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A sensor based in a graphite–polyurethane composite electrode modified with the mesoporous nanostructured silica with hexagonal array of pores called Santa Barbara Amorphous type material (SBA-15) containing nickel was built. The presence of Ni, incorporated during the synthesis of SBA-15, resulted in an increase in sensitivity when compared to the other electrodes based on the unmodified SBA-15. A procedure was proposed for the determination of Cu2+ in ethanol biofuel by square wave stripping voltammetry with linear response in concentration levels of 1.0×10−8 and 1.0×10−7 mol L−1, resulting in a limit of detection of 1.83×10−10 mol L−1 and precision (RSD) of 2.09 %.

Catalytic activity is usually related to the acid-base properties of the catalyst material. Metal-organic frameworks (MOFs) have been evaluated as potential catalysts for several reactions. Cu-BTC (with a well-defined crystalline structure) and Fe-BTC (with a gel-like porous structure) have both shown the presence of Lewis surface acid sites based on the observed performance in different catalytic reactions. In this work, experiments of Inverse Gas Chromatography (IGC) and n-butylamine thermo desorption analysis were carried out in order to determine the acid-base properties of both materials. The IGC measurements allow to access the acid-base properties of the material surface by using acidic, basic and amphoteric molecules. Otherwise the n-butylamine thermo desorption measurements allow the quantification of those acid and basic sites from the n-butylamine desorption curves of a sample previously saturated with that probe molecule. The Lewis acid properties obtained by both methodologies showed to be more pronounced for the Fe-BTC MOF sample. The IGC measurements exhibited values of acidity constants (KA) of 0.81 and 0.60 for Fe-BTC and Cu-BTC, respectively. Furthermore the n-butylamine thermo desorption experiments indicate total acidities of 2.06 and 0.49 mmol g−1 for Fe-BTC and Cu-BTC, respectively.

The adsorption of carbon dioxide on amino silanes-functionalized MCM-41 and SBA-15 materials is reported. The functionalization of mesoporous silicas was made by post-synthesis method, by impregnation of 3-aminopropyltriethoxysilane. The obtained materials were characterized by X-ray diffraction, scanning and transmission electron microscopies, nitrogen adsorption-desorption and X-ray photoelectron spectroscopy measurements. The carbon dioxide adsorption capacities for the samples were carried out under ambient pressures. The obtained results evidenced that amino-silanes with a terminal amine (–NH2) were functionalized through covalent coupling of this group on the surface of the channels in the ordered mesoporous silica, meaning that the amine is anchored on the surface of the bigger pores of the MCM-41 and SBA-15 support. For functionalized materials, the CO2 adsorption capacity of the AMCM-41 increased from 0.18 to 1.1 mmol·g−1, whereas for ASBA-15, it was from 0.6 to 1.8 mmol·g−1. The Lagergren kinetic algorithms were applied in order to validate the obtained results, evidencing the enhanced carbon dioxide adsorption capacity and stability of the functionalized ordered mesoporous molecular sieves.

Biodiesel is currently the most common biofuel alternative for diesel engines due to its technical, environmental and strategic advantages. In Brazil, the use of mixtures B(X) biodiesel/diesel as fuels is growing every year, mainly due to the calorific power of biodiesel, that is closer to the diesel oil, and even when added in small amounts, biodiesel provides a reasonable improvement in the fuel lubricity. The aim of this current work is to evaluate the thermal stability and physicochemical properties of biodiesel obtained from seeds of cotton, sunflower and palm. In addition, the properties of its mixtures with diesel oil in a proportion of 10 mass% (B10) were evaluated. All samples were characterized by gas chromatography and thermogravimetry. The results of the physicochemical analysis of the vegetable oils, their respective biodiesel and the B10 blends were in accordance with the Brazilian Agency of Petroleum, Natural Gas and Biodiesel (ANP) specification, except for the acid value of palm biodiesel. The palm oil and the cotton biodiesel were the most stable ones. All the samples showed a single thermal event, except palm oil that had two events. The most stable B10 blends were those obtained from mixtures of sunflower and palm. Furthermore, the addition of 10 mass% of biodiesel in mineral diesel improves the viscosity, cetane number and flashpoint, besides decreasing the sulfur content. Concerning the thermal stability of vegetable oils, the palm oil was the most stable one. However, for thermal stability of biodiesel samples, the cotton biodiesel was the most stable due to a high percentage of polyunsaturated esters present in its composition.

