JP3945854B2 - Method for producing pseudo-boehmite alumina and method for producing a carrier for hydrodesulfurization catalyst using the pseudo-boehmite alumina - Google Patents
Method for producing pseudo-boehmite alumina and method for producing a carrier for hydrodesulfurization catalyst using the pseudo-boehmite alumina Download PDFInfo
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Description
【０００１】
【発明の属する技術分野】
本発明は、硫黄化合物及び窒素化合物を含有する炭化水素油の水素化脱硫触媒の製造方法に関わり、特に、水素化脱硫触媒の原料である擬ベーマイトアルミナ及びその擬ベーマイトアルミナを用いて製造する水素化脱硫触媒の担体に関する。
【０００２】
【従来の技術】
一般に原油或いは原油から軽質留分を分離した残渣油は、硫黄含有濃度が高いため、脱硫処理した後、次工程で処理されたり、燃料として利用される。残渣油等に含まれる硫黄化合物を除去するには、一般にアルミナ或いはシリカアルミナを担体として、これに活性金属を担持させた水素化脱硫触媒を用い、水素加圧下で加熱処理する方法が用いられている。また、この脱硫処理工程では、硫黄が硫化水素となり除去される反応と同時に、窒素化合物がアンモニアとして除去される。
【０００３】
従来、このような触媒には、脱硫活性が高いこと、寿命が長いこと、安価であることが求められており、これらに重点を置いた検討がなされてきた。そして、脱硫性能という点では、ほぼ十分な性能を有するものが使われるようになった。しかし、近年、大気汚染物質の規制が強化されるに従い、窒素酸化物の排出抑制が求められるようになってきた。このため、脱硫触媒には脱硫性能もさることながら、脱窒素活性に優れるものが求められるようになった。脱窒素活性を高めるためには、触媒活性金属の担持量を増やす方法が考えられる。しかし、触媒活性金属の増量は触媒価格の向上につながる。
【０００４】
一方、脱硫触媒に用いられるアルミナ原料は、アルミニウム塩の中和法や、アルミニウムアルコキシドを加水分解するアルホール法によって得られる擬ベーマイトアルミナが主に用いられている。このような擬ベーマイトアルミナは、触媒の被毒成分であるアルカリ金属や、触媒活性に影響の大きい硫酸や塩酸等の鉱酸を除去したものを用いるのが一般的である。しかし、特公昭５０−１２３９７号広報には、安定性に優れた触媒を得るため、硫酸根を含有するアルミナ原料を用い、これを６００〜１１００℃で焼成して硫酸根を０．５〜５質量％含有するアルミナ担体を製造し、脱硫触媒とすることが記載されている。しかしながら、硫酸根を担持し、しかもこのような高温で焼成して得られる担体に活性成分を担持した触媒は、活性が著しく低下することが多い。
【０００５】
【発明が解決しようとする課題】
本発明の課題は、触媒活性金属量を増やすことなく、脱窒素活性に優れる脱硫触媒の製造を可能にする擬ベーマイトアルミナの製造方法と、その擬ベーマイトアルミナを用いる脱硫触媒用担体の製造方法を提供することにある。
【０００６】
【課題を解決するための手段】
本発明者が、アルミナ原料に注目し、鋭意検討を進めた結果、硫酸を含有する洗浄水で洗浄した擬ベーマイトアルミナを成形し、４５０〜６５０℃で焼成した担体を用いて触媒を製造すると、脱窒素活性を大幅に向上できることを見出した。しかも脱硫活性は、硫酸分を含有しない擬ベーマイトアルミナ原料を用いた触媒と同等であった。さらに、上記擬ベーマイトアルミナの製造条件を検討した結果、ｐＨ８．０〜９．５で製造した水酸化アルミニウムを濾別し、得られる水酸化アルミニウムケーキを硫酸及び／又は硫酸アンモニウム添加水で洗浄する際に、濾液のｐＨが８．０±０．５となるように管理して洗浄し乾燥する方法と、濾別した前記水酸化アルミニウムケーキを水に分散させ、攪拌しながら硫酸及び／又は硫酸アンモニウムを加えて液のｐＨを８．０±０．５とした後、濾過して乾燥する方法で製造する擬ベーマイトアルミナを用いれば、脱窒素活性に優れる脱硫触媒を製造可能であることを見出し、本発明を完成させた。
【０００７】
【発明の実施の形態】
