[1]a e 3,013,987 ME, TA-F- LOADING OF Y.O-ff-E, CUILAR SIEVES Charles R. Cas@or, IndinnapeNs, Ind., and Robert M. Milton, White Plains, N.Y., ass!,-nors to Union Carbide Corporntion, a corpoiration of New York NoDiarel@ig. FiledSept.24,1958,Ser.No.762,958 8 Cla!ms. (Cl. 252-455) Th is invention relqtes to a nrocess for preparing metalloa ded zeolitic niolecular sieves which are suitable for 10 us e as catalysts, scavengers, and getters. Th e use of metals as catalysts, scavengers, and getters in a number of chemical reactions and chemical syste ms is well known in the art. The effectiveness of the me tal in such cases has been found to depend, to a coq- 15 sid erable degree, on the form in which the metal is pr esent in the reactioi-i zoiie. it is an object of this invention to provide a process for introducing metals into the internal adsorption area of zeolitic molectilar sieves to provide superior - cata- 20 lyst s, scavengers, and getters. Ot her objects will be apparent frorn the subsequent dis closu@-e and appended claims. Th e process which satisi'ies the objects of the present iiiv f.@ntion comprises intimallely contactin.@ an activated 25 ze olitic molec,,ilar sieve in an ine.-t atynosphere with a de composable fltiid compound of the metal to be contai ned in the z@-olitic molecular sieve, whereby said deco mposable compound is adsorbed by the zeolitic molecula r sieve in the inner adsorption region of the zeolitic 30 mo lecular sieve, and reducin- the adsorbed decon-lposable compound in said activat@ed zeoltic molectilar sieves to the elemental metal whereby said elemental metal is ret ained in the inner adsorption region of said zeo litic mo lecular sieve. The term "decomposable" is employed 35 he rein to mean the capability of the metal compouncl to be separated into the elemental metal on the one hand an d the rest of the compotind on the otber hand by the pr ocesses described in the specification and within the dis closed limitati(yns. 40 Ze olitic molectilar sieves' both natural and synthetic, are metal aluminosilicates. The crystalline strlcture of the se materials is such that a relatively large )bsorption are a is present inside each crystal. Access to this area ma y be had by way of openin.-S or pores in the crystal. 45 Mo lecules are selectively adsorbed by molecular sieves on the basis of their size and polarity among other things. Ze olitic molecular sieves consist basically of three-dime nsional frameworks of SiO4 and AIO,, tetrahedra, The tetr ahedra are cro,,s-linked by th.- sharing of oxygen 50 ato ms. The electrovalence of the tetrahedra contairing aiu minum is balanced by the inclusion in the crystal of a cati on, for example, metal ions, ammonium ions, amine co mplexes, or hydro.-en ions. The spaces between the tetr ahedra may be occupied by water or other adsorbate 55 mo lecules. Th e zcolites may be activated by driving off substantiall y all of the water of hydration. The space remainin @- in the crystals after activation is available fo-- adsor ption of adsorbate molecules. Any of this space ot rO oc cupied by elemental metal is avaflable for adsorption of molecales having a size, shape, and energy which permit s entry of the adsorbate molectiles into the pores of the molecular sieves. Th e zeolitic molecular sieves, to be useful in the - pres- 65 ent invention, must be capable of adsorbing benzene molecul ,-s under normal conditions of temperature arid pressur e. Included among these molecular sieves, and prefer red for the purposes of th.- present invention, are the nat ural zeolite faujasite, and synthetic zeolites X, Y, L. 70 Th e natural materials are adequately described in the ch emical art. The characteristics of the aforementioned 3 1 0 1 3 , 9 8 7 Utiited States Pat'-nt Office Patented Dec. 19, 1961 @ 2 synthetic materials, and t.he processes for making them, are provided below. The general formula for zeolite X, expressed in terms of mol fracti6ns of oxides, is as follows: 0 . 9 = 1 = 0 . 2 M 2 O : A I 2 0 3 : 2 . 