Patent GB-727898-A (GB)
Title: Method of prolonging the period of activity of cuprous salt catalysts in the synthesis of acrylonitrile
IPC: B01J27/06
Filed: 1951-09-07
Abstract: In the synthesis of acrylonitrile from hydrocyanic acid and acetylene in the presence of an aqueous cuprous salt catalyst, the p  period of activity of the cuprous salt catalyst, the period of activity of the cuprous salt catalyst is prolonged by contacting the catalyst with a solid surface-active adsorption medium during the synthesis so that by-products are removed from the catalyst by adsorption on said medium.  The adsorption medium may be an inorganic substance, e.g. a surface-active earth such as <PICT:0727898/IV (b)/1> kieselguhr, or active carbon such as animal charcoal or blood charcoal, or it may be an organic substance, e.g. an artificial resin such as an aminoplast or phenoplast.  The adsorption may be effected by suspending the adsorption medium in the catalyst in which case the catalyst must be separated from the adsorption medium by filtration when the latter is exhausted, but it is preferred to incorporate the adsorption medium in a special vessel through which at least a part of the catalyst is passed and which is preferably easily interchangeable.  Suitable apparatus for continuous operation is shown in the drawing wherein the reaction tower R is provided with a main branch system S which is connected with a further branch system A in which is inserted an interchangeable vessel K for the adsorption medium.  A washing tower W for the acrylonitrile is also provided and is connected to the reaction tower R by a pipe 4 for the circulating gas, the circulation being maintained by a pump P.  In an example the catalyst is a Nieuwland catalyst consisting of cuprous chloride, ammonium chloride, copper powder, concentrated hydrochloric acid and water and is first heated to 80 DEG  C. whilst nitrogen is passed through the system by means of the pipe 2 so as to cause the catalyst to circulate through the tower R and the branch system S. The catalyst is first charged with hydrocyanic acid, which may be in anhydrous liquid form or in the form of an aqueous solution, through the pipe 1, and as soon as the nitrogen leaving the reaction tower contains about 0.5 gram of hydrocyanic acid per 100 litres it is replaced by acetylene.  After the catalyst has become brown-red and dark and small drops of oil begin to separate out the branch system A is connected whereby the catalyst flows continuously through the adsorption vessel K which is charged with active carbon.  After about 7-8 days the adsorption medium is exhausted and is therefore exchanged and the operation repeated, the catalyst becoming pale again.  A portion of the circulating gas may be removed through the pipe 3.  The acetylene used in the process may be used in concentrated form or may be diluted with an inert gas such as nitrogen.  Acetylene produced in an electric arc is suitable and the acetylene is preferably used in a purified form.  It is stated that the process may be combined with that disclosed in Specification 727,571 in which acrylonitrile is made with the use of dilute gaseous hydrocyanic acid.ALSO:<PICT:0727898/III/1> In the synthesis of acrylonitrile from hydrocyanic acid and acetylene in the presence of an aqueous cuprous salt catalyst the period of activity of the cuprous salt catalyst is prolonged by contacting the catalyst with a solid surface-active adsorption medium during the synthesis so that by-products are removed from the catalyst by adsorption on said medium.  The adsorption medium may be an inorganic substance, e.g. a surface active earth such as kieselguhr, or active carbon such as animal charcoal or blood charcoal, or it may be an organic substance, e.g. an artificial resin such as an aminoplast or phenoplast.  The adsorption may be effected by suspending the adsorption medium in the catalyst in which case the catalyst must be separated from the adsorption medium by filtration when the latter is exhausted, but it is preferred to incorporate the adsorption medium in a special vessel through which at least a part of the catalyst is passed and which is preferably easily interchangeable.  Suitable apparatus for continuous operation is shown in the drawing wherein the reaction tower R is provided with a main branch system S which is connected with a further branch system A in which is inserted an interchangeable vessel K for the adsorption medium.  A washing tower W for the acrylonitrile is also provided and is connected to the reaction tower R by a pipe 4 for the circulating gas, the circulation being maintained by a pump P.  In an example the catalyst is a Nieuwland catalyst consisting of cuprous chloride, ammonium chloride, copper powder, concentrated hydrochloric acid and water and is first heated to 80 DEG  C. whilst nitrogen is passed through the system by means of the pipe 2 so as to cause the catalyst to circulate through the tower R and the branch system S. The catalyst is first charged with hydrocyanic acid, which may be in anhydrous liquid form or in the form of an aqueous solution, through the pipe i, and as soon as the nitrogen leaving the reaction tower contains about 0.5 gramme of hydrocyanic acid per 100 litres it is replaced by acetylene.  After the catalyst has become brown-red and dark and small drops of oil begin to separate out the branch system A is connected whereby the catalyst flows continuously through the adsorption vessel K which is charged with active carbon.  After about 7-8 days the adsorption medium is exhausted and is therefore exchanged and the operation repeated, the catalyst becoming pale again.  A portion of the circulating gas may be removed through the pipe 3.  The acetylene used in the process may be used in concentrated form or may be diluted with an inert gas such as nitrogen.  Acetylene produced in an electric arc is suitable and the acetylene is preferably used in a purified form.  It is stated that the process may be combined with that disclosed in Specification 727,571, [Group IV (b)], in which acrylonitrile is made with the use of dilute gaseous hydrocyanic acid.