EP2438010A1

EP2438010A1 - Zeolite 4a with new morphological properties, its synthesis and use

Info

Publication number: EP2438010A1
Application number: EP10725495A
Authority: EP
Inventors: Boris Subotic; Cleo Kosanovic; Sanja Bosnar; Tatjana Antonic Jelic; Josip Bronic
Original assignee: Barchem LLC
Current assignee: Barchem LLC
Priority date: 2009-05-06
Filing date: 2010-05-04
Publication date: 2012-04-11
Also published as: WO2010128342A1

Abstract

The present invention discloses zeolite 4A with molar oxide composition of 1.017Na₂O • Al₂O₃ • 1.973SiO₂ • 4.725H₂O that has external specific surface area of 2.37-4.43 m²/g according to Brunauer-Emmett-Teller (BET) isotherm; and - external surface roughness as indicated by the ratio of RSSA/GSSA within the range of 2.58-2.81. Particles size of zeolite 4A are ranging from 0.4 μm to 5 μm, wherein 50% of all particles size are smaller than 1.45 μm, and 90% of all particles size are smaller than 2.35 μm. Invention can be used as detergent builder, ion-exchange agent, sorbent, and carrier of organic molecules.

Description

ZEOLITE 4A WITH NEW MORPHOLOGICAL PROPERTIES, ITS SYNTHESIS AND USE

DESCRIPTION

THE FIELD OF THE INVENTION

The present invention relates to a zeolite 4A with new morphological properties, its synthesis and use.

THE SUMMARY OF THE INVENTION

The present invention solves technical problem of improved zeolite 4A with new morphological properties, more precisely, which is characterized by spheroidal-shape, ,,face-less" particles (zeolite FLA) . The latter exhibits improved adsorption properties due to high external surface roughness and thus, significantly enhanced external specific surface area (SSA) as well as increased rate of ionic exchange. Thanks to this property, the product provides an improved alternative to existing, commercially available zeolite A as detergent builder, absorbents and carrier for active substances.

The invention also discloses a synthesis of zeolite FLA, as well as its potential uses.

PRIOR ART

Zeolites are a clas s o f aluminosilicates of general formula :

(Mⁿ⁺) _x/n [ (AlO₂ ) _x ( SiO₂ ) _y] ^« fflH₂0 . where M is metal cation (like Na⁺) ; molar ratio of silicon to aluminum, y:x is between 1:1 to >100:l; and number of crystalline water m is from 0 to >100.

Most widely employed zeolite is zeolite 4A of general formula (usually expressed as molar ratio of corresponding metal oxide, aluminum oxide and silicon dioxide) :

Na₂O • Al₂O₃ • 2SiO₂ • 4.5H₂O

The latter is mainly used as detergent ,,builder" with major function as ion-exchange (water softening) agent. Zeolite 4A binds calcium (Ca²⁺) and magnesium (Mg²⁺) ions from ordinary tap water making it soft, releasing equivalent amounts of sodium (Na⁺) cations, and thus promotes overall washing process.

Synthesis of zeolites is generally based on crystallization from aluminosilicate hydrogels (hydrothermal synthesis) . The latter are obtained by mixing of sodium silicate and sodium aluminosilicate solutions. The synthesis of zeolites is influenced by a numerous parameters such as: molar ratio of reactants Na₂O: Al₂O₃: SiO₂: H₂O, time and temperature of crystallization, intensity and kind of stirring of intermediate aluminosilicate gel, presence or absence and concentration of additional cations, alkalinity, and many others [T. Antonic, B. Subotic, N. Stubicar: Influence of gel properties on the crystallization of zeolites: Part 1: Influence of alkalinity during gel preparation on the kinetics of nucleation of zeolite A, Zeolites 18 (1997) 291-300; V. Grba, Z. Soljic: Low silica synthetic faujasite X and synthetic zeolite A formation from sodium-aluminosilicate gels, Bull. Groupe Franc. Argiles XXVII 167-175; RU 2003 122223 A; 0. Andac, M. Tather, A. Sirkecioglu, I. Ece, A. Erdem-Senatalar : Effect of ultrasound on zeolite A synthesis, Micropor. Mesopor. Mater. 79 (2005) 225-233] .

Industrial production usually involves batch- or continuous-type mixing of sodium silicate and sodium aluminate solutions yielding a homogeneous aluminosilicate hydrogel. The latter is subsequently subjected to crystallization process with minimal stirring giving zeolite A [D. Bretaudeau, F. Delprato, M. Malassis: Preparation of crystalline 4A zeolites, US 5,474,753 (1995); J. Metzger: Process for preparing crystalline sodium silico-aluminate of zeolite A type, GB 2051024A (1980); J. Deabriges: Industrial process for continuous production of zeolite A, US 4,314,979 (1979)]. Thus obtained commercially available zeolite 4A is of cubic shape particles, usually of median size 4-5 μm.

To improve ion-exchange efficacy of detergent-grade zeolite 4A, a process for production of smaller median particles size product of 2 μm was published [J. A. Kostinko: Zeolites of small particles size, GB 2040900 (1979) ] .

Further improvement was introduced by zeolite P with maximum alumina content [,,zeolite MAP": G. T. Brown, T. J. Osinga, M. J. Parkington, A. T. Steel, EP0384070 A2 (1988) Unilever] . Effective calcium binding capacity of zeolite MAP is at least 145 mg CaO/g, preferably at least 150 mg CaO/g. Zeolite MAP exchanges calcium more rapidly and binds it more firmly than zeolite 4A does, especially at low temperatures. Its magnesium exchange is also more rapid than that of zeolite 4A.

Commercially available zeolite 4A appears in cubic crystals with sharp edges and apexes (see Fig.l). This characteristic is highly unfavorable for use in the detergent formulations because of sharp apexes that cause:

(i) remaining of zeolite in the micropores of textile materials, and thus an increase of incrustations on fabrics; and

(ii) abrasion of some parts of washing machine [H. G. Smolka and J. M. Schwuger, Colloid Polym. Sci. 256 (1978) 270-277)].

