Method of manufacturing carbon fibres

Abstract

The present invention relates to a method of manufacturing carbon fibres from raw materials of renewable origin, comprising: a) synthesis of acrolein from glycerol of vegetable origin; b) ammoxidation of the acrolein to obtain acrylonitrile; c) polymerization of the acrylonitrile to a homopolymer or copolymer of acrylonitrile (PAN); d) conversion of the PAN to PAN fibres; e) partial oxidation of the PAN fibres; and f) carbonization of the partially oxidized PAN fibres. It also relates to the fibres capable of being obtained according to this method, and also to the uses thereof.

1 . Method of manufacturing carbon fibres, comprising:
 a) synthesising acrolein from glycerol of vegetable origin;   b) ammoxidizing the acrolein to obtain acrylonitrile;   c) polymerizing the acrylonitrile to a homopolymer or copolymer of acrylonitrile (PAN);   d) converting the PAN to PAN fibres;   e) partially oxidizing the PAN fibres; and   f) carbonizing the partially oxidized PAN fibres.   
     
     
         2 . Method according to  claim 1 , characterized in that the glycerol used in step (a) is obtained as a by-product of a transesterification of triglycerides of vegetable origin. 
     
     
         3 . Method according to  claim 2 , characterized in that the glycerol is obtained as a by-product in the manufacture of biodiesel from vegetable oil. 
     
     
         4 . Method according to  claim 1 , characterized in that the glycerol is dehydrated to acrolein, in step (a), by heating at a temperature ranging from 250 to 400° C. 
     
     
         5 . Method according to  claim 1 , characterized in that the acrylonitrile is copolymerized, in step (c), with at least one acrylic comonomer selected from the group consisting of methyl acrylate, methyl methacrylate and acrylic acid. 
     
     
         6 . Method according to  claim 5 , characterized in that the comonomer does not represent more than 10% by weight relative to the total weight of the monomers to be polymerized. 
     
     
         7 . Method according to  claim 1 , characterized in that, in step (e), is carried out by heating the fibres at 200-300° C. in the presence of air. 
     
     
         8 . Method according to  claim 1 , characterized in that, in step (f), is carried out by heating the fibres at a temperature between 1200 and 1500° C. in a furnace purged with an inert gas and maintained at a pressure above atmospheric pressure. 
     
     
         9 . Carbon fibres obtained following the method according to  claim 1 . 
     
     
         10 . Carbon fibres having an isotopic ratio of their  14 C content to their  12 C content which is greater than 5×10 −11 . 
     
     
         11 . (canceled) 
     
     
         12 . Method according to  claim 1 , characterized in that the glycerol is dehydrated to acrolein, in step (a), by heating at a temperature ranging from 260 to 300° C. 
     
     
         13 . Carbon fibres having an isotopic ratio of their  14 C content to their  12 C co×ntent which is greater than 10 −12 .