阅读说明：本技术 一种负载型铁钨双金属复合氧化物及其制备方法和应用 (Load type iron-tungsten bimetal composite oxide and preparation method and application thereof ) 是由 巩金龙 刘蕊 王宗宝 张先华 苏迎辉 王林 王奕然 肖海成 李庆勋 于 2019-11-05 设计创作，主要内容包括：本发明属于金属复合氧化物技术领域,公开了一种负载型铁钨双金属复合氧化物及其制备方法和应用,该催化剂是在惰性氧化物载体上均匀负载有Fe<Sub>x</Sub>WO<Sub>y</Sub>,0＜x≤2,3＜y≤6；其制备方法为将超声溶解完全后的前驱体溶液采用等体积浸渍法,浸渍到惰性氧化物载体上,超声至完全均匀；之后干燥、焙烧得到负载型铁钨双金属复合氧化物；本发明适用于甲烷等燃料的化学链自热气化、重整直接制合成气等领域,一方面可以将还原过程中吸收的热量与氧化过程中放出的热量进行耦合,实现自热重整,减少能耗；另一方面采用载氧体中的晶格氧为氧物种的来源,可以提高对合成气的选择性,增加对合成气的收率,同时可以避免空气与甲烷直接接触引起爆炸的危险。(The invention belongs to the technical field of metal composite oxides, and discloses a supported iron-tungsten bimetal composite oxide, a preparation method and application thereof x WO y X is more than 0 and less than or equal to 2, and y is more than 3 and less than or equal to 6; the preparation method comprises the steps of dipping the precursor solution after complete ultrasonic dissolution on an inert oxide carrier by an isometric dipping method, and carrying out ultrasonic treatment until the precursor solution is completely uniform; then drying and roasting to obtain a load type iron-tungsten bimetal composite oxide; the invention is suitable for the fields of chemical chain self-heating gasification of fuels such as methane and the like, direct synthesis gas preparation by reforming and the like, and on one hand, the invention can couple the heat absorbed in the reduction process with the heat released in the oxidation process, realize self-heating reforming and reduce energy consumption; on the other hand, the lattice oxygen in the oxygen carrier is adoptedThe source of the oxygen species can improve the selectivity of the synthesis gas, increase the yield of the synthesis gas and simultaneously avoid the danger of explosion caused by the direct contact of air and methane.)

1. The supported Fe-W bimetal composite oxide features that Fe is loaded homogeneously onto inert oxide carrier_xWO_yWherein x is more than 0 and less than or equal to 2, and y is more than 3 and less than or equal to 6.

2. The supported Fe-W bimetal composite oxide as claimed in claim 1, wherein Fe is_xWO_yIs a catalystThe mass fraction of (A) is 30-50%.

3. The supported iron-tungsten bimetallic composite oxide of claim 1, wherein the inert oxide support is one of silica, alumina and titania.

4. The supported Fe-W bimetal composite oxide as claimed in claim 1, wherein Fe is_xWO_yWherein x is 1 and y is 4.5.

5. A method for preparing the supported iron-tungsten bimetal composite oxide according to any one of claims 1 to 4, which is characterized by comprising the following steps:

step 1, ultrasonically treating ferric nitrate nonahydrate and ammonium metatungstate in deionized water until the ferric nitrate nonahydrate and the ammonium metatungstate are completely dissolved to obtain a precursor solution; wherein the molar ratio of the ferric nitrate nonahydrate to the ammonium metatungstate is 12x, and x is more than 0 and less than or equal to 2;

step 2, dipping the precursor solution completely dissolved by the ultrasonic in the step 1 on an inert oxide carrier by adopting an isometric dipping method, and continuously oscillating and ultrasonically dipping uniformly;

step 3, continuing to perform ultrasonic treatment on the uniformly dipped colloidal precursor solution obtained in the step 2 for 2-4 hours until the solution is completely uniform;

and 4, drying the substance obtained in the step 3 at room temperature for 10-14h, then drying at 90-120 ℃ for 10-14h, and finally roasting at 800-.