本発明の擬ベーマイトアルミナの製造方法であるが、まず、アルミニウム塩及び／又はアルミン酸塩溶液をｐＨ８．０〜９．５で中和して水酸化アルミニウムの沈殿を作る。アルミニウム塩としては、硫酸アルミニウム、塩化アルミニウム、硝酸アルミニウム等の任意のアルミニウム塩を用いることができる。また、アルミン酸塩としては、アルミン酸ナトリウム、アルミン酸カリウム等の任意のものを用いることができる。中和反応は、アルミニウム塩水溶液に水酸化ナトリウム、水酸化カリウム、アンモニア水等のアルカリ性水溶液を添加する方法、アルミン酸塩水溶液に硫酸、塩酸、硝酸等の酸の水溶液を添加する方法、アルミニウム塩水溶液とアルミン酸塩水溶液を混合する方法のいずれを用いても構わないが、製造コストの点から言えばアルミニウム塩水溶液とアルミン酸塩水溶液を混合する方法が好ましい。
【０００８】
中和反応時のｐＨは８．０〜９．５である必要がある。ｐＨが９．５を越えると、比表面積の小さなバイヤライト相が生成するため、最終的に製造した触媒の活性が低下することがある。また、ｐＨが８．０を切ると、得られる擬ベーマイトアルミナの細孔容積が低下する傾向があり、脱硫触媒に適した擬ベーマイトアルミナの製造が難しくなることがある。
【０００９】
中和沈殿時の温度であるが、５０〜７０℃の範囲に入っていることが望ましい。温度が５０℃以下では、粒子が強固に凝集する傾向があり、熟成乾燥工程を経て得られた粉の細孔容積が小さくなることがある。また、７０℃以上では、バイヤライトが析出しやすくなるため、好ましくない。中和沈殿反応の時間であるが、５分〜６０分間、好ましくは５〜３０分間、さらに好ましくは１０〜２５分間の範囲であることが望ましい。この範囲から外れると、得られる擬ベーマイトアルミナ粉末の細孔容積が０．８ｃｃ／ｇ以下となることがあり、触媒用擬ベーマイトアルミナとして使用できなくなることがある。熟成時間に関しては特に制限はないが、生産効率上から判断して、２時間以内が好ましい。熟成時間が長過ぎると、擬ベーマイトアルミナ粉の比表面積が小さくなる傾向がある。
【００１０】
熟成が終了した後、濾過により水酸化アルミニウムを濾別する。得られた水酸化アルミニウムケーキは、中和反応時に副生する塩や、酸、アルカリ等を含んでいる。このため、これらを洗浄除去するが、本発明ではこの洗浄水として硫酸及び／又は硫酸アンモニウムを添加した水を用いることに大きな特徴がある。
【００１１】
本発明における洗浄方法の典型例として、次の２つを挙げることができるが、本発明はこれに限定されるものではない。
（１）水酸化アルミニウムを濾別した後、ケーキを取り出す。そのケーキを洗浄容器に移し、水を加えて分散させた後、硫酸及び／又は硫酸アンモニウムを添加し、ｐＨを８．０±０．５とした後、濾過し乾燥して擬ベーマイトアルミナを得る。
（２）水酸化アルミニウムを濾別し直ちに水酸化アルミニウムケーキを硫酸及び／又は硫酸アンモニウム添加水で洗浄するが、この際、濾液のｐＨが８．０±０．５となるように管理して洗浄する。この場合、必要に応じて水洗工程を加える。その後、乾燥し擬ベーマイトアルミナを得る。
【００１２】
まず、上記（１）の方法であるが、濾別した水酸化アルミニウムケーキを洗浄して、或いは洗浄しないまま水酸化アルミニウムケーキを取り出す。その後、水酸化アルミニウムケーキを別の容器に移し、水を加えて分散させる。これに硫酸及び／又は硫酸アンモニウムを添加してｐＨを８．０±０．５に調節する。ｐＨを調節してから３０分間経過した後に再びｐＨを測定し、ｐＨの変化が０．３以内、好ましくは０．１以内であって、ｐＨが８．０±０．５の範囲内であれば濾過し、乾燥する。
【００１３】
乾燥後の擬ベーマイトアルミナに含まれるアルカリ金属であるが、３０００質量ｐｐｍを越えると触媒活性に影響が出ることがある。このため、３０００質量ｐｐｍ以下、好ましくは１０００質量ｐｐｍ以下、より好ましくは３００質量ｐｐｍ以下にすることが望ましい。もし、アルカリ金属イオン濃度が所定値を越えた場合は、水酸化アルミニウムケーキを洗浄する工程を加えたり、ケーキを別の容器に移してから行う硫酸及び／又は硫酸アンモニウム添加水による洗浄操作を複数回繰り返す等の処理を行う。
【００１４】
しかし、ケーキを別の容器に移してから行う硫酸及び／又は硫酸アンモニウム添加水による洗浄は、水酸化アルミニウムを濾過した後に、そのまま水酸化アルミニウムケーキを洗浄する方法に比較して操作が煩雑である。このため、水酸化アルミニウムを濾過した後に、そのまま水酸化アルミニウムケーキを洗浄する方法を採用するのが好ましい。このようにすることで、水酸化アルミニウムケーキに含まれるアルカリ金属イオン濃度を大幅に減少させることができ、後に続く工程であるケーキを別の容器に移してから行う硫酸及び／又は硫酸アンモニウム添加水による洗浄操作が１回で済むばかりでなく、得られる擬ベーマイトアルミナ中のアルカリ金属イオン濃度も減少させることができる。
