CS213974B1 - A method for decobaltizing hydroformylation products of unsaturated compounds - Google Patents

Abstract

The present invention relates to the technology of petrochemical processes. The process according to the invention consists in treating the products of hydroformylation of unsaturated compounds containing cobalt carbonyls with gas at elevated temperature and then removing the cobalt salts. The gas used is CO2, or a gas containing CO2, in an amount of 1 to 50 mol CO2 per 1 mol CO and the process is carried out at temperatures of 20 to 220 °C, preferably 40 to 140 °C, under pressures of 0.1 to 0.4 MPa. The cobalt salt formed is removed by any of the usual methods, for example by filtration, degassing or evaporation of the aldehyde-containing product.

Description

The invention relates to a method for decobaltization of products of hydroformylation of unsaturated compounds in the field of petrochemical synthesis.

The products of hydroformylation of unsaturated compounds, namely aldehydes, alkanols and other oxygen-containing compounds, have wide application in many areas of economy and technology. The main part of these products is currently required for the production of plasticizers, flotation, foaming and dissolving agents.

Hydroformylation of unsaturated compounds takes place at elevated temperature under the pressure of synthesis gas CO + H ₂ in the presence of a cobalt catalyst (cobalt carbonyl). The hydroformylation product contains oxygen-containing final compounds, hydroformylation by-products, organic solvent, unreacted unsaturated starting compounds, as well as cobalt carbonyl. The cobalt catalyst must be separated from the hydroformylation products and returned to the hydroformylation cycle, since it is necessary to ensure the purity of the isolated final product and, moreover, this is important for reasons of economy. Decobaltization of hydroformylation products determines the technology of oxosynthesis, and the consumption of cobalt compounds is evaluated as the main value characterizing the technical state of the process.

During decobaltization, cobalt carbonyls are separated from the hydroformylation products either in the form of thermally unstable carbonyls or as non-carbonyl cobalt compounds, and the cobalt-free hydroformylation products are converted into alkanols or condensed aldehydes, depending on the application.

The main requirements for decobaltization are complete recovery of the catalyst, as well as suppression of side reactions, such as oxidation, condensation and esterification of the final products of hydroformylation (aldehydes, alkanols and oxygen-containing compounds).

Incomplete separation of the cobalt catalyst can lead to contamination of the hydroformylation products with colored compounds, as well as to cobalt deposits on the reaction equipment and piping, which causes difficulties in the process and requires additional production steps.

There are known methods for decobaltization of hydroformylation products of olefins to obtain the carbonyl form of the catalyst. For example, when a strongly basic medium is applied to solutions of cobalt carbonyls in the presence of CO and H ₂ , under pressure and at elevated temperature, a cobalt carbonyl salt is formed, which is soluble in water and insoluble in organic media. The salt is then treated with a 5% sulfuric acid solution at atmospheric pressure. The hydrocarbon obtained is treated with a solvent or is carried by synthesis gas, absorbed by the olefin and fed to the reactor (FR patent specification 1,223,381, 1960} US patent specification 3,763,247, 1968} GB patent specification 1,228,348).

Such a method is complicated with respect to technological equipment and is related to the use of wastewater containing mineral salts.

There are known methods for the thermal decomposition of cobalt carbonyls, according to which the hydroformylation catalyst decomposes at elevated temperature to cobalt powder (SU patent specification 247 247, 1965} 246 633, 1965). Various embodiments of these methods have the following disadvantages: difficulties in preventing cobalt from settling on the walls of the equipment; difficulties in separating cobalt from the final products; the need to conduct the process discontinuously, i.e. in an unmodern manner; shortening of the equipment life due to erosion.

There are also known methods of decobaltization, which consist in the action of mineral acids or strong organochemical acids on the products of hydroformylation. (V.M. Gavrilova and J., Chlmchelskaya Promyshlenost, 1974, No. 10, p. 19). According to the method described in DE patent document 977 576, the product of hydroformylation is washed with a 1 to 10% acid solution at a temperature of 65 to 65 ° C and at atmospheric pressure. The mixture of aldehyde and aqueous phases containing cobalt is separated in the settling zone. Aqueous solutions of cobalt salt are converted into cobalt forms suitable for introduction into the hydroformylation reactor.

