Organo-gel: um novo sistema para a imobilização de lipases e sua aplicação em síntese orgânica

Lipases have been immobilized in microemulsion-based organogels (MBG's) and successfully utilized for the enantioselective esterification, diesterification and transesterification reactions, in organic solvents at 25ºC. This methodology is described as a new alternative for the use of enzymes in organic solvents. High enzymic stability has been observed. We have also used this methodology for the successful resolution of chiral secondary alcohols. This is a convenient way of using this catalyst in organic solvents which employs small amounts of the enzyme (250mg/mL).

Hidróxidos duplos lamelares: síntese, estrutura, propriedades e aplicações

The layered double hydroxides, known as anionic clays and represented by the general formula [M2+1-x M3+x (OH) 2]x+ Am-x/m·nH 2O, are a group of materials which are of much interest currently. They present a variety of potential applications as adsorbents, catalysts and catalyst support, ion-exchangers, antacids and as a polymer stabilizer. It is possible to obtain a broad variety of layered double hydroxides (LDHs), depending on the identity and ratio of the cations M2+ and M3+, as well as the interlamelar anion. The aim of this review is to give out some information about this class of materials, concerning to the synthesis, characterization, properties and applications.

Abordagens em síntese assimétrica

The approaches in asymmetric synthesis as the chiron approach, chiral auxiliaries, chiral reagents and asymmetric catalysis are described in a simplified way.

Propriedades texturais e catalíticas de óxidos de ferro contendo cromo e cobre

Chromium and copper-doped hematites were prepared with the aim of studying the synergistic effect of these dopants on the textural and on the catalytic properties of the iron oxides towards the high temperature shift reaction. It was found that the most active catalysts were those with the highest amount of copper. They had the Fe(II)/Fe(III) ratio near the stoichiometric value of magnetite, the highest surface areas under the reactional atmosphere and the greatest tendency to produce the active form; they also were poorly crystalline solids. The best performance was shown by the catalyst with Fe/Cu=10, heated at 300ºC. It can thus be concluded that copper acts both as textural and structural promoter in these catalysts.

Fischer-Tropsch Slurry Bubble Column Reactor Modeling

The literature part of the work reviews overall Fischer-Tropsch process, Fischer-Tropsch reactors and catalysts. Fundamentals of Fischer-Tropsch modeling are also presented. The emphasis is on the reactor unit. Comparison of the reactors and the catalysts is carried out to choose the suitable reactor setup for the modeling work. The effects of the operation conditions are also investigated. Slurry bubble column reactor model operating with cobalt catalyst is developed by taking into account the mass transfer of the reacting components (CO and H2) and the consumption of the reactants in the liquid phase. The effect of hydrostatic pressure and the change in total mole flow rate in gas phase are taken into account in calculation of the solubilities. The hydrodynamics, reaction kinetics and product composition are determined according to literature. The cooling system and furthermore the required heat transfer area and number of cooling tubes are also determined. The model is implemented in Matlab software. Commercial scale reactor setup is modeled and the behavior of the model is investigated. The possible inaccuraries are evaluated and the suggestions for the future work are presented. The model is also integrated to Aspen Plus process simulation software, which enables the usage of the model in more extensive Fischer-Tropsch process simulations. Commercial scale reactor of diameter of 7 m and height of 30 m was modeled. The capacity of the reactor was calculated to be about 9 800 barrels/day with CO conversion of 75 %. The behavior of the model was realistic and results were in the right range. The highest uncertainty to model was estimated to be caused by the determination of the kinetic rate.

