Патент USA US2406695код для вставки
Aug. 27, 1946. ' G. R. LAKE SEPAÈATION OF HYDROCARBONS BY DISTILLATIQN Filed April 25, 1941 m“ ä„6ê5@ 1 2,406,695 2,405,695 Patented Aug. 27, 1946 >UNITED i STATES PATENTg OFFICE@ 2,406,695 SEPARATION OF HYDROCARBONS BY DISTILLATION George R. Lake, Long Beach, Calif., assigner to Union Oil Company of California, Los Angeles, Calif., a corporation of California Application April 25, 1941, Serial No. 390,264 4 Claims. ( Cl. 202-39.5) 2 This invention relates to the preparation of ing at a lower temperature with one or more of pure hydrocarbons from petroleum, these pure the components so as to permit separation from the other component. For this purpose, many azeotrope formers, some of which will be referred to hereafter, have been used. While the process hydrocarbons being contained in a fraction of petroleum hydrocarbons whose components have small differences in boiling points, which renders them inseparable by ordinary fractional distilla of azeotropic distillation to separate different tion. An object of the present invention is to further the progress in preparing pure compounds from a heterogeneous petroleum mixture, using in this hydrocarbons of substantially the same> boiling point has its advantages over other methods- for effecting the separation of these components, l() particular case a method which involves fewer steps than a chemical method, and which yields a purer product than that produced by careful fractional distillation and/or extraction with se lective solvents. Y _ Another object of the invention is to prepare from a given fraction of petroleum, such as gaso line, kerosene, or a narrow boiling range hydro .carbon fraction prepared from such materials, these fractions consisting of a mixture of paraf such as extraction with selective solvents, the process has the disadvantage of frequently re quiring large and efficient fractionating columns due to the fact that in many cases the difference in boiling point between the mixture of azeotrope former and the component associated therewith on one hand and the component remaining un distilled which may or may not be associated with aromatic hydrocarbons, a fraction that is essen azeotrope former on ther other hand, is small. For example, in the case of separating toluene from parañîn and/or other non-aromatic hydro carbons having substantially the same boiling point as the toluene employing methanol as the tially paraiiinic or iso-parañînic or naphthenic azeotrope former, the azeotrope of methanol and or oleñnic or aromatic. parañin and/ or other non-aromatic hydrocarbons is distilled at a temperature ofabout 143° F.’while the azeotrope of methanol and toluene is distilled at a temperature of about 148° YF. Hence, while the small difference in the distillation tempera ñnic, iso-paraiiinic, naphthenic, oleñnic and ' A particular object of my invention is to sep arate aromatic hydrocarbons from non-aromatic hydrocarbons having the same boiling point or range, particularly from gasoline fractions con taining relatively small quantities of the aromatic tures ofthe two azeotropes permits the separa hydrocarbons desired to be recovered from the 30 tion of the toluene from the non-aromatic hy gasoline. 1 . drocarbons, whereas without the azeotrope former A particular object of my invention is to sep such separation would be practically impossible arate a component or class of components from by fractional distillation, yet this small differ a hydrocarbon mixture, the components of which presence of an added substance, hereinafter re ferred to as an azeotrope former which is adapted to form an azeotrope or lower boiling mixture with one of the components or class of compo ence in distillation temperatures requires eili cient fractionation equipment in order to effect the desired separation. Also, in some cases, it is impossible to separate one class of components from another class of components from a rela tively wide boiling range hydrocarbon fraction due to the overlap in distillation temperatures nentsand also effecting the distillation in the of the azeotrope consisting of the azeotrope Yhave substantially the same boiling point or boil- .; ing point range, by fractional distillation in the presence of a second added substance, hereinafter former and the heavier components of one class referred to as a vapor pressure depressant which of components and the lighter components of is adapted to lower the vapor pressure of the the other class of components. My invention other component or class of components. In 45 relates to an improvement in the foregoing proc other words, it is an