Surface diffusion of strong adsorbing vapours on porous carbon

Surface diffusion of strongly adsorbing hydrocarbon vapours on activated carbon was measured by using a constant molar flow method (D.D. Do, Dynamics of a semi-batch adsorber with constant molar supply rate: a method for studying adsorption rate of pure gas, Chem. Eng. Sci. 50 (1995) 549), where pure adsorbate is introduced into a semi-batch adsorber at a constant molar flow rate. The surface diffusivity was determined from the analysis of pressure response versus time, using a linear mathematical model developed earlier. To apply the linear theory over the non-linear range of the adsorption isotherm, we implement a differential increment method on the system which is initially equilibrated with some pre-determined loading. By conducting the experiments at different initial loadings, the surface diffusivity can be extracted as a function of loading. Propane, n-butane, n-hexane, benzene, and ethanol were used as diffusing adsorbate on a commercial activated carbon. It is found that the surface diffusivity of these strongly adsorbing vapours increases rapidly with loading, and the surface diffusion flux contributes significantly to the total flux and cannot be ignored. The surface diffusivity increases with temperature according to the Arrhenius law, and for the paraffins tested it decreases with the molecular weight of the adsorbate. (C) 2002 Elsevier Science Ltd. All rights reserved.

Cuticular hydrocarbons of Drosophila birchii and D-serrata: Identification and role in mate choice in D-serrata

The cuticular hydrocarbon compositions of two sympatric species of Australian Drosophila in the montium subgroup of the melanogaster group that use cuticular hydrocarbons in mate recognition have been characterized. Drosophila birchii has 34 components in greater than trace amounts, with a carbon number range of C-20 to C-33. Drosophila serrata has 21 components above trace level and a carbon number range of C-24 to C-31. These two species share eight hydrocarbon components, with all but two of them being monoenes. For both species, the (Z)-9-monoenes are the predominant positional isomer. The hydrocarbons of D. birchii are n-alkanes, n-alkenes (Z)-5-, (Z)-7-, (Z)-9-, and (Z)-11-), low to trace levels of homologous (Z,Z)-7,11- and (Z,Z)-9,13-dienes; and trace amounts of (Z,Z)-5,9- C-25:2, a major component of D. serrata. Only one methyl branched hydrocarbon was detected (2-methyl C-28), and it occurred at very low levels. The hydrocarbons of D. serrata are dominated by a homologous series of (Z,Z)-5,9-dienes, and notably, are characterized by the apparent absence of n-alkanes. Homologous series of (Z)-5-, (Z)-7-, and (Z)-9- alkenes are also present in D. serrata as well as 2-methyl alkanes. Drosophila serrata females display strong directional mate choice based on male cuticular hydrocarbons and prefer D. serrata males with higher relative abundances of the 2-methyl alkanes, but lower relative abundances of (Z,Z)-5,9- C-24:2 and (Z)-9-C-25:1.

Análise de Parafinas por APCI-FT-ICR MS : Uma Análise Rápida e Simples na Identificação de Hidrocarbonetos Saturados, Cíclicos e Poliaromáticos

A análise de hidrocarbonetos por técnicas de ionização a pressão atmosférica ou ambiente continua a ser um desafio na espectrometria de massas. Normalmente, a ionização ocorre através de mecanismos de protonação e desprotonação. Para isso, as moléculas de interesse devem apresentar um grupo básico ou ácido que proporcionem a geração de íons [M+H]+ ou [M-H]-. Para superar essa limitação, um método analítico simples, fácil, rápido e poderoso foi desenvolvido com sucesso, adaptado a partir da literatura, para ionizar saturado e insaturado, linear, ramificado, e hidrocarbonetos cíclicos, bem como hidrocarbonetos poliaromáticos e heteroaromáticos presentes em frações de hidrocarbonetos e de misturas de parafina/petróleo bruto utilizando ionização química à pressão atmosférica (APCI), favorecido pela utilização de solventes alifáticos de cadeia curta em um espectrômetro de massas FT-ICR. Entre os reagentes alifáticos estudados, isoctano proporcionou os melhores resultados quando comparado com outros solventes. Além disso, foram estudados outros interferentes do processo de ionização, como concentração da solução injetada e misturas parafina/óleo, que influenciavam desde o perfil dos espectros até as principais classes de compostos identificados. O método torna possível a ionização de hidrocarbonetos pela produção de íons [M -H]+ sem ocorrência de fragmentação.

