(744a) Aqueous Phase Reforming of Glycerol: Determining the Catalyst Support Effects

The production of biodiesel from triglyceride based agricultural products has led to a plethora of aqueous glycerol byproducts on the chemicals market. Though purification of this glycerol mixture is possible, direct conversion of the glycerol to platform chemicals or fuel products would be more cost effective and efficient and could ultimately help alleviate the world’s dependence on nonrenewable petroleum derived products. Aqueous phase reforming (APR) is one method that holds promise for the catalytic conversion of glycerol because it employs moderate operating temperatures and does not require the dehydration of biodiesel derived glycerol. APR also produces low levels of carbon monoxide and enhances the solubility of the solutes. The APR mechanism is composed of three primary processes: dehydrogenation, decarbonylation, and the water-gas shift (WGS) reaction. For this reaction, effective heterogeneous catalysts are commonly comprised of a noble metal supported on metal oxides, including common minerals.

A goal of this effort is to learn how these supported catalysts behave in aqueous environments at specific reaction conditions. This knowledge is crucial to developing an understanding of the reaction mechanism and will aid in our design of new catalysts that have greater efficiency and selectivity. It is also important to understand how the catalyst support participates in the reactions, this could include enhancing dehydrogenation and water-gas shift reactions, and determine support effects of various supports on the glycerol APR reactions and how they influence the overall catalytic activity and product distribution. To quantify these effects for various supports, we measured the presence of Brønsted and Lewis acid/base surface sites, which promote select APR reaction steps and control the hydrophobicity/hydrophilicity of the catalyst due to the presence of H⁺ and OH^- ions. These characterizing factors affect the water solvent’s interaction with the catalyst support as well as the availability of active sites and the propensity of the catalyst to deactivate due to support changes at the desired conditions. Catalysts were characterized by various methods including, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TGA), and temperature-programmed reduction/desorption (TPR/TPD). Results from these characterization methods as well as product distributions from catalytic experiments provided key insights into the primary factors impacting catalyst performance.