Method for preparing 2, 6-di-tert-butyl-p-methylphenol

Abstract

The invention relates to a method for continuously preparing 2, 6-di-tert-butyl-p-cresol in a microchannel reactor, which comprises the following steps: (1) providing a first material flow, a second material flow and a third material flow wherein the first material flow comprises o-phenol and a catalyst; the second material flow comprises liquefied isobutene; the third material flow comprises a catalyst; (2) a first reaction zone and a second reaction zone are provided, and each of the first reaction zone and the second reaction zone comprises a microchannel reactor; (3) feeding the first material flow and the second material flow into a first reaction zone for reaction to form a first reactant flow; and (4) discharging a first reactant flow from the first reaction zone, and introducing the first reactant flow and the third reactant flow into a second reaction zone located at the downstream of the first reaction zone to obtain the 2, 6-di-tert-butyl p-cresol. Wherein the reaction temperatures of the first reaction zone and the second reaction zone are respectively 40-160 DEG C; the catalyst is a strong acid catalyst. According to the method, the overall risk in the reaction process can be reduced, and the productivity is effectively improved.

Description

Technical Field

[0001] The invention relates to a method for preparing 2,6-di-tert-butyl-p-methylphenol, and in particular to a method for continuously preparing 2,6-di-tert-butyl-p-methylphenol by using a microchannel reactor. Background Art

[0002] 2,6-Di-tert-butyl-p-methylphenol (BHT) is a white crystalline powder that turns yellow and gradually darkens when exposed to light, and has a unique phenolic odor. It is soluble in organic solvents such as ethanol, acetone, alkanes, aromatic hydrocarbons, but is difficult to dissolve in water. BHT is currently widely used in China's ester-soluble antioxidant products. It has strong antioxidant capacity and good thermal stability. It can also be used as a feed additive to prevent aging and deterioration. It is a new type of rubber and plastic antioxidant.

[0003] At present, the common method for synthesizing 2,6-di-tert-butyl-p-methylphenol is to use p-cresol and isobutylene as raw materials to prepare 2,6-di-tert-butyl-p-methylphenol under the action of a catalyst. However, the existing production equipment usually mixes all the raw materials in the same reactor for reaction, and then separates and purifies the reaction solution, which easily leads to uneven mixing of the catalyst, produces more by-products, and has a long reaction cycle. At present, industrial production mainly uses kettle reactors, but due to the large heat release of the reaction and the high overall risk factor, it is restricted by the increasingly stringent environmental assessment standards and cannot use larger reactors on an industrial scale, resulting in difficulty in increasing production.

[0004] Therefore, a new synthesis method of 2,6-di-tert-butyl-4-methylphenol is needed to solve the shortcomings of the existing technology, reduce the overall risk in the reaction process, and effectively improve production capacity. Summary of the invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a method for synthesizing 2,6-di-tert-butyl-p-methylphenol by using a microchannel reactor.

[0006] The present invention provides a method for continuously preparing 2,6-di-tert-butyl-p-methylphenol in a microchannel reactor, the method comprising:

[0007] (1) providing a first material stream, a second material stream and a third material stream, wherein the first material stream comprises o-phenol and a catalyst; the second material stream comprises liquefied isobutylene; and the third material stream comprises a catalyst;

[0008] (2) providing a first reaction zone and a second reaction zone, wherein the first reaction zone and the second reaction zone respectively comprise microchannel reactors;

[0009] (3) introducing the first material flow and the second material flow into the first reaction zone for reaction to form a first reaction flow;

[0010] (4) discharging the first reactant stream from the first reaction zone, and passing the first reactant stream and the third stream into a second reaction zone located downstream of the first reaction zone;

[0011] The reaction temperatures of the first reaction zone and the second reaction zone are 40-160° C. respectively; and the catalyst is a strong acid catalyst.

[0012] In some embodiments of the present invention, the strong acid catalyst is one or more of sulfuric acid, hydrofluoric acid, phosphoric acid, hydrochloric acid or p-toluenesulfonic acid.

[0013] In some embodiments of the present invention, the molar ratio of o-phenol in the first material stream to the second material stream is in the range of 0.5:1 to 5:1, preferably 2.2:1.

[0014] In some embodiments of the present invention, the mass ratio of o-phenol to catalyst in the first material stream is 10:1-100:1.

[0015] In some embodiments of the present invention, the reaction temperatures of the first reaction zone and the second reaction zone are 70-100° C., respectively, and the reaction is maintained at a constant temperature within this temperature range.

