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Artigo Hierarchical EMT structured zeolites as improved catalysts for glycerol dehydration(Catalysis Today, 2025-01-15) Pergher, Sibele Berenice Castellã; Oliveira, Danielle da Silva; Braga, Tiago Pinheiro; Santos, Anne Gabrielle Dias; Alonso-Doncel, María del Mar; Serrano, David P.; Sachse, Alexander; Caldeira, Vinícius Patrício da Silva; https://orcid.org/0000-0002-5825-958X; https://orcid.org/0000-0003-2651-0001; https://orcid.org/0000-0003-1907-0706; https://orcid.org/0009-0002-6869-6609; https://orcid.org/0000-0003-3557-7451A fast and simple post-synthesis method for creating secondary mesoporosity in EMT zeolites was developed using an ammonium fluoride / cetyltrimethylammonium bromide (NH4F/CTAB) solution at low temperature with ultrasound irradiation. This strategy is shown to be highly effective for producing hierarchical EMT structured zeolites through the etching of both Si and Al species. The catalytic performance of these materials were assessed using glycerol dehydration as a reaction test, which is in addition a relevant reaction due to the high amounts of glycerol generated as a by-product of biodiesel production. The resulting hierarchical EMT structured zeolites exhibited improved catalytic activity and high selectivity towards acrolein (around 80 %). This innovative approach creates new opportunities for using hierarchical EMT structured zeolites in processes related with biodiesel manufactureArtigo Challenges, prospects and comprehensive evolution of zeolite-based materials for the catalytic conversion of glycerol: a review(Catalysis Today, 2025-01-15) Pergher, Sibele Berenice Castellã; Barbosa, Felipe Fernandes; Loiola, Adonay Rodrigues; Braga, Tiago Pinheiro; https://orcid.org/0000-0002-5825-958X; https://orcid.org/0000-0002-1846-2233; https://orcid.org/0000-0002-4981-6321; https://orcid.org/0000-0002-1846-2233The energetic demands of modern society urge a transition that relies on alternative and sustainable sources. Among the available possibilities focused on mitigating the use of fossil fuels, the biodiesel industry stands out. However, the excess of glycerol generated as a coproduct still raises debate regarding how it could be better used. A well-established approach is the use of the platform molecule, i.e., glycerol, in the presence of heterogeneous catalysts to obtain added value products. Zeolites are well-known for their versatility in numerous applications, such as in the oil industry. Besides, different types of aluminosilicates are being studied in the catalytic conversion of glycerol to acrolein, acetol, acrylic acid, allyl alcohol, solketal, etc. This review addresses the general properties, fundaments, synergetic aspects, theoretical modeling, resistance, and coke formation, as well as the zeolites limitations that pose obstacles for those reactions. This highlights the importance of developing zeolite materials with specific acid sites, synchronizing their amount and strength with the pore interconnectivity so that reagents diffusion within the zeolitic channels can be maximized, leading to a decrease in the obstruction of active sites and pores caused by coke deposition. A number of modifications, including hierarchization, isomorphic substitution, acidity tuning, and additional phases (SMSI effect), have been reported as alternatives for improving the performance of glycerol conversion and the resistance to deactivation. Several developments involving reactional mechanisms, coke deposition, and catalysts applied to glycerol conversion have been the subject of studies centered on process optimization, which is translated into the development of solids more resistant to deactivation. Among the zeolites with the best catalytic performance, the following stand out: BEA, MCM-22, MFI, ITQ-2, SAPO-34, and ZSM-5. Some complex technical aspects still need to be better understood so that the scalability of the catalytic conversion of glycerol becomes economically feasible, thereby arousing the interest of both the public and private sectorsArtigo The application of Al-pillared clays impregnated with cerium and Al/Ce-pillared clays for the treatment of simulated textile effluents through photocatalysis(Minerals, 2025-02-05) Pergher, Sibele Berenice Castellã; Dias, Beatriz Pinheiro; Bieseki, Lindiane; Longe, Clenildo