US2552669A - Process for purifying normal 1-olefins - Google Patents

Description

Patented May 15, 1951 raoonss:

Harris. AaDutcher, Bartlesville, kla.,.assignor. to.

Bhillips Petroleum. Gem

Delaware m ny, a. corpora ion. of.

No Drawing: Application'December 15; 1947,

' Serial No. 791,925

This invention relates to a process for the purification of olefinic hydrocarbons. In one embodiment it relates to an improved method for the separation and recovery of certain isomeric olefinic hydrocarbons. which are extremely difiicult, ifnot impossible, to separate satisfactorily by fractional distillation. In one specific;

embodiment it relates to the removal of 2- methyl-l-butene from pentene-l, and the recovery of pure pentene-l.

In certain commercial processes for the production of individual olefinic hydrocarbons from petroleum fractions or the like, thereis obtained .arather complex mixture of hydrocarbons'whose.

normal boiling points fall within relatively narrow limits. For example, in the production of C5 olefins from certain refinery streams it is-found that (with one exception) the boiling points of all of the C5 olefins fall within the range of approximately 86" F. to approximately 101 F. The sole exception is the compound S-methyl-l-butene, boiling at 68.1 F. The boiling point of normalpentane also falls within the above-mentioned range. By means of highly efficient fractionation processes, this mixture of Csolefins' particular olefin, a satisfactory method for the removal of 2-methyl-1-butene from pentene-l is greatly to be desired. If the pentene-l is to. be used in certain manufacturing processes in which the presence. of olefins other than pentene-l leads to the formation of undesired. byproducts, it, becomes particularly important that the quantity of other olefins in the final pentene-l product stream be minimized;

An object of thisv invention is to provide a process for the removal of 'close boiling, isomeric olefins from the corresponding l-olefins having, at least four and preferably not more than ten carbon atoms per molecule.

Another object is. to provide a process for the removal of isomeric olefinic hydrocarbons from pentene-l.

A further. object isto provide a process-for the production. of pentenei-l in substantially pure Claims (01. 260-677 form. from Cs hydrocarbons from cracked. res finery. streams.

' Still. another object is to. provide a process. for the; removal. of 2.-methyl-l-butene from pen.- tene-l.

Qther objects and advantages will be. apparent. to; one; skilled; in the art from the accompanying disclosure; and discussion.

The. process of thisv invention is particularly applicable to the. separation and purification of pentene-l. from admixture with certain other olefinic hydrocarbons. In accordance with this. invention, a pentene-l containing stream is sub.- jected to efiicient fractional distillation to. produce; a. fraction: boiling in the range 8.5, to. 88 F. and which contains z-methyl-lebutene and lesser quantities of other olefins, such as 2.- methylezebutene, inaddition. to pentene-l. This fraction is admixed with nitrosyl chloride in sufficient. quantity and under conditions such thata reaction occurs between the. nitrosyl. chloride andthe: isomeric C5. olefins. present, but substantially; no reaction occurs between the nitrosylchloride and the nentene-l. The penteneel may then be recovered from the reactionmixture in substantially pure. form by conventional distillation methods.

In one embodiment of the present invention a. refinery stream containing Cs olefinic and par-:-

. amnic hydrocarbons is subjected to. efiicient fractional; distillation whereby pentene-l is separated and concentrated into afraction hav.- in a r l tively na row boiling range. Thec m pound ,2-methyle-l-butene, smaller amounts of orma e tan nd iscpenta e a traces of efin of sim r b i i ran e are contained in the nb en d acti T x nt to which thes c un s m be f her eparat di by fra onal dis i s d pends of urse; 9 11- t fii ien y of he ract ona on p oc s employed. Qbviously, the substantially complete-r r moval o the n-rwtan 13. P. 96.93 F.) by highly efficient fractional distillation is within the realm of possibility. The separation ofv the; isopentane (15. P. 82.14 F.) is much more difficult by this means, and the separation of the: 2- methyl-l-butene (B, P. 87.98" F.) from pentene-l (B. P. 85.95 F.) by fractional. distillation is highly impracticable. Fortunately, for many of t ein ended use of the pe t n 1 he presr ence of minor amounts of parafiinic hydrocare bonssuch as n= and isopentane, is ofno COIISBZ- quence and their presence may be disregarded.

