Mechanism and modeling of nitrogen chemistry in combustion
TL;DR: In this article, the mechanisms and rate parameters for the gas-phase reactions of nitrogen compounds that are applicable to combustion-generated air pollution are discussed and illustrated by comparison of results from detailed kinetics calculations with experimental data.
About: This article is published in Progress in Energy and Combustion Science.The article was published on 1989-01-01. It has received 2843 citations till now. The article focuses on the topics: Combustion.
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TL;DR: In this paper, the status of fat and oil derived diesel fuels with respect to fuel properties, engine performance, and emissions is reviewed, and it is concluded that the price of the feedstock fat or oil is the major factor determining biodiesel price.
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TL;DR: In this paper, a review of the properties of biomass relevant to combustion is briefly reviewed and the compositions of biomass among fuel types are variable, especially with respect to inorganic constituents important to the critical problems of fouling and slagging.
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TL;DR: Although technological practice should minimize environmental impact, this is not always economically feasible as mentioned in this paper, and during the past decade, there has been increasing global concern over the environmental impact of technology.
Abstract: Although technological practice should minimize environmental impact, this is not always economically feasible. During the past decade, for example, there has been increasing global concern over th...
1,216 citations
Columbia University1, Brookhaven National Laboratory2, University of Texas at Austin3, Utah State University4, University of Rochester5, Pacific Northwest National Laboratory6, Texas A&M University7, Yale University8, Northwestern University9, Pennsylvania State University10, Arizona State University11, National Renewable Energy Laboratory12, Cornell University13, Washington State University14, University of Notre Dame15, Massachusetts Institute of Technology16
TL;DR: Research prospects for more sustainable routes to nitrogen commodity chemicals are reviewed, considering developments in enzymatic, homogeneous, and heterogeneous catalysis, as well as electrochemical, photochemical, and plasma-based approaches.
Abstract: BACKGROUND The invention of the Haber-Bosch (H-B) process in the early 1900s to produce ammonia industrially from nitrogen and hydrogen revolutionized the manufacture of fertilizer and led to fundamental changes in the way food is produced. Its impact is underscored by the fact that about 50% of the nitrogen atoms in humans today originate from this single industrial process. In the century after the H-B process was invented, the chemistry of carbon moved to center stage, resulting in remarkable discoveries and a vast array of products including plastics and pharmaceuticals. In contrast, little has changed in industrial nitrogen chemistry. This scenario reflects both the inherent efficiency of the H-B process and the particular challenge of breaking the strong dinitrogen bond. Nonetheless, the reliance of the H-B process on fossil fuels and its associated high CO 2 emissions have spurred recent interest in finding more sustainable and environmentally benign alternatives. Nitrogen in its more oxidized forms is also industrially, biologically, and environmentally important, and synergies in new combinations of oxidative and reductive transformations across the nitrogen cycle could lead to improved efficiencies. ADVANCES Major effort has been devoted to developing alternative and environmentally friendly processes that would allow NH 3 production at distributed sources under more benign conditions, rather than through the large-scale centralized H-B process. Hydrocarbons (particularly methane) and water are the only two sources of hydrogen atoms that can sustain long-term, large-scale NH 3 production. The use of water as the hydrogen source for NH 3 production requires substantially more energy than using methane, but it is also more environmentally benign, does not contribute to the accumulation of greenhouse gases, and does not compete for valuable and limited hydrocarbon resources. Microbes living in all major ecosystems are able to reduce N 2 to NH 3 by using the enzyme nitrogenase. A deeper understanding of this enzyme could lead to more efficient catalysts for nitrogen reduction under ambient conditions. Model molecular catalysts have been designed that mimic some of the functions of the active site of nitrogenase. Some modest success has also been achieved in designing electrocatalysts for dinitrogen reduction. Electrochemistry avoids the expense and environmental damage of steam reforming of methane (which accounts for most of the cost of the H-B process), and it may provide a means for distributed production of ammonia. On the oxidative side, nitric acid is the principal commodity chemical containing oxidized nitrogen. Nearly all nitric acid is manufactured by oxidation of NH 3 through the Ostwald process, but a more direct reaction of N 2 with O 2 might be practically feasible through further development of nonthermal plasma technology. Heterogeneous NH 3 oxidation with O 2 is at the heart of the Ostwald process and is practiced in a variety of environmental protection applications as well. Precious metals remain the workhorse catalysts, and opportunities therefore exist to develop lower-cost materials with equivalent or better activity and selectivity. Nitrogen oxides are also environmentally hazardous pollutants generated by industrial and transportation activities, and extensive research has gone into developing and applying reduction catalysts. Three-way catalytic converters are operating on hundreds of millions of vehicles worldwide. However, increasingly stringent emissions regulations, coupled with the low exhaust temperatures of high-efficiency engines, present challenges for future combustion emissions control. Bacterial denitrification is the natural analog of this chemistry and another source of study and inspiration for catalyst design. OUTLOOK Demands for greater energy efficiency, smaller-scale and more flexible processes, and environmental protection provide growing impetus for expanding the scope of nitrogen chemistry. Nitrogenase, as well as nitrifying and denitrifying enzymes, will eventually be understood in sufficient detail that robust molecular catalytic mimics will emerge. Electrochemical and photochemical methods also demand more study. Other intriguing areas of research that have provided tantalizing results include chemical looping and plasma-driven processes. The grand challenge in the field of nitrogen chemistry is the development of catalysts and processes that provide simple, low-energy routes to the manipulation of the redox states of nitrogen.
