Preparation method of sulfurized isobutylene

Abstract

The invention discloses a preparation method of sulfurized isobutylene. The preparation method comprises the following steps: 1) putting sulfur in a molten state, a basic catalyst and a sulfur transfer catalyst into a reactor, and fully mixing; the sulfur transfer catalyst is a dithiocarbamate compound, and the addition amount of the sulfur transfer catalyst is 0.1-1.0 wt% of the mass of sulfur; 2) introducing isobutene into a mixed system in the reactor, and fully reacting under the conditions of 160-200 DEG C and 2-6 MPa to obtain a reaction product; and 3) cooling the reaction product to 70-90 DEG C, standing for layering, separating the upper-layer product, and refining to obtain the sulfurized isobutylene product. According to the preparation method of the sulfurized isobutylene disclosed by the invention, the sulfur transfer catalyst is introduced, so that the sulfur utilization rate and the production efficiency of the sulfurized isobutylene are remarkably improved, and meanwhile, a sulfurized isobutylene product with stable quality is obtained.

Description

Technical Field

[0001] This application belongs to the field of organosulfur synthesis technology, and specifically relates to a method for preparing isobutylene sulfide. Background Technology

[0002] Sulfurized isobutylene (IBS) is an important extreme pressure anti-wear additive for lubricating oils, with the general molecular formula C4H8S. n (n=1-5), the main component is chain-like tert-butyl polysulfide. Due to its high sulfur content (30-50%), excellent extreme pressure anti-wear properties, and good oil solubility, it is widely used in gear oils, metalworking fluids, hydraulic oils and other fields.

[0003] Currently, the main industrial production methods for isobutylene sulfide are the ammonium polysulfide method and the one-step high-pressure synthesis. The ammonium polysulfide method uses ammonia as one of the raw materials, and the storage and use of ammonia pose safety risks, increasing safety hazards and management costs. Furthermore, the production process generates ammonia-containing wastewater, increasing wastewater treatment costs and posing environmental pollution risks. The one-step high-pressure synthesis is a newly developed process in recent years. Li Fei et al., in their paper "Product Analysis and Reaction Mechanism of One-Step High-Pressure Synthesis of Isobutylene Sulfide" (Applied Chemistry, Vol. 32, No. 7, July 2015), disclosed a method using n-octylamine as a catalyst to directly react sulfur and isobutylene under high pressure at 160-190℃ to produce isobutylene sulfide. While this method avoids the use of ammonia, it suffers from low production efficiency in industrial applications: firstly, the poor melting properties of sulfur lead to low sulfur utilization; secondly, sulfur and isobutylene undergo a dehydrogenation side reaction under alkaline catalysts, producing MDTT (4-methyl-3H-1,2-dithiamono-3-thionone) and hydrogen sulfide. MDTT, being a highly corrosive compound, requires complex post-treatment processes for removal.

[0004] To address the aforementioned issues, existing technologies, such as the method for synthesizing isobutylene sulfide disclosed in CN108409713A, transform the original batch reaction into a semi-continuous reaction by mixing elemental sulfur with the product isobutylene sulfide, thus resolving the problems of sulfur flowability and production efficiency. However, sulfur still exists in elemental form in the reaction system, and its reactivity is not significantly improved; the product still contains unreacted solid sulfur. Summary of the Invention

[0005] The technical effect to be achieved by this application is to provide a method for preparing isobutylene sulfide, which effectively improves the production efficiency of isobutylene sulfide.

[0006] To achieve the above-mentioned technical effects, this application provides a method for preparing isobutylene sulfide, comprising the following steps: 1) Molten sulfur, an alkaline catalyst, and a sulfur transfer catalyst are added to the reactor and thoroughly mixed; the sulfur transfer catalyst is a dithiocarbamate compound, and the amount of the sulfur transfer catalyst added is 0.1-1.0 wt% of the sulfur mass. 2) Isobutylene is introduced into the mixed system in the reactor and reacted fully at 160-200℃ and 2-6 MPa to obtain the reaction product; 3) Cool the reaction product to 70-90℃ and allow it to stand to separate into layers. Separate the upper layer product and refine it to obtain the sulfurized isobutylene product.

[0007] As a preferred option, the sulfur transfer catalyst is one of zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, or sodium dimethyldithiocarbamate.

