CN114433101B - Complete methanation catalyst, preparation method and application thereof and method for preparing synthetic natural gas by methanation reaction - Google Patents

Abstract

The invention provides a complete methanation catalyst, its preparation method and application and a method for preparing synthetic natural gas through methanation reaction. The method includes: (1) Weighing a specified amount of soluble salts of each component element to prepare a mixed salt solution ; (2) Prepare the precipitant solution; (4) Use the co-current coprecipitation method to drop the mixed salt solution and the precipitant solution into the sedimentation tank for co-precipitation; (5) After the precipitation, let it stand for aging; (6) Filter and wash. , the washed filter cake is refluxed with an organic solvent, then dried and roasted. The catalyst provided by the invention has excellent activity and stability, and fully meets the requirements of the catalyst for complete methanation of synthesis gas such as good low-temperature activity, good high-temperature thermal stability, and good high-temperature hydration resistance. The catalyst reacted continuously for nearly 200 hours in a small laboratory evaluation device at ultra-high space velocity (40000ml·g ^-1 ·h ^-1 ). The CO conversion rate was always ≥99%, and the _CH4 selectivity was always ≥97%.

Description

Complete methanation catalyst and its preparation method and application and methanation reaction preparation method How to generate natural gas

Technical field

The invention belongs to the fields of coal chemical industry and natural gas chemical industry, and specifically relates to a complete methanation catalyst, a preparation method of a complete methanation catalyst and a catalyst prepared by the method; and the use of the complete methanation catalyst in the complete methanation reaction of synthesis gas. Applications and a method for complete methanation of syngas.

Background technique

The characteristics of my country's energy resources are rich in coal, poor in oil (petroleum), and low in gas (natural gas). Coal consumption accounts for about 70% of primary energy consumption. Natural gas is a high-quality energy source that is clean, convenient to transport, and safe to use. With the acceleration of my country's industrialization and urbanization process and the implementation of energy conservation and emission reduction policies, the consumption proportion of clean energy such as natural gas will become larger and larger. Obtaining synthetic gas through coal or biomass gasification, and then preparing synthetic natural gas through methanation has become an effective way to make up for the shortage of gas sources. Because coal-to-natural gas has a high energy conversion rate, low water consumption, and relatively simple waste disposal, it has become one of the most effective ways to utilize coal.

The process flow of coal-to-natural gas mainly includes four parts: coal gasification, conversion, syngas purification and syngas methanation. The key to the coal-to-natural gas technical route is syngas methanation technology, and the core of syngas methanation technology is the methanation catalyst and the methanation reactor. Syngas methanation is a methanation reaction of CO with a concentration of about 20% and a small amount of CO ₂ and H ₂ in the syngas. Methanation reaction is a strongly exothermic process, and every 1% CO conversion in the reaction system will cause an adiabatic temperature rise of 72°C in the reactor. Therefore, in the existing synthesis gas methanation process, at least two reactors are generally connected in series. The first reactor must operate under high temperature and pressure in order to improve equipment utilization and production efficiency. Therefore, the catalyst must have good low-temperature activity and high-temperature stability.

At present, high-temperature and high-pressure methanation catalysts (technology) are mainly provided by foreign companies, such as Davy Company in the UK and Topsoe Company in Denmark. Since the syngas methanation reaction is a strongly exothermic reaction, the methanation reaction at high temperatures is affected by chemical equilibrium and cannot be completed completely. Therefore, the second reactor needs to be operated at a medium-low temperature (250-450°C) to completely convert the unconverted synthesis gas in the first reactor.

At present, China only has atmospheric partial methanation technology for the production of city gas and methanation catalysts for gas purification of trace amounts of CO/ _CO2 . There are no mature catalysts and supporting processes for methanation in the coal-to-natural gas process. In recent years, coal-to-natural gas projects under construction in China mainly use foreign methanation technology, which requires the payment of huge patent royalties. Therefore, it is very necessary to develop syngas methanation catalysts and corresponding supporting processes and reactors with independent intellectual property rights.

Contents of the invention

The object of the present invention is to provide a catalyst for complete methanation of synthesis gas and its preparation method. The catalyst prepared by this method has high activity (CO conversion rate is close to 100%) and high methane selectivity when applied to complete methanation reaction of synthesis gas. (CH ₄ selectivity close to 98%), strong raw material processing capacity, and the catalyst has the characteristics of good high-temperature thermal stability, strong anti-coking performance, and good high-temperature hydrothermal stability, which fully meets the requirements for coke oven gas or coal-based synthesis gas production. Requirements for complete methanation catalysts for synthetic natural gas.

According to a first aspect of the present invention, the present invention provides a complete methanation catalyst, which contains: Ni element, alkaline earth metal element, rare earth metal element, alkali metal element and Al ₂ O ₃ .

Preferably, in terms of oxides, the Ni content is 5 to 20 wt%, the alkaline earth metal content is 5 to 20 wt%, the rare earth metal content is 2 to 10 wt%, the alkali metal content is 0.5 to 5 wt%, and the Al ₂ O ₃ content is 45 -87.5wt%.

Preferably, the specific surface area of the catalyst is 158-240 m ² /g, more preferably 200-231 m ² /g; and/or the NiO grain size is 6-20 nm, preferably 7-9 nm.

Preferably, the catalyst is obtained by coprecipitating a co-precipitant solution and a mixed salt solution of each component element in parallel flow to obtain a filter cake, which is dried, roasted and shaped. Preferably, the filter cake is refluxed with an organic solvent before drying.

Preferably, the organic solvent is one or more of C1-C4 alcohols, C3-C5 ketones, and C2-C4 ethers; preferably, the organic solvent is one of methanol, ethanol, diethyl ether, and acetone. or more; and/or the volume ratio of the organic solvent to the filter cake is 3 to 10:1; and/or the conditions for the reflux treatment include: the temperature is 60-100°C, and the time is 2-30 hours.

Preferably, the alkaline earth metal element is one or more of Be, Mg, Ca, Sr and Ba, preferably one or more of Mg, Ca and Ba, further preferably Mg and/or Ca; And/or the rare earth metal element is one or more of Y, La, Ce, Pr and Sm, preferably one or more of Y, La and Ce, further preferably La and/or Ce; And/or the alkali metal element is one or more of K and Cs, preferably K.

