A platinum-based methanol combustion catalyst with high thermal stability and a preparation method and application thereof

Abstract

The application discloses a high-thermal-stability platinum-based methanol combustion catalyst as well as a preparation method and application thereof. The catalyst is a noble metal Pt catalyst with a titanium-lanthanum-aluminum composite oxide TiLaAlOx as a carrier. The molar amount of Ti elements in the TiLaAlOx composite oxide carrier is 50-90% of the sum of the molar amounts of Ti, La and Al. The loading amount of Pt in the catalyst is 0.01-4 wt%. The catalyst prepared by the application has excellent thermal stability and activity. After high-temperature aging of the catalyst at 950 DEG C, the activity of the catalyst can still be maintained close to that of a fresh catalyst, and the catalyst overcomes the shortcoming that a traditional noble metal catalyst with titanium dioxide as a carrier is easy to sinter and deactivate under high-temperature conditions. The catalyst has simple preparation process, low cost, good catalytic activity for various low-carbon oxygen-containing organic waste gas, and great industrial application potential and value.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of new energy and energy-saving technology and catalytic combustion environmental protection, and particularly relates to a platinum-based methanol combustion catalyst with high thermal stability and a preparation method and application thereof. BACKGROUND

[0002] Green methanol with CO2, hydrogen and biomass as raw materials is a new carrier of (carbon, hydrogen) energy, which is liquid at room temperature and pressure, and is convenient to store, transport and use. Methanol has a wide source, a huge industrial scale and a sustainable development of the whole industry chain. The excellent environmental protection of methanol fuel is more eye-catching, and it is an ideal new clean and renewable fuel. Using methanol as fuel is more energy-saving, environmentally friendly and low-carbon.

[0003] However, direct combustion and thermal combustion of methanol are easy to cause NOx pollution, and catalytic combustion is a nitrogen-free combustion technology that is increasingly valued by scientists. However, high thermal stability of the catalyst in the high-temperature environment of the combustion reaction is an important index, so it is of great significance to develop high-temperature-resistant combustion catalysts under the double-carbon strategy. The existing patent CN112657528A discloses a preparation method of a methanol catalytic combustion composite catalyst, which adds high-temperature boron nitride, which is more conducive to the catalytic combustion reaction, improves the conversion rate of methanol, reduces by-products, and the temperature is as high as 800℃, but the preparation elements are more and the process is more complicated. Patent CN110075887A provides a preparation method of a palladium-supported catalyst for methanol catalytic combustion and its application. The palladium on the surface of the catalyst shows a high dispersion state, which can reduce the amount of palladium metal, but the catalytic activity is poor, and the minimum temperature for converting methanol into CO2 is 175℃. Patent CN110743545A discloses a noble metal catalyst with excellent hydrothermal stability and its preparation method and application. The carrier surface is loaded with an oxidation layer containing metal oxide AOx; the oxidation layer surface is loaded with an active layer containing noble metal active component N and metal oxide BOx; A and B are selected from at least one of Al, Ce, Mn, Cr, Zr and Sn, A and B are the same metal element; the active metal in the noble metal active component N is selected from at least one of Pd, Pt and Rh, and the catalyst is a monolithic catalyst, which breaks through the defects that the traditional combustion catalyst for catalyzing methane is easy to deactivate under water-containing and high-temperature conditions, but the maximum heat-resistant temperature is only 600℃. SUMMARY

[0004] In view of the problems of the current methanol combustion catalyst, such as low activity of activated carbon, poor thermal stability and complex preparation process, the present application provides a high-thermal-stability platinum-based methanol combustion catalyst with high catalytic activity, good thermal stability and simple process, a preparation method and application thereof.The catalyst of the present application takes TiO2 as the main carrier template, and a small amount of La and Al elements are doped in the TiO2 lattice, wherein Ti and La combine to form lanthanum aluminate with a melting point above 1500 DEG C, thereby providing high thermal stability for the catalyst, and the high specific surface area of Al2O3 disperses the lanthanum aluminate and noble metal, thereby providing highly dispersed noble metal Pt active sites for the catalyst.

[0005] The present application improves the heat resistance of the catalyst, improves the dispersion of the active component, increases the interaction between the active component and the carrier, and reduces the migration of the active component by regulating the chemical properties and surface structure of the catalyst carrier components.

