Navegando por Autor "Pergher, Sibele Berenice Castellã"

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Acid treatments of montmorillonite-rich clay for Fe removal using a factorial design method
(ABM, ABC, ABPol, 2013) Bieseki, Lindiane; Bertell, Francine; Treichel, Helen; Penha, Fabio G.; Pergher, Sibele Berenice Castellã
Montmorillonite clays are of great interest for industrial processes such as catalysis and adsorption. The textural properties of clays can be modified in an attempt to increase their uses. This paper describes the acid treatment of natural montmorillonite clay. The materials were characterized using X-ray diffraction (XRD), atomic absorption spectroscopy (AA) and BET surface area measurements. Three different acids (HCl, HNO3 and H2SO4) were tested, and HCl and H2SO4 were more efficient for removing Fe from the clay. The results indicate that HCl better preserves the material structure because less Al is removed. A central composite design (CCD) 22 was applied to evaluate the treatment using HCl. The temperature and concentration presented positive effects on the removal of Fe, Al and Mg. Combinations of the HCl acid solution concentration and temperature, such as 4 mol.L-1/50 °C and 1 mol.L-1/75 °C, assured that Fe was removed with less damage to the structure.
Adsorção de tensoativos e polímero em rocha reservatório
(Universidade Federal do Rio Grande do Norte, 2015-06-26) Cunha Bisneto, Manuel Carneiro; Wanderley Neto, Alcides de Oliveira; Pergher, Sibele Berenice Castellã; Braga, Tiago Pinheiro; Medeiros, Ana Catarina da Rocha
No processo de exploração de petróleo, quando a energia na formação não é suficiente para produzir o óleo naturalmente, faz-se necessário intervir no poço e a esse processo intitula-se de recuperação de óleo, que pode ser denominado de recuperação avançada de petróleo quando se utiliza processos químicos, como sistemas a base de tensoativos e polieletrólitos. Os tensoativos têm a propriedade de se adsorver em interface reduzindo a tensão interfacial e facilitar o escoamento do óleo dos poros da rocha para o interior do reservatório, enquanto que o polímero tem a propriedade de deslocar o banco de óleo a partir da alta viscosidade que os sistemas poliméricos oferecem. Os polieletrólitos também podem se adsorver na rocha. Para melhor entender o processo de recuperação se faz necessário estudar os fenômenos de adsorção das moléculas químicas na rocha reservatório e para isso aplicou-se as técnicas de potencial zeta e espalhamento dinâmico da luz. O arenito desagregado apresenta carga negativa e a adição da solução de ácido acético inverte a carga, passando a ser positiva. Os tensoativos aniônicos, óleo de coco saponificado (OCS) e Dodecil sulfato de sódio (SDS) se adsorvem ao arenito em concentrações abaixo e acima da concentração micelar crítica (CMC). A quitosana também se adsorve consideravelmente ao arenito. A adsorção acontece até o momento que satura toda a superfície das partículas do arenito desagregado e a concentração de saturação para a quitosana e SDS é 0,005%, enquanto para o OCS não há um valor crítico de saturação pois há o fenômeno da protonação. Para a combinação de quitosana-OCS a saturação se dá a 0,002%, enquanto que para a Quitosana-SDS e OCS-SDS não há um ponto crítico de saturação. A combinação de Quitosana-SDS-OCS apresenta aumento de carga até 0,004% e diminuição até 0,005% e partir deste valor há saturação da superfície do arenito. Os tamanhos de partículas foram determinados a partir da técnica de espalhamento dinâmico da luz. Os tamanhos de partículas confirmam que há interação das moléculas químicas estudadas sobre a partícula de arenito desagregado.
