CN114011425A - Bifunctional catalyst, preparation method, application and application method thereof - Google Patents

Bifunctional catalyst, preparation method, application and application method thereof Download PDF

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CN114011425A
CN114011425A CN202111493033.0A CN202111493033A CN114011425A CN 114011425 A CN114011425 A CN 114011425A CN 202111493033 A CN202111493033 A CN 202111493033A CN 114011425 A CN114011425 A CN 114011425A
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roasting
temperature
nitrate
oxidative dehydrogenation
stirring
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CN114011425B (en
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郝芳
池金善
刘平乐
熊伟
吕扬
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Xiangtan University
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    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/002Mixed oxides other than spinels, e.g. perovskite
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J23/00Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
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    • B01J23/76Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/83Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with rare earths or actinides
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    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
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    • B01J23/76Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
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    • B01J23/8472Vanadium
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    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J23/00Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/76Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/84Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/85Chromium, molybdenum or tungsten
    • B01J23/88Molybdenum
    • B01J23/887Molybdenum containing in addition other metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/8871Rare earth metals or actinides
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J27/00Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
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    • CCHEMISTRY; METALLURGY
    • C07ORGANIC CHEMISTRY
    • C07CACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C5/00Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms
    • C07C5/42Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by dehydrogenation with a hydrogen acceptor
    • C07C5/48Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by dehydrogenation with a hydrogen acceptor with oxygen as an acceptor
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    • B01J2523/00Constitutive chemical elements of heterogeneous catalysts
    • CCHEMISTRY; METALLURGY
    • C07ORGANIC CHEMISTRY
    • C07CACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2601/00Systems containing only non-condensed rings
    • C07C2601/12Systems containing only non-condensed rings with a six-membered ring
    • C07C2601/16Systems containing only non-condensed rings with a six-membered ring the ring being unsaturated
    • YGENERAL 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
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Abstract

The invention belongs to the technical field of catalysts. The invention provides a bifunctional catalyst, which is prepared by modulating the feeding molar ratio of various metal salts to obtain a series of perovskite type composite materials LaxA1‑ xFeyM1‑yO3And then the bifunctional catalyst is prepared by modifying an alkali metal compound. The invention also provides a method for preparing cyclohexene by cyclohexane chemical chain circulation oxidative dehydrogenation, which is obtained by preparationThe bifunctional catalyst is placed in a fixed bed reactor, and is activated after air is introduced at a set temperature; introducing nitrogen to purge the reaction tube; mixing cyclohexane and nitrogen, introducing the mixture into a reactor to contact with a catalyst to perform oxidative dehydrogenation; and after the reaction is finished, introducing air to complete the regeneration of the bifunctional catalyst. The development and application of the new technology for efficiently preparing cyclohexene by the chemical chain oxidative dehydrogenation of cyclohexane can effectively solve the bottleneck of cyclohexene capacity which hinders the popularization of green processes for producing caprolactam and adipic acid by a cyclohexene route.

Description

Bifunctional catalyst, preparation method, application and application method thereof
Technical Field
The invention relates to the technical field of catalysts, in particular to a bifunctional catalyst, and a preparation method, application and an application method thereof.
Background
Cyclohexene is an important organic intermediate and is widely applied to the industries of textile, pharmacy, automobiles, pesticides, food and the like. Can be used as raw materials for preparing adipic acid, cyclohexyl formic acid, cyclohexene oxide and the like; are commonly used as extractants, stabilizers for high octane gasoline, etc. in the petroleum industry.
At present, more technical methods for industrially producing cyclohexene exist. Conventionally, cyclohexanol dehydration, halogenated cyclohexane dehydrohalogenation and the like have been carried out. Because cyclohexanol, halogenated cyclohexane and alkali metal or alkaline earth metal with higher cost are used as raw materials, the production process is complex and the cost is higher. The benzene liquid phase partial hydrogenation method is a preferred method for producing cyclohexene recently, and has the advantages of short flow, few steps and the like compared with the traditional processes such as cyclohexane dehydrogenation, cyclohexanol dehydration and the like. But benzene hydrogenation reaction is extremely unfavorable to cyclohexene production in thermodynamics, and complete hydrogenation is extremely easy to produce cyclohexane. The current industrialization technical index is only set to S40 > 80%. The method has low production efficiency and high separation energy consumption, and adopts a noble metal ruthenium black catalyst and a Zn salt auxiliary agent as a catalytic system. Meanwhile, in order to prevent the deactivation of the noble metal Ru catalyst, the method requires strict calibration on the purity of the raw material benzene and has high production cost. Although researchers at home and abroad are continuously researching more efficient benzene partial hydrogenation catalytic systems, the contradiction between the reaction conversion rate and the cyclohexene selectivity is difficult to solve.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a bifunctional catalyst, and a preparation method, application and an application method thereof.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a bifunctional catalyst which is prepared from the following raw materials in parts by mass: 7-8 parts of lanthanum nitrate, 0.8-1.2 parts of alkaline earth metal precursor, 7.5-8.5 parts of ferric nitrate, 0.2-0.9 part of transition metal precursor and 0.4-0.6 part of alkali metal compound.
Preferably, the lanthanum nitrate is lanthanum nitrate hexahydrate; the ferric nitrate is ferric nitrate nonahydrate;
the alkaline earth metal precursor comprises strontium nitrate, magnesium nitrate hexahydrate or calcium nitrate tetrahydrate;
the transition metal precursor comprises ammonium metavanadate, cobalt nitrate hexahydrate or molybdenum nitrate pentahydrate;
the alkali metal compound comprises lithium carbonate or potassium carbonate.
The invention also provides a preparation method of the catalyst, which comprises the following steps:
(1) mixing lanthanum nitrate, an alkaline earth metal precursor, ferric nitrate, a transition metal precursor, a complexing agent, water and dihydric alcohol to obtain sol;
(2) drying and roasting the sol in sequence to obtain a composite material;
(3) and mixing the composite material, the alkali metal compound and water, and then drying and roasting in sequence to obtain the bifunctional catalyst.
