U.S. patent application number 12/158561 was filed with the patent office on 2009-07-09 for vapor-grown carbon fiber and production process thereof.
This patent application is currently assigned to SHOWA DENKO K.K.. Invention is credited to Takanori Aoki, Tomoyoshi Higashi, Eiji Kambara, Katsuyuki Tsuji.
Application Number | 20090176100 12/158561 |
Document ID | / |
Family ID | 38188370 |
Filed Date | 2009-07-09 |
United States Patent
Application |
20090176100 |
Kind Code |
A1 |
Higashi; Tomoyoshi ; et
al. |
July 9, 2009 |
VAPOR-GROWN CARBON FIBER AND PRODUCTION PROCESS THEREOF
Abstract
The present invention provides a process for producing a
vapor-grown carbon fiber by supplying a raw material at least
containing a carbon source and a catalyst and/or catalyst precursor
compound into a heating zone, wherein the raw material further
containing an oxygen-containing carbon source compound which is
selected from the group consisting of ketones and ethers. The
process for producing a vapor-grown carbon fiber according to the
present invention does not leave a residue in a reaction device
because a raw material used contains a particular oxygen-containing
carbon source compound and, thereby, can continuously produce a
vapor-grown carbon fiber.
Inventors: |
Higashi; Tomoyoshi;
(Kanagawa, JP) ; Kambara; Eiji; (Kanagawa, JP)
; Tsuji; Katsuyuki; (Kanagawa, JP) ; Aoki;
Takanori; (Kanagawa, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W., SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
SHOWA DENKO K.K.
Minato-ku, Tokyo
JP
|
Family ID: |
38188370 |
Appl. No.: |
12/158561 |
Filed: |
March 14, 2006 |
PCT Filed: |
March 14, 2006 |
PCT NO: |
PCT/JP2006/305473 |
371 Date: |
June 20, 2008 |
Current U.S.
Class: |
428/408 ;
423/447.1; 423/447.2 |
Current CPC
Class: |
D01F 9/1277 20130101;
Y10T 428/30 20150115; D01F 9/1272 20130101; B82Y 30/00 20130101;
D01F 9/127 20130101; C01B 32/162 20170801; C01B 2202/36 20130101;
B82Y 40/00 20130101; C01B 2202/34 20130101 |
Class at
Publication: |
428/408 ;
423/447.1; 423/447.2 |
International
Class: |
D01F 9/12 20060101
D01F009/12 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 22, 2005 |
JP |
2005-369933 |
Claims
1. A process for producing a vapor-grown carbon fiber by supplying
a raw material at least containing a carbon source and a catalyst
and/or catalyst precursor compound into a heating zone, wherein the
raw material further contains an oxygen-containing carbon source
compound selected from the group consisting of ketones and
ethers.
2. The process for producing a vapor-grown carbon fiber according
to claim 1, wherein the catalyst and/or catalyst precursor compound
is in a solid or liquid state at an ordinary temperature and
pressure, the oxygen-containing carbon source compound is in a
liquid state at an ordinary temperature and pressure, and the
catalyst and/or catalyst precursor compound is dissolved or
suspended in the oxygen-containing carbon source compound to be
supplied into the heating zone.
3. The process for producing a vapor-grown carbon fiber according
to claim 2, wherein the oxygen-containing carbon source compound in
which the catalyst and/or catalyst precursor compound has been
dissolved or suspended is vaporized before being supplied into the
heating zone.
4. The process for producing a vapor-grown carbon fiber according
to claim 1, wherein the oxygen-containing carbon source compound
has a boiling point of 80.degree. C. or more at an ordinary
pressure.
5. The process for producing a vapor-grown carbon fiber according
to claim 4, wherein the oxygen-containing carbon source compound
has a boiling point of 115.degree. C. or more at an ordinary
pressure.
6. The process for producing a vapor-grown carbon fiber according
to claim 5, wherein the oxygen-containing carbon source compound
has a boiling point of 150.degree. C. or more at an ordinary
pressure.
7. The process for producing a vapor-grown carbon fiber according
to claim 1, wherein the solubility of the catalyst and/or catalyst
precursor compound at 25.degree. C. in the oxygen-containing carbon
source compound is 1 g or more per 100 g of the oxygen-containing
carbon source compound.
8. The process for producing a vapor-grown carbon fiber according
to claim 1, wherein the ketones are acetone, 2-butanone,
2-pentanone, 3-pentanone, 3-methyl-2-butanone, acetylacetone,
3-hydroxy-3-methyl-2-butanone, 3,3-dimethyl-2-butanone,
2-methyl-3-pentanone, 3-methyl-2-pentanone, 4-methyl-2-pentanone,
2-hexanone, 3-hexanone, cyclopentanone, hydroxyacetone,
2-heptanone, 3-heptanone, 4-heptanone, 2,4-dimethyl-3-pentanone,
4-methoxy-4-methyl-2-pentanone, 4-hydroxy-4-methyl-2-pentanone,
cyclohexanone, 2,6-dimethyl-4-heptanone, 3-methylcyclohexanone, and
isophorone.
9. The process for producing a vapor-grown carbon fiber according
to claim 1, wherein the ethers are anisole, ethoxybenzene,
2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, furan,
tetrahydrofuran, 2,3-dihydrofuran, 2,5-dihydrofuran, 1,3-dioxolane,
pyrane, tetrahydropyrane, 1,3-dioxane, 1,4-dioxane, diethyl ether,
di-n-propyl ether, di-i-propyl ether, n-butyl methyl ether, s-butyl
methyl ether, t-butyl methyl ether, n-butyl ethyl ether, t-butyl
ethyl ether, di-n-butyl ether, di-s-butyl ether, ethyleneglycol
monomethyl ether, ethyleneglycol monoethyl ether, ethyleneglycol
mono-n-propyl ether, ethyleneglycol mono-i-propyl ether,
ethyleneglycol mono-n-butyl ether, ethyleneglycol mono-s-butyl
ether, ethyleneglycol mono-i-butyl ether, ethyleneglycol
mono-t-butyl ether, ethyleneglycol mono-2-ethylhexyl ether,
ethyleneglycol dimethyl ether, ethyleneglycol diethyl ether,
ethyleneglycol di-n-propyl ether, ethyleneglycol di-i-propyl ether,
ethyleneglycol di-n-butyl ether, ethyleneglycol di-s-butyl ether,
ethyleneglycol di-i-butyl ether, ethyleneglycol di-t-butyl ether,
propyleneglycol monomethyl ether, propyleneglycol monoethyl ether,
propyleneglycol mono-n-propyl ether, propyleneglycol mono-i-propyl
ether, propyleneglycol mono-n-butyl ether, propyleneglycol
mono-s-butyl ether, propyleneglycol mono-i-butyl ether,
propyleneglycol mono-t-butyl ether, propyleneglycol dimethyl ether,
propyleneglycol diethyl ether, propyleneglycol di-n-propyl ether,
propyleneglycol di-i-propyl ether, propyleneglycol di-n-butyl
ether, propyleneglycol di-s-butyl ether, propyleneglycol di-i-butyl
ether, propyleneglycol di-t-butyl ether, diethyleneglycol,
diethyleneglycol monomethyl ether, diethyleneglycol monoethyl
ether, diethyleneglycol mono-n-propyl ether, diethyleneglycol
mono-i-propyl ether, diethyleneglycol mono-n-butyl ether,
diethyleneglycol mono-s-butyl ether, diethyleneglycol mono-i-butyl
ether, diethyleneglycol mono-t-butyl ether, diethyleneglycol
dimethyl ether, diethyleneglycol diethyl ether, diethyleneglycol
di-n-propyl ether, diethyleneglycol di-i-propyl ether,
diethyleneglycol di-n-butyl ether, diethyleneglycol di-s-butyl
ether, diethyleneglycol di-i-butyl ether, diethyleneglycol
di-t-butyl ether, dipropyleneglycol, dipropyleneglycol monomethyl
ether, dipropyleneglycol monoethyl ether, dipropyleneglycol
mono-n-propyl ether, dipropyleneglycol mono-i-propyl ether,
dipropyleneglycol mono-n-butyl ether, dipropyleneglycol
mono-s-butyl ether, dipropyleneglycol mono-i-butyl ether,
dipropyleneglycol mono-t-butyl ether, dipropyleneglycol dimethyl
ether, dipropyleneglycol diethyl ether, dipropyleneglycol
di-n-propyl ether, dipropyleneglycol di-i-propyl ether,
dipropyleneglycol di-n-butyl ether, dipropyleneglycol di-s-butyl
ether, dipropyleneglycol di-i-butyl ether, dipropyleneglycol
di-t-butyl ether, triethyleneglycol dimethyl ether,
tetraethyleneglycol dimethyl ether, 3-methoxy-1-butanol,
3-methoxy-3-methyl-1-butanol, tetrahydrofurfuryl alcohol,
ethyleneglycol monomethyl ether acetate, ethyleneglycol monoethyl
ether acetate, ethyleneglycol monobutyl ether acetate,
propyleneglycol monomethyl ether acetate, propyleneglycol monoethyl
ether acetate, diethyleneglycol monoethyl ether acetate, and
diethyleneglycol monobutyl ether acetate.
10. The process for producing a vapor-grown carbon fiber according
to claim 1, wherein the carbon source is at least one compound
selected from the group consisting of carbon monoxide, carbon
dioxide, methane, ethane, propane, butane, pentane, hexane,
heptane, cyclohexane, ethylene, propylene, butene, butadiene,
acetylene, benzene, toluene and xylene.
