New insights into the influence of intra-particle transport and inorganic species on the pyrolysis mechanism of lignocellulosic biomass

Biomass is currently an important player in the renewable energy sector and it is expected to perform a key role, as source of green carbon, in both energy and chemicals & materials production in the short and mid-term future. However, biomass presents a hierarchical structure, with high heterogeneity regarding its physical and chemical properties, which poses important challenges regarding the optimization of both conversion process and product quality. This is especially relevant for low-cost biomass, as for example agricultural and forestry residues, due to the presence of impurities such as inorganic species. Generally, thermochemical conversion processes are more robust with respect to biomass high variability and technologies such as pyrolysis are especially adequate for the direct production of chemicals and materials. However, new product-oriented process development requires a better understanding of the multi-scale chemical and physical processes involved in the pyrolysis of biomass. In this way, models need to include more detailed feedstock-specific chemical mechanisms, that account as well for the influence of intra-particle morphology and microstructure on the chemical conversion. In this work, the impact of intra-particle transport limitations, triggering secondary reactions, are considered. In particular, the combined influence of inorganic species, considered catalysts of some of these secondary reactions, and intra-particle transport limitations on the pyrolysis mechanism of lignocellulosic biomass is investigated.