Biodiesel has become an alternative to mineral diesel; it already has been in 7% biodiesel to diesel. The intention of the Brazilian government to increase the biodiesel content in the mixture to 10% which will promote an increase in demand for raw materials for the production of biodiesel. Among them is the beef tallow which is presented as one of the cheapest raw materials among the available ones. Associated with this increase in production has been the need to improve the processes of synthesis and analyze their properties as oxidative stability (OS) in mixtures with mineral diesel. Based on this, this study aimed to analyze the physicochemical properties and oxidative stability tallow biodiesel B10 and its beef mixture. In the present work, beef tallow biodiesel was synthesized through methylic rout and was mixture to mineral diesel type B (10 wt %) without anything additives. Physic-chemical properties of biodiesel samples and that mixture were determinate, indicating that both samples are agreement with Brazilian Specifications, and the mixture has showed around 10% less sulfur than diesel. Furthermore, oxidative stability of beef tallow biodiesel is higher than at stipulated in norm. DOI: http://dx.doi.org/10.17807/orbital.v7i1.680

The hydrothermal synthesis of MCM-22 zeolite was carried out using silica, sodium aluminate and hexamethyleneimine, under static conditions at 150 °C for a period of 10 days, followed by washing with deionized water, drying overnight and calcination at 650 °C. The obtained material was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The XRD analysis evidenced that MCM-22 presented a well defined MWW structure. The FT-IR spectrum confirmed the efficiency of the hexamethyleneimine as an organic template used to direct the structure of the MCM-22 zeolite under static conditions. The SEM image indicated that the particles are spherical in shape, with a diameter of ca. 10 μm. The acid properties of the MCM-22 zeolite, as determined by n-buthylamine adsorption, were investigated in the temperature ranges of 105 to 300 °C and 300 to 525 °C, relative to medium and strong acid sites, respectively.

This study aimed to evaluate the activity of Al-MCM-41, as mesoporous heterogeneous catalyst, for the thermal and catalytic degradation of a Brazilian heavy crude oil (14°API), via thermogravimetry. The American Petroleum Institute gravity (°API) is a measure of how light of heavy petroleum is when compared to water. The API value is an inverse measure of the relative density of a petroleum liquid, and it is used to compare the relative densities of petroleum samples. The catalytic activity was investigated as a function of different concentration of Al-MCM-41 (1, 3, 5, 10 and 20 mass%) added to the oil, as well as the apparent activation energy relative to degradation process. The TG runs were carried out at temperature range of 30–900 °C, at heating rates of 5, 10 and 20 °C min−1, under nitrogen atmosphere. From TG/DTG tests, the material presented effective catalytic activity when added to the heavy oil at concentration higher than 5 mass%. This property was clearly evidenced by the activation energy values. By the application of Ozawa–Flynn–Wall kinetic model, it was observed that when the amount of catalyst was increased, the value of the apparent activation energy decreased from 103 kJ mol−1 (without catalyst) to 70 kJ mol−1 (with 20 mass% of catalyst).

Because of increases in the burning of fossil fuels, there is an increased emission of pollutant gases (e.g. CO2) into the atmosphere. An alternative to minimize these emissions is to capture these gases using porous materials, such as layered double hydroxides (LDHs). In this study, LDHs were synthesized by co-precipitation of ion salts of Mg2+ and Al3+. After the synthesis, the materials were treated with a template to expand the layers. The samples were then characterized by X-ray diffraction, thermogravimetric analysis/derivative thermogravimetry, adsorption/desorption of nitrogen, scanning electron microscopy/energy-dispersive X-ray spectroscopy and transmission electron microscopy. A CO2 adsorption study was then performed to determine the adsorption capacity of the material in accordance with the contact time between the gas and the adsorbent. The adsorption capacities of LDHs and LDHs-P123 for CO2 were 0.72 and 1.36 mmol/g, respectively, showing satisfactory results post-treatment.

Biofuel production is acquiring an important role as an energy alternative. Several research groups have proposed the use of heterogeneous catalysts in order to replace homogeneous catalysts. A new group of basic catalysts has been prepared with the aim of being used as heterogeneous catalysts in biodiesel production. The catalysts KNO3/Al2O3 have been characterized and evaluated in the transesterification processes. They were characterized by X-ray diffraction and Scanning electron micrographs. The catalytic activity was evaluated in the transesterification of sunflower oil in biodiesel. The thermal stability of the biodiesel and the percentage of esters were evaluated. Through the TG curves, the samples of 2 and 4 % of KNO3/Al2O3 have presented two mass loss and partial conversion of triglycerides in esters. Thus, the sample that contains 4 % KNO3/Al2O3 has shown better catalytic activity in the transesterification reaction of sunflower oil, with a conversion rate of 60 % ethyl esters. On the other hand, the samples of 6 and 8 % of KNO3/Al2O3 have revealed only mass loss.

