Method for preparing acrylic acid reaction catalyst through direct oxidation of propane

Abstract

The invention discloses a preparation method for preparing an acrylic acid reaction catalyst by a propane direct oxidation method, and relates to a preparation method of an acrylic acid reaction catalyst, which comprises the following steps: adding a salt or hydroxide solution containing alkaline earth metal elements into a precursor for preparing the catalyst, heating and stirring until slurry is formed, and roasting after spray drying to obtain the acrylic acid reaction catalyst. The basic general formula of the obtained catalyst is Mo1VaTebNbcAdO, Mo is a molybdenum element, V is a vanadium element, Te is a tellurium element, Nb is a niobium element, A is at least one of alkaline earth metal elements such as Ca, Mg, Sr, Ba and the like, a, b, c and d respectively represent the molar ratio of each element to Mo, a is 0.2-0.6, b is 0.1-0.6, c is 0.01-0.2, and e is 0.005-0.08. The catalyst is applied to preparation of acrylic acid by a propane direct method, the conversion rate of propane is 55-65%, and the selectivity of acrylic acid is 65-82%. The catalyst prepared by the method is high in catalytic activity, good in selectivity and stable in performance.

Description

Technical Field

[0001] The present invention relates to a preparation process of a catalyst, and specifically, to a method for preparing a catalyst for the direct oxidation of propane to acrylic acid. Background Art

[0002] Acrylic acid is an important organic chemical product. Currently, it is mainly produced industrially through a two-step oxidation reaction of propylene. That is, first, propylene is oxidized to acrolein by a certain catalyst at a certain temperature, and then directly oxidized to acrylic acid by another catalyst at a different temperature. The two-step process for preparing acrylic acid from propylene is mature, and the conversion rate of propylene and the yield of acrylic acid are also relatively considerable. However, the two-step method requires at least two different catalyst systems, and different reaction conditions also require at least two reactors and corresponding control systems, resulting in a relatively high equipment investment. Moreover, in terms of raw materials, compared with propylene, propane has a wider source and a lower price. Using propane instead of propylene can greatly reduce the raw material cost. The direct oxidation of propane to acrylic acid has a simple process route, a reduced raw material cost, and a relatively low investment in the corresponding equipment system. The development of an efficient catalyst in this reaction is one of the core technologies of the entire process route.

[0003] Currently, in the reports on catalysts for the direct oxidation of propane to acrylic acid, composite multi-metal oxides (MMOs) are considered the most promising catalyst systems. Among them, the MoVTeNbO multi-metal oxide is considered the most promising catalytic system for the direct oxidation of propane to acrylic acid. Currently, there are various methods for preparing the composite oxide catalysts used in the reaction of direct oxidation of propane to acrylic acid. The hydrothermal method or the slurry method is the most frequently used method. Patent CN116328796 and CN109565663 respectively used the hydrothermal method and the slurry method to prepare the MoVTeNbO catalyst, achieving the highest acrylic acid selectivities of 67.5% and 72.3% respectively. Patent CN113492017 loaded the MoVTeNbO catalyst on mesoporous-microporous composite titanium silicalite molecular sieve by using the slurry method. Although the highest acrylic acid selectivity was only 56.08, the propane conversion rate reached 69.21%. In addition, there are also literatures proposing that methods such as the high-pressure hydrothermal method, the reflux method, and the spray drying method have also been used to prepare the MoVTeNbO series catalysts. The high-pressure hydrothermal method was first proposed in "The Journey of Supercritical Fluids, 2022, 181: 1-7". By using a pressure above 3.0 Mpa, the time required for the hydrothermal method was rapidly shortened, and the MoVTeNbO catalyst with the highest acrylic acid selectivity of 74.1% was prepared. The reflux method was proposed in "Catal. Sci. Technol" (2023, 13: 4802-4812) to prepare the MoVTeNbO catalyst. The reflux reaction with controlled conditions for a long time is helpful for the formation of the active phase. Finally, the acrylic acid selectivity of the catalyst reached 69%. "Catalysis Surveys from Asia, 2024, 28: 231-242" and "Catal Lett, 2024, 26: 4692-4707" both used the spray drying method for preparation. Due to its rapid drying process, the spray drying method can greatly shorten the drying time of the catalyst, effectively increase the content of the effective active phase of the catalyst, and improve the performance of the catalyst. Their acrylic acid selectivities reached 79.5% and 72.1% respectively. However, although many methods have been proven to be applicable to the preparation of MoVTeNbO multi-metal oxide catalysts, due to the complex multi-component elements of this type of catalyst, the multi-step nature of the preparation process, and the sensitivity of the parameters, the reproducibility of the prepared catalysts may be affected by multiple factors. In order to ensure that the prepared MoVTeNbO catalyst has excellent reproducibility and stable catalytic performance, the preparation process and preparation time of the catalyst should be shortened as much as possible.In addition to stability, the further improvement of the performance of the MoVTeNbO catalyst depends on the modification of the catalyst itself. To endow MoVTeNbO with more excellent performance, element doping or precursor modification is the most common method. However, not all element doping has a positive effect on the direct oxidation of propane to acrylic acid. Similarly, even for the same element doping, the choice of the compound containing this element will also affect the performance of MoVTeNbO. For example, if a certain metal element is to be introduced, different anions may have an impact on the precursors of the multi-component elements, and even inhibit the formation of Anderson-type heteropolyacids that can generate the active M1 phase. The following presents the relevant content of element modification mentioned in some patents: Patent CN109569577 used the co-precipitation method to add Ce with the action of organic acids, obtaining a catalyst with a maximum acrylic acid rotary evaporation rate of 80%; Patent CN109569667 carried out reduction modification on the catalyst precursor solvent through the reduction action of hydrazine compounds, obtaining a maximum acrylic acid selectivity of 76.1%; CN111468136 selected Cr, Co, Zr, Ga, and Mn for modification, obtaining a catalyst with a maximum acrylic acid yield of 84.1%, but the propane conversion rate was relatively low, only 38.5%; CN112156795 selected noble metals Pt, Au, and Pd for modification, effectively reducing the CO selectivity and obtaining a catalyst with a maximum acrylic acid selectivity of 77%; CN117339606 introduced Ni salts by the co-precipitation method, obtaining a catalyst with a maximum acrylic acid selectivity of 82.7%, but two reaction sections with different temperatures were used; CN117339607, in addition to Ni, also added B using boride to prepare the MoVTeNbNiBO catalyst, with a maximum acrylic acid selectivity reaching 82%; CN115487834 obtained the MoVTeNbSbSiO catalyst by adding different antimony sources and surface silanization, obtaining a catalyst with a maximum acrylic acid selectivity of 80.2%.

