White oil for polystyrene, preparation method and application thereof

Abstract

The present invention relates to the technical field of polystyrene white oil preparation, and is a polystyrene white oil preparation method and application thereof. The polystyrene white oil is obtained by the following method: first, paraffin-based distillate oil is subjected to a hydrogenation treatment reaction, an isomerization pour point depression reaction, and a hydrogenation supplementary refining reaction in sequence to obtain a three-stage hydrogenation product oil; then, the three-stage hydrogenation product oil is subjected to a vacuum fractionation and a hydrogenation deep aromatic saturation reaction to obtain the product. The polystyrene white oil of the present invention has a high distillation range, a high flash point, a suitable hydrocarbon composition, excellent ultraviolet light stability and thermal stability, can better meet the processing and molding characteristics of polymers, and has a high product yield and better economic efficiency.

Description

Technical Field

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

[0002] Polystyrene (PS) is a high-molecular-weight polymer derived from the polymerization of styrene monomers. These include general-purpose polystyrene (GPPS), expanded polystyrene (EPS), and high-impact polystyrene (HIPS). Due to its high molecular weight, polystyrene exhibits high melt viscosity during processing, resulting in high energy consumption and low production efficiency. To improve processing performance, polystyrene-specific white oil (referred to as "PS white oil") is often added as a lubricant during the polymerization process. PS white oil not only reduces melt viscosity and mechanical wear, but also enhances the plasticity, toughness, and elasticity of the finished product. It also acts as an internal lubricant, reducing friction between molecules and within the mold.

[0003] As a filler oil for polystyrene, PS white oil must meet the highest quality level of white oil products - food and pharmaceutical grade. This requires extremely low sulfur, nitrogen and aromatic hydrocarbon contents, and key indicators such as carbonized matter and ultraviolet absorbance must meet food and pharmaceutical grade levels to ensure that polystyrene has excellent stability while meeting the needs of human health and environmental protection. In addition, PS white oil must also have low evaporation loss, suitable viscosity and carbon type distribution, and high C N The addition of polystyrene white oil to the styrene polymerization process (2% to 8%) is increased to ensure good processability with polystyrene while reducing processing costs. During the polystyrene synthesis process, PS white oil and other materials are introduced into the reactor one after another. After the reaction is completed, volatile substances must be removed by vacuum. Therefore, the flash point, distillation range, evaporation loss and other indicators of PS white oil are crucial for process control.

[0004] Currently, PS white oil production primarily uses naphthenic distillate as a raw material, produced through a combined furfural refining and hydrogenation process. However, this method has the following problems: (1) the product has a low flash point, poor distillation range, and large evaporation losses, making it difficult to meet the requirements for high-quality PS white oil; (2) the oil quality stability is poor, making it difficult to meet the high standards required for polystyrene processing; and (3) the process is complex, energy-intensive, and poses environmental pollution issues.

[0005] Chinese patent publication CN101392186B discloses a white mineral oil for polystyrene. This invention produces a crystalline polystyrene white mineral oil with a high distillation range, narrow composition, suitable hydrocarbon profile, and a high degree of refinement. This product meets the thermal and UV stability requirements for crystalline polystyrene oils, improves the polymer's melt index, adjusts its Vicat softening point, and facilitates polymer processing, pelletization, molding, tensile strength, and impact strength. This product can completely replace imported products, changing the current situation of complete reliance on imports. The invention also provides a technology for producing PS white oil using sulfur trioxide gas vulcanization, a method that requires harsh conditions, high energy consumption, and produces solid wastes such as acid slag and waste clay, resulting in severe environmental pollution and poor economic efficiency.

[0006] Chinese patent document with authorization publication number CN106479565B discloses a polystyrene-specific white oil and its preparation method, and Chinese patent document with authorization publication number CN114479934B discloses a polystyrene-specific white oil preparation method and polystyrene-specific white oil. These two patents use cycloalkyl distillate oil and paraffin-based distillate oil as raw materials, respectively, to prepare PS white oil through solvent refining and hydrogenation processes. However, the former does not fully consider the requirements for oil distillation range and flash point, and both patents have solvent handling difficulties and environmental pollution issues.

[0007] Chinese patent document No. CN 117487589A discloses a C N Polystyrene white oil with moderate value and its preparation method. The patent proposes a method for preparing PS white oil using mixed raw materials and a three-stage hydrogenation process, but the process has a single raw material source, low yield, and small parameter adjustment flexibility, making it difficult to achieve industrial production.

[0008] In summary, it is difficult for existing technologies to simultaneously meet the requirements of high C N value, reasonable distillation range distribution, excellent light and thermal stability, and low evaporation loss. Summary of the Invention

[0009] The present invention provides a polystyrene special white oil and its preparation method and application, which overcomes the shortcomings of the above-mentioned prior art and can effectively solve the problem that the existing polystyrene white oil is difficult to meet the requirements of high C N value, reasonable distillation range distribution, excellent light and thermal stability, low evaporation loss and low product yield.

[0010] One of the technical solutions of the present invention is achieved by the following measures: a white oil for polystyrene is obtained by the following method:

[0011] In the first step, a paraffin-based distillate oil having an initial boiling point of 395° C. to 420° C. and an end boiling point of 520° C. to 550° C. is subjected to a hydrotreating reaction under the action of a hydrotreating catalyst to obtain a hydrotreated product oil, wherein the hydrotreating reaction includes a hydrofining reaction and a hydrocracking reaction, and the reaction temperature of the hydrofining reaction is higher than the reaction temperature of the hydrocracking reaction, and the temperature difference between the two is 2° C. to 10° C.;

[0012] In the second step, the hydrotreated product oil is subjected to an isomerization-depressing reaction under the action of an isomerization-depressing catalyst to obtain a hydroisomerized product oil;

[0013] In the third step, the hydroisomerized oil is subjected to a hydrorefining reaction over a hydrorefining catalyst to obtain a three-stage hydrorefining oil, which is then fractionated using a multi-sideline distillation method to obtain a distillate with a boiling point above 420°C.

