A carregar...
Publicação
Aplicação de catalisadores heterogéneos na despolimerização redutiva de resíduos plásticos
| Nome: | Descrição: | Tamanho: | Formato: | |
|---|---|---|---|---|
| 2.51 MB | Adobe PDF |
Orientador(es)
Resumo(s)
As propriedades extraordinárias do plástico e as necessidades crescentes da sociedade fomentaram
a sua produção massiva, levando a um descontrolo da gestão dos resíduos descartados. Assim, é
urgente investigar novos métodos que eliminem e valorizem os resíduos plásticos.
O presente trabalho focou-se na utilização de nanomateriais como catalisadores heterogéneos na
despolimerização redutiva de resíduos plásticos, visto que esta metodologia já demonstrou ser uma
solução eficiente.
Preparou-se o complexo MoO2Cl2(thf)2 que foi suportado num material mesoporoso MCM-41 e
em nanopartículas magnéticas de Fe3O4 revestidas com sílica. A síntese destes materiais foi
confirmada pelas técnicas de DRX, FTIR, SEM e TEM. A quantificação do Mo presente nos materiais
MCM-Mo (2) e NPM-Si-Mo (5) foi efetuada por ICP-MS, tendo-se obtido os valores 3,15 e 4,32%,
respetivamente.
A despolimerização redutiva de diferentes poliésteres e de um policarbonato foi realizada
utilizando os materiais preparados como catalisadores, pinacolborano como agente redutor e tolueno
ou benzeno deuterado como solventes, às temperaturas de 110 ou 160 ºC, sob atmosfera ambiente. Os
valores de conversão e rendimento foram determinados por espetroscopia de 1H RMN.
Os resultados obtidos revelaram-se muito promissores, tendo-se alcançado rendimentos moderados
a excelentes. O melhor resultado obtido nas reações realizadas com o material MCM-Mo (2) foi
observado na despolimerização redutiva do poli(succinato de butileno) (PBS), originando o
pinBO(CH2)4OBpin com 80% de rendimento. O material NPM-Si-Mo (5) apresentou uma maior
atividade na despolimerização da poli(caprolactona) (PCL), obtendo-se o pinBO(CH2)6OBpin com
95% de rendimento. Estes catalisadores foram também testados em 4 reações consecutivas,
verificando-se que a sua atividade catalítica diminui ao longo das reações sem alterações significativas
na estrutura do suporte.
Assim, a despolimerização redutiva de plásticos utilizando o material MCM-41 e nanopartículas
magnéticas como suportes do complexo MoO2Cl2(thf)2 apresenta-se como uma boa estratégia e
poderá contribuir para melhorar esta metodologia ao recorrer a catalisadores heterogéneos.
The extraordinary properties of plastic and the growing needs of society caused its massive production, leading to careless disposal of the waste produced. Therefore, it is urgent to improve the research for new methods that eliminate and value plastic waste. The present work aimed to use nanomaterials as heterogeneous catalysts in the reductive depolymerization of plastic waste, since this methodology has already proven to be an efficient solution. The MoO2Cl2(thf)2 complex was prepared and anchored to a mesoporous material MCM-41 and to Fe3O4 magnetic nanoparticles coated with silica. Their synthesis was confirmed by XRD, FTIR, SEM and TEM techniques. The quantification of the Mo present in the materials MCM-Mo (2) and NPM-Si-Mo (5) was performed by ICP-MS, obtaining the values 3,15 and 4,32%, respectively. The reductive depolymerization of different polyesters and a polycarbonate was carried out using the prepared materials as catalysts, pinacolborane as the reducing agent and toluene or deuterated benzene as solvents at 110 or 160 ºC, under an ambient atmosphere. The yield and conversion values were determined by 1H NMR spectroscopy. The results obtained turned out to be quite promising, achieving good to excellent yields. The best result obtained in the reactions performed with the material MCM-Mo (2) was observed in the reductive depolymerization of polybutylene succinate (PBS), forming pinBO(CH2)4OBpin with 80% yield. The material NPM-Si-Mo (5) showed a higher activity for the depolymerization of polycaprolactone (PCL), obtaining pinBO(CH2)6OBpin with 95% yield. These catalysts were also tested in 4 consecutive reactions, verifying a decrease in their catalytic activity without any significant changes in their support structure. Therefore, the reductive depolymerization of plastics using an MCM-41 material and magnetic nanoparticles to support the MoO2Cl2(thf)2 complex presents itself as a good strategy and can contribute to improving this methodology by using heterogeneous catalysts.
The extraordinary properties of plastic and the growing needs of society caused its massive production, leading to careless disposal of the waste produced. Therefore, it is urgent to improve the research for new methods that eliminate and value plastic waste. The present work aimed to use nanomaterials as heterogeneous catalysts in the reductive depolymerization of plastic waste, since this methodology has already proven to be an efficient solution. The MoO2Cl2(thf)2 complex was prepared and anchored to a mesoporous material MCM-41 and to Fe3O4 magnetic nanoparticles coated with silica. Their synthesis was confirmed by XRD, FTIR, SEM and TEM techniques. The quantification of the Mo present in the materials MCM-Mo (2) and NPM-Si-Mo (5) was performed by ICP-MS, obtaining the values 3,15 and 4,32%, respectively. The reductive depolymerization of different polyesters and a polycarbonate was carried out using the prepared materials as catalysts, pinacolborane as the reducing agent and toluene or deuterated benzene as solvents at 110 or 160 ºC, under an ambient atmosphere. The yield and conversion values were determined by 1H NMR spectroscopy. The results obtained turned out to be quite promising, achieving good to excellent yields. The best result obtained in the reactions performed with the material MCM-Mo (2) was observed in the reductive depolymerization of polybutylene succinate (PBS), forming pinBO(CH2)4OBpin with 80% yield. The material NPM-Si-Mo (5) showed a higher activity for the depolymerization of polycaprolactone (PCL), obtaining pinBO(CH2)6OBpin with 95% yield. These catalysts were also tested in 4 consecutive reactions, verifying a decrease in their catalytic activity without any significant changes in their support structure. Therefore, the reductive depolymerization of plastics using an MCM-41 material and magnetic nanoparticles to support the MoO2Cl2(thf)2 complex presents itself as a good strategy and can contribute to improving this methodology by using heterogeneous catalysts.
Descrição
Tese de Mestrado, Química, 2024, Universidade de Lisboa, Faculdade de Ciências
Palavras-chave
Despolimerização redutiva Resíduos plásticos Catalisadores heterogéneos MCM-41 Nanopartículas magnéticas Teses de mestrado - 2024