CN109701557B - Composite catalyst, activated composite catalyst, and preparation method and application thereof - Google Patents
Composite catalyst, activated composite catalyst, and preparation method and application thereof Download PDFInfo
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Abstract
The invention belongs to the field of catalysts, and relates to a composite catalyst, an activated composite catalyst, and a preparation method and application thereof. The composite catalyst comprises: the carbon-based composite material comprises continuous phase carbon, dispersed phase Raney alloy particles and dispersed phase titanium-containing oxide, wherein the dispersed phase Raney alloy particles and the dispersed phase titanium-containing oxide are respectively uniformly or nonuniformly dispersed in the continuous phase carbon, the continuous phase carbon is obtained by carbonizing at least one organic matter capable of being carbonized, and the titanium-containing oxide is obtained by thermal decomposition of titanium-containing sol-gel. The catalyst is a composite catalyst taking carbon, titanium-containing oxide and active metal as matrixes, wherein the titanium-containing oxide can be used as a carrier for strengthening the particle strength under the condition of carbon loss, and meanwhile, the acidity of the surface of the catalyst is provided, and the selectivity of catalytic reaction can be adjusted.
Description
Technical Field
The invention belongs to the field of industrial catalysts, and particularly relates to a composite catalyst, an activated composite catalyst, and preparation methods and applications thereof.
Background
In the field of catalysis, the "raney process" is a process for the preparation of an active metal catalyst, which comprises: i) preparing an alloy containing more than two components of active metals, and ii) then extracting at least one of the metal components, leaving a metal component with a porous structure and a higher catalytic activity. Step ii) is also referred to as "activation". Raney, for example, originally invented a raney nickel catalyst (Industrial and Engineering Chemistry,1940, vol.32,1199) which was prepared by the following method: firstly preparing nickel-aluminum alloy, then dissolving aluminum element in the alloy by using strong alkaline solution, and leaving nickel metal with porous structure and high catalytic activity.
The Raney nickel catalyst is the most common Raney nickel catalyst, the Raney nickel catalyst is usually in a powder form, is inflammable and inconvenient to operate, is mainly used in small-scale catalytic hydrogenation reaction in the field of fine chemical engineering, and cannot be used in common fixed bed reaction.
In order to expand the application field of the raney nickel catalyst, it is a research direction that has attracted much attention in recent years to form the raney nickel catalyst by a certain method, especially to process the raney nickel catalyst into a fixed bed catalyst.
Patent application CN1557918A discloses a formed Raney nickel catalyst and its preparation method, the catalyst is made of aluminum and one or more of Ni, Co, Cu, Fe to form alloy powder, inorganic substances such as pseudo-boehmite are used as adhesive, natural or synthetic organic substances such as sesbania powder, carboxymethyl cellulose are used as pore template agent, the catalyst is directly kneaded, formed and roasted, and activated by caustic alkali solution, the obtained catalyst has certain shape and strength, and can be used as fixed bed catalyst. However, the preparation process of the catalyst is complex, the catalyst needs to be roasted at a high temperature of 900 ℃, and the high-temperature roasting causes considerable particle sintering, so that the utilization rate of active metal is low, and the activity of the catalyst is low. And the obtained catalyst contains an inorganic oxide carrier (such as alumina, silica and the like), and the acid-base property of the carrier causes the selectivity of the catalyst to be low. In addition, the catalyst is difficult to recover metals and is seriously polluted.
Patent US5536694 discloses a shaped catalyst obtained by using alloy powder of Ni, Al, Co, etc. as starting material, using auxiliary powder of lubricant, plasticizer, etc. to shape it, and then carrying out the steps of roasting, alkali activation, etc. The catalyst has complex preparation process, needs to be roasted at the high temperature of 700-850 ℃, and the high-temperature roasting causes considerable particle sintering, so that the utilization rate of metal is lower, and amorphous Raney metal is reduced, which leads to the reduction of activity.
In a word, the fixed bed raney catalyst prepared from the powder alloy is difficult to mold and operate, the preparation cost is high, various additives need to be added in the molding process, the content of residual impurities after molding is high, the activity and selectivity of the catalyst can be influenced by the residual additives in the molding process, high-temperature roasting can cause considerable particle sintering, amorphous state raney metal is reduced, and the activity is reduced.
