United States Patent (19) 11 Patent Number: 5,278,112 Klatte (45) Date of Patent: Jan

III US0052781 12A United States Patent (19) 11 Patent Number: 5,278,112 Klatte (45) Date of Patent: Jan. 11, 1994

(54 CHEMICALLY IMPREGNATEDZEOLITE Primary Examiner-Carl F. Dees AND METHOD FOR CHEMICALLY Attorney, Agent, or Firm-Limbach & Limbach IMPREGNATING AND COATING ZEOLITE 57) ABSTRACT 76) Inventor: Fred Klatte, Two Spruce St., San A process for impregnating zeolite with permanganate, Francisco, Calif. 941 18 such as potassium permanganate, and a product of such process. The process preferably includes the steps of (21) Appl. No.: 975,680 dehydrating zeolite crystals to have about 5% moisture 22 Filed: Nov. 13, 1992 content, mixing the dehydrated zeolite crystals with solid permanganate (preferably potassium permanga 51) Int. Cl...... B01J 29/04; B01J 37/02 nate crystals), immersing the solid mixture in, or spray 52 U.S. Cl...... 502/62; 502/60 ing the solid mixture with, water at about 190 F. and 58) Field of Search ...... 502/60, 62, 86 mixing the resulting slurry, and then drying the mixed 56) References Cited slurry to produce permanganate-impregnated Zeolite crystals having about 15% moisture content. In other U.S. PATENT DOCUMENTS preferred embodiments, the inventive method includes 3,049,399 8/1962 Gamson et al...... 21/53 the steps of impregnating zeolite with a quaternary ammonium cation (QAC) and then coating the impreg FOREIGN PATENT DOCUMENTS nated zeolite with permanganate, or impregnating zeo 0063436 10/1982 European Pat. Off...... 502/60 lite with permanganate and then coating the impreg 0188138 7/1986 European Pat. Off. .... 502/60 nated zeolite with a QAC. Either coating acts as a pro 0067521 6/1981 Japan ...... SO2/60 tective agent for the impregnating substance in each 0000827 1/1985 Japan ...... 502/60 zeolite crystal's interior, and allows regulated time re OTHER PUBLICATIONS lease control of the impregnating substance, thus per mitting a controlled diffusion (or absorption) rate in Material Safety Data Sheet (5 pages), Chemax, Inc. applications in which the coated, impregnated zeolite is (Jan. 30, 1992). employed to absorb contaminants from air or water. Cadena, et al., Treatment of Waters Contaminated with Combinations of coated and uncoated zeolite crystals BTX and Heavy Metals Using Tailored Zeolites, Feb. can be chosen to match specific environmental circum 1992, New Mexico Waste-Management Education and stances calculable by analysis of the air or water to be Research Consortium, Technical Completion Report treated. Mixtures of coated and uncoated QAC-impreg (Project No. WERC-91–41), 22 pages. nated zeolite can be used to react with organics such as Gao, et al., Use of Tailored Zeolites for Removal of Ben benzene, toluene, and xylene, and mixtures of coated zene and Toluene from Water, 45th Purdue Industrial and uncoated permanganate-impregnated zeolite can be Waste Conference Proceedings, pp. 509-515, Lewis used to react with hydrogen sulfide, acetone, ethylene Publishers, Inc. Chelsea, Mich., 1991. glycols, formaldehyde, and other contaminants. Brochure entitled "Carusorb (R) 200," by Carus (1 page). 38 Claims, 1 Drawing Sheet

5,278,112 1. 2 tassium permanganate. However, we have recognized CHEMICALLY IMPREGNATED ZEOLTE AND that, under certain conditions, such permanganate METHOD FOR CHEMICALLY MPREGNATING impregnated zeolite reacts too rapidly to be practically AND COATING ZEOLITE useful for some air filtration applications. For example, when air contaminated with 50 ppm of hydrogen sulfide FIELD OF THE INVENTION is caused to flow (at a rate of 15 liters per minute) The invention relates to processes for producing through a bed of the inventive permanganate-impreg chemically impregnated zeolite and coated, chemically nated zeolite crystals (where the crystals have size impregnated zeolite, and to the products of such pro about 0.25 inch X 0.125 inch, and the bed has volume of cesses. A preferred embodiment of the invention is a O 75 cubic centimeters, and dimensions 1'(1d)x6"), the process for chemically impregnating zeolite crystals crystals typically become saturated with hydrogen sul with either a quaternary ammonium cation or a perman fide within about 48 hours. Although the impregnated ganate, and then coating the impregnated zeolite crys zeolite crystals usefully absorb hydrogen sulfide from tals with the other of these two substances. air, the hydrogen sulfide absorption rate is significantly 15 higher than can be achieved using conventional per BACKGROUND OF THE INVENTION manganate-impregnated alumina products, and is unde Zeolites are hydrated metal aluminosilicate con sirably high for some applications. pounds with well-defined (tetrahedral) crystalline struc For both air (and other gas) and water filtration appli tures. Because Zeolite crystals (both natural and syn cations, it would be desirable to reduce the rate at thetic) have a porous structure with connected channels -which permanganate-impregnated zeolite absorbs se extending through them, they have been employed as lected contaminants, and to control such absorption molecular sieves for selectively absorbing molecules on rate. Similarly, it would be desirable to reduce the rate the basis of size, shape, and polarity. at which QAC-impregnated zeolite absorbs selected Volumes packed with zeolite crystals (for example, contaminants, and to control such absorption rate. small zeolite crystals chosen to have size in the range 25 However, until the present invention, it was not known from 0.2 mm to several millimeters) have been en ployed in water and air (or other gas) filtration systems how to achieve either of these objectives. to selectively absorb contaminants from a flowing SUMMARY OF THE INVENTION stream of water or gas. It has been proposed to treat zeolite crystals by im In one class of embodiments, the invention is a pro pregnating them with quaternary ammonium cations cess for impregnating zeolite crystals with a permanga (such as tetramethylammonium, tetraethylammonium, nate, such as potassium permanganate. The product of hexadecyltrimethylammonium, dibenzyldimethylam such process is another embodiment of the invention. A nonium, benzyltriethylammonium, and cetyltrime preferred embodiment of the inventive process results thylammonium), to enhance the zeolite's capacity to 35 in zeolite crystals uniformly impregnated with potas absorb heavy metal, benzene, toluene, and xylene con sium permanganate (having a potassium permanganate taminants from water. See, for example, Cadena, et al., content of about 4% and a moisture content of about "Treatment of Waters Contaminated with BTX and 15%), and includes the following steps: dehydrating the Heavy Metals Using Tailored Zeolites,' New Mexico zeolite crystals until they have about 5% moisture con Waste-management Education and Research Consor tent, then mixing the dehydrated zeolite crystals with tium Technical Completion Report for Project No. solid potassium permanganate (preferably with a weight WERC-91-41 (February 1992). If not impregnated with ratio P/T substantially equal to 4%, where P is the a quaternary ammonium cation (QAC), zeolite does not potassium permanganate weight and T is the total function adequately as a molecular sieve for organic weight of the final product of the process), immersing chemicals such as benzene, toluene, and xylene. 45 the solid zeolite and permanganate mixture in (or spray It has also been proposed to impregnate an aqueous ing the solid mixture with) water whose temperature is solution of permanganate (such as permanganate of above room temperature (preferably the water tempera potassium, sodium, magnesium, calcium, barium, or ture is about 190 F), thoroughly mixing the resulting lithium) into pores of substrates such as silica gel, alu slurry, and finally air drying the mixed slurry to pro mina, silica-alumina, activated bauxite, and activated 50 duce permanganate-impregnated zeolite crystals having clay. The resulting impregnated porous substrates have about 15% moisture content. Typically, four pounds of been employed for filtering and deodorizing air. See, for potassium permanganate, fifteen pounds of water, and example, U.S. Pat. No. 3,049,399, issued Aug. 14, 1962, 86 pounds of dehydrated (5% moisture) zeolite crystals to Gamson, et al. are employed to produce each 100 pounds of the prod However, zeolite crystals have not been impregnated 55 uct of this process. (throughout their volume) with permanganate. Variations on the preferred embodiment described Further, because permanganates are strong oxidizing above produce zeolite crystals uniformly impregnated agents, those skilled in the art have avoided exposing with potassium permanganate, having a potassium per quaternary ammonium cations or salts to permanga manganate content greater than 4%, and preferably, as nates (to avoid violent reactions of the type predicted in high as in the range from 8% to 10%. In these varia the literature). For this reason, it has not been proposed tions, the dehydrated zeolite crystals are mixed with to treat a permanganate-impregnated substrate (such as solid potassium permanganate with a weight ratio P/T permanganate-impregnated zeolite) with a quaternary greater than 4%, where P is the potassium permanga ammonium cation or salt. Nor has it been proposed to nate weight and T is the total weight of the final prod treat a substrate impregnated with a QAC (quaternary 65 uct of the process. ammonium cation) to permanganate, In variations on the described embodiments, a per We have found that zeolite crystals can readily be manganate other than potassium permanganate is em impregnated with a