CN113070054A - Preparation method of non-supported catalyst, product and application - Google Patents

Preparation method of non-supported catalyst, product and application Download PDF

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CN113070054A
CN113070054A CN202110228785.8A CN202110228785A CN113070054A CN 113070054 A CN113070054 A CN 113070054A CN 202110228785 A CN202110228785 A CN 202110228785A CN 113070054 A CN113070054 A CN 113070054A
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catalyst
reaction
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urea
urea hydrolysis
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CN113070054B (en
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胡小夫
张锡乾
汪洋
王凯亮
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China Huadian Engineering Group Co Ltd
Huadian Environmental Protection Engineering and Technology Co Ltd
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Huadian Environmental Protection Engineering and 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
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/10—Magnesium; Oxides or hydroxides thereof
    • 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
    • B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/20—Vanadium, niobium or tantalum
    • B01J23/22—Vanadium
    • 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
    • B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/24—Chromium, molybdenum or tungsten
    • B01J23/28—Molybdenum
    • 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
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
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    • B01J35/613—10-100 m2/g
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
    • C01C1/00—Ammonia; Compounds thereof
    • C01C1/02—Preparation, purification or separation of ammonia
    • C01C1/08—Preparation of ammonia from nitrogenous organic substances
    • C01C1/086—Preparation of ammonia from nitrogenous organic substances from urea
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Abstract

The invention provides a preparation method of an unsupported catalyst, which comprises the following steps: s1 anatase type TiO2Preparing; the preparation of S2 non-supported catalyst, its product and application are also disclosed. The invention adopts anatase type titanium dioxide and alkaline metal oxide to mix, knead and compress to prepare non-load type catalyst for urea hydrolysis to prepare ammonia, which is beneficial to the generation of urea catalytic hydrolysis reaction, can improve the selectivity of the catalyst and reduce the generation of by-products of isocyanic acid and biuret, thereby preventing the corrosion of equipment; the adoption of non-supported catalyst can effectively prevent abrasionThe activity of the catalyst is reduced, the physicochemical property of the catalyst is stable and the catalyst can be used for a long time, and the running cost of the system is reduced; the application device of the method is simple in production and operation method, does not need special maintenance and monitoring of the catalyst dosage, and further reduces the cost.

Description

Preparation method of non-supported catalyst, product and application
Technical Field
The invention relates to the technical field of flue gas denitration, in particular to a preparation method, a product and application of an unsupported catalyst, and belongs to the technical field of air pollution control.
Background
Selective Catalytic Reduction (SCR) denitration technology is widely applied at home and abroad due to high efficiency. Common reducing agents used in the SCR denitration technology include liquid ammonia, ammonia water and urea. Liquid ammonia and aqueous ammonia belong to dangerous chemicals, all have great potential safety hazard to transportation, connect and unload, if take place to leak will exert an influence to the safety in production of power plant, resident and ecological environment on every side. And the urea is a nontoxic and harmless chemical product, has good performance indexes and operation control safety, is stable in chemical property, cannot explode suddenly and has no danger at all. Upgrading of denitration reducing agents from liquid ammonia to urea is imperative in coal-fired power plants. The technology for preparing ammonia by urea catalytic hydrolysis has the advantages of low reaction temperature, high reaction speed, short response time and the like and is widely applied. However, in the prior art of ammonia production by urea catalytic hydrolysis, liquid acid or alkali is generally adopted as a catalyst, a reaction system is in a homogeneous catalysis state, a homogeneous catalyst needs to be put in periodically, the homogeneous catalyst is not easy to recycle after the reaction is finished, and the problems of high operation cost, strong corrosion to equipment and the like exist.
The technology for preparing ammonia by urea heterogeneous catalytic hydrolysis is expected to become a promising technology for preparing ammonia by urea catalytic hydrolysis due to the advantages of easy solid-liquid separation, low operating cost and the like. The supported catalyst generally adopts metal or metal oxide as an active component of the catalyst, the active component is dispersed on the surface of the catalyst, and the active component is easy to lose due to abrasion along with the advance of reaction time, so that the activity of the catalyst is reduced.
