CN113398947A - Catalyst for chemical chain methane oxidation coupling reaction and preparation method and application thereof - Google Patents

Abstract

The invention discloses a catalyst for chemical chain methane oxidation coupling reaction and a preparation method and application thereof. The catalyst consists of manganese composite oxide and sodium tungstate, and has the following structural general formula: a-Na₂WO₄/b‑MnMO_xWherein: MnMO_xRepresents a manganese composite oxide; m represents a non-manganese element selected from the group consisting of titanium, iron, cobalt, nickel, lithium, silicon, lead, tin, germanium, gallium, antimony, bismuth, tellurium, selenium,At least one of zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, barium, magnesium, cerium, lanthanum, praseodymium, neodymium, samarium, calcium, strontium, barium, potassium, sodium, and lithium; a and b represent Na respectively₂WO₄And MnMO_xThe catalyst comprises 100 parts by mass of the catalyst, wherein the value range of a is 5-15, and a + b is 100. The catalyst disclosed by the invention has the advantages of high lattice oxygen content, high activity, high selectivity and good reaction-regeneration cycle performance.

Description

Catalyst for chemical chain methane oxidation coupling reaction and preparation method and application thereof

Technical Field

The invention relates to a catalyst, a preparation method and application thereof, in particular to a catalyst for chemical chain methane oxidation coupling reaction, a preparation method and application thereof, and belongs to the technical field of catalysis.

Background

Olefins (e.g., ethylene) are important chemical feedstocks and methane is considered a desirable feedstock for the production of ethylene due to its large reserves and low cost. There are processes for producing olefins from methane, such as the Bensen process, the partial oxidation process, and the catalytic pyrolysis process (Liaoning chemical, 1985,1, 11). Because the traditional Bensen method has a byproduct of chlorohydrocarbon, which causes certain difficulty in separation, and the catalytic pyrolysis method can generate a large amount of carbon deposition, which seriously influences the stability and the service life of the catalyst, the methane oxidation coupling method becomes the main research direction for preparing the olefin at present.

In the traditional oxidative coupling reaction (OCM) of methane, methane and oxygen are simultaneously introduced into a reactor according to a certain proportion, under the conditions of high temperature and existence of a catalyst, a part of methane reacts with the catalyst to generate methyl free radicals, and the methyl free radicals are coupled and dehydrogenated to generate ethylene. However, in this process, since methane coexists with oxygen, free oxygen has high activity at high temperature, resulting in deep oxidation of ethylene, and thus low selectivity and yield of olefins. In addition, the existence of methane and oxygen in high-temperature environment has explosion risk, which greatly limits the industrial development.

Compared with the traditional mode, the chemical chain can separate the methane oxidative coupling from the reaction of the mixed gas hidden with huge explosion risks into two independent and safer oxidation-reduction series reactions, thereby greatly reducing the possibility of explosion risks. The process operation of the chemical chain mode can effectively solve the safety problem, and the core of the process of constructing the high-efficiency chemical chain methane oxidation coupling reaction (CL-OCM) lies in the breakthrough improvement of the oxygen storage capacity of the selective crystal lattice of the catalyst. Only by synchronously improving the process operation and the catalyst performance, the problems of safety and production can be simultaneously solved, and the win-win of process safety and high-efficiency catalysis is realized. Literature [ chem.Eng.J.,2016,306:646-]Reports the conventional ratio of 2Mn of methane oxidative coupling catalyst₂O₃-5Na₂WO₄/SiO₂The catalyst is used for the CL-OCM reaction process, although better conversion rate and selectivity can be obtained, and the fact that methane on the catalyst can be selectively oxidized and coupled by lattice oxygen is proved to realize the CL-OCM reaction process based on the lattice oxygen oxidation mechanism, the dosage of the catalyst is 1 g, the pulse volume of the methane is 1 ml, the conversion ratio of alkane (mass ratio) is about 1350, and the alkane ratio is very large, so that the selective lattice oxygen amount available for reaction in the catalyst is very small, and the catalyst is inactivated after about 10 chemical cycles. Literature [ ACS Energy Lett.2018,3,1730-]Reporting lithium doped Mg₆MnO₈The catalyst is used in the CL-OCM reaction process, although the available lattice oxygen content is greatly improved, the hydrocarbon selectivity can be only 50%, which shows that the deep oxidation degree is very serious, and the selectivity is not enough to meet the industrial requirement. Patent CN201811254599 discloses MnO₂-Na₂WO₄/SiO₂The catalyst for coupling by chemical chain methane oxidation has a reduced alkane ratio of about 150 compared with the two works mentioned above, but has a industrial treatment capacity of 50000m for raw material methane³For the production plant of/d, the quantity of catalyst required to be recycled is 5000 tons per day, which means that the reactor required is very bulky, indicating the high activity and selectivity of the existing catalystsThe content of lattice oxygen is far from the requirement of industrial production, and has no industrial application value.

In summary, although research on CL-OCM is being conducted, the core problem is very prominent, i.e. the content of lattice oxygen with high activity and high selectivity of the catalyst is not improved in a breakthrough manner.

Disclosure of Invention

Aiming at the problems in the prior art, the invention aims to provide a catalyst for chemical chain methane oxidation coupling reaction, which has high activity, high selectivity, high lattice oxygen content and good reaction-regeneration cycle performance, and a preparation method and application thereof.

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

a catalyst for the oxidizing and coupling reaction of chemical chain methane is prepared from the composite Mn-O (MnMO)_x) And sodium tungstate (Na)₂WO₄) The composition has the following structural general formula: a-Na₂WO₄/b-MnMO_xWherein: MnMO_xRepresents a manganese composite oxide; m represents a non-manganese element selected from at least one of titanium, iron, cobalt, nickel, lithium, silicon, lead, tin, germanium, gallium, antimony, bismuth, tellurium, selenium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, barium, magnesium, cerium, lanthanum, praseodymium, neodymium, samarium, calcium, strontium, barium, potassium, sodium, and lithium; a and b represent Na respectively₂WO₄And MnMO_xThe catalyst comprises 100 parts by mass of the catalyst, wherein the value range of a is 5-15, and a + b is 100%.

