Патент USA US2411588код для вставки
Patented Nov. 26, 1946 2,411,588 our-r131)v STATES PAT-ENTEROFFICE John W. Packie, Green Village, ‘and William S. Craft, Elizabeth,iN. J., assignors to Standard Oil Development Company, a corporation of Delaware I > Application December 16,1944, Serial No. 568,498 10 Claims. (Cl. 260—681.5)_ This invention relates to improvements in the separation and concentration of diole?ns from mixtures. of saturated and unsaturated hydro carbons containing diole?ns and relates par ticularly to‘ the separation and concentration of ~ 2 produce butadiene substantially free of these acetylenes. _ An object of this invention. is to selectively separate the less soluble ole?ns from an- am moniacal cuprous salt solution containing ole butadiene by the use of a cuprous salt solution; ?ns and diole?ns. Another object of this in Organic products, obtained on crackingpe vention is to separate diole?ns without a sub-~ troleum, brown coal, brown coal tar, synthetic stantial loss of ammonia from the solution. A para?ins and the like in the presence or absence further object of this invention is to obtain a of additional gas or vapors such as steam, hy 10 diole?n product low in acetylene content. These drogen,v nitrogen, carbon dioxide and the like,v and other objects of the invention will be clearly frequently contain both ole?ns and diole?ns understood upon reading the following descrip that are» gaseous at ordinary temperatures and tion with reference to the accompanying draw pressures. It is. very dii?cult to separate. the ' ing showing a flow sheet of the process. I gaseous product into its component parts even by 15 refrigeration as theaboiling points of the said ole?ns and diole?ns lie very close, for example, in the case of .butene-I and butadiene, the boiling points of which are —6.24° Ci. andv —4.5° C. A, method used extensively at present in the separation and concentration of the ole?n or di-~ ole?n is one in which a solvent is used to extract the desired ole?n or diole?n which is there after separated from the. solvent. A- solvent used extensively is an aqueous solution of am moniacal cuprous salt. One‘ of the di?iculties encountered in using the ammoniacal cuprous Referring to the drawing, hydrocarbon ‘feed vapors consisting of ole?ns and diole?ins plus I some other minor impurities enter extractor 2 through line I. This tower contains either, bubble plates or packed sections and operates at about 0 pounds per square inch gauge and 30° F. Ammoniacal cuprous acetate solvent enters the top of extractor 2 through line 3v and ?ows down‘ the tower countercurrently to the hydrocarbon vapors rising in the tower. The unabsorbed hy drocarbon vapors leave the‘ top of extractori.l through line 4'. In this tower most of the buta diene and: essentially all of the acetylenes con tained in the feed are dissolved in the solvent. ole?n generallycontain‘s a small fraction of other soluble ingredients. When butadiene is ab 30 However, about 5 tov 20% of the ole?ns are also dissolved in the solvent and must be selectively sorbed by ammoniacal cuprous. acetate, the solu removed. The solvent ?ows from extractor 2 tion contains not only the diole?n but alsoa through stripper l5 wherein it is contacted coun salt in that the solution of either the diole?n or ~ small fraction of the ole?n and acetylenes. A complication encountered is the: di?iculty of tercurrently‘with recycled butadiene vapors. in‘ troduced into the bottom of stripper l5 through preparing. a butadiene product. sufficiently free 35 line 5. In the. stripper most of the undesired from acetylenes‘ to meet speci?cations. Since hydrocarbons. (principally ole?ns) are stripped the copper solutionused as the solvent has a from the‘ solvent thereby leaving in solution es high dissolving power for acetylenes, methyl sentially pure butadiene, and some dissolved acetylene, ethyl acetylene. and vinyl acetylene acetylenes. The solvent leaves thefbottom of are undesirably removed along with the. diole?ns. 40 stripper l5 through line 6 and is heated to 60—90° For example in the case of a hydrocarbon, gas containing butadiene and 0.1% of any of the acetylenes designated, a copper solution. brought to equilibrium therewith-at 80° F. and 25p. s. i. a. total pressure. contains» 0.023 mols of dissolved acetylenes per liter of solution or about 0.1% by weight. Whenthe rich. solution is heated to re lease the butad-iene, a large. proportion, ot-these F. and