Advanced Oxidation of Toluene Using Ni-Olivine Catalysts: Part 1. Synthesis, Characterization, and Evaluation of Ni-Olivine Catalysts for Toluene Oxidation

Abstract

This research focused on advanced oxidation of toluene by evaluating Ni-olivine catalysts in combination with ozone. Specifically, our objectives were to: (1) synthesize catalysts via electroless plating (ELP) and thermal impregnation (TI) techniques to impregnate nickel onto the olivine surface; (2) characterize Ni-olivine catalysts by Brunauer-Emmett-Teller specific surface area, electron microscopy, energy dispersive spectroscopy, and x-ray photoelectron spectroscopy to understanding the mechanisms of toluene oxidation; (3) determine the catalytic activity of the newly synthesized Ni-olivine catalysts in the oxidation of toluene; and (4) evaluate the influence of varying toluene and ozone concentrations on Ni-olivine oxidation efficiencies. Testing was performed in a continuous packed bed reactor (200C). Toluene (200 to 600 ppmv) and ozone (70 to 800 ppmv) were injected into the heated reactor, while inlet and outlet concentrations were measured using gas chromatography. Results indicated that 90% of toluene was oxidized within a 1 s residence time using ELP and TI catalyst synthesis techniques and 70 ppmv ozone. Microscopic and spectroscopic analyses revealed porous structures and a nickel film uniformly coating the electroless plated olivine surface, mostly comprised of Ni-P-O, while the thermally impregnated Ni-olivine possessed sparingly deposited Ni2O3 compounds on the surface. An increase in ozone concentrations increased toluene oxidation efficiencies, whereas an increase in toluene concentrations temporarily decreased toluene oxidation efficiencies. Knowledge obtained from this research can be used for synthesizing advanced catalysts for toluene oxidation at significantly lower temperature.