Search

Ageing behavior is one of the crucial factor for selection of material by designers and engineers, mainly for structural applications. Investigation of the ageing effect on biocomposites would supplement current knowledge and may help in encouraging their uses in real life applications. The current experimental investigation aims to determine the variation in various properties of Bagasse fibers reinforced Poly Lactic Acid (PLA) biocomposites during accelerated thermal ageing. Specimens of biocomposite were fabricated and exposed to temperature cycles of −20 °C and 65 °C (12 h each) for 12 weeks and characterized after every 4 weeks of exposure. Tensile and flexural properties exhibited steady improvement on exposure up to 8 weeks, followed by a reduction after ageing for 12 weeks. It can be concluded from X-ray diffraction (XRD) and dynamic mechanical analysis (DMA) that significant change in crystalline and glass transition behavior happens during the exposure period.

Transesterification of propylene carbonate (PC) and ethanol is a potent non-phosgene route for the synthesis of diethyl carbonate (DEC). In the present study, hydroxyapatite was synthesized and modified using Zn and Mg (Zn/HAP and Mg/HAP). Modified hydroxyapatite was used as catalyst for the synthesis of DEC. The thermal analysis of the catalytic precursor was studied using thermogravimetric-differential thermal analysis. The structural analysis, surface morphology, and nature of active sites over the catalyst surface were studied using techniques such as Fourier transform infrared spectroscopy, X-ray diffraction, N2 adsorption-desorption, scanning electron microscopy, and CO2 temperature-programmed desorption. Effects of reaction conditions like reaction temperature, reaction time and ethanol/PC molar ratio on DEC yield were also studied. The effects of Mg and Zn on HAP were found to be promotional for the synthesis of DEC using PC and ethanol. Mg/HAP was found to be the best among the three catalysts studied owing to its high basicity. Maximum DEC yield of 52.1 % was obtained in 5 h at 433 K using Mg/HAP catalyst.

Propylene carbonate is an important organic carbonate having wide applications. In the present work, thermodynamic analysis of propylene carbonate synthesis routes was performed. Benson group contribution method and Rozicka–Domalski model were used to estimate the heat of formation and the heat capacities of some of the components, respectively. Urea alcoholysis was found to be a favorable method for producing propylene carbonate under mild conditions. This route was further studied experimentally using various MgAl and ZnAl hydrotalcite derived catalysts. The catalysts were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption–desorption, and Fourier transform infrared spectroscopy (FTIR) techniques. Yield of PC was found to be strongly correlated to the basicity of catalysts. Addition of a third element, Ca or La, was found to reduce the surface area of the catalysts. Fluorinated MgAlO (MgAlO-F) was found to possess greater basicity than MgAlO and greater catalyt...

Diethyl carbonate, an important member in the family of organic carbonates, is a fuel additive like dimethyl carbonate (DMC). It holds an extra edge of having better gasoline/water distribution coefficient than DMC, and also DEC is widely used as an electrolyte in lithium ion batteries. Ethanolysis of ethyl carbamate (EC) is the most economical and greener route for DEC synthesis. Zn–Al–M (M=Ca, La, Mg and Y) have been synthesized using two methods and their activity have been explored DEC systhesis from EC and ethanol. The catalysts were characterized using thermogravimetric analysis, Brunauer, Emmett and Teller surface area, N2 adsorption–desorption textural analysis, X-ray diffraction (XRD), Fourier transform infrared spectroscopy, temperature-programmed desorption (TPD), atomic-force microscopy and Raman spectroscopy. Pure metal oxides were observed during the XRD analysis and Al2O3 was found to be in amorphous form. Third metal oxide prepared from impregnation method was found to be present on the surface as well as in impregnated form. CO2-TPD analysis showed close correlation between the basicity and the DEC yield. Zn–Al–Mg, prepared from precipitation method, being most basic, was found to be most effective although the performances of Zn–Al–Ca and Zn–Al–La were good. The effect of precipitants was also studied by synthesizing Zn–Al–Mg using NaOH and liquid NH3 as precipitants. DEC yield of 40.2% and turn over frequency of 1055 mgDEC gcat −1 h−1 was obtained in 5 h at 190 °C using Zn–Al–Mg prepared from precipitation method. Effect of reaction conditions was also studied and equilibrium constant of the reaction was estimated using the Benson group contribution method.

In this study, thermodynamic analysis of various possible synthesis routes of diethyl carbonates (DEC), a benign organic carbonate, was carried out and a comparative analysis was performed. Chemical equilibrium constants at standard conditions were calculated using Gibbs free energy of the system. The Benson group contribution method was used to estimate standard heat of formation and standard entropy change of some raw materials/components like dimethyl carbonate. Variation of heat capacity (Cp) with temperature was estimated for different components from the Rozicka-Domalski model. Variation of chemical equilibrium constants with temperature and pressure was studied for various routes. Synthesis of DEC from ethylene carbonate (EC) was also found to be better considering equilibrium constants at room temperature. The CO2 route was found to be the most unfavourable route for DEC synthesis due to stability of CO2 molecules. Moreover, DEC synthesis through the urea route was found to be best at high temperatures since the equilibrium constants were found to increase exponentially. Experiments were conducted for DEC synthesis using the EC route at two temperatures. Activity coefficients were calculated using the UNIFAC model. Experimentally and theoretically determined chemical equilibrium constant values were found to be similar. PRO/II was also used to minimize Gibbs free energy of the system and estimate the equilibrium constants and the results were comparable with those obtained by the equilibrium constant method and the trend was found to be the same for both the methods.

