Process for the preparation of sulfocarbamide

Abstract

The application discloses a preparation method of sulfolane, which comprises the following steps: (1) butadiene and sulfur dioxide are reacted in the presence of a polymerization inhibitor in a cyclopentane solvent to obtain a cyclobutene sulfone solution; then the obtained cyclobutene sulfone solution is subjected to flash evaporation to obtain a gas phase and a liquid phase; the gas phase is condensed and recycled; the liquid phase is subjected to steam stripping with cyclopentane gas to obtain cyclobutene sulfone; (2) the cyclobutene sulfone is subjected to catalytic hydrogenation to obtain a hydrogenation product; the hydrogenation product is subjected to steam stripping; the gas phase part is subjected to solvent refining after condensation, and the obtained solvent is recycled; the liquid phase part is subjected to product refining to obtain sulfolane. The synthesis solvent and the hydrogenation solvent of the application are both cyclopentane, the cyclobutene sulfone is prevented from solidifying at room temperature, sulfur dioxide in the cyclobutene sulfone is effectively removed by blowing off with cyclopentane gas, and the gas can be recycled after deep cooling and liquefaction.

Description

Technical Field

[0001] This invention relates to the field of sulfolane synthesis technology, and more specifically to a method for preparing sulfolane. Background Technology

[0002] Sulfolane is a highly efficient polar organic solvent, miscible with water and many other solvents, and readily soluble in aromatic hydrocarbons and alcohols. It exhibits strong solubility for many organic compounds and some inorganic compounds, but shows very low solubility for alkane compounds, cycloalkanes, and polymers of methacrylates, styrene, and vinylidene chloride. Sulfolane can also be used as a reaction solvent. As a solvent, sulfolane products are mainly used in aromatic hydrocarbon extraction, natural gas desulfurization, pharmaceutical intermediates, and organic chemical solvents, offering advantages such as high safety, good solubility, easy recovery, and good selectivity.

[0003] The most common process for producing sulfolane is the hydrogenation of sulfolane. Butadiene reacts with sulfur dioxide in the presence of a polymerization inhibitor to produce sulfolane. After desulfurization, hydrogenation is performed to generate sulfolane. To achieve a high butadiene conversion rate, excess sulfur dioxide is typically added. However, this excess sulfur dioxide dissolves in sulfolane and poisons the hydrogenation catalyst. Therefore, desulfurization is necessary before the hydrogenation reaction. Current techniques generally involve flash evaporation followed by air or nitrogen stripping, resulting in sulfur dioxide loss and the formation of hazardous waste. Furthermore, the low freezing point of sulfolane synthesized from sulfur dioxide and butadiene, coupled with improper temperature control, can cause equipment and pipeline blockages. Therefore, properly handling excess sulfur dioxide is a key technology in the synthesis of sulfolane. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of equipment and pipeline blockage in the existing technology, and to provide a method for preparing sulfolane. In the preparation process of sulfolane, cyclopentane is used as a solvent, which can lower the freezing point of sulfolane and solve the problem of easy solidification at room temperature, thus avoiding equipment and pipeline blockage. At the same time, cyclopentane is used as the stripping gas, and the sulfur dioxide gas released can be recycled after deep cooling, reducing production costs, reducing waste gas emissions, and avoiding environmental pollution.

[0005] To achieve the above objectives, the present invention provides a method for preparing sulfolane, the method comprising the following steps:

[0006] (1) Butadiene and sulfur dioxide react in cyclopentane solvent in the presence of a polymerization inhibitor to obtain cyclobutene sulfone solution; then the obtained cyclobutene sulfone solution is flash evaporated to obtain gas phase and liquid phase; the gas phase is condensed and recycled, and the liquid phase is stripped with cyclopentane gas to obtain cyclobutene sulfone.

[0007] (2) The cyclobutene sulfone is subjected to catalytic hydrogenation to obtain the hydrogenation product; the hydrogenation product is evaporated, the gas phase is purified by solvent after condensation, and the obtained solvent is recycled; the liquid phase is purified to obtain cyclobutene sulfone.

[0008] The beneficial technical effects achieved by the present invention through the above technical solution are as follows:

[0009] (1) In the preparation process of cyclobutene sulfone, the present invention uses cyclopentane as a solvent to lower the freezing point of cyclobutene sulfone, solve the problem that it is easy to solidify at room temperature, and avoid causing equipment and pipeline blockage. At the same time, cyclopentane is used as a stripping gas to effectively remove sulfur dioxide from cyclobutene sulfone. The sulfur dioxide-containing gas removed can be recycled after deep cooling, avoiding waste gas emissions, reducing pollution, and lowering production costs.

