DE960007C - Process for the production of higher ketones by reacting a secondary aliphatic alcohol with an aliphatic ketone - Google Patents

Description

The invention relates to a process for the preparation of ketones by reacting a secondary aliphatic alcohol with an aliphatic ketone in the presence of a catalyst, The ketones produced in this way are referred to as "higher" ketones because they have a larger number of carbon atoms, contained as the starting material (lower) ketones.

It is known that higher ketones can be made by reacting secondary aliphatic ones Alcohols and ketones in the presence of a catalyst with dehydrating and dehydrating Properties where the reaction proceeds at higher temperatures and atmospheric pressure or higher pressure. A typical reaction is that between methyl ethyl ketone and sec-butyl alcohol according to the following equation:

CH ₃ • CO • C ₂ H ₅ -I-CH ₃ • CH (CH) -CH ₃ - CH, H (CH) CO

CH ₃

₂₅₃
-CH ₂ -CH (CH ₃ ) -CH ₂ -CO-C ₂

+ H ₂ O

In this reaction the main reaction product is 5 "methyl-3-heptanone, as indicated in the equation, although some 3,4-D1-methyl-2-hexanone and smaller amounts of the corresponding C ₈ alcohols (5-methyl-3 -heptanol and 3,4-dimethyl-2-hexanol)

the catalyst is quickly equilibrated between that reacting as the starting material Alcohol and the ketone formed when the alcohol is dehydrated, as well as between the as Starting material present ketone and the alcohol that is produced in the hydrogenation of this ketone forms, a. Accordingly, in some cases, using only Alcohol or ketone (together with hydrogen) ίο work as a starting component, with that as The ketone produced by the reaction always has twice as many carbon atoms as the starting material. However, since the higher ketone formed as a reaction product is mainly due to conversion between an alcohol and a (lower) ketone is formed, whereby a ketone arises, which has a number of carbon atoms that is the sum of the carbon atoms in the corresponding Corresponding to alcohol and ketone components, the present invention becomes general described as a reaction between an alcohol and a ketone.

When carrying out reactions of the type described above, the most varied have been so far Catalysts have been used which contain one or more components that exert a dehydrating effect, and also contain one or more components with a dehydrating effect. Mixed catalysts of this type are known; they include those in which the dehydrating Component made of an oxide, hydroxide, carbonate or other salt of metals, like magnesium, aluminum, beryllium, barium, zirconium, cerium or thorium, is made during the dehydrogenating part of the catalyst made of one or more metals, such as copper, silver, Chromium, manganese, nickel, tungsten, cobalt, iron, cadmium, uranium, tin or zinc, consists of this component either in metal form or in the form of oxides, hydroxides or salts with organic or inorganic acids can be present. How to get a mixed catalyst which has given good results, by impregnation of activated alumina (the dehydrating component) with a solution a copper salt or with both a copper salt and a zinc, manganese or iron salt, whereupon the impregnated material is roasted and the copper oxide formed in this way then in a Hydrogen atmosphere is reduced to copper. The mixed catalysts described above vary somewhat in terms of their activity, measured against the total amount of reaction components, which are converted into the various reaction products, and also in the selectivity, measured by the yield of the desired higher ketones formed. conversion and yield are also by the type and. the proportions of the reaction components as well as influenced by the reaction conditions. However, so far it has been for a certain degree of conversion impossible to achieve yields above about 75 to 85%, and in many cases it will Yield as low as 50% or less. The term "degree of conversion" means in the present case Description of the total percentage of alcohol and ketone components that make up the The entirety of the various products that result from the reaction is converted. In the However, determining the amount of these newly formed products will only be such organic products which have a carbon chain longer than any one the respondent. The amounts of water and any lower alcohols formed and Ketones, which during the reaction (e.g. by dehydration of the alcoholic reaction component) are not taken into account. Accordingly, the conversion values given here are evenly slightly lower than the real conversion values. The term "yield" is used to indicate the percentage of said converted portion, which applies to the specified product.

The invention provides a process by which a substantial increase in the yield is achieved on higher ketones, which by reacting a secondary aliphatic Alcohol can be obtained with an aliphatic ketone, each of these components being preferred Contains 3 to 7 carbon atoms. The invention particularly relates to extraction of Cfj-ketones, which by reacting sec-butyl alcohol be formed with methyl ethyl ketone.

