A method for preparing dialkyl polysulfide

Abstract

The invention discloses a method for preparing dialkyl polysulfide, specifically: add alpha-olefin compound, sulfur element and solid catalyst to reactor No. 1, under inert gas atmosphere, the temperature is raised to 110 ℃~130 ℃, react 8~12h;Add alpha-olefin compound, sulfur element and solid catalyst to reactor No. 2, under inert gas atmosphere and closed condition, transfer the mixed material of reactor No. 1 to reactor No. 2, the temperature is raised to 110 ℃~130 ℃, react 6~10h, and obtain dialkyl polysulfide. The inventive method only uses olefin and elemental sulfur as raw materials, and can also obtain light-colored products without using hydrogen sulfide, mercaptan and halogen-containing substances. The color of the prepared dialkyl polysulfide is substantially consistent with the color of the product prepared by olefin, elemental sulfur and hydrogen sulfide;At the same time, the sulfur content of the product obtained by the inventive method can reach 40%.

Description

Technical Field

[0001] The invention relates to a method for preparing dialkyl polysulfide. Background Art

[0002] With the development of industrial technology, various lubricating oils (gear oil, engine oil, cutting oil, forming oil) are widely used in the processes of various equipment and various metal products to improve the service life of equipment and production efficiency. The extreme pressure anti-wear additives contained in lubricating oils mainly include sulfur-based, phosphorus-based and chlorine-based additives. Sulfur-based additives are mainly represented by compounds such as sulfided olefins and sulfided animal fats; among them, dialkyl polysulfides represented by sulfided olefins are the most widely used additives in various lubricating oils.

[0003] The preparation process of dialkyl polysulfide is mainly affected by its synthetic raw materials. According to different raw materials, it can be divided into the following categories: 1) US20020016268, JP4069399, JP2008222997, etc. use olefins, elemental sulfur and hydrogen sulfide as raw materials. The synthetic product has light color (product color is yellow) and low odor. It is also the main process route for current production, but the hydrogen sulfide used is a highly toxic substance. 2) US5338468, etc. use olefins and elemental sulfur as raw materials. The synthetic product has dark color (product color is black) and low sulfur content, narrow application field and low market acceptance. 3) WO2000043359 and US5530163 use thiol and elemental sulfur as raw materials. The synthetic product has light color and low odor, but the price of thiol is high and the toxicity is high, resulting in weak market competitiveness. 4) US4204969, US5410088, etc. use halogenated sulfur and olefins as raw materials, and the synthesized products are light in color, but a large amount of wastewater will be generated when removing the chlorine element in the product. 5) US5410088, CN1534019, etc. use halogenated hydrocarbons, elemental sulfur, and sodium sulfide or thiourea as raw materials, and the synthesized products are light in color, but the by-products containing halogen substances need to be washed with water, which will generate a large amount of wastewater. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a method for preparing dialkyl polysulfide, which uses only olefins and elemental sulfur as raw materials, and can also obtain light-colored products without using hydrogen sulfide, mercaptans and halogen-containing substances. The color of the prepared dialkyl polysulfide is basically consistent with the color of the product prepared from olefins, elemental sulfur and hydrogen sulfide; at the same time, the sulfur content of the product prepared by the method of the present invention can reach 40%.

[0005] Technical solution: The method for preparing dialkyl polysulfide of the present invention comprises the following steps:

[0006] (1) Adding α-olefin compound, sulfur and solid catalyst to reactor No. 1, raising the temperature to 110° C. to 130° C. under an inert gas atmosphere, and reacting for 8 to 12 hours; the transfer time is after 8 to 12 hours of reaction;

[0007] (2) Add α-olefin compounds, sulfur and solid catalyst to reactor No. 2, transfer the mixed material in reactor No. 1 to reactor No. 2 under an inert gas atmosphere and in a sealed condition, increase the temperature to 110° C. to 130° C., react for 6 to 10 hours, and obtain the target product, dialkyl polysulfide.

[0008] Wherein, in step (2), the pressure of the reaction system is maintained at 0.8-0.9 MPa.

[0009] Wherein, in step (1) and step (2), the solid catalyst is nano KOH / γ-Al2O3; the γ-Al2O3 carrier is loaded with KOH in an amount of 10 to 30% by mass of the catalyst (nano KOH / γ-Al2O3).

[0010] In order to improve the reaction efficiency, the present invention uses nano KOH / γ-Al2O3 as a catalyst. Nano KOH / γ-Al2O3 is a super base. In the reaction process of α-olefin compounds and sulfur, it has good catalytic activity and can effectively reduce the reaction activation energy, thereby promoting the reaction.

