JP2021058848A - Catalyst for pyrolysis of hydrocarbon and carbon nanotube and hydrogen production method using the same - Google Patents
Catalyst for pyrolysis of hydrocarbon and carbon nanotube and hydrogen production method using the same Download PDFInfo
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- 239000003054 catalyst Substances 0.000 title claims abstract description 59
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 title claims abstract description 55
- 239000001257 hydrogen Substances 0.000 title claims abstract description 55
- 229910052739 hydrogen Inorganic materials 0.000 title claims abstract description 55
- 229930195733 hydrocarbon Natural products 0.000 title claims abstract description 51
- 150000002430 hydrocarbons Chemical class 0.000 title claims abstract description 51
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 39
- 229910021393 carbon nanotube Inorganic materials 0.000 title claims abstract description 33
- 239000002041 carbon nanotube Substances 0.000 title claims abstract description 33
- 239000004215 Carbon black (E152) Substances 0.000 title claims abstract description 25
- 238000004519 manufacturing process Methods 0.000 title claims description 22
- 238000000197 pyrolysis Methods 0.000 title abstract 2
- 239000002245 particle Substances 0.000 claims abstract description 141
- 229910052595 hematite Inorganic materials 0.000 claims abstract description 73
- 239000011019 hematite Substances 0.000 claims abstract description 73
- LIKBJVNGSGBSGK-UHFFFAOYSA-N iron(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Fe+3].[Fe+3] LIKBJVNGSGBSGK-UHFFFAOYSA-N 0.000 claims abstract description 73
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 57
- 229910052761 rare earth metal Inorganic materials 0.000 claims abstract description 19
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 10
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 6
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 28
- 238000005979 thermal decomposition reaction Methods 0.000 claims description 19
- 239000010941 cobalt Substances 0.000 claims description 5
- 229910017052 cobalt Inorganic materials 0.000 claims description 5
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 5
- 229910052779 Neodymium Inorganic materials 0.000 claims description 4
- 229910052684 Cerium Inorganic materials 0.000 claims description 3
- 229910052772 Samarium Inorganic materials 0.000 claims description 3
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 claims description 3
- 230000004048 modification Effects 0.000 claims description 3
- 238000012986 modification Methods 0.000 claims description 3
- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 claims description 3
- KZUNJOHGWZRPMI-UHFFFAOYSA-N samarium atom Chemical compound [Sm] KZUNJOHGWZRPMI-UHFFFAOYSA-N 0.000 claims description 3
- 229910052706 scandium Inorganic materials 0.000 claims description 3
- SIXSYDAISGFNSX-UHFFFAOYSA-N scandium atom Chemical compound [Sc] SIXSYDAISGFNSX-UHFFFAOYSA-N 0.000 claims description 3
- 229910052777 Praseodymium Inorganic materials 0.000 claims description 2
- 150000002431 hydrogen Chemical class 0.000 claims description 2
- PUDIUYLPXJFUGB-UHFFFAOYSA-N praseodymium atom Chemical compound [Pr] PUDIUYLPXJFUGB-UHFFFAOYSA-N 0.000 claims description 2
- 239000007864 aqueous solution Substances 0.000 description 26
- 239000007789 gas Substances 0.000 description 26
- 229910052598 goethite Inorganic materials 0.000 description 23
- AEIXRCIKZIZYPM-UHFFFAOYSA-M hydroxy(oxo)iron Chemical compound [O][Fe]O AEIXRCIKZIZYPM-UHFFFAOYSA-M 0.000 description 23
- 238000006243 chemical reaction Methods 0.000 description 18
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 15
- 150000001875 compounds Chemical class 0.000 description 15
- 239000013078 crystal Substances 0.000 description 13
- 238000005245 sintering Methods 0.000 description 11
- 230000007423 decrease Effects 0.000 description 10
- 229910052742 iron Inorganic materials 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 9
- 238000000354 decomposition reaction Methods 0.000 description 9
- 238000000034 method Methods 0.000 description 7
- 239000000725 suspension Substances 0.000 description 7
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 6
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 6
- 239000007900 aqueous suspension Substances 0.000 description 6
- 229910052799 carbon Inorganic materials 0.000 description 6
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 5
- 230000032683 aging Effects 0.000 description 5
- 239000011248 coating agent Substances 0.000 description 5
- 238000000576 coating method Methods 0.000 description 5
- 238000010438 heat treatment Methods 0.000 description 5
- 238000007254 oxidation reaction Methods 0.000 description 5
- 230000001603 reducing effect Effects 0.000 description 5
- 239000007787 solid Substances 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- DIZPMCHEQGEION-UHFFFAOYSA-H aluminium sulfate (anhydrous) Chemical compound [Al+3].[Al+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O DIZPMCHEQGEION-UHFFFAOYSA-H 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 238000000921 elemental analysis Methods 0.000 description 4
- 230000001590 oxidative effect Effects 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 3
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 3
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 3
- 239000011790 ferrous sulphate Substances 0.000 description 3
- 235000003891 ferrous sulphate Nutrition 0.000 description 3
- 229910000359 iron(II) sulfate Inorganic materials 0.000 description 3
- 229910052749 magnesium Inorganic materials 0.000 description 3
- 239000011777 magnesium Substances 0.000 description 3
- 229910052759 nickel Inorganic materials 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 229910000029 sodium carbonate Inorganic materials 0.000 description 3
- 229910052727 yttrium Inorganic materials 0.000 description 3
- OBOSXEWFRARQPU-UHFFFAOYSA-N 2-n,2-n-dimethylpyridine-2,5-diamine Chemical compound CN(C)C1=CC=C(N)C=N1 OBOSXEWFRARQPU-UHFFFAOYSA-N 0.000 description 2
- 208000005156 Dehydration Diseases 0.000 description 2
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 239000003513 alkali Substances 0.000 description 2
- VSCWAEJMTAWNJL-UHFFFAOYSA-K aluminium trichloride Chemical compound Cl[Al](Cl)Cl VSCWAEJMTAWNJL-UHFFFAOYSA-K 0.000 description 2
- -1 ammonium aluminate Chemical class 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 description 2
- 239000001569 carbon dioxide Substances 0.000 description 2
- 238000004140 cleaning Methods 0.000 description 2
- 229940044175 cobalt sulfate Drugs 0.000 description 2
- 229910000361 cobalt sulfate Inorganic materials 0.000 description 2
- KTVIXTQDYHMGHF-UHFFFAOYSA-L cobalt(2+) sulfate Chemical compound [Co+2].[O-]S([O-])(=O)=O KTVIXTQDYHMGHF-UHFFFAOYSA-L 0.000 description 2
- 230000018044 dehydration Effects 0.000 description 2
- 238000006297 dehydration reaction Methods 0.000 description 2
- 229910001873 dinitrogen Inorganic materials 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 2
- 239000011261 inert gas Substances 0.000 description 2
- SZVJSHCCFOBDDC-UHFFFAOYSA-N iron(II,III) oxide Inorganic materials O=[Fe]O[Fe]O[Fe]=O SZVJSHCCFOBDDC-UHFFFAOYSA-N 0.000 description 2
- 229910052746 lanthanum Inorganic materials 0.000 description 2
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 description 2
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 2
- 229910052750 molybdenum Inorganic materials 0.000 description 2
