Abstract: A feed gas mixture with SO.sub.2 partial pressure of at least about 0.5 atmosphere and an O.sub.2 :SO.sub.2 mole ratio of between about 0.7:1 and about 1:1 is passed in plug flow through a packed bed of conversion catalyst. The catalyst bed is cooled to produce a temperature profile including a first zone of increasing temperature, a second zone of substantially constant temperature and a third zone of declining temperature. The exit temperature is sufficiently low for high equilibrium conversion values. The effluent is cooled to condense liquid sulfur trioxide, while the sulfur trioxide remaining in the gas stream can be absorbed into oleum and/or sulfuric acid. Enriched oleum can be prepared by blending condensed sulfur trioxide into oleum or sulfuric acid.

Abstract: A novel process for producing hydrogen and sulfur via the thermal decomposition of hydrogen sulfide is disclosed. The thermal decomposition of hydrogen sulfide is accomplished by passing a hydrogen sulfide containing gas through a reaction chamber containing a refractory material that has been preheated to a temperature between about 982.degree. C. and about 1816.degree. C. so that a gas stream comprising hydrogen, sulfur and hydrogen sulfide is produced. While one reaction chamber is used for decomposition, another is being preheated with hot gases such as a sulfur dioxide-oxygen mixture from a sulfur burner. When the peak temperature in the first reaction chamber declines to a selected value, the functions of the two reaction chambers are reversed.

Abstract: Sulfur dioxide is reduced to sulfur and hydrogen sulfide with a gaseous reducing agent in the presence of a catalyst by a process involving mixing a sulfur dioxide-containing gas stream with a portion of the gaseous reducing agent and passing the resulting mixture through a first reactor to effect reduction of a portion of the sulfur dioxide to hydrogen sulfide and sulfur, mixing the gas stream from the first reactor with the remaining gaseous reducing agent, and splitting the resulting mixture into two gas streams which are in parallel passed through a second and third reactor to effect reduction of sulfur dioxide to form hydrogen sulfide and sulfur. Periodically, the flow in the first and third reactors is reversed to thereby subject these reactors to periodically alternating heat absorbing and desorbing cycles while the flow in the second reactor is always maintained in the same direction.