JP4061902B2 - Method for producing porous potassium carbonate - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、多孔質炭酸カリウムの製造方法に関するものである。
【０００２】
【従来の技術】
炭酸カリウムは、水酸化カリウム水溶液に二酸化炭素含有ガスを反応させて直接炭酸カリウムを得る直接法と、水酸化カリウム水溶液に二酸化炭素含有ガスを反応させていったん炭酸水素カリウムを得た後に、これをか焼分解して炭酸カリウムとする炭酸水素カリウム法の主に二通りにより製造されている。
【０００３】
直接法は、製造設備の機器点数が少なく、かつ生産性が良いために幅広く採用されている。ただし、この方法では含水炭酸カリウム結晶を得た後に乾燥させる際、しばしば非常に細かい粒子（ダスト）が発生し、取り扱いが困難となる。そこで、水酸化カリウム水溶液を直接流動床乾燥装置内部に噴霧し、加熱した二酸化炭素含有ガスを吹き込むことで、比重が高く球形に近い結晶が得られることが知られている。
【０００４】
炭酸水素カリウム法は、直接法ほど生産性は高くないが、多孔質で比表面積が大きく、他の薬剤との反応性が高く、溶解速度も速いなど活性の高い炭酸カリウム結晶を得ることができる。
【０００５】
上述の二通りの方法以外にも、イオン交換法によって塩化カリウムから直接炭酸カリウム水溶液を得る方法が開示されているが（ＵＳＰ５４４９５０６号明細書）、この方法によって得られる該水溶液は希薄であるため、炭酸カリウムを取り出す際には大型機器を用いた濃縮工程を経なければならないほか、その後の晶析によって活性の高い炭酸カリウム結晶を得ることは困難であった。
【０００６】
【発明が解決しようとする課題】
炭酸カリウムは、特殊ガラス、せっけん製造、食品工業及び顔料の製造など幅広い用途に使用されている。有機薬品の製造における触媒や中間体原料として使用されることも多く、より活性が高い炭酸カリウムの提供が求められている。例えば、特開平１０−２７９５３５や特開平９−１８８６９０には特定の粒径で比表面積が大きい炭酸カリウム粉末を使用することが開示されているが、活性のさらなる改良が望まれている。
【０００７】
【課題を解決するための手段】
本発明は、平均粒子径１００〜１０００μｍの炭酸水素カリウム結晶を、露点０℃以下でかつ温度が１０〜５０℃の乾燥空気を導入しながら、１００〜４００℃の被か焼物温度でか焼することを特徴とする多孔質炭酸カリウムの製造方法を提供する。
【０００８】
【発明の実施の形態】
以下に、本発明の実施の形態について図面を参照して説明する。図１は、本発明を用いた多孔質炭酸カリウム製造の好適な例の概要を示したものである。
【０００９】
（炭酸水素カリウム結晶の製造）
炭酸水素カリウムは、水酸化カリウム及び／又は炭酸カリウムを含む水溶液と二酸化炭素含有ガスを反応させて得たものが好ましい。具体的には、次式（１−１）、（１−２）に示す反応が生じていると考えられる。
２ＫＯＨ＋ＣＯ２ →Ｋ２ＣＯ３＋Ｈ２Ｏ （１−１）、
Ｋ２ＣＯ３＋ＣＯ２＋Ｈ２Ｏ→２ＫＨＣＯ３ （１−２）。
【００１０】
平均粒子径１００〜１０００μｍの炭酸水素カリウム結晶は、水酸化カリウム及び／又は炭酸カリウムを含む水溶液の濃度及び液温、さらに、該水溶液に吹き込む二酸化炭素含有ガス中の二酸化炭素濃度を、好適には以下に示す条件に調節して反応させることによって得られる。
【００１１】
まず、水酸化カリウム及び／又は炭酸カリウムを含む水溶液がＫ２Ｏ換算濃度１５質量％以上であることが好ましい。Ｋ２Ｏ換算濃度が１５質量％未満の場合は、該水溶液の体積あたりの炭酸水素カリウム結晶析出量が減少するため、生産性の点で好ましくない。ここで、Ｋ２Ｏ換算濃度とは水溶液中に含まれる全てのカリウム分をＫ２Ｏとして計算したときの質量％濃度を指す。また、該水溶液の濃度はＫ２Ｏ換算で２０〜５０質量％であることがさらに好ましく、３０〜４７質量％であることが最も好ましい。濃度が５０質量％を超える場合、析出する炭酸水素カリウム結晶の粒子径が小さくなりやすく、平均粒子径１００〜１０００μｍの結晶が得られにくいので好ましくない。
【００１２】
次に、水酸化カリウム及び／又は炭酸カリウムを含む水溶液を二酸化炭素含有ガスと反応させる際、水溶液の液温は２０〜９０℃であることが好ましく、４０〜８０℃であることがさらに好ましい。２０℃未満及び９０℃超過の場合にも析出する炭酸水素カリウム結晶の粒子径が小さくなりやすく、平均粒子径１００〜１０００μｍの結晶が得られにくいため好ましくない。
