Details

Autor(en) / Beteiligte

• Gogar, Ravikumar

Titel

Economic Production of Furans from Lignocellulosic Sugars

Ort / Verlag

ProQuest Dissertations & Theses

Erscheinungsjahr

2020

Quelle

ProQuest Dissertations & Theses A&I

Beschreibungen/Notizen

• Lignocellulosic biomass is a sustainable and abundant feedstock for the production of fuels and chemicals. Biomass-derived furans – 5-hydroxymethyl furfural (HMF) and furfural, are versatile platform molecules that can be converted to drop-in fuels and precursors for synthetic materials. The lack of efficient pathways to furans from lignocellulosic sugars constitutes a major barrier to their industrial production. This hurdle is particularly severe with respect to the conversion of lignocellulosic sugars (glucose and xylose) to furans, stabilization of furans, especially HMF, and recovery of furans. It is now widely published that the better yield of furans is observed by dehydration of keto-isomers (fructose and xylulose) than aldo-isomers (glucose and xylose). However, cellulose fraction of naturally abundant lignocellulose yields aldoses (glucose and xylose) and isomerization of aldoses to ketoses is equilibrium limited. Further, in aqueous media HMF undergoes undesirable subsequent reactions such as rehydration to form levulinic acid and formic acid and degradative polymerization with itself and sugars, especially glucose, to form humins at high temperature. To address these challenges of efficient conversion of sugars, stabilization, and recovery of furans, our team recently developed hybrid enzyme-chemo-catalytic process for high-yield production of mixed-furans (HMF and furfural). In this process, glucose and xylose in biomass hydrolysates are first isomerized to corresponding ketoses (i.e. fructose and xylulose) using immobilized glucose-xylose isomerase. This enzymatic step is closely integrated with selective extraction of the ketoses into a water-immiscible octanol phase containing lipophilic quaternary ammonium salt and aryl boronic acid that have a selective affinity for ketoses. As a result, the isomerization and extraction occur simultaneously to drive the isomerization equilibrium towards formation of the ketose isomers – a process termed Simultaneous Isomerization and Reactive Extraction (SIRE). Next, the keto-sugars in the octanol phase are back extracted into an acidic ionic liquid medium that is uniquely suited for dehydration reactions – a process step termed Back Extraction (BE). Thereafter, the ketose-rich sugar mixture undergoes dehydration to furans in the ionic liquid which is part of a biphasic reaction mixture with tetrahydrofuran (THF) which allows extraction and stabilization of the furans as they are formed. Finally, the furans are recovered from THF by distillation. We performed the techno-economic assessment (TEA) for a furan production facility operating at feed rate of 1,000 MT of biomass hydrolysate sugars (dry-basis) per day via the SIRE-BE-Dehydration pathway. The discounted cash flow analysis of a process design that corresponded closely with experimental conditions (concentrated sugar feed and high yield dehydration) and conventional downstream processing, estimated the Minimum Furan Selling Price (MFSP) to be $2.4/kg when feedstock is sourced at $0.3/kg-dry-sugar. With integration of novel and energy efficient product and chemical recovery methods, the MFSP was significantly lower at $1.42/kg - a promising price-point for industrially important chemical products from furans. Sensitivity analyses identified overall furan yield, feedstock sugar costs, and energy cost to recover product furans from ionic liquid as the dominant contributors to the selling price. To improve the process economics, modification in BE and dehydration step of SIRE-BE-Dehydration process is proposed. Use of acidic aqueous media in BE step eliminates the need of ionic liquid and yet results into a concentrated sugar solution with high fructose-to-glucose ratio. For dehydration, use of renewable solvent - 1,2-dimethoxyethane (DME) having low heat of vaporization (383 kJ/kg, BP 85°C) as co-solvent is proposed after screening solvents and reaction optimization studies. The presence of polar aprotic solvent DME as co-solvent, selectively converts fructose into HMF, leaves glucose unreacted, and lowers the energy requirement as well as avoids the need of vacuum operation in separation processes. A pathway to recover unreacted glucose and HMF from the product mixture of water-DME by phase splitting using toluene as the ternary solvent is also demonstrated. The updated techno-economic assessment of the SIRE-BE process followed by dehydration in water-DME solvent system estimates a minimum selling price (MSP) of $1.32/kg-HMF solubilized in toluene at a concentration ideally suited for further product upgrading. Finally, the innovative SIRE process was studied in a flow reactor and transient studies were compared with the theoretical model.