[0010] (2) The synthesis solvent and hydrogenation solvent of the present invention both use cyclopentane. The cyclopentane undergoes the entire process of sulfolane synthesis, namely synthesis, flash evaporation, stripping, hydrogenation, evaporation and purification, to achieve recycling. This process does not introduce other substances, which simplifies the system involved in the entire production process, reduces the production separation cost, and is beneficial to environmental protection. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the preparation process of sulfolane provided in one embodiment of the present invention. Detailed Implementation

[0012] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0013] This invention provides a method for preparing sulfolane, the method comprising the following steps:

[0014] (1) Butadiene and sulfur dioxide react in cyclopentane solvent in the presence of a polymerization inhibitor to obtain cyclobutene sulfone solution; then the obtained cyclobutene sulfone solution is flash evaporated to obtain gas phase and liquid phase; the gas phase is condensed and recycled, and the liquid phase is stripped with cyclopentane gas to obtain cyclobutene sulfone.

[0015] (2) The cyclobutene sulfone is subjected to catalytic hydrogenation to obtain the hydrogenation product; the hydrogenation product is evaporated, the gas phase is purified by solvent after condensation, and the obtained solvent is recycled; the liquid phase is purified to obtain cyclobutene sulfone.

[0016] In step (1) of the present invention, most of the sulfur dioxide in cyclobutene sulfone can be separated and recovered by flash evaporation, and then the liquid phase is stripped with cyclopentane gas to remove unreacted products containing sulfur dioxide and remove the remaining sulfur dioxide in cyclobutene sulfone. The stripped gas produced is cryogenically liquefied and recycled.

[0017] In this invention, the inventors discovered through extensive research that using cyclopentane as a solvent in the preparation of cyclobutene sulfone can lower the freezing point of cyclobutene sulfone, solving the problem of its easy solidification at room temperature and avoiding equipment and pipeline blockage. At the same time, using cyclopentane as a stripping gas can effectively remove sulfur dioxide from cyclobutene sulfone. The sulfur dioxide-containing gas removed can be recycled after deep cooling, reducing production costs.

[0018] In this invention, both the synthesis solvent and the hydrogenation solvent are cyclopentane. The cyclopentane undergoes the entire synthesis process of sulfolane, namely synthesis, flash evaporation, stripping, hydrogenation, evaporation and purification, to achieve recycling. This process does not introduce other substances, which simplifies the system involved in the entire production process, reduces production separation costs, and is beneficial to environmental protection.

[0019] In some embodiments of the present invention, the polymerization inhibitor is selected from 1,2-dihydro-2,2,4-trimethylquinoline polymers.

[0020] In some preferred embodiments of the present invention, the 1,2-dihydro-2,2,4-trimethylquinoline polymer comprises: a 1,2-dihydro-2,2,4-trimethylquinoline dimer and at least one polymer selected from 1,2-dihydro-2,2,4-trimethylquinoline polymer trimers, 1,2-dihydro-2,2,4-trimethylquinoline polymer tetramers, and 1,2-dihydro-2,2,4-trimethylquinoline polymer pentamers.

[0021] In this invention, the 1,2-dihydro-2,2,4-trimethylquinoline dimer refers to the product of polymerization of two 1,2-dihydro-2,2,4-trimethylquinoline compounds; the 1,2-dihydro-2,2,4-trimethylquinoline trimer refers to the product of polymerization of three 1,2-dihydro-2,2,4-trimethylquinoline compounds; the 1,2-dihydro-2,2,4-trimethylquinoline tetramer refers to the product of polymerization of four 1,2-dihydro-2,2,4-trimethylquinoline compounds; and the 1,2-dihydro-2,2,4-trimethylquinoline pentamer refers to the product of polymerization of five 1,2-dihydro-2,2,4-trimethylquinoline compounds.

[0022] In this invention, the inventors discovered through extensive research that the 1,2-dihydro-2,2,4-trimethylquinoline polymer contains 1,2-dihydro-2,2,4-trimethylquinoline dimer, which can improve the yield of cyclobutene sulfone product while also increasing the selectivity of cyclobutene sulfone.

[0023] Further research by the inventors revealed that when the content of 1,2-dihydro-2,2,4-trimethylquinoline dimer in the 1,2-dihydro-2,2,4-trimethylquinoline polymer is ≥80wt%, its polymerization inhibitory effect is better, which can further improve the yield of cyclobutene sulfone product.

[0024] According to a specific embodiment of the present invention, by way of example, in the 1,2-dihydro-2,2,4-trimethylquinoline polymer, the content of 1,2-dihydro-2,2,4-trimethylquinoline dimer is 80 wt%, and the remaining 20 wt% is at least one polymer selected from 1,2-dihydro-2,2,4-trimethylquinoline polymer trimer, 1,2-dihydro-2,2,4-trimethylquinoline polymer tetramer and 1,2-dihydro-2,2,4-trimethylquinoline polymer pentamer.

