An overview and analysis of the thermodynamic and kinetic models used in the production of 5-hydroxymethylfurfural and furfural

Lignocellulosic biomass appears as an attractive bio-based substrate for platform chemicals, such as 5-hydroxymethylfurfural (HMF) and furfural (Fur). These furans are produced by the dehydration of C6 sugars (glucose, fructose) and C5 sugars (xylose), respectively, with acidic media. Production of these platform chemicals are plagued by undesired side reactions, through rehydration of HMF to levulinic and formic acid, as well as the polymerization to humins taking place under monophasic conditions. As a mitigation strategy, biphasic systems are proposed as an alternative to enhance selectivity, this process intensification approach conducts a hybrid reaction with in situ extraction of the furans. Considerable progress has been made on the development of catalysts, complex feedstock and the utilization of biphasic systems, covered extensively in other reviews. However, there is still a lack of a systematic and critical analysis of the data and models used in the evaluation of liquid-liquid equilibria (LLE) for the partitioning of furans and the kinetic models for the chemical reactions. This work identifies and evaluates thermodynamic models for the prediction of LLE, specifically NRTL, UNIQUAC and ePC-SAFT (for salt additives) and elaborates on the use of COSMO-RS as a predictive method for solvent screening. Extraction solvents used in conjunction with these models were ranked according to partition coefficients and classified with the CHEM21 guides. A normalised macrokinetic reaction network is developed and methods of assessment for mass transfer imitations are evaluated, including the activation energies obtained. Although the typical range for the production of HMF and Fur is quite wide, in many cases it falls between 110 and 150 kJ mol-1.