Targeted chemical upgrading of lignocellulosic biomass to platform molecules

Abstract

This review presents an overview of the initial targeted chemical processing stages for conversion of lignocellulosic biomass to platform molecules that serve as intermediates for the production of carbonbased fuels and chemicals. We identify four classes of platform molecules that can be obtained in an initial chemical processing step: (i) sugars, (ii) dehydration products, (iii) polyols and (iv) lignin monomers. Special emphasis is placed on reporting and comparing parameters that affect process economics and/or sustainability, including product yields, amount of catalyst used, processing conditions, and product concentrations. We discuss the economic trade-offs associated with choices related to these parameters, depending on the product that is targeted. We also address the effects of real biomass on the ability to recover, recycle, and potentially regenerate catalysts and solvents used in the biomass conversion processes.

Improving Heterogeneous Catalyst Stability for Liquid-phase Biomass Conversion and Reforming

“…[6] We have recently reviewed the targeted deconstruction of lignocellulosic material and the initial biomass deconstruction steps that generally produce the carbohydrate monomers of the aforementioned polysaccharides (mainly glucose and xylose), or the dehydration products of these monomers (including furans or levulinic acid). [7] Lignin deconstruction processes are much less mature, and most exploratory processes include the hydrogenolysis or oxidation to syringyl and guaicyl derivatives. [7,8] These main routes for the deconstruction of biomass into platform molecules usually occur in water using various combinations of acids, [9,10] bases, [11] solvents [12][13][14] or ionic liquids.…”

Solvent‐Enabled Nonenyzmatic Sugar Production from Biomass for Chemical and Biological Upgrading

“…[21][22][23] For this reason,a lternate systems using significantly less catalyst have also been explored, including dilute acid hydrolysis [24,25] or hydrothermalb iomass depolymerization. [13,[26][27][28] However,a tm ost temperatures (below 510-570 K) and low acid contents( >3%), the rate of sugar degradation and dehydration to furans or other degradation products is of the same order of magnitude as the rate of polysaccharide depolymerization, especially for the cellulose fraction of biomass. [13,25,29,30] Therefore, both pure water and dilute acid systemsr equire impractical high-temperature and short-residence time processes to achieve high yields (e.g.,5 10-670K for minutes to seconds).…”

“…[14][15][16][17] Both of these methods can achieve soluble carbohydrate yields upwards of 90 %a nd produce concentrated solutionso fc arbohydrates (> 100 gL À1 ). [10,13,18] Ionic liquids are also attractive solvents for cellulose dissolution and soluble carbohydrate production. [19,20] Although these processes can be used to produce sugars from biomass,t he cost of producing and/or recovering the enzyme, mineral acid, or solvent still represents as ignificant portion of the final process.…”

“…[13,[26][27][28] However,a tm ost temperatures (below 510-570 K) and low acid contents( >3%), the rate of sugar degradation and dehydration to furans or other degradation products is of the same order of magnitude as the rate of polysaccharide depolymerization, especially for the cellulose fraction of biomass. [13,25,29,30] Therefore, both pure water and dilute acid systemsr equire impractical high-temperature and short-residence time processes to achieve high yields (e.g.,5 10-670K for minutes to seconds). [24,27,29] Organic solvents such as alcohols and ketones have been used during pretreatment to improvet he deconstruction of biomass notably by increasing lignin solubility.…”

“…Concentrated mineral acids such as sulfuric or hydrochloric acid have been used to hydrolyze hemicellulose and cellulose to soluble oligomers almost quantitatively. [9][10][11][12][13] Recently,atwo-stage process consisting of at hermochemical or pretreatment stage followed by enzymatic hydrolysis has been one of the most prominently researched biomass depolymerization methods. [14][15][16][17] Both of these methods can achieve soluble carbohydrate yields upwards of 90 %a nd produce concentrated solutionso fc arbohydrates (> 100 gL À1 ).…”