CA2125314A1 - Zeolite materials with enhanced ion exchange capacity - Google Patents
Zeolite materials with enhanced ion exchange capacityInfo
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- CA2125314A1 CA2125314A1 CA002125314A CA2125314A CA2125314A1 CA 2125314 A1 CA2125314 A1 CA 2125314A1 CA 002125314 A CA002125314 A CA 002125314A CA 2125314 A CA2125314 A CA 2125314A CA 2125314 A1 CA2125314 A1 CA 2125314A1
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B39/00—Compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites; Their preparation; After-treatment, e.g. ion-exchange or dealumination
- C01B39/02—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof; Direct preparation thereof; Preparation thereof starting from a reaction mixture containing a crystalline zeolite of another type, or from preformed reactants; After-treatment thereof
- C01B39/026—After-treatment
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
- B01J20/10—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising silica or silicate
- B01J20/16—Alumino-silicates
- B01J20/18—Synthetic zeolitic molecular sieves
- B01J20/186—Chemical treatments in view of modifying the properties of the sieve, e.g. increasing the stability or the activity, also decreasing the activity
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J29/00—Catalysts comprising molecular sieves
- B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
- B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
- B01J29/08—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the faujasite type, e.g. type X or Y
- B01J29/084—Y-type faujasite
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J29/00—Catalysts comprising molecular sieves
- B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
- B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
- B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B39/00—Compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites; Their preparation; After-treatment, e.g. ion-exchange or dealumination
- C01B39/02—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof; Direct preparation thereof; Preparation thereof starting from a reaction mixture containing a crystalline zeolite of another type, or from preformed reactants; After-treatment thereof
- C01B39/20—Faujasite type, e.g. type X or Y
- C01B39/24—Type Y
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B39/00—Compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites; Their preparation; After-treatment, e.g. ion-exchange or dealumination
- C01B39/02—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof; Direct preparation thereof; Preparation thereof starting from a reaction mixture containing a crystalline zeolite of another type, or from preformed reactants; After-treatment thereof
- C01B39/36—Pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11
- C01B39/38—Type ZSM-5
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
- B01J2229/10—After treatment, characterised by the effect to be obtained
- B01J2229/16—After treatment, characterised by the effect to be obtained to increase the Si/Al ratio; Dealumination
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
- B01J2229/30—After treatment, characterised by the means used
- B01J2229/36—Steaming
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
- B01J2229/30—After treatment, characterised by the means used
- B01J2229/37—Acid treatment
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
- B01J2229/30—After treatment, characterised by the means used
- B01J2229/38—Base treatment
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- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Inorganic Chemistry (AREA)
- Crystallography & Structural Chemistry (AREA)
- Analytical Chemistry (AREA)
- Silicates, Zeolites, And Molecular Sieves (AREA)
Abstract
In accordance with the present invention, there are now provided zeolite materials with enhanced ion exchange capacity, which are obtained by treating ZSM-5, Y and X
zeolites with aqueous solutions of sodium carbonate and sodium hydroxide. With such a treatment, some silicon species are selectively removed from the zeolite frameworks, thus increasing the density of the tetrahedral Al sites. The invention concerns also the use of the thus obtained zeolites for the removal of Ca and Mg ions from hard waters.
zeolites with aqueous solutions of sodium carbonate and sodium hydroxide. With such a treatment, some silicon species are selectively removed from the zeolite frameworks, thus increasing the density of the tetrahedral Al sites. The invention concerns also the use of the thus obtained zeolites for the removal of Ca and Mg ions from hard waters.
Description
This invention relates to a method of preparing zeolite materials with enhanced ion exchange capacity and to the zeolite materials obtained thereby as well as their use for the removal of Ca and Mg ions from hard waters.
The prior art describes synthetic zeolites, different methods of preparation and the use of synthetic/natural zeolites in various adsorption/separation, ion exchange and catalytic processes. The zeolites modified according to the invention have enhanced ion exchange properties when compared with the parent zeolites.
These properties make them very suitable in all processes involving ion-exchange, particularly in the removal of Ca and Mg ions from hard waters, as discussed below.
Zeolites and related materials are very interesting porous materials whose regular tridimensional networks of micropores have led to extremely important applications in selective adsorption/separation, ion exchange and catalysis. The framework of a normal zeolite contains tetrahedral Si and Al atoms, the latter being the sites for cations that can be exchanged with others, including protons.
The Si/Al ratio of some zeolites can be increased by dealumination. Such methods include chemical treatment [acid, ammonium hexafluorosilicate (HFS), ethylenediaminetetraacetic acid, acetylacetone, etc]
and hydrothermal treatment1~6. However, these techniques were essentially applied - to zeolite ` materials with high Si/Al ratio with the intention to decrease the Al content of the zeolite surface2~6 without provoking either total or partial structural collapse. Recently, Le Van Mao et al7~9 showed that under mild and carefully controlled conditions, treatment with FS of aluminium-rich zeolites, such as A- and X-type zeolites resulted in mesoporous aluminosilicates with fairly sharp pore size distribution.