Chinese petrochemical company patent application CN201410083872 discloses a composite catalyst, which comprises the following main components: continuous phase carbon and dispersed phase Raney alloy particles, wherein the dispersed phase Raney alloy particles are uniformly or non-uniformly dispersed in the continuous phase carbon, and the continuous phase carbon is obtained by carbonizing a carbonizable organic matter or a mixture thereof. The catalyst has the advantages of simple preparation method and low cost, and the obtained catalyst has high activity and good particle strength. The application of the patent obtains a practical fixed bed Raney catalyst with industrial application value, but the catalyst also has defects that on one hand, the carbon is not strong as a framework in high-temperature oxidation resistance, oxidation loss is easy to occur under the oxygen atmosphere or oxygen-containing compound high-temperature condition, the particle strength is damaged, and then catalyst particle pulverization, reactor blockage and safe production are influenced; on the other hand, the carbon skeleton surface properties are close to neutral and are not suitable for certain reactions requiring acidic assistance.
Therefore, the fixed bed Raney catalyst which is high in temperature, resistant to oxygen and surface acidic has high practical application value.
Disclosure of Invention
The invention aims to provide a Raney composite catalyst for a fixed bed, which has simple preparation process, can maintain the strength of catalyst particles in oxygen atmosphere, and has the surface properties of porous carbon and titanium-containing oxide.
A first aspect of the present invention provides a composite catalyst comprising: the carbon-based composite material comprises continuous phase carbon, dispersed phase Raney alloy particles and dispersed phase titanium-containing oxide, wherein the dispersed phase Raney alloy particles and the dispersed phase titanium-containing oxide are respectively uniformly or nonuniformly dispersed in the continuous phase carbon, the continuous phase carbon is obtained by carbonizing at least one organic matter capable of being carbonized, and the titanium-containing oxide is obtained by thermal decomposition of titanium-containing sol-gel.
According to a preferred embodiment of the present invention, the raney alloy particles comprise raney metal and a leachable element. The term "raney metal" as used herein refers to a catalytically active metal that is insoluble when activated by raney. The raney metal is preferably selected from at least one of nickel, cobalt, copper and iron. The term "leachable elements" as used herein refers to elements that are soluble when activated by the raney process. The leachable element is preferably selected from at least one of aluminum, zinc, and silicon.
In a preferred embodiment, the raney alloy is selected from nickel-aluminium alloy, cobalt-aluminium alloy, copper-aluminium alloy.
In one embodiment, the weight ratio of the raney metal to the leachable element is 1: 99-10: 1, preferably 1: 10-4: 1.
in order to improve the activity or selectivity of the catalyst, the Raney alloy can also be introduced with a promoter to form the Raney alloy with multiple components, and the promoter is selected from at least one of Mo, Cr, Ti, Pt, Pd, Rh and Ru. The content of the accelerator is preferably 0.01 to 5wt% based on the total weight of the raney alloy particles.
As used herein, the term "carbonizable organic" refers to those organic species that can be converted to a higher carbon containing synthetic material by treatment at a temperature and under oxygen-deficient or oxygen-free atmosphere conditions to volatilize all or a substantial portion of the non-carbon elements therein, such as hydrogen, oxygen, nitrogen, sulfur, and the like. The obtained carbon-containing synthetic material has the performances of high temperature resistance, high strength, high modulus, porosity and the like.
In one embodiment, the carbonizable organic substance is preferably an organic polymer compound, including natural organic polymer compounds and synthetic organic polymer compounds.
In a preferred embodiment, the carbonizable organic substance is a synthetic organic high molecular compound selected from at least one of rubber, thermosetting plastic, and thermoplastic plastic; the rubber is preferably styrene-butadiene rubber and/or polyurethane rubber; the thermosetting plastic is preferably at least one selected from epoxy resin, phenolic resin and furan resin; the thermoplastic is preferably selected from at least one of polystyrene, styrene-divinylbenzene copolymer and polyacrylonitrile.
In another preferred embodiment, the carbonizable organic substance is a natural organic polymer compound selected from at least one of starch, modified starch, viscose, lignin, cellulose, and carboxymethyl cellulose.
In still another preferred embodiment, the carbonizable organic substance is selected from at least one of coal, natural asphalt, petroleum asphalt, and coal tar asphalt.
The organic matter that can be carbonized may also be a conductive high molecular compound selected from at least one of polyaniline, polypyrrole, and polythiophene.
