United States Patent (19) (11) 3,899,444 Stephens (45) Aug. 12, 1975

54 EXHAUST GAS CATALYST SUPPORT 75) Inventor: Ruth E. Stephens, Royal Oak, Mich. Primary Examiner-Carl F. Dees Attorney, Agent, or Firm-Donald L. Johnson; Robert 73) Assignee: Ethyl Corporation, Richmond, Va. A. Linn; Joseph D. Odenweller 22 Filed: Dec. 22, 1972 (21) Appl. No.: 317,831 57 ... ' ABSTRACT A thermally stable and attrition resistant catalyst sup Related U.S. Application Data port consisting essentially of an alumina coating on an 63 Continuation-in-part of Ser. No. 224,240, Feb. 7, inert substrate. The alumina coating has a rare earth 1972. metal substantially uniformly distributed throughout. Catalyst compositions utilizing this sup 52 U.S. Cl...... 252/455 R; 252/462; 252/463; port, processes for preparing both support and cata 252/471; 423/213.5 lyst, and a method of treating internal combustion en (51) Int. Cl..... B01j 11/40; B01j 1 1/06; B01j 1 1/32 gine exhaust gases and preventing crystallization of 58) Field of Search...... 252/462, 463, 455 R, 457; alumina are disclosed. Catalysts consisting essentially 423/213.5 of an alumina matrix containing rare earth metal oxide and a catalytic metal oxide are also disclosed. The 56 References Cited atom ratio of rare earth metal to aluminum in the sup UNITED STATES PATENTS port is 1:5.7-25. The atom ratio of catalytic metal to

3,284,370 1 1/1966 Clifford et al...... 252/462 rare earth metal to aluminum in the catalysts is 3,554,929 1/1971 Aarons...... 252/462 1:0.8-1.4:8-20. 3,741,725 6/1973 Graham ...... 423/213.5 3,781,406 12/1973 Roth et al...... 252/462 X 42 Claims, No Drawings 3,899,444 2 EXHAUST GAS CATALYST SUPPORT an effective catalyst should exhibit the following prop This application is a continuation-in-part of applica erties: tion Ser. No. 224,240, filed Feb. 7, 1972. a. Catalyst should be effective at a relatively low tem perature so that it will function soon after the en BACKGROUND OF THE INVENTION 5 gine has started, i.e., it must have a short warm-up This invention relates to an improved method for period or a low activation temperature. preparing stabilized alumina catalyst supports. More b. It should be highly efficient in oxidizing exhaust particularly, it relates to the use of novel and inexpen hydrocarbons and monoxide. sive materials to prepare a stabilized activated alumina c. It should have a long life, i.e., catalyst support which when used with suitable metal O 1. It should not be easily poisoned. containing catalysts has been found to be especially ef 2. It should withstand at least 800°C. likely to de fective in the oxidation of automotive exhaust gases. velop during operation. Even more specifically, this invention relates to the use 3. It should not be abraded by the frequent shaking of alumina to which is added a rare earth metal com and occasional shocks characteristic of a pulsat pound thereby forming an activated, stabilized catalyst 15 ing exhaust gas stream. support when calcined at elevated temperatures. Rare Extensive research in this field has revealed that earth metals are also known as Series met many catalysts will effectively oxidize the carbon mon als and include metals having an atomic number from oxide and hydrocarbons contained in the exhaust gas 57 through 71, but more generally from 57 through 63. from internal combustion engines. However, these cat It has been well known that alumina is an excellent 20 alysts have uniformly failed to be economically feasible support for catalysts in a wide range of chamical reac in automotive catalytic converters due to their short tions. In fact, in many cases alumina has been shown to life. have catalytic activity of its own and will therefore A primary reason for short catalyst life is the trans often enchance the activity of the catalyst it is support formation of the alumina support from an amorphous ing. It is further known that the activity of an alumina 25 or lower crystalline state (e.g., gamma, eta) to a highly supported catalyst will be dependent on the surface crystalline state by either thermal or chemical means. area. It is advantageous to retain a maximum surface In the more crystalline state, the catalyst is subject to area when the alumina is calcined. At very high tem fracture along the crystal's grain boundary, resulting in peratures phase changes occur which convert the desir powdering, dusting, and eventually loss of catalyst. The able eta or gamma phases into the less desirable theta 30 formation of more crystalline material can be caused or alpha phases, resulting in a great drop in the surface by phase transformation of the amorphous or transi aca. tional alumina to crystalline a-alumina through action According to U.S. Pat. No. 3,291,564, it is known to of heat over a period of time. Further, the interaction use , cesium, or compounds to stabi of alumina with catalyst metals forming metal alumi lize the alumina support and prevent loss of surface 35 nates also results in crystalline structures. In fact, many area and phase changes at high temperature. of the more active oxidation catalysts, particularly cop According to British Pat. No. 1,231,276, potassium, per, not only interact with alumina to form aluminates , and particularly barium, stabilize alumina, but but also promote formation of highly crystalline alu only when the active catalyst is impregnated in an inter mina phases. After formation of such crystalline struc mediate zone between the surface and the carrier core. 40 tures, thermal and mechanical shock loss of catalyst by Catalysts consisting essentially of an alumina support attrition and hence shortened life. containing