[0025] The inventors' research indicates that as long as the content of 1,2-dihydro-2,2,4-trimethylquinoline dimer in the 1,2-dihydro-2,2,4-trimethylquinoline polymer is ≥80wt%, excellent polymerization inhibition effect can be guaranteed. The remaining material is any one or more of the following: 1,2-dihydro-2,2,4-trimethylquinoline polymer trimer, 1,2-dihydro-2,2,4-trimethylquinoline polymer tetramer, and 1,2-dihydro-2,2,4-trimethylquinoline polymer pentamer.

[0026] In some preferred embodiments of the present invention, the content of 1,2-dihydro-2,2,4-trimethylquinoline dimer in the 1,2-dihydro-2,2,4-trimethylquinoline polymer is ≥80wt%, preferably 80-95wt%, and more preferably 90-95wt%.

[0027] In this invention, the contents of dimers, trimers, and tetramers in the 1,2-dihydro-2,2,4-trimethylquinoline polymer were determined by mass spectrometry.

[0028] In this invention, the 1,2-dihydro-2,2,4-trimethylquinoline polymer is obtained from the market.

[0029] In some embodiments of the present invention, the molar ratio of sulfur dioxide to butadiene is 1.1-1.8:1, preferably 1.1-1.3:1, and more preferably 1.25-1.3:1.

[0030] In some embodiments of the present invention, the amount of the polymerization inhibitor is 0.01-1 wt% of the amount of butadiene, preferably 0.5-1 wt%.

[0031] In some embodiments of the present invention, the mass content of cyclopentane solvent in the reaction system of step (1) is not less than 20%; preferably 30%-60%, and more preferably 40%-50%.

[0032] In some embodiments of the present invention, the cyclopentane solvent is derived from the solvent obtained in step (2) solvent purification, and any deficiency is supplemented from external sources.

[0033] In some embodiments of the present invention, the reaction pressure is 2.2-3 MPa and the temperature is 95℃-125℃.

[0034] In some embodiments of the present invention, the flash evaporation is carried out under a slightly positive pressure of 65°C-75°C.

[0035] In some embodiments of the present invention, the stripping is carried out in a stripping tower; the liquid from flash evaporation enters from the top of the stripping tower, the stripping steam is cyclopentane gas, the temperature of the cyclopentane gas is greater than 60°C, the gas containing cyclopentane and sulfur dioxide from the stripping tower is cryogenically liquefied, and then returned to the reaction cycle for reuse, and the liquid phase at the bottom of the tower continues to perform the operation of step (2).

[0036] In some embodiments of the present invention, the pressure of the catalytic hydrogenation reaction is greater than 1.5 MPa, preferably greater than 2 MPa, and more preferably 2.5-3 MPa.

[0037] In some embodiments of the present invention, the catalytic hydrogenation reaction is carried out in the presence of a homogeneous hydrogenation catalyst and a hydrogenation activator.

[0038] In some embodiments of the present invention, the homogeneous hydrogenation catalyst is selected from at least one homogeneous nickel-containing organic catalyst.

[0039] In some preferred embodiments of the present invention, the homogeneous hydrogenation catalyst is preferably a mixed solution of an organic nickel salt and cyclopentane; more preferably, the organic nickel salt is selected from at least one of nickel naphthenate, nickel neodecanoate and nickel octanoate.

[0040] In some embodiments of the present invention, the hydrogenation activator is selected from triisobutylaluminum and / or triethylaluminum, preferably triethylaluminum, and the solvent of the hydrogenation activator is cyclopentane.

[0041] In some preferred embodiments of the present invention, the descaling is carried out in a descaling tower; the hydrogenated product is heated and then enters the descaling tower for vaporization and flash evaporation, the gas phase is condensed and then purified by solvent, and the liquid phase at the bottom of the tower is purified by product purification; the gas phase temperature at the feed position of the descaling tower is greater than 150°C, preferably 180-200°C, the bottom temperature is greater than 220°C, preferably 230-250°C, and the operating pressure at the top of the descaling tower is a slightly positive pressure.

[0042] In this invention, the descaling tower can be a packed tower or a plate tower, preferably a packed tower, and the packing can be structured packing or random packing, preferably random packing.

[0043] In some preferred embodiments of the present invention, the solvent purification is carried out in a solvent purification tower; the light components containing cyclopentane from the distillation are purified in the solvent purification tower to obtain high-purity cyclopentane, and the non-condensable vapor at the top of the tower is cryogenically liquefied and recycled.

[0044] In this invention, the liquid phase at the bottom of the tower is returned to the descaling preheater.

