Preparation method and application of a heteropoly acid catalyst

Abstract

The present application provides a preparation method of a heteropoly acid catalyst, which comprises: adding fibrous insoluble substances into an aqueous solution of a compound containing active elements, spray drying to obtain a powder, loading and shaping, then storing the semi-finished product in a closed container, and then roasting and passing low dew point air during the cooling process. The obtained catalyst shows excellent mechanical strength and catalytic activity when used in the production of unsaturated carboxylic acid.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalysts, in particular to a preparation method of a heteropoly acid catalyst, which can be used for the preparation of unsaturated carboxylic acids, especially for the preparation of methacrylic acid from methacrolein. BACKGROUND

[0002] Methacrolein gas phase oxidation to methacrylic acid is one of the key steps in the production of methyl methacrylate (MMA) by a three-step process using t-butanol / isobutylene as the starting material. The catalyst for this step is a heteropoly acid. The specific surface area of heteropoly acid is low, and it is sensitive to moisture, which makes its strength and activity batch stability poor, and the industrial scale-up production of the catalyst a great challenge.

[0003] CN 201080033562.6 mentions producing a catalyst by supplying humidified air while drying an aqueous solution containing a catalytic component, however, the industrial spray drying requires a large amount of air, and the humidification brings additional production costs, and the amount of humidification water is difficult to control due to seasonal and weather changes.

[0004] CN 201910990571.7 mentions placing the prepared catalyst in an environment with a relative humidity of 0-7 g / m 3 for 0.5-12 hours, then sealing and packaging for storage to obtain a catalyst with improved strength, but using this method there is a risk of permanent loss of catalyst activity, and it is difficult to uniformly humidify a large amount of catalyst.

[0005] Although the literature has made many attempts to improve the stability of the preparation of heteropoly acid catalysts, it is clear that due to their respective limitations, the prior art still needs improvement. SUMMARY

[0006] In view of the above problems in the prior art, the present application provides a preparation method of a heteropoly acid catalyst, and the catalyst obtained therefrom and its application. The preparation method is simple and has good repeatability. The catalyst of the present application exhibits excellent mechanical strength and catalytic activity when used in the production of unsaturated carboxylic acids. In particular, it exhibits excellent conversion rate and selectivity when used in the oxidation of methacrolein to prepare methacrylic acid.

[0007] To achieve the above object, the present application adopts the following technical solutions:

[0008] In one aspect of the present application, a preparation method of a heteropoly acid catalyst is provided, which comprises the following steps:

[0009] 1) adding fibrous insoluble B to solution A, spray drying to obtain powder C; the solution A is an aqueous solution comprising compounds of active elements, the active elements including molybdenum (Mo), phosphorus (P), vanadium (V), copper (Cu), arsenic (As) and antimony (Sb);

[0010] 2) after optional mixing with additional fibrous insoluble B, coating the powder C on a carrier to obtain semi-product D;

[0011] 3) storing the semi-product D in a closed container for 1-60 min to obtain semi-product E;

[0012] 4) calcining the semi-product E, and during the calcination cooling process, passing air with a dew point temperature of 20℃ or lower until the relative humidity at the furnace exit temperature is 0.2-5% to obtain the catalyst.

[0013] In a preferred embodiment of the present application, the active elements further include one or more of tellurium (Te), boron (B), germanium (Ge), tungsten (W), uranium (U), bismuth (Bi), iron (Fe), cobalt (Co), ruthenium (Ru) and nickel (Ni).

[0014] Without being bound by any theory, the present inventors have found that by adding fibrous insoluble B to solution A, the moisture content of the powder C obtained by spray drying is stabilized at a relatively high level, and is less affected by the outlet temperature of spray drying and the humidity of spray drying air, which saves the cost of air humidification mentioned in the prior art, and the present inventors have unexpectedly found that this makes the catalyst production more stable and reliable.

[0015] In a preferred embodiment of the present application, the fibrous insoluble B is inorganic fiber and / or organic fiber, more preferably a combination of inorganic fiber and organic fiber.

[0016] In a preferred embodiment of the present application, the inorganic fiber is one or more of aluminum silicate fiber, glass fiber, quartz fiber, carbon fiber and silicon carbide fiber.

[0017] In a preferred embodiment of the present application, the organic fiber is one or more of microcrystalline cellulose, lignin fiber, cellulose powder, polyester fiber and polyolefin fiber.

