CN115463672A - Method for obtaining catalyst for preparing acrylic acid by using propane as raw material - Google Patents
Method for obtaining catalyst for preparing acrylic acid by using propane as raw material Download PDFInfo
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- CN115463672A CN115463672A CN202210919435.0A CN202210919435A CN115463672A CN 115463672 A CN115463672 A CN 115463672A CN 202210919435 A CN202210919435 A CN 202210919435A CN 115463672 A CN115463672 A CN 115463672A
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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
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/02—Sulfur, selenium or tellurium; Compounds thereof
- B01J27/057—Selenium or tellurium; Compounds thereof
- B01J27/0576—Tellurium; Compounds thereof
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G39/00—Compounds of molybdenum
- C01G39/006—Compounds containing, besides molybdenum, two or more other elements, with the exception of oxygen or hydrogen
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
- C07C51/21—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen
- C07C51/215—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of saturated hydrocarbyl groups
Abstract
The invention discloses a method for obtaining a catalyst for preparing acrylic acid by using propane as a raw material, which comprises the steps of catalyst precursor drying, grinding and surface treatment; relates to the matching of catalyst preparation technology and reaction conditions. The catalyst is a crystal phase oxide composed of molybdenum, vanadium, tellurium, antimony and niobium sources, and is obtained by grinding and crushing and carrying out gas phase surface treatment on a silane compound. The reaction conditions are characterized by a steady state feed composition comprising a moderate carbon dioxide concentration and a relatively low water vapor concentration. By adopting the combination, the yield of the acrylic acid can be increased, and the concentration of the propionic acid by-product in the product and the discharge of industrial wastewater can be effectively reduced.
Description
Technical Field
The invention relates to the technical field of chemical catalysts, in particular to a method for obtaining a catalyst for preparing acrylic acid by taking propane as a raw material.
Background
Acrylic acid is an important raw material for petrochemical, light industry and medical production, can be used for producing super absorbent resin, synthetic resin, flocculating agent and the like, and still expands the application range. Generally, acrylic acid is produced by a contact oxidation reaction of propylene and oxygen at about 400 ℃ in the presence of a Mo-Bi catalyst to give acrolein, and then, by a contact oxidation reaction of acrolein and oxygen at about 300 ℃ in the presence of a Mo-V catalyst to give acrylic acid.
Propane is a cheaper feedstock than propylene and there are many patents and papers disclosing the possibility of producing acrylic acid by the one-step oxidation of propane. In contrast, the price of propylene is higher than that of propane, and with the exploitation and the widespread utilization of shale gas, the price difference between the two is further increased. Many catalysts for the production of acrylic acid from propane have been disclosed. One is a metal oxide catalyst composed of Mo, V, te or Sb, nb or Ta as disclosed in JP-A-2007-31400.
Propionic acid is a common by-product in the production of acrylic acid by the gas phase catalytic oxidation of propylene and propane. The concentration of propionic acid in acrylic acid is an important specification item that negatively affects the quality of the acrylic acid product. Generally, the propionic acid concentration in the crude acrylic acid (unrectified acrylic acid) obtained by the gas-phase catalytic oxidation of propylene is less than 1000ppm, which is a value that can be accommodated by existing techniques. According to the patent publication, the propionic acid concentration in the gas-phase contact oxidation of propane is several thousand ppm. To commercialize the gas-phase catalytic oxidation of propane, the reduction of propionic acid production is an important issue.
Since propionic acid has a boiling point close to that of acrylic acid, it is difficult to remove propionic acid by distillation. As a method for reducing propionic acid, the method of crystallization separation, although effective, requires additional equipment investment, and increases the production cost of acrylic acid.
Japanese patent publication No. 2012/091869 discloses a method for reducing propionic acid by-product, in short, the molar ratio of steam amount to propane is reduced in the gas phase contact oxidation of propane. Japanese patent No. 5460759 discloses that the reaction gas after the gas phase contact oxidation reaction of propane is passed through iron phosphate or CsMo 12 PAsV 0.2 Cu 0.2 Sb 0.1 The metal oxide catalyst of (3) can reduce propionic acid. JP-A-10-21883 discloses that the generation of propionic acid can also be reduced by subjecting the gas after the gas phase contact oxidation reaction of propane to Mo, bi, fe, co, ni, na, B, K, si complex acid compound at 450 ℃.
However, in the above invention, when the amount of steam is reduced, the composition of the raw material mixed gas may enter the explosion range, which may cause a safety hazard. To eliminate this concern, it is desirable to reduce the air/propane ratio, but limit the conversion of propane.
