Note: Descriptions are shown in the official language in which they were submitted.
PREP~RATION OF KETONES
.
~A~KGROUND OF THE INVENTION
The present invention relates generally to a method
for preparing ketones from ketones and carboxylic acids. More
particularly, it relates to an entirely new process for the
production of unsymmetrical ketones from ketones and carboxylic
acids over a ceria-alumina catalyst system in the temperature
range of 300 to 550C. utilizing a very short contact time over
the catalyst to achieve a conversion in the range of ~5 percent
or more while recovering most of the unconverted reactants for
recycling. An excellent example of such a reaction is the
reaction of acetone with pivalic acid over a ceria-alumina
catalyst to produce pinacolone.
Pinaco].one is an intermediate which is useful in the
preparation of pharmaceutical products and pesticides for which
improved methods of manufacture 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
quantities of pinacol but such processes have thus ~ar failed
to receive much commercial utilization because of the cost
factors involved in these methods.
A thermo-chemical route as taught by literature
utilizes a pyrolysis of one or two carboxylic acids to yield
symmetrical or unsymmetrical ketones, respectively. This type
of reaction has been used commerci.ally with the significant
disadvantage that the raw materials used in the manufacture of
the ketones are ccstly because the selectivity of the reaction
; to unsymmetrical ketones is low.
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ThereEore, as ~ith all chemlcal processes, it would
be very desirable to be able to reduce the cost of a thermo~
chemical route to the pinacolone or other ketones for use in
the chemical industry on a commercial basis.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to
provide a method for the preparation of ketones from ketones
and carboxylic acids so as to produce a high yield of the ketone
while lowering the overall cost of capital lnvestment 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 chem:Lca].
reactions within the range of commercial utiliza~ion.
These and other ob~ects of the present invention,
and the advantages thereof over the prior art forms, will become
apparent to those skilled in the art Erom the detailed disclosure
of the present invention as set forth heleinbelow.
A method has been found for the production of ketones
comprlsing the steps of: introducing a ketone and a carboxylic
acid into a chamber; passing the mixture of the ketone and the
carb~oxylic 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 acld; passing
the mixture through a catalyst bed consisting essentially 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;
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)457
passing the mixture through a catalyst bed consisting essentially
of a ceria-compo~lnd on an alumina support; alld recovering the
unsymmetrical ketone.
D~SCRIPTI ~
Unsymmetrical ketones may be produced according to
~he general reaction R2C0 ~ 2R'C02H to yield 2RR'C0 ~ C02 ~ H20
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 shor~
contac~ time in a temperature range of 300 to 550C. Unsymme-
trical ketones resulting from the above-cited reaction can be
recovered in yields up to 80~ or more. Groups representative
of R and R' in the above-clted starting materials would i.nclude
aliphatic groups such as methyl, ethyl, propyl7isopropyl,t-butyl,
:~ pentyl, he~yl, and benzyl as well as aromatic substituents such
as phenyl, p-tolyl and naphthyl.
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, lS 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-alumina catalyst at a temperature near
470C. to produce pinacolone. When using a two:one molar ratio
of acetone:pivalic acid with a ten second contact time, the
conversion of the pivalic acid to pinacolone was in the range
of 80~ of theoretical. Additionally most of the unconverted
reactants can be recovered and refed into the reactor zone to
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57
accomplish higher yields. By recycling reactants virtually 100%
conversion rates are possible. This resul~s in about t~o moles
of pinacolone being produced per e~ery one mole of acetone
consumed.
The catalyst can be a cerium acetate converted to
ceria on an alumina support such tha~ a good activity will be
produced if the ceria concentration is in the range of 1 to 10%
ca~culated 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-1~8~ ~is equals~
approximately 190 square meters per gram, and the range oE ceria
is preferably 5 to lOZ. ~o treatment prior to use is necessary
but a slight aging of the catalyst has been found during initial
use, as is usual with such catalyst systems. Thereafter thi~
system will provide good activity of a steady na~ure for time
pèriods in excess of 1,000 hours of use. The ceria-alumina catalyst
provides a distinct advantage over thoria catalysts because the
ceria is not radioaceive thus eliminating a hazard of thoria and
the inconvenience o~ Nuclear Regulatory Commission licensing and
regulation~ covering its use.
~ t is bel~eved that the above-described acetone and
pivalic acid reaction to obtain pinacolone may proceed as follows.
2(CH3)3C-COOH + CH3COCH3 ceri -alumina~
2CH3-COC(CH3) 3 ~ C2 ~ H~O
It will be noticed ~hat two moles of the pivalic acid combine with
one mole of the acetone ~o provide two moles of pinacolone. It is
believed that the pivalic acid forms a complex with the ceria-
alumina catalyst system by losing the acidic hydrogen atom off
of the pivalic acid. Thereafter the carbon to oxygen double bond
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v~3
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45'7
is attacked 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 of the acetone by its methyl group there~o.