Complexes of copper(II) with 3-(ortho-substituted phenylhydrazo)pentane-2,4-diones: syntheses,properties and catalytic activity for cyclohexane oxidation

Reactions of copper(II) with 3-phenylhydrazopentane-2,4-diones X-2-C6H4-NHN = C{C(= O)CH3}(2) bearing a substituent in the ortho-position [X = OH (H2L1) 1, AsO3H2 (H3L2) 2, Cl (HL3) 3, SO3H (H2L4) 4, COOCH3 (HL5) 5, COOH (H2L6) 6, NO2 (HL7) 7 or H (HL8) 8] lead to a variety of complexes including the monomeric [CuL4(H2O)(2)]center dot H2O 10, [CuL4(H2O)(2)] 11 and [Cu(HL4)(2)(H2O)(4)] 12, the dimeric [Cu-2(H2O)(2)(mu-HL2)(2)] 9 and the polymeric [Cu(mu-L-6)](n)] 13 ones, often bearing two fused six-membered metallacycles. Complexes 10-12 can interconvert, depending on pH and temperature, whereas the Cu(II) reactions with 4 in the presence of cyanoguanidine or imidazole (im) afford the monomeric compound [Cu(H2O)(4){NCNC(NH2)(2)}(2)](HL4)(2)center dot 6H(2)O 14 and the heteroligand polymer [Cu(mu-L-4)(im)](n) 15, respectively. The compounds were characterized by single crystal X-ray diffraction (complexes), electrochemical and thermogravimetric studies, as well as elemental analysis, IR, H-1 and C-13 NMR spectroscopies (diones) and ESI-MS. The effects of the substituents in 1-8 on the HOMO-LUMO gap and the relative stability of the model compounds [Cu(OH)(L-8)(H2O)]center dot H2O, [Cu(L-1)(H2O)(2)]center dot H2O and [Cu(L-4)(H2O)(2)]center dot H2O are discussed on the basis of DFT calculations that show the stabilization follows the order: two fused 6-membered > two fused 6-membered/5-membered > one 6-membered metallacycles. Complexes 9, 10, 12 and 13 act as catalyst precursors for the peroxidative oxidation (with H2O2) of cyclohexane to cyclohexanol and cyclohexanone, in MeCN/H2O (total yields of ca. 20% with TONs up to 566), under mild conditions.

Synthesis and structural characterization of iron complexes with 2,2,2-tris(1-pyrazolyl)ethanol ligands: Application in the peroxidative oxidation of cyclohexane under mild conditions

The reactions of FeCl2 center dot 2H(2)O and 2,2,2-tris(1-pyrazolyl) ethanol HOCH2C(pz)(3) (1) (pz = pyrazolyl) afford [Fe{HOCH2C(pz)(3)}(2)][FeCl4]Cl (2), [Fe{HOCH2C(pz)(3)}(2)](2)[Fe2OCl6](Cl)(2)center dot 4H(2)O (3 center dot 4H(2)O), [Fe{HOCH2C(pz)(3)}(2)] [FeCl{HOCH2C(pz)(3)}(H2O)(2)](2)(Cl)(4) (4) or [Fe{HOCH2C(pz)(3)}(2)]Cl-2 (5), depending on the experimental conditions. Compounds 1-5 were isolated as air-stable crystalline solids and fully characterized, including (1-4) by single-crystal X-ray diffraction analyses. The latter technique revealed strong intermolecular H-bonds involving the OH group of the scorpionate 2 and 3 giving rise to 1D chains which, in 3, are further expanded to a 2D network with intercalated infinite and almost plane chains of H-interacting water molecules. In 4, intermolecular pi center dot center dot center dot pi interactions involving the pyrazolyl rings are relevant. Complexes 2-5 display a high solubility in water (S-25 degrees C ca. 10-12 mg mL(-1)), a favourable feature towards their application as catalysts (or catalyst precursors) for the peroxidative oxidation of cyclo-hexane to cyclohexanol and cyclohexanone, with aqueous H2O2/MeCN, at room temperature (TON values up to ca. 385). (C) 2011 Elsevier B. V. All rights reserved.

