3,199,953 United States Patent Office Patented Aug. 10, 1965

2 hydrocarbyl groups. Benzoic and alkyl-substituted ben 3,199,953 zoic acids are preferred. All the above acids are char PROCESS FOR PRODUCTION OF ANHYDROUSEHY acterized by their resistance to chemical attack by hydro DROGEN SEROMIDE FROM BEROMEDE Shigeto Suzuki, San Francisco, Calif., assignor to Cali gen under the present reaction conditions. fornia Research Corporation, San Francisco, Calif., a 5 Example 1 corporation of Delaware into a turbomixer having approximately a 100 ml. No Drawing. Filled Nov. 22, 1963, Ser. No. 325,771 capacity was charged 61 grams of benzoic acid and 15 7 Claims. (C. 23-54) grams (approximately 0.15 mol) of . This invention relates to a method of generating anhy O The mixture was heated to a temperature in the range drous from lithium bromide. More 250-260° C. with stirring, and nitrogen gas at a flow rate particularly, it relates to the production of anhydrous of 235 ml. per minute was passed through the heated -free hydrogen bromide suitable for use in the mixture. After one hour at temperature, approximate free radical addition of hydrogen bromide to olefinic ly 80% of the theoretical amount of hydrogen bromide hydrocarbons. had been evolved. At two hours, 89% of the theoretical It is known to produce anhydrous hydrogen bromide 5 hydrogen bromide had been evolved. The reaction is by a variety of chemical routes, but these do not lend substantially complete after 4 hours of reaction time. themselves to processes where efficient regeneration and recycle of anhydrous hydrogen bromide is required. Example 2 Moreover, in the customary art method, i.e., the inter 20 As in Example 1 except that 10.3 grams (0.10 mol) of action of the strong mineral acid, concentrated sulfuric bromide and 61 grams (0.5 mol) of benzoic acid acid, with bromide salts, a concurrent formation of ele were charged to the reactor. The reaction mixture was mental bromine and by-product sulfate salt cake greatly stirred vigorously at 225 C. for one hour, during which complicates the process. The bromine must be removed time nitrogen was passed through the mixture at a rate from the hydrogen bromide because of its exceptional 25 of 55 ml. per minute. No hydrogen bromide was de chemical reactivity. Its presence as an impurity in an tectable in the off-gas. At the end of the period, an hydrous hydrogen bromide, in general, yields undesirable additional 10.3 grams of were added, by-products in reaction systems requiring dry hydrogen and the process was continued for an additional hour at bromide. 250 C. Again, no trace of hydrogen bromide could be It has now been found that anhydrous hydrogen 30 detected in the off-gas. At this point, 0.3 gram of lithium bromide is produced by heating a solution of substantially bromide was added to the reaction mixture and the heat anhydrous lithium bromide in an organic carboxylic acid ing continued at 250 C. for an additional 1.5 hours. at a temperature above about 150° C. The hydrogen Except for a trace of hydrogen bromide due to the lithium bromide is evolved as a gas essentially free of elemental bromide added, no additional hydrogen bromide was bromine and may be directly used for free radical cata detectable in the off-gas. lyzed addition reactions of hydrogen bromide to olefinic When bromide or bromide were hydrocarbons as in the preparation of n-alkyl . used in place of lithium bromide in similar experiments, In a preferred embodiment of the present invention, no detectable hydrogen bromide was noted. lithium bromide is dissolved in benzoic acid and heated. I claim: At about 150° C., a noticeable evolution of hydrogen 40 S. Process for the production of anhydrous hydro bromide occurs. After about two hours' reaction time at gen bromide which comprises heating a solution consist 250-260° C., the reaction is about 90% complete. ing essentially of substantially anhydrous lithium bromide Removal of the hydrogen bromide from the liquid re in an organic carboxylic acid, said heating being at a action medium is facilitated by the introduction of an temperature in the range from about 150-350° C. and inert gas such as nitrogen, carbon dioxide and the like recovering the resulting evolved hydrogen bromide gas. into the solution. With increasing temperature, the rate 2. The process as in claim wherein an inert gas is of evolution of hydrogen bromide correspondingly in introduced into said heated solution. creases. On the other hand, no particular advantage 3. Process for the production of anhydrous hydro accrues by carrying out the reaction above about 350 C. gen bromide which comprises heating a solution consist Suitable organic carboxylic acids for use in the present 50 ing essentially of substantially anhydrous lithium bromide process are those acids having boiling points of at least in an organic carboxylic acid, said heating being at a 150° C.; preferably, the acids have boiling points of temperature in the range from about 150-350° C., said above 250° C. Representative acids useful in the present oragnic carboxylic acid being characterized by the gen process are benzoic, (o, m, or p)-toluic, pivalic, dode eral formula: canoic, stearic, pimelic, glutaric, caprylic, capric, hexa 55 R(CO2H) hydrobenzoic, lauric, 2-ethylhexanoic, hydrocinnamic, myristic, palmitic, ox-naphthylacetic, sebacic, ox-naphthoic, wherein “n” is a number in the range 1-2, inclusive, isobutyric, butyric, isovaleric, hexanoic, isocaproic, 4 wherein “R” is a hydrocarbyl radical having from 3-18 methylhexanoic, heptanoic, cyclohexanecarbocyclic, n carbon atoms selected from the group consisting of alkyl, undecyclic and the like. In general, the Suitable acids 60 cycloalkyl, aryl, alkylaryl and alkylcycloalkyl groups, and have less than 20 carbon atoms per molecule, from 1 to recovering the resulting evolved hydrogen bromide gas. 2 carboxyl groups and are characterizable by the general 4. The process of claim 3 wherein and inert gas is in formula R(CO2H), where n is 1-2 and R is a hydro troduced into said heated solution. carbyl radical containing from 3-18 carbon atoms, includ 5. Process for the production of anhydrous hydrogen ing alkyl, cycloalkyl, aryl, alkylaryl, and alkylcycloalkyl 65 bromide gas which comprises heating a solution consisting 3,199,953 3 - 4. - essentially of substantially anhydrous lithium bromide 7. The process of claim 5 wherein said acid is benzoic dissolved in an organic carboxylic acid, said heating being acid. at a temperature in the range from about 150-350 C., References Cited by the Examiner said acid being characterized by the general formula: Jacobson's "Encyclopedia of Chemical Reactions,” HOCCHR 5 volume 4, page 316, Reinhold Pub. Corp., New York. J. W. Mellor's "A Comprehensive Treatise on Inorgan wherein R is selected from the group consisting of hydro ic and Theoretical Chemistry, volume 2, 1922 edition, gen and alkyl radicals, said acid having less than 20 car page 66, Longmans, Green & Co., New York. bon atoms. 6. The process of claim 5 wherein an inert gas is in troduced into said heated solution. 10 MAURICE. A. BRINDISI, Primary Examiner.