【発明の詳細な説明】[Detailed description of the invention]
本発明は、強度および耐摩耗性に優れたアルミ
ナ質触媒担体の製造方法に関するものである。
自動車の排気ガス浄化のために、アルミナ等の
触媒担体に白金等の触媒成分を担持させた触媒が
使用されていることは既に知られている。この触
媒は、触媒としての作用はもちろんのこと、エン
ジンの始動から少なくとも一定時間内に定常状態
で作動しなければならず、また走行時の振動にも
耐えなければならない等のことから、一定の暖機
性や耐摩耗性が要求されているが、この要求は、
通常触媒担体によつて得ている。
かかる触媒特性に優れた担体として、アルミナ
質触媒担体が最も多く使用されており、従来その
製造方法としては、バイヤー法で得られた水酸化
アルミニウムを部分脱水し、これを粉砕し、造粒
してから飽和水蒸気圧中で養生し、乾燥、焼成す
る、というのが一般的であつた。
しかしながら、以上の方法で得られるアルミナ
質触媒担体においては、ある一定以上の強度を確
保するためには、密度を大きくする必要があり、
このため触媒重量が増大するという欠点があつ
た。また密度が大きくなると、触媒床の暖機性が
著しく悪化するという問題もあつた。
以上のような欠点を解決する方法として、本発
明者等はさきに造粒物の養生を苛性アルカリ水溶
液中やアルミン酸ナトリウム水溶液中で行なつて
担体の強度を向上せしめる方法を提案した。しか
しながら、この方法では、強度は向上するが、耐
摩耗性は大巾には向上しないという欠点があつ
た。
本発明は、以上のような欠点を解決したもの
で、比強度が大きくしかも耐摩耗性に優れた触媒
担体の製造方法を提供するものである。
本発明は、アルミナ水和物、例えば水酸化アル
ミニウムを部分脱水し、この部分脱水物をそのま
ま或いは粉砕し、必要ならば適当な添加物と一緒
に混合し、造粒してから〓焼し、この造粒物を苛
性アルカリ水溶液中で養生した後、乾燥、焼成す
ることを特徴とする触媒担体の製造方法に関する
ものである。
本発明は、特にアルミナ粉状物を〓焼した後、
苛性アルカリ水溶液で処理することを特徴とし、
本発明における〓焼とは1000℃以下の比較的低い
温度での加熱操作と理解されたい。この〓焼温度
としては使用するアルミナおよび更に加える添加
物等によつても多少異なるが、好ましくは150℃
以上である。
本発明において、適する添加物としては、例え
ばセルロース等の有機化合物、CeO2、MgO、
Fe2O3、MnO2、Mn2O3、Cr2O3、TiO2、CuO、
CoO、Co2O3、NiO等の各種酸化物が挙げられ
る。また本発明において使用してより苛性アルカ
リ水溶液としては、特に限定しないがNaOH、
KOHおよびBa（OH）2の各水溶液が好ましい。苛
性アルカリ水溶液処理は、好ましくは飽和水蒸気
圧下で行なわれる。
以下、実施例で本発明を更に詳しく説明する。
実施例 １
バイヤー法で製造された平均粒径40μの水酸化
アルミニウムを部分脱水した後、平均粒径12μま
で粉砕して皿型造粒機で粒径2.8〜4.0mmψのアル
ミナ粉状体を製造した。
上記アルミナ粉状体を80゜〜500℃の各温度で５
時間〓焼した後、３％NaOH水溶液中で養生し
た。この養生は160℃の飽和水素気圧下で10時間
行なつた。養生した各アルミナ粒状体は水洗して
付着或いは固溶しているNa+を除去して、担体中
のNa量をNa2Oとして0.2％以下とした。この後、
アルミナ粒状体を150℃で３時間乾燥し、800℃で
３時間焼成して再活性化した。
以下のようにして得られた活性アルミナ粒状体
について、以下に示す方法によつて圧壊強度、嵩
密度および耐アトリシヨン性を調べた。
(1) 圧壊強度測定法
木屋式硬度計によつて活性アルミナ粒状体の
強度を測定し、20粒の平均値を圧壊強度とし
た。
(2) 嵩密度測定法
100c.c.のメスシリンダー中に活性アルミナ粒
状体約40c.c.を充填し、その体積と重量とから嵩
密度を算出した。
(3) アトリシヨン率の測定法
第１図に示すアトリシヨン試験機により測定
を行なつた。まず供試活性アルミナ粒状体50c.c.
