Fischer-Tropsch synthesis(FTS) is the key step in converting syngas into clean fuels. Traditional supported catalysts for FTS are problematic because the active metal crystalline size is positively related to metal lo...Fischer-Tropsch synthesis(FTS) is the key step in converting syngas into clean fuels. Traditional supported catalysts for FTS are problematic because the active metal crystalline size is positively related to metal loading. Therefore, increasing active metal loading may reduce the cobalt time yield(CTY) since a high CTY is usually obtained when the Co size is 8 nm. Here, a ZIF-67(Zeolitic imidazolate framework-67) with a MOF(Metal organic framework) structure is used as a precursor to prepare the Co@C catalyst with not only high cobalt loading(55.6 wt%) but also with a small cobalt crystal size(as small as 8.6 nm). Coreshell Co@C@SiO2-X catalysts with different SiO2 shell thicknesses were successfully prepared by coating different amounts of TEOS on the outer surface of Co@C to modify product selectivity. Compared with40 wt% Co/SiO2 catalyst, core-shell Co@C@SiO2-X catalysts exhibited improved FTS performance. Furthermore, different gaseous hourly space velocities(GHSVs) were used to obtain CO conversion at similar levels to compare CTY and the turnover frequency(TOF). Among the catalysts, the Co@C@SiO2-1 catalyst, with its better mass transfer ability and suitable hydrophilic property, presented the highest TOF(9.75 × 10-3 s-1) and lowest CH4 selectivity(9.75%). In addition, heavy hydrocarbons were effectively suppressed with the increase in shell thickness due to the increased mass transfer resistance.展开更多
基金financial support from the National Natural Science Foundation of China (21506154)the Program of Introducing Talents of Discipline to Universities (B06006)。
文摘Fischer-Tropsch synthesis(FTS) is the key step in converting syngas into clean fuels. Traditional supported catalysts for FTS are problematic because the active metal crystalline size is positively related to metal loading. Therefore, increasing active metal loading may reduce the cobalt time yield(CTY) since a high CTY is usually obtained when the Co size is 8 nm. Here, a ZIF-67(Zeolitic imidazolate framework-67) with a MOF(Metal organic framework) structure is used as a precursor to prepare the Co@C catalyst with not only high cobalt loading(55.6 wt%) but also with a small cobalt crystal size(as small as 8.6 nm). Coreshell Co@C@SiO2-X catalysts with different SiO2 shell thicknesses were successfully prepared by coating different amounts of TEOS on the outer surface of Co@C to modify product selectivity. Compared with40 wt% Co/SiO2 catalyst, core-shell Co@C@SiO2-X catalysts exhibited improved FTS performance. Furthermore, different gaseous hourly space velocities(GHSVs) were used to obtain CO conversion at similar levels to compare CTY and the turnover frequency(TOF). Among the catalysts, the Co@C@SiO2-1 catalyst, with its better mass transfer ability and suitable hydrophilic property, presented the highest TOF(9.75 × 10-3 s-1) and lowest CH4 selectivity(9.75%). In addition, heavy hydrocarbons were effectively suppressed with the increase in shell thickness due to the increased mass transfer resistance.
