Fabrication of 3-D confined spaces with Au NPs: Superior dispersion and catalytic activity.

Gold nanoparticles (Au NPs) as an active noble-metal site have received great attention because of its superior catalytic activity in diverse reactions. However, the activity of Au NPs is strongly dependent on its size and dispersion degree. Therefore, we developed an efficient solid-state reduction (SSR) strategy for the first time to promote the dispersion degree and size of Au NPs in template-occluded KIT-6 (AK) as a support by taking advantage of (i) 3-dimentonal cubic mesoporous structure of support (ii) confined spaces present between template (Pluronic (P) 123) and silica wall of AK where Au NPs locate (iii) interaction of both P123 as template and silica walls of AK with Au NPs highly efficient for Au NPs dispersion and (iv) SSR strategy which avoids competitive adsorption of solvent in the conventional fabrication process. The results revealed that Au-based AK (AuAK) has much better dispersion of Au NPs with smaller sizes than template-free KIT-6 (CK). Moreover, the catalytic activity of AuAK in reduction reactions of p-nitrophenol (P-NP) to p-aminophenol (P-AP) and Methylene blue (MB) to Leuco MB (LMB) is superior than AuCK as well as to those Au-catalysts synthesized via conventional strategies previously. The catalytic performance is also related well with characterization results.

Effect of vanadium contamination on the framework and micropore structure of ultra stable Y-zeolite.

Y-zeolites are the main component of fluid catalytic cracking (FCC) catalyst for conversion of crude petroleum to products of high demand including transportation fuel. We investigated effects of vanadium which is present as one of the impurities in FCC feedstock on the framework and micropore structure of ultra-stable (US) Y-zeolite. The zeolite samples were prepared and characterized using standard techniques including: (1) X-ray diffraction, (2) N2 adsorption employing non local density functional theory method, NLDFT, (3) Transmittance and Pyridine FTIR, (4) Transmittance electron microscopy (TEM), and (5) (27)Al and (29)Si MAS-NMR. Results revealed that in the presence of steam, vanadium caused excessive evolution of non inter-crystalline mesopores and structural damage. The evolved mesopore size averaged about 25.0nm at 0.5wt.% vanadium loading, far larger than mesopore size in zeolitic materials with improved hydrothermal stability and performance for FCC catalyst. A mechanism of mesopore formation based on accelerated dealumination has been proposed and discussed. Vanadium immobilization experiments conducted to mitigate vanadium migration into the framework clearly showed vanadium is mobile at reaction conditions. From the results, interaction of vanadium with the passivator limits and decreases mobility and activity of vanadium into inner cavities of the zeolite capable of causing huge structure breakdown and acid sites destruction. This study therefore deepens insight into the causes of alteration in activity and selectivity of vanadium contaminated catalyst and hints on a possible mechanism of passivation in vanadium passivated FCC catalyst.