Search

Catalytic distillation is a technology that combines a heterogeneous catalytic reaction and the separation of reactants and products via distillation in a single reactor/distillation system. This process combines catalysis, kinetics, and mass transfer to obtain more selective products. The heterogeneous catalyst provides the sites for catalytic reactions and the porous surface for liquid/vapor separation. The advantages of catalytic distillation are energy savings, low waste streams, catalyst longevity, higher conversion, and product selectivity; these properties are interesting for petrochemical and petroleum industries. For this study, 100 mL of atmospheric residue of petroleum (ATR) was distilled in the presence of 1.0 g of a micro/mesoporous catalyst composed of a HY-MCM-41, and the reactor used was an OptiDist automatic distillation device, operating according to ASTM D-86 methodology. The products were collected and analyzed by gas chromatography. The samples of ATR, HY/ATR, and HY-MCM-41/ATR were analyzed by thermogravimetry (TG) to determine the activation energies (Ea) relative to the thermal decomposition of the process, using the Ozawa–Flynn–Wall (OFW) kinetic model. The obtained results show a potential catalytic distillation system for use in the reaction of heavy petroleum fractions and product separation from the HY/MCM-41 micro/mesoporous catalyst. The TG data revealed two mass loss events for ATR in the ranges of 100–390 and 390–590 °C, corresponding to volatilization and thermal cracking, respectively. The Ea determined for the thermal degradation of the ATR without a catalyst was in the range of 83–194 kJ/mol, whereas in the presence of the HY-MCM-41 catalyst, it decreased to 61–105 kJ/mol, evidencing the catalytic effect of the micro-mesoporous material. The chromatography analysis allowed for the identification of gasoline and a major production of diesel and gasoil when the HY-MCM-41 mixture was used as the catalyst, evidencing the synergism of the combined effect of the acid sites, the crystalline phase, and the microporosity of the HY zeolite with the accessibility of the hexagonal mesoporous structure of the MCM-41 material. [ABSTRACT FROM AUTHOR]

The nanostructured lanthanide-silica materials of the Ln–SiO2 type (Ln = La, Ce, Pr, Nd, Eu, Gd, Dy, Yb, Lu) were synthesized by the hydrothermal method at 100 °C, using cetyltrimethylammonium as a structural template, silica gel and sodium silicate as a source of silicon, and lanthanide oxides, with Si/Ln molar ratio = 50. The resulting materials were calcined at 500 °C using nitrogen and air, and characterized by X-ray diffraction (XRD), Fourier-Transform infrared absorption spectroscopy, scanning electron microscopy, thermogravimetry (TG), surface area by the BET method and acidity measurements by n-butylamine adsorption. The XRD and chemical analysis indicated that the SiO2 presented a hexagonal structure and the incorporation of lanthanides in the structure changes the properties of the Ln–SiO2 materials. The heavier the lanthanide element, the higher the Si/Ln ratio. The TG curves showed that the decomposition of the structural template occurs in the materials at temperatures below 500 °C. The samples showed variations in specific surface area, mean pore diameter and silica wall thickness, depending on the nature of the lanthanide. The incorporation of different lanthanides in the silica generated acid sites of varied strength. The hydrothermal stability of the Ln–SiO2 materials evaluated at high temperatures, evidenced that the properties can be controlled for application in adsorption and catalysis processes. [ABSTRACT FROM AUTHOR]

The hydrothermal synthesis of aluminophosphate molecular sieve type AlPO4-11 was processed from chemicals containing psueudobohemite, 85% phosphoric acid, water, and di-isopropylamine as templating agent. The crystallization of the samples was studied by taking samples in times from 2 to 74 h. The obtained white powder products were characterized by X-ray diffraction patterns (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetry (TG) and differential scanning calorimetry (DTG) data and pH measurement of the mother liquor. The pore volume, as determined from TG and DTG curves, was ca. 0.17 cm3g−1. The percent relative crystallinity was determined by XRD and FT-IR methods. The crystallization kinetics evidenced that the hydrothermal synthesis of AlPO4-11 exhibited in its initial phase a behavior of first order reaction with a specific velocity constant of ca. 0.25 h−1, as determined from XRD and FT-IR data. The results obtained by both X-ray diffraction and infrared spectroscopy are comparable, and FT-IR is found to be a rapid method for estimating crystallinity and structure of aluminophosphate. [ABSTRACT FROM AUTHOR]

The preparation, characterization and application of materials based on montmorillonite natural clay containing aluminum polyhydroxocomplexes of Keggin type ions (Al13) as intercalating agent and hydrated lanthanum complexes were carried out. The introduction of Al and La inside the interlayer space increased the basal distance d(001) of the clay. The evaluated materials, designed as Natural Montmorillonite Clay (NMC), Al13-PILC and LaAl13-PILC were characterized by X-ray diffraction for evaluating the basal spacing of the clay, nitrogen adsorption for determination of the specific surface area and pore size of the materials and scanning electron microscopy, in order to observe the morphology. The catalytic activity was verified on the pyrolysis of Atmospheric Residue of petroleum (ATR), at temperature of 500 °C, in a micro-reactor coupled to gas chromatograph and mass spectrometry. The results showed that LaAl13-PILC material presented high catalytic activity for this process. The lanthanum preferably fills the interlayer space of the Al13-PILC, generating acid sites and therefore increasing the activity for ATR cracking. The obtained products were hydrocarbons in the range of light gases (C2-C4), gasoline (C5-C10) and diesel (C11-C20). This result is due the combination of porosity and acid properties of the PILC samples. [ABSTRACT FROM AUTHOR]

