Cellulose Conversion Into Hexitols and Glycols in Water: Recent Advances in Catalyst Development

Abstract

Conversion of biomass cellulose to value-added chemicals and fuels is one of the most important advances of green chemistry stimulated by needs of industry. Here we discuss modern trends in the development of catalysts for two processes of cellulose conversion: (i) hydrolytic hydrogenation with the formation of hexitols and (ii) hydrogenolysis, leading to glycols. The promising strategies include the use of subcritical water which facilitates hydrolysis, bifunctional catalysts which catalyze not only hydrogenation, but also hydrolysis, retro-aldol condensation, and isomerization, and pretreatment (milling) of cellulose together with catalysts to allow an intimate contact between the reaction components. An important development is the replacement of noble metals in the catalysts with earth-abundant metals, bringing down the catalyst costs, and improving the environmental impact.

Unidimensional Approximation of the Diffuse Electrical Layer in the Inner Volume of Solid Electrolyte Grains in the Absence of Background Ions

“…E.g., attraction of protonated cellulose to the catalyst surface is theorized to play an important role in its hydrolysis over solid acids. [20] Attraction of the substrate is particularly important for bifunctional catalysis where some of the catalytic sites are unconditionally surface-bound (e. g., the metal in metalaugmented solid acids for combined hydrolysis and hydrogenation of polysachharides [60][61][62][63] ). Another possibility is preferential orientation of polar molecules in the electric field of EDLs.…”

Direct Conversion of Almond Waste into Value-Added Liquids Using Carbon-Neutral Catalysts: Hydrothermal Hydrogenation of Almond Hulls Over a Ru/Cnf Catalyst

“…When a hydrogen-rich atmosphere is achieved at hydrothermal conditions, these species can undergo different transformations (Li et al, 2018). These include hydrogenations yielding sugar alcohols, such as sorbitol and mannitol (Manaenkov et al, 2019;Sun and Liu, 2011), dehydrogenations to produce gluconic acid, and/or dehydration, generating 5-hydroxymethylfurfural (5-HMF) (Remón et al, 2018c). This latter can be subsequently decomposed into levulinic and formic acids by hydrolysis.…”

“…Simultaneously, glucose and fructose can be further decomposed into small oxygenates via the retro-aldol reaction. On the one hand, the former can evolve towards erythrose and 2-hydroxy acetaldehyde (Manaenkov et al, 2019), while the latter can decompose into 2,3dihydroxypropanal and 1,3-dihydroxypropan-2-one. Erythrose may lead to the formation of erythritol and/or 1,2-butanol via hydrolytic dehydration (Li et al, 2018).…”

“…Additionally, 2-butanol can be subsequently produced from both species and evolve to butane-2-one. In addition, ethane-1,2-diol can be formed from 2-hydroxy-acetaldehyde (Manaenkov et al, 2019), whose subsequent decomposition might lead to the formation of ethanol and/or acetaldehyde, both of which can subsequently evolve towards acetic acid (Remón et al, 2018d).…”

Hydrogenolysis of biomass-derived sorbitol over La-promoted Ni/ZrO2 catalysts

“…Although the catalytic system reported in the previous literature can efficiently realize sorbitol hydrogenolysis, the commonly used alkaline additives are slightly soluble CaO or Ca(OH) 2 , which can easily corrode equipment and cause poor product separation. 28,29 Therefore, the development of new solid-alkali-supported metal catalysts can effectively solve this problem. In this paper, using the inexpensive alkaline additive La 2 O 3 and inexpensive active Ni, we prepared Ni/La 2 O 3 /ZrO 2 catalysts with different Ni/La ratios by using the initial wetness impregnation method.…”