CN111545219B - Catalyst and preparation method thereof - Google Patents

Catalyst and preparation method thereof Download PDF

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CN111545219B
CN111545219B CN202010368643.7A CN202010368643A CN111545219B CN 111545219 B CN111545219 B CN 111545219B CN 202010368643 A CN202010368643 A CN 202010368643A CN 111545219 B CN111545219 B CN 111545219B
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catalyst
deionized water
carbon nano
drying
alumina
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CN111545219A (en
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赵玉平
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Shaanxi Yuanheng Pharmaceutical Technology Co ltd
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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
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/89—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals
    • B01J23/8926—Copper and noble metals
    • 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
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/34—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation
    • B01J37/348—Electrochemical processes, e.g. electrochemical deposition or anodisation
    • 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
    • C07C45/28—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation of CHx-moieties
    • 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
    • Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts

Abstract

The invention provides a catalyst for preparing acrolein by propylene oxidation and a preparation method thereof, wherein the catalyst has a massive integral structure, good mass and heat transfer effects, and high conversion rate and selectivity of the catalyst to acrolein, and can effectively maintain catalytic performance especially under the condition of high airspeed.

Description

Catalyst and preparation method thereof
Technical Field
The invention relates to a catalyst and a preparation method thereof, relates to a catalyst for preparing acrolein by propylene oxidation and a preparation method thereof, and belongs to the field of preparing a propylene selective oxidation catalyst by an electrochemical method.
Background
Acrolein is the simplest unsaturated aldehyde, and because the molecule contains C=C and C=O double bonds, the chemical property is active, and the acrolein is an important organic chemical intermediate, for example, the acrolein can be further oxidized to generate acrylic acid, further acrylic acid cool can be synthesized, propanol and glycerol can be synthesized through reduction, and the acrolein is an important raw material for synthesizing perfume, preservative and emulsifier.
The catalytic oxidation of propylene is the most dominant synthesis method for producing acrolein in industry at present, and various patents report on the preparation of acrolein by propylene oxidation:
the China patent CN200810235193 Hefei technology development Co., ltd. Discloses a catalyst for producing acrolein by direct oxidation of propylene, the catalyst contains molybdenum (Mo), bismuth (Bi), iron (Fe), cobalt (Co) or/and nickel (Ni) and oxygen (O), the difference from the prior art is that the catalyst is obtained by mixing a catalyst (I) containing cesium (Cs) and a catalyst (II) containing potassium (K) according to the mass percentage of 10-50% and 50-90%, and then kneading, forming, drying and roasting, the catalysts (I) and (II) are as follows: moa, wb, bic, fed, (Co or/and Ni) e, sif, csg, ox (I), moa, wb, bic, fed, (Co or/and Ni) e, sif, kg, ox (II), wherein subscript a, b, c, d, e, f, g, x is the atomic number of the corresponding element and a:10-12; b:0-2, a+b=12; c:0.5-2, d:0.5-2, e:3-6, when Co and Ni are simultaneously present, the ratio of the relative amounts thereof is arbitrary; f:1-3min; g: and 0.01-0.3, wherein x is the sum of the oxygen atoms in the oxides of the corresponding elements, namely, physical mixing of different active components is adopted to improve the catalytic effect of the catalyst.
The Chinese petrochemical Co Ltd Shanghai petrochemical Co Ltd CN201210412591 discloses an acrolein catalyst and a preparation method thereof, wherein the catalyst is obtained by mixing a powdery catalyst precursor taking at least one of SiO2 or Al2O3 as a carrier, a binder and a molybdenum additive, molding and finally roasting; the technical scheme that the molybdenum additive consists of 50-100% of ammonium heptamolybdate and 0-50% of molybdenum trioxide in mole percentage solves the technical problem well, and can be used in the industrial production of acrolein catalyst by propylene oxidation, and the single pass yield of acrolein reaches more than 75% by adopting a molybdenum-bismuth catalyst.
