AU709491B2 - Method for producing olefin oligomers, using a modified mordenite based catalyst - Google Patents

Description

1A The present invention relates to a process for the production of oligomers of olefins. For example, it permits the production of premium grade, jet fuel and car diesel oil from light C 2 to C 8 olefins.

The starting olefins can come from any appropriate source and can also be produced by conversion of methanol.

The process according to the invention is particularly appropriate for refiners and/or petrochemists having a supply of methanol on the one hand and on the other hand one or more light C 2 to C 8 olefin production units, such as catalytic cracking, vapour phase cracking or catalytic dehydrogenation units.

The process according to the invention more particularly makes it possible to obtain: *0 1 good quality premium grade, 2) excellent quality jet fuel, 3) very good quality diesel fuel for diesel engines.

According to the present invention there is provided a method for producing oligomers, in which at least one monoolefin having 2 to 8 carbon atoms is placed in contact with mordenite which has been obtained by the following series of operations: a) subjecting non-dealuminized mordenite 30 substantially in the H or NH4 form to at least one treatment with steam at a temperature of at least 450 0 C to 600 0 C at a partial steam pressure above 60%, and b) treating the resulting product, at least once, with an acid at a concentration between 0.5 and S\\me l b 0\ h o m e$\Sabene\Keep\Speci\20048-97-institutrandupet.doc 15/02/99 1B The process according to the invention more particularly applicable in the following cases: a) The fresh charge is solely constituted by methanol which is initially supplied into a catalytic decomposition zone, where it is converted into water and light olefins mainly constituted by propylene and then, following the separation of the water formed, the light olefins are fed into a oligomerization zone, where they are transformed into a mixture of premium grade and bases for jet fuel and diesel engine fuel.

b) The fresh charge is solely constituted by light

C

2 to C 8 olefins either from a catalytic cracking unit, or 15 from a vapour phase cracking unit, or from a catalytic S00 dehydrogenation unit or from other supply sources. This fresh change is then directly supplied into the oligomerization section, where it is converted into a .o mixture of premium grade and bases for jet or diesel engine fuel.

9. 9 0* *o S. \\malb01\home$\Sabene\Keep\Speci\20048-97-inscitutfrandupet.doc 15/02/99 I

I

-2 c) The fresh charge is constituted by a mixture of the two preceding charges.

In the catalytic decomposition zone, the conversion of methanol into water and light olefins is carried out in the vapour phase in the presence of an acid zeolitic catalyst operating either in a fixed bed, or preferably in a fluidized catalytic system at a temperature of approximately 450 to 650 0 C (preferably 530 to 5900C), under a pressure of 0.01 to 1 MPa (preferably 0.05 to 0.5 MPa) with a liquid charge flow rate (space velocity) of approximately 5 to 100 volumes per catalyst volume and per hour, whereby the charge can be constituted either by pure methanol, or by a mixture in any proportion of steam and methanol.

The oligomerization reaction is performed in the liquid phase, in the supercritical phase or in the gaseous phase, in the presence of an acid zeolitic catalyst in the form of a fixed bed, at a temperature of approximately 50 to 400°C (preferably between 150 and 300°C), under a pressure of 2 to 10 MPa (preferably 3 to 7 MPa) and with a liquid hydrocarbon flow rate (space velocity) of approximately 0.3 to 4 volumes per catalyst volume and per hour.

The catalysts used for the reactions of converting the methanol into olefins and oligomerizing the light olefins are constituted by modified H form mordenites. However, the characteristics of the catalytic phases are optimized for each type of reaction.

For the reaction of transforming methanol into light olefins, it is possible to use known catalytic systems described in detail in European Patent 0084748 and US Patent 4 447 669. The H form mordenite has in this case a Si/Al ratio exceeding 80 and preferably between 100 and 150. These high Si/Al ratios are obtained by a dealumination procedure involving an alternation of calcinations under steam and acid treatments. The steam contents retained for the calcinations are below 60% and the treatment temperatures are between 500 and 6800C. The acid attacks are carried out in between 2 and 9 N concentrated acid solutions. It should be noted that the use of dealuminated mordenite is preferable to that of MFI type -3zeolites recommended by MOBIL OIL ("methanol conversion to light olefins" by Clarence D. Chang, Catal. Rev. Sci. Eng. 26 (3 and 4) pp. 323-345, 1984), because mordenite leads to higher propylene and butene yields.

The low ethylene rate obtained with mordenite is an important point, because it makes it possible to increase the diesel oil and jet fuel yields during the second stage of oligomerizing the olefins.

The use of H form zeolites for the reaction of oligomerizing light C to C 8 olefins has been proposed by numerous authors (US 4 487 985 US 4 513 156 US 4 417 086 US 4 414 423 US 4 417 088 US 4 414 423 US 4 423 268 M. OCCELLI, J. HSU and L. GALYA in J. Mol. Catal. 32, 1985, 377). According to the prior art, the most efficient zeolites for this oligomerization reaction must satisfy very strict criteria.

Two principle criteria have been defined, namely the constraint index (CI) of MOBIL OIL and the hydrogen transfer index (HTI of CHEVRON).

