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The nature of new zeolite overgrowth has been characterized. Two overgrown samples were studied. Each sample was made up of the phases faujasite and EMT. By Rietveld refine- ment of the powder patterns the structure of both phase...
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The nature of new zeolite overgrowth has been characterized. Two overgrown samples were studied. Each sample was made up of the phases faujasite and EMT. By Rietveld refine- ment of the powder patterns the structure of both phases including the distribution of cations in the overgrowth was determined as well as the weight fractions of the phases in both samples. The growth of FAU crystals on the surface of EMT crystals is epitactic, as show by HRSEM Images.
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LAB (Linear Alkyl Benzene) isomers were obtained by the alkylat on of benzene with 1-dodecene over FAU, BEA and EMT zeolites in the presence of decane as solvent. The initial activities were compared by fitting the kinetics early ...
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LAB (Linear Alkyl Benzene) isomers were obtained by the alkylat on of benzene with 1-dodecene over FAU, BEA and EMT zeolites in the presence of decane as solvent. The initial activities were compared by fitting the kinetics early data with a pseudo first order law in dodecene. These were in agreement with those determined from the slope of the conversion versus time curve at zero conversion. The activity and stability were discussed in terms of he residual Na~+ content, Si/Al ratio and porous structure of the catalysts. The selectivity to the most desired 2-phenyl dedecane isomer was found to increase with increased porous catalysts. Yields in the preferred isomer over BEA catalysts were very close to those provided by the FAU open structure catalysts in spite of a much lower conversion over BEA catalysts. Deactivation affected not only the alkylation reaction, but the isomerisation of the olefin as well, over BEA catalysts.
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El present treball documenta la primera observació de l’espècie Fulvia fragilis (Forssk?l in Niebuhr, 1775), originària de l’oceà índic, a la costa de Benicarló (el Baix Maestrat). La troballa es produeix dins del projecte...
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El present treball documenta la primera observació de l’espècie Fulvia fragilis (Forssk?l in Niebuhr, 1775), originària de l’oceà índic, a la costa de Benicarló (el Baix Maestrat). La troballa es produeix dins del projecte de censar sistemàticament les tanatocenosis de les platges per assolir un coneixement de la biodiversitat de mol·luscs presents en les aigües del litoral maestratenc i comen?ar a bastir sèries temporals per intentar avaluar les variacions en la fauna, en un moment en què la influència antròpica és tan important. S’ha recollit només un exemplar a la platja del Barranc de Polpís, amb un cens d’una hora d’esfor?. El treball constata que ja ha arribat a Benicarló una espècie lessepsiana. La qual cosa, en primer lloc, indica que s’està naturalitzant també al litoral del Maestrat potser a partir d’un nucli d’una població ja aclimatada al delta de l’Ebre. En segon lloc, referma la convicció que aquesta espècie està colonitzant la Mediterrània occidental (més freda) i que no es queda arraconada a la mar de Llevant (més càlida). és un dada, incipient, que podria estar apuntant cap al que alguns autors ha qualificat de tropicalització de la Mediterrània. Hipòtesi molt provisional que caldrà avaluar amb moltes més dades.
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The adsorption of triethyl phosphate on FAU type zeolite has been investigated by using FT-IR spectroscopy. Zeolites are a large and diverse class of volcanic aluminosilicate crystalline materials which have many useful applicatio...
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The adsorption of triethyl phosphate on FAU type zeolite has been investigated by using FT-IR spectroscopy. Zeolites are a large and diverse class of volcanic aluminosilicate crystalline materials which have many useful applications. They are used in oil cracking, adsorption Of nuclear waste as well as production of controlled-release fertilizers for agriculture, adsorption of ammonia and other odour-volatiles, as cation absorbers in household detergents, as molecular sieves and for many other uses. Zeolites, which are known by their porous structure, are used widely to remove pollutants from nature. In this point of view, zeolites are special type of mineral which is playing an increasing role to solve environmental problems. In this study, we used NaY and NaX zeolites as adsorbents. After adsorption process, characteristic wavenumbers of triethyl phosphate had been observed by FT-IR spectroscopy. Addition to that, elemental analysis results had been supported that adsorption occurred on zeolite surface.
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Introduction: Knowledge of vector insect species, their habitat, and geographical distribution is crucial for determining the risk of transmission of the etiological agents that cause disease in humans, which allows defining strat...
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Introduction: Knowledge of vector insect species, their habitat, and geographical distribution is crucial for determining the risk of transmission of the etiological agents that cause disease in humans, which allows defining strategies for prevention, surveillance, and control in line with the characteristics of each area.
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Topology reconstruction from FAU to MWW structure has been explored in the presence of hexamethyleneimine, NaOH and SiO2. The samples prepared at different crystallization stages were characterized by XRD, SEM, TEM, and Si-29/Al-2...
