Continuous preparation method of lauroyl chloride

Abstract

The invention discloses a continuous preparation method of lauroyl chloride, which comprises the following steps: heating and melting lauric acid to obtain lauric acid melt; the method comprises the following steps: preparing an overflow diode reactor, continuously introducing phosgene and lauric acid melt into a first tubular reactor, reacting at 50-100 DEG C to obtain a photochemical reaction solution, continuously overflowing the photochemical reaction solution into a second tubular reactor, continuously reacting the unfinished reaction solution, and driving light by nitrogen to obtain lauroyl chloride. The continuous preparation method disclosed by the invention has the advantages of simple process, low online liquid carrying amount, convenience in operation, low cost and the like, and the obtained product is low in chromaticity, high in purity, few in impurities, suitable for industrial production and wide in application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis and relates to a continuous preparation method of lauroyl chloride. Background Art

[0002] Lauroyl chloride, also known as dodecanoyl chloride, is a colorless and transparent liquid. Its English name is Lauroyl chloride. Its boiling point is 145℃ (2.4kPa), 134-137℃ (1.47kPa), and its refractive index is 1.445. It is soluble in ether and decomposes in water and alcohol. In the prior art, lauroyl chloride is generated by the reaction of lauric acid with phosphorus trichloride, thionyl chloride, and phosgene. Lauroyl chloride is mainly used to synthesize amino acid surfactants in the personal care industry, such as shampoo, shower gel, facial cleanser, etc. Its market demand is growing year by year at a growth rate of 7%-10%. The wettability of amino acid surfactants is better than that of fatty alcohol polyoxyethylene ether (AE), and it has excellent foaming properties, fine and long-lasting foam, strong antibacterial and anti-bacterial properties, corrosion resistance, and antistatic ability, low toxicity, low irritation, and good biodegradability. It is also conducive to reducing environmental pollution and is widely used in food, cosmetics, medicine, oil extraction, mineral flotation and other industries. Since the downstream products are in the daily chemical industry, the lauroyl chloride content, color and odor are required to be extremely high.

[0003] The phosgene method for producing acyl chloride requires the use of a catalyst to promote the reaction of phosgene and carboxylic acid, reduce the reaction temperature and increase the reaction rate, thereby achieving higher efficiency. Chinese document patent CN100564342C mentions the use of organic amines as catalysts, such as N,N-dimethylformamide (DMF), triethylamine, pyridine, N-methylpyrrole, 1,3-dimethyl-2-imidazolidinone, tetramethylguanidine, etc., which react with bis(trichloromethyl) carbonate (also known as triphosgene) in an organic solvent. Chinese document patent CN113387796A mentions the use of 4-dimethylaminopyridine (DMAP) as a catalyst to react with phosgene in an organic solvent to generate lauroyl chloride. Some documents also mention the use of palladium trichloride, aluminum trichloride, etc. as catalysts. However, these catalysts still have defects: the catalytic activity of triethylamine, aluminum chloride, pyridine, imidazole, etc. is poor, and the reaction time is long, which is not conducive to industrial production; the product obtained by using palladium chloride is of good quality, but its price is high and the economic efficiency is poor, which is not suitable for industrial production; using DMF and 4-dimethylaminopyridine as catalysts, the compound is dispersed in the product in the form of brown-black tar after the reaction, resulting in a decrease in product quality and an increase in chromaticity. In order to obtain high-quality acyl chloride, the acyl chloride must be purified by distillation and refining, but the yield decreases, the cost is high, and there are inevitably catalyst residues. Amino acid surfactants are mainly used in daily chemical products such as shampoo and facial cleansers. The fatty acyl chloride used to prepare amino acid surfactants has strict requirements on catalyst residues, and the catalyst residues must be controlled. The production of lauroyl chloride by phosgene method is one of the dangerous processes. Developing this process in the direction of low cost, process safety and environmental protection is the current trend of domestic and foreign technology development. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a continuous preparation method of lauroyl chloride with low online liquid carrying volume, few impurities, low chroma, no odor and high product purity.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions.

