Coal gasification slag denitration catalyst as well as preparation method and application thereof

Abstract

The invention provides a coal gasification slag denitration catalyst and a preparation method thereof, and belongs to the technical field of coal gasification slag denitration catalyst preparation. The preparation method of the coal gasification slag denitration catalyst comprises the following steps: mixing coal gasification slag and an acetic acid solution to obtain a mixed system, standing and aging the mixed system, and heating and drying to obtain a coal gasification slag acetic acid modified product; grinding and sieving the coal gasification slag acetic acid modified product to obtain coal gasification slag acetic acid modified powder; and calcining the coal gasification slag acetic acid modified powder to prepare the acetic acid modified coal gasification slag denitration catalyst. The preparation method disclosed by the invention is simple and feasible in process, low in cost and suitable for industrial large-scale batch production, and high-value recycling of solid waste coal gasification slag can be realized. After acetic acid modification treatment provided by the invention, the denitration activity of the coal gasification slag denitration catalyst is remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of coal gasification slag denitration catalyst preparation, and specifically relates to a coal gasification slag denitration catalyst and a preparation method and application thereof. Background Art

[0002] NO x It is mainly caused by the burning of fossil energy and solid waste. It is one of the main pollutants in the atmosphere and has an impact on human health. In addition, the emission standards are becoming increasingly stringent. x The removal of NOx cannot be delayed. Currently, the conventional choice of denitrification technology is selective catalytic reduction (SCR), and NH3-SCR technology is the main one. NH3-SCR technology requires NH3 as a reducing agent, so there is a problem of NH3 escape. At the same time, the reaction byproduct NH4HSO4 also poses a safety risk of clogging the pipeline. In addition, the vanadium catalyst used in this process is toxic and harmful to the human body and the environment. Therefore, how to reduce NOx to NH3-SCR under ammonia-free conditions? x Catalytic denitrification into environmentally friendly nitrogen and oxygen has gradually become a research hotspot in this technology.

[0003] As the core technology of modern coal chemical industry, coal gasification is an important part of promoting the green transformation of coal and carrying out clean and efficient utilization. As an efficient and environmentally friendly coal conversion technology, it has good development prospects in related industries. Coal gasification slag is a solid residue waste. It is formed in the process of coal gasification. It is a solid residue formed by various inorganic substances in coal and residual carbon during the physical and chemical changes. Coal gasification slag is mainly amorphous glass, and its chemical composition mainly includes SiO2, Al2O3, CaO, Fe2O3, MgO and C. Coal gasification slag can be recycled as a solid waste resource according to its own characteristics. However, the main recycling methods of coal gasification slag are low-lying land reclamation, mine filling and even direct stacking. These treatment methods not only have extremely low recycling value, but also cause soil and groundwater pollution, and even damage the ecological environment and cause disasters. Therefore, finding new recycling methods for coal gasification slag and realizing high-value utilization of coal gasification slag is not only conducive to saving resources and protecting the environment, but also has great significance for the overall sustainable development of the coal industry.

[0004] Coal gasification slag contains abundant carbon, silicon and aluminum resources, with huge output, unique porous structure and good hydration activity. It is a natural porous material with adsorption and carrier functions. At present, the bulk high-value utilization of coal gasification slag is mainly to directly use unmodified coal gasification slag as adsorption material and catalyst carrier, and use modified coal gasification slag as catalyst. However, there are few related studies on the preparation of denitration catalysts from coal gasification slag. The Chinese patent with publication number CN113499778A discloses "a coal gasification slag cement kiln high-temperature flue gas denitration catalyst and its preparation method", which dries the coal gasification slag and then activates it with ethanol. The denitration rate can only be guaranteed at a temperature higher than 850 ℃. On the one hand, the use of anhydrous ethanol has the risk of flammability and explosion, and the cost is high; on the other hand, the long-term denitration stability of the denitration catalyst prepared by this process needs to be improved. Summary of the invention

