GB2114110A - Process for synthesising ZSM-5 type zeolites having a low sodium content - Google Patents

Abstract

A process for preparing a ZSM-5 type zeolite comprising not more than 1.6% by weight of sodium oxide. An ethanolaminic component (EA) is mixed with a Na, an Al and a Si compound and water, the EA being selected from mono-ethanolamine, di- ethanolamine and ethanolaminic mixture comprising at least 1% of mono-ethanolamine and at least 50% of triethanolamine. The molar ratios between the reactants, expressed as oxides (except for EA) are: Na2O:Al2O3=from 1 to 15 EA:Al2O3=from 20 to 140 SiO2:Al2O3=from 20 to 100 H2O:Al2O3=from 950 to 6000 Na:(Na+EA)=from 0.05 to 0.5. The crystallised, dried and thermally activated product is a zeolite catalyst useful in the conversion of hydrocarbons by an acid catalysed reaction, particularly in the isomerization of meta-xylene, the disproportionation of toluene and the cracking of an n-hexane/3-methyl- pentane mixture.

Description

SPECIFICATION Process for synthesising ZSM-6 type zeolites having a low sodium content This invention relates to a process for synthesising zeolites of the ZSM-5 type by employing an ethanolamine compound during the formation of the crystallisation gel.

From published Italian Patent Application No. 22 639 A/79 it is known that by using an ethanolamine in the synthesis process, a zeolite of the ZSM-5 type is obtained. Because of the availability of ethanolamines (hereinafter referred to as EA) the synthesis of the most useful types of zeolites, and in particular ZSM-5 zeolite, starting from an ethanolamine, is a viable possibility.

However, the syntheses performed so far have been carried out with triethanolamine (TEA) only, and require extreme operating conditions (high temperatures > 1 900C and long process times > 8 to 9 days). Furthermore, the sodium content in the resulting zeolite is unacceptably high, since when the acid form (or H-form) of the zeolite is required (the acid form being the most useful for many types of catalysis) a long and complex ion exchange procedure is then necessary.

According to the present invention, there is provided a process for the preparation of a zeolite of the ZSM-5 type, comprising not more than 1.6%, and preferably not more than 0.1% by weight of Na2O, the process comprising the step of admixing an ethanolaminic component, H2O and at least a Na compound, an Al compound and a Si compound, in which said ethanolaminic component is selected from mono-ethanolamine, di-ethanolamine and an ethanolaminic mixture comprising at least 1%, and preferably 2%, by weight of monoethanolamine, and at least 50% by weight of triethanolamine, the molar ratios between said components in the reaction mixture, expressed as oxides (except for the ethanolaminic component) being as follows: Na2O:Al203=from 1 to 1 5 SlO2:Al203=from 20 to 100 EA:Al203=from 20 to 140 H2O::AI203=from 950 to 6000 Na-iNa+EA)=from 0.05 to 0.5.

The Na:(Na+EA) ratio will be hereinafter indicated as the SP ratio. It is understood that Al and Si may be partially or fully replaced gallium and germanium, respectively.

According to a preferred embodiment of the invention, said ratios are as follows: Na20:Al203=from 2 to 10 SiO2:AI203=from 20 to 60 EA:Al203=from 25 to 60 H2O:AI203=from 950 to 3000 SP=from 0.10 to 0.30.

The H2O:SiO2 molar ratio (the silicic dilution) is preferably in the range of 30 to 60. The H2O:(Na+EA) molar ratio (the global cationic dilution) is preferably in the range of 1 5 to 60, and more preferably 1 5 to 40. The ratio between the silicic dilution and the global cationic dilution is preferably in the range of 0.8 to 2.8.

The use of diethanolamine (DEA) and especially of mono-ethanolamine (MEA) in the process of the present invention allows one to obtain, directly from the synthesis, a zeolite of the ZSM-5 type having a sodium content lower than that of the corresponding product obtained using triethanolamine (TEA) alone. The sodium content achieved by each ethanolamine follows the sequence MEA < DEA TEA.

