The increasing concentration of greenhouse gases in the atmosphere, caused by human activity, is considered the main cause for the increase in the average temperature of the planet. As a result, the search for renewable alternatives to fossil fuels has intensified, such as the transformation of biomass from agriculture into renewable fuels. For example, pyrolysis oil, also known as bio-oil, is obtained by heating dry biomass to high temperatures, in the absence of oxygen, with subsequent cooling. Bio-oil is a complex mixture of organic compounds that can be used in place of petroleum to produce fuels and other chemicals.

However, bio-oil has a high content of molecules containing oxygen. This leads to undesirable properties such as low energy density and thermal and chemical instability. In order to improve these characteristics and get a product similar to petroleum, bio-oil must undergo improvement processes in which catalyst-assisted chemical reactions eliminate those oxygenated compounds.

The most effective catalysts for this reaction must contain a combination of an active metal phase – responsible for hydrogenation and dehydrogenation reactions – and an oxophilic support – which promotes the activation of oxygenated compounds.

In this context, Karen A. Resende et al. investigated [1] new catalysts for hydrodeoxygenation of bio-oils using phenol as a model compound. The group investigated nickel ($\rm Ni$), cerium ($\rm Ce$) and niobium ($\rm Nb$) compounds – denoted $\rm Ni/Ce_{1-x}Nb_xO_2$ – with different concentrations of $\rm Nb$ and $\rm Ce$ and therefore different crystal structures.

To evaluate the structural modification promoted in the catalyst by adding $\rm Nb$, the researchers used the DXAS, XAFS2, XDS and XPD beamlines from the Brazilian Synchrotron Light Laboratory (LNLS).

The researchers observed that the addition of niobium increased deoxygenation capacity and reaction selectivity to deoxygenated compounds (benzene), suggesting that niobium’s oxophilic properties are responsible for promoting deoxygenation of the studied molecule.

Source: [1] Karen A. Resende, Adriano H. Braga, Fabio B. Noronha, Carla E. Horia; Hydrodeoxygenation of phenol over Ni/Ce1-xNbxO2 catalysts. Applied Catalysis B: Environmental 245 (2019) 100–113. DOI: 10.1016/j.apcatb.2018.12.040