Patented Nair. 19, 1946 2,396,639 UNITED STATES PATENT OFFICE 2,396,639 PREPARATION OF ETHYL CHLoRIDE Richard Pence Carter, Elsmere, Del, assignor to Hercules Powder. Company, Wilmington, Del, a corporation of Delaware. . . No Drawing. Application June 23, 1943, Serial No. 491,973 7 Claims. (CI. 260-657) This invention relates to a process for the Eacample l preparation of ethyl chloride; more particularly, it relates to preparation from ethanol and hydro A body of aqueous zinc chloride having a con gen chloride, centration of 45% zinc chloride was placed in Processes for preparing ethyl chloride from a jacketed glass-lined autoclave to a depth of ethanol and hydrogen chloride with the aid of about 16 inches and heated to a temperature of a zinc chloride catalyst have long been known. 145° C. The temperature was held at 145 C. However, such processes have not been satisfac throughout the operation. Warm 95% (by vol tory in efficiency. Batch processes have required ume) ethyl alcohol was introduced into the bot inordinately long reaction periods for completion 0 tom of the zinc chloride solution at a rate of 0.17 of the reaction. Continuous processes have been part per hour per part of zinc chloride solution. unsatisfactory in that reaction of the ethanol Concurrently substantially anhydrous hydrogen has been incomplete, or, under more drastic re chloride was introduced into the bottom of the action conditions, considerable loss of ethanol by zinc chloride solution at a rate of 0.13 part per formation of ethylene has resulted. 5 hour per part of zinc chloride solution. ... Ethyl In accordance with the present invention, chloride vapor and water vapor were drawn from highly efficient conversion of ethanol to ethyl the vapor space above the zinc chloride solution chloride, with substantially complete reaction and as they were formed. The pressure in the auto negligible loss of ethanol to by-products, is ac clave was maintained at 30 pounds per square complished by bringing ethanol and hydrogen inch gage pressure during the operation. Under 20 these conditions the concentration of the zinc. chloride in mutual contact in a bath of aqueous chloride solution remained substantially constant zinc chloride under controlled and correlated at the initial concentration. The evolved vapors conditions of temperature, pressure, and zinc were led through a scrubber in which they passed chloride concentration. Briefly, the improve countercurrent to a stream of Water at a temper ments in yield and efficiency of reaction are ob 25 tained by reacting the ethanol and hydrogen ature of 80 C. which removed any hydrogen chlo chloride in aqueous zinc chloride solution at a ride from the vapors. The scrubber was operated temperature in the range from 138 C. to 160° C., at a pressure of 30 pounds per square inch. The and at a gage pressure between about 20 pounds Scrubbed vapor was then cooled to a temperature and about 50 pounds per square inch, with the 30 of 20° C. at a pressure of 30 pounds per square zinc chloride at a concentration between about inch under which conditions substantially com 40% and about 50% by weight of the zinc chlo plete condensation took place. The condensed ride plus the water in the solution, and with the ethyl chloride was then separated by decantation temperature and pressure correlated to maintain from the water condensed therewith. The proc the zinc chloride concentration in the rangemen ess was operated continuously in this manner to tioned. produce ethyl chloride of 99-100% purity. The The reaction can be carried out in a batch pro overall yield of ethyl chloride based on the ethyl cedure, but since the reaction is completed very alcohol fed to the reactor Was 98% of the theo rapidly under the controlled conditions herein retical. Accounted for losses. Were 0.4% in the above mentioned, continuous operation is most 40 scrubber and 0.9% in the separator in which the practical and represents the preferred mode of condensate was resolved into product and con procedure. A very satisfactory procedure com densed water vapor. Unaccounted for losses were prises introducing ethanol and hydrogen chloride 0.7%. into a bath of aqueous zinc chloride maintained Eacample 2 Within the pressure, temperature and concentra 45 Aqueous zinc chloride solution having a zinc tion ranges mentioned while withdrawing water chloride concentration of 47% was placed in a vapor and ethyl chloride vapor therefrom at sub jacketed glass-lined autoclave to a depth of stantially the rate at which they are formed, any about 16 inches as in Example 1. It was heated Water introduced as such being considered as part so to a temperature of 155° C. The temperature of the water vapor formed. In this manner the was held at 155 C, throughout