Progress in the Studies on Sn-Zeolites by Solid-State Nuclear Magnetic Resonance
XIAO Yao1,2, XIA Chang-jiu3, YI Xian-feng,1, LIU Feng-qing1,2, LIU Shang-bin4, ZHENG An-min,1
1. State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China
2. University of Chinese Academy of Sciences, Beijing 100049, China
3. State Key Laboratory of Catalytic Materials and Reaction Engineering, Research Institute of Petroleum Processing, SINOPEC, Beijing 100083, China
4. Institute of Atomic and Molecular Sciences, Taipei 10617, China
Due to their excellent catalytic performances in the conversion of biomass molecules such as glucose and lactic acid, the Sn-containing zeolite catalysts have received wide attention. Understanding detailed structures and acidity properties of the active sites and the corresponding catalytic reaction mechanisms is a critical step in developing fundamental insights into the catalytic function and exploiting more highly active zeolite catalysts. Solid-state nuclear magnetic resonance (NMR) spectroscopy provides useful information on the local structures and acidity properties of active centers, as well as the catalytic reaction mechanisms in zeolites. This review briefly introduces the application of solid-state NMR technique in the studies on Sn-containing zeolites. Further challenges and perspectives are also discussed.
Keywords:solid-state nuclear magnetic resonance (NMR)
;
Sn-zeolite
;
active center
;
acidity
;
reaction mechanism
XIAO Yao. Progress in the Studies on Sn-Zeolites by Solid-State Nuclear Magnetic Resonance. Chinese Journal of Magnetic Resonance[J], 2021, 38(4): 571-584 doi:10.11938/cjmr20212926
图1
(A) 不同处理条件下,Sn-Beta分子筛的119Sn MAS NMR谱图:(a)煅烧;(b)煅烧后脱水;(c)煅烧脱水后再水合.(B)脱水Sn-Beta分子筛的(a) 119Sn MAS与(b~d)不同CP接触时间[(b) 0.2 ms,(c) 1.0 ms,(d) 2.0 ms]的1H-119Sn CP MAS NMR谱图.(C)不同温度真空脱水的119Sn-Beta分子筛的1H-119Sn CP-CPMG MAS NMR谱图.(D) (a)脱水与(b)未脱水Sn-Beta分子筛的119Sn DP-CPMG MAS NMR谱图,*表示旋转边带(根据文献[6]和[26]修改)
Fig.1
(A) 119Sn MAS NMR spectra of Sn-Beta after different treatments: (a) Calcined; (b) Dehydrated after calcination; (c) Rehydrated after step (b). (B) (a) 119Sn MAS and (b~d) 1H-119Sn CP MAS NMR spectra of dehydrated Sn-Beta. The CP contact times from 1H to 119Sn were varied: (b) 0.2 ms, (c) 1.0 ms, (d) 2.0 ms. (C) 1H-119Sn CP-CPMG MAS NMR spectra of 119Sn-Beta sample dehydrated under vacuum conditions at different temperatures. (D) 119Sn DP-CPMG MAS NMR spectra of (a) dehydrated and (b) hydrated Sn-Beta. The spinning sidebands are marked as asterisks (Reproduced from Refs. [6] and [26])
图2
(a) 脱水119Sn-Beta在水汽中(H2O/Sn=4)暴露不同时间的119Sn DP-CPMG MAS NMR谱图变化;(b) δSn −581,−689和−703三处不同119Sn NMR信号积分面积与暴露时间之间的关联;(c) Sn-Beta分子筛Sn位点的水合机制(根据文献[26]修改)
Fig.2
