GB1572012A - Process for the etherification of olefins and ethers produced thereby - Google Patents

Description

(54) PROCESS FOR THE ETHERIFICATION OF OLEFINS AND NOVEL ETHERS PRODUCED THEREBY (71) We, SUNTECH INC., a corporation organised under the laws of the State of Pennsylvania, United States of America, of 24() Radnor-Chester Road, St. Davids, Pennsylvania 1()()87, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to novel ethers and to processess for the preparation thereof. More particularly, this invention relates to an improved method for the continuous separation and recovery of products from reactants during the course of the reaction involving the svnthesis of ethers from branched olefins and alcohols in the presence of an acid catalyst.

The reaction of olefins with alcohols using acid catalysts such as 1)-toluene sulphonic acid to form ethers is known.

This method, as in similar prior art methods. involves a homogeneous, single liquid-phase reaction in which, because of considerations of thermodynamic equilibrium, it is often necessary that large excesses of alcohol should be present to maximise the yield.

This. in turn. leads to a serious disadvantage in that the large amounts of alcohol must then be handled during recycling. together with unreacted olefin and catalyst, after the separation of ether product. This separation is conventionally accomplished by neutralising the acid, and water-washing the alcohol from the organic phase before distilling the unreacted olefin from the product. The neutralisation step, in turn. is undesirable because the acid catalyst is converted thereby to a less valuable salt, and distillation of the unreacted alcohol from the reaction medium is necessary for recycle.

Taken as a whole, then. this conventional homogeneous, single-phase system is charicterized by complicated and economically disadvantageous separation and recovery systems together with the handling of large volumes of excess alcohol.

In accordance with the present invention. we have found that, quite surprisingly, the forevoill process can be substantially improved upon, and the disadvantages largely eliminated, by the addition of small amounts of water to the etherification reaction medium. By thus introducing small amounts of water into the reaction system, there is obtained an essentially complete separation of the unreacted olefin and ether product into an upper phase. and the acid catalyst and excess alcohol into a bottom phase without interruption of the reaction. By then continuously or periodically removing the upper phase. while the reaction is proceeding. recovery of the ether product is then greatly facilitated. while at the same time the handling of the acid and alcohol is eliminated sine these reactants remain ill sitit in the reactor, or else are recovered as a single phase and returned to the reactor without the need for neutralization or distillation. This ready handling of the unreacted olefin is particularly advantageous in the case of those olefins having longer. higher molecular weight bunch chains. since the tendency in those cases is for the equilibrium of the reaction to shift away from the product, and back towards the olefin starting material. In those cases. therefore, it is economically imperative that the unreacted materials. which are present in larger volume than in the case of low molecular weight olefins, should be recycled to the reactor. Using the present system. much, if not all. of this handling and recvcling is thus avoided.

As a further advantage of the novel process, we have also found that, surprisingly, the reaction rate is not greatly diminished despite the fact that the olefin and alcohol reactants are in two separate phases. Moreover, it is also surprising that, despite the addition of water to the olefin and ether, selectivitv in these systems remains extremely high. and, surprisingly. alcohol coproducts are not formed.

('ertain novel ethers produced by this process, which have not heretofore been described, are also claimed herein. the accompanying drawing is a simplified schematic diagram illustrating one preferred embodiment of the invention as shown and described in Example 2 below.

The process of this invention, except for the novel features described above, comprises a conventional etherification reaction in which an olefin is reacted with an alcohol in the presence of an acid catalyst. The olefin may generally be a branched or cyclic mono-, di- or triolefin having from 4 to 20 carbon atoms, for example, diisobutylene, dipentene, 2-mcthylpentene-2. a-pinene. α-methylstyrene or the like. The alcohol may generally be a linear or branched C1 to C." saturated alcohol, desirably such a compound as methanol, ethanol. propanol or butanol. The acid catalyst is desirably a sulphonic acid. such as p-toluene sulphonic acid. benzene sulphonic acid. or methane sulphonic acid. although other catalysts such as sulphuric acid. BF3 etherate, hydrochloric acid or phosphoric acid may likewise be employed. Of these. p-toluene sulphonic acid is preferred.

