GB2075019A

GB2075019A - Methyl Tertiarybutyl Ether

Info

Publication number: GB2075019A
Application number: GB8113051A
Authority: GB
Original assignee: Toyo Soda Manufacturing Co Ltd
Current assignee: Tosoh Corp
Priority date: 1980-05-02
Filing date: 1981-04-28
Publication date: 1981-11-11
Also published as: GB2075019B; JPS56154423A; FR2481694B1; FR2481694A1; JPS6144849B2

Abstract

Methyl tertiarybutyl ether is produced by reacting isobutylene or a hydrocarbon mixture containing isobutylene with methanol in the presence of a perfluorocarbon polymer having sulfonic acid groups as a catalyst.

Description

SPECIFICATION Process for Producing Methyl Tertiarybutyl Ether Background of the Invention: Field of the Invention: The present invention relates to a process for producing methyl tertiarybutyl ether (hereinafter referring to as MTBE). More particularly, it relates to a process for producing MTBE by reacting isobutylene or a hydrocarbon mixture containing isobutylene with methanol in a presence of a catalyst.

Description of the Prior Arts: MTBE is remarkably useful as an octane number improver for gasoline. It has been known to produce it by reacting isobutylene with methanol in the presence of a catalyst.

Various catalysts have been proposed, for example, (1) mineral acids such as sulfuric acid or aromatic sulfonic acids (U.S. Patent No.

2,720,547); (2) metal sulfates (Japanese Examined Patent Publication No. 12168/1977); (3) silica-phosphomolybdenate (U.S. Patent No.

3,135,807); (4) heteropoly-acids (Japanese Unexamined Patent Publication Na.

14909/1979); (5) strong acid type ion-exchange resins (Japanese Unexamined Patent Publication No. 6912/1976, No. 62206/1977 and No.

50113/1978 etc.). These catalysts, however, have the following disadvantages as catalysts for industrial uses, not to be always, satisfactory.

That is, a separation of a catalyst from the reaction mixture is not simple and a treatment of a waste acid is not easy in the case (1); a catalyst is easily decomposed at high temperature in the case (2); a polymerization of an olefin easily occurs in the case (3); a catalytic activity is not high in the case (4) and ion-exchange resins obtained by a sulfonation of copolymers of styrene and a polyunsaturated compound such as divinylbenzene or by a condensation of phenolsulfonic acid and formaldehyde in a form of gel or macroporous mass have been used as desired catalysts in the case (4).

The reaction for producing MTBE, however, is an exothermic reaction of 18.6 kcal./mol (4000 K).

When these resins are used in a fixed bed system whose temperature control is not easily attained, a deterioration of the resin such as a decomposition by the heat and a formation of a free acid may easily occur.

On the other hand, when these resins are used in a fluidized bed system whose temperature control is easy, a formation of a free acid from the resin and a deterioration of the resin are caused by a friction etc. In such cases, the free acid decomposes MTBE and accordingly, it is necessary to provide an additional step of separating the acid in a purification step as disclosed in Japanese Unexamined Patent Publication No. 65809/1978.

Summary of the Invention: It is an object of the present invention to provide a process for producing MTBE in which a catalyst is not easily deteriorated and a formation of a free acid is effectively prevented.

The foregoing and other objects of the present invention have been attained by providing a process for producing methyl tertiarybutyl ether by reacting isobutylene or a hydrocarbon mixture containing isobutylene with methanol in the presence of a perfluorocarbon polymer having sulfonic acid groups as a catalyst.

Detailed Description of the Preferred Embodiments: The present invention has been attained by various studies for overcoming the disadvantages in the conventional processes.

The perfluorocarbon polymers having sulfonic acid groups used as the catalyst in the present invention, can be copolymers of a vinyl fluoride monomer and another vinyl monomer which have sulfonic acid groups and polymers obtained by crosslinking the copolymer with a crosslinking agent such as divinylbenzene and a fluorinated unsaturated compound.

An example of the perfluorocarbon polymer having sulfonic acid groups which can be used in the present invention is one having the general formula

wherein R represents a group of the formula,

R, representing F or C110 perfluoroalkyl group, Y representing F or a trifluoromethyl group and m representing 1,2 or 3 in the second formula; n represents 0 or 1; I represents a digit; and k represents a digit. Other perfluorocarbon polymers having sulfonic acid groups and analogous compositions, which are conventionally used in a chloroalkali electrolysis in a form of membrane for ensuring physical insulation between anolyte and catholyte and for performing transportation of sodium cations from anolyte to catholyte, can also be used in the present invention.

