Supported catalyst for preparing acrylic acid by oxidizing propylene and method for preparing acrylic acid by oxidizing propylene

Abstract

The present invention discloses a supported catalyst for propylene oxidation to produce acrylic acid and a method for producing acrylic acid by propylene oxidation. The oxidation catalyst structure, active components, and injection process provided by the present invention are used in acrylic acid oxidation and its waste-burning system process. This addresses the problem of catalyst deactivation and reduced organic matter conversion in acrylic acid waste-burning systems caused by oxidation catalyst dust and byproduct terephthalic acid (PTA) clogging the waste-burning catalyst, both at the source and from a process perspective.

Description

Technical Field

[0001] The present invention relates to the field of organic synthesis, and in particular to a metal honeycomb structure catalyst suitable for preparing acrylic acid by propylene oxidation, a method for preparing acrylic acid by propylene oxidation, and a waste gas treatment process. Background Art

[0002] Acrylic acid is an important petrochemical raw material, widely used as a synthetic intermediate and primarily consumed as a polymer. It can be directly polymerized or polymerized via esterification to form acrylate esters. Currently, acrylic acid is most widely used in the production of thickeners, superabsorbent polymers, flocculants, and builders. Industrially, acrylic acid plays a major role in the synthesis of acrylate esters, such as butyl acrylate, methyl acrylate, and ethyl acrylate. Acrylate esters are primarily used in coatings, plastic modification additives, and rubber. In short, acrylic acid and its esters have a wide range of applications and high demand, making them a vital component of today's petrochemical industry.

[0003] The criteria for evaluating the quality of catalysts in the acrylic acid oxidation reaction stage are not only reflected in the quality of the product, but also the accompanying side reactions that also affect the catalyst's suitability for actual production. Some high-boiling-point byproducts such as maleic acid and PTA can clog the back-end equipment or catalyst along with the reaction gas stream, causing adverse consequences such as increased system pressure, reduced catalyst activity, and reduced yield. In severe cases, it can even affect operation and cause equipment shutdown. For long-term industrialized and stable production, it is more desirable to develop catalysts that produce less high-boiling-point substances as side reactions. Existing studies have shown that adding some elements other than the main active ingredient to the catalyst can reduce byproduct high-boiling-point compounds. For example, alkali metal elements (patent CN111757779A) can reduce the byproduct aromatic compounds of high-boiling-point compounds. However, currently reported uses widely used granular catalyst carriers. However, granular catalysts can undergo friction powdering during actual operation, and the resulting catalyst powder can also cause back-end blockage.

[0004] The acrylic acid waste gas incineration device uses catalytic combustion to convert organic waste gas into non-toxic and harmless gas, avoiding serious pollution to the surrounding air. As domestic environmental protection indicators continue to improve, the requirements for waste gas treatment equipment are also getting higher and higher. At present, the waste gas incineration devices of domestic acrylic acid manufacturers often have the problem of the catalyst surface being covered with a large amount of dust, resulting in the catalyst service life being less than the expected years. The spent catalyst needs to be frequently replaced, resulting in a large amount of financial and human resources. Taking our company's acrylic acid and ester unit as an example, during the one year since the new catalyst was put into use, all process production parameters were within the normal range. However, it was found during operation that its waste gas emission indicators continued to rise. After rigorous measurement, it was found that the non-methane total hydrocarbon content had exceeded 200ppm, and the new catalyst needed to be replaced again to ensure environmental protection indicators. In order to meet environmental protection requirements, solving this problem is imminent. Summary of the Invention

[0005] The purpose of the present invention is to solve the problem of high clogging of the rear-end waste combustion system by the by-product PTA in the current production of acrylic acid by propylene oxidation, and to provide a supported catalyst for producing acrylic acid by propylene oxidation and a method for producing acrylic acid by propylene oxidation.

