Special white oil for polystyrene as well as preparation method and application thereof

Abstract

The invention relates to the technical field of preparation of white oil special for polystyrene, in particular to white oil special for polystyrene and a preparation method and application thereof.The white oil special for polystyrene is obtained according to the following method that firstly, paraffin-based distillate oil is sequentially subjected to a hydrotreating reaction, an isodewaxing reaction and a hydrofinishing reaction, and then three-stage hydrogenated generated oil is obtained; and carrying out vacuum fractionation and hydrogenation deep aromatic hydrocarbon saturation reaction on the third-stage hydrogenation generated oil. The white oil special for polystyrene has the characteristics of being high in distillation range, high in flash point, suitable in hydrocarbon composition, excellent in ultraviolet light stability and thermal stability, capable of better meeting the processing and forming requirements of polymers, high in product yield and better in economical efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of special white oil for polystyrene, and is a special white oil for polystyrene, a preparation method thereof and an application thereof. Background Art

[0002] Polystyrene (PS) is a high molecular polymer obtained by the polymerization reaction of styrene monomers, including general-purpose polystyrene (GPPS), foaming polystyrene (EPS), high-impact polystyrene (HIPS), etc. Due to the high molecular weight of polystyrene, the melt viscosity is large during the processing, resulting in high energy consumption and low production efficiency. To improve the processing performance, it is usually necessary to add special white oil for polystyrene (abbreviated as "PS white oil") as a lubricant during the polymerization process. PS white oil can not only reduce the melt viscosity, reduce mechanical wear, but also improve the plasticity, toughness and elasticity of the product, and at the same time play an internal lubrication role, reducing the friction between molecules and between the mold.

[0003] As the filling oil of polystyrene, the internal quality of PS white oil is required to reach the highest quality grade of white oil products - food and medicine grade, that is, extremely low sulfur, nitrogen and aromatic hydrocarbon contents, and key indicators such as easily carbonizable substances and ultraviolet absorbance reach the food and medicine grade level to ensure that polystyrene has excellent stability, and at the same time meet the requirements of human health and environmental protection; in addition, PS white oil also needs to have low evaporation loss, appropriate viscosity, carbon type distribution, and a higher C N value to increase its addition amount (2% to 8%) during the styrene polymerization process to ensure good processability with polystyrene while reducing the processing cost. During the synthesis process of polystyrene, PS white oil and other materials enter the reactor successively. After the reaction is completed, volatile substances need to be removed by vacuum. Therefore, indicators such as flash point, distillation range, and evaporation loss of polystyrene white oil are crucial for process control.

[0004] Currently, the production of PS white oil mainly uses naphthenic fraction oil as raw material and is prepared by a combination process of furfural refining and hydrogenation. However, this method has the following problems: (1) The product has a low flash point, poor distillation range, and large evaporation loss, making it difficult to meet the requirements of high-quality PS white oil; (2) The quality stability of the oil product is poor, making it difficult to ensure the high-standard requirements of polystyrene processing; (3) The process is complex, with high energy consumption, and there are environmental pollution problems.

[0005] The Chinese patent document with the authorization announcement number CN101392186B discloses a white mineral oil for polystyrene. This invention has obtained a white mineral oil for crystal polystyrene with a high distillation range, narrow components, suitable hydrocarbon composition, and deep refining degree, meeting the requirements of crystal polystyrene oil for thermal stability and ultraviolet light stability, and can improve the melt index of the polymer, adjust the Vicat softening point, which is beneficial to the processing and granulation of the polymer, molding processability, tensile strength, and impact strength improvement, etc. This product can completely replace the products of imported companies, changing the situation of complete dependence on imports. This invention provides a technology for producing PS white oil by sulfur trioxide gas sulfidation method. This method has harsh conditions, high energy consumption, and produces solid wastes such as acid slag and waste clay, resulting in serious environmental pollution and poor economy.

[0006] The Chinese patent document with the authorization announcement number CN106479565B discloses a special white oil for polystyrene and its preparation method, and the Chinese patent document with the authorization announcement number CN114479934B discloses a preparation method of a special white oil for polystyrene and the special white oil for polystyrene. These two patents respectively use naphthenic fraction oil and paraffin-based fraction oil as raw materials, and prepare PS white oil through solvent refining and hydrogenation processes. However, the former does not fully consider the requirements of the oil distillation range and flash point, and both have problems of difficult solvent treatment and environmental pollution.

[0007] The Chinese patent document with the publication number CN 117487589A discloses a C N value - moderate white oil for polystyrene and its preparation method. This patent proposes a method for preparing PS white oil by using a mixed raw material and a three - stage hydrogenation process. However, this process has a single raw material source, low yield, and small flexibility in parameter adjustment, making it difficult to realize industrial production.

[0008] In summary, the existing technologies are difficult to simultaneously meet the requirements of high C N value, reasonable distillation range distribution, excellent photo - thermal stability, and low evaporation loss of PS white oil. Summary of the Invention

[0009] The present invention provides a special white oil for polystyrene, its preparation method and application, overcoming the above - mentioned deficiencies of the existing technologies, and effectively solving the problems that the existing polystyrene white oil is difficult to simultaneously meet the requirements of high C N value, reasonable distillation range distribution, excellent photo - thermal stability, low evaporation loss, and low product yield.

[0010] One of the technical solutions of the present invention is achieved through the following measures: A special white oil for polystyrene is obtained by the following method: First step: Subject the paraffinic distillate oil with an initial boiling point of 395°C to 420°C and a final boiling point of 520°C to 550°C to a hydrotreating reaction under the action of a hydrotreating catalyst to obtain a hydrotreated product oil. Among them, the hydrotreating reaction includes a hydrorefining reaction and a hydrocracking reaction. The reaction temperature of the hydrorefining reaction is higher than that of the hydrocracking reaction, and the temperature difference is 2°C to 10°C; Second step: Subject the hydrotreated product oil to an isodewaxing reaction under the action of an isodewaxing catalyst to obtain a hydroisomerized product oil; Third step: Subject the hydroisomerized product oil to a hydrofinishing reaction under the action of a hydrofinishing catalyst to obtain a three-stage hydrotreated product oil. Fractionate the three-stage hydrotreated product oil by a multi-side line draw and distillation method to obtain a distillate oil with a boiling point higher than 420°C; Fourth step: Subject the distillate oil with a boiling point higher than 420°C to a deep hydroaromatic saturation reaction under the action of a deep hydrodearomatization catalyst to obtain a special white oil for polystyrene.