de; https://orcid.org/0000-0002-5825-958X; https://orcid.org/0000-0003-3282-4154; https://orcid.org/0000-0002-0088-0963; https://orcid.org/0000-0002-0537-7646The objective of this study is to utilize a simulation employing advanced oxidation processes (AOPs) from photodegradation to examine the treatment of textile effluents. The selection of textile effluents as the material to be degraded is justified by the significant volume of water containing dyes, such as methylene blue (MB), generated daily by the textile industry. Often, this water is discarded without undergoing effective treatment. The purification of textile effluents would enable the reuse of water within the textile production cycle, thereby promoting sustainability. This study focuses on AOPs, which are extensively utilized in photocatalytic processes. The catalytic precursor material consists of two types of clay: a commercial clay and a natural clay. The natural clay is pillared with Al and impregnated with Ce, while the commercial clay is also pillared with Al and impregnated with Ce. Both clays are also pillared with a mixed pillar of Al and Ce. This results in three comparable materials. These clays are characterized by the presence of montmorillonite as their predominant mineral component. The selected clays were commercial bentonite and natural clay (FCN). Photocatalytic performance validation tests were conducted using UV-Vis spectroscopy. Material characterization methods included crystallographic analysis (by X-Ray diffraction (XRD)), chemical composition (by X-Ray fluorescence (XRF)), morphological studies (by scanning electron microscopy (SEM)) and textural property analysis (by N2 adsorption). The outcomes of these investigations offer signification insights into the potential applications of these materials in the treatment of textile effluents and the development of more sustainable processes within the textile industry. Furthermore, the results contribute to the advancement of photocatalytic material designArtigo Synthesis of LTA zeolite from beach sand: a solution for CO2 capture(Coatings, 2025-03-14) Pergher, Sibele Berenice Castallã; Longe, Clenildo de; Silva, Aryandson da; Câmara, Anne Beatriz Figueira; Bieseki, Lindiane; Carvalho, Luciene Santos de; Mello, Mariele Iara Soares de; https://orcid.org/0000-0002-5825-958X; https://orcid.org/0000-0002-0537-7646; https://orcid.org/0000-0003-0509-3667; https://orcid.org/0000-0002-4135-5639; https://orcid.org/0000-0002-0088-0963; https://orcid.org/0000-0002-8047-8471; https://orcid.org/0000-0002-5979-2474Emissions caused by polluting gases, such as carbon dioxide, are one of the main contributors to the generation of the greenhouse effect that leads to global warming, responsible for climate change. An alternative to mitigating these emissions is the use of adsorbents capable of capturing CO2. Zeolites are considered one of the most effective adsorbents in gas adsorption and separation technologies due to their high specific area and pore size and, consequently, greater adsorption capacity when compared to other commonly used materials. Despite this, reagents used in syntheses as the source of silica often make obtaining these materials more expensive. Seeking to overcome this limitation, in this work, materials (for CO2 capture) were developed with a zeolitic structure using a low-cost alternative source of silica from beach sand called MPI silica to make the synthesis process eco-friendly. The crystallization time of the materials was studied, obtaining an LTA zeolite with MPI silica in a period of 1 h (ZAM 1 h), with a relative crystallinity of 74.26%. The materials obtained were characterized using the techniques of X-ray diffraction (XRD), X-ray fluorescence (XRF), absorption spectroscopy in the infrared region with Fourier transform (FTIR), scanning electron microscopy (SEM), and thermal analysis. The evaluation of the experimental adsorption isotherms showed that the zeolite LTA Aerosil®200 (standard zeolite) and MP had adsorption capacities of 5.25 mmol/g and 4.83 mmol/g of CO2, respectively. The evaluation of mathematical models indicated that the LTA zeolites fit the Temkin model best and had the same trend, with calculated adsorption capacities of 3.97 mmol/g and 3.75 mmol/g, respectivelyArtigo Structural and textural properties of Al/Cu - and Al/Zn-pillared clays for ethanol