|Title of Invention||
IMPROVED PROCESS FOR THE PURIFICATION OF SULPHANILIC ACID OF PURIFIED GRADE
|Abstract||The present invention relates to the improved process for the purification of sulphanilic acid purified grade comprising the steps of preparation of sulphanilic acid solution by dissolving the sulphanilic acid of technical grade at elevated temperature with constant stirring and then added with activated carbon. Then the solution is subjected to Alteration in filter press to remove water insoluble materials and that filtrate is cooled to below room temperature to recrystallize white sulphanilic acid purified grade in precipitation tanks. After that the solution is then subjected to centrifugation to separate the white coloured wet cake of sulphanilic acid purified grade from the supernatant mother liquor and the remaining spent medium is recycled. Thus produced white coloured sulphanilic acid wet cake is dried and pulverized to fine powder of white coloured sulphanilic acid of purified grade having the purity (amine content) above 99%.|
THE PATENTS ACT, 1970
(39 OF 1970)
THE PATENTS RULES, 2003
(See Section 10 and rule 13)
IMPROVED PROCESS FOR THE PURIFICATION OF SULPHANILIC ACID OF PURIFIED GRADE
SANTOSH PHULCHAND MEHTA
House no. 17, Near SBI Dapoli, Tal: Dapoli, Dist:- Ratnagiri MAHARASHTRA, INDIA
The following specification particularly describes the invention and the manner in which
it is to be performed
FIELD OF THE INVENTION
Present invention relates to a process for the purification of sulphanilic acid. More particularly present invention relates to a process for the purification of sulphanilic acid to purified grade, which is above 99% purity (amine content) and white in colour.
BACKGROUND OF THE INVENTION
Millions of pounds of sulphanilic acid are consumed annually, primarily to produce dyestuffs but some is also used in the synthesis of other materials including substantial amount of phenylhydrazine-p-sulfonic acid. The major portion of the sulphanilic acid is consumed in the manufacture of fluorescent whitening agents. Such fluorescent dyestuffs are applied to paper, woven and non-woven textiles, and are components of soap and detergent laundering agents. Such fluorescent whitening agents are marketed under the Tinopal trademark. For example, in excess of a million pounds a year is used for the manufacture of one of the whiteners applied to paper. Because of its overwhelming economic importance, the application of the invention to sulphanilic acid is stressed. Thus, any savings effected in the production and purification of sulphanilic acid are of major economic interest.
GB1356000 describes the process for the preparation of sulphanilic acid. In accordance with the process of the invention, the starting material is introduced into the fluidized bed in fine dispersion as a flowable melt or solution, with or without the use of water as solvent. The fine dispersion can be achieved by spraying with one-component or two-component nozzles, in the latter case, an inert gas serving as the atomizing medium. A particle size of from 1 to 5 mm for example is advantageously maintained. The 60 kg of
sulphonic acid is placed in a fluidized bed reactor having a bed surface of 0.26 m2 and upwardly through a sieve plate having 5% of free cross-sectional area there is passed 1000 kg per hour of air at a temperature of 280°C, corresponding to a fluidization rate of 1.5 m/second with reference to an air outlet temperature of about220°C. 120 kg per hour of molten aniline sulphate is sprayed in through a centrally disposed two-component nozzle. 108 kg per hour of sulphanilic acid is withdrawn from the fluidized bed through a continuously regulatable screw. The sulphanilic acid has a purity of 98 to 99%.
EP0063270 emphasizes the process for the preparation of sulphanilic acid by classical baking method. In this procedure the production of p-sulphanilic acid is done by the so-called baking procedure by conversion of aniliniumhydrogensulphate at increased temperature in an inert solvent, by the fact characterized that the conversion to presence of surplus aniline is made and that the distance of the reaction water from the reaction mixture at least partly with 180 to 280°C, if necessary under pressure is accomplished.
The classical process for making sulphanilic acid is the "baking" process wherein aniline acid and sulphuric acid are mixed together to form the solid aniline hydrogen sulfate salt (Fiat Report 1313) (1945). In one variant, a batch-type process, a layer of the solid salt several centimeters thick is spread on lead or iron trays. The loaded trays are then slowly passed through an oven or tunnel kiln and heated to above the rearrangement and water elimination temperature. The eliminated water is vented from the kiln and condensed together with any vaporized aniline. When the trays emerge, conversion to sulphanilic acid is substantially complete, the trays are emptied and the cycle is repeated by reloading the trays with additional aniline hydrogen sulfate.
