Cooperative catalysis of Co-promoted Zn/HZSM-5 catalysts for ethane dehydroaromatization

Zn/HZSM-5 is a promising catalyst for ethane dehydroaromatization despite rapid deactivation within 13 h. Herein, the effect of introducing a cobalt promoter into the Zn/HZSM-5 catalyst was investigated to improve catalytic performance. Co-promoted Zn/HZSM-5 was superior to unpromoted Zn/HZSM-5 in terms of both catalytic activity and stability. Additionally, the total yield of benzene, toluene, and xylene over 1CoZn/HZSM-5 was 10.2%, even after 25 h of reaction, compared to the total yield over Zn/HZSM-5 catalyst at less than 1% at the time. XRD, UV-vis, TEM, and H2-TPR demonstrated that Co introduction improved ZnO dispersion in the prepared catalysts. Furthermore, the characterization of the spent catalyst via XRD, TEM, Raman, TGA, and N2 adsorption/desorption proposed that the conversion of graphite coke precursor to carbon nanotube and amor-phous carbon prevented the micropores in the zeolite from being blocked. Thus, a considerable number of Bronsted acid sites in micropore could be preserved, thereby enhancing their catalytic stability. However, excessive Co clusters favored C-C and C-H bond dissociation, primarily producing methane and coke rather than aromatics. Therefore, adding an appropriate amount (1 wt%) of Co to Zn/HZSM-5 improves catalytic performance and the resistance to deactivation.