Method for reducing formation of carbon deposition in integration of CO2 capture and methane dry reforming
By controlling the reaction time and gas concentration of Ni/CaO-Al2O3 materials, the problem of carbon deposition was solved, the cycle stability and service life of the materials were improved, and the cost of industrial applications was reduced.
Patent Information
- Application Number
- CN202511048673.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-29
- Publication Date
- 2025-10-17
AI Technical Summary
The existing Ni/CaO-Al2O3 bifunctional material is prone to carbon deposition during the integrated process of CO2 capture and methane dry reforming, resulting in poor material sintering and cycle stability, affecting process efficiency.
By controlling the reaction time of Ni/CaO-Al2O3 material in the CO2 adsorption and CH4 conversion stages, and combining appropriate CO2 partial pressure and CH4 concentration, the reaction time of the conversion stage can be shortened to 5-10 minutes, thus inhibiting the formation of carbon deposits.
It effectively reduces carbon buildup, improves the cycle stability and service life of materials, reduces the cost of industrial applications, and avoids non-selective cracking of methane caused by insufficient CaCO3 decomposition.
Smart Images
Figure CN120789879A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application discloses a method for reducing carbon deposition of Ni / CaO-Al2O3 material in a CO2 capture-methane dry reforming integrated process. Specifically, by adjusting the reaction time of the conversion stage in the cycle process and maintaining a suitable CO2 partial pressure to promote the methane dry reforming reaction, the complete cracking of CH4 is reduced. BACKGROUND
[0002] With the rapid development of industry, the emission of CO2 in the atmosphere has increased dramatically, exacerbating global climate change. Therefore, it is urgent to develop effective strategies to reduce carbon dioxide emissions, especially in the industrial field, which accounts for more than 90% of direct and indirect greenhouse gas emissions in industrial processes. Considering the huge demand for decarbonization of global carbon fixation sources, it is of great value to explore the path of converting CO2 and readily available hydrocarbons into high-value products.
[0003] Under the dual demands of global carbon emission reduction and energy sustainable development, the CO2 capture-methane dry reforming integration (ICCU-DRM) technology captures low-concentration CO2 and in-situ dry reforming reaction (DRM) with methane, simultaneously achieving carbon dioxide emission reduction and efficient synthesis gas preparation, while reducing energy consumption and operating costs and promoting carbon resource recycling.
[0004] Ni-CaO-based dual functional materials (DFMs) as the core component of the ICCU-DRM system have attracted much attention due to their low cost, high CO2 adsorption capacity, and good catalytic activity. However, in the methane dry reforming (DRM) conversion stage of ICCU-DRM, methane cracking is prone to form carbon deposition on the surface of DFMs, which in turn induces material sintering, affecting the long-term cycle stability of DFMs. It is worth noting that the Ni / CaO-Al2O3 dual functional material developed by researchers has shown high CO2 capture capacity and good cycle stability in other ICCU reaction systems, such as ICCU-methanation and ICCU-reverse water gas shift. Therefore, developing a method specifically targeting the characteristics of the ICCU-DRM process that can effectively reduce carbon deposition of Ni / CaO-Al2O3 material in the methane dry reforming conversion stage is crucial for improving the overall performance and cycle stability of the technology. SUMMARY
[0005] The present application aims to solve the problems of insufficient carbon deposition resistance, poor cycle stability, and low process efficiency of dual functional materials in existing CO2 capture-methane dry reforming integration technology, and provides a method for reducing carbon deposition formation using Ni / CaO-Al2O3 dual functional materials in integrated CO2 capture and methane dry reforming.
[0006] The present application is realized by the following technical solutions:
[0007] A method for reducing carbon deposition in integrated CO2 capture and dry methane reforming, characterized in that the method comprises the following steps:
[0008] (1) CO2 adsorption stage: passing a mixed gas containing CO2 through a bed of Ni / CaO-Al2O3 material at an adsorption temperature of 600-700℃, wherein CaO adsorbs CO2 to form CaCO3;
[0009] (2) CH4 conversion stage: switching the material after adsorption in step (1) to a mixed gas containing CH4 for dry methane reforming reaction at a regeneration temperature of 600-700℃, controlling the reaction time of the conversion stage to be 5-10 minutes, so that CaCO3 decomposition and dry methane reforming reaction reach dynamic equilibrium, and carbon deposition is inhibited;
[0010] In the Ni / CaO-Al2O3 material, the loading of Ni is 8-12%, and the mass ratio of CaO to Al2O3 is 2:1 to 10:1.
[0011] Preferably, in the CO2 adsorption stage, the adsorption temperature is 650℃, the CO2 concentration is 10-20%, the balance gas is N2, the total gas flow is 50-200 ml / min, and the adsorption time is 10-20 minutes.
