Thermogravimetric mass spectrometry of lignin pyrolysis under the co-action of CaO and K2HPO4·3H2O

Abstract

The pyrolysis processes of lignin under the action of CaO and K2HPO4·3H2O alone or in coordination were studied by thermogravimetric mass spectrometry (TG-MS). The experimental results showed that after addition of CaO, CaO immobilized the “CO2-like active intermediates” produced during lignin pyrolysis, which reduced the amount of CO2 emission in the first stage and lowered the temperature of CO2 emission in the second stage. After addition of K2HPO4·3H2O, lignin pyrolysis was remarkably advanced. K2HPO4·3H2O catalyzed methyl breakages in the first two pyrolysis stages, and it hindered the release of volatile matter in the third stage to promote the formation of more coke. K2HPO4·3H2O catalyzed the reactions toward formation of aromatic ring products and phenols. After addition of CaO and K2HPO4·3H2O, the initial pyrolysis stage was milder than that with K2HPO4·3H2O alone, and the weight loss peak was sharper in the second stage. In the pyrolysis stage, the trend of CH4, CO, M/Z = 46, toluene, and furfural emission showed that there was a synergistic effect between K2HPO4·3H2O and CaO.