- 239000011733 molybdenum Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- BWHMMNNQKKPAPP-UHFFFAOYSA-L potassium carbonate Chemical compound [K+].[K+].[O-]C([O-])=O BWHMMNNQKKPAPP-UHFFFAOYSA-L 0.000 description 2
- 230000002265 prevention Effects 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 description 2
- BNGXYYYYKUGPPF-UHFFFAOYSA-M (3-methylphenyl)methyl-triphenylphosphanium;chloride Chemical compound [Cl-].CC1=CC=CC(C[P+](C=2C=CC=CC=2)(C=2C=CC=CC=2)C=2C=CC=CC=2)=C1 BNGXYYYYKUGPPF-UHFFFAOYSA-M 0.000 description 1
- ATRRKUHOCOJYRX-UHFFFAOYSA-N Ammonium bicarbonate Chemical compound [NH4+].OC([O-])=O ATRRKUHOCOJYRX-UHFFFAOYSA-N 0.000 description 1
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910002651 NO3 Inorganic materials 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 1
- 229910021536 Zeolite Inorganic materials 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 229910001854 alkali hydroxide Inorganic materials 0.000 description 1
- 150000008044 alkali metal hydroxides Chemical class 0.000 description 1
- 150000001447 alkali salts Chemical class 0.000 description 1
- ANBBXQWFNXMHLD-UHFFFAOYSA-N aluminum;sodium;oxygen(2-) Chemical compound [O-2].[O-2].[Na+].[Al+3] ANBBXQWFNXMHLD-UHFFFAOYSA-N 0.000 description 1
- 239000001099 ammonium carbonate Substances 0.000 description 1
- 235000012501 ammonium carbonate Nutrition 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 229910002090 carbon oxide Inorganic materials 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- GVPFVAHMJGGAJG-UHFFFAOYSA-L cobalt dichloride Chemical compound [Cl-].[Cl-].[Co+2] GVPFVAHMJGGAJG-UHFFFAOYSA-L 0.000 description 1
- UFMZWBIQTDUYBN-UHFFFAOYSA-N cobalt dinitrate Chemical compound [Co+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O UFMZWBIQTDUYBN-UHFFFAOYSA-N 0.000 description 1
- 229910001981 cobalt nitrate Inorganic materials 0.000 description 1
- 238000000748 compression moulding Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 230000001186 cumulative effect Effects 0.000 description 1
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 229960002089 ferrous chloride Drugs 0.000 description 1
- 238000005755 formation reaction Methods 0.000 description 1
- 238000004817 gas chromatography Methods 0.000 description 1
- 238000010191 image analysis Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000003112 inhibitor Substances 0.000 description 1
- 150000002505 iron Chemical class 0.000 description 1
- NMCUIPGRVMDVDB-UHFFFAOYSA-L iron dichloride Chemical compound Cl[Fe]Cl NMCUIPGRVMDVDB-UHFFFAOYSA-L 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 150000002681 magnesium compounds Chemical class 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
- 125000004430 oxygen atom Chemical group O* 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 229910000027 potassium carbonate Inorganic materials 0.000 description 1
- CHWRSCGUEQEHOH-UHFFFAOYSA-N potassium oxide Chemical compound [O-2].[K+].[K+] CHWRSCGUEQEHOH-UHFFFAOYSA-N 0.000 description 1
- 229910001950 potassium oxide Inorganic materials 0.000 description 1
- KVOIJEARBNBHHP-UHFFFAOYSA-N potassium;oxido(oxo)alumane Chemical compound [K+].[O-][Al]=O KVOIJEARBNBHHP-UHFFFAOYSA-N 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000002407 reforming Methods 0.000 description 1
- 239000012266 salt solution Substances 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 229910001388 sodium aluminate Inorganic materials 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- 229910052718 tin Inorganic materials 0.000 description 1
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 229910052723 transition metal Inorganic materials 0.000 description 1
- 150000003624 transition metals Chemical class 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
- 229910052720 vanadium Inorganic materials 0.000 description 1
- GPPXJZIENCGNKB-UHFFFAOYSA-N vanadium Chemical compound [V]#[V] GPPXJZIENCGNKB-UHFFFAOYSA-N 0.000 description 1
- 239000010457 zeolite Substances 0.000 description 1
Images
Abstract
Description
本発明は、炭化水素の熱分解用触媒並びにそれを用いたカーボンナノチューブ及び水素製造方法に関し、特に、ヘマタイト粒子を含む触媒並びにそれを用いたカーボンナノチューブ及び水素製造方法に関する。 The present invention relates to a catalyst for thermal decomposition of hydrocarbons and a method for producing carbon nanotubes and hydrogen using the same, and more particularly to a catalyst containing hematite particles and a method for producing carbon nanotubes and hydrogen using the same.
従来から、炭化水素を原料ガスとして、これを炉内で加熱することにより分解してカーボンナノチューブや水素を製造することが知られている。また、上記カーボンナノチューブや水素の製造のために、種々の触媒が用いられることも知られている。例えば特許文献１には、カーボンナノチューブ製造用触媒であって、主成分として鉄及びアルミニウムを含む触媒が開示されている。また、特許文献１では、当該触媒の成分として、マグネシウムやコバルト、ニッケル、クロム、マンガン、モリブデン、タングステン、バナジウム、錫又は銅から選ばれる少なくとも１種の遷移金属を含んでもよい旨が記載されている。 Conventionally, it has been known that hydrocarbons are used as raw material gases and decomposed by heating them in a furnace to produce carbon nanotubes and hydrogen. It is also known that various catalysts are used for the production of the carbon nanotubes and hydrogen. For example, Patent Document 1 discloses a catalyst for producing carbon nanotubes, which contains iron and aluminum as main components. Further, Patent Document 1 describes that the catalyst component may contain at least one transition metal selected from magnesium, cobalt, nickel, chromium, manganese, molybdenum, tungsten, vanadium, tin and copper. There is.
この他に、特許文献２には、カーボンナノチューブ成長用板状触媒として、鉄、コバルト、カルシウム、ニッケル及びモリブデンからなる群から選択された１成分以上と、マンガン、アルミニウム、マグネシウム及びケイ素からなる群から選択された１成分以上とを含む触媒が開示されている。さらに、特許文献３には、カーボンナノチューブ合成用触媒として、触媒活性種がコバルト、鉄及びニッケルからなる群より選ばれる１種類以上を含有し、第一の担持体としてマグネシウム及び／又はマグネシウム化合物と、第二の担持体として酸化珪素、酸化アルミニウム、ゼオライト及び酸化チタンからなる群より選ばれる１種類以上とを含有する触媒が開示されている。 In addition to this, Patent Document 2 describes a group consisting of one or more components selected from the group consisting of iron, cobalt, calcium, nickel and molybdenum, and a group consisting of manganese, aluminum, magnesium and silicon as a plate-like catalyst for growing carbon nanotubes. A catalyst containing one or more components selected from the above is disclosed. Further, Patent Document 3 contains one or more catalytically active species selected from the group consisting of cobalt, iron and nickel as a catalyst for synthesizing carbon nanotubes, and magnesium and / or a magnesium compound as a first carrier. , A catalyst containing at least one selected from the group consisting of silicon oxide, aluminum oxide, zeolite and titanium oxide as a second carrier is disclosed.
上述のように、特許文献１〜３に開示されるような種々の触媒が知られているものの、未だ原料ガスである炭化水素に対する反応効率をさらに向上し、得られるカーボンナノチューブ及び水素の収率をさらに向上できる触媒が求められている。 As described above, although various catalysts as disclosed in Patent Documents 1 to 3 are known, the reaction efficiency with hydrocarbons as a raw material gas is still further improved, and the yields of carbon nanotubes and hydrogen obtained can be obtained. There is a demand for a catalyst that can further improve the above.
本発明は、前記の問題に鑑みてなされたものであり、その目的は、炭化水素の熱分解効率をさらに向上できる触媒を得て、高い効率でカーボンナノチューブ及び水素を製造できるようにすることにある。 The present invention has been made in view of the above problems, and an object of the present invention is to obtain a catalyst capable of further improving the thermal decomposition efficiency of hydrocarbons so that carbon nanotubes and hydrogen can be produced with high efficiency. is there.
前記の目的を達成するために、本発明では、触媒をヘマタイト粒子で構成し、アルミニウム及び希土類元素をヘマタイト粒子に含有させた。ここで言うヘマタイト粒子とは、Ｘ線回折（ＸＲＤ）により分析した結晶相が、ヘマタイトが主相である粒子のことである。 In order to achieve the above object, in the present invention, the catalyst is composed of hematite particles, and aluminum and rare earth elements are contained in the hematite particles. The hematite particles referred to here are particles in which the crystal phase analyzed by X-ray diffraction (XRD) has hematite as the main phase.
