Bifunctional molybdenum phosphate catalyst with tunable acidity–basicity for the sustainable synthesis of glycerol carbonate via solvent‐free carbonylation of glycerol with urea

Abstract

Tuning the surface acidity–basicity via molecular level control of the chemical composition of the catalyst is one of the thrust areas of research. Herein, we first report a bifunctional molybdenum phosphate catalyst with tunable acidity–basicity for the sustainable synthesis of glycerol carbonate involving glycerol and urea. The catalyst has been thoroughly characterized by using powder X‐ray diffraction, Fourier‐transform infrared, X‐ray photoelectron spectroscopy, N2 physisorption, field emission scanning electron microscopy, transmission electron microscopy, temperature programmed desorption (TPD), Py‐IR, 31P nuclear magnetic resonance and thermogravimetric analysis. It has been observed that the physicochemical properties of the catalysts changed considerably by varying the metal and phosphorus concentrations. The molybdenum phosphate catalyst with Mo/P molar ratio = 1:3 was found most active, having the highest acidity to basicity ratio. Interestingly, the reason could be associated to the presence of higher Brønsted acidity, as evidenced from the TPD and Py‐IR results. The physicochemical properties of the used catalyst suggest it as a stable and reusable catalyst. A study on operating parameters was carried out to optimize catalytic performance to obtain glycerol conversion up to 95% at a glycerol carbonate selectivity of 99%. This remarkable catalytic performance could be attributed to the bifunctional nature of the catalyst.

Tuning catalysis by surface-deposition of elements on oxidation catalysts via atomic layer deposition

“…This is an indicator why the PO x -deposition has a more pronounced effect on the surface properties like the acidity. However, the addition of P and B is discussed to add acidic features as dopants, 79 increased P-content in Mo-phosphate lead to higher acidity, 98 and surface P–OH groups were shown to contribute to the Brønsted-acidity in VPP. 99 On the contrary, in case of supported alumina 100 or zeolite 101 catalysts, the addition of phosphates was utilized to reduce acidity.…”