Novel thermal-swing sorption-enhanced reaction process concept for hydrogen production by low-temperature 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 degrees C and removes the byproduct CO2 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 CH4-to-H-2 conversion. A K2CO3 promoted hydrotalcite is used as the CO2 selective chemisorbent in the reactor, which is periodically regenerated by steam purge at 590 degrees C. Model simulations of the TSSER process using recently measured CO2 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 CO2 desorption data from the chemisorbent and its thermal stability are reported.