Multi-metallic catalyst doped with phosphorus and a lanthanide

Abstract

The invention relates to a catalyst comprising a support, at least one noble metal M, tin, phosphorus and at least one lanthanide group element, the content of phosphorus element being comprised between 0.4 and 1% by weight, and the content of lanthanide group element(s) being less than 1% by weight with respect to the weight of the catalyst. The invention also relates to the process for the preparation of the catalyst and the use thereof in reforming.

Claims

1. A catalyst comprising a support, at least one noble metal M, tin, 0.4 to 1% by weight phosphorus with respect to the weight of the catalyst and 0.01 to 0.5% by weight cerium by weight with respect to the weight of the catalyst.

2. The catalyst according to claim 1, having a content of noble metal M of 0.02 to 2% by weight with respect to the weight of the catalyst.

3. The catalyst according to claim 1, in which the metal M is platinum or palladium.

4. The catalyst according to claim 1, having a tin content of 0.005 to 10% by weight with respect to the weight of the catalyst.

5. The catalyst according to claim 1, in which the support comprises silica, alumina or silica-alumina.

6. The catalyst according to claim 1, which additionally contains a halogenated compound.

7. The catalyst according to claim 6, in which the content of halogenated compound is 0.1 to 8% by weight with respect to the weight of the catalyst.

8. A process for reforming a hydrocarbon feedstock, comprising contacting said feedstock under reforming conditions with a catalyst according to claim 1.

9. A catalyst comprising a support, at least one noble metal M, tin, phosphorus and having a content of phosphorus of 0.4 to 1% by weight, and a content of lanthanide group element(s) being less than 1% by weight with respect to the weight of the catalyst having a atomic ratio Sn/M of 0.5 to 4.0, a P/M ratio of 0.2 to 30.0, and a lanthanide(s)/M ratio of 0.1 to 5.0.

10. The catalyst according to claim 9, in which the content of lanthanide group element is 0.01 to 0.5% by weight with respect to the weight of the catalyst.

11. The catalyst according to claim 9, in which the lanthanide group element is cerium.

12. A process for the preparation of a catalyst according to claim 9, comprising the following successive stages: a) preparing a support comprising tin, phosphorus and a noble metal, b) drying the support obtained in stage a) under a flow of a neutral gas or under a flow of a gas containing oxygen at a temperature less than 200 C., and calcining at a temperature of 350 to 650 C., c) impregnating the dried and calcined support obtained in stage b) with an impregnation solution comprising a precursor of at least one lanthanide group element, d) drying the support obtained in stage c) under a flow of a neutral gas or under a flow of a gas containing oxygen at a temperature less than 200 C., and calcining at a temperature of 350 to 650 C. to produce the catalyst.

13. The method according to claim 9, in which stage a) comprises the following stages: a1) preparing a support comprising tin by introducing a tin precursor during forming of the support, a2) impregnating the tin-containing support obtained in stage a1) with an impregnation solution comprising at least one precursor of a noble metal and a phosphorus precursor.

14. The method according to claim 9, in which stage a) comprises the following stages: a1) preparing a support comprising tin and phosphorus by introducing the tin precursor and the phosphorus precursor during forming of the support, a2) impregnating the support containing tin and phosphorus obtained in stage a1) with an impregnation solution comprising at least one precursor of a noble metal.

15. The method according to claim 9, in which the catalyst obtained after stage d) is subjected to a treatment under hydrogen.

16. A process for reforming a hydrocarbon feedstock, comprising contacting said feedstock under reforming conditions with a catalyst according to claim 9.

17. A process for the preparation of a catalyst according to claim 1, comprising the following successive stages: a) preparing a support comprising tin, phosphorus and a noble metal, b) drying the support obtained in stage a) under a flow of a neutral gas or under a flow of a gas containing oxygen at a temperature less than 200 C., and calcining at a temperature of 350 to 650 C., c) impregnating the dried and calcined support obtained in stage b) with an impregnation solution comprising a precursor of cerium, d) drying the support obtained in stage c) under a flow of a neutral gas or under a flow of a gas containing oxygen at a temperature less than 200 C., and calcining at a temperature of 350 to 650 C. to produce the catalyst.