[0008] Furthermore, the sulfur transfer catalyst is zinc dibutyldithiocarbamate, and the amount of sulfur transfer catalyst added is 0.3-0.8 wt% of the sulfur mass.

[0009] As a preferred option, the alkaline catalyst is one of n-octylamine, di-n-octylamine, tri-n-octylamine, and triethylamine.

[0010] Furthermore, the amount of alkaline catalyst added is 2-8 wt% of the sulfur mass.

[0011] As a preferred option, the molar ratio of sulfur to isobutylene is 1.5-2.5:1.

[0012] As a preferred option, the lower product obtained after separating the upper product in step 3) is recovered sulfur; after step 3), the following steps are also included: The recovered sulfur is melted and then returned to step 1) for reuse.

[0013] As a preferred option, in step 3), the refining process includes: subjecting the upper product to vacuum distillation, distilling off unreacted isobutylene from the top of the column, and obtaining the sulfurized isobutylene product from the bottom of the column.

[0014] Furthermore, following step (3), the following is also included: The by-product residue generated during the refining process is returned to the reactor in step 1) for recycling.

[0015] As a preferred option, in step 1), the sulfur transfer catalyst is premixed with the alkaline catalyst and then added to the reactor together with molten sulfur.

[0016] The beneficial effects of this application are as follows: 1. The method provided in this application involves a one-step reaction of molten sulfur, isobutylene, a basic catalyst, and a sulfur transfer catalyst, promoting the conversion and recycling of unreacted sulfur through a sulfur transfer mechanism. The sulfur transfer catalyst is a dithiocarbamate, specifically the dithiocarbamate ion (R2NCS2). - It is a strong nucleophile with an SCS ternary structure, readily reacting with the S8 ring, attacking the weak SS bond of S8, and converting the inert S8 ring into a highly reactive monosulfide (S) or polysulfide (S). x Free radicals / ions prevent S8 self-polymerization, efficiently participate in the one-step sulfurization process of isobutylene, and significantly improve sulfur utilization.

[0017] 2. The scheme provided in this application establishes a dual sulfur conversion pathway in the reaction system by introducing a sulfur transfer catalyst, including a basic catalyst catalyzing the ring-opening of sulfur to form sulfur ions (S). n 2- The traditional pathway involves the reaction of sulfide ions with isobutylene to form isobutylene sulfide, as well as the reaction of sulfur transfer catalysts with sulfur to form polysulfide intermediates (such as ZDBC-S). n This intermediate transfers sulfur atoms to isobutylene molecules to generate isobutylene sulfide. Through the synergistic effect of the dual pathways, the production efficiency of isobutylene sulfide is effectively improved.

[0018] 3. The solution provided in this application enriches the sulfur transfer catalyst in the residue of the tower bottom through a refining process, and returns the enriched residue to the reactor for recycling, thereby realizing the recycling of the sulfur transfer catalyst and reducing energy consumption and raw material consumption. Detailed Implementation

[0019] The embodiments of the technical solution of this application will be described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0020] Example 1 This embodiment provides a method for preparing sulfide isobutylene, and the specific steps are as follows: 1) Weigh 440 kg of industrial sulfur (99.5% purity) and heat it to 145°C under nitrogen protection to completely melt the sulfur, obtaining molten sulfur; weigh 18 kg of n-octylamine as an alkaline catalyst, with an addition amount of 4.1 wt% of the sulfur mass; weigh 2.2 kg of zinc dibutyldithiocarbamate as a sulfur transfer catalyst, with an addition amount of 0.5 wt% of the sulfur mass; Octylamine was added to molten sulfur and mixed for 10 minutes at 145°C and 150 rpm to ensure that the alkaline catalyst was uniformly dispersed in the molten sulfur. Subsequently, ZDBC was slowly added to the reactor while stirring during the addition process to ensure that the sulfur transfer catalyst was uniformly dispersed in the mixture of molten sulfur and alkaline catalyst, thus obtaining a fully mixed reaction mixture. 2) Heat the mixture obtained in step 1) to 175℃, and slowly feed 610 kg of isobutylene (560 kg of fresh isobutylene and 50 kg of recycled isobutylene) into the mixture in the reactor using a high-pressure metering pump. Control the feed rate of isobutylene to gradually increase the reaction pressure to 4.0 MPa. After the isobutylene feed is complete, maintain the reaction temperature at 175±2℃, the reaction pressure at 4.0±0.2 MPa, and the stirring speed at 150 rpm, and continue the reaction for 60 minutes. During the reaction, observe the pressure changes to judge the reaction progress. When the pressure no longer decreases, it indicates that the reaction is basically complete and the reaction product is obtained. 3) After the reaction is complete, stop heating, slowly reduce the pressure to atmospheric pressure, cool the reaction product to 75°C, transfer it to a settling tank, and keep it at that temperature for 1.5 hours. After settling, the material naturally separates into two layers: the upper layer is a pale yellow liquid (crude isobutylene sulfide), and the lower layer is a dark liquid (unreacted molten sulfur). Separate the upper product through the upper valve, and transfer the upper product to a vacuum distillation apparatus for purification. Distillation separation is carried out under a vacuum of -0.07 MPa and a temperature of 150-165°C to obtain the isobutylene sulfide product. 4) Discharge the lower layer product (recovered sulfur) from the bottom valve, heat it to 145°C and keep it in a molten state, then return it to step 1) and mix it with fresh sulfur for reuse; 5) The residue in the bottom of the tower enriched with ZDBC is returned to the reactor in step 1) for recycling.