[0018] In a preferred embodiment of the present application, the inorganic fiber and the organic fiber independently have a diameter of 0.5-200 microns, for example 10 microns, 50 microns, 100 microns, 150 microns, etc.; a length of 2-1000 microns, for example 10 microns, 100 microns, 200 microns, 400 microns, 800 microns, etc.; and an aspect ratio of 5-200, for example 10, 50, 100, 150, etc.

[0019] In a preferred embodiment of the present application, the water content is 5-10wt%, for example 6wt%, 7wt%, 8wt%, 9wt% and the like, and the content of the fibrous insoluble B is 1-20wt%, preferably 5-18wt%, for example 2wt%, 4wt%, 6wt%, 8wt%, 10wt%, 12wt%, 14wt%, 16wt% and the like, based on the weight of the powder C.

[0020] Without being bound by any theory, the present inventors have found that due to the introduction of the fibrous insoluble B, the water content of the spray-dried powder C can reach a relatively high level, i.e. even in the case of relatively low humidity of the spray-drying air, the water content can be stabilized at a level of 5-10wt%, and the water content of the powder C is positively correlated with the content of the fibrous insoluble B, i.e. within the addition range of the present application, the water content of the powder C gradually increases with the increase of the amount of the fibrous insoluble B added. However, beyond the addition range of the present application, the rule cannot be guaranteed.

[0021] Without being bound by any theory, the present inventors have found that the fibrous insoluble B of the present application can remain in the powder C after spray-drying, and it can also be used as a forming aid of the catalyst, playing the role of strengthening, pore-forming, lubricating and moisturizing. According to the needs, further fibrous insoluble B can be added to the spray-dried powder before forming, but the present application preferably adds these fibrous insoluble B in the spray-drying process at one time.

[0022] In a preferred embodiment of the present application, before step 1), the following step is further included: adding a compound containing an active element into water, and dissolving at a temperature of 90-98°C (for example 92°C, 94°C, 96°C and the like) to obtain the solution A.

[0023] As can be understood by those skilled in the art, after determining the active elements required by the catalyst, those skilled in the art can realize the preparation of suitable solution A by adding the compounds containing the corresponding elements into water under the conditions of heating dissolution and the like. For example, after adding molybdenum trioxide, vanadium pentoxide, antimony pentoxide, phosphoric acid, arsenic acid and copper oxide into water, and stirring under heating reflux, the solution A is obtained. The feeding conditions of each compound depend on the proportion of each active element in the required catalyst, which can be reasonably selected and adjusted by the skilled person.

[0024] In a preferred embodiment of the present application, in step 2), an alcohol aqueous solution is used as a binder, for example, the powder C is coated on the carrier by centrifugal granulation in a centrifugal granulation coating machine.

[0025] In a preferred embodiment of the present application, the concentration of the aqueous alcohol solution is 80-100%, preferably 85-95wt%, such as 90wt% and the like; more preferably, the alcohol is one or more of methanol, ethanol, n-propanol and isopropanol.

[0026] In a preferred embodiment of the present application, in step 1), the amount of the fibrous insoluble B added is 0.1-15wt% based on the weight of solution A, such as 1wt%, 5wt%, 10wt% and the like.

[0027] In a preferred embodiment of the present application, in step 2), if additional fibrous insoluble B is added, the amount of the additional fibrous insoluble B added is 1-10wt% based on the sum of the additional fibrous insoluble B and the powder C, such as 2wt%, 4wt%, 6wt%, 8wt% and the like.

[0028] In a preferred embodiment of the present application, in step 2), the skilled person can select a suitable catalyst carrier, preferably the carrier is a porcelain ball, more preferably a porous inert porcelain ball. For example, the diameter of the porous inert porcelain ball is 3.5-4.5mm, the water absorption is 10%-30%, the bulk density is 1-1.5g / cm 3 .

[0029] In a preferred embodiment of the present application, in step 3), the storage is static storage or dynamic storage.

[0030] Without being bound by any theory, the present inventors have found that, compared with directly performing the calcination treatment after the shaping, the strength of the catalyst can be significantly improved by storing the semi-finished product in a closed container for a certain period of time, which can be due to the fact that the storage in the closed container inhibits the volatilization of ethanol / water or the volatilized ethanol / water reinforces the coating structure. The treatment time of the semi-finished product D in the closed container is 1-60min, such as 5min, 10min, 15min, 20min, 25min, 30min, 35min, 40min, 45min, 50min, 55min and the like. Too short or too long time is not conducive, which is reflected in the activity or strength of the catalyst affected by the treatment time.