In this manner producers of zeolite A tend to adopt the synthesis procedure to obtain zeolite crystals with truncated edges and apexes, similar to these shown in Fig.2 [DE 2412838 (Henkel) ; G. Smolka and J. M. Schwuger, Colloid Polym. Sci. 256 (1978) 270] .

Japanese authors have published ,,spherical" type of zeolite 4A, but as can be seen from the SEM picture of the product obtained by this procedure, this invention actually involves a mixture of cubic particles with sharp edges and apexes, cubic particles with truncated edges, cubic particles with rounded edges and apexes, amorphous aluminosilicate in different proportions and sizes and their aggregates. This was presumably caused by influence of sodium chloride (NaCl) used (beside sodium aluminate and sodium silicate solutions) in their synthesis as ion-adjusting agent in preparation of corresponding aluminosilicate gel [M. Aoki, M. Keiko: Production of A type zeolite, JP2793376 (1991) Kobe Steel Ltd.].

In modern compact detergent powders zeolite is not only an ion- exchanger, but also a carrier of active washing components, especially non-ionic surfactants. In this manner production of this kind of detergent powders demands the builders having not only high ion-exchange capacity and efficacy (for calcium and magnesium cations) , but also a high adsorption capacity for non-ionic surfactants .

The technical problem of high adsorption capacity of zeolite 4A (with preserved high calcium ion-exchanging capacity and efficacy) by the present invention is solved on a new and more efficient manner as will be demonstrated in detailed description of the invention.

DETAILED DESCRIPTION OF THE INVENTION

We have been found that under some specific synthesis conditions, the particles of the product (zeolite 4A) completely loss the crystal faces followed by roughening of particle surfaces which causes significant increasing of external surface area. Thus obtained product was named "face-less" zeolite 4A (zeolite FLA) .

Practically, a shape of zeolite crystals changes from those well known in the art as either cubic (see Fig.l) or eventually cubic with truncated (see Fig.2) or rounded apexes and edges (see Fig.3), into spheroidal one (see Fig.4). This results in significantly increased external surface area, increased reaction yield, enhanced adsorption ability and increased exchange rate of calcium and magnesium ions from solutions of the FLA type of zeolite 4A.

Brief description of figures:

Figure 1: SEM photograph of typical cubic crystals of zeolite 4A having sharp edges and apexes (prior art) .

Figure 2: SEM photograph of cubic crystals of zeolite 4A with truncated edges and apexes (prior art) .

Figure 3: SEM photograph of cubic crystals of zeolite 4A with rounded edges and apexes (prior art) .

Figure 4: SEM photograph of zeolite FLA particles magnified for (a) 10.00Ox and (b) for 33.00Ox (invention).

Figure 5: Crystal size distributions by number (A) and by volume (B) of zeolite A crystals having the regular cubic shape with sharp edges and apexes (see Fig.l). N₀ and V₀ are the number and volume percentage of the particles (crystals) having the equivalent spherical diameter D.

Figure 6: Crystal size distributions by number (A) and by volume (B) of zeolite A crystals having cubic shape with truncated edges and apexes (see Fig.2) . W₀ and V₀ are the number and volume percentage of the particles (crystals) having the equivalent spherical diameter D. Figure 7: Crystal size distributions by number (A) and by volume (B) of zeolite A crystals having cubic shape with rounded edges and apexes (see Fig.3) . N₀ and V₀ are the number and volume percentage of the particles (crystals) having the equivalent spherical diameter D.

Figure 8: Crystal size distributions by number (A) and by volume (B) of zeolite FLA particles (see Fig.4) of sample FLA-I. W₀ and V_D are the number and volume percentage of the particles (crystals) having the equivalent spherical diameter D.

Figure 9: Crystal size distributions by number (A) and by volume (B) of zeolite FLA particles (see Fig.4) of sample FLA-2. N₀ and V₀ are the number and volume percentage of the particles (crystals) having the equivalent spherical diameter D.

Figure 10: Crystal size distributions by number (A) and by volume (B) of zeolite FLA particles (see Fig.4) of sample FLA-3. W_n and V₀ are the number and volume percentage of the particles (crystals) having the equivalent spherical diameter D.

Figure 11: Schematic presentation of RSSA versus GSSA shown on the adsorption of nitrogen of (a) standard cubic zeolite A and b) zeolite FLA.

Figure 12: Scheme of a complex of non-ionic surfactant polyoxyethylene (23) laurate after adsorption onto the surface of zeolite FLA particle.

Zeolite FLA was synthesized by the following general procedure:

(i) Preparation of aluminosilicate hydrogel; The synthesis precursor is prepared by mixing of sodium aluminate solution (having appropriate chemical composition with respect to Na₂O, Al₂O₃ and H₂O) and sodium silicate solution (having appropriate chemical composition with respect to Na₂O, SiO₂ and H₂O) at temperatures (Tp) from room temperature (20⁰C) to 90⁰C. Thus obtained aluminosilicate hydrogel was characterized by the following composition (molar ratio) :

XNa₂O • Al₂O₃ • ySiO₂ • ZH₂O x/z = Na₂O/H₂O; in the range from 0.037 to 0.042; y = SiO₂/Al₂O₃; in the range from 1.2 to 1.4; y/z = SiO₂/H₂O; in the range from 0.018 to 0.032;

(ii) Crystallization of zeolite FLA; Crystallization is carried out by heating of the thus obtained aluminosilicate hydrogel at temperatures (T_R) between 65-90⁰C (T_R ≥ T_P) , under stirring, until the solid phase of gel is completely transformed into crystalline phase (zeolite) (60-135 min; depending on the chemical composition of the reaction mixture and reaction temperature, T_R) ;

(iii) Separation of zeolite: Crystallized zeolite suspended in the liquid phase (mother liquor) is separated by either centrifugation or vacuum filtration.

Separated zeolite FLA is subjected to washing with several portions of demineralized water in order to remove all residual reagents (from the mother liquor) adsorbed on the product crystals until pH of filtrate is 9-10.

(iv) Drying of washed zeolite FLA is carried out at 80-150⁰C for up to 24 h.

The progress of the reaction (crystallization process) was monitored by optical microscope (magnification of 100Ox) , and finally by X-ray diffraction (XRD) of powdered samples. The crystallization is finished at a time (t_R = t_R(end)) when entire amount of amorphous aluminosilicate gel is transformed into crystalline phase (zeolite) .

