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

Abstract

Low temperature Water-Gas Shift (WGS) reaction is investigated over MOFsupported 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 onWGS behaviour. 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 a ect WGS activity, i.e. CO conversion signi cantly, 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 signi cantly, 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 a ected 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 con guration 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.