Technically, this method places high demands on the material of the hydroformylation and decobaltization equipment, because the acids are corrosive, additional process steps are required, and moreover, this method is associated with wastewater pollution.

There are known methods of decobaltization by the action of oxidizing acids, which rely on the rapid conversion of cobalt carbonyls in the salt in the presence of an oxygen source (air, 0 ₂ , Η ₂ θ2' ^Peroxld ^)·

The direct action of the oxygen-containing gas on the hydroformylation product facilitates the conversion of the cobalt dissolved in it into the cationic form. Acids that serve as a source of anions are supplied separately or are released during the production of catalytically active forms of cobalt from C0(00CR) ₂ . The oxidation process is carried out at a temperature of 20 to 60 °C under a pressure of 0.1 to 4.0 MPa, the oxidation time is several seconds to 60 minutes. The amount of oxidizing agent is over 1 mol of active oxygen per mol of cobalt. The cobalt salts formed, as well as the acids, are separated from the product according to one of the methods listed below:

separation in the form of an aqueous solution, filtration of the precipitate, separation of the oil-soluble cobalt salts in the form of a muddy product by distillation, selective extraction of the cobalt salt with a low-boiling solvent (see for example Patent No. 1,377,920, 1964, DE Patent No.

272,911, 1966; SU Patent File 169 103, 1961, Organio Syntheses via Metal Carbonyls, v.l., N.Y.-London-Sydney, 1968, ed. J. Wender,

P. Full).

When oxygen acts on cobalt carbonyls, the oxidation of aldehydes to acids occurs, as well as the formation of esters from alkanols and the acids formed or introduced. An increase in the acid and ester concentrations in the hydroformylation products leads to a decrease in the yields of the final product, making it difficult to separate the aldehydes or alkanols from the mixture containing acids, which have a boiling point close to the boiling point of the aldehydes or alkanols. In addition, increased requirements are placed on the hydrogenation catalyst with regard to resistance to acids.

The amount of by-products depends on the excess of oxygen per mole of cobalt, on the cobalt content, on the process temperature, as well as on the structure and molecular weight of the aldehyde*

Furthermore, a method is known (SU patent document 169 103) in which the product of hydroformylation of oleyls is treated with oxygen at 20 to 80 °C in the presence of naphthenic acids. In this process, cobalt carbonyls are converted into a thermostable, oil-soluble form of cobalt naphthenate, from which aldehydes, solvent and a portion of the by-products are distilled off. The residue after distillation contains cobalt naphthenate and is returned to the main circulation.

The disadvantage of the method lies in the formation of acids from oxoaldehydes. For example (KA Alekseeva in the collection Production of butyraldehydes and butyl alcohols Polyohsmle maslyanyh aldehydes 1 butlloryoh splrtov, 1977, Tl pp. 76 to 85, Leningrad, VNIINEFTECHIM) when oxidizing the product of catalytic hydroformylation of propylene, which contains 0.2 wt. 4 Co and 70 wt. <f> butylaldehyde (at a content of 0 ₂ 2 mol per mol of Co and a temperature of 60 ° C), 0.5 to 1.5 wt. i is oxidized relative to butyraldehyde, and when oxidizing the same from catalytic hydroformylation of dodeoene under the same conditions, 1.5 to 5.0 wt.

The increase in the concentration of acids corresponding to the aldehyde in the hydroformylate product reduces the advantages of oxidative methods of decobaltization and forces preference to more complicated methods that ensure less formation of by-products.

The invention aims to obtain a highly valuable final product under mild conditions and by changing technological parameters by selecting a reaction participant for the decomposition of cobalt carbonyls contained in the products of hydroformylation of olefins and to simplify the technology of the method by limiting the formation of by-products (acids) and by eliminating operations for their separation.

