US3336406A - Preparation of polymethyladamantanes - Google Patents

Description

1- I I A. SCHNEIDEIIQ ETAL 3,336,406

PREPARATION OF POLYMETHYLADAMANTANES I Filed Sp L 10, 1965 5 heets-Sheet 1 FIG. I

. T EX-OVTHE'RM FOR INITIALSTAGE 0F PERHYDROACENAPHTHENE ISOMERIZATION HEATING MEDIUM CARBON I 20 40 so so Too, 'TIME, MINUTES I NVENTORS ABRAHAM SCHNEIDER EDWARD .1. JANOSKI B ROY w; MC GINNIS' QQMW.

ATTORNEY Aug. 15,1967

v A; SCHNEIDER ETAL PREPARATION OF POLYMETHYLADAMANTANES Filed Sept.- 10, 1965 3 heets-Sheet 2 $52.2 d2 2954mm ooN v GI 02 iii/53019 55 me zofifi wzoww.

.LOHOOHd NOGHVOOHGAH NI /o 1M INVENTORS ABRAHAM SCHNEIDER EDWARD J. JANOSKI BY ROY w. MC emms ATTORNEY 3 heets-Sheet 3 ,3- DlMETHYL-A Y Al-SCHNEIDER E AL PREPARATION OF POLYMETHYLAQAMANT-ANES 1 FORMATION OF I FROM PERHYDROACENAPTHENE Filedse 'pt 10 1-965v E3035 zomm omer z 0 ts MINUTES 40 so REACTION TIME",

United States Patent 3 336 406 PREPARATION OF POLYMETHYLADAMANTANES Abraham Schneider, Overhrook Hills, and Edward J.

Janoski, Havertown, Pa., and Roy W. McGinnis, Wil- 3,336,406 Patented Aug. 15, 1967 less the catalyst does not cause an inordinate amount of cracking to occur. Hence a high yield of the desired ultimate isomerization product can be obtained in relatively short reaction times.

In practicing the present invention any perhydroaror fif gi fi gf g 3523122 3 fi s g gg g Plum 5 matic hydrocarbon which has three rings and from twelve Filed Sept. 10, 1965, Ser. No. 486,307 to fourteen carbon atoms lHClllSlV8 can be used. A table 16 Claims. (Cl. 260-666) of numerous tricyclic aromatics which can be hydrogenated to produce corresponding C C perhydrocar- This invention relates to the catalytic isomerization of bons is presented in the aforesaid patent. Any such per- C -C tricyclic perhydroaromatic hydrocarbons to prohydroaromatic hydrocarbon will readily isomerize under duce polymethyladamantanes. More particularly the inthe conditions herein specified to form a product having vention concerns the conversion of such perhydroaromatic an adamantane nucleus and methyl substituents located hydrocarbons into adamantanes having the same number at bridgehead positions. Since the nucleus has ten carbon of carbon atoms and from two to four methyl groups at- 15 atoms, the product will have from two to four carbon tached to bridgehead carbon atoms of the adamantane atoms in excess of those required for forming the nucleus, nucleus. Specific bridgehead polymethyladamantanes predepending upon the particular perhydroaromatic selected pared according to the invention are the following: 1,3- as starting material. These excess carbon atoms will all dimethyladamantane; 1,3,5 trimethyladamantane; and appear as methyl groups located at bridgehead positions 1,3,5,7-tetramethyladamantane. in the final isomerization product.

