Data underlying the research on: Direct discerning reaction pathways in methanol-to-hydrocarbons by transient operation - FASPA

Monitoring complex catalytic pathways under industrially-relevant conditions is one of the key challenges in catalysis chemistry and technology. Herewith we describe a direct technique called ‘fast scanning-pulse analysis’ (FASPA) that allows the direct characterization and detailed kinetic analysis of intimately interweaved catalytic pathways. The power and potential of the FASPA approach are demonstrated with an industrially relevant methanol-to-hydrocarbons (MTH) process over H-ZSM-5 zeolite. This reaction proceeds via a hydrocarbon pool (HCP) mechanism producing olefins and aromatics. The HCP is built-up upon exposure to methanol during the induction period, followed by a transition regime to a <em>quasi</em>-steady state MTH operation. This FASPA technique allows (sub-)second resolution of the full temporal products response upon a methanol pulse providing direct and quantitative insight into the MTH reactions. Globally two consecutive pathways can be discerned: a very fast primary product formation in the presence of methanol in a narrow active MTH reaction zone, followed by a slower formation of light aromatics, which is closely related to the decomposition and release of HCP species and secondary reactions in absence of methanol in the downstream part of the catalyst bed. The time delay between the appearance of inert tracer and primary products represents the time needed to build-up the HCP in the induction period, where methane is observed prior to other products. The primary products (alkanes, olefins, and light aromatics) are nearly instantaneously formed from the pulsed methanol. These results demonstrate the highly dynamic character of the HCP in the MTH process over H-ZSM-5.

在工业相关条件下监测复杂催化路径，是催化化学与工业技术领域的核心挑战之一。本文介绍一种名为“快速扫描脉冲分析（fast scanning-pulse analysis, FASPA）”的直接表征技术，可实现对高度交织的催化路径的直接表征与精细化动力学分析。我们以氢型ZSM-5分子筛上的工业相关甲醇制烃类（methanol-to-hydrocarbons, MTH）反应体系，验证了FASPA方法的效能与应用潜力。该反应通过烃池（hydrocarbon pool, HCP）机理进行，产物涵盖烯烃与芳烃。烃池在诱导期内通过接触甲醇逐步形成，随后经历过渡阶段，最终达到准稳态的MTH反应运行模式。FASPA技术可实现亚秒级分辨率的甲醇脉冲进料后全时段产物响应监测，从而为MTH反应提供直接且定量的认知。整体而言，可识别出两条连续的反应路径：一是在狭窄的活性MTH反应区内，甲醇存在时快速生成初级产物；二是在催化剂床层下游无甲醇的环境中，与烃池物种分解释放及二次反应密切相关的轻芳烃缓慢生成过程。惰性示踪剂与初级产物的出现时间差，对应诱导期内烃池构建所需的时长，该阶段甲烷会先于其他产物生成。初级产物（烷烃、烯烃与轻芳烃）可由脉冲进料的甲醇近乎瞬时生成。上述结果证实了氢型ZSM-5分子筛上MTH反应过程中烃池的高度动态特性。