Preparation method of a Pt-loaded monolithic catalyst with sulfur resistance, Pt-loaded monolithic catalyst and application thereof

Abstract

The present invention provides a method for preparing a Pt monolithic catalyst with sulfur resistance, the method comprising: step 1: coating a slurry formed by mixing alumina and a modifier with a mass ratio of 100:1 to 10:3 and an appropriate amount of a binder on a cordierite carrier, drying and calcining to obtain a carrier with a coating; step 2: immersing one end of the carrier with the coating in an alkaline aqueous solution, drying and calcining the carrier with the coating, so that one end of the catalyst is loaded with an alkaline compound to form an upper functional area; step 3: immersing the other end of the catalyst in a mixed solution formed by a platinum salt and a bismuth salt, drying and calcining the catalyst, so that the other end of the catalyst is loaded with Pt to form a lower functional area. The catalyst prepared by the present invention can be used for the treatment of sulfur-containing gas pollutants (carbon monoxide, methane and propane), and has good activity and stability in the catalytic combustion process of sulfur-containing gases.

Description

Technical Field

[0001] The present invention relates to the field of energy technology, and in particular to a preparation method of a Pt-loaded monolithic catalyst with sulfur resistance, the Pt-loaded monolithic catalyst and applications. Background Art

[0002] With the depletion of oil resources and the increasing prominence of environmental pollution, natural gas has been widely used in gas turbine combustion chambers and natural gas vehicles due to its cleanliness and high thermal efficiency. The nitrogen oxides produced by direct combustion of natural gas (flame combustion) will cause certain environmental pollution, and the combustion reaction temperature is high (1300-1400℃) and the combustion efficiency is low. Therefore, catalytic combustion is one of the effective ways to rationally utilize methane. Among the catalyst systems used for catalytic combustion of methane (precious metal catalysts and transition metal oxide catalysts), the loaded Pt-based catalyst has received extensive attention because it has the best catalytic performance and can make methane have a lower ignition temperature and complete combustion temperature. Although the loaded Pt-based catalyst can achieve complete oxidation of methane at a lower temperature, there are also some problems that need to be solved for the Pt-based catalyst.

[0003] For gas fuel vehicles and special machinery internal combustion engines, the natural gas they use contains a certain amount of sulfur. PtO is generally considered to be the active phase of the catalyst for oxidizing methane. When the active phase PtO of the catalyst encounters sulfur compounds in natural gas, it will generate stable sulfides, resulting in the loss of active species Pt, thereby reducing the catalytic activation of the catalyst. It can be seen that the sulfation of the catalyst surface is the main factor leading to the reduction of catalytic performance: sulfur compounds are easily converted into SO x , and exist as stable sulfate species on the surface of PtO particles, resulting in a reduction in the number of active sites. In addition, the generated sulfate species will also migrate to the support, resulting in the sulfation of the support.

[0004] In addition, low concentrations of sulfur are sufficient to cause the supported Pt-based catalyst to be poisoned and deactivated in the methane catalytic combustion reaction, and the poisoning effect is almost irreversible. In addition, the regeneration of the poisoned and deactivated catalyst is difficult, and its activity cannot be fully restored through regeneration treatment.

[0005] Therefore, in the field of energy technology, how to obtain a catalyst that can be used under sulfur-containing conditions to avoid reduced activation efficiency caused by sulfation of the catalyst surface has become a technical problem that needs to be solved urgently. Summary of the invention

[0006] To solve the above problems, in a first aspect, the present invention provides a method for preparing a Pt-loaded monolithic catalyst having sulfur resistance, the method comprising:

[0007] Step 1: coating a slurry formed by mixing alumina and a modifier in a mass ratio of 100:1 to 10:3 and an appropriate amount of a binder on a cordierite carrier, drying and calcining to obtain a carrier with a coating;

[0008] Step 2: After immersing one end of the coated carrier in an alkaline solution, the coated carrier is dried and calcined so that one end of the coated carrier is loaded with an alkaline compound to form an upper functional area; wherein the alkaline solution is composed of one or two solutions of KOH, NaOH, K2CO3, and Na2CO3;

[0009] Step 3: After immersing the other end of the coated carrier in a mixed solution of platinum salt and bismuth salt, the coated carrier is dried and calcined to obtain a Pt-loaded integral catalyst, so that the other end of the coated carrier is loaded with Pt to form a lower functional area.

[0010] Preferably, in step 1, the mass ratio of the aluminum oxide to the modifier in the coating is 10:1;

[0011] The loading amount of the coating in the coated carrier is 50 g / L-150 g / L.

[0012] Preferably, in step 1, the drying time is 4h to 5h, and the drying temperature is 120°C to 200°C; the roasting time is 4h to 5h, and the roasting temperature is 500°C to 600°C; and the stirring time required for mixing is 3h to 6h.

[0013] Preferably, in step 1, the binder is one or more of aluminum sol, silica sol, polyvinyl alcohol, hydroxymethyl cellulose, and titanium sol, and the modifier is one or more of titanium oxide, zirconium oxide, tin oxide, vanadium pentoxide, and tungsten trioxide.

