Showing papers by "Masatake Haruta published in 2023"

Selective formation of acetate intermediate prolongs robust ethylene removal at 0 °C for 15 days

Abstract: Abstract Efficient ethylene (C 2 H 4 ) removal below room temperatures, especially near 0 °C, is of great importance to suppress that the vegetables and fruits spoil during cold-chain transportation and storage. However, no catalysts have been developed to fulfill the longer-than-2-h C 2 H 4 removal at this low temperature effectively. Here we prepare gold-platinum (Au-Pt) nanoalloy catalysts that show robust C 2 H 4 (of 50 ppm) removal capacity at 0 °C for 15 days (360 h). We find, by virtue of operando Fourier transformed infrared spectroscopy and online temperature-programmed desorption equipped mass spectrometry, that the Au-Pt nanoalloys favor the formation of acetate from selective C 2 H 4 oxidation. And this on-site-formed acetate intermediate would partially cover the catalyst surface at 0 °C, thus exposing active sites to prolong the continuous and effective C 2 H 4 removal. We also demonstrate, by heat treatment, that the performance of the used catalysts will be fully recovered for at least two times.

Gold/Substituted Hydroxyapatites for Oxidative Esterification: Control of Thin Apatite Layer on Gold Based on Strong Metal-Support Interaction (SMSI) Results in High Activity.

Abstract: Gold nanoparticles (Au NPs) deposited on various cation- and anion-substituted hydroxyapatites (Au/sHAPs) show oxidative strong metal-support interaction (SMSI), wherein a thin layer of the sHAP covered the surface of the Au NPs by heat treatment in an oxidative atmosphere. Calcination of Au/sHAPs at 300 °C caused a partial SMSI and that at 500 °C gave fully encapsulated Au NPs. We investigated the influence of the substituted ions in sHAP and the degree of the oxidative SMSI on the catalytic performance of Au/sHAPs for oxidative esterification of octanal or 1-octanol with ethanol to obtain ethyl octanoate. The catalytic activity depends on the size of the Au NPs but not on the support used, owing to the similarity of the acid and base properties of sHAPs except for Au/CaFAP. The presence of a large number of acidic sites on CaFAP lowered the product selectivity, but all other sHAPs exhibited similar activity when the Au particle size was almost the same, owing to the similarity of the acid and base properties. Au/sHAPs_O2 with SMSI exhibited higher catalytic activity than Au/sHAPs_H2 without SMSI despite the fact that the number of exposed surface Au atoms was decreased by the SMSI. In addition, the oxidative esterification reaction proceeded even though the Au NPs were fully covered by the sHAP layer when the thickness of the layer was controlled to be less than 1 nm. The substrate can access the surfaces of the Au NPs covered by the thin sHAP layer (<1 nm), and the presence of the sHAP structure in close contact with the Au NPs resulted in significantly higher catalytic activity compared with that for fully exposed Au NPs deposited on the sHAPs. This result suggests that maximizing the contact area between the Au NPs and the sHAP support based on the SMSI enhances the catalytic activity of Au.