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Catalytic conversion of lignin by immobilized Cu[H4]salen and [H2]salen complexes under hydrothermal conditions

Zhou Xue-Fei

Drewno : prace naukowe, doniesienia, komunikaty

2020

vol. 63, nr 205

81--91

A comparative investigation was made of the effect of catalysis by immobilized Cu([H4]salen) on the hydrothermal conversion of organosolv lignin. The immobilization and hydrogenation of the complexes led to increased yield of liquid products compared with the corresponding unimmobilized and unhydrogenated complexes in catalytic conversion of lignin. In addition, the method of immobilization of the complexes affected the catalytic performance in lignin conversion, in which a higher yield of liquid products was obtained with the SB-immobilized complexes (ship-in-bottle method) than with the IM-immobilized complexes (impregnation method). The yield of liquid products obtained with Cu([H2]salen) at 250°C and 4 MPa O2 in water was 6.00%, compared with 16.80% and 22.08% respectively for Cu([H4]salen)/IM and Cu([H4]salen)/SB. Additionally, the addition of organic solvent had a marked effect on the catalytic performance of Cu([H4]salen), and the highest yield of liquid products (27.06%) was observed with Cu([H4]salen)/SB in water/methanol (80/20, v/v). The total yield of liquid products varied depending on temperature and oxygen pressure, and reached 46.01% under reaction conditions of 280°C and 6 MPa O2 in water/methanol (80/20, v/v). GC-MS analysis showed the main compounds in the liquid products to be phenols, with a yield of 32.16%. Other compounds included alcohols, ketones, aromatics, olefins, cycloalkanes, and alkanes. A mechanism for their formation was proposed based on the oxidation of a lignin model compound under hydrothermal conditions.

Catalytic oxidation of lignin to aromatics over salen-porphyrin complex as a biomimetic catalyst

Lu Xu-Jie, Zhou Xue-Fei, Zhu Zheng-Liang, Sun Yali, Tang Kai, Lei Fu-Hou, Liu Zu-Guang, Wang Ting

Drewno : prace naukowe, doniesienia, komunikaty

2019

vol. 62, nr 203

67--80

The aim of this work is to enable increased production of aromatics by the use of salen-porphyrin complex (ZnPSC6) as a binuclear catalyst for the catalytic oxidation of Indulin AT lignin. Catalytic activity was enhanced by the increase in active sites, as confirmed by the results observed in the conversion of lignin model compounds and Indulin AT lignin compared with processes using the mononuclear complexes Zn(salen) and Zn(Phe-TPP). The yields of long and convoluted aromatics from the catalytic oxidation of Indulin AT lignin with ZnPSC6 reached high values after reaction at 80°C for 24 h. Notably, the formation of vanillin was promoted by the increase in active sites over ZnPSC6. This was followed by a significant decrease of β-O-4 linkages and refractory condensed substructures in the lignin, induced by ZnPSC6. This may be expected to be an important area for further study.