On the other hand, the Si/Al ratio of some zeolites such as the ZSM-5 zeolite can be decreased by Si leaching in the presence of hot alkali (NaOH or sodium carbonate) solutions9~11. However, severe structural collapses were reported9~11. This means that the zeolite frameworks are more or less severely damaged by these treatments. Moreover, there might be recrystallization into other zeolite structures or other species when aluminium-rich zeolites were treated with hot alkali solutions12.
Therefore, only a method of zeolite modification which is capable of lowering the Si/Al ratio, i.e., increasing the Al content or the density of the Al sites (number of sites per weight unit), without changing the tetrahedral configuration of these sites can produce materials with a higher cation exchange capacity. In fact, only the Al sites with the tetrahedral configuration correspond to the actual cation-exchange sites in a zeolite structure.
The present invention relates to such a method of zeolite modification. Surprising results are obtained with the modification of ZSM-5, Y and X zeolites by treating these zeolites with aqueous solutions of sodium carbonate under mild and severely controlled conditions. Sodium hydroxide is preferably used for adjusting the pH of the alkaline solution to the desired value which ranges from 11.5 to 13.0 (from 11.0 - to 12.5 in the suspension, i.e. in the presence of the zeolite sample) according to the Si/Al atomic ratio of the parent zeolite. The higher the Si/Al ratio of the parent zeolite, the lower is the pH value required for the treating solution. The concentration of the sodium carbonate solution varies from 0.5 to 1.5 M and preferably 0.8 M. The amount of NaOH added to adjust the pH of the solution is equivalent to preparing a solution of 0.0 to 0.5 N NaOH, preferably of 0.01 N for ZSM-5 zeolites (Si/Al ratio of parent zeolite: higher than 18) and 0.2-0.3 N for Y and X-zeolites (Si/Al ratio of 2.4 and 1.3, respectively). It is necessary to heat the suspension to 60C-90C, preferably to 80C.
Several periods of 4 h treatments may also be needed to significantly increase the content of the (tetrahedral) Al sites up to 60 % for the ZSM-5, 40 % for the Y
zeolites, and 20 % for the X-zeolite. Finally, careful washing the resulting solid with hot water is necessary to remove all the leached species.
In order to show the usefulness of the resulting materials, experiments were carried out in the presence of hard waters containing Ca and Mg ions, in an experimental set-up which reproduced the conditions existing in a washing machine.
Treatment of zeolites:
The basic procedure for sodium carbonate (SC) treatment was as follows: 5.0 g of zeolite were placed into a Teflon~ beaker containing 150 ml of 0.8 mol/liter sodium carbonate solution, the pH of which was previously adjusted to the desired value with NaOH. The suspension, under moderate stirring, was heated to 80C
for 4 h. The suspension was allowed to settle, and the liquid was then rapidly removed. A fresh volume of sodium carbonate solution was added, and the suspension was again very midly stirred at 80C for a further 4 h.
The same procedure might be repeated several times.
Then, the suspension was-filtered, and the solid was washed carefully with hot water as follows: the suspension obtained by adding 30 ml of water to 1 g of solid was heated under very mild stirring at 80C for 3 h. The suspension was allowed to settle, and the liquid was then rapidly removed. A fresh volume of water was added, and the suspension was again mildly stirred at 80C for a further 3 h. The resulting solid was then dried in an oven at 120C overnight.
(Common) Procedures for Characterizinq the zeolites materials:
Characterization techniques included the determination of: i) the chemical composition by atomic absorption spectrometry; ii) the structure and the degree of crystallinity by X-ray powder diffraction; iii) the Brunauer-Emmett-Teller (BET) and Langmuir surface area, and the mesopore-size distribution by adsorption-desorption of nitrogen (temperature of liquid nitrogen, 77K) using the Micromeretics Model ASAP 2000 and the data interpretation method of Barrett et al13; iv) the micropore size distribution by adsorption of argon (temperature of liquid argon, 87 K), using the Micromeretics Model 2000 M and the data interpretation method of Horvath and Kawazoe14; v) chemical environment of the Si component and the configuration of the Al species, using the technique of solid-state MAS (magic angle sample spinning)-NMR of 29Si and 27Al.
Tests of removal of Calcium and Maqnesium from hard water:
Prior to ion-exchange testing, the zeolites were dehydrated overnight at 120C. The ion-exchange tests were carried out as follows: the hard water (700 ml;
Ca2+= 80.2 ppm and Mg2+= 24.2 ppm) was placed in a flask containing a strong magnetic stirring bar. The flask was placed in a water bath which was heated at a constant temperature (25C) by a hot plate equipped with a magnetic stirrer which ensured a strong and constant stirring action throughout the experiment.
