Browsing by Author "Fernandes, Auguste"
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- Alkali-activated binders produced from petrochemical fluid catalytic cracking catalyst wastePublication . Costa, Carla; Ferreira, Cátia; Ribeiro, Maria Filipa; Fernandes, AugusteThis paper describes research on the viability of producing alkali activated binders using the aluminosilicate catalyst waste-generated by the fluid catalytic cracking (wFCC) unit in the Portuguese oil refinery company-as precursor. For this purpose, alkali-activated wFCC catalyst based mortars and cement pastes were produced. Tests were carried out to evaluate the effect of initial solids composition (wFCC catalyst/Ca(OH) 2 ratio) on mortars workability or mechanical strength. The mineralogy and microstructure of the hardened alkali activated wFCC catalyst pastes were studied by means of Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The results obtained at macroscale showed that the content of Ca(OH) 2 incorporated in the binder has a significant effect on compressive strength of hardened mortars. At microscale, FTIR and XRD results confirmed the occurrence of alkali-activation of the wFCC catalyst which leads to the formation of distinctive amorphous and crystalline products. Moreover, the obtained results also suggest that initial solids composition influences the alkali-activation reaction kinetics and mechanism.
- An insight into dapsone co-crystals: sulfones as participants in supramolecular interactionsPublication . Martins, Inês; Martins, Marta; Fernandes, Auguste; André, Vânia; Duarte, M. TeresaHerein we disclose a new pathway for the design of dapsone co-crystals exploring the formation of N-H center dot center dot center dot O/N interactions using amide and pyridinic derivatives as potential co-formers. Two new co-crystals of dapsone, a sulfonamide antibiotic, with epsilon-caprolactam and 4,4'-bipyridine have been synthesized preferentially by traditional solution techniques, but mechanochemistry has also been addressed. The full structural characterization of these forms is discussed and shows that: (a) in the co-crystal with epsilon-caprolactam the typical N-NH2 center dot center dot center dot O-SO2 interactions of dapsone molecules and the cages formed between them are disrupted by a new N-NH2 center dot center dot center dot O-CONH interaction, in which epsilon-caprolactam molecules further form amide center dot center dot center dot amide R-2(2)(8) synthons and (b) in the co-crystal with 4,4'-bipyridine, the N-NH2 center dot center dot center dot O-SO2 interactions between dapsone molecules are maintained and additional N-NH2 center dot center dot center dot N-pyridine interactions are responsible for the formation of 4,4'-bipyridine channels between dapsone cages. Moreover, the thermal stability of these co-crystals is also discussed, showing that the co-formers leave the structure and hence the reported melting corresponds to the melting of pure dapsone.
- Ball milling modified SAPO-11 based catalysts for n-Decane hydroisomerizationPublication . Ferreira, Luisa; Ribeiro, Filipa; Fernandes, Auguste; Martins, AngelaBifunctional Pt/SAPO-11 catalysts were prepared using as acid matrix the microporous silico-aluminophosphate, SAPO-11, synthesized under microwave radiation. After synthesis, the material was physically modified using a ball mill, changing the grinding time but keeping frequency constant. The metal function (0.5 wt.% Pt) was introduced through mechanical mixture with commercial Pt loaded alumina. The catalysts were characterized by several techniques: powder X-Ray Diffraction, pyridine adsorption followed by infrared spectroscopy, low temperature N-2 adsorption, Hg intrusion porosimetry and electronic microscopy (SEM). The characterization data show modifications of structural and textural properties of the samples as the milling time increases. The catalytic behaviour of Pt/SAPO-11 materials was studied for hydroisomerization of long chain n-alkanes, using n-decane as model molecule, aiming to increase the production of mono-branched isomers. The catalytic results show that, under optimized milling conditions (60 min; 50 Hz) the selectivity into mono-branched isomers increased when compared with parent catalyst.
- Effects of oxidante acid treatments on carbon-templated hierarchical SAPO-11 materials: synthesis, characterization and catalytic evaluation in n-decane hydroiosomerizationPublication . Bertolo, Raquel; Silva, João; Ribeiro, Filipea; Maldonado-Hodar, Francisco J.; Fernandes, Auguste; Martins, Ângela Maria PereiraHierarchical SAPO-11 was synthesized using a commercial Merck carbon as template. Oxidant acid treatments were performed on the carbon matrix in order to investigate its influence on the properties of SAPO-11. Structural, textural and acidic properties of the different materials were evaluated by XRD, SEM, N-2 adsorption, pyridine adsorption followed by IR spectroscopy and thermal analyses. The catalytic behavior of the materials (with 0.5 wt.% Pt, introduced by mechanic mixture with Pt/Al2O3), were studied in the hydroisomerization of n-decane. The hierarchical samples showed higher yields in monobranched isomers than typical microporous SAPO-11, as a direct consequence of the modification on both porosity and acidity, the later one being the most predominant. (C) 2014 Elsevier B.V. All rights reserved.
