CN109776292B - Method for synthesizing 3-pentanone - Google Patents
Method for synthesizing 3-pentanone Download PDFInfo
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- CN109776292B CN109776292B CN201910221935.5A CN201910221935A CN109776292B CN 109776292 B CN109776292 B CN 109776292B CN 201910221935 A CN201910221935 A CN 201910221935A CN 109776292 B CN109776292 B CN 109776292B
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Abstract
The invention discloses a method for synthesizing 3-pentanone, which comprises the steps of grinding and drying graphite powder, mixing the ground and dried graphite powder with a screened active ingredient aqueous solution, carrying out ultrasonic oscillation and microwave drying to obtain a precursor of a graphene doped active ingredient, heating and expanding to obtain a graphene doped catalyst, introducing propionaldehyde and oxygen into a fixed bed reactor, filling an oxidation catalyst and a reaction catalyst into a catalyst bed layer, introducing water vapor into two sides of the reaction catalyst bed layer, heating the reactor to 340-fold-material 360 ℃ under a normal pressure condition, detecting the content of 3-pentanone by combining gas chromatography, preparing the 3-pentanone with high selectivity and high yield, few byproducts and easy purification.
Description
Technical Field
The invention relates to the technical field of chemical raw material preparation, and particularly relates to a method for synthesizing 3-pentanone.
Background
3-pentanone is used as an important fine chemical raw material and a high-end solvent, is a key intermediate of a herbicide pendimethalin and an anti-avian influenza drug tamiflu, has the use amount increased year by year, and is widely applied to the fields of synthetic dyes, medicines, agriculture and the like. The main physicochemical properties of 3-pentanone are: melting point-40 deg.C, boiling point 101.5 deg.C, density 0.815, refractive index n 20/D1.392, flash point 55 deg.F, relative polarity 0.265, pH 6.2.
In the prior art, the synthesis method of 3-pentanone mainly comprises a 3-pentanol oxidation method, a methyl ethyl ketone and methanol one-step method, a methanol butanone one-step method, a piperylene method, an acid-acid method and the like. Wherein, the 3-pentanol oxidation method is that the 3-pentanol is oxidized in the presence of potassium dichromate and sulfuric acid, the oxidation temperature is 90 ℃, the filtration is carried out after the reaction is finished, and the fraction at the temperature of 101-104 ℃ is collected by fractionation. The acid-acid method is the most widely applied method most suitable for industrial production at present, is formed by decarboxylation of propionic acid, and has the advantages of high conversion rate and yield, good selectivity and no obvious three-waste problem. Zhang Yi et al report MnO2/γ-Al2O3The synthesis of 3-pentanone on catalyst is studied by using gamma-Al2O3The catalyst is used as a carrier, metal oxide is used as an active ingredient, propionic acid is used as a raw material, 3-pentanone is synthesized on a fixed bed reactor, the yield can reach more than 90%, and the conversion rate can reach 100%.
The patent of application No. 200910030193.4 discloses a catalyst for synthesizing 3-pentanone, which comprises an active component, an auxiliary agent and a carrier, wherein the active component is composed of one or more of lanthanide series and actinide series rare earth oxides, the carrier is one or more of zirconia, alumina, titanium dioxide and silicon dioxide, the auxiliary agent is one or more of alkali metal or alkaline earth metal oxides, the content of 2-pentanone and methyl isopropyl ketone in a reaction product of synthesizing 3-pentanone from propionic acid is reduced, and the separation difficulty of 3-pentanone is greatly reduced.
Through research on the method for synthesizing 3-pentanone by propionic acid in the prior art, the following aspects which can be improved are found to exist: (1) the selectivity to 3-pentanone is not high, a large amount of propionaldehyde byproducts exist, and the propionaldehyde can be used as a reaction raw material to prepare 3-pentanone; (2) when gamma-alumina or carbon nanotube is used as carrier, the reaction temperature of 410-420 deg.C is required for reaction in a fixed bed reactor, and the high temperature can reduce the activity of the catalyst, which can not be used in multiple batches, thus increasing the production cost.
