Pretreatment method of ammonia decomposition hydrogen production catalyst

Abstract

The invention relates to the field of catalyst pretreatment, and discloses a pretreatment method of an ammonia decomposition hydrogen production catalyst. A pretreatment method of an ammonia decomposition hydrogen production catalyst comprises the following steps: in the presence of an activation gas, the ammonia decomposition hydrogen production catalyst is subjected to n-stage programmed heating activation treatment and then is subjected to cooling treatment, n is 2-5, and n is an integer; the activation gas comprises an activation atmosphere and a carrier gas, and the activation atmosphere comprises hydrogen and / or water vapor; in the n-section programmed heating and activating treatment, the proportion of the activating atmosphere in the activating gas is sequentially reduced; the proportion of the activation atmosphere in the activation gas used in the previous section of activation treatment is 2-65% higher than that in the activation gas used in the next section of activation treatment; the temperature of the previous section of activating treatment is 25-400 DEG C lower than that of the next section of activating treatment. According to the method, multi-stage activation treatment is selected, so that the pretreated ammonia decomposition hydrogen production catalyst can be suitable for high-temperature reaction, and the stability of the catalyst is improved.

Description

Technical Field

[0001] The invention relates to the technical field of catalyst pretreatment, and in particular to a pretreatment method for a catalyst for hydrogen production by decomposing ammonia. Background Art

[0002] At present, hydrogen almost comes from the catalytic steam reforming of fossil fuels, which is also the most mature commercial hydrogen production technology. However, the hydrogen extracted by catalytic reforming will be accompanied by impurity gases such as carbon monoxide and carbon dioxide, and cannot be directly used as fuel cell fuel. Therefore, using hydrogen-rich carrier ammonia as a raw material for carbon-free hydrogen production is an efficient, clean and safe hydrogen production technology. In order to achieve safe and green hydrogen production, it is particularly important to develop catalysts that can efficiently catalyze the decomposition of ammonia. At present, ammonia decomposition catalysts are divided into precious metal catalysts with ruthenium and platinum as active components and non-precious metal catalysts with iron and nickel as active components.

[0003] At present, ruthenium is the catalyst with the highest catalytic activity for ammonia decomposition, but it is relatively expensive and the cost of the prepared catalyst is high. In order to improve the utilization rate of ruthenium atoms, the catalyst generally needs to be pretreated before the ammonia decomposition reaction to obtain higher activity. Chinese patent application CN110270341A discloses a Ru-based catalyst, which is used for ammonia decomposition and hydrogen production after being reduced by hydrogen at 800°C. Although this pretreatment method can reduce the active phase, the high reduction temperature will enhance the interaction between the metal carrier and the active phase grain size, resulting in poor ammonia decomposition activity at low temperatures. Summary of the invention

[0004] The purpose of the present invention is to overcome the problem in the prior art that the activation temperature of the ammonia decomposition hydrogen production catalyst is too high, resulting in poor ammonia decomposition activity, and to provide a pretreatment method for the ammonia decomposition hydrogen production catalyst. The method uses a multi-stage activation treatment to improve the activity of the ammonia decomposition hydrogen production catalyst, so that the pretreated ammonia decomposition hydrogen production catalyst can be suitable for high-temperature reactions, thereby improving the stability of the ammonia decomposition hydrogen production catalyst.

[0005] The present invention provides a pretreatment method for a catalyst for producing hydrogen by decomposing ammonia, wherein the pretreatment method comprises the following steps:

[0006] In the presence of an activation gas, the catalyst for hydrogen production by decomposing ammonia is first subjected to a programmed temperature increase activation treatment for n stages, and then subjected to a temperature reduction treatment, wherein n is 2-5 and n is an integer;

[0007] The activation gas includes an activation atmosphere and a carrier gas, and the activation atmosphere includes hydrogen and / or water vapor;

[0008] In the n-stage programmed temperature activation treatment, the proportion of the activation atmosphere in the activation gas decreases successively;

[0009] The proportion of the activated atmosphere in the activated gas used in the first stage of the activation treatment is 2-65% higher than the proportion of the activated atmosphere in the activated gas used in the second stage of the activation treatment;

[0010] The temperature in the first stage of activation treatment is 25-400°C lower than the temperature in the second stage of activation treatment.

[0011] Preferably, the activation gas flow rate in the latter activation treatment is 5-20 mL / min·g lower than that in the former activation treatment, preferably 5-15 mL / min·g lower.