11. The process for producing a vapor-grown carbon fiber according
to claim 10, wherein the carbon source is at least one compound
selected from the group consisting of carbon monoxide, carbon
dioxide, methane, ethane, propane, butane, pentane, hexane,
heptane, cyclohexane, ethylene, propylene, butene, butadiene and
acetylene.
12. The process for producing a vapor-grown carbon fiber according
to claim 1, wherein the carbon source comprises at least
methane.
13. The process for producing a vapor-grown carbon fiber according
to claim 12, wherein the content of methane in the 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.degree. C.
14. 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.degree. C. or less.
15. 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.degree. C. for 0.05 seconds or more before arriving at
the high-temperature part of the heating zone.
16. The process for producing a vapor-grown carbon fiber according
to claim 1, wherein the residence time at a temperature of
1,100.degree. C. or more in the heating zone is 0.001 second or
more.
17. The process for producing a vapor-grown carbon fiber according
to claim 12, 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.
18. The process for producing a vapor-grown carbon fiber according
to claim 17, 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.
19. 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 raw material
satisfies the following relationship: (Atomic number of a catalyst
element)/(Number of carbon atoms)=0.000005 to 0.0015.
20. 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.
21. 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.
22. A vapor-grown carbon fiber produced by the process for
producing a vapor-grown carbon fiber according to claim 1.
23. The vapor-grown carbon fiber according to claim 22, having an
average fiber length of 10 .mu.m or more.
24. The vapor-grown carbon fiber according to claim 23, having the
average fiber length of 13 .mu.m or more.
Description
TECHNICAL FIELD
[0001] The present invention relates to a process for efficiently
producing a vapor-grown carbon fiber such as a carbon nanotube.
RELATED ART
[0002] A carbon fiber obtained by the vapor-growth process
(vapor-grown carbon fiber) can have a large aspect ratio with
relative ease. Accordingly, studies thereon have been aggressively
carried out and there are a large number of reports on the
production process. A carbon nanotube (that is, a carbon fiber
having a fiber diameter on the nanometer order) has attracted
particular attention in recent years, and can be synthesized by
applying this vapor-growth process.
[0003] FIG. 1 is a schematic view showing one example of a reaction
apparatus for continuously producing a carbon fiber by the
vapor-growth process. In one example of the general production
process, CO, methane, acetylene, ethylene, benzene, toluene or the
like is used as the carbon source which is the raw material of the
carbon fiber. A carbon source which is a gas at an ordinary
temperature and pressure is supplied, in the gaseous state, by
being mixed with a carrier gas. In the case of a liquid, the carbon
source is vaporized in a vaporizer 4, mixed with a carrier gas and
then supplied, or is sprayed in a liquid state into the heating
zone 1. The carrier gas used is, for example, nitrogen gas, which
is an inert gas, or hydrogen gas, which is reducing gas. In some
cases, the carbon source is supplied into a depressurized
apparatus.
[0004] As for a catalyst of a process for producing a vapor-grown
carbon fiber, a supported catalyst in which a metal is supported on
a support such as alumina, or an organic metal compound such as
ferrocene, is used. In the case of using a supported catalyst, the
supported catalyst is subjected to a necessary pretreatment by
previously placing and heating it in a heating zone 1, and then a
carbon source is supplied and reacted thereon (this is the example
shown in FIG. 1). Alternatively, the reaction is performed by
continuously or pulsedly supplying a supported catalyst which has
been pretreated, from outside of the system. It is also possible
that an organic metal compound readily dissolvable in a carbon
source, such as ferrocene, is employed as a catalyst precursor, and
continuously or pulsedly fed to the heating zone together with a
carbon source, and thereby a carbon fiber is produced by utilizing
metal particles generated by thermal decomposition of the catalyst
precursor as a catalyst.
[0005] The product obtained by a process for producing a
vapor-grown carbon fiber performed in the apparatus shown in FIG. 1
is collected in the heating zone 1 heated by the heater 2 and the
receiver 3 located at the end thereof, and then, after a
predetermined time of reaction, is recovered.
[0006] The production process of a carbon fiber by a vapor-phase
method is roughly classified into the following three types
according to the method of supplying a catalyst or a precursor
compound of the catalyst:
[0007] (1) a substrate or boat comprising an alumina or graphite
supporting a catalyst or a precursor compound thereof is placed in
a heating zone, and contacted with a gas of a carbon source
supplied in a vapor phase;
[0008] (2) a particulate catalyst or a precursor compound thereof
is dispersed in a liquid-state carbon source or the like, and
continuously or pulsedly supplied to a heating zone from outside of
the system, and thereby contacted with a carbon source at a high
temperature; and
[0009] (3) a metallocene, carbonyl compound and like dissolvable in
a liquid-state carbon source is used as a catalyst precursor
compound, and a carbon source comprising this catalyst precursor
compound dissolved therein is supplied to a heating zone, whereby a
catalyst and the carbon source, which is a hydrocarbon or the like,
are contacted at a high temperature.
[0010] As for the process of (2) and (3) above, Japanese Unexamined
Patent Publication No. 6-146117 and No. 9-78360 describe, in the
examples, a method comprising dissolving ferrocene in benzene as a
carbon source and supplying the obtained solution to a heating
zone. Japanese Unexamined Patent Publication No. 2004-339676
describes, in the examples, a method comprising dissolving
ferrocene in benzene, toluene or p-xylene as a carbon source and
supplying the obtained solution to a heating zone.
[0011] The purpose of the present invention is to provide a simple
and effective process for producing a vapor-grown carbon fiber
wherein the process does not leave a residue in a reaction
apparatus, and thereby enables continuous production of a
vapor-grown carbon fiber and, as a result, cost-effective
production thereof.
DISCLOSURE OF THE INVENTION
[0012] As a result of intensive investigations to solve the
above-descried subjects, the present inventors have found that a
process for producing a vapor-grown carbon fiber does not leave a
residue in a reaction apparatus when a raw material used further
contains a particular compound, and thereby achieve the present
invention.
[0013] That is, the present invention relates to the following (1)
to (24).
[0014] (1) A process for producing a vapor-grown carbon fiber by
supplying a raw material at least containing a carbon source, and a
catalyst and/or catalyst precursor compound into a heating
zone,
[0015] wherein the raw material further contains an
oxygen-containing carbon source compound selected from the group
consisting of ketones and ethers.
[0016] (2) The process for producing a vapor-grown carbon fiber as
described in (1) above, wherein the catalyst and/or catalyst
precursor compound is in a solid or liquid state at an ordinary
temperature and pressure, the oxygen-containing carbon source
compound is in a liquid state at an ordinary temperature and
pressure, and the catalyst and/or catalyst precursor compound is
dissolved or suspended in the oxygen-containing carbon source
compound to be supplied into the heating zone.
[0017] (3) The process for producing a vapor-grown carbon fiber as
described in (2) above, wherein the oxygen-containing carbon source
compound in which the catalyst and/or catalyst precursor compound
has been dissolved or suspended is vaporized before being supplied
into the heating zone.
[0018] (4) The process for producing a vapor-grown carbon fiber as
described in any one of (1) to (3) above, wherein the
oxygen-containing carbon source compound has a boiling point of
80.degree. C. or more at an ordinary pressure.
[0019] (5) The process for producing a vapor-grown carbon fiber as
described in (4) above, wherein the oxygen-containing carbon source
compound has a boiling point of 115.degree. C. or more at an
ordinary pressure.
[0020] (6) The process for producing a vapor-grown carbon fiber as
described in (5) above, wherein the oxygen-containing carbon source
compound has a boiling point of 150.degree. C. or more at an
ordinary pressure.
[0021] (7) The process for producing a vapor-grown carbon fiber as
described in any one of (1) to (6) above, wherein the solubility of
the catalyst and/or catalyst precursor compound at 25.degree. C. in
the oxygen-containing carbon source compound is 1 g or more per 100
g of the oxygen-containing carbon source compound.
[0022] (8) The process for producing a vapor-grown carbon fiber as
described in any one of (1) to (7) above, wherein the ketones are
acetone, 2-butanone, 2-pentanone, 3-pentanone, 3-methyl-2-butanone,
acetylacetone, 3-hydroxy-3-methyl-2-butanone,
3,3-dimethyl-2-butanone, 2-methyl-3-pentanone,
3-methyl-2-pentanone, 4-methyl-2-pentanone, 2-hexanone, 3-hexanone,
cyclopentanone, hydroxyacetone, 2-heptanone, 3-heptanone,
4-heptanone, 2,4-dimethyl-3-pentanone,
4-methoxy-4-methyl-2-pentanone, 4-hydroxy-4-methyl-2-pentanone,
cyclohexanone, 2,6-dimethyl-4-heptanone, 3-methylcyclohexanone, and
isophorone.
