JPS5869824A - Preparation of isoprene - Google Patents

Abstract

PURPOSE:In reacting an isobutylene source with a formaldehyde source in the presence of both an acidic catalyst and water, to obtain the titled compound easily in an enlarged reaction temperature range with suppressing the formation of a by-product which is not easily subjected to after-treatment, by using >= a fixed amount of water. CONSTITUTION:In reacting at least one isobutylene source selected from the group consisting of isobutylene, tertiary butanol, and an alkyl tertiary butyl ether with a formaldehyde source such as an aqueus solution of formaldehyde using an acidic catalyst such as hydrochloric acid, etc. in the presence of water in a liquid phase, the amount of water used is >=15pts.wt. based on 1pt.wt. formaldehyde resulting from the formaldehyde source in the reaction system, preferably 20-100pts.wt., and the reaction temperature is 100-240 deg.C, preferably 130-220 deg.C, to give the desired compound, >=2mol isobutylene is preferably used based on 1mol formaldehyde.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing isoprene by a one-step reaction in a liquid phase, and more specifically, the present invention relates to a method for producing isoprene by a one-step reaction in a liquid phase. The present invention relates to a method for producing isoprene.

Inbutylene, tertiary butanol (hereinafter abbreviated as TB), methyl tert-butyl ether (hereinafter referred to as M
A method for producing imprene from an imbutyleno source such as TBlm (abbreviated as TBlm) and a formaldehyde source such as formaldehyde, paraformaldehyde, etc. by a liquid phase one-step reaction in the presence of an acidic catalyst is conventionally known.

For example, as a specific example, isobutyre/! A method of reacting τB and formaldehyde in the presence of a metal chloride and a sulfate and a phosphate (Japanese Patent Publication No. 48-28884)
-Iij, No. 49-1092.6), a method of reacting the above-mentioned inbutylene source and formaldehyde source in the presence of boron trifluoride, sulfonic acid, mineral acid or cation exchange resin (No. 41 Publication No. 49-10927 No. 49-1
No. 0928, No. 50-10283), etc. are known.

These one-step methods have the basic advantage of fewer reaction steps compared to the so-called two-step method, which synthesizes isoprene from isobutyne/formaldehyde via dimethyldioquinane, which has already been industrialized. However, on the other hand, the selectivity is still insufficient, producing a large amount of by-products that are difficult to handle, and the allowable range of reaction temperature is limited to a maximum wIk of 110 to 200C, leaving little room for choice. Therefore, the inventors of the present invention have carried out intensive studies to improve these drawbacks of the prior art, and as a result, they have discovered that a solution that allows a large amount of water to exist is extremely effective, and have completed the present invention. Thus, according to the present invention, at least one imbutylene source selected from imbutylene, tertiary butanol, and tertiary pether ether in alcohol and a formaldehyde source are mixed in a liquid phase in the presence of an acidic catalyst and water. There is provided a method for producing isoprene, characterized in that in producing isoprene by reaction, 915 parts by weight or more of water is present in the reaction system per 1 part by weight of formaldehyde generated from a formaldehyde source.

In the present invention, the inbutylene source used as a reaction raw material is isobutylene, TEBA round alkyl tertiary butyl ether], and a specific example of the alkyl tertiary butyl ether in alcohol is MBK. These isobutylene sources may be used alone, or in the form of a mixture of two or more. On the other hand, any formaldehyde source that can be used can generate formaldehyde in the reaction system. Specific examples include gases obtained by oxidation of methanol and containing formaldehyde, aqueous formaldehyde solutions, formaldehyde polymers (e.g., paraformaldehyde, trio), formaldehyde precursors (e.g., methylal), etc. It will be done. Paraformaldehyde is dissolved in an aqueous formaldehyde solution to increase the formaldehyde concentration, and even a formaldehyde aqueous solution containing methanol as a stabilizer can be used in the same way.Easy to handle and easily obtained. Formaldehyde aqueous solutions are preferred because of the need for water in the reaction system.

The ratio of isoptylene/IK to formaldehyde used is appropriately selected depending on the reaction conditions, but usually at least 2 moles of imbutylene produced from the diisobutylene source per mole of formaldehyde produced from the formaldehyde source, preferably at least S mole. When the amount of isobutylene source used is small, the conversion rate of formal hydroxide tends to decrease and the production of by-products also tends to increase. On the other hand, if the amount of isobutylene source used becomes excessively large, the cost required to recover unreacted inbutylene increases, so from this point of view, it is appropriate to set the amount of formaldehyde to 1 mol of isobutylene/20 mol or less. An acidic catalyst is used in the reaction between the inbutylene source and the formaldehyde source.

