A. Macario

Immobilization of Lipase on microporous and mesoporous materials: studies of the support surfaces

Abstract In this paper the performance of different supports respect to the lipase immobilization was investigated. The used enzyme was the lipase from Rhizomucor miehei (RML - commercial name: Palatase). The immobilization tests on mesoporous materials (MCM-41), de laminated zeolites (ITQ-2 and ITQ-6), Na-Silicalite-1, H-Silicalite-1 and F AU zeolites, were carried out by adsorption. The pore size, morphology, crystal dimension, acidity, hydrophobicity and chemical composition of the supports, strongly influence the amount of the enzyme adsorbed. The Na-silicalite-1 support shows the best lipase immobilization capacity, with an efficiency of c.a. 74% respect to the 41% of MCM-41 and the 27% of ITQ-2 type materials, while no enzyme is retained on the zeolite FAU (zeolite X). The preliminary activity tests using the lipase-support as a catalyst, were carried out for the reaction of hydrolysis of triglycerides. The activity observed for the lipase-Na-Silicalite-1 and the lipase-MCM-41 catalysts is 86% and 78%, respectively, respect to the activity of the free lipase enzyme in solution.

Study of lipase immobilization on zeolitic support and transesterification reaction in a solvent free-system

In order to understand the role of the acid–base, electrostatic and covalent interactions between enzyme and support, the catalytic behavior of the Rhizomucor miehei lipase (RML) immobilized on zeolite materials has been studied. The highest lipase activities were obtained when this enzyme, immobilized by adsorption, interacts through acid–base binding forces with the support surface, resulting in activation of the enzyme catalytic center. Due to the interest in biodiesel production by mild enzymatic transesterification, this heterogeneous biocatalyst has been used in transesterification of fatty acids contained in olive oil. The results show a high oleic acid conversion for several reaction cycles with a higher total biodiesel productivity compared to that using the free enzyme.

Direct synthesis of zeolites self-bonded pellets for biocatalyst immobilization

In this work, the preparation, by direct synthesis, of Silicalite-1 self-bonded pellets as supports for immobilization of lipase enzyme is presented. The Silicalite-1 pellets have been prepared in view of the results obtained from the lipase enzyme adsorption on the most suitable supports in powder form. The different pellet preparation procedures strongly influence the final properties of the product. The main synthesis parameter that leads to pellets having high performance, especially regarding the crystal cohesion in aqueous system, is the alkalinity of the synthesis mixture. All possible attachment sites of the support surface of the self-bonded pellets prepared without a binding agent are available to the enzyme. The amount of the enzyme retained on the pellet surface (275 mg/g) is comparable to the amount adsorbed on the powder Silicalite-1 support.

Synthesis and characterization of metal-benzene-tricarboxylate oxidation catalysts

The MOFs materials containing copper, zinc or both metals together combined with benzenetricarboxilate linkers have been prepared in solvothermal process and characterized. The products were tested as catalysts for low temperature oxidation of cyclohexene. They showed considerable activity and selectivity which depended markedly on kind of metal contributing in the structure. The samples containing copper and zinc together are more active than that with the only copper, whereas the latter one shows higher selectivity to cyclohexenone.

Adsorption of carbon dioxide and nitrogen on silica lite-1 and M41S type materials

Abstract The ability of silicalite-1 and M41S type materials to adsorb pure CO 2 and N 2 has been experimentally studied by determining the adsorption isotherms at 20°C. The experimental data have been analyzed using the Langmuir and Freundlich adsorption isotherm models. In both adsorbents N 2 adsorption is strongly reduced in connection to the sodium amount in the synthesis gel, while no significant effects have been observed in the CO 2 adsorption performance. This way, a CO 2 /N 2 selectivity increase is obtained. The silicalite-1 type adsorbents are characterized by good CO 2 /N 2 selectivity (5.9-10.2) and high working capacity for CO 2 (4.0-4.8 w-%). In comparison, a very high CO 2 /N 2 selectivity (> 7.4), but a significantly lower working capacity for CO2 (1.4-1.9) has been recorded for M41S type materials.

High-silica MEL structures: synthesis parameters modification and catalytic results on Beckmann rearrangement reaction

The synthesis of silicalite-2 (MEL structure) is reported in order to understand the effect, on chemico-physical properties, of some parameter modifications during the synthesis, such as silica source. MEL type zeolites with intergrowth with MFI-type structure were prepared and the percentage of the two phases has been changed. The effect of synthesis parameters on crystals shape and size was investigated. Silicalite-2 catalysts were tested in the vapour phase Beckmann rearrangement of cyclohexanone oxime. In some cases interesting results leading to long catalyst lifetime (over 80 hours) and interesting caprolactam selectivity (>90%) are obtained.