object of my invention to ess whereby I effect an increase in the difference increase the difference between the vapor pres between the aforesaid distillation temperatures, sures of the components desired to be separated thereby facilitating the separation of dilïerent by fractional distillation. components or different classes of components.:V I have discovered that in the aforesaid process of azeotropic distillation, the presence 0f a cer tain substance, i. e. a vapor pressure depressant , It is known to separate specific hydrocarbons or hydrocarbon fractions from a mixture of dif Vferent classes of hydrocarbons by a fractional ldistillation process known as azeotropic distilla ' which has an aflinity for the higher boiling com tion wherein a substance is added to the mixture ponent or higher boiling azeotrope ordinarily re to be distilled which will form an azeotrope boil .55 maining as still bottoms during the aforesaid 2,406,695 3 tion of the component remaining undistilled. At when separating heptanes, octanes, nonanes, de canes and/or naphthene hydrocarbons having similar carbon atoms from toluene, xylenes and substantially aifected. For example, in the af ore used in substantially anhydrous form in order to azeotropic distillation has the effect of depress ing the vapor pressure or retarding the distilla ethyl benzene. -Some of the azeotrope formers the same time, the distillation temperature of the `azeotrope formed with one of the components Ul mentioned herein .are more eflicient when used in the‘presence of water while others must be which is first distilled from the mix-ture is not mentioned obtain the best results. For exampley methyl ethyl ketone may contain from 0 to 25% by vol case of separating toluene from paraffin and/or other non-aromatic hydrocar bons employing an azeotrope former, the presence ume of water to be operative. As vapor pressure depressants which I have found are phenolic compounds such as cresylic of a vapor pressure depressant during the dis tillation does not appreciably affect the distilla acid, phenol, Xylenol and resorcinol. In general, when choosing azeotrope formers tion temperature at which the azeotrope con sisting of azeotrope former and the parailin and/or other non-aromatic hydrocarbons is dis tilled; however, the vapor pressure depressant materially retards the distillation of the higherboiling azeotrope of the azeotrope former and toluene so that it Will require a somewhat higher still temperature, depending of course, upon the particular `substance employed as the vapor pressure depressant in order to distill it, than whenk the distillation is eiîected in the absence of the vapor pressure depressant. This is particu and vapor pressure depressants for eiîecting the distillation, it is preferable to employ an azeo trope former having substantially the same boil ing point as the stock, and preferably boiling not more than about 100° E'. below or about 40° F. above the boiling point of the stock. When choosingV a vapor pressure depressant, it is pref erable to choose one boiling substantially above the boiling point of the stock, preferably boiling greater than about 100° F; above that of> the stock. Moreover, when choosing azeotrope larly true in the case where the azeotrope former formers and vapor pressure depressants for ef fecting the distillation it is, of course, necessary only forms an azeotrope with the non-aromatic hydrocarbons and does not form an azeotrope with the undistilled aromatic hydrocarbons. In toselect pairs which arenot chemically reactive with each other because if they did react the this manner, the difference in distillation tern reaction products would not necessarily be either peratures of the paranin or non-aromatic hydro carbons associated> with azeotrope former and the toluene,_ whether associated with azeotrope former or not, is increased considerably so that it is possible to effect a sharper and more enicient separation of the toluene fromv the paraliin azeotrope formers or vapor pressure depressants. In carrying out they process, the distillation of the mixture of hydrocarbon fraction, azeotrope former and vapor pressure depressant is con tinued until all of one of the components has been distilled from the mixture, and/or other non-aromatic hydrocarbons. It is possible that the presence of the vapor pressure depressant will require a higher still tempera ture to remove the azeotrope of paraffin and/or other' non-aromatic hydrocarbons than without 40 its presence, yet the still temperature required to distill the azeotrope of toluene and azeotrope former is increased to a greater extent or pro