CS209761B1 - A method for producing 2-ethylhexanol - Google Patents

Abstract

The invention falls within the field of petrochemical synthesis. The method for producing 2-ethylhexanol according to the invention consists in obtaining 2-ethylhexanol by catalytic hydrogenation of 2-ethylhexenal at an elevated temperature of 200 to 290 °C and at an elevated pressure of 10 to 30 MPa in the presence of a catalyst containing zinc and chromium, which additionally contains copper oxide. The weight ratio of copper oxide : zinc oxide : copper oxide is (12.3 to 54) : (11.0 to 52.2) : (6 to 23.2).

Description

The invention relates to a process for producing 2-ethylhexanol by hydrogenation of 2-ethylhexenal.

2-Ethylhexanol is widely used as a solvent for natural and synthetic resins, as a component for additives to fuels and oils, ester lubricants and emulsifiers, flotation and extraction agents. The processing of 2-ethylhexanol into esters, especially phthalates, which are used as plasticizers for vinyl polymers, especially for polyvinyl chloride, is particularly advantageous. Plasticizers based on 2-ethylhexanol are advantageously characterized by a number of valuable properties compared to other plasticizers. They have a slight solubility in water, stability at elevated temperatures, frost resistance, good color stability, and resistance to aging.

A method of producing 2-ethylhexanol by hydrogenation of 2-ethylhexenal over a silver-chromium catalyst is known (GB patent specification No. 1,097,819) at a temperature of 165°C and a pressure of 10 MPa.

The process proceeds with a high degree of conversion and with high selectivity. However, the catalyst is particularly unstable and the presence of minor impurities in 2-ethylhexenal, such as acids, water, traces of cobalt and traces of iron, leads to the cell being disrupted or to a rapid loss of activity. In addition, the space velocity of the feedstock does not exceed 0.2 h ^-1 .

A method of producing 2-ethylhexanol by condensation of n-butyraldehyde in the presence of alkali and subsequent rectification of the condensate and hydrogenation of the obtained 2-ethylhexenal on a copper-nickel-chromium catalyst at a temperature of 150 to 170 °C, at atmospheric pressure is also known (GB patent specification no. 1 244 442). The addition of nickel to the copper-chromium catalyst makes it possible to obtain 2-ethylhexanol, which is almost free of unsaturated compounds. The space velocity (0.18 h”1) and stability to the effect of harmful impurities, however, remain at the level of the copper-chromium catalyst.

The hydrogenation of 2-ethylhexenal over a catalyst containing a small amount of silica at a temperature of 125°C, a pressure of 3 to 5 MPa and a space velocity of 0.3 h ^-1 is described (GB Patent No. 1,219,038). However, the yield of the final product, 2-ethylhexanol, does not exceed 80% due to the low degree of conversion of the 2-ethylhexenal used.

A process for hydrogenating 2-ethylhexenal over a catalyst containing manganese on diatomaceous earth at a temperature of 160° C. is known (FR Patent No. 2,058,532). This catalyst is also characterized by a low space velocity and low stability to the action of acids, water, traces of cobalt and iron.

2-Ethylhexenal obtained by condensation of pure n-butyraldehyde in the presence of alkali and subsequent rectification of the condensate contains practically none of the aforementioned harmful impurities and can be hydrogenated to 2-ethylhexanol on the aforementioned copper-containing catalysts without reducing their activity and stability.

However, the raw material base for the synthesis of 2-ethylhexanol has now been considerably expanded. New methods have also been proposed for the production of 2-ethylhexenal from n-butyraldehyde synthesized by oxosynthesis without prior separation of n-butyraldehyde from the hydroformylation product, for example, using cobalt salts circulated in the oxosynthesis process as condensation catalysts (USSR Patent No. 258,296; USSR Patent No. 559,547).

When carrying out the process in this way, a fraction of dimer products is separated from the condensation catalyst, which, in addition to 2-ethylhexenal, contains admixtures of butyric acids, water, esters and other secondary products of the process, admixtures of cobalt and iron. The above-mentioned catalysts are not suitable for the hydrogenation of such products.

