JP2004196574A - Spinel-containing ferrite spherical porous silica particle and its manufacturing method - Google Patents
Spinel-containing ferrite spherical porous silica particle and its manufacturing method Download PDFInfo
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- JP2004196574A JP2004196574A JP2002365961A JP2002365961A JP2004196574A JP 2004196574 A JP2004196574 A JP 2004196574A JP 2002365961 A JP2002365961 A JP 2002365961A JP 2002365961 A JP2002365961 A JP 2002365961A JP 2004196574 A JP2004196574 A JP 2004196574A
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Images
Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、含スピネル型フェライト球状多孔質シリカ粒子、その製造方法及び用途に関するものである。より詳細には、ケイ酸エステルをシリカ源として使用し、そこから生成するシリカ溶存種と、水混和性有機溶媒に予めスピネル型フェライト組成に調整し溶解した金属塩との混合溶液相、あるいはスピネル型フェライト微粒子との懸濁液相において、アルキルアミンの秩序形成能に基づいてミクロ構造の規則性と、マクロ形態の規則性を同時に得ることを利用した、スピネル型フェライト微粒子を含む球状多孔質シリカ粒子及びその製造方法に関するものである。
【０００２】
【従来の技術】
磁性を有する酸化物粒子としては、マグネタイト（Ｆｅ３Ｏ４）やマグヘマイト（γ-Ｆｅ２Ｏ３）等の酸化鉄が代表として挙げられるが、スピネル型フェライト（ＭIIＯ・ＭIII ２Ｏ３；ＭIIはＦｅ，Ｎｉ、Ｃｏ、Ｃｕ、Ｚｎ、Ｍｎ、Ｍｇ等の２価金属元素あるいは１価金属元素であるＬｉ、ＭIIIは３価のＦｅ金属元素を表す）、ガーネット型フェライト、Ｂａフェライト等のフェライト類が良く知られている。これらの中で磁性体と言われるものには、外部磁場なしで自発磁化を有するものや、磁場の中に置かれると磁気を帯びるものがあり、このような磁気特性を利用して、吸着・分離剤、磁石、磁気記録材料、記憶・演算素子、電子写真用磁性キャリヤ、酵素免疫法診断試薬用の磁性担体への応用、さらにはがん細胞が熱に弱い特徴を利用した温熱療法（ハイパーサーミア）等種々の応用研究が行われている。
【０００３】
一方、従来より磁性体を含むシリカ多孔性粒子についても良く知られ、種々の磁性材料として、また吸着剤や担体に磁気的吸着性を付与する目的にも使用されている。
【０００４】
このようなシリカ多孔性粒子としては、▲１▼多孔質シリカ粒子を水中に分散させ酢酸アンモニウムを添加後、この懸濁液に酸化剤として亜硝酸水溶液を加え、さらにアンモニア水でｐＨ調整しながら塩化鉄水溶液を滴下することにより得られる平均粒径０．２〜５４μｍの磁性シリカ多孔質粒子（特許文献１）、▲２▼ケイ酸アルカリ水溶液とフェライト微粉末、カルボキシメチルセルロースを含む懸濁液に硫酸を添加して、ケイ酸アルカリの中和過程を経て得られる粒子径０．５〜５０μｍの磁性シリカ多孔質粒子（特許文献２）、▲３▼窒素雰囲気下でテトラエトキシオルトシリケート（ＴＥＯＳ）と塩酸との反応で作製したＳｉアルコキシドポリマーを１−ペンタノールに溶解後、市販の磁性流体を添加し、得られた懸濁液をポリビニルアルコールに投入後、さらにアンモニア水を加えて得られる粒子径１〜２０μｍの球状磁性シリカ多孔質粒子（特許文献３）、▲４▼テトラメチルシリケート（ＴＭＳ）に、塩酸とエタノールを添加後、イソプロパノールに溶解したトリｎ−ブトキシ鉄を加え作製した混合溶液を、イソプロパノールとアンモニア水との混合反応液に滴下して得られる粒子径０．３〜０．４μｍの球状磁性シリカ多孔質粒子（特許文献４）などが知られている。
【０００５】
しかし、これら球状磁性シリカ多孔質粒子は、シリカマトリックス中の細孔配列に規則性はなく、細孔径分布も一様でない等機能向上の観点からも解決すべき検討課題が残され、マグネタイトや、フェライトの超微粒子を水や有機溶媒に懸濁させて得られる磁性流体を利用したり、シリカ多孔体を磁性体前駆体となる金属元素を含む溶液で処理するなど、磁性体とシリカマトリックスとを複合化させるためには複雑な工程を経ることから長時間を要するなどの問題点があった。
【０００６】
【特許文献１】特開平７−２６７６２７号公報
【特許文献２】特開平１０−８１５０７号公報
【特許文献３】特開平１１−３１３６７０号公報
【特許文献４】特開平９−３２８３１６号公報
【０００７】
【発明が解決しようとする課題】
本発明の目的は、規則配列した微細孔と、粒子間隙に起因する細孔とを有するシリカマトリックス中に、磁性体微粒子が高分散に存在する新規な含スピネル型フェライト球状多孔質シリカ粒子およびこのものを有利に合成できる方法を提供することにある。
【０００８】
【課題を解決するための手段】
本発明者等は、上記課題の解決方法について鋭意検討した結果、ミクロ構造の規則性と、マクロ形態の規則性を同時に得られる、アルキルアミンの秩序形成能を利用すると、上記課題が解決できることを見いだし本発明を完成するに至った。
本発明によれば、下記一般式（１）
ＳｉＯ２・ｎ（ＭIIＯ・ＭIII ２Ｏ３） （１）
（式中、ＭIIは１価あるいは２価金属元素、ＭIIIは３価金属元素を表し、ｎは０．００１乃至０．１５の数である。）
で表される化学的組成を有する含スピネル型フェライト球状多孔質シリカ粒子であって、回折角０．５乃至５度（ＣｕＫα）に細孔の規則配列構造を示すＸ線回折ピークを有し、細孔径１．０乃至５．０ｎｍに０．２５ｍｌ／ｇ以上の微細孔に基づく細孔容積を持つと同時に細孔容積の極大値を有し、好ましくはＢＥＴ比表面積７００ｍ２／ｇの含スピネル型フェライト球状多孔質シリカ粒子が提供される。
【０００９】
また、本発明の含スピネル型フェライト球状多孔質シリカ粒子においては、
１．走査型顕微鏡観察による短軸（Ｄｓ）と長軸（ＤＬ）との長さの比（Ｄｓ／ＤＬ）で表される真球度０．９以上の粒子が９０重量％以上で、且つ粒径が５〜２００μｍの単分散球状粒子乃至球状粒子の凝集体からなることを特徴とする含スピネル型フェライト球状多孔質シリカ粒子からなること、
２．シリカマトリックス中に含まれるスピネル型フェライトの１次粒子の長径が１００ｎｍ以下であり、電子顕微鏡観察において単分散している結晶性粒子であること、
が好ましい。
【００１０】
また、本発明によれば、水混和性有機溶媒、アルキルアミン及び水混和性有機溶媒に可溶な１、２及び３価の金属を含む化合物とケイ酸エステルを含む混合液に、攪拌下に水或いは酸性水溶液を添加し、生成するアルキルアミン複合分解生成物粒子を球形に成長させ、球形粒子中のアルキルアミン等の有機成分及び水分を除去することを特徴とする含スピネル型フェライト球状多孔質シリカ粒子の製造方法が提供される。
さらに、本発明によれば、水混和性有機溶媒に分散したスピネル型フェライト微粒子に、アルキルアミン及びケイ酸エステルを混合した懸濁液に、攪拌下に水或いは酸性水溶液を添加し、生成するアルキルアミン複合分解生成物粒子を球形に成長させ、球形粒子中のアルキルアミン等の有機成分及び水分などの無機成分を除去することを特徴とする含スピネル型フェライト球状多孔質シリカ粒子の製造方法が提供される。
【００１１】
また、本発明の製造方法においては、
１．ケイ酸エステル１モル当たり１、２価及び３価金属元素の全割合が０．００５乃至０．１５のモル比で用いること、
２．ケイ酸エステル１モル当たりアルキルアミンを０．２５乃至０．４５モルの量で用いること、
３．水混和性有機溶媒をケイ酸エステル１モル当たり０．８乃至３．５モルの量で用いること、
４．水をケイ酸エステル１モル当たり３４乃至４２モルの量で添加すること、
５．酸をケイ酸エステル１モル当たり０．０８モル以下の量で用いること、
６．水混和性有機溶媒が１価乃至多価のアルコールであること、
７．ケイ酸エステルが炭素数が１乃至４のアルコールのケイ酸エステルであること、
が好ましい。
【００１２】
本発明によれば、更に、前記含スピネル型フェライト球状多孔質シリカ粒子からなることを特徴とする吸着剤、触媒、触媒担体、特に磁気ヒステリシスを利用した発熱体が提供される。
【００１３】
【発明の実施の形態】
