JP2004113848A - Catalyst, method of manufacturing the same, and electrode catalyst - Google Patents
Catalyst, method of manufacturing the same, and electrode catalyst Download PDFInfo
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- JP2004113848A JP2004113848A JP2002276816A JP2002276816A JP2004113848A JP 2004113848 A JP2004113848 A JP 2004113848A JP 2002276816 A JP2002276816 A JP 2002276816A JP 2002276816 A JP2002276816 A JP 2002276816A JP 2004113848 A JP2004113848 A JP 2004113848A
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- 239000003054 catalyst Substances 0.000 title claims abstract description 118
- 238000004519 manufacturing process Methods 0.000 title claims description 13
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 93
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 75
- 239000011882 ultra-fine particle Substances 0.000 claims abstract description 44
- 229910052751 metal Inorganic materials 0.000 claims abstract description 43
- 239000002184 metal Substances 0.000 claims abstract description 43
- 150000004706 metal oxides Chemical class 0.000 claims abstract description 41
- 229910044991 metal oxide Inorganic materials 0.000 claims abstract description 39
- 238000000034 method Methods 0.000 claims abstract description 31
- 239000002023 wood Substances 0.000 claims abstract description 30
- 239000010875 treated wood Substances 0.000 claims abstract description 20
- 229920000642 polymer Polymers 0.000 claims abstract description 14
- 239000002243 precursor Substances 0.000 claims abstract description 14
- 230000008569 process Effects 0.000 claims abstract description 13
- 229930195733 hydrocarbon Natural products 0.000 claims abstract description 11
- 150000002430 hydrocarbons Chemical class 0.000 claims abstract description 11
- 239000004215 Carbon black (E152) Substances 0.000 claims abstract description 8
- 229920000098 polyolefin Polymers 0.000 claims abstract description 5
- 229910021645 metal ion Inorganic materials 0.000 claims abstract description 4
- 229920002488 Hemicellulose Polymers 0.000 claims abstract description 3
- 239000007864 aqueous solution Substances 0.000 claims abstract description 3
- 239000001913 cellulose Substances 0.000 claims abstract description 3
- 229920002678 cellulose Polymers 0.000 claims abstract description 3
- 229920005610 lignin Polymers 0.000 claims abstract description 3
- 239000011148 porous material Substances 0.000 claims description 29
- 239000002923 metal particle Substances 0.000 claims description 16
- 239000002131 composite material Substances 0.000 claims description 11
- 150000001875 compounds Chemical class 0.000 claims description 11
- 239000002245 particle Substances 0.000 claims description 10
- 229910052723 transition metal Inorganic materials 0.000 claims description 10
- 150000003624 transition metals Chemical class 0.000 claims description 10
- -1 wood under pressure Chemical class 0.000 claims description 8
- 239000011368 organic material Substances 0.000 claims description 2
- 150000003839 salts Chemical class 0.000 claims description 2
- 239000010949 copper Substances 0.000 abstract description 31
- 239000011651 chromium Substances 0.000 abstract description 21
- 239000000446 fuel Substances 0.000 abstract description 21
- 229910052802 copper Inorganic materials 0.000 abstract description 19
- 239000000463 material Substances 0.000 abstract description 18
- 238000003763 carbonization Methods 0.000 abstract description 16
- 229910052804 chromium Inorganic materials 0.000 abstract description 13
- 239000002699 waste material Substances 0.000 abstract description 11
- 239000002994 raw material Substances 0.000 abstract description 10
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 abstract description 9
- 229910001385 heavy metal Inorganic materials 0.000 abstract description 9
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 abstract description 3
- 239000000243 solution Substances 0.000 abstract description 3
- 239000003755 preservative agent Substances 0.000 abstract description 2
- 230000002335 preservative effect Effects 0.000 abstract description 2
- 150000001495 arsenic compounds Chemical class 0.000 abstract 1
- 239000003171 wood protecting agent Substances 0.000 abstract 1
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 48
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 description 21
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 18
- 229910002091 carbon monoxide Inorganic materials 0.000 description 18
- 230000003197 catalytic effect Effects 0.000 description 14
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 12
- 239000003792 electrolyte Substances 0.000 description 12
- 230000006870 function Effects 0.000 description 12
- 238000006356 dehydrogenation reaction Methods 0.000 description 10
- 230000000694 effects Effects 0.000 description 9
- 239000007789 gas Substances 0.000 description 9
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 8
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 8
- 229910001868 water Inorganic materials 0.000 description 8
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 7
- 229910052785 arsenic Inorganic materials 0.000 description 7
- 238000010248 power generation Methods 0.000 description 7
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 description 6
- 239000001569 carbon dioxide Substances 0.000 description 6
- 229910002092 carbon dioxide Inorganic materials 0.000 description 6
- 239000003575 carbonaceous material Substances 0.000 description 6
