The catalytic naphtha reforming is one of the largest processes of petroleum industry that is used to rebuild the low-octane hydrocarbons in the naphtha to more valuable high-octane gasoline called reformate without changing the boiling point range. An atmospheric pressure pin to plate dielectric barrier discharge (DBD) plasma was used to remove carbonaceous contaminant from the coked Pt-Sn/Al 2 O 3 catalysts during the naphtha reforming process. The effects of treatment time and flow ratios of O 2 /Ar and O 2 / He on the carbon content of the coked catalysts were investigated. The produced radicals and active species of the plasma process were identified by optical emission spectroscopy. To confirm removing the coke from the catalyst, thermal gravimetric/differential thermal analysis and temperature programmed oxidation analysis were done. Effects of treatment time and flow ratios of O 2 /Ar and O 2 /He on the carbon content of the coked catalysts were investigated by applying elemental analysis. The results of X-ray diffraction, X-ray fluorescence, Brunauer-Emmett-Teller, and CO adsorption showed that the structure and specifications of regenerated catalysts remained without significant changes during the plasma treating. The catalyst performance test revealed that DBD plasma regenerated catalysts increased the aromatic content of the feed as well as the fresh catalysts. The results showed that the plasma treatment method for regeneration of Pt-Sn/Al 2 O 3 can be applied at lower temperature and pressure relative to the thermal regeneration method.
In this study, magnetic metal-organic framework composite (Fe 3 O 4 @ TMU-12) was fabricated and used as an efficient sorbent for magnetic solid-phase extraction of the diazinon and chlorpyrifos from environmental water samples. By simultaneous use of magnetic solid-phase extraction and high-performance liquid chromatography, a simple, quick, exact, and affordable method for the determination of diazinon and chlorpyrifos was achieved. The extraction conditions and efficiency of the magnetic framework composite for diazinon and chlorpyrifos were investigated. Under optimal conditions, the relative recoveries and preconcentration factors of the studied compounds were obtained in the range of 92.0%-99.3% and 201-210, respectively. The calibration curves were obtained in the range of 2-250 μg L À1 and 4-250 μg L À1 for diazinon and chlorpyrifos in water samples, respectively. The LODs were 0.5 and 0.8 μg L À1 for diazinon and chlorpyrifos, respectively (based on S/N = 3). The precision evaluated in terms of the relative standard deviations of intra-and inter-day tests ranged from 3.4% to 3.8% and from 3.9% to 4.1%, respectively. The results show that the Fe 3 O 4 @TMU-12 combine advantages of magnetic nanoparticles and metal-organic frameworks, and are the promising sorbents in the magnetic solid-phase extraction of diazinon and chlorpyrifos from environmental water samples.
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