METHOD FOR PREPARING AN IZM-2 BASED CATALYST BY A SPECIFIC HEAT TREATMENT AND USE OF SAID CATALYST FOR THE ISOMERISATION OF PARAFFINIC FEEDSTOCKS TO MIDDLE DISTILLATES
20230381758 · 2023-11-30
Assignee
Inventors
Cpc classification
B01J37/0203
PERFORMING OPERATIONS; TRANSPORTING
C10G45/62
CHEMISTRY; METALLURGY
B01J2229/40
PERFORMING OPERATIONS; TRANSPORTING
C10G45/64
CHEMISTRY; METALLURGY
B01J37/0009
PERFORMING OPERATIONS; TRANSPORTING
B01J2229/34
PERFORMING OPERATIONS; TRANSPORTING
International classification
B01J37/00
PERFORMING OPERATIONS; TRANSPORTING
C10G45/62
CHEMISTRY; METALLURGY
C10G45/64
CHEMISTRY; METALLURGY
Abstract
The present invention relates to a method for preparing a bifunctional catalyst using an IZM-2 zeolite, a hydrogenating function and a matrix. The preparation method according to the invention uses a specific heat treatment of the catalyst which improves its selectivity for the isomerisation of paraffinic feedstocks in middle distillates.
Claims
1. A process for preparing a bifunctional catalyst comprising an acid function constituted by IZM-2 zeolite, a hydrogenating function comprising at least one noble metal from group VIII of the Periodic Table, chosen from platinum and palladium, and a matrix, said process comprising at least the following steps: i) a step of preparing the support for the catalyst by shaping IZM-2 zeolite with a matrix such that the weight percentage of zeolite is advantageously between 1% and 50% relative to the weight of the support, ii) a step of depositing at least one noble metal from group VIII of the Periodic Table by impregnation of the support prepared in step i), enabling a solid to be obtained, with an aqueous solution comprising at least the following compounds: at least one ammoniacal compound chosen from the platinum(II) tetramine salts of formula Pt(NH.sub.3).sub.4(OH).sub.2, Pt(NH.sub.3).sub.4(NO.sub.3).sub.2 or Pt(NH.sub.3).sub.4X.sub.2, the platinum(IV)hexamine salts of formula Pt(NH.sub.3).sub.6X.sub.4; the platinum(IV) halopentamine salts of formula (PtX(NH.sub.3).sub.5)X.sub.3; the platinum N-tetrahalodiamine salts of formula PtX.sub.4(NH.sub.3).sub.2; and the halogenated compounds of formula H(Pt(acac).sub.2X); the palladium(II) salts Pd(NH.sub.3).sub.4SO.sub.4 or Pd(NH.sub.3).sub.4X.sub.2, wherein X is a halogen chosen from chlorine, fluorine, bromine and iodine, X preferably being chlorine, and “acac” represents the acetylacetonate group (of empirical formula C.sub.5H.sub.7O.sub.2), an acetylacetone-derived compound, iii) at least one heat treatment step wherein said solid prepared in step ii) is brought into contact with at least one gas mixture containing oxygen, water, chlorine and/or at least one chlorinated compound, said heat treatment step being carried out between 200° C. and 1100° C.
2. The process as claimed in claim 1, wherein step i) is performed by blending-extrusion.
3. The process as claimed in claim 1, wherein said matrix used in step i) is alumina.
4. The process as claimed in claim 1, wherein the support obtained on conclusion of step i) is subjected to a drying step performed at a temperature of between 50° C. and 180° C.
5. The process as claimed in claim 1, wherein the X is chlorine.
6. The process as claimed in claim 1, wherein the aqueous solution from step ii) comprises ammoniacal compounds chosen from the platinum(II) tetramine salts of formula Pt(NH.sub.3).sub.4(OH).sub.2, Pt(NH.sub.3).sub.4(NO.sub.3) or Pt(NH.sub.3).sub.4X.sub.2, the platinum(IV) hexamine salts of formula Pt(NH.sub.3).sub.6X.sub.4; the platinum(IV) halopentamine salts of formula (PtX(NH.sub.3).sub.5)X.sub.3; the platinum N-tetrahalodiamine salts of formula PtX.sub.4(NH.sub.3).sub.2; and the halogenated compounds of formula H(Pt(acac).sub.2X); X and “acac” having the abovementioned meaning.
