Bifunctional catalysts, methods for their preparation and use

Abstract

The present application relates to the field of methane refining catalyst, and discloses a bifunctional catalyst and a preparation method and application thereof.The bifunctional catalyst comprises a carrier and active component I, active component II and an auxiliary agent supported on the carrier, the active component I is nickel and / or nickel oxide, the active component II is manganese dioxide, the auxiliary agent is La2O3, and the carrier is a magnesium-aluminum composite oxide comprising MgAl2O4, and the content of MgAl2O4 is 93-100 wt%.Based on the total amount of the bifunctional catalyst, the content of the active component I calculated in terms of nickel is 10-20 wt%, the content of the active component II is 5-15 wt%, the content of the auxiliary agent is 0.1-2 wt%, and the content of the carrier is 74-85 wt%.The bifunctional catalyst can crack paraffin vapor in the slurry bed outlet process gas into small molecular hydrocarbons, and can also make the process gas achieve the effect of high-temperature methanation refining similar to the ordinary separation paraffin series process.

Description

Technical Field

[0001] This invention relates to the field of methane refining catalysts, specifically to bifunctional catalysts, their preparation methods, and applications. Background Technology

[0002] Syngas, composed of CH4, H2, CO, and CO2, is an ideal feedstock for producing SNG / LNG. Converting syngas into natural gas yields significant economic and social benefits. Developing suitable syngas-to-methane technology, tailored to the composition of syngas, is an effective and crucial approach to utilizing syngas.

[0003] Currently, low-temperature methanation is gradually becoming a new direction for methane production. Due to its higher chemical equilibrium, larger throughput, fewer equipment requirements, and no need for recirculation, low-temperature methanation is widely used in methane production. Slurry bed methanation is a relatively advanced reaction device in low-temperature processes. Its reaction zone exhibits highly uniform temperature, making it extremely difficult for temperatures to runaway or become excessively high. It also features rapid heat transfer and high methanation efficiency, making slurry bed technology excellent in methanation production. However, slurry bed methanation is subject to process limitations. The process gas exiting the slurry bed contains paraffin vapor and paraffin entrained in the liquid droplets. This requires cooling and condensation separation, followed by heat exchange and reheating before entering the subsequent refining process. The cooling, condensation, and reheating process requires several pieces of equipment, including condensers, separation tanks, cold water circulation pumps, heat exchangers, and heaters, and involves heat loss and power consumption. The separated paraffin-water mixture increases the pressure on wastewater discharge. If the process gas from the slurry bed outlet enters the subsequent refining stage directly without heat exchange, paraffin wax will accumulate on the surface of the subsequent refining catalyst, forming a phenomenon similar to catalyst waxing, which gradually deactivates the catalyst physically.

[0004] Currently available paraffin decomposition catalysts typically employ catalytic cracking catalysts, using ZSM-5 molecular sieves or platinum-impregnated ZSM-5 molecular sieves in fluidized beds for catalytic cracking reactions. However, the process, catalyst lifetime, and catalyst morphology are not suitable for fixed-bed systems. Furthermore, for the removal of trace amounts of paraffin, non-precious metal systems are generally used for cracking to reduce catalyst costs. In addition, there are currently no reports of catalysts with dual functions of dewaxing and methanation refining.

[0005] CN104588066A discloses a methanation catalyst and its preparation method. This method involves loading active components and magnesium aluminum spinel onto a mesoporous molecular sieve. Through the interaction between the magnesium aluminum spinel and the active components, and with the synergistic effect of the mesoporous molecular sieve, it can improve the CO2 conversion rate in each stage of the multi-stage methanation reaction of coke oven gas. However, this methanation catalyst requires the interaction of multiple active components and the coordination of the mesoporous molecular sieve. Furthermore, it does not address how to reduce and / or remove paraffin in the process gas during the refining process. In addition, the magnesium aluminum spinel used in conventional methanation catalysts is calcined at a low temperature during preparation, which cannot effectively form a complete spinel morphology and corresponding microstructure. The residual alumina in the support is relatively large, which generates more carbon deposits during the paraffin cracking process, affecting the activity and lifespan of the catalyst. Summary of the Invention

[0006] The purpose of this invention is to overcome the problem of poor paraffin tolerance and easy deactivation of existing methane refining catalysts.

[0007] To achieve the above objectives, the first aspect of the present invention provides a bifunctional catalyst, the bifunctional catalyst comprising a support and active component I, active component II and an auxiliary agent supported on the support, wherein active component I is nickel and / or nickel oxide, active component II is manganese dioxide, the auxiliary agent is La2O3, the support is a magnesium-aluminum composite oxide, the magnesium-aluminum composite oxide comprising MgAl2O4, and the content of MgAl2O4 is 93-100 wt% based on the total amount of the magnesium-aluminum composite oxide;

[0008] Based on the total amount of the bifunctional catalyst, the content of active component I (calculated as nickel) is 10-20 wt%, the content of active component II is 5-15 wt%, the content of the promoter is 0.1-2 wt%, and the content of the support is 74-85 wt%.

