• Resources Recycling
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• v.17 no.6
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• pp.50-56
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• 2008

A polypropylene fraction collected from the stream of post-consumer plastics was pyrolyzed. The aim of this study is to observe the dependence of yield of BTEX-aromatics normally used as solvent on the reaction temperature. To reach the goal, three experiments were carried out at different temperature between 650 and $700^{\circ}C$, using a fluidized bed reactor that shows an excellent heat transfer. In the experiments, product gases were used as a fluidizing medium to maximize the amount of BTEX-aromatics at fixed flow rate and feed rate during the pyrolysis. Oil, gas and char were obtained as product fractions. Product gases were analyzed with GCs(TCD, FID) and with a GC-MS system for qualitative analysis. For an accurate analysis of product oil, the product oil was distilled under vacuum, and separated the distillation residues from oil fractions that were actually analyzed with a GC-MS system. As the reaction temperature went higher, the content of BTEX-aromatics increased. The maximal yield of BTEX-aromatics was obtained at $695^{\circ}C$ with a value of about 30%. The main compounds of product gas were $CH_4$, $C_2H_4$, $C_2H_6$, $C_3H_6$, $C_4H_{10}$ and the product gas had an higher heating value about 45MJ/kg. It could be used as a heat source for a pyrolysis plant or for other fuel applications.

• Applied Chemistry for Engineering
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• v.34 no.1
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• pp.15-22
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• 2023

Recent studies have actively investigated ways to improve the economic feasibility and efficiency of the Fischer-Tropsch process by increasing the yields of the monocyclic aromatic compounds (BTEX). In this study, ethylene was selected as a model of F-T-derived hydrocarbons, and the ethylene-to-aromatics (ETA) reaction was investigated according to changes in acid characteristics, mesopores, and crystallinity of HZSM-5 (HZ5). Fluorinated HZ5 was prepared by calcination followed by impregnation of an aqueous NH₄F solution having different molar concentrations in HZ5, and the structural and chemical properties of F/HZ5 were investigated through Brunauer-Emmett-Teller (BET), solid-state nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), NH₃-temperature-programmed desorption (TPD), and pyridine-IR spectroscopy. The ETA reactions were performed at 673 K under 0.1 MPa, and fluorinating HZ5 by an aqueous NH₄F solution of 0.17 M improved ethylene conversion, BTEX selectivity, and catalytic stability due to acidity, mesopore fraction, and crystallinity.

• Environmental Analysis Health and Toxicology
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• v.17 no.2
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• pp.95-107
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• 2002

This study was designed to investigate the characteristics of atmospheric concentrations of toxic volatile organic compounds (VOCs) in Korea. Target compounds included 1,3-butadiene, aromatics such as BTEX, and a number of carbonyl compounds. In this paper, as the first part of the study, the performance of sampling and analytical methods was evaluated for the measurement of selected VOCs and carbonyl compounds in the ambient air. VOCs were determined by the adsorbent tube sampling and automatic thermal desorption coupled with GC/MSD analysis, while carbonyls by the DNPH-silica cartridge sampling with HPLC analysis. The methodology was investigated with a wide range of performance criteria such as repeatability, linearity. lower detection limits, collection efficiency, thermal conditioning, breakthrough volume and calibration methods using internal standards. In addition, the sampling and analytical methods established in this study were applied to real field samples duplicately collected in various ambient environments. Precisions for the duplicate samples appeared to be comparable with the performance criteria recommended by USEPA TO-17. The overall precision of the sampling and analytical methods was estimated to be within 20 ∼ 30% for major aromatic VOCs such as BTEX, whereas the precision for major carbonyl compounds such as formaldehyde and acetaldehyde was within 10 ∼ 20% for field samples. This study demonstrated that the adsorbent sampling and thermal desorption method can be reliably applied for the measurement of BTEX in ppb levels frequently occurred in common indoor and ambient environments.

