Changes in aromaticity during coal liquefaction

Abstract

any light onto this controversy, so steps B and C have been listed separately.The oberved order of reaction with respect to H+ concentration is empirical in this work, since, according to the mechanism, the order should in fact be unity. However, the evidence of acid-catalyzed aldol condensation of MEK precludes exact first-order acid dependence.Other Results. The findings of Neish et al. (1945) cannot be refuted on the basis of this work. The Neish system contained a very strong acid with no effective water concentration, so a different mechanism is conceivable. Neish also reported the formation of the cyclic ketal, 2ethyl-2,4,5-trimethyl dioxolane, by the condensation of 1 mol each of 2,3-butanediol and MEK. This compound was not detected in our work, presumably because the equilibrium lies in favor of 2,3-butanediol and MEK in aqueous solution (see Fife et al., 1967Fife et al., , 1970Fife et al., , 1971. ConclusionsAqueous 2,3-butanediol was shown to react in a pseudo-first-order reaction in the presence of sulfuric acid to form methyl ethyl ketone. The reaction could be described by a pinacol rearrangement mechanism and had an activation energy of 36 kcal/mol. An empirical order of reaction with respect to H+ concentration of 1.53 was determined. MEK yields exceeding 90 mol % could be consistently obtained, but evidence of acid-catalyzed aldol condensation was noted.The pseudo-first-order reaction incorporated the temperature, acid concentration, and initial reactant concentration, and predicted, a priori, the reaction time course for both MEK and 2,3-butanediol.Dehydration of 2,3-butanediol to MEK in fermentation broths is feasible, and the current model can be used as the first step in the development of a more complete model which is directly applicable to 2,3-butanediol fermentation broths.

An investigation of the role of water on retrograde/condensation reactions and enhanced liquefaction yields. Final report

“…Most of the solid-state NMR studies have used CP/MAS 13C techniques to study the basic carbon structure of coal and how it changes with rank, the origin and evolution of coal, and the behavior of coal under various heating and processing conditions. Most of the applications of solid-state NMR to study coal liquefaction have dealt with changes in the carbon aromaticity between products and the original coal (Wilson et al 1982;Foster et al 1983;Bockrath et al 1984;Finseth et al 1985;Vassallo et al 1987; Shin et al 1989). …”

Modeling of coal liquefaction kinetics based on reactions in continuous mixtures. Part I: Theory

“…12 is not altogether arbitrary. A general progression in the molecular weight distribution and the functionalities present in lumped components such as oils, asphaltenes, and preasphaltenes has been reported (Wilson et al, 1982), these lumped fractions being obtained by using progressively stronger solvents.…”

“…Improved techniques for analysis and characterization of coal products such as proton and carbon-1 3 nuclear magnetic resonance (Wilson et al, 1982;Yoshida et al, 1982) and Fouriertransformed infrared spectroscopy (Painter and Coleman, 1979) have aided in providing extensive information on the possible mechanistic pathways for liquefaction reactions. This has facilitated the formulation of working models for liquefaction kinetics based on the proposed mechanism.…”

The use of NMR techniques for the analysis of water in coal and the effect of different coal drying techniques on the structure and reactivity of coal. Final report

“…Most of the solid-state NMR studies have used CP/MAS I3C techniques to study the basic carbon structure of coal and how.it changes with rank, the origin and evolution of coal, and the behavior of coal under various heating and processing conditions. Most of the applications of solid-state NMR to study coal liquefaction have dealt with changes in the carbon aromaticity between products and the original coal (Wilson et al 1982;Foster et al 1983;Bockrath et al 1984;Finseth et al 1985;Vassallo et al 1987;Shin et al 1989). …”