A bifunctional catalyst and its preparation method and method for directly preparing ketone from olefin

Abstract

The present invention relates to a bifunctional catalyst comprising a carrier and an active component; the carrier is amorphous silica gel, and the active component is an all-silicon molecular sieve encapsulating a metal element; the metal element provides dehydrogenation active centers for the bifunctional catalyst, and the carrier and the all-silicon molecular sieve provide Lewis acid centers for the bifunctional catalyst. The present invention provides a bifunctional catalyst containing an all-silicon molecular sieve encapsulating copper and a preparation method thereof. The method comprises the following steps: mixing a silicon source I, a copper source, an additive, a dispersant, a nitrogen-containing heterocyclic compound, an alkali source, and H2O in a proportional manner, followed by hydrothermal treatment to obtain an all-silicon molecular sieve encapsulating copper oxide; and mixing a silicon source II, the prepared all-silicon molecular sieve encapsulating copper oxide, sesbania powder, a porogen, and H2O in a proportional manner, followed by molding to obtain the bifunctional catalyst containing the all-silicon molecular sieve encapsulating copper oxide. The present invention also provides a method for directly preparing ketones from olefins, using the above-mentioned bifunctional catalyst.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic ketone preparation, and particularly relates to a catalyst used for directly preparing ketone from olefin and a preparation method thereof. Background Art

[0002] Ketones are compounds consisting of a carbonyl group linked to two hydrocarbon groups. Ketones are chemically active and readily undergo nucleophilic addition reactions with hydrocyanic acid, Grignard reagents, hydroxylamine, and alcohols, and can also be reduced to alcohols. Due to the polarization of the carbonyl group, ketones with α-H groups can undergo halogenation reactions; under alkaline conditions, ketones with methyl groups can undergo haloform reactions. Furthermore, low-carbon ketones, such as acetone and methyl ethyl ketone, can also be used as solvents. Therefore, organic ketones have a wide range of applications, with acetone and cyclohexanone being particularly important chemical raw materials.

[0003] Typically, the preparation methods of organic ketones include oxidation / dehydrogenation of secondary alcohols, acylation of aromatic hydrocarbons, and reaction of carboxylic acid derivatives with organometallic compounds. Acetone is typically produced using the cumene process, where propylene and benzene are alkylated to produce cumene, which is then oxidized to produce cumene hydroperoxide. The hydrolysis of cumene hydroperoxide produces acetone and phenol. Methyl ethyl ketone is produced using a two-step hydration and dehydrogenation process, where n-butene is directly hydrated under acid catalysis to produce sec-butanol, or to produce a sulfate ester intermediate, which is then hydrolyzed to produce sec-butanol. Finally, the sec-butanol is dehydrogenated to produce methyl ethyl ketone. Cyclohexanone is produced through two methods: cyclohexane oxidation and cyclohexene hydration. In the oxidation process, cyclohexane is oxidized to produce a mixed solution of cyclohexanol and cyclohexanone. In the hydration process, cyclohexene is hydrated under an acid catalyst to produce cyclohexanol, which is then dehydrogenated to produce cyclohexanone.

[0004] Based on the above analysis, olefins are key precursors for organic ketone production, and olefin hydration to secondary alcohols and secondary alcohol dehydrogenation are important processes in organic ketone production. However, due to thermodynamic equilibrium limitations, the single-pass conversion rates of both n-butene direct hydration and cyclohexene hydration are difficult to reach 10%, which reduces the production efficiency of organic ketones and increases the energy consumption of the olefin cycle. Therefore, process innovation is urgently needed to improve the production efficiency and economic efficiency of organic ketones. Since the conversion rate of secondary alcohol dehydrogenation can reach over 50% under the action of dehydrogenation catalysts, coupling the hydration reaction with the dehydrogenation reaction is expected to promote the hydration reaction, thereby increasing the single-pass conversion rate of olefins and the production efficiency of organic ketones. However, the hydration reaction is typically carried out below 200°C (160°C for n-butene and 130°C for cyclohexene), while the dehydrogenation reaction is usually carried out above 220°C. If the coupling reaction is below 200°C, the dehydrogenation efficiency of the secondary alcohol is low, and the dehydrogenation has a poor effect on promoting the hydration reaction; if the coupling reaction is above 200°C, the olefins are likely to aggregate or react with the alcohol ketone, thereby reducing the selectivity of the ketone and the effective utilization of the olefins. Summary of the Invention

[0005] In response to the existing problems of low conversion rate and production efficiency in the olefin hydration and secondary alcohol dehydrogenation reactions in the preparation of ketones from olefins, one object of the present invention is to provide a method for the direct catalytic synthesis of ketones from olefins. This method involves the direct conversion of olefins to ketones using a bifunctional catalyst having both hydration and dehydrogenation active sites. A second object of the present invention is to provide a bifunctional catalyst having both hydration and dehydrogenation active sites and a method for preparing the same.

[0006] In a first aspect of the present invention, a bifunctional catalyst is provided, comprising a carrier and an active component; the carrier is amorphous silica gel, and the active component is an all-silicon molecular sieve encapsulating a metal element; the metal element provides a dehydrogenation active center for the bifunctional catalyst, and the metal element is selected from at least one of Group IB metals; the carrier and the all-silicon molecular sieve provide Lewis acid centers for the bifunctional catalyst, and the acid content is 7.6 to 137.4 μmol / g.

