DE2025726B2 - Process for the production of cyclohexanone - Google Patents

Description

The present invention relates to the production of cyclohexanone by hydrogenation of phenol. Cyclohexanone is an intermediate product for the manufacture of polyamide fibers.

A number of patents are known in this field, e.g. B. U.S. Patents 829 166, 2,857,432, 2,873,296, 3,076,810, British patent 890 095, Dutch patent 701, French patent specification 1 467 482, patent specification 51 635 of the Office for Invention and Patent system in East Berlin, Czechoslovak patent specification 123 285 and copyright of the USSR 282.

German Patent 1,298,098 describes a mixture with 10 to 40 ⁿ / o calcium oxide as the carrier for the catalyst, it being particularly pointed out that the use of aluminum oxide alone without calcium oxide does not give the desired effect. For this reason, the catalyst is subjected to a complicated reduction, initially with hydrogen at 300 ° C. and then by treatment with hydrazine hydrate solution, washing free of chlorine ions and renewed reduction at 185 ° C. The loading capacity of the catalyst is low and is 0.15 to 0 , 3 kg of phenol per liter of catalyst per hour, with regeneration by purging with nitrogen and a controlled amount of air being necessary every 900 hours, which causes great difficulties.

In German patent specification 1,144,267, the process is carried out in the liquid phase which has previously been thoroughly cleaned of traces of iron, halogen, nitrogen compounds and soda. The hydrogenation of the phenol prepared in this way is carried out in the presence of a powdery catalyst suspended in the phenol which contains approximately 5 ^fl / o palladium on activated charcoal. In the method according to the invention is in the

ίο gas phase worked, with much better results both in terms of activity and in terms of selectivity, performance and working time of the catalyst are achieved.
The technical advantages of the present invention are as follows: The process according to the invention is simpler than the production of cyclohexanone from phenol, which was previously carried out in two stages, with phenol hydrogenating in the presence of a nickel catalyst to cyclohexanol in the first stage

and in the second stage the cyclohexanol obtained in the presence of an iron-zinc catalyst up to Cyclohexanone is hydrogenated with an appropriate intermediate rectification, since phenol is direct and one-step with the pallet used according to the invention

medium catalyst is hydrogenated to cyclohexanone. So the. Cyclohexanol dehydration away, so that the efficiency of the system increases considerably, the phenol load being 1 volume per volume Catalyst can be increased up to about twice.

The advantages of the method according to the invention are further apart from the greater efficiency of the plant can be seen mainly in the fact that the catalyst with similar yields as the known

Process must be regenerated less often. Due to the higher performance of the system, you get increased yields per unit of time.

In the patents mentioned are processes for the hydrogenation of phenol in the presence of a

Palladium catalyst, including a process for the hydrogenation of phenol in the gas phase, described. These methods have the following disadvantages:

1. Difficult separation of the catalyst powder from the reaction product in the sump phase hydrogenation of phenol;

2. fairly high palladium content (usually about 5 weight percent) in most catalysts;

3. low performance, which is related to the low activity of the catalyst to be used;

4. Cumbersome preparation of the catalyst;

5. Low yield of cyclohexanone in the gas phase hydrogenation, based on the unit of time.

The aim of the present invention is to eliminate the disadvantages mentioned.

The invention therefore relates to a process for the preparation of cyclohexanone by hydrogenation of phenol in the vapor phase at 100 to 150 ° C with a molar ratio of hydrogen to phenol from 3 to 10 and a pressure of at most 2 atm in the presence of a palladium catalyst, which is on an aluminum oxide is applied, the one basic compound, which is characterized by

What is shown is that the palladium catalyst eliminates the phenol through the catalyst layer

Catalyst used in which the palladium is observed in.

a thin layer not more than 0.3 mm thick. The increase in the thickness of the PaI-in an amount of 0.3 to 1 percent by weight on the charge layer on the carrier leads to diffusion Carrier has been applied and which is used as a 5 inhibition, i. H. to reduce the catalyst niche Compound 3 to 10 percent by weight of a performance.