7. The process as claimed in claim 6, wherein said solution comprises ammoniacal compounds chosen from the platinum(II) tetramine salts of formula Pt(NH.sub.3).sub.4(OH).sub.2, Pt(NH.sub.3).sub.4(NO.sub.3) or Pt(NH.sub.3).sub.4X.sub.2.
8. The process as claimed in claim 1, wherein the impregnation solution also contains at least one ammonium salt not containing any noble metals, chosen from ammonium nitrate NH.sub.4NO.sub.3, ammonium chloride NH.sub.4Cl, ammonium sulfate (NH.sub.4).sub.2SO.sub.4, ammonium hydroxide NH.sub.4OH, ammonium bicarbonate NH.sub.4HCO.sub.3 and ammonium acetate NH.sub.4H.sub.3C.sub.2O.sub.2, alone or as a mixture, and preferably from ammonium nitrate NH.sub.4NO.sub.3, ammonium chloride NH.sub.4Cl and ammonium acetate NH.sub.4H.sub.3C.sub.2O.sub.2, alone or as a mixture.
9. The process as claimed in claim 8, wherein the mole ratio between the ammonium salt and the noble metal is between 0.1 and 400.
10. The process as claimed in claim 1, wherein said heat treatment of step iii) is carried out at a temperature above 300° C. and below 700° C.
11. The process as claimed in claim 1, wherein the chlorinated compound is an inorganic or organic, and preferably organic, chlorinated compound chosen from carbon tetrachloride, dichloropropane, dichloroethane and chloroform.
12. The process as claimed in claim 1, wherein a step wherein the solid from step ii) is brought into contact with a gas containing oxygen but free of chlorine and/or at least one chlorinated compound is used between step ii) and the heat treatment step iii), until the desired temperature for the implementation of step iii) is reached.
13. The process as claimed in claim 12, wherein the temperature for performing step iii) is above 300° C. and below 700° C.
14. A catalyst comprising an acid function constituted by IZM-2 zeolite, a hydrogenating function comprising at least one noble metal from group VIII of the Periodic Table chosen from platinum and palladium, and a matrix, obtained via the process as claimed in claim 1.
15. A process for the isomerization of a paraffinic feedstock containing between 9 and 25 carbon atoms, said process comprising placing said paraffinic feedstock in contact with at least said catalyst as claimed in claim 14, said process being performed at a temperature of from 200° C. to 500° C., a partial pressure of hydrogen of from 0.3 to 5.5 MPa, a total pressure of from 0.45 to 7 MPa, and a feed space velocity, expressed in kg of feedstock introduced per kilogram of catalyst and per hour, of from 0.25 to 30 h.sup.−1.
16. The process as claimed in claim 15, wherein said paraffinic feedstock is produced from renewable resources chosen from plant oils, algae oils or algal oils, fish oils and fats of plant or animal origin, or mixtures of such feedstocks.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0134]
[0135]
[0136]
[0137]
[0138]
[0139]
[0140]
[0141] The following examples illustrate the invention without, however, limiting the scope thereof.
EXAMPLES
Example 1 (not in Accordance with the Invention): Preparation of the Isomerization Catalyst a
Synthesis of the IZM-2 Zeolite
[0142] The IZM-2 zeolite was synthesized in accordance with the teaching of patent FR 2 918 050 B. A colloidal silica suspension known under the trade name Ludox HS-40, sold by Aldrich, is incorporated into a solution composed of sodium hydroxide (Prolabo), 1,6-bis(methylpiperidinium)hexane dibromide structuring agent, aluminum hydroxide (Aldrich) and deionized water. The molar composition of the mixture is as follows: 1 SiO.sub.2; 0.0042 Al.sub.2O.sub.3; 0.1666 Na.sub.2O; 0.1666 1,6-bis(methylpiperidinium)hexane; 33.3333 H.sub.2O. The mixture is stirred vigorously for 30 minutes. The mixture is then transferred, after homogenization, into a Parr autoclave. The autoclave is heated for 5 days at 170° C. with spindle stirring (30 rpm). The product obtained is filtered, washed with deionized water to reach neutral pH and then dried overnight at 100° C. in an oven. The solid is then introduced into a muffle furnace and calcined therein so as to remove the structuring agent. The calcination cycle comprises a temperature increase up to 200° C., a hold of two hours at this temperature, a temperature increase up to 550° C., followed by a hold of eight hours at this temperature and finally a return to ambient temperature. The temperature rises are performed at a rate of 2° C./minute. The solid thus obtained is then refluxed for 2 hours in an aqueous ammonium nitrate solution (10 ml of solution per gram of solid, ammonium nitrate concentration of 3M) so as to exchange the sodium alkaline cations with ammonium ions. This refluxing step is performed four times with fresh ammonium nitrate solution, and the solid is then filtered off, washed with deionized water and dried in an oven overnight at 100° C. Finally, to obtain the zeolite in its acid (protonated H.sup.+) form, a step of calcination is performed at 550° C. for 10 hours (temperature increase rate of 2° C./minute) in a traversed bed under dry air (2 normal liters per hour and per gram of solid). The solid thus obtained was analysed by X-ray diffraction and identified as consisting of IZM-2 zeolite.
