A method for preparing raw film bulk ester using a microchannel continuous flow reactor

Abstract

The invention discloses a method for preparing raw film bulk ester by using a microchannel continuous flow reactor, comprising: preheating a mixture of salicylic acid ester and isophorol, and then introducing the mixture into a microchannel continuous flow reactor with an ester exchange catalyst for reaction, and obtaining the raw film bulk ester by post-processing after the reaction is completed; the microchannel continuous flow reactor comprises one or N reaction units connected in series, each reaction unit being formed by connecting a microchannel reactor and a falling film evaporator in series. The method has mild reaction conditions, produces few by-products, has high reaction selectivity, and can realize continuous production.

Description

Technical Field

[0001] The invention relates to the technical field of raw film bulk ester preparation, and in particular to a method for preparing raw film bulk ester by adopting a microchannel continuous flow reactor. Background Art

[0002] Original membrane ester, chemical name 3,3,5-trimethylcyclohexanol salicylate, molecular formula C 16 H 22 O3 is a highly efficient UV absorber that can efficiently absorb UV rays with a wavelength of 295 to 315 nm. Original membrane ester has high fat solubility and can be added to polyvinyl chloride plastics, nitrocellulose, acrylic resins and polyurethane coatings as a light stabilizer; original membrane ester has good biocompatibility and good safety, and can be added to high-end cosmetics as a chemical sunscreen to protect the skin from damage by UV radiation.

[0003] In 1944, Fries' patent US2369084A first disclosed the structure of raw membrane esters. Currently, raw membrane esters are mostly produced industrially by transesterification. US Patent US462802A discloses a method for synthesizing raw membrane esters by transesterification using sodium methoxide as a catalyst. The catalyst in this method is expensive and cannot be recycled. In addition, the large amount of waste salt generated by treating alkaline wastewater is also difficult to handle.

[0004] Patent JP2006104192A discloses a method for preparing a raw film loose ester, which uses methyl salicylate and isophorol in a reactor, uses organic tin as a catalyst, and has a reaction temperature of 140 to 170°C. After reacting for 2 to 20 hours, the raw film loose ester is obtained by an ester exchange method. The yield in the embodiment is about 75 to 92%. The reaction formula is as follows:

[0005]

[0006] The existing preparation method mainly adopts intermittent operation, with long reaction time, high reaction temperature and high degree of back mixing. The long-term high-temperature heating of a large amount of materials aggravates the occurrence of side reactions and generates more by-products. These by-products not only have a huge impact on the raw material conversion rate and product yield, but also the products generated by the side reactions are difficult to separate. They will continue to accumulate as the raw materials are applied, and ultimately have an adverse effect on industrial production. Summary of the invention

[0007] In the process of synthesizing raw membrane esters through a series of ester exchange, the researchers found that the following two side reactions led to low product selectivity and decreased product yield:

[0008] Side reaction 1:

[0009]

[0010] Side reaction 2:

[0011]

[0012] Side reaction 1 is that the phenolic hydroxyl group of methyl salicylate breaks the bond with the byproduct methanol under the condition of long-term high temperature heating to produce methyl o-methoxybenzoate (by Figure 2 and 3 GC graph and Figure 4 The mass spectrum of the reaction product is inferred to be the byproduct), and water is generated. The occurrence of this side reaction leads to a decrease in the conversion rate of methyl salicylate, and the generated water causes the hydrolysis of methyl salicylate to generate salicylic acid and methanol. The generation of salicylic acid may cause the alkaline catalyst in the reaction system to deteriorate and deactivate, and the generation of methanol will not only inhibit the main reaction, but also continue to participate in other side reactions. The content of methyl o-anisyl benzoate in the reaction process often reaches 1%-3%, so inhibiting the generation of methyl o-anisyl benzoate is an urgent problem to be solved in the production process.

[0013] Side reaction 2 is that the original film ester reacts with methanol at high temperature to form (3,3,5-trimethylcyclohexyl)-2-methoxybenzoate (composed of Figure 2 and 3 GC graph and Figure 5 The mass spectrum of the product is speculated to be the by-product). Since the operating temperature during the reaction and the subsequent separation process is high, the reaction occurs in large quantities. The occurrence of this reaction is also a key factor leading to a decrease in the final yield of the original membrane bulk ester. The product often reaches 2%-5% in the later stage, and its boiling point is close to that of the original membrane bulk ester, making it difficult to separate. Therefore, inhibiting the production of this product is beneficial to improving the yield of the original membrane bulk ester and the purity of the product.

