Kinetic analysis for low temperature catalytic hydro de-chlorination of PCBs (poly-chlorinated biphenyls) A thesis submitted to the Graduate School of the University of Cincinnati in partial fulfillment of the requirements for the degree of Master of Science in Material Science and Engineering at the Department of Mechanical and Materials Engineering of the College of Engineering and Applied Sciences by Akshay Anil Khopade B.E Polymer Engineering University of Pune, 2014 at March 2019 Committee Members: Mingming Lu, PhD (Chair) Gregory Beaucage, PhD Mark Wang, PhD Fumin Ren, PhD ABSTRACT The environmental report published by the United Nations in 2018 paints a very grim picture of our environmental health around the world. Persistent organic pollutants (POPs) like polychlorinated biphenyls (PCBs) are one of the major causes of this environmental degradation. The Stockholm Convention is a global treaty that seeks to contain additional contamination of environment with POPs and, wherever feasible, remediate the contamination that has already occurred. Although the production of PCBs has been banned around the world, affordable and effective PCB cleanup technologies are still in high demand, as existing treatment technologies are very costly. The project studies a low temperature removal technology using catalytic hydrogenation. Two types of PCBs were studied in a flask system, 3 PCB and 2, 3 PCB. The catalyst studied for the hydro de-chlorination reaction is palladium on activated carbon and triethylamine (Pd/C and Et3N). Parameters such as reaction time, gas flow rate and catalyst dose were investigated. In addition, the kinetics of the hydro de-chlorination reactions were studied, which is essential in large scale commercial applications. Reaction rate constants at different temperatures viz. 200C (room temperature), 500C and 800C, were investigated to better understand the activation energy. The de-chlorination rates at different temperatures were compared, which suggested a different optimum temperature for the hydro de-chlorination of 3- PCB and 2,3 - PCB. The Ea was 4.4 kJ/mole and 16.8 kJ/mole for 3 PCB and 2, 3 PCB respectively. The low Ea indicates that the reactions may be controlled by mass transfer of hydrogen. Keywords: Polychlorinated Biphenyls, Catalytic hydro de-chlorination, Remediation 1 2 Acknowledgements I would like to thank Dr. Mingming Lu, my committee chair and research advisor, for extending her knowledge and expertise towards this thesis. I also deeply appreciate other committee members: Dr. Gregory Beaucage, Dr. Fumin Ren and Dr. Mark Wang, for imparting their experience and support for my master’s research. The support from the Environmental Protection Agency (EPA Phase 1 & 2) is fully appreciated. I would like to thank my other colleagues: Junsong Zhang, Son Dong, Kolawale Omayosi and Juan Xu for their help in the experimentation and analysis. Lastly, I would like to thank my mom, dad and my fiancée Jolie Williams for their unending belief in me. 3 Table of Contents ABSTRACT………………………………………………………………………. 1 Acknowledgements……………………………………………………………….. 3 List of Figures…………………………………………………………………….. 7 List of Tables……………………………………………………………………… 9 Chapter 1 INTRODUCTION…...……………………………………………….. 10 Chapter 2 LITERATURE REVIEW…...………………………………………... 12 2.1 Health effects of PCBs..……………………………………………………………. 12 2.2 Sources of exposure to PCBs..……………………………………………………... 14 2.3 Classification of methods of PCB remediation……….……………………………. 16 2.3.1 Catalytic oxidation reactions.…………………………………………………….. 18 2.3.2 Catalytic hydro de-chlorination reaction…………………………………………. 22 Chapter 3 EXPERIMENTATION……………………………………………….. 25 3.1 Materials...………………………………………………………………………….. 25 3.2 Reaction setup……………………………………………………………………… 26 3.3 Chromatographic analysis………………………………..…………………………. 28 4 Chapter 4 RESULTS…...……….……………………………………………….. 32 4.1 Effect of the ratio of palladium doping on catalyst...……………………………….. 33 4.2 Gas flow rate and partial pressure…………………………………………………... 43 4.2.1 Total gas flow rate………………………………………………………………... 46 4.2.1.1 2,3 - PCB……………………………………………………………….. 46 4.2.1.2 3 - PCB…………………………………………………………………. 51 4.2.2 Partial pressure……………………………………………………………………. 56 4.2.2.1 2,3 - PCB……………………………………………………………….. 56 4.2.2.2 3 - PCB…………………………………………………………………. 61 4.3 Reaction temperature…….………………………………………………………… 66 4.4 Order of the reaction………………………………………………………………... 71 4.5 Activation Energy…………………………………………………………………... 76 Chapter 5 SUMMARY AND FUTURE WORK ..……………………………… 82 5.1 Summary…………………………………………………………………………… 82 5.2 Future work………………………………………………………………………… 86 References……………………………………………………………………….. 87 Appendix………………………………………………………………………… 92 List of congeners of PCB………………………………………………………………. 