RU2424224C2 - Method for introduction and reclamation of cobalt during hydroformylation of propylene - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention discloses introduction of cobalt in form of a cobalt salt solution into a process for hydroformylation of propylene performed in the presence of a cobalt catalyst, where the said cobalt salt solution is specifically cobalt butyrate dissolved in a high-boiling azeotropic mixture of dimethyl acetamide (DMA) and dimethyl formamide (DMF) in butyric acid. Regeneration of a catalyst which is a mixture of cobalt butyrate and the azeotropic mixture of DMA and DMF with butyric acid is performed by treating the still residue after distillation of the end products with water, followed by stripping off the obtained aqueous extract and returning the stripped off residue to the hydroformylation step.

EFFECT: simple hydroformylation process.

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Description

The invention relates to the field of organic synthesis, namely to the production of isomeric oil aldehydes from propylene and synthesis gas by the method of oxosynthesis by the hydroformylation reaction. Applied to propylene:

In addition to the main reaction, the corresponding butyl alcohols, as well as the products of the secondary conversion of aldehydes and alcohols: esters, acetals, dimers, aldehyde condensation products, and other secondary, mainly high-boiling compounds, are obtained with appreciable yield by hydrogenation of aldehydes.

In most industrial plants, propylene hydroformylation is carried out at a temperature of 120-150 ° C and pressure up to 30 MPa in the presence of a cobalt hydrocarbonyl catalyst, the concentration of which in the reaction zone is 0.1-0.4 wt.% In terms of metallic cobalt.

Technical and economic indicators of the process are largely determined by the method of introducing cobalt into the process, its regeneration and return to the process.

The technology of introducing cobalt and its regeneration according to the acid-evaporation scheme, according to which cobalt is introduced into the process in the form of oil-soluble salts of organic acids (2-ethylhexanoic, naphthenic and the like), dissolved in a high boiling organic solvent, for example, in a bottoms obtained during distillation from the reaction mass of the target products (ed. St. USSR No. 178814, No. 245759, No. 372199, No. 403665, No. 858913).

At the stage of carbonylation, under the influence of synthesis gas at a temperature of 130-180 ° C and a pressure of up to 30 MPa, 2-ethylhexanoic acid is reduced, and cobalt in the composition of the catalytic complex HCo (CO) ₄ - cobalt hydrocarbonyl acquires zero valency. From the carbonylation step, the resulting product mixture, to which propylene is added, enters the aldehyde synthesis step. Then, the catalysis from the stage of synthesis of aldehydes enters the oxidative decobaltization reactor, in which oil aldehydes (mainly n-butyric) are oxidized with the formation of superbutyric acid. Subbutyric acid, interacting with cobalt hydrocarbonyl, leads to its decay. In this case, cobalt passes into the composition of cobalt butyrate, again acquiring a valency of +2. Then, as a result of the exchange reaction of cobalt butyrate with 2-ethylhexanoic acid, cobalt passes into cobalt 2-ethylhexanate, which dissolves well in the product mixture. Since this reaction is reversible, excess 2-ethylhexanoic acid is added to the reactor to ensure its completeness.

However, cobalt butyrate, which is hardly soluble in it, is precipitated in the product mixture. In addition to cobalt butyrate, sediment called cobalt sludge also contains other, unidentified forms of cobalt compounds.

During air bubbling, cobalt sludge, which is in the micro-suspension state in the oxidative decobaltization reactor, is removed from the reactor, and then, as a result of coagulation of the micro-suspension particles, the sludge is deposited in the equipment along the path of its further movement, which especially affects the operation of the unit for the synthesis products separation, hindering the normal operation of the equipment . This necessitates regular stops for washing and cleaning equipment from sludge, which reduces production productivity. Sludge discharged (usually manually) from the system is usually sent to specialized plants for the recovery of cobalt from it using a multi-stage, costly technology.

A known method of regeneration of cobalt from cobalt-containing sludge obtained in the process of hydroformylation of olefins. The sludge discharged from the equipment is processed in a separate installation by dissolving it in 2-ethylhexanoic acid (RF patent for application No. 2007120357/04, decision to grant a patent dated 04.02.2009). The sludge is treated in an apparatus equipped with a stirrer and heating elements with stirring and at a temperature of at least 190 ° C for at least 4 hours. In this case, the sludge decomposes with the formation of a solution of cobalt 2-ethylhexanate in 2-ethylhexanoic acid. The resulting solution is recycled to the process.