[0012] The pretreatment method provided by the present invention, through multi-step temperature-variable activation, solves the problems that part of the active phase cannot be completely activated at low temperature and the active phase has a large size during high-temperature sintering. It can effectively control the active phase to maintain a small grain size and improve the catalytic activity of the ammonia decomposition hydrogen production catalyst.

[0013] The pretreatment method provided by the present invention can inhibit the sintering of the active phase and improve the dispersion of the active phase by changing the proportion of the activation atmosphere in the activation gas, thereby improving the catalytic activity of the catalyst.

[0014] The pretreatment method provided by the invention has simple overall process, good repeatability and is easy to carry out large-scale production. DETAILED DESCRIPTION

[0015] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0016] The present invention provides a pretreatment method for a catalyst for producing hydrogen by decomposing ammonia, wherein the pretreatment method comprises the following steps:

[0017] In the presence of an activation gas, the catalyst for hydrogen production by decomposing ammonia is first subjected to a programmed temperature increase activation treatment for n stages, and then subjected to a temperature reduction treatment, wherein n is 2-5 and n is an integer;

[0018] The activation gas includes an activation atmosphere and a carrier gas, and the activation atmosphere includes hydrogen and / or water vapor;

[0019] In the n-stage programmed temperature activation treatment, the proportion of the activation atmosphere in the activation gas decreases successively;

[0020] The proportion of the activated atmosphere in the activated gas used in the first stage of the activation treatment is 2-65% higher than the proportion of the activated atmosphere in the activated gas used in the second stage of the activation treatment;

[0021] The temperature in the first stage of activation treatment is 25-400°C lower than the temperature in the second stage of activation treatment.

[0022] In the present invention, preferably, n is 2-3, and n is an integer.

[0023] The pretreatment method provided by the present invention, through multi-step temperature-variable activation, solves the problems that part of the active phase cannot be completely activated at low temperature and the active phase has a large size during high-temperature sintering. It can effectively control the active phase to maintain a small grain size and improve the catalytic activity of the ammonia decomposition hydrogen production catalyst.

[0024] The pretreatment method provided by the present invention can inhibit the sintering of the active phase and improve the dispersion of the active phase by changing the proportion of the activation atmosphere in the activation gas, thereby improving the catalytic activity of the catalyst.

[0025] The pretreatment method provided by the present invention has a simple overall process, good repeatability, and is easy to scale up for production. The ammonia decomposition hydrogen production catalyst obtained by the pretreatment method provided by the present invention can be used in ammonia decomposition to produce fuel cell-grade hydrogen, and has high catalytic activity. The method has mild reaction conditions and is environmentally friendly.

[0026] In the present invention, it should be noted that the first section and the second section refer to the first and the second of two adjacent sections of programmed temperature activation treatment. Taking two sections as an example for schematic explanation, the first section refers to the first section of programmed temperature activation treatment, and the second section refers to the second section of programmed temperature activation treatment. If there are n sections of programmed temperature activation treatment, the same applies.

[0027] In the present invention, preferably, the activation atmosphere is water vapor. The advantage of adopting this preferred embodiment is that the sintering of the active phase can be suppressed, the dispersion of the active phase can be improved, and thus the catalytic activity of the catalyst can be improved.

[0028] In the present invention, the activation degree can be effectively controlled by controlling the proportion of the activation atmosphere in the activation gas at each activation stage. Preferably, the proportion of the activation atmosphere in the activation gas used in the first stage of the activation treatment is 10-60% higher than the proportion of the activation atmosphere in the activation gas used in the second stage of the activation treatment. The advantage of adopting this preferred embodiment is that sufficient activation atmosphere is introduced under low temperature conditions to activate the active components while avoiding the agglomeration of active metals.

[0029] In the present invention, by controlling the treatment temperature of each activation stage, it is avoided that the active phase size in the ammonia decomposition hydrogen production catalyst is too large due to a temperature rise, and the activity of the ammonia decomposition hydrogen production catalyst is improved. Preferably, the temperature of the first stage of activation treatment is 75-300°C lower than the temperature of the second stage of activation treatment. The advantage of adopting this preferred embodiment is that the catalyst activation is carried out at a low temperature to prevent the aggregation of the active phase during the activation process.

[0030] In the present invention, by controlling the flow rate of the activation gas in each activation stage, it is further avoided that the active phase size in the ammonia decomposition hydrogen production catalyst is too large due to one stage of activation, thereby improving the activity of the ammonia decomposition hydrogen production catalyst. Preferably, the activation gas flow rate in the latter stage of activation treatment is 5-20 mL / min·g of ammonia decomposition hydrogen production catalyst lower than the activation gas flow rate in the previous stage of activation treatment, preferably 5-15 mL / min·g of ammonia decomposition hydrogen production catalyst lower. The advantage of adopting this preferred embodiment is to avoid the agglomeration of active components caused by activating the catalyst at high temperature, thereby destroying the stability of the active components of the catalyst.