introduced into the top of desorber 1 above the top plate. This desorber- contains either bubble plates or a combination of plates and packed‘ sections and is maintained at a pres sure of 5 to 25 pounds persquare inch gage, and a temperature of (SO-90° F. Under‘ these moderate conditions , very little desorption of acetylenes occurs and from the top section of the desorber tower ‘l, essentially pure low acet butadiene’ productvv tormeet the speci?cation of 50 ylene-content butadiene vapor is withdrawn 1000 P. P. M., it is accordingly necessary for the through line L6 as product. The partially de' acetylenes released in the hot zone tov be sub sorbed solvent passes down through desorber 'l sequently reabsorbed. Since. these impurities and is collected on pan 8. The solvent is with. tend to .ta?ect or impair the reaction} qualities drawn through line 9 by pump I2 and heatedto acetylenes. are released also. For the ?nal of’ the butadiene“ product, it is very desirable to 150-1809 F. in heat exchanger l0 and heater II, 2,411,588 3 4 tion having thus been set forth and a speci?c illustration of the same given, what is claimed as new and useful and desired to be secured by Letters Patent is: 1. In the extraction of butadiene from mix and is returned to the tower below pan 8. Essen tially all the diole?n'remaining in solution is rejected at this point together with consider able amounts of ammonia, water, and acetylene. These vapors pass up through the tower con tures of saturated and unsaturated, hydrocarbons tacting the descending cooler solvent, and most with ammoniacal cuprous salt solution, the im of the ammonia and water vapor and a portion provements which comprise passing the mixture of the vaporized acetylenes are reabsorbed. The .of saturated and unsaturated hydrocarbons in unabsorbed vapors comprising butadiene and a large amount of acetylene are removed through 10 countercurrent flow to an aqueous solution of ammoniacal cuprous salt at a temperature of line 5 and recycled to the stripper [5. Lean sol- ' about 30° F. and a pressure of 0 pounds per square vent leaving the bottom of desorber ‘I is cooled inch, stripping the aqueous solution of am and recycled to absorber 2 through line 3. moniacal cuprous salt by passing the said aqueous The extraction of butadiene from a dilute buta solution of ammoniacal cuprous salt in counter diene feed using ammoniacal cuprous acetate sol— current flow to a mixture of butadiene and acetyl vent involves the following three steps: ene, heating the stripped ammoniacal cuprous 1. Absorption-In this step, the desired buta diene is dissolved in the solvent along with a small salt solution to a temperature between 60—90° F. to release substantially pure butadiene as an over amount of undesired hydrocarbons. This step may be carried out with the hydrocarbon phase 20 head product, further heating the ammoniacal cuprous salt solution to a temperature ranging in either the liquid or vapor state. from 150—l80° F. and recovering butadiene high 2. Stripping.—ln this step, the undesired hy in acetylene as a sidestream, and using said side drocarbons of lower solubility than the desired stream as the stripping medium in said stripping product are removed from the solvent, leaving essentially pure butadiene in the solvent. The 25 step. 2. In the extraction of butadienes from hydro stripping may be carried out with the hydrocar carbon mixtures containing both saturated and bon phase in either the liquid or vapor state. unsaturated hydrocarbons, the improvements 3. Desorption-In this step, the pure butadiene which comprise passing a mixture of saturated is recovered from the solvent by vaporization 30 and unsaturated hydrocarbons in countercurrent therefrom. ?ow to an aqueous solution of, an ammoniacal The conditions of operation given in the above cuprous acetate, maintained at a temperature of description are not to be construed as limiting but about 30° F., stripping the aqueous solution of as being merely representative. For example, the the ammoniacal cuprous acetate by passing it in temperatures and pressures given may be varied 35 countercurrent flow to a ,gas containing buta diene, heating the thus stripped aqueous solution The essential feature of this invention is the of ammoniacal cuprous acetate to a temperature two-stage desorption of butadiene from the rich ranging from Bil-430° F. 