Liquid decolorizing agent for decolorizing crude styrene and decolorizing method of crude styrene

Abstract

The invention relates to a liquid decolorizing agent for decolorizing crude styrene and a decolorizing method of crude styrene. The liquid decolorizing agent contains 70-90 wt% of a decolorizing component and the balance of a polymerization inhibitor. Wherein the decolorizing component contains a first decolorizing component and optionally a second decolorizing component, and the first decolorizing component contains citraconic anhydride. The decolorizing agent disclosed by the invention is liquid at normal temperature, stable in property and good in decolorizing effect.

Description

Technical Field

[0001] This application relates to a liquid decolorizing agent for decolorizing crude styrene and a method for decolorizing crude styrene. Background Technology

[0002] Styrene is an important organic chemical raw material used to produce resins, rubber, and other chemical products, with wide applications. The cracked gasoline produced as a byproduct of naphtha steam cracking to ethylene production units contains 3-5% by mass of styrene. In existing cracked gasoline hydrogenation processes, styrene is hydrogenated to ethylbenzene, resulting in resource waste. Separating this portion of styrene using an extraction distillation process not only provides a cost-effective way to obtain high-value styrene but also further reduces hydrogen consumption in cracked gasoline hydrogenation units, enhancing the subsequent utilization value of cracked C8.

[0003] Due to the high impurity content of cracked gasoline, styrene obtained through the C8 cracking extraction process is yellow and must undergo decolorization and refining to meet quality standards. However, of the two existing decolorization processes, while concentrated nitric acid oxidation decolorization can yield superior grade styrene with a Pt-Co color number <10, it requires acid washing and water washing processes, generating large amounts of high-COD, high-salt wastewater, polluting the environment. Diene reaction decolorization utilizes the Diels-Alder reaction between maleic anhydride-like dienesophils and colored conjugated dienes in crude styrene to generate heavy components, achieving decolorization. However, this method has unstable decolorization effects, and maleic anhydride has a high melting point, requiring stable heat tracing and insulation for both storage tanks and pipelines. However, due to the small amount of decolorizing agent injected and the narrowness of the pipelines, there is still a risk of blockage at interfaces, which can lead to plant shutdown. Furthermore, maleic anhydride polymerizes with styrene, easily clogging equipment. Industrially, the reboiler at the bottom of the refining tower typically needs cleaning every 2-3 months, significantly increasing operating costs. Therefore, the use of maleic anhydride for decolorization affects the stable operation of the equipment and requires significant investment in equipment and pipelines.

[0004] US3763015A discloses a method for separating styrene from thermally cracked petroleum. First, the thermally cracked petroleum is distilled off to recover a fraction with a boiling point between 120°C and 160°C. This fraction is then extractively distilled using an organic polar solvent containing a nitrite polymerization inhibitor, wherein styrene is soluble. The solvent is removed, and the styrene-containing fraction is treated with nitric acid and washed with water or an alkali. The resulting product is fractionated to recover essentially colorless, high-purity styrene. However, this method has the drawback of generating large amounts of high-COD, high-salinity wastewater, polluting the environment.

[0005] CN101514138 discloses a decolorizing agent for treating styrene recovered from cracked gasoline. The decolorizing agent consists of 50-90% by mass of maleic anhydride and the balance being a mono-olefin compound with adjacent electrophilic groups. This technology can yield styrene products with a Pt-Co color number <10, but the large amount of decolorizing agent added leads to severe polymerization of styrene with maleic anhydride, resulting in a low styrene recovery rate.

[0006] CN104211560 discloses a decolorization method for recovering styrene from the C8 fraction of cracked gasoline. The decolorizing agent used in this method consists of a compound of hydrazine and urea compounds containing -NH2, along with an alkaline compound and an alcohol. The decolorizing agent reacts with crude styrene, followed by washing with deionized water, drying, or vacuum distillation to remove the decolorizing agent and obtain the styrene product. This method requires a large amount of decolorizing agent and generates a large amount of high-nitrogen, styrene-containing wastewater.

[0007] CN111205158 discloses a method for decolorizing and refining styrene from cracked C8 fractions. The crude styrene is first distilled and dehydrated. The dehydrated styrene reacts with maleic anhydride to obtain a product with a higher boiling point. This product is then separated by distillation to obtain the styrene product. However, this method, using distillation for dehydration, inevitably leads to styrene polymerization. Furthermore, the polymer must undergo a decolorization reaction before entering the styrene refining tower, and is finally separated at the bottom of the tower, affecting the entire decolorization process. During the decolorizing agent injection process, the high freezing point of maleic anhydride makes it difficult to control the heating and insulation temperature, resulting in instability in the injection process, easy pipe blockage, and significant fluctuations in the color of the styrene product.

