Patent Publication Number: US-2013253238-A1

Title: Method for producing lubricating base oil with low cloud point and high viscosity index

Description:
FIELD OF THE INVENTION 
     The present invention relates to a method for producing a lubricating base oil with a low cloud point (&lt;−5° C.) and a high viscosity index (&gt;120). 
     BACKGROUND OF THE INVENTION 
     Patent CN101134910A discloses a method for lowering the pour point and the cloud point of a lubricating oil distillate. In the method, a catalytic dewaxing process is adopted, and the catalyst includes nickel metal as an active component, which is contained in a support of a ZSM-5 molecular sieve. The pour point of a light deasphalted hydrotreated oil can be lowered from 9° C. to −24° C., and the cloud point can be lowered from 12° C. to −16° C. The method has the following obvious disadvantage: the yield and the viscosity of the base oil product will be greatly decreased when the wax content in the feed stock is high, and the drops of the pour point and the cloud point need to be increased. 
     Patent CN1524929 discloses a method for lowering the cloud point of a lubricating base oil, in which a lube stock is first subjected to solvent pre-dewaxing, the pour point of the dewaxed oil is −5° C. to 15° C.; the pre-dewaxed oil is subjected to hydrotreating to reduce the sulfur content and the nitrogen content; the pre-dewaxed oil after hydrotreating is subjected to isodewaxing, to obtain a lubricating base oil with a low cloud point. In order to avoid increase of the severity of the reaction and a resulted severe cracking reaction, in the method, most of the wax needs to be removed through a solvent pre-dewaxing process, and then a hydrotreating and isodewaxing process is performed. The pour point of the dewaxed oil of the method should be not higher than 15° C., otherwise the cloud point of the isomerization product cannot be lowered to less than 0° C., even cannot be lowered to less than 5° C. 
     U.S. Pat. No. 6,699,385 discloses a method for lowering the cloud point through an isodewaxing process. In order to avoid increase of the severity of the reaction and a resulted severe cracking reaction, the waxy feed stock needs to be first fractionated, and a light fraction is subjected to isodewaxing, and the cloud point can only be decreased to about 0° C. 
     All the methods for dewaxing a lubricating base oil disclosed in the published patents and documents above do not clarify or imply a method for producing a base oil with a low pour point, a low cloud point and a high viscosity index by an isomerization-asymmetrical cracking reaction process, and compared with the method disclosed in the published patents and documents, the yield of a base oil, especially the yield of a heavy base oil of an isomerization-symmetric cracking reaction process is higher. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a method for producing a lubricating base oil having a low cloud point (&lt;−5° C.) and a high viscosity index (&gt;120), wherein a highly waxy heavy fraction oil having an initial boiling point of 300° C. to 460° C., a wax content of 5% or more, a pour point of −20° C. or more and a cloud point of −5° C. or more is used as raw material to produce a API (American Petroleum Institute) II, III (see the classification standard in Table 1) type lubricating base oil having a low pour point and a high viscosity index by a hydrogenation pre-refining-isomerization/asymmetrical cracking-supplementary refining three-stage hydrogenation process. 
     The production method provided by the present invention includes: (1) a hydrorefining process: at a certain hydrogen pressure, a waxy feed stock contacts a hydrorefining catalyst and is subjected to desulfurization, denitrogenation, aromatic saturation and an ring-opening reaction, products of the hydrorefining reaction are separated by a stripping column, and the bottom fraction enters a hydroisomerization/asymmetrical cracking process; (2) a hydroisomerization/asymmetrical cracking process: at a certain hydrogen pressure, a bottom product of the stripping column contacts an isomerization-asymmetrical cracking catalyst and is subjected to isomerization-asymmetrical cracking and a hydrogenation saturation reaction, to obtain a product having a low pour point, a low cloud point, a low aromatic content and a high viscosity index, and then all the product directly enters a hydrofinishing process; (3) a hydrofinishing process: at a certain hydrogen pressure, the isomerization-asymmetrical cracking reaction product contacts a hydrofinishing catalyst and is subjected to a hydrogenation saturation reaction, to obtain a hydrofinishing oil having good light stability and thermal stability; and (4) a product separation process: the product obtained in the hydrofinishing process is separated into a gas phase product and a liquid phase product by a hot high-pressure separator and a cold low-pressure separator, the liquid product passes through a normal-pressure fractionating column and a reduced-pressure fractionating column to extract naphtha, kerosene, diesel oil and light, middle and heavy lubricating base oil having a low pour point and a high viscosity index. 
     According to the method of the present invention, the feed stock includes anyone of furfural refined oil, foots oil, cerate (soft wax), propane deasphalted oil (DAO), hydrocracking unconverted oil (UCO), Fischer-Tropsch wax, vacuum gas oil and other waxy oils or a mixture thereof. 
     According to the method of the present invention, the hydrorefining catalyst includes 60 wt % to 90 wt % of one or more of alumina, silica and titania, and 10 wt % to 40 wt % of one or more of molybdenum trioxide, tungsten trioxide, nickel oxide and cobalt oxide. 
     According to the method of the present invention, before use, the hydrorefining catalyst is pre-sulfurated by hydrogen sulfide or sulfur-containing feed stock at a temperature of 150 to 350° C. in the presence of hydrogen. This type of pre-vulcanization may be carried out ex situ or in situ. 
     According to the method of the present invention, the hydrorefining process conditions are: reaction temperature: 350° C. to 410° C., hydrogen partial pressure: 10 MPa to 18 MPa, space velocity (LHSV): 0.5 h −1  to 2.0 h −1 , and volume ratio of hydrogen to oil:300 Nm 3 /m 3  to 1000 Nm 3 /m 3 . 
     According to the method of the present invention, the oil obtained by stripping separation of the hydrorefining product has a total sulfur content of no higher than 10 μg/g and a total nitrogen content of no higher than 5 μg/g. 
     According to the method of the present invention, the isomerization-asymmetrical cracking catalyst is at least one of the following one-dimensional 10-membered ring mesoporous composite molecular sieves: a ZSM-22/ZSM-23 composite molecular sieve, a ZSM-23/ZSM-22 composite molecular sieve, a ZSM-5/SAPO-11 composite molecular sieve, a ZSM-22/SAPO-11 composite molecular sieve, a ZSM-23/SAPO-11 composite molecular sieve, an EU-1/SAPO-11 composite molecular sieve, and a NU-87/SAPO-11 composite molecular sieve. The content of the molecular sieve is 40% to 80%, and the rest is alumina and at least one group VIII noble metal, where the noble metal is Pt and/or Pd and has a content of 0.3 wt % to 0.6 wt %. The average pore diameter of the catalyst is 0.3 nm to 0.8 nm, the average pore volume is 0.1 ml/g to 0.4 mug, and the BET specific surface area is 120 m 2 /g to 300 m 2 /g. 
     According to the method of the present invention, before use, the isomerization/asymmetrical cracking catalyst needs to be pre-reduced at a temperature of 150 to 450° C. in the presence of hydrogen. 
     According to the method of the present invention, the isomerization/asymmetrical cracking process conditions are: reaction temperature: 260° C. to 410° C., hydrogen partial pressure: 10 MPa to 18 MPa, volume space velocity: 0.5 h −1  to 3.0 h −1 , volume ratio of hydrogen to oil:300 Nm 3 /m 3  to 1000 Nm 3 /m 3 . 
     According to the method of the present invention, the hydrofinishing catalyst includes amorphous silica-alumina and at least one group VIII noble metal. 
     According to the method of the present invention, the hydrofinishing catalyst has a ratio of SiO 2 :Al 2 O 3  of 1:1 to 9, an average pore radius of 1.0 nm to 5.0 nm, a pore volume of 0.3 ml/g to 1.0 ml/g, and a BET specific surface area of 260 m 2 /g to 450 m 2 /g. The noble metal is Pt and/or Pd, and the content of the noble metal is 0.3 wt % to 0.6 wt %. 
     According to the method of the present invention, before use, the hydrofinishing catalyst is generally pre-reduced at a temperature of 150° C. to 450° C. in the presence of hydrogen. 
     According to the method of the present invention, the hydrofinishing reaction conditions are: reaction temperature: 180° C. to 320° C., hydrogen partial pressure: 10 MPa to 18 MPa, volume space velocity: 0.5 h −1  to 3.0 h −1 , volume ratio of hydrogen to oil:300 Nm 3 /m 3  to 1000 Nm 3 /m 3 . 
     According to the method of the present invention, the normal-pressure distillation and reduced-pressure distillation process are to separate the oil mixture after supplementary refining by normal-pressure distillation and reduced-pressure distillation, to obtain a naphtha, a middle fraction oil and a lubricating base oil. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows product distribution of Example 1 and Comparative Example 1. 
         FIG. 2  shows product distribution of Example 2 and Comparative Example 2. 
         FIG. 3  is a flowchart of an isomerization-asymmetrical cracking/supplementary refining process of a lubricating base oil. 
         FIG. 4  is a flowchart of a hydrorefining/isodewaxing/hydrofinishing process of a lubricating base oil. 
         FIG. 5  is a flowchart of a hydrorefining/isomerization-asymmetrical cracking/hydrofinishing process of a lubricating base oil. 
         FIG. 6  is a flowchart of an isomerization-asymmetrical cracking/hydrofinishing process of a lubricating base oil. 
     
