Preparação, caracterização e aplicação de aerógeis e xerógeis, de paládio, platina e rutênio-estanho dispersos em sílica como catalisadores em reações de interesse ambiental

Abstract

Aerogels and Xerogels were synthesized by sol-gel method, characterized and utilized as catalysts in environmental interest reactions. This process is unique for the production of catalytic material with specific morphological, textural and chemical properties, allowing the introduction of different catalytic phases dispersed in an inert matrix. Materials obtained by this process were used as catalysts in reactions as partial oxidation, epoxidation, nitroxidation, amination, hydrogenolysis, etc. In this work, 8 series of catalysts were prepared: SiO2 pure matrix aerogels and xerogels and the composities Pd/SiO2 and Pt/SiO2. All samples were treated thermally at 300, 500, 700 and 900ºC. The catalysts (xerogels) formed by RuSn supported on silica were obtained mixing to the silica matrix a precursor complex RuCp(PPh3)2SnCl3 or salts of RuCl3 and SnCl2, changing the salts quantities. The obtained materials were characterized by: - X-ray diffraction, for the phase identification; - Gas adsorption, for determination of the surface specific area and porosity; - Thermal analysis (DTA/TG); - Atomic absorption, for the Pd and Pt contents determination; - Temperature programmed reduction (TPR) analysis; - Scanning electronic microscopy (SEM) for morphological analyses; - And electronic microprobe (WDS) for chemical analyses. The RuSn xerogels were characterized also by DRIFTS and 119Sn Mössbauer spectroscopy. The catalytic reactions studied were the hydrogendechlorination of CCl4, in gas phase, and clorobenzene, in liquid and gas phases, clorobenzene oxidation, in gas phase, and 1,5-ciclooctadiene, in liquid phase. The reactions products were analyzed by gas chromatography, 1H and 13C nuclear magnetic resonance and mass spectrometry.