In the present invention, the titanium-containing oxide is preferably an oxide of titanium, and is particularly preferably selected from TiO and TiO2And Ti2O3At least one of (1). The titanium-containing oxide is obtained via a titanium-containing sol-gel thermal decomposition. Wherein, the titanium-containing sol can be obtained by various conventional methods in the field, preferably, the titanium-containing sol is obtained by titanate hydrolysis, and the hydrolysis is generally carried out in an ethanol medium; the titanate is preferably tetraisopropyl titanate and/or tetrabutyl titanate.
The content of the Raney alloy particles in the composite catalyst can be changed in a wide range, the content of the titanium-containing oxide can be determined according to requirements, and preferably, the content of the Raney alloy particles is 10-90wt% based on the total weight of the composite catalyst.
In the present invention, the content of the titanium-containing oxide may vary within a wide range depending on the intended properties and uses of the composite catalyst, and may be 0.5 to 50 wt% in terms of the titanium element. According to one embodiment of the present invention, the content of the titanium-containing oxide may be 1 wt% to 20 wt%.
The particle size of the raney alloy particles of the present invention can be selected within a wide range. For example, the average particle size may be from 0.1 to 1000 microns, preferably from 1 to 500 microns, more preferably from 10 to 100 microns.
The shape of the composite catalyst is not particularly limited in the present invention as long as it is suitable for a fixed bed or fluidized bed process. Suitably, the composite catalyst may be in the form of spheres, hemispheres, rings, semi-rings, cylinders, semi-cylinders, hollow cylinders, prisms, cuboids, cubes, teeth, irregular particles or a combination thereof.
The particle size of the composite catalyst of the invention may vary within wide limits depending on the preparation process and the intended use of the catalyst. The average equivalent diameter of the composite catalyst is typically in the range of 0.3mm to 20mm, preferably in the range of 0.5mm to 10mm, more preferably in the range of 1mm to 8 mm.
The carbon, the titanium-containing oxide and the Raney alloy are organically combined together by a high-molecular processing and molding method, so that the Raney metal composite catalyst suitable for the fixed bed is prepared. On one hand, a carbonizable organic matter and the Raney alloy are mixed and then carbonized to obtain a carbon and Raney alloy composite, the Raney alloy plays a role in promoting the carbonization process and can ensure that the carbonization is more complete, after the carbonization, the Raney alloy is dispersed in a continuous phase of the carbon and is firmly combined with the continuous phase carbon, and the continuous phase carbon has a porous structure, so that the composite catalyst has high strength. Therefore, the activated catalyst has high catalytic activity. On the other hand, the titanium-containing oxide functions as an auxiliary skeleton and provides surface properties different from those of carbon, such as surface acidity for promoting chemical reactions, and therefore, the catalyst of the present invention also has better strength and is particularly suitable for reactions requiring acidic assistance.
A second aspect of the present invention provides a method for preparing the above-mentioned composite catalyst, which comprises the steps of:
a. preparing a curable composition, the curable composition or a cured product thereof comprising a carbonizable organic; the curing composition may be in the form of a liquid, gel, paste or powder;
b. mixing raney alloy particles, a titanium-containing sol and the curable composition obtained in step a, then curing the resulting mixture, and optionally pulverizing the cured mixture to obtain a catalyst precursor;
c. under the protection of inert gas, carbonizing the catalyst precursor at high temperature to obtain the composite catalyst.
In the method of the present invention, the raney alloy particles, titanium-containing sol and carbonizable organic substance are as described in the first aspect.
According to a specific embodiment of the present invention, the method for preparing the composite catalyst comprises the steps of:
a. preparing a curable composition according to a common curing formula of carbonizable organic matters, wherein the curable composition is in a liquid state or a powder state; hydrolyzing titanate to obtain titanium-containing sol;
b. b, uniformly mixing the Raney alloy particles, the titanium-containing sol and the curable composition obtained in the step a, and then carrying out die pressing and curing on the obtained mixture to obtain a catalyst precursor, wherein the titanium-containing sol is changed into gel;
c. under the protection of inert gas, carbonizing the catalyst precursor at high temperature to obtain the composite catalyst.
The composition of the curable composition generally depends on the carbonizable organic selected. In some embodiments, when the selected carbonizable organic is a thermoplastic, the curable composition may consist essentially of a powder of the thermoplastic. Such curable compositions can be cured by heating-cooling.
