Method for continuously synthesizing diethyl oxalate by microreactor

Abstract

The invention discloses a method for continuously synthesizing diethyl oxalate by a microreactor, which belongs to the field of organic chemical synthesis, and comprises the following steps: dissolving oxalic acid and a catalyst in ethanol to form a reaction material, conveying the reaction material to a tubular reactor I, sequentially passing through a cooling pipe and a molecular sieve filler pipe, and then conveying into a tubular reactor II, collecting reaction liquid; the method realizes rapid and continuous synthesis without metal catalysis, and is low in cost, short in reaction time, simple to operate, safe, efficient and suitable for industrial production.

Description

Technical Field

[0001] The invention relates to the field of organic chemical synthesis, and in particular to a method for synthesizing diethyl oxalate using a micro-reaction technology. Background Art

[0002] As an environmentally friendly organic solvent, diethyl oxalate is widely used in resin, coating, ink, glue, paint and other industries. Its synthesis methods mainly include traditional esterification and carbon monoxide catalytic oxidative coupling.

[0003] The traditional esterification process has a long production cycle and high unit consumption. Non-patent document 1 adopts two steps. First, by increasing the reaction pressure (101.3kpa to 243.1kpa), the reaction is carried out at 100℃ to 110℃ for 1 to 1.5 hours, and the esterification process reaches a dynamic equilibrium with a conversion rate of 50.23% to 56.2%. In the second step, the esterification reaction is carried out at normal pressure for 6 hours, and the one-way conversion rate of oxalic acid reaches more than 90%. The total esterification process time is about 8 hours.

[0004] Non-patent document 2 adopts a carbon monoxide catalytic oxidative coupling method, and the optimal process parameters are: temperature 90°C to 130°C, residence time 1.5s to 3s, pressure 100kpa to 300kpa, molar concentration of ethyl nitrite 10% to 20%, molar concentration of carbon monoxide 20% to 30%, and space-time yield of diethyl oxalate 578g / (L·h).

[0005] Patent document 1 (CN 106542997 A) proposes the synthesis of diethyl oxalate by catalysis of modified graphene, wherein hydroxylated graphene oxide is added to a reactor for synthesizing diethyl oxalate before the reaction, the reaction temperature is 120°C, and the reaction is carried out until no water is discharged, and the yield of the target product is 99.1%.

[0006] In order to improve reaction efficiency and shorten reaction time, metal catalysts are more often used. The process conditions are relatively harsh, with high temperature and high pressure, and the requirements for industrial production are high.

[0007] Non-patent literature 1: Zhang Tianyi. Process optimization for the synthesis of diethyl oxalate [D]. Beijing University of Chemical Technology, 2000, pp. 31-56.

[0008] Non-patent document 2: Wang Mingyu. Macrokinetic study on the synthesis of diethyl oxalate by low-pressure gas-phase catalytic coupling of CO [D]. Tianjin University, 2008, pp. 24-41.

[0009] The above contents are only used to assist in understanding the technical solution of the present invention and do not constitute an admission that the above contents are prior art. Summary of the invention

[0010] The main purpose of the present invention is to provide a method for continuously synthesizing diethyl oxalate using a microreactor, and the introduction of a molecular sieve filler tube can continuously adsorb water generated in the reaction, so that the reaction proceeds in the direction of the product, greatly improving the reaction yield, avoiding operations such as azeotropic dehydration, and effectively improving production efficiency.

[0011] To achieve the above object, the present invention provides a method for continuously synthesizing diethyl oxalate in a microreactor, comprising the following steps:

[0012] Oxalic acid and a catalyst are dissolved in ethanol to form a reaction mass, the reaction mass is transported to a tubular reactor I, and sequentially passes through a cooling tube and a molecular sieve packing tube, and then is transported to a tubular reactor II, and the reaction liquid is collected;

[0013] The molar ratio of oxalic acid to catalyst is 1:(0.1-0.6); the concentration of oxalic acid in ethanol is 20 mg / mL-100 mg / mL;

[0014] The catalyst is selected from one of concentrated sulfuric acid or p-toluenesulfonic acid;

[0015] The temperature of the tubular reactor I is 60°C to 120°C;

[0016] The temperature of tubular reactor II is 60°C to 120°C;

[0017] The residence time of the reaction materials in the tubular reactor I is 6 min to 35 min, preferably 12.56 min;

[0018] The residence time of the reaction material in the cooling tube is 2 min;

[0019] The residence time of the reaction materials in the tubular reactor II is 6 min to 35 min, preferably 12.56 min;

[0020] The inner diameter of the tubular reactor I is 0.4 mm to 3 mm, and the liquid holding capacity is 10 mL to 40 mL;

[0021] The inner diameter of the cooling tube is 0.4mm to 3mm;

[0022] The molecular sieve in the molecular sieve packing tube is

[0023] The inner diameter of the tubular reactor II is 0.4 mm to 3 mm, and the liquid holding capacity is 10 mL to 40 mL;

[0024] The material of the tubular reactor I is polytetrafluoroethylene or stainless steel;

[0025] The cooling tube is made of polytetrafluoroethylene or stainless steel;

[0026] The material of the molecular sieve packing tube is stainless steel;

[0027] The material of the tubular reactor II is polytetrafluoroethylene or stainless steel.

