Title of Invention

A BATCH REACTOR FOR PRODUCING METALOXIDES

Abstract A batch reactor for producing metal oxides of formula: M'x Oy or M"a M'"b 0z where M', M" and M'" are metals which form water soluble nitrates, O is Oxygen and a, b, x, y and z are integral or fractional numbers, same or different, on kilogram/industrial scale, by gel combustion reaction of aqueous solutions of metal nitrate(s) and an organic reducing agent selected from aliphatic carboxylic acids such as citric acid, oxalic acid or their salts, such as acetates, the reactor comprising a reaction vessel having an inlet for charging the feedstock and an outlet for the fumes generated during the reaction, means for heating the reaction vessel and means for controlling the temperature of the reaction vessel, characterized in that the reaction vessel is a substantially cylindrical having a diameter: height ratio in the reason of 1:1 to 1:5 , and having means for agitating the reaction mixture comprising at least two impellers adapted to rotate at desired speeds in the same or opposite directions, wherein at least one of said impellers adapted to dip into the reactant mix and at least one of said impellers adapted to be situated in the space above the reactant mix level at the time of start of the reaction; and in that said temperature control being adapted to control the temperature of reaction mass in a manner such that the initial temperature is just enough to initiate the reaction and is thereafter maintained below 200°C throughout the reaction.
Full Text FORM 2
THE PATENTS ACT 1970 (39 of 1970)
COMPLETE SPECIFICATION
(See Section 10; Rule 13)
1 A BATCH REACTOR FOR PRODUCING METAL OXIDES
2. (a) Secretary, Department of Atomic Energy, Government of India, (b) Anushakti Bhavan, Chhatrapati Shivaji Maharaj Marg, Mumbai 400 001 Maharashtra, India, (c) an Indian company.

ORIGINAL
707/MUM/2003
10/07/03


The following specification particularly describes the nature of the invention and the manner in which it is to be performed.



GRANTED
21-12-2004

Field of the invention:
The present invention relate's to a batch reactor for gel combustion reaction. The present invention particularly relates to a batch reactor for safely carrying out gel combustion reactions such as between nitrate as the oxidising reactant and an organic reducing reactant on an industrial scale, which reactions on scale-up may be explosive in nature. Chemical reactors of present invention are widely applicable in carrying out safely any gel combustion reaction in aqueous medium under controlled conditions.
Background and prior art
Gel combustion reaction is known so far only in the laboratory scale work in g level. The scale up of such unsafe reactions to kilogram and industrial scale is not possible due to the vigor of such reactions with flame and gas evolution. Such reactions are also exothermic, pyrophoric and explosive. So far there are no batch reactors known to carry out such reactions on kilogram and industrial scale. These reactions are useful to produce oxides of many metals including mixed metal oxide ceramics. However, due to non availability of any safe reactor for carrying
t
out such hazardous reactions, these products are made on bulk scale by alternative lengthy routes.
US 5728362 teaches such an alternative process for preparing mixed metal oxide powder, in which aerosol-droplets are generated from the tuned solution of the reactants in certain proportion, and sprayed into a heated gas jet.
Journal of Material Science Letters, 9, (1990), 1205 teaches preparation of ceria by combustion synthesis process which involves rapid decomposition of a saturated aqueous solution containing ceric ammonium nitrate and urea, carbohydrazide, oxalyl dihydrazide or tetraformal trisazine redox mixtures. The combustion of redox compounds and mixtures dissolved in the minimum quantity of water was carried out in a cylindrical Pyrex dish of capacity 300 cm3 by

introducing it into a furnace maintained at 350 ± 10 °C. The quantity of each of ceric ammonium nitrate and redox mixture used in this experiments were of the order of 10 g and taken stoichiometrically.
Journal of Material Research, 14 (1999), 1524 teaches a preparation of yttria powder by gel combustion starting with yttrium nitrate and citric acid in a molar ratio varying from 0.098 to 0.7. The experiment was carried out in a 50 ml glass beaker on a hot plate to produce 1.13 g of yittria. The powder was calcined at a temperature of 750°C.
Therefore, there is a need for a batch reactor for safely carrying out gel combustion reactions in kilogram or industrial scale.
Objects of the invention
Accordingly, the main object of the present invention is to provide a batch reactor to scale up gel combustion synthesis reactions, which are explosive in nature, in a safe way.
A further object of the present invention is to provide a batch reactor for gel combustion reactions manufacturing products of high purity.
Summary of the invention
According to the present invention there is provided a batch reactor for producing metal oxides of formula: M'xOy or M"aM'"bOz
where M', M" and M'" are metals which form water soluble nitrates, O is Oxygen and a, b, x, y and z are integral or fractional numbers, same or different, on kilogram/industrial scale, by gel combustion reaction of aqueous solutions of metal nitrate(s) and an organic reducing agent selected from aliphatic carboxylic acids such as citric acid, oxalic acid or their salts, such as acetates, the reactor comprising a reaction vessel having an inlet for charging the feedstock and an outlet for the fumes generated during the reaction, means for heating the reaction vessel and means for controlling the

