Method for preparing m-hydroxybenzotrifluoride (MHBTF)

Abstract

The present invention provides a process (100) for the preparation of m-hydroxybenzotrifluoride (MHBTF) in a batch mode, which achieves a high yield of 98 to 99% and a purity of 99.1 to 99.9%. The method (100) may include a first stage of treating and diazotizing (A) 3-aminohydroxytrifluorotoluene with sulfuric acid (H2SO4) to obtain a diazotized sulfate of 3-aminohydroxytrifluorotoluene. Further, the second stage B may include hydrolyzing the diazotized sulfate of 3-aminotrifluorotoluene in the presence of toluene to obtain crude m-hydroxytrifluorotoluene (MHBTF), and further recovering and reusing the acid effluent (sulfuric acid) consumed in the first stage of the process of preparing m-hydroxytrifluorotoluene. Stage B may include separating the crude m-hydroxybenzotrifluoride in the organic layer from the aqueous layer by alkali wash of the organic layer. The third stage C may include distilling the organic layer to obtain pure m-hydroxybenzotrifluoride.

Description

[0001] Cross-references to related applications and priorities

[0002] This application is the national phase of International Application No. PCT / IB2023 / 051348 filed on February 15, 2023, which claims priority to Indian Provisional Patent Application No. 202221028146 filed on May 17, 2022, which is incorporated herein by reference. Technical Field

[0003] The subject matter described herein generally relates to methods for preparing 3-hydroxybenzotrifluoride, also known as meta-hydroxybenzotrifluoride (MHBTF). In particular, the subject matter relates to methods for preparing high purity meta-hydroxybenzotrifluoride (MHBTF) with improved yield.

[0004] background

[0005] 3-Hydroxybenzotrifluoride or m-hydroxybenzotrifluoride (hereinafter also referred to as "3-HBTF" or "MHBTF") is a colorless to pale yellow liquid used as an intermediate in the synthesis of agricultural chemicals such as herbicides.

[0006]

[0007] In the prior art, CN101781174B discloses a method for synthesizing m-hydroxytrifluorotoluene by diazotizing 3-trifluoromethylaniline in the presence of urea, followed by hydrolysis and steam distillation.

[0008] In the prior art, CN106916052A discloses a method for preparing m-trifluoromethylphenol, which comprises reacting aminotrifluorotoluene with sodium nitrite as a diazotizing agent in the presence of 98% sulfuric acid.

[0009] In the prior art, CN111559959A discloses a method for synthesizing p-trifluoromethylphenol, which involves a diazotization reaction between p-trifluoromethylaniline, a strong acidic cation exchange resin and sodium nitrite.

[0010] In the prior art, conventional methods for preparing MHBTF have deficiencies in many aspects, such as lower yield, product loss, reactant loss, high impurity content and effluent recovery.

[0011] Therefore, there has long been a need to develop an economical process for preparing meta-trifluorotoluene products, that is, utilizing different reaction routes with different reaction conditions, minimizing the consumption of reactants, minimizing the loss of reactants, and thus improving the overall purity and yield of meta-trifluorotoluene (MHBTF). In addition, there has long been a need to recover and reuse the spent acids and other solvents used in the MHBTF preparation process mode to achieve environmental and cost benefits.

[0012] Overview

[0013] Before describing the present system and its components, it should be understood that the present disclosure is not limited to the specific system and its arrangement described, as there may be many possible embodiments that are not explicitly shown in the present disclosure. This content is intended to introduce concepts related to the preparation method of meta-hydroxytrifluorotoluene (MHBTF). This summary is not intended to identify essential features of the claimed subject matter, nor is it intended to detect or limit the scope of the claimed subject matter.

[0014] As disclosed herein, the present subject matter provides a method for preparing m-hydroxybenzotrifluoride (MHBTF). The method for preparing m-hydroxybenzotrifluoride (MHBTF) may include various one or more steps.

