Perovskite type composite metal oxide oxygen carrier catalyst as well as preparation method and application thereof

Abstract

The invention discloses a perovskite type composite metal oxide oxygen carrier catalyst as well as a preparation method and application thereof, and belongs to the field of biomass chemical chain gasification / reforming. The oxygen carrier catalyst is of a La, Fe and Ni co-doped SrTiO3 perovskite structure, and active components Fe and Ni are embedded into a main body SrTiO3 perovskite crystal phase structure in an oxide or simple substance form; the method comprises the following steps: preparing an aqueous solution of lanthanum nitrate, strontium nitrate, nickel nitrate, ferric nitrate and citric acid, adding a mixed solution of tetrabutyl titanate and ethylene glycol into the aqueous solution, heating in a water bath, and stirring to form gel; drying and calcining the gel to obtain intermediate powder; and the intermediate powder is oxidized and reduced to form a high-temperature crystal structure under different atmospheres, and the perovskite type composite metal oxide oxygen carrier catalyst is obtained. The oxygen carrier catalyst provided by the invention has high tar conversion rate and stable cycle activity in the biomass chemical chain gasification / reforming process.

Description

Technical Field

[0001] This invention relates to the field of biomass chemical looping gasification / reforming, specifically to a perovskite-type composite metal oxide oxygen carrier catalyst, its preparation method, and its application. Background Technology

[0002] Biomass is the only renewable energy source containing hydrocarbons. Gasification technology converts it into gases such as CO and H2, providing high-quality feedstock for subsequent processes in the synthesis of liquid fuels / chemical products, power generation, and heating, thus achieving high-quality, multi-pathway utilization of biomass. However, the high volatile content of biomass inevitably leads to the production of tar as a byproduct during gasification. The presence of tar causes a series of problems, including pipeline blockage, reduced gasification efficiency, equipment corrosion, and environmental pollution. Reducing tar content or effectively removing tar is a significant technological bottleneck in biomass gasification. Compared to physical methods such as washing, filtration, and electrostatic capture, chemical methods such as catalytic cracking, reforming, and partial oxidation can convert tar into smaller molecule gases, without secondary pollution, and simultaneously utilize the energy from the tar, making them popular methods for tar removal.

[0003] Chemical looping gasification / reforming is a novel tar conversion technology that utilizes the partial oxidation and catalytic action of an oxygen-carrying catalyst to convert large tar molecules into smaller molecules such as CO and H2, achieving efficient tar conversion. The oxygen-carrying catalyst is regenerated and potential carbon deposits are eliminated by circulating it between the gasification / reforming reactor and the air combustion reactor, facilitating continuous system operation. The oxygen-carrying catalyst integrates oxygen carrying, heat carrying, and catalytic functions; therefore, the development of high-performance oxygen-carrying catalysts is crucial for chemical looping gasification / reforming technology.

[0004] Currently, oxygen-carrying catalysts mainly consist of metal oxides such as Ni, Fe, and Cu, along with supports and additives. Their preparation methods typically employ solution impregnation to load the metal oxides onto the support. Patent CN115069256A discloses an oxygen carrier and its application in the chemical looping gasification of cellulosic solid waste, using NiO supported on Ca2Fe2O5 as the oxygen carrier. Patent CN117358243A discloses a method for preparing an oxygen-carrying reforming bifunctional catalyst and its application, using Fe2O3 and NiO supported on Al2O3 as the oxygen carrier catalyst. Patent CN114574250A discloses a method and apparatus for producing clean syngas through biomass chemical looping gasification, using CuO supported on olivine as the oxygen carrier. During the chemical looping process, oxygen-carrying catalysts continuously undergo oxygen gain (oxidation) and oxygen loss (reduction) reactions, and the structure of the oxygen-carrying catalyst continuously changes with these oxygen gains and losses. Because the active oxide components loaded onto the support by the impregnation method are only distributed on the surface of the oxygen-carrier catalyst and are difficult to enter the bulk phase, the continuous insertion and precipitation of oxygen elements leads to unstable surface structure, making it prone to sintering, rapid performance degradation, and poor cycle stability. In addition, chemical looping usually uses a fluidized bed reactor to achieve the circulation of oxygen-carrier catalyst particles. During the circulation process, the oxygen-carrier catalyst particles inevitably collide and abrade, and the surface active materials of the supported oxygen carrier are more easily worn away and degraded.

[0005] Therefore, developing composite metal oxide oxygen carrier catalysts with specific crystal forms and stable structures is an important development direction for chemical looping gasification / reforming technology. Perovskite-type metal oxides are composed of cubic ABO3, exhibiting a unique atomic arrangement structure. The A ion is located at the corner of the cubic unit cell and is typically a lanthanide element or alkaline earth metal with a large radius; the B ion is located in the oxygen octahedron and is generally a transition metal. The ABO3 structure has high compatibility and stability, as long as the ionic radii of the A and B sites conform to r(A... n+ )≈2r(B m+ The cations at the A and B sites can be replaced by most metal cations with different oxidation states or oxidation radii. Therefore, ion doping is often used to further control its lattice properties.