[0031] The storage treatment process of the semi-finished product D in the closed container is a static process or a dynamic process, preferably a dynamic process. The closed container only needs to be able to isolate ethanol / water, which can be a sealed plastic bag, an aluminum foil bag, a glassware, a metal tank and the like, and is preferably a closed container with rotation in industry, which is not limited in form.

[0032] In a preferred embodiment of the present application, in step 4), the calcination temperature is 290-330°C, such as 300°C, 310°C, 320°C, etc.; the calcination time is 1-10h, such as 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, etc. Before the temperature is raised to the calcination temperature, a slow temperature raising procedure can be set at a relatively low temperature stage to completely remove organic substances such as ethanol and moisture.

[0033] The present inventors have found that, during the cooling process after calcination, the use of air with a dew point temperature of 20°C or lower and the control of the relative humidity at the temperature of the catalyst when it is discharged from the furnace are helpful to obtain a catalyst product with required strength and activity.

[0034] In the present application, during the cooling process after calcination, air with a dew point temperature of 20°C or lower is used, and more preferably, air with a dew point temperature of -40°C to 10°C (such as -35°C, -30°C, -25°C, -20°C, -15°C, -10°C, -5°C, 5°C, etc.) is used. Too low dew point temperature is not easy to achieve and is relatively costly, while too high dew point temperature cannot achieve the desired effect of the catalyst of the present application. In addition, the relative humidity at the temperature of the catalyst when it is discharged from the furnace is preferably controlled to be 0.2-5%, such as 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, and 4.5%, etc. Subsequently, the catalyst can be discharged from the furnace and subjected to subsequent process operations at a reasonable temperature range.

[0035] In another aspect of the present application, it relates to a catalyst obtained by the preparation method as described above, wherein the active elements of the catalyst satisfy the following formula:

[0036] Mo 12 P a V b Cu c As d Sb e X f Og

[0037] wherein X is one or more of tellurium, boron, germanium, tungsten, uranium, bismuth, iron, cobalt, ruthenium, and nickel; a = 0.5-3 (such as 1, 1.5, 2, 2.5, etc.); b = 0.1-2 (such as 0.5, 1, 1.5, etc.); c = 0.01-1 (such as 0.05, 0.1, 0.5, etc.); d = 0.01-2 (such as 0.05, 0.1, 0.5, 1, 1.5, etc.); e = 0.001-0.5 (such as 0.005, 0.01, 0.05, 0.1, 0.3, etc.); f = 0-0.5 (such as 0.1, 0.2, 0.3, 0.4, etc.); and g is the atomic ratio of oxygen required to satisfy the valence of each element.

[0038] In a preferred embodiment of the present application, the water content of the catalyst is ≤ 1.0%, and the attrition index is < 1%. At this water content, the catalyst can be stably stored for a long time, and even if moisture absorption during catalyst loading is considered, it does not affect its industrial use and the exertion of its catalytic performance.

[0039] In another aspect of the present application, it relates to the use of the catalyst obtained by the preparation method as described above or the catalyst as described above in the preparation of unsaturated carboxylic acid from unsaturated aldehyde.

[0040] In a particularly preferred embodiment of the present application, it relates to the use of the catalyst obtained by the preparation method as described above or the catalyst as described above in the preparation of methacrylic acid from methacrolein.

[0041] In a particularly preferred embodiment of the present application, when the catalyst of the present application is used for the oxidation of methacrolein to prepare methacrylic acid, the reaction conditions can be, for example: the reaction temperature is 280-360℃, the reaction pressure is 0.01-0.15 MPa, the volume space velocity of the raw material mixed gas is 800-2000 h-1, the molar concentration of methacrolein in the mixed gas is 3-8%, the molar ratio of oxygen to methacrolein is 1-4:1, the molar ratio of water vapor to methacrolein is 2-10:1, and the remaining gas in the mixed gas is nitrogen. -1

[0042] In addition to the beneficial effects mentioned above, compared with the prior art, the beneficial effects of the present application mainly lie in: by controlling the pre-spray drying process, post-coating treatment process and post-calcination process during the preparation of heteropoly acid, a high-performance industrial catalyst can be stably manufactured, which, when applied to the production of unsaturated carboxylic acid (especially methacrylic acid), simultaneously exhibits excellent mechanical strength and catalytic activity. DETAILED DESCRIPTION

[0043] The method provided by the present application will be further described in detail below, but the present application is not limited in any way by this.