According to the invention, the secondary aliphatic alcohol and the aliphatic ketone are initially in the vapor phase in the presence of a mixed dehydrogenation-dehydration catalyst at a higher temperature, preferably between 240 and 300 ⁰ , and at a relatively high pressure (e.g. a pressure above 12 , 25 atm), whereupon the resulting vaporous reaction mixture is brought into contact with a catalyst at a relatively low pressure (i.e. between about 1.05 and 3.50 atm) and at an elevated temperature, preferably above about 225 ° containing a dehydrating component. When the process is carried out in this manner, the yield of the desired higher ketone can be increased by at least 10%. If temperatures well above 240 to 300 ⁰ and pressures well below 12.25 atmospheres are used in the first working stage, the degree of conversion achieved drops sharply, as does the active life of the catalyst. On the other hand, if higher pressures are used during the second stage of the process, the gaseous effluent from the first reaction zone will flow virtually unaltered through the second zone and the yield of higher ketones in the gaseous product will not be increased.

The catalyst used in the second or low pressure stage can be one that is only Has, or may, have dehydrating properties

be a mixed catalyst such as B. such of the type described above, which has both dehydrating and dehydrating properties Has. So this catalyst can one or more of the metals copper, silver, chromium, Contain manganese, nickel, tungsten, cobalt, iron, cadmium, uranium, lead, tin or zinc, or it can contain one or more of these metals along with one or more dehydrating metals Contain metal oxides, hydroxides or salts. For example, supplies metallic. copper excellent results; also mixtures of copper with difficult to reducible metal oxides, like zinc oxide, manganese oxide or magnesium oxide.

However, since you can use any type of mixed catalyst can be used, provided that it only has dehydrating properties, are preferred the same catalysts in both the high pressure and low pressure stages of the present procedure. Surprisingly, it has been found that mixed Dehydration - dehydrogenation - catalysts whose activity has been reduced so much that their use in the first or high-pressure stage of the process without regenerative treatment is no longer expedient, with excellent Results in the second or lower pressure stage of the process can be used or for even superior to the more active catalyst used in the first stage for this purpose. The method according to the invention can accordingly be carried out with good results in such a way that that you first the gaseous alcohol-ketone mixture by a mixed dehydration - Passing through dehydrogenation catalyst of high activity and then the thus obtained Gaseous products are passed through a bed of the same catalyst, its activity as a catalyst in the high pressure stage of the process by prior use under high Pressure has been greatly reduced in the course of the process.

A system which is suitable for carrying out the method according to the invention is shown in the drawing. The drawing shows a flow diagram of a continuous system in which a combined stream 1 of low boiling components that are recycled and a stream of new feed material 2 first through a reaction vessel R ₁ and then through line 3 to a reaction vessel R _2, respectively be passed via line 4 through the reaction vessel R ₂ and then through line 5 into the reaction vessel R ₁ , the waste

The flow from the second reaction vessel is then passed through line 6 (or lines 7 and 6) into a first distillation column D ₁ , where the low-boiling components are separated off, and then through line 8 into a second distillation column D ₂ , in which the desired higher ketone is separated from the small amounts of the higher-boiling substances. The ketone is withdrawn at the top through line 9, the higher-boiling constituents as residue through line 10. In this system it is provided that a catalyst of the same composition is used both in reaction vessel R ₁ and in reaction vessel R ₂ , although - if that System once working - the catalyst in one or the other of the reaction vessels is relatively inactive with respect to the first or high pressure stage of the process. So you can, as indicated by the solid flow lines, the combined stream of light, separated products and fresh feed at a temperature between 240 and 300 ⁰ and at a pressure above 12.25 atmospheres first through the catalyst in the reaction vessel R ₁ and then at high temperature and at low pressure between 1.05 to 3.50 atm by the catalyst in the reaction vessel R ₂ are derived: the effluent from R ₂ is dsann into the distillation columns D ₁ and D. ₂ This procedure can be followed until the catalyst in .R ₁ diminishes in its action, whereupon the system is switched off while the catalyst in R _{2 is} either regenerated on the spot or replaced by fresh catalyst. When the plant is put back into operation, the gaseous stream of the fresh charge is then first through the dashed line 4 through the "now active catalyst in the reaction vessel R ₂ at a pressure above 12.25 atm and at a temperature between 240 and 300 ⁰ and then passed via line 5 at low pressure through the catalyst with reduced activity in the reaction vessel R. ₁ the effluent from _R1 then flows into the distillation columns D ₁ and D. ₂ then, when the catalyst is exhausted in R _2, the flow of the gases is reversed again, the catalyst in the reaction vessel R _{1 being} regenerated or replaced in preparation for the next working cycle.This procedure not only has the advantage of increasing the yield of the desired higher ketone, but also extends the life of a certain catalyst mass without reducing the overall performance of a certain volume of the reaction vessels.

The outflow from the first used of the two reaction vessels R ₁ or R ₂ can, if desired, be passed through a (not shown) separation vessel for gas and liquid, and the non-condensable hydrogen and other gases separated in this way can be discharged from the system before the condensed portions of the exhaust gases are reheated and introduced as steam into the second reaction vessel.

The stream of the low-boiling fractions to be recycled from D ₁ can also be passed through a dehydration column (not shown) before the anhydrous gases formed are mixed with the feed material and fed to the reaction vessels.

