Thermal Stabilities of Phenolic Resoles Prepared from Four Phenolic Compounds as Model Components of Bio-Oil

Graphical Reactivities of 2-methylphenol, 2-methoxyphenol, 4-methylphenol and 4-methoxyphenol with formaldehyde, and the thermal stabilities of the resoles are investigated. The reactivity of ortho phenol is found higher than that of para phenol. The resole of para phenol has a higher thermal stability than that of ortho phenol. The resole of methylphenol generally has a higher thermal stability than that of methoxyphenol. Bio-oil formaldehyde resole (BFR) can be used as adhesive in plywood industry. However, the BFR has a lower thermal stability, and the reason is still unclear. Herein, the reactivities of four representative phenolic compounds in bio-oil, including two ortho phenols (2-methylphenol, 2-methoxyphenol) and two para phenols (4-methylphenol and 4-methoxyphenol), as well as the thermal stabilities of the prepared resoles are investigated. The results show that the reactivity of an ortho phenol is higher than that of a para phenol. The resole prepared from a para phenol has a higher thermal stability than that of an ortho phenol. The resole of an ortho phenol decomposes even when heated at the low temperature of 100 °C. The resole of a methylphenol generally has a higher thermal stability than that of a methoxyphenol. Based on the results, the reason for the low reactivity of bio-oil and the low thermal stability of BFR are speculated.