Method for synthesizing o-cresol and / or p-cresol by adopting micro-channel reactor

Abstract

The invention relates to the field of cresol synthesis, in particular to a method for synthesizing o-cresol and / or p-cresol by adopting a micro-channel reactor. The method comprises the steps that catalytic liquid, methylbenzene and an H2O2 aqueous solution are introduced into a microchannel reactor to be subjected to a contact reaction, reaction effluent is obtained, o-cresol and / or p-cresol are / is separated from the reaction effluent, and the catalytic liquid comprises a catalyst and a solvent. The method provided by the invention has the advantages of high selectivity and total yield of o-cresol and p-cresol, safety, environmental protection and simple process.

Description

Technical Field

[0001] The invention relates to the field of cresol synthesis, and in particular to a method for synthesizing o-cresol and / or p-cresol by using a microchannel reactor. Background Art

[0002] o-Cresol is used in the production of pesticides (such as dimethyltetrachloride), antioxidants, plasticizers, preservatives, and polymerization inhibitors, as well as in the pharmaceutical and dye industries. It is also used in the production of o-cresol-formaldehyde epoxy resin. Due to the development of electronic information technology and intelligent technology, domestic demand for o-cresol-formaldehyde epoxy resin has grown rapidly, driving a rapid increase in demand for o-cresol. However, domestic production cannot meet demand, and part of the demand depends on imports.

[0003] p-Cresol can be used to produce chemical intermediates, antioxidants, and preservatives, and is widely used in the pesticide, pharmaceutical, fragrance, and dye industries.

[0004] Currently, the main methods for preparing cresol include sulfonation alkali fusion, chlorination hydrolysis, cumene oxidation, phenol alkylation, diazotization hydrolysis, and direct oxidation. Among them, the sulfonation alkali fusion method has high energy consumption, requires large amounts of strong acid, and is environmentally unfriendly. Chlorination hydrolysis, cumene oxidation, phenol alkylation, diazotization hydrolysis, and direct oxidation methods produce numerous byproducts, have poor selectivity for the target product, and exhibit low yields. Furthermore, the chlorination hydrolysis and cumene oxidation methods suffer from long process routes. The diazotization hydrolysis and direct oxidation methods also require large amounts of strong acid and are environmentally unfriendly. Summary of the Invention

[0005] The present invention aims to overcome the problems of prior art, such as low selectivity and total yield of o-cresol and p-cresol, high usage of strong acid, and complex processes, by providing a method for synthesizing o-cresol and / or p-cresol using a microchannel reactor. The method provided by the present invention has the advantages of high selectivity and total yield of o-cresol and p-cresol, safety, environmental friendliness, and a simple process.

[0006] Below the method for the synthetic o-cresol and / or p-cresol of employing micro passage reactor provided by the invention is described in detail.Should be appreciated that description herein is only used for illustration and explanation of the present invention, is not intended to limit the present invention.The endpoints of the scope disclosed in this article and any value are not limited to this accurate scope or value, and these scopes or values ​​should be interpreted as comprising the value approaching these scopes or value.For numerical range, between the endpoint value of each scope, between the endpoint value of each scope and the independent point value, and between the independent point value, can be combined with each other and obtain one or more new numerical ranges, and these numerical ranges should be considered as specifically disclosed in this article.

[0007] The present invention provides a method for synthesizing o-cresol and / or p-cresol using a microchannel reactor. The method comprises: introducing a catalyst solution, toluene, and an aqueous H2O2 solution into the microchannel reactor for contact reaction to obtain a reaction effluent; and separating o-cresol and / or p-cresol from the reaction effluent. The catalyst solution comprises a catalyst and a solvent. The method has the aforementioned characteristics, high selectivity and total yield of o-cresol and p-cresol, good safety, environmental friendliness, and a simple process.

[0008] In the present invention, the concentration of the H2O2 aqueous solution can be selected in a wide range, which is exemplified below but does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the concentration of the H2O2 aqueous solution is 3-50wt%, preferably 20-50wt%.

[0009] In the present invention, the feed rate of the microchannel reactor can be selected in a wide range, which is exemplified below, but does not limit the scope of the present invention.

