Патент USA US2355392код для вставки
Patented Aug. `8, 1944 2,355,392 n, UNITED STATES PATENT oFFlcE raocEss Foa TREATMENT or nrnvaocaaaons » Èeorge G. OberfellfBal-tlesvillc, Okla., assigner to , Phillips Petroleum Company, a corporation of Delaware Application August 12, 1940, Serial No. 352,306 6 Claims. (cl. 26o-681.5) Y ' i ._ This invention relates to a process for the depolymerization to yield the original dioleflns separation and concentration of dioleflnic hydro- rather than cracking toform lower hydrocarbons, carbons such as butadiene and the like from mix hydrogen, aromatica-etc. tures containing other hydrocarbons. More par Dioleñns, such as butadiene and isoprene, ticularly it refers to the separation of diolefins undergo two distinct types of polymerization; by a process in which said dioleiins are succes one leads to the lformation of dimers of a' cyclic 1 sively converted to polymers of- relatively low nature and the other to the formation of more or molecular weight, separated in polymer form by less rubbery polymers of .high molecular weight distillation or other suitable methods, and finally , and open branched or unbranched chain struc 10 ture. 'I‘he formation of the higher polymers is generally favored by low temperatures, such as An object of this invention is to separate di i 20o-300° F. or lower, and by polymerization ~ oleiins from mixtures containing other hydrocar bons such as parailins and monoleflns. catalysts, such as oxygen, peroxides and other - recovered as monomeric dioleilns by a depolymer ization treatment. - «active oxygen’ containing compounds, alkali Another object of this invention is to produce 15 metals, acids, and metal halides. In general diolefins in concentrated' form suitable for use in chemical conversion processes. Ithese are either catalysts or chemicals which re x act with the diolefln to form addition complexes. ,Another object of this invention is to freeof I propose to carry out the polymerization of diolefins hydrocarbon mixtures such as are pro dioleiins under conditions which favor the forma- ` duced by cracking operations. 20 tion of dimers `rather than the higher polymers. The manufacture of butadiene, isoprene, and To accomplish this, I have found thatI can similar Íconjugated dioleñns from petroleum hy drocarbons by cracking, dehydrogenation, and ` similar methods is handicapped by the fact that operate in the temperature range 30G-900° F.' The -rate of reaction of course increases with the temperature. Elevated pressures are gener- ` the desired dioleiin generally is obtained in a 25 ally advantageous and I have found that pres very dilute form. in admixture with other hydro sures 'within the range of atmospheric to around carbons. For example, the four-carbon-atom 500 pounds perl square inch gauge are particu fraction of gases from vapor phase oil cracking larly effective. Higher pressures, however, may ' stills will usually containless than 15 to 20 per be employed where desirable, limited only by the cent of butadiene. Pyrolysis of butane gas under 30 'degree of polymerization of the dioleiin. Solid conventional conditions likewise gives very low contact catalysts such as fuller’s earth, bauxite, percentages of butadiene. As a rule, a similar activated alumina, and silica gel favor the forma fraction from other cracking processes will con tion of the dimer in both liquid and vapor phase. tain much smaller percentages of butadiene. ' It is also frequently advantageous to use inhibi In commercial processes utilizing dioleflns lit is _very advantageous, if not economically impera tivel to have said diolefins in concentrated form. I For example, in the conversion of butadiene to synthetic rubber by copolymerization with un ' saturated nitriles and other costly organic de rivatives, it is generally uneconomical to start with a butadiene product of less than 90-95 per cent purity. For other processes and conditions, tors which repress the formation of the higher polymers, particularly in the lower part of the temperature range specified above. While I may apply my invention directly to hydrocarbon fractions of comparatively wide boiling range, I -prefer to separate fractions of rather narrow distillation range containing the desired diolefln and then subject the said frac--l it may be economical to use lower concentrations tions to the polymerization treatment.v For ex ample, I may separate a fraction boiling from 15° of butadiene, but generally higher concentrations to 30° F. containing butadiene and `a fraction ' than can be Produced directly are desired. _ boiling from 85° to 105° F. containing isoprene I have conceived the idea of producing a con centrate of diolefin from a hydrocarbon mixture for treatment by my process. containing said dloleñn in a _dilute form by poly-A merizing the dioleiln under conditions favoring the formation of low polymers, preferably the dimer, then separating the polymers from the un polymerized hydi'ocarbe'tms> by - suitable means. such as fractional distillation, and then treating Since the dimers which I form in my- 'poly-f merization step boil at much higher temperatures than the original dioleflns, the separation of poly mer may be readily accomplished by- ordinary distillation. For example, the dimer of butadiene boils above 320°> F. while butadiene boils at about 23° F. However, I do not limit myself to that the low vpolymers under conditions which favor uA method of separation. The separation ofthe- ascaaoa vent extraction, fractional precipitation> at low temperatures or other convenient methods. The depolymerization step is best carried out under conditions of relatively high temperature, low pressure, and relatively short heating times. Pressures of atmospheric down to a very few millimeters of mercury, absolute, are advanta -geous and I prefer the range 3 to 100 mm. Tem ` peratures of 900°_to 1300° F. are preferred, but ~ . coil 46. heated-by furnace 41. Lower and higher boiling fractions are withdrawn from the frac polymer may be accomplished‘ for example by sol tionatingsystem 4|,.through pipes 42 and 44, respectively. Products from the polymerization coil 45 after suitable cooling are fractionated in fractionator 49 anda normally liquid polymer is withdrawn through expansion valve 80 and pipe . 