JPS62277342A - Production of aliphatic carboxylic acid ester - Google Patents

Abstract

PURPOSE:To obtain a compound useful as organic solvent, plasticizer, raw material for plastic, etc., economically and in high yield, by esterifying an aliphatic carboxylic acid with a formed in the presence of a high-temperature treated solid phosphoric acid catalyst in a gaseous phase. CONSTITUTION:An aliphatic carboxylic acid (e.g. formic acid or acetic acid) shown by formula R1COOH (R1 is H or 1-4C alkyl or alkenyl) is reacted with a formula (e.g. dimethoxymethane) shown by the formula R2O-CH2-OR2 (R2 is 1-4C alkyl) in the presence of a solid phosphoric acid catalyst (e.g. phosphoric acid supported on diatomaceous earth) which is calcined at high temperature of 500-1,100 deg.C at 130-400 deg.C in a gaseous phase to give the aimed substance. The molar ratio of the carboxylic acid/the formula is 2/1-1/5 in the reaction. EFFECT:Defects such as use of acid in a large amount in a liquid phase and waste acid treatment, etc., is improved and by-products are suppressed without using an extremely excess amount of an alcohol in gaseous phase.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for producing aliphatic carboxylic acid ester, which is an industrially useful substance, from aliphatic carboxylic acid and formal. .

Aliphatic carboxylic acid esters are useful as raw materials for organic solvents, plasticizers, plastic raw materials, and many other chemicals.1 Typical examples include ethyl acetate, butyl acrylate, and MMA. .

(Prior art) Esterification of aliphatic carboxylic acids is carried out using 1 e.g. Kirk-O
thmer Encyclopedia of Che
Mical Technology (3rd) vol.
, 9 P, 291, it is common to react an aliphatic carboxylic acid and an alcohol in the liquid phase in the presence of an acid catalyst to obtain the desired ester.

RCO○H+R' ○H1 RC○ ○ R' 10 82 0
(1) At this time, as shown in equation (1), it is an equilibrium reaction, so in order to increase the esterification rate, the ester and water on the right side are removed from the reaction system, or alcohol is used in excess, so that the equilibrium is changed to the right side. A method of proceeding is taken.

As the acid catalyst, a mineral acid such as sulfuric acid, a macroporous cation exchange resin, or a strongly acidic cation exchange resin such as Amberlyst 15 is used.

(Problem to be solved by the invention) When acid expansion is used as an acid catalyst in the esterification of aliphatic carboxylic acids in a liquid phase reaction, the acid is diluted with the water produced in one reaction, so new acid must be added. It also has the disadvantage of requiring a large amount of waste acid treatment. On the other hand, with cation exchange resins.

Although such drawbacks can be avoided, the practical heat-resistant temperature for continuous industrial use is limited to 90 to 100°C, which is slow for one reactor, and requires a large amount of catalyst. This requires a large reactor.

Furthermore, the catalyst has low durability and needs to be replaced every 6 months to 1 year, resulting in high catalyst costs.

In order to improve these drawbacks of liquid phase reactions, attempts have been made to esterify catalytically in the gas phase, but although this solves the catalyst problem, it is difficult to achieve a high esterification rate. be. Therefore, it is necessary to use alcohol in large excess, and the economic burden of recovering a large amount of unreacted alcohol is large.

(Means for Solving the Problems) The inventors have discovered that a high esterification rate can be achieved by using formal in place of alcohol in a gas phase esterification reaction and reacting aliphatic carboxylic acids under a solid phosphoric acid catalyst treated at high temperature. I found out what I can get.

That is, in the present invention, aliphatic carboxylic acid and formal
In the presence of a solid phosphoric acid catalyst treated at high temperature at 0 to 1100°C,
This is a method for producing an aliphatic carboxylic acid ester, characterized by carrying out the reaction in a gas phase.

The aliphatic carboxylic acid of interest here has a general formula.

R, COOH (R, is H or an alkyl group or alkenyl group having 1 to 4 carbon atoms) is an aliphatic carboxylic acid represented by formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, These include isovaleric acid, acrylic acid, methacrylic acid, and crotonic acid.

Also, as a formal, it is a general formula.

R,0-CH2-○R2 (R2 is an alkyl group having 1 to 4 carbon atoms), and specifically includes dimethoxymethane (methylal), jetoxymethane, dipropoxymethane, and poroxymethane. , dibutoxymethane,
Such as di-t-butoxymethane.

