A process for the preparation of 1,2-dihydroxy benzene

Abstract

The present disclosure relates to a process for the preparation of 1,2-dihydroxy benzene. The process of the present disclosure is simple, cost-effective and scalable. The process of the present disclosure provides 1,2-dihydroxy benzene with a comparatively high yield and high selectivity.

Description

[0001] A PROCESS FOR THE PREPARATION OF 1,2-DIHYDROXY BENZENE FIELD

[0002] The present disclosure relates to a process for the preparation of 1,2-dihydroxy benzene.

[0003] DEFINITIONS

[0004] As used in the present disclosure, the following term is generally intended to have the meaning as set forth below, except to the extent that the context in which it is used indicates otherwise.

[0005] Selectivity: Selectivity refers to the preferential formation of one product over the other possible products in a chemical reaction.

[0006] BACKGROUND

[0007] The background information herein below relates to the present disclosure but is not necessarily prior art.

[0008] 1,2-dihydroxy benzene (also known as catechol or pyrocatechol) is a versatile organic compound with a broad industrial significance. It is used as a precursor in the synthesis of agrochemicals, polymers and pharmaceuticals. In addition, it is also used in cosmetics and as a food preservative due to its antioxidant properties. 1,2-dihydroxy benzene has a structure of Formula I:

[0009] OH OH

[0010]

[0011] Formula I

[0012] Conventional processes for the preparation of 1,2-dihydroxy benzene are associated with certain drawbacks, such as the use of toxic and expensive reagents / catalysts, thereby making the process uneconomical and environmentally unsustainable. Further, the conventional processes have low selectivity, leading to low yield of product as well as tedious workup steps resulting in the formation of impurities, thereby affecting the purity of the final product.Therefore, there is felt a need to provide a process for the preparation of 1,2-dihydroxy benzene that mitigates the aforestated drawbacks or at least provides a useful alternative.

[0013] OBJECTS

[0014] Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:

[0015] 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.

[0016] Another object of the present disclosure is to provide a process for the preparation of 1,2-dihydroxy benzene.

[0017] Yet another object of the present disclosure is to provide a process for the preparation of 1,2-dihydroxy benzene with a comparatively high yield and high selectivity.

[0018] Still another object of the present disclosure is to provide a simple and cost-effective process for the preparation of 1,2-dihydroxy benzene.

[0019] Yet another object of the present disclosure is to provide an environment-friendly and commercially scalable process for the preparation of 1,2-dihydroxy benzene.

[0020] 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.

[0021] SUMMARY

[0022] The present disclosure relates to a process for the preparation of 1,2-dihydroxy benzene. The process comprises the following steps:

[0023] a. 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 nitrobenzene;b. reducing nitrobenzene by using a reducing agent in a first fluid medium at a temperature in the range of 55 °C to 75 °C for a time period in the range of 30 minutes to 60 minutes to obtain a second reaction mixture comprising aminobenzene;

[0024] c. diazotizing aminobenzene by using a diazotizing agent in a second fluid medium at a temperature in the range of -10 °C to 10 °C for a time period in the range of 10 minutes to 45 minutes, followed by hydrolysis at a temperature in the range of 40 °C to 50 °C for a time period in the range of 10 minutes to 45 minutes to obtain a third reaction mixture comprising phenol; and

[0025] d. hydroxylating phenol by using a hydroxylating agent in the presence of a catalyst in a third fluid medium at a temperature in the range of -10 °C to 10 °C for a time period in the range of 30 minutes to 180 minutes to obtain a fourth reaction mixture comprising 1,2-dihydroxy benzene.

[0026] In accordance with the present disclosure, the nitrating agent is selected from the group consisting of a mixture of nitric acid and sulphuric acid, a mixture of nitric acid and acetic anhydride and a mixture of nitric acid and phosphoric acid.

[0027] In accordance with the present disclosure, the reducing agent is selected from the group consisting of hydrogen and non-noble metal catalysts; and wherein the non-noble metal catalyst is selected from the group consisting of nickel (Ni), cobalt (Co), iron, tin (stannum), niobium, molybdenum, vanadium, chromium and manganese and a combination thereof.

[0028] In accordance with the present disclosure, the first fluid medium is at least one selected from the group consisting of ethanol and water.

[0029] In accordance with the present disclosure, the diazotizing agent is selected from the group consisting of a combination of sodium nitrite 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, sulphuric acid and phosphoric acid.

[0030] In accordance with the present disclosure, the hydroxylating agent is selected from the group consisting of hydrogen peroxide, peracetic acid and m-chloroperbenzoic acid (mCPBA).