The synthesis of zeolite FLA proceeded smoothly giving the fully crystalline product in excellent (>95%) -to-almost quantitative utilization of reactants (calculated on starting SiO₂) .

When the crystallization was completed, isolated product was identified as zeolite 4A by: (i) X-ray diffraction (XRD) analysis;

(ii) Fourier transform infrared (FTIR) spectroscopy; and with (iii) chemical analysis of the product by atomic absorption spectroscopy (contents of SiO₂, Al₂O₃, and Na₂O) . The content of zeolitic water was determined by the mass difference before and after calcinations at 800⁰C for 2 hours.

The corresponding average chemical composition of zeolite FLA from the present invention is as follows:

1.017Na₂O • Al₂O₃ • 1.973SiO₂ • 4.725H₂O

Shape of zeolite 4A particles (crystals) is determined from scanning- electron microscope (SEM) photographs of appropriate samples. Zeolite FLA was compared with all known morphological forms of zeolite 4A:

(i) zeolite 4A of cubic shape crystals with sharp edges and apexes (see Fig.1) ;

(ii) zeolite 4A of cubic shape crystals with truncated edges and apexes (see Fig.2); and

(iii) zeolite 4A of cubic shape crystals with rounded edges and apexes (see Fig.3).

Samples of these standards were prepared according to procedures developed in our laboratory (see Example 1), and observed by SEM (Figures 1-3) .

In contrast to all these known morphological forms (Figures 1-3) of zeolite 4A, the FLA type of zeolite A from the present invention is characterized by unexpected spheroidal shape of each single particle (not particles aggregates); see Figure 4. More unexpectedly, zeolite FLA is characterized by expressed external surface roughness without distinguishing crystal faces (SEM; magnification 30.00Ox).

The high external surface roughness of zeolite FLA is also indicated by unexpectedly high ratio between real specific surface area ratio

(RSSA) determined by the Brunauer-Emmett-Teller (BET) and geometrical specific surface area (GSSA) [A. Peiquey et al . , Carbon 39 (2001) 507-514; K. Kaneko, C. Ishii, Colloids and Surfaces 67 (1992) 203- 212] calculated from the corresponding crystal size distribution curves of zeolite FLA (RSSA/GSSA = 2.58-2.8; see Table 4) relative to the ratio RSSA/GSSA of the standard morphological form of zeolite 4A

(= 0.91-1.12; see Table 4). The BET method is commonly used for measurement of specific surface areas of solid substances. In the case of porous materials such as zeolites, the BET method is employed for measurement of total SSA meaning a sum of external SSA and SSA of all pores in a given sample. This kind of measurement is carried out at elevated pressures allowing gaseous adsorbate (e.g. nitrogen) to enter into the zeolite pores^.

Alternatively, the BET method offers a possibility of measuring only the external specific surface area (SSA), i.e., sum of external areas of all particles contained in unit mass of sample (without corresponding area of pores inside each particle!), if a working mode is at low pressures. This technique was used for determination of external specific surface area of samples in the present invention.

On the basis of the measured data, real external specific surface areas of the samples are calculated from BET isotherms. Results are presented in Table 1.

For comparison, all three samples of known morphological forms of cubic shape zeolite 4A (see Figures 1-3) were used as standards (see Table 1) .

Table 1. Real external specific surface area (RSSA) (BET) (calculated from the BET absorption isotherm) which corresponds to known cubic shape-based morphological forms of zeolite 4A and zeolite FLA.

External real (measured) specific surface area (RSSA) significantly depends on particles size of a given sample. Since it is practically impossible to obtain zeolite FLA and all three known cubic shape- based zeolites 4A of the same particles size distribution, comparable differences can be seen from the ratio of RSSA and geometrical specific surface area (GSSA) . In this manner one can practically exclude the differences in particles size distribution. Practically the ratio of RSSA/GSSA allows us to compare external (without those derived from internal pores) specific surface areas of samples with different particles size distributions. In this context, the ratio RSSA/GSSA represents a measure of the external surface roughness. In this invention high external surface roughness is considered to represent ratio RSSA/GSSA > 2.

In order to calculate the geometrical specific surface areas (GSSA) of samples of all three known cubic shape-based morphological forms of zeolite 4A (Figs.1-3), as well as of zeolite FLA (sample FLA-I; Fig.4), measurements of particles size distributions were carried out by laser light-scattering particle size analyzer (Mastersizer 2000) . Corresponding particles size distribution curves are given in Figures 5-7 (known zeolites 4A) , and 8 (zeolite FLA, samples FLA 1-3, Figures 8-10) .

Thus obtained particles size distribution data were used for determination of the average crystal size (L_av) , specific number of particles (N_s) , and geometrical specific surface area (GSSA) by using the equations (1-3) [Z. I. Kolar, J. J. M. Binsma, B. Subotic, J. Cryst. Growth 116 (1992) 473; B. Subotic, N. Masic, I. Smit in: B. Drzaj, S. Hocevar, S. Pejovnik (Eds.), Zeolites: Synthesis, Structure, Technology and Application, Studies in Surface Science and Catalysis No.24, Elsevier, Amsterdam (1985) 207].

G₃-YNi-L] GSSA = —^ -_T (3)

G₂-p-∑Ni-L] L = Gi¹D (Li = Gi- D₁) linear (edge length) size of crystals having the measured equivalent spherical diameter (D) (see Figs.5-10), i.e., diameter of the sphere having the same volume as the cubic particle which size is determined by the linear dimension (e.g. edge length, L) ;

Ni = number frequency of the particles (crystals) having the size L₁; p = 2 g/cm³ is the density of zeolite A;

Gi = L/D = ratio between a linear dimension (edge length, L) of a cubic particle and its (measured) equivalent spherical diameter D, (see Table 2) ;

G₂ = surface geometrical shape factor (see Table 2); G₃ = volume geometrical shape factor (see Table 2) .

