CN117696073A

CN117696073A - Limited domain type catalyst capable of being used for direct dehydrogenation and oxidative dehydrogenation of propane at same time, and preparation method and application thereof

Info

Publication number: CN117696073A
Application number: CN202311719242.1A
Authority: CN
Inventors: 敬方梨; 皮元洋; 罗仕忠; 张辉; 向欢; 文婕
Original assignee: Southwest Petroleum University
Current assignee: Southwest Petroleum University
Priority date: 2023-12-14
Filing date: 2023-12-14
Publication date: 2024-03-15

Abstract

The invention belongs to the technical field of energy and new materials, and discloses a finite field type catalyst capable of being used for direct dehydrogenation and oxidative dehydrogenation of propane at the same time, and a preparation method and application thereof. The invention provides a preparation method of a supported catalyst with a coiled structure, which comprises the steps of modifying a silicon-aluminum oxide carrier with the coiled structure by using a modifier, then dipping the modified carrier in an aqueous solution containing active metal, and drying, roasting and reducing to obtain the catalyst. The catalyst can be simultaneously used for the direct dehydrogenation and oxidative dehydrogenation of propane, and solves the problems of low thermal stability, narrow application range and the like of the existing catalyst; active metal is loaded at a specific position in the impregnation process, so that the selectivity and stability of the catalyst are improved; transition metal iron is introduced, and the iron is limited in a specific space, so that the catalyst can be used in the oxidative dehydrogenation reaction of propane and carbon dioxide, and the application range of the catalyst is expanded.

Description

Limited domain type catalyst capable of being used for direct dehydrogenation and oxidative dehydrogenation of propane at same time, and preparation method and application thereof

Technical Field

The invention relates to the technical field of energy and new materials, in particular to a finite field type catalyst capable of being used for direct dehydrogenation and oxidative dehydrogenation of propane at the same time, and a preparation method and application thereof.

Background

Technologies for producing propylene by direct dehydrogenation and oxidative dehydrogenation of propane have received a lot of attention in recent years. In particular, the direct dehydrogenation of propane to propylene is considered one of the most promising propylene production processes, which produce propylene which is not a mixture and which yields high yields. Although the oxidative dehydrogenation of propane (OPDH) has good thermodynamic conditions, the reaction atmosphere is complex, the propane utilization is low, and the propylene yield is low. In contrast, the direct dehydrogenation (PDH) technology of propane, in which the reaction components are simple, has been put into industrial production.

In the direct dehydrogenation reaction, activation of the C-H bond of propane is the most important step in determining the catalytic performance of the catalyst. However, the product propylene molecules are more active than propane molecules. Side reactions, including cracking, deep dehydrogenation or polymerization, occur during direct dehydrogenation, resulting in low selectivity and coke formation. Thus, catalysts with excellent properties must facilitate the cleavage of C-H rather than C-C. In general, the C-C bond is more reactive than the C-H bond in the dehydrogenation of propane at high temperatures, and cleavage reactions tend to occur. And when Pt is used as an active component of the catalyst, the C-H bond can be selectively activated, so that deep cracking of propane is fundamentally inhibited to form byproducts. Although the Pt catalyst has the advantages of high propane conversion rate, good propylene selectivity and the like, the Pt catalyst has more serious problems of reduced catalytic active center, rapid catalyst deactivation, even irreversible deactivation and the like caused by easy sintering and easy coking of Pt particles at high temperature besides high price of Pt. In view of this, one improves the catalytic performance of Pt-based catalysts by selectively adding a second active component (i.e., promoter) to the catalyst, which inhibits propylene adsorption in the propane dehydrogenation reaction by alloying with Pt, reduces side reactions, controls the amount of coking, and thus improves catalyst activity and selectivity. The most commonly used metal promoters are tin (Sn), gallium (Ga), zinc (Zn), copper (Cu), cerium (Ce), lanthanum (La), and the like. It is believed that the promoter enhances propylene selectivity due to the electron effect, and in the alloy catalyst, the promoter transfers electrons to Pt, giving it a negative charge on its surface, thereby enhancing propylene selectivity. In addition, the auxiliary agent can also inhibit deposition of carbon deposit and delay the deactivation rate of the catalyst.

For oxidative dehydrogenation reactions, an effective catalyst needs not only to selectively activate the C-H bonds, inhibit C-C cleavage, but also to have an affinity for the activation of the oxidant. CO ₂ As typical acidic molecules, they are not as oxidative as O ₂ Then strong (O) ₂ Oxidation of alkanes or alkenes at high temperatures, which renders the reaction uncontrollable), CO ₂ The molecules will preferentially adsorb on the basic sites of the catalyst, whereas propane will tend to adsorb on the acidic sites. Thus, catalysts having suitable acidity and basicity are also key factors in achieving satisfactory catalytic performance. Heretofore, crO _x The base materials are considered to be the most promising catalysts in oxidative dehydrogenation reactions due to their high activity. It is widely believed that propane is found in tetrahedral Cr during the reaction process ⁶⁺ In situ dehydrogenation to propylene, with simultaneous reduction to octahedral Cr ³⁺ . Reduced Cr ³⁺ Can be re-oxidized into Cr ⁶⁺ Thereby completing the redox cycle. Reduced Cr at low Cr content ³⁺ Can migrate to form Cr ₂ O ₃ Clusters, which can be produced in situ by H ₂ Further reduction to Cr ²⁺ . Deep reduced Cr ²⁺ For CO ₂ Has strong adsorption capacity and passes CO ₂ Is re-oxidized to Cr ³⁺ CO is formed simultaneously. Thus, crO _x The catalytic performance of the base catalyst is related to the dispersibility of the catalytically active species and the interaction between the catalytically active sites and the support. However, crO _x The inherent toxicity and serious side reactions of (a) greatly prevent the application of (b) in industrial production. Besides Cr, fe, V, co, in and other metals are often used for research on oxidative dehydrogenation of propane, and the metals can simultaneously show oxidability and reducibility to catalyze different reaction processes due to various valence states in the reaction process, but the catalytic mechanism of the catalysts in oxidative dehydrogenation is not clear, and high-performance commercializable catalysts cannot be designed through the reaction mechanism and the catalyst structure.