The constraint index CI normally makes it possible to characterize the geometrical selectivity properties of the zeolites. It is defined in detail in US 4 324 940 and in fact constitutes an approximate measurement of the relative cracking rate of n-hexane and 3 -methylpentane. Using the CI as the selection criterion for zeolites which may have interesting properties in the oligomerization of olefins, it is necessary according to the -prior art to be in a range between 2 and 12 (US 4 324 940 US 4 487 985 US 4 513 156). The selected zeolites are then mainly the following: ZSM 5, ZSM 11, ZSM 23 and ZSM 37. These zeolites are essentially characterized by pore apertures with 10 oxygens. Thus, the most open zeolites (pore apertures with 12 oxygens) such as mordenite,

ZSM

4, zeolite Y, zeolite beta have very low CI values 1 US 4 324 940).

Thus, it would appear that according to this prior art, apertures with are necessary for the oligomerization reaction of olefins, excluding the most open zeolites like mordenite. In fact, standard

H

form mordenite (zeolon 900 H) leads to mediocre performance characteristics OCCELLI, J. HSU and L. GALYA, J. Mol. Catal. 32 (1985) 377).

The second criterion which has been defined for selecting zeolites so -4that they have good performance characteristics in oligomerization is the hydrogen transfer index (HTI), which is defined in detail in US 4 417 086. The HTI is defined as the ratio of the quantities of 3 -methylpentene and 3 -methylpentane produced from n-hexene for conversions between and 70%. On the basis of this criterion, use should only be made of those zeolites whose HTI is above 10 and preferably above 25 (US 4 417 086 US 4 414 423 US 4 417 088). ZMS 5 with a HTI exceeding would again appear to be a preferred material. Even dealuminated mordenite with a HTI of only 1 must be excluded. Thus, according to this criterion, it would appear to have characteristics even inferior to those of amorphous silica-aluminas (US 4 417 088 US 4 417 086).

Finally, no matter which of the performance criteria CI or HTI is adopted for the oligomerization reaction of olefins, dealuminated or non-dealuminated mordenite is a material having little or no interest.

However, dealuminated mordenite, according to a special procedure, has been proposed for a very special olefin oligomerization reaction, namely the selective oligomerization of isobutene in a mixture of hydrocarbons containing other olefins, in particular 1 and 2 -butenes, the latter not having to be converted (US 4 513 166 US 4 454 367). It is known that the conversion of isobutene by oligomerization is a very easy reaction not requiring a high acidity. It can be performed on amorphous silicaalumina under not very severe operating conditions (US 4 268 700 US 4 324 938 US 4 392 002 US 4 423 264 EP 132172 FR 2 498 306 FR 2 495 605 FR 2 517 668 FR 2 508 899).

As will become apparent from the examples a mordenite modified according to a procedure differing from that of the invention can oligomerize isobutene without necessarily oligomerizing the other olefins present in the charge. According to US 4 513 166 and US 4 454 367, dealuminated mordenites permitting a selective transformation of isobutene have Si/Al ratios between 50 and 200, a pyridine retention capacity at 300 0

C

of 0.05 to 0.25 millimole/gram- 1 and are prepared by calcination cycles under steam-acid attack. Calcination is necessarily carried out at a r II 5 temperature exceeding 600 0 C, under a partial steam pressure below and acid attack is carried out in a solution with a concentration exceeding 4 N. It is also preferable, following the calcination cycles under steam (50% H 2 0) acid attack, to carry out a subsequent calcination between 400 and 7000C, in order to better stabilize the solid. The mordenites dealuminated according to the thus described procedure are very poor catalysts for the oligomerization of light olefins with a view to obtaining bases for diesel and/or jet fuels. This is probably due to two factors, on the one hand their non-optimized acidity, i.e. very low and on the other hand their imperfect crystalline organization. Thus, it is known that pyridine is an excessively strong and therefore inadequately selective base. It is adsorbed on all the acid sites present in the modified zeolites, no matter whether they are of the Br6nsted or Lewis types. The measurement of the pyridine quantity remaining adsorbed at 300 0 C on a zeolite gives access to the total quantity of acid sites present on the surface of the solid, but provides no precise information of the type of acid site (Bronsted or Lewis) and on their force distribution. Under these conditions, pyridine does not discriminate between medium force and strong force sites. Moreover, it has been shown that the acid attack following calcination under steam of a zeolite MACEDO, F. RAATZ, R. BOULET, E. FREUND, Ch. MARCILLY, Preprints of Poster Papers, the 7th International Zeolite Conference, Tokyo, July S 1986) must be carefully optimized in such a way that the cationic aluminiums liable to be formed during this calcination and which are specific poisons of the strong sites of the structure or framework are eliminated.

Moreover, for an identical Si/Al ratio, a well crystallized zeolite has a stronger acidity than the same solid, whose structure is less well organized.

In the applications aimed at by the present invention, it is preferred to transform by oligomerization all the olefins present in the charge

(C

2 to C 8 Unlike in the prior art (US 4 454 367 and US 4 513 166) it is no longer a question of selectively oligomerizing the isobutene.

From this standpoint, it is"known that the oligomerization rates of the light olefins vary in the sense: V isobutene V propene V 1butene and l-pentene V-2-butene V ethylene.

