Process for preparing a mesoporized catalyst, catalyst thus obtained and use thereof in a catalytic process

Abstract

The invention relates to a process for preparing a catalyst comprising a mesoporized zeolite, comprising the steps of: preparation of a protonic mesoporized zeolite, which contains at least one network of micropores and at least one network of mesopores, and treatment in a gas or liquid phase containing ammonia or ammonium ions. The invention also related to the obtained catalyst and the use of this catalyst in hydroconversion processes.

Claims

1. A process for preparing a catalyst comprising a mesoporized zeolite with healed zeolitic structure, including the steps of: A) preparation of a protonic mesoporized zeolite, which contains at least one network of micropores and at least one network of mesopores, and B) treatment of the protonic mesoporized zeolite obtained in step A) in a gas phase containing a source of ammonia to re-insert extra-framework zeolite Al atoms in octahedral coordination and Al atoms in pentahedral coordination into framework position where Al atoms are in tetrahedral coordination and obtaining a catalyst containing less extra-framework of zeolite Al atoms than the zeolite prepared during step A), thus obtaining a mesoporized zeolite with healed zeolitic structure.

2. The process according to claim 1, wherein the step A) includes the steps of: a) suspending a parent zeolite as starting material or a composite material comprising the parent zeolite in a basic pH aqueous solution comprising at least one strong base and/or an inorganic or organic weak base, at a concentration ranging from 0.001 to 2 M, at room temperature, with magnetic or mechanical stirring, b) neutralizing the medium by addition of at least one acid, at a concentration ranging from 0.005 to 2 M, at room temperature, with stirring, c) separating the zeolite obtained from the liquid and optionally washing it with a solvent, d) optionally drying the washed zeolite, e) optionally performing at least one ion exchange treatment of the zeolite from step c) or of the optionally dried zeolite from step d); f) optionally washing the zeolite, g) calcining the zeolite obtained, and h) recovering the protonic mesoporized zeolite.

3. The process according to claim 2, wherein the parent zeolite or a composite material comprising the parent zeolite as starting material has an atomic Si/Al ratio within the zeolite framework between 10 and 50.

4. The process according to claim 2, wherein, in step a), the basic pH solution/ zeolite weight ratio is in the range of 4 to 100.

5. The process according to claim 2, wherein, in step e), a ion exchange solution/mesoporized zeolite weight ratio may range from 3 to 75.

6. The process according to claim 1, wherein the volume percentage of the ammonia source is between 1 and 50 vol %.

7. The process according to claim 1, wherein the treatment according to step B) takes place in the temperature range between 15 and 600? C.

8. The process according to claim 1, including an extrusion step and/or a modification step of the final mesoporized zeolite catalyst (step B)) or of the protonic mesoporized zeolite (step A)) with metals, said metals being chosen from compounds of group VIII, from group VIB and mixture thereof, followed by a calcination step.

9. The process according to claim 2, including an extrusion step applied after step A) using the protonic mesoporized zeolite and before step B), followed by step B) and then by a subsequent modification step with metals, said metals being chosen from compounds of group VIII, from group VIB and mixture thereof, followed by a calcination step.

10. The process according to claim 8, wherein metals from Group VIB are chosen from the group consisting of Cr, Mo and W and metals from Group VIII are chosen from the group consisting of Fe, Ru, Os, Co, Rh, Jr, Ni, Pd, and Pt.

11. The process according to claim 1, wherein after the step A) and before the step B), said process includes a treatment step of the protonic mesoporized zeolite with water vapour.

12. The process according to claim 2, wherein the strong base is selected from the group consisting of NaOH and KOH, and the inorganic or organic weak base is selected from the group consisting of sodium carbonate, sodium citrate and tetraalkyl ammonium hydroxide.

13. The process according to claim 6, wherein the volume percentage of the ammonia source is between 3 and 40 vol %.

14. The process according to claim 6, wherein the volume percentage of the ammonia source is between 5 and 30 vol %.

15. The process according to claim 7, wherein the treatment according to step B) takes place in the temperature range between 20 and 350? C.

