JP4205459B2

JP4205459B2 - Hydrocarbon reforming method

Info

Publication number: JP4205459B2
Application number: JP2003070159A
Authority: JP
Inventors: 修千代田; 勝見宮本; 俊夫清水
Original assignee: Cosmo Oil Co Ltd
Current assignee: Cosmo Oil Co Ltd
Priority date: 2003-03-14
Filing date: 2003-03-14
Publication date: 2009-01-07
Anticipated expiration: 2023-03-14
Also published as: JP2004277214A

Description

【０００１】
【発明の属する技術分野】
本発明は、炭化水素からの水素の製造、とりわけ燃料電池に使用される水素の製造に関わる炭化水素の改質方法に関するものである。
【０００２】
【従来技術の説明】
都市ガス、ＬＰＧ、ガソリン、灯油等の炭化水素からの水素の製造は、得られる生成ガス中の水素濃度が高いことから水蒸気改質法により行われるのが一般的であり、この水蒸気改質法は下記の式１で示される。
Ｃ_mH_n ＋ｍＨ₂Ｏ＝ｍＣＯ＋（ｎ/２＋ｍ）Ｈ₂ （式１）
（式１中、Ｃ_mＨ_nは炭化水素の平均分子式を表す。）
特に燃料電池用の水素の製造では、改質ガスの特性および熱バランスの観点からも以下の理由により水蒸気改質法が適した方法と考えられる。
▲１▼水蒸気改質法は出口ガス中の水素濃度が約７０%（ドライベース）と高く、燃料電池での高い発電効率が期待できる。
▲２▼水蒸気改質反応は激しい吸熱反応であり、外部から熱を供給する必要があるが、この外部からの熱の供給源として設けられている加熱用バーナーの燃料として、燃料電池の排ガスを使用することができる。即ち、燃料電池に供給される水素の発電利用率は１００％ではなく、燃料電池の排ガス中には低濃度ではあるが水素が残存しており、該残存水素を上記加熱用バーナーの燃料として使用することができる。
【０００３】
一般に、燃料電池と、該燃料電池で使用する水素を炭化水素の水蒸気改質により発生させる改質器などを組み込んだ燃料電池発電パッケージ、とりわけ例えば家庭用の小型燃料電池発電パッケージにおいては、該パッケージを小型にする上で、組み込む改質器も小型にする必要がある。そして、一般に、この改質器には、水蒸気改質触媒を充填した触媒床が設けられており、該触媒床を加熱するための加熱用バーナーが設けられているが、改質器の小型化に伴い、該バーナーも小型で本数も少ないものとなっており、また、該バーナーは、一般に触媒床の後段出口部近傍に設けられている。したがって、この改質器の触媒床においては、加熱用バーナーの設置位置に近い後段出口部と、該設置位置から離れた前段入口部とで温度勾配が発生する傾向にある。例えば、バーナーに近い触媒床後段の出口部では６５０〜８５０℃程度の高温であるのに対し、バーナーから離れた触媒床前段の入口部では３５０〜５５０℃程度の低温になる傾向が見られる。
【０００４】
また、一般に、灯油は、熱量あたりのコスト（エネルギー単価）が低廉で経済的であり、安全面から一般家庭における取り扱い性が高く、インフラの整備も充実しており、輸送性にも優れている。そのため、灯油は、家庭などで用いられる小型燃料電池発電パッケージ用の水素製造用燃料として注目されている。しかし、灯油を原料とした水蒸気改質反応では、低温、特に５００℃以下の低温域で改質反応性が低下し、しかも触媒上への炭素析出から触媒が劣化傾向を示しやすい。
【０００５】
この灯油を水素を製造するための水蒸気改質反応の原料として用いるためには、反応温度が低い領域をできるだけ少なくすることが重要な技術である。そのため、小型燃料電池発電パッケージに用いる小型改質器の触媒床温度を上昇させるための技術として、バーナー用燃料供給量を増加させたり、電気ヒーターを使用して触媒床の温度を上昇させる方法がある。これらの方法の他に、低温部と高温部で異なる２種類の水蒸気改質触媒を充填する手法（特許文献１参照）や、水蒸気改質反応の原料へ空気などの酸素含有ガスを加え、下記の式２で示されるような炭化水素の発熱反応を利用して触媒床の入口部などの温度を上昇させる方法（特許文献２、特許文献３参照）も提案されている。
Ｃ_mＨ_n ＋ｍ/２Ｏ₂ ＝ｍＣＯ＋ｎ/２Ｈ₂ （式２）
（式２中、Ｃ_mＨ_nは炭化水素の平均分子式を表す。）
【０００６】
上記小型改質器の触媒床温度を上昇させるための技術の内、バーナー用燃料供給量を増加させる方法では、例えば上記のように加熱用バーナーが触媒床の出口近傍に設置されている小型改質器において、
バーナーの設置位置から離れた触媒床の入口部の温度が上昇するようにバーナーへの燃料供給量を増加させると、バーナー近傍の触媒床温度が所定以上の高温となり、触媒および反応器材質に不具合が生じる可能性がある。
また、上記電気ヒーターを使用して触媒床の温度を上昇させる方法では、小型燃料電池発電パッケージ内部での電力消費が嵩むため発電効率の低下が発生する傾向が高くなる。
また、上記低温部と高温部で異なる２種類の水蒸気改質触媒を充填する手法では、十分に水蒸気改質反応を達成することができない。水蒸気改質触媒の改良によって、より低温域でも灯油留分等の改質反応を実施できる可能性があり、従来から水素プラントに用いられているニッケルを主な活性成分とする触媒系に代えて、ルテニウムを主な活性成分とする水蒸気改質触媒が注目されている。しかし、このルテニウムを主な活性成分とする触媒でも、上記のような低温域では、重質な炭化水素を原料とした場合には充分な性能を有しているとはいえない。すなわち、従来提案されているいずれの水蒸気改質触媒でも、反応温度を５００℃以上、好ましくは５５０℃以上の温度域まで高める工夫が不可欠である。
また、上記水蒸気改質反応の原料へ酸素含有ガスを加えて炭化水素の発熱反応を利用する方法では、水蒸気改質反応で生成された水素も燃焼に消費されるため、水素濃度が低下する傾向が見られたり、多量の空気を酸素含有ガスとして導入すると、窒素により水素が希釈されるなど、得られる水素含有ガスが燃料電池用水素として好ましくない傾向が見られる。また、ルテニウム系触媒は軽質から中重質炭化水素類の改質に優れた活性を示すが、酸素が反応系に共存すると揮発性のルテニウム酸化物（ＲｕＯ₄等）が生成し、活性成分のルテニウムが昇華したり、下流側に溢出するなど不具合が懸念される。
【０００７】
上述したような諸問題を解決する技術が求められており、小型燃料電池発電パッケージの改質器に好適に適用できて、小型燃料電池発電パッケージのランニングコストの低減を図れるような、灯油などの炭化水素を原料として効率的に水素を製造し得る炭化水素の改質方法が望まれている。
【０００８】
【特許文献１】
特開平３−８０１０２号公報
【特許文献２】
特開２００１−１４６４０６号公報
【特許文献３】
特開２００２−１０４８０９号公報
【０００９】
【発明が解決しようとする課題】
本発明の目的は、上記従来技術の諸問題を解決し、小型燃料電池発電パッケージの改質器に好適に適用できて、小型燃料電池発電パッケージのランニングコストの低減を図れるような、灯油などの炭化水素を原料として効率的に水素を製造し得る炭化水素の改質方法を提供することにある。
【００１０】
【課題を解決するための手段】
本発明者らは、上記目的を達成すべく鋭意検討したところ、触媒床にそれぞれ触媒作用の異なる特定の触媒を直列３段に充填し、該触媒床に炭化水素類、水蒸気および空気などの酸素含有ガスを接触させる改質方法により、前述の小型燃料電池発電パッケージに組み込む小型改質器において、反応効率の低下、触媒の劣化、炭素析出等を抑制して、効率的に灯油などの炭化水素を改質でき、効率的に水素を生成させ得ることを見出し、発明を完成するに至った。
【００１１】
すなわち、本発明は、上記目的を達成するために、以下の（１）〜（７）の炭化水素の改質方法を提供する。
（１）酸素含有ガス、炭化水素、および水蒸気の原料混合物を、加熱用バーナーが触媒床の後段出口部近傍に設けられた触媒床に、該触媒床の前段入口部から供給して水素を主成分とするガスを製造する炭化水素の改質方法において、該触媒床の前段に炭化水素の部分酸化反応活性を示す触媒を、中段に担体の焼成温度が５００〜７００℃であって低温での炭化水素の水蒸気改質反応活性を示す触媒を、後段に担体の焼成温度が７００〜９００℃であって、かつ前記中段の触媒より担体の焼成温度が高温である炭化水素の水蒸気改質反応活性を示すと共に優れた耐熱性を示す触媒をそれぞれ充填し、該触媒床の前段入口温度が３５０〜５５０℃であり、前記供給する酸素含有ガス中の酸素量が、Ｏ _２と前記炭化水素中の炭素との比（Ｏ _２／Ｃ（モル比））で０．００１〜０．２５であり、前記供給する水蒸気の量が、Ｈ _２Ｏと前記炭化水素中の炭素との比（Ｈ _２Ｏ／Ｃ（モル比））で１．５〜５．０であることを特徴とする炭化水素の改質方法。
（２）触媒床の前段に充填した触媒がＲｈ、ＰｔおよびＰｄから選ばれた少なくとも１種を含んでいることを特徴とする上記（１）に記載の炭化水素の改質方法。
（３）触媒床の中段に充填した触媒がＲｕを含んでいることを特徴とする上記（１）に記載の炭化水素の改質方法。
（４）触媒床の後段に充填した触媒がＲｕまたはＮｉを含み、かつ破壊強度が５ｋｇ／ｃｍ^２以上５０ｋｇ／ｃｍ^２以下であることを特徴とする上記（１）に記載の炭化水素の改質方法。
