MXPA01005161A - Catalyzed particulate oxidizer for reducing particulate emissions from a diesel engine and method - Google Patents

Abstract

Operation of a diesel engine with low particulate emissions is achieved through the use of a catalyzed particulate oxidizer (14) designed to cause a large number of impacts of particulates with catalyzed surfaces. The catalyzed particulate oxidizer (14) can be precatalyzed or uncatalyzed initially, but catalyzed during use by a catalyst fed prior to or after combustion in the engine. Preferably, the fuel will contain a catalytic additive (29), such as diphenyl cyclooctadiene platinum (II) or platinum acetylacetonate and/or a fuel soluble organo-metallic compound of cerium, iron, copper or manganese. Alternatively, the platinum group metal or other catalytic compound can be added to the exhaust or combustion air. The catalyzed particulate oxidizer has a plurality of parallel plates having catalyzed undulating surfaces provided to create a large number of contact points forthe particulates in the exhaust gas.

Description

CATALYTIC PARTICULATE OXIDIZER AND METHOD FOR. REDUCE PARTICULATE EMISSIONS FROM A DIESEL ENGINE TECHNICAL FIELD The invention relates to methods that allow a diesel engine to operate efficiently with low particle emissions. Emissions in the form of particles, for example, PM 10 and PM 2.5, coming in particular from diesel engines, are considered as health risks by an increasing number of organizations dedicated to regulation and health. There are a number of technologies to control NOx emissions and to control particles from diesel. However, to date, there is no available technology to reduce diesel particle emissions to less than 0.1 g / bhp-Hr and at the same time control NOx emission without creating service and reliability problems or requiring fuel. with an excessively low content of sulfur (less than 50 ppm).

BACKGROUND OF THE INVENTION Diesel engines provide advantages in terms of fuel economy and for this reason are favored. However, there is an inevitable exchange between the economy on the one hand, which favors the complete combustion, and the N0X emissions, produced in large quantities under these conditions. In addition, there is an inevitable exchange between emissions of N0X and particles and hydrocarbons (HC). There is no known technology available to take full advantage of the diesel economy without being punished in terms of particulate and / or NOx emissions. When primary measures (actions affecting the combustion process itself) are taken to reduce NOx emissions in diesel engines, fuel economy is usually reduced and particle emission is increased. On the other hand, the combustion conditions chosen to reduce the pollution coming from the emission of particles and to obtain an adequate fuel economy, tend to increase the emission of NOx. Among the current strategies to reduce NOx emissions, it seems that exhaust gas recirculation (EGR) is a suitable candidate, but with this, the increases in the emission of particles, in addition to the economy of fuel, will be an important technical challenge. The delay in injection timing (ITR), like the EGR, could also be used to reduce the emission of N0X but this results in an increase in fuel consumption and increases the emission of particles . The use of particle traps for diesel engines has become commonplace due to an inevitable inherent exchange between N0X and particulate emissions - when taking measures to reduce one, the other increases. In concept, the use of a trap could allow NOx emissions to be reduced to a high degree by techniques