Nondeactivating Nanosized Ionic Catalysts for Water−Gas Shift Reaction

Abstract

The water-gas shift reaction (WGS) is an important reaction to produce hydrogen. In this study, we have synthesized nanosized catalysts where Pt ion is substituted in the +2 state in TiO 2 , CeO 2 , and Ce 1-x Ti x O 2-δ . These catalysts have been characterized by X-ray diffraction and X-ray photoelectron spectroscopy (XPS), and it has been shown that Pt 2+ in these reducible oxides result in solid solutions like Ti 0.99 Pt 0.01 O 2-δ , Ce 0.83 Ti 0.15 Pt 0.02 O 2-δ , and Ce 0.98 Pt 0.02 O 2-δ . These catalysts were tested for the water gas shift reaction both in the presence and absence of hydrogen. It was shown that Ti 0.99 Pt 0.01 O 2-δ exhibited higher catalytic activity than Ce 0.83 Ti 0.15 Pt 0.02 O 2-δ and Ce 0.98 Pt 0.02 O 2-δ . Further, experiments were conducted to determine the deactivation of these catalysts. There was no sintering of Pt and no carbonate formation; therefore, the catalyst did not deactivate even after prolonged reaction. There was no carbonate formation because of the highly acidic nature of Ti 4+ ions in the catalysts.

Support‐dependent activity of noble metal substituted oxide catalysts for the water gas shift reaction

“…A detailed account of the synthesis can be found elsewhere. 23,27,29 All the compounds were characterized by powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). XRD were recorded on Philips X'pert diffractometer with CuKa radiations.…”

“…Further details can be found elsewhere. 23,27,29 Catalytic activity tests All the reactions were carried out in 4 mm ID quartz tube reactors with the catalysts packed in the form of granules between ceramic wool. The reactor was heated from outside using an electric furnace.…”

“…In substituted CeO 2 and TiO 2 compounds, the noble metals retained their ionic state after the reaction. 23,27 In substituted ZrO 2 compounds, Pt ions were observed to get reduced to metallic state after the reaction. 23 The XRD patterns and XPS spectra of all the compounds before and after the reaction can be found in our previous works.…”

“…23 The XRD patterns and XPS spectra of all the compounds before and after the reaction can be found in our previous works. 23,27,29 Modeling the WGS reaction over different supports Dual Site Mechanism. From the XPS of the noble metals before and after the reaction, it is clear that in all the CeO 2 -based catalysts, the metal remains in the ionic state during the reaction.…”

“…In one of our previous studies, we have reported the time variation of the CO concentration during the WGS under daily startup-shutdown conditions. 27 The conversion of CO decreased for La-substituted catalyst even after maintaining exactly identical conditions throughout the course of the reaction. Spectroscopic studies revealed the formation of surface carbonate resulting in a decrease in the activity of the catalyst with reaction time.…”