[0028] The method for continuously synthesizing diethyl oxalate in a microreactor provided by the present invention has the following advantages: the continuous flow microreaction process has the advantages of intrinsic safety, efficient mass transfer and heat transfer, controllable reaction, small equipment footprint, etc., and the introduction of a molecular sieve filler tube can continuously adsorb water generated in the reaction, so that the reaction proceeds in the direction of the product, greatly improving the reaction yield, avoiding operations such as azeotropic dehydration, and effectively improving production efficiency. The present invention realizes rapid and continuous synthesis without metal catalysis, low cost, short reaction time, simple operation, safety and efficiency, and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention is a schematic diagram of a process flow of a method for continuously synthesizing diethyl oxalate using a microreactor according to an embodiment of the present invention.

[0030] Figure Number and Name:

[0031] 1. Horizontal flow pump; 2. Tubular reactor I; 3. Cooling tube; 4. Molecular sieve packing tube; 5. Tubular reactor II; 6. Valve;

[0032] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the embodiments of the present disclosure clearer, the technical solution of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings of the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0034] The present invention provides a method for continuously synthesizing diethyl oxalate in a microreactor. Figure 1 As shown, the following steps are included:

[0035] Oxalic acid and a catalyst are dissolved in ethanol to form a reaction mass, the reaction mass is transported to a tubular reactor I, and sequentially passes through a cooling tube and a molecular sieve packing tube, and then is transported to a tubular reactor II, and the reaction liquid is collected;

[0036] Wherein, the molar ratio of oxalic acid to catalyst is 1:(0.1-0.6), catalyst; the concentration of oxalic acid in ethanol is 20 mg / mL-100 mg / mL; the catalyst is selected from concentrated sulfuric acid or p-toluenesulfonic acid; the temperature of tubular reactor I is 60°C-120°C; the temperature of tubular reactor II is 60°C-120°C; the residence time of the reaction mass in tubular reactor I is 6min-35min, preferably, 12.56min; the residence time of the reaction mass in the cooling tube is 2min; the residence time of the reaction mass in tubular reactor II is 6min-35min, preferably, 12.56min; the inner diameter of tubular reactor I is 0.4mm-3mm, and the liquid holdup is 10mL-40mL; the inner diameter of the cooling tube is 0.4mm-3mm; the molecular sieve in the molecular sieve filler tube is The inner diameter of the tubular reactor II is 0.4 mm to 3 mm, and the liquid holding capacity is 10 mL to 40 mL; the material of the tubular reactor I is polytetrafluoroethylene or stainless steel; the material of the cooling tube is polytetrafluoroethylene or stainless steel; the molecular sieve packing tube is a stainless steel semi-preparative packing column, the diameter of the packing column is 10 mm, and the length is 300 mm; the material of the tubular reactor II is polytetrafluoroethylene or stainless steel.

[0037] It should be noted that the selected catalyst includes sulfuric acid, hydrochloric acid, aromatic sulfonic acid, or a heterogeneous acid catalyst. If no catalyst is used, a high temperature of 200°C to 300°C must be used (see Non-Patent Document 1 in Background Technology for details).

[0038] Example 1

[0039] Weigh 25.0 g of oxalic acid (oxalic acid) and 5.2 mL of concentrated sulfuric acid (0.34 equivalents) (the molar ratio of oxalic acid to catalyst is about 1:0.35) and dissolve them in ethanol, adjust the volume to 500 mL, the concentration of oxalic acid in ethanol is 50 mg / mL, as the reaction material, pump it into the tubular reactor I at a flow rate of 2 mL / min through a horizontal flow pump for reaction, the reaction temperature is 100°C, and the residence time is 12.56 min, wherein the liquid load of the tubular reactor I is 25.12 mL, and the inner diameter is 2 mm; then pass through a cooling tube and a molecular sieve filling tube, the residence time of the reaction material in the cooling tube is 2 min, the inner diameter of the cooling tube is 2 mm, and the molecular sieve filling tube is a stainless steel semi-preparative filling column (with molecular sieve, 10*300mm); then transported to tubular reactor II to continue the reaction, the reaction temperature was 100°C, the residence time was 12.56min, wherein the liquid load of tubular reactor I was 25.12mL, and the inner diameter was 2mm; the reaction liquid was collected, the total reaction time was 27.12min, and the reaction yield was 93.1% through high performance liquid phase quantitative analysis.