This work investigated the synthesis of biodiesel from palm oil, its thermal stability using the Ozawa–Flynn–Wall and Vyazovkin kinetic models and its thermoxidation using thermogravimetry. The obtained biodiesel was in accordance with the specifications of Resolution No. 7/2008 of the ANP. The 97.4% wt conversion of palm oil to methyl esters confirmed the efficiency of the conversion of fatty acids into esters. The thermal analysis was performed on a thermobalance using heating rates of 5, 10 and 20 °C min−1. The oil exhibited two mass losses, and the biodiesel exhibited only one mass loss. The average values of the obtained apparent activation energies were 184.6 and 191.3 kJ mol−1 for palm oil and 64.1 and 65.3 kJ mol−1 for biodiesel. Additionally, the results indicate that thermal analysis can be used as a tool for monitoring the thermoxidation of biodiesel as a function of time.

The mesoporous material AlSBA-15 with Si/Al molar ratio of 25 was synthesized by the hydrothermal method and characterized by X-ray diffraction and nitrogen adsorption. This is a promising material in the field of catalysis, particularly for petroleum refining, since their mesopores facilitate the accessibility of large hydrocarbon molecules to the active sites of AlSBA-15, producing light hydrocarbons. In order to evaluating the catalytic activity of AlSBA-15, a sample of ca. 10 % in mass of this solid was physically mixed with atmospheric residue of petroleum (ATR) and heated in a thermobalance from room temperature up to 900 °C, under nitrogen atmosphere. From TG curves, it was observed a reduction in the onset temperature, when AlSBA-15 was used as catalyst for the degradation process of ATR. The kinetic model proposed by Ozawa–Flynn–Wall yielded some kinetic parameters to determine the apparent activation energy of the degradation, evidencing the efficiency of the mesoporous material, since there was a decrease in the activation energy for the catalytic degradation. The ATR alone and mixed with AlSBA-15 was also heated in a pyrolysis reactor coupled to a gas chromatograph and mass spectrometer (Py-GC/MS). From the chromatograms, it was observed an increase in the yield of hydrocarbons in the range of gasoline and diesel derived from the catalytic process. These results are due to the combination of the mesoporosity and acidity of the AlSBA-15 for application in the process of pyrolysis of hydrocarbons molecules constituents of the ATR.

Acid leaching of aluminosilicates is an interesting procedure for preparing high surface porous silica. Thermal behavior of vermiculite leached with a nitric acid solution at various concentrations was studied by thermogravimetry and differential scanning calorimetry. Activation energies of the dehydration process in selected temperature zones were determined by two different methods: Ozawa–Flynn–Wall and Friedman. The material obtained was characterized through Fourier transform infrared spectroscopy, X-ray diffraction, and nitrogen adsorption at 77 K to relate them to the estimated activation energies.

Niobium catalysts supported on sodium vermiculite (Nb2O5/V0) and vermiculite treated with hydrochloric acid (Nb2O5/V3) were prepared by the incipient impregnation method. The unsupported catalyst, niobium pentoxide, was also synthesized. The catalysts were characterized by X-ray diffraction, adsorption-desorption of nitrogen, scanning electron microscopy coupled with energy dispersive spectroscopy, UV–vis diffuse reflectance spectroscopy and Raman spectroscopy. The characterization techniques used in the analysis of the physico-chemical properties of the catalysts showed the presence of Nb2O5 on sodium vermiculite (V0) and activated vermiculite (V3) in different phases. The best dispersion of niobium oxide, as expected, was on the V3 support (SBET = 464.5 m2 g−1), due to its greater specific area compared to V0 (SBET = 0.7 m2 g−1). The rapid pyrolysis of the glycerol in the presence of catalysts Nb2O5/V0, Nb2O5/V3 and Nb2O5 was investigated using Py-GC–MS. The results showed high decomposition of glycerol with Nb2O5 (82.2%), with higher yields of oxygenated products such as organics acids (25.1%), alcohols (19.8%) and esters (23.7%). In comparison, in the presence of Nb2O5/V3 decarboxylation was greater (CO2 = 6.4%), no esters were identified, and production of organics acids (15.9%), alcohols (19.7%) and aldehyde (10.8%) were favored. Nb2O5/V0 formed products similar to pyrolysis, probably because the catalyst has low acidity and small specific area. Thus, the results of glycerol pyrolysis application showed better performance of Nb2O5 and Nb2O5/V3, due to the efficiency in obtaining oxygenated products with industrial applicability through glycerol.

