分子筛膜包覆Fe基核壳型催化剂催化CO加氢直接制低碳烯烃

In this project, firstly we will try to modulate the structure and electronic property of Fe active sites with various promoters (K, Na, S, Mn and Zn). And then a kind of core-shell catalyst with promoters-modulated Fe as the core and a zeolite (ZSM-5 and SAPO-34) as the shell will be prepared. By tuning the active sites of Fe with various promoters, high selectivity of lower olefins will be obtained. The mass-transport property, confinement effect and hydrocracking of zeolite shell will also be modulated by optimizing its thickness, pore size and acidity in order to restrain the formation of long chain hydrocarbons. As a result, direct production of lower olefins with high yield from syngas will be achieved. The influences of promoters on the Fe active sites, the thickness, pore size and acidity of zeolite shell on the activity and selectivity of Fe based Fischer-Tropsch synthesis to olefins (FTO) catalysts will be investigated. The relationship between the structure and the performance of the core-shell catalysts will be illustrated. The research results will be helpful to exploit novel Fe based FTO catalysts with high efficiency. This project is very important for the development of the technology for direct conversion of coal based syngas to lower olefins. It is also vital to reduce the excessive dependence on petroleum resources in china.

项目拟采用（K、Na、S、Mn和Zn）助剂优化Fe金属活性位的结构和电子性质，以（ZSM-5和SAPO-34）分子筛膜包覆经助剂优化的Fe活性金属核构建核壳催化剂。通过助剂对Fe活性位的调变提高低碳烯烃选择性，通过对分子筛膜厚度、孔道尺寸、酸性质的优化，调变分子筛膜壳的传质扩散、空间限域和酸性裂解作用，抑制产物中长链烃生成，实现合成气经费托合成一步高选择性制低碳烯烃（FTO）。揭示助剂对Fe活性位的调变机制，分子筛膜厚度、孔道尺寸、酸性质对Fe基FTO催化剂活性和选择性的影响规律，明确催化剂的构效关系，为开发新型高效Fe基FTO催化剂提供基础。本项目对发展煤基合成气直接制取低碳烯烃技术，降低我国对石油资源的过度依赖具有重要的意义。

低碳烯烃C2-4=（乙烯、丙烯和丁烯）是重要的基本化工原料，目前低碳烯烃主要来源于石油裂解。基于我国缺油、少气、富煤的资源特点，为缓解对石油资源的依赖，开发煤基合成气制低碳烯烃技术具有重要的战略意义。. 合成气经费托合成反应是制取低碳烯烃的有效途径之一，但费托合成反应产物遵循ASF分布，低碳烯烃的选择性控制仍然是挑战性难题。项目设计合成了两段双功能催化剂FeZnNa/Zeolites，考察了不同种类分子筛，包括HY、NaY、ZSM-5、SAPO-34、Hβ、Liβ、Naβ、Kβ和Rbβ；系统优化了两段催化剂组分比例、装填方式、以及反应过程参数（反应温度、压力、空速和H2/CO比）；FeZnNa/Naβ两段催化剂获得最优FTO反应性能，CO转化率和C2-4=选择性分别高达92.9%和50.5%，C2-4=选择性突破了传统费托合成ASF分布限制，并且该催化剂可稳定反应100 h，具有良好的工业应用潜力。通过BET、XRD、MES、NH3-TPD、SEM和Raman等多种表征手段对FeZnNa和分子筛的表征分析，建立了催化剂合理构-效关系，阐明了双功能组分间距、分子筛酸强度和孔结构对FTO反应低碳烯烃的影响规律。. 研究金属助剂优化活性金属Fe过程中，发现碱土金属Sr具有优异的电子助剂作用，兼具结构分散作用，可有效提升铁基催化剂的烯烃选择性，抑制甲烷生成；Sr的助剂作用优于同族的其它碱土金属。. 此外，项目进一步拓展双功能催化反应耦合的策略用于CO2选择性加氢反应，研制了铜铁矿/ZSM-5双功能催化剂，可催化CO2一步选择性加氢制芳烃，芳烃选择性可达到70%左右，具有较好应用前景，拓展了项目的应用潜力。.