具体的に、本発明に係る触媒は、炭化水素の熱分解用触媒であって、ヘマタイト粒子を含み、前記ヘマタイト粒子は、粒子中の全鉄（Ｆｅ）元素に対して０．１〜３ｍｏｌ％の希土類元素を含有し、粒子中の全Ｆｅ元素に対して５〜５５ｍｏｌ％のアルミニウム（Ａｌ）元素を含有することを特徴とする。 Specifically, the catalyst according to the present invention is a catalyst for thermal decomposition of hydrocarbons and contains hematite particles, and the hematite particles are 0.1 to 3 mol% with respect to the total iron (Fe) element in the particles. It is characterized by containing 5 to 55 mol% of aluminum (Al) elements with respect to all Fe elements in the particles.
本発明に係る触媒によると、炭化水素の熱分解効率を向上できて、高い効率で炭化水素からカーボンナノチューブ及び水素を製造できる。特に、本発明に係る触媒では、ヘマタイト粒子が全Ｆｅ元素に対して５〜５５ｍｏｌ％のＡｌ元素を含んでいるため、炭化水素の分解効率を向上できる。Ａｌの含有量が５ｍｏｌ％未満の場合には、炭化水素の分解効率が低くなり、カーボンナノチューブ及び水素の生成量が低下し、一方、５５ｍｏｌ％を超える場合には、ヘマタイト粒子全体のうち、Ｆｅの占める割合が低下するため、やはり炭化水素の分解効率が低くなり、カーボンナノチューブ及び水素の生成量が低下する。さらに、本発明に係る触媒では、ヘマタイト粒子が焼結防止効果向上のために全Ｆｅ元素に対して０．１〜３ｍｏｌ％の希土類元素を含有しているため、ヘマタイト粒子の焼結を防止できて焼結による触媒効果の低下を防止できる。希土類元素の含有量が０．１ｍｏｌ％未満の場合には、焼結防止効果が十分には得られず、炭化水素の熱分解反応時に粒子が肥大化し、炭化水素の分解効率が低減し、一方、３ｍｏｌ％を超える場合には、粒子と炭化水素との接触効率が低減し、やはり炭化水素の分解効率が低減することとなる。 According to the catalyst according to the present invention, the thermal decomposition efficiency of hydrocarbons can be improved, and carbon nanotubes and hydrogen can be produced from hydrocarbons with high efficiency. In particular, in the catalyst according to the present invention, since the hematite particles contain 5 to 55 mol% of Al element with respect to the total Fe element, the decomposition efficiency of hydrocarbon can be improved. When the Al content is less than 5 mol%, the decomposition efficiency of hydrocarbons becomes low and the amount of carbon nanotubes and hydrogen produced decreases, while when it exceeds 55 mol%, Fe in the whole hematite particles As the proportion of hydrogen decreases, the decomposition efficiency of hydrocarbons also decreases, and the amount of carbon nanotubes and hydrogen produced decreases. Further, in the catalyst according to the present invention, hematite particles contain 0.1 to 3 mol% of rare earth elements with respect to all Fe elements in order to improve the sintering prevention effect, so that hematite particles can be prevented from sintering. It is possible to prevent a decrease in the catalytic effect due to sintering. When the content of rare earth elements is less than 0.1 mol%, the effect of preventing sintering is not sufficiently obtained, the particles are enlarged during the thermal decomposition reaction of hydrocarbons, and the decomposition efficiency of hydrocarbons is reduced, while the decomposition efficiency of hydrocarbons is reduced. If it exceeds 3, mol%, the contact efficiency between the particles and the hydrocarbon is reduced, and the decomposition efficiency of the hydrocarbon is also reduced.
本発明に係る触媒において、前記ヘマタイト粒子は、粒子中の全Ｆｅ元素に対して１０ｍｏｌ％未満のコバルト（Ｃｏ）元素を含有することが好ましい。 In the catalyst according to the present invention, the hematite particles preferably contain less than 10 mol% of cobalt (Co) element with respect to all Fe elements in the particles.
このようにすると、ヘマタイト粒子の還元性を促進できる。 In this way, the reducing property of the hematite particles can be promoted.
本発明に係る触媒において、前記希土類元素は、スカンジウム（Ｓｃ）、イットリウム（Ｙ）、ランタン（Ｌａ）、セリウム（Ｃｅ）、プラセオジウム（Ｐｒ）、ネオジム（Ｎｄ）及びサマリウム（Ｓｍ）から選択される少なくとも１種であってもよい。 In the catalyst according to the present invention, the rare earth element is selected from scandium (Sc), ittrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd) and samarium (Sm). It may be at least one kind.
本発明に係る触媒において、前記ヘマタイト粒子は、紡錘状であり、平均長軸径が１０００ｎｍ以下であることが好ましく、平均短軸径が２００ｎｍ以下であることが好ましく、また、平均短軸径に対する平均長軸径の比率（平均長軸径／平均短軸径）が２〜９であることが好ましい。 In the catalyst according to the present invention, the hematite particles are spindle-shaped, and the average major axis diameter is preferably 1000 nm or less, the average minor axis diameter is preferably 200 nm or less, and the average minor axis diameter is relative to the average minor axis diameter. The ratio of the average major axis diameter (average major axis diameter / average minor axis diameter) is preferably 2 to 9.
これらのようにすると、炭化水素とヘマタイト粒子との接触性を向上できて、触媒による炭化水素の熱分解効率を向上することができる。 By doing so, the contact property between the hydrocarbon and the hematite particles can be improved, and the thermal decomposition efficiency of the hydrocarbon by the catalyst can be improved.
本発明に係る触媒において、前記ヘマタイト粒子は、ＢＥＴ比表面積が１０ｍ２／ｇ以上であることが好ましい。 In the catalyst according to the present invention, the hematite particles preferably have a BET specific surface area of 10 m 2 / g or more.
このようにすると、炭化水素とヘマタイト粒子との接触性を向上できて、触媒による炭化水素の熱分解効率を向上することができる。 In this way, the contact property between the hydrocarbon and the hematite particles can be improved, and the thermal decomposition efficiency of the hydrocarbon by the catalyst can be improved.
本発明に係るカーボンナノチューブ及び水素製造方法は、上記本発明に係る触媒のいずれかを用いて炭化水素を熱分解することを含むことを特徴とする。 The carbon nanotube and hydrogen production method according to the present invention is characterized by comprising thermally decomposing hydrocarbons using any of the catalysts according to the present invention.
本発明に係るカーボンナノチューブ及び水素製造方法によると、上記本発明に係る触媒を用いるため、炭化水素の熱分解効率を向上できるので、高い効率でカーボンナノチューブ及び水素を製造できる。 According to the method for producing carbon nanotubes and hydrogen according to the present invention, since the catalyst according to the present invention is used, the thermal decomposition efficiency of hydrocarbons can be improved, so that carbon nanotubes and hydrogen can be produced with high efficiency.
本発明に係るカーボンナノチューブ及び水素製造方法において、前記炭化水素は少なくともメタンを含むことが好ましく、また、前記カーボンナノチューブ及び水素はメタン直接改質により得られることが好ましい。この場合、メタン直接改質を利用するため、水素及びカーボンナノチューブの他に、一酸化炭素や二酸化炭素が生成されないので好ましい。 In the carbon nanotube and hydrogen production method according to the present invention, the hydrocarbon preferably contains at least methane, and the carbon nanotube and hydrogen are preferably obtained by direct methane modification. In this case, since direct methane modification is used, carbon monoxide and carbon dioxide are not generated in addition to hydrogen and carbon nanotubes, which is preferable.
本発明に係る触媒並びにそれを用いたカーボンナノチューブ及び水素製造方法によると、炭化水素の熱分解効率を向上できて、高い効率で炭化水素からカーボンナノチューブ及び水素を製造できる。 According to the catalyst according to the present invention and the carbon nanotubes and hydrogen production method using the catalyst, the thermal decomposition efficiency of hydrocarbons can be improved, and carbon nanotubes and hydrogen can be produced from hydrocarbons with high efficiency.