【００１５】
水酸化アルミニウムを濾過した後に、そのまま水酸化アルミニウムケーキを洗浄する場合に用いる洗浄液は、イオン交換水、硫酸添加水、硫酸アンモニウム添加水、塩酸添加水、塩化アンモニウム添加水、硝酸添加水、硝酸アンモニウム添加水から選ばれる１種以上を単独で、或いは組み合わせて使用することができる。
【００１６】
ケーキを別の容器に移してから行う硫酸及び／又は硫酸アンモニウム添加水による洗浄では、水酸化アルミニウムの沈殿条件、熟成条件、洗浄の有無、洗浄や濾過時の温度、水酸化アルミニウム量等によりケーキに含まれるアルカリ金属イオン濃度が大きく変化する。このため、使用する硫酸及び／又は硫酸アンモニウム添加水の硫酸分の濃度は一定とはならない。しかし、硫酸分（添加する硫酸及び硫酸アンモニウム）の濃度が低すぎると、最終的に擬ベーマイトアルミナ中に含まれる硫酸分が不足し、水素化脱硫触媒としたときの脱窒素活性が十分でなくなることがある。このため、水酸化アルミニウム分散液に含まれる硫酸分の濃度は、０．００１〜０．２モル／ｌ、好ましくは０．０１〜０．１モル／ｌとなるように、硫酸と硫酸アンモニウムの添加量を調節する。つまり、硫酸の添加によってｐＨが８．０±０．５になった場合でも、体積あたりの硫酸分濃度が０．００１モル／ｌを切るような場合は、硫酸アンモニウムを添加した液を用いる。
【００１７】
次に、前記（２）の方法であるが、水酸化アルミニウムを濾別した後、引き続いて硫酸及び／又は硫酸アンモニウムを添加した水で濾過洗浄する。そして、イオン交換水で濾過洗浄を３０分間行なった時の濾液のｐＨが８．０±０．５となった時を洗浄の終了とする。硫酸及び／又は硫酸アンモニウム添加水の濃度は、濾液のｐＨが８．０±０．５となるように調製する必要がある。
【００１８】
しかし、洗浄に要する時間、硫酸及び／又は硫酸アンモニウム添加水の液量、硫酸及び／又は硫酸アンモニウム添加水中の硫酸濃度、水酸化アルミニウムの沈殿条件、予備水洗等の水洗条件、温度、水酸化アルミニウム量等により大きく変化する。従って、予め予備試験を行い、硫酸及び／又は硫酸アンモニウム添加水による洗浄条件を決めるのが望ましい。硫酸及び／又は硫酸アンモニウム添加水中の硫酸分濃度は、初期、中期、最終の３段階程度に濃度を変えるのが望ましい。通常、初期洗浄用が０．０００１〜０．０２モル／ｌ、中期洗浄用が０．０００１〜０．０１モル／ｌ、最終洗浄用が０．０００１〜０．００５モル／ｌ程度である。
【００１９】
この場合、必要に応じて予備水洗等の水洗工程を加えることができる。特に水酸化アルミニウムを濾別した直後に水洗工程を加えると、アルカリ金属イオン濃度を大幅に低下させることができ、濾液のｐＨコントロールが容易になる。また、予備水洗を省略した場合は、硫酸の添加量が多くなり、硫酸及び／又は硫酸アンモニウム含有洗浄水と接触している部位近傍の水酸化アルミニウムの再溶解が起こりやすくなり、水酸化アルミニウム層の閉塞をきたすことがある。この意味でも予備水洗工程を加えることが望ましい。
【００２０】
また、乾燥後の擬ベーマイトアルミナに含まれるアルカリ金属であるが、前記と同様に３０００質量ｐｐｍ以下、好ましくは１０００質量ｐｐｍ以下、より好ましくは３００質量ｐｐｍ以下にすることが望ましい。もし、アルカリ金属イオン濃度が所定値を越えた場合は、水洗処理を加えたり、硫酸及び／又は硫酸アンモニウム添加水による洗浄時間を延長する等の処理条件の変更を行う。
【００２１】
濾過洗浄中の注意点であるが、水酸化アルミニウムケーキは、濾過中に洗浄水がなくなると洗浄水の編流を起こしやすくなるため、洗浄水は常にケーキ面より上になるように補充する必要がある。
【００２２】
以上の洗浄処理後に乾燥するが、スプレードライまたはその他の通常用いられている乾燥装置を使用することができる。乾燥温度は特に制限はないが、温度が高すぎると擬ベーマイトアルミナからガンマーアルミナへ相転移するため好ましくない。このため、２００℃以下の通常用いられている温度で乾燥する。このようにして製造された擬ベーマイト粉は、窒素吸着法による全細孔容積が０．８〜１．８ｃｃ／ｇの範囲にある。
【００２３】
本発明の擬ベーマイトアルミナを用いて触媒担体を製造する場合は、混練、打錠成形等の通常用いられている成型方法を用いることができる。特に、混練法では、細孔容積、細孔分布、平均細孔径等の調整を、混練時に添加する解膠剤の種類や濃度あるいは混練時間によってある程度変更可能である。従って、触媒の用途に応じた担体の製造が可能となる点で好ましい方法である。
【００２４】