を550℃で約１時間焼成した後重量を測定し、
この時の重量をW1とした。次にこの試験を最
大直径130mm、最小直径20mm、円錐の高さ230
mm、頂角90゜のガラス管からなる第１図に示す
アトリシヨン試験機のアトリシヨン筒３内に入
れ、ノズル１より空気をアトリシヨン筒３に送
入し、アトリシヨン筒３内の活性アルミナ粒状
体を５分間アトリシヨン運動させた。尚、アト
リシヨン筒３内に吹きこまれた空気は、上部の
金網製のキヤツプ２から系外へ放出される。そ
の後、活性アルミナ粒状体をアトリシヨン筒３
から取り出し、550℃で１時間焼成して重量を
測定した。この重量をW2とし、アトリシヨン
率を次式により算出した。
アトリシヨン率（％）＝W1−W2／W1×100
また、比較例として造粒したアルミナ粒状体
を〓焼後、養生をNaOH水溶液中でなく、水
中（比較例１）で行なつた場合と、〓焼せずに
そのまま３％NaOH水溶液中（比較例２）ま
たは水中（比較例３）で養生した場合のアルミ
ナ粒状体の特性も同様に測定した。以上のよう
に測定した結果を第２図、第３図および第４図
に示す。第２図は、養生前のアルミナ粒状体〓
焼温度とアトリシヨン率の関係を示すグラフ
で、図中Ａ線は本発明（実施例１）によるも
の、Ｂ線は〓焼後水中養生した比較例１を示し
たものである。また、図中の白丸、白三角印は
〓焼せずに養生したもので、それぞれ比較例２
および３を示す。第３図は、〓焼温度と圧壊温
度の関係を示すグラフ、第４図は、〓焼温度と
嵩密度の関係を示すグラフで、図中のＡ線およ
びＢ線ならびに白丸、白三角印は、第２図と同
様のものを示している。これらの図から明らか
なように、本発明によればアルミナ粒状体の強
度、耐アトリシヨン性が著しく向上し、しかも
嵩密度も小さくなる。
実施例 ２
〓焼後の養生を５％KOH水溶液中で行なう以
外は実施例１と全く同様にして行なつたところ、
実施例１と同様の結果が得られた。
実施例 ３
バイヤー法で製造された平均粒径40μの水酸化
アルミニウムを部分脱水した後、平均粒径12μま
で粉砕した。次にこのアルミナ粒末80重量％と結
果セルロース20重量％とを混合し、この粉末を皿
型造粒機で粒径2.8〜4.0mmψのアルミナ粒状体に
造粒した。
上記アルミナ粒状体を次の４とうりで処理し、
それぞれアルミナ粒状体の特性を実施例１と同様
の方法で調べた。
(1) 前記アルミナ粒状体を400℃で10時間〓焼し
た後、160℃の飽和水蒸気圧下で10時間、３％
NaOH水溶液中で養生した。この後、水洗し
て担体中のNa+をNa2O量として0.2％以下とし
た後、200℃で３時間乾燥し、820℃で３時間焼
成して本発明による触媒担体Ａを得た。
(2) 前記アルミナ粒状体を400℃で10時間〓焼し
た後、160℃の飽和水蒸気圧下で10時間水中養
生した。この後、200℃で３時間乾燥し、820℃
で３時間焼成して触媒担体Ｂを得た。
(3) 前記アルミナ粒状体を160℃の飽和水蒸気圧
下で10時間水中養生した。この後200℃で３時
間乾燥し、820℃で３時間焼成して触媒担体Ｃ
を得た。
(4) 前記アルミナ粒状体を160℃の飽和水蒸気圧
下で10時間３％NaOH水溶液中で養生した。
この後水洗して担体中のNa+をNa2O量として
0.2％以下としてから、200℃で３時間乾燥し、
820℃で３時間焼成して触媒担体Ｄを得た。
以上の触媒担体Ａ、Ｂ、Ｃ、Ｄの特性を調べた
結果を第１表に示す。
The present invention relates to a method for producing an alumina catalyst carrier having excellent strength and wear resistance. It is already known that a catalyst in which a catalyst component such as platinum is supported on a catalyst carrier such as alumina is used for purifying exhaust gas from automobiles. This catalyst not only functions as a catalyst, but also has to operate in a steady state for at least a certain period of time after the engine starts, and must also withstand vibrations during driving. Warm-up properties and abrasion resistance are required;
It is usually obtained by using a catalyst carrier. Alumina catalyst carriers are most commonly used as carriers with excellent catalytic properties, and the conventional method for producing them is to partially dehydrate aluminum hydroxide obtained by the Bayer process, crush it, and granulate it. It was common practice to cure the material under saturated steam pressure, dry it, and then fire it. However, in the alumina catalyst carrier obtained by the above method, in order to ensure strength above a certain level, it is necessary to increase the density.