[0011] The following is a further optimization and / or improvement of one of the above technical solutions of the invention: In the above first step, the hydrotreating catalyst includes a hydrorefining catalyst and a hydrocracking catalyst. The filling mass ratio between the hydrorefining catalyst and the hydrocracking catalyst between the catalyst beds is (60 to 75):(25 to 40).

[0012] In the above first step, the carrier of the hydrorefining catalyst is one or more of activated alumina, activated silica, and amorphous silica-alumina. The active metals in the hydrorefining catalyst are three or more of Ni, W, Co, and Mo. The total weight of the active metals, calculated as the weight of their oxides, accounts for 15% to 30% of the weight of the hydrorefining catalyst. The hydrorefining catalyst is subjected to a sulfiding treatment before use.

[0013] In the above first step, the carrier of the hydrocracking catalyst is one of a mixture of amorphous silica-alumina and β-zeolite, and a mixture of amorphous silica-alumina and Y-zeolite. The active metals in the hydrocracking catalyst are two or more of W, Ni, Co, and Mo. The total weight of the active metals, calculated as the weight of their oxides, accounts for 10% to 20% of the weight of the hydrocracking catalyst. The hydrocracking catalyst is subjected to a sulfiding treatment before use.

[0014] In the above first step, the process conditions of the hydrorefining reaction: the hydrogen partial pressure is 14 MPa to 20 MPa, the volume ratio of hydrogen to paraffinic distillate oil is 800 to 1200:1, the reaction temperature is 360°C to 390°C, and the volume space velocity is 0.53h -1 to 0.67h -1, Hydrocracking reaction process conditions: hydrogen partial pressure is 14 MPa to 20 MPa, volume ratio of hydrogen to paraffinic distillate oil is 800 to 1200:1, reaction temperature is 350 °C to 380 °C, and volume hourly space velocity is 1.0 h -1 to 1.6 h -1 .

[0015] In the above-mentioned third step, the three-stage hydrogenated product oil is fractionated by a multi-side line extraction and rectification method. A vacuum tower is used for fractionation. The bottom temperature of the vacuum tower is controlled at 300 °C to 320 °C, the top temperature of the vacuum tower is controlled at 35 °C to 45 °C, the top reflux ratio is controlled at 0.15 to 0.25, the extraction temperature of the upper side line of the special white oil for polystyrene is controlled at 300 °C to 310 °C, and the top vacuum degree of the vacuum tower is controlled at 55 mmHg to 65 mmHg.

[0016] In the above-mentioned second step, the carrier of the isomerization and dewaxing catalyst is one of the mixtures of SAPO-11 molecular sieve and ZSM-22 molecular sieve, and the mixture of SAPO-11 molecular sieve and ZSM-48 molecular sieve. The active metals in the isomerization and dewaxing catalyst are Pt and Pd with a mass ratio of (3 to 2):1. The total weight of the active metals accounts for 0.4% to 1.0% of the weight of the isomerization and dewaxing catalyst. The isomerization and dewaxing catalyst is reduced and activated by hydrogen before use. The pressure of hydrogen reduction and activation is 0.3 MPa to 1.0 MPa.

[0017] In the above-mentioned third step, the carrier of the hydrogenation supplementary refining catalyst is one or more of ZSM-5 molecular sieve, ZSM-11 molecular sieve and ZSM-12 molecular sieve. The active metal in the hydrogenation supplementary refining catalyst is one of Pt and Pd. The weight of the active metal accounts for 0.2% to 0.6% of the weight of the hydrogenation supplementary refining catalyst. The hydrogenation supplementary refining catalyst is reduced and activated by hydrogen before use. The pressure of hydrogen reduction and activation is 0.3 MPa to 1.0 MPa.

[0018] In the above-mentioned fourth step, the carrier of the hydrogenation deep de-aromatization catalyst is one of ZSM-5 molecular sieve, ZSM-22 molecular sieve and ZSM-48 molecular sieve. The active metal in the hydrogenation deep de-aromatization catalyst is one of Pt and Pd. The weight of the active metal accounts for 0.2% to 0.6% of the weight of the hydrogenation deep de-aromatization catalyst. The hydrogenation deep de-aromatization catalyst is reduced and activated by hydrogen before use. The pressure of hydrogen reduction and activation is 0.3 MPa to 1.0 MPa.

[0019] In the above-mentioned second step, the isomerization and dewaxing reaction process conditions: hydrogen partial pressure is 14 MPa to 20 MPa, reaction temperature is 310 °C to 350 °C, and volume hourly space velocity is 0.5 h -1 to 1.2 h -1 , and the volume ratio of hydrogen to the hydrogenated treatment product oil is (500 to 800):1.

[0020] In the third step above, the process conditions for the hydrogenation supplementary refining reaction are as follows: the hydrogen partial pressure is 14 MPa to 20 MPa, the reaction temperature is 220 °C to 250 °C, and the volume hourly space velocity is 0.8 h -1 to 1.5 h -1 , and the volume ratio of hydrogen to the hydrogenation isomerization product oil is (500 to 800):1.

[0021] In the fourth step above, the process conditions for the hydrogenation deep aromatics saturation reaction are as follows: the hydrogen partial pressure is 14 MPa to 20 MPa, the reaction temperature is 200 °C to 250 °C, and the volume hourly space velocity is 0.5 h -1 to 1.5 h -1 , and the hydrogen-oil volume ratio is (500 to 800):1.

[0022] In the first step above, the C N value of the paraffinic base distillate oil is not more than 25%, and the C A value is not more than 15%.

[0023] In the fourth step above, the C N value of the special white oil for polystyrene is between 31% and 38%, the ultraviolet light stability is +30, the thermal stability is +30, the distillation temperature of 2.5% at 10 mmHg is greater than 280 °C, the open flash point is greater than 250 °C, and the evaporation loss is less than 1.0%.

[0024] The second technical solution of the present invention is achieved by the following measures: a method for preparing a special white oil for polystyrene, which is carried out according to the following method: In the first step, a paraffinic base distillate oil with an initial boiling point of 395 °C to 420 °C and a final boiling point of 520 °C to 550 °C is subjected to a hydrotreating reaction under the action of a hydrotreating catalyst to obtain a hydrotreating product oil. Among them, the hydrotreating reaction includes a hydrorefining reaction and a hydrocracking reaction, and the reaction temperature of the hydrorefining reaction is higher than that of the hydrocracking reaction, and the temperature difference is 2 °C to 10 °C; In the second step, the hydrotreating product oil is subjected to an isomerization and dewaxing reaction under the action of an isomerization and dewaxing catalyst to obtain a hydrogenation isomerization product oil; In the third step, the hydrogenation isomerization product oil is subjected to a hydrogenation supplementary refining reaction under the action of a hydrogenation supplementary refining catalyst to obtain a three-stage hydrogenation product oil, and the three-stage hydrogenation product oil is fractionated by a multi-side line extraction and distillation method to obtain a distillate oil with a boiling point higher than 420 °C; In the fourth step, the distillate oil with a boiling point higher than 420 °C is subjected to a hydrogenation deep aromatics saturation reaction under the action of a hydrogenation deep de-aromatization catalyst to obtain a special white oil for polystyrene.