[0014] The technical problem to be solved by the present invention is to provide a method for preparing raw film bulk ester using a microchannel continuous flow reactor, the method has mild reaction conditions, few by-products produced by the reaction, high reaction selectivity, and can realize continuous production.

[0015] The technical solution of the present invention is as follows:

[0016] A method for preparing raw film bulk ester using a microchannel continuous flow reactor, comprising:

[0017] The salicylic acid ester and isophorol are mixed and preheated, and then introduced into a microchannel continuous flow reactor with an ester exchange catalyst for reaction, and after the reaction is completed, the original film loose ester is obtained through post-treatment;

[0018] The microchannel continuous flow reactor comprises one or N reaction units connected in series, each reaction unit being formed by a microchannel reactor and a falling film evaporator connected in series;

[0019] Among them, 2≤N≤10.

[0020] Compared with the intermittent kettle reaction mode in the prior art, the present invention utilizes a microchannel reactor to reduce the reaction temperature and improve the reaction rate. At the same time, it is unexpectedly found that the problem that the traditional reaction mode cannot solve is solved, and the generation of by-products (methyl o-methoxybenzoate and (3,3,5-trimethylcyclohexyl)-2-methoxybenzoate) is suppressed. The present invention is used in conjunction with a falling film evaporator. Due to the characteristics of the falling film evaporator such as short residence time and suitability for processing heat-sensitive materials, by-products such as methanol can be quickly removed, and the reaction is promoted to the right. At the same time, due to the characteristics of the microchannel reactor such as small liquid holding volume, the safety factor is high, and the reaction can be continuously operated. The material in the microchannel continuously moves forward, and the back-mixing degree is low, thereby realizing continuous generation and having industrial application value.

[0021] Preferably, the number of the reaction units connected in series is 3 to 6.

[0022] Preferably, the preheating temperature is 80° C. to 100° C., and the reaction temperature in the microchannel reactor is 80° C. to 100° C. Since the reaction liquid undergoes efficient heat exchange on the microchannel wall, the reaction temperature is effectively reduced, local overheating, uneven heat transfer and other problems are avoided, the generation of by-products is reduced, the synthesis of the target product original membrane bulk ester is facilitated, and the difficulty of post-processing is reduced.

[0023] The microchannel reactor is in a slightly negative pressure state, and preferably, the reaction pressure is -0.01 MPa to -0.05 MPa.

[0024] Due to the miniaturization of the internal channel size, the heat transfer and mass transfer coefficients are 1-3 orders of magnitude higher than those of conventional reactions, which enhances the mass and heat transfer of the reactants. The reaction liquid is mixed in a very short time, and the reaction time is reduced from 6 to 10 hours to 0.3 to 30 minutes, which greatly improves the reaction efficiency. Preferably, the residence time of the reaction material in the microchannel reactor is 0.5 minutes to 20 minutes (when there are multiple reaction units, the residence time is the total residence time); as a further preference, the residence time is 1.5 minutes to 10 minutes.

[0025] Preferably, the flow rate of isophorol is 5 g / min to 200 g / min, and the flow rate of salicylate is 5 g / min to 300 g / min; further preferably, the flow rate of isophorol is 5 g / min to 50 g / min, and the flow rate of salicylate is 5 g / min to 75 g / min; further preferably, the flow rate of isophorol is 14 g / min to 30 g / min, and the flow rate of salicylate is 18 g / min to 38 g / min.

[0026] Preferably, the salicylate is one or more of methyl salicylate, ethyl salicylate, isopropyl salicylate, isobutyl salicylate and isopentyl salicylate.

[0027] Preferably, the transesterification catalyst is a combination of one or more of an acidic catalyst or a basic catalyst, organic titanium, and organic tin (dibutyltin oxide, methylphenyltin oxide, tetraethyltin, dibutyltin diacetate, and diphenyltin dilaurate).

[0028] Preferably, the acidic catalyst is sulfuric acid or p-toluenesulfonic acid;

[0029] The alkaline catalyst is sodium methoxide.

[0030] Preferably, the molar ratio of the isophorol to the salicylic acid ester is 1:1 to 3;

[0031] The molar ratio of the catalyst to the salicylic acid ester is 0.01% to 10%.

[0032] Preferably, the hydraulic radius of the microchannel in the microchannel reactor is 0.1mm-1.0mm, the microchannel length is 100m-200m, and the microchannel structure of the microchannel reactor is an enhanced mixing heart-shaped structure, a Z-shaped structure, a T-shaped structure, a T-shaped structure with a wave or a convex ridge chaotic structure.

