A method for synthesizing isoparaffin solvent oil

Abstract

The present invention discloses a method for synthesizing isoparaffin solvent oil, the method comprising the following steps: (1) low carbon olefins enter a polymerization reaction zone, and a polymerization reaction is carried out under the action of a polymerization catalyst; (2) the material after the polymerization reaction of step (1) enters a hydrofining reaction zone, and a hydrogenation saturation reaction is carried out under the action of a hydrofining catalyst; (3) the product after the reaction of step (2) is separated by gas-liquid separation, and the liquid product is distilled to obtain isoparaffin solvent oil products of various fraction ranges; wherein, the polymerization catalyst described in step (1) contains a mesoporous ZSM-23 molecular sieve, and the content of the mesoporous ZSM-23 molecular sieve is at least 30% based on the weight of the polymerization catalyst. The method adopts a fixed bed process, has the advantages of easy separation of products, reduced environmental pollution, etc., and the obtained isoparaffin solvent oil has a high yield, a high isoparaffin content, and a high degree of isomeric branching.

Description

Technical Field

[0001] The invention relates to a method for synthesizing isoparaffin solvent oil, in particular to a method for synthesizing isoparaffin solvent oil by using low-carbon olefins as raw materials through a polymerization and hydrogenation combined process. Background Art

[0002] As one of the five major categories of petroleum products, solvent oil has an increasing market demand. my country's fine chemicals, electronics industry, household products, and daily chemicals have also continuously improved their requirements for solvent performance. Foreign companies such as ExxonMobil, Idemitsu, Shell, and Total all have their own technical specifications for clean solvent oil products, and their products are serialized, which are divided into normal alkane solvent oil, cycloalkane solvent oil, and isoalkane solvent oil according to the hydrocarbon composition.

[0003] At present, isoparaffin solvent oil has the characteristics of being sulfur-free and aromatic-free, having little odor, low toxicity, good stability, good solubility, low freezing point and low surface tension. In addition, the relative inertness of the saturated isoparaffin structure can minimize or eliminate harmful reactions in industrial production processes and consumer applications. It is a very environmentally friendly high-end solvent oil and is widely used in washing daily chemicals, cosmetics, printing and dyeing diluents, ink solvents, metal processing cleaning agents, rust-proof oils, odorless sprays, odorless oil coatings, paints, organic sol formulas, advanced dry cleaning oils, etc.

[0004] At present, the production of isoparaffin solvent oil in China mainly uses isoparaffin and olefin as raw materials, and obtains isoparaffin solvent oil through alkylation reaction, hydrogenation and distillation. There are also isoparaffin solvent oils that are obtained by hydrogenation isomerization and alkane-olefin separation using FT synthetic oil as raw material. At present, foreign countries use synthetic processes to produce environmentally friendly isoparaffin solvent oils. The content of aromatic hydrocarbons and various impurities in the products is very low, which can reduce the odor of the solvent to an extremely low level or even odorless, and thus it is accepted by many industries that have demands for health and environmental protection. Compared with isoparaffin solvent oils produced by alkylation, hydrogenation isomerization, alkane-olefin separation and other processes, the synthetic process has a more ideal structural composition, higher purity of isoparaffins, no aromatic hydrocarbons, significant quality and performance advantages, and a large increase in product added value.

[0005] CN101921621A discloses a method for producing isoparaffin solvent oil by using distillate oil or light deoiling as raw materials and adopting a combined process of hydrotreating-hydroisomerization-supplementary refining. The isoparaffin solvent oil obtained by the method has an isoparaffin content of >90%, and has the characteristics of strong raw material adaptability and good product quality. However, the aromatic content in the isoparaffin solvent oil obtained by the method is >0.03%, which does not meet the requirements of green clean solvent oil.

[0006] US5866748 discloses a method for producing isoparaffin solvent oil. The isoparaffin solvent oil is produced by using a hydrogenation isomerization method using a Fischer-Tropsch product of a C8-C20 fraction with a high content of normal alkanes as a raw material. This method uses the Fischer-Tropsch reaction product as a raw material, and has strict restrictions on the properties of the raw material. Only a specific fraction with a high content of normal alkanes can be used as a raw material, so the scope of technical application is limited. At the same time, the higher value olefins in the Fischer-Tropsch synthetic oil are wasted.

