Density Functional Theory Calculations of the Activation of Methanol by a Broensted Zeolitic Proton

Blaszkowski, SR; Santen, van Ra Rutger

doi:10.1021/j100030a017

Cited by 166 publications

(160 citation statements)

References 7 publications

Supporting

Mentioning

139

Contrasting

Unclassified

Order By: Relevance

“…Clusters of adsorbed methanol molecules have been proposed in the cages of zeolite catalysts [40,55,57,58]. Blaszkowski and van Santen [59] observed the end-on configuration where the hydroxyl groups of the methanol are directed towards the basic oxygen of the zeolite as a favourable geometry for methanol adsorption using density functional theory (DFT) calculations.…”

Section: Comparing Desorption Of Methanol To Dmementioning

confidence: 99%

Mechanistic Insights into the Desorption of Methanol and Dimethyl Ether Over ZSM-5 Catalysts

et al. 2017

View full text Add to dashboard Cite

The desorption of methanol and dimethyl ether has been studied over fresh and hydrocarbon-occluded ZSM-5 catalysts with Si/Al ratios of 25, 36 and 135 using a temporal analysis of products reactor. The catalysts were characterized by XRD, SEM, N 2 physisorption and pyridine FT-IR. The crystal size increases with Si/Al ratio from 0.10 to 0.78 µm. The kinetic parameters were obtained using the Redhead method and a plug flow reactor model with coupled convection, adsorption and desorption steps. ZSM-5 catalysts with Si/Al ratios of 25 and 36 exhibit three adsorption sites (low, medium, and high temperature sites), while there is no difference between medium and high temperature sites at a Si/Al ratio of 135. Molecular adsorption on the low temperature site and dissociative adsorption on the medium and high temperature sites give a good match between experiment and the plug flow reactor model. The DME desorption activation energy was systematically higher than that of methanol. Adsorption stoichiometry shows that methanol and DME form clusters onto the binding sites. When non-activated re-adsorption is accounted for, a local equilibrium is reached only on the low and medium temperature binding sites. No differences were observed, other than in site densities, when extracting the kinetic parameters for fresh and activated ZSM-5 catalysts at full coverage. Graphical AbstractElectronic supplementary material The online version of this article (https://doi

show abstract

Section: Comparing Desorption Of Methanol To Dmementioning

confidence: 99%

Mechanistic Insights into the Desorption of Methanol and Dimethyl Ether Over ZSM-5 Catalysts

et al. 2017

View full text Add to dashboard Cite

show abstract

“…Cluster calculations as described above have been shown to give good results for the interaction of molecules with zeolites. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] In the calculations of the shifts of the frequency of the zeolite OH stretch vibration the anharmonicity has been included. This has been done by representing the potential energy in the 1-dimensional vibrational Hamiltonian by a polynomial:…”

Section: Computational Detailsmentioning

confidence: 99%

“…The adsorption of water and methanol has been studied both on clusters [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] representing a small part of the zeolite and in periodic calculations [19][20][21][22][23][24][25][26] including the zeolite crystal structure. The role of the zeolite structure on the activation of methanol has been studied in periodic approach but the conclusions are somewhat contradictory.…”

Section: Introductionmentioning

confidence: 99%

The heterogeneity of the hydroxyl groups in chabazite

Mihaleva

Santen

Jansen

2003

The Journal of Chemical Physics

View full text Add to dashboard Cite

Two different clusters that have the topology of chabazite but different shapes have been used as a model for the Brønsted sites in chabazite. One of the clusters consists of eight tetrahedral atoms ͑8T͒ arranged in a ring and the other represents an intersection of two 8T rings. The adsorption of water and methanol on the two stable proton positions in chabazite has been studied using the B3LYP functional. The coordination of water and methanol with respect to the zeolite fragments were found to be similar, but with methanol situated closer to the acid site than water. The anharmonic zeolite OH stretch frequencies were found to be in the range of 2170-2500 cm Ϫ1 and 1457-2074 cm Ϫ1in the presence of water and methanol, respectively. As a measure of the acidity of the bridging hydroxyl groups in chabazite the shift of the zeolite OH stretch frequency upon adsorption has been used. We have found that the proton attached to the oxygen atom O 1 to be more acidic than the proton attached to the oxygen atom O 3 . Also, in the closed ring clusters the zeolite hydroxyl groups are more acidic than in the open clusters. This is not due to a steric effect as the orientation of the adsorbates with respect to the zeolite site is very similar for both clusters. The anharmonicities of the zeolite O-H bond account for about 40% in the redshift upon the adsorption of water or methanol.

show abstract

“…This will be illustrated for the reaction rate of dehydration of CH3OH to produce dimethyl ether catalysed by zeolitic protons [5 ].…”

Section: Introductionmentioning

confidence: 99%

Computational-chemical advances in heterogeneous catalysis

Santen

1996

Journal of Molecular Catalysis A: Chemical

View full text Add to dashboard Cite

show abstract

Density Functional Theory Calculations of the Activation of Methanol by a Broensted Zeolitic Proton

Cited by 166 publications

References 7 publications

Mechanistic Insights into the Desorption of Methanol and Dimethyl Ether Over ZSM-5 Catalysts

Mechanistic Insights into the Desorption of Methanol and Dimethyl Ether Over ZSM-5 Catalysts

The heterogeneity of the hydroxyl groups in chabazite

Computational-chemical advances in heterogeneous catalysis

Contact Info

Product

Resources

About