[0008] CN110922289 discloses a decolorizing agent for recovering styrene from cracked gasoline and its application method. The decolorizing agent is composed of cinnamaldehyde and its derivatives, a nitrile radical polymerization inhibitor, and a solvent, with weight percentages of 55-70%, 5-15%, and 15-30%, respectively. However, the actual decolorizing effect of cinnamaldehyde and its derivatives used in this method is poor, making it difficult to achieve a Pt-Co color number <10. Furthermore, the price is high, the usage is excessive, and the economic efficiency is low.

[0009] CN108752160 discloses a method for extracting crude styrene from cracked gasoline to reduce C9, remove impurities, decolorize, and reduce trace amounts of water. This method includes two steps: the preparation of a liquid-phase compound decolorizing agent and the distillation extraction of styrene. However, this method involves multiple decolorizing agent components, complex formulation, and a lengthy process, making it unsuitable for practical production operations. While adding a peroxide-based initiator can improve the decolorization reaction efficiency, it also significantly increases the reaction between the decolorizing agent and styrene, as well as the self-polymerization reaction of styrene itself, leading to serious polymerization problems and making implementation difficult.

[0010] CN104276926 discloses a method for decolorizing crude styrene obtained from the extractive distillation of C8 fraction of cracked gasoline. The method involves feeding crude styrene into a dehydration tower for distillation and dehydration, separating water at the top of the tower, and then adding a decolorizing agent to the dehydrated styrene obtained at the bottom of the tower before feeding it into a styrene refining tower for further distillation. The styrene product is obtained at the top of the tower. However, this method, using distillation dehydration, inevitably leads to styrene polymerization, and the polymer must undergo a decolorization reaction before entering the styrene refining tower, finally separating at the bottom, thus affecting the entire decolorization process.

[0011] CN109422619 discloses a method for decolorizing crude styrene obtained from cracked gasoline. This method involves contacting crude styrene with a dienophilic compound to allow for a complete reaction. The reacted material is then fed into the middle of a decolorizing and refining tower, where a decolorizing co-solvent is added. After vacuum distillation, the refined styrene is discharged from the top of the tower or a side stream at the top, while tar-laden components are discharged from the bottom. The decolorizing co-solvent is an organic compound containing nitrogen or oxygen, with a boiling point of 160-205℃. This method continuously generates hazardous waste containing styrene, which is difficult and costly to treat. Summary of the Invention

[0012] The purpose of this disclosure is to provide a liquid decolorizing agent for decolorizing crude styrene and a method for decolorizing crude styrene. The decolorizing agent disclosed herein is a liquid at room temperature, has stable properties, and has a good decolorizing effect.

[0013] To achieve the above objectives, the first aspect of this disclosure provides a liquid decolorizing agent for decolorizing crude styrene, the liquid decolorizing agent containing 70-90% by weight of a decolorizing component and the balance being a polymerization inhibitor; wherein the decolorizing component contains a first decolorizing component and optionally a second decolorizing component, the first decolorizing component containing citral anhydride.

[0014] Optionally, the liquid decolorizing agent comprises 75-90% by weight of a decolorizing component and the balance being a polymerization inhibitor.

[0015] Optionally, the weight ratio of the first decolorizing component to the second decolorizing component is 1:(0-0.6), preferably 1:(0-0.5). The second decolorizing component is selected from dienophiles. Preferably, the second decolorizing component is selected from one or more of maleic anhydride, butynediary dicarboxylic acid, azodicarboxylic acid ester, benzoquinone, acrylate, benzoic acid and vinyl aldehyde.

[0016] The second aspect of this disclosure provides a method for decolorizing crude styrene, the method comprising: contacting a liquid decolorizing agent provided in the first aspect of this disclosure with crude styrene to carry out a decolorization reaction, and distilling the resulting reaction mixture.

[0017] Optionally, the amount of the liquid decolorizing agent is 0.02-5% by weight of the crude styrene, preferably 0.4-1% by weight.

[0018] Optionally, the decolorization reaction conditions include: a reaction time of 1-12 hours and a reaction temperature of 20-70°C; preferably, the reaction time is 3-7 hours and the reaction temperature is 40-60°C.

[0019] Optionally, the distillation conditions include: the number of trays in the refining distillation column is 5-50, the top pressure is 1-15 kPa, the top reflux ratio is 0.5-4.0, and the top temperature is 50-85℃.

