Selective defunctionalization of biomass derived chemicals using hydrosilylation to value-added chemicals

Abstract

Due to problems associated with the use of fossil fuels, new, sustainable methods are needed to synthesize biofuels and chemicals from readily available biomass. In this project, we report a method to quantitatively convert biomass derived chemicals into value-added chemicals and biofuels using hydrosilylation. Cost effective silanes, such as PMHS and TMDS, which are biproducts in silicone industries, were used as reducing agents together with B(C6F5)3, which is a commercially available catalyst. This metal-free reaction method is carried out in room temperature under mild conditions and analyzed with gas chromatography and NMR spectroscopy. Biomass derived chemicals such as levulinic acid (LA), γ-valerolactone (GVL), 2-methyltetrahydrofuran (2-MTHF), alkyl levulinates, 2-pentanol (2-POH) and valeric acid (VA) are defunctionalized into chemicals with reduced oxygen content. These chemicals, GVL, 2-MTHF, 2-POH, 1,4-pentanediol (1,4-PeD) and pentane/pentene, were successfully synthesized in a high yield. We discovered that a complete deoxygenation of biomass derived chemicals to pentane/pentene could be done in one-step hydrosilylation and even possible under 1h. This synthetic pathway has not been explored before and opens a new sustainable way to produce biofuel chemicals from biomass derived chemicals. As this is still a new reaction pathway, it still needs to be optimized and explored further with different biomass derived compounds.

Popular Abstract

For centuries, humans have used fossil fuel and the growing consumption has caused many problems. The combustion of fossil fuel releases excess CO2 into the atmosphere and contributes to global warming. In addition, fossil fuel is a limited supply. The carbon from fossil fuel comes from animals and plants decaying for several million years and accumulates underground as crude oil, natural gas and coal, which we extract for fuel production. The combustion releases the accumulated carbon from underground and introduce it to the natural carbon cycle. Because of this ever-growing issue, sustainable ways of producing chemicals and biofuel are in focus. Instead of using chemicals that are limited and contribute to increased CO2 in the atmosphere, a renewable resource such as biomass, which is carbon neutral, would be a good solution and substitution for fossil fuel. From biomass we can extract polymers and convert it to many useful chemicals and biofuel.
From biomass the lignocellulose is extracted for its ability to reduce to chemicals with less oxygen content. The lignocellulose is made up of carbohydrate polymers such as cellulose and hemicellulose, but also of aromatic polymers like lignin. These polymers are then broken down to less complex molecules like glucose and fructose, which then can be converted to different platform chemicals (chemicals which are used to produce many value-added chemicals) like levulinic acid, which is 1 of the top 12 chemicals used as building blocks for different chemicals (figure 1).

Figure 1. Cellulose which is extracted from biomass and is converted to platform chemicals like levulinic acid.

From levulinic acid, many chemicals can be synthesized and the main method for doing so is using hydrogenation. Chemicals like γ-valerolactone (GVL), 2-methyltetrahydrofuran (2-MTHF) and alkyl levulinates can be used as biofuels, 2-pentanol (2-POH) is used as solvent, 1,4-pentanediol (1,4-PeD) is used as plasticizer for rubber, cosmetic and electrical equipment, to name a few. The use of hydrogenation involves high pressure of H2 and high temperature together with noble metals, such as iridium and ruthenium, as catalyst. This method has some drawbacks such as the high temperature, high pressure, and the use of noble metals. Another method called hydrosilylation, which has been rarely used to defunctionalize biomass chemicals, uses silanes as reduction agent. The advantages with hydrosilylation are that it can be done under mild condition, without noble metal catalyst and could be used as substitution to hydrogenation.

The aim of this project is to explore hydrosilylation of biomass derived chemicals, like levulinic acid and levulinates, into value-added chemicals and biofuel. This also includes other biomass derived chemicals like γ-valerolactone (GVL), 2-methyltetrahydrofuran (2-MTHF), 2-pentanol (2-POH) and valeric acid (VA). The hydrosilylation is done with polymethylhydrosiloxane (PMHS), tetramethyldisiloxane (TMDS) and triethylsilane (Et3SiH) as reduction agent and a metal free catalyst, B(C6F5)3. The silanes used are air stable and both PMHS and TMDS are biproducts from the silicone industry, which makes them cheap. The reactions are carried out under mild conditions. The products of aim are GVL, 2-MTHF, 2-POH, 1,4-pentanediol and hydrocarbons like pentane/pentene.

• author: Tan, Mattias
• supervisor: Nitish Kumar Garg
• organization: Department of Chemistry
• course: KEML10 20211
• year: 2021
• type: M2 - Bachelor Degree
• subject: Chemistry
• keywords: Hydrosilylation, Biomass derived chemicals, Value-added chemicals, Inorganic chemistry
• language: English
• id: 9056197
• date added to LUP: 2021-06-28 11:50:23
• date last changed: 2021-06-28 11:50:23