rare earth metal are disclosed in U.S. Thus, it is an object of this invention to provide a cat Pat. Nos. 3,483,138 and 3,545,917. These catalysts dif alyst support which is thermally stable and attrition re fer from the presently claimed catalyst supports in that sistant. A further object is to provide a thermally stable the present supports have the alumina-rare earth metal and attrition resistant catalyst composition suitable for oxide composition as a coating on an inert substrate or use in the exhaust gas of an internal combustion engine. core. Also, the present support compositions have a de A still further object of this invention is to provide a fined atom ratio of rare earth metal to aluminum in the process for producing a thermally stable and attrition coating. resistant catalyst support and catalyst. Another object Laminar catalysts having an alumina core with a first of this invention is to provide a method of lowering the layer of Lanthanide Series metal oxide and an outer noxious constituents of engine exhaust gas such as car layer of oxide are disclosed in U.S. Pat. No. bon monoxide, hydrocarbons and oxides con 3,226,340. These catalysts differ from the presently tained in internal combustion engine exhaust gases claimed catalysts in that the rare earth metal oxide and using the thermally stable and attrition resistant sup copper oxide are disclosed to be in discrete lamina and, 55 port and catalyst composition provided. Another ob hence, do not have an alumina matrix containing a cat ject is to provide a method of preventing crystallization alytic metal and a rare earth metal. of alumina at high temperature. Other patents relating to rare earth metal catalysts are U.S. Pat. Nos. 3,453,333; 2,152,908; 2,148, 129; SUMMARY OF THE INVENTION 2,129,733; 3,395,004; 3,284,370; 3,153,635; and 60 The above and other objects are accomplished by 2,945,057. providing a catalyst support composition consisting es The extremely severe conditions which prevail in the sentially of an inert substrate or core coated with an catalytic oxidation of and hydrocar alumina containing from about 1 to about 45 weight bons contained in the exhaust gases from internal com is percent based on said alumina of a rare earth metal bustion engines set unusually severe criteria for such oxide uniformly distributed throughout said alumina catalysts, and this makes the selection of an effective coating. In the preferred embodiments to be described catalyst extremely difficult. It is generally agreed that later the atom ratio of rare earth metal to aluminum in 3,899,444 3 4 said alumina coating is 1 to about 5.7-25. Preferred composition consisting essentially of an inert substrate rare earth metal oxides are oxide, neodym coated with an alumina selected from amorphous and ium oxide, and oxide and mixtures transitional alumina, said alumina coating containing thereof. from about 1 to about 45 weight per cent based on said In a further aspect of this invention there is provided alumina coating of a rare earth metal oxide uniformly a method of retarding change in the crystalline phase distributed throughout said alumina coating. More in alumina on heating to elevated temperatures, for ex preferably, the rare earth metal oxide is present in an ample, about 900°C., said method comprising incorpo amount to provide an atom ratio of rare earth metal to rating uniformly throughout said alumina a rare earth aluminum of 1 to 5.7-25 in said coating. A more pre metal oxide in an amount of from about 1 to about 45 10 ferred range is 1 to 8-20. weight per cent based on said alumina and, more pref The alumina coating can be either amorphous or erably, an amount that provides an atom ratio of rare transitional alumina which are well known and com earth metal to aluminum of 1 to about 5.7-25. mercially produced in various forms. Alumina is made In a still further aspect, this invention provides a cata in amorphous, transitional, and refractory forms. The lyst suitable for use in the exhaust gas of an internal 15 transitional aluminas are meta stable forms which are combustion engine, said catalyst consisting essentially produced by heating alpha- or beta-alumina tri of an alumina matrix containing a catalytic metal and hydrates or alpha-alumina monohydrate forming the a rare earth metal oxide. The atom ratio of catalytic various transitional aluminas such as gamma, delta, eta, metal to rare earth metal to aluminum in said matrix is theta, kappa, chi, and rho, depending both on the tem to 0.8-1.4 to 8-20. The alumina matrix may comprise 20 perature and time of heating. Usually a mixture of these the entire catalyst or may be applied as a coating on an transitional aluminas is formed. On prolonged heating, inert substrate or carrier such as another alumina. Pre particularly at very high temperatures such as 1,150°C., ferred catalytic metals are copper oxide, platinum, pal the transitional aluminas are converted to “alpha ladium, oxide, oxide, alumina which is a stable refractory type alumina not oxide, oxide, oxide, oxide, and vari 25 applicable for use in the alumina coating but which can ous combinations of these with each other and addi be used as the inert substrate. In addition to the refac tional materials. tory and transitional forms described above, there is a A still further aspect of the invention is a process for truly amorphous alumina which is characterized by preparing a thermally stable and attrition resistant cata having no definite X-ray diffraction pattern. This amor lyst support, said process comprising 30 phous material is usually present along with the transi a. forming an aqueous