Metathesis of ethylene with 2-butenes over WOx-, MoOx- and ReOx-based catalysts: understanding the fundamentals of catalyst functioning

乙烯与2-丁烯的复分解制丙烯是一个大规模的过程，其中WOx-（很少有MoOx-和ReOx-）催化剂与助催化剂（MgO）一起使用。尽管学术界和工业界对这种反应进行了深入的研究，但在催化剂的功能方面仍然存在许多根本性的问题。他们的回答将为催化剂设计和确定最佳丙烯形成所需的反应条件提供基础。为了缩小这一差距，目前的项目旨在i)为开发活性和稳定的2-丁烯乙烯复分解催化剂提供基础；Ii)确定催化剂的最佳操作条件；iii)建立构效关系。为了实现项目目标，将合成一系列具有明确的MOx （M = W， Mo或Re）结构的WOx， MoOx和reox基催化剂，并通过互补技术进行全面表征。该催化剂将在稳态和瞬态条件下用于乙烯与反式2-丁烯的复分解。阐明了不同因素（如MOx种类的分散、载体材料的种类、还原剂在分解料中的存在或作为促进剂的分解无活性共催化剂的存在、催化剂预处理）对原位形成的活性物质（金属-羰基）数量的影响。将进行操作测试（IR, Raman, UV-vis），以监测预处理和复分解反应期间催化剂组成和结构的变化。所获得的基本见解将用于改进催化剂的合理设计以及有效催化剂操作的一般指南，包括气相和固体促进剂的存在。

The metathesis of ethylene with 2-butenes to propene is a large-scale process, in which WOx- (and rarely MoOx- and ReOx-) based catalysts together with a co-catalyst (MgO) are applied. Despite the fact that such reaction is thoroughly investigated by academia and industry, there is still a lot of fundamental questions concerning catalyst functioning. Their answering will provide a basis for catalyst design and for identification of reaction conditions required for optimal propene formation. To close such gap, the current project is intended i) to provide fundamentals for the development of active and stable catalysts for the metathesis of ethylene with 2-butenes; ii) to identify optimal conditions of catalyst operation; and iii) to establish structure-reactivity relationships. In order to achieve the project goals, a series of WOx-, MoOx- and ReOx-based catalysts with a well-defined MOx (M = W, Mo or Re) structure will be synthesized and thoroughly characterized by complementary techniques. The catalysts will be tested in metathesis of ethylene with trans-2-butene under steady-state and transient conditions. The influence of different factors (e.g. dispersion of MOx species, the kind of support material, the presence of reducing agent in metathesis feed or metathesis-inactive co-catalysts with these both being used as promoters, catalyst pre-treatment) on the amount of in situ formed active species, which are metal-carbenes, is to be elucidated. Operando tests (IR, Raman, UV-vis) will be performed in order to monitor the changes in catalyst composition and structure during pre-treatment and metathesis reaction. The obtained fundamental insights will be applied for a rational design of improved catalysts as well as general guidelines for efficient catalyst operation including the presence of gas-phase and solid promoters.