5 - 4 - 0 - 5 S i O 2 : 0 t O 8 H 2 o i i In the forinula "M" represents a c@tion, for example hydrogen or a metal, and "n" its valence. The zeolite is activated or made capable of adsorbing certain molecules by the removal of water from the crystal as by heating. Thus the actual number of mols of water present in the crystal will depend upon the degree of dehydration or activation of the crystal. Heating to temperatures of about 350' C. has been found sufficient to remove substantially all of the adsorbed water. The cation represented in the,formula above by the letter "M" can be changed by conventional ion-exchange techniques. The sodium form of the zeolitd, designated sodiurn zeolite X, is the most convenient to manufacture. For this reason the other forms of zeblite X are usually obtained by the modification of sodium zeolite X. The typical formula for sodiurn zeolite X is 0 . 9 N a 2 O : A I 2 0 3 : 2 . 5 S i O 2 : 6 . I H 2 0 The major lines in the X-ray diffraction pattern of zeolite X are set forth in Table A below: T A B L E A d Value of Reflection In A, 1001/lo 14 42-@-0 2-- ----------------- 100 8.92=LO.i ---------------------------------------- --------------------------- 18 4.41-f-0.05 -------------------------------------- -------------- 9 3.80=LO.05 --------------------------------------- ------------- 21 3.33-4-0.05 -------------------------------------- -------------- 18 2.88=LO.05 ----------------- ----------- ----------------------- 19 2.70-4-0.05 -------------------------------------- -------------- 8 2.66=1=0.05 ----------------------------------------- ---------- @8 In obtaining the X-ray diffraction powder patterns, standard techniques were employed. The radiation was the KOC doublet of copper and a Geiger counter spectrometer with a strip chart'Pen recorder was used. The peak heights, 1, and the positions as a function of 20, where 0 is the Bragg angle, were read from the spectrometer charge. From these, the relative intensities, 10 where To is the intensity of the strongest line or peak, and d(obs) the interplanar spacing in A., corresponding t o the recorded lines were calculated. The X-ray patterns indicate a cubic unit cell of dimensions between 24.5 A. and 25.5 A. To make sodium zeolite X, reactants are mixed in aqqeous solution and held at about 100' C. until the crystals of zeolite are f6rmed. Preferably the reactants should be such that in the solution the following ratios prevail: SiO2/A]203 @ ------------------------------- 3-5 Na2O/SiO2 -------------- I ----------------- 1.2- 1.5 H20/Na2O --------------- --------------- 35- 60 The chemical formula for zeolite Y expressed in terms of oxides mole ratios may be written as 0 . 9 - 0 . 2 N a 2 O : A I 2 0 3 : W S i O 2 : X H 2 0 wherein "W" is a value greater thah 3 up to about 5 and "X" may be a value up to about 9. Zeolite Y has a characteristic X-ray powder diffraction pattern which may be employed to identify zeolite Y. The X-ray powder diffraction data dre shown in Table B. The values,for the interplanar spacing, d, are expressed
[2]3 4 in angstrom units. The relative intensity of the lines TABLE C of the X-ray powder diffraction data are expressed as 16.1-0.3 3.17-0.01 VS, very strong; S, strong; M, medium; W, weak; and 7.52-0.04 3.07-.-@-0.01 VW, very weak. 6.00-0.02 2.91- 0.01 TABLE B 5 4.57- 0.03 2.65-0.01 4.35- 0.04 2.46-0.01 h3+l-2+12 d in A. Intensity 3.91- 0.02 2.42-0.01 3.47-0.02 2.19-0.01 --------------------------------- 3 14.3- 14.4 VS 220 --------------------------------- 8 8.73- 8.80 M 3.28-0.02 311 --------------------------------- 11 7.45- 7.50 Al 10 331 --------------------------------- 19 5.67- 5.71 S Altbou-@h there are a number of cations that may be 333, 511@ ---------------------------- 27 4.75- 5.08 l@,l present in zeolite L, it is preferred to synthesize the po440 --------------------------------- 32 4.37-4. 79 M 620 --------------------------------- 40 3.90- 4.46 IV tassium and potassium-sodium forms of the zeolite, i.e., 533 --------------------------------- 43 3. 77- 3.93 S 444 -------------------- ------------ 49 3. 57-3. 79 VW the form i@i which the exchangeable catio-@is present are 551, 711 ----------------------------- 51 3.46- 3.48 VW 15 siibstantially all potassiur@i or potassium and sodium ions. 642 --------------------------------- 56 3.30k3.33 S 553, 731 ----------------------------- 50 3.22- 3.24 NV The reaeLa-- @its accordingly employed are readily available 733 --------------------------------- 67 3.02-3. 01 M and -enerally water soluble. The exchan.-eable cations 660, 622 --------------- X ------------ 72 2.91- 2.93 ill present in the zeolite may then conveni,-ntly be replaced 555, -51 ----------------------------- 75 2.85- 2.87 S 840- 80 2.7e)- 2.78 Al by other exchan-cable cations. 753, 83 2. 71-2. 73 IV 664 --------------------------------- 88 2. 