'to release substantially solution with the withdrawal, as product, of the pure butadiene as anoverhead product, further low acetylene-content butadiene vapor from the initial ?ash and the recycle of the high acetylene 40 heating the ammoniacal cuprous acetate solution to a temperature ranging from 150-180° F. to content butadiene vapor from the‘ second flash expel substantially all of the remainder of the back to the stripper. This type of operation per butadiene and using the butadiene recovered in mits consistently meeting the acetylene speci?ca~ the second step as the stripping medium in the tion on the product butadiene with a minimum stripping step. number of trays in the desorber' tower. 3. In the extraction of. diole?ns from a mixture The following tabulation illustrates the mag of saturated and unsaturated hydrocarbons, the nitude of the acetylene contents of the pertinent improvements which comprise passing a mixture streams when operating with a feed containing of saturated and unsaturated hydrocarbons in about 1000 P. P. M. of acetylenes. countercurrent flow to, an aqueous solution of First stage low temperature desorption ammoniacal cuprous acetate solution to absorb widely- , ‘ v the unsaturated hydrocarbons therein, stripping Temperature _______________________ __°F__ 80 Pressure ______________________ __p. s. i. g__ 12 the thus enriched ammoniacal cuprous acetate solution with a diole?n-cuntaining gas, heating (product) ___________________ __P. P. M__ 500 ‘ the stripped ammoniacal cuprous acetate solution to a temperature ranging from (SO-90° F. and at a Acetylene content of desorbed vapor Second stage high temperature desorption pressure ranging from 5-25 pounds per square inch to release substantially pure diole?ns as the Temperature of solution introduced to second stage ___________________ __°F__ 80 » ' °F__ 165 Desorption pressure _________ __p. s. i. g__ 12 Acetylene content of vapor from reboilei' (based on hydrocarbon) ____ __P. P. ML. 10, 000 Acetylene content of recycle vapor to , 65 stripper __________________ __P. P. M__ 1, 500 Acetylene content of lean solution Mols per liter__ desired product, further heating the ammoniacal cuprous acetate solution to a temperature rang Temperature of solution from reboiler . 013 This invention has particular application in the extraction of butadiene from a dilute butadiene feed using ammoniacal cuprous acetate ‘solvent. ing from 150—180° F. to release the remainder of the diole?ns as an impure'product containing acetylene and using these impure diole?n-s as the stripping gas in said stripping step. 4. A method for preparing substantially pure butadiene comprising contacting ‘a hydrocarbon gas containing butadiene, acetylenes, paraf?ns and ole?ns with an aqueous solution of am moniacal cuprous acetate solution to absorb the unsaturated hydrocarbons, stripping the ole?ns and any physically absorbed para?ins from said cuprous acetate solution by contacting it with a However, with modi?cation, it might be appli gas rich in butadiene, releasing pure butadiene cable to other extraction systems, using different from the stripped solution by heating the said so solvents. The nature and objects of the present inven 75 lution to a temperature of 60-90” F., releasing the 2,411,588 . 5 _ 6 ~ remainder of the butadiene and an appreciable amount of the acetylene-from the solution by nent B having vapor'pressures in the presence of a selectivesolvent which contains a component C heating it to a temperature between 150 and 180° ' increasing in the order named, comprising the steps of absorbing component A, butadiene and F. and using the acetylene-containing butadiene as the stripping medium in said stripping step. '5. A process for separating butadiene from gas‘ .mixtures comprising a major portion of buta diene, ole?ns and a minor portion of acetylenes comprising the steps of absorbing‘butadiene,ole ?ns and‘ acetylenes in ammoniacalcuprous vace tate solution, stripping absorbed ole?ns from said component B in said selective solvent containing component C having a vapor pressure lower than vthe vapor pressures of component A, butadiene and component’ B to produce an enriched sol ‘ vent, stripping component B from said enriched solvent by contacting it with a mixture of com-‘ ponent A and butadiene, heating said stripped solution by contacting it with a mixture of buta solvent under conditions to produce a ?rst over diene and acetylenes, heating said stripped sol head‘vapor rich in butadiene and leave a ?rst vent under