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Fusel oil is a by-product from the fermentation of sugar to produce ethanol. With the increase in ethanol production in the last years, thousands of liters of fusel oil are also generated. Thus, alternatives for reusing fusel oil involving the transformation of isopentanol, its main constituent, into products relevant to industry have aroused interest. In this work, the use of MFI zeolites with different contents of aluminum in the transformation of isopentyl into its ester, isopentyl acetate, was studied. Its main objective was to investigate the effects of the aluminum content of zeolites on textural and chemical properties and how they influence the catalytic activity. In the work it was verified that the catalysts with larger external surface obtained better catalytic performance, suggesting that, due to the small pore diameter of the MFI structure, the reaction is limited by the effects of internal diffusion and occurs mainly at the external surface of the MFI particles.

Zeolitic imidazolate frameworks (ZIFs) containing Zn(II) cations and 2-methylimidazolate anions were synthesized at high yield in aqueous medium. Triethylamine was used as an agent for deprotonation of the organic ligand, enabling rapid formation of the microporous structure known as ZIF-8. In the absence of the deprotonator, the material formed was ZIF-L, which has a lamellar structure. The ZIFs were characterized by X-ray diffraction, CO2 and N2 physisorption, chloroform chemisorption, and scanning electron microscopy. The different amounts of triethylamine influenced not only ZIF structure, but also material characteristics as particle size and external area. The ZIFs were then evaluated as catalysts in the Knoevenagel condensation reaction, different catalytic performances were obtained depending on the amount of deprotonation agent used. The activation energy of ZIF-8 was estimated considering an irreversible pseudo-homogeneous first-order reaction, and was shown to be highly catalytically stable during consecutive reuses.

The MCM-41 silica possesses a structure characterized by a hexagonal mesoporous organization with a unidimensional system of pores. This as-synthesized silica contains cations (usually C16TA+) in the pores and catalytic sites that are basic due to the presence of the siloxy ions ( SiO−) associated with the cations. This work investigates the effects of the use of cationic alkyltrimethylammonium bromide surfactants (CnTABr, where n = 10, 12, 14, or 16) on the catalytic properties of silicas containing these occluded cations. The hybrid silicas were synthesized at a temperature of 30 °C, using a synthesis time of 2 h, and were subsequently characterized by X-ray diffractometry, thermogravimetry, and scanning electron microscopy. The basicity of the siloxy sites modified by the cations used in the synthesis of the hybrid silicas was evaluated using X-ray photoelectron spectroscopy. The results obtained using a model monoester transesterification catalytic reaction showed that the TOF0 value increased with the size of the hydrophobic tail of the surfactant and was highest for the catalyst prepared with C16TABr. In addition, the hybrid silicas presented increased relative intensity (RI%) and smaller particle size.

This work describes the synthesis of silicas containing cetyltrialkylammonium and alkyltripropylammonium (CnPr3Br, n = 14–22) surfactants in their mesopores. The aqueous dispersions of these surfactants were characterized by small-angle X-ray scattering (SAXS). The hybrid silicas synthesized from the dispersions were evaluated by X-ray diffractometry (XRD), thermogravimetric analysis, nitrogen physisorption, transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), as well as in terms of their catalytic properties. The mesoporous silicas synthesized using cetyltrialkylammonium surfactants showed increases in pore diameter and decreases in structural order as the head group of the surfactant became larger. An increase of the alkyltripropylammonium tail also resulted in silicas with larger pore diameters, but with better structural order. The mesoporous silica with the largest pore diameter (3.60 nm), which was synthesized with C22Pr3Br surfactant, exhibited a narrower pore diameter distribution and a hexagonal organization characteristic of MCM-41 silica. The catalytic properties of the hybrid silicas synthesized using the cetyltrialkylammonium surfactants were evaluated in the transesterification reaction, in which the silica containing C16Et3+ cations showed the highest catalytic performance.