[0006] The present application is realized by the following technical solutions:

[0007] A high-thermal-stability platinum-based methanol combustion catalyst, which takes titanium lanthanum aluminum composite oxide TiLaAlOx as the carrier, and has a noble metal active component Pt loaded on the carrier, wherein the loading amount of Pt is 0.01-4wt%, and is preferably 1-1.2wt%; in the titanium lanthanum aluminum composite oxide TiLaAlOx carrier, the molar amounts of Ti, La and Al are 50-90%, 5-25% and 5-25% of the total molar amount of Ti, La and Al, and are preferably 75-85%, 7.5-12.5% and 7.5-12.5%.

[0008] Further, the preparation method of the titanium lanthanum aluminum composite oxide TiLaAlOx carrier is as follows:

[0009] 1) La salt and aluminum salt are dissolved in water according to the molar ratio of La to Al, and tetrabutyl titanate solution diluted with C1-C4 alcohol solvent is added dropwise, and the pH is adjusted to 8.0-10.0 by adding alkali, and the mixture is stirred for 0.5-4 hours;

[0010] 2) then, the mixture is aged at room temperature for 10-15 hours, filtered, washed with deionized water and anhydrous ethanol for several times until the filtrate is neutral, dried, and calcined in air atmosphere to obtain TiLaAlOx composite oxide powder.

[0011] Further, in step 1), the lanthanum salt and the aluminum salt are both nitrate, and the total concentration of the lanthanum salt and the aluminum salt in the aqueous solution is 0.1-0.6mol / L, and is preferably 0.2-0.3mol / L.

[0012] Further, the mass concentration of the tetrabutyl titanate solution diluted by the C1-C4 alcohol solvent in step 1) is 40%-60%, preferably 50%; and the C1-C4 alcohol solvent is ethanol.

[0013] Further, the temperature of the calcination treatment in the air atmosphere in step 2) is 350-450℃, and the calcination time is 2-5h.

[0014] The preparation method of the catalyst is as follows: the titanium-lanthanum-aluminum composite oxide TiLaAlOx carrier powder is immersed in a Pt precursor aqueous solution, the obtained mixture is stirred in a 65-85℃ water bath for 1-3 hours and then filtered, the obtained solid after filtration is dispersed in deionized water, an excessive amount of hydrazine hydrate solution is added, the mixture is reacted at 65-85℃ for 1-3 hours to completely reduce the Pt element into a metal element, then filtered, dried, and calcined in an air atmosphere at a temperature of 400-950℃ for 2-5 hours, thereby completing the preparation.

[0015] Further, the Pt precursor is chloroplatinic acid hexahydrate.

[0016] The application further provides an application of the high-thermal-stability platinum-based methanol combustion catalyst in catalytic combustion of methanol, wherein the catalyst is loaded in a tubular reactor, methanol gas and air are introduced into the tubular reactor for catalytic combustion reaction.

[0017] Further, the concentration of the methanol gas is 1000ppm-10000ppm, preferably 2000ppm, and the methanol raw gas is mixed with air at a volume ratio of 1:15-20 after passing through a 0℃ ice water bath and then introduced into the tubular reactor for catalytic combustion reaction. -1 -1 .

[0018] The application has the following beneficial effects:

[0019] The application adopts chloroplatinic acid hexahydrate (H2PtCl6·6H2O), tetrabutyl titanate (C 16 H 36 ​La(NO3)3.nH2O, aluminum nitrate nonahydrate (Al(NO3)3.9H2O) as main raw materials, TiLaAlOx composite oxide carrier is prepared by adopting a precipitation method, Pt / TiLaAlOx catalyst is prepared by adopting an impregnation method and step-by-step loading of Pt, the molar ratio of Ti / La / Al in the catalyst is 50-90:5-25:5-25, the preparation process is simple, the catalyst cost is low, and the catalyst is a high-efficiency and stable organic gas combustion catalyst. The catalyst prepared by the method is particularly suitable for catalytic combustion of methanol, has high thermal stability, can maintain activity after high-temperature aging at 950 DEG C, and has great industrial application potential and value. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The catalytic conversion activity of the catalysts in Examples 1-12 on methanol at different reaction temperatures is tested. DETAILED DESCRIPTION

[0021] The application is further described below in combination with specific examples, but the protection scope of the application is not limited to this.