【００１３】
さらに、吹き込む二酸化炭素含有ガスの濃度は１０〜１００容量％であることが好ましい。濃度が１０容量％未満であると反応や晶析の進行に時間がかかりすぎ、生産性が低くなるため好ましくない。ここで、水酸化カリウム及び／又は炭酸カリウムを含む水溶液と二酸化炭素含有ガスの反応は、強い撹拌をかけずに二酸化炭素含有ガスを水酸化カリウム及び／又は炭酸カリウムを含む水溶液中に吹き込む形で行われることが、平均粒子径１００〜１０００μｍの結晶を得る上で好ましい。吹き込みは、炭酸水素カリウム結晶の平均粒子径が１００μｍ以上、さらに好ましくは２５０μｍ以上に成長するまで続けられるのが好ましい。具体的には、炭酸化設備に準備した１０ｍ３の水酸化カリウム及び／又は炭酸カリウムを含む水溶液に対して、毎時１００ｍ３（二酸化炭素ガス１００％換算）以上の流量で、およそ１０時間程度吹き込むことが好ましい。
【００１４】
（固液分離・循環）
上述の方法によって析出した炭酸水素カリウム結晶は、フィルタープレスによる濾過分離、デカンターによる遠心分離、シックナーによる沈降分離など、通常の固液分離操作によって結晶と母液とに分離できる。この母液は以下に示す工程を経ることによって精製され、二酸化炭素含有ガスを吹き込んで反応させる工程へと循環することができる。
【００１５】
まず、母液を濃縮し、さらに水酸化カリウムを添加することにより、液中の水酸化カリウム濃度がＫ２Ｏ換算濃度で０．０１〜１０質量％（ＫＯＨ換算濃度で０．０１〜１２質量％）、さらに好ましくは０．１〜５質量％（ＫＯＨ換算濃度で０．１〜６質量％）となるように調節する。母液中にはカリウムイオン、炭酸イオン、炭酸水素イオンが存在するが、ここに水酸化カリウムを添加し、液中の水酸化カリウムのＫ２Ｏ換算濃度が０．０１％以上となるように調節すれば、不純物である鉄、ニッケル、鉛、クロムなどの重金属又はマグネシウムを水酸化物として析出させ、続く固液分離操作によって除去することができる。特に、鉄の除去に有効である。このとき同時に、マグネシウムイオンも同様に水酸化物として除去できる。
【００１６】
一方、液中の水酸化カリウムのＫ２Ｏ換算濃度が１０質量％を超える場合、析出する水酸化物の結晶が小さくなりやすく、固液分離操作上好ましくない。したがって、水酸化カリウムのＫ２Ｏ換算濃度を１０質量％以下に調節し、水酸化物の種結晶を含有する液の一部を炭酸水素カリウム結晶を分離した後の母液に添加し、循環させることにより、大きな水酸化物の結晶を得ることが好ましい。
【００１７】
さらに、フィルタープレスによって濾過分離する場合、液中の水酸化カリウムのＫ２Ｏ換算濃度が１０質量％を超えると濾布の劣化が著しく進行し、好ましくないため、二酸化炭素ガスの一部を吹き込んで水酸化カリウムの一部を炭酸カリウムに変換することにより１０質量％以下に調節することが好ましい。ここで、二酸化炭素ガスとして、炭酸水素カリウム結晶の製造工程から排出されるガスを使用すれば、二酸化炭素ガスの有効利用が可能である。さらに、吹き込み後、液中の炭酸カリウム濃度をＫ２Ｏ換算濃度で１０〜７０質量％、さらに好ましくは３５〜５０質量％とすることが好ましい。Ｋ２Ｏ換算濃度が７０質量％以下、さらに好ましくは５０質量％以下であれば、液の粘度が高くなりすぎるのを防ぐことができ、固液分離上好ましい。一方、Ｋ２Ｏ換算濃度が１０質量％以上、さらに好ましくは３５質量％以上とすることが、続く炭酸水素カリウム結晶の製造において、不必要に大きな設備を用いる必要がないので好ましい。
【００１８】
上述の固液分離操作後の濃度に応じて、純度の高い水酸化カリウムをさらに添加することもでき、炭酸水素カリウム結晶の製造に利用することが可能となる。また、一連の操作を通じて、母液は外気に触れず、外部からの異物混入のないように取り扱う。
【００１９】
（か焼）
炭酸水素カリウムをか焼すれば、次式（２）に示す熱分解により二酸化炭素と水蒸気を放出して炭酸カリウムとなる。
２ＫＨＣＯ３→Ｋ２ＣＯ３＋ＣＯ２＋Ｈ２Ｏ （２）。
【００２０】
炭酸水素カリウム結晶から二酸化炭素と水蒸気が抜け出すことにより細孔が生じるが、この細孔の数と大きさを制御することにより活性の高い炭酸カリウムを得ることができる。良好な細孔を生じさせるには、か焼前の炭酸水素カリウム結晶の粒子径が１００〜１０００μｍであることが必要とされ、より好ましくは２５０〜５５０μｍ、最も好ましくは３００〜５００μｍであることが好ましい。１００μｍ未満では晶析後の固液分離が困難なため、含水率の高い炭酸水素カリウムケーキをか焼炉に投入することとなり、活性の高い炭酸カリウムが得られない。反対に、平均粒子径が１０００μｍ超過の場合は焼成に時間がかかり、生産性が低下するため好ましくない。
