CHEMICAL KINETICS OF ORGANOPHOSPHORUS FIRE SUPPRESSANTS A Dissertation by TRAVIS GLENN SIKES III Submitted to the Office of Graduate and Professional Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Chair of Committee, Eric L. Petersen Co-Chair of Committee, M. Sam Mannan Committee Members, Timothy Jacobs Waruna Kulatilaka Head of Department, Andreas A. Polycarpou August 2018 Major Subject: Mechanical Engineering Copyright 2018 Travis Sikes ABSTRACT Organophosphorus compounds (OPCs) have significant fire suppression capabilities but are not well understood. Chemical kinetics mechanisms can provide invaluable information about how OPCs suppress flames; however, the currently available OPC mechanisms are deficient and could use further refinement. In this dissertation, two types of experimental data were taken which can be used as benchmarks to improve mechanisms: laminar flame speeds and ignition delay times. In the laminar flame speed experiments, dimethyl methylphosphonate (DMMP), diethyl methylphosphonate (DEMP) diisopropyl methylphosphonate (DIMP), and trimethyl phosphate (TEP) were added to hydrogen/air and methane/air mixtures to assess their suppression capabilities at 0.1% and 0.3% (DMMP only) of the total mixture volume. The experiments were performed in an optically tracked, spherically expanding flame setup at 1 atm and 120 °C. Results show a 30% decrease in laminar flame speed for all OPCs at 0.1% on the methane/air parent mixture. For the hydrogen/air mixtures, the OPCs differentiate themselves by having an increasing suppression effect corresponding with higher carbon moiety, i.e., DIMP (20% overall reduction), > TEP (15%) > DEMP (13%) > DMMP (9%). The OPCs also have an increasing effect with increasing equivalence ratio on hydrogen/air. Ignition delay time experiments were performed in a glass shock tube at ICARE – CNRS. The simple OPCs studied were dimethyl phosphite (DMP), trimethyl phosphate (TMP), and diethyl phosphite (DEP). The OPCs were added as 10% of the fuel in hydrogen/ethylene mixtures diluted with 98% argon. The results show that the three OPCs behave similarly in both ii hydrogen and ethylene mixtures by decreasing the ignition delay time ~30% at high temperatures and then decreasing in effect until the neat and OPC data are indistinguishable. Additionally, quantum chemistry calculations were performed to improve an existing OPC submechanism using ROCBS-QB3 level of theory for thermochemistry and G3X-K for the transition state calculations. The thermochemistry data are an improvement on previous OPC mechanisms, but overall the model does not predict the ignition delay times. Further OPC submechanism improvement is needed to resolve simple OPC reactions so that larger OPC submechanisms will be able to properly predict OPC behavior in applications such as fire suppression. iii ACKNOWLEDGMENTS I would like to thank my advisor, Dr. Eric Petersen. It has been a long journey that began in spring 2011’s undergraduate fluid mechanics class and has led me here. I cannot imagine a better advisor and he is one of the biggest reasons why I’ve come as far as I have. He has taught me persistence in the face of adversity, to always carefully consider all possibilities for anything from an experimental error to developing a new program, and most importantly, through his own example, how to accomplish great things with a strong work ethic. Dr. Petersen is who I imagine as the ideal advisor, teacher, academic, and supervisor. Thank you for taking a chance on me and giving me your support. It has meant more than you may ever know. I would like to thank my committee co-chair, Dr. Sam Mannan, and my committee members, Dr. Jacobs, and Dr. Kulatilaka for their guidance and support throughout the course of this research. I am extremely grateful to Dr. Laurent Catoire for hosting me at ENSTA ParisTech. Through this experience I learned about French culture and was able to live the French life for 6 months. My trip was life changing and I will never forget it. I also thank Dr. Pascal Diévart for his time and patience. He taught me everything I know about quantum chemical modeling, and he has also helped me in performing the transition state theory calculations while I was busy with thermochemistry. A thank you must go to Dr. Nabiha Chaumeix and Dr. Andrea Comandini for their help both professional and personal during my time at CNRS-Orléans. I was only able to iv accomplish the quantity and quality of ignition delay experiments with their experience and expertise. Working with both of them was truly a pleasure. Thanks to my friends and colleagues within the Petersen Research Group. Being able to always have someone that I can bounce ideas off of, get help with a problem, or even just