Thermodynamic equilibrium calculations of sulfur poisoning in Ce–O–S and La–O–S systems

• Published in: Catalysis today Vol. 100; no. 3; pp. 291 - 295
• Main Authors: Karjalainen, Heidi, Lassi, Ulla, Rahkamaa-Tolonen, Katariina, Kröger, Virpi, Keiski, Riitta L.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 28-02-2005; Elsevier Science
• Subjects: Catalysis; Cerium oxide; Chemistry; Exact sciences and technology; General and physical chemistry; Lanthanum oxide; Sulfur; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Thermodynamic equilibrium; Sulfur; Cerium oxide; Thermodynamic equilibrium; Lanthanum oxide; Lanthanide compound; Heterogeneous catalysis; Calculation
• ISSN: 0920-5861; 1873-4308
• DOI: 10.1016/j.cattod.2004.09.063

Sulfur poisoning is still a problem in many application areas of exhaust gas catalysts despite the fact that the sulfur levels, e.g. in gasoline are being continuously reduced. The aim of this study was to calculate thermodynamic equilibrium compositions of sulfur in Ce–O–S and La–O–S systems in the presence of precious metals (Pt, Pd, and Rh), which all were considered as bulk materials, in order to understand the experimentally observed sulfur poisoning under the real applications of exhaust gas catalysts. Depending on temperature and oxygen partial pressure, sulfur can be present in the form of sulfates, sulfides and oxysulfides. It is thermodynamically favorable that cerium oxide reacts with SO
2 to form cerium sulfate at low temperatures and cerium oxysulfides at high temperatures. Lanthanum oxide reacts with SO
2 to form sulfate under oxidizing conditions and sulfides under reducing conditions.