In other embodiments, the curable composition may include a carbonizable organic and a solvent and/or liquid dispersant. Such curable compositions may be cured by at least partial removal of the solvent and/or liquid dispersant. The solvent and the liquidExamples of bulk dispersants include, but are not limited to, water; c1-C8Alcohols of (2), such as methanol, ethanol, isopropanol, n-butanol, 2-ethylhexanol; esters, such as ethyl acetate, methyl acetate; ketones such as acetone, methyl ethyl ketone, cyclohexanone; c5-C30Hydrocarbons such as pentane, cyclopentane, hexane, cyclohexane, heptane, octane, decane, dodecane, benzene, toluene, xylene; c1-C10The halogenated hydrocarbon of (1). The lower limit of the concentration of carbonizable organic in such curable compositions may be 5, 10, 15, 20, 25, 30, 35 or 40 wt% and the upper limit may be 20, 30, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90 or 95 wt%.
In other embodiments, the curable composition may comprise a thermosetting resin and, if desired, a curing agent. Such curable compositions can be cured by heating. Curing systems suitable for different thermosetting resins are well known to the person skilled in the art.
One or more additives selected from the group consisting of: binders, cure accelerators, dyes, pigments, colorants, antioxidants, stabilizers, plasticizers, lubricants, flow modifiers or adjuvants, flame retardants, drip retardants, antiblock agents, adhesion promoters, conductive agents, polyvalent metal ions, impact modifiers, mold release aids, nucleating agents, and the like. The used additive amount is the conventional amount, or can be adjusted according to the requirements of actual conditions.
The curable composition may be formulated as a liquid system, a liquid-solid system, a colloidal system, or a powdered solid system. The liquid system can be directly stirred uniformly; the powdery solid system can be directly and uniformly blended; the granular solid system can be pulverized by any pulverizing equipment commonly used in industry and then uniformly blended.
In step b, the weight ratio of the total weight of the raney alloy particles, titanium-containing sol and the curable composition obtained in step a may be 10: 90-90: 10, preferably 25: 75-75: 25.
in step b, a catalyst precursor is obtained by curing a mixture of the raney alloy particles, the titanium-containing sol and the curable composition and optionally pulverizing the cured mixture. The manner of curing and the process conditions depend on the composition of the curable composition and can be readily determined by one skilled in the art. For example, if a thermoplastic resin is used as the carbonizable organic in the curable composition, curing of the curable composition may be achieved by heating the mixture of the raney alloy particles and curable composition above the softening temperature of the thermoplastic resin and then cooling; if a thermosetting resin is used as the carbonizable organic substance in the curable composition, curing of the curable composition may be achieved by heating the mixture of the raney alloy particles and curable composition to initiate a curing reaction; if natural organic high molecular compounds such as starch, modified starch, cellulose, carboxymethyl cellulose and lignin are used as the carbonizable organic substance in the curable composition, curing of the curable composition can be achieved by removing the liquid medium and/or heating in the mixture of the raney alloy particles and the curable composition. If desired, the cured mixture obtained by the curing operation may be processed into particles having a desired shape and size by any method known in the art, such as cutting, clipping, stamping or crushing, using any organic polymer material processing equipment.
The carbonization, i.e. the high-temperature roasting, in the step c is generally carried out in a tubular heating furnace, the carbonization temperature is generally 400-. For example, phenolic resin is carbonized at 850 ℃ for 3 hours, and then the phenolic resin is completely carbonized to form porous carbon. The higher carbonization temperature can make the carbon obtained after carbonization more regular. Under the carbonization condition, the titanium-containing sol is solidified and decomposed to obtain the titanium-containing oxide.
The composite catalyst of the present invention can be easily activated, and a third aspect of the present invention provides a method for activating the above-mentioned composite catalyst, which comprises treating the composite catalyst with an alkali solution.
The specific method of activating the composite catalyst by lye treatment and the conditions employed are essentially known. For example, the step of lye treatment comprises: activating the composite catalyst with 0.5-30 wt% strength alkali solution at 25-95 deg.c for 5 min-72 hr to dissolve out at least part of the leachable elements in the Raney alloy. In a preferred embodiment, the lye is an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution.
A fourth aspect of the present invention provides an activated composite catalyst obtained by the above-described method.
