Application of Micromixer in Methyl Mercaptoacetate Synthesis Application of Micromixer in Methyl Mercaptoacetate Synthesis

Introduction Introduction

Methyl thioglycolate is a class of sulfur-containing functional fine chemical intermediates. The highly active sulfhydryl group (-SH) in the molecule endows it with excellent coordination, addition and chain transfer characteristics, and is widely used in the synthesis of pharmaceutical intermediates, pesticide creation, food and tobacco flavor preparation, polymer additives and other fields. In the field of polymer materials, this product can be used as the core raw material of PVC organotin heat stabilizer and polymer molecular weight precision regulator; its multi-component esterified derivatives can achieve low temperature and rapid curing of epoxy resins, and are the key supporting raw materials for the preparation of optical lenses, precision adhesives, and flexible composites. Downstream high-end application scenarios have strict standards for product purity, sulfur impurity content, and color stability. Methyl thioglycolate is a kind of functional fine chemical intermediates containing sulfur. The highly active sulfhydryl group (-SH) in the molecule endows it with excellent coordination, addition and chain transfer characteristics, and is widely used in the synthesis of pharmaceutical intermediates, pesticide creation, food and tobacco flavor preparation, polymer auxiliary preparation and other fields. In the field of polymer materials, this product can be used as the core raw material of PVC organotin heat stabilizer and polymer molecular weight precision regulator; its multi-component esterified derivatives can achieve low temperature and rapid curing of epoxy resins, and are the key supporting raw materials for the preparation of optical lenses, precision adhesives, and flexible composites. Downstream high-end application scenarios have strict standards for product purity, sulfur impurity content, and color stability.

The research on thioglycolic acid and its derivatives in our country started in the 1970s. Compared with the mature refined synthesis systems in Europe, America and Japan, the overall technical accumulation is weak and the industrialization process is lagging behind. Domestic industrialization has long relied on the traditional sulfuric acid catalytic batch kettle esterification process. This process has outstanding problems such as long reaction cycle, low raw material conversion rate, strong corrosion equipment of concentrated sulfuric acid, large discharge of three waste acid waste liquid, and large fluctuations in batch product quality. Limited by process conditions, the domestic production capacity of high-end thioglycolic acid methyl ester with low impurities and high purity is insufficient, and the high-end market has long relied on imports, which has become a key bottleneck restricting the high-end and localization of fine sulfur-containing intermediates in our country. Therefore, the development of a new type of efficient, green controllable, and high-yield continuous synthesis process is an inevitable trend in the upgrading of the methyl thioglycolate industry, and the micro-hybrid microfluidic process enhancement technology provides a feasible technological breakthrough for this. The research on thioglycolic acid and its derivatives in our country started in the 1970s. Compared with the mature refined synthesis systems in Europe, America and Japan, the overall technical accumulation is weak and the industrialization process is lagging behind. Domestic industrialization has long relied on the traditional sulfuric acid catalytic batch kettle esterification process, which has outstanding problems such as long reaction cycle, low raw material conversion rate, strong corrosion equipment of concentrated sulfuric acid, large discharge of three waste acid waste liquids, and large fluctuations in the quality of batches of products. Due to the limitation of process conditions, the domestic production capacity of high-end thioglycolate methyl ester with low impurities and high purity is insufficient, and the high-end market relies on imports for a long time, which has become a key bottleneck restricting the high-end and localization of fine sulfur-containing intermediates in our country. Therefore, the development of a new type of efficient, green controllable and high-yield continuous synthesis process is an inevitable trend for the upgrading of the thioglycolate methyl ester industry, and the micro-hybrid microfluidic process enhancement technology provides a feasible technological breakthrough for this.