[0007] The amorphous silica gel carrier and all-silicon molecular sieve serve as the skeleton structure of the bifunctional catalyst, giving it a multi-level pore structure. The specific surface area of ​​the bifunctional catalyst is 40 to 679 m 2 / g, pore volume of 0.05~0.45cm 3 / g, preferably with a specific surface area of ​​51 to 524 m 2 / g, pore volume of 0.07~0.47cm 3 / g.

[0008] Furthermore, the all-silicon molecular sieve is at least one of all-silicon Silicalite-1 and all-silicon Beta molecular sieve.

[0009] Specifically, the metal element provides a dehydrogenation active center for the bifunctional catalyst, and the metal element is selected from at least one of the Group IB metals; preferably at least one of Cu, Ag, and Au, with a content of 0.01 to 60 wt.%; more preferably at least one of Cu and Ag, with a content of 0.5 to 30 wt.%. The metal element is encapsulated in the all-silicon molecular sieve crystal. The structural characteristics of Group IB metals Cu, Ag, and Au are (n-1)d 10 ns 1 , belonging to the ds region. The n-s electrons of Group IB elements have similar powers to the (n-1)d electrons in their next outermost shell. When combined with other elements, not only can the n-s electrons participate in bonding, but the (n-1)d electrons can also partially participate under different reaction conditions. Because the next outermost shell has 18 electrons, it has a strong attraction to the outermost s electrons, making Cu, Ag, and Au inert in the environment, highly stable, resistant to oxidation at appropriate temperatures, and highly catalytically active.

[0010] Due to their molecular-scale crystalline pore structure and unique Lewis / Bronsted acidity, molecular sieves can be used as heterogeneous catalytic materials. In the bifunctional catalyst provided by this invention, Lewis acid centers provided by structural defects can coordinate with carbon-carbon double bonds. Furthermore, under the synergistic effect of the dehydrogenation active centers, the dehydrogenation of secondary alcohols promotes olefin hydration, enabling the direct conversion of olefins to ketones.

[0011] In a second aspect, the present invention further specifically provides a bifunctional catalyst comprising an all-silicon molecular sieve encapsulated with copper, with respect to the above-mentioned bifunctional catalyst. In the bifunctional catalyst comprising an all-silicon molecular sieve encapsulated with copper, the carrier is amorphous silica gel, and the active component is an all-silicon molecular sieve encapsulated with copper. The copper encapsulated within the all-silicon molecular sieve crystals provides dehydrogenation active centers for the bifunctional catalyst. The structural defects formed by the all-silicon molecular sieve and the amorphous silica gel provide Lewis acid centers for the bifunctional catalyst, wherein the all-silicon molecular sieve is selected from at least one of all-silicon Silicalite-1 and all-silicon Beta molecular sieve.

[0012] The third aspect of the present invention provides a method for preparing the aforementioned bifunctional catalyst containing the copper-encapsulated all-silicon molecular sieve. Specifically, the method for preparing the bifunctional catalyst comprises:

[0013] a. The silicon source I, a copper source, an additive, a dispersant, a nitrogen-containing heterocyclic compound, an alkali source, and H2O are mixed in proportion to obtain a mixed system; the mixed system is hydrothermally treated at 50 to 190 ℃ for 3 to 10 days, and then filtered and dried to obtain an all-silicon molecular sieve encapsulated with copper oxide;

[0014] b. The silicon source II, the all-silicon molecular sieve encapsulating copper oxide obtained in step a, sesbania powder, a porogen, and H2O are mixed in proportion and mixed evenly in a kneader to obtain a catalyst precursor; the catalyst precursor is formed, dried, calcined at 400-850°C for 1-6h, and reduced in a H2 atmosphere at 160-300°C for 12-72h to obtain a bifunctional catalyst containing an all-silicon molecular sieve encapsulating copper.

[0015] Furthermore, in step a, the silicon source I is selected from at least one of organic silicate, silica gel, white carbon black, and silica sol; in order to reduce the influence of heteroatoms in the silicon source on the catalyst crystallization product, a single silicon source is preferred; further preferably, it is an organic silicate, such as at least one of methyl orthosilicate, isopropyl silicate, ethyl silicate, tetraethoxysilane, and tetraethyl orthosilicate.

[0016] Furthermore, in step a, the copper source is selected from at least one of copper nitrate, copper chloride, tetraphenylporphyrin copper, and copper acetylacetonate.

[0017] Furthermore, the auxiliary agent in step a is selected from at least one compound containing at least one ion of alkali metal ions or alkaline earth metal ions; preferably containing Li + 、Na + , K + , Rb + 、Cs + Mg 2+ , Ca 2+ 、Ba 2+ At least one compound containing at least one ion; more preferably Li + 、Na + , K + , Rb + 、Cs + Mg 2+ , Ca 2+ 、Ba 2+ Nitrates or chlorides; more preferably containing Na + , K + 、Cs + Mg 2+ , Ca 2+ At least one compound containing at least one ion in the amorphous silica gel is preferably a nitrate or chloride of the aforementioned particles. Furthermore, the auxiliary agent may also be added in step b and calcined to be present in the amorphous silica gel. Using alkali metal or alkaline earth metal ions as auxiliary agents can prevent the acidity of the carrier silica gel from inducing side reactions.