pointed out hereinabove, howevenit. is often. essential thatthe pentene-l .be substantiallyfreei from other olefins. Accordingly, by the preferred embodiment of this invention the pentene-1 fraction is treated with nitrosyl chloride for the removal of the Z-methyl-l-butene and any other olefins (except pentene-l) that may be present. The gaseous nitrosyl chloride is preferably admixed with the liquid hydrocarbons in asuitable corrosion resistant reaction vessel equipped with stirring or agitating means and the reaction between N001 and Z-methyl-l-butene imparts a greenish color to the mixture, the intensity depending upon the concentration of the reaction product present. The reaction temperature may be within the approximate range of 0 to 100 F., but is preferably main: tained at from 60 to 80 F. in order to obtain a reasonably rapid rate of reaction without at the same time developing excessive pressures within the reaction vessel. Higher temperatures are to be avoided because they result in the decomposition of N001 and chlorination of the hydrocarbons. Pressures sufiicient to maintain the hydrocarbons in liquid phase are preferred. When the reaction between the Z-methyl-l-butene and NOCl is substantially complete, as evidenced by the persistence of the brownish color of unreacted N001 in the reaction mixture, the products are separated by fractional distillation into unreacted nitrosyl chloride (B. P. 21.7 F.), pentene-l (B. P. 85.95 F.) and the higher boiling reaction product of nitrosyl chloride with 2- methyl-l-butene and similar olefins. The pentene-l fraction is washed with dilute aqueous sodium hydroxide or the like, and with water to remove traces of N001, and then dried by distillation if desired.

The step of treating the olefinic hydrocarbons with nitrosyl chloride may be carried out either continuously or batchwise, in any suitable apparatus adapted to maintain the hydrocarbon reactants in liquid phase and to provide efficient contacting of the hydrocarbons with the nitrosyl chloride at the desired temperature.

The present invention is particularly advantageous with respect to the high percentage recovery of 1-olefins, such as pentene-l, from an olefinic mixture containing such olefins, as compared with known methods for separating l-olefins from such mixtures. It has been proposed, for example, to separate tertiary base olefins (such as Z-methyl-l-butene) from l-olefin (such as pentene-l) by treatment of the hydrocarbons with 60-70% sulfuric acid under conditions such that the tertiary base olefin is polymerized or otherwise converted to higher boiling products. It has been found, however, that an appreciable loss of pentene-l occurs under the conditions required for substantially complete removal of the Z-methyl-l-butene by the above-mentioned sulfuric acid treatment. In a typical run using 60 percent sulfuric acid and employing a contact time of 90 minutes, a pentene-l concentrate containing 44.3 weight percent pentene-l and 30.2 weight percent Z-methyl-l-butene (the remainder being chiefly normal and isopentane) was treated and it was found that the product contained 12 Weight percent of pentene-2. This, of course, represents an undesirably high loss of pentene-l as secondary base l-olefins.

due to isomerization. The nitrosyl chloride treatment of this invention, on the other hand, effects substantially complete removal of olefins of the type of 2-methyl-l-butene with almost no isomerization of, or reaction with, pentene-l, and hence makes possible a high degree of recovery of the latter compound.

Because of the reactivity of nitrosyl chloride with water, it is usually preferable to carry out the present invention under substantially anhydrous conditions. However, it has been found that in the presence of small amounts of water (1-2%) the rate of reaction of nitrosyl chloride with olefins is accelerated and that the degree of removal of Z-methyl-l-butene is even more nearly complete than when anhydrous conditions are employed. Since this is accomplished at the expense of pentene-l (by reaction with NOCl), it is preferred to exclude water from the reactants, except when pentene-l of extra high purity is to be produced.

In certain instances it may be desirable to conduct the N001 treatment in two or more stages, with intermediate separation steps for the removal of the nitrosyl chloride-2-methyl-1-butene reaction product. Such a, multiple stage process is advantageous, for example, when the pentene-l stream contains a relatively large proportion of 2-methyl-l-butene.

