JPH0236575B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel method for synthesizing isoprene, and more particularly to a one-step method for synthesizing isoprene in which a source of isobutylene and a source of formaldehyde are subjected to a liquid phase reaction in the presence of a heteropolyacid. 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 in which TBA and formaldehyde are reacted in the presence of a metal chloride, sulfate, or phosphate (Japanese Patent Publications No. 48-28884 and 49-10926), a method in which the above-mentioned isobutylene source and formaldehyde source are Method of reaction in the presence of boron chloride, sulfonic acid, mineral acid or cation exchange resin (Japanese Patent Publication No. 49-10927
No. 49-10928, No. 50-10283) are known. These one-step methods synthesize isoprene from isobutylene and formaldehyde, which have already been industrialized, via dimethyldioxane.
It has the basic advantage of fewer reaction steps compared to the so-called two-step process, but on the other hand, it is generally inferior in selectivity (in most cases, the selectivity based on formaldehyde is less than 20%). ), and depending on the type of catalyst used, the usable reaction raw materials are limited and the equipment tends to be corroded. The inventors of the present invention conducted intensive studies to improve these drawbacks of the prior art, and as a result, discovered that these drawbacks could be solved at once by using a specific heteropolyacid as a catalyst. It has arrived. Thus, according to the invention, isobutylene,
A water-soluble heteropolyacid in which at least one isobutylene source selected from TBA and alkyl tertiary butyl ether and a formaldehyde source are condensed with at least one element selected from tungsten, molybdenum, and vanadium as a coordination element in the presence of water. Provided is a one-step liquid phase synthesis method for isoprene, characterized in that the reaction is carried out in the liquid phase in the presence of. 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. In addition, there are products with increased formaldehyde concentration by dissolving paraformaldehyde in formaldehyde aqueous solution,
An aqueous formaldehyde solution containing methanol as a stabilizer can also be used in the same way. In the present invention, molybdenum,
A water-soluble heteropolyacid having at least one element selected from tungsten and vanadium as a condensed coordination element is used as a catalyst. The central element of such a heteropolyacid is selected as appropriate, but is usually phosphorus, silicon, arsenic, germanium, titanium, cerium, manganese, cobalt, chromium, iron, gallium, boron, platinum, nickel, etc. Among them, phosphorus, silicon, boron, chromium, nickel,
Iron, cobalt, and arsenic are prized. Specific examples of such heteropolyacids include phosphomolybdic acid, phosphotungstic acid, phosphomolybdovanadic acid, silicotungstic acid, silicomolybdic acid, borotungstic acid, boromolybdic acid, cobalt tungstic acid, cobalt molybdic acid, etc. is exemplified. The amount of such heteropolyacid to be used may be selected as appropriate, but it is usually per 100 parts by weight of the total amount of isobutylene source and formaldehyde source.
The amount is 0.01 to 100 parts by weight, preferably 0.1 to 10 parts by weight. The reaction in the present invention is carried out in the presence of water in the presence of a source of isobutylene, a source of formaldehyde and a heteropolyacid. The amount of water used is usually between 60 and 1500 parts by weight per 100 parts by weight of the raw isobutylene source.
parts by weight, preferably from 80 to 1000 parts by weight. In the present invention, a solvent inert to the reaction can be used together with water. Specific examples of such solvents include hydrocarbon solvents such as n-pentane, n-hexane, isohexane, n-heptane, isoheptane, n-octane, isooctane, benzene, toluene, xylene, cyclohexane, methylcyclohexane, etc. be done. Other reaction conditions in the present invention are not particularly limited and can be selected as appropriate. For example, the reaction temperature is usually 110-280℃, preferably
The temperature is 130 to 240°C, and if it is too low, the conversion rate decreases, and if it is too high, the amount of by-products tends to increase. In addition, the reaction pressure may be within the range necessary for the reaction system to form a liquid phase, and therefore it is not necessarily constant depending on conditions such as the raw materials, solvent, and temperature employed, but it is usually 10 to 150 kg/
It is in the ^cm2 range. The reaction time is usually in the range of 0.2 to 5 hours, and the molar ratio of the isobutylene source to the formaldehyde source is usually 1 mol or more of the isobutylene source per 1 mol of the formaldehyde source, preferably 1.1 to 20 mol. 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 tower, a rotating disk column type reaction tower, a multi-tubular type reactor, or a batch type or semi-tubular type reactor can be used. Either batch or continuous operation methods can be employed. According to the present invention, (1) the isoprene selectivity is superior to that of conventionally known catalyst systems; (2) Other than isobutylene as a source of isobutylene
TBA, an alkyl tertiary butyl ether, can be used. (3) As a formaldehyde source, in addition to an aqueous formaldehyde solution, solid paraformaldehyde and methylal as a formaldehyde precursor can be used. (4) There is little corrosion of the equipment due to the catalyst, and the equipment can be made from commonly used materials at low cost. and other benefits. EXAMPLES In order to illustrate the present invention more specifically, Examples will be described below, but the present invention is not limited to these Examples. In addition, in the following examples, unless otherwise specified, parts are parts by weight, ratios are weight ratios, and molar ratio is the value of (number of moles of isobutylene source/number of moles of formaldehyde available in formaldehyde source). . Further, as paraformaldehyde, one with a formaldehyde content of 80.8% was used. Example 1 13.2 parts of paraformaldehyde (molar ratio = 3.2), 0.44 parts of phosphomolybdic acid, and 875 parts of water were added to a stainless steel autoclave with an internal volume of 1 and equipped with a stirrer, and the mixture was stirred. 180
℃, then held at the same temperature for 60 minutes, then rapidly cooled, divided the contents into an organic phase and an aqueous phase, and analyzed each phase.The total amount of isoprene produced in both phases was calculated as follows: Formaldehyde 100
It was 50.7 mol per mol. Comparative Example 1 Using a conventionally known ion exchange resin (Amberlyst 15) as a catalyst and setting the reaction temperature to 110
When the reaction was carried out under the same conditions as in Example 1, except that the temperature was set at It wasn't too bad. Also, another type of ion exchange resin (Amberlite)
Even if the reaction is carried out using 200C, acid form), the amount of isoprene produced will be the same as the formaldehyde charged.
It was only 12.3 moles per 100 moles. Example 2 100 parts of MTBE, 5.85 parts of paraformaldehyde (molar ratio = 7.2), 0.183 parts of phosphomolybdic acid, water
A reaction was carried out using 394 parts of formaldehyde and other conditions according to Example 1.
58.2 moles of isoprene were obtained per mole. Example 3 100 parts of MTBE, 4.1 parts of paraformaldehyde (molar ratio = 10.3), 0.27 parts of tungstic acid, water
154 parts of the mixture was heated at 180°C using the apparatus of Example 1.
After reacting for 60 minutes, analysis revealed that the amount of isoprene produced per 100 moles of formaldehyde charged was
It was 56.0 mol. Example 4 Using the same reaction apparatus as Example 1, MTBE100
A mixture of 9.3 parts of methylal (molar ratio = 9.2), 0.27 parts of phosphomolybdic acid as a catalyst, and 150 parts of water was heated to 210° C. with stirring and immediately cooled. According to analysis after the reaction, the amount of isoprene produced was 64.3 moles per 100 moles of methylal charged. Examples 5 to 7 Into a stainless steel autoclave with an internal volume of 1, 100 parts of the raw material isobutylene source shown in Table 1, paraformaldehyde as the raw material formaldehyde source, phosphomolybdic acid as a catalyst, and water were fed as indicated. After raising the temperature to 180°C, it was held at the same temperature for 60 minutes and then rapidly cooled. After the reaction, the amount of isoprene obtained is 100% of the formaldehyde charged.
The values per mole were as shown in Table 1.