【００２１】
ここで、良好な細孔を生じさせるためには、か焼の条件を適切にする必要がある。か焼炉としては、温度管理、滞留時間管理が容易であり、不純物が混入しにくいことから、外熱式キルンを使うことが好ましい。キルンの一端から連続的に炭酸水素カリウム結晶を投入し、外側から加熱すると、炉内の炭酸水素カリウム結晶は式（２）の反応によって炭酸カリウムとなり、他端より取り出される。このとき、乾燥空気をか焼炉に導入し、か焼によって発生する二酸化炭素をパージすることが好ましい。
【００２２】
なお、この乾燥空気は露点が０℃以下で、かつ温度を１０〜５０℃に保つことが必要とされる。乾燥空気の露点が０℃を超えると式（２）の反応が進みにくくなるばかりでなく、か焼して得られる多孔質炭酸カリウムが水分を吸収する可能性があり好ましくない。か焼の際に発生する分解ガスは高湿であり、速やかに乾燥空気に置き換えることにより、吸湿を防ぐことができる。また、低温の乾燥空気を導入することにより、被か焼物温度の過昇温を抑えるのみならず、か焼後高温のまま取り扱うのが煩雑な多孔質炭酸カリウムの温度を低下させる役割も果たしている。したがって、乾燥空気の投入時の温度を１０〜５０℃とすることにより、キルン内の温度が適切に保たれる。
【００２３】
さらに、キルンの他端から、か焼して得られる多孔質炭酸カリウム１ｋｇあたり０．５ｍ３以上の割合で流しながら、１００〜４００℃の被か焼物温度でか焼することによって最も良好な製品が得られることがわかった。乾燥空気の導入容量がか焼して得られる多孔質炭酸カリウム１ｋｇあたり０．５ｍ３未満だと式（２）の反応が速やかに進行せず、生産性が低下するのみならず、均一な細孔とならず好ましくない。
【００２４】
また、キルン外壁部の加熱温度を６００℃以上に保つとともに、被か焼物温度を１００〜４００℃、好ましくは１５０〜３５０℃、最も好ましくは２００〜３００℃とすることが好ましい。被か焼物温度が１００℃未満であると、式（２）の反応が速やかに進まない。一方、被か焼物温度が４００℃を超過すると式（２）の反応が急激に進行するため細孔がつぶれてしまい好ましくない。なお、か焼炉内に滞留する時間は１〜１０時間であることが好ましく、２〜５時間であることがさらに好ましい。上述の温度範囲では、１時間未満の加熱ではか焼が十分に進まない。また、１０時間を超えてか焼すると細孔がつぶれてしまう可能性が高く好ましくない。
【００２５】
（粉砕・ふるい分け）
上述の方法により活性の高い多孔質炭酸カリウムを得ることができるが、さらに活性や分散性を改良するために粉砕し、表面積を大きくすることも可能である。
【００２６】
粉砕方法としては、衝撃式粉砕機（高速回転する羽根などによる粉砕機）、ジェットミル（衝突気流による粉砕機）、ボールミルなど、通常の粉砕方法を用いることができる。中でも風力式分級機を備えた衝撃式粉砕機を用い、粉砕機から排出される粒子を分級し、粗粒子は再度粉砕機に戻しながら粉砕する場合、高い収率で目的の粒径の多孔質炭酸カリウムを得ることができるのでより好ましい。また、ジェットミルを用いる場合にも、ふるい分けによる粗粒子除去が不要であるなど微粒子化に適しており、高い収率で目的の粒径の多孔質炭酸カリウムを得ることができるので好ましい。なお、粉砕もか焼時と同様に露点が０℃以下でかつ温度が１０〜５０℃の乾燥空気中で行うことが好ましい。
【００２７】
本発明の多孔質炭酸カリウムは、特に微細な細孔を多数有していることを特徴とする。直接法によって製造された炭酸カリウムではほとんど観測することができない、細孔径０．１〜１μｍの細孔を数多く有している。加えて、細孔質量あたりの容積が大きいほど活性の高い炭酸カリウムとなることから、細孔径０．１〜１μｍの細孔容積の合計が０．０８ｍＬ／ｇであることが好ましく、０．１ｍＬ／ｇ以上であることがさらに好ましい。
【００２８】
本発明における多孔質炭酸カリウムは薬剤との反応性や水への溶解性などが良好で活性が高いことから、各種医薬、農薬、工業薬品の合成原料、触媒、食品添加物、写真現像液、発色剤、ｐＨ調整剤、酸吸着剤、洗浄剤、除湿剤、酸性ガス除去剤、ハロゲンガス除去剤、ガラス原料などの使用用途に好適に用いられる。
【００２９】
