CHARACTERIZATION OF COKE FORMED IN THE CO_2 REFORMING OF METHANE USING FIXED- AND FLUIDIZED-BED REACTORS

摘要

CO_2 reforming of methane was investigated with regards to coke deposit on 4.5 wt% NiO/SiO_2 catalyst at 923 K, 1 atm and CO_2/CH_4=1.0 using microscale fluidized- and fixed-bed reactors, A higher catalytic activity was observed at the initial stage (0.5 h) of the fluidized-bed reforming. The amount of coke formed in a period of 11 h reaction time on stream was very limited. On the other hand, much larger amount of coke was deposited on the spent catalyst from the fixed-bed reactor, particularly the sample from the bottom of bed. By TPO analysis, carbon deposited on the spent sample recovered from fluidized bed and the top of fixed bed was found to contain both amorphous and graphitic forms, while that formed on the bottom sample of fixed bed mainly consisted of graphitic one. In addition, the CO_2 peak originated from graphitic carbon during the TPO experiment was found to shift to higher temperature in the case of the bottom sample. Also, XPS analysis showed that C-O structure was confirmed to form on the bottom catalyst sample.