Loading patent…
AssigneeJgc Corporation
InventorsFusao Nishida, Toshihiro Ueno, Tomiaki Yamada, Noriyuki Suzuki, Takehiko Takeda, Tsutomu Yanagihara, Katsuhiko Adachi, Tadashi Asanabe, Katsuaki Ohsato, Kintaro Tsuda, Keiichiro Watanabe
Estimating the term…
The present invention relates to a catalyst comprising at least a metal salt of heteropoly-acid, which is composed of a sort of heteropoly-acid and one or more metals selected from a group of the first transition metals of the periodic table. The catalyst of the present invention exhibits high activity and selectivity in the catalytic reduction of nitrogen oxides with ammonia at a temperature of from 250.degree. to 550.degree. C. and offers high resistivity to the poisonous effect of sulfur oxides. It does not entail a wasteful use of the reducing agent, because the catalyst of the present invention does not accelerate the reaction of the reducing agent such as ammonia with oxygen coexisting in the waste gas to be treated, which results in the elimination of the undesired excessive consumption of the reducing agent. Therefore, this invented catalyst may provide a commercially advantageous process for removing harmful constituents, nitrogen oxides from a waste gas which contains the same and additionally, in some cases, sulfur dioxides.
A process for reducing nitrogen oxides contained in waste gas to nitrogen with ammonia as a reducing agent at a temperature of from 250.degree. C. to 450.degree. C. in the presence of a solid catalyst on a support said catalyst being a heteropoly acid compound of a metal from the group consisting of the first transition metals of the periodic table and mixtures thereof, wherein the heteropoly acid is selected from the group consisting of silicotungstic acid, silicomolybdic acid, phosphotungstic acid and phosphomolybdic acid.
A process for reducing nitrogen oxides contained in the waste gas containing optionally sulfur oxides and oxygen to nitrogen with ammonia as a reducing agent in the presence of the catalyst comprising 1 to 30% by weight of one or more metal salts of heteropoly-acid selected from the group consisting of iron silicotungstate, copper silicotungstate, iron silicomolybdate, copper silicomolybdate, iron phosphotungstate, copper phosphotungstate, iron phosphomolybdate and copper phosphomolybdate as the active component based on the catalyst supported on the heat-resistant porous carrier having not less than 50 m.sup.2 /g of specific surface area and from 0.2 to 1.5 cc/g of pore volume, at temperature of from 250.degree. to 450.degree. C. in the GHSV of 1,000 to 50,000 HR.sup.-1, the molar ratio of NH.sub.3 /NO.sub.x being in the range of from 1.0 to 1.2.
Dependencies are inferred from the claim text.