Патент USA US2407862код для вставки
Patented Sept. 17, 1946 2,407,861 UNITED STATES PATENT 0F ICE 2,407,861 ‘ PROCESS OF TREATING HYDROCARBONS I. Louis Wolk, Bartlesville, 0kla., assignor to ' Phillips Petroleum Company, a corporation‘ of Delaware No Drawing. ApplicatioIn September 5, 1942, Serial No. 457,471 1 2 Claims. (Cl. 202-57) The present invention relates to the stabiliza tion of polymerizable organic compounds against giving rise to the numerous operating di?lculties. polymerization and oxidation during concentra The loss of even very small amounts of unsatu tion and puri?cation and to stabilizers capable rates through oxidation or polymerization may of preventing the polymerization and deteriora tion of the polymerizable compounds. Among the most important monomers used at the present time in the manufacture of synthetic are theunsaturated hydrocarbons: bu tenes, butadiene 1.3, piperylene, and their de rivatives. Acrylonitrile, styrene, methyl aciylate, and other polymerizable organic compounds may be copolymerized with the unsaturated hydro carbons to yield various rubber-like polymers having characteristic properties. The polymeri ‘ An object of the present invention is to elimi nate oxidation and polymerization of polymer zable unsaturated organic compounds‘ during their concentration and‘ puri?cation by distilla~ tion. zation is advantageously carried out in an emul ‘ undesirable reactions. For emulsion polymerization the mono A further object of the Solvent treatment, distillation, or both, may be.20 the prevention of losses of unsaturated com~ employed in the puri?cation and concentration of the monomers. While distillation is in many cases preferred as the operation by which the sition of polymeric tion products on the apparatus during distilla tion. ' ‘Another object of the present invention is to provide an effective and desirable method for the distillation of polymerizable organic compounds. Still another object is to provide suitable sta~ bilizers capable of inhibiting vapor phase poly 30 merization and/or oxidation during the distilla tion of polymerizable organic compounds. instances of record in The present invention effectively prevents the bilizers are added to protect against deteriora~ tion. Most of these stabilizers interfere with the 35 pollmerization and must be removed prior to the in the liquid phase in to concentrate near the bottom of the fractiona polymerizationprocess, Stabilizers of high boil ing point are most often used because they may be separated from the monomer by distillation tor. In some instances, fractionators may be ' prior to the polymerization procedure. Polymer 40 constructed of or contain certain metals or other I formation and decomposition of the monomer, materials which inhibit polymerization. Both ‘chie?y by oxidation, are apt to take place in the high boiling inhibitor and the contact in hibitor are inelfective for inhibition of the oxi dation and/or polymerization of the monomer in the vapor phase. I have observed that consid erable polymer formation does occur in distilla tion of monomers which contain'non-volatile or the equipment used for separation of the sta bilizer from the monomer. In the steam distilla tion of styrene, for example, for separation from the stabilizer prior to use in polymerization, con siderable trouble with polymer formation is en countered. In the conventional fractionating systems, the high boiling inhibitors. Since these inhibitors 50 are effective for the stabilization of the liquid inclusion or introduction of atmospheric or other 'oxygen in the equipment results in or favors oxidation and polymerization of these unsatu rated organic compounds with the attendant monomers in transfer and storage, polymeriza tion in the vapor phase must take place during the fractionation. present invention. pre losses in yield and deposition of polymers in the 55 apparatus and system. The conjugated diole?ns are especially likely to undergo such reactions and hence, are especially troublesome. This con dition obviously is undesirable and results in substantial losses of the monomers as well as 60 The present invention is performed by adding 2,407,861 3 _ 4 portance in the manufacture of synthetic rubber include: to the monomer an inhibitor having a suitable boiling point and solubility for incorporation in the liquid material to be purified or in the water if steam distillation is employed in the puri?ca Compound Boiling point tion. The selection of a suitable stabilizer is de ‘' 0. pendent upon the particular monomer to be in hibited thereby. Preferably the inhibitor or sta bilizer has approximately the same boiling point Vinyl chlorido_‘___.,__....