| 摘要 |
<p>There is provided a process for producing propylene glycol monoacetate which comprises the steps of (I) hydroformylating vinyl acetate with a gaseous mixture of hydrogen and carbon monoxide in an organic solvent in the presence of a substantially water-insoluble rhodium complex and a tri-substituted phosphine to form alpha -acetoxypropionaldehyde, (II) subjecting at least part of the reaction mixture obtained in step (I) to extraction with an aqueous medium to obtain an aqueous layer containing alpha -acetoxypropionaldehyde and an extraction residue containing the catalyst components, and recycling the extraction residue to the hydroformylation step (I), (III) contacting the aqueous layer containing alpha -acetoxypropionaldehyde obtained in step (II) with a carboxylic acid ester of general formula (A) ClH2l+1COOCmH2m+1(A) wherein l is an integer of 0 to 4; m is an integer of 1 to 5; and the sum of l and m is 3 to 5, or a dicarboxylic acid ester of general formula (B) ROOC(CH2)nCOOR'(B) wherein R and R' each is an alkyl group of 2 to 3 carbon atoms; and n is an integer of 0 to 2 to thereby separate alpha -acetoxypropionaldehyde extractively from the aqueous layer, and (IV) hydrogenating the alpha -acetoxypropionaldehyde contained in the extract layer as obtained in step (III) in liquid phase in the presence of a Raney nickel or modified Raney nickel catalyst under conditions such that the concentration of alpha -acetoxypropionaldehyde in the reaction mixture does not exceed 0.1 mole per liter. Further provided is an improved process for hydrogenating alpha -acetoxypropionaldehyde which is advantageously employable in the above step (IV).</p> |
