CN117732474A - Methane steam reforming catalyst and preparation method thereof, method for hydrogen production by methane steam reforming - Google Patents

Abstract

The invention relates to the field of catalysts, and discloses a methane steam reforming catalyst and a preparation method thereof, as well as a method for producing hydrogen by methane steam reforming. The catalyst includes a carrier, an active metal component and an auxiliary component loaded on the carrier; Wherein, the active metal component is Ni, and the auxiliary component is selected from at least one of rare earth metals; wherein, the average grain size of the active metal component is 3-12nm, based on the total amount of the catalyst As a benchmark, the content of the carrier is 72-94wt%, calculated as oxide, the content of the active metal component is 5.9-18wt%, and the content of the auxiliary component is 0.1-10wt%. The catalyst has both a high metal content and a small grain size of the active metal component, so it has higher reactivity and anti-coking properties. The finished catalyst can run continuously and stably for 2,000 hours under laboratory conditions without loss of It is flexible and has the feasibility of industrial application.

Description

Methane steam reforming catalyst and preparation method thereof, hydrogen production by methane steam reforming method

Technical field

The invention relates to the field of catalysts, and in particular to a methane steam reforming catalyst and a preparation method thereof, and a method for producing hydrogen by methane steam reforming.

Background technique

In the chemical industry, the largest amounts of hydrogen are used in ammonia synthesis and petroleum refining. Hydrogen is also needed in other fields, such as metallurgy, electronics, glass, medicine, food, aerospace, energy, etc. On the one hand, in recent years, with the increase in demand for hydrogen during hydroreforming and hydrocracking reactions in the oil refining process and the demand for hydrogen in petrochemical industries such as synthetic ammonia, synthetic gasoline, synthetic methanol, Fischer-Tropsch synthesis, etc., methane , naphtha, heavy oil steam reforming and coal gasification hydrogen production technology have received greater attention. In particular, society is paying more and more attention to environmental quality, the sulfur content index in gas emissions has decreased, and the processing of crude oil has continued to deepen, which has also increased the demand for hydrogen. On the other hand, hydrogen is a clean fuel with a large combustion calorific value and the product is water. It does not produce a large amount of greenhouse gases such as CO ₂ and polluting gases such as SO _x , _NO Demand is also increasing day by day.

Due to its abundant reserves, natural gas will be the main raw material for preparing synthesis gas and then producing hydrogen. Although coal is more abundant and cheaper, the investment is three times that of a natural gas-based syngas plant. Therefore, in the future, the natural gas reforming hydrogen production process will still be the most important way to produce hydrogen worldwide.

At present, the natural gas hydrogen production process is very mature, but its main disadvantage is high energy consumption, which leads to a significant increase in the production cost of hydrogen. In order to reduce the energy consumption of this process, reducing the water-to-carbon ratio is a feasible path. Major foreign hydrogen production technology companies have made attempts in this field, such as the Brown process of the United States, the AMV process of ICI, and the LCA process. In order to adapt to the requirements of the new process, corresponding efficient catalysts must be developed. In addition to the performance of conventional natural gas steam reforming catalysts, this catalyst must also have higher activity and stronger anti-coking properties so that it can operate continuously and stably for a long period under low water-to-carbon ratio.

Most of the energy-saving methane steam reforming hydrogen production catalysts currently developed at home and abroad are prepared by the impregnation method, and the commonly used hydrogen production catalyst carriers are mostly α-Al ₂ O ₃ , CaO-Al ₂ O ₃ or MgO prepared by high-temperature sintering methods. -Al ₂ O ₃ . Although this high-temperature sintered carrier has high strength, its water absorption rate is relatively low. When used to load active metals by impregnation, a high-concentration nickel nitrate solution needs to be prepared and the solution needs to be heated. At the same time, it generally needs to be impregnated two or three times. Achieve the required amount of metal.

Contents of the invention

The purpose of the present invention is to overcome the problems existing in the prior art that the active metal component in the catalyst has large grain size, low catalyst activity, poor carbon deposition resistance, and long preparation process, and provides a methane steam reforming catalyst and its Preparation method, methane steam reforming method for hydrogen production, the catalyst has high catalytic activity, good carbon deposition resistance and high stability.

In order to achieve the above objects, the first aspect of the present invention provides a methane steam reforming catalyst, which catalyst includes a carrier and an active metal component and an auxiliary component supported on the carrier; wherein the active metal component is Ni , the auxiliary component is selected from at least one of rare earth metals; wherein the average particle size of the active metal component is 3-12nm, based on the total amount of catalyst, the content of the carrier is 72 -94wt%, calculated as oxide, the content of the active metal component is 5.9-18wt%, and the content of the auxiliary component is 0.1-10wt%.

A second aspect of the present invention provides a method for preparing a methane steam reforming catalyst. The method includes: contacting a carrier carrying an organic adsorbent with an impregnating liquid, and then performing first drying and roasting;

Wherein, the impregnation liquid contains a soluble compound of an active metal component and a soluble compound of an auxiliary component, the active metal component is Ni, and the auxiliary component is selected from at least one of rare earth metals; The amount of the carrier and impregnating liquid is such that in the prepared catalyst, the content of the carrier is 81-91wt%, the content of the active metal component is 5.9-18wt% calculated as oxide, and the auxiliary component The content is 0.1-10wt%.

A third aspect of the present invention provides a methane steam reforming catalyst prepared by the above preparation method.

