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91.
Abdolreza Rezaeifard Maasoumeh Jafarpour Hossein KavousiMahboubeh Alipour Helen Stoeckli-Evans 《Polyhedron》2011,30(13):2303-2309
Benzyltributylammonium periodate (BzBu3NIO4) was prepared easily in high yield in neat water. The compound crystallized with two cations and two anions per asymmetric unit and a space group of Pna21 was determined by single-crystal X-ray diffraction. It was used practically in the clean and selective epoxidation of olefins and oxygenation of saturated hydrocarbons catalyzed by manganese (III) porphyrins in water/ethanol as a green media. The catalyst could be reused without noticeable loss of activity, and the oxidant’s by-product (BzBu3NIO3) could also be reused. The efficiency of the oxidation system depends critically upon the steric hindrances and electronic structures of both the nitrogen donors and Mn-catalysts. Some evidences suggest the involvement of a high valent Mn-oxo species as well as a six-coordinate [(L)(Por)Mn-OIO3] complex in the oxidation reactions. 相似文献
92.
93.
Marc A. Klingshirn 《Journal of organometallic chemistry》2005,690(15):3620-3626
The palladium-catalyzed hydroesterification of olefins occurs efficiently in a range of ionic liquid media. Selectivities ranging from 5-7:1 for the linear ester were obtained with styrene in a range of IL solvents. The use of ILs allowed the catalyst to be easily separated from the organic product by either extraction or distillation. The (Ph3P)2PdCl2 precatalyst could be recovered unchanged from the ionic liquid phase. The IL/catalyst phase could be recycled five times with an average yield of 68%. 相似文献
94.
In this paper, the ultrasonic-assisted desilication technique was reported as an attractive and efficient way for the preparation of hierarchical zeolites with MFI structure type. The prepared materials were used as active catalysts for the dehydration of ethanol into diethyl ether and ethylene. For all catalysts, the selectivity to diethyl ether was ca 95% or higher up to 210 °C, with catalytic activity in the range of 40–68%. In case of desilicated zeolites, at 270–290 °C, the conversion of ethanol was full with selectivity to ethylene ca 80%. MFI-type commercial zeolite was treated with a sodium and/or tetrabutylammonium hydroxide aqueous solutions (NaOH or NaOH/TBAOH) for 30 min. In the case of the application of ultrasounds, a QSonica Q700 sonicator (60 W and 20 kHz) equipped with a “1” diameter horn was used. In all cases, desilication was performed in an ice bath in order to keep the procedure conditions at low temperature.It was indicated that the use of ultrasounds during desilication procedure caused higher extraction of silicon and aluminum, which was connected with an elevated mesoporosity in relation to the samples modified in the absence of ultrasounds. Ultrasonic-assisted treatment of MFI-type zeolite caused also an apparent formation of numerous holes inside zeolite grains, resembling the look of “swiss cheese”. Furthermore, it was indicated that the samples prepared using ultrasonic irradiation exhibited enhanced catalytic properties in the dehydration of ethanol. For instance, MFI-type zeolite treated with NaOH/TBAOH alkaline mixture containing 10 mol% of TBAOH in the presence of ultrasounds (M−10 s) demonstrated higher both conversion of ethanol (59% vs. 47%) and selectivity to diethyl ether (95% vs. 93%) in comparison with zeolite modified conventionally (M−10c).The best catalyst was zeolite ultrasonically desilicated with NaOH/TBAOH solution of 70 mol% of TBAOH (M-70s). Generally, this catalyst indicated the highest conversion of ethanol, very high selectivity to diethyl ether (94-100%) at 150-210 °C and the highest selectivity to ethylene among investigated catalysts (21%, 66% and 84%) at 230 °C, 250 oC and 270 °C. 相似文献
95.