[0044] Test Method

[0045] Test and characterization of catalyst parameters:

[0046] The attrition rate (i.e. attrition index) of the catalyst is tested in accordance with the standard HG / T 2976-1999 (determination of attrition rate of fertilizer catalyst), and the testing instrument is KM-5A particle attrition tester (produced by Dalian Penghui Science and Technology Development Co., Ltd.);

[0047] ​Content of fibrous insoluble matter in spray-dried powder: 10 g of spray-dried powder was weighed into deionized water, centrifuged to remove the supernatant, and the operation of adding water and centrifugation was repeated twice. The insoluble matter was dried in an oven at 120°C for 2 h, and the mass of the insoluble matter after drying was recorded as m1. Then, the content of fibrous insoluble matter in the spray-dried powder was calculated according to the following formula:

[0048] Moisture content of spray-dried powder: 10 g of spray-dried powder was weighed into a crucible and calcined in a muffle furnace at 500°C for 2 h. The weight loss of the powder after calcination was recorded as m2. According to the amount of inorganic fiber m3 and the amount of organic fiber m4 added in solution A, the moisture content of the spray-dried powder was calculated according to the following formula:

[0049] Moisture content of catalyst product: 100 g of catalyst product was placed in an oven at 160°C and dried for 2 h. The weight loss of the catalyst after drying was recorded as m5. Then, the moisture content of the catalyst product was calculated according to the following formula:

[0050] The conversion rate and selectivity of methacrolein to methacrylic acid in the preparation of methacrylic acid by oxidation of methacrolein were defined as follows:

[0051] Methacrolein conversion rate = (amount of substance of consumed methacrolein / amount of substance of methacrolein supplied) x 100%;

[0052] Methacrylic acid selectivity = (amount of substance of generated methacrylic acid / amount of substance of consumed methacrolein) x 100%.

[0053] Catalyst activity evaluation:

[0054] The catalyst activity evaluation was analyzed using a Japan Shimadzu GC-2010 gas chromatograph, and the chromatographic column type was DB-FFAP (length 30 m, inner diameter 0.32 m, film thickness 0.5 μm).

[0055] The chromatographic operating conditions were as follows:

[0056] Injection port temperature: 260°C; detector temperature: 250°C; injection volume: 1 μL; column flow rate: 1 ml / min; split ratio 50:1; column oven temperature program: 50°C for 13 min, increased to 110°C at a rate of 20°C / min, held for 3 min, increased to 180°C at a rate of 20°C / min, held for 10 min.

[0057] Examples

[0058] Glass fiber powder was purchased from Lianyungang Wohua New Material Technology Co., Ltd., with diameter of 2-20 microns, length of 20-200 microns, and aspect ratio of 5-100; aluminum silicate fiber powder was purchased from Shandong Luyang Energy-saving Material Co., Ltd., with diameter of 1-10 microns, length of 10-200 microns, and aspect ratio of 5-100; microcrystalline cellulose was purchased from Anhui Shanhe Pharmaceutical Auxiliary Co., Ltd., with diameter of 0.5-2 microns, length of 2-50 microns, and aspect ratio of 10-100; lignin fiber was purchased from Weifang Yide Biological Technology Co., Ltd., with diameter of 10-25 microns, length of 50-200 microns, and aspect ratio of 5-20. Porous inert porcelain balls were purchased from Jiangxi Kopaik Environmental Protection Chemical Co., Ltd., with diameter of 3.9 mm, water absorption of 18%, and bulk density of 1.1 g / cm 3 .

[0059] For the raw materials appearing in the text without special indication, they are all conventional commercially available reagents.

