A confined catalyst capable of being used for propane direct dehydrogenation and oxidative dehydrogenation simultaneously, and a preparation method and application thereof

Abstract

The application belongs to the technical field of energy and new materials, and discloses a confined catalyst capable of being simultaneously used for direct dehydrogenation and oxidative dehydrogenation of propane as well as a preparation method and application thereof. The application provides a preparation method of a supported catalyst with a curled structure, wherein a modified agent is used to modify a silicon-aluminum oxide carrier with a curled structure, and then the modified carrier is immersed in an active metal-containing aqueous solution, and the catalyst is obtained through drying, calcination and reduction. The catalyst can be simultaneously used for direct dehydrogenation and oxidative dehydrogenation of propane, and solves the problems of low thermal stability and narrow application range of existing catalysts. In the impregnation process, the active metal is loaded in a specific position, thereby improving the selectivity and stability of the catalyst. Transition metal iron is introduced and confined in a specific space, so that the catalyst can also be used for the carbon dioxide oxidative dehydrogenation reaction of propane, thereby expanding the application range of the catalyst.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy and new materials, and particularly relates to a confined catalyst capable of being used for direct dehydrogenation and oxidative dehydrogenation of propane, and a preparation method and application thereof. BACKGROUND

[0002] The technology of direct dehydrogenation and oxidative dehydrogenation of propane to produce propylene has attracted extensive attention in recent years. In particular, propane direct dehydrogenation to produce propylene is considered to be one of the most promising methods for producing propylene, and the propylene produced by this method is not a mixture, and the yield of the obtained propylene is high. Although the propane oxidative dehydrogenation method (OPDH) has good thermodynamic conditions, but due to the complex reaction atmosphere, the utilization rate of propane is low, and the yield of propylene is low. In contrast, the propane direct dehydrogenation (PDH) technology with simple reaction components has been put into industrial production.

[0003] In the direct dehydrogenation reaction, the activation of the C-H bond of propane is the most important step to determine the catalytic performance of the catalyst. However, the product propylene molecule is more active than the propane molecule. In the direct dehydrogenation process, side reactions including cracking, deep dehydrogenation or polymerization occur, resulting in low selectivity and coke formation. Therefore, a catalyst with excellent performance must be beneficial to the cracking of C-H rather than C-C. Generally, the C-C bond is more active than the C-H bond in the propane dehydrogenation reaction at high temperature, and the cracking reaction is easy to occur. When Pt is used as the active component of the catalyst, it can selectively activate the C-H bond, and fundamentally inhibit the formation of by-products by deep cracking of propane. Although the Pt catalyst has the advantages of high propane conversion and good propylene selectivity, in addition to the high price of Pt, there are more serious problems such as the sintering of Pt particles at high temperature, the reduction of active catalytic sites due to coking, the rapid deactivation of the catalyst, and even irreversible deactivation. In view of this, people improve the catalytic performance of Pt-based catalysts by selectively adding a second active component (i.e. an additive) to the catalyst. The additive forms an alloy with Pt, inhibits propylene adsorption in the propane dehydrogenation reaction, reduces side reactions, and controls the amount of coking, thereby improving the activity and selectivity of the catalyst. The most commonly used metal additives are tin (Sn), gallium (Ga), zinc (Zn), copper (Cu), cerium (Ce) and lanthanum (La) and the like. It is generally believed that the additive improves the selectivity of propylene due to the electronic effect. In the alloy catalyst, the additive transfers electrons to Pt, so that the surface of Pt has a negative charge, thereby improving the selectivity of propylene. In addition, the additive can also inhibit the deposition of coke and delay the deactivation rate of the catalyst.

[0004] For oxidative dehydrogenation reaction, an effective catalyst not only needs to selectively activate C-H bond and inhibit C-C cleavage, but also needs to have affinity for the activation of oxidant. As a typical acidic molecule, CO2 is not as strong as O2 in oxidation (O2 can cause oxidation of alkanes or alkenes at high temperature, making the reaction uncontrollable), CO2 molecules will be preferentially adsorbed on the basic sites of the catalyst, and propane tends to be adsorbed on the acidic sites. Therefore, a catalyst with appropriate acidity and basicity is also a key factor to obtain satisfactory catalytic performance. So far, CrO x Based materials are considered to be the most promising catalysts in oxidative dehydrogenation reaction due to their high activity. It is generally believed that during the reaction, propane is dehydrogenated to propylene on the tetrahedral Cr 6+ site, while being reduced to octahedral Cr 3+ . The reduced Cr 3+ can be re-oxidized to Cr 6+ , thus completing the redox cycle. At low Cr content, the reduced Cr 3+ can migrate to form Cr2O3 clusters, which can be further reduced to Cr 2+ by H2 generated in situ. Deeply reduced Cr 2+ has a strong adsorption capacity for CO2 and is re-oxidized to Cr 3+ by CO2, while forming CO. Therefore, the catalytic performance of CrO x based catalysts is related to the dispersion of catalytically active species and the interaction between catalytically active sites and supports. However, the inherent toxicity of CrO x and serious side reactions greatly hinder its application in industrial production. In addition to Cr, metals such as Fe, V, Co, In, etc. are also commonly used in the study of propane oxidative dehydrogenation. These metals can exhibit both oxidation and reduction due to the presence of multiple valence states during the reaction, which is beneficial to catalyze different reaction processes, but the catalytic mechanism of these catalysts in oxidative dehydrogenation is not clear, and high-performance commercial catalysts cannot be designed through reaction mechanism and catalyst structure.

[0005] Because the reaction mechanisms of direct dehydrogenation and oxidative dehydrogenation are not the same, and the catalytic mechanisms of different catalysts are also not the same, direct dehydrogenation catalysts are not suitable for oxidative dehydrogenation reaction, and vice versa. Even if it shows catalytic effect, it is very likely that only direct dehydrogenation reaction occurs (i.e. CO2 does not participate in the reaction).

