共查询到20条相似文献,搜索用时 93 毫秒
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流化床煤气化炉内脱硫的研究 Ⅱ.脱硫剂焙烧反应动力学与脱硫反应动力学初步研究 总被引:1,自引:0,他引:1
钙质脱硫剂的焙烧反应是炉内脱硫的关键过程,本文研究了影响石灰石和白云石焙烧速率的因素。操作温度750℃以上时,焙烧速率很快。CO_2分压显著地影响焙烧过程,P_(CO)2高于平衡分压时,石灰几乎不分解。在本实验的粒度范围内,脱硫剂粒度对焙烧速率影响不大。采用未反应核收缩模型模拟焙烧过程的结果和实验结果基本一致。脱硫反应速率对气相H_2S浓度呈一级反应,操作温度特别在600~700℃的低温时显著地影响反应速率。 相似文献
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杂环化合物广泛存在于天然产物和药物分子中,许多杂环化合物还具有潜在生物活性和药理作用。因此,如何快速高效地构建小分子杂环化合物库成为当今有机合成和药物化学领域的研究热点。Ugi反应在多样性导向合成方面具有得天独厚的优势,能够解决待合成化合物数量庞大、结构复杂的难题;同时,Diels-Alder [4+2]环加成反应能够高效构建碳-碳键,以较高的立体选择性和区域选择性合成六元环系。目前,集二者于一身的Ugi/Diels-Alder串联反应在构建杂环化合物方面展现出了巨大优势和无穷潜能。本文以不同类型的DA反应分类:按照呋喃作为双烯体、吡咯作为双烯体、噻吩为双烯体、口恶唑作为双烯体、 1,2,4-三嗪作为双烯体、苯作为双烯体、不饱和键和芳环共同作为双烯体等对UDA串联反应的研究进行了综述。 相似文献
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介绍Friedel和Crafts在进行Gustavson反应的实验过程中如何发现了Zincke反应的本质,从而创立了以无水三氯化铝等金属卤化物为催化剂的烷基化和酰基化反应。 相似文献
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N-杂环卡宾催化选择性有机反应的新进展 总被引:1,自引:1,他引:0
近年来,有关N-杂环卡宾(NHC)的合成、催化性能及其应用得到了快速发展,特别是在催化选择性有机反应领域,NHC类催化剂显示出催化效率高、选择性好及性能优异等特点,而引起人们极大的关注。 本文从区域选择性、顺反异构选择性及手性选择性等方面综述了NHC催化选择性有机反应的最新进展,并予以了展望。 相似文献
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离子液体(ILs)功能化的金属有机框架(MOFs)和共价有机框架(COFs)材料兼具离子液体和MOFs/COFs的优点,是一种极具潜力的复合催化材料。MOFs和COFs材料固定的孔结构及较大的比表面积为负载高分散催化中心提供了天然的物理空间;多孔结构促使催化剂与反应物充分接触;丰富的孔道有利于运输催化反应底物和产物,进而实现催化反应的高效进行。特别是离子液体片段的引入,可以作为催化活性中心的配体(稳定剂)或分散剂,同时能够有效改善MOFs和COFs材料孔道和活性中心周围的微环境。此外,还可以充分利用离子液体片段在适当的反应条件下转化为氮杂环卡宾配体的特点,在MOFs和COFs材料中引入氮杂环卡宾有机金属配合物。因此,我们对近几年来离子液体功能化的MOFs或COFs催化体系在CO2环加成、CO2还原、C-C偶联、羰基化以及其它有机转化反应中的研究应用进行简要综述。并对复合材料在催化领域的发展进行总结和展望。 相似文献
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Dr. Oldamur Hollóczki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(22):4885-4894
The term “N-Heterocyclic carbene organocatalysis” is often invoked in organic synthesis for reactions that are catalyzed by different azolium salts in the presence of bases. Although the mechanism of these reactions is considered today evident, a closer look into the details that have been collected throughout the last century reveals that there are many open questions and even contradictions in the field. Emerging new theoretical and experimental results offer solutions to these problems, because they show that through considering alternative reaction mechanisms a more consistent picture on the catalytic process can be obtained. These novel perspectives will be able to extend the scope of the reactions that we call today N-heterocyclic carbene organocatalysis. 相似文献
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Vivek Polshettiwar 《Tetrahedron》2008,64(20):4637-4643
The first Pd-N-heterocyclic carbene (NHC) complex in the form of organic silica was prepared using sol-gel method and its application in Heck and Suzuki reactions was demonstrated. These C-C coupling reactions proceeded efficiently under the influence of microwave irradiation, with excellent yield, without any change in catalytic activity for at least five reaction cycles, with negligible Pd concentration in the end product. 相似文献
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自从1991年Arduengo第一次分离得到稳定的游离N-杂环卡宾以后,N-杂环卡宾金属络合物的研究在近几年来得到了迅速的发展。N-杂环卡宾的反应性能较高,它们与周期表中几乎所有的元素都能发生反应。N-杂环卡宾金属络合物对许多反应有催化作用,它们是一类有潜在应用价值的催化剂。本文对近年来相关的研究成果进行了综述。 相似文献
