Carbide-promoted noble metal-based catalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of propylene preparation through propane dehydrogenation, in particular to a carbide-promoted noble metal-based catalyst as well as a preparation method and application thereof. The catalyst comprises a carrier, an active metal and an active auxiliary agent, the carrier is one of a molecular sieve, silicon dioxide and aluminum oxide, the active metal is one of Pt, Rh and Ru, and the active auxiliary agent is one of alpha-WC, beta-W2C, alpha-MoC and beta-Mo2C. Compared with a traditional catalyst, the obtained carbide-promoted noble metal-based catalyst has higher propylene generation rate and selectivity in a propylene preparation reaction through propane dehydrogenation, and shows excellent long-acting stability and cyclic regeneration capacity of the catalyst.

Description

Technical Field

[0001] The present invention relates to the technical field of producing propylene by dehydrogenating propane, and in particular to a carbide-promoted noble metal-based catalyst and a preparation method and application thereof. Background Art

[0002] Propane dehydrogenation is an important industrial chemical reaction, which is often used to convert propane into propylene. Since propylene is an important raw material for the production of chemicals such as polypropylene, propylene oxide, acrylonitrile, and acrolein, this reaction has received widespread attention in recent years. Traditional propylene production processes mainly include catalytic cracking and steam cracking of petroleum naphtha and light diesel, as well as coal-based methanol to olefins processes. However, with the rapid consumption of traditional fossil energy, traditional propylene production can no longer meet the growing demand. Therefore, the development of efficient propylene production technology has become scientifically and economically critical. Propane dehydrogenation catalysts widely used in industry mainly include Pt-based and chromium oxide-based catalysts. Pt-based catalysts are expensive, while chromium oxide-based catalysts are highly toxic. Therefore, it is of great significance to develop low-cost, non-toxic alternative catalysts.

[0003] At present, the leading processes for propane dehydrogenation in industry are Oleflex and Catofin. The catalysts used in these two processes are PtSn / Al2O3 and Cr2O3 / Al2O3 catalysts respectively. Pt is a precious metal with excellent propane activation performance due to its ability to catalytically activate CH bonds. Although propane dehydrogenation is limited by thermodynamic equilibrium, high temperature conditions help to promote the reaction, but at high temperatures, Pt-based catalysts are prone to carbon deposition and sintering, resulting in irreversible deactivation of the catalyst. At present, the modification of Pt-based catalysts, on the one hand, by adding a second additive, such as Sn, Zn, Cu, etc., to adjust the geometric structure of Pt, improve the dispersion of Pt and modulate the electronic state, and inhibit structure-sensitive side reactions; on the other hand, by adjusting the carrier (such as alumina, ceria, silica, molecular sieves), the metal carrier effect is used to improve the performance of Pt-based catalysts. With the construction and commissioning of new propane dehydrogenation units, the capacity of propane dehydrogenation is expanding rapidly. However, there are still some problems in the development of catalysts for the preparation of propylene, such as relatively low propane conversion, poor stability, low propylene selectivity, etc. Therefore, it is of great scientific significance and practical value to develop new and effective strategies to find propane dehydrogenation catalysts with high catalytic activity and stability. Summary of the invention

[0004] In view of the problems existing in the above-mentioned prior art, the present invention innovatively breaks through the traditional research ideas of relying on traditional oxides or molecular sieve carriers to disperse precious metals, and utilizes the catalytic properties of transition metal carbides similar to precious metals and the strong interaction between them and active metals to effectively promote the dispersion and anchoring of precious metal Pt and inhibit carbon deposition, thereby constructing a new type of efficient carbide-promoted precious metal-based catalyst and its preparation method and application in the propane dehydrogenation to propylene reaction. The catalyst exhibits excellent catalytic activity in the process of propane dehydrogenation to propylene, has the characteristics of high conversion rate and high selectivity, and shows good industrial application potential. In addition, its preparation process is simple, the production cost is low, and it is environmentally friendly, with obvious social and economic benefits.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] On the one hand, the present invention provides a carbide-promoted precious metal-based catalyst, which includes a carrier, an active metal and an activating agent. The carrier is one of molecular sieves, silica, and alumina, the active metal is one of Pt, Rh, and Ru, and the activating agent is one of α-WC, β-W2C, α-MoC, and β-Mo2C.

