Metal modified zeolite catalyst and method for catalyzing lactone compound to generate terminal olefin

Abstract

The invention relates to the technical field of catalyst and compound preparation, in particular to a metal modified zeolite catalyst and a method for catalyzing a lactone compound to generate terminal olefin. The invention provides a metal modified zeolite catalyst. The structural general formula of the metal modified zeolite catalyst is M-SiO2; wherein the metal M is selected from any one of Ti, Cr, Mn, Co, Ni, Cu, Zn, Zr, Nb, W, Ta and Hf; in the provided metal modified zeolite catalyst, metal atoms are arranged on framework end points of a zeolite molecular sieve, so that a monatomic catalyst is formed; on one hand, the obtained catalyst has a Lewis metal site, can be beneficial to catalyzing a lactone compound to realize a decarboxylation reaction, ensures that the lactone compound can be directly catalyzed to generate terminal olefin, and can be widely applied.

Description

Technical Field

[0001] This application belongs to the technical field of catalyst and compound preparation, and particularly relates to a metal-modified zeolite catalyst and a method for catalytically generating terminal olefins from lactone compounds. Background Art

[0002] Lactone compounds refer to organic compounds that contain both a carboxyl group and a hydroxyl group in the same molecule, and the two dehydrate to form an organic compound. Lactones are formed by the esterification reaction of a single molecule with itself and dehydration, and they are also a single molecule after hydrolysis. There is only one ester group (-COO-) in the ring of lactones. Olefins refer to hydrocarbons containing a C=C bond (carbon-carbon double bond), belonging to unsaturated hydrocarbons, and are divided into chain olefins and cycloolefins. They are called monoolefins, diolefins, etc. according to the number of double bonds. One of the double bonds belongs to a relatively high-energy π bond, which is unstable and easy to break, so addition reactions will occur. The double bond group is the functional group in olefin molecules and has reactivity. It can undergo addition reactions such as hydrogenation, halogenation, hydration, hydrohalogenation, hypohalogenation, sulfuric acid esterification, epoxidation, and polymerization. It can also be oxidized to break the double bond and generate aldehydes, carboxylic acids, etc.

[0003] In chemical reactions, catalysts can be used to catalytically react lactone compounds to generate olefins. Currently, the catalysts used mainly catalytically react lactone compounds to generate a mixture of a series of olefin isomers, and the types of isomers in the obtained olefin isomer mixture cannot be controlled.

[0004] Olefins have various types of isomers such as carbon chain isomerism, position isomerism, functional group isomerism, and cis-trans isomerism. The commercial value of terminal olefins is much higher than that of other internal olefins. When generating olefin isomer mixtures on many reported catalysts, due to the need for purification, the operating costs and complexity are very high, making the catalytic process uneconomical and unsustainable. Therefore, there is an urgent need to provide a catalyst that can directly catalytically generate terminal olefins from lactone compounds to facilitate wide industrial use. Summary of the Invention

[0005] The purpose of this application is to provide a metal-modified zeolite catalyst and a method for catalytically generating terminal olefins from lactone compounds, aiming to solve the problem that there is currently no catalyst in the prior art that can directly catalytically generate terminal olefins from lactone compounds.

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

[0007] In the first aspect, this application provides a metal-modified zeolite catalyst, and the structural general formula of the metal-modified zeolite catalyst is M - SiO 2 ; wherein, the metal M is selected from any one of Ti, Cr, Mn, Co, Ni, Cu, Zn, W, Ta, and Hf.

[0008] In a second aspect, the present application provides a method for generating terminal olefins from lactone compounds, which uses a metal-modified zeolite catalyst to catalyze the reaction of each lactone compound to generate terminal olefins.

[0009] The metal-modified zeolite catalyst provided in the first aspect of the present application, since in the provided metal-modified zeolite catalyst, metal atoms are arranged at the framework endpoints of the zeolite molecular sieve, forming a single-atom catalyst; on the one hand, the obtained catalyst has Lewis metal sites, which can facilitate the decarboxylation reaction of lactone compounds, ensuring that it can directly catalyze lactone compounds to generate terminal olefins, and can be applied to the efficient production of terminal olefins from biomass-derived lactone raw materials, and is widely used in the green technology industry or the chemical industry.

[0010] The method for generating terminal olefins from lactone compounds provided in the second aspect of the present application, due to the use of the aforementioned metal-modified zeolite catalyst, based on the fact that the metal-modified zeolite catalyst has Lewis metal sites, therefore, when using it for catalytic action, terminal olefins can be directly prepared from lactone compounds, and the obtained terminal olefins have high purity and high yield, which is conducive to wide application. Description of the Drawings

[0011] 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.

