A comparative study of water-immiscible organic solvents in the production of furfural from xylose and birch hydrolysate

Abstract

Furfural (FUR) was produced from xylose using a biphasic batch reaction system. Water-immiscible organic solvents such as isophorone, 2-methyltetrahydrofuran (2-MTHF) and cyclopentyl methyl ether (CPME) were used to promptly extract FUR from the aqueous phase in order to avoid the degradation to humins as largely as possible. The effect of time, temperature, organic solvent and organic-to-aqueous ratio on xylose conversion and FUR yield were investigated in auto-catalyzed conditions. Experiments at three temperatures (170, 190 and 210 °C) were carried out in a stirred microwaveassisted batch reactor, which established the optimal conditions for achieving the highest FUR yield. The maximum FUR yields from xylose were 78 mol% when using CPME, 48 mol% using isophorone (due to its phase-behavior nature) and 71 mol% in the case of 2-MTHF at an aqueous to organic phase ratio of 1:1. Birch hydrolysate was also used to show the high furfural yield that can be obtained in the biphasic system under optimized conditions. The present study suggests that CPME can be used as a green and efficient extraction solvent for the conversion of xylose into furfural without salt addition.

An overview of the biphasic dehydration of sugars to 5-hydroxymethylfurfural and furfural: a rational selection of solvents using COSMO-RS and selection guides

“…7 for reacting batches, it can be seen that both methyl propionate and EtOAc show better values of R than H 2 O-DMSO/MIBK-2-BuOH and H 2 O-DMSO/DCM at 170°C 78 or H 2 O/MeTHF and H 2 O/CPME at 190°C. 114 On the contrary, the use of isophorone at 190°C as EP gives similar distribution coefficients ranging between 7 and 9, 114 thus being comparable to the two proposed solvents.…”

“…The authors claim that an autocatalytic effect takes place when operating with microwaves at 190°C during 3 h, reporting complete conversion of xylose with 78% selectivity; the authors also reported the use of MeTHF and isophorone as EP under the same conditions with lower performance. In addition, birch hydrolysate was employed as substrate with similar conversions and yields of 68% after only 1.5 h. 114 The biphasic dehydration of xylose with toluene as EP has been reported with different zeolites, where MOR-type M-20 (SiO 2 : Al 2 O 3 = 20 : 1) achieved 42% yield to furfural and 79% conversion of xylose after 3 h at 190°C in a screw-stirred autoclave. 115 Recently, a loading of 2.5 wt% of terephthalic acid obtained from waste polyethylene terephthalate has provided good results as catalyst in H 2 O/toluene medium leading to 71% yields at 190°C in 3 h, which was higher than when butyl acetate was the extracting agent in comparable reaction conditions, reaching 60%.…”

“…Likewise, figure displays the displays the similarity between COSMO-RS predictions of the distribution coefficient of furfural and that obtained in individual experiments at 170 and 190°C. 78,114 In this case, not as many solvent systems have been studied as in the previous case. with respect to the experimental value, particularly in the case of the latter system.…”

“…This is even more clear in the case of isophorone being used as the organic solvent, in whose case R was always very underestimated, being the relative difference using different organic to water volume ratios more remarkable than in the previous two cases. 114 Apart from errors either from the experimental side or from the model predictions, it has to be taken into account that in these reacting systems the systems do not only contain 5-HMF as a solute unless complete conversion and selectivity are achieved. This in turn means that the presence of unreacted sugars or undesired side-products like levulinic or formic acid might affect the distribution coefficients.…”

“…Fig. 7 Comparison of partition ratios of furfural reported in literature 78,114 and COSMO-RS predictions in systems where reaction was performed. Note: When several values are present in the corresponding articles, those obtained from the best conditions in terms of yield were represented.…”