Hydrogen production by steam methane reforming in membrane reactor equipped with Pd membrane deposited on NiO/YSZ/NiO multilayer-treated porous stainless steel

In this study, we prepared a Pd composite membrane with high hydrogen permeance and thermal stability on a tubular porous stainless steel (PSS) support by ethylene diamine tetraacetic acid-free electroless plating. The conventional yttria-stabilized zirconia (YSZ) was replaced with a NiO/YSZ/NiO multilayer as the diffusion barrier, and the latter was introduced on a PSS tube (diameter of 12.7 mm, length of 450 mm, and surface area of 175 cm(2)). A long-term thermal stability test revealed that the NiO/YSZ/NiO multilayer significantly reduced the growth rate of nitrogen leakage. The test was carried out for similar to 1150 h on a 2.5-mu m thick Pd membrane deposited on a NiO/YSZ/NiO/PSS tube (diameter of 25.4 mm, length of 450 mm, and surface area of 350 cm(2)). The hydrogen permeance obtained at the end of the test was 3.81x10(-3) mol m(-2) s(-1) Pa-0.5, and the H-2/N-2 selectivity was similar to 87 at a temperature of 773 K and pressure difference of 101.3 kPa. The rate of increase in nitrogen leakage during the test was 3.05x10(-11) molm(-2) s(-1) Pa-0.5 h(-1), which demonstrated the ability of the NiO/YSZ/NiO multilayer to mitigate nitrogen leakage. To produce hydrogen using the Pd composite membrane reactor, steam methane reforming was conducted under the following operating conditions: pressure, 430-1114 kPa; temperature, 883 K; and gas hourly space velocity, 1000 h(-1). The reaction yielded a methane conversion and hydrogen recovery of 75.1% and 97.9%, respectively. The permeate stream was composed of 93.1 vol% H-2, 0.6 vol% CO, 1.8 vol% CH4, and 4.5 vol% CO2. The gas composition of the permeate stream was suitable for use as fuel in a high-temperature polymer electrolyte membrane fuel cell.