NO772401L - PROCEDURES FOR REMOVAL OF METALS FROM HYDROCARBON OILS - Google Patents

Description

Procedure for removing metals from. hydrocarbon oils

The invention relates to a method for removing metals

from hydrocarbon oils by contacting the oils with a catalyst at elevated temperature and pressure and in the presence of hydrogen.

In Dutch patent application no. 7309387 catalysts are described which are activated with one or more metals (promoters) with hydrogenation activity and which satisfy the following conditions: (1) p/d> 3.5-0.02 v, where p denotes the specific average pore diameter in nm, d the specific average particle diameter in nm and v the percentage of the total pore volume that consists of pores with a diameter greater than

than 10 0 nm,

(2) the total pore volume is greater than 0.4 ml/g,

(3) v is less than 50%, and'

(4) the specific surface area is greater than 100 m 2 /g,

when the catalyst has such a p and d that the quotient p/d is not greater than 10-0.15 v, the catalyst must satisfy the following additional conditions:

(a) . the nitrogen pore volume is greater than 0.6 ml/g,'

(b) the specific surface area is greater than 150 m 2 /g,

and

(c) p is greater than 5 nm.

According to the above-mentioned Dutch patent application, these catalysts are excellently suitable for use in the hydrodemetallation of metal-containing hydrocarbon oils. As demonstrated in the examples in the Dutch patent application, it is of crucial importance that the catalysts are activated with one or more metals with hydrogenation activity (see experiment 40 where a non-activated catalyst was used for the demetallation of an oil with a total vanadium and nickel content of 245 parts by weight per million

parts by weight (ppm)).

A continued investigation into the use of catalysts satisfying the above-mentioned conditions of porosity and particle size for the hydrodemetallation of hydrocarbon oils has shown that similar catalysts, but not activated with one or more metals with hydrogenation activity, are nevertheless very suitable for this purpose, provided that the hydrocarbon oils in question have a total vanadium and nickel content of over 500 ppm. Catalysts which satisfy the above-mentioned conditions for porosity and particle size, but which have not been activated with one or more metals with hydrogenation activity, will hereafter be referred to as "non-activated catalysts" for the sake of simplicity.

The invention thus relates to a method for removing metals from hydrocarbon oils with a total vanadium and nickel content of over 500 ppm, where the oils at elevated temperature and pressure and in the presence of hydrogen are brought into contact with a non-. activated catalyst.

The present method is characterized by the fact that it is carried out using a non-activated catalyst which satisfies the conditions specified in more detail in the characterizing part of claim 1.

For further information regarding determination of p and

d reference can be made to the above-mentioned Dutch patent application.

Well-suited materials for use as catalysts for carrying out the present method are oxides of. the elements from groups II, III and IV in the periodic table or mixtures of these oxides, such as silicon dioxide, aluminum oxide, magnesium oxide, zirconium dioxide, boron oxide, silicon dioxide-aluminium oxide, silicon dioxide-magnesium oxide and aluminum oxide-magnesium oxide.

Another type of material which is very well suited for use as a catalyst in carrying out the present method is carbon black, in particular carbon black obtained as a by-product from the partial oxidation of hydrocarbons with air, oxygen or mixtures of air and

oxygen, in the presence or absence of water vapour.

Aluminum oxides, silicon dioxides and silicon dioxide-aluminum oxides are preferred as catalysts for carrying out the present method. Very suitable catalysts are aluminum oxide or silicon dioxide particles prepared by spray-drying an aluminum oxide or silicon dioxide gel, followed by shaping the spray-dried microparticles into larger particles, e.g.

by extrusion, and spherical aluminum oxide or silicon dioxide particles obtained by using the well-known oil droplet. method. This involves the formation of an aluminum oxide or silicon dioxide hydrosol which is combined with a gelling agent, after which the mixture is dispersed as droplets in an oil which can be held at an elevated temperature, and the droplets are held in the oil until they have solidified to form spherical hydrogen particles which are then separated, washed, dried and calcined. Very suitable silicon dioxide aluminum oxide catalysts are combined gels of aluminum hydroxide gel on silicon dioxide hydrogel.

