Online regeneration method of copper-based methanol reforming hydrogen production catalyst

Abstract

The invention discloses an on-line regeneration method of a copper-based methanol reforming hydrogen production catalyst, which belongs to the technical field of catalyst regeneration, and is characterized by comprising the following steps: directly adding a certain proportion of oxygen-containing gas into feed gas of a reactor in a methanol reforming hydrogen production reaction process under the conditions of not changing the operation temperature and not stopping raw material supply; oxygen-containing gas is mixed with methanol and water vapor and then enters a catalyst bed layer, and after online treatment is carried out for a period of time, supply of oxygen is stopped, so that online regeneration of catalyst activity can be completed; according to the method, the regeneration can be completed by directly introducing oxygen in the reaction process without shutdown, cooling or reaction atmosphere switching, so that the operation process is greatly simplified, and the production efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of catalytic chemical engineering, and in particular to a method for regenerating catalysts, and more specifically, to an online regeneration method for copper-based catalysts used in low-temperature (150-200°C) methanol steam reforming (MSR) hydrogen production that have become deactivated due to surface oxidation poisoning. Background Technology

[0002] Methanol, as an ideal hydrogen carrier, can produce high-purity hydrogen under relatively mild conditions (200-350℃) through methanol steam reforming (MSR, CH3OH + H2O → CO2 + 3H2). This technology has broad application prospects in areas such as providing hydrogen sources for proton exchange membrane fuel cells.

[0003] In MSR reactions, copper-based catalysts, especially the commercially available Cu / ZnO / Al2O3 catalysts, are favored due to their low cost, high activity, and low CO selectivity. However, in practical applications, especially under the low-temperature conditions (e.g., 150-200°C) desired in fuel cells, these catalysts suffer from insufficient stability and susceptibility to deactivation.

[0004] Regarding the deactivation mechanism of copper-based catalysts in the MSR process, the following are generally considered to be: (1) thermal sintering, that is, at a higher temperature (>300℃), copper nanoparticles agglomerate, resulting in a reduction in the active surface area; (2) carbon deposition, that is, carbon species generated during the reaction cover the active sites of the catalyst; (3) strong metal-support interaction (SMSI), under a reducing atmosphere, support components (such as ZnO) may migrate and encapsulate copper particles.

[0005] To address the aforementioned deactivation mechanisms, existing regeneration methods typically include: for sintered catalysts, employing an oxidation-reduction cycle to redisperse copper particles; and for catalysts deactivated by carbon deposition, high-temperature calcination in an oxygen-containing atmosphere to remove the carbon deposits. However, research indicates that under low-temperature, high-space-velocity MSR conditions, catalyst deactivation is not primarily driven by sintering or carbon deposition. Instead, a more subtle deactivation mechanism—surface oxidation of copper active sites, particularly the covering by hydroxyl groups and other substances generated by water in the reaction system—is the main cause of decreased activity. For this type of "oxidation poisoning" deactivation, traditional regeneration methods, such as simple inert gas purging, post-shutdown oxidation treatment, or re-reduction treatment, are ineffective and may even cause secondary damage to the catalyst due to the intense oxidation-reduction process, such as irreversible sintering.

[0006] Therefore, developing a regeneration method that can effectively address low-temperature oxidation poisoning, is simple to operate, operates under mild conditions, and can be carried out online is of great significance for enhancing the industrial application value of copper-based MSR catalysts. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a simple, efficient, and mild online regeneration method for restoring the activity of copper-based methanol reforming hydrogen production catalysts that have been deactivated due to surface oxidation poisoning.

[0008] To achieve the above objectives, the present invention provides the following technical solution: An online regeneration method for a copper-based methanol reforming hydrogen production catalyst is characterized by the following: during the methanol reforming hydrogen production reaction, without changing the operating temperature or stopping the feed gas supply, a certain proportion of oxygen-containing gas is directly added to the feed gas of the reactor. The oxygen-containing gas is mixed with methanol and water vapor and then enters the catalyst bed. After online treatment for a period of time, the oxygen supply is stopped, thereby completing the online regeneration of the catalyst activity.