(a) Variation of 119Sn DP-CPMG MAS NMR spectra of 119Sn-Beta with time after exposure to water (H2O/Sn=4); (b) Variation of the normalized integrated intensity of 119Sn MAS NMR signals at ca. −581, −689, and −703 ppm with time of exposure to water; (c) Dissociative adsorption scheme of water over tin sites in Sn-Beta (Reproduced from Ref. [26])
图3
(a) 脱水Sn-Beta水合前与在水汽中水合70 h的1H MAS NMR谱图;(b) Sn-Beta不同水合时间的1H MAS NMR谱图;(c) 1H和119Sn NMR归一化积分面积与水合时间的关系;(d, e)脱水Sn-Beta两种不同的水合机制(根据文献[27]修改)
Fig.3
(a) 1H MAS NMR spectra of dehydrated Sn-Beta before and after exposure to water vapors for 70 h; (b) Time-resolved 1H MAS NMR spectra acquired during the hydration of Sn-Beta; (c) Normalized intensities of 1H and 119Sn MAS NMR signals vs. hydration time; (d, e) Two different hydration mechanism in dehydrated Sn-Beta (Reproduced from Ref. [27])
Fig.4
Two-dimensional 1H-119Sn HMQC MAS NMR spectra of Sn-Beta. (a) Without dehydration; (b) Dehydrated at 298 K; (c) Dehydrated at 393 K without 119Sn decoupling; (d) Dehydrated at 393 K with 119Sn decoupling (Reproduced from Ref. [36])
2 锡硅分子筛酸特性的固体NMR研究
众所周知,作为一种固体酸催化剂,分子筛的酸性特征(酸类型、酸强度、酸浓度与酸分布等)与其催化反应性能密切相关[15, 37].尽管119Sn和1H MAS NMR方法能够准确提供锡硅分子筛的活性中心结构信息,但并不能给出这些重要的酸性特征.为解决这一难题,往往需要借助探针分子吸附的方法.通过选择合适的探针分子,就可以获得锡硅分子筛相应的酸性信息.常用的NMR探针分子主要有氘代吡啶、氘代乙腈、2-13C-丙酮、三甲基膦(TMP)、三烷基氧膦等等[13, 15, 17-22, 38-49].
Fig.5
(a) 31P-TMP NMR spectra of Sn-MFI zeolite under different methanol pressure; (b) The Lewis and Brønsted acid amounts of Sn-MFI zeolite under different methanol pressure (Reproduced from Ref. [13])
图6
不同TMPO吸附量Sn-Beta分子筛的(a) 31P与(b) 119Sn和31P MAS NMR谱图(根据文献[45]修改)
Fig.6
(a) 31P MAS NMR spectra of TMPO dosed on Sn-Beta at different loading levels; (b) 119Sn and 31P MAS NMR spectra of 119Sn-Beta with different TMPO loadings (Reproduced from Ref. [45])
Fig.7
Site time yield (STY) for (a) glucose isomerization in water and (b) aldol condensation of benzaldehyde and acetone in toluene catalyzed by different Sn-Beta catalysts plotted against the percent integrated 31P peak area normalized by P and Sn content at (a) δiso = 55.8 and 54.9 ppm and (b) δiso = 58.6 and 57.2 ppm (Reproduced from Ref. [45])
图8
Si-Beta分子筛以及各种锡硅分子筛(a)吸附TMPO的31P NMR谱图、(b)吸附2-13C-丙酮的13C CP MAS NMR谱图、(c)吸附NH3的1H NMR谱图及差谱(根据文献[46]修改)
Fig.8
(a) 31P MAS and (b) 13C CP MAS NMR spectra of Si-Beta and Sn-containing Beta zeolites recorded after adsorption of TMPO and 2-13C-acetone, respectively. (c) 1H MAS NMR or difference spectra of various dehydrated Sn-containing Beta zeolites recorded before and after adsorption of ammonia (Reproduced from Ref. [46])
Fig.9
Catalytic performance of the Sn-containing catalysts in the (a) BV oxidation of cyclohexanone and (b) cyclohexene oxide hydration, as well as the plots of reaction rates as a function of the number of accessible LAS (Reproduced from Ref. [46])