A significant disadvantage of such catalysts is also the low space velocity of the feedstock (0.2 to 0.3 h-1).

A method of synthesizing 2-ethylhexanol by condensation on cobalt salts of n-butyraldehyde, obtained by oxosynthesis and subsequent two-stage hydrogenation of the condensate obtained in this process is also known (USSR copyright certificate No. 406,823). . .

Hydrogenation is carried out in the first stage in the presence of a catalyst containing zinc and chromium, for example AlZnCr, at a temperature of 280 to 290 °C, at a pressure of 30 MPa and in the second stage in the presence of a catalyst containing copper or nickel at a temperature of 180 °C and a pressure of 25 to 30 MPa. The use of a catalyst containing zinc and chromium allows an increase in the space velocity to 1.5 to 2 h'1. In addition, the catalyst containing zinc and chromium is not susceptible to poisoning by acids, cobalt and iron impurities and has high mechanical strength.,

Admixtures of hydroformylation by-products (butyric acids, esters, acetals) are not harmful to the zinc-chromium catalyst, but are hydrogenated from 70 to 90% to valuable products, butyl alcohols, which have separate uses, which significantly improves the technical and economic values of the 2-ethylhexanol synthesis process. The selectivity of the process is 96 to 98%.

The mentioned process has a number of advantages over hydrogenation processes on copper and nickel catalysts. High selectivity (96 to 98%) can be achieved on this catalyst system only if a diluted feedstock with a 2-ethylhexenal concentration of no more than 40 to 50 weight percent is used.

When the concentration of 2-ethylhexenal is increased to 70 to 90%, the selectivity of the process decreases to 86 to 88% due to the formation of hydrocarbons.

In addition, the double bonds in the raw material are not hydrogenated on the zinc-chromium catalyst, and therefore it is necessary to carry out a second stage of hydrogenation using a catalyst containing nickel or copper.

Therefore, when carrying out the process on a large industrial scale, it is necessary to provide two reactors with internal heat removal devices, since a considerable amount of heat is generated in both the first and second hydrogenation stages.

For the hydrogenation of pure 2-ethylhexenal or a fraction of dimeric products, it was necessary to choose a catalyst that would ensure a high yield of 2-ethylhexanol using a sufficiently concentrated raw material with a high space velocity and would allow the hydrogenation of the aldehyde group and the double bond in 2-ethylhexenal in one step while maintaining the activity in terms of selective hydrogenation of hydroformylation by-products to valuable butyl alcohols.

The purpose of the invention is to increase the yield of the final product and simplify the process technology.

The invention aims to increase the yield of the final product and simplify the process technology in the hydrogenation process of pure 2-ethylhexenal or a fraction of dimeric products by developing a new modification of the catalyst.

The aforementioned problem is solved in such a way that in the process for producing 2-ethylhexanol, hydrogenation of 2-ethylhexenal or a product containing 2-ethylhexenal, at an elevated temperature in the presence of a catalyst containing zinc and chromium and separation of the final product from the hydrogenation product, according to the invention, the catalyst containing zinc and chromium additionally contains copper oxide at a weight ratio of copper oxide : zinc oxide : copper oxide (12.3 to 54) : (11.0 to 52.2) :

: (6 to 23.2) on the carrier and the process is carried out at a temperature of 200 to 290 °C and a pressure of tO to 30 MPa.'

Catalytic hydrogenation is expediently carried out at temperatures of 230 to 270 °C, since at temperatures below 230 °C a decrease in the degree of conversion and selectivity of the process is observed due to the ongoing side reactions of aldehyde condensation, which lead to the formation of a bubble-like product. At temperatures higher than 270 °C a decrease in selectivity is observed due to the cleavage reactions of the unsaturated aldehyde, which lead to the formation of hydrocarbons.

Increasing the hydrogen pressure from atmospheric to 10 MPa increases the degree of conversion of aldehydes, esters, acetals, acids and unsaturated compounds. A further increase in pressure from 10 to 30 MPa increases the degree of hydrogenation only of unsaturated compounds and does not affect the degree of conversion of the other named groups. Therefore, if it is important to obtain 2-ethylhexanol with a very high degree of purity in terms of the content of unsaturated compounds, the process is carried out expediently at pressures of approximately 30 MPa.

