Synthesis of alkyl tert-alkyl ether using zeolite catalysts

Abstract: Methyl tert-butyl ether is prepared from tertiary-butyl alcohol and methanol in one step by reaction of tertiary butyl alcohol and methanol in the presence of a catalyst comprising a hydrogen fluoride-modified zeolite at elevated temperature and moderate pressure.

Description: This invention concerns an improved process for preparing alkyl-tertiary-alkyl ethers such as methyl tertiary-butyl ether (MTBE) by the reaction of tertiary alcohol such as tertiary butanol and primary alcohol such as methanol in the presence of a catalyst comprising a hydrogen fluoride-modified zeolite. The invention is particularly advantageous in that the reaction takes place in one step; typically MTBE is generated continuously in 30+% concentration in the crude liquid product, with the crude product mix separating into an isobutylene-MTBE product-rich phase and a heavier aqueous methanol phase. Alkyl tertiary-alkyl ethers prepared by this invention, particularly MTBE, are useful as a blending component in high octane gasoline. It is known to those skilled in the art that ethers, including unsymmetrical ethers, may be prepared by reacting an alcohol with another alcohol to form the desired product. The reaction mixture, containing catalyst and/or condensing agent may be separated and further treated to permit attainment of the desired product. Such further treatment commonly includes one or more distillation operations. Methyl tert-butyl ether is finding increasing use as a blending component in high octane gasoline as the current gasoline additives based on lead and manganese are phased out. Currently all commercial processes for the manufacture of methyl tert-butyl ether are based upon the liquid-phase reaction of isobutylene and methanol (Eq. 1), catalyzed by a cationic ion-exchange resin (see, for example: Hydrocarbon Processing, Oct. 1984, p. 63; Oil and Gas J., Jan. 1, 1979, p. 76; Chem. Economics Handbook-SRI, Sept. 1986, p. 543-7051P). The cationic ion-exchange resins used in MTBE synthesis normally have the sulphonic acid functionality (see: J. Tejero, J. Mol. Catal., 42 (1987) 257; C. Subramamam et al., Can. J. Chem. Eng., 65 (1987) 613). With the expanding use of MTBE as an acceptable gasoline additive, a growing problem is the availability of raw materials. Historically, the critical raw material is isobutylene (Oil and Gas J., June 8, 1987, p. 55). It would be advantageous, therefore, to have a process to make MTBE that does not require isobutylene as a building block. It would be advantageous to have an efficient process for making MTBE by reaction of methanol with tertiary butyl alcohol, since t-butanol (TBA) is readily available commercially through isobutane oxidation. In US-A-4,144,138 (1979) to Rao et al., there is disclosed a method for recovering methyl tertiary butyl ether from etherification reaction effluent by azeotropic distillation to recover methanol-ether azeotrope overhead which is water-washed to give pure ether raffinate, the latter being azeotropically distilled to yield ether-methanol overhead which is recycled to water washing. The preparation of methyl tert-butyl ether from methyl and tert-butyl alcohols is discussed in S. V. Rozhkov et al., Prevrashch Uglevodorodov, Kislotno-Osnovn. Geterogennykh Katal. Tezisy Dokl. Vses Konf., 1977, 150 (C. A. 92:58165y). Here the TBA and methanol undergo etherification over KU-2 strongly acidic sulfopolystyrene cation-exchangers under mild conditions. This reference contains data on basic parameters of such a process. It is also pointed out that, although a plant for etherification over cation exchangers does not present any major problems, considerations include the fact that-recycling large amounts of tert-butyl alcohol and methanol, as well as isobutylene, causes the scheme to be somewhat more expensive. Also, the progress of the reaction over cation exchangers is usually complicated