Synthesis and characterization of xerogel titania modified with Pd and Ni

Pd and Ni supported on TiO2 have been synthesized by the sol–gel method and characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), N2 sorption, TGA–DTG, TEM and NH3-TPD with DRIFTS. Catalyst samples were also examined in the oxidative destruction of dichloromethane (DCM) in the presence of water vapor. Acid hydrolysis of titania precursor was performed with H2SO4 or HNO3 as hydrolysis catalysts and two procedures were used for modifying titania with Pd or Ni, namely impregnation and cogellation. Sulphated catalysts exhibited higher surface area, average pore diameter and total pore volume than those prepared with HNO3. Brönsted acid sites created by sulphate species anchored on titania favored extraction of Cl atoms from DCM molecule. DCM oxidation was much higher over sulphated catalysts as compared to un-sulphated ones, catalysts prepared by impregnation exhibited higher activity than those prepared by cogellation and Pd was more effective than Ni for burning-off coke deposited over support surface. Pd impregnated on sulphated xerogel titania was the most selective catalyst to CO2 and HCl. Therefore, bifunctional catalysts, i.e. containing palladium and Brönsted acid sites are required for total combustion of DCM at relatively low temperatures.

Graphical abstractBifunctional catalysts, i.e. containing palladium and Brönsted acid sites are required for total combustion of dichloromethane (DCM) at relatively low temperatures. DCM oxidation is much higher over sulphated catalysts as compared to un-sulphated ones, catalysts prepared by impregnation exhibit higher activity than those prepared by cogellation and Pd was more effective than Ni for burning-off coke deposited over support surface. Figure optionsDownload full-size imageDownload as PowerPoint slide