[0060] Example 1

[0061] 1) Preparation of catalyst

[0062] To 4000 g of deionized water, 500 g of molybdenum trioxide, 25 g of vanadium pentoxide, 1.4 g of antimony pentoxide, 44 g of 85wt% phosphoric acid, 20 g of 80wt% arsenic acid, and 3 g of copper oxide were added, and after stirring and refluxing at 95°C for 10 h, a rust-colored solution A was obtained. To solution A, 98 g of glass fiber powder and 22 g of microcrystalline cellulose were added to obtain a mixed slurry. The mixed slurry was spray dried on a spray dryer with inlet temperature of 290-300°C and outlet temperature of 120-130°C under uniform stirring to obtain powder C. It was detected that the water content of powder C was 9.0wt%, and the content of fibrous insoluble matter was 16.4wt%.

[0063] The composition of active elements in the powder is described as follows: Mo 12 P 1.32 V 0.95 Cu 0.13 As 0.39 Sb 0.03 O x (the ratio of oxygen varies with the valence state of each element).

[0064] In a centrifugal granulation coating machine, 300 g of powder C was coated onto 190 g of porcelain ball carrier with 85% ethanol aqueous solution as a binder to obtain semi-product D. Semi-product D was placed in an aluminum foil bag and turned over for 30 min to obtain semi-product E.

[0065] The semi-product E was calcined at 320°C for 3h, and dry air with a dew point temperature of -14.5°C was introduced during the cooling process until the temperature dropped to 60°C (relative humidity 1%), and the catalyst product was obtained after sealing and packaging.

[0066] The catalyst was tested, and the water content was 0.32%, and the attrition index was 0.57%.

[0067] 2) Oxidation reaction of methacrolein

[0068] 280ml of the catalyst product was loaded into a fused salt fixed bed reactor with an inner diameter of 25mm, and the oxidation reaction of methacrolein was carried out at a molar ratio of methacrolein / oxygen / water / nitrogen = 1 / 1.8 / 4 / 18.0, a space velocity of 1000h -1 -1, a pressure of 50kPa, and a fused salt temperature of 310°C. After 24h of continuous reaction, the sample was analyzed, and the conversion rate of methacrolein was 83.2%, and the selectivity of methacrylic acid was 83.7%.

[0069] Example 2

[0070] 1) Preparation of the catalyst

[0071] Solution A was prepared according to Example 1, 49g of glass fiber powder and 22g of microcrystalline cellulose were added to the solution to obtain a mixed slurry, and the slurry was sprayed dried on a spray dryer with an inlet temperature of 290°C-300°C and an outlet temperature of 110°C-120°C under the condition of uniform stirring to obtain powder C. The water content of powder C was 7.9%, and the content of fibrous insoluble matter was 10.6wt%.

[0072] 283.5g of the spray-dried powder C was uniformly mixed with 16.5g of glass fiber powder to obtain a mixture, and the mixture was coated on 190g of porcelain ball carriers in a centrifugal granulation coater with 95% ethanol as a binder to obtain semi-product D. The semi-product D was placed in an aluminum foil bag and turned over for 40min to obtain semi-product E.

[0073] The semi-product E was calcined at 320°C for 3h, and dry air with a dew point temperature of -5°C was introduced during the cooling process until the temperature dropped to 120°C (relative humidity 0.2%), and the catalyst product was obtained after sealing and packaging.

[0074] The catalyst was tested, and the water content was 0.17%, and the attrition index was 0.61%.

[0075] 2) Oxidation reaction of methacrolein

[0076] The catalyst activity was tested according to Example 1, the conversion rate of methacrolein was 80.9%, and the selectivity of methacrylic acid was 84.2%.

[0077] Example 3

[0078] 1) Preparation of catalyst

[0079] To 4700 g of deionized water, add 500 g of molybdenum trioxide, 27 g of vanadium pentoxide, 10.2 g of antimony pentoxide, 40 g of 85 wt% phosphoric acid, 13 g of 80 wt% arsenic acid, and 5 g of copper oxide. After stirring and refluxing at 95 °C for 10 h, a reddish-brown solution A is obtained. Add 20 g of aluminum silicate fiber powder and 40 g of lignin fiber to solution A to obtain a mixed slurry. The mixed slurry is spray-dried on a spray dryer with an inlet temperature of 300-320 °C and an outlet temperature of 100-110 °C, and powder C is obtained. The water content of powder C is 6.7 wt%, and the content of fibrous insoluble matter is 9.4 wt%.

[0080] The composition of active elements in the powder is described as follows: Mo 12 P 1.20 V 1.03 Cu 0.22 As 0.25 Sb 0.21 O x (the ratio of oxygen varies with the valence state of each element).