[0025] The third technical solution of the present invention is achieved by the following measures: An application of a special white oil for polystyrene in the preparation of polystyrene products.

[0026] The special white oil for polystyrene of the present invention has a suitable naphthene content, with a C N value between 31% and 38%, an ultraviolet light stability of +30, a thermal stability of +30, a distillation temperature of 2.5% at 10 mmHg greater than 280 °C, an open flash point greater than 250 °C, an evaporation loss less than 1.0%, and good compatibility with polystyrene. The preparation method provided by the present invention has mild reaction conditions. While effectively controlling the naphthene content, it improves the quality of the product, ensures that the quality of the product meets the requirements of food-grade white oil. At the same time, it also greatly increases the output of the special white oil for polystyrene, and the product yield is as high as over 68%. Specific embodiments

[0027] The present invention is not limited by the following embodiments, and specific implementation manners can be determined according to the technical solution of the present invention and actual situations. All chemical reagents and chemical supplies mentioned in the present invention are well-known and commonly used chemical reagents and chemical supplies in the prior art unless otherwise specified; the percentages in the present invention are mass percentages unless otherwise specified; the solutions in the present invention are aqueous solutions with water as the solvent unless otherwise specified. For example, a hydrochloric acid solution is an aqueous solution of hydrochloric acid; normal temperature and room temperature in the present invention generally refer to a temperature range of 15 °C to 25 °C, and are generally defined as 25 °C.

[0028] The present invention will be further described below in conjunction with embodiments: Example 1: The special white oil for polystyrene is obtained by the following method: First step, a paraffin-based distillate oil with an initial boiling point of 395 °C to 420 °C and a final boiling point of 520 °C to 550 °C undergoes a hydrotreating reaction under the action of a hydrotreating catalyst to obtain a hydrotreated product oil. Among them, the hydrotreating reaction includes a hydrofining reaction and a hydrocracking reaction. The reaction temperature of the hydrofining reaction is higher than that of the hydrocracking reaction, and the temperature difference is 2 °C to 10 °C; Second step, the hydrotreated product oil undergoes an isodewaxing reaction under the action of an isodewaxing catalyst to obtain a hydroisomerized product oil; Third step, the hydroisomerized product oil undergoes a hydrofinishing reaction under the action of a hydrofinishing catalyst to obtain a three-stage hydrotreated product oil. The three-stage hydrotreated product oil is fractionated by a multi-side line extraction and distillation method to obtain a distillate oil with a boiling point higher than 420 °C; Fourth step, the distillate oil with a boiling point higher than 420 °C undergoes a deep hydroaromatic saturation reaction under the action of a deep hydrodearomatization catalyst to obtain the special white oil for polystyrene.

[0029] Example 2: As an optimization of the above example, in the first step, the hydrotreating catalyst includes a hydrofining catalyst and a hydrocracking catalyst, and the filling mass ratio between the hydrofining catalyst and the hydrocracking catalyst in the catalyst bed is (60 to 75):(25 to 40).

[0030] Example 3: As an optimization of the above example, in the first step, the carrier of the hydrofining catalyst is one or more of activated alumina, activated silica, and amorphous silica-alumina. The active metals in the hydrofining catalyst are three or more of Ni, W, Co, and Mo. The total weight of the active metals, calculated as the weight of their oxides, accounts for 15% to 30% of the weight of the hydrofining catalyst. The hydrofining catalyst is subjected to sulfidation treatment before use.

[0031] Example 4: As an optimization of the above example, in the first step, the carrier of the hydrocracking catalyst is one of a mixture of amorphous silica-alumina and β-zeolite and a mixture of amorphous silica-alumina and Y-zeolite. The active metals in the hydrocracking catalyst are two or more of W, Ni, Co, and Mo. The total weight of the active metals, calculated as the weight of their oxides, accounts for 10% to 20% of the weight of the hydrocracking catalyst. The hydrocracking catalyst is subjected to sulfidation treatment before use.

[0032] Example 5: As an optimization of the above example, in the first step, the process conditions for the hydrofining reaction are as follows: the hydrogen partial pressure is 14 MPa to 20 MPa, the volume ratio of hydrogen to paraffin-based distillate oil is 800 to 1200:1, the reaction temperature is 360 °C to 390 °C, and the volume space velocity is 0.53 h -1 to 0.67 h -1 ; the process conditions for the hydrocracking reaction are as follows: the hydrogen partial pressure is 14 MPa to 20 MPa, the volume ratio of hydrogen to paraffin-based distillate oil is 800 to 1200:1, the reaction temperature is 350 °C to 380 °C, and the volume space velocity is 1.0 h -1 to 1.6 h -1 ; or / and, in the third step, the three-stage hydrogenated product oil is fractionated by a multi-side line extraction and rectification method. A vacuum tower is used for fractionation. The bottom temperature of the vacuum tower is controlled at 300 °C to 320 °C, the top temperature of the vacuum tower is controlled at 35 °C to 45 °C, the top reflux ratio is controlled at 0.15 to 0.25, the extraction temperature of the upper side line of the special white oil for polystyrene is controlled at 300 °C to 310 °C, and the top vacuum degree of the vacuum tower is controlled at 55 mmHg to 65 mmHg.

[0033] In the hydrotreating reaction of the first step of the present invention, the reaction temperatures of the two catalyst beds of the hydrofining catalyst and the hydrocracking catalyst are controlled by injecting cold hydrogen. By precisely controlling the reaction temperature difference of the present invention and reducing the hydrocracking reaction temperature, the ring-opening reaction of naphthenes can be better restricted, and the C of the raw material is improved NMeanwhile, the yield of the product is effectively increased while maintaining the value.

[0034] Example 6: As an optimization of the above example, in the second step, the carrier of the isomerization dewaxing catalyst is one of a mixture of SAPO-11 molecular sieve and ZSM-22 molecular sieve, and a mixture of SAPO-11 molecular sieve and ZSM-48 molecular sieve. The active metals in the isomerization dewaxing catalyst are Pt and Pd with a mass ratio of (3 to 2):1. The total weight of the active metals accounts for 0.4% to 1.0% of the weight of the isomerization dewaxing catalyst. The isomerization dewaxing catalyst is reduced and activated by hydrogen before use, and the pressure of hydrogen reduction activation is 0.3 MPa to 1.0 MPa.

