Catalysts
·
2025
·Vol. 15
·期 3
·277
·
IF 4
Yunhan Pu,Huajie Zhang,Yanjun Li,Chuan Yu,Xiaofei Song,Chen Yang,Mingli Fu
The conversion of methane (CH4) to methanol (CH3OH) under mild conditions remains a significant challenge in catalysis. In this study, we introduce a method to adjust the surface valence states of copper species in Cu-ZSM-5 catalysts by annealing under different atmospheres (N2, air, and H2). Among these, the 10% Cu-ZSM-5 catalyst calcined in H2showed outstanding performance, achieving a methanol productivity of 8.08 mmol/(gcat·h) and 91% selectivity at 70 °C and 3 MPa using H2O2as the oxidant. Comprehensive characterization revealed that H2annealing optimized the Cu surface to a lower valence state (predominantly Cu+), enhancing CH4adsorption and promoting H2O2activation to generate ·OH and ·CH3radicals, which drive selective CH3OH formation. In situ DRIFTS and radical trapping experiments further confirmed the critical role of Cu+in facilitating C-H bond cleavage and suppressing overoxidation.
研究领域:
催化化学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
HYDROMETALLURGY
·
2023
·
IF 4.7
Anyang Tang,Jiahe Zhang,Huazhen Cao,Huibin Zhang,Guoqu Zheng
The synthesis of refractory rhenium (Re) powders is significant for the production of rhenic products. In this work, the ultra-fine Re nanoparticles were synthesized via a combination of aqueous-phase reduction and rapid hydrogen reduction using NH 4 ReO 4 as Re source. The theoretical reduction route was determined by investigating the Eh-pH diagram of the Re -H 2 O system and conducting thermodynamic calculations. The optimal results were achieved by adjusting the experimental parameters like acid type, initial acidity, molar ratio of BH 4 − : ReO 4 − , feed rate of reductant, reaction temperature (T), and reaction time (t). The amorphous Re powders with minor oxide inclusions can be prepared under the optimized conditions of [HCl] = 1.35 mol L −1 , BH 4 − : ReO 4 − molar ratio = 5.32, feed rate = 15 mL min −1 , reaction temperature = 30 °C, and reaction time = 30 min. The maximum reduction efficiency reaches 99.5%. After annealing in hydrogen for 30 min, the crystalline Re nanoparticles with low oxygen content can be obtained. This work demonstrates the feasibility and efficacy of rapidly synthesizing ultra-fine Re nanoparticles in a solution-based approach.
研究领域:
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS
·
2022
·Vol. 33
·期 33
·25383-25391
·
IF 2.779
Zhang Cong,Liu Xiansong,Kan Xucai,Feng Shuangjiu,Zhu Yong,Yang Yujie,Zhang Zongyang
Soft magnetic composites serve in electrical applications and sustainable energy supply, the magnetic flux changes in response to changes of the applied magnetic field, with energy loss. To reduce the loss, in this paper, the soft magnetic composite Fe 50 Ni 50 powder coated with nano-SiO 2 was prepared by tetraethoxysilane sol–gel method, and the microstructure of the coating was characterized. Then, soft magnetic Fe 50 Ni 50 powder cores have been prepared, and annealed with different atmospheres. The power loss is lower when the magnetic cores were annealed in a reducing hydrogen atmosphere. The lowest power loss (1390.7 mW/cm 3 , f = 1000 kHz, B = 50 mT, 120 °C) was obtained when the cores annealed at 730 °C in H 2 atmosphere. The results show that the eddy current loss is significantly reduced by coating SiO 2 , and the power loss is reduced about 33% in high-frequency (1 MHz and 50 mT, 25 °C). From 25 to 120 °C, the power loss at 1 MHz decreases by about 33% due to the reduction of hysteresis loss and eddy current loss. The excellent properties are very applicable for the inductors of 5G technology.
研究领域:
材料科学
·
电气工程
✓ 已验证
产品关联
DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2023
·
IF 15.1
Yu Pan,Xun Liu,Meng Zhang,Qi Han,Yufei Shu,Mengxia Wang,Bei Liu,Zhongying Wang
The presence of excess fluoride ions in drinking water has raised widespread concerns, necessitating the development of effective methods for its removal. Cerium dioxide (CeO 2 ) holds promise as a selective adsorbent for fluoride ions, due to its exceptional affinity for fluoride and stability across a wide pH range. However, the impact of intrinsic properties of CeO 2 on its adsorption characteristics and mechanisms remains unclear. In this study, we prepared a range of CeO 2 materials with diverse intrinsic properties by adjusting the annealing temperature and atmosphere. Through a series of characterization techniques, we discovered a correlation between the content of oxygen vacancies, Ce(III) species, and surface hydroxyl groups (–OH), all of which decreased simultaneously with increasing air annealing temperature. With respect to the adsorption performance, the highest fluoride adsorption capacity of 111.1 mg g −1 was observed in un-CeO 2 , representing the nanomaterials with the highest oxygen vacancies. This capacity gradually decreased to 29.1 mg g −1 in 800-CeO 2 . Following fluoride adsorption, the oxygen vacancy density, Ce(III) content, and surface –OH content of all CeO 2 materials decreased. When CeO 2 materials were annealed in H 2 for 1 h, the F − adsorption density increased due to the formation of more oxygen vacancies and surface –OH. Based on our findings, we conclude that oxygen vacancies play a critical role in determining whether fluoride ions can successfully exchange with surface –OH groups and enter the crystal lattice of CeO 2 , which significantly affects the adsorption performance. The pivotal role of oxygen vacancies, as proposed in this study, provides a valuable direction for future research aimed at enhancing the fluoride adsorption performance of CeO 2 .
研究领域:
材料科学
·
环境科学
·
化学
✓ 已验证
产品关联
DOI
高影响因子
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