Preferably, in the step (1), the complexing agent is citric acid, and the dihydric alcohol is ethylene glycol;
the mass ratio of the lanthanum nitrate to the complexing agent is 7-8: 20-24;
the dosage ratio of the lanthanum nitrate to the water is 7-8 g: 180-220 mL;
the mass ratio of the lanthanum nitrate to the dihydric alcohol is 7-8: 9.5-10.5;
the mixing mode is heating stirring, the heating rate of the heating stirring is 4-6 ℃/min, the target temperature of the heating stirring is 75-85 ℃, the rotating speed of the heating stirring is 1400-1600 rpm, and the stirring time after the heating stirring reaches the target temperature is 7-9 h.
Preferably, the drying in the step (2) is vacuum drying, the temperature of the vacuum drying is 70-90 ℃, the vacuum degree of the vacuum drying is-0.12-0.08 MPa, and the time of the vacuum drying is 10-12 h;
the roasting is to carry out first roasting and second roasting in sequence;
the temperature rise rate of the first roasting is 8-12 ℃/min, the target temperature of the first roasting is 440-460 ℃, and the roasting time after the first roasting reaches the target temperature is 1-1.2 h;
the target temperature of the second roasting is 940-960 ℃, the heating rate of the temperature from the first roasting target temperature to the second roasting target temperature is 8-12 ℃/min, and the roasting time after the second roasting reaches the target temperature is 7.8-8.2 h.
Preferably, the using amount ratio of the lanthanum nitrate to the water in the step (3) is 7-8 g: 180-220 mL;
the mixing mode is stirring, the rotating speed of the stirring is 450-550 rpm, and the stirring time is 2.8-3.2 hours;
the drying temperature is 75-85 ℃, the vacuum degree of drying is-0.12 to-0.08 MPa, and the drying time is 10-12 h;
the temperature rise rate of the roasting is 8-12 ℃/min, the target temperature of the roasting is 880-920 ℃, and the roasting time after the roasting reaches the target temperature is 7.5-8.5 h.
The invention also provides the application of the bifunctional catalyst in preparation of cyclohexene by cyclohexane chemical chain circulation oxidative dehydrogenation.
A method for preparing cyclohexene by cyclohexane chemical chain circulation oxidative dehydrogenation comprises the following steps:
putting the bifunctional catalyst in a fixed bed reactor, setting the temperature, and introducing air to activate the catalyst; introducing nitrogen to purge the reactor;
introducing nitrogen carrying cyclohexane into a reactor to start oxidative dehydrogenation reaction; and after the reaction is finished, introducing nitrogen to purge the reactor again, and introducing air to complete the regeneration of the bifunctional catalyst.
Preferably, the set temperature is 740-760 ℃, the time for introducing air is 2-4 min, and the time for activating is 50-70 min;
the flow rate of purging is 20-40 mL/min, the purging time is 2-4 min, and the purging temperature is 740-760 ℃.
Preferably, the volume ratio of the cyclohexane to the nitrogen is 6.5-7.5: 1;
the temperature of the oxidative dehydrogenation reaction is 500-650 ℃, the gas flow rate of the oxidative dehydrogenation reaction is 20-40 mL/min, and the reaction volume space velocity of the oxidative dehydrogenation reaction is 1200-2400 h-1
The invention provides a bifunctional catalyst, which is prepared by modulating the feeding molar ratio of various metal salts to obtain a series of perovskite type composite materials LaxA1-xFeyM1-yO3And then the bifunctional catalyst is prepared by modifying an alkali metal compound. The alkaline earth metal precursor (A) is strontium nitrate, magnesium nitrate hexahydrate or calcium nitrate tetrahydrate, the transition metal precursor (M) is ammonium metavanadate, cobalt nitrate hexahydrate or molybdenum nitrate pentahydrate, and the alkali metal compound is lithium carbonate or potassium carbonate; the perovskite oxide modified by alkali metal salt is used as a catalyst for cyclohexane chemical chain oxidative dehydrogenation (CL-ODH), so that the use of noble metal is avoided, and the catalyst cost is reduced; according to the invention, perovskite oxides with different lattice oxygen contents and activities can be obtained by changing the type of metal elements at the A, B position, and lattice defects can be generated and the lattice oxygen content can be regulated by partially replacing A or B position atoms in a lattice with other metal atoms; the perovskite structure can enable some elements to exist in abnormal valence states or enable active metals to exist in mixed valence states, thereby showing more excellent catalytic activity. The invention also provides a method for preparing cyclohexene by cyclohexane chemical chain circulation, oxidation and dehydrogenation, the prepared bifunctional catalyst is placed in a fixed bed reactor, and the catalyst is activated after air is introduced at a set temperature; introducing nitrogen to purge the reaction tube; mixing cyclohexane and nitrogen, introducing the mixture into a reactor to contact with a catalyst to perform oxidative dehydrogenation; after the reaction is finished, nitrogen is sequentially introduced to purge the reactor again, and air is introduced to complete the regeneration of the bifunctional catalyst. The invention provides a new method for efficiently preparing cyclohexene by cyclohexane chemical chain oxidative dehydrogenationThe development and application of the technology can effectively solve the bottleneck of cyclohexene capacity which hinders the popularization of green processes for producing caprolactam and adipic acid by a cyclohexene route, and the alkane chemical chain oxidative dehydrogenation is used as a new clean and efficient process for preparing olefin, so that the technology has extremely high research value and application prospect.
Detailed Description
The invention provides a bifunctional catalyst which is prepared from the following raw materials in parts by mass: 7-8 parts of lanthanum nitrate, 0.8-1.2 parts of alkaline earth metal precursor, 7.5-8.5 parts of ferric nitrate, 0.2-0.9 part of transition metal precursor and 0.4-0.6 part of alkali metal compound
In the invention, the lanthanum nitrate is 7-8 parts, preferably 7.2-7.8 parts, and more preferably 7.4-7.6 parts.
