Patent GB-729828-A (GB)
Title: Improvements in the separation of reaction products from the synthesis of acrylonitrile
IPC: C08F6/10
Filed: 1952-09-24
Abstract: Reaction products formed in the synthesis of acrylonitrile from acetylene and hydrocyanic acid are separated from unreacted acetylene by washing the gaseous mixture leaving the reactor in a countercurrent extraction column with an organic solvent which dissolves acrylonitrile and by-products more easily than acetylene, and heating the solution in the lower part of the extraction column. The preferred solvent is acrylonitrile itself, but aliphatic or cyclic hydrocarbons, alcohols, acids, esters, ethers, acetals, or saturated nitriles may also be used.  As shown, the gaseous mixture from reactor a enters the bottom of column b and flows upwardly in countercurrent to acrylonitrile at 0 DEG  C. introduced at c.  The <PICT:0729828/IV (b)/1> solution is heated to boiling in flask h with which is associated Raschig ring column g and condenser f. Acrylonitrile circulates from flask h through cooler m and pump t back to the top of the column, an amount corresponding to that condensed being removed from time to time.  Part of the solution is withdrawn at e and heated in vessel i to remove dissolved substances, the acrylonitrile being returned to flask h; the expelled gases and vapours are cooled to 0 DEG  C. at k and to -30 DEG  C. in vessel l, where a mixture of monovinylacetylene, acetaldehyde, and acetylene condenses, the remaining gas being returned to column b.  The process may be carried out at increased pressures of 1-30 atmospheres, in which case pressure is reduced through valve n and restored by pumps o and p; in a modified process (Fig. 2, not shown) the liquid withdrawn at e is cooled to -30 DEG  C. before decompression. Specification 708,968 is referred to.ALSO:<PICT:0729828/III/1> Reaction products formed in the synthesis of acrylonitrile from acetylene and hydrocyanic acid are separated from unreacted acetylene by washing the gaseous mixture leaving the reactor in a counter-current extraction column with an organic solvent which dissolves acrylonitrile and by-products more easily than acetylene, and heating the solution in the lower part of the extraction column. If the solution is heated to its boiling point, the process may be regarded as a distillative extraction. The preferred solvent is acrylonitrile itself, but aliphatic or cyclic hydrocarbons, alcohols, acids, esters, ethers, acetals, or saturated nitriles may also be used.  As shown, the gaseous mixture from reactor a enters the bottom of column b and flows upwardly in countercurrent to acrylonitrile at 0 DEG  C. introduced at c.  Heated flash h, Raschig ring column g, and condenser f are provided at the bottom of column b. Acrylonitrile circulates from flask h through cooler m and pump t back to the top of the column, an amount corresponding to that condensed being removed from time to time.  Part of the solution is withdrawn at e and heated in vessel i to removed dissolved substances, the acrylonitrile being returned to flask h; the expelled gases and vapours are cooled to 0 DEG  C. at k and to -30 DEG  C. in vessel l, where a mixture of monovinylacetylene, acetaldehyde, and acetylene condenses, the remaining gas being returned to column b. The process may be carried out at increased pressures of 1-30 atmospheres, in which case pressure is reduced through valve n and restored by pumps o and p; in a modified process (Fig. 2, not shown) the liquid withdrawn at e is cooled to -30 DEG  C. before decompression. Specification 708,968, [Group IV (b)], is referred to.