CA1122613A - Preparation of aldehydes - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Disclosed is a new process for the preparation of aldehydes of the formula RCH2CHO by a catalytic vapor phase reaction of formic acid and a ketone of the formula RCH2COCH2H where R is hydrogen, alkyl or an aryl group.

Description

2~;13 ~REPARATION OF KETONES

BACKGROUND OF THE INVENTION

The present invention relates generally to a method for preparing aldehydes OI a specific formula from specific types of ketones and formic acid.
5 More particularly, it relates to an entirely new process for the production ofaldehydes of the formula RCH2CHO from ketones of the formula RCH2COCH2R
and formic acid over a ceria-alumina catalyst system wherein R is hydrogen, alkyl or ~ryl-and recover~ng the product.

Pinacolone is an intermediate which is useful in the preparation OI
pharmaceutical products and pesticides for which improved methods of manu-facture have been sought for some time now. An electrolytic reductive coupling of acetone to form pinacol which can be converted to pinacolone has been carried out on experimental basis for a number of years to produce small 15 quantities of pinacol, but such processes have thus far failed to receive much commercial utilization because of the cost factors involved in these methods.
A therm~chemical route as taught by literature utilized a pyrolysis of one or two carboxylic acids to yield symmetrical or unsymmetrical ketones, respectively. This type of reaction has been used commerci~lly with the 20 significant disadvantage that the raw materials used in the manufacture of the ketones are costly because the selectivity of the reaction to unsymmetrical ketones is low.
Therefore, as with all chemical processes, it would be very desirable to be able to reduce the eost of a thermo-chemical route to the pinacolone or 25 other ketones for use in the chemical industry on a commercial basis.

13L;~Z~;~3 SU~IMARY OF THE INVENTION

It is therefore an object of the present invention to provide a method for the preparation of ketones from ketones and carboxyIic acids so as to produce a high yield of the ketone whiIe lowering the overall cost of capital investment and raw materials used in such a process.
It is a further object of the present invention to provide a catalyst system for promoting such novel chemical reactions within the range of commercial utilization.
These and other objects of the present invention, and the advantages thereof over the prior art forms, will become apparent to those skilled in the art from the detailed disclosure of the present invention as set forth hereinbelow.
A method has been found for the production of ketones comprising the steps of: introducing a ketone and a carboxylic acid into a chamber; passingthe mixture of the ketone and the carboxylic acid over a heated catalytically-active material; and recovering the ketone.
It has also been found that unsymmetrical ketones can be produced by: mixing a ketone and a carboxylic acid; passing the mixture through a catalyst bed consisting essentiaIly of a ceria compound on an alumina support;
and recovering the unsymmetrical ketone.
It has also been found that an unsymmetrical ketone may be produced by: mixing two different symmetrical ketones; passing the mixture through a catalyst bed consisting essentially of a ceria compound on an alumina support;
and recovering the unsymmetrical ketone.

DESCRlPrlON OF T~E PRE~ERRED EMBODII\IENTS

Unsymmetrical ketones may be produced according to the general reaction R2CO + 2R'CO2H to yield 2RR'CO ~ CO2 + H2O wherein R is a hydrocarbon radical and R' is a hydrocarbon radical other than R. This reaction has been found to occur over catalytically-active materials with a relatively short contact time in a temperature range of 300 to 550C. Unsymmetrical ketones resulting from the above-cited reaction can be recovered in yields up to80 percent or more. Groups representative of R and R' in the above-cited starting materials would include aliphatic groups such as me~hyl, ethyl, propylJisopropyl, t-butyl, pentyl, hexyl, and benzyl as well as aromatic substituents such as phenyl, p-tolyl and naphthyl.
~ :' ~;~Z~13 It is believed that the above-cited reaction will take place by passing the vapors of the reactants over heated catalytically-active materials such as iron filings, alumina, manganous oxides, thoria, or ceria types of catalysts. The preferred catalyst system from experience, however, is a ceria compound deposited on an alumina, silica or carbon support.
In each specific case, conditions may need to be altered slightly to maximize yields. For example, acetone and pivalic acid react over a ceria-nlumina catalys~ at a temperature near 470 C to produce pinacolone. When using a 2:1 molar ratio of acetone:pivalic acid with a 10-second contact time, the conversion of the pivalic acid to pinacolone was in the range of 80 percent of theoretical. Additionally, most of the unconverted reactants can be recovered and refed into the reactor zone to accomplish higher yields. By recycling reactants, virtuaily 100 percent conversion rates are possible. This results in about two moles of pinacolone being produced per every one mole of acetone consumed.
The catalyst can be a cerium acetate converted to ceria on hn alumina support such that a good activity will be produced if the ceria concentration is in the range of 1 to 10 percent calculated as CeO2 to total weight. The amount used will depend upon the specific surface area presented by the alumina support. Where the support is alumina available from Harshaw Chemical Company under the trademark of Harshaw Al 1404 T-l~ 8~É9, this equals approximately 190 square meters per gram, and the range of ceria is preferably 5to 10 percent. No treatment prior to use is necessary, but a slight aging of thecatalyst has been found during initial use, as is usual with such catalyst systems.
Thereafter this system will provide good activity of a steady nature for time periods in excess of 1,000 hours of use. The ceria-alumina catalyst provides a distinct advantage over thoria catalysts because the ceria is not radioactive thus eliminating a hazard of thoria and the inconvenience of Nuclear Regulatory Commission licensing and regulations covering its use.
It is believed that the above-described acetone and pivalic acid reaction to obtain pinacolone may proceed as follows.

