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Adsorption dynamics of C5-C6 isomerate fractions in zeolite beta for the octane improvement of gasoline

Bárcia, Patrick da Silva; Silva, José A.C.; Rodrigues, A.E.
Fonte: AMER CHEMICAL SOC. Publicador: AMER CHEMICAL SOC.
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
521.3217%
An experimental and modeling study of the vapor-phase adsorption of C-5-C-6 paraffin fractions in a fixed bed of zeolite beta was addressed. Breakthrough experiments with mixtures containing n-pentane (nPEN), iso-pentane (iPEN), n-hexane (nHEX), 3-methylpentane (3MP), 2,3-dimethylbutane (23DMB), and 2,2-dimethylbutane (22DMB) demonstrate that the sorption hierarchy is temperature-dependent. At the optimum temperature of 583 K, an enriched high-octane molecule fraction of 22DMB, iPEN, and 23DMB can be selectively separated from the low-octane equimolar C-5-C-6 isomerate feed. For the case of feed mixtures with the typical composition of the hydroisomerization reactor product of the total isomerization process, the enriched fraction contains low research octane number (RON) nPEN, which decreases the octane quality of the product obtained. However, the use of a layered bed with zeolite 5A and zeolite beta can displace the nPEN from the enriched fraction, resulting in a maximum octane number of about 92.5 points. Aspen Adsim was used to simulate the dynamic behavior of the C-5-C-6 fraction in a non-isothermal and non-adiabatic bed, giving a good description of the set of experimental data. An optimal design of a mono/dibranched separation process can be achieved by properly tuning the operating temperature and the zeolite 5A/zeolite beta ratio on a layered fixed bed.

Separation of light naphtha for the octane upgrading of gasoline: adsorption and membrane technologies and new adsorbents

Bárcia, Patrick da Silva
Fonte: FEUP Publicador: FEUP
Tipo: Tese de Doutorado
ENG
Relevância na Pesquisa
434.64035%
The aim of this work is to contribute for the development of adsorption based separation processes with considerable potential for commercial application on the refining industry, namely, in the separation of high research octane number (HRON) paraffins from light naphtha fractions. The development of an adsorption process requires first a detailed knowledge of equilibria and kinetics of adsorption and their impact on the dynamic response of an adsorption column. Accordingly, we start collecting single and mixture adsorption equilibrium isotherms of C6 isomers, n-hexane (nHEX), 3-methylpentane (3MP), 2,3-dimethylbutane (23DMB), and 2,2- dimethylbutane (22DMB), from breakthrough experiments in zeolite beta. This adsorbent was selected because its pore system posses interesting characteristics for the separation of HRON dibranched C6 from their low research octane number (LRON) monobranched isomers. It was found that the sorption hierarchy in zeolite beta was most favourable towards the linear isomer and least favourable towards the dibranched ones. Zeolite beta demonstrated significant selectivity to discriminate between mono and dibranched C6 isomers, especially at low coverage. Based on an analysis of sorption events at the molecular level...

Remoção de bisfenol-A por adsorção

Haro, Nathalia Krummenauer
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
412.34766%
O bisfenol-A (BPA), um monômero usado na fabricação de resinas epóxi e de plásticos de policarbonato, é considerado um potente desregulador endócrino que provoca diversas doenças. O objetivo deste trabalho foi estudar a remoção de BPA, de soluções aquosas através da técnica de adsorção em batelada e em processo contínuo. Também foi investigada a capacidade de regeneração do sorvente utilizado nos testes em batelada. Para isso, foram testados diferentes adsorventes (zeólita em pó e granular modificada com quitosana, zeólita sódica e carvão ativado granular), a fim de determinar qual apresentaria maiores índices de remoção de BPA. Posteriormente foram realizados ensaios de sorção com o sólido escolhido objetivando encontrar as condições mais adequadas de processo considerando os parâmetros de pH, tempo de residência, concentração de sólido sorvente. Ainda, isotermas de equilíbrio para este sistema foram construídas. A adsorção em leito fixo foi avaliada em experimentos via planta piloto de adsorção, segundo a influência de três variáveis: efeito da massa de adsorvente utilizada (5g e 10g), vazão de alimentação (15 mL.min-1 e 20 mL.min-1) e concentração inicial (50 mg.L-1 e 100 mg.L-1). Na regeneração do carvão ativado saturado com BPA...

