JP2006182646A - Method for producing liquefied petroleum gas mainly containing propane or butane - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a liquefied petroleum gas (LPG) having low concentration of ≤2C component and high propane and/or butane concentration from a carbon-containing raw material such as natural gas or a synthetic gas. <P>SOLUTION: The method for producing the LPG comprises a lower paraffin-producing step for producing a lower paraffin-containing gas which is a mixed gas containing a low boiling-point component which is a substance having a boiling point lower than that of propane and containing propane or butane as a main component in the presence of a catalyst from the synthetic gas and a separation step for separating the low boiling-point component from the lower paraffin-containing gas to obtain the LPG mainly containing propane or butane. The method for producing the LPG comprises, further, a synthetic gas-producing step for producing the synthetic gas from the carbon-containing raw material and a recycling step for recycling the separated low boiling-point component as a raw material for the synthetic gas-producing step. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

【００２２】
メタンと二酸化炭素（ＣＯ₂）とを反応させる方法（ＣＯ₂リフォーミング）の場合、その反応は次式で示される。
【００２３】
【化２】

【００２４】
メタンとスチームと二酸化炭素（ＣＯ₂）とを反応させる方法（スチーム／ＣＯ₂混合リフォーミング）の場合、その反応は次式で示される。
【００２５】
【化３】

【００２６】
上記触媒を用いてスチームリフォーミングを行う場合、その反応温度は好ましくは６００〜１２００℃、より好ましくは６００〜１０００℃であり、その反応圧力は、好ましくは０．０９８ＭＰａＧ〜３．９ＭＰａＧ、より好ましくは０．４９ＭＰａＧ〜２．９ＭＰａＧ（Ｇはゲージ圧であることを示す）である。また、この反応を固定床方式で行う場合、そのガス空間速度（ＧＨＳＶ）は好ましくは１，０００〜１０，０００ｈｒ^-1、より好ましくは２，０００〜８，０００ｈｒ^-1である。含炭素原料に対するスチーム使用割合を示すと、含炭素原料（リサイクル原料を含めＣＯ₂を除く）の炭素１モル当り、好ましくはスチーム（Ｈ₂Ｏ）０．５〜２モル、より好ましくは０．５〜１．５モル、さらに好ましくは０．８〜１．２モルの割合である。
【００２７】
上記触媒を用いてＣＯ₂リフォーミングを行う場合、その反応温度は好ましくは５００〜１２００℃、より好ましくは６００〜１０００℃であり、その反応圧力は、好ましくは０．４９ＭＰａＧ〜３．９ＭＰａＧ、より好ましくは０．４９ＭＰａＧ〜２．９ＭＰａＧである。また、上記触媒を用いてＣＯ₂リフォーミングを固定床方式で行う場合、そのガス空間速度（ＧＨＳＶ）は１，０００〜１０，０００ｈｒ^-1、好ましくは２，０００〜８，０００ｈｒ^-1である。含炭素原料に対するＣＯ₂の使用割合を示すと、含炭素原料（リサイクル原料を含めＣＯ₂を除く）中の炭素１モル当り、好ましくはＣＯ₂２０〜０．５モル、好ましくは１０〜１モルの割合である。
【００２８】
上記触媒を用いて、含炭素原料にスチームとＣＯ₂の混合物を反応させて合成ガスを製造する（スチーム／ＣＯ₂混合リフォーミングを行う）場合、スチームとＣＯ₂との混合割合は特に制約されないが、一般的には、Ｈ₂Ｏ／ＣＯ₂モル比で、０．１〜１０で、その反応温度は好ましくは５５０〜１２００℃、より好ましくは６００〜１０００℃であり、その反応圧力は、好ましくは０．２９ＭＰａＧ〜３．９ＭＰａＧ、より好ましくは０．４９ＭＰａＧ〜２．９ＭＰａＧである。また、この反応を固定床方式で行う場合、そのガス空間速度（ＧＨＳＶ）は好ましくは１，０００〜１０，０００ｈｒ^-1、より好ましくは２，０００〜８，０００ｈｒ^-1である。含炭素原料（リサイクル原料を含めＣＯ₂を除く）に対するスチーム使用割合を示すと、含炭素原料（リサイクル原料を含めＣＯ₂を除く）の炭素１モル当り、好ましくはスチーム（Ｈ₂Ｏ）０．５〜２モル、より好ましくは０．５〜１．５モル、さらに好ましくは０．５〜１．２モルの割合である。
【００２９】
特開２０００−２８８３９４号公報に記載される触媒は、下記式で表される組成を有する複合酸化物からなり、ＭおよびＣｏが該複合酸化物中で高分散化されていることを特徴とするリホーミング用触媒である。
ａＭ・ｂＣｏ・ｃＭｇ・ｄＣａ・ｅＯ
（この式中、ａ，ｂ，ｃ，ｄ，ｅはモル分率であり、ａ＋ｂ＋ｃ＋ｄ＝１、０．０００１≦ａ≦０．１０、０．０００１≦ｂ≦０．２０、０．７０≦（ｃ＋ｄ）≦０．９９９８、０＜ｃ≦０．９９９８、０≦ｄ＜０．９９９８、ｅ＝元素が酸素と電荷均衡を保つのに必要な数である。また、Ｍは周期律表第６Ａ族元素、第７Ａ族元素、Ｃｏを除く第８族遷移元素、第１Ｂ族元素、第２Ｂ族元素、第４Ｂ族元素およびランタノイド元素の少なくとも１種類の元素である。）
特開２０００−４６９号公報に記載される触媒は、下記式で表わされる組成を有する複合酸化物からなり、ＭおよびＮｉが該複合酸化物中で高分散化されていることを特徴とするリホーミング用ニッケル系触媒である。
ａＭ・ｂＮｉ・ｃＭｇ・ｄＣａ・ｅＯ
（この式中、ａ、ｂ、ｃ、ｄ、ｅはモル分率であり、ａ＋ｂ＋ｃ＋ｄ＝１、０．０００１≦ａ≦０．１０、０．０００１≦ｂ≦０．１０、０．８０≦（ｃ＋ｄ）≦０．９９９８、０＜ｃ≦０．９９９８、０≦ｄ＜０．９９９８、ｅ＝元素が酸素と電荷均衡を保つのに必要な数であり、Ｍは周期律表第３Ｂ族元素、第４Ａ族元素、第６Ｂ族元素、第７Ｂ族元素、第１Ａ族元素およびランタノイド元素の少なくとも１種類の元素である。）
これらの触媒も、ＷＯ９８／４６５２４号公報に記載の触媒と同様にして用いることができる。
【００３０】
〔低級パラフィン製造工程〕
低級パラフィン製造工程で得られる低級パラフィン含有ガスは、プロパンまたはブタンを主成分とする。液化特性の観点から、低級パラフィン含有ガス中のプロパンとブタンの合計の含有量は、６０モル％以上であることが好ましく、７０モル％以上であることがより好ましい。
【００３１】
さらに、燃焼性および蒸気圧特性の観点から、ブタンよりプロパンが多いことが好ましく、低級パラフィン含有ガス中のプロパンの含有量は、５０モル％以上であることが好ましく、６０モル％以上であることがより好ましい。
【００３２】
本発明では、低級パラフィン含有ガスにはプロパンの沸点より低い沸点を有する低沸点成分が含まれる。低沸点成分の例としてはエタンが挙げられる。低沸点成分にメタンやエチレンが含まれていてもよい。低沸点成分の含有量は、本発明の効果を好適に得るために、５モル％以上３０モル％以下が好ましく、１０モル％以上２０モル％以下がより好ましい。
【００３３】
