JPH0329048B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel method for synthesizing isoprene, and more particularly to a method for producing isoprene in which an isobutylene source and a formaldehyde source are reacted in a liquid phase in the presence of an acid catalyst and metal ions. Isobutylene, tertiary butanol (hereinafter referred to as
A method for synthesizing isoprene from isobutylene sources such as TBA (abbreviated as TBA), methyl tertiary butyl ether (hereinafter abbreviated as MTBE), and formaldehyde sources such as formaldehyde, paraformaldehyde, etc. through a one-step liquid phase reaction. It is conventionally known. For example, specific examples include isobutylene or
A method of reacting TBA and formaldehyde in the presence of a mineral acid or an organic acid (Special Publication No. 10928/1983,
No. 50-10283 and No. 52-30483) are known. However, such conventional methods are not necessarily sufficient in terms of catalytic activity, are generally inferior in selectivity to isoprene, and have the problem of producing large amounts of by-products that are particularly difficult to handle. Therefore, the present inventors conducted intensive studies to improve these drawbacks of the conventional technology, and as a result, discovered that these drawbacks could be solved all at once by coexisting a specific metal ion with an acid catalyst, and completed the present invention. I came to the point. Thus, according to the invention, isobutylene,
In producing isoprene by reacting at least one isobutylene source selected from class butanol and alkyl tertiary butyl ether with a formaldehyde source in the liquid phase in the presence of water using an acid catalyst, the periodic table a, b, a Provided is a method for producing isoprene, characterized in that at least one metal ion selected from group B elements is present in the reaction system. The isobutylene source used as a reaction raw material in the present invention is isobutylene, TBA or alkyl tert-butyl ether, and a specific example of the alkyl t-butyl ether is MTBE. These isobutylene sources may be used alone or in the form of a mixture of two or more. 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. (eg, paraformaldehyde, trioxane), precursors of formaldehyde (eg, methylal), and the like. Further, an aqueous formaldehyde solution in which paraformaldehyde is dissolved to increase the formaldehyde concentration, or an aqueous formaldehyde solution containing methanol as a stabilizer can be similarly used. In the present invention, at least one acid catalyst selected from mineral acids and organic acids is used in the reaction between the isobutylene source and the formaldehyde source. Specific examples of such acid catalysts include inorganic acids such as sulfuric acid, nitric acid, phosphoric acid, hypophosphorous acid, phosphorous acid, etc., chlorosulfonic acid, formic acid, oxalic acid, succinic acid, citric acid, phthalic acid, para-toluene. Examples include organic acids such as sulfonic acid and trifluoromethanesulfonic acid. These acid catalysts are usually used alone, but two or more types of catalysts can be used in combination as necessary. The amount of catalyst used depends on the type of catalyst, reaction temperature,
Although it is not necessarily constant depending on conditions such as reaction time, it can be appropriately determined by conducting a simple preliminary experiment. Typically, the concentration is from 0.1 to 30 percent by weight based on the aqueous phase forming components in the reactor, namely water, acid and formaldehyde. In the present invention, it is essential to coexist metal ions of groups a, b, a, or b of the periodic table in the reaction system. Specific examples of such metal ions include lithium,
Sodium, potassium, lupidium, cesium,
Examples include metal ions such as copper, silver, magnesium, calcium, strontium, barium, and zinc, and these ions are metal nitrites and metal ions, respectively.
By adding nitrates, sulfites, sulfates, hydrogen sulfates, acetates, borates, carbonates, formates, oxalates, chlorides, phosphates, oxides, hydroxides, etc. to the system. Easily formed. The ratio of acid catalyst and metal ion used is selected as appropriate, but usually metal ion is used per mole of acid catalyst.
0.001 to 10 mol, preferably 0.1 to 2 mol,
In particular, it is preferable to use it within a range where the pH in the system is 5 or less. The reaction in the present invention is carried out in the presence of water. Although the amount of water used can be selected as appropriate, it is usually based on 1 part by weight of formaldehyde generated from the formaldehyde source.
The amount is 0.5 parts by weight or more, preferably 1 to 50 parts by weight.
Further, if necessary, a polar solvent such as alcohol or ketone, or an aliphatic or aromatic hydrocarbon solvent may be allowed to coexist with water. The molar ratio of the isobutylene source and formaldehyde source used in the reaction can be selected as appropriate, but usually 1 mol of isobutylene source per 1 mol of formaldehyde source.
The amount is 1.1 to 20 moles or more, preferably 1.1 to 20 moles. 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, and therefore is not necessarily constant depending on conditions such as the raw materials, solvent, and temperature employed, but is usually in the range of 10 to 150 kg/ ^cm2 . The reaction time is usually in the range of 0.05 to 5 hours. Furthermore, as an embodiment of the present invention, any format such as a reaction tank with stirring blades, an external circulation type reactor, a packed type reaction column, a rotating disk column type reaction column, a multi-stage column type reactor, a multi-tube type reactor, etc. However, batch, semi-batch, or continuous modes of operation can also be employed. According to the present invention, the production of by-products that are difficult to handle, especially geraniolene, can be significantly suppressed, and at the same time, the selectivity of isoprene can be significantly increased. Next, the present invention will be explained in more detail with reference to Examples. In addition, parts and percentages in the examples are based on weight unless otherwise specified. Example 71 25 in a stainless steel autoclave with external shaking
% formaldehyde aqueous solution 4 parts, water 10 parts,
After adding 14 parts of TBA, 1 part of 85% phosphoric acid, and the specified amounts of the metal compounds shown in Table 1, 7 parts of isobutylene was added.
and then heat the autoclave to 160°C.
Shaking was started at the same time as the sample was immersed in an oil bath whose temperature had been raised to 100%, and the reaction was carried out for 25 minutes. After the reaction is completed, the autoclave is cooled, then carbon tetrachloride is added to the opened autoclave to extract the organic layer, and isoprene contained in this organic layer and unreacted formaldehyde remaining in the aqueous layer are separated by gas chromatography. did. The results are shown in Table 1. For comparison, experiments were also conducted in the same manner when only the metal compound was used and when only phosphoric acid was used, and the results are also listed in Table 1.

[Table] Example 72 An experiment was conducted in the same manner as in Example 1, except that the acid shown in Table 2 was used in place of 85% phosphoric acid in Example 1, and 0.2 part of sodium sulfate was used as the metal compound. . The results are shown in Table 2. Furthermore, as a comparative example, experiments were conducted in the same manner without using sodium sulfate and without using acid, and the results are also listed in Table 2.

[Table] Example 73 An autoclave containing raw materials with the same composition as in Experiment No. 1-1 of Example 1 was immersed in an oil bath heated to 120°C, shaking was started at the same time, and after 1 hour The autoclave was taken out from the oil bath, and the autoclave was further immersed in another oil bath whose temperature had been raised to 160° C. At the same time, shaking was started and reaction was carried out for 15 minutes. As a result, the formaldehyde conversion rate is
100%, the isoprene yield based on formaldehyde is 84.4%, and the geraniolene yield is
It was 0.3%.

Claims (1)

[Claims] 1 In producing isoprene by reacting at least one isobutylene source selected from isobutylene, tertiary butanol, and alkyl tertiary butyl ether with a formaldehyde source in the liquid phase in the presence of water using an acid catalyst, the periodic table Ia,
A method for producing isoprene, characterized in that at least one metal ion selected from Group B, Group A, and Group B elements is allowed to exist in the reaction system.