Síntese e caracterização de compostos organometálicos de estanho (IV)

Organotin(IV) derivatives containing bulky R groups have been synthesized and characterized. It is discussed how their syntheses depend on the reaction conditions, such as stoichiometry of starting materials, bulkiness of the organo group attached to the Sn centre as well as temperature in which the reaction is carried out. Finally the molecular structure of Sn2Ph6, determined by X-ray diffraction is reviewed.

Preparação de compostos lamelares: síntese do hidrogenofosfato de zircônio cristalino e sua intercalação com aminas. Um experimento para estudantes de graduação

The present paper describes the synthesis of crystalline zirconium hydrogen phosphate by direct precipitation and its intercalation with pyridine and n-butylamine. The simple experiment was tested in the undergraduate inorganic chemistry laboratory course for chemistry students at IQ-UNICAMP using inexpensive reagents. The materials were characterized by powder X-ray diffraction and infrared analyses in order to obtain detailed information of the solid structure changes as a result of the intercalation process. Pyridine and n-butylamine are focused in this work as clear and elucidative examples leading to acid-base interactive processes that result in the well-formed infinite sequence of inorganic lamellar structures.

Materiais à base de óxido de ferro para oxidação de compostos presentes no efluente da despolpa do café

Materials based on pure iron oxide and impregnated with niobia (Nb2O5) were prepared. Their catalytic activities were tested on the oxidation of compounds present in the wastewater from the processing of coffee berries. Particularly caffeine and catechol were tested. The oxidation reactions were carried out with the following systems (i) UV/H2O2, (ii) photo-Fenton and (iii) heterogeneous Fenton. All materials were characterized with X-ray diffraction, Mössbauer and infrared spectroscopy. Iron was mainly in the forms of goethite and maghemite. The oxidation kinetics were monitored by UV-vis and the oxidation products were monitored by mass spectrometry. The photo-Fenton reaction presented highest oxidation efficiency, removing 98% of all caffeine and catechol contents.

Estudo de adsorção de compostos sulfurados utilizando um diesel comercial dopado com benzotiofeno e dibenzotiofeno

Desulphurization process by adsorption was studied employing a commercial diesel dooped with 1000 mg/L of benzothiophene and dibenzothiophene. The adsorbents materials employed were three types of activated alumina (acid, basic and neutral). For comparison, adsorption process was made also using oxidized diesel sample. The results showed that the adsorbents were selective for sulphur compounds removal from fuels. The contact time have influence in adsorption process achieving 80% of removal for not oxidized dibenzothiophene. The three studied alumina types showed similar behavior and a greater selective in dibenzothiophene adsorption than benzothiophene. Dibenzothiophene removal is more effective in samples not oxidized, whereas the benzothiophene was almost totally removed in oxidized sample.

Remoção de compostos orgânicos em água empregando carvão ativado impregnado com óxido de ferro: ação combinada de adsorção e oxidação em presença de H2O2

In this work, composites based on activated carbon/iron oxide (AC/Fe) were prepared in two different proportions (AC/Fe 5/1 and 1/1) and evaluated in the removal of the organic dye methylene blue (MB). Physical-chemical properties of the composites were determined by X-ray diffraction (XRD), adsorption/dessorption of N2 isotherm, temperature programmed reduction (TPR) and scanning electron microscopy (SEM). Results showed that goethite (α- FeOOH), with nanometer particle size, was formed over carbon surface for both composites. These materials showed high efficiency to remove MB from solution by combined adsorption and oxidation process. The AC/Fe 1/1 showed to be more active in (MB) oxidation then AC/Fe 5/1.

Co2 na desidrogenação oxidativa do etilbenzeno utilizando catalisadores compostos de óxido de ferro e óxido de alumínio

Materials containing aluminum and iron oxide were synthesized through the preparation of hybrid spheres and tested in the dehydrogenation of ethylbenzene in the presence of CO2. The catalytic results suggest that the high initial ethylbenzene conversion is due to the contribution of basic sites. These results also point to a competitive process between CO2 adsorption and the oxidative dehydrogenation of ethylbenzene for the basic sites (lattice oxygen). In spite of the coke deposition is originating from ethylbenzene and CO2, the amount of carbonaceous deposits was smaller with the presence of CO2, if compared with the dehydrogenation in the absence of CO2.

Avaliação da natureza da atividade catalítica de compostos de bismuto em reações de metanólise do óleo de soja

Sodium bismuthate dihydrate and two species derived from its thermal treatment were investigated as catalysts for soybean oil methanolysis and, regardless of the type of solid used, ester yields always above 76 wt% were obtained. After a single reaction course, both liquid and solid phases were characterized using several analytical methods such as X-ray diffraction and thermogravimetric analysis. As a result, the catalytic phenomenon was shown to be solely due to the leaching of alkalinecatalytic species from the solid materials.

Efeitos energético-estruturais em compostos heteropolicíclicos com oxigénio ou enxofre

The present article involves a comparative study of the influence of oxygen or sulfur heteroatoms present in the central ring of polycyclic compounds, in order to clarify the correlation between the respective thermophysical or thermochemical properties and structural characteristics. Considering the importance of these types of compounds for their broad spectrum of application in diverse fields, from pharmacology to the development of new materials, the critical interpretation of such properties for their crucial role in the reactivity of these substances is of great interest. Knowledge on these thermodynamic data for key compounds is also relevant to the prediction and understanding of the properties and behavior of other parent compounds.

