Effect of water on the secondary transformations of hydrocarbons in the Fischer–Tropsch synthesis on Co-zeolite catalysts

Recent Advances in Bifunctional Catalysts for the Fischer–Tropsch Process: One-Stage Production of Liquid Hydrocarbons from Syngas

“…131,133 For the FT process, Co particle sizes below the critical range (6−10 nm) promote an increase in CH 4 selectivity and a decrease in C 5+ . 108 However, in some cases, such as those reported by Hao et al, 116 the catalyst with the best performance was that with the largest crystallite size, approximately 27 nm, where the structure of the support, MSI, and reducibility seem to exert the greatest influence. Metal particle and mesopore sizes are important factors in the activity and selectivity of the hydrogenolysis reaction, which has been shown to affect the FT process.…”

“…The most commonly used zeolite is ZSM-5 in its protonated form, since it has strong Brønsted acidity, although other zeolites with lower Brønsted acidity (e.g., type Y zeolites) have also shown liquid hydrocarbon selectivity, especially when mesoporosity is introduced. 108 Zeolites in H-form are hydrophobic, whereas zeolites in cation form are hydrophilic. 109 Isomerization and alkylation reactions can be carried out on H-zeolite acid sites to produce branched paraffins and olefins.…”

“…An increased mesopore size accelerates mass transfer and suppresses successive demethylation, enabling the control of long-chain hydrocarbon overcracking. 108 Table 3 provides a summary of the most recent works using zeolites as supports for bifunctional catalysts in the FT process. The most commonly used metal for bifunctional catalysts is Co, followed by Fe and, to a lesser extent, metals such as Ru and Mo.…”

“…Metal particle and mesopore sizes are important factors in the activity and selectivity of the hydrogenolysis reaction, which has been shown to affect the FT process. 81,108 Kang et al 81 proposed that selectivity for hydrocarbons in the diesel range can benefit from selective hydrogenolysis, which is favored by a narrower Co size distribution with a lower fraction of smaller Co particles (<5 nm).…”

“…In terms of acidity, the Brønsted acid site has been identified as the active site responsible for hydrocracking and isomerization reactions; 40,50,108,109,112,115,142,143 branched product selectivity increases with the increase in the Brønsted acid site strength of zeolite catalysts. 131,144 Nonetheless, results have shown that a balanced amount is required, 129 since a disproportionate concentration of strong Brønsted acid sites hinders the production of hydrocarbons in the gasoline range.…”