[0015] In one embodiment, the method may include the step of reacting sulfuric acid (H2SO4) with 3-aminobenzotrifluoride at 30-55°C to obtain a reactant. The method may include the step of diazotizing the reactant in the presence of nitrosyl sulfuric acid (NSA) to obtain the diazotized sulfate of 3-aminobenzotrifluoride. The method may include the step of removing excess nitrogen oxides (NOx) in the mixture by treating the diazotized sulfate of 3-aminobenzotrifluoride with aminosulfonic acid. The method may include the step of hydrolyzing the diazotized sulfate of 3-aminobenzotrifluoride at a temperature of 70-90°C in the presence of toluene to obtain crude meta-hydroxybenzotrifluoride. The method may include the step of separating the crude meta-hydroxybenzotrifluoride in the organic layer from the aqueous layer. The method may include the step of distilling the organic layer to obtain meta-hydroxybenzotrifluoride, wherein a high yield of 98-99% and a high purity of 99.1-99.9% meta-hydroxybenzotrifluoride (MHBTF) are obtained.

[0016] List of abbreviations

[0017] MHBTF-m-Hydroxybenzotrifluoride

[0018] 3-HBTF-3-Hydroxybenzotrifluoride

[0019] 3-ABTF-3-aminobenzotrifluoride

[0020] NSA-Nitrosylsulfuric acid

[0021] NOX-Nitro-o-xylene BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The detailed description is explained with reference to the accompanying drawings. In the drawings, the leftmost digit(s) of a reference number identifies the drawing in which the reference number first appears. The same numerals are used throughout the drawings to refer to similar features and components.

[0024] Figure 1 A method (100) of preparing meta-hydroxytoluenetrifluoromethane (MHBTF) according to embodiments of the present subject matter is described.

[0025] Detailed Description

[0026] Throughout the specification, references to "various embodiments," "some embodiments," "one embodiment," or "an embodiment" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment is included in at least one embodiment. Thus, the appearance of the phrases "in various embodiments," "in some embodiments," "in one embodiment," or "in one implementation" throughout the specification do not necessarily all refer to the same embodiment. Furthermore, in one or more embodiments, the particular features, structures, or characteristics may be combined in any suitable manner.

[0027] The words "comprise", "have", "contain" and "include" and other forms thereof are equivalent and open-ended, i.e., one or more items following any one word does not imply an exhaustive list of such items, nor does it mean that it is limited to the listed one or more items.

[0028] It must also be noted that the singular forms "a," "an," and "the" include plural forms unless the context clearly dictates otherwise. Although any methods similar or equivalent to those described herein can be used in the practice or testing of the disclosed embodiments, exemplary methods are described herein. The disclosed embodiments are merely examples of the disclosure, which can be implemented in various forms.

[0029] Various modifications to the embodiments are obvious to those skilled in the art, and the general principles of the present invention can be applied to other embodiments. However, those skilled in the art can easily recognize that the present disclosure is not intended to be limited to the embodiments shown, but to be given the widest scope consistent with the principles and features described herein. The present invention will be described in detail below with reference to the accompanying drawings.

[0030] In one embodiment of the present invention, meta-hydroxybenzotrifluoride (MHBTF) may also be referred to as 3-hydroxybenzotrifluoride.

[0031] In one embodiment of the present invention, reference Figure 1 , showing a method (100) for preparing m-hydroxybenzotrifluoride (MHBTF) according to an embodiment of the present invention. The method (100) for preparing m-hydroxybenzotrifluoride (MHBTF) includes multiple steps and is further divided into three stages.

[0032] In one embodiment of the invention, method (100) may include a first stage (stage A) of diazotizing 3-aminobenzotrifluoromethane (3-ABTF) to obtain a diazotized sulfate. The method may also include a second stage (stage B), i.e., hydrolyzing the diazotized sulfate of the 3-aminobenzotrifluoromethane obtained in the first stage to obtain meta-hydroxybenzotrifluoromethane (MHBTF). Stage B may also include recovery and recycling of spent acid effluents such as spent sulfuric acid. The method may also include a third stage (stage C) of distilling the organic layer to obtain pure meta-hydroxybenzotrifluoromethane. In one embodiment, the entire process is preferably carried out in batch mode.

[0033] The first stage of the diazotization of 3-aminobenzotrifluoromethane (3-ABTF) - stage (A)

[0034] In one embodiment of the present invention, reference Figure 1 , the method (100) may include a first stage (stage A) of diazotizing 3-aminobenzotrifluoromethane (3-ABTF) to obtain a diazotized sulfate salt. The method (100) may include a step (101) of reacting sulfuric acid (H2SO4) with 3-aminobenzotrifluoromethane at 30-55°C to obtain a reactant. The step of reacting sulfuric acid (H2SO4) with 3-aminobenzotrifluoromethane may further include a sub-step of cooling the reactant to a predetermined temperature range between 0-28°C.