[0035] Example 7: As an optimization of the above example, in the third step, the carrier of the hydro-upgrading and finishing catalyst is one or more of ZSM-5 molecular sieve, ZSM-11 molecular sieve, and ZSM-12 molecular sieve. The active metal in the hydro-upgrading and finishing catalyst is one of Pt and Pd, and the weight of the active metal accounts for 0.2% to 0.6% of the weight of the hydro-upgrading and finishing catalyst. The hydro-upgrading and finishing catalyst is reduced and activated by hydrogen before use, and the pressure of hydrogen reduction activation is 0.3 MPa to 1.0 MPa.

[0036] Example 8: As an optimization of the above example, in the fourth step, the carrier of the hydro-deep dearomatization catalyst is one of ZSM-5 molecular sieve, ZSM-22 molecular sieve, and ZSM-48 molecular sieve. The active metal in the hydro-deep dearomatization catalyst is one of Pt and Pd, and the weight of the active metal accounts for 0.2% to 0.6% of the weight of the hydro-deep dearomatization catalyst. The hydro-deep dearomatization catalyst is reduced and activated by hydrogen before use, and the pressure of hydrogen reduction activation is 0.3 MPa to 1.0 MPa.

[0037] Example 9: As an optimization of the above example, in the second step, the process conditions of the isomerization dewaxing reaction are as follows: hydrogen partial pressure is 14 MPa to 20 MPa, reaction temperature is 310 °C to 350 °C, volume space velocity is 0.5 h -1 to 1.2 h -1 , and the volume ratio of hydrogen to hydrotreated product oil is (500 to 800):1.

[0038] Example 10: As an optimization of the above example, in the third step, the process conditions of the hydro-upgrading and finishing reaction are as follows: hydrogen partial pressure is 14 MPa to 20 MPa, reaction temperature is 220 °C to 250 °C, volume space velocity is 0.8 h -1 to 1.5 h -1 , and the volume ratio of hydrogen to hydroisomerized product oil is (500 to 800):1.

[0039] Example 11: As an optimization of the above examples, in the fourth step, the process conditions for the hydrogenation deep aromatics saturation reaction are as follows: the hydrogen partial pressure is 14 MPa to 20 MPa, the reaction temperature is 200 °C to 250 °C, and the volume hourly space velocity is 0.5 h -1 to 1.5 h -1 , and the hydrogen-oil volume ratio is (500 to 800):1.

[0040] Example 12: As an optimization of the above examples, in the first step, the C N value of the paraffinic distillate oil is not more than 25%, and the C A value is not more than 15%. In the fourth step, the C N value of the special white oil for polystyrene is between 31% and 38%, the ultraviolet light stability is +30, the thermal stability is +30, the distillation temperature of 2.5% at 10 mmHg is greater than 280 °C, the open flash point is greater than 250 °C, and the evaporation loss is less than 1.0%.

[0041] In the present invention, the raw material is paraffinic distillate oil, which has a high saturated hydrocarbon content and a high flash point. Using it as the raw material for polystyrene white oil has good advantages in ensuring the flash point, distillation range and photo-thermal stability of the product.

[0042] Example 13: Application of the special white oil for polystyrene in the preparation of polystyrene products.

[0043] Compared with the prior art, the beneficial effects of the present invention are as follows: First, the combination of hydrofining reaction and hydrocracking reaction, as well as the grading combination of hydrofining catalyst and hydrocracking catalyst, are adopted during the hydrotreating reaction in this application, and the temperature difference between the hydrofining reaction and the hydrocracking reaction is different, effectively retaining the naphthene hydrocarbon content, thereby increasing the proportion of naphthene carbon content in the product, that is, increasing the C N value, and improving the compatibility with polystyrene when it is applied in the preparation of polystyrene; Secondly, the hydroisomerization catalyst support of this application is one of the mixtures of SAPO-11 molecular sieve and ZSM-22 molecular sieve, and the mixture of SAPO-11 molecular sieve and ZSM-48 molecular sieve. The combination of the two molecular sieves can ensure better reduction of the pour point of the product; Next, the three-stage hydrogenated product oil is fractionated by a multi-side line draw and rectification method, which can better control the distillation temperature of 2.5% of the special white oil for polystyrene obtained at 10 mmHg to be greater than 280 °C. The polystyrene white oil prepared in this application is used as a filling oil in the polystyrene synthesis process. The polystyrene production process includes a devolatilization unit, and the function of this unit is to remove unreacted styrene monomers, solvents, oligomers and other volatile substances remaining in the polymer melt. Control the distillation temperature of the polystyrene white oil at 10 mmHg, 2.5% ≥ 280 °C, in order to prevent the polystyrene white oil from being removed during the devolatilization process, thereby affecting the plasticity, toughness and elasticity of the polystyrene product; Finally, in this application, the increased hydrotreating depth dearomatization process and the appropriate hydrotreating depth dearomatization catalyst can effectively remove trace aromatics and ensure the storage stability of the product; this process adopts a full-hydrogen process to convert non-ideal components in the raw materials into ideal components, greatly improving the yield of the special white oil for polystyrene.

[0044] Example 14: The special white oil for polystyrene is obtained by the following method: First step, using a paraffin-based distillate oil with a boiling range of 395 °C to 530 °C as the raw material, the main properties of the raw material are shown in Table 1. The raw material is mixed with hydrogen and sent to a hydrotreating reactor for hydrotreating reaction. The hydrotreating reaction conditions are shown in Table 2, and the hydrotreating catalyst composition is shown in Table 6 to obtain a hydrotreated product oil; Second step, the hydrotreated product oil is mixed with hydrogen and sent to a hydroisomerization reactor for isomerization and dewaxing reaction. The isomerization and dewaxing reaction conditions are shown in Table 3, and the isomerization and dewaxing catalyst composition is shown in Table 7 to obtain a hydroisomerized product oil; Third step, the hydroisomerized product oil is mixed with hydrogen and sent to a hydrofinishing reactor for hydrofinishing reaction. The hydrofinishing reaction conditions are shown in Table 4, and the hydrofinishing catalyst composition is shown in Table 7 to obtain a three-stage hydrogenated product oil. The three-stage hydrogenated product oil is fractionated by a multi-side line draw and rectification method to cut the fraction with a boiling range ≥ 420 °C to obtain a distillate oil with a boiling point higher than 420 °C. Among them, a vacuum tower is used for fractionation. The bottom temperature of the vacuum tower is controlled at 300 °C, the top temperature of the vacuum tower is controlled at 35 °C, the top reflux ratio is controlled at 0.25, the draw temperature of the upper side line of the special white oil for polystyrene is controlled at 300 °C, and the top vacuum degree of the vacuum tower is controlled at 55 mmHg; Fourth step, the distillate oil with a boiling point higher than 420 °C is mixed with hydrogen and sent to a hydrotreating depth dearomatization reactor for hydrotreating depth aromatic saturation reaction. The hydrotreating depth aromatic saturation reaction conditions are shown in Table 5, and the hydrotreating depth dearomatization catalyst composition is shown in Table 7 to obtain the special white oil for polystyrene.

