US2966535A - Molybdenum promoted alkylation of paraffins - Google Patents

Description

Dec. 27, 1960 A. SCHRIESHEIM EI'AL 2,966,535

MOLYBDENUM PROMOTED ALKYLATION 0F PARAEFINS Filed Aug. 22, 1958 Alan SchrieSheim George R. Gilbert Inventors John E. McCormick By g Q Attorney Unitd States Patent MOLYBDENUM PROMOTED ALKYLATION OF PARAFFINS Alan Schriesheim, Fords, George R. Gilbert, Elizabeth, and John E. McCormick, Roselle Park, N.J., assignors to Esso Research and Engineering Company, a corporation of Delaware Filed Aug. 22, 1958, Ser. No. 756,688

8 Claims. (Cl. 260-68353) The present invention concerns the alkylation of parafiin hydrocarbons with other parafiin hydrocarbons wherein desirable branched chain hydrocarbons boiling in the motor fuel range are produced. The invention is particularly directed to a process wherein simultaneous cracking, isomerization and alkylation reactions take place when an excess of a butane or a pentane, preferably isobutane, is contacted with a paraffin hydrocarbon of from 6 to 18 carbon atoms in the presence of a catalyst comprising aluminum bromide and promoting amounts of a compound containing molybdenum and oxygen. 7

The increased use of high compression internal combustion engines in the automotive industry has presented petroleum refiners with a major problem in supplying a sufiicient quantity of high octane rating motor fuels to satisfy the requirements of those engines. Heretofore, the supply of high octane rating gasoline components has been augmented principally by polymerization and alkylation processes using C and C petroleum fractions as starting materials. These processes have a number of disadvantages in that they require several separate operations and necessitate the use of olefin hydrocarbons, which are usually in relatively limited supply.

It has now been found that butanes and/or pentanes can be reacted directly with higher paraflin hydrocarbons to give good yields of C to C branched chain hydrocarbons of high octane rating by employing as a catalyst aluminum bromide supported on or mixed with an inorganic oxygen compound of molybdenum, particularly a molybdenum compound selected from the group consisting of one or more of the oxides of molybdenum and the molybdates of cobalt, nickel and iron. Although it has previously been proposed to conduct alkylation reactions of this type with aluminum halide catalysts, the 7 yields have been low, the reaction rates have not been economically attractive and satisfactory product distribution has not been obtained. However, with the catalyst systems of the present invention, much greater catalytic activity for the desired reactions is furnished than with the catalysts of the prior art.

'In accordance with the present invention, a paraffin hydrocarbon of from 6 to 18 carbon atoms is reacted with a large excess of a butane or of a pentane, in the presence of aluminum bromide and a molybdenum compound of the type mentioned above, to effect conversion of the higher hydrocarbon to saturated branched chain hydrocarbons that are predominantly in the C to C range. The temperatures employed in the reaction are generally in the range of from about 30 to about 140 F. and preferably in the range of from about 50 to about 120 F. The reaction pressures are preferably sufficiently high to keep the reacting hydrocarbons in the liquid phase. Preferably the catalyst systems employ the aluminum bromide and the molybdenum compound in the ratios of from 1 to 10 parts by weight of aluminum bromide per part by weight of the molybdenum compound.

The nature and objects of this invention will be more i atented Dec. 27, 1960 easily understood when reference is made to the accompanying drawing in which the single figure is a schematic flow plan of one process for practicing the invention.

The process will be described with particular reference to the use of isobutane as the lighter component. Referring now to the drawing in detail, a suitable butane feed stream that at least initially contains a major proportion of isobutane is obtained by means of line 11 from a suitable source and is conducted into a reaction zone 15 containing the catalyst system of the present invention. A portion of the feed stream is diverted by means of line 11a into an aluminum bromide pickup vessel 12 for the purpose of replacing aluminum bromide that may be lost from the system by solution in the product stream. The diverted stream containing dissolved aluminum bromide is removed from vessel 12 by means of line 13 and combined with the remaining portion of the feed stream entering the reaction vessel through line 11. Although the reaction may be conducted without any additional promoter, it is preferred that hydrogen bromide be employed as an auxiliary promoter. The hydrogen bromide is introduced into the reaction zone by means of line 17 and will be recycled to the reaction zone along with unreacted butanes by means of line 21.