[0018] Furthermore, the dispersant in step a is a soluble compound containing nitrogen, sulfur, or the like having lone pair electrons, and the dispersant is selected from at least one of ethylamine, ethylenediamine, propylenediamine, hexamethylenediamine, aniline, pyridine, thiophene, thiol, thiophenol, and thioether; preferably, at least one of ethylenediamine, hexamethylenediamine, and aniline.

[0019] Furthermore, the nitrogen-containing functional group in the nitrogen-containing heterocyclic compound in step a is selected from at least one of a pyrrole ring, an imidazole ring, a pyrazole ring, a pyridine ring, a pyrimidine ring, a quinoline ring, and a pyrimidine ring.

[0020] Specifically, the nitrogen-containing heterocyclic compound in step a is selected from at least one of theophylline, guanosine, adenosine, guanine, adenine, and adefovir; preferably, it is a mixture of theophylline and adenine, and the molar ratio of theophylline to adenine in the mixture is (0.4-3):1.

[0021] Furthermore, in step a, the alkaline source is selected from at least one of alkali metal hydroxide, ammonia water, urea, hydrazine hydrate, sodium carbonate, sodium bicarbonate, aliphatic amine, aliphatic alcohol amine, and quaternary ammonium base.

[0022] Specifically, the general structural formula of the quaternary ammonium hydroxide is:

[0023]

[0024] Wherein, R1, R2, R3, and R4 are each at least one C1-C4 alkyl group, wherein the C1-C4 alkyl group is selected from at least one of a C1-C4 linear alkyl group and a C3-C4 branched alkyl group. R1, R2, R3, and R4 can independently be methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, or tert-butyl.

[0025] Specifically, the aliphatic amine has the general structural formula R5(NH2)n, where n is an integer of 1 or 2. When n is 1, R5 is at least one C1-C6 alkyl group, and the C1-C6 alkyl group is selected from at least one of a C1-C6 straight-chain alkyl group and a C3-C6 branched-chain alkyl group, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, neopentyl, isopentyl, tert-pentyl, or n-hexyl group. When n is 2, R5 is at least one C1-C6 alkylene group, and the C1-C6 alkylene group is selected from at least one of a C1-C6 straight-chain alkylene group and a C3-C6 branched-chain alkylene group, such as methylene, ethylene, n-propylene, n-butylene, n-pentylene, or n-hexylene.

[0026] Preferably, the alkali source is selected from at least one of tetraethylammonium hydroxide, tetramethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tripropylamine, triethylamine, diethylamine, tributylamine, and hexylene diamine; more preferably, it is at least one of tetraethylammonium hydroxide and tetrapropylammonium hydroxide. When the alkali source is tetraethylammonium hydroxide, triethylamine, or diethylamine, a copper-encapsulated all-silicon Beta molecular sieve is prepared; when the alkali source is tetramethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tripropylamine, tributylammonium, or hexylene diamine, a copper-encapsulated all-silicon Silicalite-1 molecular sieve is prepared. The alkali source serves as a template in the molecular sieve synthesis process. By selecting alkali sources from different sources and adjusting the corresponding temperature and time during the preparation process, different types of all-silicon molecular sieves, namely, all-silicon Beta molecular sieves or all-silicon Silicalite-1 molecular sieves, are prepared.

[0027] Furthermore, the molar ratio of the silicon source I, copper source, auxiliary agent, dispersant, nitrogen-containing heterocyclic compound, alkali source, and H2O in step a is 1:(0.005-0.4):(0.0001-0.5):(0.05-1.6):(0.08-2.2):(0.15-3):(10-200).

[0028] Preferably, the molar ratio of the silicon source I, copper source, additive, dispersant, nitrogen-containing heterocyclic compound, alkali source and H2O in step a is 1:(0.01-0.25):(0.01-0.3):(0.08-1.2):(0.11-1.6):(0.2-1.8):(15-80).

[0029] In the present invention, the temperature and time of the hydrothermal reaction in step a are one of the important factors affecting the crystal form, crystal size and product morphology of the hydrothermal product. Specifically, the hydrothermal treatment temperature in step a is 50-190°C, and the hydrothermal treatment time is 3-10 days; preferably, the hydrothermal treatment temperature is 70-170°C, and the hydrothermal treatment time is 5-8 days; the hydrothermal treatment conditions are further preferably: first, hydrothermal treatment at a temperature of 170-180°C for 0.5-1 day; then, hydrothermal treatment at a temperature of 100-130°C for 1-2 days. In addition, the pressure of the hydrothermal reaction system is another important factor affecting the crystal form and crystallization rate of the product, and the autogenous pressure of the reaction system depends on the size of the free volume in the reactor. In order to improve the efficiency of the hydrothermal reaction, preferably, the total volume of the mixed system in step a is 60-85% of the capacity of the reactor, wherein the reactor is preferably a polytetrafluoroethylene reactor.

[0030] Specifically, the drying temperature in step a is 80-120°C.

