CN114713276A - Catalyst for propane dehydrogenation aromatization and preparation method and application thereof - Google Patents

Catalyst for propane dehydrogenation aromatization and preparation method and application thereof Download PDF

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CN114713276A
CN114713276A CN202210463635.XA CN202210463635A CN114713276A CN 114713276 A CN114713276 A CN 114713276A CN 202210463635 A CN202210463635 A CN 202210463635A CN 114713276 A CN114713276 A CN 114713276A
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catalyst
propane
hydrogen
hzsm
dehydroaromatization
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成康
陈惠�
李伟
曾雷
康金灿
张庆红
王野
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Xiamen University
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    • 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
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
    • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
    • B01J29/42—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively containing iron group metals, noble metals or copper
    • B01J29/44—Noble metals
    • 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
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
    • B01J35/391—Physical properties of the active metal ingredient
    • 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
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
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    • B01J35/393—Metal or metal oxide crystallite size
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    • 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
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    • 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
    • B01J37/30—Ion-exchange
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2/00—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms
    • C07C2/76—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by condensation of hydrocarbons with partial elimination of hydrogen
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
    • B01J2229/10—After treatment, characterised by the effect to be obtained
    • B01J2229/18—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself
    • B01J2229/186—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself not in framework positions
    • 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
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    • 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
    • Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts

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Abstract

A catalyst for propane dehydrogenation aromatization and a preparation method and application thereof are disclosed, wherein the catalyst is a nano alloy catalyst with limited domains in a molecular sieve crystal, and the composition of the nano alloy catalyst is recorded as Pt-M @ zeolite, wherein the load of metal Pt is 0.1% -1%, the metal M is Zn/Ga/Sn, the load is 0.1% -2%, and the zeolite is a molecular sieve carrier with different silicon-aluminum ratios. The Pt-M @ zeolite catalyst prepared by the ion exchange method has a simple preparation method, and the synthesized catalyst can improve the yield of aromatic hydrocarbon by strengthening the propane dehydrogenation process. In the reaction process, the propane conversion rate can reach 72%, the aromatic hydrocarbon yield can reach 40%, the selectivity of the byproduct methane is not higher than 5%, and compared with the traditional Zn/HZSM-5 and Ga/HZSM-5, the propane dehydrogenation and aromatization activity is higher.

Description

Catalyst for propane dehydrogenation aromatization, preparation method and application
Technical Field
The invention relates to the technical field of catalysis, in particular to a catalyst for propane dehydrogenation aromatization and a preparation method and application thereof.
Background
Aromatic hydrocarbons, especially BTX (benzene, toluene and xylene), are key raw materials for high octane gasoline, plastics, rubber, fabrics, dyes, pharmaceuticals and other important industrial chemicals. Currently, BTX is produced mainly from naphtha reforming and steam cracking, and because its production is overly dependent on non-renewable petroleum resources, the yield is difficult to meet the increasing demand of the global market. In recent years, due to the rapid development of shale gas mining technology, light alkane components become very important aromatic hydrocarbon production raw materials, and propane as an important component of shale gas has attracted extensive attention since propane aromatization was successfully realized on a metal zeolite catalyst for the first time.
Zn/HZSM-5 and Ga/HZSM-5 are commonly used for propane aromatization reaction because of their unique alkane aromatization performance. The literature reports show that the metal molecular sieve catalysts realize propane aromatization through a bifunctional way, wherein a metal species is a dehydrogenation center and is used for catalyzing propane dehydrogenation to generate a propylene intermediate product, the formed intermediate product is desorbed from the metal center and is transferred to an acid site of zeolite to generate oligomerization and cyclization reactions to form naphthenic hydrocarbon, and the naphthenic hydrocarbon is dehydrogenated on the metal to finally generate aromatic hydrocarbon. During the reaction, propane dehydrogenation and cycloalkane dehydrogenation are considered as key steps and rate determining steps of propane aromatization reaction. In addition, studies have shown that the side reactions such as methane formation by propane cracking and carbon deposit formation by excessive product dehydrogenation are the main causes of the decrease in selectivity and stability of the catalyst.