by various adsorption and diffusion factors, by swelling phenomena, and by the variable distribution of the components between the solution and ion-exchanger phase. Furthermore, said acidic cation-exchangers with an organic (polystyrene or polymethacrylate) backbone generally have a very limited stability range with regard to operating temperatures, with temperatures above 120°C normally leading to irreversible destruction of the resin and loss of catalytic activity. In US-A-2,282,469 to Frolich there is disclosed a process for preparing methyl tertiary butyl ether over a catalyst comprising Kieselguhr impregnated with phosphoric acid at a temperature of about 80°C - 180°C (175°F - 350°F). JP 7432/1982 (Provisional) teaches the use of zeolites to make dialkyl ethers containing primary or secondary alkyl groups. The zeolites have a porous structure and are represented by: M 2/n O·Al 2 O 3 ·xSiO 2 · y H 2 O where M is an alkali metal or alkaline earth metal cation or organic base cation, n is the valence of the cation and x and y are variables. US-A-4,058,576 to Chang et al. teaches the use of (pentasil-type) aluminosilicate zeolites, such as ZSM-5, having a pore size greater than 5 angstrom units and a silica-to-alumina ratio of at least 12, to convert lower alcohols to a mixture of ethers and olefins. In US-A-4,822,921 there is disclosed a method for producing MTBE by reacting tertiary butyl alcohol and methanol in the presence of a catalyst comprising an inert support, such as titania, having a phosphoric acid impregnated thereon. US-A-4,827,048 discloses a method for producing MTBE by reacting tertiary butyl alcohol and methanol in the presence of a catalyst comprising a heteropoly acid such as 12-tungstophosphoric acid or 12-molybdophosphoric acid on an inert support, such as titania. In copending U. S. Patent Application Serial No. 07/494,281, there is disclosed a method for preparing methyl tertiary butyl ether by reacting butanol and methanol in the presence of a catalyst comprising a super-acid alumina or a faujasite-type zeolite. In EP-A-0502651, a Y-type zeolite modified with fluorosulfonic acid is disclosed. EP-A-333078 discloses the synthesis of MTBE by reaction of t-butanol and methanol in a one-step reaction using a catalyst selected from the group consisting of acidic aluminas, acidic silicas, or combinations thereof and zeolites containing alumina or silica, and acidic clay mineral catalysts. It is an object of the present invention to selectively synthesize alkyl tertiary-alkyl ether such as MTBE from tertiary alcohol, e.g. tertiary butyl alcohol and primary alcohol, e.g. methanol, in one step using a catalyst which allows for rapid conversion of tertiary alcohol. It has now been discovered that hydrogen fluoride-modified zeolites can be used as catalysts for the selective synthesis of alkyl tertiary alkyl ether from tertiary alkyl alcohol and primary alcohol. The accompanying examples demonstrate good yields of MTBE when using the modified zeolites of the instant invention for such a reaction. In accordance with certain of its aspects, the present invention provides a method for preparing alkyl tert-alkyl ether from tertiary alkyl alcohol and C 1 -C 6 primary alcohol in one-step which comprises reacting tertiary alkyl alcohol and primary alcohol in the presence of a catalyst comprising a hydrogen fluoride-modified zeolite at an elevated temperature and moderate pressure. Most preferably, the invention provides a method for preparing methyl tert-butyl ether from tertiary-butyl alcohol and methanol by said process. The following description concentrates upon the reaction of methanol and tert-butyl alcohol to prepare MTBE. This important reaction does not restrict the scope of the invention. A hydrogen fluoride-modified rare earth exchanged Y-zeolite is particularly preferred. The preparation of MTBE can be represented by the following: Generally the methanol and t-butanol coreactants may be