[0045] Example 15: The special white oil for polystyrene is obtained by the following method: First step: Using a paraffin-based distillate oil with a boiling range of 410°C to 520°C as the raw material. The main properties of the raw material are shown in Table 1. Mix the raw material with hydrogen and send it to a hydrotreating reactor for hydrotreating reaction. The hydrotreating reaction conditions are shown in Table 2, and the composition of the hydrotreating catalyst is shown in Table 6 to obtain a hydrotreated product oil; Second step: Mix the hydrotreated product oil with hydrogen and send it to a hydroisomerization reactor for isomerization dewaxing reaction. The isomerization dewaxing reaction conditions are shown in Table 3, and the composition of the isomerization dewaxing catalyst is shown in Table 7 to obtain a hydroisomerized product oil; Third step: Mix the hydroisomerized product oil with hydrogen and send it to a hydrofinishing reactor for hydrofinishing reaction. The hydrofinishing reaction conditions are shown in Table 4, and the composition of the hydrofinishing catalyst is shown in Table 7 to obtain a three-stage hydrotreated product oil. The three-stage hydrotreated product oil is fractionated by a multi-side line extraction distillation method to cut the fraction with a boiling range ≥ 420°C to obtain a distillate oil with a boiling point higher than 420°C. Among them, a vacuum tower is used for fractionation. The bottom temperature of the vacuum tower is controlled at 300°C, the top temperature of the vacuum tower is controlled at 35°C, the top reflux ratio is controlled at 0.15, the extraction temperature of the upper side line of the special white oil for polystyrene is controlled at 300°C, and the top vacuum degree of the vacuum tower is controlled at 55 mmHg; Fourth step: Mix the distillate oil with a boiling point higher than 420°C with hydrogen and send it to a hydrodeep dearomatization reactor for hydrodeep aromatics saturation reaction. The hydrodeep aromatics saturation reaction conditions are shown in Table 5, and the composition of the hydrodeep dearomatization catalyst is shown in Table 7 to obtain the special white oil for polystyrene.

[0046] Example 16: The special white oil for polystyrene is obtained by the following method: First step: Using a paraffin-based distillate oil with a boiling range of 420°C to 550°C as the raw material. The main properties of the raw material are shown in Table 1. Mix the raw material with hydrogen and send it to a hydrotreating reactor for hydrotreating reaction. The hydrotreating reaction conditions are shown in Table 2, and the composition of the hydrotreating catalyst is shown in Table 6 to obtain a hydrotreated product oil; Second step: Mix the hydrotreated product oil with hydrogen and send it to a hydroisomerization reactor for isomerization dewaxing reaction. The isomerization dewaxing reaction conditions are shown in Table 3, and the composition of the isomerization dewaxing catalyst is shown in Table 7 to obtain a hydroisomerized product oil; Step 3: Mix the hydroisomerization product oil with hydrogen and send it to a hydro-upgrading reactor for hydro-upgrading reaction. The hydro-upgrading reaction conditions are shown in Table 4, and the composition of the hydro-upgrading catalyst is shown in Table 7 to obtain the three-stage hydrogenation product oil. The three-stage hydrogenation product oil is fractionated by a multi-side stream extraction and distillation method to cut the fraction with a distillation range ≥ 420 °C to obtain the fraction oil with a boiling point higher than 420 °C. Among them, a vacuum tower is used for fractionation. The bottom temperature of the vacuum tower is controlled at 300 °C, the top temperature of the vacuum tower is controlled at 35 °C, the top reflux ratio is controlled at 0.15, the extraction temperature of the upper side stream of the special white oil for polystyrene is controlled at 300 °C, and the top vacuum degree of the vacuum tower is controlled at 55 mmHg; Step 4: Mix the fraction oil with a boiling point higher than 420 °C with hydrogen and send it to a hydro-deep dearomatization reactor for hydro-deep aromatics saturation reaction. The hydro-deep aromatics saturation reaction conditions are shown in Table 5, and the composition of the hydro-deep dearomatization catalyst is shown in Table 7 to obtain the special white oil for polystyrene.

[0047] Example 17: The special white oil for polystyrene is obtained by the following method: Step 1: Use the paraffin-based fraction oil with a distillation range of 420 °C to 550 °C as the raw material. The main properties of the raw material are shown in Table 1. Mix the raw material with hydrogen and send it to a hydrotreating reactor for hydrotreating reaction. The hydrotreating reaction conditions are shown in Table 2, and the composition of the hydrotreating catalyst is shown in Table 6 to obtain the hydrotreating product oil; Step 2: Mix the hydrotreating product oil with hydrogen and send it to a hydroisomerization reactor for isomerization and dewaxing reaction. The isomerization and dewaxing reaction conditions are shown in Table 3, and the composition of the isomerization and dewaxing catalyst is shown in Table 7 to obtain the hydroisomerization product oil; Step 3: Mix the hydroisomerization product oil with hydrogen and send it to a hydro-upgrading reactor for hydro-upgrading reaction. The hydro-upgrading reaction conditions are shown in Table 4, and the composition of the hydro-upgrading catalyst is shown in Table 7 to obtain the three-stage hydrogenation product oil. The three-stage hydrogenation product oil is fractionated by a multi-side stream extraction and distillation method to cut the fraction with a distillation range ≥ 420 °C to obtain the fraction oil with a boiling point higher than 420 °C. Among them, a vacuum tower is used for fractionation. The bottom temperature of the vacuum tower is controlled at 320 °C, the top temperature of the vacuum tower is controlled at 45 °C, the top reflux ratio is controlled at 0.15, the extraction temperature of the upper side stream of the special white oil for polystyrene is controlled at 310 °C, and the top vacuum degree of the vacuum tower is controlled at 65 mmHg; Step 4: Mix the fraction oil with a boiling point higher than 420 °C with hydrogen and send it to a hydro-deep dearomatization reactor for hydro-deep aromatics saturation reaction. The hydro-deep aromatics saturation reaction conditions are shown in Table 5, and the composition of the hydro-deep dearomatization catalyst is shown in Table 7 to obtain the special white oil for polystyrene.

