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Showing papers on "Selective catalytic reduction published in 1976"


Journal ArticleDOI
TL;DR: In this paper, it was found that preadsorbed NO promotes the adsorption of CO, which was attributed to the formation of a surface isocyanate complex.

46 citations


Patent
12 May 1976
TL;DR: In this paper, vanadium oxide supported on a specific carrier of the anatase form of titanium oxide is used for selective reduction of nitrogen oxides in exhaust gases in the presence of ammonia.
Abstract: A catalyst for the selective reduction of nitrogen oxides in exhaust gases in the presence of ammonia is vanadium oxide supported on a specific carrier of the anatase form of titanium oxide

41 citations



Patent
11 Mar 1976
TL;DR: In this paper, a process for removing nitrogen oxides from gaseous mixtures comprising the same is described, where ammonia in an amount excessive over the stoichiometric amount necessary for reducing the nitrogen oxide is introduced into a reaction zone containing a catalyst.
Abstract: Process for removing nitrogen oxides from gaseous mixtures comprising the same. Ammonia in an amount excessive over the stoichiometric amount necessary for reducing the nitrogen oxides is introduced into a reaction zone containing a catalyst. Then, ammonia in a minimum amount necessary for reduction of the nitrogen oxides is introduced into the reaction zone.

30 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of catalyst composition on the CO-oxidation activities of these catalysts has been investigated, and it has been shown that the formation of both N2 and N2O from NO appears to occur predominantly by a catalyst redox mechanism.

21 citations


Patent
Akira Kato1, Shimpei Matsuda1, Shigeo Uno1, Imahashi Jinichi1, Fumito Nakajima1 
13 Oct 1976
TL;DR: In this article, a process for treating an exhaust gas containing substantially only ammonia gas and oxygen gas as reactants to decompose catalytically the ammonia gas to nitrogen and water, which comprises contacting at an elevated temperature the exhaust gas with a catalyst consisting essentially of the oxides of titanium, copper and a member selected from the group consisting of molybdenum, tungsten, vanadium, cerium, iron and mixtures thereof.
Abstract: A process for treating an exhaust gas containing substantially only ammonia gas and oxygen gas as reactants to decompose catalytically the ammonia gas to nitrogen and water, which comprises contacting at an elevated temperature the exhaust gas with a catalyst consisting essentially of the oxides of titanium, copper and a member selected from the group consisting of molybdenum, tungsten, vanadium, cerium, iron and mixtures thereof. The ammonia gas is catalytically decomposed in accord with the following chemical reaction: 2NH.sub.3 +3/2 O.sub.2 →N.sub.2 +3H.sub.2 O air pollution due to ammonia gas contained in an exhaust gas from, such as, an ammonia production plant, or copying machines using ammonia sensitive paper, is satisfactorily prevented by this process.

19 citations


Journal ArticleDOI
TL;DR: In this paper, the surface states of reduced metal oxides were studied with ESCA, and the correlation of the activities of the reduced metal oxide catalysts for the NO-CO reaction with their surface states was investigated.
Abstract: In the catalytic NO–CO reaction over metal oxide catalysts, the surface states of reduced metal oxides were studied with ESCA, and the correlation of the activities of the reduced metal oxide catalysts for the NO–CO reaction with their surface states was investigated. The surfaces of the catalysts were studied with ESCA after treatments in situ. It was revealed that the surface states of the metal oxides did not always agree with their bulk constituents. For example, it was found that the oxygen in the surface layer of the cobalt oxide after a proper reduction treatment by CO was richer than in its bulk. Moreover, the correlation between the surface states and the activities of those oxides was successfully explained. It was also concluded that, in the NO–CO reaction, the metal states were most active for the cobalt, iron, and nickel oxides, while the Cu+ state was more active than the Gu metal state for the copper oxide.

