GB2032795A

GB2032795A - Demetallisation catalyst

Info

Publication number: GB2032795A
Application number: GB7933439A
Authority: GB
Original assignee: BP PLC
Current assignee: BP PLC
Priority date: 1978-09-30
Filing date: 1979-09-26
Publication date: 1980-05-14
Also published as: GB2032795B

Abstract

A catalyst is prepared by impregnating a porous refractory support with an acidified aqueous solution of an iron group metal compound containing the latter in a molar concentration not less than 1.15. The resulting catalyst is core impregnated, i.e., the active catalytic sites are concentrated in the interior of the porous catalyst. It is useful for the demetallisation of crude petroleum or petroleum fractions, particularly residues.

Description

SPECIFICATION Demetallisation catalyst The present invention relates to novel iron group metal catalysts, to a method for their preparation and to their use.

Supported transition metal catalysts are well known and have been used extensively in hydrocarbon conversion reactions, for example in the hyd rodesulphurisation of sulphur-containing hydrocarbons. Typical catalysts comprise a Group VIA metal compound (i.e., a compound of chromium, molybdenum ortungsten) and an iron group metal compound (i.e., a compound of iron, cobalt or nickel) on a refractory porous support. The Group VIA metal may be present in amount 5 - 25% wt expressed as metal and the iron group metal in amount 1 - 10% wt expressed as metal per cent of the total weight of the catalyst. The refractory support is generally alumina.

Such catalysts may also be used for demetallising crude petroleum and petroleum fractions containing compounds of metals such as vanadium and nickel.

British patent specification 735520 discloses a process for removing vanadium and/or sodium from crude petroleum or hydrocarbons of petroleum origin comprising contacting the crude petroleum or petroleum hydrocarbons with a contact material consisting essentiaily of iron oxide and alumina, in the presence of hydrogen and under conditions of temperature and pressure such that vanadium and/or sodium are/is deposited on the contact material. The contact material may contain from 5 - 15% by weight of ferric oxide, the remainder consisting essentially of alumina.

Such catalysts are prepared by impregnating the support with a relatively dilute solution of the iron group metal compound and of the Group VIA metal compound, if present. Catalysts prepared in this way without addition of acid conditions become shell impregnated. Under more acid conditions they become homogeneously impregnated.

By shell impregnated we mean that the active catalytic sites are concentrated on the surface of the support. By homogeneously impregnated we mean that the active catalytic sites are uniformly dispersed throughout the surface and the interior of the support.

We have now discovered that by careful selection of preparation conditions it is possible to produce a catalyst which is core impregnated. By this we mean that the active catalytic sites are concentrated in the interior of the porous catalyst.

The type of impregnation in any given catalyst may be determined by electron microprobe analysis (EMPA).

Thus according to the present invention there is provided a catalyst comprising an iron group metal compound supported on a porous refractory support wherein the support is core impregnated as hereinbefore defined with the iron group metal compound.

The preferred iron group metal is iron itself.

The porous refractory support may be one or more oxides of elements of Groups Ill or IV of the Periodic Table, particularly alumina, silica, or silica-alumina.

A single oxide, particularly alumina, is preferred to limit side reactions. The alumina may contain up to 5% wt of silica or phosphate to stabilise it and/or give it the required pore characteristics.

According to another aspect of the present invention there is provided a method for the preparation of a catalyst which method comprises impregnating a porous refractory support with an acidified aqueous solution of an iron group metal compound containing the iron group metal compound in a molar concentration not less than 1.15.

Preferably the molar concentration of the iron group metal compound is not more than 5.

Suitably the pH of the impregnating solution is in the range 0 to 1.

Suitable iron group metal compounds include ferric chloride, ferric nitrate and ferric sulphate.

Suitable acids include hydrochloric acid, nitric acid and sulphuric acid.

Preferably the iron group metal compound is ferric chloride and the acid is hydrochloric acid. In this case the ratio of chloride ions to ferric ions in the impregnating solution will be greater than 3:1.

Impregnation conditions are preferably selected so that the uptake of the iron group metal compound (actual uptake) is at least 100/0 of theoretical complete impregnation (nominal uptake).

The catalyst is useful in the demetallisation of petroleum and petroleum fractions.

Thus according to a further aspect of the present invention there is provided a demetallisation process which comprises passing a feedstock containing organometallic compounds over a core impregnated (as hereinbefore defined) catalyst comprising an iron group metal compound supported on a porous refractory support under the following conditions: Broad Range Preferred Range Temperature "C 150-500 250 -430 Pressure bars 10-250 37-170 Liquid Space Velocity v/v/hr 0.1 - 20 0.2 - 15 Hydrogen Gas Flow Rate m3/m3 50-2,000 75-1,000 The process is particularly suitable for the demetallisation of hydrocarbon fractions containing organometallic compounds such as crude petroleum and fractions thereof, e.g., atmospheric and vacuum residues.

The invention is illustrated with reference to the following examples.

Examples The catalysts were prepared by impregnation according to the following standard procedure: an alumina support from AKZO Chemie (Ketjen CK 300) was impregnated with a solution of ferric chloride hydrate, filtered and washed, dried at 11 0"C and finally calcined at 500"C for 2 hr. The experiments were carried out at a constant ratio of volume of solution to weight of alumina of 1.67 ml/g except for catalyst 12 for which the ratio was 1.15 ml/g.