[0023] (9) The process for producing a vapor-grown carbon fiber as
described in any one of (1) to (8) above, wherein the ethers are
anisole, ethoxybenzene, 2-methoxytoluene, 3-methoxytoluene,
4-methoxytoluene, furan, tetrahydrofuran, 2,3-dihydrofuran,
2,5-dihydrofuran, 1,3-dioxolane, pyrane, tetrahydropyrane,
1,3-dioxane, 1,4-dioxane, diethyl ether, di-n-propyl ether,
di-i-propyl ether, n-butyl methyl ether, s-butyl methyl ether,
t-butyl methyl ether, n-butyl ethyl ether, t-butyl ethyl ether,
di-n-butyl ether, di-s-butyl ether, ethyleneglycol monomethyl
ether, ethyleneglycol monoethyl ether, ethyleneglycol mono-n-propyl
ether, ethyleneglycol mono-i-propyl ether, ethyleneglycol
mono-n-butyl ether, ethyleneglycol mono-s-butyl ether,
ethyleneglycol mono-i-butyl ether, ethyleneglycol mono-t-butyl
ether, ethyleneglycol mono-2-ethylhexyl ether, ethyleneglycol
dimethyl ether, ethyleneglycol diethyl ether, ethyleneglycol
di-n-propyl ether, ethyleneglycol di-i-propyl ether, ethyleneglycol
di-n-butyl ether, ethyleneglyqol di-s-butyl ether, ethyleneglycol
di-i-butyl ether, ethyleneglycol di-t-butyl ether, propyleneglycol
monomethyl ether, propyleneglycol monoethyl ether, propyleneglycol
mono-n-propyl ether, propyleneglycol mono-i-propyl ether,
propyleneglycol mono-n-butyl ether, propyleneglycol mono-s-butyl
ether, propyleneglycol mono-i-butyl ether, propyleneglycol
mono-t-butyl ether, propyleneglycol dimethyl ether, propyleneglycol
diethyl ether, propyleneglycol di-n-propyl ether, propyleneglycol
di-i-propyl ether, propyleneglycol di-n-butyl ether,
propyleneglycol di-s-butyl ether, propyleneglycol di-i-butyl ether,
propyleneglycol di-t-butyl ether, diethyleneglycol,
diethyleneglycol monomethyl ether, diethyleneglycol monoethyl
ether, diethyleneglycol mono-n-propyl ether, diethyleneglycol
mono-i-propyl ether, diethyleneglycol mono-n-butyl ether,
diethyleneglycol mono-s-butyl ether, diethyleneglycol mono-i-butyl
ether, diethyleneglycol mono-t-butyl ether, diethyleneglycol
dimethyl ether, diethyleneglycol diethyl ether, diethyleneglycol
di-n-propyl ether, diethyleneglycol di-i-propyl ether,
diethyleneglycol di-n-butyl ether, diethyleneglycol di-s-butyl
ether, diethyleneglycol di-i-butyl ether, diethyleneglycol
di-t-butyl ether, dipropyleneglycol, dipropyleneglycol monomethyl
ether, dipropyleneglycol monoethyl ether, dipropyleneglycol
mono-n-propyl ether, dipropyleneglycol mono-i-propyl ether,
dipropyleneglycol mono-n-butyl ether, dipropyleneglycol
mono-s-butyl ether, dipropyleneglycol mono-i-butyl ether,
dipropyleneglycol mono-t-butyl ether, dipropyleneglycol dimethyl
ether, dipropyleneglycol diethyl ether, dipropyleneglycol
di-n-propyl ether, dipropyleneglycol di-i-propyl ether,
dipropyleneglycol di-n-butyl ether, dipropyleneglycol di-s-butyl
ether, dipropyleneglycol di-i-butyl ether, dipropyleneglycol
di-t-butyl ether, triethyleneglycol dimethyl ether,
tetraethyleneglycol dimethyl ether, 3-methoxy-1-butahol,
3-methoxy-3-methyl-1-butahol, tetrahydrofurfuryl alcohol,
ethyleneglycol monomethyl ether acetate, ethyleneglycol monoethyl
ether acetate, ethyleneglycol monobutyl ether acetate,
propyleneglycol monomethyl ether acetate, propyleneglycol monoethyl
ether acetate, diethyleneglycol monoethyl ether acetate, and
diethyleneglycol monobutyl ether acetate.
[0024] (10) The process for producing a vapor-grown carbon fiber as
described in any one of (1) to (9) above, wherein the carbon source
is at least one compound selected from the group consisting of
carbon monoxide, carbon dioxide, methane, ethane, propane, butane,
pentane, hexane, heptane, cyclohexane, ethylene, propylene, butene,
butadiene, acetylene, benzene, toluene and xylene.
[0025] (11) The process for producing a vapor-grown carbon fiber as
described in (10) above, wherein the carbon source is at least one
compound selected from the group consisting of carbon monoxide,
carbon dioxide, methane, ethane, propane, butane, pentane, hexane,
heptane, cyclohexane, ethylene, propylene, butene, butadiene and
acetylene.
[0026] (12) The process for producing a vapor-grown carbon fiber as
described in any one of (1) to (11) above, wherein the carbon
source comprises at least methane.
[0027] (13) The process for producing a vapor-grown carbon fiber as
described in any one of (1) to (12) above, wherein the content of
methane in the 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.degree. C.
[0028] (14) The process for producing a vapor-grown carbon fiber as
described in any one of (1) to (13) above, wherein the temperature
at the raw material-introducing part of the heating zone is
700.degree. C. or less.
[0029] (15) The process for producing a vapor-grown carbon fiber as
described in any one of (1) to (14) above, 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.degree. C. for 0.05
seconds or more before arriving at the high-temperature part of the
heating zone.
[0030] (16) The process for producing a vapor-grown carbon fiber as
described in any one of (1) to (15) above, wherein the residence
time at a temperature of 1,100.degree. C. or more in the heating
zone is 0.001 second or more.
[0031] (17) The process for producing a vapor-grown carbon fiber as
described in any one of (1) to (16) above, 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.
[0032] (18) The process for producing a vapor-grown carbon fiber as
described in (17) above, 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.
[0033] (19) The process for producing a vapor-grown carbon fiber as
described in any one of (1) to (18) above, wherein the ratio of the
atomic number of a catalyst element and the number of carbon atoms
in the raw material satisfies the following relationship:
(Atomic number of a catalyst element)/(Number of carbon
atoms)=0.000005 to 0.0015.
[0034] (20) The process for producing a vapor-grown carbon fiber as
described in any one of (1) to (19) above, wherein the all or a
part of the gas after reaction is circulated and reused.
[0035] (21) The process for producing a vapor-grown carbon fiber as
described in (1) above, wherein a carbon fiber having an average
fiber diameter of 10 nm or more is produced.
[0036] (22) A vapor-grown carbon fiber produced by the process for
producing a vapor-grown carbon fiber as described in any one of (1)
to (21) above.
[0037] (23) The vapor-grown carbon fiber as described in (22)
above, having an average fiber length of 10 .mu.m or more.
[0038] (24) The vapor-grown carbon fiber as described in (23)
above, having the average fiber length of 13 .mu.m or more.
[0039] The process for producing a vapor-grown carbon fiber
according to the present invention does not leave a residue in a
reaction apparatus by the fact that a raw material used contains a
particular oxygen-containing carbon source compound, and thereby
can continuously produce a vapor-grown carbon fiber.
BRIEF DESCRIPTION OF DRAWINGS
[0040] FIG. 1 is a schematic view showing an example of the general
horizontal reaction apparatus for producing a vapor-grown carbon
fiber.
[0041] FIG. 2 is a schematic view showing an example of the
vertical reaction apparatus for producing a vapor-grown carbon
fiber.
BEST MODE FOR CARRYING OUT THE INVENTION
[0042] The process for producing a vapor-grown carbon fiber
according to the present invention is characterized in that a raw
material further contains an oxygen-containing carbon source
compound in addition to a carbon source, and a catalyst and/or
catalyst precursor compound.
[0043] The constituent elements of the present invention are
described in detail below.
(Oxygen-Containing Carbon Source Compound)
[0044] The oxygen-containing carbon source compound used in the
process for producing a carbon fiber according to the present
invention includes an oxygen-containing carbon source compound
selected from the group consisting of ketones and ethers. Addition
of such an oxygen-containing carbon containing compound into a raw
material used for a process for producing a vapor-phase carbon
fiber makes it possible to reduce or substantially eliminate a
residue in a reaction apparatus. It is deemed that this is because
oxygen atom of an oxygen-containing carbon source compound reacts
with a carbon residue in a reaction apparatus to remove the carbon
residue from the reaction apparatus. Incidentally, carbon atom of
an oxygen-containing carbon source compound is counted as a carbon
source described below.
[0045] When a catalyst and/or catalyst precursor compound used is
in a solid or liquid state at an ordinary temperature and pressure,
the catalyst and/or catalyst precursor compound is preferably
dissolved or suspended in the oxygen-containing carbon source
compound which is in a liquid state at an ordinary temperature and
pressure, and then supplied into a heating zone. Since ethers and
ketones, particularly ethers, used as an oxygen-containing carbon
source compound in the process of the present invention are
chemically stable, a catalyst and/or the catalyst precursor
compound such as metallocene, particularly ferrocene, can be
dissolved or dispersed therein, and thereafter supplied.
[0046] The oxygen-containing carbon source compound is preferably
one having a higher boiling point at an ordinary pressure, and/or a
large solubility of catalyst and/or catalyst precursor compound
therein. For example, boiling point at an ordinary pressure of the
oxygen-containing carbon source compound is preferably of
80.degree. C. or more, more preferably 115.degree. C. or more, and
still more preferably 150.degree. C. or more. The solubility of a
catalyst and/or catalyst precursor compound at 25.degree. C. in the
oxygen-containing carbon source compound is preferably 1 g or more,
more preferably 5 g or more, and still more preferably 10 g or more
per 100 g of the oxygen-containing carbon source compound.
