Method of producing carbon nanoparticles

Abstract

A method of producing carbon nanoparticles comprises the steps of: passing a gaseous carbon source through a heated reactor; and adding catalyst supported on substrate particles or thermally decomposable catalyst precursor supported on substrate particles to the heated reactor to form a fluidised bed; such that carbon nanoparticles are formed in the heated reactor.

1 . A method of producing carbon nanoparticles, comprising the steps of: 
 passing a gaseous carbon source through a heated reactor; and    adding catalyst supported on substrate particles or thermally decomposable catalyst precursor supported on substrate particles to the heated reactor;    maintaining a fluidised bed of the substrate particles in the heated reactor; and    forming carbon nanoparticles in the heated reactor.    
     
     
         2 . A method as claimed in  claim 1 , wherein the catalyst or catalyst precursor supported on substrate particles is introduced into the heated reactor via a gravity-fed hopper.  
     
     
         3 . A method as claimed in  claim 1 , wherein the catalyst or catalyst precursor supported on substrate particles is introduced into the heated reactor via an injection gas flow.  
     
     
         4 . A method as claimed in  claim 3 , wherein the injection gas flow reverses the direction of gas flow through the heated reactor during injection.  
     
     
         5 . A method as claimed in  claim 3 , wherein the injection gas is an inert gas.  
     
     
         6 . A method as claimed in  claim 3 , wherein the injection gas is a gaseous carbon source.  
     
     
         7 . A method as claimed in  claim 1 , wherein the reactor heated reactor is at a temperature between 500 and 1200° C.  
     
     
         8 . A method as claimed in  claim 7 , wherein the heated reactor is at a temperature between 700 and 900° C.  
     
     
         9 . A method as claimed in  claim 1 , wherein a catalyst precursor is present and is a metal salt, an organometallic species or a metal carbonyl.  
     
     
         10 . A method as claimed in  claim 9 , wherein the catalyst precursor comprises one or more of nickel, iron, molybdenum, platinum and cobalt.  
     
     
         11 . A method as claimed in  claim 9 , wherein the catalyst precursor is a metal salt and comprises a counterion consisting of nitrate, stearate, formate, oxalate, acetate or chloride.  
     
     
         12 . A method as claimed in  claim 11 , wherein the counter ion is organic.  
     
     
         13 . A method as claimed in  claim 12 , wherein the organic counter ion is C 2  to C 30  carboxylate.  
     
     
         14 . A method as claimed in  claim 1 , wherein the carbon nanoparticles contain a non-carbon dopant.  
     
     
         15 . A method as claimed in  claim 14 , wherein the non-carbon dopant is nitrogen.  
     
     
         16 . A method as claimed in  claim 1 , wherein the gaseous carbon source is one or more of acetylene, alcohol, alkane, alkene, CO, benzene, toluene, xylene, cumene, ethylbenzene, naphthalene, phenanthrene, anthracene, formaldehyde, acetaldehyde, acetone.  
     
     
         17 . A method as claimed in  claim 1 , wherein the gaseous carbon source is mixed with a diluent gas.  
     
     
         18 . A method as claimed in  claim 17 , wherein the diluent gas is one or more of hydrogen, ammonia, nitrogen, helium and argon.  
     
     
         19 . A method as claimed in  claim 17 , wherein the ratio of gaseous carbon source to diluent gas is reduced while the catalyst or catalyst precursor supported on substrate particles is introduced into the heated reactor.  
     
     
         20 . A method as claimed in  claim 1 , in which the substrate particles comprise one or more of silica, alumina, MCM and magnesium oxide.  
     
     
         21 . A method as claimed in  claim 1 , in which the substrate particles comprise a halide, nitrate, sulphate, carbonate, aluminate, aluminium chloride, arsenate, arsenite, borate, chromate, fluoroaluminate, silicate, sulphide, telluride, tungstate, vanadate or phosphate of a Group 1 or Group 2 metal.  
     
     
         22 . A method as claimed in  claim 21 , wherein the Group 1 or Group 2 metal is lithium, sodium, potassium, calcium or magnesium.  
     
     
         23 . A method as claimed in  claim 1 , wherein the average dimension of the substrate particles is between 20 microns and 1 mm.  
     
     
         24 . A method as claimed in  claim 1 , wherein the average dimension of the substrate particles is between 40 microns and 200 microns.  
     
     
         25 . A method as claimed in  claim 1 , further comprising the step of removing nanoparticles from the heated reactor.  
     
     
         26 . A method as claimed in  claim 25 , wherein nanoparticles are removed from the heated reactor by under vacuum or under pressure.  
     
     
         27 . A method as claimed in  claim 1 , wherein the process is operated continuously with simultaneous introduction of catalyst or catalyst precursor supported on substrate particles and removal of nanoparticles.  
     
     
         28 . A method as claimed in  claim 1 , wherein the method is operated non-continuously with alternating introduction of catalyst or catalyst precursor supported on substrate particles and removal of nanoparticles.  
     
     
         29 . A method as claimed in  claim 1 , wherein the carbon nanoparticles are nanotubes and/or nanofibres.  
     
     
         30 . A method as claimed in  claim 29 , wherein the nanotubes are single-walled nanotubes or multi-walled nanotubes.  
     
     
         31 . A method of producing carbon nanoparticles, comprising the steps of: 
 passing a non-carbon-containing gas through a heated reactor; and    adding catalyst or catalyst precursor supported on substrate particles to the heated reactor;    maintaining a fluidised bed of said substrate particles in the heated reactor;    passing a gaseous carbon source through the heated reactor; and    forming carbon nanoparticles in the heated reactor.    
     
     
         32 . Carbon nanoparticles produced by a method as claimed in  claim 1  or  claim 31.