Polyols and Organic Acids Adsorption Onto Activated Carbon, and Its Role in Aqueous- Phase Catalytic Hydrogenation Rates

Increasing global energy demands have driven research in both alternative renewable energy supplies and synthesis of commodity chemicals from bio-based feedstocks. Many prior studies have used noble metal supported on activated carbon as catalysts for hydrogenation reactions that are often required for such commodity chemical production and often take place in aqueous solution. To gain a deeper understanding of aqueous-phase catalysis involving activated carbon-supported catalysts, it is necessary to study interactions between species in solution and the activated carbon support. This is because the activated carbon micropores and functionalized carbon surfaces facilitate selective adsorption of organic species from water; at equilibrium this adsorption typically leads to local reactant and product concentrations in the catalyst vicinity (e.g. in activated carbon micropores) that are significantly different than those in the bulk solution phase outside the carbon support. If chemical reaction kinetics and mass transport were characterized in terms of thermodynamic activity, these differences in concentration would be inconsequential, because at equilibrium the thermodynamic activity of solution and adsorbed species are the same. However, because chemical kinetics and mass transport are commonly represented in terms of solution concentration or mole fraction, a correct description of reaction kinetics must account for the difference in concentration between solution and pore. Thus, to practically characterize reaction kinetics and product inhibition of GO hydrogenolysis and gain further insight into aqueous-phase catalytic reactions in general, we have undertaken this study to characterize the adsorption of glycerol, lactic acid, propanoic acid, and their hydrogenolysis products into activated carbon supports, with the goal of characterizing local concentrations in the catalyst pores and eventually incorporating local pore concentration into kinetic modeling and reactor design of hydrogenolysis.