Porous carbon material

Abstract

A porous carbon material comprising a material obtained from carbonization of a raw material including one or both of seaweed stem and straw, the raw material having a silicon content of at least 5 wt %, the raw material is heat treated before carbonization, and the raw material is treated by an alkali treatment after carbonization to reduce the silicon content, the porous carbon material having a value of specific surface area of at least 10 m2/g as measured by the nitrogen BET method, a pore volume of at least 0.1 cm3/g as measured by the BJH method and MP method, and an R value of 1.5 or greater, wherein the porous carbon material includes mesopores having pore sizes from 2 nm to 50 nm and obtained from the alkali treatment of the raw material after carbonization, the porous carbon material further includes macropores and micropores.

1 . A porous carbon material comprising a material obtained from carbonization of a raw material including one or both of seaweed stem and straw, the raw material having a silicon content of at least 5 wt %, the raw material is heat treated before carbonization, and the raw material is treated by an alkali treatment after carbonization to reduce the silicon content, the porous carbon material having a value of specific surface area of at least 10 m 2 /g as measured by the nitrogen BET method, a pore volume of at least 0.1 cm 3 /g as measured by the BJH method and MP method, and an R value of 1.5 or greater,
 wherein the porous carbon material includes mesopores having pore sizes from 2 nm to 50 nm and obtained from the alkali treatment of the raw material after carbonization, the porous carbon material further includes macropores and micropores,   the R value is expressed as R=B/A, the A referring to an intensity at an intersection between the baseline of a diffraction peak of the (002) plane as obtained based on powdery X-ray diffractometry of the porous carbon material and a perpendicular line downwardly drawn from the diffraction peak of the (002) plane, and the B referring to the intensity of the diffraction peak of the (002) plane.   
     
     
         2 . The porous carbon material according to  claim 1 , wherein the content of magnesium is at least 0.01 wt % but at most 3 wt %, the content of potassium is at least 0.01 wt % but at most 3 wt %, and the content of calcium is at least 0.05 wt % but at most 3 wt %. 
     
     
         3 . The porous carbon material according to  claim 1 , wherein the raw material is heat treated before carbonization in a substantially oxygen-free state. 
     
     
         4 . The porous carbon material according to  claim 1 , wherein the material has a value of specific surface area of at least 50 m 2 /g as measured by the nitrogen BET method. 
     
     
         5 . The porous carbon material according to  claim 1 , wherein the material has a value of specific surface area of at least 100 m 2 /g as measured by the nitrogen BET method. 
     
     
         6 . The porous carbon material according to  claim 1 , wherein the material has a value of specific surface area of at least 400 m 2 /g as measured by the nitrogen BET method. 
     
     
         7 . The porous carbon material according to  claim 1 , wherein the value of specific surface area of the porous carbon material is up to 1500 m 2 /g as measured by the nitrogen BET method. 
     
     
         8 . The porous carbon material according to  claim 1 , wherein the material is further washed after the alkali treatment. 
     
     
         9 . The porous carbon material according to  claim 1 , wherein the alkali treatment includes treatment with NaOH. 
     
     
         10 . An adsorbent comprising a porous carbon material comprising a material obtained from carbonization of a raw material including one or both of seaweed stem and straw, the raw material having a silicon content of at least 5 wt %, the raw material is heat treated before carbonization, and the raw material is treated by an alkali treatment after carbonization to reduce the silicon content, the porous carbon material having a value of specific surface area of at least 10 m 2 /g as measured by the nitrogen BET method, a pore volume of at least 0.1 cm 3 /g as measured by the BJH method and MP method, and an R value of 1.5 or greater,
 wherein the porous carbon material includes mesopores having pore sizes from 2 nm to 50 nm and obtained from the alkali treatment of the raw material after carbonization, the porous carbon material further includes macropores and micropores,   the R value is expressed as R=B/A, the A referring to an intensity at an intersection between the baseline of a diffraction peak of the (002) plane as obtained based on powdery X-ray diffractometry of the porous carbon material and a perpendicular line downwardly drawn from the diffraction peak of the (002) plane, and the B referring to the intensity of the diffraction peak of the (002) plane.   
     
     
         11 . The adsorbent according to  claim 10 , wherein the adsorbent is capable of adsorbing creatinine, alizarin cyanine green, lysozyme, albumin, an organic substance having a number average molecular weight of 1×10 3  to 1×10 4 , and combinations thereof. 
     
     
         12 . A method of manufacturing a porous carbon material, the method comprising:
 pre-heating a raw material at a first temperature;   carbonizing the raw material at a second temperature to obtain a porous carbon material precursor; and   treating the porous carbon material precursor with an acid or an alkali to obtain the porous carbon material,   wherein the porous carbon material has an R value of 1.5 or greater, the R value is expressed as R=B/A, the A referring to an intensity at an intersection between the baseline of a diffraction peak of the (002) plane as obtained based on powdery X-ray diffractometry of the porous carbon material and a perpendicular line downwardly drawn from the diffraction peak of the (002) plane, and the B referring to the intensity of the diffraction peak of the (002) plane.   
     
     
         13 . The method of  claim 12 , further comprising activating the porous carbon material by a gas or a chemical. 
     
     
         14 . The method of  claim 13 , wherein the gas is selected from the group consisting of oxygen, steam, carbon dioxide gas, air, and combinations thereof. 
     
     
         15 . The method of  claim 13 , wherein the chemical is selected from the group consisting of zinc chloride, iron chloride, calcium phosphate, calcium hydroxide, magnesium carbonate, potassium carbonate, sulfuric acid, and combinations thereof. 
     
     
         16 . The method of  claim 13 , wherein the activation of the porous carbon material by the gas comprises heating the porous carbon material in the gas at a third temperature. 
     
     
         17 . The method of  claim 16 , wherein the third temperature is higher than the first temperature. 
     
     
         18 . The method of  claim 13 , wherein the activation of the porous carbon material by the chemical comprises heating the porous carbon material in the chemical. 
     
     
         19 . The method of  claim 18 , further comprising washing the porous carbon material after the heating in the chemical. 
     
     
         20 . The method of  claim 19 , wherein the washing is conducted with hydrochloric acid. 
     
     
         21 . The method of  claim 20 , further comprising adjusting the pH with an aqueous alkaline solution. 
     
     
         22 . The method of  claim 21 , wherein the first temperature is lower than the second temperature. 
     
     
         23 . The method of  claim 22 , wherein the raw material is selected from the group consisting of grain husk, straw of rice plant, barley, wheat, rye, barnyard grass, foxtail millet, reed, seaweed stem, vascular plants, ferns and mosses growing on land, algae, seaweeds, and combinations thereof. 
     
     
         24 . The method of  claim 12 , wherein the raw material has a silicon content of at least 5 wt %. 
     
     
         25 . The method of  claim 12 , wherein the porous carbon material has a value of specific surface area of at least 10 m 2 /g as measured by the nitrogen BET method. 
     
     
         26 . The method of  claim 12 , wherein the porous carbon material has a pore volume of at least 0.1 cm 3 /g as measured by the BJH method and MP method regardless of the raw material used. 
     
     
         27 . The method of  claim 12 , wherein the porous carbon material includes mesopores having pore sizes from 2 nm to 50 nm and obtained from the acid treatment or the alkali treatment after carbonization. 
     
     
         28 . The method of  claim 12 , wherein the pre-heating of the raw material is performed in a substantially oxygen-free state.