This resulted in a disadvantage that the weight of the catalyst increased. There was also the problem that as the density increased, the warm-up performance of the catalyst bed deteriorated significantly. As a method for solving the above-mentioned drawbacks, the present inventors previously proposed a method in which the granules are cured in an aqueous caustic alkali solution or an aqueous sodium aluminate solution to improve the strength of the carrier. However, this method has the disadvantage that although the strength is improved, the wear resistance is not significantly improved. The present invention solves the above-mentioned drawbacks and provides a method for producing a catalyst carrier having high specific strength and excellent wear resistance. The present invention involves partially dehydrating alumina hydrate, for example, aluminum hydroxide, and using the partially dehydrated product as it is or pulverizing it, mixing it with appropriate additives if necessary, granulating it, and then calcining it. The present invention relates to a method for producing a catalyst carrier, which comprises curing the granulated material in an aqueous caustic solution, followed by drying and firing. In particular, the present invention provides the following methods:
It is characterized by being treated with a caustic alkali aqueous solution,
In the present invention, calcination should be understood as a heating operation at a relatively low temperature of 1000°C or less. The firing temperature varies somewhat depending on the alumina used and additives added, but is preferably 150°C.
That's all. In the present invention, suitable additives include, for example, organic compounds such as cellulose, CeO 2 , MgO,
Fe 2 O 3 , MnO 2 , Mn 2 O 3 , Cr 2 O 3 , TiO 2 , CuO,
Examples include various oxides such as CoO, Co 2 O 3 and NiO. In addition, the more caustic alkaline aqueous solution used in the present invention includes, but is not particularly limited to, NaOH,
Aqueous solutions of KOH and Ba(OH) 2 are preferred. The aqueous caustic solution treatment is preferably carried out under saturated steam pressure. Hereinafter, the present invention will be explained in more detail with reference to Examples. Example 1 After partially dehydrating aluminum hydroxide with an average particle size of 40μ produced by the Bayer process, it was crushed to an average particle size of 12μ to produce alumina powder with a particle size of 2.8 to 4.0 mmψ using a dish granulator. did. The above alumina powder was heated at various temperatures from 80° to 500°C.
After baking for a time, it was cured in a 3% NaOH aqueous solution. This curing was carried out for 10 hours under saturated hydrogen pressure at 160°C. Each cured alumina granule was washed with water to remove Na + attached or dissolved therein, and the amount of Na in the carrier was reduced to 0.2% or less as Na 2 O. After this,
The alumina granules were dried at 150°C for 3 hours and reactivated by firing at 800°C for 3 hours. The activated alumina granules obtained as follows were examined for crushing strength, bulk density, and attrition resistance by the methods shown below. (1) Compressive strength measurement method The strength of the activated alumina granules was measured using a Kiya hardness tester, and the average value of 20 particles was taken as the crushing strength. (2) Bulk density measurement method Approximately 40 c.c. of activated alumina granules were filled into a 100 c.c. graduated cylinder, and the bulk density was calculated from the volume and weight. (3) Measuring method of attrition rate The attrition rate was measured using the attrition tester shown in Figure 1. First, the activated alumina granules to be tested were 50c.c.
After baking at 550℃ for about 1 hour, the weight was measured.
The weight at this time was defined as W1 . Next, this test was performed with a maximum diameter of 130 mm, a minimum diameter of 20 mm, and a cone height of 230 mm.
The activated alumina granules in the attrition tube 3 are placed in the attrition tube 3 of the attrition tester shown in FIG. Atraction exercise was performed for 5 minutes. Note that the air blown into the attrition tube 3 is discharged to the outside of the system from the cap 2 made of wire mesh at the top. After that, the activated alumina granules are transferred to the attrition tube 3.