[0007] Preferably, the loading amount of the active metal is 0.01% to 3%, more preferably 0.5wt%, and the mass percentage of the active auxiliary agent is 1wt% to 30wt%, more preferably 10wt%.

[0008] Preferably, the molecular sieve includes β molecular sieve, Y molecular sieve, TS-1 molecular sieve or S-1 molecular sieve, and β molecular sieve is more preferred.

[0009] Another aspect of the present invention provides a method for preparing the above catalyst, the preparation method comprising the following steps:

[0010] 1) Mechanically grinding and mixing the active agent precursor and the carrier, immersing the mixture in a metal precursor salt solution, standing at room temperature, and freeze-drying to obtain a catalyst precursor;

[0011] 2) The catalyst precursor obtained in step 1) is subjected to programmed temperature carbonization in a carbon source gas atmosphere to obtain the catalyst.

[0012] Preferably, in step 1), the active agent precursor is selected from one of tungsten trioxide and molybdenum trioxide;

[0013] The active agent precursor accounts for 1% to 30% of the total mass of the active agent precursor and the carrier;

[0014] The grinding time is 20 to 30 minutes.

[0015] Preferably, in step 1), the metal precursor salt is selected from one of potassium chloroplatinite, sodium chloroplatinite, platinum dichloride, tetraammineplatinum nitrate, chloroplatinic acid, rhodium trichloride hydrate, and ruthenium trichloride hydrate.

[0016] Preferably, in step 1), the carrier is subjected to a drying pretreatment, the drying pretreatment temperature is 100 to 150° C., and the drying pretreatment time is 1 to 12 hours.

[0017] Preferably, in step 1), the impregnation is performed by equal volume impregnation or excess impregnation.

[0018] Preferably, in step 1), the freeze-drying temperature is -50 to -30°C, and the freeze-drying time is 6 to 10 hours.

[0019] Preferably, in step 2), the carbon source gas is a mixture of methane and hydrogen, wherein the volume percentage of methane is 15% to 20%;

[0020] The carbonization conditions are: firstly, heating to 300-500°C at 5°C / min, and then heating to 700-900°C at 1°C / min for 1-2h.

[0021] The present invention also provides an application of the catalyst in the reaction of producing propylene by dehydrogenating propane.

[0022] Preferably, the activation conditions of the catalyst are: the activation atmosphere is a mixture of methane and hydrogen, the volume percentage of methane is 15-20%; the activation temperature is 500-700°C, the activation time is 1-6h, and the heating rate is 5-20°C / min.

[0023] Preferably, the reaction conditions are: reaction temperature is 500-600° C., raw gas volume space velocity is 5000-120000 mL / g / h, and the reaction is carried out under normal pressure.

[0024] The above-obtained catalytic material was tableted and sieved to obtain a powder with a particle size of 40 to 60 mesh, and the performance was evaluated through the following process: The activity evaluation was carried out on a homemade atmospheric pressure micro-fixed bed reactor, and the evaluation device was mainly composed of three parts: a reaction gas simulation system, a reaction system, and a detection system. The quartz tube reactor in the reaction system is 40 mm long and has an inner diameter of 3 mm. The amount of the activity test sample depends on the specific situation. The upper and lower ends of the catalyst bed are filled with high-temperature cotton and quartz sand to reduce the dead volume of the reactor. The reactor is heated by a program-controlled temperature tube electric furnace with a temperature control accuracy of ±0.1 mL / min. At the beginning of the experiment, high-purity argon gas was introduced to exhaust the air, and then switched to a CH4 / H2 mixed gas for activation treatment, and then pretreated in a pure hydrogen atmosphere for 1 h. After dropping to the target temperature, it was switched to the reaction gas for propane dehydrogenation performance evaluation.

