A complementary approach to deal with the global warming issue is to apply renewable energy sources alternatives such as biodiesel. The increased production of this class of fuels has led to a surplus of glycerol. We have succeeded in using carbon dioxide (CO₂) and glycerol to produce glycerol carbonate. In addition to utilizing a biodiesel by-product, we are also using a primary greenhouse gas to make a material (glycerol carbonate) suitable to be applied in the industry e.g. to produce polyurethanes and polycarbonates, personal care products, and lubricants. The primary catalysts used in this reaction are metal oxides (MgO, CaO) and mixed metal oxide (Mg-Ca). Catalyst characterization and investigation of the performance of the catalysts for this reaction shows that Mg-Ca is a novel catalyst for this reaction to enhance the glycerol conversion and the glycerol carbonate selectivity. The results showed that by using this catalyst the highest selectivity (50.6%) of the value-added material, glycerol carbonate, among these catalysts had been achieved. The yield of glycerol carbonate from the reaction of glycerol and CO₂ highly depends on several factors such as preparation of an appropriate catalyst, electronic state, surface composition, and the reaction conditions.
Here we present the in-situ X-ray Photoelectron (XPS) studies in an effort to understand the surface interaction of several of our catalysts (MgO, CaO, and Mg-Ca) with glycerol and CO₂. An understanding of the mechanism of the catalytic process may allow us to optimize the reaction of yield and cost. We have employed the use of a Kratos Supra XPS equipped with a high-temperature gas reaction cell which allowed us to deposit glycerol on the surface of the catalysts and synchronously or simultaneously conduct reactions with CO₂ at several pressures and temperatures at several durations. Changes in the different types of oxygen, carbon, and metals' states on the surface unravel some of the complexities associated with this process.

Dr Philip Effah Boahene

Senior Research Scientist, University of Saskatchewan

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