成形した乾燥品は焼成処理を行うが、焼成温度は４５０〜６５０℃、好ましくは５００〜６００℃である。４５０℃を切ると、担体の強度が不十分となることがある。また、６５０℃を越えると触媒としたときの活性が十分でなくなることがあり、好ましくない。以上の本発明による製造方法で得られる担体に含まれる硫酸分は、硫黄として０．１〜２．０質量％の範囲になる。硫酸分濃度をもっと高めたい場合は、硫酸及び／又は硫酸アンモニウム添加水の硫酸濃度を高めることで対処可能である。
【００２５】
【実施例】
以下に本発明の具体的実施例及び比較例を示す。
【００２６】
（実施例１）
内容積１５０ｌの中和沈殿槽に７５ｌの水を張り、６０℃に加熱しておき、そこに６０℃に加熱した１モル／ｌのアルミン酸ナトリウム水溶液を約１．８ｌ／ｍで送液し、同時に６０℃に加熱した０．５モル／ｌの硫酸アルミニウム水溶液を添加した。この時のｐＨは９．０±０．１となるように溶液の添加速度は微調節した。２０分間で送液をやめ、そのままの温度で、撹拌しつつ１時間熟成して得られたスラリーを濾過した。水洗後、水酸化アルミニウムケーキを取り出し、内容積１５０ｌの攪拌槽に入れ、水を７５ｌ加えてスラリー状とした。これに硫酸を添加し、ｐＨを８．２に調節した。そのまま攪拌を３０分間続け、ｐＨを測定したところ、８．１であった。これをスプレードライヤーにて入口／出口温度２００℃/１１０℃で乾燥した。得られた擬ベーマイトアルミナ粉中のナトリウムは、１７０質量ｐｐｍ、硫酸分は硫黄として１質量％であった。
【００２７】
得られた粉をニーダー中で硝酸混練し、固形分濃度約５０質量％のドウを得た。これを押し出し成形した後１３０℃で乾燥し、６００℃で１時間焼成してアルミナ担体を得た。
【００２８】
（比較例１）
中和時のｐＨを８．５±０．１とし、水洗後のケーキを攪拌槽に入れ水だけを加えてスラリーを得た以外は実施例１と同様にして擬ベーマイトアルミナ粉末とアルミナ担体を得た。この擬ベーマイトアルミナ粉中のナトリウムは、２９質量ｐｐｍ、硫酸分は硫黄として０．３５質量％であった。
【００２９】
（比較例２）
市販の擬ベーマイトアルミナ（Ｐｕｒａｌ ＳＢ；ナトリウムは１０質量ｐｐｍ以下、硫酸分は硫黄として０．０２質量％）を用い、実施例１と同様にしてアルミナ担体を得た。
【００３０】
（比較例３）
担体の焼成温度を８００℃とした以外は実施例１と同様にして擬ベーマイトアルミナ粉末とアルミナ担体を得た。
【００３１】
触媒調製
実施例及び比較例の担体に、ニッケル、コバルト及びモリブデンを含浸させ、脱硫触媒を調製した。含浸液は、モリブデン酸、ニッケル塩、コバルト塩を含むものを用いた。含浸後、乾燥し、５５０℃で３０分間焼成し触媒とした。触媒中のニッケル、コバルト及びモリブデンの金属換算含有量を表１に示す。
【００３２】
【表１】
脱窒素活性測定試験
上記触媒を用いて、脱硫及び脱窒素試験を行った。活性試験に先立ち、触媒は、ＬＨＳＶ ２．０ｈ-1、水素圧力 ７．８×１０6Ｐａ、水素／Ｏｉｌ比５００ｌ／ｌの条件で、１質量％の二硫化炭素を含有する軽油を用い、３００℃の条件で活性化処理を行った。その後、減圧軽油を用いて試験を行った。ＬＨＳＶは２．０ｈ-1、水素圧力は７．８×１０6Ｐａ、水素／Ｏｉｌ比は４００ｌ／ｌ、反応温度は３６０℃である。その結果、脱硫活性はほぼ同等であったが、脱窒素活性は大きな差が出た。比較例２のＰｕｒａｌ ＳＢを用いて製造した触媒の活性を１００としたときの相対活性を表２に示す。
【００３４】
【表２】
【発明の効果】
本発明の擬ベーマイトアルミナを用いた触媒で、硫黄含有石油原料を脱硫、脱窒素処理すると、従来の触媒に比較して著しく脱窒素活性を高めることが可能となる。これにより、燃料中の窒素含有量を低減することが可能となり、窒素酸化物による環境汚染の影響が低減できるようになる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a hydrodesulfurization catalyst for hydrocarbon oil containing a sulfur compound and a nitrogen compound, and more particularly, pseudoboehmite alumina which is a raw material of the hydrodesulfurization catalyst and hydrogen produced using the pseudoboehmite alumina. The present invention relates to a carrier for hydrodesulfurization catalyst.