joke around with has made my graduate experience an absolute joy. I only hope that I can one day find another group of coworkers as great as the one I’m leaving, past and present. Finally, a special thanks to my family for their never-ending encouragement and to my wife for her patience during my entire graduate career and her unshakable love. v CONTRIBUTORS AND FUNDING SOURCES This work was supported by a dissertation committee consisting of my committee co-chairs Dr. Eric L. Petersen, Nelson-Jackson professor of the Department of Mechanical Engineering, and Dr. M. Sam Mannan, regents professor of the Department of Chemical Engineering and director of Mary Kay O’Connor Process Safety Center; as well as, my committee members Dr. Timothy Jacobs and Dr. Waruna Kulatilaka, professor and associate professor in the Department of Mechanical Engineering, respectively. During the oral defense Dr. Chad Mashuga, assistant professor in the Department of Chemical Engineering, stood in for Dr. M. Sam Mannan. Flame speed modeling and ignition delay time measurements in Chapter III and Chapter IV were performed with assistance from Dr. Nabiha Chaumeix, Research Director of ICARE-CNRS (Orléans, France), and Dr. Andrea Comandini of ICARE-CNRS. Quantum chemistry modeling efforts in Chapter V were performed in part with Dr. Laurent Catoire, Director of the UCP in ENSTA ParisTech, and Dr. Pascal Diévart, professor at ENSTA Paristech. Dr. Pascal Diévart has performed the Arrhenius parameter calculations for the updated reactions. All other work conducted for the dissertation was completed by the student independently. This research was supported by the Mary Kay O’Connor Process Safety Center, a STEM fellowship from the Chateaubriand Fellowship Program, .and the Defense Threat Reduction Agency (DTRA) under grant number HDTRA1-16-1-0031. vi TABLE OF CONTENTS Page ABSTRACT .......................................................................................................................ii ACKNOWLEDGMENTS ................................................................................................. iv CONTRIBUTORS AND FUNDING SOURCES ............................................................. vi TABLE OF CONTENTS .................................................................................................vii LIST OF FIGURES ........................................................................................................... ix LIST OF TABLES ...........................................................................................................xii CHAPTER I INTRODUCTION AND LITERATURE REVIEW .................................... 1 I.1 References ...................................................................................................... 8 CHAPTER II LAMINAR FLAME SPEED METHODOLOGY .................................... 11 II.1 TAMU Spherically Expanding Flame Facility ............................................ 11 II.2 Experimental Analysis ................................................................................. 16 II.3 References .................................................................................................... 23 CHAPTER III LAMINAR FLAME SPEED MEASUREMENTS.................................. 25 III.1 Methane ........................................................................................................ 28 III.2 Hydrogen ...................................................................................................... 32 III.3 Fire Suppressant Comparison ....................................................................... 36 III.4 Flame Speed Sensitivity Analysis ................................................................ 38 III.5 References .................................................................................................... 41 CHAPTER IV IGNITION DELAY TIME MEASUREMENTS .................................... 44 IV.1 Experimental Facility and Procedure ........................................................... 46 IV.2 Mixtures and Preparation ............................................................................. 53 IV.3 OPC Ignition Delay Times in Hydrogen Mixtures ...................................... 55 IV.4 OPC Ignition Delay Times in Ethylene Mixtures ........................................ 59 IV.5 References .................................................................................................... 63 vii CHAPTER V QUANTUM CHEMISTRY MODELING ................................................ 65 V.1 Heat of Formation ........................................................................................ 65 V.2 Sensible Enthalpy, Specific Heat, and Entropy ...........................................