Antioxidants from slow pyrolysis bio-oil of birch wood: Application for biodiesel and biobased lubricants

Authors: CHANDRASEKARAN, SRIRAAM - University Of Illinois; MURALI, DHEEPTHA - University Of Illinois; MARLEY, KAREN - University Of Illinois; LARSON, RICHARD - University Of Illinois; Doll, Kenneth - Ken; Moser, Bryan; SCOTT, JOHN - University Of Illinois; SHARMA, BRAJENDRA - University Of Illinois

Submitted to: ACS Sustainable Chemistry & Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/25/2016
Publication Date: 3/9/2016
Publication URL: http://handle.nal.usda.gov/10113/62481
Citation: Chandrasekaran, S.R., Murali, D., Marley, K.A., Larson, R.A., Doll, K.M., Moser, B.R., Scott, J., Sharma, B.K. 2016. Antioxidants from slow pyrolysis bio-oil of birch wood: Application for biodiesel and biobased lubricants. ACS Sustainable Chemistry & Engineering. 4:1414-1421.

Interpretive Summary: Researchers have been attempting to turn agricultural waste, and other natural materials, into useful industrial chemicals for many years. One process that is used is called pyrolysis. In this process, the material is heated, but kept away from oxygen to avoid simple combustion of the material. If this is done correctly, one of the resultant products is called bio-oil. The qualities of this oil depend on the conditions of the pyrolysis. The researchers here have found a set of conditions where a good yield of the oil from pyrolysis of wood material is a family of products called lignin dimers. This new oil product has been tested as an additive in biodiesel and in soybean oil based lubricants. The results show that the additive stops oxidation as well as the commercial standard, butylated hydroxytoluene. This research has potential to help agriculture in two ways: first, it provides an outlet for increasing the value of agricultural waste; second, it helps reduce one of the major problems with biodiesel and soybean oil based industrial lubricants.

Technical Abstract: Birch wood was slowly pyrolyzed to produce bio-oil and biochar. Slow pyrolysis conditions including reaction temperature, residence time, and particle size of the feed were optimized to maximize bio-oil yield. Particle size had an insignificant effect, whereas yields of up to 56% were achieved using an optimized reaction temperature of 450 deg C and a residence time of 2 h. Bio-oil was also produced from commercial Kraft lignin and was compared to the bio-oil obtained from birch wood. These bio-oils were characterized for elemental composition, phenolic compound identification using GC-MS, boiling point distribution using GC-FID, and molecular weight distribution using GPC. Simulated distillation indicated that a majority of the bio-oil compounds were found in the fraction between 200 and 300 deg C, followed by fractions <200 deg C and 300-400 deg C. Phenolic fractions extracted from bio-oil using an alkali method were evaluated as antioxidant additives in soy biodiesel using Mihaljevic, Rancimat, and PDSC test methods. The phenolic extract showed similar antioxidant activity as the commercial antioxidant butylated hydroxytoluene (BHT) typically used in biodiesel. These phenolic extracts were also evaluated as antioxidants in soybean oils for formulating biolubricants and exhibited improved oxidation stability similar to what was observed in soy biodiesel. It was found that many of the monomeric constituents of the phenolic mixture showed little or no antioxidant activity. However, a series of phenols present in the bio-oils exhibited molecular weights (MWs) of 302, 316, 330, and 344 corresponding to a group of dimers which may be responsible for the observed antioxidant properties.