solution of a water-soluble, de tional aluminas. The highly crystalline alpha-aluminum composable salt of a rare earth metal and a water formed on heating to high temperatures is not suitable soluble aluminum salt, because it has lower surface area and degrades into a b. evaporating the free water from said solution; 35 powder of microscopic crystallites. It has been found c. heating the resultant mixture of aluminum salt and that crystalline phase changes in amorphous alumina rare earth metal salt whereby a uniform mixture of (e.g., to alpha-alumina) and of the transitional alumi the salts if first formed and subsequently decom nas to more highly crystalline phases can be retarded posed to their oxides; and d. cooling said mixture whereby a solid thermally sta by stabilization according to this invention. In other ble and attrition resistant support material is pro 40 words, the present invention tends to stabilize an alu duced. mina support in its original phase whether it be amor For example, an active supported copper-containing phous or transitional. It is believed that crystalline catalyst can be prepared by a process comprising phase changes which occur during prolonged exposure a. forming an aqueous salt solution of water-soluble, to elevated temperatures such as occur in treating ex decomposable aluminum, lanthanum, and copper 45 haust gas are what causes most catalyst support mate salts; rial to crumble and be lost from the catalyst bed or to b. evaporating the free water from said solution compact causing excessive back pressure. This degra whereby a solid uniform mixture of said salts is pro dation is promoted by the catalytic metal oxides con duced; tained in the alumina. c. heating said mixture at a temperature of from 50 The amorphous or transitional alumina coating is about 400 to about 750°C. to decompose said salts prepared by any convenient method known in the prior to their oxides; and art, such as by decomposing a salt of aluminum; for ex d. cooling the oxide mixture whereby a copper oxide ample, the nitrate, sulfate, oxalate, acetate, and the catalyst composition in an alumina matrix having like. Commercially, large scale preparation of alumina the uniformly dispersed through 55 is carried out as a by-product of the Fickes-Sherwin out said matrix is produced. modification of the Bayer process for the manufacture The catalyst of this invention is useful as an automo of metallic aluminum. This process includes precipitat tive exhaust gas catalyst. Hence, the invention provides ing aluminum hydroxide from an alkali aluminate solu a method of lowering the noxious constituents in inter tion. The alumina gel is mixed with or co-precipitated nal combustion engine exhaust gases by contacting 60 with a rare earth metal oxide or compound thermally them at elevated temperatures with the catalysts of this decomposable to an oxide to give the required atom invention. ratio and the mixture applied to an inert substrate by known methods. The coated substrate is then calcined DESCRIPTION OF THE PREFERRED at 300-800°C. In addition, the support of this inven EMBODIMENTS 65 tion can be produced by a process involving co One preferred embodiment of this invention is a ther precipitation of the alumina and stabilizing rare earth mally stable and attrition resistant catalyst support metal oxide, as will be discussed more fully hereinafter. 3,899,444 S 6 The advantageous thermal stabilization and attrition face of an inert substrate, the atom ratio of said resistant properties are imparted to the above amor rare earth metal to aluminum in said coating being phous and transitional alumina coating when a rare 1 rare earth metal atom to each 5.7-25 aluminum earth metal compound is uniformly distributed atoms, and throughout said alumina coating as opposed to the b. drying said coating. mere surface treatment of alumina by impregnation When the support is prepared in the above manner, with an aqueous solution of a Lanthanide Series metal the stabilized support exists as a lamina or coating of compound. The rare earth metal is present in the alu alumina on an inert substrate. The alumina coating mina coating support as an oxide. Rare earth metals are contains a rare earth metal oxide, the atom ratio of rare lanthanum, , praseodymium, , pro O earth metal to aluminum in the alumina coating being methium, , , , , 1 to 5.7-25. Typical examples of inert substrates on , , , , and . which the lanthana-alumina can be deposited include Mixtures of all or part of these, available commercially all refractory materials such as zirconia, alumina as their salts, may also be conveniently employed. The zirconia, calcium aluminate, alumina-titania, alumina, most common and most practical, hence the preferred, 5 magnesia, alumina-magnesia, silica, silica-alumina, sili rare earth metals are lanthanum, praseodymium, and ca-magnesia, carbide, oxide, mullite, syn neodymium. The rare earth metals will be present in thetic and natural zeolites, silica-zirconia, kaolin, silica the alumina coating of the finally prepared support titania, magnesia-zirconia, magnesia-titania, Zirconia alone or a catalyst composition made from it in the titania, alumina-silica-magnesia, alumina-silica form of an oxide. Accordingly, the preferred stabilizing zirconia, alumina-silica-titania, alumina-magnesia agent is preferably lanthanum oxide, praseodymium zirconia, alumina-magnesia-titania, alumina-Zirconia oxide, or neodymium oxide. However, the usual start titania, silica-magnesia-zirconia, silica-magnesia ing material is a salt of a rare earth metal, usually a titania, silica-zirconia-titania, magnesia-zirconia water-soluble salt, decomposable to an oxide, of which titania, or mixtures of these support materials. the nitrate, sulfate, and acetate are preferred. 