The promise of biomass-derived transportation fuels and specialty chemicals is based on the premise that complex organic molecules in readily available biomass can be converted via a biochemical or thermochemical platform into much simpler molecular building blocks. However, the reality is that biochemical routes are not yet competitive in the commercial markets, while conventional thermochemical routes such as pyrolysis currently produce a low-quality, highly oxygenated bio-oil that is unstable due to the presence of reactive molecules and high acidity. In order to develop advanced biofuels and specialty chemicals, the pyrolysis oil needs to be upgraded and stabilized, usually employing high temperature and pressure reactors containing various catalyst beds. In the upgrading process, the unstable molecules have a great tendency to re-polymerize into higher molecular weight compounds, leading to catalyst instability and operational problems.
Professor Dorin Boldor of Louisiana State University will test the hypothesis that a microwave heating system of high energy density with a well-controlled electromagnetic field distribution, when coupled with the proper upgrading catalyst choice can significantly increase the reaction rates and increase the catalyst usable lifetime by direct volumetric heating of the catalyst bed and therefore producing a bio-oil of superior quality compared to that obtained in conventional heating systems.
For the development of a sustainable, renewable and reliable source of energy for our society, it is highly desirable to demonstrate a biomass process platform to produce a transportation fuel. The proposed research, if successful, achieves this goal by demonstrating a transformative technology for bio-oil upgrading, which can increase the lifetime of the catalysts and reduce operational costs.This is an EAGER topic in that there is no data to indicate this proposed plan will be successful. The microwave technology may have little impact on rates or on upgrading. It is conceivable that repolymerization is accelerated with greater catalyst instability. The successful completion of this research project will allow Boldor to acquire data in order to prove or disprove the likelihood of success. This data would then form the foundation of a further research program to elucidate the fundamental mechanisms behind the increased process performance at the gas-solid interface in the presence of microwave fields.
The project will train a current PhD student in the PI?s lab from an underrepresented group. She will gain and master skills critically needed in the competitive labor market of the 21st century. To further increase the impact of the research, the knowledge developed will be incorporated in the ?Biofuels and Bioproducts from Renewable Resources? course taught by the PI, which includes a Service-Learning component in which students demonstrate projects developed in class (one of which is production of bio-oil via pyrolysis) to students enrolled in middle and high school science courses.
Intellectual merit: The promise of biomass-derived transportation fuels and specialty chemicals is based on the premise that complex organic molecules in readily available biomass can be converted via a biochemical or thermochemical platform into much simpler molecular building blocks. However, this premise is faced with the reality that biochemical routes are not yet competitive in the commercial markets, while conventional thermochemical routes such as pyrolysis currently produce a low-quality, highly oxygenated bio-oil that is unstable due to the presence of reactive molecules and high acidity. In order to develop advanced biofuels and specialty chemicals, the pyrolysis oil needs to be upgraded and stabilized using high temperature and pressure reactors in the presence of catalysts beds Initial experimental runs were conducted without upgrading so as to quantify and standardize the pyrolysis method. These experimental runs included running each biomass sample at different temperatures to test for maximum yield. Along with these runs, the time data series was also generated for each biomass sample at the highest yield temperature in order to optimize the process. Optimum time and temperature for pyrolysis of cellulose, lignin, and sawdust were determined. Bio-oil yields at different temperatures for pyrolysis of sawdust had an increasing trend until an optimum value, followed by a decrease. The decrease at higher temperatures indicates the entrance into a gasification-type regimen. Once initial pyrolysis conditions were determined, upgrading experiments were conducted with two catalysts and multiple operating temperatures. The upgraded bio-oil yields ranged from 33.4 to 40.9% for cellulose, from 32.3 to 44.7% for sawdust, and from 15.1 to 21.0% for lignin. GC analysis of these samples showed that those undergoing microwave-based upgrading had the smallest amount of phenols, indicating excellent performance in deoxygentation compared to conventional heating and no upgrading. Bio-oil obtained using microwave upgrading shows higher peak area for benzenes, furans, pentenes, octanes and their alkyl derivatives, with lower peaks for phenols. No cresols or benezenediols were observed. Similar results were obtained for conventional heating at a lower temperature, with an exception that higher benzene peak was observed. Thus, even at lower catalyst bed temperature in the microwave heater, deoxygenation reaction was effective. Digital images and SEM analysis of catalysts in the different operating scenarios indicate that in microwave upgrading the catalyst experienced less fouling and depositions, with more of its surface area being free from re-condensation products. These results indicate that the microwave heating method is extremely effective at prolonging the life of the catalyst. These results were confirmed by coupling results from numerical analysis of the electromagnetic power distribution in the microwave cavity with images of catalysts collected from different locations in the upgrading tube. The low-exposure regions correspond to higher depositions, whereas the regions with high exposure to microwave energy correspond to low depositions and cleaner catalyst after the process. Broad Impact: This project assists in developing a more sustainable approach for energy generation (especially for transportation fuels) for our society. Additional benefits include preservation and protection of the environment via utilization of renewable carbon sources. This preliminary investigation maps the way forward toward developing a viable technology for production of renewable transportation fuels, which can lead to significant economic development opportunities in the rural area of the USA. The project assisted with training of a PhD student in the field of renewable energy production, who acquired and mastered critical skills needed in the competitive labor market of the 21st century. The knowledge accumulated was incorporated in a biofuel production course taught by the PI at Louisiana State University, which included a community-based Service-Learning component for the students.
