Sandun D. Fernando

Physiochemical properties of bio-oil produced at various temperatures from pine wood using an auger reactor.

A fast pyrolysis process produces a high yield of liquid (a.k.a. bio-oil) and has gained a lot of interest among various stakeholders. Nonetheless, some of the properties inherent by the bio-oil create significant challenges for its wider applications. Quality of the bio-oil and its yield are highly dependent on process parameters, such as temperature, feedstock, moisture content and residence time. In this study, the effect of temperature on bio-oil quality and its yield were examined using pine wood, an abundant biomass source in the southeastern part of the United States. Physical properties of bio-oil such as pH, water content, higher heating value, solid content and ash were analyzed and compared with a recently published ASTM standard. Bio-oil produced from pine wood using an auger reactor met specifications suggested by the ASTM standard. Thirty-two chemical compounds were analyzed. The study found that the concentration of phenol and its derivatives increased with the increase in pyrolysis temperature whereas the concentration of guaiacol and its derivatives decreased as the temperature increased. Concentration of acetic and other acids remained almost constant or increased with the increase in temperature although the pH value of the bio-oil decreased with the increase in temperature.

Adsorption of glycerol from biodiesel washwaters.

The removal of glycerol by adsorption from biodiesel washwaters has been studied at room temperature using various adsorbent materials, including activated carbons, clay minerals, and natural and synthetic zeolites. Activated carbon exhibited the best adsorption for glycerol among the examined materials. Glycerol adsorption isotherms are obtained on activated carbons after treatment under different conditions. The Langmuir isotherm coefficients and the first‐order desorption kinetic parameters for glycerol on a coconut activated carbon were determined by fitting the experimental data. The adsorption of glycerol was increased by removing the functional groups from the carbon surface at high temperatures under N2 atmosphere, and was decreased by increasing surface functional groups through HNO3 oxidation. Compared with water, glycerol tends to adsorb more favourably on a hydrophobic carbon surface than on a hydrophilic one.

Effect of hydrocarbon tail-groups of transition metal alkoxide based amphiphilic catalysts on transesterification

In liquid/liquid/solid (L/L/S) systems pertinent to two immiscible reactant liquids mixed with a solid catalyst, the reaction efficacy depends on the mass transfer limitations at the L/L/S phase boundary. Formation of an emulsion in such a system will likely reduce the mass transfer barrier significantly. The stability of such an emulsion system depends on the hydrophilicity of the head group of the catalytic emulsifier toward the more polar liquid reactant and the hydrophobicity of the tail group toward the more nonpolar liquid reactant. This study looks at the effect of the alkyl groups with varying carbon numbers in titanium alkoxide as a catalyst that also has emulsification (amphiphilic) properties to transesterify triglycerides in alcohols. All forms of oligomeric titanium alkoxides tested were highly basic. Those with smaller alkoxide groups (lower carbon numbers) tended to be more basic than those with higher carbon numbers. The chirality did not affect the degree of basicity of the alkoxides. The maximum ester yield noticed was 64.25% (with 63.85% selectivity towards transesterification) with titanium methoxide after 3 hours of reaction. It was observed that higher the number of carbon atoms in the tail group the lower the catalytic ability of the amphiphile towards transesterification. It is expected that longer the carbon-chain in the tail group stronger the emulsification ability of the amphiphile in oil-in-alcohol systems. However, when looking at the efficacy of the amphiphile for the combined emulsification and catalytic ability, it is apparent that the length of the alkoxide group needs to be compromised.

An Approach for Zika Virus Inhibition Using Homology Structure of the Envelope Protein

To find an effective drug for Zika virus, it is important to understand how numerous proteins which are critical for the virus’ structure and function interact with their counterparts. One approach to inhibiting the flavivirus is to deter its ability to bind onto glycoproteins; however, the crystal structures of envelope proteins of the ever-evolving viral strains that decipher glycosidic or drug-molecular interactions are not always available. To fill this gap, we are reporting a holistic, simulation-based approach to predict compounds that will inhibit ligand binding onto a structurally unresolved protein, in this case the Zika virus envelope protein (ZVEP), by developing a three-dimensional general structure and analyzing sites at which ligands and small drug-like molecules interact. By examining how glycan molecules and small-molecule probes interact with a freshly resolved ZVEP homology model, we report the susceptibility of ZVEP to inhibition via two small molecules, ZINC33683341 and ZINC49605556—by preferentially binding onto the primary receptor responsible for the virus’ virulence. Antiviral activity was confirmed when ZINC33683341 was tested in cell culture. We anticipate the results to be a starting point for drug discovery targeting Zika virus and other emerging pathogens.