以下、本発明を実施するための形態を図面に基づいて説明する。以下の好ましい実施形態の説明は、本質的に例示に過ぎず、本発明、その適用方法或いはその用途を制限することを意図するものではない。 Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. The following description of preferred embodiments is merely exemplary and is not intended to limit the invention, its application methods or its uses.
本発明の一実施形態に係る触媒は、炭化水素の熱分解用触媒であり、特にヘマタイト粒子を含むものである。本実施形態に係る触媒は、例えば当該触媒と炭化水素ガスとを加熱炉内で接触させて炭化水素ガスの熱分解を促進して、固体炭素と水素とを生成させるために用いられる。特に、炭化水素ガスとしてメタンガスを直接固体炭素と水素とに熱分解するメタン直接改質（ＤＭＲ）反応を利用して水素合成を行うのに用いられることが好ましい。但し、メタンガスは、必ずしも純メタンである必要はなく、少なくともメタンを含むガスであり、好ましくはメタンを主成分とするガスである。前記反応では、メタンガスを触媒と共に加熱することによりメタンが分解されて水素ガスと固体炭素が生成される。この反応では二酸化炭素等の酸化炭素ガスが発生しない点で有用である。通常、固体炭素は触媒粒子の表面に積層した形態で生成され、その形状や結晶性は触媒をはじめとする反応条件にもよるが、少なくとも一部がカーボンナノチューブなどの繊維状の結晶性炭素を生成することが可能である。従って、本発明の一実施形態に係る触媒は、カーボンナノチューブ及び水素製造方法に好適に利用可能である。 The catalyst according to one embodiment of the present invention is a catalyst for thermal decomposition of hydrocarbons, and particularly contains hematite particles. The catalyst according to the present embodiment is used, for example, to bring the catalyst and a hydrocarbon gas into contact with each other in a heating furnace to promote thermal decomposition of the hydrocarbon gas to generate solid carbon and hydrogen. In particular, it is preferably used for hydrogen synthesis by utilizing a methane direct reforming (DMR) reaction in which methane gas is directly thermally decomposed into solid carbon and hydrogen as a hydrocarbon gas. However, the methane gas does not necessarily have to be pure methane, but is a gas containing at least methane, preferably a gas containing methane as a main component. In the reaction, methane is decomposed by heating methane gas together with a catalyst to produce hydrogen gas and solid carbon. This reaction is useful in that carbon oxide gas such as carbon dioxide is not generated. Normally, solid carbon is generated in the form of being laminated on the surface of catalyst particles, and its shape and crystallinity depend on the reaction conditions including the catalyst, but at least a part of it is fibrous crystalline carbon such as carbon nanotubes. It is possible to generate. Therefore, the catalyst according to one embodiment of the present invention can be suitably used for carbon nanotubes and hydrogen production methods.
本実施形態に係る上記ヘマタイト粒子は、粒子中の全Ｆｅ元素に対して０．１〜３ｍｏｌ％の、好ましくは０．３〜２ｍｏｌ％、さらに好ましくは０．５〜１．５ｍｏｌ％の希土類元素を含有し、粒子中の全Ｆｅ元素に対して５〜５５ｍｏｌ％、好ましくは１５〜５５ｍｏｌ％、さらに好ましくは２５〜５５ｍｏｌ％のＡｌ元素を含有している。 The hematite particles according to the present embodiment are 0.1 to 3 mol%, preferably 0.3 to 2 mol%, more preferably 0.5 to 1.5 mol% of rare earth elements with respect to the total Fe elements in the particles. , 5 to 55 mol%, preferably 15 to 55 mol%, more preferably 25 to 55 mol% of Al elements with respect to the total Fe elements in the particles.
希土類元素は、粒子同士の焼結防止及び酸素原子の引き抜きによる急激なヘマタイトの還元防止のために含有されており、その含有量は上記の通りであるが、粒子中の全Ｆｅ元素に対して０．１ｍｏｌ％未満の場合には、焼結防止効果が十分でなく、炭化水素の熱分解反応時に粒子が焼結・肥大化して、水素生成量が低減する。また、粒子中の全Ｆｅ元素に対して３ｍｏｌ％を超える場合には、粒子と炭化水素ガスとの接触性が悪化して、水素生成量が低減する。 Rare earth elements are contained to prevent sintering between particles and to prevent rapid reduction of hematite due to extraction of oxygen atoms. The content is as described above, but for all Fe elements in the particles. If it is less than 0.1 mol%, the effect of preventing sintering is not sufficient, and the particles are sintered and enlarged during the thermal decomposition reaction of the hydrocarbon, and the amount of hydrogen produced is reduced. Further, when it exceeds 3 mol% with respect to the total Fe elements in the particles, the contact property between the particles and the hydrocarbon gas deteriorates, and the amount of hydrogen produced decreases.
Ａｌ元素は、還元時のＦｅ元素移動による焼結を防止するために含有されており、その含有量は上記の通りであるが、粒子中の全Ｆｅ元素に対して５ｍｏｌ％未満の場合には、炭化水素ガスの分解効率が低くなり、水素生成量が低減する。また、粒子中の全Ｆｅ元素に対して５５ｍｏｌ％を超える場合には、ヘマタイト粒子全体のうち、主触媒であるＦｅ元素の占める割合が低下するため水素生成量が低減する。Ａｌ元素はＦｅ元素と密接している方が好ましく、ヘマタイト粒子内に固溶されていることが特に好ましい。 The Al element is contained to prevent sintering due to the transfer of the Fe element during reduction, and the content thereof is as described above, but when it is less than 5 mol% with respect to the total Fe element in the particles, the Al element is contained. , The decomposition efficiency of hydrocarbon gas is lowered, and the amount of hydrogen produced is reduced. When it exceeds 55 mol% with respect to the total Fe elements in the particles, the proportion of the Fe element, which is the main catalyst, in the whole hematite particles decreases, so that the amount of hydrogen produced decreases. The Al element is preferably in close contact with the Fe element, and is particularly preferably dissolved in the hematite particles.
本実施形態に係る触媒では、以上の通り、ヘマタイト粒子中に炭化水素の熱分解反応に好適な量の希土類元素及びＡｌ元素を含有しているため、炭化水素の熱分解効率を向上できて、高い効率で炭化水素からカーボンナノチューブ及び水素を製造することができる。 As described above, in the catalyst according to the present embodiment, since the hematite particles contain an amount of rare earth elements and Al elements suitable for the thermal decomposition reaction of hydrocarbons, the thermal decomposition efficiency of hydrocarbons can be improved. Carbon nanotubes and hydrogen can be produced from hydrocarbons with high efficiency.
さらに、本実施形態において、上記ヘマタイト粒子は、粒子の還元性促進のために、粒子中の全Ｆｅ元素に対して１０ｍｏｌ％未満のＣｏ元素を含有することが好ましい。 Further, in the present embodiment, the hematite particles preferably contain less than 10 mol% of Co elements with respect to the total Fe elements in the particles in order to promote the reducing property of the particles.
本実施形態において、ヘマタイト粒子の形状は紡錘状であり、平均長軸径が１０００ｎｍ以下であり、好ましくは５００ｎｍ以下である。また、ヘマタイト粒子の平均短軸径は２００ｎｍ以下であり、好ましくは１００ｎｍ以下である。ヘマタイト粒子の平均短軸径に対する平均長軸径の比率（平均長軸径／平均短軸径）は２〜９である。平均長軸径及び短軸径は小さい程良く、従って下限は特に限定されないが工業的製造性の観点からは平均長軸径は３０ｎｍ程度、平均短軸径は５ｎｍ程度を下限とすることが適当である。一方、平均長軸径が１０００ｎｍ、平均短軸径が２００ｎｍを超えると、粒子が大きくなり、炭化水素ガスとの接触性が悪化するため、目的の水素生成量が得られ難くなる。 In the present embodiment, the hematite particles have a spindle shape and an average major axis diameter of 1000 nm or less, preferably 500 nm or less. The average minor axis diameter of the hematite particles is 200 nm or less, preferably 100 nm or less. The ratio of the average major axis diameter to the average minor axis diameter of the hematite particles (average major axis diameter / average minor axis diameter) is 2-9. The smaller the average major axis diameter and minor axis diameter, the better. Therefore, the lower limit is not particularly limited, but from the viewpoint of industrial manufacturability, it is appropriate that the average major axis diameter is about 30 nm and the average minor axis diameter is about 5 nm. Is. On the other hand, when the average major axis diameter exceeds 1000 nm and the average minor axis diameter exceeds 200 nm, the particles become large and the contact with the hydrocarbon gas deteriorates, so that it becomes difficult to obtain the desired amount of hydrogen produced.