The conversion of tricyclic perhydroaromatic hydro- In the transition from the starting material to the polycarbons of twelve or more carbon atoms to isomers having methyladamantane product it has been found that the an adamantane nucleus has been described in United isomerization path for tricyclic perhydroaromatics leads States Patent No. 3,128,316. As disclosed in the patent through an intermediate stage at which an ethyl group is this isomerization is effected at a temperature in the range attached to the adamantane nucleus at both brid ehead of 5 C. to 50 C. by means of an aluminum chloride and non-bridgehead positions. This is illustrated for the or bromide catalyst. The hydrocarbons go through vari- C perhydroaromatic, acenaphthene, by the following ous conversion stages; but if the isomerization reaction is equation:

C-C n n PERHYDRJ- l-ETHYL- Q-E'I'HYL- AC ENF. PHTHENE! ADAMANTANE ADAMANTAN E carried to completion, the ultimate product is mainly a polymethyladamantane having two or more methyl groups attached to bridgehead carbon atoms of the a-damantane nucleus. However, under the conditions taught in the patent the isomerization reaction proceeds slowly and an undesirably long reaction time is required to attain the maximum yield of the bridgehead polymethyl isomers. Merely raising the reaction temperature to above the 50 C. maximum value taught in the patent and contacting the hydrocarbon reactant with catalyst for .a long enough time to produce mainly the bridgehead polymethyl products is not satisfactory, as this tends to promote cracking reactions which cause rapid deactivation of the catalyst. Hence, according to the patent the reaction temperature is maintained below 50 C. and a long reaction time is employed in order to approach the maximum obtainable yield of the bridgehead polymethyladamantanes.

The present invention constitutes an improvement over the process of United States Patent No. 3,128,316, whereby bridgehead polymethyladamantanes of the C -C range are produced from C -C tricyclic perhydroaromatics in a considerably more rapid reaction. Accordin to the invention the tricyclic perhydroaromatic charge is contacted at a temperature in the range of 55150 0., preferably 70-120 C., and in the presence of free HCl maintained at -a partial pressure of at least 0.1 psi. with a pre-formed aluminum chloride catalyst complex. The catalyst is a liquid complex previously prepared by reacting AlCl HCl and paraffin hydrocarbon having at least seven carbon atoms per molecule as hereinafter described. It has now been found that use of HCl in the isomerization zone at a partial pressure as specified allows the catalyst to be employed at relatively high temperatures without appreciable loss of activity. Neverthe- Further isomerization converts the ethyl group to two methyl groups which preponderantly are located at bridgehead positions. Thus the major final product of the isomerization of perhydroacenaph-thene is 1,3-dimethyladamantane. However, when the isomerization is complete, an equilibrium composition is reached at which the 1,3- isomer is mixed with minor amounts of its non-bridgehead methyl isomers. By non bri-dgehead as used herein in referring to a product is meant that at least one of the substituents is attached to the adamantane nucleus at a n0nbridgehead carbon atom. There are three non-bridgehead dimethyl isomers which will appear in minor amounts with the 1,3-isomer at equilibrium. These are the following (DMA meaning dimethyladamantane): 1,2-DMA; antil,4-DMA; and syn-1,4-DMA. However, the total amount of these at equilibrium generally is less than 10%, so that 1,3-DMA is by far the predominant product resulting from complete isomerization of perhydroacenaphthene. Isomers in which both methyl groups appear at nonbridgehead positions do not occur in any appreciable amount. The foregoing applies equally well when the starting hydrocarbon is some other C tricyclic perhydroaromatic, for example, perhydrohydrindacene.

When the starting material is a C perhydroaromatic, for example, perhydrofluorene, an intermediate isomerization product again is formed in which ethyl substituents are located at bridgehead and non-bridgehead positions. In this case the intermediate isomers also contain, in addition to the ethyl group, a methyl group which may be attached at bridgehead or non-bridgehead positions. Further isomerization converts the ethyl group to two methyl groups and shifts non-bridgehead methyl groups mainly to bridgehead positions. Hence the predominant ultimate isomerization product is 1,3,5 trimethyladamantane (T MA) which occurs in equilibrium with minor amounts of non-bridgehead TMA isomers.

In the case of C perhydroaromatics an analogous intermediate isomerization stage occurs in which the intermediate product contains an ethyl group. The ethyl group subsequently disappears by conversion into methyl groups and the predominant final product is l,3,5,7-tetramethy1- adamantane.

