Siemens Aktiengesellschaft

Wolfgang Gajewski

Helmut Schmelz

Dietmar Hein

Josef Sprehe

Norbert Landgraf

Doris Vogel

Helmut Thomann

Lothar Balling

Hans Ranly

Eva-Helga Wilbert

Renate Kuschke

Richard Reppisch

A Catalyst for reducing the nitrogen oxides in flue gases by a reducing agent and a catalytically active composition are described. The catalyst increases resistance to catalyst poisons such as arsenic trioxide. The composition contains 60-90% by weight of titanium, 10-30% by weight of molybdenum, and 0.2-10% by weight of vanadium, as their respective oxides. A very pure titanium dioxide having less than 500 ppm of calcium and less than 100 ppm of iron, being 60% in the anastase modification. It has a mean particle size of 10 to 100 nm, a mean pore radius of 10 to 30 nm and a BET surface of 10 to 80 m.sup.2 per gram. The catalyst is prepared by wet-grinding a suspension of the titanium dioxide with the vanadium pentoxide and molybdenum trioxide in stated proportions. The suspension is then dried and precalcined for several hours at 450.degree. to 550.degree. C. The precalcined material is comminuted to diameters smaller than 180 .mu.m. The pulverized material is then mixed with water and coated onto a metal substrate, dried and then calcined for several hours at 450.degree. to 550.degree. C.

Catalyst for reducing nitrogen oxides

A catalyst for reducing the nitrogen oxides in flue gases by a reducing agent and a catalytically active composition is described. The catalyst increases resistance to catalyst poisons such as arsenic trioxide. The composition contains 60-90% by weight of titanium, 10-30% by weight of molybdenum, and 0-10% by weight of vanadium, as their respective oxides. A very pure titanium dioxide having less than 500 ppm of calcium and less than 100 ppm of iron, and being 60% in the anastase modification. It has a mean particle size of 10 to 100 nm, a mean pore radius of 10 to 30 nm and a BET surface of 10 to 80 m.sup.2 per gram. The catalyst is prepared by wet-grinding a suspension of the titanium dioxide with the vanadium pentoxide and molybdenum trioxide mill in stated proportions. The suspension is then dried, and precalcined for several hours at 450.degree. to 550.degree. C. The precalcined material is comminuted to smaller than 180 .mu.m. The pulverized material is then mixed with water and coated on to metal substrate, dried and then calcined for several hours at 450.degree. to 550.degree. C.

Process for producing a catalyst for reducing nitrogen oxides in flue

Catalytic material for reducing nitrous oxides in flue gases in the presence of ammonia in which titanium oxide is used as the starting material and the latter is milled together with vanadium oxide and one or more oxides of the elements tungsten, molybdenum, phosphorus, chromium, copper, iron, uranium and is thereafter subjected to at least one thermal treatment. Tungsten and molybdenum are substituted here entirely or partially by phosphorus in the form of its oxides or phosphates.

Process utilizing catalytic material for the reduction of nitrous oxides

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Buckenhof, Germany

Wolfgang Gajewski