such as exhaust gas recirculation, adjustments in engine timing or other known techniques. However, it could be a problem to capture particles in a trap due to loss of engine efficiency when the pressure drop across the trap becomes very high. In addition, the regeneration of the trap by calcination of the particles could cause physical damage to the trap and could require the use of catalytic coatings, additives for the fuel or complementary burners to help regeneration. In addition, most catalysed systems require fuel with low sulfur content. The pressure drops along the pass catalytic oxidants are much lower, but these devices are less effective at removing particles. In addition, these devices work best when the particles are relatively moistened with hydrocarbons and do not work as effectively with drier particles of the type produced by engines running on exhaust gas recirculation (EGR) used to reduce NOx emission. As usual, these only reduce the soluble organic fraction (SOF) and therefore are limited only to reductions between 10 and 50%. In WO 97/232268 of the PCT, for Van Hardeveld, et al. , a hybrid type of mechanism is described. That device is catalyzed to allow trapped particles to burn, but uses what is known as a turbulent flow precipitator to pull the particles out of the exhaust stream to be captured, collected and burned. This mechanism would have a tendency to increase the pressure drop in a manner very similar to that of the particulate filter. However, as with catalysed traps, calcination can not occur at low temperatures. When the ignition of the particles occurs, this can cause structural damage to the device. The problems can be more serious in cases in which the engine is operated for prolonged periods at low loads. Another problem with all pre-catalysed devices, including traps and oxidizers, is that they show a tendency to lose activity very quickly in the presence of sulfur. This will continue to be a problem for diesel engines in the future because diesel fuel contains significant amounts of sulfur. In the patent E.U.A. No. 5,501,714, Valentine and Peter-Hoblyn describe that the problem can be corrected for the catalytic oxidants of passage, but it does not solve the basic problems with the aforementioned technology. And in WO 97/04045 of the PCT, Peter-Hoblyn, Valentine, Sprague and Epperly describe that platinum alone or with additives based on cerium, copper or iron for the fuel could significantly reduce the equilibrium point of a trap for particles. However, low load conditions may not be high enough to control the back pressure and to avoid excess heat during regeneration. In addition, Jelles, Mak ee, Moulijn, Acres and Peter-Hoblyn reported at the 222th CIMAC Congress in Copenhagen, on Tuesday, May 19, 1998, that the platinum / cerium-based additives for fuel in combination with a filter of Catalyzed ceramics removed high levels of soot at lower temperatures than catalyzed filters or additives alone. Even with the improved performance of this system at low temperatures, the filter still exhibits inherently high back pressure and does not oxidize at temperatures below about 350 ° C. Current technology does not provide an adequate solution to the problem of diesel particles, especially for engines that are operated under conditions necessary to minimize NOx emissions. Oxidants are not effective in removing particles because they; these reduce mainly the SOF; and although the traps are effective in coling the particles, they have problems with inherent regeneration and problems of durability and high recoil pressures.