[0006] Perovskite metal oxides, due to their unique structure, possess high oxygen transport capacity, tunable oxygen vacancies, and excellent thermal stability, and are increasingly valued for maintaining lattice integrity and cycle stability under high-temperature conditions. Patent CN112877110A discloses a perovskite-type Fe-based composite oxygen carrier and its preparation method, with the general formula AFeO3, where A = Ca, Sr, or La; Patent CN116621230A discloses a perovskite-type oxygen carrier suitable for biomass chemical looping gasification processes and its preparation method, with the general formula LaCo.x Fe 1-x O3. Patent CN111996060A discloses a perovskite-structured oxide-modified ilmenite oxygen carrier and its preparation method, wherein the general formula of perovskite is A 1~x B x O3, where A is any one of Ni, Co, and Mn, and B is any one of Cu, Fe, and Ti. In the above invention, to ensure the activity of the perovskite oxygen carrier, either Cu and Fe at the B site are active elements, or Ni, Co, and Mn at the A site are active elements. During the chemical looping vaporization / reforming process, it is easy to be completely reduced (loss of oxygen) and completely oxidized (gain of oxygen), thereby destroying the cubic structure of the perovskite and affecting the cycling stability of the oxygen carrier. Patent CN115626666A reports a triperovskite-type composite metal oxide oxygen carrier, its preparation method, and its application, with the general formula A3B'B''B'''O9, where A ion is La, B' ion is Fe, Co, or Ni, B'' ion is Mn, and B''' ion is Al. This invention contains active elements Fe, Co, Ni, and Mn at the B site, as well as the difficult-to-reduce Al element, thereby maintaining a certain perovskite structure during the redox process. However, this invention requires the formation of three perovskite structures during preparation, which is a complex and demanding process. At the same time, the perovskite structures formed by other active elements at the B site besides Al will also completely lose oxygen during the reaction, causing the perovskite structure to be destroyed and the active components to agglomerate and sinter, affecting the cycle stability.

[0007] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0008] This invention addresses the problems of poor structural stability, easy wear and loss of surface active materials, and poor structural cycling stability caused by the active components of current supported oxygen carrier catalysts being distributed only in the surface phase and having difficulty entering the bulk phase, as well as the problems caused by the selection of highly active elements at the A or B sites in existing perovskite oxygen carriers to improve activity. The invention provides a perovskite-type composite metal oxide oxygen carrier catalyst, its preparation method, and its application.

[0009] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution: According to one aspect of the present invention, a perovskite-type composite metal oxide oxygen carrier catalyst is provided, wherein the general formula of the perovskite-type composite metal oxide oxygen carrier catalyst is φFe-La. x Sr 0.8-x Ni y Ti 1-yO3, the main crystal form of the perovskite-type composite metal oxide oxygen carrier catalyst is maintained as SrTiO3 perovskite structure; wherein, La replaces part of Sr; the active components Fe and Ni are embedded in the SrTiO3 perovskite lattice structure in oxide or elemental form; in the general formula, the mass content φ is 2~12%, the mole fraction x is 0.1~0.4, and the mole fraction y is 0.1~0.4.

[0010] According to one aspect of the present invention, a method for preparing a perovskite-type composite metal oxide oxygen carrier catalyst as described herein is provided, comprising: Step 1: Prepare a precursor solution, which includes ferric nitrate, lanthanum nitrate, strontium nitrate, nickel nitrate, citric acid, and water; Step 2: Mix the mixed solution of ethylene glycol and tetrabutyl titanate with the precursor solution, stir under heating conditions to form a gel; dry and calcine the gel to obtain intermediate powder; Step 3: The intermediate powder is subjected to crystal structure strengthening under different oxidizing and reducing atmospheres to obtain the perovskite-type composite metal oxide oxygen carrier catalyst.

[0011] Optionally, step one specifically includes: dissolving hydrated ferric nitrate, hydrated lanthanum nitrate, strontium nitrate, and hydrated nickel nitrate in water, and then adding citric acid to dissolve them to obtain the precursor solution. Optionally, the ratio of the total amount of nitrate and citric acid added to the volume of water is 1 mol: 15~30 mL; The ratio of the amount of citric acid to the total amount of cationic substances in the added nitrate is 1 to 2:1.