Although traditional catalysts such as Zn/HZSM-5, Ga/HZSM-5 and the like show certain catalytic performance on propane aromatization reaction, the catalytic activity of the catalysts is difficult to meet the industrial requirement, and particularly the catalytic activity of the catalysts on key steps such as propane dehydrogenation to generate propylene and naphthene dehydrogenation to generate aromatic hydrocarbon is weak, so that the overall performance of the catalysts is poor. In addition, the acidic molecular sieve is easy to generate carbon deposition side reaction, so that the stability of the catalyst is poor, and the catalytic performance needs to be further improved.
Disclosure of Invention
The invention aims to solve the problems in the prior art and provides a catalyst for propane dehydroaromatization, a preparation method and application thereof.
In order to achieve the purpose, the invention adopts the following technical scheme:
a catalyst for propane dehydrogenation aromatization is a nano alloy catalyst limited in a molecular sieve crystal and has the composition of Pt-M @ zeolite, wherein the loading amount of metal Pt is 0.1-1%, the metal M is Zn/Ga/Sn, the loading amount is 0.1-2%, and the zeolite is a molecular sieve carrier with different silicon-aluminum ratios.
A preparation method of a catalyst for propane dehydrogenation aromatization comprises the steps of respectively dissolving Pt salt and M metal salt in pure water to obtain a Pt solution and an M metal salt solution; dropwise adding the M metal salt solution into the Pt solution, and stirring at room temperature to obtain a uniform mixed solution; adding a molecular sieve into the mixed solution, and then heating for ion exchange; then the solvent is evaporated, dried, roasted and reduced.
The M metal salt is one or more of nitrate/acetate/halide/sulfate of Zn/Ga/Sn; the Pt salt is one or more of nitrate/ammonium salt/halide.
The molecular sieve is one or more of hydrogen type ZSM-5/Beta/MCM-22 molecular sieves, and the silica-alumina ratio is 10-200.
And adjusting the pH value of the mixed solution through an HCl solution to enable the pH value of the mixed solution to be 2.0-7.0.
The temperature of the ion exchange is 70-110 ℃, and the time is 4-24 h; the roasting temperature is 450-650 ℃, and the roasting time is 2-10 h.
The reducing gas used for the reduction treatment is hydrogen argon or hydrogen-nitrogen mixed gas containing 5-10% of hydrogen, the reduction temperature is 400-600 ℃, and the time is 2-4 h.
The application of the catalyst for propane dehydroaromatization is used for preparing aromatic hydrocarbon by propane dehydroaromatization reaction.
Before reaction, the catalyst needs to be pretreated by reducing gas or protective gas, then raw gas is introduced, and propane dehydrogenation aromatization is carried out under certain pressure and temperature; the reducing gas is pure hydrogen or hydrogen-argon or hydrogen-nitrogen mixed gas containing 5 to 10 percent of hydrogen, and the protective gas is nitrogen or argon; the pretreatment temperature is 400-600 ℃, and the treatment time is 1-2 h.
The reaction is carried out in a fixed bed reactor, a moving bed reactor or a fluidized bed reactor, the raw material gas is pure propane, 10-50% of propane/nitrogen or 10-50% of propane/argon mixture, the reaction temperature is 400-650 ℃, the reaction pressure is 0.1-1 MPa, and the reaction space velocity is 1000-12000 mL/h/g.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
the limited-area Pt-M @ Zeolite metal alloy molecular sieve catalyst prepared by the invention has better propane dehydrogenation aromatization performance. The initial conversion rate of the traditional 1Zn/HZSM-5 catalyst in propane aromatization reaction is about 34 percent, and the yield of aromatic hydrocarbon is about 17 percent; the propane conversion rate of the limited-range Pt-M @ Zeolite metal alloy molecular sieve catalyst prepared by the method can reach 72%, and the aromatic hydrocarbon yield can reach 40%.
The Pt-M @ Zeolite metal alloy catalyst prepared by the invention has the advantages of easily available raw materials and simple preparation process, and is suitable for industrial production.
Drawings
FIG. 1 shows the results of performance tests on catalysts prepared in example 3 and comparative examples 1 to 2;
FIG. 2 is an XRD characterization of the catalyst prepared in example 3;
FIG. 3 is NH of the catalyst prepared in example 33-a TPD profile;
FIG. 4 is a CO adsorption infrared characterization of the catalysts prepared in example 3 and comparative example 2;
FIG. 5 is a TEM representation of the catalyst prepared in example 3;
FIG. 6 is a microtome-TEM characterization of the catalyst prepared in example 3;
FIG. 7 is a Thermogravimetric (TG) analysis chart of the catalysts prepared in example 3 and comparative examples 1-2 after 10h reaction.