[0025] The beneficial effects of the present invention are:

[0026] 1) The present invention provides an effective preparation strategy for carbide-promoted precious metal-based catalysts, which effectively improves the utilization efficiency of active metals. The preparation method is simple in process, widely applicable, low in cost, environmentally friendly, and easy to scale up for production.

[0027] 2) The introduction of the carbide active agent of the present invention effectively enhances the interaction between the metal and the carrier, thereby promoting the dispersion and stabilization of the active metal, exposing more active sites, significantly improving the propane activation rate and inhibiting the deep dehydrogenation step; at the same time, the introduction of the carbide significantly modulates the acid center distribution characteristics of the catalyst carrier, reduces the strong B acid sites, reduces the negative effect of acid catalysis, and effectively inhibits the occurrence of side reactions, thereby improving the selectivity of propylene and reducing the amount of carbon deposition.

[0028] 3) The carbide-promoted noble metal-based catalyst of the present invention has a higher propylene production rate and selectivity in the propane dehydrogenation to propylene reaction than the conventional catalyst, and exhibits excellent catalyst long-term stability and recycling regeneration ability. The best activity is the carbide content of 10wt% and the Pt content of 0.5wt%. The propane conversion rate at 550℃ is 33.1%, the propylene selectivity is 95.4%, and the propylene production rate is 16.936mol C3H6 ·g Pt -1 ·h -1 , showed excellent stability in the 30h long-term test, with an inactivation rate of 0.02315h -1 , see Table 1 for details.

[0029] Table 1 Comparison of the activity of the catalyst of the present invention and the catalysts currently available in the literature in the dehydrogenation of propane to propylene

[0030]

[0031] BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The XRD spectra of the catalysts prepared in Example 1 and Comparative Example 1 are shown in FIG.

[0033] Figure 2 HAADF-STEM images of the catalysts prepared in Example 1 and Comparative Example 1, (a) to (c) are for Example 1, wherein (a) is 100 nm, (b) is 20 nm, and (c) is 5 nm, (d) to (f) are for Comparative Example 1, wherein (d) is 100 nm, (e) is 20 nm, and (f) is 5 nm;

[0034] Figure 3HAADF-STEM images and elemental analysis of the catalyst prepared in Example 1, (a) is a HAADF-STEM image, (b) to (f) are elemental analysis diagrams, where (b) is Si, (c) is Al, (d) is W, (e) is Pt, and (f) is W+Pt;

[0035] Figure 4 NH3-TPD comparison chart of the catalysts prepared in Example 1 and Comparative Example 1;

[0036] Figure 5 The following is a comparison chart of the CO adsorption infrared spectra of the catalysts prepared in Example 1 and Comparative Example 1;

[0037] Figure 6 This is a comparison chart of the propane conversion rate and propylene selectivity at 550°C of the catalysts prepared in Example 1 and Comparative Example 1;

[0038] Figure 7 This is a comparison chart of the 550°C cyclic regeneration activity of the catalyst prepared in Example 1 measured during the 30h flow time of each reaction cycle;

[0039] Figure 8 It is a comparison chart of O2-TPO and carbon deposit amount of the catalysts prepared in Example 1 and Comparative Example 1 after stability test at 550°C. DETAILED DESCRIPTION

[0040] The following non-limiting embodiments may enable a person skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0041] Unless otherwise specified, the materials used in the embodiments of the present invention can be obtained through commercial channels or prepared according to conventional methods well known to those skilled in the art.