Since the reaction mechanisms of the direct dehydrogenation reaction and the oxidative dehydrogenation reaction are not the same, the catalysis mechanisms of the different catalysts are also different, so that the direct dehydrogenation catalyst is not suitable for the oxidative dehydrogenation reaction, and vice versa, even though the catalysis effect is shown, only the direct dehydrogenation reaction (namely CO is likely to occur ₂ Not involved in the reaction).

From this, it is known that many mainstream catalysts studied today have the following problems: (1) The catalyst activity problem is that the catalyst is deactivated fast due to the influence of carbon deposition and sintering. (2) Partial catalyst activation of CO ₂ The capacity is weak, slowing down the redox cycle. (3) Most catalysts do not have the ability to catalyze both the direct and oxidative dehydrogenation of propane. Therefore, there is a need in the art to develop a catalyst that has excellent catalytic effect, high catalytic selectivity, and can be used for both direct dehydrogenation and oxidative dehydrogenation of propane.

Disclosure of Invention

The invention aims to provide a limited-area catalyst capable of being used for direct dehydrogenation and oxidative dehydrogenation of propane at the same time, and a preparation method and application thereof, so as to solve the problems that the existing catalyst is low in catalytic effect, easy to deactivate, poor in catalytic selectivity and incapable of being used for catalyzing the direct dehydrogenation and the oxidative dehydrogenation of propane at the same time.

In order to achieve the above purpose, the invention adopts the following technical scheme:

the invention provides a preparation method of a finite field catalyst for direct dehydrogenation and oxidative dehydrogenation of propane, which comprises the following steps:

(1) Reacting the silicon-aluminum oxide with a grafting agent to obtain an intercalated silicon-aluminum oxide;

(2) Performing grafting reaction on the intercalated silicon aluminum oxide and a methanol solution, and repeating the grafting reaction for 3 times to obtain methoxy grafted silicon aluminum oxide;

(3) Sequentially reacting and roasting methoxy grafted silicon aluminum oxide and long-chain organic matter solution to obtain a silicon aluminum oxide carrier with a curled structure;

(4) Modifying the silicon-aluminum oxide carrier with the coiled structure, a modifier and water to obtain a modified silicon-aluminum oxide carrier;

(5) Mixing, drying and roasting an iron source, a modified silicon aluminum oxide carrier and a solvent in sequence to obtain an iron-loaded silicon aluminum oxide;

(6) Modifying the silicon aluminum oxide loaded with iron, a modifier and water to obtain modified silicon aluminum oxide loaded with iron;

(7) And sequentially mixing, drying and roasting the platinum source, the modified iron-loaded silicon aluminum oxide and the solvent to obtain the platinum-iron catalyst with the coiled structure.

Preferably, the silicon-aluminum oxide is dried and sieved sequentially before the reaction; the drying temperature is 50-70 ℃, and the drying time is 1.5-2.5 h; the aperture of the screen used for sieving is 80-150 meshes.

Preferably, in the step (1), the grafting agent is dimethyl sulfoxide and/or N-methyl pyrrolidone; the mass volume ratio of the silicon aluminum oxide to the grafting agent is 8-12 g: 15-30 mL; the reaction temperature is 50-70 ℃; the specific steps of the reaction are as follows: firstly, carrying out ultrasonic reaction and then stirring reaction; the frequency of the ultrasonic reaction is 30-50 kHz, and the time of the ultrasonic reaction is 20-40 min; the stirring speed of the stirring reaction is 2-4 r/s, and the stirring reaction time is 22-26 h.

Preferably, in the step (2), the concentration of the methanol solution is 0.8 to 1.2mol/L; the mass volume ratio of the intercalation silicon aluminum oxide to the methanol solution is 4-6 g:50mL; the stirring speed of the grafting reaction is 2-4 r/s, and the time of the grafting reaction is 22-26 h; centrifuging the obtained product after each grafting reaction is finished; the rotational speed of centrifugation is 7000-10000 r/min, and the time of centrifugation is 5-10 min.

Preferably, in the step (3), the concentration of the long-chain organic matter solution is 0.8-1.2 mol/L; the long-chain organic matter solution is a mixed solution of long-chain organic matters and methanol; the long-chain organic matter is one or more of cetyl trimethyl ammonium chloride, 3-aminopropyl trimethoxy silane and tetrabutyl ammonium chloride; the mass volume ratio of the methoxy grafted silicon aluminum oxide to the long-chain organic matter solution is 1.5-2.5 g: 25-40 mL; the stirring speed of the reaction is 2-4 r/s, and the reaction time is 22-26 h; the roasting temperature is 350-450 ℃, and the roasting time is 3-5 h.

Preferably, in the step (4), the mass ratio of the silicon aluminum oxide carrier having a coiled structure, the modifier and the water is 1 to 3:0.5 to 1: 40-60; in the step (6), the mass ratio of the silicon aluminum oxide loaded with iron, the modifier and the water is 1-3: 0.5 to 1: 40-60; in the step (4) and the step (6), the modifier is independently cetyl trimethyl ammonium bromide and/or 3-aminopropyl triethoxysilane; the modification temperature is independently 50-70 ℃, and the modification time is independently 4-6 h.

Preferably, in the step (5), the iron source is ferric nitrate nonahydrate or ferric acetylacetonate; the mass volume ratio of the iron source, the modified silicon aluminum oxide carrier and the solvent is 0.0316-0.1447 g:1g: 15-25 mL; in the step (7), the platinum source is hexachloroplatinic acid hexahydrate; the mass volume ratio of the platinum source, the modified iron-loaded silicon aluminum oxide and the solvent is 0.0265g:1g: 15-25 mL.

