Preparation method of tert-dodecyl mercaptan

Abstract

The invention discloses a preparation method of tert-dodecyl mercaptan. The tert-dodecyl mercaptan is prepared by adopting continuous reaction rectification and catalyzing tetra-polypropylene and hydrogen sulfide to react and rectify in a rectifying tower by using solid acid. The method can effectively utilize the reaction heat released in the synthesis of tert-dodecanethiol, solves the problem of temperature runaway caused by large heat release, can break the balance of the reaction, improves the conversion rate of tetra-polypropylene to 99% or above, directly obtains a qualified product without separation of the raw material tetra-polypropylene, greatly simplifies the process flow, and obviously reduces the production cost.

Description

Technical Field

[0001] The invention belongs to the field of polymer reaction additives, and particularly relates to a method for preparing tert-dodecyl mercaptan. Background Art

[0002] Tert-dodecyl mercaptan is a very important chemical intermediate as a polymer molecular weight regulator for polymer materials such as synthetic resins and synthetic rubber. Tert-dodecyl mercaptan is produced using tetrapropylene and hydrogen sulfide as raw materials. Currently known related patents such as FR2391197, US4565893, US4102931, etc. all use fixed bed reactors and solid acids as catalysts to catalyze the addition reaction of hydrogen sulfide and olefins, with a reaction conversion rate of 80-97% and a selectivity of 95-100%.

[0003] There are many difficulties when using fixed bed for industrial production. Due to the large heat release of TDM reaction, it is easy to cause the fixed bed to overheat, resulting in catalyst deactivation and safety accidents. In order to ensure the removal of reaction heat, many complex heat removal designs need to be added. In addition, there is a reaction equilibrium in the reaction of tetrapropylene with hydrogen sulfide, resulting in the inability to fully convert tetrapropylene to propylene. The remaining tetrapropylene needs to be separated and reused. Since the boiling points of tetrapropylene and tert-dodecyl mercaptan are close, separation is very difficult and the separation energy consumption is high, which greatly increases the complexity of the process and product cost. Summary of the invention

[0004] To solve the above problems, one of the purposes of the present invention is to provide a method for preparing tert-dodecyl mercaptan by reactive distillation. The method can effectively utilize the reaction heat released in the synthesis of tert-dodecyl mercaptan through reactive distillation, solve the problem of temperature runaway caused by large heat release, and can also break the balance of the reaction, increase the conversion rate of tetrapropylene to more than 99%, and directly obtain qualified products from the raw material tetrapropylene without separation, greatly simplifying the process flow. The overall technology has obvious advantages over the fixed bed, with a short process flow and low production cost, and is suitable for industrial production.

[0005] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solution:

[0006] The invention discloses a method for preparing tert-dodecyl mercaptan by continuous reaction and distillation. The method uses solid acid to catalyze the reaction of tetrapropylene and hydrogen sulfide in a distillation tower to prepare tert-dodecyl mercaptan by distillation.

[0007] In one embodiment of the present invention, the reactive distillation tower is a packed tower or a plate tower, preferably a packed tower; preferably, the reactive distillation tower has a theoretical plate number of 10 to 40, preferably 20 to 30.

[0008] In one embodiment of the present invention, the reactive distillation tower has two feed ports, namely, an upper feed port and a lower feed port; preferably, the tetrapropylene enters from the upper feed port, and the preferred feed position is 5 to 25 theoretical plates from the top of the tower, more preferably 10 to 15 theoretical plates; preferably, the hydrogen sulfide enters from the lower feed port, and the preferred feed position is 10 to 40 theoretical plates from the top of the tower, more preferably 20 to 30 theoretical plates; preferably, the feed mass ratio of hydrogen sulfide to tetrapropylene is (0.2-1):1, preferably (0.4-0.6):1.

[0009] In one embodiment of the present invention, the acid catalyst is selected from one or more of acidic resin, molecular sieve, zirconium sulfate, silica alumina gel, preferably acidic resin and / or Y molecular sieve; preferably, the acid catalyst is loaded in the reaction distillation tower, using catalyst metal wire mesh structured packing, and the loading position is 1-40 plates, preferably 10-20 plates.

[0010] In one embodiment of the present invention, the temperature of the reactor of the reactive distillation tower is 100-200°C, preferably 110-140°C.

[0011] In one embodiment of the present invention, the top operating pressure of the reactive distillation tower is 0.1 to 100% absolute pressure.

[0012] 100kPa, preferably 0.2~5kPa.

[0013] In one embodiment of the present invention, the reflux ratio of the reaction is 1-10, preferably 3-8.

[0014] In one embodiment of the present invention, the tetrapropylene recovery rate of the tower top of the reaction is 0.1%-1%.