[0081] In a centrifugal granulation coater, 300 g of powder C is coated onto 190 g of porcelain ball carriers using anhydrous ethanol as a binder to obtain semi-product D. Semi-product D is placed in a self-sealing bag and allowed to stand for 60 min to obtain semi-product E.

[0082] Semi-product E is calcined at 290 °C for 5 h, and dry air with a dew point of -3.5 °C is passed through during the cooling process until the temperature drops to 45 °C (relative humidity 5%) and the catalyst product is sealed and packaged.

[0083] The water content of the catalyst is 0.75%, and the attrition index is 0.26%.

[0084] 2) Oxidation of methylpropyl aldehyde

[0085] The catalyst activity is tested according to Example 1, and the conversion of methylpropyl aldehyde is 82.1%, and the selectivity of methylpropyl acid is 83.8%.

[0086] Comparative Example 1

[0087] 1) Preparation of catalyst

[0088] Spray-drying powder C was prepared by referring to the preparation of solution A in Example 1, without adding the glass fiber powder and microcrystalline cellulose, and spray-drying at an inlet temperature of 290-300°C and an outlet temperature of 120-130°C. The water content was 5.5 wt%.

[0089] After mixing 250 g of the spray-drying powder with 40 g of the glass fiber powder and 10 g of the microcrystalline cellulose to obtain a mixture, the mixture was coated on 190 g of porcelain ball carriers in a centrifugal granulator coating machine using 85% ethanol as a binder to obtain semi-product D. The semi-product D was placed in an aluminum foil bag and turned over for 30 min to obtain semi-product E.

[0090] The semi-product E was calcined at 320°C, and dry air with a dew point of -20°C was passed through during the temperature decreasing process until the temperature decreased to 60°C. The catalyst product was obtained after sealing and packaging.

[0091] The water content of the catalyst was 0.13%, and the attrition index was 2.33%.

[0092] 2) Oxidation reaction of methyl propyl aldehyde

[0093] The catalyst activity was tested by referring to Example 1. The conversion rate of methyl propyl aldehyde was 73.1%, and the selectivity of methyl propyl acid was 81.7%.

[0094] Comparative Example 2

[0095] 1) Preparation of catalyst

[0096] The semi-product D was prepared by referring to Example 1, except that it was not stored in a sealed container but directly calcined. The catalyst product was obtained after calcination according to the process of Example 1.

[0097] The water content of the catalyst product was 0.32%, and the attrition index was 1.79%.

[0098] 2) Oxidation reaction of methyl propyl aldehyde

[0099] The catalyst activity was tested by referring to Example 1. The conversion rate of methyl propyl aldehyde was 81.9%, and the selectivity of methyl propyl acid was 83.5%.

[0100] Comparative Example 3

[0101] 1) Preparation of catalyst

[0102] The catalyst was prepared by referring to Example 1, except that no fibrous insoluble substance was added. The catalyst product was obtained.

[0103] The water content of the catalyst product was 0.47%, and the attrition index was 15.8%.

[0104] 2) Oxidation of methacrolein

[0105] The catalyst activity was tested according to Example 1, the conversion of methacrolein was 79.2%, and the selectivity of methacrylic acid was 84.8%.

[0106] Comparative Example 4

[0107] 1) Preparation of catalyst

[0108] The catalyst was prepared according to Example 1, the only difference being that the semi-finished product D was placed in an aluminum foil bag and the turnover time was 90 min (more than 60 min), obtaining a semi-finished product E. Then, the calcination process was carried out, and the catalyst product was obtained.

[0109] The catalyst product was tested, and the water content was 0.28%, and the attrition index was 0.21%.

[0110] 2) Oxidation of methacrolein

[0111] The catalyst activity was tested according to Example 1, the conversion of methacrolein was 55.3%, and the selectivity of methacrylic acid was 86.5%.

[0112] Comparative Example 5

[0113] 1) Preparation of catalyst

[0114] The catalyst was prepared according to Example 3, the only difference being that the air with a dew point temperature of 25°C was introduced during the cooling process until the temperature was reduced to 70°C (relative humidity 10%), and the catalyst product was obtained after sealing and packaging.

[0115] The catalyst product was tested, and the water content was 1.12%, and the attrition index was 0.09%.