    
    
     PREFERRED EMBODIMENTS 
     Examples 
     The present invention is further described with the following examples. 
     The hydrorefining catalyst and the supplementary refining catalyst used in the examples of the present invention and preparation method thereof are briefly described as follows: 
     Same hydrorefining catalyst and hydrofinishing catalyst are used in the examples and comparative examples of the present invention. The hydrorefining catalyst is prepared according to the following process: pseudo-boehmite having an appropriate pore structure is selected and used to prepare a strip-like support having a clover-shaped cross section, after the support is dried and baked, Ni element and Mo element are loaded on the alumina support by an impregnation method, and then dried and baked to obtain a hydrorefining catalyst, wherein the NiO content is 4.20%, the MoO 3  content is 18.3%, and the rest is alumina, the specific surface area is 175 m 2 /g, and the pore volume is 0.45 cm 3 /g. 
     The isomerization/asymmetrical cracking catalyst used in the examples is a 0.5% Pt/ZSM-22/SAPO-11 catalyst prepared according to the method described in Example 12 of patent CN 1762594A. 
     In a method for preparing the hydrofinishing catalyst, amorphous silica-alumina used as support is prepared by using cocurrent flow fixed pH value and silica-alumina coprecipitation. After being dried and baked, the support is squeezed into a strip having a clover-shaped cross section, and dried and baked, and then metal Pt is loaded by an impregnation method, and then dried and baked to obtain a hydrofinishing catalyst, wherein the Pt content is 0.51%, the rest is silica and alumina, the ratio of SiO 2 :Al 2 O 3  is 1:6.3, the specific surface area is 305 cm 2 /g, and the pore volume is 1.08 cm 3 /g. 
     Comparative Example 1 
     A SAPO-11 molecular sieve was synthesized by a method described in Example 18 of U.S. Pat. No. 4,440,871. Pseudo-boehmite is incorporated into a SAPO-11 molecular sieve powder in a ratio of 70% SAPO-11 molecular sieve to 30% pseudo-boehmite, and then a small amount of an adhesive such as an aqueous solution of HNO 3  was added, blended and shaped into a strip of φ1.2 mm, baked at 110° C. for 24 hours and at 600° C. for 24 hours, and pulverized into particles having a length of 1 mm to 2 mm. A sufficient amount of support particles was impregnated in a suitable amount of a Pt(NH 3 ) 4 Cl 2  solution having a concentration of 3% for 16 hours by a common pore filling impregnation method, and then dried at 120° C. for 4 hours and baked at 480° C. for 8 hours. 200 ml of the prepared catalyst was pre-reduced by pure hydrogen in situ on a high-pressure hydrogenation reaction experimental device having a catalyst load of 200 ml to obtain a 0.5% Pt/SAPO-11 catalyst. The isodewaxing catalyst reduction conditions are: hydrogen flow rate: 2000 mL/h, the temperature was raised to 250° C. at a rate of 5° C./min and maintained at 250° C. for 2 hours. Then, the temperature was raised to 450° C. at a rate of 5° C./min and maintained at 450° C. for 2 hours, and the reaction temperature was adjusted in a hydrogen flow. The hydrogenation pre-refining-isodewaxing-hydrofinishing process shown in  FIG. 4  and the process conditions shown in Table 3 were adopted, paraffin base 650N furfural refined oil was used as a raw material, of which the physical and chemical properties are shown in Table 2. The hydrorefining catalyst and the supplementary refining catalyst were the same as the catalysts used in the examples mentioned above. 
     Example 1 
     According to the process shown in  FIG. 4 , the experimental device and the feed stock were the same as those in Comparative Example 1. The other reaction conditions were the same as those in Comparative Example 1 except that the reaction temperature of isomerization/asymmetrical cracking was 351° C., and the space velocity was 0.75 h −1 . The reaction conditions of Comparative Example 1 are shown in Table 3. 
     Product distribution comparison of Example 1 and Comparative Example 1 is shown in Table 4, and main product properties are shown in Table 5. 
     According to the process shown in  FIG. 4 , paraffin base 200SN lightly dewaxed oil was used as a feed stock in the experimental device of Comparative Example 1, and the physical and chemical properties of the feed stock are shown in Table 2. The reaction conditions are shown in Table 3. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Properties of feed stocks of Comparative 
               
               
                 Example 1 and Example 1 
               
            
           
