Патент USA US2407387код для вставки
2,407,386 Patented Sept. 10, 1946 UNITED STATES PATENT OFFICE 2,407,386 RECOVERY OF SECONDARY OLEFINS FROM ACID \EXTBACTS Harold W. Scheeline, Elizabeth, N. J., assignor to Standard Oil Development Company, a cor poration of Delaware Application February 14, 1942, Serial No. 430,872 3 Claims. I This invention relates to improvements in the separation and recovery of secondary ole?ns from mixtures of ole?ns and saturated hydro carbons which are associated in gaseous and (01. 260-677) 2 product as to render the process unpro?table. In addition, in cases where butenes are to be subjected to pyrolysis, as in butadiene manu-. facture, dilution with para?ins causes (1) loss 5 of the para?in, which is a valuable material in itself (e. g. isobutane) and (2) dif?culty in re covering the desired product after pyrolysis. Pure ole?nic hydrocarbons have been sepa rated from naphthas containing the ole?ns di light liquid hydrocarbon mixtures and more particularly the separation of ole?ns having from 3 to 5 carbon atoms to the molecule from mixtures of hydrocarbons or mixtures consisting mainly of ole?ns and saturated hydrocarbons. The separation of ole?ns by fractional distillae' 10 luted with paraf?nic hydrocarbons of approxi tion from saturated hydrocarbons having the mately the same boiling point by treating the same number of carbon atoms to the molecule, naphtha with sulfuric acid under such conditions as in the case of mixtures produced by cracking of acid strength, temperature, etc., as to selec or pyrolysis of petroleum oils or other bituminous tively extract the ole?ns into the acid phase. materials, is very diiiicult. In most cases, it is 15 The acid extract containing ole?ns may then be impossible for all practical purposes, for example, subjected to conditions whereby the ole?n is re to fractionally separate by distillation propylene ‘covered and the acid returned to the extraction boiling at —48.2° C. from propane which boils at step- This has been done heretofore by Suitable —45.0° C. The separation of 4 carbon atom oledilution with water followed by steam stripping. ?ns and saturated hydrocarbons that are found 20 It is W611 known that Sulfuric acid may readily in a cracked hydrocarbon mixture is still more poiymeriZe the ole?ns and 15‘ vis Well known that, di?icult, as they are more numerous‘ and have the ole?n-sulfuric acid reaction products the following boiling points: Isobutane ' are heated without sufficient dilution, polymer Bomng Points 0 C ization and secondary oxidation reactions occur, _ ‘_1’0? ' 25 such as the formation of_tar _or carbon, with lsobutnne """""""""""""""""""""" " __6' 1_bute;1e "* ““““““““““““““““““ " . ----------------------- -' 6'1 _ ' Butadlene ““““““ ". ---------------- " —4"75 n'Buta'ne --------------------------- —- "0-6 Z'butene' tt'a’ns --------------------- -~ "IO-9g decomposition of the sulfurlc ac1d to sulfur diox ide and water. conditions It is also known that under these excess or uncombined sulfuric increases the formation of polymers. acid Also, the 3o disadvantage of extract dilution and steam strip ping process is in the expense involved in han z'butene’ C15 ------------------------- -- +33“ The 5 carbon atom group of pentanes and pen- dling, reconcentrating and reducing the carbon Content of the 11013 dilute 510? acid' tenes is even more complex and the separation According to the present invention the sec of these ole?ns from the associated saturated 350M131? ole?ns may be recovered from Ole?n hydrocarbons by‘physical means has heretofore sulfuric acid solution without any substantial not been accomplished. loss due to polymerization and secondary oxida There are many chemical processes in which it tion and without the dilution or heating of the is a decided advantage to use a substantially pure acid extract. The following description will be ole?n, unmixed with inert diluents, such as sat- 40 related to normal butene separation but the pro urated hydrocarbons. For example, in chemical cess described will also have application to the reactions with the gaseous ole?ns in which presrecovery of other secondary ole?ns, such as pro sure is advantageous, the effective pressure is pylene, normal amylene, etc. normally the partial pressure of the reactive vSulfuric acid of about 70% to 90%, preferably ole?n in the mixture. In such cases, substan- 45 83%, concentration is used to absorb the secon tially pure ole?ns permit much lower pressures dary ole?ns. This may be done at an elevated to be employed and less gas to be compressed pressure in the liquid phase or at a lower pres than in the case of gas mixtures poor in reactive sure in the gas phase. ~ ole?n. Also, in many cases the ole?n reaction When normal butenes react with H2804, the may be reversible, the proportion of the desired 50 resulting extract has been found experimentally product being dependent upon the concentrato contain some butene as such, some as secon tion of the reactive ole?n in the mixture. In dary butyl alcohol, and some as mono-or dibutyl such cases, the dilution of the ole?n with an sulfate. The extract is found to exert a consid inert diluent, such as a saturated hydrocarbon, 5 erable vapor pressure of normal butylene, de may so affect the yield of the desired reaction 5 pending on the concentration of hydrocarbon 2,407,386 3 4 and acid in the extract and on the temperature. 4 is provided and cooling coil 5 to regulate the temperature. The mixture of sulfuric acid and the hydrocarbons is then passed through pipe 8 Extracts of tertiary ole?ns, such as isobutylene, on the other hand, contain the ole?n predomi nately as the tertiary alcohol only and exert a ' negligible ole?n vapor pressure. The separation and recovery of secondary ole» into a settler l where the unabsorbed hydrocar Cl bons are removed by means of pipe 8 consisting mainly of butane. ?ns from strong sulfuric extracts is accomplished The sulfuric acid extract is removed from the settler 1 by means of pipe 9 by the counter-current action of a saturated hy drocarbon gas having at least 20° C. difference in and passed to the upper part of the liquid ex traction tower ill. In the lower part of the liquid the boiling point from the secondary ole?ns such 10 extraction tower Ill is passed a liquid para?