CN108970614B

CN108970614B - Iron-based catalyst, preparation method and application thereof

Info

Publication number: CN108970614B
Application number: CN201810864204.8A
Authority: CN
Inventors: 谢晶; 舒歌平; 章序文; 杨葛灵; 王洪学; 高山松
Original assignee: China Shenhua Coal to Liquid Chemical Co Ltd; China Energy Investment Corp Ltd; Shanghai Research Institute of China Shenhua Coal to Liquid Chemical Co Ltd
Current assignee: China Shenhua Coal to Liquid Chemical Co Ltd; China Energy Investment Corp Ltd; Shanghai Research Institute of China Shenhua Coal to Liquid Chemical Co Ltd
Priority date: 2018-08-01
Filing date: 2018-08-01
Publication date: 2021-05-18
Anticipated expiration: 2038-08-01
Also published as: CN108970614A

Abstract

The invention provides an iron catalyst, a preparation method and application thereof. The preparation method comprises the following steps: 1) mixing and reacting an iron-containing soluble salt solution with an alkaline aqueous solution to obtain a slurry-state primary product; 2) under an aerobic atmosphere, loading the primary product on a solid carrier in a spraying manner, and carrying out crystal phase transformation to obtain a secondary product of the solid carrier with FeOOH loaded on the surface; and 3) drying the secondary product in a nitrogen atmosphere to obtain the iron-based catalyst. The preparation method of the iron catalyst provided by the invention has the advantages of short process flow, low production cost, low water consumption and no waste water, and the catalyst prepared by the preparation method has high direct coal liquefaction catalytic activity.

Description

Iron-based catalyst, preparation method and application thereof

Technical Field

The invention relates to the field of coal chemical industry, and particularly relates to an iron-based catalyst, and a preparation method and application thereof.

Background

China has relatively rich coal resources and relatively short petroleum and natural gas resources. Direct coal liquefaction is a clean coal technology that converts coal into liquid products under the conditions of high temperature and high pressure by the action of a hydrogen-donating solvent and a catalyst. The main products of the process are high-quality gasoline, jet fuel oil, diesel oil, aromatic hydrocarbon and carbon chemical raw materials, and the byproducts are fuel gas, liquefied petroleum gas, sulfur, ammonia and the like, and the thermal efficiency of the process is up to 70%. Therefore, the direct coal liquefaction for producing the liquid fuel is an important way for clean coal conversion and efficient utilization, and is an effective technical means for balancing resources in coal-rich and oil-poor areas. The first megaton-level direct coal liquefaction production line in China successfully operates for nine years from 2008 production to the present, and the design and construction of the second production line and the third production line are carried out.

The direct coal liquefaction process is a complex physical and chemical process, and has a plurality of influencing factors, mainly including: the type and nature of the coal, the reactor form, the catalyst, the solvent, the reaction temperature and time, the atmosphere, etc. The direct coal liquefaction catalyst can promote the pyrolysis of coal and accelerate the hydrocracking of pyrolysis macromolecules, and improve the yield of oil and the quality of oil in products, so that how to develop and design the catalyst with high catalytic activity, good selectivity and low price is always a hotspot of direct coal liquefaction research.

Most of iron catalysts are low in price and good in activity, and are suitable for a direct coal liquefaction process which does not need to be recovered in one-time pass, so that the iron catalysts are widely researched and applied. The pyrrhotite phase (Fe1-xS) generated in situ in the catalytic coal liquefaction reaction has been identified by most researchers as the active phase of iron-based catalysts. Red mud, natural iron ore, synthetic iron sulfide, synthetic iron oxide, and oil-soluble and water-soluble iron-containing substances are used as precursors of coal liquefaction catalysts, but the properties such as crystal phase structure, particle size and dispersibility of the red mud, the natural iron ore, the synthetic iron sulfide, the synthetic iron oxide, and the oil-soluble and water-soluble iron-containing substances are different, so that the corresponding active phase properties and the catalytic coal liquefaction effect are greatly different. The types and preparation methods of the synthetic iron-based catalyst are various. In order to achieve high activity, researchers are more pursuing the synthesis of iron precursor species of lower particle size and higher dispersion.

The preparation method of the iron-based catalyst in the prior art mainly has the following defects:

defect one: the water consumption is large, and the wastewater which is difficult to treat and has high salt concentration is generated.

And defect two: the preparation process has long and complicated flow, high energy consumption and high cost, and is not suitable for large-scale development and application.

For the above reasons, further research on a preparation method of the iron-based catalyst is needed to solve the problems of large water consumption, long and complicated process flow, high energy consumption, high cost and unsuitability for large-scale development and application of the preparation method of the iron-based catalyst in the prior art.

Disclosure of Invention

The invention mainly aims to provide an iron-based catalyst, a preparation method and application thereof, and aims to solve the problems that the preparation method of the iron-based catalyst in the prior art is large in water consumption, long and complex in process flow, high in energy consumption and cost, and not suitable for large-scale development and application.

