Ethylaluminum Sesquichloride-Mediated Hydro-Alkyl Addition: A New Pathway for Producing Polyalphaolefins from Metallocene-Catalyzed High-Carbon α-Olefin Dimer and Chlorinated Alkanes

Currently, commercial low viscosity polyalphaolefins (PAOs) are primarily produced by using traditional BF3-catalyzed systems. However, due to the catalyst’s toxic, corrosive, and environmentally hazardous gaseous properties, researchers are actively investigating alternative synthetic methods for low-viscosity PAO production. In this study, we present a novel approach that employs ethylaluminum sesquichloride-mediated hydro-alkylation to convert high-carbon α-olefin dimers (which are not suitable as direct lubricant base stocks) and chlorinated alkanes into ultralow viscosity and medium-high viscosity PAO products. Chlorinated hydrocarbons demonstrate dual reactivity in this process. By incorporating triethylsilane as an effective hydrogen donor and precisely controlling the olefin dimer/chloroalkane ratio, we successfully synthesized PAO2 and PAO3.5 with ultralow pour points (−78 °C) and a selectivity of 97%, achieving low-temperature performance that is comparable to commercial standards. Excess chlorinated hydrocarbons undergo β-hydrogen transfer, producing tertiary carbocations and α-olefins, which then undergo polymerization to yield PAO20 with an enhanced high viscosity index. Gas chromatography (GC) and nuclear magnetic resonance (NMR) analyses revealed that the steric hindrance of chlorinated hydrocarbons plays a significant role in influencing reaction activity and the architecture of the resulting products. Only terminal olefin adducts were detected. Molecular topology analysis indicated that compact molecular dimensions promote pour point depression in base oils. This study utilized hydro-alkylation to transform chlorinated alkanes into high-value PAO base oils, yielding ultralow viscosity polyalphaolefins with well-defined architectures. By achieving precise molecular control through substrate modulation, we established a novel technical approach for lubricant molecular engineering with a correlation between structure and performance.