CN111606789B - Catalytic oxidation process for cycloalkanes - Google Patents

Catalytic oxidation process for cycloalkanes Download PDF

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CN111606789B
CN111606789B CN201910143401.5A CN201910143401A CN111606789B CN 111606789 B CN111606789 B CN 111606789B CN 201910143401 A CN201910143401 A CN 201910143401A CN 111606789 B CN111606789 B CN 111606789B
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cycloalkane
acid
carbon
solution
oxidation reaction
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CN111606789A (en
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史春风
康振辉
黄慧
王肖
刘阳
赵娟
蔺晓玲
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Sinopec Research Institute of Petroleum Processing
China Petroleum and Chemical Corp
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China Petroleum and Chemical Corp
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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
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/18—Carbon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C45/00—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds
    • C07C45/27—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation
    • C07C45/32—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen
    • C07C45/33—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen of CHx-moieties
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2601/00—Systems containing only non-condensed rings
    • C07C2601/12—Systems containing only non-condensed rings with a six-membered ring
    • C07C2601/14—The ring being saturated

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Abstract

The present disclosure relates to a process for the catalytic oxidation of a cycloalkane, the process comprising: and (2) contacting the cycloalkane with an oxidant in the presence of a catalyst to react, wherein the catalyst is a catalytic composite material containing carbon sites and titanium oxide. The catalytic composite material containing carbon dots and titanium oxide is used as a catalyst to catalyze the oxidation reaction of the cycloalkane, so that the selective oxidation of the cycloalkane can be realized under mild conditions, and the selectivity of ketones in the product is high.

Description

Catalytic oxidation process for cycloalkanes
Technical Field
The present disclosure relates to a process for the catalytic oxidation of cycloalkanes.
Background
Carbon-based materials include carbon nanotubes, activated carbon, graphite, graphene, fullerenes, carbon nanofibers, nanodiamonds, and the like. Scientific research on nanocarbon catalysis began in the last 90 s of the century. Researches show that the surface chemical properties of the nano-carbon material (mainly carbon nano-tubes and graphene) can be flexibly regulated, and saturated and unsaturated functional groups containing heteroatoms such as oxygen, nitrogen and the like can be modified on the surface of the nano-carbon material, so that the nano-carbon material has certain acid-base properties and redox capability, and can be directly used as a catalyst material. Research and development of new catalytic materials related to fullerene (carbon nano tube) and broadening of the application of the new catalytic materials in the fields of petrochemical industry, fine chemical industry and the like have profound theoretical significance and huge potential application prospects.
Disclosure of Invention
The purpose of the present disclosure is to provide a catalytic oxidation method of cycloalkane, which can realize selective oxidation of cycloalkane under mild conditions, and has high selectivity of ketone in the product.
In order to achieve the above object, the present disclosure provides a method for catalytic oxidation of cycloalkane, the method comprising: the method comprises the following steps of contacting cycloalkane with an oxidant in the presence of a catalyst for reaction, wherein the catalyst is a catalytic composite material containing carbon dots and titanium oxide, and the content of the carbon dots is 2-40 wt% and the content of the titanium oxide is 60-98 wt% based on the total weight of the catalytic composite material.
Optionally, the content of the carbon dots is 5 to 20 wt% and the content of the titanium oxide is 80 to 95 wt% based on the total weight of the catalytic composite material.
Optionally, the carbon dots are graphene quantum dots, carbon nanodots, or polymer dots.
Optionally, the catalytic composite has a particle size of 10 to 5000nm, preferably 10 to 1000nm.
Optionally, the step of preparing the catalytic composite comprises:
(1) Mixing a first solution containing a titanium source and a first solvent with a second solution containing an acid and a second solvent under stirring to obtain a mixed solution;
(2) And (2) mixing the mixed solution obtained in the step (1) with a third solution containing carbon points, carrying out hydrothermal reaction for 0.5-48 h at 100-400 ℃, collecting a solid product, and then drying and roasting.