The invention can easily control the loading of the Raney metal in the catalyst by controlling the adding amount of the Raney alloy in the preparation process of the catalyst and/or controlling the activation degree of the catalyst, for example, an activated catalyst with the Raney metal loading of 1-90 wt% (based on the total weight of the catalyst as 100%) can be obtained, an activated catalyst with the Raney metal loading of 10-90wt% is preferred, and an activated catalyst with the Raney metal loading of 30-80 wt% is further preferred. The invention can also easily control the content of the titanium-containing oxide in the activated catalyst by controlling the adding amount of the titanium-containing sol in the preparation process of the composite catalyst.
The catalyst is a composite fixed bed Raney type catalyst, the surface property has the characteristics of carbon and titanium-containing oxide, the carbon framework can provide a nearly neutral catalyst surface and pore channel structure, the titanium-containing oxide can provide surface acidity and enhance the particle strength of catalyst particles in an oxygen atmosphere, and even if part of the carbon framework is oxidized and lost, the catalyst particles cannot be completely pulverized due to the existence of the titanium-containing oxide, so that the safe and stable operation of a reactor is facilitated.
The catalyst prepared by the method is particularly suitable for hydrogenation or dehydrogenation reactions. Because the catalyst is a formed catalyst, the particle strength is good, and the catalyst can be used for a fixed bed or a moving bed.
The preparation method of the catalyst is simple and has low cost.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Detailed Description
The following examples further illustrate the invention but are not intended to limit the invention thereto.
Example 1
(1) And (2) uniformly mixing tetrabutyl titanate and absolute ethyl alcohol according to the mass ratio of 1:1, adding the mixed solution into deionized water, wherein the molar ratio of the mixed solution to water is 1:3, and stirring at room temperature for 2 hours to obtain the titanium-containing sol.
(2) And (2) fully and uniformly stirring 100 parts by mass of the titanium-containing sol prepared in the step (1), 100 parts by mass of liquid epoxy resin (potentilla petrochemical, CYD-128), 85 parts by mass of curing agent methyl tetrahydrophthalic anhydride (MeTHPA) (Kyoto Kovar, Kyoto), and 1.5 parts by mass of curing accelerator Triethanolamine (TEA) (Tianjin chemical reagent factory) to obtain a curable mixture system.
(3) Weighing 60g of the mixture system prepared in the step (2) and 180g of nickel-aluminum alloy powder, fully stirring and mixing, wherein the Ni content in the nickel-aluminum alloy is 48% (weight) and the aluminum content is 52% (weight), adding a proper amount of the mixture into a cylindrical mold, molding for 30mins at the temperature of 120 ℃ and the pressure of 7MPa by using a flat-plate vulcanizing instrument, molding for 90mins at the temperature of 150 ℃ and the pressure of 7MPa by using a flat-plate vulcanizing instrument, cooling and taking out to obtain the granular catalyst precursor.
(4) 100ml of catalyst precursor is measured and put into a tubular high-temperature electric furnace, the temperature is raised to 600 ℃ at the temperature-raising rate of 10 ℃/min under the nitrogen flow of 200ml/min, the temperature is kept for 3 hours at the temperature, and then the composite catalyst is obtained after cooling.
(5) Preparing 400g of 20% NaOH aqueous solution by using deionized water, and adding the 20% NaOH aqueous solution into 50ml of the composite catalyst obtained in the step (4). The resulting mixture was kept at 85 ℃ for 8 hours, then the solution was filtered off, and the solid was washed with deionized water to near neutrality to obtain an activated composite catalyst. And the activated composite catalyst is stored in deionized water for later use. The activated composite catalyst had a nickel metal loading of about 50 wt% and an elemental titanium content of about 9 wt%, based on the weight of the activated catalyst.
Example 2
(1) And (2) uniformly mixing tetrabutyl titanate and absolute ethyl alcohol according to the mass ratio of 1:1, adding the mixed solution into deionized water, wherein the molar ratio of the mixed solution to water is 1:3, and stirring at room temperature for 2 hours to obtain the titanium-containing sol.
(2) And (2) fully and uniformly stirring 50 parts by mass of the titanium-containing sol prepared in the step (1), 100 parts by mass of liquid epoxy resin (potentilla petrochemical, CYD-128), 85 parts by mass of curing agent methyl tetrahydrophthalic anhydride (MeTHPA) (Kyoto Kovar, Kyoto), and 1.5 parts by mass of curing accelerator Triethanolamine (TEA) (Tianjin chemical reagent factory) to obtain a curable mixture system.