In the present invention, the alkaline earth metal precursor is 0.8 to 1.2 parts, preferably 0.9 to 1.1 parts, and more preferably 0.95 to 1.05 parts.
In the present invention, the amount of the iron nitrate is 7.5 to 8.5 parts, preferably 7.6 to 8.4 parts, and more preferably 7.8 to 8.2 parts.
In the present invention, the transition metal precursor is 0.2 to 0.9 part, preferably 0.3 to 0.8 part, and more preferably 0.5 to 0.6 part.
In the present invention, the alkali metal compound is 0.4 to 0.6 part, preferably 0.44 to 0.56 part, and more preferably 0.48 to 0.52 part.
In the present invention, the lanthanum nitrate is preferably lanthanum nitrate hexahydrate; the ferric nitrate is preferably ferric nitrate nonahydrate.
In the present invention, the alkaline earth metal precursor preferably comprises strontium nitrate, magnesium nitrate hexahydrate, or calcium nitrate tetrahydrate.
In the present invention, the transition metal precursor preferably contains ammonium metavanadate, cobalt nitrate hexahydrate, or molybdenum nitrate pentahydrate.
In the present invention, the alkali metal compound preferably comprises lithium carbonate or potassium carbonate.
The invention also provides a preparation method of the catalyst, which comprises the following steps:
(1) mixing lanthanum nitrate, an alkaline earth metal precursor, ferric nitrate, a transition metal precursor, a complexing agent, water and dihydric alcohol to obtain sol;
(2) drying and roasting the sol in sequence to obtain a composite material;
(3) and mixing the composite material, the alkali metal compound and water, and then drying and roasting in sequence to obtain the bifunctional catalyst.
In the present invention, the complexing agent in the step (1) is preferably citric acid, and the diol is preferably ethylene glycol.
In the invention, the mass ratio of the lanthanum nitrate to the complexing agent is preferably 7-8: 20 to 24, and more preferably 7.2 to 7.8: 21 to 23, more preferably 7.4 to 7.6: 21.5 to 22.5.
In the invention, the dosage ratio of lanthanum nitrate to water is preferably 7-8 g: 180 to 220mL, more preferably 7.2 to 7.8 g: 190-210 mL, more preferably 7.4-7.6 g: 195-205 mL.
In the invention, the mass ratio of lanthanum nitrate to dihydric alcohol is preferably 7-8: 9 to 11, and more preferably 7.2 to 7.8: 9.6 to 10.4, more preferably 7.4 to 7.6: 9.8 to 10.2.
In the invention, lanthanum nitrate, alkaline earth metal precursor, ferric nitrate, transition metal precursor and water are mixed and stirred; the stirring time is preferably 50-70 min, more preferably 55-65 min, and even more preferably 58-62 min; the stirring speed is preferably 400-600 rpm, more preferably 450-550 rpm, and even more preferably 480-520 rpm; and obtaining a metal nitrate mixed solution after stirring.
In the invention, the metal nitrate mixed solution and the complexing agent are mixed and stirred; the stirring time is preferably 30-40 min, more preferably 32-38 min, and even more preferably 34-36 min; the stirring speed is preferably 800-1200 rpm, more preferably 900-1100 rpm, and even more preferably 950-1050 rpm; after the stirring, the diol was added to the mixture to conduct the next stirring.
In the invention, the mixing mode is preferably heating stirring, and the heating rate of the heating stirring is preferably 4-6 ℃/min, more preferably 4.4-5.6 ℃/min, and even more preferably 4.8-5.2 ℃/min; the target temperature of the temperature raising and stirring is preferably 75-85 ℃, more preferably 76-84 ℃, and even more preferably 78-82 ℃; the rotation speed of the temperature-rising stirring is preferably 1400-1600 rpm, more preferably 1440-1560 rpm, and even more preferably 1480-1520 rpm; the stirring time after the temperature rise stirring is carried out to reach the target temperature is preferably 7-9 h, more preferably 7.5-8.5 h, and even more preferably 7.8-8.2 h.
In the invention, the drying in the step (2) is preferably vacuum drying, and the temperature of the vacuum drying is preferably 70-90 ℃, more preferably 74-86 ℃, and more preferably 78-82 ℃; the vacuum degree of the vacuum drying is preferably-0.12 to-0.08 MPa, more preferably-0.11 to-0.09 MPa, and more preferably-0.105 to-0.095 MPa; the vacuum drying time is preferably 10-12 h, more preferably 10.5-11.5 h, and even more preferably 10.8-11.2 h.
In the present invention, the firing is preferably performed by sequentially performing the first firing and the second firing;
in the invention, the temperature rise rate of the first roasting is preferably 8-12 ℃/min, more preferably 9-11 ℃/min, and even more preferably 9.5-10.5 ℃/min; the target temperature of the first roasting is preferably 440-460 ℃, further preferably 445-455 ℃, and more preferably 448-452 ℃; the roasting time after the first roasting reaches the target temperature is preferably 1 to 1.2 hours, more preferably 1.04 to 1.16 hours, and even more preferably 1.08 to 1.12 hours.
In the invention, the target temperature of the second roasting is preferably 940-960 ℃, more preferably 945-955 ℃, and more preferably 948-952 ℃; the heating rate of heating from the first roasting target temperature to the second roasting target temperature is preferably 8-12 ℃/min, more preferably 9-11 ℃/min, and even more preferably 9.5-10.5 ℃/min; the roasting time after the second roasting reaches the target temperature is preferably 7.8-8.2 hours, more preferably 7.9-8.1 hours, and even more preferably 7.95-8.05 hours.
In the invention, the dosage ratio of the lanthanum nitrate to the water in the step (3) is preferably 7-8 g: 180 to 220mL, more preferably 7.2 to 7.8 g: 190-210 mL, more preferably 7.4-7.6 g: 195-205 mL.
In the invention, the composite material and water are mixed firstly, the mixing mode is preferably stirring, and the stirring rotating speed is preferably 400-600 rpm, more preferably 450-550 rpm, and more preferably 480-520 rpm; the stirring time is preferably 20-40 min, more preferably 24-36 min, and even more preferably 28-32 min. And obtaining a mixed system after the stirring is finished.
