RU2594483C1 - METHOD OF PRODUCING α-METHYLSUBSTITUTED CARBONYL COMPOUNDS - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing α-methylsubstituted carbonyl compounds of gthe eneral formula R¹-CO-CR³(CH₃)-R², where: R¹ and R²-hydrogen H or a linear or branched alkyl radical containing 1 to 12 carbon atoms, R³-H or CH₃ radical, which are feedstock for producing a number of chemical products and drugs, are used as solvents and can be used as a base for producing high-octane motor fuel components. Method involves conversion of initial gas-vapour mixture of carbonyl compound selected from compounds of general formula R⁴-CO-CHR⁵-R⁶, where: R⁴ and R⁶-H or a linear or branched alkyl radical containing 1 to 9 carbon atoms, R⁵-H or CH₃ radical, and methanol using copper-containing catalyst when introducing in initial reaction mix of hydrogen.

EFFECT: proposed method allows to increase the catalyst interregeneration runtime in several times, and consequently, the amount of product obtained per unit volume of the reactor.

3 cl, 1 tbl, 6 ex

Description

The invention relates to a method for the synthesis of linear and branched carbonyl compounds by gas-phase catalytic dehydrocondensation of aliphatic ketones and / or aldehydes with methanol.

Carbonyl compounds are the starting material for a number of chemical products and medicines, are used as solvents, and can also act as the basis for the production of high-octane components of motor fuel.

A known method of producing higher carbonyl compounds from the corresponding lower homologues by aldol (aldol-crotonic) condensation with further dehydration and hydrogenation of an unsaturated carbonyl compound [GB 1015003 (A), B01J 21/00, 30/10/1965]. The method has several disadvantages associated with the use of aggressive catalysts and media, multi-stage and, consequently, low overall selectivity of the process, the use of high pressures, and most importantly, does not allow to obtain branched carbonyl compounds from simple, industrially produced starting materials.

A known method for the synthesis of higher ketones from lower ones, based on the reaction of alpha-methylation of ketones with methanol [B.A. Bolotov, V.L. Klyuev. Vapor-phase condensation of methanol and acetone on copper-titanium catalysts // Journal of Applied Chemistry. - 1971. - T. 44. - V. 10. - S. 2280-2283]. The chemical essence of this method consists in the dehydrocondensation of acetone and methanol or, in other words, in the appeal (methylation) of ketones in the α-position to the carbonyl group. The process is carried out in the vapor-gas phase under relatively mild conditions (atmospheric pressure, temperatures up to 300 ° C, mixed oxide catalyst - from 15 to 80 wt.% Copper oxide on titanium oxide). It was found that, along with methyl ethyl ketone (the primary and main condensation product), branched ketone impurities are formed (methyl isopropyl, ethyl isopropyl, diisopropyl ketones). To achieve an acceptable conversion of acetone, the process is carried out with a long contact time of 23 seconds. On the Cu / TiO ₂ catalyst, the yield of the sum of ketones on the passed acetone did not exceed 50%, and methylation took place predominantly along the same acetone methyl group with the formation mainly of methyl ethyl ketone and methyl isopropyl ketone. However, the work was not further developed, which may be due to the low activity of the catalyst.

Known patent Hoechst Aktiengesellschaft [US 3932518, C07C 45/00, 01/13/1976], which stated the fundamental possibility of methylation of cyclohexanone. The process is carried out in the gas phase at 250-500 ° C in the presence of copper and / or silver containing catalysts (carriers: Al ₂ O ₃ , aluminum silicate, magnesium silicate, silica gel, carbon), modified with alkaline and alkaline earth oxides, hydroxides, alcohols or their mixture. Probably, the primary claims of the authors were much wider, since the patent provides a number of examples relating to non-cyclic ketones. In particular, the condensation of acetone with methanol is considered. The achieved yield by the sum of branched ketones on a modified alkaline earth metal mixture of a copper-containing catalyst is 70% at a contact time of 30 seconds and in a 4-fold excess of methanol.