[0010] According to a preferred embodiment of the present invention, the mass ratio of catalyst to toluene, measured by the amount passed into the microchannel reactor per unit time, is 1-10:100, for example, 2:100, 4:100, 6:100, 8:100, preferably 5-10:100.

[0011] According to a preferred embodiment of the present invention, the molar ratio of the solvent to H2O2, measured by the amount introduced into the microchannel reactor per unit time, is 1-10:1, for example, 2:1, 4:1, 6:1, 8:1, preferably 6-10:1.

[0012] According to a preferred embodiment of the present invention, the molar ratio of toluene to H2O2, measured by the amount introduced into the microchannel reactor per unit time, is 1-6:1, for example, 2:1, 3:1, 4:1, 5:1, preferably 3-6:1.

[0013] The feed rate of the microchannel reactor having the above characteristics has the advantages of higher raw material conversion rate, higher selectivity of o-cresol and p-cresol and higher total yield.

[0014] In the present invention, the type of solvent is not particularly limited, and any suitable type can be selected as long as the purpose of the present invention can be achieved. According to a preferred embodiment of the present invention, the solvent is a C1-C6 alcohol and / or a C3-C6 ketone.

[0015] In the present invention, the type of the C1-C6 alcohol is not particularly limited, and any suitable type can be selected as long as the purpose of the present invention can be achieved. According to a preferred embodiment of the present invention, the C1-C6 alcohol is methanol.

[0016] In the present invention, the type of the C3-C6 ketone is not particularly limited, and any suitable type can be selected as long as the purpose of the present invention can be achieved. According to a preferred embodiment of the present invention, the C3-C6 ketone is acetone.

[0017] In the present invention, the type of catalyst is not particularly limited, and any suitable type can be selected as long as the purpose of the present invention can be achieved. According to a preferred embodiment of the present invention, the catalyst is a molecular sieve catalyst, preferably a modified or unmodified tin-titanium-silicon molecular sieve catalyst, more preferably a modified tin-titanium-silicon molecular sieve catalyst.

[0018] In the present invention, the external specific surface area of ​​the molecular sieve catalyst can be selected in a wide range, which is exemplified below, but does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the external specific surface area of ​​the molecular sieve catalyst is 100-300m 2 / g, preferably 200-300m 2 / g.

[0019] In the present invention, the total pore volume of the molecular sieve catalyst can be selected in a wide range, which is exemplified below, but does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the total pore volume of the molecular sieve catalyst is 0.25-0.5 cm 3 / g, preferably 0.37-0.47cm 3 / g.

[0020] According to a preferred embodiment of the present invention, the process parameters of the microchannel reactor meet the following requirements: the value of V×M1 / M2 is 4.5-7.5, wherein V is the total pore volume of the molecular sieve catalyst (cm 3 / g); M1 is the mass of toluene passed into the microchannel reactor per unit time (g); M2 is the mass of catalyst passed into the microchannel reactor per unit time (g).

[0021] The catalyst having the above characteristics has high catalytic efficiency and good catalytic selectivity.

[0022] In the present invention, the element content in the modified or unmodified tin-titanium-silicon molecular sieve catalyst can be selected in a wide range, which is exemplified below but does not limit the scope of the present invention.

[0023] According to a preferred embodiment of the present invention, in the tin-titanium-silicon molecular sieve catalyst, the molar ratio of titanium to silicon is 0.005-0.03:1, for example, it can be 0.01:1, 0.015:1, 0.02:1, or 0.025:1.

[0024] According to a preferred embodiment of the present invention, in the tin-titanium-silicon molecular sieve catalyst, the molar ratio of tin to silicon is 0.005-0.02:1, for example, it can be 0.008:1, 0.011:1, 0.014:1, or 0.017:1.

[0025] The tin-titanium-silicon molecular sieve catalyst having the above-mentioned characteristics has higher catalytic efficiency and better catalytic selectivity.

