JP4163302B2 - Method for preparing hydrocarbon reforming catalyst and magnesium oxide molded body for forming catalyst carrier - Google Patents
Method for preparing hydrocarbon reforming catalyst and magnesium oxide molded body for forming catalyst carrier Download PDFInfo
- Publication number
- JP4163302B2 JP4163302B2 JP27824398A JP27824398A JP4163302B2 JP 4163302 B2 JP4163302 B2 JP 4163302B2 JP 27824398 A JP27824398 A JP 27824398A JP 27824398 A JP27824398 A JP 27824398A JP 4163302 B2 JP4163302 B2 JP 4163302B2
- Authority
- JP
- Japan
- Prior art keywords
- magnesium oxide
- catalyst
- ruthenium
- rhodium
- supported
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 239000000395 magnesium oxide Substances 0.000 title claims description 134
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 title claims description 134
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 title claims description 134
- 239000003054 catalyst Substances 0.000 title claims description 129
- 238000000034 method Methods 0.000 title claims description 49
- 229930195733 hydrocarbon Natural products 0.000 title claims description 36
- 150000002430 hydrocarbons Chemical class 0.000 title claims description 36
- 239000004215 Carbon black (E152) Substances 0.000 title claims description 31
- 238000002407 reforming Methods 0.000 title claims description 22
- 229910052751 metal Inorganic materials 0.000 claims description 51
- 239000002184 metal Substances 0.000 claims description 51
- 238000006243 chemical reaction Methods 0.000 claims description 45
- 239000010948 rhodium Substances 0.000 claims description 37
- 239000007864 aqueous solution Substances 0.000 claims description 27
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 26
- 238000010304 firing Methods 0.000 claims description 26
- 229910052799 carbon Inorganic materials 0.000 claims description 23
- 229910052703 rhodium Inorganic materials 0.000 claims description 23
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 claims description 21
- 238000000465 moulding Methods 0.000 claims description 19
- 238000001035 drying Methods 0.000 claims description 14
- 229910052707 ruthenium Inorganic materials 0.000 claims description 11
- 238000001179 sorption measurement Methods 0.000 claims description 11
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 claims description 10
- 238000001354 calcination Methods 0.000 claims description 7
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims description 6
- 239000011777 magnesium Substances 0.000 claims description 6
- 229910052749 magnesium Inorganic materials 0.000 claims description 6
- 150000003284 rhodium compounds Chemical class 0.000 claims description 6
- 150000003304 ruthenium compounds Chemical class 0.000 claims description 6
- 159000000003 magnesium salts Chemical class 0.000 claims description 5
- 239000000203 mixture Substances 0.000 claims description 5
- 230000003647 oxidation Effects 0.000 claims description 5
- 238000007254 oxidation reaction Methods 0.000 claims description 5
- 235000014113 dietary fatty acids Nutrition 0.000 claims description 4
- 239000000194 fatty acid Substances 0.000 claims description 4
- 229930195729 fatty acid Natural products 0.000 claims description 4
- 150000004665 fatty acids Chemical class 0.000 claims description 4
- 229920002134 Carboxymethyl cellulose Polymers 0.000 claims description 3
- 239000004372 Polyvinyl alcohol Substances 0.000 claims description 3
- 125000004432 carbon atom Chemical group C* 0.000 claims description 3
- 229920002451 polyvinyl alcohol Polymers 0.000 claims description 3
- 239000001768 carboxy methyl cellulose Substances 0.000 claims description 2
- 235000010948 carboxy methyl cellulose Nutrition 0.000 claims description 2
- 239000008112 carboxymethyl-cellulose Substances 0.000 claims description 2
- 239000002253 acid Substances 0.000 description 33
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 32
- 239000007789 gas Substances 0.000 description 20
- 239000002994 raw material Substances 0.000 description 16
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 12
- 230000008021 deposition Effects 0.000 description 10
- 230000000694 effects Effects 0.000 description 9
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 8
- 239000001301 oxygen Substances 0.000 description 8
- 229910052760 oxygen Inorganic materials 0.000 description 8
- 239000000126 substance Substances 0.000 description 7
- 239000001569 carbon dioxide Substances 0.000 description 6
- 229910002092 carbon dioxide Inorganic materials 0.000 description 6
- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical compound [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 description 6
- 239000000347 magnesium hydroxide Substances 0.000 description 6
- 229910001862 magnesium hydroxide Inorganic materials 0.000 description 6
- 239000002245 particle Substances 0.000 description 5
- 239000000243 solution Substances 0.000 description 5
- HQABUPZFAYXKJW-UHFFFAOYSA-N butan-1-amine Chemical compound CCCCN HQABUPZFAYXKJW-UHFFFAOYSA-N 0.000 description 4