（５）供給する炭化水素の９０質量％以上が沸点範囲３０〜３５０℃内に存在することを特徴とする上記（１）に記載の炭化水素の改質方法。
（６）供給する炭化水素中の硫黄分が１質量ｐｐｍ以下であることを特徴とする上記（５）に記載の炭化水素の改質方法。
（７）炭化水素の改質によって得られた水素を燃料電池での発電に使用することを特徴とする上記（１）〜（６）のいずれかに記載の炭化水素の改質方法。
【００１２】
本発明においては、炭化水素類と水蒸気と共に用いる酸素含有ガスの作用効果と、前段に部分酸化反応触媒、中段に低温で活性を示す水蒸気改質触媒（予備改質触媒）、後段に耐熱性に優れた水蒸気改質触媒という、特定の順序で直列に配列された特定の３種の触媒の作用効果とが相俟って、前述の小型燃料電池発電パッケージに組み込む小型改質器において、灯油などの炭化水素を原料として、反応効率の低下、触媒の劣化、炭素析出等を抑制して、効率的に水蒸気改質反応を行うことができ、効率的に水素を生成させることができる。
【００１３】
【発明の実施の形態】
以下、本発明の実施の態様について説明する。
本発明の実施に当たり、改質反応に供給する酸素含有ガスと炭化水素の比率は、酸素分子数／供給炭化水素中の炭素原子数比（以下「Ｏ₂／Ｃ」）換算で０．００１〜０．２５が適当であり、好ましくは０．０１〜０．２、さらに好ましくは０．０５〜０．１５である。供給する酸素量が０．００１より少ないと本発明で酸素含有ガスに期待する酸化反応による発熱挙動が小さく、改質触媒床、特にその前段の充分な温度上昇をもたらすことができない。逆に０．２５より多すぎると、改質反応で生成した水素の燃焼量が増加したり、使用酸素含有ガスが空気であるとき共存する窒素の影響により改質反応で得られるガス中の水素濃度が低下する。
【００１４】
また、改質反応に供給する水蒸気と炭化水素の比率は、水蒸気分子数／供給炭化水素中の炭素原子数比（以下「Ｓ／Ｃ」）換算で１．５〜５．０が適当であり、好ましくは２．０〜４．５、さらに好ましくは２．５〜４．０である。供給する水蒸気量が１．５より少ないと改質触媒上で炭素の析出を起こしやすくなり、触媒の性能や安定性が低下する懸念がある。逆に５．０より多すぎると水蒸気発生用の熱量が必要となるため、高効率燃料電池発電システムに関する技術的意味が希薄になる。
【００１５】
本発明においては、触媒床の部位を、原料混合物の流れに沿って、原料混合物の供給される入口側を前段と称し、改質反応で生成した水素を主成分とするガスが排出される出口側を後段と称し、前段と後段の中間を中段と称する。そして、本発明においては、改質触媒の触媒床として、加熱用バーナーが触媒床の後段出口部近傍に設けられたものが用いられ、該触媒床には、前段に炭化水素の部分酸化反応活性を示す触媒が、中段に低温での炭化水素の水蒸気改質反応活性を示す触媒（予備改質触媒）が、後段に炭化水素の水蒸気改質反応活性を示すと共に優れた耐熱性を示す触媒が順次直列に充填されている。そして、原料混合物は、この触媒床の前段入口部から供給され、前段、中段、後段と順次経て、改質反応で生成した水素を含むガスが後段出口部から排出される。かかる本発明における触媒床の構成の一例を模式的に図示すれば図１のとおりである。すなわち、図１に示す例においては、中空部１を有する円筒状の触媒床Ａの前段に部分酸化反応触媒２が、中段に予備改質触媒３が、後段に耐熱性に優れた水蒸気改質触媒４が順次直列に環状に充填されている。そして、触媒床Ａの後段出口部５の近傍に加熱用バーナー６が設けられており、例えば残存水素を含む燃料電池の排ガスを燃焼させた炎７によって触媒床Ａの加熱が行われ、酸素含有ガス、炭化水素、および水蒸気の原料混合物が矢印８に沿って触媒床Ａの前段入口部９に供給され、改質反応で生成した水素を含むガスが後段出口部５から矢印１０に沿って排出される。上記前段、中段および後段に充填される３種の触媒の充填量の割合は、原料炭化水素の種類、各使用触媒の特性など必要に応じて適宜設定することができる。
【００１６】
上記触媒床の前段、中段及び後段に充填される３種の触媒は、担体へ触媒種の金属もしくは金属酸化物を担持させて構成された担持触媒であることが好ましい。触媒種を担持させる方法は、特に規定しないが、含浸法、固定化法、イオン交換法、平衡吸着法などが好ましく、特に含浸法、固定化法が好ましい。なお、固定化法としては、担体へ触媒種の金属若しくは金属酸化物を担持後、アンモニア水等のアルカリ液で処理する方法を好ましく用いることができる。
また、前段には、酸素による炭化水素の酸化反応（炭化水素を主として二酸化炭素、水素へ変換）に優れた触媒で、未反応の酸素を中段以降へスリップさせることなく、触媒床の前段および中段の温度上昇に適した触媒が充填されることが好ましい。
また、中段には、未反応炭化水素を低温で水蒸気改質（予備改質）し、触媒上へ炭素を析出させることなく主として二酸化炭素、一酸化炭素、メタンなどのＣ_１化合物および水素へと転化することに適した触媒が充填されることが好ましい。
また、後段には、メタンおよび少量残存する炭化水素の水蒸気改質反応に適した触媒が充填されることが好ましい。この触媒は、優れた耐熱性、粉化等の抑制に必要な触媒破壊強度を備えることが好ましい。
上記触媒床における前段入口温度は３５０〜５５０℃が適当であり、好ましくは４００〜５００℃、さらに好ましくは４４０〜４７０℃である。温度が３５０℃より低すぎると酸素による酸化反応（部分酸化）が生じても充分な発熱を得ることができずに、充分な触媒活性を得ることができない。逆に５５０℃より高い場合には水蒸気改質反応に必要な温度が充分確保されていることから前段で部分酸化反応を行うことによる技術的意味が希薄になり好ましくない。
【００１７】
前段に充填する部分酸化反応触媒は、構成成分としてＲｈ、ＰｔおよびＰｄから選ばれた少なくとも１種を含有することが好ましく、中でもＲｈを含有することがさらに好ましい。これらの金属は酸素雰囲気下でも揮散することなく酸化による発熱反応を生じ、なおかつ未反応酸素を中段以降へスリップさせることがないためため好ましく、特にＲｈは高活性を示すため特に好ましい。Ｒｈ、Ｐｔ、Ｐｄの触媒中の含有量は、０．０１〜５．０質量％が好ましく、特に０．１〜１．０質量％が好ましい。０．０１質量％以下の含有量では酸化反応に対する触媒活性が乏しく、逆に５．０質量％を超える含有量では酸化反応に対する触媒活性の向上が認められないため、技術的な利点も少なく触媒コストの観点から実質的な上限値は５．０質量％である。
前段に充填する触媒に使用する担体の化学組成は、特に規定しないが、Ａｌ₂Ｏ₃、ＳｉＯ₂、ＺｒＯ₂、ＴｉＯ₂のうちいずれか一つ以上の成分を有していることが好ましく、特にＡｌ₂Ｏ₃、ＳｉＯ₂のうちいずれか一つ以上の成分を有していることが好ましい。また、担体の焼成温度は特に規定しないが、４００〜１０００℃が好ましく、特に６００〜８００℃が好ましい。焼成温度が４００℃以下であると触媒として使用された場合、４００℃以上の反応条件下で粉化などの構造破壊が生じて反応管の閉塞といった問題が発生する。逆に焼成温度が１０００℃以上であると担体の表面積が著しく減少して酸化反応活性が低下する恐れがある。
また、触媒破壊強度は、特に規定しないが、好ましくは２〜３０ｋｇ／ｃｍ²、さらに好ましくは５〜２０ｋｇ／ｃｍ²、である。２ｋｇ／ｃｍ²以下では触媒紛化に伴う反応管の閉塞が発生する懸念がある。上限の制限は特にないが３０ｋｇ／ｃｍ²を超えても技術的な利点は少なく、実質的な上限値は３０ｋｇ／ｃｍ²である。
【００１８】
前段に充填する触媒は、第３成分としてＲｈ、Ｐｔ、Ｐｄに加えてアルカリ金属、アルカリ土類金属あるいは希土類の酸化物を含有していることが好ましい。アルカリ金属、アルカリ土類金属あるいは希土類の酸化物は、触媒上の酸性質を制御する機能を有し、触媒上への炭素の析出を抑制する性質を有しているため、Ｒｈ、Ｐｔ、Ｐｄに加えて使用することが好ましく、アルカリ金属酸化物にはＬｉ、Ｎａ、Ｋ、Ｒｂ、Ｃｓの酸化物を使用することができ、好ましくはＮａ、Ｋ、Ｃｓの酸化物、さらに好ましくはＮａ、Ｋの酸化物を用いる。アルカリ土類金属酸化物にはＢｅ、Ｍｇ、Ｃａ、Ｓｒ、Ｂａの酸化物を使用することができ、好ましくはＭｇ、Ｃａ、Ｓｒの酸化物、さらに好ましくはＭｇ、Ｃａの酸化物である。希土類酸化物にはＬａ、Ｃｅ、Ｙの酸化物を使用することができ、好ましくはＬａ、Ｃｅの酸化物、さらに好ましくはＣｅの酸化物である。アルカリ金属、アルカリ土類金属あるいは希土類の酸化物の触媒中の含有量は０．１〜１０．０質量％が好ましく、特に０．５〜５．０質量％が好ましい。０．１質量％以下の含有量では炭素析出抑制に対する効果が乏しく、逆に１０．０質量％を超えると、添加効果が飽和する傾向が見られ、技術的意義が希薄となる。このため実質的な上限は１０．０質量％である。
【００１９】