图11
(A) (a, c)葡萄糖和(b, d)果糖分别吸附在(a, b)Si-Beta和(c, d) Sn-Beta分子筛上的13C MAS NMR谱图.(B)果糖吸附在Sn-Beta分子筛上不同CP接触时间[(a) 0.1 ms, (b) 1.0 ms, (c)无CP]的CP MAS NMR谱图(根据文献[6]修改)
Fig.11
(A) 13C MAS NMR of (a) glucose adsorbed into Si-Beta, (b) fructose adsorbed into Si-Beta, (c) glucose adsorbed into Sn-Beta, (d) fructose adsorbed into Sn-Beta. (B) Spectra from fructose adsorbed into Sn-Beta: (a) CP contact time of 0.1 ms; (b) CP contact time of 1.0 ms; and (c) no CP (Reproduced from Ref. [6])
Fig.12
(A) 13C CP MAS NMR spectra of (a) 30 μmol⋅g−1 and (b) 100 μmol⋅g−1 of 2-13C-acetone adsorbed on Sn-Beta zeolite dehydrated at 393 K, (c) 30 μmol⋅g−1 and (d) 100 μmol⋅g−1 of 2-13C-acetone adsorbed on Sn-Beta zeolite dehydrated at 673 K. (B) Proposed catalytic cycle for the reaction between acetone and cyclohexanol on Sn-Beta zeolite. (Reproduced from Ref. [50])
Insight into the effects of acid characteristics on the catalytic performance of Sn-MFI zeolites in the transformation of dihydroxyacetone to methyl lactate
Water-induced structural dynamic process in molecular sieves under mild hydrothermal conditions: Ship-in-a-bottle strategy for acidity identification and catalyst modification
... [6].Ivanova等[26]利用1H-119Sn CP-CPMG MAS NMR方法研究不同脱水温度的Sn-Beta分子筛时,发现脱水温度越高,δSn −418信号越弱[图 1(C)].当脱水温度高于250 ℃时,已经完全观测不到δSn −418处信号,表明高温脱水可能导致“open”锡位点发生聚合生成“closed”锡位点[26].值得一提的是,由于分子筛中存在的硅羟基物种也可能导致邻近的骨架“closed”锡位点产生CP信号,因此,对于锡硅分子筛“open”锡位点的归属目前仍然存在一定的争议[24-33]. ...
... Sn DP-CPMG MAS NMR谱图,*表示旋转边带(根据文献[6]和[26]修改) (A) 119Sn MAS NMR spectra of Sn-Beta after different treatments: (a) Calcined; (b) Dehydrated after calcination; (c) Rehydrated after step (b). (B) (a) 119Sn MAS and (b~d) 1H-119Sn CP MAS NMR spectra of dehydrated Sn-Beta. The CP contact times from 1H to 119Sn were varied: (b) 0.2 ms, (c) 1.0 ms, (d) 2.0 ms. (C) 1H-119Sn CP-CPMG MAS NMR spectra of 119Sn-Beta sample dehydrated under vacuum conditions at different temperatures. (D) 119Sn DP-CPMG MAS NMR spectra of (a) dehydrated and (b) hydrated Sn-Beta. The spinning sidebands are marked as asterisks (Reproduced from Refs. [6] and [26])Fig.1
... Sn DP-CPMG MAS NMR spectra of (a) dehydrated and (b) hydrated Sn-Beta. The spinning sidebands are marked as asterisks (Reproduced from Refs. [6] and [26]) Fig.1
... Davis等[6]利用13C MAS NMR结合13C标记的葡萄糖和果糖分子研究了Sn-Beta分子筛催化转化葡萄糖异构化的反应历程.如图 11(A)所示,葡萄糖和果糖吸附在无活性中心的Si-Beta分子筛上的化学位移在δC 60~100 [图 11A(a,b)];而当它们分别吸附在含有Lewis酸中心的Sn-Beta分子筛上时,明显产生了一系列新的13C NMR信号[δC 30、130、180和214;图 11A(c,d)].特别是δC 214信号的出现证实有羰基分子(醛或酮)生成,结合图 11(B)的13C CP MAS NMR实验,进一步明确该信号为果糖开环结构上的酮基.辅以理论计算,他们推测葡萄糖首先在Sn-Beta分子筛的“open”锡位点发生开环,随后酮基碳原子经过氢迁移反应异构化生成果糖[6]. ...