Sintese de materiais hibridos micro e mesoporosos MCM-41/ZSM-5 para reforma catalitica do n-Octano

Tereza S. M. Santos
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 31/12/2004 PT
Relevância na Pesquisa
411.3684%
A peneira molecular mesoporosa MCM-41 é considerada um promissor suporte catalítico, no entanto a baixa acidez deste material é uma limitação para aplicá-lo em reações que exijam sítios ácidos fortes. Uma alternativa para melhorar suas propriedades ácidas é o aumento da cristalinidade da MCM-41 pela recristalização das paredes contendo embriões de zeólitos microporosos. Neste trabalho foram utilizados dois diferentes métodos de síntese na preparação das peneiras moleculares precursoras dos materiais híbridos MCM-41/ZSM-5: o método hidrotérmico e o método à temperatura ambiente. A estrutura de poros dos aluminossilicatos preparados hidrotermicamente resistiu aos tratamentos pós-síntese enquanto apenas uma amostra sintetizada à temperatura ambiente, aquela com razão molar Si/AI 7,5, manteve os poros cilíndricos. Estes materiais foram utilizados como suportes na preparação de catalisadores Pt-MCM-41 e Pt-MCM-41/ZSM-5 por troca iônica do cloreto de tetraminaplatina, na temperatura ambiente. Os materiais foram caracterizados por difração de raios-x, espectroscopia de absorção no infravermelho, resso-nância magnética nuclear, termogravimetria, análise elementar, adsorção de nitrogênio e quimissorção de hidrogênio. Os catalisadores foram testados na isomerização do n-pentano e reforma do n-octano. Os novos catalisadores são ativos tanto na isomerização do n-pentano quanto na reforma do n-octano mantendo suas estruturas paracristalinas originais...

Simulação molecular da adsorção de hidrocarbonetos em aluminofosfatos; Molecular simulation of hydrocarbons adsorption in aluminophosphates

Sebastião Mardonio Pereira de Lucena
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 17/08/2006 PT
Relevância na Pesquisa
537.78746%
Devido a grande importância dos processos industriais de separação de xilenos por adsorção, técnicas de simulação molecular foram usadas para estudar as causas da orto-seletividade de isômeros C8 em peneiras moleculares aluminofosfatadas. Aplicaram-se campos de força aproximados e otimizados do tipo AA no ensemble grande canônico com algoritmos Monte Carlo (GCMC) convencional e dirigido. Foram calculadas isotermas monocomponentes, calores de adsorção a baixa concentração e realizamos uma detalhada análise estrutural para definir sítios de adsorção e posicionamentos moleculares nos poros das peneiras AlPO4-5, AlPO4-8, AlPO4-11 e VPI-5. Obteve-se acordo quantitativo entre as isotermas experimentais e simuladas para o sistema xilenos/AlPO4-5 e um acordo qualitativo para o sistema xilenos/AlPO4-11. A análise estrutural levou em conta as variações no interior dos poros dos aluminofosfatos que ocorre em duas regiões: uma mais larga, denominada região de grades, e outra mais estreita, que corresponde à região de janelas. A orto-seletividade evidenciada experimentalmente é causada pela forte interação xileno-peneira e pela modulação dos canais. Este conjunto de fatores determina o posicionamento das moléculas dentro dos poros. Para o orto-xileno este microambiente provoca um posicionamento face-a-face na região das grades...

Volatile Organic Compound Adsorption on a Nonporous Silica Surface: How Do Different Probe Molecules Sense the Same Surface?

Herdes, C.; Ribeiro Carrott, M.M.L.; Russo, P.A.; Carrott, P.J.M.
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
404.27863%
In this work, we compare experimental results to molecular simulation results of volatile organic compound (VOC) adsorption on nonporous silica.We adopted an effective model for the rough solid surface, obtained by a temperature annealing scheme, plus an experimental/simulation nitrogen adsorption tuning process over the silica energetic oxygen parameter. The measurement/prediction of selected VOCs, specifically, n-pentane and methylcyclohexane, is presented in terms of adsorption isotherms, with an emphasis on the angle distribution analysis of the three studied probe molecules with respect to the same modeled surface.

