Instituto de Química

URI Permanente desta comunidadehttps://repositorio.ufrn.br/handle/123456789/31488

Navegar

Agora exibindo 1 - 20 de 201

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 Cu2+ e Cr3+ em efluentes líquidos utilizando a cinza do bagaço da cana-de-açúcar
(Associação Brasileira de Cerâmica - ABCeram, 2015) Melo, Marcus Antônio de Freitas; Ferreira, P. P. L.; Braga, Renata Martins; Teodoro, N. M. A.; Melo, Vítor Rodrigo de Melo e; Melo, Dulce Maria de Araújo
Os efluentes líquidos de algumas indústrias apresentam traços de metais nocivos que possuem propriedade bioacumulativa, o que contribui para o aumento de sua toxicidade. Tendo em vista o crescimento industrial, e o consequente aumento de emissões de contaminantes em efluentes líquidos, a adsorção está entre as operações aplicadas para diminuir as concentrações dos metais a fim de atender a regulamentação ambiental vigente. A biomassa residual vem ganhando destaque no tratamento desses efluentes por se um material renovável e de baixo custo, quando comparado com os adsorventes convencionais. O objetivo deste trabalho é avaliar a eficiência da cinza do bagaço da cana-de-açúcar (CBC) na adsorção dos íons metálicos Cu2+ e Cr3+ por meio de ensaios de isoterma de adsorção. A CBC foi caracterizada quanto a sua microestrutura, composição química, área de superfície específica e morfologia, e o adsorbato foi analisado por absorção atômica de chama. A CBC apresentou-se de maneira eficaz como um bioadsorvente para ambas as soluções sintéticas, contendo os íons Cu2+ e Cr3+, presentes nos efluentes líquidos. As isotermas de adsorção presentaram um perfil crescente, indicando a eficiência na remoção média de 97,3% para o Cr3+ e 96,4% para o Cu2+, podendo este material ser aplicado como adsorvente em efluentes industriais
Adsorption of chromium ions on oil shale waste
(Brazilian Journal Of Petroleum And Gas, 2011) Melo, Marcus Antônio de Freitas; Pimentel, Patrícia Mendonça; Oliveira, Rosane Maria Pessoa Betânio; Melo, Dulce Maria de Araújo; Assunção, Ary Leonídio do Carmo; Gonzales, Gaspar
The adsorption of chromium (III) ions onto retorted shale, a waste product of the pyrolysis of oil shale, was investigated as a function of initial pH, temperature, and initial metal ion concentration. Adsorption experiments were carried out in a batch system and the uptake of the metallic ion was studied by using an initial concentration range of 200-500 mg L-1. The pseudo-first and pseudo-second order models were used to predict the rate constants of the adsorption system. Both Langmuir and Freundlich models were used to fit the equilibrium data; however, the former resulted in best fitting. Thermodynamic parameters such as enthalpy, free energy, and entropy changes were calculated. The values of such parameters showed that Cr(III) adsorption was favored at high temperatures
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 potencialidade de uso do resíduo proveniente da indústria de beneficiamento do caulim na produção de piso cerâmico
(Cerâmica Industrial, 2009-01) Andrade, Felipe Lira Formiga; Varela, Marcio Luiz; Dutra, Ricardo Peixoto Suassuna; Nascimento, Rubens Maribondo do; Melo, Dulce Maria de Araújo; Paskocimas, Carlos Alberto
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
Caracterização e uso de xisto para adsorção de chumbo (II) em solução
(Cerâmica - Associação Brasileira de Cerâmica, 2006-09) Melo, Marcus Antônio de Freitas; Pimentel, Patrícia Mendonça; Silva Júnior, C. N.; Melo, Dulce Maria de Araújo; Maldonado, G.; Henrique, Daniele de Macedo