[0031] In accordance with the present disclosure, the catalyst is selected from the group consisting of nano ferric chloride, nickel-doped in activated carbon, nickel-silica, nickel nitrate trihydrate, ferric nitrate, iron-titanium dioxide, ferrous chloride, transition metal catalysts such as copper, iron, titanium, zinc and nickel.In accordance with the present disclosure, the catalyst has a particle size in the range of 20 nm to 150 nm.

[0032] In accordance with the present disclosure, the second fluid medium and the third fluid medium is water.

[0033] In accordance with the present disclosure, a molar ratio of benzene to the nitrating agent is in the range of 1:3 to 1:6.

[0034] In accordance with the present disclosure, a molar ratio of aminobenzene to the diazotizing agent is in the range of 1:1 to 1:3.

[0035] In accordance with the present disclosure, a molar ratio of phenol to the hydroxylating agent is in the range of 1: 10 to 1:20.

[0036] In accordance with the present disclosure, the selectivity of 1, 2-dihydroxy benzene is in the range of 65 % to 90 %.

[0037] DETAILED DESCRIPTION

[0038] The present disclosure relates to a process for the preparation of 1, 2-dihydroxy benzene.

[0039] 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.

[0040] 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 one or more other features, integers, steps, operations, elements, components, and / or groupsthereof. 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.

[0041] 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.

[0042] Conventional processes for the preparation of 1,2-dihydroxy benzene are associated with certain drawbacks, such as the use of toxic and expensive reagents / catalysts, thereby making the process uneconomical and environmentally unsustainable. Further, the conventional processes have low selectivity, leading to low yield of product as well as tedious workup steps resulting in the formation of impurities, thereby affecting the purity of the final product.

[0043] The present disclosure provides a process for the preparation of 1,2-dihydroxybenzene. The process of the present disclosure is simple, environmentally friendly and economical. The process of the present disclosure provides 1,2-dihydroxy benzene with a comparatively high selectivity and high yield.

[0044] The present disclosure relates to a process for the preparation of 1,2-dihydroxybenzene. The process comprises the following steps:

[0045] a. 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 nitrobenzene;

[0046] b. reducing nitrobenzene by using a reducing agent in a first fluid medium at a temperature in the range of 55 °C to 75 °C for a time period in the range of 30 minutes to 60 minutes to obtain a second reaction mixture comprising aminobenzene;

[0047] c. diazotizing aminobenzene by using a diazotizing agent in a second fluid medium at a temperature in the range of -10 °C to 10 °C for a time period in the range of 10 minutes to 45 minutes, followed by hydrolysis at a temperature in the range of 40 °C to 50 °C for a time period in the range of 10 minutes to 45 minutes to obtain a third reaction mixture comprising phenol; andd. hydroxylating phenol by using a hydroxylating agent in the presence of a catalyst in a third fluid medium at a temperature in the range of -10 °C to 10 °C for a time period in the range of 30 minutes to 180 minutes to obtain a fourth reaction mixture comprising 1,2-dihydroxy benzene.

[0048] The process is described in detail below.

[0049] 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 nitrobenzene.

[0050] In accordance with the present disclosure, benzene is nitrated by using a nitrating agent at a temperature of 55 °C for a time period of 45 minutes to obtain a first reaction mixture comprising nitrobenzene.

[0051] In accordance with the present disclosure, the nitrating agent is selected from the group consisting of a mixture of nitric acid and sulphuric acid, a mixture of nitric acid and acetic anhydride and a mixture of nitric acid and phosphoric acid. In an exemplary embodiment, the nitrating agent is the mixture of nitric acid and sulphuric acid in a volume ratio of 1: 1.2.

[0052] In accordance with the present disclosure, a molar ratio of benzene to the nitrating agent is in the range of 1:3 to 1:6. In an exemplary embodiment, the molar ratio of benzene to the nitrating agent is 1:5.06.

[0053] In accordance with the present disclosure, the so-obtained first reaction mixture comprising nitrobenzene, is purified by following sub-steps:

[0054] i. quenching the first reaction mixture in ice to obtain a first biphasic mixture comprising a first organic layer and a first aqueous layer;

[0055] ii. separating the first organic layer, followed by washing and treating with an alkali solution to obtain a crude oily nitrobenzene; and

[0056] iii. distilling the crude oily nitrobenzene to obtain a pure nitrobenzene, with high selectivity.

[0057] In accordance with the present disclosure, the alkali solution is selected from the group consisting of sodium bicarbonate solution, potassium bicarbonate solution, calcium bicarbonate solution, sodium carbonate solution, potassium carbonate solution and calciumcarbonate solution. In an exemplary embodiment, the alkali solution is a sodium bicarbonate solution.

[0058] The crude oily nitrobenzene is distilled to obtain the pure nitrobenzene.

[0059] In a second step, nitrobenzene is reduced by using a reducing agent in a first fluid medium at a temperature in the range of 55 °C to 75 °C for a time period in the range of 30 minutes to 60 minutes to obtain a second reaction mixture comprising aminobenzene.