Made available in DSpace on 2020-12-12T01:14:44Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-30 Lately, to considerably reduce the diffusion constraints in the catalysis performed by zeolites, there has been significant interest in syntheses of partially formed zeolites with extremely accessible active sites, named embryonic zeolites. Their preparation relies on stopping the crystallization of conventional micron-sized zeolites before the zeolites reach full-crystallization, as detected by X-ray diffraction. In this current study, ZSM-5 zeolites were synthesized by using the same starting batch without an organic template and different times, obtaining amorphous, ill-crystallized, and fully grown structures that were characterized by various physicochemical methods and used in two catalytic test reactions. Using this synthesis strategy, two significant features of zeolites in catalysis are highlighted: (1) the accessibility of their inner pores for reactants and (2) the confinement effect, that is, the ability of zeolites to stabilize transition states in some catalytic reactions. As the ZSM-5 was being formed, it had a decreased activity for glycerol condensation with acetone, indicating steric restrictions to the bulky product that has a kinetic diameter (0.63 nm) considerably higher than the zeolite micropores (0.51 × 0.54 nm). On the other hand, the catalytic activity for methanol dehydration to dimethyl ether was proportional to crystallinity, as dimethyl ether intermediates adsorb within the zeolite cavities that tend to reciprocally enhance interactions giving an optimal effect in the catalytic property. Institute of Chemistry Universidade Estadual Paulista (Unesp), R. Prof. Francisco Degni 55 Chemical Engineering Department Universidade Federal de São Carlos (UFSCar), Rod. Washington Luis Km 235 School of Chemical and Biomolecular Engineering Georgia Institute of Technology, 311 Ferst Drive NW Institute of Chemistry Universidade Estadual Paulista (Unesp), R. Prof. Francisco Degni 55

The low stability of Si-MCM-41 limits its usage in the presence of water. The loss of structural order is mainly due to H2O physisorption and hydrolysis of the ≡Si-O-Si≡ bonds. In this work, it was demonstrated that water molecules could cause destruction of the pore walls. X-ray diffraction experiments revealed the effect of physisorbed water on the intensity of the diffraction peaks. In addition, partial regeneration of the hydrated samples was observed after thermal treatment. Evaluation was made of the structural stability of mesoporous silicas (Si-MCM-41) synthesized at different temperatures (30, 60, and 90 °C), as a function of time, when placed in a controlled humidity atmosphere. The materials were characterized by X-ray diffraction, which confirmed formation of the hexagonal phase at all the temperatures used. Furthermore, loss of long-range structural organization was observed when the calcined mesoporous silicas were conditioned in humid environments. In situ investigation was made of the thermal treatment of the hydrated silicas, with thermogravimetric quantification of silanols after the hydration and heating process. Transmission electron microscopy analysis revealed partial loss and/or reduction of the walls of some pores, caused by hydrolysis of the siloxane bonds (≡Si-O-Si≡). This resulted in decrease of the mean diameter of the pores that were resistant to wall degradation. X-ray diffraction analyses, as a function of temperature, showed that there was recovery of peak intensity and a shift of the diffraction peaks towards greater angles, as the duration of exposure to the heating increased, evidencing a decrease in the interplanar spacing.

The heterogeneous catalysts used to produce biodiesel include the important group of hybrid silicas that possess basic siloxy sites (≡SiO−). The basicity of these sites varies according to the size of the charge-compensation cation. In this work, hybrid silicas were synthesized in the presence of different cationic surfactants: cetyltrimethylammonium bromide (CTABr), cetylallyldimethylammonium bromide (CADMABr), and cetylpyridinium bromide (CPyBr), in order to determine their effects on the basicity of the silica produced. Characterization of the silicas showed that they presented different particle sizes and shapes, as well as differences in terms of the quantity and quality of the siloxy (≡SiO−) catalytic sites. Catalytic evaluation of the hybrid silicas employed the transesterification of a model monoester (ethyl acetate) and the transesterification of a vegetable oil (soybean oil), with both reactions conducted under mild conditions. The catalytic results for the model transesterification reaction showed the same features as those obtained with the vegetable oil, demonstrating that the use of a simple molecule was sufficient for preliminary evaluation of these catalysts.