A Hexanuclear Mixed-Valence Oxovanadium(IV,V) Complex as a Highly Efficient Alkane Oxidation Catalyst

The new hexanuclear mixed-valence vanadium complex [V3O3(OEt)(ashz)(2)(mu-OEt)](2) (1) with an N,O-donor ligand is reported. It acts as a highly efficient catalyst toward alkane oxidations by aqueous H2O2. Remarkably, high turnover numbers up to 25000 with product yields of up to 27% (based on alkane) stand for one of the most active systems for such reactions.

Pyrazole or tris(pyrazolyl)ethanol oxo-vanadium(IV) complexes as homogeneous or supported catalysts for oxidation of cyclohexane under mild conditions

The oxovanadium(IV) complexes [VO(acac)(2)(Hpz)].HC(pz)(3) 1.HC(pz)(3) (acac= acetylacetonate, Hpz = pyrazole, pz = pyrazoly1) and [VOCl2{HOCH2C(pz)(3)}] 2 were obtained from reaction of [VO(acac)(2)] with hydrotris(1-pyrazolyl)methane or of VCl(3)with 2,2,2-tris(1-pyrazolyl)ethanol. The compounds were characterized by elemental analysis, IR, Far-IR and EPR spectroscopies, FAB or ESI mass-spectrometry and, for 1, by single crystal X-ray diffraction analysis. 1 and 2 exhibit catalytic activity for the oxidation of cyclohexane to the cyclohexanol and cyclohexanone mixture in homogeneous system (TONS up to 1100) under mild conditions (NCMe, 24h, room temperature) using benzoyl peroxide (BPO), tert-butyl hydroperoxide (TBHP), m-chloroperoxybenzoic acid (mCPBA), hydrogen peroxide or the urea-hydrogen peroxide adduct (UHP) as oxidants. 1 and 2 were also immobilized on a polydimethylsiloxane membrane (1-PDMS or 2-PDMS) and the systems acted as supported catalysts for the cyclohexane oxidation using the above oxidants (TONs up to 620). The best results were obtained with mCPBA or BP0 as oxidant. The effects of various parameters, such as the amount of catalyst, nitric acid, reaction time, type of oxidant and oxidant-to-catalyst molar ratio, were investigated, for both homogeneous and supported systems. (C) 2012 Elsevier B.V. All rights reserved.

Efficient cyclohexane oxidation with hydrogen peroxide catalysed by a C-scorpionate iron(II) complex immobilized on desilicated MOR zeolite

The hydrotris(pyrazol-1-yl)methane iron(II) complex [FeCl2{eta(3)-HC(pz)(3)}] (Fe, pz = pyrazol-1-yl) immobilized on commercial (MOR) or desilicated (MOR-D) zeolite, catalyses the oxidation of cyclohexane with hydrogen peroxide to cyclohexanol and cyclohexanone, under mild conditions. MOR-D/Fe (desilicated zeolite supported [FeCl2{eta(3)-HC(pz)(3)}] complex) provides an outstanding catalytic activity (TON up to 2.90 x 10(3)) with the concomitant overall yield of 38%, and can be easy recovered and reused. The MOR or MOR-D supported hydrotris(pyrazol-1-yl)methane iron(II) complex (MOR/Fe and MOR-D/Fe, respectively) was characterized by X-ray powder diffraction, ICP-AES, and TEM studies as well as by IR spectroscopy and N-2 adsorption at -196 degrees C. The catalytic operational conditions (e.g., reaction time, type and amount of oxidant, presence of acid and type of solvent) were optimized. (C) 2013 Elsevier B.V. All rights reserved.

