧化物(TEMPO)是一种含有稳定的氮氧自由基(NO·)的有机小分子催化剂,NO·可通过自身的强选择性,在加快醛或酮转化的同时不会过氧化成为羧酸。本文阐述了TEMPO催化体系催化醇选择性氧化反应的机理,在此基础上详述了过渡金属/TEMPO、非过渡金属/TEMPO、固载化TEMPO等体系催化醇选择性氧化反应的研究情况,并探讨了TEMPO在电催化以及光催化方面的应用。指出将高活性的TEMPO催化体系改进,在发挥其高选择性、高活性优点的同时,克服其本身价格昂贵的缺点,实现催化体系的重复利用,更符合生态、绿色理念,也是未来发展的趋势。     

SBS及相关聚合物的均相催化加氢进展

对SBS及相关聚合物加氢的各种均相催化体系作了全面的介绍与评述。重点介绍了近年来发展的茂金属催化剂和贵金属催化剂，同时介绍了水／有机两相催化和离子液体两相催化体系用于聚合物加氢的最新动态，指出寻找催化活性高，催化剂易于分离和循环使用的新催化体系是实现聚合物均相催化加氢工业应用突破的关键。     

Catalytic oxidation of alcohols using molecular oxygen mediated by poly(ethylene glycol)-supported nitroxyl radicals

The selective catalytic oxidation of alcohols over a mixture of copper(I) chloride and a number of linear ‘linker-less’ or ‘branched’ poly(ethylene glycol)-supported nitroxyl radicals of the 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO) family as a catalyst system has been investigated in the presence of molecular oxygen in a batch reactor. It is found that the activity profile of the polymer-supported nitroxyl radicals is in good agreement with that of low-molecular weight nitroxyl catalysts, for example, allylic and benzylic alcohols are oxidised faster than aliphatic alcohols. The oxidations can be tuned to be highly selective such that aldehydes are the only oxidation products observed in the oxidation of primary alcohols and the oxidations of secondary alcohols yield the corresponding ketones. A strong structural effect of the polymeric nitroxyl species on catalytic activity that is dependent upon their spatial orientation of the nitroxyl radicals is particularly noted. The new soluble macromolecular catalysts can be recovered readily from the reaction mixture by solvent precipitation and filtration. In addition, the recycled catalysts demonstrate a similar selectivity with only a small decrease in activity compared to the fresh catalyst even after five repetitive cycles.     

Polyurethane‐ and Polystyrene‐Supported 2,2,6,6‐Tetramethyl‐ piperidine‐1‐oxyl (TEMPO); Facile Preparation,Catalytic Oxidation and Application in a Membrane Reactor

In this contribution, the facile synthesis of two new polymer‐supported 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) catalysts and their application in the catalytic oxidation of alcohols to carbonyl compounds are described. For attachment of the TEMPO group to the polymer an isocyanate functionalized polymer is chosen. This new approach facilitates the synthesis in comparison with previously existing methods which generally require deprotonation of TEMPO prior to reaction with the polymer. Following this approach, polyurethane (PU)‐ and polystyrene (PS)‐based TEMPO catalysts are prepared in a one‐step reaction from commercially available compounds. Both polymer‐supported catalysts showed promising yields for a variety of substrates using inorganic and/or organic co‐oxidants in biphasic and/or monophasic systems. The recyclability of the corresponding catalysts was studied in repetitive batch experiments using filtration or distillation depending on the support type. Furthermore, application of the homogeneous polyurethane‐supported TEMPO for the selective oxidation of benzyl alcohol in a continously operated membrane reactor is demonstrated.     

Catalytic oxidation of alcohols using molecular oxygen mediated by poly(ethylene glycol)-supported nitroxyl radicals

The selective catalytic oxidation of alcohols over a mixture of copper(I) chloride and a number of linear ‘linker-less’ or ‘branched’ poly(ethylene glycol)-supported nitroxyl radicals of the 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO) family as a catalyst system has been investigated in the presence of molecular oxygen in a batch reactor. It is found that the activity profile of the polymer-supported nitroxyl radicals is in good agreement with that of low-molecular weight nitroxyl catalysts, for example, allylic and benzylic alcohols are oxidised faster than aliphatic alcohols. The oxidations can be tuned to be highly selective such that aldehydes are the only oxidation products observed in the oxidation of primary alcohols and the oxidations of secondary alcohols yield the corresponding ketones. A strong structural effect of the polymeric nitroxyl species on catalytic activity that is dependent upon their spatial orientation of the nitroxyl radicals is particularly noted. The new soluble macromolecular catalysts can be recovered readily from the reaction mixture by solvent precipitation and filtration. In addition, the recycled catalysts demonstrate a similar selectivity with only a small decrease in activity compared to the fresh catalyst even after five repetitive cycles.     

