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

Recent Progress in Metal-Molecular Sieve Catalysts for Propane Dehydrogenation

“…Recently, Xu et al reported that atomically dispersed Co δ+ species could be incorporated within the S-1 framework via a ligand-free hydrothermal process. The resulting Co@MFI catalysts possess good MFI crystallinity at Co contents up to 10 wt %, which is much higher than the catalysts from a ligand-assisted synthesis approach (Co content is 1–3 wt %). ,,, The atomically dispersed Co species form a stable -Co δ+ -O δ− structure, which withstands H 2 reduction up to ∼750 °C. The authors indicate that PDH performance largely depends on the oxidation state of the Co δ+ sites.…”

“…159,160 The calcination atmosphere is another important factor to affect the microstructure of active sites. 23,76,96,123 Considering the catalysts typically require H 2 prereduction prior to PDH reaction, the H 2 direct reduction strategy is a promising process compared to conventional air calcination in terms of cost (energy) savings, as well as improving metal dispersion.…”

“…These superficial metal species would easily sinter into large particles during calcination or the PDH reaction, which is unfavorable for catalytic performance. Ren et al 96 reported that the calcination atmosphere would largely impact the Co site structure in Co/ S-1 systems, which impacts the PDH activity. The characterizations show that oxygen-free calcination (Ar, H 2 , vacuum) contributes to the formation of T d Co 2+ species within the S-1 framework.…”

“…The resulting Co@MFI catalysts possess good MFI crystallinity at Co contents up to 10 wt %, which is much higher than the catalysts from a ligandassisted synthesis approach (Co content is 1−3 wt %). 20,21,96,97 2+ and ZnO nanoparticles) may exist after the ion-exchange process, and the different Zn statuses largely depend on the zeolite topologies. In particular, the catalysts with Na-Beta support possess a smaller amount of isolated Zn 2+ sites, which inhibits the aromatization sidereactions and coke deposits compared to other topological counterparts (MFI, MEL, LTL, and FAU).…”

“…23,76,96 ■ Song − State Key Laboratory of Heavy Oil Processing, College of Science, China University of Petroleum, Beijing 102249, China; orcid.org/0000-0001-5720-204X; Email: songwy@cup.edu.cn Jian Liu − State Key Laboratory of Heavy Oil Processing, College of Science, China University of Petroleum, Beijing 102249, China; orcid.org/0000-0003-3392-9812; Email: liujian@cup.edu.cn…”