Preferably, in the step (5) and the step (7), the solvent is ethanol; the mixing time is independently 8-12 h, and the mixing stirring speed is independently 8-10 r/s; the drying temperature is independently 50-80 ℃, and the drying time is independently 10-14 h; the temperature rising rate of the roasting is independently 1-2 ℃/min, the roasting temperature is independently 580-620 ℃, and the roasting time is independently 4-6 h.

The invention also provides the finite field catalyst prepared by the preparation method of the finite field catalyst which can be used for the direct dehydrogenation and the oxidative dehydrogenation of propane, and the finite field catalyst is a platinum-iron catalyst with a coiled structure; the limited-area catalyst takes platinum as an active component, iron as an auxiliary agent, and takes the mass of a modified silicon-aluminum oxide carrier in the limited-area catalyst as a reference, wherein the loading amount of the platinum is 1wt% and the loading amount of the iron is 0.5-2 wt%.

The invention also provides application of the limited-range catalyst in direct dehydrogenation and oxidative dehydrogenation of propane.

Compared with the prior art, the invention has the following beneficial effects:

(1) The invention provides a supported catalyst with a curled structure, which can be used for direct dehydrogenation and oxidative dehydrogenation of propane, and can be used for direct dehydrogenation of propane and oxidative dehydrogenation of carbon dioxide, so that the problems of low thermal stability, narrow application range and the like of the existing catalyst are solved;

(2) The silicon aluminum oxide carrier with the coiled structure is firstly modified by using the modifier and then is immersed in the active metal solution, and the active metal is loaded at a specific position in the immersion process, so that the selectivity and the stability of the catalyst are improved;

(3) The invention introduces transition metal iron and limits the iron in a specific space, so that the catalyst can be used for the direct dehydrogenation of propane and the oxidative dehydrogenation of propane, and the application range of the catalyst is expanded.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present invention, and that other drawings can be obtained according to the provided drawings without inventive effort for a person skilled in the art.

FIG. 1 is a graph showing the relationship between the propane conversion rate and the propylene selectivity and the reaction time of the platinum-iron catalyst having a coil structure obtained in example 1;

FIG. 2 is a graph showing the relationship between the propane conversion rate and the propylene selectivity and the reaction time of the platinum-iron catalyst having a coil structure obtained in example 2;

FIG. 3 is a graph showing the relationship between the propane conversion rate and the propylene selectivity and the reaction time of the platinum-iron catalyst having a coil structure obtained in example 3;

FIG. 4 is a graph showing the relationship between the propane conversion rate and the propylene selectivity and the reaction time of the platinum-iron catalyst having a coil structure obtained in example 4;

FIG. 5 is a graph showing the relationship between the propane conversion rate and the propylene selectivity and the reaction time of the platinum-iron catalyst having a coil structure obtained in example 5;

FIG. 6 is a graph showing the relationship between the propane conversion rate and the propylene selectivity and the reaction time of the platinum-iron catalyst having a coil structure obtained in example 6;

FIG. 7 is a graph showing the relationship between the propane conversion rate and the propylene selectivity and the reaction time of the platinum-iron catalyst having a coil structure obtained in example 7;

FIG. 8 is a graph showing the relationship between the propane conversion rate and the propylene selectivity and the reaction time of the platinum-iron catalyst having a coil structure obtained in comparative example 1;

FIG. 9 is a graph showing the relationship between the propane conversion rate and the propylene selectivity and the reaction time of the platinum-iron catalyst having a coil structure obtained in comparative example 2.

Detailed Description

In the invention, the preparation of the silicon aluminum oxide comprises the following steps:

(a) Mixing tetraethyl ammonium hydroxide solution, sodium metaaluminate and sodium hydroxide to obtain a mixed solution; (b) Sequentially adding fumed silica and silicon dioxide into the mixed solution, and performing heat treatment to obtain seed crystals; (c) Mixing seed crystal, hexadecyl trimethyl ammonium bromide and water, and sequentially carrying out heat treatment, drying and calcination to obtain the silicon aluminum oxide.

In the step (a), the tetraethylammonium hydroxide solution is an aqueous solution of tetraethylammonium hydroxide; the mass fraction of the tetraethylammonium hydroxide solution is preferably 20-30%, and more preferably 25-28%; the mass ratio of the tetraethylammonium hydroxide solution, the sodium metaaluminate and the sodium hydroxide is preferably 30:0.4 to 0.5:0.15 to 0.2, more preferably 30:0.45 to 0.48:0.16 to 0.18; the temperature of mixing is preferably room temperature; the mixing time is preferably 8 to 12 minutes, more preferably 10 to 11 minutes; the stirring speed of the mixing is preferably 8 to 12r/s, more preferably 9 to 10r/s.

In the above step (b), the mass ratio of sodium metaaluminate, fumed silica and silica is preferably 0.4 to 0.5:1:8 to 10, more preferably 0.48 to 0.49:1:9 to 9.5; the specific steps of adding fumed silica and silicon dioxide in sequence are as follows: adding fumed silica into the mixed solution, mixing for 4-8 min, adding silica, mixing until the mixture is clear, and performing heat treatment; the stirring speed of the mixing is preferably 8 to 12r/s, more preferably 9 to 10r/s; the temperature of the heat treatment is preferably 120 to 160 ℃, and more preferably 140 to 150 ℃; the heat treatment time is preferably 4 to 6 hours, more preferably 5 hours.

