KR100230197B1 - Catalyst for preparing carboxylic acid, its preparation and its use - Google Patents

Abstract

A catalyst comprising 70 to 99% by weight of cobalt (III) salt and 1 to 30% by weight of iron (III) salt, wherein the acid component of the salt is acetate, propionate, naphate, adipate or phthalate, to prepare the catalyst A process for producing carboxylic acids by oxidizing hydrocarbons with oxygen or air in the presence of the catalyst.

Description

Catalysts useful for the preparation of carboxylic acids, methods for their preparation and use

The present invention relates to novel catalysts useful for the preparation of carboxylic acids, and methods for their preparation and use. The present invention specifically relates to catalysts useful for the preparation of carboxylic acids via oxidation of hydrocarbons, more particularly cyclopentane, cyclohexane, cycloheptane, C ₄ -C ₆ paraffin, toluene, o-xylene, m-xylene A very useful catalyst for oxidizing certain hydrocarbons such as p-xylene and the like. The oxidation can be done in one step by air or oxygen in the liquid phase. The catalyst of the present invention is particularly suitable for the production of dicarboxylic acids such as adipic acid, pimelic acid, glutaric acid, phthalic acid and the like, and monocarboxylic acids such as acetic acid and benzoic acid. useful.

Dicarboxylic acids are mainly used to prepare polyesters, polyamides, plasticizers, synthetic lubricants and alkyds. In particular, adipic acid is widely used to make nylon 66, premium plasticizers, synthetic lubricants, alkyds and polyurethanes. Monocarboxylic acids are used as solvents and for the synthesis of plasticizers and fine chemicals. Generally, dicarboxylic acids are prepared by catalytic oxidation of hydrocarbons using transition metal catalysts such as cobalt or manganese. In such a process, it is sometimes necessary to isolate the intermediate formed and further oxidize with an oxidant, depending on its reactivity.

As an example, adipic acid is prepared by oxidizing cyclohexane in one step to form a mixture of cyclohexanone and cyclohexanol and in two steps oxidizing the mixture with air or nitric acid. At present, the method of obtaining adipic acid is common by the method of two-step oxidation of cyclohexane. In one step, cyclohexane is oxidized in the liquid phase with air or oxygen at about 150 ° C. in the presence of cobalt or manganese catalyst to form a mixture of cyclohexanone and cyclohexanol. In two steps, the mixture is oxidized with nitric acid at 50-80 ° C. in the presence of a vanadium-copper catalyst to give adipic acid. The overall selectivity to adipic acid is around 70% for cyclohexane. In addition, a method of using a high concentration of peroxide as a catalyst for oxidizing cyclohexane, a catalyst containing bromide or a high concentration of cobalt salt is known.

The catalyst used in the process has the following disadvantages.

1. Due to the low conversion (3-8%) of cyclohexane in one pass, it is necessary to recycle about 95% of cyclohexane in the first stage.

2. High concentrations (0.2 to 10%) of peroxides are dangerous because of their explosive nature at the reaction temperatures employed (ie, about 150 ° C).

3. Undesirable by-products such as lactones and oxyacids are formed during the reaction, so the by-products need to be separated, which is complicated.

4. Using bromide catalysts will severely corrode the device. Since the method has an operating pressure of 5-25 kg / cm 2, this corrosion carries the risk of explosion. In addition, gaseous pollutants, including nitrogen oxides from nitric acid used as oxidants in stage 2, cause severe corrosion and environmental pollution.

5. A separate oxidation reactor system is required for each oxidation step.

In order to increase the product selectivity, cobalt catalysts comprising manganese, nickel, chromium, copper or zinc salts with cobalt salts are used, which have not eliminated the above mentioned drawbacks.

The process for preparing adipic acid by air oxidizing cyclohexane in one step has been studied early. K. Publication of K. Tanaka (Chem. Tech. 4 (9), 1974 p555-559, Chem. Engg, news 52 (15), 1974 p24, preprints (Div Peter Chem) Amer. Chem. Soc. 19 ( 1), 534 and Japanese Patent Nos. 75-19,534) and publications of JGD schulz and A Onopchen (J Org. Chem. 38, 1973 p3729-3733, J Org. Chem. 45, 1980 p3716 -3719 and US Pat. No. 4,263,453 disclose a one step process using a cobalt catalyst. A recent US Pat. No. 4,902,827 to Steinmetz et al. Discloses the use of high concentrations of zirconium and hafnium salts with cobalt. U. S. Patent No. 3,649, 689 discloses a method of air oxidizing cyclohexane to adipic acid using a catalyst comprising a cobalt carboxylate and a bromine compound.