[0004] Currently, the main problem affecting the performance of the MoVTeNbO catalyst is the decrease in acrylic acid yield caused by the over-oxidation of propane under high-temperature reaction conditions. And the metal elements with a slightly alkaline nature can effectively inhibit the cleavage of the C-C bond caused by the over-oxidation of certain sites to intermediates, forming by-products such as acetic acid or carbon oxides. However, elements with too strong alkalinity will lead to a significant decrease in the propane conversion rate. Therefore, finding the appropriate compounds of suitable doping elements is beneficial to improving the catalytic performance of MoVTeNbO. Currently, there is no relevant report on modifying the MoVTeNbO catalyst with alkaline earth metals. Although Patent CN1130255C has a general formula for the prepared catalyst Mo 1.0 V a X b Nb c Z d On Alkaline earth metals are mentioned in Z of the patent, but in the examples of this patent, there are no samples containing alkaline earth metal elements in the general formula, and the application scope of the catalyst prepared in this patent is for the ammoxidation of propane to prepare acrylonitrile, rather than the one-step oxidation of propane to acrylic acid. Compared with the patents mentioned above, the alkaline earth metal doping mentioned in this patent does not require complex treatment of the precursor products, such as reduction by a reducing agent, regulation by an organic acid or regulation by ammonia water, etc., which greatly shortens the catalyst preparation process and reduces influencing factors, and this is beneficial for repeatability. And compared with noble metal doping, alkaline earth metals are also beneficial in cost control. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method for a catalyst used in the direct oxidation of propane to acrylic acid. This method involves adding a salt or hydroxide solution containing a certain amount of alkaline earth metal elements to the precursor slurry used for preparing the catalyst, reacting at a certain temperature for a certain period of time until a slurry is formed, and then obtaining the catalyst through spray drying and calcination. The catalyst prepared by this method has fine particles, which is beneficial for tablet plasticity, and has good catalytic activity and is easy to repeat. When this catalyst is applied to the direct oxidation of propane to acrylic acid, the propane conversion rate is between 55% and 65%, and the acrylic acid selectivity is between 65% and 82%.

[0006] The purpose of the present invention is achieved through the following technical solutions: A preparation method for a catalyst used in the direct oxidation of propane to acrylic acid, wherein the method involves adding a salt or hydroxide solution containing alkaline earth metal elements to the precursor components for preparing the catalyst, heating and stirring until a slurry is formed, and then obtaining the catalyst through spray drying and calcination. The basic general formula of the obtained catalyst is Mo1V a Te b Nb c A d O, where Mo is molybdenum element, V is vanadium element, Te is tellurium element, Nb is niobium element, A is at least one of alkaline earth metal elements such as Ca, Mg, Sr, Ba, etc., and a, b, c, d respectively represent the molar ratios of each element relative to Mo, where a is 0.2 - 0.6, b is 0.1 - 0.6, c is 0.01 - 0.2, and d is 0.005 - 0.08.