portion than without its presence so that the net' difference inv distillation temperatures of the 45 foregoing azeotropes is greater than when the distillation is effected in the absence of the vapor pressure depressant. Y While the invention is adapted for the separa tion of hydrocarbons of characteristics different lfrom each other, I have found that this process is particularly useful for producing toluene hav ing a very high degree of purity from gasoline fractions produced from straight run or syn thetic gasolines such as lthose produced by crack 55 ing, polymerizing orv reforming. The production of substantially pure toluene is highly important >particularly when it is to be used in the manu facture of explosives by nitrating the toluene since small amounts of impurities seriously im pair the ni-tration process. . As azeotrope formers which I have found use full are aliphatic ketones such as methyl ethyl ketone, acetone and cyclic aliphatic ketones such as cyclohexanone. Of'the above mentioned azeotrope formers, I have found' methyl ethyl ketone and acetone, particularly eñicient azeotrope formers for sepa rating a hydrocarbon fraction having a boiling range between 20G-300° li'. into hydrocarbon components of different chemical characteristics and are particularly useful for separating'paraf ñn and/or naphthene hydrocarbons having 7 to 10 carbon atoms from aromatic hydrocarbons having 9 or less carbon atoms, as for example, 60 This component which` is Vaporized is condensed together with the azeotrope former. In order to separate the azeo trope former from the oil condensate, it is merely necessary to cool and/or mix the-condensate mix ture with water which dissolves in the azeotrope former and allows the hydrocarbons to separate from the azeotropeformer. By allowing this mix ture to settle, two distinct layers are formed, an upper layer consisting of the hydrocarbon and a lower layer of diluted azeotrope former. «When the azeotrope former isA used in the presence of water in the distillation operation, the‘condensate will ordinarily stratify into the two above-men tioned layers. However, it may be desirable to add additional water to the condensate' in order to insure complete separation of the azeotrope former from the hydrocarbon. The azeotrope former may berecovered from the water by sim ple distillation. If desired, the azeotrope former may be returned to the still withI additional feed stock, it being apparent that when the azeotrope former is used in the presence 0f water and a separate layer forms when the overhead is con densed that the separated layer of Water and azeotrope former may be returned directly to the still. When all of the component has* been dis tilled, the still temperature is raised and the other component is distilled from the vapor pressure 65 depressant whether alone or associated with azeo trope former. When separating one class of hydrocarbons from another class of hydrocarbons in an oil frac tion having a Wide boiling range, it is preferable to first fractionate the wideA boiling range stock into a plurality of fractions, each having a nar row boiling range. Each of' these fractions may then be separately subjected to azeotropic distilla tion in the presence of a vapor pressure depres sant in order to- effect the separation into the 2,406,695 '5 . variòus> classes of components,N These separated 6 By adding a vapor pressure depressant to the- components'may then be blended in any desired above mixture, this will tend to shift the distilla proportion. ' For example, suppose it were desired tion range of the aromatic hydrocarbons so that to separate parañin hydrocarbons from aromatic hydrocarbons in a petroleum fraction composed of these components and having a wide boiling range of, Vfor example, 200`to`400° F.; this stock 'may be fractionally distilled to produce ten frac tions, each having a'`- boiling range difference of about twenty degrees. Each fraction may then be 10 instead of the aromatic fraction having a distilla subjected to azeotropic distillation in the presence of vapor pressure depressantl to separate paraffin hydrocarbons from aromatic hydrocarbons. The -various paraii‘in hydrocarbons may then be blend tion range of 200° to 500° F., it will now- have a higher distillation range of, for example, SOO-600° F.