Made available in DSpace on 2019-10-06T02:49:28Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-07-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) NaX and NaY faujasites (with Si/Al ratios of 1.3 and 2.5, respectively) were subjected to different degrees of ionic exchange with linear monoalkylammonium cations containing between 1 and 6 carbon atoms. The products were characterized using X-ray diffraction (XRD), nitrogen physisorption, X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The Knoevenagel condensation was used as a model reaction to characterize the activity and accessibility of the catalytic sites. Ionic exchange isotherms showed that only the sodium cations present in the supercavities were exchangeable for the alkylammonium ions. The XPS results showed that the monoalkylammonium cations increased the basicity of the sites of both faujasites, with the basicity increasing with the length of the carbon chain. The catalytic activity in the Knoevenagel condensation was governed by three factors: the degree of exchange, the aluminum content, and the water content of the zeolites. Univ Fed Sao Carlos, Chem Engn Dept, Sao Carlos, SP, Brazil Univ Estadual Paulista, Phys Inst, Araraquara, SP, Brazil Univ Fed Itajuba, Itajuba, MG, Brazil Univ Estadual Paulista, Phys Inst, Araraquara, SP, Brazil

Heterogeneous catalysis for biodiesel production is a current challenge due to the low activity of solid catalysts, especially caused by diffusional resistances. Hybrid silicas, containing SiO−CTA+ provide high conversions in the transesterification of oils and model molecules, but this activity is limited to the external surface area. The generation of surface roughness in the silica particles can increase the external area of the catalysts and expose the catalytic sites. Rough silicas containing cetyltrimethylammonium (CTA+) surfactant were prepared using different [CTABr]/[TEOS] molar ratios in a biphasic system formed by diethyl ether and water. The resulting solids were characterized by FTIR, O1s XPS, TG, SEM, and TEM. These materials were applied as basic catalysts in a model transesterification reaction representing the formation of biodiesel. Increasing the CTA+ content in the synthesis resulted in higher turnover frequencies, due to the smaller particle size and greater surface roughness of the material, which enhanced the accessibility of reagents to the basic siloxy sites.

Knoevenagel condensation is a C–C bond formation reaction widely used in fine chemistry, which can be catalyzed by bases, such as Na-zeolites and supported amines. Due to the high size of the molecules that are used, its application is highly influenced by the accessibility of the catalytic sites that promote the reaction. In this context, this work studied the effect of the crystallization time of aluminosilicate precursors of LTA zeolite on the propylamine anchoring capacity. The materials were compared in terms of the amount of grafted propylamine as well as the accessibility of the sites in the Knoevenagel condensation reaction. Functionalized solids prepared with shorter times in hydrothermal synthesis were more active in the reaction due to the greater propylamine anchoring capacity. Also, the amorphous precursors of LTA zeolite were more active, due to their greater accessibility of the catalytic sites before the microporous structure was formed.

There is increasing interest in the use of heterogeneous catalysts for the production of biodiesel. In contrast to homogeneous catalysts, these materials can be readily separated from the reaction system, avoiding contamination of the products and, in principle, they can be reused. These catalysts include the mesoporous hybrid molecular sieves of the M41S family, which offer these advantages when used as catalysts. The aim of the present work was to synthesize these silicas in the form of spheres, and evaluate their activities as heterogeneous catalyst in the transesterification reaction. The hybrid silicas were characterized by small angle X-ray scattering (SAXS), X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen physisorption and thermogravimetry. The results showed that the structure and morphology of the mesoporous silicas containing an organic template could be controlled by varying the alcohol content during the synthesis, leading to the formation of materials with different phases, levels of organization and morphologies. The catalytic activities of the silicas were evaluated using the transesterification reaction of monoalcohols as a model for application in biodiesel production. These spherical hybrid silicas showed a considerable higher initial catalytic rate than the silicas with irregular shape.