Homogenization of the exchange medium was one of the key factors for the data reproducibility. 1.0 g of the zeolite sample was rapidly poured into the flask. At that moment, the time was taken as zero. Every minute, a solution sample (2 ml) was taken from the flask using a fraction collector, while a reservoir kept adding water to compensate for the volume lost. The experiment was stopped after 16 min, which corresponds approximately to the residence time of the detergent in the washing machine.
The concentrations of Ca and Mg ions remaining in each sample were determined by atomic absorption and finally given in ppm.
The concentrations, Cca, of Ca2+ and CMg, of Mg2+ were plotted against time. A polynomial function (limited to degree 2, for physically meaningful purposes) was used for curve fitting:
Cca = y = a + bt + ct2 The calcium ion removal was expressed as:
IRca t%) = [CCai - CCaf]/ccai x 100 where CCai and CCaf were the initial and final concentrations (expressed in ppm) of Ca2+. CCaf was calculated from the curve by replacing t in the previous equation by 16 (min).
Magnesium ion removal (IRMg) was determined in the same way.
The total ion removal was expressed as:
IRtot (equiv. based %) = [1 - (Ccaf + CMg )/(Cca +
CMgi)] X 100 where all the concentrations are expressed in ion equivalents.
The rate of calcium removal (in ppm min~1) is equal to ZO the first derivative of the function y:
rCa = dy/dt = b + 2 ct The initial rate of calcium removal was determined by taking t = O. So, [rCa] = b (in ppm min~l).
The rate and the initial rate of magnesium removal (rMg and [rMg]) were determined in the same way.
In the drawings which illustrate the invention, FIGURE 1 illustrates the Al MAS-NMR and Si MAS-NMR
spectra of the product obtained in Example l;
FIGURE 2 illustrates the Al MAS-NMR and Si MAS-NMR
spectra of the product obtained in Example 2; and FIGURE 3 illustrates the Al MAS-NMR and Si MAS-NMR
spectra of the product obtained in Example 3.
The invention is illustrated by means of the following non-limiting examples.
ExamPle 1:
5.0 g of ZSM-5 zeolite (sodium form) having the physico-chemical properties as reported in Table 1, were treated with 0.8 M sodium carbonate/0.01 M NaOH
solution (pH of the suspension = 11.0). The total treatment time was 12 h. The product (ZSM-5/TW), washed and dried at 120C, had the structure of the ZSM-5 zeolite and exhibited the physico-chemical properties as reported in Table 1. The corresponding 27Al MAS-NMR
and 29si MAS-NMR spectra are shown in Figure 1.
ExamPle 2:
5.0 g of Na-Y zeolite (Linde)~ having the physico-chemical properties as reported in Table 1, were treated with 0.8 M sodium carbonate/0.2 M NaOH solution (pH of the suspension = 12.2). The total treatment time was 12 h. The product (Na-Y/TW), washed and dried at 120 C, had the structure of the Y zeolite and exhibited the physico-chemical properties as reported in Table 1. The corresponding 27Al MAS-NMR and 29Si MAS-NMR spectra are shown in Figure 2.
ExamPle 3:
5.0 g of Na-X zeolite (Linde)~ having the physico-chemical properties as reported in Table 1, weretreated with 0.8 M sodium carbonate/0.3 M NaOH solution 212531q (pH of the suspension = 12.5). The total treatment time was 12 h. The product (Na-X/TW), washed and dried at 120C, had the structure of the X zeolite and exhibited the physico-chemical properties as reported in Table 1.
The corresponding 27Al MAS-NMR and 29Si MAS-NMR spectra are shown in Figure 3.
ExamPles 4 and 5:
Parent zeolites (Na-Y and Na-X, powder form) were submitted to the ion-exchange testing in the presence of the hard water, as previously described. The computed results of such tests are reported in Table 2.
Examples 6 and 7:
The products of Example 2 (Na-Y/TW) and Example 3 (Na-X/TW), respectively, were submitted to the ion-exchange testing in the presence of the hard water, as previously described. The computed results of such tests are reported in Table 2.
Example 8:
A sample of Na-A (Linde~, powder form, Si/Al = 1.00, pore size = 0.42 nm and CEC = 7.16 mequiv./g) was submitted to the ion-exchange testing in the presence of the hard water, as previously described. The result is reported in Table 2.
i) The removal of silicon from siliceous zeolites using sodium carbonate aqueous solution in very well-defined concentration leads to a significant decrease of the Si/Al ratio (Table l). However, the original structure ~ 2125314 and the surface area are essentially preserved. The average size of micropores decreases slightly, indicating that the Si removal is followed by some sort of "healing" process which results in slightly narrower zeolite micropores.
ii) All the aluminium atoms remain in the tetrahedral configuration, i.e. the signal I corresponding to Al (III) (Figures 1-3, A-l and A-2) is absent in the parent and the modified zeolites. This means that the ion-exchange capacity of the zeolite increases with such a treatment.