In order to achieve the above object, according to one aspect of the present invention, there is provided a method for preparing an iron-based catalyst, the method comprising: 1) mixing and reacting an iron-containing soluble salt solution with an alkaline aqueous solution to obtain a slurry-state primary product; 2) under an aerobic atmosphere, loading the primary product on a solid carrier in a spraying manner, and carrying out crystal phase transformation to obtain a secondary product of the solid carrier with FeOOH loaded on the surface; and 3) drying the secondary product in a nitrogen atmosphere to obtain the iron-based catalyst.

Further, in the step 1), an alkaline aqueous solution is added to the iron-containing soluble salt solution under stirring, and a slurry-state initial product is obtained after the reaction. Preferably, the primary slurry product is a primary precipitate of iron Fe (OH)₂Or Fe (OH)₃. Preferably, the end point pH of the slurry initial product is controlled between 7.5 and 9.0.

Further, in step 1), the iron-containing soluble salt solution and the alkaline aqueous solution are mixed in a cocurrent manner under stirring, and after reaction, a slurry-state primary product is obtained. Preferably, the primary slurry product is a primary precipitate of iron Fe (OH)₂Or Fe (OH)₃. Preferably, the end point pH of the slurry initial product is controlled between 7.0 and 9.0.

Further, in the step 2), the solid support is a spherical solid support. Preferably, the solid support is coal fines.

Further, in the step 2), a certain amount of air is continuously introduced to form an air atmosphere, and simultaneously the primary product is sprayed on the surface of the rapidly-turned coal dust in a spraying manner, and then the slurry-state primary product containing the iron precipitate migrates on the surface of the coal dust and undergoes crystal phase transformation to generate FeOOH, so that a secondary product loaded with FeOOH on the surface of the coal dust is obtained.

Further, the primary product spray forms droplets having a diameter of less than 300 μm.

Further, the temperature of the pulverized coal is kept between 60 and 120 ℃.

Further, the particle size of the pulverized coal is less than 150 μm.

Further, in the step 3), drying the secondary product at 150-250 ℃ for 1-5 h to obtain an iron-based catalyst; preferably, the water content in the iron-based catalyst is 1 to 4 wt%;

further, the dried iron-based catalyst is ground to 80 μm or less.

Further, the iron content in the prepared iron-based catalyst is 1-6 wt%.

Further, the iron-containing soluble salt is selected from one or more of the group consisting of ferrous sulfate, ferrous chloride, ferric sulfate and ferric nitrate; preferably, the iron-containing soluble salt is ferrous sulfate; preferably, the concentration of the iron-containing soluble salt solution is 15-30 wt%.

Further, the basic aqueous solution is a mixture of a base selected from one or more of the group consisting of ammonia, sodium carbonate and sodium hydroxide and water.

Further, the concentration of the alkaline aqueous solution is 15-30 wt%.

According to another aspect of the present invention, there is provided an iron-based catalyst prepared according to the preparation method described above.

According to another aspect of the present invention there is provided the use of an iron-based catalyst according to the preceding description in a direct coal liquefaction process.

By applying the technical scheme of the invention, the preparation method of the iron-based catalyst comprises the following steps: 1) mixing and reacting an iron-containing soluble salt solution with an alkaline aqueous solution to obtain a slurry-state primary product; 2) under an aerobic atmosphere, loading the primary product on a solid carrier in a spraying manner, and carrying out crystal phase transformation to obtain a secondary product of the solid carrier with FeOOH loaded on the surface; and 3) drying the secondary product in a nitrogen atmosphere to obtain the iron-based catalyst.

The method comprises the steps of firstly pre-precipitating iron ions or ferrous ions to obtain iron primary precipitates, then atomizing the iron primary precipitates into tiny liquid beads in a spraying mode, dripping the tiny liquid beads on a turned solid carrier, enabling the tiny liquid beads to migrate and permeate on the surface of the solid carrier and in a pore channel, enabling the iron precipitates to generate crystal phase transformation while shrinking, and finally realizing uniform and compact loading of an iron active precursor on the solid carrier.

Compared with the traditional liquid-phase precipitation method of low-concentration substrates, the preparation method of the catalyst provided by the application has three outstanding advantages. First, the preparation process flow is simpler. The traditional preparation method comprises 5 steps of precipitation, oxidation, filtration, drying, ball milling and the like, wherein each step is finished in different equipment. And secondly, the direct coal liquefaction catalytic activity of the catalyst can be obviously improved. The load uniformity and the crystal phase of the precursor are two most important properties of the iron-based catalyst and are closely related to the direct coal liquefaction catalytic activity; in the preparation method of the catalyst, iron ions are precipitated in advance and sprayed on the surface of a hot solid carrier in an atomization mode to realize one-step loading and crystal phase conversion, so that the crystal phase conversion efficiency can be enhanced, and more gamma-FeOOH crystal phases with higher activity can be obtained; secondly, the hardening of iron precipitates in the filtering and drying processes can be avoided, so that the load uniformity of the active precursor on the solid carrier is greatly improved, and the direct coal liquefaction catalytic activity is improved. And thirdly, water is greatly saved, consumption is reduced, and emission is reduced. The preparation method of the catalyst uses raw materials with higher concentration when the solution is prepared, can realize great water saving, does not need to filter liquid-phase products, does not produce waste water, and can avoid the problems of continuous production interruption and the like caused by overhigh failure rate of filter equipment such as a filter press and the like.

