Synthetic Middle-Distillate-Range Hydrocarbons via Catalytic Dimerization of Branched C6–C8 Olefins Derived from Renewable Dimethyl Ether

Abstract

2,3,3-Trimethyl-1-butene (triptene) and other branched C6–C8 olefins, having structures characteristic of the products from the low-temperature acid-catalyzed homologation of dimethyl ether (DME), were converted to distillate-range hydrocarbons (C10–C20) with high selectivity via dimerization over a commercial ion-exchange acidic resin (Amberlyst-35) under liquid-phase stirred-batch conditions operating at ambient pressure. Triptene conversion and dimer (2,2,3,5,5,6,6-heptamethyl-3-heptene) production were monitored with time at different temperatures (60, 80, and 100 °C). The dimer production rate increased with increasing temperature; however, dimer concentration decreased with increasing temperature due to competing side reactions. Dimerization, as compared to cracking, isomerization, and oligomerization, was the dominant reaction pathway during the first hours of reaction at all temperatures. Dimerization at 100 °C achieved a conversion of 35% and a molar selectivity to the desired dimer of 71% in 2 h...