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H2SO4处理的Nb2O5/γ -Al2O3催化剂表面酸性与催化性能研究 总被引:3,自引:0,他引:3
用Hammett指示剂法、红外光谱(IR)、示差扫描量热-热重法(DSC-TG)和微型催化反应装置等研究了H2SO4处理的负载型Nb2O5/γ-Al2O3催化剂表面酸性和催化异丁烯(IB)与异丁醛(IBA)反应生成2,5-二甲基-2,4-己二烯(DMHD)的催化性能。结果表明随所用H2SO4浓度增加,Nb2O5/γ-Al2O3催化剂表面酸性增强,B酸量增加,L酸量先增加后下降。经H2SO4处理的Nb2O5/γ-Al2O3催化剂的催化活性明显增加,但当H2SO4浓度超过0.05 mol·L-1时催化活性又急剧下降,这可能是因为在H2SO4处理的催化剂表面形成的强酸中心上,产物分子进一步转化为积炭且封闭催化剂活性表面,导致催化活性下降。 相似文献
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本文以间苯二吡啶(1,3-dpb)和4,4′-二苯醚二甲酸(H2oba)为配体,溶剂热合成了一个二维锌配位聚合物{[Zn(oba)(dpb)].H2O}n(1),对其进行了红外,热重,粉末单晶衍射等表征,配合物属于三斜晶系,空间群C2/c。相邻的Zn(Ⅱ)离子通过连接oba2-和dpb形成二维波浪形面,两个相邻的面相互互锁形成2D→2D的结构,并且面与面之间存在氢键。两组2D→2D的结构通过π-π作用进一步形成双层的二维超分子网络。此外,本文也研究了配合物的荧光性能。 相似文献
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二甲基硫和乙硫醇在层状K1-2xMxTiNbO5(M=Mn2+、Ni2+)上的吸附与光催化氧化作用 总被引:1,自引:0,他引:1
采用固相法制备出具有层状结构的KTiNbO5,通过离子交换制备K1-2xMxTiNbO5(M=Mn2+、Ni2+)。采用X射线粉末衍射(XRD)和紫外-可见漫反射光谱技术对样品晶体结构与光谱响应特征进行表征,采用红外光谱方法考察样品对二甲基硫(DMS)和乙硫醇(EM)吸附与光催化氧化行为。结果表明,采用Mn2+和Ni2+对KTiNbO5离子交换后,层板间距增加,对光谱吸收由紫外区移向可见光区,带隙能量由3.35eV相应地移至2.97eV和2.45eV。K1-2xMxTiNbO5对DMS和EM的吸附作用力较弱,不受阳离子影响。K1-2xMnxTiNbO5只在紫外光辐射下呈现催化活性,并将硫醚、硫醇氧化为亚砜、砜和磺酸;而K1-2xNixTiNbO5在可见与紫外光辐射下均具有光催化活性,在可见光辐射下,乙硫醇被氧化至磺酸,而在紫外光辐射下硫醇被矿化并产生硫酸盐与碳酸盐。 相似文献
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时间序列预测模型研究综述 总被引:9,自引:1,他引:9
介绍了时间序列预测模型的产生和发展,呈现了时间序列模型研究方向的理论、方法和应用,并就未来的发展势态进行了初步的探讨. 相似文献
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传统的衍射实验往往过多强调光波波动性的一面,而忽略其粒子性的一面,从而使学生对衍射现象的物理过程缺乏全面的认识。在进行光学实验的同时,借助于计算机辅助教学,可弥补这一缺点。应用蒙特卡罗方法对单缝夫琅禾费衍射现象进行了模拟,对模拟结果进行了分析和讨论。与传统方法相比,这种方法更为形象和直观,可以帮助学生理解光子等微观粒子的波粒二象性及随机性与确定性的统一。 相似文献
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Theoretical study of molecular hydrogen and spiltover hydrogen storage on two-dimensional covalent-organic frameworks
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Molecular hydrogen and spiltover hydrogen storages on five two-dimensional (2D) covalent-organic frameworks (COFs) (PPy-COF, TP-COF, BTP-COF, COF-18 A, and HHTP-DPB COF) are investigated using the grand canonical Monte Carlo (GCMC) simulations and the density functional theory (DFT), respectively. The GCMC simulated results show that HHTP-DPB COF has the best performance for hydrogen storage, followed by BTP-COF, TP-COF, COF-18 A, and PPy-COE However, their adsorption amounts at room temperature are all too low to meet the uptake target set by US Department of Energy (US-DOE) and enable practical applications. The effects of pore size, surface area, and isosteric heat of hydrogen on adsorption amount are considered, which indicate that these three factors are all the important factors for determining the H2 adsorption amount. The chemisorptions of spiltover hydrogen atoms on these five COFs represented by the cluster models are investigated using the DFT method. The saturation cluster models are constructed by considering all possible adsorption sites for these cluster models. The average binding energy of a hydrogen atom and the saturation hydrogen storage density are calculated. The large average binding energy indicates that the spillover process may pro- ceed smoothly and reversibly. The saturation hydrogen storage density is much larger than the physisorption uptake of H2 molecules at 298 K and 100 bar (1 bar = 105 Pa), and is close to or exceeds the 2010 US-DOE target of 6 wt% for hydrogen storage. This suggests that the hydrogen storage capacities of these COFs by spillover may be significantly enhanced. Thus 2D COFs studied in this paper are suitable hydrogen storage media by spillover. 相似文献
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