iii) Sodium carbonate ensures the slow release of base to the reaction medium during the treatment. However, sodium hydroxide present in the treatment suspension in relatively small amounts, provides the minimum of basicity which is required to start the selective Si removal. The more siliceous the zeolite, the lower the amount of NaOH required for such an initiation phase, and then, the easier the Si removal. However, if a too great alkalinity is used for the treatment, the zeolite structure may undergo a partial, and even a total, collapse which results in more or less amorphous materials with no commercial use.
iv) Testing with hard water shows that (Table 2): -a) the Na-A zeolite, currently used in commercial detergent builders in lieu of polyphosphates, is very efficient in the removal of Ca+2, owing to its high cation exchange capacity (CEC). However, this zeolite is not efficient in the removal of Mg+2. This is due to its narrow pore size (0.42 nm, Table 1) which can hardly accept the relatively large hydrated Mg ion. In fact, Mg is known to form complex ions with water -molecules by solvatation.
b) the Na-Y and Na-X are more efficient in the Mg+2 removal owing to their larger size (0.74 nm, Table 1).
However, their lower CEC can not provide the same level of ion removal as with the Na-A.
c) Na-X modified according to the method of the present invention (sample Na-X/TW), shows a higher efficiency in the ion removal from hard water than the Na-A (Table 2). Moreover, the initial rates of (Ca and Mg) removal are higher than those of the commercial Na-A.
~NCES
[1] D.W. Breck, in Zeolite Molecular Sieves, Structure, Chemistry and Use, Wiley, New York, lg74, p. 483.
The prior art describes synthetic zeolites, different methods of preparation and the use of synthetic/natural zeolites in various adsorption/separation, ion exchange and catalytic processes. The zeolites modified according to the invention have enhanced ion exchange properties when compared with the parent zeolites.
These properties make them very suitable in all processes involving ion-exchange, particularly in the removal of Ca and Mg ions from hard waters, as discussed below.
Zeolites and related materials are very interesting porous materials whose regular tridimensional networks of micropores have led to extremely important applications in selective adsorption/separation, ion exchange and catalysis. The framework of a normal zeolite contains tetrahedral Si and Al atoms, the latter being the sites for cations that can be exchanged with others, including protons.
The Si/Al ratio of some zeolites can be increased by dealumination. Such methods include chemical treatment [acid, ammonium hexafluorosilicate (HFS), ethylenediaminetetraacetic acid, acetylacetone, etc]
and hydrothermal treatment1~6. However, these techniques were essentially applied - to zeolite ` materials with high Si/Al ratio with the intention to decrease the Al content of the zeolite surface2~6 without provoking either total or partial structural collapse. Recently, Le Van Mao et al7~9 showed that under mild and carefully controlled conditions, treatment with FS of aluminium-rich zeolites, such as A- and X-type zeolites resulted in mesoporous aluminosilicates with fairly sharp pore size distribution.
On the other hand, the Si/Al ratio of some zeolites such as the ZSM-5 zeolite can be decreased by Si leaching in the presence of hot alkali (NaOH or sodium carbonate) solutions9~11. However, severe structural collapses were reported9~11. This means that the zeolite frameworks are more or less severely damaged by these treatments. Moreover, there might be recrystallization into other zeolite structures or other species when aluminium-rich zeolites were treated with hot alkali solutions12.
Therefore, only a method of zeolite modification which is capable of lowering the Si/Al ratio, i.e., increasing the Al content or the density of the Al sites (number of sites per weight unit), without changing the tetrahedral configuration of these sites can produce materials with a higher cation exchange capacity. In fact, only the Al sites with the tetrahedral configuration correspond to the actual cation-exchange sites in a zeolite structure.
The present invention relates to such a method of zeolite modification. Surprising results are obtained with the modification of ZSM-5, Y and X zeolites by treating these zeolites with aqueous solutions of sodium carbonate under mild and severely controlled conditions. Sodium hydroxide is preferably used for adjusting the pH of the alkaline solution to the desired value which ranges from 11.5 to 13.0 (from 11.0 - to 12.5 in the suspension, i.e. in the presence of the zeolite sample) according to the Si/Al atomic ratio of the parent zeolite. The higher the Si/Al ratio of the parent zeolite, the lower is the pH value required for the treating solution. The concentration of the sodium carbonate solution varies from 0.5 to 1.5 M and preferably 0.8 M. The amount of NaOH added to adjust the pH of the solution is equivalent to preparing a solution of 0.0 to 0.5 N NaOH, preferably of 0.01 N for ZSM-5 zeolites (Si/Al ratio of parent zeolite: higher than 18) and 0.2-0.3 N for Y and X-zeolites (Si/Al ratio of 2.4 and 1.3, respectively). It is necessary to heat the suspension to 60C-90C, preferably to 80C.