3~3C COOH + CH3cocH3 Ceria-alumina 2CH3-COC~cH3)3 + C2 H20 It wil~ be noticed that two moles of the pivalic acid combine with one mole of the acetone to provide two moles of pinacolone. It is believed that the pivalic acid forms a complex with the ceria-alumina catalyst system by losing the acidichydrogen atom off of the pivalic acid. Thereafter the carbon to oxygen double ~;Z2~13 -- 4 ~

bond is attached by the methylene anion of the acetone to provide a shift of electrons to the oxygen atom and the loss of an oxygen atom with the coupling ofthe acetone by its methyl group thereto. This results in a probable intermediateof the formula (C~3)3CCOCH2COCH3. It is believed then that this inter-mediate is hydrolyzed causing a cleavage which results in a pinacolone and an acetic acid group leaving which will thereafter react with a second complexed pivalic acid group to form more pinacolone. In this process, carbon dioxide and water are also formed.
Further examples of ketones produced from ketones and carboxylic acids include: acetone and benzoic acid to obtain acetophenone; acetone and propionic acid to obtain methyl ethyl ketone and diethyl ketone; acetone and dimethyl succinate to obtain 2,5-hexandione; acetone and phenylacetic acid to obtain phenylacetone; diethyl ketone and acetic acid to obtain acetone and methyl ethyl ketone; diethyl ketone and benzoic acid to obtain propiophenone;
benzophenone and acetic acid to obtain acetophenone; benzoic acid and methyl ethyl ketone to obtain acetophenone and propiophenone; and acetone and dimethyl terephthalate to obtain p-diacetylbenzene.
In some cases, alcohols or aldehydes may be substituted for the carboxylic acid to produce the ketones of this process. It has been found that benzyl alcohol or benzaldehyde may be substituted for benzoic acid in the reaction with acetone to obtain acetophenone. It is believed that reactions using the aldehyde or alcohol for a starting material proceed by an oxidation-reduction disproportionation of the feedstocks. It is also possible that the ketonic products are formed through carboxylic acid intermediates.
It has also been found that the ceria-alumina catalyst provides good activity for rearrangements of ketones by themselves such as methyl ethyl ketone alone to obtain acetone and diethyl ketone and acetone and diethyl ketone to obtain methyl ethyl ketone.
It is believed that the ceria-alumina catalyst will provide good activity for numerous other chemical reactions besides the ketone reactions described above. This catalyst would be useful in reactions like: benzophenone and pivalic acid to obtain t-butyl phenyl ketone; 1,3-dichloroacetone and pivalic acid to obtain monochloropinacolone; and cyclopentanone and acetic acid to obtain 2,7-octanedione.
It is also believed that the ceria-alumina catalyst will providP good activity for many other reactions falling within the following general types.

RCH2X + CH3COCH3 to yield RCH2CH2COCH3 + HX
where R is an activating group such as hydrogen, alkyl or aryl and X is a good leaving group such as a halogen.
RCH3 + RlC~2H ~o yield RCH2CORI
5 where R is an election withdrawing group such as 2 or 4 pyridyl and Rl is alkyl o.
aryl.
RCH2~C)CH2R + HCCOH to yield RCH2CHO
where R is hydrogen, alkyl or aryl.
This process will provide a distinct economic advantage over prior 10 methods, particularly for production of pinacolone over either the mixed acid pyrolysis route or the formation of the mixed anhydrides and subsequent pyrolysis to the ketones. Lower capital and operating costs are expected in the process of the present invention versus that of the mixed acid pyrolysis becausethe heat of vaporization of acetone is less than that of acetic acid, thus lS requiring less energy. This is increased by the fact that one mole of acetone is nearly equal to two moles of acetic acid used in the old methods. Further, aboutone-half as much carbon dioxide and water are produced making it easier to condense and recover the product and unreacted materials. There is also less dilution of the reaction mixture with byproduct carbon dioxide and water so that20 a reaction vessel only two-thirds to three~uarters as large as that used in the acid pyrolysis route may be used to result in a savings in the cost of catalyst and reactor. In addition, smaller condensers with lower energy requirements will be adeouate.
In order that those skilled in the art may more readily understand ~he 25 present invention and certain preferred aspects by which it may be practiced,the following specific examples are afforded to show the method of preparation of the various ketones according to the general reaction cited above.

