HU193682B - Process for the continuous production of niobium pentachloride of at least 99 mass percent purity - Google Patents

Abstract

Ferroniobium and chlorine gas are heated to 600-800 deg.C to form a mixture of (NbCl5)2, Fe2Cl6, Al2Cl6 and SiCl4 gases that are purified by passing through a column of hot NaCl pieces (at 280-300 deg.C). The impurities react with NaCl and collect at the bottom of the column in liquid form, the purified (NbCl5)2 steam is then condensed at below 280 deg.C. The granules of NaCl are of 30-40 mm dia. and are replaced regularly.

Description

The present invention relates to a process for the continuous production of niobium pentachloride (NbCl ₅ ) of at least 99% purity from ferronobium by the continuous chlorination of the starting material used in steel production, which is aluminothermally prepared.

Niobium pentachloride is known as a starting material for the preparation of lithium niobate (LiNbO ₃ ), an important material in microelectronics. The preparation of lithium niobate requires a high purity of (NbCl ₅ ) ₂ containing a few ppm impurities and can be obtained by hydrolysis, firstly niobium pentoxide (Nb ₂ O ₅ ) followed by lithium niobate during the reaction. The known process for the production of niobium pentachloride is generally only a non-developable, costly or even hazardous laboratory-scale method (GMELINS Handbuch: NIOB. System Nummer: 49, Teil B., Verlag Chemie Weinheim, 1970).

The disadvantage of the known process is that it is usually a laboratory-scale process in a quartz tube which cannot be operated due to the highly exothermic reaction. This process allows only batch production and is suitable for chlorinating only small amounts of material, because of the high heat production, there is a risk of ferronobium aggregation. In addition, the heat-resistant liner often needs to be replaced.

The chloride mixture thus obtained still has to be thoroughly purified, since during the chlorination a large amount of Fe ₂ Cl ₆ , Al ₂ Cl ₆ , SiCl ₄ , etc. also formed. A product containing 99% or more of (NbCl ₅ ) ₂ can only be produced in a very time consuming way and with significant loss of niobium.

SUMMARY OF THE INVENTION The object of the present invention is to overcome the drawbacks of the known process and to provide a process for the continuous production of niobium pentachloride having a purity of at least 99%.

In our experiments, we have found that the process can simply be carried out with high productivity in a cooled steel reactor, without corrosion, and can be easily developed into an industrial process. The chlorides can be quantitatively separated from the chlorides by modern column salt absorption. Thus, in one step of our process, with a continuously operating reactor and a salt column connected in series, purity (NbCl ₅ ) _{2 of} greater than 99.0% can be produced on an industrial scale.

It forms the basis of the invention is the recognition that if the heat generated is continuously removed during the (NbCl _{5) 2} are produced, and the starting material is continuously constant utánadagolással fed to the reactor, then (NbCl _{s) 2} continuous manufacture possible. Water is circulated around the reactor, and the use of cooling water allows the steel reactor to be operated without damage. The essence of the process according to the invention can be characterized by the following 2 equations (together with the accompanying materials):

2Nb + 5C1 ₂ = (NbCl ₅ ) ₂ 2Fe + SCI ₂ = Fe ₂ Cl ₆ , 2A 1 + ₃ C _{1 2} = Al ₂ Cl ₆ Si + ₂ Cl ₂ = SiCl ₄

According to the invention, ferroniobium and chlorine gas are continuously added to a combustion chamber at a temperature of 600-800 ° C to form (NbCl ₅ )., Fe ₂ Cl ₆ , SiCl ₄ etc. vapors are purified by passage through packed pieces with NaCl column temperature of 280-320 ° C, whereby the wipes NaCl constantly replenished, the NaCl has formed the impurity metals molten complex compounds are continuously withdrawn and purified (NbCl _{5) 2} vapors It is cooled to below 280 ° C, preferably cooled to room temperature. The cleaning process can be described as follows:

Fe ₂ Cl ₆ + 2NaCl = 2NaFeCl ₄ and

A1 ₂ C1 ₆ + 2NaCl = 2NaAICl ₄ and thus the volatility of the chlorides decreases by several orders of magnitude.

The continuous production of (NbCl ₅ ) ₂ is carried out with the following parameters. In order to prevent aggregation, a minimum of 20-30 mm of ferronobium is added. One-tenth of the amount of chlorine added is fed into the steam stream by-pass after the firebox. Thus, a constant excess of chlorine is maintained and a complete conversion of the introduced ferroniobium is ensured. For purification of (NbCl ₅ ) ₂ vapors, bulk NaCl with a minimum particle size of 30-40 mm is used and the NaCl consumed is continuously replaced. After reactor start-up, NaCl is generally added in an amount equivalent to 1/6 of the volume produced per hour.

