Catalyst for hydrodemetalization of heavy oil

Details Catalyst for hydrodemetalization of heavy oil Catalyst for hydrodemetalization of heavy oil

1998-07-22

2001-03-27

Griffin, Steven P. (Department: 1754)

Catalyst, solid sorbent, or support therefor: product or process

Catalyst or precursor therefor

Metal, metal oxide or metal hydroxide

C502S305000, C502S314000, C502S315000, C502S321000, C502S322000, C502S323000, C502S327000, C502S335000, C502S337000, C502S355000, C502S414000, C502S415000, C423S625000, C423S626000, C423S628000, C423S630000

Reexamination Certificate

active

06207611

ABSTRACT:

This invention relates to a catalyst for hydrodemetalization and/or hydrodesulfurization process of heavy oil, especially residuum oil.
For the catalyst for hydrodemetalization and/or hydrodesulfurization of heavy oil, in general, alumina with larger pores is used as a carrier matrix and the metal elements of Groups VIII and/or VIB are used as active components. Commercial available alumina can be usually used only after the alumina is treated by pore-enlarging, thus pore-enlarging of the carrier alumina is one of the critical techniques for preparing the catalyst for hydrodemetalization of heavy oil.
One of conventional methods for pore-enlarging is by adding various pore-enlarging agents to the precursor of alumina—a pseudoboehmite during the kneading process.
Using carbon black as a pore-enlarging agent is proposed by U.S. Pat. No. 4,448,896, and in EP 237240, addition of carbon fibre is described to form large pores. A mechanism of pore-enlarging by both agents mentioned above is believed that the pore-enlarging agent occupies a certain volume of space in the extrude carrier particles when mixed in solid form together with the dry pseudoboehmite powder. During calcination of the carrier at high temperature, the pore-enlarging agent is converted to gas, thereby forming a certain amount of large pores. The pore-enlarging agent does not react chemically with pseudoboehmite, but only reacts physically, so it may be termed as a physical pore-enlarging agent.
In the Chinese Patent ZL 92112511.9, it is described that adding silica sol (
2
SiO
3
) in the process of kneading pseudoboehmite can have a pore-enlarging effect. Furthermore, adding simultaneously silicon (Si) and phosphorus (P) compounds to the alumina carrier can also have a pore-enlarging effect, especially the pore-enlarging effect of phosphorus compounds is more significant. The pore-enlarging agent reacts chemically with pseudoboehmite, so it may be termed as a chemical pore-enlarging agent.
Disadvantages of the carrier and catalyst which are prepared by using solely the physical pore-enlarging agent are: (1) scattered pore distribution; (2) obviously decreased mechanical strength and bulk density. For example, a catalyst prepared by U.S. Pat. No. 4,448,896 has the peak pore diameter of 14.2 nm, the total pore volume of 0.848 ml/g, and the pore volume of pores having pore diameters of 7.5~20.0 nm is about 60% of the total pore volume; and the mechanical strength is low, only about 2.3 N/mm. A catalyst of EP 237240 has an average pore diameter in the range of 7.5~20.0 nm, the total pore volume of 0.60 ml/g, with the pore volume of pores having pore diameters of 5.0~40.0 nm being about 65% of the total pore volume. When its mechanical strength is too low a catalyst will not meet the requirements of industrial application; And if a catalyst having scattered pore distribution and decreased bulk density, the effective inner surface area of the packed catalyst per unit volume will be decreased, and consequently the activity of the catalyst corresponding to the volume space velocity will be decreased.
Using solely a chemical pore-enlarging agent will make the peptizing property of the pseudoboehmite become worse, thereby causing difficulties in the extrusion of the carrier. Furthermore, when a large amount of the chemical pore-enlarging agent is used, the pore distribution of the catalyst prepared will be more scattered.
In brief, when any one of the two pore-enlarging agents is solely used, its amount used will be restricted to a certain extent. Thus, its pore-enlarging effect is very limited, and it is hardly possible to prepare a catalyst carrier having large pores, concentrated pore distribution, and appropriate mechanical strength and bulk density. Especially, if the method for pore-enlarging is not appropriate, it will result in a scattered pore distribution and cause the efficiency of the catalyst to decrease greatly.