Geometrical surface area is the surface area of a geometrically defined body (e.g. cube, cube with truncated edges, cube with truncated edges and apexes, sphere) having the flat level surfaces [A. Peiquey et al., Carbon 39 (2001) 507-514; K. Kaneko, C. Ishii, Colloids and Surfaces 67 (1992) 203-212] . Consequently, geometrical specific surface area is the sum of geometrical surface areas of all bodies (particles) contained in unit mass of solid, as expressed by Eq. (3).

Table 2. Numerical values of the shape factors Gi, G₂ and G₃ which correspond to zeolite 4A particles of different morphologies .

The average crystal size (L_av) , specific number of particles N₃, and geometrical specific surface area (GSSA) are calculated by equations (1-3) , using the values D₁ and N₁ from the corresponding particle size distribution by number shown in:

(i) Fig.5a for cubic crystals with sharp edges and apexes;

(ii) Fig.δA for cubic crystals with truncated edges and apexes ;

(iii) Fig.7A for cubic crystals with rounded edges and apexes;

(iv) Figs .8A, 9A and 1OA for zeolite FLA (samples FLA 1-3) as well as the appropriate numerical values of the shape factors Gi, G₂ and G₃ (see Table 2), are listed in Table 3.

Table 3. Average crystal size (L_av) , specific number of particles (N₃) , and geometrical specific surface area (GSSA) of zeolite 4A particles of different morphologies.

Thus determined geometrical specific surface area (GSSA) and previously measured values of real specific surface area (RSSA) were used for calculation of the ratio between the real (RSSA) (BET) and geometrical (GSSA) external specific surface area (Table 4). Table 4. The ratios of RSSA (BET) /GSSA between the real and geometrical external specific surface areas correspond to zeolite 4A particles of different morphologies.

The results in Table 4 show that:

(1) The ratio RSSA/GSSA of the standard samples (cube, cube with truncated edges, cube with truncated edges and apexes) do not considerably depend either on the crystal shape (see Table 4) or the corresponding crystal size distributions (see Figs. 8A-10A) . The values of RSSA/GSSA ~ 1 indicate that absorption of nitrogen is characterized by formation of mono-layer on the flat surfaces of standard samples, in accordance with BET theory.

(2) Due to high external surface roughness of the particles of zeolite FLA, the ratio RSSA/GSSA of zeolite FLA is 2.22-2.4 times higher than the ratio RSSA/GSSA of zeolite A having cubic crystals with rounded edges and apexes and 2.49-3.1 times higher than the RSSA/GSSA ratios of zeolite A sharp edges and apexes and cubic crystals with truncated edges, respectively.

This means that per unit geometrical surface area (as calculated by Eq. (3)) of zeolite FLA can be adsorbed 2.22-3.1 times more of nitrogen than per the same unit geometrical surface area of standard morphological forms of zeolite A. Or, in the other words, adsorption ability of zeolite FLA is an average 2.7 times higher than the absorption ability of standard morphological forms of zeolite A having the same geometrical specific surface area and thus, the same particles size distribution as zeolite FLA (see Fig.11)

Beside a significantly enhanced external specific surface area (SSA) caused by profound external surface roughness, zeolite FLA from the present invention unexpectedly showed improvement of efficacy (rate) of uptake of calcium (Ca²⁺) and magnesium (Mg²⁺) cations. The rate of uptake of Ca²⁺ (expressed as U_Cao) and Mg²⁺ (expressed as U_Mg0) cations during the exchange process of calcium and magnesium ions from solution with sodium ions from zeolite A is a measure of efficiency regarding the rate of ion-exchange process of zeolites. The ion- exchange process was monitored with known amounts of anhydrous zeolite sample in a solution of calcium (or magnesium) chloride also of known starting concentration, at 20 ⁰C and 65 ⁰C. Determination of remained concentrations of Ca²⁺ and Mg²⁺ cations in supernatant as a function of time were conducted by atomic absorption spectroscopy (AAS) . Then, the uptakes (U_Cao/ U_Mg0) were calculated from the difference between cation concentrations in the liquid phase before and after exchange for a time t_E. Results are shown in Tables 5-8.

Table 5. Uptake (U_Ca0) during the exchange of calcium ions from solutions with sodium ions at 20 ⁰C from: (i) zeolite A crystals having cubic shape with truncated edges and apexes (see Fig.2; Example A); (ii) zeolite A crystals having cubic shape with rounded edges and apexes (see Fig.3; Example B); and (iii) zeolite FLA (see Fig.4; Example C). t_E is time of exchange.

Table 6 . Uptake (U_Ca0) during the exchange of calcium ions from solutions with sodium ions at 65 ⁰C from: (i) zeolite A crystals having cubic shape with truncated edges and apexes (see Fig.2; Example A); (ii) zeolite A crystals having cubic shape with rounded edges and apexes (see Fig.3; Example B); and (iii) zeolite FLA (see Fig.4; Example C). t_E is time of exchange.

Table 7. Uptake (U_M90) during the exchange of magnesium ions from solutions with sodium ions at 20 ⁰C from: (i) zeolite A crystals having cubic shape with truncated edges and apexes (see Fig.2; Example A); (ii) zeolite A crystals having cubic shape with rounded edges and apexes (see Fig.3; Example B); and (iii) zeolite FLA (see Fig.4; Example C) . t_E is time of exchange.

Table 8. Uptake (U_H90) during the exchange of magnesium ions from solutions with sodium ions at 65 ⁰C from: (i) zeolite A crystals having cubic shape with truncated edges and apexes (see Fig.2; Example A); (ii) zeolite A crystals having cubic shape with rounded edges and apexes (see Fig.3; Example B); and (iii) zeolite FLA (see Fig.4; Example C) . t_E is time of exchange.

Table 5 shows that the exchange of calcium ions from solution with sodium ions from (dehydrated) zeolite FLA is very fast and efficient process; 160 mg of CaO is bounded per 1 g of zeolite in less than 3 min, even at room temperature (20 ⁰C) . Under the same conditions and in the same time (3 min) only about 110-126 mg (21-31% less) of CaO is bonded per 1 g of known morphological forms of zeolite 4A.

Increase of the exchange temperature, (to 65 ⁰C) considerably increases the rates of calcium exchange for all three samples (compare Tables 5 and 6) . Again, the exchange rate of zeolite FLA is considerably higher than the exchange rates of known morphological forms of zeolite A.