(3) Weighing 55g of the mixture system prepared in the step (2) and 180g of nickel-aluminum alloy powder, fully stirring and mixing, wherein the Ni content in the nickel-aluminum alloy is 48% (weight) and the aluminum content is 52% (weight), adding a proper amount of the mixture into a cylindrical mold, molding for 30mins at the temperature of 120 ℃ and the pressure of 7MPa by using a flat-plate vulcanizing instrument, molding for 90mins at the temperature of 150 ℃ and the pressure of 7MPa by using a flat-plate vulcanizing instrument, cooling and taking out to obtain the granular catalyst precursor.
(4) 100ml of catalyst precursor is measured and put into a tubular high-temperature electric furnace, the temperature is raised to 600 ℃ at the temperature-raising rate of 10 ℃/min under the nitrogen flow of 200ml/min, the temperature is kept for 3 hours at the temperature, and then the composite catalyst is obtained after cooling.
(5) Preparing 400g of 20% NaOH aqueous solution by using deionized water, and adding the 20% NaOH aqueous solution into 50ml of the composite catalyst obtained in the step (4). The resulting mixture was kept at 85 ℃ for 8 hours, then the solution was filtered off, and the solid was washed with deionized water to near neutrality to obtain an activated composite catalyst. And the activated composite catalyst is stored in deionized water for later use. The activated composite catalyst had a nickel metal loading of about 50 wt% and an elemental titanium content of about 5wt% based on the weight of the activated catalyst.
Example 3
(1) And (2) uniformly mixing tetrabutyl titanate and absolute ethyl alcohol according to the mass ratio of 1:1, adding the mixed solution into deionized water, wherein the molar ratio of the mixed solution to water is 1:3, and stirring at room temperature for 2 hours to obtain the titanium-containing sol.
(2) Uniformly stirring 50 parts by mass of the titanium-containing sol prepared in the step (1), 100 parts by mass of liquid epoxy resin (CYD-128), 85 parts by mass of curing agent methyl tetrahydrophthalic anhydride (MeTHPA) (Kyoto Korsakoku GmbH, Guangdong) and 1.5 parts by mass of curing accelerator Triethanolamine (TEA) (Tianjin chemical reagent first plant) to obtain a curable mixture system.
(3) Weighing 60g of the mixture system prepared in the step (2) and 150g of nickel-aluminum alloy powder, fully stirring and mixing, wherein the Ni content in the nickel-aluminum alloy is 48% (weight) and the aluminum content is 52% (weight), adding a proper amount of the mixture into a cylindrical mold, molding for 30mins at the temperature of 120 ℃ and the pressure of 7MPa by using a flat-plate vulcanizing instrument, molding for 90mins at the temperature of 150 ℃ and the pressure of 7MPa by using a flat-plate vulcanizing instrument, cooling and taking out to obtain the granular catalyst precursor.
(4) 100ml of catalyst precursor is measured and put into a tubular high-temperature electric furnace, the temperature is raised to 600 ℃ at the temperature-raising rate of 10 ℃/min under the nitrogen flow of 200ml/min, the temperature is kept for 3 hours at the temperature, and then the composite catalyst is obtained after cooling.
(5) Preparing 400g of 20% NaOH aqueous solution by using deionized water, and adding the 20% NaOH aqueous solution into 50ml of the composite catalyst obtained in the step (4). The resulting mixture was kept at 85 ℃ for 8 hours, then the solution was filtered off, and the solid was washed with deionized water to near neutrality to obtain an activated composite catalyst. And the activated composite catalyst is stored in deionized water for later use. The activated composite catalyst had a nickel metal loading of about 40 wt% and an elemental titanium content of about 6 wt%, based on the weight of the activated catalyst.
Comparative example 1
This comparative example serves to illustrate the preparation of a catalyst without titanium oxide.
(1) 100 parts by mass of liquid epoxy resin (ba ling petrochemical, CYD-128), 85 parts by mass of curing agent methyl tetrahydrophthalic anhydride (MeTHPA) (Kyoto Kodak trade Co., Ltd., Guangdong Shengshida), and 1.5 parts by mass of curing accelerator Triethanolamine (TEA) (Tianjin chemical reagent Co., Ltd.) were uniformly stirred.