The CTA-MCM-41 silica hybrid contains basic sites due to the presence of siloxy anions ( SiO−) associated with CTA cations. A problem is that this material progressively loses its catalytic activity during successive reuse in transesterification reactions. The challenge of the present work was therefore to stabilize the catalytic activity of this silica hybrid by means of the encapsulation of polymers, using an initial emulsification step in the synthesis. Samples of monomers and polymers emulsified in colloidal solution were characterized using small angle X-ray scattering (SAXS), which confirmed their presence in the interior of the micelles. The solids were analyzed by X-ray diffraction, elemental analysis (CHN), infrared absorption spectroscopy, and thermogravimetry. The findings confirmed the presence of monomers and polymers in the channels of the CTA-MCM-41, and the polymers acted to increase the stability of these new materials during catalytic transesterification.

The synthesis route of MCM-41 was modified by using a cationic surfactant different from the usual CTMABr (cetyltrimethylammonium bromide). This surfactant, cetylallyldimethylammonium bromide (CADMABr), differs from CTMABr by the substitution of a methyl group located in the hydrophilic head by a polymerizable allyl group. The CADMABr surfactant and the CADMA-MCM-41 hybrid silica were synthesized using different times. Formation of the surfactant was confirmed using elemental analysis (CHN), 13C nuclear magnetic resonance (13C NMR), and small-angle X-ray scattering (SAXS) applied to the dispersions of different concentrations of the surfactants in water. The aqueous dispersions of CADMABr and the hybrid silicas were irradiated at different doses of gamma (γ) radiation in order to obtain information about the polymerization of the surfactant. The hybrid silicas were characterized using X-ray diffraction (XRD) for phase identification, together with thermogravimetry (TGA), nitrogen physisorption, and scanning electron microscopy (SEM). The catalytic properties of the silicas were evaluated using the transesterification reaction of monoalcohols as a model for application in biodiesel manufacture.

As-synthesized CTA–MCM-41 silica possesses basic siloxy ( SiO-) catalytic sites, enabling it to be used in reactions such as transesterification and Knoevenagel condensation. Its application in basic catalysis has shown promising results, but attempts to reuse it in more than one cycle has revealed rapid loss of activity due to the removal of cetyltrimethylammonium (CTA) cations from the interior of the channels. The present work describes the encapsulation of nanoparticulate methacrylic polymers during the conventional synthesis of MCM-41, resulting in hybrid silicas containing polymers in the interior of the inorganic and organic matrix. Aqueous dispersions containing surfactant and monomers were characterized by small-angle X-ray scattering (SAXS), which confirmed the expansion of the micelles due to the presence of the encapsulated monomers. Transmission electron microscopy (TEM) was used to observe the formation of polymer nanoparticles stabilized by the surfactant (cetyltrimethy lammonium bromide). Infrared absorption spectroscopy and chemical analysis showed that these particles were present in the material after the synthesis. Analysis of the silicas using SAXS and nitrogen physisorption showed the expansion of the channels of the CTA–MCM-41 and the formation of two mesopore systems in the silica. Catalytic evaluation demonstrated that the silicas synthesized in the presence of the emulsified polymers possessed better catalytic stability when low monomer contents and monomers with larger alkyl chains were used. The encapsulation of nanoparticles of methacrylic polymer in the interior of the CTA–MCM-41 channels helped to avoid leaching of the CTA cations during the reaction.

Preparation of ZSM-12 zeolite (MTW structure) functionalized with the organosilane surfactant [3-(trimethoxysilyl)propyl]octadecyldimethylammonium chloride (TPOAC) was performed in a single synthesis step employing hydrothermal crystallization. Investigation was made of the effects of Si/Al and TPOAC/SiO2 ratios on crystallinity, morphology, and catalytic activity. The MTW structure without the presence of TPOAC was obtained using Si/Al ratios ranging from 50 to 120, with values smaller than 50 favoring crystallization of the BEA phase, and values greater than 120 leading to the formation of cristobalite, a crystalline silica phase. For syntheses performed in the presence of TPOAC, an increase in its amount from 3 to 6 % enabled formation of the pure MTW structure, at all Si/Al ratios. The addition of TPOAC led to significant changes in the morphology and hydrophobicity of the zeolite particles. The effect of functionalization with TPOAC on the catalytic performance of the zeolites was evaluated using the Knoevenagel condensation between butyraldehyde and ethyl cyanoacetate as a model reaction. It was found that the presence of TPOAC in the ZSM-12 zeolite substantially increased the catalytic activity. Evaluation was also made of the type of solvent used in the reaction, and high activities were obtained in the presence of polar protic solvents.

