DESC:FIELD
The present disclosure relates to a process for synthesizing diphenyl sulfone and its derivatives.
BACKGROUND
Diphenyl sulfone is an organosulfur compound having a formula (C6H5)2SO2. It is a white solid that is soluble in organic solvents. It is used as a high temperature solvent. Such high temperature solvents are useful for processing highly rigid polymers such as Polyether ether ketone (PEEK), which dissolves only in very hot solvents.
Diphenyl sulfone
Derivatives of diphenyl sulfone such as 3,3',4,4'-Tetramethyldiphenyl sulfone is useful as an intermediate for the preparation of 3,3',4,4'-tetracarboxydiphenyl sulfone, which is further converted into its anhydride - 3,3',4,4'-tetracarboxydiphenyl sulfone dianhydride (DSDA). DSDA is an important intermediate for the preparation of industrially useful products such as polyesters, polyimides, polyetherimides, polysulfones, tetra carboxylic esters (as plasticizers), alkyd resins, and unsaturated polysetsers.

3, 3',4, 4'-Tetramethyldiphenyl sulfone
Various methods are known for the synthesis of 3, 3’, 4, 4’-tetramethyldiphenyl sulfone. Conventionally, 3, 3', 4, 4'-tetramethyldiphenyl sulfone is prepared by treating o-xylene with H2SO4, arene sulfonic acids, SO3 or Me2SO4 in the presence of a catalyst. The catalysts used in the reaction are P2O5, PO(OH)3, H3PW12O40 hydrate, fluorosulfonic acid-antimony pentafluoride (HSO3F-SbF5) and such.
However, these catalysts are expensive and hence, increase the overall running cost of the process. Therefore, there is felt a need for a process for synthesizing 3, 3’, 4, 4’-tetramethyldiphenyl sulfone that is simple and economic and gives a high yield of 3, 3’, 4, 4’-tetramethyldiphenyl sulfone without the use of catalysts.

OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows.
It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
An object of the present disclosure is to provide a process for synthesizing 3, 3’, 4, 4’-Tetramethyldiphenyl sulfone.
Another object of the present disclosure is to provide a process for synthesizing 3, 3’, 4, 4’-Tetramethyldiphenyl sulfone from o-xylene.
Still another object of the present disclosure is to provide a process for synthesizing 3, 3’, 4, 4’-Tetramethyldiphenyl sulfone without the use of a catalyst
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure relates to a process for the synthesis of diphenyl sulfone derivative, particularly, the synthesis of 3, 3', 4, 4'-tetramethyldiphenyl sulfone from o-xylene.
O-xylene is treated with oleum at a temperature in the range of 65 °C to 75 °C for a time period ranging from 1 hour to 2 hours to obtain reaction mass. The reaction mass is further equilibrated at a temperature in the range of 65 °C to 75 °C for a time period ranging from 1 hour to 2 hours and heated at a temperature in the range of 130 oC to 140 oC for a time period ranging from 1 hour to 2 hours. Thereafter, dry HCl gas is passed through the heated mass at a temperature in the range of 150 °C to 160 °C for a time period ranging from 15 hours to 20 hours, with simultaneous removal of water, to obtain a reaction mixture comprising the diphenyl sulfone derivative.
The reaction mixture is cooled to a temperature in the range of 80 oC to 85 oC. To the reaction mixture, hot water having a temperature in the range of 80 oC to 85 oC is added to obtain a residue. The so obtained residue is further cooled to a temperature in the range of 70 oC to 75 oC under stirring for a time period ranging from 30 minutes to 1 hour and filtered it through a buchner funnel and dried under vacuum to obtain the diphenyl sulfone derivative having at least 95% purity.
