Patent GB-628023-A (GB)
Title: Improvements in or relating to the production of vinyl cyanide
IPC: B01J27/24
Filed: 1947-03-28
Abstract: Vinyl cyanide is prepared by passing gaseous hydrogen cyanide and acetylene upwards through a reaction zone at 350-700 DEG  C. containing a finely-divided catalyst comprising alkali or alkaline earth metal cyanide on an inert material of low surface activity which is maintained in turbulent suspension by the gases. The product gases are preferably cooled rapidly and the condensate acidified. Suitable catalysts include mixtures of cyanides, e.g. sodium and potassium cyanide compounds such as carbonates, hydroxides, oxides, and borates which yield the cyanides with hydrogen cyanide, or double cyanide with heavy metals, e.g. zinc, copper and cadmium on such carriers as unactivated carbons, alumina, pumice, alundum, silica, silicon carbide, beryl, calcium and magnesium sulphates, porcelain, feldspar, barite and fluorspar, low in iron, nickel, manganese, cobalt and copper, and inactive metals such as chromium, aluminium, silver and gold.  The amount of cyanides in the catalyst may be about 1 per cent but 5-10 per cent or more is preferred.  Sodium potassium cyanide may be used on glowed wood charcoal of 50-200 mesh up to about 20 g./ litre, on tabular alumina of 150-250 mesh up to 12 g./litre, and on porous silicon carbide of 40-200 mesh up to 30 g./litre without agglomeration in use.  The support may be treated with a solution of the catalyst in water or ammonia, and solvent evaporated in an inert gas at 400-500 DEG  C.  The reactant gases contain at least 1, preferably 1.2-5, volumes of acetylene per volume of hydrogen cyanide.  Diluents up to 80 per cent of the total mixture may be added, for example 40-60 per cent of hydrogen.  Water vapour up to 5 per cent by volume may also be present.  Preheating to 200-250 DEG  C. may be used.  Catalyst may be carried over with the reaction products or separated in a cyclone separator or by settling. Catalyst concentrations of 35-80 per cent are preferred but may be, for example, 10-20 per cent. Fresh catalyst is added to replace that withdrawn.  Regeneration is effected by heating in a closed vessel or a stream of inert gas or, with non-combustible carriers, in oxygen and nitrogen at 400-700 DEG  C.  Re-impregnation with the active constituent may then be effected.  Acidification of the products may be effected by injecting hydrogen chloride or sulphur dioxide or by adding to the condensate organic or inorganic acids, preferably phosphoric acid.  The gaseous products may be scrubbed with a solution of phosphoric acid in vinyl cyanide at - 10 to 5 DEG  C.  In examples, reaction mixtures which may contain hydrogen and water vapour, and catalysts consisting of sodium potassium carbonate on wood charcoal, silicon carbide or tabular alumina are used.  The effects of varying the rate of flow, and catalyst concentration, and of recyling, re-generating and re-impregnating catalyst are illustrated.ALSO:Vinyl cyanide is prepared by passing gaseous hydrogen cyanide and acetylene upwards through a reaction zone at 350-700 DEG  C. containing a finely-divided catalyst comprising alkali or alkaline earth metal cyanide on an inert material of low surface activity which is maintained in turbulent suspension by the gases. The product gases are preferably cooled rapidly and the condensate acidified.  Suitable catalysts include mixtures of cyanides, e.g. sodium and potassium cyanides, compounds such as carbonates, hydroxides, oxides, and borates which yield the cyanides with hydrogen cyanide, or double cyanides with heavy metals, e.g. zinc, copper and cadmium, on such carriers as unactivated carbons, alumina, pumice, alundum, silica, silicon carbide, beryl, calcium and magnesium sulphate, porcelain, feldspar, barite, and fluorspar, low in iron, nickel, manganese, cobalt, and copper, and inactive metals such as chromium, aluminium, silver, and gold. The amount of cyanides in the catalyst may be about 1 per cent, but 5-10 per cent or more is preferred.  Sodium potassium cyanide may be used on glowed wood charcoal of 50-200 mesh up to about 20 g./litre, on tabular alumina of 150-250 mesh up to 12 g./litre, and on porous silicon carbide of 40-200 mesh up to 30 g./litre, without agglomeration in use.  The support may be treated with a solution of the catalyst in water or ammonia, and solvent evaporated in an inert gas at 400-500 DEG  C. The reactant gases contain at least 1, preferably 1.2-5, volumes of acetylene per volume of hydrogen cyanide.  Diluents up to 80 per cent of the total mixture may be added, for example, 40-60 per cent of hydrogen.  Water vapour up to 5 per cent by volume may also be present.  Pre-heating to 200-250 DEG  C. may be used.  Catalyst may be carried over with the reaction products or separated in a cyclone separator or by settling.  Catalyst concentrations of 35-80 per cent are preferred, but may be, for example, 10-20 per cent.  Fresh catalyst is added to replace that withdrawn. Regeneration is effected by heating in a closed vessel or a stream of inert gas or, with non-combustible carriers, in oxygen and nitrogen at 400-700 DEG  C. Re-impregnation with the active constituent may then be effected. Acidification of the products may be effected by injecting hydrogen chloride or sulphur dioxide or by adding to the condensate organic or inorganic acids, preferably phosphoric acid.  The gaseous products may be scrubbed with a solution of phosphoric acid in vinyl cyanide at - 10 DEG  to 5 DEG  C.  In examples, reaction mixtures, which may contain hydrogen and water vapour, and catalysts consisting of sodium potassium carbonate or wood charcoal, silicon carbide or tabular alumina are used.  The effects of varying the rate of flow, and catalyst concentration, and of recycling, regenerating and re-impregnating catalyst are illustrated.