(17d) Catalytic Bio-Oil Upgrading With Continuous Flow Microreactors

We present a high
pressure and high temperature microreactor platform for investigation of multiphase
catalytic bio-oil upgrading to increase the H/C ratio. The continuous flow
platform facilitates extraction of kinetic data. A multichannel packed-bed
microreactor has been microfabricated from silicon
and Pyrex, as shown in the figure below. To achieve rapid kinetic data, the
system is integrated with two in-line characterization tools: attenuated total reflection(ATR)- FTIR for liquid phase analysis and quadrupole mass spectrometer for gas phase analysis. The
system has the advantage of handling experiments with small amount of catalyst
(~10mg) and reagent. However, such small quantities pose challenges in
analysis. A specific system and a procedure to address these hurdles will be
presented.

Using this microreactor
platform, we investigated liquid phase hydrogenation and hydrodeoxygenation
mechanisms of lignin fragments such as phenol, anisole, guaiacol
and vanillin. Hydrogenation of phenol using water as solvent has been achieved with
99% selectivity to cyclohexanone at 100% conversion
using a Pd/Carbon catalyst. Our data suggest that
further hydrogenation of cyclohexanone to cyclohexanol is the slower step. High selectivity has been
also obtained for hydrodeoxygenation of vanillin to creosol
at 100% conversion.  To gain mechanistic
insights, we studied the effects of temperature, hydrogen pressure, residence
time, and feed composition on conversion and selectivity.
Based on the experimental conditions explored, mechanistic propositions are also
made. Finally, the influence of solvent as well as catalyst support on
selectivity for the studied reactions will be discussed.