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- Author or Editor: B. Araujo x
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Abstract
This study aims to analyze thermal stability and make a rheological assessment of sunflower oil produced in the Northeast of Brazil, resulting from the pyrolysis process. Oil samples were submitted to thermal degradation and the reaction was evaluated by the thermogravimetric technique, at temperatures between 30 and 900 °C. Apparent activation energy was determined using the model-free kinetics theory. The coaxial cylinder system at operating temperature of 40 °C was used to obtain rheological parameters. Oil was characterized by gas chromatography. The lipid profile of the oil exhibited good quality. The activation energy of the sunflower oil was 201.2 kJ mol−1. Results showed the influence of physical–chemical characteristics of vegetable oil on the thermal decomposition process. Rheological analyses confirmed Newtonian rheological behavior. The high potential of the “Catissol” variety produced in Northeast Brazil as raw material for biofuel production using pyrolysis was also demonstrated.
Abstract
This work proposed a technique to estimate the kinetic parameters of cracking reaction. High-boiling-point petroleum fractions (>623.15 K) were analyzed. The experiments were performed using a thermal analysis system with a differential scanning calorimetry module at different linear heating rates (15, 20, 25, and 30 K min−1) in the temperature range from 303.15 to 823.15 K. The Arrhenius, Kissinger, and Flynn–Ozawa–Wall methods were used to determine the kinetic parameters. The compensation effect and the dependence on the activation energy of the conversion degree were evaluated. The catalyst used was a typical FCC regenerated catalyst containing 48.3 mass% of alumina, and particle size of 67 μm. The effect of catalyst loading was studied using 3, 5, and 10 mass%. Analysis of the DSC curves showed a major transitional stage between 693.15 and 723.15 K, identified as an endothermic region of high temperature oxidation (HTO). Empirical kinetic models were produced and data were obtained from the kinetic analysis of the HTO region. Under non-isothermal heating conditions higher activation energies were found as the API gravity of the high-boiling-point petroleum fraction decreased. On the other hand, the results showed consistent effects for the dependence of the activation energy on the extent of cracking conversion under non-isothermal conditions, showing a decrease with the extent of conversion. The catalytic loading effect is remarkable, and provides an alternative route for the cracking with lower activation energy with increasing catalyst weight. The kinetic parameters formulated will be used in the mathematical modeling of the reactive molecular distillation process for upgrading high-boiling-point petroleum fractions.
Abstract
Biodiesel is defined as a mixture of mono- or di-alquil esters of vegetable oil or animal fats. During long-term storage, oxidation caused by contact with air (autoxidation) presents a legitimate concern in relation to monitoring and maintaining fuel quality. Extensive oxidative degradation may compromise the quality by adversely affecting kinematic viscosity, acid value, or peroxide value. The oxidation susceptibility of biodiesel, due to the presence of triacilglycerides of poly-unsaturated fatty acids, was evaluated in this study. Samples of sunflower, castor, and soybean biodiesels were obtained through the transesterification reaction, with the intention of achieving the thermal stability study through thermogravimetrical analyses and differential scanning calorimetry high pressure. It was furthermore observed through thermogravimetry and pressure differential scanning calorimetry curves that castor biodiesel exhibited the highest thermal and oxidative stability.
Abstract
Degradation of low density polyethylene (LDPE) was studied for the pure polymer and mixed with silicoaluminophosphate SAPO-11 catalyst. SAPO-11 was synthesized by hydrothermal method using di-isoprolpylamine as structure template, and characterized by XRD and SEM. From X-ray diffraction, it was observed that SAPO-11 was obtained with high crystallinity. Using the model-free kinetics, proposed by Vyazovkin, the activation energies were determined for the process of polymer degradation. It was found that the degradation process of 90% of LDPE mixed with SAPO-11 over a period of 1 h, occurred at a temperature of 378 °C, while for the pure LDPE, the temperature was increased to 434 °C in the same period of time and conversion, indicating that SAPO-11 was an effective catalyst for the degradation of LDPE. The activation energy for the degradation of pure LDPE was equivalent to 251 kJ mol−1. Also, when the SAPO-11 was mixed with the polymer, this value was decreased to 243 kJ mol−1.