[0014] In the fourth step, the distillate oil with a boiling point higher than 420° C. is subjected to a deep hydrogenation aromatic saturation reaction under the action of a deep hydrogenation dearomatization catalyst to obtain a white oil for polystyrene.

[0015] The following is a further optimization and / or improvement of one of the above-mentioned technical solutions:

[0016] In the first step, the hydrotreating catalyst includes a hydrorefining catalyst and a hydrocracking catalyst, and the loading mass ratio of the hydrorefining catalyst to the hydrocracking catalyst between the catalyst beds is (60 to 75): (25 to 40).

[0017] In the first step above, 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 is 15% to 30% of the weight of the hydrorefining catalyst in terms of the weight of their oxides, and the hydrorefining catalyst is sulfurized before use.

[0018] In the first step, the carrier of the hydrocracking catalyst is one of a mixture of amorphous silica-alumina and β molecular sieve and a mixture of amorphous silica-alumina and Y molecular sieve. 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 sulfurized before use.

[0019] In the first step, the hydrofining reaction process conditions are: hydrogen partial pressure of 14 MPa to 20 MPa, volume ratio of hydrogen to paraffin-based distillate oil of 800 to 1200:1, reaction temperature of 360°C to 390°C, volume space velocity of 0.53 h -1 to 0.67h-1 Hydrocracking reaction process conditions: hydrogen partial pressure of 14MPa to 20MPa, volume ratio of hydrogen to paraffin-based distillate oil of 800 to 1200:1, reaction temperature of 350℃ to 380℃, volume space velocity of 1.0h -1 to 1.6 hours -1 .

[0020] In the third step, the oil generated by the three-stage hydrogenation is fractionated by a multi-side-line distillation 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 rate is controlled at 0.15 to 0.25, the upper side-line extraction temperature of the polystyrene white oil is controlled at 300°C to 310°C, and the vacuum degree at the top of the vacuum tower is controlled at 55 mmH to 65 mmHg.

[0021] In the above-mentioned second step, the carrier of the isomerized pour point depressant 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 isomerized pour point depressant catalyst are Pt and Pd in ​​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 isomerized pour point depressant catalyst, and the isomerized pour point depressant catalyst is activated by hydrogen reduction before use, and the pressure of hydrogen reduction activation is 0.3 MPa to 1.0 MPa.

[0022] In the above-mentioned third step, the carrier of the hydrorefining catalyst is one or more of ZSM-5 molecular sieve, ZSM-11 molecular sieve and ZSM-12 molecular sieve, the active metal in the hydrorefining 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 hydrorefining catalyst, and the hydrorefining catalyst is activated by hydrogen reduction before use, and the pressure of hydrogen reduction activation is 0.3 MPa to 1.0 MPa.

[0023] In the fourth step, the carrier of the hydrogenation deep dearomatization catalyst is one of ZSM-5 molecular sieve, ZSM-22 molecular sieve and ZSM-48 molecular sieve, the active metal in the hydrogenation deep dearomatization 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 dearomatization catalyst, and the hydrogenation deep dearomatization catalyst is activated by hydrogen reduction before use, and the pressure of hydrogen reduction activation is 0.3 MPa to 1.0 MPa.

[0024] In the second step, the isomerization decondensation reaction process conditions are: hydrogen partial pressure 14MPa to 20MPa, reaction temperature 310℃ to 350℃, volume space velocity 0.5h -1 to 1.2 hours -1, the volume ratio of hydrogen to hydrotreated oil (500 to 800):1.

[0025] In the third step, the hydrogenation supplementary refining reaction process conditions are: hydrogen partial pressure 14MPa to 20MPa, reaction temperature 220℃ to 250℃, volume space velocity 0.8h -1 Up to 1.5 hours -1 , the volume ratio of hydrogen to hydroisomerized oil (500 to 800):1.

[0026] In the fourth step, the process conditions for the deep aromatic saturation reaction by hydrogenation are as follows: hydrogen partial pressure 14 MPa to 20 MPa, reaction temperature 200°C to 250°C, volume space velocity 0.5 h -1 Up to 1.5 hours -1 , hydrogen to oil volume ratio (500 to 800):1.

[0027] In the first step above, the C N The value is not greater than 25%, C A The value is not greater than 15%.

[0028] In the fourth step above, the C of polystyrene white oil N The value is between 31% and 38%, UV stability is +30, thermal stability is +30, 2.5% distillation temperature under 10mmHg is greater than 280℃, open flash point is greater than 250℃, and evaporation loss is less than 1.0%.

[0029] The second technical solution of the present invention is achieved by the following measures: A method for preparing white oil for polystyrene is carried out as follows:

[0030] In the first step, a paraffin-based distillate oil having an initial boiling point of 395° C. to 420° C. and an end boiling point of 520° C. to 550° C. is subjected to a hydrotreating reaction under the action of a hydrotreating catalyst to obtain a hydrotreated product oil, wherein the hydrotreating reaction includes a hydrofining reaction and a hydrocracking reaction, and the reaction temperature of the hydrofining reaction is higher than the reaction temperature of the hydrocracking reaction, and the temperature difference between the two is 2° C. to 10° C.;

[0031] In the second step, the hydrotreated product oil is subjected to an isomerization-depressing reaction under the action of an isomerization-depressing catalyst to obtain a hydroisomerized product oil;

[0032] In the third step, the hydroisomerized oil is subjected to a hydrorefining reaction over a hydrorefining catalyst to obtain a three-stage hydrorefining oil, which is then fractionated using a multi-sideline distillation method to obtain a distillate with a boiling point above 420°C.

[0033] In the fourth step, the distillate oil with a boiling point higher than 420° C. is subjected to a deep hydrogenation aromatic saturation reaction under the action of a deep hydrogenation dearomatization catalyst to obtain a white oil for polystyrene.