[0035] In addition, the method may include the step of diazotizing the reactants in the presence of nitrosyl sulfuric acid (NSA) (105) to obtain the diazotized sulfate salt of 3-aminotrifluorobenzol. The diazotizing agent may be selected from diazotizing agents, which include but are not limited to nitrosyl sulfuric acid (NSA).

[0036] Stage: Diazotization

[0037]

[0038] In addition, the method (100) may include a step of removing (107) excess nitrogen oxides (NOx) from the reaction mixture by treating the diazotized sulfate salt of 3-aminobenzotrifluoromethane with sulfamic acid. The sulfamic acid treatment is performed to remove excess NOx gas from the diazotized sulfate salt of 3-aminobenzotrifluoromethane, thereby increasing the overall MHBTF reaction yield to greater than 98%. In one embodiment of the present invention, sulfamic acid may be used in a molar ratio of 0.01-0.1 to remove excess NOx and form the diazotized 3-aminobenzotrifluoromethane product obtained in the diazotization stage.

[0039] It has been observed that higher sulfuric acid concentrations increase the stability of the diazo compound but reduce the rate of the hydrolysis reaction, so 40-50% sulfuric acid may be used in the first step of stage (A).

[0040] It is observed that if sodium nitrite is used instead of the nitrosyl sulfuric acid (NSA) as the diazotizing agent, the yield of the diazotized sulfate of 3-aminohydroxybenzotrifluoride is reduced to 72.6%. Therefore, in a preferred embodiment, 30-40% of nitrosyl sulfuric acid (NSA) can be used, more preferably 36-37% of nitrosyl sulfuric acid (NSA) can be used.

[0041] It is observed that in the present invention, the reactants 3-aminotrifluorotoluene (3-ABTF), sulfuric acid (H2SO4) and nitrosylsulfuric acid (NSA) can be incorporated in a molar ratio of 0.5-2: 2-7: 0.5-2, preferably a molar ratio of 1: 4.29: 1.05. Method (100), wherein 1 mole of sulfuric acid is used for the diazonium salt solution, and the additional residual sulfuric acid content in the reaction increases the fluidity of the diazonium salt solution, and the reduction in the molar number of sulfuric acid will cause the slurry to be viscous and non-flowing. The concentration of sulfuric acid not only affects the stability of the diazo product, but may also affect and reduce the rate of the hydrolysis reaction. Therefore, preferably, a sulfuric acid concentration of 40-50% is considered to be the optimal concentration for obtaining a better diazo product yield and a better conversion rate.

[0042] Higher sulfuric acid concentrations can improve and increase the stability of the diazonium species, which ultimately leads to an increased yield of the final MHBTF product. When method (100) is implemented, the bottoms obtained after distillation are minimized due to the increased diazonium mass yield.

[0043] The second stage of hydrolysis of diazotized sulfate of 3-aminobenzotrifluoride to obtain m-hydroxybenzotrifluoride (MHBTF) Phase (B)

[0044] In another embodiment of the present invention, the process (100) may include a second stage (B) of hydrolyzing the diazotized sulfate salt of 3-aminobenzotrifluoride to obtain meta-hydroxybenzotrifluoride (MHBTF). The process (100) may include hydrolyzing (109) the diazotized sulfate salt of 3-aminobenzotrifluoride at a temperature of 70-90° C. in the presence of toluene to obtain crude meta-hydroxybenzotrifluoride.

[0045] Stage: 2 Hydrolysis:

[0046]

[0047] In another embodiment of the present invention, in the step of hydrolyzing (109) the diazotized sulfate salt of 3-aminotrifluorotoluene in the presence of toluene, the predetermined temperature may be maintained between 70-90°C, preferably between 85-90°C.

[0048] In another embodiment of the present invention, the method (100) may include a step of recycling the spent acid effluent, such as spent sulfuric acid after hydrolysis of the diazotized salt. The sulfuric acid consumed in the first stage may be recycled multiple times in the method (100).

[0049] The recovery of the spent acid effluent in the hydrolysis (109) step can reach a waste acid effluent recovery rate of 50-60%, more preferably 53-55%, thereby minimizing the amount of waste liquid discharged.

