(529f) Study On the Aging Mechanism of Pyrolysis Bio-Oil

Meng, J., North Carolina State University
Tilotta, D., North Carolina State University
Adhikari, S., Auburn University
Kelley, S., North Carolina State University
Park, S., North Carolina State University

Session 16004 Biomass Pyrolysis I

AIChE 2013

November 3 ~ 8, 2013

San Francisco, CA

Study on the Aging Mechanism of Pyrolysis Bio-oil

Jiajia Meng*,1 David Tilotta,1 Sushil Adhikari,2 Stephen Kelley,1 and Sunkyu Park1

1 Department of Forest Biomaterials, North Carolina State University, Raleigh, NC 27695

2 Biosystems Engineering Department, Auburn University, Auburn, AL 36849  

*Presenting author: jmeng@ncsu.edu

The unstable nature of pyrolysis oil produced from biomass fast pyrolysis is one of the key issues that limit its application and upgrading, as aged bio-oil typically shows increased water content, viscosity, and phase separation. The aging phenomena are considered due to the polymerization of bio-oil components under acidic and thermal conditions catalyzed by the mineral compounds contained in char particles in the bio-oil. Current research on bio-oil aging is focused on characterizing the behavior together with seeking methods to slow down the aging speed. However, little research was reported on investigating the molecular-level polymerization mechanism of pyrolysis bio-oil during the aging. In this study, accelerated aging of the bio-oil produced from loblolly pine was performed with different aging time and temperature and with or without additives to access the bio-oil thermal stability by measuring water content, viscosity, acidity, molecular weight distribution, and chemical composition. With the chemical analysis of aged bio-oils, it was found that ether soluble fraction of the bio-oil was significantly reduced during the aging process and glycolaldehyde is the most reactive compound in that fraction. The pyrolytic lignin fraction, especially high molecular weight lignin, was found to gradually increase, which suggests the reaction between the compounds of ether soluble fraction and the lignin fraction. Because of the great reduction of glycolaldehyde concentration during the aging, synthetic bio-oil with different concentration of glycolaldehyde was mixed with pyrolytic lignin and aged at 80 °C to further study the role of glycolaldehyde on bio-oil aging chemistry. To elucidate the polymerization chemistry between ether soluble fraction and pyrolytic lignin fraction, model compounds, such as 13C labeled glycolaldehyde and 13C labeled phenolic compounds (phenol and guaiacol type), were reacted in a similar condition to that of accelerated aging. In addition, other suggested mechanisms of bio-oil aging will be reviewed and discussed in detail.