United States Patent [15] 3,673,270 Gosser (45) June 27, 1972

54) HYDROGENATION OF 1,3,7- 3,363,014 / 1968 Kittleman et al...... 260/666 OCTATRIENE TO 1,6-OCTADIENE AND 3,381,023 4/1968 Whiting...... 260/438.5 X 15-OCTADIENE WITH CERTAIN Primary Examiner-Paul M. Coughlan, Jr. CHROMUM CARBONYL CATALYSTS Attorney-D. R. J. Boyd 72 Inventor: Lawrence Wayne Gosser, Wilmington, Det. 57 ABSTRACT 73 Assignee: E. I. du Pont de Nemours and Company, 1,3,7-Octatriene, which can be made by the dimerization of Wilmington, Del. butadiene, can be selectively hydrogenated to 1,5-octadiene and 1,6-octadiene in the presence of a chromium carbonyl 22 Filed Dec. 11, 1970 catalyst such as chromium hexacarbonyl, pentacarbonyl( 21 Appl. No.: 97,315 ) chromium and tricarbonyl(arene)chromium com plexes. Isomer distribution in the product can be modified by 52 U.S. Cl...... 260/680R, 260/438.5R, 260/677 R the presence of monoxide. The diene products are use 51 Int. Cl...... C07c5/16, C07 c 1 1/12 ful comonomers for addition copolymers such as 58 Field of Search ...... 260/680 R,683.9,438.5 R, propylene?diene elastomeric copolymers, the diene-derived 260/666 B, 677 H units forming crosslinking sites for any of the elastomers with conventional sulfur curing systems. References Cited 56 10 Claims, No Drawings UNITED STATES PATENTS 3,135,776 6/1964 Ecke...... 260/438.5 X 3,673,270 2 HYDROGENATION OF 1,3,7-OCTATRIENETO 16 halogen substituents and having up to 10 carbon atoms in the OCTADIENE AND 15-OCTADIENE WITH CERTAIN . CHROMUM CARBONYL CATALYSTS A hydrocarbyl group is a group derived from a by removal of an atom of . Hydrocarbyl groups free FIELD OF THE INVENTION of aliphatic unsaturation therefore include radicals derived This invention relates to the selective hydrogenation of from saturated such as alkyl radicals, cycloalkyl 1,3,7-octatriene to 1,5-octadiene and 1,6-octadiene. radicals and bridged cycloalkyl radicals, and radicals derived from aromatic hydrocarbons containing one or more PRIOR ART rings which may be condensed, and which contain only satu O rated hydrocarbon substituents. Radicals derived from aro Tricarbonyl(arene) chromium complexes are known to be matic hydrocarbons can be classified according to whether catalysts for hydrogenation and isomerization of diene func they are formed by removal of a hydrogen from an aromatic tions in carboxylic acid derivatives. Frankel et al. nucleus (which are called aryl radicals), or, when the aromatic Tetrahedron Letters, No. 16, pp. 1919-1923 (1968)) have hydrocarbon contains one or more saturated hydrocarbon shown that conjugated diene or triene units in fatty acid esters 15 substituents, by removal of a hydrogen atom from a saturated such as methyl sorbate and methyl g-eleostearate are carbon atom (which are called aralkyl substituents). Examples hydrogenated to corresponding monoene or non-conjugated of suitable hydrocarbyl radicals include: methyl, ethyl, n diene units in the presence of tricarbonyl(methyl propyl, isopropyl, n-butyl, t-butyl, 2-ethylhexyl, n-octyl, 2 benzoate)chromium and similar tricarbonyl(arene)chromium methyloctyl, cyclopentyl, cyclohexyl, 4-ethylcyclohexyl, complexes. They also disclose that non-conjugated diene units 20 benzyl, 4-methylbenzyl, 3,4-dimethylbenzyl, phenyl, tolyl, in the reaction mixtures are not reduced. Rejoan et al. 2,4-dimethylphenyl and the like. Triaryl , espe Proceedings of the Eleventh Coordination Chemistry Con cially triphenyl phosphines, are preferred. ference, Elsevier Publishing Co., New York (1968) disclose chromium hexacarbonyl as a catalyst for hydrogenation of Examples of aryl radicals containing halogen or alkoxy sub 25 stituents include 4-fluorophenyl, 4-chlorophenyl, 4 methyl sorbate to methyl 3-hexenoate. bromophenyl, 4-iodophenyl, 3-chlorophenyl, 3-chloro-4- SUMMARY OF THE INVENTION methylphenyl, 3-propyl-4-fluorophenyl, 3,5-dimethyl-4- bromophenyl, 4-methoxyphenyl, 4-ethoxyphenyl, 3-methoxy The reaction of this invention is summarized by the follow 4-methylphenyl and the like. ing: 30 Tricarbonyl(arene)chromium compounds have the general formula: II) Cr(CO)(O) CIcCE -- (CII)a-CH=CH-CHsc-CH2 —---> where Q is an aromatic compound which can contain up to 14 (1,3,7-octatiene) carbon atoms and can be benzene, toluene, o-, m-, or p 35 xylene, ethylbenzene, mesitylene, hexamethylbenzene, p CH=CH-(CH2)3-CH=CHCH cymene, isopropylbenzene, 1,3-di(t-butyl)benzene, (1,6-Octa triene) , tetralin, , phenanthrene, biphenyl, diphenylmethane, 1,2-diphenylethylene, 1,4-diphenylbu tadiene, indane, fluorene and the like or