Патент USA US2405300код для вставки
Aug. 6, 1946. R_ B, GREENBURG 2,405,300 RECOVERY OF XYLENES Filed Jan. '7, 1944 Condenser www ATTORNEY. Patented Aug. 6, 1946 Vuru'rrsl) `sfm'nt s PATENT oFFicE 2,405,300 ‘ nEcovEaY or xYLENEs ' Richard B. Greenburg, Melrose ark, Pa., assign or to Allied Chemical & Dye Corporation, New York, N. Y., a corporation of New York Application January "l, 1944, Serial No. 517,335 >«t Claims. (Cl. 2055-42) 1 This invention relates to a process~for recover ing xylene hydrocarbons from mixtures contain ing them together with other hydrocarbons. In this specification and the appended claims thev term “xylene” is used in its comprehensive mean ing as referring to aromatic compounds of the benzene series boiling in the range of temper atures at which the several xylenes boil. The . term as thus used includes the three xylenes, matic hydrocarbons including oleiins and par affins or naphthenes, By fractional distillation of these oils contain ing xylene, fractions of increased xylene con tent may be obtained. These xylene fractions, however, will still contain large amounts of the other constituents of the oil having boiling points in the neighborhood of the boiling point of xy lene or forming mixtures of constant boiling points in the range of temperatures at which Xy ortho-, meta- and para-xylene, and ethyl ben 10 lene distills from the oil. > Accordingly, recovery zene. Numerous hydrocarbon oils are known which contain xylenes in varying proportions. For ex of xylene of a relatively high purity from these sources presents a diillcult problem of great in dustrial importance. ample, gasoline fractions obtained by the distil The fact that the oils containing xylene have 15 lation of certain types of petroleum frequently generally a relatively low content of xylene makes contain substantial proportions of xylene, al it particularly diiilcult to recover by fractional .though mainly consisting of other hydrocarbons. ' distillation or selective solvent extraction or a Oils of petroleum origin having a considerable combination of both of these procedures a xylene content of aromatics, including xylene, may be product of a high degree of purity. For example, treated by well known selective solvent processes 20 drip oils may contain about 5% ortho-xylene. to produce fractions rich in aromatics; for exam ple extraction of suitable fractions of such pe troleum oils with sulfur dioxide may yield frac tions of increased xylene content. In such cases Distillation of a drip oil with efficient rectifica tion of the vapors may b_e employed to recover xylene is accompanied by non-aromatic oils which may be largely paraflinic, naphthenic or oleiinic . a fraction containing more than about 80% to a fraction in which the ortho-xylene is concen trated. However, even with efficient rectification 85% ortho-xylene can rarely be obtained. Ole in character. A considerable portion of these fins together with paraflins and usually some non-aromatic oils cannot be separated from the naphthenes and traces of meta- and para-xylene, xylene by direct fractional distillation because 30 make up the remaining 15% to 20% of the ortho of the closeness of their boiling points to that xylene fraction.` The non-aromatic hydrocar of xylene or because they form constant boiling bons individually may have boiling points rang mixtures with xylene. Also synthetic hydrocar ing from considerably below' to above the boiling bon liquid and gas mixtures produced by various point of ortho-xylene, e. g. their boiling points catalytic processes may contain xylene which is may range from 100° to 155° C., whereas ortho accompanied by similar difilcultly separable con 35 xylene boils at about 144° C. Nevertheless, these non-aromatics cannot be 'separated from the stituents. While ordinarily xylene may be separated by ortho-xylene by fractional distillation of their direct fractional distillation from light oils pro-` mixtures, e. g. drip cils and cracked petroleum duced by the gasification of coal, in some cases the oils, under practical conditions.l Apparently in 40 xylene is accompanied by diflicultly separable the mixture the various hydrocarbons form azeo non-aromatic oils of the- same general character tropes with each other and this prevents their as described, owing to carbonization conditions, separation by fractional distillation. Such hy type of coal used or other special circumstances. drocarbons, those which cannot be separated by 'This is particularly true of drip oils and oil frac fractional distillation or are difilcultly separable tions recovered therefrom containing ortho-xy 45 by fractional distillation under practicable con lene and like-boiling, non-aromatic hydrocarbons, ditions for distilling oils, are >referred to as e. g. naphthenes, parafii’ns and oleiins. “like-boiling” hydrocarbons. Chemical treatment By "drip oil” I refer to those condensates from of oils containing ortho-xylene and like-boiling carburetted