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

Abstract

The invention relates to a process for preparing a hydroconversion catalyst based on modified zeolite Y, comprising the steps of: Apreparation of a modified zeolite Y, 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; Bmixing the zeolite with a binder, shaping the mixture and then calcining; Cintroducing at least one catalytic metal chosen from metals of group VIII and/or of group VIB, followed by calcination. The invention also relates to a catalyst obtained via this process and also to the use thereof.

Claims

1. A process for preparing a hydroconversion catalyst based on modified zeolite Y, comprising in the following order the steps of: (A) preparing a modified zeolite Y of faujasite structure having an intracrystalline structure comprising 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, wherein the networks are interconnected; (B) mixing the modified zeolite Y with at least one first binder, shaping the resulting mixture by extrusion and then calcining, to obtain a shaped mixture; and (C) introducing at least one catalytic metal chosen from metals of group VIIIB or group VIB into the shaped mixture, followed by calcination, wherein the step (B) including the shaping by extrusion comprises: (i) making a paste by adding to a mixture of zeolite and at least one binder an aqueous suspension comprising at least one binder, and, optionally, at least one agent chosen from the families of flocculants, peptizers or plasticizers, (ii) extrusion of the paste obtained and chopping so as to obtain the extrudates of given shape and length, (iii) drying the extruded particles, (iv) calcination of the dried extruded particles.

2. The process according to claim 1, wherein the calcination of step (B) is performed at a temperature of 400 to 700 C.

3. The process according to claim 1, wherein the at least one first binder of step (B) is chosen from silica, alumina, silica-alumina, magnesia, or a mixture thereof.

4. The process according to claim 1, wherein the mixture obtained in step (B) comprises from 10% to 90% by weight of the first binder relative to the total weight of the mixture.

5. The process according to claim 1, wherein the modified zeolite Y treated in step (A) has a ratio of the volume of small mesopores (Vs) to the volume of large mesopores (Vl), Vs/Vl, of higher than or equal to 1.

6. The process according to claim 1, wherein the modified zeolite Y treated in step (A) has a total mesopore volume of higher than or equal to 0.20 ml/g.

7. The process according to claim 1, wherein the modified zeolite Y treated in step (A) has a micropore volume of less than or equal to 0.20 ml/g.

8. The process according to claim 1, wherein the modified zeolite Y treated in step (A) has a total mesopore volume/micropore volume ratio of higher than or equal to 1.

9. The process according to claim 1, wherein step (A) comprises the following steps: a) contacting a zeolite Y with a basic aqueous solution comprising at least one base at a concentration ranging from 0.001 to 0.5 M at room temperature and under magnetic or mechanical stirring, b) filtering off the zeolite obtained in step (a) and washing with a solvent, c) optionally, drying the washed zeolite, d) contacting the washed and optionally dried zeolite with a solution of NH.sub.4NO.sub.3, e) washing the zeolite obtained in step (d) with distilled water to neutral pH, f) calcining the zeolite obtained in step (e), and g) recovering the zeolite obtained in step (f) as the modified zeolite Y.

10. The process according to claim 9, wherein the zeolite Y treated in step (a) has an Si/Al ratio of higher than or equal to 12.

11. The process according to claim 9, wherein the zeolite Y treated in step (a) has undergone at least one dealumination treatment by at least one acid or by steam.

12. The process according to claim 9, wherein the at least one base is selected from NaOH, NH.sub.4OH, KOH, sodium carbonate or sodium citrate.

13. The process according to claim 9, wherein the solvent is a polar solvent.

14. The process according to claim 13, wherein the polar solvent is pure distilled water.

15. The process according to claim 9, wherein the solution is an aqueous solution of NH.sub.4NO.sub.3 at a concentration ranging from 0.01 to 0.5 M.

16. The process according to claim 1, wherein after performing step (A) and before performing step (B), a step of steam treatment at a temperature of 250 to 450 C. is performed for a duration of 2 to 6 hours.

17. A process for preparing a hydroconversion catalyst based on modified zeolite Y, comprising in the following order the steps of: (A) preparing a modified zeolite Y of faujasite structure having an intracrystalline structure comprising 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, wherein the networks are interconnected; (C) introducing at least one catalytic metal chosen from metals of group VIIIB or group VIB into the modified zeolite Y, followed by calcination; and (B) mixing the modified zeolite Y obtained in step (C) with at least one first binder, shaping the resulting mixture by extrusion and then calcining, wherein the step (B) including the shaping by extrusion comprises: (i) making a paste by adding to a mixture of zeolite and at least one binder an aqueous suspension comprising at least one binder, and, optionally, at least one agent chosen from the families of flocculants, peptizers or plasticizers, (ii) extrusion of the paste obtained and chopping so as to obtain the extrudates of given shape and length, (iii) drying the extruded particles, (iv) calcination of the dried extruded particles.