Research progress of 1-thioglycolate methyl ester and the inherent defects of traditional processes Research progress of 1-thioglycolate methyl ester and the inherent defects of traditional processes

Domestic industry-university-research institutions have gradually completed the basic synthesis technology of methyl thioglycolate and downstream industrialization verification, and realized the localization and mass production of basic categories. Anhui Fengle Agrochemical has achieved stable synthesis of methyl thioglycolate and successfully applied it to the industrial production of thiophenesulfuron herbicide, improving the supporting industrial chain of pesticide intermediates; Guizhou Institute of Chemical Industry and Yisheng Fine Chemical have relied on this intermediate to synthesize 3-carbonyl-2-methylhydrothiophenecarboxylate methyl ester, 4-carbonyl-2-tetrahydrothiophenecarboxylate methyl ester and other high-end fragrance monomers, filling the production gap of some domestic fine fragrance raw materials, verifying the application potential of this intermediate in the field of high-end fine chemicals. Domestic industry-university-research institutions have gradually completed the basic synthesis technology of methyl thioglycolate and downstream industrialization verification, and realized the localization and mass production of basic categories. Anhui Fengle Agrochemical has achieved stable synthesis of methyl thioglycolate and successfully applied it to the industrial production of thiophenesulfuron herbicide, improving the supporting industrial chain of pesticide intermediates; Guizhou Institute of Chemical Industry and Yisheng Fine Chemical have relied on this intermediate to synthesize 3-carbonyl-2-methylhydrothiophenecarboxylate methyl ester, 4-carbonyl-2-tetrahydrothiophenecarboxylate methyl ester and other high-end fragrance monomers, filling the production gap of some domestic fine fragrance raw materials, verifying the application potential of this intermediate in the field of high-end fine chemicals.

However, from the perspective of mainstream industrial processes, the domestic methylthioglycolate production system is highly monolithic, and the core process is always the batch esterification synthesis process of thioglycolic acid and methanol catalyzed by concentrated sulfuric acid. This process has low threshold and low equipment investment, but there are underlying technical defects that are difficult to cure, which is not a simple problem of extensive operation. First, the esterification reaction is a typical reversible equilibrium reaction. The traditional kettle system has serious material backmixing, the product and water cannot be separated from the reaction system in time, the equilibrium forward movement is limited, and the raw material conversion rate and product yield are difficult to improve. Second, the homogeneous catalytic system of concentrated sulfuric acid is highly corrosive, and the reaction kettle, stirring and heat exchange equipment are eroded for a long time, resulting in high equipment operation and maintenance costs and serious depreciation losses. Third, the thermal stability of the system containing thiol functional groups is poor, and the long-term high temperature intermittent reaction can easily lead to side reactions such as thiol oxidation, coupling, and lactation, and the accumulation of impurities is serious, which cannot meet the purity requirements of high-end products. Fourth, the intermittent production mode has many human interventions, poor process parameter controllability, and weak product batch stability, making it difficult to adapt to the standardized production requirements of high-end new materials and pharmaceutical-grade Overall, the traditional batch process has been unable to adapt to the development trend of green, fine, and high-end fine chemicals, and the process iterative upgrade is imminent. However, from the perspective of mainstream industrial processes, the domestic production system of methyl thioglycolate is highly single, and the core process is always the batch esterification synthesis process of thioglycolic acid and methanol catalyzed by concentrated sulfuric acid. The process has low thresholds and low equipment investment, but there are underlying technical defects that are difficult to cure, which is not a simple problem of extensive operation. First, the esterification reaction is a typical reversible equilibrium reaction. The traditional kettle system has serious material backmixing, the product and water cannot be separated from the reaction system in time, the equilibrium forward movement is limited, and the raw material conversion rate and product yield are difficult to improve. Second, the homogeneous catalytic system of concentrated sulfuric acid is highly corrosive, and the reaction kettle, stirring and heat exchange equipment are eroded for a long time, resulting in high equipment operation and maintenance costs and serious depreciation losses. Third, the thermal stability of the system containing thiol functional groups is poor, and the long-term high temperature intermittent reaction can easily lead to side reactions such as thiol oxidation, coupling, and lactation, and the accumulation of impurities is serious, which cannot meet the purity requirements of high-end products. Fourth, the intermittent production mode has many human interventions, poor process parameter controllability, and weak product batch stability, making it difficult to adapt to the standardized production requirements of high-end new materials and pharmaceutical-grade Overall, the traditional batch process has been unable to adapt to the development trend of green, fine, and high-end fine chemicals, and the process iterative upgrade is imminent.