19 citations


Patent
12 Feb 1976
TL;DR: In this article, base metal catalysts are pretreated with selenium, sulfur or sulfur compounds and a gaseous stream comprising nitric oxide, oxygen and ammonia is passed over the pretreated catalysts.
Abstract: Base metal catalysts are pretreated with selenium, sulfur or sulfur compounds. Subsequently, a gaseous stream comprising nitric oxide, oxygen and ammonia is passed over the pretreated catalysts. The nitric oxide is reduced to nitrogen and no nitrous oxide is formed.

17 citations


Patent
19 Mar 1976
TL;DR: In this paper, exhaust gases containing residual nitric oxide constituents from a processing operation are maintained at an elevated pressure, heated to from 260° C. to 340° C in a separate heat exchanger, and subjected to multi-stage catalytic reduction with ammonia to produce purified exhaust gases.
Abstract: Exhaust gases containing residual nitric oxide constituents from a processing operation are maintained at an elevated pressure, heated to from 260° C. to 340° C. in a separate heat exchanger, and subjected to multi-stage catalytic reduction with ammonia to produce purified exhaust gases. The pressure of the thus purified exhaust gases is then relieved in an expansion turbine.

14 citations


Patent
23 Apr 1976
TL;DR: In this paper, a selective catalytic reduction of even small amts. of NO and NO2 to N2 with NH3 without side-reactions with other components of exhaust gases such as O2, CO 2, CO, water vapour or sulphur oxides is described.
Abstract: Catalyst for reducing nitrogen oxides in exhaust gases to nitrogen by contacting the exhaustion gases with gaseous ammonia, contg. a mixt. of oxides of Ti, W and/or Mo, V and opt. Sn is improved in that it contains (in atom %) Ti >=50% (pref. >=70%), W and/or Mo =50% (pref. =30%), V =1%, and Sn 0-10% (pref. =1%). The catalyst compsn. pref. contains 60 wt.% or more of a solid carrier. Purification of exhaust gases from internal combustion engines, combustion furnaces, industrial plants producing or employing HNO3 or nitrates, etc., is improved by selective catalytic reduction of even small amts. of NO and NO2 to N2 with NH3 without side-reactions with other components of exhaust gases such as O2, CO2, CO, water vapour or sulphur oxides. The selective action of the catalyst can be ascribed to the use of a small amt. of V in a narrow concn. range. The reaction proceeds in a wide temp. range (150-650 degrees C, pref. 150-550 degrees V). The catalyst has high activity and long service life.

14 citations


Patent
30 Dec 1976
TL;DR: In this paper, a method of treating a combustion exhaust gas containing nitrogen oxides was proposed. But this method required the use of a mixture of the exhaust gas, oxygen and ammonia at a temperature from 700° C to 1300° C.
Abstract: A method of treating a combustion exhaust gas containing nitrogen oxides comprises: A first step of removing nitrogen oxides by treating a mixture of the exhaust gas, oxygen and ammonia in the absence of hydrogen or in the presence of lower than 10 mole ratio of hydrogen to ammonia at a temperature from 700° C to 1300° C and A second step of adjusting a mole ratio of hydrogen to ammonia in the pretreated exhaust gas to higher than 3 and treating the mixed gas at a temperature from 490° C to 700° C.

Patent
25 Feb 1976
TL;DR: In this article, Nitrogen oxides in an exhaust gas are selectively removed by employing ammonia as a reductant and by employing a catalyst composed of alumina, copper, and at least one of the alkali metals, the alkaline earth metals and the transition metals.
Abstract: Nitrogen oxides in an exhaust gas are selectively removable by employing ammonia as a reductant and by employing a catalyst composed of alumina, copper, and at least one of the alkali metals, the alkaline earth metals and the transition metals. Optionally, the catalyst composition may include a slight amount (less than 1% by weight) of a precious metal such as rhodium, ruthenium, plantinum and palladium. This selective removal of nitrogen oxides is not impaired by the presence of O 2 , H 2 O and SO 2 in the exhaust gas.