[0012] Optionally, step two specifically includes: adding a mixed solution of ethylene glycol and tetrabutyl titanate to the precursor solution under constant temperature water bath stirring at 75~85℃, and continuously stirring until gel appears; then drying and aging the gel at 105~120℃ for 12~24h and grinding it into gel powder; calcining the gel powder in air at a temperature of 850~1050℃ for 6~12h, and cooling it to obtain the intermediate powder.

[0013] Optionally, the mass ratio of ethylene glycol to tetrabutyl titanate in the mixed solution formed by ethylene glycol and tetrabutyl titanate is 1.5~2.5:1.

[0014] Optionally, step three specifically includes: first, heating the intermediate powder from room temperature to 550-750°C in a hydrogen atmosphere and holding it for 2-4 hours; then switching to an inert atmosphere and heating to 850-1050°C and holding it for 1-2 hours, followed by cooling to room temperature; then switching to an air atmosphere, heating from room temperature to 850-1050°C and holding it for 2-4 hours, and after cooling, obtaining the perovskite-type composite oxide oxygen carrier catalyst.

[0015] Optionally, the hydrogen atmosphere is a mixture of H2 and an inert gas, wherein the volume fraction of H2 in the mixture is 3-5%. The inert atmosphere is N2 or Ar; The heating process employs programmed heating with a heating rate of 2~5℃ / min.

[0016] According to one aspect of the present invention, an application is provided for the perovskite-type composite metal oxide oxygen carrier catalyst as described herein in the tar removal process of biomass chemical looping gasification / reforming reaction.

[0017] Optionally, the process of removing tar through biomass chemical looping gasification / reforming reaction includes a gasification / reforming stage and a combustion stage, wherein the reaction temperature of both the gasification / reforming stage and the combustion stage is 800-1000℃.

[0018] Beneficial effects: (a) The φFe-La of the present invention x Sr 0.8-x Ni y Ti 1-y O3 perovskite-type composite metal oxide oxygen carrier catalyst (also known as oxygen carrier catalyst) contains a certain proportion of Ni and Fe active metal elements embedded in a SrTiO3 perovskite lattice with Ti as the main B-site ion, which does not undergo reduction reaction. A-site doping with La makes it easier for the two active elements to be embedded in the main lattice and helps to improve the activity of Fe and Ni elements. There are active sites in both the bulk phase and the surface phase, and they are evenly distributed.

[0019] (II) In the preparation of the oxygen carrier catalyst, the high-temperature crystal structure is strengthened under different oxidation / reduction atmospheres, so that the main SrTiO3 perovskite crystal phase of the oxygen carrier catalyst remains stable under both oxidation and reduction conditions. At the same time, the active components Fe and Ni are embedded in the main SrTiO3 perovskite crystal structure in oxide or elemental form. The oxygen gain and loss of Fe and Ni will not damage the structure of the main perovskite, which effectively inhibits the agglomeration and sintering of the active components and ensures the structural cycle stability.

[0020] (III) The φFe-La of the present invention x Sr 0.8-x Niy Ti 1-y The preparation method of O3 perovskite-type composite metal oxide oxygen carrier catalyst is simple, convenient to operate, and the synthesis conditions are easy to control.

[0021] (iv) The perovskite-type composite metal oxide oxygen carrier catalyst of the present invention has a dual role of partial oxidation and catalytic reforming in biomass chemical looping gasification / reforming reaction, and the tar conversion rate can reach 100%. Attached Figure Description

[0022] Figure 1 The images show the XRD patterns of the oxygen-carrier catalysts prepared in Examples 1-4 and Comparative Example 1 of this invention.

[0023] Figure 2 The image shows the XRD pattern of the oxygen-carrier catalyst prepared in Example 4 of this invention and its reaction after 30 cycles of biomass chemical looping gasification / reforming.

[0024] Figure 3 The image shows the SEM-EDS image of the oxygen-carrier catalyst prepared in Example 4 of this invention; where (A)-SEM; (B)-Fe; (C)-Ni; (D)-La; (E)-Sr; (F)-Ti.

[0025] Figure 4 The images show SEM-EDS images of the oxygen carrier catalyst prepared in Example 4 of this invention after 30 cycles of biomass chemical looping gasification / reforming; where (A)-SEM; (B)-Fe; (C)-Ni; (D)-La; (E)-Sr; (F)-Ti. Detailed Implementation

[0026] This invention provides a perovskite-type composite metal oxide oxygen carrier catalyst, its preparation method, and its application. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0027] This invention provides a perovskite-type composite metal oxide oxygen carrier catalyst, wherein the general formula of the perovskite-type composite metal oxide oxygen carrier catalyst is φFe-La. x Sr 0.8-x Ni y Ti 1-y O3, the main crystal form of the perovskite-type composite metal oxide oxygen carrier catalyst is maintained as SrTiO3 perovskite structure; wherein, La replaces part of Sr; the active components Fe and Ni are embedded in the SrTiO3 perovskite lattice structure in oxide or elemental form; In the general formula, the mass content φ is 2~12% (e.g., 5%, 8%, 10%), the mole fraction x is 0.1~0.4 (e.g., 0.2, 0.3, 0.4%), and the mole fraction y is 0.1~0.4 (e.g., 0.2, 0.3, 0.4%). This ensures both the stability of the perovskite crystal phase structure of SrTiO3 and the content of the active components required for the efficient reaction of the oxygen carrier catalyst.