[0009] The inventors of this invention discovered during their research that using water generated from the syngas methanation reaction, supplemented by a catalyst with paraffin decomposition effects, to directly carry out the subsequent refining reaction of slurry-bed methanation, the wax-resistant methanation catalyst can significantly shorten the process flow of subsequent refining in slurry-bed methanation. Especially in slurry-bed methane production systems, the water vapor in the slurry-bed outlet gas and the exothermic temperature rise during refining are very suitable for the process conditions of paraffin cracking into smaller molecules. The bifunctional catalyst provided by this invention can crack the paraffin vapor carried out by the process gas from the slurry bed into smaller molecule hydrocarbons, mainly into methane, and simultaneously perform a first-stage refining of the slurry-bed outlet process gas. Preferably, when the water-to-wax ratio is greater than 10, the bifunctional catalyst can withstand paraffin vapor up to 1000 ppm and provides good high-temperature refining effect of methanation.

[0010] A second aspect of the present invention provides a method for preparing the bifunctional catalyst described in the first aspect, the method comprising the following steps:

[0011] (1) A mixture containing magnesium oxide, boehmite and a pore-expanding agent is subjected to a first calcination to obtain a carrier; wherein the temperature of the first calcination is 800-1000℃;

[0012] (2) The active component precursor I, the active component precursor II and the auxiliary agent precursor are loaded onto the support, and then the resulting product is subjected to a second calcination; wherein the temperature of the second calcination is lower than the temperature of the first calcination.

[0013] The third aspect of this invention provides the application of the bifunctional catalyst described in the first aspect in the methanation of paraffin-containing syngas to natural gas.

[0014] Through the above technical solution, the bifunctional catalyst provided by the present invention can crack the paraffin vapor carried out by the process gas from the slurry bed into small molecule hydrocarbons. This eliminates the need to remove the paraffin vapor and paraffin entrained in the liquid droplets from the process gas at the slurry bed outlet during the subsequent purification process of syngas to methane. The process gas can directly enter the high-temperature purification reactor for primary purification, eliminating the condensation, separation, and heating steps between the slurry bed and the primary purification reactor, as well as the various equipment required for these steps. This bifunctional catalyst can also enable the process gas to achieve a high-temperature methanation purification effect similar to that of a conventional paraffin separation series process. Attached Figure Description

[0015] Figure 1 This is the XRD pattern of the carrier obtained in Embodiment 1 of the present invention. Detailed Implementation

[0016] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0017] In this invention, unless otherwise stated, the content of each component in the bifunctional catalyst is calculated by the amount of feed.

[0018] In this invention, unless otherwise stated, the pressure is gauge pressure.

[0019] As previously stated, the first aspect of the present invention provides a bifunctional catalyst, the bifunctional catalyst comprising a support and active component I, active component II and an auxiliary agent supported on the support, wherein active component I is nickel and / or nickel oxide, active component II is manganese dioxide, the auxiliary agent is La2O3, the support is a magnesium-aluminum composite oxide, the magnesium-aluminum composite oxide comprising MgAl2O4, and the content of MgAl2O4 is 93-100 wt% based on the total amount of the magnesium-aluminum composite oxide;

[0020] Based on the total amount of the bifunctional catalyst, the content of active component I (calculated as nickel) is 10-20 wt%, the content of active component II is 5-15 wt%, the content of the promoter is 0.1-2 wt%, and the content of the support is 74-85 wt%.

[0021] According to some embodiments of the present invention, preferably, the content of MgAl2O4 is 96-100 wt% based on the total amount of the magnesium-aluminum composite oxide.

[0022] According to some embodiments of the present invention, the magnesium-aluminum composite oxide preferably further includes MgO and / or Al2O3. The MgO is residual magnesium oxide that has not formed magnesium-aluminum spinel (MgAl2O4); the Al2O3 is residual aluminum oxide that has not formed magnesium-aluminum spinel (MgAl2O4).

[0023] Preferably, based on the total amount of the magnesium-aluminum composite oxide, the content of MgO is 0-5 wt%, preferably 0-3 wt%; and the content of Al2O3 is 0-2 wt%, preferably 0-1 wt%.

