<p>Here we report the synthesis, characterization and
activity of tunable Pd-doped hydrotalcites (Pd-HTs) for the decarbonylation of
furfural, hydroxymethylfurfural (HMF),
aromatic and aliphatic aldehydes under microwave conditions. The
decarbonylation activity reported is a notable improvement over prior
heterogeneous catalysts for this process. Furfural decarbonylation is optimized
in a benign solvent compatible with biomass processing - ethanol, under
relatively mild conditions and short reaction times. HMF selectively affords
excellent yields of furfuryl alcohol with no humin formation, but longer
reaction can also afford furan via tandem alcohol dehydrogenation and
decarbonylation. Yields of substituted benzaldehydes are related to calculated
Mulliken charge of the carbonyl carbon. The activity and selectivity
differences can be traced to loading-dependent differences in Pd speciation on
the catalysts. Poisoning studies show inverse correlation between Pd loading
and metal leaching: Pd-HTs with lowest Pd loading, which consist of highly
dispersed and oxidized Pd species, operate heterogeneously with
negligible metal leaching. Recycling experiments
are consistent with this trend, offering potential for further optimization to
improve robustness.</p>
Catalytic upgrading of α-angelica lactone to levulinic acid esters under mild conditions over heterogeneous catalysts