[0116] 2) Oxidation of methacrolein

[0117] The catalyst activity was tested according to Example 1, the conversion of methacrolein was 49.2%, and the selectivity of methacrylic acid was 88.7%.

[0118] Although the present application has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made by those skilled in the art without departing from the spirit and scope of the application which is defined by the following claims.

Claims

1. A method for preparing a heteropoly acid catalyst, comprising the steps of: 1) adding fibrous insoluble B to solution A, and spray drying to obtain powder C; the solution A is an aqueous solution comprising compounds of active elements, the active elements including molybdenum, phosphorus, vanadium, copper, arsenic and antimony; 2) coating the powder C on a carrier to obtain semi-product D; 3) storing the semi-product D in a closed container for 1-60 min to obtain semi-product E; 4) calcining the semi-product E, and passing air with a dew point temperature of 20℃ or lower during the calcination cooling process until the relative humidity at the furnace outlet temperature is 0.2-5%, to obtain the catalyst; wherein, in step 1), the fibrous insoluble B is added in an amount of 0.1-5wt% based on the weight of the solution A; wherein, the fibrous insoluble B is inorganic fiber and / or organic fiber; wherein, the aspect ratio of the inorganic fiber and the organic fiber is independently 5-200.

2. The production method according to claim 1, wherein, In step 2), after mixing with additional fibrous insoluble B, the powder C is coated on the carrier to obtain semi-product D.

3. The production method according to claim 1, wherein, The active elements further include one or more of tellurium, boron, germanium, tungsten, uranium, bismuth, iron, cobalt, ruthenium and nickel.

4. The production method according to claim 1, wherein The fibrous insoluble B is a combination of inorganic fiber and organic fiber.

5. The method according to claim 1, wherein, The inorganic fiber is one or more of aluminum silicate fiber, glass fiber, quartz fiber, carbon fiber and silicon carbide fiber; The organic fiber is one or more of microcrystalline cellulose, lignin fiber, cellulose powder, polyester fiber and polyolefin fiber.

6. The production method according to claim 1, wherein The diameter of the inorganic fiber and the organic fiber is independently 0.5-200 microns, and the length is independently 2-1000 microns.

7. The production process according to any one of claims 1 to 6, wherein The moisture content is 5-10wt% based on the weight of the powder C, and the content of the fibrous insoluble B is 1-20wt%.

8. The production process according to any one of claims 1 to 6, wherein Before step 1), further comprising the step of adding compounds comprising active elements into water, and heating to a temperature of 90-98℃ for dissolution to obtain the solution A.

9. The production process according to any one of claims 1 to 6, wherein, In step 2), the powder C is coated on the carrier with an alcohol aqueous solution as a binder.

10. The production method according to claim 9, wherein The concentration of the alcohol aqueous solution is 80-100%.

11. The production method according to claim 9, wherein The alcohol is one or more of methanol, ethanol, n-propanol and isopropanol.

12. The method according to any one of claims 1-6, wherein, In step 2), the carrier is porcelain ball; In step 3), the storage is static storage or dynamic storage; and / or In step 4), the calcination temperature is 290-330℃, and the calcination time is 1-10h.

13. The method of making according to claim 12, wherein, In step 2), the carrier is porous inert porcelain ball.

14. The method of producing according to claim 2, wherein, The additional fibrous insoluble B is added in an amount of 1-10wt% based on the sum of the additional fibrous insoluble B and the powder C.

15. The catalyst obtainable by the process according to any one of claims 1 to 14, wherein, The active elements of the catalyst satisfy the following formula: Mo 12 P a V b Cu c As d Sb e X f Og wherein X is one or more of tellurium, boron, germanium, tungsten, uranium, bismuth, iron, cobalt, ruthenium, nickel; a = 0.5-3; b = 0.1-2; c = 0.01-1; d = 0.01-2; e = 0.001-0.5; f = 0-0.5; g is the atomic ratio of oxygen required to satisfy the valence of each element.

16. The catalyst of claim 15, wherein, The catalyst has a water content of < 1.0% and an attrition index < 1%.

17. Use of a catalyst prepared according to any one of claims 1 to 14 or a catalyst according to claim 15 or 16 for the preparation of an unsaturated carboxylic acid from an unsaturated aldehyde.

18. Use of a catalyst prepared according to any one of claims 1 to 14 or a catalyst according to claim 15 or 16 for the preparation of methacrylic acid from methacrolein.

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