25 Of the foregoing refractories, the more preferred are The rare earth metal oxide can be present in an alumina, monolithic aluminum silicate (e.g., mullite) amount of from about 1 to about 45 percent by weight and monolithic aluminum silicates. Also, based on the weight of the alumina coating. Preferably, such inert carriers as wire mesh, expanded metal, from about 15 to about 35 percent by weight is used to beads, marble chips, nails, metal turnings, metal stabilize the amorphous alumina. screen, and the like, are very well suited since they ex It has been found that a critical relationship exists be tend the use of the support. tween the rare earth metal:aluminum atom ratio and Commercially available aluminas upon which the the degree of thermal stabilization imparted to the alu rare earth containing alumina coating may be depos mina coating of the support. Thus, it is preferred to ex ited include those sold by Aluminum Company of press the amount of rare earth metal in terms of the 35 America “Desiccant Grade Active Aluminas; Grades atom ratio of rare earth metal to aluminum in the alu F-1, F-3, and F-10," by the Kaiser Aluminum Company mina coating. This atom ratio is 0.8-1.4 atoms of rare as “KA-101,' and by Sumitomo Chemical Company as earth metal for each 8-20 atoms of aluminum. A most activated alumina “KHA, KHB, KHD, and experimen preferred ratio is about 1:10. It has been found that tal TY-1 and TY-3.’ Analysis and physical properties when the alumina contains rare earth metal and alumi 40 of typical aluminas used as inert substrates for the sta num in this ratio it is extremely resistant to crystal bilized alumina coating and catalysts of this invention phase change, even when heated to 950°C. for ex ae tended time periods. It has also been found that the support having the critical atom ratio retains this resis tance to crystal phase change at high temperature even 45 CHEMICAL ANALYSIS when it contains a catalytic metal as long as the amount Percent of catalytic metal on an atom basis does not substan AlO 85.0-98.7 NaO 0.2-2.0 tially exceed the amount of rare earth metal atoms. FeO 0.02-0.3 Suitable support compositions can be prepared in a SiO 0.02-5.0 50 Loss on Ignition, l iOOC. 0-7.0 variety of ways. For the purpose of illustration, lantha PHYSICAL PROPERTIES num will be used as the rare earth metal, although it is Surface area, mig 75-360 clear that both praseodymium and neodymium as well Form granular or balls as the other rare earth metals can be used in the same Bulk , lb/ft 43-57 Specific gravity 3-33 manner. A suitable alumina coating may be prepared Pore volume ml/g 0.25-0.6 by codeposition of decomposable salts of aluminum 55 and lanthanum. This is applied to the surface of an inert substrate such as an alumina, followed by evaporation The following examples illustrate the preparation of and heating to decompose the salts to their oxides, the stabilized support materials of this invention. forming a substantially amorphous alumina coating having lanthanum oxide uniformly distributed through EXAMPLE 1 out the alumina coating. To a mixing vessel is added 47 grams of lanthanum According to another method the catalyst support acetate and 400 grams of aluminum nitrate. The mix may be made by ture is melted by heating. The molten salts are applied a. applying a coating of a mixture of an alumina or a to an alumina containing 5 per cent SiO, by placing the compound thermally decomposable to alumina and 65 alumina in the molten mixture and stirring until the alu a rare earth metal oxide or material thermally de mina is coated. The coated alumina is then heated to composable to a rare earth metal oxide to the sur 600°C. to convert the aluminum and lanthanum salts in 3,899,444 7 8 the coating to their oxides. The uniform coating con the prevention of high temperature crystallization in tains approximately 30 weight percent of lanthanum both the support and the catalyst itself. Although the oxide uniformly distributed throughout the alumina. table gives the data for copper, any metal-containing Similar results can be obtained by substituting the oxidation catalyst which tends to promote crystalliza lanthanum acetate with praseodymium acetate or neo 5 tion or the formation of metal aluminates can be stabi dymium acetate. lized by the method of this invention.

TABLE Prevention of High Temperature Crystallization of Alumina Supports and Copper-Alumina Catalysts by Inclusion of Lanthanide Series Metals Uniformly CompositionDistributed in the Support or Catalyst X-Ray Diffraction Analysis Weight Per Cent Atom Ratio Lanthanide Example lanthanide Series Metal No. Cu/Al Series Metal/Al CuO Oxide Prepared at 600°C Heated to 900C 4 () O () () Amorphous Some crystalline Al-O 5 0.035 O 5 O Amorphous Strongly crystalline AlO 6 0.035 PrO-0.1 4 PrO-23 Amorphous Amorphous 7 0.035 LaO-0. l 4 LaO-23 Amorphous Amorphous 8 0.035 NdO-0.1 4. NdO-24 Amorphous Amorphous 9 () La O-0. 13 O LaO-30 Amorphous Amorphous O 0.09 LaO-0. 13 9 LaO-26.6 Amorphous Amorphous 1 0.17 LaO-0. 13 15.8 LaC)-24.6 Amorphous Some crystallinity 2 O.35 LaC)0.13 27.8 LaO-21.0 Amorphous Some crystallinity 3 0.7() LaC-0. 13 43.0 LaOil 6.5 Amorphous Crystalline Al-O and CuAlO,