conditions to release a portion of the bottoms product comprising said solvent con butadiene in substantially pure form as a ?rst 15 taining dissolved components A and C and the re overhead product and leave a bottom product mainder of the butadiene, further. heating the comprising said solvent containing dissolved acet solvent under conditions to produce a second ylenes, ammonia and the remainder of thebuta overhead product comprising an appreciable diene, further heating the solvent under condi amount of component A, a portion of component tions to produce a second overhead product com C and the remainder of thebutadiene, contact prising an appreciable amount of the acetylenes, ing the mixture of 7 components A and C and a portion of the ammonia and the remainder of ' butadiene with said solvent from said ?rst heat the butadiene, contacting the overhead mixture ing step to reabsorb component C, removing a of butadiene, acetylenes and ammonia with the side stream mixture comprising component A and solvent from said ?rst heating step to reabsorb 25 butadiene not reabsorbed in the solution from ammonia, removing as a side stream mixture the said ?rst heating step and using said'mixture of vapors, comprising butadiene and acetylenes not component A and butadiene as the stripping reabsorbed in the solution from the ?rst heat medium in said stripping step. ‘ 1 > ing step and using the sidestream'mixture ‘as > the stripping medium in said stripping step. 6. A process for separating butadiene from gas 9. A process for separating a gaseous mixture comprising butadiene and components A and B, component A, butadiene and component B hav ing vapor pressures in the presence ofa selective solvent increasing in the order named, compris mixtures comprising butadiene, ole?ns and acet ylenes, comprising the steps of absorbing the butadiene, acetylenes, and ole?ns in a selective ing the steps of absorbing components A and B solvent, stripping the absorbed ole?ns from said 35 and butadiene in said selective solvent to produce , selective solvent by contacting it with a mixture of an enriched solvent, stripping component B from butadiene and acetylenes, heating the stripped said enriched solvent by contacting it‘ with a solvent under conditions to release a portion of ‘mixture of butadiene and component A, heat the butadiene in substantially pure form, then ing the stripped solvent under conditions to re heating said solvent under conditions to release the remainder of the butadiene and appreciable acetylenes and using the mixture of butadiene and acetylenes thus obtained as the stripping medium in said stripping step. 7. In a process for separating butadiene from gas mixtures comprising butadiene, saturated and unsaturated hydrocarbons the steps which com lease a ‘portion of the butadiene in ‘substantially pure form, and then heating said solvent under conditions to release the remainder of the buta diene and an appreciable amount of component A and using the mixture of butadiene and com ponent A thus obtained as the stripping medium in said stripping step. 10. A process for separating a diole?n from gas prise absorbing the butadiene and unsaturated ' mixtures comprising the diole?n, ole?ns, and hydrocarbons in a selective solvent, stripping the acetylenes, comprising the steps of absorbing the selective solvent by passing the selective solvent 50 diole?n, acetylenes, and ole?ns in a selective in countercurrent ?ow to a mixture of butadiene solvent, stripping the absorbed ole?ns from said and acetylenes, heating the thus stripped solvent selective solvent by contacting it with a mixture ' to release substantially pure butadiene as an over of the diole?n and acetylenes, heating the stripped head product, further heating the solvent to a solvent under conditions to release a portion of higher temperature to release further amounts the diole?n in substantially pure form, then heat of butadiene high in acetylene as a side stream, ing said solvent under conditions to release the and using said side stream as the stripping medi remainder of the diole?n and appreciable acety um in said stripping step. lenes and using the mixture of diole?n and acety-é 8. A process for separating a gaseous mixture lenes thus obtained as the stripping medium in comprising 'major amounts of butadiene and a 60 said stripping step. > component B and minor amounts of a com ponent A, component A, butadiene and compo ' JOHN W. PACKIE. WILLIAM S. CRAFT.