JP3868246B2 - Exhaust gas treatment catalyst and exhaust gas treatment method - Google Patents
Exhaust gas treatment catalyst and exhaust gas treatment method Download PDFInfo
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- JP3868246B2 JP3868246B2 JP2001305600A JP2001305600A JP3868246B2 JP 3868246 B2 JP3868246 B2 JP 3868246B2 JP 2001305600 A JP2001305600 A JP 2001305600A JP 2001305600 A JP2001305600 A JP 2001305600A JP 3868246 B2 JP3868246 B2 JP 3868246B2
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- molybdenum
- catalyst
- exhaust gas
- titanium
- oxide
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- 239000003054 catalyst Substances 0.000 title claims description 88
- 238000000034 method Methods 0.000 title claims description 21
- 239000007789 gas Substances 0.000 claims description 49
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 claims description 43
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 30
- 229910052750 molybdenum Inorganic materials 0.000 claims description 30
- 239000011733 molybdenum Substances 0.000 claims description 30
- PQQKPALAQIIWST-UHFFFAOYSA-N oxomolybdenum Chemical compound [Mo]=O PQQKPALAQIIWST-UHFFFAOYSA-N 0.000 claims description 22
- 239000002245 particle Substances 0.000 claims description 22
- 229910000476 molybdenum oxide Inorganic materials 0.000 claims description 21
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 19
- 229910052719 titanium Inorganic materials 0.000 claims description 19
- 239000010936 titanium Substances 0.000 claims description 19
- 150000002896 organic halogen compounds Chemical class 0.000 claims description 14
- 229910052720 vanadium Inorganic materials 0.000 claims description 13
- QGZKDVFQNNGYKY-UHFFFAOYSA-N ammonia Natural products N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 11
- 239000007864 aqueous solution Substances 0.000 claims description 10
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 6
- 229910052710 silicon Inorganic materials 0.000 claims description 6
- 239000010703 silicon Substances 0.000 claims description 6
- 150000003609 titanium compounds Chemical class 0.000 claims description 6
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 5
- 150000001875 compounds Chemical class 0.000 claims description 5
- 238000012545 processing Methods 0.000 claims description 5
- 238000002156 mixing Methods 0.000 claims description 4
- 239000002244 precipitate Substances 0.000 claims description 4
- GPPXJZIENCGNKB-UHFFFAOYSA-N vanadium Chemical compound [V]#[V] GPPXJZIENCGNKB-UHFFFAOYSA-N 0.000 claims 1
- 238000004453 electron probe microanalysis Methods 0.000 description 22
- 238000004458 analytical method Methods 0.000 description 21
- 238000005259 measurement Methods 0.000 description 16
- 239000000203 mixture Substances 0.000 description 16
- 238000000354 decomposition reaction Methods 0.000 description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 14
- RSNKHMHUYALIHE-UHFFFAOYSA-N [Mo].[Si].[Ti] Chemical compound [Mo].[Si].[Ti] RSNKHMHUYALIHE-UHFFFAOYSA-N 0.000 description 13
- ZPZCREMGFMRIRR-UHFFFAOYSA-N molybdenum titanium Chemical compound [Ti].[Mo] ZPZCREMGFMRIRR-UHFFFAOYSA-N 0.000 description 13
- 239000000243 solution Substances 0.000 description 12
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 12
- XHCLAFWTIXFWPH-UHFFFAOYSA-N [O-2].[O-2].[O-2].[O-2].[O-2].[V+5].[V+5] Chemical group [O-2].[O-2].[O-2].[O-2].[O-2].[V+5].[V+5] XHCLAFWTIXFWPH-UHFFFAOYSA-N 0.000 description 11
- 229910001935 vanadium oxide Inorganic materials 0.000 description 11
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 description 9
- 229910010413 TiO 2 Inorganic materials 0.000 description 9
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 9
- 239000000843 powder Substances 0.000 description 9
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 8
- 238000010894 electron beam technology Methods 0.000 description 7
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 6
- VLAPMBHFAWRUQP-UHFFFAOYSA-L molybdic acid Chemical compound O[Mo](O)(=O)=O VLAPMBHFAWRUQP-UHFFFAOYSA-L 0.000 description 6
- 150000002013 dioxins Chemical class 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 238000002360 preparation method Methods 0.000 description 5
- 239000002002 slurry Substances 0.000 description 5
- 229910004298 SiO 2 Inorganic materials 0.000 description 4
