US 3855346 A
Paraffinic hydrocarbons are converted to other hydrocarbons by contacting with a catalyst comprising trifluoromethanesulfonic acid. In another embodiment, normal paraffins are isomerized with high selectivity to skeletal isomers containing the same number of carbon atoms by contacting same with a catalyst comprising trifluoromethanesulfonic acid and a Group Vb metal fluoride.
Description (OCR text may contain errors)
United States Patent [191 Norell [111 3,855,346 8 [451 Dec. 17, 1974 ISOMERIZATION OF PARAFFI NIC HYDROCARBONS WITH TRIFLUOROMETHANESULFONIC ACID  Inventor: John R. N0rell, Bart1esville,' Okla.
 Assignee: Phillips Petroleum Company,
- Bartlesville, Okla.
 Filed-: Jan. 28, 1972  App]. N0.: 221,777
 US. Cl. 260/683.68
 Int. Cl.; C070 5/30  Field of Search..... 260/683,68, 683.47, 683.58, 260/668 A, 683.65, 666 P; 252/439, 441
 References Cited UNITED STATES PATENTS 3.594.445 7/1971 Parker 260/68368 3,636,129 1/1972 Parker et a1. 260/683.58 3,678,120 7/1972 Bloch 260/683.65 3,766,286 10/1973 Olah 260/683.68
Primary Examiner-Delbert E. Gantz Assistant Examiner-G. J. Crasanakis 57 ABSTRACT Paraffinic hydrocarbons are converted to other hydrocarbons by contacting with a catalyst comprising trifluoromethanesulfonic acid.- In another embodi- Vb metal fluoride.
3 Claims, N0 Drawings ISOMERIZATION OF PARAFFINIC I-IYDROCARBONS WITH TRIFLUOROMETHANESULFONIC AClID a catalyst comprising trifluoromethanesulfonic acidand a Group Vb metal fluoride. In accordance with a further aspect, normal paraffims are isomerized with high selectivity to skeletal isomers containing the same number of carbon atoms by contacting the parafflns with a catalyst comprising trifluoromethanesulfonic acid and a Group Vb metal fluoride.
It is well known that the more highly branched, isomers of the paraffinic hydrocarbons occurring in petroleum gasoline fractions are more valuable than the corresponding slightly branched or straight chain hydrocarbons because of their higher octane ratings. The demand for motor fuels of greater octane number has-increased markedly as the automotive industry has provided gasoline engines with increasingly higher compression ratios to attain greater efficiency. One of the economically important ways in which the increased demands for high octane fuels can be-met is through the isomerization of the light naphtha components of such fuels.
It may be generally stated that the isoparaffinic and branched chain'paraffin hydrocarbons are of greater commercial value to the petroleum industry than the corresponding straight chain hydrocarbons. Thus, for example, 2.2-.dimethylbutane has a higher octane rat: ing than the isomeric normal hexane. Isobutane is more valuable than normal butane since the former can be used as a basis for the preparation of 8-carbon-atom, branched chainhydrocarbons by alkylation with butylene.
The isomerization of normal paraffinhydrocarbons I into the corresponding branched chain homologsis well known. For effecting the isomerization, it is ,customary to employ certain metal halides, particularly aluminum chloride or aluminum bromide, in conjunction with certain promoters such as hydrogen chloride, hydrogen bromide, or boron fluoride. Recently, strong acid systems such as solutions of fluorosulfonic acid and antimony pentafluoride have also been disclosed'as useful isomerization catalysts. An important problem arising with the use of these highly active catalysts is that they promote side reactions such as cracking and disproportionation. These side reactions are particularly evident at high conversion conditions and lead to the formation of substantial amounts of undesirable light and/or heavy side products.
Accordingly,'an object of this invention is to provide an improved hydrocarbon conversion process.
Another object of this invention is to provide an isomerization process whereby high selectivity to skeletal isomers is achieved.
Another object of this invention is to provide an improved isomerization process for the conversion of paraffmic hydrocarbons.
' .2 hours, are .employed.
A further object of this invention is to provide an improved catalyst for hydrocarbon conversion and isomerization.
Other objects and aspects as well as the several advantages of the invention will be apparent tothose skilled in the art upon further consideration of the specification and the appended claims.
