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US 4,383,123 AGranted
Manufacture of aqueous formaldehyde
AssigneeMonsanto Company
InventorsTheodore V. Ferris, Richard C. Kmetz
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Abstract
Formaldehyde manufacture by oxidative-dehydrogenation of methanol over a silver or copper catalyst. Aqueous formaldehyde solution is obtained from the reaction and is substantially stripped of methanol by a low energy process at relatively low temperature by means of recycled off-gas in a stripping column comprising at least about 1.5 theoretical transfer units for stripping methanol.
Claims18
A process for the manufacture of an aqueous solution of formaldehyde comprising the steps of:
- (a) oxidatively dehydrogenating methanol with air in the presence of a silver or copper catalyst and steam at elevated temperature;
- (b) absorbing the reaction product in an absorber comprising one or more absorption stages in series to form an aqueous formaldehyde solution containing free and combined methanol;
- and
- (c) stripping methanol from the aqueous formaldehyde solution with off-gas from the absorber in counter-current flow in a stripping column comprising at least about 1.5 theoretical transfer units for methanol stripping, the stripping being carried out at a temperature and at a ratio of stripping off-gas to aqueous formaldehyde to provide a concentration of condensible vapors of aqueous methanolic formaldehyde in the gas emerging from the stripping column of no more than about 50 mol percent.
1 more element
Dependencies are inferred from the claim text.