Process for preparing oximes

Details Process for preparing oximes Process for preparing oximes

2001-09-26

2003-05-20

Wilson, James O. (Department: 1623)

Organic compounds -- part of the class 532-570 series

Organic compounds

Amino nitrogen containing

C564S253000, C564S258000, C564S259000, C564S260000, C564S261000, C564S263000, C564S264000

Reexamination Certificate

active

06566555

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a catalytic process for preparing oximes. In this process, a carbonyl compound, preferably a cycloalkanone having from 7 to 20 carbon atoms, is reacted in the liquid phase with ammonia and hydrogen peroxide (ammoximation), over a heterogeneous catalyst system comprising two or more components of which at least one of the components comprises at least one porous, titanium-containing solid, and at least one second component comprises an acidic solid.
2. Discussion of the Background
European patent applications EP-A-0 208 311, EP-A-O 267 362 and EP-A-0 299 430 and U.S. Pat. No. 4,794,198, each of which is herein incorporated by reference, describe the preparation and activation of a catalyst based on titanium, silicon and oxygen, and its use for the synthesis of oximes from aldehydes or ketones, for example cyclohexanone, by reaction with hydrogen peroxide and ammonia. The catalysts usually have a silicon:titanium ratio of greater than 30. A typical representative catalyst is the titanium silicalite TS1.
While the synthesis of relatively small aliphatic and cycloaliphatic oximes from ketones having up to 6 carbon atoms, for example, cyclopentanone and cyclohexanone, gives good results for numerous titanium silicalite catalysts, prepared and activated as described in the above mentioned documents, the results are significantly poorer when larger or more sterically hindered carbonyl compounds, such as acetophenone and cyclododecanone, are used. In particular, the reaction rate, the percent conversion of carbonyl compound used, and the hydrogen peroxide selectivity (H
2
O
2
used for the ammoximation/total amount of H
2
O
2
required·100%) are unsatisfactory in these experiments.
In the examples of EP-A-O 267 362, conversions of over 90% at a peroxide loss of below 10% are achieved for cyclohexanone (Examples 22 and 24). Comparable reaction conditions using acetophenone give conversions of only 50.8% at a peroxide loss of 48.9%. The reaction of cyclododecanone is also claimed in the cited application, but no specific example is provided with regard to the conversion and peroxide loss obtained when reacting cyclododecanone.
The significantly poorer results obtained for large or sterically hindered carbonyl compounds can be attributed, inter alia, to the inability of large carbonyl compounds such as cyclododecanone to penetrate, or their ability to penetrate only slowly, through the pores of the titanium silicalite catalyst. This can lead to spatial separation of the substeps of hydroxylamine formation (1) and oximation of the ketone (2) (in the reaction equations shown below for cyclododecanone (CDON)).
The decomposition of hydroxylamine by reaction with hydrogen peroxide, formally represented by the stoichiometric equation (3), can occur to a considerable extent as a competing reaction, which reduces the productivity of the reaction and the hydrogen peroxide selectivity.
NH
3
+H
2
O
2
→H
2
O+NH
2
OH  (1)
NH
2
OH+CDON→CDON oxime+H
2
O  (2)
2 NH
2
OH+H
2
O
2
→4 H
2
+N
2
  (3)
German patent application DE 195 21 011 A1 (corresponding to U.S. Pat. No. 5,498,793), describes an amorphous silicon dioxide cocatalyst for the ammoximation of acetophenone and cyclododecanone, in which the addition of amorphous silicon dioxide provides for an increase in the conversion of cyclododecanone after a reaction time 8 hours to 85.5% or 85.2% (DE 195 21 011, Examples 5 and 6) compared to 76.6% without the cocatalyst. The peroxide yield at the same time increased from 65.8% to 71.4% or 72.3%. This process leads to a slight improvement in conversion and peroxide yield, but it also has a number of disadvantages which would make it uneconomical for industrial use:
The amount of catalyst and cocatalyst based on the ketone used is very high in the examples, namely up to 25% by weight in each case, for reactions using cyclododecanone as a starting material.
Despite the high catalyst concentration, the conversion rate is low and the reaction is slow.
Even after a total reaction time of 8 hours, the oxime yield is still far from complete conversion (i.e., complete conversion means an oxime yield of about 99%, preferably above 99.5%).
The mean conversion rate over a reaction time of 8 hours is 7.10 to 7.3 mg of oxime/(g of cat·min) compared to 6.38 mg of oxime/(g of cat·min) without the amorphous silicon dioxide cocatalyst.
For relatively large rings such as, for example, cyclododecanone, high conversion rates, which lead to complete conversion, are very important for industrial applications, because as the molecular weight increases, it is technically difficult to separate the unreacted ketone from the corresponding oxime.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a process in which the ammoximation proceeds with virtually complete conversion combined with a high conversion rate and good peroxide yield. The percent conversion of the carbonyl compound to an oxime should, where possible, be so high that a subsequent reaction of the carbonyl compound with an aqueous hydroxylamine solution may be dispensed with. It has surprisingly found that this object can be achieved by reacting a carbonyl compound, hydrogen peroxide and ammonia in the presence of an acidic cocatalyst together with the titanium-containing catalyst. In particular, it has been found that the conversion rate can be significantly improved thereby.
DETAILED DESCRIPTION OF THE INVENTION
Thus, an embodiment of the present invention provides for reacting a carbonyl compound, hydrogen peroxide and ammonia in the presence of a catalyst system comprising a catalyst and a cocatalyst, wherein the catalyst comprises at least one crystalline microporous or mesoporous solid comprising titanium, silicon and oxygen, and the cocatalyst comprises an acidic solid comprising an organic or inorganic support material, and the support material itself has Lewis-acid or Brönsted-acid properties, or Lewis-acid or Brönsted-acid functional groups are physically or chemically applied to the support material.
The catalyst is preferably a compound comprising titanium, silicon and oxygen, and having a porous structure, for example titanium silicalites. The porous structure may be either microporous and/or mesoporous structures. By microporous structure, we mean a structure having pores sizes which are less than 2 nm. By mesoporous structure, we mean a structure having pore sizes in the range of approximately 2 to 50 nm. Non-limiting examples of microporous titanium silicalites are the types TS1 and Ti-beta. Non-limiting examples of mesoporous structures are the titanium silicalites of the type Ti-MCM41 and Ti-HMS. The preparation of TS1 type silicalites is described, for example, in U.S. Pat. No. 4,410,501 and Bruno Notari, “Microporous Crystalline Titanium Silicates”, Advances in Catalysis, vol. 41 (1996), pp. 253-334; the preparation of Ti-beta is described, for example, in Spanish Patent 2037596; the preparation of Ti-MCM41 is described, for example, in EP 0655278; and the preparation of Ti-HMS is described, for example, by Tanev et al,
Nature,
368 (1994), pp. 321-323, each of which is incorporated herein by reference.
Suitable cocatalysts are solids which themselves have Lewis and/or Brönsted-acid properties on their surface or in the pores thereof. Non-limiting examples of such inorganic cocatalysts which have Lewis and/or Brönsted acid properties are acidic aluminum oxides and acidic, activated aluminosilicates such as bentonite, montmorillonite and kaolinite.
Alternatively, the cocatalysts may have Lewis acid and/or Brönsted acid functional groups, either chemically or physically applied thereto. Cocatalysts having chemically applied acid groups include sulfonated or phosphonated resins. Alternatively, the cocatalyst may be an inert solid support having a physically applied acidic coating, such as a coating of a sulfonated resin or an acidic inorganic material, s

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