The mixed dialkyl oxalate (mDAO) system can be industrially synthesized inexpensively from CO with methanol, ethanol, and mixed alcohols, which are widely available from CO-rich industrial waste gases and syngas. In this work, a series of mDAOs were synthesized through solvent-free partial transesterification of dimethyl oxalate (DMO) or diethyl oxalate (DEO) with higher alcohols. The physical and chemical properties of various mDAOs and different oxygenated fuels were compared, and the viability of the mDAO as an oxygenated fuel additive was tested. The experimental data indicated that the mixed methyl ethyl oxalate (mMEO) is miscible with gasoline in any proportion at a temperature above 263 K. The mixed methyl butyl oxalate (mMBO) and mixed ethyl butyl oxalates (mEBO) show better solubility in diesel than mMEO. The research octane number (RON) of the mMEO/gasoline composite fuel increased with the increase of the mMEO concentration. The flash point, kinematic viscosity, and cetane number of the diesel mixed with a content of 10−20% mMBO meet the requirements of the China national standard. Our results indicate that mDAO can be used as a promising oxygenated fuel additive for gasoline and diesel fuels.
Abstract. Taking thioacetamide (TAA) as sulfur source and mercaptoacetic acid as capping agent, water-soluble Sb 2 S 3 quantum dots were synthesized in aqueous-phase with precipitation method. The influence of temperature (65 to 85 qC) and reaction time (3 to 7 h) on morphological characteristics of the products was studied. The as-prepared Sb 2 S 3 quantum dots were characterized with X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet-visible spectrophotometry (UV-vis) and photoluminescence (PL), which suggested the Sb 2 S 3 quantum dots have uniform size distribution and excellent optical properties. Moreover, a formation mechanism of Sb 2 S 3 quantum dots was also proposed.
The laccase and ultrasmall superparamagnetic iron oxide nanoparticles (USPIO) have been assembled inside the tubular mesoporous silica via co-adsorption technology to prepare host/guest-type immobilized laccase, which is applied to degrade methoxychlor (MXC) in aqueous and reverse micelle environments. The effects of various parameters on degradation of MXC were studied. Under the optimum conditions, the degradation rate could reach maximum value of 45.6 % and remain at 20.8 % after seven cycles. Moreover, the addition of small molecular compound 2, 2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate) to the system could greatly improve the degradation efficiency. The MXC degradation process is a first-order reaction, and the activation energy of MXC degradation catalyzed by immobilized laccase (41.46 kJ mol(-1)) is relatively lower than that catalyzed by free laccase (44.91 kJ mol(-1)). Based on the degradation products measured by gas chromatograph-mass spectrometer (GC-MS) and nuclear magnetic resonance (NMR), the degradation mechanism of MXC has also been proposed.
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