2 Micromixer Structure Characteristics and Esterification Reaction Strengthening Bottom 2 Micromixer Structure Characteristics and Esterification Reaction Strengthening Bottom

The micro-mixer is the core pre-strengthening unit of the microfluidic chemical system. It relies on the precision micro-machining process to build a micron-level three-dimensional flow channel structure, which is specially designed to solve the mass transfer shortcomings of the micro-scale reaction system. It is an independent process strengthening equipment that is different from ordinary micro-channel reactors. According to the driving mode, it can be divided into active and passive types. Among them, the passive micro-mixer has no external drive energy consumption, no mechanical moving parts, stable operation, and is suitable for continuous industrial production. It has become the mainstream application type of fine esterification reaction. Its core working principle is to rely on the special bending, shunting, converging, and shearing flow channel geometric structure, and use the flow characteristics of the fluid itself to achieve rapid tearing, folding, and layered mixing of multiple strands of materials, so as to solve the problem of microscale fluid The micromixer is the core pre-strengthening unit of the microfluidic chemical system. It relies on the precision micromachining process to build a micron-level three-dimensional flow channel structure, which is specially designed to solve the mass transfer shortcomings of the microscale reaction system. It is an independent process strengthening equipment that is different from ordinary microchannel reactors. According to the driving method, it can be divided into active and passive types. The passive micromixer has no external drive energy consumption, no mechanical moving parts, stable operation, and is suitable for continuous industrial production. It has become the mainstream application type of fine esterification reaction. Its core working principle is to rely on the special bending, shunting, converging, and shearing flow channel geometry structure, and use the flow characteristics of the fluid itself to achieve rapid tearing, folding, and layered mixing of multiple strands of materials, thus solving the problem of microscale fluid mixing from the structural level.

There are essential differences in the hydrodynamic characteristics between the micro-scale system and the macro-kettle system, which is also the core reason why the micro-mixer can achieve process dimensionality reduction and efficiency. The macro-reactor can rely on high Reynolds number turbulence to achieve rapid homogeneous mixing, while the internal characteristic size of the microchannel is greatly reduced, the fluid Reynolds number is extremely low, it is always in a stable laminar flow state, and there is no turbulent disturbance ability. Fluid mixing is completed only by low-speed molecular diffusion. The mixing efficiency is extremely low, the local concentration layer difference is large, and it is prone to problems such as local catalyst enrichment and raw material ratio imbalance, which seriously restricts the esterification reaction rate and selectivity. The core value of the micromixer is to break the limit of laminar diffusion of microchannels, reconstruct the fluid flow state through the flow channel structure, change the fluid friction coefficient and flow transition interval, and achieve rapid homogeneous mixing of turbulent flow under low Reynolds number laminar flow conditions. The traditional second-level and minute-level molecular diffusion mixing is compressed to the millisecond level to achieve accurate material proportions and instantaneous homogeneous contact. There are essential differences in the hydrodynamic characteristics of the microscale system and the macroscopic kettle system, which is also the core reason why the micromixer can achieve process dimensionality reduction and efficiency. The macroscopic reactor can achieve rapid homogeneous mixing by relying on high Reynolds number turbulence, while the internal characteristic size of the microchannel is greatly reduced, the fluid Reynolds number is extremely low, it is always in a stable laminar flow state, and there is no turbulent disturbance ability. Fluid mixing is completed only by low-speed molecular diffusion. The mixing efficiency is extremely low, the local concentration layer difference is large, and the local catalyst enrichment and raw material ratio imbalance are very easy to occur, which seriously restricts the esterification reaction rate and selectivity. The core value of the micromixer is to break the limit of laminar diffusion of microchannels, reconstruct the fluid flow state through the flow channel structure, change the fluid friction coefficient and flow transition interval, and achieve rapid homogeneous mixing of turbulent flow under low Reynolds number laminar flow conditions. The traditional second-level and minute-level molecular diffusion mixing is compressed to the millisecond level to achieve accurate material proportions and instantaneous homogeneous contact.

