Catalysts fine powder, preparation

The vanadium pentoxide catalyst Is prepared as follows Suspend 5 g. of pure ammonium vanadate in 50 ml. of water and add slowly 7 5 ml. of pure concentrated hydrochloric acid. Allow the reddish-brown, semi-colloidal precipitate to settle (preferably overnight), decant the supernatant solution, and wash the precipitate several times by decantation. Finally, suspend the precipitate in 76 ml. of water and allow it to stand for 3 days. This treatment renders the precipitate granular and easy to 6lter. Filter the precipitate with suction, wash it several times with cold 5 p>er cent, sodium chloride solution to remove hydrochloric acid. Dry the product at 120° for 12 hours, grind it in a mortar to a fine powder, and heat again at 120° for 12 hours. The yield of catalyst is about 3 - 5 g. 

Catalysts are prepared by precipitation typically by mixing one solution with another solution or a suspension. The precipitate is washed and filtered (or filtered and washed), dried, calcined and crushed to a fine powder. A binder, often graphite or stearic acid is added and the powder is tabletted. 

The catalyst is prepared by suspending 20 g. of c.p. ammonium metavanadate in 200 cc. of water and adding slowly 30 cc. of concentrated hydrochloric acid (sp. gr. 1.19). The reddish-brown semi-colloidal precipitate is washed several times with water by decantation and finally suspended in 300 cc. of water and allowed to stand at room temperature for three days. This treatment makes the precipitate granular and easy to filter. The precipitate is collected on a filter using a pump and washed several times with water to free it from hydrochloric acid. It is then dried at 120° for twelve hours, finely powdered and again dried for twelve hours at 120°. 

Rhenium alkoxocomplexes are of interest as homogeneous catalysts of olefine metathesis [519], They have also been used for the preparation of fine powders ofrhenium and rhenium alloys for catalytical and powder metallurgical use [1452]. 

Copper in contact mass plays the role of a catalyst. Pure copper is obtained by the electrolysis of copper sulfate. For direct synthesis, we use the copper of two brands, Mo and Mi with 99.95-99.9% of Cu. The total impurity content (Bi, Sb, As, Fe, Ni, Pb, etc.) should not exceed 0.05-0.1%. To ensure high activity of contact mass, it is necessary to use copper powders with complex surfaces. Good results in direct synthesis are also obtained when using fine copper prepared by the mechanical spraying of copper powder or deposition of copper from copper salts. 

Inorganic powders play a key role in many fields—ceramics, catalysts, medicines, food, etc.— and many papers and books discuss powder preparation. Powder preparation is a very important step in the processing of ceramics. Table 1.1 presents the methods used for preparing fine ceramic powders. ... 

Another common catalyst prepared by coprecipitation is copper-chromium oxide, also known as "copper chromite" or Adkins catalyst.23 This catalyst is prepared by the addition of copper nitrate to a solution of ammonium dichromate in ammonia giving a precipitate copper ammonium dichromate. This precipitate is filtered, dried and then calcined at 650°-800°C, or more commonly, heated with a flame to induce a thermal reaction (Eqn. 13.5). The resulting fine powder is washed with acetic acid and dried to give the copper chromite catalyst.23 A more active catalyst is prepared by adding 10% barium nitrate by weight of copper before precipitation.24,25 Copper chromite catalysts containing calcium and were found to be less effective than those having a barium promoter.25... 

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