JPS58116428A - Preparation of isoprene - Google Patents

Abstract

PURPOSE:To prepare isoprene, in high yield, by the liquid-phase reaction of an isobutylene source with a formaldehyde source in the presence of an acidic catalyst, wherein the reaction is carried out in the presence of a large amount of water in the reaction system in two steps at low temperature and high temperature under specific conditions. CONSTITUTION:Isoprene is prepared by the liquid-phase reaction of an isobutylene source with a formaldehyde source in the presence of water and an acidic catalyst. The amount of charged water is adjusted to >=4pts.wt., preferably 5- 100pts.wt., especially 10-50pts.wt. per 1pt.wt. of formaldehyde generated from the aldehyde source, and the temperature is changed in two steps; i.e. an isoprene precursor is synthesized at <=145 deg.C, preferably 60-140 deg.C, and then the temperature of the reaction system is raised to >=150 deg.C, preferably 150-230 deg.C to decompose the precursor to isoprene. Isoprene can be prepared in high selectivity and yield by the one-step liquid-phase reaction, suppressing the production of hardly handleable by-products.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing isoprene by a liquid phase injection method.
More specifically, the present invention relates to a method for producing isogrene in a higher yield than in conventional methods, by subjecting a source of inbutylene and a source of formaldehyde to a liquid phase reaction at sequential temperatures in the presence of an acidic catalyst and a large amount of water.

Isobutylene, 5th-butanol (hereinafter abbreviated as TDA), methyl tert-butyl ether (hereinafter M
A method for producing isogrene by a liquid phase one-step reaction in the presence of an acidic catalyst from an isobutylene source such as T B' and a formaldehyde source such as formaldehyde, paraformaldehyde, etc. has been conventionally known (abbreviated as 4f4). For example, Special Publication No. 4B-28884, No. 4
No. 9-10926, No. 50-10283, etc.).

The basic principle of this method is that it requires fewer reaction steps than the so-called two-step method, which synthesizes isoprene from isobutylene and formaldehyde via 4,4-dimethyl-1,5-dioxane, which has already been commercialized. However, on the other hand, it has the disadvantage that the selectivity is still insufficient and a large amount of difficult by-products are produced.

Also known is a method in which the reaction is carried out in two stages, one at low pressure and one at high temperature, as a variant of this method. For example, special public service in 1977-
No. 2415, the inbutylene source and formaldehyde are combined with specific acids such as sulfanilic acid, orthanilic acid, etc.
7 in the presence of a small amount of water using a sulfonic acid containing a group as a catalyst.
A two-stage reaction process at 0-130C and 160-200C is described.

This method is primarily intended to prevent clogging of the equipment due to formaldehyde polymerization, but the inventors' additional tests of this method revealed that a large amount of by-products were present in the product and that the catalyst was not clogged. It was confirmed that formaldehyde reacts and lowers the basic unit.

Therefore, the present inventor conducted intensive studies to improve these shortcomings seen in the prior art, and found that when a two-step reaction at low and high temperatures was carried out in the presence of a large amount of water, unexpectedly large amounts of by-products were produced. It has been found that imprene can be obtained with high selectivity and high yield.

Thus, according to the present invention, a source of isobutylene (A), a source of formaldehyde (B), water (0) and an acidic catalyst (D
) When producing isoprene by reacting in a liquid phase in the presence of (0), the amount of component (0) charged is 94 parts by weight or more per 1 part by weight of formaldehyde generated from component (B), and the reaction temperature is 145C or less. Below, the isoprene precursor is synthesized by a liquid phase reaction, and then the temperature of the reaction system is raised to 1000 °C or higher to decompose the inoprene precursor into isoprusine.
A method for producing isoprene by a liquid-phase one-shot process is provided.

The inbutylene source used as a reaction raw material in the present invention is inbutylene, TBAfi, or tert-butyl ether in alcohol, and a specific example of the alkyl tert-butyl ether is MTBI.

These isobutylene sources may be used alone or in the form of a mixture of two or more types.On the other hand, any formaldehyde source that can be used can generate formaldehyde in the reaction system. Examples include formaldehyde-containing gas obtained by oxidation of methanol, formaldehyde aqueous solution, formaldehyde polymers (e.g. formaldehyde, trioxane), formaldehyde precursors (e.g. metheral, 4,4-dimedel-t5). −
dioxane), etc. In addition, it can be used in the same way even if the formaldehyde concentration is increased by dissolving paraformaldehyde in an aqueous formaldehyde solution, or an aqueous formaldehyde solution containing methanol as a stabilizer. Formaldehyde aqueous solutions are preferred because of the need for water in the reaction system.