5I to depolymerization coil 52 heated ins furnace 53. Unpolymerized lig'ht hydrocarbons are with drawn from fractionator 49 by means of pipe 50 considerably higher- temperatures may be used providing the heating time is made suiliciently short to limit ordinary thermal decomposition. and may be either discharged, or fractionated and partially recycled to the polymerization coil 46. The products from the depolymerization coil 52 are pumped through pipe 54 by means of pump compressor 55 to fractionating system 5B, from In general, shorter heating times are desirable at v the higher temperatures. It is advantageous in many cases to limit the‘extent of conversion per pass in this manner and to separate and recycle which a C4 fraction rich in butadiene is removed through pipe 58. A more volatile fraction which may be produced by partial cracking is with 'drawn from pipe 51. A normally liquid fraction the unconfverted,l polymer in order to obtain higher yields of the monomeric dioleñn. _ As an alternative vto the use of very low pres: sures I may dilute the polymers with an inert is withdrawn through pipe 59- and may be re cycled as a whole or fractionated to eliminate gas such as nitrogen, or with steam. The main object is yto maintain a low partial pressure of very heavy materials and the lighter fraction re cycled. » - f , dimer, and consequently of the monomeric diole‘ iin, in the reactor. The flow diagrams show only the essential ap paratus. In actual operation many modifications The use of catalysts such as silver, copper, may be advantageous. For example, heat ex platinum, iron preferably in the form of the' change between the products and the raw feed' reduced oxides, and oxides of calcium and mage of each of the furnaces may be applied. Greater nesium -in the depolymerization step may also be flexibility in operation and control may be' ef advantageous. The optimum conditions of tem 30 fected by inserting accumulators between stages perature and ñow rate foriany given catalyst of the process. Some of the fractionating sys may be determined by simple experiment; tem shown as single columns would actually com The voperation of the proce s is illustrated by prise two or possibly three columns with the usual the flow diagrams >of Figures 1 and 2. In Figure auxiliary and control equipment.l Suitable cata l a raw petroleum or natural gas fraction such 35 lysts may be used in polymerization coils I8 and 'as a Cz-I-Ca fraction enters through pipe I0 to 46 and depolymerization coils 24 -and 52. Other suitable equipment and modifications will be obvi is cracked to a suitably limited degree. The ous to those skilled in the art. products leaving vthe, cracking coil are suitably Although the flow diagrams indicate continu cooled and then passed intofractionating system 44.0 ous processes, my invention may obviously be I3 which may consist of one or, preferably, two applied as abatch process as well. The following or three fractionating columns. A C4 fraction examples include two methods of ’practicing my ’ vis removed from fractionating system I3, through invention. pipe I6 and circulated at high pressure by means Example 1.-An ethane-propane mixture is of pump Il through polymerization coil I8 heated 45 cracked at one atmosphere pressure and 1450° F. by means of furnace I9. The partially polymer temperature deeply enough to form 5 per cent of ized product is removed through pipe 20 and C4 and heavier hydrocarbons. A C4 fraction is expansion Valve 3I to fractionating system 2| in separated having `the following composition. cracking coil II heated by furnace I2 where it which the normally liquid hydrocarbons contain ing diolefin dimers are separated' and removed through line _23 and expansion .valve 32 to a de so Butßnes‘, . PAT-‘fm polymerizing coil 24. The normally gaseous hy»- ` ’drocarbons’ are withdrawn from fractionating system 2| through pipe 22 and may be wholly or in part recycled to_ polymerization coil I8 or they may be completely discharged. The oily polymer is depolymerized in coil 24 heated by furnace 25 and _maintained at a suitably low pressure by Per cent 10 »Butadiene, FAHR 50 -rsobucyœna 04H» '3o Normal butenes, CiHs ____________________ __ 10 5. 100 fl‘his C4 fractionfis digesteu at 390° F. and 500 poundsv per square _inch gauge pressure long pump-compressor 25. 