water gas such as the condensates hydrocarbons may be used to recover pure ortho-50 formed in the gas distributing lines or holders or xylene therefrom, but such known methods are the light oil which may be condensed in cooling cumbersome and expensive. the carburetted water gas lafter removal of tar. It is, therefore, an object of this invention to A common characteristic of drip oils is that in provide a process for azeotropically distilling the addition to aromatic hydrocarbons, they contain 55 xylene-containing oil in the presence of an azeo a substantial proportion of like-boiling, non-aro 2,405,300 . , ~ -3 - v ;ropic agent which is particularly eiTectiv-e for separating from the xylene klike-boiling, non aromatic compounds contained ln the oil to ob tain a commercially pure xylene product. _ It is a further object of the invention to pro vide a process for the separation of xylene from fractions of petroleum oil or drip oil containing xylene and a mixture of other hydrocarbons ~of 4 . over. the ethylene diamine being then separated _` from the xylene in any desired manner. for ex-' ample, by washing the mixture with dilute hy drochloric acid followed by a water wash of the xylene to remove the acid and dehydration of the washed xylene.I ' The ratio of ethylene diamine substantially free of water to the xylene fraction which may similar boiling range. be employed in carrying out this invention de I have discovered that ethylene diamine forms 10 pends upon the amount and nature of the hydro azeotropes with the xylenes and also with the carbon impurities in the xylene fraction, the non-xylene hydrocarbon constituents present in purity desired in the xylene residue from the dis the oil and distilling therefrom in the range of tillation, the proportion of xylene in the original temperatures at which the xylene distills from xylene fraction which is to be recovered in the the oil. The xylene azeotropes, however, boil at residue, the procedure used for distillation of the a substantially highertemperature than the non ethylene diamine-xylene mixture, and the equip `xylene ethylene diamine azeotropes, permitting ment employed. The quantity of ethylene di~ separation of the xylene. It is significant to amine used in the distillation of hydrocarbons note that the spread between the boiling point a given quantity of xylene fraction should of the xylene-ethylene diamine azeotropes and 20 from be in excess oi' that which will form azeotroplc the point at which the non-xylene-ethylene di mixtures with the non-xylene hydrocarbons which amine azeotropes begin to distill over is greater in the case of the ethylene diamine than in the case of many of the numerous other azeotropic agents tested in the extensive development work which led up to the present invention. The presence of substantial amounts of water are to be vaporized and taken over into the dis tillate. By returning most or all of the ethylene diamine collected from the distillate to the still, for example, as 'reñux liquid, the total amount of ethylene diamine necessary to eil‘ect the sep aration of the non-xylene constituents and the in the complex mixture constituted of xylene, xylene will be materially- reduced. If desired, hydrocarbons of parafilnic character distilling at fresh ethylene diamine may be introduced‘into temperatures close to that of xylene, other close 30 the xylene fraction being distilled during the boiling hydrocarbons which may be of naph course of the distillation; also, the ethylene di thenic or oleflnic character, and ethylene diamine, amine separated from the -distillate may be re should lbe avoided. Even the presence of 1% of turned continuously or periodically to the still or water is objectionable in that it involves some rectification column while the distillation of the loss of xylene. Accordingly, the preferred em 35 xylene fraction is progressing. , bodiment of the invention involves the use of sub Regulation of the temperature in the rectliica stantially anhydrous ethylene diamine as azeo tion of the vapors to meet the aforesaid condi tropic agent, e. g. the water present being limited tions is accomplished by maintaining an adequate to no more than 5% by weight of the ethylene quantity of the ethylene diamine substantially diamine. More water may be present at a sacri 40 free of water in the still or rectification column fice in the eiliciency of the process but in no event or both during the distillation of the iwlene frac should it exceed 10% by weight of the ethylene tion to selectively carry over through the rectifi diamine. The expression “ethylene diamine sub stantially free of water” is> used in this specifica tion- and appended claims to define an anhydrous ethylene diamine or an ethylene diamine con taining up to but no more than 10% water. In carrying out the distillation of the hydro carbon mixture containing xylene, close boiling cation treatment the vapors of the non aromatic hydrocarbons to be removed