[0033] Preferably, the post-treatment is reduced pressure distillation.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] (1) The present invention first mixes salicylic acid ester and isophorol, and then introduces them into a microchannel reactor together with an ester exchange catalyst. The reactants and the catalyst are mixed in a very short time, which greatly reduces the reaction time and effectively reduces the occurrence of side reaction 1;

[0036] (2) The present invention uses a microchannel reactor to carry out the reaction, which can also effectively reduce the reaction temperature. The reduction in temperature can be beneficial to the occurrence of the above-mentioned side reactions 1 and 2, and reduce the generation of by-products;

[0037] (3) The present invention connects the microchannel reactor and the falling film evaporator in series, and the reaction liquid runs forward continuously, which reduces the degree of back mixing and thus reduces the generation of by-products. At the same time, the by-product methanol in each reaction unit is removed in the falling film evaporator, which prevents the methanol by-product from mixing into the system and inhibiting the forward reaction. It also reduces the probability of side reactions 1 and 2 between methanol and methyl salicylate and the original film loose ester, and can achieve continuous production;

[0038] (4) The microchannel reactor of the present invention has a small liquid holding capacity and a higher safety factor. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A flow chart of the method for preparing raw film loose ester of the present invention;

[0040] Figure 2 This is the GC graph of the product obtained when the original film loose ester was prepared according to the method of Comparative Example 1;

[0041] Figure 3 for Figure 2 A partial enlarged view of

[0042] Figure 4 The mass spectrum of the by-product obtained by the side reaction 1 when the original membrane loose ester was prepared according to the method of comparative example 1;

[0043] Figure 5 This is the mass spectrum of the by-product obtained by side reaction 2 when the original membrane loose ester was prepared according to the method of comparative example 1. DETAILED DESCRIPTION

[0044] Figure 1 The flowchart of the method for preparing the original film loose ester of the present invention is as follows:

[0045] First, salicylic acid ester and isophorol are introduced into a preheater for mixing, and then introduced into a microchannel continuous flow reactor, wherein the microchannel continuous flow reactor comprises N reaction units connected in series, wherein 1≤N≤10, each reaction unit comprises a microchannel reactor and a falling film evaporator, the microchannel reactor and the falling film evaporator are connected in series, the first set of microchannel reactors is provided with two raw material inlets, one raw material inlet is a feed inlet for the isophorol and salicylic acid ester mixture, and the other raw material inlet is a feed inlet for an ester exchange catalyst, the catalyst is a liquid catalyst, the falling film evaporator inlet is connected to the microchannel reactor inlet, and the inlet of the falling film evaporator is connected to the inlet of the falling film evaporator. The material outlets are connected; the raw material inlet of the second falling film evaporator is connected to the material outlet of the second microchannel reactor; and so on, in the Nth microchannel reactor and the falling film evaporator, the two raw material inlets of the microchannel reactor are respectively the catalyst feeding port and the outlet material feeding port of the N-1th falling film evaporator, the raw material inlet of the Nth falling film evaporator is connected to the material outlet of the Nth microchannel mixer, the material outlet of the Nth falling film evaporator is connected to the final buffer kettle, the material collected from the buffer kettle is subjected to reduced pressure distillation to obtain the original film bulk ester product, and at the same time, the catalyst can be recovered and reused.

[0046] Example 1

[0047] The reaction equation is:

[0048]

[0049] This embodiment takes a set of sequentially connected microchannel reactor and falling film evaporator as an example to explain the present invention in detail:

[0050] The raw materials and catalysts were added at a certain flow rate by using a metering pump. Methyl salicylate 18.24 g / min (0.12 mol / min) and isophorol 14.2 g / min (purity 99%, 0.1 mol / min) were firstly preheated in a preheater with the temperature set to 90°C, and then respectively entered into a microchannel reactor with dibutyltin diacetate 0.21 g / min (0.0006 mol, 0.5 mol%). The temperature was set to 90°C and the pressure was -0.02 MPa. Isophorol, methyl salicylate and dibutyltin diacetate were fully mass-transferred and heat-transferred in the microchannel reactor. The hydraulic radius of the microchannel in the microchannel module was 0.6 mm and the length of the microchannel was 150 m. After the reaction materials stayed in the microchannel for 90 s, they entered into a falling film evaporator and the by-product methanol was removed by using the waste heat. The buffer kettle obtains a liquid product containing the product original membrane bulk ester, which is collected for 10 minutes; sampling is measured for GC, the original membrane bulk ester content is 75.53%, the methyl salicylate content is 17.31%, the isophorol content is 7.11%, the methanol content is 0.01%, the methyl o-anisole content is less than 0.01%, the (3,3,5-trimethylcyclohexyl)-2-methoxybenzoate content is less than 0.01%, and the reaction selectivity is greater than 99.9%; the reaction liquid is subjected to vacuum distillation separation to finally obtain 208.55g of the original membrane bulk ester product, and the distillation residue weighs 14.61g, which mainly contains an organic tin catalyst (liquid) and can be subsequently recycled. The original membrane bulk ester yield is 85.21%, the total content (GC) is 99.7%, and the (3,3,5-trimethylcyclohexyl)-2-methoxybenzoate content is less than 0.01%.