BRIEF DESCRIPTION OF THE INVENTION It is an object of the invention to provide a method and apparatus, which provide significant reductions in the emission of particles. It is an object of the invention to provide a method and apparatus, which provide significant, and long-term, reductions in particulate emissions and that do so with minimum maintenance. It is another object of the invention to provide a method and apparatus for optimizing the operation of a diesel engine to reduce the emission of particles, for example, to less than 0.1 g / bhp-Hr, while at the same time dealing with the reduction of NOx emissions through the use of changes in the engine such as EGR and ITR. It is another object of the invention to provide a method and apparatus for allowing the simultaneous reduction of particulate and NOx emissions from a diesel engine. It is another object of the invention to provide a method and apparatus that eliminate the low removal efficiency normally associated with the step catalytic oxidants. It is another object of the invention to provide a method and apparatus that eliminates the fuel economy punishment normally associated with a diesel particulate trap. It is even another more specific objective of the invention to provide a method and apparatus, which provide significant and long-term reductions in particle emissions, for example to less than 0.1 g / bhp-Hr, while simultaneously treating with the reduction of NOx emissions through the use of recirculation of exhaust gases and / or ITR. These and other objects are achieved by means of the present invention, which provides an improved method and apparatus for operating a diesel engine with batch emissions of particles. The method of the invention comprises: equipping a diesel engine with a catalyzed particulate oxidizer having an inlet, an outlet, a widened central chamber and a plurality of parallel plates within the chamber, the plates having catalyzed, corrugated surfaces provided to create a large number of contact points for the particles in the exhaust gases; operating the diesel engine under conditions that give rise to exhaust gases that contain particles; and passing the exhaust gases through the catalyzed particle oxidant. The catalyzed particle oxidant is also claimed. Preferably, the fuel contains an organic metal compound of the platinum group, soluble in the fuel, comprising, for example, a metal of the platinum group which is selected from the group consisting of platinum, palladium, rhodium and mixtures of two. or more of these. In an alternative embodiment, an effective metal compound from the platinum group can be added to the exhaust gases before the trap or from the air for combustion. Alternatively, you can use cerium, iron, copper, manganese, or combinations of any of these with platinum to reduce the charge of particles leaving the engine, including both the soluble fractions and the carbon soot fractions of the soot before the oxidant. The resulting activated metal soot will also promote improved oxidation when it comes into contact with the catalyzed surfaces. In another preferred aspect of the invention, the engine is operated with exhaust gas recirculation and / or injection timing delay.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood and its advantages will be more apparent when the following detailed description is read considering the attached drawings in which: Figure 1 is a schematic representation of a diesel engine with an exhaust system including a catalyzed particulate oxidizer in accordance with the invention. The. Figure 2 is a schematic representation of a catalyzed particle oxidant according to the invention. Figure 3 is a separate, schematic representation of a portion of a catalyzed particle oxidizer according to the invention; and Figure 4 is a schematic representation of a diesel engine operated with exhaust gas recirculation and an exhaust system including a catalyzed particulate oxidant according to the invention.

