Abstract: A catalyst that is used for a method of reduction removal of NOx in a exhaust gas by using ammonia as a reducing agent and has been deteriorated in activity by aggregation of vanadium oxide as an active component through long term use at a high temperature is washed with an acid aqueous solution having pH of 6 or less, and preferably 4 or less. The washing operation dissolves and removes away mainly the vanadium oxide as the aggregated active component, and then vanadium oxide as the active component is re-deposited thereon. The method of the invention enables regeneration of a thermally deteriorated catalyst, which has conventionally been impossible. The washing operation with the acid aqueous solution or an alkali aqueous solution does not influence the mechanical strength of the catalyst.

Abstract: The present invention provides a method of high-temperature denitration characterized in that NOx in an exhaust gas is reduced at 450° to 800° C. using ammonia as a reducing agent in the presence of a catalyst which comprises zirconium oxide and SO3 or SO42? and has solid acid strength (Ho) of ?11.93 or lower. The present invention also provides a method of high temperature denitration characterized in that NOx in an exhaust gas is reduced at 450° to 800° C. using ammonia as a reducing agent in the presence of a catalyst wherein at least one of tungsten oxide, molybdenum oxide and boron oxide is supported on a carrier comprising zirconium oxide and SO3 or SO42? and having solid acid strength (Ho) of ?11.93 or lower.

Abstract: The invention is to provide a method for regenerating a deteriorated denitration catalyst by an easy and simple procedure. A catalyst that is used for reduction removal of NOx contained in a exhaust gas by using ammonia as a reducing agent and has been deteriorated in activity through long term use is washed with an acid aqueous solution having pH of 4 or less, and preferably 2 or less, containing vanadium and/or tungsten. The washing operation dissolves away mainly an alkali metal, an alkaline earth metal, arsenic and sulfur, which are deteriorating components, and vanadium and tungsten having been deteriorated in activity, and simultaneously vanadium and/or tungsten as an active component is deposited thereon. Examples of the alkali metal include potassium and sodium, and examples of the alkaline earth metal include calcium.

Abstract: A purpose of the present invention is to provide a method of enabling denitration of an exhaust gas effectively at 450° to 600° C. and catalysts to be used for the method. A first catalyst comprises a composite oxide composed of titanium oxide and at least one of tungsten oxide, molybdenum oxide and boron oxide and having solid acid strength (Ho) of ?11.93 or lower. A second catalyst is a high-temperature denitration catalyst which comprises zirconium oxide and SO3 or SO42?, has solid acid strength (Ho) of ?11.93 or lower and is used at a reaction temperature of 450° to 800° C. A third catalyst is a high-temperature denitration catalyst wherein at least one of tungsten oxide, molybdenum oxide and boron oxide is supported on a carrier comprising zirconium oxide and SO3 or SO42? and having solid acid strength (Ho) of ?11.93 or lower and which is used at a reaction temperature of 450° to 800° C.

Abstract: The invention provides a process for removing NOx which is free of impairment in denitration efficiency at a reaction temperature of up to 300° C. even when the component molar ratio of NOx in the gas to be treated is NO2>NO. For use in removing NOx from the gas to be treated and containing NO2 in a larger amount than NO, that is, having a (NO2)/NOx ratio in excess of 0.5, by selective reduction with use of ammonia serving as a main reducing agent in the presence of a denitration catalyst, the process of the invention for removing NOx comprises adding to the denitration reaction system a substance for removing an excess of oxygen accumulating on catalyst active sites by selectively reducing the oxygen at not higher than 300° C., for example, at 300 to 150° C., in other words, a substance which reacts with the excess of oxygen on the catalyst active sites and becomes oxidized at not higher than 300° C.

Abstract: The present invention provides a nitrogen dioxide absorbent for the exhaust gas purifying facility designed to remove by absorption or adsorption of NO2 from a gas (such as ventilation gas from road tunnels) containing NOx in low concentrations. The absorbent is composed of a porous carrier and a basic amino acid and/or organic amine compound supported thereon. The absorbent is produced by impregnating a porous carrier sequentially with two aqueous solutions each containing in an amount of, for example, 0.5-3.0 mol/l (preferably 1.0-2.0 mol/l) of basic amino acid and 0.5-3.0 mol/l (preferably 1.0-2.0 mol/l) of organic amine compound, or impregnating a porous carrier with a solution containing 0.5-3.0 mol/l (preferably 1.0-2.0 mol/l) of basic amino acid and/or 0.5-3.0 mol/l (preferably 1.0-2.0 mol/l) of organic amine compound.

Abstract: The present invention relates to a Mn-added titania carrier obtained by adding a Mn salt to amorphous titania and baking the titania. The invention also relates to an NOx adsorbent comprising the above-mentioned titania carrier and adsorbing components comprising oxides of Ru and/or Ce supported on the carrier. The invention also relates to an NOx adsorbent comprising the above-mentioned titania carrier and adsorbing components comprising oxides of Ru and/or Ce and an oxide of at least one metal among Ag, Cu and Mn supported on the carrier. The NOx adsorbents embodying the invention are effectively used for efficiently adsorbing and removing NOx from gases which contain much moisture and low-concentration, for example, a few ppm NOx such as gases discharged by ventilation from highway tunnels.