[0009] Further settings include: The catalyst used for methanol reforming to produce hydrogen is a Cu / ZnO / Al2O3 catalyst.

[0010] The methanol reforming to hydrogen production reaction is carried out at an operating temperature of 150-250℃ and a weight hourly space velocity (WHSV) > 50 h⁻¹. -1 It is carried out under the following conditions.

[0011] The volume concentration of oxygen-containing gas in the total feed gas is controlled between 0.5% and 5%. Particularly preferably, the volume concentration of oxygen-containing gas in the total feed gas is controlled between 1% and 1.5%.

[0012] The online treatment time for introducing oxygen-containing gas is 1 to 8 hours. Particularly preferred is that the online treatment time for introducing oxygen-containing gas is 2 to 3 hours.

[0013] The mechanism of action of this invention is as follows: When the catalyst is deactivated due to its surface being covered by stable species such as hydroxyl groups, the introduced trace amounts of oxygen can deactivate the deactivated copper surface (Cu). 0 / Cu + ) oxidized to a higher valence state (Cu) 2+ This surface reconstruction process disrupts the adsorption balance of the original poisoning substances, causing them to desorb from the catalyst surface. When the oxygen supply is stopped, the reducing atmosphere such as methanol in the reaction system will rapidly reduce the oxidized copper surface back to active Cu. 0 / Cu +This process cleans and regenerates the active sites, thus achieving the desired state. Since the entire process involves only the surface of the catalyst and is conducted at the reaction temperature, drastic bulk phase changes and high-temperature treatments are avoided, preventing the sintering of copper particles.

[0014] Compared with the prior art, the present invention has the following beneficial effects: (1) Online regeneration, easy to operate: No need to stop production, cool down or change the reaction atmosphere, oxygen can be introduced directly during the reaction process to complete the regeneration, which greatly simplifies the operation process and improves production efficiency.

[0015] (2) Mild conditions and avoidance of damage: The regeneration process is carried out at low temperature of the MSR reaction, which avoids the irreversible sintering of the catalyst that may be caused by traditional high temperature regeneration methods, and effectively protects the structural stability of the catalyst.

[0016] (3) Highly targeted and effective: This method is specifically designed for the specific inactivation mechanism of low-temperature oxidation poisoning. It can effectively remove surface species that cause inactivation and has a significant effect on activity recovery, which is superior to traditional methods such as re-reduction.

[0017] (4) Economical and efficient: By extending the service life of the catalyst, the frequency of catalyst replacement is reduced, the operating cost is lowered, and it has good economic benefits and industrial application prospects. Attached Figure Description

[0018] Figure 1 This is a graph showing the change in activity of the catalyst in Example 1 over time during the methanol reforming reaction (deactivation and regeneration process).

[0019] Figure 2 The effect of different oxygen concentrations (0.5%) on catalyst regeneration efficiency.

[0020] Figure 3 The effect of different oxygen concentrations (5% oxygen concentration) on catalyst regeneration efficiency.

[0021] Figure 4 The effect of different oxygenation treatment times (1 hour) on catalyst regeneration efficiency.

[0022] Figure 5 The effect of different oxygenation treatment times (8 hours) on catalyst regeneration efficiency.

[0023] Figure 6 The effect of using traditional regeneration methods (reduction) on catalyst regeneration efficiency is investigated.

[0024] Figure 7 The effect of using traditional regeneration methods (offline oxidation) on catalyst regeneration efficiency is investigated. Detailed Implementation

[0025] The present invention will now be described in detail with reference to specific embodiments, but the present invention is not limited to these examples. Unless otherwise specified, the raw materials and reagents used in the embodiments are existing technologies or commercially available products.