- 230000003197 catalytic effect Effects 0.000 description 4
- 238000002425 crystallisation Methods 0.000 description 4
- 230000008025 crystallization Effects 0.000 description 4
- -1 for example Substances 0.000 description 4
- 238000011068 loading method Methods 0.000 description 4
- 239000008188 pellet Substances 0.000 description 4
- 238000002360 preparation method Methods 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 3
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 3
- 230000002378 acidificating effect Effects 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- ZLNQQNXFFQJAID-UHFFFAOYSA-L magnesium carbonate Chemical compound [Mg+2].[O-]C([O-])=O ZLNQQNXFFQJAID-UHFFFAOYSA-L 0.000 description 3
- 239000001095 magnesium carbonate Substances 0.000 description 3
- 229910000021 magnesium carbonate Inorganic materials 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 229910000510 noble metal Inorganic materials 0.000 description 3
- 239000000843 powder Substances 0.000 description 3
- 238000000629 steam reforming Methods 0.000 description 3
- 238000003786 synthesis reaction Methods 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 2
- 229910002091 carbon monoxide Inorganic materials 0.000 description 2
- 238000006555 catalytic reaction Methods 0.000 description 2
- UKMSUNONTOPOIO-UHFFFAOYSA-N docosanoic acid Chemical compound CCCCCCCCCCCCCCCCCCCCCC(O)=O UKMSUNONTOPOIO-UHFFFAOYSA-N 0.000 description 2
- POULHZVOKOAJMA-UHFFFAOYSA-N dodecanoic acid Chemical compound CCCCCCCCCCCC(O)=O POULHZVOKOAJMA-UHFFFAOYSA-N 0.000 description 2
- IPCSVZSSVZVIGE-UHFFFAOYSA-N hexadecanoic acid Chemical compound CCCCCCCCCCCCCCCC(O)=O IPCSVZSSVZVIGE-UHFFFAOYSA-N 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 238000007654 immersion Methods 0.000 description 2
- 239000011261 inert gas Substances 0.000 description 2
- HQKMJHAJHXVSDF-UHFFFAOYSA-L magnesium stearate Chemical compound [Mg+2].CCCCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCCCC([O-])=O HQKMJHAJHXVSDF-UHFFFAOYSA-L 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 239000003345 natural gas Substances 0.000 description 2
- 231100000572 poisoning Toxicity 0.000 description 2
- 230000000607 poisoning effect Effects 0.000 description 2
- 238000006057 reforming reaction Methods 0.000 description 2
- SVOOVMQUISJERI-UHFFFAOYSA-K rhodium(3+);triacetate Chemical compound [Rh+3].CC([O-])=O.CC([O-])=O.CC([O-])=O SVOOVMQUISJERI-UHFFFAOYSA-K 0.000 description 2
- 238000007086 side reaction Methods 0.000 description 2
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- 235000021357 Behenic acid Nutrition 0.000 description 1
- OTMSDBZUPAUEDD-UHFFFAOYSA-N Ethane Chemical compound CC OTMSDBZUPAUEDD-UHFFFAOYSA-N 0.000 description 1
- 239000005639 Lauric acid Substances 0.000 description 1
- 235000021314 Palmitic acid Nutrition 0.000 description 1
- 235000021355 Stearic acid Nutrition 0.000 description 1
- 150000001242 acetic acid derivatives Chemical class 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 239000003570 air Substances 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 229940116226 behenic acid Drugs 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 239000001273 butane Substances 0.000 description 1
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 1
- 239000000920 calcium hydroxide Substances 0.000 description 1
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 239000013065 commercial product Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000002845 discoloration Methods 0.000 description 1
- 238000010494 dissociation reaction Methods 0.000 description 1
- 230000005593 dissociations Effects 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 150000004820 halides Chemical class 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000005470 impregnation Methods 0.000 description 1
- 238000005342 ion exchange Methods 0.000 description 1
- 239000000314 lubricant Substances 0.000 description 1
- 235000019359 magnesium stearate Nutrition 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 239000002923 metal particle Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- WQEPLUUGTLDZJY-UHFFFAOYSA-N n-Pentadecanoic acid Natural products CCCCCCCCCCCCCCC(O)=O WQEPLUUGTLDZJY-UHFFFAOYSA-N 0.000 description 1
- IJDNQMDRQITEOD-UHFFFAOYSA-N n-butane Chemical compound CCCC IJDNQMDRQITEOD-UHFFFAOYSA-N 0.000 description 1
- OFBQJSOFQDEBGM-UHFFFAOYSA-N n-pentane Natural products CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 description 1
- 150000002823 nitrates Chemical class 0.000 description 1
- QIQXTHQIDYTFRH-UHFFFAOYSA-N octadecanoic acid Chemical compound CCCCCCCCCCCCCCCCCC(O)=O QIQXTHQIDYTFRH-UHFFFAOYSA-N 0.000 description 1
- OQCDKBAXFALNLD-UHFFFAOYSA-N octadecanoic acid Natural products CCCCCCCC(C)CCCCCCCCC(O)=O OQCDKBAXFALNLD-UHFFFAOYSA-N 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 239000001294 propane Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- YBCAZPLXEGKKFM-UHFFFAOYSA-K ruthenium(iii) chloride Chemical compound [Cl-].[Cl-].[Cl-].[Ru+3] YBCAZPLXEGKKFM-UHFFFAOYSA-K 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000011949 solid catalyst Substances 0.000 description 1