The invention described in japanese patent No. 5460759, while effective, still has a high propionic acid concentration after treatment, which is not a practical requirement. Further, in the present invention described in JP-A-10-21883, there is a problem that the yield of acrylic acid is reduced by a combustion side reaction after the treatment of acrylic acid.
The main object of the present invention is to provide a process for reducing the production of propionic acid while maintaining the maximum yield of propane under favorable reaction conditions.
Disclosure of Invention
The invention aims to provide a method for obtaining a catalyst for preparing acrylic acid by using propane as a raw material, which solves the technical problems in the background art.
In order to solve the technical problem, the invention adopts the following technical scheme:
the invention provides a method for obtaining a catalyst for preparing acrylic acid by using propane as a raw material, wherein the obtained catalyst comprises the following steps:
(1) Mixing a molybdenum source, a vanadium source, a tellurium source, an antimony source and a solvent, and adding a niobium source into the obtained mixture to obtain a catalyst precursor;
(2) Drying;
adding ammonia water and ammonium nitrate into the precursor liquid slurry, and drying, wherein the addition amount of the ammonia water is 0.01-0.05 mol relative to the molybdenum source, and the addition amount of the ammonium nitrate is 0.01-0.4 mol relative to the molybdenum source;
the crystal phase oxides with the components of molybdenum, vanadium, tellurium, antimony and niobium obtained by primary roasting and secondary roasting; the first stage roasting process is carried out by heating treatment in a continuous rotary furnace at 250-340 ℃ in the presence of oxygen. The heating time is 0.1 to 10 hours;
the second stage roasting is carried out under the conditions that the oxygen concentration is below 400ppm, the temperature is 480-640 ℃ and the time is 1-5 hours.
(3) Grinding and surface treatment;
the grain diameter of the active phase crystal of the catalyst is up to below 0.5 micron by grinding equipment; grinding the active phase with high surface area, removing the solvent, and drying to obtain granular powder of the active phase of the metal oxide;
treating the milled and dried metal oxide active phase with a silane compound in an anhydrous atmosphere; the silanization film-making treatment is to soak the catalyst in an anhydrous organic solvent for dissolving the silicon compound;
the metal oxide catalyst for membrane preparation is powder after grinding and drying, and the particle size of the crushed metal oxide catalyst is less than 500 microns;
the silanization film-making treatment is completed at one time or is completed by dividing into 3 to 7 times;
the particles are crushed between each silanization film-forming treatment.
The amount of the organic solvent used for the impregnation treatment is in the range of 0.5 to 100 times, and 1 to 20 times, based on the volume ratio of the catalyst. The concentration of the silicon compound contained in the organic solvent is 0.01 to 200. Mu. Mol/ml, preferably 0.1 to 100. Mu. Mol/ml. The impregnation process requires appropriate stirring for 0.5 to 24 hours.
After the metal oxide catalyst is silanized to prepare a membrane, the silicon membrane can be fixed on the surface of the metal oxide catalyst by heating to 50-300 ℃.
The general formula of the catalyst used is MoV j Te k Sb l Nb m Si d O n (ii) a Wherein Mo represents molybdenum, V represents vanadium, te represents tellurium, sb represents antimony, nb represents niobium, and Si represents silicon; i. k, l, m, and n each represent an atomic ratio of each element; wherein j is 0.01 to 1.5, k is 0.01 to 1.5, l is 0 to 0.07, m is 0.01 to 0.3, d is 0.1 to 0.5, and n is a value determined by the oxidation state of the above elements.
In this embodiment, further optimization, the aqueous solution or aqueous slurry composed of molybdenum, vanadium, tellurium, antimony, niobium source is mixed uniformly; dissolving a molybdenum compound and a vanadium compound with water, adding tellurium and antimony compounds, heating under stirring, and adding a niobium compound to obtain a precursor containing molybdenum, vanadium, tellurium, antimony and niobium; the heating temperature is above 40 ℃; the heating time is 0 to 3 hours.
In this embodiment, the heating temperature is further optimized to be 40 ℃ to 100 ℃, and the heating time is 0 to 1 hour.
In this embodiment, it is further optimized that the molybdenum source, the vanadium source, the tellurium source and the niobium source used in the preparation process are respectively molybdate, vanadate, metal tellurium or tellurium compound, antimony compound and niobate.
In this embodiment, the addition amounts of the molybdenum source, vanadium source, tellurium source, antimony source and niobium source are further optimized, and the atomic ratio of the molybdenum source to the molybdenum source is 0.01 to 1.5, 0 to 0.07, and 0.01 to 0.5, respectively, of the vanadium source, 0.3 to 1.5, respectively, and the atomic ratio of the tellurium source to the vanadium source V is 0.3 to 1.5.
