Novel hydrotalcites, syntheses, and uses

Abstract

Synthetic hydrotalcites of the general formula [M 2+ 1-x M 3+ x (OH) 2 ] x+ [A n− x/n .m H 2 O] x− where M 2+ is a divalent cation, M 3+ is a trivalent cation and A n− is an organic anion selected from straight chain carboxylates of C 16 -C 18 acids, carboxylates of aromatic acids, carboxylates of acrylic acid, unsaturated carboxylates of methacrylic acid, unsaturated carboxylates of vinylacetic acid and C 2 and higher organic acids containing heteroatoms such as nitrogen, phosphorous, sulfur and halogens are disclosed, along with methods of synthesis and uses.

1 . A method of making a synthetic hydrotalcite having the general formula  
         [M 2+   1-x M 3+   x (OH) 2 ] x+ [A n−   x/n   .m H 2 O] x−   wherein M 2+  is a divalent cation, M 3+  is a trivalent cation and A n−  is at least one organic anion comprising a carboxylate of an acid containing at least one heteroatom selected from the group consisting of nitrogen, phosphorous, sulfur and halogens, said method comprising:    reacting said trivalent cation source, M 3+  with said organic anion source, A n−  to produce an intermediate; and    reacting said intermediate with said divalent cation source, M 2+  in water to produce said synthetic hydrotalcite.    
     
     
         2 . The method of  claim 1 , wherein said step of reacting said trivalent cation source, M 3+  with said organic anion source, A n−  occurs in water.  
     
     
         3 . The method of  claim 2 , wherein the reaction time of said step of reacting said trivalent cation source, M 3+  with said organic anion source, A n−  is from about 4 to about 8 hours at a temperature of about 75°-85° C.  
     
     
         4 . The method of  claim 1 , wherein the reaction time of said step of reacting said divalent cation source, M 2+  with said intermediate is from about 4 to about 8 hours at a temperature of about 90° C.  
     
     
         5 . The method of  claim 1 , wherein said step of reacting said trivalent cation source, M 3+  with said organic anion source, A n−  occurs in an organic solvent.  
     
     
         6 . The method of  claim 1 , wherein said step of reacting said trivalent cation source, M 3+  with said organic anion source, A n−  occurs in an acid melt.  
     
     
         7 . The method of  claim 1 , wherein said trivalent cation source, M 3+  consists essentially of Al 3+ .  
     
     
         8 . The method of  claim 1 , wherein said trivalent cation source, M 3+  contains Al 3+  and up to 50% of at least one of Cr 3+  and Fe 3+ .  
     
     
         9 . The method of  claim 1 , wherein said divalent cation source, M 2+  consists essentially of Mg 2+ .  
     
     
         10 . The method of  claim 1 , wherein said divalent cation source, M 2+  contains Mg 2+  and up to 50% of at least one of Ni 2+ , Co 2+ , Zn 2+ , Cu 2+  and Mn 2+ .  
     
     
         11 . The method of  claim 1 , wherein said at least one organic anion source, A n−  comprises an amino acid.  
     
     
         12 . The method of  claim 11 , wherein said amino acid comprises 4-aminobutyric acid.  
     
     
         13 . The method of  claim 11 , wherein said amino acid comprises 6-aminocaproic acid.  
     
     
         14 . The method of  claim 1 , further comprising isolating said synthetic hydrotalcite as a solid and drying said synthetic hydrotalcite.  
     
     
         15 . The method of  claim 14 , wherein said drying is accomplished in a spray drier.  
     
     
         16 . The method of  claim 1 , wherein said synthetic hydrotalcite is capable of self exfoliation.  
     
     
         17 . The method of  claim 16 , further comprising isolating said synthetic hydrotalcite as a colloidal suspension in a solvent.  
     
     
         18 . The method of  claim 17 , wherein said solvent is water.  
     
     
         19 . The method of  claim 17  wherein said solvent is an alcohol.  
     
     
         20 . The method of  claim 17 , further comprising evaporating a portion of said solvent to produce a concentrated colloidal suspension of said synthetic hydrotalcite.  
     
     
         21 . The method of  claim 17 , further comprising evaporating a portion of said solvent to produce a paste of said synthetic hydrotalcite.