18. A hydroconversion catalyst obtained via the process according to claim 1, characterized in that the hydroconversion catalyst consists of a shaped mixture comprising: a modified zeolite Y, having an intra-crystalline structure comprising 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, wherein the networks are interconnected; at least one binder; and at least one catalytic metal chosen from metals of group VIIIB and/or of group VIB, said catalyst having the following characteristics: crystallinity of 3% to 80%, specific surface area (BET) from 150 to 550 m.sup.2/g, external specific surface area: 50-250 m.sup.2/g, total pore volume: from 0.2 to 0.6 ml/g, and zeolite content: 10% to 90% by weight.

19. The hydroconversion catalyst according to claim 18, having a crystallinity of 3% to 20%.

20. A process for hydroconversion of petroleum or heavy residues comprising a step of bringing feed into contact with the catalyst according to claim 18.

Description

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

(2) FIG. 1 shows the nitrogen sorption isotherms for a commercial zeolite Y (HY30) and for two zeolites with trimodal porosity (HYA and HYB), the volume of adsorbed nitrogen (cm.sup.3/g) being represented as a function of the partial pressure of nitrogen (P/P.sub.0),

(3) FIG. 2 represents the dV/d log D BJH adsorption curves as a function of the pore diameter (nm) measured for a commercial zeolite Y (HY30) and for two zeolites with trimodal porosity (HYA and HYB),

(4) FIGS. 3, 3A and 3B represent, respectively, a TEM-3D image of a commercial zeolite Y (HY30) and those of two zeolites with trimodal porosity (HYA and HYB),

(5) FIG. 4 represents the X-ray diffractograms of Cat-HY30 (black diffractogram), Cat-HYA (dark grey diffractogram almost superposed to the black one) and alumina (light grey diffractogram);

(6) FIG. 5 represents the nitrogen sorption isotherms for the catalysts Cat-HY30 (solid line) and Cat-HYA (dashed line);

(7) FIG. 6 represents the pore size distribution for the catalysts Cat-HY30 (solid line) and Cat-HYA (dashed line);

(8) FIG. 7 represents the electron transmission micrographs of the catalysts Cat-HY30 and Cat-HYA.

EXAMPLES

(9) The zeolite Y (CBV760, Zeolyst Int.) is referred to as HY30. The nitrogen sorption isotherm of HY30 is represented in FIG. 1, and the characteristics of HY30 are given in Table 1.

(10) This zeolite Y underwent dealumination before treatment to obtain a modified zeolite Y. It has an Si/Al ratio of 28.4, and an acidity measured by TPD NH.sub.3, of 0.32 mmol/g.

Example 1

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

(11) The compound HY30 is subjected to the following alkaline treatment: HY30 (2 g) is placed in contact with an aqueous 0.05 M NaOH solution (50 ml) for 15 minutes at room temperature and with stirring, the resulting product is filtered off and washed with water until a neutral pH (pH=7) is obtained, the filtered product is dried for 12 hours at 80 C., aqueous 0.20 M NH.sub.4NO.sub.3 solution (50 ml) is added to the dry product, and the whole is left for 5 hours at room temperature under stirring, the product obtained is washed with distilled water (350 ml), the product is then calcined at 500 C. for 4 hours (temperature gradient of 1 C./minute) with a stream of air, and then the HYA produced is recovered.

(12) The HYA produced has an Si/Al ratio of 24.8, and an acidity measured by TPD NH.sub.3 of 0.20 mmol/g.

Example 2

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

(13) The compound HY30 is subjected to the following alkaline treatment: HY30 (2 g) is placed in contact with an aqueous 0.10 M NaOH solution (50 ml) for 15 minutes at room temperature under stirring, the resulting product is filtered off and washed with water until a neutral pH (pH=7) is obtained, the filtered product is dried for 12 hours at 80 C., an aqueous 0.20 M NH.sub.4NO.sub.3 solution (50 ml) is added to the dry product, and the whole is left for 5 hours at room temperature under stirring, the product obtained is washed with distilled water (350 ml), the product is then calcined at 500 C. for 4 hours (temperature gradient of 1 C./minute) with a stream of air, and then the HYB produced is recovered.

(14) The HYB produced has an Si/Al ratio of 20.5, and an acidity measured by TPD NH.sub.3 of 0.21 mmol/g.