Several periods of 4 h treatments may also be needed to significantly increase the content of the (tetrahedral) Al sites up to 60 % for the ZSM-5, 40 % for the Y
zeolites, and 20 % for the X-zeolite. Finally, careful washing the resulting solid with hot water is necessary to remove all the leached species.
In order to show the usefulness of the resulting materials, experiments were carried out in the presence of hard waters containing Ca and Mg ions, in an experimental set-up which reproduced the conditions existing in a washing machine.
Treatment of zeolites:
The basic procedure for sodium carbonate (SC) treatment was as follows: 5.0 g of zeolite were placed into a Teflon~ beaker containing 150 ml of 0.8 mol/liter sodium carbonate solution, the pH of which was previously adjusted to the desired value with NaOH. The suspension, under moderate stirring, was heated to 80C
for 4 h. The suspension was allowed to settle, and the liquid was then rapidly removed. A fresh volume of sodium carbonate solution was added, and the suspension was again very midly stirred at 80C for a further 4 h.
The same procedure might be repeated several times.
Then, the suspension was-filtered, and the solid was washed carefully with hot water as follows: the suspension obtained by adding 30 ml of water to 1 g of solid was heated under very mild stirring at 80C for 3 h. The suspension was allowed to settle, and the liquid was then rapidly removed. A fresh volume of water was added, and the suspension was again mildly stirred at 80C for a further 3 h. The resulting solid was then dried in an oven at 120C overnight.
(Common) Procedures for Characterizinq the zeolites materials:
Characterization techniques included the determination of: i) the chemical composition by atomic absorption spectrometry; ii) the structure and the degree of crystallinity by X-ray powder diffraction; iii) the Brunauer-Emmett-Teller (BET) and Langmuir surface area, and the mesopore-size distribution by adsorption-desorption of nitrogen (temperature of liquid nitrogen, 77K) using the Micromeretics Model ASAP 2000 and the data interpretation method of Barrett et al13; iv) the micropore size distribution by adsorption of argon (temperature of liquid argon, 87 K), using the Micromeretics Model 2000 M and the data interpretation method of Horvath and Kawazoe14; v) chemical environment of the Si component and the configuration of the Al species, using the technique of solid-state MAS (magic angle sample spinning)-NMR of 29Si and 27Al.
Tests of removal of Calcium and Maqnesium from hard water:
Prior to ion-exchange testing, the zeolites were dehydrated overnight at 120C. The ion-exchange tests were carried out as follows: the hard water (700 ml;
Ca2+= 80.2 ppm and Mg2+= 24.2 ppm) was placed in a flask containing a strong magnetic stirring bar. The flask was placed in a water bath which was heated at a constant temperature (25C) by a hot plate equipped with a magnetic stirrer which ensured a strong and constant stirring action throughout the experiment.
Homogenization of the exchange medium was one of the key factors for the data reproducibility. 1.0 g of the zeolite sample was rapidly poured into the flask. At that moment, the time was taken as zero. Every minute, a solution sample (2 ml) was taken from the flask using a fraction collector, while a reservoir kept adding water to compensate for the volume lost. The experiment was stopped after 16 min, which corresponds approximately to the residence time of the detergent in the washing machine.
The concentrations of Ca and Mg ions remaining in each sample were determined by atomic absorption and finally given in ppm.
The concentrations, Cca, of Ca2+ and CMg, of Mg2+ were plotted against time. A polynomial function (limited to degree 2, for physically meaningful purposes) was used for curve fitting:
Cca = y = a + bt + ct2 The calcium ion removal was expressed as:
IRca t%) = [CCai - CCaf]/ccai x 100 where CCai and CCaf were the initial and final concentrations (expressed in ppm) of Ca2+. CCaf was calculated from the curve by replacing t in the previous equation by 16 (min).
Magnesium ion removal (IRMg) was determined in the same way.
The total ion removal was expressed as:
IRtot (equiv. based %) = [1 - (Ccaf + CMg )/(Cca +
CMgi)] X 100 where all the concentrations are expressed in ion equivalents.
The rate of calcium removal (in ppm min~1) is equal to ZO the first derivative of the function y:
rCa = dy/dt = b + 2 ct The initial rate of calcium removal was determined by taking t = O. So, [rCa] = b (in ppm min~l).
The rate and the initial rate of magnesium removal (rMg and [rMg]) were determined in the same way.
In the drawings which illustrate the invention, FIGURE 1 illustrates the Al MAS-NMR and Si MAS-NMR
spectra of the product obtained in Example l;
FIGURE 2 illustrates the Al MAS-NMR and Si MAS-NMR
spectra of the product obtained in Example 2; and FIGURE 3 illustrates the Al MAS-NMR and Si MAS-NMR
spectra of the product obtained in Example 3.
The invention is illustrated by means of the following non-limiting examples.
