NO753624L - - Google Patents

Description

“Sodium Aluminum Silicate Zeolite and

method for the production thereof".

This invention relates to a method for the production of synthetic crystalline zeolites and in particular a new zeolite, which is hereinafter referred to as zeolite zeta 1. Crystalline zeolites with molecular sieve properties can be produced by reacting silica, alumina and suitable alkali hydroxides in predetermined amounts, in an aqueous medium, followed by crystallization of the desired zeolite from the reaction mixture; however, the choice of reactants and reaction conditions is very important for the production of special zeolite species.

These zeolites consist of a giant anionic skeleton of AlO^ and SiO^ tetrahedra bound together by common oxygen atoms.

The resulting honeycomb-like skeleton contains cavities and connecting channels capable of containing embedded water or other molecules of appropriate size and shape. The skeleton's negative charge is neutralized by cations. These cations are mobile and can easily be exchanged with other cations, for example simply by contact with aqueous solutions of salts containing suitable cations.

Zeolite zeta 1 is related to zeolite ZSM5, which is described in British patent no. 1 161 974. In this patent, the source of silicon used is not clearly defined, being only stated as solid silica, and the cations which are.required for the synthesis of ZSM5 are sodium and tetrapropylammonium. It was now found that ZSM5 is obtained when the solid silica used is a newly prepared silica gel.

It was now surprisingly found that a new zeolite, zeta 1, is obtained, especially if the source of silicon is a highly dispersed solid silica (e.g. Hoechsf's "KS300"), or fumed silica, or water glass with a high silicon content where SiC>2 /Na20 ratio is greater than 3.2, together with a quaternary ammonium or phosphonium compound (excluding tetramethylammonium and tetramethylphosphonium compounds) of the formula R2 R3 R4-N.X or R-^R^jR^R^.P.X,

where

R = C 1 -C 4 alkyl, phenyl benzyl, alkyl substituted feryl or alkyl substituted benzyl;

R 2 , R 1 and R 2 = C 1 -C 2 Q alkyl and may be equal or

different; and

X = an acid radical, OH or a halogen.

In the following, the groups are denoted R-^R2R^.N and

R-^R2 R^ R^-P with the letter Q, which is conveniently tetrapropylammonium or cetyltrimethylammonium. It will be understood that breakdown products can be used instead of QX, or one can use mixtures of compounds which by mutual reaction form Q in situ; e.g. a mixture of a trialkylamine and a C-^-C^Q alcohol or a mixture of a dialkylarylamine and a C1-C2Q alcohol.

Zeolite zeta 1 can be produced at temperatures within the range 80-250°C. Suitable ratios between the volume of the reaction mixture and the volume of the autoclave are used when temperatures higher than

about. 104°C is used; too strong evaporation can

is prevented by the application of pressure by means of a permanent gas such as nitrogen.

In Table 1 are X-ray diffraction data for zeolite

zeta 1 compared to data for ZSM5. These data were obtained

using copper K^ radiation, and the d-spacings and intensities were recorded on a paper-strip type printer. In order to obtain more accurate d-distances, experiments were also carried out

with built-in standards with known d-spacings, and appropriate corrections have been made. The data given in table<1> for zeolite zeta 1,. relates to the product in example 1 below,

and they are typical of the zeolite regardless of the SiC^/Al-^O^ ratio and the cation content, because only small changes take place as a result of variations in the composition.

The product in example 1 below has the following composition after drying at 120°C: 0.4 Q20.0.7 Na2O.Al203.23.8Si02.5H20,

where Q = tetrapropylammonium, and was indicated to have a tetragonal

unit cell with a = 22.3 and c = 42.4. As shown in Table 1

o ■ o

is there good agreement between observed d-distances for zeolite zeta 1 and d-distances that were calculated for the proposed unit cell. While zeolite zeta 1 is related to ZSM5,

it can be easily distinguished from the latter by X-ray diffraction

data and unit cell dimensions.

Zeolite zeta 1 can also be distinguished from ZSM5 by. quite a big difference in aiming characteristics. While ZSM5 does not discriminate between the xylene isomers on the basis of size and adsorbs all three in abundance, zeolite zeta 1 will adsorb significant amounts only of p-xylene and rejects the m- and o-isomers, and ethylbenzene is borderline. This suggests that the openings in zeolite zeta. 1

are accessible only to molecules with kinetic diameter ^6.0Å, while the openings in ZSM5 are accessible to molecules

with kinetic diameter up to at least 6.2Å.