Chinese patent CN201210392989 is prepared by preparing a material selected from SiO 2 Or Al 2 O 3 At least one of which is a carrier and contains an active ingredient represented by the following general formula: mo12 BiaFebNicSbdXeFZgQqOx, wherein X is at least one selected from Mg, co, ca, be, cu, zn, pb or Mn; y is at least one selected from Zr, th or Ti; z is at least one selected from K, rb, na, li, tl or Cs; q is at least one of La, ce, sm or Th, wherein the antimony initiator is selected from antimony ammonium tartrate, so that the technical scheme better solves the problem, and can be used in the industrial production of acrolein by propylene oxidation, namely, the yield of acrolein and acrylic acid is more than 92% through the improvement of a molybdenum-bismuth catalyst.
It can be seen that the catalyst mainly adopted at present is a Mo-Bi-Fe-O composite oxide catalyst, and the preparation method of the catalyst mainly adopts a solution mixing precipitation method, that is, the raw materials are prepared into a solution, then mixed and stirred under certain conditions, and evaporated, dried and crushed into fine powder with certain granularity, the fine powder can be added with a binder and a powdery carrier to be kneaded and formed (extruded or pressed), the shape of the catalyst is basically solid cylinder and sheet at early stage, and the catalyst is developed into various abnormal bodies, mainly hollow cylinder, hollow sheet and ring or is adhered to an abortive macroporous sphere, such as CNCN105195166 a, but as is well known, acrolein and acrylic acid are prepared by gas phase catalytic oxidation reaction of propylene, a great amount of reaction heat is accumulated instantaneously in a reactor to form local hot spots, and if the reaction heat accumulated instantaneously is not removed effectively in time, the loss and falling of active components of the catalyst are caused, the service life of the catalyst is shortened, and the formation of byproducts is aggravated by excessive oxidation reaction is caused, so that the loss of acrolein and acrylic acid is reduced, and the yield of the catalyst is even out of control.
Namely, the prior art has the following obvious problems: (1) The loading of the active components is to coat the Mo-Bi-Fe-O composite oxide catalyst on the surface of the carrier by simple mixing, so that the catalyst is greatly wasted due to full utilization and repeated use; (2) The carrier can be used as a load only, has limited functions in mass and heat transfer, is generally spherical particles, and has extremely high limitation on mass and heat transfer for high-space-velocity reaction; (3) The research of the Mo-Bi-Fe-O composite oxide catalyst is too mature, the academic value of basic research is limited, and the research cannot be effectively further performed.
Before the advent of Mo-Bi-Fe-O based composite oxide catalysts, the widely studied catalyst was a noble metal catalyst, such as the gold-copper bimetallic catalyst system of the present invention disclosed in US3989674 a published in 1976, the catalyst support was selected from silica, alumina, magnesia, thoria, zirconia and mixtures thereof, other support materials such as diatomaceous earth, asbestos, pumice and silicon carbide could also be used, the propylene conversion of the gold-copper bimetallic catalyst was 40.8% and the selectivity for acrolein was 61.9%, i.e., the space available for the gold-copper catalyst was extremely large.
The current industrialized catalyst carrier is granular or powder alumina or silica, and the granular catalyst is troublesome to assemble and disassemble in the use process; is not easy to form and the mechanical strength can not meet the requirement; the mass transfer and heat transfer are greatly blocked, so that the treatment efficiency is reduced; the pressure drop difference between the front and the back of the catalyst bed layer is large, and the energy consumption is increased. The integral catalyst integrates the active components of the catalyst, the structured carrier and the reactor, has the advantages of large geometric surface area of a bed layer in unit volume, high mass transfer and heat transfer efficiency, reduced bed lamination, high catalytic efficiency and the like, is favorable for the adsorption of reactants on the surface of the catalyst, the desorption and release of products and the removal of heat, strengthens the chemical reaction process, and is easy to assemble, maintain and disassemble, and the reactor is considered to be one of the most promising development directions in the current heterogeneous catalysis field, but the case of preparing the acrolein catalyst by oxidizing propylene into blocks is fresh at present.
