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

Abstract

A process for preparing a hydroconversion catalyst comprising the steps of: preparing a modified zeolite of the FAU framework type, whose intracrystalline structure presents at least one network of micropores, at least one network of small mesopores with a mean diameter of 2 to 5 nm and at least one network of large mesopores with a mean diameter of 10 to 50 nm; these various networks being interconnected; mixing the zeolite with a binder, shaping the mixture, and then calcining; impregnating the shaped zeolite with at least one compound of a catalytic metal chosen from compounds of a metal from group VIII and/or from group VIB, in acidic medium, provided that at least one compound of a catalytic metal is soluble within said acidic medium and that the acid acts as a complexing or chelating agent for at least one compound of a catalytic metal.

Claims

1. Process for preparing a hydroconversion catalyst based on a modified zeolite of the FAU framework type with preserved crystallinity and interconnected trimodal porosity, comprising the steps of: A—preparation of a modified zeolite of the FAU framework type, whose intracrystalline structure presents at least one network of micropores, at least one network of small mesopores with a mean diameter of 2 to 5 nm and at least one network of large mesopores with a mean diameter of 10 to 50 nm; these various networks being interconnected with each other; B—mixing the zeolite with a binder, shaping the mixture, and then calcining and obtaining a shaped zeolite; C—impregnation of the shaped zeolite with at least one compound of a catalytic metal chosen from compounds of a metal from group VIIIB and/or from group VIB, in acidic medium, provided that at least one compound of a catalytic metal is soluble within said acidic medium and that the acid acts as a complexing or chelating agent for at least one compound of a catalytic metal, and obtaining a final catalyst exhibiting a crystallinity and a volume of micropores of from 60 to 130% of those of the shaped zeolite.

2. Process according to claim 1, wherein the acidic medium contains water as solvent.

3. Process according to claim 1, wherein the acid is an organic oxygen- or nitrogen-containing compound that contains at least one carboxylic functional group and at least one additional function group selected from carboxylic, hydroxyamic, hydroxyl, keto, amino, amido, imino, epoxy, and thio.

4. Process according to claim 1, wherein the acid is an inorganic acid selected from the group of phosphorus-containing acids.

5. Process according to claim 1, wherein the acid concentration is in the range from 0.2 to 5 M.

6. Process according to claim 1, wherein the metals are selected among nickel, cobalt, molybdenum, tungsten, platinum, palladium, ruthenium or their combination.

7. Process according to claim 1, wherein the catalyst contains from 0.1% to 20% by weight of a metal from group VIIIB and from 1% to 30% by weight of a metal from group VIB.

8. Process according to claim 1, wherein the metal from group VIIIB is nickel and/or cobalt, and the metal from group VIB is molybdenum and/or tungsten.

9. Process according to claim 1, wherein the binder is selected among alumina, silica, silica-alumina, magnesia and titania, or mixtures of one or more of these compounds.

10. Process according to claim 1, wherein the shaped zeolite is impregnated with elements of groups VIB and/or VIIIB, and at least one element selected from the group consisting of phosphorus, boron, silicon and elements of groups VIIA, VB, and VIIB.

11. Process according to claim 3, wherein the organic acid is citric acid, thioglycolic acid, or maleic acid.

12. Process according to claim 4, wherein the acid is phosphoric acid.

13. Process according to claim 5, wherein the acid concentration is in the range from 0.3 to 3 M.

14. Process according to claim 5, wherein the acid concentration is in the range from 0.5 to 2 M.

15. Process according to claim 7, wherein the catalyst contains from 0.1% to 10% by weight of a metal from group VIIIB, and from 1% to 25% by weight of a metal from group VIB.