[0031] In the present invention, the activity of the ammonia decomposition hydrogen production catalyst is further improved by controlling the heating rate of each activation stage. Preferably, the heating rate in the first stage of activation treatment is 0.1-5°C / min lower than the heating rate in the second stage of activation treatment, preferably 0.1-3°C / min lower.

[0032] In the present invention, there is no particular limitation on the components of the catalyst for hydrogen production by decomposition of ammonia. Preferably, the catalyst for hydrogen production by decomposition of ammonia comprises an alumina carrier, a metal active component and an additive, wherein the metal active component comprises Ru and a non-precious metal component, wherein the non-precious metal component is selected from at least one of Mn, Fe, Co, Ni and Cu, and the additive is selected from at least one of CeO2, MgO, CuO, CaO and La2O3. In the present invention, preferably, the additive is present in the alumina carrier in the form of an oxide.

[0033] In the present invention, there is no particular limitation on the content of each component in the ammonia decomposition hydrogen production catalyst. Preferably, based on the weight of the ammonia decomposition hydrogen production catalyst, the content of Ru is 0.1-2.5% by weight, the content of the non-precious metal component calculated as oxide is 0.1-10% by weight, the content of the auxiliary agent is 2-8% by weight, and the content of the alumina carrier is 69.5-97.8% by weight.

[0034] In the present invention, the content of each component in the ammonia decomposition hydrogen production catalyst is calculated by feeding amount.

[0035] In the present invention, there is no particular limitation on the source of the catalyst for hydrogen production by decomposition of ammonia. The catalyst can be obtained commercially or prepared by a preparation method in the prior art. The present invention has no particular limitation on the specific operation method.

[0036] In the present invention, there is no particular limitation on the type of carrier gas. Preferably, the carrier gas is selected from at least one of the inert gases.

[0037] In the present invention, there is no particular limitation on the type of the inert gas. Preferably, the inert gas is selected from at least one of nitrogen, argon, helium and neon.

[0038] In the present invention, the range of conditions for the first stage of programmed ascending temperature increase is relatively wide. Preferably, the conditions for the first stage of programmed temperature increase include: temperature of 300-420°C, heating rate of 0.3-3°C / min, pressure of normal pressure-1MPa, activation gas flow rate of 10-50mL / min·g ammonia decomposition hydrogen production catalyst, and time of 0.25-5h; further preferably, the conditions for the first stage of programmed temperature increase include: temperature of 300-400°C, heating rate of 1.5-3°C / min, pressure of normal pressure-0.1MPa, activation gas flow rate of 15-45mL / min·g ammonia decomposition hydrogen production catalyst, and time of 0.5-4h.

[0039] In the present invention, preferably, in the first stage of programmed temperature increase, the proportion of the activation atmosphere in the activation gas is 10-85% by volume, more preferably 50-80% by volume. The advantage of adopting this preferred embodiment is that the active components in the catalyst are activated under the condition of ensuring uniform dispersion of the active components.

[0040] In the present invention, the range of temperature reduction treatment conditions is relatively wide. Preferably, the temperature reduction treatment conditions include: temperature of 500-700°C, cooling rate of 0.1-2°C / min, pressure of normal pressure-1MPa, activation gas flow rate of 5-30mL / min·g ammonia decomposition hydrogen production catalyst, and time of 1-2h.

[0041] In the present invention, it should be noted that the temperature of the cooling treatment may be the reaction temperature of ammonia decomposition.

[0042] In the present invention, the content of the activated atmosphere in the cooling treatment has a wide range of selection. Preferably, in the cooling treatment, the proportion of the activated atmosphere in the activated gas is 2-30% by volume, more preferably 5-15% by volume.

[0043] In a preferred embodiment, n is 3, and the pretreatment method comprises: in the presence of an activation gas, subjecting the ammonia decomposition hydrogen production catalyst to a three-stage programmed temperature increase activation treatment and then a temperature reduction treatment.

[0044] In the present invention, the advantage of selecting three-stage pretreatment activation is that it is beneficial to the activation of active metals, avoids the agglomeration of active components, and improves the reaction activity of the catalyst.

[0045] In the present invention, preferably, the activation gas flow rate in the latter activation treatment is 5-20 mL / min·g lower than that in the former activation treatment, and more preferably 5-15 mL / min·g lower.