At present, the micro-mixing strengthening technology has been widely verified in various esterification reactions, and has the ability to improve quality and efficiency universally. Existing studies have shown that the micro-structure mixing system can increase the yield of short URL esters to more than 97%, which can increase the traditional esterification reaction rate by more than 50 times. Partial aromatic ester synthesis can achieve nearly 100% conversion and greatly compress the reaction time. A large number of studies have confirmed that the esterification reaction is highly sensitive to the uniformity of material mixing, and local material unevenness can easily lead to side reactions and reduce reaction selectivity. The extreme mass transfer strengthening ability of the micro-mixer can accurately adapt the reaction characteristics of the esterification reaction, providing excellent process adaptation conditions for easy side reactions and highly sensitive sulfur-containing esterification systems such as mercaptoacetate methyl esters. At present, the micro-mixing strengthening technology has been widely verified in various esterification reactions, and it has the ability to improve quality and efficiency universally. Existing studies have shown that the pico-structure mixing system can increase the yield of short URL esters to more than 97%, which can increase the traditional esterification rate by more than 50 times. Partial aromatic ester synthesis can achieve nearly 100% conversion and greatly compress the reaction time. A large number of studies have confirmed that the esterification reaction is highly sensitive to the uniformity of material mixing, and local material unevenness can easily lead to side reactions and reduce reaction selectivity. The extreme mass transfer strengthening ability of the micro-mixer can accurately adapt the reaction characteristics of the esterification reaction, providing excellent process adaptation conditions for easy side reactions and highly sensitive sulfur-containing esterification systems such as methyl mercaptoacetate.

Iterative Application and Microscopic Mechanism Innovation of

3 Micromixer in Synthesis of Methyl Mercaptoacetate

3 Iterative Application and Microscopic Mechanism Innovation of Micromixer in Synthesis of Methyl Mercaptoacetate

Domestic research on the synthesis of thioglycolate methyl ester by microfluidic technology has completed the technical iteration from "single microchannel reaction" to "pre-micromixing enhanced coupling reaction", which completely fills the mass transfer shortcomings of the early microchannel process. Jia Shaoming's team took the lead in using a single-pump premixed-capillary microchannel reaction system, verifying that the microscale reaction can greatly compress the esterification reaction time and improve the reaction efficiency, proving the feasibility of microfluidic technology in the synthesis of thioglycolate methyl ester. However, the process adopts a single-pump unified feed, the mixing accuracy of the premixing process is insufficient, there are problems such as macroscopic material stratification and local ratio deviation, and there are still mass transfer lag defects in the microchannel. The process strengthening effect is limited, and the technical advantages of the microreaction system cannot be fully exerted. Domestic research on the synthesis of methylthioglycolate by microfluidic technology has completed the technical iteration from "single microchannel reaction" to "pre-micromixing enhanced coupling reaction", which completely makes up for the mass transfer shortcomings of the early microchannel process. Jia Shaoming's team took the lead in using a single-pump premixed-capillary microchannel reaction system, verifying that the microscale reaction can greatly compress the esterification reaction time and improve the reaction efficiency, proving the feasibility of microfluidic technology in the synthesis of methylthioglycolate. However, the process uses a single-pump unified feed, the mixing accuracy of the premixing process is insufficient, there are problems such as macro-material stratification and local ratio deviation, and there are still defects in mass transfer hysteresis within the microchannel. The process strengthening effect is limited, which cannot give full play to the technical advantages of the microreaction system.