[0060] In accordance with the present disclosure, nitrobenzene is reduced by using a reducing agent in a first fluid medium at a temperature of 60 °C for a time period of 45 minutes to obtain a second reaction mixture comprising aminobenzene.

[0061] In accordance with the present disclosure, the reducing agent is hydrogen and a non-noble metal catalyst; wherein the non-noble metal catalyst is selected from the group consisting of nickel (Ni), Cobalt (Co), iron, tin (stannum), niobium, molybdenum, vanadium, chromium and manganese and a combination thereof. In an exemplary embodiment, the reducing agent is hydrogen and Raney nickel catalyst.

[0062] In accordance with the present disclosure, the Raney nickel catalyst promotes the efficient reduction of the nitro group, with the uptake of hydrogen.

[0063] In accordance with the present disclosure, the first fluid medium is at least one selected from ethanol and water. In an exemplary embodiment, the first fluid medium is a mixture of ethanol and water in a volume ratio of 1: 1.

[0064] In accordance with the present disclosure, the pressure of hydrogen in the reactor during reduction is maintained in the range of 100 psi to 1000 psi.

[0065] In accordance with the present disclosure, the so-obtained second reaction mixture comprising aminobenzene is purified by following sub-steps:

[0066] a) filtering the second reaction mixture to obtain a filtrate, followed by evaporating the filtrate under reduced pressure to obtain a resultant mixture comprising crudeaminobenzene; and

[0067] b) purifying the resultant mixture by distillation to obtain pure aminobenzene.In a third step, aminobenzene is diazotized by using a diazotizing agent in a second fluid medium at a temperature in the range of -10 °C to 10 °C for a time period in the range of 10 minutes to 45 minutes, followed by hydrolysis at a temperature in the range of 40 °C to 50 °C for a time period in the range of 10 minutes to 45 minutes to obtain a third reaction mixture comprising phenol.

[0068] In accordance with the present disclosure, aminobenzene is diazotized by using a diazotizing agent in a second fluid medium at a temperature in the range of 0 °C to 5 °C for 15 minutes, followed by hydrolysis at a temperature below 50 °C for a time period of 15 minutes to obtain a third reaction mixture comprising phenol.

[0069] In accordance with the present disclosure, the diazotizing agent is selected from the group consisting of a combination of sodium nitrite 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, sulphuric acid and phosphoric acid.

[0070] In an exemplary embodiment, the diazotizing agent is a combination of sodium nitrite and sulfuric acid.

[0071] In accordance with the present disclosure, a molar ratio of amino benzene to the diazotizing agent is in the range of 1:1 to 1:3. In an exemplary embodiment, the molar ratio of amino benzene to the diazotizing agent is 1: 1.08.

[0072] In accordance with the present disclosure, the second fluid medium is water.

[0073] In accordance with the present disclosure, the hydrolysis is carried out by using water.

[0074] In accordance with the present disclosure, the so-obtained third reaction mixture comprising phenol is purified by cooling the third reaction mixture to room temperature, followed by isolating and distillation to obtain pure phenol.

[0075] In a last step, phenol is hydroxylated by using a hydroxylating agent in the presence of a catalyst in a third fluid medium at a temperature in the range of -10 °C to 10 °C for a time period in the range of 30 minutes to 180 minutes to obtain a fourth reaction mixture comprising 1,2-dihydroxy benzene.

[0076] In accordance with the present disclosure, phenol is hydroxylated by using a hydroxylating agent in the presence of a catalyst in a third fluid medium at a temperature of 0 °C to 5 °C fora time period of 60 minutes to obtain a fourth reaction mixture comprising 1,2-dihydroxy benzene.

[0077] In accordance with the present disclosure, the hydroxylating agent is selected from the group consisting of hydrogen peroxide, peracetic acid and m -chloroperbenzoic acid (mCPBA). In an exemplary embodiment, the hydroxylating agent is hydrogen peroxide.

[0078] In accordance with the present disclosure, a molar ratio of phenol to the hydroxylating agent is in the range of 1:10 to 1:20. In an exemplary embodiment, the molar ratio of phenol to hydroxylating agent is 1:15.

[0079] In accordance with the present disclosure, the catalyst is selected from the group consisting of nano ferric chloride, nickel-doped in activated carbon, nickel-silica, nickel nitrate trihydrate, ferric nitrate, iron-titanium dioxide, transition metal catalysts such as copper, iron, titanium, zinc and nickel. In an exemplary embodiment, the catalyst is nano anhydrous ferric chloride.

[0080] In accordance with the present disclosure, the catalyst has a particle size in the range of 20 nm to 150 nm.

