Rolando Roque-Malherbe

Synthesis and Characterization of Zeolite Based Porous Ceramic Membranes

Abstract New porous zeolite based membranes were synthesized using a ceramic methodology and characterized by means of XRD, SEM, EDAX and permeation tests. The membranes were produced by thermal transformation of natural clinoptilolite. The XRD study showed clinoptilolite amorphization at 600–900°C. A posterior recrystallization to a siliceous phase and a compact aluminosilicate phase at 900–1150°C was also produced. The Permeability [B] and Permeance [Π] of H2 and CO2 were measured using the Darcy Law correlation. It was also applied for gaseous laminar flow using the Carman‐Kozeny equation. With the help of this equation the membrane pores sizes were measured. It was shown that the membrane porosity can be controlled by the grain size of the original natural zeolite powder. The membranes were further transformed by hydrothermal synthesis to obtain materials covered with an AlPO4‐5 molecular sieve. In conclusion, novel, inexpensive, strong, high permeation rate, and high temperature membranes were produced with natural clinoptilolite, a low cost and available material.

Rotating disk slurry electrodeposition of platinum at Y-zeolite/carbon Vulcan XC-72R for methanol oxidation in alkaline media

Platinum was electrodeposited onto Y-zeolite and Y-zeolite (Y)/Vulcan XC-72R (V) to produce Pt/Y/V and Pt/Y catalysts using a rotating disk slurry electrode technique. The activities of the two catalysts were measured towards methanol electro-oxidation in alkaline media by cyclic voltammetry and chronoamperometry. The materials were examined using electron microscopy. The results were compared to those obtained on commercial catalysts. Pt/Y/V (with 14 wt% Pt) catalyst was the most active, even more so than a commercial Pt/V catalyst with 20 wt% Pt. The Pt/Y/V catalysts contained Pt nanoparticles and tetrahedra, likely a consequence of the nucleation and growth within the zeolite framework.

Degradation of phenol by mechanical activation of a rutile catalyst

In the present paper a novel mechanochemical process for the elimination of organic pollutants dissolved in water is proposed. In this regard, phenol aqueous solutions (100mgL(-1)) were ball-milled for 0, 12, 18, 24, 36, 48, and 72h with and without a well-characterized (XRD, SEM, and N(2) Adsorption), rutile powder catalyst and the reaction products analyzed with UV and GC/MS. It was found that when the catalyst was not included in the process, phenol was not affected, but when it was included, phenol was decomposed. The catalyst itself did not change and the reaction follows a pseudo-first-order kinetics. Besides, intermediates which are characteristic of the ()OH radical mechanism were found in the reaction products. Then, a mechanism similar to those accepted for other advanced oxidation processes was proposed. The value measured for the pseudo-first-order reaction constant was very low, indicating that the reported process is inefficient. Nevertheless, this problem could be solved by applying catalysts consisting of particles with smaller diameters.

Structure and characterization of vertically aligned single-walled carbon nanotube bundles

Arrays of vertically aligned single-walled carbon nanotube bundles, SWCNTs, have been synthesized by simple alcohol catalytic chemical vapor deposition process, carried out at 800°C. The formed SWCNTs are organized in small groups perpendicularly aligned and attached to the substrate. These small bundles show a constant diameter of ca. 30nm and are formed by the adhesion of no more than twenty individual SWCNTs perfectly aligned along their length.