Perovskites as Precursors for Ni/La2O3 Catalysts in the Dry Reforming of Methane: Synthesis by Constant pH Co‐Precipitation,Reduction Mechanism and Effect of Ru‐Doping
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Stefanie Kühl Hendrik Düdder Frank Girgsdies Kevin Kähler Martin Muhler Malte Behrens 《无机化学与普通化学杂志》2017,643(16):1088-1095
LaNiO3 perovskite is an interesting precursor for Ni/La2O3 catalysts for the dry reforming of methane at high temperatures. Precursors have been synthesized by co‐precipitation without, with 2.5 at %, and with 5 at % Ru doping. The presence of Ru leads to a stabilization of the perovskite structure and hinders the decomposition into NiO and Ruddlesden‐Popper mixed oxides Lan+1NinO3n+1, which was observed for the Ru‐free sample upon calcination at 1000 °C (n = 3). Upon reduction in hydrogen, a mechanism involving at least two steps was observed and the first major step was identified as the partial reduction of the precursor leading to a LaNiO2.5‐like intermediate. The second major step is the reduction to Ni metal supported on La2O3 independent of the Ru content of the catalyst. In the presence of Ru, indications for Ni‐Ru alloy formation and for a higher dispersion of the metallic phase were found. The catalytic activity in DRM of the catalyst containing 2.5 % Ru was superior to the catalysts with more or without Ru. Furthermore, the propensity of coke formation was reduced by the presence of Ru. 相似文献
96.
用元素分析、红外光谱、紫外光谱、荧光光谱和核磁等分析手段对合成出的1.0G树枝状大分子-水杨醛席夫碱钯配合物(PAMAMSAPd)进行了表征。用其作为催化剂,研究了碘代苯与丙烯酸在有机溶剂中的偶联反应。对于碘代苯与丙烯酸的偶联反应,最佳反应条件为:惰性气氛,10mmol PhI,nPhI∶nAA∶nEt3N=1∶1.5∶2.5,3.0×10-3g PAMAMSAPd, 4mL DMF和100°C的反应温度。在该条件下,产物肉桂酸的产率可达96.5%。该树枝状大分子配合物是一种无磷、高效和稳定的Heck反应催化剂。且该催化剂经简单的过滤、溶剂洗涤进行回收,重复使用3次,产率仍能达到90.2%。 相似文献
97.
采用超声波的方法在离子液(1-丁基-3-甲基氯代咪唑盐离子液,[BMIM]Cl)中合成了直径分布在80~150 nm的MoO3纳米棒.采用X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、场发射扫描电子显微镜(FESEM)、高分辨透射电子显微镜(HRTEM)和选区电子衍射(SAED)对所合成材料的微观结构和形貌进行了表征.此外,考察了反应时间、加入[BMIM]Cl的量以及其它咪唑基离子液对产物的影响并提出了可能的反应机理.最后对在不同温度煅烧下所得的α-MoO的甲烷催化燃烧活性进行了表征. 相似文献
98.
Flow-injection analysis system (FIA system), which was based on Fe(II)-catalyzed oxidation of chromotropic acid with hydrogen peroxide, was developed for the determination of hydrogen peroxide. The chromotropic acid has a fluorescence measured at λem = 440 nm (emission wavelength) with λex = 235 nm (excitation wavelength), and the fluorescence intensity at λem = 440 nm quietly decreased in the presence of hydrogen peroxide and Fe(II), which was caused by Fe(II)-catalyzed oxidation of chromotropic acid with hydrogen peroxide. By measuring the difference of fluorescence intensity, hydrogen peroxide (1.0 × 10−8-1.0 × 10−3 mol L−1) could be determined by the proposed FIA system, whose analytical throughput was 40 samples h−1. The relative standard deviation (RSD) was 1.03% (n = 10) for 4.0 × 10−8 mol L−1 hydrogen peroxide. The proposed FIA technique could be applied to the determination of hydrogen peroxide in rain water samples. 相似文献
99.
Da-Zhen Xu 《Tetrahedron》2010,66(46):8899-8903
A new class of chiral pyrrolidine-phosphite organocatalysts, available from commercially starting materials, has been synthesized and shown to be good catalytic activity for asymmetric Michael and Aldol reactions. The reactions proceeded to give the products in good yield and in a highly selective manner. Ionic liquid [Bmim][BF4] as an efficient green solvent has been employed in the Michael addition. 相似文献
100.
Pertti Elo 《Journal of organometallic chemistry》2010,695(1):11-2337
Six titanium complexes bearing pyrazolonato and pyrazolonato-ketimine ligands have been synthesized and characterized. It was found that the ligand structure of the synthesized complexes has a significant effect on the catalytic performance of the complexes. The synthesized complexes were activated with MAO and their activities varied from negligible to high (up to 612 kgPE/(molTi h bar). The pyrazolonato-ketimine complex with a phenyl substituent in the imine part was the most active in the series and it was the only one producing polyethylenes with relatively narrow molecular weight distribution (Mw/Mn from 1.6 to 2.2). 相似文献