本発明による含スピネル型フェライト球状多孔質シリカ粒子は、前記式（１）に示す化学的組成を有し、回折角０．５乃至５度（ＣｕＫα）に細孔の規則配列構造を示すＸ線回折ピークを有し、細孔径１．０乃至５．０ｎｍに０．２５ｍｌ／ｇ以上の微細孔に基づく細孔容積を持つと同時に細孔容積の極大値を有することを特徴としている。
【００１４】
スピネル型フェライト微粒子を含有するシリカ多孔体（磁性多孔体）は良く知られているが、本発明者らの知る限り、シリカマトリックス内に形成される細孔が規則配列を有すること、細孔径１．０乃至５．０ｎｍに０．２５ｍｌ／ｇ以上の微細孔に基づく細孔容積を持つと同時に細孔容積の極大値を有すると共に包含されるスピネル型フェライト化合物がシリカマトリックス中に高分散している例を見出すことはできない。
【００１５】
本発明による含スピネル型フェライト球状多孔質シリカ粒子は、後記するＸＲＤ粉末回折パターンから明らかなように、シリカマトリックス中には平均細孔径１．５〜５ｎｍの微細孔が規則配列し、９００℃の高温においてもその規則性が完全には失われないものである。
【００１６】
また、本明細書でいう、「細孔径１．０乃至５．０ｎｍに、０．２５ｍｌ／ｇ以上の微細孔に基づく細孔容積を持つと同時に細孔容積の極大値を有する」とは、「平均細孔径に対応するピークが１．０乃至５．０ｎｍの範囲にあり、同時にこの範囲の大きさの細孔容積が０．２５ｍｌ／ｇ以上を有すること」を意味する。したがって、本発明による上記多孔質シリカ粒子は、「規則配列した均一径を有する細孔が存在するシリカマトリックス中に、スピネル型フェライト微粒子が高分散している」という特徴を有するものということができる。
【００１７】
さらに、後記するように、本発明の含スピネル型フェライト球状多孔質シリカ粒子は、窒素吸着等温線の高相対圧部に急激な立ち上がりが認められる。このことは、その生成機構上、微細孔以外に粒子間隙に基づく細孔を有し、種々の物質の吸着・脱着の際の拡散が容易に行えるという特徴を有していることになる。
【００１８】
本発明の含スピネル型フェライト球状多孔質シリカ粒子が微細孔を有しており、この微細孔が吸着サイトあるいは反応サイトを提供することになる。本発明の含スピネル型フェライト球状多孔質シリカ粒子は、細孔径１乃至５ｎｍに０．２５ｍｌ／ｇ以上の細孔容積を有することから、種々の分子、イオン等に対する吸着場や反応場として望ましい。
【００１９】
本発明の含スピネル型フェライト球状多孔質シリカ粒子は、包含されるスピネル型フェライト微粒子の存在に係わりなく、アルキルアミンとこのアルキルアミンを取り囲むシリカマトリックスとの複合体が規則的配列を有し且つ回折角（２θ；ＣｕＫα線）１乃至５°にＸ線回折ピークを有する複合体の脱アルキルアミン物（例えば焼成物）からなることが、微細孔の形成及び保持のために好ましい。
【００２０】
本発明の含スピネル型フェライト球状多孔質シリカ粒子の前駆体となるアルキルアミンとのナノ複合粒子は、回折角（２θ；ＣｕＫα線）１乃至５°にＸ線回折ピークを有するメソ構造体であることが特徴であり、この特徴により、本発明の含スピネル型フェライト球状多孔質シリカ粒子は微細孔を保持しているのである。
すなわち、本発明の含スピネル型フェライト球状多孔質シリカ粒子は、アルキルアミンとシリカ溶存種との協調的秩序形成能により生成するメソ構造体中に、スピネル化合物前駆体が包含されるにもかかわらず、有機化合物を加熱処理等により除去することにより、シリカマトリックス中に規則的に配列した微細孔を有することを特徴としている。
【００２１】
本発明の含スピネル型フェライト球状多孔質シリカ粒子は、前記したように、水混和性有機溶媒、アルキルアミン及び水混和性有機溶媒に可溶な１、２及生成する無機有機複合体を球形に成長させ、球形粒子中のアルキルアミン等を除去する方法、あるいは、水混和性有機溶媒にスピネル型フェライト微粒子を分散させ、アルキルアミン及びケイ酸エステルを混合した懸濁液に、攪拌下に水或いは酸性水溶液を添加し、生成する無機有機複合体を球形に成長させ、球形粒子中のアルキルアミン等を除去する方法等によって合成することができる。
【００２２】
本発明の含スピネル型フェライト球状多孔質シリカ粒子の生成機構は、現時点では必ずしも明らかではないが、以下のように推定される。
Ｓｉ-アルコキシドに、例えばアルコールに溶解したＣｏ(II)とＦｅ(III)を含む金属塩化物にアルキルアミンを添加すると、Ｓｉ-アルコキシドは水素結合によってアミンと規則メソ構造体を形成し、金属成分はアミンによって取り囲まれた溶存種として、前記メソ構造体との混合溶液相を形成する。塩酸水溶液の添加により、Ｓｉは正電荷を帯び（Ｉ＋）、アミン中のＮＨ２基はＮＨ３＋（Ｓ＋）に変化し、塩素イオン（Ｘ−）を媒介としてＳ＋Ｘ−Ｉ＋の規則メソ構造体が生成する。同時に金属成分は水酸化物相を形成して、メソ構造体のゲル化の際に取り込まれ、含スピネル型フェライト球状多孔質シリカ粒子前駆体が生成する。Ｓ＋Ｘ−Ｉ＋が核となって成長する１次粒子はＳ＋Ｘ−Ｉ＋の集合したメソ構造体であり、さらにこの１次粒子間の衝突により粒子成長し、スピネル組成の水酸化物を取り込んで、最終的にミクロンオーダーのマクロ形態を有する球状粒子が生成する。もちろん金属塩化物の代わりにスピネル微粒子を用いても、Ｓ＋Ｘ−Ｉ＋メソ構造体の生成は進行し、あらかじめスピネル型フェライト微粒子を含んだ球状含スピネル型フェライト球状多孔質シリカ粒子前駆体が生成する。
【００２３】
シリケート骨格を取巻く有機成分を加熱等の処理により除去することで得られる最終生成物は、メソ構造体に由来した規則細孔構造を有する多孔性粒子となる。吸着並びに反応サイトは細孔表面であり、共存する磁性体の機能を有効に活用する磁性多孔体とするためには、無機骨格中にある一定の大きさのスピネル型フェライト微粒子を高分散させることが必要である。
【００２４】
上記生成機構に基づいて製造された本含スピネル型フェライト球状多孔質シリカ粒子は、粒子内部に生成する細孔に基づいた多孔性物質であり、さらに種々の吸着・反応物質の細孔内外への拡散が容易な粒子構造であることから、スピネル型フェライト微粒子の機能発現を効果的に発揮する能力を発することができる。
【００２５】
上記した（１）又は（２）の本発明の合成法によれば、用いるアルキルアミン中の炭素数によってシリカマトリックスの細孔径が容易にコントロール可能なことはもとより、含スピネル型フェライト球状多孔質シリカ粒子前駆体を、常温常圧下、約６０分間で製造できる。また、攪拌速度、酸濃度あるいはアルコールの添加割合により粒子径の制御が可能となる。
【００２６】
本発明で使用される水混和性有機溶媒、アルキルアミン及び水混和性有機溶媒に可溶な金属化合物（金属塩並びに金属アルコキシド）或いは更にケイ酸エステルについて更に説明する。
【００２７】
本発明で使用するシリカ原料としてのケイ酸エステルとしては、Ｓi-アルコキシドで、テトラメチルオルトシリケート、テトラエチルオルトシリケート、テトライソプロピルオルトシリケート、テトラ-ｎ-ブチルオルトシリケート等を用いることが可能で好ましくはテトラエチルオルトシリケート（以下ＴＥＯＳと略す）を使用する。
【００２８】
アルコールとしては、メタノール、エタノール、プロパノール、ブタノール等を用いることができ、好ましくはエタノールを使用する。
【００２９】
アルキルアミンとしては、直鎖アルキルアミンが好ましく、カーボン数８〜１８のものが使用され、比較的廉価で常温において溶液状態にあるオクチルアミンとドデシルアミンが好ましい。
【００３０】
金属種としては、スピネル型フェライト（ＭIIＯ・ＭIII ２Ｏ３）を形成する、１価金属元素（Ｌｉ）あるいは２価金属元素（ＭII；Ｆｅ，Ｎｉ、Ｃｏ、Ｃｕ、Ｚｎ、Ｍｎ、Ｍｇ等）と３価金属元素（ＭIII；Ｆｅ）を２種類あるいは２種類以上種々の組み合わせで用いることができる。なお、フェライトの定義から、ＭIIIの金属種としては厳密にはＦｅだけであるが、本発明ではＣｒも含めて、含スピネル型フェライト球状多孔質シリカ粒子とする。
水混和性有機溶媒に可溶な１，２及び３価の金属を含む化合物としては、上記金属の塩化物、硝酸塩、硫酸塩やその水和物等アルコールに可溶な全ての金属塩を使用することができる。
【００３１】
また、酸としては、塩酸、硝酸、硫酸、酢酸等を使用することができる。
【００３２】
本発明の含スピネル型フェライト球状多孔質シリカ粒子を合成するための出発原料の混合モル比は、ＴＥＯＳ：１−アルキルアミン：アルコール：酸：水：金属元素＝１：０．２５〜０．４５：０．８〜３．５：０〜０．０８：３４〜４２：０．００５〜０．１５である。
さらに出発原料の混合方式を詳細に記述すると、ＴＥＯＳとアルコールに溶解した金属塩との混合溶液に、アルキルアミンを加え、さらに攪拌を続けながら水あるいは酸性水溶液を添加し、充分な混合状態を保持しながら、室温で約１時間反応させる。
【００３３】