[0020] Optionally, the method further includes: mixing the liquid decolorizing agent with crude styrene in a mixer, and then subjecting the resulting mixture to the decolorization reaction in a decolorization tank.

[0021] Optionally, the crude styrene is derived from cracked gasoline.

[0022] Through the above technical solution, the liquid decolorizing agent disclosed herein uses citrate anhydride as the main decolorizing component. The decolorizing agent is stable and has a good decolorizing effect. It is liquid at room temperature and does not require additional heat tracing and insulation measures.

[0023] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0024] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of a specific implementation of the decolorization system used in Embodiment 1 of this disclosure.

[0025] Explanation of reference numerals in the attached figures Detailed Implementation

[0026] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0027] The first aspect of this disclosure provides a liquid decolorizing agent for decolorizing crude styrene, the liquid decolorizing agent containing 70-90% by weight of a decolorizing component and the balance being a polymerization inhibitor; wherein the decolorizing component contains a first decolorizing component and optionally a second decolorizing component, the first decolorizing component containing citral anhydride.

[0028] The inventors of this disclosure unexpectedly discovered that when a decolorizing component containing citrine anhydride is compounded with a polymerization inhibitor as a liquid decolorizing agent for the decolorization of crude styrene, the decolorizing agent has a good decolorization effect and stable properties. It is in a liquid state at room temperature, which eliminates the need for additional heat tracing and insulation processes during the separation process after decolorization, avoids pipeline blockage problems, reduces energy consumption, and simplifies the decolorization process.

[0029] In a preferred embodiment of this disclosure, the liquid decolorizing agent contains 70-90% by weight of a decolorizing component and the balance being a polymerization inhibitor; wherein the decolorizing component comprises a first decolorizing component and a second decolorizing component, and the first decolorizing component contains citral anhydride; preferably, the first decolorizing component is citral anhydride. In this embodiment, by using a combination of the first and second decolorizing components as the decolorizing components, the liquid decolorizing agent of this disclosure exhibits better stability and decolorizing performance.

[0030] In one specific embodiment of this disclosure, the liquid decolorizing agent contains 75-90% by weight of a decolorizing component and the balance being a polymerization inhibitor. In this preferred embodiment, the liquid decolorizing agent exhibits superior decolorization effect and stability.

[0031] According to this disclosure, the weight ratio of the first decolorizing component and the second decolorizing component can vary within a wide range. In one specific embodiment, the weight ratio of the first decolorizing component and the second decolorizing component is 1:(0-0.6), preferably 1:(0-0.5). The appropriate ratio of the first decolorizing component and the second decolorizing component results in a liquid decolorizing agent with the above composition exhibiting superior stability and decolorizing performance.

[0032] According to this disclosure, the second decolorizing component may be selected from dienophiles. In one specific embodiment of this disclosure, the second decolorizing component is selected from one or more of maleic anhydride, butynediary dicarboxylic acid, azodicarboxylic acid ester, benzoquinone, acrylate, benzoic acid and vinyl aldehyde.

[0033] According to this disclosure, the polymerization inhibitor is well known to those skilled in the art. In one specific embodiment of this disclosure, the polymerization inhibitor is selected from one or more of phenolic polymerization inhibitors, ketone polymerization inhibitors, and quinone polymerization inhibitors. Preferably, the polymerization inhibitor is selected from one or more of p-tert-butylcatechol, 4,6-dinitro-o-sec-butylphenol, hydroquinone, benzoquinone, and 4-phenylmethylene-2,6-di-tert-butyl-2,5-cyclohexadien-1-one.

[0034] The second aspect of this disclosure provides a method for decolorizing crude styrene, the method comprising: contacting a liquid decolorizing agent provided in the first aspect of this disclosure with crude styrene to carry out a decolorization reaction, and distilling the resulting reaction mixture.

[0035] The decolorization method disclosed herein uses a liquid decolorizing agent that is stable and has a good decolorization effect. No additional heat tracing and insulation steps are required before it is introduced into the distillation column for separation, resulting in low energy consumption and a simpler process.

[0036] According to this disclosure, the amount of the liquid decolorizing agent can vary within a wide range. In one specific embodiment, the amount of the liquid decolorizing agent is 0.02-5% by weight of the crude styrene, preferably 0.4-1% by weight. The amount of decolorizing agent within the above range is suitable, achieving both good decolorization effect and avoiding waste of the decolorizing agent.

[0037] The temperature of the decolorization reaction affects the decolorization effect. In one specific embodiment of this disclosure, the conditions for the decolorization reaction include: a reaction time of 1-12 hours and a reaction temperature of 20-70°C; preferably, the reaction time is 3-7 hours and the reaction temperature is 40-60°C, under which the decolorization reaction has a better decolorization effect.

