Pentazole-Based Energetic Ionic Liquids: A Computational Study

The structures of protonated pentazole cations (RN5H+), oxygen-containing anions such as N(NO2)2-, NO3-, and ClO4- and the corresponding ion pairs are investigated by ab initio quantum chemistry calculations. The stability of the pentazole cation is explored by examining the decomposition pathways of several monosubstituted cations (RN5H+) to yield N2 and the corresponding azidinium cation. The heats of formation of these cations, which are based on isodesmic (bond-type conserving) reactions, are calculated. The proton-transfer reaction from the cation to the anion is investigated

3-D structure of a local minimum of the Siskin model of oil shale kerogen using the RHF/STO-3G method

photograph; posterKerogen is a mixture of organic chemical compounds that make up a portion of the organic matter in sedimentary rocks. It is insoluble in normal organic solvents because of the huge molecular weight (upwards several thousand Daltons). When heated in the Earth's crust, (oil window ca. 6 ∞-120∞C; gas window ca.120∞-150∞C) some types of kerogen release hydrocarbons in the form of crude oil or natural gas, collectively known as fossil fuels. Kerogens can also be found in rocks such as shale, as oil shale deposits. The objective of this study is to determine the theoretical 3-D structure of kerogen and its interaction with the inorganic matter of the rock for the purpose of identifying suitable means of isolating kerogen from oil shales. The RHF/STO-3G calculation of this model (1702 atoms) involves 4458 basis functions and ran on 32 quad-core nodes with 8 Gbytes of memory per node. Each optimization step takes about 5 hours to finish. Multiple initial 3-D structures are obtained using the Simulated Annealing procedures followed by ab initio optimization to identify suitable structures. This annealing/optimization process is repeated until a plausible set of the lowest energy structures is gathered. In this image,carbons are colored cyan, oxygens are colored red, nitrogens are colored blue, sulfurs are colored yellow, and hydrogens are colored gray. The tubes represent the molecule's backbone and the spheres represent the atoms. The image is prepared using VMD

Atomistic modeling of oil shale kerogens and asphaltenes along with their interactions with the inorganic mineral matrix

The goal of this project is to obtain and validate three dimensional atomistic models for the organic matter in both oil shales and oil sands. In the case of oil shales the modeling was completed for kerogen, the insoluble portion of the organic matter; for oil sands it was for asphaltenes, a class of molecules found in crude oil. The three dimensional models discussed in this report were developed starting from existing literature two dimensional models. The models developed included one kerogen, based on experimental data on a kerogen isolated from a Green River oil shale, and a set of six representative asphaltenes. Subsequently, the interactions between these organic models and an inorganic matrix was explored in order to gain insight into the chemical nature of this interaction, which could provide vital information in developing efficient methods to remove the organic material from inorganic mineral substrate. The inorganic substrate used to model the interaction was illite, an aluminum silicate oxide clay. In order to obtain the feedback necessary to validate the models, it is necessary to be able to calculate different observable quantities and to show that these observables both reproduce the results of experimental measurements on actual samples as well as that the observables are sensitive to structural differences between models. The observables that were calculated using the models include 13C NMR spectra, the IR vibrational spectra, and the atomic pair wise distribution function; these were chosen as they are among the methods for which both experimental and calculated values can be readily obtained. Where available, comparison was made to experiment results. Finally, molecular dynamic simulations of pyrolysis were completed on the models to gain an understanding into the nature of the decomposition of these materials when heated

Method of Moments of Coupled-Cluster Equations: Externally Corrected Approaches Employing Configuration Interaction Wave Functions

Abstract: A new approach to the many-electron correlation problem, termed the method of moments of coupled-cluster equations (MMCC), is further developed and tested. The main idea of the MMCC theory is that of the noniterative energy corrections which, when added to the energies obtained in the standard coupled-cluster calculations, recover the exact (full configuration interaction) energy. The MMCC approximations require that a guess is provided for the electronic wave function of interest. The idea of using simple estimates of the wave function, provided by the inexpensive configuration interaction (CI) methods employing small sets of active orbitals to define higher–than–double excitations, is tested in this work. The CI-corrected MMCC methods are used to study the single bond breaking in HF and the simultaneous breaking of both O–H bonds in H2O

Pentazole-Based Energetic Ionic Liquids: A Computational Study

The structures of protonated pentazole cations (RN5H+), oxygen-containing anions such as N(NO2)2-, NO3-, and ClO4- and the corresponding ion pairs are investigated by ab initio quantum chemistry calculations. The stability of the pentazole cation is explored by examining the decomposition pathways of several monosubstituted cations (RN5H+) to yield N2 and the corresponding azidinium cation. The heats of formation of these cations, which are based on isodesmic (bond-type conserving) reactions, are calculated. The proton-transfer reaction from the cation to the anion is investigated.This article is from Journal of Physical Chemistry A 111 (2007): 691, doi:10.1021/jp0663006.</p

Modeling of Asphaltenes: Assessment of Sensitivity of ¹³C Solid State NMR to Molecular Structure

This paper presents calculations of ¹³C solid state NMR (SSNMR) spectra of model asphaltenes. The overall goal of this work is to assess how valuable ¹³C SSNMR studies of asphaltenes can be in guiding the development of representative 3D (three-dimensional) models of asphaltenes. The calculations were done using 3D models based on previously published 2D (two-dimensional) models. The calculated spectra show overall agreement with the existing data, and the results show that the ¹³C SSNMR spectra of model asphaltenes are quite sensitive to both the 2D and the 3D structures, indicating that this property can be used to guide further model development

Anaerobic digestion of Crassulacean Acid Metabolism plants : Exploring alternative feedstocks for semi-arid lands

In this work, five Crassulacean Acid Metabolism (CAM) species from the five different genera (Agave, Ananas, Euphorbia, Kalanchoe, and Opuntia) were selected as alternative feedstocks and their biochemical methane potentials (BMP) were investigated. Batch assays were performed using sludge and rumen fluid as inocula under uncontrolled pH and at mesophilic temperature (39 °C). Mean methane yields from the CAM plants inoculated with AD sludge ranged from 281 to 382 ml/gVS. These values were not significantly different from the methane yield obtained from maize, a feedstock for biomethane and volatile fatty acid (VFA), suggesting that CAM plants may be viable as bioenergy crops on poor-quality soils in areas with low rainfall that are unsuitable for cultivation of food crops