Elena I. Basaldella

Cortisol controlled release by mesoporous silica

In this study four types of SBAs were synthesized and then impregnated with hydrocortisone. One is a straight SBA-15, obtained using Pluronics P123 as structuring agent; two others were modified using 1,3,5-trimethylbenzene as additive, and the fourth one was prepared using sodium iodide as additive. Three of these have in common a p6 mm symmetry with nanotubes packed hexagonally, yet they differ in their functional groups. The fourth sample is basically disordered. The drug release kinetics showed two stages: a fast-rate early stage dominated by the controlled release of the hydrocortisone adsorbed in the macropores of the reservoir, followed by a slow-rate delivery that we assume is controlled by the hydrocortisone diffusion through the nanopores. It is shown that the release kinetics can be strongly influenced by using different co-additives.

Effect of aluminum concentration on crystal size and morphology in the synthesis of a NaAl zeolite

Abstract Hydrothermal synthesis of a NaAl zeolite from metakaolinite was studied at different values of the initial Al concentration, while the concentrations of the other components were kept constant. The role played by aluminum on the morphology and size of the crystals thus obtained was determined. Size becomes smaller, and the classic cubic morphology of the NaAl zeolite crystals changes to cubes with bevelled edges as the aluminum concentration increases.

ZSM-5 zeolite films on cordierite modules. Effect of dilution on the synthesis medium

Abstract Continuous, multilayered ZSM-5 zeolite films have been grown by direct synthesis on cordierite modules. The influence of the H 2 O/SiO 2 ratio used in the synthesis mixture on the film properties was studied by inspecting the film formed in the external module surface at several water contents. It is shown that dilution prevents the film to become dense, modifies zeolite crystal morphology and reduces markedly the crystallization of zeolite into a non-adhered powder form.

Separation of CO2 from CH4 and CO2 capture in the presence of water vapour in NOTT-400

From a binary equimolar gas-mixture of CO2 and CH4, NOTT-400 shows CO2 separation from CH4. By kinetic uptake experiments, this material confirms a maximum of 4.3 wt% CO2 capture at 30 °C and a significant 2-fold increase (∼9.3 wt%) in CO2 capture under 40% relative humidity of water vapour.

Synthesis of zeolites from mechanically activated kaolin clays

The hydrothermal treatment in NaOH solution of clays activated by grinding leads to the formation of different zeolites, whose nature depends on the amorphization of the clay obtained by applying a periodic stress by means of an oscillating mill. In this way, hydroxysodalite, mixtures of hydroxysodalite and NaA zeolite, or NaA pure zeolite can be obtained. In the present paper, it is shown that the product varies in composition, and is enriched in NaA zeolite as the crystalline structure of the clay is destroyed by grinding. It is proved that the activation by impact grinding is an alternative method to the classical calcination for the synthesis of the NaA zeolite.

Preparation of supported Cu/ZSM-5 zeolite films for DeNOx reaction

Abstract This work reports the in situ synthesis of ZSM-5 zeolite films on cordierite and the performance of a Cu/ZSM-5-coated monolithic catalyst in the lean NO x reduction reaction. At the end of the hydrothermal crystallization, a zeolite/cordierite composite was obtained which consists of a continuous zeolite film that strongly attaches to the sustrate surface. The monolithic catalysts so prepared are active for the reduction of NO.

Ni/γ-Al2O3 catalyst from kaolinite for the dry reforming of methane

Abstract A catalyst consisting of a 5% Ni over a γ-Al 2 O 3 novel support was evaluated under high-temperature reaction conditions. The γ-Al 2 O 3 -rich phase was obtained by selective dissolution of siliceous components of heat-treated kaolinite. The support was appropriate to prepare a catalyst with high surface area (170 m 2 /g) that showed to be active and stable for dry reforming of methane at 650 °C and a CH 4 /CO 2 =0.5 molar ratio. Compared to the conventional Ni/α-Al 2 O 3 catalyst, this new material showed an improved sulfur resistance when it was reduced in hydrogen steam at the reaction temperature. In industrial conditions, CH 4 /CO 2 =1, deactivation by carbon deposition was not increased. The content and type of deposited carbon were analyzed by TPH and TPO techniques. As regeneration methods of the coked catalysts, hydrogen and oxygen carbon treatments were employed. After the treatment with hydrogen the catalyst reaches the initial activity, but with oxygen the activity only is partially regenerated.

IRON INFLUENCE IN THE ALUMINOSILICATE ZEOLITES SYNTHESIS

The level of Fe impurities in 2 well-crystallized kaolinites was modified (by addition or chemical removal treatment) to analyze the Fe influence in the aluminosilicate zeolite synthesis.The original and modified clays were heat-treated in order to change their reactivity for zeolite A synthesis, and their thermal transformations were studied by X-ray diffraction (XRD), determination of point of zero charge (PZC) and infrared (IR) techniques. It was established that many structural changes took place, regardless of the Fe clay content. Furthermore, the presence of Fe species in alkaline solution or in the solid phase did not seem to greatly influence the zeolite crystallization, because only small differences in the conversion values among samples with different Fe contents were registered. The crystallization process seemed to be related mainly to AI coordination changes produced by the thermal and Fe removal treatments used.

Modified silica matrices for controlled release of cephalexin.

SBA-15 type ordered silicas possessing amino groups attached onto their surfaces were prepared by using two different functionalization methodologies. These matrices were used for the cephalexin adsorption from aqueous solution and further kinetic study of its release into physiological solution. The materials were characterized by nitrogen adsorption/ desorption, scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), X-Ray photoelectron spectrometry (XPS) and thermo analytical methods (TG/DSC). UV-visible spectroscopy at 262 nm was used for quantitative determination of cephalexin present in liquid media. Results reveal that drug adsorption capacities and the corresponding release profiles are dependent on the number of loaded amino groups and their location, which in turn is determined by the functionalization procedure used. It was concluded that amino post-functionalization could enhance long-term cephalexin delivery in comparison with co-functionalization procedure.

Chromium removal by zeolite-rich materials obtained from an exhausted FCC catalyst: Influence of chromium incorporation on the sorbent structure.

A spent FCC catalyst was converted into a zeolitic mixture, and the product obtained was afterward used as trapping material for Cr(III) species frequently found in aqueous solutions. Eventual changes in the sorbent structure produced by Cr incorporation were studied by different characterization techniques such as point of zero charge determinations (PZC), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and infrared absorption (FTIR). The XRD and FTIR analyses indicated that chromium incorporation produces an amorphization of the material, and PZC measurements show no surface adsorption of charged chromium species. SEM and EDX analyses clearly show that after chromium sorption, the initial microspheroidal catalyst morphology was maintained, and the presence of chromium species was mainly detected in the outer microsphere surface, where the zeolite crystals were hydrothermally grown.