Table 2 gives sorption data for zeolite zeta 1 for comparison with sorption data for the ZSM5 series of zeolites,

ZSM5, 8, 11 and 12 (described in British Patent Nos. 1,161,974 and 1,334,243, US Patent No. 3,709,979 and German Patent No. 2,213,109).

'Another unusual feature of zeolite zeta 1 is the ratio of its adsorption capacity for n-hexane to water. It is common in the case of zeolites that a part of: the skeleton that is accessible to the small water molecules (2.8 Å kinetic diameter) is not accessible to the larger n-paraffin molecules, for example n-hexane (diameter 4, 2Å). In the case of zeolite X, for example, the n-hexane/water ratio is approx. 0.6. For zeolite zeta 1, this ratio is actually 2, which suggests that parts of the structure are either hydrophobic or alternatively have no affinity for water, but great affinity for hydrocarbons.

According to the present invention, a solid, crystalline sodium aluminosilicate, zeolite zeta 1, is provided with the following composition expressed as a molar ratio between oxides: (0.2-0.7)Na20. (0, 3-0, 9) Q20. Al^ . (10-150) SiO 2 . (O-30)H2O where Q is a quaternary ammonium or phosphonium group of the formula R1R2R3R4N or Ri R2 R3R4P'where = C 1 -C 20 alkyl, phenyl, benzyl, alkyl substituted phenyl or alkyl substituted benzyl; R 2 , R 4 and R 4'* = C 1 -C 2 Q -alkyl and may be the same or different; and the crystals are indicated to have a tetragonal unit cell with aQ = 22.3Å and cq = 42.4Å.. The aluminosilicates according to the invention have an X-ray diffraction pattern mainly as shown in table 1. According to the invention, a method for the production of zeolite zeta 1 is also provided as described in the previous section, characterized by reacting sodium aluminate, at least one silicon compound and at least one compound with the formula QX, where Q is as defined in the last paragraph above, and where X is an acid radical, OH or a halogen, the reaction mixture, expressed as a molar ratio, having a composition within the following range:

The silicon compound, or main silicon compound, is preferably either an aerosil or fumed silica or highly dispersed silica, such as Hoechsf's "KS300", or a water glass with a high silicon content and SiO 2 /Na 2 O from 3.2 to 4, 0, or mixtures of such silicon sources. Alternatively, silica gel is dissolved in quaternary ammonium or phosphonium hydroxide to form a silicate.

The reactions can be carried out at temperatures within the range 80-250°C. When temperatures higher than the boiling point of the mixture (ie higher than approx. 104°C) are used, an autoclave is used, and the ratio volume of reactants/volume of autoclave is within the range 0.1-0.7. The conditions used can affect the reaction time and

also the products that are formed.

The following five examples will further illustrate the invention.

EXAMPLE 1

21.2 g of solid silica (KS 300) was dissolved in 100 ml of 50% tetrapropylammonium hydroxide by boiling at 100°C for 2 hours under reflux. Next, 2.4 g of sodium aluminate (1.25 Na^.A^O^) were dissolved in 50.5 g of water, and this liquid was stirred into the silicate liquid;

stirring was continued for approx. 15 minutes, and the mixture was transferred to a 1-liter "Pyrex"-lined autoclave, where it was gently reacted at r50°C for 6 days. The autoclave was cooled to room temperature, and the slurry was filtered and washed with 2 liters of hot water and then dried at 120°C. The composition of this product was 0.7 Na2O.0.4Q2O.Al2O3.23.8Si02.5H2O, and its X-ray diffraction data are given in Table 1. Table 3 shows data concerning the sorption of n-hexane and xylenes for this sample of zeta 1, which is designated sample A, which activated the sorption balance

(which activated on the sorption balance) at 320°C for 2 hours, and for sample B, which was calcined for 24 hours at 550°C to burn off tetrapropylammonium, and which was then exchanged for 1 hour at 95° C with an excess of 10% ammonium chloride solution and then calcined at 550°C for 6 hours. The composition of sample B was: 0.29 Na 2 O.Al 2 O 3 .25 SiO 2

EXAMPLE 2

12 g of solid silica was dispersed in 14.6 g of 50% tetrapropylammonium hydroxide and 0.36 g of sodium aluminate was dissolved in 39 ml of water. The aluminate liquid was thoroughly stirred into the slurry.