[0007] The described preparation method for a catalyst used in the direct oxidation of propane to acrylic acid, wherein the molybdenum source includes one or several of molybdenum phosphate, molybdate or molybdenum oxide; the vanadium source includes one or several of vanadate, metavanadate or vanadium oxide.

[0008] The described preparation method of a catalyst for the direct oxidation of propane to acrylic acid, wherein the tellurium source includes one of tellurium dioxide and telluric acid, and dissolving it in water can obtain a tellurium-containing solution with a valence of +4 or +6.

[0009] The described preparation method of a catalyst for the direct oxidation of propane to acrylic acid, the niobium oxalate used is prepared by: weighing a quantitative oxalic acid solution and adding it to water, then adding a quantitative niobium hydroxide, heating and reacting, and then drying to obtain.

[0010] The described preparation method of a catalyst for the direct oxidation of propane to acrylic acid uses one or several of salts or hydroxides containing alkaline earth metal elements such as calcium nitrate, calcium chloride, calcium hydroxide, strontium nitrate, strontium chloride, strontium hydroxide, etc. The molar ratio of the corresponding alkaline earth metal element to Mo in the catalyst in such a solution containing alkaline earth metal elements is 0.001 - 0.08.

[0011] The described preparation method of a catalyst for the direct oxidation of propane to acrylic acid, after mixing the solutions containing the corresponding elements in sequence and reacting at 70 - 90 °C for 10 - 30 min, spray-dry the obtained precursor slurry, with the feeding rate maintained at 2.5 - 10 mL / min, the inlet temperature at 160 - 240 °C, and the outlet temperature at 90 - 120 °C.

[0012] The described preparation method of a catalyst for the direct oxidation of propane to acrylic acid, calcine the dried catalyst precursor powder. Under a nitrogen atmosphere, raise the temperature to 200 - 300 °C at a heating rate of 2 - 10 °C / min and keep it constant for 1 - 3 h, then raise the temperature to 450 - 700 °C at a heating rate of 5 - 10 °C / min, and then keep it constant for 0.5 - 3.5 h.

[0013] The advantages and effects of the present invention are: 1. The advantages of the catalyst prepared by the method of the present invention for the direct oxidation of propane to acrylic acid are very obvious, that is: the catalyst particles are fine and uniform. The use of spray drying for the catalyst greatly shortens the drying time of the catalyst precursor, shortens the catalyst preparation process, and after doping and modifying with a compound containing an alkaline earth metal element in a suitable proportion, compared with the undoped and unmodified sample, a higher content of active crystal phase is obtained. This catalyst has high catalytic activity, good acrylic acid selectivity, high catalyst stability, and is suitable for industrial scale-up of the catalyst.

[0014] 2. The present invention has found one or several compounds containing alkaline earth metal elements. This compound is added to the MoVTeNbO precursor slurry in a suitable proportion and in a certain manner, and is prepared by spray drying. It is found that the catalyst obtains a higher active crystal phase, and a catalyst with better performance for directly oxidizing propane to acrylic acid is obtained. The preparation conditions of this catalyst are mild, the preparation process is simple and easy to implement, and the repeatability is good, which is suitable for industrial scale-up. Detailed implementation mode

[0015] The present invention will be specifically described below in conjunction with the embodiments.

[0016] In the present invention, the general formula of the catalyst composition is Mo1V a Te b Nb c A d O, where Mo is molybdenum element, V is vanadium element, Te is tellurium element, Nb is niobium element, A is at least one of alkaline earth metal elements such as Ca, Mg, Sr, Ba, etc., and a, b, c, d respectively represent the molar ratios of each element relative to Mo, where a is 0.2 - 0.6, b is 0.1 - 0.6, c is 0.01 - 0.2, and d is 0.005 - 0.08.

[0017] In the present invention, the catalyst is prepared by spray drying. The specific method is as follows: heat the mixed aqueous solution containing molybdenum source, vanadium source and tellurium source and dissolve it under stirring, then successively add the aqueous solution of niobium oxalate and the aqueous solution of salt or hydroxide containing alkaline earth metal elements, heat and stir for a period of time to obtain the catalyst precursor slurry, set the spray drying program and spray dry the slurry to obtain the catalyst precursor powder, and then calcine it to obtain the catalyst.

[0018] In the present invention, the molybdenum source includes one or several of molybdenum phosphate, molybdate or molybdenum oxide; the vanadium source includes one or several of vanadate, metavanadate or vanadium oxide.

