Compact hollow fibre reactors for efficient methane conversion

Abstract

In this study, a micro-structured catalytic hollow fiber membrane reactor (CHFMR) has been prepared, characterized and evaluated for performing steam methane reforming (SMR) reaction, using Rh/CeO2 as the catalyst and a palladium membrane for separating hydrogen from the reaction. Preliminary studies on a catalytic hollow fiber (CHF), a porous membrane reactor configuration without the palladium membrane, revealed that stable methane conversions reaching equilibrium values can be achieved, using approximately 36 mg of 2 wt.%Rh/CeO2 catalyst incorporated inside the micro-channels of alumina hollow fibre substrates (around 7 cm long in the reaction zone). This proves the advantages of efficiently utilizing catalysts in such a way, such as significantly reduced external mass transfer resistance when compared with conventional packed bed reactors. It is interesting to observe catalyst deactivation in CHF when the quantity of catalyst incorporated is less than 36 mg, although the Rh/CeO2 catalyst supposes to be quite resistant against carbon formation. The “shift” phenomenon expected in CHFMR was not observed by using 100 mg of 2 wt.%Rh/CeO2 catalyst, mainly due to the less desired catalyst packing at the presence of the dense Pd separating layer. Problems of this type were solved by using 100 mg of 4 wt.% Rh/CeO2 as the catalyst in CHFMR, resulting in methane conversion surpassing the equilibrium conversions and no detectable deactivation of the catalyst. As a result, the improved methodology of incorporating catalyst into the micro-channels of CHFMR is the key to a more efficient membrane reactor design of this type, for both the SMR in this study and the other catalytic reforming reactions

Morphological and Elemental Analyses of Supported Palladium (Pd)/Silver (Ag) Composite Membranes

“…The fibers were sequentially dipped in the sensitization-activation baths of SnCl2 for 5 min, deionized water for 5 min, PdCl2 for 5 min, HCl for 2 min, and deionized water for 3 min. Air was bubbled in all baths to ensure a homogenous deposition of palladium seeds on the fiber surface, as suggested by Prasetya et al [13] . This sensitization--activation treatment was repeated 5 to 8 times until the surface of the fiber was dark brown.…”

Well-dispersed titanium dioxide and silver nanoparticles on external and internal surfaces of asymmetric alumina hollow fibers for enhanced chromium (VI) photoreductions

“…7(b)), silver and titanium were mainly observed on the ber external surface, although some particles were also observed throughout the ber cross-section Prasetya et al (2017). showed the proper deposition of Rh/CeO 2 catalysts inside the microchannels of asymmetric alumina hollow bers.…”

A compact non-PGM catalytic hollow fibre converter for on-board hydrogen production

“…recirculation, generation of preferential paths and stagnant regions), and (iii) mass transfer, resulting in improved reaction kinetics. 5,53,54 Fig. 5B schematically represents that the use of a HFC avoids the diffusion limitations typically associated with a PBR, which are caused by the tortuosity, porosity and constriction factor of the porous structure of the catalyst pellets.…”

“…3 Indeed, it has been demonstrated that the use of HFRs narrows the residence time distribution and decreases the catalyst loading and/or the operating temperatures when compared with traditional PBRs. [3][4][5] Moreover, they exhibit an exceptional area/volume ratio without compromising the pressure drop and efficiency. Furthermore, HFRs offer the advantage of improved reaction kinetics due to minimised internal and external diffusion limitations, thereby enhancing the viability of using nonprecious metal-based catalysts.…”