In carrving out this reaction. the ratio of olefin to alcohol is generallv in the range of from 1:4 to 4:1 by volume, and preferably in the range of from 1:2 to 2:1. The amount of catalyst should in general be from 1 to 20% bv weight of reactants, preferably 5 to 15%. The reaction is generallv carried out at a temperature of from about 2() to 12() C, for a period of from about ().5 to 7() hours, preferably from 2 to 1() hours.

The amount of water added to the reaction medium to provide the unique two-phase svstem of this invention should be at least 1%, desirably from about 1-'()' , by volume. in particular from I to 10% bv volume. based on the amount of the total liquid volume of the reaction medium employed. and preferably from about 3 to 10%.

While the reaction mat be earned out in a batch fashion. it will be understood, from the above description. that. most advantageously, the reaction should be conducted as a continuous process in which the upper phase containing the ether product and unreacted olefin is periodically removed, the product recovered. and the olefin recycled to the reactor together with fresh olefin feed. Makeup acid. alcohol. and water are then added to maintain the desired ratio of reactants.

The ether products of this improved process are generally known. and are of value in a wide range of industrial applications. Thus. for example. 2-methoxy-2-phenylpropane.

2-methoxy-2-methylpentane and 2.6-dimethyl-2-methoxyheptene are useful as paint additives. high octane gasoline additives and solvents. The forementioned 2-methoxv-2phenylpropane. which may be prepared by reacting a-methylstyrene with methanol. is a particularly effective paint smoothing agent when combined with a commerical latex-based paint in amounts of from about I to 5 weight percent, preferably about 3 percent.

In a further embodiment of this invention, we have now found that certain novel ethers may be produced bv this process. which compounds are also useful as paint additives, octane-improving intemal combustion engine fuel additives, industrial solvents, and the like. Thus, when 2,6-dimethyl-2-heptane is reacted with methanol, there is obtained 2.6-dimethyl-2-methoxyheptane. which is useful as a paint smoothing agent when incorporated into commerical latex paints in amounts of about 1 to 56/, @ preferably 3 weight percent. Other useful. novel ethers which may similarly be prepared include 2-methoxy-2- methyl-3-ethylhexane. formed bv reacting 9-methvl-3-ethylhexene with methanol. and useful as a paint smoothing agent and high octane fuel additive. Also. 1-methoxy-p- menthane ma, be prepared by first reacting methanol with limonene or α- or 13-pinene. and then hydrogenating the reaction product. and is useful as a paint additive.

In addition to the foregoing ethers, methyl I,t,3,3-tetramethylbutyl ether ("MTMBE") having the formula:

formed by the reaction of diisobutylene with methanol is a novel ether which may be prepared by the process of this invention. This novel material has many important industrial uses. 'l'hus, for example the MTMBE compound of this invention is useful as a low volatility industrial solvent which satisfies air pollution regulations. More particularly, this compound may be used as a solvent in laquers, paints, inks and latex paints, and as a mutual solvent for oil-soap mixtures.

MTMBE is also useful as a high-octane fuel component for motor fuels, conventionally gasolin, for internal combustion engiens having a high blending value. the use of ethers as high octane fuel components is known in the art. When used for this purpose, the MTMBE may be used alone or have admixed therewith diisobutylene in amounts of 2 to 80% by volume based on the volume of MTMBE. The amount of the octane improver to be added to the fuel may range from about 0.5 to 5.0 percent by volume based on the total volume of the fuel.

This MTMBE compound is also effective as an antifoaming agent in aqueous-organic systems in view of its emulsion-breaking characteristics.

MTMBE, when used in minor amounts, for example, 1-5%, is likewise effective as an antifoam and surface-smoothing agent for varous types of paints, particularly latex base paints, because of its low surface tension and high volatility. The use of antifoaming and surface smoothing agents in paint formulations is reviewed, for example, in CHEMICAL WEEK, January 28, 1976, p.20. MTMBE has the added advantage of volatility which most paint-smoothing agents do not have.

This novel MTMBE compound may, of course, be prepared in accordance with the above-described invention. Alternatively, the MTMBE may conveniently be prepared by the reaction of methanol with diisobutylene in the present of a soluble aromatic sulphonic acid or a solid ion-exchange resin catalyst such as Amberlyst 15 (Trade Mark for Rohm and Haas, Philadelphia, pensylvania, U.S.A.), i.e., a solid sulphonated cross-linked polymer of styrene divinyl-benzene. Sulphonic acids such as benzene sulphonic acid, methane sulphonic acid, or p-toluene sulphonic acid are also effective catalysts, of which p-toluene sulphonic acid is preferred.