[0081] The process for the preparation of nano anhydrous ferric chloride comprises the following steps:

[0082] i. mixing anhydrous ferric chloride and ethanol under stirring at a temperature of 25 °C to 35 °C to obtain a ferric chloride solution;

[0083] ii. adding diethyl ether dropwise to the ferric chloride solution under vigorous stirring and continuing stirring for a time period in the range of 30 minutes to 2 hours obtain a ferric chloride suspension.

[0084] iii. aging the ferric chloride suspension for a time period in the range of 8 hours to 16 hours to obtain a resultant mixture comprising nano anhydrous ferric chloride;

[0085] iv. filtering the resultant mixture to obtain solids and a filtrate;

[0086] v. washing the solids by using ethanol and diethyl ether followed by drying under reduced pressure at a temperature in the range of 35 °C to 40 °C for a time period in the range of 6 hours to 15 hours to obtain nano anhydrous ferric chloride.

[0087] In accordance with the present disclosure, the dropwise addition of diethyl ether under vigorous stirring induces rapid nucleation and the formation of a fine ferric chloride suspension.In accordance with the present disclosure, the washing of solids successively with ethanol and diethyl ether aids in the removal of residual solvents and impurities.

[0088] In accordance with the present disclosure, the low-temperature vacuum drying minimizes the hydrolysis and particle aggregation, yielding moisture-sensitive ferric chloride nanoparticles.

[0089] In accordance with the present disclosure, the particle size of the nano anhydrous ferric chloride is in the range of 20 nm to 80 nm.

[0090] In accordance with the present disclosure, the third fluid medium is water.

[0091] In accordance with the present disclosure, the fourth reaction mixture comprises 1,2-dihydroxy benzene (catechol) and hydroquinone. 1,2-dihydroxy benzene and hydroquinone are separated by vacuum distillation.

[0092] In accordance with the present disclosure, the yield of 1,2-dihydroxybenzene is in the range of 50 % to 70 % and the selectivity is in the range of 65 % to 90 %. In an exemplary embodiment, the yield of 1,2-dihydroxybenzene is 62 % and the selectivity is 86 %. In another exemplary embodiment, the yield of 1,2-dihydroxybenzene is 58 % and the selectivity is 72.5%. In yet another exemplary embodiment, the yield of 1,2-dihydroxybenzene is 50 % and the selectivity is 66 %.

[0093] The present invention provides an improved and efficient process for the preparation of 1,2-dihydroxybenzene starting from benzene. The process comprises the stepwise conversion of benzene to nitrobenzene, followed by its reduction to aminobenzene. The aminobenzene is subsequently transformed through controlled functional modifications to produce phenol, which is then selectively converted to 1,2-dihydroxybenzene.

[0094] In accordance with the present disclosure, a schematic representation for the preparation of 1,2-dihydroxy benzene is illustrated as Scheme A below:

[0095] HNO3, H2SO4

[0096] 1 mole

[0097]

[0098] Scheme AThe process of the present disclosure is simple, environmental friendly and economical. The process of the present disclosure provides 1,2-dihydroxy benzene with a comparatively high selectivity and high yield.

[0099] The process of the present disclosure employs optimized catalysts, tailored reaction conditions, and suitable reagents to achieve high selectivity and improved yields, while ensuring superior purity, enhanced colour quality, and minimal formation of undesired by-products. Further, the process of the present disclosure incorporates effective purification steps to maintain consistent product quality. Therefore, the process of the present disclosure is robust, commercially scalable, and industrially viable for the preparation of 1,2-dihydroxybenzene from benzene.

[0100] 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.

[0101] The present disclosure is further described in light of the following experiments, which are set forth for illustrative purposes only and not to be construed for limiting the scope of the disclosure. The following experiments can be scaled up to industrial / commercial scale, and the results obtained can be extrapolated to an industrial scale.

[0102] EXPERIMENTAL DETAILS:

[0103] Experiment 1: Process for the preparation of 1,2-dihydroxybenzene in accordance with the present disclosure

[0104] Step 1: Preparation of nitrobenzene from benzene

[0105] In a 250 mL round-bottom flask, 25 mL of concentrated sulphuric acid was mixed with 21 mL of concentrated nitric acid to obtain a nitrating agent.

[0106] 17.5 mL of benzene was added slowly in a dropwise manner to the nitrating agent under continuous stirring to obtain a first mixture. During the addition of benzene, the reaction temperature was maintained below 50 °C using external cooling. After the complete addition of benzene, the first mixture was heated to 55 °C for 45 minutes to obtain a first reaction mixture comprising nitrobenzene.After completion of the reaction, the first reaction mixture was quenched in 150 g of crushed ice to obtain a first biphasic mixture comprising a first organic layer and a first aqueous layer. The first organic layer was separated using a separating funnel, followed by washing thoroughly with water to remove residual acids and treated with 50 mL of sodium bicarbonate solution (alkali solution) to neutralize any remaining strong acids to obtain a crude yellow oily nitrobenzene. The so-obtained crude yellow oily nitrobenzene was purified by distillation, and the fraction collected in the boiling range of 206 °C to 211 °C was obtained as pure nitrobenzene.