中段に充填する予備改質触媒は、構成成分としてＲｕを含有していることが好ましく、Ｒｕに加えて第３成分としてアルカリ金属、アルカリ土類金属あるいは希土類の酸化物を含んでいることがさらに好ましい。Ｒｕは水蒸気改質反応において高活性を示すことから炭化水素の改質用触媒に適しているため、もっとも好ましく使用することができる。本発明においては、一般に、用いた酸素含有ガスの酸素は大部分が前段で反応し未反応のまま中段以降にスリップすることは少ないので、中段以降ではＲｕを好適に用いることができる。Ｒｕの触媒中の含有量は、０．１〜１０．０質量％が好ましく、特に０．５〜５．０質量％が好ましい。０．１質量％以下の含有量では水蒸気改質反応に対する触媒活性が乏しく、逆に１０．０質量％を超える含有量では水蒸気改質反応に対する触媒活性の向上効果が飽和するため、技術的な利点も少なく触媒コストの観点からも実質的な上限値は１０．０質量％である。アルカリ金属、アルカリ土類金属あるいは希土類の酸化物は、触媒上の酸性質を制御する機能を有し、触媒上への炭素の析出を抑制する性質を有しているため、Ｒｕに加えて使用することが好ましい。使用するアルカリ金属酸化物、アルカリ土類金属酸化物、および希土類酸化物としては、上記前段に充填する部分酸化反応触媒の場合と同様のものを用いることができる。また、アルカリ金属、アルカリ土類金属あるいは希土類の酸化物の触媒中の含有量は、上記前段に充填する部分酸化反応触媒の場合と同様、０．１〜１０．０質量％が好ましく、特に０．５〜５．０質量％が好ましい。０．１質量％以下の含有量では炭素析出抑制に対する効果が乏しく、逆に１０．０質量％を超えると、添加効果が飽和する傾向が見られ、技術的意義が希薄となり、実質的な上限値は、１０．０質量％である。
【００２０】
中段に充填する触媒に使用する担体の化学組成は、特に規定しないが、Ａｌ₂Ｏ₃、ＳｉＯ₂、ＺｒＯ₂、ＴｉＯ₂のうちいずれか一つ以上の成分を有していることが好ましく、特にＡｌ₂Ｏ₃、ＳｉＯ₂のうちいずれか一つ以上の成分を有していることが好ましい。また、担体の焼成温度は、特に規定しないが、４００〜８００℃が好ましく、特に５００〜７００℃が好ましい。焼成温度が４００℃未満であると触媒として使用された場合、粉化などを起こす可能性があるため好ましくない。逆に焼成温度が８００℃以上であると担体の表面積が著しく減少して水蒸気改質反応活性が低下する。
また、触媒破壊強度は、特に規定しないが、好ましくは１〜３０ｋｇ／ｃｍ²、さらに好ましくは３〜２０ｋｇ／ｃｍ²である。１ｋｇ／ｃｍ²以下では触媒紛化に伴う反応管の閉塞が発生する懸念がある。上限の制限は特にないが、３０ｋｇ／ｃｍ²を超えても技術的な利点は少なく、実質的な上限値は３０ｋｇ／ｃｍ²である。
【００２１】
後段に充填する耐熱性に優れた水蒸気改質触媒は、構成成分としてＲｕまたはＮｉを含有することが好ましく、中でもＲｕを含有することがさらに好ましい。Ｒｕは上述のように水蒸気改質反応に適している。またＮｉも同様に水蒸気改質反応に優れているが、低Ｓ／Ｃ条件等ではＲｕに比べ炭素析出しやすい傾向がある。しかしながら後段では上段、中段で炭化水素中の炭素が一酸化炭素もしくは二酸化炭素へ転化するため、反応後半においてはＳ／Ｃ（Ｃ数は未反応炭化水素由来）が高くなるので、後段においては使用することが可能となる。Ｒｕの触媒中の含有量は、０．１〜１０．０質量％が好ましく、特に０．５〜５．０質量％が好ましい。０．１質量％以下の含有量では水蒸気改質反応に対する触媒活性が乏しく、逆に１０．０質量％を超える含有量では水蒸気改質反応に対する触媒活性の向上効果が飽和するため、技術的な利点も少なく触媒コストの観点から実質的な上限値は１０．０質量％である。
【００２２】
一方、Ｎｉの触媒中の含有量は、１．０〜５０．０質量％が好ましく、特に５．０〜３０．０質量％が好ましい。１．０質量％以下の含有量では、水蒸気改質反応に対する触媒活性が低く、逆に５０．０質量％を超える含有量では水蒸気改質反応に対する触媒活性の向上効果が飽和する傾向が見られるなど技術的な利点が少なくなる。また、触媒コストも高くなる傾向もあるため、実質的な上限は５０．０質量％である。
【００２３】
後段に充填する触媒に使用する担体の化学組成は、特に規定しないが、Ａｌ₂Ｏ₃、ＳｉＯ₂、ＺｒＯ₂、ＴｉＯ₂のうちいずれか一つの成分を有していることが好ましく、特にＡｌ₂Ｏ₃、ＳｉＯ₂のうちいずれか一つ以上の成分を有していることが好ましい。また、担体の焼成温度は特に規定しないが、６００〜１０００℃が好ましく、特に７００〜９００℃が好ましい。焼成温度が６００℃以下であると触媒として使用された場合、６００℃以上の反応条件下で粉化などを起こす可能性があるため好ましくない。逆に焼成温度が１０００℃以上であると担体の表面積が著しく減少して水蒸気改質反応活性が低下する恐れがある。
また、触媒破壊強度は、５〜５０ｋｇ／ｃｍ²を有しており、好ましくは５〜３０ｋｇ／ｃｍ²、さらに好ましくは５〜２０ｋｇ／ｃｍ²である。５ｋｇ／ｃｍ²以下では触媒紛化に伴う反応管の閉塞が発生する懸念がある。上限の制限は特にないが５０ｋｇ／ｃｍ²を超えても技術的な利点は少なく、実質的な上限値は５０ｋｇ／ｃｍ²である。
後段に充填する触媒には、上記のように担体焼成温度を比較的高くし、破壊強度も比較的高くして、優れた耐熱性を有するものが使用される。
【００２４】
後段に充填する触媒は、第３成分としてＲｕまたはＮｉに加えてアルカリ金属、アルカリ土類金属あるいは希土類の酸化物を含有していることが好ましい。アルカリ金属、アルカリ土類金属あるいは希土類の酸化物は触媒上の酸性質を制御する機能を有し、触媒上への炭素の析出を抑制する性質を有しているためＲｕまたはＮｉに加えて使用することが好ましい。使用するアルカリ金属酸化物、アルカリ土類金属酸化物、および希土類酸化物としては、上記前段に充填する部分酸化反応触媒の場合と同様のものを用いることができる。また、アルカリ金属、アルカリ土類金属あるいは希土類の酸化物の触媒中の含有量は、上記前段に充填する部分酸化反応触媒の場合と同様、０．１〜１０．０質量％が好ましく、特に０．５〜５．０質量％が好ましい。０．１質量％以下の含有量では炭素析出抑制に対する効果が乏しく、逆に１０．０質量％を超える含有量では添加効果が飽和する傾向が見られ、技術的意義が希薄となるため実質的な上限は１０．０質量％である。
【００２５】
触媒床に充填する３種の触媒に関して共通する要件として以下のことを挙げることができる。
▲１▼触媒形状は、一般的な成形体を好ましく用いることができるが、打錠成形体、押し出し成形体、球型成形体、モノリス成形体がより好ましく、打錠成形体がもっとも好ましい。
▲２▼比表面積は、好ましくは５〜３００ｍ²／ｇ、さらに好ましくは１０〜２５０ｍ²／ｇである。５ｍ²／ｇ以下の比表面積では改質反応に必要な有効反応場の提供が不充分であり、改質反応活性が低下する傾向が見られる。触媒の比表面積の上限はないが、触媒担体等の物性によって決まるケースがほとんどで、一般的には３００ｍ²／ｇが上限値と考えられる。
【００２６】
原料として使用する炭化水素としては、広く一般家庭に普及し廉価である（エネルギー単価が優れている）沸点範囲３０〜３５０℃に９０％以上が存在する炭化水素、好ましくはガソリン、ナフサ、灯油、軽油、合成油、より好ましくはガソリン、ナフサ、灯油、もっとも好ましくは灯油である。炭化水素中の硫黄分は、１質量ｐｐｍ以下が適当であり、好ましくは０．２質量ｐｐｍ以下、さらに好ましくは０．１質量ｐｐｍ以下である。硫黄分が１質量ｐｐｍを超過すると改質触媒が被毒され、改質性能が低下する恐れがある。
【００２７】
使用する酸素含有ガスとしては、純酸素であっても良いし、酸素富化装置により酸素濃度を高めた空気であってもよいし、空気であっても良い。一般には、経済的観点から空気を使用することが好ましい。
この酸素含有ガスは、既に述べたように、触媒床中、とりわけその前段における部分酸化反応による発熱に利用され、触媒床、とりわけその前段の温度上昇をもたらすものである。
また、使用する水蒸気としては、従来から炭化水素の水蒸気改質反応に使用されているものを適宜使用すれば良い。
【００２８】
以上述べた本発明の炭化水素の改質方法は、前記のとおり、燃料電池発電パッケージ、とりわけ家庭用等の小型燃料電池発電パッケージに組み込む改質器に好適に適用できる改質方法であって、本発明の改質方法を適用した改質器は、リン酸型、固体高分子型など各種の公知の燃料電池と適宜組み合わせて燃料電池発電パッケージを構成することができ、当該改質器で得られた水素含有ガスを利用して各種燃料電池で発電を行うことができる。その際、当該改質器で得られた水素含有ガスは、必要に応じて、燃料電池に供給する前に、ＣＯシフト反応器、ＣＯ選択酸化反応器、水素膜分離装置、水素用ＰＳＡ装置、気液分離器等を経由させて、ＣＯの低減、水素の分離精製等を行うことができる。
【００２９】
【実施例】
以下、実施例および比較例によりさらに具体的に本発明を説明するが、本発明は以下の実施例に限定されるものではない。
【００３０】
（実施例１）
水タンクよりポンプを通じて加熱蒸発器により生成された１２０℃の水蒸気が１１４ｇ／ｈｒの量で供給され、灯油タンクよりポンプを通じて灯油が２５．４ｇ／ｈｒの量で供給され、空気がブロアーからマスフローコントローラーを通じて２０．２ＮＬ／ｈｒの量でそれぞれ反応管へ供給されている。なおここでの水蒸気、酸素の供給比率はＳ／Ｃとして３．５、Ｏ₂／Ｃとして０．１である。３種の混合物はヒーターにより加熱され、温度は２００℃である。
なお、反応に使用した原料灯油の性状を表１に示す。
該混合物を直立した円筒状の固定床流通式反応装置にその頂部から下向きに供給した。反応装置のサイズは内径１６ｍｍ（肉厚１ｍｍ）で前段（上）にはＲｈを触媒基準で０．５質量％、残りアルミナからなる触媒（Ｒｈ（０．５％）／Ａｌ₂Ｏ₃（ｂａｌ．））６ｍＬ、前段（中）にはＲｕを触媒基準で２．３質量％、Ｋ₂Ｏを触媒基準で３質量％、残りアルミナからなる触媒（Ｒｕ（２．３％）／Ｋ₂Ｏ（３％）／Ａｌ₂Ｏ₃（ｂａｌ．）１８ｍＬ、後段（下）にはＲｕを触媒基準で１．８質量％、ＣｅＯ₂を触媒基準で７．５質量％、残りアルミナからなる触媒（Ｒｕ（１．８％）／ＣｅＯ₂（７．５％）／Ａｌ₂Ｏ₃（ｂａｌ．））４２ｍＬを充填した。以下、用いた触媒については上記のように略記する。
【００３１】
なお各触媒の物理性状は下記のとおりであった。

