Patent Publication Number: US-4581212-A

Title: Zeolite EU-7

Description:
The present invention relates to a novel zeolite material, hereinafter referred to as EU-7, and to methods for its preparation. 
     Aluminosilicate zeolites are now widely used in industry. Some occur only in nature, others are only available as a result of chemical synthesis and some are available in both natural and synthetic forms. Synthetic zeolites are attracting more and more attention and it is becoming more and more possible to control the preparation of such zeolites so as to tailor their properties to particular needs. 
     According to the present invention a crystalline zeolite material, EU-7 has a composition (in terms of mole ratios of oxides) expressed by the formula: 
     
         0.5 to 2.5 R.sub.2 O:Y.sub.2 O.sub.3 :at least 20 XO.sub.2 :0 to 600 H.sub.2 O 
    
     wherein R is a monovalent cation or 1/n of a cation of valency n, X is silicon and/or germanium, Y is one or more of aluminum, iron, chromium, vanadium, molybdenum, arsenic, antimony, manganese, gallium or boron and H 2  O is water of hydration additional to water notionally present when R is H, and having an X-ray powder diffraction pattern substantially as set out in Table 1 (as determined by standard technique using copper Kα radiation) and as shown in FIG. 1. A preferred form of zeolite EU-7 has a composition expressed by the formula: 
     
         0.5 to 2.5 R.sub.2 O:Y.sub.2 O.sub.3 :20 to 5000 XO.sub.2 :0 to 600 H.sub.2 O 
    
     where R, X and Y have the meanings given hereinbefore. 
     
                       TABLE 1                                                     
______________________________________                                    
As synthesised EU7  Calcined EU7                                          
d(A)      I/I.sub.o     d(A)    I/I.sub.o                                 
______________________________________                                    
7.96      12            7.98    11                                        
6.66      15            6.66    17                                        
4.23      100           4.24    100                                       
3.97      11            3.97     9                                        
3.65       9            3.65    13                                        
3.44       2            --      --                                        
3.33      98            3.33    91                                        
3.26      51            3.27    49                                        
3.12       7            3.12     6                                        
2.915     10            2.915   10                                        
2.868      1            2.868    2                                        
2.770      3            2.772    2                                        
2.691      1            2.685    3                                        
2.522     20            2.522   17                                        
2.502     13            2.507   11                                        
2.475      1            2.475    2                                        
2.370     10            2.373   10                                        
2.344      5            2.345    5                                        
______________________________________                                    
 
    
     This definition includes both freshly prepared EU-7 (&#34;freshly prepared&#34; means the product of synthesis and washing, with optional drying, as hereinafter described) and also forms of the zeolite resulting from dehydration and/or calcination and/or ion exchange. In freshly prepared EU-7, R may include an alkali metal cation, preferably caesium, and/or ammonium and hydrogen and may include nitrogen-containing organic compounds as described below. These organic components are hereinafter referred to, for inconvenience only, as A. The peak at d(A) 4.23 sometimes exhibits a shoulder at d(A) 4.30. 
     As EU-7 is a zeolite, the organic component(s) must be held within the zeolite framework. It (they) can be removed by thermal or oxidative degradation or by displacement by suitable small molecules. However reference to Table 1 will show that there are no significant differences between the X-ray diffraction patterns for as synthesised EU-7 and calcined EU-7 (the calcination was carried out at 500° C. for 16 hours). Calcination at 960° C. was also found to have no effect on the diffraction pattern and it is believed that the thermal stability of zeolite EU-7 is very high. 
     The nitrogen-containing organic material does not constitute part of the composition for the purposes of definition. Thus, a zeolite EU-7 as made typically has the molar composition: 
     
