CS244780B1 - Process for the preparation of C 1-4 aldehydes by hydroformylation of propylene - Google Patents

Abstract

A method for producing C^ aldehydes by hydroformylation of propylene under the catalytic action of cobalt carbonyls, in which fractions boiling at most in the range of 75 to 130 °C, preferably 80 to 110 °C, are separated from the hydrolyzed distillation residue, and the distillate is returned to the crude hydroformulation product that has not yet been treated by distillation. The total yield of aldehydes is increased and the amount of heavy portions from the hydroformulation is reduced.

Description

The invention relates to a method for producing aldehydes by hydroformylation of propylene under the catalytic action of cobalt carbonyls with subsequent distillation of the product and processing of the distillation residue after deethylation of aldehydes and solvent by acid hydrolysis, distillation and recycling of the distillate into the hydroformylation product.

It is generally known that during the hydroformylation of alkenes under the catalytic action of cobalt carbonyls, a relatively significant amount of high-boiling components is formed by subsequent conversions of the desired products, i.e. aldehydes with a chain one carbon longer than the starting alkene. During the distillation treatment of the hydroformylation product, in which the isomeric aldehydes and the solvent are gradually distilled off, a mixture containing predominantly high-boiling components remains as a distillation residue. The amount of this distillation residue, usually referred to as heavy fractions from hydroformylation, is variable, most often around 10% based on the aldehydes produced.

Heavy fractions from hydroformylation contain a number of compounds from which aldehydes or alcohols can be chemically released. These compounds are primarily acetals, then esters, or ethers. Effective methods for the decomposition of these compounds are hydrolysis or hydrogenation.

In the past, several processes have been developed to increase the yield of valuable products such as aldehydes and alcohols, using acidic hydrolysis of heavy fractions from hydroformylation.

244,780

According to US Patent 3,247·260 ee, heavy fractions from propylene hydroformylation are hydrolyzed with dilute sulfuric acid, followed by alkaline hydrolysis with simultaneous steam stripping. The product obtained contains mainly aldehydes and alcohols, 2-ethyl-2-hexenal,

2-ethylhexanal and 2-ethylhexenol. The individual components can be obtained from this product by rectification. French patent 1,420,640 describes a similar process.

The processes known so far represent complex, investment- and energy-intensive, although relatively comprehensive, methods of utilizing heavy fractions from hydroformylation, the implementation of which can be advantageous only when a large amount of heavy fractions is available, i.e. only in conjunction with large-capacity hydroformylation units.

The above disadvantages are eliminated by the process according to the present invention. The method of producing aldehydes by hydroformylation of propylene at elevated temperature, elevated pressure and catalytic action of cobalt carbonyls, decobaltization of the crude hydroformylation product, gradual distillation of aldehydes and solvent from the crude product and subsequent hydrolysis of the distillation residue using dilute mineral acid at elevated temperature, consists in separating from the hydrolyzed distillation residue a fraction boiling from the beginning of the boiling of the mixture to the maximum boiling temperature, which is in the range of 75 to 130°C, preferably 80 to 110°C, and the distillate is returned to the crude hydroformylation product that has not yet been processed by distillation.

The advantage of the process according to the invention is the improvement of the yield of the desired aldehydes in the hydroformylation of propylene without high energy requirements and simplicity of implementation with maximum utilization of standard equipment commonly used in hydroformylation. The economic advantage of the process according to the invention is not limited by production capacity, so that application in smaller hydroformylation units is possible and advantageous.

The essence of the invention is the discovery that a fraction containing mainly aldehydes and

- 3,244,780 higher-boiling components, which are mainly butyl acetals of butanal and 2-methylpropanal, while the distillation can be carried out in such a way that the distillate contains only a small amount of alcohols. This can be achieved by distilling off the fraction boiling up to a maximum of 120°C, but most preferably up to 110°C. The distillate is added to the crude product before or more preferably after decobaltization with hydrophoric acid, which is then processed by distillation in a standard manner, i.e. by gradually distilling off 2-methylpropanal, butanal and solvent. At the end of this gradual distillation, heavy fractions remain as a residue, which again proceed to processing by acid hydrolysis, distillation, etc. The aldehydes contained in the distillate from the distillation of the hydrolyzed heavy fractions increase the total yield of aldehydes, the acetals present accumulate in the distillation residue

- heavy fractions and in the next cycle of acid hydrolysis they are again partially converted into aldehydes.