Preferably, the catalyst contains graphite, preferably the content of graphite is 1-5% by weight, preferably 2-4% by weight based on the total weight of the catalyst.

According to a second aspect of the present invention, the present invention provides a method for preparing a complete methanation catalyst according to one aspect of the present invention, which method includes: (1) Weighing a specified amount of soluble salts of each component element to prepare a mixed salt solution; (2) Prepare the precipitant solution; (4) Use the co-current coprecipitation method to drop the mixed salt solution and the precipitant solution into the sedimentation tank for coprecipitation; (5) After the precipitation is completed, let it stand for aging; (6) Filter Washing, the washed filter cake is refluxed with an organic solvent, then dried and roasted.

Preferably, when the alkali metal is K, the mixed salt in step (1) does not include an alkali metal salt. The method further includes: drying the refluxed filter cake, mixing it with potassium nepheline and ball milling, then roasting, and then Mix it with graphite and shape it; preferably, the nepheline is natural nepheline.

Preferably, the mixing and ball milling time is 5 to 48 hours, preferably 8 to 24 hours; and/or the addition amount of graphite is 1 to 5 wt%, preferably 2 to 4 wt%.

Preferably, the precipitating agent is NaOH and/or Na ₂ CO ₃ ; and/or the soluble nickel salt is one or more of nickel nitrate, basic nickel carbonate, nickel chloride and nickel-containing hydrate, preferably Ni(NO ₃ ) ₂ ·6H ₂ O; and/or the soluble alkaline earth metal salt is one or more of alkaline earth metal nitrates, alkaline earth metal chlorides and alkaline earth metal hydrates; and/or the soluble rare earth metal salt is One or more of rare earth metal nitrates, rare earth metal chlorides and rare earth metal hydrates; and/or the aluminum salt is aluminum-containing nitrates, aluminum-containing sulfates, aluminum-containing chlorides and aluminum-containing hydrates. of one or more.

Preferably, the total metal ion concentration in the mixed salt solution in step (1) is 0.1-1 mol/L; and/or the concentration of the coprecipitant solution is 0.2-5 mol/L, preferably 0.5-2 mol/L. ; and/or the dripping speed of the mixed salt solution and the precipitant solution stabilizes the pH value of the solution in the sedimentation tank at 7 to 13, preferably 8 to 12; at the same time, the temperature of the sedimentation tank is controlled at 25 to 90°C, preferably 40 ~80°C; and/or the time of static aging is 1 to 10 hours, preferably 1.5 to 5 hours; after static aging, take out the filter cake through filtration, and wash it with deionized water, preferably deionized water for each wash The ratio of the volume to the volume of the filter cake is 2 to 20:1, preferably 5 to 15:1, the number of washings is 1 to 10 times, preferably 2 to 6 times, and the final filtrate conductivity is less than 2 μS/cm. .

Preferably, the organic solvent is one or more of C1-C4 alcohols, C3-C5 ketones, and C2-C4 ethers; preferably, the organic solvent is one of methanol, ethanol, diethyl ether, and acetone. or more, preferably ethanol and/or acetone; and/or the volume ratio of the organic solvent to the filter cake is 3 to 10:1, preferably 3 to 6:1; and/or the conditions for reflux treatment include: temperature The temperature is 60-100°C; the time is 3-24 hours, preferably 5-12 hours.

Preferably, the drying conditions include: the temperature is 80-150°C, preferably 100-130°C; and/or the time is 1-24 hours, preferably 2-10 hours; and/or the roasting conditions include: the temperature is 500°C. ~1000°C, preferably 600-800°C; and/or time 1-10 hours, preferably 2-5 hours.

According to a third aspect of the present invention, the present invention provides a catalyst prepared by the preparation method of the present invention.

According to a fourth aspect of the present invention, the present invention provides the application of the catalyst of the present invention in the preparation of synthetic natural gas by methanation reaction.

According to a fifth aspect of the present invention, the present invention provides a method for preparing synthetic natural gas through methanation reaction, wherein the method includes: loading a catalyst in a fixed bed reactor, and allowing H ₂ is in contact with CO; the catalyst is the catalyst of the present invention.

Preferably, the contact conditions include: the molar ratio of H ₂ and CO is 2 to 4:1, preferably 3 to 4:1 by volume, the reaction temperature is 250 to 750°C, preferably 280 to 650°C; pressure It is 0 to 6MPa, preferably 1 to 4MPa; the raw gas air velocity is 1000 to 100000ml·g ^-1 ·h ^-1 , preferably 5000 to 40000ml·g ^-1 ·h ^-1 .

According to a second aspect of the invention, the invention provides a method for preparing the complete methanation catalyst of the invention, which method includes:

(1) Weigh the specified amount of soluble salts of each component element to prepare a mixed salt solution;

(2) Prepare precipitant solution;

(4) Use the co-current co-precipitation method to drop the mixed salt solution and the precipitant solution into the precipitation tank for co-precipitation;

(5) The precipitation is completed and left to stand for aging;

(6) Filtration and washing. The washed filter cake is refluxed with an organic solvent, then dried and roasted.

According to a third aspect of the invention, the invention provides a catalyst prepared according to the method of the invention.

According to a fourth aspect of the present invention, the present invention provides the application of the catalyst of the present invention in the preparation of synthetic natural gas by methanation reaction.

According to a fifth aspect of the present invention, the present invention provides a method for preparing synthetic natural gas through methanation reaction, wherein the method includes: loading a catalyst in a fixed bed reactor, and allowing H ₂ is in contact with CO; the catalyst is the catalyst of the present invention.

When the catalyst provided by the invention and the catalyst prepared by the method of the invention are used for the complete methanation reaction of synthesis gas, compared with similar catalysts in the past, the catalyst has excellent activity and stability, which fully meets the requirements for the complete methanation of synthesis gas. The required properties include good low-temperature activity, good high-temperature thermal stability, and good high-temperature hydration resistance. The catalyst reacted continuously for nearly 200 hours in a small laboratory evaluation device at ultra-high space velocity (40000 ml·g ^-1 ·h ^-1 ). The CO conversion rate was always ≥99%, and the CH ₄ selectivity was always ≥97%.