[0051] Example 2

[0052] In this example, the distillation residue (containing catalyst) obtained in Example 1 was recycled to continue the test, and the reactor was the same as that in Example 1:

[0053] Raw materials and catalysts were added at a certain flow rate using a metering pump. Methyl salicylate 18.24 g / min (0.12 mol / min) and isophorol 14.2 g / min (purity 99%, 0.1 mol / min) were first preheated in a preheater with the temperature set to 90°C, and then respectively entered a microchannel mixer with dibutyltin diacetate 1.46 g / min (recovered catalyst, concentration: ω(cat)=14.1%). The temperature was set to 90°C and the pressure was -0.02 MPa. Isophorol, methyl salicylate and dibutyltin diacetate were fully mass-transferred and heat-transferred in the microchannel reactor. The hydraulic radius of the microchannel in the microchannel module was 0.6 mm, the microchannel length was 150 m, and the reaction materials were stirred for 2 hours at room temperature. It stayed in the microchannel for 90 seconds and entered the falling film evaporator. The by-product methanol was removed by waste heat. The buffer kettle obtained a liquid product containing the product original film ester and collected it for 10 minutes. The sample was taken for GC measurement. The original film ester content was 73.25%, the methyl salicylate content was 18.88%, the isophorol content was 7.97%, the methanol content was 0.03%, the methyl o-anisole content was <0.01%, and the others were 0.01%. The reaction selectivity was >99.9%. The reaction liquid was subjected to vacuum distillation separation to finally obtain 215.2g of original film ester product and 13.28g of distillation residue. The original film ester yield was 82.67%, the total content (GC) was 99.6%, and the (3,3,5-trimethylcyclohexyl)-2-methoxybenzoate content was <0.01%.

[0054] Example 3

[0055] This embodiment takes two sets of microchannel reactors and falling film evaporators connected in sequence as an example to explain the present invention in detail:

[0056] A device for combining a microchannel reactor and a falling film evaporator for preparing raw film bulk ester comprises two sets of microchannel reactors and falling film evaporators connected in sequence. In the first set of microchannel reactors and falling film evaporators, two inlets of the microchannel reactor are respectively a feeding port for a mixture of isophorol and methyl salicylate and a catalyst feeding port, and a raw material inlet of the falling film evaporator is connected with a material outlet of the first set of microchannel reactors; in the second set of microchannel reactors and falling film evaporators, the raw material inlet of the microchannel reactor is the outlet of the first set of falling film evaporator, the raw material inlet of the falling film evaporator is connected with a material outlet of the second set of microchannel reactor, and the material outlet of the second set of falling film evaporator enters a buffer kettle, and a product is obtained through subsequent vacuum distillation.

[0057] Raw materials and catalysts are added at a certain flow rate by using a metering pump, methyl salicylate 27.35 g / min (0.18 mol / min), isophorol 21.5 g / min (purity 99%, 0.15 mol / min), first enter a preheater for preheating, the temperature is set to 90° C., and then enter a microchannel mixer with dibutyltin diacetate 0.325 g / min, wherein the temperature of the first set of microchannel reactors is set to 90° C. and the pressure is -0.02 MPa, isophorol, methyl salicylate and dibutyltin diacetate are fully transferred in the microchannel reactor for mass and heat transfer, the microchannel radius of this section module is 0.6 mm, the microchannel length is 120 m, the reactants stay in the module for 72 s, enter a falling film evaporator, and use waste heat to remove byproduct methanol; the temperature of the second set of microchannel reactors is set to 110° C. and the pressure is -0.02 MPa. The hydraulic radius of the microchannel in the microchannel module is 0.6 mm, the length of the microchannel is 30 m, the reaction material stays in the microchannel for 18 s, enters the falling film evaporator, and uses waste heat to remove the by-product methanol. The buffer kettle obtains a liquid product containing the product original film ester, which is collected for 10 minutes; sampling and GC measurement, the original film ester content is 80.92%, the methyl salicylate content is 14.58%, the isophorol content is 4.48%, the methanol content is 0.02%, the methyl o-anisole content is <0.01%, and the others are 0.01%; the reaction selectivity is >99.9%, the reaction liquid is subjected to vacuum distillation separation, and finally 355.46 g of original film ester product and 4.35 g of distillation residue are obtained, the original film ester yield is 90.74%, the total content (GC) is 99.6%, and the (3,3,5-trimethylcyclohexyl)-2-methoxybenzoate content is <0.01%.