This problem is solved by the fact that, according to the method according to the invention, the decobaltization of hydroformylation products of unsaturated compounds is carried out by decomposition of the catalyst and, when treated with gas with subsequent removal of cobalt salts, according to the invention, C0 ₂ or a gas containing C0 ₂ is used as the gas, in an amount of 1 to 50 mol C0 ₂ per 1 mol Co, at temperatures of 20 to 220 °C, under pressures of 0.1 to 0.4 MPa.

It is advisable to carry out the procedure at temperatures not exceeding 140 °C, because at higher temperatures and insufficient mixing, cobalt carbonyls may decompose, and not at temperatures below 40 °C, because at lower temperatures the oxidation rate decreases and the volume of the reaction apparatus increases.

The cobalt salt obtained is generally removed from the aldehyde-containing product by methods known per se, for example by filtration, decantation or evaporation.

The method according to the invention is carried out as follows.

The product of the catalytic hydroformylation of unsaturated compounds containing cobalt carbonyls, end products in the form of aldehydes and alkanols _{, by} -products of _the hydroformylation reaction, as well as a solvent (organic solvent or high _- boiling reaction products), is introduced into a reactor to decompose the cobalt carbonyls and is treated with C0 ₂ or a gas containing C0 ₂ in an amount of 1 to 50 mol, in particular 2 to 10 mol C0 ₂ per 1 mol CO at a pressure of 0.06 to 0.5 MPa, preferably 0.1 to 0.4 MPa, at a temperature of 20 to 220 °C, preferably 40 to 140 °C. The cobalt salt is then separated from the hydroformylation product in a conventional manner, for example by filtration, decantation or evaporation.

Cobalt carbonyls are decomposed by carbon dioxide under the conditions of the invention. In doing so, cobalt is converted into one of the carbonate forms, or, when the process is carried out in the presence of a mineral or organic acid, the cobalt salt of the respective acid:

what ₂

CO ₂ (CO)g -r 2 COCO ₃ + 8 CO co ₂ (co) _e τ _C0 ( _HC00 ) + e co + h,o RCOOH *

The reaction takes place, unlike known methods, without the usual oxidizing agents (oxygen, air, H ₂ 0 ₂ ) and at low temperatures. Carbon dioxide is an oxidizing agent whose oxidizing properties are not as strong as those of oxygen, but are sufficient to remove C0 ₂ (CO)g from the reaction products of hydroformylation of olefins. The conditions for the action of C0 ₂ on cobalt carboxylates assume a significant excess of C0 ₂ (compared to 0 ₂ ), as well as additional, but still acceptable for industrial implementation, contact times of the reactants. These conditions are balanced by the fact that reactions in which acids are formed from the corresponding aldehydes do not occur.

The use of pure carbon dioxide or carbon dioxide in the form of gases containing it for the decomposition of cobalt carbonyls turned out to be unexpected, because the oxoacids used according to the literature for the decomposition of cobalt carbonyls have a higher dissociation constant (from 10 to 10), while the dissociation constant of carbonic acid is 4.3 . 10, i.e. 2 orders of magnitude lower and react with cobalt carbonyls at temperatures of 80 to 160 °C, carbon dioxide, under the same conditions, reacts at lower temperatures.

The process according to the invention leads to a simplification of the hydroformylation of olefins, since it is possible to use the waste gases from the decobaltization step, which contain CO, Hg, C0 ₂ and olefin, especially in the case of using gaseous olefins, directly in the hydroformylation step without purification and recovery. In the oxidation of cobalt carbonyls with air, the waste gases, which contain CO, Hg, C0 ₂ , O ₂ , N ₂ and olefins, for example propylene or ethylene, are either combusted or, after purification, regenerated from O ₂ and N ₂ , since O ₂ destroys the hydroformylation and Ng represents an easy ballast.

Reducing the acidity of the environment reduces the requirements for the corrosion resistance of the reaction equipment and improves the technological properties and distillation parameters of the final products and by-products of hydroformylation of olefins, since the proportion of acids formed from aldehydes either converts into esters (with the participation of final alkanols) or forms difficult-to-separate azeotropes.

