Catalyst calcination method

Abstract

The present invention provides a calcination method for a molybdenum-vanadium-tellurium-niobium-oxygen catalyst used in a propane selective oxidation reaction to produce acrylic acid. A molybdenum-vanadium-tellurium-niobium-oxygen catalyst precursor is uniformly mixed with a heat-conducting diluent powder and a redox agent powder to obtain a mixture, which is then calcined at high temperature in an intermittent atmosphere rotary kiln. The catalyst calcined by the method has high acrylic acid selectivity and propane conversion rate in a propane selective oxidation reaction to produce acrylic acid.

Description

Technical Field

[0001] The invention relates to a technology for preparing acrylic acid in organic chemical industry, and in particular provides a calcination technology for a molybdenum-vanadium-tellurium-niobium-oxygen catalyst used in the reaction of selective oxidation of propane to prepare acrylic acid. Background Art

[0002] Acrylic acid is a fine chemical with an annual domestic demand of more than 2 million tons. Acrylic acid and its ester series products are very important organic chemical raw materials. They are widely used in coatings, chemical fibers, textiles, light industry and other industries, as well as oil extraction, oil additives, etc. New application areas are still being developed. In recent decades, the production capacity and output of acrylic acid have increased year by year, reaching 3.76 million tons and 2.5 million tons respectively in 2019. The average consumption in the past three years has exceeded 2 million tons, indicating that it is a fine chemical with great market prospects. The production technology of acrylic acid has gone through several stages of development. At present, the two-step oxidation of propylene is the main method in industry, but the cost of propylene is relatively high, about 1 to 2 times higher than the price of propane. In addition, with the depletion of oil resources and the large-scale development and utilization of natural gas resources, the direct oxidation of propane with relatively low prices to prepare acrylic acid has a very attractive application prospect. Due to the great success of the process routes of converting low-carbon alkanes such as n-butane oxidation to maleic anhydride and propane oxidation to acrylonitrile to produce high-value chemicals, people also expect to use propane instead of propylene for direct oxidation to prepare important organic chemicals such as acrylic acid. As mentioned earlier, propane is a major component of oilfield gas, natural gas, and refinery gas. It is abundant in source and relatively cheaper than propylene. At the same time, due to the short process route and reduced energy consumption, it will bring huge economic benefits and is also more environmentally friendly.

[0003] There have been some basic research reports on the one-step oxidation of propane to acrylic acid. The catalysts used mainly include three types of systems: vanadium phosphorus oxide (VPO), heteropolyacids and their salts (HPCs), and composite metal oxides (MMO). The effect of VPO and HPCs in the one-step oxidation of propane to acrylic acid is not ideal, and the highest acrylic acid yield is only 13%. Since 1990, mixed metal oxide catalyst systems represented by MoV catalysts have been widely studied and have achieved very good catalytic effects in the selective oxidation of propane to acrylic acid. As described in the Japanese patent, Mitsubishi Kasai Company has a Mo-V-Te-·Nb-O catalyst with an acrylic acid yield of up to 52.3%.

[0004] A large amount of literature shows that the preparation steps of molybdenum-vanadium catalysts are relatively long, and their catalytic performance is very sensitive to synthesis parameters. The two most commonly used synthesis methods are precipitation method and hydrothermal method. Regardless of the method used to obtain the catalyst precursor, it is necessary to undergo further high-temperature treatment to obtain a catalyst with a certain activity. The high-temperature calcination process of the catalyst precursor is not only a complex physical process, but also a complex chemical process. At present, the literature discloses the influence of external conditions such as the calcination temperature, calcination atmosphere (such as air, nitrogen, etc.) and calcination time of the molybdenum-vanadium catalyst precursor (i.e., the material to be calcined) on the catalyst performance. No research has been conducted on the catalyst precursor itself, such as the particle size of the catalyst precursor, whether a thermal conductive diluent is added, whether a calcination aid is added, etc. Summary of the invention

[0005] The main purpose of the present invention is to provide a method for calcining a molybdenum-vanadium-tellurium-niobium-oxygen catalyst for selective oxidation of propane to produce acrylic acid, wherein the calcining equipment adopts an intermittent atmosphere rotary calcining furnace.

