JPH03287563A - Production of organic carboxylic acid ester - Google Patents

Abstract

PURPOSE:To improve yield without deteriorating catalyst activity by reacting an organic carboxylic acid with an alcohol in the presence of a catalyst of sulfuric acid supported on a carrier while further supplying sulfuric acid in an amount corresponding to that of the eliminated supported sulfuric acid in obtaining the subject compound useful as coatings, adhesives, etc., from the organic carboxylic acid and the alcohol in the vapor phase. CONSTITUTION:An organic carboxylic acid (e.g. acetic acid, propionic acid or acrylic acid) is reacted with an alcohol (e.g. methanol or n-propanol) in the vapor phase in the presence of a catalyst of sulfuric acid supported on a carrier or the carrier at 100-200 deg.C under about ordinary pressure while continuously or intermittently supplying sulfuric acid as a catalyst component to afford the objective compound. Silica gel, diatomaceous earth, quartz sand, etc., are preferred as the carrier for the aforementioned catalyst. The ratio of the supported sulfuric acid is preferably about 5-20%. The amount of the sulfuric acid fed together with the reaction raw material is preferably at a molar ratio within the range of about (1/100) to (1/1000) based on the organic carboxylic acid. The sulfuric acid can be fed alone or also mixed with the reaction raw material and fed.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Field of Application> The present invention relates to a method for producing a corresponding organic carboxylic acid ester from an organic carboxylic acid and an alcohol in the gas phase.

Organic carboxylic esters are not only useful compounds used in paints, adhesives, fragrances, plasticizers, and solvents, but also unsaturated carboxylic esters are important intermediates as monomers or comonomers for various functional resins. It is a raw material.

<Prior Art> The following method is known as a method for producing a corresponding organic carboxylic acid ester from an organic carboxylic acid and an alcohol.

(1) Liquid phase: sulfuric acid, phosphoric acid, benzenesulfonic acid, p-
A method of esterification using an acidic catalyst such as toluenesulfonic acid.

(2) A method of continuous esterification using an acidic cation exchange resin as a liquid phase catalyst.

(3) Heteropolyacid catalyst as a catalyst (Japanese Unexamined Patent Publication No. 57995
No. 56, No. 57-13095), composite oxide catalyst (Japanese Patent Publication No. 42-6324, No. 45-245)
No. 64, JP-A-51-75019) or a catalyst in which an acid such as sulfuric acid, phosphoric acid, benzenesulfonic acid, etc. is supported on a carrier (British Patent No. 1.017.806, JP-A No. 1982)
A method of esterifying in a gas phase using the following methods: JP-A-5222, JP-A-43-20286).

<The invention or the problem to be solved> A method using an acidic catalyst such as sulfuric acid or phosphoric acid in a liquid phase is a commonly used method, but since esterification of organic carboxylic acids is an equilibrium reaction, In order to increase the equilibrium conversion rate, it is essential to remove and discharge by-product water from the reaction system, which requires complicated measures such as using excessive alcohol or adding other solvents to azeotropically remove the water. In addition, this method has many problems economically, such as the fact that the equipment is severely corroded.

In addition, a method using an acidic cation exchange resin as a catalyst in the liquid phase has the advantage that the reaction solution and catalyst can be easily separated and the reaction form is simplified, but the resin is relatively expensive. Furthermore, there are economic disadvantages, such as an unavoidable decrease in activity due to the heat resistance, lifespan, etc. of the resin, and the need for periodic regeneration or replacement of the resin.

Furthermore, when using unsaturated carboxylic acids such as acrylic acid, methacrylic acid, or crotonic acid as the organic carboxylic acid in these liquid phase methods, since the raw materials and products are polymerizable, polymerization may occur in the reaction equipment or connection line. Adhesion causes problems such as hindering efficient operation and reducing product recovery rate.

In the gas phase esterification method, polymerization of the unsaturated carboxylic acid does not substantially occur in the gas phase, and the equilibrium shifts in a direction favorable to the production system (AIChE Journal
al, 14(4), 606(68)), it becomes possible to solve various problems occurring in esterification in the liquid phase.