The mixture was reacted in a 1 liter "Pyrex" lined autoclave at 190°C for 7 days with stirring (50 revolutions per minute). The autoclave was cooled, and its contents filtered off and washed with 2 liters of warm water. The product was after drying at 120°C

zeta 1 with the following composition:

0.3 Na 2 O. 0.75 Q20.A1203.88Si02.18H20

EXAMPLE 3

50 g of cetyltrimethylammonium bromide was dissolved in 50 ml of water together with 0.85 g of sodium hydroxide and 1.1 g of solid sodium aluminate. Then 10.6 g of solid silica was stirred in. The mixture was reacted for 5 days at 175°C, and the dried product, obtained as in example 2, was also in this case an excellent sample of zeolite zeta 1 with the following composition: 0.5 Na2O.0.35 Q2O. Al^ . 28Si02. 9H20,

where Q = cetyltrimethylammonium.

EXAMPLE 4

19.1 g of solid silica was dispersed in 35 g of tripropylamine, and 2.2 g of solid aluminate was dissolved in 14.8 g of n-propyl alcohol + 54 ml of water. The aluminate liquid was mixed into the slurry, and the mixture was reacted for 12 days at 200°C. The dried product contained approx. 80% zeta 1 together with amorphous material.

EXAMPLE 5

636 g of solid silica was dispersed in 3 liters of 50% tetrapropylammonium hydroxide. Then 72 g of solid sodium aluminate was dissolved in 1.5 liters of water. The aluminate liquid was then stirred

.into the silica slurry, after which the mixture was transferred to a 10-liter stainless steel autoclave, where it was reacted under vigorous stirring for 5 days at 150°C. The autoclave was cooled, and the contents filtered off and washed with 20 litres. hot water. After drying at 80°C, the product had the following composition: 0.2Na2O.0.9 Q2O.Al2O3.32.5Si02.24H2O.

Acidic forms of zeolite. zeta 1 gives particularly good results when dehydrating alcohols. For example, tables 4 and 5 show data obtained by dehydration of methanol using the hydrogen form of zeta 1, and using acid-extracted mordenite and using an ultrastable zeolite of the Y type based on rare earths (REY). Zeolite zeta 1 clearly has an unusual activity in converting methanol to aromatic compounds, and it is more efficient than mordenite in this respect. The above-mentioned 'REY' had no significant activity for the production of aromatic substances.

Hydrogen-zeta 1 was prepared by calcining the zeolite from Example 1 for 24 hours at 550°C and exchanging with 10% ammonium chloride solutions (twice the amount theoretically required for complete exchange) for 1 hour at 95°C . This exchange step was repeated until three exchanges had been performed. The product was dried, pelletized and broken down into pieces of approx. 1.6 mm. This material was calcined for 18 hours at 550°C and showed the following analysis: 0.1 Na2O.& 12°3*24'7Si02'

The X-ray diffraction pattern was not significantly different from the pattern for the freshly prepared sample of zeolite zeta 1.

The acid-leached mordenite with large openings had a composition of 0.02 Na2O.Al20318Si02, and this was pellitized and calcined as above.

The above zeolite REY had the composition: 0.04 Na20.1.39 RE2°3"A12°3* 4'9Si02'°g this material was pelletized and calcined as above. Details regarding the catalyst tests are indicated in table 4. The products were analyzed as gas, phase which is miscible with water, and phase which is not miscible with water. The product analysis in table 4 clearly shows that zeolite zeta 1 is a far more active catalyst for the production of aromatic substances than acid leached mordenite. The aromatic substances from zeta 1 are far better when it comes to this

yield of the important BTX products (benzene, toluene, xylene).

While zeta 1 gave 100% conversion in these experiments, acid-treated mordenite failed significantly in methanol. REY also failed significantly, yielding only paraffins and de-fins.

