Hydrocracking, hydrogenation and hydro-deoxygenation of fatty acids, esters and glycerides: Mechanisms, kinetics and transport phenomena

• Reaction mechanism of hydrogenolysis of triglycerides into alkanes. • Overview of the reactor types used for catalytic hydrotreatment of oils and fats. • Kinetics models in the literature mostly vary from simple power law to Langmuir-Hinshelwood type. • Comprehensive microkinetic models are rarely used. • Comparison of Pt, Ni, Co, NiMo, CoMo catalyst performance reported in the literature. Article offers a review of the mechanisms, kinetics and effects of the analysed process conditions on the conversion, selectivity and catalyst chemical stability of the hydrogenation, hydrocracking and hydro-deoxygenation (HDO) transformation reactions of biomass-derived fatty acids. Sequences discussed include all functional steps from the hydrogeno-lysis of the triglyceride ester bonds to the last stage upgrading, while special simultaneous attention is put to ensuring non-equilibrium thermodynamic energetics, where recent literature methods has made some significant advances. Optimal capacity planning is assessed, intensification is simulated, and three-staged integrated processing is recommended for very unsaturated feeds. Characteristic modelling approaches applied are grouped based on complexity, pre-assumptions regarding approximated rate-determining steps (RDS) and abundant reactive intermediates (MARI). Most systematic studies are founded on the Langmuir–Hinshelwood model with simplifying mathematical expression, such as the neglecting of the adsorption of minor oxygenate compounds. The evaluation of specific defining works is presented, focusing on structure–activity relationship correlations, the exploration of activation or transition state improvement, and deactivation. Lastly, results incorporate the rating of scaling-related poison molecules, factors, impacting interaction binding constant, and coking or sintering. Catalysis is considered broadly, from the noble- or platinum group metals (PGM), such as ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag) and gold (Au), to non-critical raw materials (CRM), not only nickel (Ni), but also manganese (Mn), iron (Fe), cobalt (Co), copper (Cu), as well as zinc (Zn). The acidity of support can be varied over a range of zeolites, e.g. H-beta, H-mordenite, H-USY, H-Y and H-ZSM-5, or alumina.