Effect of pressure on the carbon deposition route in CO2 reforming of 13CH4

In production of synthesis gas (syngas) from natural gas, carbon deposition is the major cause of catalyst deactivation, specifically on Ni-based catalysts. Because the rate of carbon formation is greater than the rate of carbon gasification, carbon accumulates in the catalyst bed. In order to better understand the carbon deposition process at high pressure during dry reforming, we have tested a series of noble metal and Ni-based catalysts at pressures of one, and 14 bar using 13C-labeled methane. The source of the carbon deposition during the reactions was then studied using temperature-programmed oxidation (TPO). The results indicated that the source of carbon is different for the reactions conducted at low pressure compared to those performed at higher pressure over noble metal catalysts. At high pressure a significant amount of carbon formed on the catalysts and both methane and carbon dioxide equally contributed to carbon deposition. However, at low pressure the amounts of carbon formed on these catalysts were insignificant and came predominantly from 12CO2. It was also found that at high pressure the total amount of carbon was higher regardless of catalyst type or composition.