This paper describes the current status of an analytical procedure for the characterization of coal by programmed-temperature oxidation. Coal is mixed with a diluent to control the reaction and subjected simultaneously to oxidation and a linear increase in temperature up to 1000 °C. The evolved gases (CO2, H2O, SO2 and NO2) are monitored as functions of time and temperature. Distinctive evolution patterns are oberved among coals of different rank and between raw and treated coals. The SO2 evolution peaks obtained from oxidation of coal pyrite and decomposition of sulfate are resolved and appear at temperatures distinct from those observed from combustion of the organic structures in coal. Two major SO2 evolution maxima resulting from organic structures are observed. Each of the organic peaks has CO2 and H2O associated with it, implying that the organic matrix is oxidized in stages. Using model systems for comparison, these two major evolution maxima have been related to the probable structural types producing the evolutions. Analyses obtained with the oxidation procedure compare satisfactorily with ASTM values. Recent improvements in the oxidation conditions and detection system are discussed. The results obtained using the oxidation procedure to analyse model systems and numerous coals, including several treated coals, are discussed.

In this study it has been demonstrated that magnetic and chemisorptive techniques can be used to characterize metal speciation in catalysts such as Co/ZSM-5. In particular, the amounts of ion-exchanged cobalt and cobalt external to the zeolite can be estimated. These measurements enable one to intepret the catalytic activity and selectivity of the catalyst. In our attempts to introduce cobalt in cationic form in ZSM-5 we have used a temperature of 90/sup 0/C for exchange with aqueous cobalt nitrate solution. It appears that 0.9 wt % Co can be introduced into ZSM-5 of SiO/sub 2//Al/sub 2/O/sub 3/ = 38 under these circumstances. Co/ZSM-5 samples that were prepared by impregnation at room temperature with cobalt nitrate solution, showed approximately 2.2 wt % Co to be in a form not reducible to metallic cobalt. In earlier work the Co/ZSM-5 samples were subsequently washed with water to yield samples that contained 1.4 to 1.7 wt % Co. It is hence possible that exchange at temperatures lower than 90/sup 0/C would yield samples containing more than 0.9 wt % Co in ion-exchanged form. It is shown in this study that Co/sup 2 +//ZSM-5 can be back-exchanged and reduced to yield metallic cobalt supported onmore » H-ZSM-5. Chemisorption measurements are currently being carried out to determine the degree of dispersion of such samples. The back-exchanged samples are catalytically active in synthesis gas conversion. The method of back-exchange should be generally applicable for preparing metal-zeolite catalysts where it is desirable to free the zeolite of metal cations in order to restore the acidity to its original strength, and to have the metal on the exterior of the zeolite crystallites in a highly dispersed, catalytically active form. 14 refs., 2 figs., 3 tabs.« less