... [6]. ...
... C MAS NMR谱图.(B)果糖吸附在Sn-Beta分子筛上不同CP接触时间[(a) 0.1 ms, (b) 1.0 ms, (c)无CP]的CP MAS NMR谱图(根据文献[6]修改) (A) 13C MAS NMR of (a) glucose adsorbed into Si-Beta, (b) fructose adsorbed into Si-Beta, (c) glucose adsorbed into Sn-Beta, (d) fructose adsorbed into Sn-Beta. (B) Spectra from fructose adsorbed into Sn-Beta: (a) CP contact time of 0.1 ms; (b) CP contact time of 1.0 ms; and (c) no CP (Reproduced from Ref. [6])Fig.11
... C MAS NMR of (a) glucose adsorbed into Si-Beta, (b) fructose adsorbed into Si-Beta, (c) glucose adsorbed into Sn-Beta, (d) fructose adsorbed into Sn-Beta. (B) Spectra from fructose adsorbed into Sn-Beta: (a) CP contact time of 0.1 ms; (b) CP contact time of 1.0 ms; and (c) no CP (Reproduced from Ref. [6]) Fig.11
Insight into the effects of acid characteristics on the catalytic performance of Sn-MFI zeolites in the transformation of dihydroxyacetone to methyl lactate
... P NMR谱图;(b)不同甲醇负载量的Sn-MFI分子筛的Lewis与Brønsted酸量(根据文献[13]修改) (a) 31P-TMP NMR spectra of Sn-MFI zeolite under different methanol pressure; (b) The Lewis and Brønsted acid amounts of Sn-MFI zeolite under different methanol pressure (Reproduced from Ref. [13])Fig.5
... P-TMP NMR spectra of Sn-MFI zeolite under different methanol pressure; (b) The Lewis and Brønsted acid amounts of Sn-MFI zeolite under different methanol pressure (Reproduced from Ref. [13]) Fig.5
... 众所周知,作为一种固体酸催化剂,分子筛的酸性特征(酸类型、酸强度、酸浓度与酸分布等)与其催化反应性能密切相关[15, 37].尽管119Sn和1H MAS NMR方法能够准确提供锡硅分子筛的活性中心结构信息,但并不能给出这些重要的酸性特征.为解决这一难题,往往需要借助探针分子吸附的方法.通过选择合适的探针分子,就可以获得锡硅分子筛相应的酸性信息.常用的NMR探针分子主要有氘代吡啶、氘代乙腈、2-13C-丙酮、三甲基膦(TMP)、三烷基氧膦等等[13, 15, 17-22, 38-49]. ...