[0019] In the present invention, the compound of tellurium element is the aqueous solution of telluric acid or the solution obtained by dissolving tellurium dioxide in 30% hydrogen peroxide solution and heating and reacting, where the tellurium element is +4 or +6 valence in the solution.

[0020] In the present invention, the niobium oxalate used is prepared as follows: weigh a certain amount of oxalic acid and dissolve it in a certain amount of water, then add a certain amount of niobium hydroxide, and heat to boiling to obtain niobium oxalate.

[0021] In the present invention, the catalyst is prepared by spray drying. The salt or hydroxide containing alkaline earth metal elements used is selected from one or several of calcium nitrate, calcium chloride, calcium hydroxide, strontium chloride, strontium nitrate, strontium hydroxide, etc. The molar ratio of the corresponding alkaline earth metal element to Mo is 0.001 - 0.08.

[0022] In the present invention, the obtained precursor slurry is spray dried. The set program for spray drying is that the feeding rate is maintained at 2.5 - 10 mL / min, the set inlet temperature is 160 - 240 °C, the outlet temperature is 90 - 120 °C, the needle passing frequency is 5.0 - 10.0 s. Then, the catalyst precursor powder obtained after spray drying is calcined. Specifically, in a nitrogen atmosphere, it is heated at a heating rate of 2 - 10 °C / min to 200 - 300 °C, kept at a constant temperature of 200 - 300 °C for 1 - 3 h, and then heated at a heating rate of 5 - 10 °C / min to 500 - 700 °C, and kept at a constant temperature of 500 - 700 °C for 0.5 - 3.5 h.

[0023] In the present invention, the prepared catalyst is tableted and sieved and then used in the direct oxidation of propane to acrylic acid reaction. The specific steps are as follows: An appropriate amount of catalyst is loaded into a tubular reactor, and nitrogen, oxygen, propane and water vapor are introduced into the reactor at a certain ratio. The reaction temperature is 380 °C, and the reaction space velocity is 1900 mL / g cat ·h. The reaction product is cooled by a condenser and the product is collected to obtain a solution containing acrylic acid. Example 1

[0024] 1. Preparation of the catalyst: Weigh 5.57 g of ammonium molybdate hydrate, 0.92 g of ammonium metavanadate, and 1.67 g of tellurium-containing compound and dissolve them in 75 mL of deionized water, stir, and heat in a water bath to 70 °C until completely dissolved. The solution turns orange-red to obtain solution A; then dissolve 2.05 g of niobium oxalate in 15 mL of deionized water to obtain a colorless solution B; weigh 0.06 g of strontium hydroxide and dissolve it by heating in 15 mL of deionized water to obtain solution C; add solution B and C to solution A in a magnetic stirrer, fully stir and mix, then heat in a water bath to 85 °C, react for 20 min to form an orange-yellow slurry. Spray dry the obtained slurry, set the inlet temperature for spray drying to 210 °C, the outlet temperature to 110 °C, and the slurry feeding speed to 5 mL / min to obtain the dried precursor powder, and then perform calcination. In a nitrogen atmosphere, first heat it at a heating rate of 3 °C / min to 200 °C, keep it at a constant temperature of 200 °C for 2 h, then heat it at a heating rate of 8 °C / min to 600 °C, and keep it at a constant temperature of 600 °C for 2 h. Grind, tablet, and sieve the calcined catalyst to obtain 20 - 40 mesh catalyst particles.

[0025] Activity test of the catalyst Weigh 1.5 g of the catalyst and load it into a tubular reactor. Then, introduce nitrogen, oxygen, propane, and steam into the reactor at a certain ratio. Set the temperature of the reaction tube to 380 °C and the reaction space velocity to 1900 mL / g cat ·h. Cool the reaction product through a condenser and collect it to obtain a solution containing acrylic acid.

[0026] Catalytic performance results See Table 1. Example 2

[0027] Weigh 5.57 g of ammonium molybdate hydrate, 0.92 g of ammonium metavanadate, and 1.67 g of tellurium-containing compound, dissolve them in 100 mL of deionized water, stir, and heat in a water bath at 70 °C until completely dissolved. The solution turns orange-red to obtain solution A. Then, dissolve 2.05 g of niobium oxalate in 10 mL of deionized water to obtain a colorless solution B. Weigh 0.15 g of strontium chloride, dissolve it by heating in 10 mL of deionized water to obtain solution C. Add solutions B and C to solution A in a magnetic stirrer, stir well and mix, then heat in a water bath at 80 °C. After reacting for 15 min, an orange-yellow slurry is formed. Spray-dry the obtained slurry, set the inlet temperature of the spray dryer to 200 °C, the outlet temperature to 100 °C, and the slurry feeding rate to 6 mL / min to obtain the dried precursor powder. Then, carry out calcination. Under a nitrogen atmosphere, first raise the temperature at a rate of 5 °C / min to 250 °C, keep it constant at 250 °C for 2 h, then raise the temperature at a rate of 10 °C / min to 650 °C, and keep it constant at 650 °C for 2 h. Grind, tablet, and screen the calcined catalyst to obtain 20 - 30 mesh catalyst particles.

