Method for optimizing catalyst loading for hydrocracking process

Abstract

The invention relates to a method for optimizing layered catalytic processes. This is accomplished by testing various catalysts with a compound found in a feedstock to be tested, to determine the facility of the catalyst in hydrogenating, hydrosulfurizing, or hydrodenitrogenating the molecule, and hence the feedstock. In a preferred embodiment, the Double Bond Equivalence of the feedstock and molecule are determined, and catalysts are pre-selected based upon their known ability to work with materials of this DBE value. In preferred embodiments, the layered catalysts include a demetallization catalyst, used before hydrocracking. In additional preferred embodiments, the test feedstock contains 500 ppmw or less asphaltenes, preferably C.sub.5-asphaltenes.

Claims

1. A method for optimizing a layered catalytic process, comprising (i) contacting a model compound capable of (a) being hydrocracked, (b) being demetalized, (c) hydrodenitrogenation, and at least one of hydrogenation, hydrosulfurization and hydrodenitrogenation to a plurality of catalysts to determine an optimal catalyst for each of (b) and (c) followed by (ii) layering the optimal catalyst for each of (b) and (c) in a reaction chamber based on their activity reacting with said model compound, wherein said catalyst capable of demetallizing said model compound is placed at top of said reaction chamber, and (c) contacting a hydrocarbon containing feedstock for which double bond equivalence (DBE) has been determined to the layered catalysts under condition favoring formation of lower weight hydrocarbon from said hydrocarbon containing feedstock, wherein said model compound boils in the range of 180 C. 520 C. and is selected from the group consisting of methylnaphthalene, dibenzothiophene, and alkylated or naphtalated derivative thereof, a basic nitrogen compound and a carbazole molecule, wherein each of said plurality of catalysts is suitable for hydrocracking a substance with a DBE of said hydrocarbon containing feedstock.

2. The method of claim 1, further comprising contacting said model compound to a second plurality of catalysts suitable for hydrogenating, hydrodesulfurizing, or hydrodenitrogenating a substance with a DBE value less than said feedstock to determine an optimal, second catalyst.

3. The method of claim 1, wherein said hydrocarbons contained in said feedstock have a double bond equivalency of 24 or less.

4. The method of claim 1, wherein said feedstock has a double bond equivalency of 24 or less, and at least one of said plurality of catalysts is a VGO hydrocracking catalyst.

5. The method of claim 1, wherein said feedstock has a double bond equivalency of 25 or more, and at least one of said catalysts is a catalyst designed for heavy feedstock.

6. The method of claim 1, comprising contacting said hydrocarbon containing feedstock to said reaction chamber at a temperature of from 350 C. to 450 C.

7. The method of claim 1, comprising contacting said hydrocarbon containing feedstock to said reaction chamber at a hydrogen feed rate less than 2500 liters per liter of feedstock.

8. The method of claim 1, comprising contacting said hydrocarbon containing feedstock to said reaction vessel at a pressure of from 100 bars to 200 bars.

9. The method of claim 1, wherein at least one of said catalysts contains a metal from the IUPAC Group 4-10 of the periodic table, or is a noble metal.

10. The method of claim 9, wherein said metal is Co, Ni, W, Mo, Pt, or Pd.

11. The method of claim 1, wherein at least one of said catalysts contains amorphous alumina, silica-alumina, titania, Y zeolite, or at least one a transition metal inserted Y zeolite.

12. The method of claim 11, wherein said transition metal is one of Zr, Ti, or Hf and combinations thereof.

13. The method of claim 1, wherein said molecule is capable of being at least two of hydrogenated, hydrodesulfurized, and hydrodenitrogenated.

14. The method of claim 1, wherein said feedstock has an asphaltene content of 500 ppmw or less.

15. The method of claim 1, wherein said catalyst capable of demetallizing said model compound comprises one or more of the following properties: (i) maximum metal loading capacity of 50-100 w % based on fresh catalyst weight; (ii) at least one active phase metal at a concentration of from about 1% to about 20% by weight of said catalyst, (iii) a diameter for particles of said catalyst of from about 1 to about 3 mm; a surface area of about 60 to about 400 m.sup.2/g to about 150 m.sup.2/g, and a total pore volume of about 0.5 cm.sup.3/g to about 100 cm.sup.3/g.