[0038] In one specific embodiment of this disclosure, the distillation conditions include: a refining distillation column with 5-50 trays, a top pressure of 1-15 kPa, a top reflux ratio of 0.5-4.0, and a top temperature of 50-85°C; preferably, the column has 20-40 trays, a top pressure of 3-9 kPa, a top reflux ratio of 0.5-1.5, and a top temperature of 55-75°C. All pressures in this disclosure are absolute pressures. Decolorized styrene is obtained at the top of the column, and reaction products and trace polymers are obtained at the bottom. Under these conditions, the decolorized styrene can be separated from the decolorizing agent more effectively.

[0039] In one specific embodiment of this disclosure, the method further includes: mixing the liquid decolorizing agent with crude styrene in a mixer 102, and then subjecting the resulting mixture to the decolorization reaction in a decolorization tank 103. The mixing is performed before the decolorization reaction to ensure a more complete subsequent decolorization reaction. The mixer is well-known to those skilled in the art, and may be, for example, a static mixer or a stirrer. Preferably, the liquid decolorizing agent is stored in a storage tank 101.

[0040] In one specific embodiment of this disclosure, distillation is carried out in distillation column 104.

[0041] In one specific embodiment of this disclosure, the crude styrene is derived from cracked gasoline.

[0042] The present disclosure will be further illustrated by the following examples, but the present disclosure is not limited thereto.

[0043] Unless otherwise specified, all reagents used in the following examples and comparative examples were commercially available.

[0044] Example 1 In such Figure 1 The decolorization system shown is used for the decolorization of crude styrene, specifically: A compound liquid decolorizing agent C-1 was prepared using 4.0g of citrate anhydride, 2g of maleic anhydride, 1.0g of 4,6-dinitro-o-sec-butylphenol, and 1.0g of p-tert-butylcatechol. It was stored at room temperature in decolorizing agent container 101.

[0045] 200g of crude styrene and 1.1g of compound liquid decolorizing agent C-1 were mixed in mixer 102 at room temperature (20℃) and then added to decolorizing tank 103. The mixture was reacted at 50℃ for 4 hours. The crude styrene mixture after the decolorization reaction was separated by distillation in refining column 104. The refining column had a theoretical plate number of 35, a top pressure of 5kPa (absolute pressure), a top reflux ratio of 1.0, and a top temperature of 60℃.

[0046] The styrene yield, purity, Pt-Co color number, and bottom tar content obtained by the above decolorization method are shown in Table 1, and the same applies below.

[0047] Example 2 The crude styrene was decolorized using the same method as in Example 1, except that liquid decolorizing agent C-2 was used instead of liquid decolorizing agent C-1. Liquid decolorizing agent C-2 contained 5.0 g citrile anhydride, 1.0 g 4,6-dinitro-o-sec-butylphenol, and 0.5 g 4-phenylmethylene-2,6-di-tert-butyl-2,5-cyclohexadien-1-one.

[0048] Example 3 The crude styrene was decolorized using the same method as in Example 1, except that liquid decolorizing agent C-3 was used instead of liquid decolorizing agent C-1. Liquid decolorizing agent C-3 contained 4g of citral anhydride, 2.4g of maleic anhydride, 1g of 4,6-dinitro-o-sec-butylphenol, and 1g of p-tert-butylcatechol.

[0049] Example 4 The crude styrene was decolorized using the same method as in Example 1, except that liquid decolorizing agent C-4 was used instead of liquid decolorizing agent C-1. Liquid decolorizing agent C-4 contained 3.2g of citralic anhydride, 1.6g of maleic anhydride, 1g of 4,6-dinitro-o-sec-butylphenol, and 1g of p-tert-butylcatechol.

[0050] Example 5 The crude styrene was decolorized using the same method as in Example 1, except that 200g of crude styrene and 0.6g of compound liquid decolorizing agent C-1 were mixed in mixer 102 at room temperature and then added to decolorization tank 103.

[0051] Example 6 The crude styrene was decolorized using the same method as in Example 1, except that the decolorization reaction was carried out at a temperature of 70°C for 12 hours.

[0052] Comparative Example 1 3.5 g of maleic anhydride was melted at 60 °C. 200 g of crude styrene and 2.0 g of 4,6-dinitro-o-sec-butylphenol were added to the melted mixture. The mixture was then mixed in mixer 102 at 60 °C and added to decolorizing tank 103. The mixture was reacted at 50 °C for 4 hours. The crude styrene mixture after the decolorization reaction was separated by distillation in purification column 104. The purification column had a theoretical plate number of 35, a top pressure of 5 kPa, a top reflux ratio of 1.0, and a top temperature of 60 °C.

