From sorption-enhanced reactor to sorption-enhanced membrane reactor: A step towards H-2 production optimization through glycerol steam reforming

Abstract

The main goal of this work is to access the benefits of using a sorption-enhanced membrane reactor (SEMR) comparatively to a sorption-enhanced reactor (SER) and a traditional reactor (TR) for H-2 production through glycerol steam reforming (GSR). A SER, where a potassium-promoted hydrotalcite-like material (K-MG30) was used to capture the CO2 produced during GSR on an alumina supported Rh catalyst, was tested. An enhancement of the H-2 production was observed not only during the pre-and breakthrough of CO2 but also during the postbreakthrough as compared to the conventional TR. While the initial enhancement was mostly due to CO2 sorption and affected more directly the water-gas shift (WGS) reaction, the observed catalytic activity of K-MG30 towards glycerol decomposition and mainly WGS reaction was responsible for the improved performance during post-breakthrough. Still, considerably higher H-2 purity was obtained in the first moments. Ultimately, a much significant improvement in terms of H-2 production was observed in the SEMR, where a Pd-Ag membrane separated selectively the hydrogen from the other gases. An increment of the maximum H-2 yield in the pre- and breakthrough regions from 1.6 up to 3.6 mol center dot mol(fed glycerol)(-1) was obtained. The simultaneous removal of both H-2 and CO2 significantly benefited the WGS reaction. Consequently, only H-2 was obtained in the gas phase of the retentate stream during the pre-breakthrough period. Moreover, ultra-pure H-2 was obtained in the permeate side of the dense Pd-Ag membrane, meaning that if the SEMR is continuously operated in the pre-breakthrough region, pure H-2 would continuously be obtained in both retentate and permeate streams.