A new type of highly efficient formaldehyde (FA) absorbent of polyoxymethylene (POM), hexamethylenediamine–formaldehyde polycondensates (HF) was prepared by the condensation reaction of hexamethylenediamine (HA) and FA. The effects of the synthetic technique including FA/HA molar ratio, reaction temperature and dispersant dosage on the thermal stability of POM/HF were studied, and finely divided, slightly branched HF polycondensates with high molecular weight and relatively high processing thermal stability were obtained. The thermal stabilization effect of HF on POM was studied through the isothermal weight loss analysis, FA emission amount (FEA) measurement, and balance torque analysis, which showed that HF had better thermal stabilization effect on POM than the commonly used FA‐absorbent melamine (MA). In order to improve the crystallization performance and mechanical properties of POM, the nucleation effect of HF on POM was studied by means of polarized light microscopy (PLM), isothermal and nonisothermal differential scanning calorimetry (DSC), indicating that HF had remarkable nucleation effect on POM. The investigation of mechanical properties showed that the addition of HF could improve the impact toughness of POM to a certain degree. Copyright © 2008 John Wiley & Sons, Ltd.
The thermal analysis has been employed to yield information on the biodiesel ignition quality since the ignition quality influences the combustion and exhaust emissions of the fuels in a compression ignition (CI) engine. The chemical compositions of -10 petrodiesel (-10PD), soybean-based biodiesel (SME) and cottonseed-based biodiesel (CME) are analyzed by gas chromatography-mass spectrometry (GC-MS). Ignition temperature of -10PD, SME and CME is determined by thermogravimetry-differential scanning calorimetry (TG-DSC). The study shows that the biodiesel is mainly composed of fatty acid methyl esters: C14:0–C24:0, C16:1–C22:1, C18:2 and C18:3. Biodiesel ignition quality is better than petrodiesel. The ignition temperature of CME and SME is 207.4 and 213.9 °C respectively. The ignition quality of biodiesel is better with shorter carbon chain lengths and more saturated fatty acid methyl ester (SFAME).
The chemical compositions of biodiesel are analyzed by GC-MS, and their molecular structures are investigated on the basis of the hybrid orbital theory. The CFPP of biodiesel is studied by CFPP tester, the solution crystallization theory and the similarity-intermiscibility principle. Good correlation models are proposed for predict CFPP of biodiesel by chemical compositions and the CFPP of biodiesel-petrodiesel blends by biodiesel ratio. The study shows that biodiesel is mainly composed of SFAME (C14:0~C24:0) and UFAME (C16:1~C22:1, C18:2 and C18:3 ). Carbon atoms of the alkyl for SFAME arrange in a zigzag pattern by ∠CCC=109.5°. C-C carbon atoms of the alkenyl arrange in a zigzag pattern by ∠CCC=109.5°, too, carbon chain is curved by C=C in ∠CCC=122.0°, and curved degree increases with increasing unsaturated degree. CFPP of biodiesel is mainly determined by chemical compositions. CFPP increases with the amount and carbon chain length of SFAME. CFPP of biodiesel-petrodiesel blends is mainly determined by chemical compositions and ratio of biodiesel. To lower SFAME≥C20:0 biodiesel, such as PME, CSME, WME, SBME and RME, it blending with -10PD can formed a eutectic mixture. CFPP of the eutectic mixture is -12 °C. The biodiesel ratio for the lowest CFPP rang increases with decreasing SFAME. Such as SFAME contents in PME, CSME, WME, SBME and RME are 35.86、32.12、31.04、18.29 and 14.69 w% respectively, and the range of biodiesel ratio is 5~20、10~20、20~30、30~50 and 40~60 v% respectively. To higher SFAME≥C20:0 biodiesel, such as PNME, CFPP increases with PNME ratio.
The chemical compositions of biodiesel are analyzed by gas chromatograph-mass spectrometer (GC-MS), and theirs molecular structure are investigated on the basis of the hybrid orbital theory. Cold filter plugging point (CFPP) of biodiesel is studied by CFPP tester, the solution crystallization theory and the similarity-intermiscibility principle. Good correlation models are proposed for prediction biodiesel CFPP by chemical compositions and CFPP of biodiesel-petrodiesel blends by biodiesel ratio. The study shows that biodiesel is mainly composed of SFAME (C14:0C24:0) and UFAME (C16:1C22:1, C18:2and C18:3). Carbon atoms of the alkyl for SFAME arrange in a zigzag pattern by CCC=109.5°. C-C carbon atoms of the alkyl arrange in a zigzag pattern by CCC=109.5°, too, carbon chain is curved by C=C in CCC=122.0°, and curved degree increases with increasing unsaturated degree. CFPP of biodiesel is mainly determined by chemical compositions. CFPP increases with the amount and carbon chain length of SFAME. CFPP of biodiesel-petrodiesel blends is mainly determined by chemical compositions and ratio of biodiesel. To lower SFAMEC20biodiesel, such as PME, CSME, WME, SBME and RME, it blending with-10PD can formed a eutectic mixture. CFPP of the eutectic mixture is-12 °C. The biodiesel ratio for the lowest CFPP rang increases with decreasing SFAME. Such as, SFAME contents in PME, CSME, WME, SBME and RME are 35.86, 32.12, 31.04, 18.29 and 14.69 w% respectively, and the range of biodiesel ratio is 520, 1020, 2030, 3050 and 4060 v% respectively. To higher SFAMEC20biodiesel, such as PNME, CFPP increases with PNME ratio.
With the promotion of energy-saving and exhaust reduction policy, the application of diesel engine has been further extended. The formation and harm of nitrogen oxides (NOX) and particulate matter (PM) were mentioned in detail, which are major pollutants in diesel exhaust. Reviewed the research progress and application of diesel engine exhaust emission control technology, fuel quality improvement, internal purification and after-treatment are introduced separately. Finally, the future development direction of exhaust emission control technology was given combining research situation of diesel engine.
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