[0014] Preferably, in step 2, the mass ratio of the alkaline compound to the aluminum oxide is 1:20 to 3:10;

[0015] The alkaline compound is KOH or NaOH.

[0016] Preferably, in step 2, the drying time is 4 h to 6 h, and the drying temperature is 100° C. to 150° C.; the calcining time is 4 h to 8 h, and the calcining temperature is 400° C. to 550° C.

[0017] Preferably, in step 3, the platinum salt is any one of platinum nitrate, chloroplatinic acid, hydroxylamine platinum, and platinum acetate;

[0018] The bismuth salt is bismuth nitrate or bismuth chloride, and the mass ratio of the bismuth salt to the aluminum oxide is 1:200 to 1:5;

[0019] The mass ratio of the Pt to the aluminum oxide is 1:200 to 1:10.

[0020] Preferably, in step 3, the drying time is 4 h to 6 h, and the drying temperature is 100° C. to 150° C.; the calcining time is 2 h to 4 h, and the calcining temperature is 400° C. to 550° C.

[0021] In a second aspect, the present invention provides a Pt-loaded monolithic catalyst obtained by the preparation method of the first aspect, wherein the monolithic catalyst uses a cordierite carrier as a skeleton matrix, a modified alumina coating is loaded on the surface of the skeleton matrix, an alkaline compound is loaded on one end of the modified alumina coating to form an upper functional region, and Pt is loaded on the other end of the modified alumina coating to form a lower functional region;

[0022] Wherein, the upper functional zone is used for removing sulfur-containing compounds; and the lower functional zone is used for catalytic methane oxidation.

[0023] In a third aspect, the present invention provides an application of a Pt-loaded monolithic catalyst obtained by the preparation method of the first aspect, wherein the Pt-loaded monolithic catalyst is applied in a combustion reaction of sulfur-containing natural gas.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] The present invention provides a method for preparing a Pt monolithic catalyst with sulfur resistance, the method comprising: step 1: coating a slurry formed by mixing alumina and a modifier with a mass ratio of 100:1 to 10:3 and an appropriate amount of a binder on a cordierite carrier, drying and calcining to obtain a carrier with a coating; step 2: immersing one end of the carrier with the coating in an alkaline aqueous solution, drying and calcining the carrier with the coating, so that one end of the catalyst is loaded with an alkaline compound to form an upper functional area; step 3: immersing the other end of the catalyst in a mixed solution formed by a platinum salt and a bismuth salt, drying and calcining the catalyst, so that the other end of the catalyst is loaded with Pt to form a lower functional area. The catalyst prepared by the present invention can be used for the treatment of sulfur-containing gas pollutants (carbon monoxide, methane and propane), and has good activity and stability in the catalytic combustion process of sulfur-containing gases.

[0026] In the embodiment of the present invention, modified alumina is first coated on the carrier, and then one end of the carrier is loaded with an active component, an alkaline compound, to form an upper functional zone, and the alkaline compound is used to adsorb sulfur-containing compounds (such as sulfur dioxide and hydrogen sulfide) in sulfur-containing gas to remove sulfur from the gas, so as to ensure that the subsequent purification process is not affected by sulfur-containing compounds, so that it still has good activity and stability in the subsequent purification process of sulfur-containing gas; the active component Pt is loaded on one end without the alkaline compound to obtain a catalyst, forming a lower functional zone, and the active component Pt in the lower functional zone is used for purification, that is, to purify pollutants (such as methane, carbon monoxide and propane) in the gas after desulfurization, and oxidize methane, carbon monoxide and propane into carbon dioxide and water to complete catalytic combustion. Since the upper functional zone has removed the sulfur-containing compounds, the loss of active component Pt caused by the sulfation of the catalyst surface after the catalyst contacts sulfur during the methane oxidation process is avoided, and the poisoning and deactivation caused by the catalyst contacting sulfur directly in the methane catalytic combustion reaction is also avoided. In addition, since the catalyst is coated with sulfur-resistant modified alumina, sulfur-containing compounds or sulfates or elemental sulfur oxidized by alkaline compounds are not easily deposited on the catalyst surface, further avoiding the loss of active component Pt caused by sulfation of the catalyst surface after the catalyst contacts sulfur, and further avoiding the poisoning and deactivation of the catalyst directly caused by contact with sulfur in the catalytic combustion reaction of methane. The catalyst obtained by the preparation method provided by the present invention is particularly targeted at the treatment of sulfur-containing gas pollutants. Specifically, the catalyst of the present invention can be used for the treatment of gaseous pollutants such as carbon monoxide, methane and propane, and has good activity and stability in the catalytic combustion process of sulfur-containing carbon monoxide, methane and propane. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The present invention provides a flow chart of a method for preparing a Pt-loaded integral catalyst with sulfur resistance. DETAILED DESCRIPTION

[0028] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific examples, but should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art. Unless otherwise specified, the examples, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0029] First, refer to Figure 1 , Figure 1 The present invention provides a flow chart of a method for preparing a Pt-loaded monolithic catalyst with sulfur resistance, the method comprising:

[0030] S101, coating a slurry formed by mixing alumina and a modifier in a mass ratio of 100:1 to 10:3 and an appropriate amount of a binder on a cordierite carrier, and drying and calcining to obtain a carrier with a coating;

[0031] S102, after immersing one end of the coated carrier in an alkaline solution, drying and calcining the coated carrier, so that one end of the coated carrier is loaded with an alkaline compound to form an upper functional area; wherein the alkaline solution is composed of one or two solutions of KOH, NaOH, K2CO3, and Na2CO3;

[0032] S103, after immersing the other end of the coated carrier in a mixed solution of platinum salt and bismuth salt, the coated carrier is dried and calcined to obtain a Pt-loaded integral catalyst, so that the other end of the coated carrier is loaded with Pt to form a lower functional area.

