CN114950536A - Preparation method of high-dispersion Co-MCM-41 mesoporous molecular sieve - Google Patents

Preparation method of high-dispersion Co-MCM-41 mesoporous molecular sieve Download PDF

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CN114950536A
CN114950536A CN202210541805.1A CN202210541805A CN114950536A CN 114950536 A CN114950536 A CN 114950536A CN 202210541805 A CN202210541805 A CN 202210541805A CN 114950536 A CN114950536 A CN 114950536A
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molecular sieve
silane
mesoporous molecular
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CN114950536B (en
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李学峰
李闪闪
张立科
望申奥
赵波
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Xuchang University
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • 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
    • B01J29/041—Mesoporous materials having base exchange properties, e.g. Si/Al-MCM-41
    • B01J29/042—Mesoporous materials having base exchange properties, e.g. Si/Al-MCM-41 containing iron group metals, noble metals or copper
    • B01J29/044—Iron group metals or copper
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • 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
    • C07D301/04—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds with air or molecular oxygen
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/584—Recycling of catalysts

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  • Silicon Compounds (AREA)

Abstract

The invention discloses a preparation method of a high-dispersion Co-MCM-41 mesoporous molecular sieve, which comprises the steps of firstly synthesizing an MCM-41 mesoporous molecular sieve containing alkyl (methyl or ethyl) silane by adopting a sol-gel and cocondensation method, and then preparing Co-MCM-41 by adopting a template agent-ion exchange method, wherein the amount and the dispersion degree of introduced Co can be adjusted by adjusting factors such as the amount, the type (chain length, functional group) and the Co feeding amount. The method combines the advantages of a template agent-ion exchange method and a silane grafting method, introduces alkyl silane during the synthesis of the silicon dioxide base material, but simultaneously controls the silane amount so as not to cover silicon hydroxyl, enables metal precursors to approach and react, and finally leaves highly dispersed metal embedded on the surface of the material after high-temperature roasting. Preparing Co-MCM-41 with high Co dispersion on the surface; the used reagent is cheap and low in cost, and high-cost raw materials such as chelating agents are avoided; the product has good repeatability and is beneficial to industrial application.

