On the alternating physicochemical characteristics of Colombian coal during pyrolysis

摘要

A Colombian hard coal was stepwise pyrolyzed from 200 to 800 degrees C, and the resulting changes in surface and material properties were investigated by thermogravimetric analysis and volumetric adsorption techniques as well as by density, surface area, ATR-IR and GC/MS measurements. It was observed that a loss of volatile compounds occurred up to a pyrolysis temperature of 600 degrees C. These compounds were identified as CO, CO2 and H2O and mainly large substituted aromatic compounds and long-chain hydrocarbons. The loss of functional groups was also monitored by a decrease of related IR bands. The devolatilization was found to cause an increase in density and surface area; the adsorbed amount of CO2 and O-2 increased in this temperature region as well. The char pyrolyzed at 600 degrees C was the only sample with a hydrophobic surface. Increasing the temperature to 800 degrees C led to no further mass loss, but to a structural reorganization Of the char indicated by the reappearance of aromatic IR bands. This high-temperature restructuring resulted in a decrease of density, surface area and adsorbed gas amount. (C) 2017 Elsevier B.V. All rights reserved.