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.

Iron-sulfur-based single molecular wires for enhancing charge transport in enzyme-based bioelectronic systems.

When redox enzymes are wired to electrodes outside a living cell (ex vivo), their ability to produce a sufficiently powerful electrical current diminishes significantly due to the thermodynamic and kinetic limitations associated with the wiring systems. Therefore, we are yet to harness the full potential of redox enzymes for the development of self-powering bioelectronics devices (such as sensors and fuel cells). Interestingly, nature uses iron-sulfur complexes ([Fe-S]), to circumvent these issues in vivo. Yet, we have not been able to utilize [Fe-S]-based chains ex vivo, primarily due to their instability in aqueous media. Here, a simple technique to attach iron (II) sulfide (FeS) to a gold surface in ethanol media and then complete the attachment of the enzyme in aqueous media is reported. Cyclic voltammetry and spectroscopy techniques confirmed the concatenation of FeS and glycerol-dehydrogenase/nicotinamide-adenine-dinucleotide (GlDH-NAD(+)) apoenzyme-coenzyme molecular wiring system on the base gold electrode. The resultant FeS-based enzyme electrode reached an open circuit voltage closer to its standard potential under a wide range of glycerol concentrations (0.001-1M). When probed under constant potential conditions, the FeS-based electrode was able to amplify current by over 10 fold as compared to electrodes fabricated with the conventional pyrroloquinoline quinone-based composite molecular wiring system. These improvements in current/voltage responses open up a wide range of possibilities for fabricating self-powering, bio-electronic devices.

Reforming glycerol under electro-statically charged surface conditions

Catalysis is dependent on electronic interactions that occur between substrate molecules and surface atoms of a catalyst. Although these electronic interactions have been altered by means of adding dopants, the effect of direct extraneous alteration of electronic structure of catalyst-substrate system has not yet been studied. Here, we studied the effects of electrically charging a conductive catalyst surface (Ni–Ce/carbon) and a substrate system (glycerol nanodroplets) on the efficacy of steam reforming. The behavior of the system when the catalysts surface was excited with electrons while the substrates were positively charged was studied at varying temperatures and polarity. It was evident that throughout the temperature ranges tested, the hydrogen yields increased consistently when the system was charged as opposed to reforming under neutral conditions. Reforming under electrically charged surface conditions resulted in a 25% increase in hydrogen selectivity, and 64% increase in substrate conversion. The effects were more pronounced at temperatures below the glycerol boiling point. These results expose the possibility of controlling the outcome of a reaction by extraneous manipulation of the electronic structure of a catalyst/substrate surface.

An improved glycerol biosensor with an Au-FeS-NAD-glycerol-dehydrogenase anode

An improved glycerol biosensor was developed via direct attachment of NAD+-glycerol dehydrogenase coenzyme-apoenzyme complex onto supporting gold electrodes, using novel inorganic iron (II) sulfide (FeS)-based single molecular wires. Sensing performance factors, i.e., sensitivity, a detection limit and response time of the FeS and conventional pyrroloquinoline quinone (PQQ)-based biosensor were evaluated by dynamic constant potential amperometry at 1.3V under non-buffered conditions. For glycerol concentrations ranging from 1 to 25mM, a 77% increase in sensitivity and a 53% decrease in detection limit were observed for the FeS-based biosensor when compared to the conventional PQQ-based counterpart. The electrochemical behavior of the FeS-based glycerol biosensor was analyzed at different concentrations of glycerol, accompanied by an investigation into the effects of applied potential and scan rate on the current response. Effects of enzyme stimulants ((NH4)2SO4 and MnCl2·4H2O) concentrations and buffers/pH (potassium phosphate buffer pH 6-8, Tris buffer pH 8-10) on the current responses generated by the FeS-based glycerol biosensor were also studied. The optimal detection conditions were 0.03M (NH4)2SO4 and 0.3µm MnCl2·4H2O in non-buffered aqueous electrolyte under stirring whereas under non-stirring, Tris buffer at pH 10 with 0.03M (NH4)2SO4 and 30µm MnCl2·4H2O were found to be optimal detection conditions. Interference by glucose, fructose, ethanol, and acetic acid in glycerol detection was studied. The observations indicated a promising enhancement in glycerol detection using the novel FeS-based glycerol sensing electrode compared to the conventional PQQ-based one. These findings support the premise that FeS-based bioanodes are capable of biosensing glycerol successfully and may be applicable for other enzymatic biosensors.

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.