Quantitative Structural Description of Zeolites by Machine Learning Analysis of Infrared Spectra.

Application of machine learning (ML) algorithms to spectroscopic data has a great potential for obtaining hidden correlations between structural information and spectral features. Here, we apply ML algorithms to theoretically simulated infrared (IR) spectra to establish the structure-spectrum correlations in zeolites. Two hundred thirty different types of zeolite frameworks were considered in the study whose theoretical IR spectra were used as the training ML set.

Cu-α-diimine Compounds Encapsulated in Porous Materials as Catalysts for Electrophilic Amination of Aromatic C-H Bonds.

Electrophilic amination has emerged as a more environmentally benign approach to construct arene C-N bonds. However, heterogeneous catalysts remain largely unexplored in this area, even though their use could facilitate product purification and catalyst recovery. Here we investigate strategies to heterogenize a Cu(2,2'-bipyridine) catalyst for the amination of arenes lacking a directing group with hydroxylamine--sulfonic acid (HOSA).

Hydrogenation of ethylene over palladium: evolution of the catalyst structure by operando synchrotron-based techniques.

Palladium-based catalysts are exploited on an industrial scale for the selective hydrogenation of hydrocarbons. The formation of palladium carbide and hydride phases under reaction conditions changes the catalytic properties of the material, which points to the importance of operando characterization for determining the relation between the relative fractions of the two phases and the catalyst performance. We present a combined time-resolved characterization by X-ray absorption spectroscopy (in both near-edge and extended regions) and X-ray diffraction of a working palladium-based catalyst during the hydrogenation of ethylene in a wide range of partial pressures of ethylene and hydrogen.

In situ formation of surface and bulk oxides in small palladium nanoparticles.

Evolution of surface and bulk palladium oxides in supported palladium nanoparticles was followed in situ using X-ray absorption spectroscopy. The surface oxide was found to be easily reducible in hydrogen at room temperature, while removal of bulk oxide required heating in hydrogen above 100 °C. We also found that the co-presence of hydrogen and oxygen favours a stronger oxidation of palladium particles compared to pure oxygen.

Dehydrogenation of Ethylene on Supported Palladium Nanoparticles: A Double View from Metal and Hydrocarbon Sides.

Adsorption of ethylene on palladium, a key step in various catalytic reactions, may result in a variety of surface-adsorbed species and formation of palladium carbides, especially under industrially relevant pressures and temperatures. Therefore, the application of both surface and bulk sensitive techniques under reaction conditions is important for a comprehensive understanding of ethylene interaction with Pd-catalyst. In this work, we apply in situ X-ray absorption spectroscopy, X-ray diffraction and infrared spectroscopy to follow the evolution of the bulk and surface structure of an industrial catalysts consisting of 2.

Time-resolved operando studies of carbon supported Pd nanoparticles under hydrogenation reactions by X-ray diffraction and absorption.

The formation of palladium hydride and carbide phases in palladium-based catalysts is a critical process that changes the catalytic performance and selectivity of the catalysts in important industrial reactions, such as the selective hydrogenation of alkynes or alkadienes. We present a comprehensive study of a 5 wt% carbon supported Pd nanoparticle (NP) catalyst in various environments by using in situ and operando X-ray absorption spectroscopy and diffraction, to determine the structure and evolution of palladium hydride and carbide phases, and their distribution throughout the NPs. We demonstrate how the simultaneous analysis of extended X-ray absorption fine structure (EXAFS) spectra and X-ray powder diffraction (XRPD) patterns allows discrimination between the inner "core" and outer "shell" regions of the NP during hydride phase formation at different temperatures and under different hydrogen pressures, indicating that the amount of hydrogen in the shell region of the NP is lower than that in the core.