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Linear-regioselective hydromethoxycarbonylation of styrene using Ru-clusters/CeO2 catalyst

Chinese Journal of Catalysis 2020年第6期41卷 963-969页

作者： Jinghua An Yehong Wang Zhixin Zhang Jian Zhang Martin Gocyla rafal edunin-borkowski Feng Wang State Key Laboratory of Catalysis Dalian National Laboratory for Clean EnergyDalian Institute of Chemical PhysicsChinese Academy of SciencesDalian 116023LiaoningChina University of Chinese Academy of Sciences Beijing 100049China Ernst Ruska Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute Forschungszentrum Juelich GmbHJuelich 52425Germany

Hydroalkoxycarbonylation of olefins has been considered to be one of the most attractive methods to synthesize esters. Controlling the regioselectivities of linear esters(L) and branched esters(B) is a challenging project for researchers working in this reaction. Although most of the attention has been paid to control the regioselectivity through ligand design in homogeneous catalytic systems, study in the area is still limited. Herein, Ru-clusters/CeO2 is employed as a heterogeneous catalyst for the hydromethoxycarbonylation of styrene without any additives. After optimization of the reaction conditions, the conversion of styrene is > 99% with 83% and 12% regioselectivity of linear and branched ester, respectively. By using different supports(CeO2(nanoparticle), CeO2-rod, and CeO2-cube), three catalysts including Ru-clusters/CeO2, Ru/CeO2-rod, and Ru/CeO2-cube are prepared and applied in the reaction. Structural characterizations demonstrate that the L/B ratio is related to the Ru size of supported Ru catalysts. Further Raman characterization and NH3-TPD demonstrate that the metal-support interaction and the concentration of oxygen vacancy of the catalyst have a great influence on the Ru size. The mechanism and kinetic analysis for this reaction are also investigated in this work.

关键词： Regioselectivity Ru-clusters/CeO2 Ester Hydromethoxycarbonylation Olefins Heterogeneous catalysis

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Three-dimensional magnetization reconstruction from electron optical phase images with physical constraints

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Science China(Physics,Mechanics & Astronomy) 2024年第11期Mechanics & Astronomy) .卷 126-136页

作者： Boyao Lyu Shihua Zhao Yibo Zhang Weiwei Wang Fengshan Zheng rafal E.Dunin-borkowski Jiadong Zang Haifeng Du Anhui Province Key Laboratory of Low-Energy Quantum Materials and Devices High Magnetic Field LaboratoryHefei Institutes of Physical Science Chinese Academy of Sciences Science Island Branch Graduate School of University of Science and Technology of China Department of Physics and Astronomy University of New Hampshire Department of Physics The City College of New York Physics Program Graduate Center of the City University of New York Department of Chemistry University of New Hampshire Institutes of Physical Science and Information Technology Anhui University Spin-X Institute Center for Electron Microscopy School of Physics and OptoelectronicsState Key Laboratory of Luminescent Materials and DevicesGuangdong-Hong Kong-Macao Joint Laboratory of Optoelectronic and Magnetic Functional MaterialsSouth China University of Technology Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons Forschungszentrum Jülich

The ability to characterize three-dimensional(3D) magnetization distributions in nanoscale magnetic materials and devices is essential to fully understand their static and dynamic magnetic properties. Phase contrast techniques in the transmission electron microscope(TEM), such as electron holography and electron ptychography, can be used to record two-dimensional(2D) projections of the in-plane magnetic induction of 3D nanoscale objects. Although the 3D magnetic induction can in principle be reconstructed from one or more tilt series of such 2D projections, conventional tomographic reconstruction algorithms do not recover the 3D magnetization within a sample directly. Here, we use simulations to describe the basis of an improved model-based algorithm for the tomographic reconstruction of a 3D magnetization distribution from one or more tilt series of electron optical phase images recorded in the TEM. The algorithm allows a wide range of physical constraints, including a priori information about the sample geometry and magnetic parameters, to be specified. It also makes use of minimization of the micromagnetic energy in the loss function. We demonstrate the reconstruction of the 3D magnetization of a localized magnetic soliton — a hopfion ring — and discuss the influence of noise, choice of magnetic constants, maximum tilt angle and number of tilt axes on the result. The algorithm can in principle be adapted for other magnetic contrast imaging techniques in the TEM, as well as for other magnetic characterization techniques, such as those based on X-rays or neutrons.

关键词： three-dimensional magnetization vector field tomography differentiable programming electron holography micromagnetism

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