- 239000010421 standard material Substances 0.000 description 1
- 239000008117 stearic acid Substances 0.000 description 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- TUNFSRHWOTWDNC-HKGQFRNVSA-N tetradecanoic acid Chemical compound CCCCCCCCCCCCC[14C](O)=O TUNFSRHWOTWDNC-HKGQFRNVSA-N 0.000 description 1
- OGWLTJRQYVEDMR-UHFFFAOYSA-F tetramagnesium;tetracarbonate Chemical compound [Mg+2].[Mg+2].[Mg+2].[Mg+2].[O-]C([O-])=O.[O-]C([O-])=O.[O-]C([O-])=O.[O-]C([O-])=O OGWLTJRQYVEDMR-UHFFFAOYSA-F 0.000 description 1
- 229910052723 transition metal Inorganic materials 0.000 description 1
- 150000003624 transition metals Chemical class 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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts
Landscapes
- Hydrogen, Water And Hydrids (AREA)
- Catalysts (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は、炭化水素の改質用触媒の調製方法及びその触媒担体形成用酸化マグネシウム成形体に関するものである。
【０００２】
【従来の技術】
炭化水素を改質することによって得られる合成ガスは、水素と一酸化炭素からなる混合ガスで、アンモニア、メタノール、酢酸等の工業製品の合成原料として広く利用されている。
一般に、合成ガスは、炭化水素に触媒の存在下でスチーム及び／又は炭酸ガスを反応させることによって製造することができる（特開平５−２０８８０１号、特開平６−２７９００３号、特開平９−１６８７４０号等）。
しかしながら、この反応に於いては、その副反応として、炭素析出反応が起こって炭素が析出し、この析出炭素によって触媒被毒が生じるという問題がある。この改質反応において、貴金属を触媒金属として使用すると、Ｎｉ等の遷移金属に比べ、炭素析出が抑制され易いことは良く知られているが、この場合、貴金属が非常に高価であるため、なるべく少量の金属を反応に有効に利用し得る触媒の調製方法の確立が望まれていた。
【０００３】
【発明が解決しようとする課題】
本発明は、貴金属の担持量が少なく、使用に際しての炭素析出量の少ない炭化水素の改質用触媒の調製方法及びその触媒担体形成用酸化マグネシウム成形体を提供することをその課題とする。
【０００４】
【課題を解決するための手段】
本発明者らは、前記課題を解決すべく鋭意研究を重ねた結果、本発明を完成するに至った。即ち、本発明によれば、(i) １０００℃以上の高温で焼成して得られた比表面積が０．０１〜５ m 2 /gの担体酸化マグネシウムに、ロジウム及び／又はルテニウムを金属換算量で１０〜５０００wtppmの割合で担持させ、次いで焼成することを特徴とする炭化水素の改質用触媒の調製方法が提供される。また、本発明によれば、(i) １０００℃以上の高温で焼成して得られた比表面積が０．０１〜５ m 2 /gの担体酸化マグネシウムを得る第１工程、(ii) 該第１工程で得られた担体酸化マグネシウムに、水溶性のロジウム化合物及び／又はルテニウム化合物を含有する水溶液を用い、平衡吸着法にてｐＨ８以上のアルカリ領域でロジウム及び／又はルテニウムを金属換算量で１０〜５０００wtppmの割合で担持させる第２工程、(iii) 該第２工程で得られたロジウム及び／又はルテニウム担持酸化マグネシウムを乾燥させる第３工程、(iv) 該第３工程で得られた乾燥状態のロジウム及び／又はルテニウム担持酸化マグネシウムを焼成する第４工程からなることを特徴とする炭化水素の改質用触媒の調製方法が提供される。さらに、本発明によれば、(i) １０００℃以上の高温で焼成して得られた比表面積が０．０１〜５ m 2 /gの担体酸化マグネシウムを得る第１工程、(ii) 該第１工程で得られた担体酸化マグネシウムに、水溶性のロジウム化合物及び／又はルテニウム化合物を含有する水溶液を用い、平衡吸着法にてｐＨ８以上のアルカリ領域でロジウム及び／又はルテニウムを金属換算量で１０〜５０００wtppmの割合で担持させる第２工程、(iii) 該第２工程により得られたロジウム及び／又はルテニウム担持酸化マグネシウムを、３５℃以下で少なくとも６時間以上乾燥させる第３工程、(iv) 該第３工程で得られた乾燥状態のロジウム及び／又はルテニウム担持酸化マグネシウムを焼成する第４工程からなることを特徴とする炭化水素の改質用触媒の調製方法が提供される。さらにまた、本発明によれば、(i) １０００℃以上の高温で焼成して得られた比表面積が０．０１〜５ m 2 /gの担体酸化マグネシウムを得る第１工程、(ii) 該第１工程で得られた担体酸化マグネシウムに、水溶性のロジウム化合物及び／又はルテニウム化合物を含有する水溶液を用い、平衡吸着法にてｐＨ８以上のアルカリ領域でロジウム及び／又はルテニウムを金属換算量で１０〜５０００wtppmの割合で担持させる第２工程、(iii) 該第２工程で得られたロジウム及び／又はルテニウム担持酸化マグネシウムを、３５℃以下で少なくとも６時間以上乾燥させる第３工程、(iv) 該第３工程で得られた乾燥状態のロジウム及び／又はルテニウム担持酸化マグネシウムを、２００℃以上の高温で焼成する第４工程からなることを特徴とする炭化水素の改質用触媒の調製方法が提供される。さらにまた、本発明によれば、請求項１〜４のいずれかに記載の炭化水素の改質用触媒の調製方法で用いる担体酸化マグネシウムを形成するための酸化マグネシウム成形体であり、酸化マグネシウムと成形助剤との混合物を成形して形成されており、上記成形助剤が(i) 炭素、(ii) 炭素数１２〜２２の脂肪酸又はそのマグネシウム塩、(iii) カルボキシルメチルセルロース又はそのマグネシウム塩、及び(iv) ポリビニルアルコールの中から選ばれる少なくとも１種であり、かつその添加量が０．１〜５重量%であることを特徴とする酸化マグネシウム成形体が提供される。
【０００５】
【発明の実施の形態】
本発明においては、触媒担体として、１０００℃以上の高温で焼成して得られた比表面積が０．０１〜５ m 2 /g の酸化マグネシウム（以下、単にＭｇＯとも言う）を用いる。このＭｇＯとしては市販品を用いることができ、その形状は特に制約されず、触媒として用いられている各種の形状、例えば、粉末状、粒状、球状、柱状、筒状等の形状であることができる。ＭｇＯとしては、水酸化マグネシウムを１０００〜１５００℃、好ましくは１１００〜１３００℃で焼成して得られたものや、炭酸マグネシウム又は塩基性炭酸マグネシウムを１０００〜１５００℃、好ましくは１１００〜１３００℃で焼成して得られたものを用いることが可能である。
【０００６】
本発明により炭化水素改質用触媒（以下、単に触媒とも言う）を調製するための好ましい方法を示すと、以下の通りである。先ず、第１工程において、１０００℃以上の高温で焼成して得られた比表面積が０．０１〜５ m 2 /gの担体ＭｇＯを得る。工業触媒においては、ペレット状やリング状等の形状に成形した担体が好ましく用いられるが、このような形状のＭｇＯ成形体を用いる場合、そのＭｇＯの比表面積が前記範囲より大きくなり、結晶化度が低くなると、触媒金属の担持に際してそのＭｇＯ成形体を水溶液中に浸した場合、そのＭｇＯ成形体に割れを生じるという問題がある。また、工業触媒の場合、通常、３０〜４０ｋｇ／個の半径方向の圧縮強度を有する必要があるが、比表面積が前記範囲より大きくなり、その結晶化度が低いＭｇＯ成形体ではこのような強度を得ることが困難になる。さらに、担体ＭｇＯの結晶化度が低くなると、触媒金属の担持量が多くなり、また、触媒の酸強度が強くなりすぎて、触媒表面の酸的特性が不満足のものとなる。一方、担体ＭｇＯの結晶化度が大きくなりすぎると、触媒金属の担持量が少なくなりすぎて、十分な活性を有する触媒が得られなくなる。この点から、担体ＭｇＯの比表面積は０．０１m2/g以上であって５ m 2 /g 以下にするのが好ましい。
【０００７】
前記範囲の比表面積を有する担体ＭｇＯを得る１つの方法としては、水酸化マグネシウムを１０００〜１５００℃、好ましくは１１００〜１３００℃で焼成することにより製造することができる他、炭酸マグネシウム又は塩基性炭酸マグネシウムを１０００〜１５００℃、好ましくは１１００〜１３００℃で焼成することにより製造することができる。また、１０００℃以下の低い温度で焼成する場合も、焼成の際に副生する水の分圧を高くしてＭｇＯの結晶化促進し、ＭｇＯの結晶子サイズを制御することによって所望の担体ＭｇＯを得ることができる。さらに、市販のＭｇＯ等のその比表面積が前記範囲より小さいものは、そのＭｇＯを１０００〜１５００℃、好ましくは１１００〜１３００℃で焼成することにより、所望の担体ＭｇＯを得ることができる。
さらに、低表面積の担体ＭｇＯを得る場合、１０００℃以下の温度でその焼成系に高い水の分圧を形成することによりそのＭｇＯの結晶化を促進させることができるが、この場合、水の分圧に代えて、ＣＯ2のようなガス（気体）の高い分圧を形成することによっても、ＭｇＯの結晶化を促進させることができる。
前記焼成に際しての雰囲気としては、通常、空気雰囲気が使用されるが、他のガス、例えば、窒素ガス等の不活性ガスであってもよい。焼成時間は１時間以上、好ましくは３時間以上であり、その上限値は特に制約されないが、通常、７２時間程度である。また焼成法のみに限らず、この様な低表面積のＭｇＯを得ることができれば、いかなる方法を採用しても良い。
【０００８】
本発明による担体ＭｇＯは、高い結晶化度を有し、そのＭｇＯの表面は安定化され、強酸点を極力抑えたＭｇＯとなる。そして、このような安定化されたＭｇＯでは、酸強度（Ｈｏ）が２以上の酸点のみを有し、その量が０．０３ｍｍｏｌ／ｇより少ないＭｇＯが得られる。従って、１０００℃以上の高温焼成された高結晶化度のＭｇＯを触媒金属担持用担体として用いることにより、強酸点の発現を極力抑え、炭素析出反応が抑制された安定した活性を有する触媒を得ることが可能となる。本発明で用いるＭｇＯの表面積は０．０１〜５ｍ2／ｇ、好ましくは０．０５〜３ｍ2／ｇである。担体ＭｇＯの表面積が前記範囲より高くなると、触媒金属の担持量が多くなり、また、触媒の酸強度が強くなりすぎて、触媒表面の酸的特性が不満足のものとなる。一方、担体ＭｇＯの表面積が前記範囲より小さくなると、触媒金属の担持量が少なくなりすぎて、十分な活性を有する触媒が得られなくなる。
【０００９】
