COOL-FLAME COMBUSTION STUDIES OF SOME HYDROCARBONS BY GAS CHROMATOGRAPHY DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By GEORGE KYRYACOS, B.S., M.S. •vKHHH;- The Ohio State University 1956 Approved by: Adviser Department of Chemistry ACKNOWLEDGMENT The author is indebted to Professor Cecil E. Boord whose enthusiasm and faith in him made the progress herein reported possible. His eternal gratitude goes to his wife, LaVerne, who has stood by him with encouragement and who has sacrificed much. This investigation was made financially possible by the Firestone Tire and Rubber Company Fellowship for which the author is deeply grateful. ii TABLE OP CONTENTS Page LIST OP TABLES............ iv LIST OF ILLUSTRATIONS..... v CHAPTER I...............INTRODUCTION.......... 1 CHAPTER II. LITERATURE SURVEY ....... 3 Gas Chromatography . 3 The Cool F l a m e . 10 Mechanism of Oxidation . 15 CHAPTER III.............EXPERIMENTAL.......... 25 Gas Chromatographic Apparatus . 25 The Cool-Flame Apparatus. 35 Sampling Procedure.......... 39 The Cool Flame . J4.I Blending Studies . i+7 Hydrocarbon Cool-Flame Temperature Profiles . Lj.9 Cool Flame to Explosion .... 62 CHAPTER IV. ANALYSIS OF THE COOL-FLAME COMBUSTION PRODUCTS OF SOME HYDROCARBONS BY GAS CHROMATOGRAPHY 6^ n-Pentane. 6I4. n - H e x a n e . 71 2-Methylpentane ............... 77 3-Methylpentane ............... 82 2,2-Dimethylbutane 87 n-Heptane. 93 Discussion of the Results . 99 CHAPTER V.................SUMMARY.............118 CHAPTER VI. SUGGESTIONS FOR FURTHER RESEARCH. 120 BIBLIOGRAPHY .................................. 123 iii LIST OP TABLES TABLE Page 1. ANALYSIS OP STOICHIOMETRIC MIXTURE OP n-PENTANE-AIR BEFORE AND AFTER COOL FLAME ... 65 2. ANALYSIS OP STOICHIOMETRIC MIXTURE OF n-HEXANE-AIR BEFORE AND AFTER COOL FLAME . 72 3. ANALYSIS OF STOICHIOMETRIC MIXTURE OF 2-METHYLPENTANE-AIR BEFORE AND AFTER COOL FLAME .......................................78 1*. ANALYSIS OF STOICHIOMETRIC MIXTURE OF 3-METHYLPENTANE-AIR BEFORE AND AFTER COOL FLAME ....................................... 83 5. ANALYSIS OF STOICHIOMETRIC MIXTURE OF 2,2-DIMETHYLBUTANE-AIR BEFORE AND AFTER COOL FLAME.................................. 89 6 . ANALYSIS OF STOICHIOMETRIC MIXTURE OF n-HEPTANE-AIR BEFORE AND AFTER COOL FLAME . 95 iv LIST OP ILLUSTRATIONS FIGURE Page 1. SCHEMATIC DIAGRAM OP APPARATUS ............ 26 2. SEPARATION OF A GAS MIXTURE ON A 16-FOOT MS-5A COLUMN................................ 28 3. SEPARATION OF GAS MIXTURE ON AN 8-FOOT SILICA GEL COLUMN............................ 31 4. DETERMINATION OF MOISTURE IN ATMOSPHERE ON AN 8-FOOT SILICA GEL COLUMN PRECEDED BY A 2-INCH CALCIUM CARBIDE TUBE................. 31 5. SIXTEEN FOOT DOWTHERM-A COLUMN, \\% BY WEIGHT ON FIREBRICK C - 2 2 .......................... 33 6 . COOL-FLAME APPARATUS ....................... 36 7. PHOTOGRAPH OF n-HEXANE COOL FLAME.......... 1*2 8 . n-HEXANE BLENDED WITH AIR, ACETONE AND DIISOPROPYL.................................. 1*8 9. TEMPERATURE PROFILE OF n-PARAFFINS ........ 51 10. TEMPERATURE PROFILES OF DISUBSTITUTED PENTANES.................................... 52 11. TEMPERATURE PROFILES OF SOME CYCLOPARAFFINS AND ALKYLCYCLOPARAFFINS..................... 56 12. TEMPERATURE PROFILES OF SOME OLEFINS .... 58 13. TEMPERATURE PROFILE OF CYCLOHEXENE COOL FLAME........................................ 