[0031] Furthermore, in the step b, the silicon source II is selected from at least one of organic silicate, silica gel, white carbon black, silica sol, and molecular sieve synthesis mother liquor; in order to improve the strength of the catalyst, at least one of organic silicate, silica sol, and molecular sieve synthesis mother liquor is preferred; further preferred is at least one of silica sol and molecular sieve synthesis mother liquor. Wherein, the molecular sieve synthesis mother liquor is recovered from the filtrate after filtration in step a. Silicon source II forms amorphous silica gel after calcination, and together with the all-silicon molecular sieve obtained in step a, it serves as the main structure of the bifunctional catalyst. After the molding process, the bifunctional catalyst is formed into a specific shape and has a certain strength to ensure the stability of the bifunctional catalyst during long-term use, while preventing the material from having excessive resistance during the process of passing through the catalyst bed.

[0032] Furthermore, in step b, the porogen is selected from at least one of starch, cellulose, lignin, or a starch / cellulose / lignin modified compound, preferably at least one of cellulose, lignin, or a cellulose / lignin modified compound, among natural polymer compounds. The porogen is removed after calcination, thereby imparting a porous structure to the amorphous silica gel serving as a carrier for the bifunctional catalyst, further increasing the specific surface area of ​​the bifunctional catalyst and improving catalytic efficiency.

[0033] Furthermore, in step b, sesbania powder is used as a forming aid to increase the preparation speed of the catalyst during the forming process and improve the surface smoothness of the catalyst.

[0034] Furthermore, in the step b, the mass ratio of the silicon source II, the all-silicon molecular sieve encapsulating copper oxide, the sesbania powder, the porogen, and H2O is (5-20): (30-50): (0.1-2): (0.1-3): (40-60); the mass ratio is preferably (7-16): (35-47): (0.2-1.5): (0.3-2): (43-55).

[0035] Specifically, the molding treatment of the catalyst precursor in step b includes adding the catalyst precursor to an extruder for extrusion or adding the catalyst precursor to a tablet press for molding.

[0036] Specifically, the drying temperature in step b is 80-120°C.

[0037] Specifically, the calcination temperature in step b is 400-850°C for 1-6 hours, preferably 500-650°C for 2-4 hours. To further improve the performance of the bifunctional catalyst, calcination is performed in a steam atmosphere. The steam volume fraction is preferably 30-80%, more preferably 50%.

[0038] Specifically, the reduction temperature in step b is 160-300°C, and the reduction time is 12-72 hours. The reduction reaction is carried out in an atmosphere with a H₂ volume fraction of 10-20%. During the reduction process, the copper oxide encapsulated in the molecular sieve is reduced to copper, thereby preparing a bifunctional catalyst containing an all-silicon molecular sieve encapsulated with copper.

[0039] Furthermore, it is preferred that the Lewis acid content of the bifunctional catalyst containing the copper-encapsulated all-silicon molecular sieve is 7.6 to 137.4 μmol / g and the specific surface area is 51 to 524 m 2 / g, pore volume of 0.07~0.47cm 3 / g; preferably the Lewis acid content is 17 to 80 μmol / g, and the specific surface area is 279 to 472 m 2 / g, pore volume of 0.19~0.34cm 3 / g.

[0040] The performance of the bifunctional catalyst provided by the present invention, comprising an all-silicon molecular sieve encapsulated with copper, in the direct catalytic synthesis of ketones from olefins is primarily influenced by the content of dehydrogenation active centers and Lewis acid centers in the catalytic material. Furthermore, the acid content of the Lewis acid centers, the specific surface area, and the pore volume of the bifunctional catalyst are other important factors influencing the catalytic performance of the catalyst.

[0041] The fourth aspect of the present invention further provides a method for directly preparing ketones from olefins, wherein the method uses the above-mentioned bifunctional catalyst.

[0042] Specifically, the method for directly preparing ketones from olefins is:

[0043] At a reaction temperature of 100-400°C, a reaction pressure of 0.05-5 MPa, and an olefin mass space velocity of 0.1-1000 h -1 Under the conditions of olefin and water in a molar ratio of 1: (0.5-50) are mixed, a catalytic reaction is carried out in the presence of the bifunctional catalyst and the product is recovered.

[0044] Furthermore, the method for directly preparing ketones from olefins comprises the following steps:

[0045] At a reaction temperature of 100-400°C, a reaction pressure of 0.05-5 MPa, and an olefin mass space velocity of 0.1-1000 h -1 Under the conditions of olefin and water in a molar ratio of 1: (0.5-50), the olefin is mixed with water, and then contacted with a bifunctional catalyst to carry out a catalytic reaction; the obtained reaction material is condensed and then separated into water and oil, the aqueous phase enters the reaction cycle, the oil phase is separated and the reaction raw material olefin, the reaction product alcohol and ketone are obtained, wherein the olefin enters the reaction cycle.

[0046] In the method for directly preparing ketone from olefin, the reaction temperature is preferably 130-350°C, the reaction pressure is 0.09-2.6 MPa, and the mass space velocity of olefin is 1-100 h -1 , the molar ratio of olefin to water is 1: (2 to 30); further preferably, the reaction temperature is 160 to 300 ° C, the reaction pressure is 0.1 to 1.6 MPa, and the mass space velocity of olefin is 2 to 40 h -1 , the molar ratio of olefin to water is 1:(3~15).