Based on the above, as a catalyst for the vapor phase catalytic oxidation of propylene, improvement of its performance and use method, many patents have been issued abroad, and studies on catalyst composition have been advanced, but studies on catalyst carriers such as lower mechanical strength of the carrier have been made; the carrier powder particles are unfavorable for high space velocity catalysis, namely, the contribution of the carrier pore structure to the catalysis performance is fully exerted on the premise of ensuring that the catalyst has enough strength.
Disclosure of Invention
Based on the problems existing in the prior art, the invention provides the catalyst for preparing the acrolein by oxidizing propylene and the preparation method thereof, wherein the catalyst is of an integral block structure, the carrier is a carbon nano tube-gamma-alumina mixture, the mechanical strength is high, the pore channel structure is rich, the catalyst has a macroporous and mesoporous structure, the mass transfer effect is good, the Au-Cu alloy is loaded on the surface of the catalyst by an electrochemical method, the Au-Cu alloy active component is highly dispersed on the outer wall of the carbon nano tube, and the Au-Cu alloy/carbon nano tube-alumina catalyst has obvious benefits for improving the propylene oxidation reaction effect and radiating the catalyst bed.
The preparation method of the acrolein catalyst by propylene oxidation comprises the following steps:
(1) Preparing carbon nanotube doped polystyrene, wherein the volume porosity of the polystyrene is more than or equal to 75%: (a) Washing the styrene and divinylbenzene reagents for a plurality of times by using NaOH solution and deionized water; (b) Filling a proper amount of Span 80 and AIBN into a three-neck flask, adding washed styrene and divinylbenzene, then using a transfusion tube, gradually and slowly adding 60-80ml of deionized water into the three-neck flask with stirring, wherein the dropping time of the deionized water is 2-3h, adding carbon nano tubes after the dropping of the deionized water is completed, and continuously stirring for 3-4h to obtain an off-white emulsion; (c) Filling the gray emulsion into a test tube with the caliber of 4-6cm, sealing, drying and polymerizing for 18h to obtain gray rod-shaped polystyrene doped with carbon nano tubes, and then drying with cold air.
The carbon nano tube passes through 100 in advance o Reflux treating the mixed acid for 5H, wherein the mixed acid is 98wt.% H with the volume ratio of 2.5:1 2 SO 4 And 65% -67wt.% HNO 3 And (5) mixing acid.
(2) Filling alumina sol and drying: (a) Weighing 2.5g of pseudo-boehmite, adding the pseudo-boehmite into 40 mL deionized water in batches under stirring, vigorously stirring for 2h, and adding 1.5 mol/LHNO 3 Generating semitransparent alumina hydrosol, and continuously stirring for 7h; (b) Placing the polystyrene doped with the carbon nano tube obtained in the step (1) into alumina hydrosol, vacuumizing and filling for 1.5h by using a vacuum water pump, and then 75 o And C, drying in an oven, and repeating filling and drying for 5 times.
(3) Roasting: under the inert atmosphere condition of nitrogen protection, at 600 o C firing 24 h.
(4) Preparing Au-Cu plating solution: 5-9g/L KCN, 0.5-1g/L, cu (CN) 2K, 1.5-3g/L EDTA-2Na 3-7g/L, and ammonia water is used to adjust pH=9.8+ -0.1.
(5) Bi-directional pulse electrodeposition of Au-Cu: the current density of the forward pulse is 0.1-0.5A/dm 2 Duty ratio of 30%, negative pulse current density of 0.1-0.5A/dm2, duty ratio of 50%, temperature of 40% o C, magnetically stirring for 200-300rpm for 1-3 min.