The starting product used according to the invention is either pure 2-ethylhexenal or products containing 2-ethylhexenal, such as condensation products of the propylene hydroformylation catalyst, the fraction of dimer products separated from the propylene hydroformylation catalyst and, in addition to 2-ethylhexenal, contains butyl butyrates, butyric acids, butyric aldehydes and butyl alcohols.

Catalysts of the following composition are used as catalysts.

Table 1

Catalyst Sample No. Copper oxide Cu ₂ O ₃ Content (in weight percent) Zinc Oxide ZnO Chromium oxide Cr ₂ O ₃ 1 12.3 ± 1.5 52.2 ±2 23.2 + 1.5 2 19.8 + 2 40.6+2 18.5 + 1.0 3 54 ±3 11.5 + 1.5 14 ± 1.5 4 38 ±.1.5 30.5 ± 1.5 7 ± 1

Copper-zinc-chromium catalysts have never been used for the hydrogenation of aldehydes, especially unsaturated aldehydes. It has been shown that the use of catalysts containing copper, zinc and chromium in the proportions given in the table allows obtaining 2-ethylhexanol in a yield of 96 to 97%, regardless of the composition of the starting material. The process is carried out at a temperature of 200 to 290 °C, at a hydrogen pressure of 10 to 30 MPa, at a space velocity of the feed material of 1.5 to 3 h ^- '. In this case, the acids contained in the starting material are hydrogenated to 85 to 95%, esters to 80 to 90%, and acetals to 80 to 90%. 2-ethylhexanol, the quality of which is at world level, is separated from the hydrogenated product obtained by conventional rectification. Practically complete (over 95%) hydrogenation of double bonds allows the process to be carried out in a single reactor with a heat removal device, which greatly simplifies the technological scheme.

The concentration of 2-ethylhexenal in the raw material for the catalyst according to the invention is almost twice as high as for the aluminum-zinc-chromium catalyst, whereby the overall space-time yield, based on 2-ethylhexanol, increases considerably.

The yield of butyl alcohols by hydrogenation of by-products is not less than in the case of the aluminum-zinc-chromium catalyst. The catalyst maintains its activity and selectivity for a time sufficient for implementation on a large technical scale.

Therefore, the addition of copper to the zinc-chromium catalyst leads to the formation of a qualitatively new structure that combines the advantages of the mercury catalysts, namely the hydrogenation of double bonds and a high yield of the final product, and the catalysts containing zinc and chromium, namely stability, high space velocity, hydrogenation of by-products. Such an increase in the efficiency of the zinc-chromium catalyst after the addition of copper oxide is very surprising, since it is known that mercury catalysts are unstable to the effect of hydroformylation by-products and quickly lose their activity. In addition, the optimal hydrogenation temperature on mercury catalysts of 150 to 170 ° C is low for the hydrogenation of hydroformylation by-products, namely acids, esters, acetals. However, increasing the temperature to 230 to 270 ° C, which is optimal for the hydrogenation of by-products, leads to complete decomposition of the mercury catalyst.

The process according to the invention is illustrated by the following description of the embodiment with reference to the accompanying drawing, in which a technological scheme of the principle is shown. Fig. 1 shows a technological scheme of the hydrogenation of 2-ethylhexenal, which represents a process for the production of 2-ethylhexanol.

Hydrogenation is carried out in a continuous, circulating, high-pressure device with a reactor volume of 0.5 l (Fig. 1). The reactor is made in the form of a tube 1,000 mm high and 25 mm in diameter, which is equipped with two-part electric heating. A recess for a thermocouple is located in the upper lid of the reactor. The temperature is measured at four points according to the height of the catalyst layer. Samples of the copper-zinc-iron catalyst (the composition is given in Table 1) are introduced in the form of tablets 5 x 5 mm in size. Before starting operation, the catalyst is activated in a stream of hydrogen at an elevated temperature.