[0011] The nano KOH / γ-Al2O3 used in the present invention is synthesized by the method reported in the following literature: Effective synthesis of cis-3-hexen-1-yl acetate via transesterification over KOH / γ-Al2O3: Structure and catalytic performance, Applied Catalysis A: General 455: 1-7.

[0012] Wherein, in step (1) and step (2), the α-olefin compound is a straight-chain or branched-chain olefin compound having 8 to 18 carbon atoms.

[0013] Wherein, the α-olefin compound is α-pentene or 2,4,4-trimethyl-1-pentene.

[0014] In step (1), the α-olefin compound and the sulfur element undergo an incomplete reaction at a molar ratio of 1:1 to 2:1. The incomplete reaction of the α-olefin compound and the sulfur element during the first step can generate more intermediate mercaptans, which can fully react with the raw materials in the second step, making the color of the final product yellow.

[0015] Wherein, in step (2), the molar ratio of the α-olefin compound to the sulfur element is 1:1 to 2. By controlling the addition amount of the two, on the one hand, the sulfur content of the product can be ensured to be high, and on the other hand, the generation of by-products can be reduced.

[0016] The amount of the α-olefin compound added in step (2) is twice the amount of the α-olefin compound added in step (1).

[0017] Wherein, in step (1), the amount of solid catalyst added is 0.23-0.28% of the mass of sulfur; in step (2), the amount of solid catalyst added is 0.47-0.55% of the mass of sulfur. The addition of solid catalyst can effectively promote the efficiency of the whole reaction and shorten the reaction time.

[0018] Wherein, in step (2), after the reaction is completed, the pressure relief valve is opened, the pressure is slowly reduced to normal pressure, and the pressure is evacuated to below -0.08 MPa to remove reaction by-products and hydrogen sulfide.

[0019] After the pressure is released, the inert gas is continuously introduced for 1 to 2 hours, the temperature is lowered to 60 to 65°C, the catalyst and the unreacted sulfur are filtered out to obtain a light yellow dialkyl polysulfide; the pore size of the filter bag is 0.8 microns.

[0020] In the first step of the present invention, in order to use olefin and sulfur to react incompletely, the molar ratio is controlled at 2:1 to 1:1, and the reaction temperature is controlled at 110-120° C.; in the second step, the molar ratio of olefin to sulfur is controlled at 1:1 to 1:2, and the reaction temperature is controlled at 110-120° C. The first step and the second step are reacted in two reactors respectively, and the molar amount of olefin reacted in the second step is twice the molar amount of olefin reacted in the first step, so that the intermediate product mercaptan can be effectively consumed.

[0021] The invention uses two steps to make the product yellow in color. After the reaction of the first step is completed, the reaction product of the first step needs to be transferred to the second step reactor while hot (material heat transfer can save energy, and the pressure of the first reaction system itself is used to pump the material in the first reaction system to the second reaction system); the reaction is continued in the reactor of the second step. The by-products of the first step reaction (mercaptan and hydrogen sulfide, etc.) are used to participate in the reaction of the second step, so that light-colored dialkyl polysulfide can be produced without using hydrogen sulfide.

[0022] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The method of the present invention uses only olefins and elemental sulfur as raw materials to prepare dialkyl polysulfides, and does not use highly toxic substances such as hydrogen sulfide and mercaptan, and can also obtain a light-colored product (yellow). The color of the prepared dialkyl polysulfide is basically consistent with the color of the product prepared from olefins, elemental sulfur and hydrogen sulfide. Under four-sphere characterization, the performance of the product of the present invention is close to that of the product prepared from olefins, sulfur and hydrogen sulfide; (2) The method of the present invention also does not use halogen-containing substances to prepare light-colored products, thereby avoiding the subsequent generation of a large amount of wastewater when removing the halogen substances doped into the product; (3) The method of the present invention can also solve the problem that when amines are used as catalysts, free amines are easily doped into the product, thereby causing the dialkyl polysulfide to be easily turbid or precipitated after long-term storage. The product obtained by the method of the present invention has good long-term stability; (4) The method of the present invention can also solve the problem that the sulfur content of the final product obtained by using only olefins and elemental sulfur as raw materials in the prior art is not high. The sulfur content in the product of the present invention can reach 40%. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is an appearance diagram of the product obtained in Example 1 of the present invention;

[0024] Figure 2 This is the appearance of the product synthesized using only olefin and elemental sulfur as raw materials in Comparative Example 1;

[0025] Figure 3 This is the appearance of the product synthesized in Comparative Example 2 using olefins, elemental sulfur and hydrogen sulfide as raw materials. DETAILED DESCRIPTION