[0006] Currently, acrylic acid oxidation catalysts, both domestically and internationally, primarily consist of spherical or cylindrical hollow bulk particles. During operation, these particles fluctuate constantly with changes in gas velocity and pressure, causing surface active components to fall and internal structures to shatter, resulting in large amounts of dust entering the waste gas incineration system. Furthermore, PTA particles, a byproduct of the oxidation reaction, also enter the waste gas incineration system along with the gas. This dust and particles accumulate on the surface of the spent catalyst, clogging its pores, reducing its activity, and even causing it to become inactivated. Existing technologies currently offer no effective solution to this problem, requiring periodic shutdown for cleaning or catalyst replacement, impacting the operating cycle.

[0007] Therefore, the present invention fundamentally changes the existing structure and active ingredient composition of the acrylic acid oxidation catalyst, reducing catalyst dust and PTA byproducts. Furthermore, the process is improved by adding a blower before the waste combustion system to intercept dust and PTA. These two aspects extend the operating life of the waste combustion system and improve waste combustion efficiency.

[0008] A catalyst for propylene oxidation to acrylic acid, the general formula of the catalyst being:

[0009] Mo 12 V 4.5 Cu2A a B b Fe 2.2 O c ;

[0010] Wherein Mo, V, Cu, Fe and O represent molybdenum, vanadium, copper, iron and oxygen respectively;

[0011] A represents one or more transition metal elements Sc, Zn, and Mn;

[0012] B represents one or more rare earth elements La, Pr, and Nd;

[0013] a, b, and c represent the atomic ratios of A, B, and O;

[0014] a is 0.5-1, preferably 1;

[0015] b is 0.5-1, preferably 1;

[0016] c is a number determined by the oxidation state of each atom mentioned above.

[0017] PTA is mainly produced by propylene staying inside the catalyst for too long and undergoing deep oxidation with oxygen. Adding transition metal elements can effectively reduce the residence time of propylene in the catalyst, thereby reducing PTA by-products. When rare earth elements form bonds, the outermost electron orbital transitions can activate the bond energy of the main active components of the catalyst, Mo and V, to form a more stable crystal structure with them, making the interaction between the metal elements in the catalyst stronger. Adding rare earth elements can improve catalyst stability and reduce catalyst pulverization.

[0018] The precursor substances of the active components of the catalyst of the present invention are: Mo is ammonium paramolybdate or molybdenum nitrate, V is ammonium metavanadate, Cu is ammonium cuprate or copper nitrate, Fe is ferric nitrate or ferrous nitrate, Sc is scandium nitrate, Zn is zinc nitrate, Mn is manganese nitrate or ammonium permanganate, La is lanthanum nitrate, Pr is praseodymium nitrate, and Nd is neodymium nitrate.

[0019] A method for preparing a catalyst for propylene oxidation to acrylic acid comprises the following steps: uniformly mixing aqueous solutions of precursor substances of various elements of the catalyst's active components, feeding the mixture using a peristaltic pump at a feeding rate of 7-15 mL / min, atomizing the mixture using compressed air at a pressure of 0.4-0.6 MPa, uniformly spraying the mixture onto a metal honeycomb fixed carrier at an environment of 80-100° C., and then drying the mixture at 200-300° C.

[0020] The metal honeycomb fixed carrier of the present invention is a cylindrical structure of a precious metal honeycomb type, such as Figure 1 As shown, the high-temperature stabilized alumina carrier and the high-temperature and corrosion-resistant alloy steel skeleton ensure that the catalyst as a whole is not easy to crush, while maintaining a stable specific surface area of ​​the catalyst.

[0021] The metal honeycomb fixed carrier of the present invention has an external dimension of r25×h400 mm and a cross-sectional opening rate of 280 meshes / square inch.

[0022] During operation, the maximum bed temperature of this metal honeycomb fixed carrier must not exceed 450°C, otherwise it will easily crack. The metal honeycomb structure has relatively low resistance, which prevents localized catalyst crushing caused by intake air vibration and uneven pressure during actual operation. Furthermore, the honeycomb structure increases exhaust gas turbulence, ensuring the most uniform oxidation of propylene and air.