[0024] In the preferred embodiment described above, the magnesium-aluminum composite oxide contains a low amount of residual alumina, which helps reduce the number of acidic sites. If there is excessive alumina, during paraffin cracking, the relatively stable α-carbon at acidic sites transforms into more reactive β-carbon, easily causing the growth of carbon nanotubes on the catalyst surface, leading to catalyst deactivation due to carbon buildup. The low residual alumina content in the magnesium-aluminum composite oxide avoids this problem of carbon buildup and deactivation, thus improving the catalyst's activity and lifespan.

[0025] According to some embodiments of the present invention, preferably, the grain size of MgAl2O4 is <20 nm, more preferably 4-15 nm, and even more preferably 5-10 nm. Using the above preferred embodiments helps to improve the dispersion of the active component on the carrier surface and, together with the additives, to fix the active component, preventing the carbon nanotubes from lifting the active component from the carrier and causing it to be lost.

[0026] According to some embodiments of the present invention, preferably, the pore volume of MgAl2O4 is >0.15 mL / g, more preferably 0.25-0.35 mL / g, and even more preferably 0.27-0.33 mL / g.

[0027] According to some embodiments of the present invention, preferably, the average pore size of MgAl2O4 is 10-50 nm, more preferably 10-30 nm, and even more preferably 13-20 nm.

[0028] By adopting the above preferred embodiment, the grain size, pore volume and average pore size of MgAl2O4 meet the above conditions, which is beneficial to control the impregnation amount of active components during catalyst preparation, as well as the diffusion of paraffin molecules in the catalyst channels and the escape of paraffin cracking products.

[0029] According to some embodiments of the present invention, preferably, the molar ratio of Mg to Al in the magnesium-aluminum composite oxide is 1:2-2.04.

[0030] According to some embodiments of the present invention, in the bifunctional catalyst, the active component I is present in the form of nickel and / or nickel oxide. Activation reduction by contact with a reducing gas can reduce the nickel oxide to active nickel.

[0031] A second aspect of the present invention provides a method for preparing the bifunctional catalyst described in the first aspect, the method comprising the following steps:

[0032] (1) A mixture containing magnesium oxide, boehmite and a pore-expanding agent is subjected to a first calcination to obtain a carrier; wherein the temperature of the first calcination is 800-1000℃;

[0033] (2) The active component precursor I, the active component precursor II and the auxiliary agent precursor are loaded onto the support, and then the resulting product is subjected to a second calcination; wherein the temperature of the second calcination is lower than the temperature of the first calcination.

[0034] According to some embodiments of the present invention, preferably, in step (1), the temperature of the first calcination is 850-950°C. Using the above preferred embodiments is more conducive to increasing the MgAl2O4 content and reducing the Al2O3 content in the magnesium-aluminum composite oxide, thereby reducing carbon deposits generated during paraffin cracking and improving the activity and service life of the catalyst.

[0035] According to some embodiments of the present invention, preferably, in step (1), the first roasting time is 2-10 hours, more preferably 4-8 hours.

[0036] According to some embodiments of the present invention, preferably, in step (1), the magnesium oxide is light magnesium oxide, and the average particle size of the light magnesium oxide is 0.06-0.09 mm.

[0037] According to some embodiments of the present invention, preferably, in step (1), the average particle size of the pseudoboehmite is 0.06-0.09 mm.

[0038] Using the raw materials described in the preferred embodiments above is more conducive to obtaining a carrier that meets the above requirements.

[0039] According to some embodiments of the present invention, preferably, in step (1), the pore-expanding agent is selected from at least one of oxalic acid, nitric acid, acetic acid and sulfuric acid, preferably nitric acid.

[0040] Preferably, the ratio of the pore-expanding agent to the magnesium oxide is 1 mL: 40-60 g.

[0041] According to some embodiments of the present invention, for ease of molding, preferably, in step (1), the mixture also contains an adhesive.

[0042] Preferably, the binder is selected from at least one of guar gum powder, stearate and cellulose and their derivatives, and is preferably sodium carboxymethyl cellulose.

[0043] Preferably, the mass ratio of the adhesive to the magnesium oxide is 1:20-25.

[0044] According to some embodiments of the present invention, in order to ensure that the components in the mixture are sufficiently dispersed and have appropriate strength for subsequent molding, preferably, in step (1), the mixture also contains a solvent.

[0045] Preferably, the solvent is deionized water.

[0046] Preferably, the volume ratio of the solvent to the pore-expanding agent is 80-150:1.

[0047] According to some embodiments of the present invention, preferably, before the first calcination, step (1) further includes the sequential steps of mixing and grinding, sieving, drying, and shaping. The mixing, grinding, sieving, drying, and shaping steps are all conventional methods for preparing catalysts and can be performed with reference to existing technologies.

