Enhanced activity of a bifunctional Pt/zeolite Y catalyst with an intracrystalline hierarchical pore system in the aqueous-phase hydrogenation of levulinic acid

Mesopores in the range of 4 to 5 nm were introduced into zeolite Y (n(Si)/n(Al) = 16) by surfactant-templating. This method using a mixture of octadecyltrimethylammonium hydroxide and bromide (C(18)TAOH/C-18 TABr) yields a mesoporous zeolite (Y-C(18)TAOH) with a higher specific mesopore volume and only a small loss in crystallinity and specific micropore volume. After loading with Pt, the two bifunctional catalysts (2.7Pt/Y and 2.6Pt/Y-C(18)TAOH) were applied in the aqueous-phase hydrogenation of levulinic acid (LA) to gamma-valerolactone (GVL) (p(H2) = 2.5 MPa, 393 K). Intraparticle mass-transfer limitations present for the catalyst 2.7Pt/Y were not observed in the LA hydrogenation over the catalyst with the hierarchical pore system 2.6Pt/Y-C(18)TAOH. Changes in the acid and de-/hydrogenation functionality are shown not to be responsible for the high catalytic activity of 2.6Pt/Y-C(18)TAOH. The presence of additional mesopores in a bifunctional catalyst based on zeolite Y is proven to enhance the mass-transfer properties and the resulting catalytic activity in the aqueous-phase hydrogenation of LA for the first time.