The catalysts used for carrying out the present method can, among other things, formed by extrusion or pelletisation. In addition to these forming methods, the well-known nodulization method in particular is a very suitable forming method for the catalysts for carrying out the present method. In this method, catalyst particles with a diameter of no more than 0.1 mm are agglomerated using a granulation liquid to form particles with a diameter of at least 1.0 mm.

The demetallation activity for non-activated catalysts used for carrying out the present method, and for activated catalysts according to Dutch patent application no. 7309387 can be increased by adding hydrogen sulphide. Demetallisation of heavy hydrocarbon oils using these catalysts is therefore preferably carried out with the addition of hydrogen sulphide. In a further investigation regarding the effect of the addition of hydrogen sulphide when using the non-activated catalysts for carrying out the present method and of activated catalysts according to Dutch patent application no. 7309387 for the demetallation of heavy hydrocarbon oils, it was found that the effect of hydrogen sulphide was strong depending on the partial pressure of the hydrogen and the total applied pressure. When consideration is given to the fact that the use of hydrogen sulphide in demetallisation is economically attractive, especially when such use at.

a certain total pressure leads to an increase of the demetallization activity of over 50%, it turned out that both for the non-activated

catalysts and for the activated catalysts, this condition can be satisfied if the amount of hydrogen sulphide is chosen so that the quotient P q/<p>her Hk at least _4,200 and at most

2 2 P (P~T2

2PT-60 T

n , rri . (P„ , P„ 0 and P„ respectively denote the partial pressure of the hydrogen,

T n~ n«b

the partial pressure of the hydrogen sulphide and the total pressure in bar).

Within the limits set by the formula, the demetallization activity of the catalysts reaches an optimum at a certain P„' (PXU c).

H2S H2S

The value of P^ H^ S is different for the different catalysts

and can be determined by a number of experiments. An application of P H2Sc over or

below P „ „ , but within the specified limits, still leads to

H2S •

an increase of the demetallization activity by more than 50%, but this increase is less than the achievable maximum.

During the demetallization process, P H g can of course

or any other PT7 is regulated by continuously adding a sufficient amount of hydrogen sulfide from an external source to the oil to be demetallized.' economically considered, however, it is more appealing to the greatest extent possible to utilize the hydrogen sulphide that is released by the demetallization process and/or by a desulphurization process to be carried out after the demetallization process. This trade-off led to the following three advantageous embodiments of the present process in the presence of additional hydrogen sulfide. 1) Application of gas recycling in the demetallization process, with the largest possible proportional amount of hydrogen sulphide being left back in the recirculating gas until the desired P is reached. A certain amount of hydrogen sulfide is then continuously removed from the recirculating gas to maintain the desired hydrogen sulfide concentration. 2) Especially when a high PTjr „ is desired, it can take considerable time

time before the hydrogen sulphide concentration<n>in the recirculating gas has reached the desired value. This difficulty can be overcome by supplying hydrogen sulphide from an external source during the first stage of the process, and gradually reducing the hydrogen sulphide supply as the process takes place.

This additional amount of hydrogen sulphide can e.g. come from one

hydrodesulfurization process.

3) Instead of recycling gas for demetallization the reactor or in combination with this is used as feed gas for the demetallization reactor, waste gas from a desulphurization reactor which is arranged after the demetallization reactor. A flow chart for a combined demetallisation/desulphurisation process in the presence of hydrogen and which is based on the above principle,

is shown in the drawing and is further explained below.