Disclosure of Invention
In order to solve the problems, the invention discloses a preparation method of an unsupported catalyst, which is characterized in that anatase titanium dioxide and alkaline metal oxide synthesized by a hydrothermal method are kneaded, compressed and molded to prepare the unsupported catalyst, and the unsupported catalyst is used in a urea hydrolysis ammonia production unit of an SCR denitration system. The non-supported solid catalyst prepared by the method adopts anatase titanium dioxide as a carrier, so that the selectivity of the catalyst can be improved, and the generation of by-products of isocyanic acid and biuret can be reduced, thereby preventing equipment corrosion; the non-supported catalyst can effectively prevent the loss of active components on the surface of the catalyst caused by abrasion, thereby solving the problems of reduced catalytic activity and the like.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
a method for preparing an unsupported catalyst comprising the steps of:
s1 anatase type TiO2The preparation of (1): mixing titanium salt powder solid and NH4Dissolving F in deionized water, stirring for 20-240 min, and carrying out hydrothermal reaction on the mixed solution at 120-180 ℃ for 4-72 h; cooling at room temperature after hydrothermal reaction, washing the obtained white precipitate with deionized water and ethanol for 1-3 times respectively, drying at 60-120 ℃ for 6-24 h, and roasting in a muffle furnace at 400-600 ℃ for 4-12 h to obtain anatase TiO2Powder; the titanium salt: NH (NH)4F: the molar ratio of the deionized water is 1-3: 0.05-0.5: 150 to 500;
preparation of S2 unsupported catalyst:
s2.1 adding the anatase type TiO obtained in the step S12Sequentially adding the powder, the active component, the forming aid, the adhesive and the lubricant into a mixer, and rotationally stirring and mixing to obtain wet materials; the TiO is2The mass ratio of the powder to the active component to the forming aid to the adhesive to the lubricant is 300-450: 15-150: 2-50: 10-80: 50-200 parts of;
s2.2, performing compression molding on the wet material obtained in the S2.1 by using a tablet press, drying the molded wet material at the temperature of 60-120 ℃ for 4-24 h, and then roasting at the temperature of 450-600 ℃ for 2-24 h to obtain the non-supported catalyst.
The preparation method and the steps of the unsupported catalystS1 the titanium salt is Ti (SO)4)2、TiCl4One or more of titanium nitrate and tetraisopropyl titanium.
The active components in the step S2.1 are MgO and CrO3、MoO3、V2O5One or more of the above; the forming auxiliary agent is one or more of glass fiber, nano carbon black, carbon nano fiber, active carbon, polyethylene glycol, sodium carboxymethyl cellulose, N-3-carboxypropyloctadecylamine sodium salt and ethylene oxide; the adhesive is one or more of ammonia water, polyoxyethylene, starch, water glass and nitric acid; the lubricant is one or more of deionized water, glycerol, graphite, talcum powder, polyacrylamide, lubricating oil, sesbania powder and paraffin.
The preparation method of the non-supported catalyst comprises the following steps of S2.1, stirring for 0.5-3 hours at a rotating speed of 200-3000 r/min; s2.2, the wet material forming pressure is 100-1000 MPa; the shape of the wet material tablet is cylindrical, Raschig ring, porous plum blossom, seven-hole spherical or gear.
Unsupported catalysts prepared by the process of any preceding preparation.
The application of the non-supported catalyst in the preparation of ammonia by urea hydrolysis comprises the following specific steps: adding the non-supported catalyst particles into urea hydrolysis ammonia production equipment, pumping urea solution, heating for hydrolysis reaction, and generating ammonia gas.
The application of the unsupported catalyst, wherein the heating is steam heating; the hydrolysis reaction conditions are as follows: the pressure is 0.3-0.6 MPa, and the temperature is 120-150 ℃; the urea hydrolysis ammonia production equipment comprises a urea hydrolysis reactor and a catalytic reaction unit arranged in the urea hydrolysis reactor; the catalytic reaction unit is a reaction cage filled with non-supported catalyst particles; the reaction cage is made of anticorrosive stainless steel; the number of the non-supported catalyst particles in each reaction cage is 10-200. The number of the reaction cages is determined by the capacity of the urea hydrolysis reactor, the size of the reaction cages and the catalytic reaction activity. The arrangement of the reaction cage can solve the problems that the catalyst is easy to accumulate (the contact area of a reactant and the catalyst is reduced) to cause low reaction efficiency so as to influence the response time of a system, the catalyst is easy to wear in the reaction process to generate small particles to cause waste, the catalyst is easy to discharge along with waste liquid in the waste liquid discharge process, and the like, thereby effectively improving the catalytic efficiency and preventing the catalyst from being worn.