Other features and advantages of the present invention will be described in detail in the detailed description that follows.

Description of the drawings

The drawings are used to provide a further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the following specific embodiments, but do not constitute a limitation of the present invention. In the attached picture:

Figure 1 is the H ₂ -TPR spectrum of the catalyst obtained in Example 1;

Figure 2 is an evaluation data diagram of the methanation reaction catalyzed by the catalyst obtained in Example 1.

Detailed ways

The endpoints of ranges and any values disclosed herein are not limited to the precise range or value, but these ranges or values are to be understood to include values approaching such ranges or values. For numerical ranges, the endpoint values of each range, the endpoint values of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges. These values The scope shall be deemed to be specifically disclosed herein.

The invention provides a complete methanation catalyst, which contains: Ni element, alkaline earth metal element, rare earth metal element, alkali metal element and Al ₂ O ₃ .

According to a preferred embodiment of the present invention, calculated as oxides, the Ni content is 5 to 20 wt%, the alkaline earth metal content is 5 to 20 wt%, the rare earth metal content is 2 to 10 wt%, the alkali metal content is 0.5 to 5 wt%, and the carrier content is 45-87.5wt%. When the catalyst with the foregoing composition and parameters of the present invention is used for the complete methanation reaction of synthesis gas, compared with similar catalysts in the past, the catalyst has excellent activity and stability, and fully meets the requirements for the catalyst for complete methanation of synthesis gas. It has good low-temperature activity, good high-temperature thermal stability, and good high-temperature hydration resistance. For example, the catalyst reacted continuously for nearly 200 hours in a small laboratory evaluation device at ultra-high space velocity (40000 ml·g ^-1 ·h ^-1 ). The CO conversion rate was always ≥99%, and the CH ₄ selectivity was always ≥97%.

According to a preferred embodiment of the present invention, the content of the active metal NiO is 5 to 20 wt%, preferably 8 to 18 wt%, calculated as oxide and based on the total weight of the final catalyst.

According to a preferred embodiment of the present invention, the amount of alkaline earth metal oxide added is 5 to 20 wt%, preferably 6 to 16 wt%, calculated as oxide.

According to a preferred embodiment of the present invention, the amount of the rare earth metal oxide added is 2 to 10 wt%, preferably 3 to 8 wt%, calculated as oxide.

According to a preferred embodiment of the present invention, the alkali metal content is 0.5 to 5 wt% based on oxide.

According to a preferred embodiment of the present invention, the Al ₂ O ₃ content is 45-87.5 wt% based on oxide.

According to a preferred embodiment of the present invention, the specific surface area of the catalyst is 158-240 m ² /g, more preferably 200-231 m ² /g.

According to a preferred embodiment of the present invention, preferably, according to a preferred embodiment of the present invention, the NiO grain size of the catalyst is 6-20 nm, preferably 7-9 nm.

According to a preferred embodiment of the present invention, the catalyst is obtained by co-precipitating a co-precipitating agent solution and a mixed salt solution of each component element to obtain a filter cake, which is dried, roasted and shaped. It is preferred that the filter cake is treated with an organic solvent before drying. Reflow processing. The catalyst prepared by the aforementioned preparation method can significantly increase the specific surface area of the catalyst of the present invention, and at the same time, it has better high-temperature thermal stability.

In the present invention, the optional range of the type of organic solvent is wide. According to the preferred embodiment of the present invention, the organic solvent is one of a C1-C4 alcohol, a C3-C5 ketone, and a C2-C4 ether. One or more; preferably, the organic solvent is one or more of methanol, ethanol, diethyl ether and acetone. The high-temperature thermal stability of the catalyst can be significantly improved by using the aforementioned preferred organic solvent reflux treatment.

According to a preferred embodiment of the present invention, the volume ratio of the organic solvent to the filter cake is 3 to 10:1.

According to a preferred embodiment of the present invention, the conditions for the reflux treatment include: the temperature is 60-100°C, and/or the time is 2-30h, preferably 3-24h. Among them, the reflow time can be adjusted according to the temperature.

According to the present invention, the alkaline earth metal elements can be used in the present invention. For the present invention, one or more of Be, Mg, Ca, Sr and Ba are preferred, and one or more of Mg, Ca and Ba are preferred. or more, and more preferably Mg and/or Ca.

According to the present invention, the rare earth metal elements can be used in the present invention. For the present invention, one or more of Y, La, Ce, Pr and Sm are preferred; one or more of Y, La and Ce are preferred. or more, and more preferably La and/or Ce.

According to the present invention, the optional range of the type of the alkali metal element is wide. For the present invention, it is preferably one or both of Cs and K, and more preferably K.

According to a preferred embodiment of the present invention, the catalyst contains graphite, preferably the content of graphite is 1-5% by weight, preferably 2-4% by weight based on the total weight of the catalyst.

The object of the present invention can be achieved by using a catalyst with the foregoing composition and parameters of the present invention, and there are no special requirements for its preparation method. For the present invention, it is preferred to provide a preparation method of a complete methanation catalyst, which method includes:

(1) Weigh the specified amount of soluble salts of each component element to prepare a mixed salt solution;

(2) Prepare precipitant solution;

(4) Use the co-current co-precipitation method to drop the mixed salt solution and the precipitant solution into the precipitation tank for co-precipitation;

(5) The precipitation is completed and left to stand for aging;

(6) Filtration and washing. The washed filter cake is refluxed with an organic solvent, then dried and roasted. Preparing the catalyst of the present invention using the aforementioned preferred preparation method can improve the performance of the catalyst.

According to a preferred embodiment of the present invention, when the alkali metal element is K, the mixed salt in step (1) does not include an alkali metal salt. The method further includes: drying the refluxed filter cake and mixing it with potash The stone is mixed and ball milled, then roasted, and then mixed with graphite and shaped. By adopting this preferred embodiment, various properties of the catalyst can be significantly improved.

According to the present invention, it is preferred that the nepheline is natural nepheline.

According to a preferred embodiment of the present invention, the mixing and ball milling time is 5 to 48 hours, preferably 8 to 24 hours.

