Preparation method of isomerization catalyst and method for catalyzing conversion of olefin isomers

Abstract

The invention relates to the technical field of preparation of catalysts and compounds, in particular to a preparation method of an isomerization catalyst and a method for catalyzing conversion of olefin isomers. The invention provides the preparation method of the isomerization catalyst, the isomerization catalyst is synthesized by utilizing an acid-base co-hydrolysis method, and the provided isomerization catalyst has a strong Lewis metal site, can catalyze an inverse thermodynamic position isomerization reaction for converting internal olefin into terminal olefin, and is beneficial to simply and quickly realizing olefin isomer conversion; therefore, the catalyst is very suitable for being directly applied to the petrochemical / biomass conversion industry.

Description

Technical Field

[0001] This application belongs to the technical field of catalyst and compound preparation, and particularly relates to a preparation method of an isomerization catalyst and a method for catalyzing the conversion of olefin isomers. Background Art

[0002] As a kind of general chemical structural unit, the position isomerization of the C═C double bond of olefins can achieve the mutual conversion of olefin regioisomers, and thus can be further derived into high-value-added compounds. The olefin position isomerization reaction can usually be achieved through the pathways of metal hydrides or π-allyl metals involving polar or radical intermediates. The selectivity of olefin isomerization products can be controlled by thermodynamic or kinetic factors.

[0003] For the thermodynamically driven olefin isomerization reaction, the migration process of the double bond on the carbon chain is reversible, and it is usually the conversion from less stable isomers (such as terminal olefins or non-conjugated olefins) to more stable isomers (such as internal olefins or conjugated olefins). However, obtaining terminal olefins or non-conjugated olefins from internal olefins or conjugated olefins usually requires multiple redox or consecutive deprotonation-protonation processes, as well as the consumption of equivalent chemical reagents to be achieved. The reaction conditions of such methods are relatively harsh and the selectivity is poor, which limits their application in organic synthesis. The remote functionalization strategy can combine reversible chain walking isomerization with irreversible terminal-selective functionalization steps to obtain products of inverse thermodynamic isomerization. However, this method has not been widely combined with various functionalization reactions, and under certain conditions, a de-functionalization process is also required to obtain terminal olefin products. In most cases, terminal olefins and non-conjugated olefins are prepared by olefination of carbonyl equivalents driven by transition metals or main group oxides.

[0004] Therefore, there is an urgent need to provide a catalyst that can be used simply and quickly for catalyzing the conversion of olefin isomers to achieve the conversion of olefin isomers. Summary of the Invention

[0005] The purpose of this application is to provide a preparation method of an isomerization catalyst and a method for catalyzing the conversion of olefin isomers, aiming to solve the problem in the prior art that the conversion of olefin isomers cannot be simply and quickly achieved.

[0006] To achieve the above application purpose, the technical solution adopted in this application is as follows:

[0007] In a first aspect, this application provides a preparation method of an isomerization catalyst, including the following steps:

[0008] Mix a soluble salt of a transition metal and a silicon solution, adjust the pH to acidic, and then carry out a co-hydrolysis condensation reaction to obtain a blended solution;

[0009] Provide an organic template, mix the organic template with a blend solution, and adjust the pH to alkaline before performing a mixing reaction to prepare an alkaline gel;

[0010] Subject the alkaline gel to static crystallization to obtain a crystal sample, mix the crystal sample with zeolite molecular sieve, and then perform a calcination treatment to obtain an isomerization catalyst.

[0011] In a second aspect, the present application provides a method for converting olefin isomers. An isomerization catalyst prepared by the method for preparing an isomerization catalyst is used to catalyze the conversion of various olefin isomers into terminal olefins.

[0012] The method for preparing an isomerization catalyst provided in the first aspect of the present application synthesizes the isomerization catalyst by an acid-base co-hydrolysis method. The provided isomerization catalyst has Lewis metal sites and can catalyze the reverse thermodynamic position isomerization reaction of converting internal olefins into terminal olefins, which is conducive to simply and quickly realizing the conversion of olefin isomers, making the catalyst very suitable for direct application in the petrochemical / biomass conversion industry.

