Browsing by Author "Almeida, Ruben"
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- Gas-phase conversion of glycerol to allyl alcohol over vanadium-supported zeolite betaPublication . Almeida, Ruben; Filipa Ribeiro, M.; Fernandes, Auguste; Lourenço, João PauloVanadium oxide supported beta zeolite (Si/Al = 25, 4% V) was used as catalyst for the one-pass gas-phase conversion of glycerol to allyl alcohol without any external reductant. The catalytic data strongly suggest a consecutive reactions path involving the dehydration to acrolein over the zeolite acid sites followed by a selective reduction through a hydrogen-transfer reaction. Acidity is expected to play a major role in what concerns the selectivity, as demonstrated by the catalytic results obtained by the impregnation of vanadium on a previously Cs-exchanged sample that achieved ca. 30% selectivity to allyl alcohol at ca. 20% glycerol conversion.
- Gas-phase conversion of glycerol to allyl alcohol over vanadium-supported zeolite betaPublication . Almeida, Ruben; Ribeiro, M. Filipa; Fernandes, Auguste; Lourenço, João P.Vanadium oxide supported beta zeolite (Si/Al=25, 4% V) was used as catalyst for the one-pass gas-phase conversion of glycerol to allyl alcohol without any external reductant. The catalytic data strongly suggest a consecutive reactions path involving the dehydration to acrolein over the zeolite acid sites followed by a selective reduction through a hydrogen-transfer reaction. Acidity is expected to play a major role in what concerns the selectivity, as demonstrated by the catalytic results obtained by the impregnation of vanadium on a previously Cs-exchanged sample that achieved ca. 30% selectivity to allyl alcohol at ca. 20% glycerol conversion.
- N,N′-tetrasubstituted succinamides as new molecules for liquid–liquid extraction of Pt(IV) from chloride mediaPublication . Costa, Maria Clara; Almeida, Ruben; Assunção, Ana; Costa, Ana M. Rosa da; Nogueira, Carlos; Paiva, Ana PaulaDue to the increasing demand of platinum group metals (PGM’s), among which platinum, the search for new alternatives aiming to their extraction and recovery is nowadays of great importance. Thus, two N, N0-tetrasubstituted succinamides, N,N0-dicyclohexyl-N,N0-dimethylsuccinamide (DMDCHSA) and N,N0- dimethyl-N,N0-diphenylsuccinamide (DMDPHSA) were synthesized and investigated, for the first time, as potential molecules for the liquid–liquid extraction of Pt(IV) from chloride solutions. According to the extraction and stripping results obtained in a single contact, these succinamides can be considered promising extractants for the recovery of platinum(IV) from hydrochloric acid media, since DMDCHSA is able to extract more than 95% Pt(IV) from 4 M HCl or higher concentrations, and DMDPHSA extracts 80% and 92% Pt(IV) from 6 M and 8 M HCl solutions, respectively. Furthermore, platinum(IV) can successfully be stripped through a simple contact with seawater: 93% Pt(IV) were recovered from DMDCHSA, while 60% stripping were obtained from DMDPHSA. For each compound, the time necessary to reach equilibrium, and the effects of the type of diluent and different extractant concentrations on the Pt(IV) extraction percentage were investigated. The loading capacity of DMDCHSA and DMDPHSA toward Pt (IV) was also evaluated, and the results show that both extractants present a very high loading capacity. In addition, data obtained from successive extraction-stripping cycles suggest a good stability pattern for both succinamides.