The molten aniline hydrogen sulfate, prior to rearrangement and water elimination is corrosive, especially to iron. In the trays, while corrosion takes place, the rate of corrosion and erosion of metal is not excessive because an adherent retarding surface coating of sulphanilic acid forms on the surface of the trays. This coating also retards migration of the colored corrosion products through the rearranging mass.
US4681710 describes the process for the preparation of sulphanilic acid. In one aspect, concentrated sulphuric acid and liquid aniline are each sprayed in a mist-like pattern into the vortex of a cascading heated bed of sulphanilic acid particles formed within the rotating heated reactor. The spray patterns are so directed that they intersect, and interact with each other just prior to entering the bed so that the particles are wetted by liquid aniline hydrogen sulfate formed essentially in situ. In another aspect of the invention, a spray nozzle is installed above a cascading bed of hot sulphanilic acid particles. Immediately preceding the spray nozzle is a mixing chamber connected to two feed lines. Stoichiometric amounts of aniline and sulphuric acid are fed to the mixing chamber. High temperature molten aniline hydrogen sulfate is formed in the mixing chamber and finely divided droplets are sprayed into the vortex of the cascading bed. A preferred method of heating the fluidized, rotating reaction medium and introduced reactants is by induction heating. A water-cooled induction-heating strip is positioned beneath and along substantially at least the introductory and initial bed portions of the reactor, preferably along substantially most of the reactor feed zone. This arrangement provides maximum bed input to the reaction along that part of the inside of the reactor adjacent to and passing over the induction strip. This arrangement has the advantage or rapidly
responsive temperature control, as there is rapid heat transfer via the indicator without the lagging response caused by heat sinks. The induction is not hot and thus provides no heat sink to slow thermal responses. To control the temperature of the emerging aniline hydrogen sulfate feed, water can be blended with the aniline feed. Although some of the heat of reaction is taken up by vaporizing this added water, the overall spray pattern is more easily controlled thereby simplifying the overall process. In the process sulphanilic acid formed when aniline is treated with concentrated sulphuric acid to form the intermediate aniline acid sulfate and wherein said improvement comprises introducing the aniline and sulphuric acid components and mixtures thereof into and unto a rolling vortex formed in a heated rapidly moving, cascading bed of sulphanilic acid particles contained in a reactor rotating on a horizontal axis, said bed being heated to above 160° C. to eliminate water from and to rearrange the intermediate to said sulphanilic acid.
The task of the invention described in DE4038285 consists of creating a procedure for the production of sulphanilic acid by cheeks of the aniline hydraulic gene sulfate at temperatures from 190 to 260 C without unfavorable effects on the product quality a substantial increase of the reaction rate made possible. According to invention the task is solved by the fact that diethylamine and/or tri ethylamine and/or dibutylamin and/or pyridine and/or pico-LINE are admitted to the aniline and/or the aniline hydraulic gene sulfate/become. By mixing aniline with the stoichiometric quantity of 96% sulphuric acid at a temperature from 165° to 170° C was formed a melt from aniline hydraulic gene sulfate. These became below in that the table indicated connections specified and/or mixtures added, and of it by means of cooling rolls a product made. With these
connections and/or mixtures shifted aniline hydraulic gene sulfate continuously in a quantity of 40 kg/h a double snail reactor.
US4560746 discloses the ultrafiltration process for purification of dyes useful in foodstuffs. In accordance with that, certain dyes useful in foodstuffs are not merely concentrated, but rather are prepared in molar yields which are unprecedented in the food dyestuff industry, and at purity levels which exceed the purity standards required by the U.S. Food and Drug Administration. These unprecedented results are achieved by essentially incorporating the purification of the dyes as part of a continuous purification process, the purification being effected by subjecting an aqueous solution of the reaction mixture resulting from preparation of the dye to ultrafiltration under conditions such that the dye can be isolated by evaporation of its solution in molar yields of approximately 98% and in a state of purity of approximately 90%. In certain instances molar yields as low as around 75% are obtained, but even in such cases, the state of purity of the dyes which can be achieved by this process is around 90%. It is preferred to subject the reaction mixture, which results from the preparation of the dyes, directly to ultrafiltration without isolation of the product. Alternatively, however, the products can be isolated in crude form from the reaction mixtures, either by salting out or by spray drying, and the crude product then redissolved in water and the solution is then subjected to ultrafiltration.