           
               
               
               
            
               
                   
                 650SN 
                 Analysis 
               
               
                 Item 
                 Furfural Refined Oil 
                 Method 
               
               
                   
               
            
           
           
               
               
               
            
               
                 20° C. Density, g/cm 3   
                 0.8721 
                 GB/T 1884 
               
               
                 Kinematic Viscosity 
                 10.16 
                 GB/T 265 
               
               
                 (100° C.), mm 2 /s 
               
               
                 Kinematic Viscosity 
                 — 
                 GB/T 265 
               
               
                 (40° C.), mm 2 /s 
               
               
                 Viscosity Index 
                 — 
                 GB/T 1995 
               
               
                 Pour Point, ° C. 
                 60 
                 GB/T 3535 
               
               
                 Cloud Point, ° C. 
                 &gt;60 
                 GB/T 6986-86 
               
               
                 Sulfur Content, μg/g 
                 607 
                 ASTM D2622 
               
               
                 Nitrogen Content, μg/g 
                 322 
                 ASTM D5762 
               
               
                 Composition, % 
                   
                 SH/T0753 
               
               
                 Saturated Hydrocarbons 
                 86.08 
               
               
                 Aromatic Hydrocarbons 
                 13.58 
               
               
                 Colloid + Asphaltene 
                 0.34 
               
               
                 Distillation Range, ° C. HK 
                 421 
                 ASTM D2887 
               
               
                  5% 
                 477 
               
               
                 10% 
                 498 
               
               
                 30% 
                 516 
               
               
                 50% 
                 525 
               
               
                 70% 
                 533 
               
               
                 90% 
                 541 
               
               
                 95% 
                 550 
               
               
                 KK 
                 557 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Reaction conditions adopted in Comparative Example 1 and Example 1 
               
            
           
           
               
               
               
               
            
               
                   
                 Hydrorefining 
                 Isomerization 
                 Hydrofinishing 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 Comparative 
                   
                 Comparative 
                   
                 Comparative 
                   
               
               
                   
                 Example 1 
                 Example 1 
                 Example 1 
                 Example 1 
                 Example 1 
                 Example 1 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Average 
                 370 
                 370 
                 378 
                 351 
                 230 
                 230 
               
               
                 Temperature, ° C. 
               
               
                 Hydrogen 
                 13 
                 13 
                 12 
                 12 
                 12 
                 12 
               
               
                 Partial 
               
               
                 Pressure, MPa 
               
               
                 Liquid hourly 
                 0.90 
                 1.00 
                 0.70 
                 0.75 
                 1.50 
                 1.50 
               
               
                 Volume Space 
               
               
                 Velocity, h −1   
               
               
                 Raito of 
                 500 
                 500 
                 500 
                 500 
                 500 
                 500 
               
               
                 Hydrogen to 
               
               
                 Oil, Nm 3 /m 3   
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Product distribution of Comparative Example 1 and Example 1 
               
            
           
           
               
               
               
            
               
                   
                 Yield, % 
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Product 
                 Example 1 
                 Comparative Example 1 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Fuel Gas + Naphtha 
                 19.96 
                 15.71 
               
               
                   
                 Diesel Oil 
                 2.96 
                 11.58 
               
               
                   
                 2 cst Base Oil 
                 3.78 
                 24.86 
               
               
                   
                 5 cst Base Oil 
                 0 
                 4.49 
               
               
                   
                 10 cst Base Oil 
                 73.30 
                 47.85 
               
               
                   
                 Total Base Oil Yield 
                 77.08 
                 72.71 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 Properties of heavy base oil products 
               
               
                 of Comparative Example 1 and Example 1 
               
            
           
           
               
               
               
               
            
               
                   
                 Comparative 
                   
                 Analysis 
               
               
                 Analysis Item 
                 Example 1 
                 Example 1 
                 Method 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 Initial Boiling Point, ° C. 
                 421 
                 385 
                 GB/T 9168 
               
               
                 20° C. Density, g/cm 3   
                 0.8424 
                 0.8524 
                 GB/T 1884 
               
               
                 Pour Point, ° C. 
                 −15 
                 −15 
                 GB/T 3535 
               
               
                 Cloud Point, ° C. 
                 5 
                 −6 
                 GB/T 6986-86 
               
               
                 Aromatic Content, % 
                 1.2 
                 0 
               
               
                 Open Flash Point, ° C. 
                 265 
                 270 
                 GB/T 3536 
               
               
                 Chroma, number 
                 +30 
                 +30 
                 GB/T 3555 
               
               
                 Kinematic Viscosity 
                 60.89 
                 61.06 
                 GB/T 265 
               
               
                 (40° C.), mm 2 /s 
               
               
                 Kinematic Viscosity 
                 9.313 
                 9.423 
                 GB/T 265 
               
               
                 (100° C.), mm 2 /s 
               
               
                 Viscosity Index 
                 132 
                 136 
                 GB/T 1995 
               
               
                   
               
            
           
         
       
     