[0026] Example 1: Catalyst deactivation and online regeneration (1) Catalyst evaluation and deactivation A commercially available Cu / ZnO / Al2O3 catalyst was packed into a fixed-bed reactor. Activation was performed at 300°C in an H2 / N2 atmosphere (H2 volume ratio 10%) for 1 hour. Subsequently, the temperature was lowered to 200°C, and a mixture of methanol and water vapor (molar ratio H2O / CH3OH = 1.3) was used as the reactant gas, with the methanol weight hourly space velocity (WHSV) controlled at 124.92 h⁻¹. -1 The reaction proceeded for 2 hours, and the exhaust gas components were monitored online to calculate the hydrogen yield. The results showed that the hydrogen yield decreased by approximately 40% within 2 hours, indicating severe catalyst deactivation.

[0027] (2) Online regeneration After the above reaction has been carried out for 2 hours, the catalyst activity has decreased significantly. The reaction temperature and raw material supply are kept constant at 200℃. Oxygen is introduced into the feed gas at a rate of 1.5% (volume concentration) of the total feed gas, and the oxygen supply is continued for 2 hours.

[0028] (3) Activity evaluation after regeneration After 2 hours of treatment, oxygen supply was stopped, and the treatment continued under the original conditions (200℃, WHSV=124.92 h). -1 The MSR reaction was carried out. The results showed that the hydrogen yield recovered rapidly, and its initial yield was basically the same as that of the first stage reaction, indicating that the catalyst activity was effectively restored. The regenerated catalyst exhibited a similar deactivation trend as the fresh catalyst. The activity change curves for the entire process are shown below. Figure 1 As shown. Example

[0029] This embodiment mainly examines the effect of oxygen concentration on catalyst regeneration efficiency.

[0030] The catalyst regeneration method and activity evaluation are the same as in Example 1, except that: the amount of oxygen introduced is adjusted to account for 0.5% and 5% of the total feed gas volume concentration, and its effect on the catalyst regeneration effect is tested. Figure 2 , Figure 3 As shown.

[0031] Analysis: For example Figure 2 , Figure 3As shown, when the volume concentration of oxygen introduced is 0.5% and 5%, the catalyst activity can be restored to some extent, but the initial yield is much lower than the initial yield of the first stage reaction. This indicates that the amount of oxygen introduced, as a volume concentration of 1%-1.5% of the total feed gas, is preferably optimal. Too low an oxygen concentration is insufficient to effectively remove surface poisoning substances, while too high an oxygen concentration may cause a complete oxidation side reaction of methanol and may lead to deep oxidation and sintering of the catalyst bulk phase. Example

[0032] This embodiment mainly examines the effect of oxygenation time on catalyst regeneration efficiency.

[0033] The catalyst regeneration method and activity evaluation were the same as in Example 1, except that the oxygenation time was adjusted to 1 hour and 8 hours, and its effect on catalyst regeneration was tested. Figure 4 , Figure 5 As shown.

[0034] Analysis: For example Figure 4 and Figure 5 As shown: the online treatment time for introducing oxygen-containing gas depends on the degree of catalyst deactivation. If the oxygenation time is too short, the catalyst can be partially regenerated, but the initial yield will be lower than the initial yield of the first stage reaction. An oxygenation time of 2 hours is sufficient to achieve good catalyst regeneration. An oxygenation time of 8 hours maintains the same regeneration effect as 2 hours. Therefore, 2-3 hours is optimal.

[0035] Comparative Example 1 This embodiment mainly uses the traditional regeneration method (reduction) to regenerate the catalyst, as a control with Example 1. The MSR reaction conditions and activity evaluation are the same as steps (1) and (3) of Example 1, except that the regeneration method in step (2) is the following traditional regeneration method (reduction): The MSR reaction is stopped, and after purging in argon, it is treated with H2 / N2 (H2 volume ratio 10%) at 300°C for 2 hours. The catalyst treated as above is then regenerated under MSR conditions (200°C, WHSV=124.92 h). -1 Activity evaluation was performed, and the results are as follows: Figure 6 As shown.