Disclosure of Invention
In order to solve the technical problems, the invention aims to provide a method for synthesizing 3-pentanone, which comprises the steps of grinding and drying graphite powder, mixing the ground and dried graphite powder with a screened aqueous solution of active ingredients, performing ultrasonic oscillation and microwave drying to obtain a precursor of the graphene doped active ingredients, heating and expanding to obtain a graphene doped catalyst, introducing propionaldehyde and oxygen into a fixed bed reactor, filling an oxidation catalyst and a reaction catalyst into a catalyst bed layer, introducing water vapor into two sides of the reaction catalyst bed layer, heating the reactor to 340-360 ℃ under a normal pressure condition, detecting the content of 3-pentanone by combining gas chromatography, preparing the 3-pentanone with high selectivity and high yield, few byproducts and easy purification.
The purpose of the invention can be realized by the following technical scheme:
the invention provides a method for synthesizing 3-pentanone, which comprises the following steps:
(1) reduction and activation of the graphene doped catalyst: placing the graphene doped catalyst in a quartz cavity of a high-temperature vacuum tube furnace, activating under the protective atmosphere of nitrogen, heating to 380-400 ℃ at the speed of 3-5 ℃/min, preserving heat for 1-2h, and naturally cooling to room temperature to obtain a reaction catalyst;
(2) propionaldehyde synthesis of 3-pentanone: introducing gasification propionaldehyde and oxygen into a fixed bed reactor, filling an oxidation catalyst and a reaction catalyst into a catalyst bed layer, introducing water vapor into two sides of the reaction catalyst bed layer, heating the reactor to 340-360 ℃ under the normal pressure condition, and detecting the content of 3-pentanone by combining gas chromatography; when the peak area of 3-pentanone is maximized, introducing the reactant into a condenser for condensation, storing the condensed reactant in a collecting bottle, after centrifugal oscillation, introducing a liquid separator for oil-water phase separation, and exhausting non-condensable gas through an emptying pipe to obtain an oil phase which is a product;
the preparation method of the graphene doped catalyst comprises the following steps:
s1, graphite powder pretreatment: selecting graphite powder with the fixed carbon content of more than or equal to 99 percent and the water content of less than or equal to 0.5 percent, putting the graphite powder into a small stirring ball mill, introducing nitrogen as protective gas, taking zirconia balls as grinding media, and carrying out irregular crushing under the conditions of the rotating speed of 60-100r/min and the ball-to-material ratio of 3:1 to obtain graphene powder with the particle size of less than or equal to 1 mm;
s2, preparing a graphene doped active component precursor: placing graphene powder in a vacuum drying oven at 30-40 ℃, vacuumizing until the vacuum degree in the oven is-0.5 MPa, keeping for 6-8 hours, mixing an active ingredient aqueous solution and the graphene powder according to the mass ratio of 1:0.1-0.2 to obtain a mixed system, carrying out ultrasonic oscillation at 25 ℃ for 8min, and carrying out microwave drying until the water content is 10% -15%;
s3, preparation of a graphene doped catalyst: stirring and dispersing the graphene doped active component precursor, then placing the precursor into a high-temperature vacuum muffle furnace, wherein a heating element adopts a molybdenum disilicide heating rod, heating the precursor to 180-190 ℃ at the speed of 5-6 ℃/min, keeping the temperature until the surface of the precursor cracks and expands, closing the heating, and cooling the precursor to room temperature in the muffle furnace.
According to the preparation method of the graphene doped catalyst, in the graphite powder pretreatment process, by strictly controlling the carbon content and the moisture content of the graphite powder, the graphite powder can be driven by a main shaft of a small stirring ball mill to rotate at a high speed, so that zirconia balls do irregular motion, collision, extrusion, friction and shearing of a grinding medium to the graphite powder are promoted, the graphite powder is crushed and finely ground, and the obtained graphene has uniform particle size and good specific surface area, doping performance and conductivity.
In the preparation process of the graphene doped active ingredient precursor, graphene powder is subjected to vacuum drying and then mixed with an active ingredient aqueous solution, and the graphene doped active ingredient precursor is obtained through ultrasonic oscillation and microwave drying. Firstly, the graphene powder is not excessively expanded by heat due to vacuum drying, and the fine particle size is not blown or moved by flowing air; secondly, in the process of ultrasonic oscillation, the high-frequency sound waves oscillate the graphene powder, so that impurities adsorbed between graphene layers can be removed, adsorption of water molecules and active ingredients is facilitated, the graphene swells after absorbing aqueous solution, and the doping amount of the active ingredients is greatly increased.