(2) Weighing 50g of the epoxy system prepared in the step (1) and 150g of nickel-aluminum alloy powder, fully stirring and mixing, wherein the Ni content in the nickel-aluminum alloy is 48% (weight) and the aluminum content is 52% (weight), adding a proper amount of the mixture into a cylindrical mold, molding for 30mins at the temperature of 120 ℃ and the pressure of 7MPa by using a flat-plate vulcanizing instrument, molding for 90mins at the temperature of 150 ℃ and the pressure of 7MPa by using a flat-plate vulcanizing instrument, cooling and taking out to obtain a granular catalyst precursor.
(3) 100ml of catalyst precursor is measured and put into a tubular high-temperature electric furnace, the temperature is raised to 700 ℃ at the temperature-raising rate of 10 ℃/min under the nitrogen flow of 200ml/min, the temperature is kept for 3 hours at the temperature, and then the composite catalyst is obtained after cooling.
(4) Preparing 400g of 20% NaOH aqueous solution by using deionized water, and adding the 20% NaOH aqueous solution into 50ml of the composite catalyst obtained in the step (3). The resulting mixture was kept at 85 ℃ for 4 hours, then the solution was filtered off, and the solid was washed with deionized water to near neutrality to obtain an activated composite catalyst. And the activated composite catalyst is stored in deionized water for later use. The nickel metal loading in the activated composite catalyst was about 50 wt% based on the weight of the activated catalyst.
Example 4
The strength of the acidity and the alkalinity of the surface of the catalyst is compared by utilizing a probe reaction.
Comparing the acid-base property of the surfaces of different catalysts according to the acetone hydrogenation reaction result: the acetone hydrogenation reaction is tested by using a 200ml high-pressure reaction kettle, the reaction pressure is 2.0MPa, the reaction temperature is 155 ℃, the reactant dosage is 100ml, the catalyst dosage is 10ml, and the reaction time is 8 hours. The reaction results of the examples and comparative examples are shown in table 1.
The methyl isobutyl carbinol in the hydrogenation product is generated by the acid catalysis effect, so the content of the methyl isobutyl carbinol can be used for comparing the acidity of the surface of the catalyst, and the higher the content of the methyl isobutyl carbinol is, the higher the acidity of the surface of the catalyst is represented.
As can be seen from Table 1, the catalysts of examples 1-3 exhibited significantly higher contents of the acid-catalyzed product methyl isobutyl carbinol than the catalyst of comparative example 1, indicating that the catalyst surfaces of the present invention are quite acidic and are determined to be generated from the titanium-containing oxide component.
TABLE 1 methyl isobutyl carbinol content in acetone hydrogenation products on different catalysts
In conclusion, the catalyst of the invention is a composite catalyst taking carbon, titanium-containing oxide and active metal as matrixes, the titanium-containing oxide can be used as a carrier for strengthening the particle strength under the condition of carbon loss, and meanwhile, the acidity of the surface of the catalyst is provided, and the selectivity of catalytic reaction can be adjusted.
Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.
Claims (27)
1. A composite catalyst, comprising: the carbon-based composite material comprises continuous phase carbon, dispersed phase Raney alloy particles and dispersed phase titanium-containing oxide, wherein the dispersed phase Raney alloy particles and the dispersed phase titanium-containing oxide are respectively uniformly or nonuniformly dispersed in the continuous phase carbon, the continuous phase carbon is obtained by carbonizing at least one organic matter capable of being carbonized, and the titanium-containing oxide is obtained by thermal decomposition of titanium-containing sol-gel.
2. The composite catalyst according to claim 1, wherein the raney alloy particles comprise raney metal and leachable elements; the weight ratio of the raney metal to the leachable elements is 1: 99-10: 1.
3. the hybrid catalyst according to claim 2, wherein the raney metal is selected from at least one of nickel, cobalt, copper and iron.
4. A composite catalyst according to claim 2, wherein the leachable element is selected from at least one of aluminium, zinc and silicon.
5. A composite catalyst according to claim 2, wherein the weight ratio of the raney metal to the leachable element is 1: 10-4: 1.
6. the composite catalyst according to claim 2, wherein the raney alloy particles further comprise a promoter selected from at least one of Mo, Cr, Ti, Pt, Pd, Rh and Ru, the content of the promoter being 0.01 to 5wt% of the total weight of the raney alloy particles.
7. A composite catalyst according to claim 1, wherein the carbonizable organic substance is a synthetic organic polymer compound selected from at least one of rubber, thermosetting plastic, and thermoplastic plastic.
8. The composite catalyst according to claim 7, wherein the rubber is styrene-butadiene rubber and/or polyurethane rubber.
