CN114950536B - 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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CN114950536B
CN114950536B CN202210541805.1A CN202210541805A CN114950536B CN 114950536 B CN114950536 B CN 114950536B CN 202210541805 A CN202210541805 A CN 202210541805A CN 114950536 B CN114950536 B CN 114950536B
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molecular sieve
silane
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CN114950536A (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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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Dispersion Chemistry (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Silicon Compounds (AREA)
  • Catalysts (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 the MCM-41 mesoporous molecular sieve containing alkyl (methyl or ethyl) silane by adopting a sol-gel and Co-condensation method, then preparing Co-MCM-41 by adopting a template agent-ion exchange method, and regulating the quantity and dispersion degree of Co by adjusting factors such as silane quantity, category (chain length and functional group), co feeding quantity and the like. The method combines the advantages of a template agent-ion exchange method and a silane grafting method, and introduces alkylsilane during the synthesis of the silica-based material, but simultaneously the amount of silane can be controlled so as not to cover silicon hydroxyl groups, so that a metal precursor can approach and react, and finally, the metal precursor is baked at a high temperature, so that highly dispersed metal is embedded in the surface of the material. Preparing Co-MCM-41 with high Co dispersion on the surface; the used reagent is low in cost, and high-cost raw materials such as chelating agents and the like are avoided; the product has good repeatability in preparation 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 grafted MCM-41 mesoporous molecular sieve catalyst and a preparation method thereof.
Background
Olefin epoxidation is an important organic unit reaction. The epoxidation products of lower olefins are important basic organic chemical raw materials, such as ethylene oxide and propylene oxide, which play a significant role in the industrial production of polyesters and polyethers. The epoxidation products of higher olefins are important intermediates in fine chemistry, such as cyclohexene oxide, phenylethane, and norbornene epoxide. Thus, during the last decades, there has been a great deal of research and development into such reactions and their catalysts.
The greater yields in the epoxide are ethylene oxide and propylene oxide. The former production adopts an Ag catalyzed oxygen oxidation process, is environment-friendly and efficient, and has mature technology. The production of propylene oxide mainly adopts a chlorohydrin method and a co-oxidation method, and both of which have certain defects. The process for producing epoxypropane by the chlorohydrin method has the defects of serious pollution, high raw material unit consumption and the like, and belongs to a technology which is gradually eliminated; the catalyst used in the co-oxidation process is a molybdenum alcohol complex system and a silylated Ti/SiO 2 system. The molybdenum alcohol catalyst belongs to a homogeneous system, so that the defects of catalyst inflow products, difficulty in separation and the like are easily caused, and the development is limited; in the preparation process of the silanization Ti/SiO 2 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 preparation method is convenient to control and low in cost, belongs to a heterogeneous catalytic system and has remarkable advantages. However, the oxidizing agent used in the Ti/SiO 2 catalyst system is an organic peroxide, mainly t-butyl hydroperoxide, ethylbenzene hydroperoxide and cumene hydroperoxide, and the problems of co-production and cost increase are caused.
The titanium silicalite molecular sieve (TS-1) catalytic system invented by EniChem company is an epoch-making progress in the 80 s of the twentieth century. The process uses hydrogen peroxide as an oxidant, has very high epoxidation activity on propylene, and the reduction product is water, and belongs to a clean and environment-friendly green technology. However, the catalyst has more severe preparation conditions and higher cost. Meanwhile, because the TS-1 molecular sieve is a microporous material, the reaction of macromolecules cannot be performed, and therefore, the TS-1 molecular sieve is limited in the macromolecular reaction. In addition, the hydrogen peroxide method has obvious technical shortboards because of the defects of poor effect, low utilization efficiency and the like of the low-concentration hydrogen peroxide and the hidden danger of explosion of the high-concentration hydrogen peroxide besides the high cost of the hydrogen peroxide.