As expected, both the rate of exchange and the uptake of magnesium are lower than for calcium. Once again, the exchange rate is highest for zeolite FLA (sample C); the equilibrium uptake (r_Mg0 = U_Mg0(max)) for zeolite FLA at 20 ⁰C (approx. 60 mg MgO/g) is reached for t_E ∞ 60 min (see Table 7) , while the equilibrium uptakes for the samples A and B are not reached for t_E « 60 min, and for sample A even for 120 min. The obtained exchange rates for all the samples are more rapid at 65 ⁰C than at 20 ⁰C (compare Tables 7 and 8) . After only 2 min, a very high magnesium uptake (approx. 80 mg MgO/g) is achieved for zeolite FLA (sample C) , while this value is considerably lower for the cubic-shape zeolites 4A, 66.5 mg MgO/g (sample A) and 56.5 mg MgO/g (sample B) .

The equilibrium uptake (r_Mg0 = 85-88 mg MgO/g) for zeolite FLA (sample C) is achieved for t_E « 30 min, whilst for the cubic-shape zeolites 4A are: r_Mg0 = 75-77 mg MgO/g (sample A), and r_Mg0 = 79 mg MgO/g (sample B) for t_E w 60 min.

Calcium and magnesium binding capacities at 20 and 65 ⁰C, determined as the equilibrium uptakes (r_Ca0 = U_Cao(πιax); r_Mg0 = U_Mg0(max)) from the data in Tables 5-8, are listed in Table 9.

Table 9. Calcium (r_Ca0) and magnesium (F_Mg0) binding capacities obtained during the exchange of calcium and magnesium ions from solutions with sodium ions at 20 and 65 ⁰C from: (i) zeolite A crystals having cubic shape with truncated edges and apexes (see Fig.2; Example A); (ii) zeolite A crystals having cubic shape with rounded edges and apexes (see Fig.3; Example B); and (iii) zeolite FLA (see Fig.4; Example C).

(mg CaO/g of (mg MgO/g of dehydrated zeolite) dehydrated zeolite)

Temperature (⁰C) : 20 ⁰C 65 ⁰C 20 ⁰C 65 ⁰C Example :

A (prior art) 166 168 - 170 47 - - 49 > 76

B (prior art) 168 170 - 175 58 - - 59 79

C (invention) 167 178 - 181 63 - - 64 > 88

Although the calcium and magnesium binding capacities between the known types of zeolite A and zeolite FLA is almost the same (166-168 mg CaO/g) , the exchange rate of the latter is considerably higher than the exchange rates of known morphological forms of zeolite A (Tables 5-8) . Conclusion:

The present invention relates to the new morphological type of zeolite 4A which is characterized by spheroidal shape ,,face-less" particles (zeolite FLA) . The latter exhibits improved adsorption properties due to enhanced (through increased external surface roughness) external specific surface area (SSA). Thanks to this property, the product provides an improved alternative to existing, commercially available types of zeolite A which are cubic crystal- shape based products.

Concerning the increased external surface area of zeolite FLA, it subsequently exhibits improved adsorption properties over existing zeolites from the same class. These uses expecially involve products wherein large molecules have to be adsorbed onto the surface of zeolite FLA in order to improve technical properties of the final products .

Probably the most important field of use of zeolite FLA is in production of compact powders detergents. In this field, the zeolite FLA serves not only as ion-exchange (thus as water-softening) agent, but also as effective carrier for non-ionic surfactants, presumably due to adsorption onto very large external specific surface area of zeolite FLA (rough) particles. Adsorption process is presumably promoted by formation of complex bonds between the sodium cations (Lewis acids; which are positioned closed to the surface) and oxygen atoms (Lewis bases) from polyethyleneglycol chain of non-ionic surfactants such as ethoxylated fatty alcohols (e.g. polyethyleneglycol (23) laurate; Brij 35). Tentative structure of such complexes of zeolite FLA and adsorbing molecules (ADM) like non-ionic surfactants is shown in Figure 12.

Additionally, this particular advantage of zeolite FLA offers its wide use as efficient:

(i) sorbent (both absorbent and adsorbent) ;

(ii) carrier of other organic molecules such as various drug molecules like penicillin or acetylsalicylic acid, proteins, nucleic acids, etc., capable of forming coordination bonds (complex) with the surface of the zeolite; and as

(iii) ion-exchange agent for removal of heavy metal ions and radioisotopes from different waste solutions. EXAMPLES

General information

The X-ray diffraction patterns (XRD) of the samples were taken by a Philips PW 1820 diffractometer with vertical goniometer and CuK_α graphite radiation in the corresponding region of Braggs's angles (2θ = 5 - 50°) in steps of 0.04° and with the scan rate of 1 step/s.

Infrared transmission spectra of the samples were made by the KBr wafer technique. The spectra were recorded on an FTIR Spectrometer System 2000 FT-IR (Perkin-Elmer) .

The SEM photographs were taken by Philips XL 30 and JEOL FSM-7000F, respectively, scanning-electron microscope.

Particles (crystals) size distribution curves of the crystalline end products (zeolite A) are determined with Mastersizer 2000 (Malvern Instruments) laser light-scattering particle size analyzer.

The external specific surface areas (ESSA) of samples were measured by using Gemini 2360 Surface Area Analyzer (Micrometrics) .

Quantitative analysis of sodium (Na), aluminum (Al), and silicon (Si) in zeolite samples were performed by atomic absorption spectroscopy (AAS) by using Perkin-Elmer 3030B spectrometer.

Example 1 : Preparation of standards of cubic shape-based zeolites 4A

To obtain the samples of known morphological forms of zeolites 4A of cubic-shape crystals with sharp, truncated, and rounded edges and apexes, the aluminosilicate hydrogel precursors having the overall oxide molar batch composition:

XNa₂O • Al₂O₃ • ySiO₂ • ZH₂O x/z = Na₂O/H₂O y/z = SiO₂/H₂O y = SiO₂/Al₂O₃ with:

(i) x/z = 0.0136, y/z = 0.006, y = 2.2 for the synthesis zeolite of zeolite A with sharp edges and apexes; (ii) x/z = 0.0106, y/z = 0.0053, y = 1.3 for the synthesis zeolite of zeolite A with truncated edges;

(iii) x/z = 0.0165, y/z = 0.01, y = 1.6 for the synthesis zeolite of zeolite A with rounded edges and apexes were prepared by mixing together, at room temperature, of sodium aluminate solutions having appropriate concentrations with respect to Na₂O and Al₂O₃ and sodium silicate solutions having appropriate concentrations with respect to Na₂O and SiO₂.

