Hidrólise e degradação química da ceclulose empregando catalisadores magnéticos

Abstract

The production of chemicals from solubilization and conversion of cellulosic material is a promised important chemical platform. Several studies have shown that the conversion of cellulose into industrial products, are conducted in the presence of enzymes, inorganic acids and bases or in aqueous supercritical medium. However, in most of these procedures several inconvenient are present, for example, low selectivity and catalytic activity, difficulties to separate the products and recuperate the catalyst, corrosion problems of equipments, and large volumes of liquid wastes neutralization processes, as well as severe reaction conditions employed. If these set of processes and reactions are conducted in the presence of no toxic or corrosive compounds or materials, and that can be also recuperated and reused, several of green chemistry aspects, allied with economical view, can be attained. In this context, we studied the solubility, hydrolysis, and cellulose degradation, employing new solid catalytic systems exhibiting Lewis and/or Brøsnted acid sites. The catalytic properties of those materials were compared to the classical system based on sulfuric acid, and systems runned without addition of catalyst. The new catalytic systems, based on magnetic nanoparticles (Fe3O4/SiO2/Pt0, Fe3O4/SiO2/NH2 e Fe3O4/SiO2), displayed great potential to hydrolyze cellulose, and generating a wide range of products with industrial importance, without the inconvenience of corrosion problems associated to the use of sulfuric acid. The recuperation and reuse of the catalytic material have been carried out and evaluated, in which several recycles have been performed and compared. The reaction temperature and time are the most significant variables in the cellulose solubilization/hydrolysis/degradation process. Independently of the presence or not of catalysts, higher cellulose consumption is observed at reaction temperatures and time of 180 °C and 4 hours, respectively. In terms of selectivity, reaction temperatures of 150 and 180 °C displayed different tendencies. At 150 °C, it was observed higher production of glycosides, but at 180 °C higher production of glycosides derivatives like hydroximethylfurfural (HMF). The order of cellulose consumptions (Fe3O4/SiO2/Pt0> Fe3O4/SiO2/NH2 > Fe3O4/SiO2) was maintained in all reaction conditions tested in this work, and a clear effect of the platinum as catalyst on the conversion of the cellulose was detected