[0006] A continuous preparation method of lauroyl chloride comprises the following steps:

[0007] S1, heating and melting lauric acid to obtain a lauric acid molten liquid;

[0008] S2. Prepare an overflow-type two-stage tubular reactor, the overflow-type two-stage tubular reactor comprising a first tubular reactor and a second tubular reactor, wherein the first tubular reactor is provided with staggered trays from bottom to top, and the second tubular reactor is provided with staggered trays from bottom to top, place a molecular sieve catalyst on the trays of the first tubular reactor and the second tubular reactor, continuously introduce phosgene into the first tubular reactor from the bottom, and continuously introduce the lauric acid melt obtained in step S1 into the first tubular reactor from the top, the flow rate of phosgene is 7.4 g / min-15.0 g / min, and the flow rate of lauric acid melt is 15 g / min-29 g / min, react at 50° C.-100° C. to obtain a photochemical reaction liquid, and continuously overflow the photochemical reaction liquid into the second tubular reactor for continued reaction, and obtain lauroyl chloride after being driven out by nitrogen.

[0009] In the above-mentioned continuous preparation method of lauroyl chloride, preferably, in step S1, the heating and melting temperature is 50°C to 60°C.

[0010] In the above-mentioned continuous preparation method of lauroyl chloride, preferably, in step S2, the molecular sieve catalyst is one or more of type 3A molecular sieve, type 4A molecular sieve and type 5A molecular sieve.

[0011] In the above-mentioned continuous preparation method of lauroyl chloride, preferably, the molar ratio of the lauric acid to the phosgene is 1:1.00-1.05; in step S2, the residence time of the photochemical reaction liquid in the first tubular reactor is 30 min-60 min.

[0012] In the above-mentioned continuous preparation method of lauroyl chloride, preferably, in step S2, a first jacket is provided on the outer periphery of the first tubular reactor, a first jacket inlet is provided on the top of the first jacket, and a first jacket outlet is provided on the bottom of the first jacket, and a second jacket is provided on the outer periphery of the second tubular reactor, a second jacket inlet is provided on the top of the second jacket, and a second jacket outlet is provided on the bottom of the second jacket.

[0013] In the above-mentioned continuous preparation method of lauroyl chloride, preferably, the bottom of the first tubular reactor is provided with a first feed inlet and a reaction liquid outlet, the top of the first tubular reactor is provided with a second feed inlet and a first tail gas outlet, the bottom of the second tubular reactor is provided with a reaction liquid inlet, and the top of the second tubular reactor is provided with a product outlet and a second tail gas outlet.

[0014] In the above-mentioned continuous preparation method of lauroyl chloride, preferably, the overflow-type two-stage tubular reactor also includes a condenser, a tail gas inlet and a circulating water outlet are provided at the bottom of the condenser, a non-condensable tail gas outlet and a circulating water inlet are provided at the top, and the first tail gas outlet of the first tubular reactor and the second tail gas outlet of the second tubular reactor are respectively connected to the tail gas inlet of the condenser.

[0015] In the above-mentioned continuous preparation method of lauroyl chloride, preferably, the first tubular reactor is heated by adding heat transfer oil into the first jacket, and the second tubular reactor is heated by adding heat transfer oil into the second jacket.

[0016] In the above-mentioned continuous preparation method of lauroyl chloride, preferably, the material of the first tubular reactor and the second tubular reactor are both one of glass, ceramic and Hastelloy alloy.

[0017] In the above-mentioned continuous preparation method of lauroyl chloride, preferably, the diameter of the first tubular reactor is 30mm-40mm, the length of the first tubular reactor is 60cm-80cm, the diameter of the second tubular reactor is 30mm-40mm, and the length of the second tubular reactor is 20cm-40cm.

[0018] The invention uses lauric acid as a raw material and an overflow type two-stage tubular reactor as a reaction carrier without solvent. Under the action of a catalyst, lauric acid and phosgene react continuously in the reactor to obtain lauroyl chloride.