本実施形態において、ヘマタイト粒子のＢＥＴ比表面積は、１０ｍ２／ｇ以上であり、好ましくは２０ｍ２／ｇ以上である。ＢＥＴ比表面積が１０ｍ２／ｇ未満では、粒子が大きくなり、炭化水素ガスとの接触性が悪化するため、目的の水素生成量が得られ難くなる。 In the present embodiment, the BET specific surface area of the hematite particles is 10 m 2 / g or more, preferably 20 m 2 / g or more. If the BET specific surface area is less than 10 m 2 / g, the particles become large and the contact with the hydrocarbon gas deteriorates, so that it becomes difficult to obtain the desired amount of hydrogen produced.
以下に本発明に係る触媒の製造方法の一実施形態について説明する。本実施形態に係るヘマタイト粒子は、紡錘状ゲータイト粒子を非還元性雰囲気下で加熱処理をすることによって得られる。紡錘状ゲータイト粒子は、まず紡錘状ゲータイト種晶粒子を生成し、該種晶粒子の表面にゲータイト層を成長させることによって得られる。 An embodiment of the method for producing a catalyst according to the present invention will be described below. The hematite particles according to the present embodiment are obtained by heat-treating spindle-shaped goethite particles in a non-reducing atmosphere. Spindle-shaped goethite particles are obtained by first producing spindle-shaped goethite seed crystal particles and growing a goethite layer on the surface of the seed crystal particles.
具体的に、まず、紡錘状ゲータイト種晶粒子を得るためには、炭酸アルカリ水溶液と水酸化アルカリ水溶液との混合アルカリ水溶液を、第一鉄塩水溶液と反応させて第一鉄含有沈殿物を含む水懸濁液を生成する。次に、当該水懸濁液を非酸化性雰囲気下において熟成させた後に、該水懸濁液中に酸素含有ガスを通気して酸化反応させることによって紡錘状ゲータイト種晶粒子が得られる。なお、必要に応じて、上記混合アルカリ水溶液を第一鉄塩水溶液に加えてＣｏ化合物水溶液と反応させてもよい。上記熟成は、非酸化性雰囲気下の前記懸濁液を通常８０℃以下の温度範囲で行うのが好ましい。熟成時の温度が８０℃を超える場合には、生成物にマグネタイトが混在する場合がある。非酸化性雰囲気とするには、前記懸濁液の反応容器内に不活性ガス（窒素ガスなど）又は還元性ガス（水素ガスなど）を通気すればよい。 Specifically, first, in order to obtain spindle-shaped gateite seed crystal particles, a mixed alkaline aqueous solution of an alkaline carbonate aqueous solution and an alkaline hydroxide aqueous solution is reacted with a ferrous salt aqueous solution to contain a ferrous-containing precipitate. Produce an aqueous suspension. Next, after aging the aqueous suspension in a non-oxidizing atmosphere, spindle-shaped goethite seed crystal particles are obtained by aerating an oxygen-containing gas into the aqueous suspension to cause an oxidation reaction. If necessary, the mixed alkaline aqueous solution may be added to the ferrous salt aqueous solution and reacted with the Co compound aqueous solution. The aging is preferably carried out by subjecting the suspension in a non-oxidizing atmosphere in a temperature range of usually 80 ° C. or lower. If the temperature at the time of aging exceeds 80 ° C., magnetite may be mixed in the product. To create a non-oxidizing atmosphere, an inert gas (nitrogen gas or the like) or a reducing gas (hydrogen gas or the like) may be aerated in the reaction vessel of the suspension.
上記紡錘状ゲータイト種晶粒子の生成反応において、第一鉄塩水溶液としては、硫酸第一鉄水溶液、塩化第一鉄水溶液等を使用することができる。これらは単独で又は必要に応じ２種以上混合して用いられる。また、紡錘状ゲータイト種晶粒子の生成反応において使用される炭酸アルカリ水溶液としては、炭酸ナトリウム水溶液、炭酸カリウム水溶液、炭酸アンモニウム水溶液等を使用でき、前記水酸化アルカリ水溶液としては、水酸化ナトリウム、水酸化カリウム等が使用できる。これらはそれぞれ単独で又は必要に応じ２種以上混合して用いられる。また、紡錘状ゲータイト種晶粒子の生成反応において、Ｃｏ化合物としては、硫酸コバルト、塩化コバルト、硝酸コバルト等を使用することができる。これらは単独で又は必要に応じ２種以上混合して用いられる。Ｃｏ化合物水溶液は、酸化反応を行う前の熟成されている第一鉄含有沈殿物を含む懸濁液に添加される。 In the reaction for producing spindle-shaped gateite seed crystal particles, a ferrous sulfate aqueous solution, a ferrous chloride aqueous solution, or the like can be used as the ferrous salt aqueous solution. These are used alone or in admixture of two or more as required. Further, as the aqueous alkali carbonate solution used in the reaction for producing spindle-shaped gateite seed crystal particles, an aqueous solution of sodium carbonate, an aqueous solution of potassium carbonate, an aqueous solution of ammonium carbonate or the like can be used, and the aqueous solution of alkali hydroxide includes sodium hydroxide or water. Potassium oxide etc. can be used. These are used alone or in admixture of two or more as required. Further, in the reaction for producing spindle-shaped goethite seed crystal particles, cobalt sulfate, cobalt chloride, cobalt nitrate or the like can be used as the Co compound. These are used alone or in admixture of two or more as required. The Co compound aqueous solution is added to the suspension containing the ferrous-containing precipitate that has been aged before the oxidation reaction.
紡錘状ゲータイト種晶粒子を得た後に粒子表面にゲータイト層を成長させるために、まず、紡錘状ゲータイト種晶粒子懸濁液に、炭酸アルカリ水溶液と水酸化アルカリ水溶液との混合アルカリ水溶液を、第一鉄塩水溶液及びＡｌ化合物水溶液と反応させて第一鉄含有沈殿物を含む水懸濁液を得る。次に、該水懸濁液を非酸化性雰囲気下において熟成させた後に、該水懸濁液中に酸素含有ガスを通気して酸化反応させる。これによって、紡錘状ゲータイト種晶粒子表面にゲータイト層を成長できる。 In order to grow a gateite layer on the particle surface after obtaining spindle-shaped gateite seed crystal particles, first, a mixed alkaline aqueous solution of an alkaline carbonate aqueous solution and an alkaline hydroxide aqueous solution was added to the spindle-shaped gateite seed crystal particle suspension. It is reacted with an aqueous iron salt solution and an aqueous Al compound solution to obtain an aqueous suspension containing a ferrous precipitate. Next, after aging the aqueous suspension in a non-oxidizing atmosphere, an oxygen-containing gas is aerated in the aqueous suspension to cause an oxidation reaction. As a result, a goethite layer can be grown on the surface of the spindle-shaped goethite seed crystal particles.
