No description available.

No description available.

No description available.

Abstract A theoretical study of the Kolbe-Schmitt reaction mechanism, performed using a DFT method, reveals that the reaction between sodium phenoxide and carbon dioxide proceedswith the formation of three transition states and three intermediates. In the first step of the reaction, a polarized ONa bond of sodium phenoxide is attacked by the carbon dioxide molecule, and the intermediate NaPh-CO2 complex is formed. In the next step of the reaction the electrophilic carbon atom attacks the ring primarily at the ortho position, thus forming two new intermediates. The final product, sodium salicylate, is formed by a 1,3-proton shift from C to O atom. The mechanism agrees with the experimental data related to the Kolbe-Schmitt reaction.

Thesis advisor: Jeffery A. Byers / Chapter 1. Overview of Carbon Dioxide Hydrogenation for the Production of Formic Acid As the world’s energy demands increase, our resources dwindle and the need for a sustainable energy source is pertinent. Our current energy infrastructure is dominated by fossil fuel use. Hydrogen, on the other hand, is potentially an ideal energy carrier as it is emissions-free when burned and can be used in fuel cells. Significant advances are still needed to develop more efficient ways to produce and store H2. The hydrogenation of CO2 to formic acid and/or methanol provides an encouraging and reversible approach for a hydrogen storage material. The first example of homogeneously catalyzed hydrogenation of carbon dioxide was in 1976. Over the past 40 years, there has been excellent progress in the development of catalysts for CO2 hydrogenation. Typically, homogenous catalysts found to be effect are 2nd and 3rd row transition metals of groups 8-10. In recent years, base-metals (common and inexpensive metals) have demonstrated promising results. This chapter is designed to highlight important discoveries throughout the history of carbon dioxide hydrogenation. Chapter 2. Development of a Transition Metal / N-Heterocyclic Carbene Cooperative System for the Hydrogenation of Carbon Dioxide to Formic Acid Over the past few decades, the conversion of small molecules such as H2, N2, O2, CH4, C2H4, CO, and CO2 have attracted considerable attention. Many of these molecules are thermodynamically or kinetically stable and their usefulness depends on overcoming significant barriers. Frustrated Lewis pairs and N-heterocyclic carbenes have become common strategies to activate unreactive small molecule likes CO2 and H2. However, a hybrid approach utilizing both a transition metal and an activator has only recently been investigated for the transformation of small molecules to more useful and complex compounds. A novel method for these transformations is the use of a bifunctional catalyst system that incorporates a Lewis basic N-heterocyclic carbene and a Lewis acidic transition metal. This chapter highlights our serendipitous discovery that small quantities of bicarbonate and other inorganic salts enhanced the productivity of formic acid in CO2 hydrogenation reactions. The phenomenon was general for many noble-metal catalysts and for one of the most efficient base-metal hydrogenation catalysts. Additionally, the synthesis of a transition metal complex bearing a pendant dihydroimidazolium salt is described. Stoichiometric and catalytic applications of the newly designed complex were explored in investigate our Lewis base / transition metal approach to small molecule activation. Chapter 3. Chemistry of Iron N-Heterocyclic Carbene Complexes N-heterocyclic carbenes are one of the most versatile ligands in organometallic chemistry due to their unique properties as ancillary ligands. Although NHCs are typically potent σ-donors (a) with minor contributions from π*-backdonation (b), they also have the ability to accept electron density from the metal center as two-electron (c) or one-electron (d) interactions. Since the first examples of metal–NHC complexes were reported in the 1960’s, numerous studies have been devoted to the synthesis of new NHCs, to their characterization, and to their use as ligands in transition metal complexes. The coordination chemistry of NHCs with late transition metals has been studied extensively. However, the chemistry of iron–NHC complexes has not been developed to the same extent as other late transition metals. This chapter highlights important discoveries throughout the history of iron–NHC complexes, while emphasizing the nature of the metal–carbene bond. Chapter 4. Reactivity of Bis(amidinato)-N-Heterocyclic Carbene Iron Complexes Over the past few decades, the development of highly active and selective transition metal catalysts has attracted considerable attention. While the metal employed largely influences the expectations for catalytic activity, the importance of supporting ligands in tuning the reactivity of any given complex is vital. Our group recently synthesized a bis(amidinato)-N-heterocyclic carbene complex of iron as an analogy to the highly active bis(imino)pyridine iron complexes. We hypothesized that having an N-heterocyclic carbene as the central donor instead of pyridine could have significant impacts on the reactivity of such iron complexes. This chapter highlights the synthesis of iron bis(amidinato)-N-heterocyclic carbene complexes spanning multiple oxidation states previously described by our group. Through a combination characterization techniques, the bis(amidinato)-N-heterocyclic carbene was discovered to have unique interactions with the iron center, which change depending on the oxidation state of the metal. Additionally, we undertook investigations into the reactivity of these complexes with azides, hydrides, alkyl reagents, and ethylene. The results of which supported the capability of the bis(amidinato)-N-heterocyclic carbene ligand to act as a redox and chemical non-innocent ligand. / Thesis (MS) — Boston College, 2015. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Resumo: O dióxido de carbono (CO2) é um importante gás de efeito estufa. No entanto, um aumento gradual ameaça substancialmente o clima. Um dos principais desafios do planejamento ambiental é identificar um modelo que vincule todos os fatores do ciclo de carbono, ou seja, oceano - ecossistema terrestre - emissão antropogênica - atmosfera. Princípios básicos de Termodinâmica podem ser aplicados em uma modelagem estatística com bases em séries históricas para obter concentrações de CO2 na atmosfera, possibilitando a construção de cenários para uma melhor tomada de decisões. Por este motivo, foi desenvolvido no trabalho um modelo que interliga todos os fatores do ciclo de carbono, focalizando em quatro zonas térmicas ou climáticas (Boreal, Temperada, Tropical, Polar), para cálculos de armazenamento de CO2 atmosférico. Os resultados mostram que no ano 2100 se atingirá uma concentração de CO2 quatro vezes maior do que antes do período pré-industrial. A zona temperada emite quase a metade de dióxido de carbono à atmosfera na atualidade; para o ano 2100, essa emissão aumentará a quinze vezes mais que a zona tropical. A China será responsável em uma proporção de vinte quatro a onze com relação aos Estados Unidos. A estabilização das concentrações de CO2 na atmosfera será obtida quando as emissões de dióxido de carbono antropogênico tiverem uma diminuição de mais do que trinta e quatro por cento para o ano 2100 na zona temperada. / Abstract: Carbon dioxide (CO2) is the most important greenhouse gas. A gradual increase on its atmospheric concentration threatens significantly the climate. One of the main challenges of environment planning is to identify a model that connects all factors that determine the carbon cycle, that is, ocean - terrestrial ecosystem - anthropogenic emissions - atmosphere. Basic thermodynamic principles can be applied in a statistical modeling with historic time series to obtain atmospheric CO2 concentration, creating the possibility of construction of scenarios that will help decision making. A model that links all carbon cycle factors was developed in this dissertation work, focusing in four thermal of climatic zones (Boreal, Temperate, Tropical, and Polar) for calculations of atmospheric CO2 storage. Results show that in 2100, the atmospheric CO2 concentration will reach a value four times higher than that of the pre-industrial period. The temperate zone already emits almost half of the carbon dioxide to the atmosphere; by 2100, this emission will increase 15 times more than that corresponding to the tropical zone. China will be responsible for emissions in a proportion of 24 to 11 in comparison to that of the United States. Stabilization of CO2 concentrations in the atmosphere will be obtained when the anthropogenic carbon dioxide emissions attain a decrease of at least 34% in 2100 in the temperate zone. / Orientador: João Andrade de Carvalho Junior / Coorientador: Luiz Fernando Costa Nascimento / Banca: José Antonio Perrella Balestieri / Banca: Maria Paulete Pereira Martins Jorge / Mestre