さらに出発原料の混合モル比を詳細に記述すると、含スピネル型フェライト球状多孔質シリカ粒子の合成には、予めスピネル組成となるように調整した金属塩をアルコールに溶解し攪拌しながら、ＴＥＯＳに添加後、直ぐにアルキルアミンを加え２０秒から１０分間攪拌し、さらに攪拌を続けながら水あるいは酸性水溶液を添加し、充分な混合状態を保持しながら、室温で８０分以内好ましくは３０〜６０分程度反応させる。出発原料の混合モル比は、オクチルアミンの場合、好ましくは、ＴＥＯＳ：オクチルアミン：アルコール：酸：水：金属元素＝１：０．２５〜０．４５：０．８〜１．５：０．０４〜０．０８：３４〜４２：０．００５〜０．１５である。ドデシルアミンの場合、好ましくは、ＴＥＯＳ：ドデシルアミン：アルコール：酸：水：金属元素＝１：０．２５〜０．４５：１．４〜３．５：０〜０．０１：３４〜４２：０．００５〜０．１５である。
【００３４】
また、直接スピネル型フェライト微粒子を用いる場合にも、予めフェライト微粒子をアルコールに分散したものをＴＥＯＳに添加後、直ぐにアルキルアミンを加え２０秒から１０分間攪拌し、さらに攪拌を続けながら水あるいは酸性水溶液を添加し、充分な混合状態を保持しながら、室温で８０分以内好ましくは２０〜６０分程度反応させる。出発原料の混合モル比は金属塩をアルコールに溶解して用いる場合と同一で、オクチルアミンの場合、好ましくは、ＴＥＯＳ：オクチルアミン：アルコール：酸：水：金属元素＝１：０．２５〜０．４５：０．８〜１．５：０．０４〜０．０８：３４〜４２：０．００５〜０．１５である。ドデシルアミンの場合、好ましくは、ＴＥＯＳ：ドデシルアミン：アルコール：酸：水：金属元素＝１：０．２５〜０．４５：１．４〜３．５：０〜０．０１：３４〜４２：０．００５〜０．１５である。
【００３５】
上記いずれの場合も、反応後懸濁液から固体生成物を分離し、室温〜１００℃で充分乾燥させる。
最後に有機成分を除去して含スピネル型フェライト球状多孔質シリカ粒子を作製するために、例えば５００℃以上で３０分間以上、好ましくは５５０℃以上で１時間加熱処理する。
【００３６】
（用途）
本発明の含スピネル型フェライト球状多孔質シリカ粒子は、種々の分子、イオンの吸着・吸蔵剤あるいは形状選択性酸化触媒担体として、工業および環境保全に有用な材料などに適している。特に、スピネル型フェライト微粒子を内包することにより、外部交番磁場環境下では発熱機能を有することになり、反応場の温度制御や、吸着物質を脱着させる際の促進効果を利用することが可能である。
【００３７】
【実施例】
次に、本発明を実施例によって更に具体的に説明するが、本発明はこの実施例によって限定されない。
尚、実施例で行った各試験方法は次の方法によって行った。
【００３８】
（測定法）
（１）走査型電子顕微鏡観察：日本電子製ＪＳＭ５３００を使用し、加速電圧１０ｋＶで観察した。
（２）高分解能透過電子顕微鏡観察：日本電子製ＪＥＭ−２０００ＥＸIIを使用し、加速電圧２００ｋＶで観察した。
（３）比表面積・細孔径分布：日本ベル製ＢＥＬＳＯＲＰ２８を使用し、液体窒素温度で測定した窒素吸着等温線からＢＥＴ比表面積を求め、細孔径分布はＭＰ法、Horvath-Kawazoe法並びにＢＪＨ法により解析した。
（４）粒径：ベックマン・コールター製Coulter MultisizerIIを用い、２００ミクロンメーターのアパーチャー・チューブで測定した。
（５）真球度：走査型電子顕微鏡写真から計算した。
（６）Ｘ線粉末回折：リガク製ロータフレックスＲＵ−３００を使用し、Ｃｕ−Ｋα線源、加速電圧４０ｋＶ、８０ｍＡで測定した。
（７）磁化特性：振動試料型磁力計（ＶＳＭ）（理研電子製振動試料型磁力計、型式ＢＨＶ−３）を使用し、室温において磁気ヒステリシス曲線を測定した。
（８）発熱特性： ５６ｋＨｚの高周波を種々の磁界（３７０，４４０，４８０Ｏｅ）の下で照射し、磁性多孔体の時間−温度特性を測定した。高周波電源は第一高周波(株)製 HI-HEATER ４００５型、５ｋＷで、高周波磁界発生用ソレノイドコイル、高周波電流モニタを備え、蛍光式光ファイバ温度計(アンリツ計器(株)製 FL-2000型)によって温度測定を行った。
【００３９】
（実施例１）
予めスピネル型フェライト組成となるように調整したＦｅＣｌ３・６Ｈ２ＯとＣｏＣｌ３・６Ｈ２Ｏをエタノールに溶解し、６００ｒｐｍで攪拌しながらＴＥＯＳと混合し、オクチルアミンを加え１０分間攪拌した後、塩酸水溶液を加え、さらにそのまま１時間攪拌する。金属元素を除く混合溶液のモル比は、ＴＥＯＳ：オクチルアミン：エタノール：塩酸：水＝１：０．３４：１．１７：０．０７：３８であり、全金属元素のモル比を変化させて、包含される磁性体量を調整した。反応後懸濁液から固体生成物を濾別し、５０℃で充分乾燥させた後、６００℃以上の所定温度で１時間加熱して有機成分を除去して含スピネル型フェライト球状多孔質シリカ粒子を作製した。
表１に、磁性体含量並びに各加熱温度におけるＢＥＴ比表面積、細孔径及び細孔容積を示す。また、磁気ヒステリシス曲線から求めた飽和磁化、保持力を示す。
【００４０】
【表１】
（実施例２）
予めスピネル型フェライト組成となるように調整したＦｅＣｌ３・６Ｈ２Ｏと他の１種類あるいは複数の１価あるいは２価金属をエタノールに溶解し、６００ｒｐｍで攪拌しながらＴＥＯＳと混合し、オクチルアミンを加え１０分間攪拌した後、塩酸水溶液を加え、さらにそのまま１時間攪拌する。金属元素を除く混合溶液のモル比は、ＴＥＯＳ：オクチルアミン：エタノール：塩酸：水＝１：０．３４：１．１７：０．０７：３８であり、金属種、全金属元素のモル比を変化させて、包含される磁性体の種類と含有量を調整した。反応後懸濁液から固体生成物を濾別し、５０℃で充分乾燥させた後、８００℃で１時間加熱して有機成分を除去して含スピネル型フェライト球状多孔質シリカ粒子を作製する。
表２に、含有されるスピネル型フェライトの構成原子、磁性体含量、並びに飽和磁化と保持力を示す。
【００４２】
【表２】
（実施例３）
ＴＥＯＳを６００rpmで攪拌し、エタノールに分散したマグネタイト微粒子を添加して得られる懸濁溶液に、ドデシルアミンを加え１分間攪拌した後、塩酸水溶液を加え、さらにそのまま１時間攪拌する。金属元素を除く混合溶液のモル比は、ＴＥＯＳ：ドデシルアミン：エタノール：塩酸：水＝１：０．３５：２．９３：０．００４：３８であり、予め磁性体として添加するマグネタイトの割合を変化させて、包含される磁性体量を調整した。反応後懸濁液から固体生成物を濾別し、５０℃で充分乾燥させた後、６００℃で１時間加熱して有機成分を除去して含スピネル型フェライト球状多孔質シリカ粒子を作製する。
表３に、磁性体含量並びにＢＥＴ比表面積、細孔径及び細孔容積を示す。また、磁気ヒステリシス曲線から求めた飽和磁化、保持力を示す。
【００４４】
【表３】
つぎに、前記で得た、本発明の含スピネル型フェライト球状多孔質シリカ粒子のＸ線回折ピーク構造解析、ＳＥＭ像、粒度分布曲線、ＴＥＭ像、窒素吸着等温線、細孔径分布、などを図１〜１１によって説明する。
【００４６】
図１は、本発明の含Ｃｏフェライト球状多孔質シリカ粒子の加熱変化を示すＸＲＤ回折パターンである。具体的には、含Ｃｏフェライト球状多孔質シリカ粒子前駆体（ａ）と加熱処理においてＣｏフェライトが結晶化する過程を示すＸ線回折図であり、低角に存在する回折ピークはシリカマトリックス中の細孔配列が規則的であることを示している。なお、図１において、（ａ）加熱前の前駆体、（ｂ）実施例１-４、（ｃ）実施例１-５、（ｄ）実施例１-６並びに（ｅ）実施例１-２。○印はＣｏフェライトの回折ピークである。
【００４７】
図２は、図１のＳＥＭ像であり、Ｃｏフェライト含有量が少ない場合には単分散球形粒子となり、Ｃｏフェライト含有量が多い場合には球状粒子が凝集し易くなることが分かる。なお、図２において、（ａ）実施例１-２、（ｂ）実施例１-５である。
【００４８】
図３は、本発明の含Ｃｏフェライト球状多孔質シリカ粒子の粒度分布曲線であり、その体積基準の粒度分布曲線でＳＥＭの観察結果と良く一致している。Ｃｏフェライト含有量が少ない場合、粒子径の平均は２７．５μｍで、シャープな分布であるが、含有量が多くなると平均径の増大と粒子間の凝集によってブロードな分布となることが分かる。なお、図３において、（ａ）実施例１-２、（ｂ）実施例１-５である。
【００４９】
図４は、本発明の含Ｃｏフェライト球状多孔質シリカ粒子（実施例１-５）中のＣｏフェライト微粒子の分布状態を示すＴＥＭ像であり、８００℃で加熱処理した試料切片のＴＥＭ像から、球形のシリカマトリックス中には１００nm以下のスピネル微粒子が高分散に存在することが分かる。
【００５０】
図５は、図１の６００℃、８００℃及び９００℃加熱処理生成物の窒素吸着等温線である。７００ｍ２/ｇ以上の高いＢＥＴ比表面積はシリカマトリックス中の微細孔に基づくものであり、耐熱性にも優れていることが分かる。また、吸着等温線の高相対圧部の急激な立ち上がりは粒子間隙に起因するものであり、図２に示した数十ミクロンの球形粒子は、小粒子が集合しながら成長することによって形成されることを示唆している。なお、図５において、（Ａ）（○）実施例１-１、（□）実施例１-２、（△）実施例１-３；（Ｂ）（○）実施例１-４、（□）実施例１-５、（△）実施例１-６である。
