Granular activated carbon, and manufacturing method for same

Abstract

Provided is a granular activated carbon that can be used for applications similar to wood-based steam-activated carbons; and also provided is a method for manufacturing the same. The granular activated carbon is obtained in the following manner. An activated carbon raw material is carbonized, and then pulverized. The pulverized product is then mixed with a calcium component, and the mixture is molded. Subsequently, the molded product is carbonized and activated, followed by washing.

Claims

1. A granular activated carbon having the following properties (1) to (3): (1) an ignition residue of 2 mass fraction % or less; (2) a hardness of 80 mass fraction % or more; and (3) a pore volume of 0.55 to 0.75 mL/g, wherein a ratio of a mesopore volume to the pore volume satisfies a relationship represented by formula (1): $\begin{array}{cc}V\times 0.73\times 0.80\le \frac{\mathrm{Vmeso}}{V}\le V\times 0.73\times 1.20& \left(1\right)\end{array}$ V: pore volume (mL/g) Vmeso: volume (mL/g) of pores with a diameter of 2 to 30 nm.

2. The granular activated carbon according to claim 1, wherein the granular activated carbon is produced using at least one calcium component selected from the group consisting of calcium chloride, calcium carbonate, and calcium hydroxide.

3. The granular activated carbon according to claim 2, wherein the amount of the calcium component, in terms of calcium, is 0.5 to 1.5 parts by weight based on 100 parts by weight of carbonized raw material.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 shows the mesopore volume/total pore volume of Examples 1 to 4 and Comparative Examples 1 to 8. The solid line represents Vmeso/V=0.73×V, and the two dotted lines represent (a) Vmeso/V=0.73×0.80×V and (b) Vmeso/V=0.73×1.20×V.

(2) FIG. 2 is a graph showing the relationship between the absorbance and the adsorbed amount when Decolorization Performance Evaluation 1 is performed on the activated carbons of Example 1 and Comparative Examples 4 and 8.

(3) FIG. 3 shows an example of the hardness test plate used for the hardness measurement specified in JIS K1474.

DESCRIPTION OF EMBODIMENTS

(4) The present invention is described in detail below with reference to Examples and Comparative Examples; however, the present invention is not limited thereto.

EXAMPLES

Example 1

(5) Coconut shells (produced on Mindanao Island of the Republic of the Philippines) were carbonized at 550° C. for 8 hours, and then pulverized to an average particle diameter of 20 to 80 μm. The pulverized product (1,000 g), a calcium aqueous solution prepared by dissolving 25 g of calcium chloride (special grade chemical; produced by Wako Pure Chemical Industries, Ltd.) in 57 g of water, 250 g of hard pitch having a softening point of 110° C., 80 g of creosote, 16 g of lignin (SAN X-M, produced by Nippon Paper Industries Co., Ltd.), and 73 g of water were placed in a kneader and mixed for 25 minutes. Then, the resulting mixture was extruded from an extrusion granulator (pore size: 4 mm), and carbonization and steam activation were performed under the conditions shown in Table 1. The obtained activated product was washed by boiling in a hydrochloric acid aqueous solution (concentration: 3 wt. %) for 10 minutes, and then boiled in water for 10 minutes three times. After draining, the resulting product was dried in an electric dryer adjusted to 115±5° C., and pulverized by using a roll mill to a particle size of 0.600 to 0.212 mm, followed by particle size regulation, thereby obtaining an activated carbon.

Examples 2 to 4

(6) In Example 1, activated carbons were obtained by changing the molding formulation and the carbonization and steam-activation conditions as shown in Table 1.

Example 5

(7) Coconut shells (produced on Mindanao Island of the Republic of the Philippines) were carbonized at 550° C. for 8 hours, and then pulverized to an average particle diameter of 20 to 80 μm. The pulverized product (1,000 g), 27.5 g of calcium carbonate (special grade chemical; produced by Wako Pure Chemical Industries, Ltd.), 250 g of hard pitch having a softening point of 110′C, 80 g of creosote, 16 g of lignin (SAN X-M, produced by Nippon Paper Industries Co., Ltd.), and 130 g of water were placed in a kneader and mixed for 25 minutes. Then, the resulting mixture was extruded from an extrusion granulator (pore size: 4 mm), and carbonization and steam activation were performed under the conditions shown in Table 1. The obtained activated product was washed by boiling in a hydrochloric acid aqueous solution (concentration: 3 wt. %) for 10 minutes, and then boiled in water for 10 minutes three times. After draining, the resulting product was dried in an electric dryer adjusted to 115±5° C., and pulverized by using a roll mill to a particle size of 0.600 to 0.212 mm, followed by particle size regulation, thereby obtaining an activated carbon.