The raw material is fed from tank J_ to the upper part of reactor i by a liquid pump. Hydrogen is fed from tank 2 to the upper part of reactor i. In reactor i, hydrogenation of 2-ethylhexenal and hydroformylation by-products occurs at a temperature of 200 to 290 °C and a hydrogen pressure of 20 to 30 MPa. The chemistry of the hydrogenation process can be illustrated by the following scheme:

1. Hydrogenation of 2-ethylhexenal to an unsaturated alcohol with simultaneous isomerization of the double bond according to chain length

CH ₃ -(CH 2 ) 2 -CH=C -CH 2 -OH c ₂ h ₅ .

CH ₃ -(CH ₂ )2-CH=C -ď + h ₂ -*ch ₃ -ch ₂ -ch=ch-ch -ch ₂ -oh I \ \ I

C2H5 Η \ C ₂ H ₅

OH ₃ -CH=CH-CH ₂ -CH-CH2-OH

2-ethylhexenol c ₂ h ₅ isomeric octenols

This very interesting fact of isomerization of unsaturated alcohol was first discovered by us during the hydrogenation test of 2-ethylhexenal on an aluminum-zinc-chromium catalyst and was also confirmed for the catalyst according to the invention.

2. Hydrogenation of isomeric octenols to 2-ethylhexanol:

isomeric octenols + H ₂ ->CH ₃ -(CH ₂ ) ₃ -^H-CH2OH c ₂ h ₅

2-ethylhexanol

3. Isomerization of an unsaturated alcohol to a saturated aldehyde:

c ₂ h ₅ ch ₃ -(ch ₂ ) ₂ -ch=c-ch ₂ oh;

=*CH ₃ -( CH ₂ ) ₃ -CH-<\^ c ₂ h ₅

2-ethylhexen-2-ol-1

2-ethylhexanal

4. Hydrogenation of 2-ethylhexanal to 2-ethylhexanol c ₂ h ₅

CH ₃ -(CH ₂ ) 3 -CH-C<^ + H ₂ —K!H 3 -(CH ₂ ) 3 -CH-CH ₂ OH .

IH c ₂ h ₅

2-ethylhexanal . 2-ethylhexanol

5. Side reactions of the cleavage of unsaturated aldehyde into hydrocarbons:

CH ₃ -(CH ₂ ) ₂ -CH=CC^ ->CH 3 -(CH ₂ ) ₂ -CH=CH-CH 2 »CH 3 + GO

I H »

_{C2H5 ​}

2-ethylhexenal heptene-(3).

6, Hydrogenation of butyric acids to butyl alcohols:

y°

CH ₃ -(CH ₂ ) ₂ -C^ _h + 2H ₂ ->-CH ₃ -(CH ₂ ) ₂ -CH ₂ 0H + H ₂ 0 n-butyric acid n-butanol

CH ₃ -GH(CH ₃ )-C^^ + 2H ₂ —>-CH ₃ -CH(CH ₃ )-CH ₂ OH + H ₂ 0 isobutyric acid isobutanol

7. Hydrogenation of butyl esters to butyric acids:

a) CH ₃ -(CH ₂ ) ₂ -1-O(CH ₂ ) ₃ -CH ₃ + 2H ₂ ->2CH ₃ -(CH ₂ ) ₂ -CH ₂ OH n-butyl butyrate n-butanol

b)

c) ch ₃ -(ch ₂ ) ₂ -$-o-ch ₂ -ch -ch ₃ + 2H ₂ —>CH ₃ -(CH ₂ ) ₂ -CH ₂ OH ch ₃ isobutyl butyrate n-butanol + CH ₃ -CH(CH ₃ )-CH ₂ OH isobutanol

About CH ₃

II I

CH ₃ -CH(CH ₃ )-CO-CH ₂ -CH-CH3 + 2H ₂ -»-2CH3-CH(CH ₃ )-CH ₂ OH isobutylisobutyral isobutanol