【００５１】
図６は、本発明の含Ｃｏフェライト球状多孔質シリカ粒子のHorvath-Kawazoe法を適用して求めた細孔径分布曲線であり、高温になるほど細孔径が小さくなりバックグランドとの分離は難しくなるが、細孔径は１〜３ｎｍに分布していることが分かる。なお、図６において、（ａ）実施例１-１、（ｂ）実施例１-２、（ｃ）実施例１-４、（ｄ）実施例１-５、（ｅ）実施例１-６である。
【００５２】
図７は、本発明の含スピネル型フェライト球状多孔質シリカ粒子のうち、磁性微粒子として合成マグネタイトを用い、６００℃加熱処理して得られた含マグネタイト球状多孔質シリカ粒子のＸＲＤ回折パターンで、低角に存在する底面反射はシリカマトリックス中の細孔配列が規則的であることを示している。なお、図７において、（ａ）実施例３-１、（ｂ）実施例３-２；丸印はマグネタイトのピークであり、１０度以上の広角範囲の強度は２０倍して表示した。
【００５３】
図８は、図７の実施例３−１のＳＥＭ像で、１０〜１００ミクロンの単分散含スピネル型フェライト球状多孔質シリカ粒子であることを示している。
【００５４】
図９は、本発明のマグネタイトフェライト球状多孔質シリカ粒子の（Ａ）窒素吸着等温線と（Ｂ）細孔径分布曲線であり、図９ａ、ｂはそれぞれ図５ａの窒素吸着等温線と、ＢＪＨ法を適用して求めた細孔径分布曲線である。ＢＥＴ比表面積はいずれも約１０００ｍ２/ｇで、細孔径分布は鋭く、細孔直径のピーク値は約３ｎｍである。また、図５と同様吸着等温線の高相対圧部には粒子間隙に起因する急激な立ち上がりが認められる。なお、図９において、（ａ）実施例３-１、（ｂ）実施例３-２である。
【００５５】
図１０は、本発明のＣｏフェライトの磁気ヒステリシス曲線と、保持力の加熱温度依存性（図中小枠）にＣｏフェライトの磁気ヒステリシス曲線を示す。図中には加熱温度による保持力の変化を示す。飽和磁化はフェライト含量が多いほど大きいが、保持力は逆に小さくなりさらに温度によって減少することから、加熱温度が高いほどフェライトの結晶化が促進されると同時に粒子成長することを示している。図１０において、○実施例１-２、□実施例１-５の８００℃加熱処理生成物である。
【００５６】
図１１は、本発明の含スピネル型フェライト球状多孔質シリカ粒子の昇温特性を示し、具体的には５６ｋＨｚの交流磁界下４４０Ｏｅの入力で測定した際の昇温特性を示したものである。いずれも１０分程度で飽和温度に達し、スピネル組成とその含量あるいは微粒子径を調整することによって、ある特定の磁性多孔体特有のキュリー温度を超えることなく急速加熱が可能であることから、本発明の磁性多孔体は交流磁界下でのキュリー温度手前の一定値に迅速に加熱できる加熱法の発熱体として有用であることがわかる。
【００５７】
（実施例４）
表４に本含スピネル型フェライト球状多孔質シリカ粒子の発熱効果を示す。試料約０．５gを５６ｋＨｚの交流磁界下において、種々の磁界を印加して温度-時間曲線を測定した。定まったスピネル構成成分の磁性多孔体では、電力量を大きくすると、到達温度も高くなるが、スピネル型フェライト含有量、組成比並びに加熱温度によって顕著な差異が認められる。いずれの場合も、１０分程度で一定温度に到達しており、交流磁界下で磁性多孔体を発熱体とする、磁気加熱現象を用いた加熱法は、磁性体固有のキュリー温度以上には暴走しない、迅速な加熱法として優れていることが分かる。
【００５８】
【表４】
【発明の効果】
本発明の含スピネル型フェライト球状多孔質シリカ粒子は、シリカマトリックス中に数十ナノメータサイズのスピネル型フェライト微粒子が高分散に存在し、シリカマトリックス中には規則的配列した微細孔に起因する高比表面積・高耐熱性を有するものである。
そして、この多孔質シリカ粒子は、均一で規則配列し、大きな細孔容積を有することから、種々の吸着剤、触媒担体、さらには触媒として、工業および環境保全の両面で有用な反応プロセスに用いることが可能である。特に、本発明の含スピネル型フェライト球状多孔質シリカ粒子は交流磁場環境下における発熱体として、新規化学プロセス開発の基幹物質として価値が高い。
本発明の含スピネル型フェライト球状多孔質シリカ粒子は、ＴＥＯＳとアルコールに溶解したスピネル組成の金属化合物との均質溶液を作製するか、あるいはＴＥＯＳとスピネル型フェライト微粒子を直接混合後、細孔構造の制御剤としてアルキルアミンを用い、次いで水あるいは酸性水溶液を一気に添加し、アルキル鎖のカーボン数を変化させることにより、常温、常圧下で含スピネル型フェライト球状多孔質シリカ粒子の前駆体となる界面活性剤を含んだ有機無機ナノ複合体（メソ構造体）を短時間で作製することができ、ついで有機物を取除くことにより、直径数ミクロン〜数百ミクロンにわたるミクロンオーダーのマクロ形態を有する含スピネル型フェライト球状多孔質シリカ粒子を効率よく合成することができる。
【図面の簡単な説明】
【図１】本発明の含Ｃｏフェライト球状多孔質シリカ粒子の加熱変化を示すＸＲＤ回折パターン：（ａ）加熱前の前駆体、（ｂ）実施例１-４、（ｃ）実施例１-５、（ｄ）実施例１-６並びに（ｅ）実施例１-２。○印はＣｏフェライトの回折ピークである。
【図２】本発明の含Ｃｏフェライト球状多孔質シリカ粒子のＳＥＭ像：（ａ）実施例１-２、（ｂ）実施例１-５。
【図３】本発明の含Ｃｏフェライト球状多孔質シリカ粒子の粒度分布曲線：（ａ）実施例１-２、（ｂ）実施例１-５。
【図４】本発明の含Ｃｏフェライト球状多孔質シリカ粒子（実施例１-５）中のＣｏフェライト微粒子の分布状態を示すＴＥＭ像
【図５】本発明の含Ｃｏフェライト球状多孔質シリカ粒子の窒素吸着等温線：（Ａ）（○）実施例１-１、（□）実施例１-２、（△）実施例１-３；（Ｂ）（○）実施例１-４、（□）実施例１-５、（△）実施例１-６。
【図６】本発明の含Ｃｏフェライト球状多孔質シリカ粒子の細孔径分布：（ａ）実施例１-１、（ｂ）実施例１-２、（ｃ）実施例１-４、（ｄ）実施例１-５、（ｅ）実施例１-６。
【図７】本発明のマグネタイトフェライト球状多孔質シリカ粒子のＸＲＤ回折パターン：（ａ）実施例３-１、（ｂ）実施例３-２；丸印はマグネタイトのピークであり、１０度以上の広角範囲の強度は２０倍して表示した。
【図８】本発明のマグネタイトフェライト球状多孔質シリカ粒子（実施例３-１）のＳＥＭ像。
【図９】本発明のマグネタイトフェライト球状多孔質シリカ粒子の（Ａ）窒素吸着等温線と（Ｂ）細孔径分布曲線：（ａ）実施例３-１、（ｂ）実施例３-２。
【図１０】本発明のＣｏフェライトの磁気ヒステリシス曲線と、保持力の加熱温度依存性（図中小枠）：○実施例１-２、□実施例１-５の８００℃加熱処理生成物である。
【図１１】本発明の磁性多孔体の昇温特性：（ａ）実施例１-１、（ｂ）実施例１-２、（ｃ）実施例１-４、（ｄ）実施例１-５、（ｅ）実施例２-２、（ｆ）実施例２-３。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to spinel-containing ferrite spherical porous silica particles, a method for producing the particles, and uses thereof. More specifically, a mixed solution phase of a silica-dissolved species generated from the silicate ester as a silica source and a metal salt previously adjusted to a spinel-type ferrite composition and dissolved in a water-miscible organic solvent, or spinel Porous silica containing spinel-type ferrite fine particles, utilizing the simultaneous obtainment of microstructure regularity and macromorphic regularity based on the ability to form an alkylamine order in the suspension phase with fine ferrite fine particles The present invention relates to particles and a method for producing the particles.