[0006] Therefore, the mainstream catalysts which are currently studied have the following problems: (1) the catalyst activity problem, which is affected by carbon deposition and sintering and deactivates quickly; (2) the CO2 activation ability of some catalysts is not strong, which slows down the redox cycle; (3) most catalysts do not have the ability to be used for catalyzing direct dehydrogenation and oxidative dehydrogenation of propane at the same time. Therefore, there is an urgent need in the field to develop a catalyst which has excellent catalytic effect, high catalytic selectivity and can be used for catalyzing direct dehydrogenation and oxidative dehydrogenation of propane at the same time. SUMMARY

[0007] The purpose of the present application is to provide a confined catalyst which can be used for catalyzing direct dehydrogenation and oxidative dehydrogenation of propane at the same time, and a preparation method and application thereof, so as to solve the problems of the existing catalysts, such as low catalytic effect, easy deactivation, poor catalytic selectivity and inability to be used for catalyzing direct dehydrogenation and oxidative dehydrogenation of propane at the same time.

[0008] In order to achieve the above purpose, the present application adopts the following technical solutions:

[0009] The present application provides a preparation method of a confined catalyst which can be used for catalyzing direct dehydrogenation and oxidative dehydrogenation of propane at the same time, comprising the following steps:

[0010] (1) reacting silicon-aluminum oxide and a grafting agent to obtain intercalated silicon-aluminum oxide;

[0011] (2) grafting reaction of the intercalated silicon-aluminum oxide and a methanol solution, repeating the grafting reaction for 3 times to obtain methoxyl grafted silicon-aluminum oxide;

[0012] (3) sequentially reacting and calcining the methoxyl grafted silicon-aluminum oxide and a long-chain organic matter solution to obtain a silicon-aluminum oxide carrier with a curled structure;

[0013] (4) modifying the silicon-aluminum oxide carrier with a curled structure, a modifier and water to obtain a modified silicon-aluminum oxide carrier;

[0014] (5) sequentially mixing, drying and calcining an iron source, the modified silicon-aluminum oxide carrier and a solvent to obtain iron-loaded silicon-aluminum oxide;

[0015] (6) modifying the iron-loaded silicon-aluminum oxide, a modifier and water to obtain modified iron-loaded silicon-aluminum oxide;

[0016] (7) sequentially mixing, drying and calcining a platinum source, the modified iron-loaded silicon-aluminum oxide and a solvent to obtain a platinum-iron catalyst with a curled structure.

[0017] Preferably, the silicon-aluminum oxide is sequentially dried and sieved before being reacted; the drying temperature is 50-70℃, and the drying time is 1.5-2.5h; the mesh size of the sieve used for sieving is 80-150 meshes.

[0018] As preferred, in the step (1), the grafting agent is dimethyl sulfoxide and / or N-methyl pyrrolidone; the mass-volume ratio of the silicon-aluminum oxide and the grafting agent is 8-12 g: 15-30 mL; the reaction temperature is 50-70℃; the specific steps of the reaction are: first ultrasonic reaction and then stirring reaction; the ultrasonic reaction frequency is 30-50 kHz, and the ultrasonic reaction time 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.

[0019] As preferred, in the step (2), the concentration of the methanol solution is 0.8-1.2 mol / L; the mass-volume ratio of the intercalated silicon-aluminum oxide and the methanol solution is 4-6 g: 50 mL; the stirring speed of the grafting reaction is 2-4 r / s, and the grafting reaction time is 22-26 h; after each grafting reaction is completed, the obtained product is centrifuged; the centrifugal speed is 7000-10000 r / min, and the centrifugal time is 5-10 min.

[0020] As preferred, 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 mixture of long-chain organic matter and methanol; the long-chain organic matter is one or more of cetyltrimethylammonium chloride, 3-aminopropyltrimethoxysilane, and tetrabutylammonium chloride; the mass-volume ratio of the methoxy-grafted silicon-aluminum oxide and 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 calcination temperature is 350-450℃, and the calcination time is 3-5 h.

[0021] As preferred, in the step (4), the mass ratio of the silicon-aluminum oxide carrier with a curled structure, the modifier, and water is 1-3: 0.5-1: 40-60; in the step (6), the mass ratio of the iron-loaded silicon-aluminum oxide, the modifier, and water is 1-3: 0.5-1: 40-60; in the steps (4) and (6), the modifier is independently cetyltrimethylammonium bromide and / or 3-aminopropyltriethoxysilane; the modification temperature is independently 50-70℃, and the modification time is independently 4-6 h.

[0022] As preferred, in the step (5), the iron source is ferric nitrate nonahydrate or iron acetylacetonate; the mass-volume ratio of the iron source, the modified silicon-aluminum oxide carrier, and the solvent is 0.0316-0.1447 g: 1 g: 15-25 mL; in the step (7), the platinum source is chloroplatinic acid hexahydrate; the mass-volume ratio of the platinum source, the modified iron-loaded silicon-aluminum oxide, and the solvent is 0.0265 g: 1 g: 15-25 mL.

[0023] Preferably, in steps (5) and (7), the solvent is ethanol; the mixing time is independently 8-12 h, the mixing stirring speed is independently 8-10 r / s; the drying temperature is independently 50-80℃, the drying time is independently 10-14 h; the calcination temperature rising rate is independently 1-2℃ / min, the calcination temperature is independently 580-620℃, and the calcination time is independently 4-6 h.

[0024] The application further provides a preparation method of the confined catalyst capable of being used for direct dehydrogenation and oxidative dehydrogenation of propane.

[0025] The application further provides application of the confined catalyst in direct dehydrogenation and oxidative dehydrogenation of propane.

[0026] Compared with the prior art, the application has the following beneficial effects:

[0027] (1) The application provides a supported catalyst with a curled structure capable of being used for direct dehydrogenation and oxidative dehydrogenation of propane, which can be used in direct dehydrogenation and oxidative dehydrogenation of propane and solves the problems of low thermal stability and narrow application range of the prior catalysts.