18. The method according to claim 17, in which stage a) comprises the following stages: a1) preparing a support comprising tin by introducing a tin precursor during forming of the support, a2) impregnating the tin-containing support obtained in stage a1) with an impregnation solution comprising at least one precursor of a noble metal and a phosphorus precursor.

19. The method according to claim 17, in which stage a) comprises the following stages: a1) preparing a support comprising tin and phosphorus by introducing the tin precursor and the phosphorus precursor during forming of the support, a2) impregnating the support containing tin and phosphorus obtained in stage a1) with an impregnation solution comprising at least one precursor of a noble metal.

20. The method according to claim 17, in which the catalyst obtained after stage d) is subjected to a treatment under hydrogen.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1-3 show the results of the tests of the catalysts produced in the Examples.

EXAMPLES

(2) The following examples illustrate the invention.

Example 1: Preparation of a Catalyst A: Pt/Al2O3SnPCl (Comparative)

(3) A boehmite was synthesized by the alkalization of a solution of aluminium nitrate 0.1 mol.Math.L.sup.1 with a sodium hydroxide solution 1 mol.Math.L.sup.1 at ambient temperature and pH controlled around 10. The suspension is then ripened for one week in an oven at 95 C. without stirring. The pH of the suspension changes after ripening; the final pH is equal to 11.5. The solid is recovered by filtration and then washed in a volume of water approximately equal to the starting volume. The solid is resuspended in water and autoclaved at 150 C. for 4 h. The suspension is centrifuged and then dried under a flow of air, at ambient temperature.

(4) The support of Example 1 is prepared using the boehmite thus synthesized. A suspension containing 25% of mineral matter (expressed in % of Al.sub.2O.sub.3) is prepared by mixing a feedstock of alumina and the boehmite powder in an acidified aqueous solution containing 15% by weight of HNO.sub.3/Al.sub.2O.sub.3. Tin dichloride and phosphoric acid are added simultaneously to this suspension so as to obtain 0.3% by weight of tin and 0.4% by weight for the final solid. The solid fraction of Al.sub.2O.sub.3 is supplied at 88% by weight by the boehmite and at 12% by the feedstock of alumina. This suspension additionally contains a pore-forming agent and a surfactant. The pore-forming agent is an organic phase comprising a mixture of paraffins containing between 10 and 12 carbon atoms with a boiling point of approximately 290 C. and density of 0.75 g/cm.sup.3. The surfactant is Galoryl. These compounds are introduced in the following proportions: weight fraction of pore-forming agent/water=1.4% and weight fraction of surfactant/pore-forming agent=6%.

(5) The system is stirred at 600 rpm until a suspension is obtained with rheological properties suitable for dropping (viscosity 250 MPa.Math.s).

(6) Forming is carried out by the oil-drop method. The dropping column is fed with an ammonia solution at a concentration of 28 g/L and an organic solution constituted by the same petroleum cut as that used as pore-forming agent in the preparation of the emulsion. The suspension is dropped by means of calibrated nozzles. The beads are recovered at the bottom of the column and put in a ventilated oven at 120 C. under moist air containing 200 g of water/kg dry air for 12 h. They are then calcined under dry air at 650 C. for 3 hours. The beads obtained have a diameter of 1.9 mm.

(7) A catalyst A is prepared on this support, aiming for the deposition of 0.3% by weight of platinum and 1% by weight of chlorine on the final catalyst. 400 cm.sup.3 of an aqueous solution of hexachloroplatinic acid and hydrochloric acid is added to 100 g of alumina support containing tin. They are left in contact for 4 hours and then drained. Drying at 120 C. for 15 h is followed by calcination at 500 C. under an air flow of 100 liters per hour for 3 hours, at a rate of temperature increase of 7 C. per minute.

(8) The chlorine content above 1% by weight after calcination is adjusted to 1% by weight by a thermal treatment of partial dechlorination at 520 C. under dry air and 8000 ppmv of water is added in the space of 2.5 hours.

(9) Catalyst A obtained after dechlorination contains 0.29% by weight of platinum, 0.28% by weight of tin, 0.40% by weight of phosphorus and 1.01% by weight of chlorine.

Example 2: Preparation of a Catalyst B: CePt/Al2O3SnCl (Comparative)

(10) The support in Example 2 is prepared in a similar way to Example 1, except that only tin dichloride is added to the boehmite suspension, aiming for 0.3% by weight of tin in the final solid.