Pentacoordinated aluminum species: New frontier for tailoring acidity-enhanced silica-alumina catalysts
2020
Water-induced structural dynamic process in molecular sieves under mild hydrothermal conditions: Ship-in-a-bottle strategy for acidity identification and catalyst modification
2020
Acidity and local confinement effect in mordenite probed by solid-state NMR spectroscopy
2021
31P NMR chemical shifts of phosphorus probes as reliable and practical acidity scales for solid and liquid catalysts
... ]和[26]修改) (A) 119Sn MAS NMR spectra of Sn-Beta after different treatments: (a) Calcined; (b) Dehydrated after calcination; (c) Rehydrated after step (b). (B) (a) 119Sn MAS and (b~d) 1H-119Sn CP MAS NMR spectra of dehydrated Sn-Beta. The CP contact times from 1H to 119Sn were varied: (b) 0.2 ms, (c) 1.0 ms, (d) 2.0 ms. (C) 1H-119Sn CP-CPMG MAS NMR spectra of 119Sn-Beta sample dehydrated under vacuum conditions at different temperatures. (D) 119Sn DP-CPMG MAS NMR spectra of (a) dehydrated and (b) hydrated Sn-Beta. The spinning sidebands are marked as asterisks (Reproduced from Refs. [6] and [26])Fig.1
... Sn NMR信号积分面积与暴露时间之间的关联;(c) Sn-Beta分子筛Sn位点的水合机制(根据文献[26]修改) (a) Variation of 119Sn DP-CPMG MAS NMR spectra of 119Sn-Beta with time after exposure to water (H2O/Sn=4); (b) Variation of the normalized integrated intensity of 119Sn MAS NMR signals at ca. −581, −689, and −703 ppm with time of exposure to water; (c) Dissociative adsorption scheme of water over tin sites in Sn-Beta (Reproduced from Ref. [26])Fig.2
... Sn MAS NMR signals at ca. −581, −689, and −703 ppm with time of exposure to water; (c) Dissociative adsorption scheme of water over tin sites in Sn-Beta (Reproduced from Ref. [26]) Fig.2
... Sn NMR归一化积分面积与水合时间的关系;(d, e)脱水Sn-Beta两种不同的水合机制(根据文献[27]修改) (a) 1H MAS NMR spectra of dehydrated Sn-Beta before and after exposure to water vapors for 70 h; (b) Time-resolved 1H MAS NMR spectra acquired during the hydration of Sn-Beta; (c) Normalized intensities of 1H and 119Sn MAS NMR signals vs. hydration time; (d, e) Two different hydration mechanism in dehydrated Sn-Beta (Reproduced from Ref. [27])Fig.3
Two-dimensional 1H-119Sn HMQC MAS NMR spectra of Sn-Beta. (a) Without dehydration; (b) Dehydrated at 298 K; (c) Dehydrated at 393 K without 119Sn decoupling; (d) Dehydrated at 393 K with 119Sn decoupling (Reproduced from Ref. [36])Fig.42 锡硅分子筛酸特性的固体NMR研究
众所周知,作为一种固体酸催化剂,分子筛的酸性特征(酸类型、酸强度、酸浓度与酸分布等)与其催化反应性能密切相关[15, 37].尽管119Sn和1H MAS NMR方法能够准确提供锡硅分子筛的活性中心结构信息,但并不能给出这些重要的酸性特征.为解决这一难题,往往需要借助探针分子吸附的方法.通过选择合适的探针分子,就可以获得锡硅分子筛相应的酸性信息.常用的NMR探针分子主要有氘代吡啶、氘代乙腈、2-13C-丙酮、三甲基膦(TMP)、三烷基氧膦等等[13, 15, 17-22, 38-49]. ...
... hydration time; (d, e) Two different hydration mechanism in dehydrated Sn-Beta (Reproduced from Ref. [27]) Fig.3
Two-dimensional 1H-119Sn HMQC MAS NMR spectra of Sn-Beta. (a) Without dehydration; (b) Dehydrated at 298 K; (c) Dehydrated at 393 K without 119Sn decoupling; (d) Dehydrated at 393 K with 119Sn decoupling (Reproduced from Ref. [36])Fig.42 锡硅分子筛酸特性的固体NMR研究
众所周知,作为一种固体酸催化剂,分子筛的酸性特征(酸类型、酸强度、酸浓度与酸分布等)与其催化反应性能密切相关[15, 37].尽管119Sn和1H MAS NMR方法能够准确提供锡硅分子筛的活性中心结构信息,但并不能给出这些重要的酸性特征.为解决这一难题,往往需要借助探针分子吸附的方法.通过选择合适的探针分子,就可以获得锡硅分子筛相应的酸性信息.常用的NMR探针分子主要有氘代吡啶、氘代乙腈、2-13C-丙酮、三甲基膦(TMP)、三烷基氧膦等等[13, 15, 17-22, 38-49]. ...