In the application of the non-supported catalyst, the urea hydrolysis reactor is provided with a steam port, a product gas outlet, a feed port, a discharge port, a drain port, a coil and an isolator; the coil is positioned at the lower part in the urea hydrolysis reactor; the steam port is connected with the inlet of the coil pipe; the drain port is connected with the outlet of the coil pipe; the product gas outlet is arranged at the top of the urea hydrolysis reactor; the feed inlet is arranged at the top of the urea hydrolysis reactor; the discharge port is arranged at the bottom of the urea hydrolysis reactor; the isolator is arranged in the urea hydrolysis reactor and above the catalytic reaction unit and the coil pipe; the discharge hole is provided with a cover I; the inner side surface of the cover I is an anticorrosive stainless steel net. The isolator can solve the problem that the solid catalyst fluctuates to the upper part of the liquid along with the product gas in the catalytic hydrolysis ammonia production reaction process to cause low reaction efficiency, thereby effectively and fully utilizing the solid catalyst.
In the application of the non-supported catalyst, the non-supported catalyst particles (which can be used for 2-5 years) are deactivated and then are discharged out of the urea hydrolysis reactor from a discharge hole.
In the application of the non-supported catalyst, the reaction cage is spherical or elliptical.
Compared with the prior art, the invention has the beneficial effects that:
the invention discloses a preparation method of an unsupported solid catalyst, which is characterized in that anatase titanium dioxide and alkaline metal oxide synthesized by a hydrothermal method are kneaded, compressed and molded to prepare the unsupported catalyst, and the unsupported catalyst is used in a urea hydrolysis ammonia preparation unit of an SCR (selective catalytic reduction) denitration system. The non-supported solid catalyst prepared by the invention adopts anatase type titanium dioxide as a carrier, is beneficial to the occurrence of urea catalytic hydrolysis reaction, can improve the selectivity of the catalyst, and reduces the generation of byproducts of isocyanic acid and biuret, thereby preventing the corrosion of equipment; the non-supported catalyst can effectively prevent the catalyst activity reduction caused by abrasion, and the catalyst has stable physicochemical property and can be used for a long time, so that the operation cost of the system is reduced; the device for preparing ammonia by urea hydrolysis by using the catalyst has simple production and operation methods, does not need special maintenance and monitoring of the dosage of the catalyst, and further reduces the cost.
Drawings
FIG. 1 is a schematic diagram of a plant for producing ammonia by hydrolysis of urea;
FIG. 2 is a schematic structural view of a catalytic reaction unit;
FIG. 3 is a schematic view of a cover I for a discharge port of a urea hydrolysis reactor;
FIG. 4 is a schematic view of the isolator structure;
wherein: a-urea hydrolysis reactor; b-a catalytic reaction unit; c-catalyst particles; a D-isolator; e-the inner side of the cap I; 1-a reaction cage; 2-a steam port; 3-product gas outlet; 4-a feed inlet; 5-a discharge hole; 6-a hydrophobic port; 7-a coil pipe; 8-lid I.
Detailed Description
TABLE 1 design conditions for different examples
Figure BDA0002958010470000031
Figure BDA0002958010470000041
Embodiment 1 of the present invention: a preparation method of an unsupported catalyst comprises the following steps:
s1 anatase type TiO2The preparation of (1): mixing 30g of Ti (SO)4)2Solid and 1g NH4Dissolving F in 600mL deionized water, stirring with a magnetic stirrer for 10min, and transferring the mixed solution to the inner liner of the high-pressure reaction kettle (1)000mL) was subjected to hydrothermal reaction in an oven at 150 ℃ for 6 h. After the hydrothermal reaction, cooling the high-pressure reaction kettle at room temperature, respectively washing the white precipitate in the lining in a beaker by using deionized water and ethanol for 1 time, then drying in an oven at 80 ℃ for 12 hours, and roasting in a muffle furnace at 500 ℃ for 6 hours to obtain anatase TiO2And (3) powder.
