Enhanced ammonia decomposition in a structured membrane reactor using a Ru-coated SiC open-cell foam and a Pd-based membrane

Ammonia decomposition into nitrogen and hydrogen was carried in a structured membrane reactor in this work. The performance of the structured catalyst and the effect of hydrogen permeation through a Pd-based membrane were evaluated. The structured catalyst is based on a commercial silicon carbide open cell foam (40 PPI). The catalyst (3 wt% Ru/CeO₂) was coated by in situ-solution combustion deposition method with sequential cycles to reach the desired catalyst loading (0.31 g cm⁻³). TEM, SEM, XRD, TPR analysis and adhesion tests were used to characterize the prepared sample. A double-skinned Pd-based membrane has been prepared depositing a selective layer by electroless plating onto porous asymmetric α-Al₂O₃ support. The results proved a successful integration of structured catalyst and membrane. The beneficial effects of the proposed structured membrane reactor configuration enabled an increase in conversion up to 29 % compared with the structured catalyst system. The reaction system allowed an ammonia conversion of 98.4 % and hydrogen purity of 99.2 % at 450 °C and 4 bar. Furthermore, at fixed flow rate, the structured membrane reactor can achieve comparable conversion at operating temperatures about 55 °C lower than in the case of the structured reactor. Moreover, the proposed configuration enabled a conversion higher than the thermodynamic value at 4 and 5.5 bar at fixed temperature (480 °C) and fixed feed flow rate (62 ml min⁻¹). To the best of our knowledge, this work is the first study combining a structured catalyst and a Pd-based membrane for ammonia decomposition.