A process for the preparation of 1,3-dihydroxy benzene

Abstract

The present disclosure relates to a process for the preparation of 1,3-dihydroxy benzene. The process of the present disclosure employs suitable catalysts, reagents, and purification strategies to achieve high selectivity, enhanced yield, and superior product selectivity. The process is robust, reproducible, and readily scalable, making it industrially attractive for the commercial manufacture of 1,3-dihydroxy benzene from benzene, with reduced by-product formation and improved operational efficiency.

Description

[0001] A PROCESS FOR THE PREPARATION OF 1,3-DIHYDROXY BENZENE FIELD

[0002] The present disclosure relates to a process for the preparation of 1.3-dihydroxybenzene.

[0003] BACKGROUND

[0004] The background information herein below relates to the present disclosure but is not necessarily prior art.

[0005] 1.3-dihydroxybenzene also known as resorcinol, is used as a disinfectant or an antiseptic. It is a raw material for many specialty chemicals such as ultraviolet light absorbers, fire retardants, polycarbonates, agricultural chemicals, urethane elastomers, dyestuffs and the like. 1,3-dihydroxy benzene is represented by Formula I:

[0006] OH

[0007]

[0008] OH

[0009] Formula I

[0010] The conventional processes for the preparation of 1,3-dihydroxy benzene are associated with drawbacks such as use of toxic and expensive reagents / catalysts which make the process uneconomical. Further, the conventional processes involve tedious workup steps as well as formation of impurities that affect the purity of the final product.

[0011] Therefore, there is felt a need to provide a process for the preparation of 1,3-dihydroxy benzene that mitigates the aforestated drawbacks or at least provides a useful alternative.OBJECTS

[0012] Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:

[0013] It is an object of the present disclosure to ameliorate one or more problems of the background or to at least provide a useful alternative.

[0014] Another object of the present disclosure is to provide a process for the preparation of 1,3-dihydroxy benzene.

[0015] Yet another object of the present disclosure is to provide a process for the preparation of 1,3-dihydroxy benzene with a comparatively high purity and high yield.

[0016] Still another object of the present disclosure is to provide a simple and cost-effective process for the preparation of 1,3-dihydroxy benzene.

[0017] Yet another object of the present disclosure is to provide an environment-friendly and commercially scalable process for the preparation of 1,3-dihydroxy benzene.

[0018] 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.

[0019] SUMMARY

[0020] A process for the preparation of 1, 3-dihydroxy benzene, the process comprises the following steps:

[0021] i. nitrating benzene by using a nitrating agent at a temperature in the range of 40 °C to 55 °C for a time period in the range of 30 minutes to 120 minutes to obtain a first reaction mixture comprising 1,3 -dinitrobenzene;

[0022] ii. reducing 1,3 -dinitrobenzene by using a reducing agent in a first fluid medium at a temperature in the range of 55 °C to 75 °C at a pressure in the range of500 psi to 800 psi for a time period in the range of 1 hour to 5 hours to obtain a second reaction mixture comprising 1,3 -diaminobenzene; and

[0023] iii. optionally diazotizing 1,3 -diaminobenzene by using a diazotizing agent in a second fluid medium at a temperature in the range of -10 °C to 10 °C to obtain a third reaction mixture; and

[0024] iv. hydrolyzing the second reaction mixture in the presence of an acid catalyst in a third fluid medium under stirring at a temperature in the range of 150 °C to 400 °C for a time period in the range of 3 hours to 7 hours to obtain a product mixture comprising 1,3-dihydroxy benzene;

[0025] or

[0026] hydrolyzing the third reaction mixture at a temperature in the range of 90 °C to 100 °C for a time period in the range of 30 minutes to 180 minutes to obtain a product mixture comprising 1,3-dihydroxy benzene.

[0027] The nitrating agent is selected from the group consisting of a mixture of nitric acid and sulphuric acid.

[0028] The reducing agent is selected from the group consisting of hydrogen in the presence of Raney -Ni, hydrogen in the presence of Fe / HCl, hydrogen in the presence of Sn / HCl, hydrogen in the presence of Zn / HCl, hydrogen in the presence of Ni-TiO2and hydrogen in the presence of Ni-TiO2.

[0029] The first fluid medium is at least one selected from the group consisting of benzene, ethanol, methanol, ethyl acetate and acetonitrile.

[0030] The diazotising agent is selected from the group consisting of a combination of sodium nitrite (NaNO2) and an acid, a combination of potassium nitrite and an acid, a combination of calcium nitrite and an acid; wherein the acid is selected from the group consisting of hydrochloric acid, sulfuric acid and phosphoric acid.