Preparation of S2 unsupported catalyst
S2.1 mixing 2850g of TiO2Sequentially adding powder, 300g of MgO, 150g of glass fiber, 50g N-3-carboxypropyloctadecylamine sodium salt, 50g of ammonia water (mass concentration is 20%), 20g of polyethylene oxide and 500g of deionized water into a mixer, rotating at the rotating speed of 1400r/min for 1h to obtain wet materials;
s2.2, performing compression molding on the wet material by using a tablet press, wherein the molding pressure is 300MPa, drying the molded Raschig ring catalyst for 6 hours at 80 ℃, and then roasting the dried Raschig ring catalyst for 6 hours at 500 ℃, wherein the size phi of the Raschig ring catalyst is 16 multiplied by 6.4 multiplied by 16 mm.
Example 2: a preparation method of an unsupported catalyst comprises the following steps:
s1 anatase type TiO2The preparation of (1): 24g of Ti (SO)4)2Solids and 0.74g NH4Dissolving F in 270mL of deionized water, stirring for 10min by using a magnetic stirrer, transferring the mixed solution into the lining of a high-pressure reaction kettle (1000mL), and carrying out hydrothermal reaction in an oven at 160 ℃ for 8 h. After the hydrothermal reaction, cooling the high-pressure reaction kettle at room temperature, respectively washing the white precipitate in the lining in a beaker by using deionized water and ethanol for 1 time, then drying in a 90 ℃ drying oven for 10 hours, and roasting in a muffle furnace at 550 ℃ for 8 hours to obtain anatase TiO2And (3) powder.
Preparation of S2 unsupported catalyst
S2.1 mixing 2850g of TiO2The powder, 600g of MgO, 150g of polyethylene glycol, 50g N-3-carboxypropyloctadecylamine sodium salt, 50g of ammonia water (mass concentration is 20%), 20g of starch and 500g of glycerol are sequentially added into a mixer, and the mixer is rotated for 1h at the rotating speed of 1400r/min to obtain wet materials.
S2.2, performing compression molding on the wet material by using a tablet press, wherein the molding pressure is 300MPa, drying the molded Raschig ring catalyst for 6 hours at 80 ℃, and then roasting the dried Raschig ring catalyst for 6 hours at 500 ℃, wherein the size phi of the Raschig ring catalyst is 16 multiplied by 6.4 multiplied by 16 mm.
Example 3: a preparation method of an unsupported catalyst comprises the following steps:
s1 anatase type TiO2The preparation of (1): mixing 72g Ti (SO)4)2Solids and 0.19g NH4And F is dissolved in 900mL of deionized water, the mixture is stirred for 10min, and then the mixed solution is subjected to hydrothermal reaction in an oven at 160 ℃ for 8 h. Cooling the obtained product in a room temperature environment after hydrothermal reaction, washing the white precipitate in a beaker with deionized water and ethanol for 1 time respectively, then drying the white precipitate in a 90 ℃ drying oven for 10 hours, and roasting the white precipitate in a muffle furnace at 550 ℃ for 8 hours to obtain anatase TiO2And (3) powder.
Preparation of S2 unsupported catalyst:
s2.1 mixing 3000g TiO2Powder 150g V2O5150g of nano carbon black, 150g of sodium carboxymethyl cellulose (CMC), 150g N-3-carboxypropyloctadecylamine sodium salt, 50g of ammonia water (mass concentration is 20%), 50g of water glass and 2000g of graphite are sequentially added into a mixer, and the mixer is rotated for 0.5h at the rotating speed of 3000r/min to obtain a wet material.
S2.2, performing compression molding on the wet material by using a tablet press, wherein the molding pressure is 1000MPa, drying the molded gear-shaped catalyst for 24 hours at the temperature of 60 ℃, and then roasting the molded gear-shaped catalyst for 8 hours at the temperature of 550 ℃, wherein the size phi of the gear-shaped catalyst is 16 multiplied by 6.4 multiplied by 16 mm.
Example 4: a preparation method of an unsupported catalyst comprises the following steps:
s1 anatase type TiO2The preparation of (1): mixing 30g of Ti (SO)4)2Solid and 1g NH4Dissolving F in 600mL of deionized water, stirring for 10min by using a magnetic stirrer, transferring the mixed solution into the lining of a high-pressure reaction kettle (1000mL), and carrying out hydrothermal reaction in an oven at 160 ℃ for 8 h. After the hydrothermal reaction, cooling the high-pressure reaction kettle at room temperature, respectively washing the white precipitate in the lining in a beaker by using deionized water and ethanol for 1 time, then drying in a 90 ℃ drying oven for 10 hours, and roasting in a muffle furnace at 550 ℃ for 8 hours to obtain anatase TiO2And (3) powder.