In summary, the chlorohydrin method, the organic peroxide method and the hydrogen peroxide method are excluded, and only the most clean, environment-friendly, economical and inexpensive method using oxygen as an oxygen source can be considered. In fact, reference is made to the technical feature of using oxygen as an oxygen source in the Ag catalytic process of ethylene oxide, but the effect is found to be poor in the epoxidation process of olefins applied to the synthesis of propylene oxide, cyclohexane oxide, and the like. However, co-doped zeolites and mesoporous molecular sieves have been reported to have good catalytic performance for olefin epoxidation using oxygen as an 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, etc.) can be doped on the surface of silica-based porous materials with high dispersion, including template-ion exchange, pre-silane grafting, and silane Co-condensation. Wherein, the template-ion exchange method cannot inhibit Co-O clusters or oxides from being formed when more metal is introduced, so that the dispersity is reduced; the silane co-condensation method is difficult to avoid the problem of too high metal hydrolysis speed due to the simultaneous reaction of silane and metal precursors, and the dispersity of metal introduction cannot be regulated; the silane grafting method in advance leads silane to be grafted on the surface of the material which is baked at high temperature to form a covering mode, and a metal precursor is difficult to approach free silicon hydroxyl groups to react, so that the quantity of introduced metal is influenced. Therefore, the three methods have defects of different degrees when used independently, and the purposes of high-efficiency introduction and high dispersion of metal ions cannot be achieved.
Disclosure of Invention
In order to overcome the defects of the prior art in the preparation method of the transition metal doped silicon dioxide based material, the invention provides a preparation method of a high-dispersion Co-MCM-41 mesoporous molecular sieve,
The purpose of the invention is realized in the following way:
the preparation method of the Co high-dispersion Co-MCM-41 mesoporous molecular sieve comprises the following steps:
(1) Methyl or ethyl silane and tetraethyl orthosilicate are used as silicon sources, cetyl trimethyl ammonium bromide is used as a template agent, water is used as a solvent, ammonia water is used for regulating pH, and a mesoporous molecular sieve MCM-41 containing methyl or ethyl is synthesized by a co-condensation method under the hydrothermal condition at room temperature and is marked as Me-MCM-41 or ET-MCM-41;
(2) Mixing Me-MCM-41 or ET-MCM-41 without the template agent prepared in the step (1) with cobalt salt aqueous solution, heating and refluxing, introducing Co ions through a template agent-ion exchange method, washing and drying to prepare MCM-41 containing Co and methyl or ethyl, and recording 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) to remove the template agent and the surface methyl or ethyl groups, and finally obtaining the high-dispersion Co-MCM-41.
Has the positive beneficial effects that: the invention firstly synthesizes the MCM-41 mesoporous molecular sieve containing alkyl (methyl or ethyl) silane by adopting a sol-gel and Co-condensation method, then prepares Co-MCM-41 by adopting a template agent-ion exchange method, and can adjust the quantity and the dispersion degree of Co introduced by adjusting factors such as the quantity, the type (chain length and functional group) of silane, the feeding quantity of Co and the like. The method combines the advantages of a template agent-ion exchange method and a silane grafting method, and introduces alkylsilane during synthesis of a silicon dioxide base material, so that the purpose of dividing and dispersing free silicon hydroxyl is achieved, but simultaneously the silane amount can be controlled, the silicon hydroxyl is not covered, a metal precursor can approach and react, finally, high-temperature roasting is carried out, highly dispersed metal is left to be embedded in the surface of the material, and the purpose of controlling the high dispersion of Co on the surface of MCM-41 through a surface pre-dividing method is truly achieved. 1. Preparing Co-MCM-41 with high Co dispersion on the surface; 2. the used reagent is low in cost, and high-cost raw materials such as chelating agents and the like are avoided; 3. the product has good repeatability in preparation and is beneficial to industrial application.
Description of the drawings:
FIG. 1 is a schematic illustration of the reaction principle of methylsilane as an example of the preparation process of the present invention;
FIG. 2 is a graph showing the ultraviolet-visible spectra of the molecular sieves prepared in comparative example 2 and examples 1, 3, 6, 9, and 10.
Detailed Description
The invention is further illustrated by the following examples:
Examples 1-10 and comparative examples 1-2, the preparation method (shown in figure 1) and the catalytic evaluation process of Co-MCM-41 with highly dispersed surface Co comprise the following steps:
(1) Preparation of methyl or ethyl grafted MCM-41: firstly, adding CTAB of 2.65 g into 120 g water, stirring, adding ammonia water with the concentration of 7.92 g being 30%, stirring for 2h to be uniform, clear and transparent, and marking as a solution A; TEOS and methyl or ethyl triethoxysilane (MTEOS or ETEOS for short respectively) with the molar ratio of x (1-x) are mixed and stirred uniformly to form a solution B; finally, dropwise adding the solution B into the solution A, stirring for 2h, washing with water, filtering, and drying the filter cake overnight to obtain methyl or ethyl grafted MCM-41, which is named as Me-MCM-41 or ET-MCM-41;
(2) Preparation of highly dispersed Co-MCM-41: adding cobalt nitrate (Co (NO 3)2·6H2 O) with a certain mass into 200mL of absolute ethyl alcohol, stirring uniformly to form a solution C, adding Me-MCM-41 or ET-MCM-41 prepared in the step (1) of 2 g into the solution C, heating and refluxing, stirring for 3 h until uniform, washing with water, filtering until colorless, and drying a filter cake overnight to prepare MCM-41 containing Co and methyl or ethyl, namely Co-Me-MCM-41 or Co-ET-MCM-41;
(3) And (3) roasting 1g of Co-Me-MCM-41 or Co-ET-MCM-41 prepared in the step (2) to 6h at 550 o C to obtain the high-dispersion Co-MCM-41 mesoporous molecular sieve which is denoted as HDCoM41.