[0048] According to some embodiments of the present invention, preferably, in step (2), the active component precursor I is selected from at least one of nickel nitrate, nickel chloride, and nickel sulfate, and preferably nickel nitrate. Preferably, the active component precursor I is provided in the form of an aqueous solution. Exemplarily, the nickel nitrate may be provided in the form of a 60 wt% aqueous solution of nickel nitrate.

[0049] According to some embodiments of the present invention, preferably, in step (2), the active component precursor II is selected from at least one of manganese nitrate, manganese sulfate, and manganese chloride, preferably manganese nitrate. Preferably, the active component precursor II is provided in the form of an aqueous solution. Exemplarily, the manganese nitrate may be provided in the form of a 50 wt% aqueous solution of manganese nitrate.

[0050] According to some embodiments of the present invention, preferably, in step (2), the auxiliary agent precursor is selected from at least one of lanthanum nitrate, lanthanum chloride, and lanthanum sulfate, and preferably lanthanum nitrate. Preferably, the auxiliary agent precursor is provided in the form of an aqueous solution. Exemplarily, the lanthanum nitrate may be provided in the form of a 4 wt% aqueous solution of lanthanum nitrate.

[0051] According to some embodiments of the present invention, preferably, in step (2), the conditions for the second calcination include: a temperature of 350-500°C, preferably 400-450°C; and a time of 4-10 h, preferably 4-8 h.

[0052] According to some embodiments of the present invention, preferably, in step (2), the loading method is an impregnation method;

[0053] Preferably, the impregnation conditions include: a temperature of 60-80°C and a time of 0.5-2 hours;

[0054] Preferably, the active component precursor I is first loaded onto the support to obtain intermediate I, then the active component precursor II is loaded onto intermediate I to obtain intermediate II, and finally the auxiliary agent precursor is loaded onto intermediate II. After impregnation, each component needs to be dried and calcined to fix the component. The drying can be performed according to existing technology.

[0055] According to a preferred embodiment of the present invention, in step (2), the loading step includes:

[0056] (a) The carrier is contacted with the active component precursor I for a first impregnation, the resulting product is filtered, and the resulting solid is then dried and calcined in sequence to obtain intermediate I.

[0057] (b) The intermediate I is contacted with the active component precursor II for a second impregnation, and then the resulting product is filtered. The resulting solid is then dried and calcined in a second calcination process to obtain intermediate II.

[0058] (c) The intermediate II is contacted with the auxiliary precursor for a third impregnation, the resulting product is then filtered, and the resulting solid is then dried and calcined in the second calcination III.

[0059] The conditions for the first impregnation, the second impregnation, and the third impregnation each independently include: a temperature of 60-80℃; and a time of 0.5-2h.

[0060] The conditions for the second calcination I, the second calcination II, and the second calcination III each independently include: a temperature of 350-500℃, preferably 400-450℃; and a time of 4-10h, preferably 4-8h.

[0061] According to some embodiments of the present invention, preferably, the method further includes: contacting the product obtained from the second calcination in step (2) with a reducing gas for reduction. This operation enables the nickel oxide to be reduced to active nickel.

[0062] Preferably, the reducing gas is hydrogen or a mixture of hydrogen and nitrogen. For example, the mixture may be a mixture with a hydrogen content of 20% by volume and a nitrogen content of 80% by volume.

[0063] Preferably, the reduction conditions include: a temperature of 400-500℃ and a time of 2-6 hours.

[0064] The third aspect of this invention provides the application of the bifunctional catalyst described in the first aspect in the methanation of paraffin-containing syngas to natural gas.

[0065] According to some embodiments of the present invention, preferably, the paraffin-containing synthesis gas is a paraffin-containing slurry bed outlet process gas, wherein the paraffin vapor content is not higher than 1000 ppm, preferably 50-1000 ppm; and the water-paraffin molar ratio is higher than 10.

[0066] According to some embodiments of the present invention, preferably, the paraffin-containing synthesis gas contains 3-5% CO by volume, 7-10% CO2 by volume, 37-55% H2 by volume, 15-26.5% CH4 by volume, and 15-26.5% water vapor by volume. Preferably, the water vapor is derived from water spontaneously generated by the slurry-bed methanation reaction.

[0067] According to some embodiments of the present invention, preferably, the pressure of the paraffin-containing synthesis gas is 2.0-4.0 MPa, more preferably 2.5-3.5 MPa; and the temperature is 260-350°C, more preferably 270-320°C.

[0068] According to some embodiments of the present invention, preferably, the process conditions for the application include: a pressure of 2.0-4.0 MPa, an inlet temperature of 260-350°C, a hot spot temperature of 500-700°C, and a volumetric hourly space velocity of 1000-10000 h⁻¹. -1 .