[0013] The method for converting olefin isomers provided in the second aspect of the present application uses the isomerization catalyst prepared by the aforementioned method for preparing an isomerization catalyst to act and catalyze the conversion of various olefin isomers into terminal olefins; due to the use of this isomerization catalyst, it is conducive to realizing the conversion of various different olefin isomers into terminal olefins under the conditions of low temperature in a short time. This method is convenient, fast, green and environmentally friendly, and does not produce other pollutants, which is conducive to wide use. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0015] Figure 1 is the distribution diagram of the catalytic product (C4) of the comparative example of the present application;

[0016] Figure 2 is the SXRD diagram of the isomerization catalysts provided in Example 1 and Example 2 of the present application;

[0017] Figure 3 is the structural schematic diagram of the isomerization catalysts provided in Example 1 and Example 2 of the present application;

[0018] Figure 4 is the EXAFS data of the isomerization catalysts provided in Example 1 and Example 2 of the present application;

[0019] Figure 5It is the graph of the gaseous product change data obtained in Embodiment 3 of this application. Detailed implementation manners

[0020] In order to make the technical problems to be solved, technical solutions and beneficial effects of this application clearer and more understandable, the following further details this application in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not used to limit this application.

[0021] In this application, the term "and / or" describes the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Where A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after.

[0022] In this application, "at least one" means one or more, and "a plurality" means two or more. "At least one (item)" or its similar expression below refers to any combination of these items, including any combination of single item (item) or plural items (items). For example, "at least one (item) of a, b, or c", or, "at least one (item) of a, b, and c" can both represent: a, b, c, a - b (that is, a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively.

[0023] It should be understood that in various embodiments of this application, the magnitude of the serial numbers of the above processes does not mean the sequence of execution. Some or all steps can be executed in parallel or successively. The execution sequence of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of this application.

[0024] The terms used in the embodiments of this application are only for the purpose of describing specific embodiments, and are not intended to limit this application. The singular forms "a" and "the" used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0025] The weights of the relevant components mentioned in the specification of the embodiments of this application can not only refer to the specific contents of each component, but also represent the proportional relationship of the weights between each component. Therefore, as long as the contents of the relevant components in the specification of the embodiments of this application are scaled up or down in proportion, they are within the scope disclosed in the specification of the embodiments of this application. Specifically, the mass in the specification of the embodiments of this application can be mass units well known in the chemical industry such as μg, mg, g, kg, etc.

[0026] The terms "first" and "second" are used only for descriptive purposes to distinguish objects such as substances from each other, and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. For example, without departing from the scope of the embodiments of the present application, the first XX may also be referred to as the second XX, and similarly, the second XX may also be referred to as the first XX. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features.

[0027] The first aspect of the embodiments of the present application provides a method for preparing a heterogeneous catalyst, including the following steps:

[0028] S01. Mix a soluble salt of a transition metal and a silicon solution, adjust the pH to acidic, and then carry out a co-hydrolysis condensation reaction to obtain a blend solution;

[0029] S02. Provide an organic template, mix the organic template with the blend solution, adjust the pH to basic, and then carry out a mixing reaction to prepare a basic gel;

[0030] S03. Carry out static crystallization on the basic gel to obtain a crystal sample, mix the crystal sample with a zeolite molecular sieve, and then carry out a calcination treatment to obtain a heterogeneous catalyst.

[0031] The method for preparing a heterogeneous catalyst provided by the first aspect of the embodiments of the present application uses an acid-base co-hydrolysis method to synthesize a heterogeneous catalyst. The provided heterogeneous catalyst has Lewis metal sites and can catalyze the reverse thermodynamic position isomerization reaction of converting internal olefins into terminal olefins, which is beneficial to simply and quickly realizing the conversion of olefin isomers, making the catalyst very suitable for direct application in the petrochemical / biomass conversion industry.

[0032] In step S01, a soluble salt of a transition metal and a silicon solution are mixed, the pH is adjusted to acidic, and then a co-hydrolysis condensation reaction is carried out to obtain a blend solution.

[0033] In some embodiments, the transition metal includes any one of titanium, chromium, manganese, iron, cobalt, nickel, copper, and zinc; the provided transition metal can be anchored at the framework position of the zeolite molecular sieve, which is beneficial to improving the catalytic activity of the obtained heterogeneous catalyst to promote the in-situ conversion of internal olefins into terminal olefins through a reverse thermodynamic process, and can control the entire conversion process to only require mild reaction conditions without any additional external stimuli, making the catalyst very suitable for direct application in the petrochemical / biomass conversion industry.