- 229910021529 ammonia Inorganic materials 0.000 description 4
- 235000011114 ammonium hydroxide Nutrition 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 238000000465 moulding Methods 0.000 description 4
- 238000003756 stirring Methods 0.000 description 4
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 3
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 3
- UNTBPXHCXVWYOI-UHFFFAOYSA-O azanium;oxido(dioxo)vanadium Chemical compound [NH4+].[O-][V](=O)=O UNTBPXHCXVWYOI-UHFFFAOYSA-O 0.000 description 3
- 239000004202 carbamide Substances 0.000 description 3
- 239000003638 chemical reducing agent Substances 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 150000004045 organic chlorine compounds Chemical class 0.000 description 3
- 235000006408 oxalic acid Nutrition 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 150000003377 silicon compounds Chemical class 0.000 description 3
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 3
- 229910052721 tungsten Inorganic materials 0.000 description 3
- 239000010937 tungsten Substances 0.000 description 3
- KVGZZAHHUNAVKZ-UHFFFAOYSA-N 1,4-Dioxin Chemical compound O1C=COC=C1 KVGZZAHHUNAVKZ-UHFFFAOYSA-N 0.000 description 2
- HZAXFHJVJLSVMW-UHFFFAOYSA-N 2-Aminoethan-1-ol Chemical compound NCCO HZAXFHJVJLSVMW-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- UGACIEPFGXRWCH-UHFFFAOYSA-N [Si].[Ti] Chemical compound [Si].[Ti] UGACIEPFGXRWCH-UHFFFAOYSA-N 0.000 description 2
- 150000003863 ammonium salts Chemical class 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000010304 firing Methods 0.000 description 2
- 150000004820 halides Chemical class 0.000 description 2
- 150000004679 hydroxides Chemical class 0.000 description 2
- 150000002484 inorganic compounds Chemical class 0.000 description 2
- 238000004898 kneading Methods 0.000 description 2
- 239000005078 molybdenum compound Substances 0.000 description 2
- 150000002752 molybdenum compounds Chemical class 0.000 description 2
- JKQOBWVOAYFWKG-UHFFFAOYSA-N molybdenum trioxide Chemical compound O=[Mo](=O)=O JKQOBWVOAYFWKG-UHFFFAOYSA-N 0.000 description 2
- 150000002894 organic compounds Chemical class 0.000 description 2
- DCKVFVYPWDKYDN-UHFFFAOYSA-L oxygen(2-);titanium(4+);sulfate Chemical compound [O-2].[Ti+4].[O-]S([O-])(=O)=O DCKVFVYPWDKYDN-UHFFFAOYSA-L 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 239000012495 reaction gas Substances 0.000 description 2
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 229910000349 titanium oxysulfate Inorganic materials 0.000 description 2
- 229910000348 titanium sulfate Inorganic materials 0.000 description 2
- XJDNKRIXUMDJCW-UHFFFAOYSA-J titanium tetrachloride Chemical compound Cl[Ti](Cl)(Cl)Cl XJDNKRIXUMDJCW-UHFFFAOYSA-J 0.000 description 2
- VXUYXOFXAQZZMF-UHFFFAOYSA-N titanium(IV) isopropoxide Chemical compound CC(C)O[Ti](OC(C)C)(OC(C)C)OC(C)C VXUYXOFXAQZZMF-UHFFFAOYSA-N 0.000 description 2
- 231100000331 toxic Toxicity 0.000 description 2
- 230000002588 toxic effect Effects 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- VGVRPFIJEJYOFN-UHFFFAOYSA-N 2,3,4,6-tetrachlorophenol Chemical class OC1=C(Cl)C=C(Cl)C(Cl)=C1Cl VGVRPFIJEJYOFN-UHFFFAOYSA-N 0.000 description 1
- VXEGSRKPIUDPQT-UHFFFAOYSA-N 4-[4-(4-methoxyphenyl)piperazin-1-yl]aniline Chemical compound C1=CC(OC)=CC=C1N1CCN(C=2C=CC(N)=CC=2)CC1 VXEGSRKPIUDPQT-UHFFFAOYSA-N 0.000 description 1
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 238000003916 acid precipitation Methods 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- KCXMKQUNVWSEMD-UHFFFAOYSA-N benzyl chloride Chemical compound ClCC1=CC=CC=C1 KCXMKQUNVWSEMD-UHFFFAOYSA-N 0.000 description 1
- 238000003421 catalytic decomposition reaction Methods 0.000 description 1
- 238000010531 catalytic reduction reaction Methods 0.000 description 1
- 239000008119 colloidal silica Substances 0.000 description 1
- 229910052878 cordierite Inorganic materials 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- JSKIRARMQDRGJZ-UHFFFAOYSA-N dimagnesium dioxido-bis[(1-oxido-3-oxo-2,4,6,8,9-pentaoxa-1,3-disila-5,7-dialuminabicyclo[3.3.1]nonan-7-yl)oxy]silane Chemical compound [Mg++].[Mg++].[O-][Si]([O-])(O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2)O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2 JSKIRARMQDRGJZ-UHFFFAOYSA-N 0.000 description 1