[0026] In the present invention, the modified tin-titanium-silicon molecular sieve catalyst can achieve the purpose of the present invention as long as it meets the above requirements. There are no special requirements for its preparation method. The following exemplary description does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the preparation method of the modified tin-titanium-silicon molecular sieve catalyst includes: mixing and contacting the tin-titanium-silicon molecular sieve with an organic solution of an organosiloxane, and then drying to obtain the modified tin-titanium-silicon molecular sieve catalyst.

[0027] In the present invention, in the preparation method of the modified tin-titanium-silicon molecular sieve catalyst, the type of the organosiloxane is not particularly limited, and any suitable type can be selected as long as the purpose of the present invention can be achieved. According to a preferred embodiment of the present invention, the organosiloxane is R n -Si-(O-R') 4-n A compound of the structure, wherein R and R' are each independently a C1-C3 alkyl group, preferably a methyl or ethyl group; n is 0, 1, 2 or 3, preferably 3; preferably, the organosiloxane is selected from one or more of methoxytrimethylsilane, ethoxytriethylsilane, ethoxytrimethylsilane, and methoxytriethylsilane.

[0028] In the preparation method of the modified tin-titanium-silicon molecular sieve catalyst of the present invention, the element content of the tin-titanium-silicon molecular sieve can be selected in a wide range, which is exemplified below but does not limit the scope of the present invention.

[0029] According to a preferred embodiment of the present invention, the molar ratio of titanium to silicon in the tin-titanium-silicon molecular sieve used as the raw material is 0.01-0.035:1, for example, 0.014:1, 0.018:1, 0.022:1, 0.026:1, or 0.03:1.

[0030] According to a preferred embodiment of the present invention, the molar ratio of tin to silicon in the tin-titanium-silicon molecular sieve used as the raw material is 0.01-0.024:1, for example, 0.013:1, 0.016:1, 0.019:1, or 0.022:1.

[0031] In the present invention, in the preparation method of the modified tin-titanium-silicon molecular sieve catalyst, the type of the organic solvent is not particularly limited. As long as the purpose of the present invention can be achieved, any suitable type can be selected. According to a preferred embodiment of the present invention, the organic solvent is an organic aprotic solvent, preferably one or more of cyclohexane, n-hexane and acetone, more preferably cyclohexane and acetone, and the volume ratio of cyclohexane to acetone is 0.8-1.1:1.

[0032] In the method for preparing the modified tin-titanium-silicon molecular sieve catalyst of the present invention, the concentration of the organic solution of the organosiloxane can be selected over a wide range, as exemplified below but not intended to limit the scope of the present invention. According to a preferred embodiment of the present invention, the concentration of the organosiloxane in the organic solution is 0.0005-0.1 g / mL, preferably 0.005-0.05 g / mL.

[0033] In the present invention, in the preparation method of the modified tin-titanium-silicon molecular sieve catalyst, the mixing contact time can be selected within a wide range, which is exemplified below but does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the mixing contact time is 12-36 hours, preferably 24-36 hours.

[0034] In the present invention, in the preparation method of the modified tin-titanium-silicon molecular sieve catalyst, the drying method is not particularly limited, and any suitable method can be selected as long as it can achieve the purpose of the present invention. According to a preferred embodiment of the present invention, the drying method is vacuum rotary evaporation.

[0035] In the present invention, in the preparation method of the modified tin-titanium-silicon molecular sieve catalyst, the drying temperature can be selected in a wide range, which is exemplified below but does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the drying temperature is 50-90°C.

[0036] In the preparation method of the modified tin-titanium-silicon molecular sieve catalyst of the present invention, the drying time can be selected within a wide range, which is exemplified below but does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the drying time is 2-6 hours.

[0037] In the present invention, in the preparation method of the modified tin-titanium-silicon molecular sieve catalyst, the drying pressure can be selected within a wide range, which is exemplified below but does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the drying pressure is 50-100 kPa.

[0038] The modified tin-titanium-silicon molecular sieve catalyst prepared by the preparation method having the above characteristics has higher catalytic efficiency and better catalytic selectivity.

[0039] In the method for synthesizing o-cresol and / or p-cresol using a microchannel reactor of the present invention, the reaction temperature of the contact reaction can be selected over a wide range, which is exemplified below but does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the reaction temperature of the contact reaction is 5-85°C.