According to a preferred embodiment of the present invention, the addition amount of graphite is 1 to 5 wt%, preferably 2 to 4 wt%.

In the present invention, the co-precipitating agent and soluble salt types have a wide range of options, and the present invention has no special requirements for this.

The following are examples but not limited to the scope of the invention:

In the present invention, the co-precipitating agent is, for example, NaOH and/or Na ₂ CO ₃ , more preferably Na ₂ CO ₃ .

In the present invention, the optional range of the types of soluble nickel salts is wide, and all commonly used types can be used. For the present invention, one of nickel nitrate, basic nickel carbonate, nickel chloride and nickel-containing hydrate is preferred. or more.

According to the present invention, the soluble nickel salt is preferably Ni(NO ₃ ) ₂ ·6H ₂ O, basic nickel carbonate or NiCl ₂ ·6H ₂ O, and more preferably Ni(NO ₃ ) ₂ ·6H ₂ O.

In the present invention, the soluble alkaline earth metal salt has a wide range of options, and all commonly used types can be used. For the present invention, one or more of alkaline earth metal nitrates, alkaline earth metal chloride salts and alkaline earth metal hydrates are preferred. kind.

In the present invention, the soluble rare earth metal salts have a wide range of options, and any commonly used ones can be used in the present invention. For the present invention, one of the rare earth metal nitrates, rare earth metal chloride salts and rare earth metal hydrates is preferred. Kind or variety.

In the present invention, the optional range of aluminum salt types is wide, and all commonly used ones can be used in the present invention. For the present invention, aluminum-containing nitrates, aluminum-containing sulfates, aluminum-containing chloride salts and aluminum-containing hydrates are preferred. one or more of them.

In the present invention, it is preferred that the total metal ion concentration in the mixed salt solution described in step (1) is 0.1-1 mol/L.

In the present invention, the concentration of the co-precipitating agent solution is preferably 0.2 to 5 mol/L, preferably 0.5 to 2 mol/L.

According to a preferred embodiment of the present invention, the dripping speed of the mixed salt solution and the precipitant solution stabilizes the pH value of the solution in the sedimentation tank at 7 to 13, preferably 8 to 12; at the same time, the temperature of the sedimentation tank is controlled at 25 to 90°C. , preferably 40 to 80°C.

According to a preferred embodiment of the present invention, the standing aging time is 1 to 10 hours, preferably 1.5 to 5 hours.

According to a preferred embodiment of the present invention, after standing and aging, the filter cake is taken out through filtration and washed with deionized water. Preferably, the ratio of the volume of deionized water to the volume of the filter cake in each wash is 2 to 20:1, preferably The ratio is 5 to 15:1, and the number of washings is 1 to 10 times, preferably 2 to 6 times, and the final filtrate conductivity is less than 2 μS/cm.

In the present invention, the optional range of the type of organic solvent is wide. According to the preferred embodiment of the present invention, the organic solvent is one of a C1-C4 alcohol, a C3-C5 ketone, and a C2-C4 ether. One or more; preferably the organic solvent is one or more of methanol, ethanol, diethyl ether and acetone, more preferably ethanol and/or acetone. The high-temperature thermal stability of the catalyst can be significantly improved by using the aforementioned preferred organic solvent reflux treatment.

According to a preferred embodiment of the present invention, the volume ratio of the organic solvent to the filter cake is 3 to 10:1, preferably 3 to 6:1.

According to a preferred embodiment of the present invention, the conditions for the reflux treatment include: the temperature is 60-100°C, and/or the time is 2-30, preferably 3-24 hours, preferably 5-12 hours.

According to the present invention, the optional range of drying and roasting conditions is wide. For the present invention, preferred drying conditions include: temperature of 80-150°C, preferably 100-130°C, and/or time of 1-24 hours, Preferably it is 2 to 10 hours.

According to the present invention, preferred roasting conditions include: a temperature of 500 to 1000°C, preferably 600 to 800°C, and/or a time of 1 to 10 hours, preferably 2 to 5 hours.

According to a preferred embodiment of the present invention, the preparation of the catalyst includes the following steps:

(1) Weigh the specified amount of soluble salts of each component element to prepare a mixed salt solution;

(2) Use a certain concentration of NaOH and/or Na ₂ CO ₃ solution as the precipitating agent;

(3) Using the co-current co-precipitation method, the salt solution and the precipitant are dropped into the sedimentation tank at a certain flow rate;

(4) After precipitation, let it stand for a certain period of time;

(5) Filter and wash, and the washed filter cake is poured into an organic solvent and refluxed for a certain period of time;

(6) After the filter cake is filtered and dried, it is mixed with a certain quality of natural nepheline and ball milled;

(7) After mixing evenly, place the solid mixture in a muffle furnace for roasting;

(8) After the roasting is completed, a certain proportion of graphite is added, mixed, and sliced to form a complete methanation catalyst.

In a preferred embodiment of the present invention, the catalyst preparation method provided by the present invention is to first prepare a precipitate of mixed salts by using a co-current co-precipitation method, and then place the precipitate in an organic solvent for reflux treatment, and then dry it after a certain period of time; drying After the completion, mix the precipitate and nepheline and ball-mill it for a certain period of time before roasting; add a certain amount of graphite to the solid powder obtained after roasting, mix it thoroughly, and finally slice it into pieces to obtain the required completeness. Methanation catalyst. The catalyst prepared by the aforementioned preferred method has high mechanical strength and high-temperature sintering resistance; at the same time, because the active metal components are evenly dispersed in the system space, smaller metal grain size can be obtained, and the synthesis gas is completely methane-free. It shows excellent low-temperature activity, high-temperature sintering resistance and high-temperature hydration resistance in the chemical reaction.

According to a preferred embodiment of the present invention, the precipitant is NaOH and/or Na ₂ CO ₃ . In the precipitant solution, based on the molar concentration of alkali metal ions, the concentration is 0.2 to 5 mol/L, preferably 0.5 ~2mol/L.

According to the present invention, when performing a co-precipitation operation, the salt solution and the precipitant are dropped into the sedimentation tank at a certain flow rate, so as to control the pH value of the solution in the sedimentation tank to be stable at 7 to 13, preferably 8 to 13. 12; At the same time, the temperature of the sedimentation tank is controlled at 25 to 90°C, preferably 40 to 80°C.

