Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Reexamination Certificate
2001-11-21
2002-10-08
Davis, Brian J. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
C564S259000
Reexamination Certificate
active
06462235
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a catalytic process for producing oximes by reacting aldehydes or ketones with hydrogen peroxide and ammonia in the presence of a heterogeneous catalyst and an ammonium salt or a substituted ammonium salt.
2. Discussion of the Background
European patent applications EP-A-0 208 311, EP-A-0 267 362 and EP-A-0 299 430, as well as U.S. Pat. No. 4,794,198, describe the preparation and activation of a catalyst based on titanium, silicon and oxygen as well as its use for synthesizing oximes from aldehydes or ketones such as cyclohexanone by reaction with hydrogen peroxide and ammonia. This reaction is a so-called ammoximation. The catalysts usually exhibit a ratio of silicon: titanium of greater than 30. A typical agent is titanium silicalite TS1.
The synthesis of small aliphatic and cycloaliphatic oximes based on ketones with up to 6 carbon atoms, such as cyclopentanone and cyclohexanone, provides good results using titanium silicalite catalysts prepared and activated according to the above-mentioned documents. However, the results are clearly poorer in the case of larger or sterically higher-quality carbonyl compounds, such as acetophenone or cyclododecanone. In particular, the reaction rates, conversion of the carbonyl compounds and the yield with respect to hydrogen peroxide (H
2
O
2
used for ammoximation: H
2
O
2
necessary for total quantity×100%) are unsatisfactory.
Conversion rates of over 90% with a peroxide loss of less than 10% are achieved in the case of cyclohexanone as shown in Examples 22 and 24 of EP-A-0 267 362. However, conversion rates of only 50.8% with a peroxide loss of 48.9% are achieved with acetophenone under comparable reaction conditions. Conversion of cyclododecanone is claimed in the above-mentioned application, yet no concrete example of conversion and peroxide loss is given.
The clearly poorer yields with large or sterically high-quality carbonyl compounds can be attributed to, inter alia, the fact that large carbonyl compounds such as cyclododecanone (CDON) can either not penetrate the pores of the titanium silicalite catalyst at all, or, if they can penetrate, then only slowly. This can effectively result in a spatial separation of the partial steps of hydroxyl amine development (1) and oximation of the ketone (2), shown for the example for cyclododecanone (CDON) in the following reaction equations.
If the formed hydroxyl amine is not converted immediately or fully with the respective carbonyl compound, different secondary reactions increasingly occur, such as further oxidation of the hydroxyl amine with available hydrogen peroxide, represented formally as stoichiometric equation (3) above.
For the sake of completeness, another secondary reaction affecting peroxide selectivity is pointed out, namely the base-catalyzed or metal-catalyzed decomposition of hydrogen peroxide according to equation (4).
In German patent application DE 195 21 011 A1 (corresponding to U.S. Pat. No. 5,498,793) Enichem claims an amorphous silicon dioxide as a cocatalyst for ammoximation of acetophenone and cyclododecanone. With the addition of amorphous silicon dioxide conversion with cyclododecanone increases after an 8-hour reaction period to 85.5% or 85.2% (DE 195 21 011 A1, Examples 5 and 6), as compared to 76.6% without a cocatalyst. The peroxide yield simultaneously increases from 65.8% to 71.4% or 72.3%. The method described by Enichem results in a moderate improvement in conversion and peroxide yield, but the reaction method as described presents several disadvantages which show an industrial-scale application to be uneconomical.
The quantity of catalyst and cocatalyst in relation to the ketone is very high in the examples with each up to 25% by weight in the trials using cyclododecanone. Despite the high catalyst concentration, the conversion rate is minimal and the reaction is slow. The oxime yield is still far from reaching complete conversion, even after a total reaction time of 8 hours.
Secondary reactions according to partial steps (3) and (4) lower the space-time yield of the ammoximation, and they have an especially negative effect on peroxide selectivity. In the ammoximation of CDON without a cocatalyst, in some cases the peroxide selectivity rate is below 50%. However, with CDON it can be increased to approximately 60-70% using various cocatalysts, as described in German patent application P 100 47 435.7. However, this is still unsatisfactory for an industrial-scale process.
SUMMARY OF THE INVENTION
An object of the present invention is therefore to provide a process for ammoximation, in particular, of larger and sterically high-quality carbonyl compounds to give oximes with high peroxide selectivity, high conversion of the carbonyl compounds and high space-time yield.
Surprisingly, it was found that the above-mentioned problems are solved if an ammonium salt or a substituted ammonium salt is present during the reaction.
Accordingly, the above and other objects of the present invention have been achieved by a process for producing an oxime, comprising:
reacting a carbonyl compound in the liquid phase with hydrogen peroxide and ammonia in the presence of a) a heterogeneous catalyst and b) an ammonium salt, a substituted ammonium salt or a mixture of an ammonium salt and a substituted ammonium salt;
wherein said heterogeneous catalyst comprises titanium, silicon and oxygen;
wherein said ammonium salt or said substituted ammonium salt is represented by formula:
[R
1
R
2
R
3
R
4
]
+
X
−
wherein R
1
, R
2
, R
3
and R
4
each independently of one another represent hydrogen, an aliphatic, unbranched or branched alkyl radical having 1 to 20 carbon atoms, a cycloaliphatic radical having 3 to 12 carbon atoms, or an aromatic radical having a total of 6 to 12 carbon atoms; and
wherein X
−
represents an anion.
DETAILED DESCRIPTION OF THE INVENTION
The present invention accordingly relates to a process for producing oximes by reacting carbonyl compounds, in particular aldehydes or ketones, such as acetophenone, and cyclic ketones having 7 to 20 carbon atoms, such as cyclododecanone, in the liquid phase with hydrogen peroxide and ammonia in the presence of one or more heterogeneous catalysts and ammonium salts or substituted ammonium salts. Other constituents can be added optionally, such as, for example, acidic or neutral, inorganic or organic solids as cocatalysts and/or binders.
The heterogeneous catalyst is synthesized on the basis of titanium, silicon and oxygen. The catalyst is preferably a so-called titanium silicalite. The catalysts preferably have a micro-porous or meso-porous structure and preferably have a ratio of silicon: titanium of greater than 30. A preferred and particularly active agent is titanium silicalite TS1.
In addition to the titanium silicalite catalyst, other compounds which exhibit Lewis-acid and/or Brnsted-acid centers on the surface or in pores, can optionally be present as cocatalysts. Non-limiting, preferred examples of inorganic cocatalysts are aluminum oxides, in particular, acidic aluminum oxides, acidic activated alumosilicates, such as bentonite, montmorrilonite and kaolinite according to German patent application P 100 47 435.7, or amorphous silicon dioxide according to German patent application DE 195 21 011 A1 (Enichem). Non-limiting, preferred examples for cocatalysts synthesized on organic carrier materials are acidic and strongly acidic ion exchange resins such as Amberlyst 15 or Nafion NR 50 according to German patent application P 100 47 435.7. A functional group having Lewis-acid or Brnsted-acid properties can be physically adhered or chemically bonded to the carrier material.
As a solid material the catalyst and cocatalyst can be used both as a powder and as a molded body. The weight ratio of catalyst (preferably the above-mentioned titanium silicalite) and cocatalyst usually varies between 0.1:1 and 10:1. The solid cocatalyst preferably also assumes the function of the binder in the case of the molded bod
Oenbrink Georg
Schiffer Thomas
Thiele Georg Friedrich
Davis Brian J.
Degussa - AG
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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