A method for preparing a ferrous silicate oxygen carrier for chemical looping partial oxidation of methane to syngas

Abstract

The application belongs to the field of synthesis gas prepared by partial oxidation of methane, and discloses a design and synthesis method of Fe2SiO4 oxygen carrier for preparing synthesis gas by chemical chain partial oxidation of methane. The oxygen carrier is a metal silicate oxygen carrier, and the metal ion is ferrous ion. The iron-based oxygen carrier has the characteristics of low price, strong reaction activity, good mechanical property and the like. The Fe2SiO4 oxygen carrier designed by Factsage8.1 and synthesized by a ball milling method has good reaction activity, and has high methane conversion rate and synthesis gas selectivity.

Description

Technical Field

[0001] This invention belongs to the field of oxygen carriers and discloses a method for preparing and experimentally preparing Fe2SiO4 oxygen carrier for the chemical chain partial oxidation of methane to syngas. The prepared Fe2SiO4 exhibits good reactivity, with high methane conversion and syngas selectivity. Background Technology

[0002] According to BP's Statistical Review of World Energy 2022, coal consumption accounted for 56.2% of my country's primary energy consumption in 2022. The excessive use of coal and other energy sources has led to high carbon dioxide emissions and severe environmental pollution. With increasing energy consumption and stricter environmental requirements, vigorously developing and utilizing clean energy is imperative. Shale gas, as a new type of clean energy, has attracted much attention due to its large reserves and low carbon emissions. Currently, many countries are researching how to gradually replace coal and oil with natural gas or shale gas to achieve cleaner energy development. Since the main component of shale gas is CH4, its utilization primarily focuses on the conversion and utilization of CH4.

[0003] The conversion and utilization of CH4 includes direct and indirect conversion. Direct conversion of CH4 into chemicals presents problems such as high energy consumption and complex processes. Indirect conversion of CH4 into methane is currently the main route for methane conversion and utilization. This involves first converting CH4 into syngas, and then using Fischer-Tropsch synthesis to convert it into downstream products such as methanol and ammonia. Traditional methane-to-syngas technologies mainly include methane steam reforming, dry reforming, and partial oxidation. Methane steam reforming and dry reforming are both strongly endothermic reactions, consuming a lot of energy and incurring high costs. Partial oxidation, on the other hand, has advantages such as low energy consumption and the ability to obtain a suitable molar ratio of syngas. However, simultaneous feeding of methane and oxygen can easily lead to over-oxidation and explosions of the syngas. To address these issues, chemically chained partial oxidation of methane has attracted considerable attention as a novel syngas production technology, offering advantages such as low energy consumption and high-quality gaseous products.

[0004] The oxygen storage material in the chemical looping partial oxidation of methane is called the oxygen carrier. The oxygen carrier serves as the medium for lattice oxygen cycling between the reduction and oxidation reactors, and its physical and chemical properties are key factors influencing chemical looping technology. Researching high-performance oxygen carriers suitable for methane is a prerequisite for the implementation of chemical looping partial oxidation to syngas technology, and it is also a research focus and hot topic in this technology.

[0005] Iron-based oxygen carriers possess advantages such as low cost, high reactivity, and good mechanical properties, showing great promise for applications. Currently, researchers have developed Fe2O3 / NiO composite oxygen carriers, Fe2O3 / Al2O3 composite oxygen carriers, red mud, magnetite, and FeWO3. x Iron-based oxygen carriers such as LaFeO3, Ca2Fe2O5, and Fe2O3 / ZrO2 were used. Thermodynamic calculations and fixed-bed methane conversion performance tests using Factsage 8.1 software revealed that Fe2SiO4, as an oxygen carrier, can generate stable and high-quality syngas. Summary of the Invention

[0006] The purpose of this invention is to provide a method for synthesizing Fe2SiO4 oxygen carrier, aiming to solve the problems of low methane conversion rate and low syngas selectivity in traditional methane-to-syngas methods, and to promote the low-carbon, high-value conversion of shale gas. The main contents of this invention are as follows:

[0007] (1) Establishing the reaction system of oxygen carrier

[0008] The feasibility of Fe2SiO4 forming a complete reduction-oxidation cycle reaction system with Fe2O3 and SiO2 was calculated using FactSage 8.1 thermodynamic calculation software.

