JPS6341843B2

JPS6341843B2 -

Info

Publication number: JPS6341843B2
Application number: JP54105031A
Authority: JP
Inventors: Teruo Kumagai; Toshikatsu Mori; Akira Kato; Shinpei Matsuda; Fumito Nakajima
Original assignee: Babcock Hitachi KK; Hitachi Ltd
Current assignee: Hitachi Ltd; Mitsubishi Power Ltd
Priority date: 1979-08-20
Filing date: 1979-08-20
Publication date: 1988-08-19
Also published as: JPS5632308A

Description

[Detailed description of the invention]

本発明は、ガス中の二酸化イオウの還元方法に
関する。さらに詳しく述べれば、硫黄酸化物を含むガス
中に還元性ガスを添加し、触媒と接触せしめて、
ガス中の二酸化イオウを還元して除去する際の二
酸化イオウの還元方法に関する。従来、ガス中の二酸化イオウを還元する方法と
しては、Ni―Mo―Al₂O₃・Co―Mo―Al₂O₃等、
アルミナ、マグネシア、シリカを主成分とする触
媒を用いる方法が知られている。これらの触媒を
用いる際、200℃以下の低温における還元活性が
十分でないという欠点がある。また、主成分であ
る担体にアルミナ、マグネシア、シリカを用いる
と低温で硫酸塩化して活性を失うという欠点を有
している。本発明の目的は、上記した従来技術の欠点をな
くして、ガス中の二酸化イオウを効率よく還元す
る方法を提供することである。本発明の特徴は、酸化チタンを主成分とし、モ
リブデン、ニツケル、コバルトなどの遷移金属元
素からなる触媒を用いて、150〜500℃の温度で、
還元性ガスを添加して二酸化イオウを接触的に還
元するところにある。本発明者らは、酸化チタンを主成分として上記
の遷移金属元素を組み合わせることにより、従来
の触媒より優れた活性を示す触媒を見出した。し
かも、酸化チタンは硫黄酸化物によつて硫酸塩化
しにくく、触媒の変質が起こりにくいため触媒寿
命も長いということを確認した。本発明に使用される触媒は、酸化チタンを主成
分とし、モリブデン、ニツケル、コバルトの少な
くとも１種以上を含むことが望ましい。特に、望
ましい触媒成分は、ニツケル―モリブデンまたは
コバルト―モリブデンである。主成分の酸化チタ
ンに、アルミナ、マグネシア、シリカ等のセラミ
ツクス性物質が少量ならば含まれていてもよい。
これら、アルミナ、マグネシア、シリカの含量が
多量になると、三酸化イオウによりアルミナ、マ
グネシア、シリカ等が硫酸塩化され、触媒の細孔
構造、比表面積の変化により活性の低下をまね
く。モリブデン、ニツケル、コバルトの含有量
は、それぞれ１〜20重量％の範囲が選ばれる。こ
れより少ない場合は、二酸化イオウの還元活性が
十分でない。また、20重量％以上にしても、還元
活性は高くならず経済的でない。また、本発明に
用いられる触媒は、このほかに鉄、タングステン
等の遷移金属を少量含んでもよい。これらの成分
を含むことにより還元活性が向上することもあ
る。本発明の触媒に使用される主成分である酸化チ
タンの原料は、１m²/g以上、望ましくは10m²/g
以上の比表面積を有する酸化チタンを生成するも
のであればよい。例えば、酸化チタン粉末、ある
いはオルトチタン酸、メタチタン酸等、これらを
150℃以上で熱分解して得た酸化チタンを用いて
もよい。また、硫酸チタン、四塩化チタン等の化
合物を加水分解して得た酸化チタンを用いてもよ
い。しかし、酸化チタンは800℃以上の温度では
焼結が進行し活性が失なわれるので、焼成などの
処理温度は800℃以下で行なうことが望ましい。
モリブデン、ニツケル、コバルトの触媒成分は、
通常入手できる硝酸塩、硫酸塩、塩化物等水に可
溶なものであればよい。触媒の製造法は、公知の打錠成形法、転動造粒
法、押出成形法、あるいは担体成分に触媒成分を
含浸または沈着させて触媒を製造することができ
る。触媒の形状は、先に記した製造法によつて、円
柱状、円筒状、球状、板状、ハニカム状の形状の
ものを作ることができ、いずれも使用できる。この触媒を用いて二酸化イオウを還元する反応
温度は、150〜500℃が選ばれ、望ましくは200〜
300℃が選ばれる。反応温度がこの範囲以下では
活性が充分でない。本発明で使用される還元性ガスは、水素、一酸
化炭素、メタン、ｎ―ブタン等が選ばれるが、望
ましくは水素または一酸化炭素が選ばれる。以下、実施例をあげて本発明を具体的に説明す
る。実施例１四塩化チタン（TiCl₄）379ｇを約１の蒸留
水に徐々に滴加して溶解する。これに５規定アン
モニア水を加えて中和する。生じた沈殿を十分に
洗浄したのち、これにパラモリブデン酸アンモニ
ウム（NH₄）₆M₀₇O₂₄―4H₂O）36.7ｇを過酸化水
素とともに蒸留水で溶解した溶液を加え、さらに
硝酸ニツケル（Ni（NO₃）₂・6H₂O）38.9ｇを蒸留
水で溶解した溶液を加えて十分に混合する。得ら
れたスラリーを乾燥後、300℃で２時間予備焼成
し、これに１重量％の結晶性セルロースを成型剤
として添加し、約１時間混練してから、押出成型
により直径2.5mmの円柱状のペレツトを得た。得
られたペレツトを120℃で乾燥後、500℃で５時間
焼成して完成触媒を得た。得られた触媒は、モリ
ブデンをMoO₃として15重量％、ニツケルをNiO
として５重量％を含有する酸化チタンからなる。
触媒は、使用に先だち、水素を流しながら300℃
で2h還元させた。上記方法で調製した触媒24mlを内径40mmの石英
製反応管に充填し、下記組成のガスを空間速度
5000h―¹で反応させた。SO₂の還元率をみるた
め、反応管入口および出口のSO₂濃度の測定は、
TCDをそなえたガスクロで分析した。 SO₂ 12容量％ CO₂ 20容量％ H₂ 20容量％ H₂O 43容量％ CO ５容量％実験結果を第１表に示す。比較のため市販の
Ni―Mo―Al₂O₃触媒の実験結果も掲げた。 The present invention relates to a method for reducing sulfur dioxide in a gas. More specifically, a reducing gas is added to a gas containing sulfur oxides and brought into contact with a catalyst.
The present invention relates to a method for reducing sulfur dioxide when reducing and removing sulfur dioxide in a gas. Conventionally, methods for reducing sulfur dioxide in gas include Ni-Mo-Al ₂ O ₃ , Co-Mo-Al ₂ O ₃ , etc.