In the earlier attempts to oxidize cyclohexane in one step to produce adipic acid, the main focus was on the use of cobalt catalysts and low oxidation temperatures in the range of 80-130 ° C.

Tanaka also discloses a process for converting cobalt divalent directly into a catalytically active covar trivalent state in situ using a promoter such as acetaldehyde, 2-butanone, cyclohexanone and the like. These promoters are continuously injected into the reactor to maintain catalyst activity.

The disadvantages known so far for the one step process for preparing adipic acid are as follows.

1. The adipic acid formed is low in purity because a high proportion of cobalt (II) salt initially forms caprolactone which polymerizes rapidly into polycaprolactone.

2. Use of rare metals such as hafnium, zirconium and the like as a catalyst is expensive and complicated to monitor the concentration of the metal.

3. In order to use bromide as a catalyst, reactors and other devices need to be made of a strong corrosion resistant material, which adds cost to the process.

The main objects of the present invention are as follows;

1.oxidize hydrocarbons such as cyclohexane, cyclopentane, cycloheptane, toluene, o-xylene, m-xylene and p-xylene to the corresponding carboxylic acids by air or oxygen, with product selectivity greater than 70% and from 60 to It is to provide a useful catalyst that has a hydrocarbon conversion of 98%.

2. To provide a process for preparing the catalyst from a mixture of the corresponding cobalt (II) salt and iron (II) salt.

3. A catalyst comprising 70 to 99% by weight of cobalt (III) salt and 1 to 30% by weight of iron (III) salt, wherein the acid component of the salt is acetate, propionate, naphthenate, adipate, phthalate, or the like. In preparing carboxylic acids by oxidizing suitable hydrocarbons with air or oxygen, there is provided an improved process having a hydrocarbon conversion of 60 to 98% and a carboxylic acid selectivity of more than 70%.

4. To provide an improved process for the preparation of dicarboxylic acids in which formation of undesirable by-products such as lactones, oxygen acids and the like is substantially reduced or eliminated.

Accordingly, the present invention comprises 70 to 99% by weight cobalt (III) salt and 1 to 30% by weight iron (III) salt, wherein the acid component of the salt is selected from acetate, propionate, naphthenate, adipate or phthalate Characterized in that it provides a catalyst that is useful for the oxidation of hydrocarbons to produce carboxylic acids.

The present invention also corresponds to 0.25-8 hours at a temperature of 60-150 ° C., a pressure of 1-50 kg / cm 2, in the presence of an initiator, a solvent selected from aliphatic monocarboxylic acids having 2 to 4 carbon atoms or mixtures thereof and oxygen or air. It provides a process for preparing a catalyst useful for oxidizing hydrocarbons to produce carboxylic acids, comprising reacting a mixture of 70 to 99 weight percent cobalt (III) salt and 1 to 30 weight percent of the corresponding iron (III) salt.

The acid component of the cobalt (III) salt and iron (II) salt can be selected from acetates, propionates, naphthenates, benzoates, adipates, phthalates and the like. The amount of the salt of cobalt (II) is preferably 85 to 99% by weight, and the amount of the iron (II) salt is 1 to 15% by weight. The initiator may be selected from 2-butanone, paraaldehyde, cyclohexanone, cyclohexanol, acetaldehyde, partially oxidized hydrocarbons or mixtures thereof. The amount of initiator used is 10 to 100% by weight relative to the cobalt (II) salt. The solvent can be selected from acetic acid, propionic acid, butyric acid or mixtures thereof. The amount of initiator used is preferably 30 to 50% by weight relative to the cobalt (II) salt. The solvent used is preferably 2,000 to 12,000% by weight based on the cobalt (II) salt.

The reaction can be carried out with oxygen or air at any space velocity, with a preferred rate of 30 to 60 h ⁻¹ . The temperature used is preferably in the range of 80 to 130 ° C. The pressure is preferably in the range of 1 to 10 kg / cm 2. The contact time with air or oxygen is preferably 0.25 to 3 hours.

According to another object of the present invention,

(a) 70 to 99% by weight cobalt (III) salt and 1 to 30% by weight iron (III) salt, wherein the acid component of the salt is selected from acetate, propionate, naphthenate, adipate or phthalate Contacting the catalyst with a hydrocarbon;

(b) contacting the mixture obtained in the step with oxygen or air at a space velocity of 1 to 200 h ⁻¹ for 1 to 8 hours at a pressure of 1 to 70 kg / cm 2 and a temperature of 60 to 150 ° C .;

(c) separating the unreacted hydrocarbon and the catalyst, usually by a method;

(d) separating the formed carboxylic acid by crystallization or fractional distillation; And

(e) If desired, an improved process for preparing carboxylic acids by oxidizing hydrocarbons with oxygen or air, comprising recycling hydrocarbons, solvents and catalysts in steps (b)-(c).