[0048] Example 18: The special white oil for polystyrene is obtained by the following method: First step: Using a paraffin-based distillate oil with a boiling range of 420°C to 540°C as the raw material, the main properties of the raw material are shown in Table 1. Mix the raw material with hydrogen and send it to a hydrotreating reactor for hydrotreating reaction. The hydrotreating reaction conditions are shown in Table 2, and the composition of the hydrotreating catalyst is shown in Table 6 to obtain hydrotreated product oil. Second step: Mix the hydrotreated product oil with hydrogen and send it to a hydroisomerization reactor for isomerization and dewaxing reaction. The isomerization and dewaxing reaction conditions are shown in Table 3, and the composition of the isomerization and dewaxing catalyst is shown in Table 7 to obtain hydroisomerized product oil. Third step: Mix the hydroisomerized product oil with hydrogen and send it to a hydrofinishing reactor for hydrofinishing reaction. The hydrofinishing reaction conditions are shown in Table 4, and the composition of the hydrofinishing catalyst is shown in Table 7 to obtain three-stage hydrotreated product oil. The three-stage hydrotreated product oil is fractionated by a multi-side stream extraction and distillation method, and the fraction with a boiling range ≥ 420°C is cut to obtain a distillate oil with a boiling point higher than 420°C. Among them, a vacuum tower is used during fractionation. The bottom temperature of the vacuum tower is controlled at 320°C, the top temperature of the vacuum tower is controlled at 45°C, the top reflux ratio is controlled at 0.15, the extraction temperature of the upper side stream of the special white oil for polystyrene is controlled at 310°C, and the top vacuum degree of the vacuum tower is controlled at 65 mmHg. Fourth step: Mix the distillate oil with a boiling point higher than 420°C with hydrogen and send it to a deep hydrodearomatization reactor for deep hydroaromatic saturation reaction. The deep hydroaromatic saturation reaction conditions are shown in Table 5, and the composition of the deep hydrodearomatization catalyst is shown in Table 7 to obtain the special white oil for polystyrene.

[0049] Comparative Example 1: The special white oil for polystyrene is obtained by the following method: First step: Using a paraffin-based distillate oil with a boiling range of 420°C to 550°C as the raw material, the main properties of the raw material are shown in Table 1. Mix the raw material with hydrogen and send it to a hydrotreating reactor for hydrotreating reaction. The hydrotreating reaction conditions are shown in Table 2, and the composition of the hydrotreating catalyst is shown in Table 6 to obtain hydrotreated product oil. Second step: Mix the hydrotreated product oil with hydrogen and send it to a hydroisomerization reactor for isomerization and dewaxing reaction. The isomerization and dewaxing reaction conditions are shown in Table 3, and the composition of the isomerization and dewaxing catalyst is shown in Table 7 to obtain hydroisomerized product oil. Third step: Mix the hydroisomerized product oil with hydrogen and send it to a hydrofinishing reactor for hydrofinishing reaction. The hydrofinishing reaction conditions are shown in Table 4, and the composition of the hydrofinishing catalyst is shown in Table 7 to obtain three-stage hydrotreated product oil. The three-stage hydrotreated product oil is fractionated by vacuum fractionation, and the fraction with a boiling range ≥ 420°C is cut to obtain a distillate oil with a boiling point higher than 420°C. Step 4: Mix the fraction oil with a boiling point higher than 420 °C with hydrogen and send it to a hydro - deep de - aromatization reactor for hydro - deep aromatic saturation reaction. The conditions for the hydro - deep aromatic saturation reaction are shown in Table 5, and the composition of the hydro - deep de - aromatization catalyst is shown in Table 7, to obtain the special white oil for polystyrene.

[0050] Comparative Example 2: The special white oil for polystyrene is obtained by the following method: Step 1: Use the paraffin - based fraction oil with a distillation range of 420 °C to 540 °C as the raw material. The main properties of the raw material are shown in Table 1. Mix the raw material with hydrogen and send it to a hydro - treatment reactor for hydro - treatment reaction. The conditions for the hydro - treatment reaction are shown in Table 2, and the composition of the hydro - treatment catalyst is shown in Table 6, to obtain the hydro - treated product oil. Step 2: Mix the hydro - treated product oil with hydrogen and send it to a hydro - isomerization reactor for isomerization dewaxing reaction. The conditions for the isomerization dewaxing reaction are shown in Table 3, and the composition of the isomerization dewaxing catalyst is shown in Table 7, to obtain the hydro - isomerized product oil. Step 3: Mix the hydro - isomerized product oil with hydrogen and send it to a hydro - finishing reactor for hydro - finishing reaction. The conditions for the hydro - finishing reaction are shown in Table 4, and the composition of the hydro - finishing catalyst is shown in Table 7, to obtain the three - stage hydro - treated product oil. Subject the three - stage hydro - treated product oil to vacuum fractionation and cut the fraction with a distillation range ≥ 450 °C, namely, obtain the special white oil for polystyrene.

[0051] Experimental Example 1: Examine the performance of the special white oil for polystyrene of the present invention.

[0052] Experimental method: Examine the performance of the special white oil for polystyrene prepared in Examples 14 to 18 of the present invention. The performance includes product yield, kinematic viscosity, open flash point, pour point, evaporation loss, ultraviolet light stability, thermal stability, easily carbonizable substances, carbon type analysis (C A value and C N value), polycyclic aromatic hydrocarbons (ultraviolet absorbance), vacuum distillation range, and compatibility with styrene. At the same time, use Comparative Examples 1 to 2 as controls.

[0053] Experimental results: The performance of the special white oil for polystyrene prepared in Examples 14 to 18 of the present invention is shown in Table 8. As can be seen from Table 8, the special white oil for polystyrene prepared in Examples 14 to 18 of the present invention is measured by the method of ASTM2140, and its C A value is 0, C NThe value is 31% to 38%; determined by the method of Q / SY1440, its ultraviolet light stability is +30; determined by the method of Q / SY1439, its thermal stability is +30; determined by the method of ASTM D92, its open flash point is greater than 250 °C; determined by the method of NB / SH / T0059, its evaporation loss is less than 1%; determined by the method of ASTM D1160, the distillation temperature of 2.5% at 10 mmHg is greater than 280 °C; and the yield of the special white oil for polystyrene prepared in Examples 14 to 18 of the present invention is above 68%, and it has good compatibility with polystyrene. While for the special white oil for polystyrene prepared in Comparative Example 1 (the hydrogenation refining temperature is the same as the hydrocracking temperature) and Comparative Example 2 (no deep hydrogenation aromatic saturation reaction) of the present invention, the flash point is low, the C N value is low, the distillation temperature of 2.5% at 10 mmHg is low, the product yield is low, and the compatibility with polystyrene is poor.

