Gelatin Template Synthesis of Aluminum Oxide and/or Silicon Oxide Containing Micro/Mesopores Using the Proteic Sol-Gel Method

Amanda Sayure Kasuya De Oliveira,Adriana Perpetua Figueiredo Paulista,Ana Ellen Valentim De Alencar,Tiago Pinheiro Braga

doi:10.1155/2017/2504796

Amanda Sayure Kasuya De Oliveira, Adriana Perpetua Figueiredo Paulista + Show 2 more

Open Access

https://doi.org/10.1155/2017/2504796

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Abstract

Aluminum oxide and/or silicon oxide-based supports were synthesized by proteic sol-gel method. The characterization was performed through the analysis of TG, XRD, FTIR, SEM, and N2 physisorption. The XRD diffractograms showed an amorphous material profile. TG results indicate the total liberation of the organic and inorganic material in the calcination temperature used, occurring in different mass loss range. This piece of information was reaffirmed by the FTIR spectra, which presented characteristic bands of gelatin structure before calcinations which disappear in the spectrum of the solid after calcinations, indicating the loss of organic matter from gelatin after heat treatment. The spectra exhibited M-O stretching vibration at low wavenumbers after calcinations related to metal oxides. The acquired images by SEM suggest the obtaining of a highly porous material with very different characteristics depending on the composition of the support. The N2 isotherms indicate the presence of a micro/mesoporous oxide with interesting textural properties, particularly for the supports containing aluminum and silicon oxide. The ethanol dehydration results showed greater selectivity to diethyl ether compared to ethylene. From the reaction data, the following order of acid strength was obtained: 2Si-Al > Si-2Al > Si-Al > Al, which is related to the Si-Al ratio.

Highlights

Catalytic supports are an important class of materials which, as their name implies, fix the active sites on the solids surface in order to improve their different physicochemical properties [1–3]
It is important to highlight that the pore size detected by the images exposed in Figure 5 has a size well above the value compared with pore size determined by N2 adsorption/desorption isotherms (Figure 6); this provides an indication that it is a highly porous material, since it showed a sponge-like morphology which resulted in the high surface porosity. This morphology is justified by the synthesis method used, since a biotemplate was used in the preparation of different supports, which allows uniform distribution of metallic cations (Al3+ or Si4+) in the organic matrix. These samples during thermal treatment at high temperature suffer the gradual decomposition of organic matter in parallel with the formation of highly dispersed metal oxides, according to thermal analyses results (Figure 3), X-Ray Diffraction (XRD) diffractograms (Figure 4), and Fourier Transform Infrared Spectroscopy (FTIR) spectra (Figure 5(b)), generating cavities as a result of its elimination, which are clearly visible in the Scanning Electron Microscopy (SEM) images
Catalytic supports containing aluminum oxide and/or silicon oxide were synthesized through an alternative method, denominated proteic sol-gel, which uses as organic precursor the gelatin from porcine skin

Summary

Introduction

Catalytic supports are an important class of materials which, as their name implies, fix the active sites on the solids surface in order to improve their different physicochemical properties [1–3]. Many of the existing techniques have a considerable cost and take significant time and typically use precursors from nonrenewable sources compared to the proteic sol-gel route proposed here, which uses gelatin from porcine skin as organic precursor (renewable source) and aluminum nitrate and/or tetraorthosilicate (TEOS) as inorganic precursors. It has given enough emphasis in the synthesis of metal oxides and alloys containing nanoparticles with interesting magnetic and optical properties using the proteic sol-gel route [29–33]; the synthesis of porous supported materials with potential applications in catalysis still needs to be studied from the gelatin precursor. The present work shows the bioinspired synthesis and characterization of catalytic supports containing aluminum oxide and/or silicon using an alternative synthetic methodology from gelatin, which is efficient and of low cost

Experimental

C NH CH C N

80 Si-2Al

Conclusions