The Active Sites in the Selective Reduction of Nitrobenzene by Cobalt Aluminum Oxide Catalysts

Meijers, S.; Hoeven, TP Pruys van der; Ponec, V.; Jacobs, J Jean-Paul; Brongersma, H.H.

doi:10.1006/jcat.1996.0204

Cited by 12 publications

(5 citation statements)

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“…One possible reason for the high reactivity of nitrobenzene and other nitroaromatic compounds under conditions of heterogeneous catalytic oxidation, is the inherent high reactivity observed between nitroaromatic compounds and metal oxide surfaces. [19,31] This has been most often observed in the context of the reduction of nitroaromatic compounds; however, the surface binding/activation processes apparently also facilitate oxidation when dioxygen is present in excess. The efficient heterogeneous catalytic oxidation observed here for NB, DNT, and TNT is noteworthy given the interest in remediation of these compounds, when they are found as environmental pollutants.…”

Section: Indirect Detection Of Nitroaromatic Compounds By Catalytic Dmentioning

confidence: 97%

“…That reaction results in a mixture of organic products, although the principle product is nitrosobenzene. [19] Several experiments designed to identify the organic products of the silicon oxidation reaction were performed. A freshly etched porous Si chip was exposed to a solution of nitrobenzene for several days and the sample and solution were analyzed.…”

Section: Mechanism Of Irreversible Quenching Of Photoluminescencementioning

confidence: 99%

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Detection of Nitrobenzene, DNT, and TNT Vapors by Quenching of Porous Silicon Photoluminescence

2000

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The detection of nitroaromatic molecules in air by the quenching of the photoluminescence of porous silicon (porous Si) films has been explored. Detection is achieved by monitoring the photoluminescence (PL) of a nanocrystalline porous Si film on exposure to the analyte of interest in a flowing air stream. The photoluminescence is quenched on exposure to the nitroaromatic, presumably by an electron-transfer mechanism. Detection limits of 500 parts-per-billion (ppb), 2 ppb, and 1 ppb were observed for nitrobenzene, 2.4-dinitrotoluene (DNT), and 2,4,6-trinitrotoluene (TNT), respectively (exposure times of 5 min for each, in air). Specificity for detection is achieved by catalytic oxidation of the nitroaromatic compound. A platinum oxide (PtO2) or palladium oxide (PdO) catalyst at 250 degrees C. placed in the carrier gas line upstream of the porous Si detector, causes oxidation of all the nitroaromatic compounds studied. The catalyst does not oxidize benzene vapor, and control experiments show no difference in the extent of PL quenching by benzene with or without an upstream catalyst. The PL quenching by NO2, released in the catalytic oxidation of nitroaromatic compounds, is less efficient than the quenching of the intact nitroaromatic compound. This provides a means to discriminate nitro-containing molecules from other organic species.

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Section: Indirect Detection Of Nitroaromatic Compounds By Catalytic Dmentioning

confidence: 97%

Section: Mechanism Of Irreversible Quenching Of Photoluminescencementioning

confidence: 99%

Detection of Nitrobenzene, DNT, and TNT Vapors by Quenching of Porous Silicon Photoluminescence

2000

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“…Further studies have investigated the role of Li + , Na + , and K + ions on the activity and selectivity of Mn 3 O 4 and similarly of the mixed oxide catalyst PbO−Mn 3 O 4 . ,− The deoxygenation reaction is carried out at 573 K using an open-flow system with a fixed bed reactor and using helium as the carrier gas. A further variation of the catalyst is shown in the use of a series of mixed cobalt aluminum oxides with spinel structures, the rate of production of nitrosobenzene increasing almost linearly with increasing concentration of cobalt in the surface . The importance of these studies lies in the potential for producing nitrosobenzene from nitrobenzene on an industrial scale without the formation of the waste products that result from the batch process involving reduction to the hydroxylamine and subsequent oxidation.…”

Section: 5 Preparation From Nitro Compounds251 Direct Reductionmentioning

confidence: 99%

“…A further variation of the catalyst is shown in the use of a series of mixed cobalt aluminum oxides with spinel structures, the rate of production of nitrosobenzene increasing almost linearly with increasing concentration of cobalt in the surface. 303 The importance of these studies lies in the potential for producing nitrosobenzene from nitrobenzene on an industrial scale without the formation of the waste products that result from the batch process involving reduction to the hydroxylamine and subsequent oxidation.…”

Section: Preparation From Nitro Compoundsmentioning

confidence: 99%

Preparations ofC-Nitroso Compounds

2004

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“…These properties depend on the density of surface cations and on the surface cation distributions. Surface sensitive spectroscopies such as for example low energy ion scattering (LEIS) can be applied for the determination of these quantities [33,34]. As an example, the rate of nitrosobenzene formation by selective reduction of nitrobenzene on a mixed cobalt aluminum oxide with spinel structure increased almost linearly with increasing concentration of Co in octahedral surface sites.…”

Section: Discussionmentioning

confidence: 99%

The Role of the Synthesis Method in the Structure Formation of Cobalt Aluminate

Onfroy

Li²,

Knözinger³

2011

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Cobalt aluminate (spinel) was prepared via two synthesis routes firstly a co-precipitation method and secondly a nanocasting method. The surface chemistry of these materials was characterized by infrared-spectroscopy of the surface hydroxyl groups and of coordinatively unsaturated (cus) cations (Al and Co) by carbon monoxide CO at low temperature. The goal was to investigate whether or not the preparation of the spinel phase had an effect on this structural characteristics, namely on the inversion degree. The hydroxyl (deuteroxyl) spectra were characterized by six types of O-H stretching bands. While the O-H stretching frequencies were identical for both materials, the relative intensities of the bands were clearly different indicating a distinct distribution of the different types of hydroxyl groups which most likely originates from a distinct distribution of the cations in the two differently synthesized materials. The preparation method obviously yields spinel structures having variable degrees of inversion. Coordinatively unsaturated cus cations are exposed on the surface during the removal of O-H groups by thermal dehydroxylation. Those Lewis acid centers show an acid strength distribution which is again an indication for formation of two distinct degrees of inversion.

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The Active Sites in the Selective Reduction of Nitrobenzene by Cobalt Aluminum Oxide Catalysts

Cited by 12 publications

References 0 publications

Detection of Nitrobenzene, DNT, and TNT Vapors by Quenching of Porous Silicon Photoluminescence

Detection of Nitrobenzene, DNT, and TNT Vapors by Quenching of Porous Silicon Photoluminescence

Preparations ofC-Nitroso Compounds

The Role of the Synthesis Method in the Structure Formation of Cobalt Aluminate

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