An exhaust gas purification system includes a previous-stage oxidation catalyst device, an ammonia-based solution feeder, a Diesel Particulate Filter (DPF) device, a turbine of a turbocharger, and a NOx selective reduction catalyst device in the exhaust system of an internal combustion engine in this order from an exhaust port side. The NH.sub.3 production rate is improved, thereby improving the NOx removal rate; the temperature of the DPF device is kept high to increase the time and frequency of continuous regeneration, thus decreasing the frequency of forced regeneration of the DPF device and the amount of discharge of CO.sub.2 produced during the forced regeneration; and also corrosion of the turbine of the turbocharger by SOx is suppressed.

Close-coupled catalysts (CCC) for TWC applications are disclosed. The novel CCCs are implemented using light-weighted ceramic substrates in which a thin coating employing a low loading of Iron (Fe)-activated Rhodium (Rh) material composition, with Iron loadings and an OSM of Ceria-Zirconia, are deposited onto the substrates. Different CCC samples are produced to determine and/or verify improved light-off (LO) and NO.sub.X conversion of the CCCs. Other CCC samples produced are a CCC including a standard (non-activated) Rh thin coating and a heavily loaded CCC with a single coating of Pd/Rh material composition. The CCC samples are aged under dyno-aging using the multi-mode aging cycle and their performance tested using a car engine with ports on the exhaust to measure the emissions, according to the testing protocol in the Environmental Protection Agency Federal Test Procedure 75. During testing, the thin coatings of Fe-activated Rh exhibit improved light-off and NO.sub.x conversion efficiency.

Niobia- and tantala-doped ceria catalysts, their use in selective catalytic reduction (SCR) processes, and a compact after-treatment system for exhaust gases are disclosed. In some aspects, the catalyst comprises at least 91 wt. % of ceria and 0.1 to 9 wt. % of niobia or tantala doped on the ceria. While conventional SCR catalysts can deactivate at higher temperatures, the doped cerias, particularly ones having as little as 1 or 2 wt. % of Nb.sub.2O.sub.5 or Ta.sub.2O.sub.5, are activated toward NOx conversion by calcination. The doped cerias are also valuable for SCRF catalyzed filter applications, including an after-treatment system that comprises a diesel particulate filter having inlets and outlets, and a dual-function catalyst coated on the inlets, outlets, or both. Compared with conventional SCR catalysts, the niobia or tantala-doped cerias enable a higher level of NO.sub.2 to be present.

The present invention is concerned with the use of certain oxygen storage components. In particular, the use of special mixed oxides as oxygen storage components in exhaust catalysis is disclosed.

Organic sulfur compounds contained in refinery off gas streams having either high ort low concentrations of olefins are converted to hydrogen sulfides which can be then be removed using conventional amine treating systems. The process uses a catalytic reactor with or without a hydrotreater depending on the olefin concentration of the off gas stream. The catalytic reactor operates in a hydrogenation mode or an oxidation mode to convert a majority of organic sulfur compounds into hydrogen sulfides.

The present disclosure provides SCR catalyst compositions capable of reducing nitrogen oxide (NO.sub.x) emissions in engine exhaust. The catalyst compositions include a reducible metal oxide support containing ceria, one or more transition metal oxides as a redox promotor; and an oxide of niobium, tungsten, silicon, molybdenum, or a combination thereof as an acidic promotor. The redox promotor and the acid promotor are both supported on the reducible metal oxide support. Further provided are SCR catalyst articles coated with such compositions, processes for preparing such catalyst compositions and articles, an exhaust gas treatment system including such catalyst articles, and methods for reducing NO.sub.x in an exhaust gas stream using such catalyst articles and systems.

A method for gas treatment and purification, comprising: generating ozone from a supply of gas comprising an oxygen (O.sub.2) gas in presence of a defined voltage; oxidizing the ozone (O.sub.3), in an oxidization chamber, in presence of light of a pre-defined wavelength and at least one oxidation catalyst to generate a reactive oxygen species (ROS); feeding, in a first reactive space, the generated ROS and water from a water tank to generate the ROS comprising hydroxyl radicals; and supplying, in a second reactive space, the ROS comprising the hydroxyl radicals and a feed gas that comprises one or more contaminants to produce a first treated gas, wherein the first treated gas is produced from the reaction of the feed gas with the ROS comprising the hydroxyl radicals.