[0028] For example, the oxygen carrier catalyst can be 5wt% Fe-La 0.4 Sr 0.4 Ni 0.3 Ti 0.7 O3, 10wt%Fe-La 0.2 Sr 0.6 Ni 0.3 Ti 0.7 O3, 5wt%Fe-La 0.2 Sr 0.6 Ni 0.2 Ti 0.8 O3, 10wt%Fe-La 0.2 Sr 0.6 Ni 0.2 Ti 0.8 O3.

[0029] In this embodiment, Fe and Ni, two active metal elements, are embedded in a certain proportion into a SrTiO3 perovskite lattice dominated by Ti elements that do not undergo reduction reaction (oxide deoxygenation). By doping La at the A-site and strengthening the perovskite crystal structure under different atmospheres, the distribution of active components is adjusted while ensuring high structural stability of the oxygen carrier catalyst. The final result is an oxygen carrier catalyst in which Fe and Ni active components are uniformly and stably embedded within the SrTiO3 lattice substrate. This oxygen carrier catalyst exhibits excellent anti-agglomeration sintering performance and cycle stability, and also demonstrates high tar conversion rate.

[0030] This invention provides a method for preparing the perovskite-type composite metal oxide oxygen carrier catalyst as described above, comprising: Step 1: Prepare a precursor solution, which includes ferric nitrate, lanthanum nitrate, strontium nitrate, nickel nitrate, citric acid, and water; Step 2: Mix the mixed solution of ethylene glycol and tetrabutyl titanate with the precursor solution, stir under heating conditions to form a gel; dry and calcine the gel to obtain intermediate powder; Step 3: The intermediate powder is subjected to crystal structure strengthening under different oxidizing and reducing atmospheres to obtain the perovskite-type composite metal oxide oxygen carrier catalyst.

[0031] The perovskite-type composite metal oxide oxygen carrier catalyst prepared in this embodiment has the general formula φFe-La. x Sr 0.8- x Ni y Ti 1-y This oxygen-carrying catalyst is a La, Fe, and Ni co-doped SrTiO3 perovskite structure. The active components Fe and Ni are embedded in the SrTiO3 perovskite lattice, which is dominated by Ti ions at the B-sites and does not undergo reduction, in oxide or elemental form. La doping at the A-sites facilitates the embedding of the two active elements into the main lattice and enhances the activity of Fe and Ni. Active sites are present and uniformly distributed in both the bulk and surface phases. This oxygen-carrying catalyst exhibits high tar conversion and stable recycling activity in biomass chemical looping gasification / reforming processes.

[0032] In this embodiment, when preparing the oxygen-carrying catalyst, the high-temperature crystal structure is strengthened under different oxidation / reduction atmospheres, so that the main SrTiO3 perovskite crystal phase of the oxygen-carrying catalyst remains stable under both oxidation and reduction conditions. At the same time, the active components Fe and Ni are embedded in the main SrTiO3 perovskite crystal structure in oxide or elemental form. The gain and loss of oxygen of Fe and Ni will not damage the structure of the main perovskite, which effectively inhibits the agglomeration and sintering of the active components and ensures the structural cycle stability.

[0033] The oxygen carrier catalyst preparation method in this embodiment is simple, easy to operate, and the synthesis conditions are easy to control.

[0034] In some embodiments, step one specifically includes: dissolving hydrated ferric nitrate, hydrated lanthanum nitrate, strontium nitrate, and hydrated nickel nitrate in water, and then adding citric acid to dissolve them to obtain the precursor solution. According to φFe-La x Sr 0.8-x Ni y Ti 1-y The corresponding masses of hydrated ferric nitrate, hydrated lanthanum nitrate, strontium nitrate, and hydrated nickel nitrate were weighed according to the O3 metering ratio and dissolved in deionized water to prepare a solution. Then, citric acid was added to dissolve the solutions to prepare a precursor solution.

[0035] Furthermore, the ratio of the amount of citric acid to the total amount of cations in the added nitrate is 1 to 2:1, such as 1:1, 1.5:1, 2:1, etc. The added nitrate includes hydrated ferric nitrate, hydrated lanthanum nitrate, strontium nitrate, and hydrated nickel nitrate.

