CN110694676A - Chemical vapor deposition preparation method of mesoporous catalyst and application of mesoporous catalyst in olefin epoxidation reaction - Google Patents
Chemical vapor deposition preparation method of mesoporous catalyst and application of mesoporous catalyst in olefin epoxidation reaction Download PDFInfo
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- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J29/00—Catalysts comprising molecular sieves
- B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
- B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
- B01J29/70—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65
- B01J29/7049—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65 containing rare earth elements, titanium, zirconium, hafnium, zinc, cadmium, mercury, gallium, indium, thallium, tin or lead
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- C—CHEMISTRY; METALLURGY
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- C07D301/00—Preparation of oxiranes
- C07D301/02—Synthesis of the oxirane ring
- C07D301/03—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds
- C07D301/19—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds with organic hydroperoxides
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D303/00—Compounds containing three-membered rings having one oxygen atom as the only ring hetero atom
- C07D303/02—Compounds containing oxirane rings
- C07D303/04—Compounds containing oxirane rings containing only hydrogen and carbon atoms in addition to the ring oxygen atoms
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- B01J2229/10—After treatment, characterised by the effect to be obtained
- B01J2229/18—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself
- B01J2229/186—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself not in framework positions
Abstract
The invention discloses a chemical vapor deposition preparation method of a mesoporous catalyst and application of the mesoporous catalyst in olefin epoxidation reaction. The method adopts an in-situ synthesis method to introduce lanthanide metal into the TUD-1 carrier, then carries out chemical vapor deposition reaction on the carrier and a titanium-containing compound, and prepares the mesoporous catalyst through silanization and hydrophobic treatment. According to the invention, lanthanide metal is doped into the TUD-1 carrier by adopting an in-situ synthesis method, so that the catalyst has good dispersity. The method has the advantages that the influence on the three-dimensional pore structure is small while the acid sites of the catalyst are inhibited, the diffusion resistance of titanium-containing compound molecules in pores of the carrier can be obviously reduced, more titanium is deposited on the carrier, and the activity of the catalyst is obviously improved. The catalyst has better catalytic performance in the epoxidation reaction of olefin and alkyl hydroperoxide solution, has certain economical efficiency and is beneficial to industrial production.
Description
Technical Field
The invention relates to a preparation method of a mesoporous catalyst, in particular to a chemical vapor deposition preparation method of the mesoporous catalyst and application of the mesoporous catalyst in olefin epoxidation reaction.
Background
The 1, 2-epoxy compound is used as an important organic chemical intermediate and widely applied in various fields. The production of 1, 2-epoxy compounds mainly includes chlorohydrin process, direct oxidation of hydrogen peroxide process, and co-oxidation process. The co-oxidation method is also called a Halcon method, and the method takes alkyl hydrogen peroxide as an oxygen source to carry out epoxidation reaction with olefin, thereby avoiding the corrosion of chlorohydrin method to equipment and the pollution to environment, and being safer and more economical compared with the direct oxidation method of hydrogen peroxide.
In the co-oxidation process, the catalyst is usually selected from transition metals between IVB and VIB, such as Ti, V, Mo, W and the like, and is generally divided into homogeneous and heterogeneous catalysts. Although the homogeneous catalyst has good catalytic effect and small using amount, the homogeneous catalyst is difficult to separate and recycle and difficult to reuse, so the homogeneous catalyst is difficult to be widely applied. In contrast, heterogeneous catalysts are easy to separate and recover, have stable structures and long service lives, and are therefore easier to widely apply. Among the studies of olefin epoxidation catalysts, molybdenum-based and titanium-based catalysts have been studied most extensively and relatively mature. The titanium-containing porous silicon oxide material is used as one of heterogeneous catalysts, has good catalytic activity on selective oxidation of olefins, and is often used as a catalyst for preparing 1, 2-epoxy compounds by selective oxidation of olefins.
Since the advent of TS-1 materials, research on the preparation and application of TS-1 materials has been a focus in the field of catalysis. The synthesis method of TS-1 disclosed in US4410501 is not only harsh in preparation conditions, long in preparation period, high in preparation cost, but also small in pore size (d =0.55 nm), and cannot be used for catalyzing epoxidation reaction of high carbon number macromolecular olefins (such as styrene) or/and using alkyl hydroperoxide as an oxygen source, and thus is limited in application.
