Vanadium-loaded alumina catalyst and preparation method and application thereof

Abstract

The preparation method comprises the following steps: mixing ammonium metavanadate and hydroxyl alumina, adding the mixture into a ball-milling tank, adding grinding balls and deionized water, and sealing the ball-milling tank; fixing the ball milling tank in a ball mill, and grinding for 10-15 hours; the obtained material is taken out for freeze drying; removing moisture from the freeze-dried material, and calcining in an air atmosphere; and tabletting, crushing and sieving the calcined solid product to obtain the catalyst. The prepared catalyst can be used for high-selectivity propylene preparation through oxidative dehydrogenation of propane at a relatively low temperature, and an ODHP reaction is carried out in the reaction temperature interval, so that byproducts such as methane, ethane and ethylene are not generated, and technological operations such as subsequent gas separation and purification and the cost are avoided.

Description

Technical Field

[0001] The invention belongs to the field of industrial low-carbon alkane conversion thermal catalytic materials, and specifically relates to a vanadium-loaded alumina catalyst and a preparation method and application thereof. Background Art

[0002] Propane is an important chemical raw material, widely used in the production of polypropylene, acrylic acid, polyacrylonitrile, phenol, oxo alcohol, propylene oxide, acrolein, and downstream applications in the production and processing of medical devices, automotive products and parts, building materials, electronic communication materials, and aerospace materials. my country's propylene production and demand rank first in the world. At present, new low-carbon propylene production technologies are urgently needed to promote the green and low-carbon transformation of chemical processes. Due to the increasing shortage of oil resources, oil steam cracking and catalytic cracking technologies alone can no longer meet the rapidly growing demand for propylene. my country has huge reserves of liquefied petroleum gas resources, which are basically composed of 60% propane and 20% butane. If the corresponding low-carbon olefins are produced through the catalytic dehydrogenation technology of low-carbon alkanes, the added value of low-carbon alkanes can be effectively increased to obtain high-value-added propylene, etc., and the technology has low investment and high product yield, and has huge market development potential. At present, the more mature industrial processes for producing propylene at home and abroad include: ethylene to propylene (ETP), steam cracking (SC), Fischer-Tropsch synthesis (FT), methanol to olefins (MTO), direct dehydrogenation of propane (PDH), as well as naphtha steam cracking by-products and refining by-products.

[0003] The most commonly used process technologies for direct dehydrogenation of propane are Honeywell UOP's Oleflex process and ABB Lumus's Catofin process. However, these processes have the following problems: (1) Due to the thermodynamic equilibrium limitation, the PDH reaction requires high temperature, the equilibrium conversion rate is difficult to improve, and the process energy consumption is still high; (2) Under high temperature conditions, the propane CC bond is easy to break, which aggravates the carbon accumulation and coking on the catalyst surface, resulting in rapid catalyst deactivation and frequent regeneration; (3) The platinum-based catalysts used are expensive, and the chromium-based catalysts are toxic and harmful to the ecological environment and human body; Therefore, on the one hand, researchers have improved the activity, stability, selectivity and anti-carbon deposition ability of propane direct dehydrogenation catalysts by improving the dispersion of active sites (such as single atoms, diatomic alloys, non-precious metal doping, etc.) or adjusting the acidity or alkalinity of the catalyst; on the other hand, they have also actively explored other possible propane-to-propylene pathways. Among them, the propane oxidative dehydrogenation reaction to produce propylene can overcome the thermodynamic equilibrium limitations of the direct dehydrogenation process of propane, and has the advantages of low reaction temperature, less carbon deposition, and low cost. It is a new propylene production method with great application potential.

[0004] Adding an appropriate proportion of O2 to the propane direct dehydrogenation reaction (PDH), that is, oxygen and hydrogen produced by propane dehydrogenation are oxidized to generate water, which can shift the reaction equilibrium to the right and greatly improve the equilibrium conversion rate at the same temperature. At the same time, the heat released by the reaction of hydrogen and oxygen can be used for the reaction, reducing the external heat supply, achieving the purpose of energy conservation and emission reduction, and has great development prospects. The disadvantage is that oxygen can easily cause deep oxidation of propane and propylene, resulting in low propylene selectivity.