Correlating synthetic methods, morphology, atomic-level structure, and catalytic activity of Sn-β catalysts
... Sn去耦(根据文献[36]修改) Two-dimensional 1H-119Sn HMQC MAS NMR spectra of Sn-Beta. (a) Without dehydration; (b) Dehydrated at 298 K; (c) Dehydrated at 393 K without 119Sn decoupling; (d) Dehydrated at 393 K with 119Sn decoupling (Reproduced from Ref. [36])Fig.42 锡硅分子筛酸特性的固体NMR研究
众所周知,作为一种固体酸催化剂,分子筛的酸性特征(酸类型、酸强度、酸浓度与酸分布等)与其催化反应性能密切相关[15, 37].尽管119Sn和1H MAS NMR方法能够准确提供锡硅分子筛的活性中心结构信息,但并不能给出这些重要的酸性特征.为解决这一难题,往往需要借助探针分子吸附的方法.通过选择合适的探针分子,就可以获得锡硅分子筛相应的酸性信息.常用的NMR探针分子主要有氘代吡啶、氘代乙腈、2-13C-丙酮、三甲基膦(TMP)、三烷基氧膦等等[13, 15, 17-22, 38-49]. ...
... Sn decoupling (Reproduced from Ref. [36]) Fig.42 锡硅分子筛酸特性的固体NMR研究
众所周知,作为一种固体酸催化剂,分子筛的酸性特征(酸类型、酸强度、酸浓度与酸分布等)与其催化反应性能密切相关[15, 37].尽管119Sn和1H MAS NMR方法能够准确提供锡硅分子筛的活性中心结构信息,但并不能给出这些重要的酸性特征.为解决这一难题,往往需要借助探针分子吸附的方法.通过选择合适的探针分子,就可以获得锡硅分子筛相应的酸性信息.常用的NMR探针分子主要有氘代吡啶、氘代乙腈、2-13C-丙酮、三甲基膦(TMP)、三烷基氧膦等等[13, 15, 17-22, 38-49]. ...
Influence of hierarchical ZSM-5 catalysts with various acidity on the dehydration of glycerol to acrolein
1
2021
... 众所周知,作为一种固体酸催化剂,分子筛的酸性特征(酸类型、酸强度、酸浓度与酸分布等)与其催化反应性能密切相关[15, 37].尽管119Sn和1H MAS NMR方法能够准确提供锡硅分子筛的活性中心结构信息,但并不能给出这些重要的酸性特征.为解决这一难题,往往需要借助探针分子吸附的方法.通过选择合适的探针分子,就可以获得锡硅分子筛相应的酸性信息.常用的NMR探针分子主要有氘代吡啶、氘代乙腈、2-13C-丙酮、三甲基膦(TMP)、三烷基氧膦等等[13, 15, 17-22, 38-49]. ...
Acid sites in zeolite Y: A solid-state NMR and infrared study using trimethylphosphine as a probe molecule
2
1985
... 众所周知,作为一种固体酸催化剂,分子筛的酸性特征(酸类型、酸强度、酸浓度与酸分布等)与其催化反应性能密切相关[15, 37].尽管119Sn和1H MAS NMR方法能够准确提供锡硅分子筛的活性中心结构信息,但并不能给出这些重要的酸性特征.为解决这一难题,往往需要借助探针分子吸附的方法.通过选择合适的探针分子,就可以获得锡硅分子筛相应的酸性信息.常用的NMR探针分子主要有氘代吡啶、氘代乙腈、2-13C-丙酮、三甲基膦(TMP)、三烷基氧膦等等[13, 15, 17-22, 38-49]. ...
