Investigation On Catalysts And Sorbents Used For Sorption-Enhanced Steam Methane Reforming

Ni/MgAl catalysts and CaO-based sorbents were prepared by a co-precipitation method and a wet mixing method, respecitively. The former were test in the reaction of steam methane reforming, while the latter in CO2 sorption. The screened high-performance catalyst and sorbent were finally applied to sorption-enhanced steam methane reforming (SE-SMR). Investigations on the Ni/MgAl catalysts showed that, compared to conventional Ni/γ-Al2O3 and Ni/α-Al2O3, the Ni/MgAl catalysts prepared in this work exhibited much higher actictivies in steam methane reforming, owing to higher specific surface area and Ni metal dispersion. Among all the Ni/MgAl catalysts, the Ni0.5/Mg2.5Al catalyst with a Ni/Mg/Al atomic ratio of 0.5/2.5/1 showed the highest acitivity, and thus it was used for the kinetic study. Kinetic experiments were conducted at 1 atm and 550～700℃in a regime free of external and internal diffusion limitations. The results showed that the total conversion of CH4 and the conversion of CH4 to CO2 were greatly influenced by temperature, residence time and the molar ratio of H2O to CH4. A Langmuir-Hinshelwood-type kinetic model was found to describe the experimental data very well, and the estimated adsorption parameters showed thermodynamic consistency. Investigations on CaO-based sorbents showed that, compared to pure CaO sorbent, the 0.80CCAL sorbent, which was obtained from calcium citrate and aluminum nitrate, exhibited much higher CO2 capture capacity and excellent multiple carbonation-calcination stability. The reason is the relatively high specific surface area and the isolation effect of the inert Ca9Al6O18 that prevented CaO particles from sintering at high temperature. Finally, Investigations on SE-SMR showed that, compared to Ni0.5/Mg2.5Al and CaO, Ni0.5/Mg2.5Al and 0.80CCAL, which were placed in a fixed-bed reactor for SE-SMR, exhibited the exellent hydrogen-production efficiency. The results obtained in this work are expected to be interesting and useful for future researches on the SE-SMR process.