Hydrocarbons adsorption on templated mesoporous materials: effect of the pore size, geometry and surface chemistry

Russo, P.A.; Ribeiro Carrott, M.M.L.; Carrott, P.J.M.
Fonte: Royal Society of Chemistry Publicador: Royal Society of Chemistry
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
435.6278%
Adsorption–desorption isotherms of aromatic (mesitylene and toluene) and aliphatic (methylcyclohexane, neopentane and n-pentane) hydrocarbons were measured on ordered mesoporous materials, including MCM-41, MCM-48, SBA-15, SBA-16 and MCF silicas, a periodic mesoporous organosilica and a CMK-3 carbon, in order to evaluate the effect of the adsorbent characteristics on the organic compounds adsorption behaviour. A clear separation between aliphatic and aromatic hydrocarbons is observed at low p/po for the materials having pores accessible by narrow openings. The presence of narrow pore openings causes an increase in the volume adsorbed of mesitylene, toluene, methylcyclohexane and n-pentane prior to capillary condensation that does not occur for neopentane. The increase of the hydrophobicity and change of the surface structure, resulting from the incorporation of chloromethyl groups on the silica walls, causes the p/po at which the aromatic hydrocarbons condense to increase while the introduction of aromatic rings into the pore walls has a less significant effect on the condensation pressures. However, at low p/po, all the hydrocarbons have higher affinity for the periodic mesoporous organosilica surface than for the pure silica or silica with chloromethyl groups surfaces...

Materiais com estrutura mesoporosa ordenada contendo titânio: Preparação, Caracterização, Estudos de Adsorção e Propriedades Catalíticas

Galacho, Cristina
Fonte: Universidade de Évora Publicador: Universidade de Évora
Tipo: Tese de Doutorado
POR
Relevância na Pesquisa
304.27863%
his PhD thesis presents studies on the preparation, characterisation, thermal stability, stability during long term exposure to water vapour at 298K and evaluation of the catalytic properties of Ti-MCM-41 materials. Studies related to the synthesis and structural characterisation of Si-MCM-41 materials, prepared at room temperature, from structure directing agents with different chain lengths and by direct addition of the silica source or by its addition in alcoholic solution, allowed selection of tetra-, hexa- and octadecyltrimethylammonium bromides as the most suitable structure directing agents for the preparation of M41S type materials of high quality and exclusion of BuOH as the alcohol in the process of synthesis of the these materials. After developing and implementing a new method for the synthesis of Ti-MCM-41 materials, carried out at room temperature and based on the procedure for preparing Si-MCM-41 solids, a systematic studied of the effect of the principal synthesis parameters on the structural and chemical properties of the materials, namely, chain length of the structure directing agent, order of addition of the silicon and titanium precursors, direct or alcoholic solution addition of the titanium alcoxide, nature of the metal alcoxide used as titanium source and silicon/titanium molar synthesis ratio...

Adsorption of n-Pentane and iso-Octane for the Evaluation of the Porosity of Dealuminated BEA Zeolites

Ribeiro Carrott, M. M. L.; Russo, P. A.; Carvalhal, C.; Carrott, P. J. M.; Marques, J. P.; Lopes, J. M.; Gener, I.; Guisnet, M.; Ramôa Ribeiro, F.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
627.2427%
Adsorption of n-pentane and 2,2,4-trimethylpentane at 298 K was carried out in order to characterize the porosity of a series of HBEA dealuminated zeolites. The HBEA samples were prepared from a calcined parent sample by steaming, by treatment with hydrochloric acid and by treatment with ammonium hexafluorosilicate (HFS) solutions. The comparison of the adsorption results with those previously obtained by nitrogen adsorption, show that the use of this latter adsorptive alone is insufficient for evaluating the changes provoked by dealumination. The narrow mesopores which were found in the parent sample show distinct behaviour with respect to each of the organic adsorptives. Treatment with HFS solutions and steaming causes the most significant changes in the microporosity, decreasing the micropore volumes of the samples. The former also causes a substantial loss of external area. Treatment with HCl solutions primarily removes extra-framework aluminium species formed during calcination; while this treatment has no significant effect on the microporosity, it causes an increase in the external areas of the samples. The removal of extra-framework aluminium species from the mesopores of the calcined sample contributes towards this increase. On the other hand...

