The problems associated with the application of FT-IR to the characterization of coal structure are critically discussed. The controversies concerning band assignments are considered and it is concluded that the strong 1600 cm−1 band can be assigned to an aromatic ring stretching mode that in most coals is intensity enhanced by the presence of phenolic groups. The application of computer routines to the determination of OH and CH groups is considered. Established criteria for curve fitting are applied to the problem. Qualitative identification of functional groups is achieved, but consistent quantitative measurements will require a determination of the relationship between the extinction coefficients of resolved bands.

Concerning the Application of FT-IR to the Study of Coal: A Critical Assessment of Band Assignments and the Application of Spectral Analysis Programs

Coal oxidation at low temperatures: oxygen consumption, oxidation products, reaction mechanism and kinetic modelling

Coal oxidation at low temperatures (i.e. <100 °C) is the major heat source responsible for the self-heating and spontaneous combustion of coal and is an important source of greenhouse gas emissions. This review focuses on the chemical reactions occurring during low-temperature oxidation of coal. Current understanding indicates that this process involves consumption of O 2, formation of solid oxygenated complexes, thermal decomposition of solid oxygenated complexes and generation of gaseous oxidation products. Parameters, such as mass change, heat release, oxygen consumption, and formation of oxidation products in the gas or solid phase, have been used to qualitatively and quantitatively describe the oxidation process. Reaction mechanisms have been proposed to explain the characteristics of consumption of O2, and formation of oxidation products in the gas and solid phases. Various kinetic models have also been developed to describe the rate of oxygen consumption and the rates of formation of gaseous oxidation products in terms of the rate parameters of the relevant reactions, oxidation time, temperature, and initial concentration of oxygen in the oxidising medium. Further research emphasis should be placed on the formation of the complete reaction pathways proceeding in the oxidation process and on the development of kinetic models applicable for predicting the self-heating and gas emission in a coal seam or stockpile.

Coal oxidation at low temperatures: oxygen consumption, oxidation products, reaction mechanism and kinetic modelling, Pages 487-513

Industrial aspects of production and use of activated carbons

From coal to single-stage and two-stage products: A reactive model of coal structure

Oxidative weathering of Illinois No.6 coal

Selective alkylation of acidic hydroxyl groups in coal

The kinetic reactivities of the acidic hydroxyl groups in coal were measured. The chemical action of quaternary ammonium hydroxide bases in the presence of alkylating agents was used as the probe. Both Illinois No. 6 bituminous and Rawhide subbituminous coals contain aromatic and aliphatic hydroxyls as well as lesser amounts of carboxylic acids. Illinois coal was found to 0-alkylate at a faster rate than Rawhide coal. The reactivities of the acidic functional groups in the coals were correlated to the reactivity of acidic groups in model compounds. This was accomplished by both relative and absolute kinetic rate measurements on each coal and a series of model systems. It was discovered that the activation energy associated with the nucleophilic displacement determined the rate of 0-alkylation of the coal. Therefore, the rate of this reaction is not limited by mass transport of the chemical reagents into the coal structure. In this sense, 0-alkylation of coal is a most unique reaction.

Coal. Kinetics of O-alkylation

Disclosed is a one-step ion-exchange method for organically bonding alkali and alkaline-earth metals onto coal. The method comprises contacting the coal, at a temperature from about 20° C. to about 100° C. with, (a) an aqueous solution containing cations of one or more metals selected from the group consisting of alkali and alkaline-earth metals, and (b) an oxidizing gas.

Cation ion exchange of coal

More fundamental knowledge of coal (knowledge of its structure and its behavior during conversion processes) is essential before we can generate new technologies necessary for the efficient use of coal in the future. Herein are suggested specific basic research opportunities in the areas of coal characterization, gasification, combustion, and liquefaction, along with an assessment of the impact such research programs could have. Critical characterization needs include qualitative and quantitative determination of the chemical forms of carbon, oxygen, nitrogen, and sulfur and reliable methods for the measurement of surface area, pore volume, and weight-average molecular weights. Mechanistic studies aimed at increasing understanding of the thermal breakdown of the functionalities in coal, the behavior of coal in the presence of molecular and donor hydrogen environments, and carbon gasification and hydrocarbon synthesis reactions starting from carbon monoxide and hydrogen will lay the scientific foundation for the development of new processes for converting coal into clean usable fuels and chemicals.

https://science.sciencemag.org/content/sci/206/4422/1029.full.pdf

Ronald Liotta

Papers

Oxidative weathering of Illinois No.6 coal

Selective alkylation of acidic hydroxyl groups in coal

Coal. Kinetics of O-alkylation

Cation ion exchange of coal

Coal Science: Basic Research Opportunities