Natural gas has been proposed as a bridging feedstock for society’s transition away from a petroleum- dependent economy. However high C-H bond energies have stymied attempts to partially oxidise its principal components; methane and ethane. Harsh conditions are often employed to overcome the substrates' inert nature, therefore further conversion of more desirable primary products to deeper oxidation products such as CO2 is a key consideration. Several routes for direct oxidation of these alkanes have been reported, though few have been considered industrially viable and many involve non- environmentally benign chemistries, thereby spurning the current trend towards green chemical technologies. It has been found that commercial ZSM-5 contains trace amounts of iron which catalyses the direct oxidation of ethane to oxygenated products using H2O2 in the aqueous phase. Selectivity to carbon oxides is low (&lt; 5 %), with the reaction yielding ethylene, ethanol and acetic acid as major products. Through catalyst and process development, appreciable yields of acetic acid are observed under both stirred batch and continuous flow conditions (39 % yield/ 56 % conversion and 16 % yield/ 22% conversion respectively) at the low reaction temperature of 50 oC. Furthermore, addition of copper into the catalyst can afford high selectivity to ethylene (&gt; 30 %). A full mechanistic study has allowed elucidation of catalytic pathways, showing the versatility of this system to produce a range of C2 and C1 products. Characterisation and experimental studies have shown the active site for ethane activation to be extra- framework iron species with catalytic ethane turnover frequencies of up to 1200 molconverted molFe-1 h-1 observed. This data shows the potential for these materials to be employed in natural gas valorisation processes.

Selective oxidative upgrading of ethane under mild reaction conditions over Fe- and Cu- ZSM-5 catalysts; a stirred batch and continuous flow study

251st National Meeting (2016)

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