一种生物柴油代用品在HZSM-5分子筛催化剂上的催化热解

为了深入了解生物柴油在ZSM-5沸石上的催化反应机理,在常压的流动反应器中进行了生物柴油代用品丁酸甲酯在氢型ZSM-5(HZSM-5)催化剂上的热解和催化热解. 热解产物使用气相色谱-质谱法定性和定量测量. 动力学模型和实验表明,气相中氢提取反应是热解过程中丁酸甲酯分解的主要途径,但在HZSM-5上,丁酸甲酯则主要通过解离生成烯酮和甲醇消耗;与无催化反应相比,丁酸甲酯在HZSM-5上的初始分解温度降低了约300 K. 并且通过Arrhenius方程获得了在催化热解和均相热解条件下丁酸甲酯消耗的表观活化能. 明显降低的表观活化能证实了HZSM-5对丁酸甲酯热解的催化性能. 此外催化剂的活化温度对HZSM-5的某些催化性能具有一定的影响. 该研究对进一步的实际生物柴油燃料的催化燃烧具有一定的指导意义.     

Crosslinked plastic scintillators: A new detection system for radioactivity measurement in organic and aggressive media

The measurement of radioactive solutions containing organic or aggressive media may cause stability problems in liquid and plastic scintillation (PS) techniques. In the case of PS, this can be overcome by adding a crosslinker to the polymer structure. The objectives of this study are to synthesise a suitable crosslinked plastic scintillator (C-PS) for radioactivity determination in organic and aggressive media. The results indicated that an increase in the crosslinker content reduces the detection efficiency and a more flexible crosslinker yields higher detection efficiency. For the polymer composition studied, 2,5-diphenyloxazole (PPO) is the most adequate fluorescent solute and an increase in its concentration causes little change in the detection efficiency. The inclusion of a secondary fluorescent solute 1,4-bis-2-(5-phenyloxazolyl) benzene (POPOP) improves the C-PS radiometrical characteristics. For the final composition chosen, the synthesis of the C-PS exhibits good reproducibility with elevated yield. The obtained C-PS also displays high stability in different organic (toluene, hydrotreated vegetable oil (HVO) and methanol) and aggressive media (hydrochloric acid, nitric acid and hydrogen peroxide). Finally, the C-PS exhibits high detection efficiency both in water and in aggressive media and can also be applied in organic media showing similar or even higher detection efficiency values.     

Catalytic Pyrolysis of Biodiesel Surrogate over HZSM-5 Zeolite Catalyst

To obtain insight into the catalytic reaction mechanism of biodiesels over ZSM-5 zeolites, the pyrolysis and catalytic pyrolysis of methyl butanoate, a biodiesel surrogate, with H-type ZSM-5 (HZSM-5) were performed in a flow reactor under atmospheric pressure. The pyrolysis products were identified and quantified using gas chromatography-mass spectrometry (GC-MS). Kinetic modelling and experimental results revealed that H-atom abstraction in the gas phase was the primary pathway for methyl butanoate decomposition during pyrolysis, but dissociating to ketene and methanol over HZSM-5 was the primary pathway for methyl butanoate consumption during catalytic pyrolysis. The initial decomposition temperature of methyl butanoate was reduced by approximately 300 K over HZSM-5 compared to that for the uncatalyzed reaction. In addition, the apparent activation energies of methyl butanoate under catalytic pyrolysis and homogeneous pyrolysis conditions were obtained using the Arrhenius equation. The significantly reduced apparent activation energy confirmed the catalytic performance of HZSM-5 for methyl butanoate pyrolysis. The activation temperature may also affect some catalytic properties of HZSM-5. Overall, this study can be used to guide subsequent catalytic combustion for practical biodiesel fuels.