• Clean Technology
• /
• v.28 no.3
• /
• pp.232-237
• /
• 2022

Biorefineries, in which renewable resources are utilized, are an eco-friendly alternative based on biomass feedstocks. Alginic acid, a major component of brown algae, which is a type of marine biomass, is widely used in various industries and can be converted into value-added chemicals such as sugars, sugar alcohols, furans, and organic acids via catalytic hydrothermal decomposition under certain conditions. In this study, ruthenium-supported activated carbon and magnesium oxide were mixed and applied to the depolymerization of alginic acid in a batch reactor. The addition of magnesium oxide as a basic promoter had a strong influence on product distribution. In this heterogeneous catalytic system, the separation and purification processes are also simplified. After the reaction, low molecular weight alcohols and organic acids with 5 or fewer carbons were produced. Specifically, under the optimal reaction conditions of 30 mL of 1 wt% alginic acid aqueous solution, 100 mg of ruthenium-supported activated carbon, 100 mg of magnesium oxide, 210 ℃ of reaction temperature, and 1 h of reaction time, total carbon yields of 29.8% for alcohols and 43.8% for a liquid product were obtained. Hence, it is suggested that this catalytic system results in the enhanced hydrogenolysis of alginic acid to value-added chemicals.

• Applied Chemistry for Engineering
• /
• v.8 no.5
• /
• pp.749-755
• /
• 1997

Molybdenum phosphate(P/Mo = 0.6) has been synthesized with ammonium molybdate and phosphoric acid under aqueous solution. The kinetics of the ammoxidation of methylpyrazine over molybdenum phosphate catalyst was investigated with the variation of reaction temperature and partial pressure of methylpyrazine, oxygen and ammonia, respectively at atmospheric pressure. The catalytic activity was constant for 300hrs operation under our experimental conditions. Under the steady-state condition, the rate equation of methylpyrazine was shown as $-r=kP_{MP}P_{NH3}{^0}P_{O2}{^{\gamma}}({\gamma}=2.2;1.3{\leq}P_{O2}(kPa){\leq}4)$. The apparent activation energy was 29.6kcal/mol below 623K. The main product obtained in the ammoxidation of methylpyrazine is cyanopyrazine whose selectively was kept always over 90% regardless of conversion.

• Clean Technology
• /
• v.27 no.1
• /
• pp.69-78
• /
• 2021

Vegetable oils, such as palm oil and cashew nut shell liquid (CNSL), are used as major raw materials for bio-diesel in transportation and bio-heavy oil in power generation in South Korea. However, due to the high unsaturation degree caused by hydrocarbon double bonds and a high content of oxygen originating from the presence of carboxylic acid, the range of applications as fuel oil is limited. In this study, hydrotreating to saturate unsaturated hydrocarbons and remove oxygen in mixed bio-oil containing 1/1 v/v% palm oil and CNSL on monometallic catalysts (Ni and Cu) and bimetallic catalysts (Ni-Zn, Ni-Fe, Ni-Cu Ni-Co, Ni-Pd, and Ni-Pt) was perform under mild conditions (T = 250 ~ 400 ℃, P = 5 ~ 80 bar and LHSV = 1 h-1). The addition of noble metals and transition metals to Ni showed synergistic effects to improve both hydrogenation (HYD) and hydrodeoxygenation (HDO) activities. The most promising catalyst was Ni-Cu/��-Al2O3, and in the wide range of the Ni/Cu atomic ratio of 9/1~1/4, the conversion for HYD and HDO reactions of the catalysts were 90-93% and 95-99%, respectively. The tendency to exhibit almost constant reaction activity in these catalysts of different Ni/Cu atomic ratios implies a typical structure-insensitive reaction. The refined bio-oil produced by hydrotreating (HDY and HDO) had significantly lower iodine value, acid value, and kinetic viscosity than the raw bio-oil and the higher heating value (HHV) was increased by about 10%.

• Journal of Life Science
• /
• v.28 no.3
• /
• pp.351-356
• /
• 2018

L-Serine dehydratase (LSD) is an iron-sulfur containing enzyme that catalyzes the conversion of L-serine to pyruvate and ammonia. Among the bacterial amino acid dehydratases, it appears that only the L-serine specific enzymes utilize an iron-sulfur cluster at their catalytic site. Moreover, bacterial LSDs are classified into four types based on structural characteristics and domain arrangement. To date, only the LSD enzymes from a few bacterial strains have been studied, but more detailed investigations are required to understand the catalytic mechanism of various bacterial LSDs. In this study, LSD type II from Mycobacterium tuberculosis (MtLSD) H37Rv was expressed and purified to elucidate the biochemical and catalytic properties using the enzyme kinetic method. The L-serine saturation curve of MtLSD exhibited a typically sigmoid character, indicating an allosteric cooperativity. The values of $K_m$ and $k_{cat}$ were estimated to be $59.35{\pm}1.23mM$ and $18.12{\pm}0.20s^{-1}$, respectively. Moreover, the plot of initial velocity versus D-serine concentration at fixed L-serine concentrations showed a non-linear hyperbola decay shape and exhibited a competitive inhibition for D-serine with an apparent $K_i$ value of $30.46{\pm}5.93mM$ and with no change in the $k_{cat}$ value. These results provide insightful biochemical information regarding the catalytic properties and the substrate specificity of MtLSD.