Preparation of S2 unsupported catalyst
S2.1 mixing 4500g TiO2Powder, 600g MoO310g of carbon nanofiber, 5g of sodium carboxymethyl cellulose (CMC), 5g N-3-carboxypropyloctadecylamine sodium salt, 50g of ammonia water (mass concentration is 20%), 20g of nitric acid and 1500g of talcum powder are sequentially added into a mixer, and the mixer is rotated for 3 hours at the rotating speed of 200r/min to obtain a wet material.
S2.2, performing compression molding on the wet material by using a tablet press, wherein the molding pressure is 100MPa, drying the molded cylindrical catalyst at 120 ℃ for 4h, and then roasting at 450 ℃ for 24h, wherein the size phi of the cylindrical catalyst is 16 multiplied by 6.4 multiplied by 16 mm.
Example 5: a preparation method of an unsupported catalyst comprises the following steps:
s1 anatase type TiO2The preparation of (1): 23.8g of TiCl4Solid and 1g NH4Dissolving F in 600mL of deionized water, stirring for 10min by using a magnetic stirrer, transferring the mixed solution into the lining of a high-pressure reaction kettle (1000mL), and carrying out hydrothermal reaction in an oven at 130 ℃ for 8 h. After the hydrothermal reaction, cooling the high-pressure reaction kettle at room temperature, respectively washing the white precipitate in the lining in a beaker by using deionized water and ethanol for 1 time, then drying in a 90 ℃ drying oven for 10 hours, and roasting in a muffle furnace at 500 ℃ for 6 hours to obtain anatase TiO2And (3) powder.
Preparation of S2 unsupported catalyst
S2.1 mixing 2850g of TiO2Powder, 1500g of MgO, 150g of active carbon, 50g of sodium carboxymethyl cellulose (CMC), 50g N-3-carboxypropyloctadecylamine sodium salt, 500g of ammonia water (mass concentration is 20%), 300g of polyethylene oxide and 500g of polyacrylamide are sequentially added into a mixer, and the mixer is rotated for 1h at the rotating speed of 1400r/min to obtain a wet material.
S2.2, compressing and molding the wet material by using a tablet press, wherein the molding pressure is 300MPa, drying the molded porous plum blossom-shaped catalyst at 100 ℃ for 6h, and then roasting at 500 ℃ for 6h, wherein the size phi of the porous plum blossom-shaped catalyst is 16 multiplied by 6.4 multiplied by 16 mm.
Example 6: a preparation method of an unsupported catalyst comprises the following steps:
s1 anatase type TiO2The preparation of (1): 35.5g of titanium tetraisopropoxide solid and 1.8g of titanium tetraisopropoxide solid were added NH4Dissolving F in 600mL of deionized water, stirring for 10min by using a magnetic stirrer, transferring the mixed solution into the lining of a high-pressure reaction kettle (1000mL), and carrying out hydrothermal reaction in an oven at 130 ℃ for 8 h. After the hydrothermal reaction, cooling the high-pressure reaction kettle at room temperature, respectively washing the white precipitate in the lining in a beaker by using deionized water and ethanol for 1 time, then drying in a 90 ℃ drying oven for 10 hours, and roasting in a muffle furnace at 500 ℃ for 6 hours to obtain anatase TiO2And (3) powder.
Preparation of S2 unsupported catalyst
S2.1 mixing 2850g of TiO2Powder, 600g of MgO, 150g of glass fiber, 50g of sodium carboxymethyl cellulose (CMC), 50g N-3-carboxypropyloctadecylamine sodium salt, 50g of ammonia water (mass concentration is 20%), 20g of polyethylene oxide and 500g of paraffin are sequentially added into a mixer, and the mixer is rotated for 1h at the rotating speed of 1400r/min to obtain a wet material.
