Production of Furfural from Process-Relevant Biomass-Derived

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Production of Furfural from Process-relevant Biomassderived Pentoses in a Biphasic Reaction System Ashutosh Mittal, Stuart K. Black, Todd B. Vinzant, Marykate O'Brien, Melvin P. Tucker, and David Kenneth Johnson ACS Sustainable Chem. Eng., Just Accepted Manuscript • Publication Date (Web): 16 May 2017 Downloaded from http://pubs.acs.org on May 17, 2017

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ACS Sustainable Chemistry & Engineering

Production of Furfural from Process-relevant Biomassderived Pentoses in a Biphasic Reaction System Ashutosh Mittal†*, Stuart K. Black‡, Todd B. Vinzant†, Marykate O’Brien‡, Melvin P. Tucker‡, David K. Johnson† †

Biosciences Center, National Renewable Energy Laboratory, 15013 Denver West Parkway Golden, CO 80401 USA ‡ National Bioenergy Center, National Renewable Energy Laboratory, 15013 Denver West Parkway Golden, CO 80401 USA *Email [email protected] † Electronic supplementary information (ESI) available. See DOI: †

Biosciences Center, National Renewable Energy Laboratory 15013 Denver West Parkway Golden, CO 80401-3305, USA

‡

National Bioenergy Center, National Renewable Energy Laboratory 15013 Denver West Parkway Golden, CO 80401-3305, USA

Mailing address :

Mailing address :

ABSTRACT: Furfural is an important fuel precursor which can be converted to hydrocarbon fuels and fuel intermediates. In this work, production of furfural by dehydration of process-relevant pentose rich corn stover hydrolyzate using a biphasic batch reaction system, has been investigated. Methyl isobutyl ketone (MIBK) and toluene have been used as the water-immiscible solvents to extract furfural and enhance overall furfural yield by limiting its degradation to humins. The effects of reaction time, temperature, and acid concentration (H2SO4) on pentose conversion and furfural yield, were investigated. For the dehydration of 8 wt% pentose-rich corn stover hydrolyzate under the optimum reaction conditions, 0.05 M H2SO4, 170°C for 20 min with MIBK as the solvent, complete conversion of xylose (98-100%) and a furfural yield of 80%, were obtained. Under these same conditions, except with toluene as the solvent, the furfural yield was 77%. Additionally, dehydration of process-relevant pentose rich corn stover hydrolyzate using solid acid ion-exchange resins under optimum reaction conditions has shown that Purolite CT275 is as effective as H2SO4 for obtaining furfural yields approaching 80% using a biphasic batch reaction system. This work has demonstrated that a biphasic reaction system can be used to process biomass-derived pentose rich sugar hydrolyzates to furfural in yields approaching 80%. Keywords: Xylose, Pentose, Furfural, Biphasic, Dehydration, Biofuels

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INTRODUCTION Furfural, identified as one of the top 30 platform 1 chemicals derived from biomass , is an important fuel 2 precursor which can be converted to hydrocarbon 3 4 fuels and fuel intermediates. With current global 5 production greater than 200,000 tonnes annually it is currently a high-value commercial commodity chemical, produced primarily from agricultural wastes such as oat hulls, corn cobs and sugar cane 6 bagasse. Industrial processes for furfural production were developed as early as 1921 when the Quaker Oats batch process was developed to produce furfural from 6 oat hulls. Since then many alternative batch and 7 continuous processes have been developed with most of the batch operations primarily using sulfuric acid as a homogeneous acid catalyst and 6 temperatures ranging between 160°C and 200°C. High operating costs, and low energy efficiency coupled with low furfural yield, on the order of less than 50%, resulted in the closure of batch process 8 based plants in 1990s. Another significant industrial continuous process for furfural production was developed by Quaker Oats, which operated for 40 6 years in Belle Glade, Florida, until 1997. The continuous process utilized a traditional horizontal screw-style reactor, similar to the 1-ton per day horizontal reactor system (Metso, Norcross, GA) used at National Renewable Energy Laboratory (NREL) for 9 dilute acid pretreatment. A slightly improved furfural yield (55%) was obtained in the continuous process developed by Quaker Oats using a residence time of one hour. While this process was technically successful, the plant ultimately shut down due to the high maintenance cost of the continuous reactor 6 system. Improving furfural yield beyond 55% in industrial production has been the subject of much research 10-13 over the last 100 years. This is a difficult task because furfural, once produced, rapidly degrades through resinification and condensation reactions. Furfural resinification is a reaction in which furfural reacts with itself, while condensation reactions occur when furfural reacts with xylose or one of the intermediates of xylose-to-furfural conversion to form furfural pentose or di-furfural pentose. The loss of furfural by condensation is significantly greater than 6 the loss by resinification. Much research has been conducted in recent decades to try to minimize 14-15 degradation and improve furfural yield. Several researchers have reported on the production of furfural from the dehydration of xylose,