[0023] A method for preparing acrylic acid by oxidizing propylene comprises the following steps: in the present invention, two reactors for preparing acrylic acid by oxidizing propylene are used, one reactor is filled with a conventional spherical Mo-Bi catalyst, and the second reactor is filled with the Mo-V catalyst of the present invention, and molten salt is heated; the temperature of the first reactor is 340-380°C, the temperature of the second reactor is 250-320°C, the volume feed ratio of propylene: air: water vapor is 1: (2-10): (0.1-4), and the space velocity is 1000-2000h -1 .

[0024] The gaseous acrylic acid produced by the reaction is rapidly cooled and absorbed by desalted water in a quenching tower, and a 55-60% crude acrylic acid solution is generated in the bottom of the tower.

[0025] A process for treating acrylic acid tail gas comprises the following steps: a portion of the unabsorbed gas from the top of an acrylic acid quenching tower enters a reactor as circulating gas, and the other portion enters a waste combustion system as tail gas through a spray interceptor tank for catalytic incineration; the tail gas first passes through a heat exchanger 1 to be preheated by hot gas after the waste combustion reaction, and then enters a heat exchanger 2 to be heated to the initial temperature of the waste combustion reaction; the tail gas enters a waste combustion reactor to undergo catalytic oxidation to convert organic matter such as propane and propylene into carbon dioxide; the hot gas after the reaction passes through a heat exchanger 3 to generate steam, and then the waste heat is used to preheat the tail gas entering the waste combustion system in the heat exchanger 1, and then the tail gas is discharged.

[0026] A blow interceptor tank is installed at the front end of the waste combustion system. A wire mesh screen is placed on top of the tank, and 16-27 blow lines are installed horizontally above the screen and 10-15 cm from the top of the tank. Compressed nitrogen is used as the air source, and intermittent pulsed purges and dust removal are performed to remove solids adhering to the wire mesh surface. Blockages fall to the bottom of the tank and are discharged from the bottom along with the condensate. The blower uses compressed nitrogen at a pressure of 0.5-0.7 MPa. The air intake is set at 0.29-0.54% of the exhaust flow rate. A timed blow is used, with a flow rate every 15-30 minutes in the direction of the exhaust flow, to ensure stable gas flow into the exhaust system.

[0027] By improving the catalyst structure and active ingredients and optimizing the waste combustion process, the present invention can reduce by-product PTA particles and catalyst dust, effectively control particulate matter entering the waste combustion system, reduce blockages on the surface of the waste combustion catalyst, and extend the operating cycle of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Preferred catalyst structure in the embodiment;

[0029] Figure 2 The preferred waste combustion system process in the embodiment;

[0030] Figure 3 The preferred blowing process structure in the embodiment. DETAILED DESCRIPTION

[0031] Example 1

[0032] 2118.62 g of ammonium paramolybdate ((NH4)6Mo7O 24 ·4H2O), 526.4 g of ammonium metavanadate (NH4VO3), 376 g of copper nitrate (Cu(NO3)2), 125.96 g of manganese nitrate (Mn(NO3)2), 532.09 g of iron nitrate (Fe(NO3)3), 230.97 g of scandium nitrate (Sc(NO3)3), and 326.92 g of praseodymium nitrate (Pr(NO3)2) are fully mixed and stirred to form a 68% aqueous solution.

[0033] The catalyst was fed via a feed pump at a rate of 10 mL / min and atomized using compressed air at 0.6 MPa. The catalyst was evenly sprayed onto a metal honeycomb support in an 80°C operating room and dried at 300°C to form the support. The support had dimensions of r25 × h400 mm and a cross-sectional porosity of 280 mesh / square inch. The prepared catalyst was loaded into the second reactor; the first reactor was loaded with a conventional spherical Mo-Bi catalyst (Example 1 of Patent CN103934000A).

[0034] Propylene: air: water vapor was fed in a volumetric feed ratio of 1:8:0.1, and the catalyst was contacted and reacted at 375°C in the first reactor and 280°C in the second reactor at a space velocity of 1500 h -1 , react for 48 hours.

[0035] The reaction gas was passed through a spray interceptor tank. Seventeen nitrogen spray lines were installed above the wire mesh and 10 meters from the tank top. Nitrogen was sprayed every 15 minutes for 3 seconds. After 48 hours, solid particles at the tank bottom were collected to evaluate the quality of the intercepted particles. The nitrogen pressure was 0.7 MPa, and the air flow rate was set to 0.54% of the propylene and air inlet flows.