- 238000006243 chemical reaction Methods 0.000 description 6
- 229910052760 oxygen Inorganic materials 0.000 description 6
- 239000001301 oxygen Substances 0.000 description 6
- 238000001179 sorption measurement Methods 0.000 description 6
- 239000000126 substance Substances 0.000 description 6
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 5
- 230000004913 activation Effects 0.000 description 5
- 229910045601 alloy Inorganic materials 0.000 description 5
- 239000000956 alloy Substances 0.000 description 5
- 239000003610 charcoal Substances 0.000 description 5
- 238000005516 engineering process Methods 0.000 description 5
- 150000002894 organic compounds Chemical group 0.000 description 5
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 4
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 4
- 238000013329 compounding Methods 0.000 description 4
- 238000011161 development Methods 0.000 description 4
- 238000005984 hydrogenation reaction Methods 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 description 4
- 229910052697 platinum Inorganic materials 0.000 description 4
- 238000000629 steam reforming Methods 0.000 description 4
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 3
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- 229910004298 SiO 2 Inorganic materials 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000010000 carbonizing Methods 0.000 description 3
- 238000004517 catalytic hydrocracking Methods 0.000 description 3
- 238000001651 catalytic steam reforming of methanol Methods 0.000 description 3
- 238000005341 cation exchange Methods 0.000 description 3
- 238000007334 copolymerization reaction Methods 0.000 description 3
- 235000014113 dietary fatty acids Nutrition 0.000 description 3
- 238000009792 diffusion process Methods 0.000 description 3
- 239000010411 electrocatalyst Substances 0.000 description 3
- 239000012776 electronic material Substances 0.000 description 3
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- 238000002474 experimental method Methods 0.000 description 3
- 239000000194 fatty acid Substances 0.000 description 3
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- 150000004665 fatty acids Chemical class 0.000 description 3
- 238000010304 firing Methods 0.000 description 3
- 229910002804 graphite Inorganic materials 0.000 description 3
- 239000010439 graphite Substances 0.000 description 3
- 238000005470 impregnation Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 229910052759 nickel Inorganic materials 0.000 description 3
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 3
- 150000002902 organometallic compounds Chemical class 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 229910052763 palladium Inorganic materials 0.000 description 3
- 230000035699 permeability Effects 0.000 description 3
- IEQIEDJGQAUEQZ-UHFFFAOYSA-N phthalocyanine Chemical class N1C(N=C2C3=CC=CC=C3C(N=C3C4=CC=CC=C4C(=N4)N3)=N2)=C(C=CC=C2)C2=C1N=C1C2=CC=CC=C2C4=N1 IEQIEDJGQAUEQZ-UHFFFAOYSA-N 0.000 description 3
- 150000004032 porphyrins Chemical class 0.000 description 3
- 238000000746 purification Methods 0.000 description 3
- 229910052703 rhodium Inorganic materials 0.000 description 3
- 239000010948 rhodium Substances 0.000 description 3
- 238000003786 synthesis reaction Methods 0.000 description 3
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 239000002028 Biomass Substances 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 229910010413 TiO 2 Inorganic materials 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- 238000004891 communication Methods 0.000 description 2
- 239000004020 conductor Substances 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 230000005621 ferroelectricity Effects 0.000 description 2
- 235000019253 formic acid Nutrition 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 229910052741 iridium Inorganic materials 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 239000000395 magnesium oxide Substances 0.000 description 2
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 2
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- 239000010814 metallic waste Substances 0.000 description 2
- TZIHFWKZFHZASV-UHFFFAOYSA-N methyl formate Chemical compound COC=O TZIHFWKZFHZASV-UHFFFAOYSA-N 0.000 description 2
- 229910052750 molybdenum Inorganic materials 0.000 description 2
- 239000000178 monomer Substances 0.000 description 2
- 238000000465 moulding Methods 0.000 description 2
- 229910000510 noble metal Inorganic materials 0.000 description 2
- 230000035515 penetration Effects 0.000 description 2
- 229920005597 polymer membrane Polymers 0.000 description 2
- 238000009790 rate-determining step (RDS) Methods 0.000 description 2
- 229910052709 silver Inorganic materials 0.000 description 2
- 229910052718 tin Inorganic materials 0.000 description 2
- 229910052720 vanadium Inorganic materials 0.000 description 2
- 229910052725 zinc Inorganic materials 0.000 description 2
- 239000011701 zinc Substances 0.000 description 2
- JIAARYAFYJHUJI-UHFFFAOYSA-L zinc dichloride Chemical compound [Cl-].[Cl-].[Zn+2] JIAARYAFYJHUJI-UHFFFAOYSA-L 0.000 description 2
- MGWGWNFMUOTEHG-UHFFFAOYSA-N 4-(3,5-dimethylphenyl)-1,3-thiazol-2-amine Chemical compound CC1=CC(C)=CC(C=2N=C(N)SC=2)=C1 MGWGWNFMUOTEHG-UHFFFAOYSA-N 0.000 description 1
- 229910001316 Ag alloy Inorganic materials 0.000 description 1
- QPLDLSVMHZLSFG-UHFFFAOYSA-N Copper oxide Chemical compound [Cu]=O QPLDLSVMHZLSFG-UHFFFAOYSA-N 0.000 description 1
- 239000005751 Copper oxide Substances 0.000 description 1