Porous Silica Beads Supported TEMPO and Adsorbed NOx (PSB‐TEMPO/NOx): An Efficient Heterogeneous Catalytic System for the Oxidation of Alcohols under Mild Conditions

The combination of NO_x gas which is stored in the pore canals of porous silica beads (PSB) with a heterogeneous catalyst, PSB‐supported 2,2,6,6‐tetramethylpiperdine 1‐oxyl (PSB‐TEMPO, 1 ), afforded a highly efficient, widely applicable, and efficiently recyclable approach for the selective aerobic oxidation of alcohols. This novel catalytic system (PSB‐TEMPO/NO_x) can be employed in the oxidation of a wide range of alcohols to their corresponding aldehydes and ketones with selectivities as high as 99% at complete conversions under mild conditions. O₂ is the terminal oxidant. PSB‐TEMPO can be recycled for more than 10 times without significant loss of activity.     

无机碳材料负载固相金属催化剂研究进展

综述了无机碳材料纳米碳管、活性炭纤维和膨胀石墨作为固相金属催化剂载体的国内外研究进展,探讨催化剂的不同负载方法,分析无机碳材料负载固相金属催化剂活性的影响因素及其应用领域。发现无机碳材料负载固相金属催化剂已经应用于催化加氢、光催化、电催化、水处理及大气处理方面,将其用于烟气脱硫副产物亚硫酸盐的处理,不仅能解决催化剂浪费问题,还能避免二次污染的发生。     

加料方式对Cu-Co合成低碳醇催化剂性能的影响

低碳醇在汽油添加剂或汽油替代品减少尾气排放等方面具有潜在用途,用煤和天然气经合成气合成低碳醇的Cu-Co催化剂在较为缓和条件下具有较高的催化活性和C₂+OH醇选择性。采用不同沉淀方法制备系列Cu-Co催化剂,通过XRD、XPS、TPR和BET考察加料方式对催化剂前驱体和催化剂性能的影响。在5.0 MPa、250 ℃和空速5 000 h^-1条件下,使用加压固定床反应器考察合成低碳醇活性。研究结果表明,加料方式对催化剂性能有较大影响,采用共沉淀法制备的催化剂颗粒中各组分以纳米大小均匀分布,C₂+OH醇选择性最高;采用正加法制备的催化剂活性和C₂+OH醇选择性最低,催化剂颗粒中活性组分的分布呈壳层分布,Co在颗粒的表面富集;采用并流法和反加法制备的催化剂的醇分布遵从ASF规则,其链增长因子为0.42。实验结果表明,当Cu和Co在催化剂颗粒中以原子尺度分布时,催化活性最好。     

Clean and selective oxidation of alcohols with n-Bu4NHSO5 catalyzed by ionic liquid immobilized TEMPO in ionic liquid [bmim][PF6]

An efficient oxidation of alcohols with tetra-n-butylammonium peroxymonosulfate catalyzed by ionic liquid immobilized TEMPO in ionic liquid [bmim][PF₆] was reported. TEMPO-IL serves as a homogeneous catalyst to enhance the reaction remarkably. The oxidation proceeded to afford aldehydes or ketones in excellent yields and high selectivity without remarkable over-oxidation to carboxylic acids. It is noteworthy to mention that the catalyst and solvent could easily be recycled and reused without loss of activity. A possible mechanism for the oxidation is proposed.     

Iron Chloride/4‐Acetamido‐TEMPO/Sodium Nitrite‐Catalyzed Aerobic Oxidation of Primary Alcohols to the Aldehydes

A variety of 4‐substituted 2,2,6,6‐tetramethylpiperidyl‐1‐oxy (TEMPO) derivatives has been screened for their ability in the oxidation of primary alcohols to the aldehydes with dioxygen under mild conditions. An evaluation of the efficiency of these 4‐substituted TEMPO derivatives in the alcohol oxidation may allow an insight into the effect of the structural variations of TEMPO on the oxidation of alcohols, which should facilitate catalyst design and screening efforts. Based on the screening results of 4‐substituted TEMPO derivatives, the catalyst comprised of 4‐acetamido‐TEMPO, iron chloride and sodium nitrite, has been developed for the highly efficient oxidation of a wide range of primary alcohols including primary aliphatic alcohols to the corresponding aldehydes under mild conditions.     

CeO2 Nanocrystalline-Supported Palladium Chloride: An Effective Catalyst for Selective Oxidation of Alcohols by Oxygen

The present paper reports on the use of CeO₂ materials supported palladium chloride catalyst for selectively oxidising organic alcohols into aldehydes. Spherical, microsized rod-shaped and spindle-like CeO₂ particles are synthesised and characterised by SEM. The catalysts are prepared by loading palladium chloride onto the CeO₂ support matrix. A complete characterization of the catalysts is performed. The activity of catalysts is studied by the selective oxidation of various alcohols. The results show that (1) the catalytic activities prepared by spherical cerium are superior to the catalysts prepared by spindle-like or rod-shaped cerium and (2) the catalyst PdCl₂/CeO₂ (nanospheres) show good activity, high yield, and good stability.