Liquid phase oxidation of alkylaromatic hydrocarbons over titanium silicalites

Abstract

Although the appropriate catalyst for specific partial oxidation has not been found yet, the industrial interest in partial catalytic oxidation of alkylaromatic hydrocarbons is because of the availability of these substances from the petrochemical industry and to a number of applications for the possible oxidation products. Conventional gas phase oxidation concerns the side chain and leads mainly to benzoic acid or even to the destruction of the aromatic ring. A promising step in this direction is the oxidation with hydrogen peroxide over titanium silicalite molecular sieves TS-1. This catalytic system was successfully applied in the hydroxylation of phenol, epoxidation of alkenes, and partial oxidation of alkanes and other organic substances. The advantages of the TS-1 catalyst reside in the selectivity of the reaction and the long duration of the activity of the catalytic samples. This chapter discusses the first work directed exclusively to the investigation of toluene, ethylbenzene, 1- and 2-propylbenzene oxidation over TS-1 and TS-2 catalysts under various reaction conditions. Titanium silicalite-1 (TS-1) was the synthesized example of the original patent and titanium silicalite-2 (TS-2). The removal of occluded organics was performed by calcination of the sample at 550°C in air for about 6 h. Chemical analysis of the solid materials (Si/Ti = 50) was obtained by atomic absorption after solubilization of the sample in hydrogen fluoride (HF)–HCI solution.