The [CTA]-MCM-41 hybrid silica is a useful and simply prepared heterogeneous basic catalyst for the transesterification reaction. Here, the effect of hydrothermal treatment during catalyst preparation was investigated, with the aim of improving the structural stability of this catalyst during the reaction. It was observed that the hydrothermal step led to the formation of a material with a higher degree of organization and a greater wall thickness, which improved its structural stability. However, the catalyst prepared using this treatment presented lower catalytic activity, due to the presence of fewer active sites.

The principal aspects of the production of biodiesel using heterogeneous catalysis are presented, comparing this alternative process to conventional (homogeneous) processes and evaluating the main operational parameters. The most important techniques for the preparation and characterization of silicas with basic properties are mentioned, dividing these materials into two groups with distinct properties: as-synthesized silicas, especially the M41S family, with their pores occluded with organic cations, and functionalized silicas, with accessible pores. The catalytic properties of these silicas were evaluated in transesterifications using a model reaction and vegetable oil. Finally, a brief presentation is made of other solid catalysts with basic properties that can be used in the biodiesel production reaction.

The main objective of this work is contributing to the understanding of the ring opening of naphthenic model molecules, an important reaction to improve the cetane number of diesel fuels. Accordingly, the hydroconversion of decalin was studied over a series of Pt/Beta catalysts with different metal contents in order to evaluate the effect of changing the proportion of hydrogenation/acid functions of the catalyst on conversion and products distribution. The overall reaction rate did not change by increasing the hydrogenation activity (metal content) of the catalyst. However, ring contraction and ring opening product yields increased with metal content up to 1.0 wt% and then became constant for higher metal contents, while cracking product yields followed an opposite trend, decreasing with increasing metal content up to 1.0 wt%. This behavior clearly provides evidence of a bifunctional mechanism in the hydroconversion of decalin over Pt/BEA catalysts, since the selectivity depends on the metal/acid function balance. Although decalin is a saturated molecule, its naphthenic character and probably the presence of a tertiary carbon in its structure facilitate activation of the molecule directly on the strong acid sites of zeolite, even at relatively moderate temperatures. Thus, it is not necessary to form an olefin on a metal site, which would undergo subsequent protonation, as in a classical bifunctional mechanism, such as in hydroisomerization and hydrocracking of n-paraffins. However, the hydrogenation component of the catalyst influences the selectivity of the reaction, controlling the process of desorption/adsorption of any intermediate olefins formed. Greater hydrogenation activity implies lower availability of adsorbed carbocations that can be converted to cracking products. This proposition is consistent with the results obtained by varying the content of metal and poisoning of the hydrogenation sites in the catalysts.

The zeolite with BEA structure has been obtained using different Al amounts in the presence of tetraethylammonium as a structure directing agent. The effect of the Si/Al molar ratio on the crystal size, morphology, yield, chemical composition and catalytic properties was investigated. The materials have been characterized towards zeolitic properties by XRD, SEM, EDS, TGA, 29 Si MAS-NMR, XPS and TEM. The chemical composition of the crystals depends on the concentration of the initial reaction mixture and that a decrease in the Al content is associated with an increase in particle size. The characterization by TGA/DTA of as-synthesized zeolites with BEA structure showed that an increase of Si content resulted in the formation of [ Si O − ][TEA + ] species, this was supported by 29 Si MAS-NMR. The XPS results also showed that the chemical composition of the surface differed from that of the bulk material, this was supported by TEM/EDS results. The results of catalytic activity tests indicated that a fraction of the [ Si O − ][TEA + ] species was present on the external surfaces of the crystals, although the largest fraction appeared to be in the interior of the particles. As-synthesized BEA zeolite showed good catalytic activity and suggests that this material can be applied in other reactions involving basic sites.