Copolymers of sulfonylfluoride vinyl ether and tetrafluoroethylene and derivatives thereof such as Nafion (trade name sold by Du Pont) can be used as the catalyst after hydrolysis of sulfonylfluoride groups. THe catalyst in an acid form has a catalytic activity. The catalyst in a salt form is converted into an acid form by treating it with a mineral acid such as hydrochloric acid and nitric acid and is dried before the use.

The ion-exchange capacity of the catalyst is preferably higher than about 0.3 mg. equivalent/g.

dry catalyst in view of catalytic activity and is preferably lower than about 2.0 mg. equivalent/g.

dry catalyst in view of decrease of side reactions.

It is especially preferable to be in a range of about 0.5 to about 1.5 mg. equivalent/g. dry catalyst.

The amount of the catalyst used for the reaction is in a range of about 0.01 to about 20 wt. parts per 1 wt. part of the alcohol preferably about 0.1 wt. part to about 10 wt. parts per 1 wt.

part of the alcohol. The form of the catalyst can be powder, granule pellet or membrane.

The perfluorocarbon polymers having sulfonic acid groups are super acidic type polymers. Such polymers have been used as catalysts for oligomerization of isobutylene as one of the starting materials as disclosed in U.S. Patent No.

4,065,512. Thus, the disadvantageous side reaction should be presumed in the use of such a catalyst in the process of the present invention.

However, it is found that such a side reaction is substantially not resulted as far as the catalyst is used under the conditions of the present invention. It is preferable to carry out the reaction in preventing a high temperature and a long time one so as to prevent an oligomerization of isobutylene in the case using the catalyst in a form of a membrane.

Isobutylene as one of the starting materials used in the present invention is not limited to isobutylene having high purity but can be also a mixture containing isobutylene. The mixture can contain other hydrocarbons, for example ones having 14 carbon atoms such as 1-butene,2- butene, butadiene, n-butane and isobutane or other ,hydrocarbons together with isobutylene.

Methanol as the other starting material can be methanol in an industrial grade without any purification.

A molar ratio of isobutylene to methanol is not critical and is usually in a range of about 0.1 to about 10. The reaction is usually carried out without use of any solvent, however, it can be carried out in a solvent as desired. The reaction temperature is usually in a range of 0 to 2000 C.

At a low temperature, a reaction rate is too slow whereas at a high temperature, disadvantageous side reactions may be resulted. It is preferably in a range of about 30 to about 150 C and more preferably about 50 to about 1200 C. The reaction pressure can be in a range of the atmospheric pressure to a vapor pressure of the reaction mixture at the reaction temperature. It is preferable to carry out the reaction under an elevated pressure in view of equilibrium, and thus, the reaction pressure is usually in a range of the atmospheric pressure to about 100 atm., preferably about 2 to about 80 atm., espedaily about 3 to about 50 atm.

When the vapor pressure of the reaction mixture is lower than the desired reaction pressure, an inert gas which does not affect the reaction can be fed into the reactor to reach the desired pressure. Such inert gases can be helium, argon, nitrogen and air.

The perfluorocarbon polymers having sulfonic acid groups used as the catalyst in the present invention have excellent abrasion resistance whereby the reaction of the present invention can be effectively carried out by a liquid phase fluidized bed reaction in a suspension of the catalyst in the reaction mixture. In such reaction system, the catalyst can be in a solid form of powder, granule, grain, or pellet so as to be easily separable from the reaction mixture. The particle diameter of the catalyst is usually larger than about 1 ,am preferably larger than about 10,um especially about 0.01 to about 5 mm.

The reaction is preferably carried out under the conditions allowing to fluidize the catalyst in a liquid phase with stirring or the like. The stirring speed is in a range of about 10 to about 2000 r.p.m., preferably about 20 to about 1000 r.p.m.

or the corresponding shearing energy is applied to effectively perform the reaction without any substantial deterioration of the catalyst.

The perfluorocarbon polymers having sulfonic acid groups used as the catalyst in the present invention have excellent heat resistance whereby the reaction can be also carried out without any substantial deterioration of the catalyst even in a fixed bed reaction system. In these reaction systems, both of a continuous flow system and a batch system can be employed. However, the continuous flow system is clearly superior in view of an industrial operation.