[0028] (2) The application uses a modifier to modify the silicon-aluminum oxide carrier with a curled structure, and then impregnates the modified carrier in an active metal solution, so that the active metal is loaded in a specific position in the impregnation process, thereby improving the selectivity and stability of the catalyst.

[0029] (3) The application introduces transition metal iron and limits the iron in a specific space, so that the catalyst can be used for direct dehydrogenation of propane and oxidative dehydrogenation of propane, thereby expanding the application range of the catalyst. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only embodiments of the application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of the provided drawings.

[0031] Figure 1 The figure shows the relationship between the propane conversion rate and the propylene selectivity of the platinum-iron catalyst with a curled structure obtained in Example 1 and the reaction time.

[0032] Figure 2 Figure showing the relationship between the propane conversion and propylene selectivity of the platinum-iron catalyst with a curled structure obtained in Example 2 and the reaction time;

[0033] Figure 3 Figure showing the relationship between the propane conversion and propylene selectivity of the platinum-iron catalyst with a curled structure obtained in Example 3 and the reaction time;

[0034] Figure 4 Figure showing the relationship between the propane conversion and propylene selectivity of the platinum-iron catalyst with a curled structure obtained in Example 4 and the reaction time;

[0035] Figure 5 Figure showing the relationship between the propane conversion and propylene selectivity of the platinum-iron catalyst with a curled structure obtained in Example 5 and the reaction time;

[0036] Figure 6 Figure showing the relationship between the propane conversion and propylene selectivity of the platinum-iron catalyst with a curled structure obtained in Example 6 and the reaction time;

[0037] Figure 7 Figure showing the relationship between the propane conversion and propylene selectivity of the platinum-iron catalyst with a curled structure obtained in Example 7 and the reaction time;

[0038] Figure 8 Figure showing the relationship between the propane conversion and propylene selectivity of the platinum-iron catalyst with a curled structure obtained in Comparative Example 1 and the reaction time;

[0039] Figure 9 Figure showing the relationship between the propane conversion and propylene selectivity of the platinum-iron catalyst with a curled structure obtained in Comparative Example 2 and the reaction time. DETAILED DESCRIPTION

[0040] The present application provides a preparation method of a confined catalyst which can be used for direct dehydrogenation and oxidative dehydrogenation of propane, comprising the following steps:

[0041] (1) reacting silicon-aluminum oxide and a grafting agent to obtain intercalated silicon-aluminum oxide;

[0042] (2) grafting the intercalated silicon-aluminum oxide with a methanol solution, repeating the grafting reaction for 3 times to obtain methoxy grafted silicon-aluminum oxide;

[0043] (3) sequentially reacting and calcining the methoxy grafted silicon-aluminum oxide and a long-chain organic solution to obtain a silicon-aluminum oxide carrier with a curled structure;

[0044] (4) modifying the silicon-aluminum oxide carrier with a curled structure with a modifier and water to obtain a modified silicon-aluminum oxide carrier;

[0045] (5) mixing, drying and calcining the iron source, the modified silicon-aluminum oxide carrier and the solvent in sequence to obtain the silicon-aluminum oxide loaded with iron;

[0046] (6) modifying the silicon-aluminum oxide loaded with iron, the modifier and water to obtain the modified silicon-aluminum oxide loaded with iron;

[0047] (7) mixing, drying and calcining the platinum source, the modified silicon-aluminum oxide loaded with iron and the solvent in sequence to obtain the platinum-iron catalyst with a curled structure.

[0048] In the present application, the preparation of the silicon-aluminum oxide comprises the following steps:

[0049] (a) mixing a tetraethylammonium hydroxide solution, sodium aluminate and sodium hydroxide to obtain a mixed solution; (b) sequentially adding fumed silica and silica to the mixed solution, and then performing heat treatment to obtain a crystal seed; (c) mixing the crystal seed, cetyltrimethylammonium bromide and water, and then sequentially performing heat treatment, drying and calcination to obtain the silicon-aluminum oxide.

[0050] In the above 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 further preferably 25-28%; the mass ratio of the tetraethylammonium hydroxide solution, sodium aluminate and sodium hydroxide is preferably 30:0.4-0.5:0.15-0.2, and further preferably 30:0.45-0.48:0.16-0.18; the mixing temperature is preferably room temperature; the mixing time is preferably 8-12 min, and further preferably 10-11 min; and the mixing stirring speed is preferably 8-12 r / s, and further preferably 9-10 r / s.

[0051] In the above step (b), the mass ratio of sodium aluminate, fumed silica and silica is preferably 0.4-0.5:1:8-10, and further preferably 0.48-0.49:1:9-9.5; the specific steps for sequentially adding fumed silica and silica are as follows: fumed silica is first added to the mixed solution, mixed for 4-8 min, then silica is added, mixed until clear, and then heat treatment is performed; the mixing stirring speed is preferably 8-12 r / s, and further preferably 9-10 r / s; the heat treatment temperature is preferably 120-160℃, and further preferably 140-150℃; and the heat treatment time is preferably 4-6 h, and further preferably 5 h.

[0052] In the step (c), the mass ratio of the seed crystal, the cetyltrimethylammonium bromide and the water is preferably 1-1.5:0.2-0.5:3, and further preferably 1.2-1.4:0.3-0.4:3; the specific steps of mixing the seed crystal, the cetyltrimethylammonium bromide and the water are as follows: after the cetyltrimethylammonium bromide and the water are mixed by ultrasonic, the seed crystal is added and stirred; the frequency of the ultrasonic mixing is preferably 30-50 kHz, and further preferably 40-45 kHz; the time of the ultrasonic mixing is preferably 10-30 min, and further preferably 20-25 min; the temperature of the stirring mixing is preferably room temperature; the stirring speed of the stirring mixing is preferably 8-12 r / s, and further preferably 9-10 r / s; and the time of the stirring mixing is preferably 20-40 min, and further preferably 30-35 min.

