a b s t r a c t a r t i c l e i n f oIn the US, biodiesel producers usually follow the 19.8:1 methanol-to-FFA molar ratio for free fatty acid (FFA) esterification, as suggested by the National Renewable Energy Laboratory (NREL) without optimization studies. In this paper, both laboratory studies and industrial practices of the esterification process were compared, and an optimization study of a used vegetable oil with 5% FFA was conducted. The optimal conditions of this oil, i.e., methanol-to-FFA molar ratio of 40:1, and sulfuric acid usage of 10%, fell out of the suggested range of 19.8:1. The activation energy of the esterification reaction is 20.7 kJ/mol at the optimized condition and 45.9 kJ/mol at the 19.8:1 methanol to FFA ratio. It was found that the 19.8:1 methanol-to-FFA molar ratio worked well only within the FFA range of 15-25% while the suggested 5% sulfuric acid worked well only within the FFA range of 15-35%. Outside these ranges, especially at FFA levels less than 15%, optimization study is necessary. Regression models of methanol and acid dosing have been utilized in two industrial scale biodiesel producing facilities and have successfully reduced the FFA level to less than 0.5%.
Plastic is used widely all over the world, due to the fact that it is low cost, is easily processable, and has lightweight properties. However, the hazard of discarding waste plastic, so-called "white pollution", is becoming more and more severe. In this paper, solid-phase photocatalytic degradation of polystyrene (PS) plastic, one of the most common commercial plastics, over copper phthalocyanine (CuPc) sensitized TiO2 photocatalyst (TiO2/CuPc) has been investigated under fluorescent light irradiation in the air. UV-vis spectra show that TiO2/CuPc extends its photoresponse range to visible light, contrasting to only UV light absorption of pure TiO2. The PS photodegradation experiments exhibit that higher PS weight loss rate, lower PS average molecular weight, less amount of volatile organic compounds, and more CO2 can be obtained in the system of PS-(TiO2/CuPc), in comparison with the PS-TiO2 system. Therefore, PS photodegradation over TiO2 CuPc composite is more complete and efficient than over pure TiO2, suggesting the potential application of dye-sensitized TiO2 catalyst in the thorough photodegradation of PS plastic under fluorescent light. During the photodegradation of PS plastic, the reactive oxygen species generated on TiO2 or TiO2/CuPc particle surfaces play important roles in chain scission. The present study demonstrates that the combination of polymer plastic with dye-sensitized TiO2 catalyst in the form of thin film is a practical and useful way to photodegrade plastic contaminants in the sunlight.
A family of new ether-functionalized ILs based on trialkylimidazolium cations with one or two ether groups and TFSA − anion was synthesized and characterized. Their properties including melting point, thermal stability, viscosity, conductivity, and electrochemical windows were determined and compared to those of the trialkylimidazolium ILs without ether group. The relationship between the cations structure and IL physicochemical properties was systematically studied. Most of these ether-functionalized ILs were liquids at room temperature, and the melting points of 21 ILs were lower than −60 °C. At room temperature, 26 ILs owned the viscosities lower than 100 mPa s, and the viscosities of IM(2o1)12TFSA and IM(2o2)12TFSA were 57.4 and 54.4 mPa s.
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