Alkali carbonate and optionally 0.5 to 5 atomic The hydrogenation of the phenol represents a two-stage percent of an element of III. to VI. Subgroup processes represent: a) hydrogenation of phenol to Cyclodes periodic table, based on the palladium hexanone and b) hydrogenation of cyclohexanone to amount, and that the hydrogenation is carried out with io cyclohexanol,
a phenol transmission rate of 1 to

2 parts by weight per part by weight of catalyst per ^OH,. \ ^OH

Hour. _> V

It is advisable to carry out the hydrogenation in the presence!

a granulated palladium catalyst in which 15., '+ 2H ₂ . , + H _{2 χ /}

Palladium in a layer of C, 1 to 0.2 mm thick Level I Level II
has been applied to the ^ -alumina carrier

is to be carried out. Such a catalyst is In order to obtain a high yield of cyclohexanone

by soaking aluminum oxide with aqueous solution, one must have a sufficiently active catalyst

Palladium chloride solution at a pH of 1 ao tor, which is mainly the first reaction

to get 3. The hydrogenation is catalyzed in the presence of the stage, but with respect to the second stage

Catalyst called is characterized by a high level of activity. To the process with high performance

Effectiveness. (with high exposure, based on the phenol) through-

The alkali content of the palladium catalyst can lead to the reaction rate

carbonate, e.g. B. sodium carbonate, is not preferred 25 in the first stage due to diffusion processes

wise 4 to 6 percent by weight. inhibited, which is usually the case with a

The palladium catalyst can, if necessary, be difficult to obtain from the palladium catalyst used

nor connections of the elements of the IU. to Vl. is. We found that by applying

Subgroup of the periodic table in amounts of from Pallarium to the granules of the carrier in one

0.5 to 5 atomic percent, based on the palladium thin layer, as described above, the

amount, included. Eliminate the influence of diffusion inhibition and

Compliance with the mentioned travel conditions through a higher level of activity and at the same time

gen delivers a yield of up to 99 percent by weight, an increase in yield that can be achieved because a

based on cyclohexanone. rapid detachment of the reaction product of the first

The catalyst used according to the invention for the 35 stage (ketone) from the catalyst, without its pores

Hydrogenation of phenol in the vapor phase has to clog the degree of conversion of the ketone into

aiso the following advantages: the second stage (to alcohol) diminished.

Granulated alumina is used as the carrier. The rate of hydrogenation of the first stage

with a bulk density of about 0.5 g / ml in the presence of the palladium catalyst present

turned, the palladium content being low 40 * ors ^is 10 ^to 15 times as high as that of the second

and about 0.5% of the weight of the carrier loading stage, thus allowing a high selectivity of the process

contributes, the reduction of the catalyst is immediately conditioned.

Reactor is carried out at 150 to 17O ⁰ C, the hydrogenation We have found that to increase the phenol at a considerably greater load, activity of the catalyst for the given process being equal to 0.8 to 2 kg per kg of phenol catalysis 45 is sufficient, the said amount of palladium of 0.3 sator per hour at 110 to 150 ⁰ C and low to 1.0 percent by weight on an aluminum oxide pressure and the duration of the working period is slower, z. B. y-aluminum oxide, in a thin of the catalyst exceeds 5000 hours. Apply the high layer by soaking it with an aqueous solution of the efficiency of the catalyst in the proposed palladium salt. The depth of the process is linked to the lack of diffusion of the palladium salt solution into the y-aluminum inhibition in the hydrogenation reaction of the phenol pH palladium on the surface of the granules is the value of the palladium carrier to be used for soaking as a thin layer with a thickness of 0.1 to chloride solution, the smaller the penetration - 0.2 mm is conditional. This property of the depth of catalysis, ie the thinner the layer, must also be attributed to the high selectivity in relation to the active palladium formation of cyclohexanone, which forms the surface of the granulate. Therefore, in the absence of diffusion, the rate of hydrogenation is not hindered by the possibility of phenol decomposition.

run of side reactions and further It has been found that the optimal watering

Reaction is lowered. This goal can also be 60 depth of the granulate 0.1 to 0.2 mm, which

the additional incorporation of micrometers through the use of palladium chloride solutions

