Fe/Ni redox synergistic sodium persulfate photocatalytic depolymerization of the sinocalamus oldhami alkali lignin for the directional synthesis of aromatic aldehydes

Abstract

Background Recently, it was full of challenges to realize the mild and directional oxidative depolymerization of lignin at room temperature and pressure. The sinocalamus oldhami alkali lignin (SOAL) was depolymerized into aromatic aldehydes by cooperating LaFe0.9Ni0.1O3 (LFNO-0.1) with sodium persulfate (PDS) under visible light irradiation. Result Under the best conditions of reaction time of 105 min, catalyst dosage of 0.25 g, sodium persulfate of 0.15 g, 80% of lignin was converted and the yield of monomer compounds was up to 2.97 mg/g. In addition, the yield of p-hydroxybenzaldehyde was 1.86 mg/g respectively. And, the selectivity of p-hydroxybenzaldehyde reached about 63% in the monomer product. The effect sequence of factors in the system were as follows: holes > 1O2 > SO4−· > O2−· > ·OH, which could lead to the cleavage of the benzene ring, C-C, C–O, C-H bonds in the internal structure of lignin. Conclusion The study found that LFNO-0.1/PDS played a synergistic role in the SOAL depolymerization. The study was beneficial for mild depolymerization of lignin and conform carbon peaking and carbon neutrality goals.