usefully high concentration of po ployed to impregnate the zeolite crystals. Throughout 5,278,112 3 4. the specification, including in the claims, the term "per manganate" used alone is intended to refer to any per DETAILED DESCRIPTION OF THE manganate, including permanganate of potassium, so PREFERRED EMBODIMENTS dium, magnesium, calcium, barium, or lithium. In one class of embodiments, the invention is a pro 5 cess for impregnating zeolite crystals (for example, In other preferred embodiments, the method of the crystals having size 0.125 inchX0.10 inch, 0.25 invention includes the steps of impregnating zeolite inchx0.125 inch, 0.125 inchX0.50 inch, or 0.50 crystals with a quaternary ammonium cation (QAC) inchx 0.75 inch) with potassium permanganate, and the and then coating the impregnated zeolite with perman product of such process. A preferred embodiment of ganate, or impregnating zeolite crystals with permanga O such process, for producing zeolite crystals uniformly nate and then coating the impregnated zeolite with a impregnated with potassium permanganate, with a 4% QAC. We have unexpectedly found that the process of potassium permanganate content and a 15% moisture applying either type of coating does not produce a vio content, includes the steps of initially dehydrating the lent reaction (at most, the coating process results in a zeolite crystals to have about 5% moisture content, then minor reaction). We have also unexpectedly found that 5 mixing the dehydrated zeolite crystals with potassium the coating acts as a protective agent for the impregnat permanganate crystals (preferably with a weight ratio ing substance in each crystal's interior. The presence of P/T substantially equal to 4%, where P is the potassium the coating allows regulated time release control of the permanganate weight and T is the total weight of the impregnating substance, and thus permits a controlled final product of the process), then immersing the crystal 20 mixture in (or spraying the mixture with) water at about diffusion (or absorption) rate in applications in which 190 F., thoroughly mixing the resulting slurry, and the coated, impregnated zeolite is employed to absorb then air drying the mixed slurry to produce potassium contaminants from a fluid such as air or water. permanganate-impregnated zeolite crystals having An important aspect of the invention is that the char about 15% moisture content. Typically, the process acteristics of a QAC (or permanganate) coating on a 25 employs four pounds of potassium permanganate and zeolite crystal impregnated with permanganate (or fifteen pounds of water for every 86 pounds of dehy QAC) can be varied to control the reaction rate of the drated (5% moisture) zeolite crystals, and this mixture impregnating substance within the zeolite. Such charac (105 pounds) is dried to produce 100 pounds of perman teristics can be varied by changing the concentration of ganate-impregnated zeolite crystals having about 15% the coating solution employed to coat the impregnated 30 moisture content. FIG. 1 represents one such impreg zeolite crystal. nated crystal, having channels uniformly impregnated The coated, impregnated zeolite resulting from either with potassium permanganate 2. embodiment of the inventive method, or a mixture of Variations on the preferred embodiment described the coated, impregnated zeolite resulting from both above produce zeolite crystals uniformly impregnated embodiments, or a mixture of uncoated, impregnated 35 with potassium permanganate, having a potassium per Zeolite and the coated, impregnated zeolite resulting manganate content of X%, where X is greater than 4, from either embodiment of the inventive method, can and is preferably in the range from 8 to 10. In such variations, the dehydrated zeolite crystals are mixed be used for a variety of molecular sieving applications, with solid potassium permanganate with a weight ratio such as filtration of contaminants from fluid (such as air 40 P/T substantially equal to X%, where P is the potas or water). The number of combinations of coated and sium permanganate weight and T is the total weight of uncoated crystals can match specific environmental the final product of the process. circumstances which can be calculated by analysis of In variations on any of the above-described embodi the air or water to be treated. One result is that mixtures ments, permanganate other than potassium permanga of coated and uncoated QAC-impregnated zeolite can 45 nate (such as permanganate of sodium, magnesium, be used to react with organics such as benzene, toluene, calcium, barium, or lithium) is employed to impregnate and xylene, and mixtures of coated and uncoated per the zeolite crystals. manganate-impregnated zeolite can be used to react In another variation on the described embodiment, with hydrogen sulfide, acetone, ethylene glycols, form zeolite crystals are immersed in (or sprayed with) aque aldehyde, and other contaminants. 