         0.5 to 2.5 M.sub.2 O:0 to 150 A:Y.sub.2 O.sub.3 :20 to 5000 XO.sub.2 :0 to 300 H.sub.2 O 
    
     where M is an alkali metal, preferably caesium, ammonium or hydrogen. 
     In calcined forms of zeolite EU-7, R may be any cation including hydrogen since the organic component is either burnt out in the presence of air, leaving hydrogen as the other balancing cation, or it is removed prior to calcination for example by dissolution in water or an organic solvent. The zeolite is readily converted to the hydrogen form by ion-exchange with hydrogen ions and/or with ammonium ions followed by calcination. 
     Zeolite EU-7 may be prepared by reacting an aqueous mixture containing sources of at least one oxide XO 2 , at least one oxide Y 2  O 3  and optionally at least one organic compound selected from 
     (a) primary, secondary, tertiary and cyclic amines with 1 to 3 nitrogen atoms in the molecule and with a total of 1 to 10 carbon atoms per nitrogen atom: 
     (b) primary, secondary and tertiary alcohols with 1 to 3 hydroxyl groups in the molecule and with a total of 1 to 10 carbons per hydroxyl group; 
     (c) compounds containing both at least one amine group and at least one hydroxyl group in the molecule and with 1 to 10 carbon atoms per group; and 
     (d) mixtures of compounds selected from groups (a), (b) and/or (c), the reaction mixture having the molar composition: 
     XO 2  /Y 2  O 3  in the range 20 to 5000, preferably 30 to 120 
     M 1  OH/XO 2  in the range 0.08 to 0.7, preferably 0.15 to 0.50 
     H 2  O/XO 2  in the range 5 to 170, preferably 15 to 85 
     A/XO 2  in the range 0 to 1 preferably 0.08 to 0.5 
     M 2  Z/XO 2  in the range 0 to 1 preferably 0.08 to 0.33 
     wherein each of M 1  and M 2  represents an alkali metal, preferably caesium, ammonium or hydrogen, A represents the organic compound, X and Y have the meanings as hereinbefore defined, and Z represents an acid radical. 
     Preferred compounds of group (a) are α-ω alkane diamines having 1 to 4 carbon atoms per nitrogen atom for example hexane-1,6-diamine and more preferably butane-1,4-diamine and ethylene diamine. 
     Preferred compounds of group (b) are α-ω, alkane diols having 1 to 4 carbon atoms per hydroxyl group, for example ethylene glycol and hexane-1,6-diol. 
     A preferred organic compound for use in the preparation of EU-7 is butane-1,4-diamine. Experiments with other organic compounds, for example hexane-1,6-diamine, hexane-1,6-diol and piperazine have shown that impurities, especially cristobalite, tend to be formed along with zeolite EU-7. However, use of the smaller butane-1,4-diamine leads to a much purer EU-7 product with a much lower content of zeolite impurity. Optionally, organic components may be absent from the reaction mixture and this has the advantage that there is then no need to remove organic material from the zeolite. 
     Suitable alkali metals for use in the method of the invention include sodium, potassium, rubidium and caesium and of these it is preferred to use caesium. On occasion, however, it is preferred to use rubidium as the latter is more easily removed by ion exchange. 
     The X-ray diffraction pattern and other preliminary analysis suggest that zeolite EU-7 is a narrow pore zeolite. It seems probable therefore that the use of the relatively large caesium ions in the preparation of the zeolites leaves relatively little space for the organic mineraliser. Hence among the organic mineralisers so far tested, the relatively small molecules such as butane-1,4-diamine, appear to be the most suitable for use when caesium is used as alkali metal. 
     The preferred oxide XO 2  is silica (SiO 2 ) and the preferred oxide Y 2  O 3  is alumina (Al 2  O 3 ). 
     The silica source can be any of those commonly considered for use in synthesising zeolites, for example powdered solid silica, silicic acid, colloidal silica or dissolved silica. Among the powdered silicas usable are precipitated silica, especially those made by precipitation from an alkali metal silicate solution, such as the type known as &#34;KS 300&#34; made by AKZO, and similar products, aerosil silicas, fume silicas such as &#34;CAB-O-SIL&#34; M5 and silica gels suitable in grades for use in reinforcing pigments for rubber or silicone rubber. Colloidal silicas of various particle sizes may be used, for example 10 to 15 or 40 to 50 microns, as sold under the Registered Trade Marks &#34;LUDOX&#34;, &#34;NALCOAG&#34; and &#34;SYTON&#34;. The usable dissolved silicas include commercially available waterglass silicates containing 0.5 to 6.0, especially 2.0 to 4.0, moles of SiO 2  per mol of alkali metal oxide, &#34;active&#34; alkali metal silicates as defined in UK Pat. No. 1,193,254, and silicates made by dissolving silica in alkali metal hydroxide or quaternary ammonium hydroxide or a mixture thereof. 
     The alumina source is most conveniently a soluble aluminate, but aluminium, an aluminium salt, for example the chloride, nitrate, or sulphate, an aluminium alkoxide or alumina itself, which should preferably be in a hydrated or hydratable form such as colloidal alumina, pseudoboehmite, boehmite, gamma alumina or the alpha or beta trihydrate can alco be used. 
     The reaction mixture is conveniently reacted under autogeneous pressure, optionally with added gas, for example nitrogen, at a temperature in the range 80° to 250° C., more suitably 140° to 200° C., until crystals of zeolite EU-7 form, which can be from 1 hour to many months depending on the reactant composition and the operating temperature. Agitation is optional, but is preferable since it assists homogenisation of the reaction mixture and reduces the reaction time. Seeding of the reaction mixture with EU-7 crystals can also be advantageous if EU-7 crystals dispersed in their mother liquor are used. 
     At the end of the reaction, the solid phase is collected on a filter and washed and is then ready for further steps such as drying, calcination and ion-exchange. 
     Any alkali metal ions present in the product of the reaction have to be at least partly removed in order to prepare the catalytically active hydrogen form of EU-7 and this can be done by ion exchange with an acid, especially a strong mineral acid such as hydrochloric acid or by way of the ammonium compound made by ion exchange with a solution of an ammonium salt such as ammonium chloride. Ion exchange can be carried out by slurrying once or several times with the ion-exchange solution. The zeolite is usually calcined after ion exchange but this may be effected before ion-exchange or during ion-exchange if the latter is carried out in a number of stages. Ion exchange can also be used to replace ions present in the &#34;as made&#34; form of the zeolite by other ions and this ion-exchanged form of the zeolite can also be converted, if desired, to the hydrogen form as described above. 
     Organic material incorporated in the zeolite during the synthesis can be removed by heating at temperatures up to 1500° C. under atmospheric pressure or by heating at lower temperatures, under reduced pressure. Alternatively, organic material may be removed by dissolution in water or in a suitable organic solvent, if desired during ion-exchange. 
     Zeolite EU-7 finds use in ion-exchange, especially in nonaqueous solvents. It is also useful, especially in its hydrogen form, in sorption, especially of small molecules, for example in the sorption and separation of molecules found in air. 
     Zeolite EU-7 prepared by the method of the invention is also useful as a catalyst, for example as a hydrocarbon conversion catalyst and in the conversion of small oxygen-containing organic molecules to hydrocarbons. It may be employed using the general techniques described in the prior art for zeolite catalysis. 
    