[0022] Example 1

[0023] First step: 68.072g of tetrabutyl titanate is dissolved in 68.072g of ethanol, and the tetrabutyl titanate solution is added dropwise into 200ml of deionized water under vigorous stirring. The mixture is stirred for 3 hours, aged at room temperature for 12 hours, then filtered, washed with deionized water for multiple times until the filtrate is neutral, dried at 110 DEG C for 12 hours, and treated by calcination at 400 DEG C for 4 hours to prepare a TiO2 carrier.

[0024] Second step: 4mL of chloroplatinic acid solution (the Pt concentration in the solution is 2.5g / L) is dissolved in 20mL of deionized water, the TiO2 carrier powder obtained in step one is dispersed in the chloroplatinic acid solution, the obtained mixture is filtered after being stirred in a 75 DEG C water bath for 1 hour, then the obtained solid is dissolved in another 20mL of deionized water together with 141ul of 85% hydrazine hydrate solution. After the above mixture is reacted at 75 DEG C for 1 hour, dried at 100 DEG C for 1 hour, and treated by calcination at 400 DEG C for 4 hours, a 1wt% Pt / TiO2-400 catalyst is prepared.

[0025] Example 2

[0026] The same operation as in Example 1 is adopted, except that the 1wt% Pt / TiO2-400 catalyst in Example 1 is treated by high-temperature aging at 950 DEG C for 4 hours in an air atmosphere again to prepare a 1wt% Pt / TiO2-950 catalyst as a comparative sample.

[0027] Example 3

[0028] First step: 6.8072 g of aluminum nitrate nonahydrate was dissolved in 200 mL of deionized water to form solution A, and 61.2648 g of tetrabutyl titanate was dissolved in 61.2648 g of ethanol to form solution B. Solution A was added dropwise to solution B and ammonia solution with a concentration of 1 mol / L was added to adjust the pH value to 9.0 under vigorous stirring. The mixture was stirred for 3 hours, aged at room temperature for 12 hours, then filtered, washed with deionized water for multiple times until the filtrate was neutral, dried at 110°C for 12 hours, and treated by calcination at 400°C in air atmosphere for 4 hours to obtain Ti 90 Al 10 Ox composite oxide with a Ti / Al molar ratio of 90:10;

[0029] Second step: 4 mL of chloroplatinic acid solution (Pt concentration in solution was 2.5 g / L) was dissolved in 20 mL of deionized water, and the Ti 90 Al 10 Ox composite oxide powder obtained in step one was dispersed in the chloroplatinic acid solution, the obtained mixture was stirred in a 75°C water bath for 1 hour and then filtered, and the obtained solid was dissolved in another 20 mL of deionized water together with 141 μL of 85% hydrazine hydrate solution. After the above mixture was reacted at 75°C for 1 hour, dried at 100°C for 1 hour, and treated by calcination at 400°C for 4 hours, 1wt% Pt / Ti 90 Al 10 Ox-400 catalyst was obtained.

[0030] Example 4

[0031] The same operation as in example 3, except that the 1wt% Pt / Ti 90 Al 10 Ox-400 catalyst of example 3 was again treated by high-temperature aging at 950°C in air atmosphere for 4 hours to obtain 1wt% Pt / Ti 90 Al 10 Ox-950 catalyst as a comparative sample.

[0032] Example 5

[0033] The same operation as in example 3, except that 6.8072 g of aluminum nitrate nonahydrate was replaced by 6.4984 g of lanthanum nitrate hydrate, and finally 1wt% Pt / Ti 90 La 10 Ox-400 catalyst was obtained.

[0034] Example 6

[0035] The same operation as in example 5, except that the 1wt% Pt / Ti 90 La 10Ox-400 catalyst, again high temperature aging treatment at 950 °C temperature for 4 hours under air atmosphere, to make 1 wt% Pt / Ti 90 La 10 Ox-950 catalyst as a comparative sample.

[0036] Example 7

[0037] The same operation as Example 3, except that 6.8072 g of aluminum nitrate nonahydrate was replaced with 3.2492 g of lanthanum nitrate hydrate and 3.4036 g of aluminum nitrate nonahydrate, and the ratio of the tetrabutyl titanate solution was changed to 61.2648 g of tetrabutyl titanate dissolved in 61.2648 g of ethanol, to finally make 1 wt% Pt / Ti 90 La5Al5Ox-400 catalyst.