6. Use of the supported Fe-W bimetal composite oxide as claimed in any of claims 1-4 in preparing CO and H directly by methane three-bed autothermal gasification and reforming₂And according to the following steps:

step 1, carrying out tabletting molding treatment on the load type iron-tungsten bimetal composite oxide to obtain solid oxide particles;

step 2, putting solid oxide particles into a three-bed reactor, introducing an oxygen carrier from the top end of the fuel reactor, and reacting at the temperature of 600-; Fe-W alloy with reduced bottom of reactor and WO_g，0≤g<3；

Step 3, reduced WO_gAnd Fe-W alloy enters the top of the water vapor reactor in the bottom chamber of the fuel reactor, and the temperature is controlled at 500-900 ℃;

step 4, the solid particles separated from the bottom of the water vapor reactor enter the bottom of the air reactor, and the temperature is controlled at 600-1100 ℃;

and (3) repeating the steps 1-3 with the regenerated and freshly prepared bimetallic oxide to realize cyclic utilization.

7. The use of the supported iron-tungsten bimetallic oxide as claimed in claim 6, wherein the fuel reactor and the steam reactor are both moving bed reactors or multi-stage fluidized bed reactors.

8. The use of the supported Fe-W bimetal composite oxide as claimed in claim 6, wherein the reaction temperature in step 2 is 850-950 ℃.

9. The use of a supported Fe-W bimetal composite oxide as claimed in claim 6, wherein the reduced oxygen carrier is mainly composed of Fe-W alloy, WO_g，0≤g<3。

Technical Field

The invention belongs to the technical field of metal composite oxides, and particularly relates to a supported iron-tungsten bimetallic oxide, a preparation method thereof and application of the catalyst in directly preparing synthesis gas by three-bed autothermal reforming of fuels such as low-carbon alkane and the like.

Technical Field

In recent years, with the rapid development of national economy, the petroleum consumption of China shows an increasing trend, and the petroleum gap of China is estimated to reach 2.7 hundred million tons in 2020, and the external dependence degree reaches 60%; although the coal resources are abundant and the resource reserves are 1.34 trillion tons, the coal resources cause serious pollution when in use and bring serious challenges to environmental protection. Therefore, people are beginning to focus on natural gas, which is abundant in source and can be used as high-quality clean energy and chemical raw materials, and is expected to play a more important role in modern economy. Experts predict that the "21 st century will be the century for natural gas". The main component of natural gas is methane, usually 83% -99%, so the conversion and utilization of methane occupy a very important position in the chemical industry of natural gas.

The synthesis gas is an important intermediate product of natural gas chemical industry, the main components of the synthesis gas are hydrogen and carbon monoxide, the synthesis gas can be directly used as fuel, can also be separated to prepare pure hydrogen for a fuel cell, and can also be further converted into liquid fuel and other chemicals through Fischer-Tropsch synthesis. In recent years, with the shortage of petroleum, international demand for downstream liquid fuels and chemicals based on synthesis gas production is steadily increasing. There are generally three methods for producing synthesis gas using methane as a raw material: steam Reforming of Methane (SRM), carbon dioxide reforming of methane (CDR), and Partial Oxidation of Methane (POM).

Partial Oxidation of Methane (POM) to synthesis gas is a mild exothermic reaction. The reaction can be carried out at high airspeed, the reactor has small volume, high efficiency and low energy consumption, and the equipment investment and the like are greatly reduced. Compared with SMR, the POM technology can reduce the energy consumption by 10-30%, and in addition, the POM process is at 750-800 ℃, the equilibrium conversion rate can reach more than 90%, and the hydrogen-carbon ratio in the generated synthesis gas is close to 2, so that the POM technology can be directly used for raw gas for methanol and F-T synthesis. The process is widely valued at home and abroad, and the research work is very active. However, this reaction has the following disadvantages: (1) catalysts such as noble metals Pt and Pd are required, so that the effect is good, the sintering resistance is high, and the price is high; the nickel-based catalyst is low in price and easy to obtain, but is easy to activate due to the influence of carbon deposit; (2) the reaction is an exothermic reaction, if a fixed bed reaction is used, the problems of hot spots and heat waves can be generated, the generation of the hot spots can seriously affect the stability and the safety of a reaction system, and a plurality of researches are devoted to solving the problem; (3) the reaction must be reacted with pure oxygen, the presence of which readily oxidizes methane to CO₂And H₂O, reduces the yield of syngas, while the cost of preparing pure oxygen is expensive, which increases investment and energy consumption; (4) because the reaction rate is fast, the temperature runaway phenomenon of the catalyst bed layer is easy to occur, and the methane directly contacts and reacts with molecular oxygen, so that the danger of explosion is generated. These are obstacles restricting the realization of industrialization.

