Oxidations of bismuth

Bismuth Oxides and Bismuthates. The only oxide of bismuth that has been definitely isolated in a pure state is bismuth trioxide. An acidic oxide that approximates the composition Bi20 certainly exists. However, there is considerable question as to the exact nature of this material and the species involved. A number of other oxides have been reported, eg, bismuth oxide (1 1) [1332-64-5], bismuth oxide (1 2), bismuth oxide (2 4)... 

Bismuth trioxide may be prepared by the following methods (/) the oxidation of bismuth metal by oxygen at temperatures between 750 and 800°C (2) the thermal decomposition of compounds such as the basic carbonate, the carbonate, or the nitrate (700—800°C) (J) precipitation of hydrated bismuth trioxide upon addition of an alkah metal hydroxide to a solution of a bismuth salt and removal of the water by ignition. The gelatinous precipitate initially formed becomes crystalline on standing it has been represented by the formula Bi(OH)2 and called bismuth hydroxide [10361 -43-0]. However, no definite compound has been isolated. 

Mixed Metal Oxides and Propylene Ammoxidation. The best catalysts for partial oxidation are metal oxides, usually mixed metal oxides. For example, phosphoms—vanadium oxides are used commercially for oxidation of / -butane to give maleic anhydride, and oxides of bismuth and molybdenum with other components are used commercially for oxidation of propylene to give acrolein or acrylonitrile. 

The first catalysts used commercially to convert the propylene with high selectivity were mixed oxides of bismuth and molybdenum, referred to as bismuth molybdates. Improved catalysts consisting of a number of soHd phases have been developed, with each generation becoming more compHcated than its predecessor. Among the catalysts cited in a patent is the following Co gNi 2"Fe 3Bi (Mo0 22 Si02 with some P and K (88). Sihca is the... 

All other dangerous reactions consist of oxidations of bismuth by strong oxidants. Thus, chloric and perchloric acids lead to highly sensitive explosives (probably bismuth chlorate and perchlorate). Fuming nitric acid causes the incandescence of bismuth at ambient temperature whereas a detonation occurs when molten bismuth is mixed with concentrated nitric acid. Rnally, a bismuth/molten ammonium nitrate mixture causes a very violent or even an explosive reaction. 

Active crystal phases. Detailed studies have been performed to identify the distinct phases in the Bi—Mo—(P)—O system and to determine their specific catalytic properties. It is well known that the individual oxides of bismuth and molybdenum are not useful catalysts themselves Bi203 is moderately active but not selective while M0O3 is selective but hardly active. Yet, the combination is very active and selective at a Bi/Mo ratio between 2/3 and 2/1. The following crystal phases are identified in this range (Schuit [281]). 

The only well-established oxide of bismuth is Bi203, a yellow powder soluble in acids to give bismuth salts. It lacks acidic character and is insoluble in alkalis. From solutions of bismuth salts, alkali, or ammonium hydroxide precipitates a hydroxide, Bi(OH)3. Like the oxide, this compound is completely basic. Bismuth(V) oxide is extremely unstable and has never been obtained in pure form. The action of extremely powerful oxidizing agents on Bi203 gives a red-brown powder that rapidly loses oxygen at 100°C. 

The common oxide of bismuth is Bi203, which is found in nature as the mineral bismite, has a variety of uses including the making of enamels for cast iron. 

Gryzbowska et al. [106] compared the reaction products formed when pulses of allyl iodide or propene were passed over bismuth oxide or molybdenum oxide. A clear limitation of these experiments is that even the simplest bismuth molybdate catalysts contain neither bismuth oxide nor molybdenum oxide, but instead are made up of a binary oxide of bismuth and molybdenum, whose structure is different to that of bismuth oxide and molybdenum oxide. Gryzbowska et al. selected allyl iodide because of the very low bond dissociation enthalpy associated with the C-I bond, implying that a surface allyl species would readily form from this starting material. In addition, a lower reaction temperature was required for the reaction of allyl iodide than for propene reflecting the greater inherent reactivity of the former. 

Acrylonitrile is manufactured by passing propylene, ammonia, and air over a mixed-oxide catalyst at 400-500 C. The process is also a major source of acetonitrile and hydrogen cyanide which are obtained as the result of side reactions. Catalysts used in this process are generally mixed oxides of bismuth or antimony with other multivalent metals such as molybdenum, iron, uranium, and tin. At one time, the preferred catalyst for propylene... 