[0036] Evaluation method: 1) Collect and weigh the solid particles at the bottom of the tank to evaluate the interception effect of the injection system; 2) Place the collected solid particles and the screen into an alkaline solution, in which the acidic PTA dissolves, while the catalyst powder is insoluble in the alkali, and evaluate the amount of PTA generated by the alkaline solution consumption; 3) Place the reaction tube containing the second-stage catalyst vertically into an ultrasonic instrument, ultrasonicate at 60Hz for 15 minutes, collect the dust particles that fall from the bottom of the reaction tube, and weigh them to evaluate the amount of catalyst pulverization.

[0037] Example 2

[0038] 2118.62 g of ammonium paramolybdate ((NH4)6Mo7O 24 ·4H2O), 526.4 g of ammonium metavanadate (NH4VO3), 376 g of copper nitrate (Cu(NO3)2), 125.96 g of manganese nitrate (Mn(NO3)2), 532.09 g of iron nitrate (Fe(NO3)3), 184.78 g of scandium nitrate (Sc(NO3)3), and 261.54 g of praseodymium nitrate (Pr(NO3)2) are fully mixed and stirred to form a 68% aqueous solution.

[0039] The catalyst was fed via a feed pump at a rate of 10 mL / min and atomized using compressed air at 0.6 MPa. The catalyst was evenly sprayed onto a metal honeycomb support in an 80°C operating room and dried at 300°C to form the support. The support had dimensions of r25 × h400 mm and a cross-sectional porosity of 280 mesh / square inch. The prepared catalyst was loaded into the second reactor; the first reactor was loaded with a conventional spherical Mo-Bi catalyst (Example 1 of Patent CN103934000A).

[0040] Propylene: air: water vapor was fed in a volumetric feed ratio of 1:8:0.1, and the catalyst was contacted and reacted at 375°C in the first reactor and 280°C in the second reactor at a space velocity of 1500 h -1 , react for 48 hours.

[0041] The reaction gas was passed through a spray interceptor tank. Seventeen nitrogen spray lines were installed above the wire mesh and 10 meters from the tank top. Nitrogen was sprayed every 15 minutes for 3 seconds. After 48 hours, solid particles at the tank bottom were collected to evaluate the quality of the intercepted particles. The nitrogen pressure was 0.7 MPa, and the air flow rate was set to 0.54% of the propylene and air inlet flows.

[0042] Evaluation method: 1) Collect and weigh the solid particles at the bottom of the tank to evaluate the interception effect of the injection system; 2) Place the collected solid particles and the screen into an alkaline solution, in which the acidic PTA dissolves, while the catalyst powder is insoluble in the alkali, and evaluate the amount of PTA generated by the alkaline solution consumption; 3) Place the reaction tube containing the second-stage catalyst vertically into an ultrasonic instrument, ultrasonicate at 60Hz for 15 minutes, collect the dust particles that fall from the bottom of the reaction tube, and weigh them to evaluate the amount of catalyst pulverization.

[0043] Example 3

[0044] 2118.62 g of ammonium paramolybdate ((NH4)6Mo7O 24 4H2O), 526.4 g of ammonium metavanadate (NH4VO3), 376 g of copper nitrate (Cu(NO3)2), 125.96 g of manganese nitrate (Mn(NO3)2), 532.09 g of iron nitrate (Fe(NO3)3), 115.49 g of scandium nitrate (Sc(NO3)3), and 163.46 g of praseodymium nitrate (Pr(NO3)2) are fully mixed and stirred to form a 68% aqueous solution.

[0045] The catalyst was fed via a feed pump at a rate of 10 mL / min and atomized using compressed air at 0.6 MPa. The catalyst was evenly sprayed onto a metal honeycomb support in an 80°C operating room and dried at 300°C to form the support. The support had dimensions of r25 × h400 mm and a cross-sectional porosity of 280 mesh / square inch. The prepared catalyst was loaded into the second reactor; the first reactor was loaded with a conventional spherical Mo-Bi catalyst (Example 1 of Patent CN103934000A).