Comparative Example 1

(8) An activated carbon was obtained in the same manner as in Example 1, except that the conditions were changed as shown in Table 1, and washing was not performed.

Comparative Example 2

(9) An activated carbon was obtained in the same manner as in Example 1, except that calcium chloride was not mixed.

(10) TABLE-US-00001 TABLE 1 Comp. Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 1 Ex. 2 Molding formulation Carbonated coconut shell (g) 1000 1000 1000 1000 1000 1000 1000 Hard pitch (g) 250 250 250 250 250 250 250 Creosote (g) 80 80 80 80 80 80 80 Lignin (g) 16 16 16 16 16 16 16 Water (g) 73 73 73 73 130 73 73 Calcium chloride (g) 25 25 30 30 — 25 — Calcium carbonate (g) — — — — 27.5 — — Pt. wt. of calcium based on 0.90 0.90 1.08 1.08 1.10 0.90 0.00 100 pts. wt. of carbonated coconut shell Water dissolving calcium 57 57 57 57 — 57 57 component (g) Carbonization Carbonization reaching 650 850 650 650 650 650 650 temperature (° C.) Temperature increase rate 5 5 5 5 5 5 5 (° C./min) Retention time (min) 30 30 30 30 30 30 30 Steam activation Activation temperature (° C.) 900 900 900 900 900 900 900 Activation time (min) 150 120 120 150 135 180 150 Activation yield (%) 45.2 50.3 51.1 40.9 45.5 34.4 49.7
Performance Measurement of Activated Carbon

(11) Nitrogen adsorption isotherms of the activated carbons obtained in Examples 1 to 5 and Comparative Examples 1 and 2 above, and activated carbons obtained in Comparative Examples 3 to 8 shown below, were measured at the boiling point temperature of liquid nitrogen, and the pore distribution was determined by the CI method. Pores with a diameter of up to 2 nm were regarded as micropores, and pores with a diameter of 2 to 30 nm were regarded as mesopores. Further, the ignition residue and hardness were measured by JIS K1474.

Comparative Example 3

(12) A commercially available wood-based steam-activated carbon for purification (Purified Shirasagi-N, produced by Japan EnviroChemicals) was used.

Comparative Example 4

(13) A commercially available wood-based steam-activated carbon for purification (Shirasagi M, produced by Japan EnviroChemicals) was used.

Comparative Example 5

(14) A commercially available wood-based steam-activated carbon for purification (Shirasagi A, produced by Japan EnviroChemicals) was used.

Comparative Example 6

(15) A commercially available wood-based steam-activated carbon for catalyst support (Shirasagi FAC-10, produced by Japan EnviroChemicals) was used.

Comparative Example 7

(16) A commercially available steam-activated granular activated carbon for purification using a coconut shell as a raw material (Granular Shirasagi G2c10/20-2, produced by Japan EnviroChemicals) was used.

Comparative Example 8

(17) A commercially available steam-activated granular activated carbon for purification using a coconut shell as a raw material (Granular Shirasagi LH2c20/48, produced by Japan EnviroChemicals) was used.

(18) Tables 2 and 3 show the performance measurement results. The hardness of the activated carbons of Comparative Examples 3 to 6, which were powdered activated carbons, could not be evaluated.

(19) FIG. 1 shows the mesopore volume/total pore volume (Vmeso/V in formula (1)).