The pyrolysis of vacuum gasoil (VGO) was studied alone and in presence of HZSM-5/AlMCM-41 hybrid catalyst. This micro–mesoporous material was synthesized by the hydrothermal method using dual templates of tetrapropilamonium and cetyltrimethylammonium ions at different crystallization times. The obtained materials were washed and calcined for remotion of the organic templates. The characterization by X-ray diffraction, nitrogen surface area by the BET method, scanning and transmission electron microscopies, evidenced that typical MFI structure was embedded into the bulk of the MCM-41 matrix, in order to obtain the hybrid micro–mesoporous phase. The protonic form of the material was obtained by ion exchange with ammonium chloride solution and subsequent thermal treatment. The total acidity, as determined by n -butylamine adsorption, was equivalent to 0.75 mmol g −1 , in the temperature range of 300–500 °C, corresponding to strong acid sites. For catalytic reaction, a physical mixture of 10% of catalyst/VGO was decomposed in a thermobalance at heating rates of 5; 10 and 20 °C min −1 , from 100 to 550 °C. From TG/DTG data, applying the model-free kinetics, it was observed that the activation energy for the pyrolysis of VGO alone was ca. 125 kJ mol −1 . For VGO physically mixed to both AlMCM-41 and HZSM-5, the value decreased to ca. 80–90 kJ mol −1 , whereas for the hybrid, the value was the lowest, ca. 65 kJ mol −1 , evidencing the efficiency of the combined effect of the acid sites, crystalline phase and microporosity of ZSM-5 zeolite with the accessibility of the mesoporous of the AlMCM-41 ordered material. For determination of the catalytic properties, the samples of VGO and catalyst/VGO were submitted to pyrolysis-GC–MS system at 500 °C using helium as gas carrier. The VGO alone suffers decomposition to a wide range of hydrocarbons, typically C 17 –C 41 , while in the presence of catalyst, light fraction of hydrocarbons, in the range of liquefied petroleum gas (C 3 –C 5 ), gasoline (C 6 –C 10 ) and diesel (C 11 –C 16 ) were obtained, evidencing that the HZSM-5/AlMCM-41 hybrid material is an effective catalyst for pyrolysis of VGO.

In this work, a catalyst based on alumina impregnated with potassium iodide was synthesized and tested in the process of transesterification of rice bran oil with methanol. The reaction took place in a reflux system, with a molar ratio of 15:1 methanol:oil. The catalyst was prepared by impregnation of alumina with a solution of KI followed by calcination at 773 K for 3 h. The effect of concentration of the catalyst in the yield was verified in the range of 1–5 wt.%, and the properties of specific gravity and kinematic viscosity of the biodiesel were determined. The increasing of the yield of the reaction was observed for high amount of catalyst. When 5 wt.% of the catalyst was used in the process, the best results was obtained, with 95.2% yield. As expected, the specific gravity and kinematic viscosity decreased with the catalyst amount. From TG analysis, it was observed a mass loss of 96.2%, evidencing the high activity of the catalyst for the process.

To understand the physicochemical properties and catalytic activity during the pyrolysis of atmospheric petroleum residue, a template-free ZSM-5 zeolite was synthesized using a direct method without additional seeds or an organic structure director and compared with conventionally synthesized ZSM-5. The crystallinities of the two zeolites were evaluated by XRD and FTIR and were quite similar; however, structural analyses using SEM and argon physisorption revealed that the zeolites diverged in particle diameter and in the external surface area of the micropores. The synthesis procedure without a template incorporated additional aluminum into the crystalline network, according to ICP-AES and TPD NH3 experiments. The catalytic pyrolysis performed over the template-free ZSM-5 generated results comparable to those for pyrolysis performed over the conventional ZSM-5 according to its hydrocarbon distribution. The selectivity to aromatics compounds was exactly the same for both ZSM-5 zeolites, and these values stand out compared to thermal pyrolysis. The template-free ZSM-5 produced 20% of light hydrocarbons (C4-C6), where such compounds are olefins and paraffins of great interest to the petrochemical industry. Therefore, template-free ZSM-5 is promising for industrial use due to its lowered synthesis time, low-cost and significant distribution to light hydrocarbons.

Materials based on niobium oxide (Nb

Supported heteropolyacids (HPAs) have been used as catalysts by fine-tuning their heterogenous and Bronsted acidic properties. In this work, supported H 3 PW 12 O 40 (HPW) on MCM-41 was prepared (2–40 wt%) and applied in the intramolecular cyclization of (+)-citronellal. The synthesized materials were characterized by 31 P MAS NMR, XRD, FTIR, pyridine gaseous adsorption, low temperature nitrogen adsorption and thermal analysis. The impregnation of 20% HPW on the surface of MCM-41 decreased the characteristic crystallographic reflections of the support, suggesting that HPW modifies the long-range order. The results show that the HPW was deposited preferentially inside the mesopores of the support and affected the acid strength of the supported catalyst. FTIR studies of pyridine adsorption confirmed the presence of Bronsted and hydrogen bonded acid sites. All synthesized materials were active in the cyclization reaction, but the 20%HPW/MCM-41 sample was the most active. This catalyst showed about 96% conversion and 65% selectivity to the most important stereoisomer (−)-isopulegol, under 1 h reaction. This catalyst was reused four times with a fair degree of deactivation. The decreased activity was attributed to the formation of small agglomerates in the channels of MCM-41.