The catalyst is Au-Cu alloy/carbon nano tube-alumina catalyst, the catalyst is of a block structure, and the alumina is gamma-Al 2 O 3 The Au-Cu alloy exists in one or more forms of AuCu3, auCu or Au3Cu, and the Au-Cu alloy active component is only highly dispersed on the surface of the carbon nano tube.
The alloy Au-Cu alloy/carbon nano tube-alumina catalyst has a space velocity of 30000mL.g-1h-1, a propylene conversion rate of 93.3%, an acrolein yield of 86.0%, an acrolein selectivity of 91.2%, an acrylic acid selectivity of 4.7% and other 4.1% at 320 ℃.
The invention is described in the following points:
(1) Regarding the carbon nanotube-polystyrene template: the polystyrene template is obtained by an inverse concentrated emulsion method, the preparation principle is simply summarized as that deionized water (water phase) is dripped into styrene and divinylbenzene (oil phase) under the action of surfactant span 80, extrusion is carried out between water droplets, the liquid level of the oil phase is forced to be thinned, and after the oil phase is polymerized, water in the water phase is distilled off under the heating condition, thus the porous structure can be obtained. The macroporous structure utilizes mass transfer in the reaction process, in addition, carbon nanotubes are uniformly dispersed in the alumina matrix, and finally, the volume porosity of the carbon nanotube-polystyrene can be effectively controlled by controlling the addition of the water phase, and the porosity is preferably more than or equal to 75 percent.
Secondly, adding carbon nanotubes to the polystyrene template, wherein the main purpose is to improve the conductivity of the subsequent carrier, so that the subsequent operation of electrochemically depositing active components can be realized, and in addition, the carbon nanotubes are commercially purchased carbon nanotubes which are subjected to 100 ℃ in advance o Reflux treating the mixed acid for 5H, wherein the mixed acid is 98wt.% H with the volume ratio of 2.5:1 2 SO 4 And 65% -67wt.% HNO 3 Mixed acid, through mixed acid H 2 SO 4 /HNO 3 The treated carbon nanotubes can effectively improve the solubility and the dispersibility in the process of preparing polystyrene, are beneficial to improving the dispersity of the carbon nanotubes in the polystyrene, and in addition, the loading amount of the carbon nanotubes is 10-20 wt%, preferably 15% in consideration of the influence of the carbon nanotubes on an inverse concentrated emulsion method and the problem of agglomeration.
(2) Because the prepared carbon nano tube-polystyrene has rich pore channels and high porosity, the alumina sol is obtained by hydrolyzing pseudo-boehmite, then pumped by a vacuum pump, the alumina sol is fully filled on the surface of graphene-polystyrene, then dried, the alumina sol is dehydrated to obtain alumina, and because the alumina sol cannot be loaded on the surface of the carbon nano tube-polystyrene once by vacuumizing, a sufficient amount of alumina sol cannot be loaded on the surface of the carbon nano tube-polystyrene once by vacuumizing filling-drying treatment for a plurality of times, the mechanical strength of the alumina-carbon nano tube-polystyrene is improved along with the increase of filling times or the increase of sol concentration, and the mechanical strength of a subsequent carrier can be effectively controlled.
(3) Roasting: the baking process mainly uses high-temperature treatment to effectively crack polystyrene, and inert gas protection is needed in the high-temperature treatment process, mainly based on the following considerations: (a) The use of air, such as in a muffle furnace, for combustion, polystyrene can carbonize, introduce unwanted impurities, and the presence of carbon can significantly reduce the porosity and catalytic activity of the support; (b) The introduction of air can cause the combustion of the carbon nano tube and destroy the raw materials; regarding the baking temperature, the cracking temperature of polystyrene is between 450 and 600 o C, therefore the firing temperature should not be lower than 450 o C, the effect of the firing temperature on the crystal form and specific surface area of alumina is remarkable, as shown in table 1:
TABLE 1 baking Al at different temperatures 2 O 3 Specific surface area and crystalline form of carbon nanotube-polystyrene support
Figure DEST_PATH_IMAGE001
Based on the consideration of surface area and crystal form, 600 is preferred o And C, roasting with nitrogen.