[0045] In this invention, the solvent purification tower can be any type of tower, and the top pressure is preferably slightly positive; other operating conditions are adjusted according to actual needs; part of the cyclopentane obtained from the solvent purification tower is recycled back to the synthesis reactor, part is vaporized to the stripping tower, and part is used for catalyst preparation.

[0046] In some preferred embodiments of the present invention, the product refining is carried out in a product refining tower; the product refining tower is a vacuum tower with a top pressure of 0.1-2 kPaA, a bottom temperature of less than 185°C, and a top temperature of 75°C-120°C.

[0047] In this invention, the product refining tower can be a plate tower or a packed tower, preferably a packed tower, and more preferably a perforated plate corrugated packed tower.

[0048] In this invention, the liquid from the bottom of the stripping tower enters the bottom of the product refining tower, and the top of the tower is completely refluxed. The product is collected from the side liquid phase, cooled, and sent to the product tank. The non-condensable vapor at the top of the tower is deeply cooled, liquefied, and recycled to the synthesis reactor.

[0049] According to a particularly preferred embodiment of the present invention, a method for preparing sulfolane mainly includes steps such as synthesis reaction, flash evaporation, stripping, hydrogenation, descaling, and product purification. The following is a detailed description... Figure 1 The schematic diagram of the preparation process of sulfolane shown is used to illustrate the process. Figure 1 The box in the middle represents a section of the sulfolane synthesis process, which may be a single piece of equipment or a combination of several pieces of equipment. The arrows in the figure indicate the direction of material flow.

[0050] (1) Sulfur dioxide and butadiene react in a synthesis reactor in the presence of a polymerization inhibitor and solvent cyclopentane to synthesize cyclobutene sulfone; the obtained cyclobutene sulfone synthesis liquid is flash evaporated, and after gas-liquid separation, the gas phase is condensed and recycled back to the synthesis reactor, and the liquid phase enters from the top of the stripping tower. The stripping steam is cyclopentane gas. The temperature of the cyclopentane stripping steam is greater than 60°C and the pressure is sufficient to meet the conditions for entering the tower. The gas containing cyclopentane and sulfur dioxide at the top of the stripping tower is cryogenically liquefied and then returned to the synthesis reaction for recycling. The unreacted substances such as sulfur dioxide in the synthesis liquid are removed by stripping, and the liquid phase at the bottom of the tower enters the hydrogenation reactor for hydrogenation.

[0051] (2) The cyclobutene sulfone obtained in step (1) is hydrogenated with hydrogen in a hydrogenation reactor under the action of a homogeneous catalyst and activator to generate cyclobutene sulfone; the hydrogenation product is heated and enters the descaling tower. The hydrogenation product is decomposed at high temperature and flashed to achieve gas-liquid separation. The gas phase is condensed and sent to the solvent refining tower for solvent refining, and the liquid phase at the bottom of the tower is sent to the product refining tower for product refining; the light component containing cyclopentane from the descaling is refined in the solvent refining tower to obtain high-purity cyclopentane. The non-condensable vapor at the top of the tower is deeply cooled and liquefied and then recycled back to the synthesis reactor. The liquid phase at the bottom of the tower is returned to the descaling preheater; the liquid from the bottom of the descaling tower enters the bottom of the product refining tower. The top of the tower is completely refluxed. The product is collected from the side liquid phase and cooled and sent to the product tank. The non-condensable vapor at the top of the tower is deeply cooled and liquefied and recycled back to the synthesis reactor.

[0052] The synthesis route of sulfolane involves processes such as synthesis, flash evaporation, stripping, hydrogenation, descaling, and purification. The conditions of each process change, which will cause fluctuations in the yield and quality of the product sulfolane.

[0053] The present invention will be described in detail below through preparation examples and embodiments, but the scope of protection of the present invention is not limited to the following description.

[0054] Unless otherwise specified in the following examples and comparative examples, all conditions were performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available products.

[0055] Process parameter measurement methods: Temperature - measured by thermocouple; Pressure - observed and recorded by on-site pressure gauge and remotely transmitted by pressure transmitter; Material quantity is detected by electronic scale; Time is monitored by precision gauge;

[0056] The raw materials, additives, and catalysts used in this invention are all commercially available products, and their specifications are as follows:

[0057] Butadiene purity > 99.3%; sulfur dioxide purity > 99%; cyclopentane purity > 99.5%;

[0058] The purity of triisobutylaluminum is >99.5%; the purity of nickel naphthenate is 98.5%.

[0059] 1,2-Dihydro-2,2,4-Trimethylquinoline polymer: 90 wt% dimer, 6 wt% trimer, 3 wt% tetramer, and 1.0 wt% pentamer.