[0047] In particular, the oxygen-containing carbon source compound
preferably has a boiling point at an ordinary pressure of
115.degree. C. or more, and a solubility of catalyst and/or
catalyst precursor compound therein at 25.degree. C. of 1 g or more
per 100 g of the oxygen-containing carbon source compound. Further,
the oxygen-containing carbon source compound more preferably has a
boiling point at an ordinary pressure of 150.degree. C. or more,
and a solubility of catalyst and/or catalyst precursor compound
therein at 25.degree. C. of 1 g or more per 100 g of the
oxygen-containing carbon source compound.
[0048] The reason why the oxygen-containing carbon source compound
preferably has a higher boiling point at an ordinary pressure,
and/or a large solubility of catalyst and/or catalyst precursor
compound therein is as follows:
[0049] The minimum amount of a catalyst and/or catalyst precursor
compound required for producing a vapor-phase carbon fiber is very
small in comparison with the amount of carbon in a raw material.
Many catalysts and/or catalyst precursor compounds are in a solid
or liquid state at an ordinary temperature and pressure. However,
it is very difficult to stably supply a small amount of a catalyst
and/or catalyst precursor compound in a solid or liquid state to a
heating zone.
[0050] Therefore, when the oxygen-containing carbon source compound
is in a liquid state at an ordinary temperature and pressure, it is
possible to stably supply a catalyst and/or catalyst precursor
compound to a heating zone by dissolving or dispersing it in the
oxygen-containing carbon source compound. This is particularly
preferable when the main carbon source is a gaseous compound such
as methane, and when a carbon source has a small solubility of a
catalyst and/or catalyst precursor compound therein.
[0051] Also, when a catalyst and/or catalyst precursor compound is
dissolved in an oxygen-containing carbon source compound, if the
oxygen-containing carbon source compound has a lower boiling point
(i.e. a higher vapor pressure), the oxygen-containing carbon source
compound is vaporized before the catalyst and/or catalyst precursor
compound is sufficiently vaporized, and thereby the catalyst and/or
catalyst precursor compound is precipitated. This makes it
impossible to stably supply the catalyst and/or catalyst precursor
compound to a heating zone. Therefore, an oxygen-containing carbon
source compound preferably has a higher boiling point, when a
catalyst and/or catalyst precursor compound is dissolved or
dispersed in an oxygen-containing carbon source compound.
[0052] An oxygen-containing carbon source compound preferably has a
large solubility of a catalyst and/or catalyst precursor compound
therein in order to stably retain the catalyst and/or catalyst
precursor compound therein.
[0053] Ketones which can be used as an oxygen-containing carbon
source compound includes acetone, 2-butanone, 2-pentanone,
3-pentanone, 3-methyl-2-butanone, acetylacetone,
3-hydroxy-3-methyl-2-butanone, 3,3-dimethyl-2-butanone,
2-methyl-3-pentanone, 3-methyl-2-pentanone, 4-methyl-2-pentanone,
2-hexanone, 3-hexanone, cyclopentanone, hydroxyacetone,
2-heptanone, 3-heptanone, 4-heptanone, 2,4-dimethyl-3-pentanone,
4-methoxy-4-methyl-2-pentanone, 4-hydroxy-4-methyl-2-pentanone,
cyclohexanone, 2,6-dimethyl-4-heptanone, 3-methylcyclohexanone, and
isophorone.
[0054] Preferable ketones which can be used as an oxygen-containing
carbon source compound include ones having a boiling point of
80.degree. C. or more at an ordinary pressure. The preferable
ketones include 2-butanone, 2-pentanone, 3-pentanone,
3-methyl-2-butanone, 3,3-dimethyl-2-butanone, 2-methyl-3-pentanone,
acetylacetone, 3-hydroxy-3-methyl-2-butanone, 4-methyl-2-pentanone,
2-hexanone, 3-hexanone, cyclopentanone, hydroxyacetone,
3-heptanone, 4-heptanone, 2,4-dimethyl-3-pentanone,
3-methyl-2-pentanone, 2-heptanone, 4-methoxy-4-methyl-2-pentanone,
4-hydroxy-4-methyl-2-pentanone, cyclohexanone,
2,6-dimethyl-4-heptanone, 3-methylcyclohexanone, and
isophorone.
[0055] More Preferable ketones which can be used as an
oxygen-containing carbon source compound includes ones having a
boiling point of 115.degree. C. or more at an ordinary pressure.
The preferable ketones include acetylacetone,
3-hydroxy-3-methyl-2-butanone, 4-methyl-2-pentanone, 2-hexanone,
3-hexanone, cyclopentanone, hydroxyacetone, 3-heptanone,
4-heptanone, 2,4-dimethyl-3-pentanone, 3-methyl-2-pentanone,
2-heptanone, 4-methoxy-4-methyl-2-pentanone,
4-hydroxy-4-methyl-2-pentanone, cyclohexanone,
2,6-dimethyl-4-heptanone, 3-methylcyclohexanone, and
isophorone.
[0056] Particularly preferable ketones which can be used as an
oxygen-containing carbon source compound include ones having a
boiling point of 150.degree. C. or more at an ordinary pressure.
The particularly preferable ketones include 3-methyl-2-pentanone,
2-heptanone, 4-methoxy-4-methyl-2-pentanone,
4-hydroxy-4-methyl-2-pentanone, cyclohexanone,
2,6-dimethyl-4-heptanone, 3-methylcyclohexanone, and
isophorone.
[0057] Ethers which can be used as an oxygen-containing carbon
source compound include anisole, ethoxybenzene, 2-methoxytoluene,
3-methoxytoluene, 4-methoxytoluene, furan, tetrahydrofuran,
2,3-dihydrofuran, 2,5-dihydrofuran, 1,3-dioxolane, pyrane,
tetrahydropyrane, 1,3-dioxane, 1,4-dioxane, diethyl ether,
di-n-propyl ether, di-i-propyl ether, n-butyl methyl ether, s-butyl
methyl ether, t-butyl methyl ether, n-butyl ethyl ether, t-butyl
ethyl ether, di-n-butyl ether, di-s-butyl ether, ethyleneglycol
monomethyl ether, ethyleneglycol monoethyl ether, ethyleneglycol
mono-n-propyl ether, ethyleneglycol mono-i-propyl ether,
ethyleneglycol mono-n-butyl ether, ethyleneglycol mono-s-butyl
ether, ethyleneglycol mono-i-butyl ether, ethyleneglycol
mono-t-butyl ether, ethyleneglycol mono-2-ethylhexyl ether,
ethyleneglycol dimethyl ether, ethyleneglycol diethyl ether,
ethyleneglycol di-n-propyl ether, ethyleneglycol di-i-propyl ether,
ethyleneglycol di-n-butyl ether, ethyleneglycol di-s-butyl ether,
ethyleneglycol di-i-butyl ether, ethyleneglycol di-t-butyl ether,
propyleneglycol monomethyl ether, propyleneglycol monoethyl ether,
propyleneglycol mono-n-propyl ether, propyleneglycol mono-i-propyl
ether, propyleneglycol mono-n-butyl ether, propyleneglycol
mono-s-butyl ether, propyleneglycol mono-i-butyl ether,
propyleneglycol mono-t-butyl ether, propyleneglycol dimethyl ether,
propyleneglycol diethyl ether, propyleneglycol di-n-propyl ether,
propyleneglycol di-i-propyl ether, propyleneglycol di-n-butyl
ether, propyleneglycol di-s-butyl ether, propyleneglycol di-i-butyl
ether, propyleneglycol di-t-butyl ether, diethyleneglycol,
diethyleneglycol monomethyl ether, diethyleneglycol monoethyl
ether, diethyleneglycol mono-n-propyl ether, diethyleneglycol
mono-i-propyl ether, diethyleneglycol mono-n-butyl ether,
diethyleneglycol mono-s-butyl ether, diethyleneglycol mono-i-butyl
ether, diethyleneglycol mono-t-butyl ether, diethyleneglycol
dimethyl ether, diethyleneglycol diethyl ether, diethyleneglycol
di-n-propyl ether, diethyleneglycol di-i-propyl ether,
diethyleneglycol di-n-butyl ether, diethyleneglycol di-s-butyl
ether, diethyleneglycol di-i-butyl ether, diethyleneglycol
di-t-butyl ether, dipropyleneglycol, dipropyleneglycol monomethyl
ether, dipropyleneglycol monoethyl ether, dipropyleneglycol
mono-n-propyl ether, dipropyleneglycol mono-i-propyl ether,
dipropyleneglycol mono-n-butyl ether, dipropyleneglycol
mono-s-butyl ether, dipropyleneglycol mono-i-butyl ether,
dipropyleneglycol mono-t-butyl ether, dipropyleneglycol dimethyl
ether, dipropyleneglycol diethyl ether, dipropyleneglycol
di-n-propyl ether, dipropyleneglycol di-i-propyl ether,
dipropyleneglycol di-n-butyl ether, dipropyleneglycol di-s-butyl
ether, dipropyleneglycol di-i-butyl ether, dipropyleneglycol
di-t-butyl ether, triethyleneglycol dimethyl ether,
tetraethyleneglycol dimethyl ether, 3-methoxy-1-butahol,
3-methoxy-3-methyl-1-butahol, tetrahydrofurfuryl alcohol,
ethyleneglycol monomethyl ether acetate, ethyleneglycol monoethyl
ether acetate, ethyleneglycol monobutyl ether acetate,
propyleneglycol monomethyl ether acetate, propyleneglycol monoethyl
ether acetate, diethyleneglycol monoethyl ether acetate, and
diethyleneglycol monobutyl ether acetate.