[0046] Propylene: air: water vapor was fed in a volumetric feed ratio of 1:8:0.1, and the catalyst was contacted and reacted at 375°C in the first reactor and 280°C in the second reactor at a space velocity of 1500 h -1 , react for 48 hours.

[0047] The reaction gas was passed through a spray interceptor tank. Seventeen nitrogen spray lines were installed above the wire mesh and 10 meters from the tank top. Nitrogen was sprayed every 15 minutes for 3 seconds. After 48 hours, solid particles at the tank bottom were collected to evaluate the quality of the intercepted particles. The nitrogen pressure was 0.7 MPa, and the air flow rate was set to 0.54% of the propylene and air inlet flows.

[0048] Evaluation method: 1) Collect and weigh the solid particles at the bottom of the tank to evaluate the interception effect of the injection system; 2) Place the collected solid particles and the screen into an alkaline solution, in which the acidic PTA dissolves, while the catalyst powder is insoluble in the alkali, and evaluate the amount of PTA generated by the alkaline solution consumption; 3) Place the reaction tube containing the second-stage catalyst vertically into an ultrasonic instrument, ultrasonicate at 60Hz for 15 minutes, collect the dust particles that fall from the bottom of the reaction tube, and weigh them to evaluate the amount of catalyst pulverization.

[0049] Comparative Example 1

[0050] 2118.62 g of ammonium paramolybdate ((NH4)6Mo7O 24 4H2O), 526.4 g of ammonium metavanadate (NH4VO3), 376 g of copper nitrate (Cu(NO3)2), 125.96 g of manganese nitrate (Mn(NO3)2), 532.09 g of iron nitrate (Fe(NO3)3), and 230.97 g of scandium nitrate (Sc(NO3)3) are fully mixed and stirred to form a 68% aqueous solution.

[0051] The catalyst was fed via a feed pump at a rate of 10 mL / min and atomized using compressed air at 0.6 MPa. The catalyst was evenly sprayed onto a metal honeycomb support in an 80°C operating room and dried at 300°C to form the support. The support had dimensions of r25 × h400 mm and a cross-sectional porosity of 280 mesh / square inch. The prepared catalyst was loaded into the second reactor; the first reactor was loaded with a conventional spherical Mo-Bi catalyst (Example 1 of Patent CN103934000A).

[0052] Propylene: air: water vapor was fed in a volumetric feed ratio of 1:8:0.1, and the catalyst was contacted and reacted at 375°C in the first reactor and 280°C in the second reactor at a space velocity of 1500 h -1 , react for 48 hours.

[0053] The reaction gas was passed through a spray interceptor tank. Seventeen nitrogen spray lines were installed above the wire mesh and 10 meters from the tank top. Nitrogen was sprayed every 15 minutes for 3 seconds. After 48 hours, solid particles at the tank bottom were collected to evaluate the quality of the intercepted particles. The nitrogen pressure was 0.7 MPa, and the air flow rate was set to 0.54% of the propylene and air inlet flows.

[0054] Evaluation method: The reaction tube containing the second-stage catalyst was placed vertically in an ultrasonic instrument and ultrasonicated at 60 Hz for 15 minutes. The dust particles falling from the bottom of the reaction tube were collected and weighed to evaluate the amount of catalyst pulverization.

[0055] Comparative Example 2

[0056] 2118.62 g of ammonium paramolybdate ((NH4)6Mo7O24 ·4H2O), 526.4 g of ammonium metavanadate (NH4VO3), 376 g of copper nitrate (Cu(NO3)2), 125.96 g of manganese nitrate (Mn(NO3)2), 532.09 g of iron nitrate (Fe(NO3)3), and 326.92 g of praseodymium nitrate (Pr(NO3)2) are fully mixed and stirred to form a 68% aqueous solution.

