The antagonist effect of pressure on the thermodynamic equilibrium and the H-2 permeation rate has been studied in a small-scale membrane reactor (MR) with no sweep gas. The influence of some design parameters as membrane surface area (A(m)), catalyst volume (V-cat), methane load in feed (L-s) and gas hourly space velocity (GHSV) on the MR performance has also been evaluated. In the MR, a twofold increase of the methane conversion has been obtained by enhancing the ratio A(m)/V-cat from 0.42 to 2.1 cm(2) cm(-3). A methane conversion about three-times as much as thermodynamic equilibrium limit of a traditional reactor has been obtained when the L-s/A(m) ratio was reduced from 11.6 to 8.4 cm(3)(STP) cm(-2) min(-1). Ultimately, a methane conversion of the 68% and a hydrogen recovery approximately of 43% have been reached for a ratio A(m)/V-cat =2.1 cm(2) cm(-3) and L-s/A(m) = 8.4 cm(3)(STP)cm(-2) min(-1). Removal of hydrogen increases the tendency to carbon deposition. These effects can be reduced by operating at higher temperatures and/or pressures, but necessarily, in the presence of a reagents molar ratio higher than three. (C) 2009 Elsevier B.V. All rights reserved.