Preparation method of n-dodecyl mercaptan

Abstract

The invention discloses a preparation method of n-dodecyl mercaptan, and relates to the technical field of n-dodecyl mercaptan. According to the technical scheme, 1-dodecene and hydrogen sulfide are used as raw materials, an accelerant is added, and 1-dodecene and hydrogen sulfide are subjected to a free radical addition reaction under the initiation of ultraviolet light to obtain n-dodecyl mercaptan; wherein the accelerant is alpha, alpha-diethoxy acetophenone or alpha, alpha-dimethoxy-alpha-phenyl acetophenone, and the accelerant is alpha, alpha-diethoxy acetophenone or alpha, alpha-dimethoxy-alpha-phenyl acetophenone; the molar ratio of the 1-dodecene to the accelerant is (1-1.5): (0.045-0.05). According to the present invention, the synthesis route using the n-dodecene and the hydrogen sulfide as the raw materials has the industrial production value and the obvious economic advantage, and solves the problems of rapid catalytic system inactivation, low conversion rate, low selectivity, high by-product content, serious pollution, high cost and unsuitability for large-scale production in the existing preparation method.

Description

Technical Field

[0001] The invention relates to the technical field of n-dodecyl mercaptan, and in particular to a method for preparing n-dodecyl mercaptan. Background Art

[0002] n-Dodecyl mercaptan (NDM), also known as dodecanethiol, is an organic compound with the chemical formula C 12 H 26 S. n-Dodecyl mercaptan is often used as a polymerization regulator for synthetic rubber, synthetic fiber and synthetic resin, especially in the polymerization of styrene-butadiene rubber emulsion. In addition, it can also be used as a stabilizer for polyvinyl chloride, or used in the manufacture of drugs, pesticides, fungicides and detergents.

[0003] At present, there are three main methods for preparing n-dodecyl mercaptan: 1) using n-dodecyl aldehyde, n-dodecyl nitrile, sodium dodecyl sulfonate, and 1-halododecane as raw materials to synthesize n-dodecyl mercaptan, but this preparation method has the problems of high raw material cost and high three wastes, which is not conducive to industrial production; 2) using alkyl sulfides such as dilauryl sulfide as raw materials for cracking synthesis, which is suitable for the recovery and utilization of by-product sulfides in the process of synthesizing mercaptan. The conversion rate and yield of the main product mercaptan in this synthesis method are low, resulting in high cost and is also not suitable for industrial production; 3) using 1-dodecene or n-dodecyl alcohol as raw materials for the synthesis of n-dodecyl mercaptan. The synthetic routes of the materials have industrial production value. Among them, the process route using n-dodecanol and hydrogen sulfide as raw materials has more impurities in the product synthesized in the solid phase catalyst, the post-processing process is long, the catalyst deactivates quickly, and the unit treatment needs to go through multiple repeated processes such as crystallization and distillation. The single-pass conversion rate is only 60-70%, and the selectivity is 80%. The process route using 1-dodecene and hydrogen sulfide as raw materials adds a resin catalyst in the reactor and synthesizes the product under ultraviolet light initiation. The conversion rate is 80%, the selectivity is only 70%, and a large amount of by-products such as sulfide will be produced, and a large amount of kettle residue cannot be solved.

[0004] Therefore, in view of the problems existing in the existing method for preparing n-dodecyl mercaptan, it is necessary to provide a new method for preparing n-dodecyl mercaptan. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art, provide a method for preparing n-dodecyl mercaptan, and provide a synthetic route using n-dodecene and hydrogen sulfide as raw materials, which has industrial production value and obvious economic advantages, and solves the problems of fast deactivation of the catalytic system, low conversion rate, low selectivity, high by-products, serious pollution, high cost, and unsuitability for large-scale production in the prior preparation method.