from the xylene. Some of the xylene may also be carried over, but as long as the temperature of 114° C. in the recti ñcation zone is not exceeded, the undistilled resi due will be enriched in xylene, and by continuing the distillation under the aforesaid conditions non-aromatic hydrocarbons, and ethylene di 50 separation of the non-aromatic hydrocarbons of amine to produce relatively pure xylene, the dis similar boiling range to that of xylene from the tillation is conducted with rectiiication of the xylene will be accomplished` evolved vapors While maintaining at a point in As the distillation proceeds temperature read the rectiñcation of the vapors a temperature not ings are taken of the temperature at the top of above 114° C. By supplying to the distillation 55 the rectification column and, by supplying addi adequate amounts of ethylene diamine, this con tional azeotropic agent when required to prevent trol temperature may be maintained and the dis this temperature from rising above 114° C. an tillation continued until the unvaporized residue adequate amount of ethylene diamine substan contains at least 95 parts by weight of xylene for tially free of water will be present during the sep every 5 parts by weight of non-aromatic hydro 60 aration of the non-aromatic hydrocarbons from car-bons of similar boiling range to that of xylene.' the xylene fraction. It is not necessary that this If the control temperature should tend to rise point of control temperature be at the top of the above 114° C., this is an indication that the column, although this is a satisfactory point for amount of ethylene diamine is inadequate and determining this temperature in the equipment more of this material should be introduced. The used for fractionating the vapors and condensing closer to 114° C. the control temperature is main vthe fractionated vapors for effective use of the tained the purer the xylene product. By operat rectification column. One skilled in the distilla ing in accordance with these conditions I have tion art will recognize suitable points for main found it possible to produce from'xylene fractions taining this control temperature in any specific boiling Within the range 125° to 150° C. substan 70 apparatus according to well known distillation tially 100% pure xylene; i. e., to eifect complete principles. separation from xylene of the hydrocarbons of The distillation preferably is carried out at similar boiling range to that of xylene by con atmospheric pressure; it may, however, be carried tinuing the distillation until only xylene and out under vacuum or under superatmosphericfI ethylene diamine are left in the still or distill 75 pressure. If carried out under vacuum or super . 2,405,300 atmospheric pressure the »control temperature is modified accordingly so that it corresponds tothe boiling point of the xylene-ethylene diamine azeo ‘ lexceeded at a point in the rectification of the distilled vapors. - , The residue of the azeotropic distillation may be purified further as desired to remove any ethylene diamine which it contains and to remove any other impurities present. When the distil lation is carried to the point at which all of the ethylene diamine hasl been distilled out of the residue and the xylene constitutes substantially trope under the changed pressure. The tempera tures as given in this specification and the ap . pended claims are corrected temperatures for 1 atmosphere pressure (760 mm. of mercury). In practicing this invention in the treatment of an oil such as has been described above, con 99% or more of the total hydrocarbon content of taining xylene and other hydrocarbons, particu 10 the residue, the residue may be given a conven larly when the xylene concentration of the oil is tional treatment, for example, treatment with low or the oil is one containing materials of wide sulfuric acid and redistillation, to obtain a‘prod boiling range, it is preferred to iirst fractionally uct which is suitable for marketing as a nitration ` distill the oil to recover therefrom an enriched grade xylene of particularly high purity. xylene -fraction which contains in addition to 15 Instead of withdrawing the xylene residue from xylene other hydrocarbons which distill at the the still, the distillation may be continued „and the xylene. Although - same temperature as the xylene distilled over and separately collected xylene fractions having an end boiling point from the distillate containing the hydrocarbons above the boiling point of xylene (e. g. a boiling from which the xylene residue previously had 20 point up to 150° C.) may be azeotropically dis been separated by azeotropic distillation. If tilled in the manner hereinafter described, I pre ethylene diamine is present during the distilla fer the xylene fraction recovered in the prelim tion and collection of the xylene, the ethylene di inary distillation step be one having a maximum amine may be distilled out in the form of an azeotrope of