According to the present invention, the aging time is 1 to 10 hours, preferably 1.5 to 5 hours;

According to the present invention, the filter cake is washed with deionized water. The ratio of the volume of deionized water to the volume of the filter cake for each washing is 2 to 20:1, preferably 5 to 15:1, and the number of washings is 1 ~10 times, preferably 2-6 times, based on the final conductivity of the filtrate being less than 2 μS/cm.

According to the present invention, after the washing is completed, the filter cake is again placed in an organic solvent for reflux treatment, wherein the organic solvent can be methanol, ethanol, ether or acetone, etc., preferably ethanol and/or acetone, and the organic solvent is mixed with the filter cake. The volume ratio of the cake is 3 to 10:1, preferably 3 to 6:1; the reflux treatment time is 3 to 24 hours, preferably 5 to 12 hours.

According to the present invention, the drying temperature of the filter cake treated with the organic solvent is 80-150°C, preferably 100-130°C, and the drying time is 1-24 hours, preferably 2-10 hours.

According to the present invention, the dried sample is mixed and ball milled with a certain mass of natural nepheline for 5 to 48 hours, preferably 8 to 24 hours. The amount of nepheline added is based on the mass of the final catalyst, so that the K ₂ O The content is 0.5-5wt%, preferably 1-4wt%.

According to the present invention, the ball-milled solid powder is placed in a muffle furnace and roasted at 500-1000°C, preferably 600-800°C, and the roasting time is 1-10 hours, preferably 2-5 hours.

According to the present invention, a certain mass of graphite is added to the roasted solid powder and mixed evenly. The amount of graphite added is 1 to 5 wt%, preferably 2 to 4 wt%; then it is sliced and shaped, and the particle size can be 4× 4 or 5 × 5 to obtain the required complete methanation catalyst.

The invention provides a catalyst prepared by the preparation method of the invention.

The invention provides the application of the catalyst according to the invention in the preparation of synthetic natural gas by methanation reaction.

The catalyst prepared according to the method provided by the present invention needs to reduce and activate the active metal in the presence of hydrogen before it is used for the complete methanation reaction of synthesis gas. The reduction conditions are, for example: the reduction temperature is 300-800°C, preferably 400-400°C. 600°C, more preferably 400-550°C; the reduction time is 0.5-10 hours, preferably 1-5 hours, further preferably 2-4 hours. The reduction can be carried out in pure hydrogen, or in hydrogen and inert gas. It is carried out in a mixture of gases, such as a mixture of hydrogen, nitrogen and/or argon, and the hydrogen pressure is 0 to 2 MPa, preferably 0 to 1 MPa, and more preferably 0 to 0.5 MPa.

The invention provides a method for preparing synthetic natural gas through methanation reaction, wherein the method includes: loading a catalyst in a fixed bed reactor, and contacting H ₂ and CO under the conditions of preparing synthetic natural gas through methanation reaction; The catalyst is the catalyst according to the present invention.

According to a preferred embodiment of the present invention, the contact conditions include: in terms of volume, the molar ratio of _H2 to CO is 2 to 4:1, preferably 3 to 4:1, and the reaction temperature is 250 to 750°C, preferably 280 ~650°C; the pressure is 0~6MPa, preferably 1~4MPa; the raw gas air velocity is 1000~100000ml·g ^-1 ·h ^-1 , preferably 5000~40000ml·g ^-1 ·h ^-1 .

The following examples will further illustrate the present invention, but should not be construed as limiting the present invention.

Example 1

(1) Preparation of catalyst

Weigh 116.8g Ni(NO ₃ ) ₂ ·6H ₂ O, 190.9g Mg(NO ₃ ) ·6H ₂ O, 42.5g La(NO ₃ ) ₃ ·6H ₂ O and 853.2g Al(NO ₃ ) ₃ ·6H ₂ O was poured into 3500mL deionized water and stirred to dissolve; weigh 420g NaOH and poured into 10500mL deionized water and stirred to dissolve. The salt solution and the precipitant are co-precipitated into the sedimentation tank at a certain flow rate. The pH value of the solution in the sedimentation tank is controlled to be 9, and the temperature of the sedimentation tank is 65°C. After the precipitation is completed, let it stand for aging for 2.5 hours. Then filter and wash, the volume ratio of deionized water to filter cake is 10:1, and wash 3 times. The obtained filter cake was heated and refluxed at 80°C for 12 hours in absolute ethanol (the volume ratio of ethanol to filter cake was 5:1), and then filtered. Then place the filter cake in an oven to dry at 120°C for 8 hours, then take it out, add 13.3g of natural potassium nepheline, mix and ball mill for 12 hours; after the ball milling is completed, take it out and put it into a muffle furnace for roasting at 700°C for 2 hours. The obtained solid powder was then added with 4g of graphite and mixed thoroughly. Then it is cut into sheets with a particle size of 4×4 to obtain the required complete methanation catalyst, which is recorded as SNG-1. The specific surface area of the obtained catalyst and the grain size of NiO in the catalyst are shown in Table 1.

Although the catalyst obtained in Example 1 was calcined at 700°C, its specific surface area reached 214 m ² /g, which was obviously larger than the specific surface area of the catalyst prepared by the traditional method. XRD analysis shows that the grain size of NiO in the catalyst is 7.6nm, which is also significantly smaller than the grain size of NiO in catalysts prepared by traditional methods. The H ₂ -TPR spectrum of the catalyst is shown in Figure 1. It can be seen from Figure 1 , the main reduction temperature zone of the methanation catalyst prepared by the method of the present invention is between 350 and 700°C, indicating that the interaction between the metal Ni and the additive is weak, which is conducive to the reduction activation of the catalyst, which is suitable for the industrial application of the catalyst , which can greatly simplify the process of catalyst start-up reduction activation.

