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.

No abstract

An electrochemical biosensor for glycerol was obtained by using a novel concatenation of molecules to immobilize glycerol dehydrogenase (GlDH) on a gold electrode via layer-by-layer (LBL) self-assembly. The surface of the enzyme electrodes was characterized by cyclic voltammetry and scanning electron microscopy which confirmed the attachment of enzyme on the gold electrode with the assistance of the tethering molecules. The biosensor was assessed for its potentiometric and amperometric response to glycerol in the presence of the enzyme stimulants, ammonium sulfate and manganese chloride. The electrodes demonstrated good selectivity and reproducibility, with a amperometric response at a working voltage of 1.3 V in the 0.001 to 1 M glycerol concentration range, a 12.07 μA·M −1 sensitivity, and a 6.8 μM lower limit of detection. The average diffusion coefficient of glycerol is 8.63×10 −6 cm 2 s −1 as determined by chronoamperometry.

No abstract

No abstract

Deoxygenation is a critical step in making hydrocarbon-rich biofuels from biomass constituents. Although the thermal effects of oxygenate aromatization have been widely reported, the effect of pressure on this critical reaction has not yet been closely investigated, one primary reason being the unavailability of a reactor that can pyrolyze oxygenates, especially those in solid form, under pressurized conditions. Here, the first of a series of studies on how oxygenates behave when catalytically pyrolyzed under elevated pressure and temperature conditions is reported. Methanol, the simplest alcohol, was selected as the candidate to study the chemical phenomena that occur under pressurized catalytic pyrolysis. The reactions were carried out over the shape-selective catalyst ZSM-5 (SiO 2 /Al 2 O 3 = 30) under varying pressure (0 to 2.0684 MPa (300 psi) in 0.3447 MPa (50 psi) increments) and temperature (500 to 800°C in 50°C increments) conditions. Benzene, toluene, ethyl benzene, and xylenes (BTEX) were analyzed as the deoxygenated products of the reaction. The results indicate that the reactor pressure significantly affects deoxygenated product composition.

No abstract

Current biomass deoxygenation technologies require large quantities H2. Gaseous hydrogen is not a naturally‐occurring raw material and is largely produced industrially via natural gas/methane steam reforming. Due to its high thermodynamic stability, direct use of methane as a hydrogen‐donor for deoxygenation of complex oxygenates has not yet been demonstrated. Using catalytic pyrolysis studies performed at 700 °C with isotope labeled methane and glucose over Ni, Pt, Mo, and Ga impregnated HZSM‐5 (Si/Al ratio 30), here we show that methane, in fact, could be used as a direct hydrogen donor for deoxygenation reactions. The amount of aromatic hydrocarbons produced increased primarily in the presence of Mo (125 % increase), and to a lesser degree, Pt (50 % increase), and Ni (22 % increase) impregnated HZSM‐5 catalysts in a methane environment. Based on the metal present, results indicate the occurrence of distinct and concurrent reactions to various degrees: methane (steam) reforming and oxygenate dehydration reaction; independent aromatization of methane and oxygenates; and an intriguing methane oxygenate cross‐coupling reaction where both hydrogen and carbon from methane ending up in resultant deoxygenated aromatic products. This technique paves way for the direct use of methane/natural gas for deoxygenation reactions critical to biorefining.