Nilesh Narkhede

Recent progress on supported polyoxometalates for biodiesel synthesis via esterification and transesterification

Biodiesel is now recognized as a “green fuel” that has several advantages over conventional diesel. In the present review we discuss the catalytic esterification and transesterification reactions to the clean synthesis of biodiesel, over most readily investigated supported polyoxometalates to meet future societal demands. Here for the first time, we are reviewing biodiesel synthesis using supported lacunary polyoxometalates; also how the prevailing reaction conditions like reaction time, alcohol content, temperature, and catalyst amount affect the catalytic activity of the catalyst is discussed in detail. The new results for supported lacunary polyoxometalates are included where the effect of catalysts and supports was correlated with the catalytic activity.

Biodiesel synthesis via esterification and transesterification over a new heterogeneous catalyst comprising lacunary silicotungstate and MCM-41

Mono-vacant silicotungstate anchored to MCM-41 was synthesized by a direct post-synthesis grafting method and characterized by BET surface area measurements, FT-IR, 29Si MAS NMR, XRD and TEM. The catalytic application of the material was established for acid catalyzed synthesis of biodiesel via esterification of oleic acid and transesterification of different edible and non-edible oils such as waste cooking oil, jatropha oil, sunflower oil, cotton seed oil and mustard oil. A kinetic study was carried out for the esterification of oleic acid and it was found that esterification of oleic acid follows first order kinetics with the calculated activation energy Ea = 49.8 kJ mol−1 and pre-exponential factor A = 8.7 × 104 min−1. The expected mechanism for the biodiesel synthesis via esterification and transesterification has also been proposed.

Room temperature acetalization of glycerol to cyclic acetals over anchored silicotungstates under solvent free conditions

Heterogeneous catalysts comprising of parent Keggin type silicotungstate as well as monolacunary silicotungstate anchored to MCM-41 were synthesized and characterized by several physicochemical methods. A solvent free green route towards valorisation of glycerol via acetalization with benzaldehyde has been proposed. Both the catalysts showed very good activity as well as selectivity towards dioxolane derivatives within a short reaction time and at room temperature. The tuning of the acidity of the parent silicotungstate leads to an increase in the selectivity towards 1,3-dioxolane. The catalysts were also recycled up to four times without any significant loss in the conversion. The excellent performance of these mesoporous catalysts is attributed to their combination of acidity, wide pores and large specific surface area.

Keggin-type lacunary and transition metal substituted polyoxometalates as heterogeneous catalysts: A recent progress

ABSTRACT In this article we discussed synthesis and catalytic applications of heterogeneous catalysts based on lacunary polyoxometalates (LPOMs) and transition metal substituted polyoxometalates (TMSPOMs), however exclusively the focus has been given to the mono LPOMs and mono-TMSPOMs. As the field of supported LPOMs/TMSPOMs is upcoming important field, some aspects about choice of support as well as methods of supporting have also been described. We also include a few of our new research results in order to understand the effect of support and active species as well as choice of organic transformation.

Efficient synthesis of biodiesel over a recyclable catalyst comprising a monolacunary silicotungstate and zeolite Hβ

This paper presents a study of esterification of oleic acid as well as transesterification of soybean oil with methanol over a solid acid catalyst comprising a monolacunary silicotungstate anchored to zeolite Hβ. The optimization of the reaction parameters were carried out to get the maximum conversion. The 3.5 wt% catalyst charge at 60 °C showed 82% conversion of oleic acid with a 1 : 20 mole ratio of acid to alcohol in 10 h whereas the 4 wt% catalyst charge at 65 °C showed 96% conversion of soybean oil with a ratio of oil to alcohol of 1 : 4 (w/w) in 8 h. The catalyst was found to be readily reusable and exhibited consistency in activity upon reuse four times without appreciable loss in the conversion.

Aerobic oxidation of alcohols and alkenes over a novel lacunary phosphomolybdate anchored to zeolite Hβ

Lacunary phosphomolybdate anchored to zeolite Hβ was synthesized and characterised by various physicochemical techniques. The catalytic activity was evaluated for aerobic oxidation of benzyl alcohol and styrene. The catalyst was found to be efficient, especially in terms of selectivity for the desired benzaldehyde product (for benzyl alcohol – 90%, styrene – 72%), very high turnover number (alcohols > 3500, alkenes > 18 000) as well as recyclability. The viability of the catalyst was also extended to various alkenes and alcohols.

Facile synthesis of glycerol carbonate via glycerolysis of urea catalysed by silicotungstates impregnated into MCM-41

The present contribution includes the solvent free environmentally benign route towards synthesis of glycerol carbonate via glycerolysis of urea. The parent as well as mono lacunary silicotungstates impregnated into MCM-41 were used as efficient catalysts. The effect of different reaction parameters on the conversion of glycerol was investigated in order to optimize the reaction parameters for maximum conversion. The activities of both the catalysts have been correlated with the structural features and acidity of the catalysts and the possible mechanism has also been proposed. The catalysts were also recycled up to four times without significant loss in the activity.