such hydrocarbon the hydrogenation being conducted in the presence of a cata 40 with up to 3 substituents which can be lower alkoxy (-OR), lytic amount of neutral chromium complex having at least lower alkanecarbónyloxy (-OCOR), lower alkoxycarbonyl three carbonyl ligands attached to each chromium atom, at a (-COOR), lower alkoxycarbonylalkyl (-R-COOR), temperature of 25° to 300° C. and in the presence of hydrogen hydroxymethyl (-CH2OH), cyano (-CN), lower alkylcar at a partial pressure of about 1 to about 1,000 atmospheres. bonyl (-COR), arylcarbonyl (-COAr), amino (-NH), N 45 (lower alkyl)amino alkyl)amino (-NHR), N,N-di(lower al DETALED DESCRIPTION OF THE INVENTION kyl)amino alkyl)amino (-NR), halogen and the like. The process of this invention is carried out conventionally Examples of substituted aromatic hydrocarbons include by heating a mixture of 1,3,7-octatriene and the chromium fluorobenzene, chlorobenzene, anisole, ethyl phenylacetate, carbonyl catalyst, with or without added solvent, under methyl benzoate, 2,5-dimethoxy-1,4-di-(t-butyl)benzene, hydrogen in a pressure vessel. can be 50 benzophenone, aniline, toluidine, N-methylaniline, N,N- present in the gaseous phase if desired. The liquid reaction dimethyltoluidine, trans-1,3-diacetoxy-2,2-dimethylindane, mixture is cooled and removed from the reactor after the pres benzyl alcohol, and the like. sure of hydrogen and any carbon monoxide is released. The chromium, carbonyl catalysts are normally used in a g. Hydrocarbon components of the reaction mixture are col 55 catalyst/ml triene ratio in the range of 0.001 to 1.0, and the lected by distillation, and can be separated by conventional ratio in the range of about 0.01 to about 0.2 is preferred. means such as fractional distillation, The reaction can be run without an added solvent, i.e., neat In this reaction, 1,5- and 1,6-octadienes are the major or in the presence of an inert solvent such as hexane, products, the 1,6-isomer normally being predominant. Side cyclohexane, or . When a solvent is used, it is recom reactions also lead to small amounts of other hydrocarbon 60 mended that the proportions of solvent and catalyst are ad products such as 1,3,6-octatriene, 1,3- and 2,6-octadienes, justed so that the catalyst concentration in the reaction mix isomeric octenes and octane. The 1,6-octadiene product is es ture, including both solvent and triene, is within the range of sentially all in the cis stereoisomeric form, and the 1,5-oc 0.0005 to 1 g/ml, and preferably in the range of 0.01 to 0.05 tadiene is mainly in the cis form but may contain as much as g/ml. It is also preferred to limit the solvent to an amount 30 percent of the trans stereoisomer. 65 which allows a triene concentration of at least 10 percent in The chromium carbonyl complexes which are effective the initial reaction mixture. Inert nonpolar solvents such as catalysts in the process of this invention are chromium hex hexane have negligible effects on the rate of reaction, while acarbonyl, pentacarbonyl(trisubstituted phosphine)chromium inert polar solvents such as acetone generally enhance the rate compounds, and tricarbonyl(arene)chromium complexes. of reaction and may also effect changes in the relative propor The pentacarbonyl(trisubstituted phosphine)chromium 70 tions of 1,5- and 1,6- octadienes produced. complexes have the formula The reaction mixture may also contain ligands in excess of (LP)Cr(CO) the amount represented by the formula of the chromium com wherein each L can be alike or different and consists of a plex used as catalyst. Such ligands include carbon monoxide, hydrocarbyl group free of aliphatic unsaturation or an aryl methyl benzoate and benzene. Addition of carbon monoxide group containing saturated hydrocarbon, lower alkoxy and 75 generally results in a reduced rate of hydrogenation while in 3,673,270 3 4 creasing the extent of isomerization of 1,3,7-octatriene to the purities) in 25 ml of pure cyclohexane and 0.20 g of tricarbon 1,3,6-isomer. It is recommended that carbon monoxide, if yl(methyl benzoate)chromium were placed in a reactor lined used, be limited to a maximum partial pressure of about 50 at with Hastelloy C. The closed reactor was successively cooled mospheres. The presence of excess arene ligands does not af. in a dry ice bath, evacuated to about 1 mm Hg, warmed to fect the product distribution. room temperature and filled with hydrogen to a few hundred The partial pressure of hydrogen in the process can be in the psig. The reactor was then heated at 200 C. with agitation broad range of about 1 to about 1,000 atmospheres, and is while the hydrogen pressure was raised to and maintained at preferably in the range of about 20 to about 100 atmospheres. 