The plant comprises, in order, a hydrodemetallization unit 1, a first gas/liquid separation unit 2, a hydrodesulphurization unit 3, a second gas/liquid separation unit 4 and a unit 5 to remove hydrogen sulphide. A metal and sulphur-containing residual hydrocarbon oil .6 is subjected to hydrodemetallization together with two hydrogen and hydrogen sulfide-containing gas streams 7 and 8 and,

if desired, together with a hydrogen sulfide stream 9 from an external source. The thus obtained product 10 is separated in a liquid stream 11 with

low metal content and in a hydrogen and hydrogen sulphide-containing gas stream 7 which is recycled to the demetallisation unit. The liquid stream 11 is subjected to hydrodesulfurization together with a hydrogen-containing gas stream 12 and a hydrogen stream 13 from an external source. The product thus obtained is separated into a liquid stream 15 with a low metal and sulfur content and into a hydrogen and hydrogen sulphide containing

gas flow 16 which is divided into two parts 8 and 17 with the same composition. Part 8 is recycled to the demetallizer unit, and after hydrogen sulphide has been removed, part 17 is recycled

to the desulfurization unit as a gas stream 12.

The present method is preferably carried out by passing the hydrocarbon oils at elevated temperature and pressure and in the presence of hydrogen in an upward, downward or radial direction through one or more vertically arranged reactors containing a static layer or moving layer of the relevant catalyst particles. The present method can be carried out, e.g. by directing the hydrocarbon oils together with hydrogen upwards through a vertically arranged catalyst layer, the liquid and gas velocities used being such that the catalyst layer will expand (treatment in a "boiling" layer). In a very advantageous embodiment of the present method, the hydrocarbon oil is led through a vertically arranged catalyst layer in which new catalyst is periodically introduced during the process on top of the catalyst layer and used catalyst is removed from the bottom of the catalyst layer (treatment by silo flow). In another very advantageous embodiment of the present method, several reactors are used, each of which contains a static catalyst layer, and the reactors are used alternately for the process in question. When the process is carried out in one or more of these reactors, the catalyst is replenished in the other layers (treatment with change of static layer). If desired, the process can also be carried out by suspending the catalyst in the hydrocarbon

oil to be treated (treatment in slurry phase).

The catalysts used for carrying out the present method are preferably in the form of particles with a d of 0.5-4.0 mm, preferably 0.6-3.0 mm.

The present method is preferably carried out at a temperature of 350-450°C, a partial pressure for hydrogen of 25-200 bar and a volume rate of 0.1-10kg.kg "*".h ^. The following conditions are particularly preferred: temperature 375-425°C, partial pressure of hydrogen 50-150 bar and volume velocity 0.5-5 kg.kg "'".h \. Hydrodemetallisation of metal-containing hydrocarbon oils is of particular importance if the oil is then to be catalytically cracked, hydro-cracked or hydrodesulphurised. As a result of the hydrodemetallization, the deactivation of the catalysts used for these processes is suppressed to a considerable extent. Hydrocracking and hydrodewaxing of hydrocarbon oils can be carried out by bringing the oils at elevated temperature and pressure and in the presence of hydrogen into contact with a suitable catalyst which can be in the form of a static bed, a moving bed or a suspension of catalyst particles. In an advantageous combination of the demetallization according to the invention and hydrocracking or hydrodesulphurization, the demetallization is carried out in static layers with changing of the static layers or by silo flow, while the hydrocracking or hydrodesulphurization is carried out in the usual way in a static layer.

Examples of hydrocarbon oils with a total vanadium and nickel content of over 500 ppm and which are suitable for demetallization by the present method are crude oils and residues obtained by distillation of crude oils, such as "peaked" crude oils, long residues and short residues.

