后过渡金属催化醇对胺的N-烷基化反应研究进展

胺的N-烷基化反应是一类重要的有机合成反应,其合成产物烷基化胺更是涉及到包括化工、医疗、医药以及国防等重要领域.近年来随着化学技术,尤其是绿色催化合成技术的发展,使得该类反应已成为当前有机反应的研究热点之一.以醇作为胺的N-烷基化试剂,水是唯一的副产物,因此具有绿色环保、简单可靠的特点.但是绝大多数该类反应都需要过渡金属催化剂.从脂肪胺、芳香胺、杂环芳香胺等含氮化合物出发,综述了近年来金属催化的以醇为烷基化试剂的胺的N-烷基化反应的研究进展,主要介绍了各均相、多相金属催化反应体系,通过比较指出了每一方法的优缺点,并对今后氮烷基化反应的发展方向进行了展望.     

乳酸酯氧化脱氢制备丙酮酸酯的研究进展

生物质资源替代化石资源制取燃料和化学品已成为发展可再生能源化工的重要研究方向之一。本文综述了近年来以生物质平台分子乳酸酯为原料制备丙酮酸酯的研究工作,主要涉及的反应包括气相催化反应、液相催化反应和光催化反应。详细讨论了各种类型的催化剂对反应性能的影响;最后,对乳酸酯催化转化制取丙酮酸酯的发展前景进行了展望。     

美国“总统绿色化学挑战奖”近十年获奖回顾与启示

在介绍美国"总统绿色化学挑战奖"评选标准的基础上,通过列表统计的形式回顾了1999年至2008年以来更新合成路线奖、改进溶剂和反应条件奖、设计更安全化学品奖、绿色化学学术奖和小企业奖的获奖情况,并分析得出发展绿色化工在化学工业中占有头等重要地位的认识,提出绿色化工将是未来我国化学工业发展的必然选择.     

精细化工专业新设三相催化反应实验的建议

精细化工专业新设三相催化反应实验的建议李光兴许汉昌陈兵朱治良（华中理工大学化学系武汉４３００７４）对精细化工专业而言，其教学实验应照顾到学科的特点，尽可能地涉及无机、有机、分析、物化及化工的多学科知识；应有较好的重复性，还应无毒、无危险。笔者进行了多...     

“水上”(“on water”)有机反应

"水上"有机反应的发展是水相绿色合成反应研究领域中的一个突破。体系的非均相性质是"水上"反应的基本特征。水不仅是重要的绿色反应介质,在大多数"水上"有机反应中都能观察到水对反应的速度和选择性有明显的提升作用。采用"水上"反应的条件,可以使反应的规模扩大,有利于产物的分离、纯化。本文以反应的类型分类综述了近年来有关"水上"有机反应研究的进展,以及在绿色有机合成中的应用。     

不同离子液体反应介质在生物催化中的应用研究进展

离子液体(ILs)因其独特物理化学性质成为新型反应溶剂和催化剂,在生物催化反应中有着广阔的应用前景。根据不同ILs的水溶性,其与水可形成4种反应介质,即微水ILs单相体系、亲水性ILs-水单相体系、疏水性ILs-水两相体系和ILs微乳液体系。本文分别介绍了不同ILs反应体系中生物催化剂的催化活性、稳定性和选择性,综述了这些体系中的生物催化反应研究进展。     

过渡金属镍与可见光双催化体系的研究进展

过渡金属镍与可见光催化剂的双催化体系,为构建新型的碳-碳键及碳-杂键提供了一种新的思路,实现了许多单独催化体系难以完成的反应.双催化体系具有条件温和、绿色清洁等优势,引起了广大科研工作者的兴趣.基于近些年镍与可见光双催化反应进行了简要的概述.     

卤过氧化物酶在绿色卤化反应中的研究进展

卤化反应是一类极其重要的有机合成反应,在实验室研究和化工生产领域占据重要地位.传统卤化反应因存在使用有毒有害试剂、反应缺乏选择性等问题而亟待改进,生物酶催化策略则为突破上述瓶颈提供了可能.自然界已经进化出多种可对有机物中催化引入卤素的卤化酶.酶催化卤化反应的突出优势在于常温常压下,可使用来源温和的卤素进行高效的催化反应.催化范围包括卤化、羟卤化、卤环合和氧化脱羧等多种具有挑战性的反应.鉴于酶催化卤化反应展示出巨大的潜力,从催化活性、酶稳定性、底物浓度、催化范围等几个方面着重介绍了卤过氧化物酶在绿色卤化反应中的最新研究进展,为进一步开发绿色的卤化酶催化卤化反应提供参考.     