It has noW been found that isomerizations conducted in accordance with United States Patent No. 3,128,316 using an aluminum chloride catalyst are difficult to carry beyond the intermediate stage discussed above, i.e., where an ethyl substituent is attached to the nucleus. For example, C perhydroaromatics will form ethyladamantane but then further isomerization to convert the ethyl group to bridgehead methyl groups becomes undesirably slow. Thus, when perhydroacenaphthene is contacted at 40 C. with a pre-formed AlCl -HCl-hydrocarbon complex, a major portion can be converted to ethyladamantane in an hour or so. However after a 4-hour reaction time, typically 60% or more of the product is still ethyladamantane and only a minor amount of 1,3-dimethyladamantane will have been formed. The present invention obviates this difficulty of going beyond the ethyladamantane stage. It also shortens the time required in the initial conversion of the charge hydrocarbon to reach the ethyladamantane stage of isomerization.

The present process involves the use in the isomerization zone of free hydrogen chloride in combination with a catalyst which is a pre-formed liquid complex obtained by reacting AlCl HCl and paraffinic hydrocarbon as described below. The catalyst should contain suspended therein an excess of AlCl over that which reacts to form the complex. The isomeriation is conducted by contacting the hydrocarbon charge at a temperature of 55-150 0., preferably 70-120 0., with the catalyst which constitutes a separate liquid phase in the reactor. Gaseous HCl is added to the reactor in order to maintain therein a partial pressure of HCl of at least 0.1 pound per square inch (p.s.i) and more preferably at least 1.0 p.s.i. An HCl partial pressure in the range of 1-30 p.s.i. is typical but a much higher HCl pressure, e.g., 100500 p.s.i., can be employed without any adverse effect. These values refer to partial pressure of the HCl as measured at the tempera ture at which the reaction is conducted.

The mixture is continuously agitated to etfect initimate contact between the phases. Under the above-stated conditions the isomerization reaction takes place at an accelerated pace, proceeding to and through the ethyl intermediate stage and producing the desired bridgehead polymethyladamantane in high concentration. Some amount of cracking occurs during the reaction, resulting in the formation of small amounts of lower boiling products such as isobutane, isopentane and naphthenes of the C C range. Nevertheless the activity of the catalyst is not substantially reduced as long as free HCl at a partial pressure above 0.1 p.s.i. is maintained in the reaction zone.

The use of a temperature exceeding 55 C. materially reduces the time necessary for converting the perhydroaromatic charge to the ethyl intermediate stage. It has been found that when the perhydroaromatic and the preformed complex catalyst are contacted with each other while being heated a rapid exothermic reaction takes place when the temperature exceeds 55 C. The immediate product of this rapid reaction is the alkyladamantane containing an ethyl substituent. FIG. 1 of the accompanying drawings graphically illustrates this rapid exothermic reaction. FIG. 1 is for the isomerization of perhydroacenaphthene and shows the temperatures of the hydrocarbon reactant and of the fluid heating medium as a function of time from start-up. The procedure employed was as follows: At room temperature perhydroacenaphthene and a pre-formed AlC -HCl-hydrocarbon complex catalyst were charged to a reactor and gaesous HCl was admitted thereto to a pressure of about 25 p.s.i.g. The reactor had a jacket through which the fluid heating medium was continuously circulated and also was provided with a stirrer for intimately contacting the hydrocarbon and catalyst phases. The run was begun by starting the stirrer and by continuously pumping the heating medium through the jacket while heating it in a preheater to raise the temperature. The temperatures of the incoming heating medium and of the hydrocarbon reactant were continually measured, and the two curves of FIG. 1 show the respective values obtained as against time.

