Study On The Preparation Of Methyl P-Hydroxycinnamate By Selective Depolymerization Of Lignin

A s is known to all,the huge consumption and non-renewable nature of fossil resource are not conducive to the sustainable development.Lignin,which containing aromatic structures,would be a promising substitute for fossil resource due to the similar element composition,abundant existence and renewable advantages.These properties make the studies of lignin depolymerization become to one of spotlights in current advanced scientific research.Methyl p-coumarate?MPC?can be used to produce various fine chemicals or polymers.And the production of MPC mainly depends on petrochemical industry.According to the existing research,the ionic liquids or supported catalysts used to prepare MPC by lignin depolymerization are relatively complex.Therefore,it is necessary to build a simpler and more economical reaction system to achieve the above process.In view of these demands,a series of metal salts and metal oxides had been selected as catalysts for the selective catalytic depolymerization of lignin to prepare MPC.The main contents are summarized as follows:?1?A series of metal salts had been selected and used in the catalytic depolymerization of bagasse lignin.It is found that CuCl₂ has the highest catalytic activity and selectivity for the bagasse lignin depolymerization to prepare MPC.Under the optimal conditions,the yield and selectivity of MPC are 9.03 wt%and 71.2%,respectively.?2?Various characterization techniques?GPC?FT-IR?¹H-NMR and 2D HSQC?were applied to explore the pathway of CuCl₂ catalyzed lignin depolymerization.And the reactions of lignin model compounds were investigated to help analyze the depolymerization process.It is found that,MPC is generated by breaking the ester bond connected to the p CA?p-hydroxycinnamic acid?structure in lignin.Since the cleavage of the ester bond is much easier than the cleavage of the ether bond in this system,a highly selective catalytic depolymerization of bagasse lignin to produce MPC is achieved.?3?Considering the difficulty in recovering metal salt catalysts,a system was further constructed by using metal oxides as catalysts to depolymerize bagasse lignin to prepare MPC.The effect of different metal oxides,reaction temperature,time and solvent types on the preparation of MPC were systematically investigated.The result shows that Zn O has the highest catalytic activity for bagasse lignin depolymerization to prepare MPC.Under the optimal conditions,the yield and selectivity of MPC are 9.80 wt%and 61.6%,respectively.