[0006] A method for calcining a molybdenum-vanadium-tellurium-niobium-oxygen catalyst used in the selective oxidation of propane to produce acrylic acid.

[0007] The first step is to use ammonium molybdate, vanadyl sulfate, telluric acid, niobium oxalate and surfactant as raw materials; the molar ratio of each component is Mo:V:Te:Nb:surfactant=1.0:0.2~1.0:0.2~1.0:0.1~0.5:0.1~0.5;

[0008] The surfactant is a cationic surfactant, preferably a quaternary ammonium salt surfactant, such as hexadecyltrimethylammonium bromide and octadecyldimethylbenzylammonium chloride;

[0009] In the second step, ammonium molybdate, vanadyl sulfate, telluric acid, niobium oxalate and surfactant are prepared into a mixed solution according to the above ratio and placed in a stainless steel reactor. The temperature is increased from room temperature to 160-230°C at a heating rate of 2-10°C / min, kept at this temperature for 2-20 hours, and then naturally cooled to room temperature.

[0010] Step 3: After aging, the filter cake is taken out, filtered and dried to obtain a round cake with a diameter of 20 to 30 cm. The filter cake is initially crushed and then ground and sieved to obtain catalyst precursors of different particle sizes, wherein the particle size of the catalyst precursor is 25 microns to 500 microns.

[0011] Step 4: Evenly mix the molybdenum-vanadium-tellurium-niobium-oxygen catalyst precursor (defined as "A"), the thermal conductive diluent powder (defined as "B"), and the redox agent powder (defined as "C", a calcination aid) to obtain a mixture (A). 1.0 B x C y, wherein the value of x ranges from 0 to 5.0, the value of y ranges from 0 to 0.5, and x and y represent the weight ratios of B and C relative to A, respectively), the mixture (A 1.0 B x C y ) using an intermittent atmosphere rotary kiln to first perform low-temperature drying, and then perform low-temperature and high-temperature calcination to obtain a catalyst active powder, which is granulated to obtain a catalyst of 20 to 40 mesh;

[0012] The thermally conductive diluent powder B is one or more of elemental silicon powder, silicon carbide powder, quartz powder, corundum powder, silicon nitride and boron nitride, and the weight ratio of the thermally conductive diluent powder B to the molybdenum vanadium tellurium niobium oxygen catalyst precursor A is 0-5.0:1;

[0013] The redox agent powder C is one or both of oxalic acid and ammonium carbonate, and the weight ratio of the redox agent powder to the molybdenum-vanadium-tellurium-niobium-oxygen catalyst precursor A is 0-0.5:1;

[0014] The drying conditions are: drying in air at 80-110° C. for 0.5-1 hour.

[0015] The calcination conditions are: low-temperature calcination at 200-350° C. in 10-1000 ml / min air for 0.5-3 hours, and then high-temperature calcination at 400-700° C. in 10-5000 ml / min nitrogen for 1-5 hours.

[0016] The 20-40 mesh catalyst obtained above was used for the selective oxidation of low-carbon alkanes to produce high-value chemicals, especially for the evaluation of the selective oxidation of propane to produce acrylic acid.

[0017] Based on the above technical solution, preferably, the weight ratio of the thermally conductive diluent powder B to the molybdenum vanadium tellurium niobium oxygen catalyst precursor A is 0.5 to 3.0:1, more preferably 1.0 to 2.5, and further preferably 1.0 to 2.0:1.

[0018] Based on the above technical solution, preferably, the weight ratio of the redox agent powder C to the molybdenum vanadium tellurium niobium oxygen catalyst precursor A is 0.1 to 0.4:1, and more preferably 0.2 to 0.3:1.

[0019] Based on the above technical solution, preferably, the particle size of the molybdenum-vanadium-tellurium-niobium-oxygen catalyst precursor is between 50 microns and 300 microns, and more preferably between 80 microns and 200 microns.