50 ous potassium permanganate (having permanganate concentration in the range from about 10% to about BRIEF DESCRIPTION OF THE DRAWINGS 20%), where the weight of aqueous potassium perman FIG. 1 is a cross-sectional view of a zeolite crystal ganate is about 10% of the weight of the final product impregnated with permanganate. of the process. The crystals (after they are dried) will be FIG. 2 is a cross-sectional view of the impregnated 55 uniformly impregnated with about a 1% concentration zeolite crystal of FIG. 1, after it has been coated with a of potassium permanganate. In yet another variation on the described embodi QAC in accordance with the invention. ment, zeolite crystals are immersed in (or sprayed with) FIG. 3 is a cross-sectional view of a zeolite crystal supersaturated aqueous potassium permanganate (hav impregnated with QAC. ing permanganate concentration of 20% or higher) at FIG. 4 is a cross-sectional view of the impregnated 190° F., where the weight of aqueous potassium per zeolite crystal of FIG. 3, after it has been coated with manganate is about 10% of the weight of the final prod permanganate in accordance with the invention. uct of the process. The zeolite crystals (after they are FIG. 5 is a cross-sectional view of the impregnated dried) are uniformly impregnated with a concentration zeolite crystal of FIG. 3, after it has been immersed in 65 of potassium permanganate greater than 1%. an excessively concentrated permanganate solution (so For many applications (including air and water filtra that the permanganate has replaced the impregnating tion applications), the desired concentration of potas QAC). sium permanganate impregnated in zeolite crystals is in 5,278,112 5 6 the range from about 1% to about 4% (or from about Q is the cetyltrimethylammonium chloride weight and 1% to about 8% or 10%). T is the total weight of the final product of the process. However, as explained above, the inventive perman As a result of permanganate leaching studies on the ganate-impregnated zeolite may have an activity rate inventive QAC-coated, potassium permanganate too high or too low for some useful applications (i.e., its impregnated zeolite crystals (in which the coated, per rate of absorption of contaminants may be too high, or manganate-impregnated zeolite crystals were immersed too low, for some air or water filtration applications). in, or sprayed with, water and the permanganate con We have found that the rate at which permanganate centration in the water measured over time), we deter impregnated zeolite absorbs (or reacts with, or both mined that the QAC coating substantially slowed the absorbs and reacts with) selected contaminants can be 10 permanganate leaching rate (and thus would substan controlled (and reduced or increased to a desired level) tially slow the expected activity rate, i.e., the rate at by applying a quaternary ammonium cation (QAC) which the impregnated zeolite would absorb and/or coating to the permanganate-impregnated zeolite. We react with contaminants such as organic chemicals). have also found that the rate at which QAC-impreg This result was highly unexpected in view of the con nated zeolite absorbs selected contaminants can be con 15 ventional belief that the presence of QAC would in trolled (and reduced or increased to a desired level) by crease zeolite's absorption of organic chemicals (such as applying a permanganate coating to the QAC-impreg toluene). nated zeolite. We found that the activity rate of QAC-coated, po Thus, in a first class of preferred embodiments, the tassium permanganate-impregnated zeolite depends on inventive method includes the steps of impregnating 20 the concentration of the QAC solution with which the zeolite with permanganate (preferably, potassium per permanganate-impregnated zeolite is coated. Increasing manganate) and then coating the impregnated zeolite the QAC concentration will decrease the activity rate. with a QAC (preferably, cetyltrimethylammonium, We found that the leaching rate of permanganate from although other QACs are suitable for certain applica within QAC-coated, impregnated zeolite (and hence the tions). FIG. 2 represents one such impregnated crystal, 25 expected activity rate) is negligible if the weight ratio of whose channels contain QAC 4 in the region near the the QAC coating is in the range from 1% to 2% (i.e., if crystal's surface, and whose channels are impregnated the weight of liquid cetyltrimethylammonium chloride with potassium permanganate 2a throughout the vol employed for coating permanganate-impregnated zeo ume of the crystal inside the region containing QAC 4. lite crystals satisfies the relation 1%

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