HYDROGEN PRODUCTION VIA SORPTION-ENHANCED STEAM METHANE REFORMING USING HYBRID CATALYTIC ADSORBENT

Abstract

Synthesis of hybrid catalytic CaO-based alumina sorbent has been investigated to use for H2 production via sorption enhanced steam methane reforming. Calcium D-gluconic acid, (C12H22CaO14) and Calcium nitrate tetrahydrate (Ca(NO3)2.4H2O) were selected to study the effect of calcium precursor on CaO properties. Calcium-based sorbent derived from calcium d-gluconic acid (CG-AN) shows higher CO2 sorption capacity (0.387g CO2/g sorbent) than calcium-based sorbent derived from calcium nitrate (0.172g CO2/g sorbent) at 600˚C and atmospheric pressure under 15%v/v CO2. Adding surfactant was further applied to improve capacity of sorbent. The results show 3 mM of Hexadecyltrimethylammonium bromide (CTAB) can improve CO2 sorption capacity of CG-AN as CO2 sorption capacity can be improved to 0.45 g CO2/g sorbent whereas addition of surfactant cannot improve CO2 sorption capacity for CN-AN. In addition, stability of both sorbents were tested for 10 cycles and the results show that CG-AN-CTAB 3 mM provides higher CO2 sorption capacity than CN-AN-CTAB 3mM at all cycles; sorption capacity of CG-AN-CTAB 3 mM is reduced 36.8% from the 1st cycle to the 10th cycle and that of CN-AN-CTAB 3 mM is reduced 30.9% from the 1st cycle to the 10th cycle. When modified calcium-based sorbent was used in SESMR process at 600˚C, S/C=3 and atmospheric pressure, 12.5%Ni-CG-AN-CTAB 3mM prepared by wet mixing shows 91.2% H2 purity for 45 minutes and 83%CH4 conversion, which was higher than those of 12.5%Ni-CG-AN without CTAB of 88.7% H2 purity for 45 minutes and 79.4% CH4. In addition, it was observed from our studies that method to synthesize hybrid catalytic sorbent has an effect on H2 production. By preparing 12.5%Ni-CG-AN using sol-mixing can improved CH4 conversion to 82.3% and H2 purity to 94% for 30 minutes.