[0016] In some embodiments of the present invention, the reaction residence time of the first reaction zone and the second reaction zone is 0.5-20 minutes, respectively.

[0017] In some embodiments of the present invention, the pressures in the first reaction zone and the second reaction zone are 0.6-6 MPa, respectively. The preferred pressure range is 2.5-4.5 MPa.

[0018] In some embodiments of the present invention, the total reaction residence time of the first reaction zone and the second reaction zone is 10-20 minutes.

[0019] In some embodiments of the present invention, the feed rate of the first material stream is 5-50 g / min.

[0020] In some embodiments of the present invention, the feed rate of the second material stream is 1-20 g / min.

[0021] In some embodiments of the present invention, the feed rate of the third material stream is 0.15-1.5 g / min.

[0022] In the present invention, the method achieves the following excellent technical effects: by using the intrinsically safe reaction means of microchannel, the alkylation reaction of p-cresol and isobutylene is carried out through a small batch rapid reaction to obtain a yield better than that of the kettle process, and the strong acid is used as a catalyst. The strong acid can reduce the amount of the acid catalyst used, and the strong acid can increase the alkylation reaction rate. Through the precise temperature control and enhanced mass transfer of the microchannel reactor, the reaction is rapid and the impurities are less, so better economic benefits can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic diagram of a microchannel reactor used in some embodiments of the present invention.

[0024] Figure 2 Schematic diagram of a microchannel reactor used in other embodiments of the present invention. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is now described in conjunction with specific embodiments. It should be understood that the following examples are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0026] In the present invention, the reaction formula for synthesizing 2,6-di-tert-butyl-p-methylphenol in a microchannel reactor is as follows:

[0027]

[0028] The term "microchannel reactor" as used herein refers to a microreactor whose internal structure is mainly composed of micron-scale (usually 10 to 300 μm) channels. The microchannel reactor can be a high-throughput reactor (e.g., a high-throughput reactor available from Corning, such as a high-throughput reactor (AFR-G1) assembled from a "G1" module sold by Corning, or a high-throughput reactor (AFR-G5) assembled from a "G5" module), a flow reactor.

[0029] The "reaction zone" described herein refers to a functional area where a chemical reaction can occur independently, including at least one of the microchannel reactors. When the number of microchannel reactors is greater than one, the microchannel reactors can be connected in series and / or in parallel; the "reaction zone" also includes one or more of a preheating device, a sampling device, and a heat exchange device. The sampling device includes but is not limited to sampling by means of a pump, extrusion, osmosis, injection, etc. In some embodiments, the delivery described herein is delivered using a pump, such as a conventional plunger pump in the art.

[0030] In this article, the heat exchange device may include at least one heat exchange passage through which other liquid or gaseous media pass, arranged adjacent to the reaction passage of the microchannel reactor, and the temperature of the reactants in the reaction passage is controlled by controlling the temperature of the liquid or gaseous medium in the heat exchange passage.

[0031] Herein, the term "downstream" is intended only to describe that the reaction materials flow through the first reaction zone first and then flow through the second reaction zone, without any other limitation.

[0032] The method described herein can be carried out under isothermal or non-isothermal conditions. The isothermal method described herein means that the reaction temperature varies within the range of ±5°C (preferably ±4, 3, 2, 0.5°C) of the set temperature value.

[0033] The reaction residence time described herein = total volume flow rate of reaction materials (mL / min) / internal volume of reactor (mL). The internal volume of the reactor is provided by the supplier.

[0034] The yield described in this article = actual yield / theoretical yield × 100%

[0035] The "separation" mentioned herein refers to separating and collecting components with different properties using methods commonly used in the chemical industry, and the methods include but are not limited to separation using separation tanks and liquid separators.

[0036] As used herein, the term "(GC) analysis" refers to gas chromatography (GC) analysis.

[0037] The methods described herein can be carried out at normal pressure or elevated pressure. The pressure in any reaction zone of the methods described herein can be 0.1-5 MPa, preferably 0.1-2 MPa, for example, 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1.0 MPa.

[0038] The second material stream described herein can be prepared before, simultaneously with, or after the preparation of the first material stream.

[0039] The conversion rate described herein = (initial amount of reactants - remaining amount of reactants) / initial amount of reactants.