[0005] Traditional metal-based catalysts generally have the problem of deep oxidation of propane or propylene to CO as the reaction temperature increases. x In recent years, boron-containing catalysts have shown high propylene selectivity in the catalytic propane oxidative dehydrogenation reaction, and the main by-products are ethylene and CO. x Very few (Science, 2016, 354, 1570; Science, 2021, 372, 76 80)

[0006] The surface active sites of bulk boron-containing catalysts are limited, the effective reaction temperature is generally higher than 500°C, and the single-pass yield of propylene is less than 1g. C3H6 / (g cat ·h), which cannot meet the requirements of industrialization. China Invention (Application No. 201910569416.8) discloses a method for preparing amorphous silica (mainly SBA 15) supported boron oxide catalyst by an isovolumetric impregnation method (initial wetness impregnation method), and is applied to the oxidative dehydrogenation of low-carbon alkanes. The activation temperature of the propane oxidative dehydrogenation reaction can be as low as 400°C. However, due to the solubility limitation of boron compounds, multiple impregnations are required to prepare high-load catalysts. Therefore, the development of supported catalysts that are easy for large-scale production and have high propane oxidative dehydrogenation activity and high propylene selectivity at low temperatures (<400°C) still faces great challenges. Summary of the invention

[0007] Technical problem to be solved: In order to overcome the deficiencies in the prior art, the present invention provides a vanadium-supported alumina catalyst and its preparation method and application. The catalyst has a certain catalytic efficiency for propane oxidative dehydrogenation and can be used for high-selective production of propylene by propane oxidative dehydrogenation at a relatively low temperature (170°C-200°C).

[0008] Technical solution: A method for preparing a vanadium-loaded alumina catalyst comprises the following steps: (1) mixing ammonium metavanadate and hydroxyalumina and adding them into a ball mill, wherein the molar ratio of ammonium metavanadate, hydroxyalumina and water is 1:(2-6):(44-133), adding grinding balls and deionized water, wherein the volume ratio of water to the volume of grinding balls is 1:(2-3), and sealing the ball mill; (2) fixing the ball mill in a ball mill and grinding for 10-15 hours; (3) taking out the obtained material and freeze-drying it; (4) removing moisture from the freeze-dried material and calcining it in an air atmosphere; and (5) tableting, crushing and sieving the solid product after calcination to obtain a catalyst.

[0009] Preferably, in step (1), the molar ratio of ammonium metavanadate, aluminum oxyhydroxide and water is 1:4:88, and the volume ratio of water to the volume of grinding balls is 1:2.

[0010] Preferably, the grinding speed of the ball mill in step (2) is 400 r / min.

[0011] Preferably, the drying temperature in step (3) is -60°C and the drying time is 12-15 hours.

[0012] Preferably, the calcination step in step (4) is to first increase the temperature to 300°C at 2°C / min and calcine for 2h, then naturally cool down to 100°C, and finally increase the temperature to 450°C at 5°C / min and calcine for 4h.

[0013] Preferably, the tabletting pressure in step (5) is 8-12 MPa; the sieving is performed using 40-mesh and 60-mesh sieves and a sample receiving sieve and bottom, and the catalyst particles of 40-60 mesh are sieved.

[0014] The vanadium-loaded alumina catalyst prepared by the above method.

[0015] The vanadium-supported alumina catalyst is used in catalytic dehydrogenation of propane to produce propylene at low temperature.

[0016] The specific application scheme is as follows: under normal pressure, the reaction temperature is 170-200°C, the feed space velocity of propane is 8400-10000mL / (g·h), the mixed gas composition before the reaction is propane, oxygen and nitrogen, the C3H8 concentration is 5%-6%, C3H8:O2=1:2-1:5, and the balance gas is supplemented by nitrogen.

[0017] The above-mentioned catalyst is loaded with high-temperature resistant quartz wool as a fixed bed layer, and the catalyst loading amount is 100-300 mg; the loaded catalyst is pretreated and activated under the conditions of nitrogen passing through at room temperature with a flow rate of 20-35 mL / min and heating at a heating rate not higher than 10°C / min, and the temperature is stabilized at 170°C for not less than 20 minutes.

[0018] Beneficial effects: the preparation process of the present invention only uses ammonium metavanadate and aluminum hydroxide, which greatly reduces the cost price and can be prepared in large quantities; at the same time, the reduction in raw material cost does not affect the catalyst performance, and propane oxidative dehydrogenation is carried out at a relatively low temperature (170°C-200°C) to produce propylene with high selectivity, and the ODHP reaction is carried out in the reaction temperature range, without the generation of by-products such as methane, ethane, and ethylene, thereby avoiding subsequent process operations and costs such as gas separation and purification; the catalyst preparation conditions are simple and the cost is low, the production raw materials are simple and easy to obtain, and large-scale production can be carried out. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Raman graphs of V / Al2O3 catalyst samples prepared in Examples 1-1, 1-2, 1-3, 1-4, and 1-5.

[0020] Figure 2 For example 1-3V / Al2O 3(1:4) Scanning electron microscopy (SEM).

[0021] Figure 3 This is the scanning electron microscopy (SEM) of Comparative Example 1-1V.