[0020] Based on the above technical scheme, preferably, the reaction conditions for selective oxidation of propane to produce acrylic acid are: reaction temperature 300-400°C, reaction pressure normal pressure-0.3MPaG, reaction space velocity 500-5000h -1 .

[0021] For the molybdenum-vanadium-tellurium-niobium-oxygen catalyst precursor, the low-temperature calcination process (not higher than 350°C) includes the evaporation of water, decomposition to produce ammonia, CO and CO2, etc., while the high-temperature calcination process mainly involves phase change and crystal phase improvement. During the high-temperature reaction, the rapid and uniform transfer of heat inside the catalyst precursor is crucial. It is particularly important to select the appropriate catalyst precursor (A) particle size, mix a certain amount of diluent (B), and add a calcination aid (C) before calcination. If the catalyst precursor particles are too large, the "half-cooked" phenomenon will occur, that is, when the outer layer of the catalyst particles meets the performance requirements after calcination, the inner core does not meet the requirements, which will inevitably affect the performance of the final catalyst. There will also be problems if the particles are too small, such as being blown out by airflow. The addition of thermal conductive diluents and calcination aids will also effectively avoid the "half-cooked" phenomenon and will significantly improve the performance of the catalyst.

[0022] The catalyst obtained by the calcination method has high acrylic acid selectivity, propane conversion rate and acrylic acid space-time yield and excellent stability in the reaction of selective oxidation of propane to prepare acrylic acid. DETAILED DESCRIPTION

[0023] In the present invention, the term "intermittent atmosphere rotary kiln" refers to a high-temperature treatment device that can rotate continuously, has a continuously flowing atmosphere introduced into the interior, and intermittently calcines the catalyst precursor.

[0024] In the present invention, the size of the A particles is determined by the mesh number of the stainless steel sieve, and the shape of the A particles themselves is not a regular shape, such as a specific spherical shape.

[0025] Using propane as raw material and oxygen as oxidant, propane is converted into acrylic acid in one step through catalytic oxidation technology, and the reaction products are divided into gas and liquid phases. The gas phase components include CO, CO2, C2H4, C3H6, as well as unconverted oxygen and propane, and unconverted nitrogen; the liquid phase components are mainly acrylic acid, acetic acid, acetone and propionic acid, as well as water generated by the reaction and water for raw materials.

[0026] The propane conversion, product selectivity and acrylic acid space-time yield were calculated according to the following formula:

[0027] Propane conversion rate (%) = (the amount of propane in the feed - the amount of propane in the output) / the amount of propane in the feed × 100%

[0028] Product selectivity (%) = (Mi×Ni) / (∑Mi×Ni)×100%

[0029] (Mi: the amount of substance in a product i; Ni: the number of carbon atoms contained in a molecule of a product i)

[0030] Acrylic acid space-time yield = F(C2H6)*propane conversion*acrylic acid selectivity*72.06*100 / catalyst mass

[0031] In the above formula, F(C2H6) is the molar flow rate of ethane, and the unit of space-time yield is "g / kg-cat. / h", which represents the mass of acrylic acid generated on each kilogram of catalyst per unit time.

[0032] Sampling analysis was started after 6 hours of reaction. Sampling analysis was performed every day for catalyst life evaluation.

[0033] The present invention will be further described in the following examples, but the present invention is not limited thereto.

