Adsorption and thermal transformation of lignin model compound (ferulic acid) over HY zeolite surface studied by temperature programmed desorption mass-spectrometry, FTIR and UV–Vis spectroscopy

Abstract

The adsorption of an aqueous solution of ferulic acid (FA) on protonic zeolites was studied. Three different types of zeolites and adsorption parameters (time, solid/liquid ratio, temperature and pH) were analyzed and optimized. The HY zeolite (SiO2/Al2O3 = 12) showed an adsorption percentage of 90% at 30 °C, 5 min, 10 g L−1 and pH ≤ 3. The adsorption complexes structures on the molecular adsorbates were determined by UV–Vis DRS and FTIR spectroscopies. The FA molecule interacted through phenol and carboxyl group forming monodentate and bidentate surfaces complexes (bridge and chelate). Temperature programmed desorption mass-spectrometry (TPD MS) has been used to study the decarboxylation, demethoxylation, and transalkylation processes during pyrolysis of FA surface complexes with the formation of carbon dioxide, 4-vinylguaiacol, methanol, methane, polyaromatic hydrocarbons, phenols and others.