temperature of the reaction vessel, characterized in that the reaction vessel is
a substantially cylindrical having a diameter: height ratio in the reason of 1:1 to 1:5, and having
means for agitating the reaction mixture comprising at least two impellers adapted to rotate at desired speeds in the same or opposite directions, wherein at least one of said impellers adapted to dip into the reactant mix and at least one of said impellers adapted to be situated in the space above the reactant mix level at the time of start of the reaction;
and in that said temperature control being adapted to control the temperature of reaction mass in a manner such that the initial temperature is just enough to initiate the reaction and is thereafter maintained below 200°C throughout the reaction.
The present invention also provides a process manufacture of amorphous or crystalline, soft or hard nano, single or multi component metal oxides of formula:
M'x Oy or M"a M'"b 0z as described above in the said batch reactor, the process comprising: heating said reactants, under controlled stirring at a temperature just enough to initiate the gel combustion reaction;
maintaining the overall temperature of said reactor below 200°C throughout the reaction;
controlling the speed of the agitator as viscosity increases as the reaction proceeds; and cooling the reactor to room temperature after the reaction is over.
Detail description of the invention:
The gel combustion reactor of the present invention is useful for all gel combustion reaction and particularly in the preparation of ceria powder, which is described in our copending application No.708/MUM/2003.

reaction. The vent pipe being smaller in diameter and long above the lid the escape of powder through it is negligible.
The side heater 2 is made by covering the reactor with the conventional heating
mantle tape carrying nichrome wires of heating capacity (along with bottom , heater) to raise the temperature of the reaction vessel with its contents to about 200°C. The temperature indication is done by a thermocouple provided with on-off control. The bottom heater 10 has an electrically heated hot plate of 2 kilo Watt placed below the reactor. A thermocouple well 7 of 8 mm diameter and 30 mm long of SS tube, thermocouple 8 of chromel - alumel (K-type), and M/S Bharat Heater make temperature indicator arejjrgvided.
The heaters are electrically earthed properly for safety of the operators. The over heating is prevented by automatically switching off the heaters as and when the reactor temperature exceeds 200°C.
The reactor is placed in a fume hood with exhaust fan, in such a position that the
vent pipe opening is close to the exhaust draft of the fume hood. The reactor of
the present invention is useful for carrying out gel combustion reactions on
Kilogram scale up to 2.5 kg of the product.
The process of carrying out gel combustion reactions in conventional routes and by using the reactor of the present invention will now be described in the examples that follow. The examples are by way of illustration only and in no way restrict the scope of the invention.
Example 1: Preparation of 125 gm lanthanum strontium manganite (LSM) using the process by S-Roy-et al
In order to produce Lanthanum strontium manganite (LSM) in larger quantity using a glass beaker as described in the prior art above, a 3 liter beaker of 14.5 mm diameter and 18 mm height was taken. For 125g LSM product batch size, 75 g of lanthanum oxide was dissolved in dilute nitric acid prepared by taking 90 ml