In accordance with the invention, a process for the conversion of paraffinic hydrocarbons to other hydrocarbons is provided which comprises contacting the hydrocarbons with a catalyst comprising trifluoromethanesulfonic acid. It has been found that trifluoromethanesulfonic acid alone effects the isomerization and cracking of paraffinic hydrocarbons such as normal hexane.
Further in accordance with the invention, it has been found that normalparaffins can be isom'erized with high selectivity to branched isomers containing the 7 same number of carbon atoms by contacting the hydrocarbons with a catalyst comprising trifluoromethanesulfonic acid and a Group Vb metal fluoride.
In accordance with one specific embodiment, nhexane isomerizes to predominantly neohexane in the presence of a catalyst comprising trifluoromethanesulfonic acid and at least one of phosphorus pentafluoride, antimonypentafluoride.and arsenic pentafluoride.
Trifluoromethanesulfonic acid has various advantages not possessed by known superacid catalyst systems including (1) it has a much higher boiling point, hence less is loston recycle in continuous operation; (2) it does not attack glass so sight gages, etc. made of glass can be used; and (3) it is the strongest protonic acid known and fective.
The catalyst composition of the presentinvention comprises trifluoromethanesulfonic acid alone or trifluoromethanesulfonic acid with a metal fluoride of aGroup Vb element. Specific examples of these metal paraffinic hydrocarbon stream, it is also contemplated.
that mixtures. of various paraffinic hydrocarbons can be employed. I
The reaction conditions for isomerization of the feed can be in the range of 0 to 100 C, usually 15 to C, and pressures sufficient to maintain the hydrocarbon reactants and catalysts as liquid in the reaction zone,
-and the temperatures and pressures should be chosen accordingly. The time of contact is subject to wide variation, the length of residence time dependent in part upon the temperature and catalyst concentration employed. In general, reaction times ranging from about 5 minutes to 48 hours, preferably 15 minutes to about The mole ratio of paraffinic hydrocarbon to Group Vb metal fluoride forming the catalyst of the invention will generally be in the range 50:1 to 0.221, preferably 1:1 to 20: l The mole ratio of trifluoromethanesulfonic acid to Group Vb metal fluoride catalyst will generally hence smaller amounts of acid are efbe in the range 100:1 to 02:1, preferably 1:1 to 20:1. The mole ratio of trifluoromethanesulfonic acid to paraffinic hydrocarbon when trifluoromethanesulfonic acid alone is used as the catalyst will generally be in the into a polyethylene separatory funnel. The upper hy- .drocarbon layer was drained under nitrogen into a Fischer-Porter Aerosol compatibility bottle containing about five grams of potassium carbonate and cooled in range 0121 to 50:1, preferably 0.5:1 to 20:1. 5 a dry ice-acetone bath. The bottle was quickly capped The process of the invention is conducted as a batch with a heafl hg a Pressure g and a Slhcohe D" or a continuous operation. The apparatus employed m for wlthclrawmg Samples Phg analyses- Results can be ofa conventional nature and can comprise a sinare reported In terms of selechvmes based on the glc gle reactor equipped with sufficient stirring devices. analyses- Good agitation is important because the less dense par- EXAMPLE affinic hydrocarbon layer is not miscible with the dense liqui ac phase. U re cte reactants, ly Trifluoromethanesulfonic acid was used alone as the and other Pf 0f the macho can be separated catalyst to effect the isomerization and cracking of nfrom the desired product and from one another such as hexane i accordance i h h procedure Set f h by dist llation and returned in whole or in part to the above. The isomerization was effected at a temperature isomerization zone. The resultant product can be furof C for two hours. In both runs 25 ml (42.5 g, 0.28 ther processed as by alkylation and the like or be emmole) of trifluoromethanesulfonic acid and 17.2 g (0.2 ployed directly as a high octane gasoline blending mole n-hexane were used. The results of the normal agent. The reaction zone is preferably constructed of hexane isomerization are given below in Table 1.
