Deactivation of Ti-based and γ-Al2O3 catalysts in liquid-phase methyl oleate epoxidation reaction

Abstract

To eliminate some drawback of heterogeneous catalysts as a low stability, the deactivation scheme and surface regeneration of TiO2 (P25), TS-1 and γ-Al2O3 catalysts was investigated on the liquid-phase methyl oleate epoxidation reaction at 50 ºC. Based on the results, there are two deactivation effects illustrated on the surface after the reaction: (1) the fouling effects are found the main deactivation on this reaction. There are three types which type 1 is found in P25 and γ-Al2O3, type 2 is uncovered in TS–1 and γ-Al2O3, and type 3 is appeared in γ-Al2O3 only. The FT-IR reveals that are alkane (C–H) and alcohol groups (O–H) as a type 1, α,β–unsaturated ketone (C=O) and alkane groups (C–H) as a type 2, and stretching ester (C=O) and alkane groups (C–H) as a type 3, (2) the loss of active species due to the oxygen vacancy forming after the reaction and the leaching effect. Furthermore, the percentage of lower MO conversion of γ-Al2O3 is higher than P25 and TS-1 because the obtained fouling on the γ-Al2O3 surface is stronger adsorption than P25 and TS-1. For this reason, the fouling deposits on P25 and TS-1 were eliminated completely at 550 ºC, but not for γ-Al2O3 (700 ºC). The OV sites provide the defects on the surface which the MO conversion cannot return back to the conversion of fresh catalyst.