It has also been found that even if the sodium concentration in the initial gel or reaction mixture is high, with relatively long synthesis times and high initial Si/AI ratios and, even better, the use of ethanolaminic mixtures containing MEA even in amounts as small as 1% by weight, it is possble to achieve the preparation of a ZSM-5 type zeolite having a particularly low Na+ content (even less than 0.05% by weight). Such a low Na+ content avoids the necessity for long and complex treatments with ammonium chloride or HCI, previously required to obtain a zeolite in the acid form.

In particular, it has been found that while the use of TEA alone leads to unsatisfactory results, the use of MEA in combination with TEA results in a surprising synergistic effect. A further advantage deriving from the use of MEA in conjunction with TEA, is that of facilitating removal of the organic cation and of sodium either by washing or by exchange, thus eliminating or reducing the length of the calcining step normally carried out prior to the exchange. The calcining step has previously been necessary to obviate the high steric hindrance of the tri-substituted TEA compound. The ethanolaminic mixture comprising TEA and MEA may also include DEA and/or tetra ethanolammonium hydroxide or a salt thereof.

If MEA, and especially DEA are used, a very effective priming action is observed, in which satisfactory nucleation and crystallisation of the zeolite can occur at comparatively low temperatures (from 100 to 1 800C and preferably from 140 to 1 600C), in relatively short times, to result in wellcrystallised products.

The following sources of the starting products can be utilised: Si: a silica sol or a sodium silicate, Al: Na aluminate, Al sulphate, At203 or metallic Al, Na: NaOH, Na aluminate or a sodium silicate.

The zeolites according to the invention exhibit a well defined crystalline structure as compared with the ZSM-5 type zeolite disclosed in United States Patent Specification No. 3 702 886, according to their X-ray diffraction patterns (see Table 2).

The detailed operative conditions for the preparation of a ZSM-5 type zeolite, activated and optionally exchanged with different cations, are broadly described (for another type of zeolite) in Italian Patent Application No. 25320A/81.

It has been found that the rate of the entire process for synthesising the zeolite depends on the type of the ethanolaminic component; in fact the following order of effectiveness is observed: DEA > MEA TEA.

Under the syrthesis conditions herein described, but with the use of TEA alone, as the nucleationpriming ethanolaminic component, after heating the initial gel for 60 to 70 hours at 1 500 C, an amorphous solid or a partially crystallised product is formed, which agglomerates along with very fine crystals of diameter < 1. Conversely, when MEA and, particularly, when DEA is employed according to the invention, completely crystalline products with particles having diameters of a few microns may be obtained after only 48 hours.The crystallisation rate also depends on the Si02/Al203 molar ratio of the reaction mixture; when this ratio is higher than 100, i.e. outside the scope of the invention, the high ratio tends to favour the forming of siiicalcite, and higher temperatures and long crystallisation times are required.

The present invention relates also to the use of ZSM-5 type zeolites and zeolite catalysts prepared according to the invention for the conversion of hydrocarbons by acid-catalysed reactions.

Such reactions include cracking, hydrocracking, reforming, aromatization, dimerization, polymerization, alkylation, disproportionation, isomerization, dealkylation, transposition, esterification and dehydration.

Results of considerable interest have been attained in the isomerization of alkylbenzenes and in particular in the conversion of meta-xylene to the ortho and para isomers.

The isomerization of meta-xylene, optionally in admixture with ethylbenzene and minor proprotions of the desired products (ortho- and paraxyiene), can be carried out in the vapour phase, in the presence of H2 at a H2/hydrocarbon molar ratio of 3 to 10, at a temperature of 200 to 3500C and preferably of 250 to 3200C, at a pressure of 10 to 20 atmospheres and at a space velocity (LHSV) of 1 to 1 5 volumes of liquid hydrocarbon per volume of catalyst per hour (LHSV=from 1 to 1 5 h-1).

