Bianca Viana de Sousa

Comparative Study of Geopolymeric Materials Using Different Precursors

To obtain geopolymeric materials, different waste materials can be used as precursors to be applied as sources of alumina and silica, which are activated by alkaline solutions. The aim of this study is to compare the obtainment of geopolymeric materials using different precursors, besides a single complementary source of silica (rice husk ash) and as an activator, the sodium hydroxide. After the geopolymeric materials synthesis, they were poured into cylindrical containers and cured in the incubator at 60 °C for 6 hours, followed by curing at room temperature for 7 and 28 days. The samples were characterized, and then it was proved the obtainment of geopolymeric materials through the formation of hydrated calcium silicate. Mechanical behavior showed that the resistances of the obtained materials have been affected in accordance with the composition of precursor used in the synthesis.

Geopolymer Obtention Using Calcined Rice Husk Ash

This study aimed to synthesize geopolymer materials using the ash of burned rice husk. The material was prepared from bauxite slurry, rice hull ash was calcined at 600 °C, metakaolin and sodium hydroxide 12 M solution. The material was cured at 60 °C for 6 h and then at ambient temperature for up to 28 days. We used the same mixture of experimental design to synthesize geopolymer. Through techniques spectroscopy energy dispersive X rivers and X-ray diffraction, it appears that the silica and alumina contents of the identified raw material meets the conditions laid down as minimum for precursors with geopolymer activation potential, as evidenced by the molar ratio Si/Al sample. Geopolymer obtained from the XRD patterns showed characteristic peaks of hydrated calcium silicate. It was found that the particles had irregular shapes and sizes, and the presence of voids affecting the strength of the material. The geopolymeric material obtained showed improvements in the bending strength in a curing time of 28 days.

Synthesis and Characterization of Co/SBA-15 Catalysts

The mesoporous silica SBA-15 molecular sieve has been widely studied due to its unidirectional mesoporous structure, its high average pore diameter, its high thermal and hydrothermal stability and its ability to absorb metal ions, allowing its use as support material for catalysts. This study aimed to synthesize the Co/SBA-15 catalyst, and characterize it through the techniques of X-ray diffraction, temperature programmed reduction (TPR) and scanning electron microscopy (SEM). The SBA-15 support was synthesized from the following molar composition of reaction mixture: 1TEOS: 0.017 P123: 5.7 HCl: 173 H2O: 40 EtOH, and after calcined at 550 °C for 6 hours. The Co/SBA-15 catalyst was prepared by incorporating 10% cobalt by wet impregnation. Through the X-ray diffractograms, it was found that the impregnation has not changed the structure of the material. RTP profiles showed the presence of peaks at different temperatures that may be caused by dispersion of the cobalt.

Chemical Attacks in Geopolymeric Materials by Sulfuric Acid and Hydrochloric Acid

The geopolymeric materials present a viable alternative as concretes, the durability of these materials is associated to expected environmental conditions and one of the problems is their corrosion. The objective of this study was to assess the durability of geopolymeric materials through the chemical attack by sulfuric and hydrochloric acids with 5% concentration. After synthesis of the geopolymeric materials, followed by curing at room temperature for 28 days and then the geopolymeric materials were subjected to cycles of chemical attacks, which consisted of periods of seven days of immersion and seven days of drying at room temperature, four cycles were provided. The geopolymeric materials were characterized and it was found that they exhibit adequate resistance to chemical attack, the adequate strength consisted of determining the mass loss in each cycle attack.

Organophilization Process and Characterization of Palygorskite Clay (Attapulgite)

Natural clays can be chemically modified by surfactants, becoming organophilic. In this process, inorganic cations present in the clay mineral are exchanged for organic ones. Quaternary ammonium salts are commonly used in the organophilization process. Palygorskite is a crystalline complex magnesium aluminum silicate, with channel structure forming elongated crystals, which has physicochemical characteristics that give it properties suitable for several industrial applications such as drilling fluid and absorbing oils. The purpose of this study is to characterize the palygorskite clay and evaluate its organophilization process with the quaternary ammonium salt (CTABr) in order to use it for removing oil from emulsified solutions. Based on the results, it was observed that the organophilization process was evidenced by the X-ray diffraction due to the increase of lamellar distance and the presence of the quaternary salt peaks shown in the infrared spectrum, which makes the material viable to be applied in the treatment of emulsified oil.

