Alkylation of Tetralin with Butene/Propylene Catalyzed by Ionic Liquid and Its Lubricating Properties

Alkyltetralins similar to naphthenic base oil were successfully synthesized by Friedel–Crafts alkylation of tetralin with short-chain α-olefins (C3/C4), where the applied chemical feedstock could be obtained from coal chemical industry with ease. The Et3NHCl-AlCl3 ionic liquid (IL) as catalyst exhibited excellent catalytic performance for alkylation of tetralin with n-butene or propylene. The reaction conditions were investigated in detail to achieve the high selectivity toward multi-alkyltetralins, and the selectivity for multi-alkyltetralins could reach as high as 90% with the complete conversion of tetralin. For comparison, three alkyltetralins with various side-chain alkyl groups and number of side-chains on tetralin were isolated, which behaved as lubricating base oils for investigation. The synthetic oils exhibited an excellent low temperature fluidity, and good potential for compatibility with additives. Di-propyltetralins (DPT) and di-butyltetralins (DBT) displayed the lower friction and wear values than mono-butyltetralins (MBT), which had comparable tribological properties to the commercial naphthenic base oil 4006 (N4006).