[0060] Example 1

[0061] (1) 142.2g of sulfur dioxide, 100g of butadiene, 1g of polymerization inhibitor 1,2-dihydro-2,2,4-trimethylquinoline polymer and 103.8g of cyclopentane were added to the synthesis reactor. The reaction pressure was controlled at 2.8MPa, the reaction temperature at 105℃ and the reaction time at 3h. The conversion rate of butadiene was 99.5%.

[0062] (2) The synthesized product is fed into a flash evaporator for vaporization and flash evaporation. The pressure inside the flash evaporator is 0.105 MPaA and the temperature is 70°C. The gas phase is recycled after cryogenic liquefaction and returned to the synthesis reactor. The liquid phase enters the stripping tower from the top of the stripping tower.

[0063] (3) The stripping tower is a packed tower with φ38 rectangular saddle rings inside. It is divided into two layers, each with a height of 4 meters. The top pressure of the stripping tower is atmospheric pressure and the temperature is 70℃. 40g of cyclopentane is vaporized at 70℃ and then enters from the bottom of the stripping tower. The gas at the top of the stripping tower is cryogenically liquefied and recycled back to the synthesis reactor. The liquid at the bottom of the stripping tower is cyclobutene sulfone product. After testing, the sulfur dioxide content in the cyclobutene sulfone product is 300ppm.

[0064] (4) The liquid at the bottom of the stripping tower enters the hydrogenation reactor. The catalyst packed in the hydrogenation reactor is a mixture of nickel naphthenate, triisobutylaluminum and cyclopentane. Hydrogen enters the reactor from the outside. The hydrogen at the top of the reactor is recycled by a compressor. The hydrogen / cyclobutene sulfone molar ratio is 2:1. The hydrogenation reaction pressure is 2.0 MPaG, the reaction temperature is 70℃, and the reaction residence time is 3h. The conversion rate of cyclobutene sulfone is 99%.

[0065] (5) After the hydrogenation reaction is completed, the hydrogenation reaction liquid is heated to 180°C and fed from the middle of the dehydrogenation tower. The dehydrogenation tower is a random packed tower with two layers of φ38 random rectangular saddle rings, each layer with a height of 4 meters. The bottom temperature of the tower is 220°C, the liquid residence time in the bottom of the tower is 1.5h, the top temperature of the tower is 180°C, and the top pressure of the tower is 0.05MPaA. The vapor phase at the top of the dehydrogenation tower is cryogenically cooled to 40°C and most of it is liquefied. The non-condensable gas is further cryogenically cooled to liquefy all of it. The liquefaction temperature is -18°C. The cryogenic liquid is returned to the synthesis reaction, while the 40°C liquid enters the solvent purification tower for separation. The liquid at the bottom of the dehydrogenation tower flows by gravity to the bottom of the product purification tower.

[0066] (6) The solvent refining tower has a total reflux at the top, with a top temperature of 55°C, a top pressure of 0.05 MPaA, a bottom pressure of 0.08 MPa, and a bottom temperature of 100°C. The non-condensable gas in the top reflux tank is further cryogenically liquefied at a liquefaction temperature of -18°C. The cryogenic liquid is returned to the synthesis reaction. The solvent is extracted from the gas phase of the side stream in the middle of the tower, cooled and liquefied at a liquefaction temperature of 40°C. Part of the refined solvent is recycled back to the synthesis reaction, and part is heated and vaporized and returned to the stripping tower. The bottom material of the solvent refining tower is returned to the stripping preheater.

[0067] (7) The product refining tower is a packed tower with three-stage packing. The packing is φ38 random stacked rectangular ampere rings, with each layer being 4 meters long. The product refining tower operates under negative pressure with a top pressure of 1 kPa and a top temperature of 89°C. The top of the product refining tower is fully refluxed. The non-condensable vapor is pressurized by a vacuum pump, cryogenically liquefied, and then returned to the synthesis cycle for reuse. The product sulfolane is extracted from the side liquid phase of the sulfolane refining tower, cooled to 50°C, and then transported to the product tank as a product.

[0068] The product, weighing 211g, has a purity of 99.5% and a content of 0.3wt% for sulfolane.

[0069] Example 2

[0070] The method of Example 1 is the same, except that in the reaction system of step (1), the amount of cyclopentane solvent added is 69.2g, other operating parameters remain unchanged, and the liquid at the bottom of the stripping tower is cyclobutene sulfone product. The sulfur dioxide content in the cyclobutene sulfone product is 500ppm.

[0071] Example 3

[0072] The method of Example 1 is the same, except that in the reaction system of step (1), the amount of cyclopentane solvent added is 138.4g, other operating parameters remain unchanged, and the liquid at the bottom of the stripping tower is cyclobutene sulfone product. The sulfur dioxide content in the cyclobutene sulfone product is 240ppm.