[0107] The amount of nitrobenzene obtained was 24 g with a yield of 86% yield.

[0108] The optimization of the process for the preparation of nitrobenzene from benzene was carried out by using different amounts of benzene and the nitrating agent.

[0109] Step 2: Preparation of aminobenzene from nitrobenzene

[0110] 10 g of nitrobenzene was reduced by using 2.5 g of wet Raney nickel catalyst (non-noble metal catalyst) in a solvent mixture of 50 mL ethanol and 50 L water (first fluid medium) to obtain a second mixture. The second mixture was charged into a high-pressure reactor, sealed, and purged before pressurized with the hydrogen gas to 145 psi (10 bar), followed by heating to 60 °C for 45 minutes under vigorous stirring to obtain a second reaction mixture comprising aminobenzene.

[0111] Hydrogen uptake was continuously monitored, and the hydrogen consumption indicated the progress of the reaction. The reaction was terminated once the pressure was stabilized, which indicates completion of the reduction process.

[0112] After cessation of hydrogen consumption, the reactor was cooled to ambient temperature, and the system was vented. The second reaction mixture was filtered to remove the catalyst, followed by neutralising the filtrate to obtain a resultant mixture comprising a solid product of aminobenzene. The catalyst was neutralized with sodium meta-bisulfite.

[0113] The so-obtained solid product of aminobenzene was purified by distillation, and the fraction collected at a boiling point of 184 °C was obtained as pure aminobenzene.

[0114] The amount of aminobenzene obtained was 6.2 g with a yield of 82.6 %.

[0115] Step 3: Preparation of phenol from aminobenzeneIn an oven-dried round-bottom flask, 11.8 mL of aminobenzene, 11.8 mL of concentrated sulphuric acid (acid) and 78 mL of water (second fluid medium) were mixed under stirring before being cooled to 0 °C to 5 °C to obtain a third chilled mixture. Separately, 8.6 g of sodium nitrite was dissolved in 39 mL of water to obtain a solution. The solution was then added 5 dropwise to the chilled third mixture, followed by maintaining under cold conditions for 15 minutes to obtain the diazonium intermediate solution. The diazonium intermediate solution was subsequently heated to below 50 °C for 15 minutes to obtain a third reaction mixture comprising phenol.

[0116] 10 After completion of the reaction, the third reaction mixture was cooled to room temperature, followed by isolation and purification of phenol by distillation and collecting the pure fraction at a boiling point of 181 °C.

[0117] The amount of phenol obtained was 8 g with a yield of 67.2 %.

[0118] The optimization of the process for the preparation of phenol from aminobenzene is shown in 15 Table 1:

[0119] S. No. Chemicals Procedure Observation Results required

[0120] 1 Aminobenzene, 7.5 g aniline + 7.5 mL cone. H2SO4+ 2-layer formed on Obtained water, cone. 50 mL water was stirred and cooled to cooling, marron yield= 2.3 g, H2SO4, NaNO20 °C to 5 °C to obtain a third mixture. organic layer and % Yield - 30%

[0121] 5.5 gNaNO2was dissolved in 25 mL of colourless aqueous

[0122] water to obtain a solution. The solution layer

[0123] was added dropwise to the chilled third

[0124] mixture at cold conditions and kept for

[0125] 15 minutes to obtain the diazonium

[0126] intermediate solution. The diazonium

[0127] intermediate solution was heated to

[0128] <50 °C for 15 minutes until N2gas was

[0129] removed to obtain a third reaction

[0130] mixture comprising phenol then cooled

[0131] to room temperature.

[0132]

[0133] Aminobenzene, 7.5 g cone. H2SO4+ 30 mL water was 2-layer formed on Obtained water, cone. stirred and cooled to 0 to 5 °C, and 5 g cooling, marron yield= 0.21 g, H2SO4, NaNO2aniline was slowly added on stirring organic layer and % Yield - and stirred for 1 hour to obtain a third colourless aqueous 2.8% chilled mixture. 2.5 g NaNO2was layer

[0134] dissolved in 7.5 mL water to obtain a

[0135] solution. The solution was then added

[0136] dropwise at cold condition, to the third

[0137] mixture to obtain diazonium

[0138] intermediate solution. 30 mL water was

[0139] added to diazonium intermediate

[0140] solution. The diazonium intermediate

[0141] solution was heated to <50 °C for 15

[0142] minutes until N2gas was removed to

[0143] obtain a third reaction mixture

[0144] comprising phenol, then cooled to

[0145] room temperature.