[0058] Preferable ethers which can be used as an oxygen-containing
carbon source compound include ones having a boiling point of
80.degree. C. or more at an ordinary pressure. The preferable
ethers include tetrahydropyrane, 1,3-dioxane, 1,4-dioxane,
di-n-propyl ether, n-butyl ethyl ether, ethyleneglycol dimethyl
ether, di-n-butyl ether, di-s-butyl ether, ethyleneglycol
monomethyl ether, ethyleneglycol monoethyl ether, ethyleneglycol
mono-n-propyl ether, ethyleneglycol mono-i-propyl ether,
ethyleneglycol diethyl ether, propyleneglycol monomethyl ether,
propyleneglycol monoethyl ether, ethyleneglycol monomethyl ether
acetate, propyleneglycol monomethyl ether acetate, anisole,
ethoxybenzene, 2-methoxytoluene, 3-methoxytoluene,
4-methoxytoluene, ethyleneglycol mono-n-butyl ether, ethyleneglycol
mono-s-butyl ether, ethyleneglycol mono-i-butyl ether,
ethyleneglycol mono-t-butyl ether, ethyleneglycol mono-2-ethylhexyl
ether, propyleneglycol mono-n-butyl ether, propyleneglycol
mono-s-butyl ether, propyleneglycol mono-i-butyl ether,
propyleneglycol mono-t-butyl ether, diethyleneglycol,
diethyleneglycol monomethyl ether, diethyleneglycol monoethyl
ether, diethyleneglycol mono-n-propyl ether, diethyleneglycol
mono-i-propyl ether, diethyleneglycol mono-n-butyl ether,
diethyleneglycol mono-s-butyl ether, diethyleneglycol mono-i-butyl
ether, diethyleneglycol mono-t-butyl ether, diethyleneglycol
dimethyl ether, diethyleneglycol diethyl ether, diethyleneglycol
di-n-propyl ether, diethyleneglycol di-i-propyl ether,
diethyleneglycol di-n-butyl ether, diethyleneglycol di-s-butyl
ether, diethyleneglycol di-i-butyl ether, diethyleneglycol
di-t-butyl ether, dipropyleneglycol, dipropyleneglycol monomethyl
ether, dipropyleneglycol monoethyl ether, dipropyleneglycol
mono-n-propyl ether, dipropyleneglycol mono-i-propyl ether,
dipropyleneglycol mono-n-butyl ether, dipropyleneglycol
mono-s-butyl ether, dipropyleneglycol mono-i-butyl ether,
dipropyleneglycol mono-t-butyl ether, dipropyleneglycol dimethyl
ether, dipropyleneglycol diethyl ether, dipropyleneglycol
di-n-propyl ether, dipropyleneglycol di-i-propyl ether,
dipropyleneglycol di-n-butyl ether, dipropyleneglycol di-s-butyl
ether, dipropyleneglycol di-i-butyl ether, dipropyleneglycol
di-t-butyl ether, triethyleneglycol dimethyl ether,
tetraethyleneglycol dimethyl ether, 3-methoxy-1-butahol,
3-methoxy-3-methyl-1-butahol, tetrahydrofurfuryl alcohol,
ethyleneglycol monoethyl ether acetate, ethyleneglycol monobutyl
ether acetate, propyleneglycol monoethyl ether acetate,
diethyleneglycol monoethyl ether acetate, and diethyleneglycol
monobutyl ether acetate.
[0059] More preferable ethers which can be used as an
oxygen-containing carbon source compound include ones having a
boiling point of 115.degree. C. or more at an ordinary pressure.
The more preferable ethers includes di-n-butyl ether, di-s-butyl
ether, ethyleneglycol monomethyl ether, ethyleneglycol monoethyl
ether, ethyleneglycol mono-n-propyl ether, ethyleneglycol
mono-i-propyl ether, ethyleneglycol diethyl ether, propyleneglycol
monomethyl ether, propyleneglycol monoethyl ether, ethyleneglycol
monomethyl ether acetate, propyleneglycol monomethyl ether acetate,
anisole, ethoxybenzene, 2-methoxytoluene, 3-methoxytoluene,
4-methoxytoluene, ethyleneglycol mono-n-butyl ether, ethyleneglycol
mono-s-butyl ether, ethyleneglycol mono-i-butyl ether,
ethyleneglycol mono-t-butyl ether, ethyleneglycol mono-2-ethylhexyl
ether, propyleneglycol mono-n-butyl ether, propyleneglycol
mono-s-butyl ether, propyleneglycol mono-i-butyl ether,
propyleneglycol mono-t-butyl ether, diethyleneglycol,
diethyleneglycol monomethyl ether, diethyleneglycol monoethyl
ether, diethyleneglycol mono-n-propyl ether, diethyleneglycol
mono-i-propyl ether, diethyleneglycol mono-n-butyl ether,
diethyleneglycol mono-s-butyl ether, diethyleneglycol mono-i-butyl
ether, diethyleneglycol mono-t-butyl ether, diethyleneglycol
dimethyl ether, diethyleneglycol diethyl ether, diethyleneglycol
di-n-propyl ether, diethyleneglycol di-i-propyl ether,
diethyleneglycol di-n-butyl ether, diethyleneglycol di-s-butyl
ether, diethyleneglycol di-i-butyl ether, diethyleneglycol
di-t-butyl ether, dipropyleneglycol, dipropyleneglycol monomethyl
ether, dipropyleneglycol monoethyl ether, dipropyleneglycol
mono-n-propyl ether, dipropyleneglycol mono-i-propyl ether,
dipropyleneglycol mono-n-butyl ether, dipropyleneglycol
mono-s-butyl ether, dipropyleneglycol mono-i-butyl ether,
dipropyleneglycol mono-t-butyl ether, dipropyleneglycol dimethyl
ether, dipropyleneglycol diethyl ether, dipropyleneglycol
di-n-propyl ether, dipropyleneglycol di-i-propyl ether,
dipropyleneglycol di-n-butyl ether, dipropyleneglycol di-s-butyl
ether, dipropyleneglycol di-i-butyl ether, dipropyleneglycol
di-t-butyl ether, triethyleneglycol dimethyl ether,
tetraethyleneglycol dimethyl ether, 3-methoxy-1-butahol,
3-methoxy-3-methyl-1-butahol, tetrahydrofurfuryl alcohol,
ethyleneglycol monoethyl ether acetate, ethyleneglycol monobutyl
ether acetate, propyleneglycol monoethyl ether acetate,
diethyleneglycol monoethyl ether acetate, and diethyleneglycol
monobutyl ether acetate.
[0060] Particularly preferable ethers which can be used as an
oxygen-containing carbon source compound include ones having a
boiling point of 150.degree. C. or more at an ordinary pressure.
The preferable ethers include anisole, ethoxybenzene,
2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene,
ethyleneglycol mono-n-butyl ether, ethyleneglycol mono-s-butyl
ether, ethyleneglycol mono-1-butyl ether, ethyleneglycol
mono-t-butyl ether, ethyleneglycol mono-2-ethylhexyl ether,
propyleneglycol mono-n-butyl ether, propyleneglycol mono-s-butyl
ether, propyleneglycol mono-i-butyl ether, propyleneglycol
mono-t-butyl ether, diethyleneglycol, diethyleneglycol monomethyl
ether, diethyleneglycol monoethyl ether, diethyleneglycol
mono-n-propyl ether, diethyleneglycol mono-i-propyl ether,
diethyleneglycol mono-n-butyl ether, diethyleneglycol mono-s-butyl
ether, diethyleneglycol mono-i-butyl ether, diethyleneglycol
mono-t-butyl ether, diethyleneglycol dimethyl ether,
diethyleneglycol diethyl ether, diethyleneglycol di-n-propyl ether,
diethyleneglycol di-i-propyl ether, diethyleneglycol di-n-butyl
ether, diethyleneglycol di-s-butyl ether, diethyleneglycol
di-i-butyl ether, diethyleneglycol di-t-butyl ether,
dipropyleneglycol, dipropyleneglycol monomethyl ether,
dipropyleneglycol monoethyl ether, dipropyleneglycol mono-n-propyl
ether, dipropyleneglycol mono-i-propyl ether, dipropyleneglycol
mono-n-butyl ether, dipropyleneglycol mono-s-butyl ether,
dipropyleneglycol mono-i-butyl ether, dipropyleneglycol
mono-t-butyl ether, dipropyleneglycol dimethyl ether,
dipropyleneglycol diethyl ether, dipropyleneglycol di-n-propyl
ether, dipropyleneglycol di-i-propyl ether, dipropyleneglycol
di-n-butyl ether, dipropyleneglycol di-s-butyl ether,
dipropyleneglycol di-i-butyl ether, dipropyleneglycol di-t-butyl
ether, triethyleneglycol dimethyl ether, tetraethyleneglycol
dimethyl ether, 3-methoxy-1-butahol, 3-methoxy-3-methyl-1-butahol,
tetrahydrofurfuryl alcohol, ethyleneglycol monoethyl ether acetate,
ethyleneglycol monobutyl ether acetate, propyleneglycol monoethyl
ether acetate, diethyleneglycol monoethyl ether acetate, and
diethyleneglycol monobutyl ether acetate.