[0007] CN109161396A discloses an isoparaffin mixture with an isoparaffin content of >95%. Using Fischer-Tropsch crude liquid wax as raw material, after light and heavy removal, molecular sieves are used for adsorption to separate normal alkanes and non-normal alkanes, and non-normal alkanes are fractionated to obtain isoparaffin solvent oil. The method has a simple production process and a high isoparaffin content, but the isoparaffin solvent oil obtained by the method has a low yield and a low degree of isomeric branching. Summary of the invention

[0008] In order to overcome the shortcomings of the prior art, the present invention provides a method for synthesizing isoparaffin solvent oil. The method adopts a fixed bed process and has the advantages of easy product separation, reduced environmental pollution, etc. The obtained isoparaffin solvent oil has a high yield, high isoparaffin content, and high isomeric branching degree.

[0009] A method for synthesizing isoparaffin solvent oil, the method comprising the following steps:

[0010] (1) Low carbon olefins enter the polymerization reaction zone and undergo polymerization reaction under the action of polymerization catalyst;

[0011] (2) The material after the polymerization reaction in step (1) enters the hydrotreating reaction zone and undergoes a hydrogenation saturation reaction under the action of a hydrotreating catalyst;

[0012] (3) The product after the reaction in step (2) is subjected to gas-liquid separation, and the liquid product is distilled to obtain isoparaffin solvent oil products of various fraction ranges;

[0013] Wherein, the polymerization catalyst in step (1) contains mesoporous ZSM-23 molecular sieve, and the content of mesoporous ZSM-23 molecular sieve is at least 30% or more, preferably at least 60% based on the weight of the polymerization catalyst.

[0014] In the method of the present invention, the low-carbon olefin is a C2-C6 olefin, preferably a C4 and / or C5 olefin.

[0015] In the method of the present invention, the polymerization reaction zone and the hydrofining reaction zone may be arranged in the same reactor, or may be arranged in a plurality of separate reactors.

[0016] In the method of the present invention, the polymerization catalyst is a mesoporous ZSM-23 molecular sieve, the pore size of the mesoporous ZSM-23 molecular sieve is 3-8nm, preferably 3-6nm, and the mesopore volume accounts for 45-90% of the total pore volume of the molecular sieve, preferably 50-85%, and more preferably 55-81%.

[0017] In the method of the present invention, the relative crystallinity of the mesoporous ZSM-23 molecular sieve is 95-120%, and the relative crystallinity retention of the molecular sieve after hydrothermal treatment with water vapor at 600°C for 2 hours is 95-100%.

[0018] In the method of the present invention, the polymerization catalyst is a formed mesoporous ZSM-23 molecular sieve, and the mesoporous ZSM-23 molecular sieve accounts for 30wt% to 90wt%, preferably 60wt% to 80wt% of the polymerization catalyst.

[0019] In the method of the present invention, the polymerization catalyst is a formed mesoporous ZSM-23 molecular sieve, and the polymerization catalyst has the following properties: a specific surface area of ​​290-410 m 2 / g, pore volume is 0.31-0.5cm 3 / g, micropore specific surface area is 50-160m 2 / g, mesopore specific surface area is 150-305m 2 / g; preferably, the specific surface area is 310-390m 2 / g, pore volume is 0.34-0.45cm 3 / g, micropore specific surface area is 70-130m 2 / g, mesopore specific surface area is 191-285m 2 / g.

[0020] In the method of the present invention, the shape of the polymerization catalyst can be formed according to actual needs, such as a three-leaf clover shape, a four-leaf clover shape, a cylindrical strip shape or other suitable shapes.

[0021] In the method of the present invention, the polymerization catalyst may further contain metal halides and / or The metal halide is AlCl3 or TiCl4, and the final catalyst contains 0.1wt% to 20wt% of the metal halide, preferably 1wt% to 15wt% of the metal halide, based on the weight percentage of the final catalyst. The transition metal of the first group is Fe, Co, or Ni. Based on the weight of the final catalyst, the catalyst contains The amount of the transition metal oxide is 1wt% to 35wt%, preferably 2wt% to 8wt%.

[0022] In the method of the present invention, the polymerization reaction conditions are: reaction temperature is 20-180°C, preferably 60-120°C, pressure is 0.1-10.0MPa, preferably 1.0MPa-5.0MPa, volume space velocity is 0.5h -1 ~5.0h -1 , preferably 0.8h -1 ~2.0 h -1 .

