A METHOD OF PURIFYING EXHAUST FUMES AND A MEANS FOR PERFORMING THE METHOD

Abstract: Method for catalytic purification of exhaust fumes and is characterised in that catalytically active substances (promoters) are supplied in gaseous form from a container (4) to the catalyst in an exhaust purifier (3), thus reactivating the catalyst. The catalytically active substances comprise rare earth elements as organometallic compounds, preferably as oxalates or acetyl acetonates. The supply of catalytically active substances is controlled by a probe (6) which analyzes the composition of the gases leaving the exhaust purifier (3). The catalyst is composed of a metal alloy containing rare earth elements.

Description: A method of purifying exhaust fumes and a means for performing the method. The present invention relates to a method for catalytic purification of exhaust fumes, particularly in motor vehicles, and means for performing the method. Catalysts are used for purifying the exhaust fumes from motor vehicles, and are placed on carriers which may be porous bodies or surfaces, usually of ceramic material. The most active catalysts have been found to be precious metals such as platinum, rhodium and so on. Catalysts decline in activity through ageing, due to slow sintering and to' the influence of toxins. The influence of leaded gasoline in decreasing activity is particularly strong. Despite extensive research, the service life of automobile exhaust cata¬ lysts is still relatively limited and their sensitivity to lead is ex¬ tremely high. By using the method described in the present invention these difficulties can be circumvented and a service life can be achieved for exhaust fume catalysts which is equivalent to the service life of the automobile. Furthermore, there is no need for expensive precious metal catalysts which may well become difficult to obtain in the future. The invention is characterised in that a catalytically active substance, preferably having strong promoting and catalytic influence and relatively great volatility (vapour pressure) when heated, is supplied spotwise or continually, in gaseous form or as a mist, to the catalysts beds to be precipitated there, thus reactivating the catalysts and thereby counter¬ acting or compensating the ageing or poisoning of the catalysts. The invention will be described in more detail with reference to the accompanying drawings in which 1 denotes a combustion engine with exhaust pipe 2 and exhaust purifier 3, also serving as muffler. A catalyzer system is built into the exhaust purifier 3. A container is arranged between engine 1 and exhaust purifier 3 in such a way that the container 4 is heated by the exhaust fumes. The container 4 holds catalyzing substances which, when heated, are vaporized and then supplied to the exhaust puri¬ fier 3 via a control valve 5. The container 4 is designed to withstand overpressure. The control valve ~ is governed by a sensitive probe 6 and control unit 7 so that the quantity of catalyzing substance supplied to the exhaust purifier 3 is adjusted to meet the requirement. The control valve 5 is thus governed by the composition of the exhaust fumes. The control unit 7 is also able to control the supply of air and fuel to the engine 1. The exhaust purifier 3 consists of a metal alloy, more specifically of a' carrier with a porous outer layer containing catalyzing metals. Examples of metals in the alloy are iron, nickel, cobalt, molybdenum and chromium. Characteristic of the invention is that the outer later also includes rare earth elements, known as lanthanides, which have a strongly activating influence on the system. The following rare earth elements have been found particularly suitable as catalysts: yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, europium and gadolinium. The rare earth elements are suitably supplied in the form of oxides when the alloy is manufactured. The catalyzing structure, i.e. carrier and porous metal mixture in the exhaust purifier 3 is designed to offer a large surface for exposure to the exhaust fumes flowing through. The exhaust purifier 3 may be composed of parallel metal sheets, of corrugated metal or have honeycomb construc- tion. One method of increasing the efficiency of.the catalyst system is to coat the metal alloy with a layer of aluminium powder which is later converted to a porous layer of aluminium oxide, possibly containing dispersed lan¬ thanides. The catalyzing substances in the container 4 preferably comprise rare earth elements in the form of organometallic compounds. Examples of rare earth elements suitable for this purpose are scandium, yttrium, cerium, terbium and gadolinium. Examples of organometallic compounds are the oxalates and acetyl acetonates of these rare earth elements. When the vehicle is running, the container 4 is heated and the catalysti- cally active substances in the container are dosed through the valve 5 in gaseous form or as a mist, to the exhaust purifier where they effect reactivation of the catalyst system. The container 4 may be replenished with catalytically active substance when necessary. The vehicle may also be equipped with double containers. The container 4 can easily be re¬ placed in the vehicle. According to an alternative embodiment, the catalytically active sub-' stances are transported to the catalyst bed by a carrier gas. The method according to the invention, of supplying promoters and cata¬ lysts to the exhaust purifier via the gas, can also be used when the catalyst in the exhaust purifier 3 is attached on a carrier of more conventional type, e.g. a ceramic carrier with porous outer later of aluminium oxide or silicon oxide. Experiments indicate that this pro¬ vides considerable improvement in efficiency of the catalyst, as well as greatly increased service life. Through the invention an exhaust purifying system for motor vehicles has been developed which is considerably less expensive and has considerably longer service life than systems known hitherto. The exhaust purifier may be designed to serve also as muffler.

