A Heterogenized Molecular Catalyst for the Gas-Phase Cyclotrimerisation of Acetylene to Benzene

Coupled with acetylene production from renewable feedstocks, this reaction offers a promising pathway for the direct, low-temperature synthesis of renewable benzene. Recog-nizing the physical limitations of typical solid catalysts, which adsorb benzene too strongly, this study investigates various high-valent early transition metal chlorides – potent molecular cyclotrimerisation catalysts – as solid catalysts in this gas-phase conversion.

Alongside catalytic assessment under industrially relevant conditions, various analytical techniques such as 93Nb solid-state NMR spectroscopy, X-ray emission spectroscopy and quasi in situ X-ray photoelectron spectroscopy were applied to reveal that the catalytic function proceeds through in situ formation of catalytically active reduced species as re-ported for a homogeneous reaction environment. Investigating deactivation phenomena, various catalyst precursors and reac-tion conditions led to the design of an immobilized molecular catalyst via chemical grafting, dispersion and spatial isolation of active catalytic species on a mesoporous silica gel support.