Navegando por Assunto "Heterogeneous acid catalysis"

Agora exibindo 1 - 2 de 2

Acesso aberto (Open Access)
Atividade e estabilidade de catalisador à base de carbono sulfonado na reação de esterificação: influência da temperatura de pirólise no processo de funcionalização
(Universidade Federal do Pará, 2021-08-25) CORRÊA, Ana Paula da Luz; CONCEIÇÃO, Leyvison Rafael Vieira da; http://lattes.cnpq.br/7467898936995220
In the present study, the pyrolysis temperature on the activity and catalytic stability of sulfonated biochars, from the agroindustrial waste of murumuru kernel shell, was evaluated in the esterification reaction of oleic acid with methanol. In view of the investigation of factors related to catalytic functionalization and its impact on reuse processes, carbonaceous materials were synthesized by direct pyrolysis under different carbonization temperatures, at 450, 600 and 750 °C. The process of biochars functionalization was carried out by sulfonation with concentrated sulfuric acid at 200 °C and 4 h. The materials were characterized in terms of determining the density of sulfonic groups, Scanning Electron Microscopy (SEM), Energy Dispersion X-Ray Spectroscopy (EDS), Elemental Analysis (CNHS), Fourier Transform Infrared Spectroscopy (FT- IR), Raman Spectroscopy, Thermogravimetric Analysis (TG) and X-Ray Excited Photoelectron Spectroscopy (XPS). The influence of the variables temperature and reaction time on the catalytic performance and reuse capacity of the catalysts was also evaluated. The data obtained showed that the functionalization with sulfonic groups occurred directly in the carbon chain of the biochars, higher temperatures carbonization resulted in more stable polycondensed carbonaceous catalysts and a higher degree of structural order. The carbonized catalyst at 750 °C achieved the conversion of oleic acid in the esterification reactions of 98.37% and maintained in the third reaction cycle conversion of 89.30%. Such a catalyst also has the highest content of sulfur groups, even after reuse processes. The increase in temperature and time in the reaction medium was able to improve the reuse capacity of relatively low stability catalysts. Thus, these results show the impact of the pyrolysis temperature in obtaining catalysts with greater activity and catalytic stability in the esterification reactions, and in this way provide great support for the development of new heterogeneous sulfonated carbon-based catalysts, applied in the biodiesel production process. Furthermore, they corroborate the high potential for using the residual biomass of murumuru kernel shell in the development of a new material.
Acesso aberto (Open Access)
Preparação e avaliação de catalisador heterogêneo ácido baseado em óxido de grafeno funcionalizado para síntese de biodiesel
(Universidade Federal do Pará, 2021-09-24) SILVA, Paula Maria Melo da; CONCEIÇÃO, Leyvison Rafael Vieira da; http://lattes.cnpq.br/7467898936995220
The present study aims at the synthesis of a heterogeneous acid catalyst derived from graphene oxide, applied in the transesterification reaction of soybean oil to obtain biodiesel. The graphene oxide catalytic support was synthesized from graphite oxidation and the catalyst was functionalized by impregnation of molybdenum trioxide (MoO3) as the active phase. The synthesis of the support and the catalyst was confirmed through the characterization techniques of Fourier Transform Infrared Spectroscopy (FT-IR), Thermogravimetric Analysis (TG/DTG), Scanning Electron Microscopy (SEM), Energy Dispersion X-Ray Spectroscopy (EDS) and XRay Diffraction (DRX). The catalytic tests optimization of the transesterification reactions had as parameters evaluated the temperature in the range of 120–160 °C, the time between 1–5 h, the catalyst concentration comprised in 10% (m/m) and molar ratio oil/ alcohol in the range of 25:1–45:1. The reaction studies evidenced as an optimum point the temperature of 140 °C, time of 5 h, catalyst concentration 6% (m/m) and molar ratio of 35:1, leading to the obtainment of a biodiesel with an ester content above 90%. The catalyst also maintained its catalytic activity even in the seventh reaction cycle. Therefore, the results obtained demonstrate that the graphene oxide catalyst supported by MoO3 is a new and promising heterogeneous acid catalyst with high catalytic efficiency in the transesterification reaction for the biodiesel synthesis.