Hze-5 encapsulated pt series nanoparticle molecular sieve material with different content of auxiliary metal zn and preparation method thereof

Abstract

The application discloses an HZSM-5 encapsulated Pt series nanoparticle molecular sieve material with different contents of auxiliary metal Zn and a preparation method thereof. The preparation method of the molecular sieve material comprises the following steps: uniformly mixing a silicon source, an aluminum source, H2O, an organic template agent, a chloroplatinic acid solution and an auxiliary metal solution to obtain a uniform system; crystallizing the uniform system to obtain a molecular sieve material; drying the molecular sieve after washing to neutral to obtain a dried molecular sieve; reducing the dried molecular sieve by hydrogen to reduce Pt nanoparticles into Pt 0 . The reduced catalyst is subjected to ion exchange, and the ion-exchanged molecular sieve is subjected to high-temperature calcination to remove NH4 + , thereby obtaining an HZSM-5 encapsulated Pt series nanoparticle catalyst. The catalyst has high selectivity for ethylene, propylene, butene and aromatic hydrocarbons and is not easy to deactivate.

Description

Technical Field

[0001] This invention relates to the fields of molecular sieve synthesis and catalytic cracking technology, and in particular to an HZSM-5 encapsulated Pt-based nanoparticle molecular sieve material with different contents of auxiliary metal Zn and its preparation method. Background Technology

[0002] Ethylene, propylene, and other low-carbon olefins are essential raw materials for the petrochemical industry, and their output and production capacity represent the level of a country's chemical industry development. Currently, over 95% of the world's ethylene and 66% of its propylene are produced through naphtha-based steam cracking processes. However, this process requires high reaction temperatures (800-900℃), has the highest energy consumption in the petrochemical industry, and produces low yields of the desired low-carbon olefins, placing stringent demands on equipment. Compared to steam cracking, catalytic cracking, due to the introduction of catalysts, can significantly reduce reaction temperatures and process energy consumption, and effectively improve the selectivity of low-carbon olefins, especially propylene, thus attracting widespread attention in recent years.

[0003] Alkanes are the most abundant component of petroleum hydrocarbons, and research on the catalytic cracking of alkanes, especially light alkanes, has always been highly favored. On the one hand, the reaction properties of alkanes can, to some extent, reflect the overall cracking law of petroleum hydrocarbon feedstocks; on the other hand, as a difficult-to-crack component among alkanes, the C-C bonds and CH bonds of light alkanes are difficult to activate, and their current utilization rate in chemical industry is low. In particular, with the current situation of the increase in the gasoline-diesel ratio in the domestic petroleum processing industry and the resulting high content of light alkanes in products, their optimized utilization urgently needs to be solved. Among them, the use of catalytic cracking to convert light alkanes into low-carbon olefins and aromatics is a very promising solution.

[0004] C4 alkane catalytic cracking is a reaction that occurs with the participation of a catalyst. The distribution of cracking products is affected not only by the reaction conditions but also by the properties of the catalyst. Therefore, the development of efficient catalysts is the key to catalytic cracking technology.

[0005] Because light n-alkanes have relatively high carbon-carbon bond energies and relatively stable chemical properties, using molecular sieves as the sole active component in catalytic cracking cannot maximize the conversion of C4 hydrocarbons. Introducing metals into molecular sieves allows light n-alkanes to first undergo dehydrogenation at the metal site to generate olefins, which then undergo further catalytic conversion at acidic sites to obtain the target product. Therefore, using metal-molecular sieve bifunctional catalysts is one way to achieve efficient conversion of light hydrocarbons. In the catalytic cracking process, introducing a small amount of dehydrogenation active component into the molecular sieve to form a bifunctional catalyst is one way to improve the conversion of light alkanes. Currently, there are two main types of isobutane direct dehydrogenation catalysts used in industry: Cr-based catalysts and Pt-based catalysts. Cr-based catalysts are relatively inexpensive, but suffer from serious carbon deposition and environmental problems. Although platinum is expensive and has low abundance, Pt-based catalysts remain one of the best catalysts for non-oxidative dehydrogenation of alkanes due to their excellent CH bond breaking ability, high reactivity, and stability.