In the preparation process of the doped catalyst, a certain amount of moisture is still adsorbed in graphene, the moisture is adsorbed between layers of the graphene, and water molecules are slowly evaporated to separate from an interlayer structure of the graphene along with the uniform temperature rise, so that the graphene is heated and expanded to generate cracking sound, and active ingredients are uniformly diffused in a particle form and doped in the interlayer structure of the graphene.
According to the method for synthesizing the 3-pentanone, the graphene doped catalyst is firstly calcined and activated at high temperature in a high-temperature vacuum tube furnace under the nitrogen protection atmosphere, and then the high-purity 3-pentanone is obtained through the catalytic reaction of propionaldehyde in a fixed bed reactor. The method comprises the steps of filling an oxidation catalyst and a reaction catalyst in a catalyst bed layer skillfully, so that propionaldehyde is firstly oxidized by oxygen under the action of the oxidation catalyst to obtain propionic acid, and then decarboxylation reaction is carried out under the condition of the reaction catalyst to obtain 3-pentanone. The method takes propionaldehyde as a raw material, 3-pentanone is synthesized by one-step reaction, the purity of the obtained product reaches more than 99.5%, and the yield reaches more than 94.6%.
As a further embodiment of the present invention, the active ingredient is MnO2、CeO2、Pr6O11、La2O3、Nd2O3、ZrO2One or more of the above.
As a further scheme of the invention, the oxidation catalyst is one or more of iron acetate, zinc acetate, cobalt acetate, manganese acetate and copper acetate.
As a further proposal of the invention, the space velocity of the gasified propionaldehyde in the step (2) is 1.0 to 1.5h-1The space velocity of oxygen is 0.5-0.8h-1The space velocity of the water vapor is 1.0 to 1.2h-1。
As a further scheme of the invention, the gas chromatography detection conditions in the step (2) are as follows: the method adopts a Japanese Shimadzu GC-2018 gas chromatograph, a TCD detector, a gasification chamber temperature of 185 ℃, a column initial temperature of 140 ℃, a temperature rise speed of 3 ℃/min, a final temperature of 200 ℃ and a sample injection amount of 2 mu L.
As a further scheme of the invention, the fixed bed reactor comprises a propionaldehyde tank, an oxygen tank, a water vapor heater and a reactor main body, wherein the propionaldehyde tank and the oxygen tank are arranged in parallel, the propionaldehyde tank is connected with a main regulating valve through a first one-way regulating valve, the oxygen tank is connected with the main regulating valve through a second one-way regulating valve, and one side of the upper end of the reactor main body is connected with the main regulating valve through a mass flow meter;
one side of reactor main part upper end is equipped with the relief valve, and bottom one side of reactor main part is connected with the condenser through the back pressure valve, and the condenser has the tail gas absorption jar through the pipe connection, and the top of condenser is equipped with the blow-down pipe, and the tail gas absorption jar is airtight state and inside splendid attire has alkali lye, and the wall portion of tail gas absorption jar above the liquid level is connected with the vacuum pump.
As a further scheme of the invention, a truncated cone-shaped quartz cavity is arranged in an inner cavity of the reactor main body, the quartz cavity comprises a segmented heating zone and a catalyst bed layer which are sequentially arranged from top to bottom, the catalyst bed layer comprises a truncated cone-shaped catalyst frame and a catalyst containing cavity which are arranged from top to bottom, a through hole is formed in the catalyst frame, and the aperture of the through hole in the catalyst frame from top to bottom is gradually reduced.
As a further scheme of the invention, the number of the catalyst frames is 5-8, and the catalyst containing cavities are filled with oxidation catalyst and reaction catalyst; the side wall of the catalyst containing cavity filled with the reaction catalyst is connected with a water vapor heater.