[0002]
[Prior art]
As oxide particles having magnetism, magnetite (Fe3O4) And maghemite (γ-Fe2O3) Are typical examples, and spinel-type ferrite (MIIO ・ MIII 2O3; MIIAre the divalent metal elements such as Fe, Ni, Co, Cu, Zn, Mn, and Mg or the monovalent metal elements Li and MIIIRepresents a trivalent Fe metal element), and ferrites such as garnet-type ferrite and Ba ferrite are well known. Among these, those that are called magnetic materials include those that have spontaneous magnetization without an external magnetic field and those that become magnetized when placed in a magnetic field. Separating agents, magnets, magnetic recording materials, memory / arithmetic devices, magnetic carriers for electrophotography, application to magnetic carriers for diagnostic reagents for enzyme immunoassays, and hyperthermia (hyperthermia) utilizing the characteristics of cancer cells that are sensitive to heat Various applied researches have been conducted.
[0003]
On the other hand, porous silica particles containing a magnetic substance have been well known, and have been used as various magnetic materials and for the purpose of imparting magnetic adsorbability to adsorbents and carriers.
[0004]
As such silica porous particles, (1) after dispersing the porous silica particles in water, adding ammonium acetate, adding an aqueous nitrous acid solution as an oxidizing agent to the suspension, and further adjusting the pH with aqueous ammonia. Magnetic silica porous particles having an average particle size of 0.2 to 54 μm obtained by dropping an aqueous solution of iron chloride (Patent Document 1), (2) into a suspension containing an aqueous solution of an alkali silicate, ferrite fine powder, and carboxymethyl cellulose Magnetic silica porous particles having a particle size of 0.5 to 50 μm obtained by adding sulfuric acid and neutralizing alkali silicate (Patent Document 2), (3) Tetraethoxyorthosilicate (TEOS) under a nitrogen atmosphere Is dissolved in 1-pentanol, a commercially available magnetic fluid is added, and the resulting suspension is treated with polyvinyl alcohol. After adding to the alcohol, further adding ammonia water to obtain spherical magnetic silica porous particles having a particle diameter of 1 to 20 μm (Patent Document 3), (4) tetramethyl silicate (TMS), adding hydrochloric acid and ethanol, Spherical magnetic silica porous particles having a particle diameter of 0.3 to 0.4 μm obtained by dropping a mixed solution prepared by adding tri-n-butoxyiron dissolved in isopropanol to a mixed reaction solution of isopropanol and ammonia water (Patent Reference 4) is known.
[0005]
However, these spherical magnetic silica porous particles, there is no regularity in the arrangement of pores in the silica matrix, the study problem to be solved from the viewpoint of functional improvement such as uneven pore size distribution, magnetite, Using a magnetic fluid obtained by suspending ultra-fine particles of ferrite in water or an organic solvent, or treating a magnetic material and a silica matrix by, for example, treating a porous silica material with a solution containing a metal element serving as a magnetic material precursor. In order to form a composite, there is a problem that a long time is required because of a complicated process.
[0006]
[Patent Document 1] JP-A-7-267627
[Patent Document 2] Japanese Patent Application Laid-Open No. 10-81507
[Patent Document 3] JP-A-11-313670
[Patent Document 4] JP-A-9-328316
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide a novel spinel-containing ferrite spherical porous silica particle in which magnetic fine particles are highly dispersed in a silica matrix having regularly arranged fine pores and pores caused by particle gaps. It is an object of the present invention to provide a method by which the compounds can be advantageously synthesized.
[0008]
[Means for Solving the Problems]
The present inventors have conducted intensive studies on a method for solving the above-mentioned problem, and as a result, it has been found that the above-mentioned problem can be solved by using the order-forming ability of an alkylamine, which can simultaneously obtain microstructure regularity and macromorphic regularity. The inventors have found and completed the present invention.
According to the present invention, the following general formula (1)
SiO2・ N (MIIO ・ MIII 2O3(1)
(In the formula, MII represents a monovalent or divalent metal element, MIII represents a trivalent metal element, and n is a number from 0.001 to 0.15.)
A spinel-containing ferrite spherical porous silica particle having a chemical composition represented by the following formula, having an X-ray diffraction peak showing a regular array structure of pores at a diffraction angle of 0.5 to 5 degrees (CuKα), It has a pore volume based on micropores of 0.25 ml / g or more in a pore diameter of 1.0 to 5.0 nm, has a maximum value of the pore volume at the same time, and preferably has a BET specific surface area of 700 m2/ G of spinel-containing ferrite spherical porous silica particles.
[0009]
In the spinel-containing ferrite spherical porous silica particles of the present invention,
1. 90% by weight or more of particles having a sphericity of 0.9 or more represented by a ratio (Ds / DL) of the length of the short axis (Ds) to the long axis (DL) by scanning microscopy, and the particle diameter Is composed of spinel-containing ferrite spherical porous silica particles characterized by comprising an aggregate of monodisperse spherical particles or spherical particles of 5 to 200 μm,
2. Primary particles of the spinel-type ferrite contained in the silica matrix have a major axis of 100 nm or less, and are monodisperse crystalline particles observed by an electron microscope,
Is preferred.
[0010]
Further, according to the present invention, a mixture containing a water-miscible organic solvent, a compound containing a mono-, di- and trivalent metal soluble in an alkylamine and a water-miscible organic solvent, and a silicate ester is added under stirring. Spinel-containing ferrite spherical porous material characterized by adding water or an acidic aqueous solution to grow the generated alkylamine complex decomposition product particles into a spherical shape, and removing organic components such as alkylamine and water in the spherical particles. A method for producing silica particles is provided.
Furthermore, according to the present invention, water or an acidic aqueous solution is added with stirring to a suspension obtained by mixing an alkylamine and a silicate ester with spinel-type ferrite fine particles dispersed in a water-miscible organic solvent, and the resulting alkyl is formed. Provided is a method for producing spinel-containing ferrite spherical porous silica particles, which comprises growing amine complex decomposition product particles in a spherical shape and removing organic components such as alkylamine and inorganic components such as moisture in the spherical particles. Is done.
[0011]
Further, in the production method of the present invention,
1. The total ratio of the 1, 2, divalent and trivalent metal elements per mole of silicate ester is used in a molar ratio of 0.005 to 0.15,
2. Using the alkylamine in an amount of 0.25 to 0.45 mole per mole of silicate ester;
3. Using the water-miscible organic solvent in an amount of 0.8 to 3.5 moles per mole of silicate ester;
4. Adding water in an amount of 34 to 42 moles per mole of silicate ester;
5. Using the acid in an amount of not more than 0.08 mole per mole of silicate ester,
6. That the water-miscible organic solvent is a monohydric to polyhydric alcohol,
7. The silicate is a silicate of an alcohol having 1 to 4 carbon atoms,
Is preferred.
[0012]
According to the present invention, there is further provided an adsorbent, a catalyst, and a catalyst carrier comprising the spinel-containing ferrite spherical porous silica particles, particularly a heating element utilizing magnetic hysteresis.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
The spinel-containing ferrite spherical porous silica particles according to the present invention have a chemical composition represented by the above formula (1), and exhibit an ordered array structure of pores at a diffraction angle of 0.5 to 5 degrees (CuKα). It is characterized by having a diffraction peak, having a pore volume based on micropores of 0.25 ml / g or more in a pore diameter of 1.0 to 5.0 nm, and having a maximum value of the pore volume at the same time.