As can be seen in FIG. 1 the temperature of the hydrocarbon reactant lags behind that of the heating medium in the initial heat-up period and for a time increases at more or less the same rate as the heating fluid tmeperature increases. However, when the hydrocarbon temperature exceeds 55 C., a strong exothermic reaction sets in, causing the hydrocarbon temperature to rise sharply above that for the heating medium. This reaction corresponds to the conversion of the perhydroacenaphthene to the adamantane structure and it mainly produces ethyladamantanes. The isomerization then slows down, as evidenced by the fact that the hydrocarbon temperature soon drops back toward that of the heating medium. If the reaction were stopped at this stage, as described and claimed in our copending United States application Ser. No. 486,275, filed of even date herewith, the ethyladamantanes would constitute most of the product. For the present purpose, however the isomerization reaction is continued to obtain the bridgehead dimethyladamantane as the major product. In order for this further reaction to proceed at a reasonably rapid pace, it is necessary to have free HCl in the reactor as illustrated by FIG. 2 discussed hereinafter.

In preparing the catalyst AlCl is suspended in a paraffin hydrocarbon or mixture of paraflins having at least seven and preferably eight or more carbon atoms per molecule and gaseous HCl is passed into the mixture. It is desirable to use isoparatfins such as highly branched octanes, nonanes or decanes for this purpose but straight chain paraffins can also be used. The reaction of the AlCl HCl and paraffin hydrocarbon can be effected at room temperature, although the use of an elevated temperature such as 50100 C. generally is desirable to increase the rate of reaction. For best results at least five moles of the paraffin per mole of AlCl should be employed. Under these conditions some of the paraffin evidently breaks into fragments, yielding a C fragment which becomes the hydrocarbon portion of the complex. As reaction between the three catalyst components occurs the particles of AlCl in suspension in the hydrocarbon become converted to the liquid complex. The addition of HCl is stopped before all of the AlCl reacts so that the complex formed will contain some AlCl particles suspended therein. Alternatively HCl is added until all of the AlCl has reacted but some fresh AlCl is suspended in the resutling complex before it is used as catalyst. The complex is a reddish brown, somewhat viscous liquid which is a relatively stable material.

In carrying out the process of the invention the preformed catalyst prepared as described above and the tricyclic perhydroaromatic charge are introduced into a reaction zone and gaseous HCl is added thereto to maintain the HCl partial pressure as above specified. The proportion of catalyst complex to perhydroaromatic charged is not critical but it is usually desirable to employ a weight ratio of complex to hydrocarbon of at least 1:10. More preferably such ratio is at least 1:1 and considerably larger ratios, e.g., 10:1, can be used if desired. The reactor should be provided with means for agitating the mixture so as to effect good contact between the catalyst and hydrocarbon phases. Increases in the catalyst to hydrocarbon ratio and in the degree of agitation tend to expedite the reaction. Contacting of the catalyst and hydrocarbon phases at 55150 C. While maintaining an HCl partial pressure as previously specified is continued until at least a major portion of the tricyclic perhydroaromatic has been converted to the desired bridgehead polymethyladamantane. The contacting is then stopped and the hydrocarbon product is separated from the catalyst layer. By distilling off the lower boiling products resulting from a minor amount of cracking that occurs, the bridgehead polymethyladamantane can be obtained in high concentration which typically is of the order of 85-92%.

In a further embodiment of the invention the bridgehead polymethyladamantanes are prepared in still higher concentrations, for example, in a purity of 95% or better. In this embodiment the tricyclic perhydroaromatic charge is first reacted at a temperature of 55150 C., preferably 70120 C., and under an HCl pressure, all as above described. This produces an equilibrium product of polymethyladamantanes comprising mainly bridgehead products but also a minor but substantial amount of nonbridgehead polymethyl isomers. The temperature is then dropped to within the range of 050 C. and preferably below 30 C. and contacting of the hydrocarbon and catalyst phases is continued. This results in the formation of a new equilibrium mixture in which the proportion of bridgehead to non-bridgehead isomers is substantially increased. For example, whereas such proportion typically may be about 90:10 for an equilibrium .mixture formed at 90 C., re-equilibrium of the mixture by then contacting the catalyst and hydrocarbon phases at 25 C. typically may increase the bridgehead to non-bridgehead isomer ratio to 96:4.