[0006] Based on this, the present invention attempts to modify Pt@HZSM-5 molecular sieve by changing the content of the auxiliary metal Zn, synthesizes encapsulated platinum nanoparticle catalysts using a one-pot method, and applies them to the catalytic reaction of C4 cracking. By adjusting the content of the auxiliary metal Zn, the encapsulated Pt nanoparticle catalysts are modified to further improve the catalytic performance of HZSM-5 encapsulated Pt nanoparticle catalysts for C4 cracking and improve the selectivity of ethylene, propylene, butene and aromatic hydrocarbons. Summary of the Invention

[0007] In view of this, the present invention discloses an HZSM-5 encapsulated Pt-based nanoparticle molecular sieve material with different contents of auxiliary metal Zn and its preparation method. This catalyst effectively improves the catalytic cracking performance of C4 alkanes and increases the production of ethylene, propylene, butene and aromatic hydrocarbons, and will be widely used in the field of catalytic cracking.

[0008] The technical solution provided by this invention is specifically a method for preparing HZSM-5 encapsulated Pt-based nanoparticle molecular sieve materials with different contents of auxiliary metal Zn, characterized by comprising the following steps:

[0009] Step 1: The silicon source, aluminum source, H2O, organic template agent, chloroplatinic acid solution, and auxiliary metal solution are stirred and mixed to obtain a homogeneous system;

[0010] Step 2 involves crystallizing the homogeneous system to obtain Pt-xZn@ZSM-5 molecular sieve;

[0011] Step 3: After centrifuging and washing the molecular sieve until it is neutral, dry it to obtain dry Pt-xZn@ZSM-5 molecular sieve;

[0012] Step 4 involves reducing the dried molecular sieve with hydrogen in a 10% hydrogen-argon mixed atmosphere;

[0013] Step 5 involves ion exchange of the reduced Pt-xZn@ZSM-5 molecular sieve in an ammonium chloride solution using NH4+. + Exchange Na from the original molecular sieve + The sieve was then filtered and washed, and dried at 60°C for 12 hours to obtain dried ion-exchanged Pt-xZn@ZSM-5 molecular sieve.

[0014] Step 6: Remove NH4 from the dried Pt-xZn@ZSM-5 molecular sieve by high-temperature calcination. + Pt-xZn@HZSM-5 catalyst material was obtained.

[0015] Furthermore, the silicon source mentioned in step 1 is tetraethyl orthosilicate.

[0016] Furthermore, the aluminum source mentioned in step 1 is sodium aluminate.

[0017] Furthermore, the organic template agent mentioned in step 1 is tetrapropylammonium hydroxide.

[0018] Furthermore, the auxiliary metal solution mentioned in step 1 is zinc nitrate hexahydrate.

[0019] Furthermore, in step 1, the molar ratio of Si / Al in the homogeneous system is 80, and the homogeneous system also includes Pt, with a mass ratio of Pt to SiO2 of 5:1000.

[0020] Furthermore, the crystallization reaction in step 2 is carried out at a temperature of 170°C for 3 days.

[0021] Furthermore, in step 4, the dried molecular sieve material is reduced with hydrogen in a tube furnace at 400°C under a hydrogen-argon mixed atmosphere.

[0022] Furthermore, in step 5, an ion exchange is performed using a 10% ammonium chloride solution.

[0023] The molar ratios of Zn / Pt in the above materials are 0, 0.05, 0.1, 0.25, 0.5 and 1, respectively.

[0024] This invention provides an HZSM-5 encapsulated Pt-based nanoparticle molecular sieve material with different contents of auxiliary metal Zn and its preparation method. It is a method for preparing a highly efficient catalyst for cracking isobutane. The ZSM-5 molecular sieve encapsulated platinum-zinc nanoparticle catalyst is synthesized in a one-pot method. The resulting material has high selectivity for ethylene, propylene, butene and aromatic hydrocarbons and is not easily deactivated, which has certain practical value and significance.