conversion(Crystals, 2025-01-16) Pergher, Sibele Berenice Castellã; Santos, Lamara Maciel dos; Barbosa, Felipe Fernandes; Bieseki, Lindiane; Braga, Tiago Pinheiro; https://orcid.org/0000-0002-5825-958X; https://orcid.org/0009-0005-6440-931X; https://orcid.org/0000-0002-1846-2233; https://orcid.org/0000-0002-0088-0963; https://orcid.org/0000-0001-9543-7368A montmorillonite sample was pillared using mixed solutions of Al/Cu and Al/Zn as the pillaring agent. Al/Cu- and Al/Zn-pillared clays were applied in an ethanol conversion reaction. The catalysts prepared from montmorillonite were characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), 27Al nuclear magnetic resonance spectroscopy (MAS-NMR), and textural analysis by adsorption of N2. The synthesized materials showed basal spacing values around 1.6 nm for the Cu samples and 1.8 nm for the Zn samples. With the pillarization, textural properties such as specific area and micropore volume were optimized, and all samples showed an increase in micropore volume as well as a narrower pore distribution in the range of 0.77 nm. The insertion of 10% Zn in the pillaring solution produced a material with a greater amount of Al in the pentacoordinate position and also presented better results of conversion (80%) and selectivity to ethylene (81%) in the ethanol dehydration reactionArtigo Monitoring the dynamics of nanozeolite formation by combined in situ coherent small angle X-ray scattering techniques(Catalysis Today, 2025-01-01) Pergner, Sibele Berenice Castellã; Garcia, Paulo Ricardo de Abreu Furtado; Vinaches, Paloma; Zerba, João-Paulo; Kalile, Tiago Araújo; Rochet, Amélie; Meneau, Florian; https://orcid.org/0000-0002-5825-958X; https://orcid.org/0000-0003-2651-0001; https://orcid.org/0000-0003-1907-0706; https://orcid.org/0009-0002-6869-6609; https://orcid.org/0000-0003-3557-7451Understanding the dynamics of zeolite formation is key to synthesising high-quality zeolitic materials with controllable properties, in order to develop more efficient and performant materials. X-ray photon correlation spectroscopy (XPCS) using coherent X-rays offers new possibilities for in situ observation of nano to micron-scale fluctuation dynamics during crystal growth. An in situ cell, which is capable of collecting time-resolved coherent X-ray scattering data under hydrothermal conditions has been developed and used to study, by in situ XPCS combined with small and wide angle X-ray scattering, zeolite formation and dynamics. Analysis of the results using two-time correlations enables to accurately identify the successive growth and crystallisation steps, revealing the dissolution process of the LTA topology during the SOD growth. This approach opens a powerful new avenue for studying the dynamics of nanomaterials formation, phase transitions and growth processes under in situ conditions that will enable profound insights into the nanoscale synthesis mechanismsArtigo Influence of secondary porosity introduction via top-down methods on MOR, ZSM-5, and y zeolites on their cumene cracking performance(Catalysts, 2025-02-04) Pergher, Sibele Berenice Castellã; Souza, Josué da Cruz de; Mello, Mariele Iara Soares de; Barbosa, Felipe Fernandes; Souza, Iane Maiara Soares de; Sachse, Alexander; https://orcid.org/0000-0002-5825-958X; https://orcid.org/0000-0002-8449-9501; https://orcid.org/0000-0002-5979-2474; https://orcid.org/0000-0002-1846-2233; https://orcid.org/0000-0002-4744-9628The influence of secondary porosity and the dimensionality of zeolitic structures with 1D and 3D pore systems on the accessibility of cumene to Brønsted acid sites was evaluated in this study. Zeolites Y, ZSM-5, and MOR, obtained through NH4F leaching and basic and acid treatments, were studied. Zeolites Y and ZSM-5 showed a significant increase in specific surface area while maintaining the micropore volume as well as an increase in the concentration of Brønsted acid sites following treatment. Zeolite MOR exhibited an increase in mesopore volume and retained Brønsted acidity. The impact of the treatments on catalytic properties was evaluated through cumene cracking, which yielded high catalytic conversion for the materials. This result is consistent with the goal of the model reaction to characterize Brønsted acid sites, enhance accessibility, and reduce diffusion pathsArtigo Ordered mesopore channels of SBA-15 for