[0036] analyze: Reference Figure 6 As shown, the conventional regeneration method (re-reduction) used in Comparative Example 1 failed to effectively restore the activity of the catalyst compared with the online regeneration method in Example 1 of the present invention.

[0037] Comparative Example 2 This embodiment mainly uses a traditional regeneration method (offline oxidation) to regenerate the catalyst, as a control with Example 1. The MSR reaction conditions and activity evaluation are the same as steps (1) and (3) of Example 1, except that the regeneration method in step (2) is the following traditional regeneration method (offline oxidation): The MSR reaction is stopped, and after purging in argon, it is treated with O2 / N2 (O2 volume ratio 10%) at 200°C for 2 hours. The catalyst treated as above is then regenerated under MSR conditions (200°C, WHSV=124.92 h). -1 Activity evaluation was performed, and the results are as follows: Figure 7 As shown.

[0038] analyze: Reference Figure 7 As shown, the conventional regeneration method (offline oxidation) used in Comparative Example 2 failed to effectively restore the activity of the catalyst compared with the online regeneration method in Example 1 of the present invention.

[0039] Summarize: Compared with the 300°C high-temperature offline reduction method used in Comparative Example 1 and the offline oxidation method used in Comparative Example 2, the online regeneration method of Example 1 of this invention has significant advantages in terms of process cost and efficiency. Traditional offline methods require stopping the feed, purging with inert gas, and are accompanied by significant energy consumption for heating and cooling (e.g., Comparative Example 1 requires heating to 300°C) and several hours of non-productive downtime. Experimental data shows that none of these methods effectively restore catalyst activity. In contrast, this invention achieves isothermal (200°C) online regeneration with zero downtime and zero additional energy consumption. It only requires introducing 1.5% oxygen into the feed gas for about 2 hours to rapidly restore the hydrogen yield to a level basically consistent with the initial stage. This greatly simplifies the operation process, avoids catalyst thermal damage, significantly reduces operating costs, and improves industrial production efficiency.

[0040] The above embodiments demonstrate that the online oxygen regeneration method proposed in this invention can accurately and efficiently solve the problem of oxidation poisoning and deactivation of copper-based catalysts in low-temperature methanol reforming reactions, exhibiting significant technical advantages and practical value. Those skilled in the art should understand that the scope of this invention is not limited to the specific embodiments described above. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this invention shall still fall within the protection scope of this invention.

Claims

1. A method for on-line regeneration of a copper-based catalyst for hydrogen production by methanol reforming, characterized in that: In the hydrogen production reaction of methanol reforming, without changing the operation temperature and stopping the supply of raw material, a certain proportion of oxygen-containing gas is directly added to the feed gas of the reaction, the oxygen-containing gas is mixed with methanol and water vapor and then enters the catalyst bed, after on-line treatment for a period of time, the supply of oxygen is stopped, and the on-line regeneration of catalyst activity is completed.

2. The method according to claim 1, wherein the method is characterized by: The catalyst for hydrogen production by methanol reforming is a Cu / ZnO / Al2O3 catalyst.

3. The method according to claim 1, wherein the method is characterized by: The methanol reforming reaction for hydrogen production is carried out under the conditions of an operating temperature of 150-250°C, a weight hourly space velocity WHSV > 50 h -1 -1.

4. The method according to claim 1, wherein the method is characterized by: The volume concentration of the oxygen-containing gas in the total feed gas is controlled between 0.5% and 5%.

5. The method according to claim 4, wherein the method is characterized by: The volume concentration of the oxygen-containing gas in the total feed gas is controlled between 1% and 1.5%.

6. The method according to claim 1, wherein the method is characterized by: The on-line treatment time of the oxygen-containing gas is 1 to 8 hours.

7. The method according to claim 6, wherein the method is characterized by: The on-line treatment time of the oxygen-containing gas is 2 to 3 hours.

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