Example 3

Characterization of the Compounds HY30, HYA and HYB

(15) Nitrogen Sorption

(16) The nitrogen sorption isotherms of HY30, HYA and HYB are represented in FIG. 1.

(17) The presence of a hysteresis loop in each of the isotherms demonstrates the presence of mesopores in each of the samples.

(18) The comparison of the isotherms presented in FIG. 1 and, in particular, the increase in the amount adsorbed at highest relative pressures shows that the alkaline treatment brings about an increase in the total porosity of HYA and HYB compared to HY30.

(19) In addition, the higher the concentration of NaOH, the higher the porosity.

(20) At the lowest relative pressures, the nitrogen adsorption that corresponds to the microporosity does not appear to vary for HY30 and HYA. The harsher alkaline treatment (HYB) leads to a decrease in the micropore volume and to an even larger mesoporosity.

(21) 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. 2.

(22) As shown in FIG. 2, 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.

(23) From the sample HY30 (no alkaline treatment) to HYA (mild alkaline treatment) and then to HYB (harsh 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.

(24) 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.

(25) Table 1 shows the characteristics of HY30, HYA and HYB. 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.

(26) TABLE-US-00001 TABLE 1 Nitrogen sorption results for HY30, HYA and HYB Sample HY30 HYA HYB S.sub.ex+meso.sup.a m.sup.2/g 213 339 443 V.sub.micro.sup.b ml/g 0.21 0.16 0.07 V.sub.meso.sup.c ml/g 0.16 0.25 0.37 V.sub.small meso.sup.d ml/g 0.07 0.14 0.23 V.sub.large meso.sup.e ml/g 0.09 0.11 0.14 V.sub.macro.sup.f ml/g 0.02 0.02 0.03 V.sub.tot.sup.g ml/g 0.45 0.51 0.55 Pore diameter.sup.h (nm) small 2.7 3.1 large 28 27 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.0 = 0.99; .sup.hpore size distribution obtained from the BJH dV/dlogD adsorption curve.
X-Ray Diffraction

(27) The analysis by X-ray diffraction confirms the preservation of crystallinity of HYA that has undergone a mild alkaline treatment relative to the starting zeolite HY30.

(28) The sample HYB that has undergone a harsher alkaline treatment shows partial destruction of the long-range crystal ordering, but the overall crystallinity of the sample is preserved, as the characteristic zeolite Y reflections are still present. The preserved zeolitic nature and morphology of the zeolite Y is also confirmed by nitrogen sorption and electron microscopy.

(29) Transmission Electron Microscopy (TEM)

(30) The TEM micrographs show that the large crystals of zeolite Y remain intact, even after a harsh alkaline treatment. Inside all the particles, the presence of mesopores in the form of channels and spheres is observed, the channels penetrate into the particle, connecting the outer surface to the interior of the particle. Furthermore, the samples that have undergone an alkaline treatment appear to have a structure similar to a sponge, in contrast to the starting zeolite HY30. Based on the TEM micrographs one cannot distinguish the interconnection of the pores, their shape and dimensions.

(31) Electron Tomography (3D-TEM)

(32) 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.

(33) FIGS. 3, 3A and 3B 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.

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

(35) FIG. 3 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.

(36) FIG. 3A 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.

(37) FIG. 3B represents a cross section of 0.54 nm thickness of the sample HYB that has undergone a harsh alkaline treatment. An increase in the number of small mesopores is observed, confirming the results of the nitrogen sorption. Pores with a diameter as small as 1.2 nm can be observed, and the general density of these small mesopores appears to be greater than for HYA. As for the sample HYA, the 3D reconstruction of the entire particle represents interconnections of these small mesopores.

(38) Conclusion

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

(40) 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.

(41) 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.

(42) 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 inter-connected (the mesopore networks being interconnected with each other and via the micropores), which would make it possible to reduce the molecular diffusion limitations usually encountered, leading to an increased catalytic activity of the zeolites with trimodal porosity, as shown in the following examples.

Example 4

Shaping of the Industrial Catalyst Based on Modified Zeolite Y

(43) The commercially available modified zeolite Y, HY30 (CBV760, Zeolyst), and the zeolites with trimodal porosity HYA and HYB, were shaped by extrusion, followed by a calcination step.

(44) The zeolite powder (HY30, HYA or HYB) was mixed with a binder, alumina (Condea SB, 75% Al.sub.3O.sub.3), in an HY30/binder ratio of 80/20% by weight.

(45) Before extrusion and mixing with a binder, the zeolite powders HYA and HYB 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.

