SrTi0.9M0.1O3-δ钙钛矿型氧化物催化剂甲烷氧化偶联反应性能的研究

The structure and catalytic properties of SrTi_0.9M_0.1O_3-δ (M=Mg，Al， Zr) perovskite-type catalysts for ox-idative coupling of methane (OCM) have been studied by using X-ray diffraction (XRD)，X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption of oxygen(O₂-TPD) methods. It has been shown that doping the cations of lower valence (e.g. Mg²⁺， Al³⁺) to the B site of SrTi_0.9M_0.1O_3-δ perovskite-type catalysts results in the higher content of adsorbed oxygen species on the surface of catalysts and thus higher C₂-selectivity for OCM reaction. It is suggested that the oxygen vacancies of SrTi_0.9M_0.1O_3-δ (M=Mg， Al， Zr) perovskite-type catalysts are the sites responsible for oxygen activation， and the adsorbed oxygen species on the surface of SrTi_0.9M_0.1O_3-δ catalysts are the main active species for OCM reaction.     

CuO在CeO_2载体上的存在状态研究——氧化物-氧化物相互作用的“嵌入模型”

用X-射线衍射(XRD)和X-射线光电子能谱(XPS)研究了CuO/CeO_2体系中CuO在CeO_2表面的分散状态。结果表明,CuO在CeO_2表面的分散容量约为1.20mmol/100m~2,当CuO含量低于该分散容量时Cu~(2+)在CeO_2载体表面以嵌入形式呈离子态分布;而含量高于分散容量时则有结晶态的CuO出现。首次试用静态二次离子质谱(SSIMS)研究了CuO/CeO_2样品表面第1层中Cu~(2+)/Ce~(4+)离子的比值,结果显示CuO含量为1.22和0.61mmol CuO/100m~2 CeO_2的样品中该比值分别为0.93和0.46;程序升温还原(TPR)结果表明,表面嵌入态的Cu~(2+)比晶相CuO中的Cu~(2+)更易还原而且还原分两步进行,在约153℃和165℃出现两个还原峰。用表面相互作用的嵌入模型讨论并解释了所得实验结果。     

SrTi1-xMgxO3-δ钙钛矿型氧化物催化剂甲烷氧化偶联反应性能的研究

The structure and catalytic properties of SrTi_1-xMg_xO_3-δ perovskite-type catalysts for oxidative coupling of methane (OCM) have been studied by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Temperature-programmed desorption (O₂-TPD) methods. It has been shown that doping Mg²⁺ cations to the B site of SrTi_1-xMg_xO_3-δ perovskite-type catalysts results in the formation of oxygen vacancies in the lattices of oxide cata-lysts. With increasing the amount of Mg²⁺ doped in the B site of SrTi_1-xMg_xO_3-δ, methane conversion and C₂ selectivity first increase and then decrease remarkably. The SrTi_1-xMg_xO_3-δ catalyst with x=0.1 has the highest methane conversion and C₂ yield. It is suggested that the oxygen vacancies produced by Mg²⁺ cations doping are the sites responsible for oxygen activation, and the adsorbed oxygen species on the surface of SrTi_1-xMg_xO_3-δ catalysts are the main active species for OCM reaction. However, the over high content of the adsorbed oxygen species on the surface results in the complete oxidation of methane. Introducing water steam into feedstock can improve the catalytic properties of SrTi_1-xMg_xO_3-δ perovskite-type catalysts for OCM reaction at lower temperature. The SrTi_0.9Mg_0.1O_3-δ catalyst has the methane conversion of 28.0 % with C₂ hydrocarbons selectivity of 36.8 % under reaction temperature of 550 ℃.     

甲烷氧化偶联催化剂Li/MgO的结构及表面性质的研究

本文用XRD、TEM、XPS和荧光光谱等方法研究了一组不同Li~+含量的Li/MgO催化剂的结构及表面性质,并与它们的氧化偶联甲烷的催化性能相关联。结果表明,低配位O~(2-)(O_(3c)~(2-))是使甲烷活化的活性中心。O_(1s)结合能为531.9eV的氧物种是对甲烷氧化偶联反应的C_2选择性起作用的活性氧物种。     

铁-锆交联蒙脱土的制备和结构表征

我们首次合成了铁锆复合柱交联蒙脱土, 并用XRD, 比表面及孔径测定和Mossbauer谱学等方法进行了表征。结果表明, 铁锆交联蒙脱土比表面增大为原土的三倍以上, 其层间距可达0.88nm(d001=1.84nm)。热稳定性明显高于单一Fe柱交联蒙脱土。在500℃加热后层间距保持0.63nm~0.71nm。但由于铁柱的坍塌造成微孔减少, 比表面明显下降。Mossbauer谱研究表明, 500℃焙烧单一铁柱转变为α-Fe~2O~3, 而Fe-Zr-PILC中铁仍以超顺磁Fe^3^+存在, 单一铁柱的铁组分在400℃可还原为金属铁, 而铁锆混合柱交联蒙脱土中由于铁与锆之间存在较强的相互作用, 450℃氢气气氛中铁组分仍不能还原为金属铁。     

钙钛矿型氧化物催化剂SrTiO3的甲烷氧化偶联反应性能的研究

碱土元素氧化物是一类具有较好催化活性和选择性的甲烷氧化偶联(OCM)催化剂[1,2]。Filkova[3]等研究了不同的碱土金属氧化物促进的Nd2O3催化剂的OCM催化性能,发现在所有碱土金属氧化物-Nd2O3催化剂中,SrO-Nd2O3催化剂具有最高的生成C2烃的选择性,这可能因为SrO较强的碱性以及Sr     

[Mo2O4]2+交联层柱粘土的制备及其结构和性能的研究

以[Mo_2O_4]~(2 )溶液为交联剂制备了钼交联层柱粘土。并用XRD、IR、LRS、XPS及TPD等手段对其结构及Mo的存在状态进行了研究。结果表明:[Mo_2O_4]~(2 )被交换进入了层间,所得层柱粘土的d_(?)～13A,其柱结构为Mo_xO_y的簇状氧化物。当交联剂在粘土层间的量超过粘土的交换容量时,Mo在层外表面偏析。酸性研究显示:Mo的加入使钼交联层柱粘土的酸中心数较之原土增加,并以Lewis酸为主。用异丙醇脱水和氧化反应考察钼交联层柱粘土的催化活性,结果表明,这种层柱粘土不仅具有酸催化活性,同时由于钼的引入而具有氧化活性和抗积炭性能。     

两个相等圆孔板弯曲时的三维应力集中

根据Hellinger-Reissner原理建立了具有一个无外力圆柱表面的三维八节点杂交应力元,其假设应力场严格满足柱坐标下三维平衡方程及圆柱面上无外力边界条件;当元退化为二维时也满足协调方程。数值算例表明,这种特殊杂交应力元可高效地分析具有两个圆孔薄板和厚板的应力集中,特别是三维应力集中。