Subsequently, BASF AG (Germany) published a patent [US 4618725, С07С 45/71, 10.21.1986], in which the synthesis of alpha-methyl-substituted ketones by the reaction of aliphatic and cyclic ketones with methanol at a temperature of 350-500 ° C is claimed, pressure from 1 to 20 atm, with a contact time of 6 to 20 seconds with the addition of water vapor. A set of massive metal oxides (Ce, Cr, Fe, Mg, Mn) in the form of compressed tablets without the use of a carrier is proposed as catalysts.

In all patents noted, the reaction of ketones with methanol is carried out on oxide, preferably copper-containing, heterogeneous catalysts, at temperatures from 250 to 500 ° C and methanol / acetone ratios from 1: 1 to 10: 1. The reaction produces a mixture of linear and branched aliphatic, or unsaturated, or cyclic, or aromatic ketones. The resulting lower ketones can be separated from the low boiling products that are returned to the reaction. None of the patents has data on the duration of the experiments and there is no information on the deactivation of the catalysts.

Patent US 3932518, С07С 45/00, 01/13/1976, in its technical essence and the achieved effect is closest to the present invention and can be selected as a prototype. According to the prototype, the gas-phase process of methylation of cyclic ketones or acetone (250-500 ° C) is carried out on copper and / or silver-containing catalysts (carriers: Al ₂ O ₃ , aluminum silicate, magnesium silicate, silica gel, carbon), modified with alkaline and alkaline earth oxides, hydroxides, alcoholates, or a mixture thereof. The main disadvantage of this method is the need for the process at high contact times and in the presence of an oxygen-containing gas. This patent also does not report on the stability of the catalysts in the ketone methylation reaction, i.e. the time of the inter-regeneration run of the catalysts.

The invention solves the problem of increasing the efficiency of the process.

The technical result is an increase in the inter-regeneration run time of the catalyst by several times, and consequently, the amount of product obtained per unit volume of the reactor.

The problem is solved by the method of producing α-methyl substituted carbonyl compounds of the general formula R ¹ -CO-CR ³ (CH ₃ ) -R ² , where: R ¹ and R ² are hydrogen H or a linear or branched alkyl radical containing from 1 to 12 carbon atoms , R ³ —H or CH ₃ radical, which is carried out by reacting an initial vapor-gas mixture of a carbonyl compound selected from a number of compounds of the general formula R ⁴ —CO — CHR ⁵ —R ⁶ , where: R ⁴ and R ⁶ are H or linear or branched alkyl a radical containing from 1 to 9 carbon atoms, R ⁵ - H or CH ₃ radical, and methanol using a copper content catalyst with the introduction of hydrogen into the initial reaction mixture.

The method is carried out in the gas phase at a temperature of 150-350 ° C.

Hydrogen is introduced in an amount of not less than 0.1 vol. %

We propose the extension of the carbon chain of ketones by producing α-methyl-substituted carbonyl compounds of the general formula R ¹ —CO — CR ³ (CH ₃ ) —R ² , where: R ¹ and R ² —H or a linear or branched alkyl radical containing from 1 up to 12 carbon atoms, R ³ = H or CH ₃ radical when hydrogen is added to the initial reaction mixture. Examples of R ¹ and R ² radicals may be hydrogen H or methyl, or ethyl, or isopropyl, or isobutyl, or pentyl, or isopentyl, etc. radicals. The starting reagents are their lower homologues of the general formula R ⁴ -CO-CHR ⁵ -R ⁶ , where: R ⁴ and R ⁶ are H or a linear or branched alkyl radical containing from 1 to 12 carbon atoms, R ⁵ is H or CH ₃ radical. Examples of R ⁴ and R ⁶ radicals can also be H, or methyl, or ethyl, or isopropyl, or isobutyl, or pentyl, or isopentyl, etc. radicals. The starting carbonyl compound in a mixture with methanol in ratios from 1: 1 to 1:10 is mixed with hydrogen and passed through a layer of a copper-containing heterogeneous catalyst. The reaction mixture may be diluted with a diluent gas. As a diluent gas, one or a mixture of the following gases is used: nitrogen, and / or any inert gas, and / or carbon dioxide. Any amount of hydrogen may be added to the diluent gas, preferably not more than 5 vol. % Even a small hydrogen content in the initial reaction mixture significantly reduces the degree of catalyst deactivation and increases its inter-regeneration range.