Optionally, in step (1), the molar ratio of the titanium source, the first solvent, the second solvent, and the acid is 1: (0.1 to 100): (0.1-50): (0.1 to 10); and/or the presence of a gas in the gas,
the titanium source is tetrabutyl titanate, tetraisopropyl titanate, tetraethyl titanate, tetramethyl titanate, titanyl sulfate or titanyl chloride, or a combination of two or three of the above; and/or the presence of a gas in the gas,
the acid is acetic acid, propionic acid, hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid, or a combination of two or three of the above; and/or the presence of a gas in the atmosphere,
the first solvent is ethanol, n-propanol, isopropanol, n-butanol, tert-butanol or cyclohexanol, or a combination of two or three of the above; and/or the presence of a gas in the atmosphere,
the second solvent is water, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol or cyclohexanol, or a combination of two or three of them.
Optionally, the step of preparing the catalytic composite further comprises: in the step (1), the first solution is added into the second solution at the speed of 0.1-50 mL/min; and/or the presence of a gas in the gas,
the stirring conditions include: the stirring speed is 100-2000 r/min, preferably 200-1000 r/min, and the time is 0.1-12 h, preferably 0.5-6 h.
Optionally, in the step (2), the weight ratio of the third solution to the mixed solution is (0.01-10): 1, preferably (0.1 to 0.8): 1; and/or the presence of a gas in the atmosphere,
the drying conditions include: the temperature is 100-200 ℃, and the time is 1-12 h; and/or the presence of a gas in the gas,
the roasting conditions comprise: the temperature is 250-800 ℃, and the time is 0.5-6 h.
Alternatively, the oxidation reaction is carried out in a slurry bed reactor, and the amount of the catalyst is 10 to 100mg, preferably 20 to 60mg, based on 10mL of the cycloalkane.
Optionally, the oxidation reaction is carried out in a fixed bed reactor, and the weight hourly space velocity of the cycloalkane is 0.01-10 h -1 Preferably 0.05 to 2 hours -1 。
Optionally, the method further comprises: the oxidation reaction is carried out in the presence of an initiator; the initiator is tert-butyl hydroperoxide, cumyl hydroperoxide, ethylbenzene hydroperoxide or peroxypropionic acid, or a combination of two or three of the above;
the dosage of the initiator is 0.01-0.3 mL based on 10mL of the cycloalkane.
Optionally, the oxidant is an oxygen-containing gas, preferably air or oxygen;
the molar ratio of the cycloalkane to oxygen in the oxygen-containing gas is 1: (1-5).
Optionally, the cycloalkane is one selected from a substituted or unsubstituted monocycloparaffin of C6 to C12 and a substituted or unsubstituted bicycloalkane of C8 to C16, preferably cyclohexane or methylcyclopentane.
Optionally, the oxidation reaction conditions are: the temperature is 50-200 ℃, preferably 60-180 ℃; the time is 1 to 72 hours, preferably 2 to 24 hours; the pressure is 0 to 20MPa, preferably 0 to 10MPa.
Through the technical scheme, the catalytic composite material containing carbon dots and titanium oxide is used as the catalyst to catalyze the oxidation reaction of the cycloalkane, the cycloalkane can be selectively oxidized under mild conditions, and the conversion rate of the raw material and the selectivity of the ketone in the product are high.
Additional features and advantages of the disclosure will be set forth in the detailed description which follows.
Detailed Description
The following describes in detail specific embodiments of the present disclosure. It should be understood that the detailed description and specific examples, while indicating the present disclosure, are given by way of illustration and explanation only, not limitation.
The present disclosure provides a process for the catalytic oxidation of a cycloalkane, the process comprising: and (2) contacting the cycloalkane with an oxidant in the presence of a catalyst to react, wherein the catalyst is a catalytic composite material containing carbon sites and titanium oxide.