[0034] Among them, since the obtained heterogeneous catalyst has Lewis metal sites (3d transition metal single-atom sites), different transition metals can be anchored at the framework position of the zeolite molecular sieve, and can catalyze the reverse thermodynamic position isomerization reaction of converting internal olefins into terminal olefins.

[0035] Moreover, the sites anchored by different transition metals are all different, and the specific anchoring positions are determined according to the properties of the specific transition metals.

[0036] In some embodiments, the soluble salt includes any one of nitrates, sulfates, and hydrochlorides. According to the dissolution conditions of different transition metal salts, a specific soluble salt is further selected for preparation. In some specific embodiments, the soluble salt is selected from nitrates. Selecting nitrates for the reaction is beneficial to improving the catalytic efficiency of the entire preparation process.

[0037] In some embodiments, the silicon solution includes any one of tetraethyl orthosilicate, sodium silicate, and silicon powder. In some specific embodiments, the silicon solution is selected from tetraethyl orthosilicate. Tetraethyl orthosilicate is an organosilicon solution and is used as a reactant in this reaction process to provide silicon atoms, which can be beneficial to improving the reaction efficiency.

[0038] In some embodiments, in the soluble salt of the transition metal, the concentration of the transition metal is 0.01 - 0.02 mol / L; controlling the concentration of the transition metal in the solution is beneficial to promoting the uniform dispersion of metal ions in the solution and is more conducive to uniform reaction. In some specific embodiments, in the soluble salt of the transition metal, the concentration of the transition metal includes but is not limited to 0.01 mol / L, 0.011 mol / L, 0.012 mol / L, 0.013 mol / L, 0.14 mol / L, 0.015 mol / L, 0.016 mol / L, 0.017 mol / L, 0.018 mol / L, 0.019 mol / L, 0.02 mol / L.

[0039] Furthermore, in the step of adjusting the pH to acidic, the pH is adjusted to 1.0 - 2.0. Adjusting the overall pH of the solution to strongly acidic is mainly to prevent the formation of metal oxides or metal hydroxides before the formation of silicon oxide. In some embodiments, in the step of adjusting the pH to acidic, an acidic solution can be directly added for pH adjustment.

[0040] Furthermore, a co-hydrolysis and condensation reaction is carried out. Among them, the co-hydrolysis and condensation reaction refers to the combination of silicon atoms with oxygen atoms, as well as metal ions and oxygen atoms. In some embodiments, the time of the co-hydrolysis and condensation reaction is 20 - 22 hours, and the temperature is 25 - 27 °C. In some specific embodiments, the time of the co-hydrolysis and condensation reaction includes but is not limited to 20 hours, 20.5 hours, 21 hours, 21.5 hours, 22 hours.

[0041] In step S02, an organic template is provided, the organic template is mixed with the blend solution, and after adjusting the pH to alkaline, a mixing reaction is carried out to prepare an alkaline gel.

[0042] In some embodiments, the organic template includes any one of tetrapropylammonium hydroxide, tetra-n-butylammonium hydroxide, and tetrapropylammonium bromide; the main purpose of adding the organic template is to form the molecular sieve pores to obtain corresponding channels. In some specific embodiments, the organic template is selected from tetrapropylammonium hydroxide. Providing tetrapropylammonium hydroxide as the organic template for the reaction can ensure a relatively high reaction rate.

[0043] In some embodiments, the molar ratio of the silicon solution to the organic template is 10-11:1. In some specific embodiments, the molar ratio of the silicon solution to the organic template includes but is not limited to 10:1, 10.1:1, 10.2:1, 10.3:1, 10.4:1, 10.5:1, 10.6:1, 10.7:1, 10.8:1, 10.9:1, 11:1.

[0044] Further, the organic template is mixed with the blend solution, and after adjusting the pH to be alkaline, a mixing reaction is carried out. Among them, the purpose of adjusting the pH to be alkaline is to provide an alkaline environment system to promote the formation of "metal-hydroxyl bonds" and "silicon-hydroxyl bonds".

[0045] In some embodiments, in the step of adjusting the pH to be alkaline, the pH is adjusted to 8.0-9.8. Adjusting the pH of the entire reaction system to a weak alkaline condition, the main purpose is to control the reaction rate to keep the crystallization reaction proceeding slowly. If the alkalinity is too strong, it will cause the crystallinity and purity of the catalyst to decrease, which is not conducive to the preparation of the catalyst.