Trends in the condensation/evaporation and adsorption enthalpies of volatile organic compounds on mesoporous silica materials

Russo, P.A.; Ribeiro Carrott, M.M.L.; Carrott, P.J.M.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
524.85152%
The adsorption-desorption of toluene, methylcyclohexane, neopentane and n-pentane was measured at temperatures between 258-308K on mesoporous silica materials with different pore structures and pore sizes (MCM-41, SBA-15, SBA-16, LPC and MCF). It was found that the change in the width of the hysteresis cycles with temperature is similar for MCM-41, SBA-15 and MCF but distinct for the materials having pores accessible through very narrow openings (SBA-16 and LPC). A comparison between the plots of Vads vs potential for SBA-16, LPC and MCF suggested that the differences are a consequence of the non equilibrium evaporation mechanism of the organics from the pores of SBA-16 and LPC. The isosteric enthalpies of adsorption indicated that the strength of the gas-solid interactions for toluene is superior to those corresponding to neopentane, methylcyclohexane or n-pentane. The isosteric enthalpies associated with capillary condensation are higher than the molar condensation enthalpies for the materials with narrower mesopores. As the size of the pores increases, the difference gradually decreases and the isosteric enthalpies are identical to the molar condensation enthalpies for the materials with pores larger than ~20 nm. The apparent evaporation enthalpies were found to be higher than the apparent condensation enthalpies when the hydrocarbons isotherms exhibited developed hysteresis...

Adsorption of n-Pentane on Mesoporous Silica and Adsorbent Deformation

Gor, G.Y.; Paris, O.; Prass, J.; Russo, P.A.; Ribeiro Carrott, M.M.L.; Neimark, A.V.
Fonte: ACS Publications Publicador: ACS Publications
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
954.019%
Development of quantitative theory of adsorption-induced deformation is important, e.g., for enhanced coalbed methane recovery by CO2 injection. It is also promising for the interpretation of experimental measurements of elastic properties of porous solids. We study deformation of mesoporous silica by n-pentane adsorption. The shape of experimental strain isotherms for this system differs from the shape predicted by thermodynamic theory of adsorption-induced deformation. We show that this difference can be attributed to the difference of disjoining pressure isotherm, responsible for the solid−fluid interactions. We suggest the disjoining pressure isotherm suitable for n-pentane adsorption on silica and derive the parameters for this isotherm from experimental data of n-pentane adsorption on nonporous silica. We use this isotherm in the formalism of macroscopic theory of adsorption-induced deformation of mesoporous materials, thus extending this theory for the case of weak solid−fluid interactions. We employ the extended theory to calculate solvation pressure and strain isotherms for SBA-15 and MCM-41 silica and compare it with experimental data obtained from small-angle X-ray scattering. Theoretical predictions for MCM-41 are in good agreement with the experiment...

Numerical study of n-pentane separation using adsorption column

Silva,Adriano da; Mariani,Viviana Cocco; Souza,Antônio Augusto Ulson de; Souza,Selene Maria de Arruda Guelli Ulson
Fonte: Instituto de Tecnologia do Paraná - Tecpar Publicador: Instituto de Tecnologia do Paraná - Tecpar
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2005 EN
Relevância na Pesquisa
643.377%
This work simulated numerically the n-pentane separation of a mixture of iso-pentane, n-pentane and nitrogen, using an adsorption column with zeolite 5A. The mathematical model equations of the mass and heat transfer in the adsorption column are presented, as well as the boundary and initials conditions, beyond some hypotheses and considerations. The Volume Finite Method was used in the discretization of the equations to get the system of algebraic equations and posterior development of the computational algorithm. The numerical results using the Differencing Central (CDS) and Upwind (UDS) interpolations were compared with experimental results found in the literature. The influence of the partial pressure in the adsorption column performance was also analyzed.

The actions of some general anaesthetics on the potassium current of the squid giant axon.

