Method and catalyst for producing single walled carbon nanotubes

Abstract

A catalyst composition and method of use of the catalyst composition for producing single-walled carbon nanotubes (SWNTs). The catalyst is cobalt (Co) and molybdenum (Mo) on a silica support. The Mo occurs primarily as dispersed Mo oxide clusters on the support while the Co is primarily in an octahedral configuration in a CoMoO 4 -like phase disposed on the Mo oxide clusters. In the method, the catalyst is used and the process conditions manipulated in such a manner as to enable the diameters of the SWNTs to be substantially controlled.

What is claimed is:  
     
         1 . A catalyst composition, comprising: 
 Co and Mo disposed on a support material wherein the majority of the Mo occurs as dispersed Mo oxide clusters and the majority of the Co occurs in a CoMoO 4 -like phase with the Co therein primarily in an octahedral configuration, and wherein the CoMoO 4 -like phase occurs substantially disposed upon the dispersed Mo oxide clusters.    
     
     
         2 . The catalyst composition of  claim 1  wherein the support material is silica.  
     
     
         3 . The catalyst composition of  claim 1  wherein the molar ratio of Co:Mo is less than 3:4.  
     
     
         4 . A method of preferentially forming single walled carbon nanotubes having a particular diameter, comprising: 
 providing a catalyst comprising: 
 Co and Mo disposed on a support material wherein the majority of the Mo occurs as dispersed Mo oxide clusters and the majority of the Co occurs in a CoMoO 4 -like phase with the Co therein primarily in an octahedral configuration, and wherein the CoMoO 4 -like phase occurs substantially disposed upon the dispersed Mo oxide clusters; and  
 exposing the catalyst in a reactor to a carbon-containing gas at a temperature between about 700° C. and about 800° C. and maintaining a CO 2  concentration in the reactor below a threshold CO 2  concentration above which the conversion of ionic Co to metallic Co is inhibited, wherein the majority of the single walled carbon nanotubes thus formed have a diameter between about 0.7 nm to about 0.9 nm.  
   
     
     
         5 . The method of  claim 4  wherein in the step of providing a catalyst, the support material is silica.  
     
     
         6 . The method of  claim 4  wherein in the step of exposing the catalyst to a carbon-containing gas, the reactor has a pressure therein between about 1 atm and 7 atm.  
     
     
         7 . The method of  claim 4  wherein in the step of exposing the catalyst to a carbon-containing gas, the threshold CO 2  concentration in the reactor is 1%.  
     
     
         8 . The method of  claim 4  wherein in the step of exposing the catalyst to a carbon-containing gas, the carbon-containing gas is CO.  
     
     
         9 . The method of  claim 4  comprising the additional step of reducing the catalyst by exposing the catalyst to a heated hydrogen gas.  
     
     
         10 . A method of preferentially forming single walled carbon nanotubes having a particular diameter, comprising: 
 providing a catalyst comprising: 
 Co and Mo disposed on a support material wherein the majority of the Mo occurs as dispersed Mo oxide clusters and the majority of the Co occurs in a CoMoO 4 -like phase with the Co therein primarily in an octahedral configuration, and wherein the CoMoO 4 -like phase occurs substantially disposed upon the dispersed Mo oxide clusters; and  
 exposing the catalyst in a reactor to a carbon-containing gas at a temperature between about 800° C. and about 900° C. and maintaining a CO 2  concentration in the reactor below a threshold CO 2  concentration above which the conversion of ionic Co to metallic Co is inhibited, wherein the majority of the single walled carbon nanotubes thus formed have a diameter between about 0.9 nm to about 1.2 nm.  
   
     
     
         11 . The method of  claim 10  wherein in the step of providing a catalyst, the support material is silica.  
     
     
         12 . The method of  claim 10  wherein in the step of exposing the catalyst to a carbon-containing gas, the reactor has a pressure therein between about 1 atm and 7 atm.  
     
     
         13 . The method of  claim 10  wherein in the step of exposing the catalyst to a carbon-containing gas, the threshold CO 2  concentration in the reactor is 1%.  
     
     
         14 . The method of  claim 10  wherein in the step of exposing the catalyst to a carbon-containing gas, the carbon containing gas is CO.  
     
     
         15 . The method of  claim 10  comprising the additional step of reducing the catalyst by exposing the catalyst to a heated hydrogen gas.  
     
     
         16 . A method of preferentially forming single walled carbon nanotubes having a particular diameter, comprising: 
 providing a catalyst comprising: 
 Co and Mo disposed on a support material wherein the majority of the Mo occurs as dispersed Mo oxide clusters and the majority of the Co occurs in a CoMoO 4 -like phase with the Co therein primarily in an octahedral configuration, and wherein the CoMoO 4 -like phase occurs substantially disposed upon the dispersed Mo oxide clusters; and  
 exposing the catalyst in a reactor to a carbon-containing gas at a temperature between about 900° C. and about 1,000° C. and maintaining a CO 2  concentration in the reactor below a threshold CO 2  concentration above which the conversion of ionic Co to metallic Co is inhibited, wherein the majority of the single walled carbon nanotubes thus formed have a diameter between about 1.3 nm to about 1.7 nm.  
   
     
     
         17 . The method of  claim 16  wherein in the step of providing a catalyst, the support material is silica.  
     
     
         18 . The method of  claim 16  wherein in the step of exposing the catalyst to a carbon-containing gas, the reactor has a pressure therein between about 1 atm and 7 atm.  
     
     
         19 . The method of  claim 16  wherein in the step of exposing the catalyst to a carbon-containing gas, the threshold CO 2  concentration in the reactor is 1%.  
     
     
         20 . The method of  claim 16  wherein in the step of exposing the catalyst to a carbon-containing gas, the carbon-containing gas is CO.  
     
     
         21 . The method of  claim 16  comprising the additional step of reducing the catalyst by exposing the catalyst to a heated hydrogen gas.