[0046] In the present invention, preferably, the heating rate in the first stage of activation treatment is 0.1-5°C / min lower than the heating rate in the second stage of activation treatment, preferably 0.1-3°C / min lower.

[0047] In the present invention, the range of selection of the conditions for the first stage of programmed temperature increase is relatively wide, and preferably the conditions are the same as those described above, and will not be described in detail herein.

[0048] In the present invention, the range of conditions for the second stage of programmed temperature increase is relatively wide. Preferably, the conditions for the second stage of programmed temperature increase include: temperature of 400-550°C, heating rate of 0.4-3°C / min, pressure of normal pressure-1MPa, activation gas flow rate of 10-50mL / min·g ammonia decomposition hydrogen production catalyst, and time of 0.25-5h; further preferably, the conditions for the second stage of programmed temperature increase include: temperature of 400-500°C, heating rate of 2-3°C / min, pressure of normal pressure-0.1MPa, activation gas flow rate of 20-45mL / min·g ammonia decomposition hydrogen production catalyst, and time of 0.5-4h.

[0049] In the present invention, preferably, in the second stage of programmed temperature increase, the proportion of the activation atmosphere in the activation gas is 10-85% by volume, more preferably 40-80% by volume. The advantage of adopting this preferred embodiment is to avoid agglomeration of active components caused by activating the catalyst at high temperature, thereby improving the reaction activity of the catalyst.

[0050] In the present invention, the range of selection of the conditions for the third stage of programmed temperature increase is relatively wide. Preferably, the conditions for the third stage of programmed temperature increase include: temperature of 700-820°C, heating rate of 0.5-5°C / min, pressure of normal pressure-1MPa, activation gas flow rate of 2-35mL / min·g ammonia decomposition hydrogen production catalyst, time of 0.5-3h; further preferably, the conditions for the third stage of programmed temperature increase include: temperature of 700-800°C, heating rate of 2-5°C / min, pressure of normal pressure-0.1MPa, activation gas flow rate of 15-30mL / min·g ammonia decomposition hydrogen production catalyst, time of 1-2h.

[0051] In the present invention, preferably, in the third stage of programmed temperature increase, the proportion of the activation atmosphere in the activation gas is 2.5-20% by volume, and more preferably 5-15% by volume.

[0052] In the present invention, the range of selection of the conditions for the cooling treatment is relatively wide. Preferably, the conditions are the same as those described above and will not be described in detail herein.

[0053] The present invention will be described in detail below by way of examples. In the following examples, unless otherwise specified, all the raw materials used are commercially available.

[0054] Example 1

[0055] 11.6g of pseudo-boehmite (alumina content of 80% by mass) and 1.26g of cerium nitrate hexahydrate were ball-milled to a particle size of less than 300 meshes, and then water was added and mixed evenly. After drying and calcination, an Al2O3 carrier containing CeO2 was obtained. 0.15g of ferric nitrate nonahydrate and 0.39g of ruthenium trichloride trihydrate were loaded by an equal volume impregnation method. After washing, filtering and separation, the catalyst was dried at 120°C for 12h and calcined at 550°C for 2h in an air environment. The mass ratio of alumina, cerium dioxide, iron oxide and ruthenium was 93.2:5:0.3:1.5.

[0056] A catalyst with a particle size of 40-60 mesh is taken and loaded into a fixed bed reactor, and the catalyst is subjected to programmed temperature pretreatment.

[0057] In the first pretreatment stage, the reaction tube was heated to 350°C at a heating rate of 1.5°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 45mL / min·g catalyst, water vapor accounted for 80% and nitrogen accounted for 20%, and it was stabilized for 3h.

[0058] In the second pretreatment stage, the reaction tube was heated to 450°C at a heating rate of 2°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 38mL / min·g catalyst, water vapor accounted for 55% and nitrogen accounted for 45%, and it was stabilized for 3h.

[0059] In the third pretreatment stage, the reaction tube was heated to 750°C at a heating rate of 5°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 26mL / min·g catalyst, water vapor accounted for 10% and argon accounted for 90% of the activation gas, and it was stabilized for 1h.

[0060] In the cooling stage, the reaction tube was cooled to the reaction temperature at a cooling rate of 1.5°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 20mL / min·g catalyst, water vapor accounted for 5% and argon accounted for 95% in the activation gas, and it was stabilized for 1h.

[0061] The activity of the catalyst was evaluated at reaction temperatures of 500° C. and 550° C. using ammonia nitrogen gas with an ammonia volume concentration of 15%. 1.0 g of 40-60 mesh catalyst and 4.0 g of 40-60 mesh quartz sand were mixed and loaded. The volume space velocity was 15000 mL / (g·h). The ammonia decomposition rate was calculated according to the formula: ammonia decomposition conversion rate = (raw material ammonia content - product ammonia content) / raw material ammonia content * 100%. The results of the reaction for 6 h are shown in Table 1.