[0069] More preferably, the process conditions for the application include: pressure 2.5-3.5 MPa, inlet temperature 270-320°C, hot spot temperature 550-650°C, and volumetric hourly space velocity 2000-5000 h⁻¹. -1 .

[0070] According to some embodiments of the present invention, the reaction temperature and heat required for the bifunctional catalyst are provided externally or by the heat of reaction from other reactions. Preferably, the application includes an exothermic process gas system, and more preferably, the exothermic process gas system is a slurry-bed methane refining system.

[0071] The present invention will be described in detail below through embodiments.

[0072] Unless otherwise specified, all raw materials used in the following examples and comparative examples are commercially available products. Among them:

[0073] Light magnesium oxide was purchased from Nanjing Pharmaceutical Company. The grade / type was industrial grade, with a purity >99wt% and an average particle size of 0.063mm.

[0074] The boehmite was purchased from Shandong Aluminum Company, with the model / grade LSi-pfd-7, and its Al2O3 content was 70wt%; the average particle size was 0.09mm.

[0075] Nickel nitrate was purchased from Nanjing Chemical Reagent Factory, model / grade AR, purity >99wt%.

[0076] Unless otherwise specified, the testing equipment used in the following examples and comparative examples are all commercially available products.

[0077] in:

[0078] The XRD pattern of the support was determined by X-ray diffraction. The powder X-ray diffractometer was purchased from Bruker, model D8 advance.

[0079] The grain size was obtained by X-ray diffraction.

[0080] Pore ​​volume and average pore size were obtained by BET adsorption testing.

[0081] The hydrocarbon content was obtained by chromatographic testing, using an Agilent 8890 three-valve five-column FID analyzer.

[0082] The following examples illustrate the bifunctional catalyst and its preparation method provided by the present invention.

[0083] Example 1

[0084] (S1) Light magnesium oxide (400g), pseudoboehmite (1450g), pore expander, binder, and solvent are brought together and sequentially mixed, milled, sieved, dried, shaped, and subjected to a first calcination to obtain a carrier. The XRD test results are as follows: Figure 1 As shown in the figure, there are obvious characteristic peaks of magnesium aluminum spinel at positions 2θ = 37.2°, 45.4°, and 66.25°, indicating that the main body of the support is magnesium aluminum spinel (MgAl2O4). A characteristic peak of magnesium oxide is present at 2θ = 42.9°, which is sharp but has low intensity. No characteristic peak of aluminum oxide is observed at 2θ = 67.2°. Its composition and property parameters are shown in Table 1; where:

[0085] The conditions for the first roasting were: temperature 900℃; time 6 hours.

[0086] The pore-expanding agent is nitric acid, and its ratio with magnesium oxide is 1 mL: 50 g;

[0087] The binder is sodium carboxymethyl cellulose, and its mass ratio with magnesium oxide is 1:21.6;

[0088] The solvent is deionized water, and its volume ratio with the pore-expanding agent is 100:1.

[0089] The sieve used for sieving was a 10-mesh sieve; the drying conditions were: temperature 120℃; time 6 hours.

[0090] The catalyst particles obtained by molding have a size of Φ5*5mm;

[0091] (S2) The above-mentioned carrier (149g) is contacted with the active component precursor I for a first impregnation, and then the resulting product is filtered. The resulting solid is then subjected to drying and a second calcination I to obtain intermediate I; wherein:

[0092] The active component precursor I is nickel nitrate, which is provided in the form of a 60 wt% aqueous solution of nickel nitrate;

[0093] The conditions for the first immersion were: temperature 70℃; time 2 hours.

[0094] The drying conditions were: temperature 120℃; time 6 hours.

[0095] The conditions for the second calcination I are: temperature 420℃; time 4h;

[0096] (S3) The above intermediate I is contacted with the active component precursor II for a second impregnation, and then the resulting product is filtered. The resulting solid is then dried and calcined in a second calcination process to obtain intermediate II; wherein:

[0097] The active component precursor II is manganese nitrate, which is provided in the form of a 50 wt% aqueous solution of manganese nitrate.

[0098] The conditions for the second impregnation were: temperature 70℃; time 2 hours.

[0099] The drying conditions were: temperature 120℃; time 6 hours.

[0100] The conditions for the second calcination (II) are: temperature 420℃; time 4 hours.

[0101] (S4) The above intermediate II is contacted with the auxiliary precursor for a third impregnation, the resulting product is then filtered, and the resulting solid is subsequently dried and calcined in the second calcination stage III; wherein:

[0102] The auxiliary precursor is lanthanum nitrate, which is provided in the form of a 4 wt% aqueous solution of lanthanum nitrate.

