No abstract

The use of CO2 as a CO surrogate for the carbonylation of olefin has attracted considerable attention due to its abundance, readily availability, nontoxicity, and recyclability. In this work, we describe the synthesis of methyl propionate (MPA), a key intermediate for methyl methacrylate in the commercial Lucite Alpha process, by the ruthenium-catalyzed methoxycarbonylation of ethylene with CO2 as a carbonyl source. An efficient approach to producing MPA has been developed by adding metal halide promoters and dehydrating agents. Control experiments suggest that the NHC-Ru-hydride may be the real active species formed in situ by the reaction of Ru3(CO)12 with ionic liquid (IL). NMR data demonstrate that inorganic salts favor the formation of active species, which is an important issue for their promotion effect. In terms of the strategy to overcome chemical equilibrium by the addition of dehydrating agents and IL participation in the formation of NHC-Ru-hydride active species, a tasked IL containing a siloxyl group was employed to Ru-catalyze the methoxycarbonylation of ethylene, which showed higher catalytic efficiency in comparison to IL without a siloxyl group.

Dynamically tunable terahertz metamaterial absorbers integrating with active materials have been widely explored. However, there are still problems that need to be urgently solved, such as modulation depth deficiency, a lack of multiparameter-tunable characteristics, and so on. In this paper, a multiparameter-tunable terahertz absorber composed of two concentric double-opening resonant rings is proposed. Semiconductor silicon and germanium are introduced to fill the openings, so that the absorber possesses three different absorption modes. Regulating semiconductor conductivities using different pump lasers allows dynamic switching among the three absorption modes to be realized. Adjusting the polarization angle of incident THz waves through device rotation facilitates easy and convenient modulation of the absorption amplitude. Calculation results show that the maximum modulation range for amplitude is 0 to 90.1%. Thus, due to the existence of two regulatory degrees of freedom, absorption mode switching and amplitude modulation are realized simultaneously. Most importantly, continuous modulation of the absorption amplitude is obtained at every resonant point in all three absorption modes without frequency drift. This scheme provides a new perspective for exploring future terahertz absorbers.

The food hygiene problems caused by bacterial biofilms in food processing equipment are directly related to human life safety and health. Therefore, it is of great strategic significance to study new food sterilization technology. An acidic electrolyzed water (AEW) disinfectant is an electrochemical sterilization technology which has the characteristics of wide adaptability, high efficiency, and environmental friendliness. However, since the sterilization efficiency of AEW for biofilms is not ideal, it is necessary to increase the available chlorine content (ACC) in AEW. A feasible method to increase the ACC is by increasing the chlorine evolution reaction (CER) selectivity of the electrode for AEW preparation. In this paper, the RuO 2 @TiO 2 electrode was prepared by thermal decomposition combined with high-vacuum magnetron sputtering. Compared with the oxygen evolution reaction (OER) activity of an ordinary RuO 2 electrode, the OER activity of the RuO 2 @TiO 2 electrode is significantly reduced. However, the CER activity of the RuO 2 @TiO 2 electrode is close to the OER activity of RuO 2 . The CER mechanism of the RuO 2 @TiO 2 electrode is the second electron transfer, and the OER mechanism is the formation and transformation of OH ads . The potential difference between the CER and OER of the RuO 2 @TiO 2 electrode is 174 mV, which is 65 mV higher than that of the RuO 2 electrode, so the selectivity of the CER of the RuO 2 @TiO 2 electrode is remarkably improved. During the preparation of AEW, the ACC obtained with the RuO 2 @TiO 2 electrode is 1.7 times that obtained with the RuO 2 electrode. In the sterilization experiments on Escherichia coli and Bacillus subtilis biofilms, the logarithmic killing values of AEW prepared the by RuO 2 @TiO 2 electrode are higher than those of AEW prepared by the RuO 2 electrode.