The quantitative ratios between the when carrying out the process according to the invention Reaction components to be used are not

decisive. If the ketone to be formed is one which is formed by reacting a secondary aliphatic alcohol with an aliphatic ketone which has the same number of carbon atoms as the alcohol (such as, for example, with methyl ethyl ketone and sec-butyl alcohol), one can only work with alcohol or with a mixture of ketone and hydrogen as the starting material. As mentioned above, this is due to the fact that an equilibrium is rapidly established over the mixed catalyst under the working conditions between the starting alcohol and the ketone formed on dehydrogenation of the same and between the starting nucleus and the alcohol formed on hydrogenation of the same. So in those cases where the higher ketone is formed by combining an alcohol with a ketone which does not have the same number of carbon atoms as the alcohol, it is only necessary to maintain a feed stream whose components number the desired ratio of carbon without having to take into account whether these components are alcohols or ketones. So you can z. B. in a procedure which is nominally based on the reaction of isopropyl alcohol (a C _s compound) with methyl _{ethyl ketone (a C 4} compound) to produce a C ₇ ketone, any desired mixture of C ₃ compounds (isopropyl alcohol and acetone ) with the C ₄ compounds (methyl ethyl ketone and sec-butyl alcohol), which has a ratio of about 0.2 to 5 moles (preferably 0.2 to 0.5 moles) of the C ₃ compound for each mole of the C ₄ Connection results. During technical work, any unreacted alcohol and / or lower ketone components are preferably returned from the outflow of the reaction vessel to the reaction vessel. If, in such cases, this recycle stream has a different carbon number ratio than corresponds to the desired feed mixture, it is only necessary to add an additional component to the recycle stream which will restore the desired carbon number ratio. If z. B. C ₈ and C ₄ reaction components are combined to produce a C ₇ ketone and the recycled stream contains too little C ₃ component, this can be fed in either as isopropyl alcohol or as acetone. If, on the other hand, the C ₄ component is too small, this can be remedied by adding sec-butyl alcohol or methyl ethyl ketone. It must be noted, however, that in cases where the feedstock is excessively rich in ketones, it may be necessary to add hydrogen in order to maintain the desired ketone-alcohol balance over the catalyst.

If desired, the process according to the invention can also be carried out by feeding in a mixture of alcoholic or ketonic reaction components, a large number of higher ketone reaction products being formed at the same time. For example, the high-pressure reaction vessel can be charged with a mixture of isopropyl and sec-butyl alcohol (this mixture represents the supplementary flow in a continuous cycle process, as shown in the drawing), with C ₀ -, C ₇ -, C ₈ -, C ₉ - and higher ketones are formed in addition to C ₃ - and C ₄ ketones, which are normally returned to the reaction vessel after they have been separated from the higher ketones and other higher-boiling reaction products formed during the reaction.

The rate at which the vaporous mixture of alcohol and ketone components (if desired with hydrogen and / or diluent gas) in the desired molar ratio is passed through the catalyst beds is not critical. So can; one good Results obtained at an "hourly liquid space velocity" from -about 0.5 to S, with a preferred range between about ι and 4 lies. Under "hourly liquid roughness speed" one understands the number of parts of the volume of the feed mixture, measured in the liquid State which is part of the space filled by the catalyst per hour by the catalyst are passed through.

The following examples serve to explain the process in more detail.

95 Example 1

A catalyst was used which had been prepared by impregnating activated alumina with a concentrated aqueous solution of copper nitrate at about 80 ° in an amount such that about 10% copper, calculated on the weight of the dry catalyst, was introduced. The excess water was then evaporated and the product was dried, roasted for 3 hours at 125 ⁰ whereupon the dried material at 425 ° in a dry air stream for a further 4 hours. The roasted catalyst material was then reduced in a pure hydrogen stream at 250 ° for 4 hours, whereupon the catalyst was divided into equal proportions and placed in two steel reaction tubes connected in series. Then a mixture of methyl ethyl ketone was uind! sec-butyl alcohol evaporated in practically equimolecular amounts and passed through the catalyst in the first reaction vessel ^{at a liquid hourly space velocity of 2 at 255 ° and a pressure of 17.5 atmospheres.} The resulting vaporous mixture was then passed through the second reaction tube at about the same temperature and at the same flow rate, but at a pressure of about 2.10 atmospheres. When a sample of the effluent from the first reaction vessel was analyzed, the degree of conversion was found to be about 50% and

the yield of C ₈ ketone (which consisted of about 95%> 5-methyl-3-heptanone and about 5% 3,4-dimethyl-3-hexanone) was about 75 to 80%. In contrast, it was found that the outflow from the second reaction vessel contained _{a larger amount of C 8 ketone.} The yield from this reaction vessel was about 88 to 90% while the degree of conversion remained unchanged. >

