JP2006335645A - METHOD FOR PRODUCING t-BUTYL CARBOXYLATE - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method with which a by-product formed in carrying out an addition reaction of a carboxylic acid with isobutylene is effectively utilized and a t-butyl carboxylate is more inexpensively produced. <P>SOLUTION: The method for producing the t-butyl carboxylate comprises the following steps. an esterification step of carrying out an esterification reaction of the isobutylene with the carboxylic acid, a purification step of separating a low-boiling substance containing t-butanol from a reaction liquid obtained in the esterification step, a degradation step of subjecting at least a part of the t-butanol separated in the purification step to a dehydration reaction and converting the separated t-butanol into the isobutylene and a recycling step of feeding the isobutylene obtained in the degradation step to the esterification step. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a process for producing a carboxylic acid t-butyl ester such as methacrylic acid t-butyl ester. For example, since t-butyl methacrylate has polymerizability, it is widely used industrially as a component of various acrylic paints, and has good compatibility with other substances, low hygroscopicity, Since the polymer has characteristics such as good heat resistance, it is a compound that is expected to further expand its uses.

  Conventionally, synthesis of carboxylic acid t-butyl ester has been carried out by an addition reaction of carboxylic acid and isobutylene. For example, Patent Document 1 describes a method using a homogeneous catalyst such as sulfuric acid. However, since this method uses sulfuric acid, equipment using a corrosion-resistant material is required. Moreover, since it becomes a homogeneous reaction, the separation process of a catalyst and a reaction liquid is required. Therefore, there is a problem that the equipment cost becomes expensive.

  For this reason, Patent Document 2 discloses a method of adding carboxylic acid and isobutylene using a sulfonic acid group-containing ion exchange resin.

  However, in this method, t-butanol is produced as a by-product by the hydration reaction of water and isobutylene retained in the ion exchange resin, and isobutylene dimer or trimer is produced as a by-product depending on the reaction conditions. There was a problem that the basic unit deteriorated.

  As methods for suppressing such side reactions in the addition reaction between carboxylic acid and isobutylene, Patent Document 3 discloses a method for intentionally suppressing the conversion rate, and Patent Document 4 discloses a method for decreasing the reaction temperature with time. Has been.

  However, the method described in Patent Document 3 can slightly suppress by-products, but it is difficult to completely suppress them. Moreover, there was a problem that productivity was poor due to low conversion.

Further, in the method described in Patent Document 4, by-products can be slightly suppressed, but it is difficult to completely suppress the reaction, and the reaction temperature needs to be lowered stepwise, so that the operation becomes complicated. There was a problem.
British Patent 814360 US Patent No. 3037052 JP-A-63-135352 Japanese Patent Laid-Open No. 62-63544

  The present invention has been made in order to solve the above-described problems, and the object thereof is to effectively use a by-product when an addition reaction between a carboxylic acid and isobutylene is performed, and tert-butyl carboxylate can be produced at a lower cost. It is to provide a method for producing an ester.

  In order to solve the above-mentioned problems, the present inventors diligently studied a method for producing a carboxylic acid t-butyl ester. As a result, the by-product upon addition reaction of carboxylic acid and isobutylene contains t-butanol by hydration reaction of water and isobutylene in the system, and t-butanol in this by-product. It was found that the product can be recycled to the reaction system by dehydrating and decomposing it on the catalyst to form isobutylene, and the present invention has been completed.

That is, the first gist of the present invention is an esterification step in which isobutylene and carboxylic acid are esterified.
A purification step of separating low-boiling substances containing t-butanol from the reaction solution obtained in the esterification step;
A decomposition step in which at least a part of t-butanol separated in the purification step is subjected to a dehydration reaction to convert it to isobutylene; and
It is a manufacturing method of carboxylic acid t-butyl ester characterized by including the recycling process which supplies the isobutylene obtained at the said decomposition | disassembly process to the said esterification process.

  In the present invention, in the purification step, unreacted isobutylene is separated from the reaction solution (reaction mixture) obtained in the esterification step by degassing operation, and then low-boiling matter containing t-butanol is separated by vacuum distillation operation. It is preferable.

  The second gist of the present invention is to separate at least a part of t-butanol from the low boiling point product containing t-butanol separated in the purification step, and to supply the separated t-butanol to the decomposition step. -It is a manufacturing method of the said carboxylic acid t-butyl ester including a butanol separation process.

