Abstract
The study evaluates the effect of forced periodic cycling between methane dry reforming and carbon regeneration using a gasifying agent, such as carbon dioxide. The activity of Ce-promoted Ni–CO/Al2O3 catalyst was evaluated in a methane dry reforming process using a fixed-bed reactor under steady-state and periodic operation. Forced cycling reactions (reforming and regeneration) were conducted by manipulating the reactor feed between methane dry reforming and catalyst gasification using CO2 at cycle periods of 10, 20, and 30 min, and cycle splits of 0.8, 0.6, and 0.4. The physicochemical properties of fresh and spent catalysts were evaluated using several characterization techniques, such as the BET surface area, H2-chemisorption, and XRD. The results confirmed that methane dry reforming under periodic cycling provides an opportunity to improve methane conversion and increase the catalyst activity and longevity because of the periodic interruption of coke deposition. In particular, methane conversion deteriorated from 68% to 37% under steady-state within five hours of reforming, whereas a modest decrease in methane conversion (from 68% to 63% for a cycle period of 10 min and cycle split 0.8) was observed under periodic operation conditions. The results of catalyst characterization also demonstrated that the on-line removal of carbon during CO2 regeneration did not lead to any structural effect on the catalyst properties, and it absolutely restored the catalyst properties up to the values measured for the fresh catalyst.
•Periodic operation is an effective technique to control carbon formation during methane dry reforming.•Under different operating conditions various types of coke occurred on the surface of catalyst.•Operating the reformer under various periodic parameters resulted in different product rate profiles.