一般に、金属酸化物の表面積とその結晶子サイズは、ほぼ反比例の関係にあることが良く知られている。従って、本発明で規定しているＭｇＯの比表面積は、その粒子サイズにより規定することも可能である。例えば、比表面積が５ｍ2／ｇ以下のＭｇＯの結晶子サイズは、粒子を球形又は立方体の均一粒子と仮定することにより、ＭｇＯの密度、比表面積から算出することができる。この方法は、文献「触媒構座３（固体触媒のキャラクタリゼーション）」（１９８５年出版、講談社サイエンティフィク、触媒学会編、Ｐ２０３）に記載されている。例えば、１０１０℃で焼成した比表面積５ｍ2／ｇのＭｇＯの結晶子サイズは、３５００Åとなる。
【００１０】
また、ＭｇＯの結晶子サイズは、Ｘ線回折法を用いて測定することもできる。本明細書中の表面積が５ｍ2／ｇ以下のＭｇＯの結晶子サイズを、Ｘ線回折法を用いた「ラインブロードニング」法により測定すると、その値は、９００Å以上となった。測定装置としては、島津製作所のＸ線回折装置「ＸＲＤ−６０００」が用いられた。標準物質として、金属Ｓｉを用いて測定すると、ＭｇＯの結晶サイズは、ＭｇＯの２θ＝４２．７°の回折ピークとＳｉのＭｇＯの２θ＝２８．４°の回折ピークの半値幅から算出した。Ｘ線回折測定における測定条件を以下に示す。
Ｘ線管球：Ｃｕ（λ＝１．５４０６Å）、管電圧：４０．０ｋＶ、管電流：３０．０ｍＡ、測定範囲：４０．０〜８０．０°、ステップ幅：０．０２°、計数時間：０．６秒、スリット：ＤＳ（発散スリット）＝０．５°、ＳＳ（散乱防止）＝０．５°、ＲＳ（受光）＝０．１５ｍｍ、標準物質：金属Ｓｉ
このラインブロードニング法の詳細は、文献「実験化学構座４（固体物理化学）」（１９５６年出版、丸善、日本化学会編、Ｐ２３８〜Ｐ２５０）に記載されている。
【００１１】
前記のようにして得た担体酸化マグネシウムに対しては、第２工程（触媒金属担持工程）において、触媒金属を含む水溶液を用い、平衡吸着法にてｐＨ８以上のアルカリ領域でその触媒水溶液を担持させる。本発明では、触媒金属としては、ロジウム及び／又はルテニウムが用いられる。
前記担持工程では、触媒金属は水溶液状で担体酸化マグネシウムに担持されるが、この場合の触媒金属は水溶性化合物の形態で用いられる。このようなものとしては、ハロゲン化物、硝酸塩、硫酸塩、有機酸塩（酢酸塩等）、錯塩（キレート）等が挙げられる。
担体ＭｇＯに対する触媒金属水溶液の担持には、平衡吸着法が採用される。この方法は、担体を触媒水溶液中に浸漬し、平衡条件下で水溶液中の触媒金属を担体に吸着担持させる方法である。この場合、触媒金属を担体に担持させる時間（浸漬時間）は１時間以上、好ましくは３時間以上であり、その上限は、特に制約されないが、通常、４８時間程度である。この平衡吸着法の詳細は、文献「触媒調整化学」（１９８０年出版、講談社サイエンティフィク、Ｐ４９）に記載されている。
【００１２】
前記のようにして触媒金属を担体ＭｇＯに担持させる場合、その触媒水溶液のｐＨは８以上、好ましくは８．５以上のアルカリ領域とする。その上限値は、特に制約されないが、通常、ｐＨ１３程度である。その水溶液のｐＨ調節には、水酸化ナトリウムや水酸化カリウム、水酸化カルシウム、水酸化マグネシウム等のアルカリ性物質やアンモニア水が用いられる。
本発明においては、担体ＭｇＯに対する触媒金属の担持量は、触媒金属換算量で、担体ＭｇＯに対して１０〜５０００ｗｔｐｐｍ、好ましくは１００〜２０００ｗｔｐｐｍの割合に規定する。触媒金属担持量が前記範囲より多くなると、触媒コストが高くなるとともに、触媒の炭素析出活性が高くなり、触媒の使用に際し、炭素析出量が多くなる。一方、前記範囲より少ないと、十分な触媒活性が得られなくなる。触媒金属担持量の調節は、担体ＭｇＯに対して触媒金属水溶液を担持する際の条件、例えば、水溶液中の触媒金属濃度や、担体ＭｇＯの表面積等によって行うことができる。
【００１３】
前記のようにして、担体ＭｇＯに触媒金属を水溶液状で担持させることによって得られた触媒金属担持ＭｇＯは、第３工程（乾燥工程）において、３５℃以下の温度で６時間以上保持して乾燥させる。好ましい乾燥温度は１０〜２５℃である。乾燥時間は６時間以上であればよく、好ましくは１２時間以上であり、その上限値は、特に制約されないが、通常、約７２時間程度である。このような乾燥処理により、ＭｇＯからの急激な水分の蒸発が回避され、その結果、触媒金属は凝集することなく担体ＭｇＯに高分散状態で担持される。乾燥温度や乾燥時間が前記範囲を逸脱すると、高分散性の触媒金属を含む触媒を得ることができなくなる。
【００１４】
前記のようにして得られた乾燥物は、これを第４工程において、２００℃以上の高温で１時間以上焼成する。この場合、焼成雰囲気としては、通常、空気が用いられるが、他のガス（不活性ガス等）であってもよい。焼成温度は２００℃以上であり、好ましくは５００℃以上であり、その上限値は、特に制約されないが、通常、１１００℃程度である。好ましい焼成時間は２時間以上、より好ましくは３時間以上であり、その上限値は、特に制約されないが、通常２４時間程度である。この２次焼成により、触媒金属の熱安定性が高められ、熱安定性の良い触媒を得ることができる。
【００１５】
触媒コストの低減化を図るには、担体に担持させる触媒金属の担持量をできるだけ低減化させると同時に、十分な反応活性を発現するように、担体に担持された触媒金属粒子の凝集化をできるだけ抑制して微粒子化することが必要となる。本発明者らの研究によれば、担体ＭｇＯの結晶化を高めてその比表面積を５ｍ2／ｇ以下の範囲に保持するとともに、その担体ＭｇＯに対する触媒金属の担持量を１０〜５０００ｗｔｐｐｍと極く少量に保持し、かつその触媒金属を担体ＭｇＯに担持させるに際し、平衡吸着法により触媒金属を平衡条件下で長時間をかけてゆっくりと水溶液状で担持させ、その担持後においては、３５℃以下の温度でゆっくりと乾燥するときには、触媒金属は均一に担持され、炭化水素改質用触媒として十分な活性を有する安価な触媒が得られることが見出された。
【００１６】
前記した触媒の調製方法においては、種々の変更が可能である。例えば、担体酸化マグネシウムに触媒金属を担持させる方法としては、平衡吸着法に限らず、他の方法、例えば、慣用の含浸法や、浸漬法、イオン交換法等を用いることができる。また、触媒金属を含む水溶液を担体酸化マグネシウムに担持させた後、乾燥する場合には、場合によっては３５〜２００℃程度の加温条件を採用するし、また、その乾燥物の焼成は、場合によっては、２００〜８００℃程度の温度で行うことも可能である。
【００１７】
本発明により触媒を調製する場合、その触媒担体形成用酸化マグネシウムは、酸化マグネシウムに成形助剤を配合して形成した酸化マグネシウム成形体として用いるのが好ましい。この成形助剤を用いることによって、成形時の作業性が向上すると共に得られた成形体の強度は向上する。この場合の成形助剤としては、（ｉ）炭素（カーボン）、（ii）炭素数１２〜２２の脂肪酸又はそのマグネシウム塩、(iii）カルボキシルメチルセルロース（ＣＭＣ）又はそのマグネシウム塩及び（iv）ポリビニルアルコールの中から選ばれる少なくとも１種の化合物を用いるのが好ましい。これらの成形助剤は、通常、粉末状で用いられる。
前記カーボンとしては、グラファイト、カーボンブラック、活性炭などが用いられる。前記脂肪酸としては、ラウリン酸、ミリスチン酸、パルミチン酸、ステアリン酸、ベヘン酸等が挙げられる。
【００１８】
前記触媒担体用酸化マグネシウム成形体を製造するには、粉末状の酸化マグネシウムに成形助剤を添加し、均一に混合した後、この混合物を所要形状に成形する。粉末状酸化マグネシウムの平均粒径は１〜１０００μｍ、好ましくは１０〜１００μｍである。一方、成形助剤の平均粒径は１〜１０００μｍ、好ましくは１０〜１００μｍである。酸化マグネシウムに添加する成形助剤の量は、酸化マグネシウムと成形助剤の合計量に対し、０．１〜５重量％、好ましくは０．５〜３．０重量％である。
前記酸化マグネシウムと成形助剤との混合物を形成する場合、その成形条件としては、通常、常温で３０００〜１００ｋｇ/ｃｍ2Ｇ、好ましくは２０００〜２００ｋｇ/ｃｍ2Ｇの圧力が採用される。成形方法としては、プレス成形法が採用されるが、その他、打錠成形法等も採用することができる。成形体の形状は、特に制約されず、通常の触媒に採用されている形状であればよい。このような形状には、タブレット状、円柱状、リング状、中空円筒状等が包含される。その成形体の寸法は、通常、その長軸長さで、３〜３０ｍｍ、好ましくは５〜２５ｍｍであるが、触媒床に応じて適宜の寸法を採用すればよい。
【００１９】
本発明による前記酸化マグネシウム成形体は、焼成後の機械的強度にすぐれ、通常、３０〜７０ｋｇ／個の半径方向の圧縮強度を有する。
従って、このような成形体は、取扱い性の良好なもので、その焼成に際して、容易に破壊されるようなことはない。
また、この酸化マグネシウム成形体は、そのＭｇＯの結晶化度が低いときには、所望する担体酸化マグネシウムを得るために、通常、１０００℃以上の高温で一次焼成されるが、この一次焼成により、成形体中の成形助剤は酸化除去される。このようにして得られる酸化マグネシウムは、本発明触媒の調製に用いる担体酸化マグネシウムとして好適のものである。
【００２０】
前記のようにして得られる本発明触媒において、その触媒金属担持量は、担体ＭｇＯに対して、１０〜５０００ｗｔｐｐｍ、好ましくは１００〜２０００ｗｔｐｐｍであり、その比表面積は０．０１〜５ｍ2／ｇ、好ましくは０．０５〜３ｍ2／ｇである。
なお、本明細書中で触媒及びＭｇＯに関して言う比表面積は、「ＢＥＴ」法により、温度１５℃で測定されたものであり、その測定装置としては、柴田科学社製の「ＳＡ−１００」が用いられた。
【００２１】
前記のようにして得られる本発明の触媒は、炭化水素改質用触媒として好ましい酸的性質を有する。触媒表面に強い酸点が多量に存在すると、その酸点上で副反応である炭素析出反応が促進され、炭素が析出し、この析出炭素によって触媒被毒が生じるようになる。
【００２２】
本発明の触媒は、一般的には、その酸強度（Ｈｏ）は２より大きい、好ましくは３．３以上の酸点のみからなり、その含量は０．０３ｍｍｏｌ／ｇより少なく、好ましくは０．０２ｍｍｏｌ／ｇ以下である。酸強度（Ｈｏ）の調節は、担体ＭｇＯを１次焼成する際の温度及び時間により行うことができる。本発明の触媒は、強酸点の発現が抑制され、炭素析出活性が大きく抑制されたものである。
【００２３】
なお、本明細書で言う酸強度（Ｈｏ）は、触媒が塩基性指示薬（Ｂ-）にプロトンを与える能力として表示され、次式で表される。
Ｈｏ＝ｐＫａ（＝ｐＫB - H +）＋ｌｏｇ［Ｂ］／［Ｂ-Ｈ+］ （１）
前記式中、ＫB - H +は、塩基性指示薬Ｂ-と酸性点Ｈ+Ｂとを反応させて、塩基性指示薬の酸性体（Ｂ-Ｈ+）を生成させる反応におけるその酸性体Ｂ-Ｈ+の解離定数を示す。［Ｂ］／［Ｂ-Ｈ+］は、Ｂ-とＢ-Ｈ+の濃度比を示す。
強酸点ほど、ｐＫB - H +の小さな指示薬をより多くプロトン化するのでそのＨｏ値は小さくなる。
【００２４】
本明細書における酸強度は以下のようにして測定されたものである。
（酸強度の測定方法）
本明細書における酸強度Ｈｏ（ハメット指数）関数は、酸強度関数で、触媒学会編「触媒実験ハンドブック」（１９８６年出版、講談社サイエンティフィク）、ｐ．１７２に記載の「Ｂｅｎｅｓｉ法」により測定されたものである。触媒にｐＫａが分かっている指示薬を添加し、変色すると、ＨｏがそのｐＫａより小さい酸点があることを示す。塩基性分子であるブチルアミンを酸点に所定量吸着させ、ｐＫａの異なる指示薬で滴定すると、ブチルアミンの量から酸点の数が、ｐＫａの値から酸強度が測定できる。測定温度は室温である。
【００２５】
本発明の触媒を用いて合成ガス（水素と一酸化炭素との混合ガス）を製造するには、触媒の存在下において、炭化水素とスチーム及び／又は二酸化炭素（ＣＯ2）とを反応させるか、炭化水素と酸素とを反応させればよい。炭化水素としては、メタン、エタン、プロパン、ブタン、ナフサ等の低級炭化水素が用いられるが、好ましくはメタンが用いられる。本発明においては、炭酸ガスを含む天然ガス（メタンガス）を反応原料として有利に用いることができる。
