Quantum Chemical Modeling of Zeolite-Catalyzed Methylation Reactions: Toward Chemical Accuracy for Barriers

Svelle, Stian; Tuma, Christian; Rozanska, Xavier; Kerber, Torsten; Sauer, Joachim

doi:10.1021/ja807695p

Cited by 291 publications

(476 citation statements)

References 72 publications

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“…These deficiencies are a consequence of the approximations present in the formulation of the exchange-correlation functional and of the lack of exact cancellation of the Coulomb self-interaction energy, an effect which is known to favor solutions with delocalization of the spin density. It is also responsible for a systematic underestimation of energy barriers [15] an effect that has also been observed for surface reactions [16].…”

Section: Current Approaches To Dft Calculationsmentioning

confidence: 72%

First Principles Calculations on Oxide-Based Heterogeneous Catalysts and Photocatalysts: Problems and Advances

Pacchioni

2014

Catal Lett

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Density functional theory (DFT) has become an essential complement of experiments to interpret, rationalize, and understand structures, spectroscopic data, microscopy analyses, etc. of relevance in heterogeneous catalysis and photocatalysis. However, one of the major goals of theory in catalysis remains the prediction of reaction enthalpies and entropies, of transition state structures, and the identification of reaction mechanisms. While accurate theoretical methods are currently available to study the thermochemistry of molecular systems, this is much less so when reactions involve solid surfaces and in particular oxide materials. The problem stems from the approximate nature of the exchange-correlation functionals used in all DFT approaches. Attempts to improve the accuracy of reaction energies is at the core of the efforts made in the past 30 years to generate new functionals. In this review we will discuss some recent advances in the theoretical description of oxides and their surfaces in heterogeneous catalysis and photocatalysis. In particular, we will focus on two problems: (1) the determination of an oxide band gap and the proper alignment of the occupied and unoccupied levels with respect to the vacuum level, an aspect relevant for the red-ox properties of the material, and (2) the calculation of reaction energies at oxide surfaces. To this end, we will discuss and comment on the performance of current implementations of exchange-correlation functionals (standard GGA, GGA?U, hybrid functionals, meta-GGA, etc.) or alternative approaches (like the quasiparticle GW method), in predicting band alignment and chemical reactivity at oxide surfaces. The role of dispersion forces will be also briefly discussed.

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Section: Current Approaches To Dft Calculationsmentioning

confidence: 72%

First Principles Calculations on Oxide-Based Heterogeneous Catalysts and Photocatalysts: Problems and Advances

Pacchioni

2014

Catal Lett

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“…Comparison will also be made with previous results of Svelle and co‐workers,1 which differ from the present one in the following respect: In Svelle's report, the structures had been optimized and the harmonic frequencies had been calculated with PBE without including dispersion, whereas in the present study, PBE+D2 was used. Moreover, Svelle et al.…”

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confidence: 74%

Ab Initio Calculation of Rate Constants for Molecule–Surface Reactions with Chemical Accuracy

2016

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The ab initio prediction of reaction rate constants for systems with hundreds of atoms with an accuracy that is comparable to experiment is a challenge for computational quantum chemistry. We present a divide‐and‐conquer strategy that departs from the potential energy surfaces obtained by standard density functional theory with inclusion of dispersion. The energies of the reactant and transition structures are refined by wavefunction‐type calculations for the reaction site. Thermal effects and entropies are calculated from vibrational partition functions, and the anharmonic frequencies are calculated separately for each vibrational mode. This method is applied to a key reaction of an industrially relevant catalytic process, the methylation of small alkenes over zeolites. The calculated reaction rate constants (free energies), pre‐exponential factors (entropies), and enthalpy barriers show that our computational strategy yields results that agree with experiment within chemical accuracy limits (less than one order of magnitude).

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“…[8,[15][16][17] However, theoretical chemists are still confronted with paramount challenges to thoroughly explain experimental observations. The true challenge lies in linking the model system with experimental or industrial conditions.…”

Section: Introductionmentioning

confidence: 99%

Complex Reaction Environments and Competing Reaction Mechanisms in Zeolite Catalysis: Insights from Advanced Molecular Dynamics

Wispelaere

Ensing

Ghysels

et al. 2015

Chemistry A European J

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The methanol to olefins process is a show case example of complex zeolite-catalyzed chemistry. At real operating conditions, many factors such as framework flexibility, adsorption of various guest molecules and competitive reaction pathways, affect reactivity. In this paper we show the strength of first principle molecular dynamics techniques to capture this complexity by means of two case studies. Firstly, the adsorption behavior of methanol and water in H-SAPO-34 at 350 °C is investigated. Hereby we observed an important degree of framework flexibility and proton mobility. Secondly, we studied the methylation of benzene by methanol via a competitive direct and stepwise pathway in the AFI topology. Both case studies clearly show that a first principle molecular dynamics approach enables to obtain unprecedented insights into zeolite-catalyzed reactions at the nanometer scale.Keywords: ab initio calculations, molecular dynamics, proton mobility, methylation, zeolites 3 IntroductionChemical conversions in zeolites play an essential role in today's industrial catalysis. [1][2][3] Within the field of heterogeneous catalysis, the conversion of methanol to hydrocarbons (MTH) or olefins (MTO) over acidic zeolites received a lot of attention during the last decades, due to its relevance in the search for alternative processes to produce hydrocarbon products. [4][5][6][7] The MTO process has experimentally been developed in the past 3-4 decades and is currently being industrialized. [5] Methanol can be obtained from coal, natural gas or biomass and is in turn converted into ethene, propene or other hydrocarbons. The process proved extremely difficult to unravel at the nanoscale level due to various factors such as pressure, temperature and the occurrence of competing reaction mechanisms, which highly influence the catalytic performance of the system. Due to its complexity, it is a very challenging case study for theoretical modeling studies. [8] Currently, there is a consensus that a hydrocarbon pool (HP) mechanism operates during the methanol conversion process. Herein, an organic center is trapped in the zeolite pores and acts as co-catalyst. [9][10][11] The HP may be of aromatic or aliphatic nature and the two corresponding types of catalytic cycles are in close connection with each other, a concept that is called the dual cycle. [12] Depending on the catalyst topology and operating conditions either one or both cycles may be responsible for olefin formation during the methanol conversion process. [12][13][14] Theoretical contributions have proven to be indispensable within MTO research.Methodological developments and a steady increase in computer power, contributed to the fact that many properties, in particular rate coefficients of well-defined elementary reactions, are now routinely calculated with high accuracy. [8,[15][16][17] However, theoretical chemists are still confronted with paramount challenges to thoroughly explain experimental observations. The true challenge lies in linking the model system wit...

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Quantum Chemical Modeling of Zeolite-Catalyzed Methylation Reactions: Toward Chemical Accuracy for Barriers

Cited by 291 publications

References 72 publications

First Principles Calculations on Oxide-Based Heterogeneous Catalysts and Photocatalysts: Problems and Advances

First Principles Calculations on Oxide-Based Heterogeneous Catalysts and Photocatalysts: Problems and Advances

Ab Initio Calculation of Rate Constants for Molecule–Surface Reactions with Chemical Accuracy

Complex Reaction Environments and Competing Reaction Mechanisms in Zeolite Catalysis: Insights from Advanced Molecular Dynamics

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