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, i.e., pH ≈ 2, 473 K and autogenous pressure, the selective
silylation of the zeolite surface usingmonochlorosilanes has no considerable influence. By
using trichlorosilanes, the hydrothermal stability of zeolite Y can be improved significantly
as proven by a stability test in an aqueous solution of 0.2M levulinic acid (LA) and 0.6M
formic acid (FA) at 473 K. However, the silylationwith trichlorosilanes results in a significant
loss of total specific pore volume and total specific surface area, e.g., 0.35 cm3 g−1
and 507m2 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 g-valerolactone (GVL) was conducted over 3 wt.-% Pt on zeolite Y (3PtY)
silylated with either n-octadecyltrichlorosilane or methyltrichlorosilane using different
reducing agents, e.g., FA or H2. 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. Only by applying an excess amount of
methyltrichlorosilane, i.e., 10 mmol per 1 g of zeolite Y, presumably resulting in a high
degree of polymerization among the silanes, a recognizable improvement of the stability
of the 3 PtY catalyst could be achieved. Nonetheless, the pore blockage found for zeolite
Y silylated with an excess amount of methyltrichlorosilane was reflected in a drastically
lower GVL yield at 493 K using FA as reducing agent, i.e., 12 vs. 34% for 3PtY after 24 h.
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:84523 |
| Date | 03 April 2023 |
| Creators | Vu, Hue-Ton, Harth, Florian M., Wilde, Nicole |
| Publisher | Frontiers Research Foundation |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:article, info:eu-repo/semantics/article, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | 2296-2646, 143 |
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