Facile integration of core–shell catalyst and Pd-Ag membrane for hydrogen production from low-temperature dry reforming of methane

Abstract

Dry reforming of methane (DRM) is an important way of conversion of CH4 and CO2, two greenhouse gases, for the production of hydrogen. In this study, a catalytic membrane reactor combining an ultra-thin Pd-Ag alloy membrane with a coke-resistant Ni-SiO2@CeO2 core–shell catalyst was developed for high yield hydrogen production from DRM. The performance of membrane in the presence of gases such as CO, CO2 and CH4 was evaluated, and very little reduction in H2 flux (∼2.5 %) was observed in the presence of these gases at the relevant reaction conditions. The catalyst was tested for DRM reaction in both fixed bed reactor (FBR) and catalytic membrane reactor (CMR) to evaluate its performance at different reaction conditions. In a catalytic membrane reactor, the removal of hydrogen resulted in 1.5 times higher methane conversion compared to the calculated conversion at thermodynamic equilibrium at the used reaction conditions when hydrogen is not removed from the reaction mixture. Around 70 % of the produced H2 was recovered from the reaction stream, by virtue of the high H2 flux through the ultra-thin Pd-Ag membrane. Further, the competing reverse water gas shift reaction, that consumes the produced H2, was drastically suppressed by using membrane reactor. The suppression of reverse water gas shift reaction (RWGS) in CMR was confirmed by analyzing downstream gases using gas chromatography mass spectrometer, the result showed significantly lower H2O content for CMR than FBR. Thus, the coupling of ultra-thin membrane with a core shell catalyst synergistically improved the performance of the dry reforming of methane.