'I-‘he products are treated. enough` to convert 50 per cent of the total into 60 normally liquid hydrocarbons. The latter are ' in the fractionating system 21 consisting of _one separated by fractional distillation and are then or more columns. A Ci fraction rich in buta diene is removed from pipe 29, a fraction com»> » depolymerized bypassing through an empty tube Drising any lighter products formed by -cracking at 1 atmosphere pressure and 1022° F. at such a is discharged through pipe' 23 and a normally liquid residue is withdrawn through valve 33 and Dipe 3l and recycled through the depolymeriza irate that 20 percent per pass is converted into vgaseous products. The said’gaseous products are tion coil. _‘ - ’ - _ ’ l In Figure 2, is shown a similar apparatus suit separated and a C4 fraction is cut therefrom which is found to be concentrated butadiene. c Liquids boiling at 2o to 450° r'.v are recycled to able to apply the process of >this invention to the 70 the depolylnerization furnace. Example 2.-A C4 fraction of the vapors pro-> concentration of butadiene from such products as vapor phasev cracking gases'. 'I'hese gases enter duced in a vapor phase oil cracking process are fractionating system 4I "through pipe 4I. A C4 digestedvat 390° F._ and 500 pounds per square fraction vis withdrawn through pipe 43 by means inch gauge pressure suiliciently to convert 15 to of Pump 45 and passed through polymerizatiçml l 20’per‘l cent of the total into normally liquid hy 9,855,808 3 drocarbons. These polymeric liquid hydrocar merizationy step to conditions of elevated tempera bons are separated by fractionation and are then - . ture andv in the’~ presence ofbsuiilcient steam to passed at atmospheric pressure through a tube ?lled with bauxite at 93011'. at such a rate that 20 per cent per pass is converted into gaseous products. The said gaseous products are sepa rated and a C4 fraction rich in butadiene is cut therefrom while thenormaiiy liquid hydrocar bons arerecycled to the cracking> furnace. _ While the foregoing examples serve to illustrate two possible adaptations oi' my process they are not 'to be construed as limitations thereupon. since many other modincations within the scope of my invention will be obvioús to those skilled in the I claim :> maintain low partial pressure of the dimer which » . promote depolymerization ofthe dimer _to the monomeric diolefin, fracticnating the eilluefnt of the depolymsrization step to _separate the dioiefin from the dimer, and recycling the dimer to the' depolymerization sten» ` ` Y » 4. The process for the separation of butadiene from a mixture of C4 hydrocarbons which' com-` Prises subjecting the mixturein a polymerization step to conditions of elevated temperaturewith in the range of 300° l'. to 900° F. and superat mospheric pressure, _within fthe range or atmos pheric pressure' to about 500 pounds per square . v y l. The process for the separation of a low boiling open chain' dioleiin from a mixture of hydrocarbons having vboiling points substantially the same asV the boiling points of said diolenn which comprises subjecting the hydrocarbon mix- ' V ture in a polymerization step to conditions of ele vated temperaturel and superatmospheric pres sure which promote dimerization of said diol'eiin to the dimer thereof as the rincipal reaction occurring, separating the resisting dimer from the eiliuent of the .polymerization step. and sub iecting the dimer in a depolyinerization- step to ' conditions of'eievated temperatures and in the Ípresence of sumcient steam to maintain low par- ' tial pressure of said dimer electing conversion of said dimer to the monomeric low~boiling open inch which result in dimerization of butadiene in the presence of other Ci hydrocarbons to -the dimer thereof asthe principal reaction occurring. separating the dimer from the eilluent of the polymer-nation step. subiectins the dimer, urs de- ‘ polymerization step to conditions of elevated tem ventures in the range o! 900° l". to 1300° F. and in the presence of suiiicient steam v.to maintain low partiall pressure of the dimer which result in de polyr'nerization of dimer to monomeric butadiene,fractionating the eiiluent of the depolymeris'ation step in a fractionation step to form a fraction containing the monomeric butadiene and atrae# tion containing the dimer eiliuent oi the depoly merization step. and recycling the dimer from the fractionation step to the depolymerisation 3WD- " . ' chain dioleiin. 5. The process which comprisesrubiecting the 2. The processor claim i in which butadiene dimer of `butadiene to a temperature within the lathe low-boiling open chain dioleñn.- ' ~ 35 range of about 4900’ Il'. to about 1300“ IIL-in ad 3. The process for the separatign'of a low mixture with suiiicient steam to maintain the boiling open chain diole?n from a mixture of hy partial pressure of said dimer within the range drocarbons- having boilingpoints within about of 3 to 100 mm. eifecting depolymerisation of 15° F. of the boiling 'point of the dioiedn which said dimer- as the principal reaction oi' the proc comprises polymerizing the diolenn in the pres 40 ess. ‘ ence of said hydrocarbons in a polymerization 8. The process which comprises subjecting the> step under conditions of elevated temperature dimer of butadiene to a temperature within the and superatmospheric' pressure which- promote \ as the principal reaction dimerization of the di y oleiin to the dimer thereof having a boiling point appreciably greater than that of the diolefin. ranae of about 900' l". to about i300’ Ein ad mixture with suiiicient steam to maintain the par tialpressureo'fsaiddimerwithintherangeofä to 100mm. and in the presence of a magnesium fractionating the eilluent oi' the. polymerization ‘ oxide depolymerisation catalyst electing depoly- ' step to separate the dimer therefrom.> depoly merisation of said dimer as the principal reaction . merisingatleastapartofthedimerinthe o( the m ' eiiluent of the; polymerization _step in a depoly-` . anoressia. gamma..