     It can be seen from Tables 2 to 5 and  FIG. 1  that, the pour point of the feed stock used in the hydrorefining, isomerization-asymmetrical cracking, hydrofinishing process in Example 1 is up to 60° C., indicating that the feed stock contains a large amount of high-carbon-number wax molecules. In the method of Example 1 and Comparative Example 1, the hydrocracking reaction occurs simultaneously with isomerization. However, different from the conventional hydrocracking reaction of Comparative Example 1, Example 1 has significant features of an asymmetrical cracking reaction, that is, the cleavage of a C—C bond preferably occurs at a position close to two ends of a long-chain paraffin, so that the yields of both small-molecule products (gas and naphtha) and big-molecule products (10 cst base oil) are high, and are up to 19.96% and 73.3%, respectively, while the yields of diesel oil and light base oil (2 cst base oil) are only 2.96% and 3.78% respectively. The cracking reaction in the method of Comparative Example 1 occurs at a position close to the center of a long-chain paraffin, so that the yields of both small-molecule products (gas+naphtha) and big-molecule products (10 cst base oil) are 15.71% and 47.85% respectively, which are both lower than those in Example 1, and the yields of diesel oil and light base oil (2 cst base oil) are 11.58% and 24.86% respectively, which are both higher than those in Example 1. At the same time, the cloud point of the heavy base oil product of Example 1 is 11° C. lower than that of the heavy base oil product of Comparative Example 1. The viscosity index of the heavy base oil product of Example 1 is higher than that of the heavy base oil product of Comparative Example 1 by 4%. 
     Comparative Example 2 
     A ZSM-22 molecular sieve was synthesized by the method described in Example 2 of U.S. Pat. No. 5,783,168. Pseudo-boehmite is incorporated into a ZSM-22 molecular sieve powder in a ratio of 70% ZSM-22 molecular sieve to 30% pseudo-boehmite, and then a small amount of an adhesive such as an aqueous solution of HNO 3  was added, blended and shaped into a strip of φ1.2 mm, baked at 110° C. for 24 hours and at 600° C. for 24 hours, and breaked into particles having a length of 1 mm to 2 mm. A sufficient amount of support particles was impregnated in a suitable amount of a Pt(NH 3 ) 4 Cl 2  solution having a concentration of 3% for 16 hours by a common pore filling impregnation method, and then dried at 120° C. for 4 hours and baked at 480° C. for 8 hours. 200 ml of the prepared catalyst was pre-reduced by pure hydrogen in situ in a high-pressure hydrogenation reaction experimental device having a catalyst load of 200 ml to obtain 0.5% of Pt/ZSM-22. The catalyst reduction conditions were the same as those in Comparative Example 1. A paraffin base 200SN dewaxed oil was used as a raw material, the physical and chemical properties thereof are shown in Table 6, and a hydrorefining-isodewaxing-hydrofinishing series process (shown in  FIG. 4 ) and process conditions shown in Table 7 were adopted. 
     Example 2 
     The process, experimental device and feed stock were the same as those in Comparative Example 2. The other reaction conditions were the same as those in Comparative Example 2 except that the temperature of the isomerization/asymmetrical cracking reaction was 325° C., and the liquid hourly space velocity was 1.2 h −1 . 
     The product distributions of the reactions of Example 2 and Comparative Example 2 are shown in Table 8, and main properties of the products are shown in Table 9. 
     It can be seen from Tables 6 to 9 and  FIG. 2  that compared with Comparative Example 2, the method of Example 2 has significant features of a hydrorefining-isomerization/asymmetrical cracking-hydrofinishing, that is, the yield of a heavy base oil (5 cst base oil) is high, and the yields of small-molecule products (gas and naphtha) and big-molecule products (10 cst base oil) are both high, and are up to 19.96% and 73.3% respectively, the yields of diesel oil and a light base oil (2 cst base oil) are merely 2.96% and 3.78% respectively. The product distribution is in a bimodal distribution. At the same time, it can be seen that, the cloud point of the heavy base oil product of Example 2 is 10° C. lower than that of the heavy base oil product of Comparative Example 2. 
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 Feed stock properties 
               
            
           
           
               
               
               
            
               
                   
                 200SN 
                 Analysis 
               
               
                 Item 
                 Lightly Dewaxed Oil 
                 Standard 
               
               
                   
               
            
           
           
               
               
               
            
               
                 20° C. Density, g/cm 3   
                 0.8797 
                 GB/T 1884 
               
               
                 Kinematic Viscosity 
                 6.277 
                 GB/T 265 
               
               
                 (100° C.), mm 2 /s 
               
               
                 Kinematic Viscosity 
                 40.34 
                 GB/T 265 
               
               
                 (40° C.), mm 2 /s 
               
               
                 Viscosity Index 
                 103 
                 GB/T 1995 
               
               
                 Pour Point, ° C. 
                 −3 
                 GB/T 3535 
               
               
                 Cloud Point, ° C. 
                 15 
                 GB/T 6986-86 
               
               
                 Sulfur Content, μg/g 
                 420 
                 ASTM D2622 
               
               
                 Nitrogen Content, μg/g 
                 144 
                 ASTM D5762 
               
               
                 Composition, % 
                   
                 SH/T0753 
               
               
                 Saturated Hydrocarbons 
                 88.23 
               
               
                 Aromatic Hydrocarbons 
                 11.44 
               
               
                 Colloid + Asphaltene 
                 0.33 
               
               
                 Distillation Range, ° C. HK 
                 373 
                 ASTM D2887 
               
               
                  5% 
                 404 
               
               
                 10% 
                 414 
               
               
                 30% 
                 429 
               
               
                 50% 
                 441 
               
               
                 70% 
                 453 
               
               
                 90% 
                 478 
               
               
                 95% 
                 487 
               
               
                 KK 
                 491 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 7 
               
             
            
               
                   
               
               
                 Reaction conditions of Comparative Examples 1 and 2 
               
            
           
           
               
               
               
               
            
               
                   
                 Hydrorefining 
                 Isomerization 
                 Hydrofinishing 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 Comparative 
                   
                 Comparative 
                   
                 Comparative 
                   
               
               
                   
                 Example 2 
                 Example 2 
                 Example 2 
                 Example 2 
                 Example 2 
                 Example 2 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Average 
                 368 
                 368 
                 360 
                 325 
                 230 
                 230 
               
               
                 Temperature, ° C. 
               
               
                 Hydrogen 
                 13 
                 13 
                 12 
                 12 
                 12 
                 12 
               
               
                 Partial 
               
               
                 Pressure, MPa 
               
               
                 Liquid hourly 
                 1.0 
                 1.0 
                 0.9 
                 1.2 
                 1.5 
                 1.5 
               
               
                 Volume Space 
               
               
                 Velocity, h −1   
               
               
                 Raito of 
                 500 
                 500 
                 500 
                 500 
                 500 
                 500 
               
               
                 Hydrogen to 
               
               
                 Oil, Nm 3 /m 3   
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 8 
               
             
            
               
                   
               
               
                 Product distribution of Examples 1 and 
               
               
                 2 and Comparative Examples 1 and 2 
               
            
           
           
               
               
               
            
               
                   
                 Yield, % 
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Product 
                 Comparative Example 2 
                 Example 2 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Gas + Naphtha 
                 8.85 
                 9.74 
               
               
                   
                 Diesel 
                 8.09 
                 2.44 
               
               
                   
                 2 cst Base Oil 
                 18.35 
                 5.14 
               
               
                   
                 5 cst Base Oil 
                 67.71 
                 82.68 
               
               
                   
                 Total Base Oil Yield 
                 86.06 
                 88.82 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 9 
               
             
            
               
                   
               
               
                 Properties of heavy base oil products 
               
               
                 of Comparative Example 2 and Example 2 
               
            
           
           
               
               
               
               
            
               
                   
                 Comparative 
                   
                 Analysis 
               
               
                 Analysis Item 
                 Example 2 
                 Example 2 
                 Method 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 Initial Boiling Point, ° C. 
                 400 
                 394 
                 GB/T 9168 
               
               
                 20° C. Density, g/cm 3   
                 0.8521 
                 0.8629 
                 GB/T 1884 
               
               
                 Pour Point, ° C. 
                 −18 
                 −21 
                 GB/T 3535 
               
               
                 Cloud Point, ° C. 
                 −5 
                 −15 
                 GB/T 6986-86 
               
               
                 Open Flash Point, ° C. 
                 220 
                 235 
                 GB/T 3536 
               
               
                 Chroma, number 
                 +30 
                 +30 
                 GB/T 3555 
               
               
                 Kinematic Viscosity 
                 34.56 
                 39.39 
                 GB/T 265 
               