16. A shaped catalyst containing a modified zeolite of the FAU framework type, whose intracrystalline structure presents at least one network of micropores, at least one network of small mesopores with a mean diameter of 2 to 5 nm and at least one network of large mesopores with a mean diameter of 10 to 50 nm, these various networks being interconnected with each other; at least one binder; and at least one compound of a catalytic metal chosen from group VIIIB and/or from group VIB metals, wherein the crystallinity and micropore volume of the shaped catalyst are 60 to 130% of the crystallinity and micropore volume respectively of a shaped zeolite containing the modified zeolite of the FAU framework type having a trimodal intracrystalline porosity and the binder prior to impregnation of the at least one compound of a catalytic metal, wherein the shaped catalyst is prepared by the process of claim 1.

17. The shaped catalyst according to claim 16, wherein its crystallinity is above 70 to 120% of the crystallinity of the shaped zeolite containing a modified zeolite of the FAU framework type having a trimodal intracrystalline porosity and a binder.

18. The shaped catalyst according to claim 16, wherein its microporous volume is 70 to 120% of the microporous volume of the shaped zeolithe containing a modified zeolite of the FAU framework type having a trimodal intracrystalline porosity and a binder.

19. A hydroconversion process comprising contacting a hydrocarbon feedstock with the shaped catalyst according to claim 16.

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 pore size distribution of the parent zeolite CBV760 (HY30) and the zeolite with trimodal porosity (HYA)

(3) FIGS. 2a and b show electron tomographs of the parent zeolite CBV760 (HY30) and the zeolite with trimodal porosity (HYA)

(4) FIG. 3 shows the pore size distribution of the shaped HYA impregnated in presence of ethylene diamine (Cat-HYA), and in presence of citric acid (Cat-HYC) and in presence of phosphoric acid (Cat-HYP)

(5) FIG. 4 shows the conversion vs. temperature in hydrocracking of VGO for the shaped HYA impregnated in presence of ethylene diamine (Cat-HYA, triangles), in presence of citric acid (Cat-HYC, squares) and in presence of phosphoric acid (Cat-HYP, circles).

EXAMPLES

(6) Zeolite with trimodal porosity (HYA) was prepared according to the procedure described in WO 2010/07297.

Example 1

Preparation of a Modified Zeolite Y with Trimodal Porosity (HYA)

(7) Commercially available zeolite Y (CBV760, Zeolyst Int.), referred to as 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.

(8) The sample HYA is recovered.

(9) The characteristics of the samples HY30 and HYA are given in Table 1 and graphically represented in FIGS. 1 and 2.

(10) Characterization of the Samples HY30 and HYA

(11) Nitrogen Sorption

(12) TABLE-US-00001 TABLE 1 Results of nitrogen physisorption for HY30 and HYA Sample HY30 HYA S.sub.ex+meso.sup.a m.sup.2/g 213 339 V.sub.micro.sup.b ml/g 0.21 0.16 V.sub.meso.sup.c ml/g 0.16 0.25 V.sub.small meso.sup.d ml/g 0.07 0.14 V.sub.large meso.sup.e ml/g 0.09 0.11 V.sub.macro.sup.f ml/g 0.02 0.02 V.sub.tot.sup.g ml/g 0.45 0.51 Pore diameter.sup.h “small” — 2.7 (nm) “large” 28 27 .sup.amesopore surface area and external surface area calculated from the t-plot; .sup.bmicropore volume obtained by t-plot; .sup.cmesopore volume obtained by integration of the dV/dD BJH adsorption curve for the pores 2 to 50 nm in diameter; .sup.dvolume of the small mesopores obtained by integration of the BJH dV/dD adsorption curve for the pores 2 to 8 nm in diameter; .sup.evolume of the large mesopores obtained by integration of the BJH dV/dD adsorption curve for the pores 8 to 50 nm in diameter; .sup.fmacropore volume obtained by integration of the BJH dV/dD adsorption curve for the pores greater than 50 nm in diameter; .sup.gvolume adsorbed at p/p.sub.o = 0.99; .sup.hpore size distribution obtained from the BJH dV/dlogD adsorption curve.