上記ゲータイト層の成長反応において、Ａｌ化合物としては、硫酸アルミニウム、塩化アルミニウム、硝酸アルミニウム等の酸性塩、アルミン酸ナトリウム、アルミン酸カリウム、アルミン酸アンモニウム等のアルカリ酸塩を使用することができる。これらは単独で又は必要に応じ２種以上混合して用いられる。Ａｌ化合物の添加量は、最終生成物である紡錘状ヘマタイト粒子中の全Ｆｅ元素に対してＡｌ元素が５〜５５ｍｏｌ％含有されるように調整される。上述のように、ヘマタイト粒子中の全Ｆｅ元素に対してＡｌ元素の含有量が５ｍｏｌ％未満の場合には、炭化水素ガスの分解効率が低減し、水素生成量が低減する。また、ヘマタイト粒子中の全Ｆｅ元素に対してＡｌ元素の含有量が５５ｍｏｌ％を超える場合には、粒子全体のうち、主触媒成分であるＦｅ元素の含有割合が低下するため、炭化水素ガスの分解効率が低減し、水素生成量が低減する。 In the growth reaction of the gateite layer, as the Al compound, an acid salt such as aluminum sulfate, aluminum chloride and aluminum nitrate, and an alkali salt such as sodium aluminate, potassium aluminate and ammonium aluminate can be used. These are used alone or in admixture of two or more as required. The amount of the Al compound added is adjusted so that the Al element is contained in an amount of 5 to 55 mol% with respect to the total Fe elements in the spindle-shaped hematite particles which are the final products. As described above, when the content of the Al element is less than 5 mol% with respect to the total Fe elements in the hematite particles, the decomposition efficiency of the hydrocarbon gas is reduced and the amount of hydrogen produced is reduced. Further, when the content of the Al element exceeds 55 mol% with respect to the total Fe elements in the hematite particles, the content ratio of the Fe element, which is the main catalyst component, in the whole particles decreases, so that the hydrocarbon gas Decomposition efficiency is reduced and the amount of hydrogen produced is reduced.
上記ゲータイト層の成長反応の後、紡錘状ヘマタイト粒子を得るための加熱脱水処理に先立って焼結防止のために、まず、上記のようにして得られた紡錘状ゲータイト粒子に対して、焼結防止剤により前記紡錘状ゲータイト粒子表面を被覆処理する。焼結防止剤としては、希土類元素の化合物を用いる。希土類元素の化合物としては、スカンジウム、イットリウム、ランタン、セリウム、プラセオジウム、ネオジム、サマリウム等の１種又は２種以上の化合物が好適であり、前記希土類元素の塩化物、硫酸塩、硝酸塩等が使用できる。その使用量は、最終生成物である紡錘状ヘマタイト粒子中の全Ｆｅに対して希土類元素が０．１〜３ｍｏｌ％含有されるように調整される。ヘマタイト粒子中の全Ｆｅ元素に対して希土類元素の含有量が０．１ｍｏｌ％未満の場合には、焼結防止効果が十分でなく、水素生成反応時に粒子が肥大化し、水素生成量が低減する。また、ヘマタイト粒子中の全Ｆｅ元素に対して希土類元素の含有量が３ｍｏｌ％を超える場合には、粒子と炭化水素ガスとの接触性が悪化し、水素生成量が低減する。 After the growth reaction of the goethite layer, in order to prevent sintering prior to the heat dehydration treatment for obtaining spindle-shaped hematite particles, first, the spindle-shaped goethite particles obtained as described above are sintered. The surface of the spindle-shaped goethite particles is coated with an inhibitor. As the anti-sintering agent, a compound of a rare earth element is used. As the rare earth element compound, one or more compounds such as scandium, yttrium, lanthanum, cerium, placeodium, neodymium, and samarium are suitable, and the rare earth element chloride, sulfate, nitrate, and the like can be used. .. The amount used is adjusted so that the rare earth element is contained in an amount of 0.1 to 3 mol% with respect to the total Fe in the spindle-shaped hematite particles which are the final products. When the content of the rare earth element is less than 0.1 mol% with respect to the total Fe elements in the hematite particles, the sintering prevention effect is not sufficient, the particles are enlarged during the hydrogen production reaction, and the hydrogen production amount is reduced. .. Further, when the content of the rare earth element exceeds 3 mol% with respect to the total Fe elements in the hematite particles, the contact property between the particles and the hydrocarbon gas is deteriorated, and the amount of hydrogen produced is reduced.
上記被覆処理において、前記希土類元素の化合物に加えて前記ゲータイト成長反応で用いたＡｌ化合物を用いて被覆処理を行ってもよい。なお、希土類元素及びＡｌ化合物の被覆処理方法は、常法として用いられる乾式又は湿式のいずれの方法でもよいが、好ましくは湿式での被覆処理方法が用いられる。 In the coating treatment, the coating treatment may be performed using the Al compound used in the goethite growth reaction in addition to the compound of the rare earth element. The coating treatment method for the rare earth element and the Al compound may be either a dry method or a wet method used as a conventional method, but a wet coating treatment method is preferably used.
被覆処理の後に、非還元性雰囲気において加熱脱水処理を行うことでヘマタイト粒子が得られる。加熱温度は、３００〜１０００℃の範囲であることが好ましく、３００℃未満の場合は、粒子内に水分が多く残存し、炭化水素の熱分解による水素生成時に粒子の焼結を促進させる。一方、加熱温度が１０００℃を超えると粒子の肥大化が進み、水素生成量が低減する。 After the coating treatment, hematite particles are obtained by performing a heat dehydration treatment in a non-reducing atmosphere. The heating temperature is preferably in the range of 300 to 1000 ° C., and if it is less than 300 ° C., a large amount of water remains in the particles, which promotes sintering of the particles during hydrogen generation by thermal decomposition of hydrocarbons. On the other hand, when the heating temperature exceeds 1000 ° C., the particles become enlarged and the amount of hydrogen produced decreases.
ヘマタイト粒子は、例えばＮａ２ＳＯ４といった不純物塩除去のために洗浄するのが好ましい。特に硫黄成分は炭化水素の熱分解による水素生成量を低下させるため、少ない程好ましい。具体的にはＳ元素が粒子中の全Ａｌ元素に対して５ｍｏｌ％以下であることが好ましい。Ｓ元素を効率良く洗浄する方法としては、ｐＨを上げて洗浄することが挙げられる。具体的なｐＨとしては、８〜１１の間でＡｌ元素が溶出しない範囲で高い程好ましい。 Hematite particles are preferably washed to remove impurity salts such as Na 2 SO 4. In particular, the sulfur component is preferable because it reduces the amount of hydrogen produced by the thermal decomposition of hydrocarbons. Specifically, it is preferable that the S element is 5 mol% or less with respect to the total Al element in the particles. As a method for efficiently cleaning the S element, cleaning by raising the pH can be mentioned. As a specific pH, the higher the pH is, the more preferable it is between 8 and 11 as long as the Al element does not elute.
以下に、本発明に係る触媒並びにそれを用いたカーボンナノチューブ及び水素製造方法を詳細に説明するための実施例を示す。まず、実施例１に係るヘマタイト粒子の製造方法について説明する。 Hereinafter, examples for explaining in detail the catalyst according to the present invention and the carbon nanotubes and hydrogen production method using the catalyst will be shown. First, a method for producing hematite particles according to Example 1 will be described.
＜ゲータイト粒子の生成反応＞
１５．６ｍｏｌの炭酸ナトリウムと、１０．６ｍｏｌの水酸化ナトリウムを含む混合アルカリ水溶液３０Ｌを気泡塔の中に投入し、窒素ガスを通気しながら５０℃に調整した。次いで１２．６ｍｏｌのＦｅ２＋を含む硫酸第一鉄水溶液２０Ｌと０．７ｍｏｌのＣｏ２＋を含む硫酸コバルト水溶液１Ｌ（全Ｆｅに対しＣｏ換算で５．５ｍｏｌ％に該当する。）とを上記混合アルカリ水溶液に添加し、上記条件でさらに５時間熟成（Ｃｏ添加時期の全熟成時間に対する比率４０％）した後、空気を通気しながら、８時間酸化反応を行ってゲータイト粒子を生成させてゲータイト種晶粒子を含む懸濁液を得た。
<Goethite particle formation reaction>
30 L of a mixed alkaline aqueous solution containing 15.6 mol of sodium carbonate and 10.6 mol of sodium hydroxide was put into a bubble column, and the temperature was adjusted to 50 ° C. while aerating nitrogen gas. Next, 20 L of a ferrous sulfate aqueous solution containing 12.6 mol of Fe 2+ and 1 L of a cobalt sulfate aqueous solution containing 0.7 mol of Co 2+ (corresponding to 5.5 mol% in terms of Co with respect to the total Fe) were added to the above mixed alkali. After being added to an aqueous solution and aged for another 5 hours under the above conditions (40% of the total aging time at the time of adding Co), an oxidation reaction was carried out for 8 hours while aerating air to generate gateite particles to generate gateite seed crystals. A suspension containing particles was obtained.