A fourth aspect of the present invention provides a method for producing hydrogen by steam reforming of methane, the method comprising: under conditions of producing hydrogen by steam reforming of methane, contacting methane and water with a catalyst, wherein the catalyst is the methane steam reforming catalyst provided in the first aspect or the third aspect.

The inventor found in the research that in the prior art, in order to pursue the target high loading capacity, the impregnating solution often needs to be highly concentrated and needs to undergo multiple roastings, resulting in excessively large crystal grains of the active metal components, making it difficult to increase the activity of the catalyst. As expected, therefore, it is difficult for catalysts in the prior art to balance a higher metal loading amount and a smaller grain size of the active metal component. The methane steam reforming catalyst provided by the present invention can take into account both a higher metal loading and a smaller grain size of the active metal component, so it has higher reaction activity and anti-coking performance. The finished catalyst performs well under laboratory conditions. It can operate continuously and stably for 2000 hours without deactivation, and has the feasibility of industrial application; at the same time, the catalyst preparation method provided by the invention has a simple production process, and can meet the target amount of active metal components through one-step impregnation, thereby ensuring that the obtained catalyst contains NiO has small grain size and is easy to operate, which greatly saves catalyst production costs.

Description of drawings

Figure 1 is the XRD spectrum of the catalyst obtained in Example 1 and Comparative Example 1;

Figure 2 is the long-term reaction stability evaluation result of 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.

A first aspect of the present invention provides a methane steam reforming catalyst. The catalyst includes a carrier and an active metal component and an auxiliary component supported on the carrier; wherein the active metal component is Ni, and the auxiliary component The components are selected from at least one rare earth metal; wherein, the average grain size of the active metal component is 3-12nm, based on the total amount of the catalyst, and the content of the carrier is 72-94wt%, based on In terms of oxide, the content of the active metal component is 5.9-18wt%, and the content of the auxiliary component is 0.1-10wt%.

Compared with the methane steam reforming catalyst in the prior art, the active metal component in the catalyst of the present invention has a smaller grain size, and therefore has higher reaction activity and anti-coking performance. The finished catalyst It can operate continuously and stably for 2,000 hours without deactivation under laboratory conditions, and has the feasibility of industrial application.

According to the present invention, preferably, the average grain size of the active metal component is 4-9 nm. Under the above preferred circumstances, it is beneficial to improve the catalyst activity and anti-coking performance.

In the present invention, the average grain size of the active metal component can be measured by XRD method and calculated according to Scherrer's formula.

According to the present invention, preferably, based on the total amount of catalyst, the content of the carrier is 81-91wt%, the content of the active metal component is 8-14wt% based on the oxide, and the auxiliary group The content is 1-5wt%. Under the above preferred composition, it is beneficial to further improve the activity and stability of the catalyst.

It can be understood that when the catalyst only contains a carrier, an active metal component and an auxiliary component, the total content of the carrier, an active metal component and an auxiliary component satisfies 100%.

In the present invention, the content of each component above is measured by fluorescence analysis.

In the present invention, the carrier can be a conventional choice in the art, and can be purchased commercially or prepared by a preparation method known in the art. For example, the carrier can be an oxide carrier prepared by high-temperature sintering. Preferably, the carrier can be α-Al ₂ O ₃ , MgO-Al ₂ O ₃ , CaO-Al ₂ O ₃ , SiC and BN. At least one kind, more preferably α-Al ₂ O ₃ . When α-Al ₂ O ₃ is used as the carrier, it is more conducive to improving the catalytic reaction activity and anti-carbon deposition performance of the catalyst.

Preferably, the water absorption rate of the carrier is 0.18-0.25%.

The inventor found in the research that for high-temperature sintered carriers, due to the relatively low water absorption rate of this type of carrier, multiple impregnations are needed to ensure that the target metal loading is achieved. After using the conventional impregnation method to load active metal components, the active metal The average particle size of the components is larger, resulting in low catalyst activity and poor carbon deposition resistance. When the catalyst provided by the present invention uses a high-temperature sintered carrier, it still has a suitable crystal grain size of the active metal component, which is beneficial to improving the catalytic activity of the catalyst.

In the present invention, the rare earth metal refers to the lanthanide elements of Group IIIB in the periodic table of elements and scandium and yttrium that are chemically similar to the lanthanide elements, totaling 17 elements. Preferably, the auxiliary component is selected from at least one of La, Ce, Pr and Sm, preferably La and/or Ce. The use of the above-mentioned additive components is beneficial to improving the dispersion and anti-coking properties of active metals.

According to the present invention, preferably, in terms of elements, the molar ratio of the auxiliary component and the active metal component is 0.03-0.2:1, preferably 0.04-0.15:1. In the above preferred case, the coordination of the auxiliary component and the active metal component helps to improve the activity and stability of the catalyst.

A second aspect of the present invention provides a method for preparing a methane steam reforming catalyst. The method includes: contacting a carrier carrying an organic adsorbent with an impregnating liquid, and then performing first drying and roasting;

Wherein, the impregnation liquid contains a soluble compound of an active metal component and a soluble compound of an auxiliary component, the active metal component is Ni, and the auxiliary component is selected from at least one of rare earth metals; The amount of the carrier and impregnating liquid is such that in the prepared catalyst, the content of the carrier is 72-94wt%, the content of the active metal component is 5.9-18wt% in terms of oxide, and the additive group The content is 0.1-10wt%.