9. A composite catalyst according to claim 7, wherein the thermosetting plastic is selected from at least one of epoxy resins, phenolic resins and furan resins.
10. A composite catalyst according to claim 7, wherein the thermoplastic is selected from at least one of polystyrene, styrene-divinylbenzene copolymer and polyacrylonitrile.
11. The composite catalyst according to claim 1, wherein the carbonizable organic substance is a natural organic polymer compound selected from at least one of starch, modified starch, viscose, lignin, cellulose and carboxymethyl cellulose.
12. The composite catalyst according to claim 1, wherein the carbonizable organic substance is selected from at least one of coal, natural asphalt, petroleum asphalt, and coal tar asphalt.
13. The composite catalyst according to claim 1, wherein the organic substance that can be carbonized is an electrically conductive polymer compound selected from at least one of polyaniline, polypyrrole, and polythiophene.
14. The composite catalyst according to claim 1, wherein the titanium-containing oxide is an oxide of titanium.
15. A composite catalyst according to claim 14, wherein the titanium-containing oxide is selected from TiO, TiO2And Ti2O3At least one of (1).
16. Composite catalyst according to claim 1, wherein the titanium-containing sol is obtained by hydrolysis of titanate.
17. A hybrid catalyst according to claim 16, wherein the titanate is tetraisopropyl titanate and/or tetrabutyl titanate.
18. The hybrid catalyst according to any one of claims 1 to 17, which has at least one of the following characteristics:
-the content of the raney alloy particles is 10-90wt% based on the total weight of the composite catalyst;
-the particles of the raney alloy have an average particle size of 0.1-1000 microns;
-the composite catalyst is in the shape of spheres, hemispheres, rings, semi-rings, cylinders, semi-cylinders, hollow cylinders, prisms, cuboids, cubes, teeth, irregular particles or a combination thereof;
-the composite catalyst is in the form of particles and has an average equivalent diameter in the range of 0.3mm to 20 mm.
19. A method for preparing the composite catalyst of any one of claims 1 to 17, comprising the steps of:
a. preparing a curable composition, the curable composition or a cured product thereof comprising a carbonizable organic;
b. mixing raney alloy particles, a titanium-containing sol and the curable composition obtained in step a, then curing the resulting mixture, and optionally pulverizing the cured mixture to obtain a catalyst precursor;
c. under the protection of inert gas, carbonizing the catalyst precursor at high temperature to obtain the composite catalyst.
20. The method of claim 19, wherein the method comprises the steps of:
a. preparing a curable composition according to a common curing formula of carbonizable organic matters, wherein the curable composition is in a liquid state or a powder state; hydrolyzing titanate to obtain titanium-containing sol;
b. b, uniformly mixing the Raney alloy particles, the titanium-containing sol and the curable composition obtained in the step a, and then carrying out die pressing and curing on the obtained mixture to obtain a catalyst precursor, wherein the titanium-containing sol is changed into gel;
c. under the protection of inert gas, carbonizing the catalyst precursor at high temperature to obtain the composite catalyst.
21. The method according to claim 19 or 20, wherein the method has at least one of the following features:
-in step b, the weight ratio of the total weight of the raney alloy particles, titanium-containing sol and curable composition obtained in step a is 10: 90-90: 10;
in step c, the carbonization temperature is 400-;
in step c, the inert gas is nitrogen or argon.
22. The method of claim 21, wherein the weight ratio of the total weight of the raney alloy particles, titanium-containing sol and curable composition from step a is 25: 75-75: 25.
23. a method for activating the hybrid catalyst of any one of claims 1 to 17, which comprises treating the hybrid catalyst with a basic solution.
24. The method of claim 23, wherein the step of lye treatment comprises: activating the composite catalyst with 0.5-30 wt% concentration alkali solution at 25-95 deg.c for 5 min-72 hr.
25. An activated hybrid catalyst obtained by the method of claim 23 or 24.
26. Use of at least one of a hybrid catalyst according to any one of claims 1 to 17, a hybrid catalyst obtainable by a process according to any one of claims 19 to 22, an activated hybrid catalyst obtainable by a process according to claim 23 or 24 and an activated hybrid catalyst according to claim 25 in a hydrogenation or dehydrogenation reaction.
27. Use according to claim 26, wherein the reaction is carried out in a fixed bed reactor or a moving bed reactor.
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