Search

Four different samples of pure scheelite α-Bi2Mo3O12 were synthesized by the fast microwave-assisted hydrothermal method. By adjusting the pH in the preparation process, the morphologies and structures of the synthesized catalysts were changed. TG, XRD, SEM, TEM, BET, and XPS analyses were used to investigate the characteristics of the catalyst. The sample of α-Bi2Mo3O12 was prepared at a calcination temperature of 500 °C and pH = 1 had the highest specific surface area propylene selective oxidation properties. The conversion of propylene was 28.3% and the selectivity of acrolein was 86.4%. Compared with α-Bi2Mo3O12 prepared by co-precipitation and normal hydrothermal method, α-Bi2Mo3O12 prepared by microwave hydrothermal method has higher propylene oxidizing activity. The conversion of propylene is negatively correlated with the crystallinity of the catalyst. This is due to the fact that higher crystallinity inhibits the lattice oxygen flow between the lattices, thus inhibiting the selective oxidation and reducing the conversion of the reaction. The oxygen mobility of α-Bi2Mo3O12 samples was characterized by XPS. The results showed that the conversion of propylene of α-Bi2Mo3O12 were positively correlated with its oxygen mobility strength. A probable mechanism for the selective oxidation of propylene was proposed. This work not only offers a high-efficiency method for the rapid preparation of bismuth molybdate catalysts but also extends the application of microwave-assisted hydrothermal synthesis in the field of selective oxidation of propylene. [ABSTRACT FROM AUTHOR]

Multi-stage mild co-carbonization of different fluidized catalytic cracking slurry oil narrow fractions was investigated. The characteristics of cokes derived from mild co-carbonization were found to be better than those from rapid co-carbonization. The improvement in quality of cokes derived from mild co-carbonization was reflected in every stage compared to carbonization of a single fraction. Further study revealed that transferable hydrogens can be released at every stage of mild carbonization and that more transferable hydrogens can be released from combined fraction (from 10.7 mg/g to 2.7 mg/g) than a single fraction (from 10.6 mg/g to 2.9 mg/g). These transferable hydrogens can stabilize the carbonization system, thus leading to better carbonization performance of combined narrow fractions. [ABSTRACT FROM AUTHOR]

The effects of phosphorus on the structure and hydrofining performance of tri-metallic WMoNi/AlO catalysts prepared with W/Mo-based hybrid precursor nanocrystals were investigated. The incorporation of phosphorus weakened the metal-support interactions (MSIs) and facilitated the formation of more synergetic NiWMoS phases with higher stacks. Catalytic tests using a fluid catalytic cracking diesel fuel showed that the changes in the MSIs and the morphology of the active phases had a more positive effect on the hydrodenitrogenation activity than on the hydrodesulfurization activity. In contrast, when phosphorus was incorporated into a tri-metallic WMoNiP/ AlO catalyst prepared by a conventional incipient impregnation method, the MSIs decreased causing aggregation of the metal species which resulted in poorer hydrofining performance of the catalyst. These results show that incorporating phosphorus into a WMoNi/AlO catalyst can finely tune the structure of the active phase to enhance the hydrogenation and hydrodenitrogenation activity of the resulting tri-metallic catalyst. [ABSTRACT FROM AUTHOR]