[0040] Selectivity as described herein = amount of target product / (starting amount of reactants x conversion rate)

[0041] In this article, the term "strong acid catalyst" refers to a catalyst that can provide sufficient acidity to promote proton transfer in the reaction. The strong acid catalyst promotes the reaction by providing protons to form active positive carbon ion intermediate compounds with reactant molecules.

[0042] In some specific embodiments of the present invention, a microchannel reactor module of Corning Incorporated is used to form the first reaction zone and / or the second reaction zone, and the microchannel reaction zone module includes but is not limited to Corning G1-glass reactor and Corning G5-SiC reactor.

[0043] like Figure 1 As shown, Corning G1-glass reactor is used to form the first reaction zone and / or the second reaction zone. Reaction zone 100 includes two microchannel reactor modules 110 and 120, a heat exchanger device (not shown in the figure) and an injection device (not shown in the figure). The heat exchanger device includes a heat exchange passage adjacent to the reaction passage of the microchannel reactor module, which is connected to other liquid or gaseous media, and a control device located outside that can keep the medium in the heat exchange passage circulating and control its temperature. The injection device includes a plunger pump and a matching injection frame, which can pump the reactants into the microchannel reactor module. The pressure of the microchannel reactor is adjusted by a back pressure control valve (BPR Background Pressure Regulator). Taking Corning G1-glass reactor as an example, a first material flow 130 containing o-phenol and a catalyst and a second material flow 140 containing liquefied isobutylene enter the first reaction zone 110 through an injection device, and contact, mix, and react in the channel of the microchannel reactor to form a first reaction flow 150 and discharge from the first reaction zone 110 to enter the second reaction zone 120 located downstream of the first reaction zone. Subsequently, the first reaction flow is passed into the second reaction zone 120 located downstream of the first reaction zone 110, and contacts, mixes, and reacts with the third material flow 160 in the second reaction zone 120 to obtain a reaction flow 180 containing 2,6-di-tert-butyl-p-cresol.

[0044] like Figure 2As shown, a Corning G5-SiC reactor is used to form the first reaction zone and / or the second reaction zone. Reaction zone 200 includes 8 microchannel reactor modules numbered ① to ⑧, a heat exchanger device (not marked in the figure) and an injection device (not marked in the figure). The heat exchanger device includes a heat exchange passage adjacent to the reaction passage of the microchannel reactor module through which other liquid or gaseous media pass, and a control device located outside that can keep the medium in the heat exchange passage circulating and control its temperature. The injection device includes a plunger pump and a matching injection frame, which can pump the reactants into the microchannel reactor module. Taking Corning G5-SiC reactor as an example, a first material flow 230 containing o-phenol and a catalyst and a second material flow 240 containing liquefied isobutylene enter the first reaction zone 210 through an injection device, and contact, mix, and react in the channel of the microchannel reactor to form a first reaction flow (not marked in the figure) and be discharged from the first reaction zone 210 to enter the second reaction zone 220 located downstream of the first reaction zone. Subsequently, the first reaction flow (not marked in the figure) is passed into the second reaction zone 220 located downstream of the first reaction zone 210, and contacts, mixes, and reacts with the third material flow 260 in the second reaction zone 220 to obtain a reaction flow (not marked in the figure) containing 2,6-di-tert-butyl-p-cresol.

[0045] Unless otherwise specified, the raw materials used in the present invention are all industrial grade raw materials. In the examples, the raw material o-phenol can be purchased from Shanghai McLean Reagent Co., Ltd., with a purity of >99.5%; the raw material isobutylene can be purchased from Air Liquide Group of France, with a purity of 99.5%. Acids such as nitric acid and sulfuric acid can be purchased from Shanghai Lingfeng Chemical Reagent Co., Ltd., where the nitric acid content can reach 98%, and the sulfuric acid content can reach 98%.

[0046] General Methods

[0047] Examples 1-2 were performed using the following general procedure.

[0048] (1) p-cresol and catalyst are mixed in a mass ratio of 10:1-100:1, which is the first material flow; liquefied isobutylene is stored in a gas cylinder, and the liquefied isobutylene is pumped into the reactor by a plunger pump, and the liquefied isobutylene is the second material flow; the liquid acid catalyst is transported to the entrance of the reaction zone by a pump, which is the third material flow. The catalyst is a strong acid catalyst, and the strong acid catalyst is one or more of sulfuric acid, hydrofluoric acid, or p-toluenesulfonic acid. The mass proportion of the catalyst in all material flows is 0.2-20% (i.e., the sum of the mass of the first material flow, the second material flow, and the third material flow), preferably 1%-10%. The molar ratio of p-phenol in the first material flow to the second material flow is in the range of 0.5:1 to 5:1, preferably 2.2:1.

