ABSTRACT The catalytic dehydration of glycerol to acrolein offers an attractive route for reasonable utilization of bio‐derived glycerol. ZSM‐5 zeolites have been extensively investigated in the glycerol dehydration due to their excellent initial catalytic activity and environmental friendliness. A major challenge is the rapid deactivation of the catalyst. Tailoring of acidity and porosity of zeolites is a critical method to mitigate catalyst deactivation. However, tailoring of the zeolites with metal promoter has been barely investigated in the catalytic dehydration of glycerol. In this work, in order to investigate the impact of metal promoter on catalyst deactivation during dehydration of glycerol over the zeolite catalysts, the microporous and hierarchical ZSM‐5 zeolites were subjected to postmodification by three representative metal promoters of potassium, magnesium, and zinc (alkali, alkali‐earth, and transition metals). In the case of microporous ZSM‐5 zeolite catalysts, the introduction of these three metal promoters leads to the deterioration of the catalytic performance. The catalytic performance of hierarchical ZSM‐5 zeolites is less sensitive to the introduction of metal promoter. As for the potassium and magnesium promoters, the deterioration to the catalytic performance is observed at the high loading level (i.e., 2 wt%), whereas the zinc promoter barely leads to deterioration of original catalytic performance. It has also been demonstrated that the introduction of metal promoters generally leads to the reduction of the strength and concentration of strong acid sites of the modified zeolites, which results in the suppressed formation of aromatic species over the spent modified zeolites. However, the suppressed formation of aromatic species does not bring about the corresponding improvement in the stability. It can be found that the deactivation of the zeolite catalysts is not only due to the blockage by the aromatic species. Polyglycols and oligomeric alkoxy species are also responsible for catalyst deactivation. Therefore, the deactivation of zeolite‐based catalysts requires different perspectives, and the antideactivation of dehydration of glycerol demands the strategy beyond the tailoring of zeolite acidity.
Yu et al. (Sun,) studied this question.