经由甲醇类C1中间体的合成气高选择性制低碳烯烃的研究

The catalytic transformation of synthesis gas (syngas) is a core process for the utilization of carbon resources such as coal, shale gas and biomass. The products of syngas transformations usually follow the ASF distribution and the selectivity control is highly challenging. This project chooses lower (C2-C4) olefins as the main target products and aims at controlling the product selectivity to develop highly selective catalytic systems that can break the ASF distribution. Based on the new strategy of reaction coupling proposed by the applicants, the project will construct bifunctional catalysts to increase the selectivity to lower olefins. The catalytic system will combine reactions of the hydrogenation of CO to methanol like C1 (DME or CH3O) intermediates and the subsequent C-C coupling of C1 intermediates. The bifunctional catalysts with synergistic effects will be designed and fabricated through systematic studies on the hydrogenation of CO on metal oxide or composite metal oxide surfaces, the utilization of the catalytic properties of molecular sieves with specific pore structures in C-C coupling, and adopting new methods in nano-synthetic areas. We will deeply investigate the key factors that influence the selectivity to lower olefins over the bifunctional catalysts. The project will offer a new route and new catalytic systems for selective transformation of syngas to lower olefins, and will also provide scientific bases for the selectivity control in syngas conversions.

合成气催化转化是煤、页岩气和生物质等碳资源高效利用的核心过程。合成气转化产物常服从ASF分布，产物选择性调控极具挑战性。本项目以合成气直接转化制低碳(C2-C4)烯烃为主攻目标，围绕化学反应选择性调控这一关键科学问题，着力开拓和发展打破ASF分布的高选择性催化体系。项目基于反应耦合的研究策略，构建具有CO加氢生成甲醇类C1(二甲醚或CH3O)中间体和中间体选择性C-C偶联功能的双功能催化剂，提高低碳烯烃选择性。通过系统研究金属氧化物或复合氧化物表面的CO加氢反应，利用具有特定孔结构分子筛可催化C-C偶联反应的特性，借鉴纳米合成领域的新方法，设计和研制不同功能组分间协同作用的双功能催化剂。项目将深入探究双功能催化剂上影响低碳烯烃选择性的关键因素，为合成气制低碳烯烃提供新方法和新催化体系，同时也为合成气转化反应中产物选择性的调控提供科学基础。

合成气催化转化是煤、页岩气和生物质等碳资源高效利用的核心过程。本项目以合成气直接转化制低碳(C2-C4)烯烃为主攻目标，围绕化学反应选择性调控这一关键科学问题，着力开拓和发展打破ASF分布的高选择性催化体系。项目构建具有CO加氢生成甲醇类C1(二甲醚或CH3O)中间体和中间体选择性C-C偶联功能的双功能接力催化剂，提高低碳烯烃选择性。项目探究双功能催化剂上影响低碳烯烃选择性的关键因素，主要包括催化剂活性位本质、反应动力学因素、反应机理等重要问题。研究结果还拓展到CO2加氢反应。.探索得到具有较好生成低碳烯烃催化性能Zn-ZrO2/SSZ-13催化体系。研究发现Zn-ZrO2固溶体和具有CHA结构SSZ-13分子筛的优化是影响反应性能的重要因素。调控氧化物的Zn/Zr比、分子筛的酸量、分子筛与氧化物接触距离等因素可以提高催化性能，在CO转化率为29%时，得到较高低碳烯烃选择性78%。动力学研究表明，CH3OH/DME为反应中间体，甲醇合成为速率决定步骤， CO在Zn-ZrO2上发生朗格缪尔类型非解离吸附活化，H2在-Zn-O-上发生解离吸附活化。红外光谱证实在Zn-ZrO2上，CO/H2转化顺次经由甲酸盐、甲氧基，生成CH3OH中间体。Zn-ZrO2催化产物H2O与CO反应，经WGS反应生成CO2。.研究了尖晶石氧化物与CHA结构SAPO-34的双功能催化剂上的CO2加氢反应。尖晶石氧化物化学组成影响催化性能，ZnAl2O4/SAPO-34和ZnGa2O4/SAPO-34的CO2转化率均高于13%，低碳烯烃选择性高于86%，CO选择性小于50%，为文献报道较优值。EPR测定显示CO2加氢催化性能与氧空位浓度正相关，CO2在氧空位上活化，H2-D2交换显示H2在-Zn-O-和-Ga-O-上活化。红外光谱证实CO2/H2在尖晶石氧化物表面吸附活化后，经CO2*、甲酸盐、甲氧基中间体生成CH3OH。