[0034] The third technical solution of the present invention is achieved through the following measures: application of a special white oil for polystyrene in the preparation of polystyrene products.

[0035] The white oil for polystyrene of the present invention has an appropriate cycloalkane content, C N The value is between 31% and 38%, the UV stability is +30, the thermal stability is +30, the 2.5% distillation temperature 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 preparation method provided by the present invention has mild reaction conditions, effectively controls the cycloalkane content, improves product quality, and ensures that the product quality meets the requirements of food-grade white oil. At the same time, it also greatly increases the production of white oil for polystyrene, with a product yield of over 68%. DETAILED DESCRIPTION

[0036] The present invention is not limited to the following embodiments, and specific implementation methods can be determined based on the technical solutions of the present invention and actual conditions. Unless otherwise specified, the various chemical reagents and chemicals mentioned in the present invention are all chemical reagents and chemicals commonly known in the prior art; unless otherwise specified, the percentages in the present invention are all percentages by mass; unless otherwise specified, the solutions in the present invention are all aqueous solutions with water as the solvent, for example, hydrochloric acid solution is an aqueous hydrochloric acid solution; normal temperature and room temperature in the present invention generally refer to temperatures between 15°C and 25°C, and are generally defined as 25°C.

[0037] The present invention will be further described below in conjunction with the embodiments:

[0038] Example 1: The white oil for polystyrene is obtained by the following method:

[0039] In the first step, a paraffin-based distillate oil having an initial boiling point of 395° C. to 420° C. and an end boiling point of 520° C. to 550° C. is subjected to a hydrotreating reaction under the action of a hydrotreating catalyst to obtain a hydrotreated product oil, wherein the hydrotreating reaction includes a hydrofining reaction and a hydrocracking reaction, and the reaction temperature of the hydrofining reaction is higher than the reaction temperature of the hydrocracking reaction, and the temperature difference between the two is 2° C. to 10° C.;

[0040] In the second step, the hydrotreated product oil is subjected to an isomerization-depressing reaction under the action of an isomerization-depressing catalyst to obtain a hydroisomerized product oil;

[0041] In the third step, the hydroisomerized oil is subjected to a hydrorefining reaction over a hydrorefining catalyst to obtain a three-stage hydrorefining oil, which is then fractionated using a multi-sideline distillation method to obtain a distillate with a boiling point above 420°C.

[0042] In the fourth step, the distillate oil with a boiling point higher than 420° C. is subjected to a deep hydrogenation aromatic saturation reaction under the action of a deep hydrogenation dearomatization catalyst to obtain a white oil for polystyrene.

[0043] Example 2: As an optimization of the above example, in the first step, the hydrotreating catalyst includes a hydrorefining catalyst and a hydrocracking catalyst, and the loading mass ratio of the hydrorefining catalyst and the hydrocracking catalyst between the catalyst beds is (60 to 75): (25 to 40).

[0044] Example 3: As an optimization of the above example, in the first step, the carrier of the hydrorefining catalyst is one or more of activated alumina, activated silicon oxide and amorphous silicon aluminum, the active metals in the hydrorefining catalyst are three or more of Ni, W, Co and Mo, the total weight of the active metals is 15% to 30% of the weight of the hydrorefining catalyst in terms of the weight of their oxides, and the hydrorefining catalyst is sulfurized before use.

[0045] 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 molecular sieve, or a mixture of amorphous silica-alumina and Y molecular sieve, the active metals in the hydrocracking catalyst are two or more of W, Ni, Co and Mo, the total weight of the active metals is 10% to 20% of the weight of the hydrocracking catalyst in terms of the weight of their oxides, and the hydrocracking catalyst is sulfurized before use.

[0046] Example 5: As an optimization of the above example, in the first step, the hydrorefining reaction process conditions are: hydrogen partial pressure of 14 MPa to 20 MPa, volume ratio of hydrogen to paraffin-based distillate oil of 800 to 1200:1, reaction temperature of 360°C to 390°C, volume space velocity of 0.53 h -1 to 0.67h -1 Hydrocracking reaction process conditions: hydrogen partial pressure of 14MPa to 20MPa, volume ratio of hydrogen to paraffin-based distillate oil of 800 to 1200:1, reaction temperature of 350℃ to 380℃, volume space velocity of 1.0h -1 to 1.6 hours -1; or / and, in the third step, the oil generated by the three-stage hydrogenation is fractionated by a multi-side line distillation method, a vacuum tower is used for fractionation, the vacuum tower bottom temperature is controlled at 300° C. to 320° C., the vacuum tower top temperature is controlled at 35° C. to 45° C., the top reflux rate is controlled at 0.15 to 0.25, the side line extraction temperature of the polystyrene special white oil is controlled at 300° C. to 310° C., and the vacuum degree at the top of the vacuum tower is controlled at 55 mmH to 65 mmHg.

[0047] In the first step of the hydroprocessing reaction of the present invention, the reaction temperature of the two catalysts, the hydrorefining catalyst and the hydrocracking catalyst, is controlled by injecting cold hydrogen between the catalyst beds. The present invention can better limit the ring-opening reaction of cycloalkanes and improve the C N value while effectively improving the yield of the product.

[0048] Example 6: As an optimization of the above example, in the second step, the carrier of the isomerized pour point depressant 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 isomerized pour point depressant catalyst are Pt and Pd in ​​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 isomerized pour point depressant catalyst, and the isomerized pour point depressant catalyst is activated by hydrogen reduction before use, and the pressure of hydrogen reduction activation is 0.3 MPa to 1.0 MPa.

[0049] Example 7: As an optimization of the above example, in the third step, the carrier of the hydrorefining catalyst is one or more of ZSM-5 molecular sieve, ZSM-11 molecular sieve and ZSM-12 molecular sieve, the active metal in the hydrorefining 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 hydrorefining catalyst. The hydrorefining catalyst is activated by hydrogen reduction before use, and the pressure of hydrogen reduction activation is 0.3 MPa to 1.0 MPa.