... P MAS NMR谱图(根据文献[45]修改) (a) 31P MAS NMR spectra of TMPO dosed on Sn-Beta at different loading levels; (b) 119Sn and 31P MAS NMR spectra of 119Sn-Beta with different TMPO loadings (Reproduced from Ref. [45])Fig.6
Site time yield (STY) for (a) glucose isomerization in water and (b) aldol condensation of benzaldehyde and acetone in toluene catalyzed by different Sn-Beta catalysts plotted against the percent integrated 31P peak area normalized by P and Sn content at (a) δiso = 55.8 and 54.9 ppm and (b) δiso = 58.6 and 57.2 ppm (Reproduced from Ref. [45])Fig.7
Site time yield (STY) for (a) glucose isomerization in water and (b) aldol condensation of benzaldehyde and acetone in toluene catalyzed by different Sn-Beta catalysts plotted against the percent integrated 31P peak area normalized by P and Sn content at (a) δiso = 55.8 and 54.9 ppm and (b) δiso = 58.6 and 57.2 ppm (Reproduced from Ref. [45])Fig.7
... 58.6和57.2的“closed”锡位点)含量与催化苯甲醛与丙酮缩合反应活性之间的关联(根据文献[45]修改) Site time yield (STY) for (a) glucose isomerization in water and (b) aldol condensation of benzaldehyde and acetone in toluene catalyzed by different Sn-Beta catalysts plotted against the percent integrated 31P peak area normalized by P and Sn content at (a) δiso = 55.8 and 54.9 ppm and (b) δiso = 58.6 and 57.2 ppm (Reproduced from Ref. [45])Fig.7
... H NMR谱图及差谱(根据文献[46]修改) (a) 31P MAS and (b) 13C CP MAS NMR spectra of Si-Beta and Sn-containing Beta zeolites recorded after adsorption of TMPO and 2-13C-acetone, respectively. (c) 1H MAS NMR or difference spectra of various dehydrated Sn-containing Beta zeolites recorded before and after adsorption of ammonia (Reproduced from Ref. [46])Fig.8
... H MAS NMR or difference spectra of various dehydrated Sn-containing Beta zeolites recorded before and after adsorption of ammonia (Reproduced from Ref. [46]) Fig.8
... 锡硅分子筛催化(a)环己酮BV氧化、(b)氧化环己烯水合反应性能与可接近性Lewis酸(LAS)酸量之间的关联(根据文献[46]修改) Catalytic performance of the Sn-containing catalysts in the (a) BV oxidation of cyclohexanone and (b) cyclohexene oxide hydration, as well as the plots of reaction rates as a function of the number of accessible LAS (Reproduced from Ref. [46])Fig.9
... Catalytic performance of the Sn-containing catalysts in the (a) BV oxidation of cyclohexanone and (b) cyclohexene oxide hydration, as well as the plots of reaction rates as a function of the number of accessible LAS (Reproduced from Ref. [46]) Fig.9
... N CP MAS NMR谱图(根据文献[48]修改) 15N CP MAS NMR of pyridine adsorbed on metal-substituted zeolites (Reproduced from Ref. [48])Fig.103 锡硅分子筛催化反应机理的固体NMR研究
... C CP MAS NMR谱图.(B) Sn-Beta分子筛催化丙酮与环己醇反应机理(根据文献[50]修改) (A) 13C CP MAS NMR spectra of (a) 30 μmol⋅g−1 and (b) 100 μmol⋅g−1 of 2-13C-acetone adsorbed on Sn-Beta zeolite dehydrated at 393 K, (c) 30 μmol⋅g−1 and (d) 100 μmol⋅g−1 of 2-13C-acetone adsorbed on Sn-Beta zeolite dehydrated at 673 K. (B) Proposed catalytic cycle for the reaction between acetone and cyclohexanol on Sn-Beta zeolite. (Reproduced from Ref. [50])Fig.124 总结与展望
... C-acetone adsorbed on Sn-Beta zeolite dehydrated at 673 K. (B) Proposed catalytic cycle for the reaction between acetone and cyclohexanol on Sn-Beta zeolite. (Reproduced from Ref. [50]) Fig.124 总结与展望