[0062] Example 2

[0063] The catalyst in Example 1 was selected.

[0064] A catalyst with a particle size of 40-60 mesh is taken and loaded into a fixed bed reactor, and the catalyst is subjected to programmed temperature pretreatment.

[0065] In the first pretreatment stage, the reaction tube was heated to 400°C at a heating rate of 1.5°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 45mL / min·g catalyst, water vapor accounted for 76% and nitrogen accounted for 24% in the activation gas, and it was stabilized for 3h.

[0066] In the second pretreatment stage, the reaction tube was heated to 500°C at a heating rate of 2°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 40mL / min·g catalyst, water vapor accounted for 62% and nitrogen accounted for 38% in the activation gas, and it was stabilized for 3h.

[0067] In the third pretreatment stage, the reaction tube was heated to 800°C at a heating rate of 5°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 30mL / min·g catalyst, water vapor accounted for 5% and argon accounted for 95% in the activation gas, and it was stabilized for 1h.

[0068] In the cooling stage, the reaction tube was cooled to the reaction temperature at a cooling rate of 1.5°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 25mL / min·g catalyst, water vapor accounted for 15% and argon accounted for 85% in the activation gas, and it was stabilized for 1h.

[0069] The activity of the catalyst was evaluated according to the method of Example 1. The results are shown in Table 1.

[0070] Example 3

[0071] The catalyst in Example 1 was selected.

[0072] A catalyst with a particle size of 40-60 mesh is taken and loaded into a fixed bed reactor, and the catalyst is subjected to programmed temperature pretreatment.

[0073] In the first pretreatment stage, the reaction tube was heated to 300°C at a heating rate of 1.5°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 40mL / min·g catalyst, water vapor accounted for 70% and nitrogen accounted for 30%, and it was stabilized for 3h.

[0074] In the second pretreatment stage, the reaction tube was heated to 400°C at a heating rate of 2°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 35mL / min·g catalyst, water vapor accounted for 60% and nitrogen accounted for 40%, and it was stabilized for 3h.

[0075] In the third pretreatment stage, the reaction tube was heated to 700°C at a heating rate of 5°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 30mL / min·g catalyst, water vapor accounted for 10% and argon accounted for 90%, and it was stabilized for 1h.

[0076] In the cooling stage, the reaction tube was cooled to the reaction temperature at a cooling rate of 1.5°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 10mL / min·g catalyst, water vapor accounted for 10% and argon accounted for 90% in the activation gas, and it was stabilized for 1h.

[0077] The activity of the catalyst was evaluated according to the method of Example 1. The results are shown in Table 1.

[0078] Example 4

[0079] The catalyst of Example 1 was selected.

[0080] A catalyst with a particle size of 40-60 mesh is taken and loaded into a fixed bed reactor, and a programmed temperature pretreatment is performed on the catalyst.

[0081] In the first pretreatment stage, the reaction tube was heated to 350°C at a heating rate of 0.5°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 45mL / min·g catalyst, water vapor accounted for 80% and nitrogen accounted for 20%, and it was stabilized for 3h.

[0082] In the second pretreatment stage, the reaction tube was heated to 450°C at a heating rate of 2.5°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 38mL / min·g catalyst, water vapor accounted for 55% and nitrogen accounted for 45%, and it was stabilized for 3h.

[0083] In the third pretreatment stage, the reaction tube was heated to 750°C at a heating rate of 4.0°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 26mL / min·g catalyst, water vapor accounted for 10% and argon accounted for 90% of the activation gas, and it was stabilized for 1h.

[0084] In the cooling stage, the reaction tube was cooled to the reaction temperature at a cooling rate of 1.5°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 20mL / min·g catalyst, water vapor accounted for 5% and argon accounted for 95% in the activation gas, and it was stabilized for 1h.

[0085] The activity of the catalyst was evaluated according to the method of Example 1. The results are shown in Table 1.

[0086] Example 5

[0087] The catalyst of Example 1 was selected.

[0088] A catalyst with a particle size of 40-60 mesh is taken and loaded into a fixed bed reactor, and a programmed temperature pretreatment is performed on the catalyst.

[0089] In the first pretreatment stage, the reaction tube was heated to 350°C at a heating rate of 0.3°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 45mL / min·g catalyst, the activation gas accounted for 80% hydrogen and 20% nitrogen, and it was stabilized for 3h.

