Niobium chlorinator

Fig. 9.9. Extraction of niobium (chlorination, hydrogen purification, magnesium reduction process).

Opa.nte. There are two methods used at various plants in Russia for loparite concentrate processing (12). The chlorination technique is carried out using gaseous chlorine at 800°C in the presence of carbon. The volatile chlorides are then separated from the calcium—sodium—rare-earth fused chloride, and the resultant cake dissolved in water. Alternatively, sulfuric acid digestion may be carried out using 85% sulfuric acid at 150—200°C in the presence of ammonium sulfate. The ensuing product is leached with water, while the double sulfates of the rare earths remain in the residue. The titanium, tantalum, and niobium sulfates transfer into the solution. The residue is converted to rare-earth carbonate, and then dissolved into nitric acid. 

The reaction of chlorine gas with a mixture of ore and carbon at 500—1000°C yields volatile chlorides of niobium and other metals. These can be separated by fractional condensation (21—23). This method, used on columbites, is less suited to the chlorination of pyrochlore because of the formation of nonvolatile alkaU and alkaline-earth chlorides which remain in the reaction 2one as a residue. The chlorination of ferroniobium, however, is used commercially. The product mixture of niobium pentachloride, iron chlorides, and chlorides of other impurities is passed through a heated column of sodium chloride pellets at 400°C to remove iron and aluminum by formation of a low melting eutectic compound which drains from the bottom of the column. The niobium pentachloride passes through the column and is selectively condensed the more volatile chlorides pass through the condenser in the off-gas. The niobium pentachloride then can be processed further. 

The reaction of finely ground ores and an excess of carbon at high temperatures produces a mixture of metal carbides. The reaction of pyrochlore and carbon starts at 950°C and proceeds vigorously. After being heated to 1800—2000°C, the cooled friable mixture is acid-leached leaving an insoluble residue of carbides of niobium, tantalum, and titanium. These may be dissolved in HF or may be chlorinated or burned to oxides for further processing. 

Another solvent extraction scheme uses the mixed anhydrous chlorides from a chlorination process as the feed (28). The chlorides, which are mostly of niobium, tantalum, and iron, are dissolved in an organic phase and are extracted with 12 Ai hydrochloric acid. The best separation occurs from a mixture of MIBK and diisobutyl ketone (DIBK). The tantalum transfers to the hydrochloric acid leaving the niobium and iron, the DIBK enhancing the separation factor in the organic phase. Niobium and iron are stripped with hot 14—20 wt % H2SO4 which is boiled to precipitate niobic acid, leaving the iron in solution. 

Niobium Pent chloride. Niobium pentachloride can be prepared in a variety of ways but most easily by direct chlorination of niobium metal. The reaction takes place at 300—350°C. Chlorination of a niobium pentoxide—carbon mixture also yields the pentachloride however, generally the latter is contaminated with niobium oxide trichloride. The pentachloride is a lemon-yeUow crystalline soHd that melts to a red-orange Hquid and hydrolyzes readily to hydrochloric acid and niobic acid. It is soluble in concentrated hydrochloric and sulfuric acids, sulfur monochloride, and many organic solvents. 

Two main methods exist for the production of tantalum and niobium from the mineral raw material. The first method is based on the chlorination of raw material, followed by separation and purification by distillation of tantalum and niobium in the form of pentachlorides, TaCl5 and NbCl5 [24, 29]. Boiling points of tantalum and niobium pentachlorides (236°C and 248°C, respectively) are relatively low and are far enough apart to enable separation by distillation. 

Chlorination of ferroalloys (ferroniobium-tantalum) is a more economical and simple alternative [30]. The process is performed on a sodium chloride melt that contains iron trichloride, FeCU. Chlorine is passed through the melt yielding NaFeCl4, which interacts as a chlorination agent with the Fe-Nb-Ta alloy. Chlorination of ferroalloys allows for the production of pure tantalum and niobium pentachlorides, which are used further in the production of high purity oxides and other products. 

Niobium combusts spontaneously in fluorine when it is cold and in chlorine at... 

Chlorine Trifluoride Tech. Bull. , Morristown, Baker Adamson, 1970 Incandescence is caused by contact with bromine, iodine, arsenic, antimony (even at -10°C) powdered molybdenum, niobium, tantalum, titanium, vanadium boron, carbon, phosphorus or sulfur [1], Carbon tetraiodide, chloromethane, benzene or ether ignite or explode on contact, as do organic materials generally. Silicon also ignites [2],... 

Niobium ignites in cold fluorine, and in chlorine at 205°C, and incandesces in contact with bromine trifluoride. 

Nickel carbonyl Niobium Nitrates Air, bromine, oxidizing materials Bromine trifluoride, chlorine, fluorine Aluminum, BP, cyanides, esters, phosphorus, tin(II) chloride, sodium hypophos-... 

The metal reacts with chlorine at 300°C forming niobium pentachloride, NbCls. It reacts with hot concentrated hydrochloric acid, also forming the pentachloride. Niobium dissolves in hot concentrated sulfuric acid at 170°C. Fused alkalies such as caustic soda and caustic potash attack niobium, embrittling the metal. 

Niobium pentachloride is obtained as an intermediate during extraction of niobium from its ores (see Niobium). Also, the pentachloride is obtained readily by direct chlorination of niobium metal at 300 to 350°C ... 

The pentachloride also may be made by chlorination of niobium pentoxide in the presence of carbon at 300°C. The products, however, contain small amounts of niobium oxide trichloride, NbOCls. 

Preparation of Niobium(V) and Tantalum(V) Halides. The niobium(V) and tantalum (V) chloride and bromide were prepared in a system of sealed, evacuated bulbs by reacting the pure metal with gaseous halogen. For the chlorides the metal was maintained at 300° to 350° under a chlorine pressure of approximately 70 mm. of Hg the chlorine pressure was maintained By keeping the liquid chlorine immersed in a dry ice-acetone bath. For the bromides the metal was maintained at a temperature of 400° to 450° under a bromine pressure of approximately 250 mm. of Hg, maintained by leaving the liquid bromine at room temperature. 

The action of carbon tetrachloride or a mixture of chlorine with a hydrocarbon or carbon monoxide on the oxide.—H. N. Warren 9 obtained aluminium chloride by heating the oxide to redness with a mixture of petroleum vapour and hydrogen chloride or chlorine, naphthalene chloride or carbon tetrachloride was also used. The bromide was prepared in a similar manner. E. Demarpay used the vapour of carbon tetrachloride, the chlorides of chromium, titanium, niobium, tantalum, zirconium, cobalt, nickel, tungsten, and molybdenum H. Quantin, a mixture of carbon monoxide and chlorine and W. Heap and E. Newbery, carbonyl chloride. 

In [NbCl5(HCN)],139 the niobium atom is octahedrally surrounded by five chlorines and b the nitrogen atom of HCN the Nb—Cl bond irons to nitrogen is the shortest (2.243(1) a... 

NbCl2(RCp)2] (R = H, Me) complexes react with H202, affording [Nb(02)Cl(RCp)2]. In the complex with R = H the two oxygen atoms (O—O 1.47(1) A) and the chlorine atom are in the plane which bisects the Nb(Cp)2 bent sandwich system the coordination around niobium is thus pseudotetrahedral. In the presence of H202, [Nb(02)Cl(Cp)2] catalytically converts cyclohexene to its epoxide. 

A), and bear two chlorine atoms in apical and two acetonitrile ligands in equatorial positions. The octahedral environment of the metal is distorted as a result of niobium-niobium interactions (2.862(2)-2.872(3) A). 

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