Effect of Au Precursor and Support on the Catalytic Activity of the Nano-Au-Catalysts for Propane Complete Oxidation

Catalytic activity of nano-Au-catalyst(s) for the complete propane oxidation was investigated. The results showed that the nature of both Au precursor and support strongly influences catalytic activity of the Au-catalyst(s) for the propane oxidation. Oxidation state, size, and dispersion of Au nanoparticles in the Au-catalysts, surface area, crystallinity, phase structure, and redox property of the support are the key aspects for the complete propane oxidation. Among the studied Au-catalysts, the AuHAuCl4-Ce catalyst is found to be the most active catalyst

Measuring and modeling solids movement in a large, cold fluidized-bed test facility

Solids movement in large-particle fluidized beds was studied in an 18 in x 18 in (46 cm x 46 cm) tube-filled, cold fluidized bed test facility. Direct measurement of local solid mass flux in two dimensions at various locations inside the bed was made possible by a new instrument developed in this study. This instrument can be installed as a part of the bed internal tube array and hence does not interfere with the solid flow field being measured. The instrument makes use of the magnetic property of solid and requires a bed media consisting entirely of magnetic solid particles. Iron particles with a mean particle diameter of 0.032 in (0.8 mm) and a density of 387 lb/ft³ (6200 kg/m³) were used. Experiments were conducted at room temperature and atmospheric pressure with air as the fluidizing gas. Two gas velocities above the minimum fluidization velocity were used. The net local solid movement and the gross solid circulation pattern inside the bed were deduced from the vertical and one horizontal component of the local solid mass fluxes measured at various locations inside the bed. Two specific solid flow regions were found to exist. The net solids movement in the middle bubbling region of the bed was in the upward direction while adjacent to the bed walls the net solid movement was downward. The net lateral solid movement was not significant in the bubbling region of the bed. However, at the bottom of the bed this movement can be significantly enhanced by means of an uneven gas velocity distribution inside the bed. A theoretical model for the gross solid circulation observed in a freely bubbling fluidized bed is proposed. The theory is based on material and momentum balances of the net solid circulating flow inside the bed with the assumption that the solid particulate phase behaves as an incompressible fluid of low viscosity. The model predictions for the vertical solid mass flux in the bubbling region of the bed show a reasonable agreement with the experimental results