Formaldehyde (HCHO) is either a reactant, intermediate, or product in numerous industrial catalytic reactions; therefore, revealing the full transformation process of HCHO during heterogeneous catalysis is of prime importance in understanding the mechanisms of many HCHO-related reactions and designing more efficient catalysts. As two main intermediates in HCHO transformation, the conversion of dioxymethylene (DOM) to formate is one of the key steps. There are three recognized pathways for this step, including direct dissociation of DOM, DOM combining with surface O, or through a Cannizzaro-type reaction. Herein, we reveal that the catalytic reaction between DOM and the abundant surface OH groups is a facile pathway for the transformation of DOM to formate species on TiO 2 and also on TiO 2 -supported noble metal catalysts. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) results demonstrate that the presence of water vapor is favorable for the conversion of DOM to formate species on TiO 2 , and the loading of noble metals (Ir/Pt) on TiO 2 further promotes the activation of H 2 O, thereby boosting the transformation of DOM into formate. Density functional theory (DFT) calculations show that HCHO consumes the bridging OH groups to form DOM species first followed by the reaction between DOM and the terminal OH groups on the TiO 2 surface to produce formate, and the latter reaction is both thermodynamically and kinetically favorable. These results provide deeper insight into HCHO transformation and demonstrate another role of surface hydroxyl groups in catalytic reaction.
Seven dihydrochalcone compounds were isolated from the leaves of Malus crabapples, cv. "Radiant", and their chemical structures were elucidated by UV, IR, ESI-MS, 1 H-NMR and 13 C-NMR analyses. These compounds, which include trilobatin (A1), phloretin (A2), 3-hydroxyphloretin (A3), phloretin rutinoside (A4), phlorizin (A5), 6 11 -O-coumaroyl-4 1 -O-glucopyranosylphloretin (A6), and 3 111 -methoxy-6 11 -O-feruloy-4 1 -O-glucopyranosyl-phloretin (A7), all belong to the phloretin class and its derivatives. Compounds A6 and A7 are two new rare dihydrochalcone compounds. The results of a MTT cancer cell growth inhibition assay demonstrated that phloretin and these derivatives showed significant positive anticancer activities against several human cancer cell lines, including the A549 human lung cancer cell line, Bel 7402 liver cancer cell line, HepG2 human ileocecal cancer cell line, and HT-29 human colon cancer cell line. A7 had significant effects on all cancer cell lines, suggesting potential applications for phloretin and its derivatives. Adding a methoxyl group to phloretin dramatically increases phloretin's anticancer activity.
Metal–support
interaction (MSI) has been widely recognized
to be playing a pivotal role in regulating the catalytic activity
of various reactions. In this work, the degree of MSI between Pt and
CeO2 support was finely tuned by adjusting the activation
condition, and the obtained catalysts were tested for the oxidative
abatement of CO and HCHO under ambient conditions. The characterization
of catalysts shows that activation of strongly interacting Pt-CeO2 at higher temperatures by H2 leads to a weaker
MSI with increased electron density of Pt, and this modification of
local electronic properties is demonstrated to result in enhanced
O2 adsorption/activation to prevent the CO self-poisoning
effect, while it abates the activity of CO adsorption/activation and
oxidation of adsorbed CO. The Pt-CeO2 catalyst with a moderate
MSI, which is able to balance each step in the catalytic cycle over
Pt and Pt-CeO2 interface domains, displays the highest
activity for CO/HCHO oxidation under ambient conditions.
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