Crystallizations were carried out by heating of corresponding aluminosilicate gels at elevated temperature, in the range between 80-90⁰C under stirring by propeller in a stainless-steel reaction vessel provided with a thermostated jacket and fitted with a water- cooled reflux condenser and thermometer, until the solid phase of precursor (gel) was completely transformed into crystalline phase (zeolite) . The end-points of crystallizations were determined by monitoring samples of the reaction mixture under optical microscope (at magnification of 100Ox) . Then the products were separated by filtration and washed with several portions of demineralized water until pH of filtrate reached 9-10. Products were dried at 105⁰C for 24 h. After drying, the products (zeolite 4A) appear in the form of white fine microcrystalline powder.

Thus obtained samples (standards) of known morphological forms of zeolite 4A were analyzed by XRD and FTIR. It was found that all the analyzed samples have XRD patterns and FTIR spectra characteristic for fully crystalline zeolite 4A.

SEM photographs of samples of known morphological forms of zeolite 4A are given in Figures 1-3.

Particles size distribution curves are shown in Figures 5-7; these data are also used for calculation of geometrical specific surface area (GSSA) of the samples of these standards. Results are given in Tables 2 and 3.

These samples were also used as standards for comparative measurements of the new morphological form of zeolite FLA from the present invention for BET analyses and calculations (results are given in Tables 1-4), and for determination of total uptake and efficacy (rate) of uptake of calcium (Ca²⁺) and magnesium (Mg²⁺) ions from model aqueous solutions (results are given in Tables 5-9) . Example 2: Preparation of spheroidal shape "face-less" zeolite FLA (sample FLA-I)

Zeolite FLA (sample FLA-I) was prepared by hydrothermal treatment (heating) of aluminosilicate hydrogel: XNa₂O • Al₂O₃ • ySiO₂ • ZH₂O with x/z = Na₂O/H₂O = 0.026; y/z = SiO₂/H₂O = 0.012; y = SiO₂AAl₂O₃ = 1.3 by mixing together sodium aluminate and sodium silicate solutions at 20- 25°C.

Crystallization was carried out by heating of aluminosilicate gel at 85-90⁰C under stirring for 135 min, i.e. until the solid phase of the precursor (gel) was completely transformed into crystalline phase (monitoring of samples of reaction mixture by optical microscope at magnification of 100Ox) . Then the product was separated by vacuum filtration and washed with several portions of demineralized water until pH of filtrate reached 9-10. Product was dried at 105⁰C for 24 h. After drying, the product (zeolite FLA-I) appears in the form of white fine microcrystalline powder. Utilization of reactants (because of the "excess" of Al₂O₃ in the reaction mixture, the utilization is expressed on the basis of spent SiO₂) : 95.8% calculated on starting SiO₂.

Chemical composition of zeolite FLA:

The dried solid sample of zeolite FLA was kept in a desiccator with saturated NaCl solution for 96 h.

To determine a total content of water, a part of a sample equilibrated over saturated NaCl solution was weighed and then calcinated at 800° C for 2 h. After calcination, the samples was cooled down in a desiccator over the dry silicagel, and then weighed again. From the weights of sample before (m₀) and after calcination (m_c) , the total content of water ((H₂0)_tot in wt.%) was calculated according to Equation 4 :

(H₂0)_tot= 100x(m_o- m_c)/m_o (4)

Quantitative contents of sodium (Na), aluminum (Al), and silicon (Si): Weighted sample of calcined (waterless) product was dissolved in 1:1 HCl solution. The solution was diluted with distilled water to the concentration ranges available for measuring the concentrations of Na, Al and Si by atomic absorption spectroscopy (AAS) . From the measured concentrations of Na, Al, and Si in the solutions and quantity of the calcinated sample dissolved in known volumes of solution, the average contents of Na, Al, and Si (in oxide forms; Na₂O, Al₂O₃, SiO₂) in the sample, the following contents of Na₂O, Al₂O₃, SiO₂ and H₂O in zeolite FLA were obtained:

17.04 ± 1.37 wt. % Na₂O, 27.668 ± 1.65 wt . % Al₂O₃, 32.157 ± 1.29 wt . % SiO₂ and 23.071 ± 2.31 wt.% H₂O.

Therefore, corresponding average molar oxide composition of the zeolite FLA was: 1.017Na₂O • Al₂O₃ • 1.973SiO₂ • 4.725H₂O.

Crystal structure of zeolite FLA:

XRD and FTIR analyzes of zeolite FLA (sample FLA-I) had XRD patterns and FTIR spectra are characteristic for fully crystalline zeolite 4A.

Morphology of zeolite FLA:

SEM photograph of zeolite FLA showed that the product does not have any identifiable and observable crystal faces (e.g. [100]), but surprisingly and unexpectedly appears in the form of face-less, spheroidal particles with high external surface roughness (see SEM photograph in Fig.4).

Particle size (distribution) of zeolite FLA:

Particles of zeolite FLA have the sizes in micrometer range (about 0.4-5 μm by number; see crystal size distribution curve in Fig.8A). 50% of all particles have the size (D₅₀) less than 1.45 μm and 90% of all particles have the size (D₉₀) less than 2.35 μm. These data were also used for calculation of geometrical specific surface area (GSSA) of the sample. Results are given in Tables 2 and 3.

Measurements of real (BET) specific surface area (RSSA) :

The external specific surface area (RSSA) of the sample was determined by multiple BET method on Gemini 2360 surface area analyzer by using nitrogen as adsorbate at the temperature of liquid nitrogen (-195.6⁰C). Prior the analysis the samples were dried for one hour at 105⁰C. The external specific surface areas of the analyzed samples are calculated on the basis of BET isotherm. The results are shown in Table 1.