In the above step (c), the mass ratio of the seed crystal, cetyltrimethylammonium bromide and water is preferably 1 to 1.5:0.2 to 0.5:3, more preferably 1.2 to 1.4:0.3 to 0.4:3, a step of; the specific steps of mixing seed crystal, cetyl trimethyl ammonium bromide and water are as follows: ultrasonic mixing cetyl trimethyl ammonium bromide and water, adding seed crystal, stirring and mixing; the frequency of ultrasonic mixing is preferably 30 to 50kHz, more preferably 40 to 45kHz; the ultrasonic mixing time is preferably 10 to 30 minutes, more preferably 20 to 25 minutes; the temperature of stirring and mixing is preferably room temperature; the stirring speed of the stirring and mixing is preferably 8 to 12r/s, more preferably 9 to 10r/s; the stirring and mixing time is preferably 20 to 40 minutes, more preferably 30 to 35 minutes.

In the step (c), the temperature of the heat treatment is preferably 130 to 150 ℃, more preferably 135 to 140 ℃; the time of the heat treatment is preferably 2.5 to 3.5 days, more preferably 3 days; after heat treatment, the obtained product is sequentially filtered, centrifuged and washed; the rotational speed of the centrifugation is preferably 7000 to 10000r/min, more preferably 8000 to 9000r/min; the reagent used for washing is preferably water; the drying temperature is preferably 90 to 110 ℃, and more preferably 100 to 105 ℃; the drying time is preferably 4.5 to 5.5 days, more preferably 5 days; the calcination temperature is preferably 400 to 600 ℃, and more preferably 450 to 500 ℃; the calcination time is preferably 4.5 to 5.5 hours, more preferably 5 hours.

In the invention, before the silicon aluminum oxide reacts, drying and sieving are sequentially carried out; sieving, and taking a screen lower material for reaction; the drying temperature is preferably 50 to 70 ℃, and more preferably 60 to 65 ℃; the drying time is preferably 1.5 to 2.5 hours, more preferably 2 hours; the mesh size of the screen used for sieving is preferably 80 to 150 mesh, more preferably 100 to 120 mesh.

In the step (1) according to the invention, the grafting agent is preferably dimethyl sulfoxide and/or N-methylpyrrolidone; the mass volume ratio of the silicon aluminum oxide to the grafting agent is preferably 8-12 g:15 to 30mL, more preferably 9 to 10g: 20-25 mL; the reaction temperature is preferably 50 to 70 ℃, more preferably 60 to 65 ℃; the specific steps of the reaction are as follows: firstly, carrying out ultrasonic reaction and then stirring reaction; the frequency of the ultrasonic reaction is preferably 30 to 50kHz, more preferably 40 to 45kHz; the time of the ultrasonic reaction is preferably 20 to 40 minutes, more preferably 30 to 35 minutes; the stirring speed of the stirring reaction is preferably 2 to 4r/s, more preferably 3r/s; the stirring reaction time is preferably 22 to 26 hours, more preferably 24 to 25 hours.

In the step (1), after the reaction is finished, the obtained product is dried; the temperature of the drying is preferably 40 to 60℃and more preferably 50 to 55 ℃.

In the step (2) of the present invention, the concentration of the methanol solution is preferably 0.8 to 1.2mol/L, more preferably 1 to 1.1mol/L; the mass volume ratio of the intercalation silicon aluminum oxide to the methanol solution is preferably 4-6 g:50mL, more preferably 5 to 5.5g:50mL; the stirring speed of the grafting reaction is preferably 2 to 4r/s, more preferably 3r/s; the time of the grafting reaction is preferably 22 to 26 hours, more preferably 24 to 25 hours; centrifuging the obtained product after each grafting reaction is finished; the rotational speed of the centrifugation is preferably 7000 to 10000r/min, more preferably 8000 to 9000r/min; the time for centrifugation is preferably 5 to 10 minutes, more preferably 6 to 8 minutes.

In the step (3) of the present invention, the concentration of the long-chain organic substance solution is preferably 0.8 to 1.2mol/L, more preferably 0.9 to 1mol/L; the long-chain organic matter solution is a mixed solution of long-chain organic matters and methanol; the long-chain organic matter is preferably one or more of cetyl trimethyl ammonium chloride, 3-aminopropyl trimethoxy silane and tetrabutyl ammonium chloride; the mass volume ratio of the methoxy grafted silicon aluminum oxide to the long-chain organic matter solution is preferably 1.5-2.5 g:25 to 40mL, more preferably 1.8 to 2g: 30-35 mL; the stirring speed of the reaction is preferably 2 to 4r/s, more preferably 3r/s; the reaction time is preferably 22 to 26 hours, more preferably 23 to 24 hours; the baking temperature is preferably 350 to 450 ℃, and more preferably 380 to 400 ℃; the calcination time is preferably 3 to 5 hours, more preferably 4 to 4.5 hours.

In the step (3), after the reaction is finished, washing and air-drying the obtained product at room temperature sequentially; the reagent used for washing is preferably absolute ethanol; the number of times of washing is preferably 2 to 4 times, more preferably 3 times.

In the step (4) of the present invention, the mass ratio of the silica-alumina carrier having a coiled structure, the modifier and water is preferably 1 to 3:0.5 to 1:40 to 60, more preferably 1.5 to 2:0.7 to 0.9: 50-55; the specific steps of modifying the silicon aluminum oxide carrier with the coiled structure, the modifier and the water are as follows: mixing the silicon aluminum oxide carrier with the coiled structure with water to form suspension, and adding the modifier.

In the step (6) of the present invention, the mass ratio of the iron-supporting silicon aluminum oxide, the modifier and the water is preferably 1 to 3:0.5 to 1:40 to 60, more preferably 1.6 to 2:0.8 to 0.9: 50-52; the specific steps of modifying the silicon aluminum oxide loaded with iron, the modifier and the water are as follows: mixing the silicon aluminum oxide loaded with iron and water to form a suspension, and adding a modifier.

