Efficient and Greener Synthesis of Propylene Carbonate from Carbon Dioxide and Propylene Oxide

Several heterogeneous catalysts have been investigated for solvent-free synthesis of propylene carbonate (PC) for cycloaddition reaction of propylene oxide (PO) and carbon dioxide (CO2). The characterization of different heterogeneous catalysts has been successfully carried out using Raman spectroscopy, scanning electron microscopy, and X-ray diffraction analysis. Batch cycloaddition reaction of PC and CO2 has been conducted in a high pressure reactor. The effect of various parameters that could influence the conversion of PO and the selectivity and yield of PC such as catalyst types, catalyst loading, CO2 pressure, reaction temperature, and reaction time has been studied to find the optimum conditions and the best preferred catalyst for this reaction. Ceria and lanthana doped zirconia (Ce–La–Zr–O) catalyst has been found to be the most active and selective for synthesis of PC as compared to other heterogeneous catalysts that were tested as part of this research. Catalyst reusability studies have been conducted to investigate the long-term stability of the best performed catalyst for synthesis of PC, and it has been found that the catalyst could be reused several times without losing its catalytic activity. An artificial neural network (ANN) model has been developed for PC synthesis by cycloaddition reaction of PO and CO2 using Ce–La–Zr–O catalyst to compare the experimental data and the predicted results by ANN model. The ANN model predicted values are in good agreement with the experimental results

Organocatalysts for enantioselective synthesis of fine chemicals: definitions, trends and developments

Organocatalysis, that is the use of small organic molecules to catalyse organic transformations, has been included among the most successful concepts in asymmetric catalysis and it has been used for the enantioselective construction of C-C, C-N, C-O, C-S, C-P, and C-halide bonds. Since the seminal works in early 2000, the scientific community has been paying an ever-growing attention to the use of organocatalysts for the synthesis, with high yields and remarkable stereoselectivities, of optically active fine chemicals of interest for the pharmaceutical industry. A brief overview is here presented about the two main classes of substrate activation by the catalyst: covalent organocatalysis and non-covalent organocatalysis, with a more stringent focus on some recent outcomes in the field of the latter and of hydrogen-bond-based catalysis. Finally, some successful examples of heterogenisation of organocatalysts are also discussed, in the view of a potential industrial exploitation