When 3-pentanone is synthesized, the specific working principle of the fixed bed reactor is as follows:
(1) placing a catalytic bed loaded with an oxidation catalyst and a graphene doping reaction catalyst between catalyst frames and in a catalyst accommodating cavity, wherein the oxidation catalyst is placed in the catalyst accommodating cavity on the upper layer, and the graphene doping reaction catalyst is placed in the catalyst accommodating cavity on the lower layer; simultaneously opening a first one-way regulating valve and a second one-way regulating valve, regulating each one-way regulating valve according to the matching requirement of gasified propionaldehyde and oxygen, opening a main regulating valve after the gasified propionaldehyde is mixed with the oxygen, and directly measuring and regulating the mass flow of the passing mixed gas by a mass flow meter;
(2) mixed gas enters the reactor main body along a pipeline, the heating temperature of different catalyst bed layers is controlled in a sectional heating area in the quartz cavity in a sectional manner, and the contact area of the mixed gas and the catalyst beds is continuously increased in the process that the mixed gas enters the reactor main body through the truncated cone-shaped catalyst frame; the aperture of the through hole is gradually reduced from top to bottom, so that the resistance of the mixed gas penetrating through the catalyst bed is increased, and the gas flow rate in the direction from top to bottom is reduced; propionaldehyde and oxygen firstly pass through a bed layer filled with an oxidation catalyst to generate the oxidation reaction of propionaldehyde to generate propionaldehyde, then pass through a catalyst bed layer filled with a graphene doped reaction catalyst, under the catalysis of the reaction catalyst, water vapor is introduced from a water vapor heater, and propionic acid is subjected to a decarboxylation reaction to generate 3-pentanone;
(3) when the peak area of the 3-pentanone is detected to be the maximum by gas chromatography analysis, closing the main regulating valve and discharging reaction liquid from the bottom of the reactor main body; opening the pressure release valve to discharge residual gas on the upper part of the reactor main body; closing the pressure release valve, opening the vacuum pump, extracting vacuum to cause negative pressure environment in the condenser and the tail gas absorption tank, opening the back pressure valve, sucking reaction liquid into the condenser under the negative pressure condition, condensing in the condenser, discharging uncondensed gas from the vent pipe, sucking residual carbon dioxide and impurity gas into the tail gas absorption tank, and absorbing the residual carbon dioxide and impurity gas by alkali liquor.
The fixed bed reactor used in the invention is provided with the one-way regulating valves respectively and independently on the path of the mixed gas introduced into the reactor main body, and is matched with the main regulating valve and the mass flow meter, so that the flow ratio and the total flow of the propionaldehyde and the oxygen can be accurately controlled, the heating temperature can be accurately controlled by the sectional heating zone arranged in the reactor main body, the design of the truncated cone-shaped catalyst frame and the through hole can increase the contact area of the mixed gas and the catalyst, and simultaneously reduce the gas flow velocity from top to bottom, and promote the selectivity and forward proceeding of the reaction.
The invention has the beneficial effects that:
1. according to the method for synthesizing 3-pentanone, graphite powder is ground and dried, the ground graphite powder and the screened active ingredient water solution are subjected to ultrasonic oscillation and microwave drying to obtain a precursor of the graphene doped active ingredient, the precursor is heated and expanded to obtain the graphene doped catalyst, and the graphene doped catalyst subjected to reduction activation in a mixed atmosphere catalyzes a mixed gas to perform propionaldehyde oxidation decarboxylation one-step reaction, so that 3-pentanone can be prepared with high selectivity and high yield, few byproducts are generated, and the production cost is reduced.
2. In the preparation method of the graphene doped catalyst, graphite powder can rotate at a high speed under the driving of a main shaft of a small stirring ball mill, so that the graphite powder is collided, extruded, rubbed and sheared by a grinding medium, the graphite powder is crushed and finely ground, and the obtained graphene has uniform particle size and good specific surface area, doping performance and conductivity; the graphene powder is not excessively expanded by heat due to vacuum drying, and the fine particle size cannot be blown or moved by flowing air; the high-frequency sound waves oscillate the graphene powder, so that impurities adsorbed between graphene layers can be removed, adsorption of water molecules and active ingredients is facilitated, the graphene swells after absorbing water solution, and the doping amount of the active ingredients is greatly increased.