In a preferred embodiment, the manganese composite oxide (MnMO)_x) Has a perovskite structure and/or a spinel structure.

In a preferred embodiment, the manganese composite oxide (MnMO)_x) Selected from the group consisting of manganese titanate, manganese ferrite, manganese cobaltate, manganese nickelate, sodium manganate, lithium manganate, manganese silicate, manganese metasilicate, manganese nickel cobalt manganate, manganese plumbate, manganese stannate, manganese germanate, manganese gallate, manganese antimonate, manganese bismuthate, manganese tellurate, manganese selenate, manganese zirconate, manganese hafnate, manganese vanadate, manganese niobate, manganese tantalate, manganese chromate, manganese molybdate, manganese tungstate, iron manganite, manganese manganous manganate, manganese molybdate, manganese tungstate, manganese titanate, manganeseBarium sulfate, magnesium manganese sulfate, cerium manganate, La_0.5Sr_0.5Mn_1-mFe_mO₃、Ca_αLa_βK_1-α-βMn_0.5Fe_0.5O₃、Ca_pLa_qK_{1-p- q}Mn_0.78Fe_0.22O₃、Bi_0.5Ca_0.5-nLa_nFe_0.3Mn_0.7O₃At least one of, wherein: 0<m≤0.25，0<α≤0.25，0<β≤0.25，0<p≤0.25，0<q≤0.25，0<n≤0.25。

In a preferred embodiment, the manganese composite oxide (MnMO)_x) Has a general formula of LnAFeMnO₆Wherein: ln is selected from any one of La, Pr, Nd, Sm and Ce; a is selected from any one of Ca, Sr and Ba.

A method for preparing the catalyst comprises the following steps:

a) mixing an aqueous solution of sodium tungstate with a manganese composite oxide (MnMO)_x) Mixing uniformly to obtain slurry sticky matter;

b) drying the slurry sticky matter at 80-150 ℃;

c) and roasting the dried sample for 1-5 hours at 700-1500 ℃ in an air atmosphere to obtain the catalyst.

The catalyst for the chemical chain methane oxidation coupling reaction is prepared with the catalyst alpha-Na₂WO₄/b-MnMO_xAnd the adhesive is composed of the following structural general formula: c [ a-Na ]₂WO₄/b-MnMO_x]-dZJJ, wherein: c and d represent catalysts a to Na, respectively₂WO₄/b-MnMO_xAnd the binder ZJJ in 100 parts by mass of the molded catalyst, wherein the value of c is 85-98%, and c + d is 100%.

In a preferred embodiment, the bonding agent ZJJ is selected from SiO₂Sols and TiO₂At least one of sols.

The method for preparing the formed catalyst is an extrusion molding method and comprises the following steps:

1) catalyst a-Na₂WO₄/b-MnMO_xMixing with adhesive ZJJ in the hopper of extrusion molding machine, extruding and molding to obtain wet catalyst material;

2) drying the wet formed catalyst material prepared in the step 1) at 80-150 ℃ to obtain a dry formed catalyst material;

3) roasting the formed catalyst dry material obtained in the step 2) for 1-5 hours at 700-1000 ℃ in an air atmosphere to obtain the formed catalyst.

The preparation method of the shaped catalyst is a spray forming method and comprises the following steps:

A) catalyst a-Na₂WO₄/b-MnMO_xMixing with adhesive ZJJ and water, and homogenizing to obtain emulsion-like uniform viscous substance;

B) spray drying and forming the emulsion-shaped uniform sticky substance prepared in the step A) by a spray dryer to obtain a spray forming catalyst;

C) roasting the spray-formed catalyst obtained in the step B) for 1-5 hours at 700-1000 ℃ in an air atmosphere to obtain the formed catalyst.

One application of the catalyst of the invention is as a catalyst for chemical chain methane oxidation coupling reaction.

One application of the shaped catalyst of the invention is as a catalyst for chemical chain methane oxidation coupling reaction.

In a preferred scheme, the temperature of the chemical chain methane oxidation coupling reaction is 750-850 ℃.

In a preferred embodiment, the mass ratio of the catalyst to methane (i.e., the alkane ratio) in the chemical chain methane oxidation coupling reaction is 5-20.

In a preferable scheme, the residence time of methane molecules in the catalyst bed layer in the chemical chain methane oxidation coupling reaction is 5-15 seconds.

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

experiments show that: the catalyst provided by the invention has high lattice oxygen content, and is not used in the chemical chain methane oxidation coupling reactionOnly realizes the separation of methane and gas-phase oxygen to avoid explosion risks, realizes the selective regulation of lattice oxygen in an oxygen storage body, weakens the deep oxidation of methane, and ensures that the reaction for preparing olefin by chemical chain methane oxidation coupling can obtain economic methane conversion rate (16-30%) and C under the conditions of shorter retention time (5-15 seconds), lower alkane ratio (5-20) and lower reaction temperature (750-850℃)₂-C₃The selectivity is 75-84%, the content of olefin in the product is high, and the catalyst has the advantages of high activity, high selectivity and good reaction-regeneration cycle performance and is an excellent catalyst for the chemical chain methane oxidation coupling reaction. In addition, the preparation method is simple, the raw materials are easy to obtain, the cost is low, the controllability is strong, and the large-scale production is easy to realize.

