Thermal decomposition of guaiacol in sub- and supercritical water and its kinetic analysis

The conversion of biomass waste into resources as a recycling process is receiving increased interest due to the perceived need for a sustainable global carbon cycle and environmental considerations. Several treatment processes are being developed. Hydrothermal treatment is one of the most effective approaches, because water at high temperatures and high pressures behaves as a reaction medium with remarkable properties. In this work, the reaction behavior of guaiacol as a biomass model compound was studied in subcritical water at 483–563 K and in supercritical water at 653–673 K using a batch reactor. Guaiacol can be considered representative of the aromatic ring structures present in lignin, a major component of woody biomass. The chemical species formed in aqueous products were identified by gas chromatography/mass spectrometry and quantified using high-performance liquid chromatography. The effect of pressure and reaction time on the conversion process of guaiacol is discussed. The results obtained indicate that this method has potential for efficient organic waste conversion.     

Noncatalytic liquefaction of tar with low-temperature hydrothermal treatment

Water at hydrothermal and supercritical conditions is considered a promising solvent for the degradation of hazardous waste into harmless compounds. Tar liquefaction experiments were conducted using a batch-type reactor at temperatures between 623 K and 673 K and at pressures between 25 and 40 MPa. A reaction mechanism for tar liquefaction is proposed. Moreover, on the basis of the experimental results, this method could become an efficient method for tar liquefaction, producing high yields of valuable chemical intermediates.