mixed in any proportion in order to generate the desired methyl t-butyl ether, but preferably the molar ratio of methanol to t-butanol in the feed mixture should be between 10:1 and 1:10, if the yield of desired MTBE is to be maximized. In order to achieve maximum selectivity to MTBE, and optimum conversion per pass, an excess of methanol in the liquid feed is desirable. The most preferred methanol-to-tertiary butanol molar ratio is from 1:1 to 5:1. In certain circumstances, it may be particularly desirable that the TBA conversion be high enough (e.g. 80% or greater), such that the crude product mix phase separates into an isobutylene-MTBE product-rich phase and a heavier aqueous methanol phase. Preferably such a product phase separation would be achieved at as low an etherification temperature as possible, but particularly in the range 160-200°C. The synthesis of Eq. 2 can also be conducted where the t-butanol and methanol reactants are mixed with certain other components including water, ketones such as acetone, peroxides and hydroperoxides such as di-t-butyl peroxide and allyl t-butyl peroxide, as well as esters such as t-butyl formate. Typically each of said classes of components makes up less than 10% of the total feed mixture. The same process may also be applied to the preparation of other alkyl tertiary alkyl ethers. For example, said process may be applied to the reaction of a C 1 -C 6 primary alcohol such as methanol, ethanol, n-propanol and n-hexanol with a C 4 -C 10 tertiary alcohol such as, for example, tertiary butanol and tertiary amyl alcohol. Reaction of methanol with tertiary amyl alcohol (2-methyl-2-butanol) would then yield methyl tertiary amyl ether (TAME). Alternatively a mixture of alcohols, e.g., a mixture of C 1 -C 5 alcohols, could be reacted to give a mixture of alkyl tert-alkyl ethers. Good results were realized using certain crystalline aluminosilicate zeolites as catalysts for the reaction represented in Equation 2, particularly the isostructural group of faujasite zeolites that include the synthetic Y-zeolites. The preferred Y-zeolites are the rare earth exchanged Y-zeolites. The unit cells of zeolites X and Y are cubic, a o ≈ 2.5 nm, and each contains 192 silicon- or aluminum-centered oxygen tetrahedra which are linked through shared oxygen atoms. Because of the net negative charge on each of the aluminum-centered tetrahedra, each unit cell contains an equivalent number of charge-balancing cations. These are exclusively sodium ions in zeolites in their synthesized form. Typical cell contents for the Y-zeolites in the hydrated form are: Na 56 [(A10 2 ) 56 (SiO 2 ) 136 ] 250 H 2 O Y-zeolites are distinguished on the basis of the relative concentration of silicon and aluminum atoms and the consequent effects on detailed structure and related chemical and physical properties. The aluminum atoms in the unit cell of Y-zeolite vary from 76 to 48 giving a Si:Al ratio between 1.5 and 3.0. Both the cation concentration and charge density on the aluminosilicate structure are lower for Y-zeolites than for X-zeolites, where the aluminum atoms in the unit cell vary from 96 to 77. The feature which determines the difference between faujasites and other zeolites built up from sodalite units is the double 6-membered ring or hexagonal prism, by which the units are linked. The sodalite unit, or β-cage, can be represented by a truncated octahedron, with the 24 silicon or aluminum atoms (designated T atoms) taking positions at the vertices. The 36 oxygen atoms are displaced from the midpoints of the edges joining the vertices in order to attain tetrahedral configuration around the T atoms. The free diameter of the void within the β-cage is 0.66 nm, but only the smallest molecules can enter through the 0.22 nm diameter opening in the distorted ring of six oxygen atoms associated with each hexagonal face. Each sodalite unit is linked tetrahedrally across hexagonal faces by six bridging oxygens to