Reactions of 2‑Methyltetrahydropyran on Silica-Supported
Nickel Phosphide in Comparison with 2‑Methyltetrahydrofuran
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Abstract
The reactions of 2-methyltetrahydropyran
(2-MTHP, C<sub>6</sub>H<sub>12</sub>O) on Ni<sub>2</sub>P/SiO<sub>2</sub> provide insights
on the interactions between a cyclic ether, an abundant component
of biomass feedstock, with a transition-metal phosphide, an effective
hydrotreating catalyst. At atmospheric pressure and a low contact
time, conditions similar to those of a fast pyrolysis process, 70%
of products formed from the reaction of 2-MTHP on Ni<sub>2</sub>P/SiO<sub>2</sub> were deoxygenated products, 2-hexene and 2-pentenes, indicating
a good oxygen removal capacity. Deprotonation, hydrogenolysis, dehydration,
and decarbonylation were the main reaction routes. The reaction sequence
started with the adsorption of 2-MTHP, followed by ring-opening steps
on either the methyl substituted side (Path I) or the unsubstituted
side (Path II) to produce adsorbed alkoxide species. In Path I, a
primary alkoxide was oxidized at the α-carbon to produce an
aldehyde, which subsequently underwent decarbonylation to 2-pentenes.
The primary alkoxide could also be protonated to give a primary alcohol
which could desorb or form the final product 2-hexene. In Path II,
a secondary alkoxide was oxidized to produce a ketone or was protonated
to a secondary alcohol that was dehydrated to give 2-hexene. The active
sites for the adsorption of 2-MTHP and <i>O</i>-intermediates
were likely to be Ni sites
