Direct conversion of CO2 to long-chain hydrocarbon fuels over K–promoted CoCu/TiO2 catalysts

A series of TiO2 supported Co–Cu catalysts with the weight percent of potassium oxides ranged from 0 to 3.5 wt.% were synthesized. This work investigates the influence of potassium promoter on CO2 hydrogenation to long-chain (C5+) hydrocarbons. The introduction of suitable amount of K into the CoCu/TiO2 catalyst remarkably promoted the formation of C5+ hydrocarbons and suppressed methane formation. The temperature-program desorption measurements demonstrate that the addition of K increases the chemisorption of CO2, whereas H2 adsorption is decreased, which enhanced production of liquid fuels. However, these effects were not obvious with the addition of excess amount of K due to the slight change of surface K content. A maximum C5+ yield with CO2 conversion of 13% and C5+ selectivity of 35.1 C-mol% is obtained over the CoCu/TiO2 catalyst with 2.5 wt.% of potassium promoter loading, which also exhibits a substantial stability.