A Highly Efficient Pt/TiO2-NaY-x Catalyst for RWGS reaction: Enhancement Effect of Adsorbent NaY-x on CO2 Hydrogenation Conversion

Abstract

Selective removal of H₂O in-situ from the reverse water gas shift (RWGS) reaction system is an effective approach to intensify the CO₂ conversion dictated by thermodynamics. Here, a composite material is prepared by combining a water adsorbent zeolite NaY-2 which modified by hydrothermal treatment at 500°C with Pt/TiO₂ catalyst. The synthesized Pt/TiO₂-NaY-2 exhibits much higher activity and CO selectivity than conventional Pt/TiO₂. It shows the highest CO₂ conversion of 42.3% and consistently exceeds the corresponding thermodynamic equilibrium conversion (28.6%) over 120 h on stream with 100% CO selectivity at 340°C. The persistent catalytic enhancement is mainly attributed to the well aligning between the desorption temperature of H₂O on NaY-2 (270°C, 330°C) and the reaction temperature. The introduced NaY-2 demonstrates an electronic effect on Pt/TiO₂ during the reduction process and generates an electron-rich Pt species. The created Pt^δ− sites on Pt/TiO₂-NaY-2 possess higher intrinsic catalytic activity than Pt⁰ sites on Pt/TiO₂. The interaction also reduces Pt average particle size and thus weakens the adsorption of CO on Pt, which inhibits the methanation side reaction then improves the CO selectivity on Pt/TiO₂-NaY-2. The RWGS reactions on the synthesized Pt-based catalysts proceed through intermediate decomposition mechanism exposed by in-situ IR spectroscopy. The findings of this work provide information of high interest to guide future research on RWGS reaction intensified process via in-situ removal of H₂O.