Haydon, D A; Urban, B W
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /04/1986 EN
Relevância na Pesquisa
319.55053%
A number of small organic molecules with general anaesthetic action have been examined for their effects on the voltage-dependent potassium current of the squid giant axon. They include representatives of the three classes of anaesthetics examined in previous studies on the sodium current (Haydon & Urban, 1983a, b, c), i.e. the non-polar molecules n-pentane, cyclopentane and CCl4, several n-alkanols and the inhalation anaesthetics chloroform, halothane, diethyl ether and methoxyflurane. Potassium currents under voltage clamp were recorded in intact and in intracellularly perfused axons before, during and after exposure to the test substances, and the records were fitted with equations similar to those proposed by Hodgkin & Huxley (1952). Shifts in the curves of the steady-state activation against membrane potential and reductions in the potassium conductance at 60 or 70 mV membrane potential have been tabulated. On the same intact axons, all the anaesthetics with the exception of methoxyflurane reduced potassium currents less than sodium currents by about a factor of two or more. For the n-alkanols, butanol to decanol, the concentrations required to reduce the potassium current at 60 mV membrane potential by 50% were determined. For n-butanol to n-heptanol...

Some effects of aliphatic hydrocarbons on the electrical capacity and ionic currents of the squid giant axon membrane.

Haydon, D A; Requena, J; Urban, B W
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /12/1980 EN
Relevância na Pesquisa
328.2947%
1. The electrical properties of squid giant axons were examined by means of admittance bridges at frequencies from 0.5 to 300 kHz. A simple equivalent circuit was used to estimate the membrane capacity. 2. The calculated membrane capacities decreased monotonically over the whole frequency range. 3. At 100 kHz and higher frequencies the membrane capacity was independent of potential. 4. At frequencies greater than 20 kHz, exposure of the axons to saturated or 0.9 saturated solutions of n-pentane (275-306 micrometer) reduced the capacity per unit area by 0.1-0.15 micro F cm-2. 5. At 1 kHz the effect of the saturated pentane solutions depended on the membrane potential. In axons having potentials between -60 and zero mV the pentane solutions lowered the capacity, whereas for potentials between -160 and -60 mV they produced little or no change. 6. Saturated solutions of n-hexane, n-heptane and n-octane exhibited qualitatively similar, but quantitatively smaller influences on the membrane capacity, the changes declining as the chain length increased. 7. Under voltage clamp, the peak inward and steady-state outward currents were partially suppressed by the hydrocarbons. Saturated solutions of n-pentane usually reduced the former (reversibly) by 60-80% and the latter by 20-40%. Solutions of n-hexane...

Síntese, caracterização e estudo da regeneração do silicoaluminofosfato-11 (SAPO-11); Synthesis, characterization and study of the regeneration of silicoaluminophosphate-11 (SAPO-11)

Chellappa, Thiago
Fonte: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Ciência e Engenharia de Materiais; Processamento de Materiais a partir do Pó; Polímeros e Compósitos; Processamento de Materiais a part Publicador: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Ciência e Engenharia de Materiais; Processamento de Materiais a partir do Pó; Polímeros e Compósitos; Processamento de Materiais a part
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
304.26365%
heterogeneous catalyst such as a silicoaluminophosphate, molecular sieve with AEL (Aluminophosphate eleven) structure such as SAPO-11, was synthesized through the hydrothermal method starting from silica, pseudoboehmite, orthophosphoric acid (85%) and water, in the presence of a di-isopropylamine organic template. For the preparation of SAPO-11 in a dry basis it was used as reactants: DIPA; H3PO4; SiO4; Pseudoboehmite and distilled water. The crystallization process occurred when the reactive hydrogel was charged into a vessel and autoclaved at 200ºC for a period of 72 hours under autogeneous pressure. The obtained material was washed, dried and calcined to remove the molecular sieves of DIPA. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), nitrogen adsorption (BET) and thermal analysis (TG/DTG). The acidic properties were determined using adsorption of nbutylamine followed by programmed thermodessorption. This method revealed that SAPO-11 shows an acidity that ranges from weak to moderate. However, a small quantity of strong acid sites could be detected there. The deactivation of the catalysts was conducted by artificial coking followed by the cracking of the n-hexane in a fixed bed with a continuous flow micro-reactor coupled on line to a gas chromatograph. The main products obtained were: ethane...