In the existing technology, methane steam reforming hydrogen production catalysts are mostly prepared by the impregnation method. Due to the influence of the water absorption of the carrier, multiple impregnations or a higher impregnation solution concentration are often required, resulting in an increase in the grain size of the active metal component. , the activity is limited, and the preparation process is increased, resulting in an increase in catalyst production costs. The inventor of the present invention found in the research that the use of organic adsorbents pre-adsorbed on the surface of the carrier can strengthen the adsorption of active metal components and auxiliary components to the surface of the carrier, and can achieve active metal components at a lower concentration of the impregnation solution. The efficient loading of additives and additives helps reduce the grain size of active metal components and improve the catalytic activity and stability of the catalyst.

According to the present invention, preferably, the amount of the carrier carrying the organic adsorbent and the impregnating liquid is such that, based on the total amount of the catalyst produced, the content of the carrier is 81-91 wt%, calculated as oxide, so The content of the active metal component is 8-14wt%, and the content of the auxiliary component is 1-5wt%. Under the above preferred composition, it is beneficial to further the activity and stability of the catalyst.

According to the present invention, preferably, in terms of elements, the molar ratio of the soluble compounds of the auxiliary component and the soluble compound of the active metal component is 0.03-0.2:1, preferably 0.04-0.15:1; in the above preferred Within the molar ratio range, through the coordination of the additive components and the active metal components, it helps to improve the catalyst activity and stability.

In the present invention, the carrier can be a conventional choice in this field, for example, it can be an oxide carrier prepared by high-temperature sintering method, for example, the carrier can be α-Al ₂ O ₃ , MgO-Al ₂ O ₃ , CaO -At least one of Al ₂ O ₃ , SiC and BN, preferably α-Al ₂ O ₃ . When α-Al ₂ O ₃ is used as the carrier, it is more conducive to improving the catalytic reaction activity and anti-carbon deposition performance of the catalyst.

In the present invention, preferably, the carrier is a molded carrier, and the molding can be a conventional molding method in the art, such as extrusion molding or compression molding.

In the present invention, preferably, the auxiliary component is selected from at least one of La, Ce, Pr and Sm, preferably La and/or Ce. The use of the above-mentioned additive components is beneficial to improving the catalyst activity and anti-coking performance. At the same time, through the synergistic effect between the additive components and the active metal components, it helps to inhibit the further growth of the crystal grains of the active metal components. big.

According to the present invention, the types of soluble compounds of the active metal component are well known to those skilled in the art and can be routinely selected in the art. For example, the soluble compound of the active metal component is selected from at least one of nickel nitrate and/or nickel acetate; further preferably, it is nickel nitrate.

According to the present invention, preferably, the concentration of the soluble compound of the active metal component in the impregnation liquid is 0.5-2.5g/mL, and further preferably 0.8-1.5g/mL; within the above concentration range, it is beneficial to further reduce the The grain size of the active metal component improves the catalyst activity and anti-coking properties.

According to the present invention, the types of soluble compounds of the auxiliary component are well known to those skilled in the art and can be conventionally selected in the art. For example, the soluble compound of the auxiliary component is selected from at least one of metal nitrates, chlorides and acetates; nitrates are further preferred.

In the present invention, the soluble compounds of the active metal component and the auxiliary component may all contain crystal water, which is well known to those skilled in the art and will not be described in detail here.

In the present invention, the contact between the organic adsorbent-loaded carrier and the impregnation liquid can be carried out by conventional operations in the art, such as an equal volume impregnation method or a supersaturated impregnation method. Preferably, the contact includes: placing the organic adsorbent-loaded carrier into contact with the impregnation liquid. The carrier is immersed in the immersion liquid for contact. Preferably, only one impregnation is performed until adsorption saturation is performed in the preparation method. The adsorption saturation can be judged based on the adsorption rate curve obtained in the laboratory. After immersing for a certain period of time, if the adsorption amount no longer changes significantly, the adsorption saturation can be judged.

According to the present invention, the contact conditions can be adjusted according to actual needs, as long as the above-mentioned adsorption saturation can be achieved. Preferably, the contact time is 10-60 minutes, preferably 20-35 minutes.

In the present invention, preferably, the preparation method includes only one contact process. That is, the target upper amount requirements of active metal components and auxiliary components can be met through one-step impregnation, thereby avoiding the grain growth of the active metal components caused by multiple impregnations (including drying and roasting).

In the present invention, the first drying and roasting can be performed using conventional operations and conditions in the art, and the present invention is not particularly limited thereto. Preferably, the first drying conditions include: drying temperature is 60-140°C, preferably 70-110°C; drying time is 1-6h, preferably 2-4h.

Preferably, the calcination conditions include: calcination temperature is 300-800°C, preferably 400-550°C; calcination time is 1-5h, preferably 2-4h.

According to the present invention, preferably, the organic adsorbent is selected from at least one of starch, glucose, α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin and maltosaccharin; preferably, it is selected from glucose, β-cyclodextrin and maltosaccharin. -At least one of cyclodextrin and γ-cyclodextrin; further preferably β-cyclodextrin and/or γ-cyclodextrin; using the above-mentioned preferred organic adsorbent is beneficial to promoting the active metal component and assisting The effective adsorption of agent components increases the amount of metal loading in one impregnation process.

