Comparative study of heterogeneous photocatalytic decomposition of tetrachloroethene and trichloroethene in the gas phase

Márta Hegedüs, András Dombi

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

The selectivity issues in the catalytic multiphase reduction of functionalized halogenated aromatics (halogenated benzenes, nitrobenzene, benzonitrile, and benzaldehyde) over Pd/C, Pt/C, and Raney-Ni were studied. The presence of a quaternary ammonium salt, Aliquat 336, in the biphasic catalytic reduction system with Pd/C, Pt/C, Raney-Ni could affect the reaction rate and selectivity in different ways. It could accelerate reduction of certain groups, e.g., of aromatic chlorine, though at the same time it could impede reduction of other functions, such as carbonyl, hydroxyl, and nitrile groups. Aliquat 336 increased the reaction regioselectivity, e.g., in the same reduction of p-chlorobenzaldehyde, which could undergo the processes of either dechlorination or reduction of carbonyl group. The presence of Aliquat 336 on the catalyst could interfere into the processes of substrate coordination on the surface, thereby restricting certain geometrical conformations, such as the flat adsorption of the aromatic ring or, instead, coordinating certain groups on the catalyst in a way that favored their reaction. In p-chlorobenzaldehyde or in p-chloronitrobenzene, dechlorination preceded reduction of the other function over Pd/C and vice versa over Pt/C. In the reaction of p-chloronitrobenzene to aniline, nitrobenzene was formed with the yield of ≤ 70% on Pd/C, while on Pt/C ≤ 60% of p-chloroaniline was formed. Aside from the effects produced by Aliquat 336 on the reaction rate, regio- and chemoselectivity, another important factor was the pH of the aqueous system.

Original languageEnglish
Pages (from-to)129-136
Number of pages8
JournalApplied Catalysis A: General
Volume271
Issue number1-2
DOIs
Publication statusPublished - Sep 10 2004

Fingerprint

Tetrachloroethylene
Trichloroethylene
Gases
Decomposition
Regioselectivity
Dechlorination
Nitrobenzene
Reaction rates
Nitriles
Catalysts
Catalyst selectivity
Chlorine
Aniline
Benzene
Ammonium Compounds
Hydroxyl Radical
Conformations
Salts
Adsorption
trioctylmethylammonium

Keywords

  • Dichloroacetyl chloride
  • Heterogeneous photocatalysis
  • Perchloroethene
  • Product acceleration
  • Titanium dioxide
  • Trichloroacetyl chloride
  • Trichloroethene

ASJC Scopus subject areas

  • Catalysis
  • Process Chemistry and Technology

Cite this

Comparative study of heterogeneous photocatalytic decomposition of tetrachloroethene and trichloroethene in the gas phase. / Hegedüs, Márta; Dombi, András.

In: Applied Catalysis A: General, Vol. 271, No. 1-2, 10.09.2004, p. 129-136.

Research output: Contribution to journalArticle

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