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 °C. Blends of 10%, 15%, and
20% RCFP biocrude in light gas oil were also upgraded over a NiMo
hydrotreating catalyst at 350 °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.