[0038] Example 8

[0039] The same operation as Example 7, except that 1 wt% Pt / Ti 90 La5Al5Ox-400 catalyst, again high temperature aging treatment at 950 °C temperature for 4 hours under air atmosphere, to make 1 wt% Pt / Ti 90 La5Al5Ox-950 catalyst as a comparative sample.

[0040] Example 9

[0041] The same operation as Example 7, except that 3.2492 g of lanthanum nitrate hydrate was replaced with 6.4984 g of lanthanum nitrate hydrate, 3.4036 g of aluminum nitrate nonahydrate was replaced with 6.8072 g of aluminum nitrate nonahydrate, and the ratio of the tetrabutyl titanate solution was changed to 54.4576 g of tetrabutyl titanate dissolved in 54.4576 g of ethanol, to finally make 1 wt% Pt / Ti 80 La 10 Al 10 Ox-400 catalyst.

[0042] Example 10

[0043] The same operation as Example 9, except that 1 wt% Pt / Ti 80 La 10 Al 10 La5Al5Ox-400 catalyst, again high temperature aging treatment at 950 °C temperature for 4 hours under air atmosphere, to make 1 wt% Pt / Ti 80 La 10 Al 10 La5Al5Ox-950 catalyst as a comparative sample.

[0044] Example 11

[0045] The same operation as in Example 7, except that 3.2492 g of lanthanum nitrate hydrate was replaced by 16.246 g of lanthanum nitrate hydrate, 3.4036 g of aluminum nitrate nonahydrate was replaced by 17.018 g of aluminum nitrate nonahydrate, and the ratio of the tetrabutyl titanate solution was changed to 34.036 g of tetrabutyl titanate dissolved in 34.036 g of ethanol, to finally obtain 1 wt% Pt / Ti 50 La 25 Al 25 Ox-400 catalyst.

[0046] Example 12

[0047] The same operation as in Example 11, except that the 1 wt% Pt / Ti 50 La 25 Al 25 Ox-400 catalyst was again high-temperature aging treated at a temperature of 950°C for 4 hours in an air atmosphere to obtain 1 wt% Pt / Ti 50 La 25 Al 25 Ox-950 catalyst as a comparative sample.

[0048] Application Example 1:

[0049] Catalytic combustion experiments of the catalysts in Examples 1-12 on methanol gas: The catalysts were loaded into a tubular reactor together with quartz sand at a mass ratio of 1:1 (the purpose of loading quartz sand was to disperse the catalysts), and methanol gas was introduced into the tubular reactor together with air for catalytic combustion reaction. The experimental conditions were as follows: air was used as a dilution gas for methanol to dilute methanol to a concentration of 2000 ppm to obtain methanol raw gas, and the methanol raw gas was mixed with another air at a volume ratio of 4.28:79.05 after passing through a 0°C ice water bath (to ensure that the saturated vapor pressure of methanol was the same, and the concentration of the prepared methanol raw gas did not change), and then introduced into the tubular reactor for catalytic combustion reaction at different reaction temperatures, and the total mixed gas reaction space velocity was WHSV = 50000 mL·g -1 ·h -1 .

[0050] The catalytic conversion activity of the catalysts in Examples 1-12 on methanol at different reaction temperatures was as shown in Table 1, wherein the temperature data results of complete methanol conversion (conversion > 90%) were as shown in Table 1: Figure 1

[0051] Table 1

[0052]

[0053] ​Table 1 above lists unary, binary, and ternary catalysts composed of 1 wt% Pt loading, supported on TiO2 and doped with different proportions of La and Al. (1 wt% Pt / Ti) A La B Al C O x (Examples 1-12) Catalytic oxidation activity of methanol. Temperature (T) at which methanol is completely converted (conversion rate > 90%). 90 The lower the T value, the higher the oxidation activity of the catalyst; fresh catalyst calcined in air at 400℃ and aged catalyst calcined in air at 950℃, T 90 The smaller the temperature difference, the better the thermal stability.

[0054] Based on the catalytic activity comparison of Examples 1 and 2, Examples 3-4, and Examples 5-6 in Table 1, their fresh catalysts calcined in air at 400°C, after being calcined in air at 950°C, showed a higher TL in the catalytic combustion of methanol. 90 The significant increase in temperature and the marked decrease in catalytic activity indicate that the catalyst has poor high-temperature stability. Furthermore, in industrial applications involving large-scale catalytic combustion of methanol, the actual temperatures are extremely high, reaching 700-800℃. Therefore, catalysts with poor high-temperature stability are not well-suited for use in methanol catalytic combustion reactions.