[0028] The catalyst activity test conditions are the same as those in Example 1, and the reaction results are shown in Table 1. Example 3

[0029] Weigh 4.46g of hydrated ammonium molybdate, 0.72g of ammonium metavanadate, and 1.34g of a tellurium-containing compound and dissolve them in 70mL of deionized water, stir, and heat in a water bath to 70°C until they are completely dissolved. The solution turns orange-red to obtain solution A. Then, dissolve 1.61g of niobium oxalate in 10mL of deionized water to obtain a colorless solution B. Weigh 0.048g of strontium hydroxide and dissolve it in 10mL of deionized water by heating to dissolve, to obtain solution C. Add solutions B and C to solution A in a magnetic stirrer, stir and mix thoroughly, heat in a water bath to 80°C, and react for 15 minutes. An orange-yellow slurry is formed, and the obtained slurry is spray dried. The inlet temperature of the spray drying is set to 220°C, the outlet temperature is set to 100°C, and the slurry feed rate is 5mL / min to obtain a dried precursor powder, which is then calcined. Under a nitrogen atmosphere, the temperature is first increased to 200°C at a heating rate of 3°C / min, and maintained at a constant temperature at 200°C for 2h, and then increased to 600°C at a heating rate of 8°C / min, and maintained at a constant temperature at 600°C for 2h. The calcined catalyst is ground, tableted, and sieved to obtain 20-40 mesh catalyst particles.

[0030] The catalyst activity test conditions were consistent with those in Example 1, and the reaction results are shown in Table 1. Example 4

[0031] Weigh 4.54g of molybdenum oxide, 1.25g of vanadium sulfate and 0.05mol / L niobium oxalate solution, heat and stir at 85°C for 30min, then add 1.67g of an aqueous solution containing a tellurium compound to mix, and obtain solution A. Weigh 0.042g of calcium chloride and dissolve it in 10mL of deionized water to obtain solution B. Solution B is added to solution A, stirred at 85°C, and the reaction is continued for 20min. The slurry is spray dried, and the spray drying is set to an inlet temperature of 220°C, an outlet temperature of 100°C, and a slurry feed rate of 5mL / min to obtain a dried precursor powder, which is then calcined. In a nitrogen atmosphere, the temperature is first increased to 200°C at a heating rate of 3°C / min, and the temperature is maintained at 200°C for 2h, and then the temperature is increased to 600°C at a heating rate of 8°C / min, and the temperature is maintained at 600°C for 2h. The calcined catalyst is ground, tableted, and sieved to obtain 20~40 mesh catalyst particles.

[0032] The catalyst activity test conditions were consistent with those in Example 1, and the reaction results are shown in Table 1. Example 5

[0033] Weigh 1.82 g of molybdenum oxide, 0.52 g of vanadyl sulfate and mix them with a niobium oxalate solution of 0.06 mol / L. Heat and stir at 70 °C for 10 min, then add 0.67 g of an aqueous solution containing a tellurium compound for mixing to obtain solution A. Weigh 0.015 g of calcium hydroxide and dissolve it in 10 m of deionized water to obtain solution B. Add solution B to solution A, stir in a water bath at 80 °C, and continue the reaction for 15 min. Spray-dry the slurry, set the inlet temperature of the spray dryer to 180 °C, the outlet temperature to 90 °C, and the slurry feeding rate to 4 mL / min to obtain the dried precursor powder. Then carry out calcination. Under a nitrogen atmosphere, first raise the temperature at a rate of 3 °C / min to 200 °C, hold at 200 °C for 2 h, then raise the temperature at a rate of 8 °C / min to 600 °C, and hold at 600 °C for 2 h. Grind, tablet, and screen the calcined catalyst to obtain 20 - 40 mesh catalyst particles.

