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Catalytic Applications of Zeolites in Industrial Processes
Published in Subhash Bhatia, Zeolite Catalysis: Principles and Applications, 2020
The largest petrochemical application of zeolites is in the ZSM-5-catalyzed xylene isomerization processes. The principal source of xylene is the product from catalytic reformers. The objective is to convert C8 aromatic streams which contain about 20% ethylbenzene, 20% o-xylene, 40% m-xylene, and 20% p-xylene from reformers or pyrolysis gasoline units to equilibrium mixtures of xylenes from which the most valuable product, p-xylene, can then be separated. Typically these C8 streams which contain 20% ethylbenzene are costly to be separated by distillation. In a conventional process scheme, p-xylene is removed either by low temperature crystallization or molecular sieve adsorption, e.g., UOP’s Parex process. To increase the yields of the more desirable p- and o-isomers, various isomerization processes have been designed.
Chemicals from Aromatic Hydrocarbons
Published in James G. Speight, Handbook of Petrochemical Processes, 2019
Of the xylenes, o-xylene is used to produce phthalic anhydride and other compounds. Another xylene, p-xylene is used in the production of polyesters in the form of terephthalic acid or its methyl ester (Figure 8.1). Terephthalic acid is produced from p-xylene by two reactions in four steps. The first of these is oxidation with oxygen at 190°C (375°F): CH3C6H4CH3+O2→HOOCC6H4CH3
Hydrocarbons as Fuels and Petrochemicals: Shaping the Past, Dominating the Present, Complicating the Future
Published in Richard J. Sundberg, The Chemical Century, 2017
Catalytic reforming also generated significant amounts of aromatic compounds (see Section 2.1.4). In the 1950s as the production of benzene from coal began to decrease, improved processes for isolation of benzene from petroleum were developed. Dow and UOP developed a process that involved preferential extraction into a glycol–water mixture. Later, sulfolane was used as the extraction solvent. With the introduction of polyesters derived from terephthalic acid, p-xylene (1,4-dimethylbenzene) became a valuable intermediate and was also isolated by selective extraction.
Analysis of Temperature Effect on the Gasoline Evaporation in Fire Investigation by HS-GC-MS
Published in Combustion Science and Technology, 2023
Marek Hodálik, Veronika Veľková, Danica Kačíková
Weathering (evaporation) is one of the most common processes affecting primarily liquid accelerants. Weathering consists in the faster evaporation of the most volatile compounds (Turner et al. 2018). The remaining most volatile compounds are then present at quantities below the limits of quantification (LOQ) of the analytical methods. As a result, the more stable heavier compounds evaporate slowly and are therefore present in relatively higher amounts (Aliaño-González et al. 2018). Weathering occurs at any temperature, from room temperature to temperatures exceeding 1000°C (flashover) (De Haan and Icove 2014; Willis et al. 2020). The lack of residual compounds in the samples due to weathering is reflected in the chromatograms, which differ from the chromatograms of the fresh samples, which are used as reference samples (Hondrogiannis, Newton, and Alibozek 2019; Monfreda and Gregori 2011). If the gasoline has been exposed to significant weathering, according to Baerncopf, McGruffin, and Smith (2011) the following compounds are most often missing on the chromatographs: ethylbenzene, m-xylene, p-xylene and o-xylene.
Insights into the potential mechanism underlying liver dysfunction in male albino rat exposed to gasoline fumes
Published in Egyptian Journal of Basic and Applied Sciences, 2021
Folarin Owagboriaye, Sulaimon Aina, Rasheed Oladunjoye, Titilola Salisu, Adedamola Adenekan, Gabriel Dedeke
A total of 23 hydrocarbon components were detected in the gasoline used for this study (Supplementary Table S1). Toluene has the highest percentage composition in the gasoline sample. This was followed by o-xylene, naphthalene, undecane, ethylbenzene and p-Xylene. A total of seventeen (17) hydrocarbon components, including gasoline metabolites, were detected in the liver of the experimental rats (Table 3). Benzene was detected in the liver of rats in all the groups. However, benzene level was significantly reduced in group I. Paracyclophane and ethylbenzene were only detected in the liver of rats in group III. Similarly, 4,7-Methano-1 H-indene, Azulene, Cyclobutane, 3-Phenylthiane, Quinoline and 1-benzylindole were only detected in the liver of rats in group V.
Emission of volatile organic compounds from new furniture products and its impact on human health
Published in Human and Ecological Risk Assessment: An International Journal, 2019
Meihong Yan, Yunbo Zhai, Pengtu Shi, Yanjun Hu, Haijian Yang, Hongjie Zhao
A standard solution that contained nine VOCs (benzene, toluene, ethylbenzene, m-xylene, p-xylene, o-xylene, n-undecane, styrene, and n-butyl acetate) was used to carry out the quantitative analysis. Four to six point calibrations were carried out by injection of 1–50 μl standard solution in methanol (100 μg/ml) to clean Tenax-TA tubes, which were purged with 100 ml/min nitrogen for 5 min. Then the tubes were analyzed by GC and the calibration curves for nine substances were obtained (R2 > 0.997). The recovery ratios of these nine compounds that were analyzed were 94%–109%. The samples were thermal desorbed into the GC (FID) for VOCs identification and quantization based on retention time and peak area of the corresponding calibration curve. A DB-WAX capillary column (30 m × 0.25 mm × 0.25 μm) was used for the separation of VOCs. The GC temperature program was initially set at 60°C for 6 min, and then increased to 150°C at 30°C/min to be maintained for 2 min, after then by 30°C/min up to 180°C, which was held for 3 min. The sum of the concentration of the nine target VOCs was defined as 9VOC. Duplicate analysis was performed, the relative standard deviation of nine VOCs was less than 7% and the precision was good (relative error <3.92%).