[0050] The method (100) may further include the step of separating the crude meta-hydroxytrifluorotoluene in the organic layer from the aqueous layer (111). The separation step (111) may also include separating the organic layer from the aqueous layer and alkaline washing the organic layer with ammonia, calcium hydroxide, sodium bicarbonate and sodium hydroxide (NaOH), preferably sodium carbonate (Na2CO3).

[0051] The organic layer is distilled to obtain the third stage of m-hydroxybenzotrifluoride (MHBTF) - stage (C)

[0052] In the next stage (C), the organic layer is distilled (113) to obtain meta-hydroxybenzotrifluoride, wherein meta-hydroxybenzotrifluoride (MHBTF) is obtained with a high yield of between 98-99% and a high purity of between 99.1-99.9%.

[0053] In another embodiment of the present invention, the distillation step (113) is preferably a fractional distillation.

[0054] In one embodiment of the present invention, the purity of meta-hydroxybenzotrifluoride (MHBTF) obtained by the method (100) may be between 99% and 99.9%.

[0055] In one embodiment of the present invention, the yield of m-hydroxybenzotrifluoride (MHBTF) obtained by the method (100) may be between 98% and 99%.

[0056] According to a preferred embodiment of the present disclosure, m-hydroxybenzotrifluoride (MHBTF) is prepared by a batch process. In one embodiment of the present disclosure, the batch process may include diazotizing 3-aminobenzotrifluoride (3-ABTF) to obtain a diazotized sulfate. In addition, 3-aminobenzotrifluoride is reacted with sulfuric acid at 30-55° C. to obtain a reactant, which is cooled at 25-28° C. The addition amount of sulfuric acid is 40-50%. In addition, 36.5% of nitrosylsulfuric acid (NSA) of a diazotizing agent can be added to the reaction to form a diazonium salt of 3-aminobenzotrifluoride. The diazonium salt of 3-aminobenzotrifluoride can be further treated with aminosulfonic acid in a molar ratio between 0.01-0.1 to remove unwanted nitrogen oxides (NOx) gas from diazotized 3-aminobenzotrifluoride.

[0057] The disclosed process steps can increase the overall yield of the final product. 3-aminobenzotrifluoromethane, sulfuric acid and nitrosylsulfuric acid (NSA) are combined in a molar ratio of 0.5-2:2-7:0.5-2.

[0058] The method further follows the step of hydrolyzing the diazotized sulfate salt of 3-aminobenzotrifluoride in the presence of toluene at 70-90°C to obtain crude meta-hydroxybenzotrifluoride (MHBTF). The method may further include the step of recovering 53-55% of the acidic spent sulfuric acid from the reactants after the hydrolysis step. The recovery of spent sulfuric acid is adjusted so that the yield increase is not affected. Spent acid concentrations exceeding the specified range may cause diazotization problems and may decompose and form unwanted HF.

[0059] Then, the organic layer was alkaline washed with sodium carbonate (Na2CO3) to separate the crude meta-hydroxybenzotrifluoride from the aqueous layer into the organic layer. The organic layer was then fractionated to obtain pure meta-hydroxybenzotrifluoride (MHBTF).

[0060] In one embodiment, a pure meta-hydroxybenzotrifluoride (MHBTF) is disclosed, which has the appearance of a transparent colorless to light yellow liquid, wherein the purity of the meta-hydroxybenzotrifluoride (MHBTF) product obtained by the method (100) is 99.1-99.9%, and wherein the MHBTF may contain no more than 0.2% of 3-aminobenzotrifluoride, and the moisture content is no more than 0.2%.

[0061] The following experiments further illustrate the present invention. Unless expressly stated otherwise, all parts and percentages are by weight. Example

[0062] Example 1: Using NaNO 2 Preparation of MHBTF (batch mode)

[0063] 10.65 mol of 50-55% sulfuric acid and 2.48 mol of 3-aminoBTF were added to a reactor at 30-40°C to obtain a reactant. The reactant was cooled to 25-30°C. Then, 2.61 mol of 40% sodium nitrite was added to the solution for diazotization. The diazotization reactant was kept for 1 hour. In another reactor, 3.17 parts / volume of toluene was added. Toluene was further heated to 80-85°C. A diazo substance was added at the same temperature for hydrolysis. After the diazo substance was added to the second reactor, the reaction was kept for 1 hour, and then the reactant was cooled for stratification and post-treatment. The organic layer was separated from the aqueous layer and neutralized. The neutralized organic layer was treated for toluene recovery and distillation of the product. The yield was 72-73% and the purity was 99.5-99.7%.

