Abstract Crude acetone cyanohydrin synthesized in a synthesis step from hydrocyanic acid and acetone in the presence of an alkaline catalyst and containing unreacted hydrocyanic acid and acetone is subjected, after neutralization of the alkaline catalyst, to a purification process which comprises: subjecting the crude acetone cyanohydrin to a first distillation step in which a flash distillation is carried out at a relative mild vacuum thereby to remove a first distillate composed principally of hydrocyanic acid and impurities of lower boiling points; subjecting substances not distilled in the first flash distillation to a second distillation a relatively higher temperature and a mild vacuum thereby to remove a second distillate composed principally of acetone; and recovering the substances not distilled in the second distillation as a purified acetone cyanohydrin. This purification process is characterized in that: the hydrocyanic acid and any accompanying acetone are recovered from the first distillate and are recirculated to the synthesis step; at least one portion of the acetone of the second distillate is caused to contact crude acetone cyanohydrin containing the alkaline catalyst thereby to cause absorption thereof; and the resulting absorption liquid is recirculated to the synthesis step.
Inventors
👤 Y Iida
👤 H Kaio
👤 M Ikeda
👤 Y Yamamoto
Bibliographic Details
Application Number—
JurisdictionUS
Data Sourcegoogle_patents
Last Synchronized2026-11-03 20:56
CPC Classifications
C; C07; C07C; C07C255/00
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
27 words
A process for producing acetone cyanohydrin according to claim 1 in which said first distillation is a flash distillation carried out by a wetted-wall heat exchange technique.
Claim 2
Dependent Claim
51 words
A process for producing acetone cyanohydrin according to claim 1 in which said first distillation is carried out under the conditions of a pressure of from 200 mm. Hg, absolute, to atmospheric pressure, a temperature below 140* C, and a mean residence time in the step of less than 30 minutes.
Claim 3
Dependent Claim
49 words
A process for producing acetone cyanohydrin according to claim 1 in which said second distillation is carried out under the conditions of a residence time of acetone cyanohydrin at said heating zone of less than 10 minutes and a decomposition rate of acetone cyanohydrin of less than 0.2 percent.
Claim 4
Dependent Claim
40 words
A process for producing acetone cyanohydrin according to claim 1 in which the temperature of said crude acetone cyanohydrin containing an alkaline catalyst and contacted by at least one portion of said second distillate is from -25* to +20* C.
Claim 5
Dependent Claim
40 words
A process for producing acetone cyanohydrin according to claim 1 in which the temperature of said crude acetone cyanohydrin containing an alkaline catalyst and contacted by at least one portion of said second distillate is from -20* to 0* C.
Claim 6
Dependent Claim
48 words
A process as claimed in claim 1, in which the recovered purified acetone cyanohydrin, withdrawn from the bottom of said second distillation stage at step (g) is further introduced to a dehydration stage whereby a further purified acetone cyanohydrin is recovered from the bottom of said dehydration stage.