共查询到19条相似文献,搜索用时 218 毫秒
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本文研究了H-SAPO-34催化甲醇和丁醇转化反应及其产物分布的差异,结合气相色谱-质谱(GC-MS)联用、13C交叉极化魔角旋转核磁共振(13C CP MAS NMR)技术捕获了反应过程中生成的重要反应中间物种.甲醇转化过程以乙烯、丙烯和丁烯为主要产物;而丁醇转化过程中主要产物是丁醇脱水生成的丁烯,反应初期以丙烯和丁烯作为主要产物.两种醇类转化均以低碳烯烃作为主要产物,且存留物种和13C CP MAS NMR分析均观察到芳烃物种,说明H-SAPO-34催化甲醇和丁醇转化存留在催化剂上的有机物种相近.虽然起始于不同的醇类反应,但H-SAPO-34上限域空间的酸催化环境都能引导甲醇和丁醇制取低碳烯烃的反应过程. 相似文献
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甲醇制烯烃过程是由非石油路线生成低碳烯烃的重要途径之一.分子筛因具备独特的孔结构和可调变的酸性质,而成为甲醇制烯烃过程的核心催化剂.固体核磁共振(NMR)是鉴定物质结构、阐释催化反应机理的强有力的工具,在甲醇制烯烃的研究中被广泛应用.本文主要总结了近年来利用原位固体NMR、多维多核NMR、脉冲梯度场NMR等固体NMR技术研究甲醇制烯烃反应机理取得的重要进展.原位固体NMR可以在真实反应条件下监测催化反应中反应物、中间体和产物的动态演变过程;多维多核NMR可以在不破坏催化剂结构情况下确定反应中间体结构信息,特别是129Xe NMR可以很灵敏探测反应中催化剂的孔道结构变化;脉冲梯度场NMR可用于测定孔道内分子的扩散系数,阐明分子筛的扩散机制. 相似文献
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七叶亭衍生物含有药效性较高的苯二酚基团,具有各种生物活性.本文以七叶亭(化合物1)为母体,通过将苯基引入到4位、将甲氧基与羟基分别引入到5、6、7和8位,得到一系列七叶亭衍生物2~14.首先以七叶亭为例,以DMSO-d6作为溶剂,采集了它的多种核磁共振(NMR)谱图(包括1H NMR、13C NMR、1H-13C HSQC、1H-13C HMBC),并进行了较详细的化学位移归属;然后对七叶亭衍生物2~14的1H和13C NMR进行了全归属;另外,讨论了取代基变化对七叶亭及其衍生物上的1H和13C NMR化学位移的影响;最后,使用GIAO和CSGT两种量子化学计算方法计算了七叶亭及其衍生物上的1H和13C NMR化学位移,并与它们的实测值做了比较. 相似文献
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以4-氨基-5-氯-2,3-二氢苯并呋喃-7-羧酸和1-(3-甲氧基丙基)-4-哌啶胺为原料,通过酰胺缩合反应合成了普卡必利.普卡必利化学名为4-氨基-5-氯-2,3-二氢-N-[1-(3-甲氧基丙基)-4-哌啶基]-7-苯并呋喃甲酰胺,是二氢苯并呋喃的衍生物5-H4受体拮抗剂,是一种治疗慢性便秘的重要药物.普卡必利结构中存在多个化学环境非常接近的碳原子,核磁共振(NMR)谱图相对复杂.本文首先应用超高效液相色谱-串联质谱(UPLC-MS/MS)和液相色谱-高分辨质谱(LC-HRMS)对其元素组成进行了分析,进而用一维和二维NMR谱(包括1H NMR、13C NMR、DEPT、1H-1HCOSY、1H-13C HSQC、1H-13C HMBC)对普卡必利的1H和13C NMR信号进行了指认归属,确定了其结构.本工作对苯并呋喃衍生物及相关下游药物合成工艺的进一步优化,以及相关衍生药物的研究具有参考价值. 相似文献
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本文采用原位连续流动条件和间歇条件下的固体核磁共振技术,以及二维13C-13C基于偶极耦合的结合R2(COmbined R2 Driven,CORD)自旋扩散序列的核磁共振实验捕获了H-SSZ-13分子筛催化乙醇脱水过程中多种中间物种,并揭示了各种中间物种的动态演变过程.结果发现H-SSZ-13分子筛催化乙醇脱水过程中,存在两种不同吸附构型的乙醇、活化态的乙醚、乙氧基以及三乙基氧鎓离子,并首次通过原位固体核磁共振技术观测到乙烯的生成.这些结果加深了相关研究者对乙醇脱水反应的认识. 相似文献
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Solid-state NMR studies of the adsorption and photooxidation of ethanol on mixed TiO2--SnO2 photocatalysts 总被引:1,自引:0,他引:1
In situ solid-state NMR methodologies have been used to investigate the photocatalytic oxidation of ethanol (CH3CH2OH) over a series of SnO2-based photocatalysts. The adsorption of ethanol on commercially available SnO2 powder was studied using both cross-polarization 13C NMR and REDOR experiments, and showed the formation of two surface ethanol species, hydrogen-bonded ethanol at surface hydroxyl groups and ethanol chemisorbed to the SnO2 surface (Sn–OCH2CH3). 13C NMR of the adsorbed ethanol was used to characterize the surface of monolayer SnO2–TiO2 coupled photocatalysts supported on porous Vycor glass. In situ solid-state NMR studies showed that the photooxidation of ethanol over the monolayer photocatalysts was slower than that over a supported TiO2 monolayer photocatalyst due to the build-up of reaction intermediates such as acetic acid on the catalyst surface. 119Sn NMR experiments characterized the tin species on the porous Vycor glass support. 相似文献
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V. M. Mastikhin V. V. Terskikh O. B. Lapina S. V. Filimonova M. Seidl H. Knzinger 《Solid state nuclear magnetic resonance》1995,4(6):369-379