Ilmaan johdettavien epäpuhtauksien päästökartoitus Porvoon öljynjalostamolla

Työn tarkoituksena oli laatia suunnitelma ilmaan johdettavien epäpuhtauksien päästökartoitukselle Porvoon öljynjalostamolla. Raskasmetallien, metaanin, fluorivetyhapon, rikkivedyn ja ammoniakin merkittävät päästöpaikat ja -tarkkailumenetelmät kartoitettaisiin tulevaa päästöraportointia varten. Tarkkailun alaisten komponenttien muodostuminen, kulkeutuminen ja merkittävät päästöpaikat Porvoon jalostamolla selvitettiin kirjallisuuslähteiden, jalostamon toimintajärjestelmän ohjeiden sekä työntekijöiden haastattelujen perusteella. Merkittäviä häiriöpäästötilanteita kartoitettiin ja arvioitiin jalostamon poikkeamatilastojen ja haastattelujen avulla. Normaalitoiminnan aikana tarkkailun alaisista epäpuhtauksista vapautuu ilmaan merkittäviä määriä ainoastaan metaania ja raskasmetalleja. Metaania vapautuu ilmaan polttoprosesseissa sekä hajapäästönä. Raskasmetallipäästöjä syntyy pohjaöljyn poltossa energialaitoksella sekä leijukatalyyttisessä krakkauksessa. Rikkilaitosten häiriötilanteista aiheutuu rikkivety- ja ammoniakkipäästöjä pääasiassa soihtujärjestelmän kautta. Alkylointiyksikön vuodoissa voi vapautua fluorivetyhappoa ilmaan. Päästömääriä arvioidaan pääosin laskennallisesti. Päästökartoitussuunnitelma on kokonaisuudessaan tämän työn liitteenä. Näyttäisi siltä, että TRS-yhdisteiden, ammoniakin ja fluorivetyhapon ilmapäästöt eivät ole merkittäviä Porvoon öljynjalostamolla. Uuden pohjaöljy-yksikön käyttöönotto on vähentänyt myös raskasmetallipäästöjä energialaitoksella. Metaanipäästö vaikuttaa kartoitukseen sisällytettävistä epäpuhtauksista merkityksellisimmältä Porvoon öljynjalostamolla.

Uso de irradiação de microondas na determinação espectrofotométrica de cromo com EDTA

Cr(III) slowly forms a violet complex with EDTA at pH 2.5-5.0 under normal conditions. The complex formation can be accelerated by irradiating the reacting mixture with microwave energy. The complex Cr(III)-EDTA is completely formed within 3 minutes of microwave irradiation and followed by a simple and rapid method for spectrophotometric determination of chromium. The method may be successfully applied to determination of chromium in catalyst.

Catalytic Wet Oxidation of Paper Mill Debarking Water

The objective of the research was to study the influence of temperature, oxygen pressure, catalysts loading and initial COD concentration of debarking wastewater on the pollutants during the catalytic oxidation. More importantly, how the addition of catalyst affects the wet oxidation process. The whole work was divided into two main sections, theoretical and experimental parts. The theoretical part reviews the pulp and paper industry from wood processing to paper production as well as operations that generate wastes. Treatment methods applicable for industrial pulp and paper mill effluents were also discussed. Wet oxidation and catalytic wet oxidation processes including mechanism, reactions, kinetics and industrial applications were previewed. In the experimental part, catalytic wet oxidation process were studied at 120-180°C, 0-10 bar oxygen pressure, 0-1 g/L catalyst concentration and 1000-3000 mg/L initial COD concentration. Responses, such as Chemical oxygen demand (COD), Total organic carbon (TOC), colour, lignin/tannin, Biochemical oxygen demand (BOD) and pH were measured. In the experiment, the best conditions occurred at 180°C, 10 bar, l g/L catalyst concentration and 3000mg/L initial COD. At these conditions; 74% COD, 97% lignin/tannin, 54% TOC, 90% colour were removed from the wastewater. pH was greatly reduced from 7 to 4.6. Lignin/tannin was removed most. Lignin/tannin showed linear dependency with colour during oxidation. Temperature made the most impact in reducing contaminants in debarked wastewater.

O efeito do ultra-som em reações químicas

Unusual chemical phenomenon associated with ultrasound is on account of cavitation effect. The ultrasound increase the rate and yield of chemical reaction on account of its ability to emulsify liquids. When the ultrasound is used in metallic catalyst reaction the activity of catalyst is increased because the ultrasound clean the surface of catalyst. Sonogels have a fine porosity and large specific surface improving different properties. This paper deals with ultrasound phenomenon and gives some examples of reactions and properties where this radiation takes an important role.