[0026] Example 1

[0027] The preparation method of dialkyl polysulfide of the present invention specifically comprises the following steps:

[0028] (1) preparing two two-liter autoclaves, both equipped with a heating device and a stirring mechanism, and the two autoclaves can transfer materials to each other; the two autoclaves are marked as 1# autoclave and 2# autoclave respectively;

[0029] (2) Add 160 g of α-decene, 146 g of sulfur and 0.8 g of KOH / γ-Al2O3 (30%) to the reactor #1, evacuate the reactor and fill it with nitrogen; repeat this operation 2 to 3 times to exhaust all the oxygen in the reactor; raise the temperature to 120°C and react for 8 hours;

[0030] (3) 320 g of α-decene, 584 g of elemental sulfur and 1.6 g of KOH / γ-Al2O3 (30%) were added to the 2# reactor, and the reactor was first evacuated and filled with nitrogen; this operation was repeated 2 to 3 times to exhaust the oxygen in the reactor; the temperature of the 2# reactor was raised to 120° C., and the product of the 1# reactor was transferred to the 2# reactor in a sealed state, and the pressure of the reaction system was maintained at above 0.8 MPa under an inert atmosphere of nitrogen or helium, and maintained under this reaction condition for more than 6 hours;

[0031] (4) After the reaction is completed, open the pressure relief valve, slowly reduce the pressure to normal pressure, and evacuate to below -0.08 MPa to remove reaction by-products and substances such as hydrogen sulfide; then continue to introduce nitrogen or helium for 1 hour, and finally reduce the temperature to 60°C, filter (the pore size of the filter bag is 0.8 microns), remove the catalyst and sulfur that has not participated in the reaction, and obtain a yellow product dialkyl polysulfide.

[0032] Example 2

[0033] The preparation method of dialkyl polysulfide of the present invention specifically comprises the following steps:

[0034] (1) preparing two two-liter autoclaves, both equipped with a heating device and a stirring mechanism, and the two autoclaves can transfer materials to each other; the two autoclaves are marked as 1# autoclave and 2# autoclave respectively;

[0035] (2) Add 128 g of 2,4,4-trimethyl-1-pentene, 146 g of elemental sulfur and 0.7 g of KOH / γ-Al2O3 (20%) to the reactor #1. The reactor is first evacuated and filled with nitrogen. This operation is repeated 2 to 3 times to exhaust all the oxygen in the reactor. The temperature is raised to 110°C and the reaction is carried out for 10 hours.

[0036] (3) 256 g of α-decene, 584 g of elemental sulfur and 1.4 g of KOH / γ-Al2O3 (20%) were added to the 2# reactor, and the reactor was first evacuated and filled with nitrogen; this operation was repeated 2 to 3 times to exhaust the oxygen in the reactor; the temperature of the 2# reactor was raised to 110° C., and the materials in the 1# reactor were transferred to the 2# reactor in a sealed state, and the pressure of the reaction system was maintained above 0.9 MPa under an inert atmosphere of nitrogen or helium, and maintained under this reaction condition for more than 8 hours;

[0037] (4) After the reaction is completed, open the pressure relief valve, slowly reduce the pressure to normal pressure, and evacuate to below -0.08 MPa to remove reaction by-products and substances such as hydrogen sulfide; then continue to introduce nitrogen or helium for 1 hour, and finally reduce the temperature to 60°C, filter (the pore size of the filter bag is 0.8 microns), remove the catalyst and sulfur that has not participated in the reaction, and obtain a yellow product dialkyl polysulfide.

[0038] Comparative Example 1

[0039] Comparative Example 1 refers to the prior art US5338468, which uses only olefins and elemental sulfur as raw materials to synthesize dialkyl polysulfide:

[0040] 1 mol of 2,4,4-trimethyl-1-pentene was added to a stainless steel reactor together with 1.9 mol of elemental sulfur, 1.1 mol of water and 0.32 mol of NH3. The reactants were heated to 165°C, reacted under pressure for 8 hours, cooled to 100°C, the residual pressure was vented through a scrubber and the reaction mixture was phase separated, the organic layer was sparged with gas for 2 hours and filtered.