contaminant adsorption: characterization, kinetic, equilibrium, and thermodynamic studies(Molecules, 2025-02-24) Pergher, Sibele Berenice Castellã; Silva, Francisco Emanuel da; Spaolonzi, Marcela Pires; Vieira, Melissa Gurgel Adeodato; https://orcid.org/0000-0002-5825-958X; https://orcid.org/0000-0002-1782-3025; https://orcid.org/0000-0003-3362-7005; https://orcid.org/0000-0002-3487-799XSBA-15 is used in various processes, including adsorption, due to its textural properties, mesoporous channels, and silanol groups on the surface. These characteristics make it a promising material for the adsorption of emerging contaminants. This work evaluated the potential use of SBA-15 for the adsorption of bisphenol A (BPA), ciprofloxacin (CIP), and losartan (LS). This study showed that the material has highly ordered mesoporous channels and silanol groups on the surface, which influenced the affinity tests. SBA-15 exhibited the highest adsorption capacity (0.1317 mmol g−1) and removal percentage (60%) for CIP among the contaminants assessed. The adsorption mechanism was elucidated, revealing different interactions for each molecule. The kinetic curves for CIP adsorption indicated that the process reached saturation in 20 min, the equilibrium isotherm showed the highest adsorption at 15 °C, and the thermodynamic study shows an exothermic behavior and spontaneous process. The simplified batch design estimated that 27 g of SBA-15 is required to treat 10 L of 0.2 mmol L−1 initial CIP concentration solution and achieve 90% adsorption removal. This material demonstrated satisfactory performance in absorbing emerging contaminantsArtigo Novel preparation of polyphenylacetylene semiconductor: potential application in supercapacitors(Catalysis Today, 2025-03-01) Pergher, Sibele Berenice Castellã; Borba, Katiúscia Machado Nobre; Trindade, Letícia Guerreiro da; Zanchet, Letícia; Diaz, Urbano; Garcia, Fernando Rey; Bernardo-Gusmão, Katia; https://orcid.org/0000-0002-5825-958X; https://orcid.org/0000-0003-1266-8078; https://orcid.org/0000-0001-6785-0761; https://orcid.org/0000-0003-1573-2223; https://orcid.org/0000-0003-3115-6844; https://orcid.org/0000-0003-1472-8724The use of MCM-41 led to the development of a silylated hybrid material (MS), which in turn played a crucial role in obtaining semiconducting polyphenylacetylene, with a conductivity of 8.13 × 10−5 S m−1. MS was also responsible for reducing the polyphenylacetylene band gap from 2.13 eV to 1.83 eV. When used in a capacitor, polyphenylacetylene exhibited stability after 3000 charge/discharge cycles and a capacitance seven times higher than that of poly(o-methoxyaniline) (POMA) polymerArtigo Catalyst screening for conversion of Chlorella sp. to aromatic fuel additives: a sustainable strategy for CO2 capture(Journal of Analytical and Applied Pyrolysis, 2025-01) Pergher, Sibele Berenice Catellã; Calixto, Guilherme Quintela; Souza, Josué da Cruz de; Alves, José Luiz Francisco; Deus Junior, Joemil Oliveira de; Marques, Júlio de Andrade Oliveira; Souza, Iane Maiara Soares de; Melo, Dulce Maria de Araújo; Braga, Renata Martins; https://orcid.org/0000-0002-5825-958X; https://orcid.org/0000-0002-8449-9501; https://orcid.org/0000-0003-3098-3530; https://orcid.org/0000-0002-5633-1808; https://orcid.org/0000-0002-4744-9628; https://orcid.org/0000-0001-9845-2360; https://orcid.org/0000-0002-6232-0945Developing biofuels with characteristics similar to current fossil fuels and compatibility with existing petroleum infrastructure (drop-in biofuels) is gaining prominence, aligning with global efforts towards carbon-neutral economies and decarbonization of the transportation sector. The originality of the current study involves two directions: first, the use of Chlorella sp. microalgae, cultivated under simulated post-combustion gas, as a raw material for producing drop-in biofuel precursors; and second, an investigation of the catalytic activity of hierarchical zeolites in the deoxygenation and denitrogenation of volatile pyrolysis products, enhancing hydrocarbon content. To accomplish this, a micro-furnace-type temperature-programmable pyrolyzer coupled with chromatographic separation and mass spectrometry detection (Py-GC/MS) was utilized to assess the upgrading effectiveness of distinct zeolites (faujasite-type, MFI-type, and mordenite-type) on volatile pyrolysis products. All tested