CN114558624B - Mesoporous nano microsphere nickel magnesium calcium composite oxide catalyst and application thereof - Google Patents

Abstract

The invention relates to a mesoporous nanometer microsphere nickel magnesium calcium composite oxide catalyst and its application. The specific preparation steps are as follows: (1) prepare nickel salt and magnesium salt into an aqueous solution; (2) add a polymer surfactant to the above solution, and prepare nano-microsphere nickel-magnesium composite oxide after hydrothermal treatment; (3) ) Preparing the calcium salt into an aqueous solution; (4) Impregnating the calcium salt solution into the nano microsphere nickel magnesium calcium composite oxide to obtain the mesoporous nano microsphere nickel magnesium calcium composite oxide catalyst. The mesoporous nano-microsphere nickel magnesium calcium composite oxide catalyst provided by the invention can catalyze the co-conversion of methane and carbon dioxide to produce acetic acid, and has good catalytic activity and selectivity.

Description

A kind of mesoporous nano-microsphere nickel magnesium calcium composite oxide catalyst and its application

Technical field

The invention relates to the technical field of catalyst preparation, and in particular to a mesoporous nano-microsphere nickel magnesium calcium composite oxide catalyst and its application.

Background technique

With the rapid development of modern industry, a large amount of fossil fuels are consumed, and the content of _CO2 in the atmosphere has also increased. The excessive CO ₂ content in the atmosphere has had an extremely negative impact on the ecological balance and climate, and the issue of CO ₂ emissions has attracted widespread social attention. At the same time, mankind is faced with the problem of increasing scarcity of fuel resources. Energy resources are becoming increasingly poor, especially the absolute shortage of oil resources, which has become an important factor hindering sustainable economic development. As a potential carbon source material, _CO2 is a renewable resource with great potential. However, directly emitting CO ₂ into the atmosphere is a waste of resources and causes environmental pollution. Therefore, carrying out the separation, fixation and conversion of CO ₂ to convert and utilize the abundant CO ₂ in nature can not only reduce the greenhouse effect, but also generate organic matter. Fuel, and other organic chemical raw materials or chemical products, it can also reduce environmental pollution problems caused by the reaction of other chemical raw materials. Of course, there is currently a considerable gap between the amount of _CO2 emitted by industry and the amount of _CO2 consumed by utilizing _CO2 . However, carbon dioxide is a cheap and abundant carbon resource, so it is resource-intensive to strengthen the conversion and utilization of _CO2 . , environmental and economic benefits (CatalToday., 2015, 256, 88).

CO ₂ and CH ₄ are the main greenhouse gases. Using CH ₄ and CO ₂ as raw materials to directly convert into acetic acid is a reaction with 100% atomic utilization rate, which can comprehensively utilize CO ₂ and CH ₄ resources. The direct conversion of CH ₄ and CO ₂ into acetic acid can realize the conversion of small molecular substances CO ₂ and CH ₄ that are difficult to activate, and at the same time reduce the impact of these two major greenhouse gases on the environment. It has environmental protection, science, economic and other aspects. Research value (ACS Catal., 2021, 11, 3384). Wilcox et al. first used AspenPlus ^TM to perform Gibbs free energy minimization calculations. The results showed that the conversion rate of methane increased with the increase of pressure and temperature, but even if the reaction feed composition was 95% CO ₂ and 5% CH ₄ And when carried out under the most favorable thermodynamic conditions of 1000K and 100atm, the conversion rate of methane is only 1.6×10 ^-6 . At the same time, the team also developed 5% Pd/C and 5% Pd/Al ₂ O ₃ catalysts. CO ₂ and CH ₄ generate gas-phase acetic acid at about 400°C under the 5% Pd/Al ₂ O ₃ catalyst, and the acetic acid yield is 1.5 ×10 ^-6 μg·g ^-1 ·h ^-1 (Catal Today., 2003, 88, 83). Professor Huang Wei and others developed the V ₂ O ₅ -PdCl ₂ /Al ₂ O ₃ catalyst. O ₂ was introduced during the reaction process, so that the highest production rate of acetic acid directly produced from methane and carbon dioxide was 180 μg·g ^-1 ·h ^-1 , the introduction of O ₂ can lower the reaction energy barrier, allowing the reaction to proceed at a lower temperature (J. Nat. Gas. Chem., 2004, 2, 13). However, the preparation cost of noble metal catalysts such as Pd is high and the catalytic activity is still poor. Therefore, there is an urgent need to develop new and efficient non-precious metal catalysts for the direct production of acetic acid from _CO2 and _CH4 .

Contents of the invention

The purpose of the present invention is to provide a mesoporous nano-microsphere nickel magnesium calcium composite oxide catalyst. Another purpose of the present invention is to utilize the application of the above catalyst in the synthesis of acetic acid to achieve the co-conversion preparation of activated CH ₄ and CO ₂ Acetic acid.

The technical solution of the present invention is: Magnesium oxide (MgO) is a common oxide with a rock salt structure and plays an important role in the fields of chemical industry and nanotechnology. Using magnesium oxide to chemically adsorb CO ₂ can help reduce atmospheric CO ₂ content, and it is roughly estimated that more than 2GtCO ₂ can be eliminated every year. Nickel (Ni)-based catalysts are commonly used active components for methane activation. Compared with precious metal catalysts, they have the advantages of low price and high affinity. However, nickel-based catalysts suffer from carbon deposition and deactivation problems, which restricts their rapid development. As we all know, the crystal type of MgO and NiO belongs to cubic NaCl, and the difference in ionic radii of Mg ²⁺ (0.065nm) and Ni ²⁺ (0.070nm) is small. Therefore, regardless of the composite ratio of MgO and NiO, a Ni _x Mg _(1-x) O solid solution can be formed. The Ni _x Mg _(1-x) O solid solution catalyst with an alkaline surface produced by the combination of MgO and NiO has the characteristics of MgO and NiO and helps inhibit carbon deposition. At the same time, in order to further suppress carbon deposition, it is a good choice to add a second metal for modification. Usually, alkali metal oxides (such as K ₂ O, Cs ₂ O, etc.), alkaline earth metal oxides (such as CaO, etc.) are selected. ) as a modifier. Therefore, the patent of the present invention prepares a mesoporous nickel magnesium calcium composite oxide catalyst. While ensuring high catalytic activity and stability, the introduction of mesopores can enhance the enrichment and activation of the reaction raw materials methane and carbon dioxide on the surface of the catalyst.

The specific technical solution of the present invention is: a mesoporous nano-microsphere nickel magnesium calcium composite oxide catalyst, which is characterized in that it is prepared by the following method. The specific steps are as follows:

(1) Prepare nickel salt and magnesium salt into an aqueous solution;

(2) Add polymer surfactant to the above solution, stir, heat with water, cool to room temperature, centrifuge, wash, and vacuum dry;

(3) Prepare the calcium salt into an aqueous solution, pour the solid powder obtained in step (2) into the prepared calcium salt solution, age it in a water bath, and obtain mesoporous nano-microsphere nickel magnesium calcium composite after centrifugation, washing, and vacuum drying. Oxide catalyst. The resulting catalyst is labeled PE-CaO-NiO-MgO.

Preferably, the nickel salt described in step (1) is one of nickel nitrate, nickel chloride, nickel carbonate or nickel sulfate; the magnesium salt is one of magnesium nitrate, magnesium chloride, magnesium sulfate or magnesium oxalate; the nickel salt and The mass ratio of magnesium salt is 1: (1~20).

Preferably, the polymer surfactant described in step (2) is one of polyvinylpyrrolidone, carboxymethylcellulose or sodium polyacrylate; the mass ratio of nickel salt to polymer surfactant is 1:(1~ 8).

Preferably, the hydrothermal temperature described in step (2) is 100-200°C, the hydrothermal time is 6-30h; the vacuum drying temperature is 50-80°C, and the vacuum drying time is 4-12h.

Preferably, the calcium salt described in step (3) is one of calcium nitrate, calcium sulfate, calcium chloride, calcium carbonate or calcium oxide; the mass ratio of calcium salt to nickel salt is 1: (1-16).

Preferably, the water bath temperature in step (3) is 40-80°C, the aging time is 4-16h; the vacuum drying temperature is 40-80°C, and the vacuum drying time is 8-20h.

The invention also provides an application of the above-mentioned mesoporous nano-microsphere nickel magnesium calcium composite oxide catalyst in the synthesis of acetic acid. The specific steps are: mixing the catalyst with high-temperature resistant fiber wool and loading it into a fixed bed reactor; After purging with inert gas, the temperature is raised to the required reduction temperature. At this temperature, the inert gas is switched to reducing gas to start reduction. After the reduction is completed, the reducing gas is switched to methane and carbon dioxide to react.

Preferably, the mass ratio of the above-mentioned catalyst to high-temperature resistant fiber wool is (1-8):1; the inert gas can be one of nitrogen, argon or helium; the reducing gas is hydrogen or a mixture of hydrogen and nitrogen, where The volume fraction of hydrogen is 5 to 100%; the reduction temperature is 300 to 500°C; the reduction time is 1 to 5 hours; the volume ratio of methane and carbon dioxide is (1 to 6):1, and the reaction pressure is 1 to 30 atm. The temperature is 450~700℃.

Beneficial effects:

The patent of this invention prepares a mesoporous nickel magnesium calcium composite oxide catalyst. While ensuring high catalytic activity and stability, the introduction of mesopores can enhance the enrichment and activation of the reaction raw materials methane and carbon dioxide on the surface of the catalyst. The catalyst can catalyze the co-conversion of methane and carbon dioxide to produce acetic acid, and has good catalytic activity and selectivity.

Detailed ways

The present invention will be described in more detail below using examples. These examples are only descriptions of the best embodiments of the present invention and do not limit the scope of the present invention in any way.

Example 1

Step 1. Add 2.9079g nickel nitrate and 2.9079g magnesium nitrate to 100mL deionized water and stir;

Step 2. Add polyvinylpyrrolidone (the mass ratio of nickel salt to polyvinylpyrrolidone is 1:1), stir, hydroheat at 100°C for 30h, centrifuge, wash, and vacuum dry at 50°C for 12h;

Step 3. Add calcium nitrate (the mass ratio of calcium salt to nickel salt is 1:1) to 100 ml of deionized water to prepare a calcium salt solution. Add the prepared calcium salt solution to the solid obtained in the above step (2), 40 After 16 hours in a water bath at ℃, centrifuged, washed, and vacuum dried at 40 ℃ for 20 hours, the mesoporous nanosphere nickel magnesium calcium composite oxide catalyst was obtained. The catalyst obtained after the above four steps was recorded as PE-CaO-NiO-MgO-1.

Example 2

Step 1. Add 2.3769g nickel chloride and 11.8845g magnesium chloride to 100mL deionized water and stir;

Step 2. Add polyvinylpyrrolidone (the mass ratio of nickel salt to polyvinylpyrrolidone is 1:3), stir, hydroheat at 130°C for 24h, centrifuge, wash, and vacuum dry at 60°C for 10h;

Step 3. Add calcium carbonate (the mass ratio of calcium salt to nickel salt is 1:4) to 100 ml of deionized water to prepare a calcium salt solution, and add the solid obtained in the above step (2) to the prepared calcium salt solution. After 13 hours of water bathing at 50°C, centrifugation, washing, and vacuum drying at 60°C for 16 hours, the mesoporous nanosphere nickel magnesium calcium composite oxide catalyst was obtained. The catalyst obtained through the above four steps was recorded as PE-CaO-NiO-MgO-2.

Example 3

Step 1. Add 1.187g nickel carbonate and 11.87g magnesium sulfate to 100mL deionized water and stir;

Step 2. Add carboxymethyl cellulose (the mass ratio of nickel salt to carboxymethyl cellulose is 1:4) to the above solution, stir, hydroheat at 150°C for 12 hours, centrifuge, wash, and vacuum dry at 70°C for 8 hours;

Step 3. Add calcium sulfate (the mass ratio of calcium salt to nickel salt is 1:7) to 100 ml of deionized water to prepare a calcium salt solution, and add the solid obtained in the above step (2) to the prepared calcium salt solution. After 10 hours of water bathing at 60°C, centrifugation, washing, and vacuum drying at 70°C for 10 hours, the mesoporous nanosphere nickel magnesium calcium composite oxide catalyst was obtained. The catalyst obtained through the above four steps was recorded as PE-CaO-NiO-MgO-3.

Example 4

Step 1. Add 2.6285g nickel sulfate and 13.1425g magnesium oxalate to 100mL deionized water and stir;

Step 2. Add carboxymethylcellulose (the mass ratio of nickel salt to carboxymethylcellulose is 1:6) to the above solution, stir, hydroheat at 180°C for 10h, centrifuge, wash, and vacuum dry at 80°C for 4h;

Step 3. Add calcium chloride (the mass ratio of calcium salt to nickel salt is 1:10) to 100 ml of deionized water to prepare a calcium salt solution, and add the solid obtained in the above step (2) to the prepared calcium salt solution. , after 6 hours in a water bath at 70°C, centrifuge, wash, and vacuum dry at 80°C for 8 hours to obtain the mesoporous nanosphere nickel magnesium calcium composite oxide catalyst. The catalyst obtained through the above four steps is recorded as PE-CaO-NiO-MgO-4 .

Example 5

Step 1. Add 1.187g nickel carbonate and 17.805g magnesium sulfate to 100mL deionized water and stir;

Step 2. Add sodium polyacrylate (the mass ratio of nickel salt to sodium polyacrylate is 1:8) to the above solution, stir, hydroheat at 200°C for 6 hours, centrifuge, wash, and vacuum dry at 80°C for 4 hours;

Step 3. Add calcium oxide (the mass ratio of calcium salt to nickel salt is 1:13) to 100 ml of deionized water to prepare a calcium salt solution, and add the solid obtained in the above step (2) to the prepared calcium salt solution. After 4 hours in a water bath at 80°C, centrifuge, wash, and vacuum dry at 80°C for 12 hours to obtain a mesoporous nanosphere nickel magnesium calcium composite oxide catalyst. The catalyst obtained through the above four steps is recorded as PE-CaO-NiO-MgO-5.

Example 6

Step 1. Add 1.4540g nickel nitrate and 24.7180g magnesium chloride to 100mL deionized water and stir;

Step 2. Add sodium polyacrylate (the mass ratio of nickel salt to sodium polyacrylate is 1:7) to the above solution, stir, hydroheat at 180°C for 10h, centrifuge, wash, and vacuum dry at 60°C for 8h;

Step 3. Add calcium sulfate (the mass ratio of calcium salt to nickel salt is 1:12) to 100 ml of deionized water to prepare a calcium salt solution, and add the solid obtained in the above step (2) to the prepared calcium salt solution. After 6 hours in a water bath at 70°C, centrifugation, washing, and vacuum drying at 60°C for 16 hours, the mesoporous nanosphere nickel magnesium calcium composite oxide catalyst was obtained. The catalyst obtained after the above four steps was recorded as PE-CaO-NiO-MgO-6.

Example 7

Step 1. Add 1.1871g nickel carbonate and 20.1807g magnesium oxalate to 100mL deionized water and stir;

Step 2. Add polyvinylpyrrolidone (the mass ratio of nickel salt to polyvinylpyrrolidone is 1:6), stir, hydroheat at 200°C for 6 hours, centrifuge, wash, and vacuum dry at 80°C for 4 hours;

Step 3. Add calcium chloride (the mass ratio of calcium salt to nickel salt is 1:15) to 100 ml of deionized water to prepare a calcium salt solution, and add the solid obtained in the above step (2) to the prepared calcium salt solution. , after 8 hours of water bathing at 80°C, centrifugation, washing, and vacuum drying at 80°C for 8 hours, the mesoporous nanosphere nickel magnesium calcium composite oxide catalyst was obtained. The catalyst obtained after the above four steps was recorded as PE-CaO-NiO-MgO-7 .

Example 8

Step 1. Add 1.4539g nickel nitrate and 29.0780g magnesium chloride to 100mL deionized water and stir;

Step 2. Add carboxymethylcellulose (the mass ratio of nickel salt to carboxymethylcellulose is 1:8) to the above solution, stir, hydroheat at 160°C for 15h, centrifuge, wash, and vacuum dry at 60°C for 12h;

Step 3. Add calcium nitrate (the mass ratio of calcium salt to nickel salt is 1:16) to 100 ml of deionized water to prepare a calcium salt solution. Add the solid obtained in the above step (2) to the prepared calcium salt solution. After 4 hours in a water bath at 80°C, centrifuge, wash, and vacuum dry at 60°C for 13 hours to obtain a mesoporous nanosphere nickel magnesium calcium composite oxide catalyst. The catalyst obtained through the above four steps is recorded as PE-CaO-NiO-MgO-8.

Mesoporous nano-microsphere nickel magnesium calcium composite oxide catalyst is used to catalyze the co-conversion of methane and carbon dioxide into acetic acid:

Application example 1

Mix 0.2g mesoporous nano-microsphere nickel magnesium calcium composite oxide PE-CaO-NiO-MgO-1 catalyst and 0.2g high temperature resistant fiber cotton, add it to the fixed bed reactor, purge it with inert gas nitrogen, and raise the temperature. to 300°C, switch to hydrogen reduction with a volume fraction of 5% for 5 hours; raise the temperature to 700°C, and introduce methane and carbon dioxide with a volume ratio of 1:1 at 1 atm. The acetic acid selectivity is 80.41%, and the highest acetic acid production rate is 232mmol·kg _cat ^-1 ·h ^-1 .

Application example 2

Mix 0.4g mesoporous nano-microsphere nickel magnesium calcium composite oxide PE-CaO-NiO-MgO-2 catalyst and 0.2 g high temperature resistant fiber cotton, add it to the fixed bed reactor, and purge it with inert gas helium. Raise the temperature to 400°C, switch to hydrogen reduction with a volume fraction of 10% for 4 hours; raise the temperature to 600°C, and introduce methane and carbon dioxide with a volume ratio of 2:1 at 3 atm. The acetic acid selectivity is 85.51%, and the highest acetic acid production rate is 294mmol·kg _cat ^-1 ·h ^-1 .

Application example 3

Mix 0.6g of mesoporous nano-microsphere nickel magnesium calcium composite oxide PE-CaO-NiO-MgO-3 catalyst with 0.2g of high temperature resistant fiber cotton, add it to the fixed bed reactor, and purge it with inert gas argon. Raise the temperature to 400°C, switch to hydrogen reduction with a volume fraction of 20% for 3 hours; raise the temperature to 550°C, and introduce methane and carbon dioxide with a volume ratio of 3:1 at 6 atm. The acetic acid selectivity is 88.34%, and the highest acetic acid production rate is 319mmol·kg _cat ^-1 ·h ^-1 .

Application example 4

Mix 0.8g mesoporous nano-microsphere nickel magnesium calcium composite oxide PE-CaO-NiO-MgO-4 catalyst and 0.2 g high temperature resistant fiber cotton, add it to the fixed bed reactor, purge it with inert gas nitrogen, and raise the temperature. to 400°C, switch to hydrogen reduction with a volume fraction of 50% for 2.5 hours; raise the temperature to 500°C, and introduce methane and carbon dioxide with a volume ratio of 4:1 at 10 atm. The acetic acid selectivity is 87.26%, and the highest acetic acid production rate is 301mmol·kg _cat ^-1 ·h ^-1 .

Application example 5

Mix 1.0g mesoporous nano-microsphere nickel magnesium calcium composite oxide PE-CaO-NiO-MgO-5 catalyst with 0.2 g high temperature resistant fiber cotton, add it to the fixed bed reactor, purge it with inert gas nitrogen, and raise the temperature. to 500°C, switch to hydrogen reduction with a volume fraction of 100% for 1 hour; cool to 450°C, and introduce methane and carbon dioxide with a volume ratio of 5:1 at 30 atm. The acetic acid selectivity is 95.16%, and the highest acetic acid production rate is 399mmol·kg _cat ^-1 ·h ^-1 .

Application example 6

Mix 1.2g mesoporous nano-microsphere nickel magnesium calcium composite oxide PE-CaO-NiO-MgO-6 catalyst with 0.2 g high temperature resistant fiber cotton, add it to the fixed bed reactor, purge it with inert gas nitrogen, and raise the temperature. to 500°C, switch to hydrogen with a volume fraction of 80%, and reduce for 3 hours; maintain 500°C, and introduce methane and carbon dioxide with a volume ratio of 4.5:1 at 20 atm. The acetic acid selectivity is 93.53%, and the highest acetic acid production rate is 360mmol·kg _cat ^-1 ·h ^-1 .

Application example 7

Mix 1.4g of mesoporous nano-microsphere nickel magnesium calcium composite oxide PE-CaO-NiO-MgO-7 catalyst with 0.2 g of high temperature resistant fiber cotton, add it to the fixed bed reactor, and purge it with inert gas argon. Raise the temperature to 400°C, switch to hydrogen reduction with a volume fraction of 100% for 2 hours; lower the temperature to 450°C, and introduce methane and carbon dioxide with a volume ratio of 4:1 at 30 atm. The acetic acid selectivity is 90.24%, and the highest acetic acid production rate is 327mmol·kg _cat ^-1 ·h ^-1 .

Application example 8

Mix 1.6g of mesoporous nano-microsphere nickel magnesium calcium composite oxide PE-CaO-NiO-MgO-2 catalyst with 0.2 g of high temperature resistant fiber cotton, add it to the fixed bed reactor, and purge it with inert gas helium. Raise the temperature to 500°C, switch to hydrogen reduction with a volume fraction of 100% for 1.5 hours; raise the temperature to 600°C, and introduce methane and carbon dioxide with a volume ratio of 6:1 at 30 atm. The acetic acid selectivity is 97.89%, and the highest acetic acid production rate is 424mmol·kg _cat ^-1 ·h ^-1 .

Table 1 Comparison of catalytic performance of PE-CaO-NiO-MgO catalysts

Note: The reference for Comparative Example 1 is Catal. Today., 2003, 88, 83; the reference for Comparative Example 2 is J. Nat. Gas. Chem., 2004, 2, 13.

Claims (6)

1. The application of the mesoporous nano microsphere nickel magnesium calcium composite oxide catalyst in synthesizing acetic acid comprises the following specific steps: mixing a catalyst and high-temperature-resistant fiber cotton, then filling the mixture into a fixed bed reactor, introducing inert gas for purging, then heating to a required reduction temperature, switching the inert gas into reducing gas for starting reduction at the temperature, and switching the reducing gas into methane and carbon dioxide for reaction after the reduction is finished; wherein the mass ratio of the catalyst to the high temperature resistant cellucotton is (1-8): 1; the inert gas may be one of nitrogen, argon or helium; the reducing gas is hydrogen or mixed gas of hydrogen and nitrogen, wherein the volume fraction of the hydrogen is 5-100%; the reduction temperature is 300-500 ℃; the reduction time is 1-5 h; the volume ratio of methane to carbon dioxide is (1-6), 1, the reaction pressure is 1-30 atm, and the reaction temperature is 450-700 ℃;

the mesoporous nano microsphere nickel magnesium calcium composite oxide catalyst is prepared by the following steps:

(1) Preparing nickel salt and magnesium salt into aqueous solution;

(2) Adding a high molecular surfactant into the solution, stirring, cooling to room temperature after hydrothermal treatment, centrifuging, washing and vacuum drying;

(3) And (3) preparing calcium salt into aqueous solution, pouring the solid powder obtained in the step (2) into the prepared calcium salt aqueous solution, aging in water bath, centrifuging, washing and drying in vacuum to obtain the mesoporous nano microsphere nickel-magnesium-calcium composite oxide catalyst.

2. The use according to claim 1, wherein: the nickel salt in the step (1) is one of nickel nitrate, nickel chloride, nickel carbonate or nickel sulfate; the magnesium salt is one of magnesium nitrate, magnesium chloride, magnesium sulfate or magnesium oxalate; the mass ratio of the nickel salt to the magnesium salt is 1 (1-20).

3. The use according to claim 1, wherein: the macromolecular surfactant in the step (2) is one of polyvinylpyrrolidone, carboxymethyl cellulose or sodium polyacrylate; the mass ratio of the nickel salt to the high molecular surfactant is 1 (1-8).

4. The use according to claim 1, wherein: the hydrothermal temperature in the step (2) is 100-200 ℃, and the hydrothermal time is 6-30 hours; the vacuum drying temperature is 50-80 ℃, and the vacuum drying time is 4-12 h.

5. The use according to claim 1, wherein: the calcium salt in the step (3) is one of calcium nitrate, calcium sulfate, calcium chloride, calcium carbonate or calcium oxide; the mass ratio of the calcium salt to the nickel salt is 1 (1-16).

6. The use according to claim 1, wherein: the water bath temperature in the step (3) is 40-80 ℃, and the aging time is 4-16 h; the vacuum drying temperature is 40-80 ℃, and the vacuum drying time is 8-20 h.