Analysis of Primary Reactions in Biomass Oxidation with O2 in Hot-Compressed Alkaline Water

The present study investigated oxidation of pulverized Japanese cedar with O-2 in hot-compressed alkaline water, employing a newly developed flow-through fixed-bed reactor (percolator). It allowed us to determine the rate of the primary extraction that was free from the secondary reactions of extract in the aqueous phase and those over the residual solid, solubility of extractable matter, and mass transport processes. Quantitative kinetic analysis revealed that the cedar consisted of three kinetic components (C1-C3) that underwent extraction in parallel following first-order kinetics with different rate constants. Further analysis revealed the chemical compositions of the kinetic components (C1 -C3) that underwent extraction in parallel following first-order kinetics with different rate constants. Further analysis revealed the chemical compositions of the kinetic components, which were mixtures of carbohydrates and lignin. C1 was converted most rapidly by nonoxidative reactions such as alkali-catalyzed hydrolysis, while C2 was converted by oxidative degradation. The product distributions from C1 and C2 (CO2, lower organic acids, oligosaccharides, acid-soluble, and acid-insoluble lignins) were steady throughout their conversion. Both C1 and C2 thus behaved as single reactants; nevertheless, those were lignin/carbohydrates mixtures. It was also demonstrated that the extraction rate of C2 was proportional to the concentration of dissolved O-2. C3 was the most refractory component, consisting mainly of glucan and very minimally of the lignin, xylan, mannan, galactan, and arabinan.

Automated summary

The study investigated the oxidation of pulverized Japanese cedar using O-2 in hot-compressed alkaline water, revealing that the cedar consisted of three kinetic components undergoing extraction in parallel following first-order kinetics. Further analysis uncovered that these components were mixtures of carbohydrates and lignin, with C1 and C2 being converted at different rates while maintaining steady product distributions, and C3 being the most refractory component mainly composed of glucan.