[0057] The catalyst was fed via a feed pump at a rate of 10 mL / min and atomized using compressed air at 0.6 MPa. The catalyst was evenly sprayed onto a metal honeycomb support in an 80°C operating room and dried at 300°C to form the support. The support had dimensions of r25 × h400 mm and a cross-sectional porosity of 280 mesh / square inch. The prepared catalyst was loaded into the second reactor; the first reactor was loaded with a conventional spherical Mo-Bi catalyst (Example 1 of Patent CN103934000A).

[0058] Propylene: air: water vapor was fed in a volumetric feed ratio of 1:8:0.1, and the catalyst was contacted and reacted at 375°C in the first reactor and 280°C in the second reactor at a space velocity of 1500 h -1 , react for 48 hours.

[0059] The reaction gas was passed through a spray interceptor tank. Seventeen nitrogen spray lines were installed above the wire mesh and 10 meters from the tank top. Nitrogen was sprayed every 15 minutes for 3 seconds. After 48 hours, solid particles at the tank bottom were collected to evaluate the quality of the intercepted particles. The nitrogen pressure was 0.7 MPa, and the air flow rate was set to 0.54% of the propylene and air inlet flows.

[0060] Evaluation method: Collect solid particles at the bottom of the tank and place the collected solid particles and the sieve into alkaline solution, in which the acidic PTA dissolves, while the catalyst powder is insoluble in the alkali. The amount of PTA generated is evaluated by the consumption of the alkaline solution.

[0061] Comparative Example 3

[0062] The second reactor was loaded with a conventional spherical Mo-V catalyst (Example 1 of Patent CN1031488A), which does not contain transition metal elements and rare earth metal elements. The first reactor was loaded with a conventional spherical Mo-Bi catalyst (Example 1 of Patent CN103934000A).

[0063] Propylene: air: water vapor was fed in a volumetric feed ratio of 1:8:0.1, and the catalyst was contacted and reacted at 375°C in the first reactor and 280°C in the second reactor at a space velocity of 1500 h -1 , react for 48 hours.

[0064] The reaction gas was passed through a spray interceptor tank. Seventeen nitrogen spray lines were installed above the wire mesh and 10 meters from the tank top. Nitrogen was sprayed every 15 minutes for 3 seconds. After 48 hours, solid particles at the tank bottom were collected to evaluate the quality of the intercepted particles. The nitrogen pressure was 0.7 MPa, and the air flow rate was set to 0.54% of the propylene and air inlet flows.

[0065] Evaluation method: 1) Collect solid particles at the bottom of the tank, place the collected solid particles and the sieve into alkaline solution, in which acidic PTA dissolves, while the catalyst powder is insoluble in alkali, and evaluate the amount of PTA generated by the consumption of alkaline solution; 2) Place the reaction tube containing the second-stage catalyst vertically into an ultrasonic instrument, ultrasonicate at 60Hz for 15 minutes, collect the dust particles that fall from the bottom of the reaction tube, and weigh them to evaluate the amount of catalyst pulverization.

[0066] Comparative Example 4

[0067] 2118.62 g of ammonium paramolybdate ((NH4)6Mo7O 24 ·4H2O), 526.4 g of ammonium metavanadate (NH4VO3), 376 g of copper nitrate (Cu(NO3)2), 125.96 g of manganese nitrate (Mn(NO3)2), 532.09 g of iron nitrate (Fe(NO3)3), 230.97 g of scandium nitrate (Sc(NO3)3), and 326.92 g of praseodymium nitrate (Pr(NO3)2) are fully mixed and stirred to form a 68% aqueous solution.

[0068] The catalyst was fed via a feed pump at a rate of 10 mL / min and atomized using compressed air at 0.6 MPa. The catalyst was evenly sprayed onto a metal honeycomb support in an 80°C operating room and dried at 300°C to form the support. The support had dimensions of r25 × h400 mm and a cross-sectional porosity of 280 mesh / square inch. The prepared catalyst was loaded into the second reactor; the first reactor was loaded with a conventional spherical Mo-Bi catalyst (Example 1 of Patent CN103934000A).

[0069] Propylene: air: water vapor was fed in a volumetric feed ratio of 1:8:0.1, and the catalyst was contacted and reacted at 375°C in the first reactor and 280°C in the second reactor at a space velocity of 1500 h -1 , react for 48 hours.