[0064] Example 2: Method for preparing m-hydroxytrifluorotoluene using nitrosylsulfuric acid (NSA) as a diazotizing agent - batch model

[0065] 10.65 kmol of 60-65% sulfuric acid was placed in a reactor. 2.48 kmol of 3-amino BTF was added at 30-40°C to obtain a reaction mixture. The reaction mixture was then cooled to 25-30°C. Then, 2.61 kmol of 35%-37% nitrosyl sulfuric acid was added to the reaction mixture as a diazotizing agent. The diazotization reaction lasted for 1 hour to obtain diazotized amino BTF. 20% aminosulfonic acid was added to the reactant containing diazotized amino BTF to deactivate excess nitrosyl sulfuric acid and remove NOx from the reaction mixture. In another reactor, 3.17 parts by volume of toluene was added and heated to 80-85°C. Then, the diazotized amino BTF material was added to the reactor and hydrolyzed at the same temperature. After the addition of the diazotized amino-BTF, the reactant was kept for 1 hour and further cooled for stratification and post-processing. The neutralized organic layer was processed to recover toluene and distillation products. The yield is 82-87% and the purity is 99.6-99.8%.

[0066] Example 3: Preparation of m-hydroxytrifluorotoluene using nitrosylsulfuric acid (NSA) as a diazotizing agent in batch mode method

[0067] 10.65 kmol of 15-20% sulfuric acid was added to the reactor. Then, 2.48 kmol of 3-aminoBTF was added at a temperature of 30-40°C to obtain a reaction mixture. The reaction mixture was then cooled to 25-30°C. Next, 2.61 kmol of 35%-37% nitrosyl sulfuric acid was added to the reaction mixture as a diazotizing agent. The reaction mixture was kept for 1 hour for diazotization to obtain diazotized aminoBTF. Then, 20% aminosulfonic acid was added to the reactants containing diazotized aminoBTF to deactivate excess nitrosyl sulfuric acid and remove excess NOx in the reaction mixture. In another reactor, 3.17 parts by volume of toluene was added and heated to 80-85°C. Then, the diazotized aminoBTF material was added to the reactor and hydrolyzed at the same temperature. After the addition of the diazotized aminoBTF, the reactants were kept for 1 hour for further cooling for stratification and post-processing. The neutralized organic layer was processed to recover toluene and distillation products. The yield is 75-80% and the purity is 99.5-99.7%.

[0068] Example 4: Preparation of m-Hydroxytrifluorotoluene using Nitrosylsulfuric acid as a Diazotizing Agent (NSA) - Batch model

[0069] 10.65 kmol of 50-55% sulfuric acid is added to the reactor. 2.48 kmol of 3-amino BTF is added at a temperature of 30-40°C to obtain a reaction mixture. The reaction mixture is then cooled to 25-30°C. 2.61 kmol and 35%-37% nitrosyl sulfuric acid are added to the reaction mixture as a diazotizing agent. The diazotization reaction is continued for 1 hour to obtain diazotized amino BTF. Then, 20% of aminosulfonic acid is added to the reactants containing diazotized amino BTF to deactivate excess nitrosyl sulfuric acid and remove NOx from the reaction mixture. 3.17 parts by volume of toluene are added to another reactor and heated to 80-85°C. Then, the diazotized amino BTF material is added to the reactor and hydrolyzed at the same temperature. After the addition of the diazotized amino BTF, the reactants are kept for 1 hour and further cooled for stratification and post-processing. The neutralized organic layer is processed to recover toluene and distillation products. The yield is 80-85% and the purity is 99.7-99.95%.