Regarding electrodeposition: by adopting the bidirectional pulse plating, the pulse plating can not only increase the activation polarization of the cathode, but also reduce the concentration polarization of the cathode, and the working principle is mainly to utilize the relaxation change of current pulse or voltage pulse. When the current is on, metal ions near the cathode are fully reduced; when the current is turned off, the discharge metal ions consumed around the cathode are restored to the original concentration again. The current is repeatedly turned on and off in a period, so that the relaxation change of the pulse current is mainly used for reducing metal ions, especially reducing the surfaces of the carbon nanotubes in the pore channels. CN-and EDTA in the electroplating solution are complexing agents, the main effect of the complexing agents is that the CN-is moderate in complexing strength, cu and Au ions can be complexed simultaneously, and the EDTA is an auxiliary complexing agent, but is unfavorable for alloy formation when the complexing agent is absent. The main pH range should be kept at all times during electrodeposition to prevent hydrolytic precipitation of metal ions, and ammonia water is used to adjust ph=9.8±0.1.
Finally, regarding the loading position of the active metal on the surface of the carrier, based on the understanding that the carbon nanotubes are conductive and the alumina is nonconductive, it is obvious that the active component is dispersed on the surface of the carbon nanotubes, but rarely adheres to the surface of the alumina through physical adsorption, and as shown in fig. 1, the active component is mainly distributed on the carbon nanotubes, and the particle size is 5-10nm.
The scheme of the invention has the following beneficial effects:
(1) The catalyst has a block structure, good mass and heat transfer effects, and high conversion rate and selectivity of the catalyst to acrolein;
(2) The specific surface area of the catalyst is large, and the active components exist on the surface of the catalyst in an alloy state;
(3) By the electrochemical deposition method, the alloy components can be effectively and selectively controlled to be only supported on the outer wall of the carbon nano tube, and the catalytic performance is supported on the surface of alumina.
(4) The catalyst performance can be effectively maintained under the condition of high airspeed.
Drawings
FIG. 1 is a TEM image of an Au-Cu alloy of the present invention on a carbon nanotube surface.
Detailed Description
Example 1:
(1) Preparing carbon nanotube doped polystyrene, wherein the volume porosity of the polystyrene is more than or equal to 75%: (a) Washing the styrene and divinylbenzene reagents for a plurality of times by using NaOH solution and deionized water; (b) Filling a proper amount of Span 80 and AIBN into a three-neck flask, adding washed styrene and divinylbenzene, then using a perfusion tube, gradually and slowly adding 70ml of deionized water into the three-neck flask with stirring, wherein the dripping time of the deionized water is 3 hours, adding carbon nano tubes after the dripping of the deionized water is completed, and continuously stirring for 3 hours to obtain an off-white emulsion; (c) Filling the mouth with the off-white emulsionAnd (3) sealing, drying and polymerizing for 18 hours in a test tube with the diameter of 4-6cm to obtain gray rod-shaped polystyrene doped with the carbon nano tube, and then drying with cold air. The carbon nano tube passes through 100 in advance o Reflux treating the mixed acid for 5H, wherein the mixed acid is 98wt.% H with the volume ratio of 2.5:1 2 SO 4 And 65% -67wt.% HNO 3 And (5) mixing acid.
(2) Filling alumina sol and drying: (a) Weighing 2.5g of pseudo-boehmite, adding the pseudo-boehmite into 40 mL deionized water in batches under stirring, vigorously stirring for 2h, and adding 1.5 mol/LHNO 3 Generating semitransparent alumina hydrosol, and continuously stirring for 7h; (b) Placing the polystyrene doped with the carbon nano tube obtained in the step (1) into alumina hydrosol, vacuumizing and filling for 1.5h by using a vacuum water pump, and then 75 o And C, drying in an oven, and repeating filling and drying for 5 times.