In recent years, various researchers have proposed a novel process for the oxidation of CH using lattice oxygen provided by the oxide₄The partial oxidation is carried out to prepare the synthesis gas, namely chemical looping reforming technology (chemical looping reforming)ing, CLR) which uses lattice oxygen in an oxygen carrier to replace molecular oxygen, supplies oxygen element required by oxidation reaction to fuel, and controls lattice oxygen/fuel value to enable CH₄Partial oxidation to obtain CO and H₂Synthesis gas as the main component.

The oxygen carrier circulates between the two reactors and provides lattice oxygen for the reduction reaction in the reforming reactor through an oxidative regeneration process in the air reactor; while transferring heat from the air reactor oxidation regeneration to the reforming reactor. Thus, the physicochemical properties of the oxygen carrier are critical to the overall chemical looping reforming system. Generally, the oxygen carrier should have the following characteristics: (1) good reaction performance; (2) the wear resistance is good, and the loss in the reaction process is reduced; (3) high selectivity, selective partial oxidation of fuel to CO and H₂(ii) a (4) Negligible carbon deposition and good fluidization properties (no sintering); (5) the raw materials are cheap and easy to obtain, and the production cost is low; meanwhile, the preparation method also needs to have the properties of easy preparation, environmental friendliness, no secondary pollution and the like. At present, oxygen carriers which are widely researched and applied to the CLR process comprise CuO and MnO₂，NiO，Fe₂O₃，WO₃Monometallic oxides of transition metals, fluorite oxides CeO₂Perovskite type oxide La_0.8Sr_0.2Co_0.8Fe_0.2O_3－δ。

Copper oxide and manganese oxide based oxygen carriers are not suitable for partial oxidation reaction of methane because of high lattice oxygen activity, and methane is more prone to be completely oxidized into carbon dioxide and water when the copper oxide and manganese oxide based oxygen carriers are subjected to reduction reaction with methane. Nickel-based oxygen carriers are widely used for their good reactivity. However, the reduction of nickel oxide to form elemental nickel greatly promotes the decomposition of methane, resulting in severe carbon deposition and deactivation of the oxygen carrier. Iron-based oxides are less expensive and less toxic than nickel-based oxides, and thus have been widely studied as novel oxygen carriers. However, since it has lower activation power for methane than nickel oxide and is heavily sintered at a higher reaction temperature, Al is required₂O₃And SiO₂Iso-carriersTo reduce its crystal size and thus overcome the above-mentioned disadvantages. Cerium oxide is another widely used redox catalyst that exhibits superior performance due to its higher lattice oxygen transfer rate during the partial oxidation of methane reforming to syngas. However, due to its limited oxygen carrying capacity, it is not suitable for large scale applications. The tungsten oxide has better sintering resistance due to higher stability (the melting point of metal tungsten is higher than 3400 ℃). And WO₃The selectivity to syngas is high and therefore has received much attention in chemical looping reforming technology. However, because tungsten oxide has good thermal stability and weak activation capability to methane, the activation capability to methane and the selectivity of synthesis gas are improved by adding another metal oxide through the synergistic effect of the two metal oxides.

Based on the previous description of NiO-WO₃-Al₂O₃In this work, we have found that as the reaction proceeds, the hydrogen to carbon ratio gradually increases and the catalyst gradually deactivates. The main reason is the formation of NiO-WO₃Phase separation of solid solutions due to mismatch in ion diffusion rates and carbon deposition due to mismatch in the rate of methane activation by metal ions and the rate of oxygen supply by lattice oxygen.

Disclosure of Invention

The invention aims to solve the technical problems that the prior single metal oxide in the technology of preparing synthesis gas by chemical looping has low reaction activity and poor stability, and the carbon deposition amount in the Ni-W bimetal oxide is gradually increased along with the increase of the cycle times, and the catalyst is gradually inactivated, provides a supported iron-tungsten bimetal oxide, a preparation method thereof and the application of methane three-bed autothermal reforming for directly preparing synthesis gas, and couples Fe₂O₃Metal oxide having high activation ability for methane, WO₃The total selectivity of the metal oxide to the synthesis gas is high, and the advantage of the gas-solid parallel flow operation type three-bed reactor self-heating reforming is realized, and the direct conversion of methane into the high-selectivity synthesis gas is realized by utilizing the equal-volume impregnation preparation method which is simple and easy to implement and low in cost.

