Residue curves map analysis for tert-amyl methyl ether synthesis by reactive distillation in kinetically controlled conditions with energy-saving evaluation

Distillation is a largely used separation operation, but at the same time it is intensively energy consuming. Distillation columns need huge amount of energy due to evaporation steps involved; more than half of the process heat distributed to plant operations ends up in the reboilers of distillation columns. ∞/∞ analysis is a framework that allows studying distillation systems, checking the feasibility, detecting multiple steady states and getting the influence of the distillate flow rate and recycle streams on purities in early stage of process design. Also, ∞/∞ analysis is useful to evaluate new alternatives for existing processes and to propose energy-efficient alternatives by process integration. Process intensification is an issue of constant interest, providing strategies to develop more effective and cheaper technologies with lower environmental impact. The originality of this paper lies in the applicability of this framework to kinetically controlled reactive distillation including hybrid systems. TAME synthesis is used as an illustrative example. Energy savings obtained by using reactive distillation are evaluated comparing with the traditional system consisting of reactor and distillation columns. The solution proposed, subsequent to the validation by rigorous simulation, offers a 20% decrease in the number of stages and a reboiler energy saving of 10%.     

Bioreactors Based on Monolith‐Supported Ionic Liquid Phase for Enzyme Catalysis in Supercritical Carbon Dioxide

Bioreactors with covalently supported ionic liquid phases (SILP) were prepared as polymeric monoliths based on styrene–divinylbenzene or 2‐hydroxyethyl methacrylate–ethylene dimethacrylate, and with imidazolium units loadings ranging from 54.7 to 39.8 % wt IL per gram of polymer. The SILPs were able to absorb Candida antarctica lipase B (CALB), leading to highly efficient and robust heterogeneous biocatalysts. The bioreactors were prepared as macroporous monolithic mini‐flow systems and tested for the continuous flow synthesis of citronellyl propionate in supercritical carbon dioxide (scCO₂) by transesterification. The catalytic activity of these mini‐flow‐bioreactors remained practically unchanged for seven operational cycles of 5 h each in different supercritical conditions. The best results were obtained when the most hydrophobic monolith, M‐SILP‐ 8 ‐CALB, was assayed at 80 °C and 10 M Pa, reaching a total turnover number (TON) of 35.8×10⁴ mol product/mol enzyme. The results substantially exceeded those obtained for packed‐bed reactors with supported silica‐CALB‐Si‐4 catalyst under the same experimental conditions.     

The effects of freezing and freeze-drying of Oenococcus oeni upon induction of malolactic fermentation in red wine

Summary The use of Oenococcus oeni starter cultures for the induction of malolactic fermentation (MLF) in wine permits control over the timing of the process and the quality of the wine. Successful inoculation of bacterial starter cultures into wine depends on the selection of suitable strains and on the preparation and conservation of those cultures. Medium for Leuconostoc oenos (MLO) is the best medium for easy and rapid growth of O. oeni cultures under laboratory controlled conditions for isolation and identification. However, this study showed that O. oeni cells inoculated in MLO failed to induce MLF in wine while cells grown in Medium of Preculture (MP) or wine, stored at −20 °C or freeze-dried retained the ability to induce MLF when inoculated in wine. Our results suggest that the use of freeze-dried cultures of O. oeni previously grown in MP is the best choice for industrial application.     

Use of chlorophyll and carotenoid pigment composition to determine authenticity of virgin olive oil

The chlorophyll and carotenoid pigment profile of 50 mono-variety virgin olive oils was used to develop an index of authenticity for the product. The presence of carotenoids other than those described, or chlorophyll derivatives at another level of degradation, were found to be determing elements of this index for “virgin” olive oil quality. In addition, the ratio of chlorophyll/carotenoid should be around 1, and the ratio of minor carotenoids/lutein should be about 0.5, with a limited variability. These characteristics may be expected of virgin olive oil in general and are independent of variety. Finally, the percentage of lutein, violaxanthin, and total pigment content may be used to distinguish between mono-variety virgin olive oils.     

Sol–Gel Preparation of Lead Zirconate Titanate Powders and Ceramics: Effect of Alkoxide Stabilizers and Lead Precursors

Lead zirconate titanate (PZT) (52/48) powders were prepared by a sol–gel process, using different raw materials to introduce the lead component together with several solvents and chemical modifying agents. A study of the effect of these variables on crystallization behavior was conducted to determine the best conditions for preparing monophasic submicrometer-sized PZT perovskite powders in the morphotropic region. In the present work, well-crystallized, submicrometer-sized single-phase perovskite PZT powders were obtained after heat treatment at 600°C for 1 h. The dependence of this crystallization temperature on the preparation conditions was observed. The sol–gel-derived submicrometer-sized PZT powders were sintered to ∼96% of relative density after 2 h at 950°–970°C. The sintered ceramics exhibited a dielectric permittivity of 1000, a piezoelectric coefficient of 135 pC·N⁻¹, a remanent polarization of 20 μC·cm⁻², and a coercive field of 10.6 kV·cm⁻¹.     

Physical Properties of Chalcogenide and Chalcohalide Glasses

The physical properties of glasses in the Ge₃₀As₁₀Se_{(60— x )}Te _x system with x = 25, 28, 30, and 35 at.% Te, the Ge₃₀As₁₀Se₃₀Te_{(30— y )}I _y system with y = 5, 10, 20, and 30 at.% I, the Ge₃₀As₁₀Se₃₅Te_{(25— z )}I _z system with z = 2, 6, 10, and 20 at.% I, and the [Ge₃₀As₁₀Se₃₀Te₃₀]_{(100— w )}I _w system with w = 0, 5, 10, and 20 at.% I have been investigated. The changes in the glass transition temperature, density, coefficient of thermal expansion, hardness, and viscosity are attributed to the delocalized metallic bonding character of Te in the substitution of Te for Se in the Ge-As-Se-Te glass system and the network-terminating role of iodine in the substitution of I for Te in the Ge-As-Se-Te-I glass system, respectively.     

Transparent glass and glass-ceramic in the binary system NaPO3-Ta2O5

Transparent and homogeneous tantalum phosphate glasses were prepared in the binary system (100-x)NaPO₃-xTa₂O₅ with x varying from 10 to 50 mol%. Thermal, structural, and optical properties, as well as crystallization mechanisms, were investigated by thermal analysis, X-ray diffraction, Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopies, optical absorption, transmission electron microscopy in terms of Ta₂O₅ content. FTIR and Raman results support the tantalum insertion in the phosphate chains with [TaO₆] polyhedra cross-linking the phosphate units. At higher Ta₂O₅ content, [TaO₆] clusters are formed and connected to the phosphate network by P-O-Ta bonds. This structural evolution is in good agreement with the thermal features measured by differential scanning calorimetry (DSC) with a strong increase of the T_g temperatures up to 920°C, high thermal stability against crystallization for low Ta₂O₅ content and increasing of crystallization tendency for the most Ta-concentrated samples. Besides, due to the progressive insertion of [TaO₆] units, the precipitation of Na₂Ta₈O₂₁ perovskite-like phase was identified in the sample with 50 mol% of Ta₂O₅. The optimal heat treatment conditions were identified using DSC measurements and a transparent glass-ceramic from 50NaPO₃ to 50Ta₂O₅ composition was prepared. The obtaines glass-ceramic has great potential for optical applications, such as host for rare-earth ions, nonlinear optical materials, and ferroelectric domain.