[0061] An oxygen-containing carbon source compound used for the
present invention can be used in an amount such that the molar
ratio of oxygen atom in the oxygen-containing carbon source
compound to carbon atom in the carbon source becomes 100 to 100,000
ppm, particularly 1,000 to 3,000 ppm.
(Carbon Source)
[0062] As a carbon source, any compound can be used as long as it
has carbon atom. The useful carbon compound includes inorganic
gases such as carbon monoxide, carbon dioxide; alkanes such as
methane, ethane, propane, butane, pentane, hexane, heptane, octane;
alkene such as ethylene, propylene, butene, butadiene; alkynes such
as acetylene; monocyclic aromatic hydrocarbons such as benzene,
toluene, xylene, stylene; Polyclic compounds having condensed rings
such as indene, naphthalene, anthracene, phenanthrene; cyclic
paraffins such as cyclopropane, cyclopentane, cyclohexane; cyclic
olefins such as cyclopentene, cyclohexene, cyclopentadiene,
dicyclopentadiene; alicyclic hydrocarbon compounds having condensed
rings such as steroid. These compounds also can be used as an
oxygen-containing carbon source compound If they satisfy the
requirements as an oxygen-containing carbon source.
[0063] Also, compounds containing oxygen, nitrogen, sulfur,
phosphorus, halogen, and like can be used as a carbon source. The
mixtures of the carbon sources naturally can be used. Particularly,
a carbon source containing sulfur also can be used as a sulfur
source described below.
[0064] When a catalyst and/or catalyst precursor compound used is
dissolved or dispersed in an oxygen-containing carbon source
compound, a carbon source which is preferable in view of carbon
fiber productivity and cost includes carbon monoxide, carbon
dioxide, methane, ethane, propane, butane, pentane, hexane,
heptane, cyclohexane, ethylene, propylene, butene, butadiene,
acetylene, benzene, toluene, xylene, and mixtures thereof. A
particularly preferable carbon source includes methane.
[0065] Further, in this case, a compound in a gaseous state at an
ordinary temperature can easily be used as a carbon source
compound. The compound in a gaseous state at an ordinary
temperature includes carbon monoxide, carbon dioxide, methane,
ethane, propane, butane, pentane, hexane, heptane, cyclohexane,
ethylene, propylene, butene, butadiene, acetylene, particularly
methane, and mixtures thereof.
[0066] It is particularly effective to dissolve or disperse a
catalyst and/or catalyst precursor compound in an oxygen-containing
carbon source compound according to the present invention, when all
or part of a carbon source, and optionally the other contents such
as carrier gas, is in a gaseous state at an ordinary temperature
and pressure, and/or when all or part of a carbon source, and
optionally the other contents such as carrier gas, is in a liquid
state at an ordinary temperature and pressure, but has no or
substantially no solubility of a catalyst and/or catalyst precursor
compound therein at 25.degree. C.
[0067] When methane is used as a carbon source, the methane
concentration in the supplied raw material is preferably at or more
than 15 mol % to less than 100 mol %, more preferably from 30 to 95
mol %, still more preferably from 45 to 90 mol %. If the methane
concentration in the raw material is excessively low, the
productivity of a carbon fiber decreases, whereas if the methane
concentration is excessively high, a non-fibrous product may
possibly be produced. The "raw material supplied" means a
composition containing a carbon source, an oxygen-containing carbon
source compound, a catalyst and/or catalyst precursor, a carrier
gas, etc., i.e. a composition containing all components supplied to
a heating zone.
[0068] When methane is used as a carbon source, the carbon source
other than methane, which is used along with methane, is preferably
not used in an excessively large amount. This is because if used in
a large amount, the carbon source inhibits the properties of
methane. The carbon source other than methane is used in such an
amount that the total amount of carbon atom contained in such a
carbon source is preferably 60% or less, more preferably 40% or
less, still more preferably 20% or less, further still more
preferably 10% or less, and most preferably 5% or less, based on
the total amount of carbon atom contained in methane. If the carbon
source other than methane is used in an excess amount, the amount
of a non-fibrous solid matter produced abruptly increases.
Regarding this concentration, however, carbon monoxide and carbon
dioxide are not considered as a carbon source since these behave
differently from the other carbon source.
(Catalyst)
[0069] The catalyst used for the present invention is not
particularly limited as long as it is a substance capable of
accelerating the growth of a carbon fiber. The catalyst is, for
example, at least one metal (particularly, a fine particle thereof)
selected from the group consisting of Groups 3 to 12 of the 18
Groups-Type Periodic Table of Elements recommended by IUPAC in
1990, preferably at least one metal selected from the group
consisting of Groups 3, 5, 6, 8, 9 and 10, more preferably iron,
nickel, cobalt, ruthenium, rhodium, palladium, platinum or a rare
earth element.
(Catalyst Precursor Compound)
[0070] The "catalyst precursor compound" means a compound which is
thermally decomposed upon heating and, in some cases, further
reduced to provide the catalyst. The catalyst precursor compound
includes an organic metal compound, a metal salt, etc. For example,
metallocene as a catalyst precursor compound is thermally
decomposed upon heating to provide fine metal particles which work
as a catalyst. Especially, ferrocene is thermally decomposed upon
heating to provide fine iron particles. Accordingly, as for the
catalyst precursor compound, a compound of providing the
above-described metal can be suitably used. More specifically, the
catalyst precursor compound is, for example, a metal compound
containing at least one element selected from the group consisting
of Groups 3 to 12, preferably a compound containing at least one
element selected from the group consisting of Groups 3, 5, 6, 8, 9
and 10, and most preferably a compound containing iron, nickel,
cobalt, ruthenium, rhodium, palladium, platinum or a rare earth
element.
[0071] It is also possible to add a metal compound containing at
least one element, selected from the group consisting of Groups 1
to 17 as a modification component (so-called co-catalyst), to the
main component to modify the catalytic performance of the main
component metal.
(Support)
[0072] The catalyst and/or catalyst precursor compound may also be
used, if desired, by loading it on a support. The support is
preferably a compound stable in the heating zone, and examples of
such a compound include alumina, silica, zeolite, magnesia,
titania, zirconia, graphite, activated carbon and carbon fiber.
However, this support must be introduced together with a carbon
source, etc. into a heated furnace without previously charging it
into a reaction furnace.
(Amounts of Catalyst, Etc.)
[0073] The amount of the catalyst or catalyst precursor compound to
be used is, in terms of the ratio of the atomic number of an a
catalyst element (for example, Fe) to the number of carbon atoms in
the carbon source, preferably 0.000005 to 0.0015, more preferably
from 0.00001 to 0.001, still more preferably from 0.00002 to
0.0005, and most preferably from 0.00004 to 0.0004. If this ratio
is less than 0.000005, the amount of catalyst is too small and the
number of fibers may decrease or the fiber diameter may increase,
whereas if the ratio exceeds 0.0015, not only the profitability is
low but also coarsened catalyst particles, not functioning as a
catalyst, may be mixed in the fiber. As for the total number of
carbon atoms of the carbon source in the raw material, when the
catalyst precursor compound contains a carbon, the carbon atoms
thereof are also included. That is, the total number of carbon
atoms is a total amount of all carbon atoms excluding carbons
contained in the carbon monoxide and carbon dioxide in the supplied
raw material.
(Method of Supplying Raw Material)
[0074] The method of supplying the raw material is not particularly
limited. A carbon source, and an oxygen-containing carbon source
compound containing a catalyst and/or catalyst precursor compound
dissolved or suspended therein may be vaporized and supplied in the
gaseous state, or a part or all thereof may be supplied in a liquid
state. In order to efficiently produce a carbon fiber, these raw
materials are preferably vaporized before the production of carbon
fiber starts, and then supplied. More preferably the solution or
suspension containing the catalyst and/or catalyst precursor is
vaporized and thoroughly mixed with the carbon source, and then
supplied.
(Carrier Gas)
[0075] In the production of the vapor-grown carbon fiber of the
present invention, it is recommended to use a carrier gas in
addition to the above-described composition. As for the carrier
gas, hydrogen, nitrogen, helium, argon, krypton or a mixed gas
thereof may be used, but a gas containing an oxygen molecule (that
is, oxygen in the molecular state (O.sub.2)), such as air, is not
suited. The catalyst precursor compound for use in the present
invention is sometimes in the oxidized state and in such a case, a
hydrogen-containing gas is preferably used as the carrier gas.
Accordingly, the carrier gas is preferably a gas containing
hydrogen at a concentration of 1 vol % or more, more preferably 30
vol % or more, and most preferably 85 vol % or more, and this is,
for example, a gas of 100 vol % hydrogen or a gas of hydrogen
diluted with nitrogen. The hydrogen gas concentration used here is
based only on the carrier gas, but the amounts of a carbon source,
the gasified catalyst and/or catalyst precursor compound and the
like are not considered.
(Sulfur Compound)
[0076] In the production of the vapor-grown carbon fiber of the
present invention, a sulfur compound considered to be effective in
controlling the carbon fiber diameter may be used in combination.
The sulfur compound which can be used in the present invention
includes sulfur; thiophene; hydrogen sulfide; carbon sulfide;
mercaptans such as methyl mercaptan, tert-butyl mercaptan; sulfides
such as dimethyl sulfide; and disulfides such as dimethyl
disulfide. The preferred sulfur compound includes thiophene, carbon
disulfide, dimethyl sulfide and dimethyl disulfide, and more
preferred sulfur compound includes dimethyl sulfide and dimethyl
disulfide.