(2) Activity evaluation

Weigh 0.5g of the SNG-1 catalyst and load it into the microchannel reactor, and reduce it at 500°C for 3 hours in a pure hydrogen atmosphere under normal pressure for activation. After the reduction is completed, the temperature is lowered to 350°C in a hydrogen atmosphere, and the raw material gas (H ₂ /CO = 3/1) is switched to carry out the reaction. The reaction space velocity is 10000 ml·g ^-1 ·h ^-1 and the reaction pressure is 2MPa. Gas chromatography online sampling analyzed the exhaust gas composition, and the calculation was as follows: X _CO =99%, S _CH4 =97%.

The stability evaluation data of the catalyst obtained in Example 1 is shown in Figure 2, specifically the methanation reaction performance catalyzed by the catalyst with a reaction time of 0 to 200 hours. As can be seen from Figure 2, the reaction performance of the catalyst is very stable.

Example 2

(1) Preparation of catalyst

Weigh 140.2g Ni(NO ₃ ) ₂ ·6H ₂ O, 135.2g Mg(NO ₃ ) ·6H ₂ O, 26.6g La(NO ₃ ) ₃ ·6H ₂ O and 897.4g Al(NO ₃ ) ₃ ·6H Pour ₂ O into 2250mL deionized water and stir to dissolve; weigh 405.6g NaOH and pour it into 14480mL deionized water, stir and dissolve. The salt solution and the precipitant are co-precipitated into the sedimentation tank at a certain flow rate. The pH value of the solution in the sedimentation tank is controlled to be 8, and the temperature of the sedimentation tank is 55°C. After the precipitation is completed, let it stand for 5 hours. Then filter and wash, the volume ratio of deionized water to filter cake is 8:1, and wash 5 times. The obtained filter cake was heated to 75°C for reflux treatment in absolute ethanol (the volume ratio of ethanol to filter cake was 6:1) for 8 hours, and then filtered. Then place the filter cake in an oven to dry at 110°C for 10 hours, then take it out, add 26.7g of natural potassium nepheline, mix and ball mill for 20 hours; after the ball milling is completed, take it out and put it into a muffle furnace for roasting at 600°C for 4 hours. The obtained solid powder was then added with 6g of graphite and mixed thoroughly. Then it is cut into sheets with a particle size of 5×5 to obtain the required complete methanation catalyst, which is designated as SNG-2. The specific surface area of the obtained catalyst and the grain size of NiO in the catalyst are shown in Table 1.

(2) Activity evaluation

The catalyst was activated and the methanation reaction was carried out under the same conditions as in Example 1. The tail gas composition was analyzed by gas chromatography online sampling and calculated as follows: X _CO =100%, S _CH4 =98.2%.

Example 3

(1) Preparation of catalyst

Weigh 93.4g Ni(NO ₃ ) ₂ ·6H ₂ O, 152.7g Mg(NO ₃ ) ·6H ₂ O, 15.9g La(NO ₃ ) ₃ ·6H ₂ O and 1000g Al(NO ₃ ) ₃ ·6H ₂ Pour O into 9050 mL of deionized water and stir to dissolve; weigh 434.2g NaOH and pour into 5430 mL of deionized water and stir to dissolve. The salt solution and the precipitant are co-precipitated into the sedimentation tank at a certain flow rate. The pH value of the solution in the sedimentation tank is controlled to be 10, and the temperature of the sedimentation tank is 75°C. After the precipitation is completed, let it stand for aging for 1.5 hours. Then filter and wash, the volume ratio of deionized water to filter cake is 12:1, and wash twice. The obtained filter cake was heated to 70° C. and refluxed for 16 hours in absolute ethanol (the volume ratio of ethanol to filter cake was 8:1), and then filtered. Then place the filter cake in an oven to dry at 100°C for 16 hours, then take it out, add 6.7g of natural potassium nepheline, mix and ball mill for 16 hours; after the ball milling is completed, take it out and put it into a muffle furnace for roasting at 800°C for 1 hour. The obtained solid powder was then added with 8g of graphite and mixed thoroughly. Then it is cut into sheets with a particle size of 4×4 to obtain the required complete methanation catalyst, which is designated as SNG-3. The specific surface area of the obtained catalyst and the grain size of NiO in the catalyst are shown in Table 1.

(2) Activity evaluation

The catalyst was activated and the methanation reaction was carried out under the same conditions as in Example 1. It consists of gas chromatography online sampling and analysis of exhaust gas. Calculated: X _CO =93.2%, S _CH4 =96.7%.

Example 4

(1) Preparation of catalyst

The catalyst was prepared in the same manner as in Example 1, except that NaOH was replaced by Na ₂ CO ₃ and the amount used was 556.5 g. The required complete methanation catalyst was obtained, designated as SNG-4. The specific surface area of the obtained catalyst and the grain size of NiO in the catalyst are shown in Table 1.

(2) Activity evaluation

The catalyst was activated and the methanation reaction was carried out under the same conditions as in Example 1, and the tail gas composition was analyzed by gas chromatography online sampling. Calculated: X _CO =99.5%, S _CH4 =97.6%.

Example 5

(1) Preparation of catalyst

The catalyst was prepared according to the same method as in Example 1, except that the washing solvent was an equal amount of acetone to obtain the required complete methanation catalyst, designated as SNG-5. The specific surface area of the obtained catalyst and the grain size of NiO in the catalyst are shown in Table 1.

(2) Activity evaluation

The catalyst was activated and the methanation reaction was carried out under the same conditions as in Example 1, and the tail gas composition was analyzed by gas chromatography online sampling. Calculated: X _CO =96.8%, S _CH4 =95.9%.

Example 6

(1) Preparation of catalyst

The catalyst was prepared according to the same method as in Example 1, except that a 10 ml solution containing 8.5 g of potassium nitrate was used instead of the natural potassium nepheline and the resulting dry filter cake was thoroughly mixed and ball milled for 12 hours, then taken out and placed in a muffle furnace. Calculate at 700°C for 2 hours to maintain the same K ₂ O quality as in Example 1. The obtained solid powder was then added with 4g of graphite and mixed thoroughly. Then it is cut into sheets with a particle size of 4×4 to obtain the required complete methanation catalyst. The resulting catalyst was designated SNG-6. The specific surface area of the obtained catalyst and the grain size of NiO in the catalyst are shown in Table 1.