[0070] The reaction generated gas passes through the injection interception tank, and 17 nitrogen injection pipelines are set above the wire mesh and 10m away from the tank top. The injection control is not turned on to collect solid particles at the bottom of the tank.

[0071] Evaluation method: Collect and weigh the solid particles at the bottom of the tank to evaluate the interception effect of the injection system.

[0072] Table 1 Catalyst composition and evaluation indicators

[0073]

Claims

1. A supported catalyst for propylene oxidation to acrylic acid, the general formula of the catalyst being: Mo 12 V 4.5 Cu2A a B b Fe 2.2 O c ; Wherein Mo, V, Cu, Fe and O represent molybdenum, vanadium, copper, iron and oxygen respectively; A represents transition metal elements Sc and Mn; B represents one or more rare earth elements Pr and Nd; a, b, and c represent the atomic ratios of A, B, and O; a is 0.5-1; b is 0.5-1; c is a number determined by the oxidation state of each atom mentioned above.

2. The supported catalyst according to claim 1, characterized in that The method for preparing the supported catalyst includes the following steps: uniformly mixing aqueous solutions of precursor substances of various elements of the catalyst active component, feeding them by a peristaltic pump at a feeding rate of 7-15 mL / min, atomizing them with compressed air at a pressure of 0.4-0.6 MPa, uniformly spraying them onto a metal honeycomb fixed carrier in an environment of 80-100°C, and then drying them at 200-300°C.

3. The supported catalyst according to claim 2, characterized in that The precursor substances of the elements of the active components of the catalyst are: Mo is ammonium paramolybdate or molybdenum nitrate, V is ammonium metavanadate, Cu is ammonium cuprate or copper nitrate, Fe is ferric nitrate or ferrous nitrate, Sc is scandium nitrate, Mn is manganese nitrate or ammonium permanganate, Pr is praseodymium nitrate, and Nd is neodymium nitrate.

4. A method for preparing acrylic acid by oxidizing propylene, comprising the following steps: In two reactors for propylene oxidation to acrylic acid, one reactor is loaded with a Mo-Bi catalyst and the second reactor is loaded with the supported catalyst according to claim 1. The temperature of the first reactor is 340-380°C, the temperature of the second reactor is 250-320°C, the volume feed ratio of propylene: air: water vapor is 1: (2-10): (0.1-4), and the space velocity is 1000-2000h -1 .

5. The method according to claim 4, characterized in that It also includes an acrylic acid tail gas treatment process, which includes the following steps: a portion of the unabsorbed gas from the top of the acrylic acid quenching tower enters the reactor as circulating gas, and the other portion enters the waste combustion system as tail gas through a spray interception tank for catalytic incineration.

6. The method according to claim 5, characterized in that The exhaust gas undergoing catalytic incineration first passes through the first heat exchanger, where it is preheated by the hot gas after the waste-combustion reaction, and then enters the second heat exchanger to be heated to the initial temperature of the waste-combustion reaction; the exhaust gas enters the waste-combustion reactor and is catalytically oxidized to convert organic matter into carbon dioxide; the hot gas after the reaction passes through the third heat exchanger to produce steam, and then the waste heat is used to preheat the exhaust gas entering the waste-combustion system in the first heat exchanger before being discharged.

7. The method according to claim 5, characterized in that A wire mesh is provided on the top of the spray intercepting tank, and 16 to 27 spray pipelines are horizontally provided above the wire mesh and 10 to 15 cm away from the top of the spray intercepting tank.

8. The method according to claim 7, characterized in that The blowing pipeline uses compressed nitrogen as the gas source and performs pulse blowing and dust removal intermittently.

9. The method according to claim 8, characterized in that The nitrogen pressure is 0.5-0.7 MPa, and the intake air volume is set to 0.29-0.54% of the exhaust gas flow rate.

10. The method according to any one of claims 7 to 9, characterized in that: The spraying pipeline sprays once every 15-30 minutes along the direction of the exhaust gas flow.

Images