Moisture triggers the growth of existing form I nuclei but it exerts a weaker effect on nucleation, and the presence of residual ethanol greatly accelerates the transformation.

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Different glass fibers in woven forms were used as supports for Pt and Pd catalysts and were tested in toluene and CO total oxidation at atmospheric pressure. The catalytic activity and the ignition-extinction temperatures were investigated in relation to chemical composition of the supports, the types of active metal used (Pt, Pd), and the surface concentration of the metal. The experimental results suggest the modified glass fibers as suitable supports for efficient catalysts for complete oxidation. The catalysts can be used at moderate temperatures (150-250 • C) and at high gas hourly space velocity (GHSV = 30 000 h −1 ). The main design parameters of structured catalytic bed reactors, based on glass fiber catalyst, are discussed.

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Physical mixtures of alkali and earth alkali metal carbonates and commercially available zeolites were investigated as solid catalysts for the Knoevenagel condensation. Best results for the model reaction between benzaldehyde and ethyl cyanoacetate were obtained for a 1:4 mixture of Na 2 CO 3 with 4 Å molecular sieves (MS). The effects of the following parameters were investigated: structure of substrate, type and basicity of metal carbonate and zeolite, and temperature. Between 50 and 90°C chemical yields up to >90% were obtained without continuous removal of water and with reasonable catalyst activities and reaction times. Na 2 CO 3 -MS 4 Å proved to be active for the condensation of several aldehydes and ketones with a variety of active methylene components.Résumé : On a évalué la possibilité d'utiliser des mélanges physiques de carbonates de métaux alcalins ou alcalinoterreux et de zéolites commercialement disponibles comme catalyseurs solides pour des condensations de Knoevenagel. Les meilleurs résultats pour la réaction modèle entre le benzaldéhyde et le cyanoacétate d'éthyle ont été obtenus avec un mélange 4:1 de Na 2 CO 3 avec du MS 4 Å. On a étudié les effets des paramètres suivants: structure du substrat; type et basicité du carbonate métallique et du zéolite; température. Entre 50 et 90°C, on a obtenu des rendements chimiques allant jusqu'à plus de 90 % sans nécessité d'enlever l'eau de façon continue, avec des activités catalytiques et des temps de réaction raisonnables. Le mélange Na 2 CO 3 -MS 4 Å s'avère actif pour la condensation de plusieurs aldéhydes et cétones avec une grande variété de composés comportant un méthylène actif.Mots clés : condensation de Knoevenagel, catalyseurs basiques solides, mélanges de zéolite -carbonate de sodium.[Traduit par la Rédaction] Siebenhaar et al. 569