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Abstract(s)
Estudos já feitos demonstram que a reação de transesterificação utilizada na produção de biodiesel, pode ser catalisada com grande eficiência recorrendo a catalisadores heterogéneos com base em óxido de cálcio. O óxido de cálcio (CaO), por ser barato, altamente ativo e facilmente disponível, é um dos catalisadores sólidos mais utilizados. O CaO pode ser adquirido de materiais residuais da indústria alimentar, tais como conchas e cascas de moluscos cuja constituição é maioritariamente carbonato de cálcio que é facilmente convertido em óxido de cálcio. No entanto, durante sucessivas utilizações vão aparecendo alguns problemas relacionados com a perda gradual de atividade dos catalisadores sendo, por isso, necessário afinar e otimizar as variáveis processuais (Serio, 2006; Reyero et al., 2014; Boey et al., 2011). A performance catalítica poderá ser melhorada através da utilização de catalisadores à escala nanométrica devido à maior área superficial específica (Rai e Silva, 2011). Para além dos elevados rendimentos obtidos na produção de Biodiesel, o uso de catalisadores nanoestruturados à base de CaO apresentam ainda a vantagem de serem catalisadores simples, seguros e baratos (Ranu e Stolle, 2016).
No presente trabalho, foi investigada a conformação dos catalisadores sob a forma de materiais nanoestruturados. Os catalisadores foram preparados recorrendo à técnica de “Ball Milling”, uma técnica simples, segura e isenta de solventes. Contudo, não foi possível atingir a escala nanométrica, tendo-se conseguido catalisadores com tamanho de partícula de aproximadamente 2 μm.
Após o processo de “Screenning” dos catalisadores, o CaO, CaO-SiO2, CaO-Al2O3 e CaO-CNT foram os catalisadores que apresentaram melhor atividade catalítica, sendo ainda muito fáceis de recuperar da mistura reacional.
Os catalisadores CaO, CaO-Al2O3, e CaO-CNT apresentam boa estabilidade catalítica na reação de transesterificação de triglicéridos em biodiesel. Os testes de estabilidade catalítica com estes catalisadores resultaram em 3 etapas reacionais, com conversões em ésteres metílicos superiores a 98,5%, cumprindo o definido pela Norma Europeia EN14214.
Studies have shown that the transesterification reaction used in the production of biodiesel can be catalyzed with great efficiency using heterogeneous catalysts based on calcium oxide. Calcium oxide (CaO), being cheap, highly active and readily available, is one of the most commonly used solid catalysts. CaO can be purchased from waste materials from the food industry, such as shells whose constitution is mostly calcium carbonate which is easily converted to calcium oxide. However, after successive catalytic cycles a gradual loss of activity occurs, and for that reason several process variables should be optimized (Serio, 2006; Reyero et al., 2014; Boey et al., 2011). The catalytic performance can be improved using catalysts at nanometric scale due to the related higher specific surface area (Rai e Silva, 2011). In addition to the high yields in Biodiesel production, the use of CaO-based nanostructured catalysts also has the advantages of being simple, safe and cheap (Ranu and Stolle, 2016). In the present work, the conformation of the catalysts as nanostructured materials was investigated. The catalysts were prepared using the Ball Milling technique, a simple, safe and solvent-free synthetic technique. However, the nanoscale was not achieved, with catalysts having a particle size of approximately 2 μm. After catalytic screening, CaO, CaO-SiO2, CaO-Al2O3 and CaO-CNT were the most active catalysts, being very easy to separate from the liquid mixture. The catalysts CaO, CaO-Al2O3, and CaO-CNT showed good catalytic stability in the transesterification reaction of triglycerides in to biodiesel. The catalytic stability tests with these catalysts resulted in 3 reactional steps, with conversions in methyl esters above 98,5%, complying with the European Standard EN14214.
Studies have shown that the transesterification reaction used in the production of biodiesel can be catalyzed with great efficiency using heterogeneous catalysts based on calcium oxide. Calcium oxide (CaO), being cheap, highly active and readily available, is one of the most commonly used solid catalysts. CaO can be purchased from waste materials from the food industry, such as shells whose constitution is mostly calcium carbonate which is easily converted to calcium oxide. However, after successive catalytic cycles a gradual loss of activity occurs, and for that reason several process variables should be optimized (Serio, 2006; Reyero et al., 2014; Boey et al., 2011). The catalytic performance can be improved using catalysts at nanometric scale due to the related higher specific surface area (Rai e Silva, 2011). In addition to the high yields in Biodiesel production, the use of CaO-based nanostructured catalysts also has the advantages of being simple, safe and cheap (Ranu and Stolle, 2016). In the present work, the conformation of the catalysts as nanostructured materials was investigated. The catalysts were prepared using the Ball Milling technique, a simple, safe and solvent-free synthetic technique. However, the nanoscale was not achieved, with catalysts having a particle size of approximately 2 μm. After catalytic screening, CaO, CaO-SiO2, CaO-Al2O3 and CaO-CNT were the most active catalysts, being very easy to separate from the liquid mixture. The catalysts CaO, CaO-Al2O3, and CaO-CNT showed good catalytic stability in the transesterification reaction of triglycerides in to biodiesel. The catalytic stability tests with these catalysts resulted in 3 reactional steps, with conversions in methyl esters above 98,5%, complying with the European Standard EN14214.
Description
Trabalho final de mestrado para obtenção do grau de mestre em Engenharia Química e Biológica
Keywords
Óxido de cálcio Calcium oxide Biodiesel Biodiesel Catálise heterogénea Heterogeneous catalysis Energia renovável Renewable energy Reação de transesterificação Transesterification reaction Ball milling
Citation
LINO, Catarina Isabel dos Santos - Desenvolvimento de catalisadores heterogéneos nanoestruturados para produção de biodiesel. Lisboa: Instituto Superior de Engenharia de Lisboa, 2019. Dissertação de mestrado.
Publisher
Instituto Superior de Engenharia de Lisboa