The method according to the invention is applicable to any hydroformylation process of hydroformylation of olefins, in which cobalt carbonyls are separated, such as acrylic acid, but its use instead of oxidative decobaltization in hydroformylation processes of higher olefins (with a molecular weight of over 60), as well as branched chain olefins and polyfunctional unsaturated compounds is particularly advantageous, since the use of lower temperatures and higher concentrations of cobalt catalyst in this process ensures a high rate of hydroformylation and the necessary qualitative composition of the catalysts. Oxidative decobaltization of products from catalytic hydroformylation of olefins with a high molecular weight or products with an increased concentration of cobalt catalyst using O ₂ increases the formation of acids from 0.5 to 1% to 5 to 104, based on the theoretically calculated amount of the final aldehyde.

Similar to cobalt carbonyls, solutions that do not contain any oxygen-containing compounds can be converted into cobalt salts by the action of C0 _{2 .}

For a better understanding of the method according to the invention, the following specific examples are given.

Example 1

The product of ethylene hydroformylation containing 65.0 g of propionaldehyde, 30 g of organic solvent, 7 g of hydroformylation by-products and 0.15 g of cobalt carbonyl (calculated as Co) is treated in a three-necked glass flask equipped with a stirring device, a reflux condenser and a device for the release of gaseous products, with 0.6 l of carbon dioxide (10 mol COg per mol Cf) at 40 °C for 90 minutes. The treated product is filtered off from cobalt salts, which are returned to the hydroformylation process. The product of ethylene hydroformylation freed from cobalt salts and containing 64.8 g of propionaldehyde and not more than 0.0015 wt. 4 Co, is added to further treatment, for example, to hydrogenation. Aldehyde losses do not exceed 0.3 4.

Example 2

The product of propylene hydroformylation, containing 45 g of butyric acid aldehyde and butyl alcohols, 55 g of organic solvent and hydroformylation by-products and 0.20 g of Co ₂ (CO)g (calculated as Co), is treated with 0.3 l of carbon dioxide (3.7 mol C0 ₂ per 1 mol Co) at 90 °C for 25 minutes. The apparatus is analogous to that in Example 1. The cobalt compounds are filtered off and the product of propylene hydroformylation containing 44.8 g of butyric acid aldehyde and butyl alcohol and not more than 0.002 wt. % CO is distilled to separate the aldehyde. The aldehyde losses do not exceed 0.2%.

Example 3

The amount and composition of the product of propylene hydroformylation are as in Example 2.

The product of the hydroformylation of propylene is treated in a pressure vessel at a pressure of 0.2 MPa with a gas mixture of 20% air and 80% CC ₂ (1.3 mol C0 ₂ per 1 mol Co). The content of cobalt compounds in the hydroformylation product does not exceed 0.002 wt.

% Co and aldehyde loss is not over 0.4

Example 4

The product of butylene hydroformylation, which contains 60 g of valeric acid aldehyde, 40 g of solvent and reaction by-products, 1.5 g of naphthenic acids, 0.12 g of cobalt carbonyls (calculated as Co), is treated with 0.8 liters of carbon dioxide (16.7 mol COg per 1 mol Co) in a pressure vessel with stirring at a temperature of 70 °C for 30 minutes. The desired aldehydes and solvent are distilled off from the product of catalytic butylene hydroformylation free of cobalt carbonyls. The residue, which contains 0.12 g of sparingly soluble cobalt salts, is fed to the hydroformylation stage and the separated aldehydes in an amount of 59.7 g are fed to the processing.

The distillation product does not contain any cobalt compounds. The aldehyde loss does not exceed 0.5 Example 5

The product of the catalytic hydroformylation of n-decene, which contains 50 g of undecylaldehydes, 45 g of fatty and unsaturated hydrocarbons, by-products and 0.13 g of cobalt carbonyls (calculated as Co), is treated with 0.4 l of carbon dioxide (7.85 mol COg per 1 mol Co) at a temperature of 60 °C and a pressure of 0.2 MPa and the precipitated cobalt salts are filtered off. The hydroformylation product, which does not contain any cobalt carbonyls (Co content 0.001 wt. %), is hydrogenated in the presence of catalysts. The product of the catalytic hydrogenation contains 49 g of undecylalkanols. The loss of the final product with respect to hydrogenation is not more than 2 °k.