four other sodalite units. The larger void spaces enclosed by sodalite units and hexagonal prisms are termed α-cages, or supercages. The α-cage is a 26-hedron with a free diameter of ≈1.3 nm, and it can be entered through four distorted 12-member rings of diameter 0.80-0.90 nm. In this way each α-cage is tetrahedrally joined to four others giving a complex system of void space extending throughout the zeolite structure. The α- and β-cages together give Y-zeolites, along with X-zeolites, the largest void volume of any known zeolites, which is ca. 50 vol% of the dehydrated crystal. From the catalytic viewpoint, the α-cages are by far the most important, since, unlike the β-cages, they permit entry of numerous aliphatic and aromatic compounds. Particularly effective in the subject synthesis are the synthetic Y-zeolites. Preferably said zeolites should be in a strongly acidic form whereby some, or all, of the cations (Group I or II, alkali or alkaline earth metal ions such as sodium, potassium, calcium or magnesium) are exchanged by protons either through ammonium exchange followed by thermal stabilization (deammoniation, removal of NH 3 ) at elevated temperatures (e.g. 400-500°C) through mineral acid treatment, etc. Alternatively, said Y-zeolites may be dealuminized by hydrothermal treatment, by mineral acid treatment or by treatment with ethylenediaminetetraacetic acid (EDTA) or other chelating agents, in which case said dealuminized Y-zeolites should have a Si:Al ratio of greater than three. A further possibility is that said Y-zeolites may be rare-earth exchanged with, for example, a mixture of rare-earth salts, by treatment with lanthanum salts, etc. Said rare-earth exchanged Y-zeolites would then have a Si:Al ratio of 1.5 to 3. The exchange of the sodium ions of the Y-zeolite by rare earth ions has been reviewed (see, for example, R. Rudham and A. Stockwell, The Chemical Society Specialist Periodical Report - Catalysis, Vol. I, 1977, Chapter 3). Illustrative of suitable Y-zeolites for the practice of this invention include Linde SK-500, a rare-earth exchanged Y-zeolite, having a Si:Al ratio of 1.5→2 and 10-20% added alumina binder, and PQ Corporation's CP 304-37, a thermally-stabilized, ammonium-exchanged Y-zeolite having a silica:alumina ratio of ca. 11:1, with a silica-alumina binder, as well as CP 316-26, another ammonium exchanged Y-zeolite this time having a silica-to-alumina ratio of 80. The hydrogen fluoride-modified zeolite may be prepared by treating the Y-zeolite or dealuminized Y-zeolite with hydrogen fluoride, with an aqueous solution of hydrofluoric acid, or with a solution of HF in a suitable organic solvent. Preferably the hydrogen fluoride is added to said zeolite as a solution of hydrofluoric acid in distilled water. Methods of preparing these HF-modified catalysts are illustrated in the accompanying Examples 1 to 3. Said catalysts may be in the form of powders, pellets, granules, spheres, shapes and extrudates. The examples described herein demonstrate the advantages of using extrudates. The reaction may be carried out in either a stirred slurry reactor or in a fixed bed continuous flow reactor. The catalyst concentration should be sufficient to provide the desired catalytic effect. Etherification can generally be conducted at temperatures from 20° to 250°C; the preferred range is 80° to 200°. The total operating pressure may be from 0 to 6895 kPa gauge pressure (gp) or higher. The preferred pressure range is 344 to 3440 kPa gp. Typically, MTBE is generated continuously in up to ca. 35 wt% concentration or greater in the crude liquid product at total liquid hourly space velocities (LHSV) of up to 6 or higher and relatively mild conditions, where: LHSV = Volume Of Total Liquid Feed Run Through The Reactor Per Hour Volume of Catalyst In Reactor "By the present invention, it is possible to prepare alkyl-tertiary-alkyl ethers such as MTBE with high conversion and high selectivity by the