[0023] In the method of the present invention, the hydrorefining reaction zone is loaded with a conventional hydrorefining catalyst in the art, which may be a non-precious metal hydrorefining catalyst or a precious metal hydrorefining catalyst. The present invention preferably uses a precious metal hydrorefining catalyst.

[0024] In the method of the present invention, the hydrofining reaction conditions are: reaction temperature is 120°C to 350°C, preferably 150°C to 300°C, reaction pressure is 3.0MPa to 12.0MPa, preferably 5.0MPa to 10.0MPa, volume space velocity is 0.5h -1 ~5.0 h -1 , preferably 0.8h -1 ~3.0h -1 , the volume ratio of hydrogen to oil is 200:1~1500:1, preferably 600:1~1200:1.

[0025] Compared with the prior art, the method for synthesizing isoparaffin solvent oil of the present invention has the following advantages:

[0026] (1) The method of the present invention uses a polymerization catalyst containing mesoporous ZSM-23. The ZSM-23 molecular sieve has both the acidic properties of a microporous structure that can be adjusted and the macroporous characteristics of a mesoporous structure. The catalytic performance is stable, which further improves the product selectivity and stability of the olefin polymerization reaction and increases the yield of isoparaffin solvent oil.

[0027] (2) The synthetic isoparaffin solvent oil obtained by the present invention has many isomeric branches, concentrated carbon numbers, extremely low impurities, no aromatic hydrocarbons, and an isoparaffin content of >99%.

[0028] (3) The present invention adopts a fixed-bed synthesis and hydrogenation combined process, which solves the problems of corrosion of traditional low-carbon olefin polymerization reaction equipment, high chlorine content of products, and environmental pollution caused by wastewater generated by catalyst post-treatment. It saves energy and reduces consumption, can significantly reduce process costs, and is in line with the concept of green development. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention is a schematic flow diagram of a method for synthesizing isoparaffin solvent oil. DETAILED DESCRIPTION

[0030] A specific method and process for producing synthetic isoparaffin solvent oil according to the present invention is shown in Figure 1 :The raw materials first enter the R1 reactor of the synthesis reaction zone to undergo olefin polymerization reaction, and the polymerized olefin is mixed with hydrogen and enters the R2 reactor of the hydrogenation supplementary refining reaction zone to further remove olefin. The reaction products of the hydrogenation supplementary refining reaction zone are separated into gas and liquid, and the liquid products enter the distillation tower to obtain isoparaffin solvent oil products of various fraction ranges after distillation.

[0031] The analysis method of the present invention is as follows: The specific surface area and pore volume of the catalyst or molecular sieve are measured by using an ASAP 2405 physical adsorption instrument from Micromeritics, USA, where the specific surface area refers to the sum of the micropore specific surface area and the mesopore specific surface area. The loaded metal content is measured by atomic absorption spectroscopy.

[0032] The XRD spectrum of the sample was obtained by a Dmax2500 X-ray diffractometer produced by Rigaku Corporation of Japan, and the relative crystallinity of the sample was calculated. The sum of the heights of the diffraction peaks at 2θ of about 11.3 and 19.5-23° in the XRD spectrum of conventional ZSM-23 molecular sieve was taken as 100% crystallinity, and the relative crystallinity of other samples was obtained by comparison.

[0033] A non-limiting method for preparing a formed mesoporous ZSM-23 molecular sieve polymerization catalyst comprises the following steps:

[0034] (1) Preparation of mesoporous ZSM-23 molecular sieve;

[0035] (2) The mesoporous ZSM-23 molecular sieve prepared in step (1) is mixed with a binder and a peptizing agent to form a mold

[0036] After drying and calcination, the final formed ZSM-23 molecular sieve catalyst is obtained.

[0037] In the method of the present invention, the binder used can be selected from small-pore alumina, and the pore volume of the small-pore alumina used is 0.3-0.5 ml / g, and the specific surface area is 200-400 m 2 / g. The peptizing agent used can be one or more of aluminum sulfate, citric acid, nitric acid, acetic acid, oxalic acid, etc.