According to the present disclosure, the content of the carbon dots is 2 to 40% by weight and the content of the titanium oxide is 60 to 98% by weight, based on the total weight of the catalytic composite material. The catalytic composite material can realize the oxidation of the cyclane under a mild condition, and the selectivity of the ketone in the product is high. In order to better achieve the object of the present disclosure, it is preferable that the content of the carbon dots is 5 to 20% by weight and the content of the titanium oxide is 80 to 95% by weight, based on the total weight of the catalytic composite.
According to the present disclosure, carbon Dots (CDs) refer to carbon particles having fluorescent properties with a size of less than 20nm. The chemical structure of the carbon dots may be sp 2 And sp 3 The hybrid carbon structure of (3) has a single-layer or multi-layer graphite structure, and may be polymer-based aggregated particles. The carbon dots mainly comprise graphene quantum dots, carbon nanodots and polymer dots. The graphene quantum dots refer to a carbon core structure with a single layer or less than 5 layers of graphene and chemical groups bonded at edges. The size of the graphene quantum dots has a typical anisotropy, the transverse dimension is larger than the longitudinal height, and the graphene quantum dots have a typical carbon lattice structure. Graphene quantum dots are a class of materials that physicists use to study the photoelectric band gap of graphene, and typically require electron beam etching of large sheets of graphene. Carbon nanodots are generally spherical structures that can be classified into lattice-evident carbon nanodots and lattice-free carbon nanodots. Due to the diversity of the carbon nano-dot structure, the carbon nano-dot luminescent centers prepared in different modes and the luminescent mechanism have great difference. Specifically, it can be classified into carbon quantum dots having distinct lattices and carbon nanodots having/not having lattices. The carbon quantum dots with obvious crystal lattices have obvious quantum size dependence, and the optimal fluorescence emission peak is red-shifted along with the size increase. The lattice-free carbon nano-dots have no quantum size effect, the luminescent centers of the lattice-free carbon nano-dots are not completely controlled by the carbon cores, and the surface groups have non-negligible influence on luminescence. The polymer dots are typically cross-linked flexible aggregates formed from non-conjugated polymers by dehydration or partial carbonization, with no carbon lattice structure present. Polymer dots are a class of materials from which carbon dots extend. The polymer dots comprise fluorescent polymer dots formed by moderate crosslinking or carbonization of non-conjugated macromolecules and fluorescent polymer dots formed by assembly of carbon cores and polymers.
Methods for preparing such carbon dots are well known to those skilled in the art in light of this disclosure. The raw material source of the carbon dots may generally include both inorganic carbon sources and organic carbon sources. The specific preparation method can comprise methods such as an arc discharge method, a laser ablation/passivation method, an electrochemical method, a pyrolysis method, a field-assisted method and the like. The carbon dots can be prepared in one step by a high temperature pyrolysis method, usually using citrate as a carbon source or using citric acid and glutathione together as a carbon source.
According to the present disclosure, the carbon dots are preferably graphene quantum dots, carbon nanodots or polymer dots, and the carbon dots are commercially available or can be prepared by methods known in the art. The particle size of the carbon dots is generally 3 to 20nm.
According to the present disclosure, the titanium oxide (TiO) 2 ) The particle size of (a) may be 10 to 5000nm.
According to the present disclosure, the catalytic composite may have a particle size of 10 to 5000nm, preferably 10 to 1000nm. In the present disclosure, the particle size refers to the maximum three-dimensional length of the particle, i.e., the maximum distance between two points on the particle.
In accordance with the present disclosure, the objects of the present disclosure are achieved with a catalytic composite having the above-described features. In a preferred embodiment, the step of preparing the catalytic composite may comprise:
(1) Mixing a first solution containing a titanium source and a first solvent with a second solution containing an acid and a second solvent under stirring to obtain a mixed solution;
(2) And (2) mixing the mixed solution obtained in the step (1) with a third solution containing carbon points, carrying out hydrothermal reaction for 0.5-48 h at 100-400 ℃, collecting a solid product, and then drying and roasting.