reaction of tertiary alcohols such as tert-butanol and primary alcohols such as methanol continuously. In the preparation of MTBE, at the 160°C of operating temperature, the product separates into an isobutylene/MTBE product rich phase and a heavier aquous phase, and subsequent purification is so easy. MTBE obtained by the present invention is useful as a blending component in high octane gasoline." The examples which follow illustrate the one-step synthesis of MTBE from TBA and MeOH (Eq. 2) using hydrogen fluoride-treated Y-type zeolites particularly the form of extrudates. Conversions of t-butanol (TBA, wt%) are estimated in the following examples using the equation: (Wt% Conc. of TBA in Feed - Wt% Conc. of TBA in Product) Wt% Conc. of TBA in Feed x 100 Selectivities of methyl t-butyl ether (MTBE, mole %) and isobutylene (C 4 H 8 , mole%) are estimated from: Moles of MTBE (or C 4 H 8 in Product) moles of TBA converted x 100 It may be noted that: 1) Comparing etherification data in Table I and Example 4, using the hydrogen fluoride-treated zeolite Linde SK-500, prepared by the method of Example 1, with data for SK-500 extrudates alone (Comparative Example A or Table IV) it is seen that: a) The tBA conversion levels with the HF-treated zeolites of Example 4 at all operating temperatures, but particularly at 140° to 160°C, are measurably higher than for SK-500 alone. b) Only the HF-modified zeolite of Example 4 achieves product phase separation into an isobutylene-MTBE product rich phase and a heavier aqueous methanol phase at the 160°C operating temperature. 2) Comparing etherification data in Example 5 and Table II, using the HF-treated zeolite, CP-304-37 of Example 2, with data for CP-304-37 extrudate alone (Comparative Example B or Table V) it may be noted that: a) While the tBA conversion levels with both the HF-treated zeolite and the untreated CP-304-37 are similar, and near equilibrium, at the lower temperatures (e.g. 100-140°C), b) only the HF-treated zeolite gives product phase separation into an isobutylene-MTBE rich phase and a heavier aqueous methanol phase at the 160°C operating temperature. Of note, comparative Example B of this invention is also included in related, copending U. S. patent Application Serial No. 07/494,281. 3) Generally an excellent performance is also realized in Example 6 for the HF-treated zeolite CP-316-26, prepared by the method of Example 3. Etherification data are summarized in Table III. Again product phase separation is achieved at 160°C operating temperature. 4) In Example 7, the HF-modified Y-zeolite of Example 1 provided excellent etherification activity over 23 days of operation using a crude tBA/MeOH feedstock also containing water, MTBE, isopropanol, acetone, di-t-butyl peroxide and t-butyl formate (see Table VI). EXAMPLE 1 This example illustrates the preparation of a hydrogen fluoride-modified Y-zeolite. To 100g of Y-zeolite (Linde SK-500, a rare-earth exchanged Y-zeolite having a Si:Al ratio of 1.5→2 and 10-20% added alumina binder, in 1.6 mm diameter extrudated form) was added a solution of 48% hydrofluoric acid (50g) in distilled water (100g). The mixture was stirred for 24 hours under nitrogen, filtered and the solids washed with distilled water and dried in vacuo at 40°C, overnight, and at 150°C for 4 hours. The recovered white extrudates were found to contain on analysis: F - , 6.30% H 2 O, 0.76% Acidity, 0.15 meq/g EXAMPLES 2 AND 3 The examples illustrate the preparation of two other hydrogen fluoride-modified Y-zeolites. Following the procedures of Example 1, two Y-zeolites: a) CP-304-37, a thermally-stabilized, ammonium exchanged Y-zeolite from PQ Corporation having a silica:alumina ratio of Ca. 11:1, with 80% silica-alumina binder (SiO 2 :Al 2 O 3 ratio 16:84), in 1.6 mm diameter extruded form, and b) CP-316-26, an ammonium exchanged Y-zeolite from PQ Corporation having a silica-to-alumina ratio of 80, also in 1.6 mm diameter extruded form, were treated