[0031] The second fluid medium is at least one selected from the group consisting of water, methanol, ethanol, and acetonitrile.The third fluid medium is water and the acid catalyst is at least one selected from the group consisting of water, sulphuric acid, hydrochloric acid and nitric acid.

[0032] The molar ratio of benzene to the nitrating agent is in the range of 1: 1 to 1:3.

[0033] The molar ratio of diamino benzene to the diazotising agent is in the range of 1:1 to 1:3.

[0034] The selectivity of 1, 3-dihydroxy benzene is in the range of 70 % to 100 %.

[0035] DETAILED DESCRIPTION

[0036] The present disclosure relates to a process for the preparation of 1,3 -dihydroxy benzene.

[0037] Embodiments, of the present disclosure, will now be described herein. Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.

[0038] The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," “including,” and “having,” are open ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and / or components, but do not forbid the presence or addition of oneor more other features, integers, steps, operations, elements, components, and / or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.

[0039] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed elements.

[0040] The terms first, second, third, etc., should not be construed to limit the scope of the present disclosure as the aforementioned terms may be only used to distinguish one element, component, region, layer or section from another component, region, layer or section. Terms such as first, second, third etc., when used herein do not imply a specific sequence or order unless clearly suggested by the present disclosure.

[0041] The conventional processes for the preparation of 1,3-dihydroxy benzene are associated with drawbacks such as use of toxic and expensive reagents / catalysts which make the process uneconomical. Further, the conventional processes involve tedious workup steps as well as formation of impurities that affect the purity of the final product.

[0042] The present disclosure provides a process for the preparation of 1,3-dihydroxy benzene.

[0043] The process of the present disclosure is simple, environment friendly and economical. The process of the present disclosure provides 1,3 dihydroxy benzene with a comparatively high purity and high yield.

[0044] In an embodiment of the present disclosure, the process for the preparation of 1,3-dihydroxy benzene comprises the following steps:

[0045] i. nitrating benzene by using a nitrating agent at a temperature in the range of 40 °C to 55 °C for a time period in the range of 30 minutesto 120 minutes to obtain a first reaction mixture comprising 1,3- dinitrobenzene;

[0046] ii. reducing 1,3 -dinitrobenzene by using a reducing agent in a first fluid medium at a temperature in the range of 55 °C to 75 °C at a pressure in the range of 500 psi to 800 psi for a time period in the range of 1 hour to 5 hours to obtain a second reaction mixture comprising 1,3- diaminobenzene; and

[0047] iii. optionally diazotizing 1,3-diaminobenzene by using a diazotizing agent in a second fluid medium at a temperature in the range of -10 °C to 10 °C to obtain a third reaction mixture; and iv. hydrolyzing the second reaction mixture in the presence of an acid catalyst in a third fluid medium under stirring at a temperature in the range of 150 °C to 400 °C for a time period in the range of 3 hours to 7 hours to obtain a product mixture comprising 1,3 -dihydroxy benzene;

[0048] or

[0049] hydrolyzing the third reaction mixture at a temperature in the range of 90 °C to 100 °C for a time period in the range of 30 minutes to 180 minutes to obtain a product mixture comprising 1,3-dihydroxy benzene.

[0050] The process is described in detail below:

[0051] In a first step, benzene is nitrated by using a nitrating agent at a temperature in the range of 40 °C to 55 °C for a time period in the range of 30 minutes to 120 minutes to obtain a first reaction mixture comprising 1,3-dinitrobenzene.

[0052] In an embodiment of the present disclosure, the nitrating agent is selected from the group consisting of a mixture of nitric acid and sulphuric acid, mixture of nitric acid and acetic anhydride and a mixture of nitric acid and phosphoric acid. In an exemplary embodiment, the nitrating agent is a mixture of nitric acid and sulphuric acid.In an exemplary embodiment of the present disclosure, the molar ratio of benzene to the nitrating agent is in the range of 1: 1 to 1:3. In an exemplary embodiment of the present disclosure, the molar ratio of benzene to the nitrating agent isl:2.

[0053] In an embodiment of the present disclosure, benzene is nitrated by using a nitrating agent at a temperature in the range of 40 °C to 55 °C. In an exemplary embodiment, benzene is nitrated by using a nitrating agent at a temperature below 55 °C.

[0054] Benzene is added dropwise into the nitrating mixture under continuous stirring to ensure uniform mixing. Throughout the addition, the reaction temperature is maintained below 55° C to prevent over-nitration and unwanted side reactions.

[0055] In an embodiment of the present disclosure, benzene is nitrated by using a nitrating agent for a time period in the range of 30 minutes to 120 minutes. In an exemplary embodiment, benzene is nitrated by using a nitrating agent for 45 minutes.