[0009] (2) Determine the thermodynamic properties of the reaction system

[0010] To determine the thermodynamic properties of the established reaction system, the performance of the reaction system at different temperatures and molar masses, as well as the constants at equilibrium and the conversion rate of CH4, were calculated using FactSage 8.1.

[0011] (3) Determine the optimal reaction temperature

[0012] By comparing the reaction performance at different temperatures using FactSage 8.1, 900℃ was determined as the reaction temperature for the fixed-bed experiment.

[0013] (4) Fixed-bed experiments at different air velocities

[0014] To investigate the performance of the designed Fe2SiO4 oxygen carrier, α-Fe2O3, Fe, and SiO2 were mixed uniformly in a molar ratio of 2:2:3, and then ball-milled and calcined to obtain Fe2SiO4. A suitable amount of high-temperature quartz wool was placed in a quartz tube to fix the sample in a constant temperature zone. The sample and quartz sand were weighed at a mass ratio of 1:2 and mixed uniformly before being placed in the quartz tube. The quartz tube reactor was then fixed in the reaction bed and sealed. Argon gas was purged at 50 ml / min for 30 min to remove air from the reaction tube. The temperature was raised to 300 °C and held for 30 min to remove possible impurities on the oxygen carrier, then the temperature was raised to the set temperature of 900 °C. A 5% CH4 / Ar mixture was introduced at a flow rate of 10 ml / min, with space velocities of 300, 600, and 900 ml / h. -1 The reaction was carried out at a constant temperature for 52 minutes.

[0015] Compared with existing iron-based oxygen carriers, the main advantages of the Fe2SiO4 oxygen carrier chemical chain partial oxidation method for producing syngas from methane in this invention are: the oxygen carrier has a lower cost, a higher CH4 conversion rate during the conversion of CH4 to syngas, no CO2 byproduct is detected, and the target product syngas has a higher selectivity. Attached Figure Description

[0016] Figure 1 The effect of reaction temperature on the equilibrium composition of the reaction.

[0017] . Figure 2 The sample XRD pattern

[0018] Figure 3 It is 600 ml (g·h). -1 CH4 conversion rate and H2 / CO molar ratio at space velocity

[0019] Figure 4 It is 600 ml (g·h). -1 Gas concentration at space velocity Detailed Implementation Plan

[0020] This invention provides a method for preparing Fe2SiO4 oxygen carrier and an experimental method thereof. The invention will be described in detail below with reference to the embodiments, but the scope of protection of this invention is not limited to the following embodiments.

[0021] Example 1:

[0022] (1) Weighing and mixing raw materials: Mix the weighed α-Fe2O3, Fe and SiO2 evenly in a molar ratio of 2:2:3;

[0023] (2) Ball milling: The mixture obtained in step (1) is placed in a ball mill jar, and after being introduced into a protective atmosphere of argon, it is placed in a ball mill for ball milling. The rotation speed is set to 550 rad / min and the grinding time is 4 h.

[0024] (3) Calcination: The mixture obtained in step (2) is placed in a quartz boat and calcined in a tube furnace under argon atmosphere protection. The heating rate is 10 °C / min. The temperature is raised to 900 °C and held for 4 h. Finally, the power is turned off and the mixture is allowed to cool naturally to room temperature to obtain Fe2SiO4.

[0025] (4) Setting out: Take an appropriate amount of high-temperature quartz wool and put it into the quartz tube to fix the sample and keep it in the constant temperature zone. Weigh the sample and quartz sand at a mass ratio of 1:2 and mix them evenly before putting them into the quartz tube.

[0026] (5) Purging: Purge the reaction tube with argon gas at a rate of 50 ml / min for 30 min to remove air;

[0027] (6) Fixed bed heating: The temperature is raised to 300 ℃ and held for 30 min to remove possible impurities on the oxygen carrier, and then the temperature is raised to the set temperature of 900 ℃ at a rate of 10 ℃ / min.

