EP1206319A1 - PRETREATMENT OF A Pt/Sn-BASED CATALYST - Google Patents

PRETREATMENT OF A Pt/Sn-BASED CATALYST

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Publication number
EP1206319A1
EP1206319A1 EP00931745A EP00931745A EP1206319A1 EP 1206319 A1 EP1206319 A1 EP 1206319A1 EP 00931745 A EP00931745 A EP 00931745A EP 00931745 A EP00931745 A EP 00931745A EP 1206319 A1 EP1206319 A1 EP 1206319A1
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EP
European Patent Office
Prior art keywords
catalyst
dehydrogenation
oxidation
reduction
effected
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP00931745A
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German (de)
French (fr)
Inventor
P l SÖRAKER
Staale Förre JENSEN
Erling Rytter
Morten RÖNNEKLEIV
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Equinor ASA
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Statoil ASA
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Publication of EP1206319A1 publication Critical patent/EP1206319A1/en
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C5/00—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms
    • C07C5/32—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by dehydrogenation with formation of free hydrogen
    • C07C5/321—Catalytic processes
    • C07C5/324—Catalytic processes with metals
    • C07C5/325—Catalytic processes with metals of the platinum group
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/12—Oxidising
    • B01J37/14—Oxidising with gases containing free oxygen
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/16—Reducing
    • B01J37/18—Reducing with gases containing free hydrogen
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J38/00—Regeneration or reactivation of catalysts, in general
    • B01J38/04—Gas or vapour treating; Treating by using liquids vaporisable upon contacting spent catalyst
    • B01J38/12—Treating with free oxygen-containing gas
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/007—Mixed salts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/56—Platinum group metals
    • B01J23/62—Platinum group metals with gallium, indium, thallium, germanium, tin or lead
    • B01J23/622—Platinum group metals with gallium, indium, thallium, germanium, tin or lead with germanium, tin or lead
    • B01J23/626—Platinum group metals with gallium, indium, thallium, germanium, tin or lead with germanium, tin or lead with tin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/90—Regeneration or reactivation
    • B01J23/96—Regeneration or reactivation of catalysts comprising metals, oxides or hydroxides of the noble metals
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2521/00—Catalysts comprising the elements, oxides or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium or hafnium
    • C07C2521/02—Boron or aluminium; Oxides or hydroxides thereof
    • C07C2521/04—Alumina
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2521/00—Catalysts comprising the elements, oxides or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium or hafnium
    • C07C2521/10—Magnesium; Oxides or hydroxides thereof
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2523/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00
    • C07C2523/14—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00 of germanium, tin or lead
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2523/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00
    • C07C2523/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00 of noble metals
    • C07C2523/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00 of noble metals of the platinum group metals
    • C07C2523/42—Platinum
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/584—Recycling of catalysts

Definitions

  • the present invention relates to a process of a pre-treatment activation of a Pt/Sn based catalyst and a catalyst activated by such a pre-treatment.
  • catalysts are permanently deactivated due to poisoning and sintering and have to be replaced at given time intervals, generally after 1 to 5 years in operation depending on feedstreams and reaction conditions.
  • the catalysts have to be treated according to a special pre-treatment procedure before the catalyst can operate at optimum performance (see e.s. WO 92/06784 where conditions for optimal reduction of a cobalt catalyst is described).
  • WO 92/06784 where conditions for optimal reduction of a cobalt catalyst is described.
  • catalysts have to be replaced at short intervals it is of major importance to reduce the pre-treatment time.
  • the lifetime of a typical Pt/Sn based dehydrogenation catalyst is up to 3 years.
  • the catalyst used in the STAR process has an expected lifetime of 1 to 2 years in commercial operation, while the catalyst used in the Oleflex process (Pt/Sn/Cs on Al 2 0 3 ) has an expected lifetime of 1 to 3 years [Catalytica (1993)].
  • Significant losses in alkene production can be foreseen if a long activation period is needed after each catalyst replacement.
  • Such catalysts, or variations thereof, can also be used for a number of chemical processes that involve mainly or partly dehydrogenation or hydrogenation steps. A long activation period is also a disadvantage connected to unexpected stops and experimental development in the laboratory.