触媒の比表面積はＢＥＴ法（窒素吸着量）により、また触媒破壊強度は木屋式測定器での側面破壊強度によりそれぞれ測定を行った。
【００３２】
反応評価に先立って水素流通下で反応装置に具備されているヒーターを使用して５００℃、２時間の前処理還元を施した。その際の水素流通量は１３２ｍＬ／ｍｉｎである。
前処理還元終了後、電気炉のヒーター設定値を変更して一本式バーナー使用を想定した温度勾配となるようにヒーター設定値をセットした。その際の反応管各部の温度として、▲１▼前段触媒の上１０ｍｍ、▲２▼前段触媒上部、▲３▼前段触媒下部、▲４▼中段触媒上部、▲５▼中段触媒下部、▲６▼下段触媒上部、▲７▼下段触媒下部、▲８▼下段触媒の下１０ｍｍの８点を測定した。▲１▼の温度が４５０℃、▲８▼の温度が６８５℃になったことを確認して水蒸気、灯油、空気の順で反応管へ供給した。
反応開始後１０時間後の出口ガス中をＴＣＤおよびＦＩＤ式ガスクロマトグラフにより分析し、乾燥ガス中の水素体積濃度（Ｄｒｙ−％）、Ｃ₁転化率から反応速度定数を算出した。また使用後触媒上へのＣ析出量（各触媒床の最上部に充填されていた触媒１０粒の平均値）および触媒に担持した金属の質量減少率を測定した。
本発明における触媒活性の指標として、水素濃度が高く（５０Ｄｒｙ−％以上）、反応速度定数が大きく（９０以上）、炭素析出量が少なく（１質量％以下）、金属の減少率も抑制されて（１質量％以下）おり、本発明の目的にかなう触媒特性を示した。
出口水素濃度、反応速度定数、炭素析出量および金属の質量減少率を表２に示した。なお、表２には、反応管各部の温度ならびに使用後触媒の粉化の有無も合わせ示した。
【００３３】
（実施例２）
前段に充填した触媒量を１２ｍＬ、中段へ充填した触媒量を１５ｍＬ、後段へ充填した触媒量を３９ｍＬへ変更し、▲１▼温度を３５０℃、Ｓ／Ｃを１．５、Ｏ₂／Ｃを０．２５へそれぞれ変更した以外は実施例１と同様の条件で反応評価を行った。反応評価試験の結果、本発明の目的にかなう触媒特性を示すことが明らかとなった。結果を表２に示す。
【００３４】
（実施例３）
前段に充填した触媒をＰｔ（０．５％）／Ａｌ₂Ｏ₃（ｂａｌ．）（比表面積１２５ｍ²／ｇ、破壊強度８．６ｋｇ／ｃｍ²、担体焼成温度７００℃）とし、前段へ充填した触媒量を１ｍＬ、中段へ充填した触媒量を２３ｍＬへ変更し、▲１▼温度を５５０℃、▲８▼温度を６９５℃、Ｓ／Ｃを５．０、Ｏ₂／Ｃを０．００１へそれぞれ変更した以外は実施例１と同様の条件で反応評価を行った。反応評価試験の結果、本発明の目的にかなう触媒特性を示すことが明らかとなった。結果を表２に示す。
【００３５】
（実施例４）
前段に充填した触媒をＰｄ（０．５％）／Ａｌ₂Ｏ₃（ｂａｌ．）（比表面積１２２ｍ²／g、破壊強度８．２ｋｇ／ｃｍ²、担体焼成温度７００℃）とし、前段へ充填した触媒量を９ｍＬ、中段へ充填した触媒量を１８ｍＬ、後段へ充填した触媒量を３９ｍＬへ変更し、▲１▼温度を４００℃、Ｓ／Ｃを２．０、Ｏ₂／Ｃを０．２へそれぞれ変更した以外は実施例１と同様の条件で反応評価を行った。反応評価試験の結果、本発明の目的にかなう触媒特性を示すことが明らかとなった。結果を表２に示す。
【００３６】
（実施例５）
後段に充填した触媒をＮｉ（１０．０％）／Ａｌ₂Ｏ₃（ｂａｌ．）（比表面積９６ｍ²／ｇ、破壊強度９．３ｋｇ／ｃｍ²、担体焼成温度８００℃）とし、前段へ充填した触媒量を１ｍＬ、中段へ充填した触媒量を３０ｍＬ、後段へ充填した触媒量を３５ｍＬへ変更し、▲１▼温度を５００℃、▲８▼温度を６９０℃、Ｓ／Ｃを４．５、Ｏ₂／Ｃを０．０１へそれぞれ変更し、使用した原料油の硫黄分を１．０質量ｐｐｍへと変更（硫黄分が１．０質量ｐｐｍとなるようにベンゾチオフェン：Ｃ₈Ｈ₆Ｓを添加・混合）した以外は実施例１と同様の条件で反応評価を行った。反応評価試験の結果、本発明の目的にかなう触媒特性を示すことが明らかとなった。結果を表２に示す。
【００３７】
（実施例６）
中段に充填した触媒をＲｕ（２．３％）／Ａｌ₂Ｏ₃（ｂａｌ．）（比表面積１９４ｍ²／ｇ、破壊強度５．５ｋｇ／ｃｍ²、担体焼成温度６００℃）へ変更し、▲１▼温度を４４０℃、▲８▼温度を６８０℃、Ｓ／Ｃを２．５、Ｏ₂／Ｃを０．１５へそれぞれ変更し、使用した原料油の硫黄分を０．２質量ｐｐｍへと変更（硫黄分が０．２質量ｐｐｍとなるようにベンゾチオフェン：Ｃ₈Ｈ₆Ｓを添加・混合）した以外は実施例１と同様の条件で反応評価を行った。反応評価試験の結果、本発明の目的にかなう触媒特性を示すことが明らかとなった。結果を表２に示す。
【００３８】
（実施例７）
前段へ充填した触媒量を３ｍＬ、中段へ充填した触媒量を２１ｍＬへ変更し、▲１▼温度を４７０℃、▲８▼温度を６９０℃、Ｓ／Ｃを４．０、Ｏ₂／Ｃを０．０５へそれぞれ変更し、使用した原料油をナフサ（性状は表３参照）へと変更した以外は実施例１と同様の条件で反応評価を行った。反応評価試験の結果、本発明の目的にかなう触媒特性を示すことが明らかとなった。結果を表２に示す。
【００３９】
（比較例１）
前段に充填した触媒をＲｕ（２．３％）−Ｋ₂Ｏ（３％）／Ａｌ₂Ｏ₃（ｂａｌ．）（比表面積１８０ｍ²／ｇ、破壊強度５．４ｋｇ／ｃｍ²、担体焼成温度６００℃：実施例１では中段に使用）とし、前段へ充填した触媒量を１２ｍＬ、中段へ充填した触媒量を１５ｍＬ、後段へ充填した触媒量を３９ｍＬへ変更し、▲１▼温度を３５０℃、Ｓ／Ｃを１．５、Ｏ₂／Ｃを０．２５へそれぞれ変更し、使用した原料油の硫黄分を０．１質量ｐｐｍへと変更した以外は実施例１と同様の条件で反応評価を行った。反応評価試験の結果、前段に充填した触媒中に担持した貴金属の減少率が１５質量％であったため本発明の目的にそぐわない結果であった。結果を表４に示す。
【００４０】
（比較例２）
▲８▼温度を６８０℃、Ｏ₂／Ｃを０へそれぞれ変更した以外は実施例１と同様の条件で反応評価を行った。反応評価試験の結果、前段および中段に充填した触媒上へのＣ析出量がそれぞれ２．３と１．６質量％であったため本発明の目的にそぐわない結果であった。結果を表４に示す。
【００４１】
（比較例３）
中段に充填した触媒をＲｕ（１．８％）−ＣｅＯ₂（７．５％）／Ａｌ₂Ｏ₃（ｂａｌ．）（比表面積１１０ｍ²／ｇ、破壊強度９．７ｋｇ／ｃｍ²、担体焼成温度８００℃：実施例１では後段に使用）とし、前段へ充填した触媒量を１ｍＬ、中段へ充填した触媒量を２３ｍＬへ変更し、▲１▼温度を５５０℃、▲８▼温度を６９５℃、Ｓ／Ｃを５．０、Ｏ₂／Ｃを０．００１へそれぞれ変更し、使用した原料油の硫黄分を０．１質量ｐｐｍへと変更した以外は実施例１と同様の条件で反応評価を行った。反応評価試験の結果、反応速度定数が８６であったため本発明の目的にそぐわない結果であった。結果を表４に示す。
【００４２】
（比較例４）
前段へ充填した触媒量を１２ｍＬ、中段へ充填した触媒量を１５ｍＬ、後段へ充填した触媒量を３９ｍＬへ変更し、▲１▼温度を３５０℃、Ｓ／Ｃを１．５、Ｏ₂／Ｃを０．４５へそれぞれ変更し、使用した原料油の硫黄分を０．１質量ｐｐｍへと変更した以外は実施例１と同様の条件で反応評価試験を行った。反応評価試験の結果、水素体積濃度が４０Ｄｒｙ−％であったため本発明の目的にそぐわない結果であった。結果を表４に示す。
【００４３】
（比較例５）
前段へ充填した触媒量を１ｍＬ、中段へ充填した触媒量を２３ｍＬへ変更。▲１▼温度を５５０℃、▲８▼温度を６９５℃、Ｓ／Ｃを０．５、Ｏ₂／Ｃを０．００１へそれぞれ変更し、使用した原料油の硫黄分を０．１質量ｐｐｍへと変更した以外は実施例１と同様の条件で反応評価試験を行った。反応評価試験の結果、前段および中段に充填した触媒上へのＣ析出量がそれぞれ２．５と１．５質量％であったため本発明の目的にそぐわない結果であった。結果を表４に示す。
【００４４】
（比較例６）
前段へ充填した触媒量を９ｍＬ、中段へ充填した触媒量を１８ｍＬ、後段へ充填した触媒量を３９ｍＬへ変更し、▲１▼温度を３００℃、▲８▼温度を６８０℃、Ｓ／Ｃを２．０、Ｏ₂／Ｃを０．２へそれぞれ変更し、使用した原料油の硫黄分を０．１質量ｐｐｍへと変更した以外は実施例１と同様の条件で反応評価試験を行った。反応評価試験の結果、反応速度定数が７７であったため本発明の目的にそぐわない結果であった。結果を表４に示す。
【００４５】
（比較例７）
後段に充填した触媒量をＲｕ（１．８％）−ＣｅＯ₂（７．５％）／Ａｌ₂Ｏ₃（ｂａｌ．）（比表面積１８０ｍ²／ｇ、破壊強度２．５ｋｇ／ｃｍ²、担体焼成温度３００℃）へ変更し、使用した原料油の硫黄分を０．１質量ｐｐｍへと変更した以外は実施例１と同様の条件で反応評価試験を行った。反応評価試験の結果、後段に充填した触媒粒子の一部が粉化していたため本発明の目的にそぐわない結果であった。結果を表４に示す。
【００４６】
（比較例８）
後段に充填した触媒をＲｕ（１．８％）−ＣｅＯ₂（７．５％）／Ａｌ₂Ｏ₃（ｂａｌ．）（比表面積１５ｍ²／ｇ、破壊強度１０ｋｇ／ｃｍ²以上、担体焼成温度１１００℃）へ変更し、▲１▼温度を５５０℃、▲８▼温度を６９５℃、Ｓ／Ｃを５．０、Ｏ₂／Ｃを０．００１へそれぞれ変更し、使用した原料油の硫黄分を０．１質量ｐｐｍへと変更した以外は実施例１と同様の条件で反応評価試験を行った。反応評価試験の結果、反応速度定数が７４であったため本発明の目的にそぐわない結果であった。結果を表４に示す。
【００４７】
以上の結果から本発明の条件下では高い水素濃度のガスを生成し、高い反応速度定数を示し、また触媒もＣ析出や金属の減少あるいは粉化などの問題を生じることがないことが明らかとなった。
【００４８】
【表１】