               
                 (40° C.), mm 2 /s 
               
               
                 Kinematic Viscosity, 
                 5.713 
                 6.273 
                 GB/T 265 
               
               
                 (100° C.), mm 2 /s 
               
               
                 Viscosity Index 
                 104 
                 105 
                 GB/T 1995 
               
               
                   
               
            
           
         
       
     
     Example 3 
     According to the process shown in  FIG. 4 , the experimental device is the same as that in Comparative Example 1, and the feed stock is a 100N cerate obtained from crude oil by processes of reduced-pressure distillation, furfural refining and acetone-toluene dewaxing, of which the physical and chemical properties are shown in Table 10. Under the process conditions shown in Table 11, the resulting product distribution is shown in Table 12, and the main properties of the products are shown in Table 13. 
     Example 4 
     According to the process shown in  FIG. 4 , the experimental device is the same as that in Comparative Example 1, and the feed stock is a 400N cerate shown in Table 10. Under the process conditions shown in Table 11, the resulting product distribution is shown in Table 12, and the main properties of the products are shown in Table 13. 
     It can be seen from Tables 10 to 13 that the distribution of the product of the isomerization/asymmetrical cracking in Example 3 is similar to those of the products of isomerization/asymmetrical cracking in Examples 1 and 2, the product mainly includes light component products (gas and naphtha) and a 2 cst base oil product, and the yields of the two products are 17.32% and 70.83% respectively, and the diesel yield is 11.87%, indicating a bimodal distribution of a high yield of the light component product and the heavy component product and a low yield of the middle fraction. The product distribution in Example 4 is similar to that in Example 3, and the feature of bimodal distribution is more significant. The pour points and the cloud points of the 2 cst and 6 cst base oil products of Examples 3 and 4 are very low, and the viscosity index of the 6 cst base oil is up to 123, which meets the requirements of API Group III base oil. 
     
       
         
           
               
             
               
                 TABLE 10 
               
             
            
               
                   
               
               
                 Properties of feed stocks of Examples 3 and 4 
               
            
           
           
               
               
               
            
               
                 Analysis Item 
                 100N Cerate 
                 400N Cerate 
               
               
                   
               
            
           
           
               
               
               
            
               
                 Density (20° C.), g/cm 3   
                 0.8319 
                 0.8643 
               
               
                 Kinematic Viscosity (40° C.), mm 2 /s 
                 8.292 
                 41.77 
               
               
                 Kinematic Viscosity (100° C.), mm 2 /s 
                 2.476 
                 7.205 
               
               
                 Viscosity Index 
                 128 
                 136 
               
               
                 Pour Point, ° C. 
                 27 
                 33 
               
               
                 Sulfur Content, μg/g 
                 490 
                 534 
               
               
                 Nitrogen Content, μg/g 
                 176 
                 430 
               
               
                 Composition, % 
               
               
                 Saturated Hydrocarbons 
                 90.11 
                 83.51 
               
               
                 Aromatic Hydrocarbons 
                 9.17 
                 15.35 
               
               
                 Polar Compounds 
                 0.72 
                 1.14 
               
               
                 Distillation Range, ° C. HK 
                 307 
                 370 
               
               
                  5% 
                 342 
                 422 
               
               
                 10% 
                 348 
                 450 
               
               
                 30% 
                 358 
                 469 
               
               
                 50% 
                 367 
                 477 
               
               
                 70% 
                 376 
                 486 
               
               
                 90% 
                 386 
                 498 
               
               
                 95% 
                 392 
                 505 
               
               
                 KK 
                 404 
                 510 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 11 
               
             
            
               
                   
               
               
                 Process conditions of Examples 3 and 4 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 Isomerization- 
                   
               
               
                   
                   
                 Asymmetrical 
               
               
                 Process 
                 Hydrorefining 
                 Cracking 
                 Hydrofinishing 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Conditions 
                 Example 3 
                 Example 4 
                 Example 3 
                 Example 4 
                 Example 3 
                 Example 4 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Average 
                 365 
                 370 
                 320 
                 360 
                 230 
                 230 
               
               
                 Temperature, 
               
               
                 ° C. 
               
               
                 Hydrogen 
                 13.0 
                 13.0 
                 12.0 
                 12.0 
                 12.0 
                 12.0 
               
               
                 Partial 
               
               
                 Pressure, 
               
               
                 MPa 
               
               
                 Volume 
                 1.0 
                 1.0 
                 0.8 
                 0.5 
                 1.33 
                 0.83 
               
               
                 Space 
               
               
                 Velocity, h −1   
               
               
                 Raito of 
                 350 
                 560 
                 350 
                 560 
                 350 
                 560 
               
               
                 Hydrogen to 
               
               
                 Oil, 
               
               
                 Nm 3 /Nm 3   
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 12 
               
             
            
               
                   
               
               
                 Product distributions of Examples 3 and 4 
               
            
           
           
               
               
               
            
               
                   
                 Yield, % 
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Product 
                 Example 3 
                 Example 4 
               
               
                   
                   
               
               
                   
                 Gas + Naphtha 
                 17.32 
                 16.54 
               
               
                   
                 Diesel 
                 11.87 
                  5.81 
               
               
                   
                 2 cst Base Oil 
                 70.81 
                 — 
               
               
                   
                 6 cst Base Oil 
                 — 
                 77.65 
               
               
                   
                 10 cst Base Oil  
                 — 
                 — 
               
               
                   
                 Total Base Oil Yield 
                 70.81 
                 77.65 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 13 
               
             
            
               
                   
               
               
                 Properties of base oil products of Examples 3 and 4 
               
            
           
           
               
               
               
            
               
                   
                 Feed stock 
                   
               
            
           
           
               
               
               
               
            
               
                   
                 100N Cerate 
                 400N Cerate 
                 Analysis 
               
               
                 Product 
                 2 cst base oil 
                 6 cst base oil 
                 Method 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 Density (20° C.), 
                 0.8340 
                 0.8504 
                 GB/T 1884 
               
               
                 g/cm 3   
               
               
                 Pour Point, ° C. 
                 −25 
                 −30 
                 GB/T 3535 
               
               
                 Cloud Point, ° C. 
                 −15 
                 −19 
                 GB/T 6986-86 
               
               
                 Open Flash Point, ° C. 
                 176 
                 214 
                 GB/T 3536 
               
               
                 Chroma, number 
                 +30 
                 +30 
                 GB/T 3555 
               
               
                 Kinematic Viscosity 
                 9.520 
                 35.34 
                 GB/T 265 
               
               
                 (40° C.), mm 2 /s 
               
               
                 Kinematic Viscosity 
                 2.588 
                 6.168 
                 GB/T 265 
               
               
                 (100° C.), mm 2 /s 
               
               
                 Viscosity Index 
                 102 
                 123 
                 GB/T 1995 
               
               
                   
               
            
           
         
       
     