The sample was taken out, baked at 550°C for 1 hour, and its weight was measured. This weight was defined as W 2 , and the attrition rate was calculated using the following formula. Attrition rate (%) = W 1 - W 2 /W 1 × 100 In addition, as a comparative example, the granulated alumina granules were cured in water (Comparative Example 1) instead of in the NaOH aqueous solution. The properties of the alumina granules were measured in the same manner when they were cured in a 3% NaOH aqueous solution (Comparative Example 2) or in water (Comparative Example 3) without being baked. The results of the measurements as described above are shown in FIGS. 2, 3, and 4. Figure 2 shows alumina granules before curing.
This is a graph showing the relationship between baking temperature and attrition rate. Line A in the figure shows the product according to the present invention (Example 1), and line B shows Comparative Example 1 which was cured in water after baking. In addition, the white circles and white triangles in the figure are those of Comparative Example 2, respectively, which were cured without baking.
and 3 are shown. Figure 3 is a graph showing the relationship between firing temperature and crushing temperature, and Figure 4 is a graph showing the relationship between firing temperature and bulk density. Lines A and B, white circles, and white triangles in the figure are , which shows something similar to FIG. As is clear from these figures, according to the present invention, the strength and attrition resistance of the alumina granules are significantly improved, and the bulk density is also reduced. Example 2 The process was carried out in the same manner as in Example 1 except that the curing after baking was carried out in a 5% KOH aqueous solution.
Similar results as in Example 1 were obtained. Example 3 Aluminum hydroxide with an average particle size of 40μ produced by the Bayer method was partially dehydrated and then ground to an average particle size of 12μ. Next, 80% by weight of this alumina powder and 20% by weight of cellulose were mixed, and this powder was granulated into alumina granules having a particle size of 2.8 to 4.0 mmψ using a dish granulator. The above alumina granules are treated in the following four ways,
The characteristics of each alumina granule were investigated in the same manner as in Example 1. (1) After firing the alumina granules at 400℃ for 10 hours, 3%
Cured in NaOH aqueous solution. Thereafter, the carrier was washed with water to reduce Na + in the carrier to 0.2% or less as Na 2 O, dried at 200°C for 3 hours, and calcined at 820°C for 3 hours to obtain catalyst carrier A according to the present invention. (2) The alumina granules were calcined at 400°C for 10 hours and then cured in water at 160°C under saturated steam pressure for 10 hours. After this, dry at 200℃ for 3 hours, and then dry at 820℃.
The catalyst carrier B was obtained by firing for 3 hours. (3) The alumina granules were cured in water for 10 hours under saturated steam pressure at 160°C. After this, the catalyst carrier C was dried at 200℃ for 3 hours and calcined at 820℃ for 3 hours.
I got it. (4) The alumina granules were cured in a 3% NaOH aqueous solution for 10 hours under saturated steam pressure at 160°C.
After this, the carrier is washed with water to convert the Na + in the carrier into the amount of Na 2 O.
After reducing it to 0.2% or less, dry it at 200℃ for 3 hours,
Catalyst carrier D was obtained by firing at 820°C for 3 hours. Table 1 shows the results of investigating the characteristics of the above catalyst carriers A, B, C, and D.
【表】
実施例 ４
バイヤー法で製造された平均粒径40μの水酸化
アルミニウムを部分脱水した後、平均粒径8μま
で粉砕した。このアルミナ粒末72重量％、結晶セ
ルロース20重量％および平均粒径1μの酸化セリ
ウム（CeO2）８重量％を混合し、この粉末を皿
型造粒機で粒径2.8〜4.0mmψの粒状体に造粒し
た。
上記粒状体を用いて、実施例３と同様の方法で
試験した。ここで造粒された粒状体を400℃で10
時間〓焼した後、３％NaOH水溶液中で養生し
たものを担体Ｅ、同様に〓焼後、水中養生したも
のを担体Ｆ、粒状体を〓焼せずそのまま水中で養
生したものを担体Ｇ、そのまま３％NaOH水溶
液中で養生したものを担体Ｈとした。以上の担体
Ｅ、Ｆ、Ｇ、Ｈの特性を第２表に示す。[Table] Example 4 Aluminum hydroxide with an average particle size of 40μ produced by the Bayer method was partially dehydrated and then ground to an average particle size of 8μ. 72% by weight of this alumina powder, 20% by weight of crystalline cellulose, and 8% by weight of cerium oxide (CeO 2 ) with an average particle size of 1μ are mixed, and this powder is made into granules with a particle size of 2.8 to 4.0 mmψ using a dish-type granulator. It was granulated. A test was conducted in the same manner as in Example 3 using the above granular material. The granules granulated here are heated to 400℃ for 10
Time: After baking, the material was cured in 3% NaOH aqueous solution as carrier E. Similarly, after baking, the material was cured in water as carrier F. The granules were cured in water without being baked as carrier G. Carrier H was obtained by curing in a 3% NaOH aqueous solution. The properties of the above carriers E, F, G, and H are shown in Table 2.