【００４９】
【表２】

【００５０】
【表３】

【００５１】
【表４】

【００５２】
【発明の効果】
本発明によれば、小型燃料電池発電パッケージの改質器に好適に適用できて、小型燃料電池発電パッケージのランニングコストの低減を図れるような、灯油などの炭化水素を原料として効率的に水素を製造し得る炭化水素の改質方法が提供される。
【図面の簡単な説明】
【図１】本発明に係る触媒床の構成の一例を模式的に示す図である。
【符合の説明】
１中空部
２部分酸化反応触媒
３予備改質触媒
４耐熱性に優れた水蒸気改質触媒
５後段出口部
６加熱用バーナー
７炎
８矢印
９前段入口部
１０矢印
Ａ触媒床[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for reforming hydrocarbons related to the production of hydrogen from hydrocarbons, and particularly to the production of hydrogen used in fuel cells.
[0002]
[Description of Related Art]
Production of hydrogen from hydrocarbons such as city gas, LPG, gasoline, and kerosene is generally performed by a steam reforming method because the hydrogen concentration in the resulting product gas is high. This steam reforming method Is represented by the following Equation 1.
C_mH_n  + MH₂O = mCO + (n / 2 + m) H₂  (Formula 1)
(In Formula 1, C_mH_nRepresents the average molecular formula of hydrocarbons. )
In particular, in the production of hydrogen for fuel cells, the steam reforming method is considered to be a suitable method from the viewpoint of the reformed gas characteristics and the heat balance for the following reasons.
(1) In the steam reforming method, the hydrogen concentration in the outlet gas is as high as about 70% (dry base), and high power generation efficiency in the fuel cell can be expected.
(2) The steam reforming reaction is a violent endothermic reaction, and it is necessary to supply heat from the outside. The fuel cell exhaust gas is used as fuel for the heating burner provided as a heat source from the outside. Can be used. That is, the power generation utilization rate of hydrogen supplied to the fuel cell is not 100%, and hydrogen remains in the exhaust gas of the fuel cell at a low concentration, and the remaining hydrogen is used as fuel for the heating burner. can do.
[0003]
In general, in a fuel cell power generation package incorporating a fuel cell and a reformer that generates hydrogen used in the fuel cell by steam reforming of hydrocarbons, particularly in a small fuel cell power generation package for home use, the package Therefore, it is necessary to reduce the size of the reformer to be incorporated. In general, this reformer is provided with a catalyst bed filled with a steam reforming catalyst, and a heating burner for heating the catalyst bed is provided. Accordingly, the number of burners is small and the number of the burners is small, and the burners are generally provided in the vicinity of the rear outlet of the catalyst bed. Therefore, in the catalyst bed of this reformer, a temperature gradient tends to be generated between the rear-stage outlet near the installation position of the heating burner and the front-stage inlet far from the installation position. For example, the high temperature is about 650 to 850 ° C. at the outlet portion in the rear stage of the catalyst bed close to the burner, whereas the low temperature is about 350 to 550 ° C. at the inlet portion in the front stage of the catalyst bed away from the burner.
[0004]
In general, kerosene has a low cost per unit of heat (unit price of energy), is economical, is easy to handle in ordinary households from the safety aspect, has well-developed infrastructure, and has excellent transportability. . For this reason, kerosene has attracted attention as a fuel for producing hydrogen for small fuel cell power generation packages used in homes and the like. However, in the steam reforming reaction using kerosene as a raw material, the reforming reactivity is lowered at a low temperature, particularly in a low temperature range of 500 ° C. or lower, and the catalyst tends to show a deterioration tendency due to carbon deposition on the catalyst.
[0005]
In order to use this kerosene as a raw material for the steam reforming reaction for producing hydrogen, it is an important technique to reduce the region where the reaction temperature is low as much as possible. Therefore, as a technique for increasing the catalyst bed temperature of the small reformer used in the small fuel cell power generation package, there are methods of increasing the fuel supply amount for the burner or increasing the temperature of the catalyst bed using an electric heater. is there. In addition to these methods, an oxygen-containing gas such as air is added to the raw material of the steam reforming reaction (see Patent Document 1), or a method of filling two different steam reforming catalysts in the low-temperature part and the high-temperature part. There has also been proposed a method of increasing the temperature of the inlet of the catalyst bed using the exothermic reaction of hydrocarbons represented by Formula 2 (see Patent Document 2 and Patent Document 3).
C_mH_n  + M / 2O₂  = MCO + n / 2H₂        (Formula 2)
(In Formula 2, C_mH_nRepresents the average molecular formula of hydrocarbons. )
[0006]
Among the techniques for increasing the catalyst bed temperature of the small reformer, in the method of increasing the fuel supply amount for the burner, for example, as described above, the small reformer in which the heating burner is installed near the outlet of the catalyst bed. In the genitalia,
If the amount of fuel supplied to the burner is increased so that the temperature at the inlet of the catalyst bed away from the burner installation position rises, the catalyst bed temperature in the vicinity of the burner becomes higher than the specified temperature, causing problems with the catalyst and reactor materials. May occur.
Further, in the method of increasing the temperature of the catalyst bed using the electric heater, the power consumption inside the small fuel cell power generation package is increased, so that the power generation efficiency tends to decrease.
In addition, the method of filling two types of steam reforming catalysts different in the low temperature part and the high temperature part cannot sufficiently achieve the steam reforming reaction. There is a possibility that reforming reaction such as kerosene fractions can be carried out even at lower temperatures by improving the steam reforming catalyst. Instead of the catalyst system mainly using nickel, which has been used in hydrogen plants in the past, A steam reforming catalyst having ruthenium as a main active component has attracted attention. However, even a catalyst having ruthenium as a main active component does not have sufficient performance in the low temperature range as described above when a heavy hydrocarbon is used as a raw material. That is, in any conventionally proposed steam reforming catalyst, it is essential to devise a method for raising the reaction temperature to a temperature range of 500 ° C. or higher, preferably 550 ° C. or higher.
Further, in the method of using an exothermic reaction of hydrocarbons by adding an oxygen-containing gas to the raw material for the steam reforming reaction, hydrogen generated by the steam reforming reaction is also consumed for combustion, and thus the hydrogen concentration tends to decrease. When a large amount of air is introduced as an oxygen-containing gas, the resulting hydrogen-containing gas tends to be unfavorable as hydrogen for fuel cells, such as dilution of hydrogen with nitrogen. Ruthenium-based catalysts show excellent activity for reforming light to medium heavy hydrocarbons, but when oxygen coexists in the reaction system, volatile ruthenium oxide (RuO)._FourEtc.), and the active ingredient ruthenium sublimates or overflows downstream.
[0007]
There is a need for a technique for solving the above-described problems, and it can be suitably applied to a reformer of a small fuel cell power generation package, such as kerosene, which can reduce the running cost of the small fuel cell power generation package. There is a demand for a hydrocarbon reforming method capable of efficiently producing hydrogen using hydrocarbons as a raw material.
[0008]
[Patent Document 1]
Japanese Patent Laid-Open No. 3-80102
[Patent Document 2]
JP 2001-146406 A
[Patent Document 3]
JP 2002-104809 A
[0009]
[Problems to be solved by the invention]
The object of the present invention is to solve the above-mentioned problems of the prior art, and can be suitably applied to a reformer of a small fuel cell power generation package, such as kerosene, which can reduce the running cost of the small fuel cell power generation package. An object of the present invention is to provide a hydrocarbon reforming method capable of efficiently producing hydrogen from a hydrocarbon as a raw material.
[0010]
[Means for Solving the Problems]
The inventors of the present invention diligently studied to achieve the above object. As a result, the catalyst bed was filled with specific catalysts having different catalytic actions in three stages in series, and the catalyst bed was filled with oxygen such as hydrocarbons, water vapor and air. In the small reformer incorporated in the above-mentioned small fuel cell power generation package by the reforming method in which the contained gas is brought into contact, hydrocarbons such as kerosene are efficiently suppressed by suppressing reduction in reaction efficiency, catalyst deterioration, carbon deposition, etc. The inventors have found that hydrogen can be efficiently generated and hydrogen can be generated efficiently, and the present invention has been completed.
[0011]
  That is, in order to achieve the above object, the present invention provides the following (1) to (7) Hydrocarbon reforming method.
  (1) A raw material mixture of oxygen-containing gas, hydrocarbon, and water vapor is supplied from a front inlet of the catalyst bed to a catalyst bed provided with a heating burner in the vicinity of the rear outlet of the catalyst bed. In the hydrocarbon reforming method for producing a gas as a component, a catalyst showing a partial oxidation reaction activity of hydrocarbons is provided in the middle stage of the catalyst bed.The firing temperature of the carrier is 500 to 700 ° C.A catalyst that shows hydrocarbon steam reforming reaction activity at low temperaturesThe calcining temperature of the carrier is 700 to 900 ° C., and the calcining temperature of the carrier is higher than that of the middle catalyst.Each of them is packed with a catalyst that exhibits hydrocarbon steam reforming reaction activity and excellent heat resistance,The upstream inlet temperature of the catalyst bed is 350 to 550 ° C., and the amount of oxygen in the supplied oxygen-containing gas is O ₂ To carbon in the hydrocarbon (O ₂ / C (molar ratio)) is 0.001 to 0.25, and the amount of water vapor supplied is H ₂ Ratio of O to carbon in the hydrocarbon (H ₂ O / C (molar ratio)) is 1.5 to 5.0A method for reforming hydrocarbons.
  (2The method for reforming hydrocarbons as described in (1) above, wherein the catalyst packed in the previous stage of the catalyst bed contains at least one selected from Rh, Pt and Pd.
  (3The method for reforming hydrocarbons as described in (1) above, wherein the catalyst packed in the middle stage of the catalyst bed contains Ru.
  (4) The catalyst packed in the latter stage of the catalyst bed contains Ru or Ni and has a breaking strength of 5 kg / cm²50 kg / cm²The hydrocarbon reforming method as described in (1) above, wherein
  (590) The hydrocarbon reforming method as described in (1) above, wherein 90% by mass or more of the hydrocarbon to be supplied is present in a boiling range of 30 to 350 ° C.
  (6) The above (characterized in that the sulfur content in the hydrocarbon to be supplied is 1 mass ppm or less.5The method for reforming hydrocarbons described in 1).
  (7(1) The hydrogen obtained by reforming hydrocarbons is used for power generation in a fuel cell.6) The hydrocarbon reforming method according to any one of the above.
[0012]
In the present invention, the effect of the oxygen-containing gas used together with hydrocarbons and steam, the partial oxidation reaction catalyst in the former stage, the steam reforming catalyst (preliminary reforming catalyst) showing activity at low temperature in the middle stage, and the heat resistance in the latter stage In combination with the action and effect of three specific catalysts arranged in series in a specific order, which is an excellent steam reforming catalyst, in the small reformer incorporated in the aforementioned small fuel cell power generation package, kerosene, etc. Using the above hydrocarbon as a raw material, it is possible to efficiently perform a steam reforming reaction by suppressing a reduction in reaction efficiency, catalyst deterioration, carbon deposition and the like, and to efficiently generate hydrogen.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described.
In the practice of the present invention, the ratio of the oxygen-containing gas and hydrocarbons supplied to the reforming reaction is the ratio of the number of oxygen molecules / the number of carbon atoms in the supplied hydrocarbon (hereinafter referred to as “O₂/ C ") is suitably 0.001 to 0.25, preferably 0.01 to 0.2, and more preferably 0.05 to 0.15. If the amount of oxygen to be supplied is less than 0.001, the exothermic behavior due to the oxidation reaction expected for the oxygen-containing gas in the present invention is small, and a sufficient temperature rise of the reforming catalyst bed, particularly the preceding stage, cannot be brought about. On the other hand, if the amount is more than 0.25, the amount of hydrogen produced in the reforming reaction increases, or hydrogen in the gas obtained by the reforming reaction due to the influence of nitrogen coexisting when the oxygen-containing gas used is air. The concentration decreases.
[0014]
The ratio of steam and hydrocarbons supplied to the reforming reaction is suitably 1.5 to 5.0 in terms of the number of water vapor molecules / the number of carbon atoms in the supplied hydrocarbon (hereinafter “S / C”). , Preferably 2.0 to 4.5, more preferably 2.5 to 4.0. If the amount of water vapor to be supplied is less than 1.5, carbon is likely to be deposited on the reforming catalyst, and there is a concern that the performance and stability of the catalyst may be reduced. On the other hand, if it is more than 5.0, the amount of heat for generating water vapor is required, so the technical meaning of the high-efficiency fuel cell power generation system becomes dilute.
[0015]
In the present invention, the portion of the catalyst bed is referred to as the front stage where the raw material mixture is supplied along the flow of the raw material mixture, and the outlet from which the gas mainly composed of hydrogen generated by the reforming reaction is discharged. The side is referred to as the rear stage, and the middle between the front stage and the rear stage is referred to as the middle stage. In the present invention, as the catalyst bed of the reforming catalyst, a heating burner provided near the rear outlet of the catalyst bed is used. In the catalyst bed, the hydrocarbon partial oxidation reaction activity is provided in the previous stage. The catalyst showing the steam reforming reaction activity of hydrocarbons at low temperatures in the middle stage (preliminary reforming catalyst), the catalyst showing the steam reforming reaction activity of hydrocarbons in the latter stage and excellent heat resistance It is sequentially filled in series. The raw material mixture is supplied from the upstream inlet of the catalyst bed, and the gas containing hydrogen generated by the reforming reaction is exhausted from the downstream outlet through the upstream, middle, and downstream. An example of the configuration of the catalyst bed in the present invention is schematically shown in FIG. That is, in the example shown in FIG. 1, the partial oxidation reaction catalyst 2 is provided in the front stage of the cylindrical catalyst bed A having the hollow portion 1, the pre-reforming catalyst 3 is provided in the middle stage, and the steam reforming having excellent heat resistance in the subsequent stage. The catalyst 4 is sequentially packed in an annular shape in series. A heating burner 6 is provided in the vicinity of the rear outlet 5 of the catalyst bed A. For example, the catalyst bed A is heated by the flame 7 in which the exhaust gas of the fuel cell containing residual hydrogen is burned, and contains oxygen. A raw material mixture of gas, hydrocarbon, and water vapor is supplied along the arrow 8 to the upstream inlet 9 of the catalyst bed A, and the gas containing hydrogen generated by the reforming reaction is discharged from the downstream outlet 5 along the arrow 10. Is done. The ratio of the filling amounts of the three kinds of catalysts filled in the preceding stage, middle stage, and latter stage can be appropriately set as required, such as the type of raw material hydrocarbon and the characteristics of each catalyst used.
[0016]
  It is preferable that the three types of catalysts filled in the preceding, middle, and subsequent stages of the catalyst bed are supported catalysts that are configured by supporting a metal or a metal oxide of the catalyst species on a support. A method for supporting the catalyst species is not particularly limited, but an impregnation method, an immobilization method, an ion exchange method, an equilibrium adsorption method and the like are preferable, and an impregnation method and an immobilization method are particularly preferable. As an immobilization method, a catalyst metal or metal oxide is supported on a carrier and then treated with an alkaline solution such as ammonia water.DoThe method can be preferably used.