Patent
23 Nov 1976
TL;DR: In this article, exhaust gases containing residual nitric oxide constituents from a processing operation are maintained at an elevated pressure, heated to from 260° to 340° C, and subjected to catalytic reduction with ammonia to produce purified exhaust gases.
Abstract: Exhaust gases containing residual nitric oxide constituents from a processing operation are maintained at an elevated pressure, heated to from 260° to 340° C., and subjected to catalytic reduction with ammonia to produce purified exhaust gases. The pressure of the thus purified exhaust gases is then relieved in an expansion turbine.

Patent
01 Nov 1976
TL;DR: In this article, the authors proposed to enable NOx to be decomposed effectively by reduction even in the coexistence of SOx, by contacting the gas containing NOx with the catalyst obtained by supporting more than one kind out metals of the 1B group, the 5A group, etc of the periodic table, with the carrier consisting of calcium silicate as the main component, in the presence of O2 and NH3.
Abstract: PURPOSE:To enable NOx to be decomposed effectively by reduction even in the coexistence of SOx, by contacting the gas containing NOx with the catalyst obtained by supporting more than one kind out metals of the 1B group, the 5A group, etc of the periodic table, lanthanoid and Sn with the carrier consisting of calcium silicate as the main component, in the presence of O2 and NH3

Patent
20 Nov 1976
TL;DR: In this paper, a process wherein iron ores are used as a moving bed catalyst in catalytic reduction of nitrogen oxides in exhaust gas using ammonia is described, and the authors describe the process as follows:
Abstract: PURPOSE:A process wherein iron ores are used as a moving bed catalyst in catalytic reduction of nitrogen oxides in exhaust gas using ammonia.

Journal ArticleDOI
TL;DR: In this paper, the reduction of NO by H2 and CO was studied over a number of Pd, Ag, and Fe mixed catalysts supported on y-alumina with and without the addition of oxygen.
Abstract: The reduction of NO by H2 and CO was studied over a number of Pd, Ag, and Fe mixed catalysts supported on y-alumina with and without the addition of oxygen. Ag/Fe—AI2O3 is more active for the reduction of NO by H2 at low CO concentrations than the single components Ag and Fe. The three-component catalyst Pd/Ag/Fe has a remarkable selectivity for the NO reduction by H2 and CO even at O2 concentrations of 2°/o at the inlet. Both effects are attributed to a possible adlineation of NO on iron and silver phase boundaries. Carbon monoxide blocks considerably the reduction by H2 over Pd and Pt catalysts up to about 350 °C.

Patent
26 Oct 1976
TL;DR: In this article, a method of catalytic reduction, using NH3, of the NOx in the exhaust gas containing SOx from various stationary gas generating sources, catalysts which remove the NOix for a long period of time at high efficiency without being subjected to the deterioration in their activity occurring in the SOx are used.
Abstract: PURPOSE:In a method of catalytic reduction, using NH3, of the NOx in the exhaust gas containing SOx from various stationary gas generating sources, catalysts which remove the NOx for a long period of time at high efficiency without being subjected to the deterioration in their activity occurring in the SOx are used.

Patent
30 Aug 1976
TL;DR: In this paper, a mixture of ammonium carbamate and excess ammonia is separated from urea synthesis effluent in the form of a gaseous mixture of ammonia and carbon dioxide.
Abstract: Carbon dioxide is reacted with a stoichiometric excess of ammonia at urea synthesis temperatures and pressures in a urea synthesis zone with the mol ratio of ammonia to carbon dioxide being in the range of from 5:1 to 12:1. The urea synthesis effluent from the urea synthesis zone is pressurized to a pressure higher than the urea synthesis pressure, and heated to a temperature higher than the urea synthesis temperature in a separation zone, wherein unreacted ammonium carbamate and excess ammonia contained in said urea synthesis effluent are separated from urea synthesis effluent in the form of a gaseous mixture of ammonia and carbon dioxide. The thus separated gaseous mixture of ammonia and carbon dioxide is recycled to said urea synthesis zone by means of the pressure difference.

Journal Article
TL;DR: In this paper, the effect of catalyst composition on the CO-oxidation activities of these catalysts was investigated, and the presence of product N/sub 2/O during the low-temperature CO-NO reaction was explained.


