镧化合物的甲烷氧化偶联催化活性研究

研究了镧的氧化物，氢氧化物，碳酸盐催化剂的甲烷氧化偶联活性，利用催化剂具备明显活性所需达到的“起始温度”高低作为催化剂活性强弱的判据，得到了各个催化剂的活性强弱次序：ＬａＯＯＨ（Ｌａ（ＯＨ）３）＞Ｌａ２Ｏ２ＣＯ３（Ｂ）＞Ｌａ２Ｏ３＞Ｌａ２Ｏ２ＣＯ３（Ａ）＞Ｌａ２（ＣＯ３）３，使用ＸＲＤ、ＦＴ－ＸＲＤ等分析手段对催化剂进行了表征     

AN EXPERIMENTAL STUDY OF METHANE OXIDATIVE COUPLING IN FIXED BED REACTORS WITH A DISTRIBUTED OXYGEN FEED

Methane oxidative coupling has been carried out in a reactor with a distributed oxygen feed. The system consists of a catalytic bed of Li/MgO in a quartz reactor with one inlet for methane and one or more inlets for oxygen. To enable the comparison between the co-fed mode and the distributed feed mode, an especial experimental design was used in order to maintain the same contact time in the co-fed and in the distributed feed modes, and in order to minimize the temperature gradients caused by the exothermic oxidation process. The results clearly show that a distributed oxygen feed may give rise to significant increases in the hydrocarbon selectivity obtained at a given methane conversion,     

固体电解质电化学反应器中甲烷氧化偶联反应的模拟

建立了固体电解质电化学反应器的数学模型,采用修正的Newton-Raphson法求解模型方程.利用该模型对以质量浓度为1%Sr/La_2O_3-Ag为催化电极的固体电解质电化学反应器中的电能与目的产物乙烯、乙烷共生进行了研究.考察了外加负载、反应温度、进料组成等因素对甲烷氧化偶联(OCM)反应和输出电流的影响,并将计算结果与实验结果进行了比较,得到了令人满意的结果.     

甲烷催化燃烧的实验研究

在含铂的Ｍｏｎｏｌｉｔｈ催化剂上进行了甲烷的催化燃烧反应。实验表明，室温下必须先用氢气来点火，甲烷才能催化燃烧。甲烷催化燃烧的允许工作温度为９００～１１００℃，过低的温度导至熄火，过高则会使铂催化剂失活。在实验的反应条件下，甲烷进料浓度范围很窄为４％—６％（体积）。为实现甲烷的稳定燃烧必须对反应条件提出较高的自动化要求     

METHANE COUPLING USING CATALYTIC MEMBRANE REACTORS

The purpose of this review article is to provide readers with an extensive account on methane-coupling reactions performed in membrane reactors available in literature up to 2000. The principles, advantages or disadvantages, and crucial problems of all kinds of membrane reactors used in methane coupling are discussed. Some areas such as solid oxide membrane reactors for methane oxidative coupling are treated less extensively, as it has always been reviewed by other researchers. More emphasis has been placed in catalytic proton or mixed proton and electron-hole conducting membrane reactors, as they have greater potentials and have received less attention in the literature.     

METHANE COUPLING USING CATALYTIC MEMBRANE REACTORS

The purpose of this review article is to provide readers with an extensive account on methane-coupling reactions performed in membrane reactors available in literature up to 2000. The principles, advantages or disadvantages, and crucial problems of all kinds of membrane reactors used in methane coupling are discussed. Some areas such as solid oxide membrane reactors for methane oxidative coupling are treated less extensively, as it has always been reviewed by other researchers. More emphasis has been placed in catalytic proton or mixed proton and electron-hole conducting membrane reactors, as they have greater potentials and have received less attention in the literature.     

CATALYTIC COMBUSTION OF METHANE OVER PALLADIUM-BASED CATALYSTS

Palladium-based catalysts are widely applied in exhaust catalytic converter and catalytic combustion systems. The mechanism for methane oxidation on a Pd-based catalyst is complex. Catalyst activity is influenced by variations in the process pressure and temperature, by the gas mixture composition, by the type of support and various additives, and by pretreatment under reducing or oxidizing atmospheres. In this paper, we review the literature on supported Pd catalysts for combustion of methane. The mechanisms involved are discussed taking into consideration the oxidation/reduction mechanisms for supported palladium, poisoning, restructuring, the form of oxygen on the surface, methane activation over Pd and PdO phases, and transient behavior. Our review helps explain the array of experimental results reported in the literature.     