- so that the fraction now distilling between 100-300° F. will be substantially paraflinic, that distilling between 300°-400° F. will be a mixture of parafûnic and aromatic fractions while the fraction remaining in the still which distills above » 400° F. in the presence of the vapor pressure de pressant will be substantially aromatic. Thus, by effecting the distillation and separately col ed to produce a hydrocarbon fraction having the 15 lecting the above fractions and removing azeo same boiling range as the original stock andcom posed ¿of substantially paraffin hydrocarbons. This may be done with the'various aromatic hy trope former and vapor pressure depressant, we will now have the three oil fractions named above, i. e. one paraliinic boiling between 20D-400° F., drocarbons. I have found that by carrying out one aromatic boiling between 3D0-500° F. and one the process in this manner that a sharper separa 20 a mixture of the two. Since the aromatic hydro tion of components may be obtained from stocks carbons boiling between 3D0-500° F. and the having wide boiling ranges than if these stocks ’were subjected directly to the distillation without prior separation into narrow .boiling range frac tions. The foregoing procedure of separating a wide paraflinic hydrocarbons boiling'between 20G-400°r boiling range fraction into narrow outs and sub jecting each fraction to separate azeotropic dis tillation in the presence of a vapor pressure de F. have been separately recovered, the mixed frac tion will be composed of aromatic hydrocarbons boiling in the lower boiling range- of the stock, i. e. 20G-300° F. and parafûn hydrocarbons boil ing in the higher range 0f the stock, i. e. 40o-500° F. After removing the azeotrope former by mix ing with water and stratifying, the aromatic hy pressant and then blending the components of like characteristics is particularly useful in the drocarbons may be readily separated from the production of high viscosity index lubricating oils. In order to produce high quality lubricating oils from naphthene base crude oils, it is generally vnecessary to subject the lubricating oil fractions to extraction with solvents capable of effecting Since there is a Wide diiïerenoe in boiling points a separation of relatively non-paraiñnic from relatively parañinic oil fractions. However, due to the wide boiling range of the lubricating oil paraflinic hydrocarbons by fractional distillation. between these aromatic and paraiñnic hydrocar bons, separation is readily accomplished. By blending all' of the aromatic hydrocarbons thus separated, we will have an aromatic hydrocarbon fraction having the same boiling range as the original stock. The same can be done with the various paraflinic fractions. This same procedure fractions, it has been impossible to accomplish 40 can be used to treat lubricating oil stocks in order this by azeotropic distillation of the entire lubri to recover the more paraflinic oil fractions which give high quality lubricants. ' cating oil fraction. However, by carrying out the jazeotropic distillation in the presence of a vapor The foregoing process is also applicable to the pressure depressant, the lubricating oil stock may separation of wax from oils containing the same. be separated into fewer fractions, each having a 45 This is possible due to the fact that »the wax com ponents 'are pure paraffin hydrocarbons while the wide boiling range and thereby reducing the num oil fractions are not pure parañìn hydrocarbons. ber of azeotropic distillations necessary to effect . - s Thus, the wax components will form an aZeo While the foregoing separation of a wide boil trope with azeotrope formers having a lower boil ing range oil fraction into narrow cuts before 50 _ing point than the fluid oil components in the lubricating oil stock. The boiling point of the lat >azeotropic distillation of each cut in the presence >ter is depressed by the presence of the vapor pres of a vapor pressure depressant is preferred, I may sure depressant. When a lubricating stock is eñîect the separation of a wide boiling oil fraction Vcomposed of wax, relatively paraflinic and rela- f into its different components such as aromatic >the desired separation. and paraf’rlnic components, by the following pro 55 tively non-paraflinic oil fraction, azeotropic dis tillation in the presence of the vapor pressure de cedure, When the azeotrope former is added to pressant ywill first cause the distillation of the such an oil fraction, an azeotrope is formed with waxy constituents and then the non-waxy rela one class of components thus lowering their boil tively more paraflinic fractions which may be sep ing point. The boiling point range ofthe azeo trope, however, ranges below and within the lower 60 arately collected. This wax separating procedure may be carried out on either narrow boiling frac _portion of the boiling range of the other class of tions as described above or on a wide boiling frac components