xylene. The xylene may be sepa boiling point of ortho-xylene, i. e. 145° C. Fur 25 rated in any suitable manner from this azeotrope, ther, it is preferred that the xylene fraction re for example, by treatment with HCl of 10% con covered by the preliminary distillation of the centration which will remove the ethylene di crude xylene oil be so cut as to exclude therefrom amine from the xylene. boiling point substantially corresponding to the the forerunnings which do not contain substan tial proportions of xylene, for example, to exclude The following example is illustrative of the use of my invention for the recovery of xylene from oils containing it together with like-boiling, non any materials distilling below 125° C. and pref erably below 135° C. A xylene fraction such as may be obtained by aromatic hydrocarbons: the preliminary distillation hereinabove de process of this example is, diagrammatically illus I An apparatus suitable for carrying out the scribed, e. g. a fraction boiling Within the range 35 trated in the accompanying~ drawing. It com 125° to 150° C., preferably 135° to 145° C., and prises a still l with heater 2 and rectification col which may contain parafiins, naphthenes or ole umn 3 of conventional design. A condenser 4 is ñns, is subjected to a second distillation and recti provided to which the vapors from the top of the fication of the vapors in the presence of ethylene column pass and in which they» are cooled and diamine substantially free of water. When the 40 condensed. A pipe 5 returns a portion of the con hydrocarbon mixture is subjected to fractional densate from the condenser to the top of the rec distillation with rectification of the vapors under tiñcation column to serve as reilux in the column. conditions such that a temperature not exceeding lA second pipe 6 is provided for drawing 01T a por 114° C. is maintained at a point inthe rectifica tion of the> condensate as product. Pipes 1 and 8 45 tion of the vapors, the azeotropes of non-aromatic are provided for introduction of liquids into still hydrocarbons and ethylene diamine may be dis I and a pipe 9 for withdrawal of residue from tilled oiî from the mixture to leave a residue con this still. taining at least 95 parts by weight of xylene to every 5 parts by weight of like-boiling non-aro ' f By fractional distillation of an aromatic petro leum oil a cut was taken distilling over at 127° to matic hydrocarbons originally present in the 50 150° C. in which the xylene of the petroleum oil xylene fraction and not separable therefrom by was concentrated. This xylene fraction con ' tained 58% by volume xylene. To every 100 vol umes of the xylene cut introduced into still I, 100 volumes of an ethylene diamine substantially After the distillation has been carried to the point where the residue contains xylene of a de 65 free from water (95% ethylene diamine and 5% Water) was added and the mixture distilled with sired purity with respect to non-aromatic hydro rectification of the vapors in a conventional rec carbons of similar boiling 'range to xylene, the tiñcation'column 3 supplied with reflux obtained distillation may be stopped and the residue with by returning to the column through pipe 5 a part drawn from the still, This residue ordinarily ofthe condensate from the vapors leaving the top will contain xylene and other hydrocarbons in the of the column. Another part of this condensate proportion of 95 or more parts xylene to 5 or less direct fractional distillation in the absence of the azeotropic agent. » parts of the total hydrocarbons other than xylene. By suitably limiting the top boiling point of the xylene fraction which is azeotropically distilled 65 a residue of the azeotropic distillation may be produced of desired purity of ' its yhydrocarbon content greater than 95 parts xylene to 5 parts non-aromatic hydrocarbons. A residue contain ing the xylene substantially free of non-aromatic ' hydrocarbons may be obtained by distilling a was drawn olli as overhead distillate through pipe 6. " Distillation started with the vapors at the top of the column at a temperature of 103.6° C. This temperature rose during the distillation to 114° C. ' and the last fraction distilled over at that tem xylene. The perature contained 95% by volume hydrochloric acid ~ residue was washed with 10% solution to remove ethylene diamine and the oil separated from the solution was found to contain xylene fraction having a top boiling point not 98% by volume xylene. ' higher than 145° C. in the presence of ethylene It is, of course, obvious preliminary distilla diamine in amount such that a temperature of tion of a crude xylene oil to obtain a xylene substantially 11B-114° C. is reached but is not 75 2,405,300 . fraction suitable for recovery oi' xylene therefrom by the areotropic distillation need not be carried out in immediate conjunction with the azeo tropic distillation. 