[0050] Example 8: As an optimization of the above example, in the fourth step, the carrier of the hydrogenation deep dearomatization catalyst is one of ZSM-5 molecular sieve, ZSM-22 molecular sieve and ZSM-48 molecular sieve, the active metal in the hydrogenation 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 hydrogenation deep dearomatization catalyst. The hydrogenation deep dearomatization catalyst is activated by hydrogen reduction before use, and the pressure of hydrogen reduction activation is 0.3 MPa to 1.0 MPa.

[0051] Example 9: As an optimization of the above example, in the second step, the isomerization decondensation reaction process conditions are: hydrogen partial pressure 14MPa to 20MPa, reaction temperature 310℃ to 350℃, volume space velocity 0.5h -1 to 1.2 hours -1 , the volume ratio of hydrogen to hydrotreated oil (500 to 800):1.

[0052] Example 10: As an optimization of the above example, in the third step, the hydrogenation supplementary refining reaction process conditions are: hydrogen partial pressure 14MPa to 20MPa, reaction temperature 220℃ to 250℃, volume space velocity 0.8h -1 Up to 1.5 hours -1 , the volume ratio of hydrogen to hydroisomerized oil (500 to 800):1.

[0053] Example 11: As an optimization of the above example, in the fourth step, the process conditions for the deep aromatic saturation reaction by hydrogenation are as follows: hydrogen partial pressure 14 MPa to 20 MPa, reaction temperature 200°C to 250°C, volume space velocity 0.5 h -1 Up to 1.5 hours -1 , hydrogen to oil volume ratio (500 to 800):1.

[0054] Example 12: As an optimization of the above example, in the first step, the C of the paraffinic distillate oil N The value is not greater than 25%, C A The value is not more than 15%. In the fourth step, the C of polystyrene white oil N The value is between 31% and 38%, UV stability is +30, thermal stability is +30, 2.5% distillation temperature under 10mmHg is greater than 280℃, open flash point is greater than 250℃, and evaporation loss is less than 1.0%.

[0055] In the present invention, the raw material used is paraffin-based distillate oil, which has a high saturated hydrocarbon content and a high flash point. As the raw material of polystyrene white oil, it has good advantages in ensuring the flash point, distillation range and light and heat stability of the product.

[0056] Example 13: Application of the polystyrene-specific white oil in the preparation of polystyrene products.

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] First, the combination of hydrotreating reaction and hydrocracking reaction, as well as the graded combination of hydrotreating catalyst and hydrocracking catalyst used in the hydrotreating reaction of the present application, and the different temperature differences between the hydrotreating reaction and the hydrocracking reaction effectively retain the cycloalkane content, thereby increasing the proportion of cycloalkane carbon content in the product, that is, increasing C Nvalue, so that it can be used in the preparation of polystyrene to improve its compatibility with polystyrene;

[0059] Then, the hydroisomerization catalyst carrier of the present application 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 composite of the two molecular sieves can ensure a better reduction in the pour point of the product.

[0060] Next, the three-stage hydrogenation product oil is fractionated using a multi-side line extraction distillation method, which can better control the distillation temperature of the obtained polystyrene-specific white oil at 2.5% under 10 mmHg to be greater than 280°C. The polystyrene white oil prepared in this application is used as a filler oil in the polystyrene synthesis process. The polystyrene production process includes a devolatilization unit, which is used to remove unreacted styrene monomer, solvent, oligomers and other volatile substances remaining in the polymer solution. The distillation temperature of the polystyrene white oil at 10 mmHg is controlled to be 2.5% or greater than 280°C to prevent the polystyrene white oil from being removed during the devolatilization process, thereby affecting the plasticity, toughness and elasticity of the polystyrene product;

[0061] Finally, in this application, the added hydrogenation deep dearomatization process and the appropriate hydrogenation deep dearomatization catalyst can effectively remove trace aromatics and ensure the storage stability of the product; the process adopts a full hydrogenation process to convert non-ideal components in the raw materials into ideal components, greatly improving the yield of polystyrene white oil.

[0062] Example 14:

[0063] The white oil for polystyrene is obtained by the following method:

[0064] In the first step, a paraffin-based distillate oil with a distillation range of 395°C to 530°C is used as a 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 a hydrotreating reaction. The hydrotreating reaction conditions are shown in Table 2, and the hydrotreating catalyst composition is shown in Table 6 to obtain a hydrotreating product oil.

[0065] In the second step, the hydrotreated product oil is mixed with hydrogen and sent to a hydroisomerization reactor for isomerization and pour point depressing reaction. The isomerization and pour point depressing reaction conditions are shown in Table 3, and the isomerization and pour point depressing catalyst composition is shown in Table 7 to obtain the hydroisomerization product oil;

[0066] In the third step, the hydroisomerization product oil is mixed with hydrogen and sent to a hydroprocessing supplementary refining reactor for a hydroprocessing supplementary refining reaction. The hydroprocessing supplementary refining reaction conditions are shown in Table 4, and the hydroprocessing supplementary refining 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 extraction distillation method, and the fraction with a distillation range of ≥420°C is cut to obtain a distillate oil with a boiling point higher than 420°C. A vacuum tower is used for fractionation, the vacuum tower bottom temperature is controlled at 300°C, the vacuum tower top temperature is controlled at 35°C, the top reflux rate is controlled at 0.25, the upper side line extraction temperature of the polystyrene special white oil is controlled at 300°C, and the vacuum degree at the top of the vacuum tower is controlled at 55 mmHg;

[0067] In the fourth step, the distillate oil with a boiling point higher than 420°C is mixed with hydrogen and sent to a hydrogenation deep dearomatization reactor for a hydrogenation deep aromatic saturation reaction. The conditions of the hydrogenation deep aromatic saturation reaction are shown in Table 5, and the composition of the hydrogenation deep dearomatization catalyst is shown in Table 7 to obtain a white oil for polystyrene.