with hydrofluoric acid, washed and dried in vacuo. The recovered extrudates were found to contain: Example 2: (HF/CP-304-37): F - , 1.78% H 2 O, 0.14% Acidity, 0.024 meq/g Example 3: (HF/CP-316-26): F - , 4.65% H 2 O, 1.86% Acidity, 0.085 meq/g EXAMPLE 4 This example illustrates the production of methyl t-butyl ether from t-butanol and methanol using a hydrogen fluoride-modified Y-zeolite. Synthesis was conducted in a tubular reactor (13mm int. diam., 304mm long), constructed of 316 stainless steel, operated upflow and mounted in a furnace controllable to ±1.0°C and fitted with pumps allowing flow control to <±1cc/hr. The reactor was also fitted with a pressure regulating device and equipment for monitoring temperature, pressure and flow rate. The reactor was charged at the beginning of the experiment with 25cc hydrogen fluoride treated Y-zeolite extrudates prepared by the method of Example 1. A screen of glass wool was placed at the top and bottom of the reactor to ensure the catalyst would remain in the middle portion. The catalyst bed was treated with a methanol/t-butanol (1.1:1 molar mix) upflow, at a flow rate of 50cc/hr, while the reactor was held at 120°C, with a total pressure of 2070 kPa. Samples of crude product effluent were collected periodically on-stream, in 316ss bombs, and analyzed by glc and gc-ir. Typical analyses data for samples taken under these conditions are summarized in Table I. Performance at a series of other temperatures (140°, 160°, 180°C) and flow rates (160cc/hr) was determined using the same procedures. These results are given in Table I. Of note, t-butanol conversion levels and isobutylene/MTBE selectivities at 140°C and 160°C are as follows: Sample Operating Temp(°C) TBA Conv.(%) Molar Selectivity (%) C 4 H 8 MTBE 3 140 67 32 64 5 160 84 a a a Not Determined Product phase separation into a isobutylene-MTBE product-rich phase and a heavier aqueous methanol phase was achieved at both the 160°C and 180°C operating temperatures. EXAMPLE 5 This example illustrates the production of methyl t-butyl ether from t-butanol and methanol using another hydrogen fluoride-modified Y-zeolite. Following the procedures of Example 4, the reactor was charged with 25cc of the hydrogen fluoride-treated Y-zeolite of Example 2 and performance was monitored over a series of temperatures (100-180°C) and feed rates (LHSV=2→5). The results are summarized in Table II. Calculated tBA conversions and C 4 H 8 /MTBE selectivities are as follows: Sample Operating Temp(°C) TBA Conv.(%) Molar Selectivity (%) C 4 H 8 MTBE 6 140 71 32 63 7 160 89 a a a Not Determined EXAMPLE 6 This example illustrates the production of methyl t-butyl ether from t-butanol and methanol using another hydrogen-modified Y-zeolite. Following the procedures of Example 4, the reactor was charged with 25cc of the hydrogen fluoride-treated Y-zeolite of Example 3 and performance was monitored over a series of temperatures (120-180°C) and feed rates (LHSV=2→6). The results are summarized in Table III. Calculated tBA conversions and C 4 H 8 /MTBE selectivities are as follows: Sample Operating Temp(°C) TBA Conv.(%) Molar Selectivity (%) C 4 H 8 MTBE 3 140 70 29 68 6 160 86 a a a Not Determined COMPARATIVE EXAMPLE A This comparative example illustrates the performance of an unmodified Y-zeolite in the production of methyl t-butyl ether from t-butanol and methanol over a range of conditions. Using the equipment and procedures of Example 4, 25cc of Y-zeolite (Linde SK-500, 1.6 mm diameter extrudates) was charged to the reactor system and performance was monitored over range of operating temperatures (100-180°C) and flow rates (50-160cc/hr). The results are summarized in Table IV. Calculated tBA conversion and C 4 H 8 /MTBE selectivities at 140° and 160°C are typically as follows: Sample Operating Temp(°C) TBA Conv.