When Amberlyst 15, for example is employed, the MTMBE is readily prepared by refluxing the diisobutylene and methanol together for 12 to 24 hours in the present of the catalyst, and thereafter the ether product is recovered by conventional techniques which are disclosed in detail in the examples below. In the process of the invention, it will be understood that unreacted starting materials may be recycled to extinction, thus providing an ultimate yield of 100%. In this alternative process, the diisobutylene and methanol should preferably be present in stiochiometric quantities, although an excess of either reactant may be used if desired, in a ratio of 3:1 by volume. The catalyst should preferably be present in amounts of 5-15% by weight based on the weight of the total reaction mixture.

The foregoing invention will now be illustrated by, although not limited to, the following examples: Example 1 A mixture of 30 ml of diisobutylene, 20 ml of methanol, 11 grams of p-toluene sulphonic acid and 5 ml of water was stirred for 24 hours at 60 C. After this time, two layers had formed having the following composition: gas chromatography (g.c.) of neutralised aliquots: Top layer (29 ml) Diisobutylene > 84% methyl-1,1,3,3-tetramethylbutylether ~15% methanol + water < 1% Bottom layer (27 ml) Diisobutylene trace methyl-1,1,3,3-tetramethylbutylether < 1% methanol + water > 99% Example 2 A mixture of 40 gallons of diisobutylene, 40 gallons of methanol, 80 pounds of po-toluene sulphonic acid and 1 gallon of water was stirred vigorously at 60 C for 24 hours in a glass-linead reactor 1, fitted with a stirrer, under nitrogen. After the phases has settled, aliquots of each phase were neutralised with dry sodium carbonate. The top phase contained 81% diisobutylene, 19% methyl-1,1,3,3-tetramethylbutyl ether and ~1% methanol and water. The bottom phase contained < 1% diisobutylene, < 2% methyl 1,1,3,3-tetramethylbutyl ether and 97% aqueous methanol.

The stirrer was stopped and the top layer was then decanted, passed through to a caustic water wash 2 to remove traces of acid and methanol, and distilled in a still 3 from a pad of hexadecane with added quinoline to ensure that the medium be basic so that the ether product would not decompose during distillation. Unreacted diisobutylene (about 32 gal) was returned to the reactor through a line 4 and the product, 1,1,3,3-tetramethylbutyl ether, 7.1 gallons, b.p.:290-295 F was isolated.

Diisobutylene (8 gal) and methanol (0.5 gal) were added to the reactor to approximate the original concentrations (40 gallons each). The reaction proceeded at 60 C and, after 24 hours, approximately 19% of the top basic phase was again converted to methyl-1,1,3,3tetramethylbutyl ether.

Example 3 A mixture of 30 mls. of 2,6-dimethyl-2-heptane, 30 mls, of methanol, 6 grams of p-toluene sulphonic acid and 3.0 ml. of water was stirred at 60-65 C for 24 hors. After this time, glpc analysis showed that the neutralised top layer contained nearly 17% of 2,6-dimethyl-2-methoxy-heptane. Distillation of the top layer gave a pure ether cut, 3.3 grams, which was shown to be 2,6-dimethyl-2-methoxy-heptane by mass spectrometry: #-cleavage to give fragments: (CH3)2(CH3O)C, mass-73, 100%; nmr spectrum: 3 protons at 3.1 ppm (CH3O) and 6 protons at 1.1 ppm ( > C(CH3)2); ir spectrum: absorption at 9.2 (C-O) and elemental analysis.

Example 4 A mixture of 30 mls of 2-methyl-3-ethylhexene-1, 30 mls of methanol, 6 grams of p-toluene sulphonic acid and 3.0 ml of water was reacted in the manner of Example 3 to give 3 grams of an ether which was shown to be 2-methoxy-2-methyl-3-ethylhexane by mass spectrometry: #-cleavage to give a (CH3)2(CH3O)C fragment, mass-73, 100% as well as ethyl and methyl fragments; nmr spectrum: 3 protons at 3.1 ppm (CH3O), 7 protons at 1.3 ppm(br) (CH2 and CH), 6 protons at 1.1 ppm (s) ( > C(CH3)2) and 6 protons at 0.9 (tr) (CH2CH3); ir spectrum: absorption at 9.2 (C-O) and elemental analysis.

