Do Heui Kim

Hydrothermal Conversion of Alginate into Uronic Acids over a Sulfonated Glucose-Derived Carbon Catalyst

Alginate, the major constituent of algal biomass, was hydrolyzed into uronic acids over sulfonated glucose‐derived carbon catalysts using water as a green solvent under mild temperature conditions (100, 120, and 140u2009°C). The catalytic activity was compared with that of sulfuric acid and other commercial solid acid catalysts such as carbon black, activated carbon, Amberlyst‐15, and zeolites. The carbon catalysts were further treated with nitric acid or sulfuric acid to impart acid properties. The sulfonic group is an active site in the catalysis of the hydrolysis of alginate, and phenolic hydroxyl and carboxylic groups on the carbon surface showed negligible effects on the hydrolysis reactions in the temperature region. A high local acid density of the sulfonated glucose‐derived carbon catalyst (Glu‐SO3H) facilitates the cleavage of the 1,4‐glycosidic bond as alginate adsorbs onto the carbon catalyst surface by a carbohydrate–π interaction. Mannuronic acid and guluronic acid were further degraded into humins or epimerized into other uronic acids, which led to the decrease in the yield of target monomers. The highest monomer yield of 19.6u2009% was obtained if alginate was treated hydrothermally over the sulfonated carbon at 140u2009°C for 1u2005h. The catalytic activity of Glu‐SO3H for the alginate conversion is higher than that of commercial acid catalysts used in this study.

Effect of Soot on N2O Formation Over Pt Based Diesel Oxidation Catalyst Supported on Microporous TiO2

The N2O formation over the diesel oxidation catalyst supported on microporous TiO2 has been investigated in the presence of the soot to simulate cold start or regeneration condition. The platinum (Pt) catalyst entrapped in micropore was resulted in the increase of the catalytic activity compared to the Pt catalyst supported on alumina. Also, it was shown that the presence of the soot with the oxidation catalyst enhanced the N2O formation.

Decomposition of Lignin Using MO–MgAlOy Mixed Oxide Catalysts (M=Co, Ni and Cu) in Supercritical Ethanol

In this study, we performed the depolymerization reaction of concentrated sulfuric acid hydrolysis lignin (CSAHL) in supercritical ethanol without supplying external hydrogen. Cu demonstrated the highest monoaromatic yield of 18.4xa0wt% among Co, Ni and Cu when incorporated into MgAlOy. With increasing the amount of Cu loading, it was found that the optimum Cu loading was 30xa0wt%, where the number of acid sites had the maximum. In case of CuO–MgAlOy sample with higher Cu loading than 30xa0wt%, the decrease in the acid sites and the significant sintering of Cu metal during reaction were observed, leading to the decline in the monoaromatic yield.

Catalytic Hydrogenation of Macroalgae-Derived Alginic Acid into Sugar Alcohols

Alginic acid, a major constituent of macroalgae, iss hydrogenated into sugar alcohols over carbon-supported noble metals for the first time. Mannitol and sorbitol are the major products of the catalytic hydrogenation of alginic acid, which consists of two epimeric uronic acids. The main reaction pathway is the consecutive hydrogenations of the aldehyde and carboxyl ends of alginic acid dimers, followed by the cleavage of the C-O-C linkage into monomeric units by hydrolysis. The highest yield of C6 sugar alcohols is 61u2009% (sorbitol: 29u2009%; mannitol: 28u2009%; galactitol: 4u2009%). The low sorbitol/mannitol ratio is in contrast to that from cellulose hydrogenation, owing to the composition of alginic acid and isomerization between sugar alcohols under the catalytic system. This new green route to producing sugar alcohols from alginic acid might provide opportunities to diversify biomass resources.