Characterization of char from pyrolysis of chlorogenic acid

Pyrolysis of chlorogenic acid was studied under varying conditions of tempe rature and reaction environment. The objective was to study the effect of p yrolysis conditions on the composition of the solid residue, i.e., char. Ru ns were made at atmospheric pressure under oxidative and non-oxidative (ine rt) atmospheres and at temperatures ranging from 250 to 750 degrees C. The characterization of char was done in terms of its elemental composition and surface area, and by Fourier transform infrared (FTIR) and solid-state C-1 3 nuclear magnetic resonance (NMR) spectroscopy. The surface morphology of char was studied by scanning electron microscopy (SEM). The char yield in n on-oxidative runs decreased from 80% at 250 degrees C to 20% above 550 degr ees C. In oxidative runs, the char was completely oxidized at 550 degrees C . The surface area of char increased with temperature to a maximum of 196 m (2)/g at 650 degrees C. SEM analysis indicated that the pyrolysis of chloro genic acid first formed a melt followed by formation of varying structures that decomposed rapidly at high temperatures. The WC and O/C ratios of the char decreased as the temperature increased. NMR analysis showed that the r esonance bands corresponding to carbonyl groups mostly disappeared above 35 0 degrees C and the phenolic groups became almost totally absent in 650 deg rees C char. The aromatic character of char was enhanced with increasing te mperature. FTIR studies indicated a gradual decrease in the intensities of OH and C=O stretches at high temperatures. At 750 degrees C, most bands dis appeared, resulting in a char that was mainly an aromatic polymer of carbon atoms. The oxidative pyrolysis enhanced mainly the surface area at the exp ense of char yield. The results are consistent with the analysis of the evo lved gases.