This paper studied the changes of P-aryl ether bonds in the delignification of wheat straw lignins in the absence of ester and a-ether linkages. Saponification was employed to remove the ester linkages of the phenolic acids, followed by a mild acid hydrolysis to bring about the cleavage of the a-ether linkages. Considering that some lignin was removed by saponification and mild acid hydrolysis, the result indicated that only 30-40% of the straw lignin removed during the soda cooking was due to the cleavage of β-aryl ether bonds. In the case of straw lignin, there was a rapid and extensive cleavage of β-aryl ether linkages at 140°C . Condensation reaction played an important role at 170°C, even at the initial stage of the soda cooking.
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