Ye Tiantian,Liu Hanfang,Wang Fupeng,Xie Huijie,Ran Saisai,Xu Wei,Liu Jia,Li Bin,Lin Haifeng,Chai Yongming,Wang Lei
Here, we demonstrate a simple in situ synthesis of Pd@silicate-1 (S-1), using [Pd(NH 2 CH 2 CH 2 NH 2 ) 2 ]Cl 2 as a metal precursor and steam-assisted crystallization (SAC) method. The ultra-small Pd nanoparticles (NPs) (~ 1 nm) can be successfully in situ encapsulated into the silicate-1 matrix with well dispersion. The obtained Pd@S-1 catalyst possesses high crystallinity, a large specific surface area and pore volume. More importantly, Pd NPs encapsulated into silicate-1 matrix can avoid the aggregation and sintering during catalytic reaction. Meanwhile, micropores of silicate-1 can improve the selectivity of the products in the hydrogenation of biomass furfural. Consequently, Pd@S-1 catalyst shows excellent catalytic activity in the selective hydrogenation of biomass furfural with selectivity of 95.7% and activity of 83.7% in the condition of relatively low temperature (458 K). Therefore, this strategy provides a new idea for the synthesis of molecular sieve supported metal catalysts.
Restricting reactive metal nanoclusters into a microporous zeolite matrix (metal@zeolite) can not only prevent the sintering of metal species but can also regulate their catalytic selectivities to certain products. However, there are some problems with current synthesis methods for these structures, such as low metal utilization or/and low product yield. Herein, we report a general strategy to encapsulate different noble metal nanoclusters (e.g., Pd, Pt, Rh, and Ru) into various zeolites (e.g., S-1, ZSM-5, SSZ-13, NaA, and beta). The key point of this strategy is the soft gel precursor (H2O/Si < 4) in the posthydrolysis evaporation process, which significantly improves metal utilization. Combined with the high temperature crystallization process, the space-time yield has been significantly improved, simultaneously. As a typical example, the metal utilization and space-time yield of Pd@S-1 synthesized through this method were nearly 2 and 67 times higher than those of the typical hydrothermal route, respectively. Compared with a supported Pd/SiO2 nanocatalyst, Pd@S-1 exhibited higher catalytic activity and selectivity in hydrogenation of p-chloronitrobenzene (p-CNB).
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