Investigation of water gas shift reaction over MOF assisted precious metal catalysts

Low temperature Water-Gas Shift (WGS) reaction is investigated over MOF-supported Pt/MIL-53(Al) catalysts in 250-300 oC range and steam-to-carbon (S/C) ratios of 1.67, 2.33 and 3. Pt metal loadings of 0.5, 1.0 and 1.5 per cent by weight are compared. Apart from using it as a support, MIL-53(Al) is physically coupled to a well-known WGS catalyst, 1.5wt.%Pt/CeOx/Al2O3, for the purpose of understanding the impact of using a MOF structure on WGS behavior. The catalysts are prepared by the incipient-to-wetness impregnation technique using deionized water as the solvent. Highest CO conversion over the MOF-supported catalyst is found to be 72% at 300 oC and at S/C=2.33. Increase in S/C ratio and temperature are found to affect WGS activity, i.e. CO conversion significantly, while increase in Pt loading led to marginal elevations in activity. It is observed that the addition of MIL-53(Al) as either a support or alone increases CO consumption significantly, but this does not carry over to H2 production. Extra tests show that steam addition over MIL-53(Al) is the primary cause of CO disappearance. H2 is not affected by the mechanism that causes CO to decrease over MIL-53(Al). Single MIL-53(Al), single 1.5wt.%Pt/CeOx/Al2O3 and their combination are tested. It is found that combined configuration has the highest CO conversion of 64% at 300 oC and S/C=2.33. MIL-53(Al) is found to be inert under the reaction conditions studied. SEM comparison of fresh and spent Pt/MIL-53(Al) shows that sintering occured throughout the reaction.