Highly Efficient Mesoporous Mg/γ-Al2O3 Catalysts for Ozonation of Saline Petroleum Effluents

Abstract

Abstract γ-Al2O3 is promising for catalytic ozonation because it produces HO° radicals. To improve its basicity and/or its oxidative character, highly mesoporous γ-Al2O3 was doped with different metals M alone or in mixture (M = Mg, Ca, Zn, Fe, Ba, Zr, Cu, Co, Ni, Ce, Ti, with 0.05 < M/Al < 0.5 molar ratio) prepared either by incipient wetness deposition or by direct sol-gel. Tests to determine the basic and oxidative character of the catalysts have been set up. Results show that Mg-doped alumina materials exhibited the highest basicity and Cu,Mg-doped alumina materials the highest oxidative character. These materials (5 g/L) were tested in the catalytic ozonation of a synthetic saline (NaCl = 50 g/L) petroleum effluent such as produced water (TOC = 216 mg/L) containing phenols, acetic acid and polycyclic aromatic hydrocarbons. Among these catalysts, Mg-doped alumina with molar ratio Mg/Al = 0.1, 0.2 prepared by incipient wetness deposition were the more efficient catalysts. Under reuse the Mg-doped alumina catalyst (Mg/Al = 0.1) exhibited the highest ozonation rate with 98% TOC removal in 5 h. This remarkable behavior was attributed to the in-situ formation during ozonation of spinel (MgAl2O4) nanoparticles at the surface of Mg-doped alumina particles.