[0014]
Porous silica (magnetic porous material) containing spinel-type ferrite fine particles is well known, but as far as the present inventors know, pores formed in a silica matrix have an ordered arrangement, and a pore diameter of 1 The spinel-type ferrite compound having a pore volume based on micropores of 0.25 ml / g or more in the range of 0.0 to 5.0 nm and having the maximum value of the pore volume and being included therein is highly dispersed in the silica matrix. I can't find any examples.
[0015]
The spinel-containing ferrite spherical porous silica particles according to the present invention have a regular arrangement of micropores having an average pore diameter of 1.5 to 5 nm in the silica matrix, as shown in the XRD powder diffraction pattern described later. Even at high temperatures, its regularity is not completely lost.
[0016]
Further, as used herein, “having a pore volume based on micropores of 0.25 ml / g or more at the same time as having a pore volume of 1.0 to 5.0 nm and having a maximum value of the pore volume” It means that “the peak corresponding to the average pore diameter is in the range of 1.0 to 5.0 nm, and at the same time, the pore volume in this range has a volume of 0.25 ml / g or more”. Therefore, it can be said that the porous silica particles according to the present invention have a feature that "the spinel-type ferrite fine particles are highly dispersed in a silica matrix having pores having regularly arranged uniform diameters". .
[0017]
Furthermore, as described later, in the spinel-containing ferrite spherical porous silica particles of the present invention, a sharp rise is recognized in the high relative pressure portion of the nitrogen adsorption isotherm. This means that, due to its generation mechanism, it has pores based on particle gaps in addition to micropores, and can easily diffuse various substances during adsorption and desorption.
[0018]
The spinel-containing ferrite spherical porous silica particles of the present invention have fine pores, and these fine pores provide an adsorption site or a reaction site. Since the spinel-containing ferrite spherical porous silica particles of the present invention have a pore volume of 0.25 ml / g or more at a pore diameter of 1 to 5 nm, they are desirable as an adsorption field or a reaction field for various molecules and ions.
[0019]
The spinel-containing ferrite spherical porous silica particles of the present invention have a regular arrangement of a complex of an alkylamine and a silica matrix surrounding the alkylamine, regardless of the presence of the included spinel-type ferrite fine particles. It is preferable for the formation and retention of micropores to consist of a complex dealkylamine (for example, a calcined product) having an X-ray diffraction peak at a bending angle (2θ; CuKα ray) of 1 to 5 °.
[0020]
The nanocomposite particles with an alkylamine serving as a precursor of the spinel-containing ferrite spherical porous silica particles of the present invention are mesostructures having an X-ray diffraction peak at a diffraction angle (2θ; CuKα ray) of 1 to 5 °. Due to this feature, the spinel-containing ferrite spherical porous silica particles of the present invention retain micropores.
That is, the spinel-containing ferrite spherical porous silica particles of the present invention have a mesostructure formed by the ability to form a coordinated order between the alkylamine and the silica-dissolved species, even though the spinel compound precursor is included in the mesostructure. It is characterized by having fine pores regularly arranged in a silica matrix by removing organic compounds by heat treatment or the like.
[0021]
As described above, the spinel-containing ferrite spherical porous silica particles of the present invention, as described above, make the water-miscible organic solvent, the alkylamine and the water-miscible organic solvent soluble 1, 2 and the resulting inorganic-organic composite into a spherical shape. A method of growing and removing alkylamines and the like in spherical particles, or a method in which spinel-type ferrite fine particles are dispersed in a water-miscible organic solvent, and a suspension obtained by mixing an alkylamine and a silicate is mixed with water or water under stirring. It can be synthesized by a method of adding an acidic aqueous solution, growing the resulting inorganic-organic composite into a sphere, and removing alkylamine and the like in the spherical particles.
[0022]
The formation mechanism of the spinel-containing ferrite spherical porous silica particles of the present invention is not necessarily clear at present, but is presumed as follows.
When an alkylamine is added to a metal chloride containing, for example, Co (II) and Fe (III) dissolved in alcohol, to the Si-alkoxide, the Si-alkoxide forms an ordered mesostructure with the amine by hydrogen bonding, and the metal component Forms a mixed solution phase with the mesostructure as a dissolved species surrounded by the amine. With the addition of the aqueous hydrochloric acid solution, Si becomes positively charged (I+), The NH2 group in the amine is NH3+(S+) And the chlorine ion (X−) Through S+X−A regular mesostructure of I + is generated. At the same time, the metal component forms a hydroxide phase and is taken in at the time of gelation of the mesostructure to produce a spinel-containing ferrite spherical porous silica particle precursor. S+X−I+The primary particles that grow with nuclei as S+X−I+And the particles grow by collision between the primary particles, take in the hydroxide having the spinel composition, and finally form spherical particles having a macro morphology on the order of microns. Of course, even if spinel fine particles are used instead of metal chloride, S+X−I+Generation of the mesostructure proceeds, and a spherical spinel-containing ferrite spherical porous silica particle precursor containing spinel-type ferrite fine particles in advance is generated.
[0023]
A final product obtained by removing an organic component surrounding the silicate skeleton by a treatment such as heating is a porous particle having an ordered pore structure derived from the mesostructure. The adsorption and reaction sites are on the surface of the pores.To make a magnetic porous material that makes effective use of the function of the coexisting magnetic material, it is necessary to highly disperse a certain size of spinel-type ferrite fine particles in the inorganic skeleton. is necessary.
[0024]
The present spinel-containing ferrite spherical porous silica particles produced based on the above generation mechanism are porous substances based on pores generated inside the particles, and furthermore, various kinds of adsorbed / reacted substances can enter and exit the pores. Since it has a particle structure that can be easily diffused, the ability to effectively exert the function of the spinel-type ferrite fine particles can be exhibited.
[0025]
According to the synthesis method of the present invention (1) or (2), the pore diameter of the silica matrix can be easily controlled by the number of carbon atoms in the alkylamine used, and the spinel-containing ferrite spherical porous silica can be easily controlled. The particle precursor can be manufactured under normal temperature and normal pressure in about 60 minutes. Further, the particle size can be controlled by the stirring speed, the acid concentration, or the proportion of the alcohol added.
[0026]
The water-miscible organic solvent, alkylamine, and metal compounds (metal salts and metal alkoxides) or further silicate esters soluble in the water-miscible organic solvent used in the present invention will be further described.
[0027]
As the silicate as the silica raw material used in the present invention, Si-alkoxide, tetramethyl orthosilicate, tetraethyl orthosilicate, tetraisopropyl orthosilicate, tetra-n-butyl orthosilicate and the like can be preferably used, and it is preferable. Tetraethyl orthosilicate (hereinafter abbreviated as TEOS) is used.
[0028]
As the alcohol, methanol, ethanol, propanol, butanol and the like can be used, and ethanol is preferably used.
[0029]
As the alkylamine, a linear alkylamine is preferable, and one having 8 to 18 carbon atoms is used. Octylamine and dodecylamine which are relatively inexpensive and are in a solution state at ordinary temperature are preferable.
[0030]
As the metal species, spinel type ferrite (MIIO ・ MIII 2O3) To form a monovalent metal element (Li) or a divalent metal element (MIIFe, Ni, Co, Cu, Zn, Mn, Mg, etc.) and trivalent metal elements (MIIIFe) can be used in two kinds or in various combinations of two or more kinds. From the definition of ferrite, MIIIStrictly speaking, Fe is only Fe as a metal species, but in the present invention, spinel-containing ferrite spherical porous silica particles including Cr are used.
As compounds containing 1,2 and trivalent metals soluble in water-miscible organic solvents, all metal salts soluble in alcohols such as chlorides, nitrates, sulfates and hydrates of the above metals can be used. can do.
[0031]
Further, as the acid, hydrochloric acid, nitric acid, sulfuric acid, acetic acid and the like can be used.
[0032]
The mixing molar ratio of the starting materials for synthesizing the spinel-containing ferrite spherical porous silica particles of the present invention is TEOS: 1-alkylamine: alcohol: acid: water: metal element = 1: 0.25 to 0.45 : 0.8 to 3.5: 0 to 0.08: 34 to 42: 0.005 to 0.15.
To describe the method of mixing the starting materials in detail, alkylamine is added to a mixed solution of TEOS and a metal salt dissolved in alcohol, and water or an acidic aqueous solution is added while stirring is continued to maintain a sufficient mixed state. While reacting at room temperature for about 1 hour.
[0033]
To describe the molar ratio of the starting materials in detail, for the synthesis of spinel-containing ferrite spherical porous silica particles, a metal salt adjusted to have a spinel composition was dissolved in alcohol and added to TEOS while stirring. After that, immediately add the alkylamine, stir for 20 seconds to 10 minutes, add water or an acidic aqueous solution while continuing to stir, and keep the mixture in a sufficient state for 80 minutes at room temperature, preferably for about 30 to 60 minutes. Let it. In the case of octylamine, the mixing molar ratio of the starting materials is preferably TEOS: octylamine: alcohol: acid: water: metal element = 1: 0.25 to 0.45: 0.8 to 1.5: 0. 04-0.08: 34-42: 0.005-0.15. In the case of dodecylamine, preferably, TEOS: dodecylamine: alcohol: acid: water: metal element = 1: 0.25-0.45: 1.4-3.5: 0-0: 0.01: 34-42: 0.005 to 0.15.