[0077] These sulfur compound may be supplied in the gaseous state
or by dissolving it in a solvent. The total molar number of sulfur
supplied is suitably 100 times or less, preferably 10 times or
less, more preferably 2 times or less, of the molar number of a
catalyst element. If the amount of sulfur supplied is excessively
large, this is not only unprofitable but also it also inhibits the
growth of a carbon fiber, and is not preferred.
(Synthesis of Carbon Fiber)
[0078] The synthesis of a vapor-grown carbon fiber is achieved by
supplying the raw materials described above and, if desired, a
carrier gas to a heating zone, and contacting these under heating.
The reactor (heating zone) is not particularly limited as long as
predetermined residence time and heating temperature are obtained,
but a vertical or horizontal tubular furnace is preferred in view
of the supply of raw material and the control of residence
time.
[0079] If the temperature in the heating zone is too low, a solid
product as well as a carbon fiber is not produced at all or is
produced in an extremely small amount, whereas if the temperature
is excessively high, a carbon fiber does not grow or only a thick
fiber is obtained. Therefore, particularly when methane is used as
a carbon source, the temperature in the high-temperature part of
the heating zone is preferably from 1,100 to 1,500.degree. C., more
preferably from 1,150 to 1,350.degree. C.
[0080] When methane is used as a carbon source, the main component
of the carbon source in the gas after the reaction is methane which
can be a carbon source. Accordingly, all or a part of the gas after
reaction can be circulated and reused by supplying it to the
heating zone as-is or after adding carbon source, carrier gas, etc.
thereto.
[0081] FIG. 2 shows one example of the reaction apparatus. In this
case, a quartz-made reaction tube 1 used as a heating zone is
equipped with a heater 2 and, at the top, is connected to a supply
line of mixing and supplying raw material components of a carrier
gas, a carbon source such as methane and a liquid raw material
component containing a catalyst and/or catalyst precursor compound.
In this supply line, a vaporizer 4 is disposed. At the bottom of
the reaction tube 1, a receiver 3 for collecting the produced
carbon fibers is provided. By using such an apparatus, the heater 2
is set to a predetermined temperature of 1,100.degree. C. or more,
and raw materials are introduced from the introduction line 4 and
reacted.
[0082] When methane is used as a carbon source, the fundamental
mechanism of the present invention is mainly such that a carbon
fiber produced upon contact of methane with a catalyst at a low
temperature of 1,000.degree. C. or less is effectively grown in the
diameter direction at a high temperature of 1,000.degree. C. or
more by using a carbon source, for example, methane, an aliphatic
hydrocarbon such as ethylene and propylene and/or an aromatic
hydrocarbon such as benzene, which all are a decomposition product
of methane.
[0083] If raw materials are directly supplied to a high-temperature
zone, a carbon source is rapidly decomposed and forms a non-fiber
solid matter before forming a carbon fiber. In order to avoid this
problem, the temperature at the raw material-introducing part from
which a raw material is induced into the reaction tube, that is,
the heating zone, must be kept lower than the temperature in the
high-temperature part of the heating zone. The temperature of the
raw material-introducing part is preferably 700.degree. C. or less,
more preferably 600.degree. C. or less, still more preferably
400.degree. C. or less. The residence at 1,000.degree. C. or less
must be kept to a certain period of time by introducing the raw
material into the low-temperature region. In particular, the
residence time at 600 to 1,000.degree. C. is important, and the raw
material is preferably caused to stay in this temperature range for
0.05 seconds or more, preferably 0.5 seconds ore more, still more
preferably from 1.0 to 30 seconds.
[0084] The actual gas temperature in the region is hard to measure.
Therefore, the temperature used here is a value obtained, for
example, by inserting a platinum-platinum.13% rhodium alloy
thermocouple capable of measuring even a temperature of
1,000.degree. C. or more into the heating zone. To be precise, this
measured value is affected by radiation and does not necessarily
agree with the gas temperature but can be satisfactorily used as an
index for specifying the preferred condition of the present
invention.
[0085] The residence time in the temperature range of 600 to
1,000.degree. C. is a time of passage of the raw material gas
through a region where the temperature measured as above on the
inlet side of the reaction apparatus elevates from 600.degree. C.
to 1,000.degree. C. The residence time is calculated on the
assumption that the raw material gas creates a plug flow in this
region and the temperature of the raw material gas is elevated to
the temperature measured as above. In the case where the
temperature at the upstream end of heating zone or the temperature
of ejection part of a nozzle or the like inserted into the heating
zone as a feed line having an inner diameter smaller than, for
example, 1/5 as compared with the heating zone, exceeds 600.degree.
C., the residence time is a residence time in the region from the
upstream end of heating zone or the ejection part of a nozzle or
the like to a part where the temperature is elevated to
1,000.degree. C. In this case, the residence time is calculated on
the assumption that the raw material creates a plug flow in this
region and the temperature of the raw material gas is elevated to
the temperature measured as above.
[0086] The residence time at a temperature of 1,100.degree. C. or
more can be determined in the same manner as the residence time in
the temperature range of 600 to 1,000.degree. C. This residence
time is, for example, 0.001 second or more, preferably 0.01 second
or more, more preferably from 0.1 to 30 seconds. However, the
residence time at a temperature of 1,100.degree. C. or more can be
arbitrarily determined depending on the desired fiber thickness,
raw material concentration, temperature in the high-temperature
part, or the like.
(Shape of Carbon Fiber, Etc.)
[0087] As described above, when methane is used as a carbon source,
the carbon fiber obtained by the process of the present invention
become a thick fiber by using a high temperature of 1,100.degree.
C. or more. Accordingly, the production process of the present
invention is particularly suited for the production of a relatively
thick fiber rather than the production of a carbon fiber having a
very small outer diameter, such as single wall or dual wall carbon
fiber. More specifically, the production process of the present
invention is optimal as a production process of a carbon fiber
having an average outer diameter of 10 nm or more, preferably 50 nm
or more, and most preferably 100 nm or more. The outer diameter of
a carbon fiber as used herein can be determined, for example, by
measuring the outer diameter of the images of about 100 fibers in a
photograph from an SEM.
[0088] Furthermore, the present invention is characterized in that,
despite it being a production process with high productivity, a
carbon fiber having a long fiber length can be produced. That is,
the production process of the present invention is optimal as a
production process of a carbon fiber having an average fiber length
of 10 .mu.m or more, preferably 13 .mu.m or more, and most
preferably 15 .mu.m or more. The length of a carbon fiber as used
herein can be determined, for example, by measuring the length of
the images of about 100 fibers in a photograph from an SEM,
similarly to the case of the outer diameter.
[0089] According to the present invention, the effectiveness of a
catalyst or a catalyst precursor can be remarkably enhanced. That
is, a carbon fiber can be-efficiently obtained even with a small
amount of a catalyst. In a carbon fiber produced by a normal
process, a catalyst (e.g., iron) of about 50,000 mass ppm generally
remains. Therefore, the carbon fiber produced is subjected to
firing (at around 1,500.degree. C.) or graphitization treatment (at
2,000 to 3,000.degree. C.) in an inert gas so as to enhance the
physical properties. A part of iron or the like as the catalyst is
vaporized or transpired by this treatment, and the catalyst
residual amount decreases in the carbon fiber after graphitization
treatment. On the other hand, according to the production process
of the present invention, the catalyst content in the carbon fiber
can be extremely decreased even in the state not subjected to a
treatment such as firing and graphitization. For example, a carbon
fiber having a catalyst content of 5,000 ppm or less or, under
preferred conditions, a catalyst content of 500 ppm or less can be
obtained in the state not subjected to a treatment such as firing
and graphitization, and therefore depending on usage, the
graphitization treatment is not necessary.
[0090] In the process of the present invention, the average outer
diameter of the fiber obtained tends to change by varying the ratio
of the catalyst and/or catalyst precursor compound to a carbon
source such as methane. That is, the fiber diameter becomes small
when the ratio of the catalyst and/or catalyst precursor compound
is increased, and becomes large when the ratio is decreased. This
reveals that the average outer diameter of the carbon fiber
obtained can be controlled merely by changing the composition of a
raw material carbon source and a catalyst without changing the
reaction apparatus or detailed conditions. For example, a carbon
fiber having a fiber outer diameter of 80 to 150 nm can be very
easily produced.
EXAMPLES
[0091] The present invention is described in greater detail below
by referring to Examples, but the present invention is not limited
thereto.
[0092] The reagents and the like used in Examples and
[0093] Comparative Examples below are as follows:
<Reagents>
TABLE-US-00001 [0094] 1. Carbon Source Methane: Takachiho Trading
Co., Ltd. 2. Catalyst Precursor Compound Ferrocene: Nippon Zeon
Co., Ltd. 3. Solvent for dissolving and supplying catalyst
precursor compound (Compound which is in a liquid state at an
ordinary temperature and pressure) Benzene: Wako Pure Chemical
Industries, Ltd. Tetrahydropyrane: Wako Pure Chemical Industries,
Ltd. Toluene: Wako Pure Chemical Industries, Ltd. p-xylene: Wako
Pure Chemical Industries, Ltd. Cyclohexanone: Wako Pure Chemical
Industries, Ltd. Diethyleneglycol dimethyl ether: Tokyo Chemical
Industry Co., Ltd. Tetrahydrofuran: Wako Pure Chemical Industries,
Ltd. Acetone: Wako Pure Chemical Industries, Ltd. 4. Other
Components Thiophene: Wako Pure Chemical Industries, Ltd.
