Analaysis of the pyrolysis products of terminalia brownii wood

Abstract

Terminalia brownii wood is used by Sudanese women to impart characteristic smoky odour and brown colour to the skin by exposing bodies to the destructive distillation volatile products of the wood chips. objective of this study was to analyze the volatile products of the wood to the presence of any hazardous pyrolytic products, with special emphasis on polycyclic aromatic hydrocarbons that are known to be For this purpose air dry T.br0wnii wood chips obtained from the market were used. Elemental analysis of the wood showed that it is of carbon, hydrogen, oxygen and minor amounts of nitrogen and sulphur. pyrolysis experiments were carried out with three different methods. In the method comminuted wood was carbonized in the temperature interval 650°C) in an electrically heated retort oven. In the second method wood were pyrolyzed in a specially designed and made for this study galvanized retort heated by gas. In the third method powdered wood meal was pyrolyzed a modern analytical pyrolyzer directly coupled with a high-resolution chromatograph combined with a mass spectrometer providing a fast, as well temperature-programmed analytical pyrolysis The condensable pyrolysis products formed two layers, a lighter organic layer and a heavier tar layer. The characteristic smoky odour \ concentrated in the tar layer especially in the water distillate of the tar, while aqueous organic layer had a mild smoky odour.Some subfractions of aqueous organic layer had sweet odours. Some diesters of phthalic acid with higher alcohols were detected in neutral fractions of both layers obtained by the first two methods, while temperature-programmed analytical pyrolysis showed that these esters w found among the products obtained at temperature interval 250-270 “C.

The presence of such esters among the pyrolysis products of lignocellulosic materials has not been reported in literature. The study confirmed the already stated in literature fact that slow methods result in numerous products compared to the fast pyrolysis probably due to side and recombination reactions accompanying the formei method. Such numerous products can not be satisfactorily separated by thir layer or column chromatography, but only by high-resolution ga chromatography combined with mass spectrometry. The presence of polycyclic aromatic hydrocarbons, although not detected can not be excluded since some of the unidentified high-molecular-weigh1 compounds had prominent parent ion peaks in their mass spectra, characteristic of such compounds.