Experimental study of the deactivation of Ni/AlMCM-41 catalyst in the direct conversion of ethene to propene

Abstract

In this work, an experimental study of the deactivation and regarding a possible regeneration procedure in the ETP-reaction using Ni/AlMCM-41 (Si/Al=60) was carried out. ETP experiments at different temperatures and long time on-stream were carried out. Characterization of the catalyst after experiments was performed using powder-XRD, N2-physisorption, NH3-TPD, TPO and TEM. At 250 and 350°C the catalyst did not suffer significant deactivation after 107h on-stream. Nevertheless, the yield of propene was low. A severe deactivation of the catalyst was observed at 450°C where propene was the main reaction product. Regeneration of the catalyst after 30h on-stream at temperatures lower than 350°C could be performed using a mixture of 5 vol.% oxygen in N2. The regeneration of the catalyst was not possible after 30h on-stream at 450°C. Filamentous carbon and Ni reduction are considered responsible of the deactivation of the catalyst at 450°C. The analysis of the obtained results suggests that a conjunct polymerization process takes place and is the precursor of the reaction products and the carbon species. However, a detailed study of the mechanism of the ETP-reaction should be done for a better understanding of the deactivation of Ni/AlMCM-41.