After 400 hours of continuous operation and after the degree of conversion had dropped to about 40%, the plant was shut down while the catalyst in the low-pressure reaction vessel (the activity of which had been reduced slightly for the high-pressure phase of the reaction) was regenerated by burning out air at about 275 ° and subsequent reduction with hydrogen for several hours at about 250 °. The direction of flow of the gases was then reversed, so that the fresh material fed in was first passed through the regenerated catalyst at a pressure of 12.25 atmospheres and a temperature of 25 5 ° and then through the now deactivated catalyst in the other reaction vessel at approximately the same temperature , but was conducted at a greatly reduced pressure of about 2.10 atmospheres. Analysis of the products from the individual reaction vessels showed that the degree of conversion was again around 50%, the yield of C ₈ ketones in the effluent from the first reaction

tion vessel was about 80% and from the second reaction vessel about 90 ¹ Vo. After the plant had been in operation for about an additional 400 hours, the plant was shut down to allow regeneration of the catalyst in the low pressure reaction vessel. Then the direction of flow of the gases through the reaction vessels was changed again and the system started up again. In this way, the process can continue indefinitely.

The separation of the light components from the effluent from the low pressure reaction vessel can be carried out in the procedure described above by customary methods. The ones won in this way Low boiling components are preferably dehydrated before they are placed in the high pressure reaction vessel be returned. Likewise, the desired higher ketone can be obtained from the effluent of the low pressure reaction vessel in a known manner Way to be won.

Example 2

There were those; the same reaction components and working conditions as in Example 1 were used. Here, however - while the catalyst used in the high pressure reaction vessel was the same as in Example 1 - in the low pressure reaction vessel a catalyst was used which had been prepared by impregnating small tablets of calcined diatomaceous earth with a solution of nickel nitrate in such an amount that the tablets were about 10% Nickel calculated on the dry weight of the catalyst. The impregnated catalyst was then dried and roasted in the air, whereupon the nickel oxide formed during roasting was reduced to nickel in a hydrogen atmosphere. In this case, the degree of conversion as determined by analyzing the effluent from the high pressure or the low pressure reaction vessel was about 50%. The yield of C ₈ ketone from the high pressure reaction vessel was 80%, while that of the low pressure reaction vessel was about 90%. Since the nickel-containing catalyst only has dehydrogenating properties, the direction of flow of the gases supplied through the reaction vessels cannot be reversed in this case. Instead, the process was interrupted from time to time to enable reactivation of the catalyst in the reaction vessels.

Example 3

The same reaction conditions and the same catalyst as in Example 1 were used. In the present case, however, the stream of starting gases was produced from equimotecular amounts of sec-butyl alcohol and isopropyl alcohol. Among other things, C ₆ , C ₇ , C ₈ and higher ketones were formed. In addition, C ₃ and C ₄ ketones were formed by dehydration of the corresponding alcoholic reaction components, which were separated from the drain of the low pressure reaction vessel, dehydrated and returned to the high pressure reaction vessel for mixing with the freshly introduced C ₃ and C ₄ alcohol components. The degree of conversion in this procedure, determined by analyzing the effluent from the high pressure or low pressure reaction vessel, was between about 50 and 55%. The overall yield of C ₆ and higher ketones in the effluent from the first or high pressure reactor was only about 50%, while from the second or lower pressure reactor it was 90%.

No protection is sought for the manufacture of the catalysts.

Claims (5)

Patent claims: I. Process for the preparation of higher ketones by reacting a secondary aliphatic alcohol with an aliphatic ketone at higher temperature and higher pressure and in the presence of a dehydrating and dehydrating catalyst, characterized in that a vaporous mixture of alcohol and ketone in a first process stage at a pressure above about 12.25 a-tü and an elevated temperature, preferably between 240 and 300 ⁰ , reacted in the presence of the catalyst and then the resulting vaporous reaction mixture a pressure between about 1.05 and .3.50 atmospheres and at an elevated temperature, preferably above 225 °, with a dehydrogenating component containing catalyst is brought into contact. 2. The method according to claim r, characterized in that one in both working stages Dehydration - dehydrogenation - catalyst of practically the same composition is used will. 3. Verfahret according to claim 2, characterized in that that a catalyst is used in the second stage, its activity has been reduced as a result of previous use in the first work stage. 4. The method according to claims 1 to 3, characterized in that instead of a mixture of a ketone and a secondary aliphatic alcohol with the same carbon number only this alcohol or a mixture of the Ketone and hydrogen are used as the starting material. 5. The method according to claims 1 to 4, characterized in that one works continuously and the in the Destillationi des Reaction mixture initially released low-boiling portion, if necessary after Dehydration, in admixture with the fresh stream of starting material in the Reaction zone is passed. 1 sheet of drawings © 609 «20/457 9.56 (609835 3.57)