Mesoporous silica catalyst was evaluated in the ethanolysis of soybean oil. Ethanol can be environmentally advantageous over methanol (more frequently used as reagent in biodiesel production) because it can be obtained from renewable sources whilst methanol is usually derived from mineral sources. A silica molecular sieve containing lanthanum oxide as active phase (La50SBA-15) was obtained by isomorphous substitution into the SBA-15 network using Pluronic (P123) dissolved in aqueous HCl solution with tetraethyl orthosilicate and a given amount of hydrated lanthanum chloride (Si:La = 50) at 333 K. The reaction was performed using the molar ratio ethanol:soybean oil of 20:1 at inert atmosphere (N2) at 343 K with 1wt% of catalyst mass relative to total oil mass added to the reaction mixture. The reaction was evaluated for ethyl ester conversion after 6 h. The ethyl esters content was measured using low frequency 1H NMR spectroscopy (60 MHz). The La50SBA-15 heterogeneous catalyst presented conversion of soybean oil in ethyl esters as high as 80% after reaction time of 6 h., comparing well with previous reports for methanolysis of soybean oil. Moreover, lixiviation of the active phase was not observed, thus excluding the contribution of the homogeneous catalysis to the studied transesterification process.

The nature of the solid residue formed in beef tallow biodiesel from two commercial producers in Brazil was determined by comparative analytical techniques, namely, gas chromatography with flame ionization detector (GC-FID) and thermogravimetry (TG). Pure monopalmitin and monostearin were used as reference standards for both methodologies. Analyses were carried out before and after filtration of the solids formed, which allowed the observation that the formation of precipitate reduced the levels of monoglycerides in the beef tallow biodiesel. The chromatographic and thermogravimetric results confirmed the nature of the residue as saturated monoglycerides, predominantly monostearin and monopalmitin.

Iodide potassium incorporated on mesoporous molecular sieves (SBA-15 and MCM-41) was used as heterogeneous catalysts in the transesterification of sunflower oil under different conditions of reaction time and ratio catalyst/oil (w/w). The results have showed that the system supported in SBA-15 has been more active than the supported in MCM-41, promoting a conversion to methyl esters of 84.98%.

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.

In order to obtain a fuel with properties similar to diesel, the thermal catalytic cracking (TCC) of buriti oil was accomplished over LaSBA-15 mesoporous materials. In function of the Lewis acid sites and the unidirectional pore system of the LaSBA-15, this material presented good deoxygenating activity for TCC of the oil, resulting in a reduction of the oxygenate content in the organic liquid (OL) collected above 190 °C, obtaining as main product, a mixture of hydrocarbons similar to mineral diesel, called green diesel.

In this study, the physico-chemistry characterization and kinetic study of the thermal decomposition of sunflower oil and its biodiesel were carried out. Sunflower biodiesel was synthesized by the methanol route and basic homogeneous catalysis. The physicochemical characterization of the sunflower oil and biodiesel were performed according to standards set out in the ANP resolution, and both are in accordance to the specifications. The chromatographic analysis was obtained by GC-FID. The yield of conversion of 97.4 wt% of sunflower oil in methyl esters confirms the efficiency of the conversion of the fatty acids into esters. The thermal analysis was performed on a thermobalance, using heating rates of 5, 10, and 20 °C min−1. In these three rates, we observed a single well-defined step of mass loss that describes the volatilization and decomposition of the sunflower oil and the biodiesel. The kinetic study was performed using equations of approximation and integration methods such as Coats–Redfern, Van Krevelen, and Horowitz–Metzger. The kinetic parameters reaction order (n) and apparent activation energy (E a), obtained by applying these method were correlated.

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.

Mesoporous materials type MCM-41 and AlMCM-41 were synthesized by the hydrothermal method and characterized by X-ray diffraction and nitrogen adsorption. Analyses have showed that the hexagonal structures of the materials were preserved and the template completely removed. In this work, the degradation of pure sunflower oil and mixed with mesoporous materials were evaluated. A kinetic study of the oil degradation was performed by thermal analysis under heating rates of 5, 10 and 20 °C min −1 using the model-free kinetic in order to determine the kinetic parameters for this process. From this method, the obtained values of apparent activation energy for sunflower oil/AlMCM-41 was of 167 kJ mol − 1 .

Thermogravimetry was applied in order to investigate the catalytic degradation of heavy oil (15.4oAPI) over silica-based MCM-41 mesoporous molecular sieve. This material was synthesised by the hydrothermal method, using cetyltrimethylammonium bromide as organic template. The physicochemical characterization by nitrogen adsorption, X-ray diffraction, and thermogravimetry, showed that the obtained material presents well-defined structure, with a uniform hexagonal arrangement. The thermal and catalytic degradation of heavy oil was performed by thermogravimetric measurements, in the temperature range from 30 to 900 °C, at heating rates of 5, 10, and 20 °C min−1. By using the model-free kinetics, proposed by Vyazovkin, it was determined that the activation energy to degrade the heavy oil was ca. 128 kJ mol−1, and for degradation of oil in presence of MCM-41, this value decreased to 69 kJ mol−1, indicating the performance of the mesoporores catalyst for the degradation process.

