Browsing by Author "Silva, Viviana M.T.M."
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- Analysis of the synthesis of 1,1-dibutoxyethane in a simulated moving-bed adsorptive reactorPublication . Graça, Nuno S.; Pais, Luís S.; Silva, Viviana M.T.M.; Rodrigues, AlírioThe synthesis of 1,1-dibutoxyethane was carried out in a simulated moving-bed pilot unit LICOSEP 12-26 (Novasep, France) with 12 columns packed with the commercial ion-exchange resin Amberlyst 15(Rohm & Haas, France). Experimentally the best raffinate purity obtained was 85% with a productivity of 5.04 kg L−1 d−1 and a desorbent consumption of 13.5 L kg−1. The TMBR model was used to construct reaction/separation regions and to study the influence of feed composition, switching time, flow rates and mass-transfer resistances on the SMBR performance. The SMBR process shows a potential to be a competitive, efficient and environmentally friendly way to produce 1,1-dibutoxyethane and other acetals.
- Dynamic study of the synthesis of 1,1-dibutoxyethane in a fixed-bed adsorptive reactorPublication . Graça, Nuno S.; Pais, Luís S.; Silva, Viviana M.T.M.; Rodrigues, AlírioThe synthesis of 1,1-Dibutoxyethane in a fixed-bed adsorptive reactor using Amberlyst 15 was studied for the first time. The adsorption of non-reactive pairs was investigated experimentally, at 25 °C, by frontal chromatography in a fixed-bed adsorber. In order to avoid the immiscibility of the liquid phase, the liquid-liquid equilibrium for the mixture 1-butanol/water was studied. The multicomponent equilibrium adsorption data was assumed to follow the modified Langmuir type isotherm. Reaction experiments of 1,1-Dibutoxyethane production and column regeneration were performed in the fixed-bed adsorptive reactor. This work will enable further developments in chromatographic reactors aiming at the 1,1-Dibutoxyethane process intensification.
- Isobaric vapor−liquid equilibrium data for binary system of glycerol ethyl acetal and acetonitrile at 60.0 kPa and 97.8 kPaPublication . Constantino, Dânia S.M.; Pereira, Carla S.M.; Pinho, Simão; Silva, Viviana M.T.M.; Rodrigues, AlírioIsobaric vapor−liquid equilibrium (VLE) data for the binary mixture of glycerol ethyl acetal (GEA) and acetonitrile were measured at 60.0 kPa and 97.8 kPa, using a dynamic recirculating still. The VLE data were correlated using the nonrandom two-liquid (NRTL) and universal quasichemical activity coefficient (UNIQUAC) models, and the interaction parameters of this mixture were estimated. The experimental procedure was checked by measuring VLE data at 97.8 kPa of the well known system acetone/methanol showing high conformity, as given by applying a set of VLE consistency tests. The vapor pressure of GEA was measured, for the first time, in the temperature range from 371.85 K to 456.85 K, and it is described by the following expression: ln PGEA sat (Pa) = 24.17 − 5781/T(K). The information collected is of utmost importance for the purification of GEA synthesized using simulated moving bed reactor technology.
- Oxygenated biofuels from butanol for diesel blends: synthesis of the acetal 1,1-dibutoxyethane catalyzed by amberlyst-15 Ion-exchange resinPublication . Graça, Nuno S.; Pais, Luís S.; Silva, Viviana M.T.M.; Rodrigues, AlírioThe synthesis of 1,1-dibutoxyethane or acetaldehyde dibutylacetal was studied in a batch reactor by reacting butanol and acetaldehyde in a liquid phase, using Amberlyst-15 as the catalyst. The reaction equilibrium constant was experimentally determined in the temperature range 20-40 °C at 6 atm, where Ka = 0.00959 exp[1755.3/T (K)]. The standard properties of the reaction at 298.15 K were estimated: ΔH° = -14.59 kJ mol-1, ΔG° = -3.07 kJ mol-1, and ΔS° = -38.64 J mol-1 K-1. Kinetic experiments were performed in the temperature range 10-50 °C at 6 atm. A two-parameter kinetic law based on a Langmuir-Hinshelwood rate expression, using activity coefficients from the UNIFAC method, was used. The kinetic parameters are kc = 2.39 E9 exp[-6200.9/T (K)] (mol gcat -1 min-1) and ks,D = 2.25 E-4 exp[3303.1/T (K)]. The activation energy of the reaction is 51.55 kJ mol-1. This work is an important step for further implementation of an integrated reaction-separation process, such as a simulated moving-bed reactor.