According to a preferred embodiment of the present invention, the ratio of the catalyst to the hydrocarbon is 0.01 to 0.5% by weight, the pressure is 10 to 50kg / ㎠, the temperature is 70 to 150 ℃, the space velocity 1 to 60h ^-1 .

According to a feature of the invention,

(a) contacting cyclohexane with the catalyst;

(b) contacting the mixture obtained in the step with oxygen or air at a space velocity of 1 to 200 h ⁻¹ for 1 to 8 hours at a pressure of 1 to 70 kg / cm 2 and a temperature of 70 to 150 ° C .;

(c) separating unreacted cyclohexane and the catalyst by conventional methods;

(d) separating the formed adipic acid by crystallization or fractional distillation; And

(e) If desired, an improved process for the preparation of adipic acid is provided which comprises recycling unreacted cyclohexane, solvent and catalyst from steps (b)-(c).

As described above, according to experiments for oxidizing hydrocarbons such as cyclohexane, cycloheptane, cyclopentane, toluene and xylene, the catalyst of the present invention oxidizes 70 to 79% when oxidizing cycloparaffin, toluene and xylene It was found that the carboxylic acid production selectivity of 94 to 98% and hydrocarbon conversion of 80 to 90%. Product selectivity with the catalysts disclosed above was found to be 2-4% higher than the maximum achieved with catalysts known to date. After separation of the acid product, unreacted hydrocarbons, partially oxidized hydrocarbons and solvents can be recycled to recover the acid further to increase process efficiency.

The examples set forth below are for illustrative purposes only and are not intended to limit the scope of the invention.

Examples 1-3 disclose a process for preparing the catalyst of the present invention.

Example 1

A solution of 18 g of cobalt (II) acetate (Co (OCOCH ₃ ) ₂ .4H ₂ O), ₂ g of iron (II) acetate, and 3 g of cyclohexanone dissolved in 500 g of acetic acid was heated to 95 ° C., and cobalt (III) ions and Oxygen treatment was performed for 1 hour at a space velocity of 20 h ⁻¹ until the sum of iron (III) ions totaled about 85% of the total metal ions. At this stage, the various ion concentrations (relative to total metal salts) of the catalyst prepared as above were as follows; 79% cobalt (III) acetate, 11% cobalt (II) acetate, 6% iron (III) acetate, 4% iron (II) acetate.

Example 2

17 g of cobalt (II) naphthenate, 3 g of iron (II) naphthenate and 3.5 g of 2-butanone dissolved in 400 g of acetic acid were heated to 100 ° C., and oxygen was stirred for 2 hours under a pressure of 20 kg / cm 2. Treated with. After this period about 89% of the total iron (II) ions and cobalt (II) ions in the prepared catalyst were converted to higher oxidation states. At this time, the total ion weight percentage of the prepared catalyst is as follows: cobalt (III) 79%, cobalt (II) 6%, iron (III) 13% and iron (II) 2%.

Example 3

A solution of 16 g of cobalt (II) adipate, 4 g of iron (II) adipate, and 6 g of paraaldehyde in 150 g of acetic acid was heated to 120 ° C. and treated with oxygen for 4 hours under a pressure of 10 kg / cm 2. After this treatment period, 90% of the total iron (II) ions and cobalt (II) ions were converted to higher oxidation states. The composition of the prepared catalyst is as follows with respect to the weight of the total ions; 75 wt% cobalt (III), 5 wt% cobalt (II), 15 wt% iron (III) and 5 wt% iron (II).

The catalyst prepared as in the above example oxidizes hydrocarbons such as cyclohexane, cyclopentane, cycloheptane, toluene, C ₄ -C ₆ paraffin, o-xylene, m-xylene, p-xylene, adipic acid, It can be used to prepare the corresponding dicarboxylic or monocarboxylic acids such as glutaric acid, pimelic acid, benzoic acid, acetic acid, isophthalic acid, phthalic acid, terephthalic acid and the like.

Example 4

165 g of the catalyst mixture obtained from Example 1 and 35 g of cyclohexane were reacted with oxygen at a space velocity of ²⁵ h ^{−1 at} a temperature of 95 ° C. and 20 kg / cm 2 in a 500 ml autoclave.