The ZSM-5 type zeolites prepared according to the present invention also prove to be useful in the disproportionation of toluene to benzene and to xylenes. Toluene disproportionation may be advantayeously performed in the vapour phase, in the presence of hydrogen at a H2/toluene molar ratio of 3 to 10, at a temperature of 300 to 5000C and preferably from 350 to 4500C, at a pressure of 30 to 40 atmospheres and at a space velocity (LHSV) of 1 to 5 h-'.

The ZSM-5 type zeolites prepared according to the present invention are also useful in the cracking of a mixture of n-hexane and 3-methyl-pentare.

The zeolite reaction mixture obtained according to the invention is crystallised, filtered, dried in an oven for 10 to 12 hours at 1 200C, and subsequently activated in air for 2 to 10 hours at a temperature of 400 to 6000C to provide a powdered ZSM-5 zeolite catalyst.

ZSM-5 type zeolites prepared according to the invention can be used in the acid form, either as they are prepared or when partially exchanged. Furthermore, active components can be added according to techniques other than ion exchange, such as, for example, impregnation (in dry or wet conditions), imbibition, co-precipitation and mechanical mixing.

The ZSM-5 type zeolites prepared according to this invention may be used in various forms, for example in the form of granules or extrudates. The powdered zeolite obtained from the synthesis is mixed with preferably 10 to 50% by weight of a binding material, such as clay, SiO2, Al203 or other metal oxide and then extruded. Prior to use, the extruded zeolites must be dehydrated, e.g. by heat treatment at high temperatures, optionally under vacuum. It is then advisable to carry out thermal activation in air, preferably at a temperature of 5000C to the temperature at which the structural collapse of the zeolite begins.

The following Examples illustrate the present invention.

In all the Examples, the zeolite crystallisation temperature was maintained at 1500 C. The X-ray analyses were carried out by following the method specified in published Italian Patent Application No.

23978 A/79. The Al203 and Na2O contents were determined by atomic absorption spectrometry on the solution obtained by treating the powdered zeolite samples with acid. The SiO2 content was calculated from the calcining value at 1 2000C, corrected by the Al203 and the Na2O content. The sodium aluminate consists of 57.5%Al203, 38.7% Na2O and 4.1% H2O (percentages by weight) and unless otherwise indicated the aqueous silica soi is 40% by weight of Si2O (Trade Name Ketjen Sol AS40).

Data and results of Examples 1 to 10 are reported in detail in Table 1; in Table 2 the X-ray diffraction data for the products of a few Examples is reported.

Example 1 111 g DEA (titre > 99%) were added dropwise, under stirring and at room temperature, to a solution of 3.9 g NaOH and 3.7 g sodium aluminate in 380 cm3 H20. Then 85.9 g of aqueous silica sol were added thereto under intense stirring and the conditions maintained for 1 hour. The initial molar ratios of the components, mostly referred to Al203, are recorded in Table 1. The gel which formed was transferred to a Hastelloy C autoclave and was heated to 1 500C for 60 hours, under stirring (50 rpm), under an autogenous pressure. After cooling, the suspension was discharged and filtered and the solid product was washed until the disappearance of the Na+ ions from the washing liquid, and thereafter dried at 1 200C for 12 hours.The X-ray diffraction pattern (see Table 2) revealed that the product substantially consisted of zeolite having a structure of the ZSM-5 type, the composition of which, on analysis, was the following (% by weight): SiO292.3%; Al203=6.1%, Na20=1 .6%. The SiO2/AI203 molar ratio in the zeolite ZSM-5 type was equal to 25.7.

Example 2 43 g MEA were added, under stirring and at room temperature, to a solution of 3.9 g NaOH and 3.7 g sodium aluminate in 480 cm3 H20; 85.9 g aqueous silica sol were then added under intense stirring, whereafter the procedure of Example 1 was followed, but for heating of the gel for a longer period of time (65 hours) thus obtaining a zeolite of ZSM-5 type having a high degree of crystallinity.