__...._ 7 Chloroprcne ............. . _ 59 139 2,3-dimethyl butadiene- , 70 157 Acrylonitrilc .... _ . as the monomer so_as to prevent oxidation and 78 Methyl acrylutc. . 10 polymerization during all the process steps pre ceding the polymerization step in which it is co polymerized with another monomer to form syn Styrene . _ _ _ . . . _ . _ . . _ . _ . _ . _ . . . _ . _ . _ . . _. amines are preferred, since the amines may be tolerated in minor proportions in the polymer ization step and in the resulting product. For the purpose of illustration, the boiling points of some of the aliphatic amines are listed below: Compound Boiling point. ° 0. Methylamine.......................... .. Trimethylamme _ . . with a conventional inhibitor. The stabilizer Dimetbylaminc. may be removed prior to the polymerization step 25 Ethylsmine.____. Isopropylammer as disclosed hereinafter or may in some instances Methylethylamlne be allowed to remain in the monomer since some v 95 Amylamine____ distillation. For example, separations sometimes an entrainer to aid in the fractionation. The in 183 203 210 255 264 130 146 140 266 295 155 311 _. ._. 156 N dihutylamine-.. 284 313 159 318 Sec.-octylamine ____ __ 164 327 Methyl heptylamine. 165 329 From a comparison of the boiling points it will be apparent that methylamine, trimethylamine, and dimethylamine are suitable for use in a mix ture of C4 hydrocarbons, while the ethylamine, isopropylamine, and methylethylamine are suit able for use with the C5 hydrocarbons. Ethyl propylisobutylamine is especially suited for use with styrene since the boiling points are substan tially identical. For inhibition of the higher‘ ing styrene, however, it is preferable to use a 60 mixture of acid soluble aliphatic amines boiling —7 l9 -6 21 ——5 23 1 34 4 39 26 79 86 ne-l _______ -_ 30 2-methyl butane-1. 31 88 Isoprene. -.._ 34 93 Pentene-2___. 36 97 2-methyl bute Cyclopentadiene ..... -. 38 41 100 106 Piperylene . . . . . _ . . . _ _ _ _ -_ 43 109 44 111 within the range of temperatures encountered in the distillation of the organic compounds. Such a mixture offers full protection against de terioration during distillation since the compo 65 nents are distributed through both the liquid phase and the vapor phase in the fractionator. The inhibitor passing overhead in the fraction ator is condensed with the condensate and‘may be removed from the monomer by contact with w Of these, isobutene, butadiene, isoprene, and p'iperylene are the most important in the man an aqueous acid solution. The removal is readily ‘ accomplished by intimately contacting the mon— omer with the aqueous acid solution and separat ing the puri?ed monomer from the resulting mixture. ‘ 95 104 Methylamylamine. Ethylpropylisobutylamine 45 Tripropylamine-_._ ° F. Butene-l ______ __ ufacture of synthetic rubber. 1114 196 196 198 boiling polymerizable organic compounds includ Isobutene _________________________ .. Cyclopentene ................................... _. 90 91 91 92 230 Boiling point _____ .. 174 ' 180 129 points as follows: Pen . 84 Hexylamine ...... _. carbon atoms respectively and having boiling . _ . . . . . .. 169 171 171 154 124 Among the ole?ns and diole?ns are the members of these series having four carbon atoms and ?ve 1,4-pentadiene _ _ _ _ . _ _ . 147 76 77 77 68 110 invention. My invention is applicable to the ole?ns, diole- , ?ns, styrene, acrylonitrile, and other polymeriz able and/or oxidizable unsaturated compounds. ..... __ 145 64 Isohexylamine_._ Heptylamine _______________ _. > The invention will be more readily understood by reference to the following examples which are illustrative of the process-of my invention and of compounds suitable for use in carrying out my ilin > 145 63 82 ..... .. Dnsobntylamine _ __ vention is also applicable to separation by the Butane-2 (low bo1hng)_ _ 56 63 _____ 40 Dipropylamine ___________ _. involve the formation of an azeotrope or use of 93 1 1'1 120 133 ___________ __ ......... _. of the monomers by methods other than by simple Butene-2 (high 63 45 49 may be employed equally ad vantageously in the segregation and puri?cation Butadiene-L3 _________ _. 