A solid phosphoric acid catalyst is a catalyst in which phosphoric acid such as orthophosphoric acid, pyrophosphoric acid, metaphosphoric acid, or polyphosphoric acid (triphosphoric acid, tetraphosphoric acid), or phosphate such as ammonium phosphate or calcium phosphate is supported on a carrier containing a metal oxide and calcined. It is a catalyst. Supports that can be used in the present invention include silica gel, alumina,
Zirconia.

Titania, doria, and composite oxides such as silica alumina, silica titania, and silica zirconia.

There are synthetic zeolites, natural diatomaceous earth, acid clay, zeolites, etc.

These carriers are generally used as they are without any special treatment, but calcined ones can also be used.

Further, these carriers can be used alone or in combination of two or more.

As a method for supporting phosphoric acid on a carrier, 1, for example, commercially available 8
A method in which a solution of 5% phosphoric acid diluted in water is sprayed onto a heated carrier, or a method in which the carrier is immersed in a phosphoric acid solution or a phosphate solution and then dried and fired, or a powder carrier and a phosphoric acid solution or a phosphate solution are used. A method of kneading, molding, drying and firing is used. The amount of phosphoric acid or phosphate salt supported on the carrier varies depending on the type of carrier, and cannot be generally specified, but in practice it is 1 to 100 parts by weight, preferably 2 to 30 parts by weight, per 100 parts by weight of the carrier. Appropriate.

The catalyst has a particle size of at least f3Qmesh or more, and industrially it is desirable to form the catalyst into a particle size of 2 to 5+ nm x 2 to 10 mm.

In addition, the catalyst supporting phosphoric acid was heated to
It is desirable to perform drying or pre-firing at a temperature below 0°C.

The high-temperature firing process is carried out in a high-temperature furnace that is free from contamination from the furnace material, such as a Matsufuru furnace, a rotary kiln, or a hot blast furnace with one quartz tube heating furnace. The firing atmosphere is preferably a gas inert to the catalyst, such as air or nitrogen.

High temperature firing treatment is carried out at 500-1100℃,
If the temperature is lower than ℃, the by-product of dialkyl ether cannot be ignored. Furthermore, if the temperature exceeds 1100°C, the activity of the catalyst decreases.

The firing time varies depending on the amount of phosphoric acid supported, the firing temperature, and the type of carrier. Although it cannot be specified generally, it is usually 0 to 50 hours. Generally speaking, the higher the firing temperature, the shorter the firing time. Good too.

The reaction of the present invention is preferably carried out in a continuous catalytic gas phase system, and the catalyst is preferably packed into a reactor in a fixed bed adiabatic system or fixed bed isothermal system, but a fluidized bed, moving bed, etc. format is also possible. It is also possible.

The molar ratio of raw material carboxylic acid and formal greatly affects the esterification rate. The higher the proportion of formal, the higher the esterification rate achieved.

R, C00H/CH2(OR2)2 molar ratio 2/1-11
5, preferably in the range of 171 to 1/3.

The reaction temperature is 130-400°C, preferably 150-35°C.
It is 0°C. The reaction pressure is not particularly limited and can be selected from a reduced pressure that keeps one reaction system in the gas phase to an increased pressure.

Normal pressure is generally preferred.

The contact time with the catalyst is defined by the feed rate of the raw material per unit weight of the catalyst (WH3V raw material g/catalyst ig-hr). Suitable WH3V is 0.1-50 g/g, h.

Preferably it is 0.1 to Log/g, h.

Although the catalyst of the present invention has an extremely long lifespan, it is desirable to periodically remove coke in order to maintain constant activity. Methods for removing coke include nitrous oxide and inert gas such as helium.

Alternatively, there are methods of purging by heating with steam, or by burning the coke at 400° C. or higher using air or diluted air.The latter method is effective and the catalyst activity is completely restored.

(Operation) The reaction according to the present invention produces hemiformal as a by-product according to equation (2). Since this hemiformal is dissociated into alcohol and aldehyde in the reaction system, it is presumed that a high degree of esterification can be obtained.

Furthermore, the raw material formal is easily regenerated by the reaction between hemiformal and alcohol.

