Showing papers on "Selective catalytic reduction published in 1974"

Reduction of nitrogen oxides with catalytic acid resistant aluminosilicate molecular sieves and ammonia

Abstract: Noxious nitrogen oxides in a waste gas stream such as the stack gas from a fossil-fuel-fired power generation plant or other industrial plant off-gas stream is catalytically reduced to elemental nitrogen and/or innocuous nitrogen oxides employing ammonia as reductant in the presence of a zeolite catalyst in the hydrogen or sodium form having pore openings of about 3 to 10 A.

Nitric oxide reduction with hydrogen on mixed metal oxide catalysts

Abstract: Catalytic reduction of nitric oxide with hydrogen was investigated on a number of mixed oxide and oxide mixtures in a laboratory integral reactor using a feed gas containing 520 ppm of NO and 3000 ppm of H/sub 2/ in a nitrogen carrier gas to determine catalytic activity and ammonia formation. Then some of the more promising catalysts were tested in actual automobile exhaust to determine their feasibility in catalytic reactors for NO reduction. Highest yields of NH/sub 3/ at 90 percent conversion of NO or higher in the first test were observed with rare earth nickel iron oxide and copper-vanadium oxide, copper-nickel oxides, monel, platinum, palladium, and rhodium. Each of these catalysts showed stoichiometric conversion to NH/sub 3/ at a specific temperature. Platinum and palladium maintained this stoichiometric conversion up to 500 C; monel showed a sharp drop in NH/sub 3/ yield above the temperature of stoichiometric conversion (450 C). Lowest NH/sub 3/ maxima for NO conversion levels above 90 percent were observed with ruthenium, mixed ruthenium oxides, and a series of nickel- containing catalysts. When tested in auto exhaust, ruthenium and mixed ruthenium oxides were particularly active and appeared to exhibit true selectivity for reduction of NO to N/submore » 2/. (Air Pollut. Abstr.)« less

Asymmetric hydrogenation of a carbon–nitrogen double bond in folic acid

Abstract: Asymmetric catalytic reduction of the 5–6 carbon-nitrogen double bond in folic acid has been achived by hydrogenation with an optically active rhodium catalyst.

Nitrogen oxide removal catalysts for purification of automobile exhaust gases

Abstract: The chemistry involved in the selective catalytic reduction of nitrogen oxides in automobile exhaust is outlined, and the requirements of a practical NO/sub x/ reduction catalyst are summarized. Critical reactions for the removal of NO/sub x/ are likely to be hydrogenation (with a mechanism proceeding through ammonia or some other NHn species) and/or the oxidation of carbon monoxide with the intermediary of surface N species or even isocyanates. Laboratory studies of NO/sub x/ reduction catalysts indicate the following: ruthenium is the most effective catalytic material at high values of the reducing power index of the gas mixture (i.e., high CO or low O/sub 2/ levels); rhodium is most effective over a narrow range of the reducing power index and can operate closer to stoichiometric than the other active species tested; base metal catalysts behave like Ru catalysts but require higher temperatures of operation; and platinum alone is relatively ineffective whatever the conditions of use. Limited endurance data obtained from dynamometer tests indicate it is possible to control hydrocarbons, CO, and NO/sub x/ emissions simultaneously within the old 1976 limits for at least 10,000 mi on small displacement vehicles using a dual-catalyst system.

The Role of Hydrogen in the Catalytic Reduction of Nitrogen Monoxide over Iron Oxide

Abstract: The mechanism of the reduction of nitric oxide with hydrogen over Fe2O3-γ -Al2O3 was investigated from the kinetic point of view. Two possible roles of hydrogen were tentatively considered. (1) Direct interaction with nitric oxide to form hydrogen-nitric oxide surface complex [Langmuir-Hinshelwood mechanism]. (2) Reducing action toward oxidized surface to complete catalytic sequence [redox mechanism]. The following experiments were carried out in order to elucidate the role of hydrogen.The rate of reaction of nitric oxide with the reduced surface in the absence or presence of hydrogen was compared using pulse technique. As shown in Fig.1 and Table1, the rate at an extreme initial stage was unaffected by the atmosphere, i. e., helium or hydrogen.The catalyst under working condition was found to be in oxidized state. The rate of reduction of the catalyst with hydrogen, 3x10-5mol/min g-cat, was almost the same as that of catalytic reduction of nitric oxide, 2x10-5 mol/min g-cat, obtained in a closed circulation system.These findings clearly showed that the reaction was of redox type, which was well expressed by the rate equation proposed previously.

Low-temperature catalytic reduction of nitric oxide by carbon monoxide on SnO2–CuO gels

Abstract: After thermal activation at 450°, coprecipitated SnO2–CuO gels, particularly those having a Cu : Sn atomic ratio of between 0·5 : 1 and 0·6 : 1, show high activity and high selectivity for N2 formation at low temperature (150°) in the catalytic reduction of NO with CO compared with a commercial barium-promoted copper chromite catalyst (Girdler G-22).

Manufacture of 3-aminobenzoylbenzoic acids

Abstract: Improvement in the process for the manufacture of 3-aminobenzoylbenzoic acids by catalytic reduction of the 3-nitro compounds, the improvement consisting in the reduction of the aqueous alkali metal salt solution of the 3-nitro compound in the presence of boric acid, its alkali metal or ammonium salts or mixtures thereof and in the presence of Raney nickel or nobel metal catalysts using hydrogen at atmospheric or slightly elevated pressure. The corresponding 3-aminobenzoylbenzoic acids are obtained in high yield.

Asymmetric hydrogenation of a carbon-nitrogen double bond in folic acid

Abstract: Asymmetric catalytic reduction of the 5–6 carbon-nitrogen double bond in folic acid has been achived by hydrogenation with an optically active rhodium catalyst.