hemicellulose, and cellulosic biomass. For example, Yang et al. reported 75% furfural yield from the reaction of xylose in water-tetrahydrofuran biphasic medium containing AlCl3.6H2O and NaCl under microwave heating at 140°C, and 55, 38, 56, and 64% furfural yield from corn stover, pinewood, switchgrass and poplar, respectively using the same 19 solvent system at 160°C. Chheda et al. reported a furfural selectivity of 66% at high conversions from the dehydration of xylan with 5: 5 (w/w) water: 22 DMSO system and pH 1.0 at 170°C. Zhang et al. reported 85.3% furfural yield from maple wood at 170°C in 0.1 M sulfuric acid for 50 min by employing 23-24 simultaneous solvent extraction with MIBK. The main focus of process improvements to achieve higher furfural yield can be categorized in three ways: 1) by improving furfural removal efficiency using steam or an inert gas, e.g., the Suprayield process, 25 which uses N2 stripping ; 2) by extracting furfural using a secondary organic phase in a biphasic reaction, for example: using Cyclopentyl methyl ether 26 20 (CPME) , o-nitrotoluene , tetrahydrofuran and/or γ14 valerolactone ; 3) by using different homogenous or heterogeneous solid catalysts, for example: maleic 27 21 acid , formic acid , metal salts, and/or Amberlyst 14 70. The utilization of biphasic systems for the production of sugar dehydration products such as furfural and hydroxymethyl furfural has recently gained more attention primarily because they can achieve higher product selectivities and yields than can be obtained 14, 22, 28 in an aqueous only solvent system. Xing et al 29 (2011) reported that furfural yields >90% could be achieved by conducting the acid catalyzed dehydration of pentoses in a system containing tetrahydrofuran (THF) and sufficient sodium chloride so that the THF formed a second phase into which the furfural was extracted. Xing and co-authors predicted that this system could be used to produce furfural for 366 $/metric ton, considerably below the current commercial cost of about 1750 $/metric ton. 30 Weingarten et al (2010) studied the kinetics of furfural production by dehydration of xylose in a biphasic reactor and reported that furfural yields approaching 80% could be achieved using MIBK in a biphasic reactor system at 170°C and short reaction 31 times. In addition, Lessard et al (2010) reported using a continuous biphasic system where toluene was the organic solvent used to extract furfural from the aqueous phase. In their work they found that the furfural yield reached 98% molar yield via


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+

dehydration of 12% w/w xylose solution over a (H ) mordenite-type zeolite in a biphasic plug-flow 14, 22, 28 reactor. These and other reports in the literature indicate that a biphasic reaction system may be used to produce furfural from monosaccharides in high yield; however, the literature on the production of furfural from a biomass-derived process-relevant pentose rich sugar hydrolyzate is scarce. High sugar concentrations in biorefinery hydrolyzates are desired as the further processing of such hydrolyzates to value-added products offers industrial advantages such as reduced reactor size, less energy-intensive product recovery, and reduced water consumption. In that regard, a pentose rich sugar hydrolyzate was obtained from corn stover using NREL’s 1-ton per day dilute acid pretreatment reactor. This process-relevant hydrolyzate contained xylose, arabinose, glucose, acetic acid and sugar degradation products and was representative of a hydrolyzate sample that could be produced from a dilute acid pretreatment process in a biorefinery. The objective of this work was to evaluate the production of furfural from a process-relevant pentose rich sugar hydrolyzate using a biphasic system in which furfural was extracted into a water immiscible solvent removing it from the acidic environment that would catalyze yield reducing condensation and resinification reactions. Initially, the effects of reaction time, temperature, and acid concentration (H2SO4) on xylose conversion and furfural yield were investigated with pure xylose. The optimum reaction conditions were identified that gave the highest furfural selectivity using a biphasic batch reaction system where methyl isobutyl ketone (MIBK) or toluene were used as water-immiscible solvents to extract furfural and enhance overall furfural yield by limiting its degradation to humins. We further show that under the optimum reaction conditions obtained with pure xylose, we can process a pentose rich sugar hydrolyzate obtained from corn stover using NREL’s 1-ton per day dilute acid pretreatment reactor, with equally good furfural yield and selectivity. It is expected that the optimization of reaction conditions and maximizing furfural production from a process-relevant pentose rich sugar hydrolyzate would aid in scaling up the process to industrial scale.