[0058] Example 4

[0059] This embodiment takes three sets of microchannel reactors and falling film evaporators connected in sequence as an example to explain the present invention in detail:

[0060] A device for combining a microchannel reactor and a falling film evaporator for preparing raw film bulk ester comprises three sets of microchannel reactors and falling film evaporators connected in sequence. In the first set of microchannel reactors and falling film evaporators, two raw material inlets of the microchannel reactor are respectively a feeding port for a mixture of isophorol and methyl salicylate and a catalyst feeding port, and the raw material inlet of the falling film evaporator is connected to the material outlet of the first set of microchannel reactor; in the second set of microchannel reactors and falling film evaporators, the raw material inlet of the microchannel reactor is the outlet of the first set of falling film evaporator, and the raw material inlet of the falling film evaporator is connected to the material outlet of the second set of microchannel reactor; in the third set of microchannel reactors and falling film evaporators, the raw material inlet of the microchannel reactor is the outlet of the second set of falling film evaporator, the raw material inlet of the third set of falling film evaporator is connected to the material outlet of the third set of microchannel reactor, and the material outlet of the third set of falling film evaporator enters a buffer kettle, and the product is obtained through subsequent vacuum distillation.

[0061] Raw materials and catalysts are added at a certain flow rate using a metering pump, methyl salicylate 36.5g / min (0.24mol / min), isophorol 28.4g / min (purity 99%, 0.2mol / min), first enter the preheater for preheating, the temperature is set to 90°C, and then enter the microchannel mixer with dibutyltin diacetate 0.42g / min (0.0012mol, 0.5mol%), wherein the temperature of the first set of microchannel reactors is set to 90°C and the pressure is -0.02MPa, isophorol, methyl salicylate and dibutyltin diacetate are fully transferred in the microchannel reactor for mass and heat transfer, the microchannel radius of this section module is 0.6mm, the microchannel length is 90m, the reactants stay in the module for 54s, enter the falling film evaporator, and use the waste heat to remove the by-product methanol; the temperature of the second set of microchannel reactors is set to 110°C and the pressure is -0.02MPa, the length of this section module is 45m, and the reactants stay in the module for 54s. The reaction mixture stayed in the block for 27 seconds and entered the falling film evaporator to further remove the byproduct methanol by using the residual heat. The temperature of the third microchannel reactor was set to 120°C, the pressure was -0.02MPa, and the microchannel length was 15m. The reaction mixture stayed in the microchannel for 9 seconds and entered the falling film evaporator to remove the byproduct methanol by using the residual heat. The buffer kettle obtained a liquid product containing the original film bulk ester and collected it for 10 minutes. The GC test showed that the original film bulk ester content was 84.61% and the methyl salicylate content was 12.9 5%, isophorol content 2.41%, methanol content 0.01%, methyl o-anisole <0.01%, others 0.01%; reaction selectivity >99.9%, the reaction liquid is subjected to vacuum distillation separation, and finally 482.30g of original membrane bulk ester product and 15.46g of distillation residue are obtained, the original membrane bulk ester yield is 95.03%, the total content (GC) is 99.8%, and the (3,3,5-trimethylcyclohexyl)-2-methoxybenzoate content is <0.01%.

[0062] Example 5

[0063] This embodiment takes three sets of microchannel reactors and falling film evaporators connected in sequence as an example to explain the present invention in detail:

[0064] A device for combining a microchannel reactor and a falling film evaporator for preparing raw film bulk ester comprises three sets of microchannel reactors and falling film evaporators connected in sequence. In the first set of microchannel reactors and falling film evaporators, two raw material inlets of the microchannel reactor are respectively a feeding port for a mixture of isophorol and methyl salicylate and a catalyst feeding port, and the raw material inlet of the falling film evaporator is connected to the material outlet of the first set of microchannel reactor; in the second set of microchannel reactors and falling film evaporators, the raw material inlet of the microchannel reactor is the outlet of the first set of falling film evaporator, and the raw material inlet of the falling film evaporator is connected to the material outlet of the second set of microchannel reactor; in the third set of microchannel reactors and falling film evaporators, the raw material inlet of the microchannel reactor is the outlet of the second set of falling film evaporator, the raw material inlet of the third set of falling film evaporator is connected to the material outlet of the third set of microchannel reactor, and the material outlet of the third set of falling film evaporator enters a buffer kettle, and the product is obtained through subsequent vacuum distillation.