According to the present invention, preferably, based on the total amount of the carrier carrying the organic adsorbent, the content of the organic adsorbent is 0.05-3wt%, and more preferably 0.2-1.5wt%. Under the above preferred loading amount, it helps to regulate the appropriate loading amount of active metals and auxiliary metals.

According to the present invention, preferably, the organic adsorbent-loaded carrier is obtained by the following preparation method: contacting a solution containing the organic adsorbent with the carrier, and then performing pre-water removal and second drying.

In the present invention, the "first drying" and "second drying" do not refer to the order of operations, but are only used to distinguish the drying methods and conditions in different steps.

The contact can be carried out in a conventional manner in the art, for example, by dipping or spraying to contact the solution containing the organic adsorbent with the carrier.

According to the present invention, the solution also contains a solvent. Preferably, the solvent is water.

Preferably, the concentration of the solution containing the organic adsorbent is 0.005-0.1g/mL, more preferably 0.009-0.07g/mL.

According to the present invention, preferably, the pre-water removal includes: pre-dewatering the product obtained by the contact in the presence of warm air until there is no clear water on the surface; for example, the product obtained by the contact can be placed Place it on the vibrating screen, then blow in warm air until there is no clear water on the surface.

Preferably, the temperature of the warm air is 30-80°C, preferably 35-60°C.

According to the present invention, preferably, the second drying temperature does not exceed 100°C. Excessively high second drying temperature may cause the structure of the organic adsorbent to be destroyed, thereby affecting its adsorption effect on active metal components and additive components.

In the invention, there is no specific requirement for the second drying time, as long as the contact product is thoroughly dried. It can be understood that when the quality of the contact product no longer changes significantly, it can be judged The contact product is thoroughly dried. For example, the second drying time can be 2-20 hours.

According to the present invention, preferably, the second drying method is selected from at least one of freeze drying, low temperature vacuum drying and low temperature hot air drying, preferably freeze drying.

Preferably, the freeze-drying conditions include: a temperature of -30°C to -5°C, preferably -25°C to -15°C; and a drying time of 1-10 h.

Preferably, the conditions for low-temperature vacuum drying include: vacuum degree is -0.09MPa to -0.05MPa, preferably -0.09MPa to -0.07MPa; temperature is 30-70°C, preferably 40-60°C; drying time is 2-10h.

Preferably, the conditions for low-temperature hot air drying include: hot air flow rate is 0.1-0.5m/s, preferably 0.2-0.4m/s; temperature is 40-80°C, preferably 50-70°C; drying time is 2- 10h.

Adopting the above-mentioned preferred second drying method is beneficial to stabilizing the structure of the organic adsorbent, further increasing the amount of metal added, and improving the catalytic activity and anti-carbon deposition performance of the catalyst.

A third aspect of the present invention provides a methane steam reforming catalyst prepared by the above preparation method.

A fourth aspect of the present invention provides a method for producing hydrogen by methane steam reforming, the method comprising: contacting methane and water with a catalyst under conditions of methane steam reforming hydrogen production, characterized in that the catalyst is the methane steam reforming catalyst provided in the first and third aspects above.

Using the methane steam reforming catalyst provided by the present invention to produce hydrogen by methane steam reforming can obtain a higher methane conversion rate at a lower water-to-carbon ratio.

The method for contacting methane and water with the catalyst is not particularly limited and can be a conventional choice in the field. Preferably, the contact is carried out in a fixed bed reactor.

Preferably, the conditions for hydrogen production by methane steam reforming include: the volume ratio of water and methane is (1.2-5): 1, preferably (2.5-3.5): 1; the reaction temperature is 600-900°C, preferably 650- 850°C; pressure is 0-4MPa, preferably 1.5-3.5MPa; methane carbon space velocity is 400-5000h ^-1 , preferably 600-4000h ^-1 . In the present invention, the pressure is gauge pressure, and the methane carbon space velocity is volume space velocity.

According to the present invention, preferably, the method further includes: reducing and activating the catalyst in a hydrogen-containing atmosphere before the reaction.

Preferably, the conditions for reduction activation include: reduction temperature is 300-800°C, preferably 400-600°C; reduction time is 0.5-10 hours, preferably 1-5 hours, further preferably 2-4 hours; reduction The pressure is 0-2MPa, preferably 0-1MPa, more preferably 0-0.5MPa.

According to the present invention, preferably, the hydrogen-containing atmosphere is hydrogen or a mixture of hydrogen and an inert gas; for example, the mixture may be a mixture of hydrogen, nitrogen and/or argon. Preferably, the volume content of hydrogen in the mixed gas is 10-80%, more preferably 20-60%.

The present invention will be described in detail below through examples.

In the following examples, unless otherwise specified, all reaction raw materials are commercially available.

In the following examples, the content of each component in the catalyst was measured using fluorescence analysis.

The average grain size of the active metal component was tested by XRD method and calculated according to Scherrer's formula.

The gas chromatography method is used for online sampling analysis to calculate the exhaust gas composition. The conversion rate of methane (X _CH4 ) is calculated by the following formula:

Among them, C _CH4 is the volume concentration of methane, and C _N2 is the volume concentration of nitrogen.