A method using a catalyst mainly composed of alumina, magnesia, and silica is known. When using these catalysts, there is a drawback that the reduction activity at low temperatures of 200° C. or lower is insufficient. Furthermore, when alumina, magnesia, or silica is used as the main component carrier, it has the disadvantage that it becomes sulfated at low temperatures and loses its activity. An object of the present invention is to provide a method for efficiently reducing sulfur dioxide in gas by eliminating the drawbacks of the prior art described above. The feature of the present invention is that the main component of the present invention is titanium oxide, using a catalyst made of transition metal elements such as molybdenum, nickel, and cobalt, at a temperature of 150 to 500°C.
Sulfur dioxide is catalytically reduced by adding a reducing gas. The present inventors have discovered a catalyst that exhibits superior activity to conventional catalysts by combining titanium oxide as a main component with the above-mentioned transition metal elements. Furthermore, it was confirmed that titanium oxide is difficult to be sulfated by sulfur oxides, and the catalyst has a long lifespan because it is difficult to cause deterioration of the catalyst. The catalyst used in the present invention preferably contains titanium oxide as a main component and at least one of molybdenum, nickel, and cobalt. Particularly desirable catalyst components are nickel-molybdenum or cobalt-molybdenum. The main component, titanium oxide, may contain a small amount of ceramic substances such as alumina, magnesia, and silica.
When the content of these alumina, magnesia, silica, etc. becomes large, the alumina, magnesia, silica, etc. are converted into sulfates by sulfur trioxide, leading to a decrease in activity due to changes in the pore structure and specific surface area of the catalyst. The contents of molybdenum, nickel, and cobalt are each selected to be in the range of 1 to 20% by weight. If the amount is less than this, the reducing activity of sulfur dioxide is not sufficient. Further, even if the amount is 20% by weight or more, the reducing activity will not be high and it is not economical. In addition, the catalyst used in the present invention may also contain a small amount of transition metals such as iron and tungsten. Including these components may improve the reducing activity. The raw material of titanium oxide, which is the main component used in the catalyst of the present invention, is 1 m ² /g or more, preferably 10 m ² /g.
Any material that produces titanium oxide having the above specific surface area may be used. For example, titanium oxide powder, orthotitanic acid, metatitanic acid, etc.
Titanium oxide obtained by thermal decomposition at 150°C or higher may also be used. Furthermore, titanium oxide obtained by hydrolyzing compounds such as titanium sulfate and titanium tetrachloride may also be used. However, titanium oxide progresses to sintering and loses its activity at a temperature of 800°C or higher, so it is desirable that the processing temperature such as firing be performed at a temperature of 800°C or lower.
The catalyst components of molybdenum, nickel, and cobalt are
Any commonly available nitrates, sulfates, chlorides, etc. that are soluble in water may be used. The catalyst can be produced by a known tableting method, rolling granulation method, extrusion method, or by impregnating or depositing a catalyst component on a carrier component. The shape of the catalyst can be cylindrical, cylindrical, spherical, plate-like, or honeycomb-like, and any of them can be used. The reaction temperature for reducing sulfur dioxide using this catalyst is selected to be 150 to 500°C, preferably 200 to 500°C.
