Gas diffusion in coal is controlled by nano-structure of the pores. The interconnectivity of pores not only determines the dynamics of gas transport in the coal matrix but also influences the mechanical strength. In this study, small angle neutron scattering (SANS) was employed to quantify pore accessibility for two coal samples, one of sub-bituminous rank and the other of anthracite rank. A theoretical pore accessibility model was proposed based on scattering intensities under both vacuum and zero average contrast (ZAC) conditions. The results show that scattering intensity decreases with increasing gas pressure using deuterated methane (CD4) at low Q values for both coals. Pores smaller than 40 nm in radius are less accessible for anthracite than sub-bituminous coal. On the contrary, when the pore radius is larger than 40 nm, the pore accessibility of anthracite becomes larger than that of sub-bituminous coal. Only 20% of pores are accessible to CD4 for anthracite and 37% for sub-bituminous coal, where the pore radius is 16 nm. For these two coals, pore accessibility and pore radius follows a power-law relationship. (C) 2015 Elsevier Ltd. All rights reserved.

Liquid hydrocarbons are considered as an option to store renewable energy while decoupling the supply and demand of renewable resources. They can also be used as transportation fuel or as feedstock for the chemical industry and are characterized by a high energy density. A process concept using renewable energy from fluctuating wind power and CO2 to produce liquid hydrocarbons was modeled by a flowsheet simulation in Aspen Plus (R). The capacity of the plant was set to 1 GWLHV of hydrogen input, using water electrolysis, reverse water-gas shift reaction (RWGS) and Fischer-Tropsch (FT) synthesis. A feed of 30 t/h of H-2 generated 56.3 t/h (12; 856 bbl/d) of liquid hydrocarbons. A Power-to-Liquid efficiency of 44.6% was calculated for the base case scenario. Net production cost ranged from 12.41 $/GGE to 21.35 $/GGE for a system powered by a wind power plant with a full load fraction of about 47%, depending on the assumed electricity feedstock price and electrolyzer capital cost. For systems with full load fractions between 70% and 90%, the production cost was in the range of 5.48 $/GGE to 8.03 $/GGE. (C) 2015 Elsevier Ltd. All rights reserved.

This work is focused on the esterification of fatty acids (commercial oleic mix) with zinc carboxylates (layered metal soap). About 25 experiments were performed, with and without catalyst, yielding a kinetic model based on the Eley-Rideal approach, able to predict fatty acid conversions under different conditions (molar ratio fatty acids/ethanol and temperature). An apparent first order reaction with respect to both reactants with no diffusion limitations was proposed. The activation energy of 80 kJ/mol was found. Fatty acid conversion up to 92% was reached under some conditions and the catalytic yields compared to the blank ones reached 40% in less than 90 min of reaction. This catalyst has shown a unique behavior among all other catalysts available for esterification, acting similarly to a homogeneous catalyst during the reaction but being recovered like a heterogenous catalyst at the end of the process. (C) 2015 Elsevier Ltd. All rights reserved.

An anaerobic, thermophilic microbial viscosity reducing consortium TERIB# 90 was isolated from formation fluid of an oil reservoir located in India. It was able to reduce 98% viscosity of crude oil (665 to 10 cP) at 70 degrees C on the 30th day of incubation. Sequence analysis of the clones obtained from 16S rDNA clonal library showed affiliations with the genus Moorella sp. CF4 ranging from 94% to 97% identity. Gas chromatography results indicated degradation of aromatics (56%). The metabolic capabilities of this consortium to survive and grow under selected heavy oil reservoir conditions such as high temperature, salinity and presence of oil were also evaluated. A higher percentage of viscosity reduction (75-98%) was observed at 60-70 degrees C as compared to 80 degrees C (14%). It could grow up to 2% NaCl concentration and effectively reduce viscosity up to 80% but it showed maximum viscosity reduction when no NaCl was added. Metabolites in the form of hydrogen (65%), carbon dioxide (27%), volatile fatty acids (2500 mg/L) and biosurfactant as indicated by a reduced surface tension (27 from 64 mN/m) were observed. A core flooding test was designed to explore the potential of TERIB#90 as an agent for viscosity reduction of heavy oil. The results showed that the viscosity reduction of heavy oil by the microbial metabolites and degradation of heavy fractions are the dominant mechanisms for oil recovery efficiency. The microbial processes elucidated by this consortium both in terms of targeted heavy crude oil degradation and byproduct formation ascertain its value as an economical and environmentally attractive option. (C) 2014 Elsevier Ltd. All rights reserved.

Pore connectivity is limited in shale formations, unlike in conventional reservoirs, for which cyclic void models, such as the regular-lattice model, are often used to represent the connectivity. In the cyclic models, the random assignment of throat sizes to lattice elements leads to a plateau-like variation of a capillary pressure with wetting phase saturation during a drainage displacement. Here, we develop acyclic void models in which the spatial distribution of throat sizes is not random. For certain spatial distributions these models yield a non-plateau-like drainage displacement. Such models thus provide more realistic representations of the void space in samples for which drainage experiments reveal the non-plateau-like trend of the capillary pressure versus saturation. Gas shales commonly show such a trend, and using the developed models, we predict the no-slip permeability of shale samples whose mercury intrusion capillary pressures curves were measured under confined boundary conditions. The predicted permeabilities are in good agreement with the lab measurements reported for these samples. Other models either fail to account for the non-plateau-like trend of the drainage as they adopt a random pore size distribution or they overestimate the no-slip permeability for saturated flow. The models developed here could have applications in other porous media whose drainage data do not exhibit a plateau-like variation. (C) 2014 Elsevier Ltd. All rights reserved.

The knowledge of biodiesel density over large ranges of temperature and pressure is important for predicting the behavior of fuel injection and combustion systems in diesel engines, and for the optimization of such systems. In this study, cottonseed oil was transesterified into biodiesel and its density was measured at temperatures between 288 K and 358 K and pressures between 0.1 MPa and 30 MPa, with expanded uncertainty estimated as +/- 1.6 kg m(-3). Experimental pressure-volume-temperature (pVT) cottonseed data was used along with literature data relative to other 18 biodiesels, in order to build a database used to test the correlation of density with temperarure and pressure using the Goharshadi-Morsali- Abbaspour equation of state (GMA EoS). To our knowledge, this is the first that density measurements are presented for cottonseed biodiesel under such high pressures, and the GMA EoS used to model biodiesel density. The new tested EoS allowed correlations within 0.2 kg m(-3) corresponding to average relative deviations within 0.02%. From these results of correlation with the GMA EoS mechanical coefficients such as thermal expansivity, isothermal compressibility and internal pressure were calculated. In spite of their effect in power and fuel injection, those properties are rarely presented for biodiesel, especially at high pressures. As a remarkable result of this study, it was found a crossing point for the thermal expansivity, where isothermic curves cross. The built database was used to develop and test two new full predictive models valid up to 373 K and 130 MPa. One of the proposed predictive methods (4PGMA) followed from the GMA EoS, and the other (DU) was derived from the observed linear relation between density and degree of unsaturation (DU), which depended from biodiesel FAMEs profile. The average density deviation of 4PGMA was only about 2 kg m(-3), and 3 kg m(-3) for the DU method within the temperature and pressure limits of application. These results represent appreciable improvements in the context of density prediction at high pressure when compared with other equations of state. (C) 2014 Elsevier Ltd. All rights reserved.