[0006] The technical solution of the present invention is: The preparation method of n-dodecyl mercaptan comprises the following steps: using 1-dodecene and hydrogen sulfide as raw materials, adding a promoter, and initiating ultraviolet light to allow 1-dodecene and hydrogen sulfide to undergo a free radical addition reaction to obtain n-dodecyl mercaptan; wherein the promoter is α,α-diethoxyacetophenone or α,α-dimethoxy-α-phenylacetophenone; and the molar ratio of 1-dodecene to the promoter is (1-1.5):(0.045-0.05).

[0007] Preferably, the wavelength of ultraviolet light is 360-400 nm.

[0008] Preferably, during the reaction, the flow rate of hydrogen sulfide is 2.5-4 L / min.

[0009] Preferably, the reaction temperature is 8-15°C and the reaction pressure is 1-1.5 MPa.

[0010] Preferably, the obtained n-dodecyl mercaptan is further purified, that is, the n-dodecyl mercaptan is sequentially subjected to gas-liquid separation, phase separation, alkali washing and distillation to obtain purified n-dodecyl mercaptan.

[0011] Compared with the prior art, the present invention has the following beneficial effects: The preparation method of n-dodecyl mercaptan of the present invention uses n-dodecene and hydrogen sulfide as raw materials for a synthetic route, has industrial production value, has obvious economic advantages, and solves the problems of rapid deactivation of the catalytic system, serious pollution, high cost, and unsuitability for large-scale production in the existing preparation method. In addition, the preparation method of n-dodecyl mercaptan of the present invention has a n-dodecyl mercaptan conversion rate of more than 72%, and the purity of the refined n-dodecyl mercaptan product is greater than 98.5%. DETAILED DESCRIPTION

[0012] In order to enable persons skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0013] Example 1 The preparation method of n-dodecyl mercaptan of the present embodiment is as follows: The low-pressure hydrogen sulfide in the cylinder has a pressure of 0.5MPa and enters the low-pressure storage tank. After drying, it is pressurized by the compressor and enters the high-pressure storage tank. The hydrogen sulfide in the high-pressure storage tank is continuously metered at 3L / min by a plunger metering pump at a pressure of 1.1MPa through a flow meter and enters the catalytic reactor. It mixes with the promoter α,α-diethoxyacetophenone and 1-dodecene in the catalytic reactor and undergoes a free radical addition reaction; the reaction temperature is controlled at 10°C, and after reacting for 1h, a reaction compound containing n-dodecyl mercaptan is obtained. Among them, the catalytic reactor has a built-in ultraviolet light source with a main wavelength of 360nm; the molar ratio of 1-dodecene to the promoter is 1.2:0.048.

[0014] The reaction mixture overflows into the gas-liquid separator, and the separated unreacted hydrogen sulfide returns to the low-pressure storage tank for recycling; the separated reaction liquid enters the phase separator, and the separated hydrogen sulfide tail gas enters the alkali washing tank for absorption with alkali liquid. Finally, the separated reaction liquid is measured and the components are analyzed. After analysis, the yield of n-dodecyl mercaptan is 72% and the selectivity is 83%. After the reaction liquid is further distilled, the n-dodecyl mercaptan product is obtained, which is colorless and transparent in appearance, with a purity of up to 98.7%, of which the mercaptan sulfur content is 15.65wt.%, and the density is 0.833g / cm 3 .

[0015] Example 2 The preparation method of n-dodecyl mercaptan of the present embodiment is as follows: The low-pressure hydrogen sulfide in the cylinder has a pressure of 0.5MPa and enters the low-pressure storage tank. After drying, it is pressurized by the compressor and enters the high-pressure storage tank. The hydrogen sulfide in the high-pressure storage tank is continuously metered at 4L / min by a plunger metering pump at a pressure of 1.5MPa through a flow meter and enters the catalytic reactor. It is mixed with the promoter α,α-dimethoxy-α-phenylacetophenone and 1-dodecene in the catalytic reactor and undergoes a free radical addition reaction; the reaction temperature is controlled at 15°C, and after reacting for 1h, a reaction compound containing n-dodecyl mercaptan is obtained. Among them, the catalytic reactor has a built-in ultraviolet light source with a main wavelength of 380nm; the molar ratio of 1-dodecene to the promoter is 1.5:0.05.