In addition, alcohol undergoes a reaction on the catalyst that produces dialkyl ether as a by-product according to formula (5), lowering the alcohol selectivity and interfering with the reaction of formula (4).1 The solid phosphoric acid catalyst according to the present invention It is estimated that it has the effect of suppressing the reaction of

2R20H-+ R2-0-R2+ R20(5)
(Effects) The method for producing an aliphatic carboxylic acid ester according to the present invention includes:
It does not require the use of large amounts of acid or waste acid treatment as in conventional liquid phase processes, and it achieves an extremely high conversion rate of aliphatic carboxylic acids and selectivity to esters without using a large excess of alcohol in the gas phase. can get.

Furthermore, since reactions that produce ether as a by-product are less likely to occur, a process with less alcohol loss is possible, which is of great industrial significance.

(Example) Next, the present invention will be illustrated in Examples, but of course the present invention is not limited thereto. Since the reaction product hemiformal is quantified together with formaldehyde and alcohol, the selectivity of hemiformal over formal is shown as formaldehyde selectivity.

Example 1 A solid phosphoric acid catalyst (N-501 manufactured by JGC Chemical Co., Ltd.) made by supporting phosphoric acid on commercially available diatomaceous earth was crushed into 10 to 32 meshes, baked at 900°C for 6 hours in an air atmosphere in a Matsufuru furnace, and then 20g was cut into pieces with an inner diameter of 15 mm and a length of 15 mm. A 60 cm Pyrex glass reaction tube was filled.

Molar ratio of acetic acid and methylal (dimethoxymethane) 1:2
A mixture of starting materials was supplied from the upper part of the reaction tube with a plunger pump at a rate of W HS V of 1.5 hr-'. The upper part of the reaction tube is a packed bed of glass spheres with a diameter of 1 to 2 mm, and the raw material is evaporated and preheated by a heater from the outside of the reaction tube and guided to the catalyst bed.

The temperature of the catalyst layer was 300° C., and the reaction was carried out at normal pressure. The reaction product gas from the lower part of the reaction tube was collected by cooling to obtain a reaction product liquid, which was analyzed by gas chromatography to determine the reaction results.

As a result, the conversion rate of acetic acid was 99%, and the selectivity to methyl acetate was 100%. Also, the decomposition rate of methylal is 68%,
The selectivity to formaldehyde was 98%, the selectivity to methanol was 99%, and the selectivity to dimethyl ether was 1%.

Comparative Example 1゜Example 1 except that the N-501 catalyst was not fired at high temperature
When the same raw materials were used for reaction, the conversion rate of acetic acid was 94%, the selectivity to methyl acetate was 100%, the decomposition rate of methylal was 71%, and the selectivity to formaldehyde was 96%.
%, the selectivity to methanol was 91%, and the selectivity to dimethyl ether was 9%.

Examples 2 to 8 Commercially available silica alumina (8 Volki Kagaku N-631L) was crushed into 14 to 32 meshes. This silica alumina 85
g was immersed in an aqueous solution containing 18 g of commercially available 85% phosphoric acid.

It was dried at a temperature below 100°C, then fired at 200°C for 1 hour, and then fired at a high temperature of 1000°C for 12 hours. This catalyst 15
g was filled into a 5O3-316L reaction tube with an inner diameter of 14 mm.

Table 1 shows the results of experiments using different reaction materials and two reaction conditions.

Example 9 Porous silica titania support (Ti02/Sin□=4/
1) 100g ammonium hydrogen phosphate (Ni+)
200 g of 10% aqueous solution of 211P04 was added, and the mixture was dehydrated and impregnated using a rotary evaporator. After drying this at 110°C overnight, it was fired in a Matsufuru furnace at 700°C for 12 hours. The same reaction tube as in Example 1 was filled with 20 g of the obtained catalyst. A raw material mixture of acetic acid and methylal with a molar ratio of 1:1 is pumped from the top of the reaction tube at 20 g/hr using a plunger pump.
It was supplied by The reaction was carried out in the catalyst layer at a reaction temperature of 280°C and normal pressure.

As a result of the reaction, the conversion rate of acetic acid was 94%, the selectivity to methyl acetate was 99%, the decomposition rate of methylal was 99%, the selectivity to formaldehyde was 97%, the selectivity to methanol was 98%, and the selectivity to dimethyl ether was 2. %Met.

Claims (1)

[Claims] Aliphatic carboxylic acid and formal at 500-1100℃
A method for producing an aliphatic carboxylic acid ester, characterized by carrying out the reaction in the gas phase in the presence of a solid phosphoric acid catalyst treated at high temperature.