However, this method of cobalt regeneration does not eliminate the need for regular production shutdowns for the time-consuming operation of cleaning equipment from sludge deposits. In addition, the process technology is complicated by the introduction of cobalt recovery from sludge into the circuit.

A known method of introducing cobalt into the hydroformylation process in the form of an oil-soluble salt of 2-ethylhexanoic acid in the bottom residue obtained after distillation of the target products from hydroformylation products. VAT residue is treated with an aqueous solution of acetic acid. Obtained as a result of the exchange reaction, cobalt acetate dissolved in water is sent to the reactor column, where 2-ethylhexanoic acid and a high boiling solvent are also fed. Water and acetic acid released as a result of the exchange reaction are discharged from the reactor as a distillate, and cobalt 2-ethyl hesanate in a high-boiling solvent is sent to the carbonylation stage (V. A. Rybakov, A. L. Elkin and others. “Oxosynthesis and related processes with participation of carbon monoxide. ”Publishing House CJSC Sibur-Khimprom, Perm, 2004, p. 32, 37-44).

The disadvantages of this method of introducing and regenerating cobalt in the process are:

a) the complexity of the technology due to repeated transformations of cobalt according to the schemes: 2-cobalt ethyl hexanate → cobalt bicarbonyl → cobalt 2-ethyl hexanate (through the intermediate formation of cobalt butyrate) → cobalt acetate → cobalt 2-ethyl hexanate;

b) the loss of expensive cobalt and 2-ethylhexanoic acid due to incomplete equilibrium reactions for the conversion of cobalt hydrocarbonyl to 2-ethylhexanoic acid and cobalt 2-ethylhexanate to cobalt acetate.

In order to simplify the technology and reduce the cost of the propylene hydroformylation process, it is proposed that cobalt be introduced into the process in the form of cobalt butyrate in a solution of an azeotropic mixture of lower dimethyl amides, namely N, N-dimethylformamide (DMF) and N, N-dimethylacetamide (DMAA) with n-oil acid. At the same time, we found that butyric acid and the above amides form azeotropic mixtures with a negative deviation from Raoult law, i.e. with a maximum boiling point and absolutely miscible with water. So, the solvent is an azeotropic mixture of butyric acid (boiling point 163.5 ° C) and DMF (boiling point 153.0 ° C) in the pressure range 755-765 mm Hg has a boiling point of 174.8-175.6 C and contains in its composition 35.6 vol.% DMF and 64.4 vol.% butyric acid.

The solvent is an azeotropic mixture of butyric acid and DMAA (boiling point 165.5 ° C) in the pressure range 755-765 mm Hg. - has a boiling point of 183.4-184.2 ° C and contains 51.8 vol.% DMAA and 48.2 vol.% butyric acid in its composition.

The presence of the proposed solvents in the reaction zone in amounts that ensure the dissolution of catalytic doses of cobalt does not impair the performance of the process both at the carbonylation stage and at the hydroformylation stage. At the same time, at a temperature of 170 ° C, corresponding to the boiling point of the bottom residue when the aldehyde-alcohol fraction is separated from the product mixture after the oxidative decobaltization stage and the processing time of 10-20 minutes, the cobalt sludge at the solvent: sludge ratio corresponding to the material balance completely dissolves in both solvents, and, as a result of the destruction of the sludge, the cobalt in its composition is converted into cobalt butyrate. Thus, by directing the products of oxidative decobaltization to the aldehyde-alcohol fraction distillation apparatus, in which one of our solvents will be present, a homogeneous mixture consisting of high boiling point by-products of synthesis, solvent and cobalt butyrate is obtained in the bottom distillation residue. High-boiling synthesis by-products are practically insoluble in water; therefore, the solvent, like cobalt butyrate, is easily separated from the bottom residue upon extraction with water. In the subsequent evaporation of the aqueous extract, the distilled water is reused, and the dehydrated solution of cobalt butyrate in the solvent used is recycled to the carbonylation stage.

When using the proposed method for the introduction and regeneration of cobalt

- technology of the hydroformylation process is greatly simplified, since cobalt circulation is carried out according to the scheme: cobalt butyrate ⇒ cobalt hydrocarbonyl ⇒ cobalt butyrate;

- excluded the use in the process of expensive 2-ethylhexanoic acid and acetic acid and, accordingly, their losses;

- time-consuming operation to clean the equipment from cobalt sludge and stop production on its implementation are excluded from the process;

- reduced cobalt losses.