EXA~PLE I

An apparatus suitable for use in the above-described reactions was 30 assembled having a vertical tube furnace constructed over Pyrex~!}' tubing for heating the reaction zone. The reaction tube contained a thermowell in the reaction zone to obtain accurate temperature readings. The upper section where the reactants enter contained a preheater segment to bring the reactants up to reaction temperature while the lower section contained a smaller heating 35 segment to sustain these temperatures. The preheater was thermostatically ~ 6 --controlled to provide more heat when reactants were being fed into the section to maintain the temperature. The catalyst should be positioned between glass beads so that it begins Just below upper section and runs down approximately 75 percent of the length of the lower section and between the concentric thermo-5 well and the glass that contains the reactor. The reactor was connected bymeans of a "Y" tube to a condensate receiver on the bottom and two water cooled condensers in series on the vertically straight neck. Eor example, the lower condenser may be of a six-bulb Allihn type and the upper one of the Friedrich's type. Also it might be desirable to use a feed reservoir on a triple10 beam balance connected to a metering pump to feed the reactants to the systemas a known rate. With a "Y" tube connected to the upper section of the tube furnace, the reactants may be fed in~o one branch and a thermocouple well placed in the other branch for measuring temperatures.
A thoria catalyst was prepared from 40 grams of thoria nitrate 15 tetrahydrate [Th(NO3)4~ 4H2O] in water, impregnated on 200 ml or 172 grams ofHarshaw Alumina catalyst AL1404 T 1/8~'. The wetted alumina was stripped of water in a rotary evaporator under aspirator vacuum. This was transferred to a large porcelain dish were it was heated strongly while aspirating the NOX from it through a water trap. The resulting loose material was then placed into the 20 reactor tube with glass beads ahead and behind the catalyst zone.
The system was then flushed out with acetone vapors to clear the system of any residues, and the catalyst temperature grsdually rose to 440 to 485C. The feed reservoir was changed from acetone to a 2:1 molar ratio of acetone:pivalic acid. The condensate samples removed were composed of 4 to 5 25 parts red organic layer over a colorless aqueous layer. Product purification and gas chromatographic studies of the organic layer showed the presence of pinacolone in yields ranging as high as 90 percent of theoretical on a single pass.
Recovery of reactants and recycling can achieve even higher yields.

A ceria catalyst was prepared from 100 grams of cerium acetate hydrate [C~(OAc)3- XH2O] and 400 ml of water at room temperature with agitation to dissolve nearly all of the material. The solution was filtered and rinsed with several portions of water to result in approximately d~60 ml of filtrate. The soluti~n was then combined with 1050 grams of Harshaw Alumina 35 catalyst Al 14041/8(~' and tumbled in a gallon jug. The solution was absorbed ~o leave no freely pourable liquid and thus wetting the alumina. The mixture was dried in a porcelain dish at approximately 200C for 15 hours and then installedin the apparatus according to Example 1.
The system was flushed out according to Example 1 and the feed 5 reservoir charged with a 2:1 molar ratio of acetone:pivalic acid. Pinacolone product was recovered from the condensate in yields up to 90 percent of theoretical as evidenced by gas chromatographic studies.

l~sing the apparatus of Example 1 and the catalyst of Example 2, 10 other reactions can be performed in a fashion similar to Examples 1 and 2. Ineach case, the reaction products were confirmed by mass spectra and quantita-tively measured by gas chromatographic studies. These reactions are summa-rized in the following Table 1. The Molar Ratio refers to the ratio of the reactants in the order stated in the feed reservoir. With the exception of the 15 pinacolone, no effort was made to maximize the yields.

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-ln -Thus, it should be readily apparent from the foregoing description of the preferred embodiments that the method here;nabove described accomplishes the objects of the invention and solves the problems attendant to the method of preparation of ketones.

Claims

WHAT IS CLAIMED IS:

1. A method for producing an aldehyde of the formula RCH2CHO comprising the steps of: mixing formic acid with a ketone of the formula RCH2COCH2R where R is hydrogen, alkyl or aryl; passing the mixture through a catalyst bed consisting essentially of a ceria compound on an alumina support; and recovering the product.