A stream of a higher paraffin hydrocarbon, as for example heptane, octane, dodecane or cetane, or of mixtures containing higher parafiins in the range of about 6 to 18 carbon atoms, is conducted into the reaction zone by means of line 16. Preferably the stream enters the reaction zone at a plurality of spaced points, 16a, 16b, etc., so as to insure as high a ratio as possible of isobutane to higher paraiiin at any particular point in the reaction zone.

The reaction product leaves the reaction zone through line 18 and is conducted into an initial separation zone 20 wherein light materials, including unreacted isobutane and normal butane, are removed overhead and recycled to the reaction zone by means of line 21. Hydrogen bromide, if present, will also be recycled via line 21. The heavier material, including C hydrocarbons and higher, is conducted by means of line 22 into a product separation zone 24 wherein C to C hydrocarbons are removed overhead by means of line 25 while heavier material comprising C hydrocarbons and higher as well as any aluminum bromide that has been removed from 'heavier material recycled through line 26, while including the C branched chain isomers in overhead line 25.

In place of isobutane the feed in line 11 may comprise normal butane, in which case no higher hydrocarbon feed stock will be sent initially to the reaction zone but the butane will be recycled through line 18, zone 20 and line 21 until a considerable amount of the butane has been isomerized to isobutane. The process may then continue in the manner already described, the recycle isobutane being sufficient to make the desired reaction proceed while the fresh butane feed becomes isomerized to isobutane in the reactor.

A number of factors in the process of the present invention are critical to its operation in order that proper distribution of the products may be obtained. For example, at temperatures above about F. considerable cracking occurs and the principal products are propane and lighter materials. Also it has been established that aluminum bromide alone or even in the presence of conventional hydrogen halide promoters such as hydrogen bromide, in the absence of the support, is very much less active than the catalyst system of the present invention. Furthermore in order for the reaction to proceed satisfactorily it is necessary that suficient aluminum bromide be present not only to saturate the support under the reaction conditions employed but also to leave at least a small amount dissolved in the reacting hydrocarbons.

Although the process as described in conjunction with A tane, for example, but mixtures may be used, such as a petroleum fraction containing paraffinic hydrocarbons in the range of 6 to 18 carbon atoms.

