添加剂氢化钙对碱木质素热裂解特性的影响

摘要

The calcium hydride (CaH2 )was employed as additive in alkali lignin for resolving the complicated products and low content of single component of the lignin pyrolysis.The effect of the pyrolysis vapor from alkali lignin with different proportions of CaH2 was investigated by pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS).The results indicate that the addi-tion of CaH2 reduces the components of alkali lignin pyrolysis from 51 kinds to 20 kinds,which achieves the enrichment of the key components.The addition of CaH2 further improves the content of guaiacol and methanol,which is raised by more than 70% and 100%,respectively.CaH2 has double roles of hydrogenation and catalytic convertion in the lignin pyrolysis.CaH2 promotes the reduction and transformation of the intermediate products such as ketones,acids,aldehydes and other unsaturated functional groups.Carboxyl and carbonyl groups are reduced to phenolic hydroxyl and alcoholic hydroxyl groups.The increase of phenolic hydroxyl group improves the reactivity of alkali lignin pyrolysis product,and the increase of alcoholic hydroxyl group improves the stability of the pyrolysis product.Therefore,CaH2 has a significant influence on improving the composition distribution, quality and stability of alkali lignin pyrolysis products.%针对碱木质素热裂解产物种类分布复杂、单一组分含量偏低等问题，以还原性强的氢化钙作为添加剂，利用热裂解气质联用分析法考察了添加不同质量分数氢化钙对碱木质素热裂解产物组分构成、转化及分布的影响。结果表明：氢化钙的加入使得碱木质素热裂解组分种类从51种减少到20种，促进了组分的富集；氢化钙的加入大幅度促进了碱木质素热裂解主产物愈创木酚和甲醇的生成，分别提高了70％和100％以上；氢化钙在碱木质素热裂解过程中起到加氢还原和催化转化双重作用，促进了热裂解中间产物酮类、酸类、醛类等含不饱和官能团物质的还原和转化，羧基、羰基等官能团被还原为酚羟基和醇羟基，酚羟基的增加提高了碱木质素热裂解产物反应活性，醇羟基的增加提高了热裂解产物的稳定性。添加剂氢化钙可显著改善碱木质素热裂解产物的组分分布、品质和稳定性。