     Example 5 
     According to the process shown in  FIG. 4 , the experimental device is the same as that in Comparative Example 1, and the feed stock is a 650N cerate shown in Table 9, which is a waxy oil obtained from crude oil by processes of reduced-pressure distillation, furfural refining and acetone-toluene dewaxing, and the physical and chemical properties. Under the process conditions shown in Table 14, the resulting product distribution is shown in Table 15, and the main properties of the products are shown in Table 16. 
     Example 6 
     According to the process shown in  FIG. 4 , the experimental device is the same as that in Comparative Example 1, and the feed stock is a 150BS cerate, which is a waxy oil obtained from paraffin-based crude oil by processes of reduced-pressure distillation, propane deasphalting, furfural refining and acetone—toluene dewaxing, and the physical and chemical properties thereof are shown in Table 14. Under the process conditions shown in Table 15, the resulting product distribution is shown in Table 16, and the main properties of the products are shown in Table 17. 
     It can be seen from Tables 14 to 17 that the fractions of 650SN cerate and 150BS cerate are very heavy, and the pour points thereof are very high. With regard to the two types of heavy and waxy feed stocks, the reduction of the pour point of the base oil needs to be up to 78° C. to achieve a pour point of base oil of no higher than −15° C. The features of high yields of small-molecule products (gas and naphtha) and big-molecule products (8 cst and 20 cst base oils) generated by the hydrorefining-isomerization/asymmetrical cracking-hydrofinishing and low yield of the middle fraction oil (diesel +2 cst base oil) are significant. The viscosity index of the heavy product having a low pour point is extremely high, which can be up to 140, and the pour point and the cloud point of the heavy product can be decreased to a very low level. 
     
       
         
           
               
             
               
                 TABLE 14 
               
             
            
               
                   
               
               
                 Properties of feed stocks of Examples 5 and 6 
               
            
           
           
               
               
               
               
            
               
                   
                 650N 
                 150BS 
                 Analysis 
               
               
                 Analysis Item 
                 Cerate 
                 Cerate 
                 Standard 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 Kinematic Density (20° C.), 
                 0.8646 
                 0.8710 
                 GB/T 1884 
               
               
                 g/cm 3   
               
               
                 Kinematic Viscosity (40° C.), 
                 — 
                 — 
                 GB/T 265 
               
               
                 mm 2 /s 
               
               
                 Kinematic Viscosity (100° C.), 
                 9.359 
                 25.10 
                 GB/T 265 
               
               
                 mm 2 /s 
               
               
                 Pour Point, ° C. 
                 63 
                 57 
                 GB/T 3535 
               
               
                 Sulfur Content, μg/g 
                 690 
                 752 
                 ASTM D2622 
               
               
                 Nitrogen Content, μg/g 
                 517 
                 674 
                 ASTM D5762 
               
               
                 Composition, % 
                   
                   
                 SH/T0753 
               
               
                 Saturated Hydrocarbons 
                 87.65 
                 69.1 
               
               
                 Aromatic Hydrocarbons 
                 11.31 
                 23.0 
               
               
                 Polar compounds 
                 1.04 
                 7.9 
               
               
                 Simulated Distillation, ° C. HK 
                 380 
                 410 
                 ASTM D2887 
               
               
                  5% 
                 480 
                 465 
               
               
                 10% 
                 505 
                 507 
               
               
                 30% 
                 522 
                 562 
               
               
                 50% 
                 540 
                 609 
               
               
                 70% 
                 551 
                 667 
               
               
                 90% 
                 565 
                 — 
               
               
                 95% 
                 569 
                 — 
               
               
                 KK 
                 589 
                 — 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 15 
               
             
            
               
                   
               
               
                 Process conditions of Examples 5 and 6 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 Isomerization- 
                   
               
               
                   
                   
                 Asymmetrical 
               
               
                 Reaction 
                 Hydrorefining 
                 Cracking 
                 Hydrofinishing 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Conditions 
                 Example 5 
                 Example 6 
                 Example 5 
                 Example 6 
                 Example 5 
                 Example 6 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Average 
                 370 
                 370 
                 350 
                 375 
                 230 
                 230 
               
               
                 Temperature, ° C. 
               
               
                 Hydrogen 
                 14.5 
                 14.5 
                 14.0 
                 14.0 
                 14.0 
                 14.0 
               
               
                 Partial Pressure, 
               
               
                 MPa 
               
               
                 Liquid hourly 
                 0.75 
                 0.75 
                 0.5 
                 0.5 
                 1.25 
                 1.25 
               
               
                 Volume Space 
               
               
                 Velocity, h −1   
               
               
                 Raito of 
                 750 
                 750 
                 750 
                 750 
                 750 
                 750 
               
               
                 Hydrogen to 
               
               
                 Oil, Nm 3 /Nm 3   
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 16 
               
             
            
               
                   
               
               
                 Product distributions of Examples 5 and 6 
               
            
           
           
               
               
               
            
               
                   
                 Yield, % 
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Product 
                 Example 5 
                 Example 6 
               
               
                   
                   
               
               
                   
                 Fuel Gas + Naphtha 
                 19.31 
                 18.76 
               
               
                   
                 Diesel 
                  4.03 
                  2.13 
               
               
                   
                 2 cst Base Oil 
                  8.77 
                  3.43 
               
               
                   
                 6 cst Base Oil 
                 — 
                 14.77 
               
               
                   
                 8 cst Base Oil 
                 67.89 
                 — 
               
               
                   
                 20 cst base oil  
                 — 
                 60.91 
               
               
                   
                 Total Base Oil Yield 
                 76.66 
                 79.11 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 17 
               
             
            
               
                   
               
               
                 Properties of heavy base oil products of Examples 5 and 6 
               
            
           
           
               
               
               
            
               
                   
                 Feed stock 
                   
               
            
           
           
               
               
               
               
            
               
                   
                 650N Cerate 
                 150BS Cerate 
                 Analysis 
               
               
                 Product Properties 
                 10 cst base oil 
                 20 cst base oil 
                 Method 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 Density (20° C.), 
                 0.8495 
                 0.8542 
                 GB/T 1884 
               
               
                 g/cm 3   
               
               
                 Pour Point, ° C. 
                 −19 
                 −18 
                 GB/T 3535 
               
               
                 Cloud Point, ° C. 
                 −8 
                 −6 
                 GB/T 6986-86 
               
               
                 Open Flash Point, ° C. 
                 268 
                 293 
                 GB/T 3536 
               
               
                 Chroma, number 
                 +30 
                 +30 
                 GB/T 3555 
               
               
                 Kinematic Viscosity 
                 45.17 
                 151.1 
                 GB/T 265 
               
               
                 (40° C.), mm 2 /s 
               
               
                 Kinematic Viscosity 
                 8.050 
                 19.08 
                 GB/T 265 
               
               
                 (100° C.), mm 2 /s 
               
               
                 Viscosity Index 
                 152 
                 144 
                 GB/T 1995 
               