the operation. zinc chloride solution remains substantially con Warm 95% (by volume) ethyl alcohol was intro-. stant in composition and in catalytic effectiveness duced into the bottom of the zinc chloride solu for any desired length of time. The ethyl chlo tion at a rate of 0.18 part per hour per part of ride is readily recovered from the vapors by con 55 zinc chloride solution. Concurrently substan densation and separation from water condensed. tially anhydrous hydrogen chloride was intro The following examples illustrate specific pro duced into the bottom of the zinc chloride Solu cedures in accordance with this invention. All tion at a rate of 0.14 part per hour per part of parts and percentages are by weight unless other zinc chloride solution. Ethyl chloride vapor Wise specified. 60 and water vapor were drawn from the vapor. 2 2,896,639 space above the zinc chloride solution as they per square inch grge pressure (above atmos were formed. The pressure in the autoclave pheric pressure). Preferably, the pressure is was maintained at 40 pounds per Square inch held between about 25 pounds and about 40 gage pressure during the operation. Under pounds per Square inch. Control of pressure is these conditions the concentration of the zinc 5 an important factor in the control of catalyst chloride solution, remained substantially con concentration. Pressures above about 50 stant at the initial concentration. The evolved pounds per square inch cause the retention of vapors were led through a scrubber in which too much water in the catalyst at any of the they passed countercurrent to a stream of water temperatures in the necessary temperature at a temperature of 80° C. which removed the () range and hence cause the catalyst concentra hydrogen chloride from the vapors. The Scrub tion to drop below about 40%. Pressures less ber was operated at a pressure of 40 pounds per than about 20 pounds permit a portion of the square inch. The scrubbed vapor was then alcohol vapor to pass through the catalyst bath cooled to a temperature of 20° C. at a preSSure of without reaction at temperatures low in the crit 40 pounds per square inch under which condi ical range and permit too much evaporation of tions substantially complete condensation took water at the higher temperatures, causing con place. The condensed ethyl chloride was then centration of the catalyst above the limit of separated by decantation from the water con about 50%. It is essential to the efficient oper densed therewith. The process was operated ation of the process to correlate the pressure continuously in this manner to produce ethyl 2) with the temperature of operation to maintain chloride of 99% purity. The overall yield of the concentration of the zinc chloride solution ethyl chloride, based on the theoretical obtain within the range specified. At any given tem able from the ethyl alcohol fed to the reactor perature the pressure must be sufficient to pre was 95%. The accounted for losses in this run went evaporation of Water vapor to an extent Were 1.4% in the Scrubber and 3.3% in the final 2 raising the concentration of the zinc chloride separator. The unaccounted for losses were above 50%. At the same time, the pressure 0.4%. must be less than the equilibrium water vapor The examples illustrate operations leading to preSSure of the catalyst bath as otherwise the very high yields of substantially pure ethyl chlo water does not evaporate and the zinc chloride ride. It has been found that it is essential to 30 becomes diluted below 40%. maintain the operating conditions carefully The hydrogen chloride may be in a mol ratio Within the ranges herein above specified to ob to the ethyl alcohol between about 1.0:1 and tain yields of the order obtained in the exam about 1.5:1. Preferably, the hydrogen chloride ples. will be in a molal excess of the ethyl alcohol, The temperature of the zinc chloride is main 35 for example, in a mol ratio between 1,07:1 and tained from 138 C. to 160° C. and preferably is 1.12:1. held between 140° C. and 150° C. It has been Since water is produced in the reaction, it is found that higher temperatures cause consider desirable to introduce the reactants in anhydrous able loss of ethyl alcohol through formation of or substantially anhydrous form. However, this ethylene. Although it is possible to react eth 40 is not essential. Thus, the ethyl alcohol is con ylene with hydrogen chloride to form ethyl chlo veniently introduced in the usual commercial ride, the reaction is relatively incomplete and 95% by volume form. Denatured alcohols may hence appreciable formation of ethylene in the be utilized although it will be appreciated that the reaction greatly decreases the yield of ethyl denaturing agents will usually find their way