Fumed metal oxide particles and process for producing the same

Abstract

The invention provides a process for producing fumed metal oxide particles comprising providing a stream of a liquid feedstock comprising a volatizable, non-halogenated metal oxide precursor, providing a stream of a combustion gas having a linear velocity sufficient to atomize and combust or pyrolyze the liquid feedstock, and injecting the stream of the liquid feedstock into the stream of combustion gas to form a reaction mixture such that the liquid feedstock is atomized and subjected to a sufficient temperature and residence time in the combination gas stream for fumed metal oxide particles to form before the combustion gas temperature is reduced below the solidifying temperature of the metal oxide particle. The invention further provides fumed silica particles having a relatively small aggregate size and/or narrow aggregate size distribution.

1 - 30 . (canceled)  
     
     
         31 . A process for producing metal oxide particles, the method comprising: 
 injecting into a combustion gas stream a liquid feedstock comprising volatizable, non-halogenated precursor for metal oxide; and    in the combustion gas stream, combusting or pyrolyzing the liquid feedstock and forming particles comprising the metal oxide;    wherein the metal oxide is selected from the group consisting of alumina, zirconia, yttria, silica, titania, baria, niobia, rubidia, strontia and calcia.    
     
     
         32 . The process of  claim 31 , wherein the combustion gas stream has a linear velocity of at least Mach 0.2 when the liquid feedstock is injected into the combustion gas stream during the injecting.  
     
     
         33 . The process of  claim 31 , wherein the combustion gas stream has a temperature of from 2200 K to 2300 K when the liquid feedstock is injected into the combustion gas stream during the injecting.  
     
     
         34 . The process of  claim 31 , wherein during the injecting, the liquid feedstock is injected into the combustion gas stream through at least one nozzle.  
     
     
         35 . The process of  claim 34 , wherein the liquid feedstock is fed to the at least one nozzle under pressure and the liquid feedstock exits the at least one nozzle with sufficient force to atomize the liquid feedstock.  
     
     
         36 . The process of  claim 34 , wherein the force of the combustion gas stream atomizes the liquid feedstock injected into the combustion gas stream during the injecting.  
     
     
         37 . The process of  claim 31 , wherein during the injection, the liquid feedstock is injected into the combustion gas stream through two or more nozzles.  
     
     
         38 . The process of  claim 37 , wherein at least one of the nozzles is located downstream of at least one other of the nozzles.  
     
     
         39 . The process of  claim 31 , wherein during the injecting, the liquid feedstock is injected into the combustion gas when the combustion gas is flowing through a constricted portion of a reactor.  
     
     
         40 . The process of  claim 39 , wherein: 
 the reactor comprises a combustion chamber upstream of the constricted portion and an enlarged portion downstream of the constricted portion, wherein the combustion chamber has a first diameter, the constricted portion has a second diameter and the enlarged portion has a third diameter, the second diameter being smaller than each of the first diameter and the third diameter;    the combustion gas is established in the combustion chamber and flows through the constricted portion and into the enlarged portion; and    the particles form in the enlarged portion.    
     
     
         41 . The process of  claim 31 , wherein the metal oxide is one of two or more different metal oxides in the particles.  
     
     
         42 . The process of  claim 31 , comprising the combusting the liquid feedstock.  
     
     
         43 . The process of  claim 31 , comprising the pyrolyzing the liquid feedstock.  
     
     
         44 . The process of  claim 31 , wherein the metal oxide is alumina.  
     
     
         45 . The process of  claim 31 , wherein the metal oxide is zirconia.  
     
     
         46 . The process of  claim 31 , wherein the metal oxide is yttria.  
     
     
         47 . The process of  claim 31 , wherein the metal oxide is silica.  
     
     
         48 . The process of  claim 31 , wherein the metal oxide is titania.  
     
     
         49 . The process of  claim 31 , wherein the metal oxide is baria.  
     
     
         50 . The process of  claim 31 , wherein the metal oxide is niobia.  
     
     
         51 . The process of  claim 31 , wherein the metal oxide is rubidia.  
     
     
         52 . The process of  claim 31 , wherein the metal oxide is strontia.  
     
     
         53 . The process of  claim 31 , wherein the metal oxide is calcia.