[0036] In some embodiments, step two specifically includes: adding a mixed solution of ethylene glycol and tetrabutyl titanate to the precursor solution under constant temperature water bath stirring at 75~85℃, and stirring continuously until gel appears; then drying and aging the gel at 105~120℃ (in an oven) for 12~24h and grinding it into gel powder; calcining the gel powder in air at 850~1050℃ for 6~12h, and cooling (natural cooling is acceptable) to obtain the intermediate powder.

[0037] Furthermore, the mass ratio of ethylene glycol to tetrabutyl titanate in the mixed solution formed by ethylene glycol and tetrabutyl titanate is 1.5 to 2.5:1, such as 1.5:1, 2:1, 2.5:1, etc.

[0038] In some embodiments, step three specifically includes: strengthening the crystal structure of the intermediate powder under different atmospheres. First, the intermediate powder is heated from room temperature to 550~750℃ (e.g., 550℃, 650℃, 750℃, etc.) in a hydrogen atmosphere and held for 2~4h (e.g., 2h, 3h, 4h, etc.); then the atmosphere is switched to inert and the temperature is raised to 850~1050℃ (e.g., 850℃, 950℃, 1050℃, etc.) and held for 1~2h (e.g., 1h, 1.5h, 2h, etc.) before cooling to room temperature; then the atmosphere is switched to air and the temperature is raised from room temperature to 850~1050℃ (e.g., 850℃, 950℃, 1050℃, etc.) and held for 2~4h (e.g., 2h, 3h, 4h, etc.). After cooling, a perovskite-type composite oxide oxygen carrier catalyst with both high activity and good stability is obtained.

[0039] Furthermore, after the crystal structure strengthening under air atmosphere is completed, the process may include the following steps: pressing the cooled solid powder into tablets and passing them through a 40-60 mesh standard sieve to obtain the oxygen carrier catalyst.

[0040] Furthermore, the cooling can be natural cooling.

[0041] Furthermore, the hydrogen atmosphere is a mixture of H2 and an inert gas, wherein the volume fraction of H2 in the mixture is 3-5%.

[0042] Furthermore, the inert atmosphere is N2 or Ar.

[0043] Furthermore, the heating is performed using a programmed heating method with a heating rate of 2~5℃ / min, such as 3℃ / min.

[0044] This invention provides an application of the above-mentioned perovskite-type composite metal oxide oxygen carrier catalyst in the conversion and removal of tar in biomass chemical looping gasification / reforming reaction. In the gasification / reforming stage, the oxygen carrier catalyst reacts with volatile components such as tar in biomass. Under the partial oxidation and catalytic reforming effect of the Fe and Ni active sites in the oxygen carrier catalyst, the large molecules such as tar are converted into small molecule gases such as CO and H2. Fe and Ni are reduced while La, Sr, and Ti do not participate in the reaction, maintaining the main SrTiO3 perovskite crystal phase structure unchanged. In the air combustion stage, Fe and Ni in the oxygen carrier catalyst are oxidized by air and restored to their original composition and structure, realizing recycling and regeneration.

[0045] Furthermore, the reaction temperatures for both the gasification / reforming stage and the combustion stage are 800–1000°C, such as 900°C.

[0046] The present invention will be further described below through several specific embodiments.

[0047] Example 1 Step 1: Dissolve 7.2g Fe(NO3)3·9H2O, 8.8g Ni(NO3)2·6H2O, 17.8g La(NO3)3·6H2O, and 8.4g Sr(NO3)2 in 220mL of deionized water to prepare a solution. Then add 75.6g C6H8O7·H2O to dissolve and form a precursor solution. Step 2: Under constant temperature heating and stirring conditions in an 80℃ water bath, a mixed solution of 59.8g ethylene glycol and 23.8g tetrabutyl titanate was added to the precursor solution, and the mixture was stirred continuously until gelation occurred. The gel was then dried and aged in an oven at 105℃ for 12 hours, cooled, and ground into gel powder. The resulting gel powder was calcined in air at 1050℃ for 6 hours and then naturally cooled to obtain intermediate powder. Step 3: The intermediate powder was heated from room temperature to 550°C at a rate of 3°C / min under a 5% H₂ + 95% Ar atmosphere at a flow rate of 120 mL / min and held for 4 hours. Then, the temperature was switched to an Ar atmosphere at a flow rate of 120 mL / min and heated from 550°C to 1050°C at a rate of 3°C / min, held for 1 hour, and then allowed to cool naturally to room temperature. Finally, the temperature was switched to an air atmosphere at a flow rate of 120 mL / min and heated from room temperature to 1050°C at a rate of 3°C / min, held for 4 hours, and allowed to cool naturally. The solid powder was then pressed into tablets and passed through a 40-60 mesh standard sieve to obtain a composition of 5wt% Fe-La. 0.4 Sr 0.4 Ni 0.3 Ti 0.7 O3 perovskite-type composite metal oxide oxygen carrier catalyst particles (sample 1).