Detailed Description
In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and clearer, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.
Example 1
Preparation of 0.7Pt-1Ga @ HZSM-5 catalyst and testing of propane aromatization performance
Weighing 55mg Ga (NO)3)3And 21mg of [ Pt (NH)3)4](NO3)2Each of the solutions was prepared as a 15mL aqueous solution. Stirring Ga (NO) at 300rmb3)3Dropwise adding [ Pt (NH) into the solution3)4](NO3)2In the solution, the solution is continuously stirred for 3 hours at room temperature, and the pH value of the mixed solution is controlled to be 3.0; adding 1.5g of HZSM-5 molecular sieve into the uniformly stirred mixed solution, and performing ion exchange at 80 ℃ for 12 hours; evaporating the solvent to dryness, and drying in an oven at 80 ℃ overnight for 12 h; roasting in a muffle furnace at 550 ℃ for 5 hours; grinding the roasted catalyst, tabletting and molding to 30-60 meshes; and finally, treating the catalyst with a hydrogen-nitrogen mixed gas (20mL/min) containing 5% of hydrogen at 600 ℃ to obtain the metal alloy catalyst, wherein the treatment time is 2h, and the obtained catalyst particles are marked as 0.7Pt-1Ga @ HZSM-5, wherein 0.7 is the mass fraction of Pt, and 1 is the mass fraction of Ga.
0.2g of the well-formed 0.7Pt-1Ga @ HZSM-5 metal alloy catalyst is weighed and put into a quartz reaction tube at the concentration of 20mL/minH of (A) to (B)2Raising the temperature to 550 ℃ at a temperature raising speed of 10 ℃/min in a programmed manner at the gas speed, keeping the temperature for 1h, and then switching to N2(30mL/min), purge 15 min. Then, the gas was switched to a feed gas n (propane): n (nitrogen): 1, the feed gas pressure in the reactor was 0.1MPa, the reaction space velocity WHSV was 6000mL/h/g, and the evaluation of the catalytic performance of the propane dehydroaromatization reaction catalyzed by the 0.7Pt-1Ga @ HZSM-5 catalyst was started. The catalyst evaluation results are shown in Table 1.
Example 2
Preparation of 0.7Pt-1Sn @ HZSM-5 catalyst and testing of propane aromatization performance
Weighing 33mg of SnCl4And 21mg of [ Pt (NH)3)4](NO3)2Each of the solutions was prepared as a 15mL aqueous solution. The other preparation and reaction performance evaluation procedures were the same as in example 1, and the catalyst particles were obtained and recorded as 0.7Pt-1Sn @ HZSM-5, and the catalyst evaluation results are shown in Table 1.
Example 3
Preparation of 0.7Pt-1Zn @ HZSM-5 catalyst and testing of propane aromatization performance
Weighing 68mg Zn (NO)3)2·6H2O and 21mg [ Pt (NH)3)4](NO3)2Each of the solutions was prepared as a 15mL aqueous solution. The other preparation and reaction performance evaluation procedures were the same as in example 1, and the catalyst particles obtained were designated as 0.7Pt-1Zn @ HZSM-5, and the catalyst evaluation results are shown in Table 1.
Comparative example 1
Preparation of 1Zn/HZSM-5 catalyst and testing of propane aromatization performance
Weighing 68mg Zn (NO)3)2·6H2Preparing 3mL of water solution from O, uniformly stirring at room temperature for 3h under the stirring condition of 300rmb, adding 1.5g of HZSM-5 molecular sieve into the solution, fully soaking for 12h, and drying in an oven at 80 ℃ overnight for 12 h; finally, roasting in a muffle furnace at 550 ℃ for 5 h; and grinding the roasted catalyst, tabletting, forming to 30-60 meshes, and finally treating the catalyst at 600 ℃ by using a hydrogen-nitrogen mixed gas (20mL/min) containing 5% of hydrogen for 2 hours to obtain catalyst particles which are recorded as 1 Zn/HZSM-5.