Therefore, the preparation method of the iron-based catalyst provided by the invention has the advantages of short process flow, low production cost, low water consumption and no waste water, and the catalyst prepared by the preparation method has high direct coal liquefaction catalytic activity.

Detailed Description

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail with reference to examples.

The present application is described in further detail below with reference to specific examples, which should not be construed as limiting the scope of the invention as claimed.

As described in the background art, the existing preparation method of the iron-based catalyst cannot effectively solve the problems of large water consumption, long and complicated process flow, high energy consumption, high cost and unsuitability for large-scale development and application. In order to solve the above problems, the present invention provides a method for preparing an iron-based catalyst, comprising: 1) mixing and reacting an iron-containing soluble salt solution with an alkaline aqueous solution to obtain a slurry-state primary product; 2) under an aerobic atmosphere, loading the primary product on a solid carrier in a spraying manner, and carrying out crystal phase transformation to obtain a secondary product of the solid carrier with FeOOH loaded on the surface; and 3) drying the secondary product in a nitrogen atmosphere to obtain the iron-based catalyst.

The preparation method of the iron catalyst provided by the invention has the advantages of short process flow, low production cost, low water consumption and no waste water, and the catalyst prepared by the preparation method has high direct coal liquefaction catalytic activity.

In a preferred embodiment, in step 1), an aqueous alkaline solution is added to the iron-containing soluble salt solution with stirring, and after the reaction, a slurry-state primary product is obtained. Preferably, the primary slurry product is a primary precipitate of iron Fe (OH)₂Or Fe (OH)₃. Preferably, the end point pH of the slurry initial productThe value is controlled between 7.5 and 9.0. The pH value of the ferric salt precipitate in the step 1) is 7.5-9.0, so that the difficulty of generating FeOOH crystal phase species in the step 2) is reduced, and the activity of the product is further improved.

In a preferred embodiment, in step 1), the iron-containing soluble salt solution is mixed with the aqueous alkaline solution in cocurrent flow with stirring, and after the reaction, a slurry-like initial product is obtained. Preferably, the primary slurry product is a primary precipitate of iron Fe (OH)₂Or Fe (OH)₃. Preferably, the end point pH of the slurry initial product is controlled between 7.0 and 9.0. The pH value of the ferric salt precipitate in the step 1) is controlled to be 7.0-9.0, so that the difficulty of generating FeOOH crystal phase species in the step 2) is reduced, and the activity of the product is further improved.

In a preferred embodiment, in step 2), the solid support is a spherical solid support. Preferably, the solid support is coal fines. Compared with other solid carriers, the pulverized coal used in the invention has fine particles, the pulverized coal of unit mass has larger surface area, and a large amount of air can be adsorbed on the surface, so that the pulverized coal has fluidity.

In a preferred embodiment, in step 2), a certain amount of air is continuously introduced to form an air atmosphere, and the primary product is sprayed on the surface of the rapidly-stirred coal powder in a spraying manner, so that the slurry-state primary product containing the iron precipitate is then migrated on the surface of the coal powder and undergoes crystal phase transformation to generate FeOOH, and thus a secondary product loaded with FeOOH on the surface of the coal powder is obtained. In the step, the iron primary precipitate is atomized into tiny liquid beads in a spraying mode and is dripped on the turned hot coal powder, the tiny liquid beads migrate and permeate on the surface of the coal powder and in the pore passage, the iron precipitate generates crystal phase transformation while the iron primary precipitate shrinks, and finally the uniform and compact load of the iron active precursor on the coal powder is realized. The step is sprayed on the surface of hot pulverized coal in an atomizing mode to realize one-step load and crystal phase conversion, and firstly, the crystal phase conversion efficiency can be enhanced to obtain more gamma-FeOOH crystal phases with higher activity; secondly, the hardening of iron precipitates in the filtering and drying processes can be avoided, so that the load uniformity of the active precursor on the coal powder is greatly improved, and the direct coal liquefaction catalytic activity is improved.

In a preferred embodiment, the droplet diameter of the spray of the primary product is less than 300. mu.m. The size of the atomized liquid drops is controlled to be less than 300 mu m, so that the invention is favorable for preventing the initial generation of Fe (OH) caused by overlarge atomized liquid drops₂And/or Fe (OH)₃The nano crystal grains are easy to be aggregated into large particles, so that the nano crystal grains can be better dispersed on the surface of the solid carrier, nano FeOOH is formed, and the activity of the catalyst is further improved.