S2.2, performing compression molding on the wet material by using a tablet press, wherein the molding pressure is 300MPa, drying the molded seven-pore spherical catalyst at 100 ℃ for 6h, and then roasting at 500 ℃ for 6h, wherein the size phi of the seven-pore spherical catalyst is 16 multiplied by 6.4 multiplied by 16 mm.
Comparative example 1: a preparation method of a supported catalyst comprises the following steps:
s1 anatase type TiO2The preparation of (1): mixing 30g of Ti (SO)4)2Solid and 1g NH4Dissolving F in 600mL of deionized water, stirring for 10min by using a magnetic stirrer, transferring the mixed solution into the lining of a high-pressure reaction kettle (1000mL), and carrying out hydrothermal reaction in an oven at 160 ℃ for 8 h. After the hydrothermal reaction, cooling the high-pressure reaction kettle at room temperature, respectively washing the white precipitate in the lining in a beaker by using deionized water and ethanol for 1 time, then drying in a 90 ℃ drying oven for 10 hours, and roasting in a muffle furnace at 550 ℃ for 8 hours to obtain anatase TiO2And (3) powder.
Preparation of S2 Supported catalyst
S2.1 mixing 2850g of TiO2Adding the powder, 150g of glass fiber, 50g N-3-carboxypropyloctadecylamine sodium salt, 50g of ammonia water (mass concentration is 20%), 20g of polyethylene oxide and 500g of lubricating oil into a mixer in sequence at the rotating speed of 1400r/min in a rotating modeRotating for 1h to obtain wet materials. And (2) compressing and molding the wet material by a tablet press, wherein the molding pressure is 300MPa, drying the molded Raschig annular catalyst carrier at 100 ℃ for 6 hours, and then roasting at 500 ℃ for 6 hours.
S2.2, dissolving 60g of MgO in 300g of water to prepare an impregnation liquid, uniformly mixing the impregnation liquid and 300g of catalyst carrier at 50 ℃, standing for 8h, drying at 120 ℃ to constant weight, and roasting at 550 ℃ for 8 h.
Comparative example 2: a preparation method of an unsupported catalyst comprises the following steps:
s1' hydrothermal method for preparing gamma-Al2O3And (3) powder.
Preparation of unsupported catalyst S2': 2850g of gamma-Al prepared by a hydrothermal method2O3The preparation method comprises the following steps of sequentially adding powder, 600g of MgO, 150g of glass fiber, 50g of sodium carboxymethyl cellulose (CMC), 50g N-3-carboxypropyloctadecylamine sodium salt, 50g of ammonia water (mass concentration is 20%), 20g of sesbania powder and 500g of sesbania powder into a mixer, rotating at the rotating speed of 1400r/min for 1h to obtain a wet material. And (2) compressing and molding the wet material by a tablet press, wherein the molding pressure is 300MPa, drying the molded Raschig ring catalyst for 6 hours at 100 ℃, and then roasting the dried Raschig ring catalyst for 6 hours at 500 ℃, wherein the size of the Raschig ring catalyst is phi 16 multiplied by 6.4 multiplied by 16 mm.
Comparative examples 1-2 were used as in examples 9-11 below.
Example 9: use of the unsupported catalyst obtained in any of examples 1 to 6:
putting 200 non-supported catalyst particles C into a spherical reaction cage 1 made of anticorrosive stainless steel to form a catalytic reaction unit B, putting the catalytic reaction unit B into a urea hydrolysis reactor A, arranging an isolator D above the catalytic reaction unit B and a coil 7, and pumping urea solution into the hydrolysis reactor A; steam enters the coil 7 from the steam port 2 for heating and leaves the coil 7 through the drain port 6; the urea solution is hydrolyzed under the conditions of 0.3MPa and 150 ℃ to generate ammonia gas, and the ammonia gas leaves the urea hydrolysis reactor A from a product gas outlet 3; after the non-supported catalyst is deactivated for 2-5 years, discharging the catalytic reaction unit B from a discharge port 5; the discharge port 5 is provided with a cover I8, and the inner side surface E of the cover I8 is an anticorrosive stainless steel net.