8. Hydrogenation of butyraldehyde and butyl alcohol acetals:

,^0C ₄ H9 ^c 4 ^h &L + H ₂ + H ₂ 0->3C ₄ H9OH

OG ₄ Hg iso- or n-butyl acetals of iso- or n-butanol iso- or n-butyrals

The reaction products and hydrogen enter the high-pressure separator 2 through the cooler 6, where the gas and liquid phases are separated. From the upper part of the high-pressure separator, the gas is returned by the gas pump 2 through the oil separator £, 10 to the upper part of the reactor. From the high-pressure separator ]_ the reaction products enter the low-pressure separator 8. Part of the gas is discharged from the high-pressure separator 2 through the gas meter 11 into the atmosphere in order to prevent the accumulation of inert impurities in the hydrogen being circulated.

Therefore, the method according to the invention provides, compared to the known method, an increase in the yield of the final product, 2-ethylhexanol, by approximately 10% by reducing the rate of formation of hydrocarbons and simplifying the technology by carrying out the process in one reactor with a device for removing heat instead of two-stage hydrogenation. In addition, in the method according to the invention, the energy consumption for heating the raw material decreases, since the optimal hydrogenation temperature on the copper-zinc-chromium catalyst is 230 to 270 ° C, which is 30 to 50 ° C lower than the optimal hydrogenation temperature on the aluminum-zinc-chromium catalyst.

For a better understanding of the nature of the invention, examples of specific embodiments are given below.

Example

Hydrogenation is carried out according to the scheme shown in Fig. 1. The raw material is the condensation product of n-butyraldehyde obtained by oxosynthesis in the presence of cobalt salt (4,550 g), which contains: 3,640 g of 2-ethylhexenal (80 wt. %); 332.2 g of 2-ethylhexanal (7.3 wt. %);

32.0 g of butyraldehyde and butanol acetals (0.7 wt. %); 68.3 g of butyl alcohols (1.5 wt. 515); 332.2 g of butyl butyrates (7.3 wt. %); 13.6 g of 2-ethylhexanol (0.3 wt. %); 68.3 g of butyric acids (1.5 wt. %; 22.8 g of water (0.5 wt. %); 40.1 g of unidentified products (0.9 wt. %). The product from the raw material tank 2 is fed by liquid pump 2 at a space velocity of 1.6 h ^- ' to the upper part of the reactor 2, not filled with a copper-zinc-chromium catalyst of the following composition: cuprous oxide (Cu2O3) 12.3 ± 1.5 wt. %, zinc oxide (ZnO) 52.2 ± 2.0 wt. %, chromium oxide (CrgO^) 23.2 ± 1.5 wt. %.

Hydrogen (fed into the circulation and fresh from tank 2) also enters the upper part of reactor 2 under a pressure of 20 MPa. The hydrogen feed rate is 2.5 m3/kg of raw material. The temperature in the reactor is maintained at 230 to 240 °C.

The reaction yields 4,690 g of hydrogenation, which contains 3,934.5 g of 2-ethylhexanol (83.8 wt. 515); 361 g of butanols (7.7 wt. 515); 42.2 g of 2-ethylhexanal (0.9 wt. 515); 6.1 g of water (1.3 wt. 515); 121.9 g of hydrocarbons (2.6 wt. 515); 46.9 g of butyl butyrates (1 wt. 0); 4.7 g of acetals (0.1 wt. %) and 121.9 g of other products (2.6 wt. %).

The degree of conversion of 2-ethylhexenal is over 99,515, the selectivity of the process is 97 S5. Rectification of the obtained hydrogenation product separates 3,820 g of 2-ethylhexynol, which contains 99.3% of the basic substance and 0.018% by weight of unsaturated compounds (for other values, see Table 2, Example 1) and 343 g of butyl alcohols.

The yield of 2-ethylhexanol obtained by rectification is 94,515, based on the reacted aldehyde.

