Rapid catalytic reforming of methane with CO2 and its application to other reactions

First, indispensable requisites of the catalytic technologies for moderating the CO2 problems are enumerated. Among various conditions, high conversion rates to treat a huge amount of the feed and high tolerance against coke deposit are most important. In spite of many advantages, CO2 reforming of methane has the following general problem. Different from steam reforming, the deposited coke due to the disproportionation reaction of CO and the cracking of methane in CO2 reforming cannot be volatilized by the reaction with steam. Based on the mechanisms of the coke formation mentioned above, a number of methods to reduce or prevent the coke deposit have been tried by many researchers. Many of them compared the results by using different kinds of catalyst components and their supports. Taking into account the catalytic performance and cost of catalyst materials, nickel supported on alkaline earth oxides and rare earth oxides, especially magnesia, were studied extensively. Sufficient stability to magnesia supported catalysts was observed; however, the conversion rate is still not high enough. Steam-CO2 co-reforming and other approaches involving membrane reactors were also investigated; however, these results were basically affected by the intrinsic performance of the catalysts used and limit of diffusion in the case of the membrane. Another essential approach has been done by the author and coworkers. A nickel-based four-component composite catalyst was designed for high promotion of hydrogen spillover during the reaction progressing with high rates. Plenty of hydrogen on the catalyst surface prevented coke deposition and achieved an extraordinarily high reaction rate and high tolerance due to nocovering of coke on the active catalytic sites. The large endothermic reaction heat of CO2 reforming of methane could be compensated by simultaneous combination of catalytic combustion of a low concentration of easily combustible hydrocarbons. In this plenary lecture, almost all the studies on CO2 reforming done in the recent decade were surveyed and summarized in the light of the above requisites to contribute to the further improvement in the catalysts and their reaction processes of CO2 reforming of methane and/or natural gas. Copyright (C) 2001 John Wiley & Sons, Ltd.