0.2g of the molded 1Zn/HZSM-5 catalyst was weighed into a quartz reaction tube and charged with 20mL/min of H2Raising the temperature to 550 ℃ with a temperature raising speed of 10 ℃/min in an atmosphere programmed manner, keeping the temperature for 1h, and then switching to N2(30mL/min) and purging for 15 min. The gas was switched to a feed gas n (propane): n (nitrogen): 1, the feed gas pressure in the reactor was 0.1MPa, and the reaction space velocity WHSV was 6000mL/h/g, and the evaluation of the catalytic performance of the propane dehydroaromatization reaction of the 1Zn/HZSM-5 catalyst was started. The evaluation results of the catalyst are shown in the table 1, and the 1Zn/HZSM-5 carries out propane aromatization reaction, the conversion rate is about 34 percent, the selectivity of aromatic hydrocarbon is about 50 percent, and the yield of the aromatic hydrocarbon is about 17 percent.
Comparative example 2
0.7Pt/HZSM-5 catalyst is prepared and propane aromatization performance test is carried out
Weighing 55mg of [ Pt (NH)3)4](NO3)2Preparing 3mL of aqueous solution from tetrammine platinum nitrate, uniformly stirring at room temperature for 3h under the stirring condition of 300rmb, adding 1.5g of HZSM-5 molecular sieve into the solution, fully soaking for 12h, and drying in an oven at 80 ℃ overnight for 12 h; finally, roasting in a muffle furnace at 550 ℃ for 5 h; and grinding the roasted catalyst, tabletting, forming to 30-60 meshes, and finally treating the catalyst at 600 ℃ by using a hydrogen-nitrogen mixed gas (20mL/min) containing 5% of hydrogen for 2 hours to obtain catalyst particles which are recorded as 0.7 Pt/HZSM-5.
0.2g of the molded 0.7Pt/HZSM-5 catalyst was weighed into a quartz reaction tube and charged at 20mL/min H2Raising the temperature to 550 ℃ in an atmosphere at a temperature raising speed of 10 ℃/min, keeping the temperature for 1h, and then switching to N2(30mL/min), purge 15 min. The gas was switched to the feed gas n (propane) n (nitrogen) 1:1, the pressure of the feed gas in the reactor was 0.1MPa, the reaction space velocity WHSV was 6000mL/h/g, and the performance of the propane dehydroaromatization reaction of 0.7Pt/HZSM-5 catalyst was evaluated. The evaluation results of the catalyst are shown in the table 1, and 0.7Pt/ZSM-5 carries out propane aromatization reaction, the conversion rate is about 80%, the selectivity of aromatic hydrocarbon is about 32%, and the yield of the aromatic hydrocarbon is about 25%.
TABLE 1
Figure BDA0003621118190000051
From the evaluation results of example 1 and comparative examples 1 and 2, it can be seen that the conversion rate of the 0.7Pt-1Ga @ HZSM-5 metal alloy catalyst prepared by the present invention is maintained at about 68%, the selectivity of aromatic hydrocarbon is maintained at about 50%, the yield of aromatic hydrocarbon is about 34%, which is higher than the yield of aromatic hydrocarbon of the prepared supported 1Zn/HZSM-5 and 0.7Pt/HZSM-5 catalysts under the same conditions, and the excellent performance of the prepared 0.7Pt-1Ga @ HZSM-5 metal alloy catalyst in the propane aromatization reaction is shown.
From the evaluation results of example 2 and comparative examples 1 and 2, it can be seen that the conversion rate of the 0.7Pt-1Sn @ HZSM-5 metal alloy catalyst prepared by the present invention is maintained at about 70%, the selectivity of aromatic hydrocarbon is maintained at about 52%, the yield of aromatic hydrocarbon is about 35%, which is higher than the yield of aromatic hydrocarbon of the prepared supported 1Zn/HZSM-5 and 0.7Pt/HZSM-5 catalysts under the same conditions, and the excellent performance of the prepared 0.7Pt-1Sn @ HZSM-5 metal alloy catalyst in the propane aromatization reaction is shown.