メタンと二酸化炭素（ＣＯ2）とを反応させる方法（ＣＯ2リフォーミング）の場合、その反応は次式で示される。
【化１】
【化２】
ＣＯ2リフォーミングにおいて、その反応温度は５００〜１２００℃、好ましくは６００〜１０００℃であり、その反応圧力は加圧であり、５〜４０ｋｇ/ｃｍ2Ｇ、好ましくは５〜３０ｋｇ/ｃｍ2Ｇである。また、この反応を固定床方式で行う場合、そのガス空間速度（ＧＨＳＶ）は１，０００〜１０，０００ｈｒ-1、好ましくは２，０００〜８，０００ｈｒ-1である。原料炭化水素に対するＣＯ2の使用割合を示すと、原料炭化水素中の炭素１モル当り、ＣＯ2２０〜０．５モル、好ましくは１０〜１モルの割合である。
スチームリフォーミングにおいて、その反応温度は６００〜１２００℃、好ましくは６００〜１０００℃であり、その反応圧力は加圧であり、１〜４０ｋｇ/ｃｍ2Ｇ、好ましくは５〜３０ｋｇ/ｃｍ2Ｇである。また、この反応を固定床方式で行う場合、そのガス空間速度（ＧＨＳＶ）は１，０００〜１０，０００ｈｒ-1、好ましくは２，０００〜８，０００ｈｒ-1以下である。原料炭化水素に対するスチーム使用割合を示すと、原料炭化水素中の炭素１モル当り、スチーム（Ｈ2Ｏ）０．５〜５モル、好ましくは１〜２モル、より好ましくは１〜１．５モルの割合である。
本発明によりスチームリフォーミングを行う場合、前記のように、原料炭化水素の炭素１モル当りのスチーム（Ｈ2Ｏ）を２モル以下に保持しても、炭素析出を抑制して、工業的に有利に合成ガスを製造することができる。従来の場合には、原料炭化水素の炭素１モル当り２〜５モルのスチームを必要としていたことを考えると、２モル以下のスチームの使用によってリフォーミング反応を円滑に進行させ得ることは、本発明触媒の工業上の大きな利点である。
本発明の触媒は、炭化水素に、スチームとＣＯ2の混合物を反応させる際の触媒として有利に用いられる。この場合、スチームとＣＯ2との混合割合は特に制約されないが、一般的には、Ｈ2Ｏ／ＣＯ2モル比で、０．１〜１０である。
【００２７】
本発明の触媒を用いて炭化水素と酸素とを反応させる場合、その炭化水素としては、前記した如き炭化水素系が用いられるが、好ましくはメタンである。酸素源としては、酸素や、空気、富酸素化空気が用いられる。本発明においては、炭酸ガスを含む天然ガス（メタンガス）を反応原料として有利に用いることができる。
メタンと酸素とを反応させる場合、その反応は次式で示される。
【化３】
本発明の触媒を用いる前記各種の反応は、固定床方式、流動床方式、懸濁床方式、移動床方式等の各種の触媒方式で実施されるが、好ましくは固定床方式で実施される。
【００２８】
【実施例】
次に本発明を実施例によりさらに詳細に説明する。
【００２９】
実施例１
市販の純度９８．７ｗｔ％以上の酸化マグネシウム（ＭｇＯ）の粉末に滑択材として３．０ｗｔ％のカーボンを混合し、タブレット形成した１／８インチペレットを空気中で１０６０℃で３ｈ（時間）焼成し、これを触媒担体ＭｇＯ（Ａ）として用いた。
次に、３．９ｗｔ％のＲｈを含むロジウム(III）アセテート水溶液に２６ｈ（時間）浸漬した。その水溶液は水酸化マグネシウム水溶液を用い、ｐＨは９．７に調整した。このようにして、Ｒｈを触媒担体ＭｇＯ（Ａ）に平衡吸着させた後、濾過して、Ｒｈを水溶液状で吸着した触媒担体ＭｇＯ（Ａ）を得た。この場合のＲｈ担持量は、Ｒｈ金属換算量で、担体ＭｇＯ（Ａ）に対して、３７５０ｗｔｐｐｍである。
次に、Ｒｈを吸着した担体ＭｇＯ（Ａ）を空気中において３５℃の温度で５２ｈ乾燥した後、空気中において８５０℃で３ｈ焼成し、本発明触媒（Ａ）を得た。
この触媒（Ａ）は、ＲｈをＲｈ金属として担体ＭｇＯに対し３７５０ｗｔｐｐｍ含有するもので、その表面積は１．２ｍ2／ｇであった。また、その酸点は、酸強度（Ｈｏ）が３．３以上の酸点のみからなり、その含量は０．０１ｍｍｏｌ／ｇであった。
【００３０】
実施例２
市販の純度９８．０ｗｔ％の酸化マグネシウム（ＭｇＯ）を用いて形成したＭｇＯの１／８インチペレットを空気中で１０００℃で２ｈ（時間）焼成し、これを触媒担体ＭｇＯ（Ｂ）として用いた。
次に、０．１ｗｔ％のＲｕを含むルテニウム(III）クロライド水溶液に１９ｈ（時間）浸漬した。その水溶液は水酸化マグネシウム水溶液を用い、ｐＨは９．７に調整した。このようにして、Ｒｕを触媒担体ＭｇＯ（Ｂ）に平衡吸着させた後、濾過して、Ｒｕを水溶液状で吸着した触媒担体ＭｇＯ（Ｂ）を得た。この場合のＲｕ担持量は、Ｒｕ金属換算量で、担体ＭｇＯ（Ｂ）に対して、１２５ｗｔｐｐｍである。
次に、Ｒｕを吸着した担体ＭｇＯ（Ｂ）を空気中において３０℃の温度で７２ｈ乾燥した後、空気中において８６０℃で２．５ｈ焼成し、本発明触媒（Ｂ）を得た。
この触媒（Ｂ）は、ＲｕをＲｕ金属として担体ＭｇＯ（Ｂ）に対し１２５ｗｔｐｐｍの割合で含有するもので、その表面積は４．８ｍ2／ｇであった。また、その酸点は、酸強度（Ｈｏ）が３．３以上の酸点のみからなり、その含量は０．０３ｍｍｏｌ／ｇであった。
【００３１】
実施例３
市販の純度９９．９ｗｔ％の酸化マグネシウム（ＭｇＯ）に２．５ｗｔ％ステアリン酸マグネシウムを混合して成形したＭｇＯの１／８インチペレットを空気中で１２００℃で２．５ｈ（時間）焼成し、これを触媒担体ＭｇＯ（Ｃ）として用いた。
次に、２．６ｗｔ％のＲｈを含むロジウム(III）アセテート水溶液に２６ｈ（時間）浸漬した。その水溶液は水酸化マグネシウム水溶液を用い、ｐＨは９．７に調整した。このようにして、Ｒｈを触媒担体ＭｇＯ（Ｃ）に平衡吸着させた後、濾過して、Ｒｈを水溶液状で吸着した触媒担体ＭｇＯ（Ｃ）を得た。この場合のＲｈ担持量は、Ｒｈ金属換算量で、担体ＭｇＯ（Ｃ）に対して、１７５０ｗｔｐｐｍである。
次に、Ｒｈを吸着した担体ＭｇＯ（Ｃ）を空気中において２０℃の温度で３４ｈ乾燥した後、空気中において９５０℃で３．５ｈ焼成し、本発明触媒（Ｃ）を得た。
この触媒（Ｃ）は、ＲｈをＲｈ金属として担体ＭｇＯに対し１７５０ｗｔｐｐｍ含有するもので、その表面積は０．２ｍ2／ｇであった。また、その酸点は、酸強度（Ｈｏ）が３．３以上の酸点のみからなり、その含量は０．００２ｍｍｏｌ／ｇであった。
【００３２】
反応例１
実施例１で調製した触媒（Ａ）３０ｃｃを反応器に充填し、メタンのＣＯ2リフォーミング試験を実施した。
触媒は、予めＨ2気流中９００℃で１ｈ還元処理を行った後、ＣＨ4：ＣＯ2モル比＝１：０．４、ＣＨ4：Ｈ2Ｏモル比＝１：０．８５の原料ガスを、圧力２０ｋｇ／ｃｍ2Ｇ，温度８２０℃，メタン基準のＧＨＳＶ＝４０００ｈｒ-1の条件で処理した。反応開始から５ｈ経過後のＣＨ4転化率は、５０％（実験条件下でのＣＨ4の平衡転化率＝５０％）であり、また反応開始から１２００ｈ経過後のＣＨ4の転化率は、５０％であった。
ここで、ＣＨ4の転化率は、次式で定義される。
ＣＨ4の転化率（％）＝（Ａ−Ｂ）／Ａ×１００
Ａ：原料中のＣＨ4モル数
Ｂ：生成物中のＣＨ4モル数
【００３３】
反応例２
実施例２で調製した触媒（Ｂ）３０ｃｃを反応器に充填し、メタンのＣＯ2リフォーミング試験を実施した。
触媒は、予めＨ2気流中９００℃で１ｈ還元処理を行った後、ＣＨ4：ＣＯ2モル比＝１：１の原料ガスを、圧力１０ｋｇ／ｃｍ2Ｇ，温度８４０℃，メタン基準のＧＨＳＶ＝５０００ｈｒ-1の条件で処理した。反応開始から５ｈ経過後のＣＨ4転化率は、６５％（実験条件下でのＣＨ4の平衡転化率＝６５％）であり、また反応開始から４６０ｈ経過後のＣＨ4の転化率は、６５％であった。
【００３４】
反応例３
実施例３で調製した触媒（Ｃ）３０ｃｃを反応器に充填し、メタンのＣＯ2リフォーミング試験を実施した。
触媒は、予めＨ2気流中９００℃で１ｈ還元処理を行った後、ＣＨ4：ＣＯ2モル比＝１：１の原料ガスを、圧力２０ｋｇ／ｃｍ2Ｇ，温度８４０℃，メタン基準のＧＨＳＶ＝３５００ｈｒ-1の条件で処理した。反応開始から５ｈ経過後のＣＨ4転化率は、５３％（実験条件下でのＣＨ4の平衡転化率＝５３％）であり、また反応開始から２５０ｈ経過後のＣＨ4の転化率は、５３％であった。
【００３５】
【発明の効果】
本発明によれば、触媒金属の担持量が極く少量でありながら、炭素析出活性が著しく抑制された安価な炭化水素改質用触媒を得ることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for preparing a hydrocarbon reforming catalyst and a magnesium oxide molded body for forming the catalyst carrier.
[0002]
[Prior art]
Syngas obtained by reforming hydrocarbons is a mixed gas composed of hydrogen and carbon monoxide, and is widely used as a raw material for synthesizing industrial products such as ammonia, methanol, and acetic acid.
In general, synthesis gas can be produced by reacting hydrocarbons with steam and / or carbon dioxide in the presence of a catalyst (Japanese Patent Laid-Open Nos. 5-208801, 6-279003, and 9-168740). Issue).
However, in this reaction, as a side reaction, there is a problem that a carbon deposition reaction occurs to deposit carbon, which causes catalyst poisoning. In this reforming reaction, it is well known that when a noble metal is used as a catalyst metal, carbon deposition is more easily suppressed than a transition metal such as Ni, but in this case, the noble metal is very expensive, so It has been desired to establish a method for preparing a catalyst that can effectively use a small amount of metal for the reaction.
[0003]
[Problems to be solved by the invention]
It is an object of the present invention to provide a method for preparing a hydrocarbon reforming catalyst with a small amount of noble metal supported and a small amount of carbon deposition during use, and a magnesium oxide molded body for forming the catalyst carrier.
