# US 8,569,199 B2 · Vanadium-free catalyst for selective catalytic reduction and process for it's preparation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,569,199 B2 - Document ID: US8569199B2 - Status: Granted - Kind: B2 - Application number: 12/444,312 - Filed: 2007-09-17 - Published: 2010-02-11 - Granted: 2013-10-29 - Earliest claimed: 2006-10-23 - Assignees: Umicore AG & Co. KG - Applicants: Katja Adelmann; Nicola Soeger; Lothar Mussmann; Marcus Pfeifer; Gerald Jeske - Inventors: Katja Adelmann; Nicola Soeger; Lothar Mussmann; Marcus Pfeifer; Gerald Jeske - Web page: https://patentgrep.com/patent/US8569199B2 ## CPC - B01J 23/002: {Mixed oxides other than spinels, e.g. perovskite} - B01D 53/9418: {for removing nitrogen oxides by selective catalytic reduction [SCR] using a reducing agent in a lean exhaust gas} - B01J 23/10: of rare earths - B01J 23/24: Chromium, molybdenum or tungsten - B01J 23/30: Tungsten - B01J 23/888: Tungsten - B01J 27/04: Sulfides - B01D 2251/2062: Ammonia - B01D 2255/2063: Lanthanum - B01D 2255/20769: Molybdenum - B01D 2255/20776: Tungsten - B01D 2255/20784: Chromium - B01D 2255/407: Zr-Ce mixed oxides - B01D 2255/9155: Wall flow filters - B01J 37/0201: {Impregnation} - B01J 37/0248: {Coatings comprising impregnated particles} - B01J 2523/00: Constitutive chemical elements of heterogeneous catalysts - B01J 2523/3706: Lanthanum - B01J 2523/3712: Cerium - B01J 2523/48: Zirconium - Y02A 50/20: Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters - Y02T 10/12: Improving ICE efficiencies - B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS - B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28) - Y02A: TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION ## Abstract Selective catalytic reduction with ammonia or a compound that decomposes to ammonia is a known method for the removal of nitrogen oxides from the exhaust gas of primarily lean-burn internal combustion engines. The vanadium-containing SCR catalysts that have long been generally used for this are characterized by a good conversion profile. However, the volatility of vanadium oxide can, at higher exhaust gas temperatures, lead to the emission of toxic vanadium compounds. Zeolite-based SCR catalysts, which are used in particular in discontinuous SCR systems, constitute a very cost-intensive solution for the problem. A method is proposed by which a homogeneous cerium-zirconium mixed oxide is activated for the SCR reaction in a defined manner by the introduction of sulphur and/or transition metal. Using this method, a highly active, ageing-resistant SCR catalyst is provided, which represents a vanadium-free, cost-effective and high-performance alternative to the existing SCR catalysts and is suitable in particular for use in motor vehicles. ## Claims ### Claim 1 A vanadium-free catalyst for selective catalytic reduction of nitrogen oxides with ammonia or a compound that decomposes to ammonia as reducing agent, comprising a catalytically active coating on an inert support, the catalytically active coating comprises a completely or partially homogeneous cerium-zirconium mixed oxide, which contains 10 to 90 wt. % of cerium oxide based on the total weight of the homogeneous cerium-zirconium mixed oxide and which is activated for the SCR reaction by the introduction of a transition metal selected from the group consisting of chromium, molybdenum, tungsten and mixtures thereof, and whereby the vanadium-free catalyst is made by the process of impregnating the homogeneous cerium-zirconium mixed oxide with an amount of an aqueous solution of a compound of chromium, molybdenum, tungsten, or a mixture thereof, the amount of the aqueous solution being selected such that the homogeneous cerium-zirconium mixed oxide is moistened so that its pores are filled, without loss of its free-flowing properties. ### Claim 2 (depends on 1) The vanadium-free catalyst according to claim 1, wherein the homogeneous cerium-zirconium mixed oxide is doped with 1 to 9 wt. % of a rare-earth metal oxide based on the total weight of the homogeneous cerium-zirconium mixed oxide. ### Claim 3 (depends on 2) The vanadium-free catalyst according to claim 2, wherein the rare-earth metal oxide is an oxide of a metal selected from the group consisting of scandium, yttrium, lanthanum, praseodymium, neodymium, samarium, europium, gadolinium and mixtures thereof. ### Claim 4 (depends on 1) The vanadium-free