[0049] (2) Provide a first reaction zone and a second reaction zone, where the first reaction zone and the second reaction zone each include a microchannel reactor. Set the reaction temperature of the reactor to 40 - 160 °C, preferably 70 - 100 °C, and adjust the pressure of the microchannel reactor in the first reaction zone and the second reaction zone to 0.6 - 6 MPa through the back pressure control valve (BPR Background Pressure Regulator) at the outlet of the second reactor. Preferably, the pressure displayed at the front end of the system is 2.5 - 4.5 Mpa. Set the first material flow to feed at a rate of 5 - 50 grams per minute. The flow rate of the second material entering the reaction equipment is 1 - 20 grams per minute.

[0050] (3) Introduce the first material flow and the second material flow into the first reaction zone for reaction to form a first reaction material flow.

[0051] (4) Discharge the first reaction material flow from the first reaction zone, and introduce the first reaction material flow and the third material flow into the second reaction zone downstream of the first reaction zone. Obtain a reaction material flow containing 2,6 - di - tert - butyl - p - cresol. Set the third material flow to feed at a rate of 0.15 - 1.5 grams per minute. The residence time in the first reaction zone is 0.5 - 20 minutes, and the residence time in the second reaction zone is 0.5 - 20 minutes. Preferably, the total residence time of the two - stage reaction zone is 10 - 20 minutes.

[0052] After the system is stable, after about 3 times the residence time (30 - 60 minutes), start collecting samples, and perform quantitative detection with an Agilent 6890GC gas chromatograph to quantify the product concentration by peak area. After the reaction is completed, collect the reaction solution through a receiving tank at the outlet of the reactor, remove the low - boiling impurities, cool and crystallize, filter to obtain a solid, and finally obtain a white 2,6 - di - tert - butyl - p - cresol solid.

[0053] Example 1

[0054] Figure 1The reaction equipment used in Example 1 uses a Corning G1-glass reactor to form the first reaction zone and / or the second reaction zone. The reaction zone 100 includes two microchannel reactor modules 110 and 120. A material stream is prepared, wherein the first material stream contains 1000g of p-cresol and 20g of a concentrated sulfuric acid catalyst with a concentration of 98%, and the mixing ratio is 2%; the second material stream contains liquefied isobutylene, which is stored in a steel cylinder with a pressure of 0.3-1.0MPa, with a purity of 99.8%, and can be pumped into the reactor by a plunger pump. The first material stream and the second material stream are input into the first reaction zone 110 through different reactor inlets 130 and 140, and the pressure of the first reaction zone and the second reaction zone is adjusted to 4MPa by a back pressure control valve (BPR). The pump for conveying the first material stream is turned on, and the mass flow rate of the first material stream is set to 18g / min and the volume flow rate is 18ml / min. The pump for conveying the second material flow is turned on, and the mass flow rate is set to 7.2g / min, and the molar ratio of isobutylene to p-cresol is 2.2:1. The pump for conveying the first material flow is turned on, and the mass flow rate is set to 0.5g / min and the volume flow rate is 0.25ml / min. The volume of the first reaction zone 110 is 300ml, and the reaction time is 10 minutes. The volume of the second reaction zone 120 is 300ml, and the reaction time is 10 minutes. The total reaction time of the two-stage reaction zone is 20 minutes. After about three times the reaction residence time, a small sample is taken for GC (gas chromatography) analysis and sample collection begins. GC analysis shows that the purity of 2,6-di-tert-butyl-p-cresol is 99%. After the reaction is completed, the reaction solution is collected in a receiving tank for post-treatment, and 679.4g of white BHT solid is finally obtained, and the molar yield is 94.55%.