Example 1

(1) Preparation of catalyst

Weigh 100g of the formed high-temperature α-Al ₂ O ₃ carrier for later use. The water absorption rate of the carrier is 0.21%. Weigh 0.8g of β-cyclodextrin and pour it into deionized water, adjust the volume to 21mL, stir thoroughly to dissolve; then spray the solution onto the formed high-temperature α-Al ₂ O ₃ carrier, and mix evenly. After that, it is placed on a vibrating screen and dried with warm air at 40°C until there is no clear water on the surface; then the second drying is carried out by freeze drying and fully dried at -20°C for 10 hours to obtain a carrier loaded with organic adsorbent. Based on the total amount of the organic adsorbent-loaded carrier, the content of the organic adsorbent is 0.79 wt%.

Weigh 21g Ni(NO ₃ ) ₂ ·6H ₂ O and 3.6g La(NO ₃ ) ₂ ·9H ₂ O and dissolve them in 15 mL deionized water, stir and dissolve at room temperature. Take 10g of the above-mentioned organic adsorbent-loaded carrier and immerse it in the prepared impregnation liquid, let it stand for 30 minutes, then take out the adsorbed saturated carrier from the impregnation liquid, drain the water, and place it in an oven to dry at 80°C for 3 hours; after drying The sample was put into a muffle furnace and roasted at 500°C for 2 hours to obtain the required methane steam reforming hydrogen production catalyst. Fluorescence analysis results show that the content of NiO in the catalyst is 12.6wt%, the content of La ₂ O ₃ is 2.3wt%, and the rest is the carrier. In the catalyst, in terms of elements, the molar ratio of auxiliary component:active metal component is approximately 0.084:1.

The XRD spectrum of the catalyst obtained in Example 1 is shown in Figure 1. According to the diffraction half-peak width of NiO in the spectrum, the grain size of NiO is calculated to be 5.6 nm.

(2) Activity evaluation

Weigh 0.2 g of the catalyst obtained in Example 1 and load it into a fixed bed reactor, and perform reduction activation at 550°C for 3 hours in a pure hydrogen atmosphere under normal pressure. After the reduction is completed, the temperature is raised to 700°C in a hydrogen atmosphere, and the raw gas is switched for reaction. The volume ratio of water and methane in the raw gas is 2:1, the methane carbon space velocity is 4000h ^-1 , and the reaction pressure is normal pressure. Gas chromatography was used to online sample and analyze the tail gas composition, and the methane conversion rate was calculated to be 89.7%.

The obtained catalyst performed a long-term reaction under simulated reaction conditions for industrial applications at an inlet temperature of 600°C, an outlet temperature of 810°C, a water/methane volume ratio of 2.8:1, a methane carbon space velocity of 1500h ^-1 , and a reaction pressure of 2.5MPa. The stability evaluation results are shown in Figure 2. As can be seen from Figure 2, the reaction performance of the catalyst is very stable.

Example 2

(1) Preparation of catalyst

The catalyst was prepared according to the same method as in Example 1, except that the organic adsorbent was γ-cyclodextrin to obtain the required methane steam reforming hydrogen production catalyst. Fluorescence analysis results show that the content of NiO in the catalyst is 11.3wt%, the content of La ₂ O ₃ is 2wt%, and the rest is the carrier. In the catalyst, in terms of elements, the molar ratio of auxiliary component:active metal component is approximately 0.081:1.

XRD analysis results show that the grain size of NiO in the catalyst is 7.6nm.

(2) Activity evaluation

The catalyst was activated and the methane steam reforming hydrogen production reaction was carried out under the same conditions as in Example 1. The tail gas composition was analyzed by gas chromatography online sampling, and the methane conversion rate was calculated to be 86.5%.

Example 3

(1) Preparation of catalyst

The catalyst was prepared according to the same method as in Example 1, except that the second drying of the loaded organic adsorbent was vacuum drying at 50°C for 3 hours, and the vacuum degree was -0.09MPa; the required methane steam reforming hydrogen production catalyst was obtained. Fluorescence analysis results show that the content of NiO in the catalyst is 11.9wt%, the content of La ₂ O ₃ is 2.1wt%, and the rest is the carrier. In the catalyst, in terms of elements, the molar ratio of auxiliary component:active metal component is approximately 0.081:1.

XRD analysis results show that the grain size of NiO in the catalyst is 7.1nm.

(2) Activity evaluation

The catalyst was activated and the methane steam reforming hydrogen production reaction was carried out under the same conditions as in Example 1. The tail gas composition was analyzed by gas chromatography online sampling, and the methane conversion rate was calculated to be 87.9%.

Example 4

(1) Preparation of catalyst

The catalyst was prepared according to the same method as in Example 1, except that the amount of β-cyclodextrin was weighed as 1.2g. Based on the total amount of the carrier carrying the organic adsorbent, the content of the organic adsorbent was is 1.2wt%.

The required methane steam reforming hydrogen production catalyst is obtained. Fluorescence analysis results show that the content of NiO in the catalyst is 13.5wt%, the content of La ₂ O ₃ is 2.7wt%, and the rest is the carrier. In the catalyst, in terms of elements, the molar ratio of auxiliary component:active metal component is approximately 0.092:1. XRD analysis results show that the grain size of NiO in the catalyst is 6.9nm.

(2) Activity evaluation

The catalyst was activated and the methane steam reforming hydrogen production reaction was carried out under the same conditions as in Example 1. The tail gas composition was analyzed by gas chromatography online sampling, and the methane conversion rate was calculated to be 87.6%.