Implementação, validação e análise técnico-económico de alguns parâmetros analíticos no controlo de águas

Mestrado em Engenharia Química

Amarração de plataformas offshore flutuantes com cabos de poliéster

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia Civil na Área de Especialização de Estruturas

Sorption of phenanthrene on agricultural soils

Polyaromatic hydrocarbon (PAH) sorption to soil is a key process deciding the transport and fate of PAH, and potential toxic impacts in the soil and groundwater ecosystems, for example in connection with atmospheric PAH deposition on soils. There are numerous studies on PAH sorption in relatively low organic porous media such as urban soils and groundwater sediments, but less attention has been given to cultivated soils. In this study, the phenanthrene partition coefficient, KD (liter per kilogram), was measured on 143 cultivated Danish soils (115 topsoils, 0–0.25-m soil depth and 28 subsoils, 0.25–1-m depth) by the single-point adsorption method. The organic carbon partition coefficient, KOC (liter per kilogram) for topsoils was found generally to fall between the KOC values estimated by the two most frequently used models for PAH partitioning, the Abdul et al. (Hazardous Waste & Hazardous Materials 4(3):211– 222, 1987) model and Karickhoff et al. (Water Research 13:241–248, 1979) model. A less-recognized model by Karickhoff (Chemosphere 10:833–846, 1981), yielding a KOC of 14,918 Lkg−1, closely corresponded to the average measured KOC value for the topsoils, and this model is therefore recommended for prediction of phenanthrene mobility in cultivated topsoils. For lower subsoils (0.25–1-m depth), the KOC values were closer to and mostly below the estimate by the Abdul et al. (Hazardous Waste & Hazardous Materials 4(3):211–222, 1987) model. This implies a different organic matter composition and higher PAH sorption strength in cultivated topsoils, likely due to management effects including more rapid carbon turnover. Finally, we applied the recent Dexter et al. (Geoderma 144:620–627, 2008) theorem, and calculated the complexed organic carbon and non-complexed organic carbon fractions (COC and NCOC, grams per gram). Multiple regression analyses showed that the NCOC-based phenanthrene partition coefficient (KNCOC) could be markedly higher than the COCbased partition coefficient (KCOC) for soils with a clay/OC ratio <10. This possibly higher PAH sorption affinity to the NCOC fraction needs further investigations to develop more realistic and accurate models for PAH mobility and effects in the environment, also with regard to colloid-facilitated PAH transport.

PAH air pollution at a Portuguese urban area: carcinogenic risks and sources identification

This study aimed to characterize air pollution and the associated carcinogenic risks of polycyclic aromatic hydrocarbon (PAHs) at an urban site, to identify possible emission sources of PAHs using several statistical methodologies, and to analyze the influence of other air pollutants and meteorological variables on PAH concentrations.The air quality and meteorological data were collected in Oporto, the second largest city of Portugal. Eighteen PAHs (the 16 PAHs considered by United States Environment Protection Agency (USEPA) as priority pollutants, dibenzo[a,l]pyrene, and benzo[j]fluoranthene) were collected daily for 24 h in air (gas phase and in particles) during 40 consecutive days in November and December 2008 by constant low-flow samplers and using polytetrafluoroethylene (PTFE) membrane filters for particulate (PM10 and PM2.5 bound) PAHs and pre-cleaned polyurethane foam plugs for gaseous compounds. The other monitored air pollutants were SO2, PM10, NO2, CO, and O3; the meteorological variables were temperature, relative humidity, wind speed, total precipitation, and solar radiation. Benzo[a]pyrene reached a mean concentration of 2.02 ngm−3, surpassing the EU annual limit value. The target carcinogenic risks were equal than the health-based guideline level set by USEPA (10−6) at the studied site, with the cancer risks of eight PAHs reaching senior levels of 9.98×10−7 in PM10 and 1.06×10−6 in air. The applied statistical methods, correlation matrix, cluster analysis, and principal component analysis, were in agreement in the grouping of the PAHs. The groups were formed according to their chemical structure (number of rings), phase distribution, and emission sources. PAH diagnostic ratios were also calculated to evaluate the main emission sources. Diesel vehicular emissions were the major source of PAHs at the studied site. Besides that source, emissions from residential heating and oil refinery were identified to contribute to PAH levels at the respective area. Additionally, principal component regression indicated that SO2, NO2, PM10, CO, and solar radiation had positive correlation with PAHs concentrations, while O3, temperature, relative humidity, and wind speed were negatively correlated.

