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- Incorporation of niobium in SAPO-11 materials: Synthesis and characterizationPublication . Bertolo, Raquel; Martins, Angela; Silva, João; Ribeiro, Filipa; Ribeiro, Fernando Ramoa; Fernandes, AugusteThe present work concerns a new synthesis approach to prepare niobium based SAPO materials with AEL structure and the characterization ofNb species incorporated within the inorganic matrixes. The SAPO-11 materials were synthesized with or without the help of a small amine, methylamine (MA) as co-template, while Nb was added directly during the preparation of the initial gel. Structural, textural and acidic properties of the different supports were evaluated by XRD, TPR, UV-Vis spectroscopy, pyridine adsorption followed by IR spectroscopy and thermal analyses. Pure and well crystalline Nb based SAPO-11 materials were obtained, either with or without MA, using in the initial gel a low Si content of about 0.6. Increasing the Si content of the gel up to 0.9 led to an important decrease of the samples crystallinity. Niobium was found to incorporate the AEL pores support as small Nb2O5 oxide particles and also as extra framework cationic species (Nb5+), compensating the negative charges from the matrix and generating new Lewis acid sites. (C) 2011 Elsevier Inc. All rights reserved.
- 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.
- 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.