As described above, when the perfluorocarbon polymer having sulfonic acid groups is used as the catalyst, MTBE can be produced from methanol and isobutylene or a hydrocarbon mixture containing isobutylene in an advantageous industrial operation.

The present invention wili be illustrated by certain examples and references which are provided for purposes of illustration only and are not intended to be limiting the present invention.

Example I Twenty grams of potassium salt of perfluorocarbon polymer having suifonic acid groups (Nafion 501, trade name of Du Pont) were treated in 20% aqueous solution of nitric acid at room temperature for 20 hours with stirring and then the polymer was filtered and washed with 1 liter of pure water. The product was dried under a reduced pressure at 1 200C for 5 hours to obtain H type dry catalyst. The resulting catalyst had an ion exchange capacity of 0.74 mg. equivalent/g.

dry catalyst and an average particle diameter of about 0.5 mm. Into a 200 ml. autoclave, equipped with an electromagnetic stirrer, 2.5 g. of the catalyst and 26.or g. of methanol were charged and 46.05 g. of liquid isobutylene was fed to carry oui the reaction with stirring at a speed of 700 r.p.m. in an electric furnace at 800C (initial pressure of 10 kg./cm2). After the initiation of the reaction, the temperature in the reactor rised to reach the maximum temperature of 950C after 14 minutes and then, it gradually fallen to reach 800C as the original temperature in the reactor after 45 minutes from the initiation of the reaction (the pressure of 2.5 kg./cm2 at the time). At the time, the reactor was cooled to stop the reaction.

The reaction mixture was analyzed by a gas chromatography to find a conversion of methanol of 82.1% and a selectivity to MTBE of 99.7%. Any dimethyl ether and isobutylene oligomer were not detected. The catalyst was tested after the reaction by a titration for neutralization to find the fact that the amount of the acid component of the catalyst was not reduced in comparison with that before the reaction.

Example 2 In accordance with the process of Example 1 except using 1.5 g. of the catalyst, 20.04 g. of methanol and 44.33 g. of isobutylene, the reaction was carried out. In comparison with the reaction of Example 1 , the reaction speed was slightly slower and the temperature reached to the maximum value of 830C. The reaction was stopped after 100 minutes from the initiation of the reaction. The pressure was 3 kg./cm2 at this time.

The reaction mixture was analyzed by a gas chromatography to find a conversion of methanol of 73.4% and a selectivity of MTBE of 99.8%. Any dimethyl ether and isobutylene oligomer were not detected. Any reduction of the acid component of the catalyst was not found.

Reference: In accordance with the process of Example 1 except using 2.5 g. of a sulfonic acid type cation exchange resin having no fluorine component (Amberlyst 1 5, trade name) instead of the perfluorocarbon polymer having sulfonic acid groups, and using 20.27 g. of methanol and 46.05 g. of isobutylene, the reaction was carried out. After 6 minutes from the initiation of the reaction, the temperature reached to the maximum value of 1000C. After 45 minutes from the initiation of the reaction, the reaction was stopped. The reaction mixture was analyzed by a gas chromatography to find a conversion of methanol of 83.4% and a selctivity of MTBE of 99.7%.

In a titration for neutralization of the acid component of the catalyst, it was decreased from 5.10 mg. equivalent/g. dry catalyst before the use to 4.93 mg. equivalent/g. dry catalyst after the reaction.

Claims

1. A process for producing methyl tertiarybutyl ether which comprises reacting isobutylene or a hydrocarbon mixture containing isobutylene with methanol in the presence of a perfluorocarbon polymer having sulfonic acid groups as a catalyst.

2. The process according to Claim 1 wherein an ion-exchange capacity of said perfluorocarbon polymer having sulfonic acid groups is in a range of about 0.5 to 1.5 mg. equivalent/g. polymers

3. The process according to Claim 1 or 2 wherein said reaction is carried out in a liquid phase at a temperature of about 30 to 1 500C under a pressure of about 2 to about 80 atm. with said catalyst having an average particle diameter of about 0.01 to about 5 mm.

4. The process according to Claim 3 wherein said reaction is carried out in a suspension of said catalyst in said liquid phase.

5. The process according to Claim 3 wherein said catalyst is used in a form of a fixed bed.

6. A process according to Claim 1 substantially as herein described with reference to either of the Examples.