Processing biomass in conventional oil refineries:Production of high quality diesel by hydrotreating vegetable oils in heavy vacuum oil mixtures

摘要

Renewable liquid alkanes can be produced by hydrotreating of vegetable oils and vegetable oil-heavy vacuum oil(HVO)mixtures at standard hydrotreating conditions(i.e.300-450 deg C)with conventional hydrotreating catalysts(sulfided NiMo/Al2O3).The reaction pathway involves hydrogenation of the C=C bonds of the vegetable oils followed by alkane production by three different pathways:decarbonylation,decarboxylation and hydrodeoxygenation.The straight chain alkanes can undergo isomerization and cracking to produce lighter and isomerized alkanes.The carbon molar yield of straight chain C15-C18 alkanes was 71% on a carbon basis(the maximum theoretical yield for these products is 95%)for hydrotreating of pure vegetable oil under optimal reaction conditions.The rate of alkane production from pure sunflower oil is greater than the rate of hydrodesulfurization of a HVO with a 1.48 wt% sulfur content(e.g.100% conversion of sunflower oil at 350 deg C compared to 41% conversion of sulfur).The yield of straight chain alkanes increases when sunflower-oil is mixed with HVO,illustrating that dilution of HVO can improve the reaction chemistry.For example,with a 5 wt% sunflower oil-95 wt% HVO feed the maximum theoretical straight chain C15-C18 yield from the sunflower oil was higher(87%)than it was with the pure sunflower oil(75%).Mixing the sunflower oil with HVO does not decrease the rate of desulfurization indicating that sunflower oil does not inhibit the hydrotreating of HVO.