Elements of the 111th to VI. Subgroup of the period pH values of 1.5 to 3 is reached. In the two

systems to the catalyst in accordance with the attached table contains information which the

play 6 and serve 7. Changes in the layer thickness and activity of the

An increase in the reaction temperature over the 65 different impregnation conditions through Vagcnannle In addition, it is undesirable because it leads to a reduction in the pH values in order to produce the catalysis reduction the yield leads; the same thing is required for palladium chloride solutions Pressure increase and decrease of the flow rate:

Thickness of the active activist PH value layer mm (Conversion to ° / i>) 0.14 1.9 55 0.54 1.2 67 1.66 0.2 95 3.16 0.12 96

The addition of activators, e.g. B. Soda, to the catalyst allows a well developed palladium surface, d. H. obtain a finely dispersed state of the active component; the size of the Palladium surface is almost doubled in the process.

To suppress the rate of the second reaction in the hydrogenation of cyclohexanone, micro-amounts of catalyst poisons are added to the catalyst, coming from the most active points of the catalyst are adsorbed and thereby block the same. It is found that connections the elements of III. to VI. Subgroups of the periodic table, e.g. B. sulfur compounds, mercury, Cadmium and lead in the form of soluble salts can be used.

Under the conditions described above, it is possible to obtain cyclohexanone by hydrogenating phenol at a high space velocity over the catalyst of 1 to 2 kg / hour per kg of catalyst in a yield of up to 99 ^{0 Zo.}

For a better understanding of the present invention, the following examples are given.

example 1

100 ml of aqueous palladium chloride solution containing 0.5 g of palladium and 0.3 g of hydrochloric acid are gradually neutralized with soda solution up to a pH of 1.5. 100 g of reprecipitated activated γ-aluminum oxide, which is shaped as granules from A to 5 mm in size, are impregnated with this solution; under these conditions the depth of penetration of the palladium into the granulate is about 0.15 mm. The moist granules are kept in the air for 12 hours, then dried at 100 ° C. over the course of 8 hours and then soaked with 80 ml of a solution containing 5 g of soda. The granulate, dried at a temperature of 100 to 120 ° C., is introduced into a reaction tube in an amount of 20 g and rinsed with water at 140 ° C. for 5 hours at a rate of 100 l / hour. The palladium oxide is reduced to metallic palladium.

Through the catalyst obtained in this way, 25 ml of phenol per hour in the form of Vapors in a mixture with 50 l of hydrogen at 130 ° C and passed at atmospheric pressure. The reaction product contains 92 percent by weight of cyclohexanone, 5 percent by weight cyclohexanol and 3 percent by weight residual phenol. The yield based on converted phenol is 93%.

In comparison, the hydrogenation is reduced Palladium catalyst carried out, which has not been treated with soda.

100 g of j'-aluminum oxide in the form of granules 4 to 4 mm in size are soaked with 100 ml of palladium chloride solution, which has a pH of 1.6 and contains 0.5 g of palladium. The granulate is dried at 12O ⁰ C within 6 hours. 20 g of this are introduced into a reaction vessel through which hydrogen is passed at a volume rate of 2000 hours - ¹ at 140 ° for 5 hours. Phenol is hydrogenated in the presence of this catalyst under the conditions described in Example 1. This gives a product containing 72 Zo ⁰ cyclohexanone, 10% cyclohexanol and 17% unreacted phenol contains. Catalyst activity and yield have also been reduced by the absence of soda in the catalyst.

If the catalyst is prepared according to the process described in Example 1 and the soda content is merely increased from 5 to 15%, the reaction mixture, after passing through the phenol-hydrogen mixture under the conditions described in Example 1, contains 78% cyclohexanone, 20.3 ° / »Cyclohexanol and 1.7% phenol. The yield is therefore 78.5%. A hydrogenation product obtained by lowering the test temperature of 12O ⁰ C, which contains 88% of cyclohexanone, 10% of cyclohexanol and 2% phenol; the yield is about 88%. A significant increase in the proportion of soda in the catalyst therefore reduces the yield.