- 229910000570 Cupronickel Inorganic materials 0.000 description 1
- 229910001111 Fine metal Inorganic materials 0.000 description 1
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 1
- 229910002089 NOx Inorganic materials 0.000 description 1
- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical compound O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000003463 adsorbent Substances 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000007809 chemical reaction catalyst Substances 0.000 description 1
- 229910000423 chromium oxide Inorganic materials 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- YOCUPQPZWBBYIX-UHFFFAOYSA-N copper nickel Chemical compound [Ni].[Cu] YOCUPQPZWBBYIX-UHFFFAOYSA-N 0.000 description 1
- 229910000431 copper oxide Inorganic materials 0.000 description 1
- 238000006298 dechlorination reaction Methods 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000005695 dehalogenation reaction Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000010828 elution Methods 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 125000000524 functional group Chemical group 0.000 description 1
- 238000002309 gasification Methods 0.000 description 1
- 230000026030 halogenation Effects 0.000 description 1
- 238000005658 halogenation reaction Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 239000002440 industrial waste Substances 0.000 description 1
- 229910003471 inorganic composite material Inorganic materials 0.000 description 1
- 238000006317 isomerization reaction Methods 0.000 description 1
- 238000010169 landfilling Methods 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- VUZPPFZMUPKLLV-UHFFFAOYSA-N methane;hydrate Chemical compound C.O VUZPPFZMUPKLLV-UHFFFAOYSA-N 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- JCXJVPUVTGWSNB-UHFFFAOYSA-N nitrogen dioxide Inorganic materials O=[N]=O JCXJVPUVTGWSNB-UHFFFAOYSA-N 0.000 description 1
- 229910021470 non-graphitizable carbon Inorganic materials 0.000 description 1
- 230000000269 nucleophilic effect Effects 0.000 description 1
- 229920000620 organic polymer Polymers 0.000 description 1
- 125000002524 organometallic group Chemical group 0.000 description 1
- SWELZOZIOHGSPA-UHFFFAOYSA-N palladium silver Chemical compound [Pd].[Ag] SWELZOZIOHGSPA-UHFFFAOYSA-N 0.000 description 1
- 239000010893 paper waste Substances 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 231100000572 poisoning Toxicity 0.000 description 1
- 230000000607 poisoning effect Effects 0.000 description 1
- 239000005518 polymer electrolyte Substances 0.000 description 1
- 239000002685 polymerization catalyst Substances 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 230000000379 polymerizing effect Effects 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 238000000197 pyrolysis Methods 0.000 description 1
- 150000003254 radicals Chemical class 0.000 description 1
- 239000012495 reaction gas Substances 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000006722 reduction reaction Methods 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 238000002407 reforming Methods 0.000 description 1
- 230000027756 respiratory electron transport chain Effects 0.000 description 1
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
- 238000001771 vacuum deposition Methods 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
- 239000011592 zinc chloride Substances 0.000 description 1
- 235000005074 zinc chloride Nutrition 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
Description
【０００１】
【産業上の利用分野】
本発明は、金属超微粒子や金属酸化物超微粒子を高分散させた触媒とその製造方法及び燃料電池の触媒に関するものである。
【０００２】
【従来の技術】
金属触媒は、酸化、還元、加水分解、脱水素、水素化分解などの触媒機能を発揮することが知られている。白金（Ｐｔ）の他にニッケル（Ｎｉ）、鉄（Ｆｅ）、タングステン（Ｗ）などは、炭化水素からの脱水素反応を促進する作用を持つことが知られている。合金ではパラジウム−銀合金、銅−ニッケル合金には一酸化酸素の分解を行なう機能が知られている。鉄粉や酸化鉄（Ｆｅ２Ｏ３）など酸素吸収を行なう脱酸素剤としてすぐれた触媒である。また、酸化鉄（Ｆｅ２Ｏ３）は廃プラスチックの製油過程ですぐれた脱塩素触媒となることなども知られている。
【０００３】
この他、最近の環境問題への意識の高まりから、自動車の排ガスをクリアにする触媒に三元触媒が開発されており、一酸化炭素（ＣＯ）、炭化水素 （ＨＣ）、窒素酸化物 （ＮＯｘ）を酸素と反応させ二酸化炭素・水・窒素に変換するものである。この三元触媒にはアルミナ（Ａｌ２Ｏ３）、酸化マグネシウム（ＭｇＯ）、ニ酸化ケイ素（ＳｉＯ２）の化合物に白金、ロジウム、パラジウムなどの貴金属粒子を触媒として分散させている。最近は、触媒材料も多様化し、ポルフィリン錯体や、金属フタロシアニン化合物、脂肪酸金属塩化合物、ポリオレフィンを骨格とした導電性、強誘電性などを備えた高分子触媒などもつくられ有機−無機複合による触媒材料は電子材料、複合材料等の新しい分野に応用が広がっている。
【０００４】
触媒に使用する金属は、遷移金属でＰｔ、Ｐｄ、Ｎｉ、Ｃｏ、Ｆｅ、Ｃｕ、Ｖ、Ｍｏ、Ｒｈ、Ｃｒ、Ｉｒ、Ｒｕ、Ａｕ、ＡｇやＡｉ２Ｏ３、ＳｉＯ２、ＣｒＯ３、Ａｌ２Ｏ３、ＬｉＯ２、ＴｉＯ２、Ｆｅ２Ｏ３等の金属酸化物、ＬｉＣＯ３、Ｚｎ、Ａｌ、Ｓｎ等これらを意図的に複数重合したもの、及び有機化合物と共有結合した化合物、金属フタロシアニン化合物、脂肪酸金属塩化合物、ポルフィリン錯体等有機無機複合材料が使われている。
【０００５】
また、これら遷移金属を利用した触媒は、反応速度を向上させるのみならず、その生成化合物の規則性・分岐構造・組成あるいは共重合制御（ポリオレフィンのみならず極性モノマーとの共重合）などに利用され、機能制御された新たな材料創製の方法としても利用されるようになってきた。これらの触媒は、一般に金属超微粒子の形態でなんらかの担体に担持されて使用されるのが通常である。こうした担体で最も多いのは多孔質材料であり、多孔質炭素体も多く用いられている材料である。
【０００６】
多孔質炭素体の代表である活性炭は我々にとって最も身近な炭素材料であると同時に、工業的にも各種分離プロセス、精製、触媒、あるいは溶剤回収などに利用されているほか、環境汚染問題と関連した空気や水の浄化、あるいは医療用吸着材と多岐に渡る分野で使用されている。これは、活性炭に存在するラジカルや表面官能基の存在、及び活性炭自体の電子移動体としての働きが酸化還元、ハロゲン化、脱ハロゲン化、脱水素、分解、異性化、重合など優れた触媒機能を持っているためである。
【０００７】
一般に活性炭と呼ばれるものは、ミクロ孔（細孔直径２ｎｍ以下）からメソ孔（２〜５０ｎｍ）、さらにはマクロ孔（５０ｎｍ以上）までの広い範囲にわたる細孔をもち、それによって様々な大きさの物質を吸着することができる。黒鉛カ−ボンの単結晶の密度が２．２６ｇ／ｃｍ３であるのに対し、木質材料からつくる活性炭の嵩密度は０．２ｇ／ｃｍ３〜０．４ｇ／ｃｍ３と非常に小さいのは、炭素体に多くのメソ細孔とマクロ細孔が存在するためである。つまり、６００℃〜１０００℃前後で焼成した木炭等は半径２ｎｍ以下のミクロポアが占める内部表面積が１００ｍ？／１ｎｍ．ｇと極めて大きく、大容積の細孔が存在している。
【０００８】
通常、活性炭の製造においては、単位重量当たりの吸着有効表面積をどれだけ大きくできるかが課題となる。その一方で、使用目的によっては、いかに均一な孔径をもつ細孔を調製するかが重要な場合がある。特に近年、多孔質炭素体は金属超微粒子や金属酸化物超微粒子との複合化によって二酸化窒素（ＮＯ２）無害化触媒や水素ガス化触媒として燃料電池用電解質への利用が着目されており、この場合、その性能は単位容積あたりの表面積と表面活性力で評価される。
【０００９】
最近の触媒利用の一例として、燃料電池用メタノールの水蒸気改質（ＣＨ３ＯＨ＋Ｈ２Ｏ→３Ｈ２＋ＣＯ２）電極触媒がある。燃料電池はクリーンで簡便な発電システムとして着目されている。この電極触媒はメタノール等の有機化合物の脱水素化反応を行なう触媒作用で温和な条件で使用可能なことから、触媒の製造コストによっては大いに有望な発電システムとして着目されている。
