Intermediate-Temperature Reverse Water-Gas Shift under Process-Relevant Conditions Catalyzed by Dispersed Alkali Carbonates

Current reverse water-gas shift (RWGS) technologies require extreme temperatures of >900 °C. The ability to perform RWGS at lower temperatures could open new opportunities for sustainable chemical and fuel production, but most catalyst materials produce methane and coke at lower temperatures, especially at elevated pressures targeted for industrial processes. Here we show that transition-metal-free catalysts composed of K2CO3 or Na2CO3 dispersed on commercial γ-Al2O3 supports (K2CO3/γ-Al2O3 and Na2CO3/γ-Al2O3) are highly effective RWGS catalysts in the intermediate-temperature regime. At a high gas hourly space velocity of 30,000 h-1 and operating pressure of 10 bar, K2CO3/γ-Al2O3 reached RWGS equilibrium-limited CO2 conversion at 550 °C and was 100% selective for CO at all temperatures tested (up to 700 °C). Na2CO3/γ-Al2O3 was also 100% CO-selective and only slightly less active. Both catalysts were stable for hundreds of hours on stream at 525 °C and tolerated large quantities of methane and propane impurity in the CO2/H2 feed. The unique performance attributes, combined with the low-cost components and extremely simple synthesis, make dispersed carbonate RWGS catalysts attractive options for industrial application.