-6- Thus, for converting all the C 2 to Cg olefins, it is necessary to have a catalyst with strong acidity. The present invention has found that a not geometrically selective zeolite (poor CI and HTI), i.e. pore aperture with 12 oxygens, namely appropriately modified H form mordenite, makes it possible to prepare light olefin oligomerization catalysts with extremely good performance characteristics and even better than those prepared from zeolites with pore apertures and 10 oxygens (CI and HTI in the ranges recommended in the prior art). The dealumination procedure used makes it possible to achieve a high acidity and an excellent crystalline organization.

The mordenites which can be used as the basic material can have a natural or synthetic origin. However, preference is given to synthetic zeolites, because they can be prepared in a very pure phase with a controlled Si/Al ratio generally varying between 5 and 25 and more specifically between 5 and 15. If the starting mordenite contains organic structuring agents, they will be eliminated before any calcination treatment in the presence of oxygen, e.g. at 550 C, or by any other procedure known in the art.

In order to obtain the dealuminated H form, it is necessary in a first stage to eliminate the non-decomposable cations, generally Na+, present in the starting mordenite. For this purpose, there can be one or more exchanges in dilute solutions of acids such as HC1 or in solutions of

NH

4 The important point is that at the end of said first stage, which can be called decationization, almost all the alkaline cations are eliminated (Na percentage between 150 and 1000 ppm and preferably between 300 and 800 ppm) and that the solid obtained is in H form or H form precursor NH which is not substantially dealuminated (percentage dealumination 10% and preferably In a preferred manner, the H form precursor will be chosen as NH Thus, the Na+ NH 4 exchange does not lead to a dealumination of the structure. Thus, the latter is in a

NH

4 form obtained by exchange and normally free from structural defects.

In a second stage, the H form or the H form precursor, which is slightly or not dealuminated, undergoes a treatment under steam at a temperature above 4500C and preferably 550 to 6000C, under a partial steam pressure -7exceeding 60% and preferably 80%. The high partial steam pressure is an essential preparation criterion, because this high pressure leads to solids whose structure, although dealuminated, is very well recrystallized. It contains few defects. Without being bound by a particular theory, it can be assumed that a high partial steam pressure facilitates the migration of the silica from the amorphized zones and its subsequent reinsertion into the gaps of the structure left vacant by the departure of the aluminium. Following said second stage, a solid is obtained which is characterized by the presence of a small number of amorphous zones, which are precursors of a secondary porous lattice and by a crystalline structure substantially free from structural defects. The presence of amorphous zones in zeolites treated at high temperature under steam is a known phenomenon. However, the recommended operating conditions make it possible to limit to the maximum the amorphous zone proportion within the crystals. The crystallinity rates measured by X-diffraction are generally greater than 80% and more specifically 90%. The solids calcined under steam are also characterized by the presence, in structural micropores, of extra-lattice aluminic species, so that a subsequent acid attack is necessary, because said micropores are substantially blocked. However, to obtain a good oligomerization catalyst, said acid attack must be optimized.

The optimized acid attack constitutes the third stage of preparing the catalysts. In this stage, it is important to preserve or liberate the strong acid site of the solids. Thus, the acid attack must be sufficiently strong so that on the one hand it eliminates the cationic aluminiums formed during the steam treatment and which are poisons of strong sites and on the other hand to liberate the structural microporosity.

The Br6nsted-type acid sites linked with extra-lattice species are of average or low force, so that it is not indispensable to completely eliminate them. However, the acid attack must not be too strong, so as to prevent an excessive dealumination of the aluminiums of the structure.

The force to be retained for the acid attack is closely dependent on the characteristics reached after the steam calcination and in particular the crystal mesh. For structural Si/Al ratios between 10 and 40 acid -8solution concentrations (HC1, H2S04, HNO 3 etc.) between 0.5 and 5 N and preferably between 1 and 3 N will be used. For higher Si/Al structural ratios, acid solution concentrations between 5 and 20 N and preferably between 7 and 12 N will be used (the Si/Al structural ratios being determined by infrared spectroscopy for ratios between 10 and 40 and by NMR of 2 Si for higher ratios). In place of one attack in a concentrated medium, it is possible to carry out several attacks in a dilute medium. The above operating condition ranges merely illustrate the case where there is a single post-calcination acid attack, but this in no way limits the scope of the invention. Moreover, in order to reach high Si/Al ratios, i.e. higher than 40 and more specifically higher than it would be advantageous to use several calcination cycles with an optimized steam-acid attack. It is important that the acid attack is not too severe, because under these conditions there would be dealumination of the structure without recrystallization and therefore atomic vacancies would form, which constitute fragilization points for the structure.

The solids prepared according to the invention advantageously have Si/Al ratios between 10 and 100 and preferably between 20 and 60. They have a mesh volume between 2755 A 3 and 2730 A 3 (1A 10-10m) and preferably between 2745 and 2735 A 3 They preferably have an adequate acid force for the structural Al-OH to interact with a weak base such as ethylene (infrared measurement at 77°K) or a compound with weak acid characteristics such as H 2 S (infrared measurement at 25 0 These solids must also be preferably free from extra-lattice cationic species which can be detected by a fine signal (mid-height width below 5 ppm and preferably below 2 ppm) located at 0 ppm (reference Al(H20)63+) on a NMR spectrum of 27A1 measured by the rotation of the magic angle.

The following non-limitative examples illustrate the invention.

Example 1A Seven catalysts B1,B2,B3,B4,B5,B6 and B7 are prepared in accordance with the invention.

