DESC:METHOD FOR MANUFACTURING SODIUM PERMANGANATE SOLUTION
Field of the invention:
The present invention generally relates to a manufacturing method of permanganate solution and more particularly to a manufacturing method of sodium permanganate solution.
Background of the invention:
Sodium permanganate (NaMnO4) is a strong oxidizing agent having many applicationsin chemical field, primarily in applications requiring highly soluble permanganate. It is used in conditioning of metal surface, etching or de-smearing of epoxides and other plastics, in fabrication of printed circuit boards, etc. Sodium permanganate is also used for oxidizing certain objectionable impurities in purification of certain organic and inorganic chemicals. It can be also used as oxidant, disinfectant, bactericide, etc. Since the permanganate ion is a powerful oxidizing agent and its availability in concentrated solution maximizes the oxidizing property, conditions of use should be carefully controlled so as to prevent risks of fire and explosion.
Sodium permanganate (NaMnO4) cannot be made in the same way as potassium permanganate (KMnO4), because the oxidation of MnO2 in NaOH melt does not lead to the required NaMnO4, but only to the Na3MnO4 which is very unstable in dilute NaOH solution. Na3MnO4can not be converted electrolytically to the desired NaMnO4. Even if electrolytic oxidation were possible, there would still be the difficult problem of isolating the extremely soluble NaMnO4 from the alkaline mother liquor.
Sodium permanganate can be obtained by reacting a mixture of sodium hypochlorite and sodium hydroxide, with freshly prepared manganese dioxide.This reaction will only give small amounts of sodium permanganate, as during the process most of the hypochlorite decomposes.
China patent application CN98121751A discloses method of preparation of sodium permanganate by reacting NaOH and manganese oxide in presence of sulfuric acid acting as disproportionation agent. The reaction gives mixture of sodium permanganate, sodium sulfate and manganese dioxide. Manganese dioxide and sodium sulfate are removed from solution, and mother liquor is the product sodium permanganate. Although this method is advantageous in respect of low production cost, investment cost and working cost, it cannot get rid of the defects in the conventional method per se, such as high equipment requirements, harsh reaction and dangerous conditions.
Sodium permanganate can be prepared by anodic oxidation of ferromanganese in sodium carbonate solutions. The process is energy intensive, where the passivation of electrodes results in higher voltage drop and low current efficiencies, resulting in higher power consumption, which can be a problem.
Another method is by reacting potassium permanganate with aluminum sulfate in presence of sufficient water to produce aluminum permanganate, wherein aluminum permanganate is soluble in water and potassium alum is separated as insoluble. Aluminum permanganate is then reacted with oxides, hydroxides or carbonates of sodium producing sodium permanganate. The feasibility of this process is not known. This process is not cost effective.
Reacting potassium permanganate with sodium flurosilicate in presence of water at 80°C and then evaporating the resulting solution gives sodium permanganate solution.
The process of manufacturing sodium permanganate by reacting potassium permanganate with sodium flurosilicateis developed to get the commercial production with competitive price. However, PPM level of the sulfate and chloride impurities in the resulting mixture is higher than the desired levels. The method cannot meet the needs of domestic and international high-end customers. Secondly, the reaction mixture is treated with barium salt before dilution. This leads to increase the barium content in the final concentrate. Also in the manufacturing process, a concentration bucket coiled pipe is used to lead to steam in normal pressure, steam consumption is higher, restricts its production capacity. The solid waste generated is of environmental concern which is sent to stack up plies for storage. (Ref. patent applications: CN101880064A and CN107827161A). In this invention, the reaction temperature and evaporation concentration used is on higher side, which results in high cost due to steam consumption. The higher temperature results in decomposition of permanganate solution, generation of manganese impurities alkaline and increase in the pH of solution.
Accordingly, there exists a need to provide an efficient and environmentally friendly process for the production of sodium permanganate that will overcome the drawbacks of the prior art as mentioned above.
Objects of the invention:
An object of the present invention is to provide a method of manufacture of sodium permanganate solution.
Another object of the present invention is to provide an efficient, economic and environmentally friendly process for the production of sodium permanganate.
