Catalyst Surface Dispersion: Insights into Hydrogenation Kinetics and Mechanism

Adi Lavi, Efrat Ruse, Svetlana Pevzner, Eyal Ben-Yehuda, Avia Ohayon-Lavi, Oren Regev

Research output: Contribution to journalArticlepeer-review

Abstract

Catalyst-driven hydrogenation of an unsaturated organic matrix is commonly used for irreversible scavenging of hydrogen. The effect of catalyst dispersion on the hydrogenation reaction was explored as a means to deciphering the hydrogenation mechanism. The hydrogenation rate was thus measured in a model system consisting of a composite of a graphene nanoplatelet (GNP)-supported catalyst (Pd) in an organic matrix comprising the hydrogen scavenger 1,4-di(phenylethynyl)benzene (DEB). A similar activated carbon (AC)-supported Pd system in a DEB matrix was used as a reference system. We found that the rate of the hydrogenation reaction was limited by the migration of hydrogen atoms to the scavenger from the carbon-based catalyst support and could be manipulated by tuning (1) the specific surface area (SSA) of the catalyst support and (2) the mean catalyst-to-scavenger distance (catalyst dispersion quality) in the overall composite. We integrated these two key parameters into a single design parameter, termed the catalyst surface density (CSD). We found that for catalyst particles smaller than 100 nm the rate-determining step of the hydrogenation reaction was mainly dictated by the quality of the catalyst dispersion, expressed by the CSD parameter. Manipulating the CSD at a fixed composite composition yielded up to 7-fold acceleration in the hydrogenation rate, which is identical to the effect of increasing the concentration of the expensive and heavy catalyst by the same factor.
Original languageEnglish GB
Pages (from-to)8813-8821
Number of pages9
JournalJournal of Physical Chemistry C
Volume124
Issue number16
StatePublished - 2020

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