Existe um grande interesse no uso de materiais de baixo custo para remoção de metais pesados em águas residuais. Novas técnicas de processamento e adsorventes incluindo argilas, resinas sintéticas, turfa e quitosana tem sido estudados objetivando substituir o carvão ativado. No presente trabalho, xisto retortado (XR), um rejeito sólido da transformação térmica do xisto oleígeno, foi caracterizado com o objetivo de utilizá-lo como adsorventes para remoção de metais pesados. O aproveitamento desse rejeito é de grande interesse, uma vez que o Brasil possui a segunda maior reserva mundial de xisto oleígeno. Os rejeitos foram caracterizados por diferentes técnicas de caracterização, incluindo tamanho de partícula, análise termogravimétrica, fluorescência de raios X, espectroscopia na região do infravermelho, difração de raios X, e microscopia eletrônica de varredura-EDS. As características dos pós foram adequadas para os experimentos de adsorção. Estudos de adsorção de Pb2+ pelo método de banho finito foram realizados. A remoção do Pb2+ foi superior a 85%
Caracterização e usos de argilas bentonitas e vermiculitas para adsorção de cobre (II) em solução
(Cerâmica - Associação Brasileira de Cerâmica, 2002-12) Melo, Marcus Antônio de Freitas; Santos, C. P. F. dos; Melo, Dulce Maria de Araújo; Vitor Sobrinho, Eledir
Vários trabalhos tratam da remoção de metais por argilas e argilominerais. O processo de remoção geralmente ocorre por precipitação, troca iônica e adsorção. Neste trabalho estudou-se a adsorção de solução de Cu (II) em vermiculita, bentonitas sódica e cálcica, proveniente de Campina Grande-PB , tendo-se como variáveis pH, tempo de contato e concentração do adsorvente. Os ensaios foram realizados à temperatura ambiente e as medidas de Absorção Atômica foram feitas no sobrenadante e no resíduo sólido. As argilas bentonitas cálcicas, provenientes de Campina-Grande (PB), sódica de Wyoming (Wyoming-USA) e sódicas (preparadas em laboratório) e as vermiculitas (provenientes do Piauí) foram caracterizadas antes e após o processo de adsorção de Cu (II) em solução através das técnicas, análise química, TG e DTA, área superficial (BET), espectroscopia na região de infravermelho, difração de raios X e medidas de pH. Os resultados mostram que as argilas estudadas adsorvem metais pesados através da troca iônica e que a vermiculita foi mais eficaz no processo, adsorvendo 40,9% de cobre da solução em estudo, em relação às outras argilas envolvidas no processo
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 Araújo
Neste 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 ambiente
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
Carreadores de oxigênio a base de Ni obtidos por diferentes métodos de síntese para aplicação no processo de reforma de metano com recirculação química
(Associação Brasileira de Cerâmica - ABCeram, 2016) Melo, Marcus Antônio de Freitas; Alves, J. A. B. L. R.; Figueredo, G. P.; Medeiros, Rodolfo Luiz Bezerra de Araújo; Costa, Tiago Roberto da; Melo, Dulce Maria de Araújo
Carreadores de oxigênio a base de Ni e contendo La, Al e Mg foram sintetizados com sucesso por combustão assistida por microondas (N6C), combustão assistida por microondas seguida de impregnação por via úmida (N6CI) e coprecipitação (N6CP), visando sua aplicação na produção de hidrogênio a partir de metano em sistemas de recirculação química com captura de CO2. Os materiais foram preparados obedecendo a fórmula geral Nix/La2O3/Al2O3/MgO, onde x = 60% em massa, sendo o restante referente aos óxidos de lantânio (8%), alumínio (30%) e magnésio (2%). Os sólidos obtidos foram caracterizados por difração de raios X, redução a temperatura programada e reatividade para o processo de reforma de metano com recirculação química. Os testes de reatividade foram conduzidos a 900 ºC, onde inicialmente a amostra foi submetida a 8 ciclos de CAO (capacidade de armazenamento de oxigênio), e finalmente foram realizados 2 ciclos de reação, com cada ciclo contendo 15 pulsos de metano e 15 pulsos de oxigênio. Os resultados das caracterizações indicam que os métodos empregados foram