[0019] The reaction formula is as follows;

[0020]

[0021] The reaction mechanism is as follows:

[0022]

[0023] Main impurities:

[0024]

[0025] Compared with the prior art, the advantages of the present invention are:

[0026] (1) The present invention uses molecular sieve as a catalyst to solve the problems of heavy odor and poor chromaticity during the synthesis of lauroyl chloride. Molecular sieve is a material with tiny holes, generally used as a dehydrating agent, a hygroscopic agent, an acid catalyst and a selective catalyst, but has never been used to solve the problems of chromaticity and odor. The present invention uses molecular sieve as a catalyst to reduce the problems of heavy odor and poor chromaticity caused by catalyst residue. The applicant found in the study that other catalysts that catalyze the synthesis of lauroyl chloride, such as triethylamine, aluminum chloride, pyridine, imidazole, etc., have poor catalytic activity and a long reaction time, which is not conducive to industrial production. Although the quality of the product obtained by using palladium chloride is good, it is expensive and has poor economy, and is not suitable for industrial production. Using DMF and 4-dimethylaminopyridine as catalysts, after the reaction is completed, the compound is dispersed in the product in a brown-black tar-like state, causing the product quality to decline and the chromaticity to increase. The molecular sieve catalyst used in the present invention also has the advantages of being cheap and easy to obtain, being able to reduce the reaction cost, being easy to recover, having no loss, and being recyclable.

[0027] (2) In the synthesis process of lauroyl chloride of the present invention, at the reaction temperature, since lauric acid is in liquid state and has good fluidity, no solvent is needed, thus reducing the three wastes and saving costs.

[0028] (3) The present invention adopts an overflow-type two-stage tubular reactor, and the tower plate structure adopts a staggered design, which has the advantages of extending the residence time of materials, promoting uniform mixing of materials, sufficient contact with the catalyst, and the catalyst is fixed on the tower plate and can be infinitely applied. The feeding method and feeding speed are simple and controllable, the reaction liquid is continuously discharged, the online liquid load is low, and the production method is transformed from the traditional intermittent operation to continuous operation, with low energy consumption, short reaction time, stable product quality, low chroma, no odor, and few impurities.

[0029] In summary, the method of the present invention is simple in process, easy to operate, and low in cost. The chromaticity of the prepared lauroyl chloride is no more than 5 (Hazen unit-platinum-cobalt color number), has no odor, has few impurities, has a purity of more than 99.8% (quantitative determination by high-performance gas chromatography), and has a high yield of more than 98% (calculated as lauric acid). BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the structure of the overflow type two-stage tubular reactor in Examples 1 to 7 of the present invention.

[0031] Legend:

[0032] 1. First tubular reactor; 11. First feed inlet; 12. Reaction liquid outlet; 13. Second feed inlet; 14. First tail gas outlet; 2. Second tubular reactor; 21. Reaction liquid inlet; 22. Product outlet; 23. Second tail gas outlet; 3. Plate; 4. First jacket; 41. First jacket inlet; 42. First jacket outlet; 5. Second jacket; 51. Second jacket inlet; 52. Second jacket outlet; 6. Condenser; 61. Tail gas inlet; 62. Circulating water outlet; 63. Non-condensable tail gas outlet; 64. Circulating water inlet. DETAILED DESCRIPTION

[0033] The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby. The materials and instruments used in the following examples are all commercially available, wherein 3A molecular sieve, 4A molecular sieve, and 5A molecular sieve are all purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0034] Example 1

[0035] A continuous preparation method of lauroyl chloride of the present invention comprises the following steps:

[0036] S1. Add 2000 g (9.9 mol, 99%) of lauric acid into a reactor equipped with a stirrer, heat to 50° C., stir and melt to obtain a lauric acid molten liquid, and store it at a constant temperature.