In this embodiment, the atomic ratio of the source to the molybdenum is further optimized to be 0.01 to 0.4 vanadium source, 0.01 to 0.3 tellurium source, 0 to 0.05 antimony source, and 0.01 to 0.3 niobium source, and the atomic ratio of the tellurium source to the vanadium source is 0.3 to 0.8.
In this example, the drying after adding ammonia and ammonium nitrate to the precursor liquid slurry was further optimized. The amount of ammonia added is 0.01 to 0.03 mol or more relative to the molybdenum source, and the amount of ammonium nitrate added is 0.05 to 0.2 mol or more relative to the molybdenum source.
In this embodiment, the drying manner of the molybdenum, vanadium, tellurium, antimony and niobium precursors is spray drying.
In this embodiment, the first-stage roasting process is further optimized, wherein the first-stage roasting process is performed in a continuous rotary furnace in the presence of oxygen at a temperature of 280-340 ℃;
the second stage roasting is carried out under the conditions that the oxygen concentration is less than 300ppm, the roasting temperature is 570-620 ℃ and 1.5-2.5 hours;
the furnace type is one of a fixed furnace, a shuttle kiln and a rotary furnace.
In this example, it is preferable that the compound for forming a silanized film is one of tetramethoxysilane, tetraethoxysilane, trimethoxysilane, triethoxysilane, trimethylsilane, triethylsilane, hexamethyldisilane, hexamethylsilane and hexamethylsilane.
This example discloses a process for producing acrylic acid from propane, which comprises using the catalyst of claim 1;
the raw material gases include propane, air, water vapor and carbon dioxide.
The reaction method adopts single-pass conversion or tail gas circulation.
The composition when the reaction reaches a steady state can be selected according to the following conditions; the molar ratio of oxygen to propane is from 2.0 to 2.6, preferably from 2.1 to 2.5, the molar ratio of steam to propane is from 2.0 to 6.0, preferably from 3.0 to 5.0, and the molar ratio of carbon dioxide to propane is from 2.0 to 6.0, preferably from 3.0 to 5.5. The reaction temperature is 330-400 ℃, preferably 336-390 ℃. Space velocity of 400-5000 hr -1 Preferably 500 to 2400hr -1 。
In this example, further optimization is performed, and the composition when the reaction reaches a steady state can be selected according to the following conditions; the molar ratio of oxygen to propane is 2.1-2.5, the molar ratio of water vapor to propane is 3.0-5.0, and the molar ratio of carbon dioxide to propane is 3.0-5.5; the reaction temperature is 336-390 ℃; the space velocity is 500-2400 hr -1 。
In this example, it is still further optimized that the volume ratio of the organic solvent used in the impregnation treatment to the catalyst is 1 to 20 times; the concentration of the silicon compound contained in the organic solvent is 0.1 to 100. Mu. Mol/ml.
Compared with the prior art, the invention has the beneficial technical effects that: the catalyst is a crystal phase oxide composed of molybdenum, vanadium, tellurium, antimony and niobium sources, and is obtained by grinding and crushing and carrying out gas phase surface treatment on a silane compound. The reaction conditions are characterized by a steady state feed composition comprising a moderate carbon dioxide concentration and a relatively low water vapor concentration. By adopting the combination, the yield of the acrylic acid can be increased, and the concentration of the propionic acid by-product in the product and the discharge of industrial wastewater can be effectively reduced.
Detailed Description
In this embodiment, the preparation method of the Mo-V-Te-Sb-Nb-Si-O catalyst includes: mixing a molybdenum source, a vanadium source, a tellurium source, an antimony source and a solvent, and adding a niobium source into the obtained mixture to obtain a catalyst precursor; inputting the dried catalyst precursor into a continuous rotary roasting device in an atmosphere with oxygen, and carrying out primary roasting at the temperature of more than 300 ℃; and carrying out secondary roasting at the temperature of more than 450 ℃ and the oxygen concentration of less than 300ppm to prepare the Mo-V-Te-Sb-Nb-O crystal phase catalyst; grinding and crushing Mo-V-Te-Sb-Nb-O; the milled and crushed Mo-V-Te-Sb-Nb-O crystal phase is contacted with a silane compound gas or liquid phase, and is dried.
