The influence of hydrogen peroxide initiator concentration on the structure of eucalyptus lignosulfonate

In order to improve lignin-based materials’ utilization, the grafting mechanism of lignin was studied by investigating hydrogen peroxide (H 2 O 2 ) initiator's effect on the structure of eucalyptus lignosulfonate calcium (HLS). HLS was treated by low content of H 2 O 2 (H 2 O 2 /HLS wt   =   1%, 2%, 4%) under various reaction temperature and time. Changes in HLS structure were investigated by difference UV, UV, FTIR, 1 H NMR, GPC and intrinsic viscosity. The results showed that though phenolic hydroxyl group (Ph-OH) of HLS was not oxidated to the quinoid structure, its content still decreased after treated by H 2 O 2 initiator. Meanwhile, the new aryl–alkyl ether structures and increased average molecular weight were observed. A radical coupling mechanism for the decreasing Ph-OH group's content was proposed, which radicals may terminate between phenoxy and benzyl radicals. In addition, the cleavage of methoxyl-aryl ether made a decline in the content of syringyl units, while that of guaiacyl, p -hydroxyphenyl units and free aromatic C-5 hydrogen increased when HLS reacted with H 2 O 2 .