  • the alkane dehydrogenation is effected at temperatures in the range of 500 to 700 °C .
  • the oxidation/regeneration is preferable effected at temperatures in the range of 500 to 700 °C .
  • Equally the reduction by H 2 is preferable effected in the range of 500 to 700 °C .
  • the chemical process is dehydrogenation performed on a lower alkane.
  • More preferably propane is dehydrogenated.
  • the oxidation is effected by a gaseous O 2 /N 2 mixture gradually increasing the O 2 content.
  • the final part of the oxidation is effected in air.
  • this is preferably effected in H 2 in a temperature range of 500 to 700 °C .
  • dehydrogenation time this is less than half of the dehydrogenation time during normal dehydrogenation process conditions.
  • a typical dehydrogenation time is 2 hours.
  • the reduction in H 2 is particularly effected for about 2 hours.
  • a further object of the present invention is a catalyst activated by the pre-treatment set forth above.
  • the objective of this invention is to define a pretreatment procedure which decreases the time required to reach an optimum conversion level in an alkane dehydrogenation unit, using a Pt/Sn/Mg(AI)O catalyst described in patent NO 179131.
  • a pre-treatment procedure which led to an optimum dehydrogenation activity of a Pt/Sn/Mg(AI)0 catalyst obtained by impregnating Pt and Sn on a pre-calcinated Mg(AI)O carrier material.
  • the pre-treatment procedure used in the previous invention consisted of in situ reduction, followed by oxidation and a new reduction period (ROR).
  • the ROR pre-treatment procedure did not lead to an optimum dehydrogenation activity.
  • the conversion level after the first regeneration was higher than the initial conversion level after the ROR. After the next test cycle the conversion level was even higher.
  • a stable catalyst performance was not obtained before after 300h on stream, when the catalyst had been subjected to 9 cycles consisting of a dehydrogenation period followed by regeneration and reduction.
  • a pre-treatment procedure for the catalyst that dramatically decreased the required time to obtain optimum conversion level in dehydrogenation of propane was developed.
  • the catalyst was prepared according to a slightly modification of the procedure described in patent NO 179131 , using a water based acidic solution in the deposition of platinum and tin on hydrotalcite or precalcined hydrotalcite.
  • the catalysts used in the examples have an Mg/AI-ratio of 4.8.
  • the content of platinum and tin are ca. 0.25 and 0.5 wt% respectively.
  • the catalyst was calcinated at 560°C after the impregnation.
  • the catalyst was pressed to tablets, crushed and sieved to a pellet size of 0.64-1.0 mm prior to testing.
  • the reactor temperature was regulated to 600°C at a distance of 1/3 of the total catalyst bed-length from the top of the catalyst bed, while the temperature at the bottom of the catalyst bed, measured at a distance of approximately 1/3 of catalyst bed length from the bottom of the catalyst bed, was in the range of 590 to 615°C.
  • the GHSV was 1000h "1 based on propane, and the reaction gas contained 4.5% hydrogen, 32% propane and rest steam on mole basis.
  • the dehydrogenation periods usually lasted approximately 20 hours and were followed by a regeneration of the catalyst.
  • the conversion levels were calculated from on-line GC analysis. The analysis were taken with approximately 1 hours intervals. The conversion levels presented were obtained after 5h in the dehydrogenation period.
  • the regeneration of the catalyst was done by burning of the formed coke using air diluted with nitrogen.
  • the content of oxygen was initially reduced to approximately 2% and was stepwise increased to a final level of 21 % where pure air was used.
  • the regeneration period was followed by catalyst reduction using hydrogen. Both the regeneration and the reduction of the catalyst were done at 600°C.
  • the catalyst was subjected to a pre-treatment procedure consisting of the following steps:
  • the catalyst was subjected to a pre-treatment procedure consisting of the following steps:
  • the catalyst is first pre-treated according to the ROR-procedure described in Example 1.
  • Step 2 to 5 was repeated 9 times, when no further increase in the conversion level of propane in the PDH period was observed.
  • the results from the subsequent propane dehydrogenation test are shown in Figure 1 and Table 1.
