Characterisation of carbon deposits on Ni/SiO2 in the reforming of CH4-CO2 using fixed- and fluidised-bed reactors

CO2 reforming of methane was investigated with regard to carbon deposition on 4.5 wt% NiO/SiO2 catalyst at 1023 K, 1 atm and a CH4/CO2 ratio of 1.0 employing micro-fluidised- and fixed-bed reactors. A higher catalytic activity (by 20%) was observed in the initial stage (0.5 h) of the fluidised-bed reforming which may be attributed to lesser deactivation of the catalyst compared to fixed-bed operation. Only a limited amount of carbon was deposited in a period of 11 h on stream. In the case of the fixed-bed reactor, a much larger amount of carbon was found on the spent catalyst, particularly, when sampled from the bottom of the bed. TPO results suggest that carbon deposits on the catalyst samples from the fluidised-bed as well as the top of the fixed-bed are rather small and of similar nature. The carbon deposited at the bottom of the fixed-bed reactor contained two distinct species according to XPS results (corresponding to C-O and C-C bonds). (C) 2003 Elsevier Science B.V. All rights reserved.