4013-37-0Relevant articles and documents
Cleavage of aryl-ether bonds in lignin model compounds using a Co-Zn-beta catalyst
Chang, Hou-Min,Dou, Xiaomeng,Jameel, Hasan,Jiang, Xiao,Li, Wenzhi,Zhu, Chaofeng
, p. 43599 - 43606 (2020/12/25)
Efficient cleavage of aryl-ether linkages is a key strategy for generating aromatic chemicals and fuels from lignin. Currently, a popular method to depolymerize native/technical lignin employs a combination of Lewis acid and hydrogenation metal. However, a clear mechanistic understanding of the process is lacking. Thus, a more thorough understanding of the mechanism of lignin depolymerization in this system is essential. Herein, we propose a detailed mechanistic study conducted with lignin model compounds (LMC) via a synergistic Co-Zn/Off-Al H-beta catalyst that mirrors the hydrogenolysis process of lignin. The results suggest that the main reaction paths for the phenolic dimers exhibiting α-O-4 and β-O-4 ether linkages are the cleavage of aryl-ether linkages. Particularly, the conversion was readily completed using a Co-Zn/Off-Al H-beta catalyst, but 40% of α-O-4 was converted and β-O-4 did not react in the absence of a catalyst under the same conditions. In addition, it was found that the presence of hydroxyl groups on the side chain, commonly found in native lignin, greatly promotes the cleavage of aryl-ether linkages activated by Zn Lewis acid, which was attributed to the adsorption between Zn and the hydroxyl group. Followed by the cobalt catalyzed hydrogenation reaction, the phenolic dimers are degraded into monomers that maintain aromaticity. This journal is
Reductive fractionation of woody biomass into lignin monomers and cellulose by tandem metal triflate and Pd/C catalysis
Huang, Xiaoming,Morales Gonzalez, Olivia M.,Zhu, Jiadong,Korányi, Tamás I.,Boot, Michael D.,Hensen, Emiel J. M.
, p. 175 - 187 (2017/01/24)
A catalytic process for the upgrading of woody biomass into mono-aromatics, hemi-cellulose sugars and a solid cellulose-rich carbohydrate residue is presented. Lignin fragments are extracted from the lignocellulosic matrix by cleavage of ester and ether linkages between lignin and carbohydrates by the catalytic action of homogeneous Lewis acid metal triflates in methanol. The released lignin fragments are converted into lignin monomers by the combined catalytic action of Pd/C and metal triflates in hydrogen. The mechanism of ether bond cleavage is investigated by lignin dimer models (benzyl phenyl ether, guaiacylglycerol-β-guaiacyl ether, 2-phenylethyl phenyl ether and 2-phenoxy-1-phenylethanol). Metal triflates are involved in cleaving not only ester and ether linkages between lignin and the carbohydrates but also β-O-4 ether linkages within the aromatic lignin structure. Metal triflates are more active for β-O-4 ether bond cleavage than Pd/C. On the other hand, Pd/C is required for cleaving α-O-4, 4-O-5 and β-β linkages. Insight into the synergy between Pd/C and metal triflates allowed optimizing the reductive fractionation process. Under optimized conditions, 55 wt% mono-aromatics-mainly alkylmethoxyphenols-can be obtained from the lignin fraction (23.8 wt%) of birch wood in a reaction system comprising birch wood, methanol and small amounts of Pd/C and Al(III)-triflate as catalysts. The promise of scale-up of this process is demonstrated.
Novel non-hydrolytic templated sol-gel synthesis of mesoporous aluminosilicates and their use as aminolysis catalysts
Skoda, David,Styskalik, Ales,Moravec, Zdenek,Bezdicka, Petr,Babiak, Michal,Klementova, Mariana,Barnes, Craig E.,Pinkas, Jiri
, p. 24273 - 24284 (2016/03/15)
A novel non-hydrolytic sol-gel (NHSG) synthesis of mesoporous aluminosilicate xerogels is presented. The polycondensation between silicon acetate, Si(OAc)4, and tris(dimethylamido)alane, Al(NMe2)3, leads to homogeneous alu