(3) Roasting: under the inert atmosphere condition of nitrogen protection, at 600 o C firing 24 h.
(4) Preparing Au-Cu plating solution: 5g/L KCN, 0.5g/L Au (CN) 2K, 1.5g/L Cu (CN) 2K, 3g/L EDTA-2Na, the balance deionized water, and ammonia water was used to adjust pH=9.8. .
(5) Bi-directional pulse electrodeposition of Au-Cu: forward pulse current density 0.1A/dm 2 Duty cycle 30%, negative pulse current density 0.1A/dm2, duty cycle 50%, temperature 40% o And C, magnetically stirring for 1min at 200-300rpm, and finally obtaining 10wt.% of the total mass of the supported catalyst of the carbon nano tubes in the catalyst carrier.
Example 2
(1) Preparing carbon nanotube doped polystyrene, wherein the volume porosity of the polystyrene is more than or equal to 75%: (a) Washing the styrene and divinylbenzene reagents for a plurality of times by using NaOH solution and deionized water; (b) Filling a proper amount of Span 80 and AIBN into a three-neck flask, adding washed styrene and divinylbenzene, then using a perfusion tube, gradually and slowly adding 70ml of deionized water into the three-neck flask with stirring, wherein the dripping time of the deionized water is 3 hours, adding carbon nano tubes after the dripping of the deionized water is completed, and continuously stirring for 3 hours to obtain an off-white emulsion; (c) Filling the off-white emulsion into a mouth with a caliber of 4-6cmAnd (3) in a test tube with a diameter, sealing, drying and polymerizing for 18 hours to obtain gray rod-shaped polystyrene doped with the carbon nano tube, and then drying with cold air. The carbon nano tube passes through 100 in advance o Reflux treating the mixed acid for 5H, wherein the mixed acid is 98wt.% H with the volume ratio of 2.5:1 2 SO 4 And 65% -67wt.% HNO 3 And (5) mixing acid.
(2) Filling alumina sol and drying: (a) Weighing 2.5g of pseudo-boehmite, adding the pseudo-boehmite into 40 mL deionized water in batches under stirring, vigorously stirring for 2h, and adding 1.5 mol/LHNO 3 Generating semitransparent alumina hydrosol, and continuously stirring for 7h; (b) Placing the polystyrene doped with the carbon nano tube obtained in the step (1) into alumina hydrosol, vacuumizing and filling for 1.5h by using a vacuum water pump, and then 75 o And C, drying in an oven, and repeating filling and drying for 5 times.
(3) Roasting: under the inert atmosphere condition of nitrogen protection, at 600 o C firing 24 h.
(4) Preparing Au-Cu plating solution: 7g/L KCN, 0.75g/L Au (CN) 2K, 2g/L Cu (CN) 2K, 5g/L EDTA-2Na, the balance deionized water, and ammonia water was used to adjust pH=9.8. .
(5) Bi-directional pulse electrodeposition of Au-Cu: forward pulse current density 0.13A/dm 2 Duty cycle 30%, negative pulse current density 0.3A/dm2, duty cycle 50%, temperature 40% o And C, magnetically stirring for 2min at 250rpm, and finally obtaining 15wt.% of the total mass of the supported catalyst of the carbon nano tubes in the catalyst carrier, which is named as D-2.
Example 3
(1) Preparing carbon nanotube doped polystyrene, wherein the volume porosity of the polystyrene is more than or equal to 75%: (a) Washing the styrene and divinylbenzene reagents for a plurality of times by using NaOH solution and deionized water; (b) Filling a proper amount of Span 80 and AIBN into a three-neck flask, adding washed styrene and divinylbenzene, then using a perfusion tube, gradually and slowly adding 70ml of deionized water into the three-neck flask with stirring, wherein the dripping time of the deionized water is 3 hours, adding carbon nano tubes after the dripping of the deionized water is completed, and continuously stirring for 3 hours to obtain an off-white emulsion; (c) Filling the above off-white emulsion into a container with a caliber of 4-6cmAnd (3) in a test tube, sealing, drying and polymerizing for 18 hours to obtain the gray rod-shaped polystyrene doped with the carbon nano tube, and then drying with cold air. The carbon nano tube passes through 100 in advance o Reflux treating the mixed acid for 5H, wherein the mixed acid is 98wt.% H with the volume ratio of 2.5:1 2 SO 4 And 65% -67wt.% HNO 3 And (5) mixing acid.