EXPERIMENTAL SECTION

Raw Materials. Xylose, MIBK, toluene and cyclohexanol were purchased from Sigma-Aldrich. H2SO4 was purchased from Ricca Chemical Company. A process-relevant pentose rich sugar hydrolyzate was obtained from corn stover using NREL’s 1-ton per day dilute acid pretreatment Metso reactor at 150°C 32 for 10 min with 0.8 wt% H2SO4. The pH of the hydrolyzate was 2.2, and the composition of the hydrolyzate is given in Table 1.

Table 1. Compositional analysis of dilute acid pretreatment hydrolyzate Composition

g/L

Glucose

23.3

Xylose

162.2

Arabinose

18.9

Acetic acid

16.6

HMF

0.5

Furfural

6.2

Xylose Dehydration Reaction Experiments. Acid catalyzed furfural production experiments were performed at temperatures ranging from 160 to 180°C in batch mode using a Discover S-Class microwaveheated reactor (CEM Explorer, Matthews, NC) outfitted with a 48-position auto-sampler. This reactor system is equipped with a computercontrolled temperature and pressure feedback system, which is used to regulate the microwave power for rapid heating and constant temperature. The temperature inside the reactor was monitored by measuring the infrared emission from the bottom of the reactor tube and pressure was measured with a transducer on the top of the reactor. Pressure and temperature values read into the software were then used in a feedback control algorithm to maintain a constant temperature. Steam table pressures were used to validate target temperatures. Microwave frequency radiation of 2.3 GHz and a maximum pulsed-power of 200 W were used to heat the samples. Temperature, pressure and microwave power profiles were acquired using CEM’s Synergy software (version 1.27). Furfural production reactions were conducted in 10 mL glass reactor tubes filled to liquid volumes of 3 or 4.5 mL depending on the organic solvent to aqueous fraction ratio. After addition of acid, the reactor tube was capped, and then stirred for 15 minutes at 25°C


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before loading in the auto-sampler. Prior to microwave heating samples were pre-stirred at the low speed setting for 15 s, and then continuously stirred throughout microwave heating. Reaction temperature was maintained within ±2°C of the target temperature. After completion of the reaction, samples were cooled to 60°C via a stream of compressed air that was blown on the reactor tubes. Samples were kept at room temperature until the sequence was complete after which the samples were stored at 4°C until analyzed. All experiments were conducted in duplicates. To determine the reproducibility of the experiments triplicates were run at various reaction times within each series of experiments. Analysis. Samples for analysis were drawn from both the organic phase (upper) and aqueous phase (lower) prior to and after microwave heating. The monomeric sugars (xylose and arabinose) and furfural were analyzed separately using a High Pressure Liquid Chromatography (HPLC) system (Agilent 1100, Agilent Technologies, Palo Alto, CA). For sugars, separations were carried out with an Aminex HPX87H Ion Exclusion column (300 × 7.8 mm, 8 µm particle size, Catalogue No. 125-0140) and Cation H+ guard column (BioRad Laboratories, Hercules, CA) operated at 65°C. The eluent was 0.01N H2SO4 at a -1 flow rate of 0.6 mL min . The peaks were identified and quantified with a refractive index detector (RID). Furfural was analyzed using Reversed Phase HPLC analysis (RP-HPLC). In RP-HPLC, separations were carried out with a Waters C18 reversed phase column (Nova-Pak C18 Column, 60 Å, 4 µm, 3.9 mm X 150 mm) equipped with a Waters Insert C18 pre-column (Nova-Pak C18 Guard Column, 60 Å, 4 µm, 3.9 mm X 20 mm) (Waters, Milford, MA). The mobile phase was a linear gradient of 0.05 M phosphoric acid/acetonitrile: isocratic for 5 min with 5% acetonitrile, followed by a linear gradient up to 100% acetonitrile in 10 min followed by a re-equilibration step (to 5% acetonitrile) for 5 min before the next injection. The column was thermostated at 25°C and the flow rate was 1 mL/min. The furfural peak was identified and quantified using a photodiode array detector (DAD) at 270 nm. The HPLC was controlled and data analyzed using Agilent ChemStation software (Rev. B.03.02).