  • the catalyst was subjected to a pre-treatment procedure consisting of the following steps::
  • Step 3 to 5 are repeated 12 times.
  • the results from the following PDH conversion tests are shown in Figure 1 and Table 1.
  • the catalyst was subjected to a pre-treatment procedure consisting of the following steps:
  • the catalyst is first pre-treated according to the ROR-procedure described in Example 1.
  • Step 2 to 5 was repeated 6 times, when no further increase in the conversion level of propane in the PDH period was observed.
  • the results from the subsequent propane dehydrogenation tests are shown in Figure 1 and Table 1.
  • Example 5 R-(PDH-OR)*X
  • the catalyst was subjected to a pre-treatment procedure consisting of the following steps:
  • Step 3 to 6 were repeated 5 times, when it was found no further increase in conversion level in the PDH period (Step 3) are observed.
  • the results from the subsequent propane dehydrogenation test are shown in Figure 1 and Table 1.
  • the catalyst was subjected to a pre-treatment procedure consisting of the following steps:
  • Oxidation/regeneration using an O 2 /N 2 -mixture with a gradually increasing 0 2 content. (1. 5. and 10%) 1 h on each step. Different O 2 content was obtained by diluting air with N 2 . Total flow:84ml/min. T 600°C. 5. Oxidation in air. 80ml/min., 600°C, 1h.
  • Step 3 to 6 are repeated 6 times, when it was observed no further increase in conversion level in the PDH period (Step 3).
  • the results from the subsequent propane dehydrogenation test are shown in Figure 1 and Table 1.
  • Table 1 Normalised conversion of propane with time on stream. The conversion level are obtained 5 hours after finishing the regeneration/reduction period. The results are also shown in Figure 1.
  • the conversion level data for Example 1 to Example 6 are all given as normalised values, where the stabilised conversion level which are obtained on the completely pre-treated catalyst is given the value 100%.
  • a typical example of the obtained conversion level of propane to propene is given in Table 2. Similar conversion levels are also obtained in the remaining examples. However, the conversion level shows small variation due to minor changes in the reaction conditions as for instance the temperature profile in the reactor and different partial pressure in the gases entering the reactor.
  • a pre-treatment procedure which included the aforementioned ROR procedure followed by several cycles consisting of a short dehydrogenation period (2h, at 600°) followed by regeneration (oxidation) and reduction in hydrogen (Example 2) reduced the pre-treatment time to approximately 80h.
  • the initial ROR pre-treatment could also be excluded using this kind of catalyst pre-treatment.
  • a pre-treatment time of 40h was obtained using a pre-treatment consisting of an initial reduction followed by 5 cycles consisting of dehydrogenation, regeneration and reduction. A detailed description of this procedure is given in example 5.
  • the catalyst operate at a conversion level of 90% of the optimum conversion level. Within two conventional 20 hours dehydrogenation periods at 600°C, the catalyst performance was at an optimum level.
  • the catalyst was subjected to a pre-treatment procedure consisting of the following steps:
  • the catalyst was subjected to a pre-treatment procedure consisting of the following steps:
  • the catalyst was subjected to a pre-treatment procedure consisting of the following steps: 5 7. Oxidation/regeneration of the catalyst from example 8 using an 0 2 /N 2 -mixture with a gradually increasing 0 2 content. (1. 5. and 10%) 1h on each step.
  • the activation period for the Pt/Sn/Mg(AI)O dehydrogenation catalyst is reduced from 300h to approximately 50 h by using the pre-treatment procedure developed in the present invention.
  • the pre-treatment procedure consists of an initial reduction of the catalyst using hydrogen, followed by several cycles which includes a short

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
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  • Catalysts (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
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Abstract

This invention relates to a pretreatment procedure that reduces the required time to obtain the optimum activity of a Pt/Sn-based catalyst. The pretreatment activation consists of repeated cycles of 1) reduction by H2 at elevated temperatures, 2) alkane dehydrogenation at elevated temperatures, 3) oxidation/regeneration by a O2 containing gas at elevated temperatures.

Description

PRETREATMENT OF A Pt/Sn-BASED CATALYST
Field of the invention. The present invention relates to a process of a pre-treatment activation of a Pt/Sn based catalyst and a catalyst activated by such a pre-treatment.