[0028] (7) After the set temperature is reached, switch the gas and introduce a 5% CH4 / Ar mixture at a flow rate of 10 ml / min and a space velocity of 300 ml / (g·h). -1 The reaction was carried out at a constant temperature for 52 minutes.

[0029] (8) Gas collection and analysis: After the product gas is cooled to room temperature by the condenser, it passes through the rotor flow meter and then enters the chromatographic analysis. The concentrations of CH4, H2, CO and CO2 in the gas after the reaction are analyzed online by a gas chromatograph.

[0030] Experimental results show that when the space velocity is 300 ml / (g·h)... -1 At this time, the optimal CH4 conversion rate was 80.2%; when the reaction time was 24 min and the H2 / CO molar ratio was 2.

[0031] Example 2:

[0032] (1) Weighing and mixing raw materials: Mix the weighed α-Fe2O3, Fe and SiO2 evenly in a molar ratio of 2:2:3;

[0033] (2) Sample ball milling: The mixture obtained in step (1) is placed in a ball mill jar, and after being introduced into a protective atmosphere of argon, it is placed in a ball mill for ball milling. The rotation speed is set to 550 rad / min and the grinding time is 4 h.

[0034] (3) Sample calcination: The mixture obtained in step (2) was placed in a quartz boat and calcined in a tube furnace under argon atmosphere protection. The heating rate was 10 °C / min. The temperature was raised to 900 °C and held for 4 h. Finally, the power was turned off and the mixture was allowed to cool naturally to room temperature to obtain Fe2SiO4.

[0035] (4) Setting out: Take an appropriate amount of high-temperature quartz wool and put it into the quartz tube to fix the sample and keep it in the constant temperature zone. Weigh the sample and quartz sand at a mass ratio of 1:2 and mix them evenly before putting them into the quartz tube.

[0036] (5) Purging: Purge the reaction tube with argon gas at a rate of 50 ml / min for 30 min to remove air;

[0037] (6) Fixed bed heating: The temperature is raised to 300 ℃ and held for 30 min to remove possible impurities on the oxygen carrier, and then the temperature is raised to the set temperature of 900 ℃ at a rate of 10 ℃ / min.

[0038] (7) Methane isothermal reduction: After the set temperature is reached, switch the gas and introduce a 5% CH4 / Ar mixture at a flow rate of 20 ml / min and a space velocity of 600 ml / (g·h). -1 The reaction was carried out at a constant temperature for 52 minutes.

[0039] (8) Gas collection and analysis: After the product gas is cooled to room temperature by the condenser, it passes through the rotor flow meter and then enters the chromatographic analysis. The concentrations of CH4, H2, CO and CO2 in the gas after the reaction are analyzed online by a gas chromatograph.

[0040] Experimental results show that when the space velocity is 600 ml / (g·h)... -1 At this time, the optimal CH4 conversion rate was 90.6%; when the reaction time was 24 min and the H2 / CO molar ratio was 2.

[0041] Example 3:

[0042] (1) Weighing and mixing raw materials: Mix the weighed α-Fe2O3, Fe and SiO2 evenly in a molar ratio of 2:2:3;

[0043] (2) Ball milling: The mixture obtained in step (1) is placed in a ball mill jar, and after being introduced into a protective atmosphere of argon, it is placed in a ball mill for ball milling. The rotation speed is set to 550 rad / min and the grinding time is 4 h.

[0044] (3) Calcination: The mixture obtained in step (2) is placed in a quartz boat and calcined in a tube furnace under argon atmosphere protection. The heating rate is 10 °C / min. The temperature is raised to 900 °C and held for 4 h. Finally, the power is turned off and the mixture is allowed to cool naturally to room temperature to obtain Fe2SiO4.

[0045] (4) Setting out: Take an appropriate amount of high-temperature quartz wool and put it into the quartz tube to fix the sample in a constant temperature zone. Weigh the sample and quartz sand at a mass ratio of 1:2 and mix them evenly before putting them into the quartz tube.

