Ju-Hyoung Park

Reducing-Agent-Free Instant Synthesis of Carbon-Supported Pd Catalysts in a Green Leidenfrost Droplet Reactor and Catalytic Activity in Formic Acid Dehydrogenation.

The development of green synthesis methods for supported noble metal catalysts remains important challenges to improve their sustainability. Here we first synthesized carbon-supported Pd catalysts in a green Leidenfrost droplet reactor without reducing agents, high-temperature calcination and reduction procedures. When the aqueous solution containing Pd nitrate precursor, carbon support, and water is dripped on a hot plate, vapor layer is formed between a solution droplet and hot surface, which allow the solution droplet to be levitated on the hot surface (Leidenfrost phenomena). Subsequently, Pd nanoparticles can be prepared without reducing agents in a weakly basic droplet reactor created by the Leidenfrost phenomena, and then the as-prepared Pd nanoparticles are loaded on carbon supports during boiling down the droplet on hot surface. Compared to conventional incipient wetness and chemical synthetic methods, the Leidenfrost droplet reactor does not need energy-consuming, time-consuming, and environmentally unfriendly procedures, which leads to much shorter synthesis time, lower carbon dioxide emission, and more ecofriendly process in comparison with conventional synthesis methods. Moreover, the catalysts synthesized in the Leidenfrost droplet reactor provided much better catalytic activity for room-temperature formic acid decomposition than those prepared by the incipient wetness method.

Effects of modified LDPE on physico-mechanical properties of HDPE/CaCO3 composites

HDPE/CaCO3/LDPE-g-MA composites of high density polyethylene (HDPE) and calcium carbonate (CaCO3) with maleic anhydride grafted low density polyethylene (LDPE-g-MA) as a compatibilizer were prepared by melt mixing. LDPE-g-MA was prepared using a solution process. The maximum grafting degree was obtained at 6 wt% maleic anhydride (MA) and 0.2 wt% dicumyl peroxide (DCP) at 120 °C and 240 min. Functional groups not found in pure LDPE were observed with the formation of LDPE-g-MA. The successful dispersion of CaCO3 particles in the HDPE matrix using LDPE-g-MA was revealed. The crystallite size of the composites was a little higher than that of CaCO3. The mechanical properties of the HDPE/CaCO3/LDPE-g-MA composites increased with decreasing CaCO3 content. Thermogravimetric analysis (TGA) revealed a higher thermal stability for the HDPE/CaCO3/LDPE-g-MA composites than for pure HDPE. Differential scanning calorimetry (DSC) revealed that the crystallization conditions were not substantially different. However, melting enthalpy and crystallinity increased with decreasing CaCO3 content. The thermal stability was greatly improved compared to that previously reported for nano CaCO3.