THE DEHYDROGENATIQN OP ETHANE TO PRODUCE ETHYLENE AND ACETYLENE, USING SULFUR AS A DEHYDROGENATIQ N AGENT DISSERTATION Presented in partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University by Ralph Eugsene Morningstar, B.S* !\ The Ohio State University 1952 Approved by ACKNOWLEDGEMENT Tlae author expresses h.is sincere appreciation for the advice and counsel of Dr. L. K. Herndon, not only in con­ nection with, this thesis, hut also for his guidance and personal interest in other phases of the author's profess­ ional training. t S&OS 9 8 TABLE OF CONTENTS Indications page i Introduction 1 Related Literature 3 Discussion of the Literature 53 Thermodynamic Calculations 55 Construction and Operation of Equipment 68 Operation of Vaporiser 71 Calibrations 79 Analytical Methods 89 Experimental 110 Effect of Temperature and Sulfur Concentration 111 Dehydrogenation of Ethylene by Sulfur 128 Effect of Space Velocity on Reaction of Ethane and Sulfur 133 XTse of Catalysts for the Reaction of Ethane and Sulfur 137 Temperature Gradient through Reactor 146 Discussion of the Data 149 Conclusions 163 Autobiography 168 • • • \ ■■// ■■ ^ THE. DEHYDRO DERATION OF ETHANE TO PRODUCE ETHYLENE AMD ACETYLENE, USING SULFUR AS A DEHYDROGENATION AGENT Indications: . - 1 . Apparatus was cona truciied for the purpose of studying the reaction of ethane and sulfur vapor. This apparatus consisted of two parts: a, A vaporizer for the generation of sulfur vapor. Ethane was bubbled through a hath of molten sulfur at a high temperature in order to obtain the desired mixture, \ b, A reactor furnace consisting of a porcelain tube in. a high temperature combustion fuf- nace. This furnace was capable of tempera­ tures up to 20G 0°F, 2 . No appreciable dehydrogenation of ethane occurr­ ed in passage through the sulfur vaporizer. Such reaction as did occur led to the formation of acetylene, with no evidence of ethylene formation, ^ 3* The conversion of ethane to ethylene was found to be a function of temperature, with a maximum conver­ sion of 50^ being obtained, at l600°F. in the absence of sulfur vapor, VI '■ 14^ 14-. The conversion of ethane to ethylene decreased with the addition of sulfur vapor to the reaction mix­ ture* Thus at 1565°F. and a ratio of sulfur:ethane of l.ij., a conversion of 357° was obtaihe d, compared to ij.6.57° in the absence of sulfur. This was due to further de­ hydrogenation of the ethylen e. 5 * The conversion of ethane to acetylene increased with an increase in the sulfur vapor content over the range studied. A maximum conversion of ^0% was obtained at a sulfur-ethane ratio of 1.14. and a temperature of 1565°F. 6. The conversion of ethane to acetylene was found to be independent of temperature except at high tempera­ tures and high sulfhr:ethane ratios. Under these con­ ditions the conversion decreased with increasing tem­ po rature. This effect was attributed to dehydrogenation to c arbon• 7. The conversion of ethylene to acetylene was found to be less efficient than conversion of ethane to acetylene. At 1560°F. and a sulfur :e thane ratio of 1 .1+, a conversion of 30% was observed. 8. In the range of contact times in the reactor of 1 to 6 seconds, no significant trent in the dehydrogena- tion of ethane by sulfur was observed. s . ; . i 9. Lump pumice, Porocel, and chromium oxide on activated alumina were investigated as catalysts for tlie reaction of ethane and sulfur. No significant increase in conversion occurred except in the case of lump pumice at lIj_50oP. The conversion obtained in this case was no "better than that obtained in the absence of catalyst at l600°P. 10 . In general, the trends observed in this study corresponded to those predicted by thermodynamic cal­ culations. No significance was attributed to the rela­ tion between actual and calculated conversions because of uncertainties in the thermodynamic data used. , I XNTRQDUGTIOH: .. The importance of both ethylene and acetylene as raw materials for chemical manufacture cannot he overemphasized. Both these gases are obtainable from natural gas* both methane and higher hydrocarbon gases, by known means. In the case of acetylene, however, the familiar carbide route is still gen­ erally employed. For a number of reasons the carbide process is preferred, most particularly because of the greater safety and relative ease of transportation of solid calcium carbide. With the increasing trend to locate chemical manufactur­ ing plants near natural gas sources or on supply lines, the transportation factor is less important, and the use of nat­ ural gas as a raw material is rapidly expanding. In general, two methods of manufacture are employed. The first and most widely described, usually for the manu­ facture of acetylene, involves