Synthesis of beta-supported Cr/Sn bimetallic nanoparticles via ultrafast thermal shock for high yield of lactic acid

The size dependence of metal nanoparticles is a critical factor affecting catalytic activity, as their geometric and electronic properties vary significantly with size. This study proposes a strategy combining rapid Joule-heating with solid-phase synthesis to prepare Cr/Sn-Beta bimetallic catalysts of various sizes via ultrafast thermal shock (UTS, heating rate: 1850 °C/s) and conventional muffle furnace annealing (MFA, heating rate: 5 °C/min). HRTEM results reveal that the bimetallic particle size of Cr/Sn-Beta catalysts prepared via UTS technique is only 2.55 nm, compared to 6.54 nm for catalysts obtained through conventional MFA method. Combined with XRD, BET, H₂-TPR, UV–vis and FT-IR characterization, it is further confirmed that the ultra-high heating/cooling rate and second-short heating duration of the UTS method achieved efficient embedding of Cr and Sn within the zeolite micropores, which conferred precise tailoring of the particle size. The correlation between particle size and catalytic activity was investigated using the LA production from cellulose as a model reaction. In this work, the superior size effect of bimetallics nanoparticles prepared by UTS synthesis strategies was emphasized, providing insights into the geometry-activity relationship that will guide the rational design of catalysts in terms of morphology and particle size.