- KZHJGOXRZJKJNY-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Si]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O KZHJGOXRZJKJNY-UHFFFAOYSA-N 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
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- 239000010419 fine particle Substances 0.000 description 1
- 238000005470 impregnation Methods 0.000 description 1
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- 150000004706 metal oxides Chemical class 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 229910003465 moissanite Inorganic materials 0.000 description 1
- MEFBJEMVZONFCJ-UHFFFAOYSA-N molybdate Chemical compound [O-][Mo]([O-])(=O)=O MEFBJEMVZONFCJ-UHFFFAOYSA-N 0.000 description 1
- 229910052863 mullite Inorganic materials 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 150000003891 oxalate salts Chemical class 0.000 description 1
- BBJSDUUHGVDNKL-UHFFFAOYSA-J oxalate;titanium(4+) Chemical compound [Ti+4].[O-]C(=O)C([O-])=O.[O-]C(=O)C([O-])=O BBJSDUUHGVDNKL-UHFFFAOYSA-J 0.000 description 1
- SOQBVABWOPYFQZ-UHFFFAOYSA-N oxygen(2-);titanium(4+) Chemical class [O-2].[O-2].[Ti+4] SOQBVABWOPYFQZ-UHFFFAOYSA-N 0.000 description 1
- 239000008188 pellet Substances 0.000 description 1
- 150000003071 polychlorinated biphenyls Chemical class 0.000 description 1
- 235000019353 potassium silicate Nutrition 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 229910002027 silica gel Inorganic materials 0.000 description 1
- 239000000741 silica gel Substances 0.000 description 1
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
- 239000005049 silicon tetrachloride Substances 0.000 description 1
- CBXWGGFGZDVPNV-UHFFFAOYSA-N so4-so4 Chemical compound OS(O)(=O)=O.OS(O)(=O)=O CBXWGGFGZDVPNV-UHFFFAOYSA-N 0.000 description 1
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 description 1
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Images
Description
【０００１】
【発明の属する技術分野】
本発明は、排ガス処理用触媒、および排ガスの処理方法に関する。特に、排ガス中の窒素酸化物（ＮＯｘ）を除去するための脱硝触媒、及び排ガス中のダイオキシン類などの毒性有機ハロゲン化合物を除去するための有機ハロゲン化合物の除去用触媒として優れた排ガス処理用触媒、および、それを用いた排ガスの処理方法に関する。
【０００２】
【従来の技術】
現在実用化されている排ガス中の窒素酸化物除去方法としては、アンモニアまたは尿素などの還元剤を用いて排ガス中の窒素酸化物を脱硝触媒上で接触還元し、無害な窒素と水とに分解する選択的触媒還元いわゆるＳＣＲ法が一般的である。
近年、酸性雨に代表されるように窒素酸化物による環境汚染が世界的に深刻化するに伴い、脱硝技術の高効率化が要求されている。
このような状況下、チタンとバナジウムの酸化物およびモリブデン、タングステンなどの酸化物からなる脱硝触媒（特公昭５３−２８１４８号公報）や、チタンおよびケイ素からなる二元系酸化物と、バナジウム、タングステン、モリブデンなどの金属酸化物とからなる脱硝触媒（特公昭５７−３０５３２号公報）が実用化され、現在、広く用いられている。
【０００３】
これらの触媒は、いずれも優れた窒素酸化物の除去性能を有し、かつ耐久性に優れているが、さらに高性能な触媒が出現することは好ましいことである。
また、産業廃棄物や都市廃棄物を処理する焼却施設から発生する排ガス中にはダイオキシン類、ＰＣＢ、クロロフェノールなどの極微量の毒性有機ハロゲン化合物が含まれており、特にダイオキシン類は微量であってもきわめて有毒であり、人体に重大な影響を及ぼすため、その除去技術が早急に求められている。触媒分解法は最も有効な技術のひとつであり、一般的にチタン、バナジウム、タングステン、モリブデンなどの酸化物を含有する触媒が用いられているが、排ガス条件によっては充分な性能とはいえず、さらなる触媒性能の向上が望まれている。
【０００４】
【発明が解決しようとする課題】
したがって、本発明の課題は、窒素酸化物の除去性能に一層優れた脱硝触媒、及び、排ガス中のダイオキシン類等の有機ハロゲン化合物を効率良く除去するのに好適な触媒として優れた排ガス処理用触媒、および、それを用いた排ガス処理方法を提供することにある。
【０００５】
【課題を解決するための手段】
本発明者は、上記課題を解決するべく鋭意検討を行った。その結果、チタン、モリブデン、バナジウムの酸化物を含有する触媒中のモリブデン酸化物の粒子径に着目し、当該粒子径を小さく制御することによって、触媒性能（脱硝性能、ダイオキシン類分解性能）に優れた、排ガス処理用触媒を提供できることを見出した。
すなわち、本発明にかかる排ガス処理用触媒は、チタン、モリブデン、バナジウムの酸化物を含有する触媒であって、前記モリブデンの酸化物は、モリブデンの化合物をアンモニア水に溶解させてなるモリブデン水溶液とチタン化合物の水溶液とを混合して沈殿物を生成する工程を経ることにより調製されていて、粒子径が５μｍより大きいものの割合が５％以下である、ことを特徴とする。
【０００６】
さらに、本発明にかかる排ガス処理方法は、本発明の触媒を用いて窒素酸化物を含む排ガスを処理することを特徴とする。
また、本発明にかかる排ガス処理方法は、本発明の触媒を用いて有機ハロゲン化合物を含む排ガスを処理することを特徴とする。
【０００７】
【発明の実施の形態】
本発明の排ガス処理用触媒は、チタン、モリブデン、バナジウムの酸化物を含有する触媒であって、粒子径が５μｍより大きいモリブデン酸化物の割合が５％以下であることを特徴とする。
上記のような粒子の状態を分析する方法としては、特に限定されないが、例えば、ＥＰＭＡやＳＥＭ−ＥＤＳなどが挙げられる。以下、ＥＰＭＡ分析を例として説明する。
触媒表面のＥＰＭＡ分析とは、分析対象触媒中の触媒組成成分の状態を見るための分析であり、通常一般に行うＥＰＭＡ分析と同様の分析方法で行う。ＥＰＭＡ分析によって触媒の状態を分析する場合には、例えば、任意の触媒表面を少量切り出したものを測定試料とし、この測定試料における特定部分について測定を行う方法や、触媒が小さい場合にはそのまま測定試料とする方法などが挙げられるが、特に限定されない。本発明にかかる排ガス処理用触媒は、例えば、この触媒表面の測定面積を４×１０4μｍ2とした場合のＥＰＭＡ分析で規定できる。もちろん、この測定面積は条件によって適宜調整すればよい。
【０００８】
一般に、触媒表面の任意の一部分において観察される状態は触媒全体の状態をそのまま反映していると扱うことができ、例えば、触媒表面を測定面積４×１０4μｍ2でＥＰＭＡ分析した場合に、粒子径が５μｍより大きいモリブデン酸化物の前記測定面積中における割合が５％以下である場合には、触媒全体においても同様の状態であると推測することができる。なお、任意の数箇所の測定結果を平均してもよい。したがって、本発明の排ガス処理用触媒において、例えば、触媒表面を測定面積４×１０4μｍ2でＥＰＭＡ分析した場合に、粒子径が５μｍより大きいモリブデン酸化物の前記測定面積中における割合が５％以下であることは、当該触媒全体にわたる状態を意味している。
【０００９】
なお、本発明における粒子径とは、球状粒子の場合は直径を意味するが、一定の直径を持たない場合（球状でない場合）には最長の径のことを意味する。
本発明の排ガス処理用触媒は、モリブデン酸化物の粒子径が５μｍ以下、好ましくは３μｍ以下であることが特徴である。また、５μｍより大きいモリブデン酸化物の割合が５％以下、好ましくは３％以下、より好ましくは１％以下であることが特徴である。上記モリブデン粒子径およびその割合は、ＥＰＭＡチャートから実測した数平均より算出した。粒子径が５μｍより大きいモリブデン酸化物の割合が５％よりも多いと、本発明の効果が十分に達成できないので好ましくない。