(2) Filling alumina sol and drying: (a) Weighing 2.5g of pseudo-boehmite, adding the pseudo-boehmite into 40 mL deionized water in batches under stirring, vigorously stirring for 2h, and adding 1.5 mol/LHNO 3 Generating semitransparent alumina hydrosol, and continuously stirring for 7h; (b) Placing the polystyrene doped with the carbon nano tube obtained in the step (1) into alumina hydrosol, vacuumizing and filling for 1.5h by using a vacuum water pump, and then 75 o And C, drying in an oven, and repeating filling and drying for 5 times.
(3) Roasting: under the inert atmosphere condition of nitrogen protection, at 600 o C firing 24 h.
(4) Preparing Au-Cu plating solution: 9g/L KCN, 1g/L Au (CN) 2K, 3g/L Cu (CN) 2K, 7g/L EDTA-2Na, the balance deionized water, and ammonia water was used to adjust pH=9.8.
(5) Bi-directional pulse electrodeposition of Au-Cu: forward pulse current density 0.5A/dm 2 Duty cycle 30%, negative pulse current density 0.5A/dm2, duty cycle 50%, temperature 40% o C, magnetically stirring for 3min at 200-300rpm. Finally 20wt.% of the total mass of the supported catalyst of carbon nanotubes in the catalyst support was obtained.
Comparative example 1
The procedure is as in example 2 except that after the preparation, the catalyst is ground and sieved to 60-80 mesh, designated as D-1.
Comparative example 2
The same procedure as in example 2 was followed except that the active ingredient was carried by impregnation, i.e., the catalyst support was immersed in a solution of 5-9g/L KCN, 0.5-1g/L, cu (CN) 2K, 1.5-3g/L EDTA-2Na 3-7g/L, immersed for 24 hours, then frozen in a refrigerator for 2 hours, and then lyophilized in vacuo to remove water, designated as D-2.
Comparative example 3
The same preparation method as in example 2 was used, except that the carbon nanotubes were replaced with graphene, and the graphene was treated in the same manner as the carbon nanotubes and was designated as D-3.
Catalyst activity test:
raw material gas (propylene: air=1:10), reaction temperature 320 o C, space velocity of the reaction raw material is 30000mL . g -1 h -1 FID on-line analysis was performed using gas chromatography.
Table 1 catalytic activity test
Figure 170361DEST_PATH_IMAGE002
Based on the catalytic activity test of table 1, it can be obtained that (1) the prepared Au-Cu alloy/carbon nanotube-alumina catalyst of the present application has no obvious difference in catalytic performance between bulk catalyst and particle catalyst at low space velocity; (2) The method is suitable for electrochemically loading active components, is favorable for selectively adsorbing the active components on the surface of the carbon nano tube, and obtains an alloy state of the active components, wherein Au-Cu alloy is highly dispersed on the surface of the carbon nano tube, and has particularly positive influence on propylene conversion rate, selectivity and yield; (3) The graphene is used, which is inferior to the carbon nano tube, mainly because a monolayer is difficult to obtain by using a hummer method, and the uniformly dispersed graphene is necessarily of a multi-layer structure, and in the electrochemical deposition process, as a solution is easy to enter between graphene sheets to be deposited, partial catalyst active component is loaded and the problem of embedding the active component exists between the graphene sheets, and finally the active component cannot be contacted with propylene and cannot generate catalytic activity.