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RESULTS AND DISCUSSION Furfural Partitioning in a Biphasic Reactor System. The partitioning or extractability of furfural in different organic solvents was evaluated by conducting experiments wherein a solution of 5 wt% furfural in 0.1 M H2SO4 was heated with MIBK, toluene and cyclohexanol for 20 min at 170°C at three different ratios of organic solvent to aqueous: 2:1, 1:1 and 1:2 (vol/vol). Figure 1 shows the furfural partition coefficients (P) obtained with the three organic solvents, where P was calculated using equation 1.

. .

(1)

A furfural partition coefficient of 6.4 was obtained with an MIBK to aqueous fraction ratio of 2:1. This value increased only slightly to 6.6 and 6.8 as the MIBK to aqueous fraction ratio decreased to 1:1 and 1:2, respectively. For toluene and cyclohexanol comparatively lower partition coefficients were obtained compared to MIBK. Based on the furfural partitioning results obtained in this study, MIBK and toluene were selected for the majority of experiments on furfural production while cyclohexanol was evaluated as a biphasic solvent at optimum reaction conditions where maximum furfural production was obtained with MIBK and toluene.

Figure 1. Partition coefficients for furfural between MIBK, toluene, and cyclohexanol. Partition coefficients were determined for a solution of 5 wt% furfural in 0.1 M H2SO4 heated for 20 min at 170°C at three different ratios of organic solvent to aqueous: 2:1, 1:1 and 1:2 (vol/vol). The error bars shown are one standard deviation from triplicate analyses.


4

%&'

! "

100

2&3445

"

-./

67 8

" 100

80 60 40 20

01

0

"

(3) 9:7 ;994%) and high furfural yields (70–94%) could be obtained over a range of pentose sugar concentrations. Furfural Production using Solid Acid Ionexchange Resins. Dehydration of pentose rich hydrolyzate to furfural in a biphasic system was also studied using acidic ion-exchange resin catalysts (Purolite CT275, Nafion NR50). These two resins were


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chosen for this study because of their strong acid character, and because they had upper temperature limits of 180 and 200°C, respectively, whereas other acidic resins could not be used at the optimum temperature we have found in this work (170°C) and were limited to 150°C or less. These experiments were focused on evaluating the influence of solid acid catalysts over H2SO4 on the yield and selectivity of furfural production. MIBK was used as the waterimmiscible solvent. The effects of catalyst loading on pentose conversion and furfural yield were investigated under the optimum reaction conditions (170°C for 20 min) for maximizing furfural yields. As can be seen in Figure 5 xylose conversion increased from 70 to 93% and 82 to 96% using 5 and 8 wt% pentose concentrations, respectively, as the Purolite loading was increased. No effect of catalyst loading was observed on furfural yield which ranged between 80 – 83%. Both furfural selectivity and mass balance decreased with increasing catalyst loading from 100 to 90% and 97 to 83% for both 5 and 8 wt% pentose

A Conversion

5 Wt%

8 Wt%

Furfural Yield

Selectivity

concentrations, respectively. These results show that high furfural yield and selectivities of above 80% and 90%, respectively could be obtained by dehydration of pentose sugars with a Purolite loading of 125 mg/g at 170°C for 20 min. Comparing the results obtained with Purolite and Nafion (Figure 5) it can be noted that for the same catalyst loading of 125 mg/g of pentose sugars, Purolite results in higher xylose conversion and furfural yield most likely due to + having a greater H concentration than Nafion. Overall, the furfural yields obtained with Purolite CT275 are comparable to the yields obtained with the homogeneous acid catalyst used in this work (H2SO4 – Figure 5). These results clearly suggest that Purolite CT275 is as effective as H2SO4 as the acid catalyst for the dehydration of process-relevant corn stover hydrolyzate.

B Conversion 100

80

80

60

60

Furfural Yield

Selectivity

%

100

%

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


40

40

20

20 0

0 50

125 250 Purolite, mg/g Pentose Sugars

125 400 Nafion, mg/g Pentose Sugars

Figure 5. Furfural production from hydrolyzates containing 5 and 8 Wt% pentoses at 170°C for 20 min with acidic ion-exchange resin catalysts (A) Purolite CT275 (B) Nafion NR50. Effect of catalyst loading was evaluated on xylose conversion, furfural yield and selectivity. MIBK was used as the water-immiscible solvent with the organic solvent to aqueous fraction ratio of 2:1. The error bars shown are one standard deviation from triplicate analyses. Catalyst Stability. Catalyst stability was studied for Purolite CT275 by recycling the catalyst for four consecutive dehydration reactions conducted with a hydrolyzate containing 8 wt% pentose sugars at 170°C for 20 min with 125 mg Purolite CT275/g pentose sugars using MIBK as the organic solvent. The

catalyst recycling experiments were conducted similarly to the dehydration experiments as described in the Experimental section with the exception that instead of using fresh solid catalyst in each run, the solid catalyst used in the first dehydration reaction was separated and recovered from the liquid and


