CS265359B1 - Process for the production of alkoxy and aryloxycarbonyl compounds - Google Patents

Abstract

A process for the preparation of alkoxycarbonyl and aryloxycarbonyl compounds of the type R1.CHOCH.CO.R2 3 by catalytic dehydrogenation of the corresponding alkoxyalcohols or aryl alkoxy alcohols of the type R1-CHQR.CHQH. with C1 to C4 alkyl groups, wherein the alcohol vapor is passed through a chromite-zinc catalyst having a Cr: Zn molar ratio of 1: 6 to 3: 1 at a temperature of 300 to 500 ° C and a total pressure of 0.1 to 0.5 MPa from 3 to 30 mol / h, 1 kg / l, 5% to 40% by weight is added to the injected alcohol. water. The catalyst was basified with 0.1 to 2 wt. alkali metal. The resulting alkoxy ketones or alkoxyaldehydes, respectively. their aryl analogues are intermediates in the manufacture of specialty chemicals such as pesticides or drugs.

Description

The invention relates to a process for the production of alkoxy and aryloxycarbonyl compounds.

It is well known and used industrially that aldehydes and ketones can be prepared from the corresponding primary or secondary alcohols by oxidation or dehydrogenation. Oxygen or oxygen-releasing compounds can serve as the oxidizing agent, so that the reaction product is water in addition to the carbonyl compound; its separation from the formed carbonyl compound can be a technological complication.

In the case of dehydrogenation, which must always be carried out in the presence of a catalyst to achieve a good yield, hydrogen is similarly produced, which is easily separated from organic substances. While in the case of primary or secondary alcohols that do not have functional groups containing heteroatoms other than OH, the yields achieved by both methods are high, in the case of substituted alcohols, e.g. with alkoxy groups, halogens, amino groups, side reactions occur to a greater or lesser extent, which reduce the yield.

The present invention relates to a process which allows obtaining alkoxy- and aryloxycarbonyl compounds of the general formula

R ¹ .CH0R.CQR ² where R is an alkyl group up to C^, a phenyl group or a phenyl group substituted on the nucleus with alkyl groups C-, to C,. as substituents, R and E denote hydrogen or an alkyl group C-^ to by catalytic dehydrogenation of the corresponding alkoxyalcohols or aryloxyalcohol of the general formula

R ¹ .GH0R.CH0H.R ² o

in good yields.

The essence of the invention is the use of a chromitrazole catalyst, with optional suppression of side reactions by adding alkali to the catalyst and water to the reacting alcohol. Dehydrogenation is conveniently carried out by passing 2,265,359 ethoxylated alcohol, optionally with the addition of steam, over the catalyst at a temperature of 300 to 500°C.

The advantages of the proposed procedure are evident from a comparison of published data on the preparation of methoxyacetone Cf1,OCH-COCH, from 1-methoxy-2-propanol CH^OCHg.CHOH.CH,. Thus, classical oxidation with chromium trioxide gave only a 28% yield of methoxyacetone (R.R. Mariella, J.Ii. leaoh: J. Am. Chem. Soc. 71» 3558 (1949)). Catalytic dehydrogenation using catalysts from copper, zinc, nickel, iron and calcium oxides at 3θθ°0 gave 67.$% of methoxyacetone (NSR Offenlegálrtř«chrfrt 2,801 496 (1978)). Electrolytic oxidation on a nickel anode achieved only 11.6% yield of methoxyacetone at 20.3% conversion of methoxypropanol (US Patent 4,431,493 (1984)). The best result is given by patent document NSR 2,81$ 7$2 (1978), which recommends specially prepared beds of crystalline silver in multiple layers as an oxidation catalyst; when using six layers of different silver grain sizes, 89.4% of methoxypropanol was converted into methoxyacetone by air. However, significant complications must be expected in this process in separating the product vapors from the remaining nitrogen and from the water formed.

As can be seen from the examples given below, the dehydrogenation of 1-methoxy-2-propanol according to our procedure can yield methoxyacetone at 90% conversion with a selectivity of 83%, i.e. in a yield per pass of 75%. In addition, the procedure is also applicable to structural analogues of methoxypropanol.

