A method for removing hydrogen sulfide (H.sub.2S) from an acid gas comprises feeding the gas to a membrane separation unit, collecting the product gas from the membrane unit, heating the permeate stream to the necessary inlet temperature for catalytic oxidation of H.sub.2S and feeding the heated permeate stream to a catalytic oxidation unit, where H.sub.2S is oxidized to SO.sub.2. The heating of the permeate stream is accomplished by using a fraction of the feed gas to heat the permeate stream in a separate heater or by using a steam-fired heater. The method is especially suited for use on an off-shore facility.

Disclosed herein are base metal catalyst devices for removing ozone, volatile organic compounds, and other pollutants from an air flow stream. A catalyst device includes a housing, a solid substrate disposed within the housing, and a catalyst layer disposed on the substrate. The catalyst layer includes a first base metal catalyst at a first mass percent, a second base metal catalyst at a second mass percent, and a support material impregnated with at least one of the first base metal catalyst or the second base metal catalyst. The preferred catalyst composition is a combination of manganese oxide and copper oxide.

Disclosed are a catalyst for synergistic control of oxynitride and mercury and a method for preparing the same. The catalyst includes the following components by mass percentage: a carrier: TiO2 72%-98.6%, active components: V2O5 0.1%-5%, WO3 1%-10%, Cr2O3 0.1%-5% and Nb2O5 0.1%-5%, and a co-catalyst of 0.1%-3%. The present invention can be used for reducing the oxynitrides in a flue gas, meanwhile oxidizing zero-valent mercury into bivalent mercury and then controlling the reactions, has relatively high denitration performance and also has high mercury oxidation performance; compared with current commercial SCR catalysts, the mercury oxidation rate of the catalyst is improved to a great extent, which can adapt to the requirements for mercury removal in China's coal-fired power plants, the conversion rate of SO2/SO3 is relatively low, and the catalyst has a better anti-poisoning ability, and is a new catalyst with a low cost and high performance.

Methods for removing sulfur dioxide from a gas stream are disclosed. A method may include passing a gas stream comprising SO.sub.2 through a gas scrubbing apparatus. A scrubbing liquor comprising hydroxide ions and at least one oxidation catalyst may be flowed into the gas scrubbing apparatus, thereby contacting the gas stream with the scrubbing liquor. In response to the contacting, at least 90 wt. % of the sulfur dioxide may be removed from the gas stream. Concomitant to the contacting, at least some of the sulfur dioxide may react with at least some of the hydroxide ions, thereby forming sulfite ions in the scrubbing liquor. Some of the sulfite ions may be oxidized, via the oxidation catalyst, thereby forming sulfate ions in the scrubbing liquor. A used scrubbing liquor may be discharged from the scrubbing apparatus.

In a broad form the present invention relates to a method for oxidation of a species comprising sulfur in an oxidation state below +4, such as H.sub.2S, CS.sub.2, COS and S.sub.8 vapor, to SO.sub.2 said method comprising the step of contacting the gas and an oxidant with a catalytically active material consisting of one or more elements taken from the group consisting of V, W, Ce, Mo, Fe, Ca, Mg, Si, Ti and Al in elemental, oxide, carbide or sulfide form, optionally with the presence of other elements in a concentration below 1 wt %, at a temperature between 180° C. and 290° C., 330° C., 360° C. or 450° C., with the associated benefit of such a temperature being highly energy effective, and the benefit of said elements having a low tendency to form sulfates under the conditions, with the related benefit of an increased stability of the catalytically active material. The other elements present may be catalytically active noble metals or impurities in the listed materials.

A process for the removal of nitrous oxide from a gas stream having a contaminating concentration of nitrous oxide to provide a gas stream with a significantly reduced concentration of nitrous oxide is described. The process includes the use of a process system having multiple N.sub.2O decomposition reactors each of which contain a nitrous oxide decomposition catalyst and heat transfer units each of which contain a heat sink media that are operatively connected in a particular order and arrangement for use in the process. The gas stream is passed to the process system that is operated for a period of time in a specific operating mode followed by the stopping of such operation and reversal of the process flow. These steps may be repeatedly taken in order to provide for an enhanced energy recovery efficiency for a given nitrous oxide destruction removal efficiency.

A process for preparing a catalyst material, includes: (a) providing a support material having surface hydroxyl (OH) groups, the support material is ceria (CeO.sub.2), zirconia (ZrO.sub.2) or a combination, and the support material contains between 0.3 and 2.0 mmol OH groups/g of the support material; (b) reacting the support material with at least one of: (b1) a compound containing at least one alkoxy or phenoxy group bound though its oxygen atom to a metal element from Group 5 (V, Nb, Ta) or Group 6 (Cr, Mo, W); (b2) a compound containing at least one hydrocarbon group bound though a carbon atom to a metal element from Group 5 or 6; (b3) a compound containing at least one hydrocarbon group bound though a carbon atom to a metal element which is copper (Cu); and (c) calcining the product obtained in step (b).

The exhaust gas-purifying catalyst of the invention includes a noble metal, and crystallites that form CZ composite metal particles which serve as a carrier supporting the noble metal and contain at least zirconium (Zr) and cerium (Ce). The CZ composite oxide particles (crystallites) further contain crystal growth-suppressing fine particles which are fine metal particles comprising primarily a metallic element M that melts at 1,500° C. or above and which suppress crystal growth by the CZ composite oxide particles. The content of the metallic element M included in the CZ composite oxide particles, expressed in terms of the oxide thereof, is 0.5 mol % or less of the total oxide.

An oxygen absorbing agent composition including at least one type of a compound having an indane skeleton represented by the following general formula (1) and a transition metal catalyst: ##STR00001##

An exhaust gas purification catalyst includes: a first catalyst unit that consists of a hydrogen generating catalyst including a noble metal and an oxide that contains lanthanum, zirconium and an additional element such as neodymium; a second catalyst unit that consists of an oxygen storage/release material and a perovskite oxide disposed in contact with the oxygen storage/release material and represented by the general formula La.sub.xM1.sub.1-xM2O.sub.3-δ, where La is lanthanum, M1 is at least one element selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca), M2 is at least one element selected from the group consisting of iron (Fe), cobalt (Co) and manganese (Mn), x satisfies 0<x≦1, and δ satisfies 0≦δ≦1; and a holding material that holds the first catalyst unit and the second catalyst unit in a mutually separated state.