【００１０】
本発明の排ガス処理用触媒は、チタン、モリブデン、バナジウムの酸化物を含有する触媒であり、触媒の製造に常用される沈殿法、酸化物混合法、混練法、担持法、含浸法などによって製造できる触媒であるが、好ましくは、バナジウム酸化物と、予め調製されたチタンとモリブデンからなる二元系均密混合酸化物、および／または、予め調製されたチタン、ケイ素およびモリブデンからなる三元系均密混合酸化物を含有する触媒である。
予め調製されたチタンとモリブデンからなる二元系均密混合酸化物を含有する場合の触媒の組成は、各元素の酸化物換算重量比で、チタンの酸化物は好ましくは５５〜９９．４重量％、より好ましくは６０〜９０重量％、モリブデン酸化物は好ましくは０．５〜３０重量％、より好ましくは１〜２５重量％、バナジウム酸化物は好ましくは０．１〜１５重量％である。また、予め調製されたチタン、ケイ素およびモリブデンからなる三元系均密混合酸化物を含有する場合の触媒の組成は、各元素の酸化物換算重量比で、チタンの酸化物は好ましくは５〜９８．９重量％、より好ましくは１０〜９０重量％、ケイ素の酸化物は好ましくは０．５〜５０重量％、より好ましくは５〜５０重量％、モリブデン酸化物は好ましくは０．５〜３０重量％、より好ましくは１〜２５重量％、バナジウム酸化物は好ましくは０．１〜１５重量％である。
【００１１】
チタン−モリブデン均密混合酸化物、および／または、チタン−ケイ素−モリブデン均密混合酸化物を予め調製することにより、チタンとモリブデンをより均密に分散混合することができ、モリブデンの分散性が向上するとともに、モリブデン酸化物の粒子径を小さく制御し易くなる。また、チタンとモリブデンの相互作用が強められることにより高い分解活性が得られるようになる。そのため、脱硝触媒として用いた場合には、脱硝性能が向上するものと考えられる。また、有機ハロゲン化合物の除去用触媒として用いた場合には、排ガス中のダイオキシン類等の有機ハロゲン化合物を効率良く除去することができるものと考えられる。
【００１２】
本発明において「均密混合酸化物」とは、Ｘ線回折チャートにおいて、ＳｉＯ2およびＭｏＯ3の明らかな固有のピークを示さず、ＴｉＯ2については固有のピークを示さないか、もしくは示しても酸化チタンの回折ピークよりもブロードな回折ピークを示すものをいう。
本発明の排ガス処理用触媒を調製するには、チタン化合物を含む水溶液またはスラリーと、モリブデン化合物と必要に応じてケイ素化合物とを混合した後、水を除去する工程を含む製法により製造することが好ましい。チタン化合物を含む水溶液またはスラリーから水を除去する前（すなわち酸化チタンの結晶が生成する前）に、モリブデン化合物と必要に応じてケイ素化合物とを加えることで、チタン−モリブデン均密混合酸化物、または、チタン−ケイ素−モリブデン均密混合酸化物を容易に得ることができる。
【００１３】
具体的には、以下の調製方法が挙げられる。
パラモリブデン酸アンモニウム、モリブデン酸などのモリブデンの化合物を水中に分散させ、アンモニア水を加える。得られたモリブデン水溶液を攪拌しつつ四塩化チタン、硫酸チタン、テトラアルコキシチタンなどの水溶性チタン化合物の液または水溶液を徐々に滴下し、スラリーを得る。これを濾過、洗浄し、さらに乾燥した後に高温で、好ましくは３００〜６００℃で、焼成させることによりチタン−モリブデン均密混合酸化物が得られる。チタン−ケイ素−モリブデン均密混合酸化物の場合は、モリブデンとアンモニアの水溶液に予めシリカゾルを加える。
【００１４】
チタン−モリブデン均密混合酸化物、または、チタン−ケイ素−モリブデン均密混合酸化物の供給源のうち、チタン源としては、焼成してチタン酸化物を生成するものであれば、無機および有機のいずれの化合物も使用可能で、例えば、四塩化チタン、硫酸チタンなどの無機チタン化合物または蓚酸チタン、テトライソプロピルチタネートなどの有機チタン化合物を用いることができる。ケイ素源としては、コロイド状シリカ、水ガラス、微粒子ケイ素、四塩化ケイ素、シリカゲルなどの無機ケイ素化合物およびテトラエチルシリケートなどの有機ケイ素化合物から適宜選択して使用することができる。また、モリブデン源については、焼成によりモリブデン酸化物を生成するものであれば、無機および有機のいずれの化合物でもよく、例えば、モリブデンを含む酸化物、水酸化物、アンモニウム塩、ハロゲン化物などから適宜用いることができ、具体的にはパラモリブデン酸アンモニウム、モリブデン酸等が挙げられる。
【００１５】
このようにして得られたチタン−モリブデン均密混合酸化物、および、チタン−ケイ素−モリブデン均密混合酸化物は、それぞれを単独で用いても良いし、両者を混合して用いても良いし、さらには他のチタンの酸化物、例えば、酸化チタンやチタン−ケイ素均密混合酸化物と混合して使用してもよい。
バナジウム酸化物の供給原料としては、バナジウム酸化物自体の他、焼成によってバナジウム酸化物を生成するものであれば、無機および有機のいずれの化合物も用いることができる。例えば、バナジウムを含む水酸化物、アンモニウム塩、蓚酸塩、ハロゲン化物、硫酸塩などを用いることができる。
【００１６】
バナジウム酸化物の添加方法は、特に限定されず、上記のような調製方法で得られたチタン−モリブデン均密混合酸化物および／またはチタン−ケイ素−モリブデン均密混合酸化物の粉末にバナジウム源を含む水溶液を、一般にこの種の成形を行う際に用いられる有機または無機の成形助剤と共に加え、混合、混錬しつつ加熱して水分を蒸発させ、押出し可能なペースト状とし、これを押出し成形機でハニカム状等に成形する。その後、乾燥し空気中にて高温で焼成する方法が挙げられる。また、別の方法として、上記のような調製方法で得られたチタン−モリブデン均密混合酸化物および／またはチタン−ケイ素−モリブデン均密混合酸化物を予め球状、円柱状のペレット、格子状のハニカムなどの形に成形、焼成した後、バナジウム源を含む水溶液を含浸担持させる方法も採用することができる。また、チタン−モリブデン均密混合酸化物および／またはチタン−ケイ素−モリブデン均密混合酸化物の粉体を酸化バナジウム粉体と直接混練する方法で調製することもできる。
【００１７】
触媒の形状は、特に限定されるものではなく、ハニカム状、板状、網状、円柱状、円筒状など所望の形状に成形して使用することができる。また、アルミナ、シリカ、コージェライト、ムライト、ＳｉＣ、チタニア、ステンレス鋼などからなるハニカム状、板状、網状、円柱状、円筒状などの所望の形状の担体に担持して使用してもよい。
本発明の排ガス処理用触媒は、各種排ガスの処理に用いられる。排ガスの組成については特に制限はないが、本発明の触媒は、ボイラ、焼却炉、ガスタービン、ディーゼルエンジンおよび各種工業プロセスから排出される窒素酸化物の分解活性に優れるため、これら窒素酸化物を含む排ガス処理に好適に用いられる。
【００１８】
本発明の触媒を用いて脱硝を行うには、本発明の触媒をアンモニアや尿素などの還元剤の存在下、排ガスと接触させ、排ガス中の窒素酸化物を還元除去する。この際の条件については、特に制限がなく、この種の反応に一般的に用いられている条件で実施することができる。具体的には、排ガスの種類、性状、要求される窒素酸化物の分解率などを考慮して適宜決定すればよい。
なお、本発明の触媒を用いて脱硝を行う場合の排ガスの空間速度は、通常、１００〜１０００００Ｈｒ-1（ＳＴＰ）であり、好ましくは２００〜５００００Ｈｒ-1（ＳＴＰ）である。１００Ｈｒ-1未満では、処理装置が大きくなりすぎるため非効率となり、一方１０００００Ｈｒ-1を超えると分解効率が低下する。また、その際の温度は、１００〜５００℃であることが好ましく、より好ましくは１５０〜４００℃である。
【００１９】
また、本発明の触媒は、産業廃棄物や都市廃棄物を処理する焼却施設から発生する、有機ハロゲン化合物を含有する排ガスの処理にも好適に用いられる。
本発明の触媒を用いて有機ハロゲン化合物の処理を行うには、本発明の触媒を、排ガスと接触させ、排ガス中の有機ハロゲン化合物を分解除去する。この際の条件については、特に制限がなく、この種の反応に一般的に用いられている条件で実施することができる。具体的には、排ガスの種類、性状、要求される有機ハロゲン化合物の分解率などを考慮して適宜決定すればよい。アンモニアや尿素などの還元剤を添加することにより、同時に脱硝することもできる。
【００２０】
なお、本発明の触媒を用いて有機ハロゲン化合物の処理を行う場合の排ガスの空間速度は、通常、１００〜１０００００Ｈｒ-1（ＳＴＰ）であり、好ましくは２００〜５００００Ｈｒ-1（ＳＴＰ）である。１００Ｈｒ-1未満では、処理装置が大きくなりすぎるため非効率となり、一方１０００００Ｈｒ-1を超えると分解効率が低下する。また、その際の温度は、１３０〜５００℃であることが好ましく、より好ましくは１５０〜４００℃である。
【００２１】
【実施例】
以下に実施例と比較例によりさらに詳細に本発明を説明するが、本発明は下記実施例に限定されるものではない。
（ＥＰＭＡ分析）
ＥＰＭＡ分析は、（株）島津製作所ＥＰＭ−８１０を用いて、加重電圧２０ｋＶ、試料電流５０ｎＡの条件で、ＭｏＬαのＸ線像を倍率３５０倍で測定した。
（実施例１）
＜チタン−ケイ素−モリブデン均密混合酸化物の調製＞
まず、チタン−ケイ素−モリブデン均密混合酸化物を次のように調製した。シリカゾル（スノーテックス−３０、日産化学社製、ＳｉＯ2換算３０ｗｔ％含有）６．７Ｋｇと工業用アンモニア水（２５ｗｔ％ＮＨ3含有）１０３Ｋｇと水５３リットルの混合溶液に、モリブデン酸２．２５Ｋｇを加え、よく攪拌し、モリブデン酸を完全に溶解させ、均一溶液を調製した。この溶液に硫酸チタニルの硫酸溶液（テイカ社製、ＴｉＯ2として７０ｇ／リットル、Ｈ2ＳＯ4として２８７ｇ／リットル含有）２２８リットルを、攪拌しながら徐々に滴下し、沈殿を生成させた。この共沈スラリーを約２０時間静置したのち、水で十分洗浄した後、濾過し、１００℃で１時間乾燥させた。さらに、空気雰囲気下、５５０℃で４時間焼成し、さらにハンマーミルを用いて粉砕し、分級機で分級して平均粒子径１０μｍの粉体を得た。このようにして調製したチタン−ケイ素−モリブデン均密混合酸化物の組成は、ＴｉＯ2：ＳｉＯ2：ＭｏＯ3＝８０：１０：１０（酸化物重量比）であった。