Effect of S-2 and D-1 sample space velocities on catalyst conversion
TABLE 3 influence of space velocity on catalytic Activity
Figure DEST_PATH_IMAGE003
As can be seen from table 3, the catalytic performance of the powder catalyst is significantly reduced at a high space velocity, mainly the reaction gas cannot be sufficiently contacted with the catalyst, resulting in the reduction of the activity of the catalyst, but the space velocity of the catalyst with a block structure has a certain influence on the catalytic performance, but the influence is extremely low compared with the powder catalyst.
Although the present invention has been described by way of example with reference to the preferred embodiments, the present invention is not limited to the specific embodiments, and suitable modifications may be made within the scope of the invention described above.

Claims (3)

1. A preparation method of a catalyst is characterized in that the catalyst is an Au-Cu alloy/carbon nano tube-alumina catalyst, the catalyst is a catalyst for preparing an acrolein block structure by propylene oxidation, and the alumina is gamma-Al 2 O 3 The Au-Cu alloy is made of AuCu 3 AuCu or Au 3 One or more of Cu exists, the carbon nano tube is loaded in the catalyst with 10-20 wt%,
the method comprises the following steps:
(1) The process for preparing the carbon nanotube doped polystyrene is as follows:
(1-a) washing the styrene and divinylbenzene reagents multiple times with NaOH solution and deionized water;
(1-b) charging proper amounts of Span 80 and AIBN into a three-neck flask, adding the materials into the washed styrene and divinylbenzene, then gradually and slowly adding 60-80mL of deionized water into the three-neck flask by using a transfusion tube with stirring, wherein the dropping time of the deionized water is 2-3H, adding carbon nano tubes after the dropping of the deionized water is completed, and continuously stirring for 3-4H to obtain an off-white emulsion, wherein the carbon nano tubes are subjected to reflux treatment of mixed acid at 100 ℃ for 5H in advance, and the mixed acid is 98wt.% H with the volume ratio of 2.5:1 2 SO 4 And 65% -67wt.% HNO 3 Mixing acid;
(1-c) filling the off-white emulsion into a test tube with the caliber of 4-6cm, sealing, drying and polymerizing for 18 hours to obtain gray rod-shaped polystyrene doped with carbon nano tubes, and then drying with cold air;
(2) Filling alumina sol and drying;
(3) Roasting: roasting 24h at 600 ℃ under the inert atmosphere condition of nitrogen protection;
(4) Preparing an Au-Cu plating solution, wherein the Au-Cu plating solution comprises the following components: 5-9g/L KCN, 0.5-1g/L Au (CN) 2 K、1.5-3g/L Cu(CN) 2 K. 3-7g/L EDTA-2Na, the balance being deionized water, and adjusting the pH value to be 9.8+/-0.1 by using ammonia water;
(5) The Au-Cu is electrodeposited by bidirectional pulse, and the electrodepositing parameters are as follows: the current density of the forward pulse is 0.1-0.5A/dm 2 Duty ratio of 30%, negative pulse current density of 0.1-0.5A/dm 2 The duty ratio is 50%, the temperature is 40 ℃, the time is 1-3min, and the magnetic stirring is 200-300rpm.
2. The method for preparing a catalyst according to claim 1, wherein the process of step (2) is as follows: (2-a) weighing 2.5g of pseudo-boehmite, adding the pseudo-boehmite into 40 mL deionized water in batches under stirring, vigorously stirring for 2h, and adding 1.5 mol/LHNO 3 Generating semitransparent alumina hydrosol, and continuously stirring for 7h; (2-b) placing the carbon nanotube-doped polystyrene obtained in the step (1) into alumina hydrosol, vacuumizing and filling for 1.5 hours by using a vacuum water pump, drying in a 75 ℃ oven, and repeating filling and drying for 5 times.
3. A catalyst, characterized in that it is obtained by the preparation process according to any one of claims 1-2.
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