While the process of the invention has been described with particular reference to the removal of 2-methyl-l-butene from pentene-l, for the sake of clarity, the invention is not limited to the purification of this particular olefin but may be successfully employed in the purification of other olefins. Thus, my process is applicable for the purification of straight or branched chain l-olefins having the configuration Where R is any alkyl radical having at least two and preferably not more than eight carbon atoms. Olefins having this configuration will be referred to in this specification and in the claims The secondary base l-olefins are substantially unreactive with nitrosyl chloride. All olefins of any other configuration are relatively more reactive with nitrosyl chloride than are the corresponding secondary base l-olefins. These other types of olefins will be referred to in the specification and the claims as non-(secondary base l-olefins). This term is limited to olefinic hydrocarbons and is not intended to include other types of compounds that might be present, for example, the corresponding paraffin hydrocarbons. The olefins for which the process of my invention is particularly suitable are those having at least four and not more than ten carbon atoms per molecule; however in some cases olefins having up to twenty carbon atoms may be separated and purified by my process. Thus my invention may be employed in the separation of isobutylene (B. P. 19.58 F.) from butene-l (B. P. 20.73 F.) certain hexenes (particularly heXene-Z, hexene-3 and 2-methyl pentene-l) from hexene-1, and in general, in the separation of isomeric olefins from heptene-l, octene-l, etc. In the case of the higher boiling l-olefins the temperature at which the N061 treatment is carried out is preferably in the lower portion of the range indicated hereinbefore, say from 20 F. to 50 F.

Although nitrosyl chloride is the preferred reagent for use in this invention, nitrosyl bromide, N OBr, may be substituted in some cases provided Example I A mixture consisting of 80 percentby weight of pentene-l and 20 percent by weight of 2-methyl-l-butene was placed in a glass reactor provided. with a stirrer and a Dry-Ice condenser to which was added 20 percent by weight of nitrosyl chloride over a period of 3 hours at a temperature 75 F. The unreacted hydrocarbon was removed from the reaction product by distillation and. was washed first with 5 per cent sodium hydroxide solution, then with distilled water. Upon distillation the hydrocarbon was found to have a refractive index (n of 1.3715. The refractive index of the mixture prior to nitrosyl chloride treatment was 1.3728. Infrared analysis showed that the Z-methyl-l-butene content of the thus treated hydrocarbon had been reduced to about 5 weight percent by this single stage treatment.

Example II Example III To 100 grams of 95% pure pentene-l (n =1.3719) containing 2 grams of water contained in a 300 cc. glass reactor provided with a stirrer and a Dry-Ice condenser was added 8 grams of nitrosyl chloride over a period of 1 hour at 80% F. temperature. The refractive index of the recovered pentene-l was found to be n =1.3'7l2 which corresponds closely to that of the pure compound, n =1.3710.

It is to be understood that this invention should not be necessarily limited to the above discussion and description, and that modifications and variations may be made without departing from the invention and from the scope of the claims.

I claim:

1. A process for purifying a secondary base l-olefin having from 4 to 5 carbon atoms from its admixture with a fraction selected from the class consisting of C4 and C5 hydrocarbons which comprises removing from said fraction a narrow boiling fraction comprising said secondary base l-olefin and a corresponding hydrocarbon selected from the class consisting of isobutylene and Z-methyl-l-butene, treating said narrow boiling fraction with nitrosyl chloride in the presence of water in an amount within the range of 1 to 2 per cent by weight of said narrow boiling fraction at a temperature in the range between and 100 F. and under a pressure suflicient to maintain a liquid phase, whereby the nitrosyl chloride reacts with said corresponding hydrocarbons and recovering secondary base l-olefin from a resulting reaction mixture.

2. A process for purifying pentene-l from its admixture with a C fraction of hydrocarbon which comprises removing from said C5 fraction 6 a narrow boiling fraction comprising said pentene-l and 2-methyl-1-butene, treating said narrow boiling fraction with nitrosyl chloride in the presence of 2 parts by weight of water per 100 parts of said narrow boiling fraction at a temperature in the range between 60 and 80 F. and under a pressure sufficient to maintain a liquid phase whereby the nitrosyl chloride reacts with Z-methyl-l-butene and recovering pentene- ;1'from'a resulting reaction mixture.

3. A process for purifying pentenel from its admixture with a C5 fraction of hydrocarbon which comprises removing from said 05 fraction 2. narrow boiling fraction comprising said pentene-l and 2-methyl-1-butene, treating said narrow boiling fraction with nitrosyl chloride in the presence of promoter quantities of water not exceeding 2 parts by weight of water per parts of said narrow boiling fraction at a temperature in the range between 0 and 100 F. and under a pressure suflicient to maintain a liquid phase whereby the nitrosyl chloride reacts with 2-methyl-1-butene and recovering pentene-l from a resulting reaction mixture.

