No abstract

The present work aims at establishing reliable activity coefficient model for vapor−liquid equilibrium (VLE) of the system water + ethanol + glycerol, with an emphasis on the application in ethanol dehydration by extractive distillation. New experimental data were reported for ternary VLE at 100 kPa, boiling temperature of water + glycerol at 101.33 kPa, and infinite dilution activity coefficient of water and ethanol, respectively, in glycerol at five temperatures of 313.15 K to 393.15 K. The NRTL equation was used for the modeling. For extending the composition and temperature range of data source, literature data of binary VLE of water + ethanol, infinite dilution activity coefficients of water + ethanol, and excess enthalpies of water + glycerol were also used for optimization of the NRTL parameters. The correlation showed that the azeotrope of water + ethanol can be removed at a glycerol mass fraction of 0.0902. The experimental results were compared graphically with those of calculations, showing good agreement. Comparisons were also presented for experimental results and correlations available in the literature. ■ INTRODUCTIONUsing glycerol as entrainer for ethanol dehydration is an interesting topic because it aims at reducing the energy demand for bioethanol production by use of a coproduct of biodiesel. Herein, bioethanol and biodiesel are both biofuels that have received worldwide interest in recent years. Glycerol has many attractive features. It is nontoxic and environment compatible. Due to the large-scale production of biodiesel, glycerol is highly available and inexpensive. Under temperatures below 100°C, the vapor pressure of glycerol is very low. It is regarded as a typical example of biobased solvent and has received increasing attention for its use in the chemical industry. 1 The mixture of water + ethanol forms a minimum boiling point azeotrope at about 0.96 mass fraction of ethanol. Simple distillation cannot be used to distill ethanol above the azeotropic composition. The feasibility of using glycerol for extractive distillation has been verified by vapor−liquid equilibrium (VLE) measurements by Lee et al., 2 Souza et al., Results showed that the azeotrope of water + ethanol will be effectively removed by the addition of glycerol. Energy evaluation and process optimization have also been reported by García-Herreros et al., 5 Navarrete-Contreras et al., 6 and Gil et al. 7,8 NRTL parameters in the database of Aspen Plus process simulator were frequently used for the calculation of activity coefficients in the liquid phase.We have calculated VLE for the ternary system water (1) + ethanol (2) + glycerol (3) using NRTL parameters suggested by Souza et al.,4 and Aspen Plus (APV80 VLE-IG), respectively. Results showed significant deviations for different sources. Moreover, the infinite dilution activity coefficient of water in glycerol, γ 13 ∞ , deviated greatly and showed different trends of temperature dependence. Using the parameters of APV80 VLE-IG, the calculated value of γ 13 ∞ was less tha...

Metal-doped (Mn, Cu, Ni, and Fe) cobalt oxides were prepared by a coprecipitation method and were used as catalysts for the total oxidation of toluene and propane. The metal-doped catalysts displayed the same cubic spinel Co3O4 structure as the pure cobalt oxide did; the variation of cell parameter demonstrated the incorporation of dopants into the cobalt oxide lattice. FTIR spectra revealed the segregation of manganese oxide and iron oxide. The addition of dopant greatly influenced the crystallite size, strain, specific surface area, reducibility, and subsequently the catalytic performance of cobalt oxides. The catalytic activity of new materials was closely related to the nature of the dopant and the type of hydrocarbons. The doping of Mn, Ni, and Cu favored the combustion of toluene, with the Mn-doped one being the most active (14.6 × 10−8 mol gCo−1 s−1 at 210 °C; T50 = 224 °C), while the presence of Fe in Co3O4 inhibited its toluene activity. Regarding the combustion of propane, the introduction of Cu, Ni, and Fe had a negative effect on propane oxidation, while the presence of Mn in Co3O4 maintained its propane activity (6.1 × 10−8 mol gCo−1 s−1 at 160 °C; T50 = 201 °C). The excellent performance of Mn-doped Co3O4 could be attributed to the small grain size, high degree of strain, high surface area, and strong interaction between Mn and Co. Moreover, the presence of 4.4 vol.% H2O badly suppressed the activity of metal-doped catalysts for propane oxidation, among them, Fe-doped Co3O4 showed the best durability for wet propane combustion.