This results in a probable intermediate of the formula (CH3)3
CCOCH~COCH3. It is believed then that this intermediate is
hydroly~ed causing a cleavage which results in 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 acld to obtain aceto-
phenone; acetone and propionic ~cid to obtain methyl e~hyl ketone
and diethyl keto~e; acetone and dimethyl succinate to obtain
2,5-hexandione; acetone and phenylacetic acid to obtain phenyl~
acetone; 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 wich acetone to
obtain acetophenone. It i9 believed that reactions using the
aldehyde or alcohol for a starting material proceed by an oxida-
tion-reduction disproportionation of the feedst~cks. It is
also possible that the ketonic products are for~ed through
carboxylic acid intermediates.
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4~
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 ob~ain acetone and diethyl
ketone and acetone and diethyl ketone to obtain methyl ethyl
ketone.
It is believed that the ceria-alumina ca~alyst will,
provide good activity for numerous other chemical reactions
besides the ke~one reactions described above. This catalyst
would be useful in reactions like: benzophenone and pivalic acid
to obtain t-butyl phenyl ketone; 1,3-dichloroacetane and pivalic
acid to obtain monochloropinacolone; and cyclopentanone and
acetIc acid to obtain 2,7-octanedlone.
It is also believed that the ceria-alumina catalyst
will provide good activity for many other reactions falllng
within the fol1Owing general types.
RC~2X ~ CH3COCH3 to yield RCH~CH2COCH3 + HX,
where R is an activating group such as h~drogen, alkyl or aryl
and X is a good leaving group such as a halogen.
RCH3 + R~CO~H to yield RC~COR1,
where R i~ an election withdrawing group such as 2 or 4 pyridyl
and R1 is alkyl or aryl~
RC~2COCH2R f HCCOH to yield RCH2CHO
~ where R ls hydrogen, alkyl or aryl.
;` This process will provide a distinct economic advantage
over prior methods, particuLarly for production of pinacolone
over either the mixed acid pyrolysis route or the formation of
the ~ixed anhydrides and subsequent pyrolysis to the ketones.
Lower capital and operating costs are expected in the process of
the presen~ invention versus that of the mixed acid pyrolysis
because the heat of vaporization of acetone is less than that of
acetic acid, thus requiring less energy. This is increased by
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the fact that one mole of acetone is nearly equal to two moles
of acetic acid used in the old methods. Further, about one-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 that a reaction vessel only two-thirds
to three-quarters 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 adequate.
In order that those skilled in the art may more readily
understand the 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~LE 1
An apparatus suitable for use in the above-described
reactions was assembled having a vertical tube furnace construct-
ed 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
conta~ned a smaller heating segment to sustain these temperatures.
The preheater was thermostatically 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~ of the length of the lower section and between
the concentric thermowell and the glass that contains the reactor.
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The reac~or was connected by means of a "Y" tube to a condensate
receiver on the bottom and two water cooled condensers in series
on the vertically straight neck~ For example, the lower conden-
ser may be of a six bulb Allihn type and the upper one of ~he
Friedrich's type. Also it might be desirable to use a feed
reservoir on a triple beam balance connec~ed to a metering pump
to feed the reactants to ~he system at a k~own rate. With a
"Y~ tube connected to the upper section or the tube furnace, the
reactants may be fed into 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 tetrahydrate ~Th~N03)4 4~20] in water, impreg~ated on
200 ml. or 172 grams of Harshaw 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 where it was heated qtrongly while aspirating
the NOX from it through a water trap. The resulting loose
material was then placed into the reactor tube with glass beads
ahead and behind the catalyst zone.
The ~ystem was then flushed out with acetone vapors
to clear the system of any residues and the catalyst temperature
gradually rose to 440 to 485~C. 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 parts red
organic layer over a colorless aqueous layer. Product purifica-
tion and gas chromatographic studies of the organic layer showed
the presence of pinacolone in yields ranging as high as 90% of
theoretical on a single pass. Recovery of reactants and recycling
can achleve even higher yields.
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EXAMPLE 2
A ceria catalyst was prepared from 100 grams of
cerium acetate hydrate [Ce~OAc)3 XH20] and 400 ml. of water at
room temperature with agitation to dissolve nearly all of the
material. The solution was filtered and xlnsed with several
portions of water to result in approximately 460 ml. of filtrate.
The solution was then combined with 1050 grams of Harshaw
Alumina catalyst Al 1404 1/8~and tumbled in a gallon jug. The
solution was absorbed to 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 installed in
the apparatus according to Example 1.
The system was flushed out according to Example 1 and
the feed reservoir charged with a 2:1 molar ratio of acetone:
pivalic acid. Pinacolone product was recovered from ~he conden-
sate in yields up to 90~ of theoretical as evidenced by gas
chromatographic studies.
EXAMPLES 3~12
Using the apparatus of Example 1 and the catalyst of
Example 2 other reactions can be performed in a fashion similar
to Examples 1 and 2. In each case the reaction products were
confirmed by mass spectra and quantltatively measured by gas
chromatographic studies. These reactions are summarized in the
following Table 1. The Molar ~atio refers to the ratio of the
reactants in the order stated in the feed reservoir. With the
exception of the pinacolone, no effort was made to maximize
the yields.
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Q457
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-- 12 --
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Thus, it sho~llcl be readily apparent from the foregoing
description of the preEerred embocliments that the method herein-
above described accomplishes tihe objects of the invention and
solves the problems attendant to the method of preparation of
ke~ones.
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