Carboidratos como fonte de compostos para a indústria de química fina

Coal, oil, natural gas, and shale gas are biomass that is formed millions of years ago. These are non-renewable and depleting, even considering the recent discovery of new sources of oil in the presalt and new technologies for the exploitation of shale deposits. Currently, these raw materials are used as a source of energy production and are also important for the production of fine chemicals. Since these materials are finite and their (oil) price is increasing, it is clear that there will be a progressive increase in the chemical industry to use renewable raw materials as a source of energy, an inevitable necessity for humanity. The major challenge for the society in the twenty first century is to unite governments, universities, research centers, and corporations to jointly act in all areas of science with one goal of finding a solution to global problems, such as conversion of biomass into compounds for the fine chemical industry.Non-renewable raw materials are used in the preparation of fuels, chemical intermediates, and derivatives for the fine chemical industry. However, their stock in nature has a finite duration, and their price is high and will likely increase with their depletion. In this scenario, the alternative is to use renewable biomass as a replacement for petrochemicals in the production of fine chemicals. As the production of biomass-based carbohydrates is the most abundant in nature, it is judicious to develop technologies for the generation of chain products (fuels, chemical intermediates, and derivatives for the fine chemicals industry) using this raw material. This paper presents some aspects and opportunities in the area of carbohydrate chemistry toward the generation of compounds for the fine chemical industry.

REAÇÃO DE CONDENSAÇÃO DO GLICEROL COM COMPOSTOS CARBONÍLICOS. SÍNTESE, CARACTERIZAÇÃO E APLICAÇÃO EM CRISTAIS LÍQUIDOS

Condensation reactions of glycerol with aldehydes and ketones were performed under thermal heating and microwave irradiation regimes. Homogeneous and heterogeneous catalysts were tested in both conditions. A silica sulfated (SiO2-SO3H) heterogeneous catalyst demonstrated the best performance relative to a selectivity of >95% in favor of 5-membered ketals. For acetals, preference in favor of 5-membered or 6-membered functional groups depends on the nature of the catalyst. Homogenous catalysts favor the more stable 6-membered acetals, whereas heterogeneous catalysts favor the less stable 5-membered acetals. However, the isomer ratios in the acetalization reaction are too low, and hence the reaction cannot be used in a synthetic plan for functional materials. Ketalization processes mediated by SiO2-SO3H show a high selectivity in favor of a 5-membered ring (1,3-dioxolane). The scope of condensation was tested with different ketones. A mechanism for heterogeneous catalysis related to the selectivity in the cyclization process is presented herein. Solketal, a commercial product, was also obtained by a condensation reaction of glycerol and propanone, and showed a high selectivity in favor of 1,3-dioxolane. It was transformed to potential allylic and chiral intermediates. A mesogenic core was connected to the organic framework of glycerol to produce a monomer liquid crystal material with a stable smectic-C mesophase.

Tecnologia dels materials

Dins de la disciplina de Ciència i Enginyeria dels Materials, en la qual s’estudia la interrelació entre l’estructura, el processament, les propietats i les aplicacions dels materials, aquest llibre intenta descriure com les tècniques de processament industrial afecten l’estructura dels materials. L’enfocament del text se centra en el material, no pas en les tècniques emprades, temàtica més propera a les tecnologies de fabricació. El temari s’ha organitzat en cinc grans temes. Els quatre primers intenten donar els fonaments d’una tecnologia de processament (colament dels metalls, conformació per deformació, conformació per sinterització, tractaments tèrmics) mentre que el cinquè es dedica a la corrosió. El temari no inclou la tecnologia dels materials polímers que mereixeria un temari específic

Unitats didàctiques integrades de llengua catalana i literatura i llengua castellana i literatura. Batxillerat : les propietats textuals. 'Unidades didácticas integradas de lengua y literatura catalana y lengua y literatura castellana. Bachillerato : las propiedades textuales'.

Documento en formato electrónico (PDF). Esta unidad didáctica está pensada para ser aplicada en el primer curso de bachillerato. Resumen tomado parcialmente de la propia innovación

Tecnologia dels materials: amb qüestions i exercicis 2a edició [versió html]

Dins de la disciplina de Ciència i Enginyeria dels Materials, en la qual s’estudia la interrelació entre l’estructura, el processament, les propietats i les aplicacions dels materials, aquest llibre intenta descriure com les tècniques de processament industrial afecten l’estructura dels materials. L’enfocament del text se centra en el material, no pas en les tècniques emprades, temàtica més propera a les tecnologies de fabricació. El temari s’ha organitzat en cinc grans temes. Els quatre primers intenten donar els fonaments d’una tecnologia de processament (colament dels metalls, conformació per deformació, conformació per sinterització, tractaments tèrmics) mentre que el cinquè es dedica a la corrosió. El temari no inclou la tecnologia dels materials polímers que mereixeria un temari específic

Descripció de propietats moleculars i activitats biològiques emprant l'energia de repulsió electró-electró

En aquest treball es descriu l'ús de les mesures de semblança molecular quàntica (MSMQ) per a caracteritzar propietats i activitats biològiques moleculars, i definir descriptors emprables per a construir models QSAR i QSPR. L'estudi que es presenta consisteix en la continuació d'un treball recent, on es descrivien relacions entre el paràmetre log P i MSMQ, donant així una alternativa a aquest parimetre hidrofòbic empíric. L'actual contribució presenta una nova mesura, capaç d'estendre l'ús de les MSMQ, que consisteix en l'energia de repulsió electró-electró (Vee). Aquest valor, disponible normalment a partir de programari de química quàntica, considera la molècula com una sola entitat, i no cal recórrer a l'ús de contribucions de fragments. La metodologia s'ha aplicat a cinc tipus diferents de compostos on diferents propietats moleculars i activitats biològiques s'han correlacionat amb Vee com a únic descriptor molecular. En tots els casos estudiats, s'han obtingut correlacions satisfactòries.