【実施例】
［例１］
以下実施例によって本発明を説明する。全体としてのカリウム濃度がＫ２Ｏ換算で３７質量％で、そのうち水酸化カリウムの濃度がＫ２Ｏ換算で１８％である、水酸化カリウム及び炭酸カリウムを含む水溶液を６ｍ３の反応槽に張り込み、液温を７０℃に調節した。濃度が４０容量％の二酸化炭素含有ガスを反応槽の下から１２ｍ３／分で吹き込むと炭酸水素カリウム結晶が育ち、析出した。８時間後、スラリー状となった反応槽内容物を抜き取り、遠心分離によって固体相を取り出した。採取した炭酸水素カリウムケーキは４５００ｋｇで、付着水分は乾燥質量換算で４質量％、平均粒子径は４００μｍであった。
【００３０】
次に、か焼工程に移る。この炭酸水素カリウムケーキを、キルン外壁部の加熱温度を８８０℃に設定したロータリーキルンに１０ｋｇ／分で投入した。このとき、内部のケーキ温度は４００℃であった。このとき、露点が−５℃、温度３０℃の乾燥空気を１０ｍ３／分の流量で製品の取り出し口から投入口方向へ流し続けた。取り出し口から採取した多孔質炭酸カリウムの温度は５０℃であった。
【００３１】
さらに、取り出した多孔質炭酸カリウムの一部を、露点が−１０℃の乾燥空気中で、風力式分級機能を備えたホソカワミクロン社製の衝撃式粉砕器、ＡＣＭパルベライザーＡＣＭ−５型で粉砕した。これらの多孔質炭酸カリウムの性状を確認すると表１に示すとおりとなった。
【００３２】
なお、平均粒径の測定には、粉砕品についてはレーザー散乱回折式の日機装株式会社製粒度分布測定装置マイクロトラックＦＲＡ９２２０を使用し、未粉砕品についてはロータップ式ふるい分け測定により求めた。また、細孔容積の測定にはカンタクローム社製のオートソーブＩＩＩＢ（測定範囲：細孔径０．００１〜０．２μｍ）と、ＣＥ Ｉｎｓｔｒｕｍｅｎｔｓ社製の水銀圧入式ポロシメーター（測定範囲：細孔径０．２μｍ超）を使用した。
【００３３】
また、アルカリ触媒としての活性の指標として酸との反応性を測定した。塩酸との反応性は、２５℃に調整した０．５％塩酸水溶液４００ｇに乾燥処理を行った炭酸カリウム４ｇを投入し、ｐＨ５に到達する時間で評価した。
【００３４】
【表１】
［例２（比較例）］
キルン外壁部の加熱温度を１２００℃とした以外は実施例と同様に行い、炭酸カリウムを得た。か焼時の内部ケーキ温度は８３０℃であった。実施例と同様に、その一部を粉砕し、評価した。
【００３６】
【表２】
例２の炭酸カリウムは多孔質ではあるものの、比表面積、細孔容積共に例１の炭酸カリウムより小さく、また、酸との反応も遅い。したがって、例１の炭酸カリウム結晶のほうが分散性、拡散性に優れ、活性が高いことが分かる。
【００３８】
【発明の効果】
本発明の製造方法によって、薬剤との反応性や水への溶解性などが良好で、活性が高い多孔質炭酸カリウムを得ることができる。そのため、本発明の多孔質炭酸カリウムを各種医薬、農薬、工業薬品の合成原料、触媒、食品添加物、写真現像液、発色剤、ｐＨ調整剤、酸吸着剤、洗浄剤、除湿剤、酸性ガス除去剤、ハロゲンガス除去剤、ガラス原料などのなどの使用用途に好適に用いられる。
【図面の簡単な説明】
【図１】本発明の多孔質炭酸カリウムの製造を実施するための概要を示す図。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a manufacturing method of a porous carbonate potassium.
[0002]
[Prior art]
Potassium carbonate is obtained by directly reacting a carbon dioxide-containing gas with an aqueous potassium hydroxide solution to obtain potassium carbonate directly, or by reacting a carbon dioxide-containing gas with an aqueous potassium hydroxide solution to obtain potassium hydrogencarbonate once. It is produced mainly by two methods of the potassium hydrogen carbonate method to be calcined and decomposed to potassium carbonate.