Since the TS-1 catalyst can be used only for catalyzing small molecular substances, researchers have focused on the research of mesoporous titanium-silicon materials. The ordered mesoporous material is originated from M41S series mesoporous materials which are prepared by Mobil corporation in 1920 USA and mainly comprise MCM-41, and then a new chapter of development of the mesoporous materials is opened, and the mesoporous materials such as Ti-MCM-41, Ti-SBA-15, Ti-HMS and the like make great progress in the research of epoxidation reaction of macromolecular olefin or/and alkyl hydrogen peroxide serving as an oxygen source. Kuo-Tseng et al, deposited on MCM-41 by chemical vapor deposition with titanium tetrachloride as the titanium source, gave a catalyst with a yield of 94.3% in propylene epoxidation. However, Ti-MCM-41 catalyst has poor hydrothermal stability. The SBA-15 mesoporous material has a regular pore channel structure, a thicker pore wall and a larger specific surface area, and can effectively improve the hydrothermal stability after hydrophobic organic groups are introduced. The traditional Ti-SBA-15 preparation method mainly adopts a hydrothermal synthesis method, but the synthesis process is in an acid environment, and the hydrolysis process is difficult to control, so that the catalytic activity is low.
TUD-1 is a novel mesoporous material, compared with other mesoporous materials, TUD-1 has low preparation cost, the aperture can be easily finely adjusted through hydrothermal treatment, and the TUD-1 has the characteristics of high specific surface area, high hydrothermal performance and high mechanical stability, so the TUD-1 has better application prospect. Triethanolamine is used as a structure directing agent in the synthesis of the TUD-1 to guide tetraethyl orthosilicate to gradually form Si-O bonds between molecules, and finally the TUD-1 material with a three-dimensional structure and mesoporous channels is formed. The Ti-TUD-1 has an irregular three-dimensional mesoporous structure, thicker pore wall and large surface area, is quite stable under heat treatment and hydrothermal treatment, and has the epoxidation activity 5-6 times higher than that of Ti-MCM-41 on cyclohexene.
In a catalytic system using a titanium-silicon material as a catalyst, because acid centers exist on the surface of the titanium-silicon material, epoxy compounds can be decomposed by the acid sites, so that the selectivity of products is reduced, and the by-products can inhibit the reaction activity of the catalyst to a certain extent, so that the catalyst is gradually deactivated, a method for effectively inhibiting the acid centers in the catalyst is sought, and the method becomes a research point for modifying the epoxidation catalyst. The CN 105170176B of China is doped with Ga and B elements and alkali metal substances in the catalyst synthesis, wherein the influence of an acid site can be effectively eliminated to a certain extent by adding the alkali metal. CN 107224993A of China uses assistant metal salt (oxide is alkaline) to SiO2Impregnating carrier, drying and preparing catalyst by chemical vapour deposition, the added metal adjuvant can neutralize free TiO2The acidity caused by the catalyst can improve the activity of the catalyst and the selectivity of the catalyst to propylene oxide. However, the content of the metal additive doped in the carrier can not be controlled by adopting an impregnation method, and the pore channels are easy to block after roasting,even further shielding a portion of the active sites of the catalyst, the actual catalytic effect is not ideal.
Disclosure of Invention
The invention aims to provide a chemical vapor deposition preparation method of a mesoporous catalyst and application of the mesoporous catalyst in olefin epoxidation reaction. The preparation method comprises the three steps of in-situ synthesis of a lanthanide metal-doped carrier, chemical vapor deposition and liquid phase silanization. The carrier doped with lanthanide metal is prepared by adopting an in-situ synthesis method, then the carrier is subjected to chemical vapor deposition reaction with a titanium-containing compound, and then the mesoporous catalyst is prepared through silanization treatment, and the obtained catalyst has better effect in the epoxidation reaction of olefin and alkyl hydrogen peroxide solution.
The purpose of the invention is realized by the following steps:
a chemical vapor deposition preparation method of a mesoporous catalyst comprises the following three steps:
(1) uniformly mixing ethyl orthosilicate, triethanolamine, tetraethylammonium hydroxide, water and a lanthanide metal compound at room temperature to form a homogeneous solution, and then aging, drying, thermally treating and calcining to obtain a lanthanide metal-doped TUD-1 carrier;
(2) loading lanthanide-doped TUD-1 carrier into a tubular furnace, pretreating in nitrogen atmosphere, reacting the pretreated carrier with vapor of titanium-containing compound by chemical vapor deposition, and reacting with N2Purging, and roasting to obtain the catalyst after chemical vapor deposition;
(3) and (3) performing silanization treatment on the catalyst obtained in the step (2) to obtain the final product mesoporous catalyst.
Further, in the step (1), the ratio of the amounts of the substances of ethyl orthosilicate, triethanolamine, tetraethylammonium hydroxide and water is 1 (0.1 ~ 4): (0.1 ~ 2): 1 ~ 35), and the content of the oxide relative to the homogeneous solution is 0.1wt% to ~ 10wt% based on the oxide of the lanthanide metal compound.