Ion-exchange measurements: Uptakes of calcium (expressed as U_Cao) and magnesium (expressed as ϋ_Mgo) of zeolite FLA sample was determined as follows: 1.00 g of the product was placed into the flask containing 1000 ml of 0.005 molar solution of calcium chloride or magnesium chloride. During the exchange process at 20⁰C or at 65°C, the suspension was strongly mixed. At the pre-determined exchange times (t_E) , an aliquot of 50 ml was drawn off the suspension, and centrifuged to stop the exchange process and to separate the solid (zeolite) from the liquid phase (supernatant) . The supernatant was carefully removed from solid phase precipitate, and used for measuring the concentration of calcium or magnesium by atomic absorption spectroscopy (AAS) . The exchanged amount of calcium or magnesium ions was calculated from the difference between the initial concentration of calcium or magnesium ions (0.005 moldπf³) and their concentrations in the liquid phase after the exchange process was interrupted.

For comparison, the same experiments were performed with cubic-shape zeolite 4A standards (products of Example 1) .

Results are shown as the amount of CaO (U_Ca0) and MgO (U_Mg0) , respectively bounded per gram of dehydrated zeolite versus the exchange time (t_E) at 20⁰C (Tables 5 and 7) and 65°C (Tables 6 and 8) .

Corresponding ion-exchange capacities, r_Ca0 and r_Mg0, where r_Ca0 = U_Cao(^majO ^and r_Mgo = U_Mgo(max), at equilibrium exchange time (t_E = t_E(eq)) of cubic shape zeolite 4A standards were carried out with the same apparatus and analytical method. Calculated results are given in Table 9.

Reaction yield, Y_R

Reaction yield, Y_R, defined as the amount of zeolite FLA (in grams) obtained from 100 g of the reaction mixture was determined as follows: Solid phase (zeolite FLA) of the reaction mixture was separated from the liquid phase (supernatant) by vacuum filtration, at the end of crystallization process, i.e. when 95.8% of starting amount of SiO₂ vas spent for the synthesis of zeolite FLA. The solid phase on filter paper (zeolite FLA) was washed with several portions of demineralized water until pH of filtrate reached 9-10. The wet washed zeolite FLA was dried overnight at 105⁰C, and cooled down in desiccators with dry silicagel. From known amount of the reaction mixture and, m_z, of crystallized zeolite FLA, the reaction yield, Y_R, was calculated as:

Y_R (in grams per 100 g or wt. %) = 100xm_z/m_R (5)

The reaction yield of zeolite FLA obtained in this example is 9.30 wt. %.

Example 3: Preparation of spheroidal shape "face-less" zeolite FLA (sample FLA-2)

Zeolite FLA (sample FLA-2) was prepared by hydrothermal treatment (heating) of aluminosilicate hydrogel: XNa₂O • Al₂O₃ • ySiO₂ • ZH₂O with x/z = Na₂O/H₂O = 0.042; y/z = SiO₂/H₂O = 0.012; y = SiO₂Ml₂O₃ = 1.3 by mixing together sodium aluminate and sodium silicate solutions at 65- 70⁰C.

Crystallization was carried out by heating of aluminosilicate gel at 70-80⁰C under stirring for 60 min, i.e., until the solid phase of the gel was completely transformed into crystalline phase (monitoring of samples of reaction mixture by optical microscope at magnification of 100Ox) . Then the product was separated by vacuum filtration and washed with several portions of demineralized water until pH of filtrate reached 9-10. Product was dried at 105⁰C for 24 h. After drying, the product (zeolite FLA-2) appears in the form of white fine microcrystalline powder. Utilization of reactants: 95.8% calculated on starting SiO₂.

Chemical composition of zeolite FLA (sample FLA-2) :

Determined as described in Example 2. The same as in Example 2.

Crystal structure of zeolite FLA (sample FLA-2) :

Sample FLA-2 also had XRD patterns and FTIR spectra characteristic for fully crystalline zeolite 4A.

Morphology of zeolite FLA (sample-FLA-2) :

SEM photograph of sample FLA-2 also showed spheroidal shape of crystals (particles) with no identifiable crystal faces and with high external surface roughness.

Particle size (distribution) of zeolite FLA (sample FLA-2) : Particles of zeolite FLA have the sizes in micrometer range (about 0.4-5 μm by number; see crystal size distribution curve in Fig.9A). 50% of all particles have the size (D₅₀) less than 1.1 μm and 90% of all particles have the size (D₉₀) less than 1.75 μm. These data were also used for calculation of geometrical specific surface area (GSSA) of the sample. Results are given in Tables 2 and 3.

Measurements of real (BET specific surface area (RSSA) :

As described in Example 2. The results are shown in Table 1.

Ion-exchange measurements:

As described in Example 2. Results are given in Tables 5-9.

Reaction yield, Y_R

The reaction yield of zeolite FLA (as described in Example 2) obtained in this example is 14.15 wt . %.

Example 4: Preparation of spheroidal shape "face-less" zeolite FIA (sample FLA-3)

Zeolite FLA was prepared by hydrothermal treatment (heating) of aluminosilicate hydrogel: XNa₂O • Al₂O₃ • ySiO₂ • zH₂0 with x/z = Na₂O/H₂O = 0.038; y/z = SiO₂/H₂O = 0.019; y = SiO₂AAl₂O₃ = 1.3 by mixing together sodium aluminate and sodium silicate solutions at room temperature (20-23⁰C) .

Crystallization was carried out by heating of aluminosilicate gel at 65-75°C under stirring for 120 min, i.e., until the solid phase of the precursor (gel) was completely transformed into crystalline phase (monitoring of samples of reaction mixture by optical microscope at magnification of 100Ox) . Then the product was separated by vacuum filtration and washed with several portions of demineralized water until pH of filtrate reached 9-10. Product was dried at 110⁰C for 24 h. After drying, the product (zeolite FLA-3) appears in the form of white fine microcrystalline powder. Utilization of reactants : 97.2% calculated on starting SiO₂.

Chemical composition of zeolite FLA (sample FLA-3) :

Determined as described in Example 2. The same as in Example 2.

Crystal structure of zeolite FLA (sample FLA-3) : XRD patterns and FTIR spectra characteristic for fully crystalline zeolite 4A.