[0054] In summary, for the special white oil for polystyrene of the present invention, its naphthene hydrocarbon content is appropriate, the C N value is between 31% and 38%, the ultraviolet light stability is +30, the thermal stability is +30, the distillation temperature of 2.5% at 10 mmHg is greater than 280 °C, the open flash point is greater than 250 °C, the evaporation loss is less than 1.0%, and it has good compatibility with polystyrene. The reaction conditions of the preparation method provided by the present invention are mild. While effectively controlling the naphthene hydrocarbon content, the quality of the product is improved, ensuring that the quality of the product meets the requirements of food-grade white oil. At the same time, the yield of the special white oil for polystyrene is also greatly increased, and the product yield is as high as above 68%.

[0055] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effects. Non-essential technical features can be added or subtracted according to actual needs to meet the requirements of different situations.

[0056] Table 1 .

[0057] Table 2 .

[0058] Table 3 .

[0059] Table 4 .

[0060] Table 5 .

[0061] Table 6 .

[0062] Table 7 。

[0063] Table 8 。

Claims

1. A special white oil for polystyrene, characterized in that Obtained by the following method: In the first step, a paraffinic fraction oil with an initial boiling point of 395°C to 420°C and a final boiling point of 520°C to 550°C undergoes a hydrotreating reaction under the action of a hydrotreating catalyst to obtain a hydrotreated product oil. Among them, the hydrotreating reaction includes a hydrorefining reaction and a hydrocracking reaction. The reaction temperature of the hydrorefining reaction is higher than that of the hydrocracking reaction, and the temperature difference is 2°C to 10°C; In the second step, the hydrotreated product oil undergoes an isomerization and dewaxing reaction under the action of an isomerization and dewaxing catalyst to obtain a hydroisomerized product oil; In the third step, the hydroisomerized product oil undergoes a hydrofinishing reaction under the action of a hydrofinishing catalyst to obtain a three-stage hydrotreated product oil. The three-stage hydrotreated product oil is fractionated by a multi-side stream extraction distillation method to obtain a fraction oil with a boiling point higher than 420°C; In the fourth step, the fraction oil with a boiling point higher than 420°C undergoes a deep hydroaromatic saturation reaction under the action of a deep hydrodearomatization catalyst to obtain a special white oil for polystyrene.

2. The polystyrene special white oil according to claim 1, wherein In the first step, the hydrotreating catalyst includes a hydrorefining catalyst and a hydrocracking catalyst. The filling mass ratio between the hydrorefining catalyst and the hydrocracking catalyst in the catalyst bed is 60 to 75:25 to 40.

3. The special white oil for polystyrene according to claim 2, wherein In the first step, the carrier of the hydrorefining catalyst is one or more of activated alumina, activated silica, and amorphous silica-alumina. The active metals in the hydrorefining catalyst are three or more of Ni, W, Co, and Mo. The total weight of the active metals, calculated as their oxides, accounts for 15% to 30% of the weight of the hydrorefining catalyst. The hydrorefining catalyst is sulfided before use; or / and, in the first step, the carrier of the hydrocracking catalyst is one of the mixtures of amorphous silica-alumina and β-zeolite, and the mixture of amorphous silica-alumina and Y-zeolite. The active metals in the hydrocracking catalyst are two or more of W, Ni, Co, and Mo. The total weight of the active metals, calculated as their oxides, accounts for 10% to 20% of the weight of the hydrocracking catalyst. The hydrocracking catalyst is sulfided before use.

4. The polystyrene special white oil according to claim 3, wherein In the first step, the process conditions for hydrofining reaction are as follows: the hydrogen partial pressure is 14 MPa to 20 MPa, the volume ratio of hydrogen to paraffinic distillate oil is 800 to 1200:1, the reaction temperature is 360 °C to 390 °C, and the volume space velocity is 0.53 h -1 to 0.67 h -1 , and the process conditions for hydrocracking reaction are as follows: the hydrogen partial pressure is 14 MPa to 20 MPa, the volume ratio of hydrogen to paraffinic distillate oil is 800 to 1200:1, the reaction temperature is 350 °C to 380 °C, and the volume space velocity is 1.0 h -1 to 1.6 h -1 ; or / and, in the third step, the three-stage hydrogenated product oil is fractionated by a multi-side line extraction and rectification method. A vacuum tower is used for fractionation. The bottom temperature of the vacuum tower is controlled at 300 °C to 320 °C, the top temperature of the vacuum tower is controlled at 35 °C to 45 °C, the top reflux ratio is controlled at 0.15 to 0.25, the extraction temperature of the upper side line of the special white oil for polystyrene is controlled at 300 °C to 310 °C, and the top vacuum degree of the vacuum tower is controlled at 55 mmHg to 65 mmHg.

5. The polystyrene special white oil according to any one of claims 1 to 4, characterized in that In the second step, the carrier of the isomerization and dewaxing catalyst is one of the mixtures of SAPO-11 zeolite and ZSM-22 zeolite, and the mixture of SAPO-11 zeolite and ZSM-48 zeolite. The active metals in the isomerization and dewaxing catalyst are Pt and Pd with a mass ratio of 3 to 2:

1. The total weight of the active metals accounts for 0.4% to 1.0% of the weight of the isomerization and dewaxing catalyst. The isomerization and dewaxing catalyst is reduced and activated by hydrogen before use. The pressure of hydrogen reduction and activation is 0.3MPa to 1.0MPa.

6. The polystyrene special white oil according to any one of claims 1 to 4, characterized in that In the third step, the carrier of the hydrofinishing catalyst is one or more of ZSM-5 zeolite, ZSM-11 zeolite, and ZSM-12 zeolite. The active metal in the hydrofinishing catalyst is one of Pt and Pd. The weight of the active metal accounts for 0.2% to 0.6% of the weight of the hydrofinishing catalyst. The hydrofinishing catalyst is reduced and activated by hydrogen before use. The pressure of hydrogen reduction and activation is 0.3MPa to 1.0MPa.

7. The polystyrene special white oil according to claim 5, characterized in that In the third step, the carrier of the hydrofinishing catalyst is one or more of ZSM-5 molecular sieve, ZSM-11 molecular sieve, and ZSM-12 molecular sieve. The active metal in the hydrofinishing catalyst is one of Pt and Pd, and the weight of the active metal accounts for 0.2% to 0.6% of the weight of the hydrofinishing catalyst. Before use, the hydrofinishing catalyst is reduced and activated by hydrogen, and the pressure of the hydrogen reduction activation is 0.3 MPa to 1.0 MPa.

