Process intensification of the ionoSolv pretreatment: effects of biomass loading, particle size and scale-up from 10 mL to 1 L

Abstract

The ionoSolv process is one of the most promising technologies for biomass pretreatment in a biorefinery context. In order to evaluate the transition of the ionoSolv pretreatment of biomass from bench-scale experiments to commercial scale, there is a need to get better insight in process intensification. In this work, the effects of biomass loading, particle size, pulp washing protocols and 100-fold scale up for the pretreatment of the grassy biomass Miscanthus giganteus with the IL triethylammonium hydrogen sulfate, [TEA][HSO4], are presented as a necessary step in that direction. At the bench scale, increasing biomass loading from 10 to 50 wt% reduced glucose yields from 68 to 23% due to re-precipitation of lignin onto the pulp surface. Omitting the pulp air-drying step maintained saccharification yields at 66% at 50 wt% loading due to reduced fiber hornification. 100-fold scale-up (from 10 mL to 1 L) improved the efficacy of ionoSolv pretreatment and increasing loadings from 10 to 20 wt% reduced lignin reprecipitation and led to higher glucose yields due to the improved heat and mass transfer caused by efficient slurry mixing in the reactor. Pretreatment of particle sizes of 1–3 mm was more effective than fine powders (0.18–0.85 mm) giving higher glucose yields due to reduced surface area available for lignin re-precipitation while reducing grinding energy needs. Stirred ionoSolv pretreatment showed great potential for industrialization and further process intensification after optimization of the pretreatment conditions (temperature, residence time, stirring speed), particle size and biomass loading. Pulp washing protocols need further improvement to reduce the incidence of lignin precipitation and the water requirements of lignin washing.

The structure of protic ionic liquids based on sulfuric acid, doped with excess of sulfuric acid or with water

“…15 wt %) provides additional hydrogen bond donation capacity to complement and replace the diminished number of S-OH hydrogen-bond donors present in the parent acid, and this results in a change in the nature of the first shell hydrogen-bond donors around [HSO4]anions, but not in the overall pattern of hydrogen bonding. This 'hydrated' sulfuric acid:pyridine:water (1:1:2.2) system has an equivalent water content to that of the aqueous alkylammonium PILs reported by Hallett et al 4,11,12,57,[81][82][83][84][85][86] as media for delignification for cellulosic biomass, with ca. 15 wt% water in the IL and it is clear that the water molecules here are present as 'bound' water participating in the ionic liquid solvation structure and not as 'free' water.…”

“…This results in a change in the nature of the first shell hydrogen-bond donors around [HSO 4 ] À anions, but not in the overall pattern of hydrogen bonding. This 'hydrated' sulfuric acid : pyridine : water (1 : 1 : 2.2) system has an equivalent water content to that of the aqueous alkylammonium PILs reported by Hallett et al 4,11,12,57,[81][82][83][84][85][86] as media for delignification for cellulosic biomass, with ca. 15 wt% water in the IL.…”

“…This ‘hydrated’ sulfuric acid : pyridine : water (1 : 1 : 2.2) system has an equivalent water content to that of the aqueous alkylammonium PILs reported by Hallett et al . 4,11,12,57,81–86 as media for delignification for cellulosic biomass, with ca. 15 wt% water in the IL.…”

History repeats itself again: Will the mistakes of the past for ILs be repeated for DESs? From being considered ionic liquids to becoming their alternative: the unbalanced turn of deep eutectic solvents

“…Intensification and diversification strategies and an in-depth analysis were then carried out to further investigate pro and cons of the Ionosolv process. In particular, the effect of higher loading (20 wt% solid loading), time, temperature 368 as well as particle size and scaling up from 10 mL to 1 L 369 were assessed. It is worth stressing that the scaling up required optimization of the washing protocols and agitator design, with the latter not required at the bench-scale stage.…”

Room temperature ionic liquids with two symmetric ions

“…1–3 Recent promising examples include biomass treatment and the PETRONAS process for the removal of Hg from natural gas. 4,5…”