【００１０】
【発明が解決しようとする課題】
本発明の課題は、多孔質炭素体に金属超微粒子や金属酸化物超微粒子を高分散させた触媒を安価に製造でき、かつ広範囲な用途に使用できる多孔質炭素体−金属触媒複合材を提供することにある。また、本発明の別の課題は、上記の特長を有する触媒であって燃料電池用電極触媒性能に優れた材料を提供することにある。
【００１１】
【課題を解決するための手段】
これまで本発明者らは、ＣＣＡ（Ｃｒ、Ｃｕ、Ａｓ）薬剤処理木材（以下ＣＣＡ処理木材と言う。）や有機金属化合物等を炭素原料として、金属超微粒子や金属酸化物超微粒子を分散した多孔質炭素体の微細組織や細孔構造がどれだけ制御可能か、また、分子構造以外の立体的な構造を如何に制御することが可能かについて検討を行ってきた。
実験から、木材等天然炭化水素高分子化合物を前駆体とした多孔質炭素体は、ミクロ孔（細孔直径２ｎｍ以下）からメソ孔（２〜５０ｎｍ）、さらにはマクロ孔（５０ｎｍ以上）までの広い範囲にわたる細孔をもち、大きな比表面積を持っていることが判明している。
【００１２】
また、黒鉛カーボンの単結晶の密度が２．２６ｇ／ｃｍ３であるのに対し、木質材料からつくる多孔質炭素体の嵩密度は０．２ｇ／ｃｍ３〜０．４ｇ／ｃｍ３と非常に小さい。これは炭素構造中に多くのメソ細孔とマクロ細孔が存在するためである。つまり、６００℃〜１０００℃前後で焼成した木炭等は半径２ｎｍ以下のミクロポアが占める内部表面積が極めて大きく、大容積の細孔が存在していることを確かめた。その上、黒鉛カーボンに比較して固定炭素率及び電子移動体としての能力も同等で、さらに多孔質な優れた性状を持っており使用目的によっては、多面的に活用できる多孔質炭素体であることが判明した（表１）。しかし、工業的製法の確立がないため、これまで、その利用用途は限定されていた。
【００１３】
【表１】
一方、ダイレクトメタノール燃料電池 （ＤＭＦＣ）におけるメタノ−ル改質・拡散用触媒は、セパレータ及びＭＥＡの水素改質を目的とした電解質層が主要な役割を果たす。これまで主役と目されてきた合金製触媒は、合金であるが故の重さ（単位重量当たりの吸蔵量が小さい）、吸蔵−放出の繰り返しによる劣化（合金の微粉化や構造変化）、希少金属を含む場合にはその価格や資源確保など課題が多い。
【００１５】
そこで上記課題を解決するために本発明者らは、種々の検討を重ねた結果、従来の炭素粉体の調製や表面への貴金属の真空蒸着によるコーティングや、また特殊な炭素材の構造化や成形による高コスト化を解決するために、廃木材等の天然炭化水素高分子化合物を前駆体とした多孔質炭素体の製造と同時に金属超微粒子を高分散した新規触媒の創製技術を見いだした。
【００１６】
本発明は、触媒として必要な金属を金属イオン溶液にして木材や天然炭化水素高分子化合物に含浸させ、その後、炭素化する過程を経て金属超微粒子あるいは金属酸化物超微粒子をに高分散濃縮することにより、低温、省エネルギーかつ低コストで製造する多孔質炭素体に金属超微粒子を高分散担持させる多孔質炭素体と金属超微粒子や金属酸化物超微粒子の複合化した触媒の調製技術に関するものである。
【００１７】
触媒の担体として多孔質炭素体の優れた特性を最大限に引き出せるか否かは、多孔質炭素体の製造技術の開発にかかっている。つまり、本発明の微細スケールの触媒創成技術は、従来にない触媒の製造方法として燃料電池用電極触媒をはじめとする一般化学反応用触媒や電子材料、複合材料、環境浄化材料等の分野に新しい触媒の調製方法を提供し、多孔質炭素体と金属超微粒子や金属酸化物超微粒子の複合化した触媒が極めて容易にかつ低コストで製造可能となることを目的としている。また、同時に、廃棄物処理と有害重金属（廃液）処理の一方法としても効率的かつ環境に調和した手法の開発に繋がるものとなる。
【００１８】
【発明の実施の形態】
これまで本発明者らは、木材を多孔質炭素体の前駆体として用いて、これに金属超微粒子が分子レベルで高分散する多孔質炭素体の製造と、これら多孔質炭素体の微細組織や細孔構造と触媒機能がどれだけ制御可能かについて検討を行ってきた。その結果、木材や有機化合物を前駆体として炭素化し多孔質炭素体とする本発明に係る多孔質炭素体と金属超微粒子や金属酸化物超微粒子の複合化した触媒は、省エネルギ−かつ低コストで製造できること、更に、これら触媒をさらに他の高分子電解質材料と複合化することにより、導電性を向上させることなど、その機能性と特性を検討した。
【００１９】
すなわち本発明は、多孔質炭素体に金属超微粒子や金属酸化物超微粒子を高分散担持する触媒に係るものであり、触媒となる金属イオンを含む水溶液を事前に木材等天然炭化水素高分子化合物に加圧含浸させ、木材成分であるセルロース（４５％）、ヘミセルロース（３０％）、リグニン（２５％）等と金属分子を結合、あるいは木質構造の導管などの内部に分散させ、金属が分子レベルあるいはミクロンオーダーの塩などの形で分散された前駆体と成し、その後これら木材を空気を制御した状態で熱を加えて炭素化する過程を経て容易に多孔質炭素体にできること、加えて炭素化と同時に多孔質炭素体に均一かつ高分散に金属超微粒子や金属酸化物超微粒子を担持した触媒となることを発見したものであり、炭素化それ自体は木炭化等の公知の方法にしたがって行なえば良い。
【００２０】
前駆体として利用する木材や天然植物、有機物原料は、新規な物とする必要は無く、Ｃｒ、Ｃｕ等を含んでいる防腐処理を施されたＣＣＡ処理木材などの廃棄木材、また、古紙などの浸透性を有する有機物や有機化合物等が適している。なかでもＣｒ、Ｃｕ等が含浸法により数気圧から１０気圧程度で圧力注入処理されたＣＣＡ処理木材はＣｒで１０５３ＰＰＭ、Ｃｕで４２５ＰＰＭの高濃度で重金属イオンを木材に有機金属化合物として含有していることが知見されており（表２）、これらの含有重金属（クロムと銅） やその他の遷移金属、有機金属廃液等を原料として利用するのが低コスト化する上で適している。
【００２１】
【表２】
また、前記多孔質炭素体を調製する場合、金属廃液に新たな金属種を組み合わせた複合化など、規則性・分岐構造・組成・共重合制御や、その他各種ポリマ−との複合化により様々な金属の触媒機能と多孔質炭素体との組み合わせ方法をとることができる。この場合、触媒となる金属超微粒子や金属酸化物超微粒子は、遷移金属でＰｔ、Ｐｄ、Ｎｉ、Ｃｏ、Ｆｅ、Ｃｕ、Ｖ、Ｍｏ、Ｒｈ、Ｃｒ、Ｉｒ、Ｒｕ、Ａｕ、ＡｇやＡｉ２Ｏ３、ＳｉＯ２、ＣｒＯ３、Ａｌ２Ｏ３、ＬｉＯ２、ＴｉＯ２、Ｆｅ２Ｏ３等の金属酸化物、ＬｉＣＯ３、Ｚｎ、Ａｌ、Ｓｎ等これらを意図的に複数混合したもの及び共有結合した有機金属化合物、金属フタロシアニン化合物、脂肪酸金属塩化合物、ポルフィリン錯体等を原料として利用できる。
【００２３】
本発明に係る触媒としてＣｒ２Ｏ３ ならびに Ｃｕ２Ｏ の触媒活性は、すでに詳しく検討されており、主に水素化あるいは脱水素の触媒として利用されている。さらに、Ｃｕ２Ｏ−Ｃｒ２Ｏ３ の二元系触媒もメタノール合成などに利用されており、この触媒は ＣＣＡ処理木材を原料とすれば、比較的簡単に調製できることになる。
【００２４】
また、こうした二元系触媒は、二つの物質の境界が重要な役目を果たすことが多く、金属超微粒子や金属酸化物超微粒子として二元系触媒が構成されていれば、従来よりも遙かに高い触媒活性を示すことになる。実験から、ＣＣＡ処理木材を原料とした多孔質炭素体と金属酸化物超微粒子の複合化した触媒は、水素化あるいは脱水素の触媒として機能することが知見され、その触媒活性は、金属酸化物超微粒子径や多孔質炭素体中での分散状態に依存するため焼成条件との関係や炭素化工程など多孔質炭素体の製法が重要になる。
【００２５】
触媒担体となる多孔質炭素体は、原料を木炭化炉で炭化焼成（２００℃〜１０００℃）を行なうことにより、熱分解→木炭化の過程を経て体積を約１０〜２０％以下に減量、含有した金属超微粒子が数千〜数万ＰＰＭに高濃度化する。さらに８００℃〜１８００℃で水蒸気賦活、炭酸ガス等によるガス賦活、あるいは塩化亜鉛や水酸化カリウムなどを添加して焼成する薬剤賦活などにより約１／２以下に減量化し、金属超微粒子を数万〜数十万ＰＰＭの高濃度に濃縮、電気伝導度の極めてすぐれた多孔質炭素体になる。この場合、含浸法により前駆体に分散したＣｒ及びＣｕの金属超微粒子は１００％内部に残ることが発明者らの実験から確かめられており同時に構造体に微細孔（細孔直径１ｎｍ〜１０ｎｍ）が１００ｍ３／１ｎｍ．ｇの細孔容積と１０００ｍ２／ｇを超える比表面積を持った複雑な表面を持った多孔質炭素体となり優れた吸着特性と金属超微粒子の触媒機能を合わせ持った複合材料となることが確かめられた。
【００２６】
以上、上記の炭素化（木炭化）によって、数ｎｍ〜数μの多孔質炭素体に単体もしくは重合した金属酸化物超微粒子を高分散担持させた触媒が極めて容易にかつ低コストで調製可能となる。しかし、ここまでの過程で調製された多孔質炭素体は、微細構造の難黒鉛化炭素体で、無配向の乱層構造の多孔質炭素体であり、さらにこの多孔質炭素体に電気パルスと熱や圧力を加えて成形すると配向性の高い黒鉛構造となることも知見されている。
【００２７】
したがって、触媒となる金属種の選択で触媒としての適用対象は特に限定されず任意にコントロールが可能で、燃料電池用電極触媒、その他触媒機能を有する材料、電磁波吸収性の優れた材料や電子材料、環境浄化材料など新しい機能材料への利用が可能な触媒機能を有した多孔質炭素体を低コストで調製可能となる。
【００２８】
【実施例】
ＣＣＡ処理材をどのように処分するかと言う問題は、いわばリサイクル問題の究極の姿ではないかとも言える。埋め立てにも使えない、燃やすこともままならない廃木材に新たな利用法が見いだせれば、その波及効果は大きい。ＣＣＡ処理木材の特徴は、まず、触媒となる金属超微粒子は、水溶性の薬液の形で含浸させるために、木材の中にクロム（Ｃｒ）や銅（Ｃｕ）が分子レベルの高分散状態で存在する。さらに、その含有量は，木材 １ ｔｏｎ 当たり、Ｃｒで １０５３ｇ、Ｃｕで ４２５ｇ、ヒ素で ４６０ｇ 程度となる。これらの特徴を踏まえて、本発明者らは、このＣＣＡ処理木材を、多孔質炭素体を担体とする金属超微粒子及び金属酸化物超微粒子高分散型の触媒製造の原料として利用することを考えた。一般に、木材の炭素化によって、その重量は約１０〜２０％ となる。したがって、木炭になった状態でＣｒやＣｕの濃度は約５〜１０倍になる。さらに、炭素化の工程で酸素の供給等の燃焼制御処理を施せば、木炭はさらに減量化し、中に留まっているＣｒやＣｕの濃度は自由に調整可能となる。さらに、炭素化の過程で僅かに空気を混入させることで、ＣｒとＣｕの金属超微粒子を金属酸化物超微粒子とすることができるとともに炭素材の減量化も図れる。
【００２９】
こうした処理を施すことで、分子レベルで木材組織の中に高分散している金属超微粒子は、金属酸化物超微粒子となり、多孔質炭素体中に高分散状態で出現する。こういった、触媒機能を有する金属超微粒子の酸化物を担体中に高分散状態を維持して担持する技術はこれまで決定的なものがなく、まだ試行錯誤的に行われている程度である。さらに、触媒として利用後は既に確立されている廃触媒の処理工程に送れば良いだけである。つまり、埋め立ても焼却もできなかったやっかいな産業廃棄物が新たな触媒として役目を持つ上に、その後の処分方法まで決まってしまうということになる。
【００３０】
この方法は、上記の触媒の製造方法の新たな提案である。すなわち、従来の木質廃バイオマス中に、重金属イオンを含む廃液などを含浸させ、それを炭素化することで金属酸化物超微粒子として多孔質炭素体に高分散する手法である。したがって処理に困っている木質廃バイオマスと処理のやっかいな重金属廃液を同時に処理でき、さらにその処理の結果、高付加価値な新規触媒の生産できることになる。さらに、他の金属元素を含浸させることで新たな触媒機能の発現も可能となる。
【００３１】
問題はＣＣＡ処理木材に含まれるヒ素であるが、木炭化９００℃の焼成後約 ２０％のヒ素が残存していたとの報告もあり、この場合は何らかの除去技術の開発が必要になる。しかし、９００℃で昇華しないのであることから、この時点でヒ素は炭素中にもはや元素単体の形で存在しているとは考えられ難く、何らかの難分解性の化合物へと変化している可能性が高い。この点については、焼成後の炭素材を煮沸するなどして、水中へのヒ素の溶出試験などを検討すれば明らかとなる。
【００３２】
以上、上記に示した新たな視点でＣＣＡ処理木材を捉えることで、これまで難題だったＣＣＡ処理木材の処理のすべてに目途が立つと同時に新たな触媒材料に道を開くことになる。
【００３３】