[0003]
The direct method is widely used because it has a small number of manufacturing equipment and high productivity. However, in this method, when the hydrated potassium carbonate crystals are obtained and then dried, very fine particles (dust) are often generated, which makes handling difficult. Therefore, it is known that a crystal having a high specific gravity and a nearly spherical shape can be obtained by spraying an aqueous potassium hydroxide solution directly into the fluidized bed dryer and blowing in a heated carbon dioxide-containing gas.
[0004]
The potassium bicarbonate method is not as productive as the direct method, but it is possible to obtain highly active potassium carbonate crystals that are porous, have a large specific surface area, are highly reactive with other drugs, and have a high dissolution rate. .
[0005]
In addition to the above two methods, a method for obtaining an aqueous potassium carbonate solution directly from potassium chloride by ion exchange is disclosed (US Pat. No. 5,449,506), but since the aqueous solution obtained by this method is dilute, When potassium carbonate was taken out, it had to go through a concentration step using a large device, and it was difficult to obtain highly active potassium carbonate crystals by subsequent crystallization.
[0006]
[Problems to be solved by the invention]
Potassium carbonate is used in a wide range of applications such as special glass, soap production, food industry and pigment production. In many cases, it is used as a catalyst or an intermediate material in the production of organic chemicals, and there is a demand for providing potassium carbonate with higher activity. For example, JP-A-10-279535 and JP-A-9-188690 disclose the use of potassium carbonate powder having a specific particle size and a large specific surface area, but further improvement in activity is desired.
[0007]
[Means for Solving the Problems]
In the present invention, potassium hydrogen carbonate crystals having an average particle size of 100 to 1000 μm are calcined at a calcined material temperature of 100 to 400 ° C. while introducing dry air having a dew point of 0 ° C. or less and a temperature of 10 to 50 ° C. A method for producing porous potassium carbonate is provided.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an outline of a preferred example of the production of porous potassium carbonate using the present invention.
[0009]
(Production of potassium hydrogen carbonate crystals)
The potassium hydrogen carbonate is preferably obtained by reacting an aqueous solution containing potassium hydroxide and / or potassium carbonate with a carbon dioxide-containing gas. Specifically, it is considered that the reactions shown in the following formulas (1-1) and (1-2) occur.
2KOH + CO 2 → K 2 CO 3 + H 2 O (1-1),
K 2 CO 3 + CO 2 + H 2 O → 2KHCO 3 (1-2).
[0010]
The potassium hydrogen carbonate crystals having an average particle diameter of 100 to 1000 μm preferably have a concentration and a liquid temperature of an aqueous solution containing potassium hydroxide and / or potassium carbonate, and a carbon dioxide concentration in a carbon dioxide-containing gas blown into the aqueous solution. It can be obtained by adjusting the reaction under the following conditions.
[0011]
First, it is preferable that the aqueous solution containing potassium hydroxide and / or potassium carbonate has a K 2 O equivalent concentration of 15% by mass or more. When the K 2 O equivalent concentration is less than 15% by mass, the amount of precipitated potassium hydrogen carbonate crystals per volume of the aqueous solution decreases, which is not preferable in terms of productivity. Here, the K 2 O concentration in terms refer to weight percent concentration when calculated all potassium content of contained in the aqueous solution as K 2 O. Further, the concentration of the aqueous solution is more preferably 20 to 50% by mass in terms of K 2 O, and most preferably 30 to 47% by mass. When the concentration exceeds 50% by mass, the particle size of the precipitated potassium hydrogen carbonate crystals tends to be small, and crystals with an average particle size of 100 to 1000 μm are hardly obtained, which is not preferable.
[0012]
Next, when the aqueous solution containing potassium hydroxide and / or potassium carbonate is reacted with the carbon dioxide-containing gas, the liquid temperature of the aqueous solution is preferably 20 to 90 ° C, and more preferably 40 to 80 ° C. Even when the temperature is lower than 20 ° C or higher than 90 ° C, the particle size of the precipitated potassium hydrogen carbonate crystal tends to be small, and crystals having an average particle size of 100 to 1000 µm are hardly obtained.
[0013]
Furthermore, the concentration of the carbon dioxide-containing gas to be blown is preferably 10 to 100% by volume. If the concentration is less than 10% by volume, it takes too much time for the reaction or crystallization to proceed, and the productivity is lowered, which is not preferable. Here, the reaction between the aqueous solution containing potassium hydroxide and / or potassium carbonate and the carbon dioxide-containing gas is performed by blowing the carbon dioxide-containing gas into the aqueous solution containing potassium hydroxide and / or potassium carbonate without strong stirring. It is preferable to obtain the crystal having an average particle diameter of 100 to 1000 μm. The blowing is preferably continued until the average particle size of the potassium hydrogen carbonate crystal grows to 100 μm or more, more preferably 250 μm or more. Specifically, about 10 hours is blown into an aqueous solution containing 10 m 3 of potassium hydroxide and / or potassium carbonate prepared in a carbonation facility at a flow rate of 100 m 3 (equivalent to 100% carbon dioxide gas) per hour. It is preferable.