Description

Preparation method of high-dispersion Co-MCM-41 mesoporous molecular sieve
Technical Field
The invention relates to the field of chemical catalyst preparation, in particular to a high-dispersion Co surface grafting MCM-41 mesoporous molecular sieve catalyst and a preparation method thereof.
Background
Olefin epoxidation is an important organic unit reaction. Epoxidation products of lower olefins are important basic organic chemicals, such as ethylene oxide and propylene oxide, which play a significant role in the industrial production of polyesters and polyethers, etc. The epoxidation products of higher olefins are important intermediates in fine chemicals, such as cyclohexene oxide, styrene oxide, and norbornene epoxides. Thus, during the past decades, much research has been conducted into the study and development of such reactions and their catalysts.
The greater yields of the epoxides are ethylene oxide and propylene oxide. The former production adopts an oxygen oxidation process catalyzed by Ag, so that the method is environment-friendly and efficient, and the technology is mature. The production of propylene oxide mainly adopts a chlorohydrin method and an oxidation method, and both have certain defects. The process for producing the propylene oxide by the chlorohydrination belongs to the technology which is gradually eliminated due to the defects of serious pollution, high unit consumption of raw materials and the like; the catalyst used in the co-oxidation process has a molybdenum alcohol complex system and silanized Ti/SiO 2 And (4) preparing the system. The molybdenum alcohol catalyst belongs to a homogeneous system, so that the defects that the catalyst flows into a product, is difficult to separate and the like are easily caused, and the development is limited; in silanization of Ti/SiO 2 In the preparation process of the catalyst, two key steps of Ti loading and silanization by a vapor deposition method can be simultaneously carried out in one reactor, so that the method is convenient to control, low in cost, belongs to a heterogeneous catalytic system and has remarkable advantages. However, silanized Ti/SiO 2 The oxidant used in the catalytic system is organic peroxide, mainly comprising tert-butyl hydroperoxide, ethylbenzene hydroperoxide and cumene hydroperoxide, which all have the problem of co-product and cost increase.
In the 80 th century, the titanium silicalite molecular sieve (TS-1) catalytic system invented by EniChem corporation was an epoch-making progress. The process takes hydrogen peroxide as an oxidant, has very high epoxidation activity to propylene, and the reduction product is water, thus belonging to a clean and environment-friendly green technology. However, the catalyst has harsh preparation conditions and high cost. Meanwhile, the TS-1 molecular sieve is a microporous material and has no effect on macromolecular reaction, so that the reaction is limited in macromolecular reaction. Further, the hydrogen peroxide method has a significant technical shortages in that low-concentration hydrogen peroxide has disadvantages of poor effect, low utilization efficiency, etc., and high-concentration hydrogen peroxide has a potential explosion hazard, in addition to high hydrogen peroxide cost.
In summary, excluding the chlorohydrin process, organic peroxide process and hydrogen peroxide process, only the cleanest, environmentally friendly, economical and inexpensive process using oxygen as the oxygen source can be considered. In fact, the technical characteristics of using oxygen as an oxygen source in the Ag catalysis process of ethylene oxide are also referred, but the effects are found to be poor when the catalyst is applied to the epoxidation processes of olefins such as propylene oxide, cyclohexene oxide synthesis and the like. However, Co-doped zeolites and mesoporous molecular sieves have been reported in the literature to have better catalytic properties for the epoxidation of olefins using oxygen as the oxygen source. The key point of the preparation of the catalyst is how to realize high dispersion of Co ions on the surface of zeolite or mesoporous molecular sieve.
The literature reports how transition metals (such as Co, Fe, Ti and the like) can be doped on the surface of silica-based porous materials with high dispersion, and the methods comprise a template-ion exchange method, a silane pre-grafting method and a silane Co-condensation method. Wherein, the template agent-ion exchange method can not inhibit the formation of Co-O cluster or oxide when the metal is introduced more, which leads to the reduction of the dispersity; in the silane co-condensation method, because silane and a metal precursor react at the same time, the problem of excessively high metal hydrolysis speed is difficult to avoid, and the dispersity of metal introduction cannot be regulated; the silane grafting method in advance has the defect that the amount of introduced metal is influenced because silane is introduced on the surface of a material baked at high temperature in a grafting manner to form a covering mode, and a metal precursor is difficult to approach free silicon hydroxyl groups for reaction. Therefore, the three methods have different defects when used alone, and cannot achieve the purposes of high-efficiency introduction and high dispersion of metal ions.
Disclosure of Invention
In order to overcome the defects of the prior preparation method of the transition metal doped silica-based material in the prior art, the invention provides a preparation method of a high-dispersion Co-MCM-41 mesoporous molecular sieve,
the purpose of the invention is realized as follows:
a preparation method of a Co-MCM-41 mesoporous molecular sieve with high Co dispersion comprises the following steps:
(1) taking methyl or ethyl silane and tetraethyl orthosilicate as silicon sources, taking hexadecyl trimethyl ammonium bromide as a template agent, taking water as a solvent, adjusting the pH by using ammonia water, and synthesizing a mesoporous molecular sieve MCM-41 containing methyl or ethyl by a cocondensation method under the condition of room temperature water heat, wherein the mesoporous molecular sieve MCM-41 is marked as Me-MCM-41 or ET-MCM-41;
(2) mixing the Me-MCM-41 or ET-MCM-41 without removing the template prepared in the step (1) with a cobalt salt aqueous solution, heating and refluxing, introducing Co ions by a template-ion exchange method, washing and drying to prepare MCM-41 containing Co and methyl or ethyl, and marking the MCM-41 as Co-Me-MCM-41 or Co-ET-MCM-41;
