NO862770L - NEODYME CONNECTION AND PROCEDURE FOR ITS MANUFACTURING. - Google Patents

Description

The present invention relates to a new neodymium compound, and in particular neodymium hydroxynitrate, method for its production

ling and application.

One of the caveats of the present invention is a neodymium hydroxynitrate of formula I:

in which:

The characteristic features of neodymium hydroxynitrate of formula (I)

in accordance with the present invention are the following:

- its morphology:

Neodymium hydroxynitrate is provided in the form of agglomerates, the size of which varies between 0.3 and 100 µm.

With respect to the morphology of the compound, it is shown by

of fig. 1 which is carried out by a photograph, the photograph being provided by means of an electron electron microscope (G=1200). In the same photograph, one notices that the diameter is 40 µm.

- its crystal structure.:

The crystal structure has been obtained using X-ray diffraction. Neodymium hydroxynitrate is a compound with sparse crystallization

tion, as the degree of crystallization does not exceed 60 - 70%.

The X-ray spectrum obtained using monochromatic copper radiation (Ko( Cu g = 1.5418 Å) is as follows:

- chemical composition:

It conforms to the above chemical formula. It is determined qualitatively:

- by means of IR spectrophotometry.

Fig. 2 shows the IR spectrum which is obtained when the compound together with KBr is in tablet form.

The characteristic peaks in the spectrum are:

- 0H~ band = 3500 cm"} n ... -1

- i° j -i^nn -1 0<3 1400 cm

- NO^ band = 1600 cm ^

using thermal differential analysis:

The compound is calcined in a controlled atmosphere of dry air to achieve a temperature rise of 300°C per hour. The following results were obtained:

- 100°C: endothermic peak corresponding to loss in the form of r^O

- 130°C: endothermic peak corresponding to loss in the form of H^O

- 340°C: endothermic peak corresponding to loss in the form of NO^

- 540°C: endothermic peak corresponding to loss in the form of NO^

The chemical composition of the compound of the present invention is determined quantitatively:

by chemical analysis:

- the neodymium compound (100 - 150 mg) in a sample is determined by dissolving it in a few drops of 4 N nitric acid and diluting it with an acetic acid buffer (pH = 5.8), after which the solution is titrated with EDTA in the presence of xylenol orange.

- The OH group is determined in a sample by a quantity of approx

3

lOOmg is dissolved in 20 cm of 0.1N HC1 using a 0.1 Na OH - solution, - the NO^ group is reduced using Devarda reducing agent, after which it is determined by acid measurement after evaporation to dryness.

Experimental elemental analysis in weight % is as follows, the amount of water being determined as the difference:

and is in accordance with the following calculated formula: Nd(OH)2(3_ (N03)0(3_ x 1.5-2.2 ^ 0

by thermogravimetry:

The results are given in the following table:

Neodymium hydroxynitrate with formula (I) as stated above can be prepared by means of the following method; and the distinctive feature of the method according to the invention is that: - an aqueous solution of neodymium nitrate is reacted with a base, the ratio between the concentration of OH - ions in the base and the oconcentration of the neodymium nitrate solution expressed by cation

Nd^+ is greater than 2.2 and although the same ratio is

less than or equal to 2.2, the concentration of neodymium nitrate is ^.:.: .

ning expressed by cation Nd^<+> at most 1.0 mol/litre.

- the obtained precipitate f r aseparares

- it is washed

- and it is dried.

In the initial part of the process, the mixing is carried out

of the neodymium nitrate solution and the base.

In accordance with the invention, anhydrous neodymium nitrate or hydrated neodymium nitrate of formula is used

Nd(NO3)3x6<H>2<0>.

The purity of the neodymium salt used is chosen according to the intended use of the end product.

The concentration of the neodymium nitrate solution used in accordance with the method according to the invention depends on the molar ratio COH~J / CNd^+J , and is indicated in the following.

The acidity of the above solution is not critical in the present invention.

The base used is generally in the form of an aqueous solution, and blue ammonia, sodium hydroxide, potassium hydroxide, ammonium carbamate, urea, hexamethylenetetramine, etc. are chosen. Gaseous ammonia can also be used, but in accordance with the invention, an ammonia solution is preferred.