Description

DESCRIPTION OF THE FIGURES

(1) The invention is now described with reference to the attached non-limiting drawings, in which:

(2) FIG. 1 represents the X-ray diffractograms of the Pt-exchanged zeolite Y (HY30, CBV760, Zeolyst Int.), of the mesoporized zeolite Y before steaming (HYA), the mesoporized zeolite Y after steaming (HYA-st), the ammonia-treated non-steamed (HYA-NH3) and ammonia-treated steamed (HYA-st-NH3) samples respectively.

(3) FIG. 2 shows the pore size distribution for the Pt-exchanged zeolite Y (HY30, CBV760, Zeolyst Int.), of the mesoporized zeolite Y before steaming (HYA), the mesoporized zeolite Y after steaming (HYA-st), the ammonia-treated non-steamed (HYA-NH3) and ammonia-treated steamed (HYA-st-NH3) samples respectively.

(4) FIG. 3 shows the .sup.27Al MAS NMR spectra of the Pt-exchanged zeolite Y (HY30, CBV760, Zeolyst Int.), of the mesoporized zeolite Y before steaming (HYA), the mesoporized zeolite Y after steaming (HYA-st), the ammonia-treated non-steamed (HYA-NH3) and ammonia-treated steamed (HYA-st-NH3) samples respectively.

(5) FIG. 4 shows the .sup.29Si MAS NMR spectra of the Pt-exchanged zeolite Y (HY30, CBV760, Zeolyst Int.), of the mesoporized zeolite Y before steaming (HYA), the mesoporized zeolite Y after steaming (HYA-st), the ammonia-treated non-steamed (HYA-NH3) and ammonia-treated steamed (HYA-st-NH3) samples respectively.

EXAMPLES

(6) The zeolite Y (CBV760, Zeolyst Int.) is referred to as HY30.

(7) The characteristics of HY30 are given in Table 2 and graphically represented in FIGS. 1 to 5.

Example 1

Preparation of a Mesoporized Zeolite Y (HYA) and its Steaming (HYA-st)

(8) The compound HY30 is subjected to the following alkaline treatment: HY30 (200 g) is placed in contact with an aqueous 0.05 M NaOH solution (2500 ml) for 15 minutes at room temperature and under stirring, the resulting product is filtered off and washed with water, the filtered product is dried for 12 hours at 80? C., aqueous 0.20 M NH.sub.4NO.sub.3 solution (2500 ml) is added to the dry product, and the whole is left for 5 hours at room temperature under stirring. This manipulation is performed trice. the product obtained is washed with water, the product is then calcined at 500? C. for 4 hours (temperature gradient of 1? C./minute) in a stream of air, and then the HYA is recovered.

(9) HYA-st is prepared by steaming HYA at 300? C. for 4 hours (temperature gradient 5? C./min).

(10) The characteristics of the samples are given in Table 2, graphically represented in FIGS. 1-5 and discussed in Examples 3 and 4.

Example 2

Treatment of a Mesoporized Zeolite Y before and after Steaming (HYA/HYA-st) with Gaseous NH3 (HYA-NH3/HYA-st-NH3)

(11) HYA and HYA-st are respectively subjected to the following treatment: The sample (2 g) is placed in a U-formed glass tube and calcined at 550 ? C. (1? C/min) for 6 hours in a flow of He, Then, the sample is cooled down to 150 ? C. in a flow of He and stabilized for 30 minutes, The gas is switched from pure He to 10 vol % NH.sub.3 in He, The samples are cooled to the room temperature and stabilized for 30 minutes in a flow of 10 vol % NH.sub.3 in He, HYA-NH.sub.3 and HYA-st-NH.sub.3 are respectively recovered.

(12) The characteristics of the samples are given in Tables 1 and 2, graphically represented in FIGS. 1-5 and discussed in Examples 3 and 4.

Example 3

Characterization of the Compounds HYA-st and HYA-st-NH3 before Impregnation with Pt

(13) Table 1 summarizes several characteristics of the HYA-st and HYA-st-NH3. The framework atomic Si/Al is decreasing after NH.sub.3-treatment, pointing to the re-insertion of some extra-framework Al into the framework positions. The distribution of different Al species shows that mostly pentahedral Al is transformed to tetrahedral framework Al upon NH.sub.3-treatment. The re-insertion of Al into the framework positions can be associated with the healing of the structure of zeolite Y.