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Topology reconstruction from FAU to MWW structure has been explored in the presence of hexamethyleneimine, NaOH and SiO2. The samples prepared at different crystallization stages were characterized by XRD, SEM, TEM, and Si-29/Al-27/C-13 MAS NMR to investigate the intermediates in the topology reconstruction from FAU to MWW structure. It has been demonstrated for the first time that topology reconstruction from FAU to MWW structure was caused by the "synergism" of hexamethyleneimine, NaOH, and SiO2, which was supported by transformation from FAU to SOD structure without SiO2 and the preservation of FAU structure without NaOH. It is also clearly proved that FAU structure was directly reconstructed into MWW structure by the combination of all above mentioned characterizations, especially XRD and Si-29/Al-27 MAS NMR. MWW structure zeolite was generated at the consumption of FAU structure zeolite, which is worthy to be noticed that solid silica gel was completely consumed at the end of topology reconstruction. As shown in SEM and TEM images, MWW structure zeolite was reconstructed gradually from exterior to interior of FAU structure zeolite, which was clearly observed by the FAU MWW co-existing zeolites as intermediate states. The reconstructed MWW structure zeolite has high relative crystallinity. (C) 2014 Elsevier Inc. All rights reserved.
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FAU-type zeolite was prepared using Irish shale rock and tested as a catalyst in the liquid-phase esterification of oleic acid (a model test reaction for biodiesel production). A systematic study was conducted (over the stated pre...
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FAU-type zeolite was prepared using Irish shale rock and tested as a catalyst in the liquid-phase esterification of oleic acid (a model test reaction for biodiesel production). A systematic study was conducted (over the stated preparation ranges) by varying the water: shale ratio (4: 1-15: 1 by mass), and mixing (1-24 h), aging (6-48 h) and hydrothermal treatment times (6-72 h) to determine the optimal parameters. XRD confirmed that the product purity was highly dependent on the experimental conditions used. The BET surface area of the calcined FAU-type zeolite was 571 m(2) g(-1) and its crystal purity was comparable to that of a commercial zeolite Y. The prepared zeolite was catalytically active in the esterification of oleic acid with ethanol reaching a maximum of 78% conversion after 90 mins, which is practically identical to that recorded for commercial zeolite Y. (C) 2017 Elsevier Ltd. All rights reserved.
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By using the thermally induced phase transformation initial zeolites were converted into pure carnegieite, stuffed derivative of cristobalite. The polymorphs obtained from Na-LTA are stoichiometric (NaAlSiO_4), since those obtaine...
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By using the thermally induced phase transformation initial zeolites were converted into pure carnegieite, stuffed derivative of cristobalite. The polymorphs obtained from Na-LTA are stoichiometric (NaAlSiO_4), since those obtained from Na-FAU zeolite are non-stoichiometric carnegieite crystallize in cubic and orthorhombic forms. ~(29)Si MAS NMR spectra show a very large but expecting difference between stoichiometric and non-stoichiometric carnegieite. The spectrum of stoichiometric carnegieite has only one peak Si(4Al), while the spectrum of non-stoichiometric carnegieite consist few superimposed peaks assigned to Si(4Al), while the spectrum of non-stoichiometric carnegieite consist few superimposed peaks assigned to Si(4Al), Si(3Al), Si(3Al), Si(2Al), Si(1Al) and Si(0Al). DTA study indicates the occurrence of displactive phase transition of all synthesized carnegieite. The transition temperature is depending on silicon aluminum order: T_m = 690 ℃ for stoichiometric, T_m = 565 and 660 ℃ for non-stoichiometric, low-temperature and high-temperature carnegieite, respectively.
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Maximizing the production of petrochemicals from crude oil at the expense of fuels is among the most important targets for refiners. In this conversion, catalyst composition and formulation play a key role. Here we present a thoro...
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Maximizing the production of petrochemicals from crude oil at the expense of fuels is among the most important targets for refiners. In this conversion, catalyst composition and formulation play a key role. Here we present a thorough study of the effect of formulated FCC catalyst composition on the one-step cracking of Arabian light crude oil. Our results demonstrate that over a 35 wt. % yield to light olefins can be achieved on spray-dried catalysts containing 1 : 1 mixtures of ZSM-5 and FAU zeolites (alongside binder and clay). Coke deposition and catalyst deactivation can be correlated to the nature and content of each zeolite component.
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Eight initially clear solutions(with a general formula based on molar ratios of the components,xNaOH:(5.86 - x)TMAOH:1.0-Al_2O_3:3.40SiO_2:370H_2O:19.6EtOH:6.0iso-PrOH,x = 0.06-0.86)with various sodium concentrations were prepared...
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Eight initially clear solutions(with a general formula based on molar ratios of the components,xNaOH:(5.86 - x)TMAOH:1.0-Al_2O_3:3.40SiO_2:370H_2O:19.6EtOH:6.0iso-PrOH,x = 0.06-0.86)with various sodium concentrations were prepared for synthesis of FAU/LTA zeolites at 98.0 deg C.The synthesis process was studied using in situ calorimetry and the solid products were characterized using XRD,SEM and TG-DSC.At low sodium concentration(x = 0.06),the product is nearly pure FAU while with increasing x from 0.06 to 0.86,LTA gradually becomes dominant.In addition,the sodium concentration has a strong influence on crystal size but limited influence on the chemical composition of the resulting zeolite(s).At x = 0.86,the conversion yields of both silica and alumina are about 50%.When x decreases from 0.86 to 0.06,both conversion yields rapidly decrease to only about 4%.In contrast,the conversion yield of sodium remains at a much higher level(75-100%).There appears to be a maximum crystallization rate at x = 0.16-0.26.Crystallization of both FAU and LTA zeolites is exothermic and the crystallization enthalpy for FAU is higher in magnitude than for LTA.
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