'The >xylene fraction may be produced in one plant, transported to and treated later in another plant to azeotropically distill it. Nor is my invention limited to any particular procedure for the production of the xylene irac 8 ' ethylene diamine substantially free from water while maintaining at a point in the rectincation oi' the vapors a temperature not above 114° C. by maintaining the presence of -said ethylene di amine at said point, whereby said non-aromatic hydrocarbons are removed as azeotropic distillate with ethylene diamine, and continuing the saidv distillation until the unvaporized residue of the contains at least 95 parts by weight ethylene diamine substantially free of water any 10 ’distillation of xylene to each 5 parts by weight of non oil containing xylene together with non-aromatic aromatic hydrocarbons which distill from said hydrocarbons which, when the oil is distilled, va fraction in theabsence of ethylene diamine in porize therefrom in the same temperature range the same temperature range as the xylene. tion. My invention contemplates distilling vwith _ as the xylene, and, therefore, are not separable 3. A process for the recovery of substantially . from the xylene by direct fractional distillation. 15 pure xylene from a complex hydrocarbon fraction boiling within the range of 135°' to 145° C. con claims, the term “xylene fraction” refers to all taining xylene and at least 15% of non-aromatic such xylene-containing oils, yWhether produced hydrocarbons which distill from said fraction in by fractional distillation of xylene-containing the same temperature range as the xylene dis materials or by any other means. As has been 20 tills therefrom, which comprises distilling said pointed out above, these xylene fractions in gen fraction and rectifying the vapors evolved there eral contain substantial quantities (15% or more) from in the prœence of ethylene diamine sub o_f non-aromatic hydrocarbons which it is par stantially free from water while maintaining at ticularly difficult, and in many cases impossible, a point in the rectincation of the vapors a tem to separate from the xylene by any practicable 25 perature not above .114° C. by maintaining the method of fractional distillation or solvent ex-‘ presence of said ethylene diamine at said point traction. The process of my invention is particu and continuing the said distillation until sub larly valuable as a means for recovering relatively stantially all of the non-aromatic hydrocarbons pure xylene from such fractions. Y As used in this specincation and the appended I claim: Y present in said fraction are removed as an azeo 30 tropìc mixture with ethylene diamine, leaving a residue of the distillation containing the xylene complex hydrocarbon fraction having a top substantially free of non-aromatic hydrocarbons. boiling point no higher than 150° C. containing 4. A process for the recovery of substantially xylene and non-aromatic hydrocarbons which pure xylene from a complex hydrocarbon frac~ distill from said fraction in the ‘same tempera 35 tion having a top boiling point not higher than ture range as the xylene distills therefrom, which 145° C. containing xylene and non-aromatic comprises azeotropically distillìng said fraction hydrocarbons including parañinic hydrocarbons 1. A process for the recovery of xylene from a and rectifying the vapors evolved therefrom in the presence of ethylene diamine substantially and which may also include naphthenicand ' oleñnic hydrocarbons, said non-aromatic hydro free from water, thereby removing said non 40 carbons normally distilling from said fraction at aromatlc hydrocarbons as azeotropic distillate about the same temperature at which the xylene with ethylene diamine, and maintaining the pres distills therefrom, which process comprises dis~ ence of ethylene diamine during said distillation tilling said fraction and rectifying the vapors .until the residue of distillation contains at least evolved therefrom in the presence of ethylene 95 parts by weight of xylene to every 5 parts by diamine substantially free from water present in weight of non-aromatic hydrocarbons which amount such that a temperature of substantially distill in the absence of ethylene diamine in the 113-114° C. is reached but is not exceeded at a same temperature range as the xylene. 2. A process for recovering xylene from a xylene fraction boiling within the range of 125° to 150° C. containing xylene and non-aromatic hydrocarbons which distill from the xylene frac tion in the same temperature range as the xylene distills therefrom, which process comprises, dis tilling said xylene fraction and rectifying the vapors evolved therefrom in the presence of point in the rectification zone, and continuing the distillation in the presence of ethylene di amine until substantially all of the non-aromatic hydrocarbons in said fraction are removed as azeotropic distillate with the ethylene diamine, leaving a residue containing the xylene substan tially free of non-aromatic hydrocarbons. RICHARD B. GREENBURG.