Adsorption of Reformer Off-Gas on Nax Zeolite and Metal Organic Framework (mil53(ai)): Equilibria and Kinetics

Abstract

Synthetic gas produced from steam methane reforming (SMR off -gas) is a mixture of H2, CO, CO2, and CH4 can be used in fuel cell after purification. In this study adsorption as a purification tool was used to obtain high H2 content of gas mixture from SMR off gas. Zeolites and metal organic framework were used as an adsorbent. CO2 equilibrium studies on K rich NaX zeolites, prepared with ultrasonic and traditional methods, and metal organic framework MIL53 (Al) shows high adsorption on zeolites than MIL53(Al) up to 1 atm. K rich zeolites give lower adsorption than NaX zeolite. Adsorption isotherms obtained for MIL53 (Al) is linear ( favorable for zeolites). This makes MIL53(Al) is an promising adsorbent for high pressure application. Adsorption equilibrium at 5 atm shows that NaX zeolite is good adsorbent for the SMR off gas with the following orders: CO2>CH4>CO> H2. Kinetics of SMR off gas in MIL 53 (Al) were studied by using Zero Length Column (ZLC) method. The results show that the calculated diffusivities are strongly dependent on temperature but weakly dependent on purge flow rate. The study reveals that transport is controlled by intracrystalline diffusion. The activation energy on diffusion are nearly same (about 41 kJ/mol) and not change with respect to kinetic diameter of SMR off gases. Heat of SMR off gas adsorption on MIL53(Al) obtained from Henry’s constant shows that adsorption is exothermic. The study shows that the ZLC method is an effective tool to investigate the diffusion kinetics of SMR off-gas gases in MIL53(Al).