17 79 merization step without adversely affecting the ° C’. 45 35 The aliphatic amines, particularly the tertiary Hydrocarbon 39 7 34 ........ ._ aliphatic amines, the mercaptans, and the alkyl sul?des may, for example, be allowed to remain in the monomers charged to the emulsion poly 19 4' _ Tert.-butylamine ............... . _ . ° F. -7 ........ .. ..... ._ of the stabilizers, althou h effective in preventing deterioration of the monomer, do not appreci use of selective solvents. 177 205 in the present invention, the aliphatic alkyl part higher boiling than the compound inhibited or I may use a volatile inhibitor in conjunction polymerization. The inhibitors 173 80 146 Of the stabilizers or inhibitors suitable for use thetic rubber latex. One addition of such a stabi lizer is usually sufiicient since the stabilizer re mains in admixture with the monomer through all .the process steps. In any event, at least part of the inhibitor exists in the vapor phase during dis tillation. The boiling point of the inhibitor may be such that it is entirely gaseous at the temper ature and pressure of the distillation. I may use 20 a mixture of the inhibitors, part lower boiling and ably retard copolymerization. ° F. -—14 Other polymerizable organic materials. of im 75 - I The mercaptans may also be used as inhibitors 2,407,861 in accordance with the present invention. The hydrazines enumerated may be used as inhibi boiling points of some of the mercaptans suitable for use are as follows: Compound Boiling point “.__\_\__ _____ ° 0. 6 Methyl mcrcaptan ______ _ . Ethyl mercaplnn ........ _ , 97 59 67 ...... . _ 1348 152 10 88 190 N. butyl mercaptam- 98 20% N. amyl mercaptan. . Isoamy] mcrcaptan__ 125 130 257 266 149 300 _ N. hexyl mercaptan __; _______________ __ pounds with which they are used as inhibitors. , ° 1'‘. 43 3t Isopropyl mercaptan. N. propyl mercaptau____ Isobutyl morcaptan. . tors for styrene since they all will be vaporized at temperatures below those at which the styrene 5 is vaporized. The alkyl hydrazines are powerful reducing agents and are especially e?ective‘ in preventing oxidation of the unsaturated com _ Like the aliphatic amines, the dimethyl hydra zines may be removed from the hydrocarbons by contact with an aqueous acid solution. Other inhibitors which may be used in my proc ess include ammonia, B. P. —33° 0., and hydrogen sul?de, B. F. —60° C. The normally gaseous compounds may be used as inhibitors in the va Methyl and ethyl mercaptans are suitable for 15 por phase during the distillation of the polymer use in a mixture of C5 hydrocarbons, ethyl mer izable compounds by dissolving in small propor captan having thesame boiling point as Dentene tions in the compounds or by addition directly 2. Isopropyl mercaptan has substantially the ‘to the still whereby the gases are admixed with same boiling point as isoprene. N. propyl mer captan, as well as the lower boiling mercaptanes, ' may be used as inhibitor for 2,3 dimethyl bu and follow the volatile vapors from the still through the fractionation steps. The ammonia may be removed by a water wash, while the hy tadiene-1, , drogen sul?de is preferably removed by contact with aqueous alkaline solution. The following examples illustrate more clearly the application of the present invention and are not to be construed as limiting the invention in _ any way captans are readily removed from the polymer izable organic liquid prior to the polymerization step by contact with an aqueous alkaline solu tion. The alkali wash serves to remove organic ' peroxides as well as the mercaptans. Traces of alkali in the monomer are not objectionable in emulsion polymerization. Example I A mixture containing 50% butadiene along with a substantial proportion of butenes-2 as im purities is fed to a distillation system comprising . a packed column operated at about 75 pounds per The alkyl sul?des may be used in my process. square inch absolute and with a kettle tempera Those having suitable boiling points are: "" ture of about 113° F. Butadiene of about 98% purity is taken overhead and butene removed Compound N Methyl from the bottom. Phenyl-beta-naphthylamine Boiling point about .05% by weight, is used asinhibitor. After operating 48 