本発明の低級パラフィン製造工程には、合成ガスから上記低級パラフィン含有ガスを得る反応を促進することのできる触媒を用いることができる。例えば、メタノール合成触媒成分とゼオライト触媒成分とを含有する触媒を用いることができる。ここで、メタノール合成触媒成分とは、ＣＯ＋２Ｈ₂→ＣＨ₃ＯＨの反応において触媒作用を示すものを指す。また、ゼオライト触媒成分とは、メタノールの炭化水素への縮合反応および／またはジメチルエーテルの炭化水素への縮合反応において触媒作用を示すゼオライトを指す。
【００３４】
上記触媒として、たとえば、メタノール合成用触媒である４質量％Ｐｄ／ＳｉＯ₂、Ｃｕ−Ｚｎ−Ａｌ混合酸化物［Ｃｕ：Ｚｎ：Ａｌ＝４０：２３：３７（原子比）］およびＣｕ系低圧メタノール合成用触媒（商品名：ＢＡＳＦ Ｓ３−８５）から選ばれる少なくとも一種と、ＳｉＯ₂／Ａｌ₂Ｏ₃＝７．６の高シリカＹ型ゼオライトとを混合した混合触媒を用いることができる。前者と後者の混合比は、例えば質量比で１：１程度とすることができる。
【００３５】
また、ゼオライト触媒成分に対するメタノール合成触媒成分の含有比率（質量基準）は、０．５以上［メタノール合成触媒成分／ゼオライト触媒成分］であることが好ましく、１．０以上［メタノール合成触媒成分／ゼオライト触媒成分］であることがより好ましい。また、ゼオライト触媒成分に対するメタノール合成触媒成分の含有比率（質量基準）は、３．０以下［メタノール合成触媒成分／ゼオライト触媒成分］であることが好ましく、２．０以下［メタノール合成触媒成分／ゼオライト触媒成分］であることがより好ましい。ゼオライト触媒成分に対するメタノール合成触媒成分の含有比率を上記の範囲にすることにより、より高選択率、高収率でプロパンを製造することができる。
【００３６】
メタノール合成触媒成分は、メタノール合成触媒としての機能を有し、ゼオライト触媒成分は、メタノールおよび／またはジメチルエーテルの炭化水素への縮合反応に対して酸性が調整された固体酸ゼオライト触媒としての機能を有する。そのため、ゼオライト触媒成分に対するメタノール合成触媒成分の含有比率は、触媒の持つメタノール合成機能とメタノールからの炭化水素生成機能の相対比に反映される。また、本発明において一酸化炭素と水素を反応させて主成分がプロパンまたはブタンである液化石油ガスを製造するにあたって、一酸化炭素と水素をメタノール合成触媒成分によってメタノールに十分転化させることが望まれ、かつ、生成したメタノールをゼオライト触媒成分によって十分に主成分がプロパンまたはブタンである液化石油ガスに転化させることが望まれる。ゼオライト触媒成分に対するメタノール合成触媒成分の含有比率（質量基準）を０．５以上［メタノール合成触媒成分／ゼオライト触媒成分］とすることにより、一酸化炭素と水素をメタノール合成触媒成分によってメタノールに好適に転化させることができる。この観点から、さらには、上記含有比率が０．８以上［メタノール合成触媒成分／ゼオライト触媒成分］であることがより好適である。また、生成したメタノールがプロパンまたはブタンを主成分とする液化石油ガスに選択的に転化するには０．８以上［メタノール合成触媒成分／ゼオライト触媒成分］であることが好ましい。また、ゼオライト触媒成分に対するメタノール合成触媒成分の含有比率（質量基準）を３．０以下［メタノール合成触媒成分／ゼオライト触媒成分］とすることにより、生成したメタノールをゼオライト触媒成分によって好適に主成分がプロパンまたはブタンである液化石油ガスに転化することができる。この観点から、さらには、上記含有比率が２．０以下［メタノール合成触媒成分／ゼオライト触媒成分］であることがより好適である。
【００３７】
そのような触媒の組成としてのメタノール合成触媒成分は、一酸化炭素と水素からメタノールが合成できる触媒としての機能を持つものであればよい。一般にメタノール合成触媒と知られる市販のものでも、文献等に明らかにされているものでも良い。そのようなものとしては、Ｃｕ−Ｚｎ系、Ｃｕ−Ｚｎ−Ｃｒ系、Ｃｕ−Ｚｎ−Ａｌ系、Ｃｕ−Ｚｎ−Ａｇ系、Ｃｕ−Ｚｎ−Ｍｎ−Ｖ系、Ｃｕ−Ｚｎ−Ｍｎ−Ｃｒ系、Ｃｕ−Ｚｎ−Ｍｎ−Ａｌ−Ｃｒ系などいずれもＣｕ−Ｚｎ系およびそれに第三成分が加わったもの、あるいは、Ｎｉ−Ｚｎ系のもの、Ｍｏ系のもの、Ｎｉ−炭素系のもの、さらにはＰｄなど貴金属系のものなどが挙げられる。
【００３８】
上記触媒の組成としてのゼオライト触媒成分は、生成したメタノールをプロパンまたはブタンが主成分である液化石油ガスに選択的に転化できる触媒としての機能をもつものであればよい。そのようなものとしては、メタノールおよび／またはジメチルエーテルの炭化水素への縮合反応に対して酸性が調整された固体酸ゼオライト触媒としての機能を有するものから選ばれる。そのような触媒のゼオライト触媒成分の構造、物性としては、一般にメタノールおよび／またはジメチルエーテルから低級オレフィン炭化水素への縮合反応に高い選択性を示すＳＡＰＯ−３４などの小細孔ゼオライトないしモルデナイトなどのような細孔内での反応分子の拡散が３次元でないゼオライトよりも、一般にメタノールおよび／またはジメチルエーテルからアルキル置換芳香族炭化水素への縮合反応に高い選択性を示すＺＳＭ−５、ＭＣＭ−２２などの中細孔ゼオライトないしベータやＹ型などの大細孔ゼオライトなどの細孔内での反応分子の拡散が３次元であるゼオライトが好ましい。そのときＳｉＯ₂／Ａｌ₂Ｏ₃モル比が１０〜５０の値を有するいわゆる高シリカゼオライトが好ましく、そのようなものとして例えばＵＳＹや高シリカタイプのベータなどの金属イオン交換などによって酸性が調整された固体酸ゼオライトが用いられる。
【００３９】
本発明の低級パラフィン製造工程は、上記のような触媒を用いて一酸化炭素と水素とを反応させ、液化石油ガス、好ましくは主成分がプロパンである液化石油ガスを製造するには、次のような操作条件にて行うことが好ましい。
【００４０】
反応温度は、メタノール合成触媒成分とゼオライト触媒成分各々が優れた活性を示すのに好適な温度として、２７０℃以上が好ましく、３００℃以上がより好ましい。また、反応温度は、触媒の使用制限温度の観点から、また平衡規制と反応熱除去回収の容易さの観点から、４００℃以下が好ましく、３７０℃以下がより好ましい。
【００４１】
反応圧力は、メタノール合成触媒成分が優れた活性を示す圧力として、１．０ＭＰａ以上が好ましく、２．０ＭＰａ以上がより好ましい。また、反応圧力は、メタノール合成触媒成分が優れた活性を示すのに好適で、それを超えると圧縮機の動力として余分なエネルギーを用いることとなり本発明の技術の経済性が低下するので、１０ＭＰａ以下が好ましく、５ＭＰａ以下がより好ましい。
【００４２】
ガス空間速度はメタノール合成触媒成分とゼオライト触媒成分各々が優れた転化率を示す接触時間を与えればよく、それ未満では製造されるＬＰＧ生産量に対して必要以上に大きな反応器を用意することとなり本発明の技術の経済性が低下するので、５００ｈｒ^-1以上が好ましく、２０００ｈｒ^-1以上がより好ましい。また、ガス空間速度は、メタノール合成触媒成分とゼオライト触媒成分各々が優れた転化率を示す接触時間を与えるために、１００００ｈｒ^-1以下が好ましく、５０００ｈｒ^-1以下がより好ましい。
【００４３】
低級パラフィン製造のための反応器に送入されるガス中の一酸化炭素の濃度は、原料ガス一酸化炭素と水素が反応するのに好適な一酸化炭素の圧力すなわち分圧を確保するとともに原料原単位向上のため、２０モル％以上が好ましく、２５モル％以上がより好ましい。また、反応器に送入されるガス中の一酸化炭素の濃度は、一酸化炭素の転化率の観点から、４０モル％以下が好ましく、３５モル％以下がより好ましい。
【００４４】
低級パラフィン製造のための原料ガスにおいて一酸化炭素と水素の濃度は、一酸化炭素を好適に反応させるためには、一酸化炭素１モルに対して１．５モル以上が好ましく、１．８モル以上がより好ましい。また、この原料ガスにおいて水素の濃度は、一酸化炭素が好適に反応し主成分がプロパンまたはブタンである液化石油ガスを得ることのできる量があればよく、余剰の水素は原料ガスの全圧を不必要に上げることになり技術の経済性を低下させるため、一酸化炭素１モルに対して３．０モル以下が好ましく、２．３モル以下がより好ましい。
【００４５】
反応器に挿入されるガスは、低級パラフィン製造の原料である一酸化炭素および水素に、二酸化炭素を加えたものであってもよい。また、その二酸化炭素としては、反応器から排出される二酸化炭素をリサイクルするあるいはそれに見合う量を用いることによって、反応器の中で一酸化炭素からのシフト反応による二酸化炭素の生成を実質的に軽減ないしさせなくすることも出来る。また、反応器に挿入されるガスには水蒸気を含有させることもできる。また、反応器に挿入されるガスは分割して挿入して反応温度の制御に用いることも出来る。
