Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture – Nitrogen or nitrogenous component
Patent
1998-06-02
2000-11-28
Griffin, Steven P.
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
Nitrogen or nitrogenous component
4232132, 502324, 502325, 502329, 502331, 502332, 502342, 502343, 502345, 502346, 502524, B01J 802, B01J 2372, B01J 2360, B01J 2302, B01J 2332
Patent
active
061531618
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the catalytic reduction of NO, NO.sub.2 or mixtures thereof in exhaust gases, in particular combustion exhaust gases and especially combustion exhaust gases from internal combustion engines which are operated with air, preferably in excess, for example diesel and lean-mix engines, with the use of hydrocarbons, carbon monoxide, hydrogen or mixtures thereof as reducing agents.
The non-prior published DE-A-44 20 932 discloses that a specific copper/zinc spinel may be used for reducing NO.sub.x from automobile exhaust gases. These copper/zinc spinels are very difficult to prepare in a reproducible manner and exhibited insufficient resistance to SO.sub.2 which is contained in the exhaust gases of diesel engines.
EP-A-42 471 discloses a process for the catalytic oxidation of carbon monoxide to carbon dioxide, in which the catalyst contains the metals copper, zinc and aluminum as metal oxides. At least 60% of the copper present is bound to the aluminum oxide as copper oxide/aluminum oxide spinel. From 1 to 20% by weight of zinc oxide are arranged in the cavities of the porous spinel. This catalyst is used in ammonia production for low-temperature conversion of CO.
DE-A-43 01 470 discloses a CuAl.sub.2 O.sub.4 spinel which is combined with tin, lead and an element of Main Group II of the Periodic Table of the Elements as an oxide or a salt or in elemental form and then calcined to give a spinel. The known spinel of this type is used for decomposing N.sub.2 O.
The emissions of oxides of nitrogen in the modern industrial states are governed by the emitters comprising traffic and power stations and industrial plants fired by means of fossil fuels. While the power station and industrial emissions are declining through the construction of appropriate waste gas purification plants, the contribution of traffic is becoming more and more prevalent.
In the case of gasoline engines, the oxides of nitrogen can be reduced in a known manner by means of a three-way catalyst in a stoichiometric procedure, the uncombusted or partially oxidized components of the exhaust gas being ideally available in a stoichiometric ratio as a reducing agent for the resulting oxides of nitrogen.
In the diesel engine and in the lean-mix engine operated superstoichiometrically with an excess of air, this method of reducing oxides of nitrogen is in principle not possible owing to the superstoichiometric procedure. On the other hand, emissions of oxides of nitrogen from diesel engines, in particular in the direct injectors which have advantageous consumption and predominate in the commercial vehicle sector, account for a high proportion of the total emissions.
The advantageous consumption of lean-mix engines compared with engines with lambda regulation and three-way catalyst favors the increased use of lean-mix engines.
Noble metal-containing catalysts which, however, produce nitrous oxide (N.sub.2 O) in the reduction of the oxides of nitrogen in the presence of oxygen are also known.
It is an object of the present invention to remedy the abovementioned disadvantages.
We have found that this object is achieved by a novel and improved process for the reduction of NO.sub.x, where x is 1 and 2, in exhaust gases over heterogeneous catalysts with hydrocarbons, carbon monoxide, hydrogen or mixtures thereof in the presence of oxygen at from 100 to 650.degree. C. and an absolute pressure of from 0.5 to 50 bar, wherein the heterogeneous catalysts used are bimodal or polymodal compounds of the general formula I titanium, vanadium, molybdenum, tungsten or mixtures thereof, and where cobalt, nickel, copper, zinc, tin or mixtures thereof, nickel, copper, zinc or mixtures thereof and in the tetrahedral sites and M in the octahedral sites, it also being possible for A to occupy octahedral sites if an equivalent amount of M occupies tetrahedral sites, that they are not spinels which fulfill the following condition:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plot of cumulative pore volume against pore diameter of th
REFERENCES:
patent: 4274981 (1981-06-01), Suzuki et al.
patent: 4963520 (1990-10-01), Yoo et al.
patent: 5587135 (1996-12-01), Fetzer et al.
Fetzer Thomas
Hartweg Martin
Morsbach Bernd
Roitzheim Ralf-Dirc
Seibold Andrea
BASF - Aktiengesellschaft
Griffin Steven P.
Medina Maribel
LandOfFree
Process for reducing NO.sub.x from exhaust fumes does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for reducing NO.sub.x from exhaust fumes, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for reducing NO.sub.x from exhaust fumes will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1721922