(13g) Mechanistic and Kinetic Analysis of the Aqueous Phase Hydrogenation of Levulinic Acid Over Ru/C

Mechanistic and
kinetic analysis of the aqueous phase hydrogenation of Levulinic Acid over Ru/C

Omar A. Abdelrahman and Jesse Q. Bond

The conversion of Levulinic Acid (LA) to gamma-Valerolactone
(GVL) via catalytic hydrogenation has been shown to be a viable pathway for
turning LA into a more versatile feedstock chemical. The capability to produce
GVL from LA in a dilute aqueous solution as it is currently produced would
provide a cost effective conversion strategy, hence warranting the
investigation of the aqueous phase hydrogenation of LA. This could possibly be
achieved by the use of Ruthenium supported on Carbon in a reducing environment.
In order to evaluate this option, the poorly understood aqueous phase
hydrogenation of LA was investigated by undertaking a kinetic as well as a
mechanistic study of the process. Experiments considered two pathways from LA
to GVL, which differ according to the order in which subsequent hydrogenation
and dehydration occur (Figure 1). Through aqueous phase kinetic experiments, the
pathway in which hydrogenation precedes dehydration is proposed to be dominant
for the production of GVL, particularly at low temperatures. A kinetic model
for the overall hydrogenation is proposed, and estimated reaction orders and
apparent activation energies are reported. Significant loss in activity was
observed with the Ru/C catalyst, which warranted an investigation into the nature
as well as extent of deactivation. Remedies for the severe deactivation of the
catalyst primarily involve rational selection of catalyst support to minimize deactivation
via attrition and leaching.   

Figure 1 - Proposed mechanistic pathways for the production
of GVL from LA