Alkylation of benzene with propylene in a flow-through membrane reactor and fixed-bed reactor: preliminary results
(MDPI, 2012-05-18) Torres-Rodríguez, Miguel; Gutiérrez-Arzaluz, Mirella; Mugica-Álvarez, Violeta; Aguilar-Pliego, Julia; Pergher, Sibele Berenice Castellã
Benzene alkylation with propylene was studied in the gas phase using a catalytic membrane reactor and a fixed-bed reactor in the temperature range of 200–300 °C and with a weight hourly space velocity (WHSV) of 51 h−1. β-zeolite was prepared by hydrothermal synthesis using silica, aluminum metal and TEAOH as precursors. The membrane’s XRD patterns showed good crystallinity for the β-zeolite film, while scanning electron microscopy SEM results indicated that its random polycrystalline film was approximately 1 μm thick. The powders’ specific area was determined to be 400 m2×g−1 by N2 adsorption/desorption, and the TPD results indicated an overall acidity of 3.4 mmol NH3×g−1. Relative to the powdered catalyst, the catalytic membrane showed good activity and product selectivity for cumene.
An Introduction to Zeolite Synthesis Using Imidazolium-Based Cations as Organic Structure-Directing Agents
(MDPI, 2017-08-06) Pergher, Sibele Berenice Castellã; Vinaches, Paloma; Gusmão, Katia Bernardo
Zeolite synthesis is a wide area of study with increasing popularity. Several general reviews have already been published, but they did not summarize the study of imidazolium species in zeolite synthesis. Imidazolium derivatives are promising compounds in the search for new zeolites and can be used to help understand the structure-directing role. Nearly 50 different imidazolium cations have already been used, resulting in a variety of zeolitic types, but there are still many derivatives to be studied. In this context, the purpose of this short review is to help researchers starting in this area by summarizing the most important concepts related to imidazolium-based zeolite studies and by presenting a table of recent imidazolium derivatives that have been recently studied to facilitate filling in the knowledge gaps
Anchoring via covalent binding of β-diimine-nickel complexes in SBA-15 and its application in catalytic reactions
(Elsevier, 2015-08-05) Rossetto, Enéderson; Nicola, Bruna Pes; Souza, Roberto Fernando de; Pergher, Sibele Berenice Castellã; Gusmão, Katia Bernardo
The β-diimine ligands 2-(phenyl)amine-4-(phenyl)imine-2-pentene (L1) and 2-(2,6-dimethylphenyl)amine-4-(2,6-dimethylphenyl)imine-2-pentene (L2) were anchored covalently to SBA-15. The ligands were combined with (3-chloropropyl) trimethoxysilane (CPTMS), which is a trialkoxysilane group, and anchored to a mesoporous SBA-15 support through a complexation of the silanols of the silica matrix with nickel. These complexes were synthesized as catalysts precursors for ethylene and propylene oligomerization processes. The support was first synthesized and calcined before being anchored to the ligand, generating the nickel complex. These materials were characterized using various techniques such as 13C and 29Si NMR, small angle XRD, thermogravimetric analysis, N2 adsorption, transmission electron microscopy, elemental analysis and flame atomic absorption spectroscopy. The heterogenized complexes are active and selective during ethylene and propylene oligomerization, generating C4 and C6 products and alkylation products ranging from C10–C16. The alkylation process being a parallel reaction. The Ni-β-diimine/SBA-15 (SC1) complexes showed an activity of 7.2 × 103 h−1 for the ethylene oligomerization with 98% selectivity toward α- and C4 products and an activity of 2 × 103 h−1for the propylene oligomerization with a 13% selectivity toward C6 linear products. The results of the oligomerization reactions reveal the influence of the support on the products obtained
Assessment of two immobilized lipases activity and stability to low temperatures in organic solvents under ultrasound-assisted irradiation
(Springer, 2012-03) Batistella, Luciane; Ustra, Mara K.; Richetti, Aline; Pergher, Sibele Berenice Castellã; Treichel, Helen; Oliveira, J. V.; Lerin, Lindomar; Oliveira, Débora de
Both stability and catalytic activity of two commercial immobilized lipases were investigated in the presence of different organic solvents in ultrasound-assisted system. In a general way, for Novozym 435, the use of ethanol as solvent led to a loss of activity of 35% after 10 h of contact. The use of iso-octane conducted to a gradual increase in lipase activity in relation to the contact time, reaching a maximum value of relative activity of 126%. For Lipozyme RM IM, after 5 h of exposure, the enzyme presented no residual activity when ethanol was used as solvent. The solvents tert-butanol and iso-octane showed an enhancement of about 20 and 17% in the enzyme activity in 6 h of exposure, respectively. Novozym 435 and Lipozyme IM presented high stability to storage after treatment under ultrasound-assisted system using n-hexane and tert-butanol as solvents.