A significant difference of the proposed method for introducing cobalt into the process of hydroformylation of propylene and its regeneration is the introduction of cobalt in the form of butyrate dissolved in a mixed solvent, which is a high boiling azeotropic mixture of lower acid dimethyl amides, namely N, N-dimethylformamide or N, N-dimethylacetamide, s butyric acid, and the regeneration of cobalt from the obtained products after hydroformylation is carried out by aqueous extraction from the bottom residue after distillation of the target products Ukta with subsequent evaporation of the obtained extract and return to the process at the stage of hydroformylation of the residue from the residue containing cobalt butyrate and solvent.

The industrial applicability of the proposed method is confirmed by the following examples.

Example 1

23.1 g of a solution containing 5.7 g of cobalt butyrate and 15.6 g of an azeotropic mixture of DMAA with butyric acid was charged into a temperature-controlled autoclave. The solution is heated to a temperature of 170 ° C, after which synthesis gas is introduced into the autoclave. The carbonylation process is carried out at a pressure of 25-30 MPa, after which the temperature is reduced to 125-145 ° C and 420 g of propylene are introduced into the autoclave, continuing to supply synthesis gas until the pressure in the system and in the autoclave is equalized. Propylene solvents are hydroformylation products. The contents of the reactor are cooled to a temperature of 50 ° C, depressurized and transferred to a distillation flask equipped with a bubbler. Air is passed through the bubbler for 20-30 minutes, regulating its supply by controlling the temperature in the flask, which should not exceed 50 ° C. At the same time, cobalt carbonyls are practically absent in the reaction products, and pink-violet slurry is observed on the walls of the flask. After that, the distillate is distilled off from the contents of the flask to a temperature in the liquid of 170 ° C. The result is 661 g of distillate (aldehyde-alcohol fraction) and 80.3 g of bottoms, and there are no sludge deposits on the walls of the flask. Cube residue cooled to a temperature of 40-50 ° C is poured into a separatory funnel and 80.3 g of water is added to it. After vigorous stirring and subsequent settling, 58.6 g of an almost solvent-free oil layer is unloaded from the separatory funnel (less than 0 , 01%) and cobalt (less than 1 mg / l), as well as 102 g of the aqueous layer.

After evaporation of the aqueous layer, 80.5 g of an aqueous distillate containing 0.2 g of butyric acid were obtained, and in the residue, almost the entire initial solution of cobalt butyrate was used for subsequent use.

Example 2

4.8 g of cobalt butyrate and 13 g of an azeotropic mixture of DMF with butyric acid are charged into the autoclave. The process of carbonylation and hydroformylation of propylene is carried out under the conditions of example 1. In this case, 350 g of propylene mixed with 54 g of high-boiling synthesis by-products used to dissolve the propylene were reacted. The cooled hydroformylation products are transferred to a distillation flask.

In the distillation flask, as in example 1, the operations of oxidative decobaltization of the products of hydroformylation and distillation of the aldehyde-alcohol fraction are carried out.

The result is 552 g of distillate and 105 g of bottoms. 54 g are separated from the bottom residue for subsequent use in the hydroformylation process, and the remaining 51 g are transferred to a separatory funnel.

51 g of water is added to the separatory funnel, and after intensive mixing and subsequent settling, 38.4 g of the oil layer are obtained — high-boiling synthesis products that are practically free of cobalt and solvent, as well as 64.4 g of the water layer.

As a result of the evaporation of the aqueous layer, 46.6 g of an aqueous distillate containing 0.14 g of butyric acid are obtained, and the residue is a solution of cobalt butyrate in an azeotropic mixture of DMF and butyric acid in an amount of 17.8 g, which is used for repeated use.

Claims (1)

The method of introducing and regenerating cobalt in the process of hydroformylation of propylene in the form of a solution of cobalt salt of an organic acid in a high boiling solvent, its regeneration by distillation (rectification) of target products from reaction products, followed by processing of the bottom residue to transfer the obtained cobalt compound to its original form, characterized in that cobalt is introduced into the hydroformylation process in the form of cobalt butyrate dissolved in a high boiling azeotropic mixture of N, N-dimethyl-formamide or N, N-dimethyl-acetate bromide with butyric acid, and cobalt recovery is carried out together with the solvent from the distillation residue after distillation of the desired products obtained by the hydroformylation extraction residue with water followed uparkoy obtained extract product and returning after uparki containing cobalt butyrate and a solvent to the hydroformylation.