[0025] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit the disclosure of the present invention. Attached Figure Description

[0026] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 XRD patterns of Pt-xZn@HZSM-5 catalysts with different Zn contents provided in the embodiments of the present invention;

[0029] Figure 2 Transmission electron microscope (TEM) images of the Pt-Zn@HZSM-5 catalyst provided in the embodiments of this invention;

[0030] Figure 3 Transmission electron microscopy (TEM) image of the Pt-0.1Zn@HZSM-5 catalyst with Zn / Pt = 0.1 provided in the embodiments of the present invention;

[0031] Figure 4 The isobutane conversion curves are shown in the embodiments of the present invention, which describe the catalytic cracking of isobutane by Pt-xZn@HZSM-5 catalysts with different Zn contents.

[0032] Figure 5 The following is a graph showing the yield curves of ethylene and propylene catalytic cracking of isobutane using Pt-xZn@HZSM-5 catalysts with different Zn contents, as provided in the embodiments of the present invention.

[0033] Figure 6 The stability curve of the Pt-0.1Zn@HZSM-5 catalyst with Zn / Pt=0.1 provided in the embodiments of the present invention for catalytic cracking of isobutane at 625℃ is shown. Detailed Implementation

[0034] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of methods consistent with some aspects of the invention as detailed in the appended claims.

[0035] This implementation scheme provides a method for synthesizing molecular sieve materials containing Pt-based nanoparticles encapsulated with different amounts of the additive metal HZSM-5, including the following steps:

[0036] The silicon source, aluminum source, H2O, organic template agent, chloroplatinic acid solution, and auxiliary metal solution were stirred and mixed to obtain a homogeneous system;

[0037] The homogeneous system was crystallized to obtain the Pt-xZn@ZSM-5 catalyst;

[0038] The Pt-xZn@ZSM-5 catalyst was centrifuged, washed until neutral, and then dried to obtain a dry Pt-xZn@ZSM-5 catalyst.

[0039] The dried Pt-xZn@ZSM-5 catalyst was reduced with hydrogen in a 10% hydrogen-argon mixed atmosphere to obtain a Pt-xZn@ZSM-5 catalyst containing 0-valent Pt.

[0040] The above-mentioned Pt-xZn@ZSM-5 catalyst containing 0-valent Pt underwent ion exchange in a 10% ammonium chloride solution, followed by calcination in air to remove NH4. + HZSM-5 encapsulated Pt-based nanoparticle catalyst was obtained;

[0041] The silicon source mentioned above is tetraethyl orthosilicate;

[0042] The aluminum source mentioned above is sodium aluminate.

[0043] The aforementioned auxiliary metal is zinc nitrate hexahydrate.

[0044] The aforementioned organic template agent is tetrapropylammonium hydroxide.

[0045] The molar ratios of Zn and Pt are 0, 0.05, 0.1, 0.25, 0.5 and 1, respectively.

[0046] When synthesizing HZSM-5 encapsulated Pt-based nanoparticle molecular sieve materials with different contents of auxiliary metals, the amount of auxiliary metals was changed, and the amount of chloroplatinic acid solution and the silicon-aluminum ratio were also determined. Preferably, SAR=80 and Pt:SiO2=5:1000 are the best conditions for synthesizing HZSM-5 encapsulated Pt-based nanoparticle molecular sieves with different contents of auxiliary metals.

[0047] The crystallization reaction was carried out at 170℃ for 3 days. Experiments have verified that this temperature is the optimal temperature for crystallization.

[0048] In the above technical solution, a one-pot method is used to synthesize Pt-based nanoparticle molecular sieve materials encapsulated with metal ZSM-5 containing different amounts of additives.

[0049] The dried molecular sieve material was subjected to hydrogen reduction at 400℃ in a 10% hydrogen-argon mixed atmosphere for 3.5 hours.