[0056] In an embodiment of the present disclosure, the first reaction mixture is quenched by using ice to obtain a first reaction mass comprising crystalline precipitate of dinitrobenzene. The first reaction mass is filtered, washed with cold water to remove residual acids and air-dried to obtain crude dinitrobenzene. The crude dinitrobenzene is subsequently purified by vacuum distillation to obtain pure dinitrobenzene.

[0057] In a second step, 1,3-dinitrobenzene is reduced by using a reducing agent in a first fluid medium at a temperature in the range of 55 °C to 75 °C, a pressure in the range of 500 psi to 800 psi for a time period in the range of 1 hour to 5 hours to obtain a second reaction mixture comprising 1,3-diaminobenzene.

[0058] In an embodiment of the present disclosure, the reducing agent is selected from the group consisting of hydrogen in the presence of Raney -Ni, hydrogen in the presence of Fe / HCl, hydrogen in the presence of Sn / HCl, hydrogen in the presence of Zn / HCl, hydrogen in the presence of Ni-TiCb and hydrogen in the presence of Ni-TiC>2. In an exemplary embodiment, the reducing agent is hydrogen in the presenceof Raney-Ni. The Raney nickel catalyst facilitates the selective hydrogenation of both nitro groups, thereby converting 1,3 -dinitrobenzene to 1,3-diaminobenzene.

[0059] In an embodiment of the present disclosure, water is formed as the reduction byproduct.

[0060] In an embodiment of the present disclosure, the first fluid medium is at least one selected from the group consisting of benzene, ethanol, methanol, ethyl acetate and acetonitrile. In an exemplary embodiment, the first fluid medium is a mixture of benzene and ethanol.

[0061] In an embodiment of the present disclosure, 1,3-dinitrobenzene is reduced by using a reducing agent at a temperature in the range of 55 °C to 75 °C. In an exemplary embodiment, 1,3-dinitrobenzene is reduced by using a reducing agent at a temperature of 65 °C.

[0062] In an embodiment of the present disclosure, 1,3-dinitrobenzene is reduced by using a reducing agent at a pressure in the range of 500 psi to 800 psi. In an exemplary embodiment, 1,3-dinitrobenzene is reduced by using a reducing agent at a pressure of 725 psi.

[0063] In an embodiment of the present disclosure, 1,3-dinitrobenzene is reduced by using a reducing agent for a time period in the range of 1 hour to 5 hours. In an exemplary embodiment, 1,3-dinitrobenzene is reduced by using a reducing agent for a time period of 4 hours.

[0064] The second reaction mixture is cooled to a temperature in the range of 25 °C to 35 °C followed by filtration to obtain solids (catalyst) and a filtrate. The filtrate is subjected to removal of solvent under reduced pressure to obtain a crude 1,3-diaminobenzene which was further purified by vacuum distillation to obtain a pure 1,3-diaminobenzene.In a third step, in an embodiment of the present disclosure, 1,3 -diaminobenzene is optionally diazotized by using a diazotizing agent in a second fluid medium at a temperature in the range of -10 °C to 10 °C to obtain a third reaction mixture.

[0065] In an embodiment of the present disclosure, the diazotising agent is selected from the group consisting of a combination of sodium nitrite (NaNO2) and an acid, a combination of potassium nitrite and an acid and a combination of calcium nitrite and an acid; wherein the acid is selected from the group consisting of hydrochloric acid (HCl), sulphuric acid (H2SO4) and phosphoric acid. In an exemplary embodiment, the diazotising agent is a combination of sodium nitrite (NaNO2) and hydrochloric acid (HCl).

[0066] In an embodiment of the present disclosure, the second fluid medium is at least one selected from the group consisting of water, methanol, ethanol, and acetonitrile. In an exemplary embodiment, the second fluid medium is water.

[0067] In an exemplary embodiment, the diazotization is carried out at a temperature of 0 °C.

[0068] The diazotisation of 1,3-diaminobenzene is carried out at a temperature below 5 °C to prevent premature decomposition of the diazonium intermediates and to facilitate the formation of the highly reactive bis-diazonium salt.

[0069] In a fourth step, in an embodiment, the second reaction mixture is hydrolysed at a temperature in the range of 90 °C to 100 °C for a time period in the range of 30 minutes to 180 minutes to obtain a product mixture comprising 1,3-dihydroxy benzene

[0070] In an exemplary embodiment, the hydrolysis is carried out at 95 °C.

[0071] In an exemplary embodiment, the hydrolysis is carried out for 120 minutes.The bis-diazonium salt undergoes controlled hydrolysis and decomposition at the predetermined temperature and time period conditions, thereby releasing nitrogen gas to obtain a product mixture comprising 1,3 -dihydroxybenzene.

