Estudo da adsorção de compostos sulfurados empregando zeólitas contendo zinco

This paper deals with an adosrption of sulphur compounds employing zeolites containing zinc. The zeolites employed were commercial NaY and Beta. The zinc was incorporated in three levels: 0.5; 1.0 and 5%. The sulphur compounds studied were benzothiophene and dibenzothiofene. The results showed that both zeolites can be employed for adsorption of benzothiophene and dibenzothiophene. The Zn incorporation (0.5%) promotes an increase in zeolites adsorption ability. The DBT adsorbs more than BT, probably because it strongly interacts with zeolite structure. The BT adsorbs more in NaY than in beta probably because the NaY zeolite has a high intern volume. This is not observed for DBT.

Estudo e caracterização da zeólita OFF Tipo T empregando diferentes fontes de silício

Offretite T zeolite was synthesized using different source of Si (Ludox AS-30, Ludox LS-30 and Aerosil 200 Degussa). The obtained materials were characterized by different complementary techniques: XRD, textural analysis by N2 adsorption, IV, SEM and chemistry analysis. This zeolite has an intermediary structure between offretite and erionite zeolites. In all experiments offretite T phase was obtained. Offretite phase presenting better crystalility are obtained in synthesis with stirring and employing aerosil as silicon source. This zeolite presents a potencial application as catalyst for hydroisodewaxing process.

Remoção de Pb2+ e Cr3+ em solução por zeólitas naturais associadas a rochas eruptivas da formação serra geral, bacia sedimentar do Paraná

The capacity of natural zeolites and its host rock (dacite) to remove Pb2+ and Cr3+ from aqueous solutions has been investigated. Results showed that both samples prefer to remove Pb2+ instead of Cr3+. Almost 100% of Pb2+ was removed from solutions with concentration until 50 mg L-1 and 100 mg L-1 of this metal, respectively by dacite and zeolite. The equilibrium of metals adsorption process was reached during the first 30 min by both materials. Na+ can be used to recover Pb2+, but not to remove Cr3+ from the treated samples. The Sips model showed a good fit for experimental data of this study.

Síntese hidrotermal de sodalita básica a partir de um rejeito de caulim termicamente ativado

Basic sodalite was successfully synthesized by hydrothermal method using kaolin waste as source of Aluminum and Silicon. This waste is mainly composed by kaolinite and is produced in large amount by kaolin processing industries for paper coating from the Amazon region. Initially, the waste has been calcined at 700 ºC for 2 h and then reacted with the following solutions: Na2CO3 and mixture of Na2CO3 + NaOH to 150 ºC with autogenous pressure for 24 h. The raw materials and transformed materials were characterized by XRD, FTIR and SEM. In both studied media, well-crystallized, basic sodalite was the only phase synthesized, while in the literature usually a mixture of zeolites is obtained.

Desenvolvimento e validação de um método analítico simples e rápido por espectroscopia UV para quantificação de aciclovir em matrizes hidrofílicas de liberação prolongada

This work reports the validation of an analytical UV spectrophotometric method to assay acyclovir in hydrophilic matrices (assay and dissolution studies). The method was linear in the range between 2.5-20 µg mL-1, presenting a good correlation coefficient ( r = 0,9999). Precision and accuracy analysis showed low relative standart deviation (< 2.0 %) and a good recoveries percentual (98.9-100 %). The procedure was linear, accurate, and robust. The method is simple and cheap. It does not use polluting reagents and can be applied in dissolution studies, being an adequate alternative to assay acyclovir in hydrophilic matrices tablets.

Preparação e propriedades de zeólitas faujasita contendo cátions amônio

Sodium faujasite zeolites with Si/Al ratio of 1.4 and 2.5 were exchanged with methylammonium cations. The influence of framework aluminum and ion exchange degree in their basic properties were evaluated. These properties were assessed in the Knoevenagel catalytic condensation. The sodium ion exchange was restricted to the supercavity and the exchange degree depended on the cation volume and on the Si/Al ratio. The higher catalytic activity is achieved for the zeolite with the lower Si/Al ratio exchanged with the monomethylammonium cation. The best performance of this catalyst is attributed to the higher basicity in combination with elevated micropore volume.

Incorporação de dióxido de titânio em zeólitas para emprego em fotocatálise heterogênea

This work proposes the study of heterogeneous photocatalysis using TiO2 impregnated in zeolites beta, ZSM-5, mordenite, NaXb, NaXp and NaY for the decomposition of methylene blue. The catalysts were characterized by XRD, IR, textural analyses by N2 adsorption, SEM, DRS and the reaction of decomposition was monitored by UV visible. The results indicated that didn't have structural changes in the catalysts after Ti impregnations, only in the case of NaY and NaX zeolites. The better photocatalyst to metylene blue decomposition was beta/Ti zeolite due had one structure more accessible (with bigger porous) helping in TiO2 dispersion and catalytic active.