-9- The starting material used for preparing these various catalysts is a small pore mordenite, reference Alite 150 of Societe Chimique de la Grande Paroisse. Its chemical formula in the anhydrous state is Na,A10 2 (Si0 2 5 its benzene adsorption capacity is 1% by weight with respect to the dry solid weight and its sodium content is 5.3% by weight. 500 grams of this powder are immersed in a 2 M ammonium nitrate solution and the suspension is heated to 950C for 2 hours. The volume of the ammonium nitrate solution is equal to 4 times the dry zeolite weight (vol/wt This cation exchange operation is repeated 3 times. After the third exchange, the product is washed with water at 200C for 20 minutes with a vol/wt ratio equal to 4. The sodium content expressed as a percent by weight relative to the dry zeolite passes from 5.5 to The product is then filtered and various batches undergo calcination in a confined atmosphere, at a temperature which varies as a function of the degree of dealumination of the structure which it is wished to obtain (table The calcination time is fixed at 2 hours. The partial steam pressure within the reactor is approximately 90%. The crystallinity of the various solids following said calcination stage is equal to or greater than 99* On each of the solids an acid attack takes place with nitric acid, whose concentration increases with the degree of dealumination of the structure obtained during the preceding stage (table During acid attack, the solid is refluxed in the nitric acid solution for 2 hours with the vol/wt ratio of 8. The product is then filtered and generously washed with distilled water.

The atomic Si/Al ratios obtained for each of the solids are given in table 1.

Each modified solid is then shaped by kneading with an aluminic binder, at a rate of 20% by weight of binder, followed by passage through a die.

The diameter 1.2 mm extrudates obtained are then dried and calcined between 150 and 5000C for approximately one hour.

Catalyst B7, of overall Si/Al ratio of 115, is obtained by performing a 10 second calcination-acid attack cycle at a temperature of 6500C with a N nitric acid solution on catalyst B6.

Table 1 Catalyst B l B2 B3 B4 B5 B6 Calcination temperature (oC) Overall atomic Si/Al ratio Atomic Si/Al IV ratio of structure Normality of nitric acid solution Overall atomic Si/Al ratio 500 5.5 520 5.5 530 5.5 550 5.5 570 5.5 600 9 16 23 38 57 86 1 N 1.3N 2 N 7N 10 N 9 16 23 38 57 86 after calcination after acid attack Example 1B 7 catalysts B'1, B'2, B'3, B'4, B'5, B'6 and B'7 according to the invention are prepared. These catalysts differ from those described in example 1A, in that the starting material used for preparing them is no longer mordenite Alite 150 of Societe Chimique de la Grande Paroisse, but a wide pore mordenite, reference TSZ 600 NAA supplied by TOYO-SODA. Its chemical formula in the anhydrous state is Na, A10 2 (Si0 2 5.1 and its sodium content is 5.7%.

All the exchange, calcination, acid attack, shaping and calcination stages are performed under the same conditions as described in example 1A.

The atomic Si/Al ratios differ only slightly (table II).

I

11 Table II Catalyst Calcination temperature (oC) Overall atomic Si/Al ratio Atomic Si/Al IV ratio of structure Normality of nitric acid solution Overall atomic Si/Al ratio after calcination after acid attack B'1 500 5.1 B'2 520 5.1 B'3 530 5.1 B'4 550 5.1 B'5 570 5.1 B'6 600 5.1 8 14 20 36 55 83 a. S 1 N 1.3N 2 N 3N 10 N 8 14 20 36 55 83 Catalyst B'7 of Si/Al ratio 110 is obtained by carrying out a second calcination-acid attack cycle at a temperature of 6500C with a 10 N nitric acid-solution on catalyst B'6.

Example 2A The seven catalysts B1,B2,B3,B4,B5,B6 and B7 described in example 1A were tested in the oligomerization of a C 3 vapour phase cracking fraction with a view to obtaining a maximum of base for a jet fuel and diesel fuel. The operating conditions were as follows: Temperature 2100C Pressure 5.5 MPa Hourly liquid charge flow rate equal to 0.7 times the catalyst volume.

I

12 The charge had the following composition by weight: Propane Propene Isobutane n-butane 1-butene isobutene 2-butenes 5.22% 94.20% 0.16% 0.10% 0.08% 0.16% 0.08% oroe oo "Z I o 100 On leaving the reactor, the products respectively had the weight compositions given in table III.

Table III Catalysts B2 B3 B4 B5 B6 Constituents methane ethane 0.02 propane propene isobutane n-butane 1-butene isobutene 2 -butenes

C

5 oligomers 10.82 49.27 0.88 0.11 0.03 0.02 0.06 38.79 0.01 11.89 22.70 1.43 0.54 0.01 10.38 5.18 1.24 0.11 0.01 9.56 8.62 2.07 7.25 0.71 0.60 0.10 0.10 0.01 0.01 7.88 18.27 0.46 0.10 0.01 0.02 6.81 27.41 0.66 0.13 0.01 0.01 0.06 64.89 0.05 0.04 0.03 0.05 0.05 63.37 83.04 87.53 83.37 73.22 100 100 100 100 100 100 100 13 The different C5+ oligomers have the characteristics given in table IV.