3. In the fixed bed reactor, three one-way regulating valves are respectively and independently arranged on the paths of the three gases introduced into the reactor main body, and the flow ratio and the total flow of propionaldehyde and oxygen can be accurately controlled by matching with a main regulating valve and a mass flow meter; the sectional heating zone arranged in the reactor main body can accurately control the heating temperature of different catalyst bed layers in a sectional manner; the catalyst frame is in a circular truncated cone shape, so that the contact area of the mixed gas and the catalyst is continuously increased in the process of entering the reactor main body; the design of the aperture of the through hole increases the resistance of the mixed gas penetrating the catalyst bed, reduces the gas flow rate from top to bottom, promotes the full contact of the mixed gas and the catalyst, and improves the selectivity and the forward direction of the reaction.
Drawings
The invention will be further described with reference to the accompanying drawings.
FIG. 1 is a schematic view of the structure of a fixed bed reactor of the present invention.
FIG. 2 is a cross-sectional view of the reactor body of the present invention.
In the figure: 1. a propionaldehyde tank; 2. an oxygen tank; 3. a water vapor heater; 4. a reactor body; 5. a first one-way regulating valve; 6. a second one-way regulating valve; 8. a main regulator valve; 9. a mass flow meter; 10. a quartz chamber; 11. a segmented heating zone; 12. a catalyst bed layer; 13. a pressure relief valve; 14. a back pressure valve; 15. a condenser; 16. a tail gas absorption tank; 17. a vacuum pump; 18. an emptying pipe; 121. a catalyst frame; 122. catalyst holding chamber.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
A method for synthesizing 3-pentanone, comprising the steps of:
(1) reduction and activation of the graphene doped catalyst: placing the graphene doped catalyst in a quartz cavity of a high-temperature vacuum tube furnace, activating under the protective atmosphere of nitrogen, heating to 380-400 ℃ at the speed of 3-5 ℃/min, preserving heat for 1-2h, and naturally cooling to room temperature to obtain a reaction catalyst;
(2) propionaldehyde synthesis of 3-pentanone: introducing gasification propionaldehyde and oxygen into a fixed bed reactor, filling an oxidation catalyst and a reaction catalyst into a catalyst bed layer, introducing water vapor into two sides of the reaction catalyst bed layer, heating the reactor to 340-360 ℃ under the normal pressure condition, and detecting the content of 3-pentanone by combining gas chromatography; when the peak area of 3-pentanone is maximized, introducing the reactant into a condenser for condensation, storing the condensed reactant in a collecting bottle, after centrifugal oscillation, introducing a liquid separator for oil-water phase separation, and exhausting non-condensable gas through an emptying pipe to obtain an oil phase which is a product; wherein the space velocity of gasifying propionaldehyde is 1.0-1.5h-1The space velocity of oxygen is 0.5-0.8h-1The space velocity of the water vapor is 1.0 to 1.2h-1(ii) a The gas chromatography detection conditions are as follows: the method adopts a Japanese Shimadzu GC-2018 gas chromatograph, a TCD detector, a gasification chamber temperature of 185 ℃, a column initial temperature of 140 ℃, a temperature rise speed of 3 ℃/min, a final temperature of 200 ℃ and a sample injection amount of 2 mu L.
The preparation method of the graphene doped catalyst comprises the following steps:
s1, graphite powder pretreatment: selecting graphite powder with the fixed carbon content of more than or equal to 99 percent and the water content of less than or equal to 0.5 percent, putting the graphite powder into a small stirring ball mill, introducing nitrogen as protective gas, taking zirconia balls as grinding media, and carrying out irregular crushing under the conditions of the rotating speed of 60-100r/min and the ball-to-material ratio of 3:1 to obtain graphene powder with the particle size of less than or equal to 1 mm;
s2, preparing a graphene doped active component precursor: placing graphene powder in a vacuum drying oven at 30-40 ℃, vacuumizing until the vacuum degree in the oven is-0.5 MPa, keeping for 6-8 hours, mixing an active ingredient aqueous solution and the graphene powder according to the mass ratio of 1:0.1-0.2 to obtain a mixed system, carrying out ultrasonic oscillation at 25 ℃ for 8min, and carrying out microwave drying until the water content is 10% -15%;
s3, preparation of a graphene doped catalyst: stirring and dispersing the graphene doped active component precursor, then placing the precursor into a high-temperature vacuum muffle furnace, wherein a heating element adopts a molybdenum disilicide heating rod, heating the precursor to 180-190 ℃ at the speed of 5-6 ℃/min, keeping the temperature until the surface of the precursor cracks and expands, closing the heating, and cooling the precursor to room temperature in the muffle furnace.