[0004]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have completed the present invention. That is, according to the present invention, (i) the amount of rhodium and / or ruthenium converted into metal in the carrier magnesium oxide having a specific surface area of 0.01 to 5 m 2 / g obtained by firing at a high temperature of 1000 ° C. or higher. A method for preparing a catalyst for reforming hydrocarbons is provided in which the catalyst is supported at a rate of 10 to 5000 wtppm and then calcined. According to the present invention, (i) a first step of obtaining carrier magnesium oxide having a specific surface area of 0.01 to 5 m 2 / g obtained by firing at a high temperature of 1000 ° C. or higher , (ii) the first step An aqueous solution containing a water-soluble rhodium compound and / or ruthenium compound is used as the carrier magnesium oxide obtained in one step, and rhodium and / or ruthenium is 10 in terms of metal in an alkaline region having a pH of 8 or higher by an equilibrium adsorption method. A second step of loading at a rate of ˜5000 wtppm, (iii) a third step of drying the rhodium and / or ruthenium-supported magnesium oxide obtained in the second step, and (iv) a dried state obtained in the third step A method for preparing a hydrocarbon reforming catalyst comprising the fourth step of calcining the rhodium and / or ruthenium-supported magnesium oxide is provided. Furthermore, according to the present invention, (i) a first step of obtaining carrier magnesium oxide having a specific surface area of 0.01 to 5 m 2 / g obtained by firing at a high temperature of 1000 ° C. or higher , (ii) the first step An aqueous solution containing a water-soluble rhodium compound and / or ruthenium compound is used as the carrier magnesium oxide obtained in one step, and rhodium and / or ruthenium is 10 in terms of metal in an alkaline region having a pH of 8 or higher by an equilibrium adsorption method. A second step of loading at a rate of ˜5000 wtppm, (iii) a third step of drying the rhodium and / or ruthenium supported magnesium oxide obtained in the second step at 35 ° C. or lower for at least 6 hours, (iv) the step A method for preparing a hydrocarbon reforming catalyst comprising the fourth step of calcining the rhodium and / or ruthenium-supported magnesium oxide obtained in the third step is proposed. It is. Furthermore, according to the present invention, (i) a first step of obtaining carrier magnesium oxide having a specific surface area of 0.01 to 5 m 2 / g obtained by firing at a high temperature of 1000 ° C. or higher , (ii) An aqueous solution containing a water-soluble rhodium compound and / or ruthenium compound is used as the carrier magnesium oxide obtained in the first step, and rhodium and / or ruthenium is converted into a metal equivalent in an alkaline region having a pH of 8 or higher by an equilibrium adsorption method. A second step of loading at a rate of 10 to 5000 wtppm, (iii) a third step of drying the rhodium and / or ruthenium-supported magnesium oxide obtained in the second step at 35 ° C. or lower for at least 6 hours, (iv) A modified hydrocarbon comprising the fourth step of firing the rhodium and / or ruthenium-supported magnesium oxide obtained in the third step at a high temperature of 200 ° C. or higher. Process for the preparation of use catalyst. Furthermore, according to the present invention, there is provided a magnesium oxide molded body for forming a carrier magnesium oxide used in the method for preparing a hydrocarbon reforming catalyst according to any one of claims 1 to 4, is formed by molding a mixture of a molding aid us is, the molding auxiliary (i) carbon, (ii) a fatty acid or its magnesium salt having 12 to 22 carbon atoms, (iii) carboxymethyl cellulose or its magnesium And (iv) at least one selected from polyvinyl alcohol, and an added amount thereof is 0.1 to 5% by weight.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, as a catalyst carrier, the specific surface area obtained by firing at a high temperature of at least 1000 ° C. is 0.01 to 5 m 2 / g of magnesium oxide (hereinafter, also simply referred to as MgO) is used. As this MgO, a commercial product can be used, and the shape is not particularly limited, and may be various shapes used as a catalyst, for example, powder, granular, spherical, columnar, cylindrical, etc. it can. MgO is obtained by baking magnesium hydroxide at 1000 to 1500 ° C, preferably 1100 to 1300 ° C, or magnesium carbonate or basic magnesium carbonate at 1000 to 1500 ° C, preferably 1100 to 1300 ° C. It is possible to use what was obtained.
[0006]
A preferred method for preparing a hydrocarbon reforming catalyst (hereinafter also simply referred to as catalyst) according to the present invention is as follows. First, in the first step, a carrier MgO having a specific surface area of 0.01 to 5 m 2 / g obtained by firing at a high temperature of 1000 ° C. or higher is obtained. In an industrial catalyst, a carrier molded into a shape such as a pellet or a ring is preferably used. When an MgO molded body having such a shape is used, the specific surface area of MgO is larger than the above range, and the crystallinity is If the MgO molded body is immersed in an aqueous solution when the catalyst metal is supported, the MgO molded body is cracked. Further, in the case of an industrial catalyst, it is usually necessary to have a radial compressive strength of 30 to 40 kg / piece, but in the case of an MgO molded body having a specific surface area larger than the above range and a low crystallinity, such strength. It becomes difficult to get. Further, when the crystallinity of the carrier MgO is lowered, the amount of the catalyst metal supported is increased, and the acid strength of the catalyst becomes too strong, so that the acid characteristics of the catalyst surface become unsatisfactory. On the other hand, if the crystallinity of the carrier MgO is too large, the amount of catalyst metal supported becomes too small to obtain a catalyst having sufficient activity. From this point, the specific surface area of the carrier MgO is preferably 0.01 m 2 / g or more and 5 m 2 / g or less .
[0007]
As one method for obtaining a carrier MgO having a specific surface area in the above range, it can be produced by calcining magnesium hydroxide at 1000 to 1500 ° C., preferably 1100 to 1300 ° C., or magnesium carbonate or basic carbonate. It can be produced by firing magnesium at 1000-1500 ° C, preferably 1100-1300 ° C. Also, when firing at a low temperature of 1000 ° C. or lower, the desired carrier MgO is controlled by increasing the partial pressure of water produced during firing to promote crystallization of MgO and controlling the crystallite size of MgO. Can be obtained. Furthermore, when the specific surface area of commercially available MgO or the like is smaller than the above range, the desired support MgO can be obtained by firing the MgO at 1000 to 1500 ° C., preferably 1100 to 1300 ° C.
Furthermore, when obtaining a low surface area support MgO, crystallization of the MgO can be promoted by forming a high partial pressure of water in the firing system at a temperature of 1000 ° C. or lower. The crystallization of MgO can be promoted by forming a high partial pressure of a gas (gas) such as CO 2 instead of the pressure.
As an atmosphere for the firing, an air atmosphere is usually used, but another gas, for example, an inert gas such as nitrogen gas may be used. The firing time is 1 hour or longer, preferably 3 hours or longer, and the upper limit is not particularly limited, but is usually about 72 hours. Moreover, not only a baking method but any method may be adopted as long as such a low surface area MgO can be obtained.
[0008]
The carrier MgO according to the present invention has a high crystallinity, the surface of the MgO is stabilized, and MgO with a strong acid point suppressed as much as possible is obtained. And in such stabilized MgO, an acid strength (Ho) has only an acid point of 2 or more, and MgO whose amount is less than 0.03 mmol / g is obtained. Therefore, by using MgO having a high degree of crystallinity, which is fired at a high temperature of 1000 ° C. or higher, as a carrier for supporting a catalytic metal, a catalyst having a stable activity in which the occurrence of a strong acid point is suppressed as much as possible and the carbon deposition reaction is suppressed is obtained. It becomes possible. The surface area of MgO used in the present invention is 0.01 to 5 m 2 / g, preferably 0.05 to 3 m 2 / g. When the surface area of the support MgO is higher than the above range, the supported amount of the catalyst metal increases, and the acid strength of the catalyst becomes too strong, so that the acid characteristics of the catalyst surface become unsatisfactory. On the other hand, when the surface area of the support MgO is smaller than the above range, the amount of the catalyst metal supported becomes too small to obtain a catalyst having sufficient activity.
[0009]
In general, it is well known that the surface area of a metal oxide and its crystallite size are in an inversely proportional relationship. Therefore, the specific surface area of MgO defined in the present invention can be defined by the particle size. For example, the crystallite size of MgO having a specific surface area of 5 m 2 / g or less can be calculated from the density and specific surface area of MgO by assuming that the particles are spherical or cubic uniform particles. This method is described in the document “Catalyst Constitution 3 (Characterization of Solid Catalyst)” (published in 1985, Kodansha Scientific, edited by the Catalysis Society of Japan, P203). For example, the crystallite size of MgO having a specific surface area of 5 m 2 / g fired at 1010 ° C. is 3500 mm.
[0010]
The crystallite size of MgO can also be measured using an X-ray diffraction method. When the crystallite size of MgO having a surface area of 5 m 2 / g or less in the present specification was measured by a “line broadening” method using an X-ray diffraction method, the value was 900 mm or more. As a measuring apparatus, an X-ray diffractometer “XRD-6000” manufactured by Shimadzu Corporation was used. When measured using metal Si as a standard substance, the crystal size of MgO was calculated from the half-value width of the diffraction peak of 2θ = 22.7 ° of MgO and the diffraction peak of 2θ = 28.4 ° of MgO of Si. The measurement conditions in the X-ray diffraction measurement are shown below.
X-ray tube: Cu (λ = 1.5406 mm), tube voltage: 40.0 kV, tube current: 30.0 mA, measurement range: 40.0 to 80.0 °, step width: 0.02 °, counting time : 0.6 seconds, slit: DS (divergence slit) = 0.5 °, SS (scattering prevention) = 0.5 °, RS (light reception) = 0.15 mm, standard material: metallic Si
Details of this line broadening method are described in the document “Experimental Chemistry Structure 4 (Solid Physical Chemistry)” (published in 1956, Maruzen, edited by The Chemical Society of Japan, P238-P250).
[0011]
For the support magnesium oxide obtained as described above, in the second step (catalyst metal supporting step), an aqueous solution containing the catalyst metal is used, and the aqueous catalyst solution is supported in an alkaline region having a pH of 8 or higher by the equilibrium adsorption method. Let In the present invention, rhodium and / or ruthenium is used as the catalyst metal.
In the supporting step, the catalyst metal is supported on the support magnesium oxide in the form of an aqueous solution. In this case, the catalyst metal is used in the form of a water-soluble compound. Examples of such compounds include halides, nitrates, sulfates, organic acid salts (such as acetates), complex salts (chelates), and the like.
An equilibrium adsorption method is used for supporting the catalytic metal aqueous solution on the support MgO. In this method, the support is immersed in the aqueous catalyst solution, and the catalytic metal in the aqueous solution is adsorbed and supported on the support under equilibrium conditions. In this case, the time for which the catalyst metal is supported on the carrier (immersion time) is 1 hour or more, preferably 3 hours or more, and the upper limit is not particularly limited, but is usually about 48 hours. Details of this equilibrium adsorption method are described in the document "Catalyst Preparation Chemistry" (published in 1980, Kodansha Scientific, P49).
[0012]
When the catalyst metal is supported on the carrier MgO as described above, the pH of the catalyst aqueous solution is 8 or more, preferably 8.5 or more. The upper limit is not particularly limited, but is usually about pH 13. For adjusting the pH of the aqueous solution, an alkaline substance such as sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, or aqueous ammonia is used.
