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Bond cleavage of lignin model compounds into aromatic monomers using supported metal catalysts in supercritical water

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ABSTRACT

More efficient use of lignin carbon is necessary for carbon-efficient utilization of lignocellulosic biomass. Conversion of lignin into valuable aromatic compounds requires the cleavage of C–O ether bonds and C–C bonds between lignin monomer units. The catalytic cleavage of C–O bonds is still challenging, and cleavage of C–C bonds is even more difficult. Here, we report cleavage of the aromatic C–O bonds in lignin model compounds using supported metal catalysts in supercritical water without adding hydrogen gas and without causing hydrogenation of the aromatic rings. The cleavage of the C–C bond in bibenzyl was also achieved with Rh/C as a catalyst. Use of this technique may greatly facilitate the conversion of lignin into valuable aromatic compounds.

No MeSH data available.


Recycling results for conversion of 2-phenethyl phenyl ether in supercritical water at 673 K for 1 h and a water density of 0.5 g cm−3 with Pd/C as a catalyst.
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f3: Recycling results for conversion of 2-phenethyl phenyl ether in supercritical water at 673 K for 1 h and a water density of 0.5 g cm−3 with Pd/C as a catalyst.

Mentions: We investigated the possibility of reusing the heterogeneous catalysts Pd/C, Pt/C, and Rh/C by using them three times for the conversion of 2-phenethyl phenyl ether. The catalysts were recovered by filtration after the reaction and dried in an oven. The catalysts were then reused without any further treatment. The reactant 2-phenethyl phenyl ether was added each time, and the yields were calculated based on the amount of added reactant. The phenol yields with Pd/C were nearly unchanged; they varied from 40.9 C% (1st run) to 38.6 C% (2nd run) and 40.9 C% (3rd run) (Fig. 3), the indication being that Pd/C was not deactivated during the conversion of 2-phenethyl phenyl ether in supercritical water. In the case of Pt/C and Rh/C, the phenol yield increased gradually with recycling of the catalysts (see Supplementary Figs 1 and 2). The reason for the increase of phenol yield with catalyst recycling is still unclear; however, the stability and recyclability of the catalysts for the conversion of 2-phenethyl phenyl ether were experimentally demonstrated.


Bond cleavage of lignin model compounds into aromatic monomers using supported metal catalysts in supercritical water
Recycling results for conversion of 2-phenethyl phenyl ether in supercritical water at 673 K for 1 h and a water density of 0.5 g cm−3 with Pd/C as a catalyst.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5384005&req=5

f3: Recycling results for conversion of 2-phenethyl phenyl ether in supercritical water at 673 K for 1 h and a water density of 0.5 g cm−3 with Pd/C as a catalyst.
Mentions: We investigated the possibility of reusing the heterogeneous catalysts Pd/C, Pt/C, and Rh/C by using them three times for the conversion of 2-phenethyl phenyl ether. The catalysts were recovered by filtration after the reaction and dried in an oven. The catalysts were then reused without any further treatment. The reactant 2-phenethyl phenyl ether was added each time, and the yields were calculated based on the amount of added reactant. The phenol yields with Pd/C were nearly unchanged; they varied from 40.9 C% (1st run) to 38.6 C% (2nd run) and 40.9 C% (3rd run) (Fig. 3), the indication being that Pd/C was not deactivated during the conversion of 2-phenethyl phenyl ether in supercritical water. In the case of Pt/C and Rh/C, the phenol yield increased gradually with recycling of the catalysts (see Supplementary Figs 1 and 2). The reason for the increase of phenol yield with catalyst recycling is still unclear; however, the stability and recyclability of the catalysts for the conversion of 2-phenethyl phenyl ether were experimentally demonstrated.

View Article: PubMed Central - PubMed

ABSTRACT

More efficient use of lignin carbon is necessary for carbon-efficient utilization of lignocellulosic biomass. Conversion of lignin into valuable aromatic compounds requires the cleavage of C–O ether bonds and C–C bonds between lignin monomer units. The catalytic cleavage of C–O bonds is still challenging, and cleavage of C–C bonds is even more difficult. Here, we report cleavage of the aromatic C–O bonds in lignin model compounds using supported metal catalysts in supercritical water without adding hydrogen gas and without causing hydrogenation of the aromatic rings. The cleavage of the C–C bond in bibenzyl was also achieved with Rh/C as a catalyst. Use of this technique may greatly facilitate the conversion of lignin into valuable aromatic compounds.

No MeSH data available.