In situsolid-state NMR for heterogeneous catalysis: a joint experimental and theoretical approach

Abstract

In situ solid-state NMR is a well-established tool for investigations of the structures of the adsorbed reactants, intermediates and products on the surface of solid catalysts. The techniques allow identifications of both the active sites such as acidic sites and reaction processes after introduction of adsorbates and reactants inside an NMR rotor under magic angle spinning (MAS). The in situ solid-state NMR studies of the reactions can be achieved in two ways, i.e. under batch-like or continuous-flow conditions. The former technique is low cost and accessible to the commercial instrument while the latter one is close to the real catalytic reactions on the solids. This critical review describes the research progress on the in situ solid-state NMR techniques and the applications in heterogeneous catalysis under batch-like and continuous-flow conditions in recent years. Some typical probe molecules are summarized here to detect the Brønsted and Lewis acidic sites by MAS NMR. The catalytic reactions discussed in this review include methane aromatization, olefin selective oxidation and olefin metathesis on the metal oxide-containing zeolites. With combining the in situ MAS NMR spectroscopy and the density functional theoretical (DFT) calculations, the intermediates on the catalyst can be identified, and the reaction mechanism is revealed. Reaction kinetic analysis in the nanospace instead of in the bulk state can also be performed by employing laser-enhanced MAS NMR techniques in the in situ flow mode (163 references).

Solid-State NMR Spectroscopy of Metal–Organic Framework Compounds (MOFs)

“…During the past decades, solid-state NMR spectroscopy has been successfully used for characterizing the structure of these materials as well as for studying so-called host–guest interactions with adsorbed species, e.g., xenon, carbon dioxide, and many others including in situ studies of catalytic reactions and diffusion processes (see, e.g., [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16]).…”

UV Raman Spectroscopic Characterization of Catalysts and Catalytic Active Sites

“…However, the characterization of catalytic active sites and the understanding of catalytic active sites remain challenging [4,5]. Over the past decades, numerous techniques have been developed and used for the study of heterogeneous catalysis [6][7][8][9][10][11][12][13]. For example, Weckhuysen et al [14] have monitored in situ phase changes in a complex iron-based Fisher-Tropsch catalyst and the nature and location of produced carbon species by scanning transmission X-ray microscopy, opening new opportunities for nanometer-resolution imaging of a range of important chemical processes occurring on solids in gaseous or liquid environments; Baiker et al [15,16] have systematically examined the catalytic solid/liquid interfaces using attenuated total reflection Fourier transform infrared spectroscopy, the kinetics of complex reactions can be followed by quantifying the concentration of reactants and products simultaneously in a non-destructive way with the in situ technique.…”

Characterization of Metal‐zeolite Composite Catalysts: Determining the Environment of the Active Phase

“…Developing new techniques . Other than the conventional techniques, more advanced and upgraded in situ techniques such as FTIR, NMR, XAS and TEM have been rapidly developed and applied in many catalytic reaction studies. More recently, atom probe tomography (APT) was used to study the aluminum distribution in a steamed ZSM‐5 zeolite .…”