Drawings

FIG. 1 shows 6.5Na prepared in example 1₂WO₄/93.5FeMnO₃An X-ray diffraction pattern of the catalyst;

FIG. 2 shows 10-Na prepared in example 2₂WO₄/90-FeMnO₃An X-ray diffraction pattern of the catalyst;

FIG. 3 shows 6.5-Na prepared in example 3₂WO₄/93.5-Fe_0.8Mn_1.2O₃An X-ray diffraction pattern of the catalyst;

FIG. 4 shows 6.5-Na prepared in example 4₂WO₄/93.5-Fe_1.4Mn_0.6O₃An X-ray diffraction pattern of the catalyst;

FIG. 5 shows 6-Na prepared in example 5₂WO₄/94-MnFe₂O₄An X-ray diffraction pattern of the catalyst;

FIG. 6 shows 5-Na prepared in example 6₂WO₄/95-Mn₇SiO₁₂An X-ray diffraction pattern of the catalyst;

FIG. 7 shows 15-Na prepared in example 7₂WO₄/85-MnSiO₃An X-ray diffraction pattern of the catalyst;

FIG. 8 shows 95[6.5-Na ] prepared in example 8₂WO₄/93.5-FeMnO₃]-5ZJJ X-ray of shaped catalystA diffraction pattern;

FIG. 9 shows 85[6.5-Na ] prepared in example 9₂WO₄/93.5-Fe_0.8Mn_1.2O₃]-15X-ray diffraction pattern of 15ZJJ shaped catalyst;

FIG. 10 shows 2Mn as prepared in comparative example 1₂O₃-5Na₂WO₄/93SiO₂An X-ray diffraction pattern of the catalyst;

fig. 11 is a calculation result of the lattice oxygen utilization ratio and the lattice oxygen utilization efficiency of the catalyst of example 1 and the catalyst of comparative example 3;

FIG. 12 is the results of methane conversion and product selectivity for the shaped catalyst of example 9 tested in 50 reaction-regeneration cycles of chemical chain methane oxidation coupling;

figure 13 is an X-ray diffraction (XRD) pattern of the shaped catalyst of example 9 after the 50 th reaction-regeneration cycle test.

Detailed Description

The technical scheme of the invention is further detailed and completely explained by combining the embodiment, the comparative example and the application example.

In the present application, the methane conversion and product selectivity are calculated by carbon atom normalization, which is specifically defined as:

the conversion rate is [ 1-the concentration of methane in the tail gas/(the concentration of methane in the tail gas + the concentration of CO in the tail gas)₂Concentration +2 × total concentration of ethylene and ethane in tail gas +3 × total concentration of propylene and propane in tail gas)]×100％；

Selectivity [ ∑ n × olefin and paraffin concentration in tail gas/(CO concentration in tail gas + CO in tail gas)₂Concentration +2 × total concentration of ethylene and ethane in tail gas +3 × total concentration of propylene and propane in tail gas)]X 100%, where n is the number of carbon atoms in the product.

The utilization rate and utilization efficiency of the catalyst lattice oxygen are calculated by adopting an oxygen element conservation method, and are specifically defined as follows:

the utilization rate of the catalyst lattice oxygen (total amount of lattice oxygen consumed by methane conversion/theoretical amount of lattice oxygen that the catalyst can be consumed) × 100%;

catalyst lattice oxygen utilization efficiency ═ AConversion of alkane to produce the target product C₂-C₃The amount of lattice oxygen consumed/total amount of lattice oxygen consumed by methane conversion). times.100%.

Example 1

Preparation of catalyst for chemical chain methane oxidation coupling reaction: 6.5-Na₂WO₄/93.5-FeMnO₃：

1) 10 g of ferric manganate FeMnO was weighed₃Powder is moved into an agate mortar to be fully ground for standby; 0.78 g of sodium tungstate dihydrate (Na) was weighed out₂WO₄·2H₂O) is dissolved in 7 ml of deionized water to prepare sodium tungstate aqueous solution, and then the sodium tungstate aqueous solution is dripped into the ferric manganese FeMnO₃Fully grinding the powder to uniformly mix the powder to obtain slurry-like sticky matter;

2) drying the sample obtained in the step 2) at 100 ℃;

3) roasting the sample obtained in the step 3) for 3 hours at 900 ℃ in an air atmosphere to obtain the catalyst.

FIG. 1 is an X-ray powder diffraction (XRD) pattern of the catalyst prepared in this example, as seen from FIG. 1, in which FeMnO was contained in the catalyst prepared in this example₃And Na₂WO₄Two phases.

The present embodiment may also make the following evolution:

in step 1), FeMnO₃Alternative materials are manganese titanate, manganese cobaltate, manganese nickelate, sodium manganate, lithium manganate, manganese silicate, manganese metasilicate, lithium nickel cobalt manganate, manganese ferrite, manganese plumbate, manganese stannate, manganese germanate, manganese gallate, manganese antimonate, manganese bismuthate, manganese tellurate, manganese selenate, manganese zirconate, manganese hafnate, manganese vanadate, manganese niobate, manganese tantalate, manganese chromate, manganese molybdate, manganese tungstate, barium manganate, magnesium manganate, cerium manganate, LnAFeMn O₆(Ln＝La,Pr,Nd,Sm,Ce；A＝Ca,Sr,Ba)、La_0.5Sr_0.5Mn_1-mFe_mO₃、Ca_αLa_βK_1-α-βMn_0.5Fe_0.5O₃、Ca_pLa_qK_1-p-qMn_0.78Fe_0.22O₃、Bi_0.5Ca_0.5-nLa_nFe_0.3Mn_0.7O₃At least one of (1), wherein 0<m≤0.25，0<α≤0.25，0<β≤0.25，0<p≤0.25，0<q≤0.25，0<n is less than or equal to 0.25, and the rest conditions are unchanged.

In the step 2), the drying temperature can be any value within the range of 80-150 ℃, and the rest conditions are unchanged.

In the step 3), the roasting temperature can be any value within the range of 700-1500 ℃, and the rest conditions are unchanged.

In the step 3), the roasting time can be any value within the range of 1-5 hours, and the rest conditions are unchanged.

Example 2

Preparation of catalyst for chemical chain methane oxidation coupling reaction: 10-Na₂WO₄/90-FeMnO₃：

1) 9.63 g of iron manganate FeMnO was weighed₃Powder is moved into an agate mortar to be fully ground for standby; 1.2 g of sodium tungstate dihydrate (Na) was weighed₂WO₄·2H₂O) is dissolved in 10 ml of deionized water to prepare sodium tungstate aqueous solution, and then the sodium tungstate aqueous solution is dripped into the ferric manganese FeMnO₃Fully grinding the powder to uniformly mix the powder to obtain slurry-like sticky matter;

2) drying the sample obtained in the step 2) at 100 ℃;

3) roasting the sample obtained in the step 3) for 5 hours at 1000 ℃ in an air atmosphere to obtain the catalyst.

FIG. 2 is an X-ray powder diffraction (XRD) pattern of the catalyst prepared in this example, from FIG. 2, it can be seen that the catalyst prepared in this example contains FeMnO₃And Na₂WO₄Two phases.

The present embodiment may also make the following evolution:

in step 1), FeMnO₃Can be replaced by manganese titanate, manganese cobaltate, manganese nickelate, manganese ferrite, sodium manganate, lithium manganate, manganese silicate, manganese metasilicate, nickel cobalt lithium manganate, manganese plumbate, manganese stannate, manganese germanate, manganese gallate, manganese antimonate, manganese bismuthate, manganese tellurate, manganese selenate, manganese zirconate, manganese hafnate, manganese vanadate, manganese niobate, manganese tantalate, manganese chromate, manganese molybdate, manganese tungstate, manganese manganate, manganese tungstate, manganeseBarium sulfate, magnesium manganese sulfate, cerium manganate, LnAFeMnO₆(Ln＝La,Pr,Nd,Sm,Ce；A＝Ca,Sr,Ba)、La_0.5Sr_0.5Mn_1-mFe_mO₃、Ca_αLa_βK_1-α-βMn_0.5Fe_0.5O₃、Ca_pLa_qK_1-p-qMn_0.78Fe_0.22O₃、Bi_0.5Ca_0.5-nLa_nFe_0.3Mn_0.7O₃At least one of (1), wherein 0<m≤0.25，0<α≤0.25，0<β≤0.25，0<p≤0.25，0<q≤0.25，0<n is less than or equal to 0.25, and the rest conditions are unchanged.

In the step 2), the drying temperature can be any value within the range of 80-150 ℃, and the rest conditions are unchanged.

In the step 3), the roasting temperature can be any value within the range of 700-1500 ℃, and the rest conditions are unchanged.

In the step 3), the roasting time can be any value within the range of 1-5 hours, and the rest conditions are unchanged.

Example 3

Preparation of catalyst for chemical chain methane oxidation coupling reaction: 6.5-Na₂WO₄/93.5-Fe_0.8Mn_1.2O₃：

1) Weighing 10 g of iron manganese ferrite_0.8Mn_1.2O₃Powder is moved into an agate mortar to be fully ground for standby; 0.78 g of sodium tungstate dihydrate (Na) was weighed out₂WO₄·2H₂O) is dissolved in 7 ml of deionized water to prepare sodium tungstate aqueous solution, and then the sodium tungstate aqueous solution is dropwise added into the ferric manganese Fe_0.8Mn_1.2O₃Fully grinding the powder to uniformly mix the powder to obtain slurry-like sticky matter;

2) drying the sample obtained in the step 2) at 150 ℃;

3) roasting the sample obtained in the step 3) for 3 hours at 950 ℃ in an air atmosphere to obtain the catalyst.

FIG. 3 is an X-ray powder diffraction (XRD) pattern of the catalyst prepared in this example, from FIG. 3, it can be seen that the catalyst prepared in this example contains Fe_0.8Mn_1.2O₃And Na₂WO₄Two phases.

Example 4

Preparation of catalyst for chemical chain methane oxidation coupling reaction: 6.5-Na₂WO₄/93.5-Fe_1.4Mn_0.6O₃：

1) Weighing 10 g of iron manganese ferrite_1.4Mn_0.6O₃Powder is moved into an agate mortar to be fully ground for standby; 0.78 g of sodium tungstate dihydrate (Na) was weighed out₂WO₄·2H₂O) is dissolved in 7 ml of deionized water to prepare sodium tungstate aqueous solution, and then the sodium tungstate aqueous solution is dropwise added into the ferric manganese Fe_1.4Mn_0.6O₃Fully stirring the powder to uniformly mix the powder to obtain slurry-like sticky matter;

2) drying the sample obtained in the step 2) at 150 ℃;

3) roasting the sample obtained in the step 3) for 3 hours at 950 ℃ in an air atmosphere to obtain the catalyst.

FIG. 4 is an X-ray powder diffraction (XRD) pattern of the catalyst prepared in this example, from FIG. 4, it can be seen that the catalyst prepared in this example contains Fe_1.4Mn_0.6O₃And Na₂WO₄Two phases.

Example 5

Preparation of catalyst for chemical chain methane oxidation coupling reaction: 6-Na₂WO₄/94-MnFe₂O₄：

1) Weighing 10 g of manganese ferrite MnFe₂O₄Powder is moved into an agate mortar to be fully ground for standby; 0.72 g of sodium tungstate dihydrate (Na) was weighed out₂WO₄·2H₂O) is dissolved in 7 ml of deionized water to prepare sodium tungstate aqueous solution, and then the sodium tungstate aqueous solution is dropwise added into the manganese ferrite MnFe₂O₄Fully stirring the powder to uniformly mix the powder to obtain slurry-like sticky matter;

2) drying the sample obtained in the step 2) at 150 ℃;

3) roasting the sample obtained in the step 3) for 3 hours at 950 ℃ in an air atmosphere to obtain the catalyst.

FIG. 5 is an X-ray powder diffraction (XRD) pattern of the catalyst prepared in this example, from FIG. 5, it can be seen that the catalyst prepared in this example contains (Fe-Mn) O₃、Mn₂O₃、Fe₂O₃And Na₂WO₄A plurality of phases.

Example 6

Preparation of catalyst for chemical chain methane oxidation coupling reaction: 5-Na₂WO₄/95-Mn₇SiO₁₂：

1) Weighing 10 g of manganese silicate Mn₇SiO₁₂Powder is moved into an agate mortar to be fully ground for standby; 0.6 g of sodium tungstate dihydrate (Na) was weighed out₂WO₄·2H₂O) is dissolved in 7 ml of deionized water to prepare sodium tungstate aqueous solution, and then the sodium tungstate aqueous solution is dropwise added to the manganese silicate Mn₇SiO₁₂Fully grinding the powder to uniformly mix the powder to obtain slurry-like sticky matter;

2) drying the sample obtained in the step 2) at 150 ℃;

3) roasting the sample obtained in the step 3) for 3 hours at 700 ℃ in an air atmosphere to obtain the catalyst.

FIG. 6 is an X-ray powder diffraction (XRD) pattern of the catalyst prepared in this example, from FIG. 6, it can be seen that the catalyst prepared in this example contains Mn₇SiO₁₂、Na₂WO₄And SiO₂Three phases.

Example 7

Preparation of catalyst for chemical chain methane oxidation coupling reaction: 15-Na₂WO₄/85-MnSiO₃：

1) Weighing 10 g of manganese metasilicate MnSiO₃Powder is moved into an agate mortar to be fully ground for standby; 2.0 g of sodium tungstate dihydrate (Na) was weighed out₂WO₄·2H₂O) is dissolved in 15 ml of deionized water to prepare sodium tungstate aqueous solution, and then the sodium tungstate aqueous solution is dripped into the manganese metasilicate MnSiO₃Fully grinding the powder to uniformly mix the powder to obtain slurry-like sticky matter;

2) drying the sample obtained in the step 2) at 90 ℃;

3) roasting the sample obtained in the step 3) for 1 hour at 900 ℃ in an air atmosphere to obtain the catalyst.

FIG. 7 is an X-ray powder diffraction (XRD) pattern of the catalyst prepared in this example, from FIG. 7, it can be seen that the catalyst prepared in this example contains SiO₂，Mn₇SiO₁₂And Na₂WO₄A phase.

Example 8

Preparation of shaped catalyst 95[6.5-Na ] for chemical chain methane Oxidation coupling reaction₂WO₄/93.5-FeMnO₃]-5ZJJ：

1) 190 g of 6.5-Na prepared by the method of example 1 were weighed₂WO₄/93.5-FeMnO₃Transferring the catalyst powder into a hopper of an extrusion molding machine, adding 33.3 g of 30 wt% silica sol into the catalyst powder at room temperature, fully and uniformly mixing, and performing extrusion molding to obtain a molded catalyst wet material;

2) drying the wet formed catalyst material prepared in the step 1) in an oven at 100 ℃ to obtain a dry formed catalyst material;

3) and (3) roasting the dry material of the formed catalyst obtained in the step 2) for 2 hours at 800 ℃ in an air atmosphere to obtain the formed catalyst.

FIG. 8 is an X-ray powder diffraction (XRD) pattern of the shaped catalyst comprising FeMnO as shown in FIG. 8 prepared in this example₃、Na₂WO₄、SiO₂And TiO₂A phase.

The present embodiment may also make the following evolution:

in step 1), the catalyst is 6.5-Na₂WO₄/93.5-FeMnO₃Catalysts a-Na which were prepared by other examples may be substituted₂WO₄/b-MnMO_xThe other conditions were unchanged.

In the step 1), the amount of the 30 wt% silica sol can be any value within the range of 13.3-100 g, and the rest conditions are unchanged.

In step 1), the silica sol may be TiO₂Sol and the rest conditions are unchanged.

In step 1), the silica sol may be SiO₂And TiO₂The remaining conditions were unchanged.

In the step 2), the drying temperature can be any value within the range of 80-150 ℃, and the rest conditions are unchanged.

In the step 3), the roasting temperature can be any value within the range of 700-1000 ℃, and the rest conditions are unchanged.

In the step 3), the roasting time can be any value within the range of 1-5 hours, and the rest conditions are unchanged.

Example 9

Preparation of shaped catalyst 85[6.5-Na ] for chemical chain methane Oxidation coupling reaction₂WO₄/93.5-Fe_0.8Mn_1.2O₃]-15ZJJ：

1) 425 g of 6.5-Na prepared by the method of example 3 were weighed₂WO₄/93.5-Fe_0.8Mn_1.2O₃Catalyst powder, at room temperature, with 125 g of 30% by weight silica sol, 187.5 g of 20% by weight TiO₂Mixing the sol with 1762.5 g of deionized water, and fully homogenizing by an ultrasonic homogenizer to generate a latex-like uniform viscous substance with the solid content of 20 wt%;

2) conveying the emulsion-shaped uniform sticky substance prepared in the step 1) to a spray dryer QFN-8000T through a feed pump, and performing spray drying and forming through the spray dryer;

3) roasting the spray-formed catalyst obtained in the step 2) for 2 hours at 950 ℃ in an air atmosphere to obtain the formed catalyst.

FIG. 9 is an X-ray powder diffraction (XRD) pattern of the shaped catalyst of this example, which contains FeMnO as seen in FIG. 9₃、Na₂WO₄、SiO₂And TiO₂A phase.

Comparative example 1

According to the document [ chem. Eng. J.,2016,306:646-]Preparation method of (1), preparation of comparative catalyst: 2Mn₂O₃-5Na₂WO₄/93SiO₂：

1) 5 g of SiO are weighed₂Placing the powder in a mortar; 0.11 g of Mn was weighed₂O₃Powder and SiO₂Mixing the powder, and fully and uniformly grinding the mixed powder in a mortar;

2) 0.29 g of sodium tungstate dihydrate is weighed into a 10 ml small beaker, 5 g of deionized water is added, the mixture is fully stirred until the sodium tungstate is completely dissolved, and then the mixture is dropwise added into the Mn₂O₃With SiO₂Continuously and fully grinding the mixed powder to obtain slurry sticky matter;

3) drying the slurry sticky matter obtained in the step 2) at 100 ℃, and calcining the dried slurry sticky matter for 3-4 hours at 1000 ℃ in an air atmosphere to obtain the catalyst of the comparative example.

FIG. 10 is an X-ray powder diffraction (XRD) pattern of a comparative catalyst prepared in this example, from FIG. 10, containing Mn₂O₃、Na₂WO₄And SiO₂Three phases.

Comparative example 2

According to the literature [ Sci.adv.,2017,3: e1603180]Preparation method of (1), preparation of comparative catalyst: 2Mn₂O₃-5Na₂WO₄-3TiO₂/90SiO₂：

1) 4.8 g of SiO were weighed out separately₂Powder, 0.11 g Mn₂O₃Powder and 0.2 g TiO₂Putting the powder into a mortar and fully grinding the powder to be uniformly mixed;

2) weighing 0.29 g of sodium tungstate dihydrate into a 10 ml small beaker, adding 5 g of deionized water, fully stirring until the sodium tungstate is completely dissolved, then dropwise adding the mixture into the uniform mixed powder, and continuously fully grinding to obtain a slurry sticky matter;

3) drying the slurry sticky matter obtained in the step 2) at 100 ℃, and calcining the dried slurry sticky matter for 3-4 hours at 800 ℃ in an air atmosphere to obtain the catalyst of the comparative example.

Comparative example 3

Preparation of comparative catalyst: 6.5Na₂WO₄-46.8Mn₂O₃/46.7SiC：

1) 5 g of Mn are weighed out separately₂O₃Powder and 5 g SiC powder (substituted MnMO)_xOf the corresponding part in the composite oxideMO_x) Fully grinding and then putting into a 250 ml beaker;

2) 0.78 g of sodium tungstate dihydrate (Na) was weighed out₂WO₄·2H₂O) dissolving in 35 ml of deionized water to prepare sodium tungstate aqueous solution, and then carrying out incipient wetness impregnation on the sodium tungstate aqueous solution in the uniform mixture obtained in the step 1) to obtain slurry-like sticky matter;

3) drying the slurry-like sticky substance obtained in the step 2) at 100 ℃ for 3 hours, and grinding the dried slurry-like sticky substance into uniform powder;

4) roasting the uniform powder obtained in the step 3) for 3 hours at 1000 ℃ in an air atmosphere to obtain the catalyst of the comparative example.

Comparative example 4

Preparation of comparative catalyst: 6.5Na₂WO₄-46.8Fe₂O₃/46.7SiC：

1) 5 g of Fe are weighed out separately₂O₃Powder and 5 g SiC powder (substituted MnMO)_xMn of the corresponding portion in the composite oxide₂O₃) Fully grinding and then putting into a 250 ml beaker;

2) 0.78 g of sodium tungstate dihydrate (Na) was weighed out₂WO₄·2H₂O) dissolving in 35 ml of deionized water to prepare sodium tungstate aqueous solution, and then carrying out incipient wetness impregnation on the sodium tungstate aqueous solution in the uniform mixture obtained in the step 1) to obtain slurry-like sticky matter;

3) drying the slurry-like sticky substance obtained in the step 2) at 100 ℃ for 3 hours, and grinding the dried slurry-like sticky substance into uniform powder;

4) roasting the uniform powder obtained in the step 3) for 3 hours at 1000 ℃ in an air atmosphere to obtain the catalyst of the comparative example.

Application example

The purpose of the application example was to examine the catalytic performance of the catalysts of the examples and comparative examples for the chemical chain methane oxidation coupling reaction. The catalyst reaction evaluation was performed on a continuous flow fixed bed microreaction device. A quartz tube reactor was used, having an inner diameter of 8 mm and a length of 700 mm. The tail gas after methane reaction is swept by helium gas and collected by a gas collecting bag, and CO are obtained₂、CH₄、C₂-C₃Separating with 5A molecular sieve and PLOT-U parallel capillary column (DIKMA)And quantitatively analyzed by a TCD detector.

Application example 1

The catalyst (1 g, 1 ml) was first pretreated as follows: introducing pure methane gas continuously at a flow rate of 10 ml/min for 7.5 minutes, purging with helium gas at a flow rate of 10 ml/min for 5 minutes, introducing oxygen gas at a flow rate of 10 ml/min for oxidation for 7.5 minutes, and repeating the above cycle for 5 times to stabilize the catalyst; then, under the reaction conditions reported in the literature [ chem.Eng.J.,2016,306:646-654], namely: the reaction temperature is 750-; the reaction results are shown in table 1.

TABLE 1 catalytic performance of catalysts of examples and comparative examples under the conditions of this application example for coupling reaction of chemical chain methane oxidation

As can be seen from table 1, the catalyst provided by the present invention has not only significantly improved activity, but also significantly improved selectivity, compared to the catalyst of comparative example 1 reported in the literature [ chem.eng.j.,2016,306: 646-.

Application example 2

Judging whether the catalyst is economical to be used in the chemical chain methane oxidation coupling reaction process, whether the catalyst can obtain high methane conversion rate and high product selectivity at a low catalyst-to-methane ratio needs to be considered. To test the reactivity of the catalysts of the invention at lower catalyst alkane ratios, the catalysts of the examples were tested under the following conditions: 1 g (about 1 ml) of catalyst, the reaction temperature is 750-; the catalyst is firstly pretreated as follows: pure methane gas was continuously fed at a flow rate of 10 ml/min for 7.5 minutes, purged with helium at a flow rate of 10 ml/min for 5 minutes, and then oxidized with oxygen at a flow rate of 10 ml/min for 7.5 minutes, and the above cycle was repeated 5 times to stabilize the catalyst, and the test results are shown in table 2.

Table 2 catalytic performance of the catalysts of the examples and comparative examples for the coupling reaction of chemical chain methane oxidation at a catalyst alkane ratio of 18

As can be seen from Table 2, when the catalyst of the embodiment of the invention is used for catalyzing the chemical chain methane oxidation coupling reaction, higher conversion rate and selectivity can be maintained at a lower alkane ratio; the catalysts of comparative examples 1 and 2 can only convert less than 1% of methane under the alkane ratio of 18 because the available lattice oxygen content is very low, which shows that the catalysts of the invention have high activity and high selectivity, and the lattice oxygen content is improved in a breakthrough manner; in addition, Mn is used₂O₃-Na₂WO₄The catalyst of comparative example 3, which is an active component, has poor selectivity although a high methane conversion rate can be obtained; with Fe₂O₃-Na₂WO₄The catalyst of comparative example 4, which is an active component, is poor in both activity and selectivity; in sharp contrast, with FeMnO₃-Na₂WO₄The catalyst of example 1 of the present invention, which is an active component, is not only high in activity but also good in selectivity; the single manganese oxide and the single iron oxide have no good catalytic effect, and the manganese-iron composite oxide is adopted in the invention, so that the prepared catalyst has unexpectedly high activity and selectivity.

FIG. 11 shows the lattice oxygen utilization and lattice oxygen utilization of the catalysts of example 1 and comparative example 3 of the present inventionThe calculation result of the efficiency is utilized. As can be seen from FIG. 11, Mn is the same as the theoretical oxygen storage amount₂O₃-Na₂WO₄Although the utilization rate of lattice oxygen is high, the utilization efficiency (corresponding to selectivity) of lattice oxygen is far lower than that of FeMnO₃-Na₂WO₄It indicates that methane is in Mn₂O₃-Na₂WO₄Deep oxidation is very severe, so although the oxygen utilization rate is high, most of the lattice oxygen is consumed by deep oxidation, resulting in poor selectivity. And FeMnO₃-Na₂WO₄The utilization efficiency of the lattice oxygen is obviously higher than that of Mn while the utilization efficiency of the lattice oxygen is kept higher₂O₃-Na₂WO₄Thus, high conversion and selectivity are obtained. This further illustrates the significant advances and unexpected results achieved by the present invention over the prior art.

Application example 3

The purpose of this application example was to investigate the effect of the alkane reagent on the catalytic performance of the inventive catalyst for chemical chain methane oxidation coupling reactions. Example 1 catalyst 1 g (-1 ml), reaction temperature 800 ℃, methane 75, 100, 150 ml was fed to the catalyst at a flow rate of 10 ml/min, helium purge flow rate 10 ml/min, i.e. catalyst to alkane ratio 18, 13.5, 9, residence time all 6 seconds. The catalyst is firstly pretreated as follows: pure methane gas was continuously fed at a flow rate of 10 ml/min for 7.5 minutes, purged with helium at a flow rate of 10 ml/min for 5 minutes, and then oxidized with oxygen at a flow rate of 10 ml/min for 7.5 minutes, and the above cycle was repeated 5 times to stabilize the catalyst, and the test results are shown in table 3.

Table 3 example 1 catalytic performance of catalyst for chemical chain methane oxidation coupling reaction at 800 ℃ with different alkane ratios

As can be seen from Table 3, the catalysts of the examples of the present invention are used to catalyze the coupling reaction of chemical chain methane oxidation, even thoughHigher methane conversion (19%) can still be obtained with a catalyst alkane ratio as low as 9, C₂-C₃The hydrocarbon selectivity can reach 83 percent.

Application example 4

The purpose of this application example was to examine the effect of methane residence time on the catalytic performance of the inventive catalyst for chemical chain methane oxidation coupling reactions. Example 1 catalyst 1 g (-1 ml), reaction temperature 800 ℃, and 100 ml of methane (i.e., a catalyst-to-methane ratio of 13.5) were fed to the catalyst at flow rates of 2 ml/min, 5 ml/min, and 10 ml/min, respectively, and the helium purge flow rate was 2 ml/min, 5 ml/min, and 10 ml/min, respectively. The catalyst is firstly pretreated as follows: pure methane gas was continuously fed at a flow rate of 10 ml/min for 7.5 minutes, purged with helium at a flow rate of 10 ml/min for 5 minutes, and then oxidized with oxygen at a flow rate of 10 ml/min for 7.5 minutes, and the above cycle was repeated 5 times to stabilize the catalyst, and the test results are shown in table 4.

Table 4 example 1 catalysis of the catalyst for the oxidative coupling of chemical chain methanes at 800 c with different methane residence times

Results

As can be seen from Table 4, the catalysts of the examples of the present invention are useful for catalyzing chemical chain methane oxidation coupling reactions, and the longer methane residence time is favorable for methane conversion, but results in a decrease in selectivity.

Application example 5

The purpose of this application example was to investigate the reaction-regeneration cycling stability of the catalyst of the present invention for chemical chain methane oxidation coupling reactions. Using 1 g (. about.1 ml) of the shaped catalyst of example 9, the reaction conditions were: introducing 75 ml of methane (namely the solvent-methane ratio is 18) into the catalyst at the flow rate of 10 ml/min at the temperature of 800 ℃, wherein the helium purging flow rate is 10 ml/min, and the methane retention time is 6 seconds; regeneration conditions are as follows: at 800 ℃, 75 ml of oxygen was introduced into the reacted catalyst at a flow rate of 10 ml/min, and after purging with helium gas at a flow rate of 10 ml/min for 5 minutes, the next reaction-regeneration cycle was performed, and the test results are shown in fig. 12.

FIG. 12 is the results of methane conversion and product selectivity for 50 reaction-regeneration cycle tests of the shaped catalyst of example 9 of the present invention used for chemical chain methane oxidation coupling. As can be seen from FIG. 12, the formed catalyst of the present invention has methane conversion rate and product selectivity always maintained at about 22% and 75-80% in 50 reaction-regeneration cycle tests, and has good stability.

Figure 13 is an X-ray diffraction (XRD) pattern of the shaped catalyst of example 9 after the 50 th reaction-regeneration cycle test. As can be seen in FIG. 13, the FeMnO in the catalyst after reaction with methane₃The phase is reduced by methane and is not converted into MnFe₂O₄Besides the phase, a small amount of MnWO₄And MnTiO₃Generating, oxidizing and regenerating the reduced catalyst by oxygen, and obtaining MnFe₂O₄The phase is converted into FeMnO again₃Phase, it shows that the shaped catalyst of the present invention has very good reaction-regeneration cycle performance.

In summary, the invention adopts manganese composite oxide as lattice oxygen storage body and adds Na₂WO₄The auxiliary agent realizes the regulation and control of the activity and selectivity of the manganese composite oxide lattice oxygen, constructs the catalyst which has the advantages of selective methane oxidation and easy oxygen regeneration of the reduction catalyst

The chemical cycle of mutual conversion can realize long-time storage and release of lattice oxygen in the manganese composite oxide, so that the catalyst shows better reaction-regeneration performance, and further shows higher methane catalyst activity, and simultaneously, the deep oxidation of methane is weakened by matching with the addition of a regulation and control selectivity promoter, so that the reaction is carried out towards the direction of generating hydrocarbons, and finally, the catalyst has the characteristics of high activity and selectivity and high oxygen storage amount of lattice oxygen, and can obtain 18-24% of methane conversion rate and 75-80% of C under the conditions of lower alkane ratio of 18 and shorter methane retention time of 6 seconds₂-C₃Selectively is chemicalThe excellent catalyst for the oxidation coupling reaction of the chain methane has better industrial application prospect.

Finally, it should be pointed out here that: the above is only a part of the preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention, and the insubstantial modifications and adaptations of the present invention by those skilled in the art based on the above description are intended to be covered by the present invention.

Claims (10)

1. The catalyst for the chemical chain methane oxidation coupling reaction is characterized by consisting of a manganese composite oxide and sodium tungstate, and has the following structural general formula: a-Na₂WO₄/b-MnMO_xWherein: MnMO_xRepresents a manganese composite oxide; m represents a non-manganese element selected from at least one of titanium, iron, cobalt, nickel, lithium, silicon, lead, tin, germanium, gallium, antimony, bismuth, tellurium, selenium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, barium, magnesium, cerium, lanthanum, praseodymium, neodymium, samarium, calcium, strontium, barium, potassium, sodium, and lithium; a and b represent Na respectively₂WO₄And MnMO_xThe catalyst comprises 100 parts by mass of the catalyst, wherein the value range of a is 5-15, and a + b is 100.

2. The catalyst of claim 1, wherein: the manganese composite oxide has a perovskite structure and/or a spinel structure.

3. The catalyst of claim 1, wherein: the manganese composite oxide is selected from manganese titanate, manganese ferrite, manganese cobaltate, manganese nickelate, lithium manganate, manganese silicate, manganese metasilicate, nickel cobalt lithium manganate, sodium manganate, manganese plumbate, manganese stannate, manganese germanate, manganese gallate, manganese antimonate, manganese bismuthate, manganese tellurate, manganese selenate, manganese zirconate, manganese hafnate, manganese vanadate, manganese niobate, manganese tantalate, manganese chromate, manganese molybdate, manganese tungstate, iron manganate, barium manganate, magnesium manganate, cerium manganate, La, Mn_0.5Sr_0.5Mn_1-mFe_mO₃、Ca_αLa_βK_1-α-βMn_0.5Fe_0.5O₃、Ca_pLa_qK_1-p-qMn_0.78Fe_0.22O₃、Bi_0.5Ca_0.5-nLa_nFe_0.3Mn_0.7O₃At least one of, wherein: 0<m≤0.25，0<α≤0.25，0<β≤0.25，0<p≤0.25，0<q≤0.25，0<n≤0.25。

4. The catalyst of claim 1, wherein: the general formula of the manganese composite oxide is LnAFeMnO₆Wherein: ln is selected from any one of La, Pr, Nd, Sm and Ce; a is selected from any one of Ca, Sr and Ba.

5. A process for preparing the catalyst of any one of claims 1 to 4, comprising the steps of:

a) uniformly mixing the aqueous solution of sodium tungstate with the manganese composite oxide to obtain slurry sticky matter;

b) drying the slurry sticky matter at 80-150 ℃;

c) and roasting the dried sample for 1-5 hours at 700-1500 ℃ in an air atmosphere to obtain the catalyst.

6. A shaped catalyst for the oxidative coupling of chemical methyl ethers, characterized in that it is prepared from the catalyst a-Na of any one of claims 1 to 4₂WO₄/b-MnMO_xAnd the adhesive is composed of the following structural general formula: c [ a-Na ]₂WO₄/b-MnMO_x]-dZJJ, wherein: c and d represent the catalysts a to Na, respectively₂WO₄/b-MnMO_xAnd the binder ZJJ, wherein the mass fraction of the binder and the molded catalyst accounts for 100 parts by mass, the value range of c is 85-98, and the value range of c + d is 100.

7. A process for preparing the shaped catalyst of claim 6, which is an extrusion molding process comprising the steps of:

1) mixing the catalysta-Na₂WO₄/b-MnMO_xMixing with adhesive ZJJ in the hopper of extrusion molding machine, extruding and molding to obtain wet catalyst material;

2) drying the wet formed catalyst material prepared in the step 1) at 80-150 ℃ to obtain a dry formed catalyst material;

3) roasting the formed catalyst dry material obtained in the step 2) for 1-5 hours at 700-1000 ℃ in an air atmosphere to obtain the formed catalyst.

8. A process for preparing the shaped catalyst of claim 6, which is a spray-forming process comprising the steps of:

A) catalyst a-Na₂WO₄/b-MnMO_xMixing with adhesive ZJJ and water, and homogenizing to obtain emulsion-like uniform viscous substance;

B) spray drying and forming the emulsion-shaped uniform sticky substance prepared in the step A) by a spray dryer to obtain a spray forming catalyst;

C) roasting the spray-formed catalyst obtained in the step B) for 1-5 hours at 700-1000 ℃ in an air atmosphere to obtain the formed catalyst.

9. Use of a catalyst according to any one of claims 1 to 4, wherein: used as a catalyst for the chemical chain methane oxidation coupling reaction.

10. Use of the shaped catalyst of claim 6, wherein: used as a catalyst for the chemical chain methane oxidation coupling reaction.

Images