[0037] S2. Prepare overflow two-stage tubular reactor, such as Figure 1As shown, the reactor includes a first tubular reactor 1 and a second tubular reactor 2. The diameter of the first tubular reactor 1 is 36 mm and the length is 80 cm. The diameter of the second tubular reactor 2 is 36 mm and the length is 20 cm. The two-stage reactors are connected by a curved glass tube with a diameter of 1 cm and a total length of 12 cm. The first tubular reactor 1 and the second tubular reactor 2 are both provided with left and right staggered trays 3 from bottom to top. One end of each tray 3 is provided on the side wall of the reactor, and the other end is spaced from the opposite side so that the material moves forward in a baffled manner from bottom to top in the reactor, which can extend the residence time of the material, make the material mixed evenly, and fully contact with the catalyst. The outer periphery of the first tubular reactor 1 is provided with a first jacket 4, and the outer periphery of the second tubular reactor 2 is provided with a second jacket 5. The first tubular reactor 1 is provided with a first feed port 11 and a reaction liquid outlet 12 at the bottom, a second feed port 13 and a first tail gas outlet 14 at the top, a first jacket inlet 41 at the top, and a first jacket outlet 42 at the bottom. The second tubular reactor 2 is provided with a reaction liquid inlet 21 at the bottom, a product outlet 22 and a second tail gas outlet 23 at the top, a second jacket inlet 51 at the top, and a second jacket outlet 52 at the bottom. The overflow type two-stage tubular reactor also includes a condenser 6, which can be a graphite condenser. The condenser 6 is provided with a tail gas inlet 61 and a circulating water outlet 62 at the bottom, and a non-condensable tail gas outlet 63 and a circulating water inlet 64 at the top. The first tail gas outlet 14 and the second tail gas outlet 23 are respectively connected to the tail gas inlet 61 of the condenser 6.

[0038] The catalyst 3A molecular sieve is placed on the tray 3 of the first tubular reactor 1 and the second tubular reactor 2, and heat transfer oil is introduced into the first jacket 4 and the second jacket 5 respectively. In the first jacket 4, the heat transfer oil enters from the first jacket inlet 41 and flows out from the first jacket outlet 42, and the temperature of the first tubular reactor 1 is controlled at 80°C. In the second jacket 5, the heat transfer oil enters from the second jacket inlet 51 and flows out from the second jacket outlet 52, and the temperature of the second tubular reactor 2 is controlled at 80°C. During the reaction process, the liquid level of the first tubular reactor 1 is flush with the liquid level of the second tubular reactor 2. Circulating water is introduced from the circulating water inlet 64 of the condenser 6 and flows out from the circulating water outlet 62 to condense the tail gas in the condenser 6.

[0039] Phosgene is continuously introduced into the reactor from the first feed port 11 at the bottom of the first tubular reactor 1, and the lauric acid melt obtained in step S1 is continuously introduced into the reactor from the second feed port 13 at the top of the first tubular reactor 1. The flow rate of phosgene is 7.4 g / min, the flow rate of lauric acid melt is 15 g / min, and the molar ratio of lauric acid (or lauric acid melt) to phosgene is 1:1.00. The two are mixed in the reactor for reaction, and the reaction temperature is maintained at 80°C. The obtained photochemical reaction is controlled to be The residence time of the reaction liquid is 59 minutes, and the photochemical reaction liquid continuously overflows from the reaction liquid outlet 12 at the bottom of the first tubular reactor 1 to the second tubular reactor 2. The unreacted lauric acid and phosgene continue to react in the second tubular reactor 2 under the catalysis of the catalyst to obtain crude lauroyl chloride. After being driven out by nitrogen, lauroyl chloride is obtained with a content of 99.90% (quantitatively determined by high performance gas chromatography), a chromaticity of 3 (Hazen unit - platinum-cobalt color number), and a yield of 99.0% (based on lauric acid).

[0040] In this embodiment, the tail gas generated by the first tubular reactor 1 and the tail gas generated by the second tubular reactor 2 are both introduced into the condenser 6 for condensation treatment, and the non-condensable tail gas is discharged into the tail gas alkali liquid absorption tower.