Example 3 Example 2 was repeated, but with heating of the gel for a longer period of time (75 hours), thus obtaining a zeolite of ZSM-5 type (see Table 2) having a high degree of crystallinity and an exceptionally low Na content (see Table 1).

Example 4 43 g MEA were added, under stirring and at room temperature to a solution consisting of 3.9 9 NaOH and 1.9 g sodium aluminate in 480 cm3 H20; then, under stirring, 85.9 g of aqueous silica sol were added, and the procedure continued as in Example 1, but with heating of the gel for a shorter time (48 hours). There was obtained a zeolite of ZSM-5 type having a high degree of crystallinity and an extremely low Na content (see Table 1).

Example 5 (Comparative) 43 g MEA were added, under stirring and at room temperature, to a solution consisting of 3.9 g NaOH and 0.95 g sodium aluminate in 480 cm3 H20; then 85.9 g aqueous silica sol were added under intense stirring and the procedure continued as in Example 1, but with heating of the gel for a shorter time (48 hours). As it is apparent from the results shown in Table 1, the high SiO2/AI203 ratio reduces the crystallisation rate, so providing a product consisting of small amounts of zeolite ZSM-5 type and predominantly of an amorphous material.

Example 6 (Comparative) 52.5 g of a raw mixture of EA, containing (as determined by gas chromatography) 78% by weight TEA, 8% by weight DEA, 2% by weight MEA and 12% by weight of heavier derivatives, predominantly tetraethanol ammonium hydroxide, were added, under stirring and a room temperature to a solution consisting of 3.9 g NaOH and 3.7 g sodium aluminate in 480 cm3 H20. 85.9 g aqueous silica sol were then added under intesne stirring, and the procedure continued as in Example 1, except for the crystallisation time. After 65 hours the product was still completely amorphous and only after 75 hours was the start of the crystallisation observed.

Example 7 163.5 g of the raw mixture of Example 6, were added, under stirring and at room temperature, to a solution of 3.9 g NaOH and 3.7 g sodium aluminate in 300 cm3 H20. 85.9 g aqueous silica sol were then added under intense stirring, and the procedure of Example 6 continued, to obtain a ZSM-5 type zeolite (see Table 2) having a good degree of crystallinity and an extremely low Na content (see Table 1).

Example 8 (Comparative) 52.5 g pure TEA (titre 99%) were added, under stirring and at room temperature, to a solution consisting of 3.9 g NaOH and 3.7 g sodium aluminate in 480 cm3 H20. 85.9 g aqueous silica sol were then added under intense stirring, and the procedure of Example 1 continued, except for the crystallisation time. After 65 hours, the product obtained was still completely amorphous.

Example 9 (Comparative) 52.5 g pure TEA were added, under stirring and at room temperature, to a solution of 3.9 g NaOH and 3.7 g sodium aluminate in 480 cm3 H20. 114.5 g aqueous silica sol containing 20% by weight of SiO2 (Ludox AS) were then added under intense stirring. The procedure was continued as in Example 1.

but for the crystallisation time. After 65 hours the product was still completely amorphous and only after 75 hours were appreciable amounts of ZSM-5 type zeolite observed.

Example 10 (Comparative) 163.5 g pure TEA were added, under stirring and at room temperature, to a solution consisting of 3.9 g NaOH and 3.7 g sodium aluminate in 300 cm3 H20. 85.9 g aqueous silica sol (40% by weight of SiO2) as employed in Examples 1 to 8 were then added under vigorous stirring. The procedure was continued as in Example 1, but for the crystallisation time. After 65 hours the product was still completely amorphous and only after 75 hours were appreciable amounts of ZSM-5 type zeolite observed (Table 2).

The use of the zeolite samples of the foregoing Examples in hydrocarbon conversion reactions will now be illustrated in the following Examples.