[0015] Another object of the present invention is to provide a tert-dodecyl mercaptan.

[0016] A tert-dodecyl mercaptan is prepared by the above method.

[0017] Unless otherwise specified, the pressures described in the present invention are all absolute pressures.

[0018] Compared with the prior art, the present invention has the following positive effects:

[0019] 1. Reactive distillation can effectively utilize the reaction heat released in the synthesis of tert-dodecyl mercaptan to solve the problem of temperature rise caused by large heat release.

[0020] 2. In addition, the reaction balance can be broken, and the conversion rate of tetrapropylene can be increased to more than 99%. The raw material tetrapropylene can be directly obtained into qualified products without separation, and the process flow is greatly simplified. The overall process flow is short, the equipment and investment costs are small, the production cost is low, and it is suitable for industrial production. DETAILED DESCRIPTION

[0021] The preferred embodiments of the present invention will be described in more detail below by way of examples. Although the examples describe preferred embodiments of the present invention, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein.

[0022] 1. Sources of raw materials and catalysts:

[0023] Tetrapropylene was purchased from Mobil; hydrogen sulfide was purchased from Dalian Date Gas Co., Ltd. with a purity greater than 99%; molecular sieves, Y molecular sieves, were purchased from Nankai Molecular Sieve Factory; resins were purchased from Dow, A45 resin; silica alumina was purchased from Qingdao Shuoyuan Silica Gel Technology Co., Ltd., and zirconium sulfate was purchased from Waterman Company.

[0024] 2. Analysis methods:

[0025] instrument Manufacturer Analytical methods Gas chromatography Agilent Normalization

[0026] Chromatographic column: DB-5, HP-5 or wax chromatographic column, gas chromatography analysis method, column temperature 50℃, maintain for 5min, increase the temperature to 220℃ at 10℃ / min; FID detector detection, injection volume 0.5μL.

[0027] Process conditions table:

[0028] 1 2 3 4 Number of plates 10 40 20 30 Four polypropylene feed ports 2 25 10 15 Hydrogen sulfide feed port 10 40 20 30 catalyst 1-10 1-40 5-15 10-20 Feed ratio 0.2 1 0.4 0.6 Bottom temperature 100 200 110 140 pressure 0.1 100 0.2 5 R 1 10 3 8 Extraction 0.1 1 0.2 0.7

[0029] Example 1

[0030] A small-scale distillation tower with an inner diameter of 20 mm, a height of 300 mm, and a 1.5x1.5 mm triangular spiral packing is used. The theoretical plates are 10, and the catalyst Y molecular sieve is loaded on 1-10 plates (full tower). The feed rate of tetrapropylene is 1 g / min, the feed temperature is 40 degrees, the feed position is 60 mm from the top of the tower, and the theoretical number of plates is 2. The feed rate of hydrogen sulfide is 0.2 g / min, the feed temperature is 50 degrees, the feed position is 300 mm from the top of the tower, and the theoretical number of plates is 10. The top pressure is maintained at 0.1 kPa, the reflux ratio is 1, and the top tetrapropylene recovery rate is 0.1. Under this condition, the bottom temperature is 100 ° C. The bottom of the tower produces tert-dodecyl mercaptan product with a purity of >99.8% and a yield of 99.9%.

[0031] Example 2

[0032] A small-scale distillation tower with an inner diameter of 20 mm, a height of 1200 mm, and a 1.5x1.5 mm triangular spiral packing was used. The theoretical plates were 40, and the catalyst A-45 resin catalyst was loaded on 1-40 plates (the whole tower). The feed rate of tetrapropylene was 1 g / min, the feed temperature was 80 degrees, the feed position was 750 mm from the top of the tower, and the theoretical number of plates was 25. The feed rate of hydrogen sulfide was 1 g / min, the feed temperature was 100 degrees, the feed position was 1200 mm from the top of the tower, and the theoretical number of plates was 40. The top pressure was maintained at 100 kPa, the reflux ratio was 10, and the top tetrapropylene recovery rate was 1. Under this condition, the bottom temperature was 200 ° C. The bottom of the tower produced tert-dodecyl mercaptan product with a purity of >99.8% and a yield of 99%.

[0033] Example 3

[0034] A small-scale distillation tower with an inner diameter of 20 mm, a height of 600 mm, and a 1.5x1.5 mm triangular spiral packing is used. The theoretical plates are 20, and the catalyst zirconium sulfuric acid is loaded on 5-15 plates (150 mm-750 mm from the top of the tower). The feed rate of tetrapropylene is 1 g / min, the feed temperature is 70 degrees, the feed position is 300 mm from the top of the tower, and the theoretical number of plates is 10. The feed rate of hydrogen sulfide is 0.4 g / min, the feed temperature is 90 degrees, the feed position is 600 mm from the top of the tower, and the theoretical number of plates is 20. The top pressure is maintained at 0.2 kPa, the reflux ratio is 3, and the top tetrapropylene recovery rate is 0.2. Under this condition, the bottom temperature is 110°C. The bottom of the tower produces tert-dodecyl mercaptan product with a purity of >99.8% and a yield of 99.8%.

