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Unraveling the Role of Formic Acid and the Type of Solvent in the Catalytic Conversion of Lignin: A Holistic Approach
Author(s) -
OreguiBengoechea Mikel,
Gandarias Inaki,
Arias Pedro L.,
Barth Tanja
Publication year - 2017
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.201601410
Subject(s) - lignin , catalysis , formic acid , chemistry , solvent , organic chemistry , chemical engineering , engineering
The role of formic acid together with the effect of the solvent type and their synergic interactions with a NiMo catalyst were studied for the conversion of lignin into bio‐oil in an alcohol/formic acid media. The replacement of formic acid with H 2 or isopropanol decreased the oil yield to a considerable degree, increased the solid yield, and altered the nature of the bio‐oil. The differences induced by the presence of H 2 were comparable to those observed in the isopropanol system, which suggests similar lignin conversion mechanisms for both systems. Additional semi‐batch experiments confirmed that formic acid does not act merely as an in situ hydrogen source or hydrogen donor molecule. Actually, is seems to react with lignin through a formylation–elimination–hydrogenolysis mechanism that leads to the depolymerization of the biopolymer. This reaction competes with formic acid decomposition, which gives mainly H 2 and CO 2 , and forms a complex reaction system. To the best of our knowledge, this is the first time that the distinctive role/mechanism of formic acid has been observed in the conversion of real lignin feedstock. In addition, the solvent, especially ethanol, seems also to play a vital role in the stabilization of the depolymerized monomers and in the elimination/deformylation step.