Integrated reactive catalytic fast pyrolysis

Abstract

This study investigates hydrotreating biocrude produced by reactive catalytic fast pyrolysis (RCFP), a direct biomass liquefaction process that combines a robust hydrodeoxygenation catalyst for in situ pyrolysis with excess hydrogen at ambient (low) pressure. The RCFP process leverages advantages from catalytic fast pyrolysis (process simplicity and improved biocrude quality) and biomass hydropyrolysis (enhanced hydrodeoxygenation) to produce a thermally stable biocrude that can be upgraded in a single hydroprocessing step or coprocessed with petroleum refining intermediates to produce gasoline- and diesel-range hydrocarbons. RCFP biocrude (9.4 kg, 19.3 wt % oxygen, dry basis) was hydrotreated continuously for 144 h, in a pilot-scale hydroprocessing unit, at 138 barg (2000 psig) hydrogen pressure, 0.31 h(-1) space velocity, and an average temperature of 300 degrees C. Blends of 10%, 15%, and 20% RCFP biocrude in light gas oil were also upgraded over a NiMo hydrotreating catalyst at 350 degrees C in hydrogen at 50-70 barg (725-1015 psig). The stand-alone hydrotreating results indicate that, even though there was no pressure drop increase indicative of reactor fouling, hydrotreating catalyst deactivation was evident as the product density increased from 0.852 to 0.955 kg/L after 144 h time-on-stream. Additionally, the oxygen content of the upgraded liquid product increased from 1.4 wt % to 5.5 wt % over the course of the experiment. In the coprocessing test, little or no catalyst deactivation was observed with the 10% RCFP blend on the basis of the density of the hydrotreated products. However, the hydrotreating catalyst activity was lower during upgrading of the 20% and 15% blends. On the basis of hydrodesulfurization of light gas oil, the relative activity of the hydrotreating catalyst decreased by 40% during the 1000 h coprocessing test. Fortunately, this level of deactivation measured at this small scale does not correlate to a prohibitively large deactivation rate at the industrial scale.