Biodiesel can contain unsaturated fatty acids, which are susceptible to oxidation, being able to change into polymerized compounds. Oxidative stability is very important in the quality control of oils and biodiesel. In this study, biodiesel samples were produced through the methyl route, using a homogeneous catalyst. The determination of methyl esters was performed by gas chromatography in order to confirm the conversion of the carboxylic acids present in the raw material for the methyl esters. Also proved the presence of methyl linoleate and methyl oleate to the major constituent of biodiesel. The thermal and oxidative stability of sunflower and cotton oils and their biodiesel, using TG and P-DSC techniques were investigated. The use of P-DSC to measure the oxidative induction time was very important. These measurements were used to evaluate the cotton and sunflower oils, and their respective biodiesel. It was found that the thermal-oxidative stability of vegetable oils and their biodiesel were similar, due to the fact that both presented chemical composition and percentages of fatty acids similar.

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.

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.

In this study, were studied the degradation of pure sunflower oil and mixed with H-Beta zeolite. This zeolite was synthesized by the hydrothermal method, followed by calcination and ion exchanged. The characterization of the zeolite was performed by X-ray diffraction and nitrogen adsorption/desorption by the method of BET. The analysis showed that H-Beta zeolite presented a good crystallinity and the template was completely removed from the catalyst. The thermal and catalytic degradation study was carried out using the TG/DTG method in multiple heating rates of 5, 10, and 20 °C min−1. The isoconversion method proposed by Vyazovkin was applied to determine the kinetic parameters for degradation of the sunflower oil. The activation energy for the degradation process of pure sunflower oil was 193 kJ mol−1, while for sunflower oil mixed with 20% of H-Beta zeolite was equivalent to 88 kJ mol−1. It was verified that for the degradation of 90% of the sunflower oil mixed with H-Beta, for a period of 1 h, a temperature of 356 °C was required, whereas for the pure vegetable oil, this value was of 387 °C, at the same time period, showing that the catalyst was effective for the degradation process of sunflower oil.

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.

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.

Model-free kinetic studies for volatilization of Brazilian sunflower oil and its respective biodiesel were carried out. The biodiesel was obtained by the methylic route using potassium hydroxide as catalyst. Both sunflower oil and biodiesel were characterized by physicochemical analyses, gas chromatography, simulated distillation and thermogravimetry. The physicochemical properties indicated that the oil and biodiesel samples are in accordance with the specifications of the Brazilian National Agency of Petroleum, Natural Gas and Biofuels (ANP). Gas chromatography indicated that the biodiesel was obtained with a content of ester of ca. 97.35 wt%. The TG curves indicated that the temperatures for volatilization of biodiesel are lower than for sunflower oil, which is explained by their different compositions and properties. The value of the apparent activation energy for the volatilization process, as determinated by the Vyazovkin Method, was higher for sunflower oil than for biodiesel.

Lanthanum-incorporated SBA-15 mesoporous molecular sieves were synthesized in a two-stage hydrothermal procedure from a precursor solution containing lanthanum chloride. The products were characterized by powder X-ray diffraction, thermogravimetric analysis, X-ray fluorescence, and nitrogen porosimetry. Taken together, the analyses indicated that the products formed highly ordered mesostructures with large average pore sizes, and suggested that the lanthanum was incorporated in the SBA-15 both into the framework as well as within the mesopores. Catalytic dehydration of ethanol over the LaSBA-15 products shows that they have weak Lewis acid and basic functionalities, indicative of the presence of lanthanum oxide in these samples.

The aim of this work is to determine the acti- vation energy for the thermal decomposition of poly (ethylene terephthalate)—PET, in the presence of a MCM- 41 mesoporous catalyst. This material was synthesized by the hydrothermal method, using cetyltrimethylammonium as template. The PET sample has been submitted to ther- mal degradation alone and in presence of MCM-41 catalyst at a concentration of 25% in mass (MCM-41/PET). The degradation process was evaluated by thermogravimetry, at temperature range from 350 to 500 C, under nitrogen atmosphere, with heating rates of 5, 10 and 25 C min -1 . From TG, the activation energy, determined using the Flynn-Wall kinetic method, decreased from 231 kJ mol -1 , for the pure polymer (PET), to 195 kJ mol -1 , in the pres- ence of the material (MCM-41/PET), showing the catalyst efficiency for the polymer decomposition process.