Example 1

A residual hydrocarbon oil with a total vanadium and nickel content of 1250 ppm and which had been obtained after "topping" and dewatering a crude oil from South America, was catalytically hydrodemetallized using six different non-activated catalysts. For. for this purpose, the oil together with hydrogen was directed downwards through a cylindrical, vertically arranged, static catalyst layer at a temperature of 410°C, a hydrogen partial pressure (measured at the reactor inlet) of 150 bar, a volume rate of 2.1 kg of newly supplied hydrocarbon oil per kg of catalyst per hour and a gas quantity of 1000 NI H2/kg newly added oil. The liquid reaction product was divided into two parts with the same composition and in a volume ratio of 22:1. The smaller part was removed from the system,

and the larger part was recycled to the reactor inlet.

The results of the demetallization experiments together with the properties of the catalysts used are compiled in table A. To determine p and v and also the total pore volume and the nitrogen pore volume, the nitrogen adsorption/desorption method and mercury penetration method were used which are described in, Dutch patent application no. 7309387.

The properties of the catalysts are judged on the basis of V max •

max •

and k, r. V . is the maximum amount of vanadium, expressed as

i, o maKS•

% by weight of new catalyst, which the catalyst particles can absorb in their pores, and k, ,. is the activity of the catalyst, expressed in kg.kg ..h .(ppm V) , after half of the catalyst's lifetime (expressed by absorbed amount of vanadium) has passed,

k^ g is calculated from the equation

k-^ i- = (volume velocity in kg.kg "'".h x

ppm V. in supply - ppm y. j product

(ppm V in product) 1 f 5•

The effect of a catalyst is judged to be good under the conditions used for this demetallization if the conditions are satisfied that V, is greater than 30% by weight and that k, j- is greater than 0.08 kg.kg<-1>.h< -1>.(ppm V).

Trials 1 and 2 where the above conditions apply

W . and k, . was satisfied, demetallization tests are according to maKs. _L ,d

the invention. In experiment no. 1 where a catalyst was used with 10-0.15 v > p/d > 3.5-0.02 v, this catalyst also satisfied the additional conditions according to the invention - in terms of total pore volume ( 0.40 ml/g), v ( <50%) , nitrogen pore volume (^0.0 ml/g), surface area (^150 iri 2 /g) and p (>5 nm). In experiment no. 2 where a catalyst with p/d > 10-0.15 v was used, this catalyst also satisfied the additional conditions according to the invention regarding total pore volume (>0.40 ml/g),

v (<50%) and surface area (> 100 m 2/g).

Experiments no. 3-6 where the above conditions what

applies to V . and k, r were not satisfied, the demetallization maKs• i,b

experiments that fall outside the scope of the invention. At attempt no. 3

a catalyst with 10-0.15 > p/d > 3.5-0.02 v, but with a nitrogen pore volume of less than 0.6 ml/g was used. At attempt no. 4

became a catalyst with 10-0.15 v > p/d > 3.5-0.02 v, but with

2

a surface area of less than 150 m /g used. At attempt no. 5

became a catalyst with p/d > 10-0.15 v, but with an overall pore-

volume of less than 0.4 ml/g used. In experiment no. 6, a catalyst with p/d 3.5-0.02 was used.

Example 2

Experiment 1 according to example 1 was repeated several times, each. time using a different partial pressure for hydrogen sulphide.

In these experiments, hydrogen sulphide was supplied from an external source. In all experiments, a constant total pressure (measured at the reactor inlet) of 150 bar was used. The results of these experiments are compiled in table B. For experiments no. 8-10, a Pu H2S 0/PH„ 2 was used which satisfied the condition

and an increase of the demetallation activity of over 50% was achieved. In experiment no. 7, a P„ 0/P„ was used which did not

H2S H2

pacified the above-mentioned condition, and an increase of metal- . ization activity was obtained which was less than 50%. '

Claims (15)

