Method for separating ammonia from mixtures of gases from acrylonitrile synthesis

Claim 1

IN A PROCESS FOR THE PRODUCTION OF ACRYLONITRILE WHEREBY PROPYLENE AND AMMONIA ARE REACTED IN THE GAS PHASE WITH AN OXIDATION CATALYST AT AN ELEVATED TEMPERATURE TO PRODUCE AN EFFLUENT GAS MIXTURE CONSISTING ESSENTIALLY OF WATER VAPOR, ACRYLONITRILE, HYDROGEN CYANIDE, AMMONIA AND CARBON DIOXIDE, THE IMPROVEMENT COMPRISING THE SEPARATION OF THE AMMONIA WHEREBY CHEMICAL REACTIONS IN THE EFFLUENT GAS MIXTURE BETWEEN AMMONIA WITH ACRYLONITRILE AND HYDROGEN CYANIDE ARE SUBSTANTIALLY SUPPRESSED, BY COOLING THE EFFLUENT MIXTURE TO A TEMPERATURE BETWEEN ABOUT 30 TO 40*C., SCRUBBING THE EFFLUENT MIXTURE WITH AN AQUEOUS SOLUTION OF A MEMBER SELECTED FROM THE GROUP CONSISTING OF AMMONIUM BICARBONATE AND A MIXTURE OF AMMONIUM CARBONATE AND AMMONIUM BICARBONATE, SAID AQUEOUS SOLUTION BEING SATURATED WITH CARBON DIOXIDE AND BEING MAINTAINED AT A TEMPERATURE BELOW THE DECOMPOSITION TEMPERATURE OF CARBON DIOXIDE-AMMONIA COMPOUNDS AND THE CONCENTRATION OF AMMONIUM CARBONATES IN SAID SCRUBBING SOLUTION BEING UP TO 20% BY WEIGHT, CALCULATED AS AMMONIUM BICARBONATE, AND SUBSEQUENTLY RECOVERING THE ABSORBED AMMONIA AND CARBON DIOXIDE FROM THE SAID SOLUTION.