[0012] Preferably, in the CH4 conversion stage, the reaction temperature is 650℃, the CH4 concentration is 1-5%, the balance gas is N2, the total gas flow is 50-200 ml / min, and the reaction time is preferably 5-7 minutes.
[0013] Preferably, the mass ratio of CaO to Al2O3 is 6:1 to 8:1.
[0014] Compared with the prior art, the beneficial effects of the present application are reflected in:
[0015] This study is the first to reduce carbon deposition from the perspective of conversion stage reaction time. By real-time monitoring of the gas composition (CO2, CH4, CO and H2) at the outlet of the fixed bed, the dynamic changes in the content of each gas during the reaction process were analyzed. The results showed that the decrease in CO2 content was the main cause of the non-selective cracking of methane. Therefore, by shortening the reaction time, the insufficient supply of CO2 generated by the decomposition of CaCO3 can be effectively avoided, thereby reducing the non-selective cracking of methane. After using this method, the amount of carbon deposition significantly decreases with the shortening of the reaction time. Under the premise of ensuring the performance of DFMs, the problems of DFM deactivation and reaction pipeline blockage caused by carbon deposition are effectively solved, the cycle stability of DFMs is improved, the service life is prolonged, and the cost of industrial application is reduced. BRIEF DESCRIPTION OF DRAWINGS
[0016] Figure 1 Schematic diagram of the device for integrating CO2 capture and dry reforming of methane according to the present application;
[0017] Wherein, 1-methane; 2-carbon dioxide; 3-hydrogen; 4-nitrogen; 5-reducing valve; 6-ball valve; 7-mass flow meter; 8-check valve; 9-reactor; 10- condenser; 11-dryer; 12-gas analyzer.
[0018] Figure 2 Figure 2 is a comparison chart of the cyclic performance of Ni / CaAl-8 in Example 2 of the present application at reaction times of 5, 7 and 10 minutes, including CO2 capture capacity, CH4 conversion rate, CO2 conversion rate and carbon deposition amount.
[0019] Figure 3 Figure 3 is a comparison chart of the cyclic performance of Ni / CaAl-4 in Example 3 of the present application at reaction times of 5, 7 and 10 minutes, including CO2 capture capacity, CH4 conversion rate, CO2 conversion rate and carbon deposition amount.
[0020] Figure 4 Figure 4 is a comparison chart of the cyclic performance of Ni / CaAl-2 in Example 4 of the present application at reaction times of 5, 7 and 10 minutes, including CO2 capture capacity, CH4 conversion rate, CO2 conversion rate and carbon deposition amount.
[0021] Figure 5 Figure 5 is a comparison chart of the cyclic performance of Ni / CaO in Comparative Example 1 of the present application at reaction times of 5, 7 and 10 minutes, including CO2 capture capacity, CH4 conversion rate, CO2 conversion rate and carbon deposition amount.
[0022] Figure 6 Figure 6 is a comparison chart of the cyclic performance of Ni / CaO and Ni / CaAl-x (x = 2, 4, 6) in Comparative Example 2 of the present application at a reaction time of 3 minutes, including CO2 capture capacity, CH4 conversion rate, CO2 conversion rate and carbon deposition amount. DETAILED DESCRIPTION
[0023] The specific embodiments of the present application are described below, but the present application is not limited thereto.
[0024] Example 1:
[0025] A certain amount of calcium nitrate, aluminum nitrate and nickel nitrate were dissolved in water, and anhydrous sodium citrate was added as a gelling agent. Ni / CaO-Al2O3 DFMs were synthesized by a citric acid-assisted sol-gel method. A certain amount of calcium nitrate, aluminum nitrate and nickel nitrate were dissolved in deionized water, and then anhydrous citric acid was added. The molar ratio of calcium nitrate to aluminum nitrate to nickel nitrate was 6.28-9.42:0-3.45:1. The molar ratio of total metal ions to anhydrous citric acid to deionized water was set to 1:1.2:60. The solution was stirred vigorously in a water bath at 80°C for 6 hours. The obtained gel was dried in an oven at 120°C overnight, and then calcined in a muffle furnace at 800°C in air for 2 hours at a heating rate of 5°C / min. The prepared DFMs are represented as Ni / CaAl-x (x=2, 4, 8), where x represents the mass ratio of CaO / Al2O3. For comparison, a Ni / CaO sample without Al2O3 was prepared using the same method. The loading of Ni in all bifunctional materials was uniform at 10 wt%. The sol was formed by stirring in a water bath at 80°C for 6 hours; then, it was placed in a 120°C oven to dry for 12 hours to obtain a dry gel; the dry gel was calcined at 800°C in an air atmosphere for 2 hours to obtain Ni / CaO and Ni / CaAl-x materials. Wherein x represents the mass ratio of CaO to Al2O3, and the loading of Ni is uniform at 10 wt%.
