The investigation into the different Co species over Silicalite-1 via modulating heat-treatment atmosphere for propane dehydrogenation

Abstract

Co-based catalysts have attracted much attention for propane dehydrogenation (PDH) because of their low price, environmental friendliness, and high activity, while the synthesis of anti-reduction Co species to suppress cracking side reactions to realize high-performance PDH is critical. In this work, different Co species over Silicalite-1 are synthesized via modulating heat-treatment atmosphere and investigated for PDH systematically. In comparison with O2-included calcination catalyst, the TOF of Co-S-1-Ar (41.9 h−1) for PDH is about nine times that of Co/S-1-Air (4.6 h−1). According to the combined characterizations, it is confirmed that the highly dispersed tetrahedral coordinated Co2+ species incorporated into Silicalite-1 framework with Lewis acid sites over Co-S-1-Ar is responsible for the superior PDH performance, while bulk aggregated Co3O4 species in Co/S-1-Air has much lower catalytic performance. Through in-situ FT-IR characterization, it is revealed that Co2+ species over Co-S-1-Ar is incorporated into Silicalite-1 framework via replacing the silanol nests of Silicalite-1, in which the Co precursors are driven by Ar to reach the silanol nests highly dispersed and then further anchored by silanol nests and incorporated Silicalie-1 framework with Co2+ species under high temperature calcination, and the other oxygen-free calcination atmosphere, such as H2 and vacuum, are also intensified to be practicable.