[0021] Examples 2-7 The difference between Examples 2-7 and Example 1 lies in the amount of substances added in each step and the process control. The other conditions and steps are the same as in Example 1. The control parameters for each step in Examples 1-7 are detailed in Table 1.

[0022] Comparative Example 1 The difference between this comparative example and Example 1 is as follows: In step 1), no sulfur transfer catalyst ZDBC was added; only the basic catalyst n-octylamine (18 kg, accounting for 4.1 wt% of the sulfur mass) was used. In step 2), the reaction time was extended to 75 minutes. The remaining conditions and steps were the same as in Example 1.

[0023] Comparative Example 2 The difference between this comparative example and Example 1 is that the amount of ZDBC added in step 1) is 0.05 wt% of the sulfur mass (i.e. 0.22 kg), while the other conditions and steps are the same as in Example 1.

[0024] Comparative Example 3 The difference between this comparative example and Example 1 is that the amount of ZDBC added in step 1) is 1.2 wt% of the sulfur mass (i.e., 5.3 kg), while the other conditions and steps are the same as in Example 1.

[0025] Comparative Example 4 This comparative example adopts the technical solution disclosed in CN108409713A: Step 1) Mix elemental sulfur (440 kg) with isobutylene sulfide (440 kg), heat to 180°C to melt the sulfur, add sodium sulfide catalyst (0.5% of the molar amount of sulfur, i.e. 1.1 kg), and mix thoroughly.

[0026] Step 2) Isobutylene (610 kg) was introduced into the mixed system and reacted at 180 °C and 4 MPa for 12 hours (720 minutes) to obtain the reaction product.

[0027] Step 3) Cool the reaction product to 75°C and allow it to stand to separate into layers. Separate the upper layer product and refine it to obtain the sulfurized isobutylene product.

[0028] Table 1. Process conditions for each embodiment and comparative example Samples were taken from the sulfurized isobutylene products obtained in step S3 for each embodiment and comparative example. The sulfur content of isobutylene sulfide was determined according to GB / T 388-2012 "Determination of Sulfur Content in Petroleum Products (Lamp Method)" (expressed as mass percentage (wt%)). The total content of the main components (chain tert-butyl polysulfides, including C4H8S, C4H8S2, C4H8S3, etc.) of isobutylene sulfide was calculated by peak area normalization using gas chromatography-mass spectrometry and expressed as mass percentage (%). The content of the byproduct MDTT was determined by gas chromatography. The kinematic viscosity of isobutylene sulfide was determined according to GB / T 265-1988 "Determination of Kinematic Viscosity and Calculation of Dynamic Viscosity of Petroleum Products". The density of isobutylene sulfide was determined according to GB / T 1884-2000 "Determination of Density of Petroleum and Liquid Petroleum Products (Density Meter Method)" and the copper strip corrosion of isobutylene sulfide was determined according to GB / T 5096-2017 "Test Method for Copper Strip Corrosion of Petroleum Products". Calculate the sulfur utilization rate (%) for the entire reaction process, and weigh the recovered sulfur obtained in step 4). Based on the mass (kg) of the recovered sulfur, calculate the percentage of unreacted sulfur relative to the input sulfur. The measurement results are shown in Table 2 below.