[0012] Figure 1 It is the distribution diagram of the catalytic product (C4) of the comparative example of the present application;

[0013] Figure 2 It is the SXRD diagram of the isomerization catalysts provided in Example 1 and Example 2 of the present application;

[0014] Figure 3 It is the structural schematic diagram of the isomerization catalysts provided in Example 1 and Example 2 of the present application;

[0015] Figure 4 It is the EXAFS data of the isomerization catalysts provided in Example 1 and Example 2 of the present application. Detailed Embodiments

[0016] In order to make the technical problems to be solved, technical solutions and beneficial effects of the present application more clearly understood, the following further details the present application in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0017] In this application, the term "and / or" describes the relationship between related objects and indicates that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, or B exists alone. Here, A and B can be singular or plural. The character " / " generally indicates that the related objects before and after are in an "or" relationship.

[0018] In this application, "at least one" means one or more, and "a plurality" means two or more. "At least one of the following" or a similar expression means any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can both represent: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively.

[0019] 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 order of execution. Some or all of the steps can be executed in parallel or sequentially. The execution order 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.

[0020] 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.

[0021] The weight of the relevant components mentioned in the specification of the embodiments of this application not only can refer to the specific content of each component, but also can represent the proportional relationship of the weights between the components. Therefore, as long as the content of the relevant components in the specification of the embodiments of this application is scaled up or down in proportion, it is 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.

[0022] The terms "first" and "second" are only used for descriptive purposes to distinguish objects such as substances from each other, and cannot be understood 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 this application, the first XX can also be called the second XX, and similarly, the second XX can also be called the first XX. Thus, the features defined with "first" and "second" can explicitly or implicitly include one or more of such features.

[0023] In the first aspect of the embodiments of the present application, a metal-modified zeolite catalyst is provided. The structural general formula of the metal-modified zeolite catalyst is M - SiO 2 ; wherein, the metal M is selected from any one of Ti, Cr, Mn, Co, Ni, Cu, and Zn.

[0024] In the first aspect of the embodiments of the present application, for the provided metal-modified zeolite catalyst, since the metal atoms are arranged at the framework endpoints of the zeolite molecular sieve, a single-atom catalyst is formed. On the one hand, the obtained catalyst has Lewis metal sites, which can facilitate the decarboxylation reaction of lactone compounds, ensuring the direct catalytic conversion of lactone compounds into terminal olefins. It can be applied to the efficient production of terminal olefins from biomass-derived lactone raw materials and is widely used in the green technology industry or the chemical industry.

[0025] In some embodiments, in the metal-modified zeolite catalyst, the metal single atoms are bonded to the framework positions of the zeolite. In some specific embodiments, when the metal is cobalt atoms, the obtained cobalt atoms are bonded to the T6 framework position of the zeolite molecular sieve. In some specific embodiments, when the metal is zinc atoms, the obtained zinc atoms are bonded to the T2 framework position of the zeolite molecular sieve.

[0026] In some embodiments, based on the mass of the metal-modified zeolite catalyst being 100%, the mass percentage of the metal is 1.0% - 2.0%. In some specific embodiments, based on the mass of the metal-modified zeolite catalyst being 100%, the mass percentage of the metal includes but is not limited to 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%.

[0027] In some embodiments, the metal-modified zeolite catalyst has an MFI-type zeolite molecular sieve structure.

[0028] In some embodiments, the metal-modified zeolite catalyst is a single-atom catalyst, and the crystal structure of the single-atom catalyst is the space group Pnma.

[0029] In some embodiments, the unit cell parameters of the metal-modified zeolite catalyst are as follows: a is b is c is

[0030] In some embodiments, the metal-modified zeolite catalyst is synthesized by an acid-base co-hydrolysis method. The specific preparation method includes the following steps:

[0031] Mix the soluble salt of metal M and tetraethyl orthosilicate, adjust the pH to 1.0, and stir and mix for 20 hours to carry out a co-hydrolysis and condensation reaction to obtain a blended solution;

[0032] Provide tetrapropylammonium hydroxide as an organic template, mix the tetrapropylammonium hydroxide with a blend solution, adjust the pH to 9.8, and then carry out a mixing reaction for 20 hours to prepare an alkaline gel.

[0033] Subject the alkaline gel to static crystallization at 180 °C for 72 hours to obtain a crystal sample. Centrifuge the crystal sample, wash it, and then perform a drying treatment. Among them, the conditions for centrifugation are at room temperature, centrifuging at a speed of 5000 - 5500 rpm for 5 - 10 minutes, the temperature for the drying treatment is 70 - 75 °C, and the time is 20 - 22 hours. Mix the crystal sample with zeolite molecular sieve and then calcine it at 550 °C for 5 hours to remove the organic template and activate the zeolite molecular sieve, obtaining a metal-modified zeolite catalyst.