[Table] Example 8 Using the same reaction apparatus as in Example 1, 100 parts of TBA,
12.3 parts of formaldehyde aqueous solution (4.6 parts as formaldehyde, 6.7 parts of water: molar ratio = 8.8), 0.09 parts of silicotungstic acid, and 169 parts of water were charged, heated to 210°C with stirring, immediately quenched, and analyzed after the reaction was completed. As a result, 68.1 moles of isoprene were produced per 100 moles of formaldehyde charged. Example 9 A mixture consisting of 100 parts of TBA, 5.5 parts of paraformaldehyde (molar ratio 9.1), 0.35 parts of phosphomolybdic acid, and 193 parts of water was heated to 160°C using the same reaction apparatus as in Example 1, and then heated to the same temperature. The reaction was carried out for 90 minutes. According to the analysis results after the reaction, 64.3 mol of isoprene was produced per 100 mol of formaldehyde charged. Examples 10 to 13 Using the reaction apparatus of Example 1, reaction examples were shown in which the hydrocarbon solvents shown in Table 2 were used together with water as a solvent. Catalyst, water, per 100 parts of isobutylene source
The type and amount of hydrocarbon solvent and the amount of isoprene produced per 100 moles of formaldehyde charged are as shown. All reactions were carried out after raising the temperature to 180℃.
After keeping at the same temperature for 60 minutes, the process was terminated by rapid cooling.

【table】

Claims (1)

[Claims] 1 At least one isobutylene source selected from isobutylene, tertiary butanol, and alkyl tertiary butyl ether and a formaldehyde source are condensed with at least one element selected from tungsten, molybdenum, and vanadium in the presence of water to form a coordination element. A liquid phase synthesis method for isoprene, which is characterized in that the reaction is carried out in a liquid phase in the presence of a water-soluble heteropolyacid.