The performance of high purity hydrogen production from methanol for a compact steam reformer with a hydrogen purification membrane was investigated experimentally. A 77 wt.% Pd/23 wt.% Ag membrane with 25µm thickness and CuO/ZnO/ Al 2 O 3 catalyst were used. Heating was performed by a Bunsen type burner using City Gas 13A. The methanol reforming and purification of H 2 were investigated at different reference catalyst zone temperatures (589-689K), pressures at the retentate side (0.2-0.5MPa), steam to methanol(S/C) ratios (0.8-1.6) and reactant flow rates (1.7 ×10 -4 to 4.4 ×10-4 mol/s). The results show that at high reference temperature, high pressure and certain points of the reactant flow rate, the maximum hydrogen permeation rate is obtained when the S/C ratio is around 1. The modified Sieverts' equation which considers the decrease in H 2 concentration at the membrane surface, was proposed. The experimental result was lower than the permeation rate estimated by the modified Sieverts' equation, which is probably caused by the adsorption of non-H 2 species during permeation. It is further demonstrated that the modified Sieverts' equation is able to estimate a more reasonable hydrogen permeation rate in comparison to the estimation by the ordinary Sieverts' equation. In addition, it is shown that the compact methanol steam reformer with a Pd/Ag membrane is able to produce high purity hydrogen with very low CO concentration, which fulfills the Polymer Electrolyte Fuel Cell (PEFC) requirement (<10ppm).

The effect of feed flow rate of hydrogen mixture on the H 2 permeation for a flat sheet Pd/Ag membrane with stagnating flow at the upstream side was investigated experimentally and theoretically. A 77wt.% Pd/23wt.% Ag flat sheet membrane with 25μm thickness and 0.02m diameter was used. The permeation rate of H 2 was investigated under various feed flow rates (1.489 × 10 -5 -2.976 × 10 -4 mol/s), for pressures of 0.20-0.30MPa and reference membrane temperatures of 523-723K. Experimental results demonstrated that when the feed flow rate is decreased, the H 2 permeation rate decreases. This is supposed to be due to the phenomena of hydrogen concentration decrease at the membrane surface of the upstream side, as a result of the effect of H 2 permeation itself. When a theoretical equation that takes into account the effect of H 2 permeation is used, the H 2 permeation mole flux can be predicted quantitatively by using the concentration of H 2 of the feed mixture. This shows that the diffusive transport effect plays an important role as well as the convective transport effect when determining H 2 concentration at the membrane surface. In addition, the normalization of the theoretical results shows that the trend of the decrease in the H 2 permeation mole flux with respect to the feed mole flux follows the first order lag function, regardless of the inlet H 2 partial pressures.

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