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排序方式: 共有365条查询结果,搜索用时 15 毫秒
81.
甲醛具有致畸和致癌性,是主要的室内污染物。催化氧化法甲醛转化效率高,没有二次污染,相关研究日益受到关注。本文详细介绍了贵金属和非贵金属两类主要的甲醛氧化催化剂,探讨了活性组分、载体、催化剂助剂等催化剂组成对于其理化性质和反应性能的影响规律,讨论了制备方法、反应物中的水含量等因素对于催化反应的影响,分析了催化剂失活的主要因素。研究表明,催化剂表面活性氧、表面羟基、氧空位数量以及对反应物的吸脱附和存储能力是影响催化活性的关键因素。贵金属催化剂,特别是Pt催化剂具有较好的催化性能,可在较低温度实现甲醛充分转化;非贵金属催化剂具有可变价态,通过催化剂的合理设计可以具有足够的催化活性,其原料资源丰富,价廉易得,应用前景广阔。 相似文献
82.
R. Schneider D. Kiessling R. Herzschuh G. Wendt 《Reaction Kinetics and Catalysis Letters》1997,61(2):245-250
The total oxidation of CH3Cl, CH2Cl2 and ClH2C-CH2Cl has been investigated on a LaMnO3 perovskite type catalyst. Depending on the reaction temperature, a reversible deactivation of the catalyst was observed.
Small amounts of by-products were formed at low reaction temperatures. 相似文献
83.
Co-based catalysts are often utilized due to their high Fischer-Tropsch synthesis (FT) activity,C+5 hydrocarbon selectivity, low water-gas shift reaction (WGS) activity and relatively low cost. Selective control of C5+ hydrocarbons and the catalyst longevity are critical in the design of cobalt catalysts.Thus, various methods to improve the performance of Co catalysts have been suggested. The progress in cobalt catalysts reviewed in the last few decades, mainly involved the support, promoter, preparation and deactivation of Co-based catalysts. 相似文献
84.
This article describes a pilot plant test, which was carried out to examine the effect of start-up operation conditions on catalytic performance in the commercial hydrotreating equipment. From the simulated several pilot tests, it was found that the operation conditions of this commercial equipment were very severe and the hydrogen supply to the catalyst active site was critical. When the heavy residue containing large amount of asphaltene was supplied at the start of run (SOR) in the commercial equipment, the permanent adsorption of carbonaceous deposit on the active site should cause leading the catalyst deactivation. 相似文献
85.
N. George B. V. Kamath A. G. Basrur K. R. Krishnamurthy 《Reaction Kinetics and Catalysis Letters》1997,60(2):379-386
The function of hydrogen used as carrier gas in catalytic dehydrogenation is to increase the selectivity and stability of
catalysts. It slows down catalyst deactivation by either inhibiting deposition of potential coke precursors or facilitating
their desorption by rehydrogenation. This function, in gas-solid catalytic dehydrogenation appears to be interphase mass transfer
controlled by increased hydrogen linear flow velocities decreasing the extent of deactivation. Besides, deactivation appears
to progress through two regimes, an initial short term followed by a long term deactivation. 相似文献
86.
Joachim Laun Mariia Vorobii Andres de los Santos Pereira Ognen Pop‐Georgievski Vanessa Trouillet Alexander Welle Christopher Barner‐Kowollik Cesar Rodriguez‐Emmenegger Thomas Junkers 《Macromolecular rapid communications》2015,36(18):1681-1686
Surface‐initiated photo‐induced copper‐mediated radical polymerization is employed to graft a wide range of polyacrylate brushes from silicon substrates at extremely low catalyst concentrations. This is the first time that the controlled nature of the reported process is demonstrated via block copolymer formation and re‐initiation experiments. In addition to unmatched copper catalyst concentrations in the range of few ppb, film thicknesses up to almost 1 μm are achieved within only 1 h.
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89.
Stereospecific reversible deactivation radical polymerization of biomass‐based acrylates for precise control of tacticity and molecular weight 下载免费PDF全文
Hitoshi Tanaka Tatsuya Kibayashi Kazuya Okuda Shoichi Kashihara 《Journal of polymer science. Part A, Polymer chemistry》2017,55(3):445-456
Reversible deactivation radical polymerization (RDRP) of biomass‐based acrylates, (S )‐ and (R )‐2‐isopropyl‐5‐methylene‐1,3‐dioxolan‐4‐ones (S‐MiPDO and R‐MiPDO), was successfully performed to produce a well‐defined polymer with simultaneously controlled tacticity and molecular weight, and low dispersity (? < 1.3). In particular, meso triad (mm ) of the polymer was continuously controlled as designed from 28.1% to about 100% by changing the molar ratio of S‐MiPDO/R‐MiPDO in feed. In kinetic studies, the rate of RDRP was strongly influenced by the stereostructures of the propagating radical, and it was much lower in isospecific RDRP than atactic one in reversible chain transfer catalyzed polymerization (RTCP) in contrast to atom transfer radical polymerization (ATRP) where the rate would not change regardless of the tacticity. Increase of molecular weight and low ? of the polymer were also observed in reversible addition‐fragmentation chain transfer (RAFT) polymerization of MiPDO. In addition, block copolymers including stereoblock copolymers were feasibly synthesized by RTCP of styrene and methyl methacrylate using poly(MiPDO) prepolymer. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 445–456 相似文献
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