Example 6

The product of hydroformylation of n-tridecene, which contains 86 g of tetradeoylaldehyde, 13 g of by-products and unreacted aldehyde and 0.15 g of cobalt carbonyls (calculated as Co) is treated with 1 liter of C0 ₂ at 40 °C for 90 minutes. The apparatus is as in Example 1. The degree of decomposition of the cobalt carbonyls is here over 99 # (cobalt content in the product below 0.0008 wt. %). The loss of aldehyde in the decobaltization stages is not over 1

Example 7

The product from the catalytic hydroformylation of acrylonitrile, which contains 30 g of beta cyanopropanal, 67 g of toluene, 2 g of by-products and 0.12 g _{of cobalt} carbonyls (calculated as Co) is treated at 50 °C for 10 minutes with a gas mixture consisting of 10% _H2O , 40% Ng and 50% CO (25 mol CO per 1 mol Co). The precipitated cobalt compounds (0.115 g Co) are decanted and filtered off. The aldehyde freed from cobalt compounds and containing 0.005 wt. % Co is distilled off and hydrogenated. The loss of aldehyde in the decobaltization stages is not more than 2%.

Example 8

The butylene hydroformylation product, which contains 60 g of valeraldehyde, 40 g of solvent and reaction by-products, 1.5 g of naphthenic acids and 0.12 g of cobalt carbonyls (calculated as Co), is treated at 20°C with 2.4 liters of CO (50 mol CO per 1 mol Co). The apparatus is as in Example 4. The degree of decomposition of the cobalt carbonyls is over 99%. The hydroformylation product, which contains 60 g of valeraldehyde and does not contain any cobalt, is sent for processing after distillation. The residue containing 0.12 g of cobalt naphthenate (calculated as Co) is returned to the hydroformylation process. No loss of aldehyde was observed.

Example 9

The product of the catalytic hydroformylation of n-deoene, which contains 50 g of undecylenic aldehyde, 45 g of hydrocarbons and by-products, as well as 0.13 g of cobalt carbonyls (calculated as Co), is treated with 2 mol of COg per 1 mol of Co at 140°C, under a pressure of 0.4 MPa, for 5 minutes. The apparatus is as in Example 5. The degree of decomposition of cobalt carbonyls is 100%. The loss of aldehyde does not exceed 1%.

Example 10 ' The product of propylene hydroformylation, which contains 45 g of butyraldehyde and butyl alcohols, 55 g of solvent and by-products of the hydroformylation reaction, as well as 0.20 g of Cog(CO)g ( _after gf _{is known as Co} ) _{is treated at} a pressure of _0.3 MPa and a temperature of 90 °C with a gas mixture of 30% argon and 70% COg (1 mol COg per 1 mol Co). The apparatus is as in Example 2. The degree of decomposition of cobalt carbonyls is over 99%. The cobalt compounds are filtered off and the product of propylene hydroformylation, which contains 44.8 g of butyraldehyde and butyl alcohols and not over 0.002 wt. % Co, is distilled in order to separate the aldehydes. The losses of aldehydes and alkanols are not over 0.45

Example 11

A 300 g solution of cobalt carbonyls in pentadiene, containing 0.1 g of Co, is treated with COg (2 mol COg per 1 mol Co) in a pressure vessel at a temperature of 220 °C and a pressure of 0.2 MPa. After filtering off insoluble cobalt compounds, it does not contain more than 0.001 g of Co.

Claims (2)

1. A process for decobaltizing hydroformylated products of unsaturated compounds by decomposing the catalyst with gas and subsequently removing cobalt salts, characterized in that carbon dioxide or gas is used as the gas. No. 213974 8 containing carbon dioxide, in an amount of 1 to 50 moles of COg per 1 mol of cobalt and decobalt, is carried out at temperatures of 20 to 220 ° C at a pressure of from 1 to 0.4 MPa. 2. The process according to claim 1, wherein the decobaltification is carried out at a temperature of 40 to 140 [deg.] C.