Metal-modified zeolite catalysts and methods of catalyzing the formation of terminal olefins from lactone compounds

Abstract

The application relates to the technical field of catalysts and compound preparation, in particular to a metal-modified zeolite catalyst and a method for catalyzing lactone compounds to generate terminal olefins. ‑ 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 the skeleton end points of a zeolite molecular sieve to form a monatomic catalyst; on one hand, the obtained catalyst has Lewis metal sites, can be beneficial to catalyzing lactone compounds to realize decarboxylation, and can ensure that the lactone compounds can be directly catalyzed to generate terminal olefins, and can be widely applied.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalysts and compound preparation, and particularly relates to a metal-modified zeolite catalyst and a method for catalyzing lactone compounds to generate terminal olefins. BACKGROUND

[0002] Lactone compounds refer to organic compounds containing both carboxyl and hydroxyl groups in the same molecule, which are dehydrated to form. Lactone is formed by esterification and dehydration of a molecule itself, and is also a molecule after hydrolysis. There is only one ester group (-COO-) in the ring of lactone. Olefins refer to carbon-hydrogen compounds containing C=C bonds (carbon-carbon double bonds), which belong to unsaturated hydrocarbons and are divided into alkenes and cycloalkenes. According to the number of double bonds, they are called mono-olefins, di-olefins, etc. One of the double bonds is a π bond with higher energy, which is unstable and easy to break, so addition reaction occurs. The double bond group is the functional group in the olefin molecule, which has reactivity and can undergo addition reactions such as hydrogenation, halogenation, hydration, halogenation, hypohalogenation, sulfate esterification, epoxidation, polymerization, etc. It can also be oxidized to break the double bond to form aldehyde, carboxylic acid, etc.

[0003] In chemical reactions, catalysts can be used to catalyze lactone compounds to generate olefins. Currently, the catalysts used mainly catalyze lactone compounds to generate a series of isomer mixtures of olefins, and the isomer mixtures of olefins cannot control the type of isomer.

[0004] Olefins exist in various types of isomers such as carbon chain isomerism, position isomerism, functional group isomerism, and cis-isomerism. The commercial value of terminal olefins is much higher than that of other internal olefins. When olefin isomer mixtures are produced on many reported catalysts, the operation cost and complexity are very high because purification is needed, making the catalytic process uneconomical and unsustainable. Therefore, it is urgent to provide a catalyst that can directly catalyze lactone compounds to generate terminal olefins, which is conducive to widespread use in industry. SUMMARY

[0005] The purpose of the present application is to provide a metal-modified zeolite catalyst and a method for catalyzing lactone compounds to generate terminal olefins, which aims to solve the problem that there is no catalyst in the prior art that can directly catalyze lactone compounds to generate terminal olefins.

[0006] To achieve the above application purpose, the technical scheme adopted by the present application is as follows:

[0007] In a first aspect, the present application provides a metal-modified zeolite catalyst, and the structure of the metal-modified zeolite catalyst is represented by the general formula M - SiO2; 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 application provides a method for producing terminal olefins from lactone compounds, which comprises catalyzing reactions of each lactone compound with a metal-modified zeolite catalyst to produce terminal olefins.

[0009] The metal-modified zeolite catalyst provided in the first aspect of the application has metal atoms arranged at the end points of the framework of the zeolite molecular sieve to form a single-atom catalyst. On the one hand, the obtained catalyst has Lewis metal sites, which can facilitate the catalysis of decarboxylation of lactone compounds to ensure that the lactone compounds can be directly catalyzed to produce terminal olefins. The catalyst can be applied to the efficient production of terminal olefins from biomass-derived lactone raw materials and can be widely applied to green technology industries or chemical industries.