1,153 citations
Cites background from "Mechanism and modeling of nitrogen ..."
...Oxidation of N2 to nitric oxide (NO) and nitrogen dioxide (NO2), which are collectively referred to as NOx (the representation of neutral forms of oxidized nitrogen), occurs naturally in lightning and also during combustion of fuels in air (6)....
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TL;DR: In this article, a computational study was performed for the formation and growth of polycyclic aromatic hydrocarbons (PAHs) in laminar premixed acetylene and ethylene flames.
1,117 citations
References
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TL;DR: In this paper, the authors evaluated data on the kinetics and thermodynamic properties of species that are of importance in methanepyrolysis and combustion, including H, H2, O, O2, OH, HO2, CH2O, CH4, C2H6, HCHO, CO2, CO, HCO, CH3, CH5, CH6, CH7, CH8, CH9, CH10, CH11, CH12, CH13, CH14, CH15, CH16, CH17, CH
Abstract: This document contains evaluated data on the kinetics and thermodynamic properties of species that are of importance in methanepyrolysis and combustion. Specifically, the substances considered include H, H2, O, O2, OH, HO2, H2O2, H2O, CH4, C2H6, HCHO, CO2, CO, HCO, CH3, C2H5, C2H4, C2H3, C2H2, C2H, CH3CO, CH3O2, CH3O, singlet CH2, and triplet CH2. All possible reactions are considered. In arriving at recommended values, first preference is given to experimental measurements. Where data do not exist, a best possible estimate is given. In making extrapolations, extensive use is made RRKM calculations for the pressure dependence of unimolecular processes and the BEBO method for hydrogen transfer reactions. In the total absence of data, recourse is made to the principle of detailed balancing, thermokinetic estimates, or comparisons with analogous reactions. The temperature range covered is 300–2500 K and the density range 1×1016–1×1021 molecules/cm3. This data base forms a subset of the chemical kinetic data base for all combustion chemistry processes. Additions and revisions will be issued periodically.
1,803 citations
Book•
01 Jan 1985
TL;DR: In this paper, various topics in the area of combustion and explosives are discussed, including basic physical concepts of the science of combustion, the time-independent theory of thermal explosions, time-dependent statement of the problem of the initiation of chemical reaction waves in fuel mixtures, laminar flames, complex and chain reactions in flames, the gas dynamics of combustion dynamics, and diffusional combustion of gases.
Abstract: Various topics in the area of combustion and explosives are discussed. The general subjects considered include: basic physical concepts of the science of combustion, the time-independent theory of thermal explosions, time-dependent statement of the problem of the initiation of chemical reaction waves in fuel mixtures, laminar flames, complex and chain reactions in flames, the gas dynamics of combustion, and diffusional combustion of gases. 561 references.
1,585 citations
01 Mar 1990
TL;DR: The Chemkin general-purpose chemical kinetics package uses a data base that contains polynomial fits to specific heats, standard state enthalpies, and standard state entropy as mentioned in this paper.
Abstract: The Chemkin general-purpose chemical kinetics package uses a data base that contains polynomial fits to specific heats, standard state enthalpies, and standard state entropies The fourteen coefficient fits are in the same form as used in the NASA Complex Chemical Equilibrium Program (Gordon and McBride, 1971) This report represents a compilation of the data that is currently in use at Sandia National Laboratories 16 refs
579 citations
01 Jan 1984
TL;DR: In this article, a critical survey of reaction rate coefficient data important in describing high-temperature combustion of H2, CO, and small hydrocarbons up to C4 is presented.
Abstract: This chapter is a critical survey of reaction rate coefficient data important in describing high-temperature combustion of H2, CO, and small hydrocarbons up to C4. A recommended reaction mechanism and rate coefficient set is presented. The approximate temperature range for this mechanism is from 1200 to 2500 K, which therefore excludes detailed consideration of cool flames, low-temperature ignition, or reactions of organic peroxides or peroxy radicals. Low-temperature rate-coefficient data are presented, however, when they contribute to defining or understanding high-temperature rate coefficients. Because our current knowledge of reaction kinetics is incomplete, this mechanism is inadequate for very fuel-rich conditions (see Warnatz et al., 1982). For the most part, reactions are considered only when their rates may be important for modeling combustion processes. This criterion eliminates considering many reactions among minor species present at concentrations so low that reactions of these species cannot play an essential part in combustion processes. The philosophy in evaluating the rate-coefficient data was to be selective rather than exhaustive: Recent results obtained with experimental methods capable of measuring isolated elementary reaction rate parameters directly were preferred, while results obtained using computer simulations of complex reacting systems were considered only when sensitivity to a particular elementary reaction was demonstrated or when direct measurements are not available. Theoretical results were not considered.
547 citations
450 citations