【００２２】
＜バナジウム酸化物の添加＞
次に、８リットルの水にメタバナジン酸アンモニウム１．２９Ｋｇとシュウ酸１．６７Ｋｇさらにモノエタノールアミン０．４Ｋｇを混合し、溶解させ、均一溶液を調製した。先に調製したチタン−ケイ素−モリブデン均密混合酸化物粉体１９Ｋｇをニーダーに投入後、成形助材とともにバナジウム含有溶液を加え、よく攪拌した。さらに適量の水を加えつつブレンダーでよく混合した後、連続ニーダーで十分混練りし、ハニカム状に押し出し成形した。得られた成形物を６０℃で乾燥後、空気雰囲気下、４５０℃で５時間焼成して目的の触媒（１）を得た。この時の組成は、重量比で、チタン−ケイ素−モリブデン均密混合酸化物：Ｖ2Ｏ5＝９５：５（酸化物換算重量比で、ＴｉＯ2：ＳｉＯ2：ＭｏＯ3：Ｖ2Ｏ5＝７６：９．５：９．５：５）であった。
【００２３】
触媒（１）の触媒表面を測定面積４×１０4μｍ2でＥＰＭＡ分析したところ、粒子径が５μｍより大きいモリブデン酸化物の前記測定面積中における割合は０％であった。
触媒（１）のＥＰＭＡ分析により撮影した電子線写真を図１に示す。図１中の白い部分がモリブデン酸化物を表している。
（実施例２）
＜チタン−モリブデン均密混合酸化物の調製＞
まず、チタン−モリブデン均密混合酸化物を次のように調製した。工業用アンモニア水（２５ｗｔ％ＮＨ3含有）１２１Ｋｇと水８６リットルの混合溶液に、モリブデン酸２．２５Ｋｇを加え、よく攪拌し、モリブデン酸を完全に溶解させ、均一溶液を調製した。この溶液に硫酸チタニルの硫酸溶液（テイカ社製、ＴｉＯ2として７０ｇ／リットル、Ｈ2ＳＯ4として２８７ｇ／リットル含有）２５７リットルを、攪拌しながら徐々に滴下し、沈殿を生成させた。この共沈スラリーを約２０時間静置したのち、水で十分洗浄した後、濾過し、１００℃で１時間乾燥させた。さらに、空気雰囲気下、５５０℃で４時間焼成し、さらにハンマーミルを用いて粉砕し、分級機で分級して平均粒子径１０μｍの粉体を得た。このようにして調製したチタン−モリブデン均密混合酸化物の組成は、ＴｉＯ2： ＭｏＯ3＝９０：１０（酸化物重量比）であった。
【００２４】
＜バナジウム酸化物の添加＞
実施例１のバナジウム酸化物の添加工程において、チタン−ケイ素−モリブデン均密混合酸化物の代わりに、チタン−モリブデン均密混合酸化物を用いた以外は、実施例１と同様の調製方法でバナジウム酸化物を添加し、触媒（２）を調製した。この時の組成は、重量比で、チタン−モリブデン均密混合酸化物：Ｖ2Ｏ5＝９５：５（酸化物換算重量比で、ＴｉＯ2： ＭｏＯ3：Ｖ2Ｏ5＝８５．５：９．５： ５）であった。
触媒（２）の触媒表面を測定面積４×１０4μｍ2でＥＰＭＡ分析したところ、粒子径が５μｍより大きいモリブデン酸化物の前記測定面積中における割合は０％であった。
【００２５】
触媒（２）のＥＰＭＡ分析により撮影した電子線写真を図２に示す。図２中の白い部分がモリブデン酸化物を表している。
（参考例）
市販の酸化チタン粉体（ＤＴ−５１（商品名）、ミレニアム社製）２０Ｋｇに、メタバナジン酸アンモニウム１．４７Ｋｇ、シュウ酸１．８Ｋｇを水５リットルに溶解させた溶液と、パラモリブデン酸アンモニウム２．８Ｋｇおよびモノエタノールアミン１．０７Ｋｇを水３リットルに溶解させた溶液とを加え、成形助材とともに混合し、ニーダーで混練りした後、押出成形機でハニカム状に成形した。得られた成形物を６０℃で乾燥後、空気雰囲気下、３５０℃で５時間焼成して目的の触媒（３）を得た。この時の組成は、酸化物換算重量比で、ＴｉＯ２： ＭｏＯ３：Ｖ２Ｏ５＝８５：１０： ５であった。
【００２６】
触媒（３）の触媒表面を測定面積４×１０4μｍ2でＥＰＭＡ分析したところ、粒子径が５μｍより大きいモリブデン酸化物の前記測定面積中における割合は０．７％であった。
触媒（３）のＥＰＭＡ分析により撮影した電子線写真を図３に示す。図３中の白い部分がモリブデン酸化物を表している。
（比較例１）
市販の酸化チタン粉体（ＤＴ−５１（商品名）、ミレニアム社製）２０Ｋｇに、三酸化モリブデン粉体２．３５Ｋｇ、および、メタバナジン酸アンモニウム１．４７Ｋｇ、シュウ酸１．８Ｋｇを水５リットルに溶解させた溶液を加え、成形助材とともに混合し、ニーダーで混練りした後、押出成形機でハニカム状に成形した。得られた成形物を６０℃で乾燥後、空気雰囲気下、５００℃で５時間焼成して目的の触媒（４）を得た。この時の組成は、酸化物換算重量比で、ＴｉＯ2： ＭｏＯ3：Ｖ2Ｏ5＝８５：１０： ５であった。
【００２７】
触媒（４）の触媒表面を測定面積４×１０４μｍ２でＥＰＭＡ分析したところ、粒子径が５μｍより大きいモリブデン酸化物の前記測定面積中における割合は５．４％であった。
触媒（４）のＥＰＭＡ分析により撮影した電子線写真を図４に示す。図４中の白い部分がモリブデン酸化物を表している。
（脱硝性能試験および有機塩素化合物分解試験）
実施例１、実施例２、参考例、および比較例１で得られた触媒（１）〜（４）を用いて下記の条件で脱硝性能試験および有機塩素化合物分解試験を行った。処理対象となる有機塩素化合物としてはクロロトエルエン（以下、ＣＴと略す）を用いた。
【００２８】
脱硝率およびＣＴ分解率は下記の式に従って求めた。
脱硝率（％）＝[（反応器入口ＮＯｘ濃度）−（反応器出口ＮＯｘ濃度）]÷（反応器入口ＮＯｘ濃度）×１００
ＣＴ分解率（％）＝[（反応器入口ＣＴ濃度）−（反応器出口ＣＴ濃度）]÷（反応器入口ＣＴ濃度）×１００
＜脱硝反応ガス組成＞
ＮＯｘ：２００ｐｐｍ
ＳＯ2：１０００ｐｐｍ
ＮＨ3：２００ｐｐｍ
Ｏ2：１０％
Ｈ2Ｏ：１５％
Ｎ2：バランス
ガス温度：２５０℃
空間速度：１２０００Ｈｒ-1
＜ＣＴ分解反応ガス組成＞
ＣＴ：３００ｐｐｍ
Ｏ2：１０％
Ｈ2Ｏ：１５％
Ｎ2：バランス
ガス温度：１７０℃
空間速度：２０００Ｈｒ-1
得られた脱硝率及びＣＴ分解率を表１に示した。
【００２９】
【表１】
【発明の効果】
本発明によると、モリブデン酸化物の粒子径を小さく制御することによって、触媒性能（脱硝性能、ダイオキシン分解性能）に優れた排ガス処理触媒を得ることができる。
そのため、脱硝触媒として用いた場合には、脱硝性能が向上する。
また、有機ハロゲン化合物の除去用触媒として用いた場合には、排ガス中のダイオキシン類等の有機ハロゲン化合物を効率良く除去することができる。
【図面の簡単な説明】
【図１】 実施例１で調製した触媒（１）のＥＰＭＡ分析による電子線写真
【図２】 実施例２で調製した触媒（２）のＥＰＭＡ分析による電子線写真
【図３】 参考例で調製した触媒（３）のＥＰＭＡ分析による電子線写真
【図４】 比較例１で調製した触媒（４）のＥＰＭＡ分析による電子線写真[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust gas treatment catalyst and an exhaust gas treatment method. Particularly, a denitration catalyst for removing nitrogen oxides (NOx) in exhaust gas, and an exhaust gas treatment catalyst excellent as a catalyst for removing organic halogen compounds such as dioxins in exhaust gas. And an exhaust gas treatment method using the same.
[0002]
[Prior art]
As a method of removing nitrogen oxides in exhaust gas currently in practical use, nitrogen oxides in exhaust gas are catalytically reduced on a denitration catalyst using a reducing agent such as ammonia or urea, and decomposed into harmless nitrogen and water. The selective catalytic reduction is the so-called SCR method.
In recent years, as environmental pollution due to nitrogen oxides has become more serious worldwide, as represented by acid rain, higher efficiency of denitration technology has been demanded.
Under such circumstances, a denitration catalyst (Japanese Examined Patent Publication No. 53-28148) composed of an oxide of titanium and vanadium and an oxide such as molybdenum and tungsten, a binary oxide composed of titanium and silicon, vanadium and tungsten. A denitration catalyst (Japanese Patent Publication No. 57-30532) made of a metal oxide such as molybdenum has been put into practical use and is now widely used.