[0072] The third reaction mixture is cooled to room temperature and extracted with a solvent to obtain a biphasic mixture comprising an organic phase and an aqueous phase. The solvent is removed from the organic phase to obtain crude 1.3-dihydroxybenzene (resorcinol), which was further purified, by recrystallization to obtain pure 1,3-dihydroxybenzene.

[0073] In an embodiment of the present disclosure, the selectivity of 1, 3 -dihydroxy benzene is in the range of 70 % to 100 %. In an exemplary embodiment, the selectivity of 1, 3-dihydroxy benzene is 80 %.

[0074] In a fourth step, in another embodiment of the present disclosure, the second reaction mixture is hydrolysed in the presence of an acid catalyst in a third fluid medium under stirring at a temperature in the range of 150 °C to 400 °C for a time period in the range of 3 hours to 7 hours to obtain a product mixture comprising 1.3-dihydroxy benzene.

[0075] In an exemplary embodiment, 1,3-diaminobenzene is hydrolysed at a temperature of 240 °C.

[0076] In an exemplary embodiment, 1,3-diaminobenzene is hydrolysed for a time period of 4 hours.

[0077] In another embodiment of the present disclosure, the third fluid medium is water.

[0078] In another embodiment of the present disclosure, the acid catalyst is selected from the group consisting of sulphuric acid, hydrochloric acid and nitric acid. In an exemplary embodiment, the acid catalyst is sulphuric acid.In another embodiment of the present disclosure, the product mixture is cooled to a temperature in the range of 25 °C to 35 °C, and subjected to extraction and recrystallization to obtain pure 1,3 -dihydroxybenzene.

[0079] In another embodiment of the present disclosure, and the selectivity of 1, 3-dihydroxy benzene is in the range of 70 % to 100 %. In an exemplary embodiment, the selectivity of 1, 3 -dihydroxy benzene is 100 %.

[0080] In accordance with an embodiment of the present disclosure, the schematic representation for the preparation of 1,3 -dihydroxy benzene is illustrated as Scheme A below:

[0081] OH

[0082]

[0083] 1,3-Dihydroxy-benzene

[0084] Scheme A

[0085] The present disclosure provides a simple, environment-friendly and economical process for the preparation of 1,3 -dihydroxy benzene and provides a comparatively high yield and high purity of 1,3-dihydroxy benzene.

[0086] The process for the preparation of 1,3-dihydroxy benzene of the present disclosure is a multi-step process starting from benzene. In the first step, benzene undergoes vigorous nitration reaction to predominantly form dinitrobenzene, with reactionparameters optimized to minimize the formation of unwanted regio-isomers. The resulting dinitrobenzene is then efficiently reduced using an appropriate catalytic hydrogenation system to obtain high-purity diaminobenzene. In the subsequent hydrolysis step, two possible routes are employed. In the first route, diaminobenzene undergoes a carefully controlled diazotization reaction, allowing its selective conversion to resorcinol while minimizing side reactions and degradation. The second route proceeds via a hydrolysis reaction of 1,3-diaminobenzene.

[0087] The overall process of the present disclosure employs suitable catalysts, reagents, and purification strategies to achieve high selectivity, enhanced yield, and superior product purity. The process of the present disclosure is robust, reproducible, and readily scalable, making it industrially feasible for the commercial manufacture of 1,3-dihydroxy benzene from benzene, with reduced by-product formation and improved operational efficiency.

[0088] The foregoing description of the embodiments has been provided for purposes of illustration and is not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.

[0089] The present disclosure is further described in light of the following experiments which are set forth for illustration purposes only and not to be construed as limiting the scope of the disclosure. The following experiments are scalable to industrial / commercial process.

[0090] Experimental Details:

[0091] Experiment 1: Process for the preparation of 1,3-dihydroxy benzene in accordance with the present disclosure

[0092] Step 1: Preparation of 1, 3-dinitrobenzene from Benzene:57 mL of concentrated sulphuric acid and 33 mL of concentrated nitric acid were mixed in a 250 mL round-bottom flask and cooled by using an external ice bath to obtain a nitrating mixture. 20 ml of Benzene was added to the nitrating mixture slowly and dropwise, ensuring continuous stirring to maintain uniform mixing. Throughout the addition, the reaction temperature was rigorously controlled and kept below 50 ° C to prevent over-nitration and unwanted side reactions. After complete addition of benzene, the reaction mass was gradually heated to 55 °C and maintained at 55 °C for 40 minutes to 45 minutes to ensure complete conversion to dinitrobenzene to obtain a first reaction mixture.

