WITHDRAWN On the Mechanism of the Ring-Opening of Biomass Derived 2-Pyrones to Produce High Value Chemicals (original) (raw)
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Partially saturated 2-pyrone molecules undergo ring-opening and decarboxylation via retro-Diels–Alder (rDA) reaction. Density functional theory (DFT) simulations were utilized to calculate the intrinsic activation barrier and reaction energies of the steps involved in rDA reaction of biomass-derived 5,6-dihydro-4-hydroxy-6-methylpyran-2-one (5DHHMP), 4-hydroxy-3,6-dimethyl-pyran-2-one (4HDMP) and 4-hydroxy-6-(2-oxo-propyl)-3,6-dihydro-pyran-2-one (4HOPP). The rDA reaction of the three molecules in water proceeds in two steps via the formation of a zwitterionic intermediate. The calculated activation barrier (E a ¼ 61 kJ mol À1) for the rDA reaction of 5DHHMP in water compares well with the experimentally measured value. In the absence of hydrogen bonding interactions such as in the solvent n-hexane and gas-phase, the rDA reaction is concerted and activation barriers of the three molecules were estimated to be relatively higher. Substituents at C 6 , C 4 and C 3 position in partially saturated 2-pyrones showed a clear effect on the reactivity of the molecules which was correlated back to the resultant normal electron demand frontier molecular orbital (FMO) gap of the product diene and dienophile. The electronic and geometric (steric) effects of the substituents were separated by including several other structurally similar molecules having variations in the position, type and number of substituents. In general, the electronic effect of the substituents follow a linear trend, where FMO gap for normal electron demand serves as a good descriptor of the reactivity. The geometric effect was represented on a linear scale to quantify the steric hindrance offered by the methyl substituents. Molecules having no hydroxyl substituent at C 4 such as 6-methyl-3,6-dihydro-2H-pyran-2-one (4HMTHP) and 4,6,6-trimethyl-3,6-dihydro-2H-pyran-2-one (DTMP) showed a concerted route for rDA reaction in water without the formation of the intermediate. The rates of rDA reaction of the molecules were observed to be accelerated in water as compared to n-hexane. In solvents, the reactivity of the molecule doesn't correlate to the FMO gap of the products, likely due to the differential stabilization of the reactant and transition state. In general, polar solvents (water, DMSO, ethanol and methanol) were calculated to show lesser activation energy despite of a greater FMO gap as compared to non-polar solvents (n-hexane). In a solvent, the rDA reaction of the molecules follows a Brønsted–Evans–Polanyi (BEP) relationship. In presence of a Brønsted acid catalyst the rDA reaction of 5DHHMP proceeds via the formation of an oxocarbenium ion which further helps in facilitating the reaction with a significantly reduced activation barrier (E a ¼ 15 kJ mol À1).
2013
2-Pyrones, such as triacetic acid lactone, are a promising class of biorenewable platform chemicals that provide access to an array of chemical products and intermediates. We illustrate through the combination of results from experimental studies and first-principle density functional theory calculations that key structural features dictate the mechanisms underlying ring-opening and decarboxylation of 2-pyrones, including the degree of ring saturation, the presence of C═C bonds at the C4═C5 or C5═C6 positions within the ring, as well as the presence of a β-keto group at the C4 position. Our results demonstrate that 2-pyrones undergo a range of reactions unique to their structure, such as retro-Diels-Alder reactions and nucleophilic addition of water. In addition, the reactivity of 2-pyrones and the final products formed is shown to depend on the solvent used and the acidity of the reaction environment. The mechanistic insights obtained here provide guidance for the selective conversion of 2-pyrones to targeted chemicals.
Mechanistic insights into the ring-opening of biomass derived lactones
Deoxygenation of biomass-derived lactone molecules such as g-valerolactone (GVL) by catalytic ringopening and decarboxylation facilitate the production of a variety of fuels and chemicals. Density functional theory (DFT) calculations were performed to reveal the mechanism of the ring-opening step.
Journal of Heterocyclic Chemistry, 2007
Cycloaddition of acetylbenzoyl ketene generated in situ as an intermediate during one-step reaction between excess benzoylacetone and oxalylchloride to C=C double bond of cyclic enol form of benzoylacetone gave 3-acetyl-5-benzoyl-6-methyl-2-phenyl-4(4H)-pyrone 1a. Condensation reactions of 1a together with 3,5-dibenzoyl-2,6-diphenyl-4(4H)-pyrone 1b and 3-benzoyl-5-ethoxycarbonyl-2,6-diphenyl-4(4H)-pyrone 1c with two-fold excess primary amines provided a series of 3-benzoyl-1-alkyl-5-(1-alkylimino-ethyl)-6-phenyl-2-methyl-4(1H)-pyridinone 2, 3,5-dibenzoyl-1-alkyl-2,6-diphenyl-4(1H)-pyridinone 3a-c and 3-benzoyl-1-alkyl-5-ethoxycarbonyl-2,6-diphenyl-4(1H)-pyridinone 3d,e derivatives, respectively. In addition, while prolonged reaction of n-pentylamine with unsymmetrical pyrone derivative 1a gives a symmetrical pyridinone derivative namely 3,5-dibenzoyl-2,6-dimethyl-1-pentyl-4(1H)-pyridinone 5, much prolonged action n-pentylamine and then aqueous n-pentylamine on 1b resulted in degradation of the 4-pyrone ring to give dibenzoylmethane.
