Characterization of deposited coke on Ni/SiO[subscript 2].MgO catalyst from carbon dioxide reforming of methane under periodic operation

Abstract

In this work, the detailed study on the coke formation taking place in the periodic operation of the carbon dioxide reforming of methane on a commercial Ni/SiO[subscript 2].MgO catalyst was investigated by using various analytical methods including BET surface area measurement, SEM, XRD, and TPO in order to characterize the coke formed at reaction temperature range of 650-750 degrees Celsius and various reaction times. It was found that at least two different cokes were formed on the surface of catalyst at this temperature range. At low temperature, conversions of methane and carbon dioxide and yield of hydrogen were almost constant throughout reaction time. Coke was formed during the methane cracking period but was incompletely removed in the regeneration period. At this temperature, coke was mostly formed in filamentous form. In contrast, at high temperature, conversions of methane and carbon dioxide and yield of hydrogen decreased continuously with increasing reaction time. A lesser amount of coke was obtained but it was formed in encapsulating form. Thus, it affected the activity of catalyst.