【００４６】
反応は固定床、流動床、移動床などで行うことができるが、反応温度の制御と触媒の再生方法の両面から選定することが好ましい。たとえば、固定床としては、内部多段クエンチ方式などのクエンチ型反応器、多管型反応器、複数の熱交換器を内包するなどの多段型反応器、多段冷却ラジアルフロー方式や二重管熱交換方式や冷却コイル内蔵式や混合流方式などその他の反応器、などを用いることが出来る。
【００４７】
また、触媒は、温度制御を目的として、シリカ、アルミナなどあるいは不活性で安定な熱伝導体で希釈して、あるいは、熱交換器表面に塗布して用いることもできる。
【００４８】
〔分離工程〕
分離工程において、上記低級パラフィン含有ガスから、水分などを必要に応じて分離したのち、低沸点成分を分離する。これによってプロパンまたはブタンを主成分とする液化石油ガスを得ることができる。適宜、高沸点パラフィンガス（ブタンより沸点の高い成分）を分離することもできる。液化石油ガスを得るために、必要に応じて加圧および／または冷却を行っても良い。
【００４９】
この分離は、例えば気液分離、吸収分離、蒸留など公知の方法によって行うことができる。より具体的には、加圧常温での気液分離や吸収分離、冷却しての気液分離や吸収分離あるいはその組み合わせによることができる。あるいは膜分離や吸着分離によることも、これらと気液分離、吸収分離、蒸留との組み合わせによることもできる。低沸点成分を分離するには、製油所で通常用いられるガス回収プロセス（「石油精製プロセス」石油学会／編、講談社サイエンティフィク、１９９８年、ｐ２８〜ｐ３２記載）を適用することができる。上記低沸点成分の分離方法としては、上記高沸点パラフィンガス（ブタンより沸点の高い成分）あるいはガソリンなどを吸収液として用い、プロパンまたはブタンを主成分とする液化石油ガスを吸収させる吸収プロセスが好ましい。
【００５０】
民生用としては、使用時の安全性の観点から、例えば、分離によってＬＰＧ中の上記低沸点成分の含有量を５モル％以下とする。
【００５１】
〔リサイクル工程〕
分離された低沸点成分は、改質工程の原料として再利用することができる物質を含む。従って、この残ガスは改質工程にリサイクルされる。リサイクルするためには、適宜リサイクルラインに昇圧手段を設けるなど、リサイクルに係る公知の技術を採用することができる。
【００５２】
【実施例】
図１に本発明の方法を実施するに好適なＬＰＧ製造装置の一例を示す。
【００５３】
含炭素原料としてメタンがライン１１および１２を経て改質器１に供給される。ここでは水蒸気改質を行うため、図示しないが水蒸気がライン１２に供給される。また、改質器は改質のために必要な熱を供給するための加熱手段も備えるが、図では省略する。
【００５４】
改質器内に備えられた改質触媒１ａの存在下にメタンが改質され、水素、一酸化炭素、二酸化炭素および水蒸気を含む合成ガスが得られる。
【００５５】
この合成ガスは反応器２に供給され、反応器内に備えられた触媒２ａの存在下に合成ガスからエタン、プロパン、ブタンを含む生成ガスが得られる。
【００５６】
この生成ガスは分離器３に供給される。常温加圧蒸留により、塔底からプロパンの沸点以上の沸点を持つ物質が得られ、塔頂からプロパンの沸点より低い沸点を持つ物質が残ガスとして得られる。こうしてライン１５から製品となるＬＰＧが得られ、リサイクルライン１６により残ガスがリサイクルされる。
【００５７】
図示しないが、昇圧機、熱交換器、バルブ、計装制御装置などは、必要に応じて設けられる。
【００５８】
上記構成の装置を用い、ＬＰＧを製造した。条件および結果を以下に記す。
【００５９】
（低級パラフィンの製造）
メタノール合成触媒成分として市販のＣｕ−Ｚｎ系メタノール合成触媒（日本ズードヘミー社製）を機械的に粉末にしたものを用意した。別途、ゼオライト触媒成分として、ＳｉＯ₂／Ａｌ₂Ｏ₃モル比が１４．５の値を有するプロトン型ＺＳＭ−５ゼオライト粉末を調製した。このメタノール合成触媒成分とゼオライト触媒成分とを質量基準で同量均一混合して、加圧成型・整粒したのち、水素気流中にて３００℃、３時間還元して触媒を得た。
【００６０】
この調製した触媒を反応管に充填して、組成が水素６２．０モル％、一酸化炭素３１．０モル％、二酸化炭素５．０モル％、メタン２．０モル％の原料ガスを流通させた。反応条件は、反応温度３２５℃、反応圧力２．０ＭＰａ、ガス空間速度３０００ｈｒ^-1とした。生成物をガスクロマトグラフィーにより分析したところ、一酸化炭素の転化率は７１％であった。一酸化炭素の二酸化炭素へのシフト反応転化率は３５％、炭化水素への転化率は３７％であった。また、生成した炭化水素ガスの炭素基準で７５％がプロパンおよびブタンであり、そのプロパンおよびブタンの内訳は炭素基準でプロパンが５６％、ブタンが４４％であった。
【００６１】
（低沸点成分の分離、リサイクル）
ＬＰＧの製造からの反応ガスを気液分離ののち、モレキュラーシーブにて乾燥後、０℃付近に保持されたオクタン溶液にバブルさせる方法でメタン３．７モル％、エタンおよびエチレン１．２モル％、二酸化炭素２１．１モル％、未反応一酸化炭素１２．０モル％および水素６２．０モル％の組成のガスを低沸点分として分離して、圧縮機にて２．５ＭＰａまで昇圧して、合成ガス製造工程に原料ガスの一部６７モル％として送入した。
【００６２】
（合成ガス製造）
ＬＰＧの製造工程からの低沸点分リサイクルガス６７．０モル％、天然ガス１４．７モル％、スチーム１４．８モル％、二酸化炭素３．５モル％の組成の原料ガスを、ＷＯ９８／４６５２４号公報触媒調製例９に従って調製したＲｕ／焼結低表面積化マグネシア触媒が充填された外熱式反応管型の装置にて、触媒を予め水素気流中９００℃で１ｈｒ還元処理を行ったのち、反応温度８７０℃、圧力２．１ＭＰａ、ＧＨＳＶ２０００ｈｒ^-1の操作条件にて改質して水素５８モル％、一酸化炭素２９モル％、二酸化炭素６モル％、メタン７モル％の組成の合成ガスを得た。この組成からこの合成ガスは低級パラフィンの製造で原料として使うことができる。
【００６３】
【発明の効果】
本発明により、天然ガスなどの含炭素原料あるいは合成ガスからプロパンおよび／またはブタンを選択性良く製造することができる。
【図面の簡単な説明】
【図１】本発明を実施するに好適なＬＰＧ製造装置の一例について、主要な構成を示すプロセスフロー図である。
【符号の説明】
１ 改質器
１ａ 改質触媒
２ 反応器
２ａ 触媒
３ 分離器
１１、１２、１３、１４、１５ ライン
１６ リサイクルライン[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing liquefied petroleum gas from synthesis gas, and also relates to a method for producing liquefied petroleum gas from a carbon-containing raw material such as natural gas.
[0002]
[Prior art]
Liquefied petroleum gas (LPG) refers to a compressed petroleum-based or natural gas-based hydrocarbon that is gaseous at normal temperature and pressure, or simultaneously cooled to a liquid state, and its main component is propane or butane. Liquefied petroleum gas is useful as a fuel for households and mobiles.
[0003]
