Hydrogen production by methane steam reforming using metallic nickel hollow fiber membranes

The metallic nickel hollow fiber membranes (NHFMs) consisting of a dense skin layer integrated on porous nickel substrate were fabricated in a single extrusion step by using a 90 wt% NMP-H2O solution and water as the respective internal and external coagulants during the spinning process. The resultant asymmetric Ni hollow fibers by sintering were directly applied to hydrogen production from methane steam reforming (MSR), where the porous internal surface functioned as a catalyst bed for MSR reactions, and the external dense skin layer served as the membrane for hydrogen extraction from the reaction products. The effects of the feed composition in terms of steam-to-methane ratio (H2O/CH4) and methane concentration; the operational parameters including temperature, space velocity, and the sweep gas flow rate on the performance of the hollow fibers were investigated. The results reveal that the reaction operational temperature should be above 800 °C and the H2O/CH4 ratio controlled around 3 so as to achieve both high methane conversion and high H2 production rate. When operated at 1000 °C and 25,937 h−1 methane space velocity, the maximum H2 production rate reached 50.84 mmol m−2 s−1 while the methane conversion reached at 98.58%. In order to produce pure hydrogen, steam may be used as the sweep fluid instead of inert gases such as nitrogen to prevent the dilution of the permeated gaseous hydrogen. The prepared asymmetric NHFMs also demonstrate high chemical stability in the reformate gases and high resistance to carbon deposition at above 800 °C, and thus may be a promising way of cost-effective hydrogen production by MSR at high temperatures.