  In this invention, it is preferable to isolate | separate at least one part of t-butanol by distillation operation in a t-butanol separation process.

  In the present invention, it is preferable to continuously perform the esterification step, the purification step, the t-butanol separation step, the decomposition step, and the recycling step.

  ADVANTAGE OF THE INVENTION According to this invention, by-product at the time of carrying out addition reaction of carboxylic acid and isobutylene can be utilized effectively, and carboxylic acid t-butyl ester can be manufactured at lower cost.

  Hereinafter, the production method of the present invention will be described. In addition, the pressure in this specification is an absolute pressure.

The carboxylic acid used in the esterification step esterification process, for example, acetic acid, (meth) acrylic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, caproic acid, isocaproic acid, 2-methyl valeric acid Propiolic acid, crotonic acid, pentenoic acid, linolenic acid, linoleic acid, oleic acid, ricinoleic acid, arachidonic acid and the like. In addition, (meth) acrylic acid is a general term for acrylic acid and methacrylic acid. Of these, methacrylic acid is preferred.

  In carrying out the esterification step, it is preferable to use a catalyst. The catalyst is not particularly limited as long as the carboxylic acid and isobutylene are esterified to produce a carboxylic acid t-butyl ester. For example, a strongly acidic ion exchange resin, a mineral acid, an alkylsulfonic acid, or the like is used. it can. Among these, strong acid ion exchange resins are preferable because they are solid acids and the product and catalyst can be easily separated.

  It does not specifically limit as a form of the reactor which implements an esterification process, A tubular reactor, a tank reactor, etc. can be used. When the esterification catalyst is a solid acid, a fixed bed tubular reactor is preferred. The method of supplying the reaction fluid to the reactor may be a single pass, or a part of the fluid after passing through the reactor may be circulated to the reactor inlet.

  The reaction temperature in the esterification step is preferably -20 to 20 ° C, more preferably -10 to 10 ° C. In order to sufficiently increase the reaction rate, the reaction is preferably performed at −20 ° C. or higher, and in order to suppress the isobutylene multimerization reaction, the reaction is preferably performed at 20 ° C. or lower.

  The reaction pressure in the esterification step is preferably 600 to 900 torr, more preferably 700 to 800 torr. In order to sufficiently dissolve isobutylene in carboxylic acid and proceed the reaction, 600 torr or more is preferable, and 900 torr or less is preferable because inexpensive equipment is required.

  In the esterification step, the water in the system and the isobutylene are hydrated together with the esterification reaction of isobutylene and carboxylic acid. This hydration reaction produces t-butanol as a by-product. Examples of the moisture source in the system include those contained in the raw material carboxylic acid, those contained in the catalyst, and the like. In particular, when a sulfonic acid group-containing ion exchange resin is used as a catalyst, hydration tends to occur due to the nature of the sulfonic acid group, and the water retained in the resin by hydration reacts with isobutylene and a large amount of t-butanol is added as a by-product. To be born.

Purification step The reaction mixture obtained by the esterification step is sent to the purification step. The purification step is a step of purifying and separating low-boiling substances containing t-butanol, and the purification separation method is not particularly limited, and can be carried out by a usual separation method such as distillation separation, membrane separation, and adsorption separation. . Of these, distillation separation is preferred from the economical viewpoint. The distillation apparatus is not particularly limited, and a degassing tank, a plate tower, a packed tower, a thin film evaporator, a flash distillation tower, and the like can be used.

  The pressure in the purification step is preferably 10 to 1000 torr, more preferably 50 to 800 torr. The pressure is preferably 10 torr or more because it can be easily achieved by a generally performed decompression method, and 1000 torr or less is preferable in order to avoid the polymerization by suppressing the increase in the temperature of the fluid to be purified.

  The temperature of the purification step is preferably 200 ° C. or lower at the bottom and preferably 100 ° C. or lower at the top.

  The purification step may be composed of a plurality of separation operations. In order to make it easy to condense the low-boiling products mainly composed of purified t-butanol, unreacted isobutylene having a low boiling point should be separated from the reaction mixture after the esterification step by degassing before the purification step. Is preferred. The temperature at which unreacted isobutylene is separated is preferably −10 to 100 ° C., the pressure is preferably atmospheric pressure or lower, and more preferably 10 to 100 torr.