As can be seen from Table 1 and FIG. 1, the 0.7Pt-1Zn @ HZSM-5 catalyst prepared in example 3 has high propane aromatization activity, and the catalyst is slowly deactivated within 6h of reaction time, and the reaction performance is maintained at a high level. When the catalyst 0.7Pt-1Zn @ HZSM-5 is used, the initial conversion rate of propane can reach 72%, the selectivity of aromatic hydrocarbon is kept about 56%, and the yield of aromatic hydrocarbon can reach 40%. The aromatic hydrocarbon yield is far higher than that of the prepared supported 1Zn/HZSM-5 and 0.7Pt/HZSM-5 catalysts under the same conditions, and the excellent performance of the prepared 0.7Pt-1Zn @ HZSM-5 metal alloy catalyst in propane aromatization reaction is shown.
FIG. 2 is an XRD pattern of the 0.7Pt-1Zn @ HZSM-5 metal alloy catalyst prepared in example 3, and X-ray powder diffraction (XRD) was used to characterize the crystalline structure of the 0.1Pt-1Zn @ HZSM-5 catalyst, and the testing was performed on a Smart Lab-SE physical X-ray diffractometer. The test conditions were Cu (K α) (λ ═ 0.15418nm), the tube voltage was set at 35kV, and the tube current was 30 mA. As can be seen from the characterization of FIG. 2, 0.7Pt-1Zn @ HZSM-5 is an MFI structure, and no diffraction peaks of Zn and Pt species are observed, indicating that Zn and Pt are in a uniformly dispersed state.
FIG. 3 is the NH of the 0.7Pt-1Zn @ HZSM-5 metal alloy catalyst prepared in example 33TPD plot, NH3TPD adsorption and desorption was used to characterize the acid content of the 0.7Pt-1Zn @ HZSM-5 metal alloy catalyst and experiments were performed on a Micromeritics Auto Chem II 2920 Autoamtor. Tabletting, molding and sieving the catalyst to obtain small particles, and weighing 0.1g of 30-60 mesh catalyst particles into a U-shaped quartz tube. The catalyst is firstly blown under the Ar atmosphere of 20mL/min to remove adsorbed moisture and the like, the temperature is raised to 600 ℃ at the temperature rise rate of 10 ℃/min in the blowing process, the temperature is kept for 1h, and then the temperature is lowered to 100 ℃; then, the Ar gas was switched to 10 vol% NH3Ar gas with the gas velocity of 30mL/min is adsorbed for 1 h; then, 10 vol% NH3The Ar gas is switched to 30mL/min, purging is carried out for 1h, and unadsorbed and physically adsorbed NH is removed3And raising the temperature of the catalyst to 600 ℃ at a temperature raising rate of 10 ℃/min to perform a temperature programmed desorption experiment. The acid content of the sample 0.7Pt-1Zn @ HZSM-5 in FIG. 3 was converted to 874. mu. mol/g, demonstrating that the catalyst has a higher acid content.
FIG. 4 is an in situ infrared plot of carbon monoxide adsorption for the 0.7Pt-1Zn @ HZSM-5 metal alloy catalyst prepared in example 3, used to characterize the structure and electronic state of the metal species on the 0.7Pt-1Zn @ HZSM-5 catalyst, tested on an infrared spectrometer Nicolet 6700. 2071cm on the IR spectrum for the 0.7Pt/HZSM-5 catalyst-1An absorption peak occurs, which is caused by linear adsorption of CO on unsaturated Pt sites. When zinc is CO-doped in the catalyst, the CO absorption peak on the infrared spectrum is red-shifted to 2056cm for the 0.7Pt-1Zn @ HZSM-5 catalyst-1The red shift of the absorption peak is caused by the Pt-Zn alloy formed by part of Zn and Pt, and specifically, part of the electrons of Zn are transferred to the 5d orbit of Pt, increasing the electron density of Pt, causing the vibration frequency of CO adsorbed on the metal site to change, and the adsorption peak to shift to the low wave number direction.
FIG. 5 is a TEM image of a 0.7Pt-1Zn @ HZSM-5 metal alloy catalyst prepared in example 3, used to characterize the particle size information of the metal nanoparticles, using a Philips FEI F20 TEM transmission electron microscope at an acceleration voltage of 200 kV. The particle size statistics show that the metal is nanoparticles of about 2.4 nm.
FIG. 6 is a microtome-TEM image of the prepared 0.7Pt-1Zn @ HZSM-5 metal alloy catalyst, and it can be seen from the cross-sectional view of the molecular sieve that the metal alloy nanoparticles are uniformly distributed in the molecular sieve, which shows that the synthesized catalyst is a limited-area nano alloy catalyst.