The following examples serve to illustrate the process of the present invention.

Example 1

400 ml of heavy fractions from the hydroformylation of propylene (the distillation residue after distilling off the aldehydes and the toluene solvent) were stirred for 30 min with 300 ml of 10% HNO^ at a temperature of 60°C in a flask equipped with a reflux condenser. Then the mixture was separated into aqueous and organic phases. The organic phase was distilled on a laboratory distillation apparatus using a packed column (packing

- wire spirals with a diameter of 4 mm) 0.5 m long at a reflux ratio of 1:5. The mixture began to distill at a temperature at the top of the column of 60°C. Two distillation fractions were separated: a fraction with a boiling point up to 110°C and a fraction with a boiling point in the range of 110 to 120°C.

Distillation balance:

1st fraction (up to 110°C) 2nd fraction (110 to 120°C) 79.0g 48.6g the rest 185.8 grams total 313.4 grams mass of the starting mixture .315.5 grams losses 2.1 grams

- 4 Analyses of distillation fractions (chromatographic)

1·fraction 2nd faction the rest heavy fractions before hydrolysate 2-methylpropanal 6.2 0.2 0.2 0.3 butanal 29.3 0.7 1.0 0.4 2-methylpropanol 5.2 9.6 0.6 0.4 butanol 2.0 75.8 1.8 0.9 C ₁₂ acetals 16.5 15.3 to bear to carry

The β fraction, boiling at up to 110 ^° C, contains mainly aldehydes and a significant amount of acetals. The fraction can be added (recirculated) to the crude hydroformylation product and then distilled in a standard manner to obtain pure aldehydes, with practically all acetals remaining in the distillation residue. The distillation residue after gradual distillation of aldehydes and solvents contains less than 1% by weight of aldehydes. The increase in the yield of aldehydes is determined by the amount of the circulated distillation fraction.

Example 2

300 ml of heavy fractions from the hydroformylation of propylene were stirred with 300 ml of 7% at 65°C for 45 min in the same manner as in Example 1. The mixture was then separated into organic and aqueous phases, the organic phase was analyzed and distilled using the same laboratory column as in Example 1 at a reflux ratio of 1:10. The fraction boiling up to 80°C _and the fraction boiling in the range of 0 to 110°C were separated.

Distillation balance:

default (hydrolyzed) heavy fractions 526.6 1st faction (up to 80°C) 49.1 2nd faction (80 to 110°C) 61.0 the rest 414.1

- 5 Distillation fraction analyses: 244,780

Hydrolyz. heavy parts 1st faction 2· faction 2-methylpropanal 2.0 19.4 — butanal 9.1 71.2 3.7 2-methylpropanol 3.4 - 7.5 butanol 9.9 - 4.3 acetals 16.2 - 42.3

Fractions 1 and 2 are added to the crude hydroformylation product, from which the pure aldehydes and solvent are separated by efficient three-stage distillation, with the scetals being concentrated in the residue.

Claims (1)

Process for producing aldehydes by hydroformylating propylene at elevated temperature, elevated pressure and catalytic action of cobalt carbonyl, decobaltizing the crude hydroformylation product, gradually distilling off aldehydes and solvent from the crude product, followed by hydrolyzing the distillation residue with dilute mineral acid at elevated temperature. the distillation residue separates the boiling fractions from the start of the boiling of the mixture to a maximum boiling point which is in the range of 75 to 130 ° C, preferably 80 to 110 ° C, the distillate being returned to the still untreated crude hydrdformylation product.