[0029] Table 2. Test results of each embodiment and comparative example. Based on the systematic study of the above embodiments and comparative examples, the following conclusions are drawn: As can be seen from Table 2, compared with Comparative Example 4, the sulfur utilization rate of Example 1 increased from 84.5% to 95.4%, the unreacted sulfur decreased from 65 kg to 20 kg, the MDTT content decreased from 4.2% to 2.3%, the product purity increased from 97.5% to 98.5%, and the copper sheet corrosion improved from level 2 to level 1, which fully demonstrates the significant superiority of the technical solution of this application.

[0030] Comparative Example 1 showed a sulfur utilization rate of only 82.0%, with unreacted sulfur reaching 70 kg (15.9%), consistent with existing one-step high-pressure synthesis technologies. Comparative Example 2 showed a sulfur utilization rate of 86.5%, with limited effectiveness. Comparative Example 3 showed a sulfur utilization rate reduced to 88.5%, with a product purity of only 96.8% and copper sheet corrosion grade 2. In contrast, Examples 2-3 showed sulfur utilization rates of 89.0-97.0%, unreacted sulfur reduced to 3.4-10.2%, and product purity ≥98%. This indicates that the addition and dosage of sulfur transfer catalyst have a significant impact on the technical effect; excessive catalyst can lead to negative effects such as catalyst aggregation and deactivation, decreased product purity, and increased side reactions.

[0031] In summary, this application significantly improves sulfur utilization by introducing a sulfur transfer catalyst, resulting in stable and excellent product quality. It also features a wide range of process parameters with strong adaptability and eliminates the use of harmful substances such as ammonia, achieving green and environmentally friendly production. The above embodiments fully verify the superiority and feasibility of the technical solution presented in this application. Furthermore, the beneficial effects of this application are significant.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A process for the preparation of sulfided isobutene, characterized in that, The method comprises the following steps: 1) mixing sulfur in molten state, alkaline catalyst and sulfur transfer catalyst in a reactor; the sulfur transfer catalyst is a dithio carbamate compound, and the addition amount of the sulfur transfer catalyst is 0.1-1.0 wt% of the mass of sulfur; 2) introducing isobutene into the mixed system in the reactor, and fully reacting under the conditions of 160-200 ℃ and 2-6 MPa to obtain a reaction product; 3) cooling the reaction product to 70-90 ℃, standing and separating, separating the upper layer product, and obtaining a sulfurized isobutene product through refining treatment.

2. The production method according to claim 1, wherein The sulfur transfer catalyst is one of zinc diethyl dithio carbamate, zinc dibutyl dithio carbamate and sodium dimethyl dithio carbamate.

3. The production method according to claim 1 or 2, characterized by, The sulfur transfer catalyst is zinc dibutyl dithio carbamate, and the addition amount of the sulfur transfer catalyst is 0.3-0.8 wt% of the mass of sulfur.

4. The production method according to claim 1, wherein The alkaline catalyst is one of n-octylamine, di-n-octylamine, tri-n-octylamine and triethylamine.

5. The production method according to claim 4, wherein The addition amount of the alkaline catalyst is 2-8 wt% of the mass of sulfur.

6. The production method according to claim 1, wherein The molar ratio of sulfur to isobutene is 1.5-2.5:

1.

7. The production method according to claim 1, wherein The lower layer product obtained after separating the upper layer product in step 3) is recycled sulfur; After step 3), the method further comprises: Returning the recycled sulfur to step 1) after melting for recycling.

8. The production method according to claim 1, wherein In step 3), the refining treatment comprises: performing vacuum distillation on the upper layer product, distilling unreacted isobutene from the top of the column, and obtaining the sulfurized isobutene product from the bottom of the column.

9. The production method according to claim 1 or 8, wherein After step 3), the method further comprises: Returning the by-product residue generated in the refining treatment process to the reactor in step 1) for recycling.

10. The production method according to claim 1, wherein In step 1), the sulfur transfer catalyst and the alkaline catalyst are pre-mixed, and then the mixture is put into the reactor together with molten sulfur.

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