concentrated nitric acid in water to make the total volume 600 ml. About 7.5g of strontium nitrate was dissolved in dilute nitric acid prepared by taking 8.5 ml concentrated nitric acid in water to make the total volume 60 ml. Both these solutions were prepared in glass beaker separately and then mixed along with 125-g solid manganese acetate. The mixed solution was filtered to remove undissolved matter. The solution was heated on a hot plate only at about 80°C till gel was formed. Then as the temperature went up and the combustion reaction started, even though the mixture was continuously stirred, the beaker broke apart spreading the partially finished reaction product along with reactants on the working fume hood spoiling the experiment.
Example II: Preparation of Lanthanum strontium manganite (LSM) using the reactor of the present invention
The reactor vessel was put on the hot plate. The side heaters were connected to the power supply. The agitator was placed in position. After keeping the vent pipe towards the exhaust fan the top lid of the vessel was closed by tightening the C-clamps. The bulb at the light port was put on to see the inside of the reactor through the view port.
For 250g LSM product batch size, 150g of lanthanum oxide was dissolved in dilute nitric acid prepared by taking 180 ml concentrated nitric acid in water to make the total volume 1200 ml. About 15g of strontium nitrate was dissolved in dilute nitric acid prepared by taking 17 ml concentrated nitric acid in water to make the total volume 120-ml. Both these solutions were prepared in glass beaker separately and then mixed along with 250g solid manganese acetate. The mixed solution was filtered to remove undissolved matter. The above mixed solution was then taken inside the reactor through the feed inlet opening the valve. This valve was closed after the whole solution was taken. All the heaters were put on and the temperature was monitored to control it at 80°C till a viscous gel was formed by evaporation. The reaction mass gradually dried up when the temperature was allowed to rise but not above 200°C. During this rise of temperature the combustion reaction set in with fire. The agitator and the exhaust ventilation were

run after taking the reactants solution in the reactor till product was taken out of the reactor. When the fire inside the reactor stopped, it is understood that the reaction is complete. The heaters were put off, the vessel was allowed to cool near to room temperature and then the product was taken out from the top of the reactor.
The product was characterized by XRD and particle size analysis. The XRD pattern indicated formation of monophasic LSM. The particle size was in sub-micron range.
The yield of LSM was over 90%. However, the yield of this product by continuous spray pyrolysis technique, as has been indicated by Central Glass and Ceramic Research Institute (CGCRI), Kolkata visiting scientist to BARC, to be about only 60%.
Example III: Preparation of Magnesium doped lanthanum chromite (LCM) using the reactor of the present invention
The procedure was same as in the above Example-ll, but the following ingredients were taken for 125g product: 80g of lanthanum oxide was dissolved in 98 ml of concentrated nitric acid and the volume was made up to 800 ml by adding water. To this 52g of chromium oxide, 6.6g magnesium nitrate and 197g of citric acid were added and dissolved.
As in example II above, this product also was characterized by XRD and particle size analysis and was found to be satisfactory.
While this compound LSM could not be synthesized on Kg scale by the prior art process as found in Example I, Example II shows that it could be safely synthesized using the reactor of the present invention.
Advantages of the Invention
Oxides of metals that have water soluble nitrate salts can be produced in large scale using this reactor. The oxides, produced by this reactor, can be single oxide

eg AI2O3, BeO etc. ahd multi-component oxides e.g. Lanthanum strontium manganite (La1-x Srx Mn03), magnesium doped lanthanum chromite (La1-x MgxCr03) etc, crystalline or amorphous, hard or soft as per the product requirement.
This process is improved one with respect to other processes for making nano materials with high phase purity and chemical homogeneity. The sol-gel process, e.g. involving alkoxide precursor where nano-size particle products are also obtained is longer and costlier. Batch combustion reactor is also suitable to produce small quantity high value products cost effectively for limited and critical applications. This invention provides environmental friendly means to obtain the above products. This generates no waste. The reaction yield in this reactor is above 90%.
The reactor of the present invention is safe to carry out such gel combustion reactions.

WE CLAIM :
1. A batch reactor for producing metal oxides of formula: M'x Oy or M"a M'"b 0z
where M', M" and M'" are metals which form water soluble nitrates, O is Oxygen and a, b, x, y and z are integral or fractional numbers, same or different, on kilogram/industrial scale, by gel combustion reaction of aqueous solutions of metal nitrate(s) and an organic reducing agent selected from aliphatic carboxylic acids such as citric acid, oxalic acid or their salts, such as acetates, the reactor comprising a reaction vessel having an inlet for charging the feedstock and an outlet for the fumes generated during the reaction, means for heating the reaction vessel and means for controlling the temperature of the reaction vessel, characterized in that the reaction vessel is
a substantially cylindrical having a diameter: height ratio in the reason of 1:1 to 1:5 , and having
means for agitating the reaction mixture comprising at least two impellers adapted to rotate at desired speeds in the same or opposite directions, wherein at least one of said impellers adapted to dip into the reactant mix and at least one of said impellers adapted to be situated in the space above the reactant mix level at the time of start of the reaction;
and in that said temperature control being adapted to control the temperature of reaction mass in a manner such that the initial temperature is just enough to initiate the reaction and is thereafter maintained below 200°C throughout the reaction.
2. A batch reactor according to claim 1, wherein said reaction vessel is made of stainless steel.
3. A batch reactor according to claim 2, wherein said stainless steel of 316 type.