<Synthesis of Carbon Fiber>
Comparative Example 1
[0095] A vertical furnace equipped with a heating zone 1 of the
quartz-made reaction tube (inner diameter: 31 mm, outer diameter:
36 mm, length of heating zone: about 400 mm) shown in FIG. 2 was
used. The temperature of the heating zone 1 was elevated to
1,200.degree. C. with an N.sub.2 stream, the supply of N.sub.2 was
then stopped, and H.sub.2 as a carrier gas was instead flowed into
the heating zone 1 at 1 NL/min. After the temperature was
stabilized, ferrocene and dimethyl disulfide were dissolved into
benzene (a compound which is in a liquid state at an ordinary
temperature and pressure; boiling point at an ordinary pressure is
80.degree. C.), and the resulting solution was introduced into a
vaporizer 4 heated at 200.degree. C. to introduce each component in
the amount shown in Table 1, vaporized and then entrained in
H.sub.2. In this state, a solid product was not produced.
Thereafter, the flow rate of H.sub.2 was decreased to 0.5 NL/min
and methane was mixed with hydrogen at a flow rate of 0.5 NL/min.
In this way, all compounds were supplied in the gaseous state into
the reaction tube. The unit "NL" as used herein indicates a volume
(liter) in the standard state (0.degree. C., 1 atm).
[0096] In order to determine the residence time, the temperature
was elevated to 1,200.degree. C. with a He stream at 1 NL/min, and
when the temperature was stabilized, the inside temperature of the
quartz tube was measured by using a platinum-platinum.13% rhodium
alloy thermocouple. As a result, the temperature was 600.degree. C.
at 24 cm from the top of the quartz tube and 1,000.degree. C. at 29
cm. The residence time therebetween was determined and found to be
0.59 seconds. The temperature was higher than 1,100.degree. C. at
33 cm from the top of the quartz tube and was lower than
1,1000.degree. C. at 60 cm. The residence time therebetween was
determined and found to be 2.25 seconds.
[0097] As a result of reaction, a grayish cobweb-like deposit was
produced between the bottom of reaction tube and the collector 3.
After the temperature was lowered, the deposit was recovered and
the carbon recovery percentage was determined by dividing the
amount of the recovered deposit by the amount of carbon initially
contained in the carbon source used, and found to be 44%. The
conditions and results of the test are shown in Table 1.
[0098] The concentration of methane is determined according to the
following equations:
Concentration of Methane ( mol % ) = Amount of Methane Supplied ( m
mol / min ) / Amount of Raw materials Supplied ( m mol / min )
.times. 100 ##EQU00001## [ Amount of Raw materials Supplied ( m mol
/ min ) ) = Amount of Methane Supplied ( m mol / min ) + Amount of
Carrier Gas Supplied ( m mol / min ) + Amount of Carbon Sources
other than Methane Supplied ( m mol / min ) + Amount of Ferrocene
Supplied ( m mol / min ) + Amount of Sulfur Compound Supplied ( m
mol / min ) ] ##EQU00001.2##
[0099] The ratio of a residue in the column (%) is determined
according to the following equation:
Ratio of Residue in the column ( % ) = Amount of Residue in Column
( g ) / [ Amount of Residue in Column ( g ) + Amount of Material
Collected Outside Column ( g ) ] ##EQU00002##
[0100] With regard to the experimental conditions, ratios of a
total amount of carbon atom in carbon sources supplied other than
methane to a total amount of carbon atom in methane supplied (%)
are calculated according to the following equation, and shown in
Table 2:
Ratio of Total Amount of Carbon Atom in Carbon Sources Supplied
Other Than Methane to Total Amount of Carbon Atom in Methane
Supplied ( % ) = [ Carbon Atom Amount in Carrier Gas ( m mol / min
) + Carbon Atom Amount in Carbon Sources other than Methane ( m mol
/ min ) + Carbon Atom Amount in Ferrocene ( m mol / min ) + Carbon
Atom Amount in Sulfur Compound ( m mol / min ) ] / Carbon Atom
Amount in Methane ( m mol / min ) .times. 100 ##EQU00003##
[0101] Also, the cobweb-like product was observed by a scanning
electron microscope. Out of the product, the average outer diameter
was examined on about 100 pieces, as a result, the product was
found to be a fibrous material having an average outer diameter of
200 nm.
Comparative Example 2
[0102] The reaction was performed according to the method of
Comparative Example 1 except that toluene is used in the input
amount shown in Table 1 in place of benzene as a compound which is
in a liquid state at an ordinary temperature and pressure. The
conditions and results of the test are shown in Tables 1 and 2. The
carbon recovery percentage was 37% and the product was a fibrous
material having an average outer diameter of 200 nm.
Comparative Example 3
[0103] The reaction was performed according to the method of
Comparative Example 1 except that p-xylene is used in the input
amount shown in Table 1 in place of benzene as a compound which is
in a liquid state at an ordinary temperature and pressure. The
conditions and results of the test are shown in Tables 1 and 2. The
carbon recovery percentage was 50% and the product was a fibrous
material having an average outer diameter of 150 nm.
Example 1
[0104] The reaction was performed according to the method of
Comparative Example 1 except that acetone is used in the input
amount shown in Table 1 in place of benzene as a compound which is
in a liquid state at an ordinary temperature and pressure. The
conditions and results of the test are shown in Tables 1 and 2. The
carbon recovery percentage was 28% and the product was a fibrous
material having an average outer diameter of 200 nm.
Example 2
[0105] The reaction was performed according to the method of
Comparative Example 1 except that tetrahydrofuran is used in the
input amount shown in Table 1 in place of benzene as a compound
which is in a liquid state at an ordinary temperature and pressure.
The conditions and results of the test are shown in Tables 1 and 2.
The carbon recovery percentage was 32% and the product was a
mixture of similar amounts of a spherical shape material having an
average diameter of 170 nm and a fibrous material having an average
outer diameter of 200 nm.
Example 3
[0106] The reaction was performed according to the method of
Comparative Example 1 except that tetrahydropyrane is used in the
input amount shown in Table 1 in place of benzene as a compound
which is in a liquid state at an ordinary temperature and pressure.
The conditions and results of the test are shown in Tables 1 and 2.
The carbon recovery percentage was 31% and the product was a
fibrous material having an average outer diameter of 200 nm.
Example 4
[0107] The reaction was performed according to the method of
Comparative Example 1 except that cyclohexanone is used in the
input amount shown in Table 1 in place of benzene as a compound
which is in a liquid state at an ordinary temperature and pressure.
The conditions and results of the test are shown in Tables 1 and 2.
The carbon recovery percentage was 32% and the product was a
fibrous material having an average outer diameter of 170 nm.
Example 5
[0108] The reaction was performed according to the method of
Comparative Example 1 except that diethyleneglycol dimethyl ether
is used in the input amount shown in Table 1 in place of benzene as
a compound which is in a liquid state at an ordinary temperature
and pressure. The conditions and results of the test are shown in
Tables 1 and 2. The carbon recovery percentage was 32% and the
product was a fibrous material having an average outer diameter of
200 nm.
TABLE-US-00002 TABLE 1 Conditions and Results of Test Hydrocarbon
Compound Introduced Boiling Amount of Concen- Amount of Point at
Amount of Dimethyl- Shape of tration Methane Ordinary Amount
Ferrocene disulfide Carbon Produced Amount of of Methane introduced
Pressure Introduced Introduced Introduced Recovery Carbon Solid
Residue in (mol %) (mmol/min) (.degree. C.) (mmol/min) (mmol/min)
(mmol/min) Percentage Content Column Comp. 50 22 Benzene 80 0.012
0.0005 0.0002 44% Fibrous material 38% Ex. 1 with fiber diameter of
about 200 nm Comp. 50 22 Toluene 110 0.010 0.0005 0.0002 37%
Fibrous material 72% Ex. 2 with fiber diameter of about 200 nm
Comp. 50 22 P-xylene 138 0.009 0.0005 0.0002 50% Fibrous material
87% Ex. 3 with fiber diameter of about 150 nm Ex. 1 50 22 Acetone
56 0.015 0.0005 0.0002 28% Mixture of 0% Fibrous material and
Spherical material (main) Ex. 2 50 22 Tetra- 67 0.013 0.0005 0.0002
32% Mixture of 0% hydrofuran Fibrous material and Spherical
material Ex. 3 50 22 Tetra- 88 0.011 0.0005 0.0002 31% Fibrous
material 0% hydropiran with fiber diameter of about 200 nm Ex. 4 50
22 Cyclo- 155 0.010 0.0005 0.0002 32% Fibrous material 0% hexanone
with fiber diameter of about 170 nm Ex. 5 50 22 Diethylene- 162
0.008 0.0005 0.0002 32% Fibrous material 0% glycol with fiber
dimethyl diameter of about ether 200 nm
TABLE-US-00003 TABLE 2 Condition of Test Ratio of Total Amount of
Carbon Atoms Contained in Carbon Source other than Methane to Total
Amount of Carbon Atoms Contained in Methane (%) Comp. Ex. 1 0.35
Comp. Ex. 2 0.35 Comp. Ex. 3 0.35 Ex. 1 0.35 Ex. 2 0.35 Ex. 3 0.35
Ex. 4 0.35 Ex. 5 0.35
* * * * *