CS212732B2 - Method of transforming carbon oxide and hydrocarbons contained in exhaust gases - Google Patents

Description

ČESKOSLOVENSKA

THE REPUBLIC OF SOCIALIST (19) FILL OUT THE PATEHIU 212732 (Π) (B2) (22) Registered 01 09 72 (21) (PV 621-78) (51) Int. C1.3 B 01 D 53/34 (32) (31) (33) Priority from 18 07 72 OftAD FOR INVENTIONS AND DISCOVERIES (27097 A / 72) Italy (40) Published 31 03 81 (45) Published 15 07 84 (72) (73)

The inventor of BUONOMO FRANCO dr., FAT1ORE VITTORIO dl ', ZANONI GIANFRANCO and, simultaneously, dr., NOTARI BRUNO dr., SAN DONATO MILANESE (Italy) patent holder (54 J Method of converting carbon monoxide and hydrocarbons contained in exhaust gas 1

BACKGROUND OF THE INVENTION The present invention relates to a method for reducing harmful gases contained in vehicle exhaust gases. More particularly, the invention relates to a process for the complete combustion of a composition comprising carbon monoxide and residues containing partially burned carbon as well as totally burnt hydrocarbons during their conversion to carbon dioxide and water, using a catalytic composition.

An ever-increasing number of combustion engine vehicles produce in the form of exhaust gases an ever-increasing content of carbon monoxide in the atmosphere. This results in the risk of air pollution. According to observations conducted in the United States, it is now found that only 500 tonnes of organic products, 8,000 tonnes of carbon monoxide and 700 tonnes of nitrous oxide are released into the air every day in Los Angeles. 70% of said organic substances, 50% of nitrogen oxides and practically 10% of carbon monoxide are produced by exhausts of internal combustion engines.

It is evident that this situation is constantly deteriorating to critical values and that the strong need for improvement of the present condition is the basis for these harmful substances. Among these gases, carbon monoxide is the most dangerous, due to its toxicity. 2

Hydrocarbons in combination with nitrogen oxides are the cause of photochemical smoke that forms during the day in urban areas that have insufficient natural ventilation. The damage caused by this type of mist is evident on certain types of plant in growing cases of human eye and respiratory diseases.

Widespread research has been carried out on the mechanism of smog formation and it has been shown that the primary mechanism is nitrogen dioxide (NOa) photodissociation, in which nitric oxide (NO) and atomic oxygen (O) are formed. The latter react products of incomplete combustion of the hydrocarbons contained in the atmosphere to form peroxyacyl nitrates and ozone (Os), which have a strong effect on vegetation and at the same time a strong inflammatory effect.

In order to reduce the concentration of these substances in the atmosphere and to be able to directly affect the main source of pollution, the main focus was on industrial objects that are directly or indirectly at the forefront of the solution to the problem. Over the last twenty years, four basic directions have been developed: 1. homogeneous afterburning 2. catalytic converters 212732 212732 3. modification of intake and ignition systems 4. engine modification in combination with gasoline composition.

It has already been argued by long experimental practice that while altering the air suction systems, changing the ignition and changing the composition of the fuels, it is possible to achieve a partial reduction in emissions, satisfactory results can only be achieved by the use of afterburning systems, either homogeneously or catalytic. In particular, permissible contamination values can only be achieved with the aid of suitable catalytic converters.

The use of suitable catalytic converters appears to be particularly useful in the treatment of exhaust gas cleaning problems. The devices needed to solve this problem have small dimensions and low cost. These devices can operate at all times as well as at high speeds and when the engine is warm when operating in the car, at low speed and at cold start. In summary, the devices operate reliably under different conditions that may occur during operation of the motor vehicle. In any case, it is to be understood that the catalytic converters are in operation in contact with hot exhaust gases in conditions that are physically variable, for example, cq refers to thermal values and must be effective for a wide-range and qualitative range mixtures. In these mixtures, in addition to carbon monoxide, certain amounts of hydrocarbons and other organic products are present, and for these reasons, the catalysts must be of such a nature as to ensure the oxidation of all these compounds to carbon dioxide in order to effectively reduce the amount of harmful substances discharged into the carbon dioxide. air. Although many solutions have been suggested, none of them could be practically used. The state of the art proposes essentially the use of noble metals such as platinum or a plurality of mixtures of different metals. While the advantage of using platinum is its high efficiency in oxidation reactions and the high sensitivity to the other materials, the considerable disadvantage of using platinum lies in its high cost and the need for regeneration from the spent catalyst. Another disadvantage of using platinum lies in the high amount of platinum used for auto mobiles. which are the main cause of air pollution. Thus, it is difficult to make a decision to use such a metal and all decisions for and against must be carefully considered.

