Influence of titanium species type in siliceous beta zeolites on their catalytic activity in the process of selective diphenyl sulphide oxidation with hydrogen peroxide

Abstract

Siliceous beta zeolite containing titanium was evaluated as a catalyst for the selective oxidation of diphenyl sulphide (Ph₂S) using hydrogen peroxide as the oxidising agent. Various titanium content was introduced into the SiBEA materials with vacant T-atom sites by post-synthetic methods, such as chemical vapour deposition and wet impregnation. Materials with diverse titanium loading were analysed in terms of their chemical composition using inductively coupled plasma optical emission spectrometry (ICP-OES), crystalline structure using X-ray diffraction (XRD), textural properties by low-temperature N₂ sorption and surface acidity by ammonia temperature-programmed desorption (NH₃-TPD). The form and aggregation of catalytically active species were examined by UV-vis diffuse reflectance spectroscopy (UV-vis DRS). Titanium was incorporated into materials mainly in the form of tetrahedrally coordinated framework cations, except for the Ti_xSiBEA-I samples, where anatase crystallites were identified. All the samples were characterised by high catalytic activity in the studied process. The influence of Ti(IV) framework species on Ph₂S oxidation and selectivity towards diphenyl sulphone (Ph₂SO₂) were analysed and discussed.