Study on the product characteristics of pyrolysis lignin with calcium salt additives

Abstract

This study investigated and compared the product characteristics of pyrolysis lignin under different catalytic effects resulting from various calcium salts. The pyrolysis of lignin was conducted in a fixed-bed reactor with calcium salt additives, which included CaCl2, Ca(OH)2, and Ca(HCOO)2. The compositions of gas and bio-oil were detected using gas chromatography/mass spectrometry (GC/MS). The characterizations of chars were examined using Brunauer-Emmett-Teller (BET) surface area and scanning electron microscopy (SEM). The results indicate that all three types of calcium salts helped to promote bio-oil yield and inhibit gas and char from forming. Regarding the composition of gas products, calcium salt additives increased the concentrations of H2 and CH4 while decreasing the concentration of CO. In addition, calcium salt additives facilitated the formation of phenol and alkyl-phenols in bio-oil, but reduced the yields of guaiacol and vanillin, in the order CaCl2 < Ca(OH)2 < Ca(HCOO)2. Furthermore, when compared with the addition of CaCl2, the chars prepared by the addition of Ca(OH)2 and Ca(HCOO)2 had relatively higher BET surface areas. In conclusion, Ca(HCOO)2 had the greatest positive influence in regard to the product quality of lignin pyrolysis whilst also elevating the yield of value-added chemicals in bio-oils.