• Environmental Analysis Health and Toxicology
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• v.17 no.3
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• pp.207-217
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• 2002

This study was designed to investigate the characteristics of atmospheric concentrations of toxic volatile organic compounds (VOCs) in Korea. Target compounds included 1,3-butadiene, aromatics such as BTEX, and a number of carbonyl compounds. In this paper, as the second part of the study, the seasonal and locational concentrations of atmospheric VOCs were evaluated. Sampling was conducted seasonally at seven sampling sites. each of them representing a large urban area (commercial and residential), a small urban area (commercial and residential), an industrial area (a site within the complex and a residential), and a background place in Korea. In general, higher concentrations were found in the petro-chemical industrial site than other sites, while VOCs measured in commercial (heavy -traffic) sites were higher than residential sites. Seasonality of VOCs concentrations were not so much clear as other combustion related pollutants such as sulfur dioxide, indicating that the VOCs are emitted from a variety of sources, not only vehicle exhaust and point sources but fugitive emissions. Except the industrial site, the concentrations of VOCs measured in this study do not reveal any serious pollution status, since the levels did not exceed any existing ambient standards in the U.K. and/or Japan. However, the increasing number of petrol -powered vehicles and the rapid industrialization in Korea may result in the increased levels of VOCs concentrations in many large urban areas in the near future, if there is no appropriate programme implemented for the control of these compounds.

• Journal of Korean Society for Atmospheric Environment
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• v.30 no.5
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• pp.477-491
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• 2014

This study was carried out to evaluate the concentration variations of volatile organic compounds (VOCs) in the office environments located in a large urban area with respect to seasonality, smoking status, types of ventilation and heating. Indoor air sampling was undertaken in 37 and 30 offices in Daegu city during summer and winter, respectively. The VOC samples were collected using adsorbent tubes, and were determined by thermal desorption coupled with GC/MS analysis. The analytical method was validated for repeatability, method detection limits (MDL), and duplication precision. A total of 34 VOCs of environmental concern were determined, including 15 aromatics and 19 halogenated hydrocarbons. Average concentrations of BTEX appeared to 1.91 ppb, 22.98 ppb, 3.44 ppb, and 3.70 ppb, respectively. These values were relatively higher levels than those measured at homes and outdoor roadsides reported by other researches. In general, the concentrations of VOCs were higher in winter than summer, in smoking offices than non-smoking offices, in forced ventilation type than natural ventilation type, and in combustion heating than non-combustion heating offices. However, such differences were not always significant at a level of 0.05 by statistical tests (t-test and/or Mann-Whitney test) with some exceptions for BTEX and styrene. This study demonstrated that smoking status, ventilation type and presence of combustion sources indoors could be important factors on the elevated concentrations of some VOCs in the office environment.

• Journal of Korean Society for Atmospheric Environment
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• v.34 no.2
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• pp.244-258
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• 2018

We performed this study to investigate the spatial, seasonal, and daily variations of the concentrations of volatile organic compounds (VOCs) in Pohang, where large steel industrial complexes are located. Ambient air sampling was undertaken at 4 sites during 4 seasons. Each sample was taken for 4 hours continuously for 8 consecutive days per season at each site. Three sites were located within the Pohang city, but one as a control site in Gyeongju. A total of 72 individual VOCs were determined by thermal desorption coupled with GC/MS, including aliphatics, aromatics, carbonyls and halides. The most abundant VOC was toluene, being followed by ethylbenzene and xylenes. Benzene concentrations(c.a. 0.7 ppb) were found to be much lower than the national ambient standard of 1.5 ppb. Overall, the VOCs levels in Pohang appeared to be lower than other national industrial complexes in Korea such as Shiwha-Banwol, Yeosu-Gwangyang, Gumi, and Ulsan. This implies that steel industry may not give significant impacts on the atmospheric levels of VOCs as much as petrochemical, electronic, and/or textile industries, where large amounts of organic solvents are used.