(13) The development of mesoporosity is confirmed by a BJH (Barret-Joyner-Halenda) analysis of the pore size distribution. The pore size distributions, derived from the adsorption part of the isotherm, are represented in FIG. 1. As shown in FIG. 1, the BJH adsorption clearly shows two distinct regions of pores: a region of “small mesopores” centred at 3 nm a region of “large mesopores” centred at 30 nm.

(14) From the sample HY30 (no alkaline treatment) to HYA (alkaline treatment), the intensity of the peak corresponding to the small mesopores increases significantly, whereas the intensity of the peak corresponding to the large mesopores shows only a small increase coupled with weak broadening.

(15) This shape of the BJH adsorption curves shows that the alkaline treatment of HY30 essentially induces the formation of small mesopores, whereas an increase in the volume of the large mesopores is less pronounced. Furthermore, the dimensions of the two types of mesopores do not appear to be dependent on the conditions of the alkaline treatment.

(16) Table 1 shows the characteristics of HY30 and HYA. Notably, the corresponding volumes of the small and large mesopores are derived from the integration of the BJH adsorption part for a chosen range of diameters.

(17) Electron Tomography (3D-TEM)

(18) In contrast to conventional TEM microscopy, electron tomography allows better observation of the internal structure of the complex network of pores of the studied samples. In order to confirm the presence of the trimodal porosity demonstrated by the nitrogen sorption, the samples were subjected to an analysis by 3D-TEM, and the 3-dimensional (3D) reconstructions of the chosen particles were obtained.

(19) FIGS. 2a and 2b represent a section by 3D reconstruction of each of the three samples. Since the slices observed have a thickness of between 0.5 and 0.8 nm, they are not affected by the overlap characteristics as it is the case for conventional TEM micrographs.

(20) The lightest regions correspond to the pores, and the dark regions represent the solid matter.

(21) FIG. 2a represents a cross section of the sample HY30, 0.82 nm thick. The vapour and acid treatment led to creation of large mesopores in the form of channels and spheres of a broad diameter range, as shown by nitrogen sorption. The channel-shaped mesopores intersect and penetrate the particle from the outside inwards. The presence of isolated cavities is also confirmed. Although the nitrogen sorption shows that small mesopores are present, and their volume is virtually identical to that of the large mesopores, those appear to be absent.

(22) FIG. 2b represents a cross section of 0.82 nm thickness of the sample HYA that has undergone a mild alkaline treatment. A new series of small mesopores has appeared, and the walls of the mesopores in the form of channels and cavities are more irregular. The formation of small mesopores and their diameter (2-5 nm) can be measured with great precision and is in accordance with the results obtained by nitrogen sorption. Furthermore, the small mesopores appear to be uniformly distributed over the entire volume of the particle and are interconnected.

(23) The various characterization techniques demonstrate the particular mesoporous structure of the modified zeolites Y.

(24) The vapour treatment followed by an acid treatment (HY30) leads essentially to the generation of mesopores of about 30 nm, having a shape of channels and cavities.

(25) An additional alkaline treatment leads to the formation of a new network of small mesopores. The zeolites modified by the alkaline treatment and described in WO 2010/072 976 have a trimodal pore system, containing micropores, small mesopores and large mesopores.

(26) Without wishing to be bound by this theory, it appears from the 3D-TEM analysis that these various networks of micropores and mesopores, and in particular, the new pores formed (network of small mesopores), are interconnected (the mesopore networks being interconnected with each other and via the micropores).

Example 2

Shaping of HYA

(27) The zeolite with trimodal porosity HYA was shaped by extrusion, followed by a calcination step.

(28) The zeolite powder was mixed with a binder, alumina (Condea SB, 75% Al.sub.3O.sub.3), in an HYA/binder ratio of 80/20% by weight.

(29) Before extrusion and mixing with a binder, the zeolite powder HYA underwent a mild water vapour treatment (“steaming”) for 4 hours at 300° C.-500° C. once the final temperature was reached at a heating rate of 1-3° C./min starting from room temperature so as to repair/hydrolyse the aluminium bonds that may have been broken during the alkaline treatment.