In the invention, a mixing system and an alkali metal compound are mixed, the mixing mode is preferably stirring, and the stirring speed is preferably 450-550 rpm, more preferably 460-540 rpm, and more preferably 480-520 rpm; the stirring time is preferably 2.8-3.2 h, more preferably 2.9-3.1 h, and even more preferably 2.95-3.05 h; standing after the stirring is finished, wherein the standing time is preferably 1.8-2.2 h, more preferably 1.9-2.1 h, and even more preferably 1.95-2.05 h; after the completion of the standing, the mixture was obtained and subjected to the next drying.
In the invention, the drying temperature is preferably 75-85 ℃, more preferably 76-84 ℃, and more preferably 78-82 ℃; the degree of vacuum of the drying is preferably-0.12 to-0.08 MPa, more preferably-0.11 to-0.09 MPa, and even more preferably-0.105 to-0.095 MPa; the drying time is preferably 10-12 h, more preferably 10.5-11.5 h, and even more preferably 10.8-11.2 h.
In the invention, the heating rate of the roasting is preferably 8-12 ℃/min, more preferably 9-11 ℃/min, and even more preferably 9.5-10.5 ℃/min; the target temperature of roasting is preferably 880-920 ℃, more preferably 890-910 ℃, and even more preferably 895-905 ℃; the roasting time after the roasting reaches the target temperature is preferably 7.5-8.5 hours, more preferably 7.6-8.4 hours, and even more preferably 7.8-8.2 hours.
In the invention, the roasting is preferably refined after the roasting is finished, the refining mode is preferably ball milling, and the speed of the ball milling is preferably 400-600 rpm, more preferably 450-550 rpm, and more preferably 480-520 rpm; the ball milling time is preferably 1.8-2.2 h, more preferably 1.9-2.1 h, and even more preferably 1.95-2.05 h. And after the ball milling is finished, obtaining the bifunctional catalyst.
The invention also provides the application of the bifunctional catalyst in preparation of cyclohexene by cyclohexane chemical chain circulation oxidative dehydrogenation.
A method for preparing cyclohexene by cyclohexane chemical chain circulation oxidative dehydrogenation comprises the following steps:
putting the bifunctional catalyst in a fixed bed reactor, setting the temperature, and introducing air to activate the catalyst; introducing nitrogen to purge the reactor;
introducing nitrogen carrying cyclohexane into a reactor to start oxidative dehydrogenation reaction; and after the reaction is finished, introducing nitrogen to purge the reactor again, and introducing air to complete the regeneration of the bifunctional catalyst.
In the invention, the set temperature is preferably 740-760 ℃, more preferably 745-755 ℃, and more preferably 748-752 ℃; the time for introducing the air is preferably 2-4 min, more preferably 2.5-3.5 min, and even more preferably 2.8-3.2 min; the flow rate of the air is preferably 20-40 mL/min, more preferably 25-35 mL/min, and even more preferably 28-32 mL/min; and activating after the air introduction is finished, wherein the activation time is preferably 50-70 min, more preferably 55-65 min, and more preferably 58-62 min.
In the invention, the flow rate of the purging is preferably 20-40 mL/min, more preferably 25-35 mL/min, and even more preferably 28-32 mL/min; the purging time is preferably 2-4 min, more preferably 2.5-3.5 min, and even more preferably 2.8-3.2 min; the temperature of the purging is preferably 740 to 760 ℃, more preferably 745 to 755 ℃, and even more preferably 748 to 752 ℃.
In the invention, the volume ratio of the cyclohexane to the nitrogen is preferably 6.5-7.5: 1, more preferably 6.6 to 7.4: 1, more preferably 6.8 to 7.2: 1.
in the invention, nitrogen carrying cyclohexane is introduced into a reactor and then contacts with a catalyst, wherein the contact temperature is preferably 500-650 ℃, more preferably 550-600 ℃, and more preferably 560-590 ℃; the flow rate of the gas for contact is preferably 20-40 mL/min, and more preferably 25-35 mL/minMore preferably 28-32 mL/min; the reaction volume space velocity of the contact is preferably 1200-2400 h-1More preferably 1400 to 2200 hours-1More preferably 1600 to 2000h-1The contact time is preferably 4 to 6min, more preferably 4.4 to 5.6min, and even more preferably 4.8 to 5.2 min.
In the invention, after the contact is finished, nitrogen is adopted for secondary purging, and the flow rate of the secondary purging is preferably 20-40 mL/min, more preferably 25-35 mL/min, and more preferably 28-32 mL/min; the time for the secondary purging is preferably 2-4 min, more preferably 2.5-3.5 min, and even more preferably 2.8-3.2 min; the temperature of the secondary purging is preferably 500-650 ℃, further preferably 550-600 ℃, further preferably 560-590 ℃, and the time of the secondary purging is preferably 2-4 min, further preferably 2.4-3.6 min, further preferably 2.8-3.2 min.
In the invention, the contact and the secondary purge are a cycle, and the repetition frequency of the cycle is preferably 3-4 times.
In the invention, after the contact and the secondary purging are finished, an oxidative dehydrogenation reaction is started, wherein the temperature of the oxidative dehydrogenation reaction is preferably 500-650 ℃, more preferably 550-600 ℃, and more preferably 560-590 ℃; the flow rate of the gas for the oxidative dehydrogenation reaction is preferably 20-40 mL/min, more preferably 25-35 mL/min, and even more preferably 28-32 mL/min; the reaction volume airspeed of the oxidative dehydrogenation reaction is 1200-2400 h-1More preferably 1400 to 2200 hours-1More preferably 1600 to 2000h-1The time for oxidative dehydrogenation is preferably 4-6 min, more preferably 4.4-5.6 min, and even more preferably 4.8-5.2 min.