Avaliação da conversão e seletividade durante a reação de desidratação/desidrogenação do glicerol usando catalisadores a base de Cu-Fe2O3/Al2O3
(Universidade Federal do Rio Grande do Norte, 2017-06-28) Rocha, Ana Luiza Souza; Braga, Tiago Pinheiro; Monickarla Teixeira Pegado da Silva; Da silva, Monickarla Teixeira Pegado; Pergher, Sibele Berenice Castellã
A busca por fontes alternativas de energia tem impulsionado o aumento da produção de biodiesel tendo como subproduto, o glicerol. Tendo em vista o decréscimo do valor de mercado do glicerol, o setor industrial tem buscado a conversão do glicerol em produtos de melhor valor agregado como o acetol. O trabalho visa a avaliação da conversão e seletividade do glicerol em acetol usando catalisador heterogêneo a base Cu-Fe2O3/Al2O3. Os métodos de síntese do catalisador consiste nos precursores poliméricos (suporte) e impregnação úmida (fase ativa) seguida das técnicas de caracterização de DRX obtendo características de material amorfo e TG fornecendo informações sobre a decomposição térmica dos materiais sintetizados e por último, a análise de desempenho catalítico resultando em conversão maior que 90% e seletividade acima de 86% com catalisador contendo cobre.
Bentonites impregnated with TiO2 for photodegradation of methylene blue
(Elsevier, 2010-05) Rossetto, Enéderson; Petkowicz, Diego Ivan; Santos, João Henrique Zimnoch dos; Pergher, Sibele Berenice Castellã; Penha, Fábio Garcia
Four bentonites and one diatomite from Rio Negro (Argentina) were used as supports for titanium oxide (TiO2). The materials were characterized by X-ray diffraction, scanning electron microscopy, infrared spectroscopy, textural analysis by nitrogen adsorption, elemental analysis and diffuse reflectance spectroscopy. The specific surface areas calculated by the BET method were 76, 46, 80, and 31 for the bentonites and 153 m2/g for diatomite and were not changed by impregnation with TiO2. SEM analysis revealed agglomerates, probably due to titania domains on the surface. The properties of the lamellar materials were maintained after TiO2 impregnation, and all materials showed methylene blue photodegradation activity. The bentonites showed a higher activity than the commercial catalyst P25, likely due to the TiO2 distribution and better accessibility.
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 Castellã
The 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)
Bifunctional noble metal/zeolite catalysts for upgrading low-quality diesel fractions via selective opening of naphthenic rings
(Royal Society of Chemistry, 2016-04-04) Pergher, Sibele Berenice Castellã; Martínez, Agustín; Arribas, María A.