In the step (4) and the step (6) according to the invention, the modifier is independently preferably cetyltrimethylammonium bromide and/or 3-aminopropyl triethoxysilane; the temperature of the modification is independently preferably 50 to 70 ℃, and more preferably 60 to 65 ℃; the time for the modification is independently preferably 4 to 6 hours, more preferably 5 to 5.5 hours.

In the step (4) and the step (6), after modification is finished, filtering, washing and drying the obtained products in sequence; the reagent used for washing is preferably water; the number of times of washing is independently preferably 2 to 4 times, more preferably 3 times; the drying temperature is preferably 40 to 60℃and more preferably 50 to 55 ℃.

In the step (5) of the present invention, the iron source is preferably ferric nitrate nonahydrate or ferric acetylacetonate; when the iron source is ferric nitrate nonahydrate, the mass volume ratio of the iron source, the modified silicon aluminum oxide carrier and the solvent is preferably 0.0362-0.1447 g:1g:15 to 25mL, more preferably 0.05 to 0.1g:1g: 20-22 mL; when the iron source is ferric acetylacetonate, the mass-volume ratio of the iron source, the modified silicon aluminum oxide carrier and the solvent is preferably 0.0316-0.1265 g:1g:15 to 25mL, more preferably 0.04 to 0.12g:1g: 20-22 mL; the specific steps of mixing the iron source, the modified silicon aluminum oxide carrier and the solvent are as follows: mixing an iron source and a part of solvent to obtain a mixed solution; mixing the modified silicon-aluminum oxide carrier with the residual solvent to obtain a suspension; mixing the suspension with the mixed solution; the amount of the partial solvent is preferably 1/2 of the total amount of the solvent.

In the step (7) of the present invention, the platinum source is preferably chloroplatinic acid hexahydrate; the mass volume ratio of the platinum source, the modified iron-carrying silicon aluminum oxide and the solvent is preferably 0.0265g:1g:15 to 25mL, more preferably 0.0265g:1g: 20-22 mL; the specific steps of mixing the platinum source, the modified iron-loaded silicon aluminum oxide and the solvent are as follows: mixing a platinum source with a part of solvent to obtain a mixed solution; mixing the modified iron-loaded silicon aluminum oxide with the residual solvent to obtain a suspension; mixing the suspension with the mixed solution; the amount of the partial solvent is preferably 1/2 of the total amount of the solvent.

In the step (5) and the step (7) according to the present invention, the solvent is preferably ethanol; the mixing time is independently preferably 8 to 12 hours, more preferably 10 to 11 hours; the stirring speed of the mixing is independently preferably 8 to 12r/s, more preferably 9 to 10r/s; the mixing here is a mixing between the suspension and the mixed liquid; the drying temperature is independently preferably 50 to 80 ℃, and more preferably 60 to 70 ℃; the drying time is independently preferably 10 to 14 hours, more preferably 11 to 12 hours; the temperature rising rate of the roasting is independently preferably 1-2 ℃/min, and more preferably 1.5 ℃/min; the baking temperature is independently preferably 580-620 ℃, and more preferably 590-600 ℃; the baking time is preferably 4 to 6 hours, more preferably 5 to 5.5 hours.

The invention prepares the silicon aluminum oxide carrier with the coiled structure, adopts the silicon aluminum oxide carrier with the coiled structure, uses the modifier to modify the carrier firstly, then impregnates the active metal solution, and is favorable for loading the active metal at a specific position in the impregnation process. Meanwhile, transition metal iron is introduced, and the iron is limited in a specific space, so that the prepared limited-area catalyst is simultaneously used for direct dehydrogenation and oxidative dehydrogenation of propane, and the application range of the catalyst is expanded.

The invention also provides the finite field catalyst prepared by the preparation method of the finite field catalyst which can be used for the direct dehydrogenation and the oxidative dehydrogenation of propane, and the finite field catalyst is a platinum-iron catalyst with a coiled structure; the limited-area catalyst takes platinum as an active component, iron as an auxiliary agent, and the loading amount of platinum is preferably 1wt% based on the mass of a modified silicon-aluminum oxide carrier in the limited-area catalyst; the iron loading is preferably 0.5 to 2wt%, more preferably 1 to 1.5wt%.

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.

In the following examples and comparative examples, the activity of the platinum-iron catalyst in the direct dehydrogenation of propane is expressed in terms of propane conversion and propylene selectivity, and the calculation formula is as follows:

the activity of the platinum-iron catalyst in the oxidative dehydrogenation of propane is expressed in terms of propane conversion and propylene selectivity, and the calculation formula is as follows:

example 1

(1) Sequentially adding 30g of tetraethylammonium hydroxide aqueous solution with mass fraction of 25%, 0.48g of sodium metaaluminate and 0.16g of sodium hydroxide into a 100mL beaker, stirring at room temperature for 10min at a speed of 8r/s, adding 1g of fumed silica into the mixture at the stirring speed, stirring for 5min, adding 9g of silica, stirring until the mixture is clear, filling the mixture into a 50mL reaction kettle, placing the reaction kettle into an oven, reacting at 140 ℃ for 5h, and cooling to room temperature to obtain light yellow sticky seed crystals;

(2) Adding 2.5g of cetyl trimethyl ammonium bromide into 15g of deionized water, carrying out ultrasonic treatment (ultrasonic frequency is 40 kHz) for 20min, clarifying the solution, adding 6g of seed crystal, stirring at a speed of 8r/s for 30min at room temperature, loading into a reaction kettle, placing into a baking oven, and keeping at 140 ℃ for 3d; filtering the product, centrifuging at 9000r/min, washing with water, drying at 100deg.C for 5d, and calcining at 500deg.C for 5h in a muffle furnace to obtain layered silicon-aluminum oxide;

