• Applied Chemistry for Engineering
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• v.2 no.3
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• pp.253-261
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• 1991

Polyamic acids, precursor polymers of polyimides have been obtained by the solution polycondensation of benzophenone tetracarboxylic dianhydride (BTDA) with 4, 4'-diamino diphenyl methane (MDA) and/or 3, 3'-dimethyl benzidine (OTB). The reaction was carried in two solvent systems such as m-cresol and m-cresol/xylene mixture. The results of TGA analysis showed that the polyimide films had good thermal stability with the initial decomposition temperature ranging from $540^{\circ}$ to $590^{\circ}$. According to DSC analysis of polymers, the glass transition temperature was over $340^{\circ}$. Polyimide film samples, showed good mechanical and electrical properties, had over $16Kg/mm^2$ of tensile strength and about 200 KV/mm of dielectric breakdown voltage. The properties of the copolymer from MAD/OTB were better than those of the homopolymer from MDA. And the polymer synthesized in m-cresol had lower properties than that obtained in m-cresol/xylene.

• Analytical Science and Technology
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• v.24 no.2
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• pp.119-126
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• 2011

Abstract: The amount of benzene, toluene, ethylbenzene, and o-xylene (BTEX) in 30 kinds of bottled waters purchased from market and 9 kinds of tap waters from home were determined using headspace solid phase microextraction (HS-SPME). The sample was stirred at 1200 RPM G for 4 min using a magnetic bar with $100\;{\mu}m$ PDMS as adsorbent for BTEX. Then it was desorbed from the fiber for 1 min at room temperature. Quantitation was achieved using standard calibration method. The limit of detection was determined as benzene 0.39 (${\pm}0.04$) ng/mL, toluene 0.08 (${\pm}0.04$) ng/mL, ethylbenzene 0.04 (${\pm}0.01$) ng/mL, and o-xylene 0.05 (${\pm}0.02$) ng/mL. Benzene and o-xylene were not detected in any samples, but toluene was detected in 11 samples, and ethylbenzene was detected just in 3 samples among 30 investigated bottled waters. The concentration range of investigated materials for toluene and o-xylene were $0.24({\pm}0.09)\sim2.95\;({\pm}0.08)\;ng/mL$, $0.08({\pm}0.06)\sim0.93({\pm}0.10)\;ng/mL$, respectively.

• Applied Chemistry for Engineering
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• v.21 no.4
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• pp.417-423
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• 2010

In this study, an effective method to prepare granular binderless ZSM-5 which is as efficient p-xylene separatory adsorbent was explored. Colloidal silica sol 30 wt% solution as an inorganic binder and microcrystalline cellulose as an organic additive were added to ZSM-5 powder ($SiO_2/Al_2O_3$ = 50). Adsorbent with enough strength (0.721 kgf), high crystallinity (94.6%) and high BET specific surface area ($379.2m^2$/g) was obtained by calcination, binderless treatment, ${NH_4}^+$ ion exchange, and activation after spherical granulation process. A batch type adsorption experiment was proceeded with solutions comprising 3 xylene isomers by 1 : 1 : 1 weight ratio to evaluate adsorption characteristics of prepared absorbent. As a result, the obtained binderless ZSM-5 granule showed a higher selective adsorption performance for para-xylene than that of commercial adsorbent.

• Journal of the Korean Chemical Society
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• v.25 no.1
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• pp.26-29
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• 1981

Reactions of m-xylene were studied in a fixed-bed type micropulse reactor over cation-exchanged dealuminated mordenite and zeolite Y catalysts. Over H-mordenite catalysts higher catalyst pretreatment temperature as well as dealumination resulted in the increase of the formation of disproportionation product. $Ba^{2+}- and Mg^{2+}-$exchanged mordenite catalysts showed the shape selectivity in the disproportionation reaction of m-xylene, that is, the formation of trimethylbenzene decreasing sharply as the degree of cation exchange increased.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.1
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• pp.79-84
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• 2008