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Jun‐Long Li Yan‐Qing Liu Wen‐Lin Zou Rong Zeng Xiang Zhang Yue Liu Bo Han Yu He Hai‐Jun Leng Qing‐Zhu Li 《Angewandte Chemie (International ed. in English)》2020,59(5):1863-1870
Fluorinated ketones are widely prevalent in numerous biologically interesting molecules, and the development of novel transformations to access these structures is an important task in organic synthesis. Herein, we report the multicomponent radical acylfluoroalkylation of a variety of olefins in the presence of various commercially available aromatic aldehydes and fluoroalkyl reagents through N‐heterocyclic carbene organocatalysis. With this protocol, over 120 examples of functionalized ketones with diverse fluorine substituents have been synthesized in up to 99 % yield with complete regioselectivity. The generality of this catalytic strategy was further highlighted by its successful application in the late‐stage functionalization of pharmaceutical skeletons. Excellent diastereoselectivity could be achieved in the reactions forging multiple stereocenters. In addition, preliminary results have been achieved on the catalytic asymmetric variant of the olefin difunctionalization process. 相似文献
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Liejin Zhou Xingxing Wu Xing Yang Chengli Mou Runjiang Song Shuyan Yu Huifang Chai Lutai Pan Zhichao Jin Yonggui Robin Chi 《Angewandte Chemie (International ed. in English)》2020,59(4):1557-1561
The combined use of gold as transition metal catalyst and N‐heterocyclic carbene (NHC) as organic catalyst in the same solution for relay catalytic reactions was disclosed. The ynamide substrate was activated by gold catalyst to form unsaturated ketimine intermediate that subsequently reacted with the enals (via azolium enolate intermediate generated with NHC) effectively to form bicyclic lactam products with excellent diastereo‐ and enantio‐selectivities. The gold and NHC coordination and dissociation can be dynamic and tunable events, and thus allow the co‐existence of both active metal and carbene organic catalysts in appreciable concentrations, for the dual catalytic reaction to proceed. 相似文献
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Prof. Dr. Yong Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(58):13231-13247
Engineered heme proteins and biomimetic iron porphyrins have been found to possess excellent catalytic properties for numerous carbene transfer reactions. Computational studies, including the use of DFT calculations and molecular dynamics simulations, have been employed to help understand some important mechanistic aspects of heme carbene transfer reactions. This review summarizes advances in the computational results published in the following two areas: 1) the electronic and geometric structures of heme carbenes; spectroscopic properties; and effects of carbene substituent, porphyrin substituent, axial ligand, and spin state on heme carbene formation; and 2) mechanisms of heme carbenoid X−H (X=C, Si, B, N, S) insertions and cyclopropanation, including effects of heme carbene structural components and protein environment, as well as oxidation state and spin state. A brief outlook of future development is also addressed. 相似文献
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介绍了近几年来酶的催化多功能性及其应用于有机合成反应研究的最新进展. 包括酶催化多功能性的几种主要类型和相应催化多功能性在Michael加成、Markovnikov加成、羟醛缩合反应、氧化反应及串联反应中的应用. 相似文献