[0038] In the method of the present invention, the drying conditions are as follows: the drying temperature is 60°C to 180°C, preferably 90°C to 120°C, and the drying time is 0.5h to 20.0h, preferably 3.0h to 6.0h; the roasting conditions are as follows: the roasting temperature is 350°C to 750°C, preferably 500°C to 650°C, and the roasting time is 0.5h to 20.0h, preferably 3.0h to 6.0h. The drying and roasting can be carried out in an oxygen-containing atmosphere, with no particular restriction on the oxygen concentration, such as air atmosphere, etc., or in an inert atmosphere, such as nitrogen atmosphere, etc.

[0039] In the method of the present invention, the preparation of mesoporous ZSM-23 molecular sieve comprises the following steps:

[0040] a. preparing or selecting amorphous silicon dioxide;

[0041] b. treating amorphous silica with an alkali;

[0042] c ZSM-23 molecular sieve was prepared using alkali-treated amorphous silica as the silicon source.

[0043] In step a of the above method, the amorphous silicon dioxide has a specific surface area of ​​600-1300m 2 / g, preferably 700-1200m 2 / g; pore volume is 0.6-1.3cm 3 / g, preferably 0.7-1.2cm 3 / g; the pore diameter is 1-15nm, preferably 2-10nm.

[0044] In step a of the above method, the amorphous silica preparation process is as follows: adding a silicon source to deionized water and dispersing it evenly, then adding a surfactant and stirring; adjusting the solution pH to 1-5, preferably 1.5-4, and heating it in a water bath for a period of time; filtering, washing, drying, and calcining to obtain amorphous silica.

[0045] In the above method, during the preparation of amorphous silicon dioxide, the silicon source is an inorganic silicon source, preferably one or more of water glass, silica sol or white carbon black.

[0046] In the above method, during the preparation of amorphous silicon dioxide, the surfactant is one or more of hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, and octadecyltrimethylammonium bromide.

[0047] In the above method, during the preparation of the amorphous silica, the molar ratio of the silicon source in terms of SiO2 to the surfactant is 1:(0.02-0.3), preferably 1:(0.05-0.2).

[0048] In the above method, during the preparation of the amorphous silicon dioxide, the molar ratio of the silicon source in terms of SiO2 to deionized water is 1:(30-300), preferably 1:(50-220).

[0049] In the above method, during the preparation of the amorphous silica, the heating temperature is 30-80°C, preferably 40-70°C, and the heating time is 0.5-8h, preferably 3-6h.

[0050] In step b of the above method, the alkali treatment is to add the amorphous silicon dioxide prepared in step a into an alkaline solution and heat and stir.

[0051] In the above method, the alkali treatment adopts inorganic alkali treatment, and the inorganic alkali is one or more of sodium hydroxide, potassium hydroxide or ammonia water.

[0052] In the above method, the alkali treatment heating and stirring time is 0.5-12h, preferably 2-8h; the heating temperature is 25-60°C, preferably 30-50°C.

[0053] In the above method, the molar ratio of amorphous silica calculated as SiO2 to the inorganic base is 0.05-0.24, preferably 0.06-0.22.

[0054] In step c of the above method, in preparing ZSM-23 molecular sieve using alkali-treated amorphous silicon dioxide as a silicon source, any method for preparing ZSM-23 molecular sieve known in the prior art may be used, and a method for preparing ZSM-23 molecular sieve that is not yet known in the prior art but will be known in the future may also be used. For example, a known method is disclosed in U.S. Pat. No. 4,990,342 of Mobil Oil Corporation.

[0055] In step c of the above method, preferably, alkali-treated amorphous silicon dioxide is used as a silicon source, and the silicon source is mixed with an aluminum source, an alkali source (MOH), a template (R), and water to form a gel, and the ZSM-23 molecular sieve is obtained after crystallization, filtration, washing, drying, and calcination;

[0056] More preferably, the molar ratio of silicon source (in terms of SiO2): aluminum source (in terms of Al2O3): alkali source (in terms of hydroxide): template: H2O in the gel is 1: (0.003-0.03): (0.03-0.3): (0.05-2): (10-90); further preferably, the molar ratio of silicon source (in terms of SiO2): aluminum source (in terms of Al2O3): alkali source (in terms of hydroxide): template: H2O in the gel is 1: (0.005-0.02): (0.03-0.16): (0.08-1.6): (20-70);

[0057] More preferably, the gel is crystallized at 150-200°C, preferably 170-180°C, for 24-96h, preferably 36-72h, and then filtered, washed, dried, and calcined to obtain a ZSM-23 molecular sieve;

[0058] More preferably, the drying temperature is 80-120° C., the drying time is 4-12 hours, the roasting temperature is 500-600° C., and the roasting time is 2-6 hours.