[0146] Aminobenzene, 5 g of aniline and 50 mL of water were The solution turned Obtained yield water, cone. stirred, and 10 mL of cone. H2SO4was blackish because = 0.5 g, H2SO4, NaNO2added and cooled to 0 °C to 5 °C to the temperature % Yield - 10% obtain a third mixture. 5 g NaNO2was went high

[0147] dissolved in 10 mL water to obtain a

[0148] solution. The solution was added

[0149] dropwise and maintained at 0 °C to 5 °C

[0150] for 15 minutes to obtain diazonium

[0151] intermediate solution. The diazonium

[0152] intermediate solution was heated to 80

[0153] °C to obtain a third reaction mixture

[0154] comprising phenol.

[0155] Aminobenzene, 5 g aniline and 25 mL water were white foam was Organic layer water, cone. stirred and cooled to 0 to 5 °C. 5 mL appearing on the 1 - 0.55g, H2SO4, Urea, cone. H2SO4and 5 mL water were addition of urea, the 11%, Organic NaNO2added while maintaining at 0 °C, to 5 reaction turns layer 2 -

[0156]

[0157] °C to obtain a third mixture.5 g NaNO2blackish after 10 0.25g, 5%, was dissolved in 10 mL water to obtain min, two-layer Organic layer a solution. The solution was added separation, maroon 3 - 0.01g, dropwise to the third mixture and organic layer and 0.2% maintained at 0 °C, to 5 °C for 10 aqueous layer

[0158] minutes and a pinch of urea was added

[0159] and heated to < 50 °C to obtain a third

[0160] reaction mixture comprising phenol.

[0161] Aminobenzene, 1.2 g of aniline was mixed with 1.2 mL white liquid Obtained yield water, cone. of concentrated sulphuric acid and 7.8 obtained on = 0.7 g, H2SO4, NaNO2mL of water to obtain a mixture. The distillation % Yield = mixture was stirred and cooled to a 57.9% temperature range of 0 °C to 5°C to

[0162] obtain a chilled third mixture. Then 0.8

[0163] g of sodium Nitrite, was dissolved in 5

[0164] mL of water to obtain a solution The

[0165] solution was added dropwise into the

[0166] chilled third mixture followed by

[0167] maintaining under cold conditions for

[0168] 15 minutes to obtain diazonium

[0169] intermediate solution. The diazonium

[0170] intermediate solution was heated to a

[0171] temperature of less than 50 °C for 15

[0172] minutes to obtain a third reaction

[0173] mixture comprising phenol. Then the

[0174] third reaction mixture was cooled down

[0175] to room temperature and extracted with

[0176] ethyl acetate.

[0177] Aminobenzene, 11.8 g of Aniline was mixed with 11.8 white liquid Obtained yield water, cone. mL of concentrated sulphuric acid and obtained on = 5.6 g, H2SO4, NaNO278 mL of water under stirring and distillation % Yield = cooled to a temperature range of 0 °C 47% to 5 °C to obtain a chilled third mixture.

[0178]

[0179] Then 8.6 g of Sodium Nitrite was

[0180] dissolved in 39 mL of water to obtain a

[0181] solution. The solution was added

[0182] dropwise to chilled third mixture

[0183] followed by maintaining under cold

[0184] conditions for 15 minutes to obtain

[0185] diazonium intermediate solution. The

[0186] diazonium intermediate solution was

[0187] heated to a temperature of less than

[0188] 50°C for 15 minutes to obtain a third

[0189] reaction mixture comprising phenol.

[0190] Then the third reaction mixture was

[0191] cooled down to room temperature and

[0192] extracted with ethyl acetate.

[0193] Aminobenzene, 11.8 g of aniline was mixed with 11.8 white liquid Obtained yield water, cone. mL of concentrated sulphuric acid and obtained on = 8 g, H2SO4, NaNO278 mL of water under stirring and distillation % Yield = cooled to a temperature range of 0 to 5 67.2% °C to obtain a chilled third mixture.

[0194] Then 8.6 g of Sodium Nitrite was

[0195] dissolved in 39 mL of water to obtain a

[0196] solution The solution was added

[0197] dropwise to chilled third mixture

[0198] followed by maintaining under cold

[0199] conditions for 15 minutes to obtain

[0200] diazonium intermediate solution. The

[0201] diazonium intermediate solution was

[0202] heated to a temperature of less than 50

[0203] °C for 15 minutes to obtain a third

[0204] reaction mixture comprising phenol.

[0205] Then the third reaction mixture was

[0206] cooled down to room temperature and

[0207] extracted with ethyl acetate.