the cracking and reforming of hydrocarbons ranging from methane to light oils. Electric discharge is often used to supply the required energy. In the second method, controlled oxidation is used to form unsaturates, usually from an ethane rich feed gas. Various means of con­ trolling the reaction are used. o \ : ^=9 It is the object of the present investigation to study a different type of oxidation process, the oxidation, or de- hydrogenation, of ethane by means of sulfur* With this milder oxidizing agent, the f o m tion of unsaturates in good yield and In a readily recoverable form should he obtained. By­ product hydrogen sulfide will be oxidized to sulfur and re­ turned to the system* RELATED LITERATURE ?. Both ethylene and acetylene are finding increasingly wide -use as chemical raw materials. Smith and Holliman Harold M. Smith and W, C. Holliman, ’'Utilization of Natural Gas for Chemical Products", 1*0 , 7547* S. Bureau of Mines, (19470, chart 7. summarize some of the uses for ethylene: ’’Ethylene is used as a fuel for cutting and welding, as an anesthetic, as a refrigerant and as an accelerator for plant growth sod food ripening. In addition, it is an Intermediate in the manufacture of the following items with uses as indi­ cated: acenaphthene (dyestuff intermediate), acetic acid and anhydride, acetylene, alkylates (motor and aviation gasoline), anthracene, benzene, butadiene, butylene, diisopropyl (high aa ti-knock motor fuel), ethyl alcohol, ethylbenzene, ethyl ether (anesthetic, solvent), ethyl halides and polyhalides, ethyl mercaptan, ethylsulfhric acid and diethylsulfate (ethyl alcohol Intermediate) ethyl and ethylene nitro compounds, ethylene chlorohydrin (disinfectant, insecticide, solvent), ethylene halides, ethylene oxide, ethylene glycol, ethanol- amines, formaldehyde, Intermediates for plastics and resins, mustard gas, naphthalene, neohexane (high anti-knock motor fuel), oxalic acid, polymers of ethylene (synthetic rubbers and plastics, lubricants and additives), styrene, toluene, vinyl and vinylidene chloride (textiles and plastics), and a host of others”. Smith and Holliman ~ Ibid, chart 1+ also present a comprehensive summary of the general methods of the preparation of hydro­ carbon materials. nl. Decomposition ( thermal, catalytic, electric).; The splitting of the hydrocarbon molecule into smaller molecules or into carbon and. hydrogen by heat alone (pyrolysis), with the aid of catalysts, or by electric discharge, generally accompanied, especially in pyrolysis, by recombination, of some of the. products into new compounds. 2 . Oxidation (thermal, catalytic); reaction of the hydrocarbon molecule with oxygen, air , or oxygen-containing compounds, activated by heat or catalyst, whereby oxygen is introduced into the hydrocarbon molecule, or the molecule is changed to carbon monoxide and hydrogen, carbon dioxide and hydrogen, ca? finally to carbon dioxide and water. £!?. {3 3. Halogenation (thermal, catalytic, pfeotolytic): Reaction of the hydrocarbon molecule with a halogen (fluorine, chlorine, bromine, iodine) activated by heat, light or cata­ lyst, whereby one or more halogen atoms replace an; equivalent number of hydrogen atoms in the hydrocarbon molecule. Ij.. Nitration (thermal, vapor phase): Reaction of the hydrocarbon molecule with nitric acid, accelerated by heat and pressure, whereby a nitro group, NOg, is introduced into the hydrocarbon by replacing a hydrogen atom. Rs Sulfurisafelon : Reaction o f th© hydrocarbon molecule with sulfur or hydrogen sulfide to form sulfur-containing compounds such as organic sulfides, mercaptans, disulfides, thiophenee. * 6. Desulfurization (catalytic): Removal of the sulfur atom from a sulfur-carbon-hydrogen molecule to-f&rs-e-sulfur- free molecule. Activated by catalyst. 7. Hydrogenation (Catalytic, thermal catalytic): Ad­ dition of hydrogen atoms to an unsaturated hydrocarbon mole­ cule to produce one or more saturated molecules. Activated by catalyst or heat and catalyst. Known as destructive hydro­ genation when original unsaturated molecule is "cracked" to form more than one subsequently hydrogenated smaller molecule, or non-destructive when no cracking occurs. 8* Dehydrogenation (catalytic, thermal): A farm of con­ trolled decomposition whereby hydrogen atoms are removed from hydrocarbon molecules to form less highly saturated molecules. Known as destructive dehydrogenation when original' molecule is "cracked" to form more than one smaller molecule, or non-dest­ ructive when no breaking <Sf carbon-carbon bonds occurs. 9. Alkyla tion ( the rrnal , catalytic): Chemical union of an alkyl radical to a hydrocarbon molecule. Used particularly to designate combination of olefin and isoparaffin or aromatic under conditions