DE1193020B - Process for the production of boron nitride - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

Number;
File number:
Registration date:
Display day:

COIb

German class: 12 i- 21/06

1193 020
U 6059IV a / 12 i
March 13, 1959
May 20, 1965

The invention relates to a method for producing boron nitride by passing nitrogen, ammonia or an stickstoffabspaltenden gas a to 1600 ⁰ C, heated to 1200 mixture of boron oxide, boric acid or a boroxydabspaltenden compound, carbon and a catalyst, treating the reaction mixture with dilute Mineral acid and separation of boron nitride.

It is known to produce boron nitride from a batch of B ₂ O ₃ + CaO + NH ₄ Cl by treatment with NH ₃ at 1100 to 1200 ^{° C.}

According to an older known process, titanium nitrogen compounds are obtained from titanic acid or other titanium compounds by heating with carbon in a stream of nitrogen, alkali salts being added to the mixture. _{Another method is to add ilmenite (FeO · TiO 2} ) in the production of titanium nitrogen compounds to lower the working temperature, the iron of which, together with an alkali oxygen compound, namely Na ₂ CO ₃ , develop a catalytic effect.

For the production of cohesive bodies from boron nitrogen and titanium nitride, it is known from the Oxides by means of organic binders to produce moldings, which are then heated in the Ammonia stream are annealed.

Finally, it is known to produce boron nitride by using a mixture of boric acid and Carbon is passed at high temperature nitrogen and the mixture also carbonates of Mg, Contains Ca and Ba or oxides of manganese.

The disadvantage of the known processes is that the yields are too low, if not high Nitrogen pressure was applied, and that the end product often contained considerable amounts of Carbon, boron, boron carbide and unreacted boron oxide is contaminated.

According to the invention, the catalyst used is now MoO ₃ , Cr ₂ O ₃ , Nb ₂ O ₅ or a mixture of equal parts of BaCO ₃ and MnO ₂ .

The amount of the catalyst or the catalyst mixture is not more than 10% of the starting mixture.

It is advantageous if ammonium chloride is used to produce a porous mixture is added.

The reaction temperature is generally above 1200 ^° C. and preferably in the range from 1200 to 1600 ^° C. The temperature which is optimal in the special case can change depending on the type of catalyst used. Also can be the optimal amount

Process for the production of boron nitride

Applicant:

United States Borax & Chemical Corporation,

Los Angeles, Calif. (V. St. A.)

Representative:

Dr. K.-R. Eikenberg. Patent attorney,

Hanover, Am Klagesmarkt 10-11

Named as inventor:

Anthony Arthur Robinson Wood,

Watford, Hertfordshire;

Eric Campbell Shears, London (Great Britain)

Claimed priority:
Great Britain March 24, 1958

of the catalyst used change according to the type of the catalyst.

The proportion by weight of the catalyst in the heated mixture is from about 1 to 10 ° / ₀ of the total weight of the mixture.
Details can be found in the examples given below. The ratio of boron oxide or the compound which splits off boron oxide and carbon can be stoichiometric, but an excess of boron oxide is preferred so that there is definitely no carbon in the end product.

The particular advantages of the new process are the good yields at atmospheric pressure and the relatively high degree of purity of the boron nitride.

In the method according to the invention is used for

Maintaining the conversion rate the heated mixture by adding ammonium chloride kept porous. Namely, it has been found that the rate of conversion varies according to a certain period of time, say after 20 minutes, decreases, of course, the rate of conversion itself depends on the respective temperature and other conditions. It is believed that this tendency to decrease the rate of conversion is due to that the boron oxide or the substance releasing boron oxide melts together, so that the surface, which is available for the reaction is reduced and the nitrogen-containing one passes through

509 570/340

Gas is opposed to increased resistance by the mixture. For this purpose is ammonium chloride mixed into the heated mixture. The heated mixture can also be crushed at intervals be, followed by heating and passing nitrogen or nitrogen-releasing gas after Chopping is continued. Alternatively, the mixture can also be used continuously during the reaction time be moved, for example in a continuously rotating rotary kiln.

The constituents of the mixture used are preferably made up in paste form and closed Grains shaped. Mixing can be done with water if necessary. The shaping into grains can be made by passing through a sieve.

The optimal duration of the heating and transfer of nitrogen or nitrogen-releasing gas or the total duration depends on the duration of the comminution, on the type and quantity of the catalyst and the temperature used. In some cases it can be on the order of several Hours lie.