Abstract: The invention discloses a NOx adsorption and removal apparatus employed in the method of passing NOx containing gas into the adsorber 1 filled with NOx adsorbent to adsorb a specific volume of NOx on the adsorbent, passing hot air into the adsorber to desorb NOx, and regenerating the adsorbent, wherein the adsorber is divided in plural zones arranged parallel in the gas flow direction. In this invention, by regenerating after adsorbing NOx in each zone, the regenerating apparatus can be reduced in size, and the energy may be saved by effective utilization of preheat.

Abstract: The invention provides first to fourth adsorbents for removing low-concention nitrogen oxides. The first adsorbent comprises a carrier of gamma-alumina, and ruthenium supported-thereon. The second adsorbent comprises a carrier of anatase-type titania, and ruthenium supported thereon. The third adsorbent comprises ceramic paper retaining a carrier of anatase-type titania thereon, and ruthenium supported on the ceramic paper. The fourth adsorbent comprises ceramic paper retaining a carrier of anatase-type titania thereon, and a ruthenium halide and a halide of addition metal which are co-supported on the ceramic paper. These adsorbents are free of the influence of moisture and therefore usable without necessitating energy-consuming dehumidification or only with dehumidification on a reduced scale.

Abstract: The invention provides first to fourth adsorbents for removing low-concentration nitrogen oxides. The first adsorbent comprises a carrier of gamma-alumina, and ruthenium supported thereon. The second adsorbent comprises a carrier of anatase-type titania, and ruthenium supported thereon. The third adsorbent comprises ceramic paper retaining a carrier of anatase-type titania thereon, and ruthenium supported on the ceramic paper. The fourth adsorbent comprises ceramic paper retaining a carrier of anatase-type titania thereon, and a ruthenium halide and a halide of addition metal which are co-supported on the ceramic paper. These adsorbents are free of the influence of moisture and therefore usable without necessitating energy-consuming dehumidification or only with dehumidification on a reduced scale.

Abstract: Disclosed is a method of adsorbing and removing NOx, by washing with water a gas discharged by ventilation from highway tunnels in a washing tower as pretreatment, and then adsorbing NOx in the gas with a rotary NOx adsorption unit. The washed gas may be heated by a heater which is placed between the washing tower and the rotary NOx adsorption unit.

Abstract: The invention provides a method of removing NOx by adsorption wherein a gas containing NOx at a low concentration is brought into contact with an adsorbent comprising a copper salt supported on zeolite serving as a carrier, whereby the NOx is adsorbed and removed efficiently. The adsorbent for use in this method comprises at least one copper salt supported on natural or synthetic zeolite, the copper salt being selected from the group consisting of copper chloride, double salt of copper chloride and ammine complex salt of copper chloride. The apparatus of the invention for purifying an NOx-containing gas comprises an adsorptive dehumidifier for dehumidifying the gas with a dehumidifying agent and regenerating the agent with a purified gas, and an adsorptive denitration unit for denitrating the dehumidified gas. The denitration unit has an adsorbent regenerating zone provided with a channel for recycling an NH.sub.

Abstract: A catalyst structure comprises a shape retaining metal core of the desired shape, a particle holding layer attached to the core and made of a glass fiber product and catalyst particles held in the layer.

Abstract: A plate-shaped denitrating catalyst comprising a metal net, a finely divided porous carrier retained on the metal net with a binder and covering the metal net, and an active component supported on the carrier.

Abstract: A highly active denitrating catalyst is produced by converting the surface layer of steel material to an aluminum alloy, treating the resulting steel material with an aluminum dissolving solution to dissolve out the aluminum and to render the surface layer porous, and immersing the steel material having the porous surface layer in a solution containing a vanadium compound to cause the porous surface layer to support the vanadium compound.

Abstract: A denitrating catalyst having a porous coating is produced by immersing a catalyst base of porous metal in a silica-containing coating bath, drying the catalyst base to form a carrier having a porour silica coating, immersing the carrier in a solution containing an active component and drying the resulting carrier to cause the carrier to support the active component thereon.

Abstract: A denitrating catalyst is produced by plating the surface of unactivated metal with aluminum and immersing the resulting layered product in an aqueous aluminum-dissolving solution to dissolve out the aluminum into the aqueous solution and to thereby activate the surface of the metal.

Abstract: Exhaust gas cleaning catalysts are produced by alloying copper and aluminum with at least one of the elements, nickel and chromium, and eluting by alkali or acid means aluminum from the cooled alloy surface. Small amounts of other metals from the fourth or fifth period V.about. VIII groups, may be added to the catalysts by alloying, or by impregnation, for enhanced catalytic properties. The catalysts exhibit improved reduction of NO and oxidation of CO in an exhaust gas stream, in the presence of Pb, SO.sub.2, moisture and hydrocarbons (H.C) and at relatively low temperatures.