               
                   
               
            
           
         
       
     
     Example 7 
     A hydrocracking UCO is a heavy fraction oil generated from a reduced-pressure fraction oil by a hydrorefining-hydrocracking reaction, the impurities such as sulfur and nitrogen have been removed, and most of the aromatic hydrocarbons have been subjected to hydrosaturation and ring-opening, such that the hydrocracking UCO needs not to be subjected to a hydrorefining reaction to remove sulfur and nitrogen, and needs not to be subjected to a hydrorefining-reaction to improve the viscosity index, and the isomerization-asymmetrical cracking/hydrofinishing shown in  FIG. 6  can be adopted. Hydrogenation evaluation was performed on the experimental device, and a hydrocracking UCO having the physical and chemical properties shown in Table 18 was uses as a feed stock. Under the process conditions shown in Table 19, the resulting product distribution is shown in Table 20, and main properties of the product are shown in Table 21. It can be seen from Tables 18 to 21 that the hydrocracking UCO has a low sulfur content and nitrogen content, and a high viscosity index and pour point. After an isomerization-asymmetrical cracking/hydrofinishing with mild process conditions, the product distribution has features of high yields of small-molecule products (gas and naphtha) and big-molecule products (8 cst and 20 cst base oils) and low yield of the middle fraction oil (diesel +2 cst base oil), and the cloud point of the product achieves −15° C. 
     
       
         
           
               
             
               
                 TABLE 18 
               
             
            
               
                   
               
               
                 Properties of the feed stock of Example 7 
               
            
           
           
               
               
               
            
               
                 Analysis Item 
                 Hydrocracking UCO 
                 Analysis Standard 
               
               
                   
               
            
           
           
               
               
               
            
               
                 Kinematic Density (20° C.), 
                 0.8245 
                 GB/T 1884 
               
               
                 g/cm 3   
               
               
                 Kinematic Viscosity (40° C.), 
                 15.74 
                 GB/T 265 
               
               
                 mm 2 /s 
               
               
                 Kinematic Viscosity (100° C.), 
                 3.824 
                 GB/T 265 
               
               
                 mm 2 /s 
               
               
                 Viscosity Index 
                 139 
                 GB/T 1995 
               
               
                 Pour Point, ° C. 
                 33 
                 GB/T 3535 
               
               
                 Sulfur Content, μg/g 
                 2.787 
                 ASTM D2622 
               
               
                 Nitrogen Content, μg/g 
                 1.778 
                 ASTM D5762 
               
               
                 Composition, % 
                   
                 SH/T0753 
               
               
                 Saturated Hydrocarbons 
                 98.75 
               
               
                 Aromatic Hydrocarbons 
                 1.11 
               
               
                 Polar Compounds 
                 0.14 
               
               
                 Distillation Range, ° C. HK 
                 331 
                 ASTM D2887 
               
               
                  5% 
                 367 
               
               
                 10% 
                 375 
               
               
                 30% 
                 392 
               
               
                 50% 
                 409 
               
               
                 70% 
                 433 
               
               
                 90% 
                 473 
               
               
                 95% 
                 491 
               
               
                 KK 
                 516 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 19 
               
             
            
               
                   
               
               
                 Process conditions of Example 7 
               
            
           
           
               
               
               
            
               
                   
                 Isomerization- 
                   
               
               
                   
                 Asymmetrical 
               
               
                 Process Conditions 
                 Cracking 
                 Hydrofinishing 
               
               
                   
               
            
           
           
               
               
               
            
               
                 Average Temperature, ° C. 
                 310 
                 230 
               
               
                 Hydrogen Partial Pressure, 
                 12.4 
                 12.4 
               
               
                 MPa 
               
               
                 Liquid Hourly Volume Space 
                 1.0 
                 1.7 
               
               
                 Velocity, h −1   
               
               
                 Raito of Hydrogen to Oil, Nm 3 /Nm 3   
                 350 
                 350 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 20 
               
             
            
               
                   
               
               
                 Product distribution of Example 7 
               
            
           
           
               
               
               
            
               
                   
                 Product 
                 Product Yield, % 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                 Fuel Gas + Naphtha 
                 15.9 
               
               
                   
                 Diesel 
                 4.66 
               
               
                   
                 2 cst Base Oil 
                 1.09 
               
               
                   
                 4 cst Base Oil 
                 78.35 
               
               
                   
                 Total Base Oil Yield 
                 79.44 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 21 
               
             
            
               
                   
               
               
                 Properties of the 4 cst base oil product of Example 7 
               
            
           
           
               
               
               
            
               
                 Analysis Item 
                 4 cst Base Oil 
                 Analysis Method 
               
               
                   
               
            
           
           
               
               
               
            
               
                 Density (20° C.), g/cm 3   
                 0.8288 
                 GB/T 1884 
               
               
                 Pour Point, ° C. 
                 −18 
                 GB/T 3535 
               
               
                 Cloud Point, ° C. 
                 −15 
                 GB/T 6986-86 
               
               
                 Open Flash Point, ° C. 
                 204 
                 GB/T 3536 
               
               
                 Chroma, number 
                 +30 
                 GB/T 3555 
               
               
                 Kinematic Viscosity (40° C.), 
                 17.58 
                 GB/T 265 
               
               
                 mm 2 /s 
               
               
                 Kinematic Viscosity (100° C.), 
                 3.974 
                 GB/T 265 
               
               
                 mm 2 /s 
               
               
                 Viscosity Index 
                 124 
                 GB/T 1995 
               
               
                   
               
            
           
         
       
     
     Example 8 
     An Fischer-Tropsch wax is a hydrocarbon product with high-carbon-number long-chain normal paraffins as the main component synthesized in the presence of a Co-based catalyst. The wax mainly includes C 8  to C 45  normal paraffins, and the distribution of maximum carbon number is around C 18 . After cutting off components distillated at less than 320° C., the distribution of maximum carbon number of the Fischer-Tropsch wax is slight shifted to a higher carbon number.  FIG. 3  shows carbon number distribution of a product synthesized in the presence of a Co-based catalyst and an Fischer-Tropsch wax after cutting off components distillated at less than 320° C. by atmospheric distillation. The Fischer-Tropsch wax substantially does not contain impurities such as sulfur and nitrogen and aromatic hydrocarbons, and needs not to be subjected to a hydrorefining reaction to remove sulfur and nitrogen, and needs not to be subjected to a hydrorefining reaction to improve the viscosity index, and can be directly subjected to an isomerization-asymmetrical cracking/hydrofinishing shown in  FIG. 6 . The experimental device of isodewaxing is the same as that in Comparative Example 1, the components distillated at more than 320° C. in the Fischer-Tropsch wax was used as a feed stock, of which the physical and chemical properties are shown in Table 22. Under the process conditions shown in Table 23, the resulting product distribution is shown in Table 24, and main properties of the product are shown in Table 25. It can be seen from Tables 22 to 25 that, the distribution of the product after the isomerization-asymmetrical cracking/hydrofinishing has the feature of bimodal distribution. Meanwhile, the cloud point of the 2 cst base oil product achieves −6° C., and the viscosity index is up to 162. 
     