Within the scope of the catalysts prepared according to the invention, it is preferable to work with dealuminated mordenites with a Si/Al ratio between 20 and 60 because 1) the activity of the catalyst is greater and leads to very high oligomer yields (83 to 88% on table III); 2) the 1800 diesel cut yield is also higher in the preferred range, as well as the characteristics of said diesel cut following hydrogenation and in particular the cetane number.

*e* a oe e 14 Table IV Catalyst B2 B3 B4 B5 B6 r r r Characteristics TOTAL C 5

OLIGOMER

density 20 0

C

bromine number naphtha cut PI-180 0 C (wt diesel cut> 1800C (wt DIESEL CUT 180 0

C

AFTER HYDROGENATION bromine number turbidity point smoke point (180 300 0 C cut) (mm) cetane number NAPHTHA CUT PI 1800C octane number:

RON

MON

Example 2B 0.785 71 31 69 0.4 <-50 0.790 68 0.797 62 0.803 58 0.799 60 28 24 20 23 33 72 76 80 77 67 0.787 70 0.772 83 49 51 33 37 0.5 0.3 0.4 0.3 0.6 <-50 <-50 <-50 <-50 (-50 *c The seven catalysts B'1, B'2, B'3, B'4, B'5, B'6 and example lB were tested in the oligomerization of the cracking fraction, whose weight composition is given The operation conditions were the same as in example B'7 described in

C

3 vapour phase in example 2A.

2A.

On leaving the reactor, the products respectively had the weight compositions given in table V.

15 Table V Catalysts Constituents methane ethane propane propene isobutane n-butane 1-butene isobutene 2 -butenes Cj 5+oligomers B'2 B'3 B'5 B16 B'7 0.02 10.34 53.69 0.82 0.11 0.03 0.02 0.07 34.90 0.01 11.95 28.73 1.44 0.54 0.01 0.01 0.06 57.25 0.02 10.45 11.96 1.16 0.18 0.01 0.05 76.19 9.66 8.72 2.17 6.22 0.72 0.61 0.10 0.10 0.01 7.97 17.33 0.48 0.10 0.01 0.05

S.

*5a* 6.92 25.81 0.69 0.13 0.01 0.01 0.06 66.35 100 0.03 87.32 0.04 84.30 100 100 100 100 100 100 The different C 5 oligomers had the characteristics given in table

VI.

S

S

S

SS

S S 16 Table VI Catalyst Characteristics TOTAL C5 OLIGOMER density 20 0

C

bromine number naphtha cut PI-180 0 C (wt diesel cut 1800C (wt DIESEL CUT 180 0

C

AFTER HYDROGENATION bromine number turbidity point smoke point (180 300 C cut) (mm) cetane number B'1 0.784 71 31 69 0.5 <-50 B'2 0.788 69 B'3 0.794 64 B'4 0.803 58 B'5 0.800 59 B'6 0.789 69 29 26 20 22 32 71 74 80 78 68 B'7 0.775 81 46 54 33 38 a.

a. o* 0.3 0.5 0.6 0.3 <-50 <-50 <-50 <-50 <-50 a NAPHTHA CUT PI 180°C octane number: RON 96 96 96 96 96 96 9 MON 83 83 83 83 83 83 8: As in the case of example 2A, it can be seen that with the catalysts prepared according to the invention, it is preferable to work with dealuminated mordenites having a Si/Al ratio between 20 and Example 2C For comparison purposes, three mordenite-based catalysts were prepared according to the method described in US 4 513 166 and US 4 454 367, 17 operating with a partial steam pressure of 30%, i.e. using a procedure differing from that recommended in the present invention.

Catalyst Cl had a Si/A1 ratio of 53 and a pyridine retention capacity equal to 0.07 millimole/g at 300 0

C.

Catalyst C2 had a Si/Al ratio of 97 and a pyridine retention capacity of 0.14 millimole/g at 300 0

C.

Catalyst C3 had a Si/Al ratio of 155 and a pyridine retention capacity of 0.22 millimole/g at 300 0

C.

These three catalysts were used for attempting to oligomerize the C 3 vapour phase cracking fraction, whose composition is given in example S 2A. The operating conditions were the same as in example 2A.

On leaving the reactor, the products respectively had the weight compositions given in table VII.

Table VII Catalysts Cl C2 C3 Constituents methane 0.86 0.49 0.18 ethane 0.46 0.24 0.07 propane 15.17 10.89 7.28 propene 73.32 78.16 83.87 isobutane 2.44 1.46 0.63 n-butane 0.39 0.26 0.16 1-butene 0.01 0.01 0.02 isobutene 0.01 2-butenes 0.29 0.16 0.12 1,3-butadiene 0.38 0.24 0.09 oligomers 6.68 8.09 7.57 100 100 100 18 It can be seen that such catalysts are not very suitable for the oligomerization of propene. They are not very active and not very selective, there is a significant formation of by-products, particularly propane, isobutane, methane and 1,3-butadiene. Moreover, it has been found that the activity of these catalysts very rapidly decreased as a result of the very large coke formation.

Example 3A Catalysts B3, B4 and B5 of example 1A were used for oligomerizing a C 4 vapour phase cracking fraction with a view to obtaining a maximum of base for a jet and diesel fuel. This charge had the following composition by weight: propene 0.06% isobutane 1.57% n-butane 8.92% 1-butene 24.36% isobutene 43.55% 2 -butenes 21.48% 1,3-butadiene 0.06% The operating conditions were as follows: temperature 2300C pressure 5.5 MPa hourly liquid charge flow rate 0.7 times the volume of the catalyst.