[0040] In the method for synthesizing o-cresol and / or p-cresol using a microchannel reactor of the present invention, the residence time of the contact reaction can be selected over a wide range, which is exemplified below but does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the residence time of the contact reaction is 2-60 minutes.

[0041] In the present invention, the type of microchannel reactor is not particularly limited. As long as the object of the present invention can be achieved, suitable types can be selected. According to a preferred embodiment of the present invention, the microchannel reactor is selected from a plate type microchannel reactor, a tubular microchannel reactor or a plate type microchannel reactor and a tubular microchannel reactor in series in any order.

[0042] According to a preferred embodiment of the present invention, the method for synthesizing o-cresol and / or p-cresol using a microchannel reactor further comprises: first mixing a catalytic solution, toluene, and an H2O2 aqueous solution, and then introducing the mixture into the microchannel reactor.

[0043] According to a preferred embodiment of the present invention, in the method for synthesizing o-cresol and / or p-cresol using a microchannel reactor, the mixing is performed in a micromixer, and the micromixer is connected before the microchannel reactor.

[0044] According to a preferred embodiment of the present invention, the method for synthesizing o-cresol and / or p-cresol using a microchannel reactor further comprises: separating a catalyst, a solvent, and toluene from the reaction effluent, and repeatedly using the separations to synthesize o-cresol and / or p-cresol.

[0045] The method for synthesizing o-cresol and / or p-cresol by using a microchannel reactor provided by the present invention has the advantages of high selectivity and total yield of o-cresol and p-cresol, good safety, environmental friendliness and simple process. DETAILED DESCRIPTION

[0046] The present invention will be described in detail below through examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Those skilled in the art may make some non-essential improvements and adjustments to the present invention based on the above-mentioned content of the present invention.

[0047] If specific experimental procedures or conditions are not specified in the preparation examples, examples, and comparative examples, the procedures or conditions described in the literature in the field can be followed. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0048] In the preparation examples, embodiments and comparative examples, The microchannel reactor is a low-flow microchannel reactor from Corning; The micromixer is the MF-X2 micromixer from Microfluidics. The molar ratios of elements in the molecular sieves were measured by inductively coupled plasma optical emission spectrometry (ICP-OES); The external specific surface area and total pore volume of the molecular sieve were measured by BET (Bettmann-Emmett-Teller) analyzer. For the convenience of description, the value of V×M1 / M2 is recorded as n value, where V is the total pore volume of the molecular sieve catalyst (cm 3 / g); M1 is the mass of toluene passed into the microchannel reactor per unit time (g); M2 is the mass of catalyst passed into the microchannel reactor per unit time (g).

[0049] The following preparation example describes a method for preparing the raw material tin titanium silicon molecular sieve: tetraethyl orthosilicate, tetrapropylammonium hydroxide, water, Span 80, and tetrabutyl titanate are mixed and stirred. During the stirring process, tin chloride pentahydrate is added to obtain a first mixture, wherein the molar ratio of tetraethyl orthosilicate, tetrapropylammonium hydroxide, water, Span 80, tetrabutyl titanate, and tin chloride pentahydrate is 1:0.2:20:0.01:x:y, with x and y adjusted accordingly according to the requirements of the preparation example; stirring is performed at room temperature for 1 hour. The first mixture is heated at 70°C for 6 hours, then transferred to a sealed stainless steel reactor and crystallized at 160°C for 3 days to obtain a second mixture. The second mixture is filtered to obtain a solid, which is washed with water, dried at 110°C for 120 minutes, and calcined at 550°C in air for 6 hours to obtain the tin titanium silicon molecular sieve.

[0050] Preparation Example 1 The preparation method of the modified tin-titanium-silicon molecular sieve catalyst A is as follows: 10g of tin-titanium-silicon molecular sieve (the molar ratio of titanium to silicon is 0.032:1, and the molar ratio of tin to silicon is 0.023:1) is mixed with 100mL of a cyclohexane solution containing 2g of methoxytrimethylsilane, and the mixture is reacted under stirring for 24 hours. The resulting reaction product is then dried by vacuum rotary evaporation in a water bath (temperature 50°C, time 2 hours, pressure 50kPa) to obtain a modified tin-titanium-silicon molecular sieve catalyst A (the molar ratio of titanium to silicon is 0.027:1, and the molar ratio of tin to silicon is 0.019:1), with an external specific surface area of ​​254m 2 / g, with a total pore volume of 0.34 cm 3 / g.

