A process for the simultaneous removal of sulfur oxides and nitrogen oxides from power plant stack gases comprising contacting the stack gases with a supported iron oxide catalyst/absorbent in the presence of sufficient reducing agent selected from the group consisting of carbon monoxide, hydrogen, and mixtures thereof, to provide a net reducing atmosphere in the SO.sub.x /NO.sub.x removal zone. The sulfur oxides are removed by absorption substantially as iron sulfide, and nitrogen oxides are removed by catalytic reduction to nitrogen and ammonia. The spent iron oxide catalyst/absorbent is regenerated by oxidation and is recycled to the contacting zone. Sulfur dioxide is also produced during regeneration and can be utilized in the production of sulfuric acid and/or sulfur.
Disclosed is a substance which is obtained by calcining an iron hydroxide or a water-containing iron oxide and coating the surface of the resultant calcined product with alumina. This substance is useful as a catalyst in the removal of nitrogen oxides from an exhaust gas containing the nitrogen oxides.
An excellent catalyst for the reduction of nitrogen oxides is obtained by mixing a specific aluminum-containing substance with a specific iron-containing substance in water and baking the resultant precipitate.
A process and apparatus are provided whereby sulfur and nitrogen oxides as well as carbon monoxides and unburned hydrocarbons are removed from internal combustion engine exhaust gases. The gases are passed through a chamber containing a sulfide and an oxide of iron, copper or zinc. The system is partially self-regenerating and can be used in conjunction with present catalytic converter units or in lieu thereof. In certain embodiments the present invention can also replace muffler units in exhaust systems.
The present invention provides novel catalysts for the simultaneous removal of SO.sub.2 and NO.sub.x from flue gases. The catalysts may be supported or unsupported, pretreated or untreated, but allow the simultaneous reduction of SO.sub.2 to S and NO.sub.x to N.sub.2. Elemental sulfur is a useful byproduct of the process.
A process to remove SO.sub.2 from mixtures by contacting SO.sub.2 -containing mixtures with a regenerable iron-bearing sorbent such as paint rock under reaction conditions to produce iron sulfide and an effluent containing reduced amounts of SO.sub.2.
