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171.
172.
Catalytic performance of silica-supported chromium oxide catalysts in ethane dehydrogenation with carbon dioxide 总被引:1,自引:0,他引:1
The oxidative dehydrogenation of ethane into ethylene by CO2 over a series of silica-supported chromium oxide catalysts was investigated. The results showed that the catalysts were effective for the reaction and CO2 in the feed promoted the catalytic activity. The 5%Cr/SiO2 catalyst exhibited the excellent performance with 30.7% ethane conversion and 96.5% ethylene selectivity at 700oC. ESR and UV-DRS were used to probe the active sites and the species with high valent states (Cr5+ and/or Cr6+) were found to be important for the reaction. 相似文献
173.
The Ni2P/MgAlO catalysts with different MgO/Al2O3 ratios were prepared by the phosphidation of corresponding Ni/Mg Al O catalysts with triphenylphosphine in liquid phase.It was found that the MgO/Al2O3 ratio affected the Ni2P/MgAlO catalysts significantly.The Ni2P/Mg Al O catalyst with the MgO/Al2O3 ratio of 3(w/w) exhibited the highly dispersed Ni2 P particles(~9 nm) with the highest CO uptake(344 μmol/g)and thus the highest activities for the hydrotreating reactions.However,based on the CO uptakes on the used catalysts,the TOF values for the hydrodesulphurization of dibenzothiophene as well as those for the hydrogenation of tetralin on all the Ni2P/MgAlO catalysts were respectively similar,indicating that the MgO/Al2O3 ratio did not affect the intrinsic activities of Ni2 P supported on the MgAlO support for the hydrotreating reactions. 相似文献
174.
Qingchun Zhang Hanfa Zou Zhong Guo Qiang Zhang Xiaoming Chen Jianyi Ni 《Rapid communications in mass spectrometry : RCM》2001,15(3):217-223
Porous silicon powder and silica gel particles have been applied as inorganic matrices for the analysis of small molecules in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOFMS). In contrast to conventional MALDI-TOFMS, the signal interference of low-molecular analytes by the matrix has been eliminated. Almost no fragmentations of the analytes were observed. Effects of various factors, such as the particle and pore size, the suspending solution, and sample preparation procedures, on the intensity of mass spectra have been investigated. The pore structure of the inorganic matrix and penetration of the analytes into the pores must be optimized for effective desorption and ionization of the analytes. Matrices (DHB and HCCA) were covalently bound to silica gel for improvement of spectrum intensity. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
175.
自适应超静定桁架结构强度控制的研究 总被引:9,自引:1,他引:8
以超静定桁架结构为背景研究了自适应结构的承载能力,探讨作动器和杆单元的共同工作,用以进行结构分析和控制结构承载能力,后者意指通过作动器的主动变形调控结构的内力分布以获得更加合理的工作状态。 相似文献
176.
研究了酸性助剂对TiO2纳米管(TNT)负载的V2O5催化剂(V2O5/TNT)性能的影响, 发现经硫酸、磷酸或磷钨酸处理后, TNT的结构稳定, 但表面酸性和氧化-还原性发生了变化, 从而改变了甲醇选择氧化为甲缩醛的催化性能. 实验结果表明, V2O5/TNT催化剂经硫酸修饰和673 K焙烧, 其甲缩醛选择性显著提高, 且维持了较高的甲醇转化率. 催化剂表征表明, 高温焙烧促进了硫酸根与钒物种之间的强相互作用, 从而提高了催化剂的表面酸性而没有降低钒的氧化-还原性. 磷酸和磷钨酸修饰虽然也提高了V2O5/TNT催化剂的表面酸性, 但降低了其中钒氧化物的氧化-还原能力, 反而降低了催化剂的活性. 相似文献
177.
采用共沉淀法制备了高Co含量的Co/SiO2费托合成催化剂,并向其中添加一定含量的间苯二酚-甲醛树脂凝胶.结果表明,催化剂在393K干燥时,树脂会发生分解,因而仅有少量的含碳凝胶残留在催化剂中.然而,少量碳凝胶的存在显著增加了催化剂的还原度和金属钴的分散度,致使催化剂表面产生更多的活性金属Co,同时,催化剂的孔径也有所增大,因此Co/SiO2催化剂具有更高的反应活性及高碳烃选择性.其中80%Co/SiO2-C催化剂活性及高碳烃的选择性与我们前期报道的一种高活性的80%Co-8%ZrO/SiO催化剂相近. 相似文献
178.
Acidic and redox properties are two important aspects of metal oxide catalysts for selective oxidation reactions. Various methods have been used to characterize these properties, of which the isopropanol conversion is a useful probe reaction that can give qualitative information. It is well known that acidicsites catalyze the dehydration of isopropanol to propylene and basic sites catalyze the dehydrogenation of isopropanol to acetone. 相似文献
179.
180.