In the invention, nitrogen is introduced for purging again after the oxidative dehydrogenation reaction is finished, wherein the flow rate of purging again is preferably 20-40 mL/min, more preferably 25-35 mL/min, and more preferably 28-32 mL/min; the time for purging again is preferably 5-6 min, more preferably 5.2-5.8 min, and even more preferably 5.4-5.6 min; the temperature of the secondary blowing is preferably 500-650 ℃, more preferably 550-600 ℃, and more preferably 560-590 ℃; after purging is finished, introducing air, and regenerating the catalyst at the same flow rate and temperature; the regeneration time is preferably 2.5-3.5 min, more preferably 2.6-3.4 min, and even more preferably 2.8-3.2 min.
In the invention, the oxygen carrier in the perovskite oxide modified by the alkali metal salt can be oxidized and regenerated in the air, so that the carbon deposition of the catalyst is removed while the lattice oxygen is supplemented; and a large amount of heat carried after regeneration can be directly supplied to dehydrogenation reaction, so that the process energy consumption is reduced.
The technical solutions provided by the present invention are described in detail below with reference to examples, but they should not be construed as limiting the scope of the present invention.
Example 1
Dissolving 7.32g of lanthanum nitrate hexahydrate, 0.89g of strontium nitrate, 7.69g of ferric nitrate nonahydrate and 0.79g of molybdenum nitrate pentahydrate in 200mL of water, and stirring at the rotating speed of 500rpm for 60min to obtain a metal nitrate mixed solution; mixing the metal nitrate mixed solution with 22.21g of citric acid, and stirring at the rotating speed of 1000rpm for 35 min; after stirring, mixing with 9.84g of glycol, heating to 80 ℃ at the heating rate of 5 ℃/min, stirring while heating, wherein the stirring speed is 1500rpm, and continuously stirring for 8h after the temperature reaches 80 ℃ to obtain the sol.
Drying the sol at 80 ℃ and-0.1 MPa for 11h, heating the dried solid matter to 450 ℃ at the heating rate of 10 ℃/min, and roasting for 1h after the temperature reaches 450 ℃ to complete first roasting; after the first roasting and sintering, continuously heating to 950 ℃ at the heating rate of 10 ℃/min, roasting for 8h after reaching 950 ℃, and finishing the second roasting to obtain the perovskite type composite La0.8Sr0.2Fe0.9Mo0.1O3
Dissolving the obtained composite material in 200mL of water, and stirring for 30min at the rotating speed of 500rpm to obtain a mixed system; stirring the mixed system and 0.5g of lithium carbonate at the rotating speed of 500rpm for 3 hours, and standing for 2 hours after stirring to obtain a mixture; drying the mixture at 80 ℃ and-0.1 MPa for 11h to obtain a solid substance; heating the solid matter to 900 ℃ at the heating rate of 10 ℃/min, and roasting for 8h after the temperature reaches 900 ℃; ball milling is carried out for 2 hours at the rotating speed of 500rpm after the baking and sintering are finished, and the alkali gold is obtainedPerovskite type composite material Li modified by metal compound2CO3/La0.8Sr0.2Fe0.9Mo0.1O3A bifunctional catalyst.
Performing cyclohexane chemical chain circulation oxidative dehydrogenation on the bifunctional catalyst prepared in the embodiment to prepare cyclohexene, placing 5g of the catalyst prepared in the embodiment in a fixed bed reactor, introducing air at a set temperature of 750 ℃ for 3min, wherein the flow rate of the air is the same as that of the air during catalysis, and activating the catalyst at 750 ℃ for 60min after the air introduction is finished; then introducing nitrogen to purge for 3min, wherein the flow rate of purging is the same as that of catalyzing; taking nitrogen as a carrier gas, wherein the volume ratio of cyclohexane to nitrogen is 7: 1, the contact time is 5min, and the contact temperature, the gas flow rate, the reaction volume space velocity and the parameters during oxidative dehydrogenation are the same; after the contact is finished, introducing nitrogen for secondary purging for 3min, wherein the flow rate, the temperature, the reaction volume airspeed and the parameters during catalysis of the secondary purging are the same; the contacting and the secondary purging were repeated 3 times, and the oxidative dehydrogenation reaction was started after completion.
Taking nitrogen as a carrier gas, wherein the volume ratio of cyclohexane to nitrogen is 7: 1, controlling the temperature of oxidative dehydrogenation to be 500 ℃, 550 ℃, 600 ℃ and 650 ℃, respectively, controlling the gas flow rate of the oxidative dehydrogenation to be 30mL/min, and controlling the reaction volume space velocity of the oxidative dehydrogenation to be 1200h respectively-1、1500h-1、1800h-1、2100h-1、2400h-1The oxidative dehydrogenation time was 5min and the catalytic results are reported in table 1.
And after the catalysis is finished, introducing nitrogen at the same temperature and flow rate for purging again for 5min, introducing air, and keeping at the same temperature and flow rate for 3min to obtain the regenerated catalyst.
As can be seen from table 1, the conversion rate generally increases with increasing temperature, and the cyclohexene selectivity increases and decreases; the conversion and selectivity generally decline with increasing volumetric space velocity. At the oxidative dehydrogenation temperature of 600 ℃ and the volume space velocity of 1500h-1Under the condition, the conversion rate is up to 49.70 percent, the selectivity of the cyclohexene is up to 87.70 percent, and the catalyst has good catalysisEfficiency.
TABLE 1 catalytic results
Figure BDA0003399119420000101
Figure BDA0003399119420000111
Example 2
Dissolving 7.90g of lanthanum nitrate hexahydrate, 1.16g of magnesium nitrate hexahydrate, 8.29g of ferric nitrate nonahydrate and 0.27g of ammonium metavanadate in 220mL of water, and stirring at the rotating speed of 600rpm for 50min to obtain a metal nitrate mixed solution; mixing the metal nitrate mixed solution with 23.95g of citric acid, and stirring at the rotating speed of 1000rpm for 40 min; after stirring, mixing with 10.61g of ethylene glycol, heating to 78 ℃ at the heating rate of 4 ℃/min, stirring while heating, wherein the stirring speed is 1450rpm, and continuously stirring for 7.5h after the temperature reaches 78 ℃ to obtain the sol.