[0047] Specifically, the olefin is selected from at least one of chain olefins and cycloolefins; the carbon number of the carbocyclic ring in the cycloolefin is C5 to C16; the chain olefin is at least one of terminal olefins and internal olefins.

[0048] Furthermore, the structural formula of the terminal olefin is as follows:

[0049]

[0050] Wherein, R6 or R7 are each independently one of H or C1-C16 alkyl, wherein the C1-C16 alkyl is selected from at least one of C1-C16 straight-chain alkyl and C3-C16 branched-chain alkyl, and R6 or R7 cannot be H at the same time. R6 or R7 can independently be methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, etc.

[0051] Furthermore, the structural formula of the internal olefin is as follows:

[0052]

[0053] Wherein, R8 or R9 are each independently H or C1-C16 alkyl, R 10 or R 11 Each independently represents H or a C1-C16 alkyl group; the C1-C16 alkyl group is selected from at least one of a C1-C16 straight-chain alkyl group and a C3-C16 branched-chain alkyl group; R8 or R9 cannot be H at the same time, R 10 or R 11 Cannot be H at the same time. R8, R9, R 10 、R 11 They may independently be methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, and the like.

[0054] The bifunctional catalyst with both hydration and dehydrogenation provided by the present invention solves the problem of coupling olefin hydration and secondary alcohol dehydrogenation reactions in the olefin to ketone process, can directly prepare organic ketones at the same reaction temperature, and simplifies the process flow. Compared with the existing olefin to ketone technology, the present invention uses the bifunctional catalyst to catalyze the direct preparation of ketones from olefins, which increases the conversion rate of olefins from 10% to more than 25%, and the selectivity of the product organic ketone is more than 90%. While ensuring high selectivity of organic ketones, it improves the effective utilization rate of olefins and the production efficiency of products, reduces the cycle energy consumption of substrate olefins, and makes the production process of olefin to ketone more economical. In addition, the raw material silicon source II in step b is calcined to form amorphous silica gel, which together with the all-silicon molecular sieve obtained in step a serves as the main structure of the bifunctional catalyst. After molding, the bifunctional catalyst is formed into a specific shape and has a certain strength to ensure the stability of the bifunctional catalyst during long-term use and prevent excessive resistance of the material during the process of passing through the catalyst bed. DETAILED DESCRIPTION

[0055] The following describes the embodiments of the present invention through specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through different specific embodiments. The details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other unless they conflict.

[0056] The present invention will be described in detail below through specific examples. In the following examples and comparative examples, X-ray diffraction (XRD) phase diagrams were obtained using a Philips Panalytical X'pert, under the following test conditions: copper target, Kα radiation, Ni filter, super-energy detector, tube voltage 30kV, tube current 40mA; the morphology and size of the catalyst were measured using a Hitachi S4800 scanning electron microscope with an accelerating voltage of 20kV; the specific surface area and pore volume of the catalyst were measured using a nitrogen adsorption method, and the nitrogen adsorption-desorption curves were measured using a Micromeritics tristar II 3020-M specific surface analyzer. The specific surface area and pore volume were calculated using the BET and t-plot methods, with specific data shown in Table 4; the acid content was analyzed using a BIQ-RADFTS3000 Fourier transform infrared spectrometer, with specific data shown in Table 4; and the distribution of copper was analyzed using a projection electron microscope.

[0057] In the following examples and comparative examples, the specific results of conversion rate and target product selectivity are shown in Table 4, and the corresponding calculation formulas are as follows:

[0058]

[0059]

[0060] Example 1

[0061] In the presence of an aqueous solvent, a silicon source (tetraethyl orthosilicate), an auxiliary (potassium carbonate), and an alkaline source (tetrapropylammonium hydroxide) are uniformly mixed and hydrothermally treated at 60°C for 8 hours to obtain solution 1. A copper source (copper nitrate) and a dispersant (aniline) are mixed in appropriate proportions to form a uniform, transparent solution 2. Solutions 1 and 2 are mixed, and a nitrogen-containing heterocyclic compound, i.e., a 1:1 molar ratio of theophylline and adenine, is added to obtain a mixed system. The molar ratios of silicon source (I), copper source, auxiliary, dispersant, nitrogen-containing heterocyclic compound, alkaline source, and HO in the mixed system are 1:0.04:0.05:0.12:0.1:0.23:15.

[0062] After transferring the mixed system to a reactor, it was hydrothermally treated, first at 165°C for 12 hours and then at 100°C for 48 hours. After filtration, the resulting solid was dried at 110°C for 12 hours to obtain uncalcined, all-silicon Silicalite-1 molecular sieve encapsulating copper oxide.

[0063] In the presence of an aqueous solvent, a silicon source II silica sol, the copper oxide-encapsulated all-silicon Silicalite-1 molecular sieve prepared above, sesbania powder, and a porogen methylcellulose were mixed uniformly in a kneader at a mass ratio of 12:44:0.5:0.5:43 to obtain a catalyst precursor. The catalyst precursor was then extruded into a cylindrical catalyst precursor using an extruder. After drying, the precursor was calcined at 550°C for 3 hours. 2 g of the catalyst precursor was weighed and loaded into the reaction tube of a fixed-bed reactor. The catalyst precursor was then reduced at 220°C and a 15% H₂ concentration for 24 hours to obtain a bifunctional catalyst containing copper-encapsulated all-silicon Silicalite-1 molecular sieve.

