Vapor-Grown Carbon Fiber and Production Process Thereof

Abstract

The present invention provides a process for producing a vapor-grown carbon fiber by contacting a carbon source in the supplied raw material with a catalyst and/or a catalyst precursor compound in a heating zone to produce a carbon fiber in a vapor phase, wherein the carbon source at least includes methane, the concentration of methane in the supplied raw material is at or more than 15 mol % to less than 100 mol %, and the temperature in the high-temperature part of the heating zone is from 1,100 to 1,500° C. The process of the present invention is simple and effective, and in which the effectiveness of a catalyst or a catalyst precursor can be remarkably enhanced and, in turn, a carbon fiber can be produced at a low cost.

1 . A process for producing a vapor-grown carbon fiber by contacting a carbon source in the supplied raw material with a catalyst and/or a catalyst precursor compound in a heating zone to produce a carbon fiber in a vapor phase, wherein the carbon source at least includes methane, the concentration of methane in the supplied raw material is at or more than 15 mol % to less than 100 mol %, and the temperature in the high-temperature part of the heating zone is from 1,100 to 1,500° C.  
     
     
         2 . The process for producing a vapor-grown carbon fiber according to  claim 1 , wherein the temperature at the raw material-introducing part of the heating zone is 700° C. or less.  
     
     
         3 . The process for producing a vapor-grown carbon fiber according to  claim 1 , wherein the supplied raw material resides in the law temperature part of the heating zone which is at a temperature of 600 to 1,000° C. for 0.05 seconds or more before arriving at the high-temperature part of the heating zone.  
     
     
         4 . The process for producing a vapor-grown carbon fiber according to  claim 1 , wherein the residence time at a temperature of 1,100° C. or more in the heating zone is 0.001 second or more.  
     
     
         5 . The process for producing a vapor-grown carbon fiber according to  claim 1 , wherein the total amount of carbon atoms contained in the carbon source other than methane is 60% or less of the amount of carbon atoms contained in methane.  
     
     
         6 . The process for producing a vapor-grown carbon fiber according to  claim 5 , wherein the total amount of carbon atoms contained in the carbon source other than methane is 10% or less of the amount of carbon atoms contained in methane.  
     
     
         7 . The process for producing a vapor-grown carbon fiber according to  claim 1 , wherein the ratio of the atomic number of a catalyst element and the number of carbon atoms in the carbon source is  
         (atomic number of a catalyst element)/(number of carbon atoms)=0.000005 to 0.0015.  
     
     
         8 . The process for producing a vapor-grown carbon fiber according to  claim 1 , wherein the catalyst precursor compound is introduced into the heating zone after dissolving it in a compound which is in a liquid state at an ordinary temperature and pressure.  
     
     
         9 . The process for producing a vapor-grown carbon fiber according to  claim 1 , wherein the catalyst precursor compound is introduced into the heating zone after dissolving it in a compound which is in a liquid state at an ordinary temperature and pressure, and entirely vaporizing the resulted solution.  
     
     
         10 . The process for producing a vapor-grown carbon fiber according to  claim 1 , wherein the catalyst precursor compound is introduced into the heating zone after dissolving it in a compound which is in a liquid state at an ordinary temperature and pressure, entirely vaporizing the resulted solution, and mixing thus obtained gas with a methane-containing gas.  
     
     
         11 . The process for producing a vapor-grown carbon fiber according to  claim 8 , wherein the compound which is in a liquid state at an ordinary temperature and pressure is a carbon source.  
     
     
         12 . The process for producing a vapor-grown carbon fiber according to  claim 8 , wherein the solubility of the catalyst precursor compound at 25° C. in the compound which is in a liquid state at an ordinary temperature and pressure is 10 g or more per 100 g of the compound which is in a liquid state at an ordinary temperature and pressure.  
     
     
         13 . The process for producing a vapor-grown carbon fiber according to  claim 8 , wherein the compound which is in a liquid state at an ordinary temperature and pressure is at least one compound selected from the group consisting of benzene, toluene and tetrahydrofuran.  
     
     
         14 . The process for producing a vapor-grown carbon fiber according to  claim 1 , wherein the catalyst and/or catalyst precursor compound is at least one metal selected from Groups 3, 5, 6, 8, 9 and 10 of the 18 Groups-Type Periodic Table of Elements and/or a compound comprising the at least one metal.  
     
     
         15 . The process for producing a vapor-grown carbon fiber according to  claim 1 , wherein the all or a part of the gas after reaction is circulated and reused.  
     
     
         16 . The process for producing a vapor-grown carbon fiber according to  claim 1 , wherein a carbon fiber having an average fiber diameter of 10 nm or more is produced.  
     
     
         17 . A vapor-grown carbon fiber produced by the process for producing a vapor-grown carbon fiber according to  claim 1 .  
     
     
         18 . The vapor-grown carbon fiber according to  claim 17 , having an average fiber length of 10 μm or more.  
     
     
         19 . The vapor-grown carbon fiber according to  claim 18 , having the average fiber length of 13 μm or more.