Drying the sol at 78 ℃ and-0.12 MPa for 12h, heating the dried solid matter to 450 ℃ at the heating rate of 8 ℃/min, and roasting for 1h after the temperature reaches 450 ℃ to complete first roasting; after the first roasting and sintering, continuously heating to 950 ℃ at the heating rate of 8 ℃/min, roasting for 8h after reaching 950 ℃, and finishing the second roasting to obtain the perovskite type composite La0.8Mg0.2Fe0.9V0.1O3
Dissolving the obtained composite material in 190mL of water, and stirring at the rotating speed of 600rpm for 40min to obtain a mixed system; stirring the mixed system and 0.5g of lithium carbonate at the rotation speed of 550rpm for 3.2 hours, and standing for 2.2 hours after stirring to obtain a mixture; drying the mixture at 85 ℃ and-0.11 MPa for 12h to obtain a solid substance; heating the solid matter to 920 ℃ at the heating rate of 12 ℃/min, and roasting for 8.5h after the temperature reaches 920 ℃; ball milling is carried out for 2.2h at the rotating speed of 550rpm after baking and sintering, thus obtaining the perovskite type composite material Li modified by the alkali metal compound2CO3/La0.8Mg0.2Fe0.9V0.1O3A bifunctional catalyst.
Performing cyclohexane chemical chain circulation oxidative dehydrogenation on the bifunctional catalyst prepared in the embodiment to prepare cyclohexene, placing 5g of the catalyst prepared in the embodiment in a fixed bed reactor, introducing air at a set temperature of 760 ℃ for 3.5min, wherein the air flow rate is the same as the flow rate during catalysis, and activating the catalyst at 760 ℃ for 65min after the air introduction is finished; then introducing nitrogen to purge for 3.5min, wherein the flow rate of purging is the same as that of catalyzing; taking nitrogen as a carrier gas, wherein the volume ratio of cyclohexane to nitrogen is 7.5: 1, the contact time is 4min, and the contact temperature, the gas flow rate, the reaction volume space velocity and the parameters during oxidative dehydrogenation are the same; after the contact is finished, introducing nitrogen for secondary purging for 3min, wherein the flow rate, the temperature, the reaction volume airspeed and the parameters during catalysis of the secondary purging are the same; the contacting and the secondary purging were repeated 4 times, and the oxidative dehydrogenation reaction was started after the completion.
Taking nitrogen as a carrier gas, wherein the volume ratio of cyclohexane to nitrogen is 7.5: 1, controlling the temperature of oxidative dehydrogenation to be 500 ℃, 550 ℃, 600 ℃ and 650 ℃, respectively, controlling the gas flow rate of the oxidative dehydrogenation to be 30mL/min, and controlling the reaction volume space velocity of the oxidative dehydrogenation to be 1200h respectively-1、1500h-1、1800h-1、2100h-1、2400h-1The oxidative dehydrogenation time was 5min and the catalytic results are reported in table 2.
And after the catalysis is finished, introducing nitrogen at the same temperature and flow rate for purging again for 5min, introducing air, and keeping at the same temperature and flow rate for 2.5min to obtain the regenerated catalyst.
As can be seen from Table 2, in this example, when the oxidative dehydrogenation temperature was 650 ℃ and the volume space velocity was 1500 hours-1Under the condition of (3), the conversion rate is up to 49.72 percent; when the oxidative dehydrogenation temperature is 600 ℃, the volume space velocity is 1200h-1Under the condition, the selectivity of the cyclohexene can reach 80.92 percent, and the catalyst has good catalytic efficiency.
TABLE 2 catalytic results
Figure BDA0003399119420000121
Figure BDA0003399119420000131
Example 3
Dissolving 7.76g of lanthanum nitrate hexahydrate, 1.05g of calcium nitrate tetrahydrate, 8.14g of ferric nitrate nonahydrate and 0.65g of cobalt nitrate hexahydrate in 180mL of water, and stirring at the rotating speed of 600rpm for 70min to obtain a metal nitrate mixed solution; mixing the metal nitrate mixed solution with 23.53g of citric acid, and stirring at the rotating speed of 1000rpm for 35 min; after stirring, mixing with 10.42g of ethylene glycol, heating to 75 ℃ at the heating rate of 6 ℃/min, stirring while heating, wherein the stirring speed is 1400rpm, and continuously stirring for 9h after the temperature reaches 75 ℃ to obtain the sol.
Drying the sol at 90 ℃ and-0.08 MPa for 10h, heating the dried solid matter to 460 ℃ at the heating rate of 8 ℃/min, and roasting for 1.1h after the temperature reaches 460 ℃ to complete the first roasting; after the first roasting and sintering, continuously heating to 940 ℃ at the heating rate of 8 ℃/min, roasting for 7.8 hours after the temperature reaches 940 ℃, and finishing the second roasting to obtain the perovskite type composite La material0.8Ca0.2Fe0.9Co0.1O3
Dissolving the obtained composite material in 190mL of water, and stirring for 35min at the rotating speed of 600rpm to obtain a mixed system; stirring the mixed system and 0.5g of lithium carbonate at the rotation speed of 550rpm for 3.1h, and standing for 1.9h after stirring to obtain a mixture; drying the mixture at 75 ℃ and-0.105 MPa for 10h to obtain a solid substance; heating the solid substance to 910 ℃ at the heating rate of 9 ℃/min, and roasting for 7.5h after the temperature reaches 910 ℃; ball milling for 2.2h at the rotating speed of 600rpm after baking and sintering to obtain the perovskite type composite material Li modified by the alkali metal compound2CO3/La0.8Ca0.2Fe0.9Co0.1O3A bifunctional catalyst.
