Jana Kreicberga

Isolation and characterization of the phenolic fractions of wood pyrolytic oil

Abstract A fraction of pyrolytic oils (PyO) – obtained by fast pyrolysis of alder (Alnus incana), ash-tree (Fraxinus excelsior) and aspen (Populus tremula) in a laboratory scale reactor – was precipitated in water. This hydrophobic moiety of PyO is called pyrolytic lignin (PyL). The composition of the volatile monomeric compounds of PyO and the PyL fraction was determined by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). It has been found that PyL has a high content of phenolic products (between 75% and 83%), which varies depending on the wood species. The antioxidant properties of the PyL fraction were studied and it was demonstrated that the antioxidant activity determined in different tests exceeded the corresponding activity of alkali lignin. The antioxidant properties of PyL are on the same level as those of the widely used antioxidants, such as rutin, trolox, curcumine, and tert-butylhydroquinone (TBHQ). A new method was developed for the extraction of a monomeric phenol fraction (Py-monPh) from PyO by means of the organic solvent methyl tert-butyl ether (MTBE). The Py-monPh can be considered as a promising source of antioxidants.

Hyper-Rayleigh scattering and two-photon luminescence of phenylamine- indandione chromophores

Based on results of quantum chemical (QC) screening, we put under research several phenylamine indane-1,3-dione derivatives including octupolar NLO chromophore A3BI. According to these calculations, molecular first hyperpolarizability (βHRS) should be enhanced upon replacement of methyl substituents with phenyl groups. Surprisingly, βHRS values obtained in our measurements by hyper-Rayleigh scattering (HRS) are much higher than one could expect from QC. Bearing in mind that two-photon luminescence (TPL) is usual cause for overestimation of βHRS in HRS measurements, we have accomplished investigations of TPL properties of these compounds. All investigated triphenylamine derivatives exhibit strong TPL. In case of DANS and DMABI captured simultaneously, TPL spectra and HRS signal, reveal the least as clearly distinct on TPL background, thus TPL-free βHRS values can be defined. Concurrently, sharp HRS signal of DPABI is sinking in TPL and background noise along with increase in concentration. Due to fairly intensive TPL for other investigated triphenylamino compounds, the HRS signal was rather indistinguishable and therefore correct βHRS values could not be extracted.