[0034]
Also, when spinel-type ferrite fine particles are directly used, a dispersion prepared by dispersing ferrite fine particles in alcohol in advance is added to TEOS, alkylamine is immediately added, and the mixture is stirred for 20 seconds to 10 minutes. Is added, and the mixture is allowed to react at room temperature within 80 minutes, preferably about 20 to 60 minutes, while maintaining a sufficient mixed state. The mixing molar ratio of the starting materials is the same as when the metal salt is dissolved in alcohol and used, and in the case of octylamine, preferably, TEOS: octylamine: alcohol: acid: water: metal element = 1: 0.25 to 0 .45: 0.8 to 1.5: 0.04 to 0.08: 34 to 42: 0.005 to 0.15. In the case of dodecylamine, preferably, TEOS: dodecylamine: alcohol: acid: water: metal element = 1: 0.25-0.45: 1.4-3.5: 0-0: 0.01: 34-42: 0.005 to 0.15.
[0035]
In each case above, the solid product is separated from the suspension after the reaction and dried sufficiently at room temperature to 100 ° C.
Finally, in order to remove organic components and produce spinel-containing ferrite spherical porous silica particles, heat treatment is performed, for example, at 500 ° C. or more for 30 minutes or more, preferably at 550 ° C. or more for 1 hour.
[0036]
(Application)
INDUSTRIAL APPLICABILITY The spinel-containing ferrite spherical porous silica particles of the present invention are suitable as materials that are useful for industrial and environmental conservation as adsorption / occlusion agents for various molecules and ions, or shape-selective oxidation catalyst carriers. In particular, by incorporating spinel-type ferrite fine particles, it has a heat generating function under an external alternating magnetic field environment, and it is possible to utilize the effect of controlling the temperature of the reaction field and promoting the desorption of adsorbed substances. .
[0037]
【Example】
Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
In addition, each test method performed in the Example was performed by the following method.
[0038]
(Measurement method)
(1) Scanning electron microscope observation: Observation was performed at an accelerating voltage of 10 kV using JSM5300 manufactured by JEOL.
(2) High-resolution transmission electron microscope observation: Observation was performed at an accelerating voltage of 200 kV using JEM-2000EXII manufactured by JEOL.
(3) Specific surface area / pore diameter distribution: BET specific surface area was determined from nitrogen adsorption isotherm measured at liquid nitrogen temperature using BELSORP28 manufactured by Nippon Bell, and pore diameter distribution was determined by MP method, Horvath-Kawazoe method and BJH method. Analyzed.
(4) Particle size: Measured using a Coulter Multisizer II manufactured by Beckman Coulter with an aperture tube of 200 μm meter.
(5) Sphericity: calculated from a scanning electron micrograph.
(6) X-ray powder diffraction: measured using a Rigaku Rotaflex RU-300 with a Cu-Kα radiation source, an acceleration voltage of 40 kV and 80 mA.
(7) Magnetization characteristics: A magnetic hysteresis curve was measured at room temperature using a vibrating sample magnetometer (VSM) (manufactured by RIKEN ELECTRONICS, vibrating sample magnetometer, model BHV-3).
(8) Heat generation characteristics: A high frequency of 56 kHz was irradiated under various magnetic fields (370, 440, 480 Oe), and the time-temperature characteristics of the magnetic porous body were measured. The high frequency power supply is HI-HEATER 4005 type, 5 kW, manufactured by Daiichi High Frequency Co., Ltd., equipped with a solenoid coil for generating a high frequency magnetic field, a high frequency current monitor, and a fluorescent optical fiber thermometer (FL-2000 type, manufactured by Anritsu Keiki Co., Ltd.) Temperature measurement.
[0039]
(Example 1)
FeCl previously adjusted to have a spinel-type ferrite composition3・ 6H2O and CoCl3・ 6H2O is dissolved in ethanol, mixed with TEOS while stirring at 600 rpm, octylamine is added, and the mixture is stirred for 10 minutes. Then, an aqueous hydrochloric acid solution is added, and the mixture is further stirred for 1 hour. The molar ratio of the mixed solution excluding the metal elements is TEOS: octylamine: ethanol: hydrochloric acid: water = 1: 0.34: 1.17: 0.07: 38, and the molar ratio of all the metal elements is changed. The amount of the magnetic substance included was adjusted. After the reaction, the solid product is separated from the suspension by filtration, sufficiently dried at 50 ° C., and then heated at a predetermined temperature of 600 ° C. or more for 1 hour to remove an organic component, thereby containing spinel-containing ferrite spherical porous silica particles. Was prepared.
Table 1 shows the content of the magnetic substance, the BET specific surface area, the pore diameter, and the pore volume at each heating temperature. The graph also shows the saturation magnetization and coercive force determined from the magnetic hysteresis curve.
[0040]
[Table 1]
(Example 2)
Dissolve FeCl3.6H2O and one or more other monovalent or divalent metals in ethanol previously adjusted to have a spinel ferrite composition, mix with TEOS while stirring at 600 rpm, add octylamine for 10 minutes After stirring, an aqueous hydrochloric acid solution is added, and the mixture is further stirred for 1 hour. The molar ratio of the mixed solution excluding the metal element is TEOS: octylamine: ethanol: hydrochloric acid: water = 1: 0.34: 1.17: 0.07: 38. By changing, the kind and content of the included magnetic substance were adjusted. After the reaction, a solid product is separated from the suspension by filtration, sufficiently dried at 50 ° C., and then heated at 800 ° C. for 1 hour to remove organic components to produce spinel-containing ferrite spherical porous silica particles.
Table 2 shows the constituent atoms of the spinel-type ferrite, the content of the magnetic material, and the saturation magnetization and coercive force.
[0042]
[Table 2]
(Example 3)
TEOS is stirred at 600 rpm, dodecylamine is added to a suspension obtained by adding magnetite fine particles dispersed in ethanol, and the mixture is stirred for 1 minute. Then, an aqueous hydrochloric acid solution is added, and the mixture is further stirred for 1 hour. The molar ratio of the mixed solution excluding the metal element is TEOS: dodecylamine: ethanol: hydrochloric acid: water = 1: 0.35: 2.93: 0.004: 38, and the ratio of magnetite added in advance as a magnetic material is The amount of the magnetic substance included was adjusted by changing the amount. After the reaction, a solid product is separated from the suspension by filtration, sufficiently dried at 50 ° C., and then heated at 600 ° C. for 1 hour to remove an organic component to produce spinel-containing ferrite spherical porous silica particles.
Table 3 shows the magnetic substance content, the BET specific surface area, the pore diameter, and the pore volume. The graph also shows the saturation magnetization and coercive force determined from the magnetic hysteresis curve.
[0044]
[Table 3]
Next, the X-ray diffraction peak structure analysis, SEM image, particle size distribution curve, TEM image, nitrogen adsorption isotherm, pore size distribution, etc. of the spinel-containing ferrite spherical porous silica particles of the present invention obtained above are shown. This will be described with reference to 1 to 11.
[0046]
FIG. 1 is an XRD diffraction pattern showing a heating change of the Co-containing ferrite spherical porous silica particles of the present invention. Specifically, it is an X-ray diffraction diagram showing the process of crystallization of Co ferrite in a Co-containing ferrite spherical porous silica particle precursor (a) and heat treatment. The diffraction peak present at a low angle is a diffraction peak in the silica matrix. This indicates that the pore arrangement is regular. In FIG. 1, (a) the precursor before heating, (b) Example 1-4, (c) Example 1-5, (d) Example 1-6, and (e) Example 1-2 . The circles indicate the diffraction peaks of Co ferrite.
[0047]
FIG. 2 is an SEM image of FIG. 1 and shows that when the Co ferrite content is small, the particles are monodisperse spherical particles, and when the Co ferrite content is large, the spherical particles are easily aggregated. In FIG. 2, (a) Example 1-2 and (b) Example 1-5.
[0048]
FIG. 3 shows a particle size distribution curve of the Co-containing ferrite spherical porous silica particles of the present invention, and the volume-based particle size distribution curve is in good agreement with the SEM observation result. When the content of Co ferrite is small, the average particle diameter is 27.5 μm, which is a sharp distribution. However, when the content is large, the distribution becomes broad due to an increase in the average diameter and aggregation between particles. In FIG. 3, (a) Example 1-2 and (b) Example 1-5.
[0049]
FIG. 4 is a TEM image showing the distribution state of Co ferrite fine particles in the Co-containing ferrite spherical porous silica particles of the present invention (Examples 1-5). From the TEM image of the sample section heat-treated at 800 ° C. It can be seen that spinel fine particles of 100 nm or less exist in a highly dispersed state in the spherical silica matrix.