The bifunctional catalyst prepared in the embodiment is subjected to cyclohexane chemical chain circulation oxidative dehydrogenation to prepare cyclohexene, and 5g of the catalyst prepared in the embodiment is placed in a fixed bed reactor; introducing air at 755 deg.C for 4min, with the flow rate of air being the same as that during catalysis, and activating the catalyst at 755 deg.C for 70min after the introduction of air is finished; then introducing nitrogen to purge for 4min, wherein the flow rate of purging is the same as that of catalyzing; taking nitrogen as a carrier gas, wherein the volume ratio of cyclohexane to nitrogen is 6.5: 1, the contact time is 5min, and the contact temperature, the gas flow rate, the reaction volume space velocity and the parameters during oxidative dehydrogenation are the same; after the contact is finished, introducing nitrogen for secondary purging for 4min, wherein the flow rate, the temperature, the reaction volume airspeed and the parameters during catalysis of the secondary purging are the same; the contacting and the secondary purging were repeated 4 times, and the oxidative dehydrogenation reaction was started after the completion.
Taking nitrogen as a carrier gas, wherein the volume ratio of cyclohexane to nitrogen is 6.5: 1, controlling the temperature of oxidative dehydrogenation to be 500 ℃, 550 ℃, 600 ℃ and 650 ℃, respectively, controlling the gas flow rate of the oxidative dehydrogenation to be 40mL/min, and controlling the reaction volume space velocity of the oxidative dehydrogenation to be 1200h respectively-1、1500h-1、1800h-1、2100h-1、2400h-1The oxidative dehydrogenation time was 5min and the catalytic results are reported in table 3.
And after the catalysis is finished, introducing nitrogen at the same temperature and flow rate for purging again for 5min, introducing air, and keeping at the same temperature and flow rate for 3.5min to obtain the regenerated catalyst.
As can be seen from Table 3, in this example, the oxidative dehydrogenation temperature was 600 ℃ and the volume space velocity was 1500 hours-1Under the condition of (2), the conversion rate is up to 48.88%; the selectivity of cyclohexene can reach 77.55%, and the catalyst has good catalytic efficiency.
TABLE 3 catalytic results
Figure BDA0003399119420000141
Figure BDA0003399119420000151
Example 4
Dissolving 7.74g of lanthanum nitrate hexahydrate, 1.15g of magnesium nitrate hexahydrate, 8.12g of ferric nitrate nonahydrate and 0.83g of molybdenum nitrate pentahydrate in 210mL of water, and stirring at 480rpm for 70min to obtain a metal nitrate mixed solution; mixing the metal nitrate mixed solution with 23.47g of citric acid, and stirring at 1150rpm for 40 min; after stirring, mixing with 10.4g of ethylene glycol, heating to 85 ℃ at the heating rate of 6 ℃/min, stirring while heating, wherein the stirring speed is 1555rpm, and continuously stirring for 8h after reaching 82 ℃ to obtain the sol.
Drying the sol at 78 ℃ and-0.1 MPa for 12h, heating the dried solid matter to 450 ℃ at the heating rate of 10 ℃/min, and roasting for 1.2h after the temperature reaches 450 ℃ to complete the first roasting; after the first roasting and sintering, continuously heating to 950 ℃ at the heating rate of 10 ℃/min, roasting for 7.8 hours after reaching 950 ℃, and finishing the second roasting to obtain the perovskite type composite La0.8Mg0.2Fe0.9Mo0.1O3
Dissolving the obtained composite material in 220mL of water, and stirring for 40min at the rotating speed of 600rpm to obtain a mixed system; stirring the mixed system and 0.5g of potassium carbonate at the rotation speed of 550rpm for 3.1h, and standing for 1.9h after stirring to obtain a mixture; drying the mixture at 85 ℃ and-0.095 MPa for 12h to obtain a solid substance; heating the solid substance to 910 ℃ at the heating rate of 11 ℃/min, and roasting for 8.2h after the temperature reaches 910 ℃; ball milling for 2.2h at the rotating speed of 555rpm after baking and sintering to obtain the perovskite type composite material K modified by the alkali metal compound2CO3/La0.8Mg0.2Fe0.9Mo0.1O3A bifunctional catalyst.
The bifunctional catalyst prepared in the embodiment is subjected to cyclohexane chemical chain circulation oxidative dehydrogenation to prepare cyclohexene, and 5g of the catalyst prepared in the embodiment is placed in a fixed bed reactor; introducing air at 752 deg.C for 3min, with the air flow rate being the same as that during catalysis, and activating the catalyst at 752 deg.C for 60min after air introduction; then introducing nitrogen to purge for 4min, wherein the flow rate of purging is the same as that of catalyzing; taking nitrogen as a carrier gas, wherein the volume ratio of cyclohexane to nitrogen is 7: 1, the contact time is 5min, and the contact temperature, the gas flow rate, the reaction volume space velocity and the parameters during oxidative dehydrogenation are the same; after the contact is finished, introducing nitrogen for secondary purging for 4min, wherein the flow rate, the temperature, the reaction volume airspeed and the parameters during catalysis of the secondary purging are the same; the contacting and the secondary purging were repeated 3 times, and the oxidative dehydrogenation reaction was started after completion.
Taking nitrogen as a carrier gas, wherein the volume ratio of cyclohexane to nitrogen is 7: 1, controlling the temperature of oxidative dehydrogenation to be 500 ℃, 550 ℃, 600 ℃ and 650 ℃, respectively, controlling the gas flow rate of the oxidative dehydrogenation to be 30mL/min, and controlling the reaction volume space velocity of the oxidative dehydrogenation to be 1200h respectively-1、1500h-1、1800h-1、2100h-1、2400h-1The oxidative dehydrogenation time was 5min and the catalytic results are reported in table 4.
And after the catalysis is finished, introducing nitrogen at the same temperature and flow rate for purging again for 5min, introducing air, and keeping at the same temperature and flow rate for 3min to obtain the regenerated catalyst.
As can be seen from Table 4, in this example, when the oxidative dehydrogenation temperature was 650 ℃ and the volume space velocity was 1500 hours-1Under the condition of (2), the conversion rate is as high as 39.62 percent; when the oxidative dehydrogenation temperature is 600 ℃, the volume space velocity is 1200h-1Under the condition, the selectivity of the cyclohexene can reach 74.82%, and the catalyst has good catalytic efficiency.
