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

A method for producing a lubricating base oil with a low cloud point and a high viscosity index, wherein the cloud point is lower than −5° C., and the viscosity index is higher than 120, the method comprises:

• producing a lubricating base oil by a hydrorefining-isomerization/asymmetrical cracking-hydrofinishing in the presence of hydrogen, 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 a raw material;
• (1) during the hydrorefining process, a wax-containing heavy feed stock contacts a pre-refining catalyst, and is subjected to desulfurization, denitrogenation, aromatic saturation and a ring-opening reaction, a light product generated in the hydrorefining process is separated by a stripping column as a byproduct, and a heavy product enters an isomerization-asymmetrical cracking process;
• the operating conditions of the hydrorefining process are:
• reaction temperature:
• 350° C. to 410° C., hydrogen partial pressure:
• 10 MPa to 18 MPa, space velocity:
• 0.5 h−1 to 2.0 h−1, volume ratio of hydrogen to oil:300 Nm3/m3 to 1000 Nm3/m3;
• the pre-refining catalyst comprises 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;
• (2) during the hydrogenation isomerization-asymmetrical cracking process, the heavy product generated in the hydrorefining process contacts an isomerization-asymmetrical cracking catalyst, wax-containing component having a high pour point is subjected to an isomerization-asymmetrical cracking reaction, and is converted into a an isomer and an asymmetrical cracking product having a low pour point, which then directly enters a hydrofinishing process;
• the operating conditions of the hydrogenation isomerization-asymmetrical cracking process 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 Nm3/m3 to 1000 Nm3/m3;
• the catalyst:
• the content of mesoporous molecular sieve is 40% to 80%, the content of Pt and/or Pd is 0.3 wt % to 0.7 wt %, and alumina as the balance;
• (3) during the hydrofinishing process, an isomerization-asymmetrical cracking reaction product having a low pour point contacts a hydrofinishing catalyst, residual aromatics and olefins generated by the asymmetrical cracking reaction are hydrogenated and saturated, and the resulting product is separated by a fractionating column to obtain a lubricating base oil and gaseous hydrocarbons, naphtha and middle fraction oil;
• the catalyst comprises amorphous silica-alumina and at least one group VIII noble metal, the weight ratio of SiO2:Al2O3 is 1:1˜9, the average pore size is 1.0 nm to 5.0 nm, the pore volume is 0.3 ml/g to 1.0 mug, the BET specific surface area is 260 m2/g to 450 m2/g;
• the noble metal is Pt and/or Pd, and the content of the noble metal is 0.3 wt % to 0.6 wt %;
• and
• 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 Nm3/m3 to 1000 Nm3/m3.