[0022] Figure 4 FTIR graphs of V / Al2O3 catalyst samples prepared in Examples 1-1, 1-2, 1-3, 1-4, and 1-5. DETAILED DESCRIPTION

[0023] The technical solution of the present invention will be described in detail below through specific embodiments, but it should be clearly stated that these embodiments are for illustration and are not to be construed as limiting the scope of the present invention.

[0024] Example 1

[0025] This embodiment provides a V / Al2O catalyst for low-temperature propane oxidative dehydrogenation to propylene. 3(1:2) A method for preparing a catalyst, which is prepared by the following method:

[0026] (1) Take 2.9250 g NH4VO3 and 3 g AlOOH, add 20 mL deionized water and 40 mL grinding balls (5 mm), and seal the ball mill;

[0027] (2) The ball mill was fixed on a planetary ball mill and ground at 400 r / min for 10 h;

[0028] (3) The obtained solid-liquid mixture solution is taken out and placed in a freeze dryer for drying at a temperature of -60°C for 12-15 hours.

[0029] (4) The solid product is calcined in an air atmosphere to obtain a finished product. The calcination steps are as follows: first, the temperature is increased to 300° C. at 2° C. / min and calcined for 2 h, then the temperature is slowly decreased to 100° C., and finally, the temperature is increased to 450° C. at 5° C. / min and calcined for 4 h.

[0030] Example 2

[0031] This embodiment provides a V / Al2O catalyst for low-temperature propane oxidative dehydrogenation to propylene. 3(1:3) A method for preparing a catalyst, which is prepared by the following method:

[0032] (1) Take 1.9500 g NH4VO3 and 3 g AlOOH, add 20 mL deionized water and 40 mL grinding balls (5 mm), and seal the ball mill;

[0033] (2) The ball mill was fixed on a planetary ball mill and ground at 400 r / min for 10 h;

[0034] (3) The obtained solid-liquid mixture solution is taken out and placed in a freeze dryer for drying at a temperature of -60°C for 12-15 hours.

[0035] (4) The solid product is calcined in an air atmosphere to obtain a finished product. The calcination steps are as follows: first, the temperature is increased to 300° C. at 2° C. / min and calcined for 2 h, then the temperature is slowly decreased to 100° C., and finally, the temperature is increased to 450° C. at 5° C. / min and calcined for 4 h.

[0036] Example 3

[0037] This embodiment provides a V / Al2O catalyst for low-temperature propane oxidative dehydrogenation to propylene. 3(1:4) A method for preparing a catalyst, which is prepared by the following method:

[0038] (1) Take 1.4625 g NH4VO3 and 3 g AlOOH, add 20 mL deionized water and 40 mL grinding balls (5 mm), and seal the ball mill;

[0039] (2) The ball mill was fixed on a planetary ball mill and ground at 400 r / min for 10 h;

[0040] (3) The obtained solid-liquid mixture solution is taken out and placed in a freeze dryer for drying at a temperature of -60°C for 12-15 hours.

[0041] (4) The solid product is calcined in an air atmosphere to obtain a finished product. The calcination steps are as follows: first, the temperature is increased to 300° C. at 2° C. / min and calcined for 2 h, then the temperature is slowly decreased to 100° C., and finally, the temperature is increased to 450° C. at 5° C. / min and calcined for 4 h.

[0042] Example 4

[0043] This embodiment provides a V / Al2O catalyst for low-temperature propane oxidative dehydrogenation to propylene. 3(1:5) A method for preparing a catalyst, which is prepared by the following method:

[0044] (1) Take 1.1700 g NH4VO3 and 3 g AlOOH, add 20 mL deionized water and 40 mL grinding balls (5 mm), and seal the ball mill;

[0045] (2) The ball mill was fixed on a planetary ball mill and ground at 400 r / min for 10 h;

[0046] (3) The obtained solid-liquid mixture solution is taken out and placed in a freeze dryer for drying at a temperature of -60°C for 12-15 hours.

[0047] (4) The solid product is calcined in an air atmosphere to obtain a finished product. The calcination steps are as follows: first, the temperature is increased to 300° C. at 2° C. / min and calcined for 2 h, then the temperature is slowly decreased to 100° C., and finally, the temperature is increased to 450° C. at 5° C. / min and calcined for 4 h.

[0048] Example 5

[0049] This embodiment provides a V / Al2O catalyst for low-temperature propane oxidative dehydrogenation to propylene. 3(1:6) A method for preparing a catalyst, which is prepared by the following method:

[0050] (1) Take 0.9750 g NH4VO3 and 3 g AlOOH, add 20 mL deionized water and 40 mL grinding balls (5 mm), and seal the ball mill;

[0051] (2) The ball mill was fixed on a planetary ball mill and ground at 400 r / min for 10 h;

[0052] (3) The obtained solid-liquid mixture solution is taken out and placed in a freeze dryer for drying at a temperature of -60°C for 12-15 hours.