(46) The extrusion process used is described below in detail: weighing 250 g of alumina Condea, corresponding to 187.5 g of Al.sub.2O.sub.3 weighing 115 g of nitric acid (2.1% HNO.sub.3 solution) addition of nitric acid to the alumina, followed by stirring of the mixture (apparatus used: Aoustin MX2) weighing 750 g of HY30, HYA or HYB (powders) and addition to the mixture under stirring adding 10 g of a flocculant (Optimer 9779, Nalco) and 30 g of Tylose (Hoechst) adding distilled water (400 to 450 ml) until a paste of the desired consistency is obtained mixing of the paste is continued for 60 minutes extrusion of the paste using an Aoustin MXE extruder drying at 110 C. for 16 hours (temperature rise of 1 C./minute) calcination at 600 C. for 10 hours (1 C./minute).

(47) The extrudates obtained had a cylindrical shape and were about 7 mm long and 1.5 mm in diameter.

(48) The extrudates 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.

(49) The operating method used in the tests is as follows: 200 g of 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 ethylenediamine 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.

(50) The 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 Nl/hour), with observation of a colour change from purple to grey.

(51) These extrudates are now ready to be used industrially. The extrudates thus obtained based on HY30, HYA and HYB are referred to hereinbelow as Cat-HY30, Cat-HYA and Cat-HYB, respectively.

Example 5

Characterization of the Industrial Shaped Catalysts

(52) X-Ray Diffraction (Bruker D5000)

(53) The diffractograms of the catalysts Cat-HY30 (black), Cat-HYA (dark grey) and alumina (light grey) were recorded (FIG. 4). The diffractograms of Cat-HY30 and Cat-HYA are virtually identical. Reflections are observed at 28 values of 6; 11.8; 15.6; 20.2; 26.5; 30.1; 30.8, which correspond to the characteristic reflections of faujasite [Collection of simulated XRD powder patterns for zeolites, fifth revised edition, by M. M. J. Treacy and J. B. Higgins, Elsevier]. Reflections are also observed at 28 values of 47; 53; 80, corresponding to the reflections of alumina.

(54) The diffractograms of Cat-HY30 and Cat-HYA show a broad reflection centred at 2=26.5. The two reflections at 2=53 and 2=80, being intense in the diffractogramm of alumina, are very weak for the two catalysts Cat-HY30 and Cat-HYA.

(55) The two catalysts have a degree of crystallinity of about 3% to 10%.

(56) Nitrogen Sorption

(57) The adsorption and desorption measurements were carried out at the temperature of liquid nitrogen on a Micromeritics Tristar 3000 apparatus.

(58) FIG. 5 shows the nitrogen sorption isotherms for Cat-HY30 (solid line) and Cat-HYA (dashed line). These isotherms are of IV type, typical of mesoporous materials [F. Rouquerol, J. Rouquerol, K. Sing, Adsorption by Powders and Porous Solids: Principles, Methodology and Applications, Academic Press, London, 1999]. The isotherm of Cat-HY30 showed a clear decrease of the desorption profile at 0.5 p/p.sub.0, indicating the presence of large mesopores. The shape of the hysteresis of Cat-HYA suggested the presence of aggregates of particles in the form of platelets with pores of different shapes and sizes.

(59) FIG. 6 shows the pore size distribution of Cat-HY30 (solid line) and Cat-HYA (dashed line), calculated according to the BJH method applied to the adsorption curve of the isotherm. The BJH model was developed by Barrett, Joyner and Halenda [E. P. Barrett, L. G. Joyner, P. P. Halenda, J. Amer. Chem. Soc. 61 (1951) 373]. The pore size distribution graph of Cat-HY30 showed a more pronounced peak between 6 and 19 nm, while the pore volume was higher for Cat-HYA in the ranges of pore diameters of 2-6 and 20-50 nm.

(60) Table 2 shows the nitrogen sorption results for Cat-HY30 and Cat-HYA. The BET specific surface areas are similar for the two samples, while the specific surface area of Cat-HYA is 30 m.sup.2/g higher than that for Cat-HY30. The micropore volume is twice as high for Cat-HY30 compared to Cat-HYA. The mesopore and total volumes are very similar for the two samples, however, the volume of the small mesopores (2-6 nm) and of the large mesopores (20-50 nm) is higher for Cat-HYA than for Cat-HY30, 0.01 and 0.02 ml/g, respectively.

