306 / 2018-07-31 11:27:48

Cleavage of C-O bond facilities the delignification in lignocellulosics pretreatment

全体主题 > 生物质多联产

Lignin, with the extremely complex three dimension structure, is the second abundant constituent in lignocellulosic biomass, which is also the predominant resistance in chemical pulping. It’s widely reported the phenol structure in lignin was easier to be treated than the non-phenol one. In cooking with active oxygen and solid alkali (CAOSA) process, which has a superior delignification efficiency, lignin, no matter the phenol structure or non-phenol one, could be degraded into little molecular acids like formic/acetic acid. And further investigation for the cleavage of C-O bond was set with lots of model compound as substrates.
Different substrate was added into reactor (Parr, USA) accompanied with solid alkali and oxygen, and the reaction was performed at 160 °C for 3 hours. The products were separated then and the quantitative and qualitative analysis were conducted by corresponding instruments.
As the main oxidation products, contents of formic and acetic acid were determined as the indicator for aromatic ring broken. And through analyze the products of reaction with toluene/phenol/anisole, the atom O connected with aromatic ring was the key for ring-broken reaction. Additionally, different initial pH of the reaction system was proved irrelevant to the degradation reaction and the reaction could performed only with oxygen existence. Moreover, some direct evidences for ether bond cleavage were also provided by GC/MS.
In our work, it’s found that C-O bond cleavage reaction would proceeded in no matter phenol form or non-phenol form under CAOSA condition. Furthermore, the active oxygen was proved the promoter of the aromatic ring broken. The fact that higher ratio of formic to acetic acid in group with veratrole than catechol was favor on understanding the C-O bond cleavage in such condition.