(3) Weighing 10g of silicon aluminum oxide, drying at 60 ℃ for 2 hours, sieving with a 100-mesh sieve, and taking a screen lower product; adding 20mL of N-methylpyrrolidone, performing ultrasonic treatment at 60 ℃ for 30min (the ultrasonic frequency is 40 kHz), stirring at 60 ℃ for 24h at a speed of 3r/s, and directly drying a sample at 50 ℃ after the reaction is finished to obtain an intercalated silicon aluminum oxide;

(4) Weighing 5g of the intercalated silicon aluminum oxide obtained in the step (3), adding 50mL of 1mol/L methanol solution, stirring at room temperature for 24h at a speed of 3r/s to perform grafting reaction, removing methanol after the reaction by centrifugation (the rotation speed of the centrifugation is 9000 r/min), and repeating the modified grafting reaction for 3 times to obtain methoxy grafted silicon aluminum oxide;

(5) Weighing 2g of methoxy grafted silicon aluminum oxide obtained in the step (4), adding 30mL of aqueous solution of hexadecyl trimethyl ammonium chloride with the concentration of 1mol/L, stirring at the room temperature for 24 hours at the speed of 3r/s, washing with absolute ethyl alcohol for 3 times after the reaction is finished, airing at the room temperature, and roasting at 400 ℃ for 4 hours to obtain a silicon aluminum oxide carrier with a curled structure;

(6) At room temperature, 2g of silicon aluminum oxide carrier with a curled structure and 50g of deionized water are stirred and mixed at the speed of 8r/s to disperse the carrier to form suspension, then 0.9g of hexadecyl trimethyl ammonium bromide is added, and stirring is carried out at the speed of 8r/s for 4 hours at the temperature of 60 ℃ to fully modify; filtering the obtained product, washing with water, and drying at 60 ℃ to obtain a modified silicon-aluminum oxide carrier;

(7) 0.0724g of ferric nitrate nonahydrate and 10mL of absolute ethyl alcohol are weighed and mixed at the speed of 8r/s until the ferric nitrate nonahydrate is dissolved, so as to obtain a mixed solution; weighing 1g of the modified silicon-aluminum oxide carrier obtained in the step (6), adding the modified silicon-aluminum oxide carrier into 10mL of absolute ethyl alcohol, and stirring and mixing at the speed of 8r/s to obtain a suspension; adding the mixed solution into the suspension, stirring at a speed of 100r/s for 12 hours, drying at 80 ℃ for 12 hours, and roasting at 400 ℃ for 4 hours at a heating rate of 1 ℃/min to obtain the silicon aluminum oxide loaded with iron;

(8) Adding the iron-loaded silicon aluminum oxide obtained in the step (7) into 50g of deionized water at room temperature, stirring at a speed of 8r/s to enable the carrier to be dispersed to form suspension, adding 0.9g of hexadecyl trimethyl ammonium bromide, and stirring at a speed of 8r/s for 4 hours at a temperature of 60 ℃ to enable the carrier to be fully modified; filtering the obtained product, washing with water, and drying at 60 ℃ to obtain modified iron-loaded silicon-aluminum oxide;

(9) 2.65mL of aqueous solution of hexa-aqueous chloroplatinic acid with the concentration of 0.01g/mol is measured, added into 10mL of absolute ethyl alcohol and stirred and mixed at the speed of 4r/s to obtain mixed solution; adding 1g of the modified iron-loaded silicon aluminum oxide obtained in the step (8) into 10mL of absolute ethyl alcohol, and stirring and mixing at the speed of 8r/s to obtain a suspension; adding the mixed solution into the suspension, stirring at the speed of 8r/s for 12 hours, drying at 80 ℃ for 12 hours, and roasting at 400 ℃ for 4 hours at the heating rate of 1 ℃/min to obtain the platinum-iron catalyst with the coiled structure, wherein the platinum loading amount is 1wt% and the iron loading amount is 1 wt%.

The catalytic performance of the platinum-iron catalyst obtained in this example was tested as follows:

grinding and sieving a platinum-iron catalyst, selecting a platinum-iron catalyst with the mesh size of 80-100 meshes, loading 200mg of the platinum-iron catalyst into a fixed bed reactor, introducing nitrogen, heating to 580 ℃, introducing hydrogen for reduction for 1h, switching the hydrogen into propane for carrying out propane direct dehydrogenation reaction, and finishing the reaction for 8h, wherein the raw material gas comprises propane: the flow ratio of nitrogen is 1:4, space velocity is 7500 mL/(g.h). The reaction product was analyzed on line using a Fuli7970 II gas chromatograph, the relationship between the propane conversion and the propylene selectivity and the reaction time was shown in FIG. 1, and the propane conversion and the propylene selectivity were shown in Table 1.

Example 2

The differences from example 1 are: the long-chain organic compound was 3-aminopropyl trimethoxysilane, which was the same as in example 1.

The catalytic performance of the platinum-iron catalyst obtained in this example was tested, the test method was the same as in example 1, and the reaction product was analyzed on line by using a Fuli7970 II gas chromatograph, the relationship between the propane conversion and the propylene selectivity and the reaction time was shown in FIG. 2, and the propane conversion and the propylene selectivity were shown in Table 1.

Example 3

The differences from example 1 are: the long-chain organic compound was tetrabutylammonium chloride, and the same as in example 1 was repeated.

The catalytic performance of the platinum-iron catalyst obtained in this example was tested, the test method was the same as in example 1, and the reaction product was analyzed on line by using a Fuli7970 II gas chromatograph, the relationship between the propane conversion and the propylene selectivity and the reaction time was shown in FIG. 3, and the propane conversion and the propylene selectivity were shown in Table 1.

Example 4

The differences from example 2 are: the grafting agent was dimethyl sulfoxide, otherwise identical to example 2.