[0090] In the second pretreatment stage, the reaction tube was heated to 450°C at a heating rate of 2.6°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 38mL / min·g catalyst, hydrogen accounted for 55% and nitrogen accounted for 45% in the activation gas, and it was stabilized for 3h.

[0091] In the third pretreatment stage, the reaction tube was heated to 750°C at a heating rate of 5.0°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 26mL / min·g catalyst, the activation gas accounted for 10% hydrogen and 90% argon, and it was stabilized for 1h.

[0092] In the cooling stage, the reaction tube was cooled to the reaction temperature at a cooling rate of 1.5°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 20mL / min·g catalyst, hydrogen accounted for 5% and argon accounted for 95% in the activation gas, and it was stabilized for 1h.

[0093] The activity of the catalyst was evaluated according to the method of Example 1. The results are shown in Table 1.

[0094] Example 6

[0095] The catalyst in Example 1 was selected.

[0096] A catalyst with a particle size of 40-60 mesh is taken and loaded into a fixed bed reactor, and a programmed temperature pretreatment is performed on the catalyst.

[0097] In the first pretreatment stage, the reaction tube was heated to 350°C at a heating rate of 0.3°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 45mL / min·g catalyst, the activation gas accounted for 80% hydrogen and 20% nitrogen, and it was stabilized for 3h.

[0098] In the second pretreatment stage, the reaction tube was heated to 450°C at a heating rate of 1.5°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 38mL / min·g catalyst, hydrogen accounted for 55% and nitrogen accounted for 45% in the activation gas, and it was stabilized for 3h.

[0099] In the third pretreatment stage, the reaction tube was heated to 750°C at a heating rate of 1.8°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 26mL / min·g catalyst, hydrogen accounted for 10% and argon accounted for 90% in the activation gas, and it was stabilized for 1h.

[0100] In the cooling stage, the reaction tube was cooled to the reaction temperature at a cooling rate of 1.5°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 20mL / min·g catalyst, hydrogen accounted for 5% and argon accounted for 95% in the activation gas, and it was stabilized for 1h.

[0101] The activity of the catalyst was evaluated according to the method of Example 1. The results are shown in Table 1.

[0102] Example 7

[0103] The catalyst in Example 1 was selected.

[0104] A catalyst with a particle size of 40-60 mesh is taken and loaded into a fixed bed reactor, and a programmed temperature pretreatment is performed on the catalyst.

[0105] In the first pretreatment stage, the reaction tube was heated to 350°C at a heating rate of 1.5°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 45mL / min·g catalyst, water vapor accounted for 80% and nitrogen accounted for 20%, and it was stabilized for 0.5h.

[0106] In the second pretreatment stage, the reaction tube was heated to 450°C at a heating rate of 2°C / min, the reaction pressure was 0.1 MPa, the activation gas flow rate was 38 mL / min·g catalyst, water vapor accounted for 17% and nitrogen accounted for 83% in the activation gas, and it was stabilized for 0.5 h.

[0107] In the third pretreatment stage, the reaction tube was heated to 750°C at a heating rate of 5°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 26mL / min·g catalyst, water vapor accounted for 15% and argon accounted for 85% of the activation gas, and it was stabilized for 2h.

[0108] In the cooling stage, the reaction tube was cooled to the reaction temperature at a cooling rate of 1.5°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 20mL / min·g catalyst, water vapor accounted for 3% and argon accounted for 97% in the activation gas, and it was stabilized for 2h.

[0109] The activity of the catalyst was evaluated according to the method of Example 1. The results are shown in Table 1.

[0110] Example 8

[0111] The catalyst of Example 1 was selected.

[0112] A catalyst with a particle size of 40-60 mesh is taken and loaded into a fixed bed reactor, and a programmed temperature pretreatment is performed on the catalyst.

[0113] In the first pretreatment stage, the reaction tube was heated to 350°C at a heating rate of 1.5°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 45mL / min·g catalyst, water vapor accounted for 80% and nitrogen accounted for 20%, and it was stabilized for 4h.

[0114] In the second pretreatment stage, the reaction tube was heated to 400°C at a heating rate of 2°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 38mL / min·g catalyst, water vapor accounted for 55% and nitrogen accounted for 45% in the activation gas, and it was stabilized for 4h.

[0115] In the third pretreatment stage, the reaction tube was heated to 760°C at a heating rate of 5°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 26mL / min·g catalyst, water vapor accounted for 10% and argon accounted for 90% of the activation gas, and it was stabilized for 1.5h.

