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

HighlightsWhat are the main findings?A styrene yield of 91.4% was found for 10% k/CeO2at 500 °C and CO2-O2mixed atmosphere. The excellent catalytic performance of 10% k/CeO2is attributed to the alkali metal oxide modified cerium oxide and carbon dioxide induced oxygen vacancies to promote the dehydrogenation of ethylbenzene.What is the implication of the main finding?The proposed ODH strategy by using oxygen vacancies enriched catalysts offers an important insight into the efficient dehydrogenation of ethylbenzene at mild conditions.AbstractOxidative dehydrogenation (ODH) is an alternative for styrene (ST) production compared to the direct dehydrogenation process. However, ODH with O2or CO2suffers from either over-oxidation or endothermic property/low ethylbenzene conversion. Herein, we proposed an ODH process with a CO2-O2mixture atmosphere for the efficient conversion of ethylbenzene (EB) into styrene. A thermoneutral ODH is possible by the rationalizing of CO2/O2molar ratios from 0.65 to 0.66 in the temperature range of 300 to 650 °C. K modification is favorable for ethylbenzene dehydrogenation, and 10%K/CeO2achieved the highest ethylbenzene dehydrogenation activity due to the enhanced oxygen mobility and CO2adsorbability. The catalyst achieved 90.8% ethylbenzene conversion and 97.5% styrene selectivity under optimized conditions of CO2-4O2oxidation atmosphere, a temperature of 500 °C, and a space velocity of 5.0 h−1. It exhibited excellent catalytic and structural stability during a 50 h long-term test. CO2induces oxygen vacancies in ceria and promotes oxygen exchange between gaseous oxygen and ceria. The ethylbenzene dehydrogenation in CO2-O2follows 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.Keywords:ethylbenzene;oxidative dehydrogenation;ceria;CO2