The process of the present invention enables the size and production costs of the apparatus to be reduced compared to the prior art heat-insulated, intermittent, large-scale furnaces, while increasing performance.

Process-1 t (NbCl ₅ | _<2 / m ² h power density can be achieved, i.e. the total quantity produced is a linear function of the reactor cross-section.

The present invention allows very pure, less than 20 ppm iron and aluminum content (NBCI _{5) 2} -t produce, comprising four orders of magnitude less impurities than the starting material. Yields of at least 95%, but returning to the firing chamber the amount of (NbCl ₅ ) ₂ remaining in the molten complex compounds (greater than 2 to 3%), yields more than 98%.

-2193682

Example:

Of the ferro-niobium in the market and used for the production of steel - Nb: 65-67%, Fe: 28-30%, Al: 0.5-0.7, Si: -2.0-2.5% - 66.9 1.6 kg of ⁵ % ferric niobium containing 20 to 30 mm mesh are heated to glow in a combustion gas atmosphere and placed in a reactor.

The vertical reactor tube has a diameter of 150 mm and a height of 400 mm. The reactor led stone ⁰ penyébe cooling water temperature 15 ° C and a flow rate of 5 L / min, the outflowing water temperature is 40-50 ° C. After inserting the heated ferronobium, the introduction of chlorine gas is started. · ¹ through the dispensing opening 5 continuously 1.6 kg per hour - is now room temperature - ferronióbiumot added and continuously fed per hour 1.2 ^m3 of chlorine gas to the reactor through the conduit chloro. Contaminated vapors formed in the reactor ²⁰ (NbCt ₅ ) _{2 are} passed to a nickel salt column containing 30-40 mm NaCl. The vertical tubular column has a diameter of 120 mm and a height of 2 m. The amount of filling is 10-14 kg. The Salt Column 280—

Temperature of 320 ° C is provided by heating the jacket. The (NbCl ₅ ) ₂ vapors come in contact with NaCl at the bottom of the column and the purified vapors are discharged to the refrigerator at the top of the column. A constant supply of NaCl is provided through the dosing opening of the autumn stomach at a volume of 0.52 kg / h.

For the purpose of utánklórozás 0.12 m ³ / h of chlorine gas was discharged from the reactor product mixture, before ³⁵ filled with the NaCl-lal column driving.

The molten complex compounds containing the contaminating metals, NaAlCl ₄ and NaFeCl _{4, are} discharged at a rate of 2.1 kg per hour through a heated conduit at the bottom of the column. ⁰ processing suk recirculation into the reactor - the remaining niobium pentachloride extraction - occurs. Complex salts do not pollute the environment.

The primary yield is 3 kg / hr 45 (NaCl ₅ ) ₂ (96.4% of theory). Returning the molten complex compounds to the firing chamber recovers 80% of the remaining (NbCl ₅ ) ₂ . More than 98% yield is obtained. The composition of the product is characterized in that (NbCl ₅ ) ₂ : minimum 99.9%; Fe: 0.002% maximum; Al: 0.002% maximum; Si: maximum 0.005%.

Claims (4)

1.) A process for the continuous production of niobium pentachloride having a purity of at least 99% by chlorination of ferro-niobium, characterized in that the initial ferro-niobium with a particle size of 10-50 mm and the chlorine gas are continuously added in an amount of 0.8-1.2 m ³ water-cooled to - 600-800 ° C, and formed (NbC 15) 2, Fe 1, Cl 6, Al 2 Cl 6, SiCl. vapors are further mixed with chlorine gas in an amount of 0.04 to 0.16 m ^{3 of} Cl 2 / kg feedstock for post-chlorination, preferably by adding 5 to 20% of the total amount of chlorine to the product mixture leaving the reactor, then 280 to 320 ° C. The column is purged through a 1-3 m long column filled with NaCl, 20-50 mm 'in size, while the piece NaCl is continuously added in 0.2-0.5 kg NaCl / kg starting material and molten complex salt salts of the contaminating metals are continuously discharged at a rate of from 1.3 to 2.0 kg / kg of feedstock, 0 to 20% being fed back, and purified (NbCl ₅ ) ₂ in the vapor state below 280 ° C. - preferably to room temperature - condensed when cooled. 2. A process according to claim 1, characterized in that the ferro-niobium is added to the firing chamber with a particle size of 20-30 mm. 3. A process according to claim 1, characterized in that 1/10 of the chlorine used for chlorination is introduced into the steam stream by-pass after the firebox. 4. A process according to claim 1, wherein NaCl is added to the column at a particle size of 30-40 mm.