[0033] In step S101, a certain amount of aluminum oxide, a modifier and a binder are mixed, and the pH value is adjusted to 5.0 to 7.0 with an acid, and the mixture is stirred for 3 to 6 hours to form a slurry. Here, the type of acid used is not specifically limited.

[0034] The coating is modified alumina. On the one hand, the coating can make the alkaline compounds and precious metal Pt on the coating (modified alumina) load more evenly, thereby obtaining better catalytic activity; on the other hand, the coating will not allow sulfur-containing compounds to deposit on the catalyst surface. In addition, the coating can also modify the chemical state of the precious metal Pt (such as color, performance, etc.).

[0035] In specific implementation, since the monolithic catalyst is prepared in the present invention, the monolithic catalyst needs to have a substrate. Therefore, a binder is used to firmly adhere the substrate to the cordierite carrier. Among them, the substrate is modified alumina, and the modified alumina is a mixture of alumina and a modifier. The modifier is used to adjust the acidity and alkalinity of alumina. It should be noted that if the pH value of the modifier alumina is not within the range of 5.0 to 7.0, an acid is used to further adjust the pH value of the modified alumina.

[0036] In step S102, the alkaline compound may be one or two of KOH, NaOH, K2CO3, and Na2CO3, or one or two of the products obtained by calcining K2CO3 and Na2CO3 at 400°C to 500°C.

[0037] In specific implementation, the coated carrier is immersed in an impregnation solution (alkaline solution) by an equal volume impregnation method, so that the carrier is saturated, that is, the active components (one or two of KOH, NaOH, K2CO3, and Na2CO3) in the impregnation solution are allowed to enter all the pores of the carrier through adsorption. After the carrier is saturated, it is taken out of the alkaline solution for drying and roasting, and the coating (modified alumina) at one end of the obtained catalyst is loaded with active components (one or two of KOH, NaOH, K2CO3, and Na2CO3). Usually, when sulfur-containing gas is passed into the catalyst bed, the oxidation deposition of sulfur easily causes the catalyst to be sulfur-poisoned and deactivated. Since the catalyst of the present invention is loaded with active components (alkaline compounds) at the upper end, it can avoid poisoning of the active components by adsorption and oxidation, thereby achieving efficient and stable operation under a sulfur-containing atmosphere.

[0038] In specific implementation, the desulfurization process of the upper end of the catalyst is: there is adsorption in the desulfurization process, and alkaline compounds are used to adsorb sulfur-containing compounds (such as sulfur dioxide and hydrogen sulfide) in the gas; there is also oxidation in the desulfurization process. The above oxidation is specifically: if the catalyst obtained by using alkaline compounds such as KOH and NaOH is used for the oxidation of sulfur-containing methane, KOH or NaOH adsorbs and oxidizes the sulfur-containing compounds in the gas into sulfate or elemental sulfur (hydrogen sulfide into elemental sulfur, sulfur dioxide into sulfate) under the condition of a small amount of oxygen, so as to further achieve the effect of removing sulfur from the gas. In addition, since the carrier of the upper functional zone is coated with modified alumina, which is a sulfur-resistant component, sulfur-containing compounds or oxidized sulfates (such as sulfur trioxide) are not easy to deposit on the catalyst of the present invention, which further avoids the loss of active component Pt caused by the sulfation of the catalyst surface after the catalyst contacts sulfur, and further avoids the poisoning and deactivation of the catalyst after contacting sulfur in the methane catalytic combustion reaction.

[0039] It should be noted that the equal volume impregnation method refers to the solvent of the impregnation solution being the same as the pore volume of the carrier, so that the loaded active ingredient is relatively uniform. In the present invention, since only the upper part or the lower part of the carrier needs to be impregnated, the solvent of the impregnation solution is the same as half of the pore volume of the carrier. The specific pore volume of the carrier and the volume of the alkaline solution are not specifically limited here.

[0040] In step S103, the other end of the carrier with the coating refers to the end without the alkaline compound, that is, the end away from the end with the alkaline compound. The upper functional area is the adsorption area, and the lower functional area is the active area.

[0041] In the specific implementation, the other end of the coated carrier is immersed in a mixed solution of platinum salt and bismuth salt by a distributed impregnation or co-impregnation method, and the active component Pt in the impregnation solution (referring to the mixed solution) enters all the pores of the carrier through adsorption. After the carrier is saturated, the carrier is taken out of the mixed solution for drying and calcination to obtain a catalyst with the active component Pt loaded on the other end.

[0042] The gas treated in the lower functional zone includes: methane and carbon monoxide that need to be treated in the lower functional zone with a catalyst, and products (such as sulfur trioxide) oxidized by the active components (alkaline compounds) in the upper functional zone.