16. The method of claim 1, wherein said catalyst capable of demetallizing said model compound capacity for 100 w % of metal relative to weight of said demetallizing catalyst.

17. The method of claim 16, wherein said catalyst capable of demetallizing catalyst is mesoporous.

18. The method of claim 17, wherein said catalyst capable of demetallizing catalyst comprises alumina or silica.

19. The method of claim 18, wherein said catalyst capable of demetallizing catalyst further comprises Ni, Mo, or both.

20. The method of claim 19, wherein said Ni, Mo, or both comprises 2-5 w % of said demetallizing catalyst.

21. The method of claim 1, wherein said catalyst capable of demetallizing catalyst have pores of from 100-600 Angstrom diameter.

Description

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(1) The invention relates to an improved method for hydrocracking a hydrocarbon containing feedstock. Containing hydrocarbons, via contacting the feedstock with a layered catalyst system, wherein each catalyst in said system carried out a different function. Details of the methodology will be elaborated upon, infra.

Example 1

(2) This example describes how four different catalysts were evaluated to determine their efficacy in hydrogenation, and hydrocracking processes. Each catalyst was contacted with H.sub.2S, for 2 hours, at 400 C. prior to the tests in order to convert the metal oxides in the catalyst to their active, sulfided forms. To test for hydrogenation, reactions were carried out at 330 C., and for hydrocracking, at 380 C. Other relevant parameters were the residence time with the catalyst (1 hour), the initial H.sub.2 pressure (70 bars), the amount of catalyst (0.3 g), and reactant volume (1 0 ml).

(3) The results follow, with values being in relation to the best catalyst for each task, which was assigned a value of 100:

(4) TABLE-US-00001 TABLE 2 Relative Activities for Catalysts Hydrogenation Hydrocracking Catalysts/ Catalyst Catalyst of Methyl of Methyl Reactions Type Function Naphthalene Naphthalene Catalyst 1 Amorphous HDS 100 6 Catalyst 2 Amorphous HDS/HDN 68 42 Catalyst 3 Zeolite Cracking 62 74 Catalyst 4 Zeolite Cracking 82 100

(5) To elaborate further, catalyst 1 was an amorphous catalyst containing CoMo/Al, known as HDS (hydrodesulfurization) catalyst. Catalyst 2, also an amorphous catalyst, is known as an HDS/HDN (hydrodenitrogenation) catalyst and contains NiMo/SiAl. Catalyst 3 and 4 are both zeolite containing catalysts, used for hydrocracking. Catalyst 3 designed for conventional VGO feedstock contains NiMo/SiAl, while catalyst 4 is designed for heavy oils, such as deasphalted oil, contains NiMo/USY zeolite, with TiZr inserted into the zeolite framework.

(6) The experiments used methylnaphthalene, because its structure makes it ideal for both hydrogenation and hydrocracking. As it is known that in hydrocracking apparatus, the molecule is hydrogenated, first and then hydrocracked, knowing the composition of the feedstock permits one to select catalyst and order in layering.

(7) Other compounds which may be used as the model compound include dibenzothiophene, as well as alkylated or naphthalated derivatives thereof, a basic nitrogen compounds, and carbazole molecules which boil at a temperature of from about 180 C. to about 520 C.

(8) The values supra, show that for hydrocracking, catalyst 4 was the optimum choice, while catalyst 1 is preferred for hydrogenation.

(9) This data can be used, as will be shown, infra, to layer catalysts, based upon the content of the feedstock or other material being treated.

Example 2

(10) A feedstock blend was prepared, containing 15 V % demetalized oil (DMO), and 85 V % vacuum gas oil (VGO). The VGO was analyzed as containing 64% heavy VGO (HVGO) and 21% light VGO (LVGO).