[0051] Preparation Example 2 The preparation method of the modified tin-titanium-silicon molecular sieve catalyst B is as follows: according to the method of Preparation Example 1, except that the molar ratio of titanium to silicon in the raw material tin-titanium-silicon molecular sieve is 0.04:1, and the molar ratio of tin to silicon is 0.027:1; the molar ratio of titanium to silicon in the obtained modified tin-titanium-silicon molecular sieve catalyst B is 0.034:1, and the molar ratio of tin to silicon is 0.023:1, and the external specific surface area is 226m 2 / g, with a total pore volume of 0.32 cm 3 / g.

[0052] Preparation Example 3 The modified tin titanium silicon molecular sieve catalyst C was prepared by the method of Preparation Example 1, except that 8 g of methoxytrimethylsilane was contained in 100 mL of cyclohexane solution of methoxytrimethylsilane; the obtained modified tin titanium silicon molecular sieve catalyst C had a molar ratio of titanium to silicon of 0.028:1, a molar ratio of tin to silicon of 0.018:1, and an external specific surface area of ​​314 m 2 / g, with a total pore volume of 0.49 cm 3 / g.

[0053] Preparation Example 4 The modified tin-titanium-silicon molecular sieve catalyst D was prepared by following the method of Preparation Example 1, except that the solvent of the cyclohexane solution of methoxytrimethylsilane was replaced with 50 mL of cyclohexane and 50 mL of acetone; the obtained modified tin-titanium-silicon molecular sieve catalyst D had a molar ratio of titanium to silicon of 0.026:1, a molar ratio of tin to silicon of 0.019:1, and an external specific surface area of ​​272 m 2 / g, with a total pore volume of 0.39 cm 3 / g.

[0054] Example 1 A modified tin-titanium-silicon molecular sieve catalyst A and methanol were stirred to obtain a catalytic solution. The catalytic solution, toluene, and a 40 wt% aqueous H2O2 solution were introduced into a microchannel reactor for a contact reaction to produce o-cresol and p-cresol. The mass ratio of catalyst A to toluene was 7:100, the n value was 4.86, the molar ratios of methanol to H2O2 were 8:1, and the molar ratios of toluene to H2O2 were 4:1. The reaction temperature was 50°C, and the residence time was 30 minutes. The H2O2 conversion was 95.6%, the selectivity for o-cresol was 70.5%, and the selectivity for p-cresol was 19.3%.

[0055] Example 2 A modified tin-titanium-silicon molecular sieve catalyst A and methanol were stirred to obtain a catalytic solution. The catalytic solution, toluene, and a 20 wt% aqueous H2O2 solution were introduced into a microchannel reactor for a contact reaction to produce o-cresol and p-cresol. The mass ratio of catalyst A to toluene was 5:100, the n value was 6.8, the molar ratios of methanol to H2O2 were 6:1, and the molar ratios of toluene to H2O2 were 3:1. The reaction temperature was 80°C, and the residence time was 5 minutes. The H2O2 conversion was 99.6%, the selectivity for o-cresol was 69.8%, and the selectivity for p-cresol was 18.4%.

[0056] Example 3 The method of Example 1 was followed, except that the mass ratio of catalyst A to toluene was 12:100, and the value of n was 2.83. The conversion of H2O2 was 96.9%, the selectivity for o-cresol was 68.8%, and the selectivity for p-cresol was 17.4%.

[0057] Example 4 The method of Example 1 was followed, except that the molar ratio of methanol to H2O2 was 5:1. The conversion of H2O2 was 94.5%, the selectivity for o-cresol was 69.8%, and the selectivity for p-cresol was 18.1%.