[0010] The method for producing terminal olefins from lactone compounds provided in the second aspect of the application uses the aforementioned metal-modified zeolite catalyst. Since the metal-modified zeolite catalyst has Lewis metal sites, it can be used to directly prepare terminal olefins from lactone compounds. The obtained terminal olefins have high purity and high yield, which are beneficial to wide application. BRIEF DESCRIPTION OF DRAWINGS

[0011] In order to more clearly illustrate the technical solutions in the embodiments of the application, the drawings needed in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0012] Figure 1 is a catalytic product (carbon 4) distribution diagram of the comparative example of the application;

[0013] Figure 2 is an SXRD diagram of the isomerization catalyst provided in Example 1 and Example 2 of the application;

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

[0015] Figure 4 is EXAFS data of the isomerization catalyst provided in Example 1 and Example 2 of the application. DETAILED DESCRIPTION

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

[0017] In the present application, the term "and / or" describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B can represent the following three cases: A exists alone, A and B exist together, and B exists alone. Wherein A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after it.

[0018] In the present application, "at least one" means one or more, and "multiple" means two or more. "At least one" or the like means any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can mean 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.

[0019] It should be understood that the size of the sequence number of the above-mentioned processes in various embodiments of the present application does not mean the order of execution, and part or all of the steps can be executed in parallel or in sequence. The execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0020] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0021] The weight of the related components mentioned in the specification of the embodiments of the present application can not only refer to the specific content of each component, but also represent the weight ratio relationship between each component. Therefore, as long as the content of the related components in the specification of the embodiments of the present application is enlarged or reduced in proportion, it is within the scope disclosed in the specification of the embodiments of the present application. Specifically, the mass in the specification of the embodiments of the present application can be μg, mg, g, kg, etc. Mass units commonly known in the chemical field.

[0022] The terms "first", "second" are only for the purpose of description, and are used to distinguish objects such as substances from each other, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. For example, without departing from the scope of the embodiments of the present application, the first XX can also be referred to as the second XX, and similarly, the second XX can also be referred to as the first XX. Therefore, the features limited by "first" and "second" can explicitly or implicitly include one or more of the features.

[0023] The first aspect of the embodiment of the present application provides a metal-modified zeolite catalyst, and a 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 and Zn.

[0024] The first aspect of the embodiment of the present application provides a metal-modified zeolite catalyst, and a structural general formula of the metal-modified zeolite catalyst is M

[0025] In some embodiments, the metal atom in the metal-modified zeolite catalyst is combined with the framework position of the zeolite. In some specific embodiments, when the metal is selected from a cobalt atom, the obtained cobalt atom is combined with the T6 framework position of the zeolite molecular sieve. In some specific embodiments, when the metal is selected from a zinc atom, the obtained zinc atom is combined with the T2 framework position of the zeolite molecular sieve.

[0026] In some embodiments, the mass percentage content of the metal is 1.0% to 2.0% based on 100% of the mass of the metal-modified zeolite catalyst. In some specific embodiments, the mass percentage content 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% based on 100% of the mass of the metal-modified zeolite catalyst.

[0027] In some embodiments, the metal-modified zeolite catalyst is a 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 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] The soluble salt of the metal M and tetraethyl orthosilicate are mixed, the pH is adjusted to 1.0, and then stirred and mixed for 20 hours to perform a co-hydrolysis condensation reaction to obtain a co-mixed solution;

[0032] The organic template tetrapropyl ammonium hydroxide is provided, mixed with the blended solution, and mixed after adjusting the pH to 9.8 for 20 hours to prepare a basic gel;

[0033] The basic gel is subjected to static crystallization at 180℃ for 72 hours to obtain a crystal sample, which is subjected to centrifugal separation, washing, and drying treatment; the centrifugal separation is performed at room temperature at a speed of 5000-5500 rpm for 5-10 minutes, the drying treatment is performed at a temperature of 70-75℃ for 20-22 hours; the crystal sample is mixed with a zeolite molecular sieve and subjected to calcination at 550℃ for 5 hours to remove the organic template and activate the zeolite molecular sieve to obtain a metal-modified zeolite catalyst.

[0034] The second aspect of the embodiment of 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.

[0035] The method for generating terminal olefins from lactone compounds provided in the second aspect of the embodiment of the present application uses the aforementioned metal-modified zeolite catalyst, which has Lewis metal sites, so that the catalytic effect can be achieved to directly prepare terminal olefins 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: providing an inert atmosphere, uniformly mixing the lactone compound and the metal-modified zeolite catalyst to perform a reaction, and obtaining terminal olefins.