The data shown in Table I specifically illustrates the benefit that can be derived by this procedure of following the higher temperature isomerization step with a further step for equilibrating at lower temperature. Table I shows measured equilibrium values obtained for C adamantanes for equilibration at relatively high and relatively low temperatures, specifically, 83 C. and 27 C., by means of the AlCl complex catalyst.

TABLE I.-EQUILIBRIUM CONCENTRATIONS FOR C'm The tabulated data shows that equilibration at 27 C. drops the total non-bridgehead DMA content to about one-half of that for 83 C. The purity of the bridgehead isomer is increased from 90.9% to 95.7% for these temperature levels. The data also show that the amount of l-ethyladamantane, which is the main intermediate formed in going from a C perhydroaromatic to the adamantane structure, is negligible in the fully equilibrated product at either temperature level.

In practice a minor but substantial amount of cracked products will be present in the isomerization product, so that the actual content of the bridgehead isomer in the hydrocarbon phase will not be as high as shown in Table 1. However the cracked material can readily be removed by distillation and the bridgehead isomer can thus be obtained in purities as illustrated in the table.

The following examples describe runs which illustrate the capabilities of the present process. Results from these runs are depicted graphically in FIGURES 2 and 3 of the accompanying drawings, as described below.

Example 1 An AlCl complex catalyst was prepared by reacting 40 ml. of 2,2,5-trimethylhexane with 15 g. of AlCl at 65-75 C. while bubbling HCl into the mixture. After essentially all of the A101 had reacted, the mixture was cooled and allowed to stratify, and the excess hydrocarbon was decanted. The catalyst layer was washed with 30 ml. of 2,2,5-trimethylhexane and then was blown at room temperature with nitrogen to remove any excess HCl.

A shaker bomb was charged with 10.5 g. of the so-prepared complex, 5.0 g. of uncomplexed A101 and 11.0 g. of perhydroacenaphthene. The latter was a mixture of four isomers produced by hydrogenating acenaphthene employing a Raney nickel catalyst. Without any free HCl being added the bomb was immersed in a water bath which had been heated to C. With the bath maintained at such temperature the bomb was agitated for 177 minutes. Small samples of the hydrocarbon phase were taken at times of 60, 117 and 177 minutes for analysis by vapor phase chromatography. After the third sampling the mixture was cooled to 0 C. and the bomb was pressured at that temperature with HCl to a pressure of 10 p.s.i.g. The bomb was then reheated to 90 C. and was agitated to continue the isomerization. The partial pressure of HCl under these conditions was about 13.3 p.s.i. Samples were taken corresponding to total reaction of times (including the previous reaction period of 177 minutes) 237 and 297. Analyses of the various samples are shown in Table II, which lists the products in the order of increasing boiling points.

TABLE II.-ISOMERIZATION OF PERHYDROACENAPH- THENE AT 90 C. WITHOUT AND WITH FREE 1101 Reaction time, min 60 117 177 237 297 Free H01 None None None Yes Yes Composition of Product,

wt. percent:

C4 parafrins 1.6 2. 6 2. 7 2. 2 7. 4 1.4 3.1 3. 0 2. 2 6. 4 C parafiins 1. 3 trace 0.2 0.8 0. 2 01-011 naphthenes 4. 0 2.8 2. 3 3. 2 2. l 1,3-dimethyl-A 17. 8 24. 6 29. 7 68. 7 70. 1 1,2- and 1,4-dimethyl- No perhydroacenaphthene remained in the reaction mixture by the time the first product sample was taken.

In FIG. 2 the values listed in Table II for the contents of l-ethyladamantane and 1,3-dimethyladamantane have been plotted against reaction time. Reference to FIG. 2 shows that without free HCl l-ethyladamantane quickly formed and that it constituted over one-half of the reaction product when a one-hour reaction time was reached. However further conversion of this isomer did not then occur and its content remained steady at about 56%. A slow formation of the 1,3-dirnethyl isomer occurred as shown in Table II but this evidently was derived mainly through isomerization of the non-bridgehead dimethyl isomers and not l-ethyladamantane. These results show that isomerization in the absence of free HCl is not a satisfactory way of obtaining bridgehead dimethyladamantane in good yield.