Wherein the active ingredient is MnO2、CeO2、Pr6O11、La2O3、Nd2O3、ZrO2One or more combinations of; the oxidation catalyst is one or more of ferric acetate, zinc acetate, cobalt acetate, manganese acetate and cupric acetate.
Screening of Experimental conditions
Propionaldehyde conversion (%) = amount of propionaldehyde reacted/propionaldehyde air input amount × 100;
yield (%) = actual mass yield of 3-pentanone converted by reacting propionaldehyde/theoretical mass yield of 3-pentanone × 100.
Active ingredient screening
In the active ingredient screening experiment, the selected oxidation catalyst is ferric acetate, the selected heating temperature is 350 ℃, the pressure is normal pressure, and the specific screening result is shown in table 1:
TABLE 1 active ingredient screening results
As can be seen from the above table, when the active ingredient is manganese dioxide, both the conversion rate, yield and product purity of propionaldehyde are higher than those of other active ingredients, and manganese dioxide is selected as a preferred active ingredient.
Oxidation catalyst screening
In the screening of the oxidation catalyst, manganese dioxide is selected as an active component, the selected heating temperature is 350 ℃, the pressure is normal pressure, and the specific screening results are shown in table 2:
TABLE 2 Oxidation catalyst screening results
As can be seen from the above table, when the oxidation catalyst is manganese acetate, both the conversion, yield and product purity of propionaldehyde are higher than those of other oxidation catalysts. Thus, manganese acetate is a preferred oxidation catalyst.
Reaction temperature screening
When the reaction temperature is screened, manganese dioxide is selected as an active component, manganese acetate is selected as an oxidation catalyst, the reaction pressure is normal pressure, and the specific screening results are shown in table 3:
TABLE 3 reaction temperature screening results
From the above table, when the reaction temperature is 353 ℃, the conversion rate, yield and product purity of the propionaldehyde are all higher than those of other temperatures, the yield reaches 97.1%, and the product purity reaches 99.8%. Therefore, 353 ℃ is a preferred reaction temperature.
Example 2
Referring to fig. 1-2, the fixed bed reactor includes a propionaldehyde tank 1, an oxygen tank 2, a water vapor heater 3, a reactor main body 4, the propionaldehyde tank 1 is connected in parallel with the oxygen tank 2, the propionaldehyde tank 1 is connected with a total regulating valve 8 through a first one-way regulating valve 5, the oxygen tank 2 is connected with the total regulating valve 8 through a second one-way regulating valve 6, one side of the upper end of the reactor main body 4 is connected with the total regulating valve 8 through a mass flowmeter 9, a truncated cone-shaped quartz cavity 10 is arranged in an inner cavity of the reactor main body 4, the quartz cavity 10 includes a segmented heating zone 11 and a catalyst bed 12 which are sequentially arranged from top to bottom, the catalyst bed 12 includes a truncated cone-shaped catalyst frame 121 and a catalyst accommodating cavity 122 which are arranged from top to bottom, a through hole is formed in the catalyst frame 121, and the aperture of the through hole in the catalyst frame 121 from top to bottom is gradually reduced. The number of the catalyst frames 121 is 5-8, which is the same as that of the catalyst accommodating cavities 122. Preferably, five catalyst accommodating chambers 122 are filled with oxidation catalyst, and the three catalyst accommodating chambers 122 are filled with reaction catalyst. The side wall of the catalyst accommodating chamber 122 filled with the reaction catalyst is connected with a water vapor heater 3.
One side of the upper end of the reactor main body 4 is provided with a pressure release valve 13, one side of the bottom end of the reactor main body 4 is connected with a condenser 15 through a backpressure valve 14, the condenser 15 is connected with a tail gas absorption tank 16 through a pipeline, the top of the condenser 15 is provided with a vent pipe 18, the tail gas absorption tank 16 is in a closed state and is internally filled with alkali liquor, and the wall part of the tail gas absorption tank 16 above the liquid level is connected with a vacuum pump 17.