[0073] Example 4

[0074] The method of Example 1 is the same, except that in the reaction system of step (1), the amount of cyclopentane solvent added is 173g, other operating parameters remain unchanged, and the liquid at the bottom of the stripping tower is cyclobutene sulfone product. The sulfur dioxide content in the cyclobutene sulfone product is 220ppm.

[0075] Example 5

[0076] The method of Example 1 is the same, except that in the reaction system of step (1), the amount of cyclopentane solvent added is 207.6g, other operating parameters remain unchanged, and the liquid at the bottom of the stripping tower is cyclobutene sulfone product. The sulfur dioxide content in the cyclobutene sulfone product is 210ppm.

[0077] Example 6

[0078] The method of Example 1 is the same, except that in the reaction system of step (1), the amount of cyclopentane solvent added is 342.2g, other operating parameters remain unchanged, and the liquid at the bottom of the stripping tower is cyclobutene sulfone product. The sulfur dioxide content in the cyclobutene sulfone product is 205ppm.

[0079] The results of Examples 1-6 are listed in Table 1.

[0080] Table 1

[0081]

[0082] Table 1 shows the effect of the amount of cyclopentane in the cyclobutene sulfone synthesis feedstock on the sulfur dioxide content in cyclobutene sulfone. Changing the amount of cyclopentane as the synthesis solvent, while keeping other conditions constant (40g of stripped cyclopentane), resulted in changes in the sulfur dioxide content at the bottom of the stripping tower. The trend was that increasing the amount of cyclopentane decreased the sulfur dioxide content at the bottom of the stripping tower. When the content was approximately >60% of the synthesized product, the change was not significant. When the cyclopentane content accounted for 20% of the synthesis reaction, the sulfur dioxide content at the bottom of the stripping tower was 500ppm, a high sulfur dioxide content that is detrimental to subsequent hydrogenation of cyclobutene sulfone. While the sulfur dioxide content in the cyclobutene sulfone product was slightly lower when the cyclopentane content was 70% compared to when it was 60%, increasing the amount of cyclopentane would increase the energy consumption and cost of solvent recycling. Therefore, overall, a cyclopentane solvent mass content of 30%-60% satisfies both the desulfurization effect and ensures energy efficiency.

[0083] Example 7

[0084] The method is the same as in Example 1, except that in step (3), 20g of cyclopentane is vaporized at 70°C and then introduced from the bottom of the stripping tower. Other conditions remain unchanged, and the sulfur dioxide content in the cyclobutene sulfone product is 550ppm.

[0085] Example 8

[0086] The method of Example 1 is the same, except that in step (3), 60g of cyclopentane is vaporized at 70°C and then introduced from the bottom of the stripping tower. Other conditions remain unchanged, and the sulfur dioxide content in the cyclobutene sulfone product is 260ppm.

[0087] Example 9

[0088] The method of Example 1 is the same, except that in step (3), 80g of cyclopentane is vaporized at 70°C and then enters from the bottom of the stripping tower. Other conditions remain unchanged, and the sulfur dioxide content in the cyclobutene sulfone product is 210ppm.

[0089] Example 10

[0090] The method of Example 1 is the same, except that in step (3), 100g of cyclopentane is vaporized at 70°C and then introduced from the bottom of the stripping tower. Other conditions remain unchanged, and the sulfur dioxide content in the cyclobutene sulfone product is 205ppm.

[0091] Example 11

[0092] The method of Example 1 is the same, except that in step (3), 120g of cyclopentane is vaporized at 70°C and then introduced from the bottom of the stripping tower. Other conditions remain unchanged, and the sulfur dioxide content in the cyclobutene sulfone product is 201ppm.

[0093] The results of Example 1 and Examples 7-11 are listed in Table 1.

[0094] Table 2

[0095]

[0096] Table 2 shows the effect of the amount of cyclopentane stripped during the synthesis of cyclobutene sulfone on the sulfur dioxide content in cyclobutene sulfone. With other conditions unchanged, changing the amount of cyclopentane stripped from the bottom of the stripper has an effect that is constrained by the material properties and the system temperature and pressure. When the amount of cyclopentane fed into the bottom of the stripper is less than 40g, the sulfur dioxide content in cyclobutene sulfone increases significantly, while when the amount fed into the stripper is greater than 40g, the decrease in sulfur dioxide content in cyclobutene sulfone is not significant. The main reason is that cyclobutene sulfone itself undergoes cracking.

[0097] Example 12

[0098] The method of Example 1 was followed, except that in step (4), the molar ratio of hydrogen to sulfolane was 20:1, the pressure of the hydrogenation reaction was 2.0 MPaG, the reaction temperature was 70°C, the reaction residence time was 0.5 h, and the conversion rate of sulfolane was 99%.