Furthermore, in the step (1), the aging temperature is 20 ~ 60 ℃, the aging time is 12 ~ 72h, the drying temperature is 60 ~ 150 ℃, the drying time is 12 ~ 48h, the particle size of the gel during heat treatment is 1 μm ~ 1000 μm, the heat treatment temperature is 60 ~ 280 ℃, the heat treatment time is 1 ~ 12h, the calcining temperature is 500 ~ 800 ℃, and the calcining time is 5 ~ 15 h.
Further, in the step (2), the particle size of the pretreated carrier is 1 ~ 1000 μm, the temperature of the chemical vapor deposition reaction is 500 ~ 900 ℃, the time is 0.5 ~ 3h, and the vapor of the titanium-containing compound is N2The roasting after the reaction with the steam of the titanium-containing compound may be carried out in a nitrogen atmosphere or in an air atmosphere, preferably in an air atmosphere, at a roasting temperature of 500 ~ 800 ℃ for 4 ~ 8 hours.
Further, in the step (3), an organosilicon solution is adopted for silanization, the organosilicon solution is one or more than two of hexamethyldisilazane, hexamethylchlorosilazane, heptamethylchlorosilazane, trimethylchlorosilane, dimethylchlorosilane, tetramethyldisilazane, dimethyldiethoxysilane, trimethylmethoxysilane, dimethyldimethoxysilane, trimethylethoxysilane, silylamine or N-trimethylsilylimidazole, the dosage of organosilicon is 0.1% ~ 100% of the weight of the catalyst obtained in the step (2), the reaction temperature of silanization is 90 ~ 180 ℃, and the reaction time is 2 ~ 10 hours.
Further, the method also comprises the step (3) of adding an organic solvent, wherein the organic solvent is one or more of benzene, toluene, xylene, cumene, n-butane, isobutane, pentane, n-hexane, cyclohexane and heptane, preferably benzene, toluene, cumene or cyclohexane, and the mass ratio of the catalyst and the solvent obtained in the step (2) is 1 (1 ~ 50).
The mesoporous catalyst is applied to the co-oxidation reaction of olefin and alkyl hydroperoxide solution, the reaction temperature is 70 ~ 120 ℃, the time is 0.5 ~ 5h, the reaction pressure is 0.1 ~ 4MPa, the mass fraction of the catalyst in the reaction solution is 0.5% ~ 5%, the mass fraction of the alkyl hydroperoxide in the solvent is 5% ~ 40%, and the ratio of the quantity of the olefin to the quantity of the alkyl hydroperoxide is (0.5 ~ 20): 1.
Further, the method also comprises the use of a solvent, wherein the olefin is C3-C10An alkene or cycloalkene of (a); the alkyl hydroperoxide is cumene hydroperoxide, cyclohexyl hydroperoxide, tert-butyl hydroperoxide or ethylbenzene hydroperoxide; the solvent is isopropyl benzene, cyclohexane, tert-butyl alcohol, 1, 2-dichloroethane or ethylbenzene.
The invention has the beneficial effects that:
(1) according to the invention, lanthanide metal is doped into the TUD-1 carrier by adopting an in-situ synthesis method, and the carrier prepared by roasting contains lanthanide metal oxide, wherein the lanthanide metal oxide is alkalescent, so that the negative influence of an acid site of the catalyst on an epoxidation reaction can be reduced.
(2) According to the invention, lanthanide metal is doped into the TUD-1 carrier by adopting an in-situ synthesis method, compared with an impregnation method, the lanthanide metal entering the carrier is easy to control, has little influence on the pore structure of the carrier, and has good dispersity.
(3) The invention adopts the lanthanide metal-doped mesoporous TUD-1 material as a carrier, has the characteristics of low preparation cost, simple synthesis process and easy adjustment of pore diameter parameters, has a three-dimensional pore channel structure, and can ensure that olefin molecules and alkyl hydroperoxide with different kinetic diameters are contacted with titanium active sites in a pore channel by the characteristic of easy adjustment of the pore diameter parameters, thereby ensuring that the catalyst has higher activity. The three-dimensional pore channel structure can obviously reduce the pore diffusion resistance of reactant or product molecules, so that olefin molecules and alkyl hydrogen peroxide can enter the pore channel more easily to participate in reaction, epoxy products can be separated from the pore channel more easily and diffuse out of the pore channel, and the mass transfer effect is enhanced. In addition, in the chemical vapor deposition reaction process, the three-dimensional pore channel structure can also obviously reduce the diffusion resistance of titanium-containing compound molecules in pores of the carrier, so that more titanium is deposited on the carrier, and the catalytic activity is obviously improved.