【ＣＣＡ処理木材から創成する電極触媒】
ＣＣＡ処理木材に含有されている金属酸化物Ｃｒ２Ｏ３は脱水素、水素化触媒で、ＣＵ２Ｏ−Ｃｒ２Ｏ３も脱水素、水素化分解、メタノール合成、などの優れたメタノールの水蒸気改質触媒となる。つまり、前述したようにＣＣＡ処理木材中の重金属がそのまま電極触媒に使えることになる。この場合、燃料極の触媒層や空気極の拡散層は、発電効率を向上するために細孔構造を最適化する必要が求められ、三次元的な連通孔を持った多孔性の多孔質導電体を用いることが要件となる。
【００３４】
ダイレクトメタノール燃料電池 （ＤＭＦＣ）の膜−電極接合体の高性能化は触媒層に燃料極側では適度な親水性、逆に空気極側では撥水性を与え、同時に触媒層の三相界面を増大して発電効率をあげること、及び、燃料極側から空気極側へ、燃料のメタノールが浸透するのでこれを抑制する触媒層をいかにつくるかがポイントとなっている。
【００３５】
現在、メタノール等から水素を製造する水蒸気改質触媒は、銅（Ｃｕ）系触媒が高い選択性を示しているが、まだ、その性能が十分に発揮されていない。ＤＭＦＣでは、より低温（２００℃以下）で高い活性を示す触媒が望まれており触媒の熱安定性の向上や銅（Ｃｕ）系触媒に代わる遷移金属触媒の開発が課題となっている。つまり、銅（Ｃｕ）系触媒は、熱安定性が低く、熱処理（シンタリング）による活性劣化が問題となっており、それに対して、８−１０族遷移金属触媒は熱安定性が高い利点はあるが、水蒸気改質の二酸化炭素選択性が著しく低いなどの欠点がある。
【００３６】
そこで本発明は、電解質層の界面積を増大して発電効率あげる金属酸化物超微粒子を高分散させた多孔質炭素体に加え、プロトン伝導性の向上と燃料極側から空気極側へ燃料のメタノールが浸透するのを制御する反応ガス低透過性に膜／電解質一体型を意図して発明されたものである。多孔質炭素体にポリオレフィンポリマーと電解触媒として木材に金属超微粒子含浸、前駆体とした多孔質炭素体金属酸化物超微粒子複合材を調製、その結果、これらは導電性、強誘電性などにすぐれた電極体となることが知見され、フッ素系カチオン交換物質を持った高分子膜と多孔質炭素体が一体的に創成できることが見いだされた。
【００３７】
前記、空気極へのメタノールの到達を制御する機能と集電効率を合わせ持つ電極体によって、多孔質炭素体の細孔内でＣＯと酸素が高効率で反応してＣＯ２になる現象と、Ｃｒ、Ｃｕ触媒、また、有機金属重合触媒や特殊合金を併用することで１００℃の低温でもほぼ１００％のＣＯ→ＣＯ２を実現させ、同時に多孔質炭素体の吸着効果により、ＣＯと酸素を細孔内に濃縮し、担持した触媒に選択的にＣＯ酸化を行わせる作用が発現する。
【００３８】
つまり、電解質にフッ素系カチオン交換物質を持ったポリマ−と触媒を組み合わせた多孔質炭素体と高分子膜複合によるプロトン伝導性の向上、および多孔質炭素体の界面積構造を利用しＣＯ−ＣＯ２の選択的にＣＯ酸化を意図して行うこととした点が本発明の特徴と言える。
本発明に係る多孔質炭素体より成る電極体は、下記の点において優れている。
（１）界面積が極めて増大する。
（２）細孔が三次元的に連通するため流体の透過性が優れる。
（３）多孔質炭素体が導電材料であるためプロトン伝導の導電性が向上する。
（４）ナノポア（１０ｎｍ以下）な構造がＣＯと酸素を細孔内に濃縮し、金属酸化物超微粒子触媒によるＣＯ酸化を効率的に実現する。
（５） 数ナノ未満の分子レベルの金属酸化物超微粒子を多孔質炭素体に高分散化することにより、効率的な触媒活性を生じさせる。
【００３９】
上記の金属酸化物超微粒子触媒とは、周期表で３族から１１族の遷移金属と呼ばれる金属を触媒として用いたもので、有機化合物、有機高分子の合成の触媒として広く利用されている。８−１０族遷移金属触媒面でのメタノール水蒸気改質反応（ＣＨ３ＯＨ＋Ｈ２Ｏ→３Ｈ２＋ＣＯ２）は、メタノ−ル分解（ＣＨ３ＯＨ→２Ｈ２＋ＣＯ）と水性ガスシフト反応（ＣＯ＋Ｈ２Ｏ→ＣＯ２＋ Ｈ２）がカップリングして進行する機構が知られている。この場合、水性シフト反応のステップが律速段階で、そのために系内にＣＯが蓄積する。そのため、８−１０族遷移金属触媒、特に白金族元素面ではＣＯ被毒が起こり水性ガスシフト反応の選択性は著しく低くなることになる。これまで８−１０族遷移金属触媒における水性ガスシフト反応の選択性を向上させる試みがなされているが、いずれも結果において満足すべき値には至っていない。
【００４０】
そこで本発明では、銅（Ｃｕ）系触媒面でメタノールからの中間体のホルムアルデヒドにＨ２Ｏが求核的に負荷するステップを経て進行することに着目した。選択性も高くメタノールからホルムアルデヒドが生成するステップが律速段階であり、ホルムアルデヒド生成以降のステップは速やかに進行し、この反応はホルムアルデヒド生成の段階では金属銅（Ｃｕ）が、一方、ホルムアルデヒドからギ酸メチルあるいはギ酸（あるいはギ酸中間体）を生成する段階では担体の構造が関与することが知見された。つまり、触媒面においてホルムアルデヒド中間体の安定性を上げることにより二酸化炭素選択性の高い触媒となることを見いだした。
【００４１】
【酸化クロムと酸化銅の触媒としての特性】
上記のように、ＣＣＡ処理木材に含有されている金属酸化物超微粒子Ｃｒ２Ｏ３は脱水素、水素化触媒で、Ｃｕ２Ｏ−Ｃｒ２Ｏ３も脱水素、水素化分解、メタノール合成、などの優れたメタノールの水蒸気改質触媒となる。つまり、ＣＣＡ処理木材中のやっかいな重金属がそのまま燃料電池用の電極触媒に使えることになり、多孔質炭素体に金属酸化物超微粒子を高分散状態で担持させた触媒は、触媒性能に加えて細孔構造と表面活性力に優れており、ガス吸着に適したナノポア（１０ｎｍ以下）優れた吸着性能も併せ持つ。また、この多孔質炭素体は優れた導電物質であることから、ＤＭＦＣ用電解質層に触媒として利用することができる。
【００４２】
ＤＭＦＣでは電解質層に燃料極側では適度な親水性、逆に空気極側では撥水性を与え、同時に電解質層の界面積を増大して発電効率をあげること、及び、燃料極側から空気極側へ、燃料のメタノールが浸透するのでこれを抑制することが要点となる。
【００４３】
本発明では、その触媒活性が、金属酸化物超微粒子径や多孔質炭素炭中での分散状態に依存するため、原料を木炭化炭化炉で炭化焼成（２００℃〜８００℃）を制御して行なうことにより、木炭化の過程を経て体積を約１０〜２０％に減容、含有した重金属量が数千〜数万ＰＰＭに高濃度化、さらに８００℃〜１８００℃で水蒸気賦活、炭酸ガス等によるガス賦活にて減容することで金属酸化物超微粒子を数万〜数十万ＰＰＭの高濃度に縮合した、表面に微細なマクロ孔（５０ｎｍ以上）、メソ孔（２〜５０ｎｍ）、ミクロ孔（細孔直径２ｎｍ以下）の複雑な細孔を持った比表面積１０００ｍ２／ｇを超える〜数μの多孔質炭素体を調製した。この方法によって、特殊な方法を必要としないで多孔質炭素体に単体もしくは複合した金属酸化物超微粒子を高分散状態で担持させた電解質触媒が極めて容易にかつ低コストで調製可能となる。
【００４４】
発明者らは、ＣＣＡ処理木材を原料として調整した多孔質炭素体が、ＤＭＦＣの燃料極触媒層や空気極拡散層において、発電効率を向上する細孔構造を最適化する上で、三次元的な連通孔、すなわち多孔性にすぐれ吸着特性と電気伝導性、及び金属酸化物超微粒子の持つ金属触媒の活性力を合わせ持った電解質層を構成することを見いだした。
【００４５】
また、本発明では、多孔質炭素体の微細組織や細孔構造をどれだけ制御可能かにとどまらず金属酸化物超微粒子と電解ポリマーと複合した電極触媒の創製について検討を行なった。その結果、金属酸化物超微粒子による金属触媒を高分散に担持した多孔質炭素体と電解質層としてフッ素系カチオン交換物質を複合化した電解質−膜一体型電極体がＤＭＦＣ用の電解質体に有効であることが判明した。また、この電極体において銅（Ｃｕ）系触媒が二酸化炭素選択性の高い触媒となることを見いだした。
【００４６】
以上本発明の実施の形態と一部実施例を説明したが、本発明は上記に記載した一部の用途に限定したものではなく、木材等天然炭化水素高分子化合物を原料とした触媒の製造とこれらを利用した触媒の概念に広義に係るものである。
【００４７】
【発明の効果】
本発明は、ＣＣＡ処理木材等の金属超微粒子が原子レベルで分散された物を前駆体とし、その後、炭素化過程を経て多孔質炭素体とすることで多孔質炭素体に金属超微粒子や金属酸化物超微粒子を均一かつ高分散させ担持したことを特長とする触媒とその製造方法に関するものである。また、その原料から極めて安価かつ容易に製造可能であり、さらに不均一な金属超微粒子や金属酸化物超微粒子等との複合化、その後の各種モノマー再複合によって、燃料電池等の電極体に適した触媒とすることなどが特徴となる。[0001]
[Industrial applications]
The present invention relates to a catalyst in which ultrafine metal particles or ultrafine metal oxide particles are highly dispersed, a method for producing the same, and a catalyst for a fuel cell.
[0002]
[Prior art]
It is known that metal catalysts exhibit catalytic functions such as oxidation, reduction, hydrolysis, dehydrogenation, and hydrocracking. In addition to platinum (Pt), nickel (Ni), iron (Fe), tungsten (W), and the like are known to have an action of promoting a dehydrogenation reaction from hydrocarbons. It is known that palladium-silver alloys and copper-nickel alloys decompose oxygen monoxide. Iron powder or iron oxide (Fe 2 O 3 ) Is an excellent catalyst as a deoxidizer that absorbs oxygen. In addition, iron oxide (Fe 2 O 3 ) Is known to be an excellent dechlorination catalyst in the process of refining waste plastics.
[0003]
In addition, with the recent increase in awareness of environmental issues, three-way catalysts have been developed as catalysts for clearing automobile exhaust gas, and carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx ) Reacts with oxygen to convert it into carbon dioxide, water and nitrogen. The three-way catalyst includes alumina (Al 2 O 3 ), Magnesium oxide (MgO), silicon dioxide (SiO 2 Noble metal particles such as platinum, rhodium, and palladium are dispersed as catalysts in the compound of (1). In recent years, catalyst materials have been diversified, and porphyrin complexes, metal phthalocyanine compounds, fatty acid metal salt compounds, polymer catalysts based on polyolefins with conductivity, ferroelectricity, etc. have been made. Materials have been applied to new fields such as electronic materials and composite materials.