59 11*. CHROMATOGRAM OF A 20 cc. SAMPLE FROM THE COMBUSTION OF n-PENTANE TAKEN 2 cm. POST COOL FLAME ON THE DOWTHERM-A COLUMN........ 67 v FIGURE Page 15. CHROMATOGRAM OF A 20 cc. SAMPLE FROM THE COMBUSTION OF n-PENTANE TAKEN 2 cm. POST COOL FLAME ON THE SILICA GEL COLUMN......... 68 16. CHROMATOGRAM OF A .5 cc. SAMPLE FROM THE COMBUSTION OF n-PENTANE TAKEN 2 cm. POST COOL FLAME ON THE M.S.-5A COLUMN........... 69 17. CHROMATOGRAM OF A 20 cc. SAMPLE FROM THE COMBUSTION OF n-HEXANE TAKEN 2 cm. POST COOL FLAME ON THE DOWTHERM-A COLUMN......... 73 18. CHROMATOGRAM OF A 20 cc. SAMPLE FROM THE COMBUSTION OF n-HEXANE TAKEN 2 cm. POST COOL FLAME ON THE SILICA GEL COLUMN......... 7L[ 19. CHROMATOGRAM OF A .5 cc. SAMPLE FROM THE COMBUSTION OF n-HEXANE TAKEN 2 cm. POST COOL FLAME ON THE M.S.-5A COLUMN........... 75 20. CHROMATOGRAM OF A 20 cc. SAMPLE FROM THE COMBUSTION OF 2-METHYLPENTANE TAKEN 2 cm. POST COOL FLAME ON THE DOWTHERM-A COLUMN . 79 21. CHROMATOGRAM OF A 20 cc. SAMPLE FROM THE COMBUSTION OF 2-METHYLPENTANE TAKEN 2 cm. POST COOL FLAME ON THE SILICA GEL COLUMN ... 80 22. CHROMATOGRAM OF A .5 cc. SAMPLE FROM THE COMBUSTION OF 2-METHYLPENTANE TAKEN 2 cm. POST COOL FLAME ON THE M.S.-5A COLUMN . Ql 23. CHROMATOGRAM OF A 20 cc. SAMPLE FROM THE COMBUSTION OF 3-METHYLPENTANE TAKEN 2 cm. POST COOL FLAME ON THE DOWTHERM-A COLUMN . 81+ 21|. CHROMATOGRAM OF A 20 co. SAMPLE FROM THE COMBUSTION OF 3-METHYLPENTANE TAKEN 2 cm. POST COOL FLAME ON THE SILICA GEL COLUMN . 85 25. CHROMATOGRAM OF A .5 cc. SAMPLE FROM THE COMBUSTION OF 3-METHYLPENTANE TAKEN 2 cm. POST COOL FLAME ON THE M.S.-5A COLUMN. 86 vi FIGURE Page 26. CHROMATOGRAM OF A 20 cc. SAMPLE FROM THE COMBUSTION OF 2,2-DIMETHYLBUTANE TAKEN 2 cm. POST COOL FLAME ON THE DOWTHERM-A COLUMN. 90 27. CHROMATOGRAM OF A 20 cc. SAMPLE FROM THE COMBUSTION OF 2,2-DIMETHYLBUTANE TAKEN 2 cm. POST COOL FLAME ON THE SILICA GEL COLUMN . 91 28. CHROMATOGRAM OF A .5 cc. SAMPLE FROM THE COMBUSTION OF 2,2-DIMETHYLBUTANE TAKEN 2 cm. POST COOL FLAME ON THE M.S.-5A COLUMN. 92 29. CHROMATOGRAM OF A 20 cc. SAMPLE FROM THE COMBUSTION OF n-HEPTANE TAKEN 2 cm. POST COOL FLAME ON THE DOWTHERM-A COLUMN........ 30. CHROMATOGRAM OF A 20 cc. SAMPLE FROM THE COMBUSTION OF n-HEPTANE TAKEN 2 cm. POST COOL FLAME ON THE SILICA GEL COLUMN......... 97 31. CHROMATOGRAM OF A .5 cc. SAMPLE FROM THE COMBUSTION OF n-HEPTANE TAKEN 2 cm. POST COOL FLAME ON THE M.S.-5A C O L U M N ........... 98 32. n-PENTANE COMBUSTION CURVES ................. 100 33. n-HEXANE COMBUSTION CURVES .................. 101 3k. 2-METHYLPENTANE COMBUSTION CURVES ........... 102 35. 3-METHYLPENTANE COMBUSTION CURVES ........... 103 36. 2,2-DIMETHYLBUTANE COMBUSTION CURVES............101* 37. n-HEPTANE COMBUSTION CURVES .................. 105 CHAPTER I INTRODUCTION Fire has held the awe and wonder of man from the time the phenomenon was first observed to the present, A great deal of thought has gone into the understanding of the process by which burning takes place. As the energy, in the form of heat, was harnessed to do work the process of combustion received more attention in order to control the eramission of this energy to suit the conditions under which it was used. The role of combustion is governed by the conditions under which it takes place. These conditions cover a wide variety from