[0041] Comparative Example 2

[0042] Comparative Example 2 is a method of synthesizing dialkyl polysulfide with olefin, elemental sulfur and hydrogen sulfide as raw materials and amine as catalyst according to the prior art JP4069399:

[0043] After replacing the air in a stainless steel autoclave with a blade-type stirrer with nitrogen, the autoclave had a capacity of 2 liters, 450 g of 2,4,4-trimethyl-1-pentene and 0.4 g of amine (catalyst) were introduced into the autoclave and sealed, and when heated to 120°C, the internal pressure (gauge pressure) increased to 1.0 kg / cm 2 ; 220.2 g of molten sulfur was added to a dripping tank maintained at 140°C, and nitrogen was added to pressurize it to 1.5 MPa. While operating the stirring blade of the autoclave, molten sulfur was dripped from the dripping tank into the autoclave at a rate of 25 g / min, and stirred to disperse; then hydrogen sulfide was introduced into the autoclave at a rate of 6 g / min to react for 12.5 hours and react at a temperature of 120°C. After the reaction reached the end point, the temperature of the autoclave was reduced to restore the pressure to normal pressure, and the unreacted raw materials were recovered by distillation.

[0044] The long-term stability, sulfur content, and lubricity of the dialkyl polysulfides obtained in Examples 1 to 2 and Comparative Examples 1 to 2 were evaluated according to the following methods. The evaluation results are shown in Table 1.

[0045] Long-term stability test: Place 100 g of dialkyl polysulfide in a transparent glass bottle and seal it. First place it in a 50°C environment for 7 days, and observe whether the appearance is turbid or precipitated or the color is significantly deepened; then transfer it to 20±5°C and place it for 7 days, and observe whether the appearance is turbid or precipitated or the color is significantly deepened; transfer it to a 4°C environment again and place it for 7 days, and observe whether the appearance is turbid or precipitated or the color is significantly deepened; finally transfer it to -20°C and place it for more than 24 hours, and then place it at room temperature for 7 days, and observe whether the appearance is turbid or precipitated or the color is significantly deepened; if any abnormality occurs at any stage, the long-term stability fails.

[0046] The total sulfur content is tested using the ICP method, and the active sulfur method refers to the ASTM D1662 method.

[0047] Lubrication performance evaluation: Use 15# Class II hydrogenated base oil to prepare a 2% dialkyl polysulfide solution, and refer to GB / T 3142 method to test the sintering compliance of the prepared solution (P D ).

[0048] Table 1 is the performance data of dialkyl polysulfides of Examples 1-2 and Comparative Examples 1-2

[0049]

[0050] The dialkyl polysulfide prepared by the present invention can be used as an extreme pressure anti-wear agent, and can form metal sulfide on the metal surface to reduce the friction coefficient between metals, so it can be widely used in equipment lubrication and metal product manufacturing processes.

Claims

1. A method for preparing dialkyl polysulfide, characterized in that: The steps include: (1) Adding an α-olefin compound, sulfur and a solid catalyst into a No. 1 reactor, wherein the molar ratio of the α-olefin compound to the sulfur is 1:1 to 2:1; raising the temperature to 110°C to 130°C under an inert gas atmosphere, and reacting for 8 to 12 hours; the solid catalyst is nano KOH / γ-Al2O3; and the γ-Al2O3 carrier is loaded with KOH in an amount of 10 to 30% by mass of the catalyst; (2) Add α-olefin compound, sulfur and solid catalyst to reactor No. 2, wherein the molar ratio of α-olefin compound to sulfur is 1:1-2; transfer the mixed material in reactor No. 1 to reactor No. 2 under an inert gas atmosphere and in a closed state, increase the temperature to 110°C-130°C, and react for 6-10 hours to obtain a light yellow dialkyl polysulfide; the amount of α-olefin compound added in step (2) is twice the amount of α-olefin compound added in step (1).

2. The method for preparing dialkyl polysulfide according to claim 1, characterized in that: In step (2), during the reaction, the pressure in reactor No. 2 is 0.8-0.9 MPa.

3. The method for preparing dialkyl polysulfide according to claim 1, characterized in that: In step (1) and step (2), the α-olefin compound is a straight-chain or branched-chain olefin compound having 8 to 18 carbon atoms.

4. The method for preparing dialkyl polysulfide according to claim 3, characterized in that: The α-olefin compound is α-pentene or 2,4,4-trimethyl-1-pentene.

5. The method for preparing dialkyl polysulfide according to claim 1, characterized in that: In step (1), the amount of solid catalyst added is 0.23-0.28% of the mass of sulfur; in step (2), the amount of solid catalyst added is 0.47-0.55% of the mass of sulfur.

6. The method for preparing dialkyl polysulfide according to claim 1, characterized in that: In step (2), after the reaction is completed, open the pressure relief valve, slowly reduce the pressure to normal pressure, and evacuate to below -0.08 MPa.

7. The method for preparing dialkyl polysulfide according to claim 6, characterized in that: After pressure relief, continue to introduce inert gas for 1-2 hours to lower the temperature to 60-65°C.

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