In this work Ag nanoparticles supported on ZrO₂–CeO₂ promoted with different amounts of CeO₂ were synthesized by deposition–precipitation method in order to test the Catalytic Wet Air Oxidation (CWAO) of Methyl Tert-Butyl Ether (MTBE).

In recent past development of silver nanoparticles and their application in the treatment of wastewaters is becoming a major area of research. It is mainly applicable to the removal of three major pollutants like pesticides, heavy metals, and microorganisms. Variety of synthesis techniques have been reported for preparation and characterization of silver nanoparticles. In our research, we synthesized Ag nanoparticles supported on ZrO2 and ZrO2-CeO2 by a “deposit-precipitation method” as the first step and later sequentially synthesized Ag-Au supported on ZrO2 and ZrO2-CeO2 by Redox method. Catalysts were evaluated in catalytic wet air oxidation (CWAO) of methyl tert-butyl ether and phenol. The CWAO is a liquid phase process for the treatment of organic pollutants operating at temperatures in the range of 100–325°C at 5–200 bar pressures. The selectivity and efficient of catalysts were evaluated by total organic carbon (TOC) and high-performance liquid chromatograph (HPLC). Ideally, the total mineralization of pollutants into CO2 and H2O is preferred.

Three bimetallic catalysts of the type M–Cu with M = Ag, Au and Ni supports were successfully prepared by a two-step synthesized method using Cu/Al₂O₃-CeO₂ as the base monometallic catalyst. The nanocatalysts were characterized using X-ray diffraction (XRD), temperature-programmed reduction of H₂ (H₂-TPR), N₂ adsorption-desorption, scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and ultraviolet–visible spectroscopy with diffuse reflectance (DR-UV-Vis) techniques. This synthesized methodology allowed a close interaction between two metals on the support surface; therefore, it could have synthesized an efficient transition–noble mixture bimetallic nanostructure. Alloy formation through bimetallic nanoparticles (BNPs) of AgCuAlCe and AuCuAlCe was demonstrated by DR–UV–Vis, EDS, TEM and H₂-TPR. Furthermore, in the case of AgCuAlCe and AuCuAlCe, improvements were observed in their reducibility, in contrast to NiCuAlCe. The addition of a noble metal over the monometallic copper-based catalyst drastically improved the phenol mineralization. The higher activity and selectivity to CO₂ of the bimetallic gold–copper- and silver–copper-supported catalysts can be attributed to the alloy compound formation and the synergetic effect of the M–Cu interaction. Petroleum Refinery Wastewater (PRW) had a complex composition that affected the applied single CWAO treatment, rendering it inefficient.

Destruction of methyl tert-butyl ether (MTBE) in liquid phase and in a batch reactor was studied using Ruthenium catalysts over alumina support, modified with different cerium loadings. Ce loading increment causes an increase in the particle size from 1.26 nm to 2.3 nm, enhancing the MTBE oxidation (at 150 °C), and the selectivity toward CO_2. The high catalytic activity of Ru/ACe10 is attributed to the species Ce⁴⁺-O²⁻-M that could favor the oxygen transfer between the catalyst surface and the adsorbed species by a redox mechanism. Thus, CeOx plays an important role both enhancing the affinity between MTBE and catalyst during MTBE adsorption and promoting the catalytic activity for MTBE oxidation.