Example 1 Example 1 is provided for purpose of comparison only and is not in accordance with the present invention.

In the first series of experiments the initial iron concentration was constant at 0.53 M giving 5% Fe NOMINAL. The pH of the solution was varied by addition of HCI. The results are given in Table 1.

Table 1 Iron Impregnated as a Function of the Solution pH

Fe Catalyst - % Fe (ACTUAL) Fe Distribution No. 0 pH on Catalyst Impregnated in Cat 1 0.1 1.00 20 Homogeneous 2 0.3 1.04 21 Homogeneous 3 0.6 1.36 27 Homogeneous 4 0.9 2.04 41 Shell 5 1 2.28 46 Shell Neutral solutions (defined as FeCi3, 6 H2O dissolved in distilled water) gave a shell impregnated catalyst, while at pH less than 0.9 a homogeneous catalyst is obtained.It can be seen that the level of impregnation is very low, especially in the stronger acid media.

Example 2 Catalysts 6 - 8 are provided for purpose of comparison only and are not in accordance with the present invention.

In the second series of experiments, the effect of varying the iron concentration of the solution was investigated at a constant pH of 0.3. The results are given in Table 2.

Table2 fron Impregnation as a Function of its Initial Coicentration

Initial Concen- %foe Fe Catalyst tration % Fe (ACTUAL) on Cl/Fe Distribution No. molllitre (NOMINAL) Catalyst atlat in Cat.

6 0.53 5 0.88 25.06 Homogeneous 7 0.86 8 1.43 9.35 HomosBeneous 8 1.08 10 1.81 8.10 Homogeneous 9 1.29 12 5.6 6.38 Core 10 t.29 12 4.5 7.98 Core 1 1.29 12 2.4 9.28 Core 12 1.55 10 4.4 3.60 Core The results clearly show that catalysts prepared from dilute iron solutions, i.e., having an initial iron concentration less than 1.10 Mare homogeneously impregnated whereas those prepared from stronger solutions, i.e., having an initial iron concentration greater than 1.15 M are core impregnated.

Example 3 Catalyst 9 was presulphided with a gas oil doped with CS2 (3 /O by wt of sulphur) under the following conditions: Temperature "C : 140-320 at3O"/hr Pressure bars : 35 Space Velocity v/v/hr : 1 Hydrogen Gas Recycle m3/mJ : 500 The presulphided catalyst was used to demetallise a Kuwait vacuum residue containing 113 ppm Ni + V and 4.9% wt sulphur.

Operating conditions were: Temperature "C : 410 Pressure bars : 140 Space Velocity v/v/hr : 0.35 Hydrogen Gas Recycle m3/m3 : 950 The Ni+V content of the product was reduced to 42 ppm and the sulphur to 4.2%.

Thus the catalyst is highly selective for demetallisation. Selectivity may be defined as % demetallisation % desulphurisation and is 4.5.

The more selective the catalystthe lower is the hydrogen consumption. The highly selective catalyst of this example resulted in a chemical hydrogen consumption of 102.5 m3/m3.

Claims

1. Acatalystcomprising an iron group metal compound supported on a porous refractory support wherein the support is core impregnated as hereinbefore defined with the iron group metal compound.

2. A catalyst according to Claim 1 wherein the iron group metal compound is a compound of iron.

3. A catalyst according to either of the preceding claims wherein the porous refractory support is an oxide of an element of Group Ill or IV of the Periodic Table.

4. A catalyst according to Claim 3 wherein the porous refractory support is alumina.

5. A method for the preparation of a catalyst according to any of the preceding claims which method comprises impregnating a porous refractory support with an acidified aqueous solution of an iron group metal compound containing the iron group metal compound in a molar concentration not less than 1.15.

6. A method according to Claim 5 wherein the molar concentration of the iron group metal compound is not more than 5.

7. A method according to either of Claims 5 or 6 wherein the pH of the impregnating solution is in the rangeOto 1.

8. A method according to any of Claims 5 - 7 wherein the iron group metal compound is ferric chloride, ferric nitrate or ferric sulphate.

9. A method according to any of Claims 5-8 wherein the acid is hydrochloric acid; nitric acid or sulphuric acid.

10. A method according to any of Claims 5 - 9 wherein impregnation conditions are selected so that the uptake of the iron group metal compound is at least 10% of theoretical complete impregnation.

11. A process for the demetallisation of petroleum or a petroleum fraction containing organometallic compounds which process comprises passing the fraction over a core impregnated catalyst according to Claim 1 under a temperature in the range 150"- 500"C, a pressure in the range 10 - 250 bars, a liquid space velocity in the range 0.1 - 20 vivlhr and a hydrogen gas flow rate in the range 50 2,000 m31m3.

12. A process according to Claim 11 wherein the temperature is in the range 250 -430"C, the pressure in the range 37 - 170 bars, the liquid space velocity in the range 0.2 - 15 v/v/hr and the hydrogen gas flow rate in the range 75-1,000 m3/m3.

13. A process according to either of Claims 11 or 12 wherein the petroleum fraction is an atmospheric or vacuum residue.

14. A catalyst according to Claim 1 as hereinbefore described in Example 2.

15. A methodforthe preparation of a catalyst according to Claim 5 as hereinbefore described in Example 2.

16. A process for the demetallisation of a petroleum fraction containing organometallic compounds according to Claim 11 as hereinbefore described with reference to Example 3.