Diethyl carbonate (DEC) is a linear organic carbonate which has applications as a fuel additive, in production of polycarbonates, and as a solvent in lithium ion batteries. Ethanolysis of urea, as compared to other methods of DEC synthesis, has an edge having requirements of cheap and abundant raw materials. However, only few studies have been reported due to low acidity of ethanol. In the present study, cerium-zinc based oxides in various molar ratios were used for DEC synthesis from ethanol and urea. These catalysts were prepared by auto combustion technique and characterized by thermogravimetric analysis (TGA), Raman spectroscopy, X-ray diffraction (XRD), N 2 adsorption-desorption, field emission scanning electron microscope (FE-SEM), energy dispersive X-ray (EDX), Fourier transform infra-red (FTIR), and NH 3 - and CO 2 -temperature programmed desorption (TPD) methods. No additional phases except pure Ce and Zn oxide were observed in the catalyst from XRD analysis. Effects of pore surface area and surface acidity/basicity were found to be profound in the synthesis of DEC. DEC yield of 28.8% was obtained at 190 °C and 5 h using Ce 0.1 -Zn 0.9 mixed oxide. Effect of operating parameters such as ethanol/urea molar ratio, temperature, time and catalyst concentration were also studied.

Organic carbonates are green compounds with a wide range of applications. They are widely used for the synthesis of important industrial compounds including monomers, polymers, surfactants, plasticizers, and also used as fuel additives. They can be divided into two main classes: cyclic and linear carbonates. Dimethyl carbonate (DMC) and diethyl carbonate (DEC) are the important linear carbonates. Carbonyl and alkyl groups present in DMC and DEC make them reactive and versatile for synthesizing various other important compounds. Ethylene carbonate (EC), glycerol carbonate (GC) and propylene carbonate (PC) are well-known cyclic organic carbonates. Phosgenation of alcohols was widely used for synthesis of organic carbonates; however, toxicity of raw materials restricted use of phosgenation method. A number of new non-phosgene methods including alcoholysis of urea, carbonylation of alcohols using CO2, oxy-carbonylation of alcohols, and trans-esterfication of alcohols and carbonates have been developed...

Diethyl carbonate (DEC) is a well-known linear organic carbonate that has wide applications. Besides its use as a fuel additive, DEC is an excellent electrolyte for lithium ion batteries and is used for the production of polycarbonates, which are globally used engineering plastics. The synthesis of DEC from CO2 helps in CO2 mitigation. It was earlier synthesized by phosgenation of ethanol, which is a toxic and dangerous process. Certain non-phosgene routes have been developed in recent years, which include oxidative carbonylation of ethanol, trans-esterification of carbonate, alcoholysis of urea, ethanolysis of CO2 and the ethyl nitrite route for DEC synthesis. This review underlines various non-phosgene methods for the synthesis of DEC by critically evaluating the catalysts used, operating conditions and mechanism of synthesis. The performances of various catalysts have been compared graphically along with the identification of problems and potential solutions. Certain engineering aspects, including kinetics and thermodynamics of the various routes, have also been highlighted. The shortcomings and research gaps have been explicitly mentioned and discussed along with required future developments and research work for DEC synthesis.

In this paper, a series of CexZr1−xO2 solid solution spheres were synthesized by exo- and endo-templating methods and tested for dimethyl carbonate (DMC) synthesis using direct conversion of CO2. The synthesized catalysts were characterized by X-ray diffraction (XRD), N2-physisorption, scanning electron microscopy (SEM), and CO2/NH3-temperature-programmed desorption (TPD). Formation of CexZr1−xO2 solid solutions with tetragonal and cubic crystal structures depending on cerium/zirconium compositions was confirmed by XRD analysis. The specific surface area of the mixed oxide decreased and the average pore diameter increased with an increase in the ceria content, with the exception of the mixed oxides with x = 0.4–0.5 i.e. Ce0.4Zr0.6O2 and Ce0.5Zr0.5O2. The basic and acidic site density of the synthesized catalysts was in the order: ZrO2 < CeO2 < Ce0.5Zr0.5O2, and the basic and acidic site density per unit area followed the same order. The best Ce0.5Zr0.5O2 catalyst was further used for the optimization of reaction conditions such as reaction time, reaction temperature, catalyst dose and reusability for DMC synthesis. Furthermore, study of chemical equilibrium modeling was done using the Peng–Robinson–Stryjek–Vera equation of state (PRSV-EoS) along with the van der Waals one-fluid reaction condition so as to calculate change of Gibbs free energy (ΔG°) and heat of reaction (ΔH°).