(61) TABLE-US-00002 TABLE 2 Results of the nitrogen sorption for the catalysts Cat-HY30 and Cat-HYA S.sub.BET S.sub.ext.sup.a V.sub.tot.sup.f (m.sup.2/ (m.sup.2/ V.sub.micro.sup.b V.sub.meso.sup.c V.sub.small meso.sup.d V.sub.large meso.sup.e (cm.sup.3/ g) g) (cm.sup.3/g) (cm.sup.3/g) (cm.sup.3/g) (cm.sup.3/g) g) Cat- 232 135 0.04 0.26 0.09 0.05 0.31 HY30 Cat- 228 166 0.02 0.26 0.10 0.07 0.31 HYA .sup.aexternal specific surface area calculated from t-plot; .sup.bmicropore volume obtained from 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 6 nm in diameter; .sup.evolume of the large mesopores obtained by integration of the BJH dV/dD adsorption curve for the pores 20 to 50 nm in diameter.
Temperature-Programmed Desorption of NH.sub.3 (TPD NH.sub.3)

(62) The amount of Brnsted acid sites (BAS) was determined by temperature-programmed desorption of NH.sub.3. The amount of BAS was 1.3 mmol/g for Cat-HY30 and 1.2 mmol/g for Cat-HYA.

(63) Transmission Electron Microscopy (TEM)

(64) The transmission electron micrographs were recorded using a Tecnai 20 transmission electron microscope at 200 kV. The images were acquired with a magnification of 19 000. The resolution of the reconstructions is sufficient to visualize micropores down to 2 nm in diameter. FIG. 7 shows the transmission electron micrographs of a crystal of Cat-HY30 and Cat-HYA. The two crystals show high porosity, but Cat-HYA appears to have more small mesopores. A dark line surrounding the crystals probably corresponds to the binder.

Example 6

CatalysisHydrocracking of Pretreated Vacuum Gas Oil (VGO)

(65) The catalysts Cat-HY30 and Cat-HYA were tested in hydrocracking of pretreated VGO, the composition of which is given in Table 3. The operating conditions for the pretreatment of VGO were as follows:

(66) Pressure: 131 bar

(67) Temperature: 395-397 C.

(68) LHSV: 1.2 h.sup.1

(69) H.sub.2/HC ratio: 750.

(70) During the pretreatment, the lights (compounds boiling below 35 C., including H.sub.2S and NH.sub.3) were removed.

(71) TABLE-US-00003 TABLE 3 VGO composition VGO Pretreated VGO.sup.(1) Density at 15 C., g/mL 0.9189 0.8579 Density at 60 C., g/mL 0.887 0.8259 Total nitrogen, ppm 1418 13.4 Basic nitrogen, ppm 401 0 Conradson carbon, weight % 0.34 0 Asphalthenes, weight % <0.5 0 Kinematic viscosity 70 C., mm.sup.2/s 20.64 4.791 Kinematic viscosity 100 C., mm.sup.2/s 8.524 2.729 Sulfur content, ppm 10 909 18.5 Aromatics, weight % 38.4 18.9 Mono.sup.(2) 18.1 16.9 Di.sup.(2) 5.2 1 Tri.sup.(2) 15.1 1 Hydrogen content, weight % 12.35 13.62 375-.sup.(3), weight % 15.9 42.1 .sup.(1)for the conditions of the pretreatment, please see the text above. .sup.(2)correspond to compounds comprising one (mono), two (di) or three (tri) benzene rings. .sup.(3)compounds boiling below 375 C.

(72) The operating conditions of the hydrocracker were as follows:

(73) Pressure: 155 bar

(74) Temperature: 365-395 C.

(75) LHSV: 2.43 h.sup.1

(76) H.sub.2/HC ratio: 800.

(77) Table 4 gives the results for hydrocracking of pretreated VGO over Cat-HYA in comparison to Cat-HY30.

(78) The net 375+ conversion, the net yield of middle distillates (MD) and the hydrogen consumption (based on the H content determined by MINISPEC, a quantitative .sup.1H NMR method) are reported.

(79) At 380 C., 7% higher conversion is obtained over Cat-HY30 than over Cat-HYA. The yield of middle distillates (hydrocarbon fraction with a boiling point between 145 and 375 C.), at 80% conversion, is 9% by weight higher for Cat-HYA than for Cat-HY30.

(80) The use of Cat-HYA makes it possible to suppress the formation of light hydrocarbons boiling below 145 C.

(81) The hydrogen consumption is reduced from 1.55% to 0.72%, corresponding to a hydrogen saving of 54%.

(82) TABLE-US-00004 TABLE 4 Results of hydrocracking of pretreated VGO Conversion, Yield of middle weight % distillates, weight % H.sub.2 consumption, % Catalyst 380 C. At 80% conversion At 80% conversion Cat-HY30 66 ref 1.55 Cat-HYA 59 ref + 9 0.72