Rapid method for production of cerium-containing oxide organic colloids

Abstract

Improved methods for producing colloidal dispersions of cerium-containing oxide nanoparticles in substantially non-polar solvents is disclosed. The cerium-containing oxide nanoparticles of an aqueous colloid are transferred to a substantially non-polar liquid comprising one or more amphiphilic materials, one or more low-polarity solvents, and, optionally, one or more glycol ether promoter materials. The transfer is achieved by mixing the aqueous and substantially non-polar materials, forming an emulsion, followed by a phase separation into a remnant polar solution phase and a substantially non-polar organic colloid phase. The organic colloid phase is then collected. The promoter functions to speed the transfer of nanoparticles to the low-polarity phase. The promoter accelerates the phase separation, and also provides improved colloidal stability of the final substantially non-polar colloidal dispersion. The glycol ether promoter reduces the temperature necessary to achieve the phase separation, while providing high extraction yield of nanoparticles into the low-polarity organic phase. In addition, use of particular amphiphilic materials, such as heptanoic acid or octanoic acid, enable efficient extractions at ambient temperatures without the use of a glycol ether promoter.

What is claimed is: 
     
         1 . A process for preparing a colloidal dispersion, comprising:
 (a) preparing an aqueous colloidal dispersion of cerium-containing oxide nanoparticles;   (b) adding a substantially non-polar solvent, an amphiphilic material, and, optionally, a glycol ether;   (c) mixing the liquid mixture of step (b) to form an emulsion;   (d) heating the emulsion to a predetermined temperature for a predetermined time, whereafter the emulsion separates into a substantially non-polar colloidal phase and a remnant aqueous phase; and,   (e) collecting the separated substantially non-polar colloidal dispersion of cerium-containing oxide nanoparticles.   
     
     
         2 . The process of  claim 1 , wherein said temperature ranges from about 20° C. to less than 60° C. 
     
     
         3 . The process of  claim 1 , wherein said time ranges from 0 to 8 hours. 
     
     
         4 . The process of  claim 1 , wherein said glycol ether is added in its entirety during step (d). 
     
     
         5 . The process of  claim 4 , wherein said glycol ether is added 0 to 4 hours after the end of step (c). 
     
     
         6 . The process of  claim 1 , wherein said glycol ether is selected from the group consisting of diethylene glycol monomethyl ether, propylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, dipropylene glycol methyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, and combinations thereof. 
     
     
         7 . The process of  claim 6 , wherein said glycol ether is selected from the group consisting of diethylene glycol monomethyl ether, propylene glycol monomethyl ether, and a mixture thereof. 
     
     
         8 . The process of  claim 6 , wherein said glycol ether comprises about 5-25 wt. % of the total materials added during step (b). 
     
     
         9 . The process of  claim 1 , wherein said amphiphilic material is a monocarboxylic acid having from 6 to 22 carbon atoms. 
     
     
         10 . The process of  claim 9 , wherein said monocarboxylic acid is 2-ethylhexanoic acid, heptanoic acid or octanoic acid. 
     
     
         11 . The process of  claim 10 , wherein said monocarboxylic acid is heptanoic acid or octanoic acid, and said temperature is ambient temperature. 
     
     
         12 . The process of  claim 9 , wherein said monocarboxylic acid is oleic acid. 
     
     
         13 . The process of  claim 9 , wherein the amount of said carboxylic acid comprises about 25-33 wt. % of the total amount of substantially nonpolar solvent, amphiphilic material, and glycol ether added during steps (a) through (e). 
     
     
         14 . The process of  claim 1 , wherein said substantially nonpolar solvent is added in its entirety during step (d). 
     
     
         15 . The process of  claim 14 , wherein said substantially nonpolar solvent is added 0 to 1 hour after the end of step (c). 
     
     
         16 . The process of  claim 1 , wherein the amount of said substantially nonpolar solvent comprises about 50-63 wt. % of the total amount of substantially nonpolar solvent, amphiphilic material, and glycol ether added during steps (a) through (e). 
     
     
         17 . The process of  claim 1 , wherein said cerium-contain oxide nanoparticles have a nominal composition of Ce (1-x) Fe x O (2-δ) , wherein x ranges from about 0.01 to 0.8. 
     
     
         18 . The process of  claim 1 , wherein said aqueous colloidal dispersion of cerium-containing oxide nanoparticles is prepared without a conventional nanoparticle isolation step, thereby directly using the aqueous colloid resulting from the nanoparticle synthesis reaction mixture in step (a). 
     
     
         19 . The process of  claim 1 , wherein said aqueous colloidal dispersion of cerium-containing oxide nanoparticles has a pH less than or equal to seven. 
     
     
         20 . The process of  claim 1 , wherein said substantially nonpolar colloidal dispersion of cerium-containing oxide nanoparticles is used as a component of a fuel additive.