Silylated Zeolites With Enhanced Hydrothermal Stability for the Aqueous-Phase Hydrogenation of Levulinic Acid to γ-Valerolactone.A systematic silylation approach using mono-, di-, and trichlorosilanes with different alkyl chain lengths was employed to enhance the hydrothermal stability of zeolite Y. DRIFT spectra of the silylated zeolites indicate that the attachment of the silanes takes place at surface silanol groups.  Regarding hydrothermal stability under aqueous-phase processing (APP) conditions,  By using trichlorosilanes, the hydrothermal stability of zeolite Y can be improved significantly as proven by a stability test in an aqueous solution of 0.2 M levulinic acid (LA) and 0.6 M formic acid (FA) at 473 K. However, the silylation with trichlorosilanes results in a significant loss of total specific pore volume and total specific surface area, e.g., 0.35 cm3 g-1 and 507 m2 g-1 for the silylated zeolite Y functionalized with n-octadecyltrichlorosilane compared to 0.51 cm3 g-1 and 788 m2 g-1 for the parent zeolite Y. The hydrogenation of LA to γ-valerolactone (GVL) was conducted over 3 wt. While in the stability test an enhanced hydrothermal stability was found for zeolite Y silylated with n-octadecyltrichlorosilane, its stability in the hydrogenation of LA was far less pronounced. 
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