Chemistries mediating deactivation in methanol to hydrocarbons conversion and strategies to mitigate them

将甲醇转化为碳氢化合物是将煤炭和页岩气等碳原料升级为高价值燃料和化学品的最后一步。沸石分子筛的择形特性对低碳烯烃或汽油烷烃具有很高的选择性，但由于大量碳氢化合物积累在微孔内使其失去活性，因此不利于催化剂的使用寿命。这项研究的目的是探索这些非活性闭塞碳氢化合物的形成机理，并开发配方和工艺条件，以提高催化剂的寿命和选择性。这项研究将有助于确保能源和化工行业有效利用国家的化石燃料资源。甲醇到碳氢化合物的转化是自动催化进行的，定位在沸石孔内的烯烃和芳烃中间体构成了所谓的“碳氢库”，作为碳-碳键形成事件的有机助催化剂。这项研究试图研究将活跃的油气藏中间体转化为不活跃的多环烃的途径。初步结果表明，甲醇是催化过程中的氢化物供体，甲醇脱氢产物是影响油气藏失活的烷基化试剂。该项目旨在利用同位素方法结合瞬变和稳态动力学测量来确定甲醇脱氢事件发生的速度和机制。研究人员提出，可以通过(I)通过引入空间限制来改进无机催化剂以减少大体积碳氢化合物的形成或通过添加分解醛的金属氧化物来提高催化剂的寿命，以及(Ii)在气相中引入含有甲醇的气流之前引入有机助催化剂。研究人员预计，在这项研究中开发的质子形式的MFI和CHA沸石的策略将扩展到其他沸石拓扑结构，并将启发材料的设计，应用于多相催化，超越甲醇到碳氢化合物的催化。除了为本科生和研究生提供培训机会外，首席调查员还将继续开展教育和推广计划，在K-12课程中介绍催化的概念。

The conversion of methanol-to-hydrocarbons represents the final step in upgrading carbon feedstocks, such as coal and shale gas, to high-value fuels and chemicals. The shape selective characteristics of zeolites afford high selectivity to light olefins or gasoline-range hydrocarbons, but are deleterious for catalyst lifetime, as the accumulation of bulky hydrocarbons inside micropores renders them inactive. The goals of this research are to explore mechanisms involved in forming these inactive occluded hydrocarbon species, and to develop formulations and process conditions to improve catalyst lifetime and selectivity. The research will help ensure efficient utilization of the Nation's fossil fuel resources by the energy and chemical industries.Methanol-to-hydrocarbons conversion proceeds auto-catalytically with olefins- and aromatics-based intermediates localized inside the zeolite pores, constituting the so-called "hydrocarbon pool," acting as organic co-catalysts for carbon-carbon bond formation events. This research seeks to examine the pathways that mediate the conversion of active hydrocarbon pool intermediates to inactive polycyclic hydrocarbons. It is predicated upon preliminary results that suggest methanol acts as a hydride donor during catalysis and derivatives of methanol dehydrogenation act as alkylation agents effecting hydrocarbon pool deactivation. The project is aimed at determining the rate and mechanism by which methanol dehydrogenation events occur using isotopic methods combined with transient and steady state kinetic measurements. The researchers propose that catalyst lifetime can be improved by (i) modifying the inorganic catalyst by introducing spatial constraints to mitigate formation of bulky hydrocarbons or by addition of metal oxides that decompose aldehydes, and (ii) introducing an organic co-catalyst prior to introduction of methanol containing streams in the vapor phase. The researchers expect that the strategies developed in this research for proton-form MFI and CHA zeolites will extend to other zeolite topologies and will inspire the design of materials for applications in heterogeneous catalysis extending beyond methanol-to-hydrocarbons catalysis. In addition to providing opportunities for undergraduate and graduate student training, the principal investigator will pursue educational and outreach programs that introduce concepts of catalysis across the K-12 curriculum.