In a preferred embodiment, the temperature of the pulverized coal is maintained at 60 to 120 ℃. Compared with the temperature of other coal powder, the temperature of the hot coal powder is 60-120 ℃, so that the primary iron precipitate can be transferred and uniformly loaded on the surface of the coal powder in time, the uniformity of the load is further improved, and the primary iron precipitate is easy to generate high-activity FeOOH species, so that the catalytic activity is greatly improved.

In a preferred embodiment, the coal fines have a particle size of less than 150 μm. Compared with other coal powder particle sizes, the coal powder particle size of the invention is less than 150 μm, so that FeOOH is easy to be uniformly distributed on the surface of the coal powder, and the catalytic activity is further improved.

In a preferred embodiment, in the step 3), the secondary product is dried at 150-250 ℃ for 1-5 h to obtain the iron-based catalyst; preferably, the water content in the iron-based catalyst is 1 to 4 wt%. Compared with the drying temperature of other secondary products, the drying temperature of the secondary products is controlled to be 150-250 ℃, so that the drying efficiency is improved, and the active precursor is not easy to decompose. According to the invention, the water content in the catalyst is controlled by adjusting the drying time to be 1-5 h, so that the water content in the catalyst is controlled to be 1-4 wt%, the proper water partial pressure in coal liquefaction is favorably maintained, the coal liquefaction efficiency is further improved, the stability of the iron active precursor is further improved, and the activity of catalyzing direct coal liquefaction is further improved.

In a preferred embodiment, the iron-based catalyst after drying is ground to 80 μm or less. In the invention, the iron catalyst in the catalyst is ground to be less than 80 μm, so that the direct coal liquefaction catalytic activity can be further improved.

In a preferred embodiment, the iron-based catalyst is prepared to have an iron content of 1 to 6 wt%. Compared with other iron contents, the iron content in the catalyst is controlled to be 1-6 wt%, so that the water consumption for preparing raw materials is saved, and the energy consumption is further controlled; and the load uniformity of the iron active precursor on the surface of the pulverized coal is further improved, so that the activity is further improved.

In a preferred embodiment, the iron-containing soluble salt is selected from one or more of the group consisting of ferrous sulfate, ferrous chloride, ferric sulfate and ferric nitrate; preferably, the iron-containing soluble salt is ferrous sulfate. Compared with other iron sources, the iron source is preferably ferrous sulfate, the ferrous sulfate is low in cost, and the ferrous sulfate generates Fe (OH) in an alkaline environment₂Nanocrystalline grains, which are then air oxidized during drying, can form more highly active gamma-FeOOH crystalline phases.

In a preferred embodiment, the concentration of the iron-containing soluble salt solution is 15 to 30 wt%. Compared with the concentration of other iron salt solutions, the concentration of the iron salt solution is required to be 15-30 wt%, the consumption of the iron salt solution is favorably saved, the concentration of the formed slurry is moderate, the water content of the coal powder is moderate after the iron salt solution is sprayed on the surface of the coal powder, the coal powder is easy to flow, the energy consumption of drying is saved, and the crystal grain size of a catalyst precursor is moderate, so that the activity of the catalyst is further improved.

In a preferred embodiment, the basic aqueous solution is a mixture of a base selected from one or more of the group consisting of ammonia, sodium carbonate and sodium hydroxide and water; preferably, the concentration of the alkaline aqueous solution is 15-30 wt%. Compared with other alkaline solutions, the concentration of the alkaline solution is required to be 15-30 wt%, the consumption of the alkaline solution is favorably saved, the concentration of the formed slurry is moderate, the water content of the coal powder is moderate after the slurry is sprayed on the surface of the coal powder, the coal powder is easy to flow, the energy consumption of drying is saved, and high-activity FeOOH crystal phase species are easy to generate, so that the activity of the catalyst is further improved.

In addition, according to another aspect of the present invention, there is provided an iron-based catalyst prepared according to the preparation method described above.

Further, according to another aspect of the present invention, there is provided a use of the iron-based catalyst according to the foregoing description in a direct coal liquefaction process.

The beneficial effects of the present invention are further illustrated by the following examples:

example 1

Slowly dropping 25 wt% ammonia water solution into 900g 25 wt% ferrous sulfate solution, stirring rapidly, stopping dropping when pH value reaches 7.5, and stirring slowly to obtain slurry. Weighing 2000g of dried coal powder ground to the particle size of less than 150 mu m, placing the dried coal powder into a stirring reaction kettle with the volume of 8L, starting the reaction kettle to stir, and heating the heat-conducting oil. When the temperature of the coal powder rises to 80 ℃, 2L/min of air is introduced, the prepared slurry is conveyed to a spray head at the upper part of the reaction kettle for atomization through a plunger diaphragm pump, the atomization pressure is adjusted, the diameter of fog drops is controlled to be within 300 mu m, and the fog drops are sprayed on the surface of the stirred coal powder. After spraying, switching to nitrogen, raising the heating temperature of the reaction kettle to raise the temperature of the coal powder to 180 ℃, keeping for 2 hours, drying the catalyst, and finally grinding the catalyst to be below 80 mu m. Labeled as example 1# catalyst.