(11) The feedstock had a specific gravity of 0.918, an API gravity of 22.6 degrees, contained 2.2 wt % of sulfur, 751 ppmw nitrogen, 2 ppmw total Ni and V, and had a bromine number of 3.0 g/100 g feedstock. Other properties included 12.02 wt % hydrogen, an IBP (initial boiling point) of 210 C., a 10/30 of 344/411 C., a 50/70 of 451/498 C., a 90/95 of 595/655 C., and a 98 of 719 C. Maximum double bond equivalency (DBE), which is calculated for each molecule by counting the ring structures and the number of double bond present, values were 31 for Sulfur, 31 for Nitrogen, and 32 for hydrocarbons.

(12) Experiments were carried out using a two stage system with reactors in a series hydrocracking process. In the first stage, the feedstock was demetalized, hydrodenitrogenated and hydrodesulfurized, and in the second stage, it was hydrocracked.

(13) In the first stage, the feedstock was contacted to a layered catalyst system in a first reactor. The bottom layer of the layered system was a Ti, Zr-USY zeolite designed for DMO hydrocracking catalyst. It constituted 37.5 wt % of the amount of catalysts used into. An equal amount of an amorphous denitrogenation catalyst designed for VGO feedstock hydrocracking was placed on top of this.

(14) A thin layer of a demellization catalyst was loaded on the top of the reactor. Its volume was an additional 5% relative to the total load, and was sufficient to remove metals from the feedstock.

(15) After reacting with the layered catalysts, the reactor effluents moved to a second reactor, containing 25.0 wt % of a zeolite hydrocracking catalyst designed for VGO feedstock hydrocracking 4.

(16) The table, which follows, details the results of the experiment:

(17) TABLE-US-00002 Operation time hours 134 182 278 Temperature Reactor 1 C. 365 376 379 Temperature Reactor 2 C. 351 360 365 WABT C. 362 372 376 LHSV 1/hr 0.360 0.362 0.334 Density Kg/Lt 0.8475 0.8165 0.7826 Sulfur ppmw 60 12 7 Nitrogen ppmw 2 1 1 Yields C.sub.1-C.sub.4 W % 1.3 3.4 5.2 C.sub.5-85 C. W %/FF 1.4 2.5 4.1 85-149 C. W %/FF 10.5 21.0 36.8 149-185 C. W %/FF 4.7 8.7 13.4 185-240 C. W %/FF 9.6 14.0 16.6 240-315 C. W %/FF 13.0 14.1 11.8 315-375 C. W %/FF 10.5 8.9 4.6 375-560 C. W %/FF 41.6 22.3 5.1 560+ C. W %/ff 4.9 2.6 0.0 Conversion 375 C.+ wt % 48.5 72.4 94.4

(18) While metals were not measured in the streams exiting the beds, (demetallization is effective in the demetallization bed and the metal amount is small enough to measure in products), analysis showed metal was completely removed.

(19) It will be seen that nearly all sulfur and nitrogen were removed at the end of the reaction, with nearly complete conversion of the feedstock to lighter weight molecules (i.e., those which boil at temperatures of 375 C. or below.

Example 3

(20) This example shows the results of comparative experiments using different catalyst systems.

(21) As with the preceding example, a two reactor system was used.

(22) In a first set of experiments, the first reactor continued equal amounts (37.5 wt % each, based on total catalyst weight), of a Ti, Zr-USY zeolite catalyst designed for feedstock hydrocracking on top of which was placed a hydrotreating catalyst designed for VGO/Vacuum residue hydrodesulfurization (CoMo/Al, amorphous, without zeolite). The second reaction chamber contained 25 wt %, relative to total catalyst weight of NiMo/USY zeolite, hydrocracking catalyst designed for VSO feedstock hydrocracking.

(23) The catalytic system placed in the first reactor was designed for feedstocks which have a DBE >25, i.e., feedstock containing heavier molecules, (a blend of VGO and DMO), the latter of which is a solvent soluble fraction of vacuum residue, which boils at a temperature above 520 C.

(24) The second test used, in the first reactor, a catalytic system designed for lighter molecules, i.e., feedstocks with a DBE <24, which is typical of VGO feedstocks, with boiling point of 370 C. to 520 C.

(25) The first reactor contained, as its bottom layer, 60 wt % of a hydrodenitrogenation catalyst which was an amorphous, NiMo/SiAl catalyst, in contrast to the zeolite of the first example.

