4th International Conference on Thermochemical Biomass Conversion Science Bioeconomy Institute 2-5th November, 2015 Westin Chicago River North Arpa Ghosh, Robert C. Brown, Xianglan Bai Selective depolymerization of cellulose to solubilized carbohydrates in aprotic solvent systems Introduction Results and Discussion Results and Discussion

 Cellulose is the primary source of fermentable carbohydrates in biomass but it is inherently recalcitrant to Product Distribution of Cellulose Solvolysis in Non-catalytic Aprotic Solvents at Supercritical State: chemical and biological treatments. Effect of Reaction Conditions on LG Yields in 1,4-dioxane: (Published, [1])  Conventional method of enzymatic hydrolysis suffers from slow conversion rates, limited by inhibitors, involves costly enzyme production step. Temperature 350oC and 20 mg Cellulose LG Yields Correlated with Solvent Polarity Effect of Acid Concentration Effect of Mass loading of cellulose Effect of Temperature 40 50 70 60 Reaction time 8-16 min 0.25 mM 1 mg o 35 GVL 375 C Biomass/Cellulose Solid residue 60 50 100 Acetonitrile 40 10 mg 350oC 30 50 300oC 90 0.1 mM 40 25 MIBK Supercritical Polar Aprotic Solvent 80 Furfural THF 30 40 Acetone 20 mg 30 70 20 2 mM yield (%) Ethyl acetate 30 60 20 50 mg o 5-HMF 15 20 250 C

1,4-dioxane LGyield (%) LG LGyield (%) Solubilized Carbohydrates and 50 20 LGyield (%) 10 y = 0.9948x + 13.31 10 No acid 10 Minor Secondary Dehydration Products 40 R² = 0.867 10 Solubilized 5 30 0 0 0 Carbon yield (%) carbohydrates of DP >1  Hot and pressurized polar aprotic solvents can rapidly decompose cellulose to produce significantly high 20 0 0 5 10 15 0 2 4 0 5 10 10 AGF 0 5 10 15 20 25 Time of reaction (min) Time of reaction (min) Time of reaction (min) yields of solubilized carbohydrates (anhydrosugar levoglucosan is primary product). [1] 1/2 0 Polar solubility parameter, δP (MPa )  Temperature = 350oC, Initial cellulose = 20 mg Temperature = 350oC, Acid conc. = 0.25 mM Initial cellulose = 10 mg, Acid conc. = 0.25 mM This work continues to investigate the comparative study on the effect of polar aprotic solvents on the yields, Levoglucosan (LG) 70 selectivity and stability of solubilized carbohydrates with and without the acid as catalyst. Acetonitrile  60 LG Aprotic Solvent Highest yield of levoglucosan (43% LG yield) with least degradation was achieved at acid 50 THF concentration of 0.25 mM in 1,4-dioxane. Further increasing the acid-level resulted in increase of High yield of solubilized carbohydrates using a wide 40 Anhydro oligo- secondary product yields. 30 High polarity Low polarity Experimental Method range of aprotic solvents. saccharides  Lower mass loading helped in improving LG yields. Achieved up to 63% within only 5 min at 1 mg 20 10 High in Low in cellulose loading. Materials used: Solubilized product yield: 72-98% (uRIU*min/g) Area 0 monomer monomer  Increase of temperature also increases LG yield and shortens the reaction time (51% in 2 min). 22 27 Low in High in Solubilized carbohydrate yield: 63-94% oligomers oligomers Feedstock: Microcrystalline cellulose, Sigmacell, 50 m Acid catalyst: 0.1-5 mM sulfuric acid Maximum LG yield: 15-38% Retention time (min) Proposed Reaction Network for Acid-catalyzed Multiple Products from One Solvent Solvents: Acetone, Acetonitrile, Tetrahydrofuran (THF), Ethylacetate, Methyl iso-butyl ketone (MIBK), Cellulose Solvolysis in Aprotic Solvent: System: Gamma valerolactone (GVL), and 1,4-Dioxane Behavior of Aprotic Solvents in Acid-catalyzed Cellulose Solvolysis: Cellulose Dehydration at 350oC using 20 mg cellulose Reactor and Operating condition: (Manuscript in preparation) 50 LG yield with acid catalyst 40 Effectiveness factor = Cello-oligosaccharides Batch reactor type: Stainless steel mini-reactor (SS-600-6BT) of 2.5 ml capacity 20 mg cellulose reacted at 350oC with and without 5-HMF 70 LG yield without acid catalyst 30 Furfural Liquid hold-up: 1.2 ml Cellulose loading: 1-50 mg Heating bath: Techne Industrial H2SO4 as catalyst Levoglucosan 60 20 o Fluidized Bed 51 Cellobiosan (LG) LGO Temperature: 250-350 C Time of reaction: 0.75-16 min Solvent Effectiveness factor Maximum yield (%) 50 10 Levoglucosenone MIBK 0.81 (LGO) 0 40 1,6-anhydro-beta- 0.1 0.25 0.5 1 2 5 Without acid 5-HMF Furfural D-glucofuranose Acid concentration (mM) Fluidized 30 Ethyl acetate 1.46 (AGF) Bed Heater With acid 0.5 mM  Changing the acid concentration can