30 EXAMPLE 2 From the above, it can be seen that the rare earth metals act to prevent the formation of crystalline mate To a mixing vessel is added an aqueous solution con rials except at extremely high concentrations of metal taining 60 grams of lanthanum acetate and 400 grams oxide catalysts in solid solution. For example, in Exam of aluminum nitrate. The water is evaporated to pro ples 4 and 5, which don't contain any rare earth metal, duce a uniform solid mixture of lanthanum acetate and 35 both the support of Example 4 and the catalyst of Ex aluminum nitrate. The mixture was fused by melting ample 5 suffered crystal formation on heating to 900°C. and applied as a coating to the following inert sub In Examples 6-8, in which the atom ratio of rare earth strates: wire mesh, monolithic mullite honeycomb, metal to aluminum was 1:10, no crystal phase was ob marble chips, silica granules, aluminum magnesium sili served on heating to 900°C. Similar results were ob cate monolithic honeycomb. Each is heated to 600°C. 0 served at an atom ratio of 1:7.7. In Examples 1 1 to 13, to decompose to the oxide. The final catalyst support with copper ranging from 15.8 to 43 percent, the (i.e., the coating) contains 34.3 weight percent lan amount of lanthana in the catalyst was insufficient to thana. prevent formation of crystalline material and copper A suitable catalyst can be prepared from the supports aluminates. prepared in Examples 1 and 2 by impregnating the sup The foregoing has dealt mainly with the novel cata port with various amounts of copper nitrate in aqueous lyst support of this invention. A further embodiment of solution. The following example illustrates this proce the invention is a catalyst consisting essentially of an dure. alumina matrix containing a catalytic metal and a rare EXAMPLE 3 50 earth metal oxide substantially uniformly distributed in the matrix. The critical atom ratio of the catalytic metal To the catalyst support material prepared in Example to rare earth metal to aluminum is 0.1-1 to 0.8-1.4 to l is added an aqueous solution of copper nitrate. After 8-20. soaking for approximately 2 hours the remainder of the solution is drained and the impregnated support is 55 More preferably, the atom ratio of catalytic metal to dried. On heating the catalyst to about 600°C., the cop rare earth metal to aluminum is about 1:1:8-20, and per nitrate is decomposed to copper oxide. The final most preferably 1:1:10. catalyst can contain from 0.005 to about 15 weight per One aspect of this catalyst embodies a catalyst in cent copper oxide. which the catalytic metal, usually in an oxide form, and The effect of the rare earth metal oxide in preventing rare earth metal are substantially uniformly distributed phase transformation of alumina under high tempera in an alumina matrix. Such a catalyst having the speci tures is illustrated by comparing X-ray diffraction pat fied atom ratio is exceptionally resistant to thermal terns of the catalyst support after preparation and after degradation. This type catalyst can be made by a heating severely to 900°C. for 2 hours. Similarly, the method comprising: effect of the lanthana in preventing the formation of a mixing a catalytic metal compound, a rare earth crystalline-copper aluminates in copper-alumina cata metal compound and an alumina or aluminum lysts is shown by comparison of X-ray diffraction pat compound thermally decomposable to an alumina terns before and after heating to 900°C. Table 1 shows in proportion such that the atom ratio of catalytic 3,899,444 O metal to rare earth metal to aluminum is 0.1-1:0- .8-l.4:8-20; EXAMPLE 1.4 b. shaping the resultant mixture into catalyst forms; In a mixing vessel place 79 parts of cupric oxide, 163 c. drying the resultant catalyst; and parts of lanthanum oxide and 510 parts (dry basis) of d. heating the dried catalyst to an activation tempera hydrated alumina. Mix thoroughly and add sufficient ture. nitric acid to form a paste. Extrude the paste through A wide variety of catalytic metal compounds can be a 1/16 inch die and cut into 4 inch lengths. Dry at employed. The preferred catalytic metal compounds lOOC. for an hour and then heat to 600°C. over a 4 are compounds of metals in Groups IB, VB, VIB, VIIB hour period. Hold at 600°C. for an hour and then cool. and VIII such as vanadium, , , chro 10 Immerse in an aqueous solution containing 1.1 part of mium, , , manganese, , chloride until the total liquid is taken up. Dry iron, , , cobalt, , , again at 100°C. and heat to 600°C. over a 2-hour period nickel, palladium, platinum, copper, and gold. and then cool. Also, metals such as barium and can be in The above example can be repeated using 71 parts of cluded. Preferred metal compounds are those of the 15 manganese oxide in place of the copper oxide to form First Transitional Series and the noble metals such as a palladium-promoted manganese catalyst in a lan platinum and palladium. Frequently, combinations of thana stabilized alumina matrix. several metal compounds are used to supply the cata The following example illustrates another method of lytic metal in the catalyst such as combinations of making the catalyst. CuPod, CuV, CuCr, CuCrV, MnOu, CuNi, CuNiPd, 20 MnPd, CuPt, CuCrPd, CuVPd, FeCo, CuFe, CuCo, EXAMPLE 1.5 CuCoPt, and the like. The catalytic metal compounds An aluminum hydroxide gel is prepared by placing are generally oxides or compounds which are thermally 0.04 gram moles of praseodymium acetate in 1,500 ml decomposable to oxides such as hydroxides, carbon of cold 0.75 gram molar aqueous aluminum sulfate. ates, nitrates, acetates, sulfates, and the like. Examples 25 The resultant solution is added simultaneously with an are copper nitrate, copper sulfate, manganese nitrate, equivalent solution of ammonium hydroxide containing manganese acetate, iron hydroxide, manganese hy 5 grams of copper acetate to 500 ml of stirred water droxide, and the like. In the case of the noble metals maintained slightly alkaline. The precipitated alumi which are generally used in quite small amounts the ha num hydroxide gel contains praseodymium and copper. lides are acceptable, such as palladium chloride. 