[0042] Example 1

[0043] Catalyst preparation

[0044] 1) Weigh 0.5g of β-75 and 0.05g of tungsten trioxide, grind mechanically for 20min, mix, weigh 0.5g of the above mixture and mix with 367μL of 0.035mol / L chloroplatinic acid solution, stir evenly, let stand for 24h, and freeze-dry in a freeze drying oven at -50℃ for 6h to obtain a catalyst precursor;

[0045] 2) The catalyst precursor (40-60 mesh) was placed in a micro fixed bed reactor, and in an atmosphere of a CH4 and H2 mixed gas (flow rate: 150 mL / min) with a CH4 volume percentage of 20%, the temperature was increased from room temperature to 500°C at a heating rate of 5°C / min, and then increased to 900°C at a heating rate of 1°C / min, and kept warm for 2 hours. After the reaction was completed, the quartz reaction tube was cooled to room temperature and the reaction atmosphere was switched to an O2 and Ar mixed gas (flow rate: 15 ml / min) with a volume percentage of 1%. After passivation for 6-8 hours, the catalyst was taken out and recorded as 0.5wt% Pt-10wt% WC / β-75.

[0046] Catalyst activity evaluation

[0047] The propane dehydrogenation reaction to propylene was carried out in a quartz tube fixed bed reactor with an inner diameter of 3 mm. The gas flow rates of each gas required for the experiment were adjusted and controlled by a mass flow meter, and mixed and then flowed into the reactor. 50 mg of the catalyst 0.5 wt% Pt-10 wt% WC / β-75 obtained in Example 1 and an appropriate amount of quartz sand were weighed and evenly placed in a quartz tube reactor, and the catalyst was activated at 700° C. for 3 h with a CH4 and H2 mixed gas with a CH4 volume percentage of 15%, followed by pretreatment in a pure hydrogen atmosphere for 1 h, and then the performance was evaluated under the following reaction conditions, the total reaction gas flow rate was 30 ml / min, of which the propane flow rate was 5 ml / min, the H2 flow rate was 5 ml / min, and the rest was the Ar gas flow rate, and the reaction was carried out under the conditions of 550° C., normal pressure, and a gas volume space velocity of 36000 mL / g / h, and the initial propane conversion rate was measured to be 33.1%, and the selectivity was 95.4%.

[0048] Example 2

[0049] The preparation method of the catalyst in this embodiment is similar to that in embodiment 1, except that the carrier is β-150, and the prepared catalyst is recorded as 0.5wt% Pt-10wt% WC / β-150; the performance thereof is evaluated, and the initial propane conversion rate is measured to be 27.0%, and the selectivity is 95.5%.

[0050] Example 3

[0051] The preparation method of the catalyst in this example is similar to that in Example 1, except that the carrier is a dealuminated β molecular sieve, and the prepared catalyst is recorded as 0.5wt%Pt-10wt%WC / β DEL ; Its performance was evaluated and the initial propane conversion was found to be 35.1% and the selectivity was 81.8%.

[0052] Example 4

[0053] The preparation method of the catalyst in this embodiment is similar to that in Example 1, except that the carrier is S-1 molecular sieve, and the prepared catalyst is recorded as 0.5wt% Pt-10wt% WC / S-1; the performance thereof is evaluated, and the initial propane conversion rate is measured to be 28.4%, and the selectivity is 72.7%.

[0054] Example 5

[0055] The preparation method of the catalyst in this embodiment is similar to that in Example 1, except that the carrier is meso-Al2O3, and the prepared catalyst is recorded as 0.5wt% Pt-10wt% WC / meso-Al2O3; the performance thereof is evaluated, and the initial propane conversion rate is measured to be 19.4%, and the selectivity is 95.6%.