The catalyst systems employed are based on molybdenum and phosphorus. They also contain Various additives (oxides of bismuth, antimony, thorium, chromium, copper, zirconium, etc.) and occur in the form of complex phosphomolybdates, or preferably heteropolyacids deposited on an inert support (silicon carbide, a-alumina, diatomaceous earths, titanium dioxide, etc.). This makes them quite different from the catalysts used to produce acrylic acid, which do not offer sufficient activity in this case. With residence times of 2 to 5 s, once-through conversion is better than 90 to 95 per cent, and the molar yield of methacrylic acid is up to 85 to 90 per cent The main by-products formed are acetic add, acetone, acrylic add, CO, C02, etc. The major developments in this area were conducted by Asahi Glass, Daicel, Japan Catalytic Chemical, Japanese Gem, Mitsubishi Rayon, Nippon Kayaku, Standard Oil, Sumitomo Chemical, Toyo Soda, Ube, etc. A number of liquid phase processes, operating at about 30°C, in die presence of a catalyst based on silver or cobalt in alkaline medium, have been developed by ARCO (Atlantic Richfield Co,), Asahi, Sumitomo, Union Carbide, etc. 

Bismuth trloxlde 4136 Bi203 Blsmouthous oxide flowers of bismuth oxide of bismuth protoxide of bismuth teroxide of bismuth. 

R. Suhrmann (Technical University of Hanover) According to conductivity and photoelectric measurements, the first step in the oxidation of bismuth is the formation of 02 ions. At low temperatures (90°K) and low pressures (10 mm. Hg), the resistance of thin bismuth films and the work function at first decrease suddenly and then gradually increase because of the decomposition of the O2 molecules into 0 atoms. 

Occurs sometimes as metal, more frequently as sulphuret. It is a highly crystalline metal, of a reddish white colour, fusible at 476 , and even volatile in close vessels. When heated in the air it bums with a bluish flame, forming oxide of bismuth. Bismuth is an ingredient in Newton s fusible metal, and in various fusible alloys. 

A search was now made for metal oxides that can adsorb olefins in the oxidized state and whose oxidation states differ by two units. These include thaUimn, lead, indium, and bismuth. Since the oxides of bismuth and lead are of low thermal stability, attention was focussed on the oxides of thallium and indium. 

When solutions of lead or bismuth salts are treated with alkali hypo-bromite, lead peroxide and higher oxides of bismuth are formed. These products react with benzidine acetate to give benzidine blue (seepage 282). However, if bismuth salts are heated alone with alkali hydroxides, a yellow precipitate forms, [probably BiO(OH)] and, when once formed, is not converted into higher bismuth oxides on treatment with h3q)obromite. This resistance is applied in the detection of lead in bismuth salts. The following procedure is recommended in the examination of pharmaceutical bismuth preparations (e.g., bismuth sub-gallate, -tannate, -salicylate). 

The only weU-estahhshed oxide of bismuth is Bi203, which occurs in nature as the mineral hismite. Bismuth(III) oxide exists as a yellow powder. A hismuth(V) oxide is known, but it is extremely imstahle. A hydroxide - Bi(OH)3 - can also be precipitated from solutions of bismuth salts it is a white to yellowish white amorphous powder which readily loses one molecule of water to form the yellow BiO(OH) (Cotton et al., 1999 Merck Index, 1996 Gmelin, 1932). 

Salter (1869) describes the preparation of what he calls bismuth purple by passing chlorine gas through the hydrated oxide [of bismuth] suspended in a saturated solution of potash. As soon as the oxide becomes brown-red, the mixture is boiled and the hquid decanted off at once, the residue being immediately washed first with alcohol and then with water. Salter clearly felt the effort was not worthwhile. 

Rudolph Brandes (Salz-UflFeln, Lippe Detmold 18 October 1795-3 December 1842), a pharmacist and founder of the North Carman Apolheker Verein and (as a continuation of earlier journals) editor of the Archiv der Phcarmade discovered several alkaloids delphinine independently of Las saigne and Fenuelle, daturine, atropine and hyoscyamine. Brandes also analysed minerals and mineral waters, investigated suberic acid (Suberin saure, Korksaure), camphoric acid (Kamphorsdure), and coconuts. He confirmed the discovery of a higher oxide of bismuth by Stromeyer. ... 

The validity of Eq. (22-6) is dependent upon the assumption that side reactions, such as the oxidation of bismuth by the salt, are negligible. Since AF° for these reactions are large positive numbers, it is reasonable to consider bismuth as inert in this respect. Bismuth, of course, interacts with the lanthanides and magnesium very strongly, but this is taken into account by the use of activity coefficients. 

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