Synergic Effect of Active Sites in Zinc-Modified ZSM-5 Zeolites as Revealed by High-Field Solid-State NMR Spectroscopy.

Understanding the nature of active sites in metal-supported catalysts is of great importance towards establishing their structure-property relationships. The outstanding catalytic performance of metal-supported catalysts is frequently ascribed to the synergic effect of different active sites, which is however not well spectroscopically characterized. Herein, we report the direct detection of surface Zn species and 1 H-67 Zn internuclear interaction between Zn2+ ions and Brønsted acid sites on Zn-modified ZSM-5 zeolites by high-field solid-state NMR spectroscopy. The observed promotion of C-H bond activation of methane is rationalized by the enhanced Brønsted acidity generated by synergic effects arising from the spatial proximity/interaction between Zn2+ ions and Brønsted acidic protons. The concentration of synergic active sites is determined by 1 H-67 Zn double-resonance solid-state NMR spectroscopy.

[1]  Yinyong Sun,et al.  Metal-organic framework based upon the synergy of a Brønsted acid framework and Lewis acid centers as a highly efficient heterogeneous catalyst for fixed-bed reactions. , 2015, Journal of the American Chemical Society.

[2]  G. Somorjai,et al.  Effect of acidic properties of mesoporous zeolites supporting pt nanoparticles on hydrogenative conversion of methylcyclopentane. , 2014, Journal of the American Chemical Society.

[3]  Jun Huang,et al.  Mechanistic insight into the formation of acetic acid from the direct conversion of methane and carbon dioxide on zinc-modified H-ZSM-5 zeolite. , 2013, Journal of the American Chemical Society.

[4]  Jianlin Shi.  On the synergetic catalytic effect in heterogeneous nanocomposite catalysts. , 2013, Chemical reviews.

[5]  A. Singh,et al.  Synergistic Catalysis over Bimetallic Alloy Nanoparticles , 2013 .

[6]  Jiangfeng Du,et al.  Room temperature activation of methane over Zn modified H-ZSM-5 zeolites: Insight from solid-state NMR and theoretical calculations , 2012 .

[7]  Xiumei Wang,et al.  NMR-spectroscopic evidence of intermediate-dependent pathways for acetic acid formation from methane and carbon monoxide over a ZnZSM-5 zeolite catalyst. , 2012, Angewandte Chemie.

[8]  H. Dai,et al.  Co₃O₄ nanocrystals on graphene as a synergistic catalyst for oxygen reduction reaction. , 2011, Nature materials.

[9]  Anmin Zheng,et al.  Insights into the dealumination of zeolite HY revealed by sensitivity-enhanced 27Al DQ-MAS NMR spectroscopy at high field. , 2010, Angewandte Chemie.

[10]  Qiang Wang,et al.  Measurement of hetero-nuclear distances using a symmetry-based pulse sequence in solid-state NMR. , 2010, Physical chemistry chemical physics : PCCP.

[11]  V. Parmon,et al.  Significant influence of Zn on activation of the C-H bonds of small alkanes by Brønsted acid sites of zeolite. , 2008, Chemphyschem : a European journal of chemical physics and physical chemistry.

[12]  V. Ordomsky,et al.  Methane Activation over Zn-Modified MFI Zeolite: NMR Evidence for Zn−Methyl Surface Species Formation , 2008 .

[13]  Chenghua Sun,et al.  Synergistic effects of B/N doping on the visible-light photocatalytic activity of mesoporous TiO2. , 2008, Angewandte Chemie.

[14]  V. Parmon,et al.  Understanding methane aromatization on a Zn-modified high-silica zeolite. , 2008, Angewandte Chemie.

[15]  D. Massiot,et al.  MAS NMR spectra of quadrupolar nuclei in disordered solids: the Czjzek model. , 2008, Journal of magnetic resonance.

[16]  Jun Huang,et al.  Concentration and acid strength of hydroxyl groups in zeolites La,Na-X and La,Na-Y with different lanthanum exchange degrees studied by solid-state NMR spectroscopy , 2007 .

[17]  Anmin Zheng,et al.  Brønsted/Lewis acid synergy in dealuminated HY zeolite: a combined solid-state NMR and theoretical calculation study. , 2007, Journal of the American Chemical Society.

[18]  Anmin Zheng,et al.  Relationship between 1H chemical shifts of deuterated pyridinium ions and Brønsted acid strength of solid acids. , 2007, The journal of physical chemistry. B.

[19]  Anmin Zheng,et al.  Acidity of mesoporous MoO(x)/ZrO2 and WO(x)/ZrO2 materials: a combined solid-state NMR and theoretical calculation study. , 2006, The journal of physical chemistry. B.

[20]  T. T. Nakashima,et al.  Signal enhancement of NMR spectra of half-integer quadrupolar nuclei in solids using hyperbolic secant pulses , 2004 .

[21]  David G. Barton,et al.  Bifunctional pathways in catalysis by solid acids and bases , 1997 .

[22]  P. Mériaudeau,et al.  Dehydrocyclization of Alkanes Over Zeolite-Supported Metal Catalysts: Monofunctional or Bifunctional Route , 1997 .

[23]  M. Hunger.  Multinuclear solid-state NMR studies of acidic and non-acidic hydroxyl protons in zeolites. , 1996, Solid state nuclear magnetic resonance.

[24]  G. Kramer,et al.  An ab-initio study of D/H exchange between CD4 and the H-forms of zeolites FAU and MFI , 1995 .

[25]  G. Kramer,et al.  Understanding the acid behaviour of zeolites from theory and experiment , 1993, Nature.

[26]  P. Mériaudeau,et al.  The role of Ga2O3 and proton acidity on the dehydrogenating activity of Ga2O3-HZSM-5 catalysts: evidence of a bifunctional mechanism , 1990 .

[27]  H. Pfeifer,et al.  Proton MAS NMR studies of hydroxyl groups in alkaline earth cation-exchanged zeolite Y , 1989 .

[28]  Y. Ono.  Transformation of Lower Alkanes into Aromatic Hydrocarbons over ZSM-5 Zeolites , 1987 .

[29]  H. Pfeifer,et al.  1H-MAS n.m.r. studies of ZSM-5 type zeolites , 1987 .

[30]  H. Pfeifer,et al.  Study of brønsted acidity of zeolites using high-resolution proton magnetic resonance with magic-angle spinning , 1982 .

[31]  A. Hirschler.  The measurement of catalyst acidity using indicators forming stable surface carbonium ions , 1963 .

[32]  G. Hutchings,et al.  Aromatization of propane over Ga/H-ZSM-5: An explanation of the synergy observed between Ga3+ and H+ , 1991 .