Novel Thermal-Swing Sorption-Enhanced Reaction Process Concept for Hydrogen Production by Low-Temperature Steam−Methane Reforming

Abstract

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 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 H2 product with very high CH4-to-H2 conversion. A K2CO3 promoted hydrotalcite is used as the CO2 selective chemisorbent in the reactor, which is periodically regenerated by steam purge at 590 °C. Model simulations of the TSSER process using recently measured CO2 chemisorption characteristics of the promoted hydrotalcite indicate that a very compact H2 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.