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

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

[0039] The following will be described in conjunction with specific embodiments.

[0040] Embodiment 1

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

[0042] Metal-modified zeolite catalyst

[0043] The structural formula of the metal-modified zeolite catalyst is Co - SiO2.

[0044] The preparation method comprises the following steps:

[0045] The soluble salt of the transition metal, cobalt nitrate, and tetraethyl orthosilicate are mixed, the pH is adjusted to 1.0, and then stirring and mixing are performed for 20 hours to perform a co-hydrolysis condensation reaction to obtain a co-mixed solution;

[0046] The organic template tetrapropyl ammonium hydroxide is provided, the organic template tetrapropyl ammonium hydroxide is mixed with the co-mixed solution, and the pH is adjusted to 9.8, and then a mixing reaction is performed for 20 hours to prepare an alkaline gel;

[0047] The alkaline gel is subjected to static crystallization at 180 DEG C for 72 hours to obtain a crystal sample, the crystal sample is subjected to centrifugal separation, and then washing and drying treatment are performed; wherein, the centrifugal separation is performed at a rotation speed of 5000-5500 rpm for 5-10 minutes at room temperature, the drying treatment is performed at a temperature of 70-75 DEG C for 20-22 hours; the crystal sample is mixed with a zeolite molecular sieve, and then calcination treatment is performed at 550 DEG C for 5 hours to obtain the metal-modified zeolite catalyst, wherein, the content of the metal cobalt is 1.2 wt%.

[0048] Example 2

[0049] The metal-modified zeolite catalyst

[0050] The structural formula of the metal-modified zeolite catalyst is Zn - SiO2.

[0051] The preparation method comprises the following steps:

[0052] The soluble salt of the transition metal, zinc nitrate, and tetraethyl orthosilicate are mixed, the pH is adjusted to 1.0, and then stirring and mixing are performed for 20 hours to perform a co-hydrolysis condensation reaction to obtain a co-mixed solution;

[0053] The organic template tetrapropyl ammonium hydroxide is provided, the organic template tetrapropyl ammonium hydroxide is mixed with the co-mixed solution, and the pH is adjusted to 9.8, and then a mixing reaction is performed for 20 hours to prepare an alkaline gel;

[0054] The alkaline gel is subjected to static crystallization at 180 DEG C for 72 hours to obtain a crystal sample, the crystal sample is subjected to centrifugal separation, and then washing and drying treatment are performed; wherein, the centrifugal separation is performed at a rotation speed of 5000-5500 rpm for 5-10 minutes at room temperature, the drying treatment is performed at a temperature of 70-75 DEG C for 20-22 hours; the crystal sample is mixed with a zeolite molecular sieve, and then calcination treatment is performed at 550 DEG C for 5 hours to obtain the metal-modified zeolite catalyst, wherein, the content of the metal cobalt is 1.2 wt%.

[0055] Example 3

[0056] Catalytic conversion of lactone compounds to terminal olefins

[0057] The lactone compound γ-valerolactone (GVL) reactant and the metal-modified zeolite catalyst obtained in Example 1 were mixed uniformly in a nitrogen environment and reacted at 250°C for 12 hours. After the reaction, the reactor was cooled to room temperature with cold water, and the gaseous products were collected in a gas storage bag.

[0058] Example 4

[0059] Catalytic conversion of lactone compounds to terminal olefins

[0060] The lactone compound γ-valerolactone (GVL) reactant and the metal-modified zeolite catalyst obtained in Example 2 were mixed uniformly in a nitrogen environment and reacted at 250°C for 12 hours. After the reaction, the reactor was cooled to room temperature with cold water, and the gaseous products were collected in a gas storage bag.