(26) The upper layer of the catalyst system was a CoMo/Al amorphous, hydrodesulfurization catalyst. A total of 15.0 wt % of this catalyst was the top layer.

(27) The second reactor was filled with 25 wt % of the same hydrocracking catalyst used in the first set of experiments.

(28) The systems were then evaluated to determine what temperature was required to achieve a desired degree of hydrocracking.

(29) The first catalytic system (Example 2) was found to require a temperature of 370 C., to achieve the same degree of hydrocracking as the second system (Example 3), or 395 C.

(30) The foregoing examples set forth features of the invention, which relate to methods for improving or optimizing layered hydrocracking processes. The process of the invention calls upon one to determine at least one property of the feedstock to be used, such as the double bond equivalence, or DBE. This determination of these properties is well within the purview of the skilled artisan. This determination permits the artisan to make a first selection of catalysts because, as shown, supra, different catalysts are useful for feedstocks with different properties, such as ranges of DBE values.

(31) Following this step, the process involves selecting a molecule which is present in the feedstock, so as to test it, in its pure form, with various catalysts. Again, the skilled artisan can easily determine the molecular content of a feedstock.

(32) The molecule chosen must be capable of being one or more of hydrogenated, hydrodesulfurized, or hydrodenitrogenated. Indeed, it may be capable of being subject to two, or all 3 of these reactions.

(33) The test molecule is then contacted to a plurality of catalysts useful for hydrocracking feed stock with the predetermined DBE, with the catalyst being evaluated as a result of the products of the hydrocracking process.

(34) As hydrocracking reduces DBE values, the next step in the process calls for assessing a second plurality of catalysts, with the same properties as listed supra, except this second group of catalysts is chosen from catalysts known to be suitable for feedstocks with DBE values below the first group.

(35) Once an optimal catalyst is determined, the first and second catalysts are layered in a reaction chamber, followed by contact of a feedstock thereto, under conditions, such as those discussed infra, which promote formation of lower weight hydrocarbons from the feedstock.

(36) As noted, supra, in a preferred embodiment, at least one demetallization catalyst is used as well and is placed atop the layered catalysts determined supra. This permits removal of any metals in the feedstock as it reaches the tested catalysts.

(37) Demetallization catalysts are well known to the art. Common properties include porous materials including, but not being limited to, silica, alumina, titania, or combinations of these, with or without other materials. When they contain active phase materials, Ni, Mo, or NiMo are preferred, at a concentration of 2-5 w %. Exemplary properties are a maximum metal loading capacity of 100 w % (on a fresh catalyst basis), active phase metals at concentrations of from about 1% to about 20% (by weight), with Ni, Co, and Mo, alone or in combination of 2 or all 3 being preferred. The shape of the demetallization catalyst is not critical, and can be in the form of, e.g., spheres, extrudates, cylinders, trilobes, or quadrilobes, e.g. The diameter of the catalyst particles is preferably from 1-3 mm; surface area is preferably 60-150 m.sup.2, and total pore volume is preferably about 100 cm.sup.3/g, with pore sizes of from 100-600 Angstroms. When a demetallization catalyst is used, it can possess one, several, or all of these properties. For example, referring to the examples, supra, one can use a hydrodemetallization catalyst with a capacity to remove and store at least 50 w % metal (relative to fresh catalyst weight metal in its pores), but preferably 100%. The catalyst has a surface area of at least 120 m.sup.2/g and can reach 400 m.sup.2/g, a pore volume of 0.5 cc/g, preferably at least 1.5 cc/g, and be on an alumina, silica, or titania support, or a support containing two or more of these. As noted supra, several active metals are preferred, with Ni, Mo, and combinations containing or consisting of one or both of these also preferred. Particle sizes of at least 1/32 inch are preferred, and pore sizes of 100-600 Angstroms.

(38) Other facets of the invention will be clear to the skilled artisan and need not be reiterated here.

(39) The terms and expression which have been employed are used as terms of description and not of limitation, and there is no intention in the use of such terms and expression of excluding any equivalents of the features shown and described or portions thereof, it being recognized that various modifications are possible within the scope of the invention.