In the following, details of the invention are described in exemplary embodiments. The ones in the examples stated amounts relate to parts by weight. In Examples 2 to 29 inclusive, the Conversion of boron oxide into boron nitride has been intentionally kept incomplete in order to prevent the effects different catalysts can be better illustrated.

example 1

6 parts of boric acid, 2.5 parts of carbon, 1 part of calcium carbonate were mixed with 10 parts of water to form a paste. The paste was forced through a sieve to give granules on the order of 0.125 to 0.375 cm in diameter. These grains were ^{dried at 150 °} C. for 3 hours. The granules were placed in a vertical tube furnace with a heating length of approximately 30 cm and a diameter of approximately 6.3 cm. Nitrogen was bubbled through the tube furnace for 6 hours at a rate of _t 200 ml / min. The temperature of the grains was at 1400 ⁰ C. The product was removed after the reaction from the oven and extracted after cooling with dilute mineral acid, rinsed with water and finally dried at 150 ° C.

Example 2

11 parts of boric acid, 2.5 parts of carbon black and 1 part of manganese dioxide were intimately mixed with one another by crushing in a mortar. A 4 g sample of this mixture was heated ^{to 1400 °} C. in a boat in a tube 2.5 cm in diameter. Nitrogen was bubbled through at a rate of 250 ml / min. After an hour, the boat was pulled out, the contents carefully crushed and the boat with the crushed contents replaced. The heating and bubbling of nitrogen was then continued for an additional hour. The boat was then pulled out again and allowed to cool. The cooled contents were minced, extracted with dilute hydrochloric acid, washed with water and dried at 150 ⁰ C. The bound nitrogen content of the end product was determined, and from this it could be calculated that 35% of the boron originally present in the mixture had been converted into boron nitride.

Examples 3 to 29

The manufacturing process used corresponded to the manufacturing process of Example 2 with the exception that manganese dioxide was replaced by 1 part by weight of numerous other metal oxide catalysts. In the case of the use of non-oxide catalysts, amounts by weight equal to 1 part by weight were used of the corresponding metal oxide were equivalent. The results obtained are in the following Table laid down.

at
game catalyst % Conversion
in BN 3 Cesium carbonate 10.6 4th Rubidium carbonate 14.1 5 Potassium carbonate 22.1 6th Sodium carbonate 14.0 7th Lithium carbonate 12.2 8th Barium carbonate 27.2 9 Strontium carbonate 27.8 10 calcium carbonate 17.2 11 Lanthanum oxide (La ₂ O ₃ ) 23.2 12th Cerium dioxide (CeO ₂ ) 20.0 13th Zirconium dioxide (ZrO ₂ ) 5.5 14th Titanium dioxide (TiO ₂ ) 5.8 15th Vanadium pentoxide (V ₂ O ₅ ) 14.8 16 Tungsten trioxide (WO ₃ ) 20.6 17th Molybdenum trioxide (MoO ₃ ) 52.9 18th Chromium oxide (Cr ₈ O) ₃ 36.2 19th Iron oxide (Fe ₂ O ₃ ) 10.7 20th Copper oxide (CuO) 4.6 21 Zinc oxide (ZnO) 4.2 22nd Magnesium oxide (MgO) 15.2 23 Yttrium oxide (Y ₂ O ₃ ) 12.0 24 Tantalum pentoxide (Ta ₂ O ₅ ) 13.4 25th Niobium pentoxide (Nb ₂ O ₅ ) 52.4 26th Nickel monoxide (NiO) 5.1 27 Cobalt oxide (Co ₃ O ₄ ) 10.3 28 Thorium dioxide (ThO ₂ ) 6.5 29 Barium carbonate (BaCO ₃ ) and manganese dioxide (MnO ₂ ) equal parts 49.0

For purposes of comparison, it may finally be mentioned that, without using any Catalyst, the conversion of boron into boron nitride is only 1.3%.

Claims (3)

Patent claims: 1. Process for the production of boron nitride by passing nitrogen, ammonia or a nitrogen-releasing gas over a mixture of boron oxide, boric acid or a compound releasing boron oxide, carbon and a catalyst, heated ^{to 1200 to 1600 0 C, treatment of the reaction mixture with dilute mineral acids and separation of the} Boron nitride, characterized in that the catalyst used is MoO ₃ , Cr ₂ O ₃ , Nb ₂ O ₅ or a mixture of equal parts of BaCO ₃ and MnO ₂ . 2. The method according to claim 1, characterized in that the amount of the catalyst or the 5 6 Catalyst mixture is not greater than 10% of the publications considered: Starting mixture. German patent specifications No. 13 392, 203 750, 3. The method according to claim 1 and 2, characterized in 393 631, 282 748, 286 992; characterized that for the production of a porous Chemisches Zentralblatt, 1956, p. 1411 (work by Mixture ammonium chloride is added. 5 G. A. Mej er sson et. al.). 509 570/340 5.65 © Bundesdruckerei Berlin