[0068] Example 15:

[0069] The white oil for polystyrene is obtained by the following method:

[0070] In the first step, a paraffin-based distillate oil with a distillation range of 410°C to 520°C is used as a 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 a hydrotreating reaction. The hydrotreating reaction conditions are shown in Table 2, and the hydrotreating catalyst composition is shown in Table 6 to obtain a hydrotreating product oil.

[0071] In the second step, the hydrotreated product oil is mixed with hydrogen and sent to a hydroisomerization reactor for isomerization and pour point depressing reaction. The isomerization and pour point depressing reaction conditions are shown in Table 3, and the isomerization and pour point depressing catalyst composition is shown in Table 7 to obtain the hydroisomerization product oil;

[0072] In the third step, the hydroisomerization product oil is mixed with hydrogen and sent to a hydroprocessing supplementary refining reactor for a hydroprocessing supplementary refining reaction. The hydroprocessing supplementary refining reaction conditions are shown in Table 4, and the hydroprocessing supplementary refining 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 extraction distillation method, and the fraction with a distillation range of ≥420°C is cut to obtain a distillate oil with a boiling point higher than 420°C. A vacuum tower is used for fractionation, the vacuum tower bottom temperature is controlled at 300°C, the vacuum tower top temperature is controlled at 35°C, the top reflux rate is controlled at 0.15, the upper side line extraction temperature of the polystyrene special white oil is controlled at 300°C, and the vacuum degree at the top of the vacuum tower is controlled at 55 mmHg;

[0073] In the fourth step, the distillate oil with a boiling point higher than 420°C is mixed with hydrogen and sent to a hydrogenation deep dearomatization reactor for a hydrogenation deep aromatic saturation reaction. The conditions of the hydrogenation deep aromatic saturation reaction are shown in Table 5, and the composition of the hydrogenation deep dearomatization catalyst is shown in Table 7 to obtain a white oil for polystyrene.

[0074] Example 16:

[0075] The white oil for polystyrene is obtained by the following method:

[0076] In the first step, a paraffin-based distillate oil with a distillation range of 420°C to 550°C is used as a 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 a hydrotreating reaction. The hydrotreating reaction conditions are shown in Table 2, and the hydrotreating catalyst composition is shown in Table 6 to obtain a hydrotreating product oil.

[0077] In the second step, the hydrotreated product oil is mixed with hydrogen and sent to a hydroisomerization reactor for isomerization and pour point depressing reaction. The isomerization and pour point depressing reaction conditions are shown in Table 3, and the isomerization and pour point depressing catalyst composition is shown in Table 7 to obtain the hydroisomerization product oil;

[0078] In the third step, the hydroisomerization product oil is mixed with hydrogen and sent to a hydroprocessing supplementary refining reactor for a hydroprocessing supplementary refining reaction. The hydroprocessing supplementary refining reaction conditions are shown in Table 4, and the hydroprocessing supplementary refining 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 extraction distillation method, and the fraction with a distillation range of ≥420°C is cut to obtain a distillate oil with a boiling point higher than 420°C. A vacuum tower is used for fractionation, the vacuum tower bottom temperature is controlled at 300°C, the vacuum tower top temperature is controlled at 35°C, the top reflux rate is controlled at 0.15, the upper side line extraction temperature of the polystyrene special white oil is controlled at 300°C, and the vacuum degree at the top of the vacuum tower is controlled at 55 mmHg;

[0079] In the fourth step, the distillate oil with a boiling point higher than 420°C is mixed with hydrogen and sent to a hydrogenation deep dearomatization reactor for a hydrogenation deep aromatic saturation reaction. The conditions of the hydrogenation deep aromatic saturation reaction are shown in Table 5, and the composition of the hydrogenation deep dearomatization catalyst is shown in Table 7 to obtain a white oil for polystyrene.

[0080] Example 17:

[0081] The white oil for polystyrene is obtained by the following method:

[0082] In the first step, a paraffin-based distillate oil with a distillation range of 420°C to 550°C is used as a 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 a hydrotreating reaction. The hydrotreating reaction conditions are shown in Table 2, and the hydrotreating catalyst composition is shown in Table 6 to obtain a hydrotreating product oil.

[0083] In the second step, the hydrotreated product oil is mixed with hydrogen and sent to a hydroisomerization reactor for isomerization and pour point depressing reaction. The isomerization and pour point depressing reaction conditions are shown in Table 3, and the isomerization and pour point depressing catalyst composition is shown in Table 7 to obtain the hydroisomerization product oil;

[0084] In the third step, the hydroisomerization product oil is mixed with hydrogen and sent to a hydroprocessing supplementary refining reactor for a hydroprocessing supplementary refining reaction. The hydroprocessing supplementary refining reaction conditions are shown in Table 4, and the hydroprocessing supplementary refining 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 extraction distillation method, and the fraction with a distillation range of ≥420°C is cut to obtain a distillate oil with a boiling point higher than 420°C. A vacuum tower is used for fractionation, the vacuum tower bottom temperature is controlled at 320°C, the vacuum tower top temperature is controlled at 45°C, the top reflux rate is controlled at 0.15, the upper side line extraction temperature of the polystyrene special white oil is controlled at 310°C, and the vacuum degree at the top of the vacuum tower is controlled at 65 mmHg;

[0085] In the fourth step, the distillate oil with a boiling point higher than 420°C is mixed with hydrogen and sent to a hydrogenation deep dearomatization reactor for a hydrogenation deep aromatic saturation reaction. The conditions of the hydrogenation deep aromatic saturation reaction are shown in Table 5, and the composition of the hydrogenation deep dearomatization catalyst is shown in Table 7 to obtain a white oil for polystyrene.

