(300f) Computational Screening of Sorbents for Mercury Capture At Elevated Temperatures

Electricity generation from coal is a potential method to help address the world’s growing energy demands due to coal’s relatively large abundance and low cost.  Specifically, Integrated Gasification Combined Cycle (IGCC) is emerging as a promising method of coal power generation due to its increased efficiency, especially with regard to the capture of environmental pollutants.  Despite these advantages, however, a significant challenge to the large-scale implementation of IGCC is the development of more efficient techniques for pollution reduction.  Previous researchers have directed efforts at increasing this efficiency of separation through the development of solid adsorbents to capture pollutants at elevated temperatures, screening potential sorbents experimentally.  By contrast, computational methods for screening of new materials show a lot of promise—not only can these methods greatly increase the speed of the screening process, they can also reduce costs by eliminating the number of compounds that need to be tested experimentally.

In this work we show how ab initio computational techniques can be used to aid in the identification and screening of candidate materials with the desired binding energies.  Using the example of mercury vapor adsorption, the formation energies of mercury metal oxides and mercury metal sulfides were calculated using density functional theory.  The validity of the calculations was verified using experimental data whenever possible.  Those compounds determined to be the most promising were then tested for the formation energies of products that could result from competing reactions due to other components in the synthesis gas stream.  For the purposes of this study, the most probable competing reaction for the metal oxide and metal sulfide sorbents was assumed to be the reaction of the material with hydrogen to produce water vapor and hydrogen sulfide, respectively.  The results of these calculations and suggestions for future avenues of research will be discussed.