The catalyst for our process is a mixture of chromium and zinc oxides, which can be prepared by any of the known processes, e.g. by coprecipitation of hydroxides from a nitrate solution with ammonia and subsequent calcination or thermal decomposition of zinc chromate. A special feature of our catalyst is the presence of a small amount of alkali metal, which increases the activity of the catalyst and suppresses side reactions. The composition of the catalyst can vary within relatively wide limits of the molar ratio of chromium to zinc, from 1:6 to 3:1. The amount of alkali metal, preferably sodium or potassium, is suitable from 0.1 to 2.0%«

The suitable reaction temperature for the mentioned type of catalyst is 300 to $00°C, preferably around 400°C, i.e. in the region where the dehydrogenation equilibrium is shifted significantly to the side of the carbonyl compound. This is the advantage of our catalyst over copper-containing catalysts, which at temperatures above 300°C lose activity due to the reduction of the specific surface of copper. The activity of our catalysts is comparable to the activity of copper catalysts. Suitable space velocities of alkoxy alcohol are in the range of 3 to 30 mol h" ¹ kg^^., depending on the temperature and structure of the reactant. Although reduced pressure favorably affects the equilibrium composition, it is not practical for safety reasons to operate with a pressure lower than atmospheric in the reactor. The same effect can be achieved by diluting the feed with an inert gas, for example nitrogen or water vapor. Water also has a positive effect by suppressing side reactions, especially the elimination of water to form an unsaturated ether or the elimination of an alkoxy group to form a ketone, e.g. acetone from methoxypropanol. The action of water most likely consists in blocking the acid centers on the catalyst surface.

We further provide examples of catalyst preparation and reaction performance, which do not, however, exhaust the scope of the invention.

Example 1

99 g Cr(N0j)j.9 HgO and 207 g Ζη(Ν0^) ₂ ·6 HgO were dissolved in three liters of distilled water with constant stirring. A solution of 200 ml of technical NH^ ⁱⁿ 5°θ distilled water was added dropwise over the course of one hour with constant stirring. If no further precipitation of the filtrate occurred with the addition of* NH^, the solution was decanted 4 times with three liters of distilled water and the precipitate was filtered off. The precipitate was washed on the filter with 2 liters of distilled water, removed and washed again by stirring in 500 ml of distilled water.

After filtration, the catalyst was dried for 6 hours at 120°C and calcined in a nitrogen stream for 3 hours at 550°C. Its composition was 25% Cr ₂ 0^ and 75% ZnO.

Example 2

With constant stirring, 245 g Cr(N0^)j.9 H ₂ 0 ^and 105 g Ζη(Ν0^) ₂ ·δ HgO were dissolved in three liters of distilled water. The further preparation procedure was the same as in Example 1. The catalyst had a composition of 62% CrgO^» 3® ^Zn0 ·

Example 3

The catalyst from Example 2 (100 g) was immersed in 500 ml of 1% NaOH solution and left there for 20 hours. It was then filtered off and dried at 100°C.

- 4,265,359

Example 4

A series of experiments were carried out with the catalyst from Example 2 with a grain size of 0.16 to 0.40 mm in a small apparatus containing 1 g of catalyst. l-Methoxy-2-propanol was injected both pure and mixed with 20 wt. % water. Examples of the results are summarized in Table I.

Table I

Preparation of methoxyacetone by dehydrogenation of l-methoxy-2-propanol

Temperature °C

Space velocity

Product composition, % mol. (without water)

1-methoxy- methoxy- acetone others

-2-propanol acetone by-products

Spraying pure 1-methoxy “2-propanol

380 10.2 45.6 43.7 5.1 5.6 390 15.3 50.3 37.3 5.8 6.6 380 23.0 53.6 33.4 7.7 5.3 400 10.2 34.1 48.2 10.8 6.9 Spray 80 % wt. l-methoxy-2-propanol + 20% wt. water 380 8.2 10.5 75.3 6.2 8.0 390 8.2 6.2 72.0 10.7 11.1 390 18.4 28.0 62.1 4.4 5.5 400 8.2 3.9 56.4 24.0 15.7 400 18.4 10.4 64.8 11.0 13.8

^a In moles of methoxypropanol per hour per kilogram of catalyst

Example 5

An industrial catalyst produced for methanol synthesis and with a composition corresponding to the catalyst from Example 1 was used. The catalyst charge was 40 g and a mixture of 50 wt % l-methoxy-2-propanol and 20 wt % water was used as the feed. The reaction temperature was 390°C. Methoxypropanol was fed at a space velocity of 7.7 mol h' ¹ kg^ _t . After 90 hours, the product composition (without water) was 31.6 mol % unreacted l-methoxy-2-propanol, 59.1 mol % methoxyacetone, 6.4 mol % acetone and 1.9 mol % other by-products.