The ratio of the inbutylene source and formaldehyde source to be used is appropriately selected depending on the reaction conditions, but usually the theoretical amount of inbutylene 2 generated from the diisobutylene source is calculated per 1 mole of formaldehyde generated from the formaldehyde source.
If the amount is mol or more, preferably 3 mol or more, and the amount of the inbutylene source used is small, the conversion rate of formaldehyde tends to decrease and the production of by-products tends to increase. On the other hand, if the amount of isobutylene source used is excessively large, the cost required to recover unreacted imbutylene increases, so from the viewpoint of c. When carrying out the reaction between an isobutylene source and a formaldehyde source, it is essential to have a large amount of water present in the reaction system and to carry out a two-stage reaction at low and high temperatures.

The amount of water, which is the tenth requirement, is 641 parts by weight or more, preferably 5 to 100 parts by weight, more preferably 10 to 50 parts by weight, per 1 part by weight of formaldehyde generated from the formaldehyde source.
parts by weight, and if the amount of water is too small, the production of by-products cannot be suppressed. Note that "formaldehyde J generated from a formaldehyde source" herein means the theoretical value of formaldehyde liberated from a formaldehyde source supplied as a raw material.

Next, the second requirement is to carry out the reaction in advance at a temperature of 1450C or less, preferably 60 to 140C (hereinafter referred to as low temperature reaction), then 1000C or more, preferably f5 (F5
It is necessary to carry out the reaction at ~250C (hereinafter referred to as high temperature reaction).

In the preliminary low-temperature reaction process, the reaction between isoprene and formaldehyde produces 4,4-dimethyl--5-dio:?
Isoprene precursors such as San, 3-methyl-pre-3-butanediol, 3-methyl-3-buten-1-ol, etc. are synthesized. At this time, it is important to keep the reaction temperature below 145C; if this temperature is exceeded, the amount of final product isoprene produced increases at this stage.
Due to the reaction between formaldehyde and isoprene generated by the decomposition of formaldehyde or 44-dimethylform-15-dioxane present in the system, the by-product of bilanes, which is difficult to treat, increases.On the other hand, if the reaction temperature is too low, the reaction will increase. It is not practical as it reduces performance. Also, in low-temperature reactions, the reaction temperature does not necessarily need to be kept constant; it can be raised sequentially as long as it is below 145C.
Alternatively, it may be divided into two or more stages and raised in stages.

On the other hand, in the process of high-temperature reaction, isoprene is produced by decomposition of an isoprene precursor produced by low-temperature reaction. At this time, if the reaction temperature becomes too high to 150C, isoprene polymers and carbon-like or tar-like by-products will increase. In the present invention, an acidic catalyst is used in the reaction between the isobutylene 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,
Inorganic compounds such as sulfuric acid, nitric acid, phosphoric acid, hypochlorous acid, phosphorous acid, tungstic acid, molybdic acid, telluric acid, hydrobromic acid, chlorosulfonic acid, silicotungstic acid, stannic acid, hypochlorous acid, etc. , formic acid, oxalic acid, succinic acid, citric acid, phthalic acid, handleenesulfonic acid/II, trifluoromethanesulfonic acid, sulfonic acid ion exchange*m
Organic acids such as ir, double salts such as potash bright bread, chromium bright bread, etc., non-metallic inorganic strong acid salts such as ammonium sulfate, ammonium phosphate, antimore chloride, ferric sulfate, nickel sulfate, tin chloride, via Examples include metal salts such as steel phosphate II, boron phosphate, and zirconium phosphate.

Among them, phosphorus compounds such as phosphoric acid and phosphates, heteropolyacids, organic acids, and their salts are prized from the viewpoint of corrosion prevention of equipment.These acidic catalysts are usually used alone, but when necessary Two or more types of catalysts can also be used in combination as appropriate. The amount of catalyst used depends on the type of catalyst and reaction temperature.

Although it is not necessarily constant depending on conditions such as reaction time,
It can be determined appropriately by conducting simple preliminary experiments.