[0048] The XRD pattern of the prepared oxygen-carrier catalyst is as follows: Figure 1 As shown.

[0049] Example 2 Step 1: Dissolve 14.4g Fe(NO3)3·9H2O, 8.8g Ni(NO3)2·6H2O, 8.6g La(NO3)3·6H2O and 12.8g Sr(NO3)2 in 300mL of deionized water to prepare a solution. Then add 75.6g C6H8O7·H2O to dissolve and form a precursor solution. Step 2: Under constant temperature heating and stirring conditions in an 85℃ water bath, a mixed solution of 56.4g ethylene glycol and 23.8g tetrabutyl titanate was added to the precursor solution, and the mixture was stirred continuously until gelation occurred. The gel was then dried and aged in an oven at 105℃ for 24 hours, and after cooling, it was ground into gel powder. The obtained gel powder was calcined in air at 1050℃ for 6 hours and then naturally cooled to obtain intermediate powder. Step 3: The intermediate powder was heated from room temperature to 550°C at a rate of 3°C / min under a 5% H₂ + 95% Ar atmosphere at a flow rate of 100 mL / min and held for 4 hours. Then, the temperature was switched to an Ar atmosphere at a flow rate of 120 mL / min and heated from 550°C to 950°C at a rate of 3°C / min, held for 1 hour, and then allowed to cool naturally to room temperature. Finally, the temperature was switched to an air atmosphere at a flow rate of 100 mL / min and heated from room temperature to 950°C at a rate of 3°C / min, held for 4 hours, and allowed to cool naturally. The solid powder was then pressed into tablets and passed through a 40-60 mesh standard sieve to obtain a composition of 10 wt% Fe-La. 0.2 Sr 0.6 Ni 0.3 Ti 0.7 O3 perovskite-type composite metal oxide oxygen carrier catalyst particles (sample 2).

[0050] The XRD pattern of the prepared oxygen-carrier catalyst is as follows: Figure 1 As shown.

[0051] Example 3 Step 1: Dissolve 7.2g Fe(NO3)3·9H2O, 6.2g Ni(NO3)2·6H2O, 7.2g La(NO3)3·6H2O and 13.6g Sr(NO3)2 in 300mL of deionized water to prepare a solution. Then add 80.6g C6H8O7·H2O to dissolve and form a precursor solution. Step 2: Under constant temperature heating and stirring conditions in a 75℃ water bath, a mixed solution of 72.6g ethylene glycol and 29.0g tetrabutyl titanate was added to the precursor solution, and the mixture was stirred continuously until gelation occurred. The gel was then dried and aged in an oven at 110℃ for 24 hours, and after cooling, it was ground into gel powder. The obtained gel powder was calcined in air at 950℃ for 6 hours and then naturally cooled to obtain intermediate powder. Step 3: The intermediate powder was heated from room temperature to 550°C at a rate of 3°C / min under a 5% H₂ + 95% Ar atmosphere at a flow rate of 120 mL / min and held for 4 hours. Then, the temperature was switched to an Ar atmosphere at a flow rate of 120 mL / min and heated from 550°C to 950°C at a rate of 3°C / min, held for 1 hour, and then allowed to cool naturally to room temperature. Finally, the temperature was switched to an air atmosphere at a flow rate of 120 mL / min and heated from room temperature to 950°C at a rate of 5°C / min, held for 4 hours, and allowed to cool naturally. The solid powder was then pressed into tablets and passed through a 40-60 mesh standard sieve to obtain a composition of 5wt% Fe-La. 0.2 Sr 0.6 Ni 0.2 Ti 0.8 O3 perovskite-type composite metal oxide oxygen carrier catalyst particles (sample 3).

[0052] The XRD pattern of the prepared oxygen-carrier catalyst is as follows: Figure 1 As shown.

