Changes of Molecular System in Coal with Addition of Iodine

摘要

The thermal fluidity, solubility and swelling of coal are influenced by inter- and intra-molecular association forces such as hydrogen bonding and other secondary bonding present in the macromolecular structure. In our previous papers the interaction of coal molecules with iodine and tetracyanoquinodimethane, TCNQ, has been investigated Iodine and TCNQ as electron acceptors interact with coal molecules as an electron donor producing charge transfer complexes. A good correlation has been obtained between the spin concentration of coal-iodine complexes and carbon aromaticity of parent coal. This paper provides a deep insight of the interaction mechanism governed between coal and iodine by means of ESR measurement. Coal samples tested are mostly chosen from Argonne Premium coal samples. The analytical data for these samples are shown elsewhere. Zao Zhuang coal (C: 88.3, H: 5.3, O+S: 5.0 wt% d.a.f., ash: 16.7%) is also selected in this study. Iodine having a purity of >98% (guaranteed reagent) was selected as an electron acceptor. To avoid contamination of solvent molecules during the iodine doping, vapour phase method was provided. Both a known amount of coal particles (less than 100 mesh in size) placed on a glass dish and iodine powder placed on a separate dish were kept in nitrogen filled vessel at 30℃. ESR spectra were obtained using a Varian model E109 spectrometer. Spectral shape of the coal samples is considered to be narrow and broad components. Assuming that the respective narrow and broad components are consisted with a mixture of Gaussian and Lorentzian types in shape, we have examined curve deconvolution of the spectra applied by software 'Igor' (Wave Metrics).