[0043] The gas treatment in the lower functional zone includes: since the modified alumina coated on the carrier of the lower functional zone carries the active component Pt, the methane and carbon monoxide are purified by the active component Pt, that is, the methane and carbon monoxide are oxidized into carbon dioxide and water by oxidation; since the modified alumina coated on the carrier of the lower functional zone is a sulfur-resistant component, the sulfate (such as sulfur trioxide) oxidized by the alkaline compound in the upper functional zone is not easy to deposit on the catalyst of the present invention, which further avoids the loss of the active component Pt caused by the sulfation of the catalyst surface after the catalyst contacts sulfur, and further avoids the poisoning and deactivation of the catalyst after contacting sulfur in the methane catalytic combustion reaction.

[0044] In the embodiment of the present invention, modified alumina is first coated on the carrier, and then one end of the carrier is loaded with an active component, an alkaline compound, to form an upper functional zone, and the alkaline compound is used to adsorb sulfur-containing compounds (such as sulfur dioxide and hydrogen sulfide) in sulfur-containing gas to remove sulfur from the gas, so as to ensure that the subsequent purification process is not affected by sulfur-containing compounds, so that it still has good activity and stability in the subsequent purification process of sulfur-containing gas; the active component Pt is loaded on one end without the alkaline compound, and a Pt-loaded integral catalyst is obtained to form a lower functional zone, and the active component Pt in the lower functional zone is used for purification, that is, to purify pollutants (such as methane, carbon monoxide and propane) in the gas after desulfurization, and oxidize methane, carbon monoxide and propane into carbon dioxide and water to complete catalytic combustion. Since the upper functional zone has removed the sulfur-containing compounds, the loss of active component Pt caused by the sulfation of the catalyst surface after the catalyst touches sulfur during the methane oxidation process is avoided, and the poisoning and deactivation caused by the catalyst contacting sulfur in the methane catalytic combustion reaction is also avoided. In addition, since the catalyst carrier is coated with sulfur-resistant modified alumina, sulfur-containing compounds or sulfates oxidized by alkaline compounds are not easily deposited on the catalyst surface, which further avoids the loss of active component Pt caused by sulfation of the catalyst surface after the catalyst contacts sulfur, and further avoids the poisoning and deactivation of the catalyst after contacting sulfur in the catalytic combustion reaction of methane.

[0045] Preferably, in step 1, the mass ratio of the aluminum oxide to the modifier in the coating is 10:1;

[0046] The loading amount of the coating in the coated carrier is 50 g / L-150 g / L.

[0047] In specific implementation, the modifier accounts for 1% to 30% of the mass of alumina. Since the cordierite carrier cannot directly load the active component, alumina is used in the present invention, and the alumina is adhered to the cordierite carrier by a binder, and then dried and calcined to make it dry and completely adhered to the cordierite carrier without falling off; and then the respective active components are loaded on the alumina on the surface of the cordierite carrier. The modifier allows the active components to be better loaded on the alumina and loaded more evenly; and the modified alumina is a sulfur-resistant component, which will not allow sulfur-containing compounds to be deposited on its surface.

[0048] Preferably, in step 1, the drying time is 4h to 5h, and the drying temperature is 120°C to 200°C; the roasting time is 4h to 5h, and the roasting temperature is 500°C to 600°C; and the stirring time required for mixing is 3h to 6h.

[0049] Preferably, in step 1, the binder is one or more of aluminum sol, silica sol, polyvinyl alcohol, hydroxymethyl cellulose, and titanium sol, and the modifier is one or more of titanium oxide, zirconium oxide, tin oxide, vanadium pentoxide, and tungsten trioxide.

[0050] In specific implementation, zirconium oxide is preferably used as the modifier.

[0051] Preferably, in step 2, the mass ratio of the alkaline compound to the aluminum oxide is 1:20 to 3:10;

[0052] The alkaline compound is KOH or NaOH.

[0053] In specific implementation, the alkaline compound accounts for 5-30% of the mass of the aluminum oxide coating, and the mass ratio of the alkaline compound to aluminum oxide is preferably 3:20-1:5, i.e. 15%-20%; the alkaline compound is preferably KOH or NaOH.

[0054] It should be noted that when the alkaline compound is KOH or NaOH, the active component loaded on one end of the catalyst after calcination is KOH or NaOH; when the alkaline compound is K2CO3 or Na2CO3, the active component loaded on one end of the catalyst after calcination is K2O or Na2O (because the sulfur-containing gas contains CO2, when the catalyst with the active component K2O or Na2O loaded on the upper end is used to treat industrial sulfur-containing gas, the active component K2O or Na2O will still become K2CO3 or Na2CO3); when the alkaline compound is the product of K2CO3 or Na2CO3 calcined at 400°C to 500°C (i.e. K2O or Na2O), the active component loaded on one end of the catalyst after calcination is K2O or Na2O (because the sulfur-containing gas contains CO2, when the catalyst with the active component K2O or Na2O loaded on the upper end is used to treat industrial sulfur-containing gas, the active component K2O or Na2O will still become K2CO3 or Na2CO3).