[0053] In the step (c), the temperature of the heat treatment is preferably 130-150℃, and further preferably 135-140℃; the time of the heat treatment is preferably 2.5-3.5 d, and further preferably 3 d; after the heat treatment, the obtained product is sequentially filtered, centrifuged and washed; the rotating speed of the centrifugation is preferably 7000-10000 r / min, and further preferably 8000-9000 r / min; the reagent used for the washing is preferably water; the temperature of the drying is preferably 90-110℃, and further preferably 100-105℃; the time of the drying is preferably 4.5-5.5 d, and further preferably 5 d; the temperature of the calcination is preferably 400-600℃, and further preferably 450-500℃; and the time of the calcination is preferably 4.5-5.5 h, and further preferably 5 h.

[0054] In the present application, the silicon-aluminum oxide is sequentially dried and sieved before the reaction; the undersize after the sieving is used for the reaction; the temperature of the drying is preferably 50-70℃, and further preferably 60-65℃; the time of the drying is preferably 1.5-2.5 h, and further preferably 2 h; and the mesh size of the screen used for the sieving is preferably 80-150 mesh, and further preferably 100-120 mesh.

[0055] In the step (1) of the present application, the grafting agent is preferably dimethyl sulfoxide and / or N-methyl pyrrolidone; the mass-volume ratio of the silicon-aluminum oxide and the grafting agent is preferably 8-12 g: 15-30 mL, further preferably 9-10 g: 20-25 mL; the reaction temperature is preferably 50-70℃, further preferably 60-65℃; the specific steps of the reaction are: first ultrasonic reaction and then stirring reaction; the ultrasonic reaction frequency is preferably 30-50 kHz, further preferably 40-45 kHz; the ultrasonic reaction time is preferably 20-40 min, further preferably 30-35 min; the stirring speed of the stirring reaction is preferably 2-4 r / s, further preferably 3 r / s; the stirring reaction time is preferably 22-26 h, further preferably 24-25 h.

[0056] In the step (1) of the present application, after the reaction is completed, the obtained product is dried; the drying temperature is preferably 40-60℃, further preferably 50-55℃.

[0057] In the step (2) of the present application, the concentration of the methanol solution is preferably 0.8-1.2 mol / L, further preferably 1-1.1 mol / L; the mass-volume ratio of the intercalated silicon-aluminum oxide and the methanol solution is preferably 4-6 g: 50 mL, further preferably 5-5.5 g: 50 mL; the stirring speed of the grafting reaction is preferably 2-4 r / s, further preferably 3 r / s; the grafting reaction time is preferably 22-26 h, further preferably 24-25 h; after each grafting reaction is completed, the obtained product is centrifuged; the centrifugal speed is preferably 7000-10000 r / min, further preferably 8000-9000 r / min; the centrifugal time is preferably 5-10 min, further preferably 6-8 min.

[0058] In the step (3) of the present application, the concentration of the long-chain organic solution is preferably 0.8-1.2 mol / L, further preferably 0.9-1 mol / L; the long-chain organic solution is a mixture of long-chain organic matter and methanol; the long-chain organic matter is preferably one or more of cetyltrimethylammonium chloride, 3-aminopropyltrimethoxysilane and tetrabutylammonium chloride; the mass-volume ratio of the methoxyl-grafted silicon-aluminum oxide and the long-chain organic solution is preferably 1.5-2.5 g: 25-40 mL, further preferably 1.8-2 g: 30-35 mL; the stirring speed of the reaction is preferably 2-4 r / s, further preferably 3 r / s; the reaction time is preferably 22-26 h, further preferably 23-24 h; the calcination temperature is preferably 350-450℃, further preferably 380-400℃; the calcination time is preferably 3-5 h, further preferably 4-4.5 h.

[0059] In step (3) of the present application, after the reaction is completed, the obtained product is sequentially washed and air-dried at room temperature; the reagent used for washing is preferably anhydrous ethanol; the number of washing is preferably 2-4 times, and more preferably 3 times.

[0060] In step (4) of the present application, the mass ratio of the silicon-aluminum oxide carrier with curled structure, the modifier and water is preferably 1-3:0.5-1:40-60, and more preferably 1.5-2:0.7-0.9:50-55; the specific step of modifying the silicon-aluminum oxide carrier with curled structure, the modifier and water is mixing the silicon-aluminum oxide carrier with curled structure and water to form a suspension, and then adding the modifier.

[0061] In step (6) of the present application, the mass ratio of the iron-loaded silicon-aluminum oxide, the modifier and water is preferably 1-3:0.5-1:40-60, and more preferably 1.6-2:0.8-0.9:50-52; the specific step of modifying the iron-loaded silicon-aluminum oxide, the modifier and water is mixing the iron-loaded silicon-aluminum oxide and water to form a suspension, and then adding the modifier.

[0062] In step (4) and step (6) of the present application, the modifier is independently preferably hexadecyl trimethyl ammonium bromide and / or 3-aminopropyl triethoxysilane; the modification temperature is independently preferably 50-70°C, and more preferably 60-65°C; the modification time is independently preferably 4-6h, and more preferably 5-5.5h.

[0063] In step (4) and step (6) of the present application, after the modification is completed, the obtained product is sequentially filtered, washed and dried; the reagent used for washing is preferably water; the number of washing is independently preferably 2-4 times, and more preferably 3 times; the drying temperature is preferably 40-60°C, and more preferably 50-55°C.

[0064] In step (5) of the present application, the iron source is preferably ferric nitrate nonahydrate or iron 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 0.0362-0.1447g:1g:15-25mL, and more preferably 0.05-0.1g:1g:20-22mL; when the iron source is iron acetylacetonate, the mass-volume ratio of the iron source, the modified silicon-aluminum oxide carrier and the solvent is preferably 0.0316-0.1265g:1g:15-25mL, and more preferably 0.04-0.12g:1g:20-22mL; the specific step of mixing the iron source, the modified silicon-aluminum oxide carrier and the solvent is mixing the iron source and part of the solvent to obtain a mixed solution, mixing the modified silicon-aluminum oxide carrier and the remaining solvent to obtain a suspension, and mixing the suspension and the mixed solution; the amount of the part of the solvent is preferably 1 / 2 of the total amount of the solvent.

