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81.
以乙酰丙酮铜Cu(acac)2为铜源、 NH4Y分子筛为载体, 采用固相反应制备了无氯CuY催化剂, 考察了在甲醇氧化羰基化合成碳酸二甲酯过程中固相反应温度和Cu负载量对CuY催化剂催化性能的影响, 分析了CuY催化剂物相结构、 可还原性Cu物种和织构性质对催化性能的影响. 结果表明, 随着固相反应温度的升高, 与NH4Y中N 发生离子交换的Cu2+交换度和活性中心Cu+含量先增大后降低, CuY催化剂活性也呈现出相同的变化趋势; 负载量(质量分数)低于10%时, 受分子筛残留B酸位影响, 碳酸二甲酯的选择性较低, 而负载量高于12%时, CuY催化剂中出现了CuO物种, 且粒子逐渐长大, 覆盖部分活性中心, 甚至堵塞孔道, 使催化剂活性降低. 当固相反应温度为250 ℃, Cu负载量为12%时, 活性中心Cu+含量最高, 催化剂表现出最佳的催化活性, 碳酸二甲酯基于甲醇的时空收率为267.3 mg·g-1·h-1, 甲醇转化率为6.9%, 碳酸二甲酯(DMC)的选择性为69.2%. 相似文献
82.
本文采用原位核磁共振的方法研究了在真实固-液环境中共催化剂类型以及光照波长对甲醇光催化重整产物及光解水产氢产率的影响.结果发现,不同贵金属担载的锐钛矿型二氧化钛催化剂对甲醇光催化重整产物的产量和产率有着不同程度的影响,但是对其动力学特征影响不大.光照波长对甲醇光催化重整产物的产量也影响较大.通过对比甲醇氧化产率与产氢产率,发现共催化剂的种类对光催化反应速率及氧化还原能力起重要作用,且共催化剂的种类会影响体系氧化和还原能力之间的协同性. 相似文献
83.
Xupo Liu Yunfeng Zhang Shaofeng Deng Cuicui Li Jiaming Dong Jiaying Wang Zehui Yang Deli Wang Hansong Cheng 《中国化学快报》2019,30(2):299-304
Semi-IPNs were constructed by forming the crosslinking networks via the reaction between BPPO and diamine cross-linkers to overcome the dimensional swelling and methanol-permeation issues of SPEEK. 相似文献
84.
Ali M. Abdel‐Mageed Alexander Klyushin Azita Rezvani Axel Knop‐Gericke Robert Schlgl R. Jürgen Behm 《Angewandte Chemie (International ed. in English)》2019,58(30):10325-10329
The electronic and structural properties of Au/ZnO under industrial and idealized methanol synthesis conditions have been investigated. This was achieved by kinetic measurements in combination with time‐resolved operando infrared (DRIFTS) as well as in situ near‐ambient pressure X‐ray photoelectron spectroscopy (NAP‐XPS) and X‐ray absorption near‐edge spectroscopy (XANES) measurements at the O K‐edge together with high‐resolution electron microscopy. The adsorption of CO during the reaction revealed the presence of negatively charged Au nanoparticles/Au sites during the initial phase of the reaction. Near‐ambient‐pressure XPS and XANES demonstrate the build‐up of O vacancies during the reaction, which goes along with a substantial increase in the rate of methanol formation. The results are discussed in comparison with previous findings for Cu/ZnO and Au/ZnO catalysts. 相似文献
85.
Ya‐Pan Wu Jun‐Wu Tian Shan Liu Bo Li Jun Zhao Lu‐Fang Ma Dong‐Sheng Li Ya‐Qian Lan Xianhui Bu 《Angewandte Chemie (International ed. in English)》2019,58(35):12185-12189
Embedding cubane [M4(OH)4] (M=Ni, Co) clusters within the matrix of metal–organic frameworks (MOFs) is a strategy to develop materials with unprecedented synergistic properties. Herein, a new material type based on the pore‐space partition of the cubic primitive minimal‐surface net (MOF‐14‐type) has been realized. CTGU‐15 made from the [Ni4(OH)4] cluster not only has very high BET surface area (3537 m2 g?1), but also exhibits bi‐microporous features with well‐defined micropores at 0.86 nm and 1.51 nm. Furthermore, CTGU‐15 is stable even under high pH (0.1 m KOH), making it well suited for methanol oxidation in basic medium. The optimal hybrid catalyst KB&CTGU‐15 (1:2) made from ketjen black (KB) and CTGU‐15 exhibits an outstanding performance with a high mass specific peak current of 527 mA mg?1 and excellent peak current density (29.8 mA cm?2) at low potential (0.6 V). The isostructural cobalt structure (CTGU‐16) has also been synthesized, further expanding the application potential of this material type. 相似文献
86.