(%) Molar Selectivity (%) C 4 H 8 MTBE 6 140 56 35 64 8 160 78 59 39 COMPARATIVE EXAMPLE B This comparative example illustrates the performance of another unmodified Y-zeolite in the production of methyl t-butyl ether from t-butanol and methanol. Using the equipment and procedures of Example 4, 25cc of Y-zeolite (CP-304-37, 1.6 mm extrudates) was charged to the reactor system and performance was monitored over a range of operating temperatures (100°-180°C) and flow rates (50-160cc/hr). The results are summarized in Table V. Calculated tBA conversions and C 4 H 8 /MTBE selectivities at 140° and 160°C are typically as follows: Sample Operating Temp(°C) TBA Conv.(%) Molar Selectivity (%) C 4 H 8 MTBE 6 140 72 35 62 7 160 81 64 39 EXAMPLE 7 This example illustrates the performance of a HF-treated Y-zeolite in the production of methyl t-butyl ether from a crude t-butanol/methanol feedstock over an extended period. Using the unit configuration and procedures of Example 4, 50cc of the HF-treated SK-500 catalyst of Example 1 was charged to a 100cc capacity reactor system and performance was monitored over 23 days at 140°C using a crude feed mix comprising t-butanol, methanol, water, MTBE, acetone, isopropanol, di-t-butyl peroxide and t-butyl formate. The methanol to t-butanol molar feed ratio was 2:1, the feed rate was maintained at 100cc/hr. The results, are summarized in Table VI. Calculated tBA conversions are C 4 H 8 /MTBE selectivities for typical samples are as follows: Sample Time on Stream (Days) TBA Conv.(%) Molar Selectivity (%) C 4 H 8 MTBE 3R 7 34 33 68 10 23 33 25 72 Ex. CATALYST MeOH/tBA Molar Ratio Temp. (°C) LHSV Time On Steam (Days) ← PRODUCT COMPOSITION (WT%) Sample H 2 O MeOH C 4 H 8 Me 2 CO 2-PrOH tBA MTBE DTBP TBF 7 Ex. 1 2:1 FS 5.2 40.8 0.6 1.5 49.3 2.5 4.8 0.18 140 2 7 →3R 9.5 35.2 4.1 1.0 1.5 32.7 16.0 4.2 0.01 140 2 9 4R 10.0 34.7 3.7 1.0 1.4 30.7 18.4 4.0 0.01 140 2 16 6 9.2 35.2 3.3 1.0 1.4 33.2 16.5 3.9 0.01 140 2 21 9 9.8 35.6 3.1 1.0 1.4 32.8 16.1 3.7 0.01 140 2 23 →10 9.7 35.2 3.1 1.0 1.4 32.8 16.6 3.8 0.01

Claims: A process for the preparation of alkyl tertiary alkyl-ether from tertiary alcohol and primary alcohol in the presence of a catalyst, characterised in that crystalline aluminosilicate faujasite-type Y-zeolite modified with hydrogen fluoride is used as a catalyst. A process according to claim 1 for the preparation of methyl tert-butyl ether from tert-butyl alcohol and methanol in the presence of a catalyst, characterised in that crystalline aluminosilicate faujasite-type Y-zeolite modified with hydrogen fluoride is used as a catalyst. A process as claimed in Claim 2 wherein said t-butanol and methanol are present in a molar amount of 0.1 to 10 moles of methanol per mole of t-butanol. A process as claimed in Claim 2 or Claim 3 wherein said t-butanol and methanol are continuously contacted with said catalyst at a temperature of 20°C to 250°C and a pressure of atmospheric to 6895 kPa gauge pressure (1000 psig) to obtain methyl tert-butyl ether. A process as claimed in any one of Claims 1 to 4 wherein the Y-zeolite is rare-earth or ammonium exchanged. A process as claimed in any one of the preceding claims wherein the hydrogen fluoride is an aqueous solution of hydrofluoric acid. A process as claimed in any one of Claims 2 to 6 wherein methyl t-butyl ether is prepared from t-butanol and methanol in the presence of di-t-butyl peroxide, t-butyl formate or water. A process as claimed in any one of Claims 2 to 7 wherein the operating temperature is in the range 160° to 200°C and the product comprises a two-phase mix of an isobutylene-MTBE product-rich phase and a heavier aqueous methanol-rich phase. The use of a crystalline aluminosilicate faujasite-type Y-zeolite modified with hydrogen fluoride in a process of reacting t-butanol with methanol according to Claim 2.

Inventors: KNIFTON JOHN FREDERICK, SANDERSON JOHN RONALD, KNIFTON, JOHN FREDERICK, SANDERSON, JOHN RONALD
Applicants: TEXACO CHEM INC, TEXACO CHEMICAL INC.
Application year: 1992
Main classification: C07C43
IPC codes: C07C41, C07C43, C07B61, B01J29