ExamPle 1:
5.0 g of ZSM-5 zeolite (sodium form) having the physico-chemical properties as reported in Table 1, were treated with 0.8 M sodium carbonate/0.01 M NaOH
solution (pH of the suspension = 11.0). The total treatment time was 12 h. The product (ZSM-5/TW), washed and dried at 120C, had the structure of the ZSM-5 zeolite and exhibited the physico-chemical properties as reported in Table 1. The corresponding 27Al MAS-NMR
and 29si MAS-NMR spectra are shown in Figure 1.
ExamPle 2:
5.0 g of Na-Y zeolite (Linde)~ having the physico-chemical properties as reported in Table 1, were treated with 0.8 M sodium carbonate/0.2 M NaOH solution (pH of the suspension = 12.2). The total treatment time was 12 h. The product (Na-Y/TW), washed and dried at 120 C, had the structure of the Y zeolite and exhibited the physico-chemical properties as reported in Table 1. The corresponding 27Al MAS-NMR and 29Si MAS-NMR spectra are shown in Figure 2.
ExamPle 3:
5.0 g of Na-X zeolite (Linde)~ having the physico-chemical properties as reported in Table 1, weretreated with 0.8 M sodium carbonate/0.3 M NaOH solution 212531q (pH of the suspension = 12.5). The total treatment time was 12 h. The product (Na-X/TW), washed and dried at 120C, had the structure of the X zeolite and exhibited the physico-chemical properties as reported in Table 1.
The corresponding 27Al MAS-NMR and 29Si MAS-NMR spectra are shown in Figure 3.
ExamPles 4 and 5:
Parent zeolites (Na-Y and Na-X, powder form) were submitted to the ion-exchange testing in the presence of the hard water, as previously described. The computed results of such tests are reported in Table 2.
Examples 6 and 7:
The products of Example 2 (Na-Y/TW) and Example 3 (Na-X/TW), respectively, were submitted to the ion-exchange testing in the presence of the hard water, as previously described. The computed results of such tests are reported in Table 2.
Example 8:
A sample of Na-A (Linde~, powder form, Si/Al = 1.00, pore size = 0.42 nm and CEC = 7.16 mequiv./g) was submitted to the ion-exchange testing in the presence of the hard water, as previously described. The result is reported in Table 2.
i) The removal of silicon from siliceous zeolites using sodium carbonate aqueous solution in very well-defined concentration leads to a significant decrease of the Si/Al ratio (Table l). However, the original structure ~ 2125314 and the surface area are essentially preserved. The average size of micropores decreases slightly, indicating that the Si removal is followed by some sort of "healing" process which results in slightly narrower zeolite micropores.
ii) All the aluminium atoms remain in the tetrahedral configuration, i.e. the signal I corresponding to Al (III) (Figures 1-3, A-l and A-2) is absent in the parent and the modified zeolites. This means that the ion-exchange capacity of the zeolite increases with such a treatment.
iii) Sodium carbonate ensures the slow release of base to the reaction medium during the treatment. However, sodium hydroxide present in the treatment suspension in relatively small amounts, provides the minimum of basicity which is required to start the selective Si removal. The more siliceous the zeolite, the lower the amount of NaOH required for such an initiation phase, and then, the easier the Si removal. However, if a too great alkalinity is used for the treatment, the zeolite structure may undergo a partial, and even a total, collapse which results in more or less amorphous materials with no commercial use.
iv) Testing with hard water shows that (Table 2): -a) the Na-A zeolite, currently used in commercial detergent builders in lieu of polyphosphates, is very efficient in the removal of Ca+2, owing to its high cation exchange capacity (CEC). However, this zeolite is not efficient in the removal of Mg+2. This is due to its narrow pore size (0.42 nm, Table 1) which can hardly accept the relatively large hydrated Mg ion. In fact, Mg is known to form complex ions with water -molecules by solvatation.
b) the Na-Y and Na-X are more efficient in the Mg+2 removal owing to their larger size (0.74 nm, Table 1).
However, their lower CEC can not provide the same level of ion removal as with the Na-A.
c) Na-X modified according to the method of the present invention (sample Na-X/TW), shows a higher efficiency in the ion removal from hard water than the Na-A (Table 2). Moreover, the initial rates of (Ca and Mg) removal are higher than those of the commercial Na-A.
~NCES
[1] D.W. Breck, in Zeolite Molecular Sieves, Structure, Chemistry and Use, Wiley, New York, lg74, p. 483.
[2] G.W. Skeels and D.W. Breck, Proc. IV International Zeolite Conference, D. Olson and A. Bisio, Butterworths, Guilford, 1984, p.87.
[3] Q.L. Wang, G. Gianetto and M. Guisnet, Zeolites, 10, 1990, 301.
[4] G.W. Skeels and E.M. Flanigen, in Zeolites: Facts, Figures, Future, Studies in Surface Science and Catalysis, Vol. 40 Part A, P.A. Jacobs and R.A. van Santen, Elsevier, Amsterdam, 1989, p.331 and references cited therein.
[5] G.T. Kerr, J.N. Miale and R.J. Mikovsky, US Pat.