Summary of the invention
The present invention provides a method for manufacturing sodium permanganate solution. The method consists mixing potassium permanganate and sodium silicofluoride (Sodium hexaflouosilicate) in weight proportion ranging from 1.6:1 to 1.9:1 in excess water to form an aqueous solution. The aqueous solution is then heated up to 50°C to 70°C till the concentration of the reaction mass comes in a range from 15- 20 degree Baume. The crude reaction mass is then cooled to ambient temperature and filtered through a filter press obtain a filter cake and a filtered solution. The filtered solution is collected in a storage tank and subjected to forced circulation evaporation at a temperature ranging from 50°C to 65°C till the solution achieves concentration ranging from 42 to 45 degree Baume. The condensate water obtained in the evaporation process is collected in a storage tank for reuse. The concentrated solution is then crystallized by cooling the solution with chilled water. In next step, the cooled solution is centrifuged to obtain crude liquid sodium permanganate solution. The cooled liquid is diluted to a concentration from 39 to 40 degree Baume’, wherein the concentration of liquid sodium permanganate is up to 40%. The diluted solution of crude liquid sodium permanganate is micro-filtered and packaged. The filter press cake is washed with condensate water obtained in evaporation process and the washing filtrate is transferred to another storage tank. The filter press cake obtained is dissolved in stirred vessel with pure water under agitation at a temperature ranging from 50°C to 60°C to obtain a slurry and it is filtered through centrifuge. The centrifuged cake is further washed with hot water and the process of washing of filter press cake is repeated till the filter cake of K2SiF6 is light pinkinsh white in color. The filtrate obtained in the process is used as a reaction substrate.
Detailed description of the embodiments:
The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.
Accordingly, the present invention provides a method (100) for manufacturing sodium permanganate solution. The method (100) consists the steps as below:
Step (a) involves potassium permanganate and sodium silicofluoride (Sodium hexaflouosilicate) are mixed in weight proportion ranging from 1.6:1 to 1.9:1 in excess water to form an aqueous solution, wherein weight proportion of water and reactants mixture is ranging from 9:1 to 12:1.
Step (b) involves heating the aqueous solution to a temperature ranging from 50°C to 70°C, till the concentration of the reaction mass comes in a range from 15- 20 degree Baume’.
Step (c) involves cooling the crude reaction mass to ambient temperature and filtering through a filter press to obtain a filter press cake of Potassium silicofluoride (K2SiF6 ) and a filtrate containing sodium permanganate.
Step (d) involves collecting the filtrate in a storage tank and subjecting to forced circulation evaporation at a temperature ranging from 50°C to 65°C till the solution achieves concentration ranging from 42 to 45 degree Baume’. In an embodiment, the filtrate is evaporated using a falling film double effect evaporator using low pressure steam at 2.5 Kg/cm2 to 4 Kg/cm2 under vacuum (500 to 600 mm of Hg) where temperature is ranging from 50°C to 65°C till the solution achieves concentration ranging from 42 to 45 degree Baume’ In another embodiment, the condensate water obtained in the evaporation process is reused for washing the filter cake obtained in step (c).
Step (e) involves transferring the concentrated solution to a crystallizer and cooling the solution to a temperature ranging from 10°C to 0°C;
Step (f) involves centrifuging the cooled solution to obtain crude liquid sodium permanganate solution and the solids separated in centrifuging are recycled as reactant in step (a).
Step (g) involves diluting the cooled liquid (Sodium permanganate solution) to a concentration from 39 to 40 degree Baume’ wherein the concentration of liquid sodium permanganate is up to 40%. The diluted sodium permanganate solution is micro filtered and packaged.
Step (h) involves transferring the filter press cake to a separate slurry tank and mixing with water under agitation at a temperature ranging from 50°C to 60°C, to obtain a slurry. The slurry is cooled and subjected to pressure filtration to form a filter press cake.
Step (i) involve repeating the step (h) till the filter cake of K2SiF6 is colorless and recycling the filtrate as reaction substrate in step (a).
In an embodiment, the reactants - potassium permanganate and sodium silicofluoride (sodium hexaflouosilicate) are having less than 150 ppm level of sulfate content. The total reaction time for the process varies from 24 to 36 hours.
The condensate obtained in step (d), the washing filtrate obtained in step (i) and the centrifuged solids obtained in step (f) are recycled and reused in the process. Optimum utilization of raw materials is possible by repeated washing of filter cake and recycling of filtrate as reaction filtrate providing from 85 to 90% productivity. The production process is simple and can be produced with cost effective manner with taking care of environment concern.
The method (100) of the present invention is further illustrated by the following examples. These examples are given by way of illustration and should not be construed to limit the scope of present invention.
Example 1
In a reactor vessel containing 7m3 of water, 550 to 700 kg of sodium silicofluoride was added under stirring and the reaction mass was steam heated to a temperature ranging from 50°C to 60°C. To this reactor 1.1 to 1.5 tons of potassium permanganate solution was gradually added to this mixture. The reaction mixture was warmed to 60°C and subjected to digestion for 24 to 36 hours. Heating was stopped after achieving the concentration 15 to 20 degree Baume’, the reaction solution (crude sodium permanganate solution) was cooled and filtered by a filter press.