The molybdenum, vanadium, tellurium, antimony compounds and niobium compounds are mixed, the molybdenum compounds and the vanadium compounds are dissolved by water, the tellurium and antimony compounds are added, and after heating under stirring, the niobium compounds are added, and the precursor containing molybdenum, vanadium, tellurium, antimony and niobium is obtained.
The heating temperature is above 40 ℃, preferably 40-100 ℃, and the heating time is 0-3 hours, preferably 0-1 hour.
The molybdenum source, vanadium source, tellurium source and niobium source in the preparation process can adopt molybdate, vanadate, metal tellurium or tellurium compound, antimony compound and niobate which are commonly used in the field, and the specific types of the selected substances are not limited.
The addition amount of the compounds of the molybdenum source, the vanadium source, the tellurium source, the antimony source and the niobium source is 0.01-1.5 atomic percent of the vanadium source, 0.01-1.5 atomic percent of the tellurium source, 0.01-1.5 atomic percent of the vanadium source, 0-0.07 atomic percent of the antimony source and 0.01-0.5 atomic percent of the niobium source, and the atomic ratio of the tellurium source to the vanadium source is 0.3-1.5, preferably, 0.01-0.4 atomic percent of the vanadium source, 0.01-0.3 atomic percent of the tellurium source, 0-0.05 atomic percent of the antimony source and 0.01-0.3 atomic percent of the niobium source, and the atomic ratio of the tellurium source to the vanadium source is 0.3-0.8.
The niobium source may be added alone, and preferably, the niobium source is used after hydrogen peroxide is added. The amount of hydrogen peroxide added is 0.1 to 0.5 mol, preferably 0.1 to 0.3 mol, based on the niobium source.
The molybdenum, vanadium, tellurium, antimony and niobium precursors may be dried directly, preferably after adding ammonia and ammonium nitrate to the precursor liquid slurry. The amount of ammonia added is 0.01 to 0.05 mol or more, preferably 0.01 to 0.03 mol or more based on the molybdenum source. The amount of ammonium nitrate added is 0.01 to 0.4 mol or more, preferably 0.05 to 0.2 mol or more based on the molybdenum source.
The drying method of the molybdenum, vanadium, tellurium, antimony and niobium precursors is not limited. From the viewpoint of applicability to continuous operation, spray drying is preferable.
The first stage roasting engineering is a continuous rotary furnace, and is heated at 250-340 ℃ and preferably 280-340 ℃ in the presence of oxygen. The heating time is 0.1 to 10 hours, preferably 0.1 to 2 hours.
The second stage baking is carried out under conditions of an oxygen concentration of 300ppm or less, a temperature of 480 to 640 ℃ for 1 to 5 hours, preferably an oxygen concentration of 400ppm or less, a baking temperature of 570 to 620 ℃ for 1.5 to 2.5 hours. The furnace type can be selected from a fixed furnace, a shuttle kiln, and a rotary furnace.
The grinding and crushing can reduce the grain size of the active phase crystal of the catalyst to be below 0.5 micron and increase the specific surface area of the catalyst. The method of milling and pulverizing is not limited. Wet or dry ball mills, wet bead mills, air jet mills, etc. may be used. Alcohols such as methanol and ethanol can be used as the dispersion medium for the wet ball mill. The amount of the alcohol dispersion medium added was 30wt% based on the amount of the catalyst. As the dispersion medium, oxalic acid is preferably added to the alcohol in an amount of 5wt% based on the amount of the catalyst.
The active phase with high surface area is milled, desolventized and dried to obtain granular powder of the active phase of the metal oxide.
The silanization film-forming treatment is to treat the metal oxide active phase after being ground and dried by a silane compound in a waterless atmosphere. The silanization film-forming treatment may be carried out by immersing the catalyst in a vapor of a silane compound, preferably an anhydrous organic solvent in which the silicon compound is dissolved. The metal oxide catalyst for the film formation treatment may be a powder obtained by grinding and drying, and is preferably used after being crushed to have a particle size of 500 μm or less.
The kind of the compound for forming a silanized film which can be used is not limited. For example, tetramethoxysilane, tetraethoxysilane, trimethoxysilane, triethoxysilane, trimethylsilane, triethylsilane, hexamethyldisilane, hexamethylsilane and the like can be used. Tetramethoxysilane, tetraethoxysilane are preferred.
As described above, when the metal oxide catalyst is impregnated with the silicon compound, the organic solvent used is not particularly limited. Toluene, hexane, acetone, ethyl acetate and the like can be used, and toluene and hexane are preferred from the viewpoint of toxicity. The water content in the organic solvent should be less than 500ppm, preferably less than 300ppm.
