EVALUATION OF UV-PCO AIR CLEANERS PERFORMANCE AT LOW LEVEL VOCS CONCENTRATION Alireza Aghighi A Thesis in The Department of Building, Civil and Environmental Engineering Presented in Partial Fulfillment of the Requirements For the Degree of Master of Applied Science (Civil Engineering) at Concordia University, Montréal, Québec, Canada August 2013 © Alireza Aghighi, 2013 CONCORDIA UNIVERSITY School of Graduate Study This is to certify that the thesis prepared By: Alireza Aghighi Entitled: Evaluation of UV-PCO Air Cleaners Performance at Low Level VOCs Concentration and submitted in partial fulfillment of the requirements for the degree of Master of Applied Science (Civil Engineering) complies with the regulations of the University and meets the accepted standards with respect to originality and quality. Signed by the final examining committee: _______________________________ Chair Dr. Catherine Mulligan ____________________________ Examiner Dr. Kudret Demirli ____________________________ Examiner Dr. Zhi Chen ___________________________ Supervisor Dr. Fariborz Haghighat Approved by ___________________________________________________ Chair of Department or Graduate Program Director ___________________________________________________ Dean of Faculty Date ___________________________________________________ ii ABSTRACT Evaluation of UV-PCO Air Cleaners Performance at low level VOCs Concentration Alireza Aghighi Volatile organic compounds (VOCs) constitute the vast majority of indoor air contaminants. In design of ultraviolet photo-catalytic oxidation (UV-PCO) air cleaner system, the focus must be in selecting an appropriate catalyst that can transform all contaminants to harmless gases. Some produced contaminants may promote or inhibit the photocatalytic reactions, or even lead to deactivation of the catalyst. The PCO reactions of two classes of VOCs, light alcohols and alkanes (C5-C10) were studied with different types of nano titanium dioxide catalysts. The influence of relative humidity on oxidation rate of tested VOCs was discussed in detail to establish ideal operational conditions for the selected group of VOCs. A series of laboratory experiments was conducted with a pilot four-parallel duct system setup to test the VOCs in very low concentration levels which represents a typical indoor air environment. The experiments were carried out with different types of nano TiO2 catalysts with UV lamps. A new type of titanium dioxide catalyst was specifically developed for this study to enhance the efficiency of PCO system. A systematic method was used to develop and test the synthesized photocatalysts, which helped to improve the overall performance of test system. The performance of different catalysts was studied at different humidity conditions and different VOCs concentrations. The research objective was to develop a correlation between the PCO kinetic rate constants and physical characteristics of indoor VOCs. These correlations may be employed to eliminate the need of further experiments with every individual VOCs and they also could facilitate the design process of future PCO air cleaner. The physical characteristics of VOCs were used to estimate the performance of the PCO catalysts in a steady-state environmental test condition. The photocatalytic removal efficiency of VOCs and formation of intermediates and byproducts were studied with and without ozone generation UV lamps. iii ACKNOWLEDGMENTS I would first like to express my gratitude to my advisor, Dr. Fariborz Haghighat, for his guidance, support, and patience throughout the course of my study. Without him I would not have achieved my goals and his mentorship allowed me to explore and learn more than I could ever throughout my research study. I have been blessed with a wonderful research group who have supported my research efforts with helpful discussions and cooperation throughout the experimental research. I would like to specially thank Dr. Chang-Seo Lee for the valuable advices and support during my research. I would also sincerely appreciate my colleagues, Dr. Lexuan Zhong, Ms. Donya Farhanian and Ms. Mitra Bahri for their cooperation and friendship. I extend a special thanks to my parents and beloved family, for their support, guidance and love. iv Table of Contents List of Figures ................................................................................................................vii List of Tables ...................................................................................................................xi Nomenclature .................................................................................................................xii Chapter I: Introduction ..................................................................................................1 1.1. Background ..........................................................................................................1 1.2. Research Objectives .............................................................................................4 Chapter II: Literature Review ........................................................................................5 2.1. Introduction ..........................................................................................................5 2.3.1. External Mass Transfer .................................................................................7 2.3.2. Internal Mass Transfer ..................................................................................8 2.3.3. Principle of PCO Reactions .......................................................................10 2.4. Ionization Energy (IE) ........................................................................................14 2.5. Kinetic Modeling of PCO ..................................................................................15 2.5.1. Langmuir-Hinshelwood (L-H) ...................................................................16 2.6. Hydroxyl Radical (OH) ......................................................................................18 2.7. Ozone (O3) .........................................................................................................18 2.7. Catalyst ..............................................................................................................19 2.7.1. Catalyst Material .........................................................................................19 2.7.2. Catalyst Support .........................................................................................22 2.7.3. Catalyst Lifetime, Degradation ..................................................................22 2.8. Light Source .......................................................................................................23 2.8.1. Light Intensity ............................................................................................25 2.9. Temperature ........................................................................................................25 2.10. Humidity ..........................................................................................................26 2.11. Air Flow ............................................................................................................27 2.13. Volatile Organic Compounds (VOC)................................................................ 29 2.13.1. Alkanes .....................................................................................................31 Chapter III: UV-PCO Experimental Setup and Methodology ..................................34 3.1. Introduction ........................................................................................................34 3.2. PCO System........................................................................................................ 35 3.2.1 Experimental Setup .....................................................................................35 3.2.2. Generation System .....................................................................................39 3.3. Chemicals ...........................................................................................................40 3.4. Sampling Method ...............................................................................................40 3.7. Catalyst Preparation ...........................................................................................42 3.7.1. Dip-Coating .................................................................................................44 v 3.7.2. Sol-Gel (SG) ...............................................................................................45 3.7.3. Preparation Method Description .................................................................49 3.7.3. Ozone Interference .....................................................................................53 3.8. Preliminary Experiments ....................................................................................55 3.9. Experimental Test Procedure ..............................................................................56 3.10. Langmuir Adsorption Isotherm ........................................................................58 Chapter IV: Experimental Results ...............................................................................62 4.1. VOCs Kinetic and Intermediates ........................................................................62 4.1.1. Ethanol (C2H6O) .......................................................................................62