[0058] Example 5 The method of Example 1 was followed, except that the molar ratio of toluene to H2O2 was 2.5:1. The conversion of H2O2 was 93.3%, the selectivity for o-cresol was 70.2%, and the selectivity for p-cresol was 18.6%.

[0059] Example 6 The method of Example 1 was followed, except that methanol was replaced with an equal molar amount of acetone. The conversion of H2O2 was 95.3%, the selectivity for o-cresol was 70.9%, and the selectivity for p-cresol was 19.1%.

[0060] Example 7 The method of Example 1 was followed, except that Catalyst A was replaced with Catalyst B, and the n value was 4.57. The conversion of H2O2 was 93.7%, the selectivity for o-cresol was 69.8%, and the selectivity for p-cresol was 18.0%.

[0061] Example 8 The method of Example 1 was followed, except that Catalyst A was replaced with Catalyst C, and the value of n was 7. The conversion of H2O2 was 96.3%, the selectivity for o-cresol was 68.8%, and the selectivity for p-cresol was 16.6%.

[0062] Example 9 The method of Example 1 was followed, except that Catalyst A was replaced with Catalyst D, and the n value was 5.57. The conversion of H2O2 was 96.2%, the selectivity for o-cresol was 71.5%, and the selectivity for p-cresol was 19.8%.

[0063] Example 10 The method of Example 9 was followed, except that the mass ratio of catalyst D to toluene was 5:100, and the value of n was 7.8. The conversion of H2O2 was 94.8%, the selectivity for o-cresol was 69.6%, and the selectivity for p-cresol was 18.3%.

[0064] Example 11 The method of Example 9 was followed, except that the mass ratio of catalyst D to toluene was 9:100, and the value of n was 4.33. The conversion of H2O2 was 94.6%, the selectivity for o-cresol was 69.7%, and the selectivity for p-cresol was 18.5%.

[0065] Example 12 The method of Example 1 was followed, except that a micromixer was connected before the microchannel reactor. The catalyst solution, toluene, and a 40 wt% H₂O₂ aqueous solution were first introduced into the micromixer for mixing before being introduced into the microchannel reactor for contact reaction. The H₂O₂ conversion rate was 96.1%, the selectivity for o-cresol was 70.8%, and the selectivity for p-cresol was 19.5%.

[0066] Comparative Example 1 Modified tin-titanium-silicon molecular sieve catalyst A and methanol were stirred to obtain a catalytic solution. The catalytic solution, toluene, and a 40wt% H2O2 aqueous solution were introduced into a reactor. The reactor was heated in a 50°C water bath for 2 hours to produce o-cresol and p-cresol. The H2O2 conversion was 82.3%, with selectivity for o-cresol of 58.8% and p-cresol of 10.7%.

[0067] Comparative Example 2 The method of Comparative Example 1 was followed, except that Catalyst A was replaced with Catalyst D. The conversion of H2O2 was 85.4%, the selectivity of o-cresol was 59.2%, and the selectivity of p-cresol was 12.0%.

[0068] The method for synthesizing o-cresol and / or p-cresol using a microchannel reactor provided by the present invention has been described in detail above, but the present invention is not limited thereto. Within the scope of the technical concept of the present invention, the technical scheme of the present invention can be subjected to a variety of simple modifications, including combining various specific technical features in any suitable manner. In order to avoid unnecessary repetition, the present invention will no longer describe various possible combinations separately. However, these simple modifications and combinations should also be regarded as disclosed in the present invention and all fall within the scope of protection of the present invention.

Claims

1. A method for synthesizing o-cresol and / or p-cresol using a microchannel reactor, characterized in that: The method comprises: introducing a catalytic liquid, toluene and an H2O2 aqueous solution into a microchannel reactor for contact reaction to obtain a reaction effluent, and separating o-cresol and / or p-cresol from the reaction effluent, wherein the catalytic liquid comprises a catalyst and a solvent.

2. The method according to claim 1, wherein The concentration of the H2O2 aqueous solution is 3-50wt%, preferably 20-50wt%; and / or Measured by the amount of liquid introduced into the microchannel reactor per unit time: The mass ratio of catalyst to toluene is 1-10:100, preferably 5-10:100; and / or The molar ratio of solvent to H2O2 is 1-10:1, preferably 6-10:1; and / or The molar ratio of toluene to H2O2 is 1-6:1, preferably 3-6:

1.