[0041] Example 2

[0042] A continuous preparation method of lauroyl chloride of the present invention comprises the following steps:

[0043] S1. Add 2000 g (9.9 mol, 99%) of lauric acid into a reactor equipped with a stirrer, heat to 50° C., stir and melt to obtain a lauric acid molten liquid, and store it at a constant temperature.

[0044] S2. Use the same overflow two-stage tubular reactor as in Example 1, place the catalyst 3A molecular sieve on each tower plate 3, pass heat transfer oil into the first jacket 4 and the second jacket 5, control the temperature of the first tubular reactor 1 at 100°C, and control the temperature of the second tubular reactor 2 at 100°C. Phosgene is continuously introduced into the reactor from the first feed port 11 at the bottom of the first tubular reactor 1, and the lauric acid melt obtained in step S1 is continuously introduced into the reactor from the second feed port 13 at the top of the first tubular reactor 1, the flow rate of phosgene is 7.6 g / min, the flow rate of lauric acid melt is 15 g / min, the molar ratio of lauric acid to phosgene is 1:1.02, the reaction temperature is maintained at 100°C, the residence time of the obtained photochemical reaction liquid is controlled to be 59 minutes, and the photochemical reaction liquid continuously overflows from the reaction liquid outlet 12 to the second tubular reactor 2, and the unreacted lauric acid and phosgene continue to react in the second tubular reactor 2 under the catalysis of the catalyst to obtain a crude lauroyl chloride, which is driven out by nitrogen to obtain lauroyl chloride with a content of 99.82%, a chromaticity of 5, and a yield of 98.3%. The obtained tail gas is condensed, and the non-condensable tail gas is discharged.

[0045] Example 3

[0046] A continuous preparation method of lauroyl chloride of the present invention comprises the following steps:

[0047] S1. Add 2000 g (9.9 mol, 99%) of lauric acid into a reactor equipped with a stirrer, heat to 50° C., stir and melt to obtain a lauric acid molten liquid, and store it at a constant temperature.

[0048] S2. Use the same overflow two-stage tubular reactor as in Example 1, place the catalyst 3A molecular sieve on each tower plate 3, pass heat transfer oil into the first jacket 4 and the second jacket 5, control the temperature of the first tubular reactor 1 at 50°C, and control the temperature of the second tubular reactor 2 at 50°C. Phosgene is continuously introduced into the reactor from the first feed port 11 at the bottom of the first tubular reactor 1, and the lauric acid melt obtained in step S1 is continuously introduced into the reactor from the second feed port 13 at the top of the first tubular reactor 1, the flow rate of phosgene is 7.8 g / min, the flow rate of lauric acid melt is 15 g / min, the molar ratio of lauric acid to phosgene is 1:1.05, the reaction temperature is maintained at 50°C, the residence time of the obtained photochemical reaction liquid is controlled to be 58 minutes, and the photochemical reaction liquid continuously overflows from the reaction liquid outlet 12 to the second tubular reactor 2, and the unreacted lauric acid and phosgene continue to react in the second tubular reactor 2 under the catalysis of the catalyst to obtain a crude lauroyl chloride product, which is driven out by nitrogen to obtain lauroyl chloride with a content of 99.84%, a chromaticity of 5, and a yield of 98.5%. The obtained tail gas is condensed, and the non-condensable tail gas is discharged.

[0049] Example 4

[0050] A continuous preparation method of lauroyl chloride of the present invention comprises the following steps:

[0051] S1. Add 2000 g (9.9 mol, 99%) of lauric acid into a reactor equipped with a stirrer, heat to 50° C., stir and melt to obtain a lauric acid molten liquid, and store it at a constant temperature.