Alternatively, investigations have been carried out in the field of using a mixture of oxides, various wastes that do not require regeneration and are not burdened by the problem of high cost. However, these compounds are less effective and also show less efficacy and sensitivity to the compounds than platinum. It has so far been difficult for these catalysts to determine the form of use that meets the requirements for their economic use. On the other hand, however, the mixtures of oxides are the most promising catalyst compositions for the purposes described. For this reason, many combinations of oxides forming an active ingredient, generally bound to known carriers, have been patented. Catalysts of this type are further subjected to suitable processing.

The literature on the subject is influenced by the large number of combinations obtainable by using different oxides as well as by the extreme complications of obtaining catalysts to simultaneously exhibit high catalytic activity and superior mechanical properties, stability to many factors, as many factors are known. which can adversely affect the catalyst. These factors include, in particular, the proportion of the components, the process for producing the catalyst, the nature of the support, the processing to which the catalyst is subjected during processing and the like. For various reasons, the known compositions do not at the same time meet all the requirements for these catalytic compositions.

The drawbacks of the known processes are solved by the process according to the present invention. The reduction of harmful gases contained in the exhaust gases of the automotive engines is carried out by conducting the reaction compartments which at least in part form oxidation conditions. These reaction media contain a suitable catalytic composition.

Accordingly, the present invention relates to a process for converting carbon monoxide and hydrocarbons contained in the exhaust gas of a carbon dioxide combustion engine and converting the nitrogen oxides contained in exhaust gas to nitrogen and characterized by sieving the exhaust gas. containing carbon monoxide, hydrocarbons, and oxides of nitrogen, act upon the catalytic composition of formula (I)

CuMnxMeyCrzOw, (I) in which

Cu denotes copper,

Mn means manganese,

Me is a group VIII metal selected from nickel and cobalt,

Cr denotes chromium, O denotes oxygen, x, y and z denote the number of atoms of the elements present and w denotes the number of oxygen atoms, the necessary saturation of the valences and if

Me denotes nickel, x denotes zero, y denotes 1.4 and z equals 3, so that the formula I has the form

Cr3CuNii, 4Ow, 212732 5 when y is equal, x is 1 and z is 3, has the general formula I shape

CuMnCr30w, and when Me denotes cobalt, z is zero, y ranges from 1 to 6 and x moves from 1 to 2, so that Formula I has the form

Coi6Mni2CuOw, wherein the catalyst compositions are preferably supported on a gamma-oxide support of spherical shape having a porosity of 0.8 to 1 cm3 / g and a specific surface area of 150 to 350 m2 / g, wherein the conversion of carbon monoxide and hydrocarbons to carbon dioxide is effected in the oxidation zone to which oxygen is introduced and in which the temperature ranges from 300 to 750 ° C and on average 550 ° C, the conversion of nitrogen oxide to nitrogen is carried out in the reduction zone separated from the zone by oxidation, without oxygen and at temperatures of from 50 to 200 ° C lower than the temperature in the oxidation zone and on average at temperatures of 100 degrees Celsius lower, the pressure in the two zones ranges from 0.12 to 0, 14 MPaa in the individual the same or different catalytic compositions of general formula I are used.

The reaction zone may be a car muffler, wherein the reaction compartments comprise the catalyst compositions of the invention of formula I alone or mixed with known catalysts.

The oxidation conditions in the reaction zone are preferably achieved by introducing an oxidizing gas. Such a gas may be oxygen gas, preferably air.

The chemistry for the elimination of nitrogen monoxide in the exhaust gas using catalysts is as follows: NO 4 CO 2 1/2 N 2 + CO 2 NO + H 2 O H 2 O + 1/2 Ns; said products are not toxic. During the reactions described, the catalysts can mediate the formation of ammonia, which originates in the internal reaction between NO and Hz, according to the equation: NO + 5/1 H2 _NHs + H2O. The task of eliminating CO, HC and NOX can be addressed by using catalytic converters in the form of an exhaust gas damper equipped with two catalyst beds. The first serves as a NO reducing agent for NO. The second catalyst bed serves as an oxidizing agent where the final CO 2 HC Oixidation to CO? and H 2 O, as a result of the presence of the supply air below the first bed and the second bed.

This type of task appears to be more promising and acceptable, although on the other hand it is burdened by the disadvantage of the presence of ammonia in the first bed. The produced ammonia is a negative factor in the economics of nitric oxide reduction, since any amount of ammonia that may be produced in the reducing bed will be further oxidized to nitric oxide or nitrate by the catalyst bed serving as oxidizing agent.

