Date of Award

Summer 8-18-2017

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemical Engineering

Advisor

Adriaan van Heiningen

Second Committee Member

M. Clayton Wheeler

Third Committee Member

G. Peter van Walsum

Additional Committee Members

Barbara J.W. Cole

Mikhail Iakovlev

Abstract

Climate change resulting from fossil fuels combustion is motivating researchers to explore feasible routes to convert renewable biomass into biofuels and biochemicals for a sustainable society. Typically, biofuel is produced from corn or sugarcane but both feedstocks compete with human food supply. Thus, lignocellulosics as renewable feedstock represent a more ethical and ecofriendly approach. Sugarcane straw (SCS) is a cheap and abundantly available feedstock which potentially can be used for biofuels/biochemicals production. It can also help to mitigate environmental and health problems resulting from conventional practice of SCS burning in the fields.

There are different biomass conversion technologies for production of biofuels/biochemicals. The biochemical route offers advantages of high selectivity and conversion and can also produce widely different products. Prior to fermentation, it requires a fractionation process that can produce monomeric hemicellulose sugars and a cellulosic solid residue that is easily accessible to enzymes. The SO2-ethanol-water (SEW) or AVAP® process meets these requirements. However, the viability of this process is highly dependent on efficient solvent recovery and full utilization of sugars. The SEW process produces a spent liquor stream that has only about 50% sugars as monomers. Only ethanol has been used in this process as solvent so far, and no data is available regarding alcoholysis reactions that consume solvent and potentially decrease the monomeric sugar yield.

In the present thesis, the SEW process is evaluated for SCS fractionation and associated potential losses of carbohydrates and ethanol as alkyl pyranosides and by lignin alkylation. This study also investigates the effect of two other alcohols, methanol and isopropanol besides ethanol on the fractionation potential of SCS. It is the first time that a secondary alcohol is being used in the SO2-Alcohol-Water (SAW) process. The fractionation efficiency is poor using methanol but it generates methyl xylosides at a high yield. The fractionation potential of isopropanol is comparable to ethanol, however less health and safety regulations and its low process pressure make isopropanol more attractive. The kinetics of alkyl pyranoside hydrolysis in SAW liquor after solvent evaporation are measured to establish the conditions for full sugar and solvent recovery

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