Fuel Gas Upgrading Over La1−xCexCoO3 Mixed Oxide with Toluene as Model Compound

Abstract

Perovskite-type mixed oxides La1−xCexCoO3 (x = 0, 0.2, 0.4) were synthesized by sol–gel method via polyvinyl alcohol (PVA) as gelating agent. LaCoO3 and CeO2 phases were presented while intermediate phase, La(OH)3, disappeared during LaCoO3 transformation. Introduction of Ce decreased crystal size of catalyst from 22.18 to 13.38 nm. Particle size and specific surface area were in the range of 9.58–13.72 μm and 6.03–9.23 m2/g, respectively. The addition of Ce increased the reduction temperature which indicated the strong interaction between Co and perovskite structure. Catalytic activity was investigated by steam reforming of toluene at 500–800 °C. Conversions of carbon and hydrogen to CO, H2, and CH4 at steam per carbon ratio (S/C) of 2:1 were clearly higher than 4:1. Increasing S/C ratio to 4:1 inhibited syngas production efficiency by combustion and water–gas shift reaction. The presence of Ce in the catalyst did not improve activity of catalyst significantly. However the metal enhanced stability by promoting the formation of filamentous carbon on the surface such that the active sites are still accessible to the active gas during the experiment. After reforming, catalysts were transformed to La(OH)3, Co0, and Ce4O7 phases and no significant deterioration in catalytic performance was detected after 6 h. In this study steam reforming of toluene over La0.6Ce0.4CoO3 at 800 °C with S/C 2:1 yielded highest carbon conversion as CO and hydrogen conversion as H2 of 64.42 and 63.23 %. The LHV and H2/CO of produced gas at this optimum condition are 4.22 MJ/N m2 and 2.91, respectively.