The silanization film formation treatment may be performed at one time, and is preferably performed in 3 to 7 times. Each treatment may be performed successively, and preferably, the particles are pulverized between each silanization film formation treatment. The pulverization treatment equipment is not particularly limited, and a hammer mill or a high-speed pulverizer can be used. The rotation speed is 1.0 ten thousand revolutions per minute, and the preferred rotation speed is more than 3.0 ten thousand revolutions per minute.
The impregnation treatment is carried out using an organic solvent in an amount of 0.5 to 100 times, preferably 1 to 20 times, the volume ratio of the organic solvent to the catalyst. The concentration of the silicon compound contained in the organic solvent is 0.01 to 200. Mu. Mol/ml, preferably 0.1 to 100. Mu. Mol/ml. The impregnation process requires appropriate stirring for 0.5 to 24 hours.
The silanized membrane produced by the reaction of the gas phase catalytic oxidation of propane to produce acrylic acid may be supported on a support. In the case of loading, particles having a particle diameter of 1.0 to 6.0mm are used.
After the metal oxide catalyst silanization film preparation treatment, the silicon film can be fixed on the surface of the metal oxide catalyst by heating to 50-300 ℃. The content of the immobilized silicon film can be measured by fluorescent X-ray analysis, and is suitably 0.05 to 0.5 mol, preferably 0.1 to 0.3 mol, relative to the molybdenum atom in the catalyst.
The catalyst after the silylation film formation treatment may be used in the form of a powder, and is preferably used in the form of a carrier. The material of the carrier is not limited, and silica, alumina, silicon carbide, etc. can be used, but the specific surface area of the carrier material is less than 5m2/g, preferably less than 3m2/g.
The main downstream equipment of the production process of acrylic acid by propane gas phase contact oxidation mainly comprises a multitubular fixed bed reactor aiming at heat transfer of a strong exothermic reaction and a quenching absorption tower of reaction products.
The reaction conditions for producing the acrylic acid by the gas-phase catalytic oxidation of the propane comprise raw material gas composition; the feed gases typically include propane, air, water vapor and carbon dioxide. Pure oxygen or oxygen-enriched air can be selected to replace air according to the condition of the park. The reaction method can adopt single-pass conversion and can also adopt a tail gas circulation mode. The carbon dioxide may be added as a fresh raw material, and is preferably supplied as a circulating off gas pool. In either case, the composition at which the reaction reaches a steady state may be selected as follows; the molar ratio of oxygen to propane is from 2.0 to 2.6, preferably from 2.1 to 2.5, the molar ratio of steam to propane is from 2.0 to 6.0, preferably from 3.0 to 5.0, and the molar ratio of carbon dioxide to propane is from 2.0 to 6.0, preferably from 3.0 to 5.5. The reaction temperature is 330-400 ℃, preferably 336-390 ℃. Space velocity of 400-5000 hr-1, preferably 500-2400 hr-
The embodiment provides a preparation method of a Mo-V-Te-Sb-Nb-O catalyst, which comprises the following steps:
1) Adding 370.8g of ammonium tetramolybdate and 65.4g of ammonium metavanadate into 900g of mixed dry distilled water, and dissolving the mixture under stirring at 80 ℃; the following solution A and 576g of 2.0wt% aqueous ammonia were added. When the temperature of the reaction liquid was reduced to 50 c after stirring for several minutes,
adding the solution B to a viscous precipitate under stirring. After stirring for 5 minutes, 96.0g of ammonium nitrate was added to the reaction solution and stirred. Finally, the resulting slurry was spray dried to a powder.
Solution A; 44.8g of tellurium dioxide, needle-like particles containing tellurium metal (needles having an average length of 0.3 μm and an average diameter of 0.1 μm) obtained by reduction with hydrazine, 13.7g of antimony trichloride was added with stirring, and the mixture was washed with 300g of distilled water to obtain a slurry.
Solution B; 167g of oxalic acid (2 crystal water-containing compound) and 60.1g of hydrated niobic acid (73.2 wt% niobic acid), and 1719g of distilled water were added thereto and dissolved at 80 ℃. After cooling, 17.4g,30wt% hydrogen peroxide was added.
2) The first stage roasting is carried out by adopting a continuous rotary roasting furnace, putting dry powder into the furnace, and rotating and moving the furnace in an aerobic atmosphere to pass through a temperature control area.
3) The second stage roasting is carried out on the particles of the first stage roasted product under the nitrogen flow at the temperature of 600 ℃ for 1.5 hours to obtain a metal oxide crystal phase.
