Active Sites in Working Bifunctional GaH-TON Aromatization Catalysts: Kinetic Evaluation

Dmitry B Lukyanov, Tanya Vazhnova

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

The conversion of light alkanes to high value aroms. proceeds with a high selectivity over bifunctional, gallium (Ga) contg. zeolite catalysts. It is generally agreed that Ga sites are involved in dehydrogenation reaction steps and that the zeolite acid sites catalyze cracking, oligomerization, and cyclization reactions. However, understanding of the precise roles of the acid and Ga sites in the reaction mechanisms is significantly hampered since the no. of these sites in working catalysts is not known. This paper describes a kinetic approach to evaluation of the acid and Ga active sites in working Ga contg. TON zeolite catalysts that relies on the anal. of the rates of formation of the primary products of a n-butane aromatization reaction. Our results show that the rate of ethane formation at low n-butane conversions can be used as a quant. est. of acidity in working bifunctional zeolite catalysts and demonstrate, for the first time, a significant decrease in the no. of Bronsted acid sites in the Ga contg. catalysts under reaction conditions: around 47 and 79% for the catalysts with Ga loading of 1.5 and 2.5 wt. %, resp. We conclude that the redn. in acidity is assocd. with the formation of catalytically active Ga+ ions and obtain ests. for the no. and steady-state turnover activity of the acid and Ga active sites in n-butane transformation. We anticipate that our work will facilitate understanding of the precise roles of the acid and Ga sites in the mechanisms of alkane aromatization and, as a far-reaching implication, will prompt wider use of detailed kinetic studies for the evaluation of active sites in working catalysts. [on SciFinder (R)]
Original languageEnglish
Pages (from-to)18473-18480
Number of pages8
JournalJournal of Physical Chemistry B
Volume110
Issue number37
Publication statusPublished - 2006

Fingerprint

Aromatization
Gallium
Catalysts
Kinetics
Acids
Butane
Acidity
Paraffins
Oligomerization
Cyclization
Dehydrogenation
Ethane

Keywords

  • Dehydrogenation (active sites in working bifunctional GaH-TON aromatization catalysts
  • Aromatic compounds Role
  • PREP (Preparation) (active sites in working bifunctional GaH-TON aromatization catalysts
  • Aromatization catalysts
  • Aromatization kinetics
  • Zeolites Role
  • gallium TON zeolite aromatization catalyst butane activity mechanism kinetics
  • Reaction mechanism (in studying bifunctional GaH-TON aromatization catalysts
  • CAT (Catalyst use)
  • active sites in working bifunctional GaH-TON aromatization catalysts
  • USES (Uses) (theta-1
  • kinetic evaluation)
  • Acidity
  • SPN (Synthetic preparation)

Cite this

Active Sites in Working Bifunctional GaH-TON Aromatization Catalysts: Kinetic Evaluation. / Lukyanov, Dmitry B; Vazhnova, Tanya.

In: Journal of Physical Chemistry B, Vol. 110, No. 37, 2006, p. 18473-18480.

Research output: Contribution to journalArticle

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TY - JOUR

T1 - Active Sites in Working Bifunctional GaH-TON Aromatization Catalysts: Kinetic Evaluation

AU - Lukyanov, Dmitry B

AU - Vazhnova, Tanya

PY - 2006

Y1 - 2006

N2 - The conversion of light alkanes to high value aroms. proceeds with a high selectivity over bifunctional, gallium (Ga) contg. zeolite catalysts. It is generally agreed that Ga sites are involved in dehydrogenation reaction steps and that the zeolite acid sites catalyze cracking, oligomerization, and cyclization reactions. However, understanding of the precise roles of the acid and Ga sites in the reaction mechanisms is significantly hampered since the no. of these sites in working catalysts is not known. This paper describes a kinetic approach to evaluation of the acid and Ga active sites in working Ga contg. TON zeolite catalysts that relies on the anal. of the rates of formation of the primary products of a n-butane aromatization reaction. Our results show that the rate of ethane formation at low n-butane conversions can be used as a quant. est. of acidity in working bifunctional zeolite catalysts and demonstrate, for the first time, a significant decrease in the no. of Bronsted acid sites in the Ga contg. catalysts under reaction conditions: around 47 and 79% for the catalysts with Ga loading of 1.5 and 2.5 wt. %, resp. We conclude that the redn. in acidity is assocd. with the formation of catalytically active Ga+ ions and obtain ests. for the no. and steady-state turnover activity of the acid and Ga active sites in n-butane transformation. We anticipate that our work will facilitate understanding of the precise roles of the acid and Ga sites in the mechanisms of alkane aromatization and, as a far-reaching implication, will prompt wider use of detailed kinetic studies for the evaluation of active sites in working catalysts. [on SciFinder (R)]

AB - The conversion of light alkanes to high value aroms. proceeds with a high selectivity over bifunctional, gallium (Ga) contg. zeolite catalysts. It is generally agreed that Ga sites are involved in dehydrogenation reaction steps and that the zeolite acid sites catalyze cracking, oligomerization, and cyclization reactions. However, understanding of the precise roles of the acid and Ga sites in the reaction mechanisms is significantly hampered since the no. of these sites in working catalysts is not known. This paper describes a kinetic approach to evaluation of the acid and Ga active sites in working Ga contg. TON zeolite catalysts that relies on the anal. of the rates of formation of the primary products of a n-butane aromatization reaction. Our results show that the rate of ethane formation at low n-butane conversions can be used as a quant. est. of acidity in working bifunctional zeolite catalysts and demonstrate, for the first time, a significant decrease in the no. of Bronsted acid sites in the Ga contg. catalysts under reaction conditions: around 47 and 79% for the catalysts with Ga loading of 1.5 and 2.5 wt. %, resp. We conclude that the redn. in acidity is assocd. with the formation of catalytically active Ga+ ions and obtain ests. for the no. and steady-state turnover activity of the acid and Ga active sites in n-butane transformation. We anticipate that our work will facilitate understanding of the precise roles of the acid and Ga sites in the mechanisms of alkane aromatization and, as a far-reaching implication, will prompt wider use of detailed kinetic studies for the evaluation of active sites in working catalysts. [on SciFinder (R)]

KW - Dehydrogenation (active sites in working bifunctional GaH-TON aromatization catalysts

KW - Aromatic compounds Role

KW - PREP (Preparation) (active sites in working bifunctional GaH-TON aromatization catalysts

KW - Aromatization catalysts

KW - Aromatization kinetics

KW - Zeolites Role

KW - gallium TON zeolite aromatization catalyst butane activity mechanism kinetics

KW - Reaction mechanism (in studying bifunctional GaH-TON aromatization catalysts

KW - CAT (Catalyst use)

KW - active sites in working bifunctional GaH-TON aromatization catalysts

KW - USES (Uses) (theta-1

KW - kinetic evaluation)

KW - Acidity

KW - SPN (Synthetic preparation)

M3 - Article

VL - 110

SP - 18473

EP - 18480

JO - Journal of Physical Chemistry B

JF - Journal of Physical Chemistry B

SN - 1520-6106

IS - 37

ER -