Showing papers on "Selective catalytic reduction published in 1971"

Catalytic reduction of nitric oxide with various hydrocarbons

Abstract: Conversion data for the reduction of nitric oxide with C1 to C8 hydrocarbons over a bariumpromoted copper chromite catalyst were obtained in an integral flow reactor operated at atmospheric pressure and temperatures of 225°C to 525°C. In general, an increase in carbon number in the hydrocarbon studied resulted in a decrease in the required temperature for a given nitric oxide conversion. For a given carbon number the required temperature for a given nitric oxide conversion decreased with degree of saturation. The data were fitted to empirical rate expressions.

Production of hydroxylammonium nitrate

Abstract: Production of an aqueous solution of hydroxylammonium nitrate by catalytic reduction of nitrogen monoxide with hydrogen in acid solution, a platinum catalyst being used which has been partly poisoned with one or more elements of main groups V and/or VI of the Periodic Table and activated prior to the beginning of the reaction in an aqueous suspension with hydrogen. Nitric acid is continuously supplied during the reaction in an amount necessary for the end concentration of hydroxylammonium nitrate.

The catalytic reduction of calcium sulfate

Abstract: In several processes for obtaining elemental sulfur from gypsum the first step involves the reduction of calcium sulfate to calcium sulfide. However, these reactions require extremely high temperatures and relatively long reaction times. Very little work is reported concerning the use of a catalyst in reducing the cal-cium sulfate. In this study, ferric oxide was found to have a pronounced catalytic effect on the reaction. Using this catalyst a study was made of the reduction of calcium sulfate in a fluidized bed re-actor. Carbon monoxide gas was used as a reducing agent. A uni-variant search technique was employed in order to study the effect of time, temperature, weight per cent catalyst, and carbon monoxide flow rate. In addition, the auto-catalytic effect of calcium sulfide was investigated. The optimum operating temperature was found to be 680°C. At this temperature the conversion was 97.1 per cent reduction of cal-cium sulfate in 45 minutes. This compares favorably with the conversion obtained using no catalyst and much higher reaction tempera-tures. The effect of varying the temperature was found to be rel-atively pronounced. This seems to indicate that the chemical rate of reaction might be controlling. The optimum concentration of ferric oxide was found to be approximately 9 weight per cent. These runs were made at 720°C for 45 minutes. Conversion drops off sharply for concentrations below 7 weight per cent ferric oxide. Above 9 per cent concentrations the conversion is slightly smaller. The carbon monoxide flow rate had little effect on conver-sion, indicating that the controlling mechanism is not film dif-fusion. Runs made at 660°C showed definite reproducible oscillations when plotting the conversion of calcium sulfate with time. It was postulated that these oscillations were probably the result of a complex autocatalytic mechanism since an autocatalyzed reaction will behave in this manner under exceptional conditions. However, this behavior was not investigated further because a more elaborate re-actor would be required. Calcium sulfide was found to autocatalytically favor its own rate of formation. This would suggest that a certain amount of re-cycle of products would be desirable in the actual process design. At 720°C for a 10-minute run it was possible to increase the con-version by about 30 per cent by adding calcium sulfide to the re-actants . THE CATALYTIC REDUCTION OF CALCIUM SULFATE by THOMAS WILLIAM ZADICK A thesis submitted to the Graduate Faculty in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE in Chemical Engineering