However, there are serious problems such as insufficient catalyst activity and catalyst life, and this method has not been commercialized.

The object of the present invention is to improve the drawbacks of these conventional techniques and to provide an industrially advantageous method for producing organic carboxylic acid esters.

In order to achieve this objective, the present inventors conducted extensive studies to find a method for producing an excellent organic carboxylic acid ester in the gas phase.

As a result, the reason why the activity of the catalyst supporting sulfuric acid in gas phase esterification decreases is that the supported sulfuric acid is desorbed from the carrier, and sulfuric acid corresponding to the amount desorbed is continuously or intermittently If the sulfuric acid is replenished in the same manner, the catalytic amount h will not decrease at all, and even if a catalytic amount of sulfuric acid is replenished in the presence of only the carrier, extremely high esterification activity can be stably obtained. They discovered this and completed the present invention.

<Means for Solving the Problem> That is, the present invention provides a method for producing a corresponding organic carboxylic acid ester from an organic carboxylic acid and an alcohol in the gas phase, in which sulfuric acid is used as a catalyst component in the presence of a sulfuric acid-supported catalyst or a carrier. This is a method for producing an organic carboxylic acid ester, which is characterized in that the reaction is carried out under pressure without being supplied continuously or intermittently.

Examples of the carrier used in the present invention include silica-based carriers such as silica gel, diatomaceous earth, quartz sand, and quartz wool, and inorganic compounds such as silicon carbide, silica-alumina, zeolite, titania, zirconia, alumina, activated carbon, and graphite.

Although the shape or particle size of the carrier does not affect the reaction results,
It may be formed into a suitable shape, such as a spherical shape or a cylindrical shape.

The method of carrying out the reaction while continuously or intermittently supplying sulfuric acid as a catalyst in the presence of the carrier of the present invention is effective regardless of the type of carrier. There are differences in the degree of the effect of suppressing the desorption of sulfuric acid.

Among the above-mentioned carriers, silica-based carriers such as silica gel, diatomaceous earth, quartz sand, and quartz wool, and silicon carbide have excellent sulfuric acid retention ability, and therefore sufficient reaction activity can be achieved even with a small amount of sulfuric acid supplied continuously or intermittently. It is preferably used because it indicates.

Further, in the present invention, when a catalyst in which sulfuric acid is preliminarily supported on the above-mentioned carrier is used, there is an advantage that the induction period until the start of the reaction is shortened.

The method for supporting sulfuric acid on the carrier is carried out by a known general supporting method, such as the evaporation to dryness method, in which the carrier is immersed in an aqueous sulfuric acid solution, and then the water is evaporated while stirring to fix the sulfuric acid on the carrier. be exposed.

There is no particular restriction on the sulfuric acid loading rate, but it is suitably about 1 to 50%, preferably about 5 to 20%.

As a catalyst component, the amount of sulfuric acid supplied together with the reaction raw materials is usually about 1/20 to 1/20 of the organic carboxylic acid expressed in molar ratio.
1/10.000, preferably about 1/100 to 1/1.
Selected from a range of 000.

Sulfuric acid, a catalyst component, is supplied continuously or intermittently,
Sulfuric acid may be supplied alone or mixed with any of the reaction raw materials.

When sulfuric acid is intermittently supplied, a predetermined amount of sulfuric acid is periodically supplied alone or mixed with other reaction raw materials.

Since the catalytic activity and sulfuric acid retention power differ depending on the carrier, the frequency of supply of sulfuric acid and the amount of sulfuric acid supplied per time will vary depending on the carrier used, and should be determined as appropriate while taking into account the sulfuric acid 1 for the organic carboxylic acid and the catalytic activity during the reaction. It is lawful.

Examples of the organic carboxylic acids used in the present invention include saturated carboxylic acids such as formic acid, acetic acid, propionic acid and butyric acid, and unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid.

The alcohol used in the present invention is not particularly limited, but methanol, ethanol, n-propanol, 1so-propanol, n-butanol, 5ec-butanol, 1so-butanol, tert-butanol, and 2-ethyl - Aliphatic alcohols such as hexanol.