(20) TABLE-US-00002 TABLE 2 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ignition residue 0.9 1.1 0.9 1.0 0.4 (mass fracton %) Hardness 86.2 84.6 90.5 85.2 85.2 (mass fraction %) Specific surface area 1107 1076 900 1109 1143 (m.sup.2/g) Pore volume (mL/g) 0.657 0.574 0.572 0.717 0.617 Mesopore volume 0.299 0.200 0.283 0.376 0.220 (mL/g) Mesopore volume/ 0.46 0.35 0.49 0.53 0.36 total pore volume

(21) TABLE-US-00003 TABLE 3 Comp. Comp. Comp. Comp. Comp. Comp. Comp. Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ignition residue 1.6 1.0 2.5 2.9 1.0 0.9 0.5 0.8 (mass fraction %) Hardness 77.0 91.2 — — — — 98.4 94.7 (mass fraction %) Specific surface 1362 1258 999 1023 1099 1253 1303 1666 area (m.sup.2/g) Pore volume 0.828 0.586 0.58 0.591 0.693 0.748 0.601 0.775 (mL/g) Mesopore volume 0.409 0.122 0.260 0.261 0.372 0.357 0.118 0.173 (mL/g) Mesopore volume/ 0.49 0.21 0.45 0.44 0.54 0.48 0.20 0.22 total pore volume

(22) In the activated carbons of the present invention (Examples 1 to 5), the mesopore volume/total pore volume (Vmeso/V in formula (1)) was similar to that of the wood-based steam-activated carbons (Comparative Examples 3 to 6). The activated carbons of the present invention had low ignition residue, which indicates an impurity content, and had sufficient hardness as required for granular activated carbons.

(23) In contrast, in the activated carbon of Comparative Example 1 prepared without washing, the amount of impurities was not sufficiently reduced, and the hardness was low.

(24) Further, the activated carbon prepared without adding calcium (Comparative Example 2) had a smaller number of mesopores,

(25) Decolorization Performance Evaluation 1 of Activated Carbon (Measurement)

(26) The activated carbon of Example 1, the activated carbon of Comparative Example 4 (steam-activated powdered activated carbon), and the activated carbon of Comparative Example 8 (general coconut shell-activated carbon) were prepared, and each activated carbon was pulverized. The pulverization of each activated carbon was performed so that 90% or more of a suitable amount of sample was passed through the 45-μm mesh sieve specified in JIS Z 8801-1 (sieve frame size: inner diameter of the portion above the sieve surface: 75 mm). Subsequently, the pulverized activated carbons of Example 1 and Comparative Examples 4 and 8 were each added to 50 mL, of commercially available tea drink (registered trademark: Gogo No Kocha, produced by Kirin Beverage Co., Ltd.) tea-with-lemon. Each of the resulting mixtures was shaken at 25° C. for 1 hour, followed by filtration, thereby obtaining a filtrate. Next, the absorbance of each filtrate was measured at a wavelength of 390 nm, and the relationship between the residual concentration and the adsorbed amount was arranged. FIG. 2 shows the results.

(27) The activated carbon of Example 1 (the activated carbon of the present invention) had much higher decolorization performance than the coconut shell-activated carbon (Comparative Example 8). Further, even though the activated carbon of Example 1 was a granular activated carbon, its decolorization capacity was equivalent to that of the commercially available wood-based steam-activated powdered activated carbon (Comparative Example 4).

(28) Decolorization Performance Evaluation 2 of Activated Carbon (Visual Observation)

(29) The activated carbons of Examples 1 to 5 and Comparative Example 4 were prepared, and each activated carbon was pulverized. The pulverization of each activated carbon was performed in the same manner as in the pulverization in Evaluation 1 above. Subsequently, the pulverized activated carbons of Examples 1 to 5 and Comparative Example 4 were each added to 50 mL of commercially available tea drink (registered trademark: Gogo No Kocha, produced by Kirin Beverage Co., Ltd.) tea-with-lemon. Each of the resulting mixtures was shaken at 25° C. for 1 hour, followed by filtration, thereby obtaining a filtrate. The filtrates obtained by liquid treatment of the activated carbons of Examples 1 to 5 were each decolorized to about the same degree as that of the above filtrate obtained by liquid treatment in Comparative Example 4.

INDUSTRIAL APPLICABILITY

(30) The activated carbon of the present invention can be used as a purification adsorbent for liquid treatment applications, particularly applications in which the presence of impurities causes problems, for example, in the food or pharmaceutical industry as a granular activated carbon in a column passing system. Furthermore, due to its low impurity content, the activated carbon of the present invention can also be suitably used as a catalyst support, such as a fixed-bed catalyst support.