[0003]
These catalysts all have excellent nitrogen oxide removal performance and are excellent in durability, but it is preferable that higher performance catalysts appear.
In addition, the exhaust gas generated from incineration facilities that treat industrial and municipal waste contains trace amounts of toxic organic halogen compounds such as dioxins, PCBs, and chlorophenols. However, since it is extremely toxic and has a serious effect on the human body, its removal technology is urgently required. Catalytic decomposition method is one of the most effective technologies, and generally catalysts containing oxides such as titanium, vanadium, tungsten, molybdenum, etc. are used. Further improvement in catalyst performance is desired.
[0004]
[Problems to be solved by the invention]
Therefore, an object of the present invention is to provide a denitration catalyst having further excellent nitrogen oxide removal performance and an exhaust gas treatment catalyst excellent as a catalyst suitable for efficiently removing organic halogen compounds such as dioxins in exhaust gas. And providing an exhaust gas treatment method using the same.
[0005]
[Means for Solving the Problems]
The present inventor has intensively studied to solve the above problems. As a result, focusing on the particle size of molybdenum oxide in catalysts containing oxides of titanium, molybdenum, and vanadium, and controlling the particle size to be small, the catalyst performance (denitration performance, dioxin decomposition performance) is excellent. It was also found that an exhaust gas treatment catalyst can be provided.
That is, the exhaust gas treatment catalyst according to the present invention, titanium, molybdenum, a catalyst containing oxides of vanadium, oxides of the molybdenum, molybdenum aqueous solution and the titanium comprising a compound of molybdenum is dissolved in aqueous ammonia It is prepared by mixing with an aqueous solution of a compound to produce a precipitate, and the ratio of particles having a particle size larger than 5 μm is 5% or less .
[0006]
Furthermore, the exhaust gas treatment method according to the present invention is characterized by treating exhaust gas containing nitrogen oxides using the catalyst of the present invention.
The exhaust gas treatment method according to the present invention is characterized in that exhaust gas containing an organic halogen compound is treated using the catalyst of the present invention.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The exhaust gas treatment catalyst of the present invention is a catalyst containing oxides of titanium, molybdenum, and vanadium, and the ratio of molybdenum oxide having a particle size larger than 5 μm is 5% or less.
The method for analyzing the state of the particles as described above is not particularly limited, and examples thereof include EPMA and SEM-EDS. Hereinafter, EPMA analysis will be described as an example.
The EPMA analysis of the catalyst surface is an analysis for observing the state of the catalyst composition component in the catalyst to be analyzed, and is usually performed by the same analysis method as the EPMA analysis generally performed. When analyzing the state of the catalyst by EPMA analysis, for example, a sample obtained by cutting out a small amount of the surface of an arbitrary catalyst is used as a measurement sample. Although the method etc. which make a sample are mentioned, it does not specifically limit. The exhaust gas treatment catalyst according to the present invention can be defined, for example, by EPMA analysis when the measurement area of the catalyst surface is 4 × 10 4 μm 2 . Of course, this measurement area may be appropriately adjusted depending on conditions.
[0008]
In general, the state observed on an arbitrary part of the catalyst surface can be treated as directly reflecting the state of the entire catalyst. For example, when EPMA analysis is performed on the catalyst surface with a measurement area of 4 × 10 4 μm 2 , When the ratio of the molybdenum oxide having a particle diameter of more than 5 μm in the measurement area is 5% or less, it can be assumed that the same condition exists in the entire catalyst. In addition, you may average the measurement results of arbitrary several places. Therefore, in the exhaust gas treatment catalyst of the present invention, for example, when the catalyst surface is subjected to EPMA analysis with a measurement area of 4 × 10 4 μm 2 , the proportion of molybdenum oxide having a particle size larger than 5 μm in the measurement area is 5%. The following means a state throughout the catalyst.
[0009]
The particle diameter in the present invention means the diameter in the case of spherical particles, but means the longest diameter when it does not have a certain diameter (when it is not spherical).
The exhaust gas treatment catalyst of the present invention is characterized in that the particle diameter of molybdenum oxide is 5 μm or less, preferably 3 μm or less. Further, the ratio of molybdenum oxide larger than 5 μm is 5% or less, preferably 3% or less, more preferably 1% or less. The molybdenum particle diameter and the ratio thereof were calculated from the number average measured from the EPMA chart. If the proportion of molybdenum oxide having a particle diameter of more than 5 μm is more than 5%, the effect of the present invention cannot be sufficiently achieved, which is not preferable.
[0010]
The exhaust gas treatment catalyst of the present invention is a catalyst containing oxides of titanium, molybdenum, and vanadium, and is produced by a precipitation method, an oxide mixing method, a kneading method, a supporting method, an impregnation method, etc. that are commonly used for the production of the catalyst. Preferably, the catalyst is preferably a vanadium oxide, a binary mixed oxide composed of titanium and molybdenum prepared in advance, and / or a ternary system composed of titanium, silicon and molybdenum prepared in advance. It is a catalyst containing a homogeneous mixed oxide.
The composition of the catalyst in the case of containing a binary close-mixed mixed oxide composed of titanium and molybdenum prepared in advance is the oxide equivalent weight ratio of each element, and the titanium oxide is preferably 55 to 99.4 wt. %, More preferably 60 to 90% by weight, molybdenum oxide is preferably 0.5 to 30% by weight, more preferably 1 to 25% by weight, and vanadium oxide is preferably 0.1 to 15% by weight. Moreover, the composition of the catalyst in the case of containing a ternary close-mixed mixed oxide composed of titanium, silicon and molybdenum prepared in advance is an oxide equivalent weight ratio of each element, and the oxide of titanium is preferably 5 to 5 98.9 wt%, more preferably 10-90 wt%, silicon oxide is preferably 0.5-50 wt%, more preferably 5-50 wt%, molybdenum oxide is preferably 0.5-30 wt%. % By weight, more preferably 1 to 25% by weight, and vanadium oxide is preferably 0.1 to 15% by weight.
[0011]
By preparing titanium-molybdenum homogeneous mixed oxide and / or titanium-silicon-molybdenum homogeneous mixed oxide in advance, titanium and molybdenum can be more uniformly dispersed and mixed. While improving, it becomes easy to control the particle diameter of molybdenum oxide small. Further, a high decomposition activity can be obtained by strengthening the interaction between titanium and molybdenum. Therefore, when used as a denitration catalyst, it is considered that the denitration performance is improved. Further, when used as a catalyst for removing organic halogen compounds, it is considered that organic halogen compounds such as dioxins in exhaust gas can be efficiently removed.
[0012]
In the present invention, “homogeneous mixed oxide” means that in the X-ray diffraction chart, SiO 2 and MoO 3 do not show distinct intrinsic peaks, and TiO 2 does not show or exhibit intrinsic peaks. The one showing a broader diffraction peak than that of titanium oxide.
In order to prepare the exhaust gas treatment catalyst of the present invention, an aqueous solution or slurry containing a titanium compound, a molybdenum compound and, if necessary, a silicon compound are mixed and then manufactured by a production method including a step of removing water. preferable. Before removing water from the aqueous solution or slurry containing the titanium compound (that is, before the titanium oxide crystals are formed), a molybdenum compound and, if necessary, a silicon compound are added to form a titanium-molybdenum mixed oxide, Alternatively, a titanium-silicon-molybdenum homogeneous mixed oxide can be easily obtained.
[0013]
Specifically, the following preparation methods are mentioned.