Example 5 A mixture of 30 mls of 2-methylpentene-2, 30 mls of methanol, 6 grams of p-toluene sulphonic and 5 ml of water was stirred for 24 hours at 50 C. After this time, two layers were present as in the previous examples. The top layer was found to contain nearly a 60% yield of 2-methoxy-2-methylpentane. The entire reaction mixture (both phases) was neutralised by adding 120 mls of 10% sodium carbonate. Analysis by g.c. showed that 66% of the 2-methylpentene-2 has been converted to 2-methoxy-2-methylpentane.

Example 6 A mixture of 16 mls of -pinene, 16 mls of methanol, 3.2 grams of p-toluene sulphonic acid and 2.5 mls of water was stirred at 25 C for 72 hours. After stopping the stirrer, the two phases separated. The top 12 mls contained methanol, 20%, &alpha;+ -pinene, 8% olefin isomers icluding limonene and camphene, 20%, and methylterpene ethers including endoand exo- methylbornyl ether and limonene methyl ether totalling 52%. The bottom layer was over 90% methanol and a mixture of the olefins and mentioned above in less than 10%. Analysis of the layers was performed by gas chromatography, and the pure products were isolated and identified by comparasion of their ir and spectra and authentic samples. The yield of limonene methyl ether in this reaction was 33%.

Example 7 A mixture of &alpha;-pinene, 30 ml. methanol, 30ml. p-toluene sulphonic acid, 6 grams, and water, 5 ml. was stirred at 56 C for 4 hours. After settling, two layers resulted: the top layer containing 28 ml and the bottom layer, 37 ml. Analysis as in Example 6 showed the top layer to cantain methanol, 11%, &alpha;+ -pinene 21%, olefin isomers including camphene and limonene, 23%, and ethers including methylbornyl ether, methylisobornyl ether, 2methoxyisocamphene, 1-methoxy-p-menth-3-ene and 1,8-dimethoxy-p-menthane (45%).

Of this mixture, 1-methoxy-p-menth-3-ene (limonene methyl ether) comprised 31% and the others totalled 14%. The bottom layer over 90% methanol and ~10% of a mixture of olefins and ethers.

Example 8 In a manner similar to Example 7, limonene was reacted with methanol to form a mixture of terpene methyl ethers (51% yield) containing limonene methyl ether in 35% yield.

Example 9 A mixture of diisobutylene, 30 ml. methanol, 30 ml. and aqueous 40% HCl, 6 ml. was stirred at 63 C for 3 hours. After this time, stirring was stopped and the volumes of the resulting layers was measured and analysed. The top layers, 29 mls, contained 16.5% methyl 1,1,3,3-tetramethylbutyl ether and 82% unreacted diisobutylene in addition to a small amount of 1,1,3,3-tetramethylbutyl chloride and a trace of methanol. The lower layer was over 99% methanol.

FxatizpTh 10 Limonene methyl ether 20 ml, in methylcyclohexane, 40 ml, was hydrogenated over platinum oxide (Adam's Catalyst) at 150 psi to give I-methoxy-p-menthane in high yield.

Example 11 Methyl 1,1,3,3-tetramethylbutyl ether was prepared by rwefluxing a mixture of 50 ml of diisobutylene and 50 ml of methanol for 20 hours over 10 grams of dry Amberlyst 15 (trade mark) with stirring in a nitrogen atmosphere. The reaction mixture was then cooled to room temperature filtered free of Amberlyst 15 and shaken with 300 ml of water containing 20 grams of sodium carbonate. The upper phase, 50 ml, was free of methanol and gas chromatographic analysis showed it to contain two major components: diisobutylene, 80% and the product ether, 20%. This material was mixed with 15 ml of dodecane and 5 ml of quinoline to prevent decomposition of the ether during distillation. Distillation was carried out on a semi-micro spinning band column with a stainless steel band until essentially all of the diisobutylene had been removed. The material remaining in the pot was again analysed by gas chromatography. It was shown to contain only dodecane, quinoline and the product ether. The ether was distilled at atmospheric pressure away from the less volatile components of the mixture using a glass microvigeraux column. The product boiling from 146-147 C (8 ml. 16% yield) was isolated and identified.