[0055] Preferably, in step 2, the drying time is 4 h to 6 h, and the drying temperature is 100° C. to 150° C.; the calcining time is 4 h to 8 h, and the calcining temperature is 400° C. to 550° C.

[0056] Preferably, in step 3, the platinum salt is any one of platinum nitrate, chloroplatinic acid, hydroxylamine platinum, and platinum acetate;

[0057] The bismuth salt is bismuth nitrate or bismuth chloride, and the mass ratio of the bismuth salt to the aluminum oxide is 1:200 to 1:5;

[0058] The mass ratio of the Pt to the aluminum oxide is 1:200 to 1:10.

[0059] In specific implementation, the mass of the bismuth salt (in terms of Bi) accounts for 0.5-20% of the mass of the aluminum oxide, and the mass ratio of the bismuth salt to the aluminum oxide is preferably 3:20, i.e. 15%; the bismuth salt is preferably bismuth chloride.

[0060] In specific implementation, since the gaseous pollutants (carbon monoxide, methane and propane) cannot be strongly oxidized, that is, the oxidation temperature is high, the bismuth salt is used as an auxiliary agent in the present invention to further activate the oxygen, so that the reactants are shifted to low temperature as much as possible, thereby regulating the reaction temperature, and the reaction temperature is regulated within the range of 400°C to 550°C.

[0061] In a specific implementation, the mass of Pt accounts for 0.5-10% of the mass of alumina, wherein the mass ratio of the active component Pt to alumina is preferably 1:20, ie 5%.

[0062] Preferably, in step 3, the drying time is 4 h to 6 h, and the drying temperature is 100° C. to 150° C.; the calcining time is 2 h to 4 h, and the calcining temperature is 400° C. to 550° C.

[0063] In a second aspect, the present invention provides a Pt-loaded monolithic catalyst obtained by the preparation method of the first aspect, wherein the monolithic catalyst uses a cordierite carrier as a skeleton matrix, a modified alumina coating is loaded on the surface of the skeleton matrix, an alkaline compound is loaded on one end of the modified alumina coating to form an upper functional region, and Pt is loaded on the other end of the modified alumina coating to form a lower functional region;

[0064] Wherein, the upper functional zone is used for removing sulfur-containing compounds; and the lower functional zone is used for catalytic methane oxidation.

[0065] In the embodiment of the present invention, the alkaline compound in the upper functional zone is used to adsorb the sulfur-containing compounds in the sulfur-containing gas to ensure that the subsequent purification process is not affected by the sulfur-containing compounds, so that it still has good activity and stability in the subsequent catalytic combustion process of the sulfur-containing gas; the active component Pt in the lower functional zone is used for purification, that is, to oxidize the methane, carbon monoxide and propane in the gas after desulfurization, and oxidize methane, carbon monoxide and propane into carbon dioxide and water to complete catalytic combustion. The catalyst provided by the present invention is particularly aimed at the treatment of sulfur-containing gas pollutants (carbon monoxide, methane and propane).

[0066] In a third aspect, the present invention provides an application of a Pt-loaded monolithic catalyst obtained by the preparation method of the first aspect, wherein the Pt-loaded monolithic catalyst is applied in a combustion reaction of sulfur-containing natural gas.

[0067] The Pt-loaded monolithic catalyst provided in the embodiment of the present invention is used in the combustion reaction of methane, carbon monoxide and propane to oxidize methane, carbon monoxide and propane into carbon dioxide and water to complete catalytic combustion, and is particularly used in the combustion reaction of sulfur-containing gas.

[0068] In order to enable those skilled in the art to better understand the present invention, the solutions provided by the present invention are described below through multiple specific embodiments.

[0069] Example 1

[0070] After mixing alumina, ZrO2 (modifier) ​​and an appropriate amount of silica sol (binder) in a mass ratio of 10:1, adjust the pH value to 5.0 with nitric acid, and stir for 6 hours to form a slurry; apply the slurry on a cordierite carrier, dry at 120°C for 4 hours, and calcine at 500°C for 4 hours to obtain a carrier with a coating. One end of the carrier with a coating is impregnated in a KOH aqueous solution by an equal volume impregnation method, wherein the mass ratio of KOH (in terms of K) to alumina is 1:20, and the impregnated saturated carrier is dried at 120°C for 4 hours and calcine at 500°C for 4 hours to obtain a carrier with an alkaline compound loaded on one end. The other end of the carrier (the end not loaded with alkaline compounds) was immersed in a mixed solution of Pt(NO3)2 and BiCl3 (wherein the mass ratio of active component Pt to alumina was 1:50; the mass ratio of bismuth salt to alumina was 1:20) by an equal volume impregnation method. The saturated carrier was dried at 120°C for 4 hours and calcined at 500°C for 4 hours to obtain a Pt-loaded integral catalyst.