[0005] In order to overcome the defects of the above-mentioned prior art, the present invention provides a coal gasification slag denitration catalyst and a preparation method and application thereof, so as to solve the technical problems that the solvent selected in the existing coal gasification slag denitration catalyst preparation process has the risk of flammability and explosion, and the denitration efficiency is poor and the stability is not high after long-term use.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The method for preparing a coal gasification slag denitration catalyst disclosed in the present invention uses coal gasification slag as a raw material, modifies and activates the raw material with acetic acid, and then performs drying and calcination treatment to prepare a coal gasification slag denitration catalyst having high catalytic nitrogen oxide decomposition activity. The preparation method comprises the following steps: Step 1, mixing coal gasification slag with acetic acid solution to obtain a mixed system, placing the mixed system for aging treatment (so that acetic acid and coal gasification slag are in contact and reacted), and then heating and drying to obtain a coal gasification slag acetic acid modified product; Step 2, grinding and sieving the coal gasification slag acetic acid modified product obtained in step 1 to obtain coal gasification slag acetic acid modified powder; Step 3: calcining the coal gasification slag acetic acid modified powder to obtain the acetic acid modified coal gasification slag denitrification catalyst.

[0007] Preferably, in step 1, the acetic acid solution has a concentration of 0.5 to 3 mol·L -1 of acetic acid aqueous solution.

[0008] Preferably, in step 1, the coal gasification slag is coarse coal gasification slag or fine coal gasification slag; wherein the carbon content of the coarse coal gasification slag is 20% to 25%, and the carbon content of the fine coal gasification slag is 40% to 45%.

[0009] Furthermore, the coarse slag from coal gasification is collected at the slag discharge port of the gasifier, accounting for 60% to 80% of the coal gasification slag; the fine slag from coal gasification is mainly collected in the dust removal device, accounting for 20% to 40% of the coal gasification slag. Since the residence time of the coarse slag from coal gasification in the gasifier is longer than that of the fine slag, and the incomplete combustion process is more thorough than that of the fine slag, the carbon content of the coarse slag from coal gasification is generally relatively low, and the carbon content of the fine slag from coal gasification is relatively high. Acetic acid is corrosive to both coarse slag from coal gasification and fine slag from coal gasification, so mixing coarse slag from coal gasification and fine slag from coal gasification as raw materials for acetic acid modification can also improve their denitration activity. Under the same conditions, the denitration catalytic rate of the mixed coal gasification slag is between the denitration catalytic rates of the fine slag from coal gasification and the coarse slag from coal gasification in this embodiment. Overall, the method for modifying the coal gasification slag used in the present invention has no special requirements for the carbon content of the coal gasification slag, and can achieve the effect of improving the catalytic denitration activity of the coal gasification slag.

[0010] Preferably, in step 1, the ratio of coal gasification slag to acetic acid solution is (2-3) g: (3-4) mL.

[0011] Preferably, in step 1, the standing aging time is 4 to 6 hours, the heating and drying temperature is 60 to 80° C., and the heating and drying time is 10 to 12 hours.

[0012] Preferably, in step 2, the size of the sieve used for the sieving process is 80-100 mesh.

[0013] Preferably, in step 3, the calcination atmosphere is argon or nitrogen, the calcination temperature is 500-600° C., and the calcination time is 4-6 h.

[0014] The present invention also provides a coal gasification slag denitration catalyst, which is prepared by the above-mentioned preparation method.

[0015] Furthermore, the specific surface area of ​​the coal gasification slag denitrification catalyst is 234.73~291.47 S BET (m 2 / g), the active component Fe element is precipitated on the surface of the coal gasification slag denitration catalyst, and the content of the active component Fe element is 2~10At%.

[0016] The present invention also provides the use of the above-mentioned coal gasification slag denitration catalyst in denitration catalysis.

[0017] Specifically, the NO concentration of a thermal power plant was simulated at different temperatures. The flue gas concentration was set to 300-400 ppm. Under the principle of ensuring that the flue gas was in full contact with the coal gasification slag denitration catalyst, the flue gas was denitrated using the coal gasification slag denitration catalyst. Ar was the balance gas, and the gas flow rate was 80-100 mL·min -1 , airspeed is 30000~50000 h-1 Flue gas was introduced into the fixed bed reactor from room temperature, and the temperature was raised from 50°C to 600°C in steps of 50°C. Each temperature was kept for 30 min to allow the flue gas to fully and stably react with the coal gasification slag denitration catalyst. The NO concentration in the outlet flue gas at different temperatures was tested, and the denitration rate was calculated to characterize the denitration performance of the coal gasification slag denitration catalyst. When the reaction temperature reached 500°C, 1 mol·L -1 The denitrification rate of the HAc-modified coal gasification slag denitrification catalyst can reach 92.3%, and when the reaction temperature reaches 550 ℃, the denitrification rate can reach 99.99%.

