Search

Abstract: The pyrolysis behavior of polyvinyl chloride (PVC) in the presence of commercially available oxides catalysts was investigated using thermogravimetry. The pyrolysis proceeded under a heating rate of 5°C/min in the temperature range of 200–650°C. The thermogravimetric properties in terms of reduction in maximum degradation temperature and percent conversion were studied. The silica gel mesoporous catalyst, with a greater pore size and surface area, was found to be the most active materials in terms of reduction in maximum degradation temperature and increase in percent conversion. The alumina acidic, silica ppt, and alumina neutral catalysts also showed good results; however, their effects were less pronounced as compared to silica gel. The effects of these different catalysts show that surface area, pore size, and number of acidic sites are found to be the major factors for the energy efficient degradation of polymers. [ABSTRACT FROM AUTHOR]

Abstract: The thermal degradation kinetics of powder isotactic polypropylene was investigated in a thermobalance system, at non‐isothermal heating conditions with heating rate of 5, 10, 15, and 20°C min−1 in the temperature range of 30–600°C under nitrogen atmosphere. The apparent activation energy (Ea) was determined using Ozawa–Flynn–Wall, Tang Wanjun, and Coats–Redfern (modified) methods. The apparent activation energies range from 61.3 to 110.9 kJ mol−1. Increasing the heating rate shifted the Tmax to a higher level. The lower activation energy observed indicates the breakage of the bonds at weak links. Moreover, the values of activation energy are significantly controlled by the heating rate, level of conversion, and calculation technique. A comparison among the different techniques has been made on the basis of the apparent activation energy from the TG data. The activation energies determined by all the three methods are in good agreement with each other. Furthermore, the pyrolysis of model polypropylene was carried out over the temperature range 350–415°C in a salt bath using Pyrex reaction vessel. The gaseous fraction produced was collected in gas sampling bag and monitored gas chromatographically. The major hydrocarbons detected were methane, propylene, propane, 2‐methylpentane, 2,4 dimethylpentane, and 2,4 dimethylheptane. [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO2) films with dominant {001} facets coated on a titanium sheet (Ti) were synthesized with the simple hydrothermal method by using Ti as the precursor and substrate. The effect of addition of isopropanol into the hydrothermal solution on the structure, photocatalytic activity, and stability of as-synthesized TiO2 films was investigated. The presence of isopropanol obviously influenced the microstructure of as-synthesized TiO2 films, which was converted from microspheres into irregular close stack of truncated tetrahedrons. And the percentage of exposed {001} facets calculated from the Raman spectra increased from 48.2% to 57%. Accordingly, the TiO2 films prepared with addition of isopropanol showed high and stable photocatalytic activity, which is nearly 2.6 times as that of the conventional P25 TiO2 coated on Ti-substrate. In addition, the photocatalytic activity of as-synthesized TiO2 films was greatly enhanced after calcination treatment at 600°C, which can be attributed to removal of fluoride ions and organic residuals adsorbed on the surface of the catalyst. Photoluminescence (PL) technique was used for the detection of produced hydroxyl radicals COH) on the surface of UV-illuminated TiO2 using terephthalic acid as probe molecule. The photocatalytic degradation intermediates of bezafibrate were analyzed by an ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), and accordingly the degradation pathways were proposed. [ABSTRACT FROM AUTHOR]