等离子体低温活化协同甲烷化学链氧化偶联定向制取烯烃基础研究

Oxidative coupling of methane (OCM) is an important route for the synthesis of light olefins from non-petroleum routes. The critical problem in OCM is the low selectivity of target product due to the deep oxidation of reactants and products. Moreover, there is a contradiction between the severe coking during methane activation at high temperature and low efficiency of methane activation at low temperature. In order to address these challenges, a new method of chemical looping oxidative coupling of methane into olefins assisted with plasma low temperature activation is proposed. During this process, the selective activation and oriented conversion of methane can be achieved through the cooperation of oxygen carrier with the non-equilibrium plasma. The multiple oxygen carriers with the function of oxygen supply, catalysis and in situ dehydrogenation are constructed. The theoretical guidance for the initiative design of high active oxygen carriers is established. In order to clarify the mechanism of methane activation at low temperature and the selective control for C2 hydrocarbon generation, the chemical-looping coupling with non-equilibrium plasma experiment platform will be built to obtain the reaction routes for C-H bond activation, C-C bond coupling and chain termination. Additionally, the matching relationships between the structure-reactivity of oxygen carriers and the orientation evolution of fuel hydrocarbon components are discussed. And the correlative mechanism between the structure, the interfacial characterization and the acid/alkaline degree with the coke formation are also discussed. These studies can provide theoretical basis and technical support for novel and effective methane conversion technology towards C2 hydrocarbon.

甲烷氧化偶联技术是非石油路线合成低碳烯烃的重要途径，针对传统甲烷氧化偶联过程中甲烷低温活化困难和高温积碳严重的矛盾，本申请提出等离子体低温活化协同甲烷化学链氧化偶联定向制取C2烃的新思路，利用载氧体的供氧/催化功能和等离子体的活化功能耦合实现甲烷选择性活化和定向转化，解决传统反应过程中有氧存在易导致产物深度氧化、目标产物选择性低等关键问题。设计和构筑具有供氧-催化-原位脱氢作用的多功能复合载氧体，构建载氧体多尺度剪裁设计的基本理论与控制策略；搭建化学链/等离子体协同催化转化甲烷实验平台，获得多场协同作用下C-H键活化、C-C链增长和链终止的反应路径，阐明载氧体-等离子体耦合对甲烷低温活化的促进机制和对C2烃生成的选择性控制机理；掌握载氧体构效与燃料碳氢组分定向演化的匹配关系，探明载氧体结构和表界面特性、表面酸碱强度与积碳生成的关联机制。为研制新颖、高效的甲烷转化制烯烃技术提供理论支撑。

乙烯是重要的有机化工基本原料，作为石油化工产业的核心，乙烯是合成塑料、合成纤维、合成橡胶、医药、染料、农药、化工新材料以及日用化工产品的基本原料，是用途最广的基本有机化工原料。受生产规模、原料资源等条件的限制，我国乙烯产量目前还无法满足国内需求。且随着石油资源的日益枯竭以及乙烯需求量的不断增加，开辟和发展从天然气、煤炭和生物质等非石油资源合成低碳烯烃新路线，是兼具重要学术意义和重大应用价值的战略课题。甲烷氧化偶联技术是非石油路线合成低碳烯烃的重要途径，针对传统甲烷氧化偶联过程中甲烷低温活化困难和高温积碳严重的矛盾，本申请通过等离子体低温活化协同甲烷化学链氧化偶联定向制取C2烃，利用载氧体的供氧/催化功能和等离子体的活化功能耦合实现甲烷选择性活化和定向转化。设计构筑了系列核壳结构钙钛矿载氧体，探究了金属掺杂种类、外源异质离子种类、负载量及介入方式等对载氧体晶相结构、活性组分和载氧体孔道结构等对反应性能和抗积碳性能的影响，对载氧体进行了多尺度表征，优化了关键工艺参数，完成了载氧体评价；对比分析了有无等离子体作用下的甲烷氧化偶联制烯烃反应性能，分析了载氧体供氧催化和等离子体激发耦合对低温活化甲烷的促进作用。优选的载氧体MnTi载氧体在不外加热源的情况下，通过介质阻挡放电等离子体可以得到28.47%的CH4转化率，95.82%的C2+选择性和27.28%的C2+收率。进一步地，通过改变反应系统温度、等离子体放电电压以及反应甲烷空速等实验条件探究了载氧体-等离子体间的协同耦合作用，深入认识其在甲烷氧化过程中的作用机理，为研制新颖、高效的甲烷转化制烯烃技术提供了理论支撑。发表论文21篇，申请专利2件，培养硕士生3人，参加学术会议7次并2次任分会主席。