According to the present disclosure, in step (1), the molar ratio of the titanium source, the first solvent, the second solvent, and the acid may be 1: (0.1 to 100): (0.1-50): (0.1 to 10), preferably 1: (1-50): (1-25): (0.2-5). The titanium source is a compound containing titanium, and may be, for example, tetrabutyl titanate, tetraisopropyl titanate, tetraethyl titanate, tetramethyl titanate, titanyl sulfate or titanyl chloride, or a combination of two or three of them. The acid may be a common organic or inorganic acid, and may be, for example, acetic acid, propionic acid, hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid, or a combination of two or three thereof. The first solvent may be ethanol, n-propanol, isopropanol, n-butanol, tert-butanol or cyclohexanol, or a combination of two or three thereof; the second solvent may be water, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol or cyclohexanol, or a combination of two or three thereof; the first solvent and the second solvent may be the same or different in kind. The pH of the second solution may be 0 to 6.
According to the present disclosure, in order to make the mixing of the first solution and the second solution more sufficient, the preparing step of the catalytic composite material may further include: in the step (1), the first solution is added into the second solution at a speed of 0.1-50 mL/min. The mixing is performed under agitation conditions, which may include: the stirring speed is 100-2000 r/min, preferably 200-1000 r/min, and the time is 0.1-12 h, preferably 0.5-6 h.
According to the disclosure, in the step (2), the third solution is used in an amount such that the content of the carbon dots in the prepared catalytic composite material is 2 to 40 wt% and the content of the titanium oxide in the prepared catalytic composite material is 60 to 98 wt%, based on the total weight of the catalytic composite material. For example, the weight ratio of the third solution to the mixed solution may be (0.01 to 10): 1, preferably (0.1 to 0.8): 1. the hydrothermal reaction may be carried out in a conventional reactor, for example in a polytetrafluoroethylene reactor. The pressure of the hydrothermal reaction process is not particularly limited, and may be the autogenous pressure of the system, or may be under an additional applied pressure condition, and preferably, the hydrothermal reaction process is performed under the autogenous pressure (generally, in a closed vessel). The method of collecting the solid product after the hydrothermal reaction may be carried out by a conventional method such as filtration, centrifugation and the like. The conditions for drying and calcining the solid product may be conventional in the art, for example, the drying conditions may include: the temperature is 100-200 ℃, and the time is 1-12 h; the conditions for the firing may include: the temperature is 250-800 ℃, and the time is 0.5-6 h.
The catalytic oxidation process of cycloalkanes of the present disclosure may be carried out in various conventional catalytic reactors, for example, may be carried out in a batch tank reactor or a three-neck flask, or in suitable other reactors such as fixed bed, moving bed, suspended bed, and the like.
In an alternative embodiment of the present disclosure, the oxidation reaction may be carried out in a slurry bed reactor. In this case, the amount of the catalyst to be used may be appropriately selected depending on the amount of the cycloalkane and the oxidizing agent, and for example, the amount of the catalyst to be used may be 20 to 100mg, preferably 40 to 60mg, based on 10mL of the cycloalkane.
In another alternative embodiment of the present disclosure, the oxidation reaction may be carried out in a fixed bed reactor. In this case, the weight hourly space velocity of the cycloalkane may be, for example, 0.01 to 10 hours -1 Preferably 0.05 to 2 hours -1 。
According to the present disclosure, the cycloalkane may be one selected from a substituted or unsubstituted monocycloparaffin of C5 to C12 and a substituted or unsubstituted bicycloalkane of C8 to C16. Further, when the cycloalkane is one selected from the group consisting of C5-C12 substituted monocycloparaffins and C8-C16 substituted bicycloalkanes, the substituent thereof may be a halide or a methyl group. For example, the cycloalkane may be cyclohexane, cyclopentane, methylcyclohexane, halogenated cyclohexane, methylcyclopentane, halogenated cyclopentane, or the like, and cyclohexane is preferable.
The oxidizing agent is an oxidizing agent conventionally used in the art according to the present disclosure, and for example, the oxidizing agent may be an oxygen-containing gas, and further may be air or oxygen. The molar ratio of the cycloalkane to oxygen in the oxygen-containing gas may be 1: (1-5).
