Novel thermal-swing sorption-enhanced reaction process concept for hydrogen production by low-atemperature steam-methane reforming

Hydrogen production by steam reforming of natural gas is a well-established technology. The possibility of using hydrogen, a nonpolluting fuel, in fuel cells has brought new interest in developing small, efficient, fuel-cell grade hydrogen production units for residential or industrial use. A novel, step-out, low-temperature, steam-methane reforming (SMR) process concept called "thermal-swing sorption-enhanced reaction" (TSSER) is described. The concept simultaneously carries out the SMR reactions at 490-590 °C and removes the byproduct CO ₂ from the reaction zone in a single unit operation, thereby (a) circumventing the thermodynamic limitations of the SMR reactions and (b) directly producing a fuel-cell grade H ₂ product with very high CH ₄-to-H ₂ conversion. A K ₂CO ₃ promoted hydrotalcite is used as the CO ₂ selective chemisorbent in the reactor, which is periodically regenerated by steam purge at 590 °C. Model simulations of the TSSER process using recently measured CO ₂ chemisorption characteristics of the promoted hydrotalcite indicate that a very compact H ₂ generation unit can be designed that requires relatively low amounts of steam for regeneration. New CO ₂ desorption data from the chemisorbent and its thermal stability are reported.