[0116] In the cooling stage, the reaction tube was cooled to the reaction temperature at a cooling rate of 1.5°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 20mL / min·g catalyst, water vapor accounted for 5% and argon accounted for 95% in the activation gas, and it was stabilized for 1.5h.

[0117] The activity of the catalyst was evaluated according to the method of Example 1. The results are shown in Table 1.

[0118] Example 9

[0119] The catalyst of Example 1 was selected.

[0120] A catalyst with a particle size of 40-60 mesh is taken and loaded into a fixed bed reactor, and a programmed temperature pretreatment is performed on the catalyst.

[0121] In the first pretreatment stage, the reaction tube was heated to 350°C at a heating rate of 1.5°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 45mL / min·g catalyst, water vapor accounted for 80% and nitrogen accounted for 20%, and it was stabilized for 0.5h.

[0122] In the second pretreatment stage, the reaction tube was heated to 450°C at a heating rate of 2°C / min, the reaction pressure was 0.1 MPa, the activation gas flow rate was 38 mL / min·g catalyst, water vapor accounted for 55% and nitrogen accounted for 45% in the activation gas, and it was stabilized for 0.5 h.

[0123] In the third pretreatment stage, the reaction tube was heated to 750°C at a heating rate of 5°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 26mL / min·g catalyst, water vapor accounted for 10% and argon accounted for 90% of the activation gas, and it was stabilized for 2h.

[0124] In the cooling stage, the reaction tube was cooled to the reaction temperature at a cooling rate of 1.5°C / min, the reaction pressure was 0.1MPa, the activation gas flow rate was 20mL / min·g catalyst, water vapor accounted for 5% and argon accounted for 95% in the activation gas, and it was stabilized for 2h.

[0125] The activity of the catalyst was evaluated according to the method of Example 1. The results are shown in Table 1.

[0126] Example 10

[0127] The method of Example 1 is followed, except that the water vapor is replaced by hydrogen.

[0128] The activity of the catalyst was evaluated according to the method of Example 1. The results are shown in Table 1.

[0129] Comparative Example 1

[0130] The catalyst of Example 1 was selected.

[0131] Take a catalyst with a particle size of 40-60 mesh and load it into a fixed bed reactor to pretreat the catalyst. Heat the reaction tube to 700°C at a heating rate of 1.5°C / min, the reaction pressure is 0.1MPa, the activation gas flow rate is 50mL / min·g catalyst, the activation gas accounts for 15% hydrogen and 85% nitrogen, and stabilize for 3h.

[0132] The temperature was lowered to the reaction temperature according to the method of Example 1 to evaluate the activity of the catalyst. The results are shown in Table 1.

[0133] Comparative Example 2

[0134] The catalyst of Example 1 was selected.

[0135] Take a catalyst with a particle size of 40-60 mesh, load it into a fixed bed reactor, and perform a programmed temperature pretreatment on the catalyst. The reaction tube is heated to 600°C at a heating rate of 1.5°C / min, the reaction pressure is 0.1MPa, the activation gas flow rate is 100mL / min·g catalyst, the activation gas accounts for 20% hydrogen and 80% nitrogen, and stabilize for 3h.

[0136] The temperature was lowered to the reaction temperature according to the method of Example 1 to evaluate the activity of the catalyst. The results are shown in Table 1.

[0137] Table 1

[0138]

[0139]

[0140] It can be seen from the above table that the pretreated ammonia decomposition hydrogen production catalyst prepared by the pretreatment method provided by the present invention can be suitable for high-temperature reactions, thereby improving the stability of the catalyst.

[0141] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for pretreating a catalyst for hydrogen production by decomposition of ammonia, characterized in that: The pretreatment method comprises the following steps: In the presence of an activation gas, the catalyst for hydrogen production by decomposing ammonia is first subjected to a programmed temperature increase activation treatment for n stages, and then subjected to a temperature reduction treatment, wherein n is 2-5 and n is an integer; The activation gas includes an activation atmosphere and a carrier gas, and the activation atmosphere includes hydrogen and / or water vapor; In the n-stage programmed temperature activation treatment, the proportion of the activation atmosphere in the activation gas decreases successively; The proportion of the activated atmosphere in the activated gas used in the first stage of the activation treatment is 2-65% higher than the proportion of the activated atmosphere in the activated gas used in the second stage of the activation treatment; The temperature in the first stage of activation treatment is 25-400°C lower than the temperature in the second stage of activation treatment.

2. The method according to claim 1, wherein: n is 2-3, n is an integer; Preferably, the activation atmosphere is water vapor; Preferably, the proportion of the activated atmosphere in the activated gas used in the first stage of the activation treatment is 10-60% higher than the proportion of the activated atmosphere in the activated gas used in the second stage of the activation treatment; Preferably, the temperature in the first stage of activation treatment is 75-300° C. lower than the temperature in the second stage of activation treatment.