Product Analysis and Thermodynamic Simulations from the Pyrolysis of Several Biomass Feedstocks
Energy & Fuels, 2007
The pyrolysis of southern pine, red oak, and sweet gum sawdust is reported. Pyrolysis experiments were conducted under either a helium or nitrogen atmosphere at ∼371-871°C, to determine the balance between liquid and gas products. Gas-and liquid-phase pyrolysis products were identified using gas chromatography (GC) and GC/mass spectrometry (MS). A total of 109 liquid and 40 gas compounds were identified. A total of 59 chemical compounds (35 liquids and 24 gaseous products) were quantitatively determined. The influence of the gas-phase residence time and biomass feed particle size were studied. The gas residence time determined the extent of secondary reactions. Very short residence times enhanced liquid production versus gas production. Particle sizes (d < 105 µm, 105 µm < d < 149 µm, 149 µm < d < 297 µm, and d > 297 µm) did not have a pronounced effect on either the yield or product distributions, indicating that heat-transfer limitations within the particles were negligible. The pyrolysis of pine, red oak, and sweet gum sawdust yielded similar product distributions. Simulations were conducted using the ASPEN/ SP software package based on Gibbs energy minimization. At high temperatures, dominant species were hydrogen and carbon monoxide, while at lower temperatures, methane, carbon dioxide, and water were the predominant species. Above 871°C, further increases in the temperature did not affect the product distribution. Lower gasification temperatures and higher steam/carbon ratios resulted in higher hydrogen and carbon monoxide production. Mohan, D.; Pittman, C. U.; Steele, P. Pyrolysis of wood/biomasss A critical review. Energy Fuels 2006, 20, 848-889. (2) Tsai, W. T.; Lee, M. K.; Chang, Y. M. Fast pyrolysis of rice straw, sugarcane bagasse and coconut shell in an induction-heating reactor. J. Anal. Appl. Pyrolysis 2006, 76, 230-237. (3) Guéhenneux, G.; Baussand, P.; Brothier, M.; Poletiko, C.; Boissonnet, G. Energy production from biomass pyrolysis: A new coefficient of pyrolytic valorization. Fuel 2005, 84, 733-739. (4) Huber, G. W.; Iborra, S.; Corma, A. Synthesis of transportation fuels from biomass: Chemistry, catalysts, and engineering. Chem. ReV. 2006, 106, 4044-4098. (5) Bridgwater, A. V. Renewable fuels and chemicals by thermal processing of biomass. Bridgwater, A. V.; Peacock, G. V. C. Fast pyrolysis process for biomass. Renewable Sustainable Energy ReV. 2000, 4, 1-73. (9) Butt, D. A. E. Formation of phenols from the low-temperature fast pyrolysis of Radiata pine (Pinus radiata). Part 1. Influence of molecular oxygen. J. Anal Appl. Pyrolysis 2006, 76, 38-47. (10) Piskorz, J.; Majerski, P.; Radlein, D.; Scott, D. S.; Bridgwater, A. V. Fast pyrolysis of sweet sorghum and sweet sorghum bagasse. J. Anal. Appl. Pyrolysis 1998, 46, 15-29.
J. Bigorra, R. Höfer, Biomass-based Green Chemistry – sustainable solutions for modern economies
Renewable raw materials, biomass, are the basis and driver for even greater alignment of industry to the principles of green chemistry and sustainability. Nature provides a remarkably wide range of renewable raw materials with varying properties and differing chemical compositions. Renewable raw materials are therefore especially interesting as alternatives to fossil resources for energy generation and as starting materials for industrial chemistry. Since various forms of biomass are also essential for human nutrition and animal feed, their use as feedstock for other purposes must be balanced. Ideally, the biomass remaining after the nutritious components are removed can serve as a feedstock. Examples of applications that use biomass starting materials include adhesives, textile and leather,
BIOMASS AS A RENEWABLE SOURCE OF CHEMICALS FOR INDUSTRIAL APPLICATIONS
International Journal of Engineering …, 2012
Worldwide demand for cleaner burning fuels and 'clean' chemicals has been increasing from the global issues of environmental concern. This lead to a greater utilization of renewable resources to replace the old and existing fossil based feedstock for liquid fuels and chemicals. The ability to re-grow harvested biomass and recapture the carbon emitted to the atmosphere through photosynthesis allows the possibility of carbon neutrality encouraged the use of biomass. Moreso, the unstable rise of oil prices, the negative effects of petroleum on the environment and the advantages of biomass towards sustainability of resources accelerated the development and utilization of unused biomass. This paper reviewed some of the potentials of biomass as a source of chemicals for industrial applications. Pyrolysis is considered to be one of the most employed technologies for the conversion of biomass into bio-oil, char and gases. The utilization of biomass for chemical manufacture can significantly eliminate the harmful effects of fossil based chemicals on the environment.
ChemInform Abstract: Green and Sustainable Manufacture of Chemicals from Biomass: State of the Art
ChemInform, 2014
The various strategies for the valorisation of waste biomass to platform chemicals, and the underlying developments in chemical and biological catalysis which make this possible, are critically reviewed. The option involving the least changes to the status quo is the drop-in strategy of complete deoxygenation to petroleum hydrocarbons and further processing using existing technologies. The alternative, redox economic approach, is direct conversion of, for example, carbohydrates to oxygenates by fermentation or chemocatalytic processes. Examples of both approaches are described, e.g. fermentation of carbohydrates to produce hydrocarbons, lower alcohols, diols and carboxylic acids or acid catalyzed hydrolysis of hexoses to hydroxymethyl furfural (HMF) and subsequent conversion to levulinic acid (LA), γ-valerolactone (GVL) and furan dicarboxylic acid (FDCA). Three possible routes for producing a bio-based equivalent of the large volume polymer, polyethylene terephthalate (PET) are delineated. Valorisation of waste protein could, in the future, form an important source of amino acids, such as L-glutamic acid and L-lysine, as platform chemicals, which in turn can be converted to nitrogen containing commodity chemicals.