- Enhancement of sintering resistance of CaO-based sorbents using industrial waste resources for Calooping in the cement industryPublication . Teixeira, P.; Mohamed, Ismail; Fernandes, Auguste; Silva, João; Ribeiro, M Filipa; Pinheiro, CarlaKeeping a high stability and CO2 capture capacity of CaO-based sorbents during the Ca-looping process is still a challenge. The main goal and the innovative idea addressed in this study consists of investigating if solid industrial waste resources such as a coal fly ash (CFA) and a spent Fluid Catalytic Cracking (SFCC) catalyst, can be used as particle spacers to improve the sintering resistance of two CaO-based sorbents. These two inert industrial waste materials are used in the present work for increasing the CaO particles separation and consequently, reducing their coalescence and hindering severe sintering at the high Ca-looping temperatures. There are currently no studies in the literature on the use of industrial SFCC wastes in blends with CaO based sorbents acting as CaO particles spacer with the objective of reducing the Ca-looping sorbents deactivation along the cycles of carbonation-calcination. Despite the mineralogical and textural differences between the CFA and SFCC catalyst industrial wastes, the tests carried out in a fixed bed laboratory reactor showed that the addition of a small fraction of waste to the CaO sorbent (ca. 10%) seems to be an interesting option to improve the CO2 capture technology efficiency. During the Ca-looping, the volume and stability of sorbent mesopores is essential to achieve higher and stable carbonation conversion values, and since the CFA and SFCC increase the SBET, they contribute to enhance the sintering resistance. The innovative results presented in this study show that the industrial CFA and SFCC wastes have potential to be an economically attractive option thus contributing to reduce the cost of the Ca-looping cycle CO2 capture process, as well as to minimize the adverse environmental impacts of the high volume of industrial wastes generated.
- Exploring the effect of hierarchical porosity in BEA zeolite in Friedel-Crafts acylation of furan and benzofuranPublication . Nunes, Nelson; Carvalho, Ana P.; Elvas Leitao, Ruben; Martins, Filomena; Fernandes, Auguste; Rocha, João; Martins, AngelaHierarchical BEA zeolite was prepared through desilication or desilication followed by acid treatment. The catalytic performance of BEA zeolite samples was evaluated using Friedel-Crafts acylations with two substrates of different molecular sizes, furan (5.7 Å) and benzofuran (6.9 Å), in the presence of acetic anhydride as acylating agent. The application of the simplified Langmuir Hinshelwood kinetic model showed that the size of the substrate leads to different catalytic activities, with improved rate constant and turnover frequency (TOF) solely in the presence of benzofuran for both desilicated and further acid treated samples. The mesopores developed during the zeolite treatments have an important role as transportation channels by reducing diffusion limitations. The application of Quantitative Structure–Property Relationships (QSPR) allowed the finding of the most relevant properties of the zeolite and substrate with impact on the catalytic parameters.
- Modification of MOR by desilication treatments: structural, textural and acidic characterizationPublication . Paixão, Viviana; Carvalho, Ana P.; Rocha, João; Fernandes, Auguste; Martins, AngelaThe effect of several desilication experimental parameters (base concentration, temperature and time) on the characteristics of MOR zeolite was studied. The samples were characterized by X-ray diffraction, Al-27 and Si-29 MAS-NMR, chemical analysis, and FTIR (framework vibration region). The textural characterization was made by N-2 adsorption and the acidity was evaluated by pyridine adsorption followed by FTIR and by the catalytic model reaction of n-heptane cracking. The alkaline treatments promoted the Si extraction from the zeolite framework, without considerable loss of crystallinity and, as it was envisaged, an important increase of the mesoporous structure was attained. A linear correlation between the number of framework Si per unit cell. N-Si and the asymmetric stretching wavenumber, nu(i), was observed. The acidity characterization shows that the desilicated samples exhibit practically the same acid properties than the parent HMOR zeolite. The optimum desilication conditions were those used to obtain sample M/0.2/85/2, i.e., sample treated with 0.2 M NaOH solution at 85 degrees C for 2 h.
- Zooming in with QSPR on Friedel-Crafts acylation reactions over modified BEA zeolitesPublication . Aleixo, Odrigo; Elvas Leitao, Ruben; Martins, Filomena; Carvalho, Ana; Brigas, Amadeu Fernandes; Nunes, Ricardo; Fernandes, Auguste; Rocha, Joao; Martins, Angela; Nunes, NelsonThe catalytic behaviour of hierarchical BEA zeolites with Si/Al ratio of 12.5 and 32 was studied in Friedel-Crafts acylation reactions using furan, anisole and pyrrole as substrates and acetic anhydride as acylating agent. Hierarchical BEA samples were submitted to alkaline and alkaline + acid treatments. Kinetic modelling using nonlinear regressions applied to a simplified Langmuir-Hinshelwood equation showed that the Si/Al ratio of the parent materials strongly influenced the catalytic behaviour. Catalytic results were correlated with physicochemical properties using a Quantitative Structure-Property Relationship (QSPR) methodology. This approach provided detailed information about the role of key properties on the catalytic behaviour, and pointed out which properties should be modified through direct synthesis and/or post-synthesis treatments to obtain materials with optimized catalytic performance.