[0014]
(Solid-liquid separation / circulation)
The potassium hydrogen carbonate crystals precipitated by the above-described method can be separated into crystals and mother liquors by ordinary solid-liquid separation operations such as filtration separation with a filter press, centrifugal separation with a decanter, and sedimentation separation with a thickener. This mother liquor can be purified by going through the steps shown below and circulated to the step of blowing and reacting with a carbon dioxide-containing gas.
[0015]
First, by concentrating the mother liquor and further adding potassium hydroxide, the potassium hydroxide concentration in the liquid is 0.01 to 10% by mass in terms of K 2 O (0.01 to 12% by mass in terms of KOH). ), More preferably 0.1 to 5% by mass (0.1 to 6% by mass in terms of KOH). Potassium ions in the mother liquor, carbonate ions, hydrogen carbonate ions are present, here was added potassium hydroxide, adjusted to K 2 O concentration in terms of potassium hydroxide in the solution is 0.01% or more Then, heavy metals such as iron, nickel, lead and chromium or magnesium as impurities can be precipitated as hydroxides and removed by subsequent solid-liquid separation operation. In particular, it is effective for removing iron. At the same time, magnesium ions can be similarly removed as hydroxides.
[0016]
On the other hand, if the K 2 O equivalent concentration of potassium hydroxide in the liquid exceeds 10% by mass, the precipitated hydroxide crystals tend to be small, which is not preferable for solid-liquid separation operation. Therefore, the K 2 O equivalent concentration of potassium hydroxide is adjusted to 10% by mass or less, and a part of the liquid containing the hydroxide seed crystals is added to the mother liquor after separating the potassium hydrogen carbonate crystals and circulated. Thus, it is preferable to obtain a large hydroxide crystal.
[0017]
Furthermore, when separating by filtration with a filter press, if the K 2 O equivalent concentration of potassium hydroxide in the liquid exceeds 10% by mass, the filter cloth deteriorates remarkably and is not preferable. It is preferable to adjust to 10% by mass or less by converting a part of potassium hydroxide into potassium carbonate. Here, if the gas discharged | emitted from the manufacturing process of a potassium hydrogen carbonate crystal is used as carbon dioxide gas, carbon dioxide gas can be used effectively. Furthermore, after blowing, the potassium carbonate concentration in the liquid is preferably 10 to 70% by mass, more preferably 35 to 50% by mass in terms of K 2 O equivalent. If the K 2 O equivalent concentration is 70% by mass or less, more preferably 50% by mass or less, the viscosity of the liquid can be prevented from becoming too high, which is preferable for solid-liquid separation. On the other hand, the K 2 O equivalent concentration is preferably 10% by mass or more, and more preferably 35% by mass or more because it is not necessary to use an unnecessarily large facility in the subsequent production of potassium hydrogencarbonate crystals.
[0018]
Depending on the concentration after the above-mentioned solid-liquid separation operation, potassium hydroxide having a high purity can be further added, and can be used for producing potassium hydrogencarbonate crystals. Through a series of operations, the mother liquor is handled so that it does not come into contact with the outside air and is not contaminated with foreign substances.
[0019]
(Calcination)
If potassium hydrogen carbonate is calcined, carbon dioxide and water vapor are released by the thermal decomposition shown in the following formula (2) to become potassium carbonate.
2KHCO 3 → K 2 CO 3 + CO 2 + H 2 O (2).
[0020]
Pore is generated by the escape of carbon dioxide and water vapor from the potassium hydrogen carbonate crystal. Highly active potassium carbonate can be obtained by controlling the number and size of the pores. In order to produce good pores, it is necessary that the particle size of the potassium hydrogen carbonate crystals before calcination is 100 to 1000 μm, more preferably 250 to 550 μm, most preferably 300 to 500 μm. preferable. If it is less than 100 μm, solid-liquid separation after crystallization is difficult, so that a potassium hydrogen carbonate cake having a high water content is put into a calcining furnace, and highly active potassium carbonate cannot be obtained. On the other hand, when the average particle diameter is more than 1000 μm, it takes time for firing, which is not preferable because productivity decreases.
[0021]
Here, in order to produce good pores, it is necessary to make the calcination conditions appropriate. As the calcination furnace, it is preferable to use an external heating kiln because temperature management and residence time management are easy and impurities are hardly mixed. When potassium hydrogen carbonate crystals are continuously added from one end of the kiln and heated from the outside, the potassium hydrogen carbonate crystals in the furnace are converted to potassium carbonate by the reaction of the formula (2) and taken out from the other end. At this time, it is preferable to introduce dry air into the calcination furnace and purge carbon dioxide generated by calcination.
