Production of saccharides from sugar beet pulp by ultrafast hydrolysis in supercritical water

Abstract

10Sugar beet pulp (SBP) is the major by-product in sugar industry. To make profit out of this 11 undervalued residue, the FASTSUGARS process was proposed as a solution, combining 12 the advantages of supercritical water as hydrolysis medium with very short reaction times 13 in the so-called ultrafast reactors. Operating at 390 ºC, 25 MPa and reaction times between 14 0.11 and 1.15 s it was possible to convert SBP into sugars and to obtain a lignin-like solid 15 fraction. The highest yields of C-6 and C-5 sugars (61 and 71 % w/w, respectively) were 16 obtained at 0.11 s with the lowest yield of degradation products. The solid product obtained 17 at 0.14 s was thoroughly analyzed by acid hydrolysis, TGA and FTIR analysis to prove its 18 enhanced thermal properties and aromaticity. The FASTSUGARS process demonstrated 19 being a versatile and promising technology to be integrated in the future biorefineries. 20 Highlights 21• FASTSUGARS is a key step towards future sustainable biorefineries 22• Sugars were selectively recovered from sugar beet pulp using SCW as reaction medium 23• Ultrafast reactors allowed accurate control of reaction times in the range of milliseconds 24• The solid product after hydrolysis was mainly composed of an acid-insoluble fraction 25• Thorough characterization of the solid confirmed its lignin-like nature 26

Scaling up the production of sugars from agricultural biomass by ultrafast hydrolysis in supercritical water

“…If visualizing the hydrolysis of an individual biomass particle, it makes 255 reaction time or more severe reaction conditions) to get hydrolyzed to the same extent 257 than a particle half its size. Therefore, following the same reasoning already observed 258 when comparing sbp to wb results [17], initial particle size was acting as a mass transfer 259 resistance, so that under same reaction time and operating conditions, bigger particle 260 size produced lower conversion. 261…”

“…To evaluate 118 this scaling up sugar beet pulp (SBP) and wheat bran (WB) were hydrolyzed in the 119 FASTSUGARS pilot plant and results were compared to previous ones obtained in the 120 laboratory scale plant [9,17]. 121…”

“…Then, to validate these results, the results from sugar beet pulp 125 hydrolysis in the laboratory plant (labelled as sbp, from [17]) those from wheat bran 126 (wb, from [9]) were used for comparison between laboratory and pilot scale plants. 127…”

“…The objective in this section was to compare the results previously obtained in the laboratory scale plant for both sugar beet pulp, sbp [17] and wheat bran, wb [9] to the ones presented in this work. First important difference to mention was the biomass used for each set of experiments.…”

Supercritical Fluids: A Promising Technique for Biomass Pretreatment and Fractionation

“…The remaining solids after hydrolysis consisted of 85 wt.% lignin, with about 5 wt.% glucans still remaining in the hydrolysis residue. Martínez et al (2018) studied the implementation of supercritical water for hydrolysis of beet pulp at 390 • C and 250 bar, varying the reaction times between 0.11 and 1.15 s. The highest C 6 and C 5 yields of 61 and 71 wt.% were obtained at 0.11 s, respectively, and the use of short reaction times produced low concentrations of dehydration byproducts. Also, Martínez et al (2019) compared the supercritical hydrolysis of sugar beet pulp and wheat bran at laboratorial and pilot scale and concluded that long hydrolysis times were detrimental to the obtainment of high sugar yields, however, in pilot scale tests, the use of higher average particle sizes reduced sugars degradation, leading to sugar yields up to 90% of the theoretical maximum.…”