[0004]
The metal used for the catalyst is a transition metal such as Pt, Pd, Ni, Co, Fe, Cu, V, Mo, Rh, Cr, Ir, Ru, Au, Ag and Ai. 2 O 3 , SiO 2 , CrO 3 , Al 2 O 3 , LiO 2 , TiO 2 , Fe 2 O 3 Metal oxides such as LiCO 3 , Zn, Al, Sn, etc., and those obtained by intentionally polymerizing a plurality of these, and organic-inorganic composite materials such as compounds covalently bonded to organic compounds, metal phthalocyanine compounds, fatty acid metal salt compounds, and porphyrin complexes.
[0005]
In addition, catalysts using these transition metals not only improve the reaction rate, but also are used for controlling the regularity, branched structure, composition, and copolymerization of the resulting compound (copolymerization with not only polyolefins but also polar monomers). It has also been used as a method for creating new materials with controlled functions. These catalysts are generally used in the form of ultrafine metal particles supported on some carrier. The porous materials are the most common among such carriers, and the porous carbon bodies are also frequently used materials.
[0006]
Activated carbon, a representative of porous carbon bodies, is the closest carbon material to us, and is also used industrially for various separation processes, purification, catalysts, solvent recovery, etc. It is used in a wide variety of fields, including purified air and water, and medical adsorbents. This is because of the presence of radicals and surface functional groups present in activated carbon, and the function of the activated carbon itself as an electron transporter is an excellent catalytic function such as redox, halogenation, dehalogenation, dehydrogenation, decomposition, isomerization, and polymerization. Because it has.
[0007]
What is commonly referred to as activated carbon has a wide range of pores, from micropores (pore diameter less than 2 nm) to mesopores (2-50 nm), and even macropores (more than 50 nm), which allows various sizes of pores. Can adsorb substances. The density of a single crystal of graphite carbon is 2.26 g / cm. 3 Whereas, the bulk density of activated carbon made from woody material is 0.2 g / cm 3 ~ 0.4g / cm 3 Is very small because there are many mesopores and macropores in the carbon body. In other words, charcoal or the like fired at around 600 ° C. to 1000 ° C. has an internal surface area occupied by micropores having a radius of 2 nm or less of 100 m? / 1 nm. g, which is very large and has large volume pores.
[0008]
Usually, in the production of activated carbon, it is an issue how much the effective adsorption surface area per unit weight can be increased. On the other hand, depending on the purpose of use, it may be important how to prepare pores having a uniform pore diameter. In particular, in recent years, a porous carbon body has been formed of nitrogen dioxide (NO 2 2.) Attention has been focused on the use as a detoxifying catalyst or a hydrogen gasification catalyst in an electrolyte for a fuel cell. In this case, the performance is evaluated by the surface area per unit volume and surface activity.
[0009]
As an example of the recent use of catalysts, steam reforming of methanol for fuel cells (CH 3 OH + H 2 O → 3H 2 + CO 2 ) There is an electrocatalyst. Fuel cells are attracting attention as clean and simple power generation systems. Since this electrode catalyst can be used under mild conditions due to its catalytic action of performing a dehydrogenation reaction of an organic compound such as methanol, it has attracted attention as a very promising power generation system depending on the production cost of the catalyst.
[0010]
[Problems to be solved by the invention]
An object of the present invention is to provide a porous carbon body-metal catalyst composite material that can be produced at a low cost and that can be used for a wide range of applications, in which a catalyst in which ultrafine metal particles or ultrafine metal oxide particles are highly dispersed in a porous carbon body can be used. Is to do. Another object of the present invention is to provide a catalyst having the above-mentioned characteristics, which is excellent in performance of an electrode catalyst for a fuel cell.
[0011]
[Means for Solving the Problems]
Heretofore, the present inventors have dispersed metal ultrafine particles or metal oxide ultrafine particles using CCA (Cr, Cu, As) chemical-treated wood (hereinafter referred to as CCA-treated wood), an organometallic compound, or the like as a carbon material. We have studied how much the microstructure and pore structure of the porous carbon body can be controlled, and how it is possible to control the three-dimensional structure other than the molecular structure.
From experiments, it has been found that a porous carbon body using a natural hydrocarbon polymer compound such as wood as a precursor has pores ranging from micropores (pore diameter of 2 nm or less) to mesopores (2 to 50 nm) and macropores (50 nm or more). It has been found that it has a wide range of pores and a large specific surface area.
[0012]
The density of the single crystal of graphite carbon is 2.26 g / cm. 3 On the other hand, the bulk density of the porous carbon body made of wood material is 0.2 g / cm 3 ~ 0.4g / cm 3 And very small. This is because there are many mesopores and macropores in the carbon structure. That is, it was confirmed that charcoal and the like fired at around 600 ° C. to 1000 ° C. had an extremely large internal surface area occupied by micropores having a radius of 2 nm or less, and had large-volume pores. In addition, compared to graphite carbon, it has the same fixed carbon ratio and ability as an electron transfer body, and has excellent porous properties, and depending on the purpose of use, it is a porous carbon body that can be utilized in multiple ways. (Table 1). However, there has been no establishment of an industrial production method, so that its use has been limited.
[0013]
[Table 1]
On the other hand, in a methanol reforming / diffusion catalyst in a direct methanol fuel cell (DMFC), a separator and an electrolyte layer for hydrogen reforming of MEA play a major role. Until now, alloy catalysts, which have been regarded as the leading role, are weights (small occlusion amount per unit weight) due to being alloys, deterioration due to repeated occlusion-release (pulverization and structural change of alloys), rare When metals are included, there are many issues, such as securing their prices and resources.
[0015]
In order to solve the above-mentioned problems, the present inventors have made various studies, and as a result, conventional carbon powder preparation and coating of the surface by vacuum deposition of a noble metal, and structuring of a special carbon material and In order to solve the cost increase due to molding, we have found a technology to create a new catalyst in which ultrafine metal particles are highly dispersed at the same time as the production of a porous carbon body using a natural hydrocarbon polymer compound such as waste wood as a precursor.
[0016]
In the present invention, a metal required as a catalyst is made into a metal ion solution, impregnated into wood or a natural hydrocarbon polymer compound, and then highly dispersed and concentrated into ultrafine metal particles or ultrafine metal oxide particles through a carbonization process. It relates to a technology for preparing a catalyst that is a composite of a porous carbon body and a metal ultrafine particle or a metal oxide ultrafine particle in which a metal ultrafine particle is highly dispersed and supported on a porous carbon body manufactured at low temperature, energy saving and low cost. is there.
[0017]
It is up to the development of the production technology of the porous carbon body whether or not the excellent properties of the porous carbon body can be obtained as a catalyst carrier. In other words, the technology for creating a fine-scale catalyst according to the present invention is a new method for producing a catalyst, which is a new method in the fields of general chemical reaction catalysts such as fuel cell electrode catalysts, electronic materials, composite materials, and environmental purification materials. It is an object of the present invention to provide a method for preparing a catalyst, and to produce a composite catalyst of a porous carbon body and ultrafine metal particles or ultrafine metal oxide particles extremely easily and at low cost. At the same time, it will lead to the development of an efficient and environmentally harmful method as one of the waste treatment and harmful heavy metal (waste liquid) treatment.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Heretofore, the present inventors have used wood as a precursor of a porous carbon body to produce a porous carbon body in which ultrafine metal particles are highly dispersed at a molecular level, and have obtained a fine structure of these porous carbon bodies. We have been investigating how much the pore structure and catalyst function can be controlled. As a result, a catalyst in which the porous carbon body according to the present invention is carbonized into a porous carbon body by using wood or an organic compound as a precursor and a metal ultrafine particle or a metal oxide ultrafine particle is composited is energy saving and low cost. And the functionality and characteristics of these catalysts, such as improving conductivity by compounding these catalysts with other polymer electrolyte materials.
[0019]
That is, the present invention relates to a catalyst for carrying metal ultra-fine particles or metal oxide ultra-fine particles in a porous carbon body in a highly dispersed state, wherein an aqueous solution containing metal ions serving as a catalyst is prepared in advance by using a natural hydrocarbon polymer compound such as wood. And impregnated it with wood molecules, such as cellulose (45%), hemicellulose (30%), lignin (25%), and metal molecules, or disperse them inside wood-structured conduits, etc. Alternatively, it can be made into a precursor dispersed in the form of a salt on the order of microns, and then can be easily converted into a porous carbon body through a process of carbonizing these woods by applying heat while controlling air, and furthermore, the carbon content can be easily increased. At the same time as carbonization, the catalyst was found to be a catalyst carrying metal ultrafine particles and metal oxide ultrafine particles uniformly and highly dispersed in a porous carbon body. It may be carried out in accordance with the method.