The SBA-15 materials were synthesized by the hydrothermal method using tetraethyl orthosilicate as silica source and P123 as template agent. The synthesis process was accomplished varying the time during the hydrothermal processing. For the synthesis monitoring, a small amount of sample was removed at different times, and analyzed by thermal analysis in order to determine the temperature ranges related to water desorption, template decomposition and silanol condensation for the SBA-15 nanostructured materials, as well as to estimate their quality. The samples were characterized by X-ray diffraction, infrared absorption spectroscopy, scanning electron microscopy, BET surface area and pore size distribution. The activation energy relative to decomposition of P123 template was determined from TG curves, using multiple heating rates and applying the model free kinetics. From the obtained data, it is possible to monitor the hydrothermal synthesis of SBA-15 in order to control the properties and conditions to prepare ordered materials.

The degradation kinetics of the ABS terpolymer (acrylonitrile-butadiene-styrene) was investigated by means of thermogravimetric analysis. The samples were heated from 30 to 900°C in nitrogen atmosphere applying three different heating rates: 5, 10 and 20°C min−1. The Vyazovkin model-free kinetic method was used to calculate the activation energy (E) of the degradation process as a function of conversion and temperature. Between 20 and 80% of conversion, E was calculated and the figures were: for ABS GP, E is 204.5±11.5 kJ mol−1 (medium value); for ABS HI, E is 239.0±9.8 kJ mol−1; for ABS HH, E is 242.4±5.4 kJ mol−1.

This work presents a study on the catalytic cracking of natural gasoline (extracted from natural gas) over HZSM-5 zeolite. A factorial planning was carried out to evaluate the effect of temperature and W / F ratio on the cracking of natural gasoline, analyzing their effects on conversion and product distribution using an analysis based on surface response methodology. The process was optimized focusing on the maximization of the mass fractions and the production of specific products such as ethene, propene and butanes. The results have shown that the maximum selectivity and hourly mass production of ethene is obtained at high temperature (450 °C) and low catalyst weight to flow rate ratio ( W / F ) (7.2 to 8.2 g cat h/mol). Maximum selectivity of propene is obtained at 350 °C and 7.0 g cat h/mol, while the best condition for maximum mass production is found at 421 °C and 5.7 g cat h/mol. The highest mass production of butanes is favored by high temperature (450 °C) and mid range W / F ratios (12.1 g cat h/mol), while the highest selectivity is found at low temperature (350 °C).

This work describes the covalent grafting of 3,4,9,10-perylenediimides (PDI), which are fluorescent dyes with very interesting optical properties, onto the walls of mesoporous molecular sieves MCM-41 and SBA-15. The mesoporous materials were first treated with 3-aminopropyltriethoxysilane (APTES) in anhydrous toluene, generating amine-containing surfaces. The amine-containing materials were then reacted with 3,4,9,10-perylenetetracarboxylic dianhydride (PTCA), generating surface-grafted PDI. Infrared spectra of the materials showed that the reaction with amino groups took place at both anhydride ends of the PTCA molecule, resulting in surface attached diimides. No sign of unreacted anhydride groups were found. The new materials, designated as MCMN 2 PDI and SBAN 2 PDI, presented absorption and emission spectra corresponding to weakly coupled PDI chromophores, in contrast to the strongly coupled rings usually found in solid PDI samples. The materials showed a red fluorescence, which could be observed by the naked eye under UV irradiation or with a fluorescence microscope. The PDI-modified mesoporous materials showed electrical conductivity when pressed into a pellet. The results presented here show that the new materials are potentially useful in the design of nanowires.

In this work, different mesoporous materials were employed for the preparation of supported metallocene catalysts to be evaluated in ethylene polymerization and their performance was related to the chemistry of the materials surface used as support. The supports employed were MCM-41, SBA-15 and mesoporous TiO2. The performance of the prepared catalysts was compared with the homogeneous catalyst precursor system. Those mesoporous materials, as well as the prepared metallocene catalysts, were analyzed by infrared absorption spectrometry (FTIR). Polymers were also characterized by FTIR, for the determination of the number-average molecular weight, and by differential scanning calorimetry (DSC) to determine thermal characteristics of the produced polyethylene. Among the studied metallocene supported catalysts, the one based on the mesoporous support SBA-15 achieved the highest activities, almost as high as that observed for the homogeneous system.

In this paper the application of a series of CoMo/AlMCM-41 catalysts with different Si/Al ratios was studied in the model reaction of thiophene hydrodesulfurization. The results obtained showed good catalytic activity for the formation of H2S, isobutene, 1-butene, n-butane, 2-trans-butene-and 2-cis-butene.