[0055] Example 2

[0056] Figure 2The reaction equipment used in Example 2 uses a Corning G5-SiC reactor with 8 microchannel reactor modules. The reaction zone 200 includes two microchannel reactor modules 210 and 220. Prepare a material flow, wherein the first material flow contains 1000g of p-cresol and 20g of concentrated sulfuric acid catalyst with a concentration of 98%, and the mixing ratio is 2%; the second material flow contains liquefied isobutylene, which is stored in a steel cylinder with a pressure of 0.3-1.0MPa, with a purity of 99.8%, and can be pumped into the reactor by a plunger pump. The first material flow and the second material flow are input into the first reaction zone 210 through different reactor inlets 230 and 240, and the pressure of the first reaction zone and the second reaction zone is adjusted to 4MPa by a back pressure control valve (BP). Turn on the pump for conveying the first material flow, set the mass flow rate of the first material flow to 18g / min, and the volume flow rate to 18ml / min. The pump for conveying the second material flow is turned on, and the mass flow rate is set to 7.2g / min, and the molar ratio of isobutylene to p-cresol is 2.2:1. The pump for conveying the first material flow is turned on, and the mass flow rate is set to 0.5g / min and the volume flow rate is 0.25ml / min. The volume of the first reaction zone 210 is 300L, and the reaction time is 10 minutes. The volume of the second reaction zone 220 is 300L, and the reaction time is 10 minutes. The total reaction time of the two-stage reaction zone is 20 minutes. After three times the reaction residence time of about 60 minutes, a small sample is taken for GC (gas chromatography) analysis and sample collection begins. GC analysis shows that the purity of 2,6-di-tert-butyl-p-cresol is 99%. After the product reaction is completed, the reaction solution is collected in a receiving tank for post-processing, and 675.5kg of white BHT solid is finally obtained with a yield of 94%.

[0057] Comparative Example 1

[0058] In a 500L kettle reactor, isobutylene is introduced into 200 kg of p-cresol solution heated to 80°C. The molar ratio of isobutylene to p-cresol is 3.5:1. The heat release in the early stage of the reaction is huge, and the reaction temperature needs to be controlled not to exceed 85°C. After 6 hours, the heat release of the reaction decreases, and the bubbling can be reduced. After another 4 hours, the reaction is terminated, and the whole process is about 10 hours. After the product reaction is completed, the reaction liquid is collected in a receiving tank for post-treatment, and finally 338 kg of white BHT solid is obtained, with a yield of 83%.

[0059] The present invention has been described in detail above in conjunction with specific implementation methods and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art will appreciate that, without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention.

Claims

1. A method for continuously preparing 2,6-di-tert-butyl-p-cresol in a microchannel reactor, the method comprising: include: (1) providing a first material stream, a second material stream and a third material stream, wherein the first material stream comprises o-phenol and a catalyst; the second material stream comprises liquefied isobutylene; and the third material stream comprises a catalyst; (2) providing a first reaction zone and a second reaction zone, wherein the first reaction zone and the second reaction zone respectively comprise microchannel reactors; (3) introducing the first material flow and the second material flow into the first reaction zone for reaction to form a first reaction flow; (4) discharging a first reactant stream from the first reaction zone, and passing the first reactant stream and the third stream into a second reaction zone located downstream of the first reaction zone; Wherein, the reaction temperatures of the first reaction zone and the second reaction zone are 40-160° C. respectively; and The catalyst is a strong acid catalyst.

2. The method according to claim 1, It is characterized in that The strong acid catalyst is one or more of sulfuric acid, hydrofluoric acid, phosphoric acid, hydrochloric acid or p-toluenesulfonic acid.

3. The method according to claim 1, It is characterized in that The molar ratio of the ortho-phenol in the first material stream to the second material stream is in the range of 0.5:1 to 5:1, preferably 2.2:

1.

4. The method according to claim 1, It is characterized in that The mass ratio of the o-phenol to the catalyst in the first material flow is 10:1-100:

1.

5. The method according to claim 1, It is characterized in that The reaction temperatures of the first reaction zone and the second reaction zone are respectively 70-100° C., and the reaction is maintained at a constant temperature within this temperature range.

6. The method according to claim 1, It is characterized in that The reaction residence time of the first reaction zone and the second reaction zone is 0.5-20 minutes respectively.

7. The method according to claim 1, It is characterized in that The pressures of the first reaction zone and the second reaction zone are respectively 0.6-6 MPa; the preferred pressure range is 2.5-4.5 MPa.

8. The method according to claim 1, It is characterized in that The total reaction residence time of the first reaction zone and the second reaction zone is 10-20 minutes.

9. The method according to claim 1, It is characterized in that The feed rate of the first material stream is 5-50 g / min.

10. The method according to claim 1, It is characterized in that The feed rate of the second material stream is 1-20 g / min.

11. The method according to claim 1, It is characterized in that The feed rate of the third material flow is 0.15-1.5 g / min.

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