Earlier we followed the process comprising the steps of sulphanilic acid technical grade 98% dissolved in aqueous ammonia alkaline solution (1Kg in 5 L solution), then 1%
activated carbon is added & filter the solution to remove impurities & adding sulphuric acid in the mother liquor to precipitate sulphanilic acid purified grade and same is centrifuged & dried. The water effluents are treated with lime & sent to common effluent treatment for discharge.
The prior art processes for the purification of sulphanilic acid as discussed above are having the shortcomings that the processes are tedious, not economically viable and not eco-friendly. Moreover the product produced is not of a purified grade i.e. purity above 99%. Hence the present invention describes the easy, economically viable and eco-friendly process for the purification of sulphanilic acid to purified grade by using the technical grade sulphanilic acid.
An improved process for the purification of sulphanilic acid purified grade according to the present invention has following advantages in comparison to the prior art processes:
1. No requirement of ammonia for neutralization and sulphuric acid for acidification: The prior art processes uses ammonia to neutralize sulphanilic acid and to acidify that solution sulphuric acid is required. Whereas the present invention does not require ammonia and hence produces the purified grade sulphanilic acid, so there is no requirement of ammonia and sulphuric acid.
2. No water effluent production: The prior art processes at the completion of process for 1 kg of sulphanilic acid releases 5 L of water effluents and which needs further treatment in ETP and also in CETP. Whereas in the present process
the mother liquor is recycled, hence there is no water effluent production. So the process is eco-friendly and cost-effective.
3. Higher yield of the product: The yield of the sulphanihc acid obtained by this process is as high as 95% but the prior art processes produce only 85%. So there is 10% increase of yield through this process.
4. Cost-Effective: Since the present process requires lesser raw materials (ammonia and sulphuric acid), no water effluent production and approximately 10% higher yield compared to prior art processes makes the instant process economically viable and cost-effective to produce the purified grade sulphanihc acid.
SUMMARY OF THE INVENTION
The present invention aims at developing an improved process for the purification of sulphanihc acid purified grade.
Further object of the present invention is to eliminate the drawbacks and shortfalls of the prior art processes.
It is also the object of the present invention to improve the purity of the sulphanihc acid purified grade to above 99% and which is white in colour.
An improved process for the purification of sulphanihc acid of purified grade according to the present invention comprising the steps of preparation of sulphanihc acid solution by dissolving the sulphanihc acid of technical grade below 99% purity in hot water at 95°C with constant stirring and then added with activated carbon for decolourization and
also for settling the impurities. The hot mother liquor is then subjected to Alteration in filter press to remove water insoluble materials & then this filtrate is cooled to below room temperature to recrystallize white sulphanilic acid purified grade in precipitation tanks. After completion of precipitation the solution is then subjected to centrifugation to separate the white coloured wet cake of sulphanilic acid purified grade from the mother liquor and the remaining spent medium is recycled. Thus produced white coloured sulphanilic acid wet cake is dried and pulverized to fine powder of white coloured sulphanilic acid purified grade having the purity above 99% and then packed as per the requirement. The spent mother liquor water produced in the above process is recycled for up to 50 times which in turn reduces the water pollution drastically.
DETAILED DESCRIPTION OF THE INVENTION
An improved process for the purification of sulphanilic acid to purified grade according to the present invention comprising the following steps:
i. Preparation of sulphanilic acid solution;
v. Drying & Pulverization; and
vi. Recycling of mother liquor.
The process steps are illustrated in detail as below:
i. Preparation of sulphanilic acid solution:
Sulphanilic acid of technical grade of purity below 99% is dissolved in water at the temperature of 95 °C with constant stirring over a period of 10 min to ensure the complete solubility of sulphanilic acid in water. Then 0.1% activated charcoal is added to the above solution, which acts as decolourizing agent and also helps to settle the impurities at the bottom. After addition of activated charcoal is complete the solution is thoroughly stirred and allowed to settle for 10-30 min in order to settle carbon and metal impurities present in the solution.
The above settled hot mother liquor is then passed through the filter press to remove the insoluble impurities so as to obtain clear acidic solution of sulphanilic acid.