Ammonium parametric molybdate, dispersing the compound of molybdenum such as molybdic acid in water, adding aqueous ammonia. While stirring the obtained aqueous molybdenum solution, a liquid or aqueous solution of a water-soluble titanium compound such as titanium tetrachloride, titanium sulfate, or tetraalkoxytitanium is gradually dropped to obtain a slurry. This is filtered, washed, dried, and then calcined at a high temperature, preferably 300 to 600 ° C., to obtain a titanium-molybdenum homogeneous mixed oxide. In the case of a titanium-silicon-molybdenum homogeneous mixed oxide, silica sol is added in advance to an aqueous solution of molybdenum and ammonia .
[0014]
Titanium - molybdenum intimate mixed oxide, or titanium - silicon - of the source of molybdenum intimate mixed oxide, the titanium source and baking as long as it produces a titanium oxide, inorganic and organic Any of these compounds can be used. For example, inorganic titanium compounds such as titanium tetrachloride and titanium sulfate, or organic titanium compounds such as titanium oxalate and tetraisopropyl titanate can be used. The silicon source can be appropriately selected from inorganic silicon compounds such as colloidal silica, water glass, fine particle silicon, silicon tetrachloride and silica gel, and organic silicon compounds such as tetraethyl silicate. The molybdenum source may be any inorganic or organic compound as long as it generates molybdenum oxide by firing. For example, the molybdenum source is appropriately selected from oxides containing molybdenum, hydroxides, ammonium salts, halides, and the like. Specific examples thereof include ammonium paramolybdate and molybdic acid.
[0015]
The titanium-molybdenum homogeneous mixed oxide and the titanium-silicon-molybdenum homogeneous mixed oxide thus obtained may be used alone or in combination. Further, other titanium oxides such as titanium oxide and titanium-silicon intimate mixed oxide may be used.
As the supply source of the vanadium oxide, any of inorganic and organic compounds can be used as long as the vanadium oxide is generated by firing in addition to the vanadium oxide itself. For example, hydroxides containing vanadium, ammonium salts, oxalates, halides, sulfates, and the like can be used.
[0016]
The addition method of vanadium oxide is not particularly limited, and a vanadium source is added to the titanium-molybdenum mixed oxide and / or titanium-silicon-molybdenum mixed oxide powder obtained by the above preparation method. Add the aqueous solution together with organic or inorganic molding aids generally used when performing this type of molding, mix and knead the mixture to heat and evaporate the water to form an extrudable paste, which is extruded Molded into a honeycomb or the like with a machine. Then, the method of drying and baking at high temperature in the air is mentioned. As another method, the titanium-molybdenum homogeneous mixed oxide and / or the titanium-silicon-molybdenum homogeneous mixed oxide obtained by the preparation method as described above is preliminarily spherical, cylindrical pellet, lattice-like. A method of impregnating and supporting an aqueous solution containing a vanadium source after being formed and fired into a honeycomb or the like can also be employed. It can also be prepared by directly kneading titanium-molybdenum homogeneous mixed oxide and / or titanium-silicon-molybdenum homogeneous mixed oxide powder with vanadium oxide powder.
[0017]
The shape of the catalyst is not particularly limited, and the catalyst can be formed into a desired shape such as a honeycomb shape, a plate shape, a net shape, a columnar shape, or a cylindrical shape. Further, it may be used by being supported on a carrier having a desired shape such as honeycomb, plate, net, column, or cylinder made of alumina, silica, cordierite, mullite, SiC, titania, stainless steel or the like.
The exhaust gas treatment catalyst of the present invention is used for treatment of various exhaust gases. The composition of the exhaust gas is not particularly limited, but the catalyst of the present invention is excellent in the decomposition activity of nitrogen oxides emitted from boilers, incinerators, gas turbines, diesel engines and various industrial processes. It is suitably used for exhaust gas treatment.
[0018]
In order to perform denitration using the catalyst of the present invention, the catalyst of the present invention is brought into contact with exhaust gas in the presence of a reducing agent such as ammonia or urea, and nitrogen oxides in the exhaust gas are reduced and removed. The conditions at this time are not particularly limited, and can be carried out under conditions generally used for this type of reaction. Specifically, it may be appropriately determined in consideration of the type and properties of exhaust gas, the required decomposition rate of nitrogen oxides, and the like.
Incidentally, the space velocity of the exhaust gas when performing denitration using the catalyst of the present invention is usually a 100~100000Hr -1 (STP), preferably 200~50000Hr -1 (STP). If it is less than 100 Hr −1 , the processing apparatus becomes too large to be inefficient, and if it exceeds 100000 Hr −1 , the decomposition efficiency is lowered. Moreover, it is preferable that the temperature in that case is 100-500 degreeC, More preferably, it is 150-400 degreeC.
[0019]
The catalyst of the present invention is also suitably used for treating exhaust gas containing an organic halogen compound generated from an incineration facility for treating industrial waste and municipal waste.
In order to treat the organic halogen compound using the catalyst of the present invention, the catalyst of the present invention is brought into contact with exhaust gas to decompose and remove the organic halogen compound in the exhaust gas. The conditions at this time are not particularly limited, and can be carried out under conditions generally used for this type of reaction. Specifically, it may be appropriately determined in consideration of the type and properties of exhaust gas, the required decomposition rate of the organic halogen compound, and the like. By adding a reducing agent such as ammonia or urea, denitration can be performed simultaneously.
[0020]
Incidentally, the space velocity of the exhaust gas in the case of performing the processing of the organohalogen compounds using the catalyst of the present invention is usually a 100~100000Hr -1 (STP), preferably 200~50000Hr -1 (STP). If it is less than 100 Hr −1 , the processing apparatus becomes too large to be inefficient, and if it exceeds 100000 Hr −1 , the decomposition efficiency is lowered. Moreover, it is preferable that the temperature in that case is 130-500 degreeC, More preferably, it is 150-400 degreeC.
[0021]
【Example】
The present invention will be described in more detail with reference to the following examples and comparative examples, but the present invention is not limited to the following examples.
(EPMA analysis)
In EPMA analysis, an X-ray image of MoLα was measured at a magnification of 350 times under the conditions of a weighted voltage of 20 kV and a sample current of 50 nA using Shimadzu Corporation EPM-810.
Example 1
<Preparation of Titanium-Silicon-Molybdenum Density Mixed Oxide>
First, a titanium-silicon-molybdenum dense mixed oxide was prepared as follows. Silica sol (Snowtex-30, manufactured by Nissan Chemical Industries, containing 30 wt% of SiO 2 equivalent) 6.7 kg, industrial ammonia water (containing 25 wt% NH 3 ) 103 kg and 53 liters of water with 2.25 kg of molybdic acid In addition, the mixture was well stirred to completely dissolve the molybdic acid, thereby preparing a uniform solution. To this solution, 228 liters of a sulfuric acid solution of titanyl sulfate (manufactured by Teika, containing 70 g / liter as TiO 2 and 287 g / liter as H 2 SO 4 ) was gradually added dropwise with stirring to form a precipitate. The coprecipitated slurry was allowed to stand for about 20 hours, washed thoroughly with water, filtered, and dried at 100 ° C. for 1 hour. Further, it was fired at 550 ° C. for 4 hours in an air atmosphere, further pulverized using a hammer mill, and classified by a classifier to obtain a powder having an average particle diameter of 10 μm. The composition of the titanium-silicon-molybdenum homogeneous mixed oxide thus prepared was TiO 2 : SiO 2 : MoO 3 = 80: 10: 10 (oxide weight ratio).