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reused in the next three consecutive reactions. The catalyst was used without employing any washing or regeneration. The effect of catalyst recycling on pentose conversion and furfural yield are shown in Table 3. The first entry in Table 3 shows that a xylose conversion and furfural yield of 26.8 and 29.7%, respectively, were obtained when no catalyst was used. The explanation for obtaining such a high furfural yield in the absence of catalyst is due to the low pH (2.2) of the hydrolyzate obtained from the dilute acid pretreatment. The second entry (Run # 1) in Table 3 shows that xylose dehydration with 125 mg Purolite CT275/g Pentose sugars under similar reaction conditions results in a more than two-fold increase in both xylose conversion (69.1%) and furfural yield (71.5%). However, a steady decrease in both xylose conversion and furfural yield was observed after each catalytic run resulting in a xylose conversion of 33.4% and furfural yield of 38% after the fourth dehydration reaction (Runs # 2 – 4). Loss of catalytic activity with catalyst recycling has been reported in earlier xylose dehydration studies and has been partly attributed to strong adsorption of reaction products on the active sites present on the 34 catalyst. It has also been reported that most of the loss of activity of various catalysts can be recovered 34-35 by employing a catalyst regeneration step. We are currently conducting experiments in this direction. Table 3. Effect of catalyst recycling on pentose conversion and furfural yield for furfural production from a hydrolyzate with 8 wt% pentose concentration at 170°C for 20 min with 125 mg Purolite CT275/g pentose sugars. MIBK to aqueous ratio was 2:1. The experiments were conducted in duplicate.

Run # No catalyst 1 2 3 4

Xylose conversion, % 26.8

Furfural yield, % 29.7

69.1 (3.5) 57.2 36.9 33.4

71.5 (2.2) 57.0 40.1 38.0

Furfural Production in a Single Phase System. To show the effect that immiscible solvents have on the conversion of xylose to furfural, reactions were performed without the organic solvent using the

same hydrolyzate under the optimum reaction conditions found above (170°C, 20 min reaction time, with 0.05 M H2SO4). The effect of initial pentose sugar concentration on furfural yield is shown in Figure 6. The furfural yield was significantly lower in the absence of the solvent. Furfural yields were reduced by approximately 50% relative to when a solvent was present, with yields of 64 to 34% for pentose concentrations of 5 to 18%. These results clearly show that water-immiscible organic solvents such as MIBK and toluene used in a biphasic system are crucial to enhancing overall furfural yield by limiting its degradation to humins. Moreover, MIBK, as a biphasic solvent, has excellent properties such as low boiling point (117°C), low solubility in water (1.9%) and a high partition coefficient (7-8) for 23 furfural between the organic and aqueous phases. It’s high partition coefficient and low solubility in water (1.9g/100 mL) enables furfural to be extracted from the aqueous into the organic phase in high concentration. From the process point of view it is very important that furfural can be easily separated from MIBK via distillation so that it can be utilized for further upgrading reactions and so that the MIBK can be recovered and recycled back into the process making this process cost-effective and sustainable.

100 Furfural Yield

80

Yield, %

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60 40 20 0 5

8 11 18 Pentose Sugars, Wt%

Figure 6. Furfural yields from reacting a pentose sugars rich hydrolyzate in a single (aqueous) phase system at 170°C for 20 min with 0.05 M H2SO4. The error bars shown are one standard deviation from triplicate analyses.