FIG. 2 further shows that when an HCl pressure was applied to the reaction zone, the ethyladamantane isomerized rapidly and the yield of 1,3-dimethyladamantane increased sharply. This illustrates the importance of using free HCl in the reaction zone in practicing-the present invention.

Example 2 In this example perhydroacenaphthene was isomerized generally the same way as in the preceding example except that free HCl was used initially in amount equivalent to 10 p.s.i. measured at 0 C. (about 13.3 p.s.i. at the reaction temperature). Specifically the bomb contained 14.2 g. of the A101 complex, 5.0 g. of uncomplexed AlCl 14.8 g. of a mixture of the four perhydroacenaphthene isomers and the free HCl. The reaction temperature was about 89 C. Compositions of product corresponding to three reaction times as shown in Table III.

Example 3 A comparative run was made with free HCl under the conditions described in Example 2 except that the reaction temperature was maintained at about 42 C. instead of 89 C. Results are shown in Table IV.

TABLE IV.ISOUERIZATION OF PERHYDROACENAPH- THENE AT 42 0. WITH FREE HCl Reaction time, min 60 120 180 240 Free 1101 Yes Yes Yes Yes Composition of Product, wt. percent:

04 paraflins 2.1 2. 8 3.0 2. 6 C parafiins.-. 2.1 2. 8 1. 1. C6 parafilns 0.1 0.5 0.6 0. 6 01-011 naphthenes. 1. 8 2. 2 2. 3 1. 8 1,3-dimethyl-A- 3. 4 14. 8 23. 6 26. 0 1,2- and 1,4-dimethyl-A. 7. 4 4.6 2.8 2. 1 l-ethyl-A 49. 9 09. 0 65. 2 60. 5 Zethyl-A 33. 4 3. 3 1. 5 3. 9

As in the previous runs no perhydroacenaphthene remained in the product by the time the first sample was taken at one hour.

FIG. 3 shows the 1,3-dimethyladamantane content of the products of Examples 2 and 3 as a function of reaction time. A comparison of the two curves shows the importance of reaction temperature in obtaining a high yield of the bridge-head dimethyl isomer within a reasonable reaction time. This figure considered together with FIG. 2 shows that both an elevated temperature and presence of free HCl, as herein specified, are important for achieving the desired results.

When any C or C tricyclic perhydroaromatic is substituted for perhydroacenaphthene, results analogous to those shown in the foregoing examples are obtained. In the absence of free HCl, or when it is present but the -temperature is below the herein specified range, the

reaction tends to stop or be impractically slow at a stage when ethyl intermediates predominate. However, when free HCl at a partial pressure as herein specified and a temperature above 55 C. are employed, any C tricyclic perhydroaromatic can readily be isomerized to 1,3,5-trimethyladamantane and any C tricyclic perhydroaromatic can likewise be converted to 1,3,5,7-tetramethyladamantane.

We claim:

1. Method of preparing polymethyladamantane of the C -C range in which the methyl groups are located at bridge-head positions of the adamantane nucleus which comprises contacting a tricyclic perhydroaromatic having 12-14 carbon atoms at a temperature in the range of 55-150 C. and in the presence of free HCl at a partial pressure of at least 0.1 p.s.i. with a pre-formed liquid complex obtained by reacting AlCl HCl and a paraflin hydrocarbon having at least seven carbon atoms and continuing said contacting under the conditions specified until at least a major portion of the tricyclic perhydroaromatic has been converted to said bridgehead polymethyladamantane.

2. Method according to claim 1 wherein said temperature is in the range of 70-120 C.

3. Method according to claim 1 wherein the I-ICl partial pressure is at least 1.0 p.s.i.

4. Method according to claim 1 wherein a C tricyclic perhydroaromatic is used and a major portion thereof is converted to 1,3-dimethyladamantane.

