2-step lignin-first catalytic fractionation with bifunctional Pd/beta-zeolite catalyst in a flow-through reactor

02 May 2022, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

This work demonstrates an additive and hydrogen-free 2-step lignin-first fractionation in flow-through. First, solvolytic delignification renders lignin liquors with its native chemical structure largely intact; and second, beta-zeolite catalytic depolymerization of these liquors leads to similar monomer yields as the corresponding 1-step fractionation process. Higher delignification temperatures lead to slightly lower b-O-4 content in the solvated lignin, but does not affect significantly the monomer yield, so a higher temperature was overall preferred as it promotes faster delignification. Deposition of Pd on beta-zeolite resulted in a bifunctional hydrogenation/dehydration catalyst, tested during the catalytic depolymerization of solvated lignin with and without hydrogen addition. Pd/beta-zeolite displays synergistic effects (compared to the Pd/gamma-Al2O3 and -zeolite tested individually and as a mixed bed), resulting in higher monomer yield. This is likely caused by increased acidity and the proximity between the metallic and acid active sites. Furthermore, different beta-zeolite with varying SAR and textural properties were studied to shed light onto the effect of acidity and porosity in the stabilization of lignin monomers. While some of the catalysts showed stable performance, characterization of the spent catalyst reveal Al leaching (causing acidity loss and changes in textural properties), and some degree of coking and Pd sintering.

Keywords

Lignin
Zeolite
Flow chemistry
Biorefinery
Biomass
Heterogeneous catalysis

Comments

Comments are not moderated before they are posted, but they can be removed by the site moderators if they are found to be in contravention of our Commenting Policy [opens in a new tab] - please read this policy before you post. Comments should be used for scholarly discussion of the content in question. You can find more information about how to use the commenting feature here [opens in a new tab] .
This site is protected by reCAPTCHA and the Google Privacy Policy [opens in a new tab] and Terms of Service [opens in a new tab] apply.