[0065] Raw materials and catalysts are added at a certain flow rate by using a metering pump, methyl salicylate 9.2g / min (0.06mol / min), isophorol 7.1g / min (purity 99%, 0.05mol / min), first enter the preheater for preheating, the temperature is set to 80°C, and then enter the microchannel mixer with dibutyltin diacetate 0.1g / min (0.5mol%), wherein the temperature of the first set of microchannel reactors is set to 90°C and the pressure is -0.02MPa, isophorol, methyl salicylate and dibutyltin diacetate are fully transferred in the microchannel reactor for mass and heat transfer, the microchannel radius of this section module is 0.6mm, the microchannel length is 90m, the reactants stay in the module for 54s, enter the falling film evaporator, and use the waste heat to remove the by-product methanol; the temperature of the second set of microchannel reactors is set to 110°C and the pressure is -0.02MPa, the length of this section module is 45m, the reactants stay in the module for 27s s, enter the falling film evaporator, and use the waste heat to further remove the byproduct methanol; the temperature of the third microchannel reactor is set to 120℃, the pressure is -0.02MPa, the microchannel length is 15m, the reaction material stays in the microchannel for 9s, enters the falling film evaporator, and uses the waste heat to remove the byproduct methanol. The buffer kettle obtains the liquid phase product containing the product original film bulk ester, which is collected for 10min; sampling and GC measurement, the original film bulk ester content is 82.14%, and the methyl salicylate content is 13.75% , isophorol content 3.24%, methanol content 0.02%, methyl o-anisole <0.01%, others 0.01%; reaction selectivity >99.8%, the reaction liquid is subjected to vacuum distillation separation, and finally 123.20g of original membrane bulk ester product is obtained, the distillation residue weighs 1.2g, the original membrane bulk ester yield is 94.56%, the total content (GC) is 99.5%, and the (3,3,5-trimethylcyclohexyl)-2-methoxybenzoate content is <0.01%.

[0066] Example 6

[0067] This embodiment takes three sets of microchannel reactors and falling film evaporators connected in sequence as an example to explain the present invention in detail:

[0068] A device for combining a microchannel reactor and a falling film evaporator for preparing raw film bulk ester comprises three sets of microchannel reactors and falling film evaporators connected in sequence. In the first set of microchannel reactors and falling film evaporators, two raw material inlets of the microchannel reactor are respectively a feeding port for a mixture of isophorol and methyl salicylate and a catalyst feeding port, and the raw material inlet of the falling film evaporator is connected to the material outlet of the first set of microchannel reactor; in the second set of microchannel reactors and falling film evaporators, the raw material inlet of the microchannel reactor is the outlet of the first set of falling film evaporator, and the raw material inlet of the falling film evaporator is connected to the material outlet of the second set of microchannel reactor; in the third set of microchannel reactors and falling film evaporators, the raw material inlet of the microchannel reactor is the outlet of the second set of falling film evaporator, the raw material inlet of the third set of falling film evaporator is connected to the material outlet of the third set of microchannel reactor, and the material outlet of the third set of falling film evaporator enters a buffer kettle, and the product is obtained through subsequent vacuum distillation.

[0069] Raw materials and catalysts are added at a certain flow rate using a metering pump, methyl salicylate 36.5g / min (0.24mol / min), isophorol 28.4g / min (purity 99%, 0.2mol / min), first enter the preheater for preheating, the temperature is set to 90°C, and then enter the microchannel mixer with dibutyltin diacetate 0.42g / min (0.0012mol, 0.5mol%), wherein the temperature of the first set of microchannel reactors is set to 90°C and the pressure is -0.02MPa, isophorol, methyl salicylate and dibutyltin diacetate are fully transferred in the microchannel reactor for mass and heat transfer, the microchannel radius of this section module is 0.6mm, the microchannel length is 90m, the reactants stay in the module for 54s, enter the falling film evaporator, and use the waste heat to remove the by-product methanol; the temperature of the second set of microchannel reactors is set to 110°C and the pressure is -0.02MPa, the length of this section module is 45m, and the reactants stay in the falling film evaporator for 54s. The reaction mixture stayed in the module for 27 seconds and then entered the falling film evaporator to further remove the byproduct methanol by using the residual heat. The temperature of the third microchannel reactor was set to 120°C, the pressure was -0.02MPa, and the microchannel length was 15m. The reaction mixture stayed in the microchannel for 9 seconds and then entered the falling film evaporator to remove the byproduct methanol by using the residual heat. The buffer kettle obtained the liquid phase product containing the original film bulk ester and collected it for 10 minutes. The GC test showed that the original film bulk ester content was 78.93% and the methyl salicylate content was 15. .27%, isophorol content 4.70%, methanol content 0.01%, methyl o-anisole <0.01%, others 0.01%; reaction selectivity >99.9%, the reaction liquid is subjected to vacuum distillation separation, and finally 465.44g of original membrane bulk ester product and 6.5g of distillation residue are obtained, the original membrane bulk ester yield is 89.60%, the total content (GC) is 99.8%, and the (3,3,5-trimethylcyclohexyl)-2-methoxybenzoate content is <0.01%.

