• Korean Journal of Food Science and Technology
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• v.33 no.1
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• pp.7-11
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• 2001

The influence of temperature and calcium concentration on the gelation kinetics of purified Aigeok system has been investigated by small deformation oscillatory measurement. DE(degree of esterification) of the present sample was indicated of low methoxyl Aigeok polysaccharide by FT-IR. The calcium induced gelation of Aigeok has been studied. Both moduli reached the saturation value during the period of experiments. Rate constant increased with increasing calcium concentration, however above 4.08 mM calcium chloride caused a sudden drop in gel strength. The experimental result that the decrease in gel strength at high calcium concentration was seems to be phase separation or competitive inhibition between calcium ions. The storage and loss shear moduli decreased with increasing temperature. The rate constant of Aigeok system remarkably dropped above $35^{\circ}C$. Thus hydrogen bonding is prior to hydrophobic interaction for Aigeok molecule.

• Journal of the Korean Applied Science and Technology
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• v.35 no.4
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• pp.1048-1056
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• 2018

Non-edible oil sources (i.e., Palm Acid Oil, waste animal fat) usually contain relatively high amount of free fatty acids (FFA) that make them inadequate for direct base catalyzed transesterification reaction. Enzymatic biodiesel synthesis can solve several problems posed by the alkaline-catalyzed transesterification, and has certain advantages over the chemical catalysis of transesterification, as it is less energy intensive, allows easy recovery of glycerol and the transesterification of glycerides with high free fatty acid contents. In this study, we synthesized biodiesel through enzymatic catalyzed process using high free fatty acid containing waste oil in biodiesel reactor (1 ton/day) and optimized the biodiesel production processes.

• Applied Chemistry for Engineering
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• v.22 no.1
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• pp.72-76
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• 2011

In this study, we investigated the characteristics of biodiesel using the waste coffee oil which was extracted by waste coffee grounds. We tried to deduce the optimum conditions by defining the operating variables, such as mole ratio between methanol and coffee oil (6~18) and the reaction temperature ($45{\sim}60^{\circ}C$) in the biodiesel production processes. The performance was evaluated in terms of yields, contents of fatty acid methyl ester (FAME), viscosities, and heating values. The optimum reaction temperature was $55^{\circ}C$. Also, the best biodiesel was produced at the mole ratio between methanol and coffee oil of 12. The highest heating value of the produced biodiesel made from coffee oil was 39.0~39.4 MJ/kg, which satisfies the general standard for the biodiesel energy density, 39.3~39.8 MJ/kg.

• Polymer(Korea)
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• v.30 no.2
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• pp.162-167
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• 2006

Polyamic acid (PAA) was prepared from cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA) and 4,4'-fiaminodiphenyl ether (DDE). In order to impart a photosensitivity to the PAA, diazonaphthoquinone (DNQ) derivative (DI) was added. However, the addition of the DI was not enough to inhibit the dissolution of the PAA for a aqueous alkal solution. Therefore, we had synthesized poly(amic acid ester)s by an adding 1,2-epoxy-3-phenoxypropane to the PAA. That is, an acidity of the PAA could be controlled by an esterification reaction of 1,2-epoxy-3-phenoxypropane with the PAA. Significant difference of a dissolution rate of the poly(amic acid ester) between an o(posed and unexposed area was observed at an acid content of 60% and less. Resolution of the positively patterned film showed about $25{\mu}m$ at the exposure dose of $200mJ/cm^2$.

• Journal of the Korean Chemical Society
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• v.30 no.6
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• pp.548-552
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• 1986

A stereoselective synthesis of 3-phenoxybenzyl (${\pm}$)-cis and trans-3-(2,2-dichlorovinyl)-2,2-dimethyl-1-cyclopropanecarboxylic acid starting from readily available 2-methyl-3-buten-2-ol($\underline{2}$) is described. Allylic rearrangement of 2-methyl-3-buten-2-ol, in the presence of acetic acid and acetic anhydride gave 3-methyl-2-butenyl acetate($\underline{3}$). The [3,3] sigmatropic rearrangement of the allyl acetate($\underline{3}$), as the silylketene acetal, produced the ${\gamma},\;{\delta}$-unsaturated acid($\underline{4}$). Treatment of 3,3-dimethyl-4-pentenoic acid($\underline{4}$) with SOCl2 followed by esterification with 3-phenoxybenzyl alcohol yielded 3, 3-dimethyl-4-pentenoic acid ester($\underline{5}$). Addition of carbon tetrachloride to the olefin ester($\underline{6}$) furnished 4,6,6,6-tetrachloro-3,3-dimethylhexanoic acid ester ($\underline{7}$). Cyclization with potassium t-butoxide and elimination of hydrogen chloride afforded 3-phenoxybenzyl (${\pm}$) cis- and trans-3-(2,2-dichlorovinyl)-2,2-dimethyl-1-cyclopropanecarboxylic acid.

• Journal of the Korean Chemical Society
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• v.55 no.6
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• pp.1007-1011
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• 2011

Dioctyl succinates and succinic anhydride were synthesized from succinic acid in the presence of a cation exchange resin, Amberlite IR-120. The synthesis of dioctyl succinate from succinic acid and octanol was perfomed in 18 h reflux condition with Amberlite IR-120 and the isolated yield of product was over 90%. For the synthesis of succinic anhydride, succinic acid was refluxed in isopropenyl acetate for 18 h with Amberlite IR-120 as a catalyst. The long reaction time was significantly reduced to less than 10 min under microwave irradiation. The catalyst was reusable at least 4 times with keeping product yield of higher than 80%.