  In the first stage, the catalyst is excellent in the oxidation reaction of hydrocarbons with oxygen (converting hydrocarbons mainly into carbon dioxide and hydrogen), so that the unreacted oxygen is not slipped to the middle stage and the subsequent stages of the catalyst bed. It is preferable to be filled with a catalyst suitable for the temperature increase.
  In the middle stage, unreacted hydrocarbons are steam reformed (preliminary reforming) at a low temperature, and carbon such as carbon dioxide, carbon monoxide, methane, etc. is mainly deposited without depositing carbon on the catalyst.₁It is preferred that the compound and a catalyst suitable for conversion to hydrogen are packed.
  Further, the latter stage is preferably filled with a catalyst suitable for the steam reforming reaction of methane and a small amount of remaining hydrocarbon. This catalyst preferably has excellent heat resistance and catalyst destruction strength necessary for suppressing pulverization and the like.
  The front stage inlet temperature in the catalyst bed is suitably 350 to 550 ° C, preferably 400 to 500 ° C, more preferably 440 to 470 ° C. If the temperature is lower than 350 ° C., sufficient heat generation cannot be obtained even if an oxidation reaction (partial oxidation) by oxygen occurs, and sufficient catalytic activity cannot be obtained. On the other hand, when the temperature is higher than 550 ° C., the temperature necessary for the steam reforming reaction is sufficiently secured, so that the technical meaning of performing the partial oxidation reaction in the previous stage becomes less preferable.
[0017]
The partial oxidation reaction catalyst charged in the preceding stage preferably contains at least one selected from Rh, Pt and Pd as a constituent component, and more preferably contains Rh. These metals are preferable because they do not volatilize even in an oxygen atmosphere and cause an exothermic reaction due to oxidation and do not cause unreacted oxygen to slip to the middle and subsequent stages, and Rh is particularly preferable because it exhibits high activity. The content of Rh, Pt and Pd in the catalyst is preferably 0.01 to 5.0% by mass, particularly preferably 0.1 to 1.0% by mass. If the content is less than 0.01% by mass, the catalytic activity for the oxidation reaction is poor. On the other hand, if the content exceeds 5.0% by mass, the catalytic activity for the oxidation reaction is not improved. From the viewpoint of cost, the practical upper limit is 5.0% by mass.
The chemical composition of the support used for the catalyst packed in the previous stage is not particularly defined, but Al₂O_Three, SiO₂, ZrO₂TiO₂It is preferable to have any one or more components of₂O_Three, SiO₂It is preferable to have any one or more components. Moreover, although the baking temperature of a support | carrier is not specified in particular, 400-1000 degreeC is preferable and 600-800 degreeC is especially preferable. When used as a catalyst having a calcination temperature of 400 ° C. or lower, structural destruction such as pulverization occurs under reaction conditions of 400 ° C. or higher, causing a problem such as blocking of the reaction tube. On the other hand, if the firing temperature is 1000 ° C. or higher, the surface area of the carrier may be significantly reduced and the oxidation reaction activity may be reduced.
The catalyst breaking strength is not particularly specified, but preferably 2 to 30 kg / cm.²More preferably 5-20 kg / cm². 2kg / cm²In the following, there is a concern that the reaction tube may be clogged due to catalyst dusting. There is no upper limit, but 30kg / cm²However, the technical upper limit is less than 30 kg / cm.²It is.
[0018]
The catalyst charged in the previous stage preferably contains an alkali metal, alkaline earth metal or rare earth oxide as the third component in addition to Rh, Pt, and Pd. Alkali metal, alkaline earth metal or rare earth oxide has a function of controlling the acidity on the catalyst and has the property of suppressing the deposition of carbon on the catalyst, so that Rh, Pt, Pd In addition, it is preferable to use Li, Na, K, Rb, and Cs oxides as alkali metal oxides, preferably Na, K, and Cs oxides, more preferably Na, The oxide of K is used. As the alkaline earth metal oxide, oxides of Be, Mg, Ca, Sr, and Ba can be used, preferably oxides of Mg, Ca, and Sr, and more preferably oxides of Mg and Ca. As the rare earth oxide, oxides of La, Ce, and Y can be used, preferably an oxide of La, Ce, and more preferably an oxide of Ce. The content of the alkali metal, alkaline earth metal or rare earth oxide in the catalyst is preferably 0.1 to 10.0% by mass, particularly preferably 0.5 to 5.0% by mass. When the content is 0.1% by mass or less, the effect on the carbon deposition suppression is poor. Conversely, when the content exceeds 10.0% by mass, the addition effect tends to be saturated, and the technical significance becomes dilute. For this reason, the practical upper limit is 10.0 mass%.
[0019]
The pre-reforming catalyst filled in the middle stage preferably contains Ru as a constituent component, and further contains an oxide of alkali metal, alkaline earth metal or rare earth as a third component in addition to Ru. preferable. Since Ru is highly active in the steam reforming reaction, it is suitable for use as a hydrocarbon reforming catalyst, and is most preferably used. In the present invention, in general, most of the oxygen in the oxygen-containing gas used reacts in the previous stage and does not slip unreacted and then slips in the middle stage or later, so that Ru can be suitably used in the middle stage or later. The content of Ru in the catalyst is preferably 0.1 to 10.0% by mass, particularly preferably 0.5 to 5.0% by mass. If the content is less than 0.1% by mass, the catalytic activity for the steam reforming reaction is poor. Conversely, if the content exceeds 10.0% by mass, the effect of improving the catalytic activity for the steam reforming reaction is saturated. The substantial upper limit is 10.0% by mass from the viewpoint of catalyst cost with few advantages. Alkali metal, alkaline earth metal or rare earth oxides have the function of controlling the acid properties on the catalyst and have the property of suppressing the deposition of carbon on the catalyst, so they are used in addition to Ru. It is preferable to do. As the alkali metal oxide, alkaline earth metal oxide, and rare earth oxide to be used, the same ones as in the case of the partial oxidation reaction catalyst filled in the preceding stage can be used. Further, the content of the alkali metal, alkaline earth metal or rare earth oxide in the catalyst is preferably 0.1 to 10.0% by mass, particularly 0, as in the case of the partial oxidation reaction catalyst filled in the preceding stage. 0.5 to 5.0 mass% is preferable. If the content is less than 0.1% by mass, the effect of suppressing carbon deposition is poor. Conversely, if the content exceeds 10.0% by mass, the addition effect tends to be saturated, and the technical significance becomes dilute. The value is 10.0% by weight.
[0020]
The chemical composition of the support used for the catalyst packed in the middle stage is not particularly defined, but Al₂O_Three, SiO₂, ZrO₂TiO₂It is preferable to have any one or more components of₂O_Three, SiO₂It is preferable to have any one or more components. Moreover, although the baking temperature of a support | carrier is not prescribed | regulated in particular, 400-800 degreeC is preferable and 500-700 degreeC is especially preferable. When used as a catalyst, the firing temperature is less than 400 ° C., which may cause pulverization and the like. On the other hand, when the calcination temperature is 800 ° C. or higher, the surface area of the support is remarkably reduced and the steam reforming reaction activity is lowered.
Further, the catalyst breaking strength is not particularly defined, but preferably 1 to 30 kg / cm.²More preferably, 3-20 kg / cm²It is. 1kg / cm²In the following, there is a concern that the reaction tube may be clogged due to catalyst dusting. There is no upper limit, but 30kg / cm²However, the technical upper limit is less than 30 kg / cm.²It is.
[0021]
The steam reforming catalyst excellent in heat resistance to be filled in the latter stage preferably contains Ru or Ni as a constituent component, and more preferably contains Ru. Ru is suitable for the steam reforming reaction as described above. Ni is also excellent in the steam reforming reaction, but tends to deposit carbon more easily than Ru under low S / C conditions. However, since the carbon in the hydrocarbon is converted to carbon monoxide or carbon dioxide in the upper stage and the middle stage in the latter stage, S / C (C number is derived from unreacted hydrocarbon) is increased in the latter half of the reaction. It becomes possible to do. The content of Ru in the catalyst is preferably 0.1 to 10.0% by mass, particularly preferably 0.5 to 5.0% by mass. If the content is less than 0.1% by mass, the catalytic activity for the steam reforming reaction is poor. Conversely, if the content exceeds 10.0% by mass, the effect of improving the catalytic activity for the steam reforming reaction is saturated. There are few advantages and the practical upper limit is 10.0% by mass from the viewpoint of catalyst cost.
[0022]
On the other hand, the content of Ni in the catalyst is preferably 1.0 to 50.0% by mass, and particularly preferably 5.0 to 30.0% by mass. If the content is 1.0% by mass or less, the catalytic activity for the steam reforming reaction is low. Conversely, if the content exceeds 50.0% by mass, the effect of improving the catalytic activity for the steam reforming reaction tends to be saturated. The technical advantages are reduced. Moreover, since the catalyst cost tends to increase, the practical upper limit is 50.0% by mass.
[0023]
The chemical composition of the carrier used for the catalyst packed in the latter stage is not particularly defined, but Al₂O_Three, SiO₂, ZrO₂TiO₂It is preferable to have any one of the components, particularly Al₂O_Three, SiO₂It is preferable to have any one or more components. The firing temperature of the carrier is not particularly defined, but is preferably 600 to 1000 ° C, particularly preferably 700 to 900 ° C. When it is used as a catalyst having a calcination temperature of 600 ° C. or lower, it is not preferable because it may cause powdering or the like under reaction conditions of 600 ° C. or higher. On the contrary, if the calcination temperature is 1000 ° C. or higher, the surface area of the carrier is remarkably reduced and the steam reforming reaction activity may be lowered.
The catalyst breaking strength is 5 to 50 kg / cm.²Preferably 5-30 kg / cm²More preferably 5-20 kg / cm²It is. 5kg / cm²In the following, there is a concern that the reaction tube may be clogged due to catalyst dusting. There is no upper limit, but 50kg / cm²However, the technical upper limit is 50 kg / cm.²It is.
As the catalyst charged in the latter stage, a catalyst having excellent heat resistance with a relatively high carrier calcination temperature and a relatively high fracture strength as described above is used.
[0024]
The catalyst charged in the latter stage preferably contains an alkali metal, alkaline earth metal or rare earth oxide in addition to Ru or Ni as the third component. Alkali metal, alkaline earth metal or rare earth oxides have the function of controlling the acid properties on the catalyst, and have the property of suppressing carbon deposition on the catalyst, so they are used in addition to Ru or Ni. It is preferable to do. As the alkali metal oxide, alkaline earth metal oxide, and rare earth oxide to be used, the same ones as in the case of the partial oxidation reaction catalyst filled in the preceding stage can be used. Further, the content of the alkali metal, alkaline earth metal or rare earth oxide in the catalyst is preferably 0.1 to 10.0% by mass, particularly 0, as in the case of the partial oxidation reaction catalyst filled in the preceding stage. 0.5 to 5.0 mass% is preferable. If the content is less than 0.1% by mass, the effect of suppressing carbon deposition is poor. Conversely, if the content exceeds 10.0% by mass, the additive effect tends to saturate, and the technical significance is dilute. The upper limit is 10.0% by mass.
[0025]
The following can be mentioned as common requirements for the three types of catalysts packed in the catalyst bed.
(1) As the catalyst shape, a general molded body can be preferably used, but a tableting molded body, an extrusion molded body, a spherical molded body, and a monolith molded body are more preferable, and a tableting molded body is most preferable.
(2) The specific surface area is preferably 5 to 300 m.²/ G, more preferably 10 to 250 m²/ G. 5m²When the specific surface area is less than / g, the provision of an effective reaction field necessary for the reforming reaction is insufficient, and the reforming reaction activity tends to decrease. There is no upper limit for the specific surface area of the catalyst, but in most cases it is determined by the physical properties of the catalyst carrier, etc.²/ G is considered the upper limit.
[0026]
As hydrocarbons used as raw materials, hydrocarbons which are widely spread to general households and are inexpensive (excellent unit price of energy) have a boiling point range of 30 to 350 ° C., preferably 90% or more, preferably gasoline, naphtha, kerosene, Light oil, synthetic oil, more preferably gasoline, naphtha, kerosene, most preferably kerosene. The sulfur content in the hydrocarbon is suitably 1 mass ppm or less, preferably 0.2 mass ppm or less, more preferably 0.1 mass ppm or less. If the sulfur content exceeds 1 mass ppm, the reforming catalyst is poisoned and the reforming performance may be reduced.
[0027]
The oxygen-containing gas to be used may be pure oxygen, air having an oxygen concentration increased by an oxygen enricher, or air. In general, it is preferable to use air from an economic viewpoint.
As described above, this oxygen-containing gas is used for heat generation by a partial oxidation reaction in the catalyst bed, particularly in the preceding stage, and causes an increase in temperature of the catalyst bed, particularly in the preceding stage.
Moreover, what is necessary is just to use what is conventionally used for the steam reforming reaction of hydrocarbons suitably as water vapor | steam to be used.
[0028]
The hydrocarbon reforming method of the present invention described above is a reforming method that can be suitably applied to a reformer incorporated in a fuel cell power generation package, particularly a small fuel cell power generation package for home use, as described above. A reformer to which the reforming method of the present invention is applied can be combined with various known fuel cells such as phosphoric acid type and solid polymer type as appropriate to constitute a fuel cell power generation package. The generated hydrogen-containing gas can be used to generate power with various fuel cells. At that time, the hydrogen-containing gas obtained in the reformer is optionally supplied with a CO shift reactor, a CO selective oxidation reactor, a hydrogen membrane separator, a hydrogen PSA device, before being supplied to the fuel cell, Reduction of CO, separation and purification of hydrogen, and the like can be performed via a gas-liquid separator or the like.
[0029]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited to a following example.
[0030]
Example 1
120 ° C water vapor generated by a heated evaporator through a pump is supplied from a water tank in an amount of 114 g / hr, kerosene is supplied from a kerosene tank through an pump in an amount of 25.4 g / hr, and air is supplied from a blower to a mass flow controller. And 20.2 NL / hr through the reaction tube. Here, the supply ratio of water vapor and oxygen is 3.5 as S / C, O₂/ C is 0.1. The three mixtures are heated by a heater and the temperature is 200 ° C.
The properties of the raw kerosene used for the reaction are shown in Table 1.
The mixture was fed downwardly from the top into an upright cylindrical fixed bed flow reactor. The reactor has an inner diameter of 16 mm (wall thickness: 1 mm), and in the former stage (upper), Rh is 0.5 mass% based on the catalyst, and the remaining alumina catalyst (Rh (0.5%) / Al₂O_Three(Bal.)) 6 mL, and in the former stage (middle), Ru is 2.3 mass% based on the catalyst, K₂3% by mass of O based on the catalyst and the remaining alumina catalyst (Ru (2.3%) / K₂O (3%) / Al₂O_Three(Bal.) 18 mL, and in the latter part (lower), Ru is 1.8% by mass based on the catalyst, CeO.₂And 7.5% by mass of catalyst based on the catalyst, and the remaining alumina catalyst (Ru (1.8%) / CeO₂(7.5%) / Al₂O_Three(Bal.)) Was charged with 42 mL. Hereinafter, the catalyst used is abbreviated as described above.
[0031]
The physical properties of each catalyst were as follows.

