Coal structure parameters

COAL STRUCTURE PARAMETERS (weight fraction DMMF)... 

Thus we have conducted work on the structural parameters of coal hydrogenation products using the method of Brown-Ladner (1), and from the results obtained we have developed correlations of the reaction. Based on the above, the outline of the reaction mechanisms have been previously discussed and our results have been reported (2, 3J. ... 

In the present paper samples usinig several kinds of coal and various reducing agents such as H2 / H2 + CH4, D2, °2 + tetra-lin, CD + H2O, we have carried out hydrogenation reactions. We have studied the distribution and structural parameters of the reaction products and we have further discussed the reaction mechanisms involved. 

Figure 7. Structural parameters of Yubari coal hydrogenolysis products...

Figure 8. Distribution of structural parameters of asphaltene from Shin-Yubari coal hydrogenation at 450°C (O), H2 100kg/cm2 ( ), H2 75 + CHh 25 ( ),...

Figure 9. Structural parameters of asphaltene from Soya-Koishi coal by CO + H,0 and Ht reduction at 400° C...

The structural parameter changes of products of coal reduction under various reducing reaction conditions were followed up, and a discussion of the reaction mechanisms involved was made and the following conclusion were obtained. 

Figures 1-3 demonstrate the effect of KOH/precursor ratio, reaction temperature and reaction time, respectively, on porous structure parameters of carbon produced by KOH activation. While the presented relationships concern mostly carbonaceous mesophase, basically they are typical of all coal and pitch-derived materials of the study.

To evaluate further the CAMD results, a number of atomic and chemical parameters from each structure (number of atoms, fractions of aromatic carbon and hydrogen, weight fraction or each atomic species, empirical formula) were compared with the original literature for each structure. This provided a useful check on the accuracy of the computer models. Results of the computer analyses for the four coal structures are given in Table I. The total numbers of atoms only appear as guides to the size and complexity of each structure, and bear no relationship to the size of a "coal molecule" or a decomposition product. 

Identification of the constituents of complex materials such as coal may proceed in a variety of ways but generally can be classified into three methods (1) spectroscopic techniques, (2) chemical techniques, and (3) physical property methods whereby various structural parameters are derived from a particular property by a sequence of mathematical manipulations. It is difficult to completely separate these three methods of structural elucidation, and there must, by virtue of need and relationship, be some overlap. Thus, although this review is more concerned with the use of spectroscopic methods applied to the issues of coal structure, there will also be reference to the other two related methods. 

Table III. Structural Parameters of Coals and Coal Macerals...

In order to deal with a coal-derived liquid as a mixture which has a statistically average chemical structure, we choose two measurable structural parameters, aromaticity, fa Car/Ctotal) and the degree of substitution of the aromatic ring, a. To identify major atomic groups of coal-derived liquids which contribute to AHf° and S°, the following assumptions are made. 

Necessary data for estimating the standard heat of formation and the absolute entropy by Equations 3 and 4 are the elemental analysis, structural parameters, fa and a, and the normal boiling point. For a practical purpose, it will be more convenient if we could calculate AHf° and S° only from elemental analysis data and normal boiling point. The aromaticity fa for coal liquids may be estimated by the correlation shown in Figure 1. On the other hand, the value of 0 may be taken as 0.3 for its average value based on the reported data (lf3, 20, 21). Substitution of these relations into Equations 3 and 4 gives... 

The hypothetical coal molecule and thermal decomposition products for PSOC 170 are presented in Figs. 1 and 2. The structure parameters for the suggested molecule, the corresponding parameters determined for PSOC 170 and the source for the data are summarized in Table I. Some of the details of the model are as follows 1) The structure contains only one carboxyl. The carboxyl concentration is based on the yield of CO2 which is believed to be its thermal decomposition product. No other carbonyl s are included as the carbonyl peaks... 

Table V shows yields and structural parameters of SP-300 fractions. These fractions were black solid materials like the feed coal, as compared to dark-brown viscous liquids of the HVL-P fractions. The overall average molecular weight of SP-300 was more than three times that of HVL-P. SP-300 fractions have much larger R, RN and //cl than HVL-P fractions. The //cl values disclosed that there were, on the average, 2.8 aromatic clusters per molecule in SP-300, as compared to 1.1 aromatic clusters per molecule in HVL-P. Thus SP-300 fractions are high molecular weight materials,in which the degree of depolymerization is relatively low. This in turn suggests that SP-300 has retained more of the original structures of the parent coal than has HVL-P.

In order to determine whether any direct structural information about coal can be obtained from the liquids used in this study, structural parameter data are compared in Table VII. 

Table II. Proton Distribution and Structural Parameters of Coal-Liquid Fractions (7)...

Victorian brown coal occurs in five major lithotypes distinguishable by color index and petrography. Advantage has been taken of a rare 100 m continuous core to compare and contrast chemical variations occurring as a function of lithotype classification. For many parameters there is a much greater contrast between the different lithotypes than there is across the depth profile of (nearly) identical lithotypes. Molecular parameters, such as the distributions of hydrocarbons, fatty acids, triterpenoids and pertrifluoroacetic acid oxidation products, together with gross structural parameters derived from IR and C-NMR spectroscopic data, Rock-Eval and elemental analyses and the yields of specific extractable fractions are compared. 

Another possible correlation between coal structure and pyrolysis behavior is indicated by the temperature dependence of the evolution of pyrolytic water being strikingly different for the two coals. Figure 5 shows pyrolytic water evolution data for experiments in which the sample was heated at 1000°C/sec to the peak temperature indicated on the abscissa and then immediately allowed to cool at around 200°C/sec. The smooth curves are based on a single reaction, first-order decomposition model (7,8) and on the stated temperature-time history. Parameters used for the lignite have been published (8) while for the bituminous coal the Arrhenius frequency factor and activation energy were taken as 1013 sec"1 and 35 kcal/mol, respectively, with the yield of pyrolytic water ultimately attainable estimated from experimental measurements as 4.6 wt % of the coal (as-received). 

In graphical-statistical constitutional analysis (94), major structural parameters for coal are derived via a reduced molar volume , MJd. In this term, Mc is a reduced molecular weight per C atom calculated from elemental compositions, by means of... 

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