Ce_0.78Sn_0.2Pt_0.02O_2-δ: a new non-deactivating catalyst for hydrogen production via water-gas shift reaction

Abstract

We demonstrate the activity of Ce_0.78Sn_0.2Pt_0.02O_2-δ, a new catalyst, towards water-gas shift (WGS) reaction. Over 99.5% CO conversion to H₂ is observed at 300 ± 25 °C. Based on different characterization techniques we found that the present catalyst is resistant to deactivation due to carbonate formation and sintering of Pt on the surface when subjected to longer duration of reaction conditions. The catalyst does not require any pre-treatment or activation between start-up/shut-down reaction operations. Formation of side products such as methane, methanol, formaldehyde, coke etc. was not observed under the WGS reaction conditions indicating the high selectivity of the catalyst for H₂. Temperature programmed reduction of the catalyst in hydrogen (H₂-TPR) shows reversible reduction of Ce⁴⁺ to Ce³⁺, Sn⁴⁺ to Sn²⁺ and Pt⁴⁺ to Pt⁰ oxidation state with oxygen storage capacity (OSC) of 3500 μmol g^-1 at 80 °C. Such high value of OSC indicates the presence of highly activated lattice oxygen. CO oxidation in presence of stoichiometric O₂ shows 100% conversion to CO₂ at room temperature. The catalyst also exhibits 100% selectivity for CO₂ at room temperature towards preferential oxidation (PROX) of residual CO in presence of excess hydrogen in the feed.