Current regulations for diesel fuels primarily involve severe reductions in the concentrations of sulfur and polyaromatics and a minimum cetane number (51 according to current EU standards). Low-quality distillate fractions, such as the LCO fraction abundantly produced in fluid catalytic cracking (FCC) units, cannot be directly used as a blending diesel component due to their high polyaromatics content and consequently poor cetane number (CN < 25) and ignition quality. For such fractions, the increase in CN achieved by deep hydrogenation of the polyaromatics is not enough to meet the fuel specifications. Further upgrading through selective ring opening (SRO) of the produced naphthenes has been proposed as a suitable technological solution to bring the CN to the required values. As will be shown in this article, bifunctional catalysts based on noble metals loaded on acidic zeolites (and mesoporous molecular sieves) exhibit good prospects for the SRO of multi-ring naphthenes as those contained in hydrogenated distillates. Moreover, the high hydrogenation ability of the noble metal(s) makes these bifunctional catalysts suitable for the coupled hydrogenation of (poly)aromatics and the subsequent opening of the naphthenic rings. As will be illustrated here for model naphthenic and aromatic compounds, fine tuning of the hydrogenation and hydrogenolysis activities of the metallic function and the acidity and porous structure of the molecular sieve carrier becomes crucial for achieving optimum performance in SRO reactions. Finally, the relevant issue of the sulfur tolerance of these noble metal-based bifunctional SRO catalysts and their performance in the upgrading of sulfur-containing industrial feedstocks will also be addressed in this perspective article
Bionanocomposite systems based on montmorillonite and biopolymers for the controlled release of olanzapine
(Elsevier, 2017-06-01) Pergher, Sibele Berenice Castellã; Oliveira, Artur S.; Alcântara, Ana C.S.
Olanzapine (OLZ) is a drug that is used in the treatment of schizophrenia and other psychoses, and it belongs to the thienobenzodiazepine class. The OLZ molecule has low solubility decreasing bioavailability, but has high permeability in membrane biological being classified as a Class II drug substance according to the Biopharmaceutics Classification System. It was reported many side effects of administering OLZ orally. So, in order to increase the bioavailability of drug and possibly reducing some of side effects, this paper proposes a new material able to controllably release the drug in the body. To control the dissolution rate, this work proposes a system that incorporates the drug into montmorillonite (MMT) dispersed in a mixture of alginate (ALG) and xanthan gum (XG) biopolymers. The proposed hybrids and bionanocomposites were characterized by several physicochemical techniques, including XRD, IR-ATR, TG DTA, SEM-EDS and HPLC. The characterization data confirmed the intercalation of the OLZ into the MMT by the ion exchange process, as well as the interaction of the MMT-OLZ with the biopolymers. The release test, conducted under various pH conditions, showed that the proposed system exhibited a more controlled drug release than commercial tablets, indicating that the ALG-XG/MMT-OLZ bionanocomposite can act as a controlled release system for OLZ
Carboxymethylcellulose template synthesis of porous aluminium oxide from hybrid spheres: influence of the degree of substitution and polymerization
(Springer, 2016-02-12) Pergher, Sibele Berenice Castellã; Silva, Monickarla Teixeira Pegado da; Carvalho, Julyana Cardoso; Braga, Tiago Pinheiro
Catalytic supports based on aluminum oxide were synthesized by the method of hybrid spheres using carboxymethylcellulose as organic precursor (template) and aluminum nitrate as inorganic precursor. The characterizations were performed by analysis of TG, XRD, FTIR, SEM and N2 physisorption. The study of synthesis indicated that the characteristics of the biopolymer (degree of substitution and polymerization) directly influence on the limit ratio between organic and inorganic precursor in order to observe the formation of the hybrid spheres. The physicochemical properties of the final material (structure by XRD, texture by N2 physisorption and morphology by SEM) showed a direct dependence with the biopolymer properties, indicating the versatility of this synthetic route. FTIR spectra confirm the formation of a hybrid material, comparing the pure CMC spectrum with the solids after drying. N2 adsorption/desorption isotherm and SEM images confirm the formation of highly porous materials with a specific surface area between 50 and 162 m2/g
Catalytic photodegradation of dyes by in situ zeolite-supported titania
(Elsevier, 2010-04-15) Petkowicz, Diego Ivan; Pergher, Sibele Berenice Castellã; Silva, Carlos Daniel Silva da; Rocha, Zênis Novais da; Santos, João Henrique Zimnoch dos
The degradation of dyes (methylene blue, direct blue 71, direct yellow 8) by a series of titania-supported catalysts generated in situ via the impregnation of TiCl4 onto a series of zeolite, which was synthesized using rice husks as the silicon source, was individually evaluated. After calcination, the resulting supported catalysts were characterized by X-ray diffraction spectrometry, ultraviolet–visible diffuse reflectance spectroscopy, diffuse reflectance and transmittance infrared Fourier transform spectroscopy, energy dispersive X-ray scanning electron microscopy, small angle X-ray scattering and differential pulse voltammetry. The titania generated is present in the anatase phase, without affecting the zeolite framework. Catalyst activity was shown to be comparable to that of the commercial P-25 catalyst after 1 h of UV light exposition. Monitoring the catalyst performance of several batches of material showed that P-25 provided the highest photodecomposition until the third cycle. On the other hand, the activity of the in situ-supported titania catalyst, in spite of showing lower catalytic activity, remained roughly constant up to the fifth cycle. This suggests that the catalyst generated in situ is more suitable for both filtering and reuse.