[0020]
Wood, natural plants, and organic materials used as precursors do not need to be new, and waste wood such as CCA-treated wood that has been subjected to a preservative treatment containing Cr, Cu, and the like, and waste paper and the like Organic substances and organic compounds having permeability are suitable. Among them, CCA-treated wood in which Cr, Cu, etc. are pressure-injected at several to 10 atm by the impregnation method contains heavy metal ions as an organometallic compound at a high concentration of 1053 PPM for Cr and 425 PPM for Cu. (Table 2), and it is suitable to use these heavy metals (chromium and copper), other transition metals, and organic metal waste liquids as raw materials in order to reduce costs.
[0021]
[Table 2]
Further, when preparing the porous carbon body, various kinds of control such as control of regularity / branch structure / composition / copolymerization, such as compounding by combining a new metal species with a metal waste liquid, and compounding with various other polymers. A method of combining the catalytic function of the metal with the porous carbon body can be employed. In this case, the ultrafine metal particles or ultrafine metal oxide particles serving as a catalyst are transition metals such as Pt, Pd, Ni, Co, Fe, Cu, V, Mo, Rh, Cr, Ir, Ru, Au, Ag, and Ai. 2 O 3 , SiO 2 , CrO 3 , Al 2 O 3 , LiO 2 , TiO 2 , Fe 2 O 3 Metal oxides such as LiCO 3 , Zn, Al, Sn, and the like, and mixtures thereof, and organometallic compounds, metal phthalocyanine compounds, fatty acid metal salt compounds, porphyrin complexes, and the like, which are covalently bonded, can be used as raw materials.
[0023]
Cr as a catalyst according to the present invention 2 O 3 And Cu 2 The catalytic activity of O 2 has been studied in detail and is mainly used as a catalyst for hydrogenation or dehydrogenation. Further, Cu 2 O-Cr 2 O 3 Is also used for methanol synthesis, etc., and this catalyst can be prepared relatively easily by using CCA-treated wood as a raw material.
[0024]
Also, in such a binary catalyst, the boundary between two substances often plays an important role, and if the binary catalyst is constituted as ultrafine metal particles or ultrafine metal oxide particles, it will be much more than before. High catalytic activity. From experiments, it has been found that a composite catalyst composed of a porous carbon body made of CCA-treated wood and ultrafine metal oxides functions as a catalyst for hydrogenation or dehydrogenation. Since it depends on the diameter of the ultrafine particles and the state of dispersion in the porous carbon body, the method of producing the porous carbon body such as the relationship with the firing conditions and the carbonization step are important.
[0025]
The porous carbon material to be the catalyst carrier is reduced in volume to about 10 to 20% or less through a process of pyrolysis → wood carbonization by performing carbonization and firing (200 ° C. to 1000 ° C.) of the raw material in a wood carbonization furnace. The concentration of the contained ultrafine metal particles is increased to several thousand to tens of thousands of PPM. Further, at 800 ° C. to 1800 ° C., the volume is reduced to about 以下 or less by steam activation, gas activation by carbon dioxide gas or the like, or chemical activation by adding zinc chloride, potassium hydroxide, or the like, and tens of thousands of ultrafine metal particles are produced. It is concentrated to a high concentration of up to several hundred thousand PPM, and becomes a porous carbon body having extremely excellent electric conductivity. In this case, it has been confirmed from experiments by the inventors that the ultrafine particles of metal of Cr and Cu dispersed in the precursor by the impregnation method remain inside 100%, and at the same time, micropores (pore diameter 1 nm to 10 nm) are formed in the structure. Is 100m 3 / 1 nm. g of pore volume and 1000m 2 It has been confirmed that a porous carbon body having a complex surface having a specific surface area exceeding / g and a composite material having excellent adsorption characteristics and a catalytic function of ultrafine metal particles are obtained.
[0026]
As described above, by the carbonization (carbonization), it is possible to extremely easily and inexpensively prepare a catalyst in which a single or polymerized metal oxide ultrafine particle is highly dispersed and supported on a porous carbon body of several nm to several μm. Become. However, the porous carbon body prepared in the process so far is a non-graphitizable carbon body with a fine structure, a porous carbon body with a non-oriented turbostratic structure, and furthermore, an electric pulse is applied to the porous carbon body. It has also been found that a graphite structure having high orientation can be obtained by molding by applying heat or pressure.
[0027]
Therefore, the target of application as a catalyst is not particularly limited by selecting a metal species to be a catalyst, and can be arbitrarily controlled. Electrode catalysts for fuel cells, other materials having a catalytic function, materials having excellent electromagnetic wave absorption, and electronic materials In addition, a porous carbon body having a catalytic function that can be used for a new functional material such as an environmental purification material can be prepared at low cost.
[0028]
【Example】
The issue of how to dispose of CCA treated materials can be said to be the ultimate form of recycling. If there is a new use for waste wood that cannot be used for landfilling and that cannot be burned, its ripple effect will be great. The characteristic of CCA-treated wood is that, first, ultrafine metal particles as a catalyst are impregnated in the form of a water-soluble chemical solution, so that chromium (Cr) and copper (Cu) are in a highly dispersed state at the molecular level in wood. Exists. Further, the content is about 1053 g for Cr, 425 g for Cu, and about 460 g for arsenic per ton of wood. Based on these characteristics, the present inventors consider using this CCA-treated wood as a raw material for the production of highly dispersed metal ultrafine particles and metal oxide ultrafine catalysts using a porous carbon body as a carrier. Was. Generally, carbonization of wood results in a weight of about 10-20%. Therefore, the concentration of Cr or Cu in the state of charcoal increases about 5 to 10 times. Furthermore, if a combustion control process such as supply of oxygen is performed in the carbonization step, the amount of charcoal is further reduced, and the concentrations of Cr and Cu remaining therein can be freely adjusted. Furthermore, by slightly mixing air in the carbonization process, the metal ultrafine particles of Cr and Cu can be used as the metal oxide ultrafine particles, and the carbon material can be reduced.
[0029]
By performing such a treatment, the metal ultrafine particles highly dispersed in the wood structure at the molecular level become metal oxide ultrafine particles, and appear in the porous carbon body in a highly dispersed state. There is no definitive technique for supporting such a metal ultrafine particle oxide having a catalytic function while maintaining a highly dispersed state in a carrier, and the technique is still performed by trial and error. . Furthermore, after use as a catalyst, it is only necessary to send it to the treatment step of a waste catalyst that has already been established. In other words, troublesome industrial waste that could not be landfilled or incinerated has a role as a new catalyst, and also determines the subsequent disposal method.
[0030]
This method is a new proposal of the above-mentioned method for producing a catalyst. That is, this is a method in which a conventional woody waste biomass is impregnated with a waste liquid containing heavy metal ions and the like, and is carbonized to be highly dispersed as metal oxide ultrafine particles in a porous carbon body. Therefore, it is possible to simultaneously treat woody waste biomass which is in trouble with treatment and heavy metal wastewater which is troublesome to treat, and as a result of the treatment, it is possible to produce a high value-added new catalyst. Furthermore, impregnation with another metal element also enables the development of a new catalytic function.
[0031]
Although the problem is arsenic contained in CCA-treated wood, it has been reported that about 20% of arsenic remained after carbonization at 900 ° C. In this case, it is necessary to develop some removal technology. However, since arsenic does not sublime at 900 ° C., it is unlikely that arsenic is present in carbon at this point in the form of an elemental element, and it may have changed to some hardly decomposable compound. Is high. This point will become clear if a carbon material after calcination is boiled or the like, and an arsenic elution test in water is examined.
[0032]
As described above, capturing CCA-treated wood from the above-described new viewpoints provides a prospect for all of the difficulties in the treatment of CCA-treated wood, and at the same time opens the way to new catalyst materials.
[0033]
[Electrocatalysts created from CCA-treated wood]
Metal oxide Cr2O contained in CCA treated wood 3 Is a dehydrogenation / hydrogenation catalyst, CU 2 O-Cr 2 O 3 It is also an excellent methanol steam reforming catalyst for dehydrogenation, hydrocracking, methanol synthesis, etc. That is, as described above, the heavy metal in the CCA-treated wood can be used as it is for the electrode catalyst. In this case, it is necessary to optimize the pore structure of the catalyst layer of the fuel electrode and the diffusion layer of the air electrode in order to improve the power generation efficiency, and the porous porous conductive layer having three-dimensional communication holes is required. The requirement is to use the body.
[0034]
Improving the performance of the membrane-electrode assembly of the direct methanol fuel cell (DMFC) provides the catalyst layer with appropriate hydrophilicity on the fuel electrode side and water repellency on the air electrode side, and at the same time increases the three-phase interface of the catalyst layer The key points are to increase the power generation efficiency and to create a catalyst layer that suppresses the penetration of methanol as fuel from the fuel electrode side to the air electrode side.