zeolites effectively reduced oxygenated and nitrogenated compounds in the volatile pyrolysis products, enhancing their suitability for producing renewable fuel. This supports sustainable development goals by promoting affordable, clean energy and climate action. HMor yielded the highest hydrocarbon content (98.5 %), followed by HZSM-5 (97.6 %) and HY (85.5 %). Catalytic upgrading significantly increased the concentration of aromatic hydrocarbons (at least 66.3 %), with MFI-type zeolites showing the highest selectivity for valuable BETX compounds (benzene, ethylbenzene, toluene, xylene). Hydrocarbons in the gasoline range, with up to 91.7 %, predominantly align with the needs of the transportation fuel market. The principal component analysis illustrates that using MFI-type zeolites promoted the lowest selectivity for PAHs, constituting precursors for coke formation, which is advantageous for ensuring a longer catalyst lifespan. Our results are promising and encourage the conversion of microalgal biomass into renewable fuel additives for formulating drop-in biofuels, as hydrocarbon-rich volatile pyrolysis products could be directly integrated into existing biorefineries. Thus, microalgal biomass cultivated using flue gas as the carbon source can be viewed as a versatile and promising resource for producing renewable fuel additives, contributing to developing a sustainable, low-carbon futureArtigo In situ visualisation of zeolite anisotropic framework flexibility during catalysis(Catalysis Today, 2025-02-15) Pergher, Sibele Berenice Castellã; Rodrigues, Mariana Viana; Vinaches, Paloma; Polo, Carla Cristina; Silva, Marlon Muniz; Suzana, Ana Flávia; Cha, Wonsuk; Rochet, Amélie; Meneau, Florian; https://orcid.org/0000-0002-5825-958X; https://orcid.org/0000-0003-2651-0001; https://orcid.org/0000-0001-8711-3443; https://orcid.org/0000-0001-8888-4258; https://orcid.org/0000-0003-3557-7451Zeolites exhibit framework flexibility driving their chemical and catalytic properties. Since the zeolitic pores are extremely small, a slight strain generated in the crystal induces compelling changes in shape, connectivity, accessibility, and the framework chemical properties. These modifications affected the adsorption and desorption of reactants/products and the diffusion within the channels during reaction. Using in situ 3D Bragg coherent X-ray diffraction imaging, we unveil the dynamics of the zeolite structure during catalysis, contraction and/or expansion of its framework also known as zeolite framework flexibility. We imaged three-dimensionally a single faujasite zeolite crystal during the ethanol dehydration reaction revealing anisotropic lattice dynamics simultaneously to guest molecules formation. Understanding zeolite flexibility could permit to tune zeolites properties towards potentially higher adsorption and selectivityArtigo One-Pot synthesis of Ni-B2O3/Al2O3 catalysts with high resistance to coke formation for the dry reforming reaction of methane(Molecular Catalysis, 2025) Melo, Dulce Maria de Araújo; Silva, Yuri Kauã Rodrigues de Oliveira; Medeiros, Rodolfo Luiz Bezerra; Oliveira, Ângelo Anderson Silva; Batista, Willame Gomes da Silva; Azevedo, Amanda Lopes de; Araújo, Tomaz Rodrigues de; Braga, Renata Martins; https://orcid.org/0000-0001-9845-2360; https://orcid.org/0000-0001-9081-7193; https://orcid.org/0000-0002-3072-1250; https://orcid.org/0000-0002-4143-3238; https://orcid.org/0000-0003-1293-7688; https://orcid.org/0000-0003-0567-7523; https://orcid.org/0000-0002-5368-9775; https://orcid.org/0000-0002-6232-0945The production of hydrogen from dry reforming of methane (DRM) is crucial for the energy transition, aiming for a more sustainable energy matrix due to its similarity to biogas reforming, which provides a renewable substrate for large-scale synthesis gas production. In this context, the efficiency of catalysts plays a fundamental role in optimizing this process, considering the extreme operational conditions in terms of temperature and competing reactions. This study investigates the synthesis, characterization, and stability of nickel catalysts supported on alumina, using a one-pot synthetic approach via microwave-assisted combustion, compared to catalysts synthesized by the commonly used wet impregnation method. Structural characterization was performed using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and