Characterization of Pd-mordenite Catalysts for NO Decomposition
(Springer, 2010-04-01) Oliveira, Andréa Marins de; Costilla, Ignácio; Gigola, Carlos; Baibich, Ione Maluf; Silva, Victor Teixeira da; Pergher, Sibele Berenice Castellã
The aim of this study was to characterize Pd catalysts supported on three different mordenite zeolites (a commercial sample and two laboratory preparations) previously tested for the NO decomposition reaction. H2 chemisorption, TPR, FTIR spectroscopy of adsorbed CO and NO, DRS UV–vis and TPD of NO were used to characterize the catalysts. After reduction at 573 K a large fraction of Pdo particles and some Pd2+ ions were found in the commercial sample and one laboratory preparation. In contrast a sample prepared with a mordenite synthesized using a natural clay was found to exhibit mainly ionic Pd. The amount of Pdo (PdO) relative to Pd2+ depends on the oxidation temperature and the metal loading. The catalysts exhibited similar levels of activity for the NO decomposition reaction at 673 K but a different selectivity to N2O. This behavior was related to differences in metal dispersion and other surface conditions that influence the formation of PdO particles.
Cl-mediated electrochemical oxidation for treating an effluent using platinum and diamond anodes
(Elsevier, 2015-12) Moura, Dayanne Chianca de; Brito, Chrystiane do Nascimento; Quiroz, Marco Antonio; Pergher, Sibele Berenice Castellã; Martinez-Huitle, Carlos Alberto
In this work, the role of chloride with respect to the oxygen evolution reaction by using BDD and Pt/Ti anodes was investigated to understand the performance of both anodes for the electrochemical treatment of a real sample of wastewater, with lower organic load, generated at Federal University of Rio Grande do Norte. Bulk experiments were performed under real discharged effluent conditions (pH and conductivity) in order to verify the applicability of direct and mediated electrochemical oxidation by applying 2.5 and 5.0 mA cm−2. Results clearly showed that, a partial elimination of chemical oxygen demand (COD) was achieved, depending on applied current density. Using Pt/Ti, by applying 2.5 and 5.0 mA cm−2, COD removal efficiencies of 25.2% and 30.49% were obtained. Under the same conditions, a minor COD removal was achieved by using BDD electrode. However, the removal efficiencies were improved when Cl-mediated oxidation approach was employed, obtaining 63.7% and 60% for Pt/Ti by applying 2.5 and 5.0 mA cm−2, respectively; while for BDD electrode, COD removals were about 15% and 47%, under the same conditions. These figures are in agreement with the polarization curves obtained, where it was possible to confirm that the concentration of halide in solution increases the importance of Cl2/oxy-chloro radicals system depending on the electrocatalytic material and this behavior plays an important role in relation with the oxygen evolution reaction, influencing on the efficiency of electrochemical approach adopted
Cobalt-catalyzed fischer–tropsch synthesis: chemical nature of the oxide support as a performance descriptor
(American Chemical Society, 2015-04-20) Prieto, Gonzalo; Mello, Mariele I. S. de; Concepción, Patricia; Murciano, Raúl; Pergher, Sibele Berenice Castellã; Martı́nez, Agustı́n
