Process for recovery of hydrogen cyanide

A process for recovery of hydrogen cyanide contained in a gaseous mixture which comprises (a) treating the gaseous mixture with an aqueous solution of analkali metal carbonate, at a pH of at least 9.0 and at a temperature in the range of about 15.degree.C. to about 150.degree.C. and under a pressure in the range 0.5 to 5.0 atmospheres to absorb hydrogen cyanide and to produce an aqueous product solution containing alkali metal cyanide and alkali metal bicarbonate while expelling nonabsorbed gases from the product solution;

• (b) contacting the aqueous product solution from (a) with a ketone containing from three to fifteen carbon atoms at a temperature in the range of 25.degree.-100.degree.C. under a pressure in the range 0.5 to 5.0 atmospheres to produce a cyanohydrin-ketone mixture and to regenerate in aqueous solution the alkali metal carbonate, the concentration of alkali metal carbonate in the aqueous solution in step (a) being about 10-45% by weight such that the cyanohydrin-ketone mixture produced in step (b) is substantially immiscible with the aqueous solution containing the regenerated alkali metal carbonate;
• (c) separating the aqueous alkali metal carbonate solution from the cyanohydrin-ketone mixture;
• (d) recycling the carbonate solution to the gas absorption step (a);
• recovering the cyanohydrin-ketone mixture (e) and subjecting said cyanohydrin - ketone mixture to a temperature in the range of 50 - 160.degree.C and under a pressure of 0.1 to 5 atmospheres to regenerate the corresponding ketone and hydrogen cyanide from the cyanohydrin and recovering the hydrogen cyanide and ketone.