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Sensors 2015, 15(10), 27021-27034; doi:10.3390/s151027021

Why does the Conductivity of a Nickel Catalyst Increase during Sulfidation? An Exemplary Study Using an In Operando Sensor Device

1
Department of Functional Materials, Zentrum für Energietechnik (ZET), University of Bayreuth, 95440 Bayreuth, Germany
2
Department of Chemical Engineering, Zentrum für Energietechnik (ZET), University of Bayreuth, 95440 Bayreuth, Germany
*
Author to whom correspondence should be addressed.
Academic Editor: Michael Tiemann
Received: 3 September 2015 / Revised: 15 October 2015 / Accepted: 19 October 2015 / Published: 23 October 2015
(This article belongs to the Special Issue Gas Sensors—Designs and Applications)
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Abstract

In order to study the sulfidation of a catalyst fixed bed, an in operando single pellet sensor was designed. A catalyst pellet from the fixed bed was electrically contacted and its electrical response was correlated with the catalyst behavior. For the sulfidation tests, a nickel catalyst was used and was sulfidized with H2S. This catalyst had a very low conductivity in the reduced state. During sulfidation, the conductivity of the catalyst increased by decades. A reaction from nickel to nickel sulfide occurred. This conductivity increase by decades during sulfidation had not been expected since both nickel and nickel sulfides behave metallic. Only by assuming a percolation phenomenon that originates from a volume increase of the nickel contacts when reacting to nickel sulfides, this effect can be explained. This assumption was supported by sulfidation tests with differently nickel loaded catalysts and it was quantitatively estimated by a general effective media theory. The single pellet sensor device for in operando investigation of sulfidation can be considered as a valuable tool to get further insights into catalysts under reaction conditions. View Full-Text
Keywords: fixed bed catalyst; sulfur poisoning; nickel to nickel sulfide transformation; percolation; in operando fixed bed catalyst; sulfur poisoning; nickel to nickel sulfide transformation; percolation; in operando
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Fremerey, P.; Jess, A.; Moos, R. Why does the Conductivity of a Nickel Catalyst Increase during Sulfidation? An Exemplary Study Using an In Operando Sensor Device. Sensors 2015, 15, 27021-27034.

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