[0046] In some specific embodiments, the adjusted pH includes but is not limited to 8.0, 8.2, 8.4, 8.6, 8.8, 9.0, 9.2, 9.4, 9.6, 9.8.

[0047] In some embodiments, the mixing reaction time is 20-22 hours and the temperature is 25-27 °C. After a relatively long mixing reaction, among them, the mixing reaction includes but is not limited to stirring treatment. Through continuous stirring treatment, it is beneficial to prepare the alkaline gel.

[0048] In some specific embodiments, the mixing reaction time includes but is not limited to 20 hours, 20.5 hours, 21 hours, 21.5 hours, 22 hours.

[0049] In step S03, the alkaline gel is subjected to static crystallization to obtain a crystal sample, and the crystal sample is mixed with zeolite molecular sieve and then subjected to calcination treatment to obtain an isomerization catalyst.

[0050] In some embodiments, in the step of subjecting the alkaline gel to static crystallization to obtain a crystal sample, it further includes: transferring the alkaline gel to a stainless steel autoclave coated with polytetrafluoroethylene for static crystallization treatment.

[0051] In some embodiments, the temperature for static crystallization is 180°C to 200°C, and the time is 72 to 74 hours. Conducting the crystallization treatment at the above temperatures is beneficial to obtaining a product with high crystallinity and high purity. In some specific embodiments, the temperature for static crystallization includes, but is not limited to, 180°C, 185°C, 190°C, 195°C, 200°C. In some specific embodiments, the time for static crystallization includes, but is not limited to, 72 hours, 72.5 hours, 73 hours, 73.5 hours, 74 hours.

[0052] In some embodiments, the preparation method further includes: centrifugally separating the crystal sample, washing it, and then drying it.

[0053] In some embodiments, the conditions for centrifugal separation are centrifuging at a speed of 5000 - 5500 rpm for 5 - 10 minutes at room temperature. In some specific embodiments, the speed for centrifugal separation includes, but is not limited to, 5000 rpm, 5100 rpm, 5200 rpm, 5300 rpm, 5400 rpm, 5500 rpm. In some specific embodiments, the time for centrifugal separation includes, but is not limited to, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, 10 minutes.

[0054] In some embodiments, the temperature for drying is 70 - 75°C, and the time is 20 - 22 hours. In some specific embodiments, the temperature for drying includes, but is not limited to, 70°C, 71°C, 72°C, 73°C, 74°C, 75°C; the time includes, but is not limited to, 20 hours, 20.5 hours, 21 hours, 21.5 hours, 22 hours.

[0055] Further, the crystal sample is mixed with zeolite molecular sieve and then subjected to calcination treatment to obtain an isomerization catalyst.

[0056] In some embodiments, the zeolite molecular sieve is M x SiO 2 (x < 0.02), and the addition amount of the provided zeolite molecular sieve is 3 - 5 grams per time.

[0057] In some embodiments, the temperature for calcination treatment is 500 - 550°C, and the time is 4 - 5 hours. Controlling the temperature for calcination treatment at 500 - 550°C, if the temperature for calcination treatment is too high or too low, the purity and crystallinity of the obtained catalyst will be reduced. In some specific embodiments, the temperature for calcination treatment includes, but is not limited to, 500°C, 510°C, 520°C, 530°C, 540°C, 550°C; the time for calcination treatment includes, but is not limited to, 4 hours, 4.5 hours, 5 hours.

[0058] In some embodiments, the prepared isomerization catalyst has an MFI-type zeolite molecular sieve structure, which contains cobalt / nickel / copper / zinc single-atom sites and has controllable Bronsted acidity.

[0059] In one embodiment, the provided transition metal is selected from cobalt, and the obtained isomerization catalyst is a cobalt-modified zeolite molecular sieve catalyst, where the content of Co is 1.2 wt%. In another embodiment, the provided transition metal is selected from zinc, and the obtained isomerization catalyst is a zinc-modified zeolite molecular sieve catalyst, and the content of Zn is 1.5 wt%.