Abstract
Thermogravimetry (TG) was used in this study to evaluate thermal and catalytic pyrolysis of Atmospheric Petroleum Residue (ATR) which can be found in the state of Rio Grande do Norte/Brazil, after a process of atmospheric distillation of petroleum. The utilized sample in the process of catalytic pyrolysis was Al-MCM-41, a mesoporous material. The procedures for obtaining the thermogravimetric curves were performed in a thermobalance with heating rates of 5, 10, and 20 °C min−1. From TG, the activation energy was determined using the Flynn–Wall kinetic method, which decreased from 161 kJ mol−1, for the pure ATR, to 71 kJ mol−1, in the presence of the Al-MCM-41, showing the efficiency of the catalyst in the pyrolysis of Atmospheric Petroleum Residue.
Abstract
Nanoporous silica with narrow pore size distribution has attracted increasing attention as a novel material for separations and reactions involving large molecules. SBA-15 has been synthesized in an acidic medium using a triblock copolymer as template. In this work, the SBA-15 was synthesized by the hydrothermal treatment at 373 K for 48 h, of a gel with the following overall molar composition: 1.0TEOS:0.017P123:5.7HCl:193H2O, where TEOS is tetraethyl orthosilicate and P123 is poly(ethylene oxide, propylene oxide and 1,4-dioxane). The obtained material was characterized by thermogravimetry, X-ray diffraction, infrared spectroscopy and BET surface area. A kinetic study using the model free model was accomplished in the stage of decomposition of the template (P123). The obtained value of the apparent activation energy was ca. 131 kJ mol−1.
Abstract
The nanostructured hybrid AlMCM-41/ZSM-5 composite was synthesized starting from a hydrogel with molar composition SiO2:0.32Na2O:0.03Al2O3:0.20TPABr:0.16CTMABr:55H2O. The cetyltrimethylammonium bromide (CTMABr) and tetrapropylammonium bromide (TPABr) were used as templates. The above mentioned material presents morphological properties with specific characteristics, such as the surface area of the composite which is approximately half of the surface area of the conventional MCM-41. Another interesting feature is the formation of walls with the double of the density of the MCM-41 structure, which characterizes the hybrid material, resulting in a high stability material for catalytic application. The aim of this study is obtain optimized structures of the hybrid material and for this purpose variations in the synthesis time were carried out. A comparative analysis was performed including X-ray diffraction, Fourier transform infrared spectroscopy, and Thermogravimetry measurements. The model-free kinetic algorithms were applied in order to determinate conversion and apparent activation energy of the decomposition of the CTMA+ and TPA+ species from the hybrid AlMCM-41/ZSM-5.
Abstract
The capture of carbon dioxide was carried out using MCM-41 and SBA-15 as adsorbents. These mesoporous materials were synthesized by the hydrothermal method, and subsequently functionalized with the di-iso-propylamine (DIPA). Then, they were characterized by XRD, BET, and TG/DTG. The X-ray diffraction patterns of the synthesized samples showed the characteristic peaks of MCM-41 and SBA-15, indicating that the structures of these materials were obtained. The functionalized samples presented a decrease of the intensities of these peaks, suggesting a decreasing in the structural organization of the material; however, the mesoporous structure was preserved. For the adsorption capacity measurements, the materials were previously saturated with carbon dioxide at 75 °C, and then desorbed in a thermobalance in the temperature range of 25–900 °C, under helium atmosphere. Desorption tests showed that the functionalized MCM-41 presented a weight loss of 7.5 wt%, against 5.9 wt% for SBA-15. The obtained values indicate that these nanostructured materials can be used as adsorbent for carbon dioxide capture.