In a carbon-constrained economy, the decision making process for selecting carbon reducing technologies for existing single power plants, portfolios of power plants, or new power plant technologies must incorporate the monetary impact of reducing CO2 emissions. Cost of electricity and the monetary impacts of reducing criteria pollutants primarily drive power plant decisions. For example, a gas turbine power plant may upgrade its combustion system to a Dry Low NOx combustor if regulations require or provide incentives for reduced NOx emissions. Similarly, in a carbon-constrained economy, the CO2 emissions strategy selected may impact the operating profile and or equipment of the power plant. Given the wide array of CO2 mitigation strategies available for power plants, robust guidelines are needed to consistently compare varying strategies. The purpose of this study is to provide guidelines for comparing currently available and near-term CO2 mitigation strategies, while also providing guidelines for comparing new low CO2 emission technologies. Furthermore, the issue of making a decision for a portfolio of power plants versus a single plant will be explored along with fuel price sensitivity and CO2 credit trading.

Thesis (Ph. D.)--University of Michigan, 1911. / "Reprinted from the Physical review, vol. XXXIII, no. 4, October, 1911."

Thesis (Ph. D.)--Ohio State University, 2004. / Title from first page of PDF file. Document formatted into pages; contains xiii, 149 p.; also includes graphics. Includes abstract and vita. Advisor: F. Robert Tabita, Dept. of Microbiology. Includes bibliographical references (p. 144-149).

Rigorous thermodynamic and kinetic models were developed in Aspen Plus® Rate SepTM for 8 m PZ, 5 m PZ, 7 m MDEA/2 m PZ, and 5 m MDEA/5 m PZ. Thermodynamic data was regressed using a sequential regression methodology, and incorporated data for all amine, amine/water, and amine/water/CO₂ systems. The sensitivity of CO₂ absorption rate was determined in a wetted wall column simulation in Aspen Plus®, and the results were used in Microsoft Excel to determine the optimum reaction rates, activation energies, and binary diffusivities. Density, viscosity, and binary diffusivity are calculated using user-supplied FORTRAN subroutines rather than built-in Aspen Plus® correlations. Three absorber configurations were tested: adiabatic, in-and-out intercooling, and pump-around intercooling. The two intercooled configurations demonstrated comparable improvement in capacity and packing area, with the greatest improvement in 8 m PZ occurring between lean loadings of 0.20 and 0.25 mol CO₂/mol alkalinity. The effects of absorber temperature and CO₂ removal were tested in the adiabatic and in-and-out intercooled configurations. For 7 m MDEA/2 m PZ at a lean loading of 0.13 mol CO₂/mol alkalinity reducing the absorber temperature from 40 °C to 20 °C increases capacity by 64% without an appreciable increase in packing area. Increasing CO₂ removal from 90% to 99% does not double the packing area due to favorable reaction rates at the lean end of the absorber. Two stripper configurations were tested: the simple stripper and the advanced flash stripper. For all amines, absorber configurations, and lean loadings the advanced flash stripper demonstrated the better energy performance, with the greatest benefit occurring at low lean loadings. An economic estimation method was developed that converts purchased equipment cost and equivalent work to $/MT CO₂. The method is based on economic factors proposed by DOE-NETL and IEAGHG. The total cost of CO₂ decreases as lean loading decreases for all amines and configurations. Increasing CO₂ removal from 90% to 99% results in a 1% increase in the total cost of CO₂ capture. Decreasing absorber temperature for 7 m MDEA/2 m PZ from 40 °C to 20 °C decreases total cost of CO₂ capture by up to 9.3%. / text