Duminda A. Gunawardena

Thermal conversion of glucose to aromatic hydrocarbons via pressurized secondary pyrolysis

In this study, glucose, a primary building-block of biomass was subjected to secondary pyrolysis in a reactor that was retrofitted subsequent to a primary micro-pyrolysis reactor. It was observed that incorporation of a secondary reactor resulted in producing significant amounts of gasoline range hydrocarbons. The hydrocarbon yields improved further as a result of increasing pyrolysis reactor pressure and temperatures. The temperature of the secondary reactor was varied between 400 and 800°C and pressure between 0 and 150 psi. This study indicates that secondary cracking of primary pyrolysis products of biomass oxygenates undergo gas-phase homogenous molecular restructuring. The result of this process is production of substantial amounts of thermodynamically stable gasoline-range hydrocarbons even in the absence of a catalyst.

Methods and Applications of Deoxygenation for the Conversion of Biomass to Petrochemical Products

© 2013 Gunawardena and Fernando, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Methods and Applications of Deoxygenation for the Conversion of Biomass to Petrochemical Products

A THERMODYNAMIC EQUILIBRIUM ANALYSIS OF GLUCOSE CONVERSION TO HYDROCARBONS

Deoxygenation, or removal of oxygen from oxygenates, is an important element in the hydrocarbon fuel production process from biorenewable substrates. A thermodynamic equilibrium analysis gives valuable insights on the theoretical limits of desired products when a substrate is reacted under a given set of conditions. Here we report the equilibrium composition of glucose-to-hydrocarbon system by minimizing the total Gibbs energy of the system. The system was treated as a mixture of 11 components comprised of C6H6, C7H8, C8H10 (ethyl benzene), C8H10 (xylenes), C6H5 –OH, CH4, H2O, C, CO2, CO, and H2. Equilibrium compositions of each species were analyzed between temperatures 300 and 1500 K and pressures 0–15 atm. It was observed that at high temperature, CO and H2 dominate the equilibrium mixture with mole fractions of 0.597 and 0.587 respectively. At low temperatures the equilibrium mixture is dominated by CH4, CO2, H2O, and carbon. The aromatic hydrocarbon composition observed at thermodynamic equilibrium was extremely small.

Thermodynamic Equilibrium Analysis of Methanol Conversion to Hydrocarbons Using Cantera Methodology

Reactions associated with removal of oxygen from oxygenates (deoxygenation) are an important aspect of hydrocarbon fuels production process from biorenewable substrates. Here we report the equilibrium composition of methanol-to-hydrocarbon system by minimizing the total Gibbs energy of the system using Cantera methodology. The system was treated as a mixture of 14 components which had CH3OH, C6H6, C7H8, C8H10 (ethyl benzene), C8H10 (xylenes), C2H4, C2H6, C3H6, CH4, H2O, C, CO2, CO, H2. The carbon in the equilibrium mixture was used as a measure of coke formation which causes deactivation of catalysts that are used in aromatization reaction(s). Equilibrium compositions of each species were analyzed for temperatures ranging from 300 to 1380 K and pressure at 0–15 atm gauge. It was observed that when the temperature increases the mole fractions of benzene, toluene, ethylbenzene, and xylene pass through a maximum around 1020 K. At 300 K the most abundant species in the system were CH4, CO2, and H2O with mole fractions 50%, 16.67%, and 33.33%, respectively. Similarly at high temperature (1380 K), the most abundant species in the system were H2 and CO with mole fractions 64.5% and 32.6% respectively. The pressure in the system shows a significant impact on the composition of species.

