Sorption-enhanced chemical looping steam reforming of glycerol with CO2 in-situ capture and utilization

Hydrogen production from chemical looping steam reforming using an oxygen transport catalyst is definitely enhanced by CO2 in-situ capture, which shifts the chemical equilibrium and reduces the energy demands. The utilization of CO2 from this process as a reactant for chemicals and fuels could help to improve economic reasons and mitigate its impact on climate. In this study, we proposed a sorption-enhanced chemical looping steam reforming of glycerol to realize the synergetic capture and conversion of CO2 in one integrated chemical looping hydrogen production process. The process is characterized to use the oxidized NiO/NiAl2O4 as a steam reforming catalyst, the reduced NiO/NiAl2O4 as a CO2-CH4 dry reforming catalyst, and the inexpensive dolomite as a CO2 sorbent. The surface carbon that would deactivate the catalyst is combusted by air after CO2-CH4 dry reforming and the Ni on the catalyst is re-oxidized. The coupling of these different processes of chemical looping steam reforming, CO2 in-situ capture, dolomite decomposition and CO2 in-situ utilization, results in simultaneous generation of high purity hydrogen and syngas. The results demonstrated that hydrogen of above 92.5% was one-step generated and CO2 was decreased to zero in the pre-CO2 breakthrough periods. The reduced NiO/NiAl2O4 catalysts favored the CO2-CH4 dry reforming at 850 °C. The syngas of H2-to-CO molar ratios of 0.8–1.1 through the conversion of CO2 from in-situ extraction of the absorbed CO2 dolomite, was produced. The NiO/Al2O4 with 15 wt% NiO gave the highest hydrogen and syngas yields, and maintained high performance for the proposed system. The catalysts and dolomite exhibited good stability with no obvious loss of activity in 10 cycles.