30 The gel is washed, pelleted or extruded, air dried, and The useful aluminum compounds include alumina finally calcined at 600°C. to give a catalyst containing and compounds that are thermally decomposable to both copper and praseodymium uniformly distributed alumina such as crystalline alumina hydrate, aluminum throughout an alumina matrix. hydroxide, alumina gel, aluminum nitrate, aluminum Using the above procedure, similar results can be ob methylate, aluminum acetate, and the like. When alu 35 tained when the copper is substituted with decompos mina is used in the mixing operation it is beneficial to able compounds of vanadium, chromium, manganese, add sufficient nitric acid to the mixing operation to di iron or with platinum or palladium or combinations of gest a portion of the alumina to form a paste into which the foregoing. The above has described but a few meth the other ingredients are mixed. ods of making the catalyst of this invention. Other The rare earth metal compounds used in the prepara 40 methods are well known in the catalyst industry. Sev tion of the catalysts include those previously listed eral methods are described in U.S. Pat. No. 3,428,573, which are the oxides or compounds thermally decom incorporated herein by reference. These methods can posable to form oxides such as nitrates and acetates. be used by merely including the rare earth metal com The amount of each ingredient added to the mixture pound in the peptized mixture in the proper ratio. should be that which achieves the critical atom ratio of 45 Thus, it can readily be understood that according to catalytic metal:rare earth metal:aluminum of 0.1-1:0- the concentration and type of rare earth metal salt and .8-1.4:8-20. metal-containing oxidation catalyst, a wide variety of The mixture of catalytic metal compound, rare earth catalysts are contemplated for stabilization by this in metal compound and aluminum compound can be vention. Typical are catalysts having the following formed into a catalyst shape by any of the methods well SO compositions, all percentages are by weight: known in the catalyst industry. If it is in the form of a 15% copper oxide, 40% lanthana, 45% alumina paste such as obtained by peptization with nitric acid 0.005% copper oxide, 1% lanthana, 98.995% alu the mixture is most readily extruded into extrudates mina one-sixteenth to one-fourth inches in diameter and cut 4% copper oxide, 1% palladium, 15% lanthana, 80% into pieces one-eighth to one-half inches long. Dryer 55 alumina mixtures are readily compressed into pills or pellets. 10% copper oxide, 5% chromium oxide, 20% praseo Following this, the catalyst is dried to remove excess dymia, 65% alumina water by heating in an oven at about 100-150°C. and 15% manganese oxide, 35% neodymia, 50% alumina then activated by calcining at about 500-700°C. 10% iron oxide, 15% neodymia, 75% alumina Small amounts of noble metal promoters, for exam 60 5% copper oxide, 2% vanadia, 0.1% palladium, 20% ple, from 0.001-0. 1 weight percent, can be impreg praseodymia, 72.9% alumina nated on the surface of the final catalyst to improve low 14.4% copper oxide, 44.2% lanthana and 41.4% alu temperature activity by use of an aqueous solution of mina on a KHA-24 alumina support a water-soluble salt of the noble metal such as palla 65 1% manganese oxide, 1% praseodymia and 98% lan dium chloride. thana on a KHA-46 alumina support The following example illustrates this method of 15% copper oxide, 34% lanthana and 51% alumina making the catalyst. on a KA-101 alumina support 3,899,444 12 Typical of catalysts which can be stabilized by the substrate is removed and dried, following which it is lanthanide series metal are those found in U.S. Pat. calcined. Several immersions and drying operations Nos. 3,170,758; 3,220,794; 3,224,981; 3,226,340; may be employed to build up a heavier coating on the 3,227,659; 3,271,324; 3,380,810; 3,425,792; substrate. The solution used in this method contains the 3,428,573; 3,447,893; and 3,449,063, which are coating substituents in the required atom ratio. In other hereby incorporated by reference as if fully set forth. words, the amount of catalytic metal, rare earth metal Another method of making the catalyst comprises: and aluminum in the solution or sol is such that the a. forming an aqueous solution of catalytic metal atom ratio is 0.1-1 to 0.8-1.4 to 8-20. compound, rare earth metal compound and alumi The catalytic metal compound, rare earth metal com num compound, which compounds are thermally O pound and aluminum compound should be decompos decomposable to oxides, the atom ratio of catalytic able to an oxide form. Useful compounds are the ni metal to rare earth metal to aluminum in said solu trates, acetates, sulfates, and the like. A small amount tion being O. 1-1 to 0.8-1.4 to 8-20; of noble metal promoter, for example, 0.005-0.1 b. evaporating water from said solution whereby a weight percent based on the finished catalyst, can be solid mixture of said compounds is formed; and 15 impregnated into the final coated catalyst to promote c. heating said solid mixture to an activation temper low temperature activity. This can be done using an ature to form said catalyst. aqueous solution of a noble metal salt such as palla The following example illustrates this method. dium chloride. The following example illustrates the above method EXAMPLE 6 20 of preparing a coated