Example 2

Preparing 900g of 25 wt% ferrous sulfate solution, preparing 200g of 25 wt% ammonia water solution, pumping the two solutions into a 2L beaker through a peristaltic pump in a parallel flow manner for reaction, quickly stirring, controlling the pH value of the reaction to be 7.5 +/-0.1, stopping the feeding reaction after the ferrous sulfate solution is completely fed, and slowly stirring the formed slurry for later use. The subsequent steps were the same as in example 1. Labeled example 2# catalyst.

Example 3

Slowly dropping 25 wt% ammonia water solution into 550g 20 wt% ferrous sulfate solution, stirring rapidly, stopping dropping when pH value reaches 8.0, and stirring slowly to obtain slurry. Weighing 2000g of dried coal powder ground to the particle size of less than 200 mu m, placing the dried coal powder into a stirring reaction kettle with the volume of 8L, starting the reaction kettle to stir, and heating the heat-conducting oil. When the temperature of the coal powder rises to 60 ℃, 2L/min of air is introduced, the prepared slurry is conveyed to a spray head at the upper part of the reaction kettle for atomization through a plunger diaphragm pump, the atomization pressure is adjusted, the diameter of fog drops is controlled to be within 300 mu m, and the fog drops are sprayed on the surface of the stirred coal powder. After spraying, switching to nitrogen, raising the heating temperature of the reaction kettle to raise the temperature of the coal powder to 160 ℃, keeping for 3 hours, drying the catalyst, and finally grinding the catalyst to be below 80 mu m. Labeled example # 3 catalyst.

Example 4

Slowly dropping a sodium carbonate solution with the concentration of 15 wt% into 700g of a ferric nitrate solution with the concentration of 15 wt%, quickly stirring, stopping dropping when the pH value reaches 9.0, and slowly stirring the formed slurry for later use. Weighing 2000g of dried coal powder ground to the particle size of less than 100 mu m, placing the dried coal powder into a stirring reaction kettle with the volume of 8L, starting the reaction kettle to stir, and heating the heat-conducting oil. When the temperature of the coal powder rises to 60 ℃, 2L/min of air is introduced, the prepared slurry is conveyed to a spray head at the upper part of the reaction kettle for atomization through a plunger diaphragm pump, the atomization pressure is adjusted, the diameter of fog drops is controlled to be within 200 mu m, and the fog drops are sprayed on the surface of the stirred coal powder. After spraying, switching to nitrogen, raising the heating temperature of the reaction kettle to raise the temperature of the coal powder to 160 ℃, keeping for 4 hours, drying the catalyst, and finally grinding the catalyst to be below 80 mu m. Labeled example 4# catalyst.

Example 5

Slowly dropping sodium hydroxide solution with the concentration of 30 wt% into 900g ferrous chloride solution with the concentration of 30 wt%, quickly stirring, stopping dropping when the pH value reaches 8.5, and slowly stirring the formed slurry for later use. Weighing 2000g of dried coal powder ground to the particle size of less than 100 mu m, placing the dried coal powder into a stirring reaction kettle with the volume of 8L, starting the reaction kettle to stir, and heating the heat-conducting oil. When the temperature of the coal powder rises to 120 ℃, 2L/min of air is introduced, the prepared slurry is conveyed to a spray head at the upper part of the reaction kettle for atomization through a plunger diaphragm pump, the atomization pressure is adjusted, the diameter of fog drops is controlled to be within 250 mu m, and the fog drops are sprayed on the surface of the stirred coal powder. After spraying, switching to nitrogen, raising the heating temperature of the reaction kettle to raise the temperature of the coal powder to 200 ℃, keeping for 2 hours, drying the catalyst, and finally grinding the catalyst to be below 80 mu m. Labeled as example 5# catalyst.

Example 6

Slowly dropping 25 wt% ammonia water solution into 700g of 18 wt% ferric sulfate solution, rapidly stirring, stopping dropping when pH value reaches 7.0, and slowly stirring the formed slurry for later use. Weighing 2000g of dried coal powder ground to the particle size of less than 150 mu m, placing the dried coal powder into a stirring reaction kettle with the volume of 8L, starting the reaction kettle to stir, and heating the heat-conducting oil. When the temperature of the coal powder rises to 70 ℃, 2L/min of air is introduced, the prepared slurry is conveyed to a spray head at the upper part of the reaction kettle for atomization through a plunger diaphragm pump, the atomization pressure is adjusted, the diameter of fog drops is controlled to be within 300 mu m, and the fog drops are sprayed on the surface of the stirred coal powder. After spraying, switching to nitrogen, raising the heating temperature of the reaction kettle to raise the temperature of the coal powder to 150 ℃, keeping for 3 hours, drying the catalyst, and finally grinding the catalyst to be below 80 mu m. Labeled as example 6# catalyst.