[0034] Example 1

[0035] The preparation of the molybdenum-vanadium-tellurium-niobium-oxygen catalyst precursor is shown in patent ZL201410198867.2. The difference is that the amount of various raw materials is magnified by 10,000 times, and a special 500L high-pressure stainless steel synthesis reactor is used. That is, the Mo-V-Te-Nb-O catalyst is prepared by a programmed temperature hydrothermal synthesis method. First, weigh the proportion of ammonium molybdate, vanadyl sulfate, telluric acid and niobium oxalate and dissolve them in hot deionized water respectively. After heating each for 30 to 60 minutes, slowly mix the solutions together in turn, continue stirring for 10 to 30 minutes, add a certain amount of surfactant CTAB (the molar ratio is CTAB / Mo=0.04:1), continue stirring for 3 to 10 minutes, transfer it into a 500L stainless steel tube synthesis reactor, heat it from room temperature to 180°C at a heating rate of 10°C / min, keep it warm for 20 hours and then naturally cool it to room temperature, then take it out, filter it, break the gray-black filter cake, and grind it in a ball mill to obtain a powder (catalyst precursor powder) of 130 to 180 microns, and then mix silicon carbide (SiC) powder (silicon carbide powder and molybdenum) powder. The weight ratio of vanadium tellurium niobium oxygen catalyst precursor is 2.0:1) and oxalic acid (the weight ratio of oxalic acid to molybdenum vanadium tellurium niobium oxygen catalyst precursor is 0.2:1) are mixed with catalyst precursor powder and placed in an intermittent atmosphere rotary kiln. The intermittent atmosphere rotary kiln is heated from room temperature to 90°C and dried for 40 minutes. Then, air with a flow rate of 50 ml / min is introduced, and the temperature is increased to 300°C at a heating rate of 3°C / min. After being kept warm for 2 hours, the air is turned off, and nitrogen with a flow rate of 50 ml / min is immediately introduced. The temperature is increased to 600°C at a heating rate of 3°C / min and kept warm for 2 hours. The temperature is naturally lowered. The resulting product is the calcined molybdenum vanadium tellurium niobium oxygen catalyst active powder. Finally, it is formed and granulated and sieved into catalyst particles with a particle size of 20 to 30 mesh for catalyst evaluation. Take 1g of the above granular catalyst for propane oxidation reaction. The reaction conditions are: reaction temperature 380°C, total volume space velocity 2000h -1The volume ratio of propane, air and water vapor is 10:63:27 (in order to stay away from the explosion limit of propane at high temperature, the raw gas components are controlled to have a lower oxygen content, and a certain amount of water is introduced into the raw gas for dilution), and the reaction is carried out under normal pressure. The reaction results are: propane conversion rate 50.1%, propylene selectivity 75.1%, acrylic acid space-time yield 205.0g / kg-cat. / h. The reaction results are listed in Table 1.

[0036] Example 2

[0037] The catalyst preparation procedure in this example is the same as that described in Example 1, except that the particle size of the catalyst precursor powder is between 230 μm and 300 μm.

[0038] 1 g of the above granular catalyst was used for propane oxidation reaction, and the reaction conditions were the same as those in Example 1. The reaction results were: propane conversion rate was 45.1%, acrylic acid selectivity was 73.1%, and acrylic acid space-time yield was 179.6 g / kg-cat. / h. The reaction results are listed in Table 1.

[0039] Example 3

[0040] The catalyst preparation procedure in this example is the same as that described in Example 1, except that the catalyst precursor powder particles are 25 microns to 100 microns.

[0041] 1 g of the above granular catalyst was used for propane oxidation reaction, and the reaction conditions were the same as those in Example 1. The reaction results were: propane conversion rate was 50.5%, acrylic acid selectivity was 74.1%, and acrylic acid space-time yield was 203.9 g / kg-cat. / h. The reaction results are listed in Table 1.

[0042] In this example, the catalyst yield is relatively low, and some powder is carried out of the intermittent atmosphere rotary furnace by the airflow.

[0043] Example 4

[0044] The catalyst preparation procedure in this example is the same as that described in Example 1, except that the catalyst precursor powder particles are between 350 microns and 500 microns.

[0045] 1 g of the above granular catalyst was used for propane oxidation reaction, and the reaction conditions were the same as those in Example 1. The reaction results were: propane conversion rate was 39.3%, acrylic acid selectivity was 68.2%, and acrylic acid space-time yield was 146.0 g / kg-cat. / h. The reaction results are listed in Table 1.

[0046] Example 5

[0047] The catalyst preparation procedure in this example is the same as that described in Example 1, except that the weight of the silicon carbide powder and the catalyst precursor powder is 1.0.

[0048] 1 g of the above granular catalyst was used for propane oxidation reaction, and the reaction conditions were the same as those in Example 1. The reaction results were: propane conversion rate was 52.3%, acrylic acid selectivity was 72.0%, and acrylic acid space-time yield was 205.1 g / kg-cat. / h. The reaction results are listed in Table 1.