[0056] Example 6

[0057] The preparation method of the catalyst in this embodiment is similar to that in Example 1, except that: the active agent precursor is 0.025 g of tungsten trioxide; the carbonization conditions are different, firstly the temperature is increased from room temperature to 300°C at a heating rate of 5°C / min, then the temperature is increased to 700°C at a heating rate of 1°C / min, and kept warm for 1 hour. The prepared catalyst is recorded as 0.5wt% Pt-5wt% W2C / β-75, and its performance is evaluated. The initial propane conversion rate is measured to be 53.8%, and the selectivity is 84.5%.

[0058] Example 7

[0059] The preparation method of the catalyst in this embodiment is similar to that in Example 1, except that the active agent precursor is 0.025 g of tungsten trioxide, and the prepared catalyst is recorded as 0.5wt% Pt-5wt% WC / β-75; the performance thereof is evaluated, and the initial propane conversion rate is measured to be 24.5%, and the selectivity is 95.8%.

[0060] Example 8

[0061] The preparation method of the catalyst in this embodiment is similar to that in Example 1, except that the active agent precursor is 0.075 g of tungsten trioxide, and the prepared catalyst is recorded as 0.5wt% Pt-15wt% WC / β-75; the performance thereof is evaluated, and the initial propane conversion rate is measured to be 27.5%, and the selectivity is 93.5%.

[0062] Example 9

[0063] The preparation method of the catalyst in this embodiment is similar to that in Example 1, except that the active agent precursor is 0.10 g of tungsten trioxide, and the prepared catalyst is recorded as 0.5wt% Pt-20wt% WC / β-75; the performance thereof is evaluated, and the initial propane conversion rate is measured to be 30.4%, and the selectivity is 89.1%.

[0064] Example 10

[0065] The preparation method of the catalyst in this embodiment is similar to that in Example 1, except that the active agent precursor is 0.15 g of tungsten trioxide, and the prepared catalyst is recorded as 0.5wt% Pt-30wt% WC / β-75; the performance thereof is evaluated, and the initial propane conversion rate is measured to be 27.7%, and the selectivity is 96.2%.

[0066] Embodiment 11

[0067] The preparation method of the catalyst in this embodiment is similar to that in Example 1, except that the metal precursor salt solution is a chloroplatinic acid solution (concentration: 0.023 mol / L, volume: 340 μL), and the prepared catalyst is recorded as 0.3wt% Pt-10wt% WC / β-75; its performance was evaluated, and the initial propane conversion rate was measured to be 30.8%, and the selectivity was 94.6%.

[0068] Example 12

[0069] The preparation method of the catalyst in this embodiment is similar to that in Example 1, except that the metal precursor salt solution is a chloroplatinic acid solution (concentration: 0.008 mol / L, volume: 313 μL), and the prepared catalyst is recorded as 0.1wt% Pt-10wt% WC / β-75; its performance was evaluated, and the initial propane conversion rate was measured to be 22.7%, and the selectivity was 93.9%.

[0070] Embodiment 13

[0071] The preparation method of the catalyst in this embodiment is similar to that in Example 2, except that the metal precursor salt solution is a rhodium trichloride hydrate solution (concentration: 0.068 mol / L, volume: 361 μL), and the prepared catalyst is recorded as 0.5wt% Rh-10wt% WC / β-150; its performance was evaluated, and the initial propane conversion rate was measured to be 23.1%, and the selectivity was 77.5%.

[0072] Embodiment 14

[0073] The preparation method of the catalyst in this embodiment is similar to that in Example 2, except that the metal precursor salt solution is a ruthenium trichloride hydrate solution (concentration: 0.069 mol / L, volume: 362 μL), and the prepared catalyst is recorded as 0.5wt% Ru-10wt% WC / β-150; its performance was evaluated, and the initial propane conversion rate was measured to be 24.8%, and the selectivity was 85.7%.

