Search

The degradation of poly(ethylene terephthalate) (PET) was successfully achieved using ionic liquids. The products were separated according to their solubilities in boiling water. Average molecular weights of the main product were determined by gel permeation chromatography (GPC). The physicochemical properties of the product have been characterized by scanning electron microscopy equipped with an energy dispersive X-ray analyzer (SEM/EDX), X-ray diffractometer, infrared spectrometric analyzer, differential scanning calorimeter, and thermogravimetric analysis instrument. The influences of experimental parameters, such as the reaction time, reaction temperature, and addition of different catalysts on the solubility of PET were investigated. A study on the recycling of the ionic liquid shows that ionic liquid could be used repeatedly. Moreover, the solubility of PET in the recycled ionic liquid is higher than that in fresh ionic liquid. Further study shows that the increase of solubility in the recycled ionic liquid is attributable to the presence of a minor amount of water. A mechanism of the degradation of PET in 1-butyl-3-methylimidazolium chloride ([bmim]Cl) was proposed. In addition, the kinetics of this reaction was investigated. Results show that this degradation process is a first-order kinetic reaction and the activation energy is 232.79 kJ mol−1. [ABSTRACT FROM AUTHOR]

A series of carbon-based materials were illustrated to be efficient additives to improve the product distribution of isobutane/butene alkylation catalyzed by H2SO4. Among the tested materials, graphene oxide (GO) was shown to be the most efficient additive. With the presence of trace amounts (e.g., 0.1 wt %) of GO sheet, the weight percentage of C8 in the product could increase by ~11% and research octane number (RON) of the alkylate was enhanced by ~2. The presence of GO in H2SO4 led to no obvious change of the acidity. The improved product distribution could be attributed to the enhanced emulsification and better dispersion of the reactants in the acid. The lifetime of the catalytic system was extended from 110 times (with no additive) to 140 times, as the formation of acid soluble oil was inhibited when the additive was present. This efficient and environmentally benign emulsifier could be a particularly promising additive for the current alkylation process catalyzed by H2SO4. [ABSTRACT FROM AUTHOR]

The metal ion effect on the bulk VPO was investigated using the aldol condensation of methyl acetate and formaldehyde to methyl acrylate. The VPO catalyst with 2 mol % Zr exhibited the highest methyl acrylate formation rate of 18.6 μmol·g-1·min-1. A combination of X-ray diffraction, BET, TPD, XPS, and EPR, together with activity testing data, was utilized to analyze and explain the origin of the metal ion effects. The promotion of methyl acrylate production by the intercalation of Zr was associated with its interaction with the VPO phase. When Zr concentration attained 2 mol %, the Zr4+ ion was distributed in the surface adjacent layers and partially incorporated into VPO species, giving rise to a higher fraction of the β-VOPO4 entity and a relatively higher amount of the badly distorted (VO)2P2O7 entity. These findings suggested that both β-VOPO4 and distorted (VO)2P2O7 phases were required for the formation of methyl acrylate. [ABSTRACT FROM AUTHOR]

A new route to synthesizing acrylicacid from acetic acid and formalinby one-step aldol condensation reaction was proposed and developed.V–P/SiO2oxide bifunctional catalysts were designedand prepared by ultrasonic impregnation method. The catalysts werecharacterized by XRD, BET, TEM, TG/DTA, and XPS, as well as NH3- and CO2-TPD and pyridine-FTIR methods. Catalyticperformance was evaluated using a fixed-bed tubular microreactor operatingwith a CH3COOH/HCHO (HAc/FA) molar ratio of 10 under atmosphericpressure. Influences of the balance between acidic and alkaline sites,as well as ratio of V4+and V5+, on catalystactivity were further studied. Reaction parameters were systemicallyoptimized. Through a series of comparisons, V–P/SiO2binary oxide catalyst with a bulk density ratio of 1:2 was selected. [ABSTRACT FROM AUTHOR]

A new process for fuels hydrodesulfurization (HDS) utilizing solid catalyst coupled with ionic liquids (ILs) at mild operating conditions is proposed in this study. A novel Ce-Ni-Mo/γ-Al2O3 catalyst with high catalytic activity was developed and coupled with different ILs i.e. (1-Butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4), 1-butyl-2,3-dimethylimidazolium tetrafluoroborate ([BDMIM]BF4), 1-ethyl-3-methyl imidazolium tetrafluoroborate ([EMIM]BF4), and 1-butyl-3-methylimidazolium chloride salt ([BMIM]Cl)) to investigate the removal of Sulfur (S) from dibenzothiophene (DBT) used as model oil. Then the highly efficient IL [BMIM]BF4, coupled with the solid catalyst was selected to undergo a series of parallel experiments to investigate the effects of temperature, hydrogen pressure and IL/oil mass ratio toward S removal. Moreover, the IL system could be recycled four times without a significant decrease in desulfurization activity. The supposed mechanism of HDS reaction was also explained. This study can be deemed as new approach for getting cleaner fuels based on the complementary usage of ILs with solid catalysts at mild operating conditions. [ABSTRACT FROM AUTHOR]