The catalytic performance of the platinum-iron catalyst obtained in this example was tested, the test method was the same as in example 2, and the reaction product was analyzed on line by using a Fuli7970 II gas chromatograph, the relationship between the propane conversion and the propylene selectivity and the reaction time was shown in FIG. 4, and the propane conversion and the propylene selectivity were shown in Table 1.

Example 5

The differences from example 4 are: the modifier was 3-aminopropyl triethoxysilane, otherwise the same as in example 4.

The catalytic performance of the platinum-iron catalyst obtained in this example was tested, the test method was the same as in example 4, and the reaction product was analyzed on line by using a Fuli7970 II gas chromatograph, the relationship between the propane conversion and the propylene selectivity and the reaction time was shown in FIG. 5, and the propane conversion and the propylene selectivity were shown in Table 1.

Example 6

The differences from example 5 are: the iron source was iron acetylacetonate, otherwise the same as in example 5.

The catalytic performance of the platinum-iron catalyst obtained in this example was tested, the test method was the same as in example 5, and the reaction product was analyzed on line by using a Fuli7970 II gas chromatograph, the relationship between the propane conversion and the propylene selectivity and the reaction time was shown in FIG. 6, and the propane conversion and the propylene selectivity were shown in Table 1.

Example 7

The differences from example 5 are: the amount of ferric nitrate nonahydrate was 0.1447g, otherwise as in example 5.

grinding and sieving a platinum-iron catalyst, selecting a platinum-iron catalyst with the mesh size of 80-100 meshes, loading 200mg of the platinum-iron catalyst into a fixed bed reactor, introducing nitrogen, heating to 580 ℃, introducing hydrogen for reduction for 1h, switching the hydrogen into propane and carbon dioxide for reaction, finishing the reaction for 8h, and finishing the reaction of carbon dioxide in raw material gas: propane: the flow ratio of nitrogen is 1:1:4, space velocity is 9000 mL/(g.h). The reaction product was analyzed on line using a Fuli7970 II gas chromatograph, the relationship between the propane conversion and the propylene selectivity and the reaction time was shown in FIG. 7, and the propane conversion and the propylene selectivity were shown in Table 2.

Example 8

The preparation method of the platinum-iron catalyst is the same as that of example 5.

grinding and sieving a platinum-iron catalyst, selecting a platinum-iron catalyst with the mesh size of 80-100 meshes, loading 200mg of the platinum-iron catalyst into a fixed bed reactor, introducing nitrogen, heating to 580 ℃, introducing hydrogen for reduction for 1h, switching the hydrogen into propane and carbon dioxide for reaction, finishing the reaction for 8h, and finishing the reaction of carbon dioxide in raw material gas: propane: the flow ratio of nitrogen is 1:1:4, space velocity is 9000 mL/(g.h). The reaction products were analyzed on-line using a Fuli7970 II gas chromatograph and the propane conversion and propylene selectivity are shown in Table 2.

Comparative example 1

2g of commercial Al manufactured by Alfa Elisa (Tianjin) chemical Co., ltd. Model 043855 was weighed out ₂ O ₃ Adding carrier into 20mL deionized water, stirring at 8r/s to disperse the carrier, adding ferric nitrate nonahydrate solution, controlling the iron loading amount to be 1wt%, stirring at 8r/s for 12h, drying at 80 ℃ for 12h, and roasting at 400 ℃ for 4h at a heating rate of 1 ℃/min to obtain Fe/Al ₂ O ₃ .1g of Fe/Al is weighed ₂ O ₃ Adding into 20mL deionized water, stirring at 8r/s to disperse, adding chloroplatinic acid solution to make Pt load amount be 1wt.%, stirring at 8r/s for 12h, drying at 80 ℃ for 12h, and roasting at 400 ℃ for 4h at a heating rate of 1 ℃/min to obtain Pt/Fe/Al ₂ O ₃ 。

The catalytic performance of the platinum-iron catalyst obtained in this comparative example was measured by the same method as in example 1, and the reaction product was analyzed on line by using a Fuli7970 II gas chromatograph, and the relationship between the propane conversion and the propylene selectivity and the reaction time was shown in FIG. 8, and the propane conversion and the propylene selectivity were shown in Table 1.

Comparative example 2

The differences from comparative example 1 are: will be commercial Al ₂ O ₃ The support was replaced with a commercial ZSM-5 support (Si/al=130) manufactured by university of south opening catalyst plant, model NKF-5-130H, otherwise as in comparative example 1.

The catalytic performance of the platinum-iron catalyst obtained in this comparative example was measured by the same method as in comparative example 1, and the reaction product was analyzed on line by using a Fuli7970 II gas chromatograph, and the relationship between the propane conversion and the propylene selectivity and the reaction time was shown in FIG. 9, and the propane conversion and the propylene selectivity were shown in Table 1.

Comparative example 3

The differences from example 5 are: step (7) and step (8) in example 5 were omitted without adding ferric nitrate nonahydrate, and the modified iron-supporting silica alumina in step (9) was replaced with the modified silica alumina carrier obtained in step (6), except that the method was similar to example 5.

The catalytic performance of the platinum catalyst obtained in this example was measured as follows:

grinding and sieving a platinum catalyst, selecting a platinum catalyst with the mesh size of 80-100 meshes, loading 200mg of the platinum catalyst into a fixed bed reactor, introducing nitrogen, heating to 580 ℃, introducing hydrogen for reduction for 1h, switching the hydrogen into propane and carbon dioxide for reaction, and finishing the reaction for 8h, wherein the carbon dioxide in the raw material gas is as follows: propane: the flow ratio of nitrogen is 1:1:4, space velocity is 9000 mL/(g.h). The reaction products were analyzed on-line using a Fuli7970 II gas chromatograph and the propane conversion and propylene selectivity are shown in Table 2.

The propane conversion and propylene selectivity of the platinum-iron catalysts obtained in examples 1 to 6 and comparative examples 1 to 2 are shown in table 1.