65 M 20 The potassium or potassium-sodium forms of zeolite -4 931 ------------- -------------------- 01 2.59-2.61 Al L may be prepared by preparing an aqueous nietal 844 ---- - 06 2. 52-2. 54 VW 862; lo, -------------------------- 104 2. 42- 2.44 VW aluminosilicate mixture having a composition, expressed 666; 10, 2, 2 ------------------------- 109 2.38-2.39 M in ter@ns of mole ratios of oxides falling within the fol776; 11, 1, I ------------------------- 123 2. 22-2. 24 VW 990 ----------- --------------------- 128 2.18-2.20 W lowir@g range: 955; 971; 11, 3, i 131 2.16--2.18 VW 25 973; 11, 3, 3-@ --------------------------- 139 2. 10-'-). 11 W K20/(K20+Na2O) ------- From about 0.33 to about 1. SS4; 12. 0, 0------------------------- 144 2. 06-2.07 VW &@6; 10, 8, 0; 12, 4, 2 ----------------- 164 1.93--l.94 VW (K20+Na2O) /SiO2 ------- From about 0.4 to about 0.5. 10,8,2 ------------------------------ 168 1.91-I..92 VW SiO,/AI,O ----------- ---- From about 15 to about 28. 99.@; 13, 3, 3 ------------------------- 187 1.81-1.82 VW H20/(K20+Na2O) ------- From about 15 to about 41. 11, 7, 5; 13, 5, 1 ---------------------- 195 1.77-1.78 VW 10, 8, 6; 10, 10, 0; 14, 2, 0------------ 200 1.75-1.78 W 997; 11, 9, 3------------------------- 211 1.70-1.71 IV 30 maintainin.- the mixture at a temperature of about 100' C. until crystal lizatio n occurs , and separa ting the crystal s When an aqueous colloidal silica sol employed as the m-,ijor source of silica, zeolite Y may be prepared by preparing an aqueous sodium aluminosilicate mixture 35 havin.- a composition, expressed in, terms of oxide-moler-,itios, which falls witwn one of the followin-, ranges: Range I Range 2 Range 3 40 N'a2o/sios ----- ------------ 0. 20 to 0. 40 0. 41 to 0. 61 0. 61 to 0. 80 SiO2/AI203 ------------------ 10 to 40 10 to 30 7 to 30 H20/Na2O ------------------ 25 to 60 20 to 60 20 to 60 45 maintaining the mixture at a temperature of about 100' C. uiitil crystals are formed, and separating the crystals from the mother liquor. When sodium silicate is employed as the major source of silica, zeolite Y may be prepared by preparing an aque- 50 ous sodium aluminosilicate mixture having a composition, expressed in terms of oxide-mole-ratios, falling within one of the following ranges: 55 Range 1 Range 2 Range3 Na2OiSlO2 ------------------------ 0. 6 tO 1- 0 1. 5 to 1. 7 1.9 to 2.1 SiO2lAl2O3 ------------------------ 8 to 30 10 to 30 about 10 E12oiNa:o ------------------------ 12 to 90 20 to 90 40 to 90 60 maintaining the mixture at a temperature of about 100' C. until crystals are formed, and separating the crystals from the mother liquor. The composition of zeolite L, expressed in terms of 65 mole ratios of oxides, may be represented as follows: 1.04-0.2M O:AI20z:6.4-4--0.5SiO2:ylf2O 2 ii wherein "M" designates a metal, "n" represents the 70 valence of "M"; and "y" may be any value from 0 to about 7. The more si.-nificant d(A.) values, i.e., interplanar spacin-,S, for the major lines in the X-ray diffraction pattem of zeolite L, are given below in Table C. 75 from the mother liquor. To prepare the el-.mental metal-containing zeolitic molecular sieves of the present invention it is necessary to ictivate 'he zeolitic molecular sieve prior to adsorption of the @ecomposable metal compound. This may be accomplished by heatin.- the zeolitic molecular sieve up to a temperature of about 350' C. in a flowing stream of @nert dry -as or in vacuum. It has been fouiid advaiita.-,-ous to remove as much of the water from the zeolitic molecular si-@ve as is possible without destroying the crystal structure. Not only :s it then possible to absorb mor.- of the fluid decomposable metal compound, but also a very hi,--h disp.-rsion of the r-rietal throughout the adsorption region following decomposition and reduction is obtained. The metal so dispersed has a high sp,-cific slirf,,ice with a corresponding hi.-h chemical and catalytic activity. The pore size of the zeolitic molecular sieves which are useful in the present invention must be suffici.-ntly large to permit adsorption of b-.nzene. INIolecular sieves having smaller pores wiU not readily permit entry of thf, decomposable fluid metal compounds into the inner adsorption area of the crystal. The activated zeolitic molecular sieve is then brouglit into intimate contact with the decomposable fluid metal compound. The materials wliich may be loaded in the large pored zeolitic molecular sieves by the present process are copper, silver, gold, platinum, palladium, rhodium, zinc, cadmiur@i, aluminum, tin, lead, chromium, molybdenum, tun@.sten, manganese, rhenium, iron, cobalt, nickel, titanium, zirconium, vanadium and hafnitim. The reducible compounds of these materi-@ls which ai-e found to be particularly suitable are the carbonyls, carbonyl hydrides, acetyl acetonate cor@iplexes of the metals in the zero valence state, reducible halides, metal allyls and other metal-or.