92 5 Properties of Aroclor mixtures………………………………………………………… 99 Sample excel sheet used for analysis………………………………………………….. 100 2,3 Dichlorobiphenyl reaction summary……………………………………………… 101 Temperature 20oC…...………………………………………………………… 101 Temperature 50oC…...………………………………………………………… 102 Temperature 80oC…...………………………………………………………… 103 3 Chlorobiphenyl reaction summary…………………………………………………. 104 Temperature 20oC…...………………………………………………………… 104 Temperature 50oC…...………………………………………………………… 106 Temperature 80oC…...………………………………………………………… 107 Activated Carbon (20oC)……………………………………………………… 108 Calibration curves and calibration checks...…………………………………………... 109 GCMS conditions……………………………………………………………………... 113 6 List of Figures 1. Illustration of de-chlorination of a polychlorinated compound by Hydro de-chlorination ………………………………………………...… 23 2. Chemical structure of 3-chlorobiphenyl………………………………………………... 25 3. Chemical structure of 2, 3-dichlorobiphenyl…………………………………………… 25 4. Experimental setup for hydro de-chlorination………………………………………….. 26 5. Calibration curve used for 3-PCB………………………………………………………. 29 6. EDS analysis of Pd/C catalyst with 0.5% Pd doping…………………………………… 35 7. EDS analysis of Pd/C catalyst with 5% Pd doping…...………………………………… 35 8. EDS analysis of Pd/C catalyst with 10% Pd doping….………………………………… 36 9. Catalyst Pd content vs de-chlorination rate for 2, 3 - PCB……………………………... 38 10. Catalyst Pd content vs biphenyl recovery rate for 2, 3 - PCB………………………….. 39 11. Catalyst Pd content vs de-chlorination rate for 3 - PCB………………………………... 40 12. Catalyst Pd content vs biphenyl recovery rate for 3 - PCB…………………………….. 41 13. Plot of average de-chlorination vs total flow rate for 2, 3-PCB………………………... 47 14. Plot of average de-chlorination vs total flow rate for 3-PCB…………………………... 52 15. Plot of average de-chlorination vs H2 partial pressure for 2, 3-PCB…………………… 57 16. Plot of average de-chlorination vs partial pressure for 3-PCB…………………………. 62 17. Temperature vs de-chlorination rate for 3-PCB………………………………………… 68 18. Temperature vs de-chlorination rate for 2, 3-PCB……………………………………… 70 19. Concentration vs reaction rate for 3-PCB………………………………………………. 73 20. Concentration vs reaction rate for H2…………………………………………………… 74 7 21. Arrhenius equation for 2,3 PCB………………………………………………………… 78 22. Arrhenius equation for 3 PCB…………………………………………………………... 79 8 List of Tables 1. Comparison of different Pd/C catalysts used for reaction……………………………… 34 2. Weight content of Pd in activated carbon by EDS analysis…………………………….. 36 3. Summary of data points generated for the analysis of catalyst Pd content for 2, 3-PCB. 37 4. Summary of data points generated for the analysis of catalyst Pd content for 3-PCB…. 37 5. Summary of data points generated for the analysis of gas flow rate for 2, 3-PCB…….. 46 6. Average de-chlorination rate and std. dev. for gas flow rates used with 2,3-PCB……... 49 7. t-test analysis changes in reaction yield with change in total flow rate in 2,3-PCB…... 50 8. Summary of data points generated for the analysis of gas flow rate for 3-PCB………... 51 9. Average reaction rate and std. dev. for gas flow rates used with 3-PCB……………….. 54 10. t-test analysis changes in reaction yield with change in total flow rate in 3-PCB…….. 55 11. Summary of data points generated for the analysis of H2 partial pressure for 2, 3-PCB.. 56 12. Average reaction rate and std. dev. for H2 partial pressure used with 2,3-PCB………... 59 13. t-test analysis changes in reaction yield with change in partial pressure in 2,3-PCB…... 60 14. Summary of data points generated for the analysis of H2 partial pressure for 3-PCB….. 61 15. Average reaction rate and std. dev. for H2 partial pressure used with 3-PCB………….. 64 16. t-test analysis changes in reaction yield with change in H2 partial pressure for 3-PCB... 65 17. Summary of data points generated for the analysis of reaction temperature for 3-PCB.. 67 18. Summary of data points generated for the analysis of reaction temperature for 2, 3-PCB …………………………………………………….. 69 9 Chapter 1 INTRODUCTION The environmental report published by the United Nations in 2018 paints a very grim picture of our environmental health around the world [1]. Our production, consumption and disposal practices have all caused significant damage to the land, fresh-water bodies and oceans, and to the flora and fauna supporting these ecosystems. Humans have only begun to understand the adverse effects of this ecological damage to their own health, thanks to improvements in medical science and technology towards understanding the nature of pollutants. Persistent organic pollutants (POPs) are organic compounds that can persist in the environment for a long time due to the resistance to most forms of decay photolytic, chemical and biological degradation [2]. Due to their very slow degradation, they can persist in the environment