Hydrogenation of dibenzyl toluene—A competing side reaction in three phase methanation

Dibenzyl toluene (DBT), known as Liquid Organic Hydrogen Carrier, is also used as liquid phase in three phase CO 2 methanation. This study explores the hydrogenation of dibenzyl toluene as a side reaction during three phase CO 2 methanation for a range of reactor temperature ( T R = 140 °C to 320 °C) and pressure ( p R,abs = 4 bar to 20 bar). Hydrogenation of DBT and CO 2 methanation reaction are competing for hydrogen. Reaction rates of both reactions are high at high reactor pressure. Regarding reactor temperature, CO 2 methanation reaction rate is increasing with increasing temperature, whereas the DBT hydrogenation reaction rate is decreasing. This observation can be attributed to competing CO 2 methanation and catalyst deactivation at elevated reactor temperature. The CO 2 methanation reaction rate is reduced by competing DBT hydrogenation until the chemical equilibrium is reached. Catalyst deactivation is also affecting CO 2 methanation reaction rates for T R > 260 °C. • Hydrogenation of dibenzyl toluene is competing for H2 in three phase methanation. • Hydrogenation reaction rate of DBT decreases with increasing reactor temperature. • At high temperature methanation & catalyst deactivation limit DBT hydrogenation rate. • Hydrogenation reduces methanation reaction rate until chemical equilibrium is reached.