OPTIMIZING THE STRUCTURAL CHARACTERISTICS OF DRAFT TUBE IN A SPOUTED BED REACTOR FOR BEST PHOTOCATALYTIC DEGRADATION OF TOLUENE AND CO2 SELECTIVITY USING RESPONSE SURFACE METHODOLOGY

In this study, toluene degradation efficiency and carbon dioxide (CO2) selectivity in a spouted bed reactor with a porous draft tube are optimized using the response surface methodology. For this purpose, titanium dioxide (TiO2) is used as a catalyst for photocatalytic degradation of gaseous toluene in a dynamic mode under ultraviolet (UV) irradiation. The influence of the draft tube parameters' (including height, diameter, gap, and porosity) on toluene degradation efficiency and CO2 selectivity (as the response variables) is investigated by central composite design. Analysis of variance (ANOVA) is applied to evaluate the significance of the variables' effects and the interaction between them. Results show that maximum toluene degradation efficiency of 78.1% and maximum CO2 selectivity of 88.7% are obtained at 1.99 cm draft tube height, 1.3 cm draft tube diameter, 1.3 cm gap, and 60% draft tube porosity. The highest F-values indicate that the gap is the most important variable affecting the toluene degradation efficiency and CO2 selectivity, while the draft tube diameter is the second most important variable. The results of experiments at optimal levels of parameters with three replications show a maximum toluene degradation efficiency of 78.8% (SD = 0.62) and maximum CO2 selectivity of 89.1% (SD = 0.46). The study reveals that the spouted bed reactor with a porous draft tube has a good stability for volatile organic compounds (VOCs) degradation and mineralization.