[0074] Embodiment 15

[0075] Catalyst preparation

[0076] 1) Weigh 0.5 g of dealuminated β and 0.05 g of molybdenum trioxide, grind mechanically for 20 min, mix, weigh 0.5 g of the above mixture and mix with chloroplatinic acid solution (concentration: 0.028 mol / L, volume: 467 μL), stir evenly, let stand for 24 h, and freeze-dry in a freeze drying oven at -50 ° C for 6 h to obtain a catalyst precursor;

[0077] 2) The catalyst precursor (40-60 mesh) was placed in a micro fixed bed reactor, and in a 20% CH4 / H2 atmosphere (150 mL / min), the temperature was raised from room temperature to 300°C at a rate of 5°C / min, and then raised to 700°C at a rate of 1°C / min, and kept warm for 2 hours. After the reaction was completed, the quartz reaction tube was cooled to room temperature and the reaction atmosphere was switched to a mixture of 1% O2 and Ar (flow rate: 15 ml / min). After passivation for 6-8 hours, the catalyst was taken out and recorded as 0.5wt% Pt-10wt% Mo2C / β DEL .

[0078] Catalyst activity evaluation

[0079] The propane dehydrogenation reaction to propylene was carried out in a quartz tube fixed bed reactor with an inner diameter of 3 mm. The gas flow rates required for the experiment were adjusted and controlled by mass flow meters, and the gases were mixed evenly before flowing into the reactor. Weigh 50 mg of 0.5 wt% Pt-10 wt% Mo2C / β DEL and an appropriate amount of quartz sand are evenly placed in a quartz tube reactor, the catalyst is pretreated with a CH4 and H2 mixed gas with a CH4 volume percentage of 15% at 700°C for 3h, then pretreated in a pure hydrogen atmosphere for 1h, and then the performance is evaluated under the following reaction conditions: the total reaction gas flow rate is 30ml / min, of which the propane flow rate is 5ml / min, the H2 flow rate is 5ml / min, and the rest is Ar gas flow rate. The reaction is carried out at 550°C, normal pressure, and a gas volume space velocity of 36000mL / g / h. The measured initial propane conversion rate is 30.0%, and the selectivity is 85.9%.

[0080] Example 16

[0081] The preparation method of the catalyst in this embodiment is similar to that in Example 15, except that: the carrier is TS-1; the metal precursor salt solution is chloroplatinic acid solution (concentration: 0.023 mol / L, volume: 340 μL), and a 0.3wt% Pt-10wt% Mo2C / TS-1 catalyst is prepared; its performance is evaluated, and the initial propane conversion rate is measured to be 31.6%, and the selectivity is 76.1%.

[0082] Embodiment 17

[0083] The preparation method of the catalyst in this embodiment is similar to that in Example 15, except that the carrier is Y molecular sieve, the metal precursor salt solution is chloroplatinic acid solution (concentration: 0.023 mol / L, volume: 340 μL), and the prepared catalyst is recorded as 0.3wt% Pt-10wt% Mo2C / Y; its performance was evaluated, and the initial propane conversion rate was measured to be 19.6%, and the selectivity was 95.8%.

[0084] Embodiment 18

[0085] The preparation method of the catalyst in this example is similar to that in Example 15, except that the metal precursor salt solution is a chloroplatinic acid solution (concentration: 0.023 mol / L, volume: 340 μL), and the prepared catalyst is recorded as 0.3 wt% Pt-10 wt% Mo2C / β DEL ; Its performance was evaluated and the initial conversion rate of propane was measured to be 27.3% and the selectivity was 82.7%.

[0086] Embodiment 19

[0087] The preparation method of the catalyst in this example is similar to that in Example 15, except that the metal precursor salt solution is a chloroplatinic acid solution (concentration: 0.008 mol / L, volume: 313 μL), and the prepared catalyst is recorded as 0.1 wt% Pt-10 wt% Mo2C / β DEL ; Its performance was evaluated and the initial propane conversion was found to be 20.5% and the selectivity was 85.9%.

