A DFT study of the acid-catalyzed conversion of 2,5-dimethylfuran and ethylene to p-xylene

Nima Nikbin, Phuong T. Do, Stavros Caratzoulas, Raul F. Lobo, Paul J. Dauenhauer, Dionisios G. Vlachos

Research output: Contribution to journalArticle

93 Citations (Scopus)

Abstract

We present a detailed mechanism for the conversion of DMF (2,5-dimethylfuran) and ethylene to p-xylene, obtained by gas-phase DFT electronic structure calculations. The conversion consists of Diels-Alder cycloaddition and subsequent dehydration of the cycloadduct, an oxa-norbornene derivative. We present the energetics of both the uncatalyzed and acid-catalyzed (Bronsted and Lewis) reactions. Even though the DMF-ethylene cycloaddition is thermally feasible, we show that Lewis acids can further lower the activation requirements by decreasing the HOMO-LUMO gap of the addends. The catalytic effect may be significant or negligible depending on whether the Diels-Alder reaction proceeds in the normal or the inverse electron-demand direction. We also show that Bronsted acids are extremely effective at catalyzing the dehydration of the oxa-norbornene derivative, which, according to our calculations, cannot proceed uncatalyzed. On the other hand, we conclude that Bronsted acids do not catalyze the cycloaddition. Although strong Lewis acids like Li+ can catalyze the dehydration, our calculations indicate that relatively elevated temperatures would be required as they are not as effective as Bronsted acids. We argue that the specific synthetic route to p-xylene is kinetically limited by the Diels-Alder reaction when Bronsted acids are used and by the dehydration when a Lewis acid is used, with the latter being slower than the former. Finally, we adduce experimental data that corroborate the theoretical predictions: we observe no activity in the absence of a catalyst and a higher turnover frequency to p-xylene in the Bronsted acidic zeolite HY than in the Lewis acidic zeolite NaY.

Original languageEnglish (US)
Pages (from-to)35-43
Number of pages9
JournalJournal of Catalysis
Volume297
DOIs
StatePublished - Jan 1 2013
Externally publishedYes

Fingerprint

xylene
Xylene
Discrete Fourier transforms
Ethylene
ethylene
Dehydration
Lewis Acids
Cycloaddition
acids
Acids
Zeolites
dehydration
cycloaddition
Diels-Alder reactions
Derivatives
Electronic structure
Gases
Chemical activation
2,5-dimethylfuran
4-xylene

Keywords

  • 2,5-Dimethylfuran
  • DFT
  • Dehydration
  • Diels-Alder reaction
  • p-Xylene

Cite this

A DFT study of the acid-catalyzed conversion of 2,5-dimethylfuran and ethylene to p-xylene. / Nikbin, Nima; Do, Phuong T.; Caratzoulas, Stavros; Lobo, Raul F.; Dauenhauer, Paul J.; Vlachos, Dionisios G.

In: Journal of Catalysis, Vol. 297, 01.01.2013, p. 35-43.

Research output: Contribution to journalArticle

Nikbin, Nima ; Do, Phuong T. ; Caratzoulas, Stavros ; Lobo, Raul F. ; Dauenhauer, Paul J. ; Vlachos, Dionisios G. / A DFT study of the acid-catalyzed conversion of 2,5-dimethylfuran and ethylene to p-xylene. In: Journal of Catalysis. 2013 ; Vol. 297. pp. 35-43.
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T1 - A DFT study of the acid-catalyzed conversion of 2,5-dimethylfuran and ethylene to p-xylene

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AU - Do, Phuong T.

AU - Caratzoulas, Stavros

AU - Lobo, Raul F.

AU - Dauenhauer, Paul J.

AU - Vlachos, Dionisios G.

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N2 - We present a detailed mechanism for the conversion of DMF (2,5-dimethylfuran) and ethylene to p-xylene, obtained by gas-phase DFT electronic structure calculations. The conversion consists of Diels-Alder cycloaddition and subsequent dehydration of the cycloadduct, an oxa-norbornene derivative. We present the energetics of both the uncatalyzed and acid-catalyzed (Bronsted and Lewis) reactions. Even though the DMF-ethylene cycloaddition is thermally feasible, we show that Lewis acids can further lower the activation requirements by decreasing the HOMO-LUMO gap of the addends. The catalytic effect may be significant or negligible depending on whether the Diels-Alder reaction proceeds in the normal or the inverse electron-demand direction. We also show that Bronsted acids are extremely effective at catalyzing the dehydration of the oxa-norbornene derivative, which, according to our calculations, cannot proceed uncatalyzed. On the other hand, we conclude that Bronsted acids do not catalyze the cycloaddition. Although strong Lewis acids like Li+ can catalyze the dehydration, our calculations indicate that relatively elevated temperatures would be required as they are not as effective as Bronsted acids. We argue that the specific synthetic route to p-xylene is kinetically limited by the Diels-Alder reaction when Bronsted acids are used and by the dehydration when a Lewis acid is used, with the latter being slower than the former. Finally, we adduce experimental data that corroborate the theoretical predictions: we observe no activity in the absence of a catalyst and a higher turnover frequency to p-xylene in the Bronsted acidic zeolite HY than in the Lewis acidic zeolite NaY.

AB - We present a detailed mechanism for the conversion of DMF (2,5-dimethylfuran) and ethylene to p-xylene, obtained by gas-phase DFT electronic structure calculations. The conversion consists of Diels-Alder cycloaddition and subsequent dehydration of the cycloadduct, an oxa-norbornene derivative. We present the energetics of both the uncatalyzed and acid-catalyzed (Bronsted and Lewis) reactions. Even though the DMF-ethylene cycloaddition is thermally feasible, we show that Lewis acids can further lower the activation requirements by decreasing the HOMO-LUMO gap of the addends. The catalytic effect may be significant or negligible depending on whether the Diels-Alder reaction proceeds in the normal or the inverse electron-demand direction. We also show that Bronsted acids are extremely effective at catalyzing the dehydration of the oxa-norbornene derivative, which, according to our calculations, cannot proceed uncatalyzed. On the other hand, we conclude that Bronsted acids do not catalyze the cycloaddition. Although strong Lewis acids like Li+ can catalyze the dehydration, our calculations indicate that relatively elevated temperatures would be required as they are not as effective as Bronsted acids. We argue that the specific synthetic route to p-xylene is kinetically limited by the Diels-Alder reaction when Bronsted acids are used and by the dehydration when a Lewis acid is used, with the latter being slower than the former. Finally, we adduce experimental data that corroborate the theoretical predictions: we observe no activity in the absence of a catalyst and a higher turnover frequency to p-xylene in the Bronsted acidic zeolite HY than in the Lewis acidic zeolite NaY.

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