According to the present disclosure, in order to promote the oxidation reaction, further improve the conversion of the raw material and the selectivity of the target product, the method may further include: the oxidation reaction is carried out in the presence of an initiator. The initiator may be an initiator conventionally used in the art, for example, the initiator may be t-butyl hydroperoxide, cumyl hydroperoxide, ethylbenzene hydroperoxide or peroxypropionic acid, or a combination of two or three thereof. The initiator can be used in a small amount, for example, 0.01 to 0.3mL based on 10mL of the cycloalkane.
According to the present disclosure, the conditions of the oxidation reaction may be: the temperature is 50-200 ℃, and preferably 80-180 ℃; the time is 1 to 72 hours, preferably 2 to 24 hours; the pressure is 0 to 20MPa, preferably 0 to 10MPa. In order to make the oxidation reaction more sufficient, it is preferable that the oxidation reaction is carried out under stirring.
The catalytic composite material containing carbon dots and titanium oxide is used as a catalyst to catalyze the oxidation reaction of cycloalkane, so that the selective oxidation of cycloalkane can be realized under mild conditions, and the selectivity of ketones in the product is high.
The present disclosure is described in detail below with reference to examples, but the scope of the present disclosure is not limited thereby.
Preparation examples 1-5 are provided to illustrate the preparation of the catalytic composite employed in the present disclosure.
In the following preparation examples, solutions containing carbon dots having a particle size of 9nm and a concentration of 0.01 wt% were purchased from Suzhou university. Titanium oxide was purchased from winning companies and had a particle size of 300nm. The particle size of the composite material was determined by TEM, and 20 particles were randomly selected from the TEM photograph, and the average size thereof was calculated. The method for measuring the content of the carbon points and the titanium oxide in the catalytic composite material is a roasting method, the catalytic composite material is roasted for 2 hours at the temperature of 400 ℃, the percentage of the residual weight to the weight before roasting is the content of the titanium oxide, and the percentage of the lost weight to the weight before roasting is the content of the carbon points.
Preparation of example 1
Tetrabutyl titanate and the first solvent absolute ethyl alcohol are vigorously stirred for 10min (the stirring speed is 800 revolutions per minute) to obtain a first solution. The glacial acetic acid, the second solvent water and the absolute ethyl alcohol are stirred vigorously (the stirring speed is 800 r/min), and hydrochloric acid is added to ensure that the pH value is less than 3, so as to obtain a second solution. Adding the first solution into the second solution at a speed of 3mL/min under the condition of vigorous stirring at a stirring speed of 800 revolutions per minute in a room-temperature water bath to form a light yellow mixed solution, wherein the molar ratio of tetrabutyl titanate to the first solvent to the second solvent to the acid is 1:10:5:1. and (3) mixing the third solution containing the carbon dots with the mixed solution according to the weight ratio of 0.25:1, mixing, stirring for 0.5h, transferring into a hydrothermal kettle, carrying out hydrothermal reaction for 6h at 80 ℃, collecting a solid product, drying at 105 ℃, and roasting at 500 ℃ to obtain CDs/TiO 2 Catalytic composite A1, average particle size about 150nm, CDs content 8% by weight TiO 2 The content was 92% by weight.
Preparation of example 2
A composite material was prepared according to the method of preparation example 1, except that, during the synthesis, the weight ratio of the third solution containing carbon dots to the mixed solution of the first solution and the second solution was 0.5:1, obtaining CDs/TiO 2 Composite particles A2 having an average particle size of about 65nm and a content of TiO 15% by weight 2 The content was 85% by weight.
Preparation of example 3
According to preparation example 1The method is used for preparing the composite material, and is characterized in that in the synthesis process, the molar ratio of tetrabutyl titanate to the first solvent to the second solvent to the acid is 1:60:30:10, obtaining CDs/TiO 2 Composite particles A3 having an average particle size of about 1100nm and a CDs content of 9 wt%, tiO 2 The content was 91% by weight.