Preparation of the IZM-2/Alumina Support (Step i))
[0143] The IZM-2/alumina support is obtained by blending and extrusion of the IZM-2 zeolite with an alumina gel supplied by the company Axens. The blended paste is extruded through a quadrilobal die 1.5 mm in diameter. After drying in an oven overnight at 110° C., the extrudates are calcined at 520° C. for two hours (temperature increase rate of 5° C./minute) in a traversed bed under dry air (2 normal litres per hour and per gram of solid). The weight content of IZM-2 zeolite on the support after calcination is 13% by weight.
Platinum Deposition (Step ii), in Accordance with the Invention)
[0144] The deposition is carried out by dry impregnation of the IZM-2/alumina support prepared in step i) with an aqueous solution containing platinum tetramine nitrate Pt(NH.sub.3).sub.4(NO.sub.3).sub.2. 20 g of support are typically used, and are dry-impregnated in a pan. After impregnation, the solid is left to mature for at least five hours in the laboratory air and is then dried overnight in a ventilated oven at 110° C.
Heat Treatment of the Solid from ii) (Step iii), not in Accordance with the Invention)
[0145] After drying, the solid is then calcined in a traversed bed under a flow of dry air (1 normal liter per hour and per gram of solid), the weight content of oxygen in the gas being 23% by weight, the first gas mixture being free of chlorine and containing a water content of less than 0.001% by weight in a tube furnace under the following conditions: [0146] temperature increase from ambient temperature to 150° C. at 5° C./min; [0147] hold of 1 hour at 150° C.; [0148] increase from 150° C. to 450° C. at 5° C./min; [0149] hold of 1 hour at 450° C.; [0150] decrease to ambient temperature.
[0151] On conclusion of step iii), various characterizations are carried out on catalyst A. The Pt content measured by XRF is 0.34% by weight, and its distribution coefficient measured by Castaing microprobe is 1.03.
[0152]
Example 2 (in Accordance with the Invention): Preparation of the Isomerization Catalyst B
Synthesis of IZM-2 Zeolite
[0153] This is the same zeolite as the one described in example 1.
Preparation of the IZM-2/Alumina Support (Step i))
[0154] This is the same support as the one described in example 1.
Platinum Deposition (Step ii), in Accordance with the Invention)
[0155] This is the same deposition as the one described in example 1.
Heat Treatment of the Solid from ii) (Step iii), in Accordance with the Invention)
[0156] After drying, the catalyst then undergoes a heat treatment by bringing said catalyst into contact, at ambient temperature, in a tube furnace, with a first gas mixture constituted of dry air, the weight content of oxygen in the gas being 23% by weight, the first gas mixture being free of chlorine and containing a water content of less than 0.001% by weight, under the following conditions: [0157] temperature increase from ambient temperature to 150° C. at 5° C./min under a flow of dry air (1 normal liter per hour and per gram of solid); [0158] hold of 1 hour at 150° C. under a flow of dry air (1 normal liter per hour and per gram of solid); [0159] increase from 150° C. to 450° C. at 5° C./min under a flow of dry air (1 normal liter per hour and per gram of solid); [0160] hold of 1 hour at 450° C. under a flow of dry air (1 normal liter per hour and per gram of solid); [0161] increase from 450° C. to 520° C. at 5° C./min under a flow of dry air (3.3 normal liters per hour and per gram of solid);
[0162] At the start of the hold at 520° C., water and dichloropropane are continuously injected into the first gas mixture to form the second gas mixture. The amounts injected correspond to a weight content of water of 2% by weight and of dichloropropane of 0.63% by weight in the gas mixture. The temperature hold at 520° C. is maintained for four hours. The temperature is then decreased from 520° C. to 400° C. at 5° C./min, still under the second gas mixture. At 400° C., the injection of water and dichloropropane is cut and the solid is cooled to ambient temperature under a flow of dry air (3.3 normal liters per hour and per gram of solid).