free uninhibited burning to slow oxidation such as hydrocarbon hydroperoxide formation at room tem­ perature. This study deals with the phenomenon of cool- flame oxidation which can be visualized as intermediate between the two limits stated above. The cool-flame physical aspects have been studied to some extent by subjecting a wide variety of hydrocarbons to cool-flame combustion. Temperature profiles of these hydrocarbons were obtained for comparative purposes. The chemical paths by which hydrocarbons oxidize in 1 -2- this region were studied with the aid of a recent end most excellent procedure in the form of gas chromatography. This analytical procedure was developed further for use in the analysis of cool-flame combustions by-products. It Is possible with such an analytical tool, to establish the theories of oxidative mechanism as elucidated by Oberdorfer and Boord. This was accomplished by analysing the products of combustion in various stages of oxidation in the cool-flame tube. The pure hydrocarbons chosen were n-pentane, the isomeric hexanes, and n-heptane. It is hoped that this work will stimulate the further development of gas chromatography in order to understand the process of oxidation. CHAPTER II LITERATURE SURVEY Gas Chromatography Gas chromatography encompasses all chromatographic techniques in which the traditional moving liquid phase is replaced by a moving gas. The separations effected depend upon repeated redistribution of the substances to be separated between the moving gas and the fixed phase packed in the column. The fixed phase may be an ad­ sorbent (gas adsorption chromatography) or an absorbent liquid held in an inert supporting material (gas-liquid partition chromatography). Gas chromatography can be most directly compared with distillation, for both processes depend upon repeated distribution between two phases, one of which is gaseous. In distillation the whole of the column has to be filled with the substances to be separated, for they form the phases. In gas chromatography, the substances to be separated are distinct from the phases required to fill the column. Gas chromatography is also more efficient in terms of the number of effective redistributions achieved in the column. A good rectification column will have an -3- -in­ efficiency of a few hundred theoretical plates. In gas chromatography, columns may have an efficiency of a few thousand plates. The first chromatographic experiments were carried out using absorbent columns. The material to be analysed was placed at the beginning of the column and carried through the column in a stream of nitrogen, hydrogen, or air. This technique is called elution chromatography and resulted in a chromatogram consisting of a series of peaks or vapor concentretions. If the separation was complete each peak would represent one pure component of the sample mixture. (1) Claesson in 19i(.6, introduced a modification of the gas-adsorbtion method in which the vapors were displaced from the adsorbent by a displacer vapor which is carried continuously on to the column in the gas stream. The displacement vapor was chosen so that it was more strongly adsorbed than any component of the mixture to be sepa­ rated. The resulting chromatogram consisted of a series of steps each corresponding to one pure component of the mixture.