Morphology of zeolite FIA (sample FIA-3) :

SEM photograph of sample FLA-3 also showed spheroidal shape of crystals (particles) with no identifiable crystal faces and with high external surface roughness.

Particle size (distribution) of zeolite FIA (sample FLA-3) :

Particles of zeolite FIA-3 have the sizes in micrometer range (about 0.4-5 μm by number; see crystal size distribution curve in Fig.10A) . 50% of all particles have the size (D₅₀) less than 1.3 μm and 90% of all particles have the size (D₉₀) less than 2.75 μm. These data were also used for calculation of geometrical specific surface area (GSSA) of the sample. Results are given in Tables 2 and 3.

Measurements of real (BET) specific surface area (RSSA) :

As described in Example 2. The results are shown in Table 1.

Ion-exchange measurements:

As described in Example 2. Results are given in Tables 5-9.

Reaction yield, Y_R

The reaction yield of zeolite FIA-3 (as described in Example 2) obtained in this example is 14.60 wt . %.

Example 5: Preparation of spheroidal shape "face-less" zeolite 4A (sample FIA-4)

Zeolite FIA (sample FIA-4) was prepared by hydrothermal treatment (heating) of aluminosilicate hydrogel: XNa₂O • Al₂O₃ • ySiO₂ • zH₂0 with x/z = Na₂O/H₂O = 0.038; y/z = SiO₂/H₂O = 0.023; y = SiO₂Ml₂O₃ = 1.2 by mixing together sodium aluminate and sodium silicate solutions at 50- 55°C.

Crystallization was carried out by heating of aluminosilicate gel at 70-75⁰C under stirring for 90 min, i.e., until the solid phase of the precursor (gel) was completely transformed into crystalline phase (monitoring as described in Example 2) . Then the product was separated by vacuum filtration and washed with several portions of demineralized water until pH of filtrate reached 9-10. Product was dried at 105⁰C for 24 h. After drying, the product (zeolite FLA-4) appears in the form of white fine microcrystalline powder. Utilization of reactants: 98 % calculated on starting SiO₂.

Chemical composition of zeolite FLA (sample FLA-4) : Corresponds to the sample FLA-I (see Example 2) .

Crystal structure of zeolite FLA (sample FLA-4) :

XRD patterns and FTIR spectra characteristic for fully crystalline zeolite 4A.

Morphology of zeolite FLA (sample FLA-4) :

SEM photograph of sample FLA-4 also showed spheroidal shape of crystals (particles) with no identifiable crystal faces and with high external surface roughness.

Reaction yield, Y_R

The reaction yield of zeolite FLA-4 (as described in Example 2) obtained in this example is 17.2 wt. %.

Example 6: Preparation of spheroidal shape "face-less" zeolite 4A (sample FLA-5)

Zeolite FLA (sample FLA-5) was prepared by hydrothermal treatment (heating) of aluminosilicate hydrogel: XNa₂O • Al₂O₃ • ySiO₂ • ZH₂O with x/z = Na₂O/H₂O = 0.042; y/z = SiO₂/H₂O = 0.032; y = SiO₂AAl₂O₃ = 1.4 by mixing together sodium aluminate and sodium silicate solutions at 50- 55°C. Crystallization was carried out by heating of aluminosilicate gel at 75-80⁰C under stirring for 60 min, i.e., until the solid phase of the precursor (gel) was completely transformed into crystalline phase (monitoring as described in Example 2) . Then the product was separated by vacuum filtration and washed with several portions of demineralized water until pH of filtrate reached 9-10. Product was dried at HO⁰C for 24 h. After drying, the product (zeolite FLA-5) appears in the form of white fine microcrystalline powder. Utilization of reactants: 98 % calculated on starting SiO₂. Chemical composition of zeolite FIA (sample FLA-5) : Corresponds to the sample FLA-I (see Example 2) . Crystal structure of zeolite FIA (sample FIA-5) :

XRD patterns and FTIR spectra characteristic for fully crystalline zeolite 4A.

Morphology of zeolite FIA (sample FLA-5) :

SEM photograph of sample FLA-5 showed spheroidal shape of crystals (particles) with no identifiable crystal faces and with high external surface roughness.

Reaction yield, Y_R

The reaction yield of zeolite FIA-5 (as described in Example 2) obtained in this example is 30 wt. %.

Claims

CLAIMS1. Zeolite 4A with molar oxide composition of:

1.017Na₂O • Al₂O₃ • 1.973SiO₂ • 4.725H₂O characterized by:

(i) external specific surface area of 2.37-4.43 m²/g according to Brunauer-Emmett-Teller (BET) isotherm; and

(ii) external surface roughness as indicated by the ratio of RSSA/GSSA within the range of 2.58-2.81.

2. Zeolite 4A according to claim 1, characterized by that it comprises :

(i) spheroidal shape of particles; and

(ii) particles size ranging from 0.4 μm to 5 μm, wherein 50% of all particles size are smaller than 1.45 μm, and 90% of all particles size are smaller than 2.35 μm.

3. Process for synthesis of zeolite 4A according to claims 1 and 2, characterized by:

(i) preparation of aluminosilicate hydrogel precursor by mixing of sodium aluminate and sodium silicate solution in the following molar ratio of components:

Na₂O/H₂O within the range 0.026-0.042; SiO₂/H₂O within the range 0.012-0.032;

SiO₂/Al₂O₃ within the range 1.2-1.4; (ii) crystallization of aluminosilicate gel into zeolite; and

(iii) separation of zeolite by filtration, followed by washing with water, and drying.

4. Process for synthesis of zeolite 4A according to claim 3, characterized by the mixing of starting sodium aluminate and sodium silicate solutions that is carried out at 20-70⁰C yielding aluminosilicate gel, whereas crystallization of thus obtained gel into the zeolite is performed at 65-90⁰C during 60-135 minutes.

5. Process for synthesis of zeolite 4A according to claim 4, characterized by reaction yield, Y_R, within the range 14.15-30.0 g of product per 100 g of the reaction mixture.

6. Use of the zeolite 4A according to claims 1 and 2, as detergent builder, ion-exchange agent, sorbent, and carrier of organic molecules .