A novel two-step Ru/Al2O3 catalyst impregnation method for CO selective methanation

CO selective methanation (CO-SMET) is an important method for removing CO from reforming gases. Ru/Al2O3 catalyst prepared by the conventional impregnation method is the most commonly used CO-SMET catalyst and exhibits a spontaneous eggshell-type distribution due to the strong interaction between Ru and Al2O3. The eggshell-type Ru/Al2O3 catalysts exhibited reduced catalytic activity at a high Ru loading due to the agglomeration of Ru at the thin eggshell layer, making it difficult to meet practical CO removal requirements. To address this, four types of acids were individually introduced into the impregnation solutions to weaken the strong interaction between Ru and Al2O3. The prepared catalyst introduced with HNO3 exhibited a near-uniform distribution and relatively high catalytic activity, but low CO selectivity. Subsequently, a two-step impregnation method was proposed to form a unique distribution. The prepared Ru/Al2O3 catalyst with a Ru loading of 1.5% demonstrated an excellent CO-SMET performance by removing CO to below 10 ppm with a wide temperature range of 213 degrees C-257 degrees C, corresponding to CO selectivity ranging from 87.5% to 64.4%.