Synthesis and Characterization of MgO/MCM-22 as Catalytic Support Using the Impregnation Technique

MCM-22 is a microporous molecular sieve with a system of sinusoidal three-dimensional channels that do not interconnect themselves, which presents good adsorption capacity and high acidity. Thus, this study aims to evaluate the chemical and structural properties of the catalyst MgO/MCM-22 using wet impregnation method. The synthesis of the zeolite was performed using the static hydrothermal method. Through the XRD patterns, it was possible to observe that the metal incorporation process did not cause structural changes, as well as the analysis showed small peaks related to the magnesium oxide in the structure. The micrographs presented a spherical morphology with depression in the central region. FTIR spectra showed the typical peaks of metal with little differences in the typical peaks of MCM-22.

Textural analysis of SBA-15 molecular sieve using ethanol as co-solvent

The SBA-15 molecular sieve has been widely studied due to its unidirectional mesoporous structure, high average pore diameter and high thermal and hydrothermal stability. This study aimed to evaluate the effect of ethanol co-solvent in the texture of SBA-15 molecular sieve, performing the synthesis process in different proportions of co-solvent ethanol. The SBA-15 molecular sieve was synthesized by adopting the following molar composition of reaction mixture: 1TEOS: 0.017 P123: 5.7 HCl: 173 H2O: x EtOH. In which X took the values 10, 20, 30 and 40 due to the ethanol co-solvent ratio. Analyzing the X-ray diffractograms, it was possible to observe a greater structural organization for a higher molar proportion of co-solvent. The micrographs showed agglomerates of spherical particles which by increasing molar proportion of ethanol co-solvent became larger and more defined. By the BET method, it was observed that as the proportion of co-solvent increased the specific surface area also increase and a decrease in micropores occurred, pointing to the porous nature of the material. The walls of the material became thicker as it increased the proportion of co-solvent making it the most stable material.

Experimental Planning of Mixtures to Obtain Geopolymer

This work had the aim to optimize the synthesis process of a geopolymer using experimental planning of mixtures. The geopolymer was prepared with different proportions of bauxite mud (R), rice husk ash (C) and metakaolin (M). The aluminosilicatealkaline activation was made with sodium hydroxide (NaOH) solution of 12 mol/L. Afterwards, the obtained material was submitted through a thermal treatment for 6 hours in an oven followed by a cure time of 28 days at room temperature. The final material was characterized through combinations of different techniques such as Scanning Electron Microscopy (SEM) and X-Ray Diffraction. Through carefully analysis of the flexural strength results, it was possible to conclude that the geopolymeric material (R6C2M) had a greater resistance in the seventh cure day at 0.6 MPa, however, it also can be said that the other samples presented an increase in the resistance over the 28 days of cure time.

Modeling of the Fischer-Tropsch Synthesis Aiming to Predict the Production of Paraffins and Olefins

The growing concern with the global environmental issues has resulted in a constant demand for the production of clean fuels. Therefore, researches were carried out in order to improve the gas-to-liquids technology, well represented by the Fischer-Tropsch synthesis. This synthesis is able to produce liquid fuels from syngas, a mixture of carbon monoxide and hydrogen which is obtained through the processing of the methane gas. Based on literature data, this paper suggests a kinetic model developed by making use of the Matlab® commercial application. The goal was to predict the production of hydrocarbons such as paraffins and olefins with up to six carbons in each chain. The Fischer-Tropsch synthesis was conducted with the catalyst 20% Co/ MCM-41 in fixed bed reactor at the temperature of 270 °C and atmospheric pressure. The results obtained by the model for both paraffins and olefins were compared with experimental data found in the literature.

New Routes Study for Synthesis of Molecular Sieves Type Al-MCM-41 and Al-SBA-15

The areas of research, synthesis and catalytic application of zeolites as molecular sieves are a field of great development and prominence in recent decades. Needs of the industries of petrochemical and fine chemicals have been encouraging specific studies for the application of molecular sieves looking for technological, commercial, and more recently sustainable developments. In this work molecular sieves type Al-MCM-41 and Al-SBA-15 has been synthesized using new synthesis routes by replacing the silica source conventionally used by rice husk. The molecular sieves obtained were confirmed by X-ray diffraction. Through the thermograms the decomposition of the driver at different temperatures was noticed. According to SEM micrographs can be observed that the material shows an aggregate of relatively uniform short particles.