After 3 hours of reaction, the reaction mixture was flash distilled to yield 80 g of material comprising 8.7 g of unreacted cyclohexane, 10.2 g of water and 6.1 g of acetic acid. The residue was cooled to 25 ° C. to give 24.0 g of 95% adipic acid crude crystals, and 9.6 g of adipic acid with partial fractions such as cyclohexanone, cyclohexanol, cyclohexyl acetate, monocyclohexyl adipate, etc. A filtrate containing 12.1 g of oxidized product and a lower dicarboxylic acid which can be recycled and 105 g of acetic acid washing were obtained. Cyclohexane conversion was 75.1% and total selectivity to adipic acid was 71%.

Example 5

35 g of cyclohexane and 165 g of the catalyst mixture obtained from Example 2 were oxidized to oxygen at a space velocity of 20 ⁻¹ under the condition of 110 ° C., 30 kg / cm 2. After 2 hours of reaction, the reaction mixture was flash distilled to give 100 g of a material containing 10.5 g of cyclohexane, 10.1 g of water and 79.4 g of acetic acid.

The residue was cooled and filtered to give 25.3 g of 98.5% adipic acid crude crystals. The filtrate contained 11.9 g of adipic acid, the cyclohexane conversion was 82%, and the total selectivity to adipic acid was 73.8%.

Example 6

A solution of 5.0 g of cobalt (II) acetate tetrahydrate, 0.5 g of iron (II) acetate and 2 g of cyclohexanone dissolved in 160 g of glacial acetic acid was contacted with oxygen for 2 hours at a rate of 100 ml / min with stirring at 95 ° C. At this time, about 90% of the cobalt (II) salt and iron (II) salt were converted into cobalt (III) salt and iron (III) salt. Then, 35 g of cyclohexane was added and reacted with oxygen at a space velocity of ²⁵ h ⁻¹ at 95 ° C. and 49 kg / cm 2. After 4 hours reaction, the product was distilled to remove unreacted cyclohexane, water and some adipic acid. The residue was cooled and filtered to give 23.8 g of 98.5% adipic acid. The filtrate contained 9.1 g of adipic acid. Cyclohexane conversion was 71% and selectivity to adipic acid was 76.8%.

Example 7

175 g of the catalyst mixture obtained from Example 3 and 35 g of cyclohexane were oxygenated at a rate of 50 ml / min for 6 hours at 100 ° C., 30 kg / cm 2. Overall selectivity to adipic acid was 74.5% and cyclohexane conversion was 80%.

Although the examples are specifically described for the production of adipic acid only, the present invention should not be construed as limited to the production of adipic acid only. The process of the present invention is also useful for the preparation of dicarboxylic acids such as glutaric acid, pimelic acid, phthalic acid, isophthalic acid and tefephthalic acid and monocarboxylic acids such as acetic acid, propionic acid and benzoic acid. This is illustrated in the examples below.

Example 8

130 g of a catalyst comprising 40 g of p-xylene and 80% by weight cobalt (III) acetate, 10% by weight iron (III) acetate, 8% by weight cobalt (II) acetate and 2% by weight iron (II) acetate It was reacted with oxygen at a space velocity of 30 h ⁻¹ for 4 hours at 10 kg / cm 2. The oxide was flash evaporated to give 30.0 g of distillate comprising 4.0 g of unreacted p-xylene, 8.2 g of water and the remaining acetic acid. The residue was cooled and filtered, the solid was dissolved in acetic acid and dried to give 51.9 g of crude terphthalic acid of 98% corresponding to 90% p-xylene conversion. The solution was recycled to obtain 53.5 g of terephthalic acid, corresponding to 95% selectivity to terephthalic acid.

Example 9

6 g of a catalyst comprising 40 g of m-xylene and 85% by weight of cobalt (III) acetate, 8% by weight of iron (III) acetate, 5% by weight of cobalt (II) acetate and 2% by weight of iron (II) acetate and 200g of acetic acid. The solution was reacted with oxygen at a space velocity of ²⁵ h ⁻¹ at 135 ° C. and 20 kg / cm 2. Flash evaporation of the oxide yielded 18.5 g of distillate consisting of 3.5 g of unreacted m-xylene, 8.5 g of water and 6.5 g of acetic acid. After the residue was cooled to room temperature, it was filtered, the solid was dissolved in acetic acid and dried to give 53.4 g of 98% isophthalic acid corresponding to 93.5% selectivity based on the reacted m-xylene (conversion 91.2%). The filtrate was recycled and the selectivity to isophthalic acid was 97%.