1. Process for removing metals from hydrocarbon oils, characterized in that a hydrocarbon oil with a total vanadium and nickel content of more than 500 ppm at elevated temperature and pressure and in the presence of hydrogen is brought into contact with a non-activated catalyst that satisfies the following conditions: (1) p/d > 3.5-0.02 v, where p denotes the specific average pore diameter in nm, d the specific average particle diameter in mm and v the percentage thereof. total pore volume consisting of pores with a diameter greater than 100 nm, (2) the total pore volume is greater than 0.4 ml/g, (3) v is less than 50%, and (4) the specific surface area is greater than 100 m 2 /g, in that when the catalyst has such a p and d that the quotient p/d is not greater than 10-0.15 v, the catalyst must satisfy the following additional conditions: (a) the nitrogen pore volume is greater than 0.6-ml/g, (b) the specific surface area is greater than 150 m 2 /g, and (c) p is greater than 5nm. 2. Method according to claim 1, characterized in that an oxide of an element from group II, III or IV in the periodic table or a mixture of these oxides is used as catalyst. 3. Method according to claim 1 or 2, characterized in that silicon dioxide, aluminum oxide or silicon dioxide-aluminum oxide is used as catalyst. 4. Method according to claims 1-3, characterized in that catalysts are used with a d of 0.5-4.0 mm, preferably 0.6-3.0 mm. 5. Method according to claims 1-4, characterized in that it is carried out with siQ flow or in static layers with changing of the static layers. 6. Method according to claims 1-5, characterized in that it is carried out with the addition of hydrogen sulphide. 7. Method according to claim 6, characterized in that it is carried out in the presence of such an amount of hydrogen sulphide that the quotient Pu C/P„ satisfies the condition H2S H2 where P P and'P„ denote respectively. the partial pressure of hydrogen, H2 , H2 S the partial pressure for hydrogen sulphide and the total pressure in bar. 8.. Method according to claim 6 or 7, characterized in that the method is carried out using hydrogen sulfide which is released by the demetallization process and/or by a desulphurization process to be carried out after the demetallization process. 9. Method according to claim 8, characterized in that <x> recycling of gas is used in the demetallization process, with the largest possible proportion of hydrogen sulphide being left back in the recirculating gas until the desired PH' 2Se has been reached, after which a certain amount of hydrogen sulphide is continuously removed from the recirculating gas to maintain the desired hydrogen sulphide concentration. 10. Method according to claim 9, characterized in that. during the first stage of the process, hydrogen sulphide is supplied to the process from an external source, and that the quantity of the supplied hydrogen sulphide is gradually reduced as the process takes place. 11. Method according to claim 8, characterized in that a metal and sulfur-containing residual hydrocarbon oil is hydro-demetallized together with two hydrogen and hydrogen sulfide-containing gas streams (A and B) and, if desired, together with a hydrogen sulfide stream from an external source, that the product obtained is separated into a liquid stream with a low metal content and into a gas stream containing hydrogen and hydrogen sulphide which is recycled as gas stream A to the demetallation reactor, including that the liquid stream with a low metal content together with a hydrogen-containing gas stream (C) and a hydrogen stream from an external source is hydrodesulfurized, that the product obtained is separated into a liquid stream with a low metal and sulfur content and into a gas stream containing hydrogen and hydrogen sulfide which is divided into two parts with the same composition, one part of which is recycled to the demetallization reactor as gas stream B and the other part after removal of hydrogen sulphide is recycled to the desulphurisation reactor as gas stream C. 12. Method according to claims 1-11, characterized in that it is carried out to demetallize hydrocarbon oils which are then converted catalytically by cracking. hydrocracking or hydrodegumming. 13. Method according to claim 1-12, characterized in that it is carried out at a temperature of 350-450°C, a partial/pressure for hydrogen of 25-200' bar and a volume rate of 0.1-10 kg.kg -1.h-1. 14. Method according to claim 13, characterized in that it is carried out at a temperature of 375-425°C, a partial pressure for hydrogen of 50-150 bar and a volume velocity of 0.5-5 kg.kg-1^-1. 15. Installation for carrying out the method according to claim 11, characterized in that it is substantially similar to the installation schematically shown in the drawing.