Note: Descriptions are shown in the official language in which they were submitted.
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.
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-- 3 --
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.
613
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
Z613
~ 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.
EXAMPLE 2
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
Z613
-- 7 --
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.
EXAMPLES 3-12
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.
-- 8 --
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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.