4) Jet mill grinding the resulting metal oxide was ground with a jet mill to give an average diameter of 0.28 μm.
5) 200g of the metal oxide obtained in the above procedure was supported on 200g of a spherical alumina carrier having an average diameter of 1.9mm by using a roll granulator. Drying at 120 ℃ for 1 hour to obtain the supported metal oxide with the average particle size of 4.0 mm.
Evaluation of acrylic acid production from propane
Two borate glass reaction tubes (each called a first section and a second section) with the inner diameter of 18mm are connected in series, are respectively provided with independent temperature control, and are heated by a thermoelectric band to be connected with an outlet of the first section and an inlet of the second section. 5.4g (filling volume 4.6 ml) of the metal oxide-supported catalyst prepared above was packed in each reaction tube. The reaction temperature (the temperature of a thermocouple inserted longitudinally into the catalyst-packed layer) in the second stage was 360 ℃ and the line temperature was 140 ℃ in the first stage. Introducing into the inlet of the first stage reaction tube at a space velocity of 600hr-1, reacting raw materials including propane, oxygen, steam, nitrogen, and raw material gas containing carbon dioxide at a molar ratio of 1.0/2.5/5.5/4.7/3.5, and synthesizing acrylic acid. The gas after the reaction was analyzed by Gas Chromatography (GC), and the propane conversion and the acrylic acid yield were calculated by the following formulas.
Propane conversion (%) =100 × (propane supplied-unreacted propane)/propane supplied ]
Acrylic acid selectivity (%) =100 × [ produced acrylic acid/(supply propane-unreacted propane) acrylic acid yield (%) = (propane conversion × acrylic acid selectivity)/100
The concentration of propionic acid was quantified by FID-GC. The results of the evaluation were that the propane conversion was 72.1%, the acrylic acid yield was 26.1%, and the propionic acid concentration was 798ppm, and the detailed results are shown in Table 1. This result indicates that the Mo-V-Te-Sb-Nb-O crystal phase, although active after polishing, had poor selectivity and low acrylic acid yield.
Comparative example 2
Comparative example 1 is different from comparative example 1 in two points,
the preparation method of the catalyst comprises the step of additionally preparing a membrane by surface silanization between the step 4) of grinding by a jet mill and the step 5) of loading. 200g of the metal oxide obtained in the above-mentioned manner was pulverized into an average particle diameter of 250 μm or less. In a flask equipped with a rotary evaporator, 8.0g of tetramethoxysilane loaded with 21.0ml/min of nitrogen was dried under reduced pressure for 0.5 hour at 80 ℃ and rotated for 53 hours while keeping contact between the metal oxide and steam. Its atomic ratio is fluorescent X-ray composition according to analysis, mo/V/Te/Sb/Nb/Si =1.0/0.28/0.14/0.03/0.16/0.09 (molar ratio);
the reaction raw material comprises propane, oxygen, steam, nitrogen and raw material gas with the molar ratio of 1.0/2.5/9.0/4.7/0 of carbon dioxide.
As shown in Table 1, the yield of the silanization-treated Mo-V-Te-Sb-Nb-O catalyst was significantly increased, but the acrylic acid concentration was 2301ppm and the product specification was not satisfied (less than 1000 ppm)
Example 1
Only the composition of the reaction raw materials was adjusted as compared with comparative example 2. The reaction raw material composition is that the mole ratio of propane, oxygen, steam, nitrogen and carbon dioxide is 1.0/2.5/7.0/4.7/2.0. The detailed results are shown in Table 1. This result showed that the acrylic acid concentration was reduced to 1334ppm while the acrylic acid yield was increased.
Example 2
Only the composition of the reaction raw materials was adjusted as compared with comparative example 2. The reaction raw material comprises raw material gas with the molar ratio of propane, oxygen, steam, nitrogen and carbon dioxide of 1.0/2.5/5.5/4.7/3.5. The detailed results are shown in Table 1. This result showed that the acrylic acid concentration was reduced to 823ppm while the acrylic acid yield was increased to 61.9%.
Example 3
Only the composition of the reaction raw materials was adjusted as compared with comparative example 2. The reaction raw material composition is that the mole ratio of propane, oxygen, steam, nitrogen and carbon dioxide is 1.0/2.5/4.5/4.7/4.5. The detailed results are shown in Table 1. This result showed that the acrylic acid concentration was reduced to 810ppm while the acrylic acid yield was increased to 62.2%.