Preparation of example 4
A composite material was prepared according to the method of preparation example 1, except that, during the synthesis, the weight ratio of the third solution containing carbon dots to the mixed solution of the first solution and the second solution was 1:1, obtaining CDs/TiO 2 Composite particles A4 having an average particle size of about 30nm, a CDs content of 33% by weight, tiO 2 The content was 67% by weight.
Preparation of example 5
A composite material was prepared according to the method of preparation example 1, except that, during the synthesis, the weight ratio of the third solution containing carbon dots to the mixed solution of the first solution and the second solution was 0.05:1, obtaining CDs/TiO 2 Composite particles A5 having an average particle size of about 420nm, a content of CDs of 4 wt.%, tiO 2 The content was 96% by weight.
Examples 1 to 11 are intended to illustrate the catalytic oxidation process of cycloalkanes of the present disclosure.
In the following examples and comparative examples, the oxidation products were analyzed by gas chromatography (GC: agilent, 7890A) and gas chromatography-mass spectrometer (GC-MS: thermo Fisher Trace ISQ). Conditions for gas chromatography: nitrogen carrier gas, temperature programmed at 140K: 60 ℃,1 minute, 15 ℃/minute, 180 ℃,15 minutes; split ratio, 10:1; the injection port temperature is 300 ℃; detector temperature, 300 ℃. On the basis, the conversion rate of raw materials and the selectivity of target products are calculated by respectively adopting the following formulas:
naphthene conversion% = (molar amount of naphthene added before reaction-molar amount of naphthene remaining after reaction)/molar amount of naphthene added before reaction × 100%;
target product selectivity% = (molar amount of target product formed after reaction)/molar amount of cycloalkane added before reaction × 100%.
Example 1
50mg of the composite particles A1 as a catalyst and 10mL of cyclohexane were charged into a 250mL autoclave, 0.1mL of t-butyl hydroperoxide (TBHP) as an initiator was added dropwise to the above system, the system was sealed, oxygen (oxygen to cyclohexane molar ratio: 5:1) was introduced, the mixture was stirred at 130 ℃ and 2.0MPa for 5 hours, the temperature was lowered, samples were taken under reduced pressure, and the catalyst was separated by centrifugation and filtration, and the results of analysis of the oxidation products are shown in Table 1.
Examples 2 to 5
Cyclohexane was catalytically oxidized by the method of example 1, except that the same amount of the composite particles A2 to A5 was used instead of A1, respectively. The results of the oxidation product analysis are shown in Table 1.
Example 6
60mg of the composite particles A1 as a catalyst and 10mL of cyclohexane were charged into a 250mL autoclave, 0.2mL of cumyl hydroperoxide as an initiator was added dropwise to the above system, the system was sealed, oxygen (the molar ratio of oxygen to cyclohexane was 2:1) was introduced, the mixture was stirred at 100 ℃ and 2.5MPa for 8 hours, the temperature was lowered, the pressure was reduced, sampling was performed, the catalyst was separated by centrifugation and filtration, and the results of analysis of the oxidation products are shown in Table 1.
Example 7
10mg of the composite particles A1 as a catalyst and 10mL of cyclohexane were charged into a 250mL autoclave, 0.1mL of t-butyl hydroperoxide as an initiator was added dropwise to the above system, the system was sealed, oxygen was introduced (the molar ratio of oxygen to cyclohexane was 4:1), the mixture was stirred at 130 ℃ and 2.0MPa for 5 hours, the temperature was lowered, the pressure was released, a sample was taken, and the catalyst was separated by centrifugation and filtration, and the results of analyzing the oxidation products are shown in Table 1.
Example 8
80mg of the composite particles A1 as a catalyst and 10mL of cyclohexane were charged into a 250mL autoclave, 0.1mL of t-butyl hydroperoxide as an initiator was added dropwise to the above system, the system was sealed, oxygen (molar ratio of oxygen to cyclohexane was 1:1) was introduced, the mixture was stirred at 130 ℃ and 2.0MPa for 5 hours, the temperature was lowered, the pressure was released, sampling was carried out, and the catalyst was separated by centrifugation and filtration, and the results of analysis of the oxidation products are shown in Table 1.