Dr. Zhao Liu Prof. Dr. Charles C. Sorrell Dr. Pramod Koshy Dr. Judy N. Hart 《Chemphyschem》2019,20(16):2074-2081
Methanol decomposition is a promising method for hydrogen production. However, the performance of current catalysts for this process is not sufficient for commercial applications. In this work, methanol adsorption on the CeO2 low-index surfaces is studied by density functional theory (DFT). The results show that methanol always dissociates spontaneously on the (100) surface, whereas dissociation on the (110) surface is site-selective; dissociation does not occur at all on the (111) surface, where only weak physisorption is found. The results confirm that surfaces with higher energies are more catalytically active. Analysis of the surface geometries shows that the dominant factors for the dissociation of methanol are the degree of undercoordination and the charges of the surface ions. The adsorption energy of each methanol molecule decreases with increasing coverage and there is a transition threshold between dissociative and associative adsorption. The present work indicates that a strategy to design catalysts with high activity is to maximize exposure of surfaces on which the ions have a high degree of undercoordination and a strong tendency to donate/accept electrons. The results demonstrate the importance of appropriately selecting and controlling exposed facets and particle morphology for optimizing catalyst performance. 相似文献
87.
ABSTRACTNeutron diffraction measurements of H/D isotopic substitution have been performed for seven H/D substituted methanol-water mixtures of 0.3?mol fraction of methanol (xM) under the supercritical (618?K, 100?MPa) and ambient (298?K, 0.1?MPa) conditions. The seven structure factors obtained were subjected to an empirical potential structure refinement (EPSR) modelling to derive all site-site pair correlation functions, coordination number distributions, spatial density functions, and cluster distributions. Water has a four coordinated structure in the first coordination shell under both ambient and supercritical conditions; however, the spatial density distribution of water molecules in the second coordination shell is delocalised under the supercritical condition. The mean coordination number of all atomic pairs with hydrophilic interactions decreases in the supercritical state. On the other hand, the mean coordination number of interactions between the hydrophobic part of methanol and water molecule is less sensitive to temperature. In the supercritical condition, water clusters with a wide size distribution are generated in a methanol-water mixture as well as in pure water. Since the critical temperature of a methanol-water mixture is lower than that of pure water, it can be concluded that the addition of methanol can generate fragment water clusters at a lower temperature. 相似文献
88.
本文运用密度泛函理论B3LYP方法,对C、O、H采用6-311+G(2d,p)基组,计算研究了钴络合物催化甲醇羰基化制甲酸甲酯反应的微观机理,优化了各反应物、中间体和过渡态的构型特征,用频率分析方法和内禀反应坐标方法对过渡态进行了验证,同时对各中间体进行电荷分析.对比了催化过程与非催化过程的能垒.结果表明,有催化剂参与后反应活化能明显降低. 相似文献
89.
90.
以二苯基-1-甲基咪唑膦(dpim)为配体制备了一种新型的配合物催化剂Ni(dpim)2Cl2. 循环伏安研究表明,Ni(dpim)2Cl2配合物在氮气气氛下表现出两步还原的电化学行为,在-0.7 V下为两电子的不可逆还原,在-1.3 V下为单电子准可逆还原. 向电解液中通入CO2后,在-1.3 V下的还原峰变得不可逆,且其峰电流从0.48 mA·cm-2增大到0.55 mA·cm-2. 在质子源(CH3OH)存在的条件下,该还原峰电流可继续增大到0.72 mA·cm-2. 该研究结果表明,Ni(dpim)2Cl2配合物对CO2还原具有良好的电催化性能,且其电催化还原过程符合ECE机理. 在-1.3 V下恒电位电解得到的还原产物主要为CO,催化转换频率(Turnover of Frenquency, TOF)为0.17 s-1. 相似文献