[0060] By collecting synchrotron X-ray diffraction (SXRD) data on the BL02B2 beamline of the synchrotron radiation source SPring-8, it can be analyzed that the cobalt / zinc-modified zeolite catalysts have similar SXRD patterns and exhibit typical Bragg diffraction patterns of MFI zeolite. The highly symmetric Bragg peaks indicate that the metal modification process is very uniform. At the same time, since no obvious peak differences or additional Bragg peaks are observed, there is no aggregation of metal oxides on the crystal surface. To determine the positions of cobalt / zinc atoms in the zeolite framework, the SXRD data was further subjected to Rietveld refinement (as Figure 2 ). Further, the atomic and structural parameters of the crystal microporous material were finely adjusted (including fractional coordinates (x, y, z) and site occupancy factors [SOFs]). Since the metal species share the same position with silicon atoms, during the process of determining the positions of metal species, we determined the positions by comparing the SOFs of silicon T atoms. Since the occupancy factor of an atom depends on the electron density of the element, the metal species will give a higher occupancy than silicon due to its larger electron density. Therefore, through Rietveld refinement (as Figure 3 ), it was determined that T6 is the site of cobalt in the cobalt-modified molecular sieve, and T2 is the site of zinc in the zinc-modified molecular sieve.

[0061] Furthermore, the coordination environment of the metal-modified sites was studied by extended X-ray absorption fine structure spectroscopy (EXAFS). First, the EXAFS data of the sample was analyzed by wavelet transform ( Figure 3 ). The highest WT intensity belongs to the lobe centered on , corresponding to the oxygen atoms around the cobalt / zinc center. In addition, no obvious backscattering was observed in the higher k-space , indicating the absence of metal aggregation. The quantitative analysis fitting summary of the EXAFS data is as Figure 4 and Table 1.

[0062] Table 1

[0063]

[0064] In the second aspect of the embodiments of the present application, a method for converting olefin isomers is provided. An isomerization catalyst prepared by the preparation method of the isomerization catalyst is used to catalyze the conversion of each olefin isomer into a terminal olefin.

[0065] For the method for converting olefin isomers provided in the second aspect of the embodiments of the present application, the conversion method uses the isomerization catalyst prepared by the aforementioned preparation method of the structure catalyst to act, and catalyzes the conversion of each olefin isomer into a terminal olefin; due to the use of this isomerization catalyst, it is beneficial to realize the conversion of various different olefin isomers into terminal olefins under the condition of relatively low temperature in a short time. This method is convenient, fast, environmentally friendly, does not produce other pollutants, and is conducive to wide use.

[0066] In some embodiments, the preparation method includes: under a certain pressure, heating each olefin isomer with continuous stirring to 120 °C, reacting for 12 hours, and then cooling to room temperature to obtain a terminal olefin.

[0067] In some specific embodiments, the method for converting olefin isomers includes the following steps:

[0068] Under the condition of one atmospheric pressure, the obtained isomerization catalyst and butene isomers are mixed, heated to 120 °C with continuous stirring, and reacted for 12 hours. After the reaction, the reactor is cooled to room temperature with cold water. Further, the gaseous product is collected with a gas storage bag and analyzed by a gas chromatography-mass spectrometry (GC-MS) instrument. It can be analyzed that the content of terminal butene has increased, indicating that this isomerization catalyst has played a role in controlling the activation energy of the inverse thermodynamic configuration isomerization of butene.

[0069] The following is illustrated with specific examples.

[0070] Example 1

[0071] Isomerization catalyst and its preparation method

[0072] Including the following steps:

[0073] Mix the soluble salt of transition metal cobalt nitrate and tetraethyl orthosilicate, adjust the pH to 1.0, and then stir and mix for 20 hours to carry out a co-hydrolysis and condensation reaction to obtain a blended solution;

[0074] Provide the organic template tetrapropylammonium hydroxide, mix the organic template tetrapropylammonium hydroxide with the blended solution, adjust the pH to 9.8, and then carry out a mixing reaction for 20 hours to prepare an alkaline gel;

[0075] The alkaline gel was subjected to static crystallization at 180 °C for 72 hours to obtain a crystal sample. The crystal sample was centrifuged, washed and then dried. Among them, the conditions for centrifugation were centrifuging at a speed of 5000-5500 rpm for 5-10 minutes at room temperature, and the drying temperature was 70-75 °C for 20-22 hours. The crystal sample was mixed with zeolite molecular sieve and calcined at 550 °C for 5 hours to obtain an isomerization catalyst, in which the content of cobalt metal was 1.2 wt%.

