(779h) Tuning Nanoparticle Alloys to Enhance C-H Bond Activation for the Catalytic Dehydrogenation of Ethane

Authors: 
Cybulskis, V. - Presenter, Purdue University
Gallagher, J., Argonne National Laboratory
Tseng, H. T., Purdue University
Wu, Z., Purdue University
Wegener, E., Purdue University
Kropf, A. J., Argonne National Laboratory
Ravel, B., National Institute of Standards and Technology
Greeley, J. P., Purdue University
Ribeiro, F., Purdue University
Miller, J., Purdue University

Tuning
Nanoparticle Alloys to Enhance C-H Bond Activation for the Catalytic
Dehydrogenation of Ethane

Viktor J.
Cybulskis1, James R. Gallagher2,
Han-Ting Tseng1, Brandon Bukowski1, Zhenwei Wu1,
Evan Wegener1, A. Jeremy Kropf2, Bruce Ravel3,
Jeffrey Greeley1, Fabio H.
Ribeiro1,Jeffrey T. Miller1

1  Chemical Engineering, Purdue University,
West Lafayette, IN 47907, USA

2  Chemical Sciences and Engineering,
Argonne National Laboratory, Argonne, IL 60439, USA

3  Materials Measurement Laboratory,
National Institute of Standards and Technology, Gaithersburg, MD 20899, USA

Supported Pt catalysts are widely used in
a number of industrial hydrocarbon processes, including hydrogenation, isomerization,
naphtha reforming, and dehydrogenation reactions, due to their affinity for
paraffinic C-H bonds [1]. While structure insensitive reactions, such as alkane
dehydrogenation, can occur on isolated metal sites, larger nanoparticle
ensembles are known to catalyze side reactions, such as cracking and
hydrogenolysis [2]. Recent work by Childers et al. [3] has demonstrated that Zn
addition to SiO2-supported Pt catalysts enhances propylene
selectivity during propane dehydrogenation by forming an intermetallic alloy
that effectively isolates Pd surface sites via a geometric effect.

In the present study, we demonstrate how
the addition of Zn to Pt/SiO2
leads to near 100% ethylene selectivity during ethane dehydrogenation (EDH) at 600
¡C by forming a
high-symmetry Pt1Zn1 alloy with isolated Pt sites that effectively
eliminate concomitant C-C bond cleavages. Kinetic measurements and in situ
resonant inelastic X-ray scattering (RIXS) experiments indicate that Zn
also modifies the electronic structure of Pt and increases the EDH turnover
frequency (TOF) per exposed surface Pt by a factor of ten compared to monometallic
Pt/SiO2. The molecular level insight obtained from this
study provides a model that suggests control of the geometric structure of the
active sites affects alkene selectivity, while control of the promoter affects
the adsorbate binding strength and TOF.

References:

[1]   J. J. H. B. Sattler, J.
Ruiz-Martinez, E. Santillan-Jimenez, and B. M. Weckhuysen, Chem. Rev. 114
(2014) 10613.

[2]   M. Boudart, G. Djega-Mariadassou,
Kinetics of Heterogeneous Catalytic Reactions, Princeton, 1984, pp. 155-193.

[3]   D.J. Childers, N.M. Schweitzer,
S.M.K. Shahari, R.M. Rioux, J.T. Miller, R.J. Meyer, J. Catal. 318 (2014) 75.