[0070] Example 7

[0071] This embodiment takes three sets of microchannel reactors and falling film evaporators connected in sequence as an example to explain the present invention in detail:

[0072] A device for combining a microchannel reactor and a falling film evaporator for preparing raw film bulk ester comprises three sets of microchannel reactors and falling film evaporators connected in sequence. In the first set of microchannel reactors and falling film evaporators, two raw material inlets of the microchannel reactor are respectively a feeding port for a mixture of isophorol and methyl salicylate and a catalyst feeding port, and the raw material inlet of the falling film evaporator is connected to the material outlet of the first set of microchannel reactor; in the second set of microchannel reactors and falling film evaporators, the raw material inlet of the microchannel reactor is the outlet of the first set of falling film evaporator, and the raw material inlet of the falling film evaporator is connected to the material outlet of the second set of microchannel reactor; in the third set of microchannel reactors and falling film evaporators, the raw material inlet of the microchannel reactor is the outlet of the second set of falling film evaporator, the raw material inlet of the third set of falling film evaporator is connected to the material outlet of the third set of microchannel reactor, and the material outlet of the third set of falling film evaporator enters a buffer kettle, and the product is obtained through subsequent vacuum distillation.

[0073] Raw materials and catalysts are added at a certain flow rate using a metering pump, methyl salicylate 36.5g / min (0.24mol / min), isophorol 28.4g / min (purity 99%, 0.2mol / min), first enter a preheater for preheating, the temperature is set to 90°C, and then enter a microchannel mixer with tetraethyltin 0.23g / min (0.001mol, 0.5mol%), wherein the temperature of the first set of microchannel reactors is set to 90°C and the pressure is -0.02MPa, isophorol, methyl salicylate and tetraethyltin fully carry out mass transfer and heat transfer in the microchannel reactor, the microchannel radius of this section module is 0.6mm, the microchannel length is 90m, the reactants stay in the module for 54s, enter the falling film evaporator, and use waste heat to remove the by-product methanol; the temperature of the second set of microchannel reactors is set to 110°C and the pressure is -0.02MPa, the length of this section module is 45m, the reactants stay in the module The reaction mixture was kept in the falling film evaporator for 27 seconds and then used the residual heat to further remove the byproduct methanol. The temperature of the third microchannel reactor was set to 120°C, the pressure was -0.02MPa, and the length of the microchannel was 15m. The reaction mixture stayed in the microchannel for 9 seconds and then used the residual heat to remove the byproduct methanol. The buffer kettle obtained the liquid product containing the original film bulk ester and collected it for 10 minutes. The GC test showed that the original film bulk ester content was 72.66% and the methyl salicylate content was 18.8 0%, isophorol content 8.51%, methanol content 0.01%, methyl o-anisole <0.01%, others 0.02%; reaction selectivity >99.9%, the reaction liquid is subjected to vacuum distillation separation, and finally 428.55g of original membrane bulk ester product and 7.3g of distillation residue are obtained, the original membrane bulk ester yield is 82.23%, the total content (GC) is 99.5%, and the (3,3,5-trimethylcyclohexyl)-2-methoxybenzoate content is <0.01%.

[0074] Comparative Example 1

[0075] This embodiment takes the intermittent reactor of the prior art as an example to explain the present invention in detail:

