Title of Invention

"AN IMPROVED PROCESS FOR THE PRODUCTION OF RESORCINOL"

Abstract

An improved process for the production of resorcinol An improved process for the production of resorcinol by disulphonating benzene subjecting the disulphonated mass to neutralisation with sodium sulphite solution obtained as a raffinate at a pH 2.5 to 4.0 followed by alkali neutralisation, then subjecting the neutralised mass to alkali fusion at a pH 7.0 to 8.0 at a tempera- o ture in the range of 70-130 C and further to acid   neutralisation with sulphurdioxide at a pH 6.5 to 7.0 °     at   a   temperature  in the  range of   60-90  C   to   obtain resorcinol.

Full Text

The present invention relates to an improved process for the production of resorcinol. The main usage of the invention is for neutralisation of the products of disulphonation and alkali fusion reaction in relation to the production of resorcinol from benzene by sulphonation and alkali fusion technology. The invented process provides a novel method for .neutralisation of benzene meta disulphonic acid with sodium sulphite solution (obtained as a raffinate in the process itself) and the sulphurdioxide evolved is used, in turn, to acidify the quenched alkali fusion melt thereby liberating resorcinol. Commercially,resorcinal is prepared from benzene through sulphonation,disulphonation and alkali fusion technology.Benzene is sulphonated with 108/1 sulphuric acid when benzene monosulphonic acid is formed.The benzene monosulphonic acid is further sulphonated with oleum to benzene meta disulphonic acid. The benzene meta disulphonic acid is converted to sulphonate by neutralising with alkali.By reaction of the sulphonate with fused alkali metal hydroxide,alkali metal salt of resorcinol is produced which on hydrolysis with an acid produces resorcinol. The conventional process C Refs: (i) E.E. Gilbert, Ind.Eng.Chem.,43,2022C1951), C ii ) F.L.Allen,chem.Eng,74, 113(1967)3 suffers from several disadvantages,the foremost being that neutralisation has to be carried out in two separate stages, resulting in high consumption cf both acid and alkali. Moreover, the excess acid required for sulphonation may,on neutralisation, produce such huge quantities of alkali sulphate that it may affect the alkali fusion step in an adverse way. Lime has also been used in the neutralisation step with formation of gypsum which createsdisposal problem as d.iscussed in re-f.(i) above. These disadvantages were overcame by a neutralisation process as described in our Indian Patent No.141863 wherein the reaction products obtained on sulphonation as well as the alkali fusion mass of the sulphonate are neutralised by mixing the two streams. The solution after mixing contains resorcinol, sodium salt of benzene meta disulphonic acid & sodium sulphate .The entire mass is diluted with minimum quantity of water so that it goes completely into solution. The liberated resorcinol could be separated by any suitable means such as solvent extraction. The alkali sulphate and disuiphonate in solution are separated by fractional crystallisation for which a bulk quantity of water is to be evaporated. This process for neutralisation suffers from the disadvantage that it requires evaporation of a large volume of water for recovering the feed material for the fusion reaction, namely, benzene meta disuiphonate.Besides,the recovered benzene meta disuiphonate contains variable percentage of sodium sulphate depending upon the stage of crystal lisation .This results in variation in the composition of the feed mass for fusion thereby affecting the efficiency of the fusion reaction. Furthermore,this method of neutralisation of disulphonated as well as the alkali fusee mass suffers from the inherent drawback that the sulphurdioxide produced during the reaction creates pollution hazard and disposal problem. The main object of the present invention is to provide an improved process for the production of resorcinol which obviates drawbacks as detailed above. Another object of the present invention is to remove the drawback of the hitherto known process for the method of neutralisation of the disulphonated as well as alkali fusion mass as discussed above. Still another object of the present invention is to minimise the acid and alkali consumption. Yet another object of the present invention is to utilise the sulphurdioxide generated during the neu-tralisation of the disulphonated mass for acidifying the quenched fusion melt and avoid pollution hazards. Accordingly the present invention provides an improved process for the production of resorcinol which comprises disulphonating benzene subjecting the disul-phonated mass to neutralisation with sodium sulphite solution obtained as a raffinate at a pH 2.5 to 4.0 followed by alkali neutralisation, then subjecting the neutralised mass to alkali fusion at a pH 7.0 to 8.0 at o a temperature in the range of 70-130 C and further to acid neutralisation with sulphurdioxide at a pH 6.5 to o 7.0 at a temperature in the range of 60-90 C to obtain resorcinol. In an embodiment of the present invention the disulpdonated mass is First neutralised by treatment with sodium sulphite solution to a pH of 2.5 to 4.0 and then further neutralised with alkali to a pH of 7.0 to 8.0 in the temperature range of 70°C to 130°C In another embodiment of the present invention the quenched alkali fusion melt is acidified with the sulphurdioxide to a pH of 60-90oc of 6.5 to 7.0 in the temperature range of 60 - 90 C. In yet another embodiment of the present invention the resorcinol formed is separated from the acidified alkali fusion meit by solvent extraction or layer separation and the raffinate containing sodium sulphite is used for the neutralisation of the benzene disulphonated mass. In this process benzene is monosulphonated with 100 sulphuric acid and further disulphonated with oleum.The disuiahonated mass is -First