乙醇羰基化催化剂研究进展

将乙醇羰基化制备丙酸及丙酸乙酯的催化研究状况分均相催化和非均相催化两大类进行了详细介绍;分别叙述了两类催化反应过程中活性金属、助剂、配体或载体的选择对催化剂性能的影响;提出现有研究的不足和今后的研究方向。     

面向21世纪的煤化工

介绍了煤化工的现状及发展概况,展望了它的发展趋势。并根据我国的现状提出了一些建议。     

High productivity methanol carbonylation catalysis using iridium: The Cativa™ process for the manufacture of acetic acid

Methanol carbonylation to acetic acid is catalysed with high rates at low water concentrations using an iridium/iodide based catalyst. The catalyst system exhibits high stability allowing a wide range of process conditions and compositions to be accessed without catalyst precipitation. Two distinct classes of promoters have been identified for the reaction: simple iodide complexes of zinc, cadmium, mercury, indium and gallium and carbonyl complexes of tungsten, rhenium, ruthenium and osmium. The promoters exhibit a unique synergy with iodide salts, such as lithium iodide, under low water conditions. A rate maximum exists at commercially attractive low water conditions, and optimisation of the process parameters gives acetic acid with a selectivity in excess of 99% based upon methanol. The levels of liquid by-products formed are a significant improvement over that achieved with the conventional high water rhodium based catalyst system used in the Monsanto process and the quality of the product obtained under low water concentrations is exceptional. The Cativa™ process has now been successfully commercialised on three world scale plants.     

管式环流反应器在乙酸/乙酐羰基合成中的应用

介绍了以乙酸甲酯和甲醇为原料合成年产20 kt乙酐和20 kt乙酸的过程,并且介绍了在以LiI为促进剂的铑-碘均相催化剂作用下、170~199℃的温度范围及5.0 MPa压力条件下,管式环流反应器在乙酸/乙酐合成中的应用。分析了反应器内流体的流动特点和羰基合成的反应过程,建立了数学模型。计算得到了反应器内反应物料转化率、各组分浓度、温度和冷却水温度等各种参数沿物料流动方向的分布,同时对反应器进行了热稳定性分析。计算结果表明,当系统在操作过程中转化率偏离定常态0.000 1,温度偏离定常态0.000 1℃时,转化率和温度能分别在4×10-6s和8×10-6s内回到定常态,整个反应体系是稳定的。     

Ni—Pd／C双金属催化剂上乙醇羰基化合成丙酸的研究

考察了Ni—Pd／C双金属催化剂上乙醇气相羰基化合成丙酸的反应。实验结果表明,活性炭负载Ni—Pd双金属催化剂相比普通非贵金属催化剂具有更高的活性及选择性,优化的反应工艺条件为压力0．15MPa,温度220℃,nCO：nEtOH,n：2．0：1,乙醇液体空速1．5h^-1。在上述条件和少量碘乙烷存在下,乙醇羰基化反应产物中丙酸及丙酸酯的选择性可高达96．7％,通过GC—MS对反应产物分析,分析了反应过程的机理。     

AlCl_3单独催化的甲苯羰基化反应机理的研究

利用核磁及红外等表征方法,研究了无助剂存在时,AlCl3作催化剂的甲苯羰基化反应机理。研究表明,反应的中间物是,并尝试解释反应机理。     

The Intermolecular Pauson-Khand Reaction: Applications,Challenges, and Opportunities

The rapid assembly of complex organic molecules from simple and structurally diverse building blocks is a prevalent challenge in organic synthesis. The Pauson-Khand reaction (PKR) is a method of choice for the construction of five membered rings that has historically been popularized as a late-stage intramolecular cyclization method. The intermolecular version of the PKR, on the other hand, constitutes a powerful approach for the rapid assembly of densely functionalized cyclopentanic cores at early stages of a synthetic sequence. Despite its potential, the intermolecular PKR is much less prevalent in the organic synthesis literature due to several historical limitations, most importantly a reduced scope with respect to the alkene component of the reaction. The last decade has witnessed important developments in the area including a) experimental and theoretical studies that provide a good mechanistic understanding of the reaction and its selectivity, b) methodological developments that have broadened the scope of potential alkene partners, and c) the development of catalytic enantioselective versions that provide useful levels of enantioselectivity. In parallel, remarkable synthetic applications of the intermolecular PKR have emerged, including (enantioselective) total syntheses of complex natural products (polycyclic terpenes, alkaloids, prostanes) as well as examples of industrial relevance. A fundamental limitation of the PKR that needs to be addressed in the future is the current lack of a ligand-accelerated version of the reaction, which would be a promising advance towards developing more efficient and general catalytic (enantioselective) reactions.     

Kinetic modeling of homogeneous catalytic processes

Homogeneous catalysis by soluble metal complexes is gaining considerable attention due to their unique applications and features like high activity and selectivity. In this paper, a brief review of kinetic modeling in homogeneous catalysis has been presented. Approaches using empirical as well as molecular level rate models have been discussed. Special features relevant to asymmetric catalysis and multiple rate controlling steps have also been addressed. A case study on kinetics of carbonylation of 1-(4-iso-butylphenyl)ethanol using a homogeneous palladium catalyst has been discussed.     

Importance of metal location in M-H zeolite for synergistically catalyzing dimethyl ether carbonylation

Mordenite (MOR) has shown great potential to catalyze dimethyl ether (DME) carbonylation to methyl acetate (MA) in industry.The synergy between metal species and Brφnsted acid sites accelerates DME conversion.Here we designed and prepared two catalysts with different Ag locations by seed-directed growth method and two-step impregnation method (named as Ag@HMOR and Ag/HMOR-out,respec-tively),to explain the effect of Ag location on catalytic performance.The results of TEM,XPS,CO-IR and UV-Vis showed that Ag species mainly presented as Ag0 species over both Ag@HMOR and Ag/HMOR-out.Meanwhile,Ag0 species mainly located in the micropores of Ag@HMOR,while as for Ag/HMOR-out,Ag0 mainly existed on external surface.After comparing the performance of the catalysts with different Ag positions,we confirmed that the Ag0 species encapsulated in the channels of HMOR pro-moted the DME carbonylation,which revealed the importance of spatial adjacency on the acid-metal catalysts.     

低温低压二步法合成甲醇

二步法合成甲醇,其第一步是甲醇羰基化合成甲酸甲酯;第二步是甲酸甲酯氢解合成甲醇。二步法反应的优点是使反应温度和压力降低、选择性提高、产物甲醇不含水,使提纯容易。从而低能耗、高产率地合成甲醇。