[0208]

[0209] Aminobenzene, 11.8 g of Aniline was mixed with 11.8 white liquid Obtained yield water, cone. mL of concentrated sulphuric acid and obtained on = 8.1 g, % H2SO4, NaNO278 mL of water under stirring and distillation Yield = 68% cooled to a temperature in the range of

[0210] 0 °C to 5 °C to obtain a chilled third

[0211] mixture Then 8.6 g of Sodium Nitrite

[0212] was dissolved in 39 mL of water to

[0213] obtain a solution. The solution was

[0214] added dropwise to the chilled third

[0215] mixture, followed by maintaining

[0216] under cold conditions for 15 minutes to

[0217] obtain diazonium intermediate

[0218] solution. The diazonium intermediate

[0219] solution was heated to a temperature of

[0220] less than 50 °C for 15 minutes to obtain

[0221] a third reaction mixture comprising

[0222] phenol Then the third reaction mixture

[0223] was cooled down to room temperature

[0224] and extracted with ethyl acetate.

[0225]

[0226] From Table 1, it is seen that maintaining a temperature of less than 50 °C is crucial during the hydrolysis step in order to obtain high yield of phenol. Further the addition of bases such as urea leads to lower yield of phenol.

[0227] Step 4: Preparation of 1,2-dihydroxy benzene from phenol

[0228] Process for the preparation of nano anhydrous ferric chloride catalyst in accordance with the present disclosure

[0229] 2.7 g (10 mmol) of anhydrous ferric chloride was dissolved in 100 ml of absolute ethanol under stirring at room temperature (27 °C) to obtain a ferric chloride solution.

[0230] 150 ml of diethyl ether was added dropwise to the ferric chloride solution under vigorous stirring and allowed to stir for another 1 hour obtain a ferric chloride suspension.

[0231] The ferric chloride suspension was aged for 12 hours to obtain a resultant mixture comprising nano anhydrous ferric chloride. The resultant mixture was filtered to obtain solids and a filtrate.The solids were washed successively by using ethanol and diethyl ether followed by drying under reduced pressure at 35 °C for 10 hours to obtain nano anhydrous ferric chloride having a particle size in the range of 20 nm to 80 nm.

[0232] In an oven-dried round-bottom flask, 10 g of phenol was dissolved in 100 mL of distilled water (third fluid medium), followed by the addition of 1 g of nano anhydrous ferric chloride catalyst to obtain a fourth mixture. The fourth mixture was cooled in an ice bath to maintain the temperature strictly within 0 °C to 5 °C, followed by slow and dropwise addition of 50 mL of 30% hydrogen peroxide (hydroxylating agent) and the reaction was allowed to proceed under stirring for 1 hour to obtain a fourth reaction mixture comprising 1,2-dihydroxybenzene and hydroquinone. The progress and composition of the reaction mixture were monitored using Gas Chromatography (GC).

[0233] After the completion of the reaction, the fourth reaction mixture comprising 1,2- dihydroxybenzene and hydroquinone was subsequently separated through vacuum distillation, and the fractions collected at the boiling points of 245 °C and 287 °C were 1,2- dihydroxybenzene and hydroquinone, respectively.

[0234] The amount of 1,2-dihydroxybenzene obtained was 7.2 g with a yield of 62 % and a melting point of 105 °C, and a selectivity of 69 %.

[0235] The amount of hydroquinone obtained was 1.2 g with a yield of 10.2 % and a melting point of 172 °C, and a selectivity of 31%.

[0236] The optimization of the catalyst in the process for the preparation of 1,2-dihydroxy benzene from phenol is shown in Table 2:

[0237] S. No. Catalyst Selectivity Yield

[0238] 1 Nano-Anhydrous FeCl31,2-dihydroxy benzene- 1,2-dihydroxy benzene- 86%, hydroquinone- 14% 62%, hydroquinone- 10.2%, balance unreacted phenol

[0239] 2 Nickel-doped in 1,2-dihydroxy benzene- 1,2-dihydroxy benzene- activated carbon (1:10 75%, hydroquinone- 25% 27%, hydroquinone- 19%, ratio) balance unreacted phenol

[0240]

[0241] 3 Ni-silica (1:10 ratio) 1,2-dihydroxy benzene- 1,2-dihydroxy benzene- 82%, hydroquinone- 18% 20.5%, hydroquinone- 4.5%, balance unreacted phenol

[0242] 4 Nickel nitrate tri hydrate 1,2-dihydroxy benzene- 1, 2-dihydroxy benzene- 72.5%, hydroquinone- 58%, hydroquinone- 22%, 27.5% balance unreacted phenol

[0243] 5 Ferric nitrate 1,2-dihydroxy benzene- 1,2-dihydroxy benzene- 66%, hydroquinone- 44% 50%, hydroquinone- 26%, balance unreacted phenol

[0244]

[0245] From Table 2, it is observed that variations in the type of catalyst significantly influence the product selectivity and yield towards 1,2-dihydroxy benzene and hydroquinone. The selectivity of 1,2-dihydroxybenzene obtained by the process of the present disclosure ranges from 66 % to 86 % while the yield of 1,2-dihydroxybenzene ranges from 50 % to 62%. The highest selectivity and yield of 1,2-dihydroxybenzene is obtained by using nano anhydrous ferric chloride as a catalyst.