[0034] The catalyst activity test conditions are the same as those in Example 1, and the reaction results are shown in Table 1. Example 6

[0035] Weigh 4.46 g of ammonium molybdate hydrate, 1.8 g of ammonium metavanadate, and 1.34 g of a tellurium-containing compound, dissolve them in 70 mL of deionized water, stir, and heat in a water bath to 70 °C until completely dissolved. The solution turns orange-red to obtain solution A; then dissolve 1.61 g of niobium oxalate in 10 mL of deionized water to obtain a colorless solution B; weigh 0.083 g of strontium nitrate, dissolve it by heating in 10 mL of deionized water to obtain solution C; add solutions B and C to solution A in a magnetic stirrer, fully stir and mix, then heat in a water bath to 85 °C, react for 15 min to form an orange-yellow slurry. Spray-dry the obtained slurry, set the inlet temperature of the spray dryer to 220 °C, the outlet temperature to 110 °C, and the slurry feeding rate to 9 mL / min to obtain the dried precursor powder. Then carry out calcination. Under a nitrogen atmosphere, first raise the temperature at a rate of 5 °C / min to 200 °C, hold at 200 °C for 2 h, then raise the temperature at a rate of 10 °C / min to 600 °C, and hold at 600 °C for 2 h. Grind, tablet, and screen the calcined catalyst to obtain 20 - 40 mesh catalyst particles.

[0036] The catalyst activity test conditions are the same as those in Example 1, and the results are shown in Table 1. Example 7

[0037] Weigh 5.57 g of ammonium molybdate hydrate, 0.92 g of ammonium metavanadate, and 1.67 g of tellurium-containing compound, dissolve them in 80 mL of deionized water, stir, and heat in a water bath to 65 °C until completely dissolved. The solution turns orange-red to obtain solution A; then dissolve 2.05 g of niobium oxalate in 10 mL of deionized water to obtain a colorless solution B; weigh 0.07 g of calcium nitrate, dissolve it by heating in 15 mL of deionized water to obtain solution C; add solutions B and C to solution A in a magnetic stirrer, stir well and mix, then heat in a water bath to 80 °C, react for 15 min to form an orange-yellow slurry, spray-dry the obtained slurry, set the inlet temperature of the spray dryer to 200 °C, the outlet temperature to 100 °C, and the slurry feeding rate to 6 mL / min to obtain the dried precursor powder, and then carry out calcination. Under a nitrogen atmosphere, first raise the temperature at a rate of 5 °C / min to 250 °C, keep it at 250 °C for 2 h, then raise the temperature at a rate of 10 °C / min to 650 °C, and keep it at 650 °C for 2 h. Grind, tablet, and screen the calcined catalyst to obtain 20-40 mesh catalyst particles.

[0038] The catalyst activity test conditions are the same as those in Example 1, and the results are shown in Table 1. Example 8

[0039] Weigh 2.23 g of ammonium molybdate hydrate, 0.36 g of ammonium metavanadate, and 0.67 g of tellurium-containing compound, dissolve them in 30 mL of deionized water, stir, and heat in a water bath to 65 °C until completely dissolved. The solution turns orange-red to obtain solution A; then dissolve 0.81 g of niobium oxalate in 5 mL of deionized water to obtain a colorless solution B; weigh 0.04 g of calcium nitrate, dissolve it by heating in 5 mL of deionized water to obtain solution C; add solutions B and C to solution A in a magnetic stirrer, stir well and mix, then heat in a water bath to 80 °C, react for 15 min to form an orange-yellow slurry, and then carry out spray drying, set the inlet temperature to 210 °C, the outlet temperature to 110 °C, and the slurry feeding rate to 4.6 ml / min, and then carry out calcination. First raise the temperature at a rate of 5 °C / min to 200 °C, keep it at 200 °C for 2.5 h, then raise the temperature at a rate of 7 °C / min to 600 °C, and keep it at 600 °C for 2 h. Grind, tablet, and screen the calcined catalyst to obtain 20-40 mesh catalyst particles.

[0040] The catalyst activity test conditions are the same as those in Example 1, and the results are shown in Table 1. Example 9

[0041] Weigh 3.45 g of ammonium molybdate hydrate, 1.4 g of ammonium metavanadate, and 1.05 g of tellurium-containing compound, dissolve them in 50 mL of deionized water, stir, and heat in a water bath at 80 °C until completely dissolved. The solution turns orange-red to obtain Solution A. Then, dissolve 1.2 g of niobium oxalate in 10 mL of deionized water to obtain a colorless Solution B. Weigh 0.057 g of calcium hydroxide, dissolve it in 5 mL of deionized water, and then add it to Solution A simultaneously with Solution B. React in a water bath at 80 °C for 15 min, perform spray drying, set the inlet temperature at 200 °C, the feeding rate at 5 mL / min, calcine after drying, increase the temperature at a rate of 5 °C / min to 200 °C, keep it at 200 °C for 2.5 h, then increase the temperature at a rate of 10 °C / min to 600 °C, and keep it at 600 °C for 2 h. Grind, tablet, and screen the calcined catalyst to obtain 20 - 40 mesh catalyst particles.

[0042] The catalyst test conditions are the same as those in Example 1, and the results are shown in Table 1.

