CS248317B1 - Process for hydrogenation of aldehydes - Google Patents

Abstract

A method for hydrogenation of aldehydes to the corresponding alcohols in the presence of a catalyst on a support formed by silicon oxide with nickel oxide or chromium oxide as active components, in which the hydrogenation takes place at a pressure of 0.5 to 15 MPa in the temperature range of 70 to 190 °C and at a 1.1 to 20-fold excess of hydrogen compared to the stoichiometric ratio on a thinly deposited catalyst layer, the starting nickel compound of which is nickel carbonate and the macroporous system of which is formed by thermal decomposition of nickel carbonate.

Description

The invention relates to a process for hydrogenating aldehydes, in particular n-butyraldehyde, isobutyraldehyde and 2-ethylhexenal to the corresponding alcohols, i.e. n-butanol, isobutanol and 2-ethylhexanol.

An important petrochemical process is the hydroformylation of propylene to form a mixture of n-butyraldehyde and isobutyraldehyde.

These two aldehydes are hydrogenated in the next technological stage to the respective alcohols - n-butanol and isobutanol, separated after pre-distillation, or possibly in a mixture. After separation from isobutyraldehyde, a part of n-butyraldehyde is subjected to an aldolization reaction to form an aldehyde with twice the number of hydrocarbon atoms in the chain, i.e. 2-ethylhexenal. This aldehyde is also hydrogenated to an alcohol, which in this case is 2-ethylhexanol. In the case of large sales of 2-ethylhexanol, it is possible to aldolize all n-butyraldehyde and produce only isobutanol and 2-ethylhexanol as final products. The mentioned alcohols are raw materials for the production of esters used as plasticizers, components of acrylate polymers, components of paints, etc.

Hydrogenation of aldehydes to the corresponding alcohols is carried out in a reactor with a fixed catalyst bed. Hydrogenation is usually carried out at a pressure in the range of 3 to 10 MPa and the hydrogenated aldehyde or their mixture diluted with the circulated respective alcohol or mixture of alcohols flows down the catalyst bed, with the majority of the reaction mixture of aldehydes and alcohols being present in the reactor in the liquid phase. Hydrogen is fed into the hydrogenation reactor simultaneously with the diluted hydrogenated aldehyde or mixture of aldehydes. The temperatures at the inlet to the hydrogenation

248 317 reactor temperatures usually range from 70 °C to 130 ^° C, with it being advantageous to maintain the temperature at the reactor inlet higher than 90 °C. The maximum temperature in the reactor, controlled by the removal of reaction heat or its absorption into the substances fed to the reactor, should not exceed 170 °C, exceptionally 190 °C, in order to prevent fission reactions.

□As catalysts for the hydrogenation of aldehydes, supported catalysts are usually used in which the active components are Ni, Cr, Cu, Co or mixtures thereof. Suitable supports are natural diatomaceous earth, synthetic silica or mixtures thereof.

When hydrogenating aldehydes to the corresponding alcohols, it is usually necessary to comply with strict product quality requirements, characterized by the maximum permissible concentration of unreacted aldehyde.

It has now been found that the function of a hydrogenation reactor for the conversion of aldehydes to alcohols, especially n-butyraldehyde, isobutyraldehyde and 2-ethylhexenal to the corresponding alcohols, in the presence of a catalyst on a support formed by silica with nickel oxide or chromium as the active component, can be improved by the method according to the invention, in which the hydrogenation takes place at a pressure of 0.5 to 15 MPa in the temperature range of 70 to 190 °C and a 1.1 to 20-fold excess of hydrogen compared to the stoichiometric ratio on a fixed layer of catalyst, the starting nickel compound of which is nickel carbonate and the macroporous system of which is formed by thermal decomposition of nickel carbonate. The catalyst is prepared by precipitating a sodium silicate solution with hydrochloric acid in the presence of an electrolyte, filtering the precipitate, washing it and mixing it directly or after drying with nickel carbonate, water, binder and granulating additives. The resulting mass is then shaped and heat-treated at temperatures of 350 to 600 *C. If necessary, a chromium compound is added simultaneously with nickel carbonate or it is additionally saturated in one stage. The functional characteristics of the catalyst are also favorably influenced by the suitably chosen particle shape.

