Energy & Fuels, Vol.22, No.5, 3299-3302, 2008
Highly efficient zirconium-catalyzed batch conversion of 1-butene: A new route to jet fuels
Quantitative conversion of 1-butene to a Schultz-Flory distribution of oligomers has been accomplished by use of Group 4 transition-metal catalysts in the presence of methylaluminoxane (MAO). The oligomerization reaction was carried out at ambient temperature in a sealed reaction vessel with complete conversion of 1-butene at catalyst turnover numbers of > 17 000. The combination of high catalyst activity without concomitant production of high polymer led to a highly efficient production of new hydrocarbon jet fuel candidates. The reaction proceeds with high regioselectivity; however, because achiral catalysts were used, several diastere-oisomeric structures were produced and observed in the gas chromatography-mass spectrometry (GC-MS) chromatograms. The single and specific dimer formed in the reaction, 2-ethyl-l-hexene, was easily removed by distillation and then dimerized using acid catalysis to afford a mixture of mono-unsaturated C-16 compounds. Changes in the oligomerization catalyst led to production of fuels with excellent cold-flow viscosity without the need for a high-temperature distillation. Thus, removal of the dimer followed by catalytic hydrogenation (PtO2) led to a 100% saturated hydrocarbon fuel with a density of 0.78 g/mL, a viscosity of 12.5 cSt at -20 degrees C (ASTM 445), and a calculated heat of combustion of 44+ MJ/kg. By back-addition of hydrogenated dimer in varying amounts (6.6, 11.5, and 17 wt %), it was possible to tailor the viscosity of the fuel (8.5, 7, and 6.5 cSt, respectively).