[0093] The first reaction mixture was then carefully quenched by pouring it over 150 g of crushed ice to obtain a first reaction mass comprising yellow crystalline precipitate of dinitrobenzene. The first reaction mass is filtered, washed with cold water to remove residual acids and air-dried to obtain crude dinitrobenzene. The crude dinitrobenzene is subsequently purified by vacuum distillation to obtain a pure fraction of dinitrobenzene. The pure fraction was collected at the characteristic boiling point of 291 °C. The process yielded 35.8 g of purified dinitrobenzene, corresponding to a yield of 94% to obtain pure 1, 3 dinitrobenzene.

[0094] Step 2: Preparation of 1,3-diaminobenzene from 1,3-dinitrobenzene:

[0095] A mixture of 30 g of the so obtained 1,3-dinitrobenzene and 4 g of wet Raney nickel catalyst was suspended in a solvent blend consisting of 187 mL of benzene and 187 mL of ethanol to obtain a reaction slurry. The reaction slurry' was transferred to a high-pressure hydrogenation reactor, securely sealed, and purged to remove atmospheric oxygen and pressurized by using high-purity hydrogen gas to 725 psi (50 bar) and heated to 65 °C for 4 hours under vigorous stirring to obtain a second reaction mixture comprising 1,3-diaminobenzene.

[0096] Under these conditions, the Raney nickel catalyst effectively facilitated the selective hydrogenation of both nitro groups, converting 1,3-dinitrobenzene to 1,3- diaminobenzene, with water formed as the reduction by-product.The progress of the reaction was monitored by observing hydrogen uptake. Once the pressure consumption was stabilized, indicating completion, the second reaction mixture was cooled to ambient temperature and depressurized in a controlled manner.

[0097] The second reaction mixture was filtered to obtain solids (pyrophoric Raney nickel catalyst) and filtrate. The filtrate was subjected to solvent removal under reduced pressure to obtain a crude 1,3 -diaminobenzene.

[0098] The crude 1,3 -diaminobenzene was further purified by vacuum distillation to obtain pure 1,3-diaminobenzene at its characteristic boiling point of 282 °C. The final isolated yield of 1,3 dinitro benzene was 9.5 g, corresponding to 50% conversion efficiency.

[0099] Table 1 below discloses the various catalysts that have been used in the reduction of 1,3-dinitrobenzene and the selectivity and yield of 1,3-diaminobenzene obtained using these catalysts.

[0100] Sl. No. Catalyst 1,3- 1,3-diaminobenzene Yield diaminobenzene % Selectivity

[0101] 1 Raney Nickel 100% 50%

[0102] 2 Fe / HCl 94% 46%

[0103] 3 Sn / HCl 78% 26%

[0104] 4 Zn / HCl 63% 20%

[0105] 5 Ni-TiO2 55% 18%

[0106] 6 Ni / SiO2 32% 15%

[0107] 7 SnC12 27% < 10%

[0108] 8 Cu-Cr 27% < 10%

[0109] 9 Commercial catalyst 15% < 10%

[0110] 10 Ni Metal powder 11% < 10%

[0111] 11 Tin powder 10% < 10%

[0112]

[0113] From Table 1, it is seen that 1,3 -diaminobenzene is obtained with higher yield as well as higher selectivity by using the catalysts of the present disclosure than the commercial catalysts or catalysts such as Ni powder and tin powder.

[0114] Step 3: Diazotization of 1, 3-diaminobenzene

[0115] 10 g of 1,3 -diaminobenzene was dissolved in 80 mL of water and 20 mL of concentrated hydrochloric acid ensuring complete protonation of the amine groups followed by cooling to 0 °C to obtain a cooled acidic diamine solution. The cooled acidic diamine solution was maintained at a temperature in the range of 0 °C to 5 °C using an ice-salt bath to prevent premature decomposition of the diazonium intermediates.

[0116] A cold aqueous solution of sodium nitrite (13.4 g dissolved in 30 mL of water) was then added slowly, dropwise, over 15 minutes to 30 minutes to the stirred acidic diamine solution, while maintaining the temperature below 5° C to obtain a third reaction mixture comprising bis-diazonium salt.

[0117] Step 4: Embodiment I: Preparation of 1,3-dihydroxybenzene

[0118] After completion of the addition, the third reaction mixture was gradually heated to 90 °C to 100 °C and maintained at a temperature of 95 °C for 2 hours to obtain a product mixture comprising 1,3-dihydroxy benzene. Under these conditions, the diazonium functionalities undergo controlled hydrolysis and decomposition, releasing nitrogen gas and converting the bis-diazonium salts into 1,3- dihydroxybenzene.

[0119] The product mixture was allowed to cool to room temperature and extracted with ethyl acetate to obtain a biphasic mixture comprising an organic (ethyl acetate) phase and an aqueous phase. Ethyl acetate (solvent) was removed from the organic phase under reduced pressure to obtain crude 1,3-dihydroxybenzene (resorcinol), which was further purified, by recrystallization.