[0040] It should be noted that the material of the tubular reactor I is stainless steel, the material of the cooling tube is stainless steel, the material of the molecular sieve packing tube is stainless steel, and the material of the tubular reactor II is stainless steel.

[0041] Example 2

[0042] The difference between this embodiment and embodiment 1 is that the cooling tube, the molecular sieve filling tube and the tubular reactor II are omitted, and the other conditions remain unchanged.

[0043] The total reaction time was 12.56 min, and the reaction yield was 73.1% as determined by HPLC quantitative analysis.

[0044] Example 3

[0045] The difference between this embodiment and embodiment 1 is that concentrated sulfuric acid is replaced by 14.3 g of p-toluenesulfonic acid (0.34 equivalent), the material of the tubular reactor I is polytetrafluoroethylene, the material of the cooling tube is polytetrafluoroethylene, the material of the molecular sieve packing tube is stainless steel, the material of the tubular reactor II is polytetrafluoroethylene, and the other conditions remain unchanged.

[0046] The total reaction time was 27.12 min, and the reaction yield was 23.9% as determined by HPLC quantitative analysis.

[0047] Example 4

[0048] The difference between this embodiment and embodiment 1 is that the molar ratio of oxalic acid to catalyst is about 1:0.1, the concentration of oxalic acid in ethanol is 20 mg / mL, the temperature of tubular reactor I is 60°C, the residence time of the reaction mass in tubular reactor I is 6 min, the inner diameter of tubular reactor I is 0.4 mm, and the liquid holdup is 10 mL; the temperature of tubular reactor II is 60°C, the residence time of the reaction mass in tubular reactor II is 6 min, the inner diameter of tubular reactor II is 0.4 mm, and the liquid holdup is 10 mL; the other conditions remain unchanged.

[0049] The total reaction time was 14 min. The reaction yield was 78.5% as determined by HPLC quantitative analysis.

[0050] Example 5

[0051] The difference between this embodiment and embodiment 1 is that the molar ratio of oxalic acid to catalyst is about 1:0.6, the concentration of oxalic acid in ethanol is 100 mg / mL, the temperature of tubular reactor I is 120°C, the residence time of the reaction mass in tubular reactor I is 35 min, the inner diameter of tubular reactor I is 3 mm, and the liquid holdup is 40 mL; the temperature of tubular reactor II is 120°C, the residence time of the reaction mass in tubular reactor II is 35 min, the inner diameter of tubular reactor II is 3 mm, and the liquid holdup is 40 mL; the other conditions remain unchanged.

[0052] The total reaction time was 72 min. The reaction yield was 88.0% as determined by HPLC quantitative analysis.

Claims

1. A method for continuously synthesizing diethyl oxalate using a microreactor, characterized in that: The following steps are involved: Oxalic acid and a catalyst are dissolved in ethanol to form a reaction mass, the reaction mass is transported to a tubular reactor I, and sequentially passes through a cooling tube and a molecular sieve packing tube, and then is transported to a tubular reactor II, and the reaction liquid is collected; The molar ratio of oxalic acid to the catalyst is 1:(0.1-0.6); and the concentration of oxalic acid in ethanol is 20 mg / mL-100 mg / mL.

2. The method according to claim 1, characterized in that The catalyst is selected from concentrated sulfuric acid or p-toluenesulfonic acid.

3. The method according to claim 2, characterized in that The temperature of the tubular reactor I is 60°C to 120°C; The temperature of tubular reactor II is 60°C to 120°C.

4. The method according to claim 3, characterized in that The residence time of the reaction materials in the tubular reactor I is 6 min to 35 min; The residence time of the reaction material in the cooling tube is 2 min; The residence time of the reaction materials in tubular reactor II is 6 min to 35 min.

5. The method according to claim 3, characterized in that: The residence time of the reaction mass in the tubular reactor I is 12.56 min; The residence time of the reaction material in the cooling tube is 2 min; The residence time of the reaction materials in tubular reactor II is 12.56 min.

6. The method according to claim 5, characterized in that The inner diameter of the tubular reactor I is 0.4 mm to 3 mm, and the liquid holding capacity is 10 mL to 40 mL; The inner diameter of the cooling tube is 0.4mm to 3mm; The molecular sieve in the molecular sieve packing tube is The inner diameter of the tubular reactor II is 0.4 mm to 3 mm, and the liquid holding capacity is 10 mL to 40 mL.

7. The method according to claim 6, characterized in that The material of the tubular reactor I is polytetrafluoroethylene or stainless steel; The cooling tube is made of polytetrafluoroethylene or stainless steel; The material of the molecular sieve packing tube is stainless steel; The material of the tubular reactor II is polytetrafluoroethylene or stainless steel.

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