Issue 12, 2024

One-pot reductive liquefaction of sawdust to renewables over MoOx–Al2O3 variants: insight into structure–activity relationships

Abstract

Valorization of forest residual products can offer a vital pathway to derive bio-based chemicals and fuel components. Herein, we report the effective and direct conversion of sawdust biomass over a supported Mo-oxide catalyst that results in a dominant fraction of aliphatic/cyclic alkanes and alkylbenzenes with low residual solids. The reductive liquefaction was conducted in an autoclave reactor using a series of MoOx–Al2O3 variants in the range of 340–400 °C with an initial H2 pressure of 35 bar for 4 h. At 340 °C, a correlation between Mo-loadings and reactivity for depolymerization and hydrodeoxygenation was found optimal for a surface density of 3.2 Mo-atoms per nm2 corresponding to 8 wt% Mo-loading. The liquefied fraction showed high selectivity (∼38%) for the formation of cycloalkanes and alkylbenzenes. At higher temperatures (400 °C) enhanced reactivity over the optimal catalyst showed higher cycloalkane and alkylbenzenes formation (∼57%) at a low biomass-to-catalyst feed mass ratio (3 : 1). At a higher ratio (10 : 1), alkylphenols (∼41%) are the leading product fraction followed by cycloalkanes and alkylbenzenes (∼34%) with a high liquefied monomer bio-oil product yield of 39.4 wt%. Catalyst characterization via XRD, Raman, H2-TPR, and XPS analysis revealed that the origin for this reactivity arises from the Mo species formed and stabilized over the support surface. A well dispersed, octahedral, higher fraction of easily reducible Mo-species (Mo5+) was evident over the optimal catalyst which enables enhanced C–O cleavage facilitating the hydrodeoxygenation reaction. Moreover, the solid residue yield could be reduced to below 5 wt% by optimizing the reaction conditions and particle size of the sawdust.

Graphical abstract: One-pot reductive liquefaction of sawdust to renewables over MoOx–Al2O3 variants: insight into structure–activity relationships

Supplementary files

Article information

Article type
Paper
Submitted
28 Nov 2023
Accepted
13 May 2024
First published
14 May 2024
This article is Open Access
Creative Commons BY license

Sustainable Energy Fuels, 2024,8, 2668-2681

One-pot reductive liquefaction of sawdust to renewables over MoOx–Al2O3 variants: insight into structure–activity relationships

M. A. Salam, Q. K. Tran, P. H. Ho, Y. W. Cheah, J. Wojtasz-Mucha, C. Kugge, E. Nejadmoghaddam, L. Olsson and D. Creaser, Sustainable Energy Fuels, 2024, 8, 2668 DOI: 10.1039/D3SE01539D

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