In addition, the reaction time and reaction pressure may be selected as appropriate; in low-temperature reactions, the reaction time is usually 10 minutes to 5 hours, preferably 50 minutes to 5 hours, and the reaction pressure Fi1 to 80 ka.
/r:m''. On the other hand, in high-temperature reactions, the reaction time is usually 5 minutes to 2 hours, preferably 10 minutes to 1 hour, and the reaction pressure is 5 to j50ke/? A polar solvent such as an alcohol or a ketone or an aliphatic or aromatic hydrocarbon solvent can also be allowed to coexist with water.According to the present invention, isoprene can be produced in a simplified process without isoprene precursor isolation. 0 can be produced in high yield, and the production of by-products that are difficult to process can be significantly suppressed.

Next, the present invention will be explained in more detail with reference to Examples.

In addition, parts and weights in the examples are based on weight unless otherwise noted. Example 1 In an external shaking stainless steel autoclave, 4 parts of a 25% formaldehyde aqueous solution, 50 parts of water, 14 parts of TB and 85% of aqueous formaldehyde solution were added. After charging 1 part of chinoic acid, 11 parts of inbutylene was charged, and then a low temperature reaction and a high temperature reaction were performed according to the conditions shown in Table 1. Add carbon and extract the organic layer,
Isoprene contained in this organic layer and unreacted formaldehyde remaining in the aqueous layer were analyzed by gas chromatography. For comparison, experiments were also conducted in the same manner without changing the reaction temperature. The results are shown in Table IK.

Example 2 A low-temperature reaction was carried out in the same manner as in Experiment No. (1-5) of Example 1, except that the amount of 85-thiphosphoric acid charged was changed to 13 parts, and then a high-temperature reaction was carried out under the predetermined conditions shown in Table 2. The reaction was carried out. The results are shown in Table 2.

Table 2 Actual Example 3 The reaction was carried out in the same manner as in Experiment No. (1, 5) of Example 1 (11 parts) except that the ratio of water and formaldehyde in the raw materials was changed. Table 5 shows the results.

Table 3 These results show that when the amount of water is small, the amount of pyran by-product is large and the yield of isoprene is significantly reduced.

Example 4 Low temperature reaction was carried out in advance at 90G for 120 minutes and then at 140C for 3
Example 1 except that the process is performed in two stages of 0/0.
The reaction was carried out according to Experiment No. (1-1). As a result, the conversion rate of formaldehyde was 100 s (To),
The yield of isoprene was 798 mol, and the yield of biran was 52 mol. The reaction was carried out according to Experiment No. 1 (1-1). The results are shown in Table 4.

Table 4 Example 6 The reaction was carried out in accordance with Experiment No. (1-5)K of Actual Example 1, except that the amounts of TBA and inbutylene used in Example 1 were changed to 7 parts and 6 parts, respectively. As a result, the isoprene yield was 7 & 9 mol and the bilane yield was 4.3.
It was morchi.

Example 7 A serpentine stainless steel pipe with an inner diameter of 6 m and a length of 9.1 quotient was used as a reactor, a 7.1 ml portion from the inlet direction was maintained at 120 CK, and the remaining 17 I 11 portion was maintained at 190 C.
K: Maintained. Next, 7 parts of form and 2 parts of dehyde were added to this reactor.
, 1%, water 8 (10%% TBA 12.5%.

Supplying an aqueous solution consisting of 5.4% phosphoric acid and isobutylene at flow rates of 145 #/H and 551/H, respectively;
The reaction was carried out continuously under a pressure of 25 ktl/rx"G. As a result, the conversion rate of formaldehyde was 10
The yield of isoprene was 87.4 mol.

Example 8 MTBK was used in place of isobutylene used in Example 7.
The reaction was carried out according to Actual Example 7 except that the ratio of #/H was supplied. As a result, the conversion rate of formaldehyde was 1
00% resin, isoprene yield Applicant: Zeon Corporation

Claims (1)

[Claims] t inbutylene source (A) and formaldehy) [(B)
When producing isoprene by reacting in the liquid phase in the presence of water (0) and an acidic catalyst (→), the amount of component (C) charged is 4 parts by weight of formaldehyde generated from component (B).
The isoprene precursor is synthesized by a liquid phase reaction under conditions where the amount of N is 1 part or more and the reaction temperature is 145C or less, and then the reaction system is heated to 1000C or more to decompose the isoprene precursor into isoprene. Ill production method of isoprene by liquid phase injection method.