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51.
52.
Preparation of Nano-Sized γ-Al2O3 Supported Iron Catalyst for Fischer-Tropsch Synthesis by Solvated Metal Atom Impregnation Methods
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Two types of small iron clusters supported on γ-Al2O3-RT(dehydroxylated at room temperature) and γ-Al2O3-800 (dehydroxylated at 800 ℃) were prepared by solvated metal atom impregnation (SMAI) techniques. The iron atom precursor complex, bis(toluene)iron(0) formed in the metal atom reactor, was impregnated into γ-Al2O3 having different concentrations of surface hydroxyl groups to study the effect of surface hydroxylation on the crucial stage of iron cluster formation. Catalysts prepared in this way were characterized by TEM, M(o)ssbauer, and chemisorption measurements, and the results show that higher concentration of surface hydroxyl groups of γ-Al2O3-RT favors the formation of more positively charged supported iron cluster Fen/γ-Al2O3-RT, and the lower concentration of surface hydroxyl groups of γ-Al2O3-800 favors the formation of basically neutral supported iron cluster Fen/γ-Al2O3-800. The measured results also indicate that the higher concentration of surface hydroxyl groups causes the rapid decomposition of precursor complex, bis(toluene)iron(0), and favors the formation of relatively large iron cluster. Consequently, these two types of catalysts show different catalytic properties in Fischer-Tropsch reaction. The catalytic pattern of Fen/γ-Al2O3-RT in F-T reaction is similar to that of the unreduced α-Fe2O3 and that of Fen/γ-Al2O3-800 is similar to that of the reduced α-Fe2O3. 相似文献
53.
Pure X-ray diffraction profiles have been analysed for polyamide 1010 and PA1010--BMI system by means of multipeak fitting resolution of X-ray diffraction.The methods ofvariance and fourth moment have been applied to determine the particle size and strainvalues for theparacrystalline materials.The results indicated that both variance and fourthmoment of X-ray diffraction line profile yielded approximately the same values of theparticle size and the strain.The particle sizes of(100)reflection have been found todecrease with increasing BMI content,whereas the strain values increased. 相似文献
54.
用WAXD和SAXS方法研究了聚酰胺1010的聚集态结构和结晶结构的辐射损伤过程和机理。辐射交联与裂解主要在非晶区和结晶表面或中间相发生;辐射损伤并从这里开始,随辐射剂量增大,非晶化逐渐向晶区伸展,有氢键的(010)晶面损伤几率高于(100)晶面;辐射后效应导致新的交联与裂解生成,主要影响(010)晶面的形成与完善,使L100及Wc变小。 相似文献
55.
Yuan L Feng W Yamato K Sanford AR Xu D Guo H Gong B 《Journal of the American Chemical Society》2004,126(36):11120-11121
Highly efficient, one-step macrocyclizations leading to the formation of macrocyclic hexa(aramides) in high yields (69-82%) are described. The one-step macrocyclizations were facilitated by the preorganization or folding of the backbones of uncyclized precursors in the course of macrocyclization. The preorganization of backbones was achieved by the presence of localized three-centered hydrogen bonds that were adopted in the design of a class of closely related, backbone-rigidified foldamers. The macrocyclization involved reactions between diacid chloride 1 and diamine 2. The crude reaction mixtures and products were conveniently examined by mass spectrometric method (MALDI-TOF). Compared to most traditional one-step macrocyclizations that usually require high dilution conditions and often lead to very low overall yields of the desired products, cyclic hexamers 3 were obtained as the overwhelmingly major product under a variety of reaction conditions, suggesting the generality of this approach. 相似文献
56.
研究了水质、滤膜、溶液浓度、糖液pH值、混浊度的变化与白砂糖色值的关系。研究结果表明,溶液的pH变化影响最严重。不调整糖液pH与用HCl或NaOH调整糖液pH对比所得白砂糖色值的结果是满意的。标准偏差112~186,相对标准偏差116%~225%,调pH使结果偏高,导致产生系统误差。因此:测定白砂糖色值不宜调整糖液的pH。 相似文献
57.
提出了控制电位电解和恒电流电解两类电解沉积的压电频移分析法测定的理论公式,用实验结果验证了它的正确性. 相似文献
58.
氢分子在金属表面的解离吸附与氢原子在金属体相的扩散是个典型的表面过程.前者在甲烷化及合成氨等基础化工反应中起着关键作用;后者常常导致金属材料的脆化与断裂,但过渡金属及其合金是安全和优良的储氢材料.因此,研究氢分子在金属表面的解离吸附与氢原子在金属体相的扩散,是多相催化与金属物理广泛感兴趣的课题,具有重要的理论和应用价值.本文采用分子动力学方法初步探讨了二者之间的关联.分子催化动力学为从微观层次上研究上述课题提供了一种理论方法.本文采用经过我们改进的半经验LEPS方法,计算了氢分子在Pd(100)和(110)晶面的解离和氢原子在钯表面与体相扩散的相互作用位能面,并根据计算结果探讨了其微观机理. 相似文献
59.
The pervaporation and vapor permeation performance of symmetrical and asymmetrical polycarbonate membranes, prepared via a dry-phase inversion and wet-phase inversion methods, respectively, were studied by measuring the permeation rate and separation factor. It was found that the polymer concentration effect on the pervaporation performance for the symmetrical polycarbonate membrane was lower than that for the asymmetrical polycarbonate membrane. Compared with pervaporation, vapor permeation has a significantly increased separation factor with a decreased permeation rate for the symmetrical polycarbonate membrane. Water molecules preferentially dissolve into the symmetrical polycarbonate membrane and diffuse easily through the membrane. 相似文献
60.
An extended family of aryl-substituted alkaline earth metal silylamides M{N(2,4,6-Me3C6H2)(SiMe3)}donor(n) was prepared using alkane elimination (Mg), salt elimination (Ca, Sr, Ba), and direct metalation (Sr, Ba). Three different donors, THF, TMEDA (TMEDA = N,N,N',N'-tetramethylethylenediamine), and PMDTA (PMDTA = N,N,N',N',N'-pentamethyldiethylenetriamine) were employed to study their influence on the coordination chemistry of the target compounds, producing monomeric species with the composition M{N(2,4,6-Me3C6H2)(SiMe3)}2(THF)2 (M = Mg, Ca, Sr, Ba), M{N(2,4,6-Me3C6H2)(SiMe3)}2TMEDA (M = Ca, Ba), and M{N(2,4,6-Me3C6H2)(SiMe3)}2PMDTA (M = Sr, Ba). For the heavier metal analogues, varying degrees of agostic interactions are completing the coordination sphere of the metals. Compounds were characterized using IR and NMR spectroscopy in addition to X-ray crystallography. 相似文献