[0059] The prepared mesoporous ZSM-23 molecular sieve, small-pore alumina and nitric acid were mixed and shaped, and then dried at 120°C for 8 hours and calcined at 600°C for 4 hours to prepare a catalyst. The small-pore alumina used had a pore volume of 0.5 ml / g and a specific surface area of ​​300 m 2 / g. Through analytical characterization, the specific surface area of ​​the catalyst is 335m 2 / g, pore volume is 0.48cm 3 / g, micropore specific surface area is 80m 2 / g, mesopore specific surface area is 255m 2 / g, the catalyst contains 75wt% ZSM-23 molecular sieve.

[0060] The hydrogenation refining catalyst in the method of the present invention can be prepared according to the method described in CN103769194A, using amorphous silicon aluminum and SBA-15 / Y composite molecular sieve as carriers to prepare a catalyst containing 0.1wt% to 0.5wt% of Pt and 0.3wt% to 0.8wt% of Pd, and the specific surface area of ​​the catalyst is 380 to 500m 2 / g, and the pore volume is 0.6~0.9ml / g.

[0061] In order to better illustrate the present invention, the following is further described in conjunction with examples, but the present invention is not limited to these examples. The physicochemical properties of the hydrorefining catalyst of the present invention are shown in Table 1.

[0062] Table 1. Physicochemical properties of olefin polymerization catalysts

[0063]

[0064] Table 2. Physicochemical properties of hydrorefining catalysts

[0065]

[0066] Embodiment 1:

[0067] Isobutylene was used as the raw material. The properties of the raw material are shown in Table 3. The catalyst in Table 1 was used in the synthesis reaction zone. The reaction conditions in the synthesis reaction zone were as follows: the volume space velocity was 1.0 h -1The reaction temperature is 80°C and the pressure is 3.0MPa. The catalyst in Table 2 is used in the hydrogenation refining reaction zone. The reaction conditions are the reaction temperature is 190°C and the volume space velocity is 1.0h -1 , pressure is 6.0MPa, and hydrogen-oil volume ratio is 1000:1. The process conditions and results are shown in Table 4.

[0068] Embodiment 2:

[0069] Isobutylene was used as the raw material, and the catalyst in Table 1 was used in the synthesis reaction zone. The reaction conditions in the synthesis reaction zone were as follows: the volume space velocity was 0.9 h -1 The reaction temperature is 100°C and the pressure is 3.0 MPa. The catalyst in Table 2 is used in the hydrogenation refining reaction zone. The reaction conditions are the reaction temperature is 190°C and the volume space velocity is 1.0 h -1 , pressure is 6.0MPa, and hydrogen-oil volume ratio is 1000:1. The process conditions and results are shown in Table 4.

[0070] Embodiment 3:

[0071] The catalyst in Table 1 was used as a carrier, 300 g was added to a 1.0 M ferric nitrate solution, stirred evenly, soaked at 30°C for 3 hours, and then vacuum dried at 70°C for 3 hours. Then, it was calcined at 500°C for 8 hours.

[0072] Through analysis and characterization, the specific surface area of ​​the catalyst is 305m 2 / g, pore volume is 0.43cm 3 / g, micropore specific surface area is 75m 2 / g, mesopore specific surface area is 230m 2 / g. The iron oxide content in the catalyst is 3.55 wt%, and the mass content of ZSM-23 molecular sieve is 67.5%.

[0073] Using isobutylene as raw material, the above catalyst is used in the synthesis reaction zone, and the reaction conditions in the synthesis reaction zone are as follows: the volume space velocity is 1.0h -1 The reaction temperature is 80°C and the pressure is 3.0MPa. The catalyst in Table 2 is used in the hydrogenation refining reaction zone. The reaction conditions are the reaction temperature is 190°C and the volume space velocity is 1.0h -1 , pressure is 6.0MPa, and the volume ratio of hydrogen to oil is 1000:1.

