Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2002-04-12
2003-10-28
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S318000, C568S346000, C568S350000, C568S388000, C568S391000, C568S403000, C568S458000, C568S465000
Reexamination Certificate
active
06639112
ABSTRACT:
The invention relates to an improved catalytic process for preparing ketones by pyrogenation starting from the corresponding acids, alcohols, aldehydes or esters, employing temperatures of between 250 and 500° C. According to this process the pyrogenation reaction is conducted in liquid phase.
The production of ketones from the corresponding acids by pyrogenation has been widely described in the literature. The general process consists in contacting the acids in vapor phase with a catalyst maintained at a high temperature of between 300 and 550° C. depending on the nature of the reactants.
For a detailed description of this process, refer to Bull. Soc. Chim. 1909, 4(5), C.R. 1913, p. 220 and Bull. Soc. Chim. 1909, 4(5), No. 172.
The prior art's recommended catalyst is a metal oxide. A detailed review of the respective merits of the various metal oxides is given in Brennst. Chem. 1967, 48(3), 69-73.
As an appropriate catalyst mention may be made of thorium oxide, calcium oxide, iron oxide (Fe
2
O
3
), uranium oxide, manganous oxide (MnO), zirconium, manganese dioxide deposited on alumina, titanium oxide and the oxides of rare earths (oxides of the metals ranging from lanthanum (of atomic number 57) to lutetium (of atomic number 71), including scandium and yttrium) such as CeO
2
, La
2
O
3
or Nd
2
O
3
deposited on gamma alumina.
The preparation of dialkyl ketones by pyrogenation of esters has also been described (cf. JP 48 076 806, 1972). There again, vapors of the ester are contacted with the catalyst (a zirconium) maintained at 400° C.
The same type of pyrogenation reaction, starting from aldehydes, was studied by the company Eastman Kodak. The process described in FR 1 533 651 employs the pyrogenation of vapors of aldehyde in contact with a catalyst maintained at 500° C., based on cerium oxide on alumina.
Alcohols may likewise be used as the starting product of the pyrogenation reaction for the purpose of preparing dialkyl ketones. JP 48 076 808, 1972, relates accordingly to a process which comprises contacting vapors of alcohol with a catalyst of the metal oxide type maintained at 420° C.
Generally speaking, the pyrogenation processes proposed hitherto in the art recommend contacting the reactants (acids, aldehydes, alcohols or esters) in vapor phase with the catalyst. The disadvantage associated with this type of process is the unavoidable formation of heavy impurities which gradually poison the catalyst.
In effect, the heavy impurities formed are deposited on the catalyst as they are formed and reduce its activity.
Regeneration of the catalyst requires prolonged shutdown of the reactors, without taking into account the fact that it does not allow the initial activity level to be attained and that it does not obviate replacement of the catalyst after a certain number of regeneration phases.
The process of the invention is aimed in particular at solving the problem of poisoning of the catalyst.
Surprisingly, the present inventors have shown that by conducting the reaction in liquid phase, in an appropriate solvent, i.e., by contacting the reactants with the catalyst in this solvent, it is possible to prevent poisoning of the catalyst.
Another advantage of the process of the invention is that it allows the use of a wide spectrum of catalysts. The success of the pyrogenation reaction is not dependent on the choice of metal oxides as catalyst. It is possible, for example, to operate in the presence of a variety of metal salts.
On the other hand, unlike the processes described in the prior art, the process of the invention does not require the employment of a catalyst which meets specific requirements in relation to particle size and specific surface.
Yet another advantage of the process of the invention is the possibility of operating at temperatures which generally are lower as compared with the temperatures required by the prior art processes.
The invention relates more specifically to a process for preparing ketones of formula I
in which:
A and B, which are identical or different, represent an optionally substituted saturated aliphatic hydrocarbon group; an optionally substituted aromatic hydrocarbon group; or an optionally substituted saturated carbocyclic group;
said process comprising reacting, at a temperature between 250 and 500° C., a compound of formula II:
A—X II
with a compound of formula III:
B—Y III
in which:
A and B are as defined above; and X and Y, which are identical or different, represent a hydroxyl function, a carboxyl function, a —COH function or an ester function,
in a heat carrier solvent having a boiling point of more than 250° C., in the presence of a catalyst comprising at least one compound of an element selected from alkali metals, alkaline earth metals, lanthanides, Si, Al, Zn, Cu, Ni, Co, Fe, Mo, Mn, Cr, V, Ti, Zr, U, Rh, Tl, Ag, Cd, Pb, Y, Sc and Th, in which the element is in the divalent state or has a higher valence.
A saturated aliphatic hydrocarbon group is a linear or branched saturated hydrocarbon group containing preferably from 1 to 40 carbon atoms or better still from 1 to 22 carbon atoms.
An aromatic hydrocarbon group is a carbocyclic aromatic group containing from 2 to 20 carbon atoms and consisting of an aromatic nucleus (monocyclic aromatic group) and/or of two or more aromatic nuclei which are fused or attached in pairs by &sgr; bonds, the resulting structure forming either a star structure or a linear structure.
A saturated carbocyclic group is a cyclic, monocyclic or polycyclic hydrocarbon group containing preferably from 2 to 20 carbon atoms. According to the invention, the polycyclic radicals consist of rings fused with one another or attached in pairs by &sgr; bonds, the resulting structure forming either a star structure or a linear structure.
The substituents carried by the saturated aliphatic hydrocarbon groups, the aromatic hydrocarbon groups and the saturated carbocyclic groups are those which are compatible with the pyrogenation reaction, i.e., those which do not give rise to secondary reactions.
According to one particularly preferred embodiment of the invention, A and B, which are identical or different, represent alkyl optionally substituted by one or more alkoxy, aryl or cycloalkyl radicals; aryl optionally substituted by one or more alkoxy, alkyl or cycloalkyl radicals; or cycloalkyl optionally substituted by one or more alkyl, alkoxy or aryl radicals.
An alkyl is a linear or branched aliphatic hydrocarbon chain containing preferably from 1 to 20 carbon atoms, better still from 1 to 10 carbon atoms, for example from 1 to 6 carbon atoms.
One preferred example of a substituted alkyl radical is an arylalkyl radical.
In the alkoxy radical, the alkyl part is as defined above.
An aryl is an aromatic hydrocarbon radical which is monocyclic or optionally consists of two or more fused aromatic nuclei, preferably C
6
-C
18
, for example C
6
-C
10
, such as phenyl, naphthyl, phenanthryl and anthryl.
The cycloalkyl radicals are monocyclic or polycyclic carbocyclic radicals (and especially monocyclic or bicyclic radicals) containing preferably from 3 to 10 carbon atoms, better still from 3 to 8 carbon atoms.
The term “polycyclic cycloalkyl” is intended to denote radicals comprising monocyclic nuclei fused with one another and/or monocyclic nuclei attached in pairs by a bonds. Mention may be made for example of cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctanyl, adamantyl or norbornanyl.
An ester function is a functional group —CO—OR′ in which R′ represents a saturated or aromatic hydrocarbon radical, or else a radical containing both a saturated part and an aromatic part.
By way of example, R′ represents alkyl optionally substituted by one or more alkoxy, aryl or cycloalkyl radicals; aryl optionally substituted by one or more alkoxy, alkyl or cycloalkyl radicals; or cycloalkyl optionally substituted by one or more alkyl, alkoxy or aryl radicals. More particularly it is preferred for R′ to represent alkyl.
The asymmetric ketones of formula I in
Barts Samuel
Burns Doane Swecker & Mathis L.L.P.
Rhodia Chimie
Witherspoon Sikarl A.
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