- Process intensification for the ethyl lactate synthesis : integrated pervaporation reactorPublication . Pereira, Carla S.M.; Silva, Viviana M.T.M.; Pinho, Simão; Rodrigues, AlírioEthyl lactate is an important organic ester, which is biodegradable, produced by renewable resources and can be used as food additive, perfumery, flavor chemicals, solvent and pharmaceutical preparations[1]. It is a green solvent and could replace a range of environment-damaging halogenated and toxic solvents (for example: Nmethylpyrrolidone, toluene)[2]. The conventional way to produce ethyl lactate is the esterification of lactic acid with ethanol in the presence of an acid catalyst, according to the reaction: Ethanol + Lactic Acid ¬¾H ®Ethyl Lactate + Water + The conversion of this reaction is limited by the chemical equilibrium and in order to obtain higher ethyl lactate yields it is necessary to shift the reaction towards products formation.
- Synthesis of 1,1-dibutoxyethane in a simulated moving bed adsorptive reactorPublication . Graça, Nuno S.; Pais, Luís S.; Silva, Viviana M.T.M.; Rodrigues, AlírioThe synthesis of 1,1-Dibutoxyethane was carried out in a Simulated Moving Bed pilot unit LICOSEP 12-26 (Novasep, France) with 12 columns packed with the commercial ionexchange resin Amberlyst 15 (Rohm & Haas, France). Experimentally it was obtained a raffinate purity of 85% with a productivity of 5,04 Kg.L-1.d-1 and a desorbent consumption of 15, 5 L.Kg-1. The influence of the different operation parameters was studied by simulation. The results showed that the SMBR process presents a potential to be a competitive, efficient and environmentally friendly way to produce 1,1- Dibutoxyethane and other acetals.
- Thermal effects on the synthesis of 1,1-dibutoxyethane in a fixed-bed adsorptive reactorPublication . Graça, Nuno S.; Pais, Luís S.; Silva, Viviana M.T.M.; Rodrigues, AlírioThe effects of temperature on the synthesis of 1,1-dibutoxyethane (DBE) in a fixedbed adsorptive reactor were studied by performing both adsorption/desorption and reaction/regeneration experiments at 15 and 35 °C. The Langmuir-type isotherm parameters at 15 and 35 °C were obtained from the adsorption/desorption experiments. The reaction/regeneration experiments showed an increase in both conversion and productivity with increasing temperature. Isothermal and nonisothermal mathematical models were used to simulate the reactor operation with different Damköhler numbers. The simulated results suggest that the reactor productivity can be improved by using the adiabatic operation mode on the fixedbed adsorptive reactor, obtaining a productivity for DBE of 71.8 mol kg–1h–1.
- Thermal effects on the synthesis of acetals in a simulated moving bed adsorptive reactorPublication . Graça, Nuno S.; Pais, Luís S.; Silva, Viviana M.T.M.; Rodrigues, AlírioThe effect of temperature on simulated moving bed adsorptive reactor performance was studied by simulation with both isothermal and non-isothermal mathematical models. Simulated results with isothermal mathematical model showed an improvement of SMBR performance criteria and the increase on reaction/separation regions with temperature. It was shown by simulations with non-isothermal mathematical model that the SMBR performance can be also improved by using the adiabatic operation mode. This study of the thermal effects on SMBR operation is an important step for a further implementation of energy integration concepts such as autothermal operation.