196 Producing Fuels and Fine Chemicals from Biomass Using Nanomaterials
As discussed in the previous chapter, microporous acidic catalysts might not
be the ideal choice in terms of nonsoluble cellulose as substrate. In fact, materials
with a high external surface area due to small particle sizes are the preferred
kind of materials in terms of increased interactions of the solid catalyst with
the substrate. In recent years, many investigations have been published utilizing
dissolved heteropoly acids (HPA) in combination with supported metals as hydro-
genation catalysts [51]. However, by partial substitution of HPA protons by metal
ions, low to nonsoluble species still providing Brønsted acidity can be obtained
with a high stability in an aqueous ...