The specific surface area of the catalyst was measured by the BET method (nitrogen adsorption amount), and the catalyst breaking strength was measured by the side breaking strength with a Kiya type measuring device.
[0032]
Prior to the reaction evaluation, pretreatment reduction was performed at 500 ° C. for 2 hours using a heater provided in the reaction apparatus under hydrogen flow. In this case, the hydrogen flow rate is 132 mL / min.
After the pretreatment reduction, the heater set value of the electric furnace was changed and the heater set value was set so as to obtain a temperature gradient assuming the use of a single burner. At that time, the temperature of each part of the reaction tube was as follows: (1) 10 mm above the front stage catalyst, (2) upper part of the front stage catalyst, (3) lower part of the front stage catalyst, (4) upper part of the middle stage catalyst, (5) lower part of the middle stage catalyst, (6) 8 points of 10 mm below the upper part of the lower catalyst, (7) the lower part of the lower catalyst, and (8) the lower part of the lower catalyst were measured. After confirming that the temperature of (1) was 450 ° C. and the temperature of (8) was 685 ° C., steam, kerosene, and air were supplied to the reaction tube in this order.
The outlet gas 10 hours after the start of the reaction was analyzed by TCD and FID type gas chromatograph, and the hydrogen volume concentration (Dry-%) in the dry gas, C₁The reaction rate constant was calculated from the conversion rate. In addition, the amount of C deposited on the catalyst after use (the average value of 10 particles of catalyst packed at the top of each catalyst bed) and the mass reduction rate of the metal supported on the catalyst were measured.
As an index of the catalyst activity in the present invention, the hydrogen concentration is high (50 Dry-% or more), the reaction rate constant is large (90 or more), the carbon deposition amount is small (1 mass% or less), and the metal reduction rate is also suppressed. (1% by mass or less) and exhibited catalytic properties that meet the object of the present invention.
Table 2 shows the outlet hydrogen concentration, reaction rate constant, carbon deposition amount, and metal mass reduction rate. Table 2 also shows the temperature of each part of the reaction tube and the presence or absence of powdered catalyst after use.
[0033]
(Example 2)
The amount of catalyst charged in the first stage was changed to 12 mL, the amount of catalyst charged in the middle stage was changed to 15 mL, and the amount of catalyst charged in the latter stage was changed to 39 mL. (1) Temperature was 350 ° C., S / C was 1.5, O₂The reaction was evaluated under the same conditions as in Example 1 except that / C was changed to 0.25. As a result of the reaction evaluation test, it has been clarified that the catalyst characteristic meets the object of the present invention. The results are shown in Table 2.
[0034]
(Example 3)
The catalyst packed in the previous stage is Pt (0.5%) / Al₂O_Three(Bal.) (Specific surface area 125 m²/ G, breaking strength 8.6 kg / cm²The calcining temperature of the carrier is 700 ° C.), the amount of catalyst charged in the previous stage is changed to 1 mL, the amount of catalyst charged in the middle stage is changed to 23 mL, (1) temperature is 550 ° C., (8) temperature is 695 ° C., and S / C is 5.0, O₂The reaction was evaluated under the same conditions as in Example 1 except that / C was changed to 0.001. As a result of the reaction evaluation test, it has been clarified that the catalyst characteristic meets the object of the present invention. The results are shown in Table 2.
[0035]
(Example 4)
The catalyst packed in the previous stage is Pd (0.5%) / Al₂O_Three(Bal.) (Specific surface area 122 m²/ G, breaking strength 8.2 kg / cm², Carrier calcining temperature 700 ° C.), the amount of catalyst packed in the first stage was changed to 9 mL, the amount of catalyst packed in the middle stage was changed to 18 mL, the amount of catalyst charged to the second stage was changed to 39 mL, and (1) the temperature was 400 ° C., S / C 2.0, O₂The reaction was evaluated under the same conditions as in Example 1 except that / C was changed to 0.2. As a result of the reaction evaluation test, it has been clarified that the catalyst characteristic meets the object of the present invention. The results are shown in Table 2.
[0036]
(Example 5)
The catalyst filled in the latter stage is Ni (10.0%) / Al₂O_Three(Bal.) (Specific surface area 96 m²/ G, breaking strength 9.3 kg / cm², Carrier calcining temperature 800 ° C.), the amount of catalyst charged in the first stage is changed to 1 mL, the amount of catalyst charged in the middle stage is changed to 30 mL, the amount of catalyst charged in the latter stage is changed to 35 mL, and (1) the temperature is 500 ° C., (8) Temperature is 690 ° C, S / C is 4.5, O₂/ C was changed to 0.01 respectively, and the sulfur content of the used raw material oil was changed to 1.0 mass ppm (benzothiophene: C so that the sulfur content would be 1.0 mass ppm)₈H₆The reaction was evaluated under the same conditions as in Example 1 except that S was added and mixed. As a result of the reaction evaluation test, it has been clarified that the catalyst characteristic meets the object of the present invention. The results are shown in Table 2.
[0037]
(Example 6)
The catalyst packed in the middle stage is Ru (2.3%) / Al₂O_Three(Bal.) (Specific surface area 194 m²/ G, breaking strength 5.5 kg / cm²(1) temperature is 440 ° C, (8) temperature is 680 ° C, S / C is 2.5, O₂/ C was changed to 0.15 respectively, and the sulfur content of the used raw material oil was changed to 0.2 mass ppm (benzothiophene: C so that the sulfur content becomes 0.2 mass ppm)₈H₆The reaction was evaluated under the same conditions as in Example 1 except that S was added and mixed. As a result of the reaction evaluation test, it has been clarified that the catalyst characteristic meets the object of the present invention. The results are shown in Table 2.
[0038]
(Example 7)
The amount of catalyst charged in the previous stage was changed to 3 mL, and the amount of catalyst charged in the middle stage was changed to 21 mL. (1) Temperature was 470 ° C, (8) Temperature was 690 ° C, S / C was 4.0, O₂The reaction was evaluated under the same conditions as in Example 1, except that / C was changed to 0.05 and the used raw material oil was changed to naphtha (see Table 3 for properties). As a result of the reaction evaluation test, it has been clarified that the catalyst characteristic meets the object of the present invention. The results are shown in Table 2.
[0039]
(Comparative Example 1)
The catalyst packed in the previous stage is Ru (2.3%)-K.₂O (3%) / Al₂O_Three(Bal.) (Specific surface area 180 m²/ G, breaking strength 5.4 kg / cm², Carrier calcining temperature 600 ° C .: used in the middle stage in Example 1), the catalyst amount charged in the former stage was changed to 12 mL, the catalyst quantity charged in the middle stage was changed to 15 mL, and the catalyst quantity charged in the latter stage was changed to 39 mL, (1) Temperature is 350 ° C., S / C is 1.5, O₂The reaction was evaluated under the same conditions as in Example 1 except that / C was changed to 0.25 and the sulfur content of the used raw material oil was changed to 0.1 mass ppm. As a result of the reaction evaluation test, the reduction rate of the noble metal supported in the catalyst packed in the previous stage was 15% by mass, which was not suitable for the purpose of the present invention. The results are shown in Table 4.
[0040]
(Comparative Example 2)
(8) Temperature is 680 ° C, O₂The reaction was evaluated under the same conditions as in Example 1 except that / C was changed to 0. As a result of the reaction evaluation test, the amounts of C deposited on the catalyst packed in the previous stage and the middle stage were 2.3 and 1.6% by mass, respectively, which was not suitable for the purpose of the present invention. The results are shown in Table 4.
[0041]
(Comparative Example 3)
The catalyst packed in the middle stage is Ru (1.8%)-CeO.₂(7.5%) / Al₂O_Three(Bal.) (Specific surface area 110 m²/ G, breaking strength 9.7 kg / cm²The calcining temperature of the carrier is 800 ° C. (used in the latter stage in Example 1), the amount of catalyst charged in the former stage is changed to 1 mL, the amount of catalyst charged in the middle stage is changed to 23 mL, and (1) temperature is 550 ° C., (8) 695 ° C., S / C 5.0, O₂The reaction was evaluated under the same conditions as in Example 1 except that / C was changed to 0.001 and the sulfur content of the used raw material oil was changed to 0.1 mass ppm. As a result of the reaction evaluation test, the reaction rate constant was 86, which was not suitable for the purpose of the present invention. The results are shown in Table 4.
[0042]
(Comparative Example 4)
The catalyst amount charged to the front stage was changed to 12 mL, the catalyst amount charged to the middle stage was changed to 15 mL, and the catalyst amount charged to the rear stage was changed to 39 mL. (1) Temperature was 350 ° C., S / C was 1.5, O₂A reaction evaluation test was performed under the same conditions as in Example 1 except that / C was changed to 0.45 and the sulfur content of the used raw material oil was changed to 0.1 ppm by mass. As a result of the reaction evaluation test, the hydrogen volume concentration was 40 Dry-%, which was not suitable for the purpose of the present invention. The results are shown in Table 4.
[0043]
(Comparative Example 5)
The amount of catalyst charged in the previous stage was changed to 1 mL, and the amount of catalyst charged in the middle stage was changed to 23 mL. (1) Temperature is 550 ° C, (8) Temperature is 695 ° C, S / C is 0.5, O₂A reaction evaluation test was conducted under the same conditions as in Example 1 except that / C was changed to 0.001 and the sulfur content of the used raw material oil was changed to 0.1 mass ppm. As a result of the reaction evaluation test, the amounts of C deposited on the catalyst packed in the previous stage and the middle stage were 2.5 and 1.5% by mass, respectively, which was not suitable for the purpose of the present invention. The results are shown in Table 4.
[0044]
(Comparative Example 6)
Change the amount of catalyst packed in the first stage to 9 mL, the amount of catalyst packed in the middle stage to 18 mL, and the amount of catalyst packed in the second stage to 39 mL. (1) Temperature is 300 ° C, (8) Temperature is 680 ° C, S / C 2.0, O₂A reaction evaluation test was performed under the same conditions as in Example 1 except that / C was changed to 0.2 and the sulfur content of the used raw material oil was changed to 0.1 ppm by mass. As a result of the reaction evaluation test, the reaction rate constant was 77, which was not suitable for the purpose of the present invention. The results are shown in Table 4.
[0045]
(Comparative Example 7)
The amount of catalyst charged in the latter stage is Ru (1.8%)-CeO.₂(7.5%) / Al₂O_Three(Bal.) (Specific surface area 180 m²/ G, breaking strength 2.5 kg / cm²The reaction evaluation test was performed under the same conditions as in Example 1, except that the carrier firing temperature was changed to 300 ° C. and the sulfur content of the used raw material oil was changed to 0.1 mass ppm. As a result of the reaction evaluation test, some of the catalyst particles packed in the latter stage were pulverized, which was not suitable for the purpose of the present invention. The results are shown in Table 4.
[0046]
(Comparative Example 8)
The catalyst packed in the latter stage is replaced with Ru (1.8%)-CeO.₂(7.5%) / Al₂O_Three(Bal.) (Specific surface area 15 m²/ G, breaking strength 10 kg / cm²As described above, (1) temperature is changed to 550 ° C, (8) temperature is 695 ° C, S / C is 5.0, O₂A reaction evaluation test was conducted under the same conditions as in Example 1 except that / C was changed to 0.001 and the sulfur content of the used raw material oil was changed to 0.1 mass ppm. As a result of the reaction evaluation test, the reaction rate constant was 74, which was not suitable for the purpose of the present invention. The results are shown in Table 4.
[0047]
From the above results, it is clear that under the conditions of the present invention, a gas with a high hydrogen concentration is generated, a high reaction rate constant is exhibited, and the catalyst does not cause problems such as C precipitation, metal reduction or powdering. became.
[0048]
[Table 1]