The catalysts analysed in the current work are variations of MCM-41. The properties of these highly ordered mesoporous aluminosilicates were adjusted by an isomorphous substitution of Si by a trivalent cation, in this case Al3+, generating catalysts of the AlMCM-41 type. The materials were synthesized with a silicon/aluminium ratio of 40, through two methods of impregnation of the metal: conventional and post-synthesis alumination. With the aim of determining the density of the acid sites of the Al40MCM-41 prepared by post-synthesis and conventional alumination, studies of the adsorption of n-butylamine probe molecule were carried out. Further, the studied material was characterized by thermogravimetry measurements, providing the profile of decomposition of the samples, which allowed calculation of the densities of the acid sites. The model-free kinetic algorithms were applied in order to determinate conversion and apparent activation energy. Comparison of energy-dispersive X-ray fluorescence and X-ray photoelectron spectroscopy measurements indicated that the post-synthesis method was more favourable based on the metal positioning, 'anchored' in the surface of the catalyst. The textural properties of the calcined Al40MCM-41 prepared by post-synthesis and conventional alumination were characterized by X-ray diffraction, N2 isothermal adsorption measurements (Brunauer -- Emmett -- Teller and Barrett -- Joyner -- Halenda), transmission electron microscopy, and X-ray photoelectron spectroscopy. [ABSTRACT FROM AUTHOR]

AlMCM-41 molecular sieves were synthesized starting from a hydrogel with the following molar composition—4.58 SiO2:0.0485 Na2O:1 CTMABr:0.038 Al2O3:200 H2O. Cethyltrimethylammonium bromide (CTMABr) was used as structure template. The obtained materials were characterized by XRD, FT-IR and TG/DTG. The model-free kinetic algorithms were applied in order to determinate conversion, isoconversion and apparent activation energy to decomposition of the CTMA+ species from the AlMCM-41 materials. [Copyright &y& Elsevier]

Diesel fuel mixtures with high concentrations of biodiesel have been investigated to analyze the technical feasibility of their use in diesel cycle engines regarding thermal and oxidative properties. The results of combined techniques of oxidative stability, high Pressurized Differential Scanning Calorimetry (P-DSC), Calculated Cetane Index (CCI), and calorific power were used to verify the effect of the thermal-oxidative stability as a function of the percentage of biodiesel in the mixtures. The obtained results evidenced that the thermal and oxidative stability decreased with the addition of biodiesel from 50 to 5% v/v. Low stability fuels require rapid use as the oxidation compounds degrade the product and impair vehicle performance, as well as lead to corrosion and clogging problems in various mechanical systems. [ABSTRACT FROM AUTHOR]

The article offers information on the 14th International Congress on Thermal Analysis and Calorimetry and VI Congresso Brasileiro de Análise Tármica e Calorimetria which will be held in São Pedro, Brazil on September 14-18, 2008.

The fifth CBRATEC (V Congresso Brasileiro de Análise Térmica e Calorimetria) conference was held in April 02–05, 2006 in Poços de Caldas, MG. One third of the 370 participants was graduates and Ph.D. students well representing the continuous interest in thermal analysis among Brazilian researchers. The structure of conference was characteristic and refreshing, since every morning one of the leading Brazil thermoanalysts held an opened teaching course especially for the representatives of the young generation. After then plenary lecturers and keynote speakers (J. Rouquerol, Cs. Novák, D. Burlett, M. Suchyta and A. Riga) occupied the podium. The afternoon sessions consisted of mainly short lectures and poster exhibitions; both provided excellent possibility for the Ph.D. students to introduce their scientific work. The scope of conference covered practically all aspects of thermal analysis. Since 1998, when the first CBRATEC conference was held, the participation of young scientists and the organization of teaching courses played essential role for them. As an effort to increase international experiences, the universities pay continuous attention to foreign language education (first of all English), so the communication between the invited international researchers, the representatives of the instrument companies and the domestic conference attendants became much more efficient in recent years. During the conference the new Executive Committee was elected. Prof. Valter José Fernandes Junior was elected as President of ABRATEC supported by the members of the Executive (Jivaldo do Rosário Matos (Vice-President), Massao Ionashiro, Lázaro Moscardini D’Assunção, Clóvis Augusto Ribeiro, Elias Yuki Ionashiro, Carlos Isidoro Braga, Manoel Luiz Cunha Rodrigues, Rodrigo Maciel). In recognition of his continuous cooperation for the development of thermoanalytical researches in Brazil and its scientific divulgation in Thermal Analysis, the ‘Special Award’ of ABRATEC (Brazilian Association for Thermal Analysis and Calorimetry) was presented to Prof. Csaba Novák. For their outstanding achievements in developing the international relation of ABRATEC, Honourable Membership of the Thermoanalytical Sub-Branch of the Hungarian Chemical Society was presented to Prof. Jivaldo do Rosário Matos, Massao Ionashiro, Prof. Valter José Fernandes Junior and Prof. Éder Tadeu Gomes Cavalheiro at the opening ceremony. At last but not least, according to the decision of ICTAC Council during the 13th ICTAC (2004, Chia Laguna, Italy) Brazil was elected as the host of ICTAC 14 in 2008. The Brazilian thermoanalytical community feels extremely honored to be entrusted with the organization of the 14thICTAC Conference that will take place in São Pedro, SP, in September 14–19, 2008, where the scientists, researchers and students, who are acting in the field of thermal analysis and calorimetry are cordially invited. The link to the conference site is www.ictac14.com.br. [ABSTRACT FROM AUTHOR]