[0163] On conclusion of step iii), various characterizations are carried out on catalyst B. The Pt content measured by XRF is 0.34% by weight, and its distribution coefficient measured by Castaing microprobe is 1.03.
[0164]
[0165] As for catalyst A, it is noted that, locally, the weight percentage of Pt decreases as the amount of alumina increases relative to the amount of IZM-2, which reflects preferential deposition of the platinum on the IZM-2 zeolite.
Example 3 (not in Accordance with the Invention): Preparation of the Isomerization Catalyst C
Synthesis of the IZM-2 Zeolite
[0166] This is the same zeolite as the one described in example 1.
Preparation of the IZM-2/Alumina Support (Step i))
[0167] The IZM-2/alumina support is obtained by blending and extrusion of the IZM-2 zeolite with an alumina gel supplied by the company Axens. The blended paste is extruded through a quadrilobal die 1.5 mm in diameter. After drying in an oven overnight at 110° C., the extrudates are calcined at 550° C. for two hours (temperature increase rate of 5° C./minute) in a traversed bed under dry air (2 normal litres per hour and per gram of solid). The weight content of IZM-2 zeolite on the support after calcination is 13% by weight.
Platinum Deposition (Step ii), in Accordance with the Invention)
[0168] The deposition is carried out by dry impregnation of the IZM-2/alumina support prepared in step i) with an aqueous solution containing platinum tetramine nitrate Pt(NH.sub.3).sub.4(NO.sub.3).sub.2. 20 g of support are typically used, and are dry-impregnated in a pan. After impregnation, the solid is left to mature for at least five hours in the laboratory air and is then dried overnight in a ventilated oven at 110° C.
Heat Treatment of the Solid from ii) (Step iii), not in Accordance with the Invention)
[0169] After drying, the solid is then calcined in a traversed bed under a flow of dry air (1 normal liter per hour and per gram of solid), the weight content of oxygen in the gas being 23% by weight, said dry air being free of chlorine and containing a water content of less than 0.001% by weight in a tube furnace under the following conditions: [0170] temperature increase from ambient temperature to 150° C. at 5° C./min; [0171] hold of 1 hour at 150° C.; [0172] increase from 150° C. to 450° C. at 5° C./min; [0173] hold of 1 hour at 450° C.; [0174] decrease to ambient temperature.
[0175] On conclusion of step iii), various characterizations are carried out on catalyst C. The Pt content measured by XRF is 0.26% by weight, and its distribution coefficient measured by Castaing microprobe is 1.00.
[0176]
[0177] It is thus observed that, for weight % Al.sub.2O.sub.3/(weight % Al.sub.2O.sub.3+weight % IZM-2) ratios which tend toward 1, i.e. for analysed zones not containing any IZM-2 zeolite, the weight % of platinum tends toward a zero value.
Example 4 (in Accordance with the Invention): Preparation of the Isomerization Catalyst D
Synthesis of the IZM-2 Zeolite
[0178] This is the same zeolite as the one described in example 1.
Preparation of the IZM-2/Alumina Support (Step i))
[0179] This is the same support as the one described in example 3.
Platinum Deposition (Step ii), in Accordance with the Invention)
[0180] This is the same deposition as the one described in example 3.