(4) The invention adopts a chemical vapor deposition method to make the vapor of the titanium-containing compound and the carrier carry out chemical vapor deposition reaction to prepare the catalyst for chemical vapor deposition. The catalyst prepared by the method has highly dispersed active sites and catalytic activityThe performance is good, the preparation is simple, the repeatability is good, and the defect that the hydrolysis process is difficult to control in the preparation of a hydrothermal synthesis method can be effectively avoided; compared with the dipping method, the method is not easy to form large-size TiO outside the framework2The active sites are highly dispersed, and the catalytic activity is good.
(5) The obtained catalyst for chemical vapor deposition is subjected to silanization modification, so that the hydrophobic property of the surface of the catalyst can be improved, olefin and alkyl hydroperoxide molecules are easier to approach and adsorb, and the reaction activity of the catalyst is improved; but also can neutralize the weak acidity of the surface, reduce the occurrence of side reaction and improve the epoxidation selectivity of the catalyst.
In conclusion, the catalyst prepared by the preparation method provided by the invention can obtain a very good technical effect in catalyzing the epoxidation reaction of olefin and alkyl hydroperoxide solution, and the preparation method is relatively simple, low in preparation cost and good in reproducibility.
Detailed Description
The present invention is further illustrated by the following specific examples, which should be noted that the following examples are only illustrative and the present invention is not limited thereto.
Example 1
Preparation of Ti-TUD-1 catalyst doped with metallic La:
take 0.14gLa (NO)3)3·6H2O dissolved in 11.03g H2O, then evenly mixing with 25.06g of TEA, dropwise adding the mixture into 35.00g of TEOS, stirring for 30min, dropwise adding 29.69g of TEAOH solution with the mass fraction of 25%, stirring for 2.5h to form a homogeneous transparent solution, aging at room temperature for 48h in a dark place, drying by blowing at 100 ℃ in a drying oven for 24h, carrying out dynamic heat treatment on a rubber block with the particle size of 900 ~ 2000 mu m in a homogeneous reactor at 180 ℃ for 8h after grinding, finally roasting in a muffle furnace at the temperature rise rate of 5 ℃/min at 600 ℃ for 10h to prepare a carrier La-TUD-1 doped with metal La, placing 4g of the carrier La-TUD-1 with the particle size of 100 ~ 300 mu m in a tubular furnace, and placing in a 200ml/min N2After pretreatment at 400 ℃ for 2h at the flow rate, the temperature is rapidly raised to 700 ℃ at 100ml/minN2Introducing 150 ℃ saturated TiCl at a flow rate4Steaming for 1.5h at 200ml/minN2Blowing at a flow rate, cooling to room temperature, taking out, and finally roasting in a muffle furnace at a heating rate of 10 ℃/min and 600 ℃ for 6h to obtain the catalyst La-Ti-TUD-1 after chemical vapor deposition. 3.0g of La-Ti-TUD-1 was dispersed in 50.0g of toluene, and then hexamethyldisilazane (0.5 times the mass of the catalyst) was added to the suspension, followed by reflux stirring at 140 ℃ for 5 hours. The resulting powder was filtered, washed three times with 50ml of toluene, and then dried in a vacuum oven at 110 ℃ for 12 hours to obtain a silylated catalyst La-Ti-TUD-1 (S). The titanium content is 1.53%, the lanthanum content is 0.38%, and the average pore diameter is 18.2 nm.
Example 2
Preparation of Ti-TUD-1 catalyst doped with metallic La:
the procedure of example 1 was followed, differing from example 1 in that the silylation procedure was: 2.0gLa-Ti-TUD-1 was dispersed in 30.0g of cyclohexane, and then trimethylchlorosilane in an amount of 1.5 times the mass of the catalyst was added to the suspension, followed by stirring at 110 ℃ under reflux for 5 hours. The resulting powder was filtered, washed three times with 50ml of cyclohexane and then dried in a vacuum oven at 100 ℃ for 12 hours to obtain the silylated catalyst La/Ti-TUD-1 (S). The titanium content is 1.53%, the lanthanum content is 0.38%, and the average pore diameter is 18.3 nm.