-anic compounds such as cyclopentadieriyl metal compounds and ethyteric complex compounds of the noble metals. Of these m,-tals those f,,llling in grOLIPS VIB, VIIB, and VII'L of the periodic table (Handbool,, of Chemistry and Physics, Thirty-first Edition, i)age 336, Cheniical Rubber Publishiilg Co., 1949) are most suitably introduced to the molecular sieve as carbonyl or carbonyl hydrides, those falling in -roup IB as ac?tyl aectonate complexes with the metal in the zero valence state, those
[3]5 falling in groups IIA, IIIA, and IVA as the metal alkyls and those falling in group INIB as the volati'le halides. The reduction of the compound may be either cheniical or thermal. In the case of chemical redtiction the reducing agent may be deposited first in the inner sorption area and the reducible cortipound introduced subseqtiently, or alternatively the reducible compound may be sorbed into the inner sorption area and the reducing agent introduced subsequently. These several variations of thermal and chemical reductions are illustrated in the following examples. Example I A portion of zeolite X (22.7 grams) was activated by heating it to 350' C. This activated zeolite was trealted with volatile iron pentacarbonyl under reduced pressure untiladsorptionofthecarbonylbythezeoliteceased. '.he treated material was heated slowly to 250' C. under a purging stream of nitrogen until the iron pentacarbonyl was deconiposed leaving elemental iron in the crystals of zeolite X. The zeolite X assumed a deep purple color. It was found that the iron-loaded zeolite was highly reactive to oxidatio-@i. As soon as the material was exposed to air, the color of a portion of it changed from purple to the cbaracteristic color of iron oxide while some of the iron-loaded zeolite turned black after the exposure. It was shown by the behaviour of the material in a magnetic field that the different colors were due to the presence of different oxides of iron. The oxidized material was analyzed. The results of the analysis indicated 8.1 weightpercent iron in the ze6lite pores. - Adsorption data iiidicated that the iron-loaded zeolite X contained 8.2 weightpercent iron prior to the decomposition of the iron carbonyl. This agreement in iron content indicated that a negli.-ible amount of Fe(CO)5 was desorbed in the decomposition process and that practically quantative decomposition took place. Exaniple 11 The preparation of nickel-loaded zeolite X was carried out in the same manner as the preparation of the ironcontaining material except that nickel tetracarbonyl was used. The resulting product was similar to the iron-loaded zeolite except that it was a gray color. No noticeable color change occurred on exposure to air. Example III Copper acetylacetonate (1 gram) was dissolved in 50 milliliters of chloroform. To this so-lution was added 10 grams of activated zeolite X powder. The resulting slurry was allowed to stand for about 30 minutes. The powder was then filtered off and purged with dry hydrogen gas to remove the last traces of chloroform.. The dry powder was heated to about 400' C. for 4 hours under a dry hydrogen pur.-e to decompose the adsorbed copper salt. X-ray diffraction analysis of the resulting product indicated the retention of the zeolite X structure and the presence of copper in the zeolite X. Experimental results indicate that decomposable conipounds can be adsorbed by molecular sieves when the compounds are either gaseous, liquid or in solution. Accordingly, the term fluid is. employed herein to include gases, liqt,.ids, and solutions. Care should be taken, of course, to avoid heating the compounds tO their decomposition temperatures prior to their adsorption by the molecular sieves. Care should be taken to avoid heating the zeolitic molecular sieves to a temperature at which destruction of the crystal structure occurs. The carbonyls used in the foregoing examples decompose at temperatures above about 150' C. and for that rea@on it is preferred to adsorb these carbonyls at temperatures below about 100' C. Best results have been obtained when the adsorption and desorption are carried out under reduced pressure, but the processes described above are also operable at atmospheric or higher pressures. 