Parametric investigation of Ru-based catalysts for CO2 reforming of glycerol

Glycerol is the major side product of the biodiesel production via transesterification. Reforming processes of glycerol has started to draw attention due to increased biodiesel demand in the world. Apart from conventional reforming processes, dry reforming of glycerol is very promising due to its consumption with CO2, a major greenhouse gas. Literature is very scarce about catalysis of GDR over noble metal catalysts. Therefore, this study aims to develop active and stable Ru based catalysts for glycerol dry reforming process. Ruthenium is selected due to it being cheaper than Rh and other noble metals and showing promise as the active metal of the catalyst. Effects of reaction parameters, namely reaction temperature, molar CO2 to glycerol feed ratio (CO2/G), and residence time on reactant conversions and product yields and selectivities were investigated. Single oxide supported Ru catalysts were tested in activity experiments and the promising Ru/La2O3 (RuLa) and Ru/ZrO2 (RuZr) catalysts were tested in stability experiments for 72 hours. Both Ru/La2O3 and Ru/ZrO2 were not stable, where they had deactivated approximately by 20 and 30%, respectively. From literature, positive effect of binary oxide supports on catalytic activity and stability was known. Thus, 5 binary oxide supported Ru catalysts were tested and among them, Ru/La2O3-ZrO2 (RuLZ) was exhibited superior activity and product selectivity. Optimum conditions for RuLZ were, 750 °C, CO2/G = 3, and residence time of 0.5 mg min NmL^(-1). Under these conditions RuLZ have exhibited 32.1% CO2 and 73% glycerol conversion, which are 90% and 100% of the equilibrium conversions, respectively. RuLZ have also exhibited 92 and 96% of the thermodynamic H2 and CO selectivity, respectively. Produced syngas had H2/CO ratio of 0.7. RuLZ have shown the most important improvement at catalyst stability; after 72 hours it has deactivated by 13%.