Platinum catalysts supported on MWNT for catalytic wet air oxidation of nitrogen containing compounds

Abstract

Multi-walled carbon nanotubes (MWNT) activated by nitric acid oxidation were used to prepare supported platinum (1% Pt) catalysts by the excess solution impregnation method. Three different platinum precursors were used to prepare the impregnation solutions, namely diiodo dicarbonyl platinum(II) [PtI 2(CO) 2], dimethyl (1,5-cyclooctadiene) platinum(II) [Pt(CH 3) 2(C 8H 12)] and hydrogen hexachloroplatinate(IV) hexahydrate H 2PtCl 6·6H 2O. The catalysts were characterized by transmission electron microscopy (TEM) analysis and H 2 chemisorption. They were tested in the catalytic wet air oxidation (CWAO) of aniline aqueous solutions (200 °C and 6.9 bar of oxygen partial pressure). The Pt/MWNT catalyst prepared from H 2PtCl 6·6H 2O showed the best performance with respect to combined activity and selectivity for aniline conversion to non-organic compounds. This catalyst was used in CWAO (150 °C and 6.9 bar of oxygen partial pressure) of aqueous solutions of various textile dyes such as the monoazo dye chromotrop 2R (C2R), the diazo dye erionyl red B (ERB) and the triazo dye solophenyl green BLE (SG) 155%. It was found that the selectivity for dye removal decreased in the order diazo > monoazo > triazo. The CWAO of a textile wastewater was also performed using the same catalyst and identical reaction conditions. Complete color removal and 51.2% TOC abatement was obtained under these conditions.