Carbon nanofibers and procedure for obtaining said nanofibers

Abstract

The object of the present invention is carbon nanofibers mainly characterized by their high specific volume of mesopores, their high gas adsorption capacity and presenting a graphitic hollow structure. A second object of this invention is a procedure for obtaining such carbon nanofibers, which makes use of a metallic nickel catalyst and specific process furnace parameters that combined with the chemical composition of the furnace atmosphere and the fluidodynamic conditions of the gas stream inside the furnace, result in a faster growth of the carbon nanofibers and also in a higher quality of the carbon nanofibers obtained.

1 . Procedure for obtaining carbon nanofibers in a furnace from the catalytic decomposition of a hydrocarbon in vapour phase using a floating catalyst, by the growth of the graphitic filament, wherein:
 The catalytic particle comprises two phases, a first solid phase of metallic nickel and a second phase of a nickel sulphide compound in liquid state during the growth of the graphitic filament; and   The catalytic particle is carried by the gas stream inside the process furnace.   
     
     
         2 . Procedure for obtaining carbon nanofibers according to  claim 1  characterized in that the sulfur contained in the nickel sulfide of the catalytic particle is supplied to the furnace gas stream atmosphere. 
     
     
         3 . Procedure for obtaining carbon nanofibers according to  claim 1  characterized in that the catalytic particle is generated inside the furnace from a chemical compound including sulfur in its chemical composition. 
     
     
         4 . Procedure for obtaining carbon nanofibers according to  claim 1  characterized in that the process temperature is in the range from 900° C. to 1250° C. 
     
     
         5 . Procedure for obtaining carbon nanofibers according to  claim 4  characterized in that the process temperature is in the range from 1100° C. to 1200° C. 
     
     
         6 . Procedure for obtaining carbon nanofibers according to  claim 1  characterized in that the sulfur-nickel molar ratio is in the range from 0.5 to 5. 
     
     
         7 . Procedure for obtaining carbon nanofibers according to  claim 6  characterized in that the sulphur-nickel molar ratio is in the range from 1.2 to 3. 
     
     
         8 . Procedure for obtaining carbon nanofibers according to  claim 1  characterized in that the circulation velocity of the gas stream in the furnace is from 0.1 to 12 m/s. 
     
     
         9 . Procedure for obtaining carbon nanofibers according to  claim 8  characterized in that the circulation velocity of the gas stream in the furnace is from 0.2 to 1.5 m/s. 
     
     
         10 . Procedure for obtaining carbon nanofibers according to  claim 1  characterized in that the residence time of the gas stream in the process furnace is in the range from 1 to 15 s. 
     
     
         11 . Procedure for obtaining carbon nanofibers according to  claim 10  characterized in that the residence time of the gas stream in the process furnace is in the range from 2 to 8 s.