Fases estacionárias modernas para cromatografia líquida de alta eficiência em fase reversa

This review first discusses the limitations of many of the supports and stationary phases used in reversed phase high performance liquid chromatography and then describes those, developed more recently, that present better stabilities and more versatile selectivities. Emphases will be given to stationary phases that use higher purity silicas, hybrid silicas, monolithic silicas, metallic oxides and mixed oxides as supports and those that have embedded polar groups or contain phenyl or fluoro groups as the stationary phase as well as the phases used for mixed mode or hydrophilic interaction separations. These modern stationary phases facilitate the analysis of complex mixtures.

Catalisadores heterogêneos para a produção de monoésteres graxos (biodiesel)

The recent increase in the world biodiesel demand, along with the need to reduce costs while improving the environmental sustainability of the entire biodiesel production chain, have led to the search for heterogeneous catalysts that would be efficient and highly amenable to recycling. Many classes of materials have been tested for these purposes. Among these are zeolites, ion-exchange resins, inorganic oxides, guanidines, metal complexes, layered compounds and ionic liquids. This review article describes the structure, properties, synthesis and performance of compounds that are catalytic active in both esterification and transesterification reactions.

A green synthesis of α,β-unsaturated carbonyl compounds from glyceraldehyde acetonide

The catalytic behavior of Cs-exchanged and Cs-impregnated zeolites (X and Y) was studied using the Knoevenagel condensation between glyceraldehyde acetonide and ethyl acetoacetate in order to produce the corresponding α,β-unsaturated carbonyl compound that is an important intermediate for fine chemicals. The influence of reaction temperature, type of zeolite, and basicity of the sites on the catalytic behavior of the samples was evaluated. All zeolites were active for the studied reaction. The formation of the main condensation product was favored at lower reaction temperatures. Products of further condensations were also observed especially for samples that were only dried before catalytic test.

Produção de biodiesel via transesterificação etílica com zeólitas básicas

Soybean oil transesterification with ethanol was carried out in a batch reactor using USY zeolites modified with barium and strontium (15 wt.%) as catalysts. A series of three catalytic cycles were performed for each zeolite without any loss of activity. The biodiesel product was analyzed by HPLC and FT-Raman, and the catalysts by pyridine and CO2 adsorption. Ba/USY provided higher conversions (> 97%) than Sr/USY (< 75%). The increased catalytic activity of Ba/USY was attributed to two different effects: a larger number of basic sites; and a lower interaction between barium species and HUSY BrØnsted sites.

Síntese e caracterização de copolímeros do tipo ABA para encapsulação de hemoglobina bovina

The use of biopolymers for the development of oxygen carriers has been extensively investigated. In this work, three different ABA triblock copolymers were synthesized and used to encapsulate purified bovine hemoglobin, using a double emulsion technique. The effect of polymer composition, homogenization velocity, and addition of a surfactant, on the protein entrapment was evaluated. These copolymers, which have a hydrophilic block, achieved higher values of encapsulation efficiency than the corresponding homopolymers. The increase in homogenization strength also promoted an increase in encapsulation efficiency. Capsules formation occurred even in the absence of PVA.

Preparação, caracterização e estudos de biodegradação de blendas à base de PDLLA e PVP

Poly(D,L-lactide), PDLLA, is a polymer with potential applications in medical, environmental, and pharmaceutical areas. Despite its versatility, the hydrophobicity limits its applications. To overcome this problem, one strategy is the preparation of blends with hydrophilic polymers such as poly(vinylpyrrolidone), PVP. In this study, we report the preparation and characterization of blends based on PDLLA and PVP and the biodegradation studies by the Sturm test. It was observed that the components of the blends PDLLA/PVP are thermodynamically immiscible, however the biodegradation is faster than that of pure PDLLA.

Geração de mesoporos em zeólitas ZSM-5 e seus efeitos na conversão do etanol em olefinas

Developing mesoporosity in HZSM-5 zeolites is an alternative for improving their catalytic performance on chemical reactions. In this work, alkaline and thermal treatments were used to produce mesoporosity. These treatments increased mesoporous area and volume. They also influenced the acid properties of the samples. Concerning catalytic performance, treatments modified reaction product distribution. Whereas alkaline treatment favored formation of olefins and increased propene ratio in the beginning of the reaction, thermal treatment resulted in formation of only ethylene due to the low acidity of the sample.

Revisão dos tratamentos químicos da fibra natural para mistura com poliolefinas

The use of natural fibers as reinforcement in polymer composites has been a focus of interest. However, these composites exhibit lower mechanical properties than those of pure polymers because of the low interfacial interactions between the hydrophobic polymer matrix and the hydrophilic fiber. To overcome this problem, different chemical treatments applied to the fibers have been reported. One of the most used treatments is mercerization, which can improve adhesion between the fiber and polymeric matrix. Another chemical treatment involves the use of acids (stearic and oleic acids). The chemically treated fibers used in composite materials showed improved mechanical properties.