[0074] Embodiment 4:

[0075] The catalyst in Table 1 was used as a carrier, 300 g was added to a 1.0 M nickel nitrate solution, stirred evenly, soaked at 30°C for 6 hours, and then vacuum dried at 80°C for 3 hours. Then, it was calcined at 500°C for 8 hours.

[0076] Through analysis and characterization, the specific surface area of ​​the catalyst is 303m2 / g, pore volume is 0.43cm 3 / g, micropore specific surface area is 73m 2 / g, mesopore specific surface area is 230m 2 / g. The nickel oxide content in the catalyst is 2.32 wt%, and the mass content of ZSM-23 molecular sieve is 66.2%.

[0077] Using isobutylene as raw material, the above catalyst is used in the synthesis reaction zone, and the reaction conditions in the synthesis reaction zone are as follows: the volume space velocity is 1.0h -1 The reaction temperature is 80°C and the pressure is 3.0MPa. The catalyst in Table 2 is used in the hydrogenation refining reaction zone. The reaction conditions are the reaction temperature is 190°C and the volume space velocity is 1.0h -1 , pressure is 6.0MPa, and the volume ratio of hydrogen to oil is 1000:1.

[0078] Embodiment 5:

[0079] The catalyst in Table 1 was used as a carrier, 300 g was added to a 1.0 M ferric nitrate solution, stirred evenly, soaked at 30°C for 3 hours, and then vacuum dried at 70°C for 3 hours. Then, it was calcined at 500°C for 8 hours.

[0080] 40g of anhydrous aluminum chloride was dissolved in 2000ml of tetrahydrofuran, and then 50g of the support was mixed with the solution and kept at reflux temperature for 12h. Finally, the supported catalyst was dried at 120°C in vacuum for 6h to obtain the supported catalyst.

[0081] Through analytical characterization, the specific surface area of ​​the catalyst is 298m 2 / g, pore volume is 0.43cm 3 / g, micropore specific surface area is 73m 2 / g, mesopore specific surface area is 226m 2 / g. The composition of the catalyst is as follows: the content of aluminum chloride in the supported catalyst is 3.50wt%, the content of iron oxide in the catalyst is 3.55wt%, and the mass content of ZSM-23 molecular sieve is 65.3%.

[0082] Using isobutylene as raw material, the above catalyst is used in the synthesis reaction zone, and the reaction conditions in the synthesis reaction zone are as follows: the volume space velocity is 1.0h -1 The reaction temperature is 80°C and the pressure is 3.0MPa. The catalyst in Table 2 is used in the hydrogenation refining reaction zone. The reaction conditions are the reaction temperature is 190°C and the volume space velocity is 1.0h -1 , pressure is 6.0MPa, and the volume ratio of hydrogen to oil is 1000:1.

[0083] Comparative Example

[0084] Isobutylene was used as raw material, conventional anhydrous AlCl3 was selected as a synthesis catalyst, and the synthesis reaction was carried out in a reactor, the catalyst addition amount was 3%, the reaction temperature was 60°C, the reaction pressure was 2.0Mpa, and the reaction time was 2h. The synthesized product was subjected to fixed bed hydrorefining to obtain isoparaffin solvent oil, and the hydrogenation process conditions were the same as those in Example 1. The process conditions and results are shown in Table 4.

[0085] Table 3. Isobutylene raw material properties

[0086]

[0087] Table 4 Process conditions and results of examples and comparative examples

[0088]

Claims

1. A method for synthesizing isoparaffin solvent oil, characterized in that: The method comprises the following steps: (1) Low carbon olefins enter the polymerization reaction zone and undergo polymerization reaction under the action of polymerization catalyst; (2) The material after the polymerization reaction in step (1) enters the hydrotreating reaction zone and undergoes a hydrogenation saturation reaction under the action of a hydrotreating catalyst; (3) The product after the reaction in step (2) is subjected to gas-liquid separation, and the liquid product is distilled to obtain isoparaffin solvent oil products of various fraction ranges; Wherein, the polymerization catalyst in step (1) contains mesoporous ZSM-23 molecular sieve, and the content of the mesoporous ZSM-23 molecular sieve is at least 30% based on the weight of the polymerization catalyst; The mesoporous ZSM-23 molecular sieve has a pore volume of 3-8 nm mesopores accounting for 45-90% of the total pore volume of the molecular sieve; The polymerization catalyst contains metal halide and / or Group VIII transition metal oxide, wherein the metal halide is AlCl3 or TiCl4, and the final catalyst contains 0.1wt% to 20wt% of the metal halide based on the weight percentage of the final catalyst; the Group VIII transition metal is Fe, Co, or Ni, and the catalyst contains 1wt% to 35wt% of the Group VIII transition metal oxide based on the weight of the final catalyst; The polymerization catalyst has the following properties: specific surface area of ​​290-410m 2 / g, pore volume is 0.31-0.5cm 3 / g, micropore specific surface area is 50-160m 2 / g, mesopore specific surface area is 150-305m 2 / g.