(3) and (3) roasting the Co-Me-MCM-41 or Co-ET-MCM-41 prepared in the step (2), and removing the template agent and surface methyl or ethyl groups to finally obtain the high-dispersion Co-MCM-41.
Has the positive and beneficial effects that: the invention firstly adopts sol-gel and cocondensation method to synthesize MCM-41 mesoporous molecular sieve containing alkyl (methyl or ethyl) silane, then prepares Co-MCM-41 by template agent-ion exchange method, and can adjust the amount and dispersion degree of Co introduced by adjusting the silane amount, kind (chain length, functional group) and Co feeding amount. The method combines the advantages of a template agent-ion exchange method and a silane grafting method, introduces alkyl silane during the synthesis of the silicon dioxide base material, achieves the purpose of dividing and dispersing free silicon hydroxyl groups, can control the amount of silane at the same time, cannot cover the silicon hydroxyl groups, enables metal precursors to approach and react, and finally carries out high-temperature roasting to leave highly dispersed metal embedded on the surface of the material, thereby really achieving the purpose of controlling the high dispersion of Co on the surface of MCM-41 by a surface pre-dividing method. 1. Preparing Co-MCM-41 with high Co dispersion on the surface; 2. the used reagent is cheap and low in cost, and high-cost raw materials such as chelating agents are avoided; 3. the product has good repeatability and is beneficial to industrial application.
Description of the drawings:
FIG. 1 is a schematic diagram of the reaction scheme of the preparation process of the present invention, using methylsilane as an example;
FIG. 2 is a chart of the UV-Vis spectra of the molecular sieves prepared in comparative example 2 and examples 1, 3, 6, 9, 10.
Detailed Description
The invention will be further described with reference to the following specific examples:
examples 1 to 10 and comparative examples 1 to 2, the preparation method (shown in the attached figure 1) and the catalytic evaluation process of the Co-MCM-41 with highly dispersed surface Co comprise the following steps:
(1) preparation of methyl or ethyl grafted MCM-41: firstly, adding 2.65 g of CTAB into 120 g of water, stirring, adding 7.92 g of 30% ammonia water, stirring for 2 h until the mixture is uniform, clear and transparent, and marking as a solution A; is prepared from TEOS and methyl or ethyl triethoxysilane (MTEOS or ETEOS, respectively) in different ratiosx:(1-x) Mixing and stirring to be uniform to form a solution B; finally, dropwise adding the solution B into the solution A, stirring for 2 h, washing with water, filtering, and drying a filter cake overnight to obtain methyl or ethyl grafted MCM-41 which is marked as Me-MCM-41 or ET-MCM-41;
(2) and preparing high-dispersion Co-MCM-41: mixing a certain mass of cobalt nitrate (Co (NO) 3 ) 2 ·6H 2 O) is put into 200mL of absolute ethyl alcohol and is evenly stirred to form a solution C; adding 2 g of Me-MCM-41 or ET-MCM-41 prepared in the step (1) into the solution C, heating, refluxing, stirring for 3 h until the mixture is uniform, washing with water, filtering until the mixture is colorless, and drying a filter cake overnight to obtain MCM-41 containing Co and methyl or ethyl, wherein the MCM-41 is marked as Co-Me-MCM-41 or Co-ET-MCM-41;
(3) subjecting 1g of Co-Me-MCM-41 or Co-ET-MCM-41 prepared in step (2) to 550 treatment o And C, roasting for 6 hours to obtain the high-dispersion Co-MCM-41 mesoporous molecular sieve which is marked as HDCoM 41.
(4) And a catalytic reaction evaluation process:
into a 100 ml three-neck flask, put1.05 g (10 mmol) of styrene and 20 ml of N, N-dimethylformamide (DMF, solvent) are added and stirring is started; controlling the temperature through an oil bath, and heating to the required temperature; start of introduction of O 2 Maintenance of O 2 The reaction start time was defined as the time measured at the time when 0.2 g of HDCoM41 powder was further charged as a catalyst below the liquid level of the reaction solution in the gas-guide tube. After stirring for 2 h, the catalyst was filtered off and the amounts of the individual components of the liquid product were analysed by chromatography. Conversion of styrene (Conversion of styrene, abbreviation)C st ) And styrene oxide Selectivity (Selectivity to styrene oxide, abbreviation)S so ) The definitions of (A) and (B) are respectively shown as the following two formulas:
Figure DEST_PATH_IMAGE002
in the formula (I), the compound is shown in the specification,n st, 0 andn st the amounts (mol) of the substances at the beginning and at the end of the styrene reaction, respectively,n so the amount (mol) of the substance which is the product styrene oxide at the end of the reaction.
The amounts of change and the reaction results in examples and comparative examples are shown in the following table, in units of grams (g),
Figure DEST_PATH_IMAGE003
note: Me/Si, Et/Si and Co/Si-molar ratio of methyl, ethyl and cobalt to total silicon atoms on charging.
FIG. 1: the reaction principle schematic diagram (taking methylsilane as an example) of the preparation process of the high-dispersion Co-MCM-41 mesoporous molecular sieve is shown.
The invention firstly adopts sol-gel and cocondensation method to synthesize MCM-41 mesoporous molecular sieve containing alkyl (methyl or ethyl) silane, then prepares Co-MCM-41 by template agent-ion exchange method, and can adjust the amount and dispersion degree of Co introduced by adjusting the silane amount, kind (chain length, functional group) and Co feeding amount. The method combines the advantages of a template agent-ion exchange method and a silane grafting method, introduces alkyl silane during the synthesis of the silicon dioxide base material, achieves the purpose of dividing and dispersing free silicon hydroxyl groups, can control the amount of silane at the same time, cannot cover the silicon hydroxyl groups, enables metal precursors to approach and react, and finally carries out high-temperature roasting to leave highly dispersed metal embedded on the surface of the material, thereby really achieving the purpose of controlling the high dispersion of Co on the surface of MCM-41 by a surface pre-dividing method. 1. Preparing Co-MCM-41 with high Co dispersion on the surface; 2. the used reagent is cheap and low in cost, and high-cost raw materials such as chelating agents are avoided; 3. the product has good repeatability and is beneficial to industrial application.