Background of invention
During industrial operation catalysts are permanently deactivated due to poisoning and sintering and have to be replaced at given time intervals, generally after 1 to 5 years in operation depending on feedstreams and reaction conditions. Usually the catalysts have to be treated according to a special pre-treatment procedure before the catalyst can operate at optimum performance (see e.s. WO 92/06784 where conditions for optimal reduction of a cobalt catalyst is described). Especially when catalysts have to be replaced at short intervals it is of major importance to reduce the pre-treatment time. The lifetime of a typical Pt/Sn based dehydrogenation catalyst is up to 3 years. The catalyst used in the STAR process (Pt/Sn on zink aluminate) has an expected lifetime of 1 to 2 years in commercial operation, while the catalyst used in the Oleflex process (Pt/Sn/Cs on Al203) has an expected lifetime of 1 to 3 years [Catalytica (1993)]. Significant losses in alkene production can be foreseen if a long activation period is needed after each catalyst replacement. Such catalysts, or variations thereof, can also be used for a number of chemical processes that involve mainly or partly dehydrogenation or hydrogenation steps. A long activation period is also a disadvantage connected to unexpected stops and experimental development in the laboratory.
The catalysts mentioned in the present invention are earlier described in patent applications number 932173 and 981126. Summary of the invention.
There is a need for methods of quicker obtaining Pt/Sn based dehydrogenation catalysts at the maximal catalytic activity than has been possible with the prior art technology that may require several hundred hours on stream before the approximate maximal activity is obtained. Such a method would improve the total yields of dehydrogenation products obtained during the lifetime of a dehydrogenation catalyst.
The disadvantages of the prior art technique are overcome by a process of a pretreatment activation of a Pt/Sn based dehydrogenation catalyst, wherein a Pt/Sn/Mg(AI)O catalyst is subjected to repeated cycles of 1.) reduction by H2 at elevated temperatures. 2.) alkane dehydrogenation at elevated temperatures; 3.) oxidation/regeneration by a O2 containing gas at elevated temperatures;
Preferably the alkane dehydrogenation is effected at temperatures in the range of 500 to 700 °C .
Also the oxidation/regeneration is preferable effected at temperatures in the range of 500 to 700 °C .
Equally the reduction by H2 is preferable effected in the range of 500 to 700 °C .
Particularly the chemical process is dehydrogenation performed on a lower alkane.
More preferably propane is dehydrogenated.
In a preferred process the oxidation is effected by a gaseous O2/N2 mixture gradually increasing the O2 content.
In a preferred process the final part of the oxidation is effected in air. With respect to the reduction step this is preferably effected in H2 in a temperature range of 500 to 700 °C .
With respect to the dehydrogenation time this is less than half of the dehydrogenation time during normal dehydrogenation process conditions. A typical dehydrogenation time is 2 hours.
Good results have been obtained when the first part of the oxidation is effected for about 3 hours, whereas the final part of the oxidation is effected for about 1 hour.
The reduction in H2 is particularly effected for about 2 hours.
The best results are achieved when the number of cycles are 6 to 12, but fewer cycles also have a significant effect.
It is expected that an optimum pretreatment activation procedure to a large extent will depend on the exact composition and preparation method of the catalyst. This means that there will be large variations in the preferred number of cycles, gas compositions and required times for each step.
A further object of the present invention is a catalyst activated by the pre-treatment set forth above.
Detailed description of invention
As already mentioned above, the objective of this invention is to define a pretreatment procedure which decreases the time required to reach an optimum conversion level in an alkane dehydrogenation unit, using a Pt/Sn/Mg(AI)O catalyst described in patent NO 179131. In this previous invention we describe a pre- treatment procedure which led to an optimum dehydrogenation activity of a Pt/Sn/Mg(AI)0 catalyst obtained by impregnating Pt and Sn on a pre-calcinated Mg(AI)O carrier material. The pre-treatment procedure used in the previous invention consisted of in situ reduction, followed by oxidation and a new reduction period (ROR). In the present invention, it was surprisingly observed that by using a slightly modified metal impregnation procedure, the ROR pre-treatment procedure did not lead to an optimum dehydrogenation activity. During testing of the dehydrogenation catalyst it was observed that the conversion level after the first regeneration was higher than the initial conversion level after the ROR. After the next test cycle the conversion level was even higher. A stable catalyst performance was not obtained before after 300h on stream, when the catalyst had been subjected to 9 cycles consisting of a dehydrogenation period followed by regeneration and reduction. A pre-treatment procedure for the catalyst that dramatically decreased the required time to obtain optimum conversion level in dehydrogenation of propane was developed.