[0034] The second aspect of the embodiments of the present application provides a method for generating terminal olefins from lactone compounds, using a metal-modified zeolite catalyst to catalyze the reaction of various lactone compounds to generate terminal olefins.

[0035] For the method for generating terminal olefins from lactone compounds provided in the second aspect of the embodiments of the present application, due to the use of the aforementioned metal-modified zeolite catalyst, and based on the fact that the metal-modified zeolite catalyst has Lewis metal sites, therefore, when using it for catalytic action, terminal olefins can be directly prepared from lactone compounds, and the obtained terminal olefins have high purity and high yield, which is conducive to wide application.

[0036] In some embodiments, the method for generating terminal olefins from lactone compounds includes the following steps: Provide an inert atmosphere, mix the lactone compounds and the metal-modified zeolite catalyst evenly and carry out a reaction to obtain terminal olefins.

[0037] In some embodiments, the reaction temperature is 250 - 270 °C, and the reaction time is 12 - 14 hours. In some specific embodiments, the reaction temperature includes but is not limited to 250 °C, 255 °C, 260 °C, 265 °C, 270 °C; the reaction time includes but is not limited to 12 hours, 12.5 hours, 13 hours, 13.5 hours, 14 hours.

[0038] In some embodiments, in the terminal olefins, the mass percentage content of 1-butene exceeds 95 wt%.

[0039] The following is illustrated with specific examples.

[0040] Example 1

[0041] Metal-modified zeolite catalyst and its preparation method

[0042] Metal-modified zeolite catalyst

[0043] The structural formula of the metal-modified zeolite catalyst is Co - SiO 2 .

[0044] The preparation method includes the following steps:

[0045] Mix the soluble salt of transition metal cobalt nitrate and tetraethyl orthosilicate, adjust the pH to 1.0, stir and mix for 20 hours, carry out a co-hydrolysis condensation reaction to obtain a blended solution;

[0046] Provide the organic template tetrapropylammonium hydroxide, mix the organic template tetrapropylammonium hydroxide with the blended solution, adjust the pH to 9.8, and carry out a mixing reaction for 20 hours to prepare an alkaline gel;

[0047] Carry out static crystallization of the alkaline gel at 180 °C for 72 hours to obtain a crystal sample, carry out centrifugal separation on the crystal sample, wash it and then carry out a drying treatment; among them, the conditions for centrifugal separation are at room temperature, centrifugally separate at a rotation speed of 5000 - 5500 rpm for 5 - 10 minutes, the temperature for drying treatment is 70 - 75 °C, and the time is 20 - 22 hours; mix the crystal sample with zeolite molecular sieve and then carry out a calcination treatment at 550 °C for 5 hours to obtain the metal-modified zeolite catalyst, among which the content of metal cobalt is 1.2 wt%.

[0048] Example 2

[0049] Metal-modified zeolite catalyst

[0050] The structural formula of the metal-modified zeolite catalyst is Zn - SiO 2 .

[0051] The preparation method includes the following steps:

[0052] Mix the soluble salt of transition metal zinc nitrate and tetraethyl orthosilicate, adjust the pH to 1.0, stir and mix for 20 hours, carry out a co-hydrolysis condensation reaction to obtain a blended solution;

[0053] Provide the organic template tetrapropylammonium hydroxide, mix the organic template tetrapropylammonium hydroxide with the blended solution, adjust the pH to 9.8, and carry out a mixing reaction for 20 hours to prepare an alkaline gel;

[0054] The alkaline gel was statically crystallized 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 at room temperature, centrifuging at a speed of 5000 - 5500 rpm for 5 - 10 minutes, the drying temperature was 70 - 75 °C, and the time was 20 - 22 hours. The crystal sample was mixed with zeolite molecular sieve and calcined at 550 °C for 5 hours to obtain a metal-modified zeolite catalyst, where the content of zinc metal was 1.5 wt%.

[0055] Example 3

[0056] Catalyze lactone compounds to form terminal olefins

[0057] Provide a nitrogen environment, mix the lactone compound γ-valerolactone (GVL) reactant and the metal-modified zeolite catalyst obtained in Example 1 evenly, and react at 250 °C for 12 hours. After the reaction, cool the reactor to room temperature with cold water, and collect the gaseous product with a gas storage bag.

[0058] Example 4

[0059] Catalyze lactone compounds to form terminal olefins

[0060] Provide a nitrogen environment, mix the lactone compound γ-valerolactone (GVL) reactant and the metal-modified zeolite catalyst obtained in Example 2 evenly, and react at 250 °C for 12 hours. After the reaction, cool the reactor to room temperature with cold water, and collect the gaseous product with a gas storage bag.