Claims: CLAIMS 1. A method for catalytic purification of exhaust fumes c h a ¬ r a c t e r i s e d in that catalytically active substances acting as promoters are supplied via the exhaust fumes to a catalytic exhaust puri¬ fier, thereby reactivating the catalyst in the exhaust purifier. c 2. A method according to claim 1, c h a r a c t e r i s e d in that the catalytically active substances are utilized in the form of oxalates. 3. A method according to claim 2, c h a r a c t e r i s e d in that the catalytically active substances are utilized in the form of' ^ ■ Q acetyl acetonates. 4. A method according to claims 1-3, c h a r a c t e r i s e d in that the catalytically active substances comprise rare earth elements. 5. A method according to claims 1-4, c h a r a c t e r i s e d in that the catalytically active substances are vaporized in container ~- (4) which is heated by the exhaust fumes from an engine (1), that the catalytically active substances are supplied via a valve (5) to the cata¬ lyst in an exhaust purifier (3), thereby acting as promoters. 6. A method according to claim 5, c h a r a c t e r i s e d in that the valve (5) is controlled by a probe (6) which analyzes the gases 20 leaving the exhaust purifier (3) so that the supply of catalytically active substances through the valve (5) is controlled depending on the composition of the gases leaving the exhaust purifier (3). 7. A means for catalytic purification of exhaust fumes, c h a ¬ r a c t e r i s e d in that a container (4), preferably a pressure 25 container, is arranged after an engine (1), in connection with an exhaust pipe (2), so that the container (4) is heated by the combustion gases leaving the engine (1), that the container (4) contains catalytically active substances which, when heated, are supplied via a valve (5) to the exhaust fumes in the exhaust purifier (3) containing catalyst and thus 30 reactivates said catalyst. 8. A means according to claim 7, c h a r a c t e r i s e d in that the catalytically active substances in the container (4) constitute rare earth elements as organometallic compounds. 9. A means according to claim 8, c h a r a c t e r i s e d in that the catalyst in the exhaust purifier (3) consists of a metal alloy such as a metal carrier having a porous outer layer wherein catalytically active metals are included in the alloy, which layer may be a mixture or an alloy in which the catalytic component is included. 10. A means according to claim 9, c h a r a c t e r i s e d in that the catalytically active material includes one or more rare earth elemen . 11. A means according to claims 7-10, c h a r a c t e r i s e d in that the valve (5) is controlled by a probe (6) which analyzes the gases leaving the exhaust purifier (3). 12. A means according to claims 7-11, c h a r a c t e r i s e d in that the exhaust purifier (3) is designed to also serve as muffler.

Inventors: OEBERG LARS OVE, OEBERG, LARS, OVE
Applicants: OEBERG LARS OVE, OEBERG, LARS, OVE
Application year: 1986
Main classification: B01J38
IPC codes: B01D53, B01J38