Validation of the H2 production stage via SER under relevant conditions for the Ca/Cu reforming process practical application

Abstract

The joint performance of a CaO-based sorbent and a Ni-based commercial catalyst has been assessed under relevant conditions for the SER stage in the Ca/Cu H2 production process. These conditions comprise processing CH4 space velocities suitable for the scaling up of the process, operation of the system at pressure, and testing materials that had experienced up to 200 oxidation/reduction cycles. The system, catalyst and CaO-based sorbent, was able to fulfil the SER equilibrium composition up to 2.5kgCH4h−1kgcat−1, CH4 space velocity that would allow the scaling up of the process. In this way, a gas stream containing up to 95% vol. H2 was obtained at 923K, steam to carbon ratios of 3.2 and 4, sorbent to catalyst weight ratios from 4 to 15 and for operation pressures between 1 and 9bar. The effect of oxidation/reduction cycles on catalyst performance was assessed, and the mixture sorbent and aged catalyst was able to process up to 2.5kgCH4h−1kgcat−1, corroborating the operational limit determined for the fresh materials.The total operation pressure (from 1 to 9bar) did not have an important influence on H2 yield, and/or materials performance. Sorbent carbonation reaction rates up to 4.42*10−2kmolh−1kgsorb−1 were determined in the experiments, being this parameter responsible of the limit in CH4 space velocity that can be successfully converted through this sorbent/catalyst system. The experimental results have been successfully described by a pseudo-homogeneous reactor model that incorporates the main kinetic expressions of the reactions involved in the SER stage.