[0070] Example 5: Preparation of m-Hydroxytrifluorotoluene using Nitrosylsulfuric acid as a diazotizing agent (NSA) - Batch model

[0071] 10.65 kmol of 40-50% sulfuric acid is added to the reactor. Then, 2.48 kmol (16.17%) 3-amino BTF is added at 30-40°C to obtain a reaction mixture. The reaction mixture is then cooled to 25-30°C. Then, 2.61 kmol of 35%-37% nitrosyl sulfuric acid is added to the reaction mixture as a diazotizing agent, and the reaction mixture is kept for 1 hour. Then, 20% sulfamic acid is added to the reaction mixture to deactivate excess nitrosyl sulfuric acid and other NOx components. 80% of the sulfamic acid solution is composed of water. In another reactor, about 3.17 parts by volume of toluene is added and heated to 80-85°C. At the same temperature, the diazotized material is added to the reactor for hydrolysis. The reaction is kept for 1 hour, and further cooled for stratification and post-processing. The neutralized organic layer is treated to recover toluene and distilled product. The yield is 98-99% and the purity is 99.95%.

[0072] Example 6: Recovery and Reuse of Sulfuric Acid from MHBTF Production Process

[0073] Referring to the aforementioned Examples 2-5, after the hydrolysis step, 50-60% of the spent acid effluent is recovered, the spent acid effluent having a strength of 50-55%, more preferably 53-55% reusable sulfuric acid, thereby achieving minimum liquid discharge of the effluent. The recycled effluent from the main process (100) can then be reused for the preparation of MHBTF, as shown in the following Examples 7A-7C.

[0074] Example 7A: Method for preparing MHBTF using sulfuric acid recovered from Examples 2-5

[0075] 10.65 kmol of spent sulfuric acid diluted to 40-50% (from the first cycle of spent sulfuric acid in Example 6) was placed in a reactor. Then, at a temperature of 30-40°C, 2.48 kmol of 3-aminoBTF was added to the reactor to obtain a reactant. The reactant was then cooled to 25-30°C. Then, 2.61 kmol of 35%-37% nitrosyl sulfuric acid was added to the reaction mixture as a diazotizing agent, and the reaction was maintained for 1 hour. Then, 20% aminosulfonic acid was added to the reaction mixture to deactivate excess nitrosyl sulfuric acid, wherein the remaining 80% sulfuric acid solution was water. In another reactor, about 3.17 parts by volume of toluene was added and heated to 80-85°C. Then, the diazonium of aminoBTF was added to the reactor containing heated toluene and hydrolyzed at the same temperature. After the diazonium substance of aminoBTF was added to the reaction mixture, the reaction was maintained for 1 hour, the substance was cooled, and stratification and post-treatment were performed. The neutralized organic layer was treated to recover toluene and distillation products. The yield is 98-99% and the purity is 99.6-99.9%.

[0076] Example 7B:Process for preparing MHBTF using recycled sulfuric acid from Examples 2-5

[0077] 10.65 kmol of spent sulfuric acid diluted to 40-50% (secondary circulation of spent sulfuric acid from Example 6) was placed in a reactor. Then, 2.48 kmol of 3-aminoBTF was further added to the reactor at a temperature of 30-40°C to obtain a reaction mixture. The reaction mixture was cooled to 25-30°C and 2.61 kmol of 35%-37% nitrosylsulfuric acid was added to the reaction mixture as a diazotizing agent. The reaction mixture was kept for 1 hour to obtain diazotized 3-aminoBTF. Then, 20% aminosulfonic acid was added to inactivate excess nitrosylsulfuric acid and NOx. In another reactor, 3.17 parts by volume of toluene was added and heated to 80-85°C, and then the diazotized 3-aminoBTF substance was hydrolyzed at the same temperature. After the addition of the diazotized 3-aminoBTF, it was kept for 1 hour and cooled for stratification and post-treatment. The organic layer was neutralized and sent for recovery of toluene and product distillation. The yield was 98-99% and the purity was 99.6-99.9%.

[0078] Example 7C: Method for recovering sulfuric acid during the MHBTF preparation process of Examples 2-5

[0079] 10.65 kmol of spent sulfuric acid (the third cycle of spent sulfuric acid from Example 6) diluted to 40-50% was placed in a reactor. At a temperature of 30-40°C, 2.48 kmol of 3-aminoBTF was further added to the reactor to obtain a reaction mixture. The reaction mixture was then cooled to 25-30°C, and 2.61 kmol of 35%-37% nitrosyl sulfuric acid was added to the reaction mixture as a diazotizing agent. The reaction mixture was kept for 1 hour to obtain diazotized 3-aminoBTF. Then, 20% aminosulfonic acid was added to inactivate excess nitrosyl sulfuric acid and NOx. In another reactor, 3.17 parts by volume of toluene was added and heated to 80-85°C. The diazotized 3-aminoBTF substance was then hydrolyzed at the same temperature. After adding the diazotized 3-amino-BTF, it was kept for 1 hour and cooled for stratification and post-treatment. The organic layer was neutralized and sent to recover toluene and product distillation. The yield was 98-99% and the purity was 99.6-99.9%.