Example 3
Preparation of a Ce-doped Ti-TUD-1 catalyst:
take 0.20gCe (NO)3)3·6H2O dissolved in 11.03g H2O, then evenly mixing with 25.06g of TEA, dropwise adding the mixture into 35.00g of TEOS, stirring for 30min, dropwise adding 29.69g of TEAOH solution with the mass fraction of 25%, stirring for 2.5h to form a homogeneous transparent solution, aging at room temperature for 36h in a dark place, drying by blowing at 100 ℃ in a drying oven for 24h, carrying out dynamic heat treatment on a rubber block with the particle size of 900 ~ 2000 mu m in a homogeneous reactor at 190 ℃ for 6h after grinding, finally roasting in a muffle furnace at the temperature rise rate of 5 ℃/min at 600 ℃ for 10h to prepare a carrier Ce-TUD-1 doped with metal Ce, putting 4g of the carrier Ce-TUD-1 with the particle size of 100 ~ 300 mu m in a tubular furnace, and putting the carrier Ce-TUD-1 in a 200ml/min N2After pretreatment at 400 ℃ for 2h at the flow rate, the temperature is rapidly raised to 600 ℃ at 100ml/minN2Introducing 150 ℃ saturated TiCl at a flow rate4Steam for 1.5h at 200ml/min N2Blowing at a flow rate, cooling to room temperature, taking out, and finally roasting in a muffle furnace at a heating rate of 10 ℃/min and a temperature of 600 ℃ for 6h to obtain the catalyst Ce-Ti-TUD-1 after chemical vapor deposition. 3.0g of Ce-Ti-TUD-1 was dispersed in 50.0g of toluene, and then hexamethyldisilazane (0.5 times the mass of the catalyst) was added to the suspension, followed by stirring at 140 ℃ under reflux for 5 hours. The resulting powder was filtered, washed three times with 50ml of toluene, and then dried in a vacuum oven at 110 ℃ for 12 hours to obtain a silylated catalyst, Ce-Ti-TUD-1 (S). The prepared catalyst has titanium content of 1.75%, cerium content of 0.50% and average pore diameter of 18.1 nm.
Example 4
Preparation of metal Pr-doped Ti-TUD-1 catalyst:
taking 0.25g Pr (NO)3)3·6H2O dissolved in 13.25g H2O, then uniformly mixing with 22.06g of TEA, dropwise adding the mixture into 30.00g of TEOS, stirring for 30min, dropwise adding 26.32g of TEAOH solution with the mass fraction of 25%, stirring for 2h to form a homogeneous transparent solution, aging for 48h at 40 ℃, drying for 12h by blowing at 110 ℃ in a drying oven, grinding, dynamically heat treating the rubber blocks with the particle size of 900 ~ 2000 mu m in a homogeneous reactor at 160 ℃ for 10h, finally roasting in a muffle furnace at the temperature rise rate of 5 ℃/min at 700 ℃ for 8h to prepare the metal Pr-TUD-1 doped carrier, putting 4g of the Pr-TUD-1 with the particle size of 100 ~ 300 mu m in a tubular furnace, and putting in a 200ml/min N2After pretreatment at 400 ℃ for 2h at the flow rate, the temperature is rapidly raised to 700 ℃ at 100ml/minN2Introducing 150 ℃ saturated TiCl at a flow rate4Steam for 2h at 200ml/minN2Blowing at a flow rate, cooling to room temperature, taking out, and finally roasting in a muffle furnace at a heating rate of 10 ℃/min and 700 ℃ for 5h to obtain the chemical vapor deposition catalyst Pr-Ti-TUD-1. 3.0g of Pr-Ti-TUD-1 was dispersed in 50.0g of toluene, and then hexamethyldisilazane (0.5 times the mass of the catalyst) was added to the suspension, followed by reflux stirring at 140 ℃ for 5 hours. The obtained powder was filtered, washed three times with 50ml of toluene, and then dried in a vacuum oven at 110 ℃ for 12 hours to obtain a silylated catalyst Pr-Ti-TUD-1 (S). The titanium content is 1.86%, the praseodymium content is 0.65%, and the average pore diameter is 22.5 nm.
Example 5
The catalysts prepared in examples 1,2, 3 and 4 were used in the epoxidation of 1-pentene with Cumene Hydroperoxide (CHP) solution, and the reaction was carried out in a batch reactor. Adding 0.31g of catalyst into a reaction kettle, then adding 6.14g of cumene hydroperoxide oxidizing solution with the mass percent of 25 percent, finally adding 4.72g of 1-pentene, sealing the reaction kettle, filling nitrogen to 1.5MPa, and reacting for 1h at the temperature of 120 ℃. After the reaction is finished, cooling the reaction product in ice water bath to below 5 ℃, opening an outlet valve of the reaction kettle, absorbing the released gas by the cumene, and then emptying the reaction kettle. And mixing the reaction liquid with the tail gas absorption liquid cumene for analysis and detection.
The content of cumene hydroperoxide before and after the reaction is titrated and analyzed by an iodometry method, the content of 1, 2-epoxy pentane generated by the reaction is analyzed by a gas chromatography internal standard method, and an internal standard substance is isooctane. The reaction results are shown in table 1.