[0016] The reaction mixture overflows into the gas-liquid separator, and the separated unreacted hydrogen sulfide returns to the low-pressure storage tank for recycling; the separated reaction liquid enters the phase separator, and the separated hydrogen sulfide tail gas enters the alkali washing tank for absorption with alkali liquid. Finally, the separated reaction liquid is measured and the components are analyzed. After analysis, the yield of n-dodecyl mercaptan is 75% and the selectivity is 85%. After the reaction liquid is further distilled, the n-dodecyl mercaptan product is obtained, which is colorless and transparent in appearance, with a purity of up to 98.8%, of which the mercaptan sulfur content is 15.67wt.%, and the density is 0.835g / cm 3 .

[0017] Example 3 The preparation method of n-dodecyl mercaptan of the present embodiment is as follows: The low-pressure hydrogen sulfide in the cylinder has a pressure of 0.5MPa and enters the low-pressure storage tank. After drying, it is pressurized by the compressor and enters the high-pressure storage tank. The hydrogen sulfide in the high-pressure storage tank is continuously metered at 2.5L / min by a plunger metering pump at a pressure of 1MPa through a flow meter and enters the catalytic reactor. It is mixed with the promoter α,α-dimethoxy-α-phenylacetophenone and 1-dodecene in the catalytic reactor and undergoes a free radical addition reaction; the reaction temperature is controlled at 8°C, and after reacting for 1h, a reaction compound containing n-dodecyl mercaptan is obtained. Among them, the catalytic reactor has a built-in ultraviolet light source with a main wavelength of 400nm; the molar ratio of 1-dodecene to the promoter is 1:0.045.

[0018] The reaction mixture overflows into the gas-liquid separator, and the separated unreacted hydrogen sulfide returns to the low-pressure storage tank for recycling; the separated reaction liquid enters the phase separator, and the separated hydrogen sulfide tail gas enters the alkali washing tank for absorption with alkali liquid. Finally, the separated reaction liquid is measured and the components are analyzed. After analysis, the yield of n-dodecyl mercaptan is 72% and the selectivity is 78%. After the reaction liquid is further distilled, the n-dodecyl mercaptan product is obtained, which is colorless and transparent in appearance, with a purity of up to 98.6%, of which the mercaptan sulfur content is 15.66wt.%, and the density is 0.834g / cm 3 .

[0019] Comparative Example 1 The difference from Example 1 is that no promoter is added to the catalytic reactor.

[0020] The final yield of n-dodecyl mercaptan prepared in Comparative Example 1 was 8%, the selectivity was 90%, and the reaction solution was further distilled to obtain n-dodecyl mercaptan product, which was colorless and transparent in appearance, with a purity of 98.6%, wherein the mercaptan sulfur content was 15.68wt.%, and the density was 0.835g / cm 3 .

[0021] It can be seen from Example 1 and Comparative Example 1 that when no promoter is added, although the selectivity of the product is increased, the conversion rate is sharply reduced. This is because when no promoter is added, ultraviolet irradiation alone cannot effectively promote the synthesis reaction of thiols, and only a very small amount of raw materials undergo thiol addition reaction. Although thiol products cannot be synthesized, a series of side reactions will occur between olefins.

[0022] Comparative Example 2 The difference from Example 1 is that the molar ratio of 1-dodecene to the promoter is 1:0.08.

[0023] The final yield of n-dodecyl mercaptan prepared in Comparative Example 2 was 60%, and the selectivity was 61%. After the reaction solution was distilled, n-dodecyl mercaptan was obtained. The product was colorless and transparent, with a purity of 98.5%, a mercaptan sulfur content of 15.62wt.%, and a density of 0.836g / cm 3 .

