Bridges in coal

Such bridges in coal structure have been reported only recently. Alkyl substituted methylene and ethylene bridges have been detected in a Wyodak coal by Benjamin et al.. In the present study, some of the branched chain bridges may have been formed by rearrangement of the straight chain bridges during transalkylation. ... 

FIGURE 18.3 Hypothetical representation of the functional groups and intemuclear bridges in coal. (From Cooper, B.R., Ed., Scientific Problems of Coal Utilization, United States Department of Energy, Washington, DC, 1978.)... 

The first gas company was established in 1812 in London to produce gas from coal and to light the Westminster Bridge. In 1816, the first gas plant for the manufacture of syngas from coal was built in the United States to light the streets of the city of Baltimore. By 1826, gas plants were also built to manufacture gas for lighting the streets of Boston and New York City. Soon thereafter, gas plants and distribution networks were built to light the streets of most major cities throughout the world. 

Both reactions act to reduce hydrogen bonding within the coal structure which may have a direct positive impact on liquefaction reactivity. More indirectly, these reactions lower the concentration of OH species in coal-derived products and hence, reduce the extent of retrogressive condensation via ether bridge formation. Reducing production of THF-insoluble condensation products increases the net THF-soluble coal conversion observed during the liquefaction experiment. None of the spectra from coals pretreated with alkyl alcohols and HCl showed any significant evidence of alkylation at carbon sites in the coal. 

Currently, there are no accurate methods available for quantifying the aliphatic bridges in the coal macromolecule. Quantitative nature of the application of infrared (IR) spectroscopy is limited to certain general types of functional groups or bond types. Nuclear magnetic resonance spectroscopy, despite the success of dipolar dephasing techniques to decipher the extent of substitution on carbon atoms, is still inadequate to distinguish distinct structural entities . 

For the above reaction to occur, the aromatic nuclei in compound 1 should carry activating groups, such as hydroxyl, alkoxy, or fused ring aromatics". As a result of reaction with BF3 and phenol, the macromolecular structure of coal should undergo rupture at the aliphatic bridges, and these bridges are transferred to phenol molecules to produce bisphenols. Analysis of the bisphenols should provide information on the aliphatic bridges present in coal structure. 

TABLE III. Relative Concentrations of Aliphatic Bridges in Transall lated Products from Fresh and Oxidized San Juan Coal... 

Figure 1.2. Schematic representation of structural groups and connecting bridges in bituminous coal according to Wiser.8b...

Relationship Between Number of Methylene Bridges and Degree of Depolymerization. A relationship between the number of methylene bridges in a coal and the extent of depolymerization was mentioned briefly by us (3) in a recent publication. The data were based on NMR analysis of the benzene ... 

Coal Code No. Not Phenol Soluble Product Wt. % dmmf Coal Bridge Hydrogens Wt. % Total H in Coal Calc. Mol. Wt. of Monomeric Unit per CH2 Mol. Wt. of Soluble Part of Coal... 

Figure 6.174 Group I, category M1 - methane transmitter for continuous monitoring of the CH4 concentration in coal mines. Catalytic oxidation. The heat generated hereby causes a temperature rise in a branch of a resistor bridge.

Kinetic investigations of BF3-catalyzed benzyl group transfer in benzylphenol systems were reported by Heredy (13). These systems were chosen for investigation because of the particular interest in the role that -CH2- bridges may play in coal depolymerization. 

After reviewing the information on the reactivities of various bridge structures that may be present in coal, it is instructive to summarize... 

The following comments are made with regard to a correlation of the depolymerization product yields with the relative reactivities of aliphatic-aromatic carbon and oxygen-carbon bridge structures in coal ... 

Coal tar creosote is widely used for the preservation and water-proofing of wood which is used for utility poles, railroad ties, log homes, fence posts, bams, bridges, piers, and marine pilings. Creosote is also used in roofing and road paving is used and/or produced in coke oven operations, and in the aluminum, iron, and steel industries and is used therapeutically in coal-tar based shampoos, as a treatment for... 

In coals, the alkyl sidechains are short, as are the bridges between rings and so there is less opportunity to form long-chain paraffinic products. Instead, more hydrogen atoms per carbon are required to cap radicals and to remove a smaller number of carbons in the gas and liquid products. The net effect is an inefficient use of hydrogen that results in aromatization of a significant fraction of the aliphatic carbons. 

---