[0052] S2. Use the same overflow two-stage tubular reactor as in Example 1, place the catalyst 3A molecular sieve on each tower plate 3, pass heat transfer oil into the first jacket 4 and the second jacket 5, control the temperature of the first tubular reactor 1 at 80°C, and control the temperature of the second tubular reactor 2 at 80°C. The lauric acid melt obtained in step S1 is continuously fed into the reactor from the second feed port 13 at the top of the first tubular reactor 1, and phosgene is continuously fed into the reactor from the first feed port 11 at the bottom of the first tubular reactor 1, the flow rate of the lauric acid melt is 29 g / min, the flow rate of phosgene is 14.3 g / min, the molar ratio of lauric acid to phosgene is 1:1.00, the reaction temperature is maintained at 80°C, the residence time of the photochemical reaction liquid is controlled at 30 min, the photochemical reaction liquid continuously overflows from the reaction liquid outlet 12 to the second tubular reactor 2, the unreacted lauric acid and phosgene continue to react in the second tubular reactor 2 under the catalysis of the catalyst to obtain a crude lauroyl chloride, which is driven out by nitrogen to obtain lauroyl chloride with a content of 99.80%, a chromaticity of 4, and a yield of 98.1%. The obtained tail gas is condensed, and the non-condensable tail gas is discharged.

[0053] Example 5

[0054] A continuous preparation method of lauroyl chloride of the present invention comprises the following steps:

[0055] S1. Add 2000 g (9.9 mol, 99%) of lauric acid into a reactor equipped with a stirrer, heat to 50° C., stir and melt to obtain a lauric acid molten liquid, and store it at a constant temperature.

[0056] S2, using the same overflow type two-stage tubular reactor as in Example 1, the first tubular reactor 1 has a diameter of 36 mm and a length of 60 cm, the second tubular reactor 2 has a diameter of 36 mm and a length of 40 cm, and the other conditions are the same as in Example 1. Catalyst 3A molecular sieve is placed on each tray 3, heat transfer oil is introduced into the first jacket 4 and the second jacket 5, the temperature of the first tubular reactor 1 is controlled at 80°C, and the temperature of the second tubular reactor 2 is controlled at 80°C. The lauric acid melt obtained in step S1 is continuously fed into the reactor from the second feed port 13 at the top of the first tubular reactor 1, and phosgene is continuously fed into the reactor from the first feed port 11 at the bottom of the first tubular reactor 1, the flow rate of the lauric acid melt is 29 g / min, the flow rate of phosgene is 14.9 g / min, the molar ratio of lauric acid to phosgene is 1:1.04, the reaction temperature is maintained at 80°C, the residence time of the obtained photochemical reaction liquid is controlled to be 30 min, the photochemical reaction liquid continuously overflows from the reaction liquid outlet 12 to the second tubular reactor 2, the unreacted lauric acid and phosgene continue to react in the second tubular reactor 2 under the catalysis of the catalyst to obtain a crude lauroyl chloride, which is driven out by nitrogen to obtain lauroyl chloride with a content of 99.87%, a chromaticity of 5, and a yield of 98.6%. The obtained tail gas is condensed, and the non-condensable tail gas is discharged.

[0057] Example 6

[0058] A continuous preparation method of lauroyl chloride of the present invention comprises the following steps:

[0059] S1. Add 2000 g (9.9 mol, 99%) of lauric acid into a reactor equipped with a stirrer, heat to 50° C., stir and melt to obtain a lauric acid molten liquid, and store it at a constant temperature.

[0060] S2. Use the same overflow two-stage tubular reactor as in Example 1, place the catalyst 4A molecular sieve on each tower plate 3, pass heat transfer oil into the first jacket 4 and the second jacket 5, control the temperature of the first tubular reactor 1 at 80°C, and control the temperature of the second tubular reactor 2 at 80°C. The lauric acid melt obtained in step S1 is continuously fed into the reactor from the second feed port 13 at the top of the first tubular reactor 1, and phosgene is continuously fed into the reactor from the first feed port 11 at the bottom of the first tubular reactor 1, the flow rate of the lauric acid melt is 29 g / min, the flow rate of phosgene is 14.8 g / min, the molar ratio of lauric acid to phosgene is 1:1.03, the reaction temperature is maintained at 80°C, the residence time of the obtained photochemical reaction liquid is controlled to be 30 min, the photochemical reaction liquid continuously overflows from the reaction liquid outlet 12 to the second tubular reactor 2, the unreacted lauric acid and phosgene continue to react in the second tubular reactor 2 under the catalysis of the catalyst to obtain a crude lauroyl chloride, which is driven out by nitrogen to obtain lauroyl chloride with a content of 99.83%, a chromaticity of 5, and a yield of 98.4%. The obtained tail gas is condensed, and the non-condensable tail gas is discharged.