＜ゲータイト粒子の成長反応＞
次いで、前記懸濁液の入った気泡塔に８．０ｍｏｌの炭酸ナトリウムと、６．３ｍｏｌの水酸化ナトリウムと、１．１ｍｏｌのＡｌ３＋を含む硫酸アルミニウムとを含む混合水溶液１０Ｌを投入し、窒素ガスを通気しながら５０℃に調整した。さらに６．３ｍｏｌのＦｅ２＋を含む硫酸第一鉄水溶液３．５Ｌを気泡塔中に投入して上記条件で０．５時間熟成した後、空気を通気しながら、２時間酸化反応を行ってゲータイト粒子を成長させ、ゲータイト粒子を含む懸濁液を得た。その後、フィルタープレスで電気伝導度１００μＳ／ｃｍまで水洗を行ってプレスケーキを得た。
<Growth reaction of goethite particles>
Next, 10 L of a mixed aqueous solution containing 8.0 mol of sodium carbonate, 6.3 mol of sodium hydroxide, and 1.1 mol of aluminum sulfate containing Al 3+ was put into the bubble column containing the suspension, and nitrogen was added. The temperature was adjusted to 50 ° C. while aerating the gas. Further, 3.5 L of ferrous sulfate aqueous solution containing 6.3 mol of Fe 2+ was put into the bubble column and aged for 0.5 hours under the above conditions, and then an oxidation reaction was carried out for 2 hours while aerating air to goethite. The particles were grown to give a suspension containing goethite particles. Then, it was washed with water to an electric conductivity of 100 μS / cm with a filter press to obtain a press cake.
＜ヘマタイトの製造条件＞
次いで、上記のようにして得られたゲータイト粒子７７０ｇ（Ｆｅとして８．７ｍｏｌ）を含有するプレスケーキを１５Ｌの水中に十分に分散させた後、当該分散液に、前記ゲータイト粒子中の全Ｆｅに対しＡｌとして２．５ｍｏｌ％に該当する硫酸アルミニウムを含む硫酸アルミニウム水溶液と０．１Ｍの水酸化ナトリウム水溶液を、ｐＨ９に調整しながら添加した。その後、前記ゲータイト粒子中の全Ｆｅに対しＹ（イットリウム）として０．５ｍｏｌ％に該当する塩化イットリウムを含む塩化イットリウム水溶液と０．１Ｍの水酸化ナトリウム水溶液を、ｐＨ９に調整しながら添加した。その後フィルタープレスで水洗し、得られたプレスケーキを圧縮成型機を用いて孔径４ｍｍの成型板で押し出し成型して１２０℃で乾燥してＹ化合物が被覆されたゲータイト粒子成型物を得た。Ｙ化合物が被覆されたゲータイト粒子を、空気中において６６０℃で加熱脱水してＹ化合物を含有するヘマタイト粒子を得た。その後、ヘマタイト粒子を水洗し、得られたケーキを１２０℃で乾燥した後、カッターミルで粉砕し、実施例１のヘマタイト粒子（粉末）を得た。
<Manufacturing conditions for hematite>
Next, a press cake containing 770 g of goethite particles (8.7 mol as Fe) obtained as described above was sufficiently dispersed in 15 L of water, and then the dispersion liquid was added to all Fe in the goethite particles. On the other hand, an aluminum sulfate aqueous solution containing aluminum sulfate corresponding to 2.5 mol% as Al and a 0.1 M sodium hydroxide aqueous solution were added while adjusting the pH to 9. Then, an aqueous yttrium chloride solution containing 0.5 mol% of yttrium chloride as Y (yttrium) and a 0.1 M aqueous sodium hydroxide solution were added to the total Fe in the goethite particles while adjusting the pH to 9. Then, it was washed with water by a filter press, and the obtained press cake was extruded by a molding plate having a pore size of 4 mm using a compression molding machine and dried at 120 ° C. to obtain a goethite particle molded product coated with a Y compound. The goethite particles coated with the Y compound were heated and dehydrated in air at 660 ° C. to obtain hematite particles containing the Y compound. Then, the hematite particles were washed with water, the obtained cake was dried at 120 ° C., and then pulverized with a cutter mill to obtain hematite particles (powder) of Example 1.
上記実施例１と同様にして、一部の製造条件を変更して実施例２〜１７及び比較例１〜４のヘマタイト粒子を得た。実施例１〜１７及び比較例１〜４におけるゲータイト粒子の生成反応、ゲータイト粒子の成長反応及びヘマタイト粒子の製造条件について、それぞれ以下の表１〜３に示す。なお、実施例２〜１７及び比較例１〜４において、表１〜３に示す実施例１との差異以外は、実施例１と同一の条件を用いた。 In the same manner as in Example 1 above, some production conditions were changed to obtain hematite particles of Examples 2 to 17 and Comparative Examples 1 to 4. The reaction for producing goethite particles, the reaction for growing goethite particles, and the conditions for producing hematite particles in Examples 1 to 17 and Comparative Examples 1 to 4 are shown in Tables 1 to 3 below, respectively. In Examples 2 to 17 and Comparative Examples 1 to 4, the same conditions as in Example 1 were used except for the difference from Example 1 shown in Tables 1 to 3.
＜ヘマタイト粒子の特性分析＞
実施例８のヘマタイト粒子の粒子形態を電子顕微鏡にて観察した。その写真を図１に示す。図１に示すように、実施例８のヘマタイト粒子は、紡錘状の粒子であり、概ねその粒径は、平均長軸径が１３４ｎｍ、平均短軸径が２４ｎｍであり、平均長軸径／平均短軸径は５．６であった。実施例３のヘマタイトの電子顕微鏡でのヘマタイト粒子の元素分析から算出したＮｄ／Ｆｅ、Ａｌ／Ｆｅ、Ｃｏ／Ｆｅはそれぞれ１．１、６．０、４．０であり、ＸＲＦから算出した値とほぼ同じであり、各元素はヘマタイト粒子内あるいは表面上に存在している。
<Characteristic analysis of hematite particles>
The particle morphology of the hematite particles of Example 8 was observed with an electron microscope. The photograph is shown in FIG. As shown in FIG. 1, the hematite particles of Example 8 are spindle-shaped particles, and their particle sizes are approximately 134 nm in average major axis diameter and 24 nm in average minor axis diameter, and average major axis diameter / average. The minor axis diameter was 5.6. Nd / Fe, Al / Fe, and Co / Fe calculated from the elemental analysis of hematite particles with the hematite electron microscope of Example 3 were 1.1, 6.0, and 4.0, respectively, and the values calculated from XRF. Each element is present in or on the surface of hematite particles.