catalyst according to claim 1, wherein the homogeneous cerium-zirconium mixed oxide which is activated contains 2 to 20 wt. % of a transition metal selected from the group consisting of chromium, molybdenum, tungsten and mixtures thereof. ### Claim 5 (depends on 4) The vanadium-free catalyst according to claim 4, wherein the homogeneous cerium-zirconium mixed oxide which is activated additionally contains 0.1 to 10 wt. % of a transition metal selected from the group consisting of manganese, iron, cobalt, nickel, copper, ruthenium, rhodium, palladium, silver, iridium, platinum, gold and mixtures thereof. ### Claim 6 (depends on 4) The vanadium-free catalyst according to claim 4, wherein the homogeneous cerium-zirconium mixed oxide which is activated contains 0.01 to 5 wt. % of sulphur. ### Claim 7 (depends on 1) The vanadium-free catalyst according to claim 1, wherein the support consists of ceramic or metal. ### Claim 8 (depends on 7) The vanadium-free catalyst according to claim 7, wherein a ceramic flow-through honeycomb monolith or a ceramic wall-flow filter substrate is used as the support. ### Claim 9 (depends on 1) The vanadium-free catalyst according to claim 1, wherein after hydrothermal aging, the vanadium-free catalyst exhibits nitrogen oxide conversions of about 80% in the temperature range above 300° C. ### Claim 10 A vanadium-free catalyst for selective catalytic reduction of nitrogen oxides with ammonia or a compound that decomposes to ammonia as a reducing agent, said vanadium-free catalyst comprises a catalytically active coating on an inert support and is hydrothermally aged and exhibits nitrogen oxide conversions of about 80% in the temperature range above 300° C., wherein the catalytically active coating comprises a completely or partially homogeneous cerium-zirconium mixed oxide, which contains 10 to 90 wt. % of cerium oxide based on the total weight of the homogeneous cerium-zirconium mixed oxide and which is activated for the SCR reaction by the introduction of a transition metal selected from the group consisting of chromium, molybdenum, tungsten and mixtures thereof; wherein the vanadium-free catalyst is made by the process of impregnating the homogeneous cerium-zirconium mixed oxide with an amount of an aqueous solution of a compound of chromium, molybdenum, tungsten, or a mixture thereof, the amount of the aqueous solution being selected such that the homogeneous cerium-zirconium mixed oxide is moistened so that its pores are filled, without loss of its free-flowing properties. ### Claim 11 (depends on 1) A process for the selective catalytic reduction of nitrogen oxides with ammonia or a compound that decomposes to ammonia as reducing agent which comprises carrying out the reduction in the presence of the catalyst of claim 1. ### Claim 12 (depends on 1) A process for the removal of nitrogen oxides from exhaust gases of primarily lean-burn internal combustion engines in motor vehicles which comprises passing the exhaust gases in contact with the catalyst of claim 1. ### Claim 13 A method of improving the SCR activity of a catalyst that contains a homogeneous cerium-zirconium mixed oxide which comprises activating the homogeneous cerium-zirconium mixed oxide, which contains 10 to 90 wt. % of cerium oxide based on the total weight of the homogeneous cerium-zirconium mixed oxide by impregnating the homogeneous cerium-zirconium mixed oxide with an amount of aqueous solution of a compound of chromium, molybdenum, tungsten or mixtures thereof, the amount of aqueous solution being selected such that the homogeneous cerium-zirconium mixed oxide is moistened so that its pores are filled, without loss of its free-flowing properties, wherein after hydrothermal aging, the catalyst exhibits nitrogen oxide conversions of about 80% in the temperature range above 300° C. ### Claim 14 (depends on 13) The method according to claim 13, wherein a homogeneous cerium-zirconium mixed oxide, which additionally contains 1 to 9 wt. % of a rare-earth metal oxide based on the total weight of the homogeneous cerium-zirconium mixed oxide is used. ### Claim 15 (depends on 13) The method according to claim 13, wherein a homogeneous cerium-zirconium mixed oxide which additionally contains sulphur is used. ### Claim 16 (depends on 14) The method according to claim 14, wherein a homogeneous cerium-zirconium mixed oxide which additionally contains sulphur is used.