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ASSOCIATED CONTENT CONCLUSIONS In this work, we have demonstrated that a biphasic reaction system can be used to convert pentose sugars to furfural in biomass derived process-relevant hydrolyzates in yields approaching 80%. At the optimum reaction conditions, 0.05 M H2SO4, 170°C for 20 min with MIBK as the solvent, complete conversion of xylose (98-100%) and a furfural yield of 80%, were obtained. Under these same conditions except with toluene as the solvent the furfural yield was 77%. Additionally, Purolite CT275 solid acid ionexchange resin could be used for production of furfural in 80% yield from the same hydrolyzate at the same optimum reaction conditions that were effective with H2SO4. The results of this work suggest that furfural yields >80% may be obtained at higher temperatures and shorter reaction times (e.g., 190°C, 5-7 min). However, due to the pressure limitation of the current microwave system, such conditions were not attempted. An alternative approach using a plug flow reactor is envisioned that would allow higher reaction temperatures and shorter residence times that may avoid furfural degradation and lead to even higher furfural yields. Moreover, a solid acid catalyst would be more suitable for use in the plug flow reactor and could make it possible to reach furfural yields approaching 90%.

REFERENCES 1. Werpy, T.; Petersen, G.; Aden, A.; Bozell, J.; Holladay, J.; White, J.; Manheim, A.; Eliot, D.; Lasure, L.; Jones, S. Top value added chemicals from biomass. Volume 1-Results of screening for potential candidates from sugars and synthesis gas; DTIC Document: 2004. 2. Cai, C. M.; Zhang, T.; Kumar, R.; Wyman, C. E., Integrated furfural production as a renewable fuel and chemical platform from lignocellulosic biomass. J. Chem. Technol. Biotechnol. 2014, 89 (1), 2-10. 3. Climent, M. J.; Corma, A.; Iborra, S., Conversion of biomass platform molecules into fuel additives and liquid hydrocarbon fuels. Green Chem. 2014, 16 (2), 516-547. 4. Lange, J. P.; van der Heide, E.; van Buijtenen, J.; Price, R., Furfural—a promising platform for lignocellulosic biofuels. ChemSusChem 2012, 5 (1), 150-166. 5. Dutta, S.; De, S.; Saha, B.; Alam, M. I., Advances in conversion of hemicellulosic biomass to furfural and upgrading to biofuels. Catal. Sci. Technol. 2012, 2 (10), 2025-2036.

Supporting Information Supporting Information of this article can be found under http://dx.doi.org/: Effect of acid concentration on furfural yield at 170 and 180°C for the dehydration of pentose sugars (8 wt%) in a biomass hydrolyzate (Figure S1).

AUTHOR INFORMATION Corresponding Author *E-mail: [email protected] ORCID Ashutosh Mittal: 0000-0002-0434-0745 Notes The authors declare no competing financial interest.

ACKNOWLEDGEMENTS This work was supported by the U.S. Department of Energy (DOE) under Contract No. DE-AC3608GO28308 with the National Renewable Energy Laboratory. Funding for the work was provided by the DOE Office of Energy Efficiency and Renewable Energy, Bioenergy Technologies Office (BETO).

6. Zeitsch, K. J., The Chemistry and Technology of Furfural and its Many By-Products. Elsevier Science: 2000. 7. Karinen, R.; Vilonen, K.; Niemelä, M., Biorefining: heterogeneously catalyzed reactions of carbohydrates for the production of furfural and hydroxymethylfurfural. ChemSusChem 2011, 4 (8), 1002-1016. 8. Dashtban, M.; Gilbert, A.; Fatehi, P., Production of furfural: overview and challenges. J. Sci. Technol. Forest Prod. Process 2012, 2 (4), 44-53. 9. Humbird, D.; Davis, R.; Tao, L.; Kinchin, C.; Hsu, D.; Aden, A.; Schoen, P.; Lukas, J.; Olthof, B.; Worley, M., Process design and economics for biochemical conversion of lignocellulosic biomass to ethanol: dilute-acid pretreatment and enzymatic hydrolysis of corn stover. 2011. 10. Hurd, C. D.; Isenhour, L. L., Pentose reactions. I. Furfural formation. J. Am. Chem. Soc. 1932, 54 (1), 317-330. 11. Dunlop, A., Furfural formation and behavior. Ind. Eng. Chem. 1948, 40 (2), 204-209. 12. Fulmer, E. I.; Christensen, L.; Hixon, R.; Foster, R., The Production of Furfural from Xylose


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For Table of Contents Use Only (Graphical Abstract) Title: Production of Furfural from Process-relevant Biomass-derived Pentoses in a Biphasic Reaction System Authors: Ashutosh Mittal, Stuart K. Black, Todd B. Vinzant, Marykate O’Brien, Melvin P. Tucker, David K. Johnson Synopsis: Biomass-derived sugars were efficiently converted to furfural for the production of sustainable fuels and chemicals.


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Production of Furfural from Process-Relevant Biomass-Derived

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