NL7908147A - METHOD FOR PREPARING KETONES. - Google Patents

Description

V

N.O. 28,040 *

Process for the preparation of ketones

The invention relates to a process for the preparation of ketones.

The selective preparation of a ketone by heterogeneously catalyzed, oxidative decarbonylation of an aldehyde containing one carbon atom more than the ketone in the gas phase is known to acetone (German Patent Application 28 02 672.½). In the preparation of acetone, isobutanal is decarbonylated oxidatively to acetone in the gas phase on metal oxide catalysts. No other processes are known in the art in which aldehydes in the gas phase 10 are selectively oxidized oxidatively to the corresponding carbon atom-less ketones, so it should be assumed that the high selectivity in the oxidative decarbonylation of an aldehyde in the gas phase to the single case of isobutanal / acetone is limited. This assumption was first confirmed even by a number of tests with other aldehydes (comparative examples 5 to 9).

Therefore, the invention was based on the problem of providing a process for the selective preparation of ketones with at least 4 carbon atoms.

The problem is solved according to the invention by using linear or branched alkyl, alkenyl, alkylaryl, alkenylaryl, alkylcycloalkyl, alkenylcycloalkyl, alkyl or alkyloalkyl, to prepare ketones with at least 4 carbon atoms and of the formula I alkylcycloalkenyl, or alkenylcycloalkenyl groups of 1 to 25 carbon atoms or together represent a macrocyclic ring of 5 to 18 carbon atoms and the radicals may contain groups of heteroatoms, aldehydes of the formula II, wherein R 1 and R 2 have the meanings indicated in the gas phase in a concentration of the aldehyde in the gas supplied as the starting product of 1 to 3 vol.% of oxygen or oxygen-containing gases at a temperature of from 120 to 270 ° C and with a contact time of 0.2 to 10 seconds, optionally in the presence of indifferent diluents to metal oxide catalysts containing an oxide of the elements copper and / or manganese and optionally zinc oxide and / or graphite.

Surprisingly, it has been found that the selective oxidative decarbonylation of aldehydes to ketones in the gas phase is not limited to isobutanal / acetone, but a general reaction principle is 7908147 2 4 s * τ if copper and / or manganese oxide are used as catalysts and aldehydes are aldehydes. which contain a tertiary carbon atom with one hydrogen atom in the α position relative to the carbonyl group (see formula 2).

The groups and R 2 may represent alkyl, alkenyl, alkylaryl, alkenylaryl, alkylcycloalkyl, alkenylcycloalkyl, alkylcycloalkenyl or alkenylcycloalkenyl groups having 1 to 18 carbon atoms. The groups and R 2 together may also contain a macrocycle ring with 5 to 18 carbon atoms. The limitation of the 10 groups with respect to the number of carbon atoms thereof is not determined by the reaction mechanism, the conversion or the selectivity, but by the necessity to evaporate the aldehydes. Thus, at suitable low pressures, aldehydes with more carbon atoms can also be used. Since, in practice, aldehydes with groups containing more than 18 carbon atoms are relatively rare and since these aldehydes are difficult to gas-phase, aldehydes with groups containing no more than 18 carbon atoms are preferred.

The groups R1 and R1 can also contain hetero atoms, such as, for example, Si, N, P, As, 0, S, Se, F, Cl, Br or J, etc., the hetero atoms depending on the nature of each to one or more carbon atoms, such as, for example, the groups of the formulas 3 * etc., between two or more carbon atoms, such as, for example, the groups of the formulas 5> 6, etc., or in connection with other atoms as a group of one or more carbon atoms, such as, for example, the groups with Fornral® 7, 8, etc., or between two or more carbon atoms, such as, for example, the group of the formula 9, etc., may be bonded.

