ALUMINA SUPPORTED MANGANESE-BASED CATALYSTS FOR CATALYTIC OZONATION OF ACETONE AND TOLUENE IN AIR
Date
2021-09-14
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
0000-0002-7171-2027
Type
Thesis
Degree Level
Doctoral
Abstract
Volatile organic compounds (VOCs) are hazardous substances produced from anthropogenic emissions and are among the main sources of air pollution. Catalytic ozonation is an efficient process for VOCs removal from indoor air at room temperature. In this Ph.D. thesis, alumina supported Mn oxides which are considered as one of the most active catalysts for ozonation of VOCs are used to oxidize acetone and toluene in air at room temperature. The primary aim of this research is to develop the catalyst for catalytic ozonation of VOCs at room temperature. Therefore, the influence of addition of second metal oxide, catalyst preparation procedure, and calcination temperature on catalytic properties and activity in ozonation of VOCs were investigated. In addition, kinetics and mechanism of the catalytic ozonation reaction were studied to clarify the role of metal oxide and support in the reaction pathway.
It was found that addition of manganese and cobalt at lower loading levels (2.5% or 5%) to single metal oxide catalysts improved the catalytic activity significantly. By changing the loading of the secondary metals, its oxidation state changed. It is suggested that lower oxidation state of the secondary metal improves ozone decomposition and oxidation of acetone.
Polyol process can produce catalysts with smaller manganese cluster size, higher surface area, and lower oxidation states than impregnation method which led to enhancing the VOC conversion. An increase in the calcination temperature increased the manganese particle size while reducing the surface area and dispersion of the catalyst. The results indicated that the oxidation state of manganese shifted to lower values by increasing the calcination temperature. An increase in the calcination temperature to 800 ÂșC, increased acetone oxidation, while no significant change was observed in toluene oxidation. In the binary mixture of acetone and toluene, the oxidation behaviors were different from the single component system. The toluene conversion was promoted whereas the acetone conversion was inhibited.
Kinetic modeling was conducted on catalytic ozonation of acetone using the catalysts that exhibited the best catalytic activity. The kinetic experimental data were expressed well by Langmuir-Hinshelwood dual-site (LHd) mechanism, indicating that both MnOx and Al2O3 sites are essential and involved in the reaction. The cooperation of these sites on the surface of the catalysts provides the adjacent attack and migration of intermediates and enables the dual-site mechanism.
Description
Keywords
Catalytic ozonation, VOC, Calcination Temperature, Preparation Method,
Mixed Oxides, Manganese Oxides, Kinetic Study
Citation
Degree
Doctor of Philosophy (Ph.D.)
Department
Chemical and Biological Engineering
Program
Chemical Engineering