[0099] By comparing Example 12 with Example 1, it can be seen that, under the same sulfolane conversion rate, increasing the molar ratio of hydrogen to sulfolane in Example 1 can significantly shorten the hydrogenation reaction time.

[0100] Example 13

[0101] The method of Example 1 is the same, except that in step (4), the pressure of the hydrogenation reaction is 2.5 MPa, other process conditions remain unchanged, the reaction residence time is 2 h, and the conversion rate of cyclobutene sulfone can reach 99%.

[0102] Example 14

[0103] The method is the same as in Example 1, except that in step (4), the pressure of the hydrogenation reaction is 3.0 MPa, other process conditions remain unchanged, the reaction residence time is 1.9 h, and the conversion rate of cyclobutene sulfone can reach 99%.

[0104] By comparing Examples 13 and 14 with Example 1, it can be seen that, under the same sulfolane conversion rate, increasing the hydrogenation reaction pressure can significantly shorten the reaction time. However, when the hydrogenation reaction pressure is increased to more than 2.5 MPa, the reduction in reaction time is not significant.

[0105] Comparative Example 1

[0106] (1) 142.2g of sulfur dioxide, 100g of butadiene and 1g of polymerization inhibitor 1,2-dihydro-2,2,4-trimethylquinoline polymer were added to the synthesis reactor. The reaction pressure was controlled at 3.5MPa, the reaction temperature at 105℃ and the reaction time at 3h. The conversion rate of butadiene was 99.5%.

[0107] (2) The synthesized product is fed into a flash evaporator for vaporization and flash evaporation. The pressure inside the flash evaporator is 0.105 MPaA and the temperature is 70℃. The gas phase is recycled after cryogenic liquefaction and returned to the synthesis reactor. It was found that when the synthesis reaction liquid is vaporized, some cyclobutene sulfone sublimates and is carried into the gas phase, causing cyclobutene sulfone to freeze on the surface of the heat exchange equipment and block the equipment. The liquid phase enters the stripping tower from the top of the stripping tower.

[0108] (3) The stripping tower is a packed tower with φ38 rectangular saddle rings inside, divided into upper and lower layers, each layer is 4 meters high; the top pressure of the stripping tower is atmospheric pressure and the temperature is 70℃. 40g of nitrogen gas is vaporized at 75℃ and enters from the bottom of the stripping tower. The gas at the top of the stripping tower is cryogenically liquefied and recycled back to the synthesis reactor. The liquid at the bottom of the stripping tower is cyclobutene sulfone product. After testing, the sulfur dioxide content in the cyclobutene sulfone product is 300ppm.

[0109] The stripped steam from the top of the stripping tower cannot be recovered and reused; it can only be treated as waste gas in the waste gas treatment unit.

[0110] A comparison of Comparative Example 1 and Example 1 shows that, under the same butadiene conversion rate, Example 1, using cyclopentane as the solvent for cyclobutene sulfone synthesis, has a reaction pressure of 2.8 MPa, while Comparative Example 1, without cyclopentane, has a reaction pressure of 3.5 MPa. This indicates that using cyclopentane as the solvent for cyclobutene sulfone synthesis can significantly reduce the reaction pressure. The stripping tower uses cyclopentane as the stripping agent, and the waste gas can be recycled after deep cooling, resulting in no waste. The flash vapor can be condensed and recycled without obstruction. However, in the synthesis reaction without cyclopentane as a solvent, the reaction pressure increases, and the flash vapor from the synthesis reaction liquid, after stripping and condensation, causes cyclobutene sulfone buildup in the heat exchanger, clogging the heat exchange equipment. Furthermore, the nitrogen stripping process generates waste gas that cannot be deep-cooled and recovered, requiring waste gas treatment and resulting in waste.

[0111] Comparative Example 2

[0112] The method of Example 1 is different in that the hydrogenated liquid is directly used as a catalyst to prepare the solvent after the gas phase is de-chilled in step (5). The amount of catalyst is the same, the molar ratio of hydrogen to sulfolane is 2:1, the pressure of hydrogenation reaction is 2.0 MPaG, the reaction temperature is 70℃, the reaction residence time is 3h, and the conversion rate of sulfolane is 85%.

[0113] Comparing Comparative Example 2 with Example 1, it can be seen that when the top oil and gas of the hydrogenation liquid descaling tower are directly condensed and liquefied as a hydrogenation catalyst and activator solvent, the presence of sulfur dioxide leads to catalyst poisoning, resulting in a significant reduction in reaction efficiency under otherwise identical conditions.