(11) Impregnation in excess with platinum is carried out on this support, aiming for the deposition of 0.3% by weight of platinum and 1% by weight of chlorine on the final catalyst, in the same way as described in Example 1.

(12) After calcination, dry impregnation of cerium nitrate is carried out, aiming for 0.15% by weight on the final catalyst. Before impregnation with Ce, the catalyst is left in a water-saturated atmosphere overnight at ambient temperature. 42 cm.sup.3 of an aqueous solution of cerium nitrate is added to 70 g of alumina support containing tin. They are left in contact for 30 minutes. After impregnation, the solid is again left overnight to ripen at ambient temperature in a water-saturated atmosphere. It is dried at 120 C. for 15 h and then calcined at 500 C. under an air flow of 100 liters per hour for 3 hours, at a rate of temperature increase of 7 C. per minute. The chlorine content is adjusted as described in Example 1 in the space of 2 hours.

(13) Catalyst B obtained after dechlorination contains 0.28% by weight of platinum, 0.29% by weight of tin, 0.16% by weight of cerium and 0.99% by weight of chlorine.

Example 3: Preparation of a Catalyst C: CePt/Al2O3SnP0.4Cl (According to the Invention)

(14) A catalyst C is prepared from the support in Example 1, containing 0.3% by weight of tin and 0.4% by weight of phosphorus, by impregnations with platinum and then cerium as described in Example 2.

(15) Catalyst C obtained after dechlorination contains 0.30% by weight of platinum, 0.14% by weight of cerium, 0.28% by weight of tin, 0.39% by weight of phosphorus and 1.02% by weight of chlorine.

Example 4: Preparation of a Catalyst D: CePt/Al2O3SnP0.8Cl (According to the Invention)

(16) The support in Example 4 is prepared in a similar way to Example 1, except that the phosphorus content aimed for is 0.8% by weight on the final catalyst.

(17) Next, platinum and then cerium are impregnated as described in Example 2.

(18) Catalyst D obtained after dechlorination contains 0.28% by weight of platinum, 0.15% by weight of cerium, 0.30% by weight of tin, 0.76% by weight of phosphorus and 1.04% by weight of chlorine.

Example 5: Preparation of a Catalyst E: PtCe/Al2O3SnP0.4Cl (According to the Invention)

(19) A catalyst E is prepared from the support in Example 1, containing 0.3% by weight of tin and 0.4% by weight of phosphorus, by impregnations with cerium and then platinum, which differs from Example 2 in the order of the introduction of elements by impregnation. The contents aimed for, 0.15% by weight of cerium and 0.30% by weight of platinum, are identical.

(20) Catalyst E obtained after dechlorination contains 0.30% by weight of platinum, 0.09% by weight of cerium, 0.29% by weight of tin, 0.39% by weight of phosphorus and 0.99% by weight of chlorine.

Example 6: Preparation of a Catalyst F: CePt/Al2O3SnP0.3Cl (Comparative)

(21) The support in Example 6 is prepared in a similar way to Example 1, except that the phosphorus content aimed for is 0.3% by weight on the final catalyst.

(22) Next, platinum and then cerium are impregnated as described in Example 2.

(23) Catalyst F obtained after dechlorination contains 0.28% by weight of platinum, 0.16% by weight of cerium, 0.29% by weight of tin, 0.28% by weight of phosphorus and 1.01% by weight of chlorine.

Example 7: Preparation of a Catalyst G: CePt/Al2O3SnP1.15Cl (Comparative)

(24) The support in Example 6 is prepared in a similar way to Example 1, except that the phosphorus content aimed for is 1.15% by weight on the final catalyst.

(25) Next, platinum and then cerium are impregnated as described in Example 2.

(26) Catalyst G obtained after dechlorination contains 0.28% by weight of platinum, 0.15% by weight of cerium, 0.30% by weight of tin, 1.12% by weight of phosphorus and 0.98% by weight of chlorine.

Example 8: Preparation of a Catalyst H: CePt/Al2O3SnP0.4Cl (Comparative)

(27) A catalyst H is prepared from the support of Example 1, containing 0.3% by weight of tin and 0.4% by weight of phosphorus, by impregnations with platinum and then cerium as described in Example 2, except that the cerium content aimed for is 1.1% by weight.

