Study on the External Surface Acidity of MCM-22 Zeolite:  Theoretical Calculation and31P MAS NMR

2004 ◽  
Vol 108 (4) ◽  
pp. 1386-1391 ◽  
Author(s):  
Yan Wang ◽  
Jianqin Zhuang ◽  
Gang Yang ◽  
Danhong Zhou ◽  
Ding Ma ◽  
...  
Keyword(s):  
Theoretical Calculation ◽  
External Surface ◽  
Surface Acidity ◽  
Mas Nmr

A MAS NMR and DRIFT study of the Ga species in Ga/H-ZSM5 catalysts and their effect on propane ammoxidation

2005 ◽  
Vol 83 (6-7) ◽  
pp. 574-580 ◽  
Author(s):  
Prem Pal ◽  
Juliette Quartararo ◽  
Sharifah B Abd Hamid ◽  
Eric G Derouane ◽  
Jacques C Védrine ◽  
...  
Keyword(s):  
Main Product ◽  
External Surface ◽  
Catalytic Performance ◽  
Mas Nmr ◽  
Propane Ammoxidation ◽  
Bifunctional Mechanism ◽  
Propane Activation ◽  
Cationic Exchange ◽  
Zeolite Crystals

71Ga, 27Al, and 29Si MAS NMR and DRIFT spectroscopies were used to characterize the state of gallium in Ga/H-ZSM5 catalysts tested for their ability to catalyse the ammoxidation of propane. Ga species were observed in two different possible environments: octahedrally coordinated gallium in small Ga2O3 particles at the external surface of the zeolite crystals, octahedrally coordinated gallium in GaO(OH) or related species, and tetrahedrally coordinated gallium in cationic-exchange positions inside the zeolite. Redox (H2–O2) cycles promote the migration of gallium from the GaO(OH) or Ga2O3 species at the external surface of the zeolite crystals to cationic-exchange sites within the zeolite channels. The redox treatment definitely had a beneficial effect on its catalytic performance for the ammoxidation of propane, which is known to occur via a bifunctional mechanism. The main product was acetonitrile at high Ga and Al contents while acrylonitrile was also observed as a side product at high Ga and low Al contents.Key words: ZSM5, MFI, in situ studies, MAS NMR, DRIFT, propane activation, ammoxidation.

An investigation of the surface acidity of mesoporous Al-containing MCM-41 and of the external surface of ferrierite through pivalonitrile adsorption

1999 ◽  
Vol 182 (2) ◽  
pp. 225-235 ◽  
Author(s):  
Marcella Trombetta ◽  
Guido Busca ◽  
Maurizio Lenarda ◽  
Loretta Storaro ◽  
Massimo Pavan
Keyword(s):  
External Surface ◽  
Surface Acidity ◽  
Mcm 41

Mechanochemical Approach for Selective Deactivation of External Surface Acidity of ZSM-5 Zeolite Catalyst

2015 ◽  
Vol 7 (8) ◽  
pp. 4488-4493 ◽  
Author(s):  
Satoshi Inagaki ◽  
Koki Sato ◽  
Shunsuke Hayashi ◽  
Junichi Tatami ◽  
Yoshihiro Kubota ◽  
...  
Keyword(s):  
Zeolite Catalyst ◽  
External Surface ◽  
Surface Acidity

scholarly journals Probing the Surface Acidity of Supported Aluminum Bromide Catalysts

Catalysts ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 869 ◽  
Author(s):  
Md Ashraful Abedin ◽  
Swarom Kanitkar ◽  
Nitin Kumar ◽  
Zi Wang ◽  
Kunlun Ding ◽  
...  
Keyword(s):  
Solid Acid ◽  
Surface Acidity ◽  
Acid Sites ◽  
Magic Angle Spinning ◽  
Mas Nmr ◽  
Solid Catalyst ◽  
Magic Angle ◽  
Aluminum Bromide ◽  
Oh Groups ◽  
27Al Mas Nmr

Solid acid catalysis is an important class of reactions. The principal advantages of solid acid catalysts as compared to their corresponding fluid acids include minimal waste and ease of product separation. One type of these catalysts is based on aluminum bromide (Al2Br6), which is a stronger Lewis acid than Al2Cl6. In this report, Al2Br6 is grafted on commercial mesoporous silica (CMS), SBA-15 and silica gel to create a solid catalyst similar to the silica-supported Al2Cl6 superacid. These supported Al2Br6 catalysts were characterized by NH3-Temperature Programmed Desorption (TPD), pyridine Diffuse Reflectance for Infrared Fourier Transform Spectroscopy (DRIFTS) and Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR). Formation of acid sites was confirmed and quantified with NH3-TPD. Both Lewis and Brønsted sites were observed with DRIFTS using pyridine as a probe molecule. In addition, thermal stability of acid sites was also studied using DRIFTS. 27Al MAS NMR analysis showed tetrahedral, pentahedral and octahedral co-ordination of Al, confirming that Al2Br6 reacted with –OH groups on silica surface. Performance of these catalysts was evaluated using acid-catalyzed 1-butene isomerization. Conversion above 80% was observed at 200 °C, corresponding to thermodynamic equilibrium.

scholarly journals Zeolite-based catalysts for the removal of trace olefins from aromatic streams

2020 ◽  
Vol 10 (3) ◽  
pp. 107-114
Author(s):  
Jakkidi Krishna Reddy ◽  
Shruti Lad ◽  
Kshudiram Mantri ◽  
Jagannath Das ◽  
Ganesan Raman ◽  
...  
Keyword(s):  
Solid State ◽  
Surface Area ◽  
Active Sites ◽  
External Surface ◽  
Mas Nmr ◽  
Fast Diffusion ◽  
External Surface Area ◽  
Olefin Conversion ◽  
The Family ◽  
Pore Clogging

Abstract Removal of trace olefins from aromatic liquids was investigated on UZM-8 and MCM-22, which are the family of MWW zeolites. Both these zeolites were synthesized with similar Si/Al ratio and characterized by various techniques such as XRD, SEM, ICP, N2 adsorption, Ammonia TPD and solid-state MAS-NMR. Olefin conversion activity over UZM-8 was found to be significantly higher than that of MCM-22. In addition to this, deactivation of UZM-8 was slower than the MCM-22. UZM-8 with irregular stacking of MWW layers possess high external surface area and exposes more number of active sites to the reactant molecules. Mesopores generated due to the disordered layers of UZM-8 allows the fast diffusion of the substrate molecules in which pore clogging does not occur, thus making it more active and slow deactivation than that of MCM-22. Graphic abstract

Effect of Adsorbed Water Molecules on the Surface Acidity of Niobium and Tantalum Oxides Studied by MAS NMR

2021 ◽  
Author(s):  
Xin Chen ◽  
Daofeng Huang ◽  
Lulu He ◽  
Li Zhang ◽  
Yuanhang Ren ◽  
...  
Keyword(s):  
Surface Acidity ◽  
Adsorbed Water ◽  
Mas Nmr ◽  
Water Molecules
Sign in / Sign up

Export Citation Format

Share Document