Example AIsonn, erization of xylene The samples obtained in Examples 1, 2, 5, 6, 8, 9 and 10 were activated at 5400C for 10 hours in air and were then treated in a flask equipped with a reflux cooler with an aqueous solution of ammonium chloride at 5% by weight; the weight ratio between the solution and zeolite was equal to 1 9. Under moderate stirring, the flask was heated to 70 to 800C for 1 hour; the decanted product was subjected to the same operating four further times with a fresh solution of NH4CI each time. At the conclusion of the exchange, the product was washed with distilled water, until the disappearance of the Cl ions from the washing liquid, and was dried at 1 200C for 12 hours.By successive activation of the compound in air at 5400C for 10 hours, the so-calied acid form or "H-zeolite" was obtained.

The products of Examples 1,2, 5, 6, 8, 9 and 10 so exchanged, and the unexchanged samples obtained in Examples 3, 4 and 7, were homogeneously mixed with 10% by weight of alumina and kneaded with a suitable amount of H20 to allow the resulting mass to be extruded into small cylinders of 1 mm diameter. The extrudates were dried for 12 hours at 110 to 1 200C and activated and 540"C for 2 hours.

The resulting catalysts were tested in the isomerization of m-xylene as follows: 1 5 cm3 of catalyst (apparent volume) were introduced into an electrically heated steel reactor having a diameter of 1 6 mm, into which a mixture consisting of meta-xylene and hydrogen in the molar ratio of 1:5 was fed at a pressure of 15.0 atmospheres and at a space velocity of 6 cm3/cm3/hour. The results, at different reaction temperatures are shown in Table 4.

Example B-Toluene disproportionation The sample of Example 3, formed into an extrudate as described in Example A, was tested as a catalyst for the disproportionation reaction of toluene. 30 cm3 of catalyst (apparent volume) were fed to the reactor of Example A; test conditions and results are recorded in Table 3.

Example C-Cracking of a n-hexane+3-methyl-pentane mixture The samples of Examples 1 to 10, prepared in accordance with Example A, were ground and sieved to particle sizes from 1 5 to 80 mesh. 3.8 cm3 ot he catalyst so obtained (apparent volume) were poured into an electrically heated steel reactor having a diameter of 10 mm, into which a mixture consisting of n-hexane, 3-methyl pentane and helium in the molar ratios 1:1:8 was fed, at atmospheric pressure and at a space velocity of 1 cm3/cm3/h. The results, at different reaction temperatures, are reported in Table 4.

Table 1

Example 1 Example 2 Example 3 Example 4 Example 5{b} (DEA) (MEA) (MEA) (MEA) (MEA) 1) Initial molar ratios 8io2:AI2o3 27.6 27.6 27.6 55.1 107.3 Na2O:AI203 3.5 3.5 3.5 5.7 10.3 EA:A1203 50.9 33.9 33.9 66.1 132.1 H2o:Al2o3 1150 1400 1400 2750 5500 H2O:8io2 41.9 51.6 51.6 51.6 51.6 Na/(Na+EA) 0.12 0.17 0.17 0.15 0.13 H20::(Na+EA)(C) 20.0 34.8 34.8 35.8 36.3 2) Crystallisation time (hours) 60 65 75 48 48 3) Final composition: SiO2 (% by weight) 92.3 92.0 93.2 96.7 97.1 Al203 (% by weight) 6.1 6.7 6.8 3.3 1.8 Na2O (% by weight) 1.6 1.3 0.03 0.04 1.1 SiO2/Al2O3 (molar) 25.7 23.3 23.3 49.8 91.7 4) Structure ZSM-5 ZSM-5 ZSM-5 ZSM-5 amorphous+ ZSM-5 5) Crystallinity high high high high low Table 1 (continued)