3. The method according to claim 1 or 2, wherein: The activation gas flow rate in the latter stage of activation treatment is 5-20 mL / min·g lower than that in the former stage of activation treatment, and preferably 5-15 mL / min·g lower.

4. The method according to any one of claims 1 to 3, wherein: The heating rate in the first stage of activation treatment is 0.1-5°C / min lower than that in the second stage of activation treatment, preferably 0.1-3°C / min lower.

5. The method according to any one of claims 1 to 4, wherein: The ammonia decomposition hydrogen production catalyst comprises an alumina carrier, a metal active component and an additive, wherein the metal active component comprises Ru and a non-precious metal component, wherein the non-precious metal component is selected from at least one of Mn, Fe, Co, Ni and Cu, and the additive is selected from at least one of CeO2, MgO, CuO, CaO and La2O3; Preferably, based on the weight of the ammonia decomposition hydrogen production catalyst, the content of Ru is 0.1-2.5% by weight, the content of the non-precious metal component calculated as oxide is 0.1-10% by weight, the content of the auxiliary agent is 2-8% by weight, and the content of the alumina carrier is 69.5-97.8% by weight.

6. The method according to any one of claims 1 to 5, wherein: The carrier gas is selected from at least one of the inert gases; Preferably, the inert gas is selected from at least one of nitrogen, argon, helium and neon.

7. The method according to any one of claims 1 to 6, wherein: The conditions of the first stage of programmed temperature increase include: temperature of 300-420°C, heating rate of 0.3-3°C / min, pressure of normal pressure-1MPa, activation gas flow rate of 10-50mL / min·g ammonia decomposition hydrogen production catalyst, and time of 0.25-5h; Preferably, the conditions of the first stage of programmed temperature increase include: temperature of 300-400°C, heating rate of 1.5-3°C / min, pressure of normal pressure-0.1MPa, activation gas flow rate of 15-45mL / min·g ammonia decomposition hydrogen production catalyst, and time of 0.5-4h; Preferably, in the first stage of programmed temperature increase, the proportion of the activation atmosphere in the activation gas is 10-85% by volume, more preferably 50-80% by volume.

8. The method according to any one of claims 1 to 7, wherein: The cooling treatment conditions include: temperature of 500-700°C, cooling rate of 0.1-2°C / min, pressure of normal pressure-1MPa, activation gas flow rate of 5-30mL / min·g ammonia decomposition hydrogen production catalyst, and time of 1-2h; Preferably, in the temperature reduction treatment, the proportion of the activation atmosphere in the activation gas is 2-30% by volume, more preferably 5-15% by volume.

9. The method according to any one of claims 1 to 8, wherein: n is 3, and the pretreatment method comprises: in the presence of an activation gas, first subjecting the ammonia decomposition hydrogen production catalyst to a three-stage programmed temperature increase activation treatment, and then subjecting it to a temperature reduction treatment.

10. The method according to claim 9, wherein: The conditions of the second stage of programmed temperature increase include: temperature of 400-550°C, heating rate of 0.4-3°C / min, pressure of normal pressure-1MPa, activation gas flow rate of 10-50mL / min·g ammonia decomposition hydrogen production catalyst, and time of 0.25-5h; Preferably, the conditions of the second stage of programmed temperature increase include: temperature of 400-500°C, heating rate of 2-3°C / min, pressure of normal pressure-0.1MPa, activation gas flow rate of 20-45mL / min·g ammonia decomposition hydrogen production catalyst, and time of 0.5-4h; Preferably, in the second stage of programmed temperature increase, the proportion of the activation atmosphere in the activation gas is 10-85% by volume, and more preferably 40-80% by volume.

11. The method according to claim 10, wherein: The conditions of the third stage of programmed temperature increase include: temperature of 700-820°C, heating rate of 0.5-5°C / min, pressure of normal pressure-1MPa, activation gas flow rate of 2-35mL / min·g ammonia decomposition hydrogen production catalyst, and time of 0.5-3h; Preferably, the conditions for the third stage of programmed temperature increase include: temperature of 700-800°C, heating rate of 2-5°C / min, pressure of normal pressure-0.1MPa, activation gas flow rate of 15-30mL / min·g ammonia decomposition hydrogen production catalyst, and time of 1-2h; Preferably, in the third stage of programmed temperature increase, the proportion of the activation atmosphere in the activation gas is 2.5-20% by volume, more preferably 5-15% by volume.

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