Mechanochemical Synthesis of Fuels from Sustainable Sources Utilizing Solid Catalysts

Mechanochemistry requires less solvents which results in less waste generation. The question becomes can we apply mechanochemistry to current chemical reactions and reduce the generation of waste. This process can be simple or can be very extensive resulting in the generation of large amounts of waste and very little product. A significant advantage of mechanochemistry is the reduced need for solvents that would be common place for reactions. Mechanochemistry transfers energy to reagents via impacts from milling media. Energy can be transferred to the reagents no matter their state-of-matter. Much of the current studies in mechanochemistry today are done using reagents in their solid-state, organic or inorganic compounds. Mechanochemistry is not limited to just solid-state, reactions in liquid-state and even gas-state are possible to utilize for reagents. The transition to biofuels as a means of curbing the emissions of greenhouse gases has given rise to several questions such as what to use as the feedstock and which process is most costefficient. Chapter 2 of this research focused on another question that being the interactions between biofuels and different materials. This research performed a long-term study on the interaction between polymers and biofuels. Similar research has been conducted, but where the difference lies is that the polymer selected was given shape, o-ring, to perform a specific function, stop leaks. What was observed is that after prolonged exposure to biofuels the o-ring decreased in volume, which would result in leaking of fuel. To counter this degradation two different aromatic compounds were tested by dissolving them into the biofuels. With as little as 1% w/w of aromatic compound the decrease in volume observed in the biofuels without aromatic compounds was not observed. Propane is commonly used fuel for heating homes, cooking, to fueling vehicles. Currently the primary source of propane is from oil refining. Chapter 3 of this research details the synthesis of propane from biomasses, that would normally be discarded, utilizing mechanochemistry. The methods used reduced the need for solvents and unlike other methods currently employed to make propane, no toxic materials were generated. The starting material was cassava pulp, a biomass high in cellulose. The cellulose was converted to simple sugars, which were then converted to 1,3-dihydroxyacetone, and then finally converted to propane. Each step of this process was performed mechanochemically, reducing the need for solvent, each catalyst was naturally occurring and easily recyclable. The catalyst used for the conversion to propane was itself synthesized mechanochemically with no solvents required. One aspect of green chemistry is the reduction of waste generation from chemical reactions/process. Another aspect of green chemistry is finding new catalysts that are less environmentally damaging. Mechanochemistry has been proven to reduce the need for solvents, or remove the need all together, and transitioning to solid catalysts can reduce the solvent need to extract the catalyst. Chapter 4 of this research combined mechanochemistry and the use of a solid catalyst for the synthesis of oil of wintergreen, a common esterification reaction. Esterification reactions are common in academia, industry, and pharmacology, and as a result large amounts of solvents are needed for wash and separation steps. Utilizing both mechanochemistry and solid catalysts the amount of solvent can be reduced. Similar to esterification transesterification is a common chemical reaction that is performed in academia, industry, and pharmacology typically catalyzed with bases i.e. sodium hydroxide. The advantage of catalysts such as these is that the reactions are very quick with high yields. The disadvantage to using catalysts such as sodium hydroxide is that they cannot be recycled. Chapter 5 focused on the synthesis of biodiesel, which is commonly synthesized via transesterification of triglycerides with a short-chain alcohol. Transitioning to solid catalysts would allow for the recycling of the catalyst, which would reduce waste generation. Another focus was the transitioning from methanol to ethanol. Fatty acid methyl esters are formed from the transesterification of a triglyceride with methanol and is the more commonly synthesized biodiesel as it requires less energy than longer chain alcohols, thus making it faster as well. However, methanol is toxic to people and the environment, where ethanol is safer. The focus of this research became finding a solid catalyst that would promote transesterification using ethanol as the alcohol via mechanochemistry