JPS60224641A - Production of isoprene - Google Patents

Abstract

PURPOSE:To produce isoprene, in high yield and selectivity, by reacting an isobutylene source with a formaldehyde source in liquid phase in the presence of an acidic catalyst, water and diisobutylene. CONSTITUTION:Isoprene is produced by the liquid-phase reaction of an isobutylene source selected from isobutylene, t-butanol and alkyl t-butyl ethers with a formaldehyde source in the presence of an acidic catalyst and water, using <=10mol of isobutylene per 1mol of formaldehyde. In the above process, the reaction is carried out in the presence of diisobutylene. The amount of diisobutylene is preferably 0.5-50pts.wt. per 1pt.wt. of the stoichiometric amount of formaldehyde, and the diisobutylene produced as a by-product during the reaction is preferably recycled. The acidic catalyst is preferably phosphoric acid, phosphoric acid salt, heteropolyacid, organic acid or their salt to prevent the corrosion of the apparatus.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing isoprene by a liquid phase one-step process,
More specifically, the present invention relates to a method for producing inoprene in high yield by subjecting an inbutylene source and a formaldehyde source to a liquid phase reaction in the presence of diisobutylene.

Isobutylene, tertiary butanol (hereinafter abbreviated as TDA), methyl tert-butyl ether (hereinafter M
A method for producing isoprene from an isobutylene source such as TBE (abbreviated as TBE) 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.

A specific example of such a one-step method is a method in which the reaction is carried out in the presence of an organic solvent (for example, Japanese Patent Publication No. 49-10927,
49-10928) and a method of reacting in the coexistence of water and a hydrocarbon solvent (Japanese Unexamined Patent Publication No. 57-130928) are also known. Furthermore, a method for producing isoprene by decomposing 44-dimethyl-L3-dioxane in the presence of water and various organic solvents (Japanese Patent Publication No. 10925/1982) is also known.

However, neither method was necessarily satisfactory in terms of yield and selectivity of isoprene.

Therefore, the present inventors conducted intensive studies to improve these drawbacks seen in the conventional technology, and as a result, they discovered that isoprene can be obtained with high selectivity and high yield by carrying out a liquid phase reaction in the presence of diisobutylene. , 4IK isoptile/isoprene is suppressed from oligomerization, and the selectivity based on isobutylene is significantly improved, and the present invention has been completed.

Thus, according to the present invention, isoprene is produced by liquid-phase reaction of at least one isobutylene source selected from inbutylene, tertiary-butanol, and alkyl tertiary-butyl ether and a formaldehyde source in the presence of an acidic catalyst and water. Provided is a method for producing isoprene, characterized in that diisobutylene is present in the reaction system. A specific example of the alkyl tert-butyl ether is MTBE. These isobutylene sources may be used alone or preferably in the form of a mixture of two or more parts.

On the other hand, the formaldehyde source used may be any source that can generate formaldehyde in the reaction system, and specific examples thereof include a formaldehyde-containing gas obtained by oxidizing methanol, an aqueous formaldehyde solution, and a formaldehyde polymer (e.g. For example, formaldehyde precursors (for example, methisil, 44-dimethyl-L3-dioxane, glycol formal), etc. may be mentioned.

In addition, formaldehyde in which rose formaldehyde is dissolved in an aqueous formaldehyde solution to increase the formaldehyde concentration, or an aqueous formaldehyde solution containing methanol as a stabilizer can be used in the same way. Formaldehyde aqueous solutions are preferred because of the need for water in the reaction system.

The ratio of the isobutylene source and formaldehyde source to be used is appropriately selected depending on the reaction conditions.

Usually, the theoretical amount of isobutylene from the inbutylene source per mole of formaldehyde from the formaldehyde source is at least 1 mole, preferably at least 2 moles, and when the amount of isobutylene source used is small, the conversion rate of formaldehyde is There is also a tendency for the production of by-products to decrease and the production of by-products to increase.

On the other hand, if the amount of inbutylene source used becomes excessively large, the cost required to recover the unreacted inbutylene source will increase, so from this point of view, 2
The acidic catalyst used in the reaction may be any substance that exhibits acidity under the reaction conditions in the presence of water, and a specific example thereof is hydrochloric acid. Inorganic substances such as sulfuric acid, nitric acid, phosphoric acid, hypophosphorous acid, sulfurous acid, tungstic acid, molybdic acid, telluric acid, hydrobromic acid, chlorosulfo/acid, silicotungstic acid, stannic acid, hypochlorous acid, etc. acid, formic acid, oxalic acid,
Organic acids such as succinic acid, citric acid, phthalic acid, paratoluene/sulfonic acid, trifluoromethanesulfonic acid, sulfonic acid type ion exchange resins, dodoki double salts such as potassium light bread and chromium light bread, ammonium sulfate, ammonium phosphate, Non-metallic inorganic strong acid salts such as antimony chloride, ferric sulfate, nickel sulfate, tin chloride, cupric pyrophosphate, boron phosphate, SyI! Examples include metal salts such as zirconium. Among these, phosphorus compounds such as phosphoric acid and phosphates, heteropolyacids, organic acids, and their salts are prized for their ability to prevent corrosion of equipment.

