Patent GB-981662-A (GB)
Title: Improvements in or relating to the production of acrylonitrile
Filed: 1963-07-10
Abstract: <PICT:0981662/C1/1> Components of the gaseous mixture resulting from the vapour phase catalytic oxidation of propylene in the presence of ammonia to produce acrylonitrile, and which contains, in addition to acrylonitrile, hydrogen cyanide, acetonitrile, acrolein, ammonia and carbon dioxide, are separated and recovered by a process comprising washing the gases with water to produce a solution containing less than 6.5% by weight of acrylonitrile and extractively distilling this solution at 40 DEG  to 70 DEG  C. employing water as extractant to separate substantially all of the acrylonitrile and hydrogen cyanide as overhead distillate and substantially all the acetonitrile, acrolein and ammonia and a major part of the carbon dioxide as base product.  The process may be performed in the manner illustrated in the Fig.  The gaseous oxidation product is fed into column 1 via line 2 and washed with water from line 3 to form an aqueous solution containing less than 6.5% by weight of acrylonitrile. Uncondensed gases escape through line 4 whilst the aqueous solution is fed to column 5 and extractively distilled with water entering through the head of this column.  The head fraction of this distillation is passed to column 9, where sulphonic acid from 10 removes any ammonia present, and then to distillation column 8, where acrylonitrile is separated from the hydrocyanic acid.  The latter is removed through line 11 whilst acrylonitrile is drawn off through line 14 after being purified by distillation in column 13.  The base product from column 5 is passed to column 16, where ammonia together with small quantities of carbon dioxide, hydrogen cyanide and acrolein (exit via 17) are separated by distillation from an aqueous solution of acetonitrile (exit via 18).  The base fraction of column 13 and the head fraction of column 16 may be recycled to the catalytic reactor (not shown).  In an example hydrocyanic acid of 97% purity was obtained from line 11.ALSO:<PICT:0981662/C2/1> Components of the gaseous mixture resulting from the vapour phase catalytic oxidation of propylene in the presence of ammonia to produce acrylonitrile, and which contains, in addition to actylonitrile, hydrogen cyanide, acetonitrile, acrolein, ammonia and carbon dioxide, are separated and recovered by a process comprising washing the gases with water to produce a solution containing less than 6.5% by weight of acrylonitrile and extractively distilling this solution at 40 DEG  to 70 DEG  C. employing water as extractant to separate substantially all of the acrylonitrile and hydrogen cyanide as overhead distillate and substantially all the acetonitrile, acrolein and ammonia and a major part of the carbon dioxide as base product.  The process may be performed in the manner illustrated in the Figure.  The gaseous oxidation product is fed into column 1 via line 2 and washed with water from line 3 to form an aqueous solution containing less than 6.5% by weight of acrylonitrile. Uncondensed gases escape through line 4 whilst the aqueous solution is fed to column 5 and extractively distilled with water entering through the head of this column.  The head fraction of this distillation is passed to column 9, where sulphuric acid from 10 removes any ammonia present, and then to distillation column 8, where acrylontrile is separated from the hydrocyanic acid.  The latter is removed through line 11 whilst acrylonitrile is drawn off through line 14 after being purified by distillation in column 13.  The base product from column 5 is passed to column 16, where ammonia together with small quantities of carbon dioxide, hydrogen cyanide and acrolein (exit via 17) are separated by distillation from an aqueous solution of acetonitrile (exit via 18). The base fraction of column 13 and the head fraction of column 16 may be recycled to the catalytic reactor (not shown).