[0120] The purified 1,3-dihydroxybenzene was collected at its characteristic boiling point of 282 °C. The isolated yield of 1,3-dihydroxybenzene was 2.6 g, corresponding to,with a measured melting point of 110 °C, consistent with standard literature values for 1,3-dihydroxybenzene. The selectivity of 1,3-dihydroxybenzene obtained is 80 %.

[0121] Embodiment 2: Preparation of 1,3-dihydroxybenzene (hydrolysis of 1,3-diamino benzene) in the presence of an acid catalyst

[0122] 10g of 1, 3 -diaminobenzene obtained in Step 2 was added to 8ml sulfuric acid and 100 ml of water to obtain a mixture. The mixture was enclosed in a pressure-reactor and heated to 240 °C under stirring to undergo exothermic hydrolytic transformation to obtain a product mixture comprising 1,3-dihydroxy benzene. The internal pressure of the vessel increases as the reaction accelerates, providing an indirect indication of conversion progress. Once the pressure reaches a peak and then begins to diminish — signaling the consumption of reactive intermediates and the attenuation of exothermic activity — the reaction is considered to be completed.

[0123] The product mixture was cooled to room temperature, and the internal pressure was released in a controlled manner. The resulting reaction mixture was subjected to standard analytical and purification operations to separate the hydrolysis product from by-products and the reaction medium. The purified product was collected at its characteristic boiling point of 282 °C. The isolated yield of 1,3-dihydroxybenzene was 5.1 g, corresponding to a 50% yield, with a measured melting point of 110 °C, consistent with standard literature values for 1,3-dihydroxybenzene.

[0124] Experiment 2: Preparation of 1,3-dihydroxy benzene by varying the reaction conditions

[0125] Step-ii: Preparation of 1,3-diamino benzene by varying the reaction parameterTable 2: Variation of reaction parameters for the conversion of m-nitro benzene to metaphynelenediamine (1,3-diamino benzene

[0126] liilll ■i

[0127] Vol.

[0128] SI iillli 1- ■ill ■it Aei Illi

[0129] <>• of iiiii Cataly ilii mt III iiiiiiiii m- liilll mII iiii Ill lOiill Results / Se N iiiii w a lOiii st C-ata Illi iiiii p Pressor iWi llii timed leetivity 0. B ter wne noi iyst tBil jll e(pjii)

[0130] n,el

[0131] Ill ■iillll Illi (n» <n,l> IIIII liilll i

[0132] iiiii

[0133] Con Selectivity, Fe 5m 85

[0134] 1 10 150 8 60 70- Nitro - c. 90 3 10

[0135] Filling 1 0 aniline HC1

[0136] 74% Selectivity, 1,2-DNB - Comm

[0137] 38%, p- 13 300- 70

[0138] 2 10 20 - ercial

[0139] - 8 - - 6 80 Nitroanilin catalys 0 350 0

[0140] e-28%, o- t Nitrotolue ne-2.5% 5.2

[0141] Con Selectivity, (co - Fe 17.

[0142] 3 Nitr

[0143] - 20 9.8

[0144] mm c. RT - - - - o. Filling 8g aniline HC1

[0145] ) 14%

[0146] Ni / S No MPDA 4 2.8 - 10 iO

[0147] - 0.29 - - RT - - 5 - 2 formed so37 No MPDA 5 10 - - Raney

[0148] - 1 - - lo 270 3 20

[0149] Nickel 5

[0150] 0 formed Selectivity, MPDA - Zn 0.1%, 6 1.3 20 - - 0.8 - - RT - - 3 - dust DNB 2.9%, impurities Con 1 Selectivity, Fe 1.5

[0151] 7 2 25 - - 8 c. 97 - - to - MPDA - Filling ml

[0152] HC1 2 79% Con 1

[0153] 1 Selectivity, 8 2 25 - Fe

[0154] - 7.2 c. 97 - - F to - MPDA - illing ml

[0155] HC1 2 87% Con 1

[0156] 20 1 Selectivity, 9 20 - Fe 50 0

[0157] - 97 - - - MP 0 Filling c. ml to DA - HC1 2 84%

[0158] 1

[0159] Con Selectivity, to

[0160] c. MPDA - 1 Fe Im 2

[0161] 3 25 - - 7 97 - - - 74 0 Filling HC1 %,

[0162] 1

[0163] Aniline - 16% F Con 1 MPDA 1 40 e 14

[0164] 37 - - Filling 70 c. 99 - - to - Strong 1 0 in ml

[0165]

[0166] HC1 2 TLC Spotteflon (200ml stirrer Aq)

[0167] MPDA

[0168] Strong 10 10 - - Raney 4 - - 52 70 70 4 100

[0169] 0 0 TLC Spot Nickel (150 ml Aq) Selectivity, Con 1 MPDA - 2.5

[0170] 7.7 62 - - Fe 12 97 - - - 86%

[0171] Filling c. ml to, HC1 2 Aniline - 14% MPDA - 100% selectivity, Cone 0.1593, Hg ie 40% Con 1 conversion 40 Fe

[0172] - - 17.