[0065] In step (7) of the present application, the platinum source is preferably chloroplatinic acid hexahydrate; the mass-volume ratio of the platinum source, the modified iron-loaded silicon-aluminum oxide and the solvent is preferably 0.0265 g:1 g:15-25 mL, and further preferably 0.0265 g:1 g:20-22 mL; the specific steps for mixing the platinum source, the modified iron-loaded silicon-aluminum oxide and the solvent are as follows: mixing the platinum source and part of the solvent to obtain a mixed solution; mixing the modified iron-loaded silicon-aluminum oxide and the remaining solvent to obtain a suspension; mixing the suspension and the mixed solution; and the amount of the part of the solvent is preferably 1 / 2 of the total amount of the solvent.

[0066] In step (5) and step (7) of the present application, the solvent is preferably ethanol; the mixing time is independently preferably 8-12 h, and further preferably 10-11 h; the stirring speed of mixing is independently preferably 8-12 r / s, and further preferably 9-10 r / s; the mixing here refers to the mixing between the suspension and the mixed solution; the drying temperature is independently preferably 50-80℃, and further preferably 60-70℃; the drying time is independently preferably 10-14 h, and further preferably 11-12 h; the temperature rising rate of calcination is independently preferably 1-2℃ / min, and further preferably 1.5℃ / min; the calcination temperature is independently preferably 580-620℃, and further preferably 590-600℃; and the calcination time is independently preferably 4-6 h, and further preferably 5-5.5 h.

[0067] The present application prepares a silicon-aluminum oxide carrier with a curled structure, and uses the silicon-aluminum oxide carrier with a curled structure, uses a modifier to modify the carrier, and then impregnates an active metal solution, which is beneficial to the loading of the active metal in a specific position in the impregnation process. Meanwhile, a transition metal iron is introduced and limited in a specific space, so that the prepared limited catalyst is used for direct dehydrogenation and oxidative dehydrogenation of propane, and the application range of the catalyst is expanded.

[0068] The present application also provides a preparation method of the limited catalyst which can be used for direct dehydrogenation and oxidative dehydrogenation of propane, and the limited catalyst prepared by the preparation method; the limited catalyst is a platinum-iron catalyst with a curled structure; the limited catalyst takes platinum as an active component and iron as an additive; and the loading amount of platinum is preferably 1 wt% based on the mass of the modified silicon-aluminum oxide carrier in the limited catalyst; and the loading amount of iron is preferably 0.5-2 wt%, and further preferably 1-1.5 wt%.

[0069] The present application also provides the application of the limited catalyst in direct dehydrogenation and oxidative dehydrogenation of propane.

[0070] The technical solutions provided by the present application are described in detail below in conjunction with the examples, but they should not be understood as limiting the scope of protection of the present application.

[0071] In the following examples and comparative examples, the activity of platinum-iron catalysts in the direct dehydrogenation of propane is expressed in terms of propane conversion and propylene selectivity, and the calculation formula is as follows:

[0072]

[0073]

[0074] The activity of platinum-iron catalysts in the oxidative dehydrogenation of propane is expressed in terms of propane conversion and propylene selectivity, and the calculation formula is as follows:

[0075]

[0076]

[0077] Example 1

[0078] (1) 30 g of a 25% mass fraction tetraethylammonium hydroxide aqueous solution, 0.48 g of sodium metaaluminate, and 0.16 g of sodium hydroxide were sequentially added to a 100 mL beaker, stirred at a speed of 8 r / s for 10 min at room temperature, then 1 g of fumed silica was added thereto at the same stirring speed, stirred for 5 min, then 9 g of silica was added, and after stirring to clarify, it was loaded into a 50 mL reaction kettle and placed in an oven, reacted at 140°C for 5 h, and then cooled to room temperature to obtain a light yellow viscous seed crystal;

[0079] (2) 2.5 g of cetyltrimethylammonium bromide was added to 15 g of deionized water, ultrasonically treated (ultrasonic frequency 40 kHz) for 20 min, then the solution was clarified, 6 g of seed crystal was added, stirred at a speed of 8 r / s for 30 min at room temperature, loaded into a reaction kettle and placed in an oven, and kept at 140°C for 3 d; the product was filtered, centrifuged at a speed of 9000 r / min, washed with water, dried at 100°C for 5 d, and then calcined at 500°C for 5 h in a muffle furnace to obtain a layered silicoalumina oxide;

[0080] (3) 10 g of the silicoalumina oxide was weighed and dried at 60°C for 2 h, sieved through a 100 mesh sieve, and the undersize was taken; 20 mL of N-methylpyrrolidone was added thereto, ultrasonically treated (ultrasonic frequency 40 kHz) at 60°C for 30 min, then stirred at a speed of 3 r / s for 24 h at 60°C, and after the reaction was completed, the sample was directly dried at 50°C to obtain an intercalated silicoalumina oxide;

[0081] (4) Weigh 5 g of the intercalated silicon-aluminum oxide obtained in step (3) and add 50 mL of methanol solution with a concentration of 1 mol / L. Stir at a speed of 3 r / s for 24 h at room temperature to perform the grafting reaction. Remove the methanol after the reaction by centrifugation (at a speed of 9000 r / min), and repeat the above modification and grafting reaction for 3 times to obtain a methoxy grafted silicon-aluminum oxide;

[0082] (5) Weigh 2 g of the methoxy grafted silicon-aluminum oxide obtained in step (4) and add 30 mL of aqueous solution of cetyltrimethylammonium chloride with a concentration of 1 mol / L. Stir at a speed of 3 r / s for 24 h at room temperature. After the reaction, wash with anhydrous ethanol for 3 times, air dry at room temperature, and calcine at 400 °C for 4 h to obtain a silicon-aluminum oxide carrier with a curly structure;

