Hydrogen production from sorption enhanced steam reforming of biogas via nickel over modified CaO sorbent

Abstract

This research composed of two parts: (i) CO2 sorption study and (ii) hydrogen production performance tests using multifunctional catalysts. In the CO2 sorption section, the first group of metals (Mg2+, Sr2+ and Al3+) was loaded on CaO and tested the CO2 sorption and desorption performance over 10 cycles. Mg-CaO-HW offered the best stability in terms of CO2 sorption/desorption. Whereas Al-CaO-HW and Sr-CaO-HW exhibited a decrease in CO2 sorption capacity corresponding to 6 and 12% reduction. The second group of metals loading on CaO were Zr4+, Ce4+ and La3+. The results indicated that Zr-CaO-HW and Ce-CaO-HW possessed stable CO2 capacities over the 10 cycles. On the other hand, La-CaO-HW showed a decrease in the CO2 sorption capacity of 16%. This was due to the low-temperature oxygen storage properties of Zr-CaO-HW and Ce-CaO-HW, which enhanced the mobility of oxygen. In the section of H2 production, three sequences of Ni2+ loading on modified CaO were investigated. The results showed that Ni-Al-CaO-HW is the best multifunctional catalyst. The stability of Ni-Al-CaO-HW shows that CH4 conversion is still higher than 90% during the pre-breakthrough period for 5 cycle operations. Furthermore, Ni2+ was loaded on the modified sorbents Zr-CaO-HW, Ce-CaO-HW and La-CaO-HW. The results showed that Ni-Zr-CaO-HW and Ni-Ce-CaO-HW produced H2 at stable purities but with decreasing CH4 conversions. This was attributed to the loss of nickel active sites at the surface of the multifunctional catalysts due to the formation of CaCO3.