Cobalt catalysts are widely studied to produce fuel-grade long chain hydrocarbons through the Fischer-Tropsch synthesis (FTS). In this work, mesoporous titanosilicate supports were synthesized using a surfactant-free process and impregnated with cobalt (15 wt.%) using incipient wetness impregnation. The catalysts were promoted with 1 mol.% noble metal (Ag, Pt, Ru) and different concentrations of Mn (5, 10, 20 mol.%). The dispersion of cobalt increased from 4.9 % to 6.6-7.1 % with the addition of promoters. The reduction behavior of the catalysts were studied using TPR and XANES. The addition of Ag and Mn decreased the temperature required to reduce the catalyst by 34 °C (Figure). The extent of reduction between the different catalysts at 400 °C was comparable among all the tested catalysts. The FTS activity of the catalysts were studied in a fixed-bed reactor at 220 °C, 250 psi, 2000 h-1 and H2/CO = 2. The addition of noble metal promoters increased the CO conversion by 5-11 % while also increasing the CH4 (~3) and CO2 (~7.5%) selectivities. Furthermore, the Pt-promoted catalysts underwent deactivation at a rate of 0.07 %/h compared to 0.03 %/h for Ag-promoted catalyst. The addition of Mn increased the C5+ selectivity by ~5 % while reducing CH4 selectivity by ~6.2 %. The addition of both Ag and Mn to the catalyst had a synergistic effect on the catalyst performance. The catalyst with composition Co:Mn:Ag = 100:10:1 possessed both the lowest deactivation rate and highest C5+ selectivity. The reaction parameters (temperature, pressure, GHSV) of this catalyst were optimized using Box-Behnken method. The optimal reaction conditions were found to be 219 °C, 300 psi and 1800 h-1. The time-on-stream activity of the catalyst was tested for 400 h under these reaction conditions. The catalyst showed a starting CO conversion of 87 % with a deactivation rate of 0.02 °C/h. The catalyst was regenerated at 500 °C under flowing air and showed a CO conversion of 85.6 %.

Effects of noble metal (Ag, Pt and Ru) and Mn promoters on the reducibility, Fischer-Tropsch activity and selectivity of mesoporous titanosilicate-supported cobalt catalyst

ACS Spring Meeting 2021

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