[0049] Example 6

[0050] The catalyst preparation procedure in this example is the same as that in Example 1, except that the weight ratio of silicon carbide powder to catalyst precursor powder is 3.0:1. 1 g of the above granular catalyst is used for propane oxidation reaction, and the reaction conditions are the same as those in Example 1. The reaction results are: propane conversion rate 48.4%, acrylic acid selectivity 75.4%, acrylic acid space-time yield 198.8 g / kg-cat. / h. The reaction results are listed in Table 1.

[0051] Example 7

[0052] The catalyst preparation procedure in this example is the same as that in Example 1, except that the weight ratio of silicon carbide powder to catalyst precursor powder is 4.0:1. 1 g of the above granular catalyst is used for propane oxidation reaction, and the reaction conditions are the same as those in Example 1. The reaction results are: propane conversion rate 43.2%, acrylic acid selectivity 75.2%, acrylic acid space-time yield 178.6 g / kg-cat. / h. The reaction results are listed in Table 1.

[0053] Example 8

[0054] The catalyst preparation procedure in this example is the same as that in Example 1, except that the weight ratio of silicon carbide powder to catalyst precursor powder is 5.0:1. 1 g of the above granular catalyst is used for propane oxidation reaction, and the reaction conditions are the same as those in Example 1. The reaction results are: propane conversion rate 39.8%, acrylic acid selectivity 75.9%, acrylic acid space-time yield 164.6 g / kg-cat. / h. The reaction results are listed in Table 1.

[0055] Example 9

[0056] The catalyst preparation procedure in this example is the same as that in Example 1, except that the weight ratio of oxalic acid to catalyst precursor powder is 0.1:1. 1 g of the above granular catalyst is used for propane oxidation reaction, and the reaction conditions are the same as those in Example 1. The reaction results are: propane conversion rate 47.4%, acrylic acid selectivity 74.9%, acrylic acid space-time yield 193.4 g / kg-cat. / h. The reaction results are listed in Table 1.

[0057] Example 10

[0058] The catalyst preparation procedure in this example is the same as that in Example 1, except that the weight ratio of oxalic acid to catalyst precursor powder is 0.3:1. 1 g of the above granular catalyst is used for propane oxidation reaction, and the reaction conditions are the same as those in Example 1. The reaction results are: propane conversion rate 49.5%, acrylic acid selectivity 74.6%, acrylic acid space-time yield 197.5 g / kg-cat. / h. The reaction results are listed in Table 1.

[0059] Embodiment 11

[0060] The catalyst preparation procedure in this example is the same as that in Example 1, except that the weight ratio of oxalic acid to catalyst precursor powder is 0.4:1. 1 g of the above granular catalyst is used for propane oxidation reaction, and the reaction conditions are the same as those in Example 1. The reaction results are: propane conversion rate 47.3%, acrylic acid selectivity 75.0%, acrylic acid space-time yield 193.3 g / kg-cat. / h. The reaction results are listed in Table 1.

[0061] Example 12

[0062] The catalyst preparation procedure in this example is the same as that in Example 1, except that the weight ratio of oxalic acid to catalyst precursor powder is 0.5:1. 1 g of the above granular catalyst is used for propane oxidation reaction, and the reaction conditions are the same as those in Example 1. The reaction results are: propane conversion rate 46.5%, acrylic acid selectivity 75.1%, acrylic acid space-time yield 190.2 g / kg-cat. / h. The reaction results are listed in Table 1.

[0063] Embodiment 13

[0064] The catalyst preparation procedure in this example is the same as that in Example 1, except that the heat-conducting diluent is silicon powder (Si). 1 g of the above granular catalyst is used for propane oxidation reaction, and the reaction conditions are the same as those in Example 1. The reaction results are: propane conversion rate is 49.5%, acrylic acid selectivity is 74.6%, and acrylic acid space-time yield is 201.2 g / kg-cat. / h. The reaction results are listed in Table 1.