The effect of the chemical nature of the oxide support on the performance of cobalt Fischer–Tropsch catalysts is investigated. A series of supports is synthesized via monolayer coverage of porous γ-Al2O3 with various oxides representative of a wide range of Lewis acid–base character, as quantified by UV–vis spectroscopy coupled to alizarin adsorption. Incorporation of cobalt (20 wt %) results in model catalysts with identical porosities and similar Co particle sizes (>10 nm), allowing the study of support effects without overlap from diffusional or particle size factors. Under realistic reaction conditions, the initial TOF scales with the acidity of the oxide support, whereas the cobalt time yield and selectivity to industrially relevant C13+ hydrocarbons show a volcano dependence, with a maximum at an intermediate acid–base character. As inferred from in situ CO-FTIR, “selective” blockage of a few cobalt sites, though crucial for CO hydrogenation, by atoms from basic oxides and “unselective” site blockage via decoration of Co nanoparticles (strong metal–support interaction) with acidic, reducible oxides cause a decrease in reaction rate for supports with pronounced alkaline and acidic character, respectively. The extent of secondary isomerization reactions of α-olefin products, of relevance for chain reinsertion processes and product selectivity, also correlates with the support acidity. For a TiOx/Al2O3 as support, a remarkable C13+ productivity exceeding 0.09 molC gCo–1 h–1 is achieved, owing to the combination of optimal activity and selectivity. These results provide a unifying view of the support effects over a considerably broad study space and delineate a blueprint toward advanced Fischer–Tropsch catalysts.
Color and shade parameters of ultramarine zeolitic pigments synthesized from kaolin waste
(ABM, ABC, ABPol, 2014) Menezes, Raquel Aranha de; Paz, Simone Patrícia Aranha da; Angélica, Rômulo Simões; Neves, Roberto de Freitas; Pergher, Sibele Berenice Castellã
Ultramarine pigments were successful synthesized from zeolite A obtained from kaolin waste. This waste has been used as an excellent source of silicon and aluminum for zeolite synthesis because of its high kaolinite concentrations and low contents of other accessory minerals. The cost is naturally less than the industrialized product. Color additives (Sulfur and Sodium Carbonate) were mixed with different proportions of zeolite A and further calcined for 5 h at 500 °C. They were characterized by XRD and XRF in addition to visual classification by color and shade. These products show colors from blue to green at different shades, both influenced by the amount of additives and cooling rate after calcination. Thus, a different quantity of the same additives in the same zeolitic matrix provides an increase in the color intensity. Cooling rate after calcination induces the color change which is substantially important in the pigments production
Cristalização Induzida por Semente na Síntese Hidrotérmica de Zeólita com Estrutura FAU a partir de Pó de Vidro Residual
(Universidade Federal do Rio Grande do Norte, 2022-02-11) Sousa, Paulla Beatriz França de Sousa; Pergher, Sibele Berenice Castellã; Bieseki, Lindiane; 0000-0002-0088-0963; http://lattes.cnpq.br/4894556873583410; 0000-0002-5825-958X; http://lattes.cnpq.br/5249001430287414; 0000-0002-5050-3429; http://lattes.cnpq.br/5713269061250256; Pergher, Sibele Berenice Castellã; 0000-0002-5825-958X; http://lattes.cnpq.br/5249001430287414; Bieseki, Lindiane; 0000-0002-0088-0963; http://lattes.cnpq.br/4894556873583410; Araújo, Antônio Souza de; 0000-0002-1223-2939; http://lattes.cnpq.br/9770622597949866; Lima, Roberto Rodrigues Cunha; 0000-0003-4409-0071; http://lattes.cnpq.br/7537998627242126