DETAILED DESCRIPTION OF A PREFERRED MODALITY The term "diesel engine" is intended to include all compression-ignition engines, for both mobile (including marine power plants) and stationary power plants, and two-stroke types per cycle, four times per cycle and those of the rotating type . The term "hydrocarbon-type fuel" is intended to include all those liquid and gaseous fuels prepared from "distilled fuels" or "petroleum". The term "distilled fuel" means all those prepared by distillation of petroleum or petroleum fractions and residues. The term "petroleum" has the intention in its normal sense to include all those materials without considering their origin normally included within the meaning of the term, including hydrocarbon-type materials, without taking into account the viscosity, which are recovered from fuels fossils The term "diesel fuel" includes "distilled fuels" including diesel fuels that meet the ASTM definition for diesel or other fuels even when these are not entirely made up of distilled materials and may comprise alcohols, ethers, organo-nitrogenous compounds and the like (for example, methanol, ethanol, diethyl ether, methyl ethyl ether, nitromethane). Also included are emulsions and liquid fuels derived from vegetable and mineral sources such as corn, alfalfa, slate and hard coal. These fuels may also contain other additives known to those skilled in the art, including colorants, cetane-based improvers, antioxidants such as 2,6-di-tert-butyl-4-methylphenol, corrosion inhibitors, rust inhibitors such as the alkylated succinic acids and the anhydrides, bacteriostatic agents, gum inhibitors, metal deactivators, lubricants for the upper part of the cylinder, antifreeze agents and the like. Referring to Figure 1, this shows a diesel engine 10 fueled with fuel coming from a tank 11. Preferably the fuel is catalyzed with a metal compound of the platinum group or with one or more other catalyst compounds, such as cerium , iron or manganese. The latter material can be used alone or in combination with a metal-based catalyst of the platinum group. The exhaust gases from the engine will pass through the exhaust pipe 12, bringing with it the catalytic metals released from the cerium-based catalyst compositions of the fuel additive, and preferably also based on platinum, to an oxidant. of catalyzed particles (CPO) 14. The CPO can be catalyzed either by installing it or by accumulating a catalyst deposit by running the engine with a metal-based fuel additive from the platinum group. In Figure 2 the CPO of the invention is shown in schematic form in longitudinal cross section. The CPO 14 is shown with an inlet 16, an outlet 18 and a widened central chamber 20. Within the chamber 20 is a plurality of substantially parallel plates 22 with catalyzed, undulating surfaces provided to create a large number of contact points for the particles contained in the exhaust gases, which enter at 16 and exit at 18. Preferably the plates will be made from a ceramic or silica-alumina composition such as cordierite, silicon carbide, glass or metal fibers , porous glass or metal substrates, or the like, or an appropriate metal such as alloys of the type used in automotive exhaust systems. Among the appropriate catalysts are those which are known to be useful for catalysing traps and catalytic step oxidants. Among these stand out the platinum group metals such as platinum, palladium and rhodium. The oxidant may or may not be precoated with a thin layer coating to provide a high surface area before catalyzing it. It is an advantage of the invention that thin-film coating is not required. Referring to figure 3, this section shows schematically a section of an increased CPO to illustrate the dynamics of the process. The channels 24 are formed between the individual plates 22. The channels have sufficient width to allow the exhaust gases to pass through them with a minimum pressure drop. The exact configuration of the channels will vary depending on many design and manufacturing variables. The tops 26 and valleys 28 formed in the sheet cause the gases to change direction frequently. The particles, although small, have a mass that causes them to collide with the walls of the channels formed by the plates while the gases easily veer following the undulations in the plates. The particles are not collected, but are at least partially oxidized by frequent collisions against the catalyzed surfaces of the plates 22. In the drawings it is observed that the corrugations have an inverted V-shape, but other appropriate shapes can also be used, including sinusoidal shapes, inverted V with flattened top and the like. In some embodiments it may be desirable to install the plates in sections along the length of the chamber. For example, the plates could be assembled between 2 and 5 sections, each filling the cross section of the chamber, but extending only a portion of its length. In this case, the sections would be separated by a smaller space, preferably of 12.7 cm, for example between 0.635 cm and 7.62 cm. As indicated above, the fuel will preferably also contain an organic metal compound from the group of the soluble platinum in the fuel, for example from platinum, palladium or rhodium. Among these are the metal compounds of the platinum group which are selected from the group consisting of platinum acetylacetonate and compounds having the general formula XPtR? R in which X is a ligand containing at least one carbon-carbon bond not saturated with an olefinic, acetylenic or aromatic p-bond configuration and R-? and R 2 are, independently, benzyl, phenyl, nitrobenzyl or alkyl having 1 to 10 carbon atoms, for example, diphenyl cyclo-octadiene of platinum (II) • The metal compounds of the platinum group are described for example in the previous patents EUA Nos. 4,892,562 and 4,891,050 for Bowers and Sprague, 5,034020 for Epperly and Sprague, 5,215,652 for Epperly, Sprague, Kelso and Bowers and 5,266,083 for Peter-Hoblyn, Epperly, Kelso and Sprague, in WO 90/07561 for Epperly, Sprague, Kelso and Bowers and in the US patent application Serial No. 08 / 597,517, filed January 31, 1996 by Peter-Hoblyn, Valentine and Sprague, incorporated in the present invention for reference. In cases where the application allows it, a mixture of these compounds can be used with one or more of the metal compounds of the platinum group such as soaps, acetylacetonates, alcoholates, β-diketonates and sulfonates, for example of the type which will be described in more detail later.

