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 fl...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 rereac tor under atmospheric pressure.The pyrolysis products were identified and quantified using gas chroma to graphy-mass spec trome try(GC-MS).Kine tic 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 but anoa te pyrolysis.The act iva tion t empera ture may also affec t some catalytic proper ties of HZSM-5.Overall,this study can be used to guide subsequent catalytic combustion for practical biodiesel fuels.展开更多
La2Ce2O7 (LCO) is a promising candidate for thermal barrier coatings (TBCs) due to that it provides better thermal insulation than yttria-stabilized zirconia (YSZ) does. In this work, a TBC LCO was produced by solutio...La2Ce2O7 (LCO) is a promising candidate for thermal barrier coatings (TBCs) due to that it provides better thermal insulation than yttria-stabilized zirconia (YSZ) does. In this work, a TBC LCO was produced by solution precursor plasma spraying (SPPS). After the solution precursors were prepared and the spraying parameters were optimized, the thermophysical properties and thermal shock performance of the coatings were tested. It was found that the SPPS coating with segmentation crack density of 6 mm^-1 had the porosities of about 33.5% at spray distances of 35 mm. The thermal conductivity of the SPPS coatings is 0.50-0.75 W·m^-1·K^-1, much lower than that of the atmospheric plasma spraying (APS) coatings (0.85-1.25 W·m^-1·K^-1). The thermal shock performance of the SPPS coatings reached 60 cycles, much better than the APS coatings. This improvement is due to the segmentation cracks in the coatings, which can improve strain tolerance and effectively relieve internal stress. This study provides reference significance for further research on thermal barrier coatings.展开更多
基金This work was supported by the National Natural Science Foundation of China(No.51676176 and No.51976207)the Fundamental Research Funds for the Central Universities(No.WK2320000038)the Foundation of State Key Laboratory of Coal Combustion(No.FSKLCCA1909).
文摘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 rereac tor under atmospheric pressure.The pyrolysis products were identified and quantified using gas chroma to graphy-mass spec trome try(GC-MS).Kine tic 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 but anoa te pyrolysis.The act iva tion t empera ture may also affec t some catalytic proper ties of HZSM-5.Overall,this study can be used to guide subsequent catalytic combustion for practical biodiesel fuels.
基金financially supported by the National Natural Science Foundation of China (Nos. 51571002 and 51401003)Beijing Municipal Natural Science Foundation(Nos. 2172008 and KZ201310005003)
文摘La2Ce2O7 (LCO) is a promising candidate for thermal barrier coatings (TBCs) due to that it provides better thermal insulation than yttria-stabilized zirconia (YSZ) does. In this work, a TBC LCO was produced by solution precursor plasma spraying (SPPS). After the solution precursors were prepared and the spraying parameters were optimized, the thermophysical properties and thermal shock performance of the coatings were tested. It was found that the SPPS coating with segmentation crack density of 6 mm^-1 had the porosities of about 33.5% at spray distances of 35 mm. The thermal conductivity of the SPPS coatings is 0.50-0.75 W·m^-1·K^-1, much lower than that of the atmospheric plasma spraying (APS) coatings (0.85-1.25 W·m^-1·K^-1). The thermal shock performance of the SPPS coatings reached 60 cycles, much better than the APS coatings. This improvement is due to the segmentation cracks in the coatings, which can improve strain tolerance and effectively relieve internal stress. This study provides reference significance for further research on thermal barrier coatings.
