Preparação e caracterização de biocatalisadores heterogêneos para a produção de biolubrificante

Abstract

In recent years, biolubricants have been gaining prominence in comparison with conventional petroleum-based lubricants. This trend is observed in almost all sectors relying on these products, regardless of their applications. The factors that contribute to such growing trend are the environmental problems caused by coventional lubricants and the depletion of oil reserves that have increased the need for renewable and biodegradable lubricants. In addition, biolubricants can be produced using several types of oleaginous feedstock and distinct chemical reactions that can be efficiently catalyzed by lipases, which make them quite attractive in the context of Green Chemistry. Thereby, ion-exchange supports have been prepared via sequential functionalization of silica-based materials with (3-Glycidyloxypropyl)trimethoxysilane (GPTMS) (Epx-SiO2) and activation with glycine (Gly-Epx-SiO2) in order to immobilize lipase from Themomyces lanuginosus (TLL) via adsorption and then use the biocatalyst obtained in the synthesis of biolubricant. Rice husk silica (RHS) was selected as support with the aim of comparing its performance with commercial silica (Immobead S60S). Sequential functionalization/activation of SiO2-based supports has been confirmed by AFM, SEM and N2 adsorption-desorption analyses. Maximum TLL adsorption capacities of 14.8 ± 0.1 mg/g and 16.1 ± 0.6 mg/g using RHS and Immobead S60S as supports, respectively, have been reached. The Sips isotherm model has been used, which was well fitted to experimental data on TLL adsorption. Catalytic activities of immobilized TLL were assayed by olive oil emulsion hydrolysis and butyl stearate synthesis via an esterification reaction. Hydrolytic activity of the biocatalyst prepared with a commercial support (357.6 ± 11.2 IU/g) was slightly higher than that of Gly-Epx-SiO2 prepared with RHS (307.4 ± 7.2 IU/g). On the other hand, both biocatalysts presented similar activity (around 90% conversion within 9-10 h of reaction) and operational stability after 6 consecutive cycles of butyl stearate synthesis in batch systems.