Non-Patent Document 1 discloses a method for producing LPG from synthesis gas obtained by reforming hydrocarbons such as methane. In this document, 4 wt% Pd / SiO2, which is a catalyst for methanol synthesis. ₂ Cu—Zn—Al mixed oxide [Cu: Zn: Al = 40: 23: 37 (atomic ratio)] or Cu-based catalyst for low-pressure methanol synthesis (trade name: BASF S3-85) and SiO ₂ / Al ₂ O _Three A method for producing a C2-C4 paraffin with a selectivity of 69-85% from a synthesis gas via methanol and dimethyl ether using a hybrid catalyst comprising a high-silica Y-type zeolite of = 7.6 is disclosed. However, it cannot be said that the content of components having 2 or less carbon atoms in the product is low, and the composition of the product is not suitable for LPG products.
[0004]
[Non-Patent Document 1]
“Selective Synthesis of LPG from Synthesis Gas”, Kaoru Fujimoto et. al. Bull. Chem. Soc. Jpn, 58, 3059-3060 (1985)
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a method capable of producing propane and / or butane from synthesis gas with high selectivity and producing LPG having a low concentration of components having 2 or less carbon atoms and a high concentration of propane and / or butane. That is.
[0006]
Another object of the present invention is to provide a method capable of producing LPG having a low concentration of components having 2 or less carbon atoms and a high propane and / or butane concentration from a carbon-containing raw material such as natural gas.
[0007]
[Means for Solving the Problems]
According to the present invention, a lower paraffin-containing gas, which is a mixed gas containing propane or butane as a main component, containing a low-boiling component, which is a substance having a boiling point lower than that of propane, is produced from synthesis gas in the presence of a catalyst. Lower paraffin production process,
A separation step of separating the low boiling point component from the lower paraffin-containing gas to obtain a liquefied petroleum gas mainly composed of propane or butane;
A process for producing liquefied petroleum gas mainly composed of propane or butane is provided.
[0008]
According to the present invention, there is also provided a synthesis gas production process for producing synthesis gas from a carbon-containing raw material, and a low-boiling component that is a substance having a boiling point lower than that of propane in the presence of a catalyst from the synthesis gas. A lower paraffin production process for producing a lower paraffin-containing gas which is a mixed gas mainly composed of
A separation step of separating the low boiling point component from the lower paraffin-containing gas to obtain a liquefied petroleum gas mainly composed of propane or butane;
A recycling step of recycling the separated low boiling point component as a raw material for the synthesis gas production step;
A process for producing liquefied petroleum gas mainly composed of propane or butane is provided.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
[Syngas production process]
The carbon-containing raw material is a substance containing carbon, and H ₂ O, O ₂ And CO ₂ Reacts with at least one selected from ₂ Those capable of generating CO and CO can be used, and those known as a raw material for synthesis gas can be used. For example, lower hydrocarbons such as methane and ethane can be used. Natural gas, naphtha, coal and the like can also be used.
[0010]
Since a catalyst is used in the present invention, the carbon-containing raw material is preferably one having a low content of a catalyst poisoning substance such as sulfur. Moreover, when a catalyst poisoning substance is contained in a carbon-containing raw material, the process of removing a catalyst poisoning substance, such as desulfurization, can be employ | adopted as needed.
