Incorporating mesoporosity into zeolite catalysts has been regarded as an innovative technology that improves diffusivity and catalytic lifetime. Here, we propose a facile synthesis of the hierarchically structured ZSM-5 with accompanying intracrystalline mesopores, which was achieved by controlling the growth rate of the zeolite nanocrystals without using extra additives. As the crystallization temperature is strongly related to the formation of primary nanocrystals and their further growth, which fills gaps between those nanocrystals, the hierarchically structured ZSM-5 zeolite was synthesized at low crystallization temperatures (<140 °C). 27 Al MAS NMR and UV-vis-DRS analyses revealed that the hierarchically structured ZSM-5 prepared in the present study contained Al located in the straight channel at a higher proportion than the conventional microporous ZSM-5. The substitution of Al was calculated to be more difficult at the channel intersection than at other T-sites, supporting the experimental results. The hierarchically structured ZSM-5 exhibited excellent stability as well as selectivity for a methanol-to-olefin reaction. Reaction free energies calculated along the hydrocarbon pool mechanism pathway revealed that the Al located in the straight channel drives the reaction through the alkene-based cycle, which is responsible for the high olefin selectivity of the hierarchically structured ZSM-5.
Our zirconium phosphate (ZrP)‐promoted Ru/Co/ZrP/SiO2 catalyst reveals a high catalytic activity and stability during Fischer–Tropsch synthesis. Surface modification with ZrP on SiO2 support with an appropriate amount of phosphorous component prevents cobalt particle aggregation and enhances its stability. These positive effects of ZrP are mainly induced by the spatial confinement of cobalt particles in a thermally stable ZrP matrix, and the catalytic performance was greatly improved when the P/(Zr+P) molar ratio was 0.134 on the CoZrP(0.5) catalyst.
Ap hosphorous-modified Al 2 O 3 support was prepared by the impregnation methoda nd applied for the preparation of cobalt-based Fischer-Tropsch synthesis (FTS) catalysts (Co/P-Al 2 O 3 ), which were calcined at different temperatures. The Co/ P-Al 2 O 3 showed as ignificant increaseo ft hermals tability with ah igher catalytic performance without severe deactivation even above ac alcination temperature of 600 8Cc ompared with the unmodified Co/Al 2 O 3 .T hese findings are explained by the suppressed cobalt aluminate formation and less pronounced aggregation of cobaltp articles. The suppressed aggregation of cobalt particles is attributed to the localized presence of aluminump hosphate by forming at hermally stable metal-phosphorous oxo-species on Al 2 O 3 surfaces thus suppressing the migration of cobalt particles to the outer pore mouths of the support. These effects significantly enhance the catalytic activity with ah igher thermal stabilityo ft he catalysts.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.