[0053] (4) The solid product is calcined in an air atmosphere to obtain a finished product. The calcination steps are as follows: first, the temperature is increased to 300° C. at 2° C. / min and calcined for 2 h, then the temperature is slowly decreased to 100° C., and finally, the temperature is increased to 450° C. at 5° C. / min and calcined for 4 h.

[0054] Comparative Example 1

[0055] This embodiment provides a method for preparing a V catalyst for low-temperature propane oxidative dehydrogenation to propylene catalyst, which is prepared by the following method:

[0056] (5) Take 3 g NH4VO3, add 20 mL deionized water and 40 mL grinding balls, and seal the ball mill;

[0057] (6) The ball mill was fixed on a planetary ball mill and ground at 400 r / min for 10 h;

[0058] (7) The obtained solid-liquid mixture solution is taken out and placed in a freeze dryer for drying at a temperature of -60°C for 12-15 hours.

[0059] (8) The solid product was calcined in an air atmosphere to obtain a finished product. The calcination steps were as follows: first, the temperature was raised to 300° C. at 2° C. / min and calcined for 2 h, then the temperature was slowly lowered to 100° C., and finally, the temperature was raised to 450° C. at 5° C. / min and calcined for 4 h.

[0060] Table 1 Catalyst activity evaluation results

[0061]

[0062] As can be seen from the table, the catalyst in Example 3 has the highest propylene selectivity and moderate propane conversion, indicating that the preferred catalyst in the present invention is V / Al2O 3(1:4) , which has a good ability to catalyze propane oxidative dehydrogenation to produce propylene at low temperature. Therefore, Example 4 provides a low-temperature and highly selective thermal catalyst.

[0063] The above are only preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the structure of the present invention, which will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A method for preparing a vanadium-supported alumina catalyst, characterized in that: The method comprises the following steps: (1) mixing ammonium metavanadate and aluminum hydroxide and adding them into a ball mill, wherein the molar ratio of ammonium metavanadate, aluminum hydroxide and water is 1:(2-6):(44-133), adding grinding balls and deionized water, wherein the volume ratio of water to the volume of grinding balls is 1:(2-3), and sealing the ball mill; (2) fixing the ball mill in a ball mill and grinding for 10-15 hours; (3) taking out the obtained material and freeze-drying it; (4) removing moisture from the freeze-dried material and calcining it in an air atmosphere; and (5) tableting, crushing and sieving the solid product after calcination to obtain a catalyst.

2. The method for preparing the vanadium-supported alumina catalyst according to claim 1, characterized in that: In step (1), the molar ratio of ammonium metavanadate, aluminum hydroxide and water is 1:4:88, and the volume ratio of water to the volume of grinding balls is 1:

2.

3. The method for preparing the vanadium-supported alumina catalyst according to claim 1, characterized in that: The grinding speed of the ball mill in step (2) is 400 r / min.

4. The method for preparing the vanadium-supported alumina catalyst according to claim 1, characterized in that: The drying temperature in step (3) is -60°C and the drying time is 12-15 hours.

5. The method for preparing the vanadium-supported alumina catalyst according to claim 1, characterized in that: The calcination step in step (4) is to first increase the temperature to 300°C at 2°C / min and calcine for 2h, then naturally cool to 100°C, and finally increase the temperature to 450°C at 5°C / min and calcine for 4h.

6. The method for preparing the vanadium-supported alumina catalyst according to claim 1, characterized in that: The tabletting pressure in step (5) is 8-12 MPa; the sieving is performed using 40 mesh and 60 mesh as well as a sample receiving sieve and a bottom, and the catalyst particles of 40-60 mesh are sieved.

7. The vanadium-supported alumina catalyst prepared by the method according to any one of claims 1 to 6.

8. Use of the vanadium-supported alumina catalyst according to claim 7 in catalytic dehydrogenation of propane to produce propylene at low temperature.

9. The use according to claim 8, characterized in that: Under normal pressure, the reaction temperature is 170-200°C, the feed space velocity of propane is 8400-10000mL / (g·h), the mixed gas composition before the reaction is propane, oxygen and nitrogen, the C3H8 concentration is 5%-6%, C3H8:O2=1:2-1:5, and the balance gas is supplemented by nitrogen.

10. The use according to claim 9, characterized in that: The catalyst is loaded with high temperature resistant quartz wool as a fixed bed layer, and the catalyst loading amount is 100-300 mg; the loaded catalyst is pretreated and activated at room temperature, with nitrogen introduced at a flow rate of 20-35 mL / min and heated at a heating rate of no more than 10°C / min, and the temperature is stabilized at 170°C for no less than 20 minutes.

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