The following examples will serve to illustrate the advantages of using the herein described pre-treatment procedure for the activation of the Pt/Sn-Mg(AI)O dehydrogenation catalyst. The examples should not, however, limit the scope of the present invention.
General
The catalyst was prepared according to a slightly modification of the procedure described in patent NO 179131 , using a water based acidic solution in the deposition of platinum and tin on hydrotalcite or precalcined hydrotalcite. The catalysts used in the examples have an Mg/AI-ratio of 4.8. The content of platinum and tin are ca. 0.25 and 0.5 wt% respectively. The catalyst was calcinated at 560°C after the impregnation. The catalyst was pressed to tablets, crushed and sieved to a pellet size of 0.64-1.0 mm prior to testing.
All pre-treatment procedures were performed in situ in a laboratory scale fixed bed titanium reactor with subsequent testing for propane dehydrogenation. The inner diameter of the reactor was 9 mm. A titanium tube with an outer diameter of 3 mm was located in the centre of the reactor. The reactor temperature was controlled by a thermocouple placed in the 3 mm tube inside the reactor. The catalyst pellets ( approximately 3 g) was placed on a titanium sinter in the reactor. The total pressure in the reactor was 1.1 bar, and the reactor temperature was 600°C. However, due to the endothermic nature of the reaction a temperature gradient was observed in the reactor. The reactor temperature was regulated to 600°C at a distance of 1/3 of the total catalyst bed-length from the top of the catalyst bed, while the temperature at the bottom of the catalyst bed, measured at a distance of approximately 1/3 of catalyst bed length from the bottom of the catalyst bed, was in the range of 590 to 615°C. The GHSV was 1000h"1 based on propane, and the reaction gas contained 4.5% hydrogen, 32% propane and rest steam on mole basis.
The dehydrogenation periods usually lasted approximately 20 hours and were followed by a regeneration of the catalyst. The conversion levels were calculated from on-line GC analysis. The analysis were taken with approximately 1 hours intervals. The conversion levels presented were obtained after 5h in the dehydrogenation period.
The regeneration of the catalyst was done by burning of the formed coke using air diluted with nitrogen. The content of oxygen was initially reduced to approximately 2% and was stepwise increased to a final level of 21 % where pure air was used. The regeneration period was followed by catalyst reduction using hydrogen. Both the regeneration and the reduction of the catalyst were done at 600°C.
Example 1 (ROR)
The catalyst was subjected to a pre-treatment procedure consisting of the following steps:
1. Heating from ambient temperature to 600°C in nitrogen, 100ml/min.
2. Reduction in H2. 20ml/min, 600°C, 2h.
3. Oxidation in a flow containing 40ml/min N2 and 10ml/min air. 600°C. 1 h. 4. Oxidation in air. 50 ml/min., 600°C, 1 h.
5. Reduced in H2. 600°C. 2h. 20ml/min.
The results from the subsequent propane dehydrogenation tests are shown in Figure 1 and Table 1.
Example 2: (ROR - (PDH(600°C)-OR)*X)
The catalyst was subjected to a pre-treatment procedure consisting of the following steps:
1. The catalyst is first pre-treated according to the ROR-procedure described in Example 1.
2. PDH ( Propane Dehydrogenation) at 600°C. in a stream consisting of C3H8 (70ml/min). H2 (10ml/min) and steam (140 ml/min) for 2h. 3. Oxidation/regeneration using an 02/N2-mixture with a gradually increasing O2 content. (1 , 5 and 10%). Each step lasted 1h. Different O2 content was obtained by diluting air with N2. Total flow:84ml/min., T=600°C.