Example 10

5.0 g of catalyst and 150 g of acetic acid comprising 30 g of cyclocrotane and 80% by weight cobalt (III) acetate, 12% by weight iron (III) acetate, 6% by weight cobalt (II) acetate and 2% by weight iron (II) acetate The containing solution was reacted with air at 95 ° C. and 45 kg / cm 2 for 4 hours at a space velocity of 60 h ⁻¹ . The obtained oxide was flash distilled to obtain 50 g of a distillate consisting of 4 g of unreacted cyclopentane, 10 g of water and 36 g of acetic acid. The residue contained 34.3 g of glutaric acid, corresponding to 86% cyclopentane conversion and 71% selectivity to glutaric acid.

Example 11

500 g of an acetic acid solution containing 500 g of acetic acid solution containing 4.0 g consisting of 85% by weight of cobalt (III) acetate, 8% by weight of iron (III) acetate, 5% by weight of cobalt (II) acetate and 2% by weight of iron (II) acetate and 50g of toluene It was reacted with oxygen at a space velocity of 40 h ⁻¹ for 4 hours at ° C. 61.7 g of benzoic acid, 2.1 g of benzaldehyde and 1.0 g of unreacted toluene were obtained from the oxidation product. This corresponds to 98% hydrocarbon conversion, 95% selectivity to benzoic acid, and more than 4% selectivity to benzaldehyde.

Claims (10)

A catalyst useful for oxidizing hydrocarbons to produce carboxylic acids, comprising 70 to 99% by weight cobalt (III) salt and 1 to 30% by weight iron (III) salt. The catalyst of claim 1 wherein the acid component of the salt is selected from acetate, propionate, naphthenate, adipate or phthalate. Cobalt (II) for a period of 0.25-8 hours at a temperature of 60-150 ° C., a pressure of 1-50 kg / cm 2 in the presence of an initiator, a solvent selected from aliphatic monocarboxylic acids having 2 to 4 carbon atoms or mixtures thereof and oxygen or air. A process for the preparation of a catalyst useful in the preparation of carboxylic acids via oxidation of hydrocarbons, comprising reacting a mixture of 70 to 99% by weight salt and 1 to 30% by weight iron (II) salt. The method of claim 3, wherein the reaction occurs at a space velocity in the range of 10 to 90 h ⁻¹ . The amount of the cobalt (II) salt is 80 to 99 weight, the amount of the iron (II) salt is 1 to 20% by weight, the amount of the initiator is 10 to 100% by weight based on the weight of the cobalt (II) salt, The amount of the solvent is 2,000 to 12,000% by weight relative to the weight of the cobalt (II) salt, the space velocity is 30 to 60h ^-1 , the temperature is 80 to 150 ℃, the pressure is 1 to 25kg / ㎠ and the period is 0.5 To 3 hours. 4. The process of claim 3 wherein the initiator is 2-butanone, cyclohexanol, cyclohexanone, acetaldehyde, partially oxidized hydrocarbon or mixtures thereof. 4. The process of claim 3 wherein said solvent is acetic acid, propionic acid, butyric acid or mixtures thereof. (a) 70 to 99% by weight cobalt (III) salt and 1 to 30% by weight iron (III) salt, wherein the acid component of the salt is selected from acetate, propionate, naphthenate, adipate or phthalate Contacting the catalyst with a hydrocarbon; (b) the mixture obtained in the step of contacting with oxygen or air at a space velocity of 1 to 200 h ⁻¹ for a period of 1 to 8 hours at a temperature of 60 to 150 ° C. and a pressure of 1 to 70 kg / cm 2; (c) separating unreacted hydrocarbons and catalyst by conventional methods; (d) separating the formed carboxylic acid by crystallization or fractional distillation; And (e) if necessary, recycling the recovered hydrocarbons, the solvent and the catalyst in steps (b)-(c), to oxidize the hydrocarbons with oxygen or air to produce carboxylic acids. The method of claim 8, wherein the ratio of the catalyst to the hydrocarbon is 0.01 to 0.5% by weight, the pressure is 10 to 50kg / ㎠, the temperature is 70 to 150 ℃ and the space velocity is 10 to 90h ^-1 How to. (a) 70 to 99% by weight cobalt (III) salt and 1 to 30% by weight iron (III) salt, wherein the acid component of the salt is a catalyst selected from acetate, propionate, naphate, adipate or phthalate Contacting to cyclohexane; (b) contacting the mixture obtained in the step with oxygen or air at a temperature of 70 to 150 ° C. at a pressure of 1 to 70 kg / cm 2 at a space velocity of 1 to 200 h ⁻¹ for 1 to 8 hours; (c) separating unreacted cyclohexane and the catalyst by conventional methods; (d) separating the formed adipic acid by crystallization or fractional distillation; And (e) if necessary, oxidizing cyclohexane using a catalyst, comprising the step of recycling unreacted cyclohexane, the solvent and the catalyst in steps (b)-(c) to produce adipic acid. How to.