On leaving the reactor the products respectively had the weight compositions given in table VIII.

19 Table VIII Catalysts Constituents methane ethane propane propene isobutane n-butane l-butene isobutene 2 -butenes 19, 3 -butadiene C5 +oligomers B3 B4 B6 0.16 0.08 5.26 13.92 0.97 0.61 5.97 0.17 0.09 4.89 13.43 0.29 0.50 3.44 0.12 0.06 4.36 12.70 1.44 0.69 8.81 73.03 77.19 71.82 100 100o 100 The different C 5 oligomers had the characteristics given in table IX.

20 Table IX Catalyst B3 B4 Characteristics TOTAL C 5

OLIGOMER

density 200C 0.780 0.786 0.782 bromine number 68 65 66 naphtha cut PI-180 C (vt 34.5 30 33 diesel cut 180°C (wt 65.5 70 67 DIESEL CUT 1800C AFTER HYDROGENATION bromine number 0.6 0.4 .0.4 turbidity point C) <-50 <-50 smoke point (180 300 0 C cut) (mm) 31 31 31 cetane number 30 31 31 NAPHTHA CUT PI 0 180 C octane number: RON 99 98 99 MON 85 84 Example 3B For comparison purposes, catalysts Cl, C2 and C3 of example 2C were used for attempting to oligomerize the C 4 vapour phase cracking fraction, whose composition is given in example 3A. The operating conditions were the same as in example 3A.

21 On leaving the reactor, the products respectively had the weight compositions given in table X.

Table X

S

Catalysts Constituents methane ethane propane propene isobutane n-butane 1-butene isobutene 2-butenes 1,3-butadiene

C

5 oligomers 1.44 1.04 0.56 0.41 4.69 3.44 0.04 0.05 8.86 6.91 19.73 16.78 18.27 19.07 0.44 0.87 24.45 24.39 1.11 0.81 20.41 26.23 100 100 0.78 0.30 2.52 0.05 5.48 14.65 20.93 1.74 23.40 0.61 29.54 100 Although this type of catalyst is suitable for the oligomerization of isobutene, which is an easy reaction, it is not very suitable for the oligomerization of n-butenes, which are only very slightly converted.

Moreover, these catalysts are not very selective, because there is a large by-product formation, particulary n-butane, isobutane, propane, methane and 1,3-butadiene. Furthermore, as in the case of example 2B, there is a very rapid deactivation of the catalyst as a result of the formation of coke.

Example 4 Catalyst B4 of example 1A was used for oligomerizing a C 2 catalytic cracking fraction with a view to obtaining a maximum of base for jet and diesel fuel. This charge had the following weight composition: 22 ethane ethylene propane propane 4.29% 93.55% 1.36% 0.80% The operating conditions were as follows: temperature pressure hourly charge flow times the catalyst 280 0

C

5.5 MPa rate (brought to the liquid state) equal to volume.

C 4 C On leaving the reactor, the products had the following weight composition: methane 0.11% ethane 6.83% ethylene 5.89% propane 2.26% propene 0.41% isobutane 2.86% n-butane 0.27%

C

5 oligomers 81.37% 100 The C 5 oligomer had the following characteristics:

C

*r C C4*S bromine number density at 20 0

C

TBP distillation PI (OC) vol.

PF (OC) 59 0.801 curve 38 211 476

I_

23 This oligomer was then fractionated in a distillation column with theoretical plates and with a reflux ratio of 5/1.

The PI 1800 naphtha cut, which represented 43% by weight of the total oligomer, had a clear research octane number (RON) equal to 91.

The 1800C heavy cut, which represented 57% by weight of the total oligomer, was then hydrogenated in the presence of a catalyst based on palladium deposited on alumina. After hydrogenation, the product had the following characteristics: C. S 0O

S

OS S S S 0*c *5@

S

5.55 S S

S

S5 S S 0S** bromine number turbidity point smoke point cetane number 0.4 -500C 34 mm (180 300 0 C cut) 41 Example Catalyst B4 of example 1A was used for oligomerizing a C 3 catalytic cracking fraction with a view to obtaining bases for jet and diesel fuel.

This charge had the following weight composition: ethane ethylene propane propene isobutane n-butane 1-butene isobutene 0.18% 0.13% 23.75% 71.25% 3.10% 0.77% 0.27% 0.55% The operating conditions were as follows: temperature pressure hourly liquid 220 0 C 5.5 MPa charge flow rate 0.7 times the catalyst volume.

24 On leaving the reactor, the products had the following weight composition: ethane ethylene propane propene isobutane n-butane 1-butene isobutene C5 oligomers 0.18% 0.07% 27.05% 1.99% 3.52% 0.77% 0.01% 66.41% 66.41% 100 The C5 oligomer had the following characteristics: bromine number 57 density at 20 0 C 0.804 TBP distillation curve PI (oC) vol. 259 PF (OC) 494 This oligomer was then fractionated in a distillation column with theoretical plates with a reflux ratio of 5/1.

The PI 180 C naphtha cut, which represented 20% by weight of the total oligomer, had a clear research octane number (RON) equal to 96 and a clear motor octane number (MON) equal to 83.

