Ceramic membranes

Abstract

A filter including a porous support defining one or more channels therethrough, and a porous ceramic membrane layer on a surface of the porous support defining at least one of the one or more channels. The ceramic membrane layer includes an inorganic ceramic composition having the formula SiMpxpCyNzOmHn, where each Mp present is independently selected from a p-block element or a d-block element; p is an integer from 1 to 5; for each Mp present, xp is independently from about 0 to about 60; y is from about 0 to about 60; z is from about 0 to about 60; m is from about 0 to about 40; and n is zero or nonzero. At least one of y and z is nonzero when p is zero, and p is nonzero when y and z are both zero.

What is claimed is: 
     
         1 . A filter comprising:
 a porous support defining one or more channels therethrough; and   a porous ceramic membrane layer on a surface of the porous support defining at least one of the one or more channels, wherein the ceramic membrane layer comprises an inorganic ceramic composition having the formula SiM p   xp C y N z O m H n , wherein:
 each M p  present is independently selected from a p-block element or a d-block element; 
 p is an integer from 1 to 5; 
 for each M p  present, xp is independently from about 0 to about 60; 
 y is from about 0 to about 60; 
 z is from about 0 to about 60; 
 m is from about 0 to about 40; and 
 n is zero or nonzero, 
 wherein at least one of y and z is nonzero when p is zero, and p is nonzero when y and z are both zero. 
   
     
     
         2 . The filter of  claim 1 , wherein the porous support defines a multiplicity of channels therethrough, and the filter comprises a ceramic membrane layer on each surface of the porous support defining one of the one or more channels, wherein at least one of the ceramic membrane layers comprises the ceramic composition having the formula SiM p   xp C y N z O m H n . 
     
     
         3 . The filter of  claim 2 , wherein each of the ceramic membrane layers comprises the ceramic composition having the formula SiM p   xp C y N z O m H n . 
     
     
         4 . The filter of  claim 1 , wherein the porous support comprises aluminum oxide. 
     
     
         5 . The filter of  claim 1 , wherein the porous support is tubular. 
     
     
         6 . The filter of  claim 1 , wherein each M p  is independently boron, aluminum, zirconium, hafnium, and titanium. 
     
     
         7 . The filter of  claim 1 , wherein p is 1, and M p  is aluminum or boron. 
     
     
         8 . The filter of  claim 1 , wherein the ceramic composition comprises 1 wt % to 75 wt % silicon. 
     
     
         9 . The filter of  claim 1 , wherein the ceramic composition comprises 0 wt % to 60 wt % total M p . 
     
     
         10 . The filter of  claim 1 , wherein the ceramic composition comprises 0 wt % to 40 wt % carbon. 
     
     
         11 . The filter of  claim 1 , wherein the ceramic composition comprises 0 wt % to 50 wt % nitrogen. 
     
     
         12 . The filter of  claim 1 , wherein the ceramic composition comprises 0 wt % to 5 wt % oxygen. 
     
     
         13 . The filter of  claim 1 , wherein the pores defined by the ceramic membrane pores have a mean diameter of about 2 nm to about 50 nm. 
     
     
         14 . A method of making a filter, the method comprising:
 contacting a porous support defining one or more channels therethrough with a preceramic polymer in a liquid state to coat a surface of at least one of the channels with the preceramic polymer; and   pyrolyzing the preceramic polymer to yield a porous ceramic membrane layer on a surface of the porous support defining the at least one of the one or more channels, wherein the ceramic membrane layer comprises a ceramic composition having the formula SiM p   xp C y N z O m H n , wherein:
 each M present is independently selected from a p-block element or a d-block element; 
 p is an integer from 1 to 5; 
 for each M p  present, xp is independently from about 0 to about 60; 
 y is from about 0 to about 60; 
 z is from about 0 to about 60; 
 m is from about 0 to about 40; and 
 n is zero or nonzero, 
 wherein at least one of y and z is nonzero when p is zero, and p is nonzero when y and z are both zero. 
   
     
     
         15 . The method of  claim 14 , wherein the preceramic polymer comprises polycarbosilane, polysilazane, or a combination thereof. 
     
     
         16 . The method of  claim 14 , further comprising combining an organic solvent with the preceramic polymer before contacting the porous support with the preceramic polymer. 
     
     
         17 . The method of  claim 14 , wherein pyrolyzing the preceramic polymer comprises:
 heating the preceramic polymer in the liquid state to a first temperature to solidify the preceramic polymer in the liquid state, thereby yielding a solid preceramic polymer coating on the support; and   heating the solid preceramic polymer coating to a second temperature to yield the porous ceramic membrane on the support, wherein the second temperature is greater than the first temperature.   
     
     
         18 . The method of  claim 14 , wherein pyrolyzing the preceramic polymer comprises heating the preceramic polymer to at least 600° C. 
     
     
         19 . A method for treating boiler blowdown water from a boiler, the method comprising:
 providing feed water to the boiler;   removing blowdown water from the boiler;   providing the blowdown water to a filter element; and   providing a permeate from the filter element to the boiler, wherein a content of dissolved solids in the permeate is less than a content of dissolved solids in the blowdown water.