Catalytic decomposition of NH3 with H-2-selective microporous silica membranes for COx-free hydrogen production was studied theoretically and experimentally. The simulation study shows that NH3 conversion, H-2 yield and H-2 purity increase with the Damkohler number (Da), and their improvement is affected by the effect of H-2 extraction as well as NH3 and N-2 permeation through the membranes. The experimental study of NH3 decomposition was carried out in a bimodal catalytic membrane reactor (BCMR), consisting of a bimodal catalytic support and a H-2-selective silica layer. Catalytic membranes showed H-2 permeances of 6.2-9.8 x 10(-7) mol m(-2) s(-1) Pa-1, with H-2/NH3 and H-2/N-2 permeance ratios of 110-200 and 200-700, respectively, at 773 K. The effect of operating conditions on membrane reactor performance with respect to NH3 conversion, H-2 yield and H-2 purity was investigated, and the results were in agreement with those calculated by the proposed simulation model. (C) 2012 American Institute of Chemical Engineers AIChE J, 59: 168-179, 2013