3. The method according to claim 1 or 2, wherein: The catalyst is a molecular sieve catalyst, preferably a modified or unmodified tin-titanium-silicon molecular sieve catalyst, more preferably: the molecular sieve catalyst is a modified tin-titanium-silicon molecular sieve catalyst; and / or the molar ratio of titanium to silicon in the tin-titanium-silicon molecular sieve catalyst is 0.005-0.03:1, and the molar ratio of tin to silicon is 0.005-0.02:1; and / or The solvent is a C1-C6 alcohol and / or a C3-C6 ketone, wherein the C1-C6 alcohol is preferably methanol; and / or the C3-C6 ketone is preferably acetone.

4. The method according to claim 3, wherein: The external specific surface area of ​​the molecular sieve catalyst is 100-300m 2 / g, preferably 200-300m 2 / g; and / or The total pore volume of the molecular sieve catalyst is 0.25-0.5 cm 3 / g, preferably 0.37-0.47cm 3 / g; and / or The process parameters of the microchannel reactor meet the following requirements: V×M1 / M2 is 4.5-7.5, in, V is the total pore volume of the molecular sieve catalyst (cm 3 / g); M1 is the mass of toluene introduced into the microchannel reactor per unit time (g); M2 is the mass (g) of catalyst introduced into the microchannel reactor per unit time.

5. The method according to claim 3, wherein The preparation method of the modified tin-titanium-silicon molecular sieve catalyst comprises: mixing and contacting the tin-titanium-silicon molecular sieve with an organic solution of organosiloxane, and then drying to obtain the modified tin-titanium-silicon molecular sieve catalyst.

6. The method according to claim 5, wherein: The organosiloxane contains R n -Si-(O-R') 4-n A compound of the structure, wherein R and R' are each independently a C1-C3 alkyl group, preferably a methyl group or an ethyl group; n is 0, 1, 2 or 3, preferably 3; preferably, the organosiloxane is selected from one or more of methoxytrimethylsilane, ethoxytriethylsilane, ethoxytrimethylsilane and methoxytriethylsilane; and / or The molar ratio of titanium to silicon in the tin-titanium-silicon molecular sieve is 0.01-0.035:1, and the molar ratio of tin to silicon is 0.01-0.024:1; and / or The mass ratio of the tin-titanium-silicon molecular sieve to the organosiloxane is 1-150:1, preferably 2-50:1, more preferably 5-20:1; and / or The organic solvent is an organic aprotic solvent, preferably one or more of cyclohexane, n-hexane and acetone, more preferably cyclohexane and acetone, with the volume ratio of cyclohexane to acetone being 0.8-1.1:1; and / or In the organic solution of the organosiloxane, the concentration of the organosiloxane is 0.0005-0.1 g / mL, preferably 0.005-0.05 g / mL; and / or The mixing contact time is 12-36 hours, preferably 24-36 hours; and / or The drying conditions include: drying by vacuum rotary evaporation at a temperature of 50-90° C., a time of 2-6 hours, and a pressure of 50-100 kPa.

7. The method according to claim 1 or 2, wherein: The reaction conditions of the contact reaction include: The reaction temperature is 5-85°C; and / or The residence time is 2-60 minutes; and / or The microchannel reactor is selected from a plate microchannel reactor, a tubular microchannel reactor or a plate microchannel reactor and a tubular microchannel reactor connected in series in any order.

8. The method according to claim 1 or 2, wherein: The method further comprises: firstly mixing the catalytic liquid, toluene and H2O2 aqueous solution, and then introducing the mixture into the microchannel reactor.

9. The method according to claim 8, wherein The mixing is carried out in a micro mixer, which is connected before the microchannel reactor.

10. The method according to claim 1 or 2, wherein: The method further comprises: separating catalyst, solvent and toluene from the reaction effluent and repeatedly using the catalyst, solvent and toluene to synthesize o-cresol and / or p-cresol.