This paper describes the application of bioluminescence stimulating agents on a genetically engineered microorganism, Pseudomonas putida mt-2 KG1206, to monitor toluene analogs using in groundwater samples from petroleum hydrocarbon contaminated sites. The maximum bioluminescent response with pure chemicals followed in the order: m-methyl benzyl alchohol > m-toluate > toluene > m-xylene > benzoate > p-xylene > o-xylene. Generally, the bioluminescence production of strain mixed with groundwater samples was dependent on the contaminated total inducer concentrations. However, few samples showed opposite results, where these phenomena may be caused by the complexicity of environmental samples. Two chemicals, SL(sodium lactate) and KNO$_3$, were tested to determine a better bioluminescence stimulant. Both chemicals stimulate the bioluminescence activity of strain KG1206, however, a slightly high bioluminescence was observed with nitrogen chemical. This selected stimulant was then tested on samples collected from contaminated groundwater samples. The bioluminescence activity of all samples mixed with the strain was stimulated with KNO$_3$ amendment. This suggests that the low bioluminescence activity exhibited by the environmental groundwater samples can be stimulated by amending the culture with a proper agent, such as nitrogen compound. These findings would be useful, especially, when strain was used to monitor the groundwater samples contaminated with low inducer contaminants. Overall, the results of this study found the ability of bioluminescence producing bacteria to biosensor a specific group of environmental contaminants, and suggest the potential for more efficient preliminary application of this engineered strain in a field-ready bioassay.

• Journal of Preventive Medicine and Public Health
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• v.14 no.1
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• pp.97-110
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• 1981

This study was conducted in order to investigate the status of harmful working environ ment on twelve rubber and ten chemical products manufacturing industries in Busan area over a period of five months from lune 1 to October 31, 1980. The summarized results were as follows: 1. The highest and lowest mean values of harmful environmental elements in workroom of rubber products manufacturing industries were noted in twisting (98.7dB) and coating department (77.3dB) to noise, molding ($6.43mg/m^3$) and forming ($1.33mg/m^3$) to dust, bonding (toluene 463.7ppm, xylene 457.8ppm and benzene 111.8ppm, respectively) and splicing (toluene 90.0ppm, xylene 83.3ppm and benzene 6.7ppm, respectively) to organic solvents, respectively. Also in chemical products manufacturing, they were noted in grinding (95.1dB) and shining department (76.8dB) to noise, packing ($4.30mg/m^3$) and staining ($3.20mg/m^3$) to dust, shining (393.3ppm and 375.0ppm, respectively) and varnishing(125.5ppm and 121.7ppm, respectively) to toluene and xylene, and scattering (51.8ppm) and mixing (23.9ppm) to benzene, respectively. 2. The mean values of harmful elements in workroom of rubber products manufacturing were 86.3dB to noise, $4.16mg/m^3$ to dust, 258.2ppm to toluene, 230.3ppm to xylene, and 5 4.0ppm to benzene, respectively. Also in chemical products manufacturing, they were 85.2dB to noise, $3.69mg/m^3$ to dust, 227.9ppm to toluene, 213.2ppm to xylene, and 36.3ppm to benzene, respectively. 3. Number of workers exposed to harmful working environment, over TLV, of a total 10,195 workers in rubber products manufacturing were 1,002(9.8%) to noise, 212 (2.1%) to dust, 1,581(15.5%) to toluene, 1,509(14,8%) to xylene, and 1,524(15.0%) to benzene, respectively. Number of workers exposed to harmful working environment, over TLV, of a 1,913 workers in chemical products manufacturing were 112(5.9%) to noise, 132(6.9%) to each organic solvent, respectively. 4. The values of noise and dust of rubber and chemical products manufacturing in 1980 were lower then those in 1977, but the value of organic solvent in 1980 was similar with that in 1977.

• Journal of the Korean Institute of Gas
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• v.18 no.6
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• pp.1-6
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• 2014

This study is based on a investigation regarding the evaporation rate of a volatile liquid(methanol, tetrahydrofuran, xylene) according to changes of the temperature and wind. The weight of a volatile liquid was standardized to 24 g and the mixture was formed with the same weight ratio. In order to discover about the effect of the wind velocity, small fan was installed at 10 cm above the entrance and 30 cm away in the direction of the cylinder. The effect of the wind velocity was tested at 0 m/s, 1.63 m/s, 2.03 m/s respectively and the effect of the temperature on the volatile liquid was experimented at the temperature of $21^{\circ}C$, $32^{\circ}C$, $52^{\circ}C$ in the constant temperature water base. As a result, in case of Xylene, the evaporation rate of the tetrahydrofuran and methanol showed 1.4 mg/min, 19.8 mg/min and 10.2 mg/min respectively. Also, the effect of the evaporation rate on the temperature of the volatile liquid and on the velocity of wind was shown to be very sensitive. At the same time, the evaporation rate of the mixture showed large difference compared to that of the single volatile liquid.