[0024] It can be seen from Example 1 and Comparative Example 2 that when too much promoter is added, it is not conducive to the full progress of the reaction, affects the reaction interface between the reaction raw materials, and affects the effect of ultraviolet light, thereby causing a significant decrease in conversion rate and selectivity.

[0025] Comparative Example 3 The difference from Example 1 is that the reaction temperature is controlled at 5°C.

[0026] The final yield of n-dodecyl mercaptan prepared in Comparative Example 3 was 40%, the selectivity was 35%, and the reaction solution was further distilled to obtain n-dodecyl mercaptan product, which was colorless and transparent in appearance, with a purity of 98.5%, wherein the mercaptan sulfur content was 15.61wt.%, and the density was 0.835g / cm 3 .

[0027] It can be seen from Example 1 and Comparative Example 3 that when the reaction temperature is too low, although it has little effect on the purity of the product, it will affect the progress and speed of the reaction and reduce the selectivity and conversion rate of the reaction.

[0028] Comparative Example 4 The difference from Example 1 is that the reaction temperature is controlled at 25°C.

[0029] The final yield of n-dodecyl mercaptan prepared in Comparative Example 4 was 47%, the selectivity was 52%, and the reaction solution was further distilled to obtain n-dodecyl mercaptan product, which was colorless and transparent in appearance, with a purity of 95.4%, wherein the mercaptan sulfur content was 15.32wt.%, and the density was 0.836g / cm 3 .

[0030] It can be seen from Example 1 and Comparative Example 4 that when the reaction temperature is too high, it is beneficial to promote the progress and speed of the reaction, but at the same time it will increase the occurrence of side reactions and increase ether reactions, thereby reducing the yield and selectivity of the target product.

[0031] Comparative Example 5 The difference from Example 1 is that the hydrogen sulfide in the high-pressure storage tank is continuously metered into the catalytic reactor at a pressure of 2 MPa through a plunger metering pump and a flow meter at a rate of 3 L / min.

[0032] The final yield of n-dodecyl mercaptan prepared in Comparative Example 5 was 65%, the selectivity was 80%, and the reaction solution was further distilled to obtain n-dodecyl mercaptan product with black impurities in appearance and a purity of 81%, wherein the mercaptan sulfur content was 14.32wt.%, and the density was 0.845g / cm 3 .

[0033] It can be seen from Example 1 and Comparative Example 5 that due to the excessively high reaction pressure, hydrogen sulfide and the accelerator partially react to generate black solid impurities, which greatly affects the reaction.

Claims

1. A method for preparing n-dodecyl mercaptan, characterized in that: 1-Dodecene and hydrogen sulfide are used as raw materials, a promoter is added, and under the initiation of ultraviolet light, 1-dodecene and hydrogen sulfide undergo free radical addition reaction to obtain n-dodecyl mercaptan; wherein the promoter is α,α-diethoxyacetophenone or α,α-dimethoxy-α-phenylacetophenone; the molar ratio of 1-dodecene to the promoter is (1-1.5):(0.045-0.05).

2. The method for preparing n-dodecyl mercaptan according to claim 1, characterized in that: The wavelength of ultraviolet light is 360-400nm.

3. The method for preparing n-dodecyl mercaptan according to claim 1, characterized in that: During the reaction, the flow rate of hydrogen sulfide is 2.5-4 L / min.

4. The method for preparing n-dodecyl mercaptan according to claim 1, characterized in that: The reaction temperature is 8-15°C, and the reaction pressure is 1-1.5MPa.

5. The method for preparing n-dodecyl mercaptan according to claim 1, characterized in that: The obtained n-dodecyl mercaptan is further refined, that is, the n-dodecyl mercaptan is sequentially subjected to gas-liquid separation, phase separation, alkali washing and rectification to obtain refined n-dodecyl mercaptan.