in the hydrocarbon mixture. For tion which may be separated intoits component :examplalet us consider a hydrocarbon fraction boiling between 200 and 500° F. and composed of classes as also described above. ' paramn and aromatic hydrocarbons. By adding 65 Other objects, featuresand advantages of my invention will be apparent to those skilled in the an azeotrope former only to this mixture, an azeo art from the followingdescription of the invention trope is formed with the paraiiin hydrocarbons as taken from the drawing which represents a distilling between 100° and 400° F. Thus, the hydrocarbon material distilling from 100° F, to diagrammatic arrangement of apparatus -for car 200° F. will be substantially paraffìnic and the 70 rying out my invention. ' _ >hydrocarbon fraction distilling between 200° In the drawing, the hydrocarbon feed to be resolved into components of similar characteris and ¿100° F. will be a mixture of parafñnic and aromatic hydrocarbons, while the fraction re tics, as for example, a hydrocarbon fraction pro maining in the still which distills above 400° F. duced from catalytically treated or reformed gas vwill be substantially aromatic. oline having a boiling range of about 220 to 235° F. 2,406,695 8 pumped by pump 55 through line 5Sv into frac-vtionating column 51 in which the aromatic hy and; consisting of substantially 45%I toluene,~ 6% o‘leñns and the» remainder parafiins andv naph trolledv by valve I2 and pumped by pump i4 into line l5. Azeotrope former, such as methyl ethyl drocarbon, i. e. toluene, is distilled by steam heat in coil 58 and is removed via line 59, condensed in 60 and passed through line 5l into storage ketone, containing about 10% water, is taken from tank i6 via line I1 controlled by valve I8 umn consisting of cresylic acid are withdrawn via thenes, is taken from tank l0 via line il con tank 62. The bottoms in the fractionating col line $3 controlled by valve 64 and pumped by pump 55 through line 60 into storage tank 2l. In the foregoing, while- not disclosed, a portion of the condensate obtained» by condensing the and is pumped by pump l0 through line 20 into line l5. Vapor pressure depressant, such as cresylic acid, is taken from tank 2l via line 22 controlled by valve 23 and is pumped by pump 24 through line 25, Valve 20 and line 2l into line l5. This mixture in line l5 consisting of the hydro carbonv feed, azeotrope former and vapor pressure depressant in the ratio of approximately one part by volume of hydrocarbons,l one part of methyl ethyl ketone and- water and ñve parts of cresylic overhead from each fractionating column such as 23, 41 and 51 may be recycled tothe top of the column to act as reflux and control the frac tionation. The foregoing description is not to be taken as limiting my invention but4 only as illustrative as many variations may be made by those skilled in the art without departing from the scope of the acid, is then passed into fractionating column 23 Where the mixture is subjected to fractionation, heat being supplied by closed steam coil 2S. If 20 following claims. l'. claim: desired, the vapor pressure depressant may be in 1. A process for the treatment of a narrow troduced directly into the fractionating column boiling range complex hydrocarbon fraction to via» line 2l’ controlled by valve EES’ and throughV separate at least one component from other com either valve 25a or 2Gb depending upon whether it is desired to introduce it into the top or bottom 25 ponents contained therein which ordinarily distill from the hydrocarbon fraction in the same tem of the column. In some cases, it may be desired perature range as said component distills there to introduce the vapor pressure depressant into from. which comprises fractionally distilling said theA top of the column so as to act as reflux there complexy hydrocarbon fraction in the presence of a suiilcient amount of an aliphatic ketone having a boiling point within 100° F. below and 40° F. above the average boiling point of said complex hydrocarbon fraction to vaporize at least one in. In the fractionating column, the distillation is controlled so'as to distilloverhead an azeotrope consisting or the paraffin, olefin and naphthene hydrocarbons and the methyl ethyl ketone and water. In the example herein- given, this is ac complished at an overhead temperature of ap component of» said complex hydrocarbon fraction proximately 160° F. If desired, the azeotropic dis 35 together with said. aliphatic ketone and in the presence of a phenolic compound having a boiling tillation may be carried out either at atmospheric point of at least 100° F. above the average