[0050] The molecular sieve after hydrogen reduction undergoes ion exchange with a 10% ammonium chloride solution, followed by high-temperature calcination in a muffle furnace at 550°C.

[0051] at last, Figure 1 The present invention discloses XRD patterns of Pt-xZn@HZSM-5 catalysts with different Zn contents for embodiments. As can be seen from the figures, the characteristic peaks of the Pt-xZn@HZSM-5 catalysts with different Zn contents correspond one-to-one with those of HZSM-5 molecular sieves without any metal, indicating that encapsulating metal does not affect the crystallinity and topology of the molecular sieve.

[0052] Figure 2 Transmission electron microscopy (TEM) images of the Pt@HZSM-5 catalyst provided in the embodiments of this invention. The TEM images show that the metal nanoparticles are uniformly distributed on the HZSM-5 molecular sieve in the Pt@HZSM-5 catalyst.

[0053] Figure 3 Transmission electron microscopy (TEM) images of the Pt-0.1Zn@HZSM-5 catalyst with Zn / Pt = 0.1 provided in the embodiments of this invention. The TEM images show that the metal nanoparticles in the Pt-0.1Zn@HZSM-5 catalyst have a particle size of approximately 2-4 nm and are uniformly dispersed.

[0054] Figure 4 The present invention discloses a conversion curve of isobutane catalytic cracking using Pt-xZn@HZSM-5 catalysts with different Zn contents. The curves show that as the molar ratio of the auxiliary metals Zn and Pt increases, the conversion rate of isobutane also increases.

[0055] Figure 5 The present invention discloses a yield curve of ethylene propylene catalytic cracking of isobutane with Pt-xZn@HZSM-5 catalyst with different Zn contents for embodiments of the present invention. The curve shows that the yield of ethylene propylene is the highest when the molar ratio of auxiliary metal Zn to Pt is 0.1.

[0056] The following embodiments will further illustrate the present invention, but the content of the present invention is not limited to these embodiments.

[0057] Example 1:

[0058] Dissolve 0.01 g of sodium aluminate in 5 ml of water and stir for 10 min until clear. Add 3.1236 g of TPAOH and stir for 10 min to mix thoroughly. Add 2 g of TEOS and stir for 5 hours. Transfer the initial reaction gel to a 25 ml stainless steel hydrothermal reactor lined with polytetrafluoroethylene. Allow to crystallize at 170 °C for 3 days. The ZSM-5 catalyst is obtained.

[0059] The ZSM-5 synthesized in the previous step was centrifuged and washed multiple times to recover the solid product, and then dried in an oven at 60°C for 12 hours to obtain dried ZSM-5.

[0060] The dried sample obtained in the previous synthesis was subjected to ion exchange and stirred thoroughly in a 10% ammonium chloride solution at 80°C for four hours. This process was repeated twice. The sample was then filtered and washed, and dried in an oven at 60°C for 12 hours to obtain the dried ion-exchanged ZSM-5 molecular sieve.

[0061] The dried ion-exchanged ZSM-5 obtained in the previous step was calcined in air in a muffle furnace (conditions: initial temperature 20℃, heating rate of about 1.8℃ / min, heating to 550℃ after 300min, holding at 550℃ for 300min, and final temperature 550℃) to obtain the final catalyst HZSM-5 catalyst.

[0062] Because HZSM-5 has a certain degree of acidity, it is the best choice for cracking isobutane.

[0063] like Figure 1 The XRD pattern shows that the sample is a pure-phase HZSM-5 molecular sieve with good crystallinity.

[0064] Example 2:

[0065] Based on Example 1, 5‰ Pt was introduced into the synthesis system. 0.01 g of sodium aluminate was dissolved in 5 ml of water and stirred for 10 min until clear. 3.1236 g of TPAOH was added and stirred for 10 min to ensure homogeneity. A certain amount of a 10% (w / w) chloroplatinic acid solution and the complex formed by ethylenediamine were added to the above mixture and stirred for 10 min. 2 g of TEOS was added and stirred for 5 hours. The initial reaction gel was transferred to a 25 ml stainless steel hydrothermal reactor lined with polytetrafluoroethylene. The reactor was allowed to crystallize at 170 °C for 3 days. The Pt@ZSM-5 catalyst was obtained.