[0064] This embodiment also provides a method for directly preparing ketones from olefins, the method comprising the following steps:

[0065] The fixed-bed reactor was further heated to 250°C, and the system pressure was increased to 0.5 MPa under anaerobic conditions. A mixture of cyclohexene and H2O was introduced into the fixed-bed reactor at a molar ratio of cyclohexene to H2O of 1:10, and contacted with a bifunctional catalyst containing copper-encapsulated all-silicon Silicalite-1 molecular sieve. The mass space velocity of cyclohexene was 1.2 h -1 The obtained reaction mass is condensed and then separated into water and oil, the water phase enters the reaction cycle, and the oil phase is fractionated to obtain the reactants cyclohexene, cyclohexanol and cyclohexanone; and the cyclohexene enters the reaction cycle.

[0066] As another embodiment, after the above-mentioned direct preparation of ketones from olefins is completed, the bifunctional catalyst containing copper-encapsulated all-silicon Silicalite-1 molecular sieve loaded in the reaction tube of the fixed-bed reactor can be stored in nitrogen or reduced and then reused in the direct preparation of ketones from olefins, thereby realizing the recycling of the bifunctional catalyst.

[0067] Example 2

[0068] In the presence of an aqueous solvent, a silicon source (tetraethyl orthosilicate), an auxiliary (sodium chloride), and an alkaline source (tetrapropylammonium hydroxide) are uniformly mixed and hydrothermally treated at 40°C for 8 hours to obtain solution 1. A copper source (copper acetylacetonate) and a dispersant (ethylenediamine) are mixed in appropriate proportions to form a uniform, transparent solution 2. Solutions 1 and 2 are mixed, and a nitrogen-containing heterocyclic compound, i.e., a 1:1 molar ratio of theophylline and adenine, is added to obtain a mixed system. The molar ratios of silicon source (I), copper source, auxiliary, dispersant, nitrogen-containing heterocyclic compound, alkaline source, and HO in the mixed system are 1:0.06:0.1:0.20:0.15:0.45:20.

[0069] After the mixed system was transferred to a reactor, it was hydrothermally treated at 165°C for 15 hours and then at 115°C for 44 hours. After filtration, the obtained solid was dried at 110°C for 12 hours to obtain the uncalcined all-silicon Silicalite-1 molecular sieve encapsulating copper oxide.

[0070] In the presence of an aqueous solvent, the recovered all-silicon Silicalite-1 molecular sieve mother liquor as silicon source II, the copper oxide-encapsulated all-silicon Silicalite-1 molecular sieve prepared above, sesbania powder, and lignin as a porogen were mixed uniformly in a kneader at a mass ratio of 7.1:45.1:0.6:1.0:46.2 to obtain a catalyst precursor. The catalyst precursor was then extruded into a porous cylindrical catalyst precursor, which was dried and calcined at 650°C for 2 hours. 2 g of the catalyst precursor was then weighed and loaded into the reaction tube of a fixed-bed reactor. The catalyst precursor was then reduced at 220°C and a 15% H2 concentration for 24 hours to obtain a bifunctional catalyst containing copper-encapsulated all-silicon Silicalite-1 molecular sieve.

[0071] This embodiment also provides a method for directly preparing ketones from olefins, the method comprising the following steps:

[0072] The fixed bed reactor was further heated to 280°C and the system pressure was increased to 0.3 MPa under anaerobic conditions. A mixture of cyclohexene and H2O was introduced into the fixed bed reactor at a molar ratio of cyclohexene to H2O of 1:5 and contacted with a bifunctional catalyst containing copper-encapsulated all-silicon Silicalite-1 molecular sieve. The mass space velocity of cyclohexene was 6 h -1 The obtained reaction mass is condensed and then separated into water and oil, the water phase enters the reaction cycle, and the oil phase is fractionated to obtain the reactants cyclohexene, cyclohexanol and cyclohexanone; and the cyclohexene enters the reaction cycle.

[0073] As another embodiment, after the above-mentioned direct preparation of ketones from olefins is completed, the bifunctional catalyst containing copper-encapsulated all-silicon Silicalite-1 molecular sieve loaded in the reaction tube of the fixed-bed reactor can be stored in nitrogen or reduced and then reused in the direct preparation of ketones from olefins, thereby realizing the recycling of the bifunctional catalyst.

[0074] Example 3

[0075] In the presence of an aqueous solvent, a silicon source (tetraethyl orthosilicate), an auxiliary (strontium nitrate), and an alkaline source (tetrapropylammonium hydroxide) are uniformly mixed and hydrothermally treated at 40°C for 8 hours to obtain solution 1. A copper source (copper chloride) and a dispersant (hexylene diamine) are mixed in appropriate proportions to form a uniform, transparent solution 2. Solutions 1 and 2 are mixed, and a nitrogen-containing heterocyclic compound, i.e., a 1:1 molar ratio of theophylline and adenine, is added to obtain a mixed system. The molar ratios of silicon source (I), copper source, auxiliary, dispersant, nitrogen-containing heterocyclic compound, alkaline source, and HO in the mixed system are 1:0.15:0.17:0.5:0.8:0.9:40.

