Zhouhong Wang

Separation, hydrolysis and fermentation of pyrolytic sugars to produce ethanol and lipids

This paper describes a new scheme to convert anhydrosugars found in pyrolysis oils into ethanol and lipids. Pyrolytic sugars were separated from phenols by solvent extraction and were hydrolyzed into glucose using sulfuric acid as a catalyst. Toxicological studies showed that phenols and acids were the main species inhibiting growth of the yeast Saccharomyces cerevisiae. The sulfuric acids, and carboxylic acids from the bio-oils, were neutralized with Ba(OH)(2). The phase rich in sugar was further detoxified with activated carbon. The resulting aqueous phase rich in glucose was fermented with three different yeasts: S. cerevisiae to produce ethanol, and Cryptococcus curvatus and Rhodotorula glutinis to produce lipids. Yields as high as 0.473 g ethanol/g glucose and 0.167 g lipids/g sugar (0.266 g ethanol equivalent/g sugar), were obtained. These results confirm that pyrolytic sugar fermentation to produce ethanol is more efficient than for lipid production.

The interplay between chemistry and heat/mass transfer during the fast pyrolysis of cellulose

Biomass derived sugars are expected to play an important role as platform chemicals. Herein, we have shown that in the temperature range of 370 °C to 765 °C of the heat source a constant high sugar yield of ∼70% (C-basis) can be obtained from the fast pyrolysis of Avicel cellulose while producing hardly any gas (<1%) and solid residue (<1% above 450 °C). This opens the opportunity to combine the advantages of thermochemical processes, such as high conversion rates and products not being heavily diluted with water, with an increased value of the product slate. In this paper, firstly the screen-heater used to study the very early stages of cellulose pyrolysis is introduced and characterized. Secondly, yield data as a function of process and pyrolysis conditions are presented and interpreted, also using mathematical models, with respect to chemistry, heat transfer, mass transfer and their interplay. It has been shown that next to heat transfer and the residence time in the vapor phase also the escape rate of products from the reacting particle (mass transfer) is a key process determining the overall mass loss rate and/or the product distribution.