LGyield (%) 20 Acetone 1.82  Cellulose depolymerizes possibly through No mixing formation of cello-oligosaccharides (cellobiosan) increase the yield of useful dehydration Cellulose feedstock Gases 10 Dioxane 3.04 to finally form monomeric products. products such as levoglucosenone (LGO). 0 Solid residue Solubilized Acetonitrile 1.49 product Polar aprotic solvent THF 1.86 Reactor Conclusions Solvent system GVL 1.33  A wide range of supercritical aprotic solvents could effectively depolymerize cellulose producing up Solvolysis Product Extraction and Analysis: to 94% yield of solubilized carbohydrates within only 8-16 min without catalyst. Product Distribution in Acid-Catalyzed Cellulose Solvolysis in 1,4-dioxane:  The product from solvent liquefaction of cellulose contains mainly solubilized products, solid residue  Further enhancement of LG yield (15% to 43%) and other solubilized carbohydrate yield (63% to and negligible gases. 74%) was possible at a shorter reaction time (2-7 min) by adding very dilute acid as catalyst. 50   The solubilized fraction was extracted out of the reactors, filtered and analyzed. The solid residue was Solvolysis condition: Effective solvent for maximizing the yield of LG could be identified based on its polar solubility o 45 parameter and effectiveness factor in non-catalytic and acid-catalyzed condition, respectively. dried overnight at 50 C and weighed for mass. LG Temperature = 350 oC 40   GC-MS(Agilent 7890B GC and 5977A MSD) was used for identification and GC-FID for quantification Initial cellulose = 20 mg The selectivity and stability of LG in was high in 1,4-dioxane during the reaction. 35 AGF  of the products. HPLC and GFC were used for high molecular weight products. Acid concentration = 0.25 mM H SO LG yield could be enhanced by optimization of reaction parameters (63% yield at very low mass 30 2 4 loading). 5-HMF 25  Physical Properties of the Solvents: Tuning operating conditions, it is possible to manufacture various useful chemical building blocks 20 Lgnone  Enhanced yield of LG at a faster rate (43% in 2 min) in including fermentable sugars using aprotic polar solvents. Polar Aprotic Solvent Boiling point (oC) Critical point Polar Solubility 15 presence of very dilute acid catalyst. 1/2 Furfural Parameters (MPa ) Carbonyield (%) 10  Yield of secondary dehydration products suppressed at o 1,4-Dioxane 101 314 C and 5.21 MPa 2.1 5 Acetic minimal acid concentration. o Ethyl acetate 77 260 C and 3.9 MPa 6.6 0 acid  LG in the solvent phase is highly stable even at high References THF 66 268oC and 5.19 MPa 7.0 0 5 10 15 temperature. MIBK 116 298oC and 3.70 MPa 7.4 Time of reaction (min)  Solubilized carbohydrate yield improved from 63% to 74% [1] Ghosh, A., Brown, R. C., & Bai, X. Production of solubilized carbohydrate from cellulose using non-catalytic, supercritical depolymerization in polar aprotic solvents. Green Chemistry 2015. DOI: 10.1039/C5GC02071A Acetone 56 235oC and 4.8 MPa 13.1 by adding acid to 1,4-dioxane. [2] Bai, X. L.; Brown, R. C.; Fu, J.; Shanks, B. H.; Kieffer, M., The Influence of Alkali and Alkaline Earth Metals and the Role Additional products are solubilized carbohydrates with GVL 207-208 Not available 18.7 of Acid Pretreatments in Production of Sugars from Switchgrass Based on Solvent Liquefaction. Energy & Fuels 2014, 28 (2), DP > 1 (31% carbon yield) Acetonitrile 82 272oC and 4.87 MPa 22.1 1111-1120.

Financial support from NSF EPSCoR and Iowa Energy Center is gratefully acknowledged.