FIG. 7 is a thermogravimetric analysis graph after 10 hours of reaction of example 3 and comparative examples 1 and 2, wherein the weight loss of the catalyst is the mass of the carbon deposit formed during the reaction, and it can be seen from the results that the amount of the carbon deposit formed after 10 hours of reaction of the prepared 0.7Pt-1Zn @ HZSM-5 metal alloy catalyst is lower than the carbon deposit formed under the same conditions of the 1Zn/HZSM-5 and 0.7Pt/HZSM-5 catalysts prepared by the impregnation method in the comparative example, which shows that the prepared 0.7Pt-1Zn @ HZSM-5 metal alloy catalyst has better carbon deposition resistance.

Claims (10)

1. A catalyst for propane dehydroaromatization characterized in that: the catalyst is a nano alloy catalyst with limited domains in molecular sieve crystals, and the composition is recorded as Pt-M @ zeolite, wherein the load capacity of metal Pt is 0.1-1%, the metal M is Zn/Ga/Sn, the load capacity is 0.1-2%, and the zeolite is a molecular sieve carrier with different silicon-aluminum ratios.
2. A process for preparing a catalyst for propane dehydroaromatization according to claim 1 characterized in that: respectively dissolving Pt salt and M metal salt in pure water to obtain a Pt solution and an M metal salt solution; dropwise adding the M metal salt solution into the Pt solution, and stirring at room temperature to obtain a uniform mixed solution; adding a molecular sieve into the mixed solution, and then heating for ion exchange; then the solvent is evaporated, dried, roasted and reduced.
3. A process for the preparation of a catalyst for propane dehydroaromatization according to claim 2 wherein: the M metal salt is one or more of nitrate/acetate/halide/sulfate of Zn/Ga/Sn; the Pt salt is one or more of nitrate/ammonium salt/halide.
4. The process for preparing a catalyst for propane dehydroaromatization according to claim 2, wherein: the molecular sieve is one or more of hydrogen type ZSM-5/Beta/MCM-22 molecular sieves, and the silica-alumina ratio is 10-200.
5. The process for preparing a catalyst for propane dehydroaromatization according to claim 2, wherein: and adjusting the pH value of the mixed solution through an HCl solution to enable the pH value of the mixed solution to be 2.0-7.0.
6. A process for the preparation of a catalyst for propane dehydroaromatization according to claim 2 wherein: the temperature of the ion exchange is 70-110 ℃, and the time is 4-24 h; the roasting temperature is 450-650 ℃, and the time is 2-10 h.
7. A process for the preparation of a catalyst for propane dehydroaromatization according to claim 2 wherein: the reducing gas used for the reduction treatment is hydrogen argon or hydrogen-nitrogen mixed gas containing 5-10% of hydrogen, the reduction temperature is 400-600 ℃, and the time is 2-4 h.
8. The use of the catalyst for propane dehydroaromatization according to claim 1 and the catalyst prepared by the preparation method according to any one of claims 2 to 7 is characterized in that: used for preparing aromatic hydrocarbon by propane dehydrogenation aromatization reaction.
9. The use of claim 8, wherein: before reaction, the catalyst needs to be pretreated by reducing gas or protective gas, then raw gas is introduced, and propane dehydrogenation aromatization is carried out under certain pressure and temperature; the reducing gas is pure hydrogen or hydrogen-argon or hydrogen-nitrogen mixed gas containing 5-10% of hydrogen, and the protective gas is nitrogen or argon; the pretreatment temperature is 400-600 ℃, and the treatment time is 1-2 h.
10. The use of claim 9, wherein: the reaction is carried out in a fixed bed reactor, a moving bed reactor or a fluidized bed reactor, the raw material gas is pure propane, 10-50% of propane/nitrogen or 10-50% of propane/argon mixture, the reaction temperature is 400-650 ℃, the reaction pressure is 0.1-1 MPa, and the reaction space velocity is 1000-12000 mL/h/g.
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CN116116453A (en) * 2023-01-18 2023-05-16 厦门大学 Preparation method and application of industrial molecular sieve domain-limited metal catalyst for preparing propylene by propane dehydrogenation

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