TABLE 1 results of catalytic epoxidation reactions with different catalysts
| Examples | Catalyst and process for preparing same | CHP conversion% | 1, 2-Oxopentane Selectivity% |
| Example 1 | La-Ti-TUD-1(S) | 99.5 | 89.4 |
| Example 2 | La/Ti-TUD-1(S) | 96.3 | 82.1 |
| Example 3 | Ce-Ti-TUD-1(S) | 91.4 | 83.5 |
| Example 4 | Pr-Ti-TUD-1(S) | 97.8 | 83.3 |
Example 6
Preparation of Ti-TUD-1 catalyst doped with metallic La:
0.84g La(NO3)3·6H2o dissolved in 11.03g H2O, then evenly mixing with 25.06g of TEA, dropwise adding the mixture into 35.00g of TEOS, stirring for 30min, dropwise adding 29.69g of TEAOH solution with the mass fraction of 25%, stirring for 2.5h to form a homogeneous transparent solution, aging at room temperature for 48h in a dark place, drying by blowing at 100 ℃ in a drying oven for 24h, carrying out dynamic heat treatment on a rubber block with the particle size of 900 ~ 2000 mu m in a homogeneous reactor at 180 ℃ for 8h after grinding, finally roasting in a muffle furnace at the temperature rise rate of 5 ℃/min at 600 ℃ for 10h to prepare a carrier La-TUD-1 doped with metal La, placing 4g of the carrier La-TUD-1 with the particle size of 100 ~ 300 mu m in a tubular furnace, and placing in a 200ml/min N2After pretreatment at 400 ℃ for 2h at the flow rate, the temperature is rapidly raised to 700 ℃ at 100ml/minN2Introducing 150 ℃ saturated TiCl at a flow rate4Steam for 1.5h at 200ml/min N2Roasting for 6h at 600 ℃ in the atmosphere to obtain the catalyst La-Ti-TUD-1 after chemical vapor deposition. 3.0g of La-Ti-TUD-1 was dispersed in 50.0g of toluene, and then hexamethyldisilazane in an amount equivalent to the mass of the catalyst was added to the suspension, followed by stirring under reflux at 150 ℃ for 4 hours under a nitrogen atmosphere. The powder obtained is filtered, washed three times with 50ml of toluene and then dried in a vacuum drying oven at 110 ℃ for 12h,the silanized catalyst La-Ti-TUD-1(S) was obtained. The titanium content is 1.98%, the lanthanum content is 2.27%, and the average pore diameter is 18.1 nm.
Example 7
The catalyst prepared in example 6 was used in the epoxidation of propylene with cumene hydroperoxide solution, the reaction was carried out in a batch reactor. The rotor, 0.30g of catalyst and 5.92g of cumene hydroperoxide oxidizing solution with the mass percent of 25 percent are added into a reaction kettle in sequence, then the reaction kettle is sealed, and then 5.1g of propylene is added into the kettle in a liquid state through a advection pump. And (3) after leak detection, placing the mixture in an oil bath pot for reaction, reacting for 1h at the temperature of 110 ℃ under the self pressure, placing the mixture in ice water after the reaction is finished, cooling to the temperature below 5 ℃, discharging unreacted propylene through an exhaust valve, absorbing the unreacted propylene by using isopropylbenzene, and then emptying. And when determining that no residual gas exists in the reaction kettle, removing the reaction liquid for qualitative and quantitative analysis.
The content of cumene hydroperoxide in the reaction solution was analyzed by iodometry, the content of propylene oxide generated by the reaction was analyzed by gas chromatography internal standard method, and the internal standard substance was n-pentane. The results showed that the conversion of cumene hydroperoxide was 99.6% and the selectivity to propylene oxide was 89.8%.
Example 8
The catalyst prepared in example 1 was used in the epoxidation of 1-pentene with cyclohexyl hydroperoxide solution, the reaction was carried out in a batch reactor. Adding 0.37g of catalyst into a reaction kettle, then adding 7.51g of cyclohexyl hydrogen peroxide solution with the mass percent of 14.5%, finally adding 4.72g of 1-pentene, sealing the kettle, filling nitrogen to 1.5MPa, and reacting for 1h at 120 ℃. After the reaction is finished, cooling the reaction kettle to below 5 ℃ in ice water bath, opening an outlet valve of the reaction kettle, absorbing the discharged gas by cyclohexane and then emptying. And mixing the reaction liquid with the tail gas absorption liquid cyclohexane for analysis and detection. The content of cyclohexyl hydroperoxide before and after the reaction is titrated and analyzed by an iodometry method, the content of 1, 2-epoxy pentane generated by the reaction is analyzed by a gas chromatography internal standard method, and an internal standard substance is isooctane. The results showed that the conversion of cyclohexyl hydroperoxide was 90.0% and the selectivity to 1, 2-epoxypentane was 85.9%.