また、各実施例及び比較例のヘマタイト粒子に対して、Ｘ線回折（ＸＲＤ）（Ｄ８ ＡＤＶＡＮＣＥ、ＢＲＵＫＥＲ製）で集中法により粒子の結晶相を分析し、さらに、走査型蛍光Ｘ線（ＸＲＦ）分析装置（ＺＳＸ ＰｒｉｍｕｓＩＩ、株式会社Ｒｉｇａｋｕ製）を用いて元素分析を行った。元素分析により得られた粒子中の各元素の含有量から粒子中のＳ／Ａｌ、Ｙ／Ｆｅ、Ｎｄ／Ｆｅ、Ｃｏ／Ｆｅ、Ａｌ／Ｆｅの各元素の比率を算出した。電子顕微鏡の観察及び元素分析は、多機能電子顕微鏡（ＪＥＭ−Ｆ２００、日本電子株式会社製）エネルギー分散形Ｘ線分光器（ＥＤＳ、日本電子株式会社製）を用いた。平均長軸径及び平均短軸径の測定は、画像解析式粒度分布測定ソフトウェア（Ｍａｃ−Ｖｉｅｗ、株式会社マウンテック製）を用いて各２００点以上の粒子から算出した。ＢＥＴ比表面積は、全自動ガス吸着測定装置（ａｕｔｏｓｏｒｂ、カンタクローム社製）で測定した。それらの結果を下記表４に示す。 Further, for the hematite particles of each example and comparative example, the crystal phase of the particles was analyzed by a concentrated method by X-ray diffraction (XRD) (D8 ADVANCE, manufactured by BRUKER), and further, scanning fluorescent X-ray (XRF) Elemental analysis was performed using an analyzer (ZSX PrimusII, manufactured by Rigaku Co., Ltd.). From the content of each element in the particles obtained by elemental analysis, the ratio of each element of S / Al, Y / Fe, Nd / Fe, Co / Fe, and Al / Fe in the particles was calculated. For the observation and elemental analysis of the electron microscope, a multifunctional electron microscope (JEM-F200, manufactured by JEOL Ltd.) and an energy dispersive X-ray spectrometer (EDS, manufactured by JEOL Ltd.) were used. The average major axis diameter and the average minor axis diameter were calculated from 200 or more particles each using image analysis type particle size distribution measurement software (Mac-View, manufactured by Mountech Co., Ltd.). The BET specific surface area was measured with a fully automatic gas adsorption measuring device (autosorb, manufactured by Kantachrome). The results are shown in Table 4 below.
さらに、各実施例及び比較例のヘマタイト粒子を触媒として用いた場合において、炭化水素の熱分解により得られる水素生成量を測定した。具体的に、まず周長０．４８ｍの回転反応部（レトルト）を用いたバッチ式回転炉に、３ｇの各実施例及び比較例のいずれかのヘマタイト粒子を触媒として予め投入した。その後、不活性雰囲気で回転炉を５．６７ｒｐｍで回転させながら１時間程度で昇温し、７００℃で不活性ガスからメタンを含む１３Ａガスに切り替えてガス流量を２Ｌ／ｍｉｎとして１時間反応を行うことによって、ＤＭＲにより水素及びカーボンナノチューブを含む固体炭素を生成した。回転炉の出口における排気ガスを、マイクロガスクロマトグラフィー装置（ジーエルサイエンス株式会社製）を使用し、出口水素濃度から１時間の積算水素生成量を算出した。その結果も表４に示す。 Furthermore, when the hematite particles of each Example and Comparative Example were used as a catalyst, the amount of hydrogen produced by the thermal decomposition of hydrocarbons was measured. Specifically, first, 3 g of hematite particles of any of the Examples and Comparative Examples were charged in advance into a batch type rotary furnace using a rotary reaction unit (retort) having a circumference of 0.48 m as a catalyst. After that, the temperature was raised in about 1 hour while rotating the rotary furnace at 5.67 rpm in an inert atmosphere, and the reaction was carried out for 1 hour at 700 ° C. by switching from the inert gas to 13A gas containing methane and setting the gas flow rate to 2 L / min. By doing so, the DMR produced solid carbon containing hydrogen and carbon nanotubes. For the exhaust gas at the outlet of the rotary furnace, a micro gas chromatography device (manufactured by GL Sciences Co., Ltd.) was used, and the cumulative hydrogen production amount for one hour was calculated from the outlet hydrogen concentration. The results are also shown in Table 4.
表４に示すように、各実施例及び比較例の粒子はヘマタイト相を有するヘマタイト粒子であり、大半はヘマタイト相のみからなるヘマタイト粒子であったが、実施例５、６、１１、１７及び比較例１は、ヘマタイト相が主相であって一部マグネタイト相が含まれていた。また、表４に示すように、各実施例では、粒子中の全Ｆｅ元素に対するＹ元素の比率（Ｙ／Ｆｅ）又は粒子中の全Ｆｅ元素に対するＮｄ元素の比率（Ｎｄ／Ｆｅ）が０．１〜３ｍｏｌ％であり、且つ粒子中の全Ｆｅ元素に対するＡｌ元素の比率（Ａｌ／Ｆｅ）が５〜５５ｍｏｌ％であることが確認された。一方、各比較例では、Ｙ／Ｆｅ及びＡｌ／Ｆｅの少なくとも一方が上記数値範囲外であった。 As shown in Table 4, the particles of each Example and Comparative Example were hematite particles having a hematite phase, and most of them were hematite particles consisting only of a hematite phase. In Example 1, the hematite phase was the main phase and a part of the magnetite phase was included. Further, as shown in Table 4, in each example, the ratio of the Y element to the total Fe element in the particle (Y / Fe) or the ratio of the Nd element to the total Fe element in the particle (Nd / Fe) was 0. It was confirmed that the ratio was 1 to 3 mol% and the ratio of the Al element to the total Fe element in the particles (Al / Fe) was 5 to 55 mol%. On the other hand, in each comparative example, at least one of Y / Fe and Al / Fe was out of the above numerical range.
表４に示すように、各実施例のヘマタイト粒子を用いて水素を製造した場合は、１時間で１．５ｍｏｌ以上の水素を製造でき、一方、各比較例のヘマタイト粒子を用いた場合は、水素の製造量は１時間で１．５ｍｏｌ未満であり、各実施例のヘマタイト粒子を用いた場合よりも水素の製造効率が低いことが明らかとなった。従って、各実施例のヘマタイト粒子を触媒として用いると、高い効率で炭化水素から水素を製造でき、このため、同様にカーボンナノチューブも高い効率で製造できると考えられる。 As shown in Table 4, when hydrogen was produced using the hematite particles of each example, 1.5 mol or more of hydrogen could be produced in one hour, while when the hematite particles of each comparative example were used, hydrogen was produced. The amount of hydrogen produced was less than 1.5 mol per hour, and it was clarified that the hydrogen production efficiency was lower than that in the case of using the hematite particles of each example. Therefore, when the hematite particles of each example are used as a catalyst, hydrogen can be produced from hydrocarbons with high efficiency, and therefore, it is considered that carbon nanotubes can be produced with high efficiency as well.
以上から、粒子中の全Ｆｅ元素に対する希土類元素の比率が０．１〜３ｍｏｌ％であり、且つ粒子中の全Ｆｅ元素に対するＡｌ元素の比率が５〜５５ｍｏｌ％であるヘマタイト粒子を含む本発明に係る触媒は、炭化水素の熱分解効率を向上でき、水素及びカーボンナノチューブの製造効率を向上できて有用である。
From the above, the present invention includes a hydrocarbon particle in which the ratio of the rare earth element to the total Fe element in the particle is 0.1 to 3 mol% and the ratio of the Al element to the total Fe element in the particle is 5 to 55 mol%. Such a catalyst is useful because it can improve the thermal decomposition efficiency of hydrocarbons and the production efficiency of hydrogen and carbon nanotubes.
Claims (10)
ヘマタイト粒子を含み、
前記ヘマタイト粒子は、粒子中の全鉄（Ｆｅ）元素に対して０．１〜３ｍｏｌ％の希土類元素を含有し、粒子中の全Ｆｅ元素に対して５〜５５ｍｏｌ％のアルミニウム（Ａｌ）元素を含有することを特徴とする触媒。 A catalyst for the thermal decomposition of hydrocarbons
Contains hematite particles,
The hematite particles contain 0.1 to 3 mol% of rare earth elements with respect to the total iron (Fe) elements in the particles, and 5 to 55 mol% of aluminum (Al) elements with respect to the total Fe elements in the particles. A catalyst characterized by containing.
The method for producing carbon nanotubes and hydrogen according to claim 8 or 9, wherein the carbon nanotubes and hydrogen are obtained by direct modification of methane.
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