On this basis, the Niu Berlin team completed the key process optimization and device upgrade, and built the Niu Berlin team to complete the key process optimization and device upgrade on this basis, and built a new continuous chemical process system of double pump independent precision feeding + micro-mixer pre-homogenization + capillary continuous reaction double pump independent precision feeding + micro-mixer pre-homogenization + capillary continuous reaction . The core innovation of this process is the new continuous chemical process system realized. The core innovation of this process is to realize the decoupling and grading of the mixing process and the reaction process. The decoupling and grading of the mixing process and the reaction process , abandons the traditional mode of reaction while mixing, and first completes the global millisecond homogenization of thioglycolic acid, methanol, and p-toluenesulfonic acid catalysts through a micro-mixer, eliminating the problems of uneven distribution of the concentration layer and catalyst in the system, and then sending the homogeneous material into the micro-channel constant temperature to complete the esterification reaction, avoiding the problem of local reaction imbalance and multiple side reactions from the source., Abandoning the traditional mode of reaction while mixing, first completes the global millisecond homogenization of thioglycolic acid, methanol, and p-toluenesulfonic acid catalysts through a micro-mixer, eliminating the concentration layer and catalyst distribution of the Problems such as unevenness, and then the homogeneous material is sent into the microchannel at constant temperature to complete the esterification reaction, which avoids the problems of local reaction imbalance and multiple side reactions from the source.

The controlled experiment data under different pipe diameters and different working conditions intuitively confirms the irreplaceability of the micro-mixer. Under the 0.6mm fine pipe diameter capillary tube and the standard working condition of constant temperature at 60 ° C, when the micro-mixer is strengthened without micro-mixer, the system relies on natural molecular diffusion mixing, the material contact is uneven, the reaction is limited, and the product yield is only 86.2%; after the pre-strengthening of the micro-mixer is installed, the material mixing accuracy is greatly improved, the catalytic reaction is more sufficient, the product yield is significantly increased to 91.0%, and the single working condition yield is increased by 4.8 percentage points. The effect of quality improvement and efficiency is extremely outstanding. At the same time, the experiment shows that the micro-channel system with fine pipe diameter has stronger adaptability to micro-mixing strengthening, and the mixing efficiency is more stable, which provides a core experimental basis for industrial optimization of pipe diameter parameters. The controlled experiment data under different pipe diameters and different working conditions directly confirm the irreplaceability of the micro-mixer. Under the standard working conditions of 0.6mm fine pipe diameter capillary tube and constant temperature at 60 ° C, when there is no micro-mixer strengthening, the system relies on natural molecular diffusion mixing, the material contact is uneven, the reaction is limited, and the product yield is only 86.2%; after the pre-strengthening of the micro-mixer is installed, the material mixing accuracy is greatly improved, the catalytic reaction is more sufficient, the product yield is significantly increased to 91.0%, and the single working condition yield is increased by 4.8 percentage points, and the quality and efficiency improvement effect is extremely outstanding. At the same time, the experiments show that the micro-channel system with fine pipe diameter has stronger adaptability to micro-mixing strengthening, and the mixing synergy is more stable, which provides a core experimental basis for industrial optimization of pipe diameter parameters.

