Operando Characterization of Catalysts through use of a Portable Microreactor

Abstract

In order to more deeply understand the mechanisms of catalytic reactions, improved methods are needed to monitor changes that occur in the electronic, structural, and chemical properties of catalytic systems under the conditions in which they work. We describe here a microreactor‐based approach that integrates the capabilities of advanced X‐ray, electron, optical, and gas‐phase compositional analysis techniques under operando conditions. For several exemplary catalytic systems, we demonstrate how this approach enables the characterization of three of the major factors that contribute to structure–property correlations in heterogeneous catalysis. Specifically, we describe how this approach can be used to better understand the atomic structure and elemental composition of nanocatalysts, the physiochemical properties of the support and catalyst/support interfaces, and the gas‐ and surface‐phase chemistry that occurs under operando conditions. We highlight the generality of the approach, as well as opportunities for future developments.

Nanoparticle size evaluation of catalysts by EXAFS: Advantages and limitations

“…However, other laboratory techniques for particle size evaluation (XRD and TEM) are limited to atomic clusters larger than ca. 2 nm because of the need for a long-range atomic order (XRD), or their resolution is of the order of 1 nm (TEM) [23,24]. Thus the EXAFS technique should be considered more as complementary technique to XRD and TEM in particle size evaluation, rather than mutually excluding, because of the limited capabilities of the techniques at different scales.…”

Mechanistic Insights into Catalytic Ethanol Steam Reforming Using Isotope‐Labeled Reactants

“…However, this reaction is unfavored at the operating temperature of 350 °C, thus implying that the C 2 H 6 observed must be formed through ethylene hydrogenation [Eq. (12)] on the catalyst surface, a commonly reported feature of supported platinum‐group metal catalysts . We hypothesize that the tradeoff between C 2 H 6 and C 2 H 4 production observed at t =1.25 h implies that the ethylene hydrogenation reaction is suppressed as the catalyst deactivates, and it is consistent with the emergence of ethylene as a stable product and the simultaneous decreases in H 2 and ethanol conversion.…”

Mechanistic Insights into Catalytic Ethanol Steam Reforming Using Isotope‐Labeled Reactants

“…[29,30] However,this reaction is unfavored at the operating temperature of 350 8 8C, [31] thus implying that the C 2 H 6 observed must be formed through ethylene hydrogenation [Eq. [32][33][34] We hypothesize that the tradeoff between C 2 H 6 and C 2 H 4 production observed at t = 1.25 hi mplies that the ethylene hydrogenation reaction is suppressed as the catalyst deactivates,a nd it is consistent with the emergence of ethylene as as table product and the simultaneous decreases in H 2 and ethanol conversion. [32][33][34] We hypothesize that the tradeoff between C 2 H 6 and C 2 H 4 production observed at t = 1.25 hi mplies that the ethylene hydrogenation reaction is suppressed as the catalyst deactivates,a nd it is consistent with the emergence of ethylene as as table product and the simultaneous decreases in H 2 and ethanol conversion.…”

“…(12)] on the catalyst surface,acommonly reported feature of supported platinum-group metal catalysts. [32][33][34] We hypothesize that the tradeoff between C 2 H 6 and C 2 H 4 production observed at t = 1.25 hi mplies that the ethylene hydrogenation reaction is suppressed as the catalyst deactivates,a nd it is consistent with the emergence of ethylene as as table product and the simultaneous decreases in H 2 and ethanol conversion.…”