Construction and testing of a low-temperature water-gas shift reaction system

Abstract

The objective of this study was to construct and test of a low-temperature water-gas shift reaction system. A system consisting of mass flow controllers for gases, HPLC pump for water, an evaporation and gas-mixing section, a down-flow microreactor located in a temperature-controlled furnace, a water trap, heated stainless steel connecting lines and an on-line gas chromatograph for feed and product analysis was designed and constructed. The testing of the constructed water-gas shift (WGS) reaction system was carried out using three different catalysts prepared by sequential incipient-to-wetness impregnation with fixed platinum and different cerium oxide loadings (1.4wt.%Pt-10wt.%CeOx/ -Al2O3, 1.4wt.%Pt-5wt.%CeOx/ -Al2O3, 1.4wt.%Pt-1.25wt.%CeOx/ -Al2O3). The experimental work involved a parametric study of the effect of catalyst reduction time, reaction temperature, contact time (W/FCO), cerium oxide loading and H2O/CO ratio on CO conversion. The parametric study was first conducted on 1.4wt.%Pt-10wt.%CeOx/ -Al2O3 catalyst, except for the H2O/CO ratio that was tested only on the catalyst with the lowest cerium oxide content. Fresh catalyst samples were reduced in situ at 350oC under pure H2 flow for 2 hours as reduction time had no appreciable effect on CO conversion. W/FCO ratios tested between 0.60-1.25 mg.min.μmol-1 indicated that CO conversions increased with increasing contact time. Low-temperature WGS experiments in the 250-350oC interval showed the significant effect of reaction temperature: CO conversion increased with temperature until WGS equilibrium was reached after 300oC and then decreased with the equilibrium curve. CO conversion was the same at CeOx loadings of 5-10 weight per cent but decreased at 1.25 weight per cent. The effect of H2O/CO ratio was tested only on 1.4wt.%-1.25wt.%CeOx/ -Al2O3 for three molar ratios; the results obtained at 250oC showed that CO conversion increased gradually as H2O/CO ratio reached a value of three.