甲烷活化及转化催化剂研究进展

评述了近年来ＣＨ４活化转化的几条重要途径,其中包括ＣＨ４与ＣＯ２重整制合成气,ＣＨ４氧化偶联制高碳烃,ＣＨ４非氧同系化,分析了各途径的催化剂研究现状、催化机理及影响催化剂活性的诸多因素,并探索了ＣＨ４活化转化的新方法。     

甲烷活化与催化转化过程中的几个关键问题及对策

现有的由甲烷直接转化生产大宗化学品过程,包括氧化偶联制乙烯、选择性氧化制甲醇和脱氢低聚制芳烃等,依然停留在实验室研究阶段,无法达到工业化要求.其原因在于单程目的产物收率低,能耗高,无法和现有生产过程竞争.而其技术障碍则与甲烷C—H键活化条件苛刻、产物不稳定、催化剂选择性和稳定性差等因素相关.本文主要分析了实现甲烷活化和...     

甲烷二氧化碳低温直接转化的可能性

对近年来ＣＨ４的低温活化的研究结果进行了评述,结合对ＣＨ４的两步反应同系化及ＣＯ２加氢研究成果,提出了由ＣＨ４－ＣＯ２低温转化直接合成Ｃ＾２＋含氧化合物的两步法技术路线及催化剂体系,论证了其可能性。     

甲烷催化部分氧化制合成气催化剂的研究进展

叙述了甲烷催化部分氧化制合成气催化剂的最新研究进展,包括含钴的钙钛矿、碳化钼、碳化、Ｎｉ／α－Ａｌ２Ｏ３,Ｐｔ－Ｎｉ／α－Ａｌ２Ｏ３、ｌａＯ３＿ＮｉＯ／Ａｌ２Ｏ３等。     

甲烷氧化偶联反应的研究进展

通过对于甲烷氧化偶联法制取乙烯的反应过程中的各方面性能研究,对其进行具体分析,探讨针对不同性能的催化剂对于反应产物的各方面影响来进行具体分析。同时对于不同反应条件下的不同反应方面的影响也进行细致的研究分析,通过对于甲烷氧化偶联反应过程中的催化剂的催化机理进行研究。     

甲烷低温活化制甲醇研究进展

简要评述了当前国内外在甲烷直接部分氧化合成甲醇和甲烷经卤代后合成甲醇领域的研究进展。众多研究表明,甲烷多相催化氧化制甲醇是最具有工业化应用前景的技术,其中钼系催化剂的效果较好;以Pt、Pd配合物为催化剂的甲烷液相催化氧化法制甲醇方法具有较高的甲烷转化率和甲醇选择性,但是催化剂价格昂贵、反应条件苛刻、环境污染严重;甲烷气相均相氧化属于非催化反应,在高温高压下进行,且反应器须具备特殊的形式,结构复杂;虽然酶催化氧化法的选择性较高,但是生物酶的制备有一定难度,不适用于大范围应用,该路线目前仅限于实验室研究阶段;光催化氧化是一种环境友好的技术,反应条件温和、避免氧化剂应用,但是该类催化剂局限于半导体和盐类,还有待于进一步开发新型高效的催化剂。同时,甲烷经卤代后合成甲醇的方法对解决甲烷活化的难题具有独特优势,是一种比较有开发前景的路线,正在受到研究者们的密切关注。     

过氧化氢存在下甲烷低温转化的研究进展

围绕H₂O₂的引入方式（直接使用和原位合成）对甲烷低温转化活性的影响,对H₂O₂存在下甲烷低温转化的反应机理和催化剂优化、设计进行了综述,并对甲烷低温转化的未来发展进行了展望。     

冷等离子体在甲烷转化中的研究进展

文章综述了近几年国内外利用冷等离子体活化转化甲烷、与催化剂协同作于甲烷转化以及改性甲烷转化用催化剂中的研究进展。等离子体技术作为一种新兴技术为甲烷转化注入了新的力量,对天然气的有效利用、减少温室气体的排放和绿色化工有着重要的意义。     

甲烷部分氧化制合成气催化剂的研究进展

甲烷部分氧化（POM）反应制合成气是化学利用甲烷的有效途径之一。研究表明,甲烷部分氧化反应的工艺有能耗低和反应速率较快等优点,而且所得的H2和CO的比例适于合成甲醇等工业化学品。在该工艺过程中,所需反应容器体积小,反应效率高,可大幅度降低制备合成气的成本。开发POM反应的高效催化剂是进一步提高反应效率、实现工业化的关键途径,因此,是当前国际催化领域研究的热门课题之一。本文主要介绍了传统的金属负载型催化剂和金属氧化物催化剂用于POM反应的研究进展。     

甲烷氧化偶联制乙烯工艺研究进展

甲烷氧化偶联(OCM)途径是通过一步法获取乙烯,是现有乙烯生产中最为简捷的工艺。本文综述了该工艺催化剂系统、反应机理、工艺开发研究的新进展,并探讨了OCM过程面临的关键问题有催化剂的选择、反应器和反应流程的设计和反应温度的控制。     

甲烷等离子体化学利用及其对新世纪能源、环境和化工的影响

本文综述了甲烷等离子体的特点及其化学利用研究和开发的进展,介绍了此项技术近年来的工业试验情况,等离子体应用于甲烷可导致很高的甲烷转化率,并有可能实现甲烷资料的坑口就地转化,对分散,小气源甲烷的开发有着特殊的重要作用。     

Methane Activation on Ruthenium: The Nature of the Surface Intermediates

The identification of surface intermediates is an important step in determining the mechanism of a reaction and in developing an in-depth understanding of a catalytic process. In this work the surface species formed during methane decomposition on idealized single-crystal Ru catalysts (using high-resolution electron energy loss spectroscopy, HREELS) are compared to the surface species identified on real Ru catalysts (using neutron vibrational spectroscopy, NVS). Kinetic studies of methane homologation on single-crystal catalysts and on high surface area supported Ru catalysts have been carried out in parallel with the HREELS and NVS studies to relate rates of reaction with the concentration of particular surface intermediates.     