[0173] 35.8 Filling 85 - - 0 c. 97 - 5 to by HC1 2 calculation but couldn't extract precipitate due to black tar formation. Selectivity MPDA - 86.5%, Nitroanilin 70

[0174] 16 - 100 100 Raney 2 - - 65 150 4 700 e - 4.4%,

[0175] Nickel 0

[0176] 1,3-DNB - 7.8%, %yield = 16% MPDA - 100% selectivity, Rota evaporated Con 1 in vacuum 3 25 - - Fe 3 1 97 - - - 1.5g red Filling c. to

[0177] HC1 2 solid obtained with impurities, %yeild = 77% MPDA - For

[0178] 10 0.5%, m- 5 - - 10 Raney 3 mic 20 - - 3 - Nickel 0 Nitroanilin acid

[0179]

[0180] e -2.6%, o-Nitroanilin e -7%, 1,3- DNB 95% Selectivity MPDA - Raney 70 100%, - 187 187 4 - - 65 700 4

[0181] Nickel 0 Yield wt. =

[0182] 9 g, %yeild 400 = 47.3% Selectivity MPDA - 100%, Raney 70

[0183] - 187 187 4 - - 65 700 4 Yield wt. =

[0184] Nickel 0

[0185] 9.72g, %yeild = 400 50% Selectivity MPDA - 100%, Raney 70

[0186] - 187 187 4 - - 65 700 4 Yield wt. =

[0187] Nickel 0

[0188] 9.5g, %yeild =

[0189]

[0190] 390 51.1%From Table 2, it is seen that metaphynelenediamine is obtained with a higher selectivity by using Raney -Ni as a catalyst at relatively lower temperatures i.e. 65 °C and at a pressure of 700 psi. In entries 1 to 13 metaphynelenediamine is obtained with a higher selectivity by using 5 other catalysts such as Fe filing and Ni / SiO₂ and at a lower hydrogenation pressure using Raney-Ni catalyst.

[0191] Table 3: Variation of reaction parameters for the conversion of m-dinitro benzene to 1, 3-dihydroxy benzene by acid hydrolysis

[0192] s. Wt of Vol. Catal Wt. of Acid Vol. of Temp RPM Time Pressure Results / Selectivit N MPD of yst Cataly Nam Acid (°C) (hr) (psi) y 0. A(g) water Used st (g) e (mL)

[0193] (mL)

[0194] cone. Resorcinol 1 5 110 - - H220 225 to

[0195] SO - 4 440

[0196] 245 Selectivity: 100%.

[0197] 4 Yield: 10% cone. Resorcinol 2 5 100 - - 235 to

[0198] H2SO 12 700 4 400 to 420

[0199] 238 Selectivity: 75%, 4. Yield: 10%

[0200] Resorcinol 3 5 150 - - cone. 7 210 715 3 190 Selectivity: 1.4 %,

[0201] HC1 Yield: 2% SO427 cone. Resorcinol 4 5 200 TiO2- 1.5 H2SO 20 230 700 4 400 Selectivity: 72%,

[0202] V2O5 4 Yield: 28%

[0203] cone. Resorcinol 5 8.4 114 - - H2SO 11 230 710 4.5 410 Selectivity: 95%,

[0204] Yield: 35% 4

[0205] cone. Resorcinol 6 5 250 - - H2SO 20 235 700 4 478 Selectivity: 39 %,

[0206] 4 Yield: 11% cone. Resorcinol 7 5 200 - - H2SO 10 235 1111 5 490 Selectivity: 32 %,

[0207] Yield: 11% 4

[0208] cone. Resorcinol 8 5 350 - - H2SO 15 235 1000 3 312 Selectivity: 82%

[0209] 4 Yield: 31% cone. Resorcinol 9 5 180 - - H2SO 15 240 1010 4 520 Selectivity: 72%

[0210] 4 Yield: 25% cone. Resorcinol 10 10 220 - - H2SO 18 240 750 4 470 Selectivity: 75%

[0211] 4 Yield: 50% cone. Resorcinol 11 14 130 - - H2SO 10 250 780 4 527 Selectivity: 50%

[0212] 4 Yield: 8% cone. Resorcinol 12 13.9 135 - - H2SO 10 250 780 4 520 Selectivity: 55%

[0213]

[0214] 4 Yield: 12%cone. Resorcinol 5 200 - - H2SO 5 240 750 4.5 454 Selectivity: 55%

