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

Abstract

In a previous paper, it was demonstrated that a 1 wt% Rh catalyst supported on modified ZrO₂ 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 (C₈H₁₈) was used as a molecule representative of gasoline, and a mixture of N₂, H₂O, CO₂ and O₂ 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 °C, 520 °C and 580 °C, the complex system can be described following three consecutive steps: reforming reactions, yielding H₂ and CO₂ as primary products; reverse water gas shift (RWGS), yielding CO as secondary product; and finally methanation reactions, specially with CO, yielding CH₄ as tertiary product.