TABLE 1 Selectivity Hexane to Cracked Light Products Run Conv.,% Products (C C 'S,C 's) Heavies 2,2-DMB DlP+2-MP 3-MP materials which are resistant to corrosion by the catalyst. For example, the reactor can be a Monel lined re- 7 EXAMPLE I] actor. It is preferred that the reaction be carried out o mal exane was isomerized to its branched isounder anhydrous conditions in an inert gas atmosphere. y Contacting with a mixture of antimony P Trifluoromethanesulfonic acid fumes copiously upon fluoride (SbF and trifluoromethanesulfonic acid. In exposure to air and the Group Vb metal halides are also n 3 and m1 gmole) trlflllOrOmethanehydrolyzed on exposure to atmospheric moisture. sulfonic acid and 17.2 g (0.2 mole) n-hexane were used. In runs 3 and 4, 6.6 and 12.3 grams of antimony SPECIFIC EXAMPLES pentafluoride were used, respectively. Paraffinic hydrocarbons were isomerized to isoparaf- The results of the normal hexane isomerization are fins with liquid phase catalyst systems of the invention 40 given below in Table II.
TABLE I1 lsomcrization of n-Hexanc with SbF /CF SO H at 25C/2 Hrs.
Hexanc Selectivity to Products Run Conv.,/r Cracked Products* Hca- VlCS utilizing a Monel reactor. The procedure for carrying out the isomerization in a Monel reactor is set forth below.
The process runs were carried out in a 300 ml Monel reactor. The trifluoromethanesulfonic acid was charged under nitrogen to the reactor and cooled therein to approximately 40C. In Examples 11, 111 and 1V hereinbelow the Group Vb metal halide was then added to the cold trifluoromethanesulfonic acid until the desired weight was obtained, followed by addition of the paraffin. The reactor was then capped and placed in a thermostated Eberbach reciprocating shaker for any desirable time at a specified tempera ture.
Workup involved cooling the Monelreactor in dry ice-acetone and then rapidly pouring the cold mixture It can be seen from the above tabulated data that antimony pentafluoride and trifluoromethanesulfonic acid in the liquid phase effect hexane isomerization in 95 percent conversion to branched C isomers with only three percent selectivity to cracked (C C15 and C s) products. Neohexane formed in approximately the thermodynamic equilibrium quantity of 55 percent.
EXAMPLE 111 Normal hexane was isomerized to its branched isomers by contacting with a mixture of trifluoromethanesulfonic acid and phosphorus pentafluoride at 25 C for 2 hours. In the run 12.6-grams (0.1 mole) of phosphorus pentafluoride, 50 ml g, 0.56 mole) trifluoromethanesulfonic acid, and 17.2 g (0.2 mole) of n-hexane were used. Results of the isomerization of n-hexane are given below in Table 111.
TABLE 111 Selectivities* Mole Ratio n-C C l-C. n-C; 1-C5 2.2-DMB DIP & Run n-C JPB, "/1 Conv. 2-MP 3-MP Heavies *2.2 DMB represents 2.2 3-methylpentzmc.
It will be noted from the above table that trifluoromethanesulfonic acid in admixture with phosphorus pentafluoride effected hexane isomerization in approximately 95 percent selectivity to branched C isomers -dimethylbutune. DIP represents diisopropyl (2.3-dimethylbutanc). 2-MP represents Z-methylpcntune. and 3-MP represents 2-MP dimethylbutane than the use of trifluoromethanesulfonic acid alone.
1. A process for the'isomerization of paraffinic hywith a n-hexane conversion of 1.9 percent. drocarbons which comprises contacting a feed cornprising paraffinic hydrocarbons in a conversion zone at EXAMPLE IV isomerization conditions with a catalyst consisting of Hexane was isomerized to branched products by conifluo methanesulfonic acid.
tacting with trifluoromethanesulfonic acid in admixture 2. A process according to claim 1 wherein the parafwith arsenic pe'ntafluoride at 25 C for two hours. In the finic hydrocarbon is normal hexane. run 10.2 g (0.06 mole) of arsenic pentafluoride, 50 rnl 3. A process according to claim 1 wherein said feed (85 g, 0.56 mole) trifluoromethanesulfonic acid, and comprises paraffinic hydrocarbons having from 4 to 7, 17.2 g (0.2 mole) of n-hexane were used. The results inclusive, carbon atoms per molecule and said contactof the isomerization are given below in Table IV. ing is effected at a temperature in the range of 0-100C TABLE IV Hexane I Selectivity to Li ht Products ,C s,C s) Heavies 2,2-DMB DlP-l-Z-MP 3-MP Run Conv.,% Cracked Products g and a pressuresufficient to maintain the reactants and catalyst in the liquid phase.