When 3-pentanone is synthesized, the specific working principle of the fixed bed reactor is as follows:
(1) placing a catalyst bed loaded with an oxidation catalyst and a graphene doped reaction catalyst between catalyst frames 121 and in a catalyst accommodating cavity 122, wherein the oxidation catalyst is placed in the catalyst accommodating cavity 122 at the upper layer, and the graphene doped reaction catalyst is placed in the catalyst accommodating cavity 122 at the lower layer; simultaneously opening a first one-way regulating valve 5 and a second one-way regulating valve 6, regulating each one-way regulating valve according to the matching requirement of the gasified propionaldehyde and the oxygen, opening a main regulating valve 8 after the gasified propionaldehyde is mixed with the oxygen, and directly measuring and regulating the mass flow of the passing mixed gas by a mass flow meter 9;
(2) mixed gas enters the reactor main body 4 along a pipeline, the heating temperature of different catalyst beds is controlled in a subsection heating zone 11 in the quartz cavity 10, and the contact area between the mixed gas and the catalyst beds is continuously increased in the process that the mixed gas enters the reactor main body 4 through the round table-shaped catalyst frame 121; the aperture of the through hole is gradually reduced from top to bottom, so that the resistance of the mixed gas penetrating through the catalyst bed is increased, and the gas flow rate in the direction from top to bottom is reduced; propionaldehyde and oxygen firstly pass through a bed layer filled with an oxidation catalyst to generate the oxidation reaction of propionaldehyde to generate propionaldehyde, then pass through a catalyst bed layer filled with a graphene doped reaction catalyst, under the catalysis of the reaction catalyst, water vapor is introduced from a water vapor heater 3, and propionic acid undergoes a decarboxylation reaction to generate 3-pentanone;
(3) when the peak appearance area of 3-pentanone is detected to be maximum by gas chromatography, closing the main regulating valve 8 and discharging reaction liquid from the bottom of the reactor main body 4; opening the pressure release valve 13 to discharge the residual gas on the upper part of the reactor main body 4; closing the pressure release valve 13, opening the vacuum pump 17, pumping vacuum to form a negative pressure environment in the condenser 15 and the tail gas absorption tank 16, opening the back pressure valve 14, sucking the reaction liquid into the condenser 15 under the negative pressure condition, condensing in the condenser 15, discharging uncondensed gas from the vent pipe 18, sucking residual carbon dioxide and impurity gas into the tail gas absorption tank 16, and absorbing the residual carbon dioxide and impurity gas by alkali liquor.
In the description herein, references to the description of "one embodiment," "an example," "a specific example" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The foregoing is illustrative and explanatory only and is not intended to be exhaustive or to limit the invention to the precise embodiments described, and various modifications, additions, and substitutions may be made by those skilled in the art without departing from the scope of the invention or exceeding the scope of the claims.