       
         
           
               
             
               
                 TABLE 18 
               
             
            
               
                   
               
               
                 Properties of the feed stock of Example 8 
               
            
           
           
               
               
               
            
               
                 Analysis Item 
                 Fischer-Tropsch wax 
                 Analysis Standard 
               
               
                   
               
            
           
           
               
               
               
            
               
                 20° C. Density, g/cm 3   
                 0.8536 
                 GB/T 1884 
               
               
                 100° C. Viscosity, mm 2 /s 
                 4.673 
                 GB/T 265 
               
               
                 Pour Point, ° C. 
                 59 
                 GB/T 3535 
               
               
                 Sulfur Content, μg/g 
                 Not detected 
                 ASTM D2622 
               
               
                 Nitrogen Content, μg/g 
                 Not detected 
                 ASTM D5762 
               
               
                 Distillation Range, ° C. HK 
                 316 
                 ASTM D2887 
               
               
                  5% 
                 366 
               
               
                 10% 
                 375 
               
               
                 30% 
                 397 
               
               
                 50% 
                 409 
               
               
                 70% 
                 425 
               
               
                 90% 
                 495 
               
               
                 95% 
                 531 
               
               
                 KK 
                 549 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 18 
               
             
            
               
                   
               
               
                 Process conditions of Example 8 
               
            
           
           
               
               
               
            
               
                   
                 Isomerization- 
                   
               
               
                   
                 Asymmetrical 
                 Supplementary 
               
               
                 Process Condition 
                 Cracking 
                 Refining 
               
               
                   
               
            
           
           
               
               
               
            
               
                 Average Temperature, ° C. 
                 360 
                 230 
               
               
                 Hydrogen Partial Pressure, 
                 12.4 
                 12.4 
               
               
                 MPa 
               
               
                 Volume Space Velocity, h −1   
                 0.5 
                 0.85 
               
               
                 Raito of Hydrogen to Oil, Nm 3 /Nm 3   
                 750 
                 750 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 19 
               
             
            
               
                   
               
               
                 Product distribution of Example 8 
               
            
           
           
               
               
               
            
               
                   
                 Product 
                 Product Yield, % 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                 Fuel Gas + Naphtha 
                 23.7 
               
               
                   
                 Diesel 
                 6.63 
               
               
                   
                 2 cst Base Oil Yield 
                 69.67 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 20 
               
             
            
               
                   
               
               
                 Properties of the product of Example 8 
               
            
           
           
               
               
               
            
               
                 Product 
                 2 cst Base Oil 
                 Analysis Method 
               
               
                   
               
            
           
           
               
               
               
            
               
                 20° C. Density, g/cm 3   
                 0.8416 
                 GB/T 1884 
               
               
                 Pour Point, ° C. 
                 −15 
                 GB/T 3535 
               
               
                 Cloud Point, ° C. 
                 −6 
                 GB/T 6986-86 
               
               
                 Open Flash Point, ° C. 
                 179 
                 GB/T 3536 
               
               
                 Chroma, number 
                 +30 
                 GB/T 3555 
               
               
                 40° C. Kinematic Viscosity, mm 2 /s 
                 9.756 
                 GB/T 265 
               
               
                 100° C. Kinematic Viscosity, mm 2 /s 
                 2.912 
                 GB/T 265 
               
               
                 Viscosity Index 
                 162 
                 GB/T 1995 
               
               
                   
               
            
           
         
       
     
     INDUSTRIAL APPLICABILITY 
     In the present invention, the highly waxy heavy fraction oil having an initial boiling point of 300° C. to 460° C., a wax content of no lower than 5%, a pour point of no lower than −20° C., and a cloud point of no lower than −5° C. is used as a feed stock to produce a API (American Petroleum Institute) Group II or Group III (see the classification standard in Table 1) type lubricating base oil having a low pour point and a high viscosity index by a hydrorefining-isomerization/asymmetrical cracking-hydrofinishing three-stage hydrogenation process, wherein a critical reaction process of hydrogenation isomerization-asymmetrical cracking is involved. The isomerization/asymmetrical cracking reaction include two chemical reactions, namely, an isomerization reaction and an asymmetrical cracking reaction. When the isomerization is carried out, the linear paraffins having a high pour point and big-molecular and less-branched iso-paraffins with high pour point and high viscosity index in the feed stock are subjected to an asymmetrical cracking reaction at the same time. The so-called asymmetrical cracking reaction refers to a hydrocracking reaction occurs at a C—C bond close to the two ends of the paraffin, and a big-molecule and a small molecule are generated, wherein the small molecule belongs to the gas and naphtha fraction, and the big-molecule belongs to the lubricating base oil fraction. 
     In the asymmetrical cracking reaction, a 10-membered ring composite molecular sieve having a special pore structure is used as a catalyst support to enhance the restriction of the catalyst pores on the internal diffusion of normal paraffins and less-branched iso-paraffins, such that the cracking reaction preferably occurs at a position close to the two ends of the normal paraffins, thereby significantly improving the yield of the base oil product, especially that of the heavy base oil product. 
     The isomerization/asymmetrical cracking reaction is characterized in that the product has a bimodal distribution, that is, the yields of the light components (gas and naphtha) and the heavy base oil having a low pour point and a low cloud point are high, and the yield of a middle fraction oil (kerosene and diesel) is low. The method can solve the problems of low yield of target product, high pour point and cloud point, high aromatic content and low viscosity index and the like in the production of lubricating base oil from heavy highly waxy oil by physical processes such as solvent refining and solvent dewaxing and/or chemical processes such as hydrotreating, catalytic dewaxing, hydrotreating and hydrocracking. The process has the advantages of good adaptability to heavy highly waxy feed stock, high yield of the heavy base oil product with good properties such as viscosity, viscosity index, pour point and cloud point of the product and co-production of naphtha and a small amount of a middle fraction oil. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 API lubricating base oil Classification standard 
               
            
           
           
               
               
               
               
            
               
                   
                 Saturated Hydrocarbon 
                   
                   
               
               
                 Class 
                 Content, % 
                 Sulfur Content, % 
                 Viscosity Index 
               
               
                   
               
               
                 I 
                 &lt;90 
                 and/or &gt;0.03 
                 80~120 
               
               
                 II 
                 ≮90 
                 ≯0.03 
                 80~120 
               
               
                 III 
                 ≮90 
                 ≯0.03 
                 &gt;120 
               
            
           
           
               
               
            
               
                 IV 
                 poly-α-olefin (PAO) 
               
               
                 V 
                 Various base oils except I~IV