[0049]
[Table 2]

[0050]
[Table 3]

[0051]
[Table 4]

[0052]
【The invention's effect】
According to the present invention, hydrogen can be efficiently applied using a hydrocarbon such as kerosene as a raw material, which can be suitably applied to a reformer of a small fuel cell power generation package and can reduce the running cost of the small fuel cell power generation package. A process for reforming hydrocarbons that can be produced is provided.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing an example of the configuration of a catalyst bed according to the present invention.
[Explanation of sign]
1 Hollow part
2 Partial oxidation reaction catalyst
3 Pre-reforming catalyst
4 Steam reforming catalyst with excellent heat resistance
5 Rear exit
6 Burner for heating
7 Flame
8 Arrow
9 Front entrance
10 Arrow
A catalyst bed

Claims

A raw material mixture of oxygen-containing gas, hydrocarbon, and water vapor is supplied to a catalyst bed in which a heating burner is provided in the vicinity of the rear-stage outlet of the catalyst bed from the front-stage inlet of the catalyst bed, and mainly contains hydrogen. In the hydrocarbon reforming method for producing a gas, a catalyst exhibiting a partial oxidation reaction activity of hydrocarbon is provided in the preceding stage of the catalyst bed, and the calcination temperature of the support is 500 to 700 ° C. in the middle stage. The catalyst showing the steam reforming reaction activity is shown in the latter stage , and the steam reforming reaction activity of hydrocarbons whose carrier firing temperature is 700 to 900 ° C. and whose carrier firing temperature is higher than that of the middle stage catalyst. Each catalyst is packed with excellent heat resistance, the upstream inlet temperature of the catalyst bed is 350 to 550 ° C., and the oxygen content in the supplied oxygen-containing gas is O ₂ and the carbon in the hydrocarbon. ratio _(O 2 / C _(mode Ratio)) with a 0.001 to 0.25, the amount of water vapor the supply is, the ratio of the carbon in the hydrocarbon and _{_{H 2 O (H 2 O /}} C ( molar ratio)) 1.5 A method for reforming hydrocarbons, characterized in that it is ˜5.0 .

2. The hydrocarbon reforming method according to claim 1, wherein the catalyst packed in the previous stage of the catalyst bed contains at least one selected from Rh, Pt and Pd.

The hydrocarbon reforming method according to claim 1, wherein the catalyst packed in the middle stage of the catalyst bed contains Ru.

^2. The hydrocarbon reforming method according to claim 1, wherein the catalyst packed in the latter stage of the catalyst bed contains Ru or Ni and has a breaking strength of 5 kg / cm ² or more and 50 kg / cm ² or less.

The hydrocarbon reforming method according to claim 1, wherein 90% by mass or more of the hydrocarbon to be fed is present in a boiling range of 30 to 350 ° C.

The hydrocarbon reforming method according to claim 5 , wherein a sulfur content in the hydrocarbon to be fed is 1 mass ppm or less.

The method for reforming a hydrocarbon according to any one of claims 1 to 6 , wherein hydrogen obtained by the reforming of the hydrocarbon is used for power generation in a fuel cell.