Patent GB-691248-A (GB)
Title: Method for the production of acrylic nitrile
Filed: 1950-01-10
Abstract: <PICT:0691248/IV (b)/1> Acrylic nitrile is obtained by simultaneous passage of acetylene and hydrocyanic acid into an aqueous solution containing cuprous chloride and one or more alkali metal chlorides, the latter term including ammonium chloride, and then washing with water in a rectifying column the mixture of gases and vapours resulting from the reaction in order to obtain a solution of acrylic nitrile and a residual mixture of acetylene and vinyl acetylene, said mixture of gases and vapours being introduced into said rectifying column substantially at the reaction temperature, preferably 70 DEG to 100 DEG  C. obtaining in the production of the acrylic nitrile, or after injection of steam thereinto, so that the aqueous acrylic nitrile solution shall flow out from the base of the column at a temperature within the range of from 20 DEG  to 40 DEG  C. and said residual mixture being then rectified in the presence of a counter-current flow of a substantially non-volatile solvent of vinyl acetylene and at a temperature approximating to the boiling-point of the latter, preferably at between 0 DEG  and 10 DEG  C., so as to obtain both a solution of vinyl-acetylene from which the latter is recoverable and acetylene which is reintroduced into the cycle of operations.  Specified non-volatile solvents are gas oil, mineral oils and aniline and the solvent, e.g. gas oil, is preferably saturated with sulphur to prevent polymerization of the vinyl acetylene.  In an example described with reference to the drawing, acetylene and hydrocyanic acid are introduced into reactor 1 which contains an aqueous solution comprising cuprous chloride, ammonium chloride and hydrochloric acid maintained at 70-75 DEG  C.  The effluent gas and vapour are introduced substantially at the reactor outlet temperature into the base of a rectifying column 2 as at c, water at a temperature of 2 DEG  C. being added at the top of the column at such a rate that the effluent solution from the outlet e contains about 2 per cent acrylic nitrile.  The residual gas mixture flows out of column 2 at a temperature of 5 DEG  C. and enters the rectifying column 3 as at f, the column being filled with Raschig rings.  Gas oil saturated with sulphur is introduced into the top of the column at a temperature of 4 DEG  C.  The vinyl acetylene solution flowing out at h is degassed by heating it to 140-150 DEG C. in the apparatus 4 and the vinylacetylene then cooled in cooler 5. Half the amount of vinyl acetylene is recycled to the bottom of cooler 3 while the remainder is withdrawn at i.  The solvent flowing out from apparatus 4 is recycled to the top of column 3 via the cooler 7 which reduces its temperature to 4 DEG  C.  The acetylene from the top of column 3 is recycled to the reactor 1 through a recycling pump 8 and has added to it a volume of fresh acetylene equal to the sum total of the reacted acetylene plus the small amount which is drained off at j to eliminate the inert constituents brought in with the acetylene.  If necessary steam may be added through the conduit k to the reaction mixture flowing from the reactor 1. Continuous distillation of the effluent solution from the apparatus 2 yields crude acrylonitrile containing ethanol and small amounts of hydrocyanic acid and divinyl acetylene.  The results obtained are compared with those obtained in the same apparatus and with the same catalyst but in the absence of the solvent treatment.ALSO:<PICT:0691248/III/1> Acrylic nitrile is obtained by simultaneous passage of acetylene and hydrocyanic acid into an aqueous solution containing cuprous chloride and one or more alkali metal chlorides, the latter term including ammonium chloride, and then washing with water in a rectifying column the mixture of gases and vapours resulting from the reaction in order to obtain a solution of acrylic nitrile and a residual mixture of acetylene and vinyl acetylene, said mixture of gases and vapours being introduced into said rectifying column substantially at the reaction temperature, preferably 70 DEG  to 100 DEG C, obtaining in the production of the acrylic nitrile, or after injection of steam thereinto, so that the aqueous acrylic nitrile solution shall flow out from the base of the column at a temperature within the range of from 20 DEG C to 40 DEG C, and said residual mixture being then rectified in the presence of a counter current flow of a substantially non-volatile solvent of vinyl acetylene and at a temperature approximating to the boiling point of the latter, preferably at between 0 DEG  and 10 DEG C, so as to obtain both a solution of vinylacetylene from which the latter is recoverable and acetylene which is reintroduced into the cycle of operations.  Specified non-volatile solvents are gas oil, mineral oils and aniline and the solvent, e.g. gas oil, is preferably saturated with sulphur to prevent polymerization of the vinyl acetylene.  In an example described with reference to the drawing, acetylene and hydrocyanic acid are introduced into reactor 1 which contains an aqueous solution comprising cuprous chloride, ammonium chloride and hydrochloric acid maintained at 70-75 DEG C.  The effluent gas and vapour are introduced substantially at the reactor outlet temperature into the base of a rectifying column 2 as at c, water at a temperature of 20 DEG C being added at the top of the column at such a rate that the effluent solution from the outlet e contains about 2 per cent acrylic nitrile.  The residual gas mixture flows out of column 2 at a temperature of 5 DEG C and enters the rectifying column 3 as at f, the column being filled with Raschig rings.  Gas oil saturated with sulphur is introduced into the top of the column at a temperature of 40 DEG C. The vinyl acetylene solution flowing out at h is degassed by heating it to 140-150 DEG C in the apparatus 4 and the vinylacetylene then cooled in cooler 5.  Half the amount of vinyl acetylene is recycled to the bottom of cooler 3 while the remainder is withdrawn at i.  The solvent flowing out from apparatus 4 is recycled to the top of column 3 via the cooler 7 which reduces its temperature to 40 DEG C.  The acetylene from the top of column 3 is recycled to the reactor 1 through a recycling pump 8 and has added to it a volume of fresh acetylene equal to the sum total of the reacted acetylene plus the small amount which is drained off at j to eliminate the inert constituents brought in with the acetylene. If necessary steam may be added through a conduit k to the reaction mixture flowing from the reactor 1.  Continuous distillation of the effluent solution from the apparatus 2 yields crude acrylonitrile containing ethanal and small amounts of hydrocyanic acid and divinyl acetylene.  The results obtained are compared with those obtained in the same apparatus and with the same catalyst but in the absence of the solvent treatment.