[0002]
[Prior art]
Generally, crude oil or residual oil obtained by separating a light fraction from crude oil has a high sulfur content, and therefore, after desulfurization treatment, it is treated in the next step or used as fuel. In order to remove sulfur compounds contained in residual oil, etc., a method is generally used in which a hydrodesulfurization catalyst in which active metal is supported on alumina or silica alumina as a carrier and heat-treated under hydrogen pressure is used. Yes. Further, in this desulfurization treatment step, the nitrogen compound is removed as ammonia simultaneously with the reaction in which sulfur is converted into hydrogen sulfide and removed.
[0003]
Conventionally, such a catalyst is required to have a high desulfurization activity, a long life, and a low cost, and studies have been made focusing on these. In terms of desulfurization performance, those having almost sufficient performance have come to be used. However, in recent years, as the regulation of air pollutants has been strengthened, suppression of nitrogen oxide emissions has been demanded. For this reason, a catalyst having excellent denitrification activity as well as desulfurization performance has been required. In order to increase the denitrification activity, a method of increasing the amount of the catalytically active metal supported can be considered. However, an increase in the amount of catalytically active metal leads to an increase in catalyst price.
[0004]
On the other hand, the alumina raw material used for the desulfurization catalyst is mainly pseudoboehmite alumina obtained by an aluminum salt neutralization method or an alhole method of hydrolyzing aluminum alkoxide. As such pseudo boehmite alumina, it is common to use an alkali metal, which is a poisoning component of the catalyst, or a material from which mineral acids such as sulfuric acid and hydrochloric acid having a large influence on the catalytic activity are removed. However, in Japanese Patent Publication No. 50-12397, in order to obtain a catalyst having excellent stability, an alumina raw material containing a sulfate group is used, and this is calcined at 600 to 1100 ° C. to convert the sulfate group to 0.5 to 5%. It describes that an alumina carrier containing mass% is produced and used as a desulfurization catalyst. However, the activity of a catalyst carrying a sulfate radical and carrying an active ingredient on a carrier obtained by firing at such a high temperature often significantly decreases.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a method for producing pseudo-boehmite alumina that enables production of a desulfurization catalyst having excellent denitrification activity without increasing the amount of catalytically active metal, and a method for producing a carrier for desulfurization catalyst using the pseudo-boehmite alumina. It is to provide.
[0006]
[Means for Solving the Problems]
As a result of the inventor paying attention to the alumina raw material and proceeding diligently studying, when a pseudo-boehmite alumina washed with washing water containing sulfuric acid is molded and calcined at 450 to 650 ° C., a catalyst is produced. It has been found that the denitrification activity can be greatly improved. Moreover, the desulfurization activity was equivalent to that of a catalyst using pseudo boehmite alumina raw material not containing sulfuric acid. Furthermore, as a result of examining the production conditions of the pseudo boehmite alumina, the aluminum hydroxide produced at pH 8.0 to 9.5 was filtered off, and the resulting aluminum hydroxide cake was washed with sulfuric acid and / or ammonium sulfate added water. In addition, the pH of the filtrate is controlled to be 8.0 ± 0.5, washed and dried, and the aluminum hydroxide cake separated by filtration is dispersed in water, and sulfuric acid and / or ammonium sulfate is added while stirring. In addition, it was found that if pseudoboehmite alumina produced by a method of filtering and drying after adjusting the pH of the solution to 8.0 ± 0.5 can be used, a desulfurization catalyst having excellent denitrification activity can be produced. Completed the invention.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
In the method for producing pseudo-boehmite alumina according to the present invention, first, aluminum hydroxide and / or aluminate solution is neutralized at pH 8.0 to 9.5 to make aluminum hydroxide precipitate. Any aluminum salt such as aluminum sulfate, aluminum chloride, or aluminum nitrate can be used as the aluminum salt. Moreover, arbitrary things, such as sodium aluminate and potassium aluminate, can be used as the aluminate. The neutralization reaction is performed by adding an alkaline aqueous solution such as sodium hydroxide, potassium hydroxide, or ammonia water to an aqueous aluminum salt solution, adding an aqueous acid solution such as sulfuric acid, hydrochloric acid, or nitric acid to an aqueous aluminate solution, an aluminum salt Any method of mixing the aqueous solution and the aqueous aluminate solution may be used, but from the viewpoint of production cost, the method of mixing the aqueous aluminum salt solution and the aqueous aluminate solution is preferable.