[0103] The conditions for the third impregnation are: temperature 70℃; time 2 hours;

[0104] The drying conditions were: temperature 120℃; time 6 hours.

[0105] The conditions for the second calcination III are: temperature 420℃; time 4h;

[0106] (S5) The product obtained in step (S4) is reduced by contacting hydrogen gas; wherein:

[0107] The reduction conditions were: temperature 450℃; time 4 hours.

[0108] A bifunctional catalyst was obtained, wherein the total amount of the bifunctional catalyst was 15% by mass of nickel, 10% by mass of manganese dioxide, 0.5% by mass of lanthanum oxide, and the remainder was a support.

[0109] Example 2

[0110] The method of Example 1 was followed, except that the amount of support, active component I, active component II and the loading of the additives were different, while the rest were the same. The composition and property parameters of the obtained support are shown in Table 1. The obtained bifunctional catalyst, based on the total amount of the bifunctional catalyst, contains 10% by mass of nickel, 5% by mass of manganese dioxide, 1% by mass of lanthanum oxide, and the remainder is the support.

[0111] Example 3

[0112] The method of Example 1 was followed, except that the amount of support, active component I, active component II and the loading of the additives were different, while the rest were the same. The composition and property parameters of the obtained support are shown in Table 1. The obtained bifunctional catalyst, based on the total amount of the bifunctional catalyst, contained 20% by mass of nickel, 15% by mass of manganese dioxide, 0.1% by mass of lanthanum oxide, and the remainder was the support.

[0113] Example 4

[0114] The method of Example 1 was followed, except that the amount of support, active component I, active component II and the loading of the additives were different, while the rest were the same. The composition and property parameters of the obtained support are shown in Table 1. The obtained bifunctional catalyst, based on the total amount of the bifunctional catalyst, contains 10% by mass of nickel, 10% by mass of manganese dioxide, 0.6% by mass of lanthanum oxide, and the remainder is the support.

[0115] Example 5

[0116] The method of Example 1 was followed, except that the amount of support, active component I, active component II and the loading of the additives were different, while the rest were the same. The composition and property parameters of the obtained support are shown in Table 1. The obtained bifunctional catalyst, based on the total amount of the bifunctional catalyst, contained 14.2% by mass of nickel, 5.4% by mass of manganese dioxide, 0.4% by mass of lanthanum oxide, and the remainder was the support.

[0117] Example 6

[0118] The method of Example 1 was followed, except that the amount of support, active component I, active component II and the loading of the additives were different, while the rest were the same. The composition and property parameters of the obtained support are shown in Table 1. The obtained bifunctional catalyst, based on the total amount of the bifunctional catalyst, contained 14.2% by mass of nickel, 10% by mass of manganese dioxide, 0.8% by mass of lanthanum oxide, and the remainder was the support.

[0119] Example 7

[0120] The method of Example 1 was followed, except that the amount of support, active component I, active component II and the loading of the additives were different, while the rest were the same. The composition and property parameters of the obtained support are shown in Table 1. The obtained bifunctional catalyst, based on the total amount of the bifunctional catalyst, contained 17% by mass of nickel, 7% by mass of manganese dioxide, 1% by mass of lanthanum oxide, and the remainder was the support.

[0121] Example 8

[0122] The method of Example 1 was followed, except that the amount of support, active component I, active component II and the loading of the additives were different, while the rest were the same. The composition and property parameters of the obtained support are shown in Table 1. The obtained bifunctional catalyst, based on the total amount of the bifunctional catalyst, contained 12% by mass of nickel, 8% by mass of manganese dioxide, 0.2% by mass of lanthanum oxide, and the remainder was the support.

[0123] Example 9

[0124] The method is the same as in Example 1, except that:

[0125] In step (S1), the temperature of the first calcination is 800℃, and the rest are the same; the composition and property parameters of the obtained carrier are shown in Table 1;

[0126] In step (S2), the conditions for the first impregnation are: temperature 80℃; time 2h;

[0127] The conditions for the second calcination I are: temperature 450℃; time 4h;

[0128] In step (S3), the conditions for the second impregnation are: temperature 80℃; time 2h;

[0129] The conditions for the second calcination (II) are: temperature 450℃; time 4 hours.

[0130] In step (S4), the conditions for the third impregnation are: temperature 80℃; time 2h;

[0131] The conditions for the second roasting III are: temperature 450℃; time 4h;

[0132] In step (S5), the reduction temperature is 420°C;

[0133] The rest were the same, resulting in a bifunctional catalyst. Based on the total amount of the bifunctional catalyst, the content of nickel was 15% by mass, the content of manganese dioxide was 10% by mass, the content of lanthanum oxide was 0.5% by mass, and the remainder was a support.

