DOE OSTI2014
Technical aspects of producing alternative fuels that may eventually supplement or replace conventional the petroleum-derived fuels that are presently used in vehicular transportation have been investigated. The work was centered around three projects: 1) deriving butanol as a fuel additive from bacterial action on sugars produced from decomposition of aqueous suspensions of wood cellulose under elevated temperature and pressure; 2) using highly ordered, openly structured molecules known as metal-organic framework (MOF) compounds as adsorbents for gas separations in fuel processing operations; and 3) developing a photocatalytic membrane for solar-driven water decomposition to generate pure hydrogen fuel. Several departments within the STEM College at YSU contributed to the effort: Chemistry, Biology, and Chemical Engineering. In the butanol project, sawdust was blended with water at variable pH and temperature (150 – 250 °C), and heated inside a pressure vessel for specified periods of time. Analysis of the extracts showed a wide variety of compounds, including simple sugars that bacteria are known to thrive upon. Samples of the cellulose hydrolysate were fed to colonies of Clostridium beijerinckii, which are known to convert sugars to a mixture of compounds, principally butanol. While the bacteria were active toward additions of pure sugar solutions, the cellulose extract appeared to inhibit butanol production, and furthermore encouraged the Clostridium to become dormant. Proteomic analysis showed that the bacteria had changed their genetic code to where it was becoming sporulated, i.e., the bacteria were trying to go dormant. This finding may be an opportunity, as it may be possible to genetically engineer bacteria that resist the butanol-driven triggering mechanism to stop further fuel production. Another way of handling the cellulosic hydrolysates was to simply add the enzymes responsible for butanol synthesis to the hydrolytic extract ex-vivo. These enzymes are generally not available commercially, however, and those that are can be quite expensive. Accordingly, the genes responsible for enzyme synthesis were inserted into other microorganisms in order to accelerate enzyme production. This was demonstrated for two of the required enzymes in the overall series. In the MOF project, a number of new MOF compounds were synthesized and characterized, as well as some common MOFs well-known for their adsorption properties. Selectivity for specific gases such as CO 2 and H 2 was demonstrated, although it was seen that water vapor would frequently act as an interferent. This work underscored the need to test MOF compounds under real world conditions, i.e., room temperature and above instead of liquid N 2 temperature, and testing adsorption using blends of gases instead of pure components. In the solar membrane project, thin films of CdTe and WO 3 were applied to steel substrates and used as p-type and n-type semiconductors, respectively, in the production of H 2 and O 2 . Testing with 2 H and 18 O isotopically labeled water enabled substantiation of net water-splitting.