The normality of the basic solution used is not a critical factor with regard to the present invention,

as the above-mentioned normality can vary within a large concentration range, e.g. between 0.1 and 11 N, preferably between 2 and;il N.

From the foregoing, it appears that the ratio between the basic solution and the neodymium nitrate solution depends on the concentration of the neodymium nitrate solution.

When the molar ratio COH~ J I£Nd^+J is greater than 2.2, the concentration of the neodymium nitrate solution is not critical and can vary within a large range. The concentration expressed by the cation Nd^<+> can possibly lie in the range between 0.1 and 6.0 mol/ 1..

When the molar ratio £OH~J / fNd 3+J is less than or equal to 2.2, the concentration of the neodymium nitrate solution is at most/equal to 1.0 mol/1.1

and is preferably chosen between 0.1 and 1.0/rhol/l.

In a preferred embodiment according to the invention, the concentration of the neodymium nitrate solution expressed by the cation Nd^<+> is chosen between 0.7mol/l and 1.5mol/l, and a molar ratio rOrTj / CNd3+J between 2.2 and 3.0 .

The mixing of the above-mentioned reactants can be carried out in different ways. E.g. the mixing of the basic solution and the neodymium nitrate solution can be carried out simultaneously, without stirring, or the basic solution can be added continuously or all at once to the aqueous neodymium nitrate solution or vice versa.

The addition of the reagent solutions is regulated so that a molar ratio C0H_3 / C^D^tlJ is obtained as stated above. It is also possible to control the addition of the reagent solutions to regulate the pH, which mostly varies between 7.5 and 9.5.

The temperature in the reaction mixture is selected in particular between 10 and -50°C, preferably between 10 and 30°C.

The time used for stirring the reaction mixture varies within a large range, from less than 0.1 sec. and for several hours, e.g. 48 hours or more. A stirring time of between 5 and 30 min. is usually sufficient.

The stirring itself should be relatively vigorous. The stirring speed depends on the type of piping device and the ratio between the diameter of the stirring device and the diameter of the reactor. For example, the speed of a four-arm stirrer, which passes very close to the wall of a reactor with a diameter of 15 cm (use volume 750 cm<3>), will

be between 100 and 1000 revolutions / min.

Another step in the method comprises a separation of the obtained precipitate from the reaction mixture. The precipitate can be separated using commonly used techniques for liquid/solid separation, with filtration and centrifugation in particular being preferred and carried out for a limited period of time. In general, the separation is carried out at room temperature, most often between 15

and 2 5 .

The centrifuged precipitate or filter cake is finally washed to remove residual anions. The washing is preferably carried out using distilled or deionised water, as the temperature can vary between 5 and 90°C. The washing is carried out from one to several times, and most often from one to three times.

After washing, the amount of water present in the precipitate (filter cake) is between 20 and 80%, and generally between 20 and 50%.

The precipitate obtained after the separation and washing(s) is then dried under mild conditions.' Drying is usually carried out in air. The drying temperature can vary between room temperature

raw tour and 80°C. The drying time is a function of the temperature:

it can vary between 15 min and 48 hours, being shortened as the drying temperature increases.

The drying is preferably carried out at room temperature, the drying time being between 10 and 24 hours.

In accordance with the method described above, neodymium hydroxide with formula (I) is obtained.

Another purpose of the present invention is to obtain neodymium hydroxynitrate with the following formula:

Nd(OH) (NO,) , x z' H,0 (II)

- 2.3 x' 2.7 - 0.3 y'< 0.7 - 0.5 z 1 1.2

Nedymh<y>dro.ks<y>ni tr that with formula (II) has the following properties:

- morphology:

It is the same as for neodymium hydroxynitrate of formula (I).

- crystal structure:

X-ray diffraction analysis shows that neodymium hydroxynitrate of formula (II) is a compound with sparse crystallization, the degree of crystallization not exceeding 60 - 70%.

The X-ray spectrum obtained with the help of monochromatic copper radiation (KcC Cu g = 1.5418 Å) is as follows:

Chemical composition:

It is in accordance with the above chemical formula and is determined qualitatively:

using IR spectrophotometry.

Fig. 3 shows the IR spectrum obtained when the compound together with KBr is in tablet form.