[0022]
This dry air is required to have a dew point of 0 ° C. or lower and a temperature of 10 to 50 ° C. When the dew point of the dry air exceeds 0 ° C., not only the reaction of the formula (2) is difficult to proceed, but also the porous potassium carbonate obtained by calcination may absorb moisture, which is not preferable. The decomposition gas generated during calcination is highly humid, and moisture absorption can be prevented by quickly replacing it with dry air. In addition, by introducing low-temperature dry air, not only suppresses excessive temperature rise of the calcined object temperature, but also plays a role of lowering the temperature of porous potassium carbonate that is complicated to handle at high temperature after calcination. . Therefore, the temperature in the kiln is appropriately maintained by setting the temperature when the dry air is introduced to 10 to 50 ° C.
[0023]
Furthermore, the best product is obtained by calcining at a calcined material temperature of 100 to 400 ° C. while flowing from the other end of the kiln at a rate of 0.5 m 3 or more per 1 kg of porous potassium carbonate obtained by calcination. Was found to be obtained. When the introduction volume of dry air is less than 0.5 m 3 per 1 kg of porous potassium carbonate obtained by calcination, the reaction of formula (2) does not proceed rapidly, not only the productivity decreases but also the uniform fineness. It is not preferable because it does not become a hole.
[0024]
Further, it is preferable to keep the heating temperature of the kiln outer wall portion at 600 ° C. or higher and to set the calcined product temperature to 100 to 400 ° C., preferably 150 to 350 ° C., and most preferably 200 to 300 ° C. When the calcined product temperature is less than 100 ° C., the reaction of the formula (2) does not proceed promptly. On the other hand, if the temperature of the calcined product exceeds 400 ° C., the reaction of the formula (2) proceeds abruptly and the pores are crushed, which is not preferable. In addition, it is preferable that it is 1 to 10 hours, and it is more preferable that it is 2 to 5 hours for the time to retain in a calcination furnace. In the above temperature range, calcination does not proceed sufficiently with heating for less than 1 hour. In addition, if the calcination is performed for more than 10 hours, the possibility that the pores are collapsed is not preferable.
[0025]
(Crushing and sieving)
Although porous potassium carbonate having high activity can be obtained by the above-described method, it can be further pulverized to increase the surface area in order to improve the activity and dispersibility.
[0026]
As a pulverization method, a normal pulverization method such as an impact pulverizer (a pulverizer using a blade rotating at high speed), a jet mill (a pulverizer using a collision airflow), a ball mill, or the like can be used. In particular, when using an impact pulverizer equipped with a wind classifier, the particles discharged from the pulverizer are classified, and the coarse particles are pulverized while returning to the pulverizer again. Since potassium carbonate can be obtained, it is more preferable. Further, the use of a jet mill is also preferable because it is suitable for microparticulation such that the removal of coarse particles by sieving is unnecessary, and porous potassium carbonate having a desired particle diameter can be obtained with a high yield. The pulverization is preferably performed in dry air having a dew point of 0 ° C. or less and a temperature of 10 to 50 ° C., as in the case of calcination.
[0027]
The porous potassium carbonate of the present invention is particularly characterized by having many fine pores. It has many pores having a pore diameter of 0.1 to 1 μm, which can hardly be observed with potassium carbonate produced by the direct method. In addition, since the higher the volume per pore mass, the more active the potassium carbonate, the total pore volume with a pore diameter of 0.1 to 1 μm is preferably 0.08 mL / g, 0.1 mL / G or more is more preferable.
[0028]
Porous potassium carbonate in the present invention has good activity and high reactivity with drugs and solubility in water, so various pharmaceuticals, agricultural chemicals, synthetic raw materials for industrial chemicals, catalysts, food additives, photographic developers, It is suitably used for applications such as color formers, pH adjusters, acid adsorbents, detergents, dehumidifiers, acid gas removers, halogen gas removers, and glass raw materials.
[0029]
【Example】
[Example 1]
The following examples illustrate the invention. 37 wt% of potassium concentration in K 2 O in terms of overall, the concentration of which potassium hydroxide is 18% in K 2 O in terms, imposition of an aqueous solution comprising potassium hydroxide and potassium carbonate in a reaction vessel of 6 m 3 The liquid temperature was adjusted to 70 ° C. When carbon dioxide-containing gas having a concentration of 40% by volume was blown from the bottom of the reaction tank at 12 m 3 / min, potassium hydrogen carbonate crystals grew and precipitated. After 8 hours, the contents of the reaction vessel in the form of a slurry were extracted, and the solid phase was extracted by centrifugation. The collected potassium hydrogen carbonate cake was 4500 kg, the adhering moisture was 4% by mass in terms of dry mass, and the average particle size was 400 μm.
[0030]
Next, it moves to a calcination process. The potassium hydrogen carbonate cake was charged at 10 kg / min into a rotary kiln in which the heating temperature of the kiln outer wall was set to 880 ° C. At this time, the internal cake temperature was 400 ° C. At this time, dry air having a dew point of −5 ° C. and a temperature of 30 ° C. was kept flowing from the product outlet to the inlet at a flow rate of 10 m 3 / min. The temperature of the porous potassium carbonate collected from the outlet was 50 ° C.