Example 10: use of the unsupported catalyst obtained in any of examples 1 to 6:
putting the non-supported catalyst particles C10 into an elliptical spherical reaction cage 1 made of anticorrosive stainless steel to form a catalytic reaction unit B, putting the catalytic reaction unit B into a urea hydrolysis reactor A, arranging an isolator D above the catalytic reaction unit B and a coil pipe 7, and pumping urea solution into the hydrolysis reactor A; steam enters the coil 7 from the steam port 2 for heating and leaves the coil 7 through the drain port 6; the urea solution is hydrolyzed under the conditions of 0.6MPa and 120 ℃ to generate ammonia gas, and the ammonia gas leaves the urea hydrolysis reactor A from a product gas outlet 3; after the non-supported catalyst is deactivated for 2-5 years, discharging the catalytic reaction unit B from a discharge port 5; the discharge port 5 is provided with a cover I8, and the inner side surface E of the cover I8 is an anticorrosive stainless steel net.
Example 11: use of the unsupported catalyst obtained in any of examples 1 to 6:
putting 120 pieces of non-supported catalyst particles C into an elliptical spherical reaction cage 1 made of anticorrosive stainless steel to form a catalytic reaction unit B, putting the catalytic reaction unit B into a urea hydrolysis reactor A, arranging an isolator D above the catalytic reaction unit B and a coil 7, and pumping urea solution into the hydrolysis reactor A; steam enters the coil 7 from the steam port 2 for heating and leaves the coil 7 through the drain port 6; the urea solution is hydrolyzed under the conditions of 0.5MPa and 130 ℃ to generate ammonia gas, and the ammonia gas leaves the urea hydrolysis reactor A from a product gas outlet 3; after the non-supported catalyst is deactivated for 2-5 years, discharging the catalytic reaction unit B from a discharge port 5; the discharge port 5 is provided with a cover I8, and the inner side surface E of the cover I8 is an anticorrosive stainless steel net.
The results of the performance tests of the unsupported/supported catalysts prepared in the examples and comparative examples of the present invention are as follows:
(1) texture properties of heterogeneous catalysts
TABLE 1 texturing Properties of unsupported/supported catalysts
Sample (I) BET specific surface area/(m)2·g-1) Pore volume/(ml. g)-1)
Example 1 98 0.38
Example 2 85 0.34
Example 3 82 0.33
Example 4 78 0.31
Example 5 75 0.31
Example 6 77 0.32
Comparative example 1 81 0.33
Comparative example 2 221.5 0.83
(2) Evaluation of catalyst
Putting 2 Raschig annular catalyst particles into a micro reaction cage, putting the reaction cage into a 1000mL high-pressure reaction kettle, accurately transferring 500mL of urea aqueous solution with the mass fraction of 50%, performing hydrolysis reaction for 60min at 135 ℃ and 0.40MPa, measuring the concentration of urea in the hydrolysate, and calculating the conversion rate of the urea; the ammonia gas produced was collected and the selectivity of the catalyst was calculated. The collected solid catalyst particles are washed, dried at 120 ℃ for 6h, and then calcined at 500 ℃ for 6h, and the reusability of the catalyst particles is tested.
Table 2 conversion (/%) and selectivity (/%) of urea with different catalysts
Sample (I) Conversion (/%) Selectivity (/%)
Example 1 96.51 99.05％
Example 2 99.49 99.69％
Example 3 97.35 98.74％
Example 4 96.73 98.72％
Example 5 96.85 98.92％
Example 6 97.21 98.85％
Comparative example 1 96.58 98.87％
Comparative example 2 96.10 92.62％
TABLE 3 comparison of the Reusability of unsupported and supported catalyst particles
Figure BDA0002958010470000081
The principle of formation of the catalyst carrier in the present invention:
the reaction of thermal decomposition of basic ammonium aluminum carbonate to form alumina is as follows:
2NH4AlO(OH)HCO3→Al2O3+3H2O↑+2NH4↑+2CO2↑。

Claims (10)

1. a preparation method of an unsupported catalyst is characterized by comprising the following steps: the method comprises the following steps:
s1 anatase type TiO2The preparation of (1): mixing titanium salt powder solid and NH4Dissolving F in deionized water, stirring for 20-240 min, and carrying out hydrothermal reaction on the mixed solution at 120-180 ℃ for 4-72 h; cooling at room temperature after hydrothermal reaction, washing the obtained white precipitate with deionized water and ethanol for 1-3 times respectively, drying at 60-120 ℃ for 6-24 h, and roasting in a muffle furnace at 400-600 ℃ for 4-12 h to obtain anatase TiO2Powder; the titanium salt: NH (NH)4F: the molar ratio of the deionized water is 1-3: 0.05-0.5: 150 to 500;
preparation of S2 unsupported catalyst:
s2.1 adding the anatase type TiO obtained in the step S12Sequentially adding the powder, the active component, the forming aid, the adhesive and the lubricant into a mixer, and rotationally stirring and mixing to obtain wet materials; the TiO is2The mass ratio of the powder to the active component to the forming aid to the adhesive to the lubricant is 300-450: 15-150: 2-50: 10-80: 50-200 parts of;
s2.2, performing compression molding on the wet material obtained in the S2.1 by using a tablet press, drying the molded wet material at the temperature of 60-120 ℃ for 4-24 h, and then roasting at the temperature of 450-600 ℃ for 2-24 h to obtain the non-supported catalyst.
