Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2002-11-18
2004-03-16
Richter, Johann (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S396000, C568S862000
Reexamination Certificate
active
06706928
ABSTRACT:
This invention relates to aldol condensation processes and in particular to the condensation of ketones.
The coupling reaction of relatively small molecules to form relatively large molecules is a commercially attractive route to form a range of products having specific structures and properties. As an example, Methyl isobutyl ketone (2-methyl-4-pentanone) is the largest volume aldol reaction product of acetone. Methyl isobutyl ketone (MIBK) is an excellent solvent for cellulose and resin based coating systems and also for vinyl, epoxy and acrylic resins. It is traditionally manufactured via a three-step reaction scheme as described in Industrial Organic Chemistry, 3
rd
Edition (eds. K Weissermel and H J Arpe), Wiley (1997), p 280-281, the stages comprising (i) the base catalysed aldol condensation of acetone in the liquid phase to diacetone alcohol (DAA), (ii) the acid catalysed dehydration of DAA to mesityl oxide (MO) and (iii) the hydrogenation of MO to MIBK and further to methyl isobutyl carbinol.
These processes are complicated and the operating costs are high. The condensation equilibrium in step (i) does not favour aldol formation. In step (ii) acetone can be formed by the reaction of mesityl oxide with water and in step (iii) the less useful methyl isobutyl carbinol has to be separated by distillation. There is also a corrosive problem due to the use of liquid acids and bases.
Recently, a one-step process from acetone to MIBK has become commercially feasible and several catalytic systems have been described for this process. They mainly consist of palladium supported, for example, on KOH—Al
2
O
3
, MgO—SiO
2
or cation exchange resins (Kirk-Othmer Encyclopaedia of Chemical Technology, Vol. 13, Wiley, New York, 1979, p.907), CaO—MgO—SrO—Al
2
O
3
as described in JP-A-62258335, Nb
2
O
5
as described in JP-A-63096147; ZrO(OH)
2
-carbon as described in JP-A-63068538 and Ce, Hf and/or Ta oxides or hydroxidescarbon as described in JP-A-63096146. Very high selectivities to MIBK (>90%) are described in the 80-160° C. range and acetone conversions near 40%. The high operating pressures required, typically 10-100 atm are a disadvantage of the single-step process.
GB-A-921510 describes a liquid-phase process for the condensation of acetone to make mesityl oxide using a catalyst which is an alkali-treated activated alumina. The process is favoured at low temperatures, between about 80 and 150° C.
Tanabe et al (
Applied Catalysis
48 (1989) 63-70) describe the effect of various metal cations on the activity of magnesia catalysts in the liquid phase aldol condensation of acetone.
More recently, catalysts which operate efficiently in the gas phase at atmospheric pressure have been developed for the one-step process. These have included Pd/SAPO-34, described in U.S. Pat. No. 4,704,478, Pd/KH-ZSM-5 (in U.S. Pat. No. 5,059,724); Ni/MgO (L M Gandia et al, Appl. Catal. A: General, 101 (1993) L1-L6), Ni/ALPON (L M Gandia et al, Appl. Catal. A: General 114 (1994) L1-L7; Na/Pd/MgO (K Lin et al, Appl. Catal. A: General 147 (1996) L259-L265); Ni/Al
2
O
3
(S Narayanan et al, Appl. Catal. A: General 145 (1996) 231-236) and Pd or Ni supported on Mg/Al hydrotalcites (Y Z Chen et al, Appl. Catal. A: General 169 (1998) 207-0214).
U.S. Pat. Nos. 4,086,188 and 4,165,339 describe the gas phase condensation of aldehydes and ketones, especially acetone in the presence of catalysts comprising a complex magnesium-aluminium oxide-hydroxide mixture which is doped with lithium ions. The reactions produce isophorone and mesityl oxide and achieve isophorone: mesityl oxide ratios>1.
U.S. Pat. No. 4,599,453 describes the single stage production of higher aliphatic ketones by reacting a starting ketone with carbon monoxide in the presence of a catalyst comprising copper supported on a metal oxide.
U.S. Pat. No. 5,055,620 describes a polymorphic magnesium-oxide-pseudoboehmite composition for the aldol condensation of acetone to isophorone.
In WO-A-00/31011, the aldol condensation of aldehydes in the gas phase was described using catalysts comprising an alkali metal on an inert support.
We have now found that the condensation of ketones can be effected in the gaseous phase using a solid base catalyst thereby avoiding the need for aqueous caustic solutions with their consequent handling and effluent disposal problems.
It is an object of the present invention to provide a method of forming a carbonyl compound by the aldol condensation of at least one organic ketone. It is a further object of the invention to provide a method of making a saturated ketone or an alcohol by the hydrogenation of a carbonyl compound formed by the aldol condensation of at least one organic ketone. It is a further object of the invention to provide a catalyst which is capable of catalysing the aldol condensation of at least one ketone to form a higher organic ketone.
According to the invention, we provide a process for the production of a product ketone containing at least six carbon atoms from at least one feedstock ketone by contacting the feedstock ketone in the vapour phase with a particulate catalyst comprising at least one basic alkali metal compound supported on an inert substrate at a temperature above 175° C.
According to a second aspect of the invention, we provide a process for the production of an alcohol by the hydrogenation of a ketone containing at least six carbon atoms which has been formed from at least one feedstock ketone by contacting the feedstock ketone in the vapour phase with a particulate catalyst comprising at least one basic alkali metal compound supported on an inert substrate at a temperature above 175° C.
According to a third aspect of the invention, we provide a catalyst for catalysing the aldol condensation of a ketone at a temperature above 175° C., said catalyst comprising at least one basic alkali metal compound supported on an inert substrate.
Suitable catalysts are basic sodium, potassium, or cesium compounds such as oxides hydroxides or carbonates supported on a material such as carbon, silica, alumina, a clay, silicalite or a zeolite Preferred catalysts are alkali metal compounds supported on silica, especially potassium or sodium supported on silica. The potassium and sodium catalysts appear to have high activity and are the most selective. The catalyst preferably contains 0.1 to 25%, preferably 0.4 to 18%, by weight of the alkali metal.
The support preferably is in the form of particles having maximum and minimum dimensions in the range 0.5 to 10 mm, preferably 1 to 4 mm, and having a BET surface area in the range 50 to 500 m
2
/g. The catalyst is preferably made by impregnating the support particles with an aqueous solution of an alkali metal compound that is basic or decomposes to a basic compound upon heating, for example an alkali metal hydroxide, acetate, oxalate, nitrate or carbonate, followed by drying and calcination if necessary to effect decomposition to a basic compound.
The reaction is effected at temperatures above 175° C., particularly above 200° C., and preferably below 450° C., particularly in the range 200 to 350° C. As the temperature increases the activity increases but the selectivity tends to decrease, often with the production of hydrogenated products.
After a period of operation, the activity of the catalyst tends to decrease through the deposition of carbon as a result of side reactions. The catalyst may be periodically regenerated by burning off the carbon by heating in an oxygen-containing atmosphere, e.g. air or oxygen or air diluted with an inert gas such as nitrogen. The catalyst may be disposed as a fixed bed or a fluidised bed may be employed. In the latter case a portion of the catalyst may be continuously withdrawn and regenerated and returned to the reaction zone.
The main product of the condensation is an unsaturated ketone. Often it is desired to hydrogenate the product to the corresponding saturated ketone or its corresponding saturated alcohol. This may be effected by passing the products, possibly after separation of the starting ketone that has not rea
Johnson Matthey PLC
Pillsbury & Winthrop LLP
Richter Johann
Witherspoon Sikarl A.
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