[0083] (6) At room temperature, mix 2 g of the silicon-aluminum oxide carrier with a curly structure and 50 g of deionized water at a speed of 8 r / s to disperse the carrier to form a suspension, and then add 0.9 g of cetyltrimethylammonium bromide. Stir at a speed of 8 r / s for 4 h at 60 °C to fully modify; filter the obtained product, wash with water, and dry at 60 °C to obtain a modified silicon-aluminum oxide carrier;

[0084] (7) Weigh 0.0724 g of iron nitrate nonahydrate and 10 mL of anhydrous ethanol, and stir at a speed of 8 r / s until the iron nitrate nonahydrate is dissolved to obtain a mixed solution. Weigh 1 g of the modified silicon-aluminum oxide carrier obtained in step (6) and add to 10 mL of anhydrous ethanol to stir at a speed of 8 r / s to obtain a suspension. Add the mixed solution to the suspension, stir at a speed of 100 r / s for 12 h, dry at 80 °C for 12 h, and then calcine at 400 °C for 4 h at a temperature rising rate of 1 °C / min to obtain an iron-loaded silicon-aluminum oxide;

[0085] (8) At room temperature, add the iron-loaded silicon-aluminum oxide obtained in step (7) to 50 g of deionized water, and stir at a speed of 8 r / s to disperse the carrier to form a suspension. Then add 0.9 g of cetyltrimethylammonium bromide, and stir at a speed of 8 r / s for 4 h at 60 °C to fully modify. Filter the obtained product, wash with water, and dry at 60 °C to obtain a modified iron-loaded silicon-aluminum oxide;

[0086] (9) 2.65 mL of an aqueous solution of chloroplatinic acid hexahydrate with a concentration of 0.01 g / mol is measured and added to 10 mL of anhydrous ethanol to mix at a speed of 4 r / s to obtain a mixed solution; 1 g of the modified iron-loaded silica-alumina oxide obtained in step (8) is added to 10 mL of anhydrous ethanol to mix at a speed of 8 r / s to obtain a suspension; the mixed solution is added to the suspension, and stirred at a speed of 8 r / s for 12 h, dried at 80°C for 12 h, and then calcined at 400°C for 4 h at a temperature rising rate of 1°C / min to obtain a platinum-iron catalyst with a coiled structure, with a platinum loading of 1 wt% and an iron loading of 1 wt%.

[0087] The catalytic performance of the platinum-iron catalyst obtained in this example is detected by the following method:

[0088] The platinum-iron catalyst is ground and sieved, and platinum-iron catalysts with a mesh size of 80-100 are selected. 200 mg of the platinum-iron catalyst is loaded into a fixed bed reactor, nitrogen is introduced, and the temperature is raised to 580°C. After reduction with hydrogen for 1 h, the hydrogen is switched to propane for direct dehydrogenation of propane, and the reaction is carried out for 8 h. The flow ratio of propane to nitrogen in the raw gas is 1:4, and the space velocity is 7500 mL / (g·h). The reaction products are analyzed online by a Fuli 7970 II gas chromatograph. The relationship between propane conversion and propylene selectivity and reaction time is shown in Figure 1 , and the propane conversion and propylene selectivity are shown in Table 1.

[0089] Example 2

[0090] The difference from Example 1 is that the long-chain organic matter is 3-aminopropyltrimethoxysilane, and the others are the same as in Example 1.

[0091] The catalytic performance of the platinum-iron catalyst obtained in this example is detected by the same method as in Example 1, and the reaction products are analyzed online by a Fuli 7970 II gas chromatograph. The relationship between propane conversion and propylene selectivity and reaction time is shown in Figure 2 , and the propane conversion and propylene selectivity are shown in Table 1.

[0092] Example 3

[0093] The difference from Example 1 is that the long-chain organic matter is tetrabutylammonium chloride, and the others are the same as in Example 1.

[0094] The catalytic performance of the platinum-iron catalyst obtained in this example is detected by the same method as in Example 1, and the reaction products are analyzed online by a Fuli 7970 II gas chromatograph. The relationship between propane conversion and propylene selectivity and reaction time is shown in Figure 3 , and the propane conversion and propylene selectivity are shown in Table 1.

[0095] Example 4

[0096] The difference between the example 2 and the example 3 is that the grafting agent is dimethyl sulfoxide, and the others are the same as the example 2.

[0097] The catalytic performance of the platinum-iron catalyst obtained in the example 3 is detected, and the detection method is the same as the example 2. The reaction product is analyzed on-line by using a Fuli7970 II gas chromatograph. The relationship between the propane conversion rate and the propylene selectivity and the reaction time is shown in FIG. 2, and the propane conversion rate and the propylene selectivity are shown in Table 1. Figure 4

[0098] Example 5

[0099] The difference between the example 5 and the example 4 is that the modifier is 3-aminopropyl triethoxysilane, and the others are the same as the example 4.

[0100] The catalytic performance of the platinum-iron catalyst obtained in the example 5 is detected, and the detection method is the same as the example 4. The reaction product is analyzed on-line by using a Fuli7970 II gas chromatograph. The relationship between the propane conversion rate and the propylene selectivity and the reaction time is shown in FIG. 4, and the propane conversion rate and the propylene selectivity are shown in Table 1. Figure 5

[0101] Example 6

[0102] The difference between the example 6 and the example 5 is that the iron source is acetylacetone iron, and the others are the same as the example 5.

[0103] The catalytic performance of the platinum-iron catalyst obtained in the example 6 is detected, and the detection method is the same as the example 5. The reaction product is analyzed on-line by using a Fuli7970 II gas chromatograph. The relationship between the propane conversion rate and the propylene selectivity and the reaction time is shown in FIG. 6, and the propane conversion rate and the propylene selectivity are shown in Table 1. Figure 6

[0104] Example 7

[0105] The difference between the example 7 and the example 5 is that the amount of the iron nitrate nonahydrate is 0.1447 g, and the others are the same as the example 5.