[0043] Example 10: Weigh 3.45 g of ammonium molybdate hydrate, 1.4 g of ammonium metavanadate, and 2.56 g of tellurium-containing compound, dissolve them in 50 mL of deionized water, stir, and heat in a water bath at 80 °C until completely dissolved. The solution turns orange-red to obtain Solution A. Then, dissolve 1.2 g of niobium oxalate in 10 mL of deionized water to obtain a colorless Solution B. Weigh 0.23 g of magnesium nitrate, dissolve it in 5 mL of deionized water, and then add it to Solution A simultaneously with Solution B. React in a water bath at 90 °C for 15 min, perform spray drying, set the inlet temperature at 240 °C, the feeding rate at 5 mL / min, calcine after drying, increase the temperature at a rate of 5 °C / min to 300 °C, keep it at 200 °C for 2.5 h, then increase the temperature at a rate of 10 °C / min to 600 °C, and keep it at 600 °C for 2 h. Grind, tablet, and screen the calcined catalyst to obtain 20 - 40 mesh catalyst particles.

[0044] The catalyst test conditions are the same as those in Example 1, and the results are shown in Table 1.

[0045] Example 11: Weigh 7.5 g of ammonium molybdate hydrate, 2.73 g of ammonium metavanadate, and 5.7 g of tellurium-containing compound, dissolve them in 100 mL of deionized water, stir, and heat in a water bath at 80 °C until completely dissolved. The solution turns orange-red to obtain Solution A. Then dissolve 4.57 g of niobium oxalate in 30 mL of deionized water to obtain a colorless Solution B. Weigh 0.32 g of magnesium chloride and dissolve it in 10 mL of deionized water, and then add it to Solution A simultaneously with Solution B. React in a water bath at 80 °C for 15 min, carry out spray drying, set the inlet temperature at 160 °C, the feeding rate at 7.5 mL / min, calcine after drying, increase the temperature at a rate of 5 °C / min to 250 °C, keep it at 200 °C for 2.5 h, then increase the temperature at a rate of 10 °C / min to 700 °C, keep it at 700 °C for 2 h. Grind, tablet, and screen the calcined catalyst to obtain 30 - 50 mesh catalyst particles.

[0046] The catalyst test conditions are the same as those in Example 1, and the results are shown in Table 1. Example

[0047] Weigh 7.5 g of ammonium molybdate hydrate, 1.19 g of ammonium metavanadate, and 2.34 g of tellurium-containing compound, dissolve them in 80 mL of deionized water, stir, and heat in a water bath at 70 °C until completely dissolved. The solution turns orange-red to obtain Solution A. Then dissolve 2.28 g of niobium oxalate in 30 mL of deionized water to obtain a colorless Solution B. Weigh 0.44 g of barium nitrate and dissolve it in 10 mL of deionized water, and then add it to Solution A simultaneously with Solution B. React in a water bath at 80 °C for 15 min, carry out spray drying, set the inlet temperature at 210 °C, the feeding rate at 6 mL / min, calcine after drying, increase the temperature at a rate of 10 °C / min to 300 °C, keep it at 300 °C for 2.5 h, then increase the temperature at a rate of 15 °C / min to 700 °C, keep it at 700 °C for 2 h. Grind, tablet, and screen the calcined catalyst to obtain 30 - 50 mesh catalyst particles.

[0048] The catalyst test conditions are the same as those in Example 1, and the results are shown in Table 1. Example

[0049] Weigh 5.46 g of molybdenum oxide, 1.55 g of vanadyl sulfate and mix them with a niobium oxalate solution of 0.06 mol / L. Heat and stir at 70 °C for 10 min, then add 0.67 g of an aqueous solution containing a tellurium compound for mixing to obtain solution A. Weigh 0.194 g of barium hydroxide and dissolve it in 10 m of deionized water to obtain solution B. Add solution B to solution A, stir in a water bath at 80 °C, and continue the reaction for 15 min. Spray-dry the slurry. Set the inlet temperature of the spray dryer to 190 °C, the outlet temperature to 110 °C, and the slurry feeding rate to 6.5 mL / min to obtain the dried precursor powder. Then carry out calcination. Under a nitrogen atmosphere, first raise the temperature to 200 °C at a heating rate of 3 °C / min, hold at 200 °C for 2 h, then raise the temperature to 600 °C at a heating rate of 8 °C / min, and hold at 600 °C for 2 h. Grind, tablet, and screen the calcined catalyst to obtain 20 - 40 mesh catalyst particles.