4. A batch reactor according to claim 1, wherein said vessel has height: diameter ratio in the region of 1:1.5 to 1:3.
5. A batch reactor according to claim 1, wherein said vessel is provided with sight glasses.
6. A batch reactor according to claim 1, wherein the said vessel has a lid at the top.
7. A batch reactor according to claim 1, wherein said reactor is placed in a fume hood.
8. A batch reactor according to claim 1, wherein said outlet comprises vent passage or pipe which is directed towards the suction point of the exhaust fan of said fume hood.
9. A batch reactor according to claim 1, wherein said agitator has two paddle type impellers having the same diameter.
10. A batch reactor according to any of the preceding claims, wherein blades of said impellers are rectangular and perpendicular to the direction of motion of liquid.
11. A batch reactor according to any of the preceding claims, wherein said impellers have diameter 5/10th to 9/10th of the diameter of the said reaction vessel.
12. A batch reactor according to any of the preceding claims, wherein said two impellers are adapted to move in the same direction.
13. A batch reactor according to claim 1, wherein means for controlling the overall temperature of the reactor comprises a thermocouple provided with on-off control.
14. A process for manufacture of amorphous or crystalline, soft or hard nano, single or multi component metal oxides of formula:
M'xOyor M"aM'"bOz where M', M" and M'" are metals which form water soluble nitrates, O is Oxygen and a, b, x, y and z are integral or fractional numbers, same or different, on kilogram/industrial scale, by gel combustion reaction of aqueous solutions of metal nitrate(s) and an organic reducing agent selected from aliphatic carboxylic acids


such as citric acid, oxalic acid or their salts, such as acetates, in the batch reactor according to any of the preceding claims, the process comprising:
heating said reactants, under controlled stirring at a temperature just enough to initiate the gel combustion reaction;
maintaining the overall temperature of said reactor below 200°C throughout the reaction;
controlling the speed of the agitator so as to obtain a viscous gel; and cooling the reactor to room temperature after the reaction, is over.
15. A batch reactor for gel combustion reactions and a process for carrying out such gel combustion reactions substantially as herein described in the text, examples II and III and in the drawing.

Dated this 7th day of July 2003

Dr.Sanchita Ganguli
Of S.MAJUMDAR&CO
Applicant's Agents



Documents:

707-mum-2003-cancelled pages(21-12-2004).pdf

707-mum-2003-claims(granted)-(21-12-2004).doc

707-mum-2003-claims(granted)-(21-12-2004).pdf

707-mum-2003-correspondence(11-12-2006).pdf

707-mum-2003-correspondence(ipo)-(21-05-2007).pdf

707-mum-2003-drawing(21-12-2004).pdf

707-mum-2003-form 1(10-07-2003).pdf

707-mum-2003-form 19(28-07-2003).pdf

707-mum-2003-form 2(granted)-(21-12-2004).doc

707-mum-2003-form 2(granted)-(21-12-2004).pdf

707-mum-2003-form 3(07-07-2003).pdf

707-mum-2003-power of attorney(08-09-2003).pdf

abstract1.jpg


Patent Number 207053
Indian Patent Application Number 707/MUM/2003
PG Journal Number 43/2008
Publication Date 24-Oct-2008
Grant Date 21-May-2007
Date of Filing 10-Jul-2003
Name of Patentee SECRETARY DEPARTMENT OF ATOMIC ENERGY GOVERNMENT OF INDIA
Applicant Address ANUSHAKTI BHAVAN, CHATRAPATI SHIVAJI MAHARAJ MARG, MUMBAI 400 001, INDIA.
Inventors:
# Inventor's Name Inventor's Address
1 SAHA DR. SANDIP SO/G, HEAD, CHEMICAL PROCESSING AND DEVELOPMENT SECTION, POWDER METALLURGY DIVISION, BHABHA ATOMIC RESEARCH CENTRE, TURBHE COMPLEX, NAVI MUMBAI - 400 705, INDIA.
2 PUROHIT R. D. SO/D, CP & D SECTION, PMD, BHABHA ATOMIC RESEARCH CENTRE, TURBHE COMPLEX, NAVI MUMBAI 400 705, INDIA.
3 GHANWAT S. J. SO/D, CP & D SECTION, PMD, BHABHA ATOMIC RESEARCH CENTRE, TURBHE COMPLEX, NAVI MUMBAI 400 705, INDIA.
PCT International Classification Number B01J 8/02
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA