A highly selective Cr/ZrO2 catalyst for the reverse water-gas shift reaction prepared from simulated Cr-containing wastewater by a photocatalytic deposition process with ZrO2. Issue 6 (December 2018) - Tao, Yang
Highlights: Thermodynamic limit CO2 conversion and 100% CO selectivity at 600 °C in RWGS with Cr/ZrO2 . Excellent stability of photoreduced Cr/ZrO2 in 72 h continuous operation at 500 °C. Co-existence of Cr(0) and Cr(III) in on ZrO2 surface after photoreduction process. Intermediate role of Cr(VI) in RWGS reaction with Cr/ZrO2 as catalyst. Possibility of recover Cr species in water as high performance catalyst for CO2 utilization. Abstract: Here, we report the preparation of a Cr/ZrO2 composite catalyst for the reverse water-gas shift reaction (RWGS) that shows excellent low-temperature CO2 conversion and 100% CO selectivity. The catalyst was prepared from Cr-containing wastewater by photoreduction. Zirconia was used as a wide bandgap photocatalyst to photoreduce Cr(VI) under UV irradiation and immobilize the Cr species on the catalyst surface, resulting in a high dispersion. The results show that the obtained 1 wt%Cr/ZrO2 can catalyze the RWGS to reach the thermodynamic limit at 600 °C. The CO yield at 600 °C with photoreduced Cr/ZrO2 after calcination, 38.34%, is significantly higher than that of the catalyst prepared by impregnation. Metal hydrides were determined to be the key intermediates in the RWGS reaction with Cr/ZrO2 as the catalyst, and the cyclic conversion between Cr(VI) and Cr(III) caused by the hydrogen reduction and CO2 oxidation improves the catalytic activity. This study provides a strategy to acquire a promising RWGS catalyst for CO2 emission reduction and utilization and an attractive method to treat Cr-containing wastewater.