4. A process for purifying pentene-l from its admixture with a C5 fraction of hydrocarbon which comprises removing from said C5 fraction 2. narrow boiling fraction comprising said pentene-l and 2-methyl-1-butene, treating said narrow boiling fraction with nitrosyl chloride in the presence of water in an amount within the range of 1 to 2 per cent by weight of the said narrow boiling fraction at a temperature in the range between 0 and 100 F. and under a pressure sufiicient to maintain a liquid phase whereby the nitrosyl chloride reacts with 2-methyl-1- butene and recovering pentene-l from a resulting reaction mixture.

5. A process for purifying butene-l from its admixture with a C4 fraction of hydrocarbon which comprises removing from said C4 fraction a narrow boiling fraction comprising said butene-l and isobutylene, treating said narrow boiling fraction with nitrosyl chloride in the presence of 2 parts by weight of water per 100 parts of said narrow boiling fraction at a temperature in the range between 60 and 80 F. and under a pressure sufficient to maintain a liquid phase whereby the nitrosyl chloride reacts with isobutylene and recovering butene-l from a resulting reaction mixture.

6. A process for purifying butene-l from its admixture with a C4 fraction of hydrocarbon which comprises removing from said 04 fraction a narrow boiling fraction comprising said butene-l and isobutylene, treating said narrow boiling fraction with nitrosyl chloride in the presence of promoter quantities of water not exceeding 2 parts by weight of water per 100 parts of said narrow boiling fraction at a temperature in the range between 0 and 100 F. and under a pressure sufficient to maintain a liquid phase whereby the nitrosyl chloride reacts with isobutylene and recovering bu'tene-l from a resulting reaction mixture.

7. A process for purifying butene-l from its admixture with a C4 fraction of hydrocarbon which comprises removing from said C4 fraction a narrow boiling fraction comprising said butene-l and isobutylene, treating said narrow boiling fraction with nitrosyl chloride in the presence of water in an amount within the range of 1 to 2 per cent by weight of the said narrow boiling fraction at a temperature in the range F between 0 and 100 F. and under a pressure sufficient to maintain a liquid phase whereby the nitrosyl chloride reacts with isobutylene and recovering butene-l from a resulting reaction mixture.

HARRIS A. DUTCHER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,322,308 Moyer June 22, 1943 5 2,354,359 Beckham July 15, 1944 2,394,430 Crowder et al. Feb. 15, 1946 2,435,570 Beckham Feb. 10, 1948 OTHER REFERENCES m Tilden et al.: Jour. Chem. $00., v01. 65, 334

Tuot: Compte Rendu, vol. 204, 697-9 (1937).

Claims (1)

1. A PROCESS FOR PURIFYING A SECONDARY BASE 1-OLEFIN HAVING FROM 4 TO 5 CARBON ATOMS FROM ITS ADMIXTURE WITH A FRACTION SELECTED FROM THE CLASS CONSISTING OF C4 AND C5 HYDROCARBONS WHICH COMPRISES REMOVING FROM SAID FRACTION A NARROW BOILING FRACTION COMPRISING SAID SECONDARY BASE 1-OLEFIN AND A CORRESPONDING HYDROCARBON SELECTED FROM THE CLASS CONSISTING OF ISOBYTYLENE AND 2-METHYL-1-BUTENE, TREATING SAID NARROW BOILING FRACTION WITH NITROSYL CHLORIDE IN THE PRESENCE OF WATER IN AN AMOUNT WITHIN THE RANGE OF 1 TO 2 PER CENT BY WEIGHT OF SAID NARROW BOILING FRACTION AT A TEMPERATURE IN THE RANGE BETWEEN 0 AND 100* F. AND UNDER A PRESSURE SUFFICIENT TO MAINTAIN A LIQUID PHASE, WHEREBY THE NITROSYL CHLORIDE REACTS WITH SAID CORRESPONDING HYDROCARBONS AND RECOVERING SECONDARY BASE 1-OLEFIN FROM A RESULTING REACTION MIXTURE.