Example 4
Only the composition of the reaction raw materials was adjusted as compared with comparative example 2. The reaction raw material comprises raw material gas with the molar ratio of propane, oxygen, steam, nitrogen and carbon dioxide of 1.0/2.5/3.0/4.7/6.0. The detailed results are shown in Table 1. This result showed that the acrylic acid concentration was reduced to 734ppm, but the acrylic acid yield was slightly reduced to 60.8%.
Comparative example 3
Only the composition of the reaction raw materials was adjusted as compared with comparative example 2. Comprises the reaction raw materials of propane, oxygen, steam, nitrogen and carbon dioxide with the molar ratio of 1.0/2.5/4.5/7.2/2.0. The detailed results are shown in Table 1. The results showed that the substitution of part of carbon dioxide with nitrogen did not affect acrylic acid much, but the yield of acrylic acid decreased to 57.0%.
Comparative example 4
Only the composition of the reaction raw materials was adjusted as compared with comparative example 2. Comprises the reaction raw materials of propane, oxygen, water vapor, nitrogen and carbon dioxide with the molar ratio of 1.0/2.5/2.0/4.7/7.0. The detailed results are shown in Table 1. The results show that an excessive reduction in water vapor, even with an increase in carbon dioxide, cannot recover a decrease in propane conversion.
TABLE 1
In the description of the present invention, it is to be understood that the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are used in an orientation or positional relationship indicated for convenience in describing the present invention, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be considered as limiting.
The above embodiments are only for describing the preferred mode of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solution of the present invention by those skilled in the art should fall within the protection scope defined by the claims of the present invention without departing from the spirit of the present invention.
Claims (13)
1. A method for obtaining a catalyst for preparing acrylic acid by using propane as a raw material is characterized by comprising the following steps:
the preparation of the catalyst comprises the following steps:
(1) Mixing a molybdenum source, a vanadium source, a tellurium source, an antimony source and a solvent, and adding a niobium source into the obtained mixture to obtain a catalyst precursor;
(2) Drying;
adding ammonia water and ammonium nitrate into the precursor liquid slurry, and then drying, wherein the addition amount of the ammonia water is 0.01-0.05 mol relative to the molybdenum source, and the addition amount of the ammonium nitrate is 0.01-0.4 mol relative to the molybdenum source;
the crystal phase oxides with the components of molybdenum, vanadium, tellurium, antimony and niobium obtained by primary roasting and secondary roasting; the first-stage roasting process is carried out by heating treatment in a continuous rotary furnace in the presence of oxygen at 250-340 ℃ for 0.1-10 hours;
the second stage roasting is carried out under the conditions that the oxygen concentration is below 400ppm and the temperature is 480-640 ℃ for 1-5 hours.
(3) Grinding and surface treatment;
the grain diameter of the active phase crystal of the catalyst is up to below 0.5 micron by grinding equipment; grinding the active phase with high surface area, removing the solvent, and drying to obtain granular powder of the active phase of the metal oxide;
treating the milled and dried metal oxide active phase with a silane compound in an anhydrous atmosphere; the silanization film preparation treatment is to soak the catalyst in an anhydrous organic solvent for dissolving the silicon compound;
the metal oxide catalyst for membrane preparation is powder after grinding and drying, and the particle size of the crushed metal oxide catalyst is less than 500 microns;
the silanization film making treatment is completed at one time or is divided into 3 to 7 times;
crushing the particles between each silanization film-making treatment;
the amount of the organic solvent used for the impregnation treatment is in the range of 0.5 to 100 times, and 1 to 20 times, based on the volume ratio of the catalyst. The concentration of the silicon compound contained in the organic solvent is 0.01 to 200. Mu. Mol/ml, and the dipping process requires proper stirring for 0.5 to 24 hours.
After the metal oxide catalyst silanization film-making treatment, the silicon film can be fixed on the surface of the metal oxide catalyst by heating to 50-300 ℃.
The general formula of the catalyst used is MoV j Te k Sb l Nb m Si d O n (ii) a Wherein Mo represents molybdenum, V represents vanadium, te represents tellurium, sb represents antimony, nb represents niobium, and Si represents silicon; i. k, l, m, and n each represent an atomic ratio of each element; wherein j is 0.01 to 1.5, k is 0.01 to 1.5, l is 0 to 0.07, m is 0.01 to 0.3, d is 0.1 to 0.5, and n is a value determined by the oxidation state of the above elements.
2. The method for obtaining a catalyst for producing acrylic acid from propane as a raw material according to claim 1, wherein: wherein the aqueous solution or aqueous slurry consisting of molybdenum, vanadium, tellurium, antimony and niobium sources is uniformly mixed; dissolving a molybdenum compound and a vanadium compound with water, adding a tellurium compound and an antimony compound, heating while stirring, and adding a niobium compound to obtain a precursor containing molybdenum, vanadium, tellurium, antimony and niobium; the heating temperature is above 40 ℃; the heating time is 0 to 3 hours.
