The Studies Of Reactive Sorption Enhanced Stream Reforming Of Methane In A Palladium Membrane Reactor

It is an important issue to improve the hydrogen production efficiency and remove the by-product of CO to avoid the poison for the Pt anode, during the research of providing proton exchange membrane fuel cell(PEMFC) with hydrogen from methane stream reforming. This paper combined membrane separation technology with reactive sorption enhanced reforming(ReSER) technology to produce the extra pure hydrogen gas for PEMFC. The effects of the in-suit separation of CO2and H2on dual enhanced steam methane reforming were investigated by stimulation and experiment.Firstly, this paper built the thermodynamic model for dual enhanced steam methane reforming with the adsorption separation of CO2and membrane separation of H2. MATLAB software was used to simulate the new process according to reaction temperature, reaction pressure, molar ratio of stream to methane, CO2absorption rate and H2separation rate. The results show that if just taking one method to enhance the reaction, the separation of H2is better to improve the methane conversion than the separation of CO2, but the CO and CO2concentration of the outlet gas will increase. The dual enhanced steam methane reforming with the adsorption and membrane separation is able to not only improve the methane conversion, separate high-purity hydrogen, but also reduce the concentration of CO.Then, Pd composite membrane was prepared by electroless plating method on porous ceramic tube substrates. SEM, XPS were carried to characterize the thickness and surface morphology of pd composite membrane. Gas permeability test was used to investigate the hydrogen permeability. The results show that an uniform membrane was obtained under the optimized preparation method and the thickness of pd composite membrane is7.2μm. Under the temperature of600℃, pressure of1.3atm, the hydrogen permeation flux is0.015mol·m-2·s-1.In this paper, a novel packed-bed palladium membrane reactor was designed and applied in reactive sorption enhanced stream methane reforming. The results indicate that methane conversion with the adsorption separation of CO2and membrane separation of H2is91%under the reaction temperature of600℃, pressure of1.3atm and steam to methane molar ratio of4. Even when the temperature was lowered down to550℃, the methane conversion of82% is much higher than64% which is the theoretical values of the conventional methane steam reforming.This paper also studied the relationship between each component concentration of production and reaction time in the packed-bed palladium membrane reactor. The concentration of H2through the pd composite membrane in palladium membrane reactor is98%,which is higher than H2concentration of92% from reactive sorption enhanced stream methane reforming in packed-bed reactor. At the same time, the CO concentration of1000ppm through the pd composite membrane is less than CO concentration of1.5% from reactive sorption enhanced stream methane reforming. The results of this paper provide theoretical and experimental basis for further studies on reactive sorption enhanced stream methane reforming in membrane reactors.