hours, the distillation system was torn down and cleaned out because the system was so plugged that operation was impossible. i A large amount of pasty material was found in the still. The column was stopped by a solid white crystalline deposit. The ?rst pass of the condenser ‘was packed with a mixture of the white deposit and Raschig rings which had car . Methyl sul?de may be used as inhibitor in the distillation of the C5 hydrocarbons and chlo roprene or higher boiling polymerizable com pounds. Methylethyl sul?de is especially suit able as inhibitor for 2,3-dimethyl butadiene,1,3 and may be used with acrylonitrile or methyl acrylate. N. propyl sul?de is especially suitable for use with styrene, although the lower boiling sul?des may also be used for inhibition of poly ried over as the result of the formation of the butadiene complex. 50 The above described system was cleaned out and distillation of butadiene continued with the use of .5% methylamine and .05% phenyl-beta naphthylamine as inhibitors. After 48 hours the distillation system was operating satisfactorily. The methylamine was removed from the buta diene by an aqueous acid treatment. About 1% ‘ to the polymerization step by contacting the monomer with a mercuric or cupric salt with hydrogen sul?de was substituted for methyl amine, being added continuously to the base of the fractionator, and the distillation continued 24 hours. The hydrogen sul?de was removed by which the sul?des form addition products. Another series of compounds suitable for use 60 contact with an aqueous alkaline solution. The in my process are the lower boiling alkyl hy distillation was then continued 24 hours using drazines. small amounts of ammonia, about 1% by weight, instead of the hydrogen sul?de, continuously in Compound troduced to the system with the feed. Boiling point 65 Dimethylhydrazine (1111s.) _______ __ Dimethylhydrazine (sym.) ______ __ Methylhydrazine ________ ._ Diethylhydrazine _____________ _. Ethylhydrazine _______________________________ __ The dimethyl hydrazines may be used as in hibitors with 2,3-dimethyl butadiene-1,3, acrylo The dis tillation was shut down at the end of four days. A small amount of pasty material was found in the still. The column was not disassembled since the pressure drop through the column had not appreciably increased from the beginning of the trial runs. Example II E?iuent from the catalytic dehydrogenation of nitrile, and methyl acrylate. Any of the alkyl 75 ethylbenzene containing 2‘3.5 weight per cent styrene inhibited with .1% tertiary butyl cate 2,407,861 Example V A mixture containing 50% butadiene along with chol was fractionated in a fractionator contain ing the equivalent of 100 theoretical plates. The a substantial proportion of butenes as impurities is fed to the center of a sixty plate bubble cap column and 95% acetone is supplied to the top of the column in quantities ten times the weight of the feed. Hydrogen sul?de is introduced near benzene, together with small amounts of benzene the bottom of the column and passes overhead and toluene were taken overhead as vapors. substantially unabsorbed by the acetone. The Polymer was removed from the kettle in propor tions such that an appreciable loss of styrene was 10 liquid flowing from the bottom of the column is heated to boil out the puri?ed butadiene and is. represented. Ammonia, hydrogen sul?de, ali recirculated, while a portion of the butadiene phatic amines, alkyl hydrazines, alkyl sul?des, vapor is returned to the bottom of the column to . and mercaptans were successively introduced to maintain the'saturation of the descending sol the base of the fractionator with the result that vent. The remainder of the butadiene recovered the polymer formation was greatly decreased. from the solvent is condensed and removed as the Example III I_ product. In this manner the butadiene is easily enriched to 95% concentration.