[0134] Example 10

[0135] The method is the same as in Example 1, except that:

[0136] In step (S1), the temperature of the first calcination is 1000℃, and the rest are the same; the composition and property parameters of the obtained carrier are shown in Table 1;

[0137] In step (S2), the conditions for the first impregnation are: temperature 80℃; time 2h;

[0138] The conditions for the second calcination I are: temperature 400℃; time 4h;

[0139] In step (S3), the conditions for the second impregnation are: temperature 80℃; time 2h;

[0140] The conditions for the second calcination (II) are: temperature 400℃; time 4 hours.

[0141] In step (S4), the conditions for the third impregnation are: temperature 80℃; time 2h;

[0142] The conditions for the second calcination III are: temperature 400℃; time 4h;

[0143] In step (S5), the reduction temperature is 400℃;

[0144] The rest were the same, resulting in a bifunctional catalyst. Based on the total amount of the bifunctional catalyst, the content of nickel was 15% by mass, the content of manganese dioxide was 10% by mass, the content of lanthanum oxide was 0.5% by mass, and the remainder was a support.

[0145] Comparative Example 1

[0146] The method of Example 1 is the same except that step (S3) is omitted, and in step (S4), intermediate I is contacted with the auxiliary precursor for a third impregnation, while the rest are the same, so that the catalyst obtained does not contain active component II (manganese dioxide).

[0147] Based on the total amount of the catalyst, the content of nickel is 15% by mass, the content of lanthanum oxide is 0.5% by mass, and the remainder is a support.

[0148] Comparative Example 2

[0149] The method of Example 1 was followed, except that the temperature of the first calcination in step (S1) was 600°C, while the rest were the same. The composition and properties of the resulting support are shown in Table 1. The remaining steps were the same, and the catalyst was obtained.

[0150] Table 1

[0151]

[0152]

[0153] Note: Mg:Al refers to the molar ratio of Mg and Al in the carrier (calculated from the amount of feed).

[0154] The average pore size and pore volume are the same as those of MgAl2O4.

[0155] Test case

[0156] In an adiabatic fixed-bed reactor, the catalysts prepared in the examples and comparative examples were reacted with the slurry bed outlet process gas. The reaction conditions and catalyst activity data are shown in Table 2. The properties of the slurry bed outlet process gas are as follows:

[0157] Process gas 1: Composition: CO: 3 vol%, CO2: 7 vol%, H2: 37 vol%, CH4: 26.5 vol%, water vapor: 26.5 vol%, paraffin vapor content: 50 ppm; pressure: 2.5 MPa, temperature: 270℃.

[0158] Process gas 2: Composition: CO: 5 vol%, CO2: 10 vol%, H2: 55 vol%, CH4: 15 vol%, water vapor: 15 vol%, paraffin vapor content is 1000 ppm; pressure 3.5 MPa, temperature 320℃.

[0159] Process gas 3: Composition: CO: 4.4 vol%, CO2: 7.8 vol%, H2: 44.4 vol%, CH4: 21.7 vol%, water vapor: 21.7 vol%, paraffin vapor content: 520 ppm; pressure: 3.0 MPa, temperature: 290℃.

[0160] Table 2

[0161]

[0162]

[0163] The results above show that the bifunctional catalyst provided by this invention can decompose and crack the paraffin contained in the slurry bed outlet process gas into small molecule hydrocarbons without the need for conventional cooling and heating processes such as condensers, separators, cold water circulation pumps, heat exchangers, and heaters. This results in lower energy consumption and cost. Furthermore, the bifunctional catalyst enables the process gas to achieve a high-temperature methanation refining effect similar to that of ordinary paraffin separation series processes.

[0164] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A bifunctional catalyst, characterized in that, The bifunctional catalyst comprises a support and active component I, active component II, and an auxiliary agent supported on the support. Active component I is nickel and / or nickel oxide, active component II is manganese dioxide, and the auxiliary agent is La2O3. The support is a magnesium-aluminum composite oxide comprising MgAl2O4, MgO, and Al2O3. Based on the total amount of the magnesium-aluminum composite oxide, the content of MgAl2O4 is 93-100 wt%, the content of MgO is 0-5 wt%, and the content of Al2O3 is 0-2 wt%. The MgAl2O4 has a grain size <20 nm, a pore volume >0.15 mL / g, and an average pore size of 10-50 nm. Based on the total amount of the bifunctional catalyst, the content of active component I (calculated as nickel) is 10-20 wt%, the content of active component II is 5-15 wt%, the content of the promoter is 0.1-2 wt%, and the content of the support is 74-84 wt%.

