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| NIRE Annual Report |
| 1998 |
Desulphurization and Solubilization of High Sulphur Coal by Superacid HF/BF3Fundamental Research DivisionEnergy Resources Department |
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Objectives
Organic sulphur in coal is difficult to remove by physical means or conventional chemical processes because it is firmly linked with the organic units of coal. The objective of this research is to moderate the reaction conditions for coal desdesulphurization and solubilization through ionic reaction without gaseous hydrogen by superacid HF and HF/BF3.
The extent of desulphurization and the distribution of organic sulphur in the sample MQ and treated coals obtained from reactions at 200ºC were evaluated by XPS (Fig. 1). The organic sulphur of the sample coal was comprised of 20% oxidized, 35% sulphidic and 45% thiophenic sulphur. Heattreatment at 200ºC in the presence of toluene without acid catalyst yielded only 6% desulphurization, and no significant decrease in any sulphur forms. HF in the presence of isopentane increased desulphurization to 22% and clearly decreased both oxidized and sulphidic sulphur; thiophenic sulphur content was unchanged. HF with toluene markedly increased desulphurization to 52% mainly from decreases in sulphidic and oxidized sulphur. The conjugate Bronsted - Lewis superacid HF/7mol% BF3 produced less thiophenic sulphur as well as less oxidized and sulphidic sulphur than did the reaction with HF at 200ºC although the extent of desulphurization was only slightly increased.
The thermal treatment in tetrahydronaphthalene tetraline at 420ºC under hydrogen pressure gave 55% desulphurization, and yielded less thiophenic sulphur than that in the sample MQ coal.
The distribution of organic sulphur forms of product form the reaction with HF/BF3 was almost the same as that of thermal treated coal.
Desulphurization of coal increased with increasing of PS yield was shown in Fig. 2. There was some correlation between the extent of desulphurization and the extent of degradation of the coal. In particular, the treated coal, in which almost all sulphidic sulphur was removed, yielded coal of high extractability, indicating that removal of original sulphidic sulphur improves the coal depolymerization.
Selected Publications
1) Behaviour of Sulfur in High-Sulfur Coal in a Superacidic Medium without Gaseous Hydrogen, Fuel, 76(10), 939, 1997 2) Removal of Organic Sulphur in Coal by the Use of Anhydrous HF and Superacid HF/BF3, Chemistry Letter, 943, 1997