1,200 psig for 6 hours. Flash distillation of the reaction mix The level of hydrogen pressure has nearly negligible effect on ture under reduced pressure gave 18 g of product solution. the reaction rate in the preferred pressure range, though lower O Gas chromatography with a % inch X 25 feet 5 percent bu levels in this range are slightly favorable to higher 1,6-oc tanediol succinate column at 78 C. and thermal conductivity tadieneloctene product ratios. detection showed the absence of 1,3,7-octatriene. The major The process is conducted at temperatures in the range of product peaks were at the retention times of 1,5- and 1,6-oc 25 to 300° C. When chromium hexacarbonyl is used as the 15 tadienes. catalyst, the effective temperatures are preferably in the range of 50 to 300° C., and are most preferably in the range of 150 EXAMPLES 2-42 to 250 C. When tricarbonyl(arene)chromium complexes are These examples were conducted by the procedure of Exam used as catalysts, the effective temperatures are preferably in ple 1, and the data are presented in Table I. The gas chromato the range of 25 to 250° C., and most preferably in the range of 20 graphic data show relative proportions in "area' percent 100° to 200° C. which closely approximate weight percent (cf., Purnell 'Gas The 1,3,7-octatriene, as used in the following examples, can Chromatography", John Wiley and Sons, Inc., 285 (1962). be obtained conveniently by the catalytic dimerization of bu Gas chromatographic analyses of all products were carried tadiene (cf., Takahashi et al. Bull. Chem. Soc. (Japan), 41, out with the butanediol succinate column described in Exam 454 (1968)). The usual impurities present in triene produced 25 ple 1. In some instances the products were also analyzed by by this route are 1,3,6-octatriene (minor) and 4-vinyl each of two other columns. When all three columns were cyclohexene (major). These impurities can be removed, but used, the data in Table I are composite results. The two other their separation from 1,3,7-octatriene by distillation is not columns are as follows: easy. However, since 4-vinylcyclohexene is nearly inert in the a. A/8 inch X 15 feet column packed with 80-100 mesh gas process of the invention and can be separated readily from 3O Chrom RA containing 20 percent of 6, 6'-ox 1,5- and 1,6-octadienes by fractional distillation, its presence ydipropionitrile, using thermal conductivity detection. in the reaction mixture is not a disadvantage. In fact, the b. A 50 feet capillary column coated with solid polyphenyl presence of 4-vinylcyclohexene may be desirable because it ether, using flame ionization detection. appears to inhibit formation of by-product octenes and oc- 35 The columns were calibrated and found to have somewhat dif tane. ferent separation characteristics. They all readily separated 1,5-octadiene, 1,6-octadiene, 4-vinylcyclohexene and 1,3,7- SPECIFIC EMEBODMENTS OF THE INVENTION octatriene from each other. However, possible contaminants such as the octenes, isomeric octadienes and isomeric oc The following examples illustrate the process of the inven tatrienes could not be separated clearly in all instances. An tion. The tricarbonyl(methyl benzoate)chromium catalyst 40 analysis of their combined capabilities with representative shown in Examples 1-23 was prepared from chromium hex samples indicate the following: acarbonyl and methyl benzoate by the procedure of Nicols Butanediol succinate column and Whitting, J. Chem. Soc., 551 (1959). The pentacarbon Data are reliable with recognition that the 1,5-octadiene yl(triphenylphosphine) chromium catalyst shown in Examples fraction may contain 2-octene and some 1,4- and 1,7-oc 40-42 was prepared by a procedure analogous to that 45 tadienes, and that the 4-vinylcyclohexene fraction may described for the preparation of corresponding isonitrile com contain 1,3-octadiene. Infrared analysis of the 1,5-oc plexes by Murdoch and Henzi, J. Organometal. Chem. 5, 166 tadiene fraction shows that the 1,4- and 1,7-isomers are (1966). minor components. Composite of all three columns EXAMPLE 1. 50 Data are reliable with recognition that the 1,5-octadiene fraction may contain small amounts of 1,4- and 1,7-oc A solution of 3.0 ml of 1,3,7-octatriene (75 percent 1,3,7- tadiene and that the 4-vinylcyclohexene fraction may octatriene, with 4-vinylcyclohexene and 1,3,6-octatriene im contain 13-octadiene.