[0053] Comparative Example 2 Decolorizing agent D-1 was prepared using 5.0g maleic anhydride, 1.0g 4,6-dinitro-o-sec-butylphenol, and 1.0g p-tert-butylcatechol, and stored in decolorizing agent container 101 at 60°C.

[0054] 200g of crude styrene and 1.1g of decolorizing agent D-1 were mixed in mixer 102 at 60℃ and then added to decolorizing tank 103. The mixture was reacted at 50℃ for 4 hours. The storage tank and transport pipeline of the decolorizing agent were heated with hot water. The crude styrene mixture after the decolorization reaction was separated by distillation in refining column 104. The refining column had a theoretical plate number of 35, a top pressure of 5kPa (absolute pressure), a top reflux ratio of 1.0, and a top temperature of 60℃.

[0055] Test case (1) The purity of styrene was obtained by gas chromatography analysis of the collected styrene. The instrument was an Agilent 7890A gas chromatograph with an HP-1 capillary column, a column length of 30 m, an inner diameter of 0.25 mm, and an FID flame ionization detector.

[0056] (2) The Pt-Co color number was measured by a Lovibond colorimeter, and the analytical method was GB / T605 "General Method for Determination of Color of Chemical Reagents".

[0057] The calculation method for the results in Table 1 is as follows: Styrene yield = (Mass of collected styrene product / Mass of added crude styrene) × 100% The mass of the bottom tar = the mass of crude styrene + the mass of the decolorizing agent - the mass of the collected styrene products

[0058] As can be seen from the above, the decolorizing agent disclosed herein is stable and has a good decolorizing effect. It is liquid at room temperature and does not require additional heat tracing or insulation measures before distillation separation after decolorization.

[0059] The preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings. However, the present disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0060] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0061] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A liquid decolorizing agent for decolorizing crude styrene, the liquid decolorizing agent containing 70-90% by weight of a decolorizing component and the balance being a polymerization inhibitor; wherein, The decolorizing component comprises a first decolorizing component and optionally a second decolorizing component, wherein the first decolorizing component comprises citral anhydride.

2. The liquid decolorizing agent according to claim 1, wherein, The liquid decolorizing agent contains 75-90% by weight of the decolorizing component and the balance of the polymerization inhibitor.

3. The liquid decolorizing agent according to claim 1, wherein, The weight ratio of the first decolorizing component to the second decolorizing component is 1:(0-0.6), preferably 1:(0-0.5); The second decolorizing component is selected from dienophiles. Preferably, the second decolorizing component is selected from one or more of maleic anhydride, butynediary dicarboxylic acid, azodicarboxylic acid ester, benzoquinone, acrylate, benzoic acid and vinyl aldehyde.

4. The liquid decolorizing agent according to claim 1, wherein, The polymerization inhibitor is selected from one or more of phenolic polymerization inhibitors, ketone polymerization inhibitors, and quinone polymerization inhibitors; Preferably, the polymerization inhibitor is selected from one or more of p-tert-butylcatechol, 4,6-dinitro-o-sec-butylphenol, hydroquinone, benzoquinone, and 4-phenylmethylene-2,6-di-tert-butyl-2,5-cyclohexadien-1-one.

5. A method for decolorizing crude styrene, the method comprising: The liquid decolorizing agent according to any one of claims 1-4 is brought into contact with crude styrene to carry out a decolorization reaction, and the resulting reaction mixture is then subjected to distillation.

6. The decolorization method according to claim 5, wherein, The amount of the liquid decolorizing agent is 0.02-5% by weight of the crude styrene, preferably 0.4-1% by weight.

7. The decolorization method according to claim 5, wherein, The conditions for the decolorization reaction include: a reaction time of 1-12 hours and a reaction temperature of 20-70°C; preferably, the reaction time is 3-7 hours and the reaction temperature is 40-60°C.

8. The decolorization method according to claim 5, wherein, The distillation conditions include: the number of trays in the refining distillation column is 5-50, the top pressure is 1-15 kPa, the top reflux ratio is 0.5-4.0, and the top temperature is 50-85℃.

9. The decolorization method according to claim 5, wherein, The method further includes: mixing the liquid decolorizing agent with crude styrene in a mixer, and then subjecting the resulting mixture to the decolorization reaction in a decolorization tank.

10. The decolorization method according to claim 5, wherein, The crude styrene was derived from cracked gasoline.

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