Example 9
50mg of composite material particles A1 is used as a catalyst and filled in a fixed bed reactor, cyclohexane and tert-butyl hydroperoxide are fed into the reactor, oxygen is introduced (the molar ratio of the oxygen to the cyclohexane is 5:1), the dosage of the tert-butyl hydroperoxide is 0.1mL by taking 10mL of cyclohexane as a reference, and the weight hourly space velocity of the cyclohexane is 1h -1 The results of the analysis of the oxidation products after 5 hours at 130 ℃ and 2.0MPa are shown in Table 1.
Example 10
Cyclohexane was catalytically oxidized according to the procedure of example 1, except that t-butyl hydroperoxide was not added as an initiator. The results of the oxidation product analysis are shown in Table 1.
Example 11
Adding 50mg of composite material particles A1 as a catalyst and 10mL of methylcyclopentane into a 250mL high-pressure reaction kettle, then dropwise adding 0.1mL of tert-butyl hydroperoxide as an initiator into the system, sealing, introducing oxygen (the molar ratio of the oxygen to the cyclohexane is 5:1), stirring the mixture at 130 ℃ and 2.0MPa for 5 hours, cooling, decompressing, sampling, centrifuging, filtering and separating the catalyst, and analyzing the oxidation products, wherein the result is as follows: the methylcyclopentane conversion was 28% and the methylcyclopentanone selectivity was 76%.
Comparative example 1
Cyclohexane was catalytically oxidized according to the method of example 1, except that the same amount of carbon dots (CDs, particle size 9 nm) was used in place of the composite particles A1. The results of the oxidation product analysis are shown in Table 1.
Comparative example 2
Cyclohexane was catalytically oxidized by the method of example 1, except that the same amount of titanium oxide (TiO) was used 2 Particle size 300 nm) instead of composite particles a. The results of the oxidation product analysis are shown in Table 1.
Comparative example 3
Cyclohexane was catalytically oxidized by the method of example 1, except that the composite particles A1 were not used as a catalyst. The results of the oxidation product analysis are shown in Table 1.
TABLE 1
Sources of catalyst Cyclohexane conversion rate% Cyclohexanone selectivity,% of
Example 1 37 82
Example 2 29 80
Example 3 32 74
Example 4 26 72
Example 5 25 68
Example 6 34 81
Example 7 28 73
Example 8 30 75
Example 9 33 83
Example 10 31 74
Comparative example 1 18 39
Comparative example 2 7 22
Comparative example 3 4 15
As can be seen from table 1, the selective oxidation of cycloalkanes can be achieved under mild conditions with higher feedstock conversion and target product selectivity using the process of the present disclosure.
The preferred embodiments of the present disclosure have been described in detail above, however, the present disclosure is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present disclosure within the technical idea of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.
It should be noted that, in the foregoing embodiments, various features described in the above embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, various combinations that are possible in the present disclosure are not described again.
In addition, any combination of various embodiments of the present disclosure may be made, and the same should be considered as the disclosure of the present disclosure, as long as it does not depart from the spirit of the present disclosure.

Claims (15)

1. A process for the catalytic oxidation of a cycloalkane, the process comprising: enabling cycloalkane and an oxidant to contact in the presence of a catalyst for oxidation reaction, wherein the catalyst is a catalytic composite material containing carbon points and titanium oxide, and the content of the carbon points is 2-40 wt% and the content of the titanium oxide is 60-98 wt% based on the total weight of the catalytic composite material;
the cycloalkane is one selected from substituted or unsubstituted monocycloparaffins of C6-C12 and substituted or unsubstituted dicycloalkanes of C8-C16;
the preparation steps of the catalytic composite material comprise:
(1) Mixing a first solution containing a titanium source and a first solvent with a second solution containing an acid and a second solvent under stirring to obtain a mixed solution;
(2) Mixing the mixed solution obtained in the step (1) with a third solution containing carbon points, carrying out hydrothermal reaction at 100-400 ℃ for 0.5-48 h, collecting a solid product, and then drying and roasting;
the conditions of the oxidation reaction are as follows: the temperature is 50-200 ℃; the time is 1 to 72 hours; the pressure is 0-20 MPa;
the oxidant is an oxygen-containing gas.