[0035] Example 4

[0036] A small-scale distillation tower with an inner diameter of 20 mm, a height of 900 mm, and a 1.5 x 1.5 mm triangular spiral packing was used. The theoretical plates were 30, and the catalyst silica-alumina was loaded on 10-20 plates (300 mm-600 mm from the top of the tower). The feed rate of tetrapropylene was 1 g / min, the feed temperature was 60 degrees, the feed position was 450 mm from the top of the tower, and the theoretical number of plates was 2. The feed rate of hydrogen sulfide was 0.6 g / min, the feed temperature was 120 degrees, the feed position was 900 mm from the top of the tower, and the theoretical number of plates was 30. The top pressure was maintained at 0.7 kPa, the reflux ratio was 8, and the top tetrapropylene recovery rate was 0.7. Under this condition, the bottom temperature was 140°C. The bottom of the tower produced tert-dodecyl mercaptan product with a purity of >99.9% and a yield of 99.3%.

[0037] Comparative Example 1

[0038] Compared with Example 1, the difference is that a fixed bed reactor is used.

[0039] The inner diameter is 20mm, the height is 300mm, the catalyst Y molecular sieve is loaded with 94ml, the feed amount of tetrapropylene is 1g / min, the feed temperature is 40 degrees, the feed amount of hydrogen sulfide is 0.2g / min, and the feed temperature is 50 degrees. All feeds are from the upper part of the fixed bed. The fixed bed is insulated outside. Under this condition, the maximum temperature of the fixed bed reaches 130℃, which exceeds the upper temperature limit of the catalyst. The sampling analysis shows that the conversion rate of tetrapropylene is 88% and the selectivity is 98%. The reaction liquid is distilled and separated under the conditions of 45 distillation plates, 8 reflux ratio, 5hpa pressure, and 140℃ bottom temperature. The purity of the product is >99.8% and the yield is 85%.

[0040] It is easy to understand that the above embodiments are only examples for clear explanation and do not mean that the present invention is limited thereto. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from this are still within the protection scope of the present invention.

Claims

1. A method for preparing tert-dodecyl mercaptan by continuous reactive distillation, characterized in that: The method uses solid acid to catalyze the reaction of tetrapropylene and hydrogen sulfide in a distillation tower, and prepares tert-dodecyl mercaptan by distillation.

2. The method according to claim 1, characterized in that The reactive distillation tower is a packed tower or a plate tower, preferably a packed tower; Preferably, the number of theoretical plates of the reactive distillation tower is 10-40, preferably 20-30.

3. The method according to claim 1 or 2, characterized in that: The reactive distillation tower has two feed inlets, namely, a feed inlet at the top of the tower and a feed inlet at the bottom of the tower; Preferably, the tetrapropylene is fed from the feed port at the top of the tower, preferably at a feed position of 5 to 25 theoretical plates from the top of the tower, more preferably 10 to 15 theoretical plates; Preferably, the hydrogen sulfide enters from the feed port at the lower part of the tower, and the feed position is preferably 10 to 40 theoretical plates from the top of the tower, more preferably 20 to 30 theoretical plates; Preferably, the feed mass ratio of hydrogen sulfide to polypropylene is (0.2-1):1, preferably (0.4-0.6):

1.

4. The method according to any one of claims 1 to 3, characterized in that The acid catalyst is selected from one or more of an acidic resin, a molecular sieve, zirconium sulfate, and silica-alumina gel, preferably an acidic resin and / or a Y molecular sieve; Preferably, the acid catalyst is loaded in the reactive distillation tower using catalyst metal wire mesh structured packing, and the loading position is 1-40 plates, preferably 10-20 plates.

5. The method according to any one of claims 1 to 4, characterized in that The temperature of the reaction distillation tower kettle is 100-200°C, preferably 110-140°C; And / or, the top operating pressure of the reactive distillation tower is 0.1 to 100 kPa absolute pressure, preferably 0.2 to 5 kPa; and / or, the reflux ratio of the reaction is 1 to 10, preferably 3 to 8; And / or, the tetrapropylene recovery rate of the tower top of the reaction is 0.1%-1%.

6. A tert-dodecyl mercaptan, wherein the tert-dodecyl mercaptan is prepared by the method according to any one of claims 1 to 5.