[0106] The catalytic performance of the platinum-iron catalyst obtained in the example 7 is detected, and the detection method is as follows:

[0107] The platinum-iron catalyst is ground and sieved, and the platinum-iron catalyst with a mesh size of 80-100 is selected. 200 mg of the platinum-iron catalyst is loaded into a fixed bed reactor, nitrogen is introduced, and the temperature is raised to 580°C. After being reduced for 1 h by introducing hydrogen, the hydrogen is switched to propane and carbon dioxide for reaction. The reaction is carried out for 8 h, and the flow rate ratio of carbon dioxide:propane:nitrogen in the raw material gas is 1:1:4, and the space velocity is 9000 mL / (g·h). The reaction product is analyzed on-line by using a Fuli7970 II gas chromatograph. The relationship between the propane conversion rate and the propylene selectivity and the reaction time is shown in FIG. 8, and the propane conversion rate and the propylene selectivity are shown in Table 1.​​​Figure 7 The results are shown in Table 2.

[0108] Example 8

[0109] The preparation method of the platinum-iron catalyst is the same as that in Example 5.

[0110] The catalytic performance of the platinum-iron catalyst obtained in this example was detected, and the detection method was as follows:

[0111] The platinum-iron catalyst was ground and sieved, and platinum-iron catalysts with mesh sizes of 80-100 were selected. 200 mg of the platinum-iron catalyst was loaded into a fixed bed reactor, nitrogen was introduced, and the temperature was raised to 580°C. After reduction with hydrogen for 1 h, the hydrogen was switched to propane and carbon dioxide for reaction. The reaction was carried out for 8 h, and the flow ratio of carbon dioxide:propane:nitrogen in the raw material gas was 1:1:4, and the space velocity was 9000 mL / (g·h). The reaction products were analyzed online by a Fuli7970 II gas chromatograph, and the propane conversion rate and propylene selectivity are shown in Table 2.

[0112] Comparative Example 1

[0113] 2 g of commercial Al2O3 carrier with model number 043855 produced by Tianjin Alpha Esai Chemical Co., Ltd. was weighed and added to 20 mL of deionized water. The carrier was dispersed by stirring at a speed of 8 r / s, and a solution of iron nitrate nonahydrate was added to control the iron loading at 1 wt.%. After stirring at a speed of 8 r / s for 12 h, it was dried at 80°C for 12 h, and then calcined at 400°C with a temperature rise rate of 1°C / min for 4 h to obtain Fe / Al2O3. 1 g of Fe / Al2O3 was weighed and added to 20 mL of deionized water, and dispersed by stirring at a speed of 8 r / s. A solution of chloroplatinic acid was added to control the Pt loading at 1 wt.%. After stirring at a speed of 8 r / s for 12 h, it was dried at 80°C for 12 h, and then calcined at 400°C with a temperature rise rate of 1°C / min for 4 h to obtain Pt / Fe / Al2O3.

[0114] The catalytic performance of the platinum-iron catalyst obtained in this example was detected, and the detection method was as follows: Figure 8 The results are shown in Table 2.

[0115] Comparative Example 2

[0116] The difference from Comparative Example 1 is that the commercial Al2O3 carrier is replaced by a commercial ZSM-5 carrier with model number NKF-5-130H produced by the Catalyst Factory of Nankai University (Si / Al = 130), and the other steps are the same as those in Comparative Example 1.

[0117] The catalytic performance of the platinum iron catalyst obtained in the present comparative example was detected, and the detection method was the same as that in Comparative Example 1. The reaction products were analyzed on-line by using a Fuli 7970 II gas chromatograph. The relationship between the propane conversion rate and the propylene selectivity and the reaction time is shown in Fig. 1, and the propane conversion rate and the propylene selectivity are shown in Table 1. Figure 9

[0118] Comparative Example 3

[0119] The difference between Example 5 and the present example is that no iron nitrate nine hydrate was added, i.e., steps (7) and (8) in Example 5 were omitted, and the modified iron-loaded silicon-aluminum oxide in step (9) was replaced by the modified silicon-aluminum oxide carrier obtained in step (6). The other steps were the same as those in Example 5.

[0120] The catalytic performance of the platinum catalyst obtained in the present example was detected, and the detection method was as follows:

[0121] The platinum catalyst was ground and sieved, and platinum catalysts with a mesh size of 80-100 were selected. 200 mg of the platinum catalyst was loaded into a fixed bed reactor, nitrogen was introduced, and the temperature was raised to 580°C. After reduction by hydrogen for 1 h, the hydrogen was switched to propane and carbon dioxide for reaction. The reaction was carried out for 8 h, and the flow rate ratio of carbon dioxide:propane:nitrogen in the raw material gas was 1:1:4, and the space velocity was 9000 mL / (g.h). The reaction products were analyzed on-line by using a Fuli 7970 II gas chromatograph, and the propane conversion rate and the propylene selectivity are shown in Table 2.

[0122] The propane conversion rate and the propylene selectivity of the platinum iron catalysts obtained in Examples 1-6 and Comparative Examples 1-2 are shown in Table 1.

[0123] Table 1 Catalytic effect of the platinum iron catalysts obtained in Examples 1-6 and Comparative Examples 1-2 for direct dehydrogenation of propane

[0124]

[0125]

[0126] In Table 1, X0is the initial conversion rate; X f is the final conversion rate; and X is the average conversion rate.

[0127] The propane conversion rate and the propylene selectivity of the platinum iron catalysts obtained in Examples 7-8 and Comparative Example 3 are shown in Table 2.

[0128] Table 2 Catalytic effect of the platinum iron catalysts obtained in Examples 7-8 and Comparative Example 3 for oxidative dehydrogenation

[0129]

[0130] ​From table 1 and table 2, it can be seen that the platinum-iron catalyst with the curl structure obtained by the application can be used for direct dehydrogenation and oxidative dehydrogenation of propane at the same time, and has excellent propane conversion rate and propylene selectivity.

