PYROLYSIS AND OXIDATION OF SUFLUR MUSTARD SIMULANTS A Dissertation Presented to the Faculty of the Graduate School of Cornell University In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy by Xin Zheng January 2011 © 2011 Xin Zheng PYROLYSIS AND OXIDATION OF SULFUR MUSTARD SIMULANTS Xin Zheng, Ph. D. Cornell University 2011 The reaction kinetics of diethyl sulfide (C2H5-S-C2H5) and ethyl methyl sulfide (C2H5-S-CH3), simulants for the chemical warfare agent, sulfur mustard (ClC2H4-S- C2H4Cl), was studied at high temperatures under highly diluted conditions. This work has been undertaken with the goals to understand the destruction of sulfur mustard simulants at early stages and explore routes relevant to emissions under off-design incineration modes, such as fuel rich conditions due to inhomogeneous mixing. The studies were conducted in an atmospheric pressure, turbulent flow reactor with a Reynolds number of approximately 5000, at four different operating temperatures between 630 ºC and 740 ºC. These experiments, with an initial loading of the simulants of 150/100 ppm, involved either a nitrogen carrier gas for pyrolysis experiments or a nitrogen–oxygen carrier gas (including approximately stoichiometric conditions and fuel-lean conditions with an equivalence ratio of approximately 0.1) for oxidation experiments. On-line, extractive sampling in conjunction with analysis by fourier transform infra-red (FT-IR) spectrometry and gas chromatography/mass spectrometry (GC/MS) was performed to quantify species composition at four specific locations along the centerline of the turbulent flow reactor. Species concentrations were represented as a function of residence time in the reactor. For the pyrolysis of diethyl sulfide, a destruction efficiency of 70% was observed for the 740 ºC operating condition at a residence time of 0.06 second. Ethylene, ethane, and methane were detected at significant levels. In the oxidation experiments, the destruction of diethyl sulfide was significantly enhanced. Complete destruction was observed in the 740 ºC operating condition at a residence time of 0.06 second with low O2 loading and in the 740 ºC operating condition at a residence time of 0.03 second with high O2 loading. Carbon monoxide, carbon dioxide, formaldehyde as well as the pyrolysis product species, were detected in the oxidation experiments. The experimental investigations of diethyl sulfide were complemented by mechanism development along with thermochemical properties. The present model of H-C-S-O system consists of approximately 1000 elementary reactions among 300 species. Mechanism predictions reproduced the experimental results satisfactorily. Rate of production analysis under several conditions in the present work showed that the initiation of diethyl sulfide destruction is through unimolecular dissociation via C- S bond cleavage. Once the radical pool is established, hydrogen abstraction becomes primary destruction routes. β-scission of the derived radicals forms thioaldehydes and subsequent multi-hydrogen abstractions and β-scissions convert thioaldehydes to sulfur dioxide. Sensitivity analysis indicated that the reactions, having important effects on radical pools, to which mechanism predictions are the most sensitive. Destruction of ethyl methyl sulfide was observed to be significantly slower than that of diethyl sulfide under the same conditions as those for diethyl sulfide and similar products were experimentally observed as those from diethyl sulfide. The kinetic mechanism is still under development. The formation of the products was explained by a scheme by analogy to that of diethyl sulfide. Significantly slower rates of pyrolysis of ethyl methyl sulfide were explained by the different destruction efficiencies including lower hydrogen abstraction rates, and lower hydrogen atom production as a result of thermal decomposition pathways. BIOGRAPHICAL SKETCH Xin Zheng was born on April 13, 1979, in Shaowu, a small town surrounded by forests and mountains on the east coast of China (Fujian province). He was growing there, where he began his education at the Tongtai elementary school in 1985 and then attended No.1 middle school in 1991 and No. 1 high school in 1994. In the summer of 1997, He advanced to the University of Science and Technology of China in Hefei, the capital of Anhui province on the central-east part of China. In June of 2001, He graduated with dual bachelor degrees in Mechanical Engineering and Electronic Engineering. That fall, he entered the Fire Science Laboratory from which he obtained a Master of Science degree in Fire Protection Engineering in June of 2004. He moved to Ithaca, New York, USA, in August of 2004, where he has been studying at Cornell University, in the Sibley