(30) The extrusion process used is described below in detail: Alumina Condea, is mixed with an aqueous solution containing 2.1% nitric acid (0.59 ml per 1 g dry alumina) and then mixed during several minutes in a Z-arm mixer (Aoustin MX2) The fourfold amount (by weight) of HYA, based on the amount of the dry alumina, is added to the mixture. The mixture is mixed for 1 hour Then 2.5 wt % flocculant (Optimer® 9779, Nalco) and 7.5 wt % of Tylose®(Hoechst) are added to the mixture, whereas the percentages are based on the weight of dry alumina The mixing of the paste is continued for 1 hour At the end of this mixing, the paste is passed through a die having cylinder orifices with an inscribed diameter of 2.5 mm using an Aoustin MXE extruder The extrudates are then dried overnight at 110° C. and calcined at 600° C. for 10 hours

(31) The extrudates obtained had a cylindrical shape and were about 7 mm long and 2 mm in diameter.

(32) The extruded material was named Extr-HYA.

(33) The extrudates (Extr-HYA) then underwent a step of impregnation with metallic compounds, followed by calcination, as specified hereinbelow. The impregnation was performed via incipient wetness impregnation, a method described above.

Example 3

Impregnation of Extr-HYA with Metals in the Presence of Ethylene Diamine

(34) The preparation method used in the tests is as follows: 200 g of Extr-HYA extrudates were impregnated with 200 ml of aqueous solution containing 34.5 g of Ni(NO.sub.3).sub.2.6H.sub.2O, 54.3 g of (NH.sub.4).sub.6Mo.sub.7O.sub.24.4H.sub.2O and ethylene diamine in a molar fourfold to Ni. These amounts correspond to a target content of 3.5% by weight of NiO and 17.5% by weight of MoO.sub.3. The pH of the solution was around 9.

(35) The impregnated Extr-HYA extrudates were then dried at 110° C. for 16 hours and calcined at 500° C. (3° C./minute) for 3 hours under a stream of air (50 NI/hour), with observation of a colour change from purple to grey.

(36) These extrudates thus obtained from Extr-HYA are then ready to be used industrially and are herein below referred to as Cat-HYA.

Example 4

Impregnation of Extr-HYA with Metals in Presence of Citric Acid

(37) The operating method used in the tests is as follows: 50 g of Extr-HYA extrudates were impregnated with 45 g of 1 M aqueous solution of citric acid containing 8.81 g of Ni(NO.sub.3).sub.2.6H.sub.2O, 13.76 g of (NH.sub.4).sub.6Mo.sub.7O.sub.24.4H.sub.2O and additional 7 g of citric acid monohydrate added later directly to the suspension. These amounts correspond to a target content of 3.58% by weight of NiO and 17.63% by weight of MoO.sub.3. The pH of the solution was around 1.

(38) The impregnated Extr-HYA extrudates were then dried at 110° C. for 48 hours and calcined at 500° C. (3° C./min) for 3 hours under a stream of air (50 NI/h).

(39) These extrudates thus obtained from Extr-HYA are then ready to be used industrially and are herein below referred to as Cat-HYC.

Example 5

Impregnation of Extr-HYA with Metals in Presence of Phosphoric Acid

(40) The operating method used in the tests is as follows: 50 g of Extr-HYA extrudates were impregnated with 45 g of 1 M aqueous solution of phosphoric acid containing 8.81 g of Ni(NO.sub.3).sub.2.6H.sub.2O and 13.76 g of (NH.sub.4).sub.6Mo.sub.7O.sub.24.4H.sub.2O. These amounts correspond to a target content of 3.58% by weight of NiO and 17.63% by weight of MoO.sub.3. The pH of the solution was around 1.

(41) The impregnated Extr-HYA extrudates were then dried at 110° C. for 48 hours and calcined at 500° C. (3° C./min) for 3 hours under a stream of air (50 NI/h).