Sodium titanate was synthesized by the sol–gel method and characterized using X-ray diffraction, thermogravimetry-mass spectrometry, atomic absorption spectroscopy, scanning electron microscopy, energy-dispersive X-ray analysis and nitrogen physisorption. The non-calcined material was active as a catalyst in transesterification reactions and showed high stability. An appreciable loss of activity on the fourth reuse was accompanied by the appearance of a new species of oxygen and segregated sodium, identified by X-ray photoelectron spectroscopy (XPS). The XPS spectrum showed that the basic nature of the framework oxygen was inferior to the original basicity, which explained the decline in catalytic activity.

This work presents the synthesis of a new type of MCM-41 material, based on the polymerization in microemulsion technique. This type of synthesis, which has not been previously reported, uses microemulsion as a means of inserting polymers into the interior of the CTA-MCM-41 channels. The main difference between the traditional synthesis and that described here is in the initial step, involving formation of emulsified polymers derived from the microemulsions. The monomers used in the synthesis were butyl acrylate, butyl methacrylate, and styrene. Samples of monomers and polymers emulsified in aqueous media were characterized by small-angle X-ray scattering (SAXS) and X-ray diffractometry (XRD) was used to determine the degree of organization of the solid samples. These techniques showed the presence of the monomers and polymers in the interior of the cetyltrimethylammonium (CTA) micelles; the shift of the peak corresponding to the (100) diffraction plane to smaller 2 θ angles showed that there was an increase in the diameter of the silica channels resulting from the insertion of the polymers. Infrared absorption spectroscopy and elemental analysis were also used to characterize the solids.

This paper compares the catalytic activity of Y zeolite containing alkylammonium cations in the Knoevenagel condensation. For steric reasons, the exchange of Na + for alkylammonium cations was restricted to the faujasite supercavity, and the degree of ion exchange decreased with the radius of the organic cation. The basicity of the catalysts was analyzed using X-ray photoelectron spectroscopy (XPS) and the Knoevenagel condensation reaction, with good correlation obtained between the results of the two methods. The best catalytic activity was observed for the Y zeolite exchanged using the butylammonium cation. The better performance of this catalyst was attributed to increased accessibility of the reactants to the catalytic sites.

The aim of this work was to evaluate the catalytic properties for n-hexane isomerization of bifunctional monometallic (Ni or Pt) and bimetallic catalysts (Pt-Ni), using HMOR zeolite as support. The method used for metal dispersion in the zeolite was competitive ion exchange using ammine complexes [Ni(NH3)6]Cl2 and [Pt(NH3)4]Cl2 as precursors. The catalysts were characterized by X-Ray diffraction, X-Ray energy dispersion spectroscopy, temperature-programmed reduction and transmission electron microscopy. The n-hexane isomerization reaction using the catalysts was carried out to evaluate the catalyst activity. The reaction was carried out in a fixed bed reactor operating at 250?C, 1 atm, H2/C6 = 9 molar ratio. The profiles obtained from TPR suggest that, for bimetallic catalysts, the presence of platinum facilitates the reduction of Ni2+ cations. The bimetallic catalysts presented a higher activity in the isomerization of n-hexane when compared to the monometallic ones, as well better stability as the Pt content in the solid increases.

The reduction of zeolite particle is one of the main features currently searched; it is due to the catalytic gains that these materials come in some reactions. In this work two faujasite zeolites of type X were evaluated, a micrometer and nanometric. Zeolites in sodium form were exchanged ionically with methylammonium cations. These materials were evaluated as catalysts in the Knoevenagel condensation reaction. Steric impediments restricted the ion exchange in the micrometer zeolite and have become more predominant due to the increase in the volume of cations. In nanometric sample such impediments were less evident due to the reduction of the particles provide greater accessibility to exchangers cations to inaccessible sodium in micrometer zeolite. The best catalytic performances were achieved with zeolites containing the monomethylammonium cation. The increased of the accessibility and diffusion of the reactants and products through the pores of the nanometric zeolite provided the best butyraldehyde conversions independent the exchanger cation

