Selective oxidation of ethylbenzene over CeAlPO-5

CeAlPO-5(Al/Ce = 25, 50, 75, 100 and 125) molecular sieves were synthesized hydrothermally in fluoride medium and their structures were confirmed from an XRD analysis. The incorporation of Ce3+ into the framework was verified by XRD and DRS-UV–Vis analyses. The surface areas were in the range of 202–215 m2 g−1. The ESR spectrum revealed the presence of adsorbed oxygen which was evident from the peak at g = 2.0. The catalytic activity of molecular sieves was tested in the vapour phase oxidation of ethylbenzene between 150 and 250 °C. CeAlPO-5(25) showed higher conversion than other catalysts. The selectivity to acetophenone was above 90% at all the temperatures. The selective oxidation of methylene group was ascribed to slow rotation of the ethyl group compared to its methyl group at the reaction temperature. Cerium was not leached out in CeAlPO-5(25) even after activation of the spent catalyst at 550 °C. The time on stream study also indicated the absence of catalyst deactivation.

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► A novel route for the synthesis of CeAlPO-5 catalysts is devised.
► High activity of ethylbenzene oxidation and high selectivity to acetophenone are reported.
► A new mechanism is suggested for selective oxidation.
► The oxidation process can be applied to industries.