  In the purification step, low boilers containing t-butanol are separated from the reaction mixture. The separated low-boiler containing t-butanol can be fed directly to the cracking process, but in the low-boiler containing t-butanol, a small amount of isobutylene oligomer, carboxylic acid t-butyl ester, Since the reaction includes carboxylic acid and the like, supply to the decomposition step after the t-butanol separation step described later improves the concentration of t-butanol in the fluid supplied to the decomposition step, and the conversion rate of the decomposition step This is preferable because the selectivity is improved.

t-Butanol Separation Step The t-butanol separation step is a step of separating at least a part of t-butanol from a low-boiling substance containing t-butanol, and the separation method is not particularly limited. , Extraction separation, adsorption separation and the like. A plurality of these separation operations may be combined. Of these, distillation separation is preferred from an economical viewpoint.

  As for the temperature of the t-butanol separation step, the column bottom is preferably 200 ° C. or lower, and the column top is preferably 100 ° C. or lower.

  The pressure in the t-butanol separation step is preferably 10 to 1000 torr, more preferably 50 to 800 torr. It is preferably 10 torr or more because it can be easily achieved by a generally performed decompression method, and 1000 torr or less is preferable in order to prevent polymerization by suppressing an increase in the temperature of the fluid to be purified.

  The distillation separation apparatus is not particularly limited as long as the concentration of t-butanol in a low-boiling product containing t-butanol is increased. A plate tower, a packed tower, an evaporator, a flash evaporator, a thin film evaporator, etc. Can be used.

Decomposition process The low boiling point substance containing t-butanol separated in the purification process, or t-butanol separated in the t-butanol separation process is supplied to the decomposition process. The decomposition step is a step of converting at least a part of these t-butanols into isobutylene by a dehydration reaction.

  It is preferable to use a catalyst when carrying out the decomposition step. The catalyst is not particularly limited as long as it promotes the dehydration reaction of t-butanol, and silica alumina, sulfonic acid group-containing ion exchange resin, sulfuric acid, p-toluenesulfonic acid, activated alumina, methanesulfonic acid, etc. are used. I can do it. Of these, silica alumina is preferred.

  It does not specifically limit as a form of the reactor which implements a decomposition process, A tube type reactor, a tank type reactor, etc. can be used. When the catalyst in the cracking step is a solid acid, a fixed bed tubular reactor is preferred. The method of supplying the reaction fluid to the tubular reactor may be a single pass, or a part of the fluid after passing through the reactor may be circulated to the reactor inlet.

  In the decomposition step, it is preferable that t-butanol is supplied in a gaseous or liquid state to a reactor using a catalyst while isobutylene to be produced is efficiently and continuously taken out from the reaction system.

  For example, a distillation facility is attached separately from an external circulation type reactor having a reactor filled with a strongly acidic ion exchange resin, and isobutylene produced while continuously supplying t-butanol is directly supplied to the reactor under heating. The reaction residual liquid is continuously taken out by evaporation and introduced into a distillation facility, and t-butanol and isobutylene oligomer are supplied again to the reactor as evaporation components, or t-butanol is continuously supplied to the evaporator. For example, a method of evaporating while supplying gas and dehydrating and decomposing the gas on a solid strong acid catalyst may be used.

  50-500 degreeC is preferable and, as for the reaction temperature of a decomposition | disassembly process, 100-300 degreeC is preferable. From the viewpoint of sufficiently increasing the reaction rate, the reaction temperature is preferably 50 ° C. or higher, and a high temperature heat source is not required, and the cost is preferably 300 ° C. or lower.

  The pressure in the decomposition step is not particularly limited, but is preferably 500 to 1000 torr.

The isobutylene obtained in the recycling process decomposition process is supplied to the esterification process and recycled for use as at least part of the raw material of the esterification process.

  In the method of the present invention, it is preferable to continuously perform the esterification step, the purification step, the t-butanol separation step, the decomposition step, and the recycling step. By carrying out such a recycling step, the utilization efficiency of the raw material isobutylene is greatly improved, and the basic unit is improved, so that the carboxylic acid t-butyl ester can be produced very economically.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples.

Each selectivity and conversion rate used in the examples are defined as follows and measured using gas chromatography.

