Chromium oxide nitrate

The chromium oxides were prepared according to the following procedure [6-8]. Chromium oxide resulted from the dehydration of chromium hydroxide obtained by the addition of an ammonia solution (5M) to a solution of chromium nitrate (0.5M) The final pH was equal to 7.5 and the hydroxide formed was kept constantly stired and heated at 80°C for 1 h so as to obtain complete precipitation. This solid was filtered and washed three times with hot distilled water and dried for 16 h in an oven at 90°C. It was then submitted to a dynamic thermal treatment under nitrogen at 380°C for 8 h. The chromium oxide formed was cooled down under the same vector gas. 

The mixed chromium and nickel (5% and 10% Ni atomic) catalysts were prepared by dehydration of mixed chromium and nickel hydroxides prepared by adding an ammonia solution to a solution of chromium and nickel nitrate in order to maintain a pH = 7 1. The final pH was equal to 7.S. The hydroxyde treatment was the same as the one already described for chromium oxide. 

Chromium iron manganese brown spinel, formula and DCMA number, 7 348t Chromium iron nickel black spinel, formula and DCMA number, 7 348t Chromium isotopes, 6 476 Chromium magnesium oxide, 5 583 Chromium manganese zinc brown spinel, formula and DCMA number, 7 348t Chromium-nickel alloys, 77 100-101 Chromium-nickel-iron alloys, 17 102-103 Chromium-nickel stainless steels, 15 563 Chromium niobium titanium buff rutile, formula and DCMA number, 7 347t Chromium(III) nitrate, 6 533 Chromium nitride, 4 668... 

Hexamethylenetetramine Explosives. Several explosive compositions containing hexamine in admixtures with oxidants or as chromium, copper nitrate, perchlorate, peroxide comps are known. Several hexamine/oxidant mixtures have been patented as explosive propellant compositions ... 

Preparation of Potassium Chromate. (Perform one experiment on each table.) Melt a mixture of 1 g of potassium carbonate, 1 gof potassium hydroxide, and 2 g of potassium nitrate in an iron crucible by heating with the flame of a burner. While stirring the melt with an iron wire, introduce 1 g of finely comminuted chromite or -0.8 g of chromium oxide into the crucible. Roast the mixture for 5-10 minutes on a blowpipe. Treat the cooled melt with water. Filter the solution and evaporate it until a crystalline film appears. What is the composition of the formed crystals Why was potassium carbonate introduced into the reaction Write the equation of the reaction. 

The most extensive investigation was carried out by Guiochon and L. Jacqu6 [30] and Guiochon [17, 31]. They used the same thermogravimetric method as in their former experiments, and examined the influence of chromium oxide (0.3-8%), potassium bichromate (0.1-3%), chromium nitrate (1-5%) and also pure chromium (0.033-5.5%) [30]. 

The copper chromium oxide (Cu/Cr = 1) has been prepared by coprecipitation of copper and chromium nitrates with ammonium hydroxide, followed by thermal decomposition in flowing nitrogen up to the final temperature (370"C), according to a previously described method (8). The apparatus and the catalytic procedure have also been described elsewhere in case of gas phase reactions (5) and liquid phase reactions (7). 

A copper-chromium oxide on pumice catalyst has particular value for the dehydrogenation of primary and secondary alcohols to the corresponding carbonyl compounds (see Section 5.6.1, p. 581). Dissolve 10.4g of barium nitrate (AnalaR) in 280 ml of water at about 80 °C and add to this hot solution 87 g of copper(n) nitrate trihydrate (AnalaR) stir the mixture and heat until a homogeneous solution results. Prepare a solution of 50.4 g of recrystallised ammonium dichromate in a mixture of 200 ml of water and 75 ml of concentrated ammonia solution (d 0.880). To the ammonium chromate solution at 25-30 °C add the hot (80 °C) nitrate solution in a thin stream with stirring. Allow the mixture to cool and filter off the yellowish-brown precipitate with suction press with a glass stopper and suck as dry as possbile. Transfer the... 