[0011]
The synthesis gas is a mixed gas containing hydrogen and carbon monoxide, and may be a mixed gas composed of hydrogen and carbon monoxide, or may be mixed with hydrogen like a reformed gas obtained by reforming natural gas. A mixed gas containing carbon dioxide and water vapor in addition to carbon oxide may be used. Or the coal gas obtained by coal gasification may be sufficient.
[0012]
The synthesis gas production process is a process for producing the synthesis gas from the carbon-containing raw material, and can be performed by a known method. For example, when natural gas is used as a raw material, it can be performed by a known reforming method such as a steam reforming method or an autothermal reforming method. Steam necessary for steam reforming, oxygen necessary for autothermal reforming, and the like can be supplied as necessary. When coal is used as a raw material, synthesis gas can be produced using an air-blown gasification furnace or the like.
[0013]
Furthermore, for example, a shift reactor can be provided downstream of the reformer, and the composition of the synthesis gas can be adjusted by the shift reaction.
[0014]
The preferred composition of the synthesis gas produced from the synthesis gas production process for the present invention is that the hydrogen / CO molar ratio is 7/3 = 2.3 from the stoichiometry for the production of lower paraffins. Since hydrogen is produced by a shift reaction with water produced by the conversion reaction from LPG to LPG, the hydrogen concentration in the synthesis gas is set to 1. to 1 mol of carbon monoxide in order to react carbon monoxide suitably. 5 mol or more is preferable, 1.8 mol or more is more preferable, and it is sufficient that carbon monoxide reacts appropriately so that liquefied petroleum gas whose main component is propane or butane can be obtained. In order to unnecessarily increase the total pressure of the gas and lower the economic efficiency of the technology, the hydrogen concentration is preferably 3.0 mol or less, more preferably 2.3 mol or less with respect to 1 mol of carbon monoxide.
[0015]
In order to produce a synthesis gas having the above preferred composition, the supply ratio of the carbon-containing raw material and steam, oxygen, and carbon dioxide, the type of synthesis gas production catalyst, and the operating conditions of the reaction may be selected as appropriate. For example, as a raw material gas for a natural gas reformer, a gas having a composition in which the steam / methane molar ratio is 1.0 and the carbon dioxide / methane molar ratio is 0.4 is used. In an externally heated multi-tube reaction tube type apparatus filled with a magnesia catalyst, reaction temperature (catalyst layer outlet temperature) 800 to 900 ° C., pressure 1 to 4 MPa, gas space velocity (GHSV) 2000 hr ^-1 It can be performed under the operating conditions.
[0016]
When reforming using steam in the synthesis gas production, the steam raw material carbon ratio (S / C) is preferably 1.5 or less, more preferably 0.8 to 1.2 from the viewpoint of energy efficiency. Although it is preferable, at such a low value, the possibility of carbon deposition cannot be ignored. On the other hand, when the low-boiling components obtained in the separation process are recycled to the synthesis gas production process, not only methane contained in these components but also ethane or ethylene becomes carbon-containing raw materials, and those contained in these components are shifted. The carbon dioxide gas produced by the reaction is also CO ₂ Since it can be returned to the synthesis gas by the reforming reaction, the raw material intensity can be reduced, and even if the S / C is set to a low value as described above, CO ₂ The reforming reaction can reduce the possibility of carbon deposition. When the above-mentioned recycling is performed and synthesis gas production is performed at a low S / C, good conditions as described in, for example, WO 98/46524, JP 2000-288394 A, or JP 2000-469 A It is preferable to use a catalyst having a low carbon deposition activity while having a good synthesis gasification reaction activity. Hereinafter, these catalysts will be described.
[0017]
The catalyst described in WO98 / 46524 is a catalyst in which at least one catalyst metal selected from rhodium, ruthenium, iridium, palladium and platinum is supported on a support made of a metal oxide, The specific surface area of the catalyst is 25m ² / G and the electronegativity of the metal ions in the carrier metal oxide is 13.0 or less, and the amount of the catalyst metal supported is 0.0005 to 0 with respect to the carrier metal oxide in terms of metal. The catalyst is 1 mol%. Furthermore, from the viewpoint of preventing carbon deposition, the electronegativity is preferably 4 to 12, and the specific surface area of the catalyst is 0.01 to 10 m. ² / G is preferred.
[0018]
The electronegativity of metal ions in the metal oxide is defined by the following formula.
Xi = (1 + 2i) Xo
Here, Xi is the electronegativity of the metal ion, Xo is the electronegativity of the metal, and i is the number of valence electrons of the metal ion. When the metal oxide is a composite metal oxide, the average metal ion electronegativity is used, and the value is determined based on the electronegativity of each metal ion contained in the composite metal oxide. The sum of the product multiplied by the mole fraction of the product. Electronegativity of metal (X _o ) Uses Pauling's electronegativity. For Pauling's electronegativity, the values described in Table 15.4 of “Ryoichi Fujishiro, Moore Physical Chemistry (lower) (4th edition), Tokyo Kagaku Dojin, P707 (1974)” are used. The electronegativity of metal ions in the metal oxide is described in detail, for example, in “Catalyst Society, Catalyst Course, Vol. 2, P145 (1985)”.
[0019]
In this catalyst, the metal oxide includes a metal oxide containing one or more metals such as Mg, Ca, Ba, Zn, Al, Zr, and La. An example of such a metal oxide is magnesia (MgO).
[0020]
In the case of a method of reacting methane and steam (steam reforming), the reaction is represented by the following equation.
[0021]
[Chemical 1]

[0022]
Methane and carbon dioxide (CO ₂ ) And the reaction (CO ₂ In the case of reforming), the reaction is expressed by the following equation.
[0023]
[Chemical 2]

[0024]
Methane, steam and carbon dioxide (CO ₂ ) Reaction (steam / CO ₂ In the case of (mixing reforming), the reaction is shown by the following formula.
[0025]
[Chemical 3]

[0026]
When steam reforming is performed using the catalyst, the reaction temperature is preferably 600 to 1200 ° C., more preferably 600 to 1000 ° C., and the reaction pressure is preferably 0.098 MPaG to 3.9 MPaG, more preferably. Is 0.49 MPaG to 2.9 MPaG (G indicates a gauge pressure). When this reaction is carried out in a fixed bed system, the gas space velocity (GHSV) is preferably 1,000 to 10,000 hr. ^-1 , More preferably 2,000 to 8,000 hr ^-1 It is. The steam usage rate relative to carbon-containing raw materials is shown as follows. ₂ Preferably steam (H ₂ O) 0.5 to 2 mol, more preferably 0.5 to 1.5 mol, and still more preferably 0.8 to 1.2 mol.