[0114] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing sulfolane, characterized in that, The preparation method includes the following steps: (1) Butadiene and sulfur dioxide react in cyclopentane solvent in the presence of a polymerization inhibitor to obtain cyclobutene sulfone solution; then the obtained cyclobutene sulfone solution is flash evaporated to obtain gas phase and liquid phase; the gas phase is condensed and recycled, and the liquid phase is stripped with cyclopentane gas to remove unreacted products containing sulfur dioxide to obtain cyclobutene sulfone. (2) The cyclobutene sulfone is subjected to catalytic hydrogenation to obtain the hydrogenation product; the hydrogenation product is evaporated, the gas phase is purified by solvent after condensation, and the obtained solvent is recycled; the liquid phase is purified to obtain cyclobutene sulfone. The polymerization inhibitor is selected from 1,2-dihydro-2,2,4-trimethylquinoline polymer, wherein the content of 1,2-dihydro-2,2,4-trimethylquinoline dimer in the 1,2-dihydro-2,2,4-trimethylquinoline polymer is ≥80wt%.

2. The preparation method according to claim 1, wherein, The 1,2-dihydro-2,2,4-trimethylquinoline polymer comprises: a 1,2-dihydro-2,2,4-trimethylquinoline dimer and at least one polymer selected from 1,2-dihydro-2,2,4-trimethylquinoline polymer trimers, 1,2-dihydro-2,2,4-trimethylquinoline polymer tetramers, and 1,2-dihydro-2,2,4-trimethylquinoline polymer pentamers.

3. The preparation method according to claim 1, wherein, The molar ratio of sulfur dioxide to butadiene is 1.1-1.8:1; And / or, the amount of the polymerization inhibitor is 0.01-1 wt% of the amount of butadiene; And / or, in the reaction system of step (1), the mass content of cyclopentane solvent is not less than 20%; And / or, the cyclopentane solvent comes from the solvent obtained in step (2) solvent purification, and any shortfall is supplemented from external sources.

4. The preparation method according to claim 3, wherein, The molar ratio of sulfur dioxide to butadiene is 1.1-1.3:1; And / or, the amount of the polymerization inhibitor is 0.5 wt% of the amount of butadiene; And / or, in the reaction system of step (1), the mass content of cyclopentane solvent is 30%-60%.

5. The preparation method according to claim 1, wherein, The reaction is carried out at a pressure of 2.2-3 MPa and a temperature of 95℃-125℃. And / or, the flash evaporation is carried out under a slightly positive pressure at 65°C-75°C.

6. The preparation method according to claim 1, wherein, The stripping is carried out in a stripping tower; the liquid from flash evaporation enters from the top of the stripping tower, the stripping steam is cyclopentane gas, the temperature of the cyclopentane gas is greater than 60°C, the gas containing cyclopentane and sulfur dioxide from the stripping tower is cryogenically liquefied, and then returned to the reaction cycle for reuse, the liquid phase at the bottom of the tower continues to carry out the operation of step (2).

7. The preparation method according to claim 1, wherein, The pressure of the catalytic hydrogenation reaction is greater than 1.5 MPa, specifically greater than 2 MPa. And / or, the catalytic hydrogenation reaction is carried out in the presence of a homogeneous hydrogenation catalyst and a hydrogenation activator.

8. The preparation method according to claim 7, wherein, The pressure of the catalytic hydrogenation reaction is greater than 2 MPa; And / or, the homogeneous hydrogenation catalyst is selected from at least one of homogeneous nickel-containing organic catalysts, and the diluent for the homogeneous nickel-containing organic catalyst is cyclopentane; And / or, the hydrogenation activator is selected from triisobutylaluminum and / or triethylaluminum, and the dilution solvent for the hydrogenation activator is cyclopentane.

9. The preparation method according to claim 1, wherein, The desorption / evaporation is carried out in a desorption / evaporation tower; the hydrogenated product is heated and then enters the desorption / evaporation tower for vaporization and flash evaporation. The gas phase is condensed and then purified by solvent, and the liquid phase at the bottom of the tower is purified by product. The gas phase temperature at the feed position of the desorption / evaporation tower is greater than 150°C, the bottom temperature is greater than 220°C, and the operating pressure at the top of the desorption / evaporation tower is slightly positive.

10. The preparation method according to claim 1, wherein, The solvent refining is carried out in a solvent refining tower; the light components containing cyclopentane from the distillation are refined in the solvent refining tower to obtain high-purity cyclopentane, and the non-condensable vapor at the top of the tower is cryogenically liquefied and recycled.

11. The preparation method according to claim 1, wherein, The product refining process is carried out in a product refining tower; the product refining tower is a vacuum tower with a top pressure of 0.1-2 kPaA, a bottom temperature of less than 185°C, and a top temperature of 75°C-120°C.

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