[0046] (5) Purging: Purge the reaction tube with argon gas at a flow rate of 50 ml / min for 30 min to remove all air;

[0047] (6) Fixed bed heating: The temperature is raised to 300 ℃ and held for 30 min to remove possible impurities on the oxygen carrier, and then the temperature is raised to the set temperature of 900 ℃ at a rate of 10 ℃ / min.

[0048] (7) Methane isothermal reduction: After the set temperature is reached, switch the gas and introduce a 5% CH4 / Ar mixture at a flow rate of 30 ml / min and a space velocity of 900 ml (g·h). -1 The reaction was carried out at a constant temperature for 52 minutes.

[0049] (8) Gas collection and analysis: After the product gas is cooled to room temperature by the condenser, it passes through the rotor flow meter and then enters the chromatographic analysis. The concentrations of CH4, H2, CO and CO2 in the gas after the reaction are analyzed online by a gas chromatograph.

[0050] Experimental results show that when the space velocity is 900 ml / (g·h)... -1 At this time, the optimal CH4 conversion rate was 73.4%; when the reaction time was 24 min and the H2 / CO molar ratio was 2.

Claims

1. A design and experimental method for Fe2SiO4 oxygen carriers used in the partial oxidation of methane in a chemical chain, characterized in that, Includes the following steps: Step 1: The feasibility of Fe2SiO4 forming a complete reduction-oxidation cycle reaction system with Fe2O3 and SiO2 was calculated using FactSage 8.1 thermodynamic calculation software; Step 2: To determine the thermodynamic properties of the established reaction system, the performance of the reaction system at different temperatures and molar masses, the constants at which the reaction reaches equilibrium, and the conversion rate of CH4 were calculated using FactSage 8.

1. Step 3: Calculate and compare the reaction performance at different temperatures using FactSage 8.1, and determine 900℃ as the reaction temperature for the fixed-bed experiment; Step 4: Weigh out the analytical grade α-Fe2O3, Fe, and SiO2, mix them evenly, and put them into a ball mill jar. After introducing argon gas, put the mixture into a ball mill and mill it at 550 rad / min for 4 h to obtain a mixture. The mixture is then calcined in a tube furnace under argon atmosphere protection at a heating rate of 10 ℃ / min. The temperature is raised to 900 ℃ and held for 4 h. Finally, the power is turned off and the mixture is allowed to cool naturally to room temperature to obtain Fe2SiO4. Step 5: To investigate the performance of the designed Fe2SiO4 oxygen carrier, space velocities were tested in a fixed-bed reactor at 300, 600, and 900 ml / (g·h). -1 The performance of the oxygen carrier was assessed by reacting at a constant temperature for 52 min, and the concentrations of CH4, H2, CO, and CO2 in the gas after the reaction were analyzed online using a gas chromatograph.

2. The design and experimental method of Fe2SiO4 oxygen carrier for partial oxidation of methane in a chemical chain according to claim 1, characterized in that... The Fe2SiO4, Fe2O3, and SiO2 described in step 1 can form a complete reduction-oxidation cycle reaction system, and the Gibbs free energy is less than 0 within the reaction temperature range.

3. The design and experimental method of Fe2SiO4 oxygen carrier for partial oxidation of methane in a chemical chain according to claim 1, characterized in that... When the temperature in step 3 is 900℃, the reaction of 1 mol Fe2SiO4 with 2 mol CH4 can ensure that the equilibrium conversion rate of CH4 is greater than 85% and the selectivity of H2 and CO is greater than 70%.

4. The design and experimental method of Fe2SiO4 oxygen carrier for partial oxidation of methane in a chemical chain according to claim 1, characterized in that... The molar ratio of α-Fe2O3 (analytical grade), Fe (analytical grade), and SiO2 (analytical grade) in step 4 is 2:2:

3.

5. The design and experimental method of Fe2SiO4 oxygen carrier for partial oxidation of methane in a chemical chain according to claim 1, characterized in that... The fixed-bed experiment results in step 5 showed that CH4 conversion first increased and then decreased with increasing space velocity, with an H2 / CO ratio of 2; when the space velocity was 600 ml·(g·h) -1 At that time, the conversion rate of CH4 was the highest at 90.2%.

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