School of Mechanical and Aerospace, to complete a doctoral degree. iii ACKNOWLEDGMENTS I would like to begin by acknowledging the Army Research Office’s funding of the work present in the dissertation, under contract W911NF0410120 and through instrument grant DURIP W911NF0610142. I owe the most to my joint advisors, Professor Elizabeth Mills Fisher and Professor Frederick Caskey Gouldin, who were always to provide insightful suggestions and directions to the work, and in particular in the first couple years when I had numerous troubles with the ventilation system to get the study proceed, their encouragement made today’s achievement come true. I thank Professor Harry Floyd Davis for serving on my committee and thank Professor Paul Houston for giving advices on choosing courses in the field of chemistry. I thank my collaborators, Professor Joseph W. Bozzelli and his coworkers, Li Zhu and Rubik Asatryan, at New Jersey Institute of Technology, for their great contributions to the mechanism development. I would also like to thank the Sibley school people, in particular, Richard Schmidt and Matthew Ulinski, who always offered their hands when I needed help in the laboratory. Many people have supported me throughout my stay at Cornell and I owe a lot to all of them. I especially thank my wife, Hui Zhang, for staying in cold Ithaca with me for the Ph.D. life. I thank my great parents, Guirong Zheng and Yune Pan, and parents in law, Qinhe Zhang and Peihong Fang. iv TABLE OF CONTENTS BIOGRAPHICAL SKETCH III ACENOWLEDGEMENTS IV TABLE OF CONTENTS V LIST OF FIGURES VIII LIST OF TABLES XII CHAPTER 1 INTRODUCTION 1.1 Overview of chemical warfare agents 1 1.2 Disposal past and present: motivation for present research 5 1.3 Overview of combustion chemistry of sulfur compounds 7 1.3.1 Hydrogen sulfide oxidation and pyrolysis 8 1.3.2 Inhibition and sensitization of hydrocarbon combustion by sulfur species 10 1.3.3 Pyrolysis of sulfide and mercaptan 14 1.4 Sulfur mustard simulants 16 1.5 Dissertation overview 19 References 21 CHAPTER 2 EXPERIMENTAL AND COMPUTATIONAL STUDY OF DIETHYL SULFIDE PYROLYSIS AND MECHANISM 2.1 Introduction 26 2.2 Experimental apparatus and methodology 2 7 2.2.1 Materials 27 2.2.2 Flow reactor 2 7 2.2.3 Sampling&Analysis 29 2.3 Mechanism and model calculation 3 1 v 2.4 Results and discussion 3 3 2.5 Summary and conclusions 4 3 2.6 Acknowledgements 43 References 44 CHAPTER 3 EXPERIMENTAL AND COMPUTATIONAL STUDY OF OXIDATION OF DIEHTYL SULFIDE IN A FLOW REACTOR 3.1 Introduction 48 3.2 Experimental apparatus and methodology 49 3.3 Mechanism construction and computational method 50 3.4 Results and discussion 60 3.5 Summary and conclusions 74 3.6 Acknowledgements 75 References 76 CHAPTER 4 PYROLYSIS AND OXIDATION OF ETHYL METHYL SULFIDE IN A FLOW REACTOR 4.1 Introduction 80 4.2 Experimental apparatus and methodology 81 4.3 Results 84 4.4 Discussion 97 4.4.1 Mechanism of pyrolysis of ethyl methyl sulfide 97 4.4.2 Destruction efficiency 100 4.4.3 Mechanism of oxidation of ethyl methyl sulfide 102 4.5 Conclusions 107 4.6 Acknowledgements 107 References 108 vi APPENDIX A EXPERIMENTAL APPARATUS AND METHODOLOGY A.1 Overview 11 0 A.2 Flow reactor 110 A.2.1 Flow feed system 11 1 A.2.1.1 Main flow 11 2 A.2.1.2 Secondary flow 11 3 A.2.1.3 Reaction section 11 5 A.2.2 Sampling system 12 3 A.3 Flow conditions in the reaction section 1 29 A.3.1 Gas temperatures 1 29 A.3.2 Mixing conditions 13 0 A.3.3 Leak test on the flow reactor 13 1 A.4 Analysis methods 139 A.4.1 Fourier-transform infrared spectroscopy 139 A.4.2 Gas chromatography-Mass spectrometry 141 References 156 KINETIC MECHANISM OF PYROLYSIS OF DIETHYL SULFIDE B.1 Kinetic mechanism used for calculations performed in Chapter 2 157 B.2 Thermochemical properties for diethyl sulfide pyrolysis (Chapter 2) 163 KINETIC MECHANISM OF OXIDATION OF DIETHL SULFIDE C.1 Kinetic mechanism used for calculations performed in Chapter 3 168 C.2 Thermochemical properties for diethyl sulfide oxidation (Chapter 3) 199 vii LIST OF FIGURES 1.1 Molecular structures of blister agents 4 1.2 Molecular structures of mustard simulants 18 2.1A Pyrolysis of diethyl sulfide at 630 °C 37 2.1B Pyrolysis of diethyl sulfide at 670 °C 37 2.1C Pyrolysis of diethyl sulfide at 700 °C 38 2.1D Pyrolysis of diethyl sulfide at 740 °C 38 2.2 Element balances, defined as the mass percent of a given element that is detected in the form of quantified species shown in Figure 2.1A-D. 39 40 2.3 Comparison of experimental elemental loss with predicted contribution of major undetectable species, H2, CH3CH*S and CH2*S (regions between 40 lines) 2.4 Major reaction pathways 41 3.1A Pyrolysis of CCSCC at 630 °C 58 59 3.1B Pyrolysis of CCSCC at 670 °C 58 59 3.1C Pyrolysis of CCSCC at 700 °C 59 60 3.1D Pyrolysis of