This Small Business Innovation Research (SBIR) Phase I project is directed towards the development of new materials that can serve in several functions, all of which are important in reducing the environmental impact of the use of energy. The proposed materials will be solids capable of removing one gas (such as carbon dioxide) from a mixture of gases (such as air), and then releasing the captured gas at the desired time. To be successful, the materials must be able to hold a large amount of captured gas and be capable of undergoing a minimum of 10,000 capture/release cycles required for a year of operation. The Phase I effort will focus on the use of the materials in a process that uses bromine to convert biogas into renewable transportation fuels, such as bio-gasoline. Additional applications of the materials, such as removing carbon dioxide and other contaminants from gases will be examined in Phase II of the project. The broader/commercial impacts of this research are the demands for cleaner transportation fuels and electric power. Despite the tremendous drive to move to renewable transportation fuels, the production costs of renewable fuels remains too high to be competitive with fossil fuels. If successful, the research proposed in the Phase I project will make the production of renewable transportation fuels significantly more cost effective. Additionally, the proposed materials would also have utility in the electric power industry, where there is a growing need to capture carbon dioxide and remove sulfur oxides from flue gas.
(# 1047139) GRT, Inc. has patented and is developing technology (GRT Technology) that converts alternative and renewable feedstocks into liquid hydrocarbon fuels (the GRT Gas-to-Fuels Process) and/or commodity chemicals (e.g. the GRT Propane-to-Propylene Process). Bromine is used as an activation agent to convert the alkanes in natural gas to alkylbromides, which are then coupled using customized zeolite catalysts to higher hydrocarbons or functionalized to propylene with HBr as a byproduct. Current technology for HBr separation involves extraction and evaporation, which are energy intensive and requires expensive materials of construction. Commercial viability of this technology is contingent upon complete separation of HBr from products and its regeneration to bromine. To address these issues we proposed the development of multi-functional metal oxide-based solid reactant materials that would sequester HBr from the product stream by reacting to form a metal bromide and water. The metal oxide form of the solid reactant would then be regenerated by reaction with oxygen, simultaneously regenerating bromine for use in the bromination step and ensuring that all bromine is completely contained within the process. The ideal solid reactant would have 1) high HBr adsorption capacity, 2) matched HBr capture and bromine regeneration times, 3) little or no reactivity with the hydrocarbon product mixture, 4) stable bromine capacity greater than 2 mmol Br2/g solid reactant, 5) high mechanical and thermal stability, and 6) a form suitable for operation in a fixed bed reactor. GRT, Inc. has completed a SBIR Phase I project entitled "Enhanced Materials for Renewable Fuel Production and Efficient Emission Reduction", during which various metal oxide nanocomposite materials were synthesized and evaluated with regard to their HBr capture performance and long-term structural/mechanical stability as powders and as pellets. Two approaches were explored to make these solid reactant materials. GRT, Inc. focused on employing a sol-gel preparation to synthesize metal oxide nanocomposites with varying amounts of MgO (active component) on aluminum oxide or zirconium oxide support material with and without varying amounts of a stabilizing agent (yttria stabilized zirconia, YSZ) (Table 1) that were tested as powders and pellets. Several metal oxide materials with ≥ 2 mmol Br2/g capacities that proved cycle stable for over 200 cycles were identified (Figure 1). Binder materials were determined that formed pellets of metal oxide nanocomposites that displayed bromine capacities similar to those of powder materials and were stable over 10 cycles. The large bromine capacities, cycle stability and successful pelletization of these materials would make the GRT Processes more economically viable than the current commercial technology. Professor Galen Stucky’s group at UCSB worked on the synthesis of core-shell nanoparticles where the active metal oxide would be contained within a shell made of the support material. The core-shell structure was to prevent previously observed (GRT unpublished work) sintering of the metal oxide phase over time that led to a decrease in bromine capacity. A versatile synthetic procedure for making core-shell nanoparticles (Figure 2) with various core-shell combinations was developed and scaled up to produce gram quantities of core-shell nanoparticles. When MgO core @ZrO2 shell nanoparticles were exposed to HBr and regenerated with oxygen, it was determined that the core-shell structure remained intact (Figure 3) and that the bromine capacity was similar to analogous sol-gel prepared nanocomposite material. If methods for improving the stability of the shell prove successful, these core-shell materials have the potential to greatly enhance the commercial viability of the GRT Technology. During Phase I it was successfully demonstrated that these metal oxide nanocomposites could remove HBr from a stream containing 2-bromopropane, propylene, HBr and could be fully regenerated. Given the inadequacy of propylene supply to meet demand, the utilization of these nanocomposites in the GRT Propane-to-Propylene Process is of great interest for further research and development. If methods for decreasing the propane and coke formation prove successful, these materials have the potential to enhance the commercial viability and carbon efficiency of the GRT Propane-to-Propylene Process.