5. Method according to claim 4 wherein said temperature is in the range of 70-120 C.

6. Method according to claim 5 wherein the HCl partial pressure is at least 1.0 p.s.i.

7. Method according to claim 1 wherein a C tricyclic perhydroaromatic is used and a major portion thereof is converted to 1,3,S-trimethyladamantane.

8. Method according to claim 7 wherein said temperature is in the range of 70-120 C.

9. Method according to claim 8 wherein the HCl partial pressure is at least 1.0 p.s.i.

10. Method according to claim 1 wherein a C tricyclic perhydroaromatic is used and a major portion thereof is converted to l,3,5,7-tetramethyladamantane.

11. Method according to claim 10 wherein said temperature is in the range of 70-120 C.

12. Method according to claim 11 wherein the HCl partial pressure is at least 1.0 p.s.i.

13. Method of preparing polymethyladamantanes of the C -C range in which the methyl groups are located at bridgehead positions of the adamantane nucleus which comprises contacting a tricyclic perhydroaromatic having 12-14 carbon atoms at a temperature in the range of 55-150" C. and in the presence of free HCl at a partial pressure of at least 0.1 p.s.i. with a pre-formed liquid complex obtained by reacting AlCl HCl and paraffin hydrocarbon having at least seven carbon atoms, continuing said contacting under the conditions specified until at least a major portion of the tricyclic perhydroaromatic has been converted to polymethyladamantanes, whereby a minor but substantial proportion thereof have at least one methyl group at a non-bridgehead position, reducing the temperature of the reaction mixture to within the range-of O50 C. and continuing the contacting at said temperature of O-SO" C. until said proportion has been substantially reduced.

14. Method according to claim 1 wherein the first-mentioned temperature range is 70-l20 C. and said partial pressure is at least 1.0 p.s.i.

15. Method of preparing 1,3-dimethyladamantane in high purity which comprises contacting a C tricyclic perhydroaromatic at a temperature in the range of 55- C. and in the presence of free HCl at a partial pressure of at least 0.1 p.s.i. with a pre-formed liquid complex obtaining by reacting AlCl HCl and paraffin hydrocarbon having at least seven carbon atoms until a major portion of the tricyclic perhydroaromatic has been converted to mixed dimethyladamantanes including a minor amount of the 1,2- and 1,4-isomers, reducing the temperature of the reaction mixture to within the range of 050 C. and continuing the contacting at said temperature of 0-50 C. until said amount has been substantially reduced by isomerization thereof to 1,3-dimethyladamantane.

16. Method according to claim 15 wherein the firstmentioned temperature range is 70-120" C. and said partial pressure is at least 1.0 p.s.i.

References Cited UNITED STATES PATENTS 4/1964 Schneider 260666 6/1966 Schneider 260-666

Claims (1)

1. METHOD OF PREPARING POLYMETHYLADAMANTANE OF THE C12-C14 RANGE IN WHICH THE METHY GROUPS ARE LOCATED AT BRIDGE-HEAD POSITIONS OF THE ADAMANTANE NUCLEUS WHICH COMPRISES CONTACTING A TRICYCLIC PERHYDROAROMATIC HAVING 12-14 CARBON ATOMS AT A TEMPERATUREIN THE RANGE OF 55-150*C. AND IN THE PRESENCE OF FREE HCL AT A PARTIAL PRESSURE OF AT LEAST 0.1 P.S.I. WITH A PRE-FORMED LIQUID COMPLEX OBTAINED BY REACTING ALCL3, HCL AND A PARAFFIN HYDROCARBON HAVING AT LEAST SEVEN CARBON ATOMS AND CONTINUING SAID CONTACTING UNDER THE CONDITIONS SPECIFIED UNTIL AT LEAST A MAJOR PORTION OF THE TRICYCLIC PERHYDROAROMATIC HAS BEEN CONVERTED TO SAID BRIDGEHEAD POLYMETHYLADAMANTANE.

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