(14) In summary, a dealuminated zeolite Y has been further mesoporized by base treatment bringing with it a partial destruction of the zeolitic structure. Upon the above-described NH.sub.3-treatment, the zeolitic part of the material has been healed due to the re-insertion of extra-framework Al into the framework positions; whereas the mesoporosity remained preserved. A mesoporized zeolite Y with healed zeolitic structure has been prepared. The combination of mesoporosity and healed zeolitic structure can lead to an optimal combination of selectivity to middle distillates and high activity in numerous reactions.

(15) TABLE-US-00001 TABLE 1 Summary of the characterization results of HYA-st and HYA-st- NH3 Sample HYA-st HYA-st-NH3 Si/Al frame.sup.a 21.87 14.62 Al(tetrahedral).sup.b % 46.7 89 Al(pentahedral).sup.b % 48.7 2.9 Al(octahedral).sup.b % 4.6 8.1 .sup.aSi/Al atomic in the framework of the zeolite; .sup.bfrom the deconvolution of .sup.27Al MAS NMR spectra

Example 4

Characterization of the Compounds HY30, HYA, HYA-st, HYA-NH3 and HYA-st-NH3 Ion-exchanged with Pt for Further Catalytic Testing

(16) X-ray Diffraction

(17) FIG. 1 shows the X-ray diffractograms of the Pt-exchanged zeolite Y (HY30, CBV760, Zeolyst Int.), of the mesoporized zeolite Y before steaming (HYA), the mesoporized zeolite Y after steaming (HYA-st), the ammonia-treated non-steamed (HYA-NH3) and ammonia-treated steamed (HYA-st-NH3) samples respectively.

(18) HYA shows very weak reflections around 6.1, 9.97, 11.69, and 15.39 degrees 2?, corresponding to the reflections of the FAU structure. The reflections are weak and broad, probably, due to the small crystal size of the sample. There are no visible reflections in the diffractogram of HYA-st. After treatment with gaseous ammonia, the FAU-typical reflections appear in the diffractograms of HYA-NH3 and HYA-st-NH3, indicating the healing of the long-range zeolite structure. The crystallinity increases for the NH.sub.3-treated samples (Table 2).

(19) TABLE-US-00002 TABLE 2 Summary of the characterization results of Pt-modified HY30, HYA, HYA-st, HYA-NH3 and HYA-st-NH3 HYA- HYA- HYA- st- Sample HY30 HYA st NH3 NH3 Crystallinity % 8 0 0 21 10 Si/Al bulk n.d..sup.g n.d. n.d. n.d. n.d. Si/Al frame.sup.a 12.4 10.9 10.5 9.2 8.3 S.sub.BET.sup.b m.sup.2/g 296 299 285 467 385 S.sub.ext.sup.c m.sup.2/g 296 299 285 325 310 V.sub.tot.sup.d ml/g 0.36 0.38 0.38 0.44 0.41 V.sub.micr.sup.e ml/g 0.01 0.01 0.01 0.07 0.04 V.sub.meso.sup.f ml/g 0.22 0.23 0.23 0.32 0.27 TPD-NH.sub.3 mmol/g 0.36 0.33 0.38 0.46 0.38 Pt content wt % n.d..sup. n.d. n.d. n.d. n.d. .sup.aSi/Al in the framework of the zeolite; .sup.bBET surface area; .sup.cexternal surface area; .sup.dtotal pore volume; .sup.emicroporous volume; .sup.fmesoporous volume; .sup.gnot determined.
Nitrogen Sorption

(20) The BET surface areas of the samples HY30, HYA and HYA-st are laying between 285 and 300 m.sup.2/g. After the NH.sub.3-treatment, the BET surface areas of the corresponding samples are increasing, resulting in 467 m.sup.2/g for HYA-NH3 and 385 m.sup.2/g for HYA-st-NH3. For the samples before the ammonia-treatment, the BET surface area is corresponding to the external surface area, pointing to the absence of micropores in the samples. After the ammonia-treatment, the microporous volume increases from 0 to 0.07 mL/g for HYA-NH3 and 0.04 mL/g for HYA-st-NH3.

