Advances in Catalyst Design and Reaction Strategies for Carbon-Neutral Conversion of Bioglycerol to Propylene, 1,2-Propanediol, and Hydrogen

Abstract

The inevitable depletion of fossil resources and the anthropogenic climate change arising from their excessive utilization make necessary the search for renewable feedstocks and developing eco-friendly technologies for producing greener energy, fuels and chemicals. Through the present mini-review, we intend to share with the research community our relevant contributions to advance the production of carbon-neutral propylene, 1,2-propanediol and biohydrogen through thermo-chemical conversion of biomass-derived glycerol, aided by diverse heterogeneous catalysts. The reported achievements, which have been recently recognized by the “ACI/NBB Glycerine Innovation Award”, are organized and discussed in four marked sections. Thus, after having highlighted the possible economic and environmental benefits of producing such value-added commodities from bioglycerol excess, we present different re-designing actions to improve the properties of transition metals-based (e.g. Pt, Pd, Ni, Cu or Mo) supported on γ-Al2O3 or SiO2 for boosting glycerol transformation via: i) steam reforming, ii) aqueous-phase reforming, iii) hydrogenolysis and iv) hydrodeoxygenation reactions. Then, the catalytic role of metallic, acid and/or redox sites in these reactions is discussed together with the identification of the main factors affecting their stability under H2O-rich conditions. The effect of reaction configurations and operating conditions in the conversion of glycerol to the target product are also assessed. The gained knowledge on re-modulating catalyst properties and optimizing reaction strategies, including mechanisms and process operability, is expected to provide a comprehensive guideline for continuously improving the efficiency of bioglycerol upgrading routes.