In this study, sixteen types of lignin monomer model compounds with aldehyde and carboxyl substituents at the Cα or Cβ positions were selected, representing phenyl, p-hydroxyphenyl, guaiacyl, and syringyl structural units. The catalytic effects of alkaline earth metal ions (Ca2+ and Mg2+) on the formation of CO and CO2 during lignin pyrolysis were investigated by using density functional theory (DFT) calculations. The results revealed that Ca2+ and Mg2+ readily coordinate with oxygen-containing functional groups in lignin model compounds, forming stable complexes with lower energy states. When aldehyde, carboxyl, phenolic hydroxyl, and methoxy groups coexist, the optimal binding sites for Ca2+ and Mg2+ are O(phenolic hydroxyl)–Ca2+/Mg2+–O(methoxyl) configurations. During the pyrolysis process of lignin monomers, Ca2+ and Mg2+ selectively promote the decarbonylation of benzaldehyde-type and phenylethanal-type lignin monomer model compounds (excluding phenylethanal and 4-hydroxyphenylethanal), thereby enhancing the generation of CO. Conversely, except for the Ca2+-catalyzed decarboxylation of 4-hydroxy-3-methoxyphenylethanoic acid, Ca2+ and Mg2+ can suppress the decarboxylation of benzoic acid-type and phenylacetic acid-type lignin monomer model compounds, resulting in the reduction of CO2 formation.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |