Kinetic modeling of sorption-enhanced methane steam reforming in a PdAg membrane reactor for sustainable H2 production

CO 2 sorption-desorption kinetics fitting of Li 4 SiO 4 particles using power-law model • Validated model integrating Pd Ag membrane, CO 2 sorption, and SMR reaction kinetics • Achieved >99% CH 4 conversion and high-purity of H 2 /CO 2 via dual-separation synergy • Net solar-to-H 2 efficiency is enhanced to 35.2% via dual-separation solar reforming • Understood the enhanced CH 4 conversion mechanism in dual-product separation system Solar thermochemical hydrogen production is a promising approach for solar energy utilization and storage. Conventional steam methane reforming remains the dominant industrial H 2 production route, but its feasibility for producing low-carbon-footprint H 2 is constrained by high-temperature (>950 °C), high energy penalties associated with product separation, and high CO 2 emissions. Here, we propose a method of integrating mid-temperature (450–600 °C) concentrated solar energy-driven steam methane reforming with Pd Ag membrane for H 2 separation and Li 4 SiO 4 sorbent for in-situ CO 2 capture. Isothermal sorption-desorption experiments were carried out on synthesized K-doped Li 4 SiO 4 particles under varying temperatures and CO 2 concentrations, with the kinetics fitted by a power-law model. Moreover, a one-dimensional transient model of sorption-enhanced Pd Ag membrane reactor was validated by the fixed-bed experimental platform with a relative error of less than 2%. Systematic research based on multiphysics modeling demonstrates that the ordered conversion and synergy of H 2 and CO 2 can achieve multiple objectives of high conversion rates, significant temperature reduction, acquisition of high-purity H 2 , and decarbonization. The Pd Ag membrane and alternating Ni-catalyst/Li 4 SiO 4 sorbent maintain low H 2 /CO 2 partial pressures, driving the equilibrium toward near-complete methane conversion. Numerical results demonstrate that this method enables nearly complete conversion of CH 4 at a flow rate of 360 mL/min with simultaneous separation of high-purity H 2 at a significantly reduced temperature of 500 °C. The first-law thermodynamic, net solar-to-H 2 , and exergy efficiencies are enhanced to 70.9%, 35.2%, and 64.8%, respectively. The methane saving rate and CO 2 reduction rate are 14.4 and 39.5 g/h, respectively. Mid-temperature (450–600 °C) concentrated solar energy-driven steam methane reforming with Pd Ag membrane for H 2 separation and Li 4 SiO 4 sorbent for CO 2 in-situ capture. Download: Download high-res image (193KB) Download: Download full-size image