Due to a worldwide demand for biofuels, a need has emerged to develop new processes. Co-processing of bio-oils in refinery units is a promising alternative, especially by Fluid Catalytic Cracking (FCC). In order to promote biofuel production by co-processing a detailed mechanistic study is required based on comparison with pure vacuum gasoil (VGO) processing. Three different porous materials containing micropores and/or mesopores were tested (FCC, HY and HZSM-5). The co-processing of hydrodeoxygenated pyrolysis oil (HDO-oil) with VGO in a lab test FCC unit leads to lower product formation rates than the processing of VGO alone, except for the coke formation and the formation of more unsaturated components (essentially aromatics). The data for both VGO cracking and co-processing follow the published trends with acid site density. These results are explained by the restricted access of the oxygenated molecules into the zeolite pores and coke formation on the outside surface leading to pore blocking. Another key mechanistic feature, explaining the observed effects of co-processing on the product quality, is the competition for the zeolite acid sites between the cracking route and the deoxygenation of the oxygenated components on the outer surface.

A detailed understanding of reaction mechanisms and kinetics is required in order to develop and optimize catalysts and catalytic processes. While steady-state investigations are known to give a global view of the catalytic system, transient studies are invaluable since they can provide more comprehensive insight into elementary steps. For almost forty years temporal analysis of products (TAP) has been successfully utilized for transient studies of gas phase heterogeneous reactions, and there have been a number of advances in instrumentation and numerical modeling methods in that time. Since TAP is a complex methodology it is often viewed as a niche specialty. With the purpose to make TAP more relevant and approachable to a wider segment of the catalytic research community, part of the intention of this work is to highlight the significant contributions TAP has made to elucidating mechanistic and kinetic aspects of complex, multi-step heterogeneous reactions. With this in mind, an outlook is also disclosed for the technique in terms of what is needed to revitalize the field and make it more applicable to the recent advances in catalyst characterization (e.g. operando modes).

A promising alternative to the first generation of bio-fuels is to produce mixed bio- and fossil fuels by co-processing mixtures of biomass pyrolysis oil with crude oil fractions obtained from distillation in a conventional oil refinery. This was demonstrated to be technically feasible for fluid catalytic cracking (FCC), which is the main refinery process for producing gasoline. However, co-processing leads to more coke formation and to a more aromatic gasoline fraction. A detailed understanding is necessary on how the oxygenated moieties effect the reaction mechanism to further improve the process/catalysts. Moreover, for technical and marketing reasons, it is absolutely required to accurately determine the proportion of renewable molecules in the commercialized products. The carbon-14 method (also called radiocarbon or ¹⁴C) has been used as the most accurate and powerful method to discriminate fossil carbon from bio-carbon, since fossil fuel is virtually ¹⁴C-free, while biofuel contains the present-day “natural” amount of ¹⁴C. This technique has shown that not all FCC products share bio-carbon statistically. The coke formed during a FCC cycle and to a lesser extent the gases are found richer in ¹⁴C than gasoline. This result gives valuable information on the co-processing mechanism, supporting that the bio-oil oxygenated molecules are processed more easily at the expenses of the crude oil hydrocarbons, favouring the bio-coke and the bio-light gases production.