2. The bifunctional catalyst according to claim 1, wherein, Based on the total amount of the magnesium-aluminum composite oxide, the content of MgO is 0-3wt% and the content of Al2O3 is 0-1wt%.

3. The bifunctional catalyst according to claim 1, wherein, Based on the total amount of the magnesium-aluminum composite oxide, the content of MgAl2O4 is 96-100wt%.

4. The bifunctional catalyst according to any one of claims 1-3, wherein, The grain size of MgAl2O4 is 4-15 nm; the pore volume is 0.25-0.35 mL / g; and the average pore size is 10-30 nm.

5. The bifunctional catalyst according to claim 4, wherein, The grain size of MgAl2O4 is 5-10 nm; the pore volume is 0.27-0.33 mL / g; and the average pore size is 13-20 nm.

6. The bifunctional catalyst according to any one of claims 1-3, wherein, In the magnesium-aluminum composite oxide, the molar ratio of Mg to Al is 1:2-2.

04.

7. A method for preparing a bifunctional catalyst according to any one of claims 1-6, the method comprising the following steps: (1) A mixture containing magnesium oxide, pseudoboehmite, and a pore-expanding agent is subjected to a first calcination to obtain a support; wherein, The temperature of the first calcination is 800-1000℃; (2) The active component precursor I, the active component precursor II and the auxiliary agent precursor are loaded onto the support, and then the resulting product is subjected to a second calcination; wherein the temperature of the second calcination is lower than the temperature of the first calcination.

8. The preparation method according to claim 7, wherein, In step (1), the temperature of the first roasting is 850-950℃; the roasting time is 2-10h.

9. The preparation method according to claim 8, wherein, The first roasting time is 4-8 hours.

10. The preparation method according to claim 7, wherein, In step (1), the magnesium oxide is light magnesium oxide, and the average particle size of the light magnesium oxide is 0.06-0.09 mm.

11. The preparation method according to claim 7, wherein, In step (1), the average particle size of the pseudoboehmite is 0.06-0.09 mm.

12. The preparation method according to claim 7, wherein, In step (1), the pore-expanding agent is selected from at least one of oxalic acid, nitric acid, acetic acid and sulfuric acid.

13. The preparation method according to claim 12, wherein, The pore-expanding agent is nitric acid.

14. The preparation method according to claim 7, wherein, In step (1), the ratio of the pore-expanding agent to the magnesium oxide is 1 mL: 40-60 g.

15. The preparation method according to claim 7, wherein, In step (1), the mixture also contains an adhesive.

16. The preparation method according to claim 15, wherein, The binder is selected from at least one of guar gum, stearate, and cellulose and their derivatives.

17. The preparation method according to claim 16, wherein, The adhesive is sodium carboxymethyl cellulose.

18. The preparation method according to claim 15, wherein, The mass ratio of the adhesive to the magnesium oxide is 1:20-25.

19. The preparation method according to any one of claims 7-18, wherein, In step (2), the active component precursor I is selected from at least one of nickel nitrate, nickel chloride and nickel sulfate.

20. The preparation method according to claim 19, wherein, The active component precursor I is nickel nitrate.

21. The preparation method according to any one of claims 7-18, wherein, In step (2), the active component precursor II is selected from at least one of manganese nitrate, manganese sulfate and manganese chloride.

22. The preparation method according to claim 21, wherein, The active component precursor II is manganese nitrate.

23. The preparation method according to any one of claims 7-18, wherein, In step (2), the auxiliary precursor is selected from at least one of lanthanum nitrate, lanthanum chloride and lanthanum sulfate.

24. The preparation method according to claim 23, wherein, The precursor of the auxiliary agent is lanthanum nitrate.

25. The preparation method according to any one of claims 7-18, wherein, In step (2), the loading method is the impregnation method.

26. The preparation method according to claim 25, wherein, The immersion conditions include: a temperature of 60-80℃ and a time of 0.5-2 hours.

27. The preparation method according to any one of claims 7-18, wherein, First, the active component precursor I is loaded onto the support to obtain intermediate I. Then, the active component precursor II is loaded onto intermediate I to obtain intermediate II. Finally, the adjuvant precursor is loaded onto intermediate II.

28. The preparation method according to any one of claims 7-18, wherein, In step (2), the conditions for the second calcination include: a temperature of 350-500℃ and a time of 4-10h.

29. The preparation method according to claim 28, wherein, The conditions for the second roasting include: a temperature of 400-450℃ and a time of 4-8 hours.

30. The preparation method according to any one of claims 7-18, wherein, The method further includes: reducing the product obtained by the second roasting in step (2) by contacting it with a reducing gas.

31. The use of the bifunctional catalyst according to any one of claims 1-6 in the methanation of paraffin-containing syngas to natural gas.

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