A K Suresh
IIT Bombay, India
Posters & Accepted Abstracts: J Pet Environ Biotechnol
Glycerol, because of its multi-functionality, is a potential source of many chemicals currently produced from petroleum sources. Being a byproduct of biodiesel manufacture, the availability of glycerol has been on the increase, but the same fact results in price fluctuations, which means that the best strategies to valorize glycerol must concentrate on high value products. Here, we discuss two possibilities for the upgradation of glycerol ΓΆΒ?Β? via oxidation to glyceric and tartronic acids, and via hydrogenolysis to 1,3-propanediol. Glycerol oxidation, while a potential route to several high value chemicals, is a complex reaction, and directing it to desired compounds is a challenge. Catalysts such as Pd, Pt and Au, under alkaline conditions, favour the formation of glyceric and tartronic acids, but carbon chain scission leading to C2 and C1 compounds limits the selectivity. Both rate and selectivity of such catalysts are modulated in interesting ways by the catalyst support, with carbon supports providing the best performance. An analysis of the product spectrum under different reaction conditions suggests ways of reaction network reduction, based on which the network has been modeled, and the parameters evaluated for different catalysts. The consequences of possible transport limitations at the catalyst and/or the macro-level in a three phase reactor, especially on the selectivity of the reaction, have been evaluated. Hydrogenolysis of glycerol to 1,3-propanediol, precursor to poly (trimethylene) terephthalate, is again, a nonselective reaction since it involves attacking the secondary hydroxyl group of glycerol while leaving the two primary hydroxyls untouched. Multi-step chemical routes have been proposed, but yields have been poor. We have been experimenting on a strategy of chemically blocking the primary hydroxyls through derivatization, eliminating the secondary alcohol group, and de-derivatizing. The second step can be performed catalytically or non-catalytically. Some of the challenges associated with the reaction will be discussed on the basis of the results from our work so far.
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