[0031]
Further, a part of the taken-out porous potassium carbonate was pulverized in a dry air having a dew point of −10 ° C. by an impact pulverizer manufactured by Hosokawa Micron Corp. and ACM pulverizer ACM-5 type equipped with a wind classification function. When the properties of these porous potassium carbonates were confirmed, they were as shown in Table 1.
[0032]
The average particle size was measured by using a laser scattering diffraction type particle size distribution measuring device Microtrac FRA 9220 for the pulverized product, and by a low-tap sieving measurement for the unground product. In addition, for measuring the pore volume, Autosorb IIIB manufactured by Cantachrome (measurement range: pore diameter 0.001 to 0.2 μm) and a mercury intrusion porosimeter manufactured by CE Instruments (measurement range: pore diameter 0.2 μm). Used).
[0033]
Moreover, the reactivity with an acid was measured as an index of activity as an alkali catalyst. The reactivity with hydrochloric acid was evaluated by adding 4 g of potassium carbonate subjected to drying treatment to 400 g of 0.5% hydrochloric acid aqueous solution adjusted to 25 ° C. and reaching the pH of 5.
[0034]
[Table 1]
[Example 2 (comparative example)]
Except that the heating temperature of the outer wall of the kiln was 1200 ° C., potassium carbonate was obtained in the same manner as in the example. The internal cake temperature during calcination was 830 ° C. In the same manner as in the examples, a part thereof was pulverized and evaluated.
[0036]
[Table 2]
Although the potassium carbonate of Example 2 is porous, both the specific surface area and the pore volume are smaller than those of Example 1, and the reaction with the acid is slow. Therefore, it can be seen that the potassium carbonate crystal of Example 1 is superior in dispersibility and diffusibility and has higher activity.
[0038]
【The invention's effect】
By the production method of the present invention, it is possible to obtain porous potassium carbonate having high activity and good reactivity with drugs and water solubility. Therefore, the porous potassium carbonate of the present invention is used for various pharmaceuticals, agricultural chemicals, synthetic raw materials for industrial chemicals, catalysts, food additives, photographic developers, color formers, pH adjusters, acid adsorbents, detergents, dehumidifiers, acid gases. It is suitably used for usage such as a remover, a halogen gas remover, and a glass raw material.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline for carrying out the production of porous potassium carbonate of the present invention.
Claims (7)
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| JP2001391624A JP4061902B2 (en) | 2001-12-25 | 2001-12-25 | Method for producing porous potassium carbonate |
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| KR101191066B1 (en) | 2003-06-24 | 2012-10-15 | 아사히 가라스 가부시키가이샤 | Porous potassium carbonate having special pore structure and method for its production |
| JP4617934B2 (en) * | 2004-03-10 | 2011-01-26 | 旭硝子株式会社 | Reduction method of dioxins in fly ash of garbage incineration equipment |
| CN113998710B (en) * | 2020-07-28 | 2023-04-18 | 自然资源部天津海水淡化与综合利用研究所 | Method for separating potassium fluoride, potassium bromide, potassium carbonate and potassium bicarbonate mixed salt |
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| JPS56149317A (en) * | 1980-04-18 | 1981-11-19 | Asahi Glass Co Ltd | Manufacture of sodium hydrogencarbonate |
| JPS59121117A (en) * | 1982-12-28 | 1984-07-13 | Asahi Glass Co Ltd | Production of low-density sodium carbonate |
| JPS59223221A (en) * | 1983-06-02 | 1984-12-15 | Tokuyama Soda Co Ltd | Light granular alkali carbonate and its manufacture |
| JPS6046919A (en) * | 1983-08-25 | 1985-03-14 | Toyo Soda Mfg Co Ltd | Porous sodium carbonate having controlled alkalinity and its production |
| JPS60131823A (en) * | 1983-12-16 | 1985-07-13 | Tokuyama Soda Co Ltd | Manufacture of light-duty granular alkali carbonate |
| US4743439A (en) * | 1984-01-16 | 1988-05-10 | General Chemical Corporation | Wet calcination of alkali metal bicarbonates in hydrophobic media |
| DE3834807A1 (en) * | 1988-10-13 | 1990-05-10 | Kali Chemie Ag | METHOD FOR PRODUCING CARBONIC SALTS OF ALKALI METALS |
| JP3623267B2 (en) * | 1995-01-27 | 2005-02-23 | 月島機械株式会社 | Potassium carbonate production equipment |
| JP3899158B2 (en) * | 1997-04-02 | 2007-03-28 | 株式会社トクヤマ | Process for producing mono tertiary alkyl alkali metal carbonate |
| JP3948075B2 (en) * | 1997-10-01 | 2007-07-25 | 旭硝子株式会社 | Acid component removal agent and acid component removal method |
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