CATALYTIC COMBUSTION OF METHANE OVER PALLADIUM-BASED CATALYSTS

Palladium-based catalysts are widely applied in exhaust catalytic converter and catalytic combustion systems. The mechanism for methane oxidation on a Pd-based catalyst is complex. Catalyst activity is influenced by variations in the process pressure and temperature, by the gas mixture composition, by the type of support and various additives, and by pretreatment under reducing or oxidizing atmospheres. In this paper, we review the literature on supported Pd catalysts for combustion of methane. The mechanisms involved are discussed taking into consideration the oxidation/reduction mechanisms for supported palladium, poisoning, restructuring, the form of oxygen on the surface, methane activation over Pd and PdO phases, and transient behavior. Our review helps explain the array of experimental results reported in the literature.     

微通道内甲烷/湿空气重整转化效率实验研究

用沉淀法制备了涂覆在微通道内壁面的Ni/Al2O3催化剂,在自行搭建的实验系统上进行了微通道内甲烷/湿空气催化重整的实验研究,考察了催化壁面温度、空碳比及甲烷体积流量对甲烷/湿空气重整转化效率的影响,并与数值计算结果进行对比.结果表明,随着催化温度的升高,甲烷转化率不断升高;相同水碳比下,甲烷的催化转化率随着空碳比的增大而增大;随着甲烷体积流量的增大,甲烷转化效率呈现先增大后减小的变化规律.反应温度为1 023 K,甲烷体积流量为20 mL/min时,实验所得甲烷转化率达到最大值,为61.3％.     

THE SELECTIVE CATALYTIC REDUCTION OF NITRIC OXIDE WITH METHANE OVER NONZEOLITIC CATALYSTS

This article deals with recent progress in the development of nonzeolitic catalysts for the selective catalytic reduction (SCR) of nitrogen oxides (NO_x) with methane. Although metal-exchanged zeolitic catalysts exhibit high activities for this reaction, most of these metastable structures suffer from deactivation problems when exposed to wet exhaust streams at elevated temperatures. Nonzeolitic oxide catalysts have the potential for improved durability because many of these are thermodynamically stable structures.

The NO_x reduction activity and poisoning resistance of lanthanide oxides, Group IIA oxides, Group IIIB oxides, as well as gallium-, tin-, and palladium-based catalysts are reviewed. Current opinions on mechanistic aspects of the SCR reaction are discussed in relation to the development of more active catalytic systems.

A detailed experimental study of the SCR of NO_x over rare earth oxides has also been performed. The role of absorbed oxygen in the activation of CH₄ and consumption of CH₃ radicals is discussed and related to the catalytic properties of the rare earth oxides. The presence of highly basic centers is shown to promote catalytic activity, and the presence of weakly absorbed oxygen species is found to be detrimental to catalytic selectivity. Oxides with lower electronic conductivities are found to be more selective than catalysts with higher conductivities. The selectivities of rare earth oxides for the SCR of NO_x with methane and the oxidative coupling of methane are also compared and contrasted.     

复合材料用硅烷偶联剂的研究进展

本文针对目前复合材料界面改性研究的现状，首先分析了硅烷偶联剂的结构特征，然后对常用硅偶联剂在复合材料中的作用机理进行了探讨。此外，还介绍了新近开发的硅烷偶联剂产品，并论述了它们在玻璃纤维增强材料的应用效果，对复合材料用硅烷偶联剂的选择具有一定的指导作用。     

甲烷在高比表面积活性炭上吸附性能的研究

以中温沥青作为粘结剂,研究了石油焦基高比表面积活性炭的成型工艺对其甲烷吸附性能的影响。结果发现：随着粘结剂添加量的增大,成型活性炭对甲烷的质量吸附量逐渐减小,而体积吸附量差别不大;成型压力对成型活性炭的甲烷吸附性能没有明显影响;随着活化温度的提高和活化时间的延长,成型活性炭对甲烷的质量吸附量逐渐增多,而体积吸附量的变化不大;添加粘结剂沥青38％、88℃下炭化1．0hr后于88℃下活化1．5hr所得的高比表面积成型活性炭在299K、3．5MPa下对于甲烷的体积吸附量为170V／V,5．5MPa下的体积吸附量为237V／V。     

低浓度甲烷催化燃烧特性及Cr催化剂的研究

采用浸渍法制备了不同Cr2O3含量的Cr2O3/γ-Al2O3系列催化剂,研究了Cr2O3/γ-Al2O3催化剂焙烧温度、甲烷浓度及反应空速对甲烷催化活性的影响,并考察了催化剂的抗硫中毒能力.结果表明,该法制备的Cr2O3/γ-Al2O3系列催化剂具有较好的低温催化活性,且随Cr2O3含量的增加,催化剂活性先增加后降低;Cr2O3含量为20％的Cr2O3/γ-Al2O3催化剂的甲烷催化燃烧活性与甲烷浓度呈正相关,与反应空速呈负相关关系.实验表明,400℃焙烧制备的Cr2O3含量为20％的Cr2O3/γ-Al2O3催化剂具有较好的甲烷低温催化活性,且具有较强的抗硫中毒能力.     