The characteristic peaks in the spectrum are:

• - OH~band = 3550'cm 71 -1 no-,n': -1 -,ncn -1 c,n -1 Mn o , -1, 1400 c, , 1330cm , 1050 cm , 640 cm - NO_. band = 1630 cm ' -1

and 5 60 cm

By thermal differential analysis:

The compound is calcined in a controlled atmosphere of dry air to achieve a temperature rise of 300°C per hour.

The following results were obtained:

- 80°C : endothermic peak corresponding to loss in the form of

H20

- 130 C : endothermic peak corresponding to loss in the form of

_ 320_C ; endothermic peak corresponding to loss in the form of

NOx

-<!,>540°C : endothermic peak corresponding to loss in the form of

NOx.

The chemical composition of the compound according to the present invention is determined quantitatively:

by chemical analysis:

It is performed as shown above.

Elemental analysis, expressed in weight %, is as follows, the amount of water being determined as the difference:

and is in accordance with the following calculated formula: Nd(OH)2f3_2f7(NO3)0f3_0f70,5-1,2H2O

by thermogravimetry.

The results are given in the following table:

Neodymium hydroxynitrate with formula (II) is obtained by dehydrating neodymium hydroxynitrate with formula (I), after which the obtained compound is optionally dried.

The dehydration can be carried out in air at a reduced pressure of the order of 10"<2> to 100 mm Hg (1.33 to 1.33 . 10"<4>Pa).

The drying temperature must be lower than the melting temperature or the decomposition temperature of the compound of formula (I). The temperature can e.g. can be chosen between room temperature and 200°C. The drying time depends on the temperature, as it can be from 1 min. and up to 48 hours. When the drying temperature is selected between 80 and 150°C, the drying time varies between 1 min. and 3 hours.

Neodymium hydroxynitrate of formula (II) can likewise be obtained by

that neodymium hydroxynitrate of formula (I) is brought into contact with an organic solvent. This is usually carried out by washing the separated precipitate, usually in the form of a filter cake. One uses a volatile organic solvent and mentions in particular alcohols ethers, aliphatic ketones and especially ethanol, methanol, acetone and diethyl ether. One to several washings are carried out, and usually from one to three washings. The ratio between the solvent used compared to the amount of precipitate that is washed is not critical. Usually from 20 to 120 cm<3> of solvent are used for 10 g of precipitate. Dehydration using an organic solvent can optionally be followed by drying. Drying can be carried out in air

_2

at reduced pressure in the order of 10 to 100 mm Hg. The drying temperature can vary between room temperature and 200°C. The drying time varies within a large area, as it can be

from 30 min. to 48 hours, but is preferably chosen between 2 and 8 hours. Neodymium hydroxynitrate with formula (II) is thus obtained.

For the production of neodymium hydroxynitrate with formula (I) and (II) standard equipment can be used. Mixing of the reagent solutions can be carried out in a reactor equipped with a heating device, e.g. by circulating hot water through an outer jacket on the reactor or by means of heat exchangers (spiral-shaped). The reactor is equipped with commonly used apparatus for temperature control (thermometer) and stirring (vanes, pipe arm, propeller or turbine), as well as a device for supplying one or both reagents in the form of an aqueous solution using of e.g. a dosing pump.

The devices used in the separation and drying procedures do not require any special design. Filtration of the obtained suspension can optionally be carried out on a filter in an atmosphere of inert gas, such as nitrogen, on a filter at reduced pressure (Buchner, Nutche) or in a device with continuous filtration, e.g. a rotary filter of the Vernay type or a band filter. The precipitate is placed in a vessel made of silica, porcelain or aluminium, after which it is dried in a freely chosen drying device, e.g. in a ventilated drying cabinet, at reduced pressure or in a desiccator, most often at reduced draft obtained with the help of a water pump.

The neodymium hydroxynitrates with formula (I) and (II) can be used as starting compounds for the production of neodymium oxides or neodymium carbonates. A special application of the compounds in accordance with the invention is the production of neodymium oxide by calcining neodymium hydroxynitrate with formula (I) or (II). The neodymium hydroxynitrates of formula (I) and (II), prepared in dried form, are subjected to a calcination which is carried out at a temperature between about 650 and about 1300° C. The duration of the calcination is not critical and is usually chosen between 1 and 4 hours.