[0027]
CO using the above catalyst ₂ When performing reforming, the reaction temperature is preferably 500 to 1200 ° C., more preferably 600 to 1000 ° C., and the reaction pressure is preferably 0.49 MPaG to 3.9 MPaG, more preferably 0.49 MPaG to 2 .9 MPaG. In addition, using the above catalyst, CO ₂ When reforming is performed in a fixed bed system, the gas space velocity (GHSV) is 1,000 to 10,000 hr. ^-1 , Preferably 2,000 to 8,000 hr ^-1 It is. CO for carbon-containing raw materials ₂ The carbon-containing raw materials (CO ₂ CO) per mole of carbon in the ₂ The ratio is 20 to 0.5 mol, preferably 10 to 1 mol.
[0028]
Using the above catalyst, steam and CO ₂ To produce synthesis gas (steam / CO ₂ When performing mixed reforming), steam and CO ₂ The mixing ratio is not particularly limited, but in general, H ₂ O / CO ₂ The molar ratio is 0.1 to 10, the reaction temperature is preferably 550 to 1200 ° C., more preferably 600 to 1000 ° C., and the reaction pressure is preferably 0.29 MPaG to 3.9 MPaG, more preferably 0.49 MPaG to 2.9 MPaG. When this reaction is carried out in a fixed bed system, the gas space velocity (GHSV) is preferably 1,000 to 10,000 hr. ^-1 , More preferably 2,000 to 8,000 hr ^-1 It is. Carbon-containing materials (CO including recycled materials) ₂ The percentage of steam used with respect to carbon dioxide is excluded. ₂ Preferably steam (H ₂ O) 0.5 to 2 mol, more preferably 0.5 to 1.5 mol, and still more preferably 0.5 to 1.2 mol.
[0029]
The catalyst described in JP-A-2000-288394 is composed of a complex oxide having a composition represented by the following formula, and M and Co are highly dispersed in the complex oxide. It is a catalyst for reforming.
aM ・ bCo ・ cMg ・ dCa ・ eO
(In this formula, a, b, c, d, e are mole fractions, a + b + c + d = 1, 0.0001 ≦ a ≦ 0.10, 0.0001 ≦ b ≦ 0.20, 0.70 ≦ ( c + d) ≦ 0.9998, 0 <c ≦ 0.9998, 0 ≦ d <0.9998, e = a number necessary for the element to maintain a charge balance with oxygen, and M is a periodic table 6A Group element, Group 7A element, Group 8 transition element excluding Co, Group 1B element, Group 2B element, Group 4B element, and lanthanoid element.)
The catalyst described in Japanese Patent Application Laid-Open No. 2000-469 is made of a complex oxide having a composition represented by the following formula, and M and Ni are highly dispersed in the complex oxide. It is a nickel-based catalyst for homing.
aM ・ bNi ・ cMg ・ dCa ・ eO
(In this formula, a, b, c, d and e are mole fractions, a + b + c + d = 1, 0.0001 ≦ a ≦ 0.10, 0.0001 ≦ b ≦ 0.10, 0.80 ≦ ( c + d) ≦ 0.9998, 0 <c ≦ 0.9998, 0 ≦ d <0.9998, e = the number necessary for the element to maintain a charge balance with oxygen, and M is a group 3B element in the periodic table , A Group 4A element, a Group 6B element, a Group 7B element, a Group 1A element, and a lanthanoid element.)
These catalysts can also be used in the same manner as the catalyst described in WO98 / 46524.
[0030]
[Lower paraffin production process]
The lower paraffin-containing gas obtained in the lower paraffin production process contains propane or butane as a main component. From the viewpoint of liquefaction characteristics, the total content of propane and butane in the lower paraffin-containing gas is preferably 60 mol% or more, and more preferably 70 mol% or more.
[0031]
Furthermore, from the viewpoint of combustibility and vapor pressure characteristics, it is preferable that there is more propane than butane, and the content of propane in the lower paraffin-containing gas is preferably 50 mol% or more, and 60 mol% or more. Is more preferable.
[0032]
In the present invention, the lower paraffin-containing gas contains a low-boiling component having a boiling point lower than that of propane. An example of a low boiling point component is ethane. Methane and ethylene may be contained in the low boiling point component. The content of the low boiling point component is preferably 5 mol% or more and 30 mol% or less, and more preferably 10 mol% or more and 20 mol% or less in order to suitably obtain the effects of the present invention.
[0033]
In the lower paraffin production process of the present invention, a catalyst capable of promoting the reaction for obtaining the lower paraffin-containing gas from synthesis gas can be used. For example, a catalyst containing a methanol synthesis catalyst component and a zeolite catalyst component can be used. Here, the methanol synthesis catalyst component is CO + 2H. ₂ → CH _Three This refers to a substance that exhibits a catalytic action in the reaction of OH. The zeolite catalyst component refers to a zeolite that exhibits a catalytic action in the condensation reaction of methanol to hydrocarbons and / or the condensation reaction of dimethyl ether to hydrocarbons.
[0034]
As the catalyst, for example, 4% by mass Pd / SiO2, which is a catalyst for methanol synthesis, is used. ₂ Cu-Zn-Al mixed oxide [Cu: Zn: Al = 40: 23: 37 (atomic ratio)] and Cu-based catalyst for low-pressure methanol synthesis (trade name: BASF S3-85); SiO ₂ / Al ₂ O _Three = 7.6 A mixed catalyst in which high-silica Y-type zeolite is mixed can be used. The mixing ratio of the former and the latter can be about 1: 1 by mass ratio, for example.
[0035]
The content ratio (mass basis) of the methanol synthesis catalyst component to the zeolite catalyst component is preferably 0.5 or more [methanol synthesis catalyst component / zeolite catalyst component], and 1.0 or more [methanol synthesis catalyst component / zeolite. The catalyst component] is more preferable. Further, the content ratio (mass basis) of the methanol synthesis catalyst component to the zeolite catalyst component is preferably 3.0 or less [methanol synthesis catalyst component / zeolite catalyst component], and 2.0 or less [methanol synthesis catalyst component / zeolite. The catalyst component] is more preferable. By setting the content ratio of the methanol synthesis catalyst component to the zeolite catalyst component in the above range, propane can be produced with higher selectivity and higher yield.
[0036]
The methanol synthesis catalyst component has a function as a methanol synthesis catalyst, and the zeolite catalyst component has a function as a solid acid zeolite catalyst whose acidity is adjusted with respect to the condensation reaction of methanol and / or dimethyl ether to a hydrocarbon. . Therefore, the content ratio of the methanol synthesis catalyst component to the zeolite catalyst component is reflected in the relative ratio of the methanol synthesis function of the catalyst and the hydrocarbon generation function from methanol. Also, in the present invention, when producing liquefied petroleum gas whose main component is propane or butane by reacting carbon monoxide with hydrogen, it is desired that carbon monoxide and hydrogen be sufficiently converted to methanol by a methanol synthesis catalyst component. In addition, it is desired to convert the produced methanol into a liquefied petroleum gas whose main component is propane or butane sufficiently by the zeolite catalyst component. When the content ratio (mass basis) of the methanol synthesis catalyst component to the zeolite catalyst component is 0.5 or more [methanol synthesis catalyst component / zeolite catalyst component], carbon monoxide and hydrogen are suitably used for methanol by the methanol synthesis catalyst component. Can be converted. From this viewpoint, it is more preferable that the content ratio is 0.8 or more [methanol synthesis catalyst component / zeolite catalyst component]. In order to selectively convert the produced methanol into a liquefied petroleum gas containing propane or butane as a main component, the methanol content is preferably 0.8 or more [methanol synthesis catalyst component / zeolite catalyst component]. In addition, by setting the content ratio (mass basis) of the methanol synthesis catalyst component to the zeolite catalyst component to 3.0 or less [methanol synthesis catalyst component / zeolite catalyst component], the generated methanol is suitably contained in the zeolite catalyst component. It can be converted to liquefied petroleum gas which is propane or butane. From this viewpoint, the content ratio is more preferably 2.0 or less [methanol synthesis catalyst component / zeolite catalyst component].