It is thus clear that even in the case of the use of catalysts, the task is not easy, since the catalysts themselves must meet certain requirements, the coexistence of which is very difficult. The requirements for the catalysts used can be summarized as follows; (a) relatively low temperature efficiency at very high spatial velocities; b) high temperature and command durability; "cj" resistance to physical stress; dj the ability to selectively convert NOX to N2; resistance to toxic substances present in the exhaust gas.

The process according to the invention, which eliminates the disadvantages of the processes known per se, can be used provided that at least a part of the reaction takes place in oxidation conditions, which means for the reaction to begin under reducing conditions and then to pass to conditions oxidation. In this respect, it is only necessary to ensure that the oxidation gas feed (oxygen, air, or other) is introduced into the reaction space at least during the second treatment, and the reaction region can be logically divided into more than one zone with at least one of said zones, it is intended to initiate an exhaust gas reduction that proceeds in at least one of the following zones where the reaction is due to the oxidation gas oxidation gas supply.

The invention thus provides a complete reduction of the harmful gases contained in the exhaust gases of the car by a new simple method. In this connection, it should be pointed out that the essence of this is the use of a catalyst reactor operating at at least one initial stage in reducing conditions and at least one subsequent phase under oxidizing conditions.

Another alternative is to carry out the process initially completely in an oxidizing atmosphere, followed by reduction of the gases, which is achieved by changing the position of the oxidizer feed. This method is particularly advantageous for the start of the engine, where the oxidizing gas (without preheating) would cause intense cooling of the exhaust gases during their reduction, and it will be appreciated that in continuous operation conditions, this cooling will have no practical effect on the higher The advantages of the present invention will be further illustrated by the following non-limiting examples.

The catalyst was prepared as follows: 100 g of spheroidal gamma-alumina having a particle diameter of 2-3 mm were impregnated with a solution obtained by dissolving 30 g of CrO 2, 40 g of Ni (NO 3) 2. 6H2O and 24 grams of Cu (NO3) 2. 3 H 2 O in water, whereby the total volume of the solution was increased to 80 mL. The resulting material was then dried for 24 hours at 110 ° C. Thereafter, a portion of the material was calcined in air for 4 hours at 500 ° C, the second portion was calcined at 900 ° C for 48 hours. Sample parts were subsequently placed in an electrically heated microreactor at different times; then a synthetic mixture of the following composition was introduced into the reactor: CO 3 vol% CO 2 12 vol% NO 1 500 ppm C 4 H 10 350 ppm N 2 residue to 100% at a space velocity of 22,000 and 285,000 1 / ha at temperatures, from 200 to 500 ° C.

Analysis of the nitric oxide present in the effluent gas was carried out by means of an infrared analytical unit. The results obtained are shown in Table 1.

Temperature ° C

Table 1

Spatial velocity Reduction NO: gas h_1 catalyst

calcined at 500 ° C

, ° / o conversions: catalytic calcination at 900 ° C 200 22 000 '250 22 000 200 39 000 250 39 000 300 39 000 320 39 000 250 285 000 300 285 OOO 350 285000 400 285 000 450 285 000 500 285 000 50,2 - 98.9 - 24.3 - 40.5 50.1 98.9 100.0 100.0 100.0 10.5 11.2 22.2 24.3 41.5 39.2 60.5 65, 3 77.5 75.2 90.5 94.3

The catalyst, calcined at 900 ° C for 48 hours, was subsequently immersed in a microreactor equipped with two catalyst beds: the first bed was reduced and filled with a synthetic gas mixture containing: CO 3% CO 2 12% NO 1 500 ppm H2 1% vol. N'2 supplement up to 100 ° / o vol.

The second catalyst bed is the oxidizing effect of the oxygen introduced in an amount corresponding to its 3% concentration in the "mixture. The space velocity on each catalyst bed was 40,000 h -1".

Analysis of the effluent gas, where the temperature reduction bed was 400 ° C and the 550 ° C temperature oxidation bed, showed that the total conversion of nitric oxide was in the range of 90-95% and thus the production of ammonia in the reduction bed was reduced to negligible values.