Comparative example 1
Preparation and catalytic performance of Ti-TUD-1 without doping lanthanide metal:
take 11.03g H2Uniformly mixing O and 25.06g of TEA, dropwise adding the mixture into 35.00g of TEOS, stirring for 0.5h, dropwise adding 29.69g of TEAOH solution with the mass fraction of 25%, and stirring for 2h to form a homogeneous transparent solution; aging at room temperature in dark place for 48 h; drying for 24h in a drying oven at 100 ℃ by air blast; carrying out dynamic heat treatment for 8h after grinding; and finally, roasting the powder in a muffle furnace at the heating rate of 5 ℃/min for 10 hours at the temperature of 600 ℃ to obtain the TUD-1. 4g of TUD-1 was placed in a tube furnace at 200ml/min N2After pretreatment at 400 ℃ for 2h at the flow rate, the temperature is rapidly raised to 700 ℃ at 100ml/minN2Introducing 150 ℃ saturated TiCl at a flow rate4Steam for 1.5h at 200ml/min N2Blowing at a flow rate, cooling to room temperature, taking out, and finally roasting in a muffle furnace at a heating rate of 10 ℃/min and a temperature of 600 ℃ for 6h to obtain Ti-TUD-1. 3.0g of the above Ti-TUD-1 was dispersed in 50.0g of toluene, and then HMDS in an amount of 0.5 times the mass of the catalyst was added to the suspension, followed by stirring under reflux at 140 ℃ for 5 hours under a nitrogen atmosphere. The resulting powder was filtered, washed three times with 50ml of toluene, and then dried in a vacuum oven at 110 ℃ for 12 hours to obtain Ti-TUD-1 (S). The titanium content is 1.19%, and the average pore diameter is 23.5 nm. The procedure of example 5 was followed and the catalyst obtained was used to catalyze the epoxidation of pentene with cumene hydroperoxide solution. The results showed that the conversion of cumene hydroperoxide was 90.3% and the selectivity to 1, 2-epoxypentane was 84.8%.
It can be seen from the reaction results of examples 1, 3, 4 and comparative example 1 that doping with different lanthanide metals has different effects on the catalytic performance of the catalyst, wherein the catalyst prepared by doping with metal La has the best catalytic performance in catalyzing the reaction of pentene and cumene hydroperoxide solution.
Comparative example 2
Preparing La-Ti-TUD-1 catalyst by vapor deposition after the TUD-1 carrier is impregnated with lanthanide metal:
the procedure of comparative example 1 was followed, differing from that of comparative example 1 in that, after TUD-1 was prepared, 3g of the support TUD-1 was impregnated with 5ml of La (NO) having a concentration of 0.05g/ml3)3·6H2O water solubleDipping in the solution for 12h, then drying the carrier in vacuum at 110 ℃ for 12h, placing the carrier in a tubular furnace for titanium coating by a chemical vapor deposition method, and further preparing the catalyst, wherein the titanium content is 1.12%, and the average pore diameter is 1.7 nm. The procedure of example 5 was followed and the catalyst obtained was used to catalyze the epoxidation of pentene with cumene hydroperoxide. The results showed that the conversion of cumene hydroperoxide was 90.1% and the selectivity to 1, 2-epoxypentane was 79.8%.
From the reaction results of example 1 and comparative examples 1 and 2, it can be seen that the catalyst prepared by doping lanthanide metals into the support by the in situ synthesis method has better catalytic performance in the reaction of pentene and cumene hydroperoxide solution. Compared with the catalyst prepared by impregnating lanthanide metal with TUD-1 carrier, the pore diameter of the catalyst prepared by impregnating lanthanide metal with TUD-1 carrier is greatly reduced, and the pore diameter is only 1.7 nm.
Comparative example 3
Impregnating Ti-TUD-1 with lanthanide metal after vapor deposition to prepare La-Ti-TUD-1 catalyst:
the procedure of comparative example 1 was followed, differing from that of comparative example 1 in that, after the completion of the chemical vapor deposition reaction, the catalyst was taken out of the tube furnace and immersed in La (NO) of 0.05g/ml3)3·6H2In an aqueous O solution (catalyst: solution =1 g: 1 ml), the impregnation time was 12 hours, followed by vacuum drying at 110 ℃ for 12 hours, placing in a muffle furnace and calcining at 600 ℃ at a heating rate of 10 ℃/min for 6 hours, and finally carrying out a silylation treatment to obtain a catalyst having a titanium content of 1.17% and an average pore diameter of 1.7 nm. The procedure of example 5 was followed and the catalyst obtained was used to catalyze the epoxidation of pentene with cumene hydroperoxide solution. The results showed that the conversion of cumene hydroperoxide was 86.9% and the selectivity to 1, 2-epoxypentane was 81.2%.
From the reaction results of example 1 and comparative examples 1 and 3, the catalyst prepared by impregnating lanthanide metal with Ti-TUD-1 after the vapor deposition process had the worst catalytic performance in the reaction of pentene with cumene hydroperoxide solution and a pore diameter of only 1.7 nm.