In order to solve the technical problems, the invention is realized by the following technical scheme:

a load-type Fe-W bimetal composite oxide is prepared through uniformly loading Fe onto the carrier of inertial oxide_xWO_yWherein x is more than 0 and less than or equal to 2, and y is more than 3 and less than or equal to 6.

Further, Fe_xWO_yAccounting for 30-50% of the mass fraction of the catalyst.

Further, the inert oxide carrier is one of silicon oxide, aluminum oxide and titanium oxide.

Preferably, Fe_xWO_yWherein x is 1 and y is 4.5.

The preparation method of the supported iron-tungsten bimetal composite oxide comprises the following steps:

step 1, iron nitrate nonahydrate (Fe (NO)₃)₃·9H₂O) and ammonium metatungstate (H)₂₈N₆O₄₁W₁₂) Performing ultrasonic treatment in deionized water until the solution is completely dissolved to obtain a precursor solution; wherein ferric nitrate (Fe (NO) nonahydrate₃)₃·9H₂O) and ammonium metatungstate (H)₂₈N₆O₄₁W₁₂) The molar ratio of (A) is 12x, wherein x is more than 0 and less than or equal to 2;

step 2, dipping the precursor solution completely dissolved by the ultrasonic in the step 1 on an inert oxide carrier by adopting an isometric dipping method, and continuously oscillating and ultrasonically dipping uniformly;

step 3, continuing to perform ultrasonic treatment on the uniformly dipped colloidal precursor solution obtained in the step 2 for 2-4 hours until the solution is completely uniform;

and 4, drying the substance obtained in the step 3 at room temperature for 10-14h, then drying at 90-120 ℃ for 10-14h, and finally roasting at 800-.

The application of the supported iron-tungsten bimetallic composite oxide is applied to methane three-bed chemical chain autothermal direct synthesis gas, and the reactor and the operation process can be implemented as follows:

carrying out tabletting and forming treatment on the load type iron-tungsten bimetal composite oxide to obtain solid oxide particles;

the fuel reactor can adopt a gas-solid cocurrent flow moving bed and a multistage fluidized bed design, the fuel can be carbon-rich fuel such as natural gas, heavy oil and the like, the fuel reactor can maintain the temperature of 600-1100 ℃ for reaction, preferably 850-950 ℃, oxide enters from the bottom of the fuel reactor, the fuel enters from the bottom of the reactor, and the generated reducing gas ascends. The top outlet of the fuel reactor obtains high selectivity synthesis gas. The reduced Fe-W alloy can catalyze fuel reforming, accelerate gas phase reaction and solid phase WO₃Reduction of Fe-W alloy in reduced state at bottom of reactor and WO_g(0≤g<3) The selectivity of the synthesis gas is improved;

reaction 1: CH (CH)₄+FeWO₄＝CO+H₂+Fe-W+WO_g(0≤g<3)。

Steam reactor, reduced Fe-W alloy WO_g(0≤g<3) Entering the top of a water vapor reactor from the bottom chamber of the fuel reactor, and controlling the temperature at 500-900 ℃; the lower end of the steam reactor is filled with steam, the gas-solid contact mode can be countercurrent, cocurrent and cross current, the optimal gas-solid countercurrent contact mode is realized by a moving bed or a multi-stage fluidized bed, and the conversion rate from the steam to the hydrogen is favorably improved; reduced WO_gWith Fe-W alloy being oxidised to WO₃/WO_2.92，FeWO_4-qQ 0 < q.ltoreq.4 with hydrogen generation, WO₃/WO_2.92And FeWO which is not completely oxidized_4-q(q is more than 0 and less than or equal to 4) is separated from the bottom of the steam reactor; the gas product leaves from the top of the water vapor reactor and is condensed and separated to obtain pure hydrogen;

reaction 2: Fe-W + WO_g+H₂O＝FeWO_4-q+WO_2.96+H₂(0≤g<3),(0＜q≤4)。

Solid WO separated from the bottom of air reactor and steam reactor₃/WO_2.96And FeWO_4-q(q is more than 0 and less than or equal to 4) and enters an air reactor, and the temperature is controlled at 600-1100 ℃; WO₃/WO_2.92And FeWO which is not completely oxidized_4-q(q is more than 0 and less than or equal to 4)All is re-oxidized by air into FeWO₄(ii) a The oxidized waste water is regenerated to realize cyclic utilization, and simultaneously releases heat for the self-heating operation of the system; the reduced oxygen carrier mainly comprises Fe-W alloy, WO_g，0≤g<3；