2. The process for preparing an unsupported catalyst according to claim 1, wherein: step S1 the titanium salt is Ti (SO)4)2、TiCl4One or more of titanium nitrate and tetraisopropyl titanium.
3. The process for preparing an unsupported catalyst according to claim 1, wherein: step S2.1 the active components are MgO and CrO3、MoO3、V2O5One or more of the above; the forming auxiliary agent is one or more of glass fiber, nano carbon black, carbon nano fiber, active carbon, polyethylene glycol, sodium carboxymethyl cellulose, N-3-carboxypropyloctadecylamine sodium salt and ethylene oxide; the adhesive is one or more of ammonia water, polyoxyethylene, starch, water glass and nitric acid; the lubricant isOne or more of ionized water, glycerol, graphite, talcum powder, polyacrylamide, lubricating oil, sesbania powder and paraffin.
4. The process for preparing an unsupported catalyst according to claim 1, wherein: s2.1, stirring at a rotating speed of 200-3000 r/min for 0.5-3 h; s2.2, the wet material forming pressure is 100-1000 MPa; the shape of the wet material tablet is cylindrical, Raschig ring, porous plum blossom, seven-hole spherical or gear.
5. The unsupported catalyst obtained by the process according to any one of claims 1 to 4.
6. The application of the unsupported catalyst according to claim 5 in the preparation of ammonia by urea hydrolysis, which is characterized by comprising the following steps: adding the non-supported catalyst particles into urea hydrolysis ammonia production equipment, pumping urea solution, heating for hydrolysis reaction, and generating ammonia gas.
7. Use of the unsupported catalyst according to claim 6, characterized in that: the heating is steam heating; the hydrolysis reaction conditions are as follows: the pressure is 0.3-0.6 MPa, and the temperature is 120-150 ℃; the urea hydrolysis ammonia production equipment comprises a urea hydrolysis reactor A and a catalytic reaction unit B arranged in the urea hydrolysis reactor A; the catalytic reaction unit B is a reaction cage (1) filled with non-supported catalyst particles C; the reaction cage (1) is made of anticorrosive stainless steel; the number of the non-supported catalyst particles C in each reaction cage (1) is 10-200.
8. Use of an unsupported catalyst according to claim 7, characterized in that: the urea hydrolysis reactor A is provided with a steam port (2), a product gas outlet (3), a feed port (4), a discharge port (5), a drain port (6), a coil pipe (7) and an isolator D; the coil (7) is positioned at the lower part in the urea hydrolysis reactor A; the steam port (2) is connected with the inlet of the coil pipe (7); the drain port (6) is connected with the outlet of the coil (7); the product gas outlet (3) is arranged at the top of the urea hydrolysis reactor A; the feed inlet (4) is arranged at the top of the urea hydrolysis reactor A; the discharge hole (5) is formed in the bottom of the urea hydrolysis reactor A; the isolator D is arranged in the urea hydrolysis reactor A and above the catalytic reaction unit B and the coil (7); the discharge port (5) is provided with a cover I (8); the inner side surface E of the cover I (8) is an anticorrosive stainless steel net.
9. Use of an unsupported catalyst according to claim 8, characterized in that: and the non-supported catalyst particles C are discharged out of the urea hydrolysis reactor A through a discharge hole (5) after being deactivated.
10. Use of an unsupported catalyst according to claim 7, characterized in that: the reaction cage (1) is spherical or elliptical.
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