Claims (3)
1. A method for synthesizing 3-pentanone is characterized by comprising the following steps:
(1) reduction and activation of the graphene doped catalyst: placing the graphene doped catalyst in a quartz cavity of a high-temperature vacuum tube furnace, activating under the protective atmosphere of nitrogen, heating to 380-400 ℃ at the speed of 3-5 ℃/min, preserving heat for 1-2h, and naturally cooling to room temperature to obtain a reaction catalyst;
(2) propionaldehyde synthesis of 3-pentanone: introducing gasification propionaldehyde and oxygen into a fixed bed reactor, filling an oxidation catalyst and a reaction catalyst into a catalyst bed layer, introducing water vapor into two sides of the reaction catalyst bed layer, heating the reactor to 340-360 ℃ under the normal pressure condition, and detecting the content of 3-pentanone by combining gas chromatography; when the peak area of 3-pentanone is maximized, introducing the reactant into a condenser for condensation, storing the condensed reactant in a collecting bottle, after centrifugal oscillation, introducing a liquid separator for oil-water phase separation, and exhausting non-condensable gas through an emptying pipe to obtain an oil phase which is a product; the oxidation catalyst is one or the combination of more of ferric acetate, zinc acetate, cobalt acetate, manganese acetate and copper acetate;
the preparation method of the graphene doped catalyst comprises the following steps:
s1, graphite powder pretreatment: selecting graphite powder with the fixed carbon content of more than or equal to 99 percent and the water content of less than or equal to 0.5 percent, putting the graphite powder into a small stirring ball mill, introducing nitrogen as protective gas, taking zirconia balls as grinding media, and carrying out irregular crushing under the conditions of the rotating speed of 60-100r/min and the ball-to-material ratio of 3:1 to obtain graphene powder with the particle size of less than or equal to 1 mm;
s2, preparing a graphene doped active component precursor: placing graphene powder in a vacuum drying oven at 30-40 ℃, vacuumizing until the vacuum degree in the oven is-0.5 MPa, keeping for 6-8 hours, mixing an active ingredient aqueous solution and the graphene powder according to the mass ratio of 1:0.1-0.2 to obtain a mixed system, carrying out ultrasonic oscillation at 25 ℃ for 8min, and carrying out microwave drying until the water content is 10% -15%; the active ingredient is MnO2；
S3, preparation of a graphene doped catalyst: stirring and dispersing the graphene doped active component precursor, then placing the precursor into a high-temperature vacuum muffle furnace, wherein a heating element adopts a molybdenum disilicide heating rod, heating the precursor to 180-190 ℃ at the speed of 5-6 ℃/min, keeping the temperature until the surface of the precursor cracks and expands, closing the heating, and cooling the precursor to room temperature in the muffle furnace;
the fixed bed reactor comprises a propionaldehyde tank (1), an oxygen tank (2), a water vapor heater (3) and a reactor main body (4), wherein the propionaldehyde tank (1) and the oxygen tank (2) are connected in parallel, the propionaldehyde tank (1) is connected with a main regulating valve (8) through a first one-way regulating valve (5), the oxygen tank (2) is connected with the main regulating valve (8) through a second one-way regulating valve (6), and one side of the upper end of the reactor main body (4) is connected with the main regulating valve (8) through a mass flow meter (9);
a pressure release valve (13) is arranged on one side of the upper end of the reactor main body (4), one side of the bottom end of the reactor main body (4) is connected with a condenser (15) through a backpressure valve (14), the condenser (15) is connected with a tail gas absorption tank (16) through a pipeline, a vent pipe (18) is arranged at the top of the condenser (15), the tail gas absorption tank (16) is in a closed state and is filled with alkali liquor, and the wall part of the tail gas absorption tank (16) above the liquid level is connected with a vacuum pump (17);
a truncated cone-shaped quartz cavity (10) is arranged in an inner cavity of the reactor main body (4), the quartz cavity (10) comprises a segmented heating area (11) and a catalyst bed layer (12) which are sequentially arranged from top to bottom, the catalyst bed layer (12) comprises a truncated cone-shaped catalyst frame (121) and a catalyst containing cavity (122) which are arranged from top to bottom, through holes are formed in the catalyst frame (121), and the aperture of the through holes in the catalyst frame (121) from top to bottom is gradually reduced;
the catalyst frames (121) and the catalyst containing cavities (122) are the same in number, namely 5-8, and the catalyst containing cavities (122) are filled with oxidation catalysts and reaction catalysts; the side wall of the catalyst containing cavity (122) filled with the reaction catalyst is connected with a water vapor heater (3).
2. The method for synthesizing 3-pentanone according to claim 1, characterized in that the space velocity of the gasified propionaldehyde in step (2) is 1.0-1.5h "1, the space velocity of oxygen is 0.5-0.8 h" 1, and the space velocity of water vapor is 1.0-1.2h "1.
3. The method for synthesizing 3-pentanone according to claim 1, characterized in that the gas chromatography detection conditions of step (2) are: the method adopts a Japanese Shimadzu GC-2018 gas chromatograph, a TCD detector, a gasification chamber temperature of 185 ℃, a column initial temperature of 140 ℃, a temperature rise speed of 3 ℃/min, a final temperature of 200 ℃ and a sample injection amount of 2 mu L.
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