Material and method for treating gaseous media containing volatile organic compounds

Abstract

The invention relates to a material for treating gaseous media containing volatile organic components. According to the invention, the material is porous and exhibits an absorption capacity of approximately 20-30% in relation to the dry weight thereof, containing approximately 47-52% by weight of a composite carbon and silicon structure, approximately 12-20 wt. % carbon, approximately 5-7 wt % hydroxyl, and approximately 1-2 wt % oxygen. The invention can be used in atmospheric treatment for the preservation of living matter.

1 . A material for the treatment of gaseous media containing volatile organic compounds, the porous material presenting an adsorption capacity of about 20 to 30% with respect to its dry weight and comprising about 47 to 52 wt % of a composite structure of silicon and carbon, about 12 to 20 wt % carbon, about 5 to 7 wt % hydroxyl, and about 1 to 2 wt % oxygen.  
     
     
         2 . The material according to  claim 1 , comprising, in a peripheral volume corresponding to essentially one-third of a total volume of the material, about 75 to 85% porosity, and having pores with dimensions between 10 and 50 Å and, in a remaining central volume, about 80 to 90% cavities having dimensions between about 200 Å and 2 μm.  
     
     
         3 . The material according to  claim 1  having a specific surface of between 1200 and 2200 m 2 /g.  
     
     
         4 . The material according to  claim 1 , comprising about 20 wt % aluminum oxides and about 5 wt % iodides.  
     
     
         5 . The material according to  claim 1 , having a relative humidity lower than 2% of its dry weight.  
     
     
         6 . A process for the treatment of a gaseous medium containing volatile organic compounds, consisting of directing a flow of the gaseous medium over a porous material according to  claim 1 , to cause adsorption of the flow, which penetrates pores and cavities of the material so absorption of the flow, during which a chemical reaction occurs between the volatile organic compounds of the flow and the material, to transform the volatile organic compounds into nontoxic gases.  
     
     
         7 . The process according to  claim 6 , in which contact time between the gaseous flow and the material is between 0.08 and 0.12 sec.  
     
     
         8 . The process for obtaining a porous material according to  claim 1 , comprising: 
 preparing a base constituent of clay comprising about 30 wt % of a clay with a particle size greater than 180 μm and about 70 wt % of a clay with a particle size between 10 and 20 μm,    impregnating the base constituent with an aqueous solution comprising about 10% by volume of acetic acid, between 5 and 10% by volume of citric acid, and between 15 and 20% by volume of peroxide, the volume of the solution being essentially equal to the volume of the base constituents,    pretreating the base constituents impregnated with the aqueous solution by mixing at a first speed to create a porous structure,    mixing, under a pressure between 2 and 10 bar, the base constituent, after pretreating with an acidified liquid with a strong oxidizing potential, at a second speed lower than the first speed, to cause the acidified liquid to penetrate the pretreated constituent and to form a gel, the pretreated constituent being between 42 and 48% of the total volume mixed, while the liquid is between 58 and 52% of the total volume mixed;    mixing the gel with a solution with a strong oxido-reductive potential, which represents about 10% of the total volume, a mixture of carbon and alumina representing about 12 to 15% of the total volume, and calcium sulfate representing about 2% of the total volume;    drying the mixture produced by ultrasound treatment, and    pressing the mixture, after drying, under a pressure between 8 and 10 bar.    
     
     
         9 . The process according to  claim 8 , implemented continuously.  
     
     
         10 . The process according to  claim 8 , including heating the base constituent impregnated with the aqueous solution in pretreating, at a temperature between 200 and 250° C.  
     
     
         11 . The process according to  claim 8 , including applying ultrasound waves at pretreating, at a unit power of 2000 W and with an amplitude of 15 to 30 μm.  
     
     
         12 . The process according to  claim 8 , including, in pretreating, mixing at a third speed, lower than the first and second speeds, to enlarge the cavities and pores.  
     
     
         13 . The process according to  claim 8 , including filtering a liquid resulting from pretreating the base constituent.  
     
     
         14 . The process according to  claim 8 , in which the acidified liquid comprises about 10% by volume of a solution with a strong oxidizing potential.  
     
     
         15 . The process according to  claim 8 , including mixing the base constituent, after pretreating and the acidified liquid while being heated to a temperature between 90 and 120° C.  
     
     
         16 . The process according to  claim 8 , including mixing of the gel at a temperature between 70 and 80° C.  
     
     
         17 . The process according to  claim 8 , wherein the treatment by ultrasound waves, to dry the mixture is carried out at a length of 20 to 30 cm, under a specific output of 3- to 5000 W, an amplitude of 15 to 60 μm, and a frequency of about 20 MHz.  
     
     
         18 . The process according to  claim 8 , including drying the mixture under a partial vacuum of 120 to 150 mbar and at a temperature between 90 and 100° C.  
     
     
         19 . The process according to  claim 8 , comprising extruding the mixture, after drying.  
     
     
         20 . An apparatus for implementation of the process according to  claim 8 , comprising: 
 an impregnator including a first mixer rotating at a speed between 1200 and 1400 rpm to form a first mixture,    a first reactors including a second mixer rotating at a speed between 800 and 1000 rpm to accomplish mixing under pressure between 2 and 10 bar, to create a second mixture as a gel,    a second reactor including a mixer to create a third mixture,    a device for linear transfer of the third mixture and at least one ultrasound device delivering a power of 3 to 5000 W, on at least one part of a trajectory of said third mixture, and    a high-pressure extrusion devices.    
     
     
         21 . The apparatus according to  claim 20 , in which the impregnator includes a heating device for heating to a temperature between 200 and 250° C., as well as a device for emitting ultrasound waves.  
     
     
         22 . The apparatus according to  claim 20  including a filtration device for filtering a liquid extracted from the impregnator.  
     
     
         23 . The apparatus according to  claim 20 , wherein the impregnator includes a second mixer rotating at a speed between 500 and 800 rpm.  
     
     
         24 . The apparatus according to  claim 20 , wherein the first reactor includes a heating device heating to a temperature between 90 and 120° C.  
     
     
         25 . The apparatus according to  claim 20 , wherein the second reactor includes a heating device for heating to a temperature between 70 and 80° C.  
     
     
         26 . The apparatus according to  claim 20 , in which the linear transfer device of the second reactor includes a double screw having a rotation speed between 5 and 150 rpm.  
     
     
         27 . The apparatus according to  claim 20 , wherein the extrusion device includes a variable screw which subjects the material from the second reactor to a pressure between 8 and 10 bar.