[0050]
FIG. 5 is a nitrogen adsorption isotherm of the 600 ° C., 800 ° C., and 900 ° C. heat treatment products of FIG. It can be seen that the high BET specific surface area of 700
[0051]
FIG. 6 is a pore size distribution curve of the Co-containing ferrite spherical porous silica particles of the present invention obtained by applying the Horvath-Kawazoe method. The higher the temperature, the smaller the pore size and the more difficult it is to separate from the background. It can be seen that the pore diameter is distributed in the range of 1 to 3 nm. In FIG. 6, (a) Example 1-1, (b) Example 1-2, (c) Example 1-4, (d) Example 1-5, (e) Example 1-6. It is.
[0052]
FIG. 7 shows an XRD diffraction pattern of magnetite-containing spherical porous silica particles obtained by heating at 600 ° C. using synthetic magnetite as the magnetic fine particles among the spinel-containing ferrite spherical porous silica particles of the present invention. Bottom reflections at the corners indicate that the pore arrangement in the silica matrix is regular. In FIG. 7, (a) Example 3-1 and (b) Example 3-2; the circles indicate the peaks of magnetite, and the intensity in a wide angle range of 10 degrees or more is shown by 20 times.
[0053]
FIG. 8 is an SEM image of Example 3-1 in FIG. 7 and shows that the particles are monodisperse spinel-containing ferrite spherical porous silica particles of 10 to 100 μm.
[0054]
FIG. 9 shows (A) a nitrogen adsorption isotherm and (B) a pore diameter distribution curve of the magnetite ferrite spherical porous silica particles of the present invention. FIGS. 9a and 9b show the nitrogen adsorption isotherm of FIG. 5a and the BJH method, respectively. 6 is a pore diameter distribution curve obtained by applying the formula (1). The BET specific surface areas are all about 1000 m2 / g, the pore diameter distribution is sharp, and the peak value of the pore diameter is about 3 nm. Also, as in FIG. 5, a sharp rise due to the particle gap is observed in the high relative pressure portion of the adsorption isotherm. In FIG. 9, (a) Example 3-1 and (b) Example 3-2.
[0055]
FIG. 10 shows a magnetic hysteresis curve of the Co ferrite of the present invention and a magnetic hysteresis curve of the Co ferrite in the heating temperature dependence of the coercive force (small frame in the figure). The figure shows the change in holding force depending on the heating temperature. The saturation magnetization increases as the ferrite content increases, but the coercive force decreases and decreases with temperature, indicating that the higher the heating temperature, the faster the ferrite crystallization is promoted and the more the grains grow. In FIG. 10, these are the products of the heat treatment at 800 ° C. in Examples 1-2 and □ Examples 1-5.
[0056]
FIG. 11 shows the temperature rise characteristics of the spinel-containing ferrite spherical porous silica particles of the present invention, and specifically shows the temperature rise characteristics when measured with an input of 440 Oe under an alternating magnetic field of 56 kHz. In each case, the saturation temperature is reached in about 10 minutes, and rapid heating is possible without exceeding the Curie temperature peculiar to a specific magnetic porous material by adjusting the spinel composition and its content or fine particle diameter. It can be seen that the magnetic porous material is useful as a heating element of a heating method capable of rapidly heating to a constant value before the Curie temperature under an AC magnetic field.
[0057]
(Example 4)
Table 4 shows the heat generation effect of the present spinel-containing ferrite spherical porous silica particles. About 0.5 g of the sample was subjected to various magnetic fields under an alternating magnetic field of 56 kHz to measure a temperature-time curve. In the case of a magnetic porous body having a fixed spinel component, the temperature reached increases with an increase in the amount of power, but significant differences are recognized depending on the spinel-type ferrite content, the composition ratio, and the heating temperature. In either case, the temperature reaches a constant temperature in about 10 minutes, and the heating method using the magnetic heating phenomenon, in which a magnetic porous body is used as a heating element under an AC magnetic field, runs away above the Curie temperature inherent to the magnetic body. No, it turns out to be excellent as a quick heating method.
[0058]
[Table 4]
【The invention's effect】
The spinel-containing ferrite spherical porous silica particles of the present invention have spinel-type ferrite fine particles having a size of several tens of nanometers in a silica matrix in a highly dispersed state, and have a high ratio due to regularly arranged fine pores in the silica matrix. It has surface area and high heat resistance.
And since these porous silica particles are uniform and regularly arranged and have a large pore volume, they are used as various adsorbents, catalyst carriers, and even catalysts in reaction processes useful in both industrial and environmental conservation. It is possible. In particular, the spinel-containing ferrite spherical porous silica particles of the present invention have high value as a heating element under an alternating magnetic field environment and as a basic substance for developing a new chemical process.
The spinel-containing ferrite spherical porous silica particles of the present invention are prepared by preparing a homogeneous solution of TEOS and a metal compound having a spinel composition dissolved in alcohol, or by directly mixing TEOS and spinel-type ferrite fine particles, and then forming a porous structure. Surface activity which becomes precursor of spinel-containing ferrite spherical porous silica particles at normal temperature and normal pressure by changing the number of carbon atoms in the alkyl chain by adding water or acidic aqueous solution at a stretch using alkylamine as a control agent Organic-inorganic nanocomposites (mesostructures) containing chemicals can be produced in a short period of time, and then by removing organic matter, spinel-containing macrostructures with a micron-order macro form ranging from several microns to several hundred microns in diameter Ferrite spherical porous silica particles can be efficiently synthesized.
[Brief description of the drawings]
FIG. 1 is an XRD diffraction pattern showing a heating change of a spherical porous silica particle containing Co ferrite of the present invention: (a) a precursor before heating, (b) Examples 1-4 and (c) Examples 1-5. , (D) Example 1-6 and (e) Example 1-2. The circles indicate the diffraction peaks of Co ferrite.
FIG. 2 shows SEM images of Co-containing ferrite spherical porous silica particles of the present invention: (a) Example 1-2, (b) Example 1-5.
FIG. 3 shows a particle size distribution curve of Co-containing ferrite spherical porous silica particles of the present invention: (a) Example 1-2, (b) Example 1-5.
FIG. 4 is a TEM image showing the distribution state of Co ferrite fine particles in the Co-containing ferrite spherical porous silica particles of the present invention (Examples 1-5).
FIG. 5: Nitrogen adsorption isotherm of Co-containing ferrite spherical porous silica particles of the present invention: (A) (○) Example 1-1, (□) Example 1-2, (△) Example 1-3 (B) (○) Example 1-4, (□) Example 1-5, (△) Example 1-6.
FIG. 6 shows the pore size distribution of Co-containing ferrite spherical porous silica particles of the present invention: (a) Example 1-1, (b) Example 1-2, (c) Example 1-4, (d) Example 1-5, (e) Example 1-6.
FIG. 7: XRD diffraction patterns of magnetite ferrite spherical porous silica particles of the present invention: (a) Example 3-1; (b) Example 3-2; The intensity in the wide-angle range is shown by 20 times.
FIG. 8 is an SEM image of magnetite ferrite spherical porous silica particles of the present invention (Example 3-1).
FIG. 9 shows (A) nitrogen adsorption isotherm and (B) pore diameter distribution curve of magnetite ferrite spherical porous silica particles of the present invention: (a) Example 3-1 and (b) Example 3-2.
FIG. 10 shows the magnetic hysteresis curve of Co ferrite of the present invention and the dependency of coercive force on heating temperature (small frame in the figure): Examples 1-2 and □ 800 ° C. heat-treated products of Examples 1-5. .
FIG. 11 shows the temperature rise characteristics of the magnetic porous material of the present invention: (a) Example 1-1, (b) Example 1-2, (c) Example 1-4, (d) Example 1-5. , (E) Example 2-2 and (f) Example 2-3.
Claims (16)
ＳｉＯ２・ｎ（ＭIIＯ・ＭIII ２Ｏ３） （１）
（式中、ＭIIは１又は２価の金属元素、ＭIIIは３価の金属元素を表し、ｎは０．００５乃至０．１の数である）
で表される化学的組成を有する含スピネル型フェライト球状多孔質シリカ粒子であって、回折角０．５乃至５度（ＣｕＫα）に細孔の規則配列構造を示すＸ線回折ピークを有し、細孔径１．０乃至５．０ｎｍに０．２５ｍｌ／ｇ以上の微細孔に基づく細孔容積を持つと同時に細孔容積の極大値を有することを特徴とする含スピネル型フェライト球状多孔質シリカ粒子。The following general formula (1)
SiO 2 · n (M II O · M III 2 O 3 ) (1)
(Wherein MII represents a monovalent or divalent metal element, MIII represents a trivalent metal element, and n is a number from 0.005 to 0.1)
A spinel-containing ferrite spherical porous silica particle having a chemical composition represented by the following formula, having an X-ray diffraction peak indicating a regular array structure of pores at a diffraction angle of 0.5 to 5 degrees (CuKα), A spinel-containing ferrite spherical porous silica particle having a pore volume based on micropores of 0.25 ml / g or more in a pore diameter of 1.0 to 5.0 nm and having a maximum value of the pore volume. .
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