The Activation of a Pd/γ-alumina Catalyst During Methane Combustion: Investigation of the Phenomenon and of Potential Causes

Activation phenomena of a Pd/γ-Al₂O₃ catalyst under methane combustion reaction conditions were studied. The activation of the catalyst with time-on-stream is not due to Cl removal from the surface but seems to be related to sintering of the palladium particles. This could induce structural changes in the palladium particle, which would favor the activation of O₂ on the surface of PdO.     

Stepwise Conversion of Methane over Supported Metal-Boron Amorphous Alloy Catalysts

The stepwise conversion of CH₄ to higher hydrocarbons over HMCM-22 zeolite supported metal-boron amorphous alloy catalysts has been investigated, including: (1) the influence of metals (Co, Ni, Pt, Rh and Ru) of the catalysts on the reaction; (2) the promotional effect of V on the catalytic behavior of the catalysts; (3) the influence of hydrogenation pressure and CH₄ decomposition temperature; and (4) the nature of carbon species. It is found that the yield of C⁺ ₂ hydrocarbons is strongly dependent on the metals. Good yields of C⁺ ₂ hydrocarbon are reached only on the supported NiB and CoB catalysts. The probability of C--C chain growth is increased by V promotion without seriously affecting the activities of CH₄ decomposition and hydrogenation. The ease of carbon removal via hydrogenation is strongly affected by the CH₄ decomposition temperature. Increasing hydrogenation temperature has a negative effect on the yield of C⁺ ₂ hydrocarbons. XPS measurements show that a carbide(-like) carbon species is active and selective for hydrogenation to produce higher hydrocarbons. Its activity/selectivity is greatly reduced at high CH₄ decomposition temperatures, mainly due to transition of the reactive carbidic to unreactive graphitic form. Graphite/filamental carbons were found to be formed at high CH₄ decomposition temperature.     

NO x -Catalyzed Gas-Phase Activation of Methane: A Reaction Study

The catalytic effect of NO _x on methane oxidation in the absence of any solid catalyst has been investigated. The experimental results show that NO _x has very good catalytic activity in the partial oxidation of methane. The predominant products for reactions in a CH₄-O₂-NO _x co-feed mode are CO, CO₂, H₂O and H₂, CH₃OH, HCHO, and C₂H₄. Aromatics are also observed.     

甲烷部分氧化反应的磷钨酸催化剂研究

以磷钨酸为催化剂和氧化剂,进行了无氧条件下的甲烷气固相部分氧化的实验研究,考察了磷钨酸催化剂的制备条件、载体影响以及反应温度对甲烷部分氧化反应的影响等.磷钨酸催化剂可有效催化甲烷部分氧化反应,甲烷首先转化生成醋酸甲酯,醋酸甲酯水解生成甲醇.制备的催化剂以SiO2为载体,采用载体质量15%(wt)的磷钨酸水溶液回流浸渍4 h、120℃干燥2 h、300℃焙烧4 h制得.甲烷部分氧化反应在0.10 MPa、267～280℃进行,甲烷转化率为26.61%,目的产物收率25.82%.     

甲烷部分氧化制合成气反应的研究

用粒度为5mm的α－Al2O3、β-Al2O3、γ-Al2O3为载体，用浸渍法制备了10％（质量）Ni基催化剂。在固定床流动反应器中，在反应温度500－850℃，大空速和不同的CH4／O2摩尔比下，测定了该催化剂用于甲烷部分氧化制合成气的活性和CO选择性。500℃用H2对催化剂还2h后，进行活性测试结果,10%Ni／β-Al2O3、Ni／γ-Al2O3对POM反应无活性，只有10％Niα－Al2O3对POM反应有活性。TPR测试结果表明，这是由于10％Ni／β-Al2O3和Ni／γ-Al2O3催化剂在700℃以下未被还原所致。另外，合成气的生成速率和CO选择尾均随反应温度和空速的增大而增大，并在CH4／O2摩尔比2时有最大值。     

Quantum Mechanical–Rapid Prototyping Applied to Methane Activation

The accuracy of quantum mechanics (QM) calculations have improved to the point at which they are now useful in elucidating the detailed mechanisms of industrially important catalytic processes. This, combined with the continued dramatic decreases in the costs of computing (and the concomitant increases in the costs of experiments), makes it feasible to consider the use of QM in discovering new catalysts. We illustrate how to apply quantum mechanics to rapidly prototype potential catalysts, by considering improvements in the Catalytica Pt catalyst for activating methane to form methanol. The strategy is to first determine the detailed chemical steps of a prototype reaction (in this case, (bispyrimidine)PtCl₂). Then, we identify critical conditions that must be satisfied for a candidate catalyst to be worth considering further. This allows the vast majority of the candidates to be rapidly eliminated, permitting a systematic coverage of large numbers of ligands, metals, and solvents to be covered rapidly, enabling the discovery of new leads. This Quantum Mechanics-Based Rapid Prototyping (QM-RP) approach is the computational-chemistry analogy of combinatorial chemistry and combinatorial materials science.