CO气相催化偶联合成草酸二乙酯动力学

以工业应用为背景,研究了CO在钯系双金属催化剂上气相催化偶联合成草酸二乙酯的动力学特性。得出其速率控制步骤为CO吸附控制,并且认为在催化剂表面上存在烷氧羰基中间体COOR,进一步缔合生成草酸二乙酯,提出了机理型的动力学方程,并据此对反应历程做了探讨。     

双噁唑啉化合物偶联聚酯的研究─—聚对苯二甲酸丁二酯的偶联反应

报告双唑啉化合物（ＢＯＺ）对聚对苯二甲酸丁二酯（ＰＢＴ）的偶联扩链的研究结果，表明与偶联聚对苯二甲酸乙二酯（ＰＥＴ）一样，特性粘数（［η］）在３～６ｍｉｎ迅速达到极大值，随后缓慢下降，ＰＢＴ熔点较低，故此反应可在较低温度下进行，偶联效率与ＰＥＴ的结果相近，以丁二酸为模型化合物考察表明偶联作用是在羧基进行，同时反应的最低温度可至１６４℃左右。     

负载型杂多酸催化乙烷氧化脱氢反应的起燃特性

研究了负载在SiO₂ 上的杂多酸催化剂的乙烷氧化脱氢活性 .发现在乙烷氧化脱氢反应中存在一个活性起燃温度 ,当反应温度高于此温度时 ,反应以气相自由基反应为主 .杂多酸的酸性与乙烷在杂多酸表面的吸附有关 ,酸性越强 ,引发自由基反应的起燃温度越高     

非催化加压甲烷部分氧化制合成气

考察了非催化条件下,温度、压力和进气配比对甲烷部分氧化制合成气的影响,结果表明：甲烷的转化率随温度的升高,压力的增加,进气中氧的增加而增加;产物中合成气含量随温度的升高而增加,最高达81％以上;随着温度的升高,产物中H2／CO存在极值,在本实验的研究范围内,最大可达1．8;进气中氧增多,产物中H2／CO减小;温度升高,或压力增大,CO2的选择性也随之提高．对CO选择性的正交分析表明,进气配比对CO选择性影响最大,压力次之,温度的影响最小．     

甲苯氧化甲基化制苯乙烯双碱金属／La2O3催化剂

在常压固定床流态化反应装置上，考察了双碱金属促进的Ｌａ２Ｏ３催化剂在甲苯氧化基化反应中的催化活性、选择性。结果表明：双碱、钾促进的Ｌａ２Ｏ３体系是良好的甲苯氧化甲基化制苯乙烯催化剂。其中用质量分数各为７％的ＮａＯＨ、ＫＯＨ促进的Ｌａ２Ｏ３催化体系，在反应温度为７５０℃，空速为１３．７Ｌ／（ｇ．ｈ）、原料报分压Ｃ７Ｈ８：ＣＨ４：Ｏ２：Ｎ２＝１：１１．２：２．１：１０．４条件下，甲苯单程转化率为４６．     

H2对CO气相催化偶联制草酸二乙酯反应的失活机理

重点研究了氢气（H₂）对一氧化碳（CO）催化偶联反应制草酸二乙酯的影响,分别考察了不同H₂浓度、不同温度和不同空时条件下加入H₂对CO偶联反应的影响,结果发现H₂的加入使反应过程中CO转化率、草酸二乙酯选择性和空时收率明显下降,且在实验条件范围内,通入H₂浓度越高、反应温度越高,催化剂活性下降越快.研究得出,H₂气氛下CO偶联反应失活动力学方程为：-da/dt=k_dc^0.65_H2.进一步分析失活动力学方程可知,加氢反应过程中,H₂和CO吸附在同一个活性中心上,H₂在活性中心上的吸附抑制了CO在催化剂上的吸附,从而使得CO催化偶联反应生成草酸二乙酯的速率下降,导致加氢后CO转化率、草酸二乙酯选择性和空时收率降低.     

CHLORINE-CATALYZED OXIDATIVE PYROLYSIS OF METHANE: A PARAMETRIC STUDY

Conversion of methane and monochtoromethane to acetylene, ethane, and ethylene via homogeneous oxidative pyrolysis is investigated in an isothermal continuous flow reactor employing steam and/or oxygen as oxidizing agents. The effects of monochloromethane to methane ratio in the feed (0.304-9.981), reactor temperature (973-1423 K), and reactor space time (0.0-3.76 s) on product distribution in the reactor effluent are studied. Steam is shown to be a more effective oxidizing agent than oxygen as far as production of C₂ species is concerned. Addition of steam in the feed suppresses formation of coke, carbon monoxide, and carbon dioxide. The efficacy of oxidative pyrolysis with steam is demonstrated by the substantially high selectivity of C₂ species (up to 74%).