Brown coal hydrogen content

Tars can be hydrogenated to produce Hquid fuels. High hydrogen and low asphaltene, ie, benzene-soluble and pentane-iasoluble, contents are desirable. The central German brown coals are attractive for this reason. The tars from the eastern part of Germany require much lower pressures and less hydrogen per unit of product than do brown coals near Cologne, which can require pressures up to 71 MPa (700 atm) (see Petroleum). 

These values are summarized in Figure 2 and compared with our results on the soluble fractions from depolymerization. Van Krevelen (9) reported aromatic hydrogen values ranging from 23 to 54% for coals containing 76 to 89% carbon. Aromatic hydrogen content varies directly with rank. Brown (i) obtained values of 19-42% for a series of vitrains and showed a similar relationship with rank displaced toward lower aromatic values. Ladner and Stacey (5) analyzed two additional coals using the procedure developed by Brown, and the results fit Brown s correlation. 

Carbonate Formation During Hydrogenation. The formation of carbonate minerals during hydrogenation of low-rank coals can cause serious operational difficulties in the reactor systems. A good correlation has been found between the calcium content of a number of Victorian brown coals and the carbonate formed during hydrogenation. However, the results indicated that cations other than calcium were involved in the formation of carbonate. 

Analysis. The original coal and the various fractions were analyzed for carbon, hydrogen, and oxygen by the C.S.I.R.O. Microanalytical Service. Ash contents were determined in a standard ashing furnace (14). Phenolic, carboxylic, and carbonyl oxygen contents were determined by the State Electricity Commission of Victoria, using methods developed by them for brown coals (15). 

Indeed, early work (Storch et al., 1951 Wu and Storch, 1968) on the production of liquids from coal indicated that the lower-rank coals (particularly the brown coals, i.e., lignites) were more reactive and required a lower hydrogen pressure for liquid production than the bituminous coals. More recent work (Sturm et al., 1981) has shown that the liquid from the lower-rank coals were easier to upgrade but that coal rank alone could not account for the complexity of the liquid products, as noted elsewhere content of the liquids produced decreased. 

Brown (1955)611 has studied the IR spectra of coals with special attention on the optical densities of the two peaks at 3030 and 2920 cm-1. He found that the ratio of aromatic hydrogen to total hydrogen increased with rank. Fujii and his collegues (1970)62) noted that the absorption band at 2920 cm-1 generally increased with rank to 86% carbon but thereafter decreased sharply with higher carbon contents. 

---