[0061] Comparative Example 1

[0062] According to the method of the prior art, non-modified molecular sieve was used for conversion to produce butene. The obtained butene included different isomers. Among them, as Figure 1 shown, the isomers included 1-butene: trans-2-butene: cis-2-butene with a mass ratio of 1:1:1.

[0063] Performance Test and Result Analysis

[0064] (1) Analyze the metal-modified zeolite catalysts prepared in Example 1 and Example 2

[0065] The metal-modified zeolite catalysts prepared in Example 1 and Example 2 were used to collect 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 were observed, there is no aggregation of metal oxides on the crystal surface. 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 crystalline 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 position of the metal species, the position was 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 its 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 ).

[0066] 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 wavelet transform 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 and fitting summary of the EXAFS data are as Figure 4 and Table 1.

[0067] Table 1

[0068]

[0069] (II) Analyze the gaseous products obtained in Example 3 and Example 4

[0070] The gaseous products obtained in Example 3 and Example 4 were analyzed, and the results are shown in Table 2. The metal-modified zeolite catalysts prepared in Example 1 and Example 2 both showed very high 1-butene selectivity (>95%). To confirm the contributions of different active species (metal species / Bronsted acidity), H-ZSM-5 and ion-exchanged Co- and Zn-ZSM-5 were selected for control experiments. All zeolite samples performed poorly in terms of 1-butene isomer selectivity, approximately 30 - 40%, while the ratio between the alkene isomers was approximately 1:1:1 (1-butene: trans-2-butene: cis-2-butene). By comparing the catalytic performances of different zeolite catalysts, the data indicated that the presence of individual Co and Zn atoms was crucial for achieving high 1-butene selectivity among the butene isomers.

[0071] Table 2

[0072] Sample 1-Butene selectivity (%) ZSM-5 32.2 Co-ZSM-5 88.6 Zn-ZSM-5 83.3 Zr-ZSM-5 95.0 Nb-ZSM-5 90.2 Hf-ZSM-5 88.7 Ta-ZSM-5 93.7 W-ZSM-5 83.4

[0073] In summary, a metal-modified zeolite catalyst provided by the present application, since in the provided metal-modified zeolite catalyst, metal atoms are arranged at the framework endpoints of the zeolite molecular sieve, forming a single-atom catalyst; on the one hand, the obtained catalyst has Lewis metal sites, which can facilitate the decarboxylation reaction of lactone compounds, ensuring that lactone compounds can be directly catalyzed to produce terminal olefins, and can be applied to the efficient production of terminal olefins from biomass-derived lactone raw materials, and is widely used in the green technology industry or the chemical industry.

[0074] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A metal-modified zeolite catalyst, It is characterized in that The metal modified zeolite catalyst has the general structural formula M - SiO 2 ; wherein the metal M is selected from any one of Ti, Cr, Mn, Co, Ni, Cu, Zn, Zr, Nb, W, Ta, and Hf.

2. The metal-modified zeolite catalyst according to claim 1, It is characterized in that In the metal-modified zeolite catalyst, metal single atoms are bonded to the framework positions of the zeolite.

3. The metal-modified zeolite catalyst according to claim 1, It is characterized in that Taking the mass of the metal-modified zeolite catalyst as 100%, the mass percentage of the metal is 1.0% to 2.0%.

4. The metal-modified zeolite catalyst according to claim 1, It is characterized in that The metal modified zeolite catalyst is an MFI type zeolite molecular sieve structure.

5. The metal-modified zeolite catalyst according to claim 1, It is characterized in that The metal-modified zeolite catalyst is a single-atom catalyst, and the crystal structure of the single-atom catalyst is a space group Pnma.

6. The metal-modified zeolite catalyst according to claim 1, It is characterized in that The unit cell parameters of the metal modified zeolite catalyst are as follows: a is b is c is 7. A method for generating terminal olefins from lactone compounds, It is characterized in that The metal-modified zeolite catalyst according to any one of claims 1 to 6 is used to catalyze the reaction of various lactone compounds to generate terminal olefins.

8. The method according to claim 7, It is characterized in that The steps include: An inert atmosphere is provided, and the lactone compound and the metal-modified zeolite catalyst are uniformly mixed and reacted to obtain terminal olefins.

9. The method according to claim 8, It is characterized in that The reaction temperature is 250-270° C., and the reaction time is 12-14 hours.

10. The method according to claim 8, It is characterized in that Among the terminal olefins, the mass percentage of 1-butene exceeds 95wt%.

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