AIE I ilydrogenation of t,3,7-0ctatricine with solulble chronium catalysts Reactic)il lixtury Conditions (Canalysis - 1,3,7-OT is Temp, Timo, afCO b Example Catalyst, rig. Solvent rul. ravin. o C. lhr, p.s.i.g. Col. 1,5-OD 1,6-OD 4VCII 1,3,7-OT

A^0.20 77%-9 160 6 300 BDS 2 A^0.20 77%-9 160 6 1,250 COMP 22 ------Ar0.20 89%-1 100 6 13,000 BDS 89 AM0.070 99%-0.8 140 6 1,200 BDS 9 Arv0.40 98%-1. 140 6 1,200 BDS 63 Arav0.020 89%-3 150 6 1,270 BDS 86 AM0.20 99%-2 150 6 1,200 COMP 1. Aru0.20 89%r 50 6 1,300 BDS 1. AM-0.20 89%rul 60 6 290 BDS 16 Ar0.40 99%-3 65 6 1,200 BDS 2 Ar0.40 98%-1. 65 6 1,200 BDS 9 Arav0.20 89%a/1 200 6 1,250 COMP 0.5 A-0.20 89%-1 150 6 1,23025 BDS 88 Ar 10.20 89%-1 150 6 1,300j65 BDS 84 Ara-0.20 89%-1 175 6 1,220/15 BDS 67 Ar0.20 - 89%al 200 6 1,300/25 COMP 6.7 40 14 22 A^0.20 (GII 128- 89%-1 250 6 1,000/65 BDS -----...-- d 43 l 12 A-0.20 Collied M13-810.5 g-...-- 89%al 160 6 2)0 BIDS 21 63 10 3 Arav().20 (E1/M3r-1810.5 g.---- 89%-1 200 6 1,300/30 BDS 50 10 7 2------A^0.2) in-Cell 14-8. ------89%al 150 6 1,220 13 DS 21 66 O 2 3,673,270

TABLE I Continued (Hydrogenation of 1,3,7-0ctatriene with Soluble chromium catalysts Reaction mixture Conditions (Canalysis 1,3,7-OT a Temp, Time, HiCOb Example Catalyst -g, Solvent M-ml. aml. C. hr. p.s.i.g. Col. 1,5-OD 1,6-OID 4WCFI 1,3,7-OT

