Author
Paula Brandão
Other affiliations: Punjabi University, University of Manchester, Oak Ridge National Laboratory
Bio: Paula Brandão is an academic researcher from University of Aveiro. The author has contributed to research in topics: Ligand & Crystal structure. The author has an hindex of 28, co-authored 234 publications receiving 3011 citations. Previous affiliations of Paula Brandão include Punjabi University & University of Manchester.
Topics: Ligand, Crystal structure, Schiff base, Chemistry, Catalysis
Papers published on a yearly basis
Papers
More filters
TL;DR: In this paper, the facile synthesis of two other titanosilicates, AM-1 and AM-4, have also been reported, viz. SEM, powder XRD, single-and triple-quantum 23Na and 29Si MAS NMR, water adsorption measurements, and TGA/DSC.
Abstract: Synthetic analogues of the microporous minerals umbite (AM-2) and penkvilksite, polytype 2O (AM-3), have been prepared. The facile syntheses of two other titanosilicates, AM-1 and AM-4, have also been reported. AM-1 and the previously reported, layered titanosilicate known as JDF-L1 have been shown to have the same structure. AM-4 is a new microporous titanosilicate with a unique and unknown structure, containing eight different Na sites. All AM-n materials have been characterized by several techniques, viz. SEM, powder XRD, single- and triple-quantum 23Na and 29Si MAS NMR, water adsorption measurements, and TGA/DSC. AM-n materials are thermally stable up to ca. 600 °C. The dehydration−hydration processes seem to be reversible (or quasi reversible) for AM-1, -2, and -3 but not so for AM-4.
128 citations
TL;DR: In this article, the isomerization of glucose was studied in water at 100°C in the presence of various metallosilicates as solid base catalysts, namely the titanosilicates ETS-10, eTS-4 and AM-4.
Abstract: The isomerization of glucose was studied in water at 100 °C in the presence of various metallosilicates as solid base catalysts, namely the titanosilicates ETS-10, ETS-4 and AM-4, a sodium yttrium silicate analogue of the mineral montregianite (AV-1), an alkali calcium silicate analogue of the mineral rhodesite (AV-2), and a calcium silicate analogue of the mineral tobermorite (TOB). Fructose yields in the range of 20–40% were obtained within 2-h reaction. These results are either similar to or better than those achievable with the commercial zeolite Na–X or aqueous NaOH. Depending on the nature of the catalyst, different factors account for deactivation, such as loss of crystallinity, sodium/potassium leaching and surface passivation. Two of the more promising materials, AV-1 and TOB, were quite stable under the reaction conditions, as evidenced by powder X-ray diffraction analyses for the fresh and used catalysts. The used TOB catalyst exhibited a steady performance when recycled and for AV-1 fructose yields increased in recycling runs. The activity of the solid bases, with the exception of AV-1, could be correlated with the basicity characterized by Knoevenagel condensation tests.
102 citations
TL;DR: Microporous AM-11 crystalline niobium silicates were studied as solid acid catalysts for the dehydration of xylose in a water-toluene solvent mixture at 140-180°C as discussed by the authors.
Abstract: Microporous AM-11 crystalline niobium silicates were studied as solid acid catalysts for the dehydration of xylose in a water-toluene solvent mixture at 140–180 °C. After 6 h at 160 °C, xylose conversions of up to 90% and furfural yields of up to 50% were achieved, and the catalysts could be reused without loss of activity or selectivity. The calcined AM-11 catalysts gave higher furfural yields than HY zeolite and mordenite, under identical reaction conditions. Ordered mesoporous MCM-41-type niobium silicates with Si/Nb molar ratios of either 25 or 50 were also found to be recyclable catalysts for xylose dehydration, and gave furfural yields consistently in the range of 34–39% (after 6 h reaction at 160 °C).
87 citations
TL;DR: It is revealed that although dihydrogen phosphate is less charged than sulfate, it is still appreciably bound by the receptor at low pH, suggesting that the pyridyl nitrogen is accepting hydrogen bonds from diHydrogen phosphate.
Abstract: A hexaamine cage with pyridyl spacers was synthesized in good yield by a [2+3] Schiff-base condensation followed by sodium borohydride reduction. The protonation constants of the receptor as well as its association constants with Cl−, NO3−, AcO−, ClO4−, SO42−, H2PO4−, and H2AsO4− were determined by potentiometry at 298.2 ± 0.1 K in H2O/MeOH (50:50 v/v) and at ionic strength 0.10 ± 0.01 M in KTsO. These studies revealed that although dihydrogen phosphate is less charged than sulfate, it is still appreciably bound by the receptor at low pH, suggesting that the pyridyl nitrogen is accepting hydrogen bonds from dihydrogen phosphate. It is also shown that dihydrogen phosphate is capable of effectively competing with sulfate for the receptor at higher pH, being selective for hydrogen phosphate at pH about 7.0. 31P NMR experiments supported these findings. The fact that the receptor shows such a marked preference for hydrogen phosphate based mainly in its hydrogen bond accepting/donating ability in a highly comp...
73 citations
71 citations
Cited by
More filters
TL;DR: Dehydroisomerization of Limonene and Terpenes To Produce Cymene 2481 4.2.1.
Abstract: 3.2.3. Hydroformylation 2467 3.2.4. Dimerization 2468 3.2.5. Oxidative Cleavage and Ozonolysis 2469 3.2.6. Metathesis 2470 4. Terpenes 2472 4.1. Pinene 2472 4.1.1. Isomerization: R-Pinene 2472 4.1.2. Epoxidation of R-Pinene 2475 4.1.3. Isomerization of R-Pinene Oxide 2477 4.1.4. Hydration of R-Pinene: R-Terpineol 2478 4.1.5. Dehydroisomerization 2479 4.2. Limonene 2480 4.2.1. Isomerization 2480 4.2.2. Epoxidation: Limonene Oxide 2480 4.2.3. Isomerization of Limonene Oxide 2481 4.2.4. Dehydroisomerization of Limonene and Terpenes To Produce Cymene 2481
5,127 citations
TL;DR: An updated evaluation of potential target structures using similar selection methodology, and an overview of the technology developments that led to the inclusion of a given compound are presented.
3,536 citations