into chloride. It was found, for example, that in the ethyl chloride product. The alcohol may be operation at 40 pounds per square inch pressure, vaporized before being introduced into the cat raising the temperature to 170° C. caused a drop alyst solution or it may be introduced into the in yield to about 60%. Unaccounted for losses, hot catalyst bath in liquid form. In view of the representing reaction of ethyl alcohol to form relatively high temperature of the catalyst bath, ethylene lost as a fixed gas, came to 38-39% 5 the ethyl alcohol may evaporate therein. Simi under such operation. On the other hand, low larly, the hydrogen chloride is preferably intro ering the temperature to 137° C. when operating duced as the anhydrous or substantially anhy with a catalyst concentration of 45% zinc chlo drous gas. However, it may be introduced into ride, permitted an appreciable portion of the the catalyst bath in the form of a concentrated alcohol fed to pass through the reactor uncon 55 hydrochloric acid. verted. - It will be appreciated that where water is in The concentration of the zinc chloride solu troduced with the reactants it should be kept to tion is held between about 40% and about 50% a minimum because of the cooling effect on the by weight and preferably between 43% and 48%. bath. It may be necessary to increase the depth The catalyst concentration as expressed herein of the catalyst bath and to provide a Source of and in the claims is the percentage of zinc heat to maintain the catalyst temperature where chloride based on the weight of the zinc chloride appreciable water is added. It will also be un plus the Water present. Any hydrogen chloride derstood that where water is added in the re or alcohol which may be dissolved in the solu actants, the water vapor withdrawn must include tion is omitted from the total weight of the so ffs not only that formed by the reaction itself but lution in calculating zinc chloride concentration. that introduced with the reactants. It will be It has been found that zinc chloride concen understood also that where reference is made trations above about 50% lead to excessive for in operation to withdrawing water vapor at sub mation of ethylene from the alcohol. Concen stantially the rate formed, such water vapor will trations below above 40% are insufficiently ac 70 include all the water vapor formed, i. e., that in tive catalytically and as a result a portion of the troduced and that chemically formed. alcohol passes through the solution without re The hydrogen chloride and ethyl alcohol may acting. be premixed before introduction into the catalyst The reaction pressure is held between about solution or they may be introduced separately. 20 pounds per square inch and about 50 pounds s Preferably, the reactants are introduced into the 2,896,839 3 bottom of the catalyst solution. The depth of the at a concentration between about 40% and about catalyst solution will be sufficient to bring about 50% of the weight of the water plus the zinc substantially complete reaction of the ethyl alco chloride in the solution, the temperature of the hol to ethyl chloride at the particular rate at bath being from 138 C. to 160° C., the gage pres which the reactants are fed. Usually the solution sure over the bath being between about 20 and will be in a depth of at least about 15 inches. about 50 pounds per square inch and being corre However, instead of operating with a static bath lated with the temperature to maintain the zinc of catalyst solution, the ethyl alcohol and hydro chloride concentration in the said range, and gen chloride may be passed in the mixed vapor withdrawing ethyl chloride and water vapors from for countercurrent to a stream of zinc chloride 0. the bath at substantially the rate at which they catalyst solution, for exampie, in a packed tower, are formed, it being understood that the conditions of tem 4. A process for the preparation of ethyl chlo perature, pressure and concentration are main ride which comprises passing hydrogen chloride tained in the ranges hereinabove specified. and ethyl alcohol into a bath of aqueous zinc The ethyl chloride is easily recovered from the 5 chloride at a concentration between about 40% reaction product, vapors. Since an excess of hy and about 50% of the weight of the water plus the drogen chloride is usually employed it is usually zinc chloride in the solution, the temperature of desirable to remove this excess from the vapors. the bath being from 138 C. to 160° C., the gage Such removal is readily accomplished by passing pressure over the bath being between aboat; 20 the reaction vapors countercurrently to a stream 20 and about 50 pounds per Square inch and being of Water at a temperature which is higher than Correlated with