temperature-programmed reduction (TPR-H2). Textural properties were assessed through nitrogen (N2) adsorption. The results showed that the catalysts synthesized by the one-pot method tend to have a high dispersion of nickel particles and a larger surface area, contributing to superior catalytic activity. Catalytic stability tests revealed that the catalysts promoted with B2O3 exhibited lower deactivation and reduced coke formation compared to unpromoted catalysts; however, an increase in the amount of B2O3 raised deactivation due to sintering, which was mitigated by the one-pot method that enhances metal-support interaction. The one-pot synthetized nickel catalyst with 2.5 wt% stood out, with stability more than ten times greater than that of the conventional Ni/Al2O3 catalyst and four times greater than the promoted catalyst synthesized via impregnation. Among the 3 catalysts mentioned, the final CH4 conversions were 78 %, 72 %, and 75 %, respectively, while the H2 yields were 60 %, 55 %, and 58 % after 12 h of reaction. The findings indicate that promotion with B2O3 and the one-pot synthesis significantly improved the stability and efficiency of the catalysts, offering potential for larger-scale synthesis gas production applicationsArtigo Novo método para a estimativa das constantes de estabilidade de complexos com o edta(ICI World of Journals, 2019-05-17) Pereira, Francisco Claudece; Lima, Francisco José SantosO presente trabalho descreve uma nova metodologia na área de química analítica, que possibilita o cálculo da constante de estabilidade (de equílibrio ou de formação), dos compostos de coordenação gerados entre todos os cátions metálicos da tabela periódica, excetuando os metais alcalinos (grupo 1), juntamente com o ligante ácido etilenodiamintetraacético. A sistemática é de simples utilização, apresentando baixo custo e permitindo obter, em brevissimo tempo, o conhecimento da dimensão das constantes de formação condicional, para todos os metais coordenados com o agente complexante, para qualquer valor de pH investigado. Em adição, o método também é extensivo para outros ligantes que apresentem a mesma propriedade química de reação, que o ácido etilenodiamintetraacético realiza com os íons metálicos na mesma proporção estequiométrica de ligação. Para a execução deste estudo foram empregadas soluções do cátion cobre (II), em uma concentração de 1,0x10-2 mol L-1 e do agente complexante, também apresentando a mesma concentração do metal. O ensaio foi conduzido em um sistema tamponante, constituido de hidróxido de amônia e o sal cloreto de amônio, em um valor de pH constante igual a 10,0. O método permite o seu emprego nos procedimentos experimentais desenvolvidos tanto, em um laboratório químico, quanto em uma sala de aula, utilizada durante a realização das atividades teóricas. O agente quelante apresenta um amplo espectro de aplicação nas indústrias de produtos alimentícios, também na geração de materiais de limpeza em geral, bem como na indústria da fotografia, na produção têxtil, na manufatura do papel e similares, borrachas e afins, polímeros e derivados, dentre outras linhas de produção que destinam seus manufaturados para o consumo humanoArtigo Characterization and acidic properties of AlMCM-41 prepared by conventional and post-synthesis alumination(Australian Journal of Chemistry, 2015) Nascimento, Rubens Maribondo do; Costa, Maria José Fonseca; Chellappa, Thiago; Araujo, Antonio Souza de; Fonseca, Viviane Muniz; Fernandes Júnior, Valter José; Pacheco, Jose G. A.The catalysts analysed in the current work are variations of MCM-41. The properties of these highly ordered mesoporous aluminosilicates were adjusted by an isomorphous substitution of Si by a trivalent cation, in this case Al3þ, generating catalysts of the AlMCM-41 type. The materials were synthesized with a silicon/aluminium ratio of 40, through two methods of impregnation of the metal: conventional and post-synthesis alumination. With the aim of determining the density of the acid sites of the Al40MCM-41 prepared by post-synthesis and conventional alumination, studies of the adsorption of n-butylamine probe molecule were carried out. Further, the studied material was characterized by thermogravimetry measurements, providing the profile of decomposition of the samples, which allowed calculation of the densities of the acid