    
     In the drawing, FIG. 1 shows a typical X-ray powder defraction pattern of EU-7. 
    
    
     The zeolite and its method of preparation are illustrated by the following Examples. 
     EXAMPLE 1 
     EU-b 7 was synthesised from the molar reaction mixture of composition: 
     
         60SiO.sub.2 Al.sub.2 O.sub.3 8.33 Cs.sub.2 O3000H.sub.2 O 
    
     as follows: 
     An aluminate solution was prepared by dissolving 1.04 g of alumina trihydrate in a solution of 18.65 g of caesium hydroxide monohydrate dissolved in 15 g of distilled water in a beaker using a magnetic stirrer hot plate. This aluminate solution was then added to a mixture of 24.0 g CAB-O-SIL M5 silica, 7.88 g of hexane-1,6-diol and 300 g of water in a liter plastic beaker. An additional 42 g of water was used to rinse the aluminate solution from the beaker and was added to the reaction mixture. The mixture was stirred with a spatula until it appeared to be homogeneous. 
     The synthesis mixture was then placed in a stainless steel autoclave in which it was stirred at 300 r.p.m. and allowed to react at 180° C. Crystallisation was complete within 70 hours. 
     The zeolite was then filtered from the reaction mixture washed with distilled water and dried at 120° C. and in some cases, as specified, calcined at 550° C. for 16 hours. 
     EXAMPLES 2 to 6 
     The procedure of Example 1 was repeated using the reaction composition and conditions given in Table 2. 
     Analysis of the products of Examples 1 to 6 by X-ray powder diffraction showed that in each case a significant amount of impurity was formed as well as zeolite EU-7 (see Table 2). In Example 5 the first material to form was ferrierite which later converted to zeolite EU-7 and cristobalite. 
     