This work presents the synthesis of silicas containing cetyltrialkylammoniun surfactants in their mesopores. Initially, the aqueous dispersions of these surfactants were characterized by small-angle X-ray scattering (SAXS). The hybrid silicas obtained from these dispersions were evaluated by X-ray diffractometry (XRD) and nitrogen physisorption. The XRD showed that, increasing the head size, there is a shift of the peak corresponding to the (100) diffraction plane to smaller 2θ angles, which indicates an increase in the silicas porous diameter. The increasing of the silicas porous diameter was confirmed by nitrogen physisorption. The base catalytic properties of these hybrid silicas were evaluated in the transesterification reaction showing that those containing the cations C16Et3+ and C16Pr3+ showed better performance.

The interest in synthesizing zeolites with crystals in the nanometric size range has increased greatly in recent years; however most of the works depend on using organic structure directing agents. In this work nanosized crystals of zeolite faujasite were successfully synthesized without the use of organics. Among the synthesis parameters studied, the increased alkalinity of the synthesis gel was found to be the one that caused a decrease in the final particle size. The high alkalinity coupled with an aging step proved to be very effective in affording faujasite nanocrystals with high microporosity and external area. Thus it is possible to obtain nanocrystals of this zeolite using environmentally more friendly procedures, since they avoid the use of organic structure directing agents and their subsequent calcination.

This paper describes the properties of new X zeolite catalysts, whose anions are compensated by different methylammonium cations. The properties of these catalysts, with varying degrees of exchange, are compared with those of Y zeolites containing the same cations. For steric reasons, cation exchange was restricted to the faujasite supercavity, and the degree of ion exchange decreased with the radius of the organic cation. The basicity of the catalysts was analyzed using X-ray photoelectron spectroscopy (XPS) and the Knoevenagel condensation reaction, with good correlation obtained between the results of the two methods. The best catalytic activity was observed for the faujasite with the highest aluminum content (X zeolite), exchanged using the monomethylammonium cation. The better performance of this catalyst was attributed to its basicity, as well as the available micropore volume.

An additive group contribution method extended from the Joback and Reid method for the liquid phase was developed in order to predict enthalpies of formation and absolute entropies in the standard state. The method uses the alkanes as reference chemical substances. In the case of enthalpy of formation, the methodology was tested for 50 chemicals related to the formation reactions of biodiesel and for absolute entropy it was tested for 15 compounds. The results were compared with data from the literature. The relative deviations found in the enthalpy estimates were lower than 6% and in the predicted entropy they were lower than 3%. The method was accurate to estimate the properties for triacylglycerides, such as glycerol triacetate and glycerol trioleate (triolein). Additionally, to develop the method, two equations were derived and used to supplement gaps found in the literature regarding the absolute entropies of the gaseous and liquid phase, both in its standard state. The contribution of this work is the development of a method using the group contributions to estimate the thermodynamic properties of reactions in the liquid phase, important to the formation of biodiesel.

The zeolite Beta used in this work consists of nanosized crystallites (20-30 nm) aggregates, determined by HRTEM analysis. The influence of the zeolite structure and crystallite size on the desorption rates of linear paraffins was determined by ZLC chromatography. Desorption from Beta zeolite was faster than from USY zeolite. IR acidity analysis by adsorption and desorption of pyridine showed that Beta zeolite has a smaller number of Brønsted acid sites than USY zeolite, but that they are a little stronger. Pt-Ni/H-BEA catalysts showed higher activity than Pt-Ni/H-USY ones. This behavior can be attributed to the very small crystallites of Beta zeolite, which enable faster diffusion of the reactant and products molecules. Among bimetallic catalysts, the highest activity was observed with that containing 60% Pt. This result is very interesting in view of the cost reduction, relative to 100% Pt catalyst. Fil: Lima, Patrícia M.. Universidade do Brasília; Brasil Fil: Garetto, Teresita Francisca. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentina Fil: Cavalcante Jr., Célio L.. Universidade Estadual do Ceará; Brasil Fil: Cardoso, Dilson. Universidade Federal do São Carlos; Brasil