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When hydrogenating aldehydes under the described technological conditions using the aforementioned catalyst, a higher aldehyde conversion is achieved under otherwise identical conditions, as will be demonstrated in the example. The increased activity of the catalyst compared to existing types also allows for an increase in the service life of the catalytic charge of the hydrogenation reactor. It has been found that the deactivation of this charge occurs in a zonal manner, i.e. that the catalyst is deactivated by harmful substances contained in the processed raw material gradually layer by layer. A more active catalyst allows for the creation of a larger reserve of catalytic charge in a reactor of a given volume, into which the zone in which the main part of the hydrogenation reaction occurs is gradually moved during the deactivation of the input layers.

Example 1

Catalysts A and B, the starting component of which is nickel carbonate (composition given in Table 1) and the standard catalyst Cherox 37-02, which is used for the hydrogenation of aldehydes, were tested on a laboratory pressure flow apparatus with a volume of 200 ml. The tablets were crushed to a grain size of 2 mm and 100 g of sample was used for the tests. The raw material for the hydrogenation tests was prepared by mixing pure n-butyraldehyde /NBD/ and n-butanol /NBA/ in a ratio of 1:3. The degree of conversion of n-butyraldehyde and the selectivity of hydrogenation of n-butyraldehyde to n-butanol were evaluated. The calculations were performed according to the following formulas:

% conversion « 100

NBD in ^the feedstock__- _> _%_NBD_in_hydrogenate % NBD in the feedstock % selectivity = 100 .

% NBD in raw material - % NBD in hydrogenates

Catalyst activation was carried out with pure hydrogen at a pressure of 10 MPa, a flow rate of 120 1/h and a temperature of 350 °C.

The hydrogenation itself took place at temperatures of 110, 140 and 170°C and a volume rate of 1200 Nl/1 h.

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The test results are shown in the table^ Ta b u l k żi

type of catalyst 37-02 catalyst A catalyst B NiO content /% wt/ 12.0 10.2 10.0 ^Cr 2°3 ^wt / 2.5 - 1.4 conversion /%/ at a temperature of 110 *0 98.5 99.1 99.6 140 °C 99.3 99.8 100 170 *C 99.6 100.0 100 selectivity /50/ at a temperature of 110 °C 99.7 99.8 99.7 140 *C 97.1 98.3 99.0 170°C 96.0 97.6 98.2

Example 2

The course of the hydrogenation reaction of 2-ethylhexenal to 2-ethylhexanol using two hydrogenation catalysts was compared:

a/ standard catalyst b/ catalyst whose starting component is nickel carbonate, designated in example 1 by the letter B,

Hydrogenation was carried out in both cases in an adiabatic reactor under identical conditions: pressure:

temperature range:

molar ratio of hydrogen to aldehyde:

molar fraction of aldehyde at the reactor inlet in the mixture with the circulated alcohol:

molar fraction of aldehyde at the reactor outlet:

10.0 MPa 90 to 160”C 14.5

0.200

0.001

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When testing the activity of both catalysts, it was found that the hydrogenation reaction is in a very good approximation of a first-order reaction and that the dependence of the rate constant on temperature can be described by the equations below.

Equation of the rate constant dependence on temperature:

catalyst according to a/

1 -τ ΛΛ Λ Λ 944.47 log k = 3.4144 - -------T catalyst according to b/ log k = 3.6005 - ----1-2 T where means: k ..... rate constant /h ¹ /

T ..... temperature /K/

For the hydrogenation of 17.67 kmol/h of incoming 2-ethylhexenal to the desired output concentration under the specified operating conditions, the following volumes of catalytic charge were required:

catalyst according to a/: 5.4 m ³ catalyst according to b/: 3.6 m ³

The volume of the catalytic charge produced according to the invention represents 2/3 of the catalytic charge of the standard catalyst. When using the same volume of the reaction space when working with both catalysts, 1/3 of the volume, relative to the charge of the standard catalyst, is used to extend the working period of the catalyst produced according to the method according to the invention.

Claims (1)

SUBJECT OF THE INVENTION 248 317 Process for the hydrogenation of aldehydes, in particular n-butyraldehyde, iso-butyraldehyde and 2-ethylhexenal to the corresponding alcohols in the presence of a catalyst supported on silica with nickel oxide or chromium as active ingredients, characterized by at a temperature range of 70 to 190 Ac and at a 1.1 to 20-fold excess of hydrogen versus a stoichiometric ratio on a fixed bed catalyst catalyst whose starting nickel compound is nickel carbonate and whose macroporous system is formed by thermal decomposition of nickel carbonate. Printed by Moravian printing works, center. 11 100, the class of People's Militia 3, Olomouc