[0008]
The pH during the neutralization reaction needs to be 8.0 to 9.5. When the pH exceeds 9.5, a bayerite phase having a small specific surface area is formed, and the activity of the finally produced catalyst may be lowered. Moreover, when pH falls below 8.0, there exists a tendency for the pore volume of the obtained pseudo boehmite alumina to fall, and manufacture of the pseudo boehmite alumina suitable for a desulfurization catalyst may become difficult.
[0009]
Although it is the temperature at the time of neutralization precipitation, it is desirable to be in the range of 50 to 70 ° C. When the temperature is 50 ° C. or lower, the particles tend to agglomerate strongly, and the pore volume of the powder obtained through the aging and drying step may be small. Moreover, since bayerite tends to precipitate at 70 degreeC or more, it is unpreferable. The time for the neutralization precipitation reaction is 5 to 60 minutes, preferably 5 to 30 minutes, and more preferably 10 to 25 minutes. If it is out of this range, the pore volume of the pseudoboehmite alumina powder obtained may be 0.8 cc / g or less, and it may not be usable as pseudoboehmite alumina for a catalyst. The aging time is not particularly limited, but is preferably within 2 hours in view of production efficiency. If the aging time is too long, the specific surface area of the pseudo boehmite alumina powder tends to be small.
[0010]
After completion of aging, aluminum hydroxide is filtered off by filtration. The obtained aluminum hydroxide cake contains a salt by-produced during the neutralization reaction, an acid, an alkali, and the like. For this reason, these are removed by washing. In the present invention, water having sulfuric acid and / or ammonium sulfate added is used as the washing water.
[0011]
The following two examples can be given as typical examples of the cleaning method in the present invention, but the present invention is not limited thereto.
(1) After the aluminum hydroxide is filtered off, the cake is taken out. The cake is transferred to a washing container and dispersed by adding water, and then sulfuric acid and / or ammonium sulfate is added to adjust the pH to 8.0 ± 0.5, followed by filtration and drying to obtain pseudoboehmite alumina.
(2) Aluminum hydroxide is filtered off and the aluminum hydroxide cake is immediately washed with sulfuric acid and / or ammonium sulfate-added water. At this time, the filtrate is controlled so that the pH of the filtrate is 8.0 ± 0.5. To do. In this case, a water washing process is added as needed. Thereafter, it is dried to obtain pseudo boehmite alumina.
[0012]
First, in the method (1), the aluminum hydroxide cake separated by filtration is washed or taken out without washing. Thereafter, the aluminum hydroxide cake is transferred to another container and dispersed by adding water. To this is added sulfuric acid and / or ammonium sulfate to adjust the pH to 8.0 ± 0.5. After 30 minutes from the adjustment of the pH, the pH is measured again, and the change in pH is within 0.3, preferably within 0.1, and the pH is within the range of 8.0 ± 0.5. Filter and dry.
[0013]
Although it is an alkali metal contained in the pseudo boehmite alumina after drying, if it exceeds 3000 mass ppm, the catalyst activity may be affected. For this reason, it is desirable to set it as 3000 mass ppm or less, Preferably it is 1000 mass ppm or less, More preferably, it is 300 mass ppm or less. If the alkali metal ion concentration exceeds the predetermined value, a step of washing the aluminum hydroxide cake is added, or the washing operation with sulfuric acid and / or ammonium sulfate added water is performed several times after the cake is transferred to another container. Repeat the process.
[0014]
However, washing with sulfuric acid and / or ammonium sulfate-added water after the cake is transferred to another container is more complicated than the method of washing the aluminum hydroxide cake as it is after filtering the aluminum hydroxide. For this reason, it is preferable to employ a method of washing the aluminum hydroxide cake as it is after filtering the aluminum hydroxide. By doing in this way, the concentration of alkali metal ions contained in the aluminum hydroxide cake can be greatly reduced, and the sulfuric acid and / or ammonium sulfate added water is used after the cake, which is a subsequent process, is transferred to another container. Not only can the washing operation be performed once, but also the alkali metal ion concentration in the pseudoboehmite alumina obtained can be reduced.