Example 6(b) Example 7 Example 8(b) Example 9(9) Example 10(b) (mixture) (mixture) (TEA) (TEA) (TEA) 1) Initialmolar ratios SiO2:Al2O3 27.6 27.6 27.6 27.6 27.6 Na20:Al203 3.5 3.5 3.5 3.5 3.5 EA:AI2O3 17.0(a) 52.8(a) 17.0 17.0 52.8 H2O:Al2O3 1400 950 1400 1500 950 H2O:SiO2 51.6 34.1 51.6 54.3 34.1 Na/(Na+EA) 0.29 0.12 0.29 0.29 0.12 H2O::(Na+EA)(c) 59.6 15.8 59.6 62.8 15.8 2) Crystallisation time (hours) 75 75 65 75 75 3) Final composition: SiO2 (% by weight) - 93.4 - 92.2 91.2 Al2O3 (% by weight) - 6.5 - 5.6 Na2O (% by weight) - 0.02 - 2.2 2.3 SiO2/Al2O3 (molar) - 24.4 - 28.0 23.9 4) Structure start of ZSM-5 amorphous ZSM-5 ZSM-5 crystal lisation 5) Crystallinity low good - sufficient good (a) The mixture being calculated as pure TEA.

(b) Comparative Example.

(c) Global cationic dilution.

Table 2

ZSM-5 ZSM-5 ZSM-5 ZSM-5 ZSM-5 U.S. 3 702 886 Example 1 Example 3 Example 7 Example 10 d( ) l/lo d( ) l/lo d( ) l/lo d( ) l/lo d( ) l/lo 11.1 S 11.13 S 11.13 S | 11.13 S 11.08 S 10.0 S 10.01 S | 9.97 S 9.98 S 9.95 S 7.4 W 7.45 W 7.42 W 7.43 W 7.43 W 7.1 W 7.11 W 7.07 W 7.08 W 7.06 W 6.3 W 6.35 W 7.36 W 6.35 W 6.35 W 5.97 5.97 5.98 5.98 5.98 5.56 W 5.58 W 5.58 W 5.58 W 5.57 W 5.01 W 4.99 W 4.99 W 4.99 W 4.98 W 4.60 W 4.62 W 4.61 W 4.62 W 4.62 W 4.25 W 4.27 W 4.27 W 4.27 W 4.27 W 3.85 V.S. 3.84 V.S. 3.85 V.S. 3.85 V.S. 3.85 V.S.

3.72 S 3.73 S 3.73 S 3.73 S 3.73 S 3.64 M 3.65 M 3.65 M 3.65 M 3.65 M 3.04 W 3.06 W 3.05 W 3.05 W 3.05 W 2.99 W 2.99 W 2.98 W 2.98 W 2.98 W 2.94 W 2.96 W 2.96 W 2.95 W 2.95 W W=weak M=mean S=strong V.S.=very strong Table 3

Temperature ( C) 350 400 450 500 Pressure (atm) 40 40 40 40 Space velocity (LHSV) (h-') 1.7 1.7 1.8 1.7 H2/C7H8 (molar) 6.6 6.5 6.4 6.8 Conversion (%) 11.3 31.0 49.2 59.7 Selectivity (moles/100 moles of converted C7H8) C6H6 30.9 47.6 57.4 57.7 C8H10 41.9 42.2 39.6 25.3 Product distribution (% by weight calculated on liquids) low boilings - 0.1 0.1 0.1 benzene 3.1 12.9 24.4 32.8 toluene 92.7 71.0 51.8 45.2 ethylbenzene - 0.1 0.6 1.1 para-xylene 1.0 3.8 5.4 4.3 ortho-xylene 1.0 3.1 4.7 4.3 meta-xylene 2.0 8.5 12.2 9.8 high boilings - 0.5 0.8 2.4 Table 4

Temperature meta-xylene Example SiO2/Al2O3 Ethanolaminic C conversion no. (molar) component Structure % 1 25.7 DEA ZSM-5 275 44.1 300 46.0 325 48.0 2 23.3 MEA ZSM-5 275 40.4 300 43.0 325 46.0 3 23.3 MEA ZSM-5 275 41.7 300 44.7 325 47.0 4 49.8 MEA ZSM-5 275 17.7 300 24.3 325 31.7 5 91.7 MEA amorhous+ZSM-5 275 5.1 300 8.3 325 14.8 6 - mixture start of crystallisation 275 13.7 300 19.1 325 28.1 7 24.4 mixture ZSM-5 275 42.6 300 46.0 325 47.8 8 - TEA amorphous 275 3.9 300 30.

