|US patent 6462235 Preparation of Oximes||Bookmark|
US Patent 6462235
Process for Production of Oximes Cocatalyzed by Ammonium Salts or Substituted Ammonium Salts
Notes on the reactions:
To ensure precisely identical reaction conditions, fresh catalyst (titanium silicate TS1, Degussa-HulsAG) from the same batch was used in each of the examples. An aqueous solution of hydrogen peroxide (50% by weight, 30ppm phosphoric acid preservative) was used for all trials. There was no additional activation of the catalyst prior to reaction. The catalyst was separated off after the reaction at 75*C by way of a pressure filter and could thus be recycled with high residual activity.
5.25g (68mmol) of ammonium acetate dissolved in 300ml (243g) of ethanol were placed in a 1.6 liter heatable glass pressure reactor (Buichi autoclave), which had been flushed with N2, with magnetic coupling, gas distribution stirrer (500rpm) and pressure regulator. 5.0g of catalyst (TS1, Degussa-Huls) were suspended therein. At 40*C, 62.7g (344mmol) of cyclododecanone in 251g of ethanol were added. The reactor was heated to 80*C and the pressure was reduced to 0.1 bar, after which ammonia gas was slowly pressurized to a pressure of 1.6 bar. Approximately 13g (about 765mmol) of ammonia were added. This corresponded to approximately 2.2 eq. Relative to cyclododecanone.
During the reaction, the pressure was kept constant by means of a slight waste gas flow and the escaped ammonia was replaced (~0.4g/h), 24.5ml(28.56g) (0.41ml/min) of a 50% hydrogen peroxide solution (430mmol, 14.62g) were added via pump over a period of 60 minutes. After the peroxide was added, the reaction mixture was left to react further for another 60 minutes.
During the reaction, the ketone conversion was tracked via GC and hydrogen peroxide was determined iodometrically. After 120 minutes, the ketone conversion was 99.95%, 426mmol of peroxide were consumed, corresponding to a peroxide selectivity of 80.6%, relative to the converted ketone.
Example 2 used the procedure as in Example 1 with the following exceptions:
22.0ml (0.37ml/min) of a 50% hydrogen peroxide solution (corres. To 385mmol, 13.09g) were added via a pump over 60 minutes. Then the reaction is allowed to continue for another 60 minutes.
After 120 minutes, the ketone conversion was 99.90%, 384mmol of peroxide were consumed, corresponding to a peroxide selectivity of 89.2%
Notes of other examples:
Example 3-5 used the same procedure as Example 1 and 2 with the exception that the ammonium acetate amount was varied.
Ex. # amount of ammonium acetate (g) 120 min (% conversion of ketone)
1 5.25 99.95
2 5.25 99.90
3 2.63 99.91
4 0.53 79.42
5 (none) 32.80