[0088] Embodiment 20

[0089] The preparation method of the catalyst in this embodiment is similar to that in Example 15, except that the metal precursor salt solution is a rhodium trichloride hydrate solution (concentration: 0.068 mol / L, volume: 361 μL), and the prepared catalyst is recorded as 0.5 wt% Rh-10 wt% Mo2C / β DEL ; Its performance was evaluated and the initial conversion rate of propane was measured to be 22.6% and the selectivity was 82.8%.

[0090] Embodiment 21

[0091] The preparation method of the catalyst in this example is similar to that in Example 15, except that the metal precursor salt solution is a ruthenium trichloride hydrate solution (concentration: 0.069 mol / L, volume: 362 μL), and the prepared catalyst is recorded as 0.5 wt% Ru-10 wt% Mo2C / β DEL ; Its performance was evaluated at 550℃, normal pressure, and a weight hourly space velocity of 11.8h -1 The reaction was carried out under the conditions of , and the initial propane conversion rate was measured to be 25.8% and the selectivity was 80.5%.

[0092] Comparative Example 1

[0093] Catalyst preparation

[0094] 1) Weigh 0.5 g of β-75 and mix with chloroplatinic acid solution (concentration: 0.035 mol / L, volume 367 μL), stir evenly, let stand for 24 h, and freeze-dry in a freeze drying oven at -50 ° C for 6 h to obtain a catalyst precursor;

[0095] 2) The catalyst precursor was calcined in a muffle furnace at 500° C. for 4 h to obtain a fresh catalyst.

[0096] Catalyst activity evaluation

[0097] The propane dehydrogenation reaction to propylene was carried out in a quartz tube fixed bed reactor with an inner diameter of 3mm. The gas flow rates of each gas required for the experiment were adjusted and controlled by a mass flowmeter, and flowed into the reactor after being mixed evenly. Weigh 50mg of 0.5wt% Pt / β-75 and an appropriate amount of quartz sand and place them evenly in a quartz tube reactor. The catalyst was pretreated with a H2 and Ar mixed gas with a H2 volume percentage of 15% at 500℃ for 2h, and then the performance was evaluated under the following reaction conditions. The total reaction gas flow rate was 30ml / min, of which the propane flow rate was 5ml / min, the H2 flow rate was 5ml / min, and the rest was the Ar gas flow rate. The reaction was carried out at 550℃, normal pressure, and a gas volume space velocity of 36000mL / g / h. The initial propane conversion rate was measured to be 21.9% and the selectivity was 70.8%.

[0098] Comparative Example 2

[0099] The preparation method of the catalyst in this example is similar to that of comparative example 1, except that the carrier is dealuminated β-catalyst. The performance of the catalyst is evaluated, and the initial conversion rate of propane is 15.3%, and the selectivity is 78.1%.

[0100] like Figure 1 As shown, by analyzing the sample through XRD, the characteristic peak of α-WC can be clearly observed, and the crystallinity of the β molecular sieve is not destroyed after the high-temperature carburizing process.

[0101] like Figure 2 As shown, it can be seen from the HAADF-STEM image and particle size analysis that the dispersion of Pt nanoparticles with the addition of α-WC additive on the carrier surface is significantly improved.

[0102] like Figure 3 As shown, it can be seen from HAADF-STEM and elemental analysis that Pt and W are highly dispersed on the surface of the molecular sieve, indicating that the introduction of α-WC species promotes the dispersion of Pt on the support surface.

[0103] like Figure 4 As shown, it can be seen from the NH3-TPD diagram that the introduction of tungsten carbide significantly modulates the acid center distribution characteristics of the catalyst carrier, reduces the acid sites of B acid and L acid, and reduces the negative effect of acid catalysis.

[0104] like Figure 5 As shown, it can be seen from the CO adsorption infrared spectrum that the CO adsorption peak has a red shift after adding tungsten carbide additive, indicating that the electron cloud density of Pt has increased.