- On inspection In the steam distillation of styrene for puri of the apparatus, substantially no gum polymer ?cation and removal of high boiling inhibitor the still or pot and the associated fractionating 20 is detected. This is apparently due to the incor poration of the inhibitor, since a similar run column ?lled with Raschig rings was heated to under ordinary conditions without inhibitor re 100° C. with live steam. Styrene inhibited with sults in noticeable gum or polymer formation, phenyl-beta-naphthylamine was charged to the particularly after continued operation. still in 40 pound batches as it distilled so that no more than 5 gallons of styrene was in the pot 25 Example VI at any time. The distillation with steam con The butadiene-containing mixture of the fore tinued for two hours and forty-?ve minutes, dur going example is contacted in the apparatus of ing which time 200 pounds of styrene was charged fractionator was operated at 'a pressure of 16 pounds per square inch absolute. Styrene of 99% purity was withdrawn from a point in the lower section of the fractionator while ethyl Of this amount 180.5 pounds of the foregoing example with nitrobenzene at 10 to during the distillation. Polystyrene was carried mixture is regulated so that substantially no butadiene is present in gases escaping at the top to the still. styrene was recovered, representing a loss of 9.8% 30. 20° C. The rate of feed of the solvent and gas into and deposited in the column. The distilla of the tower. The butadiene recovered from the tion was continued an additional 4 hours during solvent accumulating at the bottom by distillation which 162 pounds of styrene was charged to the still. The distillation was considerably slower 35 as in Example V is of high purity, being in the neighborhood of 95% pure. Ammonia is used as than previously due to polymer deposition in the inhibitor. As in Example V, no appreciable poly column. The loss at the slower distillation rate mer formation takes place. was somewhat less, being about 2.5%. Following I claim: ‘ ' this distillation the still had to be shut down for 1. In the fractional distillation of a liquid poly cleaning. The perforated plate supporting the 40 merizable organic compound in a fractionation Raschig rings was found to be nearly completely zone wherein said compound is subjected to con plugged with polymer. - _ Styrene, inhibited by the addition of mixed aliphatic amines boiling within the range of 290 ditions favorable to oxidation of said compound, the improvement which comprises introducing 300° F., was distilled in the apparatus. ‘In six 45 hours operation 400 pounds of styrene was charged to the still. The loss due to polymer formation was reduced to less than 1%. Example IV 50 A C4 fraction containing butadiene admixed with butylenes, isobutylene and butane was passed into countercurrent contact with furfural con taining 5% water in a plate-type absorption col umn/ The column was operated, 'at 65 pounds 55 per square inch absolute with a top temperature of 120° F. and a bottom temperature of 240° F. The C4 fraction contained .02% phenyl-beta naphthylamine inhibitor. In a few hours the into said fractionation zone an oxidation inhibi tor substantially non-volatile under conditions of distillation in an amount sui?cient to inhibit oxi dation and polymerization of said compound in the liquid stateI and continuously introducing into said fractionation zone a second oxidation inhibitor more volatile than said organic com pound in an amount sufficient to inhibit oxidation and polymerization of said compound in the vapor state. 2. In the fractional distillation of a liquid poly merizable organic compound in a fractionation zone wherein said compound is subjected to con ditions favorable to oxidation of said compound, the improvement which comprises introducing system was shut down because of the formation 60 into said fractionation zone an oxidation inhibi- - of polymeric material in the lower section of the column. Using methylamine inhibitor, together with the phenyl-beta-naphthylamine the furfural solvent extraction of butadiene from the C4 hydrocarbons was successfully carried out with very little ly-' mer formation. The methylamine was partly absorbed in the furfural. Traces of methylamine were removed from the purified butadiene by in- ' timate contact with an aqueous acid solution. tor substantially non-volatile under conditions of distillation in an amount sufficient to inhibit oxi dation and polymerization of said compound in the liquid state, and continuously introducing I into the base of said fractionation zone a second ‘oxidation inhibitor more volatile than said or-' ganic compound in an amount su?icient to inhibit oxidation and polymerization of said compound in the vapor state. a I. LOUIS WOLK.