Evaluation of a tubular nano-composite ceramic membrane for hydrogen separation in methane steam reforming reaction

Abstract

Tubular silica/alumina membranes with three different thicknesses of selective layer (75–100 nm) were successfully applied as membrane reactors for simultaneous production and purification of hydrogen. BET analysis indicated a decreasing trend in membrane characteristics by adding successive layers, which is well in agreement with the graded structure of the substrate. These membranes showed a high permeance of 5–11 × 10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹ and good separation factor of 20–300 at various temperatures (773–1073 K) in an equimolar mixture of H₂, CH₄, CO, and CO₂. The reactor performance of the membranes was evaluated for the methane steam reforming (MSR) reaction – using a conventional nickel/alumina catalyst with 10 wt% of nickel on the alumina support – in the reaction temperature range of 773–1073 K and pressure range of 1–10 bar. X-ray diffraction measurements of the catalyst showed a good dispersion of nickel on the alumina substrate. The reactor results showed an increasing trend for H₂ yield between 3.8–30 × 10⁻⁶ mol g⁻¹ with both increasing temperature and pressure, but CH₄ conversion decreased about 30% with increasing pressure from 1 to 10 bar. These results also indicate higher values of hydrogen yield and methane conversion in comparison to the equilibrium conditions for all membranes even up to 35% by increasing either temperature or pressure.