His PhD thesis, entitled Valorization of Waste Biomass by Catalytic Pyrolysis, is part of the WASTE2ROAD project. During the project, William studied the performance of novel acidic catalysts (niobium based mixed oxides) in catalytic upgrading of pyrolysis vapours.

The best Nb-based catalyst, NbxMnyOz, exhibited similar performances in terms of liquid phase selectivity and reduction of undesired products from biomass degradation as the traditionally used HZSM-5. The effect of contaminants (paints, varnish and plastic), commonly found in construction and demolition woods, was investigated through model feedstocks that were prepared by impregnation of beech wood chips with commercial paints and varnish and with the individual inorganic compounds found in these materials (TiO₂, CaCO3, and BaSO4).

The results showed that these mineral materials remained in the chars and the properties of bio-oils were not modified by the presence of contaminants. In the last section of his thesis, William focused on co-pyrolysis of beech wood chips as lignocellulosic biomass and polyamide-6, which is a thermoplastic polymer, being used in a wide range of plastic materials.

The co-pyrolysis process resulted in a partial deactivation of the catalyst, affecting mainly the formation of non-condensable gases. Additionally, N-containing compounds were found in the bio-oils, which is detrimental to their quality as potential fuels, given that it would require subsequent HDN treatment to remove these compounds. William will defend his PhD work on March 30, 2022.