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排序方式: 共有678条查询结果,搜索用时 15 毫秒
1.
A facile one-pot synthesis of 3,5-diarylisoxazoles from α,β-unsaturated ketones and hydroxylamine hydrochloride is reported. The reaction is efficiently promoted by catalytic CuBr2 and Oxone to afford the desired products mostly in high yields and in relatively short time. The mild nature of the synthesis and short reaction time are notable advantages of the developed protocol. This protocol is effective toward various substrates having different functionalities. 相似文献
2.
Ethanol conversion to high-value-added products has attracted considerable attention in both academic research and industrial fields. In this study, we synthesized a series of tunable acid–base bifunctional Zn-Zr-Al metal oxides (represented as Zn2ZrxAl-MMO) in light of the structural topotactic transformation of Zn2ZrxAl-hydrotalcite precursors (Zn2ZrxAl-LDH). The resulting Zn2ZrxAl-MMO catalysts were employed in the conversion of ethanol to diethyl carbonate. The Zr4+ ion content of the LDH precursor plays a key role in modulating the acid-base properties and determining catalytic performance: the Zn2Zr0.1Al-MMO sample exhibits the optimal catalytic behavior with a diethyl carbonate (DEC) yield of 42.1%, which is the highest reported for metal oxide catalysts. Structure-property correlation investigations revealed that the synergic catalysis between medium-strong basic sites and weak acid sites plays a predominant role in the catalytic behavior. Furthermore, in situ Fourier transform infrared measurements showed that the weak acidic site promotes activation adsorption of the reactant (urea) and the intermediate product (ethyl carbamate), while the medium-strong basic site accelerates ethanol activation. Moreover, the Zn2Zr0.1Al-MMO catalyst has the advantages of cost effectiveness, good stability, and reusability. Therefore, the acid-base bifunctional catalysts developed in this work can be employed as promising candidates in acid-base catalytic reactions such as ethanol conversion. 相似文献
3.
Ivan Zuliani Andrea Fattori Rossella Svigelj Nicolò Dossi Cristian Grazioli Gino Bontempelli Rosanna Toniolo 《Electroanalysis》2023,35(2):e202200150
A convenient assembly recently proposed for screen printed gold electrodes (SPEs) suitable for measurements in gaseous samples is here tested for the analysis of the ethanol content in alcoholic drinks. This assembly involves the use of a circular crown of filter paper, soaked in the room temperature ionic liquid (RTIL) 1-butyl-3-methylimidazolium hydrogen sulfate, which is simply placed upon a disposable screen printed cell, so as to contact the outer edge of the gold disc working electrode, as well as peripheral counter and reference electrodes. The electrical contact between the paper crown soaked in RTIL and the SPE electrode is assured by a gasket and all components are installed in a polylactic acid holder. This assembly provides a portable and disposable electrochemical platform, assembled by the easy immobilization onto a porous and inexpensive supporting material such as paper of a RTIL characterized by profitable electrical conductivity and negligible vapor pressure. The electroanalytical performance of this device was assayed for the flow injection analysis of the ethanol concentration in some real samples of wine and beer and the results obtained are compared with the alcoholic degree reported in the relevant bottle-labels, thus highlighting a substantially satisfactory agreement. Repeatable sharp peaks (RSD=6–8 %) were detected for ethanol over a wide linear range (1–20 % v/v in water) and a detection and quantitation limit of 0.55 % v/v and 1.60 % v/v were inferred for a signal-to-noise ratio of 3 and 10, respectively. 相似文献
4.
Qiong Liu Jingjun Lin Hui Cheng Liling Wei Fuxian Wang 《Angewandte Chemie (International ed. in English)》2023,62(13):e202218720
Photocatalytic conversion of CO2 is of great interest but it often suffers sluggish oxidation half reaction and undesired by-products. Here, we report for the first the simultaneous co-photocatalytic CO2 reduction and ethanol oxidation towards one identical value-added CH3CHO product on a rubidium and potassium co-modified carbon nitride (CN-KRb). The CN-KRb offers a record photocatalytic activity of 1212.3 μmol h−1g−1 with a high selectivity of 93.3 % for CH3CHO production, outperforming all the state-of-art CO2 photocatalysts. It is disclosed that the introduced Rb boosts the *OHCCHO fromation and facilitates the CH3CHO desorption, while K promotes ethanol adsorption and activation. Moreover, the H+ stemming from ethanol oxidation is confirmed to participate in the CO2 reduction process, endowing near ideal overall atomic economy. This work provides a new strategy for effective use of the photoexcited electron and hole for high selective and sustainable conversion of CO2 paired with oxidation reaction into identical product. 相似文献
5.
Yu-Cheng Tang Zhi-Shuo Wang Heng Yi Mu-Yang Zhou Dr. Dong-Dong Zhou Prof. Jie-Peng Zhang Prof. Xiao-Ming Chen 《Angewandte Chemie (International ed. in English)》2023,62(24):e202303374
The ethanol/water separation challenge highlights the adsorption capacity/selectivity trade-off problem. We show that the target guest can serve as a gating component of the host to block the undesired guest, giving molecular sieving effect for the adsorbent possessing large pores. Two hydrophilic/water-stable metal azolate frameworks were designed to compare the effects of gating and pore-opening flexibility. Large amounts (up to 28.7 mmol g−1) of ethanol with fuel-grade (99.5 %+) and even higher purities (99.9999 %+) can be produced in a single adsorption process from not only 95 : 5 but also 10 : 90 ethanol/water mixtures. More interestingly, the pore-opening adsorbent possessing large pore apertures showed not only high water adsorption capacity but also exceptionally high water/ethanol selectivity characteristic of molecular sieving. Computational simulations demonstrated the critical role of guest-anchoring aperture for the guest-dominated gating process. 相似文献
6.