After calcination at a temperature between 700 and 900°C, a neodymium oxide is obtained with a specific surface that varies between 5 and 30 m 2 /g. Specific surface refers to specific surface B.E.T. determined by the method according to BRUNAUER, EMMET, TELLER;

described in "The Journal of American Society 1938, 60, 309".

The invention is illustrated by means of the following examples.

In Examples 1 to 3, neodymium hydroxynitrate of formula (I) is

and its representation exemplified. In example 4, neodymium hydroxynitrate of formula (II) is prepared, starting from neodymium hydroxynitrate of formula (I) prepared in the preceding. Examples 5 and 6 show the production of neodymium oxide from the neodymium hydroxynitrates of formula (I) and (II).

EXAMPLE I

In a two-liter reactor equipped with an outer jacket, in which water at a temperature of 20°C circulates, with a thermometer, an introduction device for the reagents and a :stirring device (four-armed piping), simultaneously introduce 2500 cm 3 /.fe and 1600 cm 3h of respectively: - an aqueous solution of neodymium nitrate containing Nd^+ in a concentration of 1.4 mol/l; and

- an aqueous ammonia solution with concentration 6N,

as the molar ratio (pH^//Nd3+J is equal to 4.

The temperature in the reaction mixture is 20°C, and the mixture is stirred for 20 min. The stirring speed is 400 revolutions/min. After 20 min., the mixture is filtered on a Buchner filter at room temperature.

The filter cake is washed with water with water in an amount of 100 cm3,

per 10 g of precipitate.

The obtained precipitate is dried at room temperature in a desiccator, at reduced pressure obtained by means of a water pump.

One obtains neodymium hydroxynitrate of formula (I) whose IR and X-ray diffraction spectra are confirmed by what has been given above.

EXAMPLE 2, ;

Compared to example 1, the concentrations of the neodymium nitrate solution are modified to 2.54 mol/l with regard to No!<+>, likewise the concentration of the ammonia solution to 10.5N

with the molar ratio OH"/Nd3+ being 2.5.

Neodymium hydroxynitrate with formula (I) is obtained.

EXAMPLE 3 2 '

In this example, the following reagents are used:

a solution of neodymium nitrate whose concentration is equal to 0.52mol/l and an ammonia solution whose concentration is equal to 1.7N, the molar ratio COH"J/fNd3+J being equal to 2.5.

The supply rates of the neodymium nitrate solution and the ammonia solution respectively are 4411/t;qg 34 l/t, The solutions are supplied within 0.4 sec. and at a temperature of 20°C.

Neodymium hydroxynitrate with formula (I) is obtained.

EXAMPLE 4

Neodymium hydroxynitrate of formula (I) is prepared as shown in

e.g. 1 and is then subjected to a dehydration.

For a device described in e.g. 1, is added at the same time

3 3

2500 cm/h and 1600 cm/h of respectively:

- an aqueous neodymium nitrate solution containing Nd at a concentration of 1.41. mol/l and

- and an aqueous ammonia solution with a concentration of 6 N

as the molar ratio OH /Nd<3+> is equal to 4.

The temperature in the reaction mixture is 20°c, and the mixture is stirred for 20 min. The stirring speed is 400 revolutions/min. After 20 min., the mixture is filtered on a Btlchner filter at room temperature.

The filter cake is washed with ethanol using lOOcm<3>ethanol

per 10 g of precipitate. The resulting precipitate is then dried for 2 hours in a drying cabinet at a temperature of 200°C. Neodymium hydroxynitrate with formula (II) is prepared, whose IR and X-ray diffraction spectra are shown above.

EXAMPLE 5

10 g of the compound prepared in ex. 1, is fed to a weighing vessel and placed in a tube furnace. The temperature is increased by 9°C per

my. up to a temperature equal to 700°C; which is maintained for one hour. Then cools, the weighing vessel.. inside the oven. Man^achieves 4.65 g of

a calcined compound of formula Nd2O3 (ASTM 21-579) with a specific surface BET equal to 25 m<2>/g, after calcination at a temperature of 700°C.

EXAMPLE 6

10 g of the compound prepared in example 4 is added to a weighing vessel and placed in a tube furnace. The temperature is increased by 9°C per my. up to a temperature equal to 700°C, which is maintained for one hour. The weighing vessel is then cooled inside the oven.