Claims (1)

1. A preparation method of Co-MCM-41 mesoporous molecular sieve with high Co dispersion is characterized by comprising the following steps:
(1) taking methyl or ethyl silane and tetraethyl orthosilicate as silicon sources, taking hexadecyl trimethyl ammonium bromide as a template agent, taking water as a solvent, adjusting the pH by using ammonia water, and synthesizing a mesoporous molecular sieve MCM-41 containing methyl or ethyl by a cocondensation method under the room-temperature hydrothermal condition, wherein the mesoporous molecular sieve MCM-41 is marked as Me-MCM-41 or ET-MCM-41;
(2) mixing the Me-MCM-41 or ET-MCM-41 without removing the template agent prepared in the step (1) with a cobalt salt aqueous solution, heating and refluxing, introducing Co ions by a template agent-ion exchange method, washing and drying to prepare MCM-41 containing Co and methyl or ethyl, and marking as Co-Me-MCM-41 or ET-MCM-41;
(3) and (3) roasting the Co-Me-MCM-41 or Co-ET-MCM-41 prepared in the step (2), and removing the template agent and surface methyl or ethyl groups to finally obtain the high-dispersion Co-MCM-41.
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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1557553A (en) * 2004-01-13 2004-12-29 厦门大学 Solid catalyst for preparing epoxy phenylethane by epoxidation of styrene and preparation method
EP1970364A2 (en) * 2007-03-16 2008-09-17 Sumitomo Chemical Company, Limited Method for Producing Cycloalkanol and/or Cycloalkanone
JP2008260746A (en) * 2007-03-16 2008-10-30 Sumitomo Chemical Co Ltd Method for producing cycloalkanol and/or cycloalkanone
CN101456562A (en) * 2009-01-06 2009-06-17 北京科技大学 Method for preparing mesoporous titanium silicate molecular sieve
CN105230611A (en) * 2015-10-29 2016-01-13 仲恺农业工程学院 Pesticide slow release agent with modified MCM-41 as carrier and preparation method thereof

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1557553A (en) * 2004-01-13 2004-12-29 厦门大学 Solid catalyst for preparing epoxy phenylethane by epoxidation of styrene and preparation method
EP1970364A2 (en) * 2007-03-16 2008-09-17 Sumitomo Chemical Company, Limited Method for Producing Cycloalkanol and/or Cycloalkanone
JP2008260746A (en) * 2007-03-16 2008-10-30 Sumitomo Chemical Co Ltd Method for producing cycloalkanol and/or cycloalkanone
CN101456562A (en) * 2009-01-06 2009-06-17 北京科技大学 Method for preparing mesoporous titanium silicate molecular sieve
CN105230611A (en) * 2015-10-29 2016-01-13 仲恺农业工程学院 Pesticide slow release agent with modified MCM-41 as carrier and preparation method thereof

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