(2) Activity evaluation

The catalyst was activated and the methanation reaction was carried out under the same conditions as in Example 1, and the tail gas composition was analyzed by gas chromatography online sampling. Calculated: X _CO =91.3%, S _CH4 =93.6%.

Example 7

(1) Preparation of catalyst

The catalyst was prepared according to the same method as in Example 1, except that n-propanol was used instead of ethanol to reflux the filter cake obtained by precipitation. The resulting catalyst was designated SNG-7. The specific surface area of the obtained catalyst and the grain size of NiO in the catalyst are shown in Table 1.

(2) Activity evaluation

The catalyst was activated and the methanation reaction was carried out under the same conditions as in Example 1, and the tail gas composition was analyzed by gas chromatography online sampling. Calculated: X _CO =93.5%, S _CH4 =96.1%.

Example 8

(1) Preparation of catalyst

The catalyst was prepared according to the same method as in Example 1, except that 51.1 g Ba(NO ₃ ) ₂ was used instead of Mg(NO ₃ ) ₂ ·6H ₂ O. The resulting catalyst was designated SNG-8. The specific surface area of the obtained catalyst and the grain size of NiO in the catalyst are shown in Table 1.

(2) Activity evaluation

The catalyst was activated and the methanation reaction was carried out under the same conditions as in Example 1, and the tail gas composition was analyzed by gas chromatography online sampling. Calculated: X _CO =89.9%, S _CH4 =93.6%.

Example 9

(1) Preparation of catalyst

The catalyst was prepared according to the same method as in Example 1, except that 40.8g Sm(NO ₃ ) ₃ ·6H ₂ O was used instead of La(NO ₃ ) ₃ ·6H ₂ O. The resulting catalyst was designated SNG-9. The specific surface area of the obtained catalyst and the grain size of NiO in the catalyst are shown in Table 1.

(2) Activity evaluation

The catalyst was activated and the methanation reaction was carried out under the same conditions as in Example 1, and the tail gas composition was analyzed by gas chromatography online sampling. Calculated: X _CO =93.9%, S _CH4 =95.6%.

Example 10

(1) Preparation of catalyst

The catalyst was prepared according to the same method as in Example 1, except that 10 ml of a solution containing 10.8 g of sodium nitrate (concentration of 12.7 mol/l) was used instead of natural nepheline and the resulting dry filter cake was thoroughly mixed and ball milled for 12 hours. Take it out and bake it in a muffle furnace at 700°C for 2 hours. The obtained solid powder was then added with 4g of graphite and mixed thoroughly. Then it is cut into sheets with a particle size of 4×4 to obtain the required complete methanation catalyst. The catalyst obtained was designated as SNG-10. The specific surface area of the obtained catalyst and the grain size of NiO in the catalyst are shown in Table 1.

(2) Activity evaluation

The catalyst was activated and the methanation reaction was carried out under the same conditions as in Example 1, and the tail gas composition was analyzed by gas chromatography online sampling. Calculated: X _CO =83.3%, S _CH4 =91.6%.

Comparative example 1

(1) Preparation of catalyst

The catalyst was prepared according to the same method as Example 1, except that the filter cake obtained by precipitation was not refluxed with an organic solvent, and the obtained catalyst was designated as DB-1. The specific surface area of the obtained catalyst and the grain size of NiO in the catalyst are shown in Table 1.

(2) Activity evaluation

The catalyst was activated and the methanation reaction was carried out under the same conditions as in Example 1, and the tail gas composition was analyzed by gas chromatography online sampling. Calculated: XCO=78.6%, SCH4=91.7%.

Comparative example 2

(1) Preparation of catalyst

The catalyst was prepared according to the same method as Example 1, except that no alkaline earth metal and rare earth metal promoters were added, and the obtained catalyst was designated as DB-2. The specific surface area of the obtained catalyst and the grain size of NiO in the catalyst are shown in Table 1.

(2) Activity evaluation

The catalyst was activated and the methanation reaction was carried out under the same conditions as in Example 1, and the tail gas composition was analyzed by gas chromatography online sampling. Calculated: X _CO =54.5%, S _CH4 =89.4%.

Table 1

It can be seen from the reaction results of the examples that the catalyst prepared by the method of the present invention has excellent reaction activity and methane selectivity. At the same time, the catalyst has good high-temperature stability and anti-coking performance, and can realize continuous and stable operation of the plant cycle without It does not deactivate and fully meets the performance requirements of the catalyst for complete methanation of syngas.

The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, a variety of simple modifications can be made to the technical solutions of the present invention. These simple modifications All belong to the protection scope of the present invention.

In addition, it should be noted that the specific technical features described in the above-mentioned specific embodiments can be combined in any suitable manner as long as there is no contradiction. In order to avoid unnecessary repetition, various possible combinations are not further described in the present invention.

In addition, any combination of various embodiments of the present invention can also be carried out. As long as they do not violate the idea of the present invention, they should also be regarded as the disclosed content of the present invention.

Claims (26)

