Efficient Oxidative Dehydrogenation of Ethylbenzene over K/CeO₂ with Exceptional Styrene Yield

Oxidative dehydrogenation (ODH) is an alternative for styrene (ST) production compared to the direct dehydrogenation process. However, ODH with O-2 or CO2 suffers from either over-oxidation or endothermic property/low ethylbenzene conversion. Herein, we proposed an ODH process with a CO2-O-2 mixture atmosphere for the efficient conversion of ethylbenzene (EB) into styrene. A thermoneutral ODH is possible by the rationalizing of CO2/O-2 molar ratios from 0.65 to 0.66 in the temperature range of 300 to 650 degrees C. K modification is favorable for ethylbenzene dehydrogenation, and 10%K/CeO2 achieved the highest ethylbenzene dehydrogenation activity due to the enhanced oxygen mobility and CO2 adsorbability. The catalyst achieved 90.8% ethylbenzene conversion and 97.5% styrene selectivity under optimized conditions of CO2-4O(2) oxidation atmosphere, a temperature of 500 degrees C, and a space velocity of 5.0 h(-1). It exhibited excellent catalytic and structural stability during a 50 h long-term test. CO2 induces oxygen vacancies in ceria and promotes oxygen exchange between gaseous oxygen and ceria. The ethylbenzene dehydrogenation in CO2-O-2 follows a Mars-van Krevelen (MvK) reaction mechanism via Ce3+/Ce4+ redox pairs. The proposed ODH strategy by using oxygen vacancies enriched catalysts offers an important insight into the efficient dehydrogenation of ethylbenzene at mild conditions.