The molar ratio of alcohol/organic carboxylic acid is usually about 0.1/
A suitable range is 1-10/1, preferably about 0.5/1 to 5.0/1.

The purity of the reaction raw material in the present invention does not need to be particularly high, and esterification can be carried out in the presence of a substance that does not interfere with the reaction. For example, organic carboxylic acids are often produced by gas-phase catalytic oxidation reaction of the corresponding organic aldehyde, and a dilute solution of the organic carboxylic acid obtained by the oxidation reaction can be used directly without concentration or purification. However, it is also possible to directly use the gaseous reaction mixture resulting from the above gas phase oxidation process.

There is no particular restriction on the reaction temperature, or it varies depending on the temperature at which the reaction raw materials can be kept in a gaseous state, that is, the organic carboxylic acid or alcohol used, but it is usually about 100
It is preferably used in a temperature range of .degree. C. to 200.degree.

The reaction pressure can be selected from a wide range from reduced pressure to increased pressure, and is not particularly limited, and from an industrial perspective, it is preferably around normal pressure.

The contact time between the reaction gas and the carrier (the value obtained by dividing the volume of the carrier by the flow rate of the reaction gas converted to standard temperature and standard pressure) is approximately 1 to
A suitable time is 70 seconds, preferably in the range of about 5 to 30 seconds.

The reaction is carried out using a conventional gas phase flow reactor such as a fixed bed, fluidized bed or moving bed.

In the case of a vertical gas phase reactor, it is also possible to charge the reaction raw materials from the top and take out the reaction products from the bottom, or vice versa.

2. Effects of the Invention> According to the present invention, the esterification activity is maintained by the small amount of sulfuric acid catalyst supplied, so there is essentially no activity deterioration, and organic carbonic acid esters can be selectively and highly It becomes possible to produce with high yield.

In addition, problems such as polymerization of unsaturated carboxylic acids or unsaturated carbonic acid esters in the reaction system, which are problems with esterification in the liquid phase, and corrosion of the reaction equipment when using an acidic catalyst in the liquid phase, etc. The gas phase esterification of the present invention substantially does not occur, and stable operation can be performed for a long period of time.

<Examples> The present invention will be further specifically explained with examples, but the present invention is not limited by these examples.

Note that the ester yield is defined by the following formula.

Example 1 Aqueous silica sol (Snowtex N manufactured by Nichina Kagaku ■;
SiO! = 20%) 300- and 96% sulfuric acid 9.6- were mixed and dried under reduced pressure at 120°C for 3 hours using a rotary evaporator to prepare a 20% sulfuric acid supported silica gel catalyst.

A reaction tube made of Pyrex glass having an inner diameter of 8 sides was filled with 6 mN (10 to 16 mesh) of the above catalyst, and ethyl acrylate was produced from acrylic acid and ethanol under the following conditions using nitrogen gas as a carrier.

As a catalyst, sulfuric acid corresponding to 1/670 (mole ratio) of the amount of acrylic acid supplied was dissolved in ethanol and continuously supplied.

Feed composition (mmol/hr); Acrylic acid/ethanol/Nt = 16/32/27 Total feed amount - 75 mmol/hr SV (space velocity) = 280 ml/ml - Catalyst/hr Contact time = 12.9 seconds Reaction temperature (Furnace temperature) = 145°C After trapping the product at 0°C, the trap liquid was analyzed using a gas chromatograph.

Table 1 shows the elapsed reaction time and reaction results.

Note that the reaction results were expressed based on acrylic acid.

Table 1 Comparative Example 1 Ethyl acrylate was prepared from acrylic acid and ethanol under the same conditions as in Example 1 without dissolving sulfuric acid as a catalyst in ethanol, that is, without continuously supplying sulfuric acid. Manufactured.

Table 2 shows the elapsed reaction time and reaction results.

Table 2 Example 2 20% sulfuric acid supported silica gel catalyst prepared in Example 1 6d
(10 to 16 mesh) was packed into a Pyrex glass fixed bed gas phase flow reactor, and using nitrogen gas as a carrier, n-butyl acrylate was produced from acrylic acid and n-butanol under the following conditions. Ta.