Heat Treatment of the Solid from ii) (Step iii), in Accordance with the Invention)
[0181] After drying, the catalyst then undergoes a heat treatment by bringing said catalyst into contact, at ambient temperature, in a tube furnace, with a first gas mixture of dry air, the weight content of oxygen in the gas being 23% by weight, the first gas mixture being free of chlorine and containing a water content of less than 0.001% by weight, under the following conditions: [0182] temperature increase from ambient temperature to 150° C. at 5° C./min under a flow of dry air (1 normal liter per hour and per gram of solid); [0183] hold of 1 hour at 150° C. under a flow of dry air (1 normal liter per hour and per gram of solid); [0184] increase from 150° C. to 450° C. at 5° C./min under a flow of dry air (1 normal liter per hour and per gram of solid); [0185] hold of 1 hour at 450° C. under a flow of dry air (1 normal liter per hour and per gram of solid); [0186] increase from 450° C. to 520° C. at 5° C./min under a flow of dry air (3.3 normal liters per hour and per gram of solid);
[0187] At the start of the hold at 520° C., water and dichloropropane are continuously injected into the first gas mixture to form the second gas mixture. The amounts injected correspond to a weight content of water of 2% by weight and of dichloropropane of 0.63% by weight in the gas mixture. The temperature hold at 520° C. is maintained for four hours. The temperature is then decreased from 520° C. to 400° C. at 5° C./min, still under the second gas mixture. At 400° C., the injection of water and dichloropropane is cut and the solid is cooled to ambient temperature under a flow of dry air (3.3 normal liters per hour and per gram of solid).
[0188] On conclusion of step iii), various characterizations are carried out on catalyst D. The Pt content measured by XRF is 0.25% by weight, and its distribution coefficient measured by Castaing microprobe is 0.99.
[0189]
Example 5 (in Accordance with the Invention): Preparation of the Isomerization Catalyst E
Synthesis of the IZM-2 Zeolite
[0190] This is the same zeolite as the one described in example 1.
Preparation of the IZM-2/Alumina Support (Step i))
[0191] This is the same support as the one described in example 3.
Platinum Deposition (Step ii), in Accordance with the Invention)
[0192] This is the same deposition as the one described in example 3.
Heat Treatment of the Solid from ii) (Step iii), in Accordance with the Invention)
[0193] After drying, the catalyst then undergoes a heat treatment by bringing said catalyst into contact, at ambient temperature, in a tube furnace, with a first gas mixture of dry air (3.3 normal liters per hour and per gram of solid), the weight content of oxygen in the gas being 23% by weight, the first gas mixture being free of chlorine and containing a water content of less than 0.001% by weight. The temperature is increased from ambient temperature to 520° C. at 5° C./min.
[0194] At the start of the hold at 520° C., in addition to the flow of the first gas mixture of dry air, water and dichloropropane are continuously injected in order to form a second gas mixture. The amounts injected correspond to a weight content of water of 2% by weight and of dichloropropane of 0.63% by weight in the gaseous effluent. The temperature hold at 520° C. is maintained for four hours. The temperature is then decreased from 520° C. to 400° C. at 5° C./min, still under the second gas mixture. At 400° C., the injection of water and dichloropropane is cut and the solid is cooled to ambient temperature under a flow of dry air (3.3 normal liters per hour and per gram of solid).
[0195] On conclusion of step iii), various characterizations are carried out on catalyst E. The Pt content measured by XRF is 0.25% by weight, and its distribution coefficient measured by Castaing microprobe is 1.00.
[0196]
Example 6 (not in Accordance with the Invention): Preparation of the Isomerization Catalyst F
Synthesis of the IZM-2 Zeolite
[0197] This is the same zeolite as the one described in example 1.
Preparation of the IZM-2/Alumina Support (Step i))
[0198] This is the same support as the one described in example 3.
Platinum Deposition (Step ii). Not in Accordance with the Invention)
[0199] Catalyst F is prepared by excess impregnation of the IZM-2/alumina support with an aqueous solution containing hexachloroplatinic acid, a platinum precursor not in accordance with the invention. The concentration of hexachloroplatinic acid in the solution is 1.28×10.sup.−3 mol/l.
[0200] 20 g of support are used, the pore volume of which is filled with distilled water and the solid is left to mature for one hour at ambient temperature. The solid is then immersed in 80 ml of a hydrochloric acid HCl solution of concentration 3.52×10.sup.−1 mol/I in an Erlenmeyer flask, and the whole is then stirred on a stirring table (100 rpm) at ambient temperature for one hour. The hydrochloric acid solution is then removed and the solid is immersed in 80 ml of the hexachloroplatinic acid solution described previously, and the whole is then stirred on a shaker (100 rpm) at ambient temperature for 24 hours. The impregnation solution is then removed and the solid is rinsed with 160 ml of distilled water. The solid is then dried in a ventilated oven overnight at 110° C.
