Synthesis of a Zeolite Y Coating on Stainless Steel Support

International audienceThe coating of stainless steel with zeolite Y was achieved. Zeolite Y crystals were shown to grow directly on the support provided the synthesis mixture was previously seeded. A stable, supported crystalline monolayer can then be synthesized with crystals as small as 0.2 μm. Using an unseeded synthesis mixture results in poor coverage and very low stability of the Y coating or in a stable coating of a side species, namely gmelinite. The stability of the zeolite Y coating on stainless steel is explained by the crystal growth in the nearest vicinity of the support. Partly uncompleted crystals are synthesized in this process and stabilized through chemical bonding with the support. The bonding with the support and thus the coverage are improved by an oxidic layer on the surface which can be formed upon calcination at high temperature

Key Role of the Interface Gel−Support in the Synthesis of Zeolitic Coatings

International audienceThe synthesis of zeolite Y on stainless steel using a seeded synthesis mixture brings new information on the initial steps of the formation of a zeolitic coating. Initially, an amorphous gel layer is deposited on the support. The modifications carried out on the interface constituted by this layer on the support induce direct changes on the coating. The coverage and the final crystal size for instance can be tuned with the seed content. Crystal growth is thought to occur directly from the seeds present on the support. The zeolite layer is stabilized when crystals grow individually and perpendicularly to the support and bind with the surface via a hematite interface. This initial zeolite layer can then be used in a secondary growth process during which intergranular voids can be closed. To induce growth on the support, the seeds must be well dispersed in the synthesis gel. Here seeds are thought to be constituted of a preliminary local ordering of the synthesis gel in which nanoaggregates of gel are formed from the Q0 and Q1 silicate species

Potentiometric and NMR spectroscopic study of protonations and amide hydrogen exchange rates of DTPA-bis(butylamide), DTPA-bis(glucamide), and their lanthanide(III) complexes

The macroscopic and microscopic protonations of DTPA-GlucA2 (DTPA-bis(glucamide)) have been investigated using potentiometry, 1H and 13C NMR. The protonation behavior appears to be similar to that of the corresponding bis(alkylamides), showing that it is not affected by the presence of the polyhydroxy side chains. Consideration of the various possible protonation pathways leads to the conclusion that the differences in basicity of the amino functions in DTPA and DTPA-bis(amides) result in different protonation sequences of these ligands, which is reflected in the macroscopic protonation constants. The significance for the design of DTPA-based contrast agents for MRI is discussed. Exchange rates of the amide NH of this compound and that of DTPA-bis(butylamide) (DTPA-BuA2) were determined via longitudinal relaxation rate measurements of the amide 1H resonances in H2O---D2O (9:1) as solvent. The reaction is strongly base catalyzed and the rate increases substantially upon coordination of the DTPA-bis(amide) by La(III).http://www.sciencedirect.com/science/article/B6TG5-3TKV22X-8/1/45ec5aa854f83e57a7e074ba7967b73

An alternative synthesis method for zeolite Y membranes

International audienceA new approach for the synthesis of supported zeolite Y membranes is presented, using a synthesis gel containing seeds to avoid any unnecessary ex situ pre-treatment of the support