1. A complete methanation catalyst, characterized in that the catalyst contains: Ni element, alkaline earth metal element, rare earth metal element, alkali metal element and Al ₂ O ₃ ; calculated as oxide, the Ni content is 5~20wt%, The alkaline earth metal content is 5~20wt%, the rare earth metal content is 2~10wt%, the alkali metal content is 0.5~5wt%, and the Al ₂ O ₃ content is 45-87.5wt%; the specific surface area of the catalyst is 158-240 m ² /g; NiO grain size is 6-20nm; The catalyst is co-precipitated by co-precipitating a co-precipitating agent solution and a mixed salt solution of each component element to obtain a filter cake, which is then dried, roasted and shaped. Before drying, the filter cake is refluxed with an organic solvent; The volume ratio of organic solvent to filter cake is 3~10:1; The conditions for reflow treatment include: temperature 60-100℃, time 2-30h; The organic solvent is one or more of methanol, ethanol, ether and acetone. 2. The catalyst according to claim 1, wherein the specific surface area of the catalyst is 200-231 ^m2 /g; and/or the NiO grain size is 7-9 nm. 3. The catalyst according to claim 1, wherein, The alkaline earth metal element is one or more of Be, Mg, Ca, Sr and Ba; and/or The rare earth metal element is one or more of Y, La, Ce, Pr and Sm; and/or The alkali metal element is one or more of K and Cs. 4. The catalyst according to any one of claims 3, wherein, The alkaline earth metal element is one or more of Mg, Ca and Ba; and/or The rare earth metal element is one or more of Y, La and Ce. 5. The catalyst according to claim 4, wherein, The alkaline earth metal element is Mg and/or Ca; and/or The rare earth metal element is La and/or Ce; and/or The alkali metal element is K. 6. The catalyst according to claim 1, wherein the catalyst contains graphite, and the content of graphite is 1-5% by weight based on the total weight of the catalyst. 7. The catalyst according to claim 6, wherein the content of graphite is 2-4% by weight based on the total weight of the catalyst. 8. A method for preparing the complete methanation catalyst according to any one of claims 1 to 7, characterized in that the method includes: (1) Weigh the specified amount of soluble salts of each component element to prepare a mixed salt solution; (2) Prepare precipitant solution; (4) Use the co-current co-precipitation method to drop the mixed salt solution and precipitant solution into the precipitation tank for co-precipitation; (5) The precipitation is completed and left to stand for aging; (6) Filtration and washing. The washed filter cake is refluxed with an organic solvent, then dried and roasted; The organic solvent is one or more of methanol, ethanol, ether and acetone; The volume ratio of organic solvent to filter cake is 3~10:1; The conditions for reflow treatment include: temperature 60-100℃, time 2-30h. 9. The preparation method according to claim 8, wherein when the alkali metal is K, the mixed salt in step (1) does not include an alkali metal salt, and the method further includes: The refluxed filter cake is dried, mixed with nepheline and ball milled, then roasted, and then mixed with graphite and formed. 10. The preparation method according to claim 9, wherein the nepheline is natural nepheline. 11. The preparation method according to claim 9, wherein, The mixing and ball milling time is 5 to 48 hours; and/or The addition amount of graphite is 1~5wt%. 12. The preparation method according to claim 11, wherein, The mixing and ball milling time is 8 to 24 hours; and/or The addition amount of graphite is 2~4wt%. 13. The preparation method according to claim 8, wherein, The precipitating agent is NaOH and/or Na ₂ CO ₃ ; and/or The soluble nickel salt is one or more of nickel nitrate, nickel basic carbonate, nickel chloride and nickel-containing hydrate; and/or The soluble alkaline earth metal salt is one or more of alkaline earth metal nitrates, alkaline earth metal chlorides and alkaline earth metal hydrates; and/or The soluble rare earth metal salt is one or more of rare earth metal nitrate, rare earth metal chloride salt and rare earth metal hydrate; and/or The aluminum salt is one or more of aluminum-containing nitrate, aluminum-containing sulfate, aluminum-containing chloride salt and aluminum-containing hydrate. 14. The preparation method according to claim 13, wherein, The precipitating agent is Na ₂ CO ₃ ; and/or The soluble nickel salt is Ni(NO ₃ ) ₂ •6H ₂ O. 15. The preparation method according to claim 8, wherein, The total metal ion concentration in the mixed salt solution described in step (1) is 0.1~1mol/L; and/or The concentration of the co-precipitating agent solution is 0.2~5mol/L; and/or The dripping speed of the mixed salt solution and precipitant solution stabilizes the pH value of the solution in the sedimentation tank at 7~13; at the same time, the temperature of the sedimentation tank is controlled at 25~90 ^o C; and/or The aging time is 1 to 10 hours; After standing for aging, take out the filter cake through filtration and wash it with deionized water. The number of washing times is 1 to 10 times, and the final conductivity of the filtrate is less than 2 µS/cm. 16. The preparation method according to claim 15, wherein, The concentration of the co-precipitating agent solution is 0.5~2mol/L; and/or The dripping speed of the mixed salt solution and precipitant solution stabilizes the pH value of the solution in the sedimentation tank at 8~12; at the same time, the temperature of the sedimentation tank is controlled at 40~80°C; and/or The standing aging time is 1.5~5 hours; After standing for aging, take out the filter cake through filtration and wash it with deionized water. The ratio of the volume of deionized water to the volume of the filter cake for each washing is 2~20:1, and the number of washing times is 2~6 times. The conductivity of the filtrate is less than 2µS/cm. 17. The preparation method according to claim 16, wherein, The ratio of the volume of deionized water to the volume of the filter cake for each wash is 5 to 15:1. 18. The preparation method according to claim 8, wherein, The organic solvent is one or more of methanol, ethanol, diethyl ether and acetone; and/or The volume ratio of the organic solvent to the filter cake is 3~6:1; and/or The time for reflow treatment is 5 to 12 hours. 19. The preparation method according to claim 18, wherein, The organic solvent is ethanol and/or acetone. 20. The preparation method according to claim 8, wherein, Drying conditions include: temperature 80~150 ^o C; and/or time 1~24 hours; and/or The conditions for roasting include: temperature 500~1000 ^o C; and/or time 1~10 hours. 21. The preparation method according to claim 20, wherein, Drying conditions include: temperature 100~130℃; and/or time 2~10 hours; and/or The conditions for roasting include: temperature of 600~800°C; and/or time of 2~5 hours. 22. The catalyst prepared by the preparation method according to any one of claims 8-21. 23. Application of the catalyst according to any one of claims 1-7 and 22 in the production of synthetic natural gas by methanation reaction. 24. A method for preparing synthetic natural gas by methanation reaction, wherein the method includes: loading a catalyst in a fixed bed reactor, and contacting H ₂ and CO under the conditions of preparing synthetic natural gas by methanation reaction; the catalyst is The catalyst according to any one of claims 1-7 and 22. 25. The preparation method according to claim 24, wherein, The contact conditions include: in terms of volume, the molar ratio of H ₂ and CO is 2~4:1, the reaction temperature is 250~750℃; the pressure is 0~6MPa; the raw gas space velocity is 1000~100000ml·g ^-1 • h ^-1 . 26. The preparation method according to claim 25, wherein, The contact conditions include: in terms of volume, the molar ratio of H ₂ and CO is 3~4:1, the reaction temperature is 280~650℃; the pressure is 1~4MPa; the raw gas space velocity is 5000~40000 ml·g ^-1 •h ^-1 .