5.42 g of a calcined compound with formula ^20^ is obtained

(ASTM 21-579) with a specific surface BET equal to 20 m<2>/g, after calcination at a temperature of 700°C.

Claims (15)

1. Chemical compound, characterized in that it consists of neodymium hydroxynitrate with formula (I) in which: 2. Neodymium hydroxynitrate as stated in claim 1, characterized in that the above-mentioned compound is in agglomerated form and with a dimension that varies between 0.3 and 100 µm and/or that the degree of crystallization is at most 60 to 70%. 3. Process for the production of neodymium hydroxynitrate with formula (I) as stated in claims 1-2, characterized in that - an aqueous solution of neodymium nitrate is reacted with a base when the molar ratio between the concentration of OH~ ions in the base over the concentration of the neodymium nitrate solution expressed by cation Nd <3+> is greater than 2.2, and when the above-mentioned ratio is less or equal to 2.2, the concentration of the neodymium nitrate solution expressed in terms of cation Nd <3+> is at most 1.0 mol/l, the precipitate obtained is separated, washed, and be dried. 4. Method as stated in claim 3, characterized in that the base used is selected from the group consisting of ammonia, sodium hydroxide, potassium hydroxide, ammonium carbamate, urea and hexamethylenetetramine. 5. Method as stated in claims 3 and 4, characterized in that the concentration of the base used is between 0.1 and 11 N, preferably between 2 and 11 N. 6. Method as stated in claims 3-5, characterized by using a molar ratio E- OH <-> ]] / £.Nd3+J greater than 2.2, in particular between 2.2 and 3.0, and a concentration of the neodymium nitrate solution expressed by cation Nd3 + which is between 0.1 and 6.0 mol/l, in particular between 0.7 and 1.5 mol/l, or that one uses a molar ratio EofTJ / [Nd3 "3 which is smaller or equal to 2.2, and a concentration of the neodymium nitrate solution expressed in terms of cation Nd3+ which is selected between 0.1 and 1.0 mol/l. 7. Method as stated in claims 3-6, characterized in that the aqueous neodymium nitrate solution and the basic solution are mixed simultaneously without stirring, or the basic solution is added continuously or all at once to the aqueous neodymium nitrate solution or vice versa, the addition of the reagents is regulated so that a mole ratio | <_> OH [_Nd J is obtained as stated in claim 6. 8. Method as stated in claim 6 or 7, characterized in that the addition of the reagents is regulated so that a pH between 7.5 and 9.5 is achieved, and/or that the reaction temperature used is between 10 and 50°C, and/ or that the reaction mixture is stirred for a time between less than 0.1 seconds and 48 hours, the stirring speed preferably varying between 100 and 1000 revolutions/minute. 9. Method as stated in claims 3-8, characterized in that the separation of the precipitate is accomplished by filtration or centrifugation, and/or that the obtained precipitate is washed one or more times with water, and the obtained precipitate is preferably dried at a temperature between room temperature and 80°C, preferably for a time between 15 minutes and 48 hours. 10. Chemical compound, characterized in that it consists of nedo-dym hydroxynitrate of formula (II) in which : 11. Neodymium hydroxynitrate as stated in claim 10, characterized in that the above-mentioned compound is in the form of agglomerates whose dimensions vary between 0.3 and 100 yum, and/or that the degree of crystallization is at most 60 to 70%. 12. Process for the production of neodymium hydroxynitrate of formula (II) as stated in claims 10 - 11, characterized in that neodymium hydroxynitrate of formula (I) is dehydrated and the obtained compound is optionally dried. 13. Method as stated in claim 12, characterized in that the dehydration is carried out by air drying under reduced pressure between 10 _2 and 100 mm/Hg, the drying temperature used is preferably between room temperature and 200°C, the drying time being preferably varied between 1 minute and 48 hours. 14. Method as set forth in claim 12, characterized in that the dehydration is carried out by bringing neodymium hydroxynitrate of formula (I) into contact with a volatile organic solvent, the organic solvent used preferably being ethanol, methanol, acetone or dimethyl ether. 15. Use of neodymium hydroxynitrate with formula (I) as specified in claim 1 or 2, and neodymium hydroxynitrate with formula (II) as specified in claim 10 or 11 as starting material for neodymium oxide with a specific surface area of from 5 to 30 m 2 /g after calcination at a temperature between 700 and 900°C.