Synthesis of a Bifunctional Heterogeneous Catalyst for the Conversion of Lignocellulosic Biomass into Precursors for Alternative Fuels and Fine Chemicals

The overall goal of the research described here is to develop synthetic routes to bifunctional reagents that can be tethered into silicate matrices derived from the tin functionalized cube, Si₈O₂₀(SnMe₃)₈. The critical functional group required for reaction with cubic silicate building block is a chlorosilane, and we additionally wish to incorporate both acid and ionic liquid groups. Once in hand, a crosslinking metathesis reaction will incorporate these reagents into porous silicate matrices derived from the Si₈O₂₀ cube, creating platforms with both acid and ionic liquid groups tethered to their surfaces.

The synthesis of a family of bifunctional compounds containing silyl chloride groups “tethered” to either imidazolium-based ionic liquid groups or aryl sulfonic acid groups is described. The general synthetic strategy involved an initial platinum catalyzed hydrosilation coupling of an allylbenzene or 1-allyl-3-N-benzyl-imidazolium reagent to produce a silane group containing at least one chloride substituent. Sulfonation of the aromatic rings to produce sulfonic acid groups proceeds smoothly and in high yield with chlorosulfonic acid.

These reagents were subsequently reacted with the octatrimethyltin silicate cube, to produce cross-linked silicate matrices containing different combinations of tethered imidazolium groups and sulfonic acids to their surfaces. These functionalized solids were tested for catalytic activity in the hydrolysis of the cellulose model compound, cellobiose, and the dehydration of glucose to hydroxymethyl furfural or levulinic acid.