Depending on their nature, the heteroatoms containing groups may remain indifferent or enter into reactions themselves during the oxidative decarbonylation. In view of the large number of possible groups with heteroatoms in the groups R 1 and R 2, it must be investigated in this case whether the group with the hetero atoms adversely affects selectivity in the oxidative decarbonylation of the aldehyde 33. The process according to the invention is particularly suitable for the oxidative decarbonylation of 2-ethyl-hexanal to heptanone-3 ·

The catalysts according to the invention can be prepared as solid catalysts or as support catalysts according to the usual ifO methods. Preferred support catalysts are 7908147 * 3 as they are mechanically more stable and cheaper. The copper and / or manganese content of the finished catalyst should preferably be 0.1-6 wt.%. Below 0.1% by weight, the conversion becomes too low for technical purposes and concentrations above 6% by weight do not yield any further improvement. In addition, at higher concentrations, the proportion of total combustion of the aldehyde increases. In particular, a copper and / or manganese content in the form of the oxides of 1-3% by weight is preferred. The zinc content of the finished catalyst in the form of the oxide can be 0.1 - 80% by weight. Generally, a content of 0.1 - 20% by weight is used. In particular, a zinc content of 1 - 5% by weight is preferred. At zinc contents of greater than 20 weight percent, the zinc oxide generally serves simultaneously as a support for the other catalyst components. In such a case, it has been found effective to add 2-20 wt.% Of colloidal graphite, based on the zinc oxide, to the zinc oxide. Preference is given to a graphite content of 2 -5% by weight, based on the zinc oxide, since larger amounts of graphite do not offer any advantages »

Suitable carriers for the active metal oxides are materials which, under the reaction conditions, have either indifferent or an inherent oxidative decarbonylation activity, as is the case, for example, with zinc oxide / graphite. Commercially available aluminum, zinc and titanium dioxide have proven to be particularly suitable materials for carriers. Due to the large number of differences in the individual materials used as a support, for example, in the different aluminum oxides, it is required to investigate whether the special support has a selectivity-reducing self-activity under the reaction conditions.

The application of the catalytic components to the support 30 is carried out according to the methods customary in the art, such as, for example, by impregnating the supports with saline solutions of the metals in water, drying the impregnated supports and converting the salts at elevated temperatures into the corresponding oxides. In addition, the application of the metal compounds to the support can be carried out in a single step by using solutions containing all the required metal ions or in separate steps by first applying the one metal compound to the support, drying the product and calcining and then the next component according to the same processing steps, etc. kO As forms in which the catalyst is to be introduced, the following 7908147 * k forms are suitable: spheres, tablets, strands, pellets; the catalyst can also be made into pieces.

The concentration of the aldehyde in the gas mixture can vary between 1 and 8 vol. However, larger and smaller concentrations are also possible, however the small concentrations are of no economic importance and at the larger concentrations the heat dissipation becomes a major problem. Concentrations between 2 and 5% by volume are particularly preferred.

The oxygen concentration in the gas supplied as the starting product is selected depending on the aldehyde concentration. The minimum molar ratio should be 1: 1.2. At even smaller ratios, the conversion drops rapidly. Aldehyde: oxygen molar ratios of 1: 2 to 1: 3 are preferred. However, the aldehyde / oxygen ratio may also be greater than the stated ratios. For example, the conversion can also be carried out with pure oxygen if the aldehyde concentration is not chosen too large. Air is preferably used as the oxidizing agent. In general, an indifferent diluent is added to the gas supplied as the starting product. 20 The following diluents are eligible: nitrogen, steam, carbon dioxide or carbon monoxide. Preferred diluents are nitrogen and / or steam, the nitrogen from the air used as the preferred oxidizing agent.

The reaction temperature is determined by the aldehyde used. This is 120 - 270 ° C. The residence time of the reaction components in the catalyst bed (contact time) is determined by the composition of the starting mixture and by the reaction temperature, and can be in the range of 0.2-10 sec. to swing. The contact time is preferably 1-6 sec. The conversion is generally carried out under atmospheric pressure or under slightly elevated pressure to about 5 resin. However, larger pressures can also be used. With relatively high boiling aldehydes, the reaction is carried out under reduced pressure. The degree to which the pressure is reduced is determined by the aldehyde used.

According to the process of the invention, it has hitherto been possible to selectively prepare difficult-to-obtain ketones in a simple manner.

7908147 5

Example I

(Preparation of the catalyst).

200 g of activated alumina (strands, diameter 1.6 mm, length 4 mm, a product of "Katalysatorenwerke Houdry-Huls") were impregnated with 213 g of a copper tetramine carbonate solution in water containing b. 3 wt. Copper ions The solution overlying the alumina was decanted The catalyst was dried at 110 [deg.] C. for 16 hours and calcined at 350 [deg.] C. for hours The copper content in the form of the oxide was 2.5% by weight, based on 10 the finished catalyst.