2. The method of claim 1, wherein the carbon dots are present in an amount of 5 to 20 wt% and the titanium oxide is present in an amount of 80 to 95 wt%, based on the total weight of the catalytic composite.
3. The method of claim 1, wherein the carbon dots are graphene quantum dots, carbon nanodots, or polymer dots.
4. The method of claim 1, wherein the catalytic composite has a particle size of 10 to 5000nm.
5. The method of claim 4, wherein the catalytic composite has a particle size of 10 to 1000nm.
6. The method of claim 1, wherein in step (1), the molar ratio of the titanium source, the first solvent, the second solvent, and the acid is 1: (0.1 to 100): (0.1-50): (0.1 to 10);
the titanium source is tetrabutyl titanate, tetraisopropyl titanate, tetraethyl titanate, tetramethyl titanate, titanyl sulfate or titanyl chloride, or a combination of two or three of the above;
the acid is acetic acid, propionic acid, hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid, or a combination of two or three of the above;
the first solvent is ethanol, n-propanol, isopropanol, n-butanol, tert-butanol or cyclohexanol, or a combination of two or three of the above;
the second solvent is water, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol or cyclohexanol, or a combination of two or three of them.
7. The method of claim 1, wherein the step of preparing the catalytic composite further comprises: in the step (1), the first solution is added into the second solution at the speed of 0.1-50 mL/min;
the stirring conditions include: the stirring speed is 100-2000 r/min, and the time is 0.1-12 h.
8. The method of claim 7, wherein the agitation conditions comprise: the stirring speed is 200-1000 r/min, and the time is 0.5-6 h.
9. The method according to claim 1, wherein in the step (2), the weight ratio of the third solution to the mixed solution is (0.01-10): 1;
the drying conditions include: the temperature is 100-200 ℃, and the time is 1-12 h;
the roasting conditions comprise: the temperature is 250-800 ℃, and the time is 0.5-6 h.
10. The method according to claim 9, wherein in the step (2), the weight ratio of the third solution to the mixed solution is (0.1-0.8): 1.
11. the process according to any one of claims 1 to 4, wherein the oxidation reaction is carried out in a slurry bed reactor, the catalyst being used in an amount of 10 to 100mg, based on 10mL of the cycloalkane; or,
the oxidation reaction is carried out in a fixed bed reactor, and the weight hourly space velocity of the cycloalkane is 0.01-10 h -1 。
12. The process according to claim 11, wherein the oxidation reaction is carried out in a slurry bed reactor, the catalyst being used in an amount of 20 to 60mg, based on 10mL of the cycloalkane; or,
the oxidation reaction is carried out in a fixed bed reactor, and the weight hourly space velocity of the cycloalkane is 0.05-2 h -1 。
13. The method of any one of claims 1-4, wherein the method further comprises: the oxidation reaction is carried out in the presence of an initiator; the initiator is tert-butyl hydroperoxide, cumyl hydroperoxide, ethylbenzene hydroperoxide or peroxypropionic acid, or the combination of two or three of the above substances;
the dosage of the initiator is 0.01-0.3 mL based on 10mL of the cycloalkane.
14. The method according to any one of claims 1 to 4, wherein the oxidant is air or oxygen;
the molar ratio of the cycloalkane to oxygen in the oxygen-containing gas is 1: (1-5);
the cycloalkane is cyclohexane or methylcyclopentane.
15. The method according to any one of claims 1 to 4, wherein the oxidation reaction conditions are: the temperature is 60-180 ℃; the time is 2 to 24 hours; the pressure is 0-10 MPa.
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