[0035]
At present, as for a steam reforming catalyst for producing hydrogen from methanol or the like, a copper (Cu) -based catalyst shows high selectivity, but its performance has not yet been sufficiently exhibited. In DMFC, a catalyst exhibiting high activity at a lower temperature (200 ° C. or lower) is desired, and improvement of the thermal stability of the catalyst and development of a transition metal catalyst that replaces a copper (Cu) -based catalyst have been issues. In other words, copper (Cu) -based catalysts have low thermal stability and have a problem of activity degradation due to heat treatment (sintering). On the other hand, group 8-10 transition metal catalysts have the advantage of high thermal stability. However, there are drawbacks such as the remarkably low carbon dioxide selectivity of steam reforming.
[0036]
Accordingly, the present invention provides a porous carbon body in which metal oxide ultrafine particles are highly dispersed to increase the interfacial area of the electrolyte layer to increase power generation efficiency, to improve proton conductivity and to transfer fuel from the fuel electrode side to the air electrode side. It was invented with an intention of a membrane / electrolyte integrated type having a low reaction gas permeability for controlling the permeation of methanol. A porous carbon body is impregnated with a polyolefin polymer and wood as an electrocatalyst. Ultrafine metal particles are impregnated into wood, and a porous carbon body metal oxide ultrafine particle composite material is prepared as a precursor. As a result, they have excellent conductivity, ferroelectricity, etc. It has been found that a polymer membrane having a fluorine-based cation exchange material and a porous carbon body can be integrally formed.
[0037]
By the electrode body having the function of controlling the arrival of methanol to the air electrode and the current collection efficiency, CO and oxygen react with high efficiency in the pores of the porous carbon body, and CO 2 And the use of Cr, Cu catalysts, organometallic polymerization catalysts, and special alloys together make it possible to achieve almost 100% CO → CO even at low temperatures of 100 ° C. 2 At the same time, the effect of concentrating CO and oxygen in the pores by the adsorption effect of the porous carbon body and causing the supported catalyst to selectively oxidize CO is exhibited.
[0038]
In other words, the improvement of proton conductivity by the composite of a porous carbon body and a polymer membrane in which a polymer having a fluorinated cation exchange material in the electrolyte is combined with a catalyst, and CO-CO utilizing the interfacial area structure of the porous carbon body 2 This is a feature of the present invention in that the selective oxidation of CO is performed.
The electrode body made of the porous carbon body according to the present invention is excellent in the following points.
(1) The interfacial area is extremely increased.
(2) Since the pores communicate three-dimensionally, the permeability of the fluid is excellent.
(3) Since the porous carbon body is a conductive material, the conductivity of proton conduction is improved.
(4) The nanopore (10 nm or less) structure concentrates CO and oxygen in the pores, and efficiently realizes CO oxidation by the metal oxide ultrafine particle catalyst.
(5) Efficient catalytic activity is produced by highly dispersing metal oxide ultrafine particles having a molecular level of less than several nanometers in a porous carbon body.
[0039]
The metal oxide ultrafine particle catalyst uses a metal called a transition metal of Group 3 to Group 11 in the periodic table as a catalyst, and is widely used as a catalyst for synthesizing organic compounds and organic polymers. Methanol steam reforming reaction (CH 3 OH + H 2 O → 3H 2 + CO 2 ) Is methanol decomposition (CH 3 OH → 2H 2 + CO) and water gas shift reaction (CO + H 2 O → CO 2 + H 2 Is known. In this case, the step of the aqueous shift reaction is the rate-limiting step, so that CO accumulates in the system. For this reason, CO poisoning occurs on the group 8-10 transition metal catalyst, particularly on the platinum group element side, and the selectivity of the water gas shift reaction is significantly reduced. Attempts have been made to improve the selectivity of the water gas shift reaction in Group 8-10 transition metal catalysts, but none of the results have been satisfactory.
[0040]
Therefore, in the present invention, an intermediate formaldehyde from methanol is converted to H on a copper (Cu) -based catalyst surface. 2 It was noted that O proceeds through a nucleophilic loading step. The step of generating formaldehyde from methanol is the rate-determining step with high selectivity, and the steps after formaldehyde generation proceed promptly. In this step, metallic copper (Cu) is formed at the stage of formaldehyde generation, while methyl formate or formaldehyde is converted from formaldehyde. It has been found that the stage of producing formic acid (or formic acid intermediate) involves the structure of the carrier. In other words, it has been found that a catalyst having high selectivity for carbon dioxide can be obtained by increasing the stability of the formaldehyde intermediate on the catalyst surface.
[0041]
[Characteristics of chromium oxide and copper oxide as catalysts]
As described above, metal oxide ultrafine particles Cr contained in CCA-treated wood 2 O 3 Is a dehydrogenation / hydrogenation catalyst, Cu 2 O-Cr 2 O 3 It is also an excellent methanol steam reforming catalyst for dehydrogenation, hydrocracking, methanol synthesis, etc. In other words, the troublesome heavy metals in the CCA-treated wood can be used as they are as electrode catalysts for fuel cells, and the catalysts in which metal oxide ultrafine particles are supported in a highly dispersed state on a porous carbon body, in addition to the catalytic performance, It has excellent pore structure and surface activity, and also has excellent adsorption performance of nanopores (10 nm or less) suitable for gas adsorption. In addition, since this porous carbon body is an excellent conductive material, it can be used as a catalyst in the electrolyte layer for DMFC.
[0042]
The DMFC provides the electrolyte layer with appropriate hydrophilicity on the fuel electrode side and water repellency on the air electrode side, and at the same time, increases the interfacial area of the electrolyte layer to increase power generation efficiency. Therefore, it is important to suppress the penetration of methanol as fuel.
[0043]
In the present invention, since the catalytic activity depends on the diameter of the ultrafine metal oxide particles and the state of dispersion in the porous carbon charcoal, the raw material is controlled by carbonizing and firing (200 ° C to 800 ° C) in a wood carbonizing furnace. By carrying out the process, the volume is reduced to about 10 to 20% through the carbonization process, the amount of heavy metals contained is increased to several thousand to tens of thousands of PPM, and steam activation at 800 ° C to 1800 ° C, carbon dioxide gas, etc. Ultra-fine particles of metal oxides are condensed to a high concentration of tens of thousands to hundreds of thousands of PPM by reducing the volume by gas activation by the method described above, and fine macro pores (50 nm or more), meso pores (2 to 50 nm), micro Specific surface area 1000m with complicated pores (pore diameter 2nm or less) 2 / G of a porous carbon body of more than / g was prepared. According to this method, it is possible to prepare an electrolyte catalyst in which a single or composite metal oxide ultrafine particle is supported in a highly dispersed state on a porous carbon body without requiring a special method, very easily and at low cost.
[0044]
The present inventors have found that a porous carbon body prepared from CCA-treated wood as a raw material has a three-dimensional structure in optimizing a pore structure that improves power generation efficiency in a fuel electrode catalyst layer and an air electrode diffusion layer of a DMFC. It has been found that an electrolyte layer having excellent communication pores, that is, having excellent adsorption properties and electrical conductivity, having excellent porosity, and having the activity of a metal catalyst possessed by the metal oxide ultrafine particles.
[0045]
Further, in the present invention, not only how much the microstructure and the pore structure of the porous carbon body can be controlled, but also the creation of an electrode catalyst in which metal oxide ultrafine particles are combined with an electrolytic polymer was studied. As a result, an electrolyte-membrane integrated electrode body in which a porous carbon body carrying a metal catalyst with ultra-fine metal oxide particles in a highly dispersed manner and a fluorinated cation exchange material as an electrolyte layer is effective as an electrolyte body for DMFC. It turned out to be. In addition, they have found that a copper (Cu) -based catalyst is a catalyst having high carbon dioxide selectivity in this electrode body.
[0046]
Although the embodiments and some examples of the present invention have been described above, the present invention is not limited to some of the uses described above, and the production of a catalyst using a natural hydrocarbon polymer compound such as wood as a raw material And the concept of a catalyst utilizing these in a broad sense.
[0047]
【The invention's effect】
The present invention provides a precursor obtained by dispersing metal ultrafine particles such as CCA-treated wood at the atomic level as a precursor, and then forming a porous carbon body through a carbonization process, thereby forming the metal ultrafine particles or the metal on the porous carbon body. The present invention relates to a catalyst characterized in that ultrafine oxide particles are uniformly and highly dispersed and supported, and a method for producing the same. In addition, it is extremely inexpensive and easy to manufacture from its raw materials, and is suitable for electrodes such as fuel cells by compounding with non-uniform metal ultrafine particles or metal oxide ultrafine particles, and then recombining various monomers. It is characterized in that it is used as a catalyst.
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