DETAILED DESCRIPTION
The disclosure will now be described with reference to the accompanying embodiments which do not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The following description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein has been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
In accordance with the present disclosure there is provided a process for the synthesis of diphenyl sulfone derivative from o-xylene. The process is described in detail herein below:
A predetermined amount of o-xylene is charged into a reactor. Oleum is added into the reactor containing o-xylene to obtain a mixture. Instead of oleum, H2SO4 can also be used. The molar ratio of the amount of o-xylene to oleum ranges from 1.2 to 1.4. In one embodiment 24% of oleum is used which contains 235.2 gms of SO3 and 744.8 gm of H2SO4.
The so obtained mixture is stirred at a speed in the range of 400 rpm to 500 rpm. The stirring of the mixture is carried out at a temperature in the range of 65 oC to 75 oC for a time period ranging from 1 hour to 2 hours to obtain a reaction mass.
The reaction mass is equilibrated at a temperature in the range of 65 oC to 75 oC for a time period ranging from 1 hour to 2 hours to obtain equilibrated reaction mass. In the present disclosure, the process of equilibration is a chemical equilibrium of the reactants. Chemical equilibrium is a state in which the rate of the forward reaction is equal to the rate of the backward reaction. In many chemical reactions, the forward and backward reactions can occur at the same time and are reversible. In other words, at equilibrium state, there is no net change in the concentrations of reactants and products.
The equilibrated mass is then heated at a temperature in the range of 130 oC to 140 oC for a time period ranging from 1 hour to 2 hours to obtain a heated mass.
Thereafter, dry HCl gas is passed into the reactor containing the heated mass with simultaneous removal of water from the reactor. The reaction is carried out at a temperature in the range of 150 °C to 160 °C for a time period ranging from 15 hours to 20 hours to obtain a reaction mixture comprising diphenyl sulfone derivative. The amount of dry HCl gas used in the process of the present disclosure ranges from 0.05 to 0.07 mol/ mol of oleum /hr. The removed water can be recovered for further use.
The addition of the dry HCl gas results in simultaneous removal of water. Also, it is observed that passing dry HCl gas through the reaction mixture results in an improved reaction rate. Dry HCl can be recovered and recycled easily, which gives this method an advantage over other processes where catalysts are used and which are difficult to recover.
The so obtained reaction mixture is cooled to a temperature in the range of 80 oC to 85 oC. After cooling, hot water is added into the reaction mixture to obtain a residue. In an embodiment the temperature of the hot water is in the range of 80 oC to 85 oC .
The residue is further stirred at a temperature in the range of 70 oC to 75 oC for a time period ranging from 30 minutes to 1 hour. After stirring for one hour the residue can be filtered through a funnel at a temperature in the range of 70 oC to 75 oC to obtain a solid containing the diphenyl sulfone derivative.
The solid is washed with 300 ml hot water having a temperature ranging from 70 oC to 75 oC. The solid is dried under vacuum for a time period ranging from 30 minutes to 1 hour to obtain the diphenyl sulfone derivative. The purity of the dried diphenyl sulfone derivative is at least 95% and the yield is 28%.
In an exemplary embodiment, the diphenyl sulfone derivative is 3,3',4,4'-tetramethyldiphenyl sulfone.

The per pass conversion of the reaction ranges from 30% to 50% with respect to the overall yield of 3,3',4,4'-tetramethyldiphenyl sulfone. The per pass conversion is the quantitative analysis of the chemical conversion of the percentage of reactant converts into products inside a chemical reactor or unit process, where unconverted reactants are recovered from the product stream and recycled to the reactor inlet.
The 3,3',4,4'-tetramethyldiphenyl sulfone so obtained can be used to prepare other derivatives by further oxidizing into 3,3',4,4'-tetracarboxydiphenyl sulfone and then to 3,3',4,4'-tetracarboxydiphenyl sulfone dianhydride (DSDA) by methods known in the art.
The present disclosure is further illustrated herein below with the help of the following experiments. The experiments used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of embodiments herein. These laboratory scale experiments can be scaled up to an industrial/commercial scale.