Example II

(Preparation of the catalyst).

112 g of activated alumina were impregnated with 98 ml of an aqueous solution containing 20.5 g of Zn (N0 ^) 2 · 6 H ^ O, dried at 110 ° C for 16 hours and calcined at 350 ° C for 16 hours . The calcined catalyst was then impregnated with 98 ml of an aqueous copper tetramine carbonate solution containing 1.1% wt. Copper ions and also dried at 110 ° C for 16 hours and calcined at 350 ° C for 16 hours. The finished catalyst contained 2.3 wt% copper and 2.3 wt% zinc in the form of its oxides.

Example III

(Preparation of the catalyst).

96 g of zinc oxide were mixed intensively with KO g of colloidal graphite and 30 g of water, after which the mixture was processed by pressing into tablets of diameter b mm and thickness b mm. Then the tablets were dried at 110 ° C for 16 hours and annealed at 350 ° C for 16 hours. The finished tablets were impregnated with 122 g of a copper tetramine carbonate solution containing 13.9 wt% copper ions, dried at 110 ° C for 16 hours and calcined at 350 ° C for 16 hours. The copper oxide content of the finished catalyst was 2.1% by weight, the graphite content was 3.9% by weight.

Example IV

(Preparation of the catalyst).

85 g of banded zinc oxide and 10 g of commercially available colloidal graphite were suspended in 120 ml of a manganese acetate aqueous solution containing 5 g of manganese ions. The suspension was evaporated to dryness and the resulting residue was dried at 110 ° C for 16 hours, ground, pressed into tablets (diameter b mm, thickness b mm) and tempered for 16 hours at 350 ° C. The manganese-bO content in the form of the oxide was 5% by weight, based on the recycled catalyst.

Examples V to IX (Comparative Examples) 60 ml of the catalyst described in Example II was placed in a 20 mm inner diameter steel reaction tube heated with boiling water and thermostated, after which the tube was loaded at the temperatures and contact times stated in Table A of 2 sec. under pressure in the reaction tube of 1.5 bar with gas mixtures consisting of 2.5 vol. of an aldehyde which did not contain a tertiary carbon atom with a hydrogen atom in the α-position relative to the carbonyl group, vol. # air and 52.0 vol. # steam existed. The gas mixtures leaving the reactor were examined by gas chromatography. The results obtained are summarized in Table A.

Examples X to XIV

Under the test conditions mentioned in Examples V to IX, aldhydes containing a tertiary carbon atom with a hydrogen atom in the α position relative to the carbonyl group were used. The results obtained are in Table B.

20 listed.

Similar results were obtained by using the catalysts described in Examples I, III and IV in Examples V to XIV.

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Claims (3)

A process for the preparation of ketones having at least k carbon atoms and of the formula 1, wherein R 1 and E 1 linear or branched alkyl, alkenyl, alkylaryl, alkenylaryl, alkylcycloalkyl, alkenylcycloalkyl, alkylcycloalkenyl or alkenyl cycloalkenyl groups of 1 to 18 carbon atoms or together represent a macrocyclic ring with 5 bone 18 carbon atoms and the groups may contain groups of heteroatoms, characterized in that aldehydes of the formula wherein R 2 and R 2 are the -10 have meanings in the gas phase at a concentration of the aldehyde in the gas supplied as the starting product. of 1-8 vol. # with oxygen or oxygen-containing gases at a temperature of 120-270 ° C and with a contact time of 0.2-10 seconds, optionally in the presence of indifferent diluents, to metal oxide catalysts. containing an oxide of the elements copper and / or manganese and optionally zinc oxide and / or graphite. 2. Process according to claim 1, characterized in that the amount of copper and / or manganese in the form of the oxides is 0.1-6% by weight, based on the finished catalyst. ******* 7908147 * '/ _L Z. 3. Ϋ .0 I Rt-c = ° Rri-C <-C-Ct R2 R2 AX _l_I_ I _ | _ V -CNC- II - c-N —C —Ο Ι J_ JL I II - C-COOCH * —C 9— I 3 II 1 N 0 V A I 1 —C — N — ΟΙ I I H 7 9 0 8 1 4 7