sites. The model-free kinetic algorithms were applied in order to determinate conversion and apparent activation energy. Comparison of energy-dispersive X-ray fluorescence and X-ray photoelectron spectroscopy measurements indicated that the post-synthesis method was more favourable based on the metal positioning, ‘anchored’ in the surface of the catalyst. The textural properties of the calcined Al40MCM-41 prepared by post-synthesis and conventional alumination were characterized by X-ray diffraction, N2 isothermal adsorption measurements (Brunauer– Emmett–Teller and Barrett–Joyner–Halenda), transmission electron microscopy, and X-ray photoelectron spectroscopy.Artigo Pyrolysis kinetics of elephant grass pretreated biomasses(Springer, 2014) Melo, Marcus Antonio de Freitas; Braga, Renata Martins; Costa, Tiago Roberto da; Freitas, Julio C. O.; Barros, Joana Maria de Farias; Melo, Dulce Maria de AraújoThe Elephant Grass (Pennisetum purpureum Schum) was pretreated by two independent processes, through washing with hot water (W-EG) and acid solution (AW-EG) to improve its energy properties to apply it in a thermochemical process conversion into fuel. The biomasses were analyzed by proximate and ultimate analysis; and the pyrolysis kinetics, before and after pretreatments, were evaluated by the apparent activation energy (Ea) for decomposition in the temperature range of greater volatile matter through the Model-free kinetics using thermogravimetric analysis data. The kinetics of the microcrystalline cellulose Avicel PH-101 was performed to evaluate the Ea result of pure cellulose. The pretreatments were efficient in increasing the volatile matter and heating value, decreasing moisture and ash content, and improving its energetic power to the application in fast pyrolysis process for bio-oil production. The TG results have shown that the reduction in ash content facilitates the pyrolysis process, increasing the volatile matter and decreasing the apparent activation energy equired to biomasses degradation, due to less diffusional resistances to heat and mass transfer of W-EG and AW-EG. The Avicel PH-101 showed the highest value of apparent activated energy (Ea = 276.2 kJ mol-1) which could be explained by its crystallinity, suggesting that crystalline cellulose regions are less accessible to heat diffusion than amorphous regions, requiring more energy to its degradation.Artigo Beta-spodumene:Na2CO3:NaCl system calcination: a kinetic study of the conversion to lithium salt(Elsevier, 2019-07) Nascimento, Rubens Maribondo do; Santos, Leonardo Leandro dos; Pergher, Sibele Berenice CastellãThe basic objective of the work was to evaluate the calcination step in the lithium extraction process and to obtain a kinetic model that would adjust the experimental data for the reaction of the carbonate recovery during the processing of beta-spodumene, activated by melting with sodium carbonate/sodium chloride. In this work there were obtained activation energy values using experimental data obtained from the treatment of complex systems such as minerals. This is of interest because of the contribution it makes to the field of physical chemistry. Some of the main results indicated that the best molar ratio was 3Li2O:1Na2CO3 + 5% w/w NaCl in the conversion to Li2CO3 with approximate 70% Li yield, using a 823–923 K range with a calcination cycle of 120min. The kinetic results indicated that the pseudo-second-order kinetic modeling fits the equilibrium data well under employed temperature conditions on literature, based on second stage of reaction mechanism (chemoselective exchange reaction)Artigo Síntese e caracterização de materiais mesoporosos modificados com níquel para a captura de CO2(Cerâmica - Associação Brasileira de Cerâmica, 2014) Melo, Marcus Antonio de Freitas; Nascimento, Alexsandra Rodrigues do; Figueredo, Gilvan Pereira de; Rodrigues, G.; Souza, Marcelo José Barros de; Melo, Dulce Maria de AraújoMateriais mesoporosos tipo SBA-15 e MCM-48 foram sintetizados com sucesso pelo método hidrotérmico e impregnados com níquel nas proporções de 5-20 peso% visando à captura de CO2. Os materiais obtidos foram caracterizados por meio de análise por difração de raios X, adsorção de N2 e microscopia eletrônica de varredura. Testes de captura de CO2 foram conduzidos em pressões entre 100 e 4000 KPa à temperatura constante de 298 K e