• Reproductive and Developmental Biology
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• v.28 no.2
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• pp.89-94
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• 2004

This study was conducted to determine expression of acyl-CoA synthetase 4(ACS4), which is involved in converts arachidonic acid to postaglandins, in the mouse uterus during pregnancy. In arachidonic acid metabolism, acyl-CoA synthetase plays a key role in the esterification of free arachidonic acid into membrane phospholipids. Following its release by the action of calcium dependent phospholipases, free arachidonic acid is believed to be rapidly converted to arachidonoyl-CoA and reesterified into phospholipids in order to prevent excessive synthesis of prostaglandins. Here we demonstrate that ACS4 gene are differentially regulated in the peri-implatation mouse uterus. During the preimplantation period(days 0.5∼3.5), the ACS4 gene was expressed in the uterus until day 3.5 after which the expression was downregulated. The expression of cPLA2, COX1, and COX2 gene was similar to that of ACS4 gene in the preimplantation periods. However expression levels of COX1 gene show much variation on the various days of pregnancy examined. These data, suggest that ACS4 expression in preimplantation period is involved in initial attachment reaction with cPLA2, COX1, and COX2 gene.

• Macromolecular Research
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• v.16 no.6
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• pp.549-554
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• 2008

Proton conducting crosslinked membranes were prepared using polymer blends of polystyrene-b-poly(hydroxyethyl acrylate)-b-poly(styrene sulfonic acid) (PS-b-PHEA-b-PSSA) and poly(vinyl alcohol) (PVA). PS-b-PHEA-b-PSSA triblock copolymer at 28:21:51 wt% was synthesized sequentially using atom transfer radical polymerization (ATRP). FT-IR spectroscopy showed that after thermal ($120^{\circ}C$, 2 h) and chemical (sulfosuccinic acid, SA) treatments of the membranes, the middle PHEA block of the triblock copolymer was crosslinked with PVA through an esterification reaction between the -OH group of the membrane and the -COOH group of SA. The ion exchange capacity (IEC) decreased from 1.56 to 0.61 meq/g with increasing amount of PVA. Therefore, the proton conductivity at room temperature decreased from 0.044 to 0.018 S/cm. However, the introduction of PVA resulted in a decrease in water uptake from 87.0 to 44.3%, providing good mechanical properties applicable to the membrane electrode assembly (MEA) of fuel cells. Transmission electron microscopy (TEM) showed that the membrane was microphase-separated with a nanometer range with good connectivity of the $SO_3H$ ionic aggregates. The power density of a single $H_2/O_2$ fuel cell system using the membrane with 50 wt% PVA was $230\;mW/cm^2$ at $70^{\circ}C$ with a relative humidity of 100%. Thermogravimetric analysis (TGA) also showed a decrease in the thermal stability of the membranes with increasing PVA concentration.

• Korean Journal of Agricultural Science
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• v.39 no.3
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• pp.395-405
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• 2012

Lipozyme TL IM-catalyzed esterification was carried out to produce functional hard fat (structured lipid, SL) using palm stearin (PS) and hydrolysate of pomegranate seed oil (HPSO) of 1:6 molar ratio. HPSO contained conjugated linolenic acid (CLnA, about 80%). The reaction was performed at non-solvent system and solvent (n-hexane) system using Lipozyme TL IM (10% of total substrates, w/w) for 12, 24, and 72 hr in a shaking water bath ($55^{\circ}C$ and 185 rpm), respectively. SL synthesized in non-solvent system (NH-SL) and SL synthesized in n-hexane system (H-SL) were refined after deacidification, respectively. Their physicochemical properties were compared to obtain desirable functional hard fat. The content of CLnA in NH-SL increased from 34.38% to 40.63% with increasing reaction time. Similar results also observed in H-SL resulting in 36.81~45.83% of CLnA. In triacylglycerol (TAG) composition, the main molecules of LnLnLn (Ln=linolenic acid, PN=36) and the LnLnP (P=palmitic acid, PN=40) were newly synthesized in NH-SL and H-SL with increasing reaction time. After 72 hr reaction, iodine values of NH-SL (136.49) and H-SL (140.37) showed high values because of the high content of CLnA. Solid fat index (SFI) in NH-SL was higher than that in H-SL at each measured temperature. The predominant polymorphic forms of NH-SL and H-SL obtained after esterification for 72 hr were the desirable crystalline structure of the ${\beta}$' form.

• Korean Chemical Engineering Research
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• v.51 no.5
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• pp.628-633
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• 2013

Carbon black was surface-modified to prepare styrene-based suspension polymerized toner with excellent carbon black dispersibility inside toner particles. Carbon black was oxidized first to introduce hydroxyl groups on the surfaces, then esterification between the hydroxyl groups and carboxyl groups of organic acids (oleic acid, palmitic acid, acrylic acid) was followed to obtain organically surface-modified carbon black. The surface-modification of carbon black was confirmed by FTIR. Apparent carbon black dispersibility in the monomer mixture of the binder resin was tested and the particle size of dispersed carbon black was measured by particle size analyzer. Optical micrographs showed that carbon black dispersibility inside toner particles was improved considerably when the carbon black surfacemodified with oleic acid was used. The polymerized toner prepared with the carbon black surface-modified with oleic acid showed ideal particle size and size distribution as a toner.