‘inic as propane or by extracting the ole?ns from the hydrocarbon solvent, such as pentane, by means strong ole?n-sulfuric acid extract by the counter of pipe ll, which passes in countercurrent flow current action of an inert liquid solvent such as to the sulfuric acid in the tower. The sulfuric pentane or hexane. It has been found that an acid, with most of the ole?ns removed, is then extract of 83% sulfuric acid containing 1 mol of recycled by means of pipe l2 to the reactor l. ole?n per mol of sulfuric acid at 30° C. is in The liquid pentane with the ole?n solution is equilibrium with a liquid naphtha containing 11% removed from the extraction tower by means of normal butene, while a similar extract contain pipe l3 and passed to a fractionating tower M ing 0.2 mol of ole?n per mol of sulfuric acid is in equilibrium with a naptha containing 1.2% normal butene. Therefore the corresponding ole- _ where the secondary ole?ns are distilled over to pipe 15 and the liquid paraf?nic hydrocarbon sol vent is removed by means of pipe I l and recycled to extraction tower ill. The fractionating tower ?n vapor pressures of these two extracts are cal culated to be 4.2 and 0.46 lb. per square inch, i4 is provided with a condenser I? at the upper respectively. Therefore an 83% sulfuric acid ex part and a heating coil [8 at the lower part. tract containing 1 mol of the ole?n per mol of 25 I claim: the sulfuric acid can be stripped at 30° C. and at 1. Improvements in the separation and concen atmospheric pressure by passing it down a tower tration of a secondary ole?n from a hydrocarbon oountercurrently through a stream of gaseous mixture containing the said secondary ole?n propane and the gas leaving the top of the tower which comprises contacting a hydrocarbon mix should contain approximately 25% normal butene ture containing a secondary ole?n with sulfuric and 75% propane. The butene is then recov acid of about 75%—°0% concentration, thereby ered by fractionation and the propane recycled. tion equipment. forming a solution of the secondary ole?n in said acid, extracting the secondary ole?n from said acid solution by means of a saturated hydrocar bon compound, the said saturated hydrocarbon compound having at least 20° C. difference in Alternately, a strong extract is treated counter currently with liquid pentane and the liquid pen tane leaving at the top of the extraction tower of dissolving the secondary ole?n and separable from the said secondary ole?n by fractionation. The extract leaving the bottom of the tower con tains only 0.2 mol of ole?n per mol of sulfuric acid and is recycled directly to the ole?n absorp contains approximately 10% normal butene. boiling point from the secondary ole?n, capable The 40 butene is recovered by fractionation and the pen tane recycled to the extraction tower. When some alkyl sulfate or alcohol is carried over mechanically or otherwise by the pentane, it is readily separated as bottoms in the fractionating tower and is recycled to the extraction step along with the pentane. The lean acid extract from the extraction tower is recycled directly to the ole?n absorption equipment. The stripping or the extraction process requires a suitable length of time as the reversion of al 2. Improvements in the separation and concen tration of a secondary ole?n from a hydrocarbon mixture containing the said secondary ole?n which comprises contacting a hydrocarbon mix ture containing a secondary ole?n with sulfuric “ acid of about 75%-90% concentration, thereby forming a solution of the secondary ole?n in said acid, extracting the secondary ole?n from said acid solution by means of a saturated hydro carbon compound in the liquid phase, the said saturated hydrocarbon compound having at least 20° (Indifference in boiling point from the sec cohol or alkyl sulfate to ole?ns is relatively slow. Since more time is generally allowed in extrac ondary ole?n, capable of dissolving the secondary tion equipment than in stripping equipment, there ole?n by fractionation. ole?n and separable from the said secondary are certain mechanical advantages in recovering 3. Improvements in the separation and concen the ole?n by extraction. The extraction or strip tration of a secondary ole?n from a hydrocar ping operation may be carried out at substan bon mixture containing the said secondary ole?n tially atmospheric pressure and at temperatures which comprises contacting a hydrocarbon mix below that at which substantial polymerization ture containing a secondary ole?n with sulfuric of the ole?ns in the acid extract will take place, acid of about '75%—90% concentration, thereby probably from 0 to 60° C. forming a solution of the secondary ole?n in said The invention will be more clearly understood acid, extracting the secondary ole?n from said on reading the following description with refer acid solution by means of a saturated hydrocar ence to the accompanying drawing. bon compound in the vapor phase, the said sat~ Numeral 1 designates the reactor into which is 65 urated hydrocarbon compound having at least passed, at the upper part, sulfuric acid of about 20° C. difference in boiling point from the sec 83% concentration by means of pipe 2, and a ondary ole?n, capable of dissolving the secondary mixture of hydrocarbons having four carbon ole?n and separable from the said secondary atoms to the molecule and containing both butane ’ ole?n by fractionation. and a secondary ole?n is passed by means of pipe 70 3 into a lower part of the reactor. 'An agitator HAROLD W. SCHEELINE.