The metal compound of the platinum group suitable to be used as an additive transported by the fuel or by the gas and / or as another catalyst additive material, can be added in any effective form for its intended purpose, such as for example by adding it to fuel stored in bulk, to fuel in a tank associated with the engine or by continuous or intermittent addition, such as by means of a metering device, for example 27 from tank 29 in Figure 1 to: the fuel line that reaches the engine or to the fuel return line from the engine, or in the form of a vapor, gas or aerosol to the air intake, the exhaust gases before the CPO, the exhaust gases after the CPO but before recirculating it towards the engine, or to a mixing chamber or equivalent means in which the exhaust gases mix with the incoming air. When used, metal catalyst compositions of the platinum group are preferably used at concentrations of less than 1 part by weight of metal of the platinum group in parts per million by volume of fuel (ppm). When used for the purpose of catalyzing a non-catalyzed CPO (or one that has become inactive), it is possible to use it at higher doses, for example from 1 to 25 (or more) ppm, to effect a rapid deposit of catalyst in the CPO. For the purposes of this description, all figures in "parts per million" are on a weight-to-volume basis, that is, grams / million cubic centimeters (which can also be expressed as milligrams / liter), and all percentages they are given by weight, unless otherwise indicated. Auxiliary catalysts (so-called because these are preferably used with a metal composition of the platinum group, but can be used without such) are used at effective levels for the intended purpose, preferably at levels from 1 to 200 ppm. of the fuel used, for example from 5 to 60 ppm. Among the auxiliary catalytic materials are the organometallic salts of manganese, magnesium, calcium, iron, copper, cerium, sodium, lithium and potassium, which can be used at appropriate levels, for example from about 1 to about 100 ppm and preferably from 20 to 60 ppm of the catalyst metal in combination with the metal-based catalyst of the platinum group in diesel fuels. Among these are the alcoholates, sulfonates, beta-diketonates and the soaps, which are selected for example from the group consisting of stearates, palmitates, laurates, seboates, naphthatates, other fatty acid soaps, and mixtures of two or more of these, of copper, calcium, magnesium, manganese, iron, cerium, sodium, lithium, and potassium since they are known as useful fuel additives and soluble in fuel. Among the preferred cerium compounds are: cerium (III) acetylacetonate and various cerium soaps such as cerium (III) naphtananate, cerium octoate, cerium stearate, cerium neodecanoate and the like. Many carbon compounds are trivalent compounds that comply with the formula: Ce (OOCR) 3, in which R = hydrocarbon, preferably from C2 to C2, and including aliphatic and alicyclic hydrocarbons, aryl and alkylaryl. The dosage level will be at a level of about 1 to 100 ppm cerium per parts per million fuel (mg per liter), and preferably in the range of about 5 to 30 ppm, preferably less than 20 ppm. This level can be significantly reduced over what is currently used in the art by using cerium in combination with a platinum catalyzed particle trap. Reference may be made to the aforementioned WO 97/04045 for a detailed list, said document being incorporated for reference in the present invention, of other representative compositions of auxiliary catalysts. With reference to figure 4, there is shown schematically a diesel engine 10, which operates with recirculation of exhaust gases, and an exhaust system including a catalyzed particle oxidant 14 according to the invention. During operation with EGR, the air for combustion coming from the socket 13 (at high or low pressure, cold or hot) and the exhaust gases coming from the pipe 32 (separated from the main stream of; exhaust gases 34) are mixed and fed to one or more of the cylinders of the engine 10 (e.g., diesel fuel or lean combustion gasoline). -The proportion of exhaust gases recirculated to the engine to form a mixture with air for combustion will be effective to reduce NOx production by the engine that uses the combustion air mixture compared to combustion air that does not contain exhaust gases. escape. Typically it can be recirculated from about 0 to about 30%. The combustion air mixture is typically compressed before being introduced into the cylinder or cylinders of the engine, in which it is further compressed, causing heating. The appropriate fuel is injected to the cylinders after compression. The fuel is then burned with the combustion air mixture to produce the exhaust gases which are discharged by means of the exhaust gas stream 34. The cycle just described is repeated continuously as the engine continues working in the EGR mode. The EGR reduces the combustion temperature and oxygen to the combustion chamber and reduces the amount of NOx that is produced, but as it has been observed, it increases the production of particles and unburned hydrocarbons - again the inevitable exchange between the N0X production and complete combustion. Downstream of the exhaust gas stream 34 is a CPO unit 14. The CPO is effective within a temperature window from about 150 to about 600 ° C, depending on the catalyst. During the operation of the engine which gives rise to these temperatures, the temperature of the exhaust gases in the most preferred temperature range for the CPO is maintained. At these temperatures, the conversion of NOx by means of the EGR is practical, and therefore the EGR system is operated. At other times, the ITR can be used alone or in combination with the EGR to reduce NOx emissions. Figure 4 also illustrates a control system of a type useful for maintaining proper operation of the EGR and the CPO units. If desired, the controller 36 can measure any of a number of parameters to ensure optimal reduction of NOx and optimal oxidation of the particles. The temperature of the exhaust gases (detector means 38) is an important parameter. The load of the motor is another key parameter (detector means 40), and this factor or other similar factors can be monitored to determine the amount of NOx that is being generated and the need to reduce the amount of NOx through the EGR. or changes in engine timing (not shown). The detection means provided to detect the operating parameters that indicate effective conditions to reduce the amount of NOx, detect the appropriate parameter of operation and generate an operating signal representative thereof. The controller 36 provides the control means for comparing one or more of the operating signals with the appropriate reference value or values and determining whether the NOx reduction can be effectively operated. The controller then generates the appropriate control signals that are representative of the result of the comparison. Means are provided so that they can respond to the control signals to operate the EGR unit (and / or changes in motor timing), as requested by the controller. Figure 1 shows as a representative of these last mentioned means, valve 42.