3 493 519, 1970.
3 493 519, 1970.
[6] P.E. Pickert, US Pat. 3 640 681, 1972.
[7] R. Le Van Mao, N.T.C. Vo, B. Sjiariel and G. Denes, 9th International Zeolite Conference, J.B. Higgins, R.
von Ballmoos and M.M.J. Treacy, Butterworth-Heinemann, Stoneham, MA, 1992, RP 263.
von Ballmoos and M.M.J. Treacy, Butterworth-Heinemann, Stoneham, MA, 1992, RP 263.
[8] R. Le Van Mao, N.T.C. Vo, B. Sjiariel and G. Denes, 212531~
J. Mater. Chem., 2, 1992, 565.
J. Mater. Chem., 2, 1992, 565.
[9] R. Le Van Mao, J.A. Lavigne, B. Sjiariel and C.H.
Langford, J. Mater. Chem. 3, 1993, 679.
Langford, J. Mater. Chem. 3, 1993, 679.
[10] A. Cizmek, L. Komunjer, B. Subotic, R. Aiello, F.
Crea and A. Nastro, 9th International Zeolite Conference, J.B. Higgins, R. von Ballmoos and M.M.
Treacy, Butterworth-Heinemann, Stoneham, MA, 1992, RP
247.
Crea and A. Nastro, 9th International Zeolite Conference, J.B. Higgins, R. von Ballmoos and M.M.
Treacy, Butterworth-Heinemann, Stoneham, MA, 1992, RP
247.
[11] a) R.M. Dessau, E.W. Valyocsik and N.H. Goeke, 9th International Zeolite Conference, J.B. Higgins, R. von Ballmoos and M.M. Treacy, Butterworth-Heinemann, 1992, RP 96; b) R.M. Dessau, E.W. Valyocsik and N.H. Goeke, Zeolites, 12, 1992, 776.
[12] D.W. Breck, in Zeolite Molecular Sieves, Structure, Chemistry and Use, Wiley, New York, 1974, p.
504.
2125~14 E~
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.
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,~ o o~
a~
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E~
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--~ 00, 1 o O ~ O u~ ~D
Z, o ~ o~
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o ~ . . . . .
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~ a~ a' a.
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~ a~
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.,1 ~ ' ' ' ' ' ~q ~ ~ ~ ~o a~ o ~ o ~ _ N
~1 ~
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O _~ _ U
N a) rl N
Z V u rn N ~-1 0 ~ -I ~I D
O ~ -3 O;
~ Q ~ 3 0 1 1 1~ 0 ~ ~ ~ r~
Z ~ m ~
U~ o a degree of crystallinity, DC = 100 % for all parent zeolites. b by adsorption of nitrogen. c Based on the surface area (nitrogen sorption). d Average value (in nm) as determined by adsorption of Ar. e Average value (in nm) as determined by adsorption of nitrogen.
f cation exchange capacity (dehydrated form expressed in mequiv./g) based on the Al content and the information given by the 27Al MAS-NMR.
.
o Z ~ ~
3 U~
~ ~1 u~ ~ O ~
Z
, -- X CoU~
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I
o r~
o ~ ~ ~ o~
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Z
'I ~
~ o o --i Z ~o ~D
HO
a) ~
.~ o o O ~ V ~ V
X
E-l El~ l! 1-- H H
U~
FIGURE CAPTIONS
Fiqure 1 27Al MAS-NMR spectra [chemical shift with respect to Al(OH)63+] of: (A-l) parent ZSM-5 and (A-2) ZSM-5/TW; and 29Si MAS-NMR spectra [chemical shift with respect to tetramethyl silane or TMS] of: (B-1) parent ZSM-5 and (B-2) ZSM-5/TW.
Figure 2 27A1 MAS-NMR spectra of: (A-1) parent Na-Y
and (A-2) Na-Y/TW; and 29Si MAS-NMR spectra of: (B-1) parent Na-Y and (B-2) Na-Y/TW (see Fig.1 for other details).
Fiqure 3 27Al MAS-NMR spectra of: (A-l) parent Na-X
and (A-2) Na-X/TW; and 29Si MAS-NMR spectra of: (B-l) parent Na-X ànd (B-2) Na-X/TW (see Fig. 1 for other details).
504.
2125~14 E~
X o o o~ ~ ,~ U~ I
.
Z --I oo u~ oo O ~O O ~n 1`
,~ o o~
a~
~ ~ o ~ ~ ~ el~
Z
--I o 1~ ~o ~ o I
o ~ ~ o~
E~
a) ~ u~ 00 ,. . . . . .
--~ 00, 1 o O ~ O u~ ~D
Z, o ~ o~
~q U~
I dl O ~ r~
o ~ . . . . .
C~ Z ~ --t O ~ D I`
~ a~ a' a.
