Determination of chemical properties of pyrolysis products from coals by diffuse-reflectance infrared spectroscopy and partial least squares

Typical coal samples from Venezuela were pyrolysed in nitrogen atmosphere at temperatures between 150 and 900°C. Structural changes were monitored by diffuse-reflectance infrared Fourier transform spectroscopy, i.e. DRIFTS. Segmented osculating polynomial approximation (SOPA) and numerical differentiation by the Savitzky-Golay procedure were used as spectroscopic data pre-treatment. The data was then correlated by partial least squares (PLS) and iterative predictor weighting (IPW) with volatile matter, hydrogen, carbon, nitrogen, and total sulphur contents. The method was found to be useful for the prediction of volatile matter and hydrogen contents, but not to the other physical and chemical properties of the pyrolysed products.