The ketonization of small organic acids is a valuable reaction for biorenewable applications. Ceria has long been used as a catalyst for this reaction; however, under both liquid and vapor phase conditions, it was found that given the right temperature regime of about 150-300 °C, cerium oxide, which was previously believed to be a stable catalyst for ketonization, can undergo bulk transformations. This result, along with other literature reports, suggest that the long held belief of two separate reaction pathways for either bulk or surface ketonization reactions are not required to explain the interaction of cerium oxide with organic acids. X-ray photon spectroscopy, scanning electron microscopy, and temperature programmed decomposition results supported the formation of metal acetates and explained the occurrence of cerium reduction as well as the formation of cerium oxide/acetate whiskers. After thermogravimetry/mass spectrometry and FT-IR experiments, a single reaction sequence is proposed that can be applied to either surface or bulk reactions with ceria. ABSTRACT: The ketonization of small organic acids is a valuable reaction for biorenewable applications. Ceria has long been used as a catalyst for this reaction; however, under both liquid and vapor phase conditions, it was found that given the right temperature regime of about 150−300°C, cerium oxide, which was previously believed to be a stable catalyst for ketonization, can undergo bulk transformations. This result, along with other literature reports, suggest that the long held belief of two separate reaction pathways for either bulk or surface ketonization reactions are not required to explain the interaction of cerium oxide with organic acids. X-ray photon spectroscopy, scanning electron microscopy, and temperature programmed decomposition results supported the formation of metal acetates and explained the occurrence of cerium reduction as well as the formation of cerium oxide/acetate whiskers. After thermogravimetry/mass spectrometry and FT-IR experiments, a single reaction sequence is proposed that can be applied to either surface or bulk reactions with ceria.

No abstract

Ketonization of the model bio-oil compound acetic acid was performed in a toluene-solvent condensed phase using five different CeMOx catalysts. The catalysts were characterized using a number of different techniques both before and after reaction testing to gain understanding of how material traits influence their catalytic performance. A number of potentially important catalytic properties were found to be of little importance for the respective reaction. For instance, it was discovered that there was no direct correlation between prereaction surface area with activity for ketonization at high or at low temperatures. Furthermore, better reducibility of the oxide did not appear to correlate with improved ketonization rates. XRD of postreaction materials used at different temperatures demonstrated the reaction temperature regime influenced whether the crystal structure of the fresh mixed oxide was disrupted. The precise temperature regimes were different, depending on composition of the catalytic material. Catalytic activity was then found to be maximized when metal carboxylate formation and subsequent decomposition of the carboxylate were appropriately balanced. ABSTRACT: Ketonization of the model bio-oil compound acetic acid was performed in a toluene-solvent condensed phase using five different CeMO x catalysts. The catalysts were characterized using a number of different techniques both before and after reaction testing to gain understanding of how material traits influence their catalytic performance. A number of potentially important catalytic properties were found to be of little importance for the respective reaction. For instance, it was discovered that there was no direct correlation between prereaction surface area with activity for ketonization at high or at low temperatures. Furthermore, better reducibility of the oxide did not appear to correlate with improved ketonization rates. XRD of postreaction materials used at different temperatures demonstrated the reaction temperature regime influenced whether the crystal structure of the fresh mixed oxide was disrupted. The precise temperature regimes were different, depending on composition of the catalytic material. Catalytic activity was then found to be maximized when metal carboxylate formation and subsequent decomposition of the carboxylate were appropriately balanced.

No abstract

The aldol condensation of acetaldehyde, acetone, and methyl ethyl ketone, which represent model biooil compounds, in the condensed phase, was performed using a bi-functional aluminophosphate catalyst. It was found that increasing the number and strength of the basic sites while decreasing acid sites on the catalyst caused a reduction in yield of the condensation products. In contrast, the addition of organic acids such as acetic acid at low concentrations to the catalyst-containing reaction mixture was found to increase activity. The presence of both acid and base sites was found to be necessary and their relative number was important for both the activity and selectivity of the condensation reaction. A mechanism explaining the observed phenomena was proposed.

To my wife Sarah and our newborn son Soren… iii Table of contents Chapter 1: General introduction and project goals Chapter 6: Insights into the ceria catalyzed ketonization mechanism for biofuels applications 6.1. Introduction 6.2. Experimental section 6.3. Results and discussion 6.4. Conclusions 6.5. Acknowledgements 6.6. References 6.7. Tables and figures Chapter 7: CeMO x promoted condensed phase ketonization of biomass derived carboxylic acids 7.1. Introduction 7.2. Experimental section 7.3. Results 7.4. Discussion 7.5. Conclusions 7.6. References 7.7. Tables and figures Chapter 8: General conclusions Chapter 9: Future directions v AcknowledgementsThis thesis would not be possible without the encouragement, leadership, and support of my major professor Brent Shanks. I am particularly grateful of his continuous focus on the big picture even while examining the fundamental science of a project and of his mentoring style which allows for the development of independent thinkers and researchers. I would also like to thank all members-current and past-of the Shanks' research group for helpful discussions and encouragement. In particular I would like to acknowledge Karl Albrecht, Shaojun Miao, and Sikander Hakim for their guidance during the beginnings of graduate school as well as Keenan Deutsch and Tianfu Wang for their support as I am finishing up.Undergraduate researchers Elliot Combs, Linda Lippold, Dan Weis, and Rawini D-Mudiyanselage who all contributed to this work should be recognized for their efforts as well.Performing the research and class work needed to finish this thesis and graduate school in general has consumed a significant amount of my time and efforts for the past 4-5 years. With this in mind, I'm indebted to my parents and brother; Carol, Mick, and Jared Snell for their encouragement. Most of all, I must thank my wife, Sarah Snell, who put up with my late nights and weekends needed to complete this work. For her encouragement and efforts to keep me focused on what is truly important, I will be forever grateful.