酶催化反应研究进展

简要评述了近年来酶催化反应的进展,以及近年来5种不同反应体系(有机溶剂体系、反胶束体系、低共熔体系、超临界流体体系和气相体系)中酶催化反应的进展,并对不同体系中酶促反应的主要影响因素、酶催化底物的拓宽和模拟酶研究及酶催化的手性合成等作了简要概述。参考文献52篇。     

苯酚直接羟基化制备苯二酚反应体系中催化剂的设计与性能

邻苯二酚和对苯二酚是重要的工业原料。苯酚一步羟基反应合成苯二酚的方法原子利用率高且节能高效,符合可持续发展的理念。以H_2O_2为氧化剂氧化苯酚合成苯二酚的工艺,流程简单、反应条件温和且绿色环保,成为催化合成领域的研究热点。在该反应中,苯酚的转化率和产物苯二酚的收率高低取决于催化剂的活性。本文综述了近几年在苯酚羟基化制备苯二酚反应中催化剂的研究进展。按照反应体系的不同,催化剂可被分为热催化反应体系中的催化剂和光催化反应体系中的催化剂。催化剂的催化性能主要以苯酚转化率、苯二酚的选择性和稳定性等方面作为评价指标。本文重点介绍了以H_2O_2为氧化剂的液相非均相催化体系中含金属催化剂的研究现状,并在最后对催化剂在苯酚一步羟基化制备苯二酚的反应体系中的制备与应用作了展望。     

HZSM-5催化乙醇脱水停料效应的研究

在HZSM-5分子筛催化乙醇脱水反应中观察到了停料效应：即当停止乙醇-水进料一定时间,恢复进料后乙烯选择性明显提高。通过考察不同反应条件下的停料效应,发现乙醇质量分数控制在55%附近、延长停料时间、升高反应温度和降低乙醇进料空速会提高停料效应强度,并较长时间维持高乙烯选择性。500 h的催化剂稳定性测试表明,停料效应可有效延长催化剂的使用寿命。结合含水乙醇脱水反应机理和实验结果,推测HZSM-5催化乙醇脱水停料效应产生的原因是停料时乙氧基中间体的积累和催化活性空位的再生。     

Catalytic dehydration of ethanol using transition metal oxide catalysts

The aim of this work is to study catalytic ethanol dehydration using different prepared catalysts, which include Fe(2)O(3), Mn(2)O(3), and calcined physical mixtures of both ferric and manganese oxides with alumina and/or silica gel. The physicochemical properties of these catalysts were investigated via X-ray powder diffraction (XRD), acidity measurement, and nitrogen adsorption-desorption at -196 degrees C. The catalytic activities of such catalysts were tested through conversion of ethanol at 200-500 degrees C using a catalytic flow system operated under atmospheric pressure. The results obtained indicated that the dehydration reaction on the catalyst relies on surface acidity, whereas the ethylene production selectivity depends on the catalyst chemical constituents.     

Dehydration of Ethanol to Ethylene on Ring- and Trilobe-Shaped Catalysts

The indicators of ethanol to ethylene catalytic dehydration process on trilobe- and ring-shaped samples of an alumina catalyst were compared at the fixed parameters: thermal agent temperature and catalyst load. Experiments were performed in a flow-through reactor of a laboratory setup and in a tubular reactor of a pilot installation. The use of the less active ring-shaped catalyst ensures higher values of ethanol conversion, ethylene yield, and catalyst performance and significantly lower hydraulic resistance, compared to the more active trilobe-shaped catalyst. This is caused by lower intensity of the heat absorption on the less active catalyst and, correspondingly, to the higher temperature in the ring bed due to higher bed porosity.     

Influence of activated carbon modifications on their catalytic activity in methanol and ethanol conversion reactions

Activated carbons containing different surface functionalities have been investigated as catalysts in conversion reactions of ethanol and methanol. These carbon materials were prepared from Polish brown coal by chemical activation with potassium hydroxide and modified by the oxidation or reaction with ammonia or chlorine. The main process upon ethanol decomposition was its dehydrogenation, while in the process of methanol decomposition only a few samples were catalytically active, and the only product was dimethyl ether (a product of dehydration).      

气相色谱法在线分析生物乙醇催化脱水制备乙烯的反应产物

设计并组装了在线气相色谱法测定生物乙醇脱水制备乙烯过程中的反应产物的流程和装置,被测物质包括乙烯、水、乙醛、乙醇、乙醚及丙酮。取样前应保证气态样品在保持温度为110℃以上的气体流路中畅通至少60min,进样量为1.0mL,色谱柱为填充GDX-104固定相的不锈钢柱（2m,φ4mm）,柱温为104℃。样品按规定条件通过色...     