[0071] Reference Example 1

[0072] After mixing alumina with an appropriate amount of silica sol (binder), adjust the pH value to 5.0 with nitric acid, and stir for 6 hours to form a slurry; apply the slurry on the cordierite carrier, dry at 120°C for 4 hours, and calcine at 500°C for 4 hours to obtain a carrier with a coating. The cordierite carrier is completely immersed in a KOH aqueous solution by an equal volume impregnation method, wherein the mass ratio of KOH (in terms of K) to alumina is 1:20, and the saturated carrier is dried at 120°C for 4 hours and calcine at 500°C for 4 hours to obtain a carrier with an alkaline compound loaded on one end. The other end of the carrier (the end not loaded with alkaline compounds) was immersed in a mixed solution of Pt(NO3)2 and BiCl3 (wherein the mass ratio of active component Pt to alumina was 1:50; the mass ratio of bismuth salt to alumina was 1:20) by an equal volume impregnation method. The saturated carrier was dried at 120°C for 4 hours and calcined at 500°C for 4 hours to obtain a Pt-loaded integral catalyst.

[0073] The catalysts prepared in Example 1 and Reference Example 1 were subjected to CH4 oxidation test at normal pressure using a fixed bed reactor. The catalyst test conditions were: mass space velocity 15000 ml / min. -1 l -1 , the gas composition is 1000ppmCH4+2%O2+Ar+200ppmSO2. The concentration of CH4 at the inlet and outlet of the bed is analyzed by chromatography, and the CH4 conversion rate is calculated based on this. The test results are shown in Table 1 below, which is a comparison table of methane conversion rates of catalysts after 20 hours of oxidation reaction.

[0074] As shown in Table 1, the catalyst of Example 1 is not significantly affected by the concentration of SO2, and its methane conversion rate is relatively high; compared with Reference Example 1, the catalyst of Example 1 has good sulfur resistance. Since the coating in Reference Example 1 only uses sulfur-intolerant aluminum oxide, the catalyst prepared in Reference Example 1 is still affected by sulfur-containing compounds, and the active components (basic compounds and Pt) cannot be well and evenly loaded on the carrier, which further results in poor catalyst activity and low methane conversion rate.

[0075] Table 1 is a comparison of the methane conversion rates of the catalysts after 20 hours of oxidation reaction.

[0076] Serial number Reaction temperature (℃) Conversion rate (%) Example 1 420 80 Reference Example 1 450 25 Reference Example 2 450 30 Reference Example 3 450 5 Reference Example 4 450 5 Example 2 450 85 Example 3 450 85 Example 4 450 70

[0077] Reference Example 2

[0078] After mixing alumina, ZrO2 (modifier) ​​and an appropriate amount of silica sol (binder) in a mass ratio of 10:1, adjust the pH value to 5.0 with nitric acid, and stir for 6 hours to form a slurry; apply the slurry on the cordierite carrier, dry at 120°C for 4 hours, and calcine at 500°C for 4 hours to obtain a carrier with a coating. Use an equal volume impregnation method to immerse one end of the carrier in a mixed solution of Pt(NO3)2 and BiCl3 (wherein the mass ratio of active component Pt to alumina is 1:50; the mass ratio of bismuth salt to alumina is 1:20), dry the saturated carrier at 120°C for 4 hours, and calcine at 500°C for 4 hours to obtain a catalyst.

[0079] The catalysts prepared in Example 1 and Reference Example 2 were subjected to a CH4 oxidation test at normal pressure, and the test process was the same as above. The test results are shown in Table 1. As can be seen from Table 1, the catalyst of Example 1 is not significantly affected by the concentration of SO2, and its methane conversion rate is relatively high; compared with Reference Example 2, the catalyst of Example 1 has good sulfur resistance. Since Reference Example 2 does not carry an alkaline compound that can adsorb sulfur-containing compounds, only the modified alumina on the carrier is used to prevent sulfur-containing compounds from being deposited on the catalyst.

[0080] Reference Example 3

[0081] Alumina, ZrO2 (modifier) ​​and an appropriate amount of silica sol (binder) in a mass ratio of 10:1 were mixed, the pH value was adjusted to 5.0 with nitric acid, and stirred for 6 hours to form a slurry; the slurry was applied to a cordierite carrier, dried at 120°C for 4 hours, and calcined at 500°C for 4 hours to obtain a carrier with a coating. All the carriers with coatings were impregnated in a KOH aqueous solution by an equal volume impregnation method, wherein the mass ratio of KOH (in terms of K) to alumina was 1:20, and the impregnated saturated carrier was dried at 120°C for 4 hours and calcined at 500°C for 4 hours to obtain a catalyst.

[0082] The catalysts prepared in Example 1 and Reference Example 3 were subjected to CH4 oxidation tests at normal pressure, and the test process was the same as above. The test results are shown in Table 1. As can be seen from Table 1, the catalyst of Example 1 is not significantly affected by the concentration of SO2, and its methane conversion rate is relatively high; compared with Reference Example 3, the catalyst of Example 1 has good sulfur resistance. Since Reference Example 3 does not load the active component Pt for methane oxidation, its methane conversion rate is extremely low.