In the present invention, the amount of the catalyst metal supported on the support MgO is defined as a catalyst metal equivalent amount of 10 to 5000 wtppm, preferably 100 to 2000 wtppm with respect to the support MgO. When the amount of the catalyst metal supported exceeds the above range, the catalyst cost increases and the carbon deposition activity of the catalyst increases, and the amount of carbon deposition increases when the catalyst is used. On the other hand, if the amount is less than the above range, sufficient catalytic activity cannot be obtained. The amount of the catalyst metal supported can be adjusted by the conditions for supporting the catalyst metal aqueous solution on the support MgO, for example, the catalyst metal concentration in the aqueous solution, the surface area of the support MgO, and the like.
[0013]
In the third step (drying step), the catalyst metal-supported MgO obtained by supporting the catalyst metal in the form of an aqueous solution on the support MgO as described above is held at a temperature of 35 ° C. or lower for 6 hours or more and dried. Let A preferable drying temperature is 10 to 25 ° C. The drying time may be 6 hours or more, preferably 12 hours or more, and the upper limit is not particularly limited, but is usually about 72 hours. By such a drying treatment, rapid evaporation of moisture from MgO is avoided, and as a result, the catalyst metal is supported on the support MgO in a highly dispersed state without agglomeration. When the drying temperature or drying time is out of the above range, a catalyst containing a highly dispersible catalyst metal cannot be obtained.
[0014]
The dried product obtained as described above is baked at a high temperature of 200 ° C. or higher for 1 hour or longer in the fourth step. In this case, air is usually used as the firing atmosphere, but other gases (inert gas or the like) may be used. The firing temperature is 200 ° C. or higher, preferably 500 ° C. or higher, and the upper limit is not particularly limited, but is usually about 1100 ° C. The preferred firing time is 2 hours or more, more preferably 3 hours or more, and the upper limit is not particularly limited, but is usually about 24 hours. By this secondary calcination, the thermal stability of the catalyst metal is enhanced, and a catalyst with good thermal stability can be obtained.
[0015]
In order to reduce the catalyst cost, the amount of catalyst metal supported on the support should be reduced as much as possible, and at the same time, the catalyst metal particles supported on the support should be agglomerated as much as possible so as to develop sufficient reaction activity. It is necessary to suppress and form fine particles. According to the study by the present inventors, the crystallization of the support MgO is increased to maintain the specific surface area in a range of 5 m 2 / g or less, and the supported amount of the catalyst metal on the support MgO is extremely 10 to 5000 wtppm. When the catalyst metal is held in a small amount and supported on the support MgO, the catalyst metal is slowly supported in the form of an aqueous solution under equilibrium conditions over a long period of time by the equilibrium adsorption method. It has been found that when the catalyst is dried slowly at a temperature of 5 ° C., the catalyst metal is supported uniformly and an inexpensive catalyst having sufficient activity as a hydrocarbon reforming catalyst can be obtained.
[0016]
Various modifications can be made in the above-described catalyst preparation method. For example, the method of supporting the catalyst metal on the carrier magnesium oxide is not limited to the equilibrium adsorption method, and other methods such as a conventional impregnation method, an immersion method, an ion exchange method, and the like can be used. In addition, in the case where the aqueous solution containing the catalyst metal is supported on the magnesium oxide and then dried, a heating condition of about 35 to 200 ° C. is used in some cases, and the dried product is calcined. Depending on the temperature, it may be performed at a temperature of about 200 to 800 ° C.
[0017]
When the catalyst is prepared according to the present invention, the magnesium oxide for forming the catalyst carrier is preferably used as a magnesium oxide molded body formed by blending a molding aid with magnesium oxide. By using this molding aid, workability at the time of molding is improved and the strength of the obtained molded body is improved. Molding aids in this case include (i) carbon (carbon), (ii) fatty acids having 12 to 22 carbon atoms or magnesium salts thereof, (iii) carboxymethyl cellulose (CMC) or magnesium salts thereof, and (iv) polyvinyl alcohol. It is preferable to use at least one compound selected from the group consisting of These molding aids are usually used in powder form.
As the carbon, graphite, carbon black, activated carbon and the like are used. Examples of the fatty acid include lauric acid, myristic acid, palmitic acid, stearic acid, and behenic acid.
[0018]
In order to produce the magnesium oxide molded body for the catalyst carrier, a molding aid is added to the powdered magnesium oxide and mixed uniformly, and then the mixture is molded into a required shape. The average particle size of the powdered magnesium oxide is 1-1000 μm, preferably 10-100 μm. On the other hand, the average particle size of the molding aid is 1-1000 μm, preferably 10-100 μm. The amount of the molding aid added to the magnesium oxide is 0.1 to 5% by weight, preferably 0.5 to 3.0% by weight, based on the total amount of magnesium oxide and the molding aid.
When forming a mixture of the magnesium oxide forming aid As the molding conditions, usually, at ordinary temperature 3000~100kg / cm 2 G, and preferably a pressure of 2000~200kg / cm 2 G adopted. As a molding method, a press molding method is employed, but a tableting molding method or the like can also be employed. The shape of the molded body is not particularly limited as long as it is a shape adopted for a normal catalyst. Such shapes include tablet shapes, columnar shapes, ring shapes, hollow cylindrical shapes, and the like. The dimension of the molded body is usually 3 to 30 mm, preferably 5 to 25 mm, in terms of the major axis length, but an appropriate dimension may be adopted depending on the catalyst bed.
[0019]
The magnesium oxide molded body according to the present invention has excellent mechanical strength after firing, and usually has a compressive strength in the radial direction of 30 to 70 kg / piece.
Accordingly, such a molded article has good handleability and is not easily broken during firing.
In addition, when the MgO shaped body has a low crystallinity of MgO, it is usually subjected to primary firing at a high temperature of 1000 ° C. or higher in order to obtain a desired carrier magnesium oxide. The molding aid inside is oxidized and removed. The magnesium oxide thus obtained is suitable as the carrier magnesium oxide used for the preparation of the catalyst of the present invention.
[0020]
In the catalyst of the present invention obtained as described above, the catalyst metal loading is 10 to 5000 wtppm, preferably 100 to 2000 wtppm, with respect to the support MgO, and the specific surface area is 0.01 to 5 m 2 / g, Preferably it is 0.05-3 m < 2 > / g.
In addition, the specific surface area said regarding a catalyst and MgO in this specification is measured at the temperature of 15 degreeC by "BET" method, As a measuring device, "SA-100" by Shibata Kagakusha is used. Used.
[0021]
The catalyst of the present invention obtained as described above has an acidic property that is preferable as a catalyst for hydrocarbon reforming. When a large amount of strong acid sites are present on the catalyst surface, a carbon deposition reaction as a side reaction is promoted on the acid sites, carbon is deposited, and catalyst poisoning occurs due to the deposited carbon.
[0022]
The catalyst of the present invention generally has only an acid strength (Ho) greater than 2, preferably 3.3 or higher, and its content is less than 0.03 mmol / g, preferably 0.8. It is 02 mmol / g or less. The acid strength (Ho) can be adjusted by adjusting the temperature and time when the support MgO is first calcined. In the catalyst of the present invention, the expression of a strong acid point is suppressed and the carbon deposition activity is greatly suppressed.
[0023]
The acid strength (Ho) in the present specification is expressed as the ability of the catalyst to give protons to the basic indicator (B − ), and is represented by the following formula.
Ho = pKa (= pK B - H +) + log [B] / [B - H +] (1)
In the formula, K B - H + is a basic indicator B - and the acidic sites H + B is reacted, the acid of basic indicator (B - H +) its acidic substance in the reaction to produce the B - The dissociation constant of H + is shown. [B] / [B − H + ] indicates the concentration ratio of B − and B − H + .
The stronger the acid point, the more the proton with a small pK B − H + is protonated, so the Ho value becomes smaller.
[0024]
The acid strength in this specification is measured as follows.
(Measurement method of acid strength)
The acid strength Ho (Hammett index) function in this specification is an acid strength function, edited by the Catalysis Society of Japan, "Catalyst Experiment Handbook" (published in 1986, Kodansha Scientific), p. 172, measured by “Benesi method”. Addition of an indicator with known pKa to the catalyst and discoloration indicates that Ho has an acid point smaller than its pKa. When a predetermined amount of butylamine, which is a basic molecule, is adsorbed to an acid point and titrated with an indicator having a different pKa, the number of acid points can be measured from the amount of butylamine and the acid strength can be measured from the value of pKa. The measurement temperature is room temperature.
[0025]
In order to produce synthesis gas (a mixed gas of hydrogen and carbon monoxide) using the catalyst of the present invention, hydrocarbons and steam and / or carbon dioxide (CO 2 ) are reacted in the presence of the catalyst. A hydrocarbon and oxygen may be reacted. As the hydrocarbon, lower hydrocarbons such as methane, ethane, propane, butane, and naphtha are used, and methane is preferably used. In the present invention, natural gas (methane gas) containing carbon dioxide gas can be advantageously used as a reaction raw material.
In the case of a method of reacting methane and carbon dioxide (CO 2 ) (CO 2 reforming), the reaction is represented by the following formula.
[Chemical 1]
[Chemical 2]
In the CO 2 reforming, the reaction temperature is 500 to 1200 ° C., preferably 600 to 1000 ° C., the reaction pressure is pressurization, 5 to 40 kg / cm 2 G, preferably 5 to 30 kg / cm 2 G. It is. When this reaction is carried out in a fixed bed system, the gas space velocity (GHSV) is 1,000 to 10,000 hr −1 , preferably 2,000 to 8,000 hr −1 . The proportion of CO 2 used relative to the raw material hydrocarbon is 20 to 0.5 moles of CO 2 , preferably 10 to 1 mole per mole of carbon in the raw material hydrocarbon.
