Xu, Youxun; (2024) Photon-phonon co-driven catalysis for methane conversion to high-value products. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Methane is a fundamental raw material to produce syngas, methanol, formaldehyde and other chemical products. Due to the inert of methane, the current industrial process necessitates initial steam reforming of methane at high temperatures and under high pressure to produce synthesis gas, which proceeds to produce methanol and formaldehyde. Photocatalysis, using photons as an energy source can activate and convert methane under mild conditions, however the production rate is relatively low. To enhance the production rate of methane oxidation through photocatalysis, thus promoting its practical application, the introduction of phonon energy is reasonable due to the enhanced reaction kinetics. In this thesis, photon-phonon co-driven catalysis is adopted to selectively and efficiently oxidise methane to syngas, methanol and formaldehyde under mild conditions, respectively. Firstly, an efficient catalyst of Ce1-xRuxO2 solid solution is developed for photon-phonon driven dry reforming of methane (DRM) with CO2, which shows a high H2 production rate (67 μmol h–1) and CO production rate (81 μmol h–1) in a batch reactor. Secondly, methane is selectively oxidised to CH3OH with a high production rate over Au nanoparticle modified ZnO. With the synergistic effect of photons and phonons, a remarkable CH3OH production rate of ca. 800 μmol h–1 with a high selectivity of 86% is acquired over Au-ZnO operated at 150°C. Lastly, using the cascade process comprising photocatalysis and phonon driven step (photon-phonon driven cascade catalysis), efficient methane conversion to HCHO under mild conditions has been achieved using single-atom Ru decorated ZnO with a high HCHO production rate (401.5 μmol h–1) and a high selectivity (90.4%) at 150°C. These works show the potential of photon-phonon co-driven catalysis for efficient and selective methane oxidation to high-value products.

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