Example 5

(1) Preparation of catalyst

The catalyst was prepared according to the same method as in Example 1, except that the amount of β-cyclodextrin was weighed as 0.17g. Based on the total amount of the carrier carrying the organic adsorbent, the content of the organic adsorbent was is 0.17wt%.

The required methane steam reforming hydrogen production catalyst is obtained. Fluorescence analysis results show that the concentration of NiO in the catalyst is 7.4wt%, the content of La ₂ O ₃ is 1.3wt%, and the rest is the carrier. In the catalyst, in terms of elements, the molar ratio of auxiliary component:active metal component is approximately 0.081:1. XRD analysis results show that the grain size of NiO in the catalyst is 4.6nm.

(2) Activity evaluation

The catalyst was activated and the methane steam reforming hydrogen production reaction was carried out under the same conditions as in Example 1. The tail gas composition was analyzed by gas chromatography online sampling, and the methane conversion rate was calculated to be 78.5%.

Example 6

(1) Preparation of catalyst

The catalyst was prepared according to the same method as in Example 1, except that 27g Ni(NO ₃ ) ₂ ·6H ₂ O and 4.62g La(NO ₃ ) ₂ ·9H ₂ O were weighed and dissolved in 15 mL of deionized water to obtain Required methane steam reforming hydrogen production catalyst. Fluorescence analysis results show that the concentration of NiO in the catalyst is 14.7 wt%, the content of La ₂ O ₃ is 2.7 wt%, and the rest is the carrier. In the catalyst, in terms of elements, the molar ratio of auxiliary component:active metal component is approximately 0.084:1.

XRD analysis results show that the grain size of NiO in the catalyst is 7.4nm.

It can be seen from the comparison between Example 1 and Example 6 that when the concentration of the soluble compound of the active metal component in the impregnation solution is too high, the size of the NiO grains supported on the carrier increases.

(2) Activity evaluation

The catalyst was activated and the methane steam reforming hydrogen production reaction was carried out under the same conditions as in Example 1. The tail gas composition was analyzed by gas chromatography online sampling, and the methane conversion rate was calculated to be 88.5%.

Example 7

(1) Preparation of catalyst

The catalyst was prepared according to the same method as in Example 1, except that 21g Ni(NO ₃ ) ₂ ·6H ₂ O and 1.2g La(NO ₃ ) ₂ ·9H ₂ O were weighed and dissolved in 15 mL of deionized water to obtain Required methane steam reforming hydrogen production catalyst. Fluorescence analysis results show that the concentration of NiO in the catalyst is 12.2wt%, the content of La ₂ O ₃ is 0.98wt%, and the rest is the carrier. In the catalyst, in terms of elements, the molar ratio of auxiliary component:active metal component is approximately 0.03:1.

XRD analysis results show that the grain size of NiO in the catalyst is 5.3nm.

(2) Activity evaluation

The catalyst was activated and the methane steam reforming hydrogen production reaction was carried out under the same conditions as in Example 1. The tail gas composition was analyzed by gas chromatography online sampling, and the methane conversion rate was calculated to be 86.5%.

Example 8

(1) Preparation of catalyst

The catalyst was prepared according to the same method as Example 1, except that the second drying method in the pre-adsorbed organic adsorbent was ordinary hot air drying at 120°C for 3 hours. Fluorescence analysis results show that the content of NiO in the catalyst is 9.2wt%, the content of La ₂ O ₃ is 1.7wt%, and the rest is the carrier. In the catalyst, in terms of elements, the molar ratio of auxiliary component:active metal component is approximately 0.085:1.

The loading amounts of active components and auxiliary components were significantly reduced, which shows that high-temperature hot air drying affects the structure of the organic adsorbent, making its ability to selectively adsorb cations worse. XRD analysis results show that the grain size of NiO in the catalyst is 6.6nm.

(2) Activity evaluation

The catalyst was activated and the methane steam reforming hydrogen production reaction was carried out under the same conditions as in Example 1. The tail gas composition was analyzed by gas chromatography online sampling, and the methane conversion rate was calculated to be 75.6%.

Example 9

(1) Preparation of catalyst

The catalyst was prepared according to the same method as in Example 1, except that the carrier was a high-temperature roasted MgO-Al ₂ O ₃ composite oxide with a water absorption rate of 0.22%, and the required methane steam reforming hydrogen production catalyst was obtained. Fluorescence analysis results show that the content of NiO in the catalyst is 13.1wt%, the content of La ₂ O ₃ is 2.5wt%, and the rest is the carrier. In the catalyst, in terms of elements, the molar ratio of auxiliary component:active metal component is approximately 0.087:1.

XRD analysis results show that the grain size of NiO in the catalyst is 6.4nm.

(2) Activity evaluation

The catalyst was activated and the methane steam reforming hydrogen production reaction was carried out under the same conditions as in Example 1. The tail gas composition was analyzed by gas chromatography online sampling, and the methane conversion rate was calculated to be 86.1%.

Example 10

(1) Preparation of catalyst

The catalyst was prepared according to the same method as in Example 1, except that the organic adsorbent was starch to obtain the required methane steam reforming hydrogen production catalyst. Fluorescence analysis results show that the content of NiO in the catalyst is 10.9wt%, the content of La ₂ O ₃ is 1.8wt%, and the rest is the carrier. In the catalyst, in terms of elements, the molar ratio of auxiliary component:active metal component is approximately 0.076:1.

XRD analysis results show that the grain size of NiO in the catalyst is 5.2nm.