The optimum temperature that must be maintained in the reactor must ensure that the process is carried out in the gas phase and depends on the type of initial reagent (its boiling point and the condensation temperature of the reaction products). Typically, the reaction is carried out at a temperature of 150 ° C-400 ° C. An important parameter is the contact time of the reaction mixture with the catalyst. This parameter varies from 0.1 to 20 s, preferably 1-5 s. To increase the proportion of branched ketones in the product, the contact time should be increased to 6-20 s. A large methylation depth is also achieved by recycling low-boiling low-branched products to the reactor for the purpose of remethylation. This method allows the use of any of the known copper-containing (or copper oxide) catalysts, both massive and supported, obtained using any inorganic or organic copper salt and any of the known carriers: aluminum oxide, alkaline earth metal oxides, amorphous metal silicates, crystalline metal silicates , silicalite, mesoporous silicates and metallosilicates, silica gel, fiberglass materials, carbon and polymer carriers. The catalysts may include promoters from a number of alkaline, alkaline earth and a number of transition metals in amounts from 0.1 to 5.0 wt. % of the amount of copper. The copper content in the catalyst may range from 1 to 50 wt. %, preferably in the range of 5-30 wt. % by weight of the catalyst. A large amount of copper in the catalyst, on the one hand, increases its activity, but, on the other hand, leads to unproductive consumption of methanol in the steam reforming reaction, leading to the formation of carbon oxides.

Thus, a significant and main difference between the claimed method for the synthesis of branched carbonyl compounds by methylation of their lower homologues with a methyl or methylene group in the alpha position to the carbonyl group is the presence of hydrogen in the initial reaction mixture. The addition of hydrogen allows increasing the inter-regeneration run time of the catalyst by several times, and, consequently, the amount of product obtained per unit volume of the reactor. The introduction of hydrogen into the reaction mixture maintains the catalyst in a reduced state. The positive effect of hydrogen addition is most pronounced when the process is carried out on a catalyst with a low copper content. Therefore, an additional positive effect of the addition of hydrogen to the reaction mixture is the possibility of reducing the copper content in the catalyst and reducing the loading of the catalyst into the reactor, as well as increasing the selectivity of the process.

The invention is illustrated by the following examples.

The catalytic properties of copper-containing catalysts in the ketone methylation reaction (examples No. 1-6) are presented in the table.

Example 1. Comparative

70 ml / min of a mixture of methanol (60 vol.%) And acetone (20 vol.%) In argon (20 vol.%) Is passed through a layer of 2.0 cm ^{3 of} catalyst at a temperature of 250 ° C for 10 hours. The catalyst has a molar composition of 5 · 10 ^-2 · CuO · SiO ₂ (or 6.3 wt.% CuO and 93.7 wt.% SiO ₂ ). The composition of the reaction mixture is determined by sampling directly from the gas-vapor stream, followed by analysis of organic components on a flame ionization detector, inorganic components on two heat conductivity detectors. The organic components of the reaction mixture were separated on a DB-1701 capillary column. The resulting mixture contains unreacted acetone and methanol and a mixture of ketones, namely methyl ethyl ketone, diethyl ketone, methyl isopropyl ketone, ethyl isopropyl ketone, methyl isobutyl ketone. When analyzing hydrogen, nitrogen, carbon monoxide, carbon dioxide and water, the sample is separated into separate components using packed columns with CaA zeolite (5A molecular sieve) and Porapak R. adsorbent.