In-depth analysis from the microscopic reaction mechanism level, the strengthening logic of the micromixer for the esterification of methyl thioglycolate is unique and targeted. The esterification of thioglycolate is an acid-catalyzed addition-elimination reversible reaction, and the reaction rate is highly dependent on the contact efficiency of the reactants and the utilization rate of the catalytic activity check point. In the traditional microchannel laminar diffusion blending mode, the material mixing lags behind, the methanol concentration in some areas is insufficient, the catalyst distribution is sparse, and the main reaction advances slowly; the local enrichment of acid catalysts in some areas initiates side reactions such as thioglycolyl group oxidation and lactone, which restricts the yield and purity of the product in both directions. On the one hand, it maximizes the contact efficiency between raw materials and catalysts and accelerates the kinetic rate of the main reaction; on the other hand, it eliminates the problem of local over-catalysis, precisely inhibits sulfur-containing side reactions, and realizes the multiple positive effects of "rate increase, yield increase, and impurity suppression". This is a precise regulation advantage that cannot be achieved by traditional kettle process and pure microchannel process. From the in-depth analysis of the microscopic reaction mechanism, the strengthening logic of the micromixer for the esterification of thioglycolate methyl ester is unique and targeted. The esterification of thioglycolate is an acid-catalyzed addition-elimination reversible reaction, and the reaction rate is highly dependent on the contact efficiency of the reactants and the utilization rate of the catalytic activity check point. In the traditional microchannel laminar diffusion blending mode, the material mixing lags behind, the methanol concentration in some areas is insufficient, the catalyst distribution is sparse, and the main reaction advances slowly; the local enrichment of acid catalysts in some areas initiates side reactions such as sulfhydryl group oxidation and lactone, which restricts the yield and purity of the product in both directions. The micromixer realizes the homogeneous matching of materials in the whole area through flow field reconstruction. On the one hand, it maximizes the contact efficiency of raw materials and catalysts and accelerates the kinetic rate of the main reaction. On the other hand, it eliminates the problem of excessive local catalysis, precisely inhibits the sulfur-containing side reactions, and realizes the multiple positive effects of "rate increase, yield increase, and impurity suppression", which is a precision control advantage that cannot be achieved by the traditional kettle process and pure microchannel process.

4 Technical barriers and industrial application value of micro-mixing strengthening process 4 Technical barriers and industrial application value of micro-mixing strengthening process

Compared with the traditional batch process and the ordinary micro-channel process, the pre-mixed micro-coupling system forms a unique technical barrier, which precisely solves the core pain points of the industrialization of thioglycolate methyl ester. The shortcomings of the traditional process are uneven macro-mixing, long reaction cycle, uncontrolled side reactions, and large amount of three wastes; the shortcomings of the ordinary micro-channel process are slow laminar diffusion mixing, poor adaptability to feed fluctuations, and insufficient stability of working conditions; while the micro-mixing strengthening process perfectly makes up for the defects of the two types of processes. Relying on the advantages of millisecond-level precise mixing, no concentration layer, and controllable parameters, the stability and controllability of the reaction system are greatly improved. At the same time, the process uses p-toluenesulfonic acid instead of concentrated sulfuric acid, and combines micro-mixed homogeneous catalysis to further reduce the risk of equipment corrosion and side reactions, and realize green catalytic production. Compared with the traditional batch process and the ordinary micro-channel process, the pre-mixed micro-coupling system forms a unique technical barrier, accurately solving the core pain point of the industrialization of thioglycolate methyl ester. The shortcomings of the traditional process are uneven macro mixing, long reaction cycle, runaway side reactions, and large amount of three wastes; the shortcomings of the ordinary micro-channel process are slow laminar diffusion mixing, poor adaptability to feed fluctuations, and insufficient stability of working conditions; while the micro-mixing strengthening process perfectly makes up for the defects of the two types of processes, relying on the advantages of millisecond-level precise mixing, no concentration layer, and controllable parameters, which greatly improves the stability and controllability of the reaction system. At the same time, the process uses p-methylbenzenesulfonic acid instead of concentrated sulfuric acid, coupled with micro-mixed homogeneous catalysis to further reduce the risk of equipment corrosion and side reactions, and realize green catalytic production.