At present, the main industrial catalyst of ammonia oxidation is platinum and its alloys with aluminium and rhodium. Taking into account the deficit and high cost of platinum metals, the dcCTcasing of the consumption and losses of platinum metals is an urgent problem. Therefore, several compositions of complex oxide catalysts have been developed with iron (111), cobalt and chromium oxides as an active component. Complex oxides with perovskite structure are used as new catalysts they provide selective oxidation of ammonia with an yield not less than 90 %. The authors of [33] proposed to use perovskite powders LaMeOj, where Me=Fe, Co, Ni, Cr, Mn, and La,.,Sr,Me03, where Me=Co, Mn and x=0.25-0.75. To prepare these compounds, they used the precipitation by tetraethyl ammonia from diluted nitrate solutions taken at necessary ratios. The powders as prepared are poorly molded as in the form of honeycomb stractures as well as in the form of simple granules. 

VANADIUM (V) OXIDE NITRATE AND CHROMIUM (VI) OXIDE NITRATE... 

Chromium(VI) oxide nitrate and vanadium(V) oxide nitrate were first prepared by Schmeisser and Lutzow by the reaction of chromium(VI) oxide and vanadium(V) oxide with nitrogen(V) oxide. The nitrogen(V) oxide was prepared in the solid state by dehydration of fuming nitric acid with phosphorus(V) oxide. The method described below simplifies the preparation of anhydrous nitrogen(V) oxide and shortens significantly the time required. The products obtained can be protected from hydrolysis by totally excluding water from the all-glass system. 

The same procedure is used for the preparation of chro-mium(VI) oxide nitrate except that the nitrogen(V) oxide is distilled into the reaction vessel under an atmosphere of dry oxygen (not ozone) to prevent the formation of any perchromic acid derivatives. The initial weight of anhydrous chromium(VI) oxide is 30 g. (0.30 mol). The reaction proceeds much faster than in the case of the vanadium compound, so that the reaction time need be only 24 hours. 

Chromium(VI) oxide nitrate is a dark red liquid which boils at 63 to 65° at 0.7 mm. Hg pressure. It is soluble in carbon tetrachloride. In water, it reacts immediately to form chromic and nitric acids. It is a more powerful oxidizing agent than vanadium (V) oxide nitrate, and care must be taken to avoid contact with hydrocarbons. It is corrosive to most metallic surfaces, except aluminum, and reacts in the same manner as vanadium (V) oxide nitrate does toward paper, wood, and rubber. It cannot be stored for so long a time as vanadium (V) oxide nitrate but is relatively stable in a sealed ampul in the absence of light and moisture. It can be purified by distillation in vacuum over lead(IV) oxide. 

Vanadium(V) oxide nitrate and chromium(VI) oxide nitrate, synthesis 22. 

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... 

There is a problem as to the effect of the contaminants upon the development of catalytic activity during heating. We assume that most of the nitrogen is present as potential ammonium nitrate and we note that chromium oxide is an effective catalyst for the decomposition of ammonium nitrate at about 200° (J02). We have heated the catalyst in a tube separated from a mass spectrometer by a valve. After heating to 100° for 30 minutes, the valve was opened and the gases evolved were analyzed. The tube was then pumped out and the temperature increased 50°, held for 30 minutes, analyzed, pumped out, and the temperature raised 50° again. This was continued to 400°. Except at 150- 00°,... 

Zinc-chromium oxide catalysts were prepared by co-precipitation from aqueous solutions of corresponding nitrates with aqueous ammonia. The precipitated hydroxo-compounds mixed with ZnO were dried at 120°C and the slightly wet product was then molded by squeezing out through orifices with diameter of 4 mm [6]. 

Cr(NH3)6]Cl3 Hexamminechro-mium(III) chloride, 2 196 [Cr(NH3)6](N03)3 Hexammine-chromium(III) nitrate, 3 153 Cr02Cl2 Chromyl chloride, 2 205 Cr03-2C6HoN Pyridine-chromium-(VI) oxide, 4 94... 

---