[0061] Example 7

[0062] A continuous preparation method of lauroyl chloride of the present invention comprises the following steps:

[0063] S1. Add 2000 g (9.9 mol, 99%) of lauric acid into a reactor equipped with a stirrer, heat to 50° C., stir and melt to obtain a lauric acid molten liquid, and store it at a constant temperature.

[0064] S2. Use the same overflow two-stage tubular reactor as in Example 1, place the catalyst 5A molecular sieve on each tower plate 3, pass heat transfer oil into the first jacket 4 and the second jacket 5, control the temperature of the first tubular reactor 1 at 80°C, and control the temperature of the second tubular reactor 2 at 80°C. Phosgene is continuously introduced into the reactor from the first feed port 11 at the bottom of the first tubular reactor 1, and the lauric acid melt obtained in step S1 is continuously introduced into the reactor from the second feed port 13 at the top of the first tubular reactor 1, the flow rate of the lauric acid melt is 29 g / min, the flow rate of phosgene is 14.5 g / min, the molar ratio of lauric acid to phosgene is 1:1.01, the reaction temperature is maintained at 80°C, the residence time of the photochemical reaction liquid is controlled at 30 min, and the photochemical reaction liquid continuously overflows from the reaction liquid outlet 12 to the second tubular reactor 2, and the unreacted lauric acid and phosgene continue to react in the second tubular reactor 2 under the catalysis of the catalyst to obtain a crude lauroyl chloride product, which is driven out by nitrogen to obtain lauroyl chloride with a content of 99.85%, a chromaticity of 4, and a yield of 98.6%. The obtained tail gas is condensed, and the non-condensable tail gas is discharged.

[0065] Comparative Example 1

[0066] A continuous preparation method of lauroyl chloride is basically the same as Example 1, except that 3A molecular sieve is replaced by aluminum chloride, and the content of the obtained lauroyl chloride is 90.20%, the chromaticity is 34, and the yield is 89.6%.

[0067] Comparative Example 2

[0068] A continuous preparation method of lauroyl chloride is basically the same as Example 1, except that 3A molecular sieve is replaced by N,N-dimethylformamide (DMF), and the content of the obtained lauroyl chloride is 93.90%, the chromaticity is 50, and the yield is 92.0%.

[0069] The result data obtained by the continuous preparation method of lauroyl chloride in Examples 1-7 and Comparative Examples 1-2 are shown in Table 1.

[0070] Table 1 Results of Examples 1-7 and Comparative Examples 1-2

[0071]

[0072] As can be seen from Table 1, Comparative Example 1 uses aluminum chloride as a catalyst, the content of the obtained lauroyl chloride is on the low side, the raw materials are not fully reacted, the residence time required for the reaction is long, the catalytic activity is poor, and the chromaticity is also on the high side, which is not conducive to industrial production. Comparative Example 2 uses DMF as a catalyst, and after the reaction is completed, the compound is dispersed in the product in a brown-black tar-like state, causing the product quality to decline and the chromaticity to increase. If high-quality acyl chloride is to be obtained, the acyl chloride must be purified by distillation and refining, but the yield will further decline, the cost is high, and there is inevitably still a catalyst residue, which affects the quality of downstream products.