(21) The mesoporous volume as well as the total pore volume is increasing after the ammonia-treatment, reaching 0.32 mL/g for HYA-NH3. FIG. 2 shows the pore size distribution of HYA, HYA-st, HYA-NH3 and HYA-st-NH3. All catalysts show two maxima in the mesopore region. HYA and HYA-st have maxima around 3 nm and 19 nm, whereas the ammonia-treated samples around 3.1 nm and 16 nm. Therefore, they have at least trimodal porosity taking into account the presence of micropores in these samples.

(22) Elemental Analysis

(23) .sup.27Al MAS NMR Spectroscopy

(24) FIG. 3 shows the .sup.27Al MAS NMR spectra of the Pt-exchanged HY30, of the mesoporized zeolite Y before steaming (HYA), the mesoporized zeolite Y after steaming (HYA-st), the ammonia-treated non-steamed (HYA-NH3) and ammonia-treated steamed (HYA-st-NH3) samples respectively.

(25) All samples show an intense peak at about 55 ppm, corresponding to the tetrahedrally coordinated Al species. HY30, HYA, and HYA-st contain a small amount of octahedrally coordinated Al, represented by the peak at about 0 ppm. After the treatment with ammonia, the octahedrally coordinated Al disappears, whereas the peaks at 55 ppm become more pronounced. As no washing steps were carried out during the treatment with ammonia, we assume that the octahedrally and pentahedrally coordinated Al was reinserted into the framework positions of the zeolite upon treatment with ammonia.

(26) .sup.29Si MAS NMR Spectroscopy

(27) FIG. 4 shows the .sup.29Si MAS NMR spectra of the the Pt-exchanged HY30, of the mesoporized zeolite Y before steaming (HYA), the mesoporized zeolite Y after steaming (HYA-st), the ammonia-treated non-steamed (HYA-NH3) and ammonia-treated steamed (HYA-st-NH3) samples respectively. All spectra show overlapped peaks between ?115 and ?90 ppm, corresponding to the Si coordinated to one to two Al atoms. The spectra of HY30, HYA and HYA-st are similar, whereas after the treatment with ammonia, the peaks at higher ppm-values increase. This indicates the increase of the relative amount of Si(1Al) and probably also Si(2Al) species pointing out the reconstruction of the zeolitic structure.

(28) Temperature-programmed Desorption of Ammonia TPD-NH.sub.3

(29) HY30 showed 0.36 mmol NH.sub.3/g. After the desilication (HYA), the amount of acid sites decreased to 0.33 mmol NH.sub.3/g. The steaming caused a slight increase in the overall acidity to 0.38 mmol NH.sub.3/g. By treating HYA and HYA-st in the presence of gaseous ammonia, the overall acidity of HYA increased to 0.46 and that of HYA-st remained at 0.38 mmol NH.sub.3/g.

(30) Transmission and Scanning Electron Microscopy

Example 5

CatalysisHydrocracking of Squalane

(31) The samples HY30, HYA, HYA-st, HYA-NH3 and HYA-st-NH3 containing 0.5 wt % Pt were catalytically tested in hydrocracking of squalane (Alfa Aesar, 98.8%). The tests were performed using plug-flow reactors at following operating conditions: H.sub.2 pressure: 20 barg Temperature: 180-300? C. WHSV: 3 h.sup.?1 H.sub.2/squalane ratio: 4 mol/mol.

(32) The tests were performed using 1 mL of catalyst (sieved to 120-160 ?m), activated at 450? C. (1? C./min) for 4 h in a flow of hydrogen.

(33) FIG. 5 shows the plots of conversion vs. temperature for all samples.

(34) FIG. 6 shows the product distribution plots (weight percentage vs. C-cuts) at 75% conversion based on the data obtained by simulated distillation of the products obtained at different temperatures.