With the dramatic increasing of economy, the conflict between the lack of petroleum resource and sharply increasing demand for gasoline and diesel has restricted the continuous development of economy and energy of our world. The catalytic conversion of C9 aromatics into clean fuel was studied in our laboratory using hydrotreating catalysts which were prepared by new synthesis technologies that combine vacuum-impregnation and temperatureprogrammed calcinations. Characterization results indicate that these catalysts have a high surface area, and the activity sites dispersed well on the supporter. Hydrogenation performance of reaction conditions was carried out in two-stage fixed beds. Products of gasoline (<180℃) and diesel (180-360℃) fractions were separated from intermediate products via distillation, and the analysis results demonstrate that S/N content, density, and viscosity decreased. However, the H/C molar ratio increased. The main reactions of isomerization, disproportionation, and dealkylation occurred during the conversion of C9 aromatics and the activity order accorded the mechanism of carbenium ion reaction. This study indicates that C9 aromatics could be considerably upgraded through catalytic hydroprocessing to highquality fuel in the presence of high-performance catalysts and appropriate reaction conditions. Thus, they are promising catalytic technologies and materials. Furthermore, the products could substitute gasoline and diesel partly. [ABSTRACT FROM AUTHOR]

Poly(ethylene terephthalate) (PET) is widely used for beverage bottles, electrical and electronic instruments, household wares, and so on. As a consequence of dramatically increasing consumption, recycling of post-consumer PET products has become an important environmental opportunity for sustainable usage in society. In this paper, we investigated the use of chlorine-free metallic acetate ionic liquids (ILs) as catalysts for the degradation of PET because of their lower toxicity, corrosivity, and cost. 1,3-Diethylimidazolium triaceticzincate ([deim][Zn(OAc)3]) behaved as the best in this group. The synthesized ILs and the major product, characterized by a variety of techniques and factors affecting glycolysis, were examined. Under optimum conditions, conversion of PET reached 98.05 %, and the selectivity of the bis(hydroxyethyl) terephthalate (BHET) monomer was 70.94 %. A probable mechanism for the glycolysis of PET catalyzed by [deim][Zn(OAc)3] was given. In our opinion, catalysis accounted for the synergic effect of the cation and anion of the IL. [ABSTRACT FROM AUTHOR]

The effectiveness of several zeolite catalysts was investigated using the cataluminescence (CTL) gas sensor system. Trace amounts of n-hexane in air samples were detected by this method. This research establishes that the specific pore size of the zeolite offers designable environment for selective CTL reaction, and "Lewis-type" basic sites appear to contribute to the catalytic nature of the zeolite surface. By incorporating either Cs+ or K+, the velocity and luminescence intensity of these catalytic reactions increase while going from Na to Cs, according to the basic nature of this group of cations in the following order: Cs > K > Na. The proposed sensor shows high sensitivity and selectivity to n-hexane at a mild reaction temperature of 225°C. Quantitative analysis was performed at a selected wavelength of 460 nm. The linear range of CTL intensity versus concentration of n-hexane was 0.776-23.28 μg/mL (R = 0.997, n = 7) on CsNaY, and 0.776-23.28 μg/mL (R = 0.998, n = 7) on CsNaX, with a detection limit of 0.155 μg/mL (signal-to-noise ratio 3). Interferences from foreign substances such as methanol, ethanol, 2-propanol, acetone, acetonitrile, chloroform, or dichlormethane and other alkanes, aromatics, and alkyl aromatics such as methane, n-pentane, 3 methylpentane, 3,3-dimethylpentane, methylbenzene, ethylbenzene, and sec-butylbenzene were very low or not detectable. Results of a series of GC and GC/MS experiments suggest that the possible mechanism of the reaction is the formation of an unstable transition structure with a four-member ring, and this ring most probably consists of an oxygen atom and a carbonium ion localized on the zeolite suface. [ABSTRACT FROM AUTHOR]

Selective and sensitive determination of nitrite is of great importance in practical application. In the present work, a novel nitrite sensing platform was built based on the fabrication of nitrogen-doped-carbon-coated hexagonal cobalt oxyhydroxide (CN@CoOOH) on reduced graphene oxide (RGO) using zeolitic imidazolate framework (ZIF)-67 as a precursor. The CN@CoOOH/RGO nanocomposite was confirmed by UV–visible spectroscopy, Fourier transform infrared spectroscopy, x-ray photoelectron spectrum, transmission electron microscopy, scanning electron microscopy, and x-ray diffraction. We applied the nanocomposite to detect nitrite selectively and sensitively through amperometry for the first time. The anodic current values increased with the addition of nitrite. Therefore, the concentrations of nitrite were quantitatively detected using a CN@CoOOH/RGO based sensor. A wider linear range of 0.1 to 7000 μM was obtained with a lower detection limit of 10 nM (S/N = 3). The proposed method was also applied to detect nitrite released from normal liver cells and human hepatoma cells. [ABSTRACT FROM AUTHOR]