[0131] The above only describes the preferred embodiments of the present application, and it should be pointed out that, for those skilled in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for preparing a confined catalyst that can be used simultaneously for direct dehydrogenation and oxidative dehydrogenation of propane, characterized in that, Includes the following steps: (1) React silicon aluminum oxide and grafting agent to obtain intercalated silicon aluminum oxide; (2) The intercalated silica-alumina oxide and methanol solution were subjected to a grafting reaction, and the grafting reaction was repeated 3 times to obtain methoxy-grafted silica-alumina oxide. (3) The methoxy-grafted silica-alumina oxide and the long-chain organic solution were reacted and calcined in sequence to obtain a silica-alumina oxide support with a coiled structure. (4) Modify the silicon aluminate carrier with a coiled structure, the modifier and water to obtain the modified silicon aluminate carrier; (5) The iron source, the modified silicon-aluminum oxide carrier and the solvent are mixed, dried and calcined in sequence to obtain iron-loaded silicon-aluminum oxide; (6) Modify the iron-loaded silicon-aluminum oxide, modifier and water to obtain modified iron-loaded silicon-aluminum oxide; (7) The platinum source, the modified iron-supported silicon aluminum oxide and the solvent are mixed, dried and calcined in sequence to obtain a platinum iron catalyst with a coiled structure. In step (1), the grafting agent is dimethyl sulfoxide and / or N-methylpyrrolidone; In step (2), the concentration of the methanol solution is 0.8~1.2 mol / L; the mass-to-volume ratio of the intercalated silica-alumina oxide to the methanol solution is 4~6 g:50 mL; the stirring speed of the grafting reaction is 2~4 r / s, and the grafting reaction time is 22~26 h. In step (3), the long-chain organic compound is one or more of hexadecyltrimethylammonium chloride and tetrabutylammonium chloride; the mass-volume ratio of methoxy-grafted silica-alumina oxide to long-chain organic compound solution is 1.5~2.5g:25~40mL; the calcination temperature is 350~450℃, and the calcination time is 3~5h. In steps (4) and (6), the modifiers are independently hexadecyltrimethylammonium bromide and / or 3-aminopropyltriethoxysilane.

2. The method for preparing the confined catalyst according to claim 1, which can be used simultaneously for direct dehydrogenation and oxidative dehydrogenation of propane, is characterized in that, Before the reaction, the silicon-aluminum oxide is dried and sieved sequentially; the drying temperature is 50~70℃ and the drying time is 1.5~2.5h; the sieve used for sieving has an aperture of 80~150 mesh.

3. The method for preparing the confined catalyst according to claim 2, which can be used simultaneously for direct dehydrogenation and oxidative dehydrogenation of propane, is characterized in that, In step (1), the mass-to-volume ratio of silicon aluminum oxide and grafting agent is 8~12g:15~30mL; the reaction temperature is 50~70℃; the specific steps of the reaction are: first, an ultrasonic reaction is carried out, followed by a stirring reaction; the frequency of the ultrasonic reaction is 30~50kHz, and the time of the ultrasonic reaction is 20~40min; the stirring speed of the stirring reaction is 2~4r / s, and the stirring reaction time is 22~26h.

4. The method for preparing the confined catalyst according to any one of claims 1 to 3, which can be used simultaneously for direct dehydrogenation and oxidative dehydrogenation of propane, characterized in that, In step (2), after each grafting reaction, the obtained product is centrifuged; the centrifugation speed is 7000~10000 r / min, and the centrifugation time is 5~10 min.

5. The method for preparing the confined catalyst according to claim 4, which can be used simultaneously for direct dehydrogenation and oxidative dehydrogenation of propane, is characterized in that, In step (3), the stirring speed of the reaction is 2~4 r / s, and the reaction time is 22~26 h.

6. The method for preparing the confined catalyst according to claim 1 or 5, which can be used simultaneously for direct dehydrogenation and oxidative dehydrogenation of propane, characterized in that, In step (4), the mass ratio of the silicon aluminate carrier with a curled structure, the modifier, and water is 1~3:0.5~1:40~60; in step (6), the mass ratio of the silicon aluminate carrier loaded with iron, the modifier, and water is 1~3:0.5~1:40~60; in steps (4) and (6), the modification temperature is 50~70℃ and the modification time is 4~6h.

7. The method for preparing the confined catalyst according to claim 6, which can be used simultaneously for direct dehydrogenation and oxidative dehydrogenation of propane, is characterized in that, In step (5), the iron source is ferric nitrate nonahydrate or ferric acetylacetone; the mass-volume ratio of the iron source, modified silicon aluminate oxide carrier and solvent is 0.0316~0.1447g:1g:15~25mL; in step (7), the platinum source is chloroplatinic acid hexahydrate; the mass-volume ratio of the platinum source, modified silicon aluminate oxide with iron support and solvent is 0.0265g:1g:15~25mL.

8. The method for preparing a confined catalyst according to claim 1 or 7 that can be used simultaneously for direct dehydrogenation and oxidative dehydrogenation of propane, characterized in that, In steps (5) and (7), the solvent is ethanol; the mixing time is 8-12 h, the mixing stirring speed is 8-10 r / s; the drying temperature is 50-80 °C, the drying time is 10-14 h; the calcination heating rate is 1-2 °C / min, the calcination temperature is 580-620 °C, and the calcination time is 4-6 h.

9. The confined catalyst prepared by the method for preparing the confined catalyst according to any one of claims 1 to 8, which can be used simultaneously for direct dehydrogenation and oxidative dehydrogenation of propane, is characterized in that... The confined catalyst is a platinum-iron catalyst with a coiled structure; the confined catalyst uses platinum as the active component and iron as the promoter; based on the mass of the modified silica-alumina oxide support in the confined catalyst, the platinum loading is 1 wt% and the iron loading is 0.5~2 wt%.

10. The application of the confined catalyst of claim 9 in direct dehydrogenation and oxidative dehydrogenation of propane.

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