[0050] The catalyst test conditions are the same as in Example 1, and the results are shown in Table 1. Example

[0051] Weigh 5.57 g of ammonium molybdate hydrate, 1.12 g of ammonium metavanadate, and 1.87 g of a tellurium-containing compound, dissolve them in 75 mL of deionized water, stir, and heat in a water bath to 70 °C until completely dissolved. The solution turns orange-red to obtain solution A; then dissolve 2.05 g of niobium oxalate in 15 mL of deionized water to obtain a colorless solution B; weigh 0.065 g of barium chloride, dissolve it by heating in 15 mL of deionized water to obtain solution C; add solutions B and C to solution A in a magnetic stirrer, stir and mix well, then heat in a water bath to 85 °C, and after reacting for 20 min, form an orange-yellow slurry. Spray-dry the obtained slurry. Set the inlet temperature of the spray dryer to 210 °C, the outlet temperature to 110 °C, and the slurry feeding rate to 4.5 mL / min to obtain the dried precursor powder. Then carry out calcination. Under a nitrogen atmosphere, first raise the temperature to 200 °C at a heating rate of 3 °C / min, hold at 200 °C for 2 h, then raise the temperature to 500 °C at a heating rate of 8 °C / min, and hold at 500 °C for 3 h. Grind, tablet, and screen the calcined catalyst to obtain 20 - 40 mesh catalyst particles Table 1 Reaction temperature (°C) Propane conversion rate (%) Acrylic acid selectivity (%) Example 1 380 63.43 65.14 Example 2 380 62.57 76.25 Example 3 380 63.04 77.85 Example 4 380 55.69 67.55 Example 5 380 62.74 67.13 Example 6 380 62.36 74.42 Example 7 380 61.25 72.07 Example 8 380 57.42 81.31 Example 9 380 64.79 69.22 Example 10 380 59.12 79.32 Example 11 380 60.79 69.93 Example 12 380 55.42 71.65 Example 13 380 62.51 63.57 Example 14 380 63.87 72.60 。

Claims

1. A preparation method of a catalyst for the direct oxidation of propane to acrylic acid, characterized in that, The method involves adding a salt or hydroxide solution containing an alkaline earth metal element to the precursor components for preparing the catalyst, heating and stirring until a slurry is formed, followed by spray drying and calcination to obtain the catalyst. The basic general formula of the obtained catalyst is Mo1V a Te b Nb c A d O, where Mo is molybdenum, V is vanadium, Te is tellurium, Nb is niobium, A is at least one of alkaline earth metal elements such as Ca, Mg, Sr, Ba, etc., and a, b, c, d respectively represent the molar ratios of each element relative to Mo, where a is 0.2 - 0.6, b is 0.1 - 0.6, c is 0.01 - 0.2, and d is 0.005 - 0.

08.

2. The preparation method of a reaction catalyst for directly oxidizing propane to prepare acrylic acid according to claim 1, characterized in that, The molybdenum source includes one or more of molybdenum phosphate, molybdate or molybdenum oxide; the vanadium source includes one or more of vanadate, metavanadate or vanadium oxide.

3. The preparation method of a reaction catalyst for directly oxidizing propane to prepare acrylic acid according to claim 1, characterized in that, The tellurium source includes one of tellurium dioxide and tellurous acid, and a tellurium-containing solution with a +4 or +6 valence can be obtained by dissolving it in water.

4. The preparation method of a reaction catalyst for directly oxidizing propane to prepare acrylic acid according to claim 1, characterized in that, The niobium oxalate used is prepared by weighing a quantitative oxalic acid solution and adding it to water, then adding a quantitative niobium hydroxide, heating and reacting, and then drying.

5. A preparation method of a reaction catalyst for directly oxidizing propane to prepare acrylic acid according to claim 1, characterized in that, One or more of salts or hydroxides containing alkaline earth metal elements such as calcium nitrate, calcium chloride, calcium hydroxide, strontium nitrate, strontium chloride, strontium hydroxide, etc. are used. The molar ratio of the corresponding alkaline earth metal element in such a solution containing an alkaline earth metal element to Mo in the catalyst is 0.001 - 0.

08.

6. The preparation method of a reaction catalyst for directly oxidizing propane to prepare acrylic acid according to claim 1, characterized in that, After mixing the solutions containing the corresponding elements in sequence and reacting at 70 - 90 °C for 10 - 30 min, the obtained precursor slurry is spray-dried, with the feeding rate maintained at 2.5 - 10 mL / min, the inlet temperature at 160 - 240 °C, and the outlet temperature at 90 - 120 °C.

7. The preparation method of a reaction catalyst for directly oxidizing propane to prepare acrylic acid according to claim 1, characterized in that, The dried catalyst precursor powder is calcined. Under a nitrogen atmosphere, it is heated to 200 - 300 °C at a heating rate of 2 - 10 °C / min and kept at a constant temperature for 1 - 3 h, then heated to 450 - 700 °C at a heating rate of 5 - 10 °C / min, and then kept at a constant temperature for 0.5 - 3.5 h.