Method for preparing high viscosity index poly-alpha-olefin

A method for preparing a poly-alpha-olefin comprising subjecting an α-olefin to a polymerization reaction in the presence of a metallocene catalyst to obtain the poly-alpha-olefin,

• wherein the polymerization reaction is carried out in the absence of a solvent,
• the metallocene catalyst is formed of, or is formed by interaction between, a metallocene compound and an activator, the metallocene compound having a structural formula of formula (I):
• wherein M is titanium, zirconium, or hafnium;
• X1 and X2 are each independently selected from a group consisting of halogens,
• R1, R2, R3, R4, R5, R6, R7, and R8 are each independently selected from a group consisting of H, C1-C20 alkyl, C6-C20 aryl, C1-C20 substituted alkyl, C6-C20 substituted aryl, heteroatom substituted C1-C20 alkyl, and heteroatom substituted C6-C20 aryl,
• Z is silicon that achieves valence saturation through a substituent, wherein the substituent is C1-C20 alkyl, C1-C20 substituted alkyl, or C6-C20 aryl, and
• wherein the activator is an alkylaluminium and a borate, and a molar ratio of the alkylaluminium to the borate is (0.05-50):1,
• wherein by calculating the alkylaluminium based on Al and the metallocene compound based on M, a molar ratio of the alkylaluminium to the metallocene compound is 0.1:1 to 1,000:1,
• wherein the alkylaluminium is trimethylaluminum, triethylaluminum, triisopropylaluminum, tri-n-propylaluminum, triisobutylaluminum, tri-n-butylaluminum, triisoamylaluminum, tri-n-pentylaluminum, triisohexylaluminum, tri-n-hexylaluminum, triisoheptylaluminum, triisooctylaluminum, tri-n-octylaluminum, tri-n-heptylaluminum, triisononylaluminum, tri-n-nonylaluminum, triisodecylaluminum, or tri-n-decylaluminum,
• wherein the borate is dimethylanilinium tetrakis(pentafluorophenyl) borate, diethylanilinium tetrakis(pentafluorophenyl) borate, dibutylanilinium tetrakis(pentafluorophenyl) borate, trimethylammonium tetrakis(pentafluorophenyl) borate, diethylammonium tetrakis(pentafluorophenyl) borate, or tributylammonium tetrakis(pentafluorophenyl) borate.