Ethylbenzene to styrene over alkali doped TiO2-ZrO2 with CO2 as soft oxidant

•Acid–base bifunctional TiO2-ZrO2.•Doping of alkali metal into TiO2-ZrO2.•Increasing CO2 conversion by increasing surface basicity.•Improved surface oxygen species.•Highly stable alkali doped TiO2-ZrO2 for oxidehydrogenation of ethylbenzene to styrene with CO2.

Oxidative dehydrogenation of ethylbenzene (EB) to styrene monomer (SM) over alkali metal (Na, K) doped TiO2-ZrO2 (TZ) has been studied. The EB and CO2 conversions observed over alkali doped TZ are higher than that of non-doped TZ. The enhanced CO2 conversion compared with non-doped counterparts is attributed to improved basicity, formation of TiZrO4 phase with increased CO2 affinity and insertion of K or Na into the lattice which affects the binding energy of “O” in turn providing more labile oxygen species. Alkali doping also effected in fine tuning the surface acid base properties. Moreover, these K and Na doped binary metal oxides system showed high surface area of 256 m2/g and 199 m2/g respectively. There was a 10-fold increase in the CO2 conversions in case of the doped TZ compared to non-doped TZ increasing the stability of the catalyst by decreasing coking on the surface of the catalyst in spite of the high conversions.

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