[0215] 4 Yield: 10% cone. Resorcinol 10 220 - - H2SO 18 240 750 4 470 Selectivity: 78%

[0216] 4 Yield: 50% cone. Resorcinol 10 100 - - H2SO 8 240 750 4 470 Selectivity: 82%

[0217] 4 Yield: 50% cone. Resorcinol 10 100 - - H2SO 8 240 750 4 500 Selectivity: 85%

[0218] 4 Yield: 50.7% cone. Resorcinol 10 100 - - H2SO 8 240 750 4 500 Selectivity: 89%

[0219]

[0220] 4 Yield: 51.4%

[0221] From Table 3, it can be seen that best results are obtained by hydrolysis of m-diamino benzene at 240 °C.

[0222] TECHNICAL ADVANCEMENT

[0223] The present disclosure described hereinabove has several technical advantages including, but not limited to, the realization of a process for the preparation of 1,3 -dihydroxy benzene, that:

[0224] • is simple, cost-effective and environment friendly; and

[0225] • provides 1,3-dihydroxy benzene with a comparatively high

[0226] selectivity and high yield.

[0227] 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.

[0228] The foregoing description of the specific embodiments 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 ofdescription and not of limitation. Therefore, while the embodiments herein have 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.

[0229] 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 invention to achieve one or more of the desired objects or results. While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Variations or modifications to the formulation of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention.

[0230] 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.

[0231] The numerical values given for various physical parameters, dimensions, and quantities are only approximate values and it is envisaged that the values higher than the numerical value assigned to the physical parameters, dimensions, and quantities fall within the scope of the invention unless there is a statement in the specification to the contrary.

[0232] While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment 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

CLAIMS:

1. A process for the preparation of 1, 3 -dihydroxy benzene, said process comprising the following steps:i. nitrating benzene by using a nitrating agent at a temperature in the range of 40 °C to 55 °C for a time period in the range of 30 minutes to 120 minutes to obtain a first reaction mixture comprising 1,3-dinitrobenzene;ii. reducing 1,3-dinitrobenzene by using a reducing agent in a first fluid medium at a temperature in the range of 55 °C to 75 °C at a pressure in the range of 500 psi to 800 psi for a time period in the range of 1 hour to 5 hours to obtain a second reaction mixture comprising 1,3-diaminobenzene;iii. optionally diazotizing 1,3-diaminobenzene by using a diazotizing agent in a second fluid medium at a temperature in the range of -10 °C to 10 °C to obtain a third reaction mixture; andiv. hydrolyzing said second reaction mixture in the presence of an acid catalyst in a third fluid medium under stirring at a temperature in the range of 150 °C to 400 °C for a time period in the range of 3 hours to 7 hours to obtain a product mixture comprising 1,3 -dihydroxy benzene;orhydrolyzing said third reaction mixture at a temperature in the range of 90 °C to 100 °C for a time period in the range of 30 minutes to 180 minutes to obtain a product mixture comprising 1,3-dihydroxy benzene.

2. The process as claimed in claim 1, wherein said nitrating agent is selected from the group consisting of a mixture of nitric acid and sulphuric acid.

3. The process as claimed in claim 1, wherein said reducing agent is selected from the group consisting of hydrogen in the presence of Raney-Ni, hydrogen in the presence of Fe / HCl, hydrogen in the presence of Sn / HCl, hydrogen in the presence of Zn / HCl, hydrogen in the presence of Ni-TiO2and hydrogen in the presence of Ni-TiO2.

4. The process as claimed in claim 1, wherein said first fluid medium is at least one selected from the group consisting of benzene, ethanol, methanol, ethyl acetate and acetonitrile.

5. The process as claimed in claim 1, wherein said diazotising agent is selected from the group consisting of a combination of sodium nitrite (NaNO2) and an acid, a combination of potassium nitrite and an acid and a combination of calcium nitrite and an acid; wherein said acid is selected from the group consisting of hydrochloric acid, sulphuric acid and phosphoric acid.

6. The process as claimed in claim 1, wherein said second fluid medium is at least one selected from the group consisting of water, methanol, ethanol, and acetonitrile.

7. The process as claimed in claim 1, wherein said third fluid medium is water and said acid catalyst is selected from the group consisting of hydrochloric acid, sulphuric acid and nitric acid.

8. The process as claimed in claim 1, wherein• a molar ratio of benzene to said nitrating agent is in the range of 1: 1 to 1:3; and • a molar ratio of diaminobenzene to said diazotising agent is in the range of 1: 1 to 1:3.

9. The process as claimed in claim 1, wherein the selectivity of 1,3 -dihydroxy benzene is in the range of 70 % to 100 %.

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