Heat Treatment of the Solid from ii) (Step iii), not in Accordance with the Invention)
[0201] After drying, the solid is then calcined in a traversed bed under a flow of dry air (1 normal liter per hour and per gram of solid), the weight content of oxygen in the gas being 23% by weight, said dry air being free of chlorine and containing a water content of less than 0.001% by weight in a tube furnace under the following conditions: [0202] temperature increase from ambient temperature to 150° C. at 5° C./min; [0203] hold of 1 hour at 150° C.; [0204] increase from 150° C. to 450° C. at 5° C./min; [0205] hold of 1 hour at 450° C.; [0206] decrease to ambient temperature.
[0207] On conclusion of step iii), various characterizations are carried out on catalyst F. The Pt content measured by XRF is 0.11% by weight, and its distribution coefficient measured by Castaing microprobe is 1.01.
[0208]
[0209] In contrast with catalysts A, B, C, D and E, it is noted that, locally, the weight percentage of Pt tends to increase as the amount of alumina increases relative to the amount of IZM-2, which reflects preferential deposition of the platinum on the alumina.
Example 7 (not in Accordance with the Invention): Preparation of the Isomerization Catalyst G
Synthesis of the IZM-2 Zeolite
[0210] This is the same zeolite as the one described in example 1.
Preparation of the IZM-2/Alumina Support (Step i))
[0211] This is the same support as the one described in example 6.
Platinum Deposition (Step ii), not in Accordance with the Invention)
[0212] This is the same deposition is the one described in example 6 with the platinum precursor not in accordance with the invention.
Heat Treatment of the Solid from ii) (Step iii), in Accordance with the Invention)
[0213] After drying, the catalyst then undergoes a heat treatment by bringing said catalyst into contact, at ambient temperature, in a tube furnace, with a first gas mixture of dry air, the weight content of oxygen in the gas being 23% by weight, the first gas mixture being free of chlorine and containing a water content of less than 0.001% by weight, under the following conditions: [0214] temperature increase from ambient temperature to 150° C. at 5° C./min under a flow of dry air (1 normal liter per hour and per gram of solid); [0215] hold of 1 hour at 150° C. under a flow of dry air (1 normal liter per hour and per gram of solid); [0216] increase from 150° C. to 450° C. at 5° C./min under a flow of dry air (1 normal liter per hour and per gram of solid); [0217] hold of 1 hour at 450° C. under a flow of dry air (1 normal liter per hour and per gram of solid); [0218] increase from 450° C. to 520° C. at 5° C./min under a flow of dry air (3.3 normal liters per hour and per gram of solid);
[0219] At the start of the hold at 520° C., in addition to the flow of the first gas mixture of dry air, water and dichloropropane are continuously injected to form the second gas mixture. The amounts injected correspond to a weight content of water of 2% by weight and of dichloropropane of 0.63% by weight in the gaseous effluent. The temperature hold at 520° C. is maintained for four hours. The temperature is then decreased from 520° C. to 400° C. at 5° C./min, still under the second gas mixture. At 400° C., the injection of water and dichloropropane is cut and the solid is cooled to ambient temperature under a flow of dry air (3.3 normal liters per hour and per gram of solid).
[0220] On conclusion of step iii), various characterizations are carried out on catalyst G. The Pt content measured by XRF is 0.10% by weight, and its distribution coefficient measured by Castaing microprobe is 1.04.
[0221]
[0222] In contrast with catalysts A, B, C, D and E, it is noted that, locally, the weight percentage of Pt tends to increase as the amount of alumina increases relative to the amount of IZM-2, which reflects preferential deposition of the platinum on the alumina.
Example 8: Evaluation of the Catalytic Properties of the Catalysts in Isomerization of a Paraffinic Feedstock
[0223] The catalysts were tested in the isomerization of a paraffinic feedstock composed of n-hexadecane. The tests were performed in a micro-unit using a fixed-bed reactor and working in downflow without recycling. The analysis of the hydrocarbon-based effluents is performed online by gas chromatography. Once charged into the unit, the catalyst undergoes a first step of drying under nitrogen under the following conditions: [0224] nitrogen flow rate: 2 normal liters per hour and per gram of catalyst, [0225] total pressure: 0.1 MPa, [0226] temperature increase rate from ambient temperature to 150° C.: 5° C./min, [0227] hold at 150° C. for 30 minutes.