[0065] Embodiment 14

[0066] The catalyst preparation procedure in this example is the same as that in Example 1, except that the heat-conducting diluent is a mixture of silicon powder and silicon carbide powder in equal proportions. 1 g of the above granular catalyst is used for propane oxidation reaction, and the reaction conditions are the same as those in Example 1. The reaction results are: propane conversion rate 49.8%, acrylic acid selectivity 74.8%, acrylic acid space-time yield 201.9 g / kg-cat. / h. The reaction results are listed in Table 1.

[0067] Embodiment 15

[0068] The catalyst preparation procedure in this example is the same as that in Example 1, except that the heat-conducting diluent is a mixture of silicon powder, quartz powder and silicon carbide powder in equal proportions. 1 g of the above granular catalyst is used for propane oxidation reaction, and the reaction conditions are the same as those in Example 1. The reaction results are: propane conversion rate 49.7%, acrylic acid selectivity 75.0%, acrylic acid space-time yield 203.1 g / kg-cat. / h. The reaction results are listed in Table 1.

[0069] Example 16

[0070] The catalyst preparation procedure in this example is the same as that in Example 1, except that the heat-conducting diluent is quartz powder. 1 g of the above granular catalyst is used for propane oxidation reaction, and the reaction conditions are the same as those in Example 1. The reaction results are: propane conversion rate is 49.9%, acrylic acid selectivity is 74.7%, and acrylic acid space-time yield is 203.1 g / kg-cat. / h. The reaction results are listed in Table 1.

[0071] Embodiment 17

[0072] The catalyst preparation procedure in this example is the same as that in Example 1, except that the heat-conducting diluent is corundum powder. 1 g of the above granular catalyst is used for propane oxidation reaction, and the reaction conditions are the same as those in Example 1. The reaction results are: propane conversion rate 47.0%, acrylic acid selectivity 74.0%, acrylic acid space-time yield 189.5 g / kg-cat. / h. The reaction results are listed in Table 1.

[0073] Embodiment 18

[0074] The catalyst preparation procedure in this example is the same as that in Example 1, except that the heat-conducting diluent is silicon carbide powder. 1 g of the above granular catalyst is used for propane oxidation reaction, and the reaction conditions are the same as those in Example 1. The reaction results are: propane conversion rate is 47.2%, acrylic acid selectivity is 74.5%, and acrylic acid space-time yield is 191.6 g / kg-cat. / h. The reaction results are listed in Table 1.

[0075] Embodiment 19

[0076] The catalyst preparation procedure in this example is the same as that in Example 1, except that the heat-conducting diluent is boron carbide powder. 1 g of the above granular catalyst is used for propane oxidation reaction, and the reaction conditions are the same as those in Example 1. The reaction results are: propane conversion rate is 47.6%, acrylic acid selectivity is 74.0%, and acrylic acid space-time yield is 191.9 g / kg-cat. / h. The reaction results are listed in Table 1.

[0077] Embodiment 20

[0078] The catalyst preparation procedure in this example is the same as that in Example 1, except that the heat-conducting diluent is silicon powder and corundum powder in equal proportions. 1 g of the above granular catalyst is used for propane oxidation reaction, and the reaction conditions are the same as those in Example 1. The reaction results are: propane conversion rate is 48.3%, acrylic acid selectivity is 74.9%, and acrylic acid space-time yield is 197.1 g / kg-cat. / h. The reaction results are listed in Table 1.

[0079] Embodiment 21

[0080] The catalyst preparation procedure in this example is the same as that in Example 1, except that the calcination aid is ammonium carbonate. 1 g of the above granular catalyst is used for propane oxidation reaction, and the reaction conditions are the same as those in Example 1. The reaction results are: propane conversion rate 48.5%, acrylic acid selectivity 74.5%, acrylic acid space-time yield 196.8 g / kg-cat. / h. The reaction results are listed in Table 1.

[0081] Embodiment 22

[0082] The catalyst preparation procedure in this example is the same as that in Example 1, except that the heat-conducting diluent is oxalic acid and ammonium carbonate in equal proportions. 1 g of the above granular catalyst is used for propane oxidation reaction, and the reaction conditions are the same as those in Example 1. The reaction results are: propane conversion rate 49.0%, acrylic acid selectivity 74.7%, acrylic acid space-time yield 199.4 g / kg-cat. / h. The reaction results are listed in Table 1.