(42) These extrudates thus obtained from Extr-HYA are then ready to be used industrially and are herein below referred to as Cat-HYP.

Example 6

Characterization of the Shaped and Impregnated Catalysts

(43) X-Ray Diffraction

(44) The degree of crystallinity of the samples has been determined from the diffractograms by subtracting the background assigned to the amorphous part. Table 2 gives the degrees of crystallinity for the impregnated samples compared to the extruded material before impregnation. The degree of crystallinity is 20% for the HYA impregnated in presence of ethylene diamine, 45% for the impregnation in presence of citric acid and 68% for the impregnation in presence of phosphoric acid. Compared to the extruded material before the impregnation with the metal compounds, Extr-HYA, Cat-HYA has only 34% of the crystallinity, 37% of the BET surface area, 17% of the microporous volume and 57% of the total pore volume. In contrast, Cat-HYC preserves 76% of the crystallinity of Extr-HYA, 70% of the BET surface area, 75% of the micropore volume and 69% of the total pore volume. Cat-HYP shows even higher crystallinity compared to Extr-HYA, most probably due to the partial dissolution of the amorphous material contained in the zeolitic material during the impregnation with H.sub.3PO.sub.4. This hypotheses is fortified by the higher Si/Al bulk ratio of Cat-HYP compared to Cat-HYA and Cat-HYC.

(45) TABLE-US-00002 TABLE 2 Characterization results of impregnated HYA Sample Extr-HYA Cat-HYA Cat-HYC Cat-HYP Crystallinity % 59 20 45 68 Si/Al bulk 2.8 3.25 3.1 3.3 S.sub.BET.sup.a m.sup.2/g 609 228 426 394 S.sub.ext.sup.b m.sup.2/g 329 166 209 169 V.sub.micro.sup.c ml/g 0.12 0.02 0.09 0.09 V.sub.meso.sup.d ml/g 0.36 0.26 0.25 0.21 V.sub.tot.sup.e ml/g 0.54 0.31 0.37 0.32 NH.sub.3-TPD.sup.f mmol/g 0.398 1.2 1.2 0.9 Ni Wt % — 3.1 2.5 2.8 Mo Wt % — 9.0 9.8 10.3 .sup.aBET surface area; .sup.bexternal surface area; .sup.cmicropore volume; .sup.dmesopore volume; .sup.etotal pore volume; .sup.famount of desorbed NH.sub.3
Nitrogen Physisorption

(46) Table 2 shows the nitrogen physisorption results for Extr-HYA, Cat-HYA, Cat-HYC and Cat-HYP. The BET specific surface area, the microporosity and the total pore volume are higher for the samples impregnated in the presence of an acid. The external surface area is also higher for Cat-HYC and Cat-HYP. The mesoporous volume is almost the same for all samples. This indicates the improved microporosity and maintained mesoporosity for the samples impregnated in the presence of an acid compared to the one impregnated in the presence of ethylene diamine.

(47) FIG. 3 shows the pore size distribution (PSD) of Cat-HYA, Cat-HYC and Cat-HYP. The peak in the PSD of Cat-HYA around 4 nm is an analytical artefact. The graphs are similar with the crucial difference that the PSDs of Cat-HYC and Cat-HYP show a shoulder with a maximum at 3.4 nm corresponding to small mesopores. These small mesopores were also present in the PSD of the zeolite compound with trimodal porosity. Therefore, the porous structure of the zeolite compound is better preserved for the catalysts impregnated in presence of an acid. In the PSD of Cat-HYP there is also a peak at 36.6 nm present.

(48) Temperature-Programmed Desorption of NH.sub.3 (NH.sub.3-TPD)

(49) The amount of Brønsted acid sites (BAS) was determined by temperature-programmed desorption of NH.sub.3. Table 2 shows the overall acidity of Cat-HYA, Cat-HYC and Cat-HYP. For Cat-HYA and Cat-HYC it was 1.2 mmol/g; for Cat-HYP, 0.9 mmol/g.