MgAl hydrotalcite was synthesized and used as support for Li impregnation. MgAlLi oxides were obtained from heat treatment of the Li/MgAl hydrotalcite. These materials were characterized and evaluated as catalysts for model transesterification reactions. MgAl showed negligible activity under mild reaction conditions (50 °C and 0.5 h) whereas Li incorporation greatly increased the activity. The activities were correlated to their basicity determined by TPD of CO2. Reuse tests showed catalyst deactivation after the third cycle, probably due to lithium leaching. However, the contribution to a homogeneous reaction has been dismissed. MgAlLi revealed to be a promising catalysts for transesterification reaction and thus for biodiesel production.

Bimodal porous alumina catalysts with both continuous macropores and mesopores were prepared using a dual soft template method. The addition of decahydronaphthalene as emulsifier agent successfully contributed to the formation of macropores. The effectiveness of macropore insertion was evaluated in the model reaction of ethanol dehydration at 300 °C. Judging from the results obtained by acidity measurements using temperature programmed desorption of ammonia and the performance of these catalysts in the ethanol dehydration, the introduction of macropores in the catalyst structure enhanced the ethanol conversion. Fil: Martins, Leandro. Unesp-universidade Estadual Paulista; Fil: Cardoso, Dilson. Universidade Federal do São Carlos; Brasil Fil: Hammer, Peter. Unesp-universidade Estadual Paulista; Fil: Garetto, Teresita Francisca. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentina Fil: Pulcinelli, Sandra H.. Unesp-universidade Estadual Paulista; Fil: Santilli, Celso V.. Unesp-universidade Estadual Paulista

Current specifications for gasoline impose strong restrictions on the content of aromatic compounds. Isomerization of normal paraffins to isoparaffins is considered an important petroleum reaction for the production of clean gasoline to improve its Research Octane Number (RON) and Motor Octane Number (MON). The isoparaffins are considered as an alternative to the use of oxygenated and aromatic compounds, whose maximum contents are subjected to strict regulations in order to protect the environment. In this work, catalysts supported on mordenite were obtained by competitive ion exchange using aqueous solutions of platinum complexes. Different concentrations of platinum were tested for the isomerization of n-hexane. All the catalysts obtained were shown to be selective to the formation of isomers with high-octane number, which are the products of greatest interest in the oil refining industry. The highest conversion and the best selectivity for 2,3- dmC4 di-branched component, the isomer with the highest octane number, were found with the 1.10 wt% Pt/HMOR.

The catalytic activity, epoxide selectivity and hydrogen peroxide conversion and efficiency using [Ti, Al]-beta catalysts with different Ti and Al contents have been evaluated in the epoxidation of cyclohexene at 70 °C with hydrogen peroxide and acetonitrile as the oxidant and the solvent, respectively. The catalysts tested were obtained by two methods: (1) varying the alkalinity in the initial gel (Method I), and (2) substituting part of the template agent with equivalent quantities of fluoride ions in the mother gel (Method II). Characterizations were used to examine the chemical composition, crystallinity, framework Ti and Bronsted acidity in the catalysts. The catalysts crystallized by Method II hold both less Ti and Al and showed better performances in the cyclohexene epoxidation. Catalysts obtained from more alkaline gels and crystallized for shorter times by Method I contained less Ti but more Al. These catalysts showed both lower epoxide selectivity and hydrogen peroxide efficiency. For catalysts with similar Al, but different Ti contents, those richer in Ti showed higher activity and epoxide selectivity. Catalysts with both higher Ti (Si/Ti: 50–60) and Al (Si/Al: 36–56) contents, obtained from more alkaline gels for more prolonged crystallization times by Method I showed the lowest activities, epoxide selectivities and peroxide efficiencies. The dramatic influence of the Al and Ti contents in catalysts on the epoxide yields and peroxide efficiencies were explained through the intrinsic properties of the Ti-hydroperoxo complex formed, responsible for the oxygen transfer to olefin on Ti centers having different Lewis acid strengths.