Recent progress in the development of solid catalysts for biomass conversion into high value-added chemicals

Abstract

In recent decades, the substitution of non-renewable fossil resources by renewable biomass as a sustainable feedstock has been extensively investigated for the manufacture of high value-added products such as biofuels, commodity chemicals, and new bio-based materials such as bioplastics. Numerous solid catalyst systems for the effective conversion of biomass feedstocks into value-added chemicals and fuels have been developed. Solid catalysts are classified into four main groups with respect to their structures and substrate activation properties: (a) micro- and mesoporous materials, (b) metal oxides, (c) supported metal catalysts, and (d) sulfonated polymers. This review article focuses on the activation of substrates and/or reagents on the basis of groups (a)-(d), and the corresponding reaction mechanisms. In addition, recent progress in chemocatalytic processes for the production of five industrially important products (5-hydroxymethylfurfural, lactic acid, glyceraldehyde, 1,3-dihydroxyacetone, and furan-2,5-dicarboxylic acid) as bio-based plastic monomers and their intermediates is comprehensively summarized.

Keywords: biomass; heterogeneous catalyst; metal hydroxide; metal oxide; solid catalyst; supported nanoparticle; zeolite.

Figure 1.

Comparison of the AlCl₃- and zeolite-catalyzed Friedel–Crafts acylation processes [7].

Figure 2.

Representative processes for biomass conversion into chemicals and fuels.

Figure 3.

Schematic representation of a hardwood lignin structure and common linkages found in the lignin polymer [40, 41].

Figure 4.

Examples of relevance to materials used in biomass conversion.

Figure 5.

Mechanism for the formation of Br⊘nsted and Lewis acid sites within the zeolite framework.

Figure 6.

Reaction pathways for the conversion of trioses into lactate (alkyl lactate or LA) catalyzed by a Lewis acid catalyst [113].

Figure 7.

Schematic representation of the structure of carbon-deposited and Sn-incorporated mesoporous silica catalyst at various scale lengths [118].

Figure 8.

Possible reaction mechanism for Lewis acid (Sn-β) or Br⊘nsted base (NaOH) catalyzed transformation of glucose into fructose [111, 125].

Figure 9.

Representative structure of Lewis acid center on (a) phosphate/Nb₂O₅·nH₂O and (b) phosphate/TiO₂ [149, 152].

Figure 10.

Proposed mechanism for the oxidation of a primary alcohol and successive oxidation of the corresponding aldehyde over a supported metal catalyst with O₂ [171].

Figure 11.

Reaction pathways for the catalytic oxidation of HMF to FDCA with O₂.

Figure 12.

Reaction pathways for the catalytic oxidation of glycerol with O₂.