Search Results (4)

A novel and cost-effective heterogeneous catalyst for glycerol carbonate production through transesterification was developed by impregnating smectite clay with K₂CO₃. Comprehensive structural and chemical analyses, including X-ray diffraction Analysis (XRD), Scanning Electron Microscopy (SEM)-Electron Dispersion Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET) surface area analysis measurements, were employed to characterize the catalysts. Among the various catalysts prepared, the one impregnated with 40 wt% K₂CO₃ on smectite and calcined at 550 °C exhibited the highest catalytic activity, primarily due to its superior basicity. To enhance the efficiency of the transesterification process, several reaction parameters were optimized, including the molar ratio between propylene carbonate and glycerol reactor loading of the catalyst and reaction temperature. The highest glycerol carbonate conversion rate, approximately 77.13% ± 1.2%, was achieved using the best catalyst under the following optimal conditions: 2 wt% reactor loading, 110 °C reaction temperature, 2:1 propylene carbonate to glycerol molar ratio, and 6h reaction duration. Furthermore, both the raw clay and the best calcined K₂CO₃-impregnated catalysts demonstrated remarkable stability, maintaining their high activity for up to four consecutive reaction cycles. Finally, a kinetic analysis was performed using kinetic data from several runs employing raw clay and the most active K₂CO₃-modified clay at different temperatures, observing that a simple reversible second-order potential kinetic model of the quasi-homogeneous type fits perfectly to such data in diverse temperature ranges. Full article

Biodiesel is nowadays added in 5–10% v/v to diesel, and its production involves the parallel creation of a vast glycerol amount as a by-product. Despite its many applications, there is a surplus of glycerol (Gly) that has boosted the search for new applications of this compound, now transformed into an industrial synthesis intermediate or platform chemical. Its transcarbonation is a type of reaction that occurs under mild conditions, using weak or moderate basic catalysts, and allows the parallel production of glycols of industrial interest with high selectivity, such as ethylene glycol. In this research, we have studied the activity of a Tunisian clay rich in inorganic carbonates that give it a weak basic character. The raw clay (RC) has been fully characterized by XRD, FTIR, SEM-EDS and nitrogen porosimetry. Subsequently, it has been employed as a catalyst to react glycerol (G) with ethylene carbonate (EC) to obtain glycerol carbonate (GC) and ethylene glycol (EG). The main operating variables and their effects on glycerol conversion and initial reaction rate were analyzed: catalyst concentration (2–6% w/w glycerol), reagent molar ratio (EC:G 1.5:1 to 3:1), and temperature (80–110 °C). Then, an appropriate kinetic model was selected from the results obtained under various reaction conditions, including the total deactivation of order 1 of the catalyst. The kinetic constant activation energy in this reaction using Tunisian smectite was found to be around 183.3 kJ·mol⁻¹. In the second phase of the investigation, we explored the reuse of smectite using the kinetic model to appreciate the effect of cycle-to-cycle deactivation. It can be seen that the kinetic constant of the main reaction generally decreases with the number of cycles at low temperature and goes through a maximum at high operating temperature, while the deactivation constant increases with the number of catalytic cycles. The catalyst shows more stability, in general, at higher temperatures. Full article

With the advent of biodiesel as a substitute/additive for diesel, the production of glycerol has experienced an increase, as it is an unavoidable byproduct of the biodiesel process; therefore, novel products and processes based on this triol are being very actively researched. Glycerol carbonate emerges as an advanced humectant from glycerol and a monomer for diverse polycarbonates. Its production in high yields and amounts can be achieved through the solventless transcarbonation of glycerol with other organic carbonates driven by alkaline catalysts, standing out amongst the cyclic carbonates due to its reactivity. Here, we have studied the main operational variables that affect the transcarbonation reaction of glycerol and ethylene carbonate catalyzed by zinc stearate: catalyst concentration, reagent molar ratio, and temperature. Subsequently, an appropriate kinetic model was fitted to all data obtained at 80 °C and several catalyst concentrations as well as reagent molar ratios. Finally, the selected kinetic model was extended and validated by fitting it to data obtained at several temperatures, finding that the activation energy of this reaction with this catalyst is around 69.2 kJ·mol⁻¹. The kinetic model suggests that the reaction is bimolecular and elemental and that the process is interfacial in essence, with the catalyst dispersed in a narrow space between polar (glycerol) and nonpolar (ethylene carbonate) phases. Full article

Due to growing environmental issues, research on carbon dioxide (CO₂) use is widely conducted and efforts are being made to produce useful materials from biomass-derived resources. However, polymer materials developed by a combined strategy (i.e., both CO₂-immobilized and biomass-derived) are rare. In this study, we synthesized biomass-derived poly(carbonate-co-urethane) (PCU) networks using CO₂-immobilized furan carbonate diols (FCDs) via an ecofriendly method. The synthesis of FCDs was performed by directly introducing CO₂ into a biomass-derived 2,5-bis(hydroxymethyl)furan. Using mechanochemical synthesis (ball-milling), the PCU networks were effortlessly prepared from FCDs, erythritol, and diisocyanate, which were then hot-pressed into films. The thermal and thermomechanical properties of the PCU networks were thoroughly characterized by thermogravimetric analysis, differential scanning calorimetry, dynamic (thermal) mechanical analysis, and using a rheometer. The self-healing and recyclable properties of the PCU films were successfully demonstrated using dynamic covalent bonds. Interestingly, transcarbamoylation (urethane exchange) occurred preferentially as opposed to transcarbonation (carbonate exchange). We believe our approach presents an efficient means for producing sustainable polyurethane copolymers using biomass-derived and CO₂-immobilized diols. Full article