Process design, kinetics, and techno-economic assessment of an integrated liquid phase furfural hydrogenation process

Abstract

The integrated liquid phase process for producing furfuryl alcohol involves three stages: i) liquid–liquid extraction for recovering furfural from the aqueous solution obtained after a conventional steam-stripping hydrolysis reactor, ii) the hydrogenation reaction, and iii) the final purification. The reaction kinetics employed in the modelling are obtained experimentally. 2-methyltetrahydrofuran is the selected green solvent, and it has a high partition coefficient and stability under hydrogenating conditions. A commercial CuZnAl catalyst is used for the first time in the liquid phase furfural hydrogenation reaction, recording very high furfuryl alcohol selectivity even at complete conversion. A dual-site Langmuir-Hinshelwood model is developed and validated. An original aspect of this model is the kinetic effect of the low water content (0–5 wt%) remaining in the solvent after extraction. Water reduces the reaction rate by competing for active sites with furfural and furfuryl alcohol, without promoting other side-reactions. The optimization of the process leads to very high yields of furfuryl alcohol (97%) and a net production of 2-methyltetrahydrofuran even after recirculation and solvent losses. The process shows preliminary economic viability, with a minimum selling price for furfuryl alcohol of around 1,300 $/t; a competitive value only 30% higher than the furfural price considered in the analysis. Moreover, in contrast to current industrial processes that use copper chromite catalysts, the one developed here has environmental benefits, as it avoids the prior need for energy-intensive furfural-water distillation, eliminates toxic catalyst waste, and co-generates a green solvent.