4. Oxidation in air. 80ml/min., 600°C, 1 h.
5. Reduction in H2. 20ml/min., 600°C, 2h.
Step 2 to 5 was repeated 9 times, when no further increase in the conversion level of propane in the PDH period was observed. The results from the subsequent propane dehydrogenation test are shown in Figure 1 and Table 1.
Example 3 (R-OR*X)
The catalyst was subjected to a pre-treatment procedure consisting of the following steps::
1. Heating from ambient temperature to 600°C in nitrogen, 100ml/min. 2. Reduction in H2. 20ml/min., 600°C, 2h. 3. Oxidation/regeneration using an O2/N2 mixture with a gradually increasing O2 content (1. 5. and 10%). 1 h on each step. Different O2 content was obtained by diluting air with N2. Total flow: 84ml/min. T=600°C.
4. Oxidation in air. 80ml/min., 600°C, 1 h. ? 5. Reduction in H2. 20ml/min., 600°C, 2h.
Step 3 to 5 are repeated 12 times. The results from the following PDH conversion tests are shown in Figure 1 and Table 1.
Example 4: (ROR - (PDH-OR)*X)
The catalyst was subjected to a pre-treatment procedure consisting of the following steps:
1. The catalyst is first pre-treated according to the ROR-procedure described in Example 1.
2. PDH ( Propane Dehydrogenation) at 650°C. in a stream consisting of C3H8 (70ml/min). H2 (10ml/min) and steam (140 ml/min) for 2h.
3. Oxidation/regeneration in an 02/N2 mixture with a gradually increasing O2 content (1. 5. and 10%). 1h on each step. Different O2 content was obtained by diluting air with N2. Total flow:84ml/min., T=600°C.
4. Oxidation in air. 80ml/min., 600°C, 1h.
5. Reduction in H2. 20ml/min., 600°C, 2h.
Step 2 to 5 was repeated 6 times, when no further increase in the conversion level of propane in the PDH period was observed. The results from the subsequent propane dehydrogenation tests are shown in Figure 1 and Table 1. Example 5: R-(PDH-OR)*X
The catalyst was subjected to a pre-treatment procedure consisting of the following steps:
1. Heating from ambient temperature to 600°C in nitrogen, 100ml/min.
2. Reduction in H2. 20ml/min., 600°C, 2h.
3. PDH ( Propane Dehydrogenation) at 630°C. in a stream consisting of C3H8 (70ml/min). H2 (10ml/min) and steam (140 ml/min) for 2h. 4. Oxidation/regeneration using an O2/N2-mixture with a gradually increasing O2 content. (1. 5. and 10%) 1h on each step. Different 02 content was obtained by diluting air with N2. Total flow:84ml/min. T=600°C.
5. Oxidation in air. 80ml/min., 600°C, 1h.
6. Reduction in H2. 20ml/min, 600°C, 0.5h.
Step 3 to 6 were repeated 5 times, when it was found no further increase in conversion level in the PDH period (Step 3) are observed. The results from the subsequent propane dehydrogenation test are shown in Figure 1 and Table 1.
Example 6: R-(PDH-OR)*X
The catalyst was subjected to a pre-treatment procedure consisting of the following steps:
1. Heating from ambient temperature to 600°C in nitrogen, 100ml/min.
2. Reduction in H2. 20ml/min., 600°C, 2h.
3. PDH ( Propane Dehydrogenation) at 630°C. in a stream consisting of C3H8 (70ml/min). H2 (10ml/min) and steam (140 ml/min) for 2h.
4. Oxidation/regeneration using an O2/N2-mixture with a gradually increasing 02 content. (1. 5. and 10%) 1 h on each step. Different O2 content was obtained by diluting air with N2. Total flow:84ml/min. T=600°C. 5. Oxidation in air. 80ml/min., 600°C, 1h.
6. Reduction in H2. 20ml/min, 600°C, 2h.
Step 3 to 6 are repeated 6 times, when it was observed no further increase in conversion level in the PDH period (Step 3). The results from the subsequent propane dehydrogenation test are shown in Figure 1 and Table 1.
Table 1 Normalised conversion of propane with time on stream. The conversion level are obtained 5 hours after finishing the regeneration/reduction period. The results are also shown in Figure 1.
