Physico-chemical and catalytic properties of Fe2BiMo2Ox catalyst ultrasound treated and promoted with Al2O3 in the oxidative dehydrogenation of ethylbenzene to styrene Original Research Article

It has been shown by means of X-ray diffraction (XRD) analysis that Fe2BiMo2Ox and Fe2BiMo2Al0.25Ox catalysts are multiphase systems of α-Bi2(MoO4)3, γ-Bi2MoO6, Fe2(MoO4)3, Fe2O3·3–4MoO3 and the ternary compound—FeBi3Mo2O12. Using a pulse technique has been found that Fe2BiMo2Al0.25Ox catalyst exhibits the highest catalytic activity (100% of ethylbenzene (ETB) conversion) and styrene (STY) selectivity 97.7% at 653 K and a contact time of 3.6 s in the oxidative dehydrogenation (ODH) of ETB. The acidity and basicity measurements of the surface of the catalysts were performed by using a pulse chemisorption procedure with the subsequent temperature-programmed desorption (TPD) of ammonia and acetic acid, respectively. Small additives of Al2O3 to Fe2BiMo2Ox catalyst considerably improve its catalytic activity and selectivity in the process that primarily is due to the increase of the amount of acid and moderate base sites on the catalyst surface. Active acid and base sites of the first form of NH3 and CH3COOH adsorption, respectively play an important role in STY formation. It is shown that ultrasonic treatment of F2BiMo2Ox catalyst in its preparation by precipitation from solution improves its activity and selectivity in the ODH of ETB to STY.