Study of the main reactions involved in reforming of exhaust gas recirculation (REGR) in gasoline engines

In a previous paper, it was demonstrated that a 1 wt% Rh catalyst supported on modified ZrO(2) exhibits a high activity and stability in REGR conditions. The purpose of the present study was to investigate the main reactions involved in REGR conditions in the presence of this catalyst, namely steam reforming (SR), dry reforming (DR), and the reactions producing methane, i.e. methanation, decomposition and hydrogenolysis. Isooctane (C(8)H(18)) was used as a molecule representative of gasoline, and a mixture of N(2), H(2)O, CO(2) and O(2) as model exhaust gas. A reaction scheme was proposed for REGR conditions. Based on the study of individual reactions (SR, DR and methane formation) at 450 degrees C, 520 degrees C and 580 degrees C, the complex system can be described following three consecutive steps: reforming reactions, yielding H(2) and CO(2) as primary products; reverse water gas shift (RWGS), yielding CO as secondary product; and finally methanation reactions, specially with CO, yielding CH(4) as tertiary product.