Hydrothermal gel process for preparation of silicalite particles and process for preparation of composite membrane

Abstract

A novel hydrothermal gel process for preparing silicalite particles suitable for use in composite membranes for pervaporation processes is disclosed. A novel process for preparing a silicon-silicalite composite membrane is also disclosed. The novel hydrothermal gel process produces silicalite particles having a diameter from about 0.1 micrometers to about 0.2 micrometers in high yield.

What is claimed is:  
     
         1 . A process for preparing a thin-film silicalite-silicone composite membrane, the process comprising: 
 mixing silicone rubber, iso-octane, and silicalite particles having a diameter of from about 0.1 micrometers to about 0.5 micrometers to form a membrane precursor mixture;    transmitting ultrasonic waves through the membrane precursor mixture to disperse the silicalite particles and silicone rubber;    introducing a silicone curing agent into the dispersed membrane precursor mixture;    transmitting ultrasonic waves through the membrane precursor mixture to disperse the silicone curing agent;    pre-polymerizing the membrane precursor mixture to increase the viscosity of the membrane precursor mixture; and    casting the pre-polymerized membrane precursor mixture on a support membrane.    
     
     
         2 . The process as set forth in  claim 1  wherein the silicalite particles have a diameter of from about 0.1 to about 0.2 micrometers.  
     
     
         3 . The process as set forth in  claim 1  wherein the membrane precursor mixture is pre-polymerized at about 60° C. for about 3 hours.  
     
     
         4 . The process as set forth in  claim 1  further comprising air drying the pre-polymerized membrane precursor mixture on the support membrane at room temperature for about 20 minutes followed by further curing at a temperature of about 80° C. for about 12 hours.  
     
     
         5 . The process as set forth in  claim 1  wherein the support membrane has a pore size of from about 18 to about 20 nanometers.  
     
     
         6 . The process as set forth in  claim 1  wherein the silicalite particles are pre-treated prior to forming the membrane precursor mixture, the pre-treatment comprising: 
 mixing the silicalite particles with deionized water;  
 transmitting ultrasonic waves through the mixture of silicalite particles and water to disperse the silicalite particles and form a colloid solution;  
 stilling the colloid solution for from about 1 to about 10 hours;  
 recovering the silicalite particles from the colloid solution;  
 mixing the recovered silicalite particles with an ethanol solvent; and  
 drying the silicalite particles.  
 
     
     
         7 . The process as set forth in  claim 6  wherein the recovery step comprises: 
 filtering the colloid solution to separate silicalite particles from the colloid solution and produce a liquid product filtrate; and  
 centrifuging the liquid product filtrate to separate silicalite particles from the liquid product filtrate.  
 
     
     
         8 . The process as set forth in  claim 7  wherein the colloid solution is stilled for about 4 hours.  
     
     
         9 . The process as set forth in  claim 1  wherein the silicone rubber, silicalite particles, curing agent, and iso-octane are utilized in the weight ratio 1:0.1-2:0.1:2-10, respectively.  
     
     
         10 . The process as set forth in  claim 1  wherein the ultrasonic waves are transmitted through the membrane precursor mixture at a frequency of about 42 kHz.