325 2.2 9 28.0 TEA ZSM-5 275 36.3 300 45.0 325 48.0 10 23.9 TEA ZSM-5 275 43.5 300 46.3 325 48.3 Table 4 (continued)

Product distribution (% by weight of products) (*) n-hexane+ xylene iso-hexane Example Heavy conversion Constraint no. | meta ortho para toluene products % index (**) 1 55.9 19.0 24.6 0.2 0.3 23.7 5.1 53.7 20.9 24.0 0.5 0.9 40.4 5.2 52.0 21.3 23.4 1.4 1.9 60.2 4.7 2 59.5 14.7 23.0 0.3 2.5 16.1 6.7 56.9 18.1 23.8 0.4 0.8 31.2 5.2 53.9 20.1 23.6 1.0 1.4 49.7 4.6 3 58.2 16.9 24.1 0.3 0.5 15.6 6.5 55.3 19.5 24.0 0.5 0.7 31.9 5.2 52.9 20.7 23.6 1.2 1.6 48.0 5.0 4 82.3 4.7 12.4 0.2 0.5 28.2 6.1 75.7 7.2 16.6 0.3 0.2 37.2 5.8 68.3 10.6 19.6 0.7 0.9 48.7 4.3 5 94.9 11.2 3.5 - 0.5 9.1 5.1 91.7 1.5 6.2 - 0.6 12.9 5.3 85.2 3.1 11.2 - 0.6 19.2 4.5 6 86.3 3.0 10.0 - 0.7 4.7 1.9 80.9 3.7 14.8 - 0.6 9.0 5.8 71.9 7.0 20.9 - 0.2 17.7 3.5 7 57.4 17.3 24.8 - 0.5 18.2 6.8 54.1 20.5 24.1 0.5 0.8 34.2 4.8 52.2 21.3 23.5 1.3 1.7 48.8 5.3 8 95.9 1.6 1.9 - 0.6 - - 96.8 1.1 1.2 - 0.9 - 97.6 0.3 0.4 - 1.7 - 9 63.8 12.0 23.5 0.2 0.5 - 55.0 19.4 24.1 0.6 0.9 - 52.0 21.1 23.3 1.5 2.1 - - 10 56.6 18.4 24.4 0.3 0.3 23.6 6.4 53.7 20.9 23.9 0.6 0.9 42.9 4.6 51.7 21.1 23.2 1.6 2.4 61.2 4.7 (*) Light products and ethylbenzene are present in trace amounts 1 n fraction of unconverted n-hexane (**) Constraint index 1 n fraction of unconverted 3-methyl-pentane

Claims (23)

Claims

1. A process for the preparation of a zeolite of the ZSM-5 type comprising not more than 1.6% by weight of sodium oxide, the process comprising the step of admixing and ethanolaminic component (EA), H2O, and at least a Na compound, an Al compound and a Si compound, in which said ethanolaminic component is selected from mono-ethanolamine, di-ethanolamine and an ethanolaminic mixture comprising at least 1% by weight of mono-ethanolamine and at least 50% by weight of triethanolamine, the molar ratios between said compounds in the reaction mixture, expressed (except for the ethanolaminic component) as oxides, being as follows: Na2O:AI203=from 1 to 15 EA:Al203=from 20 to 140 SiO2:AI203=from 20 to 100 H2O:AI203=from 950 to 6000, Na:(Na+EA)=from 0.05 to 0.5.

2. A process as claimed in Claim 1, in which the zeolite comprises not more than 0.1% by weight of sodium oxide.

3. A process as claimed in Claim 1 or Claim 2, in which the ratios are as follows: Na2O:AI203=from 2 to 10 EA:Al203=from 25 to 60 SiO2:AI203=from 20 to 60 H20:AI203=from 950 to 3000 Na:(Na+EA)=from 0.10 to 0.30.