From the perspective of industrialization, the micro-mixing and strengthening continuous chemical process has a strong industrial advantage. First, the amplification effect of the process is small, and the mass transfer enhancement effect of micro-mixing is reproducible. The laboratory test data can be smoothly amplified to the industrial device to avoid the problems of efficiency attenuation and quality fluctuation in the traditional process of amplification. Second, the intrinsic safety is high, the liquid holding capacity of the microsystem is extremely low, and the online storage of high-risk sulfur-containing materials is small, which completely solves the safety hazards of oxidation and polymerization in traditional high-temperature long-term reactions. Third, the green and low-carbon advantages are outstanding, with improved raw material utilization, reduced by-products, and no need for a large number of pickling and washing processes. The emission of three wastes is greatly reduced, which is suitable for the current chemical safety and environmental protection control requirements. Fourth, the product quality is upgraded, and the precise and controllable mild reaction environment can greatly reduce sulfur-containing impur From the perspective of industrialization, micro-mixing and strengthening continuous chemical technology has strong industrialization advantages. First, the amplification effect of the process is small, and the mass transfer enhancement effect of micro-mixing is reproducible. The laboratory test data can be smoothly amplified to the industrial device to avoid the problems of efficiency attenuation and quality fluctuation in the traditional process of amplification. Second, the intrinsic safety is high, the liquid holding capacity of the microsystem is extremely low, and the online storage of high-risk sulfur-containing materials is small, which completely solves the safety hazards of oxidation and polymerization in traditional high-temperature long-term reactions. Third, the green and low-carbon advantages are outstanding, with improved raw material utilization, reduced by-products, and no need for a large number of pickling and washing processes. The emission of three wastes is greatly reduced, which is suitable for the current chemical safety and environmental protection control requirements. Fourth, the product quality is upgraded, and the precise and controllable mild reaction environment can greatly reduce sulfur-containing impur Translate: Break import dependence.

Conclusion

The traditional batch esterification process of methylthioglycolate is restricted by multiple factors such as mixing efficiency, reaction balance, uncontrolled side reactions, and equipment corrosion. There are long-term industry problems such as low yield, poor quality, heavy pollution, and high cost. As the core mass transfer enhancement equipment of the microfluidic system, the micromixer can specifically solve the core problems such as low efficiency of microscale laminar mixing, uneven material, and catalytic imbalance. Through the process mode of pre-homogeneous mixed coupling microchannel continuous reaction, the yield of thioglycolate methyl ester products is significantly improved, and the sulfur-containing side reactions are effectively inhibited, so as to improve product purity and batch stability. The technology is simple in process, highly controllable, green and efficient, and has high industrial adaptability. It breaks through the bottleneck of traditional production technology and provides a new technical path for the continuous, green and domestic mass production of high-quality thioglycolate methyl ester. It has important theoretical value and engineering application value for promoting the high-end and fine upgrading of the domestic sulfur-containing fine intermediate industry. The traditional batch esterification process of thioglycolate methyl ester is restricted by multiple factors such as mixing efficiency, reaction balance, uncontrolled side reactions, and equipment corrosion. There are long-term industry problems of low yield, poor quality, heavy pollution and high cost. As the core mass transfer enhancement equipment of the microfluidic system, the micromixer can specifically solve the core problems such as low efficiency of micro-scale laminar flow mixing, uneven material, and catalytic imbalance. Through the process mode of pre-homogeneous mixed coupling microchannel continuous reaction, the yield of thioglycolate methyl ester products is significantly improved, the sulfur-containing side reactions are effectively inhibited, and the product purity and batch stability are improved. The technology is simple, highly controllable, green and efficient, and has high industrial adaptability. It breaks through the bottleneck of traditional production technology and provides a new technical path for the continuous, green, and localized mass production of high-quality thioglycolate methyl ester. It has important theoretical value and engineering application value for promoting the high-end and fine upgrading of the domestic sulfur-containing fine intermediate industry.

References References

[1] Yu Yijun, Shi De. Pesticide Application Daquan [M]. Agricultural Press, 2008. [1] Yu Yijun, Shi De. Pesticide Application Daquan [M]. Agricultural Press, 2008.

[2] Shepherd. Robin Gerald. Intermediates for Drugs and Sweet-eners. EurPat. 344.983 GBAppl88/12,718. [2] Shepherd. Robin Gerald. Intermediates for Drugs and Sweet-eners. EurPat. 344.983 GBAppl88/12,718.

Zhao Aiming. Catalyst for methyl thioglycolate reaction [D]. Jiangnan University, 2009. Zhao Aiming. Catalyst for methyl thioglycolate reaction [D]. Jiangnan University, 2009.