neutralised to a. pH o-f 2.5 to 4.0 with sodium sulphite solution obtained as a raffinate aftsr separation of resorcinol from the acidified quenched fusion melt and is further neutralised with sodium hydroxide to a pH of 7. S3 to S.3. The sulphurdioxide evolved is used to acidify the quenched oroduct of alkali fusion reaction between benzene meta disuiphonate and sodium hydroxide.The neutralisation reaction is carried out in the temperature range of 70-130 C and the mass is concentrated by evaporation to such an extent that on coaling most of the sodium sulphate crystallises out leaving the ,benzene meta disulpnonate in the solution which is evaporated to dryness. The dried benzene meta disulphonate is fused with alkali and quenched. The quenched alkali fusion melt is acidified with sulphurdioxide to a pH of 6.5 to 7.0 in the temperature range 60-90 C to liberate resorcinol. The liberated resorcinol is separated by solvent extraction or layer separation. The raffinate(after separation of resarcinol ) which contains sodium sulphite is used for the neutralisation of disulphonated mass. The novelty o-f the present invention vis—a—vis prior art lies in that the neutrralisation of the disulphonated mass of benzene is carried out with the raffinate which contains sodium sulphite(obtained after separation of resorcinol from acidified quenched fusion melt) and the sulphurdioxide that is evolved in the reaction is utilized in the process itself for acidifying the quenched fusion melt thereby obviating the environmental pollution. Thus the invented process has led to the considerable reduction in consumption of acid and alkali, and at the same time also the pollution hazard due to sulphurdioxide has also been avoided. The following example is given by way of illustration of the present invention and should not be construed to limit the scope of the present invention. EXAMPLE 390 gms. of benzene was monosulphonated by adding 993 gms. amount of 100% sulphuric acid .(addition temperature 30-50 C) and the reaction temp. 105 C) for one hour.The monosulphonated .mass was further disulphonated by adding 1338 gms. amount of 60X oleum ( addition temp.4G-70 C) and maintaining the reaction . temperature 105°C -for one hour.The disulphonated mass was diluted and -first neutralised to a pH of 4.0 in the temperature range of 70 -130 C with the raf-finate which contains sodium sulphite ( obtained a-fter separation of resorcinol from the acidi-fied quenched -fusion melt).This was further neutralised to a pH a-f 7.5 with sodium hydroxide. The sulphurdiaxide evolved during the neutralisation reaction was used for the acidification of Quenched alkali fusion melt. The neutralised disulphonated mass was concentrated to a desired level,coolea and filtered to rsmave sodium sulphate.The filtrate was evaporated to dryness to obtain solid sodium salt of benzene meta disulphonic acid . The evaporated dry mass was added to the required amount of molten alkali in a fusion pot in the temperature range 270 - 300 C under constant stirring.After the addition was over the reaction temperature was raised and maintained at 320+ 50 c for 30 - 40 minutes.The alkali fusion melt was quenched with required amount of water and filtered to remove some sodium sulphite. The filtrate was acidified with sulphurdioxide (obtained during neutralisation of disulphonated mass with sodium sulphite liquor) to a pH of 7.0 in the temperature range of 60—90 C when resorcinol was set free. The resorcinol was extracted from the acidified solution by required amount of butyl acetate and the solvent layer was separated. THe aqueous layer i,e sodium sulphite liquor was used for the neutralisation of disulphonated procuct. The butyl acetate extract was subjected to distillation and major portion of the solvent was recovered and then resorcinol was obtained by -further distillation under reduced pressure. The resorcinol obtained was 340 gms having 99.5 7. purity. In conclusion the invention has led to omission of the tidious -fractional crystallisation step inherent in the conventional process for preparation of resorcinol from benzene by sulphonation and alkali fusion technology. Secondly,the acid and alkali consumptions have been considerably reduced in the overall process, thus making the process cheaper and more economical. Thirdly, the major part of the sulphurdioxide produced during the neutralisation stage is utilized in the process itself, thereby obviating the environmental pollution. These are the slient features of the invention which have an edge over the known processes. The main advantages of the present invention are :— 1.that the fractional crystallisation step is omitted. 2.that evaporation of large volume of water is obviated and this results in reduction oF cost as well as time cycle. 3.that the acid and alkali consumptions are considerably less. 4.that the sulphurdioxide produced is utilised in the process itself,thereby obviating the environmental pollution. claim : 1. An improved process for the production of resorcinol which comprises disulphonating benzene subjecting the disulphonated mass to neutralisation with sodium sul phite solution obtained as a raffinate at a pH 2.5 to 4.0 followed by alkali neutralisation, then subjecting the neutralised mass to alkali fusion at a pH 7.0 to o 8.0 at a temperature in the range of 70-130 C and further to acid neutralisation with sulphurdioxide at a o pH 6.5 to 7.0 at a temperature in the range of 60-90 C to obtain resorcinol. 2. An improved process for the production of resorcinol substantially as herein described with reference to the example.

Documents:

110-del-1998-abstract.pdf

110-del-1998-claims.pdf

110-del-1998-correspondence-others.pdf

110-del-1998-correspondence-po.pdf

110-del-1998-description (complete).pdf

110-del-1998-form-1.pdf

110-del-1998-form-19.pdf

110-del-1998-form-2.pdf

110-del-1998-petition-137.pdf