Patent
16 Oct 1976
TL;DR: In this article, the influence of the dust contained in a waste gas in the catalytic reduction with ammonia of NOx contained in the waste gas was prevented by using a particle filter.
Abstract: PURPOSE:To prevent the influence of the dust contained in a waste gas in the catalytic reduction with ammonia of NOx contained in the waste gas.

01 Jan 1976
TL;DR: In this paper, the phase composition and chemical composition of an industrial iron catalyst for the synthesis of ammonia, SA--1N, promoted by oxides of Al, K, Ca, Mg, and V were investigated.
Abstract: The local x-ray spectral analysis method was used to investigate the phase composition and chemical composition of the oxidized and reduced phases of an industrial iron catalyst for the synthesis of ammonia, SA--1N, promoted by oxides of Al, K, Ca, Mg, and V. The formulas of the minerals forming the oxidized catalyst were determined. Migration paths of the promoting components during catalytic reduction were found. It was established that differences in the activity of individual samples are caused by a nonuniform chemical composition of the principal working phase. This is caused by an instability in the condition of industrial catalyst production.


Journal ArticleDOI
TL;DR: In this article, the catalytic reduction of NO with H2 and CO has been studied over Co/Al and Cr/Al catalysts prepared by coprecipitation, and the results suggest that most of the N2O desorbs from the surface of the co/Al catalyst before N2 is formed.
Abstract: The catalytic reduction of NO with H2 and CO has been studied over Co/Al and Cr/Al catalysts prepared by coprecipitation. The data show a much larger difference in the activities of Cr/Al and Co/Al when reducing NO with CO than in the case of H2. In both cases Cr/Al appears to be much more selective to N2 formation than Co/Al. The dependence of the selectivity on temperature is different for the two reductants on the Co/Al catalyst. The results suggest that most of the N2O desorbs from the surface of the Co/Al catalyst before N2 is formed.

Journal ArticleDOI
TL;DR: In this article, the authors used Co/Al catalysts containing oxides of alkali metals (Li, Na, Rb, Cs) as additive to catalyzed process.
Abstract: The process was carried out over Co/Al catalysts containing oxides of alkali metals (Li, Na, Rb, Cs) as additives. The presence of alkali metals generally decreases the activity of the Co/Al catalysts, except for very low concentrations of Li, Na, Rb and Cs atoms. Activity of catalyst increases with atomic weight of alkali metal additive. Possible effect of additive on catalyst structure is briefly discussed with respect to catalyzed process.

Journal ArticleDOI
TL;DR: In this article, the surface states of reduced metal oxides were studied with ESCA, and the correlation of the activities of the reduced metal oxide catalysts for the NO-CO reaction with their surface states was investigated.
Abstract: In the catalytic NO–CO reaction over metal oxide catalysts, the surface states of reduced metal oxides were studied with ESCA, and the correlation of the activities of the reduced metal oxide catalysts for the NO–CO reaction with their surface states was investigated. The surfaces of the catalysts were studied with ESCA after treatments in situ. It was revealed that the surface states of the metal oxides did not always agree with their bulk constituents. For example, it was found that the oxygen in the surface layer of the cobalt oxide after a proper reduction treatment by CO was richer than in its bulk. Moreover, the correlation between the surface states and the activities of those oxides was successfully explained. It was also concluded that, in the NO–CO reaction, the metal states were most active for the cobalt, iron, and nickel oxides, while the Cu+ state was more active than the Gu metal state for the copper oxide.

Journal ArticleDOI
TL;DR: In this article, a Co/Al catalyst containing potassium oxide as an additive was used to reduce NO with hydrogen using a differential reactor operated at atmospheric pressure, and the process was carried out over a co-al catalyst with potassium oxide, which generally produces a decrease in activity of the Co/al catalyst except for very low concentrations of potassium atoms.
Abstract: Catalytic reduction of NO with hydrogen has been studied using a differential reactor operated at atmospheric pressure. The process was carried out over a Co/Al catalyst containing potassium oxide as an additive. The presence of potassium generally produces a decrease in activity of the Co/Al catalyst except for very low concentrations of potassium atoms.