[0022]
<Addition of vanadium oxide>
Next, 1.29 kg of ammonium metavanadate and 1.67 kg of oxalic acid and 0.4 kg of monoethanolamine were mixed and dissolved in 8 liters of water to prepare a uniform solution. After adding 19 kg of the titanium-silicon-molybdenum homogeneous mixed oxide powder prepared earlier to a kneader, a vanadium-containing solution was added together with a molding aid, followed by thorough stirring. Further, after adding a proper amount of water and thoroughly mixing with a blender, the mixture was sufficiently kneaded with a continuous kneader and extruded into a honeycomb shape. The obtained molded product was dried at 60 ° C. and calcined at 450 ° C. for 5 hours in an air atmosphere to obtain the desired catalyst (1). The composition at this time was a titanium-silicon-molybdenum homogeneous mixed oxide: V 2 O 5 = 95: 5 (weight ratio in terms of oxide, TiO 2 : SiO 2 : MoO 3 : V 2 O 5). = 76: 9.5: 9.5: 5).
[0023]
When the EPMA analysis of the catalyst surface of the catalyst (1) was performed at a measurement area of 4 × 10 4 μm 2 , the ratio of molybdenum oxide having a particle diameter larger than 5 μm in the measurement area was 0%.
An electron beam photograph taken by EPMA analysis of the catalyst (1) is shown in FIG. A white portion in FIG. 1 represents molybdenum oxide.
(Example 2)
<Preparation of titanium-molybdenum homogeneous mixed oxide>
First, a titanium-molybdenum mixed oxide was prepared as follows. To a mixed solution of 121 kg of industrial ammonia water (containing 25 wt% NH 3 ) and 86 liters of water, 2.25 kg of molybdic acid was added and stirred well to completely dissolve the molybdic acid to prepare a uniform solution. The solution of titanyl sulfate sulfuric acid solution (manufactured by Tayca Corporation, 70 g / liter as TiO 2, 287 g / liter containing a H 2 SO 4) 257 liters, was gradually added dropwise with stirring, to produce a precipitate. The coprecipitated slurry was allowed to stand for about 20 hours, washed thoroughly with water, filtered, and dried at 100 ° C. for 1 hour. Further, it was fired at 550 ° C. for 4 hours in an air atmosphere, further pulverized using a hammer mill, and classified by a classifier to obtain a powder having an average particle diameter of 10 μm. The composition of the titanium-molybdenum homogeneous mixed oxide thus prepared was TiO 2 : MoO 3 = 90: 10 (oxide weight ratio).
[0024]
<Addition of vanadium oxide>
In the step of adding vanadium oxide in Example 1, vanadium was prepared in the same manner as in Example 1 except that titanium-molybdenum mixed mixed oxide was used instead of titanium-silicon-molybdenum mixed mixed oxide. An oxide was added to prepare catalyst (2). The composition at this time is titanium-molybdenum mixed oxide: V 2 O 5 = 95: 5 (weight ratio in terms of oxide, TiO 2 : MoO 3 : V 2 O 5 = 85.5: 9.5: 5).
When the catalyst surface of the catalyst (2) was analyzed by EPMA at a measurement area of 4 × 10 4 μm 2 , the ratio of molybdenum oxide having a particle diameter larger than 5 μm in the measurement area was 0%.
[0025]
An electron beam photograph taken by EPMA analysis of the catalyst (2) is shown in FIG. A white portion in FIG. 2 represents molybdenum oxide.
( Reference example )
A solution prepared by dissolving 1.47 kg of ammonium metavanadate and 1.8 kg of oxalic acid in 5 liters of water in 20 kg of commercially available titanium oxide powder (DT-51 (trade name), manufactured by Millennium), and ammonium paramolybdate 2 A solution in which 0.8 kg and 1.07 kg of monoethanolamine were dissolved in 3 liters of water was added, mixed with a molding aid, kneaded with a kneader, and then formed into a honeycomb shape with an extruder. The obtained molded product was dried at 60 ° C. and calcined at 350 ° C. for 5 hours in an air atmosphere to obtain the desired catalyst (3). The composition at this time was TiO 2 : MoO 3 : V 2 O 5 = 85: 10: 5 in terms of weight ratio in terms of oxide.
[0026]
When the EPMA analysis of the catalyst surface of the catalyst (3) was performed at a measurement area of 4 × 10 4 μm 2 , the ratio of molybdenum oxide having a particle size larger than 5 μm in the measurement area was 0.7%.
An electron beam photograph taken by EPMA analysis of the catalyst (3) is shown in FIG. A white portion in FIG. 3 represents molybdenum oxide.
(Comparative Example 1)
Commercially available titanium oxide powder (DT-51 (trade name), manufactured by Millennium) 20 kg, molybdenum trioxide powder 2.35 kg, ammonium metavanadate 1.47 kg and oxalic acid 1.8 kg in 5 liters of water The dissolved solution was added, mixed with a forming aid, kneaded with a kneader, and then formed into a honeycomb shape with an extruder. The obtained molded product was dried at 60 ° C. and calcined at 500 ° C. for 5 hours in an air atmosphere to obtain the desired catalyst (4). The composition at this time was TiO 2 : MoO 3 : V 2 O 5 = 85: 10: 5 in terms of weight ratio in terms of oxide.
[0027]
When the surface of the catalyst (4) was subjected to EPMA analysis with a measurement area of 4 × 10 4 μm 2 , the ratio of molybdenum oxide having a particle diameter of more than 5 μm in the measurement area was 5.4%.
An electron beam photograph taken by EPMA analysis of the catalyst (4) is shown in FIG. A white portion in FIG. 4 represents molybdenum oxide.
(Denitration performance test and organochlorine compound decomposition test)
Using the catalysts (1) to (4) obtained in Example 1 , Example 2, Reference Example, and Comparative Example 1, a denitration performance test and an organochlorine compound decomposition test were performed under the following conditions. As an organic chlorine compound to be treated, chlorotoluene (hereinafter abbreviated as CT) was used.
[0028]
The denitration rate and the CT decomposition rate were determined according to the following formula.
Denitration rate (%) = [(reactor inlet NOx concentration) − (reactor outlet NOx concentration)] ÷ (reactor inlet NOx concentration) × 100
CT decomposition rate (%) = [(reactor inlet CT concentration) − (reactor outlet CT concentration)] ÷ (reactor inlet CT concentration) × 100
<Denitration reaction gas composition>
NOx: 200ppm
SO 2 : 1000 ppm
NH 3: 200ppm
O 2 : 10%
H 2 O: 15%
N 2 : Balance gas temperature: 250 ° C
Space velocity: 12000Hr -1
<CT decomposition reaction gas composition>
CT: 300ppm
O 2 : 10%
H 2 O: 15%
N 2 : Balance gas temperature: 170 ° C
Space velocity: 2000Hr -1
The obtained denitration rate and CT decomposition rate are shown in Table 1.
[0029]
[Table 1]
【The invention's effect】
According to the present invention, an exhaust gas treatment catalyst excellent in catalyst performance (denitration performance, dioxin decomposition performance) can be obtained by controlling the particle diameter of molybdenum oxide to be small.
Therefore, when used as a denitration catalyst, the denitration performance is improved.
Further, when used as a catalyst for removing organic halogen compounds, organic halogen compounds such as dioxins in exhaust gas can be efficiently removed.
[Brief description of the drawings]
1 is an electron beam photograph by EPMA analysis of the catalyst (1) prepared in Example 1. FIG. 2 is an electron beam photograph by EPMA analysis of the catalyst (2) prepared in Example 2. FIG. 3 is prepared by reference example . FIG. 4 is an electron beam photograph of the catalyst (4) prepared in Comparative Example 1 by EPMA analysis.
Claims (4)
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