(28) Catalyst H obtained after dechlorination contains 0.29% by weight of platinum, 1.12% by weight of cerium, 0.31% by weight of tin, 0.38% by weight of phosphorus and 1.03% by weight of chlorine.

Example 9: Preparation of a Catalyst I: CePtP0.4/Al2O3SnCl (According to the Invention)

(29) The support of Example 2 is prepared in a similar way to Example 1, except that only tin dichloride is added to the boehmite suspension, aiming for 0.3% by weight in the final solid.

(30) Impregnation in excess with platinum is carried out according to Example 1, except that phosphoric acid is added to the solution of hexachloroplatinic acid, aiming for a content of 0.4% by weight on the final catalyst. Dry impregnation with cerium is as described in Example 2. The thermal treatments are identical to Example 2.

(31) Catalyst I obtained after dechlorination contains 0.31% by weight of platinum, 0.14% by weight of cerium, 0.30% by weight of tin, 0.40% by weight of phosphorus and 1.00% by weight of chlorine.

Example 10: Evaluation of the Performances of Catalysts a to I in Catalytic Reforming

(32) Samples of the catalysts whose preparation is described in Examples 1 to 9 were utilized in a reaction bed suitable for the conversion of a hydrocarbon-containing feedstock, of the naphtha type originating from petroleum distillation. This naphtha has the following composition: 49.6% by weight of paraffinic compounds, 35.3% by weight of naphthenes, 15.1% by weight of aromatic compounds,
for a total density of 0.7539 g/cm.sup.3. The initial and final distillation points of this feedstock are 101 and 175 C., respectively, with 95% distillation carried out at 166 C.

(33) The research octane number is close to 55.

(34) After loading in the reactor, the catalysts are activated by thermal treatment under an atmosphere of pure hydrogen, for a period of 2 h at 490 C.

(35) The catalytic performances are evaluated under conditions of reforming reactions in the presence of hydrogen and naphtha described above. The conditions for utilizing the catalyst are as follows: Reactor pressure: 0.76 MPa (7.6 barg) Feed rate of 1.8 kg/h per kg of catalyst Hydrogen/hydrocarbons molar ratio in the feedstock: 3

(36) Comparison of the catalysts is carried out at iso quality of research octane number (RON) of the liquid effluents (reformates) resulting from the catalytic conversion of the feedstock. The comparison is carried out for a RON of 100.

(37) The selectivity is expressed as yield of C.sub.5+ compounds expressed as a percentage by weight with respect to the effluent at a given activity level. During the test, the yield passes through a first phase during which it increases with time under load which corresponds to deactivation of the catalyst through coking. Then, after a plateau of variable duration, the yield values decrease with time. This is the period of catalyst deactivation. Comparisons of catalysts in terms of selectivity will be carried out on the basis of the yield values measured over the plateaux. The precision for this measurement is +/0.3 points.

(38) The activity is expressed by the temperature required to reach a given octane number (also called RON or Research Octane Number). Here, the temperature will be taken at 24 hours of testing. The precision for this measurement is +/2 C. Stability means the stability of the activity, which is generally measured by the thermal increment applied per unit time for maintaining a constant RON of 100.

(39) The results of the tests are shown in the table and in FIGS. 1 to 3 below. FIG. 1 shows the selectivity. FIG. 2 relates to the activity: a very active catalyst is expressed by a moderate temperature in order to reach the RON. FIG. 3 shows the stability: a stable catalyst is expressed by a small thermal increment.

(40) TABLE-US-00001 Yield C5+ Temperature at Thermal increment over Catalyst (% by weight) 24 h ( C.) 240 h ( C./h) A 88.4 481 0.10 B 88.3 485 0.13 C 89.1 481 0.08 D 89.4 482 0.07 E 89.0 482 0.08 F 88.4 484 0.11 G 88.7 482 0.10 H 88.6 488 0.12 I 89.2 481 0.08

(41) These results show a synergistic effect between P and Ce when the phosphorus content is comprised between 0.4 and 1.0% by weight of phosphorus and the cerium content is less than 1% by weight of cerium. This effect makes it possible to improve the selectivity and stability of the catalysts without degrading their activity.