The clear acidic solution thus obtained after filteration is then carried to the tanks for precipitation. The solution in the precipitation tank is then subjected to cooling at the temperature of 15 to 20° C for a period of 20 min. After 20 min sulphanilic acid gets precipitated and white PPT is seen at the bottom.
After precipitation the solution is subjected to centrifugation, which separates the precipitated sulphanilic acid from the mother liquor. The wet white coloured cake of sulphanilic acid is seen at the bottom of the centrifuge tubes. The supernatant thus obtained is sent back to the dissolution tank for recycling.
v. Drying and Pulverization:
The wet white cake of purified grade sulphanilic acid so obtained after centrifugation is dried in the flash dryer and pulverized to fine powder and packed as per the requirement.
vi. Recycling of mother liquor:
The supernatant mother liquor separated at the centrifugation step (iv) is again sent back to the dissolution tank, which can be reused as substitute of plain water for the preparation of sulphanilic acid solution with 15 to 20% more water to meet the quantity of water. The liquid portion is recycled for 30 cycles & after 30 cycles the solution is treated by lime & filtrate is further used for recycling and hence there is no water effluent as such.
FLOW CHART FOR PROCESS OF PURIFICATION OF SULPHANILIC ACID OF PURIFIED GRADE:
The following chart illustrates the process steps according to the invention for purification of sulphanilic acid to purified grade continuously:
Sulphanilic acid technical grade
Sulphanilic acid purified grade purity (amine content) above 99%
The following specific example presented to illustrate the best mode of carrying out the process of the present invention but does not limit the scope of the invention. 50 kg of sulphanilic acid technical grade (made by our improved process as described in co pending patent application No. 774/MUM/2005) is dissolved in the 1200 L of boiling water having temperature of 95° C for a period 10 min in the dissolution reactor (DR)& then 300 g of 0.1% activated carbon (Charcoal) is added to the boiling solution. After 10 min the same hot solution is filtered by filter press and then it is cooled to 20° C in cooling reactor (CR) for a period of 20 min. Then the crystal white coloured sulphanilic acid settles at the bottom of the reactor. After completion of precipitation the mother liquor is centrifuged to get sulphanilic acid white colour wet cake at the bottom of the centrifuge tube. Thus obtained cake is then dried in the flash dryer to get good quality sulphanilic acid purified grade with purity (amine content) above 99%. The supernatant spent mother liquor water produced after centrifugation step is recycled for up to 50 times which in turn reduces the water pollution drastically.
1. Improved process for purification of sulphanilic acid purified grade wherein
said process comprises
i) preparation of sulphanilic acid solution;
v) drying & pulverization; and
vi) recycling of mother liquor.
2. The process as claimed in claim 1 wherein the sulphanilic acid solution is prepared by dissolving the sulphanilic acid of technical grade of purity below 99% in water at elevated temperature with constant stirring for a period of 10 min.
3. The process as claimed in claim 1 or 2 wherein the solution of sulphanilic acid is added with activated charcoal.
4. The process as claimed in any of the preceding claims the activated charcoal added is 0.1%.
5. The process as claimed in claim 1 wherein the Alteration of hot mother liquor is carried by passing through the filter press.
6. The process as claimed in claim 1 wherein the precipitation is carried out in a
tank at the temperature of 15 to 20° C for a period of 20 min.
7. The process as claimed in claim 1 wherein the centrifugation is carried to separate the precipitated wet white coloured sulphanilic acid of purified grade from the supernatant mother liquor.
8. The process as claimed in claim 1 wherein the drying of wet white cake of purified grade sulphanilic acid is done in the flash dryer and then pulverized to fine powder.
9. The process as claimed in claim 1 wherein the spent mother liquor produced in the process is recycled and reused up to 50 times.
10. Improved process for purification of sulphanilic acid purified grade above 99%
purity as claimed in any of the preceding claims as substantially described with
reference to the foregoing example.
Dated 29th day of May 2006
SANTOSH PHULCHAND MEHTA
|Indian Patent Application Number||773/MUM/2005|
|PG Journal Number||41/2008|
|Date of Filing||30-Jun-2005|
|Name of Patentee||SANTOSH PHULCHAND MEHTA|
|Applicant Address||HOUSE NO. 17, NEAR SBI DAPOLI, TAL. DAPOLI, DIST. RATNAGIRI,|
|PCT International Classification Number||C07C303/00|
|PCT International Application Number||N/A|
|PCT International Filing date|