[0086] Example 18:

[0087] The white oil for polystyrene is obtained by the following method:

[0088] In the first step, a paraffin-based distillate oil with a distillation range of 420°C to 540°C is used as a 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 a hydrotreating reaction. The hydrotreating reaction conditions are shown in Table 2, and the hydrotreating catalyst composition is shown in Table 6 to obtain a hydrotreating product oil.

[0089] In the second step, the hydrotreated product oil is mixed with hydrogen and sent to a hydroisomerization reactor for isomerization and pour point depressing reaction. The isomerization and pour point depressing reaction conditions are shown in Table 3, and the isomerization and pour point depressing catalyst composition is shown in Table 7 to obtain the hydroisomerization product oil;

[0090] In the third step, the hydroisomerization product oil is mixed with hydrogen and sent to a hydroprocessing supplementary refining reactor for a hydroprocessing supplementary refining reaction. The hydroprocessing supplementary refining reaction conditions are shown in Table 4, and the hydroprocessing supplementary refining 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 extraction distillation method, and the fraction with a distillation range of ≥420°C is cut to obtain a distillate oil with a boiling point higher than 420°C. A vacuum tower is used for fractionation, the vacuum tower bottom temperature is controlled at 320°C, the vacuum tower top temperature is controlled at 45°C, the top reflux rate is controlled at 0.15, the upper side line extraction temperature of the polystyrene special white oil is controlled at 310°C, and the vacuum degree at the top of the vacuum tower is controlled at 65 mmHg;

[0091] In the fourth step, the distillate oil with a boiling point higher than 420°C is mixed with hydrogen and sent to a hydrogenation deep dearomatization reactor for a hydrogenation deep aromatic saturation reaction. The conditions of the hydrogenation deep aromatic saturation reaction are shown in Table 5, and the composition of the hydrogenation deep dearomatization catalyst is shown in Table 7 to obtain a white oil for polystyrene.

[0092] Comparative Example 1:

[0093] The white oil for polystyrene is obtained by the following method:

[0094] In the first step, a paraffin-based distillate oil with a distillation range of 420°C to 550°C is used as a 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 a hydrotreating reaction. The hydrotreating reaction conditions are shown in Table 2, and the hydrotreating catalyst composition is shown in Table 6 to obtain a hydrotreating product oil.

[0095] In the second step, the hydrotreated product oil is mixed with hydrogen and sent to a hydroisomerization reactor for isomerization and pour point depressing reaction. The isomerization and pour point depressing reaction conditions are shown in Table 3, and the isomerization and pour point depressing catalyst composition is shown in Table 7 to obtain the hydroisomerization product oil;

[0096] In the third step, the hydroisomerized oil is mixed with hydrogen and sent to a hydrorefining reactor for a hydrorefining reaction. The hydrorefining reaction conditions are shown in Table 4, and the hydrorefining catalyst composition is shown in Table 7 to obtain a three-stage hydrogenated oil. The three-stage hydrogenated oil is subjected to vacuum fractionation to cut the fraction with a distillation range of ≥420°C to obtain a distillate oil with a boiling point above 420°C.

[0097] In the fourth step, the distillate oil with a boiling point higher than 420°C is mixed with hydrogen and sent to a hydrogenation deep dearomatization reactor for a hydrogenation deep aromatic saturation reaction. The conditions of the hydrogenation deep aromatic saturation reaction are shown in Table 5, and the composition of the hydrogenation deep dearomatization catalyst is shown in Table 7 to obtain a white oil for polystyrene.

[0098] Comparative Example 2:

[0099] The white oil for polystyrene is obtained by the following method:

[0100] In the first step, a paraffin-based distillate oil with a distillation range of 420°C to 540°C is used as a 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 a hydrotreating reaction. The hydrotreating reaction conditions are shown in Table 2, and the hydrotreating catalyst composition is shown in Table 6 to obtain a hydrotreating product oil.

[0101] In the second step, the hydrotreated product oil is mixed with hydrogen and sent to a hydroisomerization reactor for isomerization and pour point depressing reaction. The isomerization and pour point depressing reaction conditions are shown in Table 3, and the isomerization and pour point depressing catalyst composition is shown in Table 7 to obtain the hydroisomerization product oil;

[0102] In the third step, the hydroisomerized oil is mixed with hydrogen and sent to a hydrorefining reactor for a hydrorefining reaction. The hydrorefining reaction conditions are shown in Table 4, and the hydrorefining catalyst composition is shown in Table 7 to obtain a three-stage hydrogenation oil. The three-stage hydrogenation oil is subjected to vacuum fractionation, and the fraction with a distillation range of ≥450°C is cut to obtain a white oil for polystyrene.

[0103] Experimental Example 1: The performance of the white oil for polystyrene of the present invention was investigated.

[0104] Experimental method: The properties of the polystyrene white oil prepared in Examples 14 to 18 of the present invention were investigated, including product yield, kinematic viscosity, open flash point, pour point, evaporation loss, UV stability, thermal stability, carbonization, carbon type analysis (C A Value and C N value), condensed ring aromatic hydrocarbons (UV absorbance), reduced pressure distillation range, and compatibility with styrene. Meanwhile, Comparative Examples 1 and 2 were used as controls.

[0105] Experimental results: The properties of the polystyrene white oils prepared in Examples 14 to 18 of the present invention are shown in Table 8. As can be seen from Table 8, the polystyrene white oils prepared in Examples 14 to 18 of the present invention are tested using the ASTM 2140 method. A The value is 0, C N The value is 31% to 38%; its UV stability is +30 as measured by the Q / SY1440 method; its thermal stability is +30 as measured by the Q / SY1439 method; its open flash point is greater than 250°C as measured by the ASTMD92 method; its evaporation loss is less than 1% as measured by the NB / SH / T0059 method; its 2.5% distillation temperature under 10mmHg is greater than 280°C as measured by the ASTMD1160 method; and the yield of the polystyrene white oil prepared in Examples 14 to 18 of the present invention is above 68%, and has good compatibility with polystyrene. The polystyrene white oil prepared in Comparative Example 1 (the hydrorefining temperature is the same as the hydrocracking temperature) and Comparative Example 2 (no hydrogenation deep aromatic saturation reaction) of the present invention has a low flash point and C N The value is low, the distillation temperature of 2.5% under 10 mmHg is low, the product yield is low, and the compatibility with polystyrene is poor.