Estudos comparativos do ciclo de regeneração de diferentes tipos de silicoaluminofosfatos

Chellappa, Thiago
Fonte: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Ciência e Engenharia de Materiais; Processamento de Materiais a partir do Pó; Polímeros e Compósitos; Processamento de Materiais a part Publicador: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Ciência e Engenharia de Materiais; Processamento de Materiais a partir do Pó; Polímeros e Compósitos; Processamento de Materiais a part
Tipo: Tese de Doutorado Formato: application/pdf
POR
Relevância na Pesquisa
394.59797%
Different types of heterogeneous catalysts of the silicoaluminophosphate type, (SAPO-5, SAPO-11, SAPO-31, SAPO-34 and SAPO-41), molecular sieves with a: AFI, AEL, ATO, CHA and AFO structure, respectively, were synthesized through the hydrothermal method. Using sources such as hydrated alumina (pseudobohemita), phosphoric acid, silica gel, water, as well as, different types of organic structural templates, such as: cetyltrimethylammonium bromide (CTMABr), di-isopropylamine (DIPA), di-n- propylamine (DNPA) and tetraethylammonium hydroxide (TEOS), for the respective samples. During the preparation of the silicoaluminophosphates, the crystallization process of the samples occurred at a temperature of approximately 200 ° C, ranging through periods of 18-72 h, when it was possible to obtain pure phases for the SAPOs. The materials were furthermore washed with deionized water, dried and calcined to remove the molecules of the templates. Subsequently the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), absorption spectroscopy in the infrared region (FT-IR), specific surface area and thermal analysis via TG/DTG. The acidic properties were determined using adsorption of n-butylamine followed by programmed termodessorption. These methods revealed that the SAPO samples showed a typically weak to moderate acidity. However...

Estudo da regeneração de aditivos para catalisadores de craqueamento aluminofosfatos (ALPO s)e silicoaluminofosfatos (SAPO s)

Silva, Arilson José do Nascimento
Fonte: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Química; Físico-Química; Química Publicador: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Química; Físico-Química; Química
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
304.63234%
Heterogeneous catalysts such as aluminophosphate and silicoaluminophosphate, molecular sieves with AEL of ALPO-11 and SAPO-11, were synthesized by the hydrothermal method with the following molar composition: 2.9 Al +3.2 P + 3.5 DIPA +32.5 H20 (ALPO-11); 2.9 Al +3.2 P + 0.5 Si + 3.5 DIPA +32.5 H20 (SAPO-11) starting from silica (only in the SAPO-11), pseudoboehmite, orthophosphoric acid (85%) and water, in the presence of a di-isopropylamine organic template. The crystallization process occurred when the reactive hydrogel was charged into a vessel and autoclaved at 170ºC for a period of 48 hours under autogeneous pressure. The obtained materials were washed, dried and calcined to remove the molecular sieves of DIPA. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), thermo gravimetric differential thermal analysis (TG/DTA) and nitrogen adsorption (BET). The acidic properties were determined using adsorption of n-butylamine followed by programmed thermodessorption. This method revealed that ALPO-11 has weaker acid sites due to structural defects, while SAPO-11 shows an acidity that ranges from weak to moderate. However, a small quantity of strong acid sites could be detected there. The deactivation of the catalysts was conducted by the cracking of the n-hexane in a fixed bed continuous flow microrreator coupled on line to a gas chromatograph. The main products obtained were: ethane...