3. The method for obtaining a catalyst for producing acrylic acid from propane as a raw material according to claim 2, wherein: the heating temperature is 40-100 ℃, and the heating time is 0-1 hour.
4. The method for obtaining a catalyst for producing acrylic acid from propane as a raw material according to claim 1, wherein: the molybdenum source, the vanadium source, the tellurium source and the niobium source used in the preparation process are respectively molybdate, vanadate, metal tellurium or tellurium compound, antimony compound and niobate.
5. The method for obtaining a catalyst for producing acrylic acid from propane as a raw material according to claim 1, wherein: the addition amount of the molybdenum source, vanadium source, tellurium source, antimony source and niobium source is 0.01-1.5 atomic percent of vanadium source, 0.01-1.5 atomic percent of tellurium source, 0.01-1.5 atomic percent of vanadium source, 0-0.07 atomic percent of antimony source and 0.01-0.5 atomic percent of niobium source, and the atomic ratio of tellurium source to vanadium source is 0.3-1.5 atomic percent.
6. The method for obtaining a catalyst for producing acrylic acid from propane as a raw material according to claim 5, wherein: the atomic ratio of the source relative to the molybdenum source is 0.01-0.4 vanadium source, 0.01-0.3 tellurium source, 0-0.05 antimony source and 0.01-0.3 niobium source, and the atomic ratio of the tellurium source to the vanadium source is 0.3-0.8.
7. The method for obtaining a catalyst for producing acrylic acid from propane as a raw material according to claim 1, wherein: adding ammonia water and ammonium nitrate into the precursor liquid slurry, and drying. The amount of ammonia water added is 0.01 to 0.03 mol or more relative to the molybdenum source, and the amount of ammonium nitrate added is 0.05 to 0.2 mol or more relative to the molybdenum source.
8. The method for obtaining a catalyst for producing acrylic acid from propane as a raw material according to claim 1, wherein: the drying mode of the molybdenum, vanadium, tellurium, antimony and niobium precursors is spray drying.
9. The method for obtaining a catalyst for producing acrylic acid from propane as a raw material according to claim 1, wherein: the first-stage roasting process is carried out in a continuous rotary furnace in the presence of oxygen at 280-340 ℃;
the second stage roasting is carried out under the conditions that the oxygen concentration is less than 300ppm, the roasting temperature is 570-620 ℃ and 1.5-2.5 hours;
the furnace type is one of a fixed furnace, a shuttle kiln and a rotary furnace.
10. The method for obtaining a catalyst for producing acrylic acid from propane as a raw material according to claim 1, wherein: the compound for preparing the film by silanization is one of tetramethoxysilane, tetraethoxysilane, trimethoxy silane, triethoxy silane, trimethyl silane, triethyl silane, hexamethyl disilane, hexamethyl silane and hexamethyl silane.
11. A process for producing acrylic acid from propane, which comprises using the catalyst according to claim 1;
the raw material gases include propane, air, water vapor and carbon dioxide.
The reaction method adopts single-pass conversion or tail gas circulation.
The composition when the reaction reaches a steady state can be selected according to the following conditions; the molar ratio of oxygen to propane is from 2.0 to 2.6, preferably from 2.1 to 2.5, the molar ratio of steam to propane is from 2.0 to 6.0, preferably from 3.0 to 5.0, and the molar ratio of carbon dioxide to propane is from 2.0 to 6.0, preferably from 3.0 to 5.5. The reaction temperature is 330-400 ℃, preferably 336-390 ℃. Space velocity of 400-5000 hr -1 Preferably 500 to 2400hr -1 。
12. The process for producing acrylic acid from propane as described in claim 11, wherein the composition at the time when the reaction reaches a steady state is selected as follows; the molar ratio of oxygen to propane is 2.1 to 2.5, the molar ratio of water vapor to propane is 3.0 to 5.0, and the oxidation is carried outThe molar ratio of carbon to propane is 3.0 to 5.5; the reaction temperature is 336-390 ℃; the space velocity is 500-2400 hr -1 。
13. The method for producing acrylic acid from propane as a raw material according to claim 11, wherein the impregnation treatment is carried out using an organic solvent in an amount of 1 to 20 times by volume relative to the catalyst; the concentration of the silicon compound contained in the organic solvent is 0.1 to 100. Mu. Mol/ml.
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