[0076] Example 2

[0077] Isomerization catalyst and its preparation method

[0078] It includes the following steps:

[0079] The soluble salts of transition metals zinc nitrate and tetraethyl orthosilicate were mixed, and the pH was adjusted to 1.0 and then stirred and mixed for 20 hours to carry out a co-hydrolysis and condensation reaction to obtain a blend solution.

[0080] The organic template tetrapropylammonium hydroxide was provided, and the organic template tetrapropylammonium hydroxide was mixed with the blend solution, and the pH was adjusted to 9.8 and then mixed and reacted for 20 hours to prepare an alkaline gel.

[0081] The alkaline gel was subjected to static crystallization at 180 °C for 72 hours to obtain a crystal sample. The crystal sample was centrifuged, washed and then dried. Among them, the conditions for centrifugation were centrifuging at a speed of 5000-5500 rpm for 5-10 minutes at room temperature, and the drying temperature was 70-75 °C for 20-22 hours. The crystal sample was mixed with zeolite molecular sieve and calcined at 550 °C for 5 hours to obtain an isomerization catalyst, in which the content of zinc metal was 1.5 wt%.

[0082] Example 3

[0083] Method for catalyzing the conversion of olefin isomers

[0084] Under the condition of one atmosphere, the isomerization catalyst obtained in Example 1 and butene isomers were mixed, heated to 120 °C with continuous stirring and reacted for 12 hours. After the reaction, the reactor was cooled to room temperature with cold water and the gaseous product was collected.

[0085] Example 4

[0086] Method for catalyzing the conversion of olefin isomers

[0087] Under the condition of one atmosphere, the isomerization catalyst obtained in Example 2 and butene isomers were mixed, heated to 120 °C with continuous stirring and reacted for 12 hours. After the reaction, the reactor was cooled to room temperature with cold water and the gaseous product was collected.

[0088] Comparative Example 1

[0089] According to the method of the prior art, non-modified molecular sieves were used for conversion to produce butene. The obtained butene includes different isomers. Among them, as Figure 1 shown, the isomers include 1-butene: trans-2-butene: cis-2-butene with a mass ratio of 1:1:1.

[0090] Performance Test and Result Analysis

[0091] (1) Analyze the isomerization catalysts prepared in Example 1 and Example 2

[0092] The synchrotron radiation X-ray diffraction (SXRD) data of the isomerization catalysts prepared in Example 1 and Example 2 were collected on the BL02B2 beamline of the synchrotron radiation light source SPring-8. It can be analyzed that the cobalt / zinc modified zeolite catalysts have similar SXRD patterns and show the typical Bragg diffraction patterns of MFI zeolites. The highly symmetric Bragg peaks indicate that the metal modification process is very uniform. At the same time, since no obvious peak differences or additional Bragg peaks were observed, there is no aggregation of metal oxides on the crystal surface. In order to determine the positions of cobalt / zinc atoms in the zeolite framework, further Rietveld refinement was performed on the SXRD data (as Figure 2 ). Further, the atomic and structural parameters of the crystal microporous material (including fractional coordinates (x, y, z) and site occupancy factors [SOFs]) were finely adjusted. Since the metal species share the same position with silicon atoms, during the process of determining the positions of metal species, the positions were determined by comparing the SOFs of silicon T atoms. Since the occupancy factor of an atom depends on the electron density of the element, the metal species will give a higher occupancy than silicon due to the larger electron density. Therefore, through Rietveld refinement, it was determined that T6 is the site of cobalt in the cobalt-modified molecular sieve, and T2 is the site of zinc in the zinc-modified molecular sieve ( Figure 3 ).

[0093] Furthermore, the coordination environment of the metal-modified sites was studied by extended X-ray absorption fine structure spectroscopy (EXAFS). First, the EXAFS data of the sample were analyzed by wavelet transform. The highest WT intensity belongs to the lobe centered on , corresponding to the oxygen atoms around the cobalt / zinc center. In addition, no obvious backscattering was observed in the higher k space , indicating the absence of metal aggregation. The quantitative analysis fitting summary of the EXAFS data is as Figure 4 and Table 2.