Example 6

1 g of the catalyst from Example 2 was used and either pure 1-methoxy-2-butanol or its mixture with 20 wt % water was sprayed onto it. Examples of experiments are given in Table II.

Table II

Temperature c

Space velocity ^and

Product composition, % mol (without water)

1-methoxy- 1-methoxy- 2-buta- other -2-b-butanol -2-butanone non by-products

Spraying pure l-methoxy-2-butanol

570 21.6 15.6 75.5 6.9 4.0 580 21.6 11.5 60.9 20.6 7.0 590 9.6 0 57.5 45.4 19.1 400 21.6 0 55.6 55.7 10.7 Find say 80% wt· 1-methoxy-2-butanol + 20% wt· water 570 17.5 15.2 74.9 10.1 1.8 580 17.5 7.5 77.6 10.2 4.7

^a In moles of 1-methoxy-2-butanol per hour per kg of catalyst

Example 7

1 g of the catalyst from Example 2 was used and 1-phenoxy-2-propanol was sprayed onto it at 590°C at a space velocity of 10.5 mol h*l kgfcat. The product contained 22.1 mol% of unreacted 1-phenoxy-2-propanol and 41.0 mol% of phenoxyacetone.

Example 8

1 g of the catalyst from Example 1 was used and a mixture of 80 wt. % 2-methoxy-1-cyclohexanol and 20 wt. % water was sprayed onto it at 400°C at a space velocity of 6.2 mol h” ¹ kg^^. The product contained (after deducting water) 68.8 % unreacted methoxycyclohexanol, 6.4 mol. % 2-methoxy-1-cyclohexanone and 6.7 mol. % cyclohexanone.

Example 9

1 g of the catalyst from Example 2 was used and a mixture of 80 wt% 2-methoxy-1-ethanol and 20 wt% water was sprayed onto it at a space velocity of 10.2 mol h~1 kg]^ at 400°C. The product contained 16.4 mol% unreacted methoxyethanol, 55.6 mol% methoxyacetaldehyde and 16.9 mol% acetaldehyde.

Example 10

265,359

The catalyst of Example 3 was compared with the catalyst of Example 2. The catalysts were tested using the 1-methoxy-2-propanol reaction. The results are summarized in Table III.

Table III

Comparison of the original and alkalized catalyst in the reaction of 1-ethoxy-2-propanol (space velocity 10.2 mol h”^ kgj^)

Temperature °C Product composition, % mol. (without water) 1-methoxy-methoxy-acetone -2-propanol acetone other by-products 390 Catalyst from Example 2 48.3 42.5 3.2 6.0 380 Catalyst from Example 3 22.3 62.5 5.2 10.0 390 20.8 65.4 5.6 8.2

Example 11

1 g of the catalyst from Example 1 was used and 1p-tolyl-2-pentanol was sprayed onto it at 395° C. at a space velocity of 7.4 mol h. ¹ ^cat* contained 37.6 mol % unreacted 1-.p-tolyl-2-pentanol and 32.0 mol % 1p-tolyl-2-pentanone.

The resulting alkoxy ketones or alkoxy aldehydes, or their aryloxy analogues, are intermediates in the production of special chemicals, e.g. pesticides or pharmaceuticals.

Claims (3)

p S κ d m S τ of the invention 265 359 A process for producing alkoxycarbonyl and aryloxycarbonyl 1? R RCHOR.CO.R type catalysts by catalytic dehydrogenation of the corresponding R ^ .CHOR.CHOH.R ² type alkoxy alcohols or aryloxyalcohols wherein R is Cj-C ^ alkyl or phenyl, or a phenyl-substituted C s-substituted phenyl group. as substituents, R and R are hydrogen or C1-C4 alkyl, characterized in that alcohol vapors are passed through a chromosinc zinc catalyst having a CrxZn molar composition of 1: 6 to 3 µl at a temperature of 300-5 ° C and at a total pressure of 0 1 to 0.5 MPa at a space velocity of 3 to 30 moles h @ -1 kg @ -1. 2. A process according to claim 1, wherein 5 to 40 wt. water. 3. The process of claim 1 wherein the catalyst is basified with 0.1 to 2 wt. alkali metal. Printed by Moravian Printing Works,