the temperature to maintain the the boiling point of ethyl chloride at the particu zinc chloride concentration in the said range, lar pressure at which this scrubbing operation is withdrawing ethyl chloride and water vapors carried out. In this manner the hydrogen chlo from the bath at substantially the rate at which ride is completely removed with only negligible 25 they are formed, and recovering the ethyl chlo losses of ethyl chloride. The hydrogen chloride ride from the vapors withdrawn. may be recovered from the Scrubbing liquor for 5. A process for the preparation of ethyl chlo reuse. The scrubbed ethyl chloride vapor is then ride which comprises passing hydrogen chloride readily recovered by cooling it to below its boil and ethyl alcohol into a bath of aqueous zinc ing point at the pressure employed, preferably to 30 chloride at a concentration between about 43% a temperature Well below the boiling point, and and about 48% of the weight of the water plus then separating the condensed ethyl chloride, as the zinc chloride in the solution, the temperature by decantation, from the condensed water vapor of the bath being from 140° C. to 150° C., the associated therewith. gage pressure over the bath being between about As shown by the examples, the process in ac 25 and about 40 pounds per square inch and be cordance with this invention is characterized by ing Correlated with the temperature to maintain substantially complete conversion of the ethyl al the zinc chloride concentration in the said range, cohol fed to ethyl chloride of high purity. The and withdrawing ethyl chloride and water vapors reaction time is only a matter of seconds so that from the bath at substantially the rate at which the process is particularly efficient in continuous 40 they are formed. operation. - 6. A process for the preparation of ethyl chlo What I claim and desire to protect by Letters ride which comprises passing hydrogen chloride Patentis: and ethyl alcohol in a ratio between about 1.07 1. In 8, process for the preparation of ethyl and about 1.12 mols hydrogen chloride per mol chloride by reaction of ethanol and hydrogen of alcohol into a bath of aqueous zinc chloride at chloride with the aid of zinc chloride as a cat a concentration between about 43% and about alyst, the improvement which consists in bringing 48% of the weight of the water, plus the zinc the ethanol and the hydrogen chloride in mutual chloride in the Solution, the temperature of the contact with an aqueous zinc chloridesolution hav bath being from 140° C. to 150° C., the gage pres ing a zinc chloride concentration of between about 50 Sure Over the bath being between about 25 and 40% and about 50% of the weight of the zinc about 40 pounds per square inch and being corre chloride plus the water in the solution, at a ten lated with the temperature to maintain the zinc perature in the range from 138 to 160° C., and chloride concentration in the said range, and at a gage pressure between about 20 and about withdrawing ethyl chloride and water vapors 50 pounds per square inach. 55 from the bath at substantially the rate at which 2. A process for the preparation of ethyl chlo they are formed. ride which cornprises passing hydrogen chloride 7. A pipcess for the preparation of ethyl chlo ride which comprises passing ethyl alcohol and and ethyl alcohol into a bath of aqueous zinc a molal excess of substantially anhydrous hydro chloride at a concentration between about 40% 60 gen chloride into a bath of aqueous zinc chloride and about 50% of the weight of the water plus having a zinc chloride concentration of about the zinc chioride in the solution, the temperature 45% by weight of the water plus the zinc chloride of the bath being from 138° C. to 160° C., the in the Solution, the teiperature of the bath being pressure over the bath being between about 20 about 145° C. and the pressure over the bath be and about 50 pounds per square inch and being 65 ing maintained at about 30 pounds per square correlated with the temperature to maintain the inch gage, withdrawing the ethyl chloride and zinc chloride concentration in the said range, and water vapors from the bath at substantially the withdrawing ethyl chloride and water vapors rate at which they are formed, scrubbing the va from the bath at substantially the rate at which pors with water at a temperature above the boil they are formed. 0 ing point of ethyl chloride to remove excess hy. 3. A process for the preparation of ethyl chlo drogen chloride, and contiensing the resulting ride which comprises passing hydrogen chloride ethyl chloride vapor. and ethyi alcohol in a ratic between about 1.0 and about .5 minols of hydrogen chloride per mol RICHARO PENCE CAREER, of alcohol, into a bath of aqueous zinc chloride s