Production of advanced biofuels: Co-processing of upgraded pyrolysis oil in standard refinery units

摘要

One of the possible process options for the production of advanced biofuels is the co-processing of upgraded pyrolysis oil in standard refineries. The applicability of hydrodeoxygenation (HDO) was studied as a pyrolysis oil upgrading step to allow FCC co-processing. Different HDO reaction end temperatures (230-340 °C) were evaluated in a 5 L autoclave, keeping the other process conditions constant (total 290 bar, 5 wt.% Ru/C catalyst), in order to find the required oil product properties necessary for successful FCC co-processing (miscibility with FCC feed and good yield structure: little gas/ coke make and good boiling range liquid yields). After HDO, the upgraded pyrolysis oil underwent phase separation resulting in an aqueous phase, some gases (mainly CO2 and CH4), and an oil phase that was further processed in a Micro-Activity Test (MAT) reactor (simulated FCC reactor). Although the oil and aqueous phase yields remained approximately constant when the HDO reaction temperature was increased, a net transfer of organic components (probably hydrodeoxygenated sugars) from the aqueous phase to the oil phase was observed, increasing the carbon recovery in the oil product (up to 70 wt.% of the carbon in pyrolysis oil). The upgraded oils were subsequently tested in a lab scale catalytic cracking unit (MAT reactor), assessing the suitability of HDO oils to be used as FCC feed. In spite of the relatively high oxygen content (from 17 to 28 wt.%, on dry basis) and the different properties of the HDO oils, they all could be successfully dissolved in and co-processed (20 wt.%) with a Long Residue, yielding near normal FCC gasoline (44-46 wt.%) and Light Cycle Oil (23-25 wt.%) products without an excessive increase of undesired coke and dry gas, as compared to the base feed only. Near oxygenate-free bio-hydrocarbons were obtained, probably via hydrogen transfer from the Long Residue. In this way, we have demonstrated on a laboratory scale that it is possible to produce hydrocarbons from ligno-cellulosic biomass via a pyrolysis oil upgrading route. The much higher coke yields obtained from the catalytic cracking of undiluted HDO oil showed the importance of co-processing using a refinery feed as a diluent and hydrogen transfer source.