[0106] In summary, the polystyrene white oil of the present invention has an appropriate cycloalkane content, C NThe value is between 31% and 38%, the UV stability is +30, the thermal stability is +30, the 2.5% distillation temperature 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 preparation method provided by the present invention has mild reaction conditions, effectively controls the cycloalkane content, improves product quality, and ensures that the product quality meets the requirements of food-grade white oil. At the same time, it also greatly increases the production of white oil for polystyrene, with a product yield of over 68%.

[0107] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or removed according to actual needs to meet the requirements of different situations.

[0108] Table 1

[0109] .

[0110] Table 2

[0111] .

[0112] Table 3

[0113] .

[0114] Table 4

[0115] .

[0116] Table 5

[0117] .

[0118] Table 6

[0119] .

[0120] Table 7

[0121] .

[0122] Table 8

[0123] .

Claims

1. A white oil for polystyrene, characterized in that Obtained as follows: In the first step, a paraffin-based distillate oil having 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 hydrotreated product oil, wherein the hydrotreating reaction includes a hydrorefining reaction and a hydrocracking reaction, the reaction temperature of the hydrorefining reaction is higher than the reaction temperature of the hydrocracking reaction, and the temperature difference is 2°C to 10°C; the hydrotreating catalyst includes a hydrorefining catalyst and a hydrocracking catalyst, the carrier of the hydrorefining catalyst is one or more of activated alumina, activated silicon oxide and amorphous silicon aluminum, and the active The metals are three or more of Ni, W, Co and Mo, and 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 sulfurized before use. The carrier of the hydrocracking catalyst is one of a mixture of amorphous silica-alumina and β molecular sieve or a mixture of amorphous silica-alumina and Y-type molecular sieve. The active metals in the hydrocracking catalyst are two or more of W, Ni, Co and Mo, and 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 sulfurized before use. In the second step, the hydrotreated product oil is subjected to an isomerization-depressing reaction under the action of an isomerization-depressing catalyst to obtain a hydroisomerized product oil, wherein the carrier of the isomerization-depressing 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 third step is to subject the hydroisomerized oil to a hydrorefining reaction under the action of a hydrorefining catalyst to obtain a three-stage hydrorefining oil, and the three-stage hydrorefining oil is fractionated by a multi-side-line extraction distillation method to obtain a distillate oil with a boiling point higher than 420° C., wherein the three-stage hydrorefining oil is fractionated by a multi-side-line extraction distillation method, a vacuum tower is used for the fractionation, the vacuum tower bottom temperature is controlled at 300° C. to 320° C., the vacuum tower top temperature is controlled at 35° C. to 45° C., the top reflux rate is controlled at 0.15 to 0.25, the upper side line extraction temperature of the polystyrene special white oil is controlled at 300° C. to 310° C., and the vacuum degree at the vacuum tower top is controlled at 55 mmHg to 65 mmHg; In the fourth step, the distillate oil with a boiling point higher than 420°C is subjected to a deep aromatic saturation reaction under the action of a deep dearomatization catalyst to obtain a 2.5% polystyrene-specific white oil with a distillation temperature higher than 280°C at 10 mmHg.

2. The polystyrene white oil according to claim 1, characterized in that In the first step, the loading mass ratio of the hydrorefining catalyst to the hydrocracking catalyst between the catalyst beds is 60 to 75:25 to 40.

3. The polystyrene white oil according to claim 2, characterized in that In the first step, the hydrorefining reaction process conditions are: hydrogen partial pressure of 14MPa to 20MPa, volume ratio of hydrogen to paraffin-based distillate oil of 800 to 1200:1, reaction temperature of 360℃ to 390℃, volume space velocity of 0.53h -1 to 0.67h -1 Hydrocracking reaction process conditions: hydrogen partial pressure of 14MPa to 20MPa, volume ratio of hydrogen to paraffin-based distillate oil of 800 to 1200:1, reaction temperature of 350℃ to 380℃, volume space velocity of 1.0h -1 to 1.6 hours -1 .

4. The polystyrene white oil according to claim 1, 2 or 3, characterized in that In the second step, the active metals in the isomerized pour point depressant catalyst are Pt and Pd in ​​a mass ratio of 3 to 2:1, and the total weight of the active metals accounts for 0.4% to 1.0% of the weight of the isomerized pour point depressant catalyst. The isomerized pour point depressant catalyst is activated by hydrogen reduction before use, and the pressure of hydrogen reduction activation is 0.3 MPa to 1.0 MPa.

5. The polystyrene white oil according to claim 1, 2 or 3, characterized in that In the third step, the carrier of the hydrorefining catalyst is one or more of ZSM-5 molecular sieve, ZSM-11 molecular sieve and ZSM-12 molecular sieve, the active metal in the hydrorefining 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 hydrorefining catalyst, and the hydrorefining catalyst is activated by hydrogen reduction before use, and the pressure of hydrogen reduction activation is 0.3 MPa to 1.0 MPa.

6. The polystyrene white oil according to claim 4, characterized in that In the third step, the carrier of the hydrorefining catalyst is one or more of ZSM-5 molecular sieve, ZSM-11 molecular sieve and ZSM-12 molecular sieve, the active metal in the hydrorefining 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 hydrorefining catalyst, and the hydrorefining catalyst is activated by hydrogen reduction before use, and the pressure of hydrogen reduction activation is 0.3 MPa to 1.0 MPa.