[0061] Comparative Example 1

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

[0063] Performance testing and result analysis

[0064] (1) Analysis of the metal-modified zeolite catalysts obtained in Example 1 and Example 2

[0065] The metal-modified zeolite catalysts obtained in Example 1 and Example 2 were analyzed by collecting the synchrotron X-ray diffraction (SXRD) data on the BL02B2 beamline of the SPring-8 synchrotron radiation source. It was found that the cobalt / zinc-modified zeolite catalysts had similar SXRD patterns and exhibited the typical Bragg diffraction pattern of the MFI zeolite. The highly symmetrical Bragg peaks indicated that the metal modification process was very uniform. At the same time, because no obvious peak difference or additional Bragg peaks were observed, there was no metal oxide aggregation on the crystal surface. In order to determine the position of the cobalt / zinc atoms in the zeolite framework, the SXRD data were further refined by Rietveld refinement (as shown in FIG. 2). Figure 2 ​). Further, the atomic and structural parameters of the crystalline microporous material were fine-tuned (including fractional coordinates (x, y, z) and site occupancy factors [SOFs]). Since the metal species share the same positions as the silicon atoms, the positions of the metal species were determined by comparing the SOFs of the 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. Thus, by Rietveld refinement, T6 was determined to be the site of cobalt in the cobalt-modified molecular sieve, and T2 was determined to be the site of zinc in the zinc-modified molecular sieve Figure 3

[0066] Further, the coordination environment of the metal-modified sites was investigated by extended X-ray absorption fine structure spectroscopy (EXAFS). The EXAFS data of the samples were first analyzed by wavelet transform. The highest wavelet transform intensity belongs to the lobe centered at corresponding to the oxygen atoms surrounding the cobalt / zinc center. In addition, no significant backscattering was observed at higher k-space indicating the absence of metal clustering. The quantitative analysis of the EXAFS data is summarized in Figure 4 and Table 1.

[0067] Table 1

[0068]

[0069] (ii) Analysis of 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. Both the metal-modified zeolite catalysts prepared in Example 1 and Example 2 showed very high 1-butene selectivity (>95%). To confirm the contribution of different active species (metal species / Bronsted acidity), H-ZSM-5 and ion-exchanged Co- and Zn-ZSM-5 were chosen for control experiments. All the zeolite samples performed poorly in 1-butene isomer selectivity, about 30-40%, while the ratio among the olefin isomers was about 1 : 1 : 1 (1-butene: trans-2-butene: cis-2-butene). By comparing the catalytic performance of different zeolite catalysts, the data indicated that the presence of a single Co and Zn atom 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, the metal-modified zeolite catalyst provided by the application has the following advantages: the metal atoms are arranged at the skeleton end points of the zeolite molecular sieve to form a monatomic catalyst; on the one hand, the obtained catalyst has Lewis metal sites, which can facilitate the catalysis of lactone compounds to realize decarboxylation, and ensure that the lactone compounds can be directly catalyzed to generate terminal olefins, and the metal-modified zeolite catalyst can be applied to the efficient production of terminal olefins from biomass-derived lactone raw materials, and is widely applied to green technology industry or chemical industry.

[0074] The above merely describes the preferred embodiments of the application and is not intended to limit the application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. A method for producing terminal olefins from a lactone compound, characterized by, The metal-modified zeolite catalyst is used to catalyze each lactone compound to generate terminal olefin; The metal-modified zeolite catalyst has a general structure of 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 metal-modified zeolite catalyst, a single atom of the metal is combined with a framework position of the zeolite. The mass percentage of the metal in the metal-modified zeolite catalyst is 1.0% to 2.0% based on 100% of the mass of the metal-modified zeolite catalyst. The metal-modified zeolite catalyst has a MFI type zeolite molecular sieve structure. The metal-modified zeolite catalyst is a single-atom catalyst, and the single-atom catalyst has a crystal structure of space group Pnma. The unit cell parameters of the metal-modified zeolite catalyst are as follows: a is 20.1 Å, b is 19.9 Å, and c is 13.4 Å.

2. The method of claim 1, wherein, The method comprises the following steps: The metal-modified zeolite catalyst is used to catalyze each lactone compound to generate terminal olefin.

3. The method of claim 2, wherein, The reaction temperature is 250 to 270 °C, and the reaction time is 12 to 14 hours.

4. The method of claim 2, wherein, The mass percentage of 1-butene in the terminal olefin is more than 95 wt%. The metal-modified zeolite catalyst is used to catalyze each lactone compound to generate terminal olefin.

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