[0026] Example 2:
[0027] The reaction device is as shown in Figure 1 The Ni / CaAl-8 prepared in Example 1 was filled into a fixed bed reactor, and the bifunctional material was reduced by passing 10% H2 / N2 at 750°C for 2 hours, and then cooled to 650°C to start the long-cycle experiment, as follows:
[0028] Adsorption stage: at an adsorption temperature of 650°C, 15% CO2 / N2 gas was passed through the bed of Ni / CaAl-8 material at a flow rate of 100 ml / min for 15 minutes;
[0029] Conversion stage: the temperature was kept at 650°C, and the atmosphere was switched to 3% CH4 / N2, and the reaction time was controlled at 5 minutes, 7 minutes and 10 minutes, respectively, wherein pure N2 (100 ml / min) was passed for 3 minutes before each switch to purge, and each cycle was repeated 20 times.
[0030] Results:
[0031] As shown in the accompanying Figure 2As shown in the figure, the carbon deposition amount is defined as 1 / 2 of the CO generation amount in the adsorption stage by the reverse Boudouard reaction. It is measured that when the reaction time in the conversion stage is 10 minutes, the carbon deposition amount of Ni / CaAl-8 after 20 cycles is 1.76 mmol / g; when the reaction time is changed to 7 minutes, the carbon deposition amount after 20 cycles is 0.89 mmol / g; when the reaction time is changed to 5 minutes, the carbon deposition amount after 20 cycles is 0.08 mmol / g; the carbon deposition amount decreases significantly with the shortening of the reaction time.
[0032] Example 3:
[0033] Reaction apparatus such as Figure 1 As shown, the Ni / CaAl-4 prepared in Example 1 was filled into a fixed bed reactor, and the dual-functional material was reduced by introducing 10% H2 / N2 at 750°C for 2 hours, and then cooled to 650°C to start a long-term cycle experiment, as follows:
[0034] Adsorption stage: At an adsorption temperature of 650°C, 15% CO2 / N2 gas was introduced at a flow rate of 100 ml / min through the Ni / CaAl-8 material bed for 15 minutes;
[0035] Conversion stage: The temperature was maintained at 650°C and the atmosphere was switched to 3% CH4 / N2. The reaction times were controlled at 5 min, 7 min, and 10 min, respectively. Pure N2 (100 ml / mi) was purged for 3 min before each atmosphere switch, and 20 cycles were performed for each reaction.
[0036] result:
[0037] As attached Figure 3 As shown in the figure, the carbon deposition amount of Ni / CaAl-4 is 1.56 mmol / g after 20 cycles; when the reaction time is changed to 7 minutes, the carbon deposition amount is 0.79 mmol / g after 20 cycles; when the reaction time is changed to 5 minutes, the carbon deposition amount is 0.12 mmol / g after 20 cycles. The carbon deposition amount decreases significantly with the shortening of reaction time.
[0038] Example 4:
[0039] Reaction apparatus such as Figure 1 As shown, the Ni / CaAl-2 prepared in Example 1 was filled into a fixed bed reactor, and the dual-functional material was reduced by introducing 10% H2 / N2 at 750°C for 2 hours, and then cooled to 650°C to start a long-term cycle experiment, as follows:
[0040] Adsorption stage: 15% CO2 / N2 gas was passed through the bed of Ni / CaAl-8 material at a flow rate of 100 ml / min for 15 minutes at an adsorption temperature of 650°C;
[0041] Conversion stage: The temperature was maintained at 650°C, and the atmosphere was switched to 3% CH4 / N2, and the reaction time was controlled at 5 minutes, 7 minutes, and 10 minutes, respectively, with 20 cycles for each. Before each switch of atmosphere, pure N2 (100 ml / min) was passed for 3 minutes for purging.
[0042] Results:
[0043] As shown in the accompanying Figure 4 carbon content of the Ni / CaAl-2 was 2.55 mmol / g after 20 cycles; when the reaction time was changed to 7 minutes, the carbon content was 1.52 mmol / g after 20 cycles; and when the reaction time was changed to 5 minutes, the carbon content was 0.25 mmol / g after 20 cycles. The carbon content decreased significantly as the reaction time was shortened.