4. A process as claimed in any preceding claim, in which the H20:SiO2 molar ratio in the reaction mixture is in the range of 30 to 60.

5. A process as claimed in any preceding claim, in which the H20:(Na+EA) molar ratio in the reaction mixture is in the range of 1 5 to 60.

6. A process as claimed in Claim 5, in which the H20:(Na+EA) molar ratio in the reaction mixture is in the range 15 to 40.

7. A process as claimed in Claim 4 and Claims 5 or 6, in which the ratio between the H20:SiO2 molar ratio and the H20:(Na+EA) molar ratio is in the range 0.8 to 2.8.

8. A process as claimed in any preceding claim, in which the ethanolaminic mixture has a monoethanolamine content of at least 2% by weight.

9. A process as claimed in any preceding claim, in which the ethanolaminic mixture also comprises diethanolamine and/or tetra-ethanolammonium hydroxide or a salt thereof.

1 0. A process for preparing a zeolite catalyst, in which the zeolite reaction mixture, obtained from said step defined in any one of Claimsl to 9, is crystallised, filtered, dried in an oven for 10 to 12 hours at 1 200C and subsequently activated in air for 2 to 10 hours at a temperature of 400 to 6000 C.

11. A process as claimed in Claim 10, in which the zeolite is kneaded with 10 to 50% by weight of a binder and then extruded, the extruded mixture being heated and dried and subsequently activated by thermal treatment in air.

12. A process as claimed in Claim 11, in which the binder is selected from clay, silica, alumina, or other metal oxide.

13. A process as claimed in Claim 11 or Claim 12, in which the thermal treatment of the extruded mixture is carried out at a temperature of 5000C to the temperature at which the structural collapse of the zeolite begins.

1 4. A process for the conversion of hydrocarbons by an acid catalysed reaction, using a zeolite or zeolite catalyst prepared according to the process of any one of Claims 1 to 13.

1 5. A process as claimed in Claim 14, for isomerizing meta-xylene or aromatic mixtures containing same, in which meta-xylene is contacted with zeolite or zeolite catalyst prepared according to the process of any one of Claims 1 to 13.

1 6. A process as claimed in Claim 15, in which the meta-xylene is contacted with the zeolite or zeolite catalyst in the vapour phase in the presence of H2 at a H2/hydrocarbon molar ratio of 3 to 10, at a temperature of 200 to 2500 C, at a pressure of 10 to 20 atmospheres and at a space velocity (LSHV as defined herein) of 1 to 1 5 h-'.

1 7. A process as claimed in Claim 14 for the disproportionation of toluene, in which toluene is contacted, in the vapour phase, with a zeolite or zeolite catalyst prepared according to the process of any one of Claims 1 to 13, in the presence of H2 at a H2/toluene molar ratio of 3 to 10, at a temperature of 300 to 5000 C, at a pressure of 30 to 40 atmospheres and at a space velocity (LHSV as defined herein) of 1 to 5 h-1.

18. A process as claimed in Claim 14 for cracking a mixture of n-hexane and 3-methyl-pentane in which said mixture is contacted with a zeolite or zeolite catalyst prepared according to the process of any one of Claims 1 to 13.

1 9. A process for the preparation of a zeolite of the ZSM-5 type substantially as hereinbefore described with reference to any one of Examples 1, 2, 3, 4 and 7.

20. A process for the preparation of a zeolite catalyst as claimed in Claim 10, substantially as herein described with reference to Examples A, B and C.

21. A process for the conversion of hydrocarbons by an acid catalysed reaction according to Claim 14, substantially as herein described with reference to Examples A, B and C.

22. A zeolite or zeolite catalyst of the ZSM-5 type prepared by the process of any one of Claims 1 to 13, and 20.

23. A zeolite or zeolite catalyst as claimed in Claim 22 comprising not more than 0.1% by weight of sodium oxide.