[0105] like Figure 6 As shown in the figure, the comparison of propane conversion and propylene selectivity at 550°C shows that the introduction of tungsten carbide significantly improves the propane dehydrogenation activity and stability of the catalyst.

[0106] like Figure 7 As shown in the figure, through the comparison of the 550°C cyclic regeneration activity measured during the 30h flow time of each reaction cycle, it can be seen that the catalyst introduced with tungsten carbide additive exhibits good stability in both the dehydrogenation reaction and the regeneration cycle.

[0107] like Figure 8 As shown, through the comparison of O2-TPO and carbon deposition of the catalysts prepared in Example 1 and Comparative Example 1 after stability at 550°C, it can be seen that the carbon deposition of the catalyst introduced with tungsten carbide additive is significantly reduced.

[0108] The present invention provides a carbide-promoted noble metal-based catalyst and a preparation method thereof. The method has a simple process, wide universality, effectively improves the utilization efficiency of active metals, and is easy to scale up production. The present invention also discloses the application of the prepared carbide-promoted noble metal-based catalyst in the propane dehydrogenation to propylene reaction, and the results show that the catalyst has excellent propane dehydrogenation to propylene performance.

[0109] The above embodiments are only preferred embodiments of the present invention and are not intended to limit the implementation methods. The protection scope of the present invention shall be subject to the scope defined in the claims. Other different forms of changes or modifications may be made based on the above description. Obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A carbide-promoted noble metal-based catalyst, characterized in that: The catalyst comprises a carrier, an active metal and an active promoter, wherein the carrier is one of molecular sieve, silicon dioxide and alumina, the active metal is one of Pt, Rh and Ru, and the active promoter is one of α-WC, β-W2C, α-MoC and β-Mo2C.

2. The catalyst according to claim 1, characterized in that The loading amount of the active metal is 0.01 wt% to 3 wt%, and the mass percentage of the active auxiliary agent is 1 wt% to 30 wt%.

3. A method for preparing the catalyst according to any one of claims 1 to 2, characterized in that: The preparation method comprises the following steps: 1) Mechanically grinding and mixing the active agent precursor and the carrier, immersing the mixture in a metal precursor salt solution, standing at room temperature, and freeze-drying to obtain a catalyst precursor; 2) The catalyst precursor obtained in step 1) is subjected to programmed temperature carbonization in a carbon source gas atmosphere to obtain the catalyst.

4. The preparation method according to claim 3, characterized in that: In step 1), the active agent precursor is selected from one of tungsten trioxide and molybdenum trioxide; The active agent precursor accounts for 1% to 30% of the total mass of the active agent precursor and the carrier; The grinding time is 20 to 30 minutes.

5. The preparation method according to claim 3, characterized in that: In step 1), the metal precursor salt is selected from one of potassium chloroplatinite, sodium chloroplatinite, platinum dichloride, tetraammine platinum nitrate, chloroplatinic acid, rhodium trichloride hydrate, and ruthenium trichloride hydrate.

6. The preparation method according to claim 1, characterized in that: In step 2), the carbon source gas is a mixture of methane and hydrogen, wherein the volume percentage of methane is 15% to 20%; The carbonization conditions are: firstly, heating to 300-500°C at 5°C / min, and then heating to 700-900°C at 1°C / min for 1-2h.

7. Use of the catalyst according to any one of claims 1 to 2 or the catalyst prepared by the preparation method according to any one of claims 3 to 6 in the reaction of dehydrogenating propane to produce propylene.

8. The use according to claim 7, characterized in that: The activation conditions of the catalyst are as follows: the activation atmosphere is a mixture of methane and hydrogen, the volume percentage of methane is 15% to 20%; the activation temperature is 500 to 700° C., and the activation time is 1 to 6 hours.

9. The use according to claim 8, characterized in that The reaction conditions are as follows: the reaction temperature is 500-600° C., the raw gas volume space velocity is 5000-120000 mL / g / h, and the reaction is carried out under normal pressure.

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