[0076] After transferring the mixed system to a reactor, it was hydrothermally treated, first at 170°C for 24 hours and then at 110°C for 30 hours. After filtration, the resulting solid was dried at 110°C for 12 hours to obtain the copper oxide-encapsulated all-silicon Silicalite-1 molecular sieve.

[0077] In the presence of an aqueous solvent, a silicon source, tetraethyl orthosilicate, the copper oxide-encapsulated all-silicon Silicalite-1 molecular sieve prepared above, sesbania powder, and a porogen, corn starch, were mixed uniformly in a kneader at a mass ratio of 15.9:35.2:1.4:1.8:45.7 to obtain a catalyst precursor. The catalyst precursor was then placed in a tablet press and formed into a flaky catalyst. After drying, the catalyst was calcined at 600°C for 2.5 hours. 2 g of the catalyst was weighed and loaded into the reaction tube of a fixed-bed reactor. The catalyst was then reduced at 220°C and a 15% H2 concentration for 24 hours to obtain a bifunctional catalyst containing copper-encapsulated all-silicon Silicalite-1 molecular sieve.

[0078] This embodiment also provides a method for directly preparing ketones from olefins, the method comprising the following steps:

[0079] The fixed bed reactor was further heated to 225°C and the system pressure was increased to 0.11 MPa under anaerobic conditions. A mixture of cyclohexene and H2O was introduced into the fixed bed reactor at a molar ratio of cyclohexene to H2O of 1:3 and contacted with a bifunctional catalyst containing copper-encapsulated all-silicon Silicalite-1 molecular sieve. The mass space velocity of cyclohexene was 2 h -1The obtained reaction mass is condensed and then separated into water and oil, the water phase enters the reaction cycle, and the oil phase is fractionated to obtain the reactants cyclohexene, cyclohexanol and cyclohexanone; and the cyclohexene enters the reaction cycle.

[0080] As another embodiment, after the above-mentioned direct preparation of ketones from olefins is completed, the bifunctional catalyst containing copper-encapsulated all-silicon Silicalite-1 molecular sieve loaded in the reaction tube of the fixed-bed reactor can be stored in nitrogen or reduced and then reused in the direct preparation of ketones from olefins, thereby realizing the recycling of the bifunctional catalyst.

[0081] Examples 4 to 7

[0082] Examples 4-7 provide a bifunctional catalyst containing copper-encapsulated all-silicon Silicalite-1 molecular sieve, its preparation method, and a method for directly preparing ketones from olefins. Compared to Example 1, Examples 4-7 use the same steps to prepare the bifunctional catalyst containing copper-encapsulated all-silicon Silicalite-1 molecular sieve, but differ in the raw materials, raw material ratios, and some preparation conditions. Details are shown in Table 1. In the methods for directly preparing ketones from olefins, the raw material used is cyclohexene, but the preparation conditions vary. Details are shown in Table 1.

[0083] Examples 8 to 10

[0084] Examples 8-10 provide a bifunctional catalyst containing copper-encapsulated all-silicon Silicalite-1 molecular sieve, its preparation method, and a method for directly preparing ketones from olefins. The steps for preparing the bifunctional catalyst containing copper-encapsulated all-silicon Silicalite-1 molecular sieve in Examples 8-10 are the same as in Example 1, but differ in the raw materials, raw material ratios, and some preparation conditions. Details are shown in Table 2. The raw materials and preparation conditions in the method for directly preparing ketones from olefins vary; details are shown in Table 2.

[0085] Examples 11-12

[0086] Examples 11-12 provide a bifunctional catalyst containing copper-encapsulated all-silicon beta molecular sieve, its preparation method, and a method for directly preparing ketones from olefins. The steps for preparing the bifunctional catalyst containing copper-encapsulated all-silicon beta molecular sieve in Examples 11-12 are the same as in Example 1, but differ in the raw materials, raw material ratios, and some preparation conditions. Details are shown in Table 3. The raw materials and preparation conditions in the method for directly preparing ketones from olefins vary; details are shown in Table 3.

[0087] Table 1. Examples 4 to 7

[0088]

[0089] Table 2. Examples 8 to 10

[0090]

[0091] Table 3. Examples 11-12

[0092]

[0093] Table 4. Bifunctional catalysts and catalytic effects of all-silicon molecular sieves containing encapsulated copper

[0094]

[0095] The present invention provides a bifunctional catalyst containing copper-encapsulated all-silicon molecular sieve. An important factor affecting its performance in the direct catalytic synthesis of ketones from olefins is the content of dehydrogenation active centers and Lewis acid centers in the catalytic material. In addition, another important factor affecting the catalytic performance of the catalyst is the amount of Lewis acid in the catalyst, the specific surface area and pore volume of the all-silicon molecular sieve. Combining Table 4 and Examples 8 to 12, it can be seen that when the specific surface area of ​​the catalyst is greater than 472 m 2 / g or less than 279m 2 / g, the olefin conversion rate will be affected to a certain extent, but the selectivity of the product organic ketone is still higher than 98%. Combining Table 4 and Examples 4 to 7, it can be seen that the selection of the nitrogen-containing heterocyclic compound and porogen as the catalyst raw material will also affect the pore volume of the catalyst, thereby affecting its catalytic performance.