[0094] Table 2

[0095]

[0096] (2) Analyze the gaseous product obtained in Example 3

[0097] Collect the gaseous product with a gas storage bag and analyze it using a gas chromatography-mass spectrometry (GC-MS) instrument. As Figure 5 shown, after isomerization, the amounts of trans-2-butene and cis-2-butene decreased significantly. In two tests, the selectivity of 1-butene among the butene isomers increased by 15 - 40%. In addition, in the control experiment with H-ZSM-5, there was no isomerization result after the reaction. The difference in catalytic performance indicates that the metal-modified molecular sieve plays a role in controlling the activation energy of the reverse thermodynamic configurational isomerization of butene.

[0098] In summary, the preparation method of the isomerization catalyst provided in this application uses an acid-base co-hydrolysis method to synthesize the isomerization catalyst. The provided isomerization catalyst has Lewis metal sites and can catalyze the reverse thermodynamic position isomerization reaction of converting internal olefins into terminal olefins, which is beneficial for simply and quickly realizing the conversion of olefin isomers, making this catalyst very suitable for direct application in the petrochemical / biomass conversion industry.

[0099] The above are only the preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent replacements, and improvements made within the spirit and principles of this application shall be included within the protection scope of this application.

Claims

1. A method for preparing a heterogeneous catalyst, characterized in that, it comprises the following steps: Mix a soluble salt of a transition metal and a silicon solution, adjust the pH to acidic, and then carry out a co-hydrolysis condensation reaction to obtain a blended solution; Provide an organic template, mix the organic template with the blended solution, adjust the pH to basic, and then carry out a mixing reaction to prepare a basic gel; Carry out static crystallization on the basic gel to obtain a crystal sample, mix the crystal sample with a zeolite molecular sieve, and then carry out a calcination treatment to obtain a heterogeneous catalyst.

2. The method for preparing a heterogeneous catalyst according to claim 1, characterized in that, the transition metal includes any one of titanium, chromium, manganese, cobalt, nickel, copper, zinc, tungsten, tantalum, hafnium; and / or, the soluble salt includes any one of nitrate, sulfate, hydrochloride; and / or, the silicon solution includes any one of tetraethyl orthosilicate, sodium silicate, silicon powder; and / or, the organic template includes any one of tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetrapropylammonium bromide.

3. The method for preparing a heterogeneous catalyst according to claim 1, characterized in that, in the soluble salt of the transition metal, the concentration of the transition metal is 0.01 - 0.02 mol / L; and / or, the molar ratio of the silicon solution to the organic template is 10 - 11:

1.

4. The method for preparing a heterogeneous catalyst according to any one of claims 1 - 3, characterized in that, in the step of adjusting the pH to acidic, the pH is adjusted to 1.0 - 2.0; and / or, in the step of adjusting the pH to basic, the pH is adjusted to 8.0 - 9.

8.

5. The method for preparing a heterogeneous catalyst according to any one of claims 1 - 3, characterized in that, the time of the co-hydrolysis condensation reaction is 20 - 22 hours, and the temperature is 25 - 27 °C; and / or, the time of the mixing reaction is 20 - 22 hours, and the temperature is 25 - 27 °C.

6. The method for preparing a heterogeneous catalyst according to any one of claims 1 - 3, characterized in that, the temperature of the static crystallization is 180 °C - 200 °C, and the time is 72 - 74 hours.

7. The method for preparing a heterogeneous catalyst according to any one of claims 1 - 3, characterized in that, the preparation method further includes: centrifugally separating the crystal sample, washing it, and then drying it; wherein, the conditions of the centrifugal separation are centrifugally separating at a rotation speed of 5000 - 5500 rpm for 5 - 10 minutes at room temperature, and the temperature of the drying treatment is 70 - 75 °C, and the time is 20 - 22 hours.

8. The method for preparing a heterogeneous catalyst according to any one of claims 1 - 3, characterized in that, the temperature of the calcination treatment is 500 - 550 °C, and the time is 4 - 5 hours.

9. A method for converting olefin isomers, characterized in that, using the heterogeneous catalyst prepared by the method for preparing a heterogeneous catalyst according to any one of claims 1 - 8 to catalyze the conversion of each olefin isomer into a terminal olefin.

10. The method for converting olefin isomers according to claim 9, characterized in that, The preparation method includes: under a certain pressure, heating each olefin isomer to 120 °C with continuous stirring, reacting for 12 hours, and then cooling to room temperature to obtain the terminal olefin.

Images