Acetone M8------89%-189%~1 10036 6 1,200 BDS 245 6.4. 1012 ------76- - 77%.--9 200 6 1,200 COMP 9, 56 22 77%-9 225 6 1,400 BDS 28 31 2 2 77%a-9 200 6 245 COMP 9 d 65 d 19 ...... 77%-9 200 6 1,300 BDS 16 57 17 89%a-1 200 6 1,000 BDS 23 56 77%al 200 6 1,300 B)S d13 d62 1. 99%~1 200 6 1,300 COMP d23 d65 ().5- 89%-1 200 6 1,300/25 BDS 6 46 11 21 89%-1 200 6 1,400/100 BDS 6 9 13 56 C3H1:^-8------89%-1 275 6 1,240f200 Comp 9. f. 33 15 17 Acetoner-8------89%-1 80 2 1,200 BDS , 5 3 10 8?) - - - - - do------89%~1 50 6 1,200 COMP 3 d70 13 4. CH12-8------99%-2 130 6 1,200 COMP d22 5 2 d69 Cs H12^-8------99%a-2 140 8 1,300 COMP d22 d24 d50 CH2^8------77%-1 60 6 1,500 COMP d2) d40 21 5 CH12=CH-8=1------89%-2 140 8 1,250 COMP 2) 3 12.5 62 C5H12^8------77%al 200 6 1,225 COMP - 8 5) 22 2.5 CH12^S.------77%-1 210 6 1,400 COMP 14 52 f C6H128------89%r-1 225 f 1,300 COME 17 d42 2 a The other component is 4WCH. b COBDS pressure, indicates when data shown,from butanediol is the initial succinate pressure column at 25°C. only. COMP indicates composite data from three different columns. See text for explanation. d The materials in these instances were also isolated by preparative GC and their identities verified by NMR. carbonyl-(methylNOTES.--Abbreviations, benzoate) chromium;MB = methylbenzoate; B -- chromium OT hexacarbonyl;= octatriene, OD C = tricarbonyl(benzene)octadiene; 4VCH=4-vinylcyclohexene; chromium; D = pentacarbonyl 1,3,7-OT = 1,3,7-octatriene; ?triphenylphosphine)- A = tri chronium. saturated hydrocarbon, said L having up to 10 carbon atoms, The 1,5- and 1,6-octadienes produced by the process of this and Q is an aromatic compound of up to 14 selected invention are useful as comonomers in the preparation of vinyl from aromatic hydrocarbons, or such aromatic hydrocarbons polymers. Polymers containing the copolymerized dienes can having up to three substituents consisting of lower alkoxy be cured by conventional means such as vulcanization. A par lower alkanecarbonyloxy, lower alkoxycarbonyl, lower alkox ticularly valuable use of the dienes is in elastomeric ycarbonylalkyl, hydroxymethyl, cyano, lower alkylcarbonyl, ethylene/propylene?diene copolymers, which are well known arylcarbonyl, amino, N-(lower alkyl)amino, N,N-di(lower al in the form of commercial EPR rubbers. In this specific use, 35 kyl)amino and halogen. 15- or 1,6-octadiene can be used in place of 1,4-hexadiene, 3. Method of claim 2 in which said reaction is conducted at which is well established as a cure-site-introducing a temperature in the range of 100° C. to about 200 C. comonomer in EPR elastomers. The embodiments of the invention in which an exclusive 4. Method of claim 2 in which the catalyst is present in an property or privilege is claimed are defined as follows: amount of 0.01 to 0.2 grams per ml. 1,3,7-octatriene. 1. Method of making 1,5-octadiene and 1,6-octadiene 40 5. Method of claim 2 in which said catalyst is tricarbon which comprises contacting at a temperature in the range of yl(methylbenzoate)chromium. 25 to 300 C., 1,3,7-octatriene with hydrogen at a partial 6. Method of claim 2 in which said catalyst is tricarbon pressure of about 1 to 1,000 atmospheres in the presence of a yl(benzene)chromium. catalytic amount of a y consisting of a neutral complex 7. Method of claim 2 in which said catalyst is hexacarbonyl of chromium containing at least three carbonyl ligands joined 45 chromium. to each chromium atom. 8. Method of claim 2 in which said catalyst is pentacarbon 2. Method of claim 1 in which said catalyst is selected from yl(triphenylphosphine)chromium. Cr(CO) 9. Method of claim 2 in which reaction is conducted at a Cr(CO)PL temperature in the range of 150 to 250 C. and Cr(CO)O 50 10. Method of claim 9 in which the catalyst is present in an wherein each L is alike or different and is a hydrocarbyl group amount of 0.01 to 0.2 grams per ml. 1,3,7-octatriene. free of aliphatic unsaturation, or an aryl group having up to three substituents consisting of halogen, lower alkoxy and k ak s k as 55

65

70

75 22, JNITED STATES PATENT OFFICE (CERTFCATE OF CORRECTION Patent No...... 3673,270 ...... Dated - June 27...l.972 Inventor(s) LaWren CC Wayne. COGSer -- . It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below: - - Cover page, Abstract lines l and 5, "pentacarbonyl( phosphine" should be -- pentacarbonyl (trisubstituted phos phine) chromium --; Col. 2, lines l-5 and 16, in two instances the words "alkyl)amino" occurring after " (lower alkyl)amino" should be deleted; Col. 6, Table I, Example 38, in the column under "l,6-OD" the number "l-O" should be -- ll --; and in the column under "l 3, 7-OT", the number "5" should be changed to -- li --

Signed and sealed this 9th day of January 1973.

(SEAL) Attest : EDWARD M. FLETCHER, JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents