阅读说明：本技术 一种高分散低载量高活性沼气双重整催化剂及其制备方法 (High-dispersion low-loading high-activity biogas double-reforming catalyst and preparation method thereof ) 是由 谢君 李文阳 钟家伟 韩冰 于 2021-10-13 设计创作，主要内容包括：本发明涉及一种高分散低载量高活性沼气双重整催化剂及其制备方法。该制备方法包括前驱体合成、离子交换、煅烧和预还原处理等步骤。本发明提供的制备方法通过将层状双金属氢氧化物前驱体AB-LDHs进行离子交换,并经煅烧及预还原处理,制得的高分散低载量高活性沼气双重整催化剂具有良好活性和优异稳定性,可推广应用于催化甲烷二氧化碳干湿双重整。(The invention relates to a high-dispersion low-loading high-activity biogas double-reforming catalyst and a preparation method thereof. The preparation method comprises the steps of precursor synthesis, ion exchange, calcination, pre-reduction treatment and the like. According to the preparation method provided by the invention, the layered double hydroxide precursor AB-LDHs is subjected to ion exchange, and is subjected to calcination and pre-reduction treatment, so that the prepared high-dispersion low-load high-activity methane double reforming catalyst has good activity and excellent stability, and can be popularized and applied to catalytic methane carbon dioxide dry-wet double reforming.)

1. A preparation method of a high-dispersion low-loading high-activity biogas double-reforming catalyst is characterized by comprising the following steps:

s1, synthesis of a layered double hydroxide precursor: obtaining a layered double hydroxide precursor AB-LDHs by a coprecipitation method of a divalent metal A salt and a trivalent metal B salt;

s2, introducing an active metal center by an ion exchange method: mixing a layered double hydroxide precursor AB-LDHs with a solution containing an active metal M salt, and performing ion exchange on active metal M ions and cations in the layered double hydroxide precursor to obtain M-AB-LDHs;

s3, calcination treatment: calcining M-AB-LDHs at 400-700 ℃ to obtain high-dispersion low-loading high-activity methane double reforming catalyst MO_x/AO-B₂O₃；

S4, pre-reduction treatment: mixing MO_x/AO-B₂O₃At H₂/N₂And carrying out pre-reduction treatment in the atmosphere to obtain the high-dispersion low-loading high-activity methane double reforming catalyst.

2. The preparation method according to claim 1, wherein the divalent metal A salt is one or more of Mg salt, Co salt or Zn salt; the trivalent metal B salt is one or two of Al salt or Sr salt; the divalent metal A salt is one or more of acetate or nitrate of the divalent metal A; the trivalent metal B salt is one or more of acetate or nitrate of the trivalent metal B.

3. The method according to claim 1, wherein the molar ratio of the element A in the divalent metal A salt to the element B in the trivalent metal B salt is 2:1 to 5: 1.

4. The preparation method according to claim 1, wherein the specific process of the coprecipitation method is as follows: dissolving divalent metal A salt and trivalent metal B salt to obtain a mixed solution, and then sequentially dropwise adding the mixed solution and a precipitator to Na₂CO₃And stirring the solution for 12-24 hours at 50-100 ℃, filtering, washing and drying to obtain the layered double hydroxide precursor AB-LDHs.

5. The preparation method according to claim 4, wherein the precipitant is NaOH solution, and the concentration of the NaOH solution is 1-2 mol/L; the Na is₂CO₃The concentration of the solution is 0.5-1 mol/L.

6. The method according to claim 1, wherein the active metal M salt in S2 is one or more of Pd salt, Pt salt, Ru salt, Rh salt, Ir salt, Co salt or Ni salt.

7. The preparation method of claim 1, wherein the mass ratio of the active metal M salt in S2 to the layered double hydroxide precursor AB-LDHs is 0.008-0.012: 1.

8. The preparation method according to claim 1, wherein the temperature is raised at a rate of 2-10 ℃/min in S3, the calcination time is 4-12 h, and the calcination atmosphere is static or flowing air atmosphere; the pre-reduction time in the S4 is 1-3 h.

9. A high-dispersion low-loading high-activity biogas double reforming catalyst is characterized by being prepared by the preparation method of any one of claims 1 to 8.

10. The use of the high dispersion low loading high activity biogas double reforming catalyst of claim 9 in catalyzing methane carbon dioxide dry-wet double reforming.

Technical Field

The invention belongs to the field of catalysts for methane double reforming reaction (methane-carbon dioxide-water dry-wet double reforming reaction), and particularly relates to a high-dispersion low-loading high-activity methane double reforming catalyst and a preparation method thereof.

Background

In recent years, with increasingly remarkable energy and environmental problems, the synthesis gas prepared by using the methane double reforming reaction draws wide attention of all countries in the world, the petroleum is searched for replacing energy, the biomass resources in China are actively utilized, and the method has great significance on energy safety and sustainable development of ecological environment in China.

Methane double reforming reaction (methane-carbon dioxide-water dry-wet double reforming reaction), namely 3CH₄+CO₂+2H₂O＝4CO+8H₂(dry-wet reforming) for producing biogas from biomass (e.g., plants, microorganisms, animals fed by plants and microorganisms, and waste products of the production thereof) while effectively utilizing two greenhouse gases to produce syngas (mainly CO + H)₂)。

In the synthesis gas, the hydrogen-carbon ratio is adjusted to be 2 (namely H)₂2) is suitable for the preparation of biomethanol. The methanol is clean oxygen-containing liquid fuel, is convenient to store and transport, rich in resources and wide in application; can be used as a liquid hydrogen storage medium, is called as liquid sunlight, and green methanol is a globally accepted carbon neutralization necessary route.

Research shows that most of VIII transition metals such as noble metals Pd, Pt, Rh and Ru and non-noble metals Ni and Co have certain catalytic activity on the double reforming reaction of the methane. Carbon deposition and active metal sintering are two main problems faced by the catalyst for the double reforming reaction of the biogas. The carbon deposition resistance of non-noble metals Ni and Co is poor, and the catalyst is easy to generate serious carbon deposition and is quickly inactivated, so that the industrial application of the catalyst is limited. The noble metal catalyst has good carbon deposition resistance, but the production cost is higher, so that the preparation of the low-loading high-dispersion noble metal catalyst has important industrial value and practical significance.

Compared with a catalyst taking a single oxide as a carrier, the catalyst taking the composite metal oxide as the carrier shows higher catalytic performance. For example, patent CN1990109A discloses a three-way catalyst with palladium supported by magnesium aluminum composite oxide, which has higher catalytic activity and stability.

Therefore, the development of the catalyst with the composite metal oxide as the carrier to realize the methane double reforming reaction has important research significance and wide application prospect.

Disclosure of Invention

The invention aims to overcome the defect or deficiency of poor catalytic activity of the existing catalyst taking a single oxide as a carrier, and provides a preparation method of a high-dispersion low-loading high-activity methane double-reforming catalyst. According to the preparation method provided by the invention, the layered double hydroxide precursor AB-LDHs is subjected to ion exchange, and is subjected to calcination and pre-reduction treatment, so that the prepared high-dispersion low-load high-activity methane double reforming catalyst has good activity and excellent stability, and can be popularized and applied to methane and carbon dioxide dry-wet double reforming reaction.

The invention also aims to provide a high-dispersion low-loading high-activity biogas double reforming catalyst.

The invention also aims to provide the application of the high-dispersion low-loading high-activity biogas double reforming catalyst in catalyzing methane carbon dioxide dry-wet double reforming.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of a high-dispersion low-loading high-activity biogas double-reforming catalyst comprises the following steps:

s1, synthesis of a layered double hydroxide precursor: obtaining a layered double hydroxide precursor AB-LDHs by a coprecipitation method of a divalent metal A salt and a trivalent metal B salt;

s2, introducing an active metal center by an ion exchange method: mixing the layered double hydroxide precursor with a solution containing an active metal M salt, and performing ion exchange on active metal M ions and cations in the layered double hydroxide precursor to obtain M-AB-LDHs;

s3, calcination treatment: calcining M-AB-LDHs at 400-700 ℃ to obtain high-dispersion low-loading high-activity methane double reforming catalyst MO_x/AO-B₂O₃；

S4, pre-reduction treatment: mixing MO_x/AO-B₂O₃At H₂/N₂Pre-reducing atmosphere to obtain the high-dispersion low-loading high-activity methane double reforming catalyst

The existing catalyst taking the bimetallic oxide as a carrier and loading the active component generally calcines the bimetallic hydroxide to obtain the bimetallic oxide, then carries out impregnation treatment on the bimetallic oxide and a solution containing the active component, and then carries out calcination and pre-reduction treatment to realize better dispersion and loading of the active component, but the catalytic activity and stability of the obtained catalyst have a certain promotion space.

The research finds that the layered double hydroxide (AB-LDHs) is an anionic clay material, has the characteristics of adjustable chemical composition of laminates, exchangeability of cations between layers, structural memory function and the like, large specific surface area, alkalinity and the like. The invention takes the layered double-metal hydroxide precursor with large specific surface area as a carrier, introduces an active metal center by using an ion exchange method, can ensure that active metal ions are embedded into a layered structure, has high dispersion and high stability, and then obtains the catalyst M/AO-B after calcination and reduction treatment₂O₃The active component has high dispersity and can have high catalytic activity and stability under low loading; in addition, the catalyst is alkaline, so that adsorption and dissociation of carbon dioxide and water vapor are facilitated in the catalysis process, carbon deposition elimination is promoted, carbon deposition generation is inhibited, the stability of the catalyst is further improved, and the catalyst can be widely applied to catalysis of methane and carbon dioxide dry-wet double reforming.

The high-dispersion low-load high-activity methane double reforming catalyst prepared by ion exchange, calcination and pre-reduction treatment by using the layered double-metal composite hydroxide as a precursor has good activity and excellent stability, specifically, the catalyst catalyzes methane carbon dioxide dry-wet double reforming with methane conversion rate of 85-98% and carbon dioxide conversion rate of 55-65% at 750-800 ℃, the molar ratio range of hydrogen to carbon monoxide in the obtained synthesis gas is 1.5-2.5, and the subsequent direct preparation of methanol is facilitated; and the stability of the catalyst is more than 40 hours.

In addition, the preparation method has the advantages of simple process, easy operation, contribution to industrial production, wide raw material source, low price and low catalyst cost.

Preferably, metal salts that form layered double hydroxides, as are conventional in the art, are all useful in the present invention.

Preferably, the divalent metal A salt is one or more of Mg salt, Co salt or Zn salt.

Preferably, the divalent metal A salt is one or more of acetate or nitrate of the divalent metal A.

Preferably, the trivalent metal B salt is one or both of an Al salt or a Sc salt.

Preferably, the trivalent metal B salt is one or more of acetate or nitrate of the trivalent metal B.

Preferably, the molar ratio of the element A in the divalent metal A salt to the element B in the trivalent metal B salt is 2: 1-5: 1.

Precipitation methods that are conventional in the art to obtain layered double hydroxide precursors AB-LDHs can be used in the present invention.

Preferably, the specific process of the coprecipitation method is as follows: dissolving divalent metal A salt and trivalent metal B salt to obtain a mixed solution, and then sequentially dropwise adding the mixed solution and a precipitator to Na₂CO₃And stirring the solution for 12-24 hours at 50-100 ℃, filtering, washing and drying to obtain the layered double hydroxide precursor AB-LDHs.

More preferably, the precipitator is a NaOH solution, and the concentration of the NaOH solution is 1-2 mol/L; the Na is₂CO₃The concentration of the solution is 0.5-1 mol/L.

More preferably, the precipitating agent has OH^-The molar ratio of the divalent metal A salt to the total of the A element in the divalent metal A salt and the B element in the trivalent metal B salt is 0.5-0.9: 1 (M)_OH ^-:M_A+B＝0.5～0.9:1)。

More preferably, the precipitator is a NaOH solution, and the concentration of the NaOH solution is 1-2 mol/L.

More preferably, the Na₂CO₃With divalent goldThe molar ratio of the sum of the A element in the metal A salt and the B element in the trivalent metal B salt is 1.3-2: 1 (M)_Na2CO3:M_A+B＝1.3～2:1)。

More preferably, the Na₂CO₃The concentration of the solution is 0.5-1 mol/L.

More preferably, the coprecipitation method is performed at 80 to 150 ℃.

Active metal M salts conventional in the art may be used in the present invention.

Preferably, the active metal M salt in S2 is one or more of Pd salt, Pt salt, Ru salt, Rh salt, Ir salt, Co salt or Ni salt.

It will be appreciated that the metal ions in the divalent metal a salt and the active metal M salt are different, i.e. when the divalent metal a salt is Co, the active metal M salt is not a Co salt.

Preferably, the active metal M salt in S2 is one or more of acetate or nitrate of the active metal M.

Preferably, the mass ratio of the active metal M salt in S2 to the layered double hydroxide precursor AB-LDHs is 0.008-0.012: 1.

Preferably, the conditions for ion exchange in S2 are: stirring at 50-100 ℃ for 12-24 h for ion exchange.

Preferably, the ion exchange in S2 further comprises filtering and washing operations.

Preferably, the temperature is raised in S3 at a rate of 2-10 ℃/min, the calcination time is 4-12 h, and the calcination atmosphere is static or flowing air atmosphere.

Preferably, the high dispersion low loading catalyst MO in S3_x/AO-B₂O₃The weight fraction of AO in the component B is 50.1-69.3 wt%₂O₃The weight fraction of the component (A) is 30.6-47.9 wt%, and the component (B) is MO_xThe weight fraction of (B) is 0.1-2 wt%.

MO_xThe value of x in (A) is such that the valence states are balanced.

Preferably, the pre-reduction time in S4 is 1-3 h.

A high-dispersion low-loading high-activity methane double reforming catalyst is obtained by the preparation method.

The high-dispersion low-loading high-activity methane double reforming catalyst is applied to catalyzing methane carbon dioxide dry-wet double reforming.

Compared with the prior art, the invention has the following remarkable effects:

the high-dispersion low-load high-activity methane double-reforming catalyst prepared by using the layered double-metal composite hydroxide as a precursor through ion exchange, calcination and pre-reduction has good activity and excellent stability.

Drawings

FIG. 1 is an X-ray powder diffraction pattern of M/MgAl-LDHs catalysts provided in examples 6 to 14;

FIG. 2 shows M/AO-B provided in examples 10 and 14₂O₃A graph (A) of the conversion rate of methane and carbon dioxide in the dry-wet double reforming of methane and carbon dioxide catalyzed by the catalyst and a graph (B) of the molar ratio of hydrogen to carbon monoxide (1-45 h);

FIG. 3 is a diagram of M/AO-B provided in example 10₂O₃The conversion rate of methane and carbon dioxide and the molar ratio of hydrogen to carbon monoxide in the dry-wet double reforming of methane and carbon dioxide catalyzed by the catalyst are shown.

Detailed Description

The invention is illustrated by the following examples. These examples are intended to illustrate the invention and are not intended to limit the scope of the invention. Experimental procedures without specific conditions noted in the examples below, generally according to conditions conventional in the art or as suggested by the manufacturer; the raw materials, reagents and the like used are, unless otherwise specified, those commercially available from the conventional markets and the like. Any insubstantial changes and substitutions made by those skilled in the art based on the present invention are intended to be covered by the claims.

Examples 1 to 5

The present example provides synthesis of layered double hydroxide precursors AB-LDHs with different molar ratios, which is prepared by the following method:

accurately weighing 5.6g NaOH, dissolving in 120mL deionized water, stirring for l0min, and preparingThe obtained solution is 0.00117mol/L NaOH aqueous solution for standby. According to the molar ratio of magnesium to aluminum of 3:1, 4:1 and 5:1, the molar ratio of cobalt to aluminum of 5:1 and the molar ratio of magnesium to strontium of 5:1, the nitrate solution is prepared by the following steps: nitrate with corresponding amount is weighed and dissolved in 100ml deionized water, and the mixed solution is obtained after the dissolution and the stirring for l0 min. 6.36g of anhydrous Na is accurately weighed₂CO₃Dissolved in 100mL of deionized water as a base solution. Slowly dropping the AB mixed solution into Na-containing solution dropwise through a dropping funnel₂CO₃The solution was placed in a beaker and stirred continuously. And meanwhile, slowly dropping a precipitator NaOH solution (1.17mol/L, 60mL) into the beaker, stirring the whole process at 65 ℃ for 18h, filtering, fully washing the solution with deionized water, and drying the solution at 110 ℃ to obtain a layered double hydroxide precursor AB-LDHs (A is Mg, Co, B is Al and Sr).

The specific amounts added are shown in Table 1.

TABLE 1 Synthesis of AB-LDHs precursors of examples 1-5 with different molar ratios and control of their amounts

The layered double hydroxide precursor prepared in the embodiments 1 to 3 is magnesium-aluminum layered composite hydroxide precursor MgAl-LDHs, the layered double hydroxide precursor prepared in the embodiment 4 is cobalt-aluminum layered composite hydroxide precursor CoAl-LDHs, and the layered double hydroxide precursor prepared in the embodiment 5 is magnesium-strontium layered composite hydroxide precursor MgSr-LDHs.

Example 6

The embodiment provides a high-dispersion low-loading high-activity biogas double-reforming catalyst PdO/MgO-Al₂O₃The preparation process comprises the following steps:

weighing MgAl-LDHs1.98g of the precursor of the layered composite hydroxide of the magnesium and the aluminum obtained in the embodiment 1; measuring palladium ionDissolving and stirring 10mL of palladium chloride solution with the concentration of 0.0113mmol/mL, adding the precursor MgAl-LDHs obtained in example 1, carrying out ion exchange on palladium ions and the magnesium-aluminum layered composite hydroxide precursor, stirring for 12h at 50 ℃, filtering and washing to obtain Pd/MgAl-LDHs (Mg/Al-3); after ion exchange is finished, the mixture is placed in a muffle furnace for roasting, and the temperature is raised to 550 ℃ at the speed of 2 ℃/min for roasting for 4 hours to obtain PdO/MgO-Al₂O₃(Mg/Al ═ 3) catalyst.

Example 7

The embodiment provides a high-dispersion low-loading high-activity biogas double-reforming catalyst PdO/MgO-Al₂O₃The preparation process comprises the following steps:

weighing MgAl-LDHs1.98g of the precursor of the layered composite hydroxide of the magnesium and the aluminum obtained in the embodiment 2; weighing 10mL of palladium chloride solution with palladium ion concentration of 0.0113mmol/mL, dissolving and stirring, adding the precursor MgAl-LDHs obtained in the example 2, carrying out ion exchange on palladium ions and the magnesium-aluminum layered composite hydroxide precursor, stirring for 12h at 50 ℃, filtering and washing to obtain Pd/MgAl-LDHs (Mg/Al ═ 4); after ion exchange is finished, the mixture is placed in a muffle furnace for roasting, and the temperature is raised to 550 ℃ at the speed of 2 ℃/min for roasting for 4 hours to obtain PdO/MgO-Al₂O₃(Mg/Al ═ 4) catalyst.

Example 8

The embodiment provides a high-dispersion low-loading high-activity biogas double-reforming catalyst PdO/MgO-Al₂O₃The preparation process comprises the following steps:

weighing MgAl-LDHs1.98g of the precursor of the magnesium-aluminum layered composite hydroxide obtained in the embodiment 3; weighing 10mL of palladium chloride solution with palladium ion concentration of 0.0113mmol/mL, dissolving and stirring, adding the precursor MgAl-LDHs obtained in the embodiment 3, carrying out ion exchange on palladium ions and the magnesium-aluminum layered composite hydroxide precursor, stirring for 12h at 50 ℃, filtering and washing to obtain Pd/MgAl-LDHs (Mg/Al ═ 5); after ion exchange is finished, the mixture is placed in a muffle furnace for roasting, and the temperature is raised to 550 ℃ at the speed of 2 ℃/min for roasting for 4 hours to obtain PdO/MgO-Al₂O₃(Mg/Al ═ 5) catalyst.

Example 9

The embodiment provides a high-dispersion low-loading high-activity biogas doubleReforming catalyst PtO₂/MgO-Al₂O₃The preparation process comprises the following steps:

weighing MgAl-LDHs1.98g of the precursor of the magnesium-aluminum layered composite hydroxide obtained in the embodiment 3; weighing 10mL of platinum chloride solution with platinum ion concentration of 0.0059mmol/mL, dissolving and stirring, adding the precursor MgAl-LDHs obtained in example 3, performing ion exchange on platinum ions and the magnesium-aluminum layered composite hydroxide precursor, stirring for 12h at 50 ℃, filtering and washing; after ion exchange is finished, the mixture is placed in a muffle furnace for roasting, and the temperature is increased to 550 ℃ at the speed of 2 ℃/min for roasting for 4h to obtain PtO₂/MgO-Al₂O₃(Mg/Al ═ 5) catalyst.

Example 10

The embodiment provides a high-dispersion low-loading high-activity biogas double-reforming catalyst RuO₂/MgO-Al₂O₃The preparation process comprises the following steps:

weighing MgAl-LDHs1.98g of the precursor of the magnesium-aluminum layered composite hydroxide obtained in the embodiment 3; measuring 10mL of ruthenium chloride solution with ruthenium ion concentration of 0.0096mmol/mL, dissolving and stirring, adding MgAl-LDHs obtained in example 3, carrying out ion exchange on ruthenium ions and a magnesium-aluminum layered composite hydroxide precursor, stirring for 12h at 50 ℃, filtering and washing; after ion exchange is finished, the mixture is placed in a muffle furnace for roasting, and the temperature is increased to 550 ℃ at the speed of 2 ℃/min for roasting for 4h to obtain RuO₂/MgO-Al₂O₃(Mg/Al ═ 5) catalyst.

Example 11

The preparation of the magnesium-aluminum layered composite hydroxide precursor MgAl-LDHs is repeated according to the processes of the embodiments 1 to 3, and then 1.98g of MgAl-LDHs precursor obtained in the embodiment 3 is weighed; weighing 10mL of rhodium chloride solution with rhodium ion concentration of 0.0029mmol/mL, dissolving and stirring, adding MgAl-LDHs precursor obtained in example 3, carrying out ion exchange on rhodium ions and a magnesium-aluminum layered composite hydroxide precursor, stirring for 12h at 50 ℃, filtering and washing; after ion exchange is finished, placing the mixture in a muffle furnace for roasting, raising the temperature to 550 ℃ at the speed of 2 ℃/min for roasting for 4h to obtain Rh₂O₃/MgO-Al₂O₃(Mg/Al ═ 5) catalyst.

Example 12

The embodiment provides a high-dispersion low-loading high-activity biogas double reforming catalyst IrO₂/MgO-Al₂O₃The preparation process comprises the following steps:

weighing MgAl-LDHs1.98g of the precursor of the magnesium-aluminum layered composite hydroxide obtained in the embodiment 3; weighing 10mL of iridium chloride solution with iridium ion concentration of 0.0067mmol/mL, dissolving and stirring, adding MgAl-LDHs obtained in example 3, performing ion exchange on iridium ions and a magnesium-aluminum layered composite hydroxide precursor, stirring for 12h at 50 ℃, filtering and washing; after ion exchange is finished, the mixture is placed in a muffle furnace for roasting, and the temperature is increased to 550 ℃ at the speed of 2 ℃/min for roasting for 4h to obtain IrO₂/MgO-Al₂O₃(Mg/Al ═ 5) catalyst.

Example 13

The embodiment provides a high-dispersion low-loading high-activity biogas double-reforming catalyst Co₃O₄/MgO-Al₂O₃The preparation process comprises the following steps:

weighing MgAl-LDHs1.98g of the precursor of the magnesium-aluminum layered composite hydroxide obtained in the embodiment 3; weighing 10mL of cobalt chloride solution with cobalt ion concentration of 0.0154mmol/mL, dissolving and stirring, adding MgAl-LDHs obtained in example 3, performing ion exchange on cobalt ions and a magnesium-aluminum layered composite hydroxide precursor, stirring for 12h at 50 ℃, filtering and washing; after ion exchange is finished, placing the mixture in a muffle furnace for roasting, raising the temperature to 550 ℃ at the speed of 2 ℃/min for roasting for 4h to obtain Co₃O₄/MgO-Al₂O₃(Mg/Al ═ 5) catalyst.

Example 14

The embodiment provides a high-dispersion low-loading high-activity biogas double-reforming catalyst NiO/MgO-Al₂O₃The preparation process comprises the following steps:

weighing MgAl-LDHs1.98g of the precursor of the magnesium-aluminum layered composite hydroxide obtained in the embodiment 3; weighing 10mL of nickel chloride solution with nickel ion concentration of 0.0154mmol/mL, dissolving and stirring, adding MgAl-LDHs obtained in example 3, performing ion exchange on nickel ions and a magnesium-aluminum layered composite hydroxide precursor, stirring for 12h at 50 ℃, filtering and washing; after ion exchange is finished, the mixture is placed in a muffle furnace for roasting, and the temperature is raised to 550 ℃ at the speed of 5 ℃/minRoasting for 4h to obtain NiO/MgO-Al₂O₃(Mg/Al ═ 5) catalyst.

Performance testing

(a) characterization

The MO prepared in the above example was subjected to the following procedures_x/AO-B₂O₃And characterizing the catalyst and a precursor M/MgAl-LDHs thereof.

1) X-ray diffraction pattern (XRD): as shown in fig. 1.

FIG. 1 is an XRD of the M/MgAl-LDHs catalysts obtained in examples 6-14, wherein the patterns of the magnesium-aluminum layered composite hydroxide after different active metal centers are introduced are respectively given, and the diffraction peaks of the magnesium-aluminum layered composite hydroxide are consistent with those of a standard card.

2) X-ray fluorescence spectrum (XRF): as shown in table 2.

Table 2 shows MO obtained in examples 6 to 14_x/AO-B₂O₃XRF of the catalyst, elemental analysis was performed using a wavelength dispersive X-ray fluorescence spectrometer (axioms max petri, netherlands panalytical v.b.). And determining the types and the contents of the trace elements in the catalyst.

TABLE 2 elemental composition table for catalysts in examples 6-14

(II) catalytic Activity

The activity evaluation of the catalyst prepared in the above example was carried out on an atmospheric fixed bed reactor. Before the activity test, the catalyst MO is firstly used_x/AO-B₂O₃(40-60 mesh, 200mg) in 10% H₂/N₂Pre-reduction activation treatment is carried out on the atmosphere (M/AO-B is obtained after reduction)₂O₃) The reduction temperature is 750 ℃, the reduction time is 1h, and the mass space velocity WHSV is 30600 mL.h^-1·g_cat ^-1，nCH₄:nCO₂:nH₂O:nN₂3: 2: 2.5: 1. the reacted gas was detected by on-line gas chromatography (Panuo, A60).

Test conditions: normal pressure, mass space velocity WHSV is 30,600mL h^-1·g_cat ^-1The test temperature interval is 600-800 ℃, the temperature interval is 50 ℃, the temperature rise rate is controlled to l0 ℃/min by adopting a temperature programming technology, each temperature point is kept for 1h, and the catalyst activity is CH₄Conversion (X)_CH4) And CO₂Conversion (X)_CO2) And (4) showing. X_CH4＝([CH₄]_in-[CH₄]_out)/[CH₄]_in100% of formula [ CH ]₄]_inAnd [ CH₄]_outRespectively as CH in raw material gas and reaction tail gas₄The content of (A); x_CO2＝([CO₂]_in-[CO₂]_out)/[CO₂]_in100% of formula (I), wherein [ CO ]₂]_inAnd [ CO ]₂]_outRespectively being CO in raw material gas and reaction tail gas₂The content of (a).

The test results are shown in Table 3.

TABLE 3 catalysis results of catalysts prepared in examples 6-14 at different temperatures

As can be seen from Table 3, CH increases with increasing temperature₄、CO₂With increasing conversion of H₂the/CO molar ratio decreases. The partial catalyst catalyzes methane carbon dioxide dry-wet double reforming at 750-800 ℃ with methane conversion rate of 85-98% and carbon dioxide conversion rate of 55-65%, and has high catalytic activity. The molar ratio of hydrogen to carbon monoxide in the obtained synthesis gas is close to 2 (1.97-2.09), and the subsequent direct preparation of methanol is facilitated. The preferred catalyst is example 10.

(III) catalyst stability

The stability of the catalysts prepared in examples 10 and 14 was tested: the activity evaluation of the catalyst prepared in the above example was carried out on an atmospheric fixed bed reactor. Before the activity test, the catalyst MO is firstly used_x/AO-B₂O₃(40-60 mesh, 200mg) in10％H₂/N₂Pre-reduction activation treatment is carried out on the atmosphere (M/AO-B is obtained after reduction)₂O₃) The reduction temperature is 750 ℃, the reduction time is 1h, the temperature rise rate is controlled to l0 ℃/min by adopting a temperature programming technology, and the temperature rises to 800 ℃ after reduction. Mass space velocity WHSV 30600mL h^-1·g_cat ^-1，nCH₄:nCO₂:nH₂O:nN₂3: 2: 2.5: 1. the reacted gas was detected by on-line gas chromatography (Panuo, A60).

And (3) testing conditions are as follows: normal pressure, mass space velocity WHSV is 30,600mL h^-1·g_cat ^-1The test temperature was maintained at 800 ℃. CH for catalyst activity₄Conversion (X)_CH4) And CO₂Conversion (X)_CO2) And (4) showing. X_CH4＝([CH₄]_in-[CH₄]_out)/[CH₄]_in100% of formula [ CH ]₄]_inAnd [ CH₄]_outRespectively as CH in raw material gas and reaction tail gas₄The content of (A); x_CO2＝([CO₂]_in-[CO₂]_out)/[CO₂]_in100% of formula (I), wherein [ CO ]₂]_inAnd [ CO ]₂]_outRespectively being CO in raw material gas and reaction tail gas₂The content of (a).

The test results are shown in fig. 2, fig. 3 and table 4.

TABLE 4800 ℃ catalysis results of 45 hours catalyzed by the catalysts prepared in examples 10 and 14

As is clear from Table 4, FIGS. 2 and 3, the stability of examples 10 and 14 was 40 hours or more at a test temperature of 800 ℃. Hydrogen to carbon ratio (i.e. H)₂the/CO) is about 2, and is suitable for preparing the biological methanol; also, example 10 exhibited a higher CH₄Conversion (90%) and CO₂Conversion (50%).

Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications are therefore intended to be included within the scope of the invention as claimed.