In view of the above-mentioned problems, an object of this invention is to invent a catalyst for hydrodemetalization of heavy oil, especially residuum oil, which has larger pore volume and pore diameters, concentrated pore distribution, appropriate mechanical strength and bulk density, especially good demetalization and desulfurization activities, and good stability of the activity. Another object of the invention is to provide a method for preparing a catalyst having good physical and chemical properties for hydrodemetalization of heavy oil, especially residuum oil.
The catalyst of the invention, using the large pore alumina as a carrier, on which the metal elements of Groups VII and/or VIB are supported has a total pore volume of about 0.70~0.90 ml/g, a specific surface area of about 110~200 m
2
/g, the peak pore diameter of 15~20 nm, with the pore volume of pores having pore diameters of 10~20 nm being over 60% of the total pore volume. Its mechanical strength is ≧7.5 N/mm. The carrier contains P
2
O
5
in an amount of 0.07~1.10 wt %
In the catalyst of the invention, MoO
3
or WO
3
is in an amount of 6.0~14.0 wt %, preferably 8.0~12.0 wt %; CoO or NiO in an amount of 2.0~6.0 wt %, preferably 2.5~3.5 wt %, and a carrier in an amount of 80~90 wt %, on the basis of the weight of the catalyts.
A technological gist of the invention is that two different types of the pore-enlarging agents, i.e., a physical pore-enlarging agent and a chemical pore-enlarging agent, are added simultaneously while mixing the the pseudoboehmite powder and water or aqueous solution.
The physical pore-enlarging agents are generally flammable solid particulates, of which the pore-enlarging principle involves that after the solid particulates and the the pseudoboehmite powder are mixed homogenously and extruded to bar under the effect of water or aqueous solution, the bars are calcined at a high temperature in oxygen-containing atmosphere, in the course of calcination the physical pore-enlarging agent is converted to gas and escapes therefrom, and a certain volume of large pores is left, so large numbers of the enlarged pores are formed in the bar alumina carrier resulted from calcination. The pore sizes in the carrier which has been treated by pore-enlarging depend on various factors such as the type of the physical pore-enlarging agent used and the like.
The chemical pore-enlarging agents are generally inorganic compounds capable of reacting with alumina and its precursors, such as phosphorus, silicon and boron compounds etc. The pore-enlarging principle of the chemical pore-enlarging agents involves that under the surface chemical reaction between the inorganic compounds as a pore-enlarging agent and the pseudoboehmite the bond between particles of the pseudoboehmite powder is weakened and then void space between each other become larger, thus parts of large pores are formed.
When either a physical or a chemical pore-enlarging agent is solely used, it is often used in a larger amount so as to achieve the desired results, thus its negative effect (disadvantages) is also revealed more apparently.
The process of preparing the catalyst of the invention comprises:
(1) weighing a given amount of the dry pseudoboehmite powder, a physical pore-enlarging agent (in an amount of 3~10 wt % based on the weight of alumina) and extruding aids, mixing them homogenously, then adding the aqueous solution of a chemical pore-enlarging agent (when it is a phosphorus compound, its amount added is in the range of 0.1~1.5 wt % based on the weight of alumina), after mixing homogenously, a plastic mass being formed;
(2) extruding the resultant material from the step (1) in an extruder;
(3) drying the resultant bars from the step (2) at 90~150° C. for 2~8 hours or drying it in the open;
(4) calcining the resultant bars from the step (3) at 840~1000° C. for 1~5 hours;
(5) impregnating the resultant bars from the step (4) by spraying with the solution containing Ni or/and Mo compound;
(6) drying the resultant material from the step (5) at 80~140° C. for 1~5 hours, or drying in the open;
(7) calcining the resultant material from the step (6) at 500~600

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