catalyst. In a stirred vessel place 600 parts of aluminum ni trate, 50 parts of cupric nitrate and 69 parts of lantha EXAMPLE 1 7 num nitrate. Add sufficient hot water to dissolve. After A solution was prepared containing 50 parts of cu stirring, heat to drive off water until a thick paste pric nitrate, 600 parts of aluminum nitrate and 69 parts forms. Spread the mixture about one-eighth inch thick 25 of lanthanum nitrate dissolved in 700 parts of water. in pans and continue drying in an oven at 100-150°C. This gives a copper: lanthanum:aluminum atom ratio of When dry, heat to 600°C. over a 4-hour period. Hold 1 : 1:8. To one-half of this solution there was added 780 at 600°C. for 1 hour. Cool and break into small pieces parts of transitional alumina (Alcoa F-1). The resultant for use as a catalyst. alumina was dried and then heated to 600°C. for 1 The above example may be modified by extruding hour. A second coating was applied by placing the the paste to form extrudate instead of spreading it in coated alumina in the remaining one-half of the above pans. The extrudate is dried and calcined as above. solution, to which was also added 1.3 parts of palla A broad range of atom ratios may be obtained follow dium chloride. After absorption, it was again dried and ing the above procedures by varying the amount of heated to 600°C. as before, giving an alumina coated each ingredient so long as the ratios stay within the pre 35 with the thermally decomposed salts of copper, lantha scribed range of 0.1-1 gram atom of catalytic metal to num, aluminum and palladium. 0.8-1.4 gram atoms of rare earth metal to 8-20 gram atoms of aluminum. An especially preferred ratio is EXAMPLE 1.8 about 1:1:8-20. An aqueous solution was prepared by mixing 25 In another embodiment the aluminum matrix con 40 grams of a mixture of rare earth nitrates (didymium ni taining the rare earth metal and catalytic metal is ap trate, product of Trona, a division of American Potash plied as a coating to an inert substrate such as those and Chemical Corp., which analyzes as oxides as 45-46 previously disclosed as useful for preparing the novel weight percent lanthana, 32-33 weight percent neo substrates of this invention. The preferred inert sup dymia, 9-10 weight percent praseodymia, 5-6 weight ports are refractories such as alumina. Highly preferred 45 percent samaria, 3-4 weight percent gadolinia, 1-2 refractories are honeycomb structured monolithic alu weight percent ceria), 2.36 grams of aluminum nitrate minum silicates such as mullite and honeycomb struc and sufficient water to make 200 ml of solution. tured monolithic aluminum magnesium silicate. A second solution was prepared by mixing manga These catalysts may be prepared by a method com nous nitrate with an equal amount of water. prising: 50 A solution was prepared by mixing 5 ml of the first a. forming an aqueous solution or slurry of a catalytic solution and 0.7 ml of the second solution. A 5-gram metal compound, a rare earth metal compound and piece of a fibrous monolithic aluminum silicate (“Fi an aluminum compound, which compounds are bral-80,' Societe Generale des Produits Refractaires) thermally decomposable to oxides, the atom ratio was immersed in the above solution until it absorbed of catalytic metal to rare earth metal to aluminum 55 the liquid. It was then dried and heated to 600°C. to de in said solution or slurry being O. 1-1 to 0.8-1.4 to compose the nitrates to their oxides, forming an effec 8-20; tive exhaust gas catalyst of this invention. (Low tem b. applying at least one coating of said solution or perature activity of the above catalyst can be improved slurry to an inert substrate; 60 by adding sufficient palladium chloride to the impreg c. drying the resultant coated substrate; and nating solution to provide about 0.01 percent palla d. heating said coated substrate to an activation tem dium in the calcined catalyst.) perature. From the above, it can be seen that in one aspect the According to one aspect of the above method, the invention can be defined as an inert substrate such as catalysts are formed by immersing the inert substrate in an alumina, zirconia, silica-alumina, mangesia, clay an aqueous solution or sol containing the catalytic 65 (e.g., mullite), aluminum magnesium silicate, and the metal compound, rare earth metal compound and alu like, impregnated one or more times with an aqueous minum compound. After a short period, the coated Solution of a catalytic metal compound, a rare earth 3,899,444 13 14 metal compound and an aluminum compound, said coating suffered severe degradation during the attrition compounds being thermally decomposable to oxides; test. This is due to crystallization of the catalyst pro the atom ratio of catalytic metal to rare earth metal to moted by the copper. Catalyst 2 shows some improve aluminum in the impregnating solution being 0.1-1 to ment in attrition resistance but still contains excess 0.8-1.4 to 8-20. The impregnating solution can option copper for the lanthanum. Catalyst 3 shows a further ally contain a small amount of noble metal compounds improvement as the aluminum content of the matrix is such as rhodium, platinum or palladium, preferably increased into the critical range. Catalyst 4 has the pre palladium, to improve low temperature activity. ferred 1:1 atom ratio of copper to lanthanum but shows Another aspect of this invention is a method of oxi the detrimental effect of lowering the aluminum con dizing carbon monoxide and hydrocarbons contained 10 tent of the matrix. Catalyst 5 is a catalyst of this inven in internal combustion engine exhaust gases by con tion and illustrates