Claims (10)
1. A chemical vapor deposition preparation method of a mesoporous catalyst is characterized by comprising the following steps:
(1) uniformly mixing ethyl orthosilicate, triethanolamine, tetraethylammonium hydroxide, water and a lanthanide metal compound at room temperature to form a homogeneous solution, and then aging, drying, thermally treating and calcining to obtain a lanthanide metal-doped TUD-1 carrier;
(2) pretreating the lanthanide-doped TUD-1 carrier in nitrogen atmosphere, carrying out chemical vapor deposition reaction on the pretreated carrier and steam containing titanium compound, and carrying out chemical vapor deposition reaction on the pretreated carrier and the steam by using N after the reaction is finished2Purging, and roasting to obtain the catalyst after chemical vapor deposition;
(3) and (3) performing silanization treatment on the catalyst obtained in the step (2) to obtain the final product mesoporous catalyst.
2. The method for preparing mesoporous catalyst according to claim 1, wherein in step (1), the ratio of the amounts of tetraethoxysilane, triethanolamine, tetraethylammonium hydroxide and water is 1 (0.1 ~ 4): (0.1 ~ 2): (1 ~ 35), and the content of oxide in the lanthanide metal compound is 0.1wt% ~ 10wt% relative to the homogeneous solution based on the oxide.
3. The chemical vapor deposition preparation method of the mesoporous catalyst according to claim 1, wherein in the step (1), the aging temperature is 20 ~ 60 ℃, the time is 12 ~ 72h, the drying temperature is 60 ~ 150 ℃, the time is 12 ~ 48h, the particle size of the gel during heat treatment is 1 μm ~ 1000 μm, the heat treatment temperature is 60 ~ 280 ℃, the time is 1 ~ 12h, the calcination temperature is 500 ~ 800 ℃ and the time is 5 ~ 15 h.
4. The method for preparing the mesoporous catalyst according to claim 1, wherein in the step (2), the particle size of the pretreated carrier is 1 μm ~ 1000 μm, the temperature of the chemical vapor deposition reaction is 500 ~ 900 ℃, and the time is 0.5 ~ 3h, and the vapor of the titanium-containing compound is N2Is entrained into the mixture.
5. The method for preparing a mesoporous catalyst according to claim 1, wherein the calcination is performed in a nitrogen atmosphere or an air atmosphere at 500 ~ 800 ℃ for 4 ~ 8h in the step (2).
6. The method for preparing mesoporous catalyst according to claim 1, wherein in step (3), the silanization treatment is performed with an organosilicon solution, the organosilicon solution is one or more selected from hexamethyldisilazane, hexamethylchlorosilazane, heptamethylchlorosilazane, trimethylchlorosilane, dimethylchlorosilane, tetramethyldisilazane, dimethyldiethoxysilane, trimethylmethoxysilane, dimethyldimethoxysilane, trimethylethoxysilane, silylamine or N-trimethylsilylimidazole, and the amount of organosilicon is 0.1% ~ 100% of the weight of the catalyst obtained in step (2).
7. The chemical vapor deposition preparation method of the mesoporous catalyst according to claim 1, further comprising adding an organic solvent in the step (3), wherein the organic solvent is one or more of benzene, toluene, xylene, cumene, n-butane, isobutane, pentane, n-hexane, cyclohexane and heptane, preferably benzene, toluene, cumene or cyclohexane, the mass ratio of the catalyst and the solvent obtained in the step (2) is 1 (1 ~ 50), the reaction temperature of the silanization treatment is 90 ~ 180 ℃, and the reaction time is 2 ~ 10 h.
8. Use of the olefin epoxidation catalyst prepared by the process of any of claims 1 ~ 7 in an olefin epoxidation reaction.
9. The use according to claim 8, wherein the oxygen source for the epoxidation reaction is alkyl hydroperoxide, the reaction temperature is 70 ~ 120 ℃, the reaction time is 0.5 ~ 5h, the reaction pressure is 0.1 ~ 4Mpa, the mass fraction of the catalyst in the reaction solution is 0.5% ~ 5%, the mass fraction of the alkyl hydroperoxide in the solvent is 5% ~ 40%, and the mass ratio of the olefin to the alkyl hydroperoxide is (0.5 ~ 20): 1.
10. The use according to claim 9, further comprising the use of a solvent, wherein said olefin is C3~C10An alkene or cycloalkene of (a); the alkyl hydroperoxide is cumene hydroperoxide, cyclohexyl hydroperoxide, tert-butyl hydroperoxide or ethylbenzene hydroperoxide; the solvent is isopropyl benzene, cyclohexane, tert-butyl alcohol, 1, 2-dichloroethane or ethylbenzene.
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