[0228] After drying, the nitrogen is replaced with hydrogen and a step of reduction under a flow of pure hydrogen is then performed under the following conditions: [0229] hydrogen flow rate: 5 normal liters per hour and per gram of catalyst, [0230] total pressure: 1.1 MPa, [0231] temperature increase rate from 150° C. to 450° C.: 5° C./min, [0232] hold at 450° C. for 1 hour.
[0233] After the reduction step, the temperature is reduced to 230° C. and the catalyst is placed in contact with n-hexadecane under the following conditions: [0234] feed space velocity of 2 g of n-hexadecane per hour and per gram of catalyst, [0235] mole ratio of hydrogen to n-hexadecane of 10, [0236] total pressure of 1.1 MPa.
[0237] The conversion is modified by varying the temperature; and at each temperature hold, two analyses of the effluent are performed, which makes it possible to calculate the catalytic performance and to check the stability of the catalytic performance for said temperature hold. Typically, the temperature is varied between 230° C. and 350° C. in temperature holds of 5° C. The analysis of the effluents is performed integrally by means of an online GC system. The temperature required to reach 50% conversion serves as a descriptor of the activity of the catalyst, while the maximum yield of hexadecane isomers obtained serves as a descriptor of the isomerizing properties of the catalyst. The yield of methane and ethane at 310° C. is used as a descriptor of the hydrogenolysing activity of the catalyst.
[0238] Table 1 thus reports the catalytic performance of the catalysts in the hydroconversion of n-hexadecane.
TABLE-US-00001 TABLE 1 catalytic performance of the catalysts in the hydroconversion of n-hexadecane E (in A C accordance S G (not in B (in (not in D with the (not in (not in Catalyst accordance) accordance) accordance) (compliant) invention) accordance) accordance) Pt deposition In In In In In Not in Not in accordance accordance accordance accordance accordance accordance accordance Heat treatment Not in In Not in In In Not in In accordance accordance accordance accordance accordance accordance accordance Temperature at 278 279 284 281 281 276 278 50% conversion (° C.) Max yield of 85 87 86 87 87 83 83 isomers (wt %) Yield of 0.09 0.03 0.09 0.03 0.02 0.02 0.02 methane and ethane at 310° C.
[0239] Catalysts A and B are prepared from the same IZM-2/alumina support, for both solids the Pt deposition protocol is in accordance with the invention, but the heat treatment after deposition of Pt on catalyst A is not in accordance with the invention. It is observed that the catalysts have comparable catalytic activities (one degree difference in activity) but that catalyst B that has undergone a treatment in accordance with the invention has a higher maximum isomerization yield. Catalyst B also has a lower hydrogenolysing activity than catalyst A at 310° C. since the yield of methane and ethane is reduced by a factor of 3.
[0240] Catalysts C, D and E are prepared from the same IZM-2/alumina support. For these three solids, the deposition of Pt is also in accordance with the invention, but the heat treatment after deposition of Pt on catalyst C is not in accordance with the invention. It is observed that catalysts D and E in accordance with the invention have a better better activity (three degrees difference). The two catalysts D and E also have a higher maximum isomerization yield than catalyst C. Catalysts D and E also have a lower hydrogenolysing activity than catalyst C at 310° C., since the yield of methane and ethane is reduced by a factor of 3 and 4.5 respectively.
[0241] Finally, catalysts F and G are prepared from the same IZM-2/alumina support as catalysts C, D and E. However, for these two catalysts, the Pt deposition protocol is not in accordance with the invention. The heat treatment of catalyst F after deposition of Pt is not in accordance with the invention, whereas that of catalyst G is. It is observed that, in this case, the heat treatment in accordance with the invention does not make it possible to improve the maximum isomerization yield, which is the same for both catalysts. Similarly, the yield of methane and ethane remains the same for both catalysts. Finally, it is observed that the maximum isomerization yields on catalysts F and G not in accordance with the invention are significantly lower than those obtained with catalysts D and E, which are in accordance with the invention and are prepared from the same IZM-2/alumina support as catalysts F and G.
[0242] It is therefore clearly noted that the systematic improvement in the maximum isomerization yield is observed for the catalysts in accordance with the invention having both a preferential localization of the Pt on or in the zeolite and a heat treatment in accordance with the invention, and is linked to a decrease in the hydrogenolysing activity of said catalysts.