the sharp drop in attrition loss when tacting the exhaust gases at elevated temperatures with all parameters fall within the critical range. Attrition a catalyst of this invention. The catalysts have been loss in the test was only 2.3%. Hydrocarbon conversion tested in the exhaust system of an Olds-type single cyl remained high through the end of test and activation inder engine, 9:1 compression ratio, with 36 cu. in. dis 15 temperature remained low. placement using indolene with 12 milliliters of tetraeth In addition to their use as exhaust gas catalyst sup yl- as “Motor Mix.' The catalysts used in the tests ports, the lanthanide series metal oxide treated alumina consisted of an alumina core coated with an alumina materials may be used in any high temperature catalyst matrix containing copper and lanthana in the indicated application or for insulators, shock absorbers, missile atom ratios. A small amount (0.1%) of palladium was 20 nose cones, and similar applications. impregnated on the final catalyst. The catalysts were The foregoing description is illustrative of the inven made following the general procedure of Example 17. tion and wide variations in catalyst composition and The engine has a split exhaust leading to two 42 cu. in. support composition as well as methods for their prepa catalyst containers having thermocouples attached be ration can be envisioned by one skilled in the art. Thus, fore and after the catalyst bed. Catalyst bed tempera 25 it is desired that the invention be limited only by the ture is usually around 870°C. The engine is operated lawful scope of the following claims. for approximately 75 hours. Throughout the standard I claim: test a secondary air supply to provide for oxida 1. A catalyst useful in treating exhaust gas of internal tion was introduced into the exhaust gas stream just combustion engines, said catalyst consisting essentially prior to the catalyst bed. During the test the engine was 30 of an alumina matrix containing a catalytic metal se continually cycled 50 seconds under idling conditions lected from the group consisting of the metals of and 150 seconds under part throttle. The operating Groups I-B, V-B, VI-B, VII-B and VIII of the Periodic conditions for the test are as follows: Table in an oxide form and a rare earth metal oxide, the ENGINE OPERATING CONDITIONS atom ratio of said catalytic metal to said rare earth 35 metal to aluminum being 0.1-1 to 0.8-1.4 to 8-20, said Idle Part Throttle catalytic metal oxide and rare earth metal oxide being Engine speed, r.p.m. 800 1340 substantially uniformly distributed throughout said alu CO, % 5.0 3.0 Ignition timing, btc lO 10 mina matrix. Added air, c OO 100 2. A catalyst of claim 1 wherein said atom ratio of 40 catalytic metal to rare earth metal to aluminum is about 1 : 1:8-20. In the “Oxidation-Reduction' modification of the 3. A catalyst of claim 2 wherein said rare earth metal above test the “added air' is stopped during the idle oxide consists mainly of lanthanum oxide. portion of the cycle. The exhaust emissions are mea 4. A catalyst of claim 1 wherein said catalytic metal sured every 24 hours during the test. After the test is 45 is copper in an oxide form. terminated, the spent catalyst is checked for hardness 5. A catalyst of claim 1 wherein said catalytic metal or attrition resistance by shaking the catalyst in a com is the combination of copper in an oxide form and pal mercial paint shaker for 1 hour and determining the ladium. weight loss as fines. This is reported in percent as attri 6. A catalyst of claim 5 wherein said rare earth metal tion loss. 50 oxide consists mainly of lanthanum oxide. Using the above-described test, several catalysts pre 7. A catalyst of claim 5 wherein said rare earth metal pared according to this invention were tested for activ oxide consists of praseodymium oxide. ity and attrition resistance. The following table gives 8. A catalyst of claim 5 wherein said rare earth metal the results of these tests. 55 oxide consists of a mixture of rare earth metal oxides TABLE 2 composed mainly of lanthanum oxide, praseodymium oxide and neodymium oxide. Atom Ratio %. Hydrocarbon End of Test 9. A catalyst of claim 1 wherein said catalytic metal Attrition Conversion Activation is manganese in an oxide form. No. Cu La Al Loss (%) Start End Temp. F. 60 10. A catalyst of claim 1 wherein said catalytic metal . 5 3.4 7.7 82 59 44() is the combination of manganese in an oxide form and 2. 2 4 56 85 63 420 palladium. 3. 2 8 5.3 85 63 420 4. 1 1 6 7.5 88 73 400 11. A catalyst of claim 10 wherein said rare earth 5. 8 23 82 76 405 metal oxide is mainly lanthanum oxide. 12. A catalyst of claim 10 wherein said rare earth 65 metal oxide is mainly praseodymium oxide. As the results show, Catalyst 1 which had 5 atoms of 13. A catalyst of claim 10 wherein said rare earth copper per atom of lanthanum in the alumina matrix metal oxide consists of a mixture of rare earth metal ox

UNITED STATES PATENT OFFICE CFRTIFICATE OF CORRECTION O PATENT NO. 5, 899,424). DATED August 12, l}75 INVENTOR(S) Ruth E. Stephens It is Certified that error appears in the above-identified patent and that said Letters Patent O are hereby Corrected as shown below: Column ll, line 4), "Sub Strate Should read -- supports -- Column ll, lines 44-45, "The preferred inert supports" Should read -- The preferred inert SubStrates - - O Column 16, Claim 57 Should depend upon Claim 56 Column l6, Claim lil, insert 'a' before "manganese compound" eigned and evealed this O fourteenth Day of October 1975 SEAL Attest.

O RUTH C. MASON C. MARSHALL D ANN Attesting Officer Connissioner of Patents and Trademarks