Use of TPD to Characterize the Strength of Amine Interaction with the Metal Surface in Pd Catalysts

Result code in IS VaVaI

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Result on the web

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DOI - Digital Object Identifier

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Result language

angličtina

Original language name

Use of TPD to Characterize the Strength of Amine Interaction with the Metal Surface in Pd Catalysts

Original language description

Palladium supported catalysts are important industrial hydrogenation catalysts. They have specific catalytic properties that differ dramatically from the properties of other metal catalysts (Ni, Co, Cu or Ru) especially in hydrogenations in which amines participate as products. A brief review of those properties forms a part of this paper. The observed distinction has often been attributed to the strong adsorption of amines onto the surface of Pd. Experimental quantification of the strength of the amine interaction with the Pd surface of the catalyst could elucidate or predict the kinetics of these reactions. This study investigated whether the readily available temperature-programmed desorption (TPD) technique could be used for this purpose, provided that real Pd supported catalysts being studied. The technique makes possible to study the chemisorption/ desorption of substrates under conditions close to the real reaction conditions of hydrogenation, in contrast to the technique of thermal desorption spectroscopy. The chemisorption of model amines on the surface of Pd/support was studied using the TPD technique in a steady stream of inert gas passing through the powder sample layer and these measurements were compared with the TPD of amines from palladium black and catalyst supports alone: namely kieselguhr, precipitated SiO2, fumed SiO2 and active carbon. Although these supports are often considered to be inert materials, measurements have surprisingly shown that the basic amine is chemisorbed to a significant degree on the support surface and, conversely, its chemisorption on Pd is negligible. Thus, the coordination bond of the amine with the surface Pd atom seems to be much weaker than the interaction of the amines with the acidic sites, and the adsorption equilibrium is shifted to the side of amine desorption at 40°C used in this TPD technique for amine adsorption – and therefore is unmeasurable by this technique. On the contrary, the measured value of the activation energy of dibutylamine desorption from the surface of fumed SiO2, being 70.2 kJ ∙ mol-1, shows a stronger interaction of amine with the surface than simple physisorption and indicates the acidic character of this catalyst support.

Czech name

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Czech description

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Type

C - Chapter in a specialist book

CEP classification

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OECD FORD branch

10403 - Physical chemistry

Project

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Continuities

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2022

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Book/collection name

Advances in Materials Science Research. Volume 53

ISBN

979-8-88697-080-7

Number of pages of the result

20

Pages from-to

162-180

Number of pages of the book

245

Publisher name

Nova Science Publishers, Inc.

Place of publication

New York

UT code for WoS chapter

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