(2) Activity evaluation

The catalyst was activated and the methane steam reforming hydrogen production reaction was carried out under the same conditions as in Example 1. The tail gas composition was analyzed by gas chromatography online sampling, and the methane conversion rate was calculated to be 84.3%.

Comparative example 1

(1) Preparation of catalyst

The catalyst was prepared according to the same method as in Example 1, except that the organic adsorbent was not adsorbed on the surface of the carrier in advance. At this time, the adsorption capacity of the carrier is poor, and it needs to be impregnated twice to meet the active metal loading requirements. The fluorescence analysis results show that after one impregnation, the content of NiO is 6.7%, the content of La ₂ O ₃ is 1.2wt%, and the rest as a carrier. After two impregnations, the NiO content in the catalyst was 11.5wt%, the La ₂ O ₃ content was 2.2wt%, and the rest was the carrier. The XRD spectrum of the obtained catalyst is shown in Figure 1. According to the diffraction half-peak width of NiO in the spectrum, the grain size of NiO is calculated to be 13.7 nm. It can also be seen from the comparison of the XRD spectra in Figure 1 that the NiO crystal grain size of the catalyst obtained in Example 1 is significantly smaller than the NiO crystal grain size of the catalyst obtained in Comparative Example 1.

From the comparison between Example 1 and Comparative Example 1, it can be seen that the carrier without organic adsorbent loading needs to be impregnated two or three times to achieve the required metal loading. Due to multiple impregnations, drying and roasting are required for each pass. Such procedures also lead to an increase in the size of NiO grains on the carrier and complicated preparation procedures, resulting in an increase in catalyst production costs.

(2) Activity evaluation

The catalyst was activated and the methane steam reforming hydrogen production reaction was carried out under the same conditions as in Example 1. The tail gas composition was analyzed by gas chromatography online sampling, and the methane conversion rate was calculated to be 72.2%.

At the same time, the unloading agent of the catalyst obtained in Example 1 after reacting for 50 hours was analyzed for carbon deposits, and compared with the unloading agent obtained by the catalyst obtained in Example 1 after reacting for 2000 hours. It was found that the unloading agent of Comparative Example 1 after reacting for 50 hours was The amount of coke deposit was 1.7wt%, while the amount of coke deposit in the unloading agent after the catalyst obtained in Example 1 reacted for 2000 hours was 0.06wt%. This shows that the catalyst prepared by the method of the present invention has excellent anti-coking properties.

Comparative example 2

(1) Preparation of catalyst

The catalyst was prepared in the same manner as in Example 1, except that no additives were added when preparing the metal impregnation solution to obtain the required methane steam reforming hydrogen production catalyst. Fluorescence analysis results show that the concentration of NiO in the catalyst is 13.5wt%, and the rest is the carrier. The calculated grain size of NiO is 6.2nm.

(2) Activity evaluation

Weigh 0.2g of the above catalyst and load it into a fixed bed reactor, and reduce it at 550°C for 3 hours in a pure hydrogen atmosphere under normal pressure for reduction activation. After the reduction is completed, the temperature is raised to 700°C in a hydrogen atmosphere, and the raw gas is switched for reaction. The volume ratio of water and methane in the raw gas is 2:1, the methane carbon space velocity is 4000h ^-1 , and the reaction pressure is normal pressure. Gas chromatography was used to online sample and analyze the tail gas composition, and the methane conversion rate was calculated to be 84.8%.

It can be seen from the above results that the preparation method of the catalyst provided by the present invention and the prepared catalyst have better reaction activity, stability and coke resistance, and can operate continuously and stably for more than 2000 hours without deactivation.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical concept of the present invention, many simple modifications can be made to the technical solution of the present invention, including the combination of various technical features in any other suitable manner. These simple modifications and combinations should also be regarded as the disclosed content of the present invention. All belong to the protection scope of the present invention.

Claims (13)

1. A methane steam reforming catalyst, characterized in that the catalyst comprises a carrier and an active metal component and an auxiliary component supported on the carrier; wherein the active metal component is Ni, and the auxiliary component is at least one of rare earth metals; wherein the average grain size of the active metal component is 3-12nm, the content of the carrier is 72-94wt% based on the total amount of the catalyst, the content of the active metal component is 5.9-18wt% based on oxide, and the content of the auxiliary component is 0.1-10wt%.

2. The catalyst of claim 1, wherein the active metal component has an average crystallite size of 4-9nm;

preferably, the carrier is present in an amount of 81 to 91wt% based on the total amount of catalyst, the active metal component is present in an amount of 8 to 14wt% based on the oxide, and the auxiliary component is present in an amount of 1 to 5wt%.

3. The catalyst according to claim 1 or 2, wherein the support is a-Al ₂ O ₃ 、MgO-Al ₂ O ₃ 、CaO-Al ₂ O ₃ At least one of SiC and BN, preferably alpha-Al ₂ O ₃ ；

Preferably, the auxiliary component is selected from at least one of La, ce, pr and Sm, preferably La and/or Ce;

preferably, the molar ratio of the auxiliary component to the active metal component is 0.03-0.2, calculated as element: 1, preferably 0.04-0.15:1.