【表】
実施例 ５
バイヤー法で製造された平均粒径40μの水酸化
アルミニウムを部分脱水した後、粉砕して平均粒
径12μのアルミナ粉末とした。この粉末と酸化マ
グネシウム（MgO）をAl2O3：MgO＝１：１（モ
ル比）となるように混合した。次にこの混合粉末
70重量％と結晶セルロース30重量％とを混合した
粉末に水を添加して押出した後、マルメライザー
で３〜４mmψの球形に整粒した。
上記粒状体を350℃で10時間〓焼した後１％
NaOH水溶液中で養生したものを担体Ｋ、同様
に〓焼後水中で養生したものを担体Ｌ、粒状体を
〓焼せずそのまま水中で養生したものを担体Ｍ、
そのまま１％NaOH水溶液中で養生したものを
担体Ｎとした。尚、この養生は全て140℃の飽和
水蒸気圧下で10時間行なつた。また養生後の各担
体は実施例１と同様にして担体特性を調べた。結
果を第３表に示す。[Table] Example 5 Aluminum hydroxide with an average particle size of 40 μm produced by the Bayer process was partially dehydrated and then ground to obtain alumina powder with an average particle size of 12 μm. This powder and magnesium oxide (MgO) were mixed so that Al 2 O 3 :MgO=1:1 (molar ratio). Next, this mixed powder
Water was added to a powder of a mixture of 70% by weight and 30% by weight of crystalline cellulose, which was extruded and then sized into spheres of 3 to 4 mm ψ using a marmerizer. 1% after baking the above granules at 350℃ for 10 hours
Carrier K is obtained by curing in NaOH aqueous solution, carrier L is obtained by curing in water after baking, carrier M is obtained by curing in water without baking, and granules are cured in water without baking.
Carrier N was obtained by curing in a 1% NaOH aqueous solution. All of this curing was carried out for 10 hours under saturated steam pressure at 140°C. Further, the characteristics of each carrier after curing were investigated in the same manner as in Example 1. The results are shown in Table 3.
【表】
以上の如く、本発明によれば従来の製造工程で
製造された触媒担体より強度が大で、しかも耐摩
耗性に優れた触媒担体を製造できる。従つて、同
一の強度および耐摩耗性を有する場合、従来の触
媒担体より密度を小さくできるので、触媒の軽量
化ならびに暖機性の面から非常に有利であり、本
発明の工業的価値は極めて大なるものである。[Table] As described above, according to the present invention, it is possible to produce a catalyst carrier which has greater strength and excellent wear resistance than catalyst carriers produced by conventional production processes. Therefore, if the strength and abrasion resistance are the same, the density can be lower than that of conventional catalyst carriers, which is very advantageous in terms of weight reduction and warm-up of the catalyst, and the industrial value of the present invention is extremely high. It is a big thing.
【図面の簡単な説明】[Brief explanation of the drawing]
第１図は、アトリシヨン試験機の一部破断図、
第２図は、〓焼温度とアトリシヨン率との関係を
示すグラフ、第３図は、〓焼温度と圧壊強度との
関係を示すグラフ、第４図は、〓焼温度を嵩密度
との関係を示すグラフである。
図中、１……ノズル、２……金網製キヤツプ、
３……アトリシヨン筒、４……アルミナ粒状体。
Figure 1 is a partially cutaway view of the attrition tester.
Figure 2 is a graph showing the relationship between firing temperature and attrition rate, Figure 3 is a graph showing the relationship between firing temperature and crushing strength, and Figure 4 is a graph showing the relationship between firing temperature and bulk density. This is a graph showing. In the figure, 1... nozzle, 2... wire mesh cap,
3... Attrition cylinder, 4... Alumina granules.