Patent GB-222279-A (GB)
Title: An improved process for drying and coating porous materials for use as adsorbents and catalysts
IPC: C01B33/113
Filed: 1923-08-17
Abstract: The aqueous phase of finely-divided or porous materials for use as adsorbents or catalysts is removed by means of an oil or vapour which wets the surface of the material and replaces the water, excess of liquid then being removed by distillation &c.  The invention may be applied to colloidal gels or gelatinous precipitates, and is described with reference to a gel of silicic acid.  The gel is immersed in a bath consisting of an oil of the paraffin series which distills at a temperature above 200 DEG  C., and the oil replaces the water in the pores of the gel.  The bath is maintained at a temperature of about 150 DEG  C., the water passing off as vapour. On heating the residual product, the excess oil is driven off and a film of oil covers the surfaces of the gel, thus preventing "ageing." The process may be carried out at a reduced pressure or the vapour of an oil distilling at 100 DEG  or 150 DEG  C., may be passed into a vessel packed with the gel and maintained at a temperature higher than the distilling temperature of the oil.  Further heating decomposes the film, replacing it by a film of carbonaceous matter, or by employing an excess of air, the carbon may be entirely removed in gaseous form, the combustion annealing the interior of the material.  An emulsifying agent such as wool grease or a soap with a heavy metal oxide as base may be added to the treating liquid in proportions not exceeding 5 per cent to assist the replacement of the water. The composition of the film may be varied.  For instance, the coating film may contain nickel, copper, silver, &c., which improve the product when it is used for catalysis.  In a modified process, a quantity of oil insufficient to fill the pores of the material is added to the material and a stream of dry gas such as air at a temperature of 120 DEG  to 150 DEG  C. is passed over the material. The water is removed and the oil creeps over the surface of the material.ALSO:The aqueous phase of finely-divided or porous materials for use as adsorbents or catalysts is removed by means of an oil or vapour which wets the surface of the material and replaces the water, excess of liquid then being removed by distillation &c. The invention may be applied to colloidal gels or gelatinous precipitates, and is described with reference to a gel of silicic acid.  The gel is immersed in a bath consisting of an oil of the paraffin series which distils at a temperature above 200 DEG  C., and the oil replaces the water in the pores of the gel.  The bath is maintained at a temperature of about 150 DEG  C., the water passing off as vapour. On heating the residual product, the excess oil is driven off and a film of oil covers the surfaces of the gel, thus preventing "ageing." The process may be carried out at a reduced pressure or the vapour of an oil distilling at 100 or 150 DEG  C. may be passed into a vessel packed with the gel and maintained at a temperature higher than the distilling temperature of the oil.  Further heating decomposes the film, replacing it by a film of carbonaceous matter, or by employing an excess of air, the carbon may be entirely removed in gaseous form, the combustion annealing the interior of the material.  An emulsifying agent such as wool grease or a soap with a heavy metal oxide as base may be added to the treating liquid in proportions not exceeding 5 per cent to assist the replacement of the water.  The composition of the film may be varied.  For instance, the coating film may contain nickel, copper, silver, &c., which improve the product when it is used for catalysis.  In a modified process, a quantity of oil insufficient to fill the pores of the material is added to the material and a stream of dry gas, such as air, at a temperature of 120 DEG  to 150 DEG  C. is passed over the material. The water is removed and the oil creeps over the surface of the material.