TABLE 4 catalytic results
Figure BDA0003399119420000161
Figure BDA0003399119420000171
From the above examples, it can be seen that the present invention provides a dual function catalyst. According to the invention, the perovskite oxide modified by the alkali metal salt is used as a catalyst for cyclohexane chemical chain oxidative dehydrogenation (CL-ODH), so that the use of noble metal is avoided, and the catalyst cost is reduced; the catalyst can provide lattice oxygen for the reaction, and alkane and O are avoided2The potential safety hidden danger is eliminated by the direct contact; the method for preparing cyclohexene by cyclohexane chemical chain cyclic oxidative dehydrogenation can be carried out under higher alkane partial pressure, so that the reaction conversion rate is further improved; the oxygen carrier in the perovskite oxide modified by the alkali metal salt can be oxidized and regenerated in the air, so that the carbon deposition of the catalyst is removed while the lattice oxygen is supplemented; after being oxidized and regenerated, the perovskite oxide modified by the alkali metal salt carries a large amount of heat which can be directly supplied to dehydrogenation reaction, so that the process energy consumption is reduced, and the application of the perovskite metal oxide in the field of catalysis is further expanded.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (10)

1. The bifunctional catalyst is characterized by being prepared from the following raw materials in parts by mass: 7-8 parts of lanthanum nitrate, 0.8-1.2 parts of alkaline earth metal precursor, 7.5-8.5 parts of ferric nitrate, 0.2-0.9 part of transition metal precursor and 0.4-0.6 part of alkali metal compound.
2. The catalyst of claim 1, wherein the lanthanum nitrate is lanthanum nitrate hexahydrate; the ferric nitrate is ferric nitrate nonahydrate;
the alkaline earth metal precursor comprises strontium nitrate, magnesium nitrate hexahydrate or calcium nitrate tetrahydrate;
the transition metal precursor comprises ammonium metavanadate, cobalt nitrate hexahydrate or molybdenum nitrate pentahydrate;
the alkali metal compound comprises lithium carbonate or potassium carbonate.
3. A process for preparing a catalyst according to claim 1 or 2, comprising the steps of:
(1) mixing lanthanum nitrate, an alkaline earth metal precursor, ferric nitrate, a transition metal precursor, a complexing agent, water and dihydric alcohol to obtain sol;
(2) drying and roasting the sol in sequence to obtain a composite material;
(3) and mixing the composite material, the alkali metal compound and water, and then drying and roasting in sequence to obtain the bifunctional catalyst.
4. The method according to claim 3, wherein the complexing agent in the step (1) is citric acid, and the diol is ethylene glycol;
the mass ratio of the lanthanum nitrate to the complexing agent is 7-8: 20-24;
the dosage ratio of the lanthanum nitrate to the water is 7-8 g: 180-220 mL;
the mass ratio of the lanthanum nitrate to the dihydric alcohol is 7-8: 9.5-10.5;
the mixing mode is heating stirring, the heating rate of the heating stirring is 4-6 ℃/min, the target temperature of the heating stirring is 75-85 ℃, the rotating speed of the heating stirring is 1400-1600 rpm, and the stirring time after the heating stirring reaches the target temperature is 7-9 h.
5. The preparation method according to claim 3 or 4, wherein the drying in the step (2) is vacuum drying, the temperature of the vacuum drying is 70-90 ℃, the vacuum degree of the vacuum drying is-0.12-0.08 MPa, and the time of the vacuum drying is 10-12 h;
the roasting is to carry out first roasting and second roasting in sequence;
the temperature rise rate of the first roasting is 8-12 ℃/min, the target temperature of the first roasting is 440-460 ℃, and the roasting time after the first roasting reaches the target temperature is 1-1.2 h;
the target temperature of the second roasting is 940-960 ℃, the heating rate of the temperature from the first roasting target temperature to the second roasting target temperature is 8-12 ℃/min, and the roasting time after the second roasting reaches the target temperature is 7.8-8.2 h.
6. The preparation method according to claim 5, wherein the use amount ratio of lanthanum nitrate to water in the step (3) is 7-8 g: 180-220 mL;
the mixing mode is stirring, the rotating speed of the stirring is 450-550 rpm, and the stirring time is 2.8-3.2 hours;
the drying temperature is 75-85 ℃, the vacuum degree of drying is-0.12 to-0.08 MPa, and the drying time is 10-12 h;
the temperature rise rate of the roasting is 8-12 ℃/min, the target temperature of the roasting is 880-920 ℃, and the roasting time after the roasting reaches the target temperature is 7.5-8.5 h.
7. Use of the bifunctional catalyst of claim 1 or 2 in the preparation of cyclohexene by chemical looping oxidative dehydrogenation of cyclohexane.
8. A method for preparing cyclohexene through chemical chain circulation oxidative dehydrogenation of cyclohexane is characterized by comprising the following steps:
putting the bifunctional catalyst in a fixed bed reactor, setting the temperature, and introducing air to activate the catalyst; introducing nitrogen to purge the reactor;
introducing nitrogen carrying cyclohexane into a reactor to start oxidative dehydrogenation reaction; and after the reaction is finished, introducing nitrogen to purge the reactor again, and introducing air to complete the regeneration of the bifunctional catalyst.
9. The preparation method according to claim 8, wherein the set temperature is 740 to 760 ℃, the time for introducing air is 2 to 4min, and the time for activation is 50 to 70 min;
the flow rate of purging is 20-40 mL/min, the purging time is 2-4 min, and the purging temperature is 740-760 ℃.
10. The method according to claim 8 or 9, wherein the volume ratio of cyclohexane to nitrogen is 6.5 to 7.5: 1;
the temperature of the oxidative dehydrogenation reaction is 500-650 ℃, and the oxidative dehydrogenation reactionThe gas flow rate is 20-40 mL/min, and the reaction volume space velocity of the oxidative dehydrogenation reaction is 1200-2400 h-1
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