• Bulletin of the Korean Chemical Society
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• v.24 no.10
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• pp.1495-1500
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• 2003

Equilibria and applications of a synergistic extraction were studied for the determination of a trace lithium by using thenoyltrifluoroacetone (TTA) and trioctylphosphine oxide (TOPO) as ligands. Several equations were derived for the extraction of lithium into m-xylene as a phase of Li-TTA·mTOPO adduct. Distribution coefficients and extraction constant were determined together with a stability constant of the adduct. The adduct was quantitatively extracted from the basic solution of higher than pH 9 by shaking for 30 minutes. m-Xylene was selected as an optimum solvent by comparing the extraction efficiency among several kinds of organic solvents. The stability constant (${\Beta}_2$) for Li-TTA/2TOPO was 150 times higher than Li-TTA/TOPO. The distribution coefficient of Li-TTA/2TOPO into m-xylene was 9.12 and the logarithmic extraction constant (log $K_{ex}$) was 6.76. Trace lithium of sub-ppm level in seawater samples could be determined under modified conditions and a detection limit equivalent to 3 times standard deviation for background absorption was 0.42 ng/mL.

• Journal of Korean Society for Atmospheric Environment
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• v.19 no.5
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• pp.491-502
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• 2003

In the present work, the distribution characteristics of ambient volatile organic compounds (VOCs) were investigated at high temporal resolution from a monitoring station located in a mid-eastern area of Seoul. A total number of 587 samples were collected during December 2002 to January 2003. The measurements of VOC were conducted by a combination of on-line air sampling and thermal desorption unit (TDU) coupled with capillary GC/FID analysis. A total of five aromatic compounds (BTEX: benzene, toluene, ethylbenzene, m, p-xylene, and o-xylene) were measured routinely at hourly intervals during the whole study period. The mean concentrations of BTEX measured in our study period were found in the order: toluene (8.99 $\pm$5.38 ppb) > benzene (0.92$\pm$0.52 ppb) > m, p-xylene (0.51$\pm$0.34 ppb) > 0- xylene (0.48$\pm$0.35 ppb) > ethyl benzene (0.43$\pm$ 0.32 ppb). The BTEX concentrations were generally higher during the daytime than the nighttime, exhibiting certain patterns on a weekly basis. Results of our analysis indicate that the unusually high concentrations of toluene, while showing good correlations with other VOCs, can be a good indicator of air pollution in the study area.

• Korean Chemical Engineering Research
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• v.58 no.4
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• pp.658-664
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• 2020

Zeolite HY is wet impregnated with Ni (0.1, 0.3, 0.4, 0.5 wt%), Pt (0.1 wt%) and reduced in presence of hydrogen to form nanosized particles of Ni and Pt. All the catalysts were characterized by XRD, TEM, ESCA, NH₃-TPD, Pyridine adsorbed FT-IR and BET. Characterization results confirm that the Ni and Pt fractions effectively rehabilitated the physio-chemical properties of the zeolite HY catalysts. Further, all the reduced catalyst were screened with hydroisomerization of m-xylene at LHSV = 2.0 h^-1 in the temperature range 250-400 ℃ in steps of 50 ℃ in hydrogen atmosphere (20 ml/g). The addition of Ni to Pt catalyst increases hydroisomerization conversion, as well as maximizes p-xylene selectivity by restricting the pore size. The increasing trend in activity continues up to 0.3 wt% of Ni and 0.1 wt% Pt addition over zeolite HY. The increasing addition of Ni increases the total number of active metallic sites to exposed, which increases the metallic sites/acid sites ratio towards the optimum value for these reactions by better balance of synergic effect for stable activity. The rate of deactivation is pronounced on monometallic catalysts. The results confirm the threshold Ni addition is highly suitable for hydroisomerization reaction for product selectivity over Ni-Pt bimetallic/support catalysts.