[0076] Into a 1000mL flask, add 245.96g of isophorol, 315.52g of methyl salicylate, and 12.3g of sodium methoxide, set up the whole set of reflux equipment, check the air tightness, turn on the stirring device, and rotate at 400rpm; turn on the electric heating jacket to control the temperature, raise the temperature to 100℃, set the reflux ratio to 1:10, start timing when liquid starts to evaporate from the top, and collect the distillate evaporated from the top at 50-60℃. When the top temperature is about to drop below 50℃, adjust the temperature of the electric heating jacket to ensure that the distillate is smoothly extracted; when the kettle temperature reaches 120℃, keep it warm for 2 hours, and start to gradually increase the temperature to 150℃. The total reaction time is 10 hours. After the reaction, cool to 50℃ and take samples for GC-MS analysis. The GC graph is shown in Figure 2 , Figure 3 for Figure 2 The enlarged picture of Figure 4 This is the MS graph at 10 min, which is the by-product methyl o-methoxybenzoate. Figure 5 The MS graph at 21 min is for the by-product (3,3,5-trimethylcyclohexyl)-2-methoxybenzoate. Combined with the internal standard method, the quantitative analysis results are as follows: 19.84% residual methyl salicylate, 10.46% residual isophorol, 57.12% HMS content, 0.5% methanol content, 2.3% methyl o-anisyl ester content, 3.1% (3,3,5-trimethylcyclohexyl)-2-methoxybenzoate content. The catalyst was removed by acid washing and alkali washing, and the reaction solution was distilled to finally obtain 328.45 g of original membrane ester, with a HMS yield of 73.58%, a total content (GC) of 95.3%, 0.2% methyl o-anisyl benzoate content, and 4.6% (3,3,5-trimethylcyclohexyl)-2-methoxybenzoate content.

[0077] When a conventional batch reactor reaction is used, in order to achieve a certain conversion rate, a higher reaction temperature and a longer reaction time are required, and the reaction will produce more by-products, methyl o-methoxybenzoate and (3,3,5-trimethylcyclohexyl)-2-methoxybenzoate, especially (3,3,5-trimethylcyclohexyl)-2-methoxybenzoate, which is not easy to remove by distillation. However, the microchannel continuous flow process of the present invention basically does not produce these two by-products.

Claims

1. A method for preparing raw film bulk ester using a microchannel continuous flow reactor, characterized in that: include: The salicylic acid ester and isophorol are mixed and preheated, and then introduced into a microchannel continuous flow reactor with an ester exchange catalyst for reaction, and after the reaction is completed, the original film loose ester is obtained through post-treatment; The microchannel continuous flow reactor comprises one or N reaction units connected in series, each reaction unit is formed by connecting a microchannel reactor and a falling film evaporator in series, and the byproduct methanol in each reaction unit is removed in the falling film evaporator; The salicylate is methyl salicylate; Among them, 2≤N≤10.

2. The method for preparing raw film bulk ester using a microchannel continuous flow reactor according to claim 1, characterized in that: The number of the reaction units connected in series is 3 to 6.

3. The method for preparing raw film bulk ester using a microchannel continuous flow reactor according to claim 1, characterized in that: The temperature of the mixed preheating is 80℃~100℃; The reaction temperature in the microchannel reactor is also 80°C to 100°C.

4. The method for preparing raw film bulk ester using a microchannel continuous flow reactor according to claim 1, characterized in that: The reaction pressure is -0.01MPa~-0.05MPa.

5. The method for preparing raw film bulk ester using a microchannel continuous flow reactor according to claim 1, characterized in that: The reaction materials stay in the microchannel reactor for 0.5 min to 20 min.

6. The method for preparing raw film bulk ester using a microchannel continuous flow reactor according to claim 1, characterized in that: The flow rate of the isophorol is 5 g / min to 200 g / min, and the flow rate of the salicylate is 5 g / min to 300 g / min.

7. The method for preparing raw film bulk ester using a microchannel continuous flow reactor according to claim 1, characterized in that: The transesterification catalyst is a combination of one or more of an acidic catalyst, a basic catalyst, organic titanium and organic tin.

8. The method for preparing raw film bulk ester using a microchannel continuous flow reactor according to claim 7, characterized in that: The acidic catalyst is sulfuric acid or p-toluenesulfonic acid; The alkaline catalyst is sodium methoxide; The organic tin is one or more of dibutyltin oxide, methylphenyltin oxide, tetraethyltin, dibutyltin diacetate or diphenyltin dilaurate.

9. The method for preparing raw film bulk ester using a microchannel continuous flow reactor according to claim 1, characterized in that: The molar ratio of the isophorol to the salicylic acid ester is 1:1-3; The molar ratio of the catalyst to the salicylic acid ester is 0.01% to 10%:

1.

10. The method for preparing raw film bulk ester using a microchannel continuous flow reactor according to claim 1, characterized in that: The hydraulic radius of the microchannel in the microchannel reactor is 0.1mm-1.0mm, the length of the microchannel is 100m-200m, and the microchannel structure of the microchannel reactor is an enhanced mixing heart-shaped structure, a Z-shaped structure, a T-shaped structure, a T-shaped structure with a wave or a convex ridge chaotic structure.

Images