1H magic-angle spinning nuclear magnetic resonance (MAS NMR) spectra of TiOx/SiO2 catalysts suggest the interaction of surface TiOx. species with Si-OH groups of the silica. Simultaneously, Ti-OH groups from surface titania species appear. The distribution of TiOx species over SiO2 is non-uniform, since a considerable part of surface OH groups remains unreacted with supported titania. Supported vanadia species interact both with Si-OH and Ti-OH groups. 51V NMR spectra suggest the interaction of vanadia with supported titania species and show the non-uniform distribution of titania over the SiO2 surface. Deposition of titania as well as vanadia produces strong electron-accepting (Lewis) sites which interact with the terminal N atom of adsorbed N2O molecules, resulting in a downfield shift of the resonance in 15N NMR spectra. The acid strength of electron-accepting sites is similar in both cases. Only about 10% of the total amount of supported titania and vanadia create Lewis sites. 相似文献
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Cyclic cross-polarization from a proton magnetization to 13C and from there back to proton coherences permits the indirect, 13C chemical shift selective detection of hydrocarbon compounds in the proton NMR channel. This excitation technique can be combined with elements of one-, two- or three-dimensional magnetic resonance imaging permitting the measurement of time-resolved spatial distributions of hydrocarbon components. Beginning this sort of CYCLCROP mapping experiment with a non-equilibrium distribution of the constituents in the system allows one to study the time evolution of the concentrations of all components that can be identified by characteristic 13C resonance lines. As applications, studies of ingress, mixing, gel formation, transport and metabolism in living plants, long-time inter- and self-diffusion in complex hydrocarbon systems are suggested. As a test experiment, the diffusion of methanol in swollen polymethylmethacrylate was examined. 相似文献
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Brønsted酸(B酸)是无定型硅铝(ASAs)表面最重要的催化活性位点.通常认为B酸位的形成只依赖于不饱和四配位铝(AlIV),且仅具有弱B酸性.通过合成五配位铝(AlV)富集的ASAs能够大幅提升高铝硅比(Al/Si)时的B酸含量及强度,克服传统AlIV富集的ASAs的酸性强化瓶颈.本文介绍了AlV在ASAs酸性强化及合成单原子催化剂中的重要作用.通过采用多种二维固体核磁共振(SSNMR)及原位质子NMR技术,证明了AlV能够大量富集在ASAs表面,着重介绍了两种基于AlV的新B酸位的形成机制,并阐明了AlV诱导单原子催化剂在ASAs表面形成的机理. 相似文献
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The adsorption of Na+ on γ-alumina surfaces at four coverages of Na2CO3 [5, 10, 15 and 20% (w/w)] was characterized by solid-state 23Na and 27Al nuclear magnetic resonance (NMR) spectroscopy. The experimental results suggest that two distinct adsorbed species are present on the alumina surface: surface species and surface salts. At the lower coverages of Na2CO3 (5 and 10%), the surface species is predominant, in which the Na+ cations are associated with the oxygen atoms of γ-alumina. Increasing the loading level to 15% results in the appearance of a second adsorbed species that is attributed to the surface salt, Na2CO3, deposited on the solid surface. Further adsorption of Na2CO3 leads to an increase in the amount of surface salt while the amount of surface species remains unchanged. 1H---27Al Cross-polarization magic angle spinning (CP-MAS) experiments give the evidence that some Na+ cations in the form of surface species are coordinated with the Brönsted acid sites of γ-alumina. This may be the main driving force that improves appreciably the catalytic efficiency of an Na2CO3---Al2O3 catalyst. 相似文献
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从产于甘肃的高山绣线菊植物中分离出一种新的化合物:白桦酯酸7',8'-二羟基肉桂酸脂.利用MS,IR,1D和2D NMR技术,其中包括1H-1H COSY,1H-13C COSY,1H-13C COLOC等对1H和13C谱进行了归属. 相似文献
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