Feed rates may vary from about 0.3 to about 2 v./v./hr.,

the drawing contemplates downflow of the stream through the higher feed rates being preferred when little or no the catalyst bed, which is preferred, upfiow can also be naphthenes are present. used. Also in place of a fixed bed process, a moving The following examples serve to illustrate the practice bed of catalyst could be used. Alternatively, a slurry of this invention. type of operation could be employed wherein a suspension EXAMPLE 1 of catalyst 15 .maintalined the reacting hygrocatbons Comparative tests were made with various catalyst the l bqmg Stirred m g fi mixtures to etfect the reaction of 80 vol. percent of isobumec g stlmpg means t t tane, 19 vol. percent of normal heptane and 1 vol. percent g y i mean; f S i Operation of methylcyclohexane, using in each test a reaction temuse t e S llrry 1S i mm t 6 mac or at 6 en perature of 72 F. and a reaction period of 3 hours. I of the reaptlon q h case of hatch operation or In each instance a mixture of 160 cc. of isobutane and as a fraction of the circulating stream 111 the case of con- 40 of a normal heptane feed (Containing 95% m0, trnuous operation, and sent to suitable separation equipand 5% of methylcyclohexane) was agitated with a mi mam Separat? the catalyst from h hYdmFaIbOnS' T ture of 23.6 grams of aluminum bromide and 47.2 grams separation equlpment may comprise a slmple seiflmg of one of the catalyst supports identified in Table II. At tank tenmfuge, or a filter for example or smtable 20 the end of each run the yield of products was determined. corxbmgngns i gl f th 1 The results obtained are shown in Tables I and II. Table b a W P E .3 a ummun I presents the relative activities of these catalyst systems, a e i i a ummm? on I; eg which were determined by dividing the time taken to conuse e t at east some a ummum 6 1S vert 60 wt. percent of the heptane into lower molecular presentun the reacting hydrocarbons over and above that Weight products using Silica gel as the catalyst support g fg g the support d th b f or promoter divided by the corresponding time for the e.reac may q i m 2} same 0 other catalyst supports studied. Table II gives the analysis hydrogen bromide promoter, additional activity results figures for the reaction product, when it is used. A range of from about 0.2 to about 2.5 weight percent, based on feed, is preferred. Table I As a minimum it is preferred that the mol ratio of Support: Relative activity isobutane and/or isopentane to higher paraflin be at SiO 100 least 5 to 1, although ratios of as low as 3 to 1 are A1 0 4 operable. Preferably the mol ratio should be no higher Cobalt molybdate on A1 0 190 than about 20 to 1. If suflicient iso-C is not present in M00 on A1 0 175 the reaction zone to effect alkylation of the materials None 0 obtained when a higher parafl'in or other higher product M00 on SiO (dry mix) 175 of the reaction is cracked by the catalyst, catalyst sludg- M00 on Si0 (sublimed) 260 Table II SiOz 6101 M00; M00: Support None S10; A1203 CoMoOr M003 Dry Sub- AlzOs A1203 Mixed ltmed Tech- Technique nique Analysis of 0 Prodnot, Weight Percent:

iso-C 0.4 12.3 1.7 32.1 26.8 27.4 38.3 11-0 0.3 1.0 0.1 3.5 7.8 3.0 5.3

Total 0, 0.7 13.7 1.8 35 6 34.6 31.3 43.6

ISO-C0 0.5 14.9 0.2 17.8 16.2 18.0 20.7 1141. 0 0.6 0 0.8 1.0 0.0 1.4

Total Cu 0.5 15.5 0.4 18.6 17.2 18.9 22.1

isoC1 46.2 65.6 75.0 43.2 46.1 44.8 30.3 11-01"--- 52.6 3.1 22.8 2.4 1.7 1.7 1.8

Total C1 98.8 68.7 97.8 45.6 47.8 46.5 32.1

ing will result. The feed stock must be essentially free of aromatic hydrocarbons and not more than about 0.02% of such material should be present. An added advantage of the catalyst systems of the present invention is that naphthene hydrocarbons may be tolerated in the feed stock up to about 20 volume percent. With increased naphthene content the reaction severity must be increased somewhat as compared to a reaction in the absence of naphthenes. This may be accomplished by raising the temperature and/or lowering the feed rate, for example.

To remove aromatics from the feed stock conventional techniques may be employed such as solvent extraction, hydrogenation, acid treating and the like, as well as treatment with selective adsorbents such as molecular sieve zeolites. It is not necessary that the higher hydrocarbons used be individual hydrocarbons such as heptane or oc- It will be seen from the data in Tables I and II that the molybdenum compounds of the present invention were very effective in promoting the activity of aluminum bromide to produce the desired reaction products.

The cobalt molybdate was used in admixture with alumina in the ratio of 15 percent molybdate to percent alumina. The percentages in the case of molybdenum oxide were 10 of the latter to of alumina. Both of these materials were available commercially as hydrofining and hydroforming catalysts, respectively. The silica-molybdenum oxide mixtures were in a 90 to 10 ratio. The silica for the mixtures was obtained by calcining silica gel for 3 hours at about 1200 F. In one case the silica and molybdenum oxide were simply mixed together while in the oher case the silica and molybdenum oxide mixture was heated to 9001000 F. for about three hours in a ceramic tube in a stream of nitrogen. This treatment caused the molybdenum oxide to be distributed through the silica by sublimation.