                       TABLE 2                                                     
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Ex-                                                                       
am-                              Organic (a)                              
ple  SiO.sub.2                                                            
            Al.sub.2 O.sub.3                                              
                    M.sub.2 O                                             
                            H.sub.2 O                                     
                                 Component                                
                                          Products                        
______________________________________                                    
1    60     1        8.33 (Cs)                                            
                            3000 10  HEXDL  EU-7 +                        
                                            Cristo-                       
                                            balite                        
2    60     1        8.33 (Cs)                                            
                            3000 20  PIPZE  EU-7 +                        
                                            Cristo-                       
                                            balite                        
3    60     1       10.8 (Cs)                                             
                            3000 10  HEXMD  EU-7 +                        
                                            Cristo-                       
                                            balite                        
4    60     2       10 (Cs) 3000 20  HEXMD  EU-7 +                        
                                            Pollucite                     
5    60     2       10 (Rb) 3000 20  HEXMD  Ferri-                        
                                            erite                         
                                            EU-7 +                        
                                            Cristo-                       
                                            balite                        
6    60     1       10 (Cs) 3000 15  HEXMD  EU-7 +                        
                                            ZSM5 +                        
                                            trace                         
                                            Cristo-                       
                                            balite                        
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 (a) HEXDL = hexane1, 6diol; PIPZE = piperazine; HEXMD = hexane1,6-diamine
                                                                          
 
    
     EXAMPLES 7 to 10 
     Synthesis mixtures having the compositions shown in Table 3 were prepared as described for examples 1 to 6 except that the reaction temperature was 150° C. in Example 9. In this case, the products obtained using caesium as the alkali metal were very much purer than those obtained in Examples 1 to 6, thereby illustrating the advantage of using butane-1,4-diamine as the organic mineraliser. 
     In Example 8, rubidium was used as the alkali metal source. Rubidium is especially useful in the synthesis of zeolite Nu-10 (see our co-pending European Patent Application published as EPA No. 77624) and hence zeolite Nu-10 was formed along with zeolite EU-7. However the composition of the reaction mixture used was not the best for either zeolite and hence cristobalite was formed by default as the main product. It was also observed that the first material to form from this mixture was ferrierite. 
     The products of Examples 1 to 10 were identified by X-ray diffraction and it was found that in each case the diffraction pattern for zeolite EU-7 did not vary significantly from that given in Table 1 As in Examples 1 to 6 it was found that in each case a significant amount of an impurity was formed as well as zeolite EU-7. 
     
                       TABLE 3                                                     
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Ex-                                                                       
am-                           Organic (a)                                 
ple SiO.sub.2                                                             
           Al.sub.2 O.sub.3                                               
                   M.sub.2 O                                              
                         H.sub.2 O                                        
                              Component                                   
                                       Products                           
______________________________________                                    
 7  60     1       10 (Cs)                                                
                         3000 20 BUTDM Very crystalline                   
                                       EU-7 + trace                       
                                       Cristobalite                       
 8  60     1       10 (Rb)                                                
                         3000 20 BUTDM Cristobalite +                     
                                       (Nu-10 +                           
                                       EU-7) as minor                     
                                       components                         
                                       Cristobalite                       
 9  60     1       10 (Cs)                                                
                         3000 20 BUTDM EU-7 + Cristo-                     
                                       balite +                           
                                       Kenyaite                           
10  60     1       10 (Cs)                                                
                         3000 20 BUTDM Very crystalline                   
                                       pure EU-7                          
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 (a) Butane1,4-diamine                                                    
 
