Process and adsorbent for gas drying

Abstract

An adsorbent and a process are disclosed for drying gases in a pressure swing dryer. The adsorbent comprises a pre-formed alumina particle having a surface area of about 250 to 550 m 2 μg with a thin layer of colloidal silica disbursed on the surface of the pre-formed alumina particle. Surprisingly the thin layer of colloidal silica does not interfere with the drying properties of the pre-formed alumina particle, while significantly improving the physical properties of the pre-formed alumina particle.

What is claimed is:  
     
         1 . A process for the drying of a compressed gas stream comprising a gas component and water, said process comprising contacting the compressed gas stream with an adsorbent to adsorb at least a portion of the water to produce a dry compressed gas stream, wherein said adsorbent comprises a shaped alumina particle having dispersed thereon a colloidal silica layer and wherein said alumina particle has a surface area between 250 and 550 m 2 /g.  
     
     
         2 . The process of  claim 1  wherein said alumina particle has a surface area between about 300 and 450 m 2 /g.  
     
     
         3 . The process of  claim 1  wherein said alumina particle has a surface area between about 300 and 400 m 2 /g.  
     
     
         4 . The process of  claim 1  wherein said alumina particle has a surface area between about 320 and 380 m 2 /g.  
     
     
         5 . The process of  claim 1  wherein the adsorbent has an attrition loss of less than 0.4 wt-%.  
     
     
         6 . The process of  claim 1  wherein the silica layer extends less than about 50 microns from the surface of the shaped particle towards the center of the particle.  
     
     
         7 . The process of  claim 1  wherein the adsorbent comprises a rehydration loss of less than about 5 wt-%.  
     
     
         8 . The process of  claim 1  wherein the shaped alumina particle is selected from the group consisting of spherical, an extrudate, a pill, a flake or a monolith.  
     
     
         9 . The process of  claim 1  wherein the gas component is selected from the group consisting of air, nitrogen, light hydrocarbons and mixtures thereof.  
     
     
         10 . The process of  claim 1  wherein the gas component comprises air.  
     
     
         11 . The process of  claim 1  further comprising periodically purging the selective adsorbent to desorb the water.  
     
     
         12 . The process of  claim 1  wherein the contacting of the compressed gas with the adsorbent takes place in a pressure swing adsorption process wherein the adsorbent is depressurized to an effective desorption pressure and purged to desorb the water.  
     
     
         13 . An air brake dryer assembly having a refillable or replaceable cartridge containing shaped particles having a colloidal silica layer dispersed on the shaped alumina carrier, at least 60 percent of the colloidal silica being present in a band extending from the surface towards the center and having a width of less than about 50 microns and wherein said shaped alumina carrier has a surface area of about 250 to 550 m 2 /g.  
     
     
         14 . The air brake dryer assembly of  claim 13  wherein said shaped alumina carrier has a surface area of about 300 to 450 m 2 /g.  
     
     
         15 . The air brake dryer assembly of  claim 13  wherein said shaped alumina carrier has a surface area of about 300 to 400 m 2 /g.  
     
     
         16 . The air brake dryer assembly of  claim 13  wherein said shaped alumina carrier has a surface area of about 320 to 380 m 2 /g.