Catalytic oxidation of volatile compounds generated during frying process using sunflower oil

Abstract

The main goal of this study is to investigate the effect of metal type, metal oxide type and metal/oxide loading on the conversion as a function of temperature for the combustion of sunflower oil over modified single step sol-gel made Al2O3 supported metal and mixed metal oxides. All catalysts were tested at 170 oC and catalysts giving good activity among them were tested also at 195 oC. As a monometallic catalysts, Ni/Al2O3 (10, 25, 50 % Ni loaded), Ni/Al2O3 (50 % Ni loaded) derived from different Ni precursors, Mn/Al2O3 (50, 70 % Mn loaded) and as a bimetallic catalysts, Ni- Mn2O3/Al2O3 with Ni/Mn mass ratios of 20:56 and 23:66 catalysts were synthesized by a modified single step sol-gel method. In addition, in synthesizing step of bimetallic catalysts, the order of adding precursor was studied. The catalytic activities of all the catalysts were compared to 3% Pt/alumina. The combustion performances of pure Al2O3 and catalyst coated aluminum plates were also considered and volatile compound analysis was monitored by GC-MS and the amounts of CO and CO2 generated during the combustion were calculated quantitatively from GC analyses. The characterization of the samples was performed by XRD and BET techniques and it was observed that among the monometallic oxide catalysts, 50% MnxOy/Al2O3 showed slightly better activity at 170 oC due to the its highly reducible oxide property. Among mixed metal/metal oxide catalysts, 20% Ni/56% Mn2O3/Al2O3 (First Ni precursor added) was the catalyst demonstrated the highest catalytic activity at both temperatures. It seems to be due to the interaction between nickel and manganese oxide. In addition, the combustion was also carried out by using catalyst coated aluminum plates to observe if the best catalyst formulation found from the studies on the powder catalysts would be applicable for the self-cleaning metal plates used in the household ovens. In fact, the catalyst coated plates showed higher conversion at 170 oC in 1 h than that observed on the powder catalyst due to the elimination of internal mass transfer limitation.