Iron Removal from High-Temperature Fischer–Tropsch-Derived Distillate through Thermal Treatment
| Autor: | Siphamandla W. Hadebe, Dieter Leckel |
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| Rok vydání: | 2013 |
| Předmět: | |
| Zdroj: | Energy & Fuels. 27:5161-5167 |
| ISSN: | 1520-5029 0887-0624 |
| DOI: | 10.1021/ef401158e |
| Popis: | Hydrotreating units at the Sasol high-temperature Fischer–Tropsch plant in Secunda, South Africa, experience a number of unplanned shutdowns because of sudden increases in pressure over the reactor beds. This is caused by a solid crust that builds up at the top of the catalyst bed. The crust constituents were studied using inductively coupled plasma (ICP), and it was found that the major constituents of the crust are iron (48 mass %) and sulfur (28 mass %), in the form of iron sulfide (Troilite), as confirmed by X-ray diffraction (XRD) spectroscopic techniques. FeS is believed to originate from dissolved iron carboxylates present in the feed streams. A range of aliphatic iron carboxylates (C₅–C₁₁) expected to be present in the distillate hydrotreater feed were subsequently synthesized and characterized using infrared (IR) spectroscopy. The thermal behavior of these carboxylates was studied using high-pressure differential scanning calorimetry (HP-DSC); decomposition temperatures established ranged from 299 to 282 °C from C₅ to C₁₁. It has been shown experimentally that iron carboxylates dissolved in feed streams may be thermally decomposed in situ and removed as iron sulfide or iron oxide in the presence or absence of H₂S, respectively. High-pressure hydrogen or nitrogen may not be necessary during thermal decomposition of the iron carboxylates. However, hydrogen gas may be necessary to prevent coking but has no significant role in iron carboxylate decomposition. Therefore, iron carboxylates may still be decomposed and removed effectively from the feed streams using an upstream guard bed even at pressures lower than those used in the hydrotreating reactor. |
| Databáze: | OpenAIRE |
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