Bifunctional catalysts of Pt/WO x –ZrO 2 (PWZ) type with 1 wt% of Pt and 10, 15 and 20 wt% of tungsten were synthesized by polymeric precursor method and after they were calcined at 600, 700 and 800 °C. The structural and textural properties of the catalysts were by X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FTIR), N 2 adsorption measurement, temperature programmed reduction by derivative thermogravimetry (TPR–DTG) and transmission electron microscopy (TEM). X-ray diffractogram revealed the presence of tetragonal ZrO 2 and platinum (Pt) as the main phases. The infrared spectra of the catalysts showed bands due O–W–O and W O bonds. The catalysts showed specific surface area values in the range of 30–160 m 2 g −1 . TPR profile showed reduction peaks at high temperatures that were related with the reduction of WO x species. Such catalysts were active in the n -heptane isomerization with high selectivity to branched product.

The preparation of Pt/MoOx-ZrO2 materials has been carried out by polymeric precursor method and with molybdenum loadings in the range 10–20 wt %. The synthesized samples were calcined at 600, 700, and 800°C. The structure and texture of the calcined Pt/MoOx-ZrO2 materials were characterized by x-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy, and N2 adsorption measurements. XRD of the calcined samples revealed the formation of crystalline ZrO2, Pt metal, and Zr(MoO4)2. Crystalline Zr(MoO4)2 was also detected by FTIR spectra. A decrease in the specific surface area was observed by nitrogen adsorption experiments when the temperatures of calcination and molybdenum loading increased.

Nanostructured titanates (TTNT) with general formula Na {sub x}H{sub 2-x}Ti{sub 3}O{sub 7}.nH{sub 2}O were synthesized by hydrothermally reacting different TiO{sub 2} anatase (distinct crystal sizes) with NaOH at 120 deg. C followed by washing with water or diluted acid and drying of the precipitate. The resulting powders with different sodium contents were submitted to various calcination temperatures up to 800 deg. C and each calcined product was characterized as for its phase structure, composition, crystallite size and textural properties, namely BET surface area, mesopore volume and pore size distribution. Thermal transformations of TTNT samples were investigated by monitoring the modifications on crystallographic (X-ray diffraction) and textural (N{sub 2} desorption isotherms) properties, revealing the influence of the type of starting anatase and sodium content over the stability of TTNT. Moreover, a detailed study on the reduction of the interlayer distance in TTNT samples upon thermal treatment allowed corroborating the formation of an intermediate nanostructured hexatitanate, just before phase transformation into the corresponding TiO{sub 2} polymorphs and/or titanate crystals, depending on the sodium content and calcination temperature.

This work describes the encapsulation of N , N ′-bis(2-phosphonoethyl)-3,4,9,10-perylenetetracarboxylic diimide (PPDI), a water-soluble perylene dye, in the channels of mesoporous silica MCM-41. The incorporation of the dye was achieved by stirring MCM-41 with aqueous solutions of PPDI. The solid material obtained by this process exhibited a red fluorescence. Diffuse reflectance and emission spectra of the fluorescent powder suggested a highly organized arrangement with the PPDI molecules self-assembled in a 1D stack inside the channels of the mesoporous silica. The new materials described here have potential applications as nanoscale optoelectronic devices, such as conducting nanowires and fluorescent gas sensors.

In the present work, samples of Brazilian gasoline type C previously mixed with hydrated ethanol at concentrations of 20, 40, 60 and 80 vol.% were analyzed by distillation, octane number, specific mass, pH and conductivity, in order to evaluate the physico-chemical properties for a better comprehension of the effects caused by the flex-fuel technology. The obtained results were compared with the specifications of the ANP – Agencia Nacional de Petroleo Gas Natural e Biocombustiveis – that is the federal regulatory agency for monitoring of the quality of fuels in Brazil. It was observed that there exists an ideal concentration of hydrated ethanol for addition in gasoline type C in order to obtain good properties for application in the flex-fuel technology.

Biodiesel is defined as the monoalkyl ester derivative of long-chain fatty acids, originated from renewable sources, such as vegetable oils or animal fats. The most common use of biodiesel is direct substitution of fossil fuels in compression−ignition engines. The heating of vegetable oils can cause complementary decomposition reactions, in which the results can also lead to the formation of polymeric compounds. This work has been carried out to study the degradation process of biodiesel in different temperatures and exposure times. The degradation process of biodiesel affected its thermogravimetric and calorimetric profiles, indicating the formation of intermediary compounds. The spectroscopic data of degraded biodiesel suggested oxidative polymerization, confirming thermal data. In the degraded biodiesel at 210 °C for 48 h, the formation of gum occurred, indicating that oxidative polymerization was completed.

Pt/WOx–ZrO2 bifunctional catalysts were synthesized using impregnation and polymeric precursor methods. After the synthesis process the samples were calcined at 600, 700 and 800°C and characterized by X-ray diffraction, nitrogen adsorption and temperature programmed reduction study by thermogravimetry. DTG-TPR profiles showed between three and five reduction events at different temperatures attributed to platinum reduction and to different stages of tungsten species reduction. A comparative study of the synthesis method influence on the DTG-TPR curves was accomplished.