The product was a clear colourless liquid having the following properties: b.p. 147 C (uncorr.), nD20 = 1.4158, S(28 ) = 22 dynes/cm using a Fisher Tensiomat. The structure was determined to be methyl-1,1,3,3-tetramethylbutyl ether by a combination of elemental analysis and ir. nmr and mass specral analysis. Elemental analysis: C:75.0% (observed); D:75.0% (calculated); H:13.7% (observed): 13.9% (calculated). Nmr analysis showed 9 protons (a) at 1.0#0.05 ppm, 6 protons (b) at 1.17 # 0.05 ppm, 2 protons (c) at 1.43 # 0.05 ppm and 3 protons at 3.10 + 0.05 ppm (d). This spectrum is completely consistent with the structure. Infrared analysis showed a very strong band characteristic of the ether group at 9.3 , a doubtlet: 7.3 (m), 7.32 (s); is characteristic of the -C(CH3)3 grouping and structure between 8.4 and 9.3 characteristic of branching at the carbon in the &alpha; position to the ether group. Mass spectral analysis shows large peaks due to mass 71 and 73 due to

bond cleavage as well as peaks due to a

fragmentation. The mass spectrum is completely consistent with the structure:

Claims (19)

WHAT WE CLAIM IS:

1. A process for the production of ethers. which comprises reacting an olefin with an alcohol in the present of an acid catalvst. in which at least 1% water, by volume, based on the total volume of the liquid reaction medium, is added to the reaction medium to provide a two-phase system in which product and unreacted olefin are in the upper phase, and catalyst and unreacted alcohol are in the bottom phase, and the reaction is continued in the presence of the water.

2. A process according to claim 1, wherein the amount of water is from 1-10% by volume based on the total volume of the reaction medium.

3. A process according to claim I or 2. wherein the two phases are separated from each other. the product recovered from the unreacted olefin, and the unseparated constituents of the bottom phase returned to the reactor.

4. A process according to claim 3, wherein the unreacted olefin is recycled to the reactor.

5. A process according to claim 1, wherein the upper phase is recovered periodically. and the bottom phase remains in situ in the reactor.

6. A process according to any of claims 1 to 5, wherein the olefin is a branched or cyclic, iiiono-. di- or tri-olefin having from 4 to 20 carbon atoms.

7. A process according to any of claims 1 to 6, wherein the catalyst is p-toluene sulphonic acid.

8. A process according to claim 1 for the preparation of methyl 1,1,3,3-tetramethylbutyl ether which comprises reaction diisobutylene with methanol in the presence of p-toluene sulphonic acid.

9. A process according to claim 8, wherein the ratio of diisobutylene to methanol is from 3:1 to 1:3 by volume.

10. A process according to any of claims 7 to 9, wherein the sulphonic acid is present in amounts of from 5-15% by weight based on the total mixture.

11. 1-methoxy-p-methane.

12. 2,6-dimethyl-2-methoxyheptane.

13. 2-methoxy-2-methyl-ethylhexane.

14. A paint composition comprising a latex-base paint having incorporated therein from 1 to 5 weight percent of 1-methoxy-p-menthane as a paint-smoothing agent.

15. Methyl 1,1,3,3-tetramethylbutyl ether having the formula:

16. A high octane fuel additive for automotive fuels comprising a mixture of methyl 1,1,3,3-tetramethylbutyl ether and from 2 to 80% by volume, based on the volume of the ether, of diisobutylene.

17. A composition comprising a latex base paint and, as an antifoam and surfacesmoothing agent thereof, and effective amount of 1,1,3,3-tetramethylbutyl ether.

18. A process for the production of ethers by the reaction of an olefin with an alcohol in the presence of an acid catalyst substantially as herein described with reference to any of the specific examples 1 to 10 and/or the accompanying drawings.

19. Ethers produced by a process as claimed in any of claims 1 to 10 and claim 18.

'(). A paint composition which comprises at least one ether as claimed in any of claims 11 to 13, t5 and 19.