7. The polystyrene white oil according to any one of claims 1 to 3 and 6, characterized in that In the fourth step, the carrier of the hydrogenation deep dearomatization catalyst is one of ZSM-5 molecular sieve, ZSM-22 molecular sieve and ZSM-48 molecular sieve, the active metal in the hydrogenation deep dearomatization 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 dearomatization catalyst, and the hydrogenation 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.

8. The polystyrene white oil according to claim 4, characterized in that In the fourth step, the carrier of the hydrogenation deep dearomatization catalyst is one of ZSM-5 molecular sieve, ZSM-22 molecular sieve and ZSM-48 molecular sieve, the active metal in the hydrogenation deep dearomatization 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 dearomatization catalyst, and the hydrogenation 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.

9. The white oil for polystyrene according to claim 5, characterized in that In the fourth step, the carrier of the hydrogenation deep dearomatization catalyst is one of ZSM-5 molecular sieve, ZSM-22 molecular sieve and ZSM-48 molecular sieve, the active metal in the hydrogenation deep dearomatization 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 dearomatization catalyst, and the hydrogenation 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.

10. The white oil for polystyrene according to any one of claims 1 to 3, 6, 8 and 9, characterized in that In the second step, the isomerization decondensation reaction process conditions are: hydrogen partial pressure 14MPa to 20MPa, reaction temperature 310℃ to 350℃, volume space velocity 0.5h -1 to 1.2 hours -1 , the volume ratio of hydrogen to hydrotreated oil is 500 to 800:1; or / and, in the third step, the hydrogenation supplementary refining reaction process conditions are: hydrogen partial pressure 14MPa to 20MPa, reaction temperature 220℃ to 250℃, volume space velocity 0.8h -1 Up to 1.5 hours -1 , the volume ratio of hydrogen to hydroisomerized oil is 500 to 800:1; or / and, in the fourth step, the process conditions for the deep aromatic saturation reaction of hydrogenation are: hydrogen partial pressure 14MPa to 20MPa, reaction temperature 200℃ to 250℃, volume space velocity 0.5h -1 Up to 1.5 hours -1 , hydrogen to oil volume ratio 500 to 800:

1.

11. The white oil for polystyrene according to claim 7, characterized in that In the second step, the isomerization decondensation reaction process conditions are: hydrogen partial pressure 14MPa to 20MPa, reaction temperature 310℃ to 350℃, volume space velocity 0.5h -1 to 1.2 hours -1 , the volume ratio of hydrogen to hydrotreated oil is 500 to 800:1; or / and, in the third step, the hydrogenation supplementary refining reaction process conditions are: hydrogen partial pressure 14MPa to 20MPa, reaction temperature 220℃ to 250℃, volume space velocity 0.8h -1 Up to 1.5 hours -1 , the volume ratio of hydrogen to hydroisomerized oil is 500 to 800:1; or / and, in the fourth step, the process conditions for the deep aromatic saturation reaction of hydrogenation are: hydrogen partial pressure 14MPa to 20MPa, reaction temperature 200℃ to 250℃, volume space velocity 0.5h -1 Up to 1.5 hours -1 , hydrogen to oil volume ratio 500 to 800:

1.

12. The polystyrene white oil according to any one of claims 1 to 3, 6, 8, 9 and 11, characterized in that In the first step, the C N The value is not greater than 25%, C A The value is not more than 15%; or / and, in the fourth step, the C of the polystyrene white oil N The value is between 31% and 38%, UV stability is +30, thermal stability is +30, open flash point is greater than 250℃, and evaporation loss is less than 1.0%.

13. A method for preparing a white oil for polystyrene according to any one of claims 2 to 12, characterized in that Proceed as follows: In the first step, a paraffin-based distillate oil having 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 hydrotreated product oil, wherein the hydrotreating reaction includes a hydrorefining reaction and a hydrocracking reaction, the reaction temperature of the hydrorefining reaction is higher than the reaction temperature of the hydrocracking reaction, and the temperature difference is 2°C to 10°C; the hydrotreating catalyst includes a hydrorefining catalyst and a hydrocracking catalyst, the carrier of the hydrorefining catalyst is one or more of activated alumina, activated silicon oxide and amorphous silicon aluminum, and the active The metals are three or more of Ni, W, Co and Mo, and 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 sulfurized before use. The carrier of the hydrocracking catalyst is one of a mixture of amorphous silica-alumina and β molecular sieve or a mixture of amorphous silica-alumina and Y-type molecular sieve. The active metals in the hydrocracking catalyst are two or more of W, Ni, Co and Mo, and 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 sulfurized before use. In the second step, the hydrotreated product oil is subjected to an isomerization-depressing reaction under the action of an isomerization-depressing catalyst to obtain a hydroisomerized product oil, wherein the carrier of the isomerization-depressing 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 third step is to subject the hydroisomerized oil to a hydrorefining reaction under the action of a hydrorefining catalyst to obtain a three-stage hydrorefining oil, and the three-stage hydrorefining oil is fractionated by a multi-side-line extraction distillation method to obtain a distillate oil with a boiling point higher than 420° C., wherein the three-stage hydrorefining oil is fractionated by a multi-side-line extraction distillation method, a vacuum tower is used for the fractionation, the vacuum tower bottom temperature is controlled at 300° C. to 320° C., the vacuum tower top temperature is controlled at 35° C. to 45° C., the top reflux rate is controlled at 0.15 to 0.25, the upper side line extraction temperature of the polystyrene special white oil is controlled at 300° C. to 310° C., and the vacuum degree at the vacuum tower top is controlled at 55 mmHg to 65 mmHg; In the fourth step, the distillate oil with a boiling point higher than 420°C is subjected to a deep aromatic saturation reaction under the action of a deep dearomatization catalyst to obtain a 2.5% polystyrene-specific white oil with a distillation temperature higher than 280°C at 10 mmHg.

14. Use of the special white oil for polystyrene according to any one of claims 1 to 12 in the preparation of polystyrene products.