An INS investigation on the effect of a regeneration cycle for post-reaction Fe-modified ZSM5 catalysts applied to xylene isomerisation reactions (MAPS)

The global demand for p-xylene production is considerable. One production route involves the use of ZSM5 zeolites to affect the isomerisation of m-xylene to p-xylene. However, catalyst deactivation constitutes a significant impediment to the process operation. In partnership with a major catalyst manufacturer (Johnson Matthey), this application seeks to use the MAPS spectrometer to examine the effect of a regeneration cycle on a series of new Fe-doped ZSM5 catalyst formulations under development.

Carbon deposition as a function of time-on-stream results in a significant reduction of activity, necessitating the zeolite to experience an oxidative treatment to burn off the ‘coke’. Laboratory testing has established that discrete Fe loadings can induce ‘soft’ coke formation (reversible via regeneration) over ‘hard’ coke (irreversible). However, the durability of the Fe-doped catalysts with respect to the regeneration treatment is uncertain.

MAPS beamtime is requested to analyse a selection of post-reaction samples after a regeneration stage. This procedure will provide spectral insight as to how the regeneration stage perturbs the catalysts’ acid site distribution, with particular emphasis on strong Brønsted acid sites. Further measurement of the samples after a second reaction sequence will be used to speciate the form of the hydrocarbonaceous species that results post-regeneration. This MAPS application is linked to an associated TOSCA proposal.

全球对二甲苯（p-xylene）的生产需求可观。其中一条生产路线采用ZSM-5分子筛（ZSM5 zeolites）催化间二甲苯（m-xylene）异构化为对二甲苯（p-xylene）。然而，催化剂失活是该工艺运行的重大阻碍。本申请与大型催化剂制造商庄信万丰（Johnson Matthey）合作，拟借助MAPS光谱仪（MAPS spectrometer），探究再生循环对一系列处于研发阶段的铁掺杂ZSM-5分子筛（Fe-doped ZSM5）催化剂配方的影响。
随运转时间（time-on-stream）延长产生的积碳会大幅降低催化剂活性，因此需对分子筛进行氧化处理以烧除积碳。实验室测试表明，不同负载量的铁可诱导生成“软积碳”（可通过再生反应可逆脱除）而非“硬积碳”（不可逆）。但铁掺杂催化剂在再生处理后的耐久性仍有待明确。
本申请请求使用MAPS束线机时，对一批经过再生阶段的反应后样品开展分析。该分析将从光谱层面揭示再生过程如何改变催化剂的酸位点分布，尤其聚焦于强布朗斯特酸位点（Brønsted acid sites）。此外，对经过第二轮反应序列后的样品进行进一步测量，可表征再生后生成的碳氢化合物物种的具体形态。本MAPS相关申请关联一项配套的TOSCA提案（TOSCA proposal）。