CONVERSION OF METHANOL AND LIGHT OLEFINS TO GASOLINE OVER A SHAPE SELECTIVE CATALYST ZSM-5

HWU, FRANK SHAW-SHYONG
Fonte: Universidade Rice Publicador: Universidade Rice
Tipo: Thesis; Text Formato: application/pdf
ENG
Relevância na Pesquisa
292.21898%
Reactions of methanol and some light olefins (including ethylene, propylene, butenes, and 3-methylbutene-1) were studied over Ni-ZSM-5 zoelite catalyst. The product distribution over a broad range of space velocities indicates the reaction sequence: dimethyl paraffins methanol (,ether) C(,2)-C(,5) olefins (,aromatics) Monomethyl aliphatics predominate over both straight-chain and dimethyl hydrocarbons. Aromatics consist mainly of toluene and xylene mixtures. At 368(DEGREES)C, compositions of butene isomers are in thermodynamic equilibrium, over the range of residence times investigated (i.e. (tau) = 22 to 648 mg-sec/cc). Equilibrium composition of xylenes is not established until (tau) = 1440 mg-sec/cc; p-xylene is kinetically favored at short residence times. The effect of temperature on the reaction of propylene shows that a maximum in conversion is achieved at 310(DEGREES)C. As the temperature goes above 310(DEGREES)C, conversion decreases, indicating the occurrence of reversible cracking reactions. Temperature is also a crucial factor in determining the product distribution, for no aromatics are observed for reaction temperatures below 310(DEGREES)C. In both propylene and cis-butene-2 conversion experiments...

Desenvolvimento de catalisadores bifuncionais de óxido de zircônio modificado por óxidos de tungstênio e molibdênio contendo platina para a reação de isomerização de n-parafinas; Development of bifunctional catalysts on zircon oxide modify by tungsten and molybdenum oxides contain platinum for nparaffin isomerization

Pedrosa, Anne Michelle Garrido
Fonte: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Química; Físico-Química; Química Publicador: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Química; Físico-Química; Química
Tipo: Tese de Doutorado Formato: application/pdf
POR
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393.97824%
Bifunctional catalysts based on zircon oxide modified by tungsten (W = 10, 15 and 20 %) and by molybdenum oxide (Mo= 10, 15 e 20 %) containg platinum (Pt = 1%) were prepared by the polymeric precursor method. For comparison, catalysts the tungsten base was also prepared by the impregnation method. After calcinations at 600, 700 and 800 ºC, the catalysts were characterized by X-ray diffraction, fourier-transform infrared spectroscopy, thermogravimetric and differential thermal analysis, nitrogen adsorption and scanning electron microscopy. The profile of metals reduction was determined by temperature programmed reduction. The synthesized catalysts were tested in n-heptane isomerization. X-ray diffractogram of the Pt/WOx-ZrO2 and Pt/MoOx-ZrO2 catalysts revealed the presence of tetragonal ZrO2 and platinum metallic phases in all calcined samples. Diffraction peaks due WO3 and ZrO2 monoclinic also were observed in some samples of the Pt/WOx-ZrO2 catalysts. In the Pt/MoOx-ZrO2 catalysts also were observed diffraction peaks due ZrO2 monoclinic and Zr(MoO4)2 oxide. These phases contained on Pt/WOx-ZrO2 and Pt/MoOx-ZrO2 catalysts varied in accordance with the W or Mo loading and in accordance with the calcination temperature. The infrared spectra showed absorption bands due O-W-O and W=O bonds in the Pt/WOx-ZrO2 catalysts and due O-Mo-O...

Adsorption of normal pentane on the surface of rutile. Experimental results and simulations

Prates Ramalho, João Paulo; Palace Carvalho, Alfredo
Fonte: Universidade de Évora Publicador: Universidade de Évora
Tipo: Artigo de Revista Científica Formato: 509715 bytes; application/pdf
ENG
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Adsorption isotherms and differential heats of normal pentane adsorption on microcrystalline rutile were measured at 303 K. The heat of adsorption of n-pentane on rutile at zero occupancy is 64 kJ/mol. The differential heats have three descending segments, corresponding to the adsorption of n-pentane on three types of surfaces. At low coverage (first segment), the adsorption is restricted to the rows A of the (110) faces along the 5-fold coordinatively unsaturated (cus) Ti4+ ions with differential heat showing a linear decrease with increasing occupancy. The second segment is attributed to bonding with atoms of the rows along the remaining faces exposed, (101) and (100). The third segment is related to a multilayer adsorption. The mean molar adsorption entropy of n-pentane is ca. -25 J/mol K less than the entropy of the bulk liquid, thus revealing a hindered state of motion of the n-pentane molecules on the surface of rutile. Simulations of the adsorption of n-pentane on the three most abundant crystallographic faces of rutile were also performed. The adsorption isotherm obtained from the combination of each face's isotherm weighted by the respective abundance was found to be in a good agreement with the experimental data. A structural characterization of n-pentane near the surface was also conducted...