4. a method of preparing a methane steam reforming catalyst, the method comprising: contacting the carrier loaded with the organic adsorbent with impregnating solution, and then performing first drying and roasting;

the impregnating solution contains a soluble compound of an active metal component and a soluble compound of an auxiliary component, wherein the active metal component is Ni, and the auxiliary component is at least one of rare earth metals; the carrier loading the organic adsorbent and the impregnating solution are used in an amount such that the content of the carrier is 72-94wt%, the content of the active metal component is 5.9-18wt% and the content of the auxiliary component is 0.1-10wt% in terms of oxide in the prepared catalyst.

5. The process according to claim 4, wherein the organic adsorbent-supporting carrier, the soluble compound of the active metal component and the soluble compound of the auxiliary component are used in such amounts that the carrier is contained in an amount of 81 to 91% by weight, the active metal component is contained in an amount of 8 to 14% by weight, and the auxiliary component is contained in an amount of 1 to 5% by weight, based on the total amount of the catalyst to be produced.

6. The production method according to claim 4 or 5, wherein the soluble compound of the auxiliary component and the soluble compound of the active metal component are used in such an amount that, on an elemental basis, the molar ratio of the auxiliary component to the active metal component in the produced catalyst is 0.03 to 0.2:1, preferably 0.04-0.15:1, a step of;

preferably, the carrier is alpha-Al ₂ O ₃ 、MgO-Al ₂ O ₃ 、CaO-Al ₂ O ₃ At least one of SiC and BN, preferably alpha-Al ₂ O ₃ ；

Preferably, the auxiliary component is selected from at least one of La, ce, pr and Sm, preferably La and/or Ce;

preferably, the concentration of the soluble compound of the active metal component in the impregnation liquid is 0.5-2.5g/mL, more preferably 0.8-1.5g/mL.

7. The preparation method according to any one of claims 4 to 6, wherein the contacting is for a period of 10 to 60min, preferably 20 to 35min;

preferably, the first drying conditions include: the drying temperature is 60-140 ℃, preferably 70-110 ℃; the drying time is 1-6h, preferably 2-4h;

preferably, the roasting conditions include: the roasting temperature is 300-800 ℃, preferably 400-550 ℃; the calcination time is 1 to 5 hours, preferably 2 to 4 hours.

8. The production method according to any one of claims 4 to 7, wherein the organic adsorbent is at least one selected from the group consisting of starch, glucose, α -cyclodextrin, β -cyclodextrin, γ -cyclodextrin and maltosaccharin; preferably at least one selected from glucose, beta-cyclodextrin and gamma-cyclodextrin; further preferred are beta-cyclodextrin and/or gamma-cyclodextrin;

preferably, the content of the organic adsorbent is 0.05 to 3wt%, more preferably 0.2 to 1.5wt%, based on the total amount of the organic adsorbent-supporting carrier.

9. The production method according to any one of claims 4 to 8, wherein the organic adsorbent-loaded carrier is obtained by the following production method: contacting the solution containing the organic adsorbent with a carrier to obtain a contact product, and then performing pre-dewatering and secondary drying;

preferably, the concentration of the organic adsorbent-containing solution is 0.005 to 0.1g/mL, more preferably 0.009 to 0.07g/mL;

preferably, the pre-dewatering comprises: pre-dewatering the contact product in the presence of warm air until no surface water is present;

preferably, the temperature of the warm air is 30-80 ℃, preferably 35-60 ℃;

preferably, the second drying temperature does not exceed 100 ℃;

preferably, the second drying mode is at least one selected from freeze drying, low-temperature vacuum drying and low-temperature hot air drying, and is preferably freeze drying;

preferably, the conditions of freeze-drying include: the temperature is between minus 30 ℃ and minus 5 ℃ and the time is between 1 and 20 hours;

preferably, the conditions of the low-temperature vacuum drying include: vacuum degree is-0.09 MPa to-0.05 MPa, temperature is 30-70 ℃, and drying time is 2-10h;

preferably, the conditions of the low-temperature hot air drying include: the temperature is 40-80 ℃, the flow rate of hot air is 0.1-0.5m/s, and the drying time is 2-10h.

10. A steam methane reforming catalyst prepared by the process of any one of claims 4 to 9.

11. A method for producing hydrogen from steam reforming of methane, the method comprising: contacting methane and water with a catalyst under conditions for steam reforming of methane to produce hydrogen, wherein the catalyst is a steam methane reforming catalyst according to any one of claims 1-3 and 10.

12. The method of claim 11, wherein the contacting is performed in a fixed bed reactor;

preferably, the conditions for steam reforming methane to produce hydrogen include: the volume ratio of water to methane is (1.2-5): 1, preferably (2.5-3.5): 1, a step of; the reaction temperature is 600-900 ℃, preferably 650-850 ℃; the pressure is 0-4MPa, preferably 1.5-3.5MPa; methane carbon space velocity of 400-5000h ^-1 Preferably 600-4000h ^-1 。

13. The method according to claim 11 or 12, wherein the method further comprises: before the reaction, the catalyst is reduced and activated in the atmosphere containing hydrogen;

preferably, the conditions of the reductive activation include: the reduction temperature is 300-800 ℃, preferably 400-600 ℃; the reduction time is 0.5 to 10 hours, preferably 1 to 5 hours, further preferably 2 to 4 hours; the reduction pressure is 0 to 2MPa, preferably 0 to 1MPa, more preferably 0 to 0.5MPa;

preferably, the hydrogen-containing atmosphere is hydrogen or a mixed gas of hydrogen and inert gas;

preferably, the volume content of hydrogen in the mixed gas is 10-80%.