Forced periodic operation via pulsing and feed switching to address methane dehydroaromatization catalyst deactivation challenge

Abstract

Methane Dehydroaromatization is a one-step catalytic reaction that converts methane into aromatics and hydrogen with zero CO2 emission from the reaction stoichiometry. This work represents an engineering approach to address the rapid catalyst deactivation challenge by implementing forced periodic operation with shorter times at the scale of minutes. A systematic study was carried out by investigating pulse and periodic feed switching on a typical Mo/HZSM-5 catalyst. A fixed operating temperature and space velocity was maintained in both reaction and regeneration, while the operational time and type of regenerating molecules using reductive (H2) and oxidative (CO2) were investigated. For both modes of regeneration, CO2 was not an efficient oxidative molecule. Pulse feeding with hydrogen improved the catalyst stability, but it minimized the rate of aromatics production. The best performance was observed for the periodic switch with H2. Even a very short regenerating during 1 min H2 after 15 min reaction, was sufficient to achieve stable operation in the tested range. The global benzene production doubled compared to the base case which is a significant improvement reached by optimizing the mode of regeneration and conditions. A mathematical model was constructed and successfully used to simulate and explain the repeated reaction-regeneration cycles for different conditions. The result here is aiming to shed light on the opportunity of the forced periodic operation as an engineering strategy to mitigate the catalyst deactivation challenge and develop a reliable and stable MDA reactor operation.