revelaram que as capacidades de adsorção variam significativamente com as propriedades texturais dos materiais com diferentes teores de níquel, atingindo valores máximos de 14,89 e 9,97 mmol g-1 para MCM-48 e SBA-15, respectivamenteArtigo Kinetic study of CTMA+ removal from the pores of the Ti-MCM-41 molecular sieve(Journal of Thermal Analysis and Calorimetry, 2014) Melo, Marcus Antonio de Freitas; Fontes, Maria do Socorro Braga; Melo, Dulce Maria de Araújo; Barros, Joana Maria de Farias; Braga, Renata Martins; Fontes, Vilsinéia dos AnjosThermogravimetry analysis was used to study the thermal decomposition of Ti-MCM-41 to determine the best calcination conditions. Ti-MCM-41 molecular sieve was synthesized using a hydrothermal route in which Ti ions were incorporated into the pore channels of MCM-41 starting from a hydrogel method according to the following molar composition: 1.00 CTMABr:4.00 SiO2:X TiO2:1.00 Na2O:200.00 H2O. Physicochemical properties of samples were investigated using XRD, FTIR, and N2 adsorption– desorption to confirm the incorporation of TiO2 nanoparticles inside of MCM-41 mesoporous without destroying its structure. The high temperatures facilitate the rapid removal of the surfactant; however, it caused destruction of the MCM-41 structure by breaking the bonds of the silica tetrahedral structure. The procedures to obtain the apparent activation energies of CTMABr decomposition were based on the kinetic model proposed by Flynn-Wall using thermal analysis of data performed with heating rates 5, 10, and 20 C min-1Artigo Caracterização físico-mecânica e ambiental de cerâmica estrutural com imobilização do íon manganês(Cerâmica Industrial, 2013) Melo, Marcus Antonio de Freitas; Câmara, Ana Paula Costa; Medeiros, Leonardo Coutinho de; Macedo, Daniel Araújo de; Galdino, José Nildo; Melo, Dulce Maria de AraújoNeste trabalho a adição do íon manganês bivalente a uma massa argilosa do Estado do Rio Grande do Norte foi estudada a fim de avaliar a viabilidade das peças sinterizadas para uso em cerâmica estrutural. A matéria-prima cerâmica foi caracterizada por análise química (FRX) e difratometria de raios-X (DRX). Assim, o íon metálico foi adicionado na forma de soluções aquosas nas concentrações de 100, 150 e 200 mg/L. Os corpos de prova obtidos por extrusão e sinterizados entre 850 e 1150 °C foram caracterizados por ensaios de solubilidade. As propriedades tecnológicas avaliadas foram: retração linear de queima, absorção de água, porosidade aparente, massa específica aparente e tensão de ruptura à flexão em três pontos. Propriedades como porosidade aparente e absorção de água não apresentaram variações significativas em função da concentração do íon manganês. Por outro lado, a tensão de ruptura à flexão cresce com o aumento da temperatura independente da concentração do íon. Quanto aos resultados, foi possível identificar que a cerâmica com imobilização do íon manganês nas concentrações entre 100 e 200 mg/L é adequada para a fabricação de diversos produtos cerâmicos, tais como tijolo maciço e revestimento semi-poroso, sem oferecer risco ao meio ambienteArtigo Kinetic study of template removal of MCM-41 derived from rice husk ash(Journal of Thermal Analysis and Calorimetry, 2013) Melo, Marcus Antonio de Freitas; Braga, Renata Martins Braga; Barros, Joana Maria de Farias Barros; Melo, Dulce Maria de Araújo; Aquino, Flávia de Medeiros; Freitas, Júlio Cézar de Oliveira; Santiago, Rodrigo CésarMolecular sieves MCM-41 were synthesized from rice husk ash (RHA) as alternative sources of silica, called RHA MCM-41. The material was synthesized by a hydrothermal method from a gel with the molar composition 1.00 CTMABr:4.00 SiO2:1.00 Na2O:200.00 H2O at 100 C for 120 h with pH correction. The cetyltrimethyl- ammonium bromide (CTMABr) was used as a structure template. The material was characterized by X-ray powder diffraction, FTIR, TG/DTG, and surface area determination by the BET method. The kinetics models proposed by Ozawa, Flynn–Wall, and Vyazovkin were used to determine the apparent activation energy for CTMA? species decomposition from the pores of MCM-41 material. The results were compared with those obtained from the MCM-41 synthesized with silica gel. The synthesized material had specific surface area, size, and pore volume as specified by mesoporous materials developed from conventional sources of silica.