3,013,987 6 sorbed metal-containing compound, the decomposition may be effected by the chemical reaction of the compound and another material. For example, hydrogen will react un(fer the proper conditions of temperature and pressure with metallic cyclopentadienyls to produce elemental metal. At pressures of between about 1000 and 2000 p.s.i.g. and at temperatures of from about 100' C. to 140' C., nickel and cobalt cyclopentadienyl break down in the presence of hydrogen to form nickel and cobalt, respec10 tively. Metal halides may also be reduced to metal by hydrogen or other materials such as nictallic sodium. This procedure whereby the reaction of two or more materials is employed to effect the deposition of elemental metal in a molecular sieve is illustrated in Examples IV 15 and V. Example IV Bis(cyclopentadienyl) nickel (10 grams) was dissolved in 100 millil-iters of nheptane at 95' C. Zeolite X powder (50 grams) which had previously been activated at 375' 20 C. was added, and the slurry was refluxed in an ar-on atmosphere for two hours. rnis was done to allow diffusion of the nickel compound into the pores of the zeolite. The slurry was transferred to a 300 milliliter pressure vessel and put in an autoclave. Hydrogen gas was intro25 duced into the vessel until the pressure reached 1200 p.s.i.g. The temperature of the reactor and contents was slowly increased at the rale of about I' C. per minute. At 80' C. a sli.-ht pressure drop of 1280 to 1200 p.s@i.g. occurred followed by a leveling off of the presstire. This indicated 30 adsorption of the hydrogen by the zeolite. At 1051 C. a major pressure drop occurred from 1200 to 1000 p.s.i.@ The pressure leveled off at about 1000 p.s.i.g. This pressure drop indicated hydrogenation of the c yclopencadienyl compound. The vessel was then cooled to room tempera35 ture, vented, and the slurry was removed to be dried under an inert atmosphere. The nickel-containing zeolite product was a uniform jet-black color. Example V 40 A platinum-ethylenic complex compound was prepared by refluxing anhydrous sodium hexachloroplatinate (6 grams) with absolute ethanol (50 milliliters). The complete reaction of the sodium hexachloroplatinate was insured by the addition of saturated ammonium. chloride 46 solution which precipitated unreacted sodium hex achloroplatinate as an insoluble ammonium salt. The resulting solution was evaporated to dryness and the platinumethylenic complex was extracted with chloroform (150 milliliters). Zeolite X powder (5 grams) was added to 60 the solution and shaken for one hour to permit the adsorption of the platinumethylenic complex from the solution by the zeolite. The solution was then filtered and the zeolite dried. The zeolite was treated with hydrogen at 150' C. to reduce the adsorbed platinu-@n ethylenic complex to free platinum metal. The resultin.- product was zeolite X containing 2.18 percent by weight metoic platinum as determined by elemental analysis. Example VI 60 Ten grams of sodium zeolite Y powder SiO2/AI203=4.4 which had been activated by heating at 350' C. to drive off the intracrystalline water was mixed with 2 grams of 65 bis-toluene chromium, and heated in a closed tube at 95' C. for two hours. This resulted in adsorption of the chromium compound into the pore system,of the molecular sieve zeolite. This was then heated to 375' C. in a fowing stream of argon gas causing decomposition of the 70 bis-toluene chromium and deposition of chromium metal within the zeolite. Analysis showed 4.9 weight percent chromium was deposited in the zeolite. Example VI] In addition to the thermal decomposition of the ad- 75 @ To illustrate the multiple loading of metals in a mole@-