Example 7

Slowly dropping 25 wt% ammonia water solution into 1700g 20 wt% ferrous sulfate solution, stirring rapidly, stopping dropping when pH value reaches 7.5, and stirring slowly for use. Weighing 2000g of dried coal powder ground to the particle size of less than 150 mu m, placing the dried coal powder into a stirring reaction kettle with the volume of 8L, starting the reaction kettle to stir, and heating the heat-conducting oil. When the temperature of the coal powder rises to 90 ℃, 2L/min of air is introduced, the prepared slurry is conveyed to a spray head at the upper part of the reaction kettle for atomization through a plunger diaphragm pump, the atomization pressure is adjusted, the diameter of fog drops is controlled to be within 300 mu m, and the fog drops are sprayed on the surface of the stirred coal powder. After spraying, switching to nitrogen, raising the heating temperature of the reaction kettle to raise the temperature of the coal powder to 220 ℃, keeping for 2 hours, drying the catalyst, and finally grinding the catalyst to be below 80 mu m. Labeled as example 7# catalyst.

Example 8

Slowly dropping 25 wt% ammonia water solution into 900g 20 wt% ferrous sulfate solution, stirring rapidly, stopping dropping when pH value reaches 7.8, and stirring slowly to obtain slurry. Weighing 2000g of dried coal powder ground to the particle size of less than 150 mu m, placing the dried coal powder into a stirring reaction kettle with the volume of 8L, starting the reaction kettle to stir, and heating the heat-conducting oil. When the temperature of the coal powder rises to 110 ℃, 2L/min of air is introduced, the prepared slurry is conveyed to a spray head at the upper part of the reaction kettle for atomization through a plunger diaphragm pump, the atomization pressure is adjusted, the diameter of fog drops is controlled to be within 230 mu m, and the fog drops are sprayed on the surface of the stirred coal powder. After spraying, switching to nitrogen, raising the heating temperature of the reaction kettle to raise the temperature of the coal powder to 250 ℃, keeping the temperature for 2.5 hours, drying the catalyst, and finally grinding the catalyst to be below 80 mu m. Labeled example 8# catalyst.

Example 9

Slowly dropping ammonia water solution with the concentration of 20 wt% into 1300g ferrous sulfate solution with the concentration of 20 wt%, quickly stirring, stopping dropping when the pH value reaches 8.0, and slowly stirring the formed slurry for later use. Weighing 2000g of dried coal powder ground to the particle size of less than 120 mu m, placing the dried coal powder into a stirring reaction kettle with the volume of 8L, starting the reaction kettle to stir, and heating the heat-conducting oil. When the temperature of the coal powder rises to 60 ℃, 2L/min of air is introduced, the prepared slurry is conveyed to a spray head at the upper part of the reaction kettle for atomization through a plunger diaphragm pump, the atomization pressure is adjusted, the diameter of fog drops is controlled to be within 250 mu m, and the fog drops are sprayed on the surface of the stirred coal powder. After spraying, switching to nitrogen, raising the heating temperature of the reaction kettle to raise the temperature of the coal powder to 190 ℃, keeping for 3 hours, drying the catalyst, and finally grinding the catalyst to be below 80 mu m. Labeled example 9# catalyst.

Example 10

Slowly dropping ammonia water solution with the concentration of 20 wt% into 1100g ferric sulfate solution with the concentration of 25 wt%, quickly stirring, stopping dropping when the pH value reaches 7.5, and slowly stirring the formed slurry for later use. Weighing 2000g of dried coal powder ground to the particle size of less than 80 mu m, placing the dried coal powder into a stirring reaction kettle with the volume of 8L, starting the reaction kettle to stir, and heating the heat-conducting oil. When the temperature of the coal powder rises to 100 ℃, 2L/min of air is introduced, the prepared slurry is conveyed to a spray head at the upper part of the reaction kettle for atomization through a plunger diaphragm pump, the atomization pressure is adjusted, the diameter of fog drops is controlled to be within 300 mu m, and the fog drops are sprayed on the surface of the stirred coal powder. After spraying, switching to nitrogen, raising the heating temperature of the reaction kettle to raise the temperature of the coal powder to 240 ℃, keeping for 2 hours, drying the catalyst, and finally grinding the catalyst to be below 80 mu m. Labeled example 10# catalyst.

Comparative example 11

The differences from example 1 are: the concentration of the ferrous sulfate solution is 10 wt%. Labeled comparative example 11# catalyst.

Comparative example 12

The differences from example 1 are: the concentration of the ferrous sulfate solution is 35 wt%. Labeled comparative example 12# catalyst.

Comparative example 13

The differences from example 1 are: the concentration of the aqueous ammonia solution was 10 wt%. Labeled comparative example 13# catalyst.

Comparative example 14

The differences from example 1 are: the concentration of the aqueous ammonia solution was 35 wt%. Labeled comparative example 14# catalyst.

Comparative example 15

The differences from example 1 are: the reaction end point pH was 6.0. Labeled comparative example 15# catalyst.

Comparative example 16

The differences from example 1 are: the end-point pH of the reaction was 9.5. Labeled comparative example 16# catalyst.

Comparative example 17

The differences from example 2 are: the diameter of the fog drops is within 400 mu m. Labeled comparative example 17# catalyst.