EXPERIMENTAL DETAILS
Experiment 1: Synthesis of 3,3’,4,4’-Tetramethyldiphenyl sulfone in accordance with the process of the present disclosure-
In a reactor 1755.5 gm of o-xylene was charged. To that, 1100 gm of 24% oleum was added over a period of 2 hours at 55 oC under stirring. The stirring was maintained for 1 hour at 70 oC to obtain an equilibrated reaction mass. The reaction mass was heated at 150 oC for 1 hour and dry HCl gas was passed through the reaction mass with continuous removal of water. The reaction mass was stirred for 16 hours at 150 oC.
To the reaction mass, hot water (80 oC) was added and stirred it for 30 minutes at 72 oC to obtain a residue. The residue was filtered through a Buchner funnel with polypropylene (pp) cloth to obtain a brown color cake (solid). The cake was further washed with hot water (70 oC) twice, with 350 ml of water in each wash. The washed cake was dried under vacuum for 30 minutes to obtain 755 gm of 3,3’,4,4’-Tetramethyldiphenyl sulfone on dry weight basis having a purity of 98.80%.
Experiment 2: Comparative Example-
A similar experiment, as described in experiment 1, was carried out without using dry HCl gas. The results obtained from the process of the present disclosure for examples 1-2 are summarized in table 1.
Table 1
Experiment No Reactants in gms Use of HCl gas Yield of diphenyl disulfone (Dry weight in gms) Purity of diphenyl disulfone
Expt 1 O-xylene (1755.5 gm) & 24% oleum (1100 gm) Using dry HCL gas 755gm 98.80%
Expt 2 O-xylene (1563.5 gm) & oleum (980 gm) without using dry HCL gas 426gm 88.31%
From the table 1, it is clear that the conversion of the reaction mass into tetramethyl diphenyl sulfone is comparatively more, when dry HCl gas is passed through the reaction mass.
TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of:
? a process for synthesizing 3,3’,4,4’-Tetramethyldiphenyl sulfone from o-xylene without the use of expensive catalysts;
? a process for synthesizing 3,3’,4,4’-Tetramethyldiphenyl sulfone which is cost effective; and
? a process for synthesizing 3,3’,4,4’-Tetramethyldiphenyl sulfone which is simple and environment friendly.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation. ,CLAIMS:1. A process for preparing diphenyl sulfone derivatives, said process comprising:
i. charging a predetermined amount of o-xylene into a reactor and adding oleum to said reactor to obtain a mixture;
ii. stirring said mixture at a temperature in the range of 65 oC to 75 oC for a time period ranging from 1 hour to 2 hours to obtain a reaction mass;
iii. equilibrating said reaction mass at a temperature in the range of 65 oC to 75 oC for a time period ranging from 1 hour to 2 hours to obtain an equilibrated mass;
iv. heating said equilibrated mass at a temperature in the range of 130 oC to 140 oC for a time period ranging from 1 hour to 2 hours to obtain a heated mass;
v. passing dry HCl gas into said reactor containing said heated mass and heating it at a temperature in the range of 150 oC to 160 oC for a time period ranging from 15 hours to 20 hours, while continuously removing water from the reactor, to obtain a reaction mixture comprising the diphenyl sulfone derivative;
vi. cooling said reaction mixture to a temperature in the range of 80 oC to 85oC and adding hot water having a temperature in the range of 80 oC to 85 oC to obtain a residue; and
vii. stirring said residue at a temperature in the range of 70 oC to 75 oC for a time period ranging from 30 minutes to 1 hour, filtering said residue at a temperature in the range of 70 oC to 75 oC followed by drying to obtain the diphenyl sulfone derivative.
2. The process as claimed in claim 1, wherein said diphenyl sulfone derivative is 3,3',4,4'-Tetramethyldiphenyl sulfone.
3. The process as claimed in claim 1, wherein the molar ratio of said o-xylene and said oleum is in the range of 1.2 to 1.4 mol/mol.
4. The process as claimed in claim 1, wherein the amount of said dry HCl gas passed in the reaction mass is in the range of 0.05 to 0.07 mol / mol of oleum / hr.
5. The process as claimed in claim 1, wherein said diphenyl sulfone derivative is characterized by a purity of at least 95%.