High-performance of CrOx/HZSM-5 catalyst on non-oxidative dehydrogenation of C2H6 to C2H4: Effect of supporting materials and associated mechanism

Abstract

Ethane (C2H6) is an important inexpensive and widely available fuel resource. High-value use of C2H6 has become increasingly important. Catalytic dehydrogenation of C2H6 to ethylene (C2H4) has attracted much attention in recent years due to its high energy efficiency. The direct non-oxidative ethane dehydrogenation (EDH) to ethylene is a promising strategy to produce ethylene and hydrogen at the same time. In this research, Cr/HZSM-5 catalyst with superior stability was synthesized and exhibited an C2H6 converting activity of 1.47 μmol/(g·s) with the corresponding C2H6 conversion and C2H4 selectivity of 37.3% and 90%, respectively. The synergistic effects of Si and Al in supporting materials were investigated by comparing Cr/HZSM-5 with SBA-15, SiO2 and Al2O3 supported ones, which contains either Al or Si with different structures. Characterization results indicated that the intimate interactions between Cr and support significantly improved the catalytic performance. The presence of Al in the support promoted the formation of more active Cr6+ species by forming the aluminum‑chromium-chromate (Cr-O-Al) structures which were more efficient to active C-H bond and form (Cr, Al)-OH groups during the reaction. Meanwhile, the formation of internal silanol group with the dissociative adsorbed H* could stabilized the active Cr phase to achieve a stable dehydrogenation activity.