[0083] Reference Example 4

[0084] After mixing alumina, ZrO2 (modifier) ​​and an appropriate amount of silica sol (binder) in a mass ratio of 10:1, adjust the pH value to 5.0 with nitric acid, and stir for 6 hours to form a slurry; apply the slurry on the cordierite carrier, dry at 120°C for 4 hours, and calcine at 500°C for 4 hours to obtain a carrier with a coating. One end of the coated carrier is impregnated in a KOH aqueous solution by an equal volume impregnation method, wherein the mass ratio of KOH (in terms of K) to alumina is 1:20, and the impregnated saturated carrier is dried at 120°C for 4 hours and calcine at 500°C for 4 hours to obtain a carrier with an alkaline compound loaded at one end. The other end of the carrier (the end without the alkaline compound loaded) is impregnated in a BiCl3 solution (wherein the mass ratio of bismuth salt to alumina is 1:20) by an equal volume impregnation method, and the impregnated saturated carrier is dried at 120°C for 4 hours and calcine at 500°C for 4 hours to obtain a catalyst loaded with precious metals.

[0085] The catalysts prepared in Example 1 and Reference Example 4 were subjected to CH4 oxidation tests at normal pressure, and the test process was the same as above. The test results are shown in Table 1. As can be seen from Table 1, the catalyst of Example 1 is not significantly affected by the concentration of SO2, and its methane conversion rate is relatively high; compared with Reference Example 4, the catalyst of Example 1 has good sulfur resistance. Since Reference Example 4 only immerses the carrier in a bismuth salt solution and does not load the active component Pt for methane oxidation, its methane conversion rate is extremely low.

[0086] Example 2

[0087] After mixing alumina, ZrO2 (modifier) ​​and an appropriate amount of silica sol (binder) in a mass ratio of 10:1, adjust the pH value to 5.0 with nitric acid, and stir for 6 hours to form a slurry; apply the slurry on a cordierite carrier, dry at 120°C for 4 hours, and calcine at 500°C for 4 hours to obtain a carrier with a coating. One end of the carrier with a coating is impregnated in a NaOH aqueous solution by an equal volume impregnation method, wherein the mass ratio of NaOH (in terms of Na) to alumina is 1:10, and the impregnated saturated carrier is dried at 120°C for 4 hours and calcine at 500°C for 4 hours to obtain a carrier with an alkaline compound loaded on one end. The other end of the carrier (the end not loaded with alkaline compounds) was immersed in a mixed solution of Pt(NO3)2 and BiCl3 (wherein the mass ratio of active component Pt to alumina was 1:50; the mass ratio of bismuth salt to alumina was 1:20) by an equal volume impregnation method. The saturated carrier was dried at 120°C for 4 hours and calcined at 500°C for 4 hours to obtain a Pt-loaded integral catalyst.

[0088] Preferred in Table 1 is sodium hydroxide.

[0089] The catalysts prepared in Example 1 and Example 2 were subjected to a CH4 oxidation test at normal pressure, and the test process was the same as above. The test results are shown in Table 1. As can be seen from Table 1, the catalysts of Example 1 and Example 2 are not significantly affected by the concentration of SO2, and their methane conversion rates are both high, and their catalysts have good sulfur resistance. Since the basic compound NaOH is loaded in Example 2, the methane conversion rate of the catalyst of Example 2 is higher than that of Example 1 (KOH).

[0090] Example 3

[0091] After mixing alumina, ZrO2 (modifier) ​​and an appropriate amount of silica sol (binder) in a mass ratio of 10:1, adjust the pH value to 5.0 with nitric acid, and stir for 6 hours to form a slurry; apply the slurry on a cordierite carrier, dry at 120°C for 4 hours, and calcine at 500°C for 4 hours to obtain a carrier with a coating. One end of the carrier with a coating is impregnated in a NaOH aqueous solution by an equal volume impregnation method, wherein the mass ratio of NaOH (in terms of Na) to alumina is 3:10, and the impregnated saturated carrier is dried at 120°C for 4 hours and calcine at 500°C for 4 hours to obtain a carrier with an alkaline compound loaded on one end. The other end of the carrier (the end not loaded with alkaline compounds) was immersed in a mixed solution of Pt(NO3)2 and BiCl3 (wherein the mass ratio of active component Pt to alumina was 1:50; the mass ratio of bismuth salt to alumina was 1:20) by an equal volume impregnation method. The saturated carrier was dried at 120°C for 4 hours and calcined at 500°C for 4 hours to obtain a Pt-loaded integral catalyst.

[0092] The catalysts prepared in Example 1 and Example 3 were subjected to a CH4 oxidation test at normal pressure, and the test process was the same as above. The test results are shown in Table 1. As can be seen from Table 1, the catalysts in Example 1 and Example 3 were not significantly affected by the concentration of SO2, and their methane conversion rates were both high, and their catalysts both had good sulfur resistance. Since the basic compound NaOH was loaded in Example 3, the methane conversion rate of the catalyst in Example 3 was higher than that in Example 1 (KOH).