[0015]
The washing liquid used for washing the aluminum hydroxide cake as it is after filtering the aluminum hydroxide is ion exchange water, sulfuric acid added water, ammonium sulfate added water, hydrochloric acid added water, ammonium chloride added water, nitric acid added water, ammonium nitrate added water. One or more selected from the above can be used alone or in combination.
[0016]
In washing with sulfuric acid and / or ammonium sulfate-added water after the cake is transferred to another container, it is added to the cake according to the precipitation conditions of aluminum hydroxide, aging conditions, presence or absence of washing, temperature during washing and filtration, the amount of aluminum hydroxide, etc. The contained alkali metal ion concentration varies greatly. For this reason, the sulfuric acid concentration of sulfuric acid and / or ammonium sulfate-added water to be used is not constant. However, if the concentration of sulfuric acid (added sulfuric acid and ammonium sulfate) is too low, the amount of sulfuric acid contained in the pseudo boehmite alumina will eventually be insufficient, and denitrification activity will not be sufficient when it is used as a hydrodesulfurization catalyst. There is. Therefore, the sulfuric acid and ammonium sulfate are added so that the concentration of sulfuric acid contained in the aluminum hydroxide dispersion is 0.001 to 0.2 mol / l, preferably 0.01 to 0.1 mol / l. Adjust the amount. That is, even when the pH becomes 8.0 ± 0.5 due to the addition of sulfuric acid, when the sulfuric acid concentration per volume falls below 0.001 mol / l, a solution to which ammonium sulfate is added is used.
[0017]
Next, in the method (2), after the aluminum hydroxide is filtered off, it is subsequently filtered and washed with water to which sulfuric acid and / or ammonium sulfate has been added. Then, when the pH of the filtrate when it is filtered and washed with ion-exchanged water for 30 minutes becomes 8.0 ± 0.5, the washing is finished. The concentration of sulfuric acid and / or ammonium sulfate-added water needs to be adjusted so that the pH of the filtrate is 8.0 ± 0.5.
[0018]
However, the time required for washing, the amount of sulfuric acid and / or ammonium sulfate added water, sulfuric acid concentration in sulfuric acid and / or ammonium sulfate added water, aluminum hydroxide precipitation conditions, water washing conditions such as preliminary water washing, temperature, aluminum hydroxide amount, etc. Will vary greatly. Therefore, it is desirable to conduct a preliminary test in advance and determine the washing conditions with sulfuric acid and / or ammonium sulfate added water. The sulfuric acid concentration in the sulfuric acid and / or ammonium sulfate-added water is preferably changed to the initial, middle and final three stages. Usually, the initial cleaning is 0.0001 to 0.02 mol / l, the intermediate cleaning is 0.0001 to 0.01 mol / l, and the final cleaning is about 0.0001 to 0.005 mol / l.
[0019]
In this case, a water washing step such as preliminary water washing can be added as necessary. In particular, when a water washing step is added immediately after the aluminum hydroxide is filtered off, the alkali metal ion concentration can be greatly reduced, and the pH of the filtrate can be easily controlled. Further, when the preliminary water washing is omitted, the amount of sulfuric acid is increased, and the aluminum hydroxide near the portion in contact with the sulfuric acid and / or ammonium sulfate-containing washing water is likely to be redissolved. May cause blockage. In this sense, it is desirable to add a preliminary water washing step.
[0020]
Moreover, although it is an alkali metal contained in the pseudo boehmite alumina after drying, it is desirable to make it 3000 ppm or less, preferably 1000 ppm or less, more preferably 300 ppm or less, as described above. If the alkali metal ion concentration exceeds a predetermined value, the treatment conditions are changed, such as adding water washing treatment or extending the washing time with sulfuric acid and / or ammonium sulfate added water.
[0021]
As a precaution during filtration washing, aluminum hydroxide cake tends to cause knitting of washing water when washing water runs out during filtration, so it is necessary to always replenish the washing water above the cake surface. There is.
[0022]
Although it dries after the above washing treatment, spray drying or other commonly used drying apparatuses can be used. The drying temperature is not particularly limited, but if the temperature is too high, the phase transition from pseudoboehmite alumina to gamma alumina is not preferable. For this reason, it dries at the temperature normally used below 200 degreeC. The pseudo boehmite powder thus produced has a total pore volume in the range of 0.8 to 1.8 cc / g by the nitrogen adsorption method.
[0023]
When the catalyst carrier is produced using the pseudo boehmite alumina of the present invention, a conventionally used molding method such as kneading or tableting can be used. In particular, in the kneading method, the adjustment of the pore volume, the pore distribution, the average pore diameter and the like can be changed to some extent depending on the kind and concentration of the peptizer added at the time of kneading or the kneading time. Therefore, it is a preferable method in that the support can be produced according to the application of the catalyst.