Proposta metodológica para avaliação preliminar de jazigos de shale gas

O potencial de um reservatório de shale gas e influenciado por um grande número de fatores, tais como a sua mineralogia e textura, o seu tipo e maturação de querogénio, a saturação de fluidos, os mecanismos de armazenamento de gás, a profundidade do reservatório e a temperatura e pressão de poros. Nesse sentido, o principal objetivo desta tese foi estabelecer uma metodologia de avaliação preliminar de potenciais jazigos de shale gas (estudo de afloramentos com base numa litoestratigrafia de alta resolução), que foi posteriormente aplicada na Formação de Vale das Fontes (Bacia Lusitânica, Portugal). Esta tese tem a particularidade de contribuir, não só para o aprofundamento da informação a nível geoquímico do local, mas também na abordagem inovadora que permitiu a caracterização petrofísica da Formação de Vale das Fontes. Para a aplicação da metodologia estabelecida, foi necessária a realização dos seguintes ensaios laboratoriais: Rock-Eval 6, picnometria de gás hélio, ensaio de resistência a compressão simples, Darcypress e a difracção de raios-X, aplicando o método de Rietveld. Os resultados obtidos na análise petrofísica mostram uma formação rochosa de baixa porosidade que segundo a classificação ISRM, e classificada como ”Resistente”, para alem de revelar comportamento dúctil e elevado índice de fragilidade. A permeabilidade média obtida situa a Formação no intervalo correspondente as permeabilidades atribuídas aos jazigos de tigh gas, indicando a necessidade de fracturação hidráulica, no caso de uma eventual exploração de hidrocarbonetos, enquanto a difracção de raios-X destaca a calcite, o quartzo e os filossilicatos como os minerais mais presentes na Formação. Do ponto de vista geoquímico, os resultados obtidos mostram que apesar do considerável teor médio de carbono orgânico total, a natureza da matéria orgânica analisada e maioritariamente imatura, composta, principalmente, por querogénio do tipo IV, o que indica a incapacidade de a formação gerar hidrocarbonetos em quantidades economicamente exploráveis.

A Study on Microstructure Characteristics of TEPs-modified Adhesives

Thermally expandable particles (TEPs) were developed by Dow Chemical Co in the early 1970´s [1] and were further developed by others [2, 3]. They are particles made up of a thermoplastic shell filled with liquid hydrocarbon. On heating them, two transformations will occur. One is the softening of shell material and the other is the gasification of the hydrocarbon liquid inside it. As a consequence, the shell will expand as the gas inside it will push the softened shell from inside out causing it to grow in size [4]. When fully expanded, the growth in volume of the particle can be from 50 to 100 times [3]. Owing to this unique behaviour, TEPs are used by the industry in a wide variety of applications mainly for weight reduction and appearance improvement for thermoplastics, inks, and coatings. In adhesive bonding, TEPs have been used for recycling purposes. Moreover, TEPs might be used to modify structural adhesives for other new purposes, such as: to increase the joint strength by creating an adhesive functionally modified along the overlap of the joint by gradual heating and/or to heal the adhesive in case of damage.

Stochastic modeling of the thermal and catalytic degradation of polyethylene using simultaneous DSC/TG analysis

Dissertação para obtenção do Grau de Mestre em Engenharia Química e Bioquímica