• Journal of the Korean Wood Science and Technology
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• v.40 no.6
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• pp.389-396
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• 2012

In this study, we investigated the kinetics of acid-catalyzed hydrolysis of xylan over a 60 min at $120^{\circ}C$. Sulfuric, oxalic and maleic acids were used as acid catalyst for hydrolysis. The calculated degradation rate constants ($k_1$) showed a correlation with the acid concentration, meaning that the stronger the acid, the higher the xylan degradation rate. Among sulfuric, oxalic and maleic acid catalyzed hydrolysis, the xylan degradation rate to xylose was highest with sulfuric acid. At equivalent solution pH, acid catalyzed hydrolysis was proportional to $H^+$ concentration. The $k_1$ of dicarboxylic acid such as oxalic and maleic acid was higher than that of sulfuric acid at same pH values during hydrolysis.

• Applied Biological Chemistry
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• v.41 no.8
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• pp.611-612
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• 1998

The transition state analog for metal catalyzed hydrolysis of an ester through cooperative interactions between metal ions as Lewis acid and peroxide was discussed.

• Elastomers and Composites
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• v.55 no.2
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• pp.128-136
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• 2020

The hydrolysis mechanisms as well as the hydrolysis measurement technique and its practical applications in material manufacturing fields are revised. This chapter, Part 1, elaborates the theoretical aspects of the hydrolysis mechanism. Acid-catalyzed and base-catalyzed hydrolysis mechanisms are reviewed. The quantitative analysis method based on the SIM technique using py-GC-MS is reviewed. Examples of hydrolysis of alkoxysilane in elastomer composites currently used in the industry and hydrolysis of amine in plastic composites are shown. Moreover, Part 2 discusses the mechanical property changes in elastomer and plastic composites after hydrolysis.

• Korean Chemical Engineering Research
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• v.56 no.4
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• pp.542-546
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• 2018

In this study, the effects of malonic acid-catalyzed pretreatment on the subsequent enzymatic hydrolysis of red macro-algae Gracilaria verrucosa for production of biosugar (total reducing sugar) were investigated. In the hydrothermal pretreatment condition of 300 mM malonic acid, 1:20 solid-to-liquid ratio at $130^{\circ}C$ for 60 min, a 49.2% biosugar yield was achieved. Moreover, by subsequent enzymatic hydrolysis after pretreatment, maximum yield of 64.5% was achieved.

• Bulletin of the Korean Chemical Society
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• v.18 no.8
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• pp.880-886
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• 1997

Ab initio calculations were carried out on the gas phase acid-catalyzed hydrolysis reactions of sulfinamide using the 3-21G* basis sets. Single point calculations were also performed at the MP2/6-31G* level. The first step in the acid-catalyzed hydrolysis of N-methylmethanesulfinamide, Ⅰ, involves protonation. The most favorable form is the O-protonated one, Ⅱ, which is then transformed into a sulfurane intermediate, Ⅲ, by addition of a water molecule. The reaction proceeds further by an intramolecular proton transfer from O to N (TS2), which is followed by N-S bond cleavage (TS3) leading to the final products. The rate determining step is the N-S bond cleavage (TS3) at the RHF/3-21G* level, whereas it becomes indeterminable at the MP2/6-31G*//3-21G* level of theory. However, the substituent effect studies with N-protonated N-arylmethanesulfinamide, ⅩⅢ, at the MP2/6-31G*//3-21G* level support the N-S bond breaking step as rate limiting.

• Fisheries and Aquatic Sciences
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• v.12 no.1
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• pp.16-23
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• 2009

Lipids were extracted from marine rotifer, Brachionus rotundiformis in order to examine the functionality of lipid enzymatic modification. The fatty acids, palmitic, linoleic, oleic and stearic acids were the dominant forms accounting for approximately 35.8%, 21.5%, 15.9% and 7.7% of the total lipid content, respectively. Lipid fractions were categorized as neutral lipids (38.5%), glycolipids (45.9%) and phospholipids (17.6%), and after extraction from the rotifer were isolated by thin-layer chromatography (TLC) as free fatty acids (FFA), monoacylglycerol (MAG), diacylglycerol (DAG) and triacylglycerol (TAG). The production of polyunsaturated fatty acid (PUFA) concentrate from rotifer lipids was studied using lipase-catalyzed hydrolysis. In addition, rotifer lipids were modified by hydrolysis using lipases such as porcine pancreas, Candida rugosa and Rhizomucor miehei. The lipase from Rhizomucor miehei was effective in extracting linoleic acid (C 18:2), while the lipase from Candida rugosa was effective in palmitic acid (C16:0) extraction.