Desproporcionamento de tolueno sobre zeólitas tipo mordenita - atividade e seletividade na obtenção de xilenos

A sodium mordenite zeolite (Na-MOR) was synthesized and modified by dealumination with chloridric acid solution (H-MOR). X-Ray Diffraction (XRD), Inductive Coupled Plasm (ICP) and Scanning Electron Micrograph (SEM) techniques were used for sample characterization. The zeolite catalytic behavior was evaluated through toluene disproportionation at 435°C. It was verified that mordenites were very selective for the disproportionation reaction and the samples with higher aluminum content showed larger initial activity, however, these samples showed too a higher deactivation velocity due to a blockage of the unidimensional porous system of the zeolite by coke deposits. The selectivity to xylene isomers was practically not influenced by the Si/Al ratio and changed with the time on stream, due to coke formation. Transition state shape selectivity inside the mordenite pores is also discussed.

A combustão catalítica do metano: estudo estatístico do efeito das variáveis de preparação e pré-tratamento de catalisadores de paládio suportado sobre a atividade catalítica

The catalytic combustion of methane on alumina supported palladium catalysts was studied. It has been reported that the activity of the catalyst increases with its time on line, despite of an increase of the palladium particle size. However, different preparation, pretreatment and testing conditions can be the reason for the observed different results. An experimental design, which allows to verify the influence of several parameters at the same time with a good statistical quality, was used. A Plackett-Burman design was selected for the screening of the variables which have an effect on the increase of the catalyst activity.

Influência da catálise ácida e básica na preparação da sílica funcionalizada pelo método sol-gel

Some aspects of the chemistry involved in the preparation and characterization of functionalized silicon oxide by sol-gel method are considered in this work. The synthesis was performed with different silicon alcoxide precursors and the influence of the acid and basic catalyst was investigated. Characterization was performed by infrared absorption spectroscopy, elemental analysis and 29Si NMR. Infrared data show Si-C and -CH2- vibrational modes at 1250 to 1280 and 2920 to 2940 cm-1, respectively. The elemental analysis confirmed the presence of organic groups in the inorganic silica network. 29Si NMR results show different hydrolisys depending on the acid or base catalysis.

Efeito da temperatura no desempenho catalítico de óxidos de ferro contendo cobre e alumínio

Aluminum and copper doped hematite was evaluated in the high temperature shift (HTS) reaction at several temperatures in order to find catalysts that can work in different operational conditions. It was found that the catalysts work in kinetic regime in the range of 300-400 ºC. Both copper and aluminum increases the activity and selectivity. Aluminum acts as textural promoter whereas copper acts as structural one. The most promising catalyst is that with both copper and aluminum which showed higher activity and selectivity than a commercial sample. This catalyst has the advantages of being non toxic and can work at low temperatures.

Caracterização textural e estrutural de V2O5/TiO2 obtidos via sol-gel: comparação entre secagem convencional e supercrítica

This work describes a modified sol-gel method for the preparation of V2O5/TiO2 catalysts. The samples have been characterized by N2 adsorption at 77K, x-ray diffractometry (XRD) and Fourier Transform Infrared (FT-IR). The surface area increases with the vanadia loading from 24 m² g-1, for pure TiO2, to 87 m² g-1 for 9wt.% of V2O5. The rutile form is predominant for pure TiO2 but became enriched with anatase phase when vanadia loading is increased. No crystalline V2O5 phase was observed in the catalysts diffractograms. Two species of surface vanadium observed by FT-IR spectroscopy a monomeric vanadyl and polymeric vanadates, the vanadyl/vanadate ratio remains practically constant.

Efeito da concentração do catalisador acetilacetonato férrico na cura de poliuretano à base de polibutadieno líquido hidroxilado (PBLH) e diisocianato de isoforona (IPDI)

The reaction between hydroxy-terminated polybutadiene and isophorone diisocyanate constitutes the base of the curing process of the most composite solid propellant used in the propulsion of solid rocket propellant. In this work, differential scanning calorimetry and viscosity measurements were used to evaluate the effect of the ferric acetylacetonate catalyst concentration on the reaction between HTBR and IPDI. These analyses show one exotherm, which shifts to lower temperatures as the catalyst concentration increases. The viscosity analyses show that the increase of temperature causes, at first, a reduction in the mixture viscosity, reaching a minimum range called gelification region (increasing the crosslinking density).