[0053] Example 4 Step 1: Dissolve 5.1g Fe(NO3)3·9H2O, 2.1g Ni(NO3)2·6H2O, 3.1g La(NO3)3·6H2O and 4.5g Sr(NO3)2 in 100mL of deionized water to prepare a solution. Then add 28.8g C6H8O7·H2O to dissolve and form a precursor solution. Step 2: Under constant temperature heating and stirring conditions in an 80℃ water bath, a mixed solution of 24.0g ethylene glycol and 9.6g tetrabutyl titanate was added to the precursor solution, and the mixture was stirred continuously until gelation occurred. The gel was then dried and aged in an oven at 105℃ for 12 hours, cooled, and ground into gel powder. The resulting gel powder was calcined in air at 1050℃ for 6 hours and then naturally cooled to obtain intermediate powder. Step 3: The intermediate powder was heated from room temperature to 550°C at a rate of 3°C / min under a 5% H₂ + 95% Ar atmosphere at a flow rate of 120 mL / min and held for 4 hours. Then, the temperature was switched to an Ar atmosphere at a flow rate of 120 mL / min and heated from 550°C to 850°C at a rate of 3°C / min, held for 1 hour, and then allowed to cool naturally to room temperature. Finally, the temperature was switched to an air atmosphere at a flow rate of 120 mL / min and heated from room temperature to 1050°C at a rate of 3°C / min, held for 4 hours, and allowed to cool naturally. The solid powder was then pressed into tablets and passed through a 40-60 mesh standard sieve to obtain a composition of 10 wt% Fe-La. 0.2 Sr 0.6 Ni 0.2 Ti 0.8 O3 perovskite-type composite metal oxide oxygen carrier catalyst particles (sample 4).

[0054] The XRD pattern of the prepared oxygen-carrier catalyst is as follows: Figure 1 As shown.

[0055] Comparative Example 1 For comparison, SrTiO3 perovskite oxygen-supported catalysts were prepared: Step 1: Add 8.1g Sr(NO3)2 to 40mL of deionized water to prepare a solution, and then add 32.1g C6H8O7·H2O to dissolve and form a precursor solution; Step 2: Under constant temperature heating and stirring conditions in an 80℃ water bath, a mixed solution of 32.5g ethylene glycol and 13.0g tetrabutyl titanate was added to the precursor solution, and the mixture was stirred continuously until gelation occurred. The gel was then dried and aged in an oven at 105℃ for 24 hours, and after cooling, it was ground into gel powder. The obtained gel powder was calcined in air at 1050℃ for 6 hours and then naturally cooled to obtain intermediate powder. Step 3: The intermediate powder was heated from room temperature to 550℃ at a rate of 3℃ / min under an atmosphere of 5v%H2 + 95%Ar at a flow rate of 120mL / min and held for 4h; then the atmosphere was switched to Ar at a flow rate of 120mL / min and the temperature was increased from 550℃ to 850℃ at a rate of 3℃ / min and held for 1h before being naturally cooled to room temperature; then the atmosphere was switched to air at a flow rate of 120mL / min and the temperature was increased from room temperature to 1050℃ at a rate of 3℃ / min and held for 4h. After natural cooling, the solid powder was pressed into tablets and passed through a 40-60 mesh standard sieve to obtain SrTiO3 perovskite oxygen carrier catalyst particles (sample 0).

[0056] The XRD pattern of the prepared oxygen-carrier catalyst is as follows: Figure 1 As shown.

[0057] Application Example 1 Weigh 1.5g of the oxygen carrier catalyst prepared in Examples 1-4 and Comparative Example 1, and add it to a vertical fixed-bed reactor with a porous sintered plate at the bottom of the quartz tube. The oxygen carrier catalyst is covered with about 5mm thick quartz wool. Ar is introduced from the top of the quartz tube at a flow rate of 135 mL / min. After purging for 30 min and raising the temperature to 850℃, (1) 5.0g of dry biomass sample is uniformly and continuously fed into the quartz wool of the quartz tube in the reactor through a screw feeding system. The volatiles such as tar produced react with the oxygen carrier catalyst under the quartz wool. The entire reaction process is stable and lasts for 20 min. GB / T Method 40508-2021 was used to determine the tar content of the gas at the lower end of the quartz tube outlet; (2) purge with 135 mL / min of Ar for 30 min; (3) introduce air at 80 mL / min and react for 20 min; (4) purge with 135 mL / min of Ar for 30 min; the above (1) to (4) steps were used to complete one complete cycle.

[0058] For comparison, 1.5g of 40-60 mesh quartz sand was weighed and added to the reactor, and the above steps (1) to (4) were performed to obtain the tar content. The tar conversion rate was obtained by comparing the tar content obtained by the oxygen carrier catalysts of samples 0-4 with the tar content obtained by the quartz sand. The tar conversion rates of different samples are shown in Table 1.

[0059] Table 1. Performance of oxygen carrier catalyst in chemical looping gasification / reforming conversion of tar

[0060] To investigate the stability of the oxygen-carrier catalyst structure during multiple cycles of reaction, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and X-ray powder diffraction (XRD) were performed on the freshly prepared oxygen-carrier catalyst (Example 4 - Sample 4) and the oxygen-carrier catalyst after 30 cycles of biomass chemical looping gasification / reforming reaction (Application Example 1). The results are as follows: Figure 2 , Figure 3 and Figure 4 As shown. 10% Fe-La after 30 cycles. 0.2 Sr 0.6 Ni 0.2 Ti 0.8 The XRD pattern of the O3 oxygen carrier catalyst shows characteristic diffraction peaks of SrTiO3 perovskite, indicating that the main body is still the perovskite crystal phase. The main active components, Fe and Ni, have not agglomerated, which shows that the perovskite-type composite metal oxide oxygen carrier catalyst has excellent anti-agglomeration sintering ability and structural stability.