Screening of transition metal/oxide-impregnated ZSM-5 catalysts for deoxygenation of biomass oxygenates via direct methane intervention

ABSTRACT Removal of oxygen from biomass (deoxygenation) is a significant challenge that needs to be overcome to effectively produce hydrocarbon-based biofuel. The present technology needs extraneous hydrogen (H2) to act as a proton donor, to effectively remove this oxygen. This work is geared toward finding an effective catalyst that accommodates the direct use of methane, instead of H2, for deoxygenation reactions. Here, we studied the impact of three oxides (Ga2O3, MoO3, Cr2O3) and two metals (Pt, Ni) impregnated (at 1, 2 and 5% loadings) on ZSM-5 support on furan conversion, benzene-toluene-ethylbenzene-xylenes (BTEX) selectivity, and coke formation when furan was catalytically pyrolyzed in methane and methane-free environments. The results indicate that Ga-, Pt- and Ni-based catalysts increase BTEX selectivity in a methane environment as opposed to methane-free conditions. The type of metal and the amount of loading had a significant impact on furan conversion as well. Ga/ZSM-5-based catalyst displayed the highest BTEX selectivity, while Ni/ZSM-5 resulted in the highest furan conversion. The results are significant since there is strong evidence of select catalysts’ ability to activate methane and in turn allow furan deoxygenation. This work paves the way to use methane (or natural gas) instead of H2 as a direct proton donor for deoxygenation reactions.

Performance Analysis of a Proton Exchange Membraneless Biological Fuel Cell Based on Lactate Dehydrogenase

Fuel cells with enzyme-coated electrodes, commonly known as enzymatic fuel cells, are closely looked at as a means to power implantable medical devices and miniaturized bioelectronic devices such as biomicroeletromechanical or nanoelectromechanical systems (bioMEMS/NEMS). This study attempts to develop a fuel cell with the proton exchange membrane (PEM) totally replaced by an enzyme coating tethered only to one electrode (anode). It was conjectured that the specificity of the enzyme to only a specific substrate at the anode coupled with the selectivity of reactions that could occur at the cathode due to thermodynamic preferences will discourage crossover reactions, making the PEM elimination possible. In the anode, lactate dehydrogenase (LDH), a NAD-dependent oxidoreductase, was immobilized on a gold-coated electrode using a layer-by-layer assembly technique. The LDH-coated anode catalyzed the oxidation of lactate to pyruvate, while Pt was used to catalyze the reduction of oxygen to water. Three parameters were selected to elucidate the behavior of the fuel cell under different load conditions. These parameters (lactate concentration, fuel cell temperature, and feed flow rate) were varied within the human physiological range to evaluate the performance as an implantable fuel cell. The cell reported an average open-circuit voltage of 261.72 ±0.01 mV, power density of 360.6 nW cm-1, and voltage efficiency of 25.05%. This experiment demonstrated that total elimination of the PEM is possible via coating only one electrode with a substrate-specific enzyme. This is a significant step toward developing power supplies for bioelectronic devices via enzymatic fuel cells, since elimination of the PEM enables unprecedented simplification of the fuel cell architecture (for miniaturization) while eliminating a component that contributes to significant internal resistance.

Thermodynamic Equilibrium Analysis of Glucose Conversion to Hydrocarbons.

Deoxygenation, or removal of oxygen from oxygenates, is an important process in hydrocarbon fuels production from biorenewable substrates. A thermodynamic equilibrium analysis on such reactions gives valuable insights on the theoretical limits of desired products when a substrate is reacted under a given set of conditions. Here we report the equilibrium composition of glucose-to-hydrocarbon system by minimizing the total Gibbs energy of the system. The system was treated as a mixture of 11 components which had C6H6, C7H8, C8H10 (ethyl benzene), C8H10 (xylenes), C6H5 –OH , CH4, H2O, C, CO2, CO, H2. Equilibrium compositions of each species were analyzed for temperatures ranging from 300 -1500 K and pressure at 0- 15 atm gauge. It was observed that at high temperature CO and H2 dominates the equilibrium mixture with mole fraction of 0.597 and 0.587 respectively. At low temperatures equilibrium mixture is dominated by CH4, CO2, H2O and atomistic carbon. The aromatic hydrocarbon composition observed at thermodynamic equilibrium is extremely small.