300℃ is chosen. If the reaction temperature is below this range, the activity will not be sufficient. As the reducing gas used in the present invention, hydrogen, carbon monoxide, methane, n-butane, etc. are selected, and preferably hydrogen or carbon monoxide is selected. Hereinafter, the present invention will be specifically explained with reference to Examples. Example 1 379 g of titanium tetrachloride (TiCl ₄ ) is gradually added dropwise to approx. 1 g of distilled water to dissolve it. Add 5N ammonia water to this to neutralize it. After thoroughly washing the resulting precipitate, a solution prepared by dissolving 36.7 g of ammonium paramolybdate (NH ₄ ) ₆ M ₀₇ O ₂₄ -4H ₂ O) in distilled water together with hydrogen peroxide was added, and further nickel nitrate ( A solution of 38.9 g of Ni (NO ₃ ) _2.6H ₂ O) dissolved in distilled water is added and mixed thoroughly. After drying the obtained slurry, it was pre-calcined at 300°C for 2 hours, 1% by weight of crystalline cellulose was added as a molding agent, kneaded for about 1 hour, and extruded into a cylindrical shape with a diameter of 2.5 mm. of pellets were obtained. The obtained pellets were dried at 120°C and then calcined at 500°C for 5 hours to obtain a finished catalyst. The obtained catalyst contained 15% by weight of molybdenum as _MoO3 and nickel as NiO3.
5% by weight of titanium oxide.
Prior to use, the catalyst was heated to 300°C under flowing hydrogen.
It was reduced for 2 hours. 24ml of the catalyst prepared by the above method was filled into a quartz reaction tube with an inner diameter of 40mm, and a gas with the following composition was added at a space velocity of
The reaction was carried out for 5000h- ¹ . To check the reduction rate of SO ₂ , measure the SO ₂ concentration at the inlet and outlet of the reaction tube.
Analyzed using gas chromatography equipped with TCD. SO ₂ 12% by volume CO ₂ 20% by volume H ₂ 20% by volume H ₂ O 43% by volume CO 5% by volume The experimental results are shown in Table 1. Commercially available for comparison
Experimental results for Ni-Mo-Al ₂ O ₃ catalyst are also presented.

【表】実施例２実施例―１において、触媒成分および組成を変
えた以外は、同様の方法で調製した触媒を用いて
同様の実験を行なつた。その実験結果を第２表に
示す。[Table] Example 2 A similar experiment was conducted using a catalyst prepared in the same manner as in Example 1, except that the catalyst components and composition were changed. The experimental results are shown in Table 2.

【table】

Claims

[Claims] 1. A method for catalytically reducing sulfur dioxide in a gas by adding a reducing gas, in which titanium oxide is used as a first component, molybdenum is used as a second component, and molybdenum is used as a third component.
A method for reducing sulfur dioxide, which comprises using as a catalyst a catalyst containing at least one of nickel and cobalt. 2. In the method described in claim 1,
A method for reducing sulfur dioxide, characterized in that the catalyst contains 3 to 20% by weight of molybdenum as an oxide, 1 to 10% by weight of at least one of nickel and cobalt as an oxide, and 70 to 96% by weight of titanium oxide. . 3. In the method described in claim 1,
A method for reducing sulfur dioxide, characterized in that the reducing gas contains hydrogen or carbon monoxide.