Example 2

The process is carried out under the conditions described in Example 1 on a catalyst of the same composition, but at a hydrogen pressure of 23 MPa, at a space velocity of the feed of the raw material of 2 h-1. The product of the alkaline condensation of n-butyraldehyde of oxosynthesis in an amount of 3,900 g is used as the raw material, which contains 3,561 g of 2-ethylhexenal (91.3 wt. %); 4,2.9 g of butanols (1.1 wt. 515); 62.4 g of butyraldehydes (1.6 wt. 515); 198.9 g of high-boiling products (5.1 wt. 515); 35.1 g of water (0.9 wt. %).

Hydrogenation yields 3,970 g of hydrogenated product, which contains 3,474 g of 2-ethylhexanol.

-209761

4 ⁷ (87.5 wt. %); 166.7 g butanols (4.2 wt. %); 107.2 g high-boiling products (2.7 wt. %); 107.2 hydrocarbons (2.7 wt. %); 79.4 g water (2.0 wt. %); 35.7, g 2-ethylhexanal (0.9 wt. %).

The degree of conversion of 2-ethylhexenal is over 99% by weight, the selectivity is 97%. In one rectification of the hydrogenated product obtained, 2-ethylhexanol is separated, which contains 99.6% of the basic substance, 0.02% by weight of unsaturated compounds. For other values, see Table 2, Example 2.

The yield of 2-ethylhexanol separated by rectification is 94%, based on the reacted aldehyde.

Example 3

The process is carried out under the conditions described in Example 1, but using a copper-zinc-chromium catalyst of the following composition: copper oxide (CuO) 19.8 ± 2.0 wt. %; zinc oxide (ZnO) 40.6 ± 2.0 wt. %; chromium oxide (Cr203) 18.5 ± 1.0 wt. %, pressure 28 to 30 MPa, space velocity of feedstock 2.3 h ^- ', temperature 245 to 255 ° C and as the raw material is used a fraction of dimer products separated from the product of propylene hydroformylation, which has the following composition: butanols 5.3 wt. %, butyl butyrates 6.1 wt. %, 2-ethyl-4-methylpentenal 0.9 wt. %, 2-ethylhexanal 8.0 wt. %, 2-ethylhexenal 70.5 wt. %, 2-ethyl-4-methylpentanol 0.2 wt. %, 2-ethylhexanol 0.5 wt. %, butyric acid 3.5 wt. %, acetals of butyraldehydes and butyl alcohols 2.0 wt. %, unidentified products 2.7 wt. %, water 0.3 wt. %.

Hydrogenation yields a product of the following composition: butanols 12.8 wt. %, butyl butyrates 0.3 wt. %, 2-ethylhexanal 0.5 wt. %, 2-ethyl-4-methylpentenol 1.2 wt. %, octenols 0.3 wt. %, 2-ethylhexanol 76.1 wt. %, butyric acids 0.5 wt. %, aoetals 0.3 wt. %, unidentified products 4 wt. %, water 1.3 wt. %, hydrocarbons 2.7 wt. %.

The total degree of aldehyde conversion is 99.3%, the selectivity of 2-ethylhexanol formation is 97.5%. During the rectification of the hydrogenation, 2-ethylhexanol is separated, which contains 99% of the basic substance, 0.02 wt. % of unsaturated compounds (Table 2, Example 3).

Example

The process is carried out under the conditions described in Example 1, but using a copper-zinc-chromium catalyst consisting of 54 ± 3 wt. % copper oxide (CuO); 11.5 i 1.5 wt. % zinc oxide (ZnO); 14 ± 1.5 wt. % strontium oxide (Ο^Οβ), at a hydrogen pressure of 10 MPa, a temperature of 257 to 265 °C and a space velocity of the feedstock of 1.5 h ^- '. The fraction of dimer products, the composition of which is given in Example 3, is used as the feedstock.

Hydrogenation yields a product of the following composition: butanols 12.3 wt. %, butyl butyrates 0.7 wt. %, 2-ethylhexanal 0.6 wt. %, 2-ethyl-4-methylpentenal 0.2 wt. %, 2-ethylhexenal 0.1 wt. %, 2-ethyl-4-methylpentanol 1.0 wt. %, octenols 1.3 wt. %, 2-ethylhexanol 75.1 wt. %, butyric acids 0.8 wt. %, unidentified products 3.4 wt. %, hydrocarbons 2.7 wt. %, water 1.5 wt. %.

