Abstract:

In the investigation,with calcium lignosulfonate as the raw material,hydrothermal experiments were per-formed in a batch reactor,and the effects of the reaction temperature and time on the hydrothermal conversion pro-ducts were discussed by means of GC/MS.The results show that (1) the products are mainly of small molecules,such as phenols,ketones and aldehydes; (2) with the rise of the reaction temperature or with the extension of the reaction time,the contents of H-0,G-0 and G-1- type phenolic compounds of the stable chemical structures in-crease,while the contents of G-3,G-4,G-5- type phenolic compounds of the complicated chemical structures and high relative molecular mass gradually decrease,and no S-1 type phenolic compounds are generated after a long enough time; (3) due to the rise of the reaction temperature and the extension of the reaction time,β- O-4 and α-O-4 linkages largely in lignin become unstable and turn to be broken,thus forming H-0 type,G-0 type,S-0- type units; and (4) under the subcritical water condition above 275℃ and at different reaction time,the guaiacol con-tents in the products are significantly higher than the contents of other phenolic compounds,which indicates that an appropriate control over the reaction temperature and time helps to extract useful phenolic compounds in industry.

Key words: lignosulfonate, GC/MS, subcritical condition, hydrothermal conversion, phenolic compound