Reaction 3: FeWO_4-q+WO_2.96+O₂＝FeWO₄(0≤g<3),(0＜q≤4)。

The invention has the beneficial effects that:

the oxide of the invention is supported (by SiO)₂For example) in WO₃And Fe₂O₃Forming the bimetal composite oxide. Adopting Fe with similar ionic radius and consistent ionic diffusion rate²⁺And W⁶⁺Forming the bimetal composite oxide. After formation of the complex oxide, as compared with WO₃In other words, WO can be greatly improved₃The activation capability to methane improves the conversion rate of methane; relative to Fe₂O₃In other words, the bond energy of Fe-O bond can be inhibited, the generation of complete oxidation products is reduced, and the yield of the synthesis gas is improved; the W-O bond can be activated, the transmission rate of lattice oxygen and the quantity of available lattice oxygen are improved, the oxygen transmission rate can be matched with the rate of generating carbon intermediate species by activating methane through iron ions, and the carbon deposition resistance of the catalyst is improved; meanwhile, because the radiuses of the iron ions and the tungsten ions are similar, the oxidation rate of the metal after the alloy is formed after the ion diffusion rate is similar, and the structural stability of the catalyst is greatly improved.

The bimetallic oxide is prepared by adopting equal-volume impregnation, the method is simple and easy to implement, has low manufacturing cost compared with the existing composite metal oxide and preparation method, is convenient for large-scale use and utilization, and realizes the preparation of directly converting fuel into synthesis gas and the near-zero energy consumption in-situ separation of products.

The bimetallic oxide can be used for a three-bed chemical-looping direct synthesis gas preparation process, and on one hand, the heat absorbed in the reduction process can be coupled with the heat released in the oxidation process, so that the autothermal reforming is realized, and the energy consumption is reduced; on the other hand, the lattice oxygen in the oxygen carrier is used as the source of oxygen species, so that the selectivity of the oxygen carrier to the synthetic gas can be improved, the yield of the synthetic gas can be increased, and the danger of explosion caused by direct contact of air and methane can be avoided. Wherein the fuel reactor is preferably a moving bed reactor or a multi-stage fluidized bed reactor with gas-solid cocurrent operation, which is beneficial to improving the conversion rate of gas and solid and the yield of synthesis gas; moreover, the synthesis gas can be prepared by self-heating by adjusting the feeding proportion of the air in the system.

Drawings

FIG. 1 is a graph of methane conversion, hydrogen selectivity, carbon monoxide selectivity, and hydrogen to carbon ratio in a fuel reactor versus cycle number for examples 1, 2, 7, 10, 11, 12, 13 under the conditions of example 19; wherein (A) is a graph of methane conversion rate as a function of cycle number; (B) the hydrogen selectivity changes with the cycle number (C) is a graph of the carbon monoxide selectivity with the cycle number; (D) the hydrogen-carbon ratio is shown as a function of the number of cycles.

FIG. 2 shows examples 1, 2, 7, 12 and 13 under the conditions of example 19, the reaction raw material methane and the reaction products CO and H in the fuel reactor are detected by gas mass spectrometry₂、CO₂、H₂Graph of relative content of O versus time; wherein (A) is a variation of example 1; (B) is a variation of example 2; (C) is a variation of example 7; (D) is a variation of example 12; (E) is a variation of example 13.

FIG. 3 is a graph of the change in methane conversion, hydrogen selectivity, carbon monoxide selectivity, and hydrogen to carbon ratio over 50 cycles in a fuel reactor under the conditions of example 19 for example 2.

Detailed Description

The present invention is further described in detail below by way of specific examples, which will enable one skilled in the art to more fully understand the present invention, but which are not intended to limit the invention in any way.