[0037]
The methanol synthesis catalyst component as the composition of such a catalyst may have any function as a catalyst capable of synthesizing methanol from carbon monoxide and hydrogen. A commercially available catalyst generally known as a methanol synthesis catalyst may be used, or may be disclosed in the literature. As such, Cu-Zn-based, Cu-Zn-Cr-based, Cu-Zn-Al-based, Cu-Zn-Ag-based, Cu-Zn-Mn-V-based, Cu-Zn-Mn-Cr-based , Cu—Zn—Mn—Al—Cr, etc., all of which are Cu—Zn and a third component added thereto, or those of Ni—Zn, Mo, Ni—carbon, Is a noble metal type such as Pd.
[0038]
The zeolite catalyst component as the composition of the catalyst is not particularly limited as long as it has a function as a catalyst capable of selectively converting the produced methanol into liquefied petroleum gas mainly composed of propane or butane. Such a catalyst is selected from those having a function as a solid acid zeolite catalyst whose acidity is adjusted with respect to the condensation reaction of methanol and / or dimethyl ether to hydrocarbon. The structure and physical properties of the zeolite catalyst component of such a catalyst are generally such as small pore zeolites such as SAPO-34 and mordenite which are highly selective in the condensation reaction from methanol and / or dimethyl ether to lower olefin hydrocarbons. In general, ZSM-5, MCM-22, and the like exhibit higher selectivity in the condensation reaction of methanol and / or dimethyl ether to alkyl-substituted aromatic hydrocarbons than zeolites in which the diffusion of reaction molecules in the pores is not three-dimensional. Zeolite having a three-dimensional diffusion of reaction molecules in the pores such as medium pore zeolite or large pore zeolite such as beta or Y type is preferred. At that time SiO ₂ / Al ₂ O _Three A so-called high silica zeolite having a molar ratio of 10 to 50 is preferable, and for example, a solid acid zeolite whose acidity is adjusted by metal ion exchange such as USY or high silica type beta is used.
[0039]
The lower paraffin production process of the present invention involves reacting carbon monoxide and hydrogen using the catalyst as described above to produce a liquefied petroleum gas, preferably a liquefied petroleum gas whose main component is propane. It is preferable to carry out under such operating conditions.
[0040]
The reaction temperature is preferably 270 ° C. or higher, more preferably 300 ° C. or higher, as a temperature suitable for each of the methanol synthesis catalyst component and the zeolite catalyst component to exhibit excellent activity. The reaction temperature is preferably 400 ° C. or less, more preferably 370 ° C. or less, from the viewpoint of the use limit temperature of the catalyst and from the viewpoint of equilibrium regulation and ease of reaction heat removal and recovery.
[0041]
The reaction pressure is preferably 1.0 MPa or more, more preferably 2.0 MPa or more, as a pressure at which the methanol synthesis catalyst component exhibits excellent activity. Also, the reaction pressure is suitable for the methanol synthesis catalyst component to exhibit excellent activity, and if it exceeds that, excess energy is used as the power of the compressor, and the economic efficiency of the technology of the present invention is reduced. The following is preferable, and 5 MPa or less is more preferable.
[0042]
The gas space velocity only needs to provide a contact time at which each of the methanol synthesis catalyst component and the zeolite catalyst component exhibits an excellent conversion rate, and if it is less than that, a reactor larger than necessary for the amount of LPG produced is prepared. Since the economic efficiency of the technology of the present invention is reduced, 500 hr. ^-1 Or more, preferably 2000 hr ^-1 The above is more preferable. Also, the gas space velocity is 10000 hr in order to provide a contact time at which the methanol synthesis catalyst component and the zeolite catalyst component each exhibit excellent conversion. ^-1 The following is preferable, 5000 hr ^-1 The following is more preferable.
[0043]
The concentration of carbon monoxide in the gas fed to the reactor for the production of lower paraffin ensures the carbon monoxide pressure suitable for the reaction between the raw material gas carbon monoxide and hydrogen, that is, the partial pressure, and the raw material. In order to improve the basic unit, 20 mol% or more is preferable, and 25 mol% or more is more preferable. Further, the concentration of carbon monoxide in the gas fed to the reactor is preferably 40 mol% or less, more preferably 35 mol% or less, from the viewpoint of the conversion rate of carbon monoxide.
[0044]
In the raw material gas for producing lower paraffin, the concentration of carbon monoxide and hydrogen is preferably 1.5 moles or more, preferably 1.8 moles per mole of carbon monoxide in order to react carbon monoxide appropriately. The above is more preferable. In addition, the hydrogen concentration in the raw material gas may be such that carbon monoxide reacts suitably so that a liquefied petroleum gas whose main component is propane or butane can be obtained, and the surplus hydrogen is the total pressure of the raw material gas. Is unnecessarily increased and the economic efficiency of the technology is lowered, so that it is preferably 3.0 mol or less, more preferably 2.3 mol or less, per 1 mol of carbon monoxide.
[0045]
The gas inserted into the reactor may be carbon monoxide and hydrogen, which are raw materials for producing lower paraffin, and carbon dioxide added thereto. As the carbon dioxide, carbon dioxide generated from the shift reaction from carbon monoxide in the reactor is substantially reduced by recycling the carbon dioxide discharged from the reactor or using an amount suitable for it. It can also be avoided. The gas inserted into the reactor can also contain water vapor. Moreover, the gas inserted into the reactor can be divided and inserted to be used for controlling the reaction temperature.
[0046]
The reaction can be carried out in a fixed bed, a fluidized bed, a moving bed, etc., but it is preferable to select from both aspects of controlling the reaction temperature and regenerating the catalyst. For example, as a fixed bed, a quench reactor such as an internal multi-stage quench system, a multi-tube reactor, a multi-stage reactor including a plurality of heat exchangers, a multi-stage cooling radial flow system or a double-tube heat exchange Other reactors such as a system, a cooling coil built-in system, and a mixed flow system can be used.
[0047]
Further, the catalyst can be used by diluting with silica, alumina or the like or an inert and stable heat conductor for application to the surface of the heat exchanger for the purpose of temperature control.
[0048]
[Separation process]
In the separation step, moisture and the like are separated from the lower paraffin-containing gas as necessary, and then the low-boiling components are separated. As a result, liquefied petroleum gas mainly composed of propane or butane can be obtained. As appropriate, high-boiling paraffin gas (a component having a higher boiling point than butane) can be separated. In order to obtain liquefied petroleum gas, you may pressurize and / or cool as needed.
