Standardization of chemical analytical techniques for pyrolysis bio‐oil: history, challenges, and current status of methods

Abstract

In this perspective, we discuss the standardization of analytical techniques for pyrolysis biooils, including the current status of methods, and our opinions on future directions. First, the history of past standardization efforts is summarized, and both successful and unsuccessful validation of analytical techniques highlighted. The majority of analytical standardization studies to-date has tested only physical characterization techniques. Here, we present results from an international round robin on the validation of chemical characterization techniques for bio-oils. Techniques tested included acid number, carbonyl titrations using two different methods (one at room temperature and one at 80 °C), 31 P NMR for determination of hydroxyl groups, and a quantitative gas chromatography-mass spectrometry (GC-MS) method. Both carbonyl titration and acid number methods have yielded acceptable inter-laboratory variabilities. 31 P NMR produced acceptable results for aliphatic and phenolic hydroxyl groups, but not for carboxylic hydroxyl groups. As shown in previous round robins, GC-MS results were more variable. Reliable chemical characterization of bio-oils will enable upgrading research and allow for detailed comparisons of bio-oils produced at different facilities. Reliable analytics are also needed to enable an emerging bioenergy industry, as processing facilities often have different analytical needs and capabilities than research facilities. We feel that correlations in reliable characterizations of bio-oils will help strike a balance between research and industry, and will ultimately help to determine metrics Perspective: Bio-oil Analytical Standardization JR Ferrell III et al.

Accelerated aging of fast pyrolysis bio-oil: a new method based on carbonyl titration

“…1-4; these errors are very low, typically below 5% RSD, which has been shown previously in the interlaboratory validation of this carbonyl titration method. 6 Of all the samples analyzed, the Oak oil was the only sample to remain single phase throughout aging at 80 C. All three 72 hour Oak samples were too thick for viscosity measurement and returned a viscosity in excess of 3000 cP, which is the limit for the size of spindle used in the viscometer. As shown in Fig.…”

“…[29][30][31] This method has been shown to be very reliable, with a variability of 5% relative standard deviation (RSD) for typical FP bio-oils. 6 Additionally, this method employs validation with a known carbonyl compound to ensure proper operation of titration equipment. Measurement of dynamic viscosity was performed in a Brookeld viscometer (Model VD2T) tted with a Wells-Brookeld cone and plate cup with a CPA40Z spindle.…”

“…Due to this complex chemical composition, detailed and reliable analysis of bio-oil remains a challenge, though some standardized chemical characterization methods have recently been published. 6 Furthermore, FP bio-oils are highly reactive. They contain organic acids, phenolic compounds and aldehydes; the presence of all three of these constituents provides the necessary components for the formation of a phenol/formaldehyde resin, similar to a resol 7 resin.…”

Results of the International Energy Agency Round Robin on Fast Pyrolysis Bio-oil Production

“…Several attempts are described in the literature to decrease TAN [24][25][26][27] . The TAN distribution is illustrated in Figure 8 and the technology related graph is presented in Figure 9.…”

Rapid Determination of Water, Total Acid Number, and Phenolic Content in Bio-Crude from Hydrothermal Liquefaction of Biomass using FT-IR

“…The method can be improved with the use of potentiometric titration but it remains time-consuming and involves the use of organic solvents. 7 Lignin is the most important source of phenolics in bio-crudes but may also arise from degradation of carbohydrates and proteins. 8,9 They are present in the volatile and semi-volatile fraction as derivatives of phenols, catechols, hydroquinones, and hydroxypyridines.…”