[0024]
The molded dry product is subjected to a firing treatment, and the firing temperature is 450 to 650 ° C, preferably 500 to 600 ° C. When the temperature is lower than 450 ° C., the strength of the carrier may be insufficient. On the other hand, if it exceeds 650 ° C., the activity as a catalyst may be insufficient, which is not preferable. The sulfuric acid content contained in the carrier obtained by the production method according to the present invention is in the range of 0.1 to 2.0% by mass as sulfur. If it is desired to further increase the sulfuric acid concentration, it can be dealt with by increasing the sulfuric acid concentration of sulfuric acid and / or ammonium sulfate added water.
[0025]
【Example】
Specific examples and comparative examples of the present invention are shown below.
[0026]
Example 1
75 liters of water is placed in a neutralization precipitation tank having an internal volume of 150 liters, heated to 60 ° C., and a 1 mol / l sodium aluminate aqueous solution heated to 60 ° C. is fed at a rate of about 1.8 liters / m. Simultaneously, 0.5 mol / l aluminum sulfate aqueous solution heated to 60 ° C. was added. The addition rate of the solution was finely adjusted so that the pH at this time was 9.0 ± 0.1. The liquid feeding was stopped in 20 minutes, and the slurry obtained by aging for 1 hour with stirring at the same temperature was filtered. After washing with water, the aluminum hydroxide cake was taken out and placed in a stirring tank having an internal volume of 150 l, and 75 l of water was added to form a slurry. Sulfuric acid was added thereto to adjust the pH to 8.2. Stirring was continued for 30 minutes, and the pH was measured and found to be 8.1. This was dried with a spray dryer at an inlet / outlet temperature of 200 ° C./110° C. Sodium in the obtained pseudo boehmite alumina powder was 170 mass ppm, and the sulfuric acid content was 1 mass% as sulfur.
[0027]
The obtained powder was kneaded with nitric acid in a kneader to obtain a dough having a solid concentration of about 50% by mass. This was extruded, dried at 130 ° C., and calcined at 600 ° C. for 1 hour to obtain an alumina carrier.
[0028]
(Comparative Example 1)
The pseudo-boehmite alumina powder and the alumina carrier were prepared in the same manner as in Example 1 except that the pH during neutralization was 8.5 ± 0.1, and the cake after washing was placed in a stirring vessel and only water was added to obtain a slurry. Obtained. The sodium in the pseudo boehmite alumina powder was 29 mass ppm, and the sulfuric acid content was 0.35 mass% as sulfur.
[0029]
(Comparative Example 2)
An alumina carrier was obtained in the same manner as in Example 1 using commercially available pseudo boehmite alumina (Pural SB; sodium was 10 mass ppm or less, and the sulfuric acid content was 0.02 mass% as sulfur).
[0030]
(Comparative Example 3)
Pseudoboehmite alumina powder and an alumina carrier were obtained in the same manner as in Example 1 except that the firing temperature of the carrier was 800 ° C.
[0031]
Catalyst preparation The desulfurization catalyst was prepared by impregnating the carriers of Examples and Comparative Examples with nickel, cobalt and molybdenum. The impregnating solution used was one containing molybdic acid, nickel salt, or cobalt salt. After impregnation, it was dried and calcined at 550 ° C. for 30 minutes to obtain a catalyst. Table 1 shows the metal equivalent contents of nickel, cobalt and molybdenum in the catalyst.
[0032]
[Table 1]
Denitrification activity measurement test Desulfurization and denitrification tests were performed using the above catalyst. Prior to the activity test, the catalyst was a gas oil containing 1% by mass of carbon disulfide under the conditions of LHSV 2.0 h −1 , hydrogen pressure 7.8 × 10 6 Pa, hydrogen / oil ratio 500 l / l, The activation treatment was performed at 300 ° C. Thereafter, a test was performed using vacuum gas oil. LHSV is 2.0 h −1 , hydrogen pressure is 7.8 × 10 6 Pa, hydrogen / oil ratio is 400 l / l, and reaction temperature is 360 ° C. As a result, the desulfurization activity was almost the same, but the denitrification activity was greatly different. Table 2 shows the relative activity when the activity of the catalyst produced using Pural SB of Comparative Example 2 is defined as 100.
[0034]
[Table 2]
【The invention's effect】
When the sulfur-containing petroleum raw material is desulfurized and denitrogenated with the catalyst using the pseudo boehmite alumina of the present invention, the denitrification activity can be remarkably enhanced as compared with the conventional catalyst. As a result, the nitrogen content in the fuel can be reduced, and the influence of environmental pollution by nitrogen oxides can be reduced.
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| CN105983447A (en) * | 2015-03-03 | 2016-10-05 | 中国石油天然气股份有限公司 | Catalyst carrier grain size control method |
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