Development and application of lamellar vanadosilicates as catalysts in the conversion of glycerol

Author(s)

Luiz Henrique Vieira

• Document type: Doctoral Thesis
• Press: Araraquara. 2018-08-13.
• Institution: Universidade Estadual Paulista (Unesp). Instituto de Química. Araraquara
• Defense date: 2018-07-30
• Advisor: Leandro Martins

Abstract

The catalytic conversion to higher value-added products is presented as an interesting alternative for the valorization of excess of glycerol available as a co-product in the biodiesel production process. This study presents the development and application of a process for the efficient transformation of glycerol into acrylic acid by single-step oxidative dehydration route, and glycerol into solketal by ketalization route, using vanadosilicate catalysts derived from zeolitic structures. Due to the unique oxidizing and acidic properties that arise with the isomorphic substitution of vanadium, compared to aluminum, in zeolitic structures, the work involves the development of vanadosilicates with the active sites presenting bi-functional characteristics for the oxidative dehydration of glycerol, where, in a first step dehydrate the glycerol to acrolein and in a second step oxidize the acrolein to produce acrylic acid. Another aspect evaluated was the acidity of the active sites required in the ketalization of glycerol with acetone to produce solketal. Lamellar zeolitic structures were used in order to allow greater accessibility to the active sites by the reagents. Among the lamellar materials, the ITQ-6 zeolite, with FER structure, has outstanding catalytic performance in relation to the purely microporous zeolites and, therefore, were the catalysts developed and investigated in this work. Two types of materials were synthesized, vanadosilicates, where the vanadium precursor was added to the synthesis mixture, and vanadium-impregnated silicates, where the wet impregnation of a vanadium salt was carried out on the catalysts followed by calcination. A wide range of techniques were applied to the materials that allowed to unveil and understand the mechanisms of formation of vanadosilicates, their behavior as a catalyst in the reaction, the identification and functionality of the active sites. Structural, textural and superficial characterizations were carried out ex situ and in situ, among them, X-ray diffraction, nitrogen physisorption, 29Si nuclear magnetic resonance, spectroscopies in the UV-Visible region, in the infrared region with Fourier transform and X-ray absorption, temperature-programmed desorption of ammonia, thermogravimetry and X-ray photoelectron spectroscopy. With this information, the operating conditions were systematically established during the synthesis and catalytic activity of these materials. The combination of accessibility, high dispersion, moderate acidity and high oxidative potential of the active sites in the micro-mesoporous materials V-ITQ-6 were determinant factors in the considerable increase of acrylic acid productivity for oxidative dehydration and solketal productivity for ketalization, when compared to purely microporous vanadosilicates, V-FER, and non-porous vanadium pentoxide. (AU)

• FAPESP's process: 14/20116-6 - Development and application of lamellar vanadosilicates as catalysts in the glycerol oxidative dehydration
• Grantee: Luiz Henrique Vieira
• Support Opportunities: Scholarships in Brazil - Doctorate