TABLE 1 catalytic Effect of the platinum iron catalysts obtained in examples 1 to 6 and comparative examples 1 to 2 for the direct dehydrogenation of propane

In Table 1, X ₀ Is the initial conversion rate; x is X _f Is the final conversion rate;is the average conversion.

The propane conversion and propylene selectivity of the platinum-iron catalysts obtained in examples 7 to 8 and comparative example 3 are shown in table 2.

TABLE 2 catalytic Effect of the platinum iron catalysts obtained in examples 7 to 8 and comparative example 3 for oxidative dehydrogenation

As can be seen from tables 1 and 2, the platinum-iron catalyst with a coiled structure obtained by the present invention can be used for both direct dehydrogenation and oxidative dehydrogenation of propane, and has excellent propane conversion rate and propylene selectivity.

The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.

Claims

1. The preparation method of the finite field catalyst for the direct dehydrogenation and the oxidative dehydrogenation of propane is characterized by comprising the following steps of:

2. The method for preparing a limiting catalyst for direct dehydrogenation and oxidative dehydrogenation of propane according to claim 1, wherein the silicon-aluminum oxide is dried and sieved sequentially before being reacted; the drying temperature is 50-70 ℃, and the drying time is 1.5-2.5 h; the aperture of the screen used for sieving is 80-150 meshes.

3. The method for preparing a limiting catalyst for direct dehydrogenation and oxidative dehydrogenation of propane according to claim 2, wherein the grafting agent in the step (1) is dimethyl sulfoxide and/or N-methylpyrrolidone; the mass volume ratio of the silicon aluminum oxide to the grafting agent is 8-12 g: 15-30 mL; the reaction temperature is 50-70 ℃; the specific steps of the reaction are as follows: firstly, carrying out ultrasonic reaction and then stirring reaction; the frequency of the ultrasonic reaction is 30-50 kHz, and the time of the ultrasonic reaction is 20-40 min; the stirring speed of the stirring reaction is 2-4 r/s, and the stirring reaction time is 22-26 h.

4. The method for preparing a finite field catalyst for direct dehydrogenation and oxidative dehydrogenation of propane according to any one of claims 1 to 3, wherein the concentration of the methanol solution in the step (2) is 0.8 to 1.2mol/L; the mass volume ratio of the intercalation silicon aluminum oxide to the methanol solution is 4-6 g:50mL; the stirring speed of the grafting reaction is 2-4 r/s, and the time of the grafting reaction is 22-26 h; centrifuging the obtained product after each grafting reaction is finished; the rotational speed of centrifugation is 7000-10000 r/min, and the time of centrifugation is 5-10 min.

5. The method for preparing a finite field catalyst for direct dehydrogenation and oxidative dehydrogenation of propane according to claim 4, wherein the concentration of the long-chain organic solution in the step (3) is 0.8-1.2 mol/L; the long-chain organic matter solution is a mixed solution of long-chain organic matters and methanol; the long-chain organic matter is one or more of cetyl trimethyl ammonium chloride, 3-aminopropyl trimethoxy silane and tetrabutyl ammonium chloride; the mass volume ratio of the methoxy grafted silicon aluminum oxide to the long-chain organic matter solution is 1.5-2.5 g: 25-40 mL; the stirring speed of the reaction is 2-4 r/s, and the reaction time is 22-26 h; the roasting temperature is 350-450 ℃, and the roasting time is 3-5 h.

6. The method for preparing a limiting catalyst for direct dehydrogenation and oxidative dehydrogenation of propane according to claim 1 or 5, wherein in the step (4), the mass ratio of the silica-alumina carrier with a coiled structure, the modifier and the water is 1-3: 0.5 to 1: 40-60; in the step (6), the mass ratio of the silicon aluminum oxide loaded with iron, the modifier and the water is 1-3: 0.5 to 1: 40-60; in the step (4) and the step (6), the modifier is independently cetyl trimethyl ammonium bromide and/or 3-aminopropyl triethoxysilane; the modification temperature is independently 50-70 ℃, and the modification time is independently 4-6 h.

7. The method for preparing a finite field catalyst for direct dehydrogenation and oxidative dehydrogenation of propane according to claim 6, wherein in the step (5), the iron source is ferric nitrate nonahydrate or ferric acetylacetonate; the mass volume ratio of the iron source, the modified silicon aluminum oxide carrier and the solvent is 0.0316-0.1447 g:1g: 15-25 mL; in the step (7), the platinum source is hexachloroplatinic acid hexahydrate; the mass volume ratio of the platinum source, the modified iron-loaded silicon aluminum oxide and the solvent is 0.0265g:1g: 15-25 mL.

8. The method for preparing a limiting catalyst for direct dehydrogenation and oxidative dehydrogenation of propane according to claim 1 or 7, wherein the solvent is ethanol in the step (5) and the step (7); the mixing time is independently 8-12 h, and the mixing stirring speed is independently 8-10 r/s; the drying temperature is independently 50-80 ℃, and the drying time is independently 10-14 h; the temperature rising rate of the roasting is independently 1-2 ℃/min, the roasting temperature is independently 580-620 ℃, and the roasting time is independently 4-6 h.

9. The finite field catalyst prepared by the preparation method of the finite field catalyst which can be simultaneously used for direct dehydrogenation and oxidative dehydrogenation of propane according to any one of claims 1-8, wherein the finite field catalyst is a platinum-iron catalyst with a coiled structure; the limited-area catalyst takes platinum as an active component and iron as an auxiliary agent; based on the mass of the modified silicon aluminum oxide carrier in the limited-area catalyst, the loading of platinum is 1wt percent, and the loading of iron is 0.5-2 wt percent.

10. Use of the constrained geometry catalyst of claim 9 in the direct dehydrogenation and oxidative dehydrogenation of propane.