Table 2 Two Catalytic Bed Test Results:

Catalyst Conversion of CO ° / o Conversion of NO%% O2 residue

VM 8B

10O 95 to 100 0.3 to 0.5 212732 10 Example 2

A sample of a catalyst known per se comprising copper and nickel was introduced into the same reactor as used in the previous example. The same gas mixture was fed. The results obtained are shown in Table 3:

Table 3 Temperature ° C Spatial velocity / h% reduction NO 300 140 000 23.2 350 140 000 34.9 400 140 000 58.9 450 140 000 80.0 500 140 000 94.3 400 285 000 41.2 450 285 000 56.2 500 285 000 71.5 550 285 000 95.0

This catalyst, placed in two catalyst beds, using the same oxidizing agent as in the previous example, demonstrates high ammonia production, with a final reduction of nitric oxide between 60 and 65%. Example 3

A sample of 1100 cm 3 of the catalyst prepared according to Example 1 was introduced into a longitudinally flowing exhaust silencer placed on a 1330 cc car. The silencer was placed in place of the original silencer. Car test results without a second oxidation damper and therefore no additional air pump are shown in Table 4.

The determination of the amount of NOX was carried out using a thermoelectron chemiluminescent device in such operating conditions as to allow the calculation of any amount of NH 3 produced.

Table 4

Test type Hydrocarbons (ppm) CO (O / o) NO (ppm) AB PT AB PT AB PT O2 728 316 2.3 1.15 1182 307 NT 0.75 809 300 2.5 1.26 1154 289 Average O2 NT 820 '469 4.5 3.5 859 151 0.5% 864 528 4.24 3.64 643 97 O2 average NT 835 234 4.95 2.45 521 76 857 451 4.75 3.53 608 100 PT - under the silencerNT = above the silencer

Table 4 - Continuation

Test type HC Reduction (%) CO NO Temperature test ° C O2 average 57 50 74 610 to 620 0.75% 62 50 75 610 to 620 O2 diameter NT 43 20 83 610 to 630 0.5% 40 18 85 610 ' up to 620 'O2 diameter NT 72 50 86 700' to 730 48 25 84 610 'to 680 Example 4 / In this example, no air was supplied as the second oxidation

The same catalyst volume as in the pre-damper, winter of the example, was placed in the longitudinal flow. The NOX emission values are shown in the following exhaust gas damper, which was shown below: located just below the engine behind the exhaust ducts.

Claims (2)

212732 11 12 Table 5 Test No Emissions NT Emissions PT Temperature Cat. HC g / km CO g / km NOX g / km HC g / km CO g / km NOX g / km ° c 1 2.75 21.06 2.06 0.81 13.19 0.35 680 2 2.37 34.12 1.5 1.56 27.06 0.11 700 3 - 2.12 25.94 0.14 650 4 - - - 1.62 35.75 0.12 650 1) 3.3 41.17 2.19 2.16 37.11 0.25 600 2) 3.75 56.25 1.56 3.44 52.34 0.12 600 1) normal carburetor2 j. Oil carburetor / km = grams. A process for converting carbon monoxide and hydrocarbons contained in exhaust gases of combustion engines into carbon dioxide and converting nitrogen oxides contained in exhaust gases into nitrogen, characterized in that the carbon monoxide-containing exhaust gases are , hydrocarbons and nitrogen oxides are treated with a catalytic composition of the formula I CuMnxMeyCr30w, (I), in which Cu denotes copper, Mn denotes manganese, Me is a group VIII metal selected from nickel and cobalt, Cr denotes chromium, O denotes oxygen, x, y and z denote the number of atoms present in the elements aw the number of oxygen atoms necessary to saturate the valences and if Me denotes nickel, x denotes zero, y corresponds to 1.4 and is equal to 3, so that the formula I is Cr3CuNii, 4Ow, if y is equal to zero, x is 1 and z is 3, the formula (I) is CuMnCr 30w, and when Me is cobalt, z is zero, y is from 1 to 6 and ranges from 1 to 2, so that Formula I has the form Q01_6M1U_2CUOW, wherein the catalytic compositions are preferably supported on a gamma-oxide support of spherical aluminum; a shape having a porosity of 0.8 to 1 cm 3 / g and a specific surface area of 150 to 350 m 2 / g, wherein the conversion of carbon monoxide and hydrocarbons into carbon dioxide is carried out in the oxidation zone to which the carbon is fed and in which the temperature ranges from 300 to 750 ° C and an average of 550 ° C and the conversion of nitrogen oxides to nitrogen is carried out in a reduction zone separated from the oxidation zone without oxygen and at temperatures of 50 to 200 ° C lower than the oxidation temperature the pressure in the two zones is between 0.1.2 and 0.14 MPa and the same or different catalytic compositions of the general formula (I) are used in each zone. Severografla, np, Plant 7, Most