B. S. LIU, Department of Chemistry, Tianjin University Tianjin 300072, P.R. China and Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong; J. W-H. LEUNG, LING LI AND A. S-C. CHEUNG, Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong; C. T. AU, Department of Chemistry and Center for Surface Analysis and Research, Hong Kong Baptist University, Kowloon Tong, Hong Kong.
The catalytic reaction of CO2 reforming of CH4 produces synthesis gas (CO and H2), which is useful as a feedstock for many industrial processes. In the past few years, many transition metal-based catalysts have been investigated but the major problems reported were catalytic deactivation due to carbon deposition and low yield. We studied the CH4/CO2 reforming over La2NiO4 and 10%NiO/CeO2-La2O3 catalysts under the condition of supersonic jet expansion via direct monitoring of the change in reactants (CH4 and CO2), product (CO) and side-product (H2O) using the sensitive technique of cavity ring-down spectroscopy. Vibration-rotational absorption lines of CH4, H2O, CO2 and CO molecules were recorded in the near infrared spectral region. We found that La2NiO4 is superior to 10%NiO/CeO2-La2O3 in performance. We have also investigated the associated reverse water-gas shift (RWGS) reaction, which affects significantly the H2/CO product ratio, over the catalysts during CH4/CO2 reforming. Our results indicated that the RWGS reaction promoted the conversion of CO2 and decreased the partial pressure of hydrogen. By proper adjustment of the pressure of the reaction system, it is possible to suppress the occurrence of RWGS reaction and increase the selectivity of CH4/CO2 reforming.