[0049]
This separation can be performed by a known method such as gas-liquid separation, absorption separation, or distillation. More specifically, gas-liquid separation or absorption separation at pressurized normal temperature, gas-liquid separation or absorption separation after cooling, or a combination thereof can be performed. Alternatively, it can be performed by membrane separation or adsorption separation, or by a combination of these with gas-liquid separation, absorption separation, or distillation. In order to separate low-boiling components, a gas recovery process commonly used in refineries (“Petroleum Refining Process”, Petroleum Society / ed., Kodansha Scientific, 1998, p28-p32) can be applied. As a method for separating the low-boiling components, an absorption process in which the high-boiling paraffin gas (a component having a higher boiling point than butane) or gasoline is used as an absorbing liquid and a liquefied petroleum gas mainly composed of propane or butane is absorbed is preferable. .
[0050]
For consumer use, from the viewpoint of safety at the time of use, for example, the content of the low boiling point component in LPG is set to 5 mol% or less by separation.
[0051]
[Recycling process]
The separated low boiling point component contains a substance that can be reused as a raw material for the reforming process. Therefore, this residual gas is recycled to the reforming process. In order to recycle, a well-known technique related to recycling can be adopted, for example, a pressure raising means is appropriately provided in the recycle line.
[0052]
【Example】
FIG. 1 shows an example of an LPG production apparatus suitable for carrying out the method of the present invention.
[0053]
Methane is supplied to the reformer 1 through lines 11 and 12 as a carbon-containing raw material. Since steam reforming is performed here, steam is supplied to the line 12 (not shown). The reformer also includes a heating means for supplying heat necessary for reforming, but it is omitted in the figure.
[0054]
Methane is reformed in the presence of the reforming catalyst 1a provided in the reformer, and a synthesis gas containing hydrogen, carbon monoxide, carbon dioxide and steam is obtained.
[0055]
This synthesis gas is supplied to the reactor 2, and a product gas containing ethane, propane and butane is obtained from the synthesis gas in the presence of the catalyst 2a provided in the reactor.
[0056]
This product gas is supplied to the separator 3. A substance having a boiling point equal to or higher than that of propane is obtained from the bottom of the column by distillation at room temperature and pressure, and a substance having a boiling point lower than that of propane is obtained as residual gas from the top of the column. Thus, LPG as a product is obtained from the line 15, and the residual gas is recycled by the recycle line 16.
[0057]
Although not shown, a booster, a heat exchanger, a valve, an instrumentation control device, and the like are provided as necessary.
[0058]
LPG was manufactured using the apparatus of the said structure. Conditions and results are described below.
[0059]
(Production of lower paraffin)
As a methanol synthesis catalyst component, a commercially available Cu—Zn-based methanol synthesis catalyst (manufactured by Nihon Zudhemy) was mechanically powdered. Separately, as a zeolite catalyst component, SiO ₂ / Al ₂ O _Three Proton type ZSM-5 zeolite powder having a molar ratio of 14.5 was prepared. The methanol synthesis catalyst component and the zeolite catalyst component were uniformly mixed on the mass basis, pressure-molded and sized, and then reduced in a hydrogen stream at 300 ° C. for 3 hours to obtain a catalyst.
[0060]
The prepared catalyst is filled in a reaction tube, and a raw material gas having a composition of 62.0 mol% hydrogen, 31.0 mol% carbon monoxide, 5.0 mol% carbon dioxide, and 2.0 mol% methane is circulated. It was. The reaction conditions were a reaction temperature of 325 ° C., a reaction pressure of 2.0 MPa, and a gas space velocity of 3000 hr. ^-1 It was. When the product was analyzed by gas chromatography, the conversion of carbon monoxide was 71%. The shift reaction conversion rate of carbon monoxide to carbon dioxide was 35%, and the conversion rate to hydrocarbons was 37%. Further, 75% of the produced hydrocarbon gas was propane and butane based on carbon, and the breakdown of the propane and butane was 56% propane and 44% butane on the carbon basis.
[0061]
(Separation and recycling of low boiling point components)
The reaction gas from the production of LPG is gas-liquid separated, dried with molecular sieves, and then bubbled into an octane solution maintained at around 0 ° C., 3.7 mol% of methane, 1.2 mol% of ethane and ethylene Then, a gas having a composition of 21.1 mol% of carbon dioxide, 12.0 mol% of unreacted carbon monoxide and 62.0 mol% of hydrogen was separated as a low boiling point component, and the pressure was increased to 2.5 MPa with a compressor. Then, a part of the raw material gas was fed into the synthesis gas production process as 67 mol%.
[0062]
(Syngas production)
A raw material gas having a composition of 67.0 mol% of low boiling point recycle gas from the LPG production process, 14.7 mol% of natural gas, 14.8 mol% of steam, and 3.5 mol% of carbon dioxide is disclosed in WO 98/46524. In the externally heated reaction tube type apparatus filled with Ru / sintered low surface area magnesia catalyst prepared according to the catalyst preparation example 9 in the publication, the catalyst was previously subjected to reduction treatment at 900 ° C. in a hydrogen stream for 1 hr. Temperature 870 ° C., pressure 2.1 MPa, GHSV 2000 hr ^-1 Thus, synthesis gas having a composition of 58 mol% hydrogen, 29 mol% carbon monoxide, 6 mol% carbon dioxide, and 7 mol% methane was obtained. From this composition, this synthesis gas can be used as a raw material in the production of lower paraffin.
[0063]
【The invention's effect】
According to the present invention, propane and / or butane can be produced with good selectivity from carbon-containing raw materials such as natural gas or synthesis gas.
[Brief description of the drawings]
FIG. 1 is a process flow diagram showing a main configuration of an example of an LPG production apparatus suitable for carrying out the present invention.
[Explanation of symbols]
1 Reformer
1a reforming catalyst
2 Reactor
2a catalyst
3 Separator
11, 12, 13, 14, 15 lines
16 Recycling line

Claims (2)

A lower paraffin production process for producing a lower paraffin-containing gas, which is a mixed gas mainly containing propane or butane, containing a low-boiling component that is a substance having a boiling point lower than that of propane in the presence of a catalyst, in the presence of a catalyst. When,
A separation step of separating the low boiling point component from the lower paraffin-containing gas to obtain a liquefied petroleum gas containing propane or butane as a main component. Production method. A synthesis gas production process for producing synthesis gas from carbon-containing raw materials;
A lower paraffin production process for producing a lower paraffin-containing gas, which is a mixed gas mainly containing propane or butane, containing a low-boiling component that is a substance having a boiling point lower than that of propane in the presence of a catalyst, in the presence of a catalyst. When,
A separation step of separating the low boiling point component from the lower paraffin-containing gas to obtain a liquefied petroleum gas mainly composed of propane or butane;
A method for producing liquefied petroleum gas mainly composed of propane or butane, comprising a recycling step of recycling the separated low-boiling component as a raw material for the synthesis gas production step.

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