[4] Lin Changzhi. Synthesis of methyl thioglycolate [J]. Anhui Chemical Industry, 2004, 30 (3): 26-27. [4] Lin Changzhi. Synthesis of methyl thioglycolate [J]. Anhui Chemical Industry, 2004, 30 (3): 26-27.

[5] Ye Xingxing, Mansur EHA, Wang Yundong, et al. Research progress of micro-mixing technology [J]. Chemical Industry Progress, 2007, 26 (6): 755-761. [5] Ye Xingxing, Mansur EHA, Wang Yundong, et al. Research progress of micro-mixing technology [J]. Chemical Industry Progress, 2007, 26 (6): 755-761.

Du Dongxing. Effects of compressibility and roughness on flow and heat transfer characteristics in microtubes [D]. Beijing: Tsinghua University, 2000. [6] Du Dongxing. Effects of compressibility and roughness on flow and heat transfer characteristics in microtubes [D]. Beijing: Tsinghua University, 2000.

[7] Yao X, Yao J, Zhang L, et al. Fast Esterification of Acetic Acids with Short Chain Alcohols in Microchannel Reactors [J]. Catalysis Letters, 2009, 132 (1-2): 147-152. [7] Yao X, Yao J, Zhang L, et al. Fast Esterification of Acetic Acids with Short Chain Alcohols in Microchannel Reactors [J]. Catalysis Letters, 2009, 132 (1-2): 147-152.

[8] Brivio M, Oosterbroek R E, Verboom W, et al. Surface effects in the esterification of 9-pyrenebutyric acid within a glass micro reactor. [J]. Chemical Communications, 2003, 2003 (15): 1924-5. [8] Brivio M, Oosterbroek R E, Verboom W, et al. Surface effects in the esterification of 9-pyrenebutyric acid within a glass micro reactor. [J]. Chemical Communications, 2003, 2003 (15): 1924-5.

[9] Benitolopez F, Tiggelaar R M, Salbut K, et al. Substantial rate enhancements of the esterification reaction of phthalic anhydride with methanol at high pressure and using supercritical CO2 as a co-solvent in a glass microreactor. [J]. Lab on A Chip, 2007, 7 (10): 1345-51. [9] Benitolopez F, Tiggelaar R M, Salbut K, et al. Substantial rate enhancements of the esterification reaction of phthalic anhydride with methanol at high pressure and using supercritical CO2 as a co-solvent in a glass microreactor. [J]. Lab on A Chip, 2007, 7 (10): 1345-51.

[10] Wiles C, Watts P, Haswell S J, et al. Solution phase synthesis of esters within a micro reactor [J]. Tetrahedron, 2003, 59 (51): 10173-10179. [10] Wiles C, Watts P, Haswell S J, et al. Solution phase synthesis of esters within a micro reactor [J]. Tetrahedron, 2003, 59 (51): 10173-10179.

Jia Shaoming, Li Yafang, Zhao Jianhong, et al. Application of microstructure reactor in synthesis of methyl thioglycolate [J]. Advances in Chemical Engineering, 2011 (S1): 56-58. [11] Jia Shaoming, Li Yafang, Zhao Jianhong, et al. Application of microstructure reactor in synthesis of methyl thioglycolate [J]. Advances in Chemical Engineering, 2011 (S1): 56-58.

Jia Shaoming. Application of microstructure reactor in synthesis of methyl thioglycolate [D]. Zhengzhou University, 2012. [12] Jia Shaoming. Application of microstructure reactor in synthesis of methyl thioglycolate [D]. Zhengzhou University, 2012.

[13] Niu Berlin, Jia Shaoming, Li Yafang, et al. Rapid synthesis of methyl thioglycolate in a microchannel reactor [J]. Journal of Nanjing University of Technology: Natural Science Edition, 2013, 35 (2): 36-40. [13] Niu Berlin, Jia Shaoming, Li Yafang, et al. Rapid synthesis of methyl thioglycolate in a microchannel reactor [J]. Journal of Nanjing University of Technology: Natural Science Edition, 2013, 35 (2): 36-40.

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