These acidic catalysts are usually used alone, but two or more types of catalysts can be used in combination as necessary. The amount of catalyst to be used is not necessarily constant depending on conditions such as the type of catalyst, reaction temperature, and reaction time, but can be appropriately determined by conducting a simple preliminary experiment.

The reaction in the present invention is carried out in the presence of water and diisobutylene. The amount of water used can be selected as appropriate, but is usually at least 0.5 parts by weight, preferably from 1 to 50 parts by weight, per 1 part by weight of formaldehyde produced from the formaldehyde source.

On the other hand, the amount of diisobutylene used is 1 part by weight of the theoretical amount of formaldehyde generated from the formaldehyde source.
Usually, it is 01 to 100 parts by weight, preferably 0.5 to 50 parts by weight. Although this diisobutylene may be newly introduced from outside the system, it is preferable to circulate and use diisobutylene produced as a by-product during the reaction process. Also, water if necessary.
In addition to diynbutylene, a polar solvent such as alcohol or ketone, or an aliphatic or aromatic hydrocarbon solvent may also be present.

Further, the reaction temperature is usually selected within the range of 60 to 230°C, but the reaction can also be carried out by dividing the temperature conditions into two stages. The reaction pressure may be within the range necessary for the reaction system to form a liquid phase (for this reason, it is not necessarily constant depending on conditions such as the raw materials, solvent, and temperature employed, but it is usually within the range of 10
~150 kg/d, and one reaction time is usually 0.0
It is in the range of 5 to 5 hours.

Furthermore, as an embodiment of the present invention, a reaction tank with stirring blades,
Any type of reactor such as external circulation type reactor, packed type reaction tower, rotating disk base type reaction tower, multi-column type reactor, multi-tube type reactor, etc., and any type of operation such as batch, semi-batch, or continuous. Can be adopted.

According to the present invention, oligomerization of isobutylene and isoprene is suppressed, and geraniole/
The generation of can be significantly suppressed. At the same time, imprene can be obtained in high yield, and in particular, the selectivity based on inbutylene can be greatly increased. Furthermore, since most of the formaldehyde is consumed by the reaction, there is no need to recover it from the reaction solution, and the production of by-products that are difficult to treat can be significantly suppressed. Furthermore, the coexistence of diisobutylene greatly reduces the gasification of low-boiling substances such as isobutylene and isoprene in the reactor, reducing thermal energy consumption. It can be used for

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

Note that parts and parts in Examples and Comparative Examples are based on weight unless otherwise specified.

Example 1 A serpentine stainless steel tube with an inner diameter of 6 mm and a length of 2 m is used as a reactor, and is maintained at a predetermined temperature by immersing it in an oil bath. Next, 2.4 g of formaldehyde and 6 g of water were added to this reactor.
An aqueous solution consisting of 6.3% TBA, 5.7% TBA, 2s% phosphoric acid, and isobutylene and diisobutylene were each supplied at predetermined flow rates by pumps, and the reaction was continuously carried out under a pressure of 201v/cdG. The liquid discharged from the reactor was collected in a pressure-resistant glass container, and the isoprene contained in the organic layer and the unreacted formaldehyde remaining in the aqueous layer were analyzed by gas chromatography. For comparison, a similar experiment was conducted in the case where diisobutylene was not supplied. The results are shown in Table 1.

Example 2 A serpentine stainless steel tube with an inner diameter of 6 mm and a length of 9.1 m was used as a reactor, and a 7.1 m section from the inlet direction was 12 mm long.
The reaction was carried out according to Example 1, except that the temperature was maintained at 0°C and the remaining 1.7 m section was maintained at 170"CK. The results are shown in Table 2, and as a comparative example, when diisoptylene/ was not supplied. An experiment was conducted in the same manner for
The reaction was carried out in accordance with Experiment No. 1-1 of Example 1, except for supplying at the ratio of . The results are shown in Table 3.

Table 3 By comparing these results with the results of Example 1, it can be seen that the effect of adding diisobutylene is uniquely superior among organic solvents.

Claims (1)

[Claims] 1. When manufacturing imprene by carrying out a liquid phase reaction of at least one imbutylene source selected from isobutylene, tertiary butanol, and alkyl tertiary butyl ether and a formaldehyde source in the presence of an acidic catalyst and water, A method for producing isoprene, characterized by the presence of diynbutylene.