[0083] Embodiment 23

[0084] The catalyst preparation procedure in this example is as described in Example 1. 1 g of the above granular catalyst was used for propane oxidation reaction, and the reaction conditions were the same as in Example 1. A catalyst stability evaluation experiment was carried out for 1015 hours under the steady-state conditions. The reaction results are listed in Table 3.

[0085] Comparative Example 1

[0086] The catalyst preparation procedure in this comparative example is the same as that described in Example 1, except that the catalyst precursor powder particles are between 700 microns and 1000 microns.

[0087] 1 g of the above granular catalyst was used for propane oxidation reaction, and the reaction conditions were the same as those in Example 1. The reaction results were: propane conversion rate was 34.4%, acrylic acid selectivity was 64.5%, and acrylic acid space-time yield was 120.9 g / kg-cat. / h. The reaction results are listed in Table 2.

[0088] Comparative Example 2

[0089] The catalyst preparation procedure in this comparative example is the same as that described in Example 1, except that the catalyst precursor powder particles are between 1200 microns and 3000 microns.

[0090] 1 g of the above granular catalyst was used for propane oxidation reaction, and the reaction conditions were the same as those in Example 1. The reaction results were: propane conversion rate was 28.4%, acrylic acid selectivity was 55.6%, and acrylic acid space-time yield was 86.0 g / kg-cat. / h. The reaction results are listed in Table 2.

[0091] Comparative Example 3

[0092] The catalyst preparation procedure in this comparative example is the same as that in Example 1, except that the weight ratio of silicon carbide powder to catalyst precursor powder is 6.0:1. 1 g of the above granular catalyst is used for propane oxidation reaction, and the reaction conditions are the same as those in Example 1. The reaction results are: propane conversion rate 29.8%, acrylic acid selectivity 75.4%, acrylic acid space-time yield 122.4 g / kg-cat. / h. The reaction results are listed in Table 2.

[0093] Comparative Example 4

[0094] The catalyst preparation procedure in this comparative example is the same as that in Example 1, except that the weight ratio of oxalic acid to catalyst precursor powder is 0.6:1. 1 g of the above granular catalyst is used for propane oxidation reaction, and the reaction conditions are the same as those in Example 1. The reaction results are: propane conversion rate 29.8%, acrylic acid selectivity 75.4%, acrylic acid space-time yield 161.1 g / kg-cat. / h. The reaction results are listed in Table 2.

[0095] Comparative Example 5

[0096] The catalyst preparation procedure in this comparative example is the same as that in Example 1, except that the weight ratio of silicon carbide powder to catalyst precursor powder is 0, i.e., no heat-conducting diluent is added. 1 g of the above granular catalyst is used for propane oxidation reaction, and the reaction conditions are the same as those in Example 1. The reaction results are: propane conversion rate 40.4%, acrylic acid selectivity 75.4%, acrylic acid space-time yield 131.1 g / kg-cat. / h. The reaction results are listed in Table 2.

[0097] Comparative Example 6

[0098] The catalyst preparation procedure in this comparative example is the same as that in Example 1, except that no calcination aid is added. 1 g of the above granular catalyst is used for propane oxidation reaction, and the reaction conditions are the same as those in Example 1. The reaction results are: propane conversion rate 46.0%, acrylic acid selectivity 69.8%, acrylic acid space-time yield 174.9 g / kg-cat. / h. The reaction results are listed in Table 2.

[0099] Comparative Example 7

[0100] The catalyst preparation procedure in this comparative example is the same as that in Example 1, except that no heat-conducting diluent and calcination aid are added. 1 g of the above granular catalyst is used for propane oxidation reaction, and the reaction conditions are the same as those in Example 1. The reaction results are: propane conversion rate 46.0%, acrylic acid selectivity 69.8%, acrylic acid space-time yield 117.6 g / kg-cat. / h. The reaction results are listed in Table 2.