O E~
~ a~
a) IU~ O ~ U O
.,1 ~ ' ' ' ' ' ~q ~ ~ ~ ~o a~ o ~ o ~ _ N
~1 ~
~1 o O ~ O o o o In o .,1~ _t o ~ Ul E3 ~ tr~ ~
O _~ _ U
N a) rl N
Z V u rn N ~-1 0 ~ -I ~I D
O ~ -3 O;
~ Q ~ 3 0 1 1 1~ 0 ~ ~ ~ r~
Z ~ m ~
U~ o a degree of crystallinity, DC = 100 % for all parent zeolites. b by adsorption of nitrogen. c Based on the surface area (nitrogen sorption). d Average value (in nm) as determined by adsorption of Ar. e Average value (in nm) as determined by adsorption of nitrogen.
f cation exchange capacity (dehydrated form expressed in mequiv./g) based on the Al content and the information given by the 27Al MAS-NMR.
.
o Z ~ ~
3 U~
~ ~1 u~ ~ O ~
Z
, -- X CoU~
~q ~ Z ~D
I
o r~
o ~ ~ ~ o~
o ~ ~ ~
Z
'I ~
~ o o --i Z ~o ~D
HO
a) ~
.~ o o O ~ V ~ V
X
E-l El~ l! 1-- H H
U~
FIGURE CAPTIONS
Fiqure 1 27Al MAS-NMR spectra [chemical shift with respect to Al(OH)63+] of: (A-l) parent ZSM-5 and (A-2) ZSM-5/TW; and 29Si MAS-NMR spectra [chemical shift with respect to tetramethyl silane or TMS] of: (B-1) parent ZSM-5 and (B-2) ZSM-5/TW.
Figure 2 27A1 MAS-NMR spectra of: (A-1) parent Na-Y
and (A-2) Na-Y/TW; and 29Si MAS-NMR spectra of: (B-1) parent Na-Y and (B-2) Na-Y/TW (see Fig.1 for other details).
Fiqure 3 27Al MAS-NMR spectra of: (A-l) parent Na-X
and (A-2) Na-X/TW; and 29Si MAS-NMR spectra of: (B-l) parent Na-X ànd (B-2) Na-X/TW (see Fig. 1 for other details).
Claims (8)
1. Method for preparing zeolite materials with enhanced ion exchange capacity, which comprises treating ZSM-5, Y and X zeolites with a solution of sodium carbonate, at a temperature between about 60 and 90°C, for a time sufficient to significantly increase Al sites in said ZSM-5, Y and X zeolites, said solution of sodium carbonate being at a concentration between about 0.5 and 1.5M, and having a pH which ranges from about 11.5 to 13.0, said method also including the step of removing liquid from the treated zeolite materials, followed by washing with hot water to remove all leached species, and drying.
2. Method according to claim 1, wherein the zeolites are treated with the sodium carbonate solution by stirring at a temperature of about 80°C.
3. Method according to claim 1, wherein the pH of the sodium carbonate solution is adjusted by adding sodium hydroxide thereto.
4. Method according to claim 1, wherein the zeolite material is ZSM-5 and the treatment is carried out for a time sufficient to increase Al sites up to 60%.
5. Method according to claim 1, wherein the zeolite material is a Y-zeolite and the treatment is carried out for a time sufficient to increase Al sites up to 40%.
6. Method according to claim 1, wherein the zeolite material is an X-zeolite and the treatment is carried out for a time sufficient to increase Al sites up to 20%.
7. Method according to claim 1, further comprising drying the treated zeolite materials at a temperature of about 120°C.
8. ZSM-5, Y and X zeolites having enhanced ion exchange capacity, produced by the method of any one of claims 1 to 7.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002125314A CA2125314A1 (en) | 1994-06-07 | 1994-06-07 | Zeolite materials with enhanced ion exchange capacity |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002125314A CA2125314A1 (en) | 1994-06-07 | 1994-06-07 | Zeolite materials with enhanced ion exchange capacity |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2125314A1 true CA2125314A1 (en) | 1995-12-08 |
Family
ID=4153752
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002125314A Abandoned CA2125314A1 (en) | 1994-06-07 | 1994-06-07 | Zeolite materials with enhanced ion exchange capacity |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2125314A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100377776C (en) * | 2006-10-17 | 2008-04-02 | 太原理工大学 | Method for preparing molecular sieve absorbent with high adsorption capacity |
| CN106315614A (en) * | 2016-08-29 | 2017-01-11 | 霍普科技（天津）股份有限公司 | Preparation method of modified Y-type molecular sieve |
-
1994
- 1994-06-07 CA CA002125314A patent/CA2125314A1/en not_active Abandoned
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100377776C (en) * | 2006-10-17 | 2008-04-02 | 太原理工大学 | Method for preparing molecular sieve absorbent with high adsorption capacity |
| CN106315614A (en) * | 2016-08-29 | 2017-01-11 | 霍普科技（天津）股份有限公司 | Preparation method of modified Y-type molecular sieve |
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