Carbon microparticle having lignin as raw material and preparation method therefor

Abstract

The present invention provides a method for preparing a carbon microparticle from an organic raw material having lignin as a main constituent, and a carbon microparticle obtained thereby. An aqueous solution with 5% total concentration of lignin and sodium hydroxide (the proportion in mass is 1:0.5) is spray-dried to prepare a complex microparticle. This is heat-processed under nitrogen atmosphere at 600° C. for one hour and let to cool. Thereafter, this is washed with water and further dried to prepare a hollow carbon microparticle such as those shown in FIG. 2 ( b ). The prepared carbon microparticle is light-weight and has an equivalent specific surface area to commercially available activated charcoal.

1 . A carbon microparticle preparation method,
 wherein a solution of organic raw material having lignin as a main constituent is turned into a micro-droplet, the micro-droplet is dried to prepare a microparticle, and the microparticle is thermally decomposed in a range of 300° C. to 1200° C. to prepare a carbon microparticle.   
     
     
         2 . A carbon microparticle preparation method,
 wherein a mixed solution of an organic raw material having lignin as a main constituent and an inorganic substance is turned into a micro-droplet, the micro-droplet is dried to prepare a microparticle, and the microparticle is thermally decomposed in a range of 300° C. to 1200° C. to prepare a carbon microparticle.   
     
     
         3 . The carbon microparticle preparation method according to  claim 2 ,
 wherein the inorganic substance is a metal compound constituted by one or more species selected from the group consisting of an oxide, a hydroxide, a carbonate and a halide of a metal, and   based on the property that a carbon wall thickness of the carbon microparticle becomes thinner as the proportion of the metal compound added increases, the proportion of the metal compound added is adjusted to control the carbon wall thickness of the microparticle.   
     
     
         4 . The carbon microparticle preparation method according to  claim 2 ,
 wherein prior to being taken out into the air, the carbon microparticle obtained during the thermal decomposition or after the thermal decomposition is brought into contact beforehand with a gas having low reactivity, thereby inactivating the surface of the carbon microparticle by reaction with the gas and inhibiting a rapid heat generation occurring when the carbon microparticle is taken out into the air.   
     
     
         5 . A carbon microparticle preparation method,
 wherein a mixed solution of organic raw materials having lignin as a main constituent and a basic compound is turned into a micro-droplet, the micro-droplet is dried to prepare a microparticle, and the microparticle is thermally decomposed in a range of 300° C. to 1200° C. and the specific surface area is increased to prepare a carbon microparticle.   
     
     
         6 . A carbon microparticle preparation method,
 wherein preprocessing to raise the constituent ratio of lignin is carried out on a pulp waste solution,   the pulp waste solution after the preprocessing is turned into a micro-droplet, the micro-droplet is dried to prepare a microparticle, and the microparticle is thermally decomposed in a range of 300° C. to 1200° C. to prepare a carbon microparticle.   
     
     
         7 . A carbon microparticle preparation method,
 wherein preprocessing to raise the constituent ratio of lignin is carried out on a pulp waste solution,   a solution comprising the pulp waste solution after the preprocessing added with an inorganic substance is turned into a micro-droplet, the micro-droplet is dried to prepare a microparticle, and the microparticle is thermally decomposed in a range of 300° C. to 1200° C. to prepare a carbon microparticle.   
     
     
         8 . The carbon microparticle preparation method according to  claim 6  or  7 ,
 wherein separation-collection of high molecular weight lignin is carried out by ultrafiltration as the preprocessing.   
     
     
         9 . The carbon microparticle preparation method according to  claim 6  or  7 ,
 wherein a process is carried out as the preprocessing, in which carbon dioxide is absorbed by the pulp waste solution to thereby decrease a hydrogen ion index and deposit a portion of an organic constituent, and the organic constituent is separated.   
     
     
         10 . A hollow carbon microparticle, which is obtained by turning a solution of lignin, or lignin and an inorganic substance into a micro-droplet, drying the micro-droplet to prepare a microparticle, and thermally decomposing the microparticle in a range of 300° C. to 1200° C. 
     
     
         11 . A hollow carbon microparticle, which is obtained by turning a solution of lignin, or lignin and a basic compound into a micro-droplet, drying the micro-droplet to prepare a microparticle, and thermally decomposing the microparticle in a range of 300° C. to 1200° C.,
 wherein the hollow carbon microparticle has an external diameter of 0.2 to 50 μm and a carbon wall thickness of 0.05 to 20 μm.   
     
     
         12 . The hollow carbon microparticle according to  claim 11 , which has a high specific surface area,
 wherein the proportion in mass of the lignin and the basic compound is 1:0.5 to 1:2.   
     
     
         13 . A hollow carbon microparticle, which is obtained by turning a solution of lignin as well as a metal compound constituted by one or more species selected from the group consisting of an oxide, a hydroxide, a carbonate and a halide of a metal into a micro-droplet, drying the micro-droplet to prepare a microparticle, and thermally decomposing the microparticle in a range of 300° C. to 1200° C.,
 wherein the hollow carbon microparticle has an external diameter of 0.2 to 50 μm, a carbon wall thickness of 5 to 200 nm and a bulk density of 3 to 20 g/L.   
     
     
         14 . The hollow carbon microparticle according to  claim 13 ,
 wherein the proportion in mass of the lignin and the metal compound is 1:3 to 1:20.   
     
     
         15 . A hollow carbon microparticle, which is obtained by turning a solution of lignin and metasilicate into a micro-droplet, drying the micro-droplet to prepare a microparticle, and thermally decomposing the microparticle in a range of 300° C. to 1200° C.,
 wherein the hollow carbon microparticle has an external diameter of 0.2 to 50 μm and a carbon wall thickness of 0.05 to 20 μm, and wherein the carbon wall thereof is constituted by a carbon nanopipe having an external diameter of 5 to 50 nm and a carbon wall thickness of 1 to 5 nm.   
     
     
         16 . The hollow carbon microparticle according to  claim 15 ,
 wherein the proportion in mass of the lignin and the metasilicate is 1:3 to 1:20.   
     
     
         17 . A hollow, non-graphite carbon microparticle, which is obtained by turning a solution of lignin and orthosilicate into a micro-droplet, drying the micro-droplet to prepare a microparticle, and thermally decomposing the microparticle in a range of 300° C. to 1200° C.,
 wherein the hollow, non-graphite carbon microparticle has an external diameter of 3 to 30 nm, a carbon wall thickness of 1 to 5 nm and a specific surface area of 1400 to 1600 m 2 /g.   
     
     
         18 . The hollow, non-graphite carbon microparticle according to  claim 17 ,
 wherein the proportion in mass of the lignin and the orthosilicate is 1:5 to 1:20.