Results of the IEA Round Robin on Viscosity and Aging of Fast Pyrolysis Bio-oils: Long-Term Tests and Repeatability

Abstract

An international round robin study of the viscosity measurements and aging of fast pyrolysis bio-oil has been undertaken recently, and this work is an outgrowth from that effort. Two bio-oil samples were distributed to two laboratories for accelerated aging tests and to three laboratories of long-term aging studies. The accelerated aging test was defined as the change in viscosity of a sealed sample of bio-oil held for 24 h at 80 °C. The test was repeated 10 times over consecutive days to determine the intra-laboratory repeatability of the method. Other bio-oil samples were placed in storage at three temperatures, 21, 5, and −17 °C, for a period of up to 1 year to evaluate the change in viscosity. The variation in the results of the accelerated aging test was shown to be low within a given laboratory. The long-term aging studies showed that storage of a filtered bio-oil under refrigeration can minimize the amount of change in viscosity. The accelerated aging test gave a measure of change similar to that of 6−12 months of storage at room temperature for a filtered bio-oil. Filtration of solids was identified as a key contributor to improving the stability of the bio-oil as expressed by the viscosity based on results of the accelerated aging tests as well as long-term aging studies. Only the filtered bio-oil consistently gave useful results in the accelerated aging and long-term aging studies. The inconsistency suggests that better protocols need to be developed for sampling bio-oils. These results can be helpful in setting standards for use of bio-oil, which is just coming into the marketplace.

Physical and Chemical Properties and Accelerated Aging Test of Bio-oil Produced from in Situ Catalytic Pyrolysis in a Bench-Scale Fluidized-Bed Reactor

“…However, such reactions are minimized in the absence of organic acids in the bio-oil. Elliot et al 40 stated viscosity as one of the major parameters to study the pyrolysis liquid stability because it correlates with the increase in the molecular weight and is a measure of the extent of aging, which is reported in terms of the aging index (eq 8).…”

Thermal stability of low and high Mw fractions of bio-oil derived from lignin conversion in subcritical water

“…The stability test was performed according to Elliott et al [25]. About 2.5 g LO and 0.5 g HO were poured into 10-mL Schott Duran bottles (with screw caps) and placed in a heating oven at 80°C.…”

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

“…It was suggested that standard samples be shared with all participants for calibration of GC and HPLC instruments. In 2012, the IEA organized a round robin between fifteen laboratories using two different bio‐oil samples . The main focus was testing viscosity (kinematic and dynamic) and a stability test, where stability was determined via change in viscosity for a sealed bio‐oil sample held at 80 °C for 24 h. Other tests were also performed, including ultimate analysis, density, water content by Karl‐Fischer, pH, filterable solids, acid number titration, and gel permeation chromatography (GPC) for molecular weight distribution.…”