• Microbiology and Biotechnology Letters
• /
• v.44 no.1
• /
• pp.48-54
• /
• 2016

In this study, biosugar production by the red-algae Eucheuma cottonii was investigated using dilute sulfuric acid-catalyzed hydrolysis and data analysis by response surface methodology. This approach yielded 25.8 g/l total reducing sugar under the conditions of $160.1^{\circ}C$, 1% (v/v) sulfuric acid, and 13.1 min. The sugar concentration showed a linear inverse correlation with the combined severity factor (CSF) of the reaction conditions. CSF was calculated as $log(t{\cdot}e{xp}[(T_H-T_R)/14.75])-pH$, where t is the coupling reaction time, $T_H$ is the target temperature, and $T_R$ is the reference temperature ($100^{\circ}C$). In addition, levulinic acid production showed a linear positive correlation with CSF. E. cottonii may represent a useful feedstock for sugar production in the field of bioenergy.

• Korean Chemical Engineering Research
• /
• v.61 no.1
• /
• pp.168-174
• /
• 2023

In commercial production processes of methyl methacrylate, there is a methacryl aldehyde as an intermediate or impurities. The existence of impurities is critical factor because of significant decrease of the conversion rate and selectivity of the entire chemical reaction. This study found that an acid was the main cause of the decrease in reactivity among various impurities because an acid rapidly lowers the activity of a catalyst and promotes a side reaction, the hetero Diels-Alder reaction. Therefore, the pretreatment methods with the removal of acid were comparatively evaluated by the selective hydrogenation reaction of the carbonyl group of the reactants. Based on several experimental conditions, we believe that proposed effective pretreatment improves productivity with appropriate economical process.

• The Journal of Natural Sciences
• /
• v.7
• /
• pp.47-51
• /
• 1995

In order to develope new asymmetric catalyst, we synthesized the following new sulfonamide derivatives start from S-Indoline-2-Carboxylic Acid via the following 5 steps. Hydroxy methyl derivative(1) was thus treated with methane sulfonyl chloride in the presence of triethylamine as base to give mesylated derivative(2) in 85% of isolated yield. The mesylate compound (2) was treated with excess sodium azide to give Azido derivative (4) in 95% isolated yield. Azido compound (3) was then reduced to the corresponding amino derivative in near quntitative yield by the hydrogenation under hydrogen atmospere in the presence of catalytic amount of Pd-C. The amino derivative (4) was converted to its sulfonamide derivatives by the treatment of compound(4) with triisopropyl benzene sulfonyl chloride in the presence of triethyl amine as base. Finally t-BOC group of the compound(5) was removed by the treatement of excess Trifluoro-acetic acid in near quantitative yield to give the target sulfonamide derivative (7) .in this paper we prepared compound(6) in 49% overall yield via the 5 steps of synthesis starting from t-Boc- 2-hydroxy methyl indoline(1) which cab be easily prepared from commercial available S-indoline-2-carboxylic acid by known methods. we plan to apply this new catalyst for the asymmetric reduction , diels-alder reaction, aldolcondensation reaction in due courses.

• Applied Chemistry for Engineering
• /
• v.26 no.5
• /
• pp.621-623
• /
• 2015

This article describes a purification method yielding high purity of MFB produced from DMT production process. Aldehyde functional group of MFB included in side-products were converted to acetal compound via reacting with methanol and further separated. Hydrolysis process of the acetal product was continued under acidic condition and highly pure MFB were obtained with 90% yield. The structure of MFB was analyzed by $^1H$ NMR and $^{13}C$ NMR spectroscopy. Also, the purity of MFB was estimated to be over 99% by GC analysis.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.35 no.9
• /
• pp.1224-1231
• /
• 2006

Sucrose esters were synthesized by transesterification of sucrose with docosahexaenoic acid ethylester mixture (DHAEE). Potassium carbonate as a base catalyst was used in the presence of dimethylsulfoxide (DMSO) for the reactions. The reactions were performed with the different reaction times and molar ratios of substrates in the presence of surfactant in vacuum. Among the reaction conditions in this study, SE#4～7 showed the relatively high conversion rate (>96%) of DHAEE, leading to the high yield of sucrose esters. In addition, the product composition was changed from sucrose mono ester to di/tri/polyesters after the prolonged reaction time while the increased molar ratio of DHAEE also resulted in the composition changes of sucrose mono ester to the sucrose di/tri/polyesters. From the reaction (SE#7), conversion ratio was 98.5% in which 87.3% mono ester and 13.7% di/tri/polyester were found, resulting in the highest content of mono ester. Therefore, the sucrose ester containing various rates of mono and di/tri/polyesters, which effects on hydrophilic lipophilic balance (HLB) values, can be manipulatively synthesized using the reaction conditions reported in this study.

• The Korean Journal of Pesticide Science
• /
• v.4 no.2
• /
• pp.29-31
• /
• 2000

New convenient and economical synthesis of 5,6-dihydro-2-methyl-1,4-oxathiin-3-carboxanilide 1 and the plausible reaction mechanism were described. Reaction of ${\alpha}$-chloroacetoacetanilide 4 (1 molar equivalent) with 2-mercaptoethanol (1.2 molar equivalent) in the presence of p-toluenesulfonic acid monohydrate (0.05 molar equivalent) as a catalyst in refluxing toluene with water trap yielded carboxin 1. The proposed mechanism is that ${\alpha}$-chloro 1,3-oxathiolane 8 which is a heuithioketal of 4 was converted to unisolable sulfonium ion 9 through neighboring group participation of sulfur followed by rearrangement to more stable oxonium ion 12 and then release acidic proton to produce the carboxin 1.