Example 7

Catalysis—Hydrocrackinq of Vacuum Gas Oil (VGO)

(50) Catalysts were tested in hydrocracking of VGO in an isothermal pilot plant, where two trains of two trickle bed reactors were operated in series. In the first reactors of each train, pretreatment of the VGO feed has been carried out, whereas in the second reactors, the effluent was hydrocracked.

(51) The reactors were loaded with a total of 40 ml of catalyst into all four reactors.

(52) The diluent to catalyst ratio was set to 1:1 for the pretreatment reactors. For hydrocracking reactors, the diluent to catalyst ratio was set to 1:2 for the top catalyst bed and 1:1 for the bottom catalyst bed. 65 mesh (or 0.210 mm) Silicon Carbide was used as the catalyst diluent.

(53) All catalysts were sulphided in situ. The sulphiding medium for pretreatment reactors was a mixture of Straight Run Gas Oil (SRGO) and 4.0% w/w DMDS. The sulphiding feed for hydrocracking reactors, was a mixture of SRGO, 4.0% w/w DMDS and 1% TBA.

(54) Table 3 gives the composition of the VGO and sulphiding feed.

(55) TABLE-US-00003 TABLE 3 Properties of VGO and sulphiding feed (SRGO + DMDS + TBA) SRGO + 4% DMDS + Feed Description VGO 1% TBA Sulphur ppm 15040 37080 Nitrogen ppm 1250 1896 Density at 15° C. g/ml 0.9128 0.8609 API 23.4 32.7 Total aromatics % wt 44.95 — Mono-Aromatics 23.97 — Di-Aromatics 11.11 — Poli-Aomatics 9.87 — Hydrogen % wt 12.354 — Viscosity, 100° C. cSts 6.5165 — Basic Nitrogen ppmwt 432.1 — MCRT % wt 0.21 — Asphaltenes % wt 0.05 — Ni ppm 0.00 — V ppm 0.23 — Fe ppm 1.35 — Ext Sim Dist D Distillation 7213 Ext Sim Dist D 7213 Fraction (% w/w) IBP 230.8 —  5 326.8 10 356.4 20 385.8 30 403.2 40 418.6 50 432.6 60 447.6 70 465.0 80 487.8 90 515.0 95 534.2 FBP 572.2

(56) Pretreatment reactors were operated at 155 barg, LHSV of 2 and H.sub.2/oil of 1000 NL/L. The temperature was adjusted between 390 and 393° C. in order to get a nitrogen slip of 13±2 ppm.

(57) The operating conditions of the hydrocrackers were as follows:

(58) Pressure: 155 bar

(59) Temperature: 390-430° C.

(60) LHSV: 2 h.sup.−1

(61) H.sub.2/oil ratio: 1000 NL/L.

(62) The net 375+ conversion, the yields pattern and the hydrogen consumption are reported in Table 4 and in FIGS. 4 and 5.

(63) Catalysts Cat-HYC and Cat-HYP are 20-22° C. more active than Cat-HYA, meaning that 20-22° C. less are required over these catalysts to reach a conversion of 80% (Table 4, FIG. 4). The yield of the fraction boiling between 145 and 375° C. is 5 wt % higher over Cat-HYC and 4 wt % lower over Cat-HYP. The hydrogen consumption is 13-16 NL/L higher over Cat-HYC and Cat-HYP than over Cat-HYA.

(64) TABLE-US-00004 TABLE 4 Results of hydrocracking of VGO at 80% net conversion Sample Cat-HYA Cat-HYC Cat-HYP T.sup.a ° C. 414 392 394 Yield(145-375° C.).sup.b wt % 54 59 50 H.sub.2 consumption NL/L 245 258 261 .sup.aTemperature to reach 80% conversion; .sup.byield of the fraction boiling between 145 and 375° C.