The cation or cations in zeolite zeta 1 can be replaced by any cation or cations of metals from groups IA, IB, II, III (including rare earths), group VHA (including manganese), group VIII (including noble metals), and with lead and<y>ismut. The exchange is preferably carried out by simple contact in aqueous solution. The acid or hydrogen form of zeolite zeta 1 can be produced by reacting

the alkali form with a wide range of acidic compounds (namely any source of hydrogen ions), or by first preparing an ammonium or alkyl or arylammonium zeolite by ion exchange followed by cleavage, preferably in air, by heating, whereby hydrogen zeta 1 is formed. If desired, catalysts made from zeolite zeta 1 can be incorporated into an inorganic base mass together with other materials, which can either be inert or catalytically active. ■ The matrix may be present as a binder that holds the small zeolite particles (0.05-10 pm) together, or it may be added as a diluent to regulate the amount of conversion in a process which, using zeolites based on zeta 1, otherwise can proceed at a much too high rate, which leads to passivation of the catalyst due to kokdanneIse. Typical inorganic diluents include kaolin clays, bentonites, montmorillonites, sepiolite, attapulgite, Fuller's earth, synthetic porous materials such as SiO2-Al2O3, SiO2-ZrO2, SiO2-Th02, SiO2~BeO, SiO2~Ti02, highly dispersed silica or combinations of these oxides. One

efficient way to mix zeolite zeta 1 with such diluents is to mix suitable aqueous slurries in a mixing nozzle

and then spray dry the slurry. Other mixing methods can also be used.

Alkaline earth forms, rare earth forms and acidic forms of zeolite zeta 1 can furthermore be exchanged or impregnated with hydration/dehydration components, such as Ni, Co, Pt, Pd Re, Rh. Good hydrocracking and reforming catalysts can be prepared in this way on the basis of zeolite zeta 1, provided that its Na 2 O content is reduced to less than 1% by weight.

Claims (16)

1. Solid crystalline sodium aluminosilicate, zeolite zeta 1, with the following composition expressed as molar ratio of oxides: (0.2-0.7) Na 2 O. (0.3-0.9)Q20.Al 03. (10-150)SiO2 . ('O-30)H2O where Q is a quaternary ammonium or phosphonium group with the formula: Rl R2 R3 R4 N or Ri R2 R3 R4 P' hvDr =C 1 -C 2 Q -alkyl, phenyl, benzyl, alkyl-substituted phenyl or alkyl-substituted benzyl-; R 2 R 3 and R 1 = C 1 -C 2 Q alkyl. and may be the same or different; and where the crystals are indicated to have a tetragonal unit cell with a = 22.3Å and c = 42.4Å. oh ' -a o 2. Aluminosilicate according to claim 1, characterized in that it has an X-ray diffraction pattern mainly as indicated in table 1. 3. Aluminosilicate according to claim 1 or 2, characterized in that Q is tetrapropylammonium. 4. Aluminosilicate according to claim 1 or 2, characterized in that Q is cetyltrimethylammonium. 5. Process for the production of zeolite zeta 1 according to any of the preceding claims, characterized by reacting sodium aluminate, at least one silicon compound and at least one compound with the formula QX, where Q is as defined in any of the claims 1, 3 or 4, and X is an acid radical, OH or a halogen, and in that the reaction mixture has a composition, expressed as a mole ratio, in the following range: 6. Method according to claim 5, characterized in that a breakdown product of QX is used instead of QX. 7. Method according to claim 5, characterized in that a mixture of compounds is used which during the reaction forms Q in situ. 8.. Method according to claim 7, characterized in that a mixture of a trialkylamine and a C1~C20~ alcohol is used. 9. Method according to claim 7, characterized in that a mixture of a dialkylarylamine and a C 1 -C 2 Q alcohol is used. 10. Method according to one of claims 5-9, characterized in that the silicon compound or the main silicon compound is an aerosil, a fumed silica, a highly dispersed silica or water glass with a high silicon content and a SiO2/N a2 0 ratio between 3.2 and 4.0. 11. Method according to one of claims 5-9, characterized in that the silicon compound or the main silicon compound is silica gel dissolved in quaternary . ammonium or phosphonium hydroxide, whereby a silicate is formed. 12. Method according to one of claims 5-11, characterized in that the reaction is carried out at a temperature within the range 80-250°C. 13. Method according to claim 12, characterized in that the reaction is carried out at a temperature above 104°C in an autoclave, the ratio volume of reactants/volume of autoclave being within the range 0.1-0.7. 14. Process for producing zeolite zeta 1 mainly as described. 15. Zeolite zeta 1 essentially as described. 16. Cation-exchanged forms of zeolite zeta, 1, characterized in that the sodium cations in zeolite zeta 1, as stated in any of claims 1-4, are replaced with hydrogen or with any cation or cations of metals from the groups IA, IB, II, III (including rare earths), group VHA (including manganese), group VIII (including precious metals), and with lead and bismuth.