2. The method according to claim 1, characterized in that: Based on the weight of the polymerization catalyst, the content of the mesoporous ZSM-23 molecular sieve is at least 60%.

3. The method according to claim 1, characterized in that: The low carbon olefin is a C2-C6 olefin.

4. The method according to claim 3, characterized in that: The low carbon olefins are C4 and / or C5 olefins.

5. The method according to claim 1, characterized in that: The polymerization catalyst is a mesoporous ZSM-23 molecular sieve, and the mesoporous pore volume of the mesoporous ZSM-23 molecular sieve with a pore diameter of 3-8 nm accounts for 50-85% of the total pore volume of the molecular sieve.

6. The method according to claim 5, characterized in that: The polymerization catalyst is a mesoporous ZSM-23 molecular sieve, and the mesoporous pore volume of the mesoporous ZSM-23 molecular sieve with a pore diameter of 3-8 nm accounts for 55-81% of the total pore volume of the molecular sieve.

7. The method according to claim 1, characterized in that: The relative crystallinity of the mesoporous ZSM-23 molecular sieve is 95-120%, and the relative crystallinity retention of the molecular sieve after hydrothermal treatment with 600° C. steam for 2 hours is 95-100%.

8. The method according to claim 1, characterized in that: The polymerization catalyst is a formed mesoporous ZSM-23 molecular sieve, and the mesoporous ZSM-23 molecular sieve in the polymerization catalyst is 30wt% to 90wt%.

9. The method according to claim 8, characterized in that: The polymerization catalyst is a formed mesoporous ZSM-23 molecular sieve, and the mesoporous ZSM-23 molecular sieve in the polymerization catalyst accounts for 60wt% to 80wt%.

10. The method according to claim 1, characterized in that: The polymerization catalyst is a formed mesoporous ZSM-23 molecular sieve, and the polymerization catalyst has the following properties: a specific surface area of ​​310-390m 2 / g, pore volume is 0.34-0.45cm 3 / g, micropore specific surface area is 70-130m 2 / g, mesopore specific surface area is 191-285m 2 / g.

11. The method according to claim 1, characterized in that: In the polymerization catalyst, based on the weight percentage of the final catalyst, the final catalyst contains 1wt% to 15wt% of metal halide; based on the weight of the final catalyst, the catalyst contains 2wt% to 8wt% of Group VIII transition metal oxide.

12. The method according to claim 1, characterized in that: The polymerization reaction conditions are: reaction temperature 20~180℃, pressure 0.1~10.0MPa, volume space velocity 0.5~5.0h -1 .

13. The method according to claim 12, characterized in that: The polymerization reaction conditions are: reaction temperature 60℃~120℃, pressure 1.0MPa~5.0MPa, volume space velocity 0.8h -1 ~2.0 h -1 .

14. The method according to claim 1, characterized in that: The hydrotreating catalyst filled in the hydrotreating reaction zone is a non-precious metal hydrotreating catalyst or a precious metal hydrotreating catalyst.

15. The method according to claim 1, characterized in that: The hydrofining reaction conditions are: reaction temperature of 120°C to 350°C, reaction pressure of 3.0MPa to 12.0MPa, volume space velocity of 0.5h -1 ~5.0 h -1 The volume ratio of hydrogen to oil is 200:1~1500:

1.

16. The method according to claim 1, characterized in that: The hydrofining reaction conditions are: reaction temperature of 150°C to 300°C, reaction pressure of 5.0MPa to 10.0MPa, volume space velocity of 0.8h -1 ~3.0 h -1 , the volume ratio of hydrogen to oil is 600:1~1200:1.

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