The acidic catalyst may be any substance that exhibits acidity under reaction conditions in the presence of water; specific examples include hydrochloric acid,
Sulfuric acid, nitric acid, phosphoric acid, picric acid, polyphosphoric acid, metaphosphoric acid, hypophosphorous acid, phosphorous, tungstic acid, molybdenum, telluric acid, thiosulfuric acid, hydrobromic acid, chlorosulfonic acid, tungsten silica Acids, boric acid, stannic acid, perrhenic acid, hypochlorous acid, inorganic acids such as formic acid, chelic acid, succinic acid, citric acid, phthalic acid, p-toluenesulfonic acid, 2-annoethanesulfonic acid, etc.)! Organic acids such as J fluoromethanesulfonic acid and sulfonic acid group ion exchange resins, double salts of potash and chromium, strong nonmetallic inorganic salts such as ammonium sulfate, ammonium phosphate, and antimony chloride, and sulfuric acid. Metal salts such as iron, ferric sulfate, nickel sulfate, aluminum chloride, tin chloride, cupric birophosphate, boron phosphate, zirconium phosphate, etc. are neutral at room temperature but reactive. A specific example of a substance that exhibits dispersibility under certain conditions is potassium iodate.
・These acidic catalysts are usually used alone, but two or more types of catalysts can be used in combination if necessary. ・However, the amount of catalyst used is not necessarily constant depending on the type of catalyst and reaction conditions. However, it can be determined appropriately by conducting a simple preliminary experiment. In the present invention, when an isobutylene source and a formaldehyde source are subjected to a liquid phase reaction in the presence of an acidic catalyst, formaldehyde 1 generated from the formaldehyde source in the reaction system. It is an essential requirement that at least 915 parts by weight of water be present, preferably from 20 to 100 parts by weight. Jinkode ``
"Formaldehyde generated from a formaldehyde source" refers to the theoretical value of formaldehyde O released from a formaldehyde source supplied as a raw material, and when formaldehyde is used, the amount charged depends on that value.

Liquid phase reaction between isobutylene source and formaldehyde source
However, in such conventional methods, the amount of water used is at most 10 times the amount of formaldehyde, and in such cases, Fi While the drawbacks of the conventional technology cannot be improved, the present invention improves the yield by increasing the amount of water used above a certain value, and eliminates by-products that are difficult to post-process, especially isoprene and formaldehyde. Other reaction conditions in the present invention are particularly limited.・For example, other solvents can be used together with water.
Pentane, luhequinane, isohe 11? Hydrocarbon solvents such as sulfur, rohebutane, n-octane, isooctane, benzene, toluene, cyclohexane, methanol,
Examples include polar solvents such as ethanol, impropatol, S-butanol, ethylene glycol, acetone, methyl ethyl ketone, and tetrahydrofuran.

In most conventional methods, the reaction temperature range is limited to a range of 110 to 200C (for example, Japanese Patent Publication No. 4B-28884
49-10926, etc.), the present invention can be carried out over a wide range of temperatures from 100 to 240C, preferably from 130 to 220C.In this case, if the temperature is too low, the yield will decrease. On the other hand, if the temperature is too high, carbon-like or tar-like by-products tend to be produced.

The reaction pressure may be within the range necessary for the reaction system to form a liquid phase, and is not necessarily constant depending on conditions such as the raw materials, solvent, and reaction temperature used, but is usually 5 to 150 k#, h.
a'' range, and the reaction time is usually α2 to 5 hours.The reaction format is also not particularly limited, and may be a batch type, a semi-batch type,
Any continuous method can be adopted.

Next, the present invention will be explained in more detail with reference to Examples. Note that parts and weights in Examples are based on weight unless otherwise specified.Example 1 External shaking stainless steel auto) After charging 4 parts of 25-formaldehyde aqueous solution, a predetermined amount of water, 20 parts of 5th-class butanol, and a predetermined amount of osssv acid aqueous solution into a rape, 11 parts of imbutyref was charged, and then the autoclave was heated to 170CK and placed in a nine-oil bath. At the same time as soaking, start shaking and carry out the reaction for a predetermined period of time. After the reaction, the autoclave was deep cooled with dry ice-acetone paint.
The autoclave was opened, the organic layer was extracted with carbon tetrachloride, and the isoprene contained in this organic layer and the unreacted formaldehyde remaining in the aqueous layer were analyzed by gas chromatography. Table 1 shows the results.

These results show that the method of the present invention has a higher isoprene yield than the conventional method, which uses less water, and can suppress the production of biran, which is a troublesome by-product that requires treatment.

Example 2 The same operations as in Experiment No. 1-2 of Example 1 were repeated except that the reaction temperature, amount of catalyst, and reaction time were adjusted. The results are shown in Table 2.

Table 2 Example 5 The reaction was carried out according to Experiment No. 1-2 of Example 1, except that the various catalysts shown in Table 5 were used in predetermined amounts in place of the phosphoric acid aqueous solution used in Example 1, and the reaction was carried out at 170C and 200C. Go nine. The results are shown in Table 5.

Table 3 From these results, it can be seen that when other acidic catalysts are used instead of the phosphoric acid catalyst, the same results as when the phosphoric acid catalyst is used are obtained.

Example 4 Experiment No. 1 of Example 1 was carried out using an expansion operation except that 55 parts of tertiary butanol was used as the raw material (in butylene), and the isoprene yield was 720. Mole is nine.

Example 5 An experiment was carried out in the same manner as in Example 4, except that 40 parts of methylbutyl ether was used in place of 5-butanol.The yield of imprene was 749 moles.

Example 6 A pot test was conducted in the same manner as in Experiment No. 1-1 of Example 1, except that 2.5 parts of methitool was used instead of the formaldehyde aqueous solution, and the isoprene yield was d74.
．． It was 4 mol.

Applicant: Zeon Corporation

Claims (1)

[Claims] t When producing Impre/ by reacting at least one imbutylene source selected from isobutylene, tertiary butanol and alkyl tert-butyl ether with a formaldehyde source in the liquid phase in the presence of an acidic catalyst and water, the reaction system 1. A method for producing Impre/, which is characterized in that 1 part by weight of formaldehyde generated from a formaldehyde source and 15 parts by weight or more of water are present in the mixture.