Normalised conversion data from Ex 1 to Ex 6 are shown in Figure 1.
The conversion level data for Example 1 to Example 6 are all given as normalised values, where the stabilised conversion level which are obtained on the completely pre-treated catalyst is given the value 100%. A typical example of the obtained conversion level of propane to propene is given in Table 2. Similar conversion levels are also obtained in the remaining examples. However, the conversion level shows small variation due to minor changes in the reaction conditions as for instance the temperature profile in the reactor and different partial pressure in the gases entering the reactor.
Table 2 Conversion data from Example 5
Time on 40,3 65,2 90,2 115,1 140 164,9 stream conversion 53,4 56,6 58,5 58,8 59,1 59,4 level [%]
The results show that by using the ROR pre-treatment procedure described in patent NO 179131 on the present catalyst the activity of the catalyst increases after each conversion cycle, consisting of a dehydrogenation period followed by regeneration/oxidation and reduction. The catalyst does not operate at an optimum performance until after 300h on stream. Using a pre-treatment procedure consisting of repeated cycles of reduction and oxidations and a final reduction (Example 3), the time to reach the optimum performance is reduced to approximately 50-150h. However, several dehydrogenation-regeneration cycles have to be conducted after the pre-treatment procedure in order to give a high and stable conversion level.
A pre-treatment procedure which included the aforementioned ROR procedure followed by several cycles consisting of a short dehydrogenation period (2h, at 600°) followed by regeneration (oxidation) and reduction in hydrogen (Example 2) reduced the pre-treatment time to approximately 80h. When the short dehydrogenation period during the pre-treatment was conducted at higher temperature, i.e. 630- 650°C even shorter pre-treatment time was obtained (Example 4). The initial ROR pre-treatment could also be excluded using this kind of catalyst pre-treatment. (Example 5 and 6). A pre-treatment time of 40h was obtained using a pre-treatment consisting of an initial reduction followed by 5 cycles consisting of dehydrogenation, regeneration and reduction. A detailed description of this procedure is given in example 5. After this pre-treatment the catalyst operate at a conversion level of 90% of the optimum conversion level. Within two conventional 20 hours dehydrogenation periods at 600°C, the catalyst performance was at an optimum level.
Unsuccessful pretreatment
Example 7: OR
The catalyst was subjected to a pre-treatment procedure consisting of the following steps:
1. Heating from ambient temperature to 600°C in nitrogen, 100ml/min.
2. Oxidation in air. 50ml/min., 600°C, 10h.
3. Reduction in H2. 20ml/min, 600°C, 2h.
The conversion after 5 hours propane dehydrogenation (same test conditions as described in example 1 to 6, 600°C) was 11%, and the selectivity was 94%.
Example 8: O-Steam-R
The catalyst was subjected to a pre-treatment procedure consisting of the following steps:
4. Oxidation/regeneration of the catalyst from example 7 using an O2/N2-mixture with a gradually increasing 02 content. (1. 5. and 10%) 1h on each step. Different 02 content was obtained by diluting air with N2. Total flow: 84ml/min.
T=600°C.
5. Steaming. 140ml/min., 600°C, 10h.
6. Reduction in H2. 20ml/min, 600°C, 2h.
The conversion after 5 hours propane dehydrogenation (same test conditions as described in example 1 to 6, 600°C) was 26%, and the selectivity was 95%. Example 9: O-Steam-R
The catalyst was subjected to a pre-treatment procedure consisting of the following steps: 5 7. Oxidation/regeneration of the catalyst from example 8 using an 02/N2-mixture with a gradually increasing 02 content. (1. 5. and 10%) 1h on each step.
Different 02 content was obtained by diluting air with N2. Total flow: 84ml/min.
T=600°C.
8. Steaming. 140ml/min., 700°C, 10h. ιo 9. Reduction in H2. 20ml/min, 600°C, 2h.
The conversion after 5 hours propane dehydrogenation (same test conditions as described in example 1 to 6, 600°C) was 7.5%, and the selectivity was 93.5%.
i5 Conclusion
The activation period for the Pt/Sn/Mg(AI)O dehydrogenation catalyst is reduced from 300h to approximately 50 h by using the pre-treatment procedure developed in the present invention. The pre-treatment procedure consists of an initial reduction of the catalyst using hydrogen, followed by several cycles which includes a short
20 dehydrogenation period.
