Promotional effect of Co cations on the catalytic activity of Co/ZSM-5 in 1,2-dichloroethane dehydrochlorination for the production of vinyl chloride monomer

In the catalytic dehydrochlorination of 1, 2-dichloroethane (DCE) for Vinyl chloride monomer (VCM) production, it is important to design catalysts with appropriate acid properties which can activate DCE, while inhibiting the further reaction of VCM. In this study, Co species were introduced into ZSM-5 through an ion-exchange method to change acid site distribution of ZSM-5. The introduction of Co cations significantly improved DCE conversion and VCM selectivity, achieving 6 and 2-fold greater than bare HZSM-5, respectively. Postmortem analyses allowed us to delineate the role of acid sites: Lewis acid sites are the major active sites, whereas Brønsted acid sites give rise to undesired secondary reactions. Thus, our results demonstrate that the introduction of Co cations increases the number of relevant active sites, and simultaneously eliminates undesirable sites. These findings help understand the effect of Brønsted and Lewis acid sites in zeolites on the DCE dehydrochlorination, providing useful information for designing rational catalysts.