A produção de materiais microporosos a baixo custo pela utilização de matérias-primas residuais como precursores principais nas rotas sintéticas vem sendo amplamente estudada. Desta forma, neste trabalho foram avaliadas as melhores condições experimentais para a utilização do pó de vidro incolor como fonte alternativa de silício na conversão em zeólitas com estrutura FAU-X. Primeiramente, os parâmetros ideais para a lixiviação ácida no pó de vidro foram estudados estatisticamente por meio da Metodologia de Superfície de Resposta (RSM). Em seguida, as sínteses hidrotérmicas foram assistidas por cristais de semente (0% a 5%, m.) da própria estrutura para induzir o crescimento da zeólita FAU, avaliando o tempo de cristalização (12, 24, 36 e 48 h) e a variação na fonte de silício (resíduo tratado e não tratado). As amostras obtidas foram caracterizadas por Difratometria de Raios-X e Fluorescência de Raios-X. A análise estatística aponta para o tratamento que resultou em uma maior lixiviação de cálcio, principalmente em função do tempo e concentração de ácido. Para as sínteses hidrotérmicas, foram observadas uma competição de fase entre as estruturas GIS, LTA, SOD e FAU nas zeólitas produzidas a partir do resíduo sem tratamento, em que com a adição de semente de 0% a 5% possibilitou o direcionamento adequado para a estrutura FAU, mas com um baixo ordenamento estrutural. Por outro lado, a eficiência no tratamento ácido para o resíduo resultou na formação da fase faujasita como principal e como fase secundária a presença da zeólita Na-P1 (estrutura GIS), obtendo um maior grau de ordenamento da estrutura a zeólita com maior quantidade de semente e menor tempo de cristalização. Portanto, a necessidade de um tratamento prévio no resíduo para obter uma fase mais pura no material sintetizado e a adição de semente para diminuir o tempo de cristalização e obter maior ordenamento estrutural foram requeridos.
Dandelion-like microspherical MCM-22 zeolite using BP 2000 as a hard template
(Sociedade Americana de Química, 2018-06-11) Pergher, Sibele Berenice Castellã; Schwanke, Anderson; Rocha, Jhonny Villarroel; Sapag, Karim; Díaz, Urbano; Corma, Avelino
The chemistry between layered MWW zeolite and carbon black pearls (BP 2000) as an inexpensive hard template was investigated to develop a rational one-pot synthesis of MCM-22 microspheres. The characterization results showed that the insertion of BP 2000 in the gel synthesis did not substantially compromise the crystallinity and microporosity, and the microscopic analyses showed that BP 2000 played a key role in controlling the final morphology of the MCM-22 zeolite, creating beautiful dandelion-like microspherical particles. The morphology obtained is due to the tortuous shape of the hard template, the particular MWW particle crystals, the interaction with the external surface of the MWW zeolitic precursor, and the synthesis conditions. The stacking of MWW crystals with edge-to-face orientations generates meso-/macrovoids, allowing access to the interiors of the microspheres. The microspheres were homogeneous with sizes ranging from 6 to 8 μm with an increase of the external surface and a macroporous size distribution centered at 200 nm, which is two times that of the traditional MCM-22 zeolite
Development of HZSM-5/AlMCM-41 hybrid micro–mesoporous material and application for pyrolysis of vacuum gasoil
(Elsevier, 2013-05) Coriolano, Ana Catarina F.; Silva, Cristiano G.C.; Costa, Maria J. F.; Pergher, Sibele Berenice Castellã; Caldeira, Vinícius P. S.; Araujo, Antonio S.
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 C17–C41, while in the presence of catalyst, light fraction of hydrocarbons, in the range of liquefied petroleum gas (C3–C5), gasoline (C6–C10) and diesel (C11–C16) were obtained, evidencing that the HZSM-5/AlMCM-41 hybrid material is an effective catalyst for pyrolysis of VGO.

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