[0101] Comparative Example 8

[0102] The catalyst preparation procedure in this comparative example is as described in comparative example 7. 1 g of the above granular catalyst was used for propane oxidation reaction, and the reaction conditions were the same as those in Example 1. A catalyst stability evaluation experiment was carried out for 1015 hours under the steady-state conditions. The reaction results are listed in Table 3.

[0103] Table 1. Reaction results of Examples 1 to 22

[0104]

[0105] Table 2. Reaction results in Comparative Examples 1 to 7

[0106]

[0107] Table 3. Evaluation results of catalyst stability (Example 3 and Comparative Example 8)

[0108]

[0109]

[0110]

Claims

1. A method for calcining a molybdenum-vanadium-tellurium-niobium-oxygen catalyst used in the selective oxidation of propane to produce acrylic acid, characterized in that: The first step is to use ammonium molybdate, vanadyl sulfate, telluric acid, niobium oxalate and surfactant as raw materials, and the molar ratio of each component is Mo:V:Te:Nb:surfactant=1.0:0.2~1.0:0.2~1.0:0.1~0.5:0.1~0.5; The surfactant is hexadecyltrimethylammonium bromide; Step 2: ammonium molybdate, vanadyl sulfate, telluric acid, niobium oxalate and surfactant are prepared into a mixed solution according to the above ratio and placed in a stainless steel reactor, and the temperature is increased from room temperature to 160-230°C at a heating rate of 2-10°C / min, and the mixture is kept at this temperature for 2-20 hours, and then naturally cooled to room temperature; The third step is to take out the aging, filter and dry the filtrate to obtain a round cake with a diameter of 20 to 30 cm. The filter cake is initially crushed and then ground and sieved to obtain a catalyst precursor. The particle size of the catalyst precursor is 25 microns to 300 microns. The fourth step is to mix the molybdenum vanadium tellurium niobium oxygen catalyst precursor with the heat conductive diluent powder and the calcination aid to obtain a mixture, dry the mixture in an intermittent atmosphere rotary kiln, and then calcine it to obtain a catalyst active powder, and granulate it to obtain a catalyst of 20 to 40 mesh; The thermally conductive diluent powder is one or more of elemental silicon powder, silicon carbide powder, quartz powder, and corundum powder, and the weight ratio of the thermally conductive diluent powder to the molybdenum-vanadium-tellurium-niobium-oxygen catalyst precursor is 1.0-3.0:1; The calcination aid is one or both of oxalic acid and ammonium carbonate, and the weight ratio of the calcination aid to the molybdenum-vanadium-tellurium-niobium-oxygen catalyst precursor is 0.1-0.5:1; The drying conditions are: drying in air at 80-110°C for 0.5-1 hour; The calcination conditions are: low-temperature calcination at 200-350° C. in 10-1000 ml / min air for 0.5-3 hours, and then high-temperature calcination at 400-700° C. in 10-5000 ml / min nitrogen for 1-5 hours.

2. The roasting method according to claim 1, characterized in that: The weight ratio of the thermal conductive diluent powder to the molybdenum-vanadium-tellurium-niobium-oxygen catalyst precursor is 1.0 to 2.5:

1.

3. The roasting method according to claim 1, characterized in that: The weight ratio of the calcination aid to the molybdenum-vanadium-tellurium-niobium-oxygen catalyst precursor is 0.1-0.4:

1.

4. The roasting method according to claim 3, characterized in that: The weight ratio of the calcination aid to the molybdenum-vanadium-tellurium-niobium-oxygen catalyst precursor is 0.2-0.3:

1.

5. The roasting method according to claim 1, characterized in that: The particle size of the molybdenum-vanadium-tellurium-niobium-oxygen catalyst precursor is 50 microns to 300 microns.

6. The roasting method according to claim 5, characterized in that: The particle size of the molybdenum-vanadium-tellurium-niobium-oxygen catalyst precursor is 80 microns to 200 microns.

7. The roasting method according to claim 1, characterized in that: The reaction conditions for the selective oxidation of propane to produce acrylic acid are: reaction temperature 300-400°C, reaction pressure normal pressure-0.3MPaG, reaction space velocity 500-5000h -1 .

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