The activity (Pr) for methylated ketones is used as a characteristic of activity:

Pr (g methylated ketone / g catalyst in h) = (Σ (N _MKi · M _MKi )) · 60 / m;

where: N _MK - the total flow of the reaction mixture at the outlet of the reactor, mol / min;

M _MKi is the molecular weight of methylated ketone, g / mol;

m is the mass of the catalyst loaded into the reactor, g

The selectivity (S) for the formation of methylated or the sum of methylated ketones from the starting ketone is calculated by the formula:

where: N _MKi is the flow of methylated ketone, mol / min;

- поток входящего исходного кетона, моль/мин; $$N_{\mathrm{TO}}^0$$

- flow of incoming feed ketone, mol / min;

N _K is the flow of the initial ketone exiting, mol / min.

As a parameter characterizing the stability of the catalyst, use the time required to reduce productivity by the amount of methylated ketones in 2 times.

The table provides information on the initial productivity and selectivity of the conversion of acetone to methylated ketones, as well as a parameter characterizing the stability of the catalyst. It can be seen that already 1.3 hours after the start of operation, the activity of the catalyst decreases by 2 times.

Example 2

The process is carried out analogously to example 1 with the difference that part of the argon is replaced by hydrogen. In general, the initial reaction mixture contains 4 vol. % hydrogen.

The test results of the catalyst are presented in the table.

It can be seen that, compared with example 1, the duration of the catalyst until the activity decreases by a factor of 2 has increased by almost 4 times.

Example 3. Comparative

The process is carried out analogously to example 1 with the difference that the catalyst has a molar composition of 1.2 · 10 ^-1 · CuO · SiO ₂ (13.8 in wt.% CuO and 86.2 wt.% SiO ₂ ).

The results are presented in the table. It is seen that an increase in the copper content in the catalyst is accompanied by an increase in the stability of its operation.

Example 4

The process is carried out analogously to example 3 with the difference that the initial gas mixture of methanol, acetone and diluent gas contains 4 vol. % hydrogen. The test results are presented in the table. It can be seen that the addition of hydrogen to the initial reaction mixture led to an increase in the duration of the catalyst by 3 times.

Example 5. Comparative

The process is carried out analogously to example 1 with the difference that the catalyst has a molar composition of 5.0 · 10 ^-1 · CuO · Al ₂ O ₃ (28 wt.% CuO and 72 wt.% Al ₂ O ₃ ).

The table shows the results. It can be seen that a further increase in the copper content compared to example 3 leads to an increase in the stability of the catalyst.

Example 6

The process is carried out analogously to example 5 with the difference that the initial gas mixture of methanol, acetone and diluent gas contains 4 vol. % hydrogen.

The test results of the catalytic properties are presented in the table. It is seen that the introduction of hydrogen into the initial reaction mixture is accompanied by an increase in the duration of the catalyst by 4 times.

It should be noted that the addition of hydrogen to the initial reaction mixture reduces the selectivity of the conversion of acetone to methylated ketones. This is due to the partial hydrogenation of acetone to propanol.

Claims (3)

1. The method of producing α-methyl substituted carbonyl compounds of the general formula R ¹ -CO-CR ³ (CH ₃ ) -R ² , where: R ¹ and R ² are hydrogen H or a linear or branched alkyl radical containing from 1 to 12 carbon atoms , R ³ is H or CH ₃ radical, by conversion of an initial vapor-gas mixture of a carbonyl compound selected from a number of compounds of the general formula R ⁴ —CO — CHR ⁵ —R ⁶ , where: R ⁴ and R ⁶ are H or a linear or branched alkyl radical, containing from 1 to 9 carbon atoms, R ⁵ - H or CH ₃ radical, and methanol using a copper-containing catalyst, characterized in that persons performed when introduced into the initial reaction mixture is hydrogen. 2. The method according to p. 1, characterized in that it is carried out in the gas phase at a temperature of 150-350 ° C. 3. The method according to p. 1, characterized in that hydrogen is introduced in an amount of not less than 0.1 vol.%.