[0066] The Pt@ZSM-5 synthesized in the previous step was centrifuged and washed multiple times to recover the solid product, and then dried in an oven at 60℃ for 12h to obtain dried Pt@ZSM-5.

[0067] The dried Pt@ZSM-5 obtained in the previous synthesis was directly reduced with hydrogen in a 10% hydrogen-argon mixture (gas flow rate 50 ml / min) (conditions: initial temperature 20℃, heating rate of about 3℃ / min, heating to 400℃ after 120 min, holding at 400℃ for 210 min, and final temperature 400℃).

[0068] The dried sample obtained in the previous synthesis was subjected to ion exchange and stirred thoroughly in a 10% ammonium chloride solution at 80°C for four hours. This process was repeated twice. Then, the sample was filtered and washed, and dried in an oven at 60°C for 12 hours to obtain the dried ion-exchanged Pt@ZSM-5 molecular sieve.

[0069] The dried ion-exchanged Pt@ZSM-5 obtained in the previous step was calcined in air in a muffle furnace (conditions: initial temperature 20℃, heating rate of about 1.8℃ / min, heating to 550℃ after 300min, holding at 550℃ for 300min, and final temperature 550℃) to obtain the final catalyst Pt@HZSM-5 catalyst.

[0070] Pt-based catalysts possess the ability to break CH bonds and exhibit excellent dehydrogenation performance, enabling isobutane to undergo dehydrogenation at the active sites of Pt nanoparticles, converting it into isobutene. Subsequently, it undergoes cracking at the acidic sites of HZSM-5, ultimately yielding basic raw materials for the petrochemical industry such as ethylene and propylene.

[0071] Example 3:

[0072] Based on Example 2, different amounts of auxiliary metal Zn were introduced into the synthesis system. Based on Example 1, 5‰ Pt was introduced into the synthesis system. 0.01 g of sodium aluminate was dissolved in 5 ml of water and stirred for 10 min until clear. 3.1236 g of TPAOH was added and stirred for 10 min to ensure homogeneity. A certain amount of a 10% (w / w) complex formed by chloroplatinic acid solution and ethylenediamine was added to the above mixture and stirred for 10 min. 2 g of TEOS was added and stirred for 5 hours. Subsequently, complexes formed by zinc nitrate hexahydrate solution and ethylenediamine with different amounts were added to the mixture after stirring for 5 hours and stirred for 0.5 hours. The initial reaction gel after stirring was transferred to a 25 ml stainless steel hydrothermal reactor lined with polytetrafluoroethylene. The mixture was allowed to crystallize at 170 °C for 3 days. The Pt-xZn@ZSM-5 catalyst was obtained.

[0073] The Pt-xZn@ZSM-5 synthesized in the previous step was centrifuged and washed multiple times to recover the solid product, and then dried in an oven at 60℃ for 12h to obtain dried Pt-xZn@ZSM-5.

[0074] The dried Pt-xZn@ZSM-5 obtained in the previous synthesis was directly reduced with hydrogen in a 5% hydrogen-argon mixture (gas flow rate 50 ml / min) (conditions: initial temperature 20℃, heating rate of about 3℃ / min, heating to 400℃ after 120 min, holding at 400℃ for 210 min, and final temperature 400℃).

[0075] The dried sample obtained in the previous synthesis was subjected to ion exchange and stirred thoroughly in a 10% ammonium chloride solution at 80°C for four hours. This process was repeated twice. Then, the sample was filtered and washed, and dried in an oven at 60°C for 12 hours to obtain the dried ion-exchanged Pt-xZn@ZSM-5 molecular sieve.