(4) And (3) a catalytic reaction evaluation process:
1.05 g (10 mmol) styrene and 20ml N of N-dimethylformamide (DMF, solvent) are put into a 100 ml three-neck flask, and stirring is started; the temperature is controlled through an oil bath, and the temperature is raised to the required temperature; the introduction of O 2 was started, the level of the reaction solution in the gas-guide tube of O 2 was kept below, and HDCoM of powder of 0.2. 0.2g was further charged as a catalyst, and the time was defined as the reaction start time. After stirring reaction 2h, the catalyst was filtered off and the liquid product was analyzed by chromatography for the individual components. The styrene conversion (Conversion of styrene, abbreviated as C st) and styrene oxide selectivity (SELECTIVITY TO STYRENE OXIDE, abbreviated as S so) are defined by the following two formulas, respectively:
Where n st, 0 and n st are the amounts (mol) of the substances at the beginning and end of the reaction of styrene, respectively, and n so is the amount (mol) of the substances of the product styrene oxide at the end of the reaction.
The amount of each of the changes and the reaction results in the examples and comparative examples are shown in the following table in units of gram (g),
Note that: molar ratio of methyl, ethyl and cobalt to total silicon atoms for Me/Si, et/Si and Co/Si-dosing.
FIG. 1: the reaction principle of the preparation process of the high-dispersion Co-MCM-41 mesoporous molecular sieve is schematically shown (methylsilane is taken as an example).
The invention firstly synthesizes the MCM-41 mesoporous molecular sieve containing alkyl (methyl or ethyl) silane by adopting a sol-gel and Co-condensation method, then prepares Co-MCM-41 by adopting a template agent-ion exchange method, and can adjust the quantity and the dispersion degree of Co introduced by adjusting factors such as the quantity, the type (chain length and functional group) of silane, the feeding quantity of Co and the like. The method combines the advantages of a template agent-ion exchange method and a silane grafting method, and introduces alkylsilane during synthesis of a silicon dioxide base material, so that the purpose of dividing and dispersing free silicon hydroxyl is achieved, but simultaneously the silane amount can be controlled, the silicon hydroxyl is not covered, a metal precursor can approach and react, finally, high-temperature roasting is carried out, highly dispersed metal is left to be embedded in the surface of the material, and the purpose of controlling the high dispersion of Co on the surface of MCM-41 through a surface pre-dividing method is truly achieved. 1. Preparing Co-MCM-41 with high Co dispersion on the surface; 2. the used reagent is low in cost, and high-cost raw materials such as chelating agents and the like are avoided; 3. the product has good repeatability in preparation and is beneficial to industrial application.

Claims (1)

1. The preparation method of the Co high-dispersion Co-MCM-41 mesoporous molecular sieve is characterized by adopting a two-step method and specifically comprising the following steps of:
adding cetyl trimethyl ammonium bromide serving as a template agent into water, stirring, adding ammonia water to adjust pH, and stirring uniformly to obtain a solution A; mixing methyltriethoxysilane or ethyltriethoxysilane with tetraethyl orthosilicate, and stirring to be uniform to form a solution B; finally, dropwise adding the solution B into the solution A, stirring, washing with water, filtering, keeping a filter cake, drying overnight, and preparing the mesoporous molecular sieve MCM-41 containing methyl or ethyl by co-condensation, namely Me-MCM-41 or ET-MCM-41; mixing Me-MCM-41 or ET-MCM-41 without the template agent with cobalt salt aqueous solution, heating and refluxing, introducing Co ions through a template agent-ion exchange method, washing and drying to obtain MCM-41 containing Co and methyl or ethyl, and marking as Co-Me-MCM-41 or Co-ET-MCM-41; and roasting the prepared Co-Me-MCM-41 or Co-ET-MCM-41 to remove the template agent and the surface methyl or ethyl groups, and finally obtaining 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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