    
     EXAMPLE 11 
     A portion of &#34;as made&#34; zeolite EU-7 prepared in Example 7 was calcined at 550° C. for 16 hours. It was then treated with IM hydrochloric acid at 75° C. for 2 hours using 1 g. of zeolite per 100 ml of solution. This ion-exchange procedure was repeated six times. Samples of the solid taken after each exchange were washed until free from chloride, dried at 110° C. for four hours and equilibrated with water vapour over saturated sodium chloride solution. The ion-exchange samples were then examined by X-ray powder diffraction. 
     It was found that there was a systematic increase in most but not all of the peak heights and there was no evidence at all of damage to the lattice. The increase in peak height is consistent with the removal of caesium ions (gram atomic absorption 46,100) from the lattice and their replacement by hydrogen ions (which have a much smaller gram atomic absorption). At least 6 ion-exchange cycles are required to remove all the exchangeable caesium ions from the lattice. 
     Samples of EU-7 from Examples 7 and 10 were analysed by X-ray fluoresence and the results are shown in Table 4. The total amount of material accounted for by the analysis is significantly below 100% and the difference is probably due to organic material which is not released until the sample is fused with lithium borate flux to form the glass disc used for the analysis. The empirical formulae given in Table 4 are based on the assumption that all the material which is not accounted for by the analysis is butane-1,4-diamine. 
     Electron micrographs of the sample from Example 7 show that in this case zeolite EU-7 crystals are rod shaped, 0.2 μ in cross-section and 1 to 4 μ long. 
     
                       TABLE 4                                                     
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Sample  SiO.sub.2                                                         
                 Al.sub.2 O.sub.3                                         
                         Cs.sub.2 O                                       
                                SiO.sub.2 /Al.sub.2 O.sub.3               
                                        Total  -a                         
______________________________________                                    
Example 7                                                                 
        81.51    4.036   12.67  34.3    97.01                             
Example 10                                                                
        78.42    3.947   14.75  33.8    95.76                             
______________________________________                                    
 -a Total includes trace elements (Ca, Mg, Na, K, Fe, Ti, etc.)           
 Empirical formula of EU7                                                 
 Example 7 34.3 SiO.sub.2 Al.sub.2 O.sub.3 1.13 Cs.sub.2 O 0.86 BUTDM 2.09
 H.sub.2 O                                                                
 Example 10 33.8 SiO.sub.2 Al.sub.2 O.sub.3 1.35 Cs.sub.2 O 1.25 BUTDM 2.0
 H.sub.2 O                                                                
 
    
     EXAMPLES 12 to 17 
     Synthesis mixtures having the compositions shown in Table 5 were prepared as described for examples 1 to 6 except for some variations in reaction temperature, as shown. Example 12 is illustrative of the synthesis of EU-7 in the absence of an organic component. Examples 13, 14 and 15 show that ethylenediamine is preferable as the organic component to both octane-1,8-diamine and dodecane-1,2-diamine. 
     
                                           TABLE 3                                 
__________________________________________________________________________
                Organic (a)                                               
Example                                                                   
     SiO.sub.2                                                            
        Al.sub.2 O.sub.3                                                  
            M.sub.2 O                                                     
                H.sub.2 O                                                 
                   Component                                              
                          T/°C.                                    
                             Products                                     
__________________________________________________________________________
12   60 1   10 (Cs)                                                       
                3000                                                      
                   None   180                                             
                             EU-7 + Cristobalite                          
                             as minor component                           
13   60 1   10 (Cs)                                                       
                3000                                                      
                   20 EDM 180                                             
                             EU-7 + Cristobalite                          
                             as minor component                           
14   60 1   10 (Cs)                                                       
                3000                                                      
                   20 ODM 180                                             
                             EU-7 + Cristobalite                          
15   60 1   10 (Cs)                                                       
                3000                                                      
                   20 DDM 180                                             
                             EU-7 + Cristobalite                          
16   60 1   10 (Cs)                                                       
                3000                                                      
                   10 HEXDM                                               
                          150                                             
                             EU-7 + trace ZSM5 +                          
                             trace Kenyaite                               
17   60 0.75                                                              
            10 (Cs)                                                       
                3000                                                      
                   15 HEXDM                                               
                          170                                             
                             EU-7 + trace                                 
                             Cristobalite + trace                         
                             Kenyaite                                     
__________________________________________________________________________
 (a) EDM = ethylenediamine;                                               
 DDM = dodecane1,2-diamine;                                               
 ODM = octane1,8-diamine;                                                 
 HEXDM = hexane1,6-diamine.