adequados à obtenção de diferentes materiais com propriedades distintas. De modo geral, os carreadores apresentaram excelentes percentuais de conversão de CH4 e elevada produção de hidrogênio. O carreador N6CP apresentou o melhor desempenho para produção de gás de síntese, com razão H2/CO igual a 2 no 15º pulso, além de ser apontado como o mais resistente à desativação por coque e com maior potencial de oxidação, consumindo 100% de O2 até o 12º pulso. Por sua vez, o N6CI perdeu bastante desempenho ao longo dos ciclos e o N6C formou a maior quantidade de coque, revelando as peculiaridades dos métodos de síntese empregados. De acordo com a distribuição dos produtos formados na etapa de redução com CH4, pode-se concluir que as reações mais frequentes foram craqueamento catalítico, combustão e reforma
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.
Catalytic upgrading of Elephant grass (Pennisetum purpureum Schum) pyrolysis vapor using WO3 supported on RHA and RHA-MCM-41
(Elsevier, 2017-01-01) Melo, Marcus Antônio de Freitas; Braga, Renata Martins; Melo, Dulce Maria de Araújo; Vitor Sobrinho, Eledir; Barros, Joana Maria de Farias; Carvalho, Alexandre Fontes Melo de; Fontes, Maria do Socorro Braga; Freitas, Júlio César de Oliveira
Recently, zeolites have been widely applied in catalytic pyrolysis to improve physical and chemical properties of bio-oil to produce energy or to selectively produce chemicals for industry. This study aims to analyze the catalytic pyrolysis products of Elephant Grass (EG) using WO3 catalysts supported on rice husk ash (RHA) silica and RHA-MCM-41, being low cost materials derived from agro industrial waste, and evaluate the catalysts activity in the formation of deoxygenated compounds. Elephant Grass has been shown as a potential energy crop that has fast growth and is easy to cultivate in different countries, including Brazil. Its energetic characterization was evaluated by proximate and ultimate analysis, High Heat Value (HHV), cellulose, hemicellulose and lignin content, chemical ash composition by FRX and bulk density. Pyrolysis analysis was performed at 500 ◦C in a Py-5200 HP-R connected to a GC–MS, and pyrolysis vapors were carried by N2 to a catalytic bed at 400 and 600 ◦C. It was noticed that increasing catalyst temperature promotes cracking reactions leading to increased aromatic content. The main oxygenated pyrolysis products of EG such as phenols, furans, ketones and acetic acid were converted at 600 ◦C using WO3/RHA catalyst into aromatics (benzene, toluene, xylene, styrene), being of high added value for chemical industry. The main influence on aromatics yields could be related to catalytic activity of WO3 promoted by its redox ability and the rise in temperature which favors cracking reactions
Ceramic pigment obtained by polymeric precursors
(Elsevier, 2005-04) Cunha, Jardel Dantas da; Melo, Dulce Maria de Araújo; Martinelli, Antonio Eduardo; Melo, Marcus Antônio de Freitas; Maia, I.; Cunha, S.D.
Fe2O3 has been used as ceramic pigment due to excellent colorimetric characteristics combined with thermal stability. The introduction of La+3 to Fe2O3 yields the precipitation of the perovskyte structure (LaFeO3) with corresponding differences in the color of the resulting pigment. The compound was synthesized from polymeric precursors and characterized by thermal and colorimetric analyses, infrared and UV–visible spectroscopy, and X ray diffraction. The characteristic light brown color of Fe2O3 changed to orange with the addition of La+3. As the calcination temperature increased from 900 °C to 1100 °C the pigment darkened as a result of the reduction of Fe+3 → Fe+2 with corresponding change of the colorimetric coordinates from L* a* b* = 49.003, 10.541, 12.609 to L* a* b* = 31.279, 6.096, 6.877

SIGAA

Navegar

Navegando Instituto de Química por Título