The degree of aldehyde conversion is 99%, the selectivity of 2-ethylhexanol formation is 95%.

2-Ethylhexanol separated by rectification of the hydrogenation contains 98.5 wt. % of the basic substance and 0.5 wt. % of unsaturated compounds. To reduce the amount of unsaturated compounds to the amount given by the standard, the hydrogenation is fed to a reactor filled with a nickel-on-diatomaceous earth catalyst.

The transhydrogenation is carried out at a temperature of 180 °C, a space velocity of 1 h ^-1 and a hydrogen pressure of 28 to 30 MPa. The hydrogenation yields 2-ethylhexanol, which contains 99% of the basic substance and 0.01 wt. % of unsaturated compounds (Table 2, Example 4). Carrying out the hydrogenation on a copper-zinc-chromium catalyst at a pressure of 10 MPa does not guarantee the necessary degree of hydrogenation of the double bond in 2-ethylhexenal. In this case, for the production of 2-ethylhexanol of the corresponding standard, it is necessary to add a second stage, transhydrogenation on catalysts containing copper or nickel.

Example 5

The process is carried out under the conditions described in Example 1 on a catalyst with the composition given in Example 1, but at a hydrogen pressure of 26 MPa, a temperature of 280 to 290 °C and a space velocity of the feedstock of 1.5 h1. A fraction of dimer products, the composition of which is given in Example 3, is used as the feedstock. The hydrogenation gives a product with the following composition: butanols 12.6 wt. %, butyl butyrates 0.5 wt. %, 2-ethylhexanal 0.5 wt. %, 2-ethyl-4-methylpentanol 1.2 wt. 56, 2-ethylhexanol 55.0 wt. 56, butyric acids 0.3 wt. 56, acetals 0.2 wt. %, unidentified products 6.4 wt. %, water 3.5 wt. 56, hydrocarbons 19.8 wt. 56.

The total degree of aldehyde conversion is 99.5%, the selectivity of 2-ethylhexanol formation is 70%. During the rectification of the hydrogenation, 2-ethylhexanol is separated in a yield of 96% with a content of basic substance of 99% and unsaturated compounds of 0.01% by weight (see Table 2, Example 6).

As can be seen from the above example, increasing the temperature to 280 to 290°C leads to a large increase in the side reaction of the degradation of 2-ethylhexenal to hydrocarbons, which has a disadvantageous effect on the selectivity of the process.

Example 6 (Comparative example)

Example 6 illustrates an experiment carried out in a known manner on an aluminum-zinc-iron catalyst at a temperature of 280 to 290 °C, a pressure of 30 MPa in the first stage and on a nickel catalyst on diatomaceous earth at a temperature of 180 °C, a space velocity of 1 h ^- ' and a pressure of 30 MPa in the second stage. The fraction of dimer products described in Example 3 serves as the raw material.

Two-stage hydrogenation yields a product with the following composition: butanols 12.6 wt. percent, butyl butyrates 1.6 wt. %, 2-ethylhexanal 1.0 wt. 56, 2-ethyl-4-methylpentanol 1.2 wt. 56, 2-ethylhexanal 1.0 wt. %, 2-ethyl-4-methylpentanol 1.2 wt. 56, octenols 0.2 wt. percent, 2-ethylhexanol 68.1 wt. 56, butyric acids 0.1 wt. %, acetyls 0.3 wt. 56, unidentified products 4.2 wt. %, water 2.2 wt. 56, hydrocarbons 8.5 wt. 56.

The degree of aldehyde conversion is 98.8 56, the selectivity of 2-ethylhexanol formation is 87.8 56.

2-Ethylhexanol separated from the hydrogenation product contains 99.56% of the basic substance, 0.02% by weight of unsaturated compounds.

Therefore, the selectivity of the reaction to form 2-ethylhexanol according to the known method is about 10 56 lower than in the method according to the invention (compare with Example 3) at the same concentration of 2-ethylhexenal used, which is 70.5 wt. %.