[0073] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as above in the preferred embodiment, it is not used to limit the present invention. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention, still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A continuous preparation method of lauroyl chloride, characterized in that: The following steps are involved: S1, heating and melting lauric acid to obtain a lauric acid molten liquid; S2. Prepare an overflow-type two-stage tubular reactor, the overflow-type two-stage tubular reactor comprising a first tubular reactor (1) and a second tubular reactor (2), wherein the first tubular reactor (1) is provided with staggered trays (3) from bottom to top, and the second tubular reactor (2) is provided with staggered trays (3) from bottom to top, place a molecular sieve catalyst on the trays (3) of the first tubular reactor (1) and the second tubular reactor (2), continuously introduce phosgene into the first tubular reactor (1) from the bottom, and continuously introduce the lauric acid melt obtained in step S1 into the first tubular reactor (1) from the top, the flow rate of phosgene is 7.4 g / min to 15.0 g / min, and the flow rate of lauric acid melt is 15 g / min to 29 g / min, react at 50° C. to 100° C. to obtain a photochemical reaction liquid, and continuously overflow the photochemical reaction liquid into the second tubular reactor (2) to continue the reaction, and obtain lauroyl chloride after being driven out by nitrogen.

2. The continuous preparation method of lauroyl chloride according to claim 1, characterized in that: In step S1, the heating and melting temperature is 50°C to 60°C.

3. The continuous preparation method of lauroyl chloride according to claim 1, characterized in that: In step S2, the molecular sieve catalyst is one or more of type 3A molecular sieve, type 4A molecular sieve and type 5A molecular sieve.

4. The continuous preparation method of lauroyl chloride according to claim 1, characterized in that: The molar ratio of the lauric acid to the phosgene is 1:1.00-1.05; in step S2, the residence time of the photochemical reaction liquid in the first tubular reactor (1) is 30 min-60 min.

5. The continuous preparation method of lauroyl chloride according to any one of claims 1 to 4, characterized in that: In step S2, a first jacket (4) is provided on the outer periphery of the first tubular reactor (1), a first jacket inlet (41) is provided at the top of the first jacket (4), and a first jacket outlet (42) is provided at the bottom of the first jacket (4); a second jacket (5) is provided on the outer periphery of the second tubular reactor (2), a second jacket inlet (51) is provided at the top of the second jacket (5), and a second jacket outlet (52) is provided at the bottom of the second jacket (5).

6. The continuous preparation method of lauroyl chloride according to claim 5, characterized in that: The first tubular reactor (1) is provided with a first feed inlet (11) and a reaction liquid outlet (12) at the bottom, the first tubular reactor (1) is provided with a second feed inlet (13) and a first tail gas outlet (14) at the top, the second tubular reactor (2) is provided with a reaction liquid inlet (21) at the bottom, and the second tubular reactor (2) is provided with a product outlet (22) and a second tail gas outlet (23) at the top.

7. The continuous preparation method of lauroyl chloride according to claim 6, characterized in that: The overflow-type two-stage tubular reactor further comprises a condenser (6), wherein a tail gas inlet (61) and a circulating water outlet (62) are provided at the bottom of the condenser (6), and a non-condensable tail gas outlet (63) and a circulating water inlet (64) are provided at the top; a first tail gas outlet (14) of the first tubular reactor (1) and a second tail gas outlet (23) of the second tubular reactor (2) are respectively connected to the tail gas inlet (61) of the condenser (6).

8. The continuous preparation method of lauroyl chloride according to claim 7, characterized in that: The first tubular reactor (1) is heated by adding heat-conducting oil into the first jacket (4), and the second tubular reactor (2) is heated by adding heat-conducting oil into the second jacket (5).

9. The continuous preparation method of lauroyl chloride according to any one of claims 6 to 8, characterized in that: The first tubular reactor (1) and the second tubular reactor (2) are both made of one of glass, ceramic and Hastelloy alloy.

10. The continuous preparation method of lauroyl chloride according to any one of claims 6 to 8, characterized in that: The diameter of the first tubular reactor (1) is 30 mm to 40 mm, the length of the first tubular reactor (1) is 60 cm to 80 cm, the diameter of the second tubular reactor (2) is 30 mm to 40 mm, and the length of the second tubular reactor (2) is 20 cm to 40 cm.

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