As a catalyst, sulfuric acid corresponding to 1/670 (mole ratio) of the amount of acrylic acid supplied was dissolved in n-butanol and continuously supplied.

Feed composition (mmol/hr); acrylic acid/n-butanol/Nt = 16/32
154 total supply amount = 102 mmol/hr SV (space velocity) = 380 m//d-catalyst/hr Contact time = 9.5 seconds Reaction temperature (furnace temperature) = 145 °C After trapping the product at 0 °C The trap liquid was analyzed using a gas chromatograph.

Table 3 shows the elapsed reaction time and reaction results.

Note that the reaction results were expressed based on acrylic acid.

Table 3 Comparative Example 2 Acrylic acid was prepared from acrylic acid and n-butanol under the same conditions as in Example 2 without dissolving sulfuric acid as a catalyst in ethanol, that is, without continuously supplying sulfuric acid. -n-butyl was produced.

Table 4 shows the elapsed reaction time and reaction results.

Table 4 Example 3 Water-based silica sol (Snowtex N-81 manufactured by Nichina Kagaku ■)
02=20%) 300- was dried under reduced pressure at 120° C. for 3 hours in a rotary evaporator to prepare silica gel.

The obtained silica gel powder has a diameter of 5II! 111 After being compressed into a cylindrical shape with a height of 5 m, it was
A carrier was obtained by firing at 250°C for 2 hours. This carrier 20
- was filled into a Pyrex glass reaction tube having an inner diameter of 1311111 mm, nitrogen gas was used as a carrier, and methyl methacrylate was produced from methacrylic acid and methanol under the following conditions.

As a catalyst, sulfuric acid corresponding to 1/670 (mole ratio) of the amount of methacrylic acid supplied was dissolved in methanol and continuously supplied.

Feed composition (mmol/hr); Methacrylic acid/methanol/N2 = 48/96
/30 total supply amount = 174 o+mol/hr SV (space velocity) ~195 ml/ml-carrier/hr
Contact time = 18.5 seconds Reaction temperature (furnace temperature) = 160''C After trapping the product at 0°C, the trapped liquid was analyzed by gas chromatography.

Table 5 shows the number of days elapsed for the reaction and the reaction results. Note that the reaction results were expressed based on methacrylic acid.

Table 5 Example 4 Water-based silica gel (Osan Kagaku Snowtex N; 5
i02=20%) 300-96% sulfur #2. After mixing OCC, use a rotary evaporator and heat at 90″C for 2
A 5% sulfuric acid-supported silica gel catalyst was prepared by drying under reduced pressure for hours.

The above catalyst 12d (10 to 16 mesh) has an inner diameter of 8
Fill a IIIll Pyrex glass reaction tube,
Using nitrogen gas as a carrier, a reaction was carried out to obtain ethyl acetate from acetic acid and ethanol under the following conditions. As a catalyst, sulfuric acid corresponding to 1/820 (molar ratio) of the amount of acetic acid supplied was dissolved in ethanol, and the sulfuric acid was continuously supplied.

Feed composition (mmol/hr); acetic acid/ethanol/N2 = 25150/32 total supply amount = 107 mmol/hr SV (space velocity) ~200 ml/ml-catalyst/hr
Contact time = 18.0 seconds Reaction temperature (furnace temperature) = 140°C After trapping the product at O''C, the trap liquid was analyzed by gas chromatography. The elapsed reaction time and reaction results are shown in Table 6. The reaction results are shown based on acetic acid.

Table 6 Comparative Example 3 Reaction to obtain ethyl acetate from acetic acid and ethanol without dissolving sulfuric acid as a catalyst in ethanol, that is, without continuously supplying sulfuric acid, and using other conditions exactly as in Example 4. I did it. Table 7 shows the elapsed reaction time and reaction results.

Table 7

Claims (1)

[Claims] 1. In a method for producing a corresponding organic carboxylic acid ester from an organic carboxylic acid and an alcohol in a gas phase,
A method for producing an organic carboxylic acid ester, which comprises carrying out the reaction while continuously or intermittently supplying sulfuric acid as a catalyst component in the presence of a sulfuric acid-supported catalyst or carrier.