<Example 1>
<< Isobutylene dissolution process >>
Methacrylic acid (containing water: 1000 ppm by weight) is supplied at a rate of 1715 g / h from the methacrylic acid supply line 8 to the isobutylene dissolution tank 1 (made of glass, content 1 L) shown in FIG. 1, and gaseous isobutylene is supplied to the isobutylene supply line. 7 and recycled isobutylene supply line 9 were blown and dissolved at 561 g / h (of which 488 g / h was recycled from each step). The isobutylene dissolved in methacrylic acid was 151 g / h, and the isobutylene not dissolved was recovered and reused as a raw material.

<< Esterification process >>
Methacrylic acid in which isobutylene is dissolved is continuously supplied to a glass column 2 with a jacket (inner diameter 50 mm, height 1200 mm) filled with 2 liters of ion exchange resin Amberlite IR-200cH (trade name) manufactured by Rohm and Haas at 1865 g / h. The esterification reaction was then carried out. The temperature in the glass column was 5 ° C. The reaction results are shown in Table 1.

《Purification process》
The obtained reaction mixture was introduced into a degassing tank 3 (made of glass, content 1 L), and isobutylene in the reaction mixture was degassed under reduced pressure at 80 torr. The separated isobutylene was recovered, sent to the recycled isobutylene supply line 9, and reused as a raw material. The degassed liquid is supplied to a vacuum distillation column 4 (glass old show, inner diameter 25 mm, height 1000 mm, equivalent to 20 theoretical plates), and high-boiling components (column bottom liquid) and low-boiling components (distillate). ). The composition of the column bottom liquid was 91.6% by weight of methacrylic acid and 8.4% by weight of tert-butyl methacrylate. The composition of the distillate is shown in Table 2.

<< Disassembly process >>
The distillate is gasified and then introduced into a reaction tube 6 (made of SUS, inner diameter 13 mm, filling height 115 mm) filled with N631HN (trade name) manufactured by JGC Chemical Co., Ltd., which is a silica-alumina catalyst. Carried out. The temperature in the reaction tube was 150 ° C. The reaction results are shown in Table 3.

  The isobutylene in the reaction mixture was recovered by cooling, sent to the recycle isobutylene supply line 9, and reused as a raw material. As a result, 11 g / h of isobutylene could be reused.

<Example 2>
As shown in FIG. 2, the same procedure as in Example 1 was performed except that a t-butanol separation step was provided after the purification step.

<< t-butanol separation step >>
The distillate separated in the purification step is supplied to a t-butanol separation tower 10 (glass old show, inner diameter 25 mm, height 500 mm, equivalent to 10 theoretical plates), and high boiling point components (column bottom liquid) and low Separated into boiling components (distillate). From the high boiling point components, methacrylic acid was recovered at 24 g / h, and the product methacrylic acid t-butyl ester was recovered at 11 g / h. Table 4 shows the composition of the low boiling point component.

The distillate was gasified by the evaporator 5 and introduced into the reaction tube 6 in the decomposition process. The results in the decomposition process are shown in Table 5.

  The isobutylene in the reaction mixture was recovered by cooling, sent to the recycle isobutylene supply line 9, and reused as a raw material. As a result, 12 g / h of isobutylene could be reused. Further, by providing the t-butanol decomposition step, the t-butanol concentration in the fluid supplied to the decomposition step was improved, and the conversion rate and selectivity of the decomposition step were improved.

It is a flowchart which shows an example of the apparatus which performs the manufacturing method of this invention. It is a flowchart which shows another example of the apparatus which performs the manufacturing method of this invention.

Explanation of symbols

1. 1. Isobutylene dissolution tank Jacketed glass column (esterification reactor)
3. Deaeration tank 4. 4. Vacuum distillation tower 5. Evaporator Reaction tube (decomposition reactor)
7). 7. Isobutylene supply line Methacrylic acid supply line9. Recycled isobutylene supply line10. t-Butanol separation tower

Claims (2)

An esterification step in which isobutylene and carboxylic acid are esterified;
A purification step of separating low-boiling substances containing t-butanol from the reaction solution obtained in the esterification step;
A decomposition step in which at least a part of t-butanol separated in the purification step is subjected to a dehydration reaction to convert it to isobutylene; and
The manufacturing method of carboxylic acid t-butyl ester characterized by including the recycling process which supplies the isobutylene obtained at the said decomposition | disassembly process to the said esterification process.   The method includes a t-butanol separation step of separating at least a part of t-butanol from the low-boiling product containing t-butanol separated in the purification step, and supplying the separated t-butanol to the decomposition step. A method for producing a carboxylic acid t-butyl ester according to 1.

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