The 180 0 C fraction, which represented 80% by weight of the total oligomer, was then hydrogenated in the presence of a catalyst based on palladium deposited on alumina. After hydrogenation, the product had the following characteristics: 25 bromine number turbidity point smoke point cetane number 0.4 -50 0

C

33 mm (180 300 0 C) cut 43 Example 6 Catalyst B4 of example 1A was used for oligomerizing a C 4 catalytic cracking fraction with a view to obtaining bases for jet and diesel fuel.

This charge had the following weight composition: oo o e o a

C.

•g

ZZ-

propane propene isobutane n-butane 1-butene isobutene 2-butenes 0.14% 0.37% 34.75% 11.93% 9.99% 15.96% 26.86% 100 The operating conditions were as follows: temperature pressure hourly liquid charge 240 0

C

5.5 MPa flow rate 0.7 times the catalyst volume.

On leaving the reactor, the products had the following weight composition: 26 propane 0.24% propene 0.05% isobutane 36.64% n-butane 14.50% 1-butene 0.12% isobutene 0.22% 2 -butenes 4.30%

C

5 oligomers 43.93% 100 S The C oligomer had the following characteristics: bromine number 64 density at 20 0 C 0.787 TBP distillation curve PI 79 50% vol. :199 PF (OC) :427 The oligomer was then fractionated in a distillation column with 40 theoretical plates and a reflux ratio of 5/1.

The PI 180°C naphtha cut, which represented 31% by weight of the total oligomer, had a clear research octane number (RON) of 97.5 and a clear motor octane number (MON) of 84.

The >180 C heavy fraction, which represented 69% by weight of the total oligomer, was then hydrogenated in the presence of a catalyst based on palladium deposited on alumina. After hydrogenation, the product had the following characteristics: bromine number 0.3 turbidity point 1-50 0

C

smoke point 31 mm (180 300 0 C cut) cetane number 27 Example 7 Catalyst B4 of example IA was used for oligomerizing a C 3

C

4 catalytic cracking fraction with a view to obtaining bases for diesel and jet fuel.

This charge had the following weight composition: propane 8.3% propene isobutane 23.3% n-butane 8% -butene 6.7% isobutene 10.7% 2-butenes 18% 100 The operating conditions were as follows:

S

temperature 225 0

C

pressure 5.5 MPa hourly liquid charge flow rate 0.7 times the catalyst volume.

On leaving the reactor, the products had the following weight composition: propane 9.42% propene 0.70% isobutane 24.64% n-butane 9.84% 1-butene 0.15% isobutene 0.26% 2-butenes 3.42% oligomers 51.57% 100 28 The C5 oligomer had the following characteristics: bromine number density at 20 0

C

TBP distillation PI (oC) vol.

PF (OC) 61 0.794 curve 77 225 456 a a. a a.

a a.

a The oligomer was then fractionated in a distillation column with 40 theoretical plates and a reflux ratio of 5/1.

The PI 180 0 C naphtha cut, which represented 25.5% by weight of the total oligomer had a clear research octane number (RON) of 96 and a clear motor octane number (MON) of 83.

The 1800C heavy fraction, which represented 74.5% by weight of the total oligomer, was then hydrogenated in the presence of a catalyst based on palladium deposited on alumina. After hydrogenation, the product had the following characteristics: bromine number turbidity point smoke point cetane number 0.4 -500C 32 mm (180 3000C fraction) 39 Example 8 Catalyst B4 of example 1A was used for oligomerizing a light C 5 105 0

C

fraction from the Fischer and Tropsch synthesis with a view to obtaining bases for jet and diesel fuel. This charge had the following weight composition: 29 propane isobutane n-butane 1-butene 2-butenes pentanes pentenes hexanes hexenes heptanes heptenes octanes octenes benzene 0.10% 0.30% 1.20% 3.40% 19.30% 5.20% 30.8% 3.6% 27.5% 0.9% 7.3% 0.4% a a..

a a a a a.

100 The operating conditions were as follows: temperature pressure hourly liquid charge 235 0

C

5. 5 MPa flow rate 0.7 times the catalyst volume.

On leaving the reactor, the products had the following weight composition: propane 0.10% isobutane n-butane 0.38% 2-butenes 0.01% pentanes 4.37% peritenes 0.19% hexanes: 6.65% hexenes 1.54% heptanes 4.81% heptenes octanes 1.22% octenes 1.09% 30 benzene 0.40%

C

9 oligomers :76.49% 100 After the stabilization of the product for eliminating the propane and butanes, the C 5 part was fractionated in a distillation column with theoretical plates and a reflux ratio of 5/1.

The PI 1800C naphtha cut, which represented 27% by weight of the total

C

5 fraction had a clear research octane number (RON) equal to 78 and a clear motor octane number (MON) of 74.

-EE-

The 180 C heavy cut, which represented 73% by weight of the total C fraction, was hydrogenated in the presence of a catalyst based on palladium deposited on alumina. After hydrogenation, the product had the following characteristics: bromine number turbidity point smoke point 33 mm (180 3000C cut) cetane number 46 Example 9 Catalyst B3 of example 1A was used for oligomerizing an olefin cut from the decomposition of methanol with a view to obtaining bases for jet and diesel fuel. This charge had the following weight composition: 31 di-methylether 0.16% methane 5.30% ethane 0.32% ethylene 9.71% propane 1.46% propene :54.60% isobutane 1.64% n-butane 0.41% 1-butene 3.82% isobutene 5.91% 2 -butenes 9.58% pentenes 5.12% hexenes 1.97% 100 The operating conditions were as follows: a a. a a.

a a a.

a a a a.

a temperature pressure hourly liquid charge 210 0

C

5. 5 MPa flow rate 0.7 times the catalyst volume.