Another experiment shows the effect of the increased pressure in the hydrogenation.

The catalyst described in Example 1 was used in the hydrogenation of phenol at one pressure of 15 at (instead of 1 at) and 120 ° C. The reaction product contained 72% cyclohexanone, 26% cyclohexanol and about 2% residual phenol. The yield was> 74%. Pressure increase in the Hydrogenation of phenol beyond the claimed range also leads to a reduction the selective action of the catalyst.

This experiment shows the effect of the reduced pH of the palladium chloride solution on the Activity of the catalyst.

100 g of γ- aluminum oxide in the form of granules are soaked in 100 ml of aqueous palladium chloride solution which contains 0.5 g of palladium and has a pH of 0.54 (instead of 1.5 according to Example 1). After treatment with 5% sodium carbonate solution, the granules are dried at 100 ° C. for 6 hours, the resulting catalyst is introduced into the reaction vessel in an amount of 20 g and flushed with hydrogen at 140 ° C. for 5 hours to reduce the palladium. Through the layer of catalyst, a üampfgemisch of 20 g of phenol and 501 of hydrogen per hour at 130 ⁰ C is passed. The reaction product contains 65 ^fl / o cyclohexanone, 2% cyclohexanol and 33% residual phenol, ie the activity of the catalyst is greatly reduced. This shows the effect of the diffusion inhibition of the reaction, since the depth of the penetration of the palladium into the granulate at pH 0.54 is 1.2 mm (instead of 0.1 to 0.2 mm at pH 1.5 to 2).

Example 2

This example shows the effect of treating the catalyst with the additive metal.

The catalyst obtained according to Example 1 is treated with a solution of 40 mg of etching sublimate in 80 ml Soaked in water and dried. When passing mixed vapors of phenol and hydrogen through the layer of this catalyst, under the conditions described in Example 1, a product is obtained

obtained, which contains 97 ¹ Vo cyclohexanone, 1% cyclohexanol and about 2% phenol. The yield is 99%.

Example 3

The catalyst is prepared as described in Example 1, then it is made with the additive metal treated. It is a solution of 10 mg of sodium sulfide in 80 ml of water, which is 2.5 atomic percent sulfur, based on the palladium content in the catalyst, corresponds to, used.

When this catalyst is tested under the conditions described in Example 1, a product obtained, the 96.5% cyclohexanone, 1% cyclo-

contains hexanol and 2.5%> phenol. The yield is 99%.

The sodium sulfide can also be added to the soda solution during the impregnation of the catalyst in a manner analogous to Example I. be admitted.

From the comparative experiments it can be seen that the lowering of the pH value of the PdCl ₂ solution below the value of 1.5, the absence of soda or increasing the soda content over 10%, carry out

ίο the hydrogenation at pressures above 2 at to reduce the activity and selectivity of the catalyst in the hydrogenation. In the same direction the effect is an increase in temperature above 150 ° C and a reduction in the flow rate of the phenol through the catalyst.

Claims (3)

Patent claims: 1. Process for the preparation of cyclohexanone by hydrogenation of phenol in the vapor phase at 100 to 150 ° C with a molar ratio of hydrogen to phenol of 3 to 10 and a pressure of at most 2 atm in the presence of a palladium catalyst supported on an alumina support is applied which contains a basic compound, characterized in that the palladium catalyst a catalyst used in which the palladium in a thin layer of at most 0.3mm thickness in an amount from 0.3 to 1 percent by weight has been applied to the carrier and the basic compound 3 to 10 weight percent of an alkali carbonate and optionally 0.5 to 5 atomic percent of an element the III. to VI. Subgroup of the periodic table, based on the amount of palladium, contains, and that the hydrogenation is carried out at a phenol flow rate of 1 to 2 parts by weight per part by weight of catalyst per hour. 2. The method according to claim 1, characterized in that there is a palladium catalyst used, in which the palladium in a layer 0.1 to 0.2 mm thick on the γ-aluminum oxide support has been applied. 3. The method according to claim 1 and 2, characterized in that there is a palladium catalyst used, which contains 4 to 6 percent by weight sodium carbonate.