The EGR unit and / or motor synchronization settings can be controlled in response to a feed advance controller in response to a number of measured parameters, including: the motor load represented by various mechanical or electronic measurements such as fuel flow, viscosity or pulse width, engine speed, intake air temperature; barometric pressure; humidity of the inlet air; Exhaust gas temperature and / or other effective parameters for particular engines. In addition, up to the point at which the detectors are available, cutoff control or feedback control can be provided based on residual gaseous species after the CPO, for example, the level of NOx, HC or CO. If desired, feedback control can be used to shut off the system in response to specific gaseous species, or any other measurable property of the exhaust gases or engine. The foregoing description is intended to teach those skilled in the art how to practice the present invention, and it is not intended to detail all obvious modifications and variations which will become apparent to those skilled in the art upon reading this description. However, it is intended that all such modifications and variations be included within the scope of the present invention which is defined by the following claims.

Claims (12)

1. NOVELTY OF THE INVENTION CLAIMS
2. Having described the present invention is considered as a novelty and therefore claimed as property contained in the following claims: 1. A method to operate a diesel engine with low emissions of particles, comprising: equip a diesel engine with a catalyzed particle oxidizer having an inlet, an outlet, a widened central chamber and a plurality of parallel plates within the chamber, the plates having undulating, catalysed surfaces provided to create a large number of contact points for the particles in the exhaust gases; operating the diesel engine by burning fuel under conditions that give rise to exhaust gases containing particles; and passing the exhaust gases through the catalyzed particulate oxidant from an inlet to an outlet and transversely to the lines placed parallel to the undulations in the undulating surfaces. 2. - A method according to claim 1, further characterized in that the fuel contains an organic compound of metal of the platinum group, soluble in water.
3. 3. - A method according to claim 1, further characterized in that the fuel contains an organo-metallic compound of cerium, iron, copper or manganese.
4. 4. - A method according to claim 1, further characterized in that the fuel contains an organic compound of metal of the platinum group, soluble in water and contains an organo-metallic compound of cerium, iron, copper or manganese.
5. 5. A method according to claim 2, further characterized in that the organic metal compound of the platinum group, soluble in water, is one that is selected from the group consisting of acetylacetonate of platinum, palladium and rhodium and of compounds that have the general formula XPtR? R2 in which X is a ligand containing at least one unsaturated carbon-carbon bond with an olefinic, acetylenic or aromatic p-bond configuration and Ri and R2 are, independently, benzyl, phenyl , nitrobenzyl or alkyl having 1 to 10 carbon atoms, for example, diphenyl cyclo-octadiene of platinum (II).
6. 6. - A method according to claim 1, further characterized in that a platinum compound is added to the exhaust gases or to the air for combustion.
7. 7. - A method according to claim 1, further characterized in that the catalyzed particle oxidant is pre-catalyzed with platinum.
8. 8. - A method according to claim 1, further characterized in that the catalyzed particulate oxidant is catalyzed by depositing a platinum group metal from an additive mixed with the fuel.
9. 9. - A method according to claim 1, further characterized in that the engine is operated with recirculation of exhaust gases to reduce NOx emissions.
10. 10. A method according to claim 1, further characterized in that the engine is operated with delay in the synchronization of the engine to reduce NOx emissions.
11. 11. A method according to claim 1, further characterized in that the engine is operated with recirculation of the exhaust gases and delayed engine synchronization to reduce NOx emissions.
12. 12. A catalyzed particulate oxidant having an inlet, an outlet, a widened central chamber and a plurality of parallel plates within the chamber, the plates having undulating, catalyzed surfaces provided to create a large number of contact points for the particles in the exhaust gases as the exhaust gases pass from the inlet to the outlet in a direction transverse to the lines parallel to the undulations in the undulating surfaces.