[0055] Comparing the catalytic reaction results of Examples 9-10 in Table 1, the aged catalyst of Example 10, after being calcined at 950°C in air, showed a higher T value when applied to the catalytic combustion of methanol. 90 The temperature was only 9°C higher than that of the catalyst calcined at 400°C in air in Example 9, indicating that the activities of the two catalysts are basically the same. The catalyst of Example 9 has excellent high-temperature resistance and good thermal stability. The catalyst of this invention with the optimal molar ratio of Ti / La / Al of 80:10:10 not only has the same activity as the more active TiO2 support, but also shows excellent thermal stability before and after aging, indicating that the catalyst has great potential and value for industrial application.

[0056] The contents described in this specification are merely an enumeration of the implementation forms of the inventive concept, and the scope of protection of this invention should not be regarded as limited to the specific forms described in the embodiments.

Claims

1. Use of a high thermal stability platinum-based methanol combustion catalyst for catalytic combustion of methanol, characterized in that The catalyst is a titanium lanthanum aluminum composite oxide TiLaAlOx as a carrier, and a noble metal active component Pt is loaded on the carrier, and the loading amount of Pt is 0.01-4 wt%; in the titanium lanthanum aluminum composite oxide TiLaAlOx carrier, the molar amounts of Ti, La and Al are 75-85%, 7.5-12.5% and 7.5-12.5% of the total molar amounts of Ti, La and Al respectively.

2. Use according to claim 1, wherein The loading amount of Pt is 1-1.2 wt%.

3. The use according to claim 1, characterized in that The preparation method of the titanium lanthanum aluminum composite oxide TiLaAlOx carrier is: 1) La salt and aluminum salt are dissolved in water according to the molar ratio of La to Al, and a tetrabutyl titanate solution diluted with a C1-C4 alcohol solvent is added dropwise, an alkali is added to adjust the pH to 8.0-10.0, and the mixture is stirred for 0.5-4 hours; 2) then it is aged at room temperature for 10-15 hours, filtered, washed with deionized water and anhydrous ethanol for multiple times until the filtrate is neutral, dried, and calcined in an air atmosphere to obtain a TiLaAlOx composite oxide powder.

4. The use according to claim 3, wherein In step 1), the La salt and the aluminum salt are both nitrate, and the total concentration of the La salt and the aluminum salt in the aqueous solution is 0.1-0.6 mol / L.

5. The use according to claim 4, wherein In step 1), the La salt and the aluminum salt are both nitrate, and the total concentration of the La salt and the aluminum salt in the aqueous solution is 0.2-0.3 mol / L.

6. The use according to claim 3, wherein In step 1), the mass concentration of the tetrabutyl titanate solution diluted with a C1-C4 alcohol solvent is 40%-60%, and the C1-C4 alcohol solvent is ethanol.

7. Use according to claim 6, wherein In step 1), the mass concentration of the tetrabutyl titanate solution diluted with a C1-C4 alcohol solvent is 50%.

8. The use according to claim 3, wherein In step 2), the temperature of the calcination treatment in the air atmosphere is 350-450℃, and the calcination time is 2-5 h.

9. The use according to claim 1, characterized in that The preparation method of the catalyst is: the titanium lanthanum aluminum composite oxide TiLaAlOx carrier powder is immersed in a Pt precursor aqueous solution, the obtained mixture is stirred in a 65-85℃ water bath for 1-3 hours and then filtered, the filtered solid is dispersed in deionized water, an excess amount of hydrazine hydrate solution is added, the mixture is reacted at 65-85℃ for 1-3 hours to completely reduce the Pt element into a metal element, then it is filtered, dried, and calcined in an air atmosphere at a temperature of 400-950℃ for 2-5 hours to complete the preparation.

10. The use according to claim 9, wherein The Pt precursor is chloroplatinic acid hexahydrate.

11. The use according to claim 1, wherein The catalyst is loaded in a tubular reactor, methanol gas and air are introduced into the tubular reactor to carry out catalytic combustion reaction, the total mixed gas passes through the catalyst bed at a reaction speed of 20000-80000 mL·g -1 ·h -1 -1·h-1, and the reaction temperature is 100℃-950℃.

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