boiling orl superatmospheric pressure or under a vacuum. point of saidr complex hydrocarbon fraction The above overhead mixture is removed from the adapted to remain in the residue together with fractionating column via line 30, condensed in at least one component of said complex hydro condenser 3l and passed via line 32 into the bot 40 carbon fraction, thereby leaving at least one com ponent of said complex hydrocarbon fraction in such as broken tile 33a, for effecting intimate the residue together with said phenolic compound countercurrent contact with` water which is in substantially completely separated from at least troduced into the washer from tank 34 Via line 35 one component of said complex hydrocarbon frac 45 controlled by valve- 35 and pumped by pump 3l tion. Y through line 38 into `the washer. The contact of 2. A process for the treatment of a narrow the condensate of methyl ethyl ketone, water and boiling range complex hydrocarbon fraction con hydrocarbons introduced into the Washer with taining relatively aromatic and relatively non the Water causes the condensate to separate into aromatic hydrocarbons to separate the relatively two phases, i. e. an upper phase consisting of the aromatic hydrocarbons from the relatively non paraffin, olefin and> naphthene hydrocarbons and aromatic hydrocarbons contained therein which a lower phase consisting of methyl Vethyl ketone ordinarily distill from said complex hydrocarbon and water. The upper phase is withdrawn via fraction in the same temperature range as the line 39» and is passed through cooler ‘40 and line relatively aromatic hydrocarbons distill there 4l to storage tank 42. The washing operation' is « from which comprises distilling said complex hy preferably carried out at an elevated temperature drocarbon fraction in the presence of a suiiicient of approximately 300° F. under superatmospheric amount .of an aliphatic ketone having a boiling pressure. point within 100o 1i'. below and 40° El. above the The lower phase is withdrawn via line 43~ con average boiling point of said complex hydrocar trolled by Valve 44 and is pumped by pump 45 60 bon fraction to vaporize the relatively non-aro through line 40 into fractionating column 41 matic hydrocarbons together with said aliphatic where the methyl ethyl ketone containing the ketone and in the presence of a suñicient amount desired amount of water, i. e. about 10%, is re of a phenolic compound having a boiling point Y moved as an azeotrope aided by heat in steam of at least 100° F. above the average boiling point coil 48, as an overhead ‘vapor via line 49, con of said complex hydrocarbon fraction adapted to densed in condenser 50 and returned via line 5l remain in the residue together with said relative to= storage tank l5. The undistilled Water sub ly aromatic hydrocarbons, thereby leavingk said stantially free from methyl ethyl ketone is re relatively aromatic hydrocarbons in the residue moved Via line 49 controlled by valve 50 and is torn of Washer 33 provided with packing material, pumped by pump 5l through line 52 to storage ” substantially completely separated from the hy tank 34. The bottoms in the fractionating column 28 consisting of aromatic hydrocarbons and vapor hydrocarbons. drocarbons other than said relatively aromatic 3. A process for separating toluene from paraf iin and other non-aromatic hydrocarbons having moved via line 53 controlled- by valve 54 and 75 similar boiling points which comprises addingv an pressure depressant, i. e. cresylic acid, are re 2,406,695 ` t 9 10 ‘ 4. A process for separating toluene from paraf ñn and other non-aromatic hydrocarbons having similar boiling points which comprises adding methyl ethyl ketone adapted to form an azeotrope boiling point‘of said hydrocarbons and adding Ul with the parañin and other non-aromatic hydro carbons and adding also cresylic acid adapted to also a phenolic compound adapted to depress the aliphatic ketone adapted to form an azeotrope with the parafûn and other non-aromatic hydro carbons, said aliphatic ketone having av boiling point Within 100° F. vbelow and 40° F. above the vapor pressure of the toluene„said phenolic com pound having a boiling point of at least 100° F. above the boiling point of said hydrocarbons and fractionally distilling the mixture to vaporize an azeotrope of said aliphatic ketone and non-aro ` matic hydrocarbons from said toluene and phe nolic compound. depress the vapor pressure of the toluene, and fractionally distilling the mixture to vaporize an -azeotrope of said methyl ethyl ketone and non aromatic hydrocarbons from said toluene and cresylic acid. lGrEORG‘rE R. LAKE.