8. The polystyrene special white oil according to any one of claims 1 to 4 and 7, characterized in that In the fourth step, the carrier of the deep hydrodearomatization catalyst is one of ZSM-5 molecular sieve, ZSM-22 molecular sieve, and ZSM-48 molecular sieve. The active metal in the deep hydrodearomatization catalyst is one of Pt and Pd, and the weight of the active metal accounts for 0.2% to 0.6% of the weight of the deep hydrodearomatization catalyst. Before use, the deep hydrodearomatization catalyst is reduced and activated by hydrogen, and the pressure of the hydrogen reduction activation is 0.3 MPa to 1.0 MPa.

9. The polystyrene special white oil according to claim 5, wherein In the fourth step, the carrier of the deep hydrodearomatization catalyst is one of ZSM-5 molecular sieve, ZSM-22 molecular sieve, and ZSM-48 molecular sieve. The active metal in the deep hydrodearomatization catalyst is one of Pt and Pd, and the weight of the active metal accounts for 0.2% to 0.6% of the weight of the deep hydrodearomatization catalyst. Before use, the deep hydrodearomatization catalyst is reduced and activated by hydrogen, and the pressure of the hydrogen reduction activation is 0.3 MPa to 1.0 MPa.

10. The special white oil for polystyrene according to claim 6, characterized in that In the fourth step, the carrier of the deep hydrodearomatization catalyst is one of ZSM-5 molecular sieve, ZSM-22 molecular sieve, and ZSM-48 molecular sieve. The active metal in the deep hydrodearomatization catalyst is one of Pt and Pd, and the weight of the active metal accounts for 0.2% to 0.6% of the weight of the deep hydrodearomatization catalyst. Before use, the deep hydrodearomatization catalyst is reduced and activated by hydrogen, and the pressure of the hydrogen reduction activation is 0.3 MPa to 1.0 MPa.

11. The polystyrene special white oil according to any one of claims 1 to 4, 7, 9, and 10, characterized in that In the second step, the process conditions for the isomerization and dewaxing reaction are as follows: hydrogen partial pressure is 14 MPa to 20 MPa, reaction temperature is 310 °C to 350 °C, and the volumetric space velocity is 0.5 h -1 to 1.2 h -1 , and the volume ratio of hydrogen to the hydrotreated product oil is 500 to 800:1; or / and, in the third step, the process conditions for the hydrogenation supplementary refining reaction are as follows: hydrogen partial pressure is 14 MPa to 20 MPa, reaction temperature is 220 °C to 250 °C, and the volumetric space velocity is 0.8 h -1 to 1.5 h -1 , and the volume ratio of hydrogen to the hydroisomerized product oil is 500 to 800:1; or / and, in the fourth step, the process conditions for the deep hydrogenation aromatics saturation reaction are as follows: hydrogen partial pressure is 14 MPa to 20 MPa, reaction temperature is 200 °C to 250 °C, and the volumetric space velocity is 0.5 h -1 to 1.5 h -1 , and the hydrogen-oil volume ratio is 500 to 800:

1.

12. The polystyrene special white oil according to claim 8, characterized in that In the second step, the process conditions for the isomerization and dewaxing reaction are as follows: hydrogen partial pressure is from 14 MPa to 20 MPa, reaction temperature is from 310 °C to 350 °C, and the volumetric space velocity is 0.5 h -1 to 1.2 h -1 , and the volume ratio of hydrogen to the hydrogenated treatment product oil is 500 to 800:1; or / and, in the third step, the process conditions for the hydrogenation supplementary refining reaction are as follows: hydrogen partial pressure is from 14 MPa to 20 MPa, reaction temperature is from 220 °C to 250 °C, and the volumetric space velocity is 0.8 h -1 to 1.5 h -1 , and the volume ratio of hydrogen to the hydroisomerization product oil is 500 to 800:1; or / and, in the fourth step, the process conditions for the deep hydrogenation aromatics saturation reaction are as follows: hydrogen partial pressure is from 14 MPa to 20 MPa, reaction temperature is from 200 °C to 250 °C, and the volumetric space velocity is 0.5 h -1 to 1.5 h -1 , and the hydrogen-oil volume ratio is 500 to 800:

1.

13. The polystyrene special white oil according to any one of claims 1 to 4, 7, 9, 10, and 12, characterized in that In the first step, the C value of the paraffin-based distillate oil is not more than 25%, and the C value is not more than 15%; or / and, in the fourth step, the C value of the special white oil for polystyrene is between 31% and 38%, the ultraviolet light stability is +30, the thermal stability is +30, the distillation temperature of 2.5% at 10 mmHg is greater than 280 °C, the open flash point is greater than 250 °C, and the evaporation loss is less than 1.0%. N value is not more than 25%, and the C A value is not more than 15%; or / and, in the fourth step, the C N value is between 31% and 38%, the ultraviolet light stability is +30, the thermal stability is +30, the distillation temperature of 2.5% at 10 mmHg is greater than 280 °C, the open flash point is greater than 250 °C, and the evaporation loss is less than 1.0%.

14. A method for preparing a special white oil for polystyrene according to any one of claims 2 to 13, characterized in that It is carried out according to the following method: In the first step, a paraffinic distillate oil with an initial boiling point of 395 °C to 420 °C and a final boiling point of 520 °C to 550 °C undergoes a hydrotreating reaction under the action of a hydrotreating catalyst to obtain a hydrotreated product oil. Among them, the hydrotreating reaction includes a hydrorefining reaction and a hydrocracking reaction. The reaction temperature of the hydrorefining reaction is higher than that of the hydrocracking reaction, and the temperature difference is 2 °C to 10 °C. In the second step, the hydrotreated product oil undergoes an isomerization and dewaxing reaction under the action of an isomerization and dewaxing catalyst to obtain a hydroisomerized product oil. In the third step, the hydroisomerized product oil undergoes a hydrofinishing reaction under the action of a hydrofinishing catalyst to obtain a three-stage hydrotreated product oil. The three-stage hydrotreated product oil is fractionated by a multi-side line extraction and distillation method to obtain a distillate oil with a boiling point higher than 420 °C. In the fourth step, the distillate oil with a boiling point higher than 420 °C undergoes a deep hydroaromatic saturation reaction under the action of a deep hydrodearomatization catalyst to obtain a special white oil for polystyrene.

15. Use of the special white oil for polystyrene according to any one of claims 1 to 13 in the preparation of polystyrene products.