Comparative example 18

The differences from example 1 are: the particle size is less than 250 mu m. Labeled comparative example 18# catalyst.

Comparative example 19

The differences from example 1 are: the temperature of the coal powder is controlled to be 40 ℃ in the spraying and crystal phase conversion processes. Labeled comparative example 19# catalyst.

Comparative example 20

The differences from example 1 are: the temperature of the coal dust is controlled to be 150 ℃ in the spraying and crystal phase conversion processes. Labeled comparative example 20# catalyst.

Comparative example 21

The differences from example 1 are: the drying temperature under nitrogen atmosphere was 280 ℃. Labeled comparative example 21# catalyst.

Comparative example 22

The differences from example 1 are: the drying time under nitrogen was 0.5 h. Labeled comparative example 22# catalyst.

Comparative example 23

The differences from example 1 are: the drying time under nitrogen was 6 h. Labeled comparative example 23# catalyst.

Comparative example 1

Preparing a coal powder loaded FeOOH catalyst by adopting liquid-phase precipitation oxidation:

slowly dropping 25 wt% ammonia water solution into 900g 25 wt% ferrous sulfate solution, rapidly stirring, and stopping dropping when pH reaches 7.5; introducing 2L/min of air for oxidation for 1h, generating FeOOH-containing slurry after the reaction is finished, adding 2000g of dry coal powder with the granularity within 150 mu m, fully and uniformly stirring, filtering the mixed slurry, adding deionized water into the obtained filter cake for pulping and washing, drying the washed filter cake in a 120 ℃ nitrogen drying oven for 12h, and grinding the solid to be below 80 mu m after drying to obtain the coal powder-loaded FeOOH powder catalyst. Labeled as contrast agent 1.

Evaluation of catalyst Performance

A certain amount of the catalysts prepared in examples 1 to 21 and the catalyst in comparative example 1 were weighed respectively to perform a coal liquefaction autoclave test under the following coal liquefaction reaction performance test conditions: the catalysts prepared in examples 1 to 21 above and the catalyst in comparative example 1 were accurately weighed, respectively, and the objective catalyst was added to a 500mL autoclave coal liquefaction reaction. The coal sample used in the test is Shenhua Shendong coal, and the addition amount of the dry coal powder is 28 g; coal liquefaction cycle oil is used as a solvent, the adding amount of the solvent is 42g, the weight ratio of Fe to dry coal is 1:100 according to the measurement standard of each added catalyst, and 0.32g of sulfur powder is added. The initial pressure of the cold hydrogen in the autoclave reaction is 10MPa, the temperature is kept at 455 ℃ for 1h, and the reaction is finished. And (2) rapidly cooling the reaction system, taking a gas sample to measure the composition of the reaction system, collecting a liquid-solid phase after the reaction, respectively performing soxhlet extraction for 48 hours by using normal hexane and tetrahydrofuran, burning ash on extraction residues, and calculating to obtain data such as coal conversion rate, hydrogen consumption, gas yield, water yield, asphalt yield, oil yield and the like, which is shown in table 1.

TABLE 1

The catalytic performance of the coal direct liquefaction oil yield is the most critical index, and for megaton coal direct liquefaction industrial devices, small fluctuation of the oil yield can greatly influence the coal direct liquefaction economy.

As can be seen from the coal liquefaction test results in table 1, it is understood from example 1, comparative example 11 and comparative example 12 that limiting the concentration of the iron salt within the preferred protection range of the present application is advantageous for improving the catalytic performance of the catalyst. The concentration of the iron salt solution is required to be 15-30 wt%, the concentration of the formed slurry is moderate, the water content of the coal powder is moderate after the slurry is sprayed on the surface of the coal powder, the coal powder is easy to flow, the grain size of a catalyst precursor is moderate, and the activity of the catalyst is improved.

It is understood from example 1, comparative example 13 and comparative example 14 that limiting the concentration of the alkali solution within the preferred protection range of the present application is advantageous for improving the catalytic performance of the catalyst. The concentration of the alkaline solution is required to be 15-30 wt%, so that the concentration of the formed slurry is moderate, the water content of the coal powder is moderate after the slurry is sprayed on the surface of the coal powder, the coal powder can easily flow, high-activity FeOOH crystal phase species are generated, and the activity of the catalyst is improved.

It is understood from example 1, comparative example 15 and comparative example 16 that limiting the pH value of the reaction to the preferable range of protection in this application is advantageous in improving the catalytic performance of the catalyst, reducing the difficulty of producing highly active FeOOH crystal phase species, and increasing the activity of the product.

As can be seen from example 1 and comparative example 17, limiting the particle size of the atomized droplets within the preferred range of protection of the present application is advantageous in improving the catalytic performance of the catalyst. In the invention, atomized liquid drops are less than 300 mu m, so that initially generated Fe (OH)₂And/or Fe (OH)₃The nano crystal grains are not easy to be aggregated into large grains and are easy to be dispersed on the surface of the coal powder to form nano FeOOH, so that the activity of the catalyst is improved.

As can be seen from example 1 and comparative example 18, limiting the particle size of the pulverized coal to the preferred range of protection is advantageous for improving the catalytic performance of the catalyst. The granularity of the coal powder is less than 150 mu m, so that FeOOH is uniformly distributed on the surface of the coal powder, and the activity is increased.

As can be seen from example 1, comparative example 19, and comparative example 20, limiting the temperature of the pulverized coal to the preferable range of protection of the present application is advantageous for improving the catalytic performance of the catalyst. According to the invention, the temperature of the hot pulverized coal is 60-120 ℃, so that the primary iron precipitate is migrated and uniformly loaded on the surface of the pulverized coal, the uniformity of the load is improved, and high-activity FeOOH species are generated, so that the catalytic activity is greatly improved; is beneficial to the crystal phase transformation to generate gamma-FeOOH species with higher activity.

As can be seen from example 1 and comparative example 21, limiting the drying temperature to the range preferred in the present application is advantageous in improving the catalytic performance of the catalyst. According to the invention, the drying temperature of the secondary product is controlled to be 150-250 ℃, so that the drying efficiency is increased, and the active precursor is not decomposed.

It is understood from example 1, comparative example 22 and comparative example 23 that limiting the drying time of the secondary product to the preferable range of protection of the present application is advantageous in improving the catalytic performance of the catalyst. According to the invention, the water content in the catalyst is controlled by adjusting the drying time to be 1-5 h, so that the water content in the catalyst is controlled to be 1-4 wt%, the water partial pressure in coal liquefaction is normal, the coal liquefaction efficiency is improved, the stability of the iron active precursor is improved, and the activity of catalyzing direct coal liquefaction is improved.

From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects:

the yield of coal liquefaction oil corresponding to most of the catalysts prepared by the method is superior to that of a contrast agent or equivalent to that of the contrast agent, and the yield of oil corresponding to a small part of the catalysts is inferior to that of the contrast agent. Meanwhile, the preparation method of the catalyst has the advantages of less equipment, less operation cost, less water consumption and no wastewater discharge.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing an iron-based catalyst, the method comprising:

1) mixing and reacting an iron-containing soluble salt solution with an alkaline aqueous solution to obtain a slurry-state primary product;

2) under an aerobic atmosphere, loading the primary product on a solid carrier in a spraying manner, and carrying out crystal phase transformation to obtain a secondary product of the solid carrier with FeOOH loaded on the surface; and

3) and drying the secondary product in a nitrogen atmosphere to obtain the iron-based catalyst.

2. The method for preparing the iron-based catalyst according to claim 1, wherein the aqueous alkaline solution is added to the iron-containing soluble salt solution under stirring in step 1), and the slurry-state initial product is obtained after the reaction.

3. The method of claim 1, wherein the iron-containing soluble salt solution and the aqueous alkaline solution are mixed in parallel flow with stirring in step 1), and the slurry-state initial product is obtained after the reaction.

4. The method for producing a iron-based catalyst according to any one of claims 1 to 3, wherein in step 2), the solid support is a spherical solid support.

5. The method of claim 4, wherein the solid support is pulverized coal.

6. The method according to claim 4, wherein the diameter of the droplets formed by spraying the primary product is less than 300 μm.

7. The method for preparing the iron-based catalyst according to claim 5, wherein the temperature of the pulverized coal is maintained at 60 to 120 ℃.

8. The method of claim 5, wherein the pulverized coal has a particle size of less than 150 μm.

9. The method for preparing the iron-based catalyst according to any one of claims 1 to 3, wherein the iron-based catalyst is obtained by drying the secondary product at 150 to 250 ℃ for 1 to 5 hours in the step 3).

10. The method according to claim 9, wherein the water content in the iron-based catalyst is 1 to 4 wt%.

11. The method according to claim 9, wherein the dried iron-based catalyst is ground to 80 μm or less.

12. The method of claim 9, wherein the iron content of the iron-based catalyst is 1 to 6 wt%.

13. The method for preparing an iron-based catalyst according to any one of claims 1 to 3, wherein the iron-containing soluble salt is one or more selected from the group consisting of ferrous sulfate, ferrous chloride, ferric sulfate and ferric nitrate.

14. The method of claim 13, wherein the soluble salt containing iron is ferrous sulfate; the concentration of the iron-containing soluble salt solution is 15-30 wt%.

15. The method of claim 13, wherein the aqueous alkaline solution is a mixture of a base selected from one or more of the group consisting of ammonia, sodium carbonate, and sodium hydroxide and water.

16. The method according to claim 13, wherein the concentration of the aqueous alkaline solution is 15 to 30 wt%.

17. The method according to claim 2, wherein the final pH of the slurry initial product is controlled to be 7.5 to 9.0.

18. The method according to claim 3, wherein the final pH of the slurry initial product is controlled to be 7.0 to 9.0.

19. An iron-based catalyst, characterized by being produced by the production method according to any one of claims 1 to 18.

20. Use of the iron-based catalyst of claim 19 in a direct coal liquefaction process.