Evaporation /concentration: The filtered reaction solution (crude sodium permanganate solution) obtained after filter press was concentrated in a double effect evaporated system under vacuum at 55°Cto 60°C, till it reached the concentration of 42 to 45 degree Baume’. The concentrated solution was then transferred to a crystallizer.
Cooling and filtration: The concentrated solution in the crystallizer was cooled to 30°C using cooling water. The solution was further cooled to a temperature ranging from 0°Cto 10°C in a time period of 2 to 4hrs by using chilled water. The resulting cooled solution was then centrifuged and the centrifuged solution was transferred to a dilution tank.The solid part separated in the centrifugation process was recycled as part of raw material for reuse as one of the reactant in next batch cycle.
Dilution, packing and weighing: In the dilution tank, required amount of pure water was added to the crude sodium permanganate solution to adjust the concentration of sodium permanganate to 40%. This solution after quality test approval was transferred to a homogenizer tank and was taken in to the measuring tank from where it was filtered through a fine micro filter and packed in the respective packaging units which were weighed after packing.
Recycling and reuse of reactants: The filter press cake residue was transferred to a slurry tank; water was added under stirring and heated to 60°Cto 70°C. After stirring for 60 minutes the slurry was centrifuged, the filtrate was pumped to the reaction intermediate tank as a reaction make up volume for next batch cycle. The washed centrifuged cake was purified as saleable product and/or converted in to a new product without generating any waste.
Advantages of the invention:
1. The method (100) uses extrapure potassium permanganate and sodium silicofluoride (sodium hexa-fluoro-silicate) having lower sulfate and chloride content, that results in a product with lower impurities.
2. The method (100) avoids use of hazardous chemicals like chlorine oxide, MnO2 and NaOH or Aluminum permanganate or ferromanganese.
3. Sodium permanganate solution produced by the method (100) is of better quality, especially low chloride, sulfate and potassium content.
4. The method (100) provides a simple production process with lower temperature range and with lower steam cost with no waste water and solid waste discharge.
5. The reaction is completed under normal pressure, the reaction conditions are easily controlled.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, and to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but such omissions and substitutions are intended to cover the application or implementation without departing from the scope of the claims of the present ,CLAIMS:We claim:
1. A method (100) for manufacture of Sodium Permanganate solution, the method (100) comprising:
a) mixing potassium permanganate and sodium silicofluoride (Sodium hexaflouosilicate) in weight proportion ranging from 1.6:1 to 1.9:1 in excess water to form an aqueous solution;
b) heating the aqueous solution to a temperature ranging from 50°C to 70°C, till the concentration of the reaction mass is in a range from 15- 20 degree Baume’;
c) cooling the crude reaction mass to ambient temperature and filtering through a filter press to obtain a filter press cake of Potassium silicofluoride (K2SiF6 ) and a filtrate containing sodium permanganate;
d) collecting the filtrate in a storage tank and subjecting to forced circulation evaporation at a temperature ranging from 55°C to 65°C till the solution achieves concentration ranging from 42 to 45 degree Baume’ and storing the condensate water obtained in the evaporation process in a storage tank ;
e) transferring the concentrated solution to a crystallizer and cooling the solution to a temperature ranging from 10°C to 0°C;
f) centrifuging the cooled solution to obtain a crude liquid sodium permanganate solution and recycling the solids separated in centrifugation as reactants in step (a);
g) diluting the cooled liquid sodium permanganate solution to a concentration from 39 to 40 degree Baume’ wherein the concentration of liquid sodium permanganate is up to 40%;
h) washing the filter cake obtained in step (c) with water and the condensate obtained in step (d) under agitation at a temperature ranging from 50°C to 60°C, to obtain a slurry and pressure filtering the slurry to form a filter cake;
i) repeating the step (h) till the filter cake is colorless, recycling the filtrate as reaction substrate in step (a), and separating the filter cake of K2SiF6 as a byproduct.
wherein the liquid sodium permanganate obtained in step (g) is packaged after micro-filtration and
2. The method (100) claimed in claim 1, wherein in step (a), the weight proportion of water and reactants mixture in the aqueous solution is ranging from 9:1 to 12:1.
3. The method (100) claimed in claim 1, wherein the filtered solution in step (c) is subjected to evaporation through a falling film double effect evaporator using low pressure steam at 2.5 Kg/cm2 to 4 Kg/cm2 under vacuum ( 500 to 600 mm of Hg).
4. The method (100) claimed in claim 1, wherein the concentrated solutionin step (e) is cooled using chilled water.
5. The method (100) claimed in claim 1, wherein the reactants potassium permanganate and sodium silicofluoride are having less than 150 ppm level of sulfate content.
Dated this 20th day of February, 2020

Ashwini Kelkar
(Agent for the applicant)
(IN/PA-2461)