Liquid-phase catalytic processing of biomass-derived oxygenated hydrocarbons to fuels and chemicals

Biomass has the potential to serve as a sustainable source of energy and organic carbon for our industrialized society. The focus of this Review is to present an overview of chemical catalytic transformations of biomass-derived oxygenated feedstocks (primarily sugars and sugar-alcohols) in the liquid phase to value-added chemicals and fuels, with specific examples emphasizing the development of catalytic processes based on an understanding of the fundamental reaction chemistry. The key reactions involved in the processing of biomass are hydrolysis, dehydration, isomerization, aldol condensation, reforming, hydrogenation, and oxidation. Further, it is discussed how ideas based on fundamental chemical and catalytic concepts lead to strategies for the control of reaction pathways and process conditions to produce H(2)/CO(2) or H(2)/CO gas mixtures by aqueous-phase reforming, to produce furan compounds by selective dehydration of carbohydrates, and to produce liquid alkanes by the combination of aldol condensation and dehydration/hydrogenation processes.     

Gas-phase reactions of cationic molybdenum and tungsten monoxide with ethanol: a combined experimental/computational exercise

The ion/molecule reactions of molybdenum and tungsten monoxide cations MO⁺ (M═Mo, W) with ethanol have been studied by Fourier transform ion-cyclotron resonance mass spectrometry (FT-ICR MS) and density functional theory (DFT) calculations. As observed in the previously reported reactions of MO₂ ⁺ (M═Mo, W) towards ethanol, the dehydration of ethanol to give rise to the elimination of neutral C₂H₄ constitutes also the dominating reaction channel for the monoxides. Likewise, both systems result in a combined dehydrogenation/dehydration process, thus forming the ionic product MOC₂H₂ ⁺; moreover, the tungsten system presents two additional reaction channels: double dehydrogenation of ethanol with concomitant formation of the ionic product WO₂C₂H₂ ⁺ and the generation of C₂H₅ ⁺ which takes place by OH^? transfer from ethanol to the tungsten atom. This combined experimental/computational study of gas-phase ion molecule reactions may shed some new light on the mechanisms that occur in complex catalytic systems.     

Insight into Three‐Coordinate Aluminum Species on Ethanol‐to‐Olefin Conversion over ZSM‐5 Zeolites

Commercial bioethanol can be readily converted into ethylene by a dehydration process using solid acids, such as Brønsted acidic H‐ZSM‐5 zeolites, and thus, it is an ideal candidate to replace petroleum and coal for the sustainable production of ethylene. Now, strong Lewis acidic extra‐framework three‐coordinate Al³⁺ species were introduced into H‐ZSM‐5 zeolites to improve their catalytic activity. Remarkably, Al³⁺ species working with Brønsted acid sites can accelerate ethanol dehydration at a much lower reaction temperature and shorten the unsteady‐state period within 1–2 h, compared to >9 h for those without Al³⁺ species, which can significantly enhance the ethanol dehydration efficiency and reduce the cost. The reaction mechanism, studied by solid‐state NMR, shows that strong Lewis acidic EFAl‐Al³⁺ species can collaborate with Brønsted acid sites and promote ethanol dehydration either directly or indirectly via an aromatics‐based cycle to produce ethylene.     

改性HZSM-5催化乙醇脱水制乙烯的研究

采用离子交换法分别制备了铁、钴、镍改性的HZSM-5分子筛催化剂.在连续流动固定床微型反应装置上对催化剂进行了活性评价,结果表明镍改性的催化剂具有较好的低温活性.采用透射电镜(TEM),X射线衍射(XRD),吡啶程序升温脱附(Py-TPD),N2-吸附脱附和程序升温氧化(TPO)等手段对催化剂反应前后的物性进行了表征,结果表明催化剂的表面酸性决定其催化乙醇脱水的性能.镍改性后,降低了催化剂的强酸量、增加了弱酸量,有利于乙醇转化率和乙烯选择性的提高,镍是比较合适的改性金属.以镍改性的HZSM-5为催化剂,对乙醇脱水制乙烯反应的工艺条件进行了优化.     

生物乙醇催化脱水制乙烯的研究进展

阐述了利用生物质能源的重要性,介绍了生物乙醇催化脱水制乙烯的发展现状,特别是其催化剂的研究状况。针对乙醇脱水制乙烯催化剂存在的问题,提出当前催化剂的发展趋势。