Avaliação do Comportamento de Diferentes Polímeros utilizados para Embalagem de Ácido Sulfúrico Concentrado
authors Juliana Isabel Sousa Cunha
supervisors Ana Margarida Madeira Viegas De Barros Timmons
thesis type mestrado integrado em engenharia química
nationality International
abstract Sulfuric acid is widely used in the chemical industry including in the production of fine chemicals, for that reason adequate storage conditions are essential to ensure its quality. As it is common to observe the development of color after long storage times, this thesis aims to study systematically the behavior of sulfuric acid in contact with several polyethylene containers used at the RNM company over time. For that purpose, the characteristics of both sulfuric acid and storage containers were evaluated over time. The acid concentration was monitored following a procedure based on the ASTM E 223 standard, and it was concluded that the concentration does not significantly change even though the acid presents coloring, at room temperature conditions. The development of color over time was assessed by UV-Vis spectroscopy. This study revealed the presence of substances whose maximum wavelength absorption varies with the storage time suggesting the conversion of the chemical species into distinct ones. As regards the study of the plastic reservoirs, several samples have been analyzed before and after being exposed to sulfuric acid using attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy coupled with X-ray dispersive spectrometry (SEM-EDS) and differential scanning calorimetry (DSC). Additionally, an extraction of the plastic additives was performed. This study included a mass balance and analyses by FTIR and UV-Vis spectroscopy and proton magnetic nuclear resonance spectrometry (1H NMR), before and after contact with concentrated sulfuric acid. From the SEM-EDS results it was possible to conclude that the sulfuric acid oxidizes the plastic. Furthermore, the FTIR-ATR and DSC have proven that additives are present in the plastic samples, when compared with a virgin polyethylene sample. After the extraction of such additives and contact with the sulfuric acid the coloring was observed and the FTIR-ATR and the 1H-NMR spectra confirmed that oxidation occurs. Thus, it was possible to conclude that the coloring observed during storage results from the contact of the sulfuric acid with the plastic container’s additives.
year published 2017
link http://hdl.handle.net/10773/22365