[0080] According to the embodiments of the present disclosure, the method (100) for preparing m-hydroxytrifluorotoluene (MHBTF) has the following advantages, including but not limited to:

[0081] The final yield of m-hydroxybenzotrifluoride (MHBTF) was increased to 99%.

[0082] Improve the purity of m-hydroxybenzotrifluoride (MHBTF) to 99.9%.

[0083] Reduce the loss of reactants such as sulfuric acid (H2SO4) by recycling.

[0084] Remove excess NOx gas from the reaction mixture, thereby increasing the yield of MHBTF.

[0085] Increasing sulfuric acid concentration results in an increase in diazonium compounds, an increase in product concentration, and a decrease in the bottom residue after distillation.

[0086] The embodiments, examples and alternatives of the preceding paragraphs or the description and drawings, including any of its various aspects or respective individual features, may be adopted independently or in any combination. Features described in conjunction with one embodiment are applicable to all embodiments, unless these features are incompatible.

Claims

1. A method (100) for preparing m-hydroxybenzotrifluoride (MHBTF), the method comprising: Reacting sulfuric acid (H2SO4) with 3-aminotrifluorotoluene at 30-55°C (101) to obtain a reactant; diazotizing (105) the reactant in the presence of nitrosyl sulfuric acid (NSA) to obtain the diazotized sulfate salt of 3-aminotrifluorotoluene; removing (107) excess nitrogen oxides (NOx) from the mixture by treating the diazotized sulfate salt of 3-aminotrifluorotoluene with aminosulfonic acid; hydrolyzing the diazotized sulfate salt of 3-aminobenzotrifluoride (109) in the presence of toluene at a temperature of 70-90° C. to obtain crude m-hydroxybenzotrifluoride; The crude m-hydroxytrifluorotoluene in the organic layer is separated from the aqueous layer (111); and The organic layer is distilled (113) to obtain meta-hydroxybenzotrifluoride, wherein meta-hydroxybenzotrifluoride (MHBTF) has a high yield between 98-99% and a high purity between 99.1-99.99%.

2. The method according to claim 1, wherein the step of reacting (101) sulfuric acid (H2SO4) with 3-aminotrifluorotoluene comprises a sub-step of cooling the reactants to 25-28°C before diazotization.

3. The method according to claim 2, wherein in the step (101) of reacting sulfuric acid, 40-50% sulfuric acid is added.

4. The method according to claim 1, wherein in the diazotization step (103), 30-40% nitrosyl sulfuric acid (NSA) is added.

5. The process of claim 1, wherein in the step (107) of hydrolysis there is a sub-step wherein a spent acid effluent is recovered from the reactants.

6. The process of claim 6, wherein 53-55% of the sulfuric acid is recycled from the reactants as a spent acid effluent.

7. The method according to claim 1, wherein the step of stratification (111) includes a sub-step of washing the organic layer with at least one base selected from the group consisting of sodium carbonate (Na2CO3), ammonia, calcium hydroxide, sodium bicarbonate and sodium hydroxide (NaOH).

8. The process according to claim 1, wherein aminosulfonic acid is used in a molar ratio of 0.01-0.1 to remove excess NOx and form the diazotized 3-aminotrifluorotoluene product obtained in the diazotization stage.

9. The method according to claim 1, wherein the molar ratio of 3-aminobenzotrifluoromethane, sulfuric acid and nitrosylsulfuric acid (NSA) is 0.5-2:2-7:0.5-2.

10. The method according to claim 1, wherein the distillation (113) of the organic layer is performed by fractional distillation.

11. A pure meta-hydroxybenzotrifluoride (MHBTF) obtained by the method (100) according to claim 1, comprising: The appearance of MHBTF is a colorless to light yellow liquid; The purity of the meta-hydroxybenzotrifluoride (MHBTF) is 99.1-99.9%. 3-aminobenzotrifluoride not more than 0.2%, and The moisture content does not exceed 0.2%.

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