Literature cited
Catalytica Oxidative Dehydrogenation and Alternative Dehydrogenation Processes Study No.4192 OD; Catalytica Studies Division: Mountain View, CA, 1993
25
Akporiaye, D., Rønnekleiv, M., Hasselgard, P., NO 179131 , 1996, assigned to Statoil.

Claims

Patent Claims
1. A process of a pre-treatment activation of a Pt/Sn based catalyst, wherein a Pt/Sn/Mg(AI)0 catalyst is subjected to one or more cycles of 1.) reduction by H2 at elevated temperatures.
2.) alkane dehydrogenation at elevated temperatures;
3.) oxidation/regeneration by a 02 containing gas at elevated temperatures;
2. The process of the claim 1 , wherein the alkane dehydrogenation is effected at temperatures in the range of 500 to 700 °C .
3. The process of the claim 1 , wherein the oxidation/regeneration is effected at temperatures in the range of 500 to 700 °C .
4. The process of the claim 1 , wherein the reduction by H2 is effected in the range of 500 to 700 °C .
5. The process of the claims 1 and 2, wherein a lower alkane is dehydrogenated.
6. The process of the claims 1 , 3, and 5, wherein propane is dehydrogenated.
7. The process of the claims 1 and 3, wherein the oxidation is effected by a gaseous mixture gradually increasing the O2 content.
8. The process of the claims 1 and 7, wherein the final part of the oxidation is effected in air.
9. The process of the claim 1 , wherein the reduction in H2 is effected in a temperature range of 500 to 700 °C .
10. The process of the claims 1 , 2, 5, and 6, wherein the dehydrogenation is effected for about 2 hours.
11. The process of the claimsl , 3, 7, and 8, wherein the first part of the oxidation is effected for about 3 hours, whereas the final part of the oxidation is effected for about 1 hour.
12. The process of the claim 1 , wherein the reduction in H2 is effected for about 2 hours.
13. The process of the claims 1 to 12, wherein the number of cycles are more than one.
14. The process of the claims 1 to 12, wherein the number of cycles are 6 to 12.
15. A catalyst activated by the pre-treatment of the claims 1 to 13.
EP00931745A 1999-05-28 2000-05-26 PRETREATMENT OF A Pt/Sn-BASED CATALYST Withdrawn EP1206319A1 (en)

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DE10060099A1 (en) * 2000-12-04 2002-06-06 Basf Ag Regeneration of a dehydrogenation catalyst
CN104248968B (en) * 2013-06-28 2017-05-31 中国石油化工股份有限公司 A kind of catalyst of propane direct dehydrogenation propylene and preparation method thereof
CN111686709B (en) * 2020-01-23 2021-06-01 中国科学院大连化学物理研究所 A kind of propane dehydrogenation to propylene supported catalyst with specific pore structure and preparation method thereof
EP4384489A1 (en) * 2021-08-13 2024-06-19 ExxonMobil Chemical Patents Inc. Processes for dehydrogenating alkanes and alkyl aromatic hydrocarbons
CN114570364A (en) * 2022-03-28 2022-06-03 福州大学 Pretreatment method of Pt-based catalyst for preparing propylene by propane dehydrogenation

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US3842139A (en) * 1973-03-12 1974-10-15 Gulf Research Development Co Dehydrogenation of paraffins over a platinum magnesium aluminate spinel
FR2603044B1 (en) * 1986-08-25 1988-11-04 Inst Francais Du Petrole PROCESS FOR REGENERATING A HYDROCONVERSION HYDROCONVERSION CATALYST
US5220091A (en) * 1992-02-26 1993-06-15 Phillips Petroleum Company Alkane dehydrogenation
NO179131C (en) * 1993-06-14 1996-08-14 Statoil As Catalyst, process for its preparation and process for dehydrogenation of light paraffins
NO300117B1 (en) * 1994-12-22 1997-04-14 Norske Stats Oljeselskap Reactor for dehydrogenation of hydrocarbons with selective oxidation of hydrogen

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