Example 7

The process is carried out under the conditions described in Example 1, but at a hydrogen pressure of 30 MPa, a temperature of 200 °C and a space velocity of the feedstock of 1.5 h ^-1 . The fraction of dimer products with the composition described in Example 3 serves as the feedstock. During hydrogenation under these conditions, the degree of conversion of 2-ethylhexenal is 92%, the selectivity of the formation of 2-ethylhexanol is 91 56 due to the formation of high-boiling condensation products. After repeated hydrogenation of the separated 2-ethylhexanol on a catalyst containing nickel, a product corresponding to the standard is obtained. Therefore, reducing the temperature of the hydrogenation process to 200 °C leads to both a certain decrease in selectivity and also to incomplete hydrogenation of 2-ethylhexenal, which is why it is again necessary to add an additional hydrogenation stage in order to achieve 2-ethylhexanol corresponding to the standard.

Examples

The process is carried out under the conditions described in Example 1, but using a copper-zinc-chromium catalyst consisting of 38 ± 1.5 wt. % copper oxide (CuO), 30.5 ± 1.5 wt. % zinc oxide (ZnO), 7 ± 1 wt. % chromium oxide (CrO), at a temperature of 260 to 270 °C, a hydrogen pressure of 26 MPa and a space velocity of the feedstock of 3 h ^-1 . The feedstock used is pure 2-ethylhexenal in an amount of 4,100 g, which contains 97 wt. % 2-ethylhexenal and 3 wt. % high-boiling products.

The reaction yields 4,180 g of hydrogenated product of the following composition: 2-ethylhexanol 93.0 wt. percent, high-boiling products 2.8 wt. %, hydrocarbons 2.8 wt. %, 2-ethylhexanal 1 wt. %, water 0.4 wt. %.

The degree of conversion of 2-ethylhexenal is 99%, the selectivity of the formation of 2-ethylhexanol is 97%.

The yield of 2-ethylhexanol separated by rectification is 94.5%, based on the reacted aldehyde, the content of the basic substance in the product is 99.7%, the content of unsaturated compounds is 0.01% (see Table 2, Example 8).

Therefore, it is possible to carry out the process under optimal conditions and in one stage, without additional hydrogenation.

Table2

Technological state of the quality of 2-ethylhexanol obtained by the method according to the invention in comparison with the values of various companies

Quality values set by the standard RGW benchmarks recommendations for standardization Japan company Mitsubishi 2-ethylhexanol obtained according to example no. 1 2 3 4 5 8 1. Platinum-cobalt color number, not more than 10 10 10 10 10 10 10 10 2. Density, ²⁰ 3 4 , g/cm ^J '0.831-0.836 0.835 0.834 0.835 0.834 0.834 0.83' 3. Content of basic substance wt. %, at least 98.0 99.0 99.3 99.6 99.0 99.0 99.0 99.7 4. Aldehyde content, wt. %, maximum 0.1 missing missing missing missing missing errors: 5. Content of unsaturated compounds, calculated as 2-ethylhexenal, wt. %, maximum 0.1 0.1 0.018 0.02 0.02 0.01 0.01 0.01 6. Acid number, mg KOH/g, maximum 0.14 0.23 0.02 0.02 0.02 0.02 0.02 0.01 7. Boiling range, °C 182-186 183 to 184 . 183 to 184 183 to 184 183 to 184 183 to 184 183 to 184

Claims (2)

SUBJECT OF THE INVENTION A process for the preparation of 2-ethylhexanol by catalytic hydrogenation of 2-ethylhexenal or a product of 2-ethylhexenal containing at elevated temperature and elevated pressure in the presence of a zinc-containing and catalyst-containing catalyst and separating the final product from the hydrogenate. copper oxide at a weight ratio of copper oxide: zinc oxide: chromium oxide (12.3 to 54): (11.0 to 52.2): (6 to 23.2) on the support and the process is carried out at a temperature of 200 to 290 ° C and a pressure of 10 to 30 MPa. 2. The process according to claim 1, wherein the process is carried out at a temperature of 230 to 270 [deg.] C.