[0246] Nickel-supported catalysts i.e. Ni-silica favor 1,2-dihydroxy benzene (catechol) formation but show low yield. In contrast, homogeneous catalysts, especially nano anhydrous FeCl3, nickel nitrate trihydrate and ferric nitrate exhibit higher overall yields with good selectivity.

[0247] Conventionally Fe-based catalysts used in the preparation of 1, 2-dihydroxy benzene provide a yield of 25 % to 30 % and a selectivity of 50:50 between 1,2-dihydroxybenzene and hydroquinone. The nano-form of ferric chloride (FeCl3) used as a catalyst in accordance with the present disclosure provides a significant enhancement in both yield and selectivity compared to conventional Fe-based catalytic systems.

[0248] The process of the present disclosure provides an improved and efficient process for the preparation of 1,2-dihydroxybenzene starting from benzene. The process comprises the stepwise conversion of benzene to nitrobenzene, followed by its reduction to aminobenzene. The aminobenzene is subsequently transformed through controlled functional modifications to produce phenol, which is then selectively converted to 1,2-dihydroxybenzene.TECHNICAL ADVANCEMENTS

[0249] The present disclosure described herein above has several technical advantages, including, but not limited to, the realization of a process for the preparation of 1,2-dihydroxy benzene that:

[0250] • is a simple and cost-effective process;

[0251] • provides 1,2-dihydroxy benzene with a comparatively high yield and high selectivity;

[0252] and

[0253] • is environment-friendly and commercially scalable.

[0254] 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.

[0255] 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 of description 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.

[0256] 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.

[0257] 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.

[0258] 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

CLAIMS:

1. A process for the preparation of 1,2-dihydroxy benzene, said process comprising the following steps:a. 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 nitrobenzene;b. reducing nitrobenzene by using a reducing agent in a first fluid medium at a temperature in the range of 55 °C to 75 °C for a time period in the range of 30 minutes to 60 minutes to obtain a second reaction mixture comprising aminobenzene;c. diazotizing aminobenzene by using a diazotizing agent in a second fluid medium at a temperature in the range of -10 °C to 10 °C for a time period in the range of 10 minutes to 45 minutes followed by hydrolysis at a temperature in the range of 40 °C to 50 °C for a time period in the range of 10 minutes to 45 minutes to obtain a third reaction mixture comprising phenol; and d. hydroxylating phenol by using a hydroxylating agent in the presence of a catalyst in a third fluid medium at a temperature in the range of -10 °C to 10 °C for a time period in the range of 30 minutes to 180 minutes to obtain a fourth reaction mixture comprising 1,2-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, a mixture of nitric acid and acetic anhydride and a mixture of nitric acid and phosphoric acid.

3. The process as claimed in claim 1, wherein said reducing agent is hydrogen and a non-noble metal catalyst; wherein said non-noble metal catalyst is selected from the group consisting of nickel (Ni), Cobalt (Co), iron, tin (stannum), niobium, molybdenum, vanadium, chromium and manganese and a combination thereof.

4. The process as claimed in claim 1, wherein said first fluid medium is at least one selected from ethanol and water.

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

6. The process as claimed in claim 1, wherein said hydroxylating agent is selected from the group consisting of hydrogen peroxide, peracetic acid and m-chloroperbenzoic acid (mCPBA).

7. The process as claimed in claim 1, wherein said catalyst is selected from the group consisting of nano ferric chloride, nickel-doped in activated carbon, nickel-silica, nickel nitrate trihydrate, ferric nitrate, iron-titanium dioxide, ferrous chloride, transition metal catalysts such as copper, iron, titanium, zinc and nickel.

8. The process as claimed in claim 7, wherein said catalyst has a particle size in the range of 20 nm to 150 nm.

9. The process as claimed in claim 1, wherein said second fluid medium and said third fluid medium are water.

10. The process as claimed in claim 1, wherein• a molar ratio of benzene to said nitrating agent is in the range of 1:3 to 1:6; • a molar ratio of amino benzene to said diazotizing agent is in the range of 1:1 to 1:3; and• a molar ratio of phenol to said hydroxylating agent is in the range of 1:10 to 1:20.

11. The process as claimed in claim 1, wherein the selectivity of 1, 2-dihydroxy benzene is in the range of 65 % to 90 %.

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