Guanghui Feng Dr. Shibin Wang Prof. Shenggang Li Ruipeng Ge Dr. Xuefei Feng Prof. Junwei Zhang Dr. Yanfang Song Dr. Xiao Dong Jiazhou Zhang Prof. Gaofeng Zeng Prof. Qiang Zhang Prof. Guijun Ma Dr. Yi-De Chuang Prof. Xixiang Zhang Prof. Jinghua Guo Prof. Yuhan Sun Prof. Wei Wei Prof. Wei Chen 《Angewandte Chemie (International ed. in English)》2023,62(15):e202218664
Using sunlight to produce valuable chemicals and fuels from carbon dioxide (CO2), i.e., artificial photosynthesis (AP) is a promising strategy to achieve solar energy storage and a negative carbon cycle. However, selective synthesis of C2 compounds with a high CO2 conversion rate remains challenging for current AP technologies. We performed CO2 photoelectroreduction over a graphene/silicon carbide (SiC) catalyst under simulated solar irradiation with ethanol (C2H5OH) selectivity of>99 % and a CO2 conversion rate of up to 17.1 mmol gcat−1 h−1 with sustained performance. Experimental and theoretical investigations indicated an optimal interfacial layer to facilitate the transfer of photogenerated electrons from the SiC substrate to the few-layer graphene overlayer, which also favored an efficient CO2 to C2H5OH conversion pathway. 相似文献
7.
Min Wang Huimin Chen Min Wang Jinxiu Wang Dr. Yongxiao Tuo Prof. Wenzhen Li Shanshan Zhou Linghui Kong Prof. Guangbo Liu Prof. Luhua Jiang Guoxiong Wang 《Angewandte Chemie (International ed. in English)》2023,62(40):e202306456
Heterostructured oxides with versatile active sites, as a class of efficient catalysts for CO2 electrochemical reduction (CO2ER), are prone to undergo structure reconstruction under working conditions, thus bringing challenges to understanding the reaction mechanism and rationally designing catalysts. Herein, we for the first time elucidate the structural reconstruction of CuO/SnO2 under electrochemical potentials and reveal the intrinsic relationship between CO2ER product selectivity and the in situ evolved heterostructures. At −0.85 VRHE, the CuO/SnO2 evolves to Cu2O/SnO2 with high selectivity to HCOOH (Faradaic efficiency of 54.81 %). Mostly interestingly, it is reconstructed to Cu/SnO2-x at −1.05 VRHE with significantly improved Faradaic efficiency to ethanol of 39.8 %. In situ Raman spectra and density functional theory (DFT) calculations reveal that the synergetic absorption of *COOH and *CHOCO intermediates at the interface of Cu/SnO2-x favors the formation of *CO and decreases the energy barrier of C−C coupling, leading to high selectivity to ethanol. 相似文献
8.
Yangyang Zhang Yanxu Chen Xiaowen Wang Yafei Feng Huaikun Zhang Prof. Genqiang Zhang 《Angewandte Chemie (International ed. in English)》2023,62(26):e202302241
Electrochemical conversion of CO2 to highly valuable ethanol has been considered a intriguring strategy for carbon neutruality. However, the slow kinetics of coupling carbon-carbon (C−C) bonds, especially the low selectivity ethanol than ethylene in neutral conditions, is a significant challenge. Herein, the asymmetrical refinement structure with enhanced charge polarization is built in the vertically oriented bimetallic organic frameworks (NiCu-MOF) nanorod array with encapsulated Cu2O (Cu2O@MOF/CF), which can induce an intensive internal electric field to increase the C−C coupling for producing ethanol in neutral electrolyte. Particularly, when directly employed Cu2O@MOF/CF as the self-supporting electrode, the ethanol faradaic efficiency (FEethanol) could reach maximum 44.3 % with an energy efficiency of 27 % at a low working-potential of −0.615 V versus the reversible hydrogen electrode (vs. RHE) using CO2-saturated 0.5 M KHCO3 as the electrolyte. Experimental and theoretical studies suggest that the polarization of atomically localized electric fields derived from the asymmetric electron distribution can tune the moderate adsorption of *CO to assist the C−C coupling and reduce the formation energy of H2CCHO*-to-*OCHCH3 for the generation of ethanol. Our research offers a reference for the design of highly active and selective electrocatalysts for reducing CO2 to multicarbon chemicals. 相似文献
9.
10.
采用等温法测定了30℃时Mg Cl2-Mg SO4-CH3CH2OH-H2O四元体系及边界三元体系Mg Cl2-CH3CH2OH-H2O和Mg SO4-CH3CH2OH-H2O的相平衡数据,绘制了相图并划分了相应的结晶区。实验结果表明,随着乙醇-水体积比不同,四元体系Mg Cl2-Mg SO4-CH3CH2OH-H2O出现了不同的结晶区,随着乙醇含量的增加,Mg Cl2和Mg SO4的溶解度越来越小,不饱和区越来越小,体系中平衡固相的结晶水含量越来越低,说明乙醇具有一定的盐析作用和脱水作用。当乙醇-水体积比为5∶5时,是获得镁盐的最佳比例。这为芒硝和白钠镁矾共生矿中镁盐的分离和提纯提供基础的理论数据。 相似文献