• Korean Chemical Engineering Research
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• v.52 no.2
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• pp.226-232
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• 2014

In this study, we investigated kinetic model for the acid-catalyzed xylan hydrolysis at temperature $120{\sim}150^{\circ}C$. Also, we analyzed the kinetic parameters for xylose production and furfural decomposition. The hydrolysis of xylan and the degradation of xylose were promoted by high reaction temperature and acid concentration. The optimal hydrolysis condition for the highest reaction rate constants ($k_1$) was different depending on the acid catalysts. Among sulfuric, oxalic and maleic acid, the xylan reaction rate constants ($k_1$) to xylose had the highest value of $0.0241min^{-1}$ when 100 mM sulfuric acid was used at $120^{\circ}C$. However, sulfuric acid induced more xylose degradation compared to oxalic and maleic acid hydrolysis. The activation energy for xylan degradation was the highest when sulfuric acid was used.

• Journal of the Korean Chemical Society
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• v.41 no.3
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• pp.138-143
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• 1997

Acid-catalyzed hydrolysis of 3,3-bis(methylthio)-2-propen-1-phenyl-1-one derivatives were studied kinetically in concentrated aqueous hydroperchloric acid(-Ho < 2.23) at $30^{\circ}C.$ The substituent effect, analysis of hydrolysis product, hydration $parameter({\omega} & {\phi}$) from the Bunnett equation and the Bunnett-Olsen equation on the rate indicate that the acid-catalyzed hydrolysis of the substrates below 3.8 M hydroperchloric acid media occurs through A-1 type reaction($3.3 >{\omega},\;0.58 >{\phi} & {\rho}< 0$) mechanism and above 3.8 M hydroperchloric acid, the reaction proceeds A-2 type reaction($0 <(\omega)$, $0 <{\phi} & (\rho)> 0$) mechanism.

• Journal of the Korean Ceramic Society
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• v.32 no.7
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• pp.783-792
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• 1995

Sol-Gel derived ferroelectric PZT thin films were fabricated on ITO/Glass and Si/SiO2 substrates. In order to investigate the effect of catalysts on the densification and crystallization of PZT thin films, a nitric acid or ammonium hydroxide was added to the PZT stock solution at the state of partial hydrolysis reaction. The measured pH for a stable PZT sol was 5.2~9.3. In case of an acid-catalyzed PZT sol, a highly condensed particulate PZT sol was formed by accelerating the hydrolysis reaction. But weakly branched polymeric PZT sol was formed with a base-catalyzed condition. The difference in densification behavior was not found in the pH range of added catalyst, but the refractive index of PZT thin film was increased rapidly as the annealing temperature increased. The PZT thin film annealed at 54$0^{\circ}C$ for 10 min was fully densified and its refractive index was above 2.4. When the annealing temperature increased, the transition from the pyrochlore phase to perovskite appeared at 54$0^{\circ}C$. The base-catalyzed PZT thin film suppressed to form the pyrochlore phase and proceeded effectively to convert the perovskite phase. This was due to the formation of polymeric molecular structure by controlling the hydrolysis and condensation reaction through the additiion of the ammonium hydroxide.

• Journal of the Korean Wood Science and Technology
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• v.52 no.2
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• pp.101-117
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• 2024

The conversion characteristics of the major components of Liriodendron tulipifera were investigated during acid-catalyzed organosolv pretreatment. Glucan in L. tulipifera was slowly hydrolyzed, whereas xylan was rapidly hydrolyzed. Simultaneous hydrolysis and degradation of xylan and lignin occurred; however, after complete hydrolysis of xylan at higher temperatures, lignin remained and was not completely degraded or solubilized. These conversion characteristics influence the structural properties of glucan in L. tulipifera. Critical hydrolysis of the crystalline regions in glucan occurred along with rapid hydrolysis of the amorphous regions in xylan and lignin. Breakdown of internal lignin and xylan bonds, along with solubilization of lignin, causes destruction of the lignin-carbohydrate complex. Over a temperature of 160℃, the lignin that remained was coalesced, migrated, and re-deposited on the surface of pretreated solid residue, resulting in a drastic increase in the number and content of lignin droplets. From the results, the characteristic conversions of each constituent and the changes in the structural properties in L. tulipifera effectively improved enzymatic hydrolysis in the range of 140℃-150℃. Therefore, it can be concluded that significant changes in the biomass recalcitrance of L. tulipifera occurred during organosolv pretreatment.