On leaving the reactor, the product had the following weight composition: dimethylether methane ethane ethylene propane propene isobutane n-butane 1-butene isobutene 2 -butenes C 5 oligomers 0.13% 5.30% 0.41% 7.19% 4.50% 3.05% 2.59% 1.02% 0.25% 0.09% 5.25% 70.22% 100 32 After stabilization of the product to eliminate the dimethylether, methane, ethane, ethylene, propane, propene, isobutane, n-butane, l-butene, isobutene and 2 -butenes, the C5+ part was fractionated in a distillation column with 40 theoretical plates and a reflux ratio of 5/1.

The PI 180 C naphtha fraction, which represented 24% by weight of the total C5+ fraction had a clear research octane number (RON) of 97 and a clear motor octane number (MON) of 84.

The >180°C heavy fraction, which represented 76% by weight of the total C5 fraction, was hydrogenated in the presence of a catalyst based on palladium deposited on alumina. After hydrogenation, the product had the following characteristics: bromine number turbidity point <-500C smoke point 33 mm (180 3000C cut) cetane number 42 This application is divided from our copending application 10281/95 and the entire disclosure in the specification of the said 10281/95 is by this cross-reference incorporated into the present specification.

33 THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. Method for producing oligomers, in which at least one mono-olefin having 2 to 8 carbon atoms is placed in contact with mordenite which has been obtained by the following series of operations: a) subjecting non-dealuminized mordenite substantially in the H or NH 4 form to at least one treatment with steam at a temperature of at least 450 0 C to 600 0 C at a partial steam pressure above 60%, and b) treating the resulting product, at least once, with an acid at a concentration between 0.5 and 2. Method according to claim 1, wherein a C 3 or C 4 olefin cut is treated.

3. Method according to claim 1 or 2, wherein the 20 sequence of operations a) and b) is repeated at least once.

4. Method according to any one of claims 1 to 3, wherein the mordenite in H or NH 4 form is derived from ionic exchange of a sodium mordenite of atomic ratio Si/Al 25 of 5 to 5. Method according to any one of claims 1 to 4, wherein the steam treatment is carried out at 550-600 0 C at a partial steam pressure above 6. Method according to any one of claims 1 to wherein steps a) and b) are performed or repeated until there is obtained in the final product an atomic ratio Si/Al of 20 to 60 and a mesh volume between 2755 A 3 and 2730 A 3 (1 A 10- 1 0 m).

7. Method according to any one of claims 1 to 6, SH:\Sigrid\keep\patents\20048-97.doc10/05/99 H: \Sigrid\keep\patents\20048-97.doc 10/05/99

Claims (8)

1. 8. Method according to any one of claims 1 to 7, wherein said acid has a pKA value below 4.
2. 9. Method according to any one of claims 1 to 8, wherein said acid treatment is performed with a volume ratio of solution expressed in cm 3 to the weight of dry solid at 100 0 C expressed as grams higher than 3. Method according to any one of claims 1 to 9, wherein the atomic ratio Si/Al of the mordenite subsequent to treatment in a) is 10-100.
3. 11. Method according to any one of claims 1 to wherein the ratio of crystallinity of the mordenite is greater than 20 12. Method according to claim 11, wherein the ratio of crystallinity of the mordenite is greater than
4. 13. Method according to any one of claims 1 to 12, wherein the acid concentration is 0.5-5N where the atomic e 25 ratio Si/Al of the product of step a) is 10-40 and 5-20N where the ratio is greater than
5. 14. Method according to any one of claims 2 to 13, wherein the olefin cut contains normal olefins, whereby said normal olefins are oligomerized.
6. 15. Process for the preparation of a mordenite catalyst, comprising: a) subjecting non-dealuminized mordenite substantially in the H or NH4* form to at least one Streatment with steam at a temperature of 450°C to 600 0 C at H:\Sigrid\keep\patents\20048-97.doc 10/05/99 35 a partial steam pressure above 60%, and b) treating the resulting product, at least once, with an acid, said acid being used at a concentration of 0.5 and
7. 16. Method for producing oligomers substantially as herein described with reference to the accompanying examples.
8. 17. Process for the preparation of a mordenite catalyst substantially as herein described with reference to the accompanying examples. Dated this 1 0 t h day of May, 1999 INSTITUT FRANCAIS DU PETROLE 20 By their Patent Attorneys GRIFFITH HACK Fellows Institute of Patent and Trade Mark Attorneys of Australia *1 e H:\Sigrid\keep\patent\200487.doc 0/05/99 J ABSTRACT: Method for producing oligomers, in which at least one mono- olefin having 2 to 8 carbon atoms is placed in contact with a mordenite which has been obtained by the following series of operations: subjecting non-dealuminized mordenite substantially in the H or NH4/ form to at least one treatment with steam at a temperature of at least 450 0 C at a partial steam pressure above 60%, and treating the resulting product, at least once, with an acid, said acid being used at a concentration between 0.5 and oo .0 *0 S