[0076] The dried ion-exchanged Pt-xZn@ZSM-5 obtained in the previous step was calcined in air in a muffle furnace (conditions: initial temperature 20℃, heating rate of about 1.8℃ / min, heating to 550℃ after 300min, holding at 550℃ for 300min, and final temperature 550℃) to obtain the final catalyst Pt-xZn@HZSM-5 catalyst.

[0077] Since molecular sieve materials are commonly used as catalysts, researchers are currently focusing on the preparation of metal nanoparticle catalysts encapsulated in zeolite molecular sieves. This example demonstrates that the HZSM-5 encapsulated Pt-based nanoparticle catalyst materials synthesized using the method described herein possess excellent catalytic cracking capabilities for isobutane.

[0078] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the following claims.

[0079] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. The application of a molecular sieve material in the catalytic cracking of isobutane to produce ethylene and propylene, characterized in that, The molecular sieve material is an HZSM-5 encapsulated Pt-based nanoparticle molecular sieve material with different contents of auxiliary metal Zn, and its preparation method includes the following steps: Step 1: The silicon source, aluminum source, H2O, organic template agent, chloroplatinic acid solution, and auxiliary metal solution are stirred and mixed to obtain a homogeneous system; Step 2 involves crystallizing the homogeneous system to obtain Pt-xZn@ZSM-5 molecular sieve; Step 3: After centrifuging and washing the molecular sieve until it is neutral, dry it to obtain dry Pt-xZn@ZSM-5 molecular sieve; Step 4: The dried molecular sieve is reduced with hydrogen in a 10% hydrogen-argon mixed atmosphere; Step 5 involves ion exchange of the reduced Pt-xZn@ZSM-5 molecular sieve in an ammonium chloride solution using NH4+. + Exchange Na from the original molecular sieve + The sieve was then filtered and washed, and dried at 60°C for 12 hours to obtain dried ion-exchanged Pt-xZn@ZSM-5 molecular sieve. Step 6: Remove NH4 from the dried Pt-xZn@ZSM-5 molecular sieve by high-temperature calcination. + Pt-xZn@HZSM-5 catalyst material was obtained.

2. The application of the molecular sieve material according to claim 1 in the catalytic cracking of isobutane to produce ethylene and propylene, characterized in that, The silicon source mentioned in step 1 is tetraethyl orthosilicate.

3. The application of the molecular sieve material according to claim 1 in the catalytic cracking of isobutane to produce ethylene and propylene, characterized in that, The aluminum source mentioned in step 1 is sodium aluminate.

4. The application of the molecular sieve material according to claim 1 in the catalytic cracking of isobutane to produce ethylene and propylene, characterized in that, The organic template agent mentioned in step 1 is tetrapropylammonium hydroxide.

5. The application of the molecular sieve material according to claim 1 in the catalytic cracking of isobutane to produce ethylene and propylene, characterized in that, The auxiliary metal solution mentioned in step 1 is zinc nitrate hexahydrate.

6. The application of the molecular sieve material according to claim 1 in the catalytic cracking of isobutane to produce ethylene and propylene, characterized in that, In the homogeneous system described in step 1, the molar ratio of Si / Al is 80, and the mass ratio of Pt to SiO2 is 5:1000.

7. The application of the molecular sieve material according to claim 1 in the catalytic cracking of isobutane to produce ethylene and propylene, characterized in that, The crystallization reaction in step 2 is carried out at a temperature of 170°C for 3 days.

8. The application of the molecular sieve material according to claim 1 in the catalytic cracking of isobutane to produce ethylene and propylene, characterized in that, In step 4, the dried molecular sieve material is reduced with hydrogen in a tube furnace at 400°C under a hydrogen-argon mixed atmosphere.

9. The application of the molecular sieve material according to claim 1 in the catalytic cracking of isobutane to produce ethylene and propylene, characterized in that, In step 5, ion exchange is performed using a 10% ammonium chloride solution.

10. The application of the molecular sieve material according to claim 1 in the catalytic cracking of isobutane to produce ethylene and propylene, characterized in that, The molar ratios of Zn / Pt in the materials are 0.05, 0.1, 0.25, and 0.5, respectively.

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