Bench scale study of electrochemically promoted catalytic CO2 hydrogenation to renewable fuels

The electropromoted CO2 hydrogenation to renewable fuels was studied over Pt on K-βAl2O3 at bench-scale, under atmospheric pressure and high gas flow rates, with varying H2/CO2 ratios and using gas compositions representative of postcombustion CO2 capture exit streams and easily scalable catalyst-electrode configurations, as an approach towards its potential practical application.Two Pt catalyst films were prepared by different methods resulting in different Pt particle size and dispersion. The catalytic activity for CO2 hydrogenation was promoted, by up to 20 times, by pumping K+ to the Pt surface. CH4 formation was favoured over the catalyst with smaller Pt particle size and was enhanced, by up to 7.6 times, on increasing potential. Higher gas flow rates favoured methanation reaction at the expense of reverse water gas shift reaction. Changing H2/CO2 ratio from 1 to 2 led to a decrease in promotion and to an increase in CO2 conversion and CH4 selectivity. CH3OH and C2H5OH formation was favoured over the less dispersed catalyst and was electrochemically enhanced up to a maximum of 27 and 16 times, respectively. Selectivity to CH3OH is almost unaffected, while CO2 conversion increases and C2H5OH selectivity and promotion levels decrease on increasing H2/CO2 ratio from 3 to 4.

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► Electropromoted CO2 hydrogenation on Pt/K-βAl2O3 under realistic conditions.
► Enhancement on activity and selectivity to renewable fuels by pumping K to Pt.
► CH4 formation favoured at lower Pt size and K contents and at higher gas flow rates.
► Selectivities to CH3OH and C2H5OH exhibit a maximum at a given K coverage.
► Selectivities to CH4 and C2H5OH increased and decreased with H2/CO2 ratio increase.