[0061] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A perovskite-type composite metal oxide oxygen carrier catalyst, characterized by, The perovskite type composite metal oxide oxygen carrier catalyst has a general formula of φFe-La x Sr 0.8-x Ni y Ti 1-y O3, and a main crystal form of the perovskite type composite metal oxide oxygen carrier catalyst is kept as a SrTiO3 perovskite structure; wherein La replaces part of Sr; active components Fe and Ni are embedded in a SrTiO3 perovskite crystal lattice structure in the form of oxides or elements; in the general formula, the mass content φ is 2-12%, the molar fraction x is 0.1-0.4, and the molar fraction y is 0.1-0.

4.

2. A method for producing the perovskite composite metal oxide oxygen carrier catalyst as claimed in claim 1, characterized by, The application relates to a preparation method of a perovskite type composite metal oxide oxygen carrier catalyst. Step 1: preparing a precursor solution, wherein the precursor solution comprises ferric nitrate, lanthanum nitrate, strontium nitrate, nickel nitrate, citric acid and water; Step 2: mixing a mixed solution formed by ethylene glycol and tetrabutyl titanate with the precursor solution, stirring under heating conditions to form a gel; drying and calcining the gel to obtain an intermediate powder; Step 3: strengthening the crystal structure of the intermediate powder under different atmospheres of oxidation and reduction to obtain the perovskite type composite metal oxide oxygen carrier catalyst.

3. The method of producing a perovskite composite metal oxide redox catalyst according to claim 2, characterized by, The step 1 specifically comprises the following steps: dissolving ferric nitrate hydrate, lanthanum nitrate hydrate, strontium nitrate and nickel nitrate hydrate in water, and then adding citric acid to dissolve to obtain the precursor solution.

4. The method for producing a perovskite composite metal oxide oxygen carrier catalyst according to claim 2 or 3, characterized by, The ratio of the total amount of substance of the added nitrate and citric acid to the volume of water is 1 mol: 15-30 mL. The ratio of the amount of substance of the citric acid to the total amount of substance of the cations in the added nitrate is 1-2:

1.

5. The method of producing a perovskite composite metal oxide redox catalyst according to claim 2, characterized by, The step 2 specifically comprises the following steps: adding a mixed solution formed by ethylene glycol and tetrabutyl titanate to the precursor solution under the condition of constant temperature water bath stirring at 75-85 DEG C, continuously stirring until a gel appears; then placing the gel in a drying and aging process at 105-120 DEG C for 12-24 hours, grinding into a gel powder; and calcining the gel powder under an air atmosphere at a temperature of 850-1050 DEG C for 6-12 hours, and cooling to obtain the intermediate powder.

6. The method of producing a perovskite-type composite metal oxide oxygen carrier catalyst according to claim 2 or 5, characterized by, The mass ratio of ethylene glycol to tetrabutyl titanate in the mixed solution formed by ethylene glycol and tetrabutyl titanate is 1.5-2.5:

1.

7. The method of producing a perovskite composite metal oxide redox catalyst according to claim 2, characterized by, The step 3 specifically comprises the following steps: firstly, heating the intermediate powder to 550-750 DEG C under a hydrogen atmosphere from room temperature and keeping for 2-4 hours; then switching to an inert atmosphere, heating to 850-1050 DEG C and keeping for 1-2 hours, and cooling to room temperature; subsequently switching to an air atmosphere, heating to 850-1050 DEG C from room temperature and keeping for 2-4 hours, and cooling to obtain the perovskite type composite oxide oxygen carrier catalyst.

8. The method of producing a perovskite-type composite metal oxide redox catalyst according to claim 7, characterized by, The hydrogen atmosphere is a mixed gas of H2 and an inert gas, and the volume fraction of H2 in the mixed gas is 3-5%. The inert atmosphere is N2 or Ar. The heating process adopts programmed heating, and the heating rate is 2-5 DEG C / min.

9. The perovskite type composite metal oxide oxygen carrier catalyst according to claim 1 is applied to removal of tar in a biomass chemical looping gasification / reforming reaction conversion process.

10. Use of the perovskite-type composite metal oxide oxygen carrier catalyst according to claim 9 for tar removal in a biomass chemical looping gasification / reforming reaction conversion, characterized in that, The biomass chemical looping gasification / reforming reaction conversion process for removing tar comprises a gasification / reforming stage and a combustion stage, and the reaction temperature of the gasification / reforming stage and the combustion stage is 800-1000 DEG C.

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