Estudos de sulfonação de Polissulfona e Polieterimida e suas aplicações como catalisadores ácidos heterogêneos em reações de esterificação e transesterificação para produção de biocombustíveis

Abstract

The research investigated homogeneous sulfonation of Polysulfone (PSU) and Polyetherimide (PEI) using acetyl sulfuric acid (ASUA) in dichloromethane. The products obtained had average degrees of sulfonation ((DS) ̅) ranging from 0.534 to 3.022 for PSU-S, and from 0.146 to 3.569 for PEI-S, according to thermogravimetric analysis. These values are consistent with those expected from theoretical studies. Composites of virgin and sulfonated polymers were produced with addition of MnFe₂O₄ magnetic nanoparticles and fibers obtained by electrospinning and centrifugal electrospinning (CES). CES technique produced PSU-S fibers with ion exchange capacity (IEC) from 0.784 to 4.005 meq/g and thicknesses ranging from 800 nm to 470 nm. PEI-S fibers with IEC of 1.124 meq/g were also obtained with ASUA, in addition to PSU and PEI crosslinked and sulfonated in a single step with concentrated sulfuric acid, glacial acetic acid, and paraformaldehyde. These sulfonated and crosslinked polymers exhibited resistance to solubilization in dichloromethane and chloroform, enabling their reuse in catalytic processes. Several materials were produced, focusing on those that stood out the most in the esterification of oleic acid (OA) with methanol to produce methyl oleate (MeO), will be highlighted. Pulverized PSU-S, with an IEC of 3.200 meq/g, converted 85.2% of OA within 10 minutes at 65°C, while pulverized PEI-S, with an IEC of 3.640 meq/g, achieved 83% under the same conditions. Electrospun PSU-S (4.005 meq/g) converted 95% of OA in 30 minutes at 65°C. Composites of PSU with sulfonated soybean hull carbon (10% w/w polymer/carbon with IEC of 5.827 meq/g) converted 69.9% of OA in 10 minutes at 65°C, reaching 97% in 30 minutes. Composites of PEI with the same carbon reached 38.6% in 10 minutes and 94.2% in 60 minutes at the same temperature. Sulfonated and crosslinked polymers exhibited MeO conversions of 78.6% for PSU and 47.7% for PEI in 60 minutes at 65°C, although IECs require further evaluation due to high dispersion among analytical measurements. The combination of sulfonation methodologies, electrospinning techniques, and the production of sulfonated composites opens new avenues for research and technological applications. These advancements are promising for creating new materials with potential use as catalytic membranes in reactors, optimizing the utilization of natural resources, and reducing environmental impact.