EXAMPLE 2 In the same manner as in Example 1 comparative tests were made to study the effect of hydrogen bromide on the reaction. In each instance a mixture of 160 cc. of isobutane and 40 cc. of a normal heptane feed (containing of methylcyclohexane) was agitated with a mixture of 23.6 grams of AlBr and 47.2 grams of 15% CoMoO and 85% A1 0 using 3-hour reaction periods and 72 F. temperature. The amount of HBr used was changed in each run. Table III presents the relative activities observed in the various runs, the activities being referred to the catalyst alone as 100. It will be noted that above about 2.5% HBr, based on feed, the promotional efiect was lost. The preferred HBr concentration is from about 0.2 to about 2.5 percent by weight, based on feed.

Table III Effect of H131 concentration on catalyst activity A1Bl'a-COI\1004A1203 catalyst Weight percent HBr Relative activity It is not intended that the scope of this invention be limited to the specific examples presented, as modifications thereof within the confines of the invention as defined by the appended claims are also contemplated.

What is claimed is:

1. A process for the production of naphtha components of high octane rating, consisting largely of branched chain parafiin hydrocarbons of from 5 to 7 carbon atoms, which comprises reacting a minor proportion of a higher paraflin hydrocarbon of from 6 to 18 carbon atoms with a major proportion of a lighter hydrocarbon selected from the group consisting of butanes and pentanes, the mol ratio of lighter hydrocarbon to higher paratiin hydrocarbon being in the range of from 3 to 1 to about 20 to 1, at temperatures of from 30 to F. in the presence of aluminum bromide associated with a support comprising an inorganic ox gen compound of molybdenum selected from the group consisting of molybdenum oxides and the molybdates of cobalt, nickel, and iron.

2. Process as defined by claim 1 wherein hydrogen bromide is employed as a promoter for the catalyst.

3. Process as defined by claim 1 wherein naphthenic hydrocarbons are present in said hydrocarbons of from 6 to 18 carbon atoms.

4. Process as defined by claim 1 wherein said oxygen compound comprises an oxide of molybdenum.

5. Process as defined by claim 1 wherein said oxygen compound comprises cobalt molybdate.

6. Process as defined by claim 1 wherein said oxygen compound of molybdenum is further associated with alumina.

7. Process as defined by claim 1 wherein said oxygen compound of molybdenum is further associated with silica.

8. Process as defined by claim 7 wherein said oxygen compound of molybdenum is sublimed onto the support.

References Cited in the file of this patent UNITED STATES PATENTS 2,221,165 Goldsby Nov. 12, 1940 2,315,129 OKelly et a1 Mar. 30, 1943 2,349,458 Owen et al. May 23, 1944 2,355,339 Story Aug. 8, 1944

Claims (1)

1. A PROCES FOR THE PRODUCTION OF NAPHTHA COMPONENTS OF HIGH OCTANE RATING, CONSISTING LARGELY OF BRANCHED CHAIN PARAFFIN HYDROCARBONS OF FROM 5 TO 7 CARON ATOMS, WHICH COMPRISES REACTING A MINOR PROPORTION OF A HIGHER PARAFFIN HYDROCARBON OF FROM 6 TO 18 CARBON ATOMS WITH A MAJOR PROPORTION OF A LIGHTER HYDROCARBON SELECTED FROM THE GROUP CONSISTING OF BUTANES AND PENTANES, THE MOL RATIO OF LIGHTER HYDROCARBON TO HIGHER PARAFFIN HYDROCARBON BEING IN THE RANGE OF FROM 3 TO 1 TO ABOUT 20 TO 1, AT TEMPERATURE OF FROM 30* TO 140*F. IN THE PRESENCE OF ALUMINUM BROMIDE ASSOCIATED WITH A SUPPORT COMPRISING AN INORGANIC OXYGEN COMPOUND OF MOLYBDENUM SELECTED FROM THE GROUP CONSISTING OF MOLYBDENUM OXIDES AND THE MOLYBDATES OF COBALT, NICKEL, AND IRON.

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