[0044] Comparative Example 1:
[0045] The reaction device was as shown in the accompanying Figure 1 The Ni / CaO prepared in Example 1 was filled into a fixed bed reactor, and the bifunctional material was reduced by passing 10% H2 / N2 at 750°C for 2 hours, and then the temperature was lowered to 650°C to start the long cycle experiment, as follows:
[0046] Adsorption stage: 15% CO2 / N2 gas was passed through the bed of Ni / CaAl-8 material at a flow rate of 100 ml / min for 15 minutes at an adsorption temperature of 650°C;
[0047] Conversion stage: The temperature was maintained at 650°C, and the atmosphere was switched to 3% CH4 / N2, and the reaction time was controlled at 5 minutes, 7 minutes, and 10 minutes, respectively, with 20 cycles for each. Before each switch of atmosphere, pure N2 (100 ml / min) was passed for 3 minutes for purging.
[0048] Results:
[0049] As shown in the accompanying Figure 5As shown, after 20 cycles, the carbon deposit on Ni / CaAl-2 was 0.55 mmol / g. When the reaction time was changed to 7 minutes, the carbon deposit was 0.25 mmol / g after 20 cycles. When the reaction time was changed to 5 minutes, the carbon deposit was 0.03 mmol / g after 20 cycles. The carbon deposit amount decreased significantly with shortening the reaction time. It is worth noting that although the carbon deposit amount of Ni / CaO was lower than that of Ni / CaAl-x, its CH4 conversion rate decreased significantly. Its activity decline is mainly due to the loss of active sites caused by sintering, rather than the improvement of its carbon deposition resistance.
[0050] The integrated CO2 capture and methane dry reforming cycle experiments on Ni / CaO and Ni / CaAl-x at different methane dry reforming reaction times showed that by shortening the reaction time, the problem of insufficient CO2 decomposition in the ICCU-DRM reaction due to insufficient CaCO3 in the late reaction period, which did not match the CH4 concentration and led to excessive methane cracking, was effectively solved, thereby further reducing the amount of carbon deposition.
[0051] Comparative Example 2:
[0052] Reaction device such as Figure 1 As shown, the Ni / CaO and Ni / CaAl-x (x=2, 4, 8) prepared in Example 1 were filled into a fixed-bed reactor, and the dual-functional materials were reduced by introducing 10% H2 / N2 at 750°C for 2 hours. The temperature was then lowered to 650°C to start a long-term cycle experiment, as follows:
[0053] Adsorption stage: At an adsorption temperature of 650°C, 15% CO2 / N2 gas was introduced at a flow rate of 100 ml / min through the Ni / CaAl-8 material bed for 15 minutes;
[0054] Conversion stage: The temperature was maintained at 650°C and switched to a 3% CH4 / N2 atmosphere. The reaction time was controlled to 3 minutes. Pure N2 (100 ml / mi) was purged for 3 minutes before each atmosphere switch. 20 cycles were performed.
[0055] result:
[0056] As attached Figure 6 As shown in the figure, although Ni / CaO and Ni / CaAl-x (x = 2, 4, 8) exhibit extremely low carbon deposition, insufficient reaction time results in excess CaCO₃ remaining in the system. Since the Tammann temperature of CaCO₃ is only 533°C, while the reaction temperature (650°C) far exceeds this value, the bifunctional materials experience severe sintering, significantly degrading their performance.
Claims
1. A method for reducing carbon deposit formation in integrated CO2 capture and methane dry reforming, characterized in that: The method comprises the following steps: (1) CO2 adsorption stage: At an adsorption temperature of 600-700℃, the mixed gas containing CO2 is passed through the Ni / CaO-Al2O3 material bed, where CaO adsorbs CO2 to generate CaCO3; (2) CH4 conversion stage: At a regeneration temperature of 600-700°C, the material adsorbed in step (1) is switched to a mixed gas containing CH4 for methane dry reforming reaction. The reaction time of the conversion stage is controlled to 5-10 minutes, so that the decomposition and regeneration of CaCO3 and the methane dry reforming reaction reach a dynamic equilibrium, thereby inhibiting the formation of carbon deposits; Wherein, in the Ni / CaO-Al2O3 material: the loading amount of Ni is 8-12%; the mass ratio of CaO to Al2O3 is 2:1 to 10:
1.
2. The method according to claim 1, characterized in that In the CO2 adsorption stage, the adsorption temperature is 650°C; the CO2 concentration is 10-20%, the balance gas is N2; the total gas flow rate is 50-200 ml / min; and the adsorption time is 10-20 minutes.
3. The method according to claim 1, characterized in that In the CH4 conversion stage, the reaction temperature is 650°C; the CH4 concentration is 1-5%, and the balance gas is N2; the total gas flow rate is 50-200 ml / min; and the reaction time is preferably 5-7 minutes.
4. The method according to claim 1, wherein The mass ratio of CaO to Al2O3 is 2:1 to 8:1.