[4]3,013,987 7 ular sieve, 0.509 gram of activated sodium X powder was cyclicly treated by adsorption of nickel carbonyl vapors at 25' C. followed by heating to between 160' C. and 185' C. to decompose the nickel carbonyl while at th-. same time evacuating the evolved carbon monoxide. After 43 5 cycles, the sample weight had increased 212 wei.-ht-perceni. It was estimated that at this point about 80 percent of @@e voluine of the large pores of the molecular siove were filled with e!emental metal. The product exhib;ted ferromagnetic properties. 10 The physical properties of this product slich as its bi.-her density and the fact that it exhibited ferromagnetism indica,e that it could be employed in structural or electrical applications. Its utility as a catalytic agent would be enhanced for those processes wherein a gradual 15 loss of the metal mi.-ht occur. Eyatnple VIII A -lass tube was charged with 15 grams of activated sod-ium zeolite X pellets and 4 grams of chromium hexa20 carbonyl in separate zones with glass wool plugs betnveen aiid outside the zoics. The tube was heated to 100' C. in an electric furnace while a flow of argon was - maintained through the tube from the chromium carbonyl zone through the zeolite zone. These conditions were main25 tained for several hours following which the temperature was raised to 375' C. to decompose the adsorbed chromium carbonyl yieldiiig elemental chromium derosited with the sodium zeolite X. Upon exposure to air the active chromium oxidized with considerable heat being 30 developed. Example IX T@venty-one grams of activated sodium zeolite X, 14 x 30 mesh crushed pellets, and 4 grams of rriolybdenum hexa35 carbonyl were placed in a Pyrex glass tube (3 cm. O.D., 58 cm. ten-th) and separated by -,) -lass Nvool plug. This Nvas then heated in a furnace to 100' C. with a slow stream of argon flovving over the carbonyl first and subsequently passed over the zeolite to adsorb the - molybdenum 40 carbonyl. Af'Ler all the molybdenum carbonyl had been - adsorbed on the zeolite, the product was heated to 375' C. A mol@tbdenum-loaded sodium zeolite Z containin.- 6.5 v,,e;ght percent molybdenum was obtai-@ied. 45 E.Val?lple X Fifty grams of activated sodium zeolite X w.-re placed in a flask and heated to 125' C. in argon. T'@ien 6 grams of Jump sodium were added with stirring and after dis50 persion in the zeolite, 12.4 grams of titanium - tetrachloride was added slom,ly with continued stirring. After reaction was completed the material had a jet black color which turned light gray when exposed to air. It contained 6.2 percent titanium. r)5 Example XI Activated sodium zeolite X was treated with a chloroform solution of cobalt acetylacetonate until a substantial quantity of the cobalt acetylacetonate was adsorbed. The 60 sodium zeolite X containin.- the adsorbed material was then subjected to a stream of hydrogen at 350' C. whereby the cobalt acetylacetonate was decomposed to cobalt metal. The product contained 0.3 weight-percent of cobalt. 65 The products produced by the process of the present invention are quite useful as catalysts, and particularly as selective catalysts for the specific catalysis of reactants vvhich are mixed with other rnaterials which are not adsorbed by the zeolitic molecular sieve. T'he adsorbed reactants 70 rcact leaving the non-adsorbed riaterials uiireacted. Similarly, the products are useful as selective - getters, ,,Cttering certain compone-@its of a mixture without affecting the other components. The metal-containing zeolitic molecular sieves are tise75 8 ful as a means for effecting the controlled addition of metals to reaction systems. Still another advanta-,e of the use ol- in-.tal-loaded zeolitic molecular sieves resides ir@ the fact that the tendency for the metal to migrate is niinimized. Normal catalysts consisting of supported metals exhibit migration of the metal during catalysis thereby giving rise to unequal distribution of catalyst material with corresponding decrease in catalytic effectiveness. Additionally, these metal-loaded zeolitic molecular sieves may be erilployed for the produc,-'@o--.i of molecular sieves loaded with other materials. For example, a chromiurn-containing zeolitic molecular sieve inay be subjected to mild oxidizing treatment whereby the chromium metal is converted to chroinium oxides. The cilromiumoxide-loaded molecular sieve may then be used as a superior selective chrome oxide catalyst. These metal-loaded zeolitic molecular sieves particularly those containin.- the ferromagnetic metals, may be advanta,-Cously utilized in electrical and/or magnetic applications. Zeolite X is described and claimed in U.S. patent apphcation Serial No. 400,389, j'iled December 24, 1953, now U.S. Patent No. 2,882,244. Zeoli',e Y is described and cl,,iimed in U.S. p,,itent application Serial No. 728,057, filed April 14, 1958. Zeolite L is described and claimed in U.S. pat-,nt application Serial No. 711,565, fhlcd january 29, 1958. What is
