Influência da temperatura e da natureza do catalisador na polimerização do glicerol

Abstract

Resumo: Neste trabalho, a polimerização do glicerol na presença de catalisador ácido (H 2 SO 4 ou H 3 PO 4 ) e básico (NaOH), para produzir resinas termofixas foi investigada. Os resultados mostraram que as variáveis como a temperatura de reação, o tipo e a concentração do catalisador são críticas para a obtenção de bons rendimentos e seletividade para materiais poliméricos. Em condições otimizadas, i.e. H 2 SO 4 como catalisador, 140 °C por 24 horas, foi possível obter polímeros com 98% de seletividade. Após polimerização, os materiais obtidos foram submetidos a extrações com diferentes solventes, i.e. água, THF e hexano. Os extratos foram caracterizados por ESI(+)-MS e por espectroscopia na região do infravermelho, que permitiram verificar a presença de oligômeros de até seis unidades monoméricas. Para menores tempos de reação, e.g. 4 horas, foi possível obter elevada seletividade (100%) para oligômeros, mas com baixa conversão de glicerol (25%). Além disso, verificou-se que os outros catalisadores (H 3 PO 4 e NaOH) apresentam baixa atividade para promover a polimerização do glicerol, e.g. rendimento de 25% após 24 horas. Palavras-chave: Glicerol, polimerização, resina termofixa, poliglicerol. Influence of Temperature and Nature of the Catalyst on Glycerol PolymerizationAbstract: In this work, an investigation was made of the glycerol polymerization in the presence of acid (H 2 SO 4 or H 3 PO 4 ) and base (NaOH) catalysts to produce thermosetting resins. The results showed that the reaction temperature and catalyst concentration are critical to obtain good yield and selectivity. Under optimum condition, i.e. H2SO4 catalyst, 140 °C for 24 hours it was possible to obtain polymers with 98% selectivity. After the polymerization the materials were submitted to extractions with different solvents, i.e. water, THF and hexane. The extracts were characterized by ESI(+)-MS (Electro-Spray Ionization Mass Spectrometry) and by FTIR, showing the presence of short-chain oligomers (up to six units). For shorter reaction times, e.g. 4 hours, it was possible to obtain high selectivity (100%) for oligomers, but with low glycerol conversion (25%). It was also observed that the other catalysts (H 3 PO 4 and NaOH) showed low activity to promote glycerol polymerization, e.g. yields of 25% after 24 hours. Keywords: Glycerol, polymerization, thermosetting resin, polyglycerol. IntroduçãoA crescente produção de biodiesel, através da transesterificação [1][2][3] de óleos vegetais ou gorduras animais (Figura 1), em todo o mundo [4] e em especial no Brasil, deve levar a um aumento significativo do volume de glicerol no mercado. Para cada tonelada de triglicerídeos processada, são produzidos pelo menos 100 kg de glicerol [4][5][6] . Como consequência, o preço do glicerol cai fortemente no mercado em todo o mundo [7] . Essa queda de preço é uma tendência mundial, não sendo diferente no Brasil, que em 2005 registrou preços de glicerol em torno de R$ 3000 t -1 , mas já em 2007, a mesma quantidade de glicerol era comercializada por R$ 1700 t -1...

Natural latex‐glycerol dressing to reduce nipple pain and healing the skin in breastfeeding women

“…The FTIR spectrum from glycerol shows the transmission bands: 849 cm −1 C‐C stretching; 1030 cm −1 C‐O stretching; 1416 cm −1 , 908 cm −1 CH 2 ; 1108 cm −1 C‐OH; 2880 and 2932 cm −1 C‐H stretching and 3286 cm −1 O‐H stretching. These transmission bands are in agreement with the results obtained by Bilanovic et al and Medeiros . FTIR spectra from NRL and NRL‐glycerol showed that there is no covalent interaction between glycerol and NRL (not show additional transmission bands).…”

“…Under these conditions, NRL and NRL‐glycerol membranes showed no hemolytic effects indicating no detectable disturbance of the red blood cell membranes. These results are similar to those obtained by Borges et al 8‐33 and Barros et al . The test was realized according to the international standard ISO 10993‐4:2002, showing that the membrane NRL‐glycerol has no cytolytic activity.…”

Preparation of magnetic mesoporous composites from glycerol and iron(III) salt

“…Several studies have shown that glycerol can be condensed in the presence of acid catalysts to produce ether-type oligomers containing two to five units; [2][3][4][5][6][7][8][9] further reaction leads to the polymerization of glycerol, producing a thermosetting resin. 3,4 Moreover, via glycerol polymerization followed by pyrolysis on the surface of clay vermiculite, a carbon-coated composite with a surface area of 835 m 2 g −1 (essentially microporous, with a significant portion of mesopores) is obtained, and is used for dye adsorption. 10 Polymerization of glycerol produces a thermosetting polymer, which can be pyrolyzed, maintaining its structure.…”

Synthesis and characterization of polyesters from glycerol by-product of biodiesel production

“…The glycerol polymers produced can have different applications, as polyols substitutes, polivinylic alcohol, lubricant, row materials to produce resins and polyurethanes. 12 Glycerol can be a plasticizer agent when added to phenolic composite and can increase the elasticity and toughness of the phenolic materials. The presence of glycerol in the phenolic network reduces the characteristic brittleness of phenolic resins by decreasing to cross-link density of the cure composites.…”