In steam reforming, the reaction temperature is 600 to 1200 ° C., preferably 600 to 1000 ° C., the reaction pressure is pressurized, 1 to 40 kg / cm 2 G, preferably 5 to 30 kg / cm 2 G. is there. When this reaction is carried out in a fixed bed system, the gas space velocity (GHSV) is 1,000 to 10,000 hr −1 , preferably 2,000 to 8,000 hr −1 or less. In terms of the steam usage ratio relative to the raw material hydrocarbon, 0.5 to 5 mol, preferably 1 to 2 mol, more preferably 1 to 1.5 mol of steam (H 2 O) per mol of carbon in the raw material hydrocarbon. Is the ratio.
When performing steam reforming according to the present invention, as described above, even if the steam (H 2 O) per mole of the raw material hydrocarbon is kept at 2 moles or less, carbon deposition is suppressed and industrially produced. Advantageously, synthesis gas can be produced. In the conventional case, considering that 2 to 5 mol of steam is required per 1 mol of carbon of the raw material hydrocarbon, the reforming reaction can proceed smoothly by using 2 mol or less of steam. This is a great industrial advantage of the inventive catalyst.
The catalyst of the present invention is advantageously used as a catalyst for reacting a mixture of steam and CO 2 with a hydrocarbon. In this case, the mixing ratio of steam and CO 2 is not particularly limited, but is generally 0.1 to 10 in terms of H 2 O / CO 2 molar ratio.
[0027]
When the hydrocarbon and oxygen are reacted using the catalyst of the present invention, as the hydrocarbon, the hydrocarbon system as described above is used, and preferably methane. As the oxygen source, oxygen, air, or oxygen-enriched air is used. In the present invention, natural gas (methane gas) containing carbon dioxide gas can be advantageously used as a reaction raw material.
When methane and oxygen are reacted, the reaction is represented by the following formula.
[Chemical 3]
The various reactions using the catalyst of the present invention are carried out in various catalyst systems such as a fixed bed system, a fluidized bed system, a suspension bed system, and a moving bed system, but are preferably carried out in a fixed bed system.
[0028]
【Example】
Next, the present invention will be described in more detail with reference to examples.
[0029]
Example 1
Commercially available powder of 98.7 wt% or more of magnesium oxide (MgO) was mixed with 3.0 wt% carbon as a lubricant, and tablet-formed 1/8 inch pellets were air-treated at 1060 ° C for 3 hours (hours) After firing, this was used as a catalyst carrier MgO (A).
Next, it was immersed in a rhodium (III) acetate aqueous solution containing 3.9 wt% Rh for 26 hours (hours). The aqueous solution was an aqueous magnesium hydroxide solution, and the pH was adjusted to 9.7. In this way, Rh was adsorbed on the catalyst carrier MgO (A) by equilibrium, and then filtered to obtain catalyst carrier MgO (A) on which Rh was adsorbed in the form of an aqueous solution. The amount of Rh supported in this case is 3750 wtppm with respect to the carrier MgO (A) in terms of Rh metal.
Next, the carrier MgO (A) adsorbing Rh was dried in air at a temperature of 35 ° C. for 52 h, and then calcined in air at 850 ° C. for 3 h to obtain the catalyst (A) of the present invention.
This catalyst (A) contains 3750 wtppm of Rh as Rh metal with respect to the carrier MgO, and its surface area was 1.2 m 2 / g. Moreover, the acid point consisted only of the acid point whose acid strength (Ho) is 3.3 or more, and the content was 0.01 mmol / g.
[0030]
Example 2
MgO 1/8 inch pellets formed with commercially available 98.0 wt% magnesium oxide (MgO) were calcined in air at 1000 ° C. for 2 h (hours) and used as catalyst support MgO (B). .
Next, it was immersed in a ruthenium (III) chloride aqueous solution containing 0.1 wt% Ru for 19 hours (hours). The aqueous solution was an aqueous magnesium hydroxide solution, and the pH was adjusted to 9.7. In this way, Ru was adsorbed on the catalyst carrier MgO (B) in equilibrium, and then filtered to obtain a catalyst carrier MgO (B) on which Ru was adsorbed in the form of an aqueous solution. In this case, the amount of Ru supported is 125 wtppm with respect to the support MgO (B) in terms of Ru metal.
Next, the carrier MgO (B) on which Ru was adsorbed was dried in air at a temperature of 30 ° C. for 72 h and then calcined in air at 860 ° C. for 2.5 h to obtain the catalyst (B) of the present invention.
This catalyst (B) contains Ru as a Ru metal in a proportion of 125 wtppm with respect to the carrier MgO (B), and its surface area was 4.8 m 2 / g. Moreover, the acid point consisted only of the acid point whose acid strength (Ho) is 3.3 or more, and the content was 0.03 mmol / g.
[0031]
Example 3
A commercially available magnesium oxide (MgO) having a purity of 99.9 wt% was mixed with 2.5 wt% magnesium stearate, and 1/8 inch pellets of MgO were fired in air at 1200 ° C for 2.5 hours (hours). This was used as catalyst support MgO (C).
Next, it was immersed in a rhodium (III) acetate aqueous solution containing 2.6 wt% Rh for 26 h (hour). The aqueous solution was an aqueous magnesium hydroxide solution, and the pH was adjusted to 9.7. In this way, Rh was adsorbed on the catalyst support MgO (C) by equilibrium, and then filtered to obtain a catalyst support MgO (C) in which Rh was adsorbed in the form of an aqueous solution. The amount of Rh supported in this case is 1750 wtppm with respect to the carrier MgO (C) in terms of Rh metal.
Next, the carrier MgO (C) adsorbing Rh was dried in air at a temperature of 20 ° C. for 34 h, and then calcined in air at 950 ° C. for 3.5 h to obtain the catalyst (C) of the present invention.
The catalyst (C) contained 1750 wtppm of Rh as Rh metal with respect to the carrier MgO, and its surface area was 0.2 m 2 / g. Moreover, the acid point consisted of only an acid point having an acid strength (Ho) of 3.3 or more, and its content was 0.002 mmol / g.
[0032]
Reaction example 1
30 cc of the catalyst (A) prepared in Example 1 was charged into a reactor, and a CO 2 reforming test of methane was performed.
The catalyst, after 1h reduction treatment beforehand with H 2 900 ° C. in a stream, CH 4: CO 2 molar ratio = 1: 0.4, CH 4: H 2 O molar ratio = 1: 0.85 of the raw material gas Was treated under the conditions of a pressure of 20 kg / cm 2 G, a temperature of 820 ° C., and a methane standard GHSV = 4000 hr −1 . The CH 4 conversion after 5 hours from the start of the reaction is 50% (equilibrium conversion of CH 4 under experimental conditions = 50%), and the CH 4 conversion after 1200 hours from the start of the reaction is 50%. %Met.
Here, the conversion rate of CH 4 is defined by the following equation.
CH 4 conversion (%) = (A−B) / A × 100
A: CH 4 molar number in the raw material B: CH 4 molar number [0033] of the product
Reaction example 2
30 cc of the catalyst (B) prepared in Example 2 was charged into a reactor, and a CO 2 reforming test of methane was performed.
The catalyst was previously reduced in an H 2 stream at 900 ° C. for 1 h, and then a raw material gas of CH 4 : CO 2 molar ratio = 1: 1 was used, a pressure of 10 kg / cm 2 G, a temperature of 840 ° C., and a methane standard GHSV. = Treated under the condition of 5000 hr -1 . The CH 4 conversion after 5 h from the start of the reaction is 65% (equilibrium conversion of CH 4 under the experimental conditions = 65%), and the CH 4 conversion after 460 h from the start of the reaction is 65%. %Met.
[0034]
Reaction example 3
30 cc of the catalyst (C) prepared in Example 3 was charged into the reactor, and a CO 2 reforming test of methane was performed.
The catalyst was previously reduced in an H 2 stream at 900 ° C. for 1 h, and then a raw material gas having a CH 4 : CO 2 molar ratio = 1: 1 was used, a pressure of 20 kg / cm 2 G, a temperature of 840 ° C., and a methane standard GHSV. = 3500 hr -1 . The CH 4 conversion after 5 hours from the start of the reaction is 53% (CH 4 equilibrium conversion under experimental conditions = 53%), and the CH 4 conversion after 250 hours from the start of the reaction is 53%. %Met.
[0035]
【The invention's effect】
According to the present invention, it is possible to obtain an inexpensive hydrocarbon reforming catalyst in which carbon deposition activity is remarkably suppressed while the amount of catalyst metal supported is extremely small.
Claims (5)
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| JP2006061772A (en) * | 2004-08-25 | 2006-03-09 | Chiyoda Corp | Method for preparing synthesis gas producing catalyst |
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| JP4189068B2 (en) * | 1998-09-30 | 2008-12-03 | 千代田化工建設株式会社 | Method for producing dimethyl ether from lower hydrocarbon gas |
| WO2003004405A1 (en) * | 2001-07-04 | 2003-01-16 | Chiyoda Corporation | Device and method for manufacturing synthesis gas from low-grade hydrocarbon gas |
| JP4528059B2 (en) * | 2004-08-24 | 2010-08-18 | 千代田化工建設株式会社 | Synthesis gas production catalyst, synthesis gas production catalyst preparation method, and synthesis gas production method |
| JP6131370B1 (en) * | 2016-06-10 | 2017-05-17 | 千代田化工建設株式会社 | Syngas production catalyst carrier and production method thereof, synthesis gas production catalyst and production method thereof, and synthesis gas production method |
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| JP2006061772A (en) * | 2004-08-25 | 2006-03-09 | Chiyoda Corp | Method for preparing synthesis gas producing catalyst |
| JP4589682B2 (en) * | 2004-08-25 | 2010-12-01 | 千代田化工建設株式会社 | Method for preparing catalyst for syngas production |
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Free format text: JAPANESE INTERMEDIATE CODE: R250 |
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| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
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| EXPY | Cancellation because of completion of term |