[0096] The present invention provides a bifunctional catalyst containing an all-silicon molecular sieve encapsulated with copper, which combines hydration and dehydrogenation functions. This solves the problem of coupling olefin hydration and secondary alcohol dehydrogenation reactions in the olefin-to-ketone process, allows the direct preparation of organic ketones at the same reaction temperature, and simplifies the process flow. Compared to existing olefin-to-ketone technologies, the present invention uses the bifunctional catalyst to catalyze the direct preparation of ketones from olefins, improving the olefin conversion rate to as high as 38.4%, and the selectivity of the product organic ketone is 95.4% or higher. While ensuring high selectivity for organic ketones, the effective utilization rate of olefins is increased, significantly improving product production efficiency, reducing the recycling energy consumption of the substrate olefin, and making the olefin-to-ketone production process more economical.

[0097] The embodiments described above are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the scope of protection of the present invention.

Claims

1. A method for directly preparing ketones from olefins, characterized in that: The method uses a bifunctional catalyst; the bifunctional catalyst includes a carrier and an active component; the carrier is amorphous silica gel, and the active component is an all-silicon molecular sieve encapsulating a metal element; the metal element provides a dehydrogenation active center for the bifunctional catalyst, the metal element is selected from at least one of Group IB metals, and the content of the metal element is 0.01 to 60 wt.%; the carrier and the all-silicon molecular sieve provide Lewis acid centers for the bifunctional catalyst, and the acid content is 7.6 to 137.4 μmol / g.

2. The method according to claim 1, characterized in that The metal element is selected from at least one of Cu, Ag, and Au; and the all-silicon molecular sieve is selected from at least one of all-silicon Silicalite-1 and all-silicon Beta molecular sieve.

3. The method according to any one of claims 1 or 2, characterized in that The bifunctional catalyst is a bifunctional catalyst containing copper-encapsulated all-silicon molecular sieve, and its active component is the copper-encapsulated all-silicon molecular sieve.

4. The method according to claim 3, characterized in that The preparation method of the bifunctional catalyst comprises: a. The silicon source I, a copper source, an additive, a dispersant, a nitrogen-containing heterocyclic compound, an alkali source, and H2O are mixed in proportion to obtain a mixed system; the mixed system is hydrothermally treated at 50 to 190 ℃ for 3 to 10 days, and then filtered and dried to obtain an all-silicon molecular sieve encapsulated with copper oxide; b. The silicon source II, the all-silicon molecular sieve encapsulating copper oxide obtained in step a, sesbania powder, a porogen, and H2O are mixed in proportion to prepare a catalyst precursor; the catalyst precursor is formed, dried, calcined at 400-850°C for 1-6h, and reduced in a H2 atmosphere at 160-300°C for 12-72h to obtain a bifunctional catalyst containing an all-silicon molecular sieve encapsulating copper.

5. The method according to claim 4, characterized in that The silicon source I is selected from at least one of organic silicate, silica gel, white carbon black, and silica sol; The copper source is selected from at least one of copper nitrate, copper chloride, copper tetraphenylporphyrin, and copper acetylacetonate; The auxiliary agent is selected from Li + 、Na + , K + , Rb + 、Cs + Mg 2+ , Ca 2+ 、Ba 2+ at least one compound containing at least one ion; The dispersant is selected from at least one of ethylamine, ethylenediamine, propylenediamine, hexamethylenediamine, aniline, pyridine, thiophene, mercaptan, thiophenol, and thioether; The alkaline source is selected from at least one of alkali metal hydroxide, ammonia, urea, hydrazine hydrate, sodium carbonate, sodium bicarbonate, aliphatic amine, aliphatic alcohol amine, and quaternary ammonium base; The nitrogen-containing heterocyclic compound is at least one selected from the group consisting of theophylline, guanosine, adenosine, guanine, adenine, and adefovir; The silicon source II is selected from at least one of organic silicate, silica gel, white carbon black, silica sol, and molecular sieve synthesis mother liquor; The porogen is selected from at least one of starch, cellulose, lignin, or a modified compound of starch / cellulose / lignin.

6. The method according to claim 5, characterized in that The nitrogen-containing heterocyclic compound is a mixture of theophylline and adenine, and the molar ratio of theophylline to adenine in the mixture is (0.4-3):

1.

7. The method according to claim 4, characterized in that In step a, the molar ratio of silicon source I, copper source, additive, dispersant, nitrogen-containing heterocyclic compound, alkali source, and H2O is 1: (0.005-0.4): (0.0001-0.5): (0.05-1.6): (0.08-2.2): (0.15-3): (10-200); the silicon source is calculated as SiO2, and the alkali source is calculated as N or OH. - count.

8. The method according to claim 4, characterized in that In step b, the mass ratio of the silicon source II, the all-silicon molecular sieve encapsulating copper oxide, the sesbania powder, the porogen, and H2O is (5-20): (30-50): (0.1-2): (0.1-3): (40-60).

9. The method according to claim 1, characterized in that The method comprises the following steps: at a reaction temperature of 100-400°C, a reaction pressure of 0.05-5 MPa, and an olefin mass space velocity of 0.1-1000 h -1 Under the conditions of olefin and water in a molar ratio of 1: (0.5-50) are mixed, a catalytic reaction is carried out in the presence of the bifunctional catalyst, and the product is recovered.

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