[0093] Example 4

[0094] After mixing alumina, ZrO2 (modifier) ​​and an appropriate amount of silica sol (binder) in a mass ratio of 10:1, adjust the pH value to 5.0 with nitric acid, and stir for 6 hours to form a slurry; apply the slurry on a cordierite carrier, dry at 120°C for 4 hours, and calcine at 500°C for 4 hours to obtain a carrier with a coating. One end of the carrier with a coating is impregnated in a NaOH aqueous solution by an equal volume impregnation method, wherein the mass ratio of NaOH (in terms of Na) to alumina is 3:10, and the impregnated saturated carrier is dried at 120°C for 4 hours and calcine at 500°C for 4 hours to obtain a carrier with an alkaline compound loaded on one end. The other end of the carrier (the end not loaded with alkaline compounds) was immersed in a Pt(NO3)2 solution (wherein the mass ratio of active component Pt to alumina was 1:50) by means of equal volume impregnation. The saturated carrier was dried at 120°C for 4 hours. After drying, the dried carrier was immersed in a BiCl3 solution by means of equal volume impregnation. The mass ratio of BiCl3 (calculated as Bi) to alumina was 1:20. After saturated impregnation, the carrier was dried at 120°C for 4 hours and calcined at 500°C for 4 hours to obtain a Pt-loaded integral catalyst.

[0095] The catalysts prepared in Example 1 and Example 4 were subjected to a CH4 oxidation test at normal pressure, and the test process was the same as above. The test results are shown in Table 1. As can be seen from Table 1, the catalysts in Example 1 and Example 4 were not significantly affected by the concentration of SO2, and their methane conversion rates were both high, and their catalysts both had good sulfur resistance. In Example 4, the platinum salt and the bismuth salt were impregnated separately, and the final catalyst still had good sulfur resistance.

[0096] For the method embodiments, for the sake of simplicity, they are all described as a series of action combinations, but those skilled in the art should know that the present invention is not limited by the order of the actions described, because according to the present invention, some steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and components involved are not necessarily required by the present invention.

[0097] The above is a detailed introduction to the preparation method of a sulfur-resistant Pt-loaded integral catalyst, a Pt-loaded integral catalyst and an application provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for a general technician in this field, according to the idea of ​​the present invention, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A method for preparing a Pt-loaded monolithic catalyst having sulfur resistance, characterized in that: The method comprises: Step 1: coating a slurry formed by mixing alumina and a modifier in a mass ratio of 100:1 to 10:3 and an appropriate amount of a binder on a cordierite carrier, drying and calcining to obtain a carrier with a coating; Step 2: After immersing one end of the coated carrier in an alkaline solution, the coated carrier is dried and calcined so that one end of the coated carrier is loaded with an alkaline compound to form an upper functional area; wherein the alkaline solution is composed of one or two solutions of KOH, NaOH, K2CO3, and Na2CO3; Step 3: After immersing the other end of the coated carrier in a mixed solution of platinum salt and bismuth salt, the coated carrier is dried and calcined to obtain a Pt-loaded monolithic catalyst, so that the other end of the coated carrier is loaded with Pt to form a lower functional area; The modifier is one or more of titanium oxide, zirconium oxide, tin oxide, vanadium pentoxide and tungsten trioxide.

2. The preparation method according to claim 1, characterized in that: In the step 1, the mass ratio of the aluminum oxide to the modifier in the coating is 10:1; The loading amount of the coating in the coated carrier is 50 g / L-150 g / L.

3. The preparation method according to claim 1, characterized in that: In step 1, the drying time is 4 h to 5 h, and the drying temperature is 120° C. to 200° C.; the roasting time is 4 h to 5 h, and the roasting temperature is 500° C. to 600° C.; and the stirring time required for the mixing is 3 h to 6 h.

4. The preparation method according to claim 1, characterized in that: In step 1, the binder is one or more of aluminum sol, silica sol, polyvinyl alcohol, hydroxymethyl cellulose, and titanium sol.

5. The preparation method according to claim 1, characterized in that: In the step 2, the mass ratio of the basic compound to the aluminum oxide is 1:20 to 3:10; The alkaline compound is KOH or NaOH.

6. The preparation method according to claim 1, characterized in that: In step 2, the drying time is 4 h to 6 h, and the drying temperature is 100° C. to 150° C.; the calcining time is 4 h to 8 h, and the calcining temperature is 400° C. to 550° C.

7. The preparation method according to claim 1, characterized in that: In step 3, the platinum salt is any one of platinum nitrate, chloroplatinic acid, hydroxylamine platinum, and platinum acetate; The bismuth salt is bismuth nitrate or bismuth chloride, and the mass ratio of the bismuth salt to the aluminum oxide is 1:200 to 1:5; The mass ratio of the Pt to the alumina is 1:200 to 1:

10.

8. The preparation method according to claim 1, characterized in that: In step 3, the drying time is 4 h to 6 h, and the drying temperature is 100° C. to 150° C.; the calcining time is 2 h to 4 h, and the calcining temperature is 400° C. to 550° C.

9. A Pt-loaded monolithic catalyst obtained by the preparation method according to any one of claims 1 to 8, characterized in that: The monolithic catalyst uses a cordierite carrier as a skeleton matrix, the surface of the skeleton matrix is ​​loaded with a modified alumina coating, one end of the modified alumina coating is loaded with an alkaline compound to form an upper functional area, and the other end of the modified alumina coating is loaded with Pt to form a lower functional area; Wherein, the upper functional zone is used for removing sulfur-containing compounds; and the lower functional zone is used for catalytic methane oxidation.

10. An application of a Pt-loaded monolithic catalyst obtained by the preparation method according to any one of claims 1 to 8, characterized in that: The application of the Pt-loaded monolithic catalyst in the combustion reaction of sulfur-containing natural gas.

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