[0018] Compared with the existing invention, the beneficial effects of the present invention are: The preparation method of the coal gasification slag denitration catalyst disclosed in the present invention, on the one hand, selects low-concentration acetic acid for activation treatment. The price of acetic acid is lower than that of anhydrous ethanol, and it has less corrosion damage to equipment, and there is no flammable and explosive safety hazard. In principle, the coal gasification slag is etched with acetic acid, so that a large number of pore structures are produced in the glassy spherical shell of the coal gasification slag, which increases the specific surface area of ​​the coal gasification slag, increases the adsorption capacity of the coal gasification slag, and also helps NO to contact the active components more fully. In the process of acid etching, the aluminosilicate shell structure of the coal gasification slag is dissolved, so that the internal metal elements are dissolved to the surface and fully exposed. On the other hand, the present invention can form a stable ion pair Fe on the catalyst surface after weak acid treatment and then drying, calcining and activation treatment. 3+ / Fe 2+ etc., as stable denitrification active centers, undergo redox reactions with NO, which is beneficial for more complete contact between active sites and reactants, and the overall performance is a longer denitrification activity, effectively reducing the reaction temperature window, thereby improving denitrification activity. From the experimental data results, the prepared denitrification agent can maintain a denitrification efficiency of not less than 90% for 12 hours under a long-term reaction at 600°C. The preparation method of the present invention is simple and easy to operate, low in cost, suitable for industrial large-scale batch production, and can achieve high-value reuse of solid waste coal gasification slag.

[0019] When the coal gasification slag denitration catalyst prepared by the present invention is used for catalytic denitration, it can directly catalytically decompose and remove nitrogen oxides in flue gas. It can be seen from the experimental results of the present invention that at 500 °C, using 1 mol·L -1 The denitration rate of the HAc-modified coal gasification slag denitration catalyst was 92.3%. -1 The denitrification rate of the HAc-modified coal gasification crude slag denitrification catalyst is 99.9%, and the removal efficiency is far higher than that of existing similar coal gasification slag denitrification catalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1The N2 adsorption and desorption isotherms (left figure) and pore size distribution diagram (right figure) of the modified coal gasification crude slag denitration catalyst prepared in the present invention; Figure 2 The figure is a relationship diagram between the NO conversion rate and the reaction temperature of the denitration catalysts of Comparative Example 1 and Comparative Example 2, so as to show the denitration activity of the unmodified coal gasification coarse slag denitration catalyst and the unmodified coal gasification fine slag denitration catalyst; Figure 3 The figure is a relationship diagram between the NO conversion rate and the reaction temperature of the denitration catalysts of Example 1 of the present invention and Comparative Example 1, to show the improvement of the denitration activity before and after the acid treatment; Figure 4 The XPS spectra before and after modification and denitration reaction are shown to show the effects of acid treatment and denitration reaction on surface elements; a) is 3 mol·L -1 HAc modified coal gasification crude slag; b) after denitrification reaction 3 mol·L -1 HAc modified coal gasification crude slag; c) unmodified coal gasification crude slag; Figure 5 The figure is a relationship diagram between the NO conversion rate and the reaction temperature of the modified coal gasification crude slag denitration catalyst of Example 1, Example 2, Example 3 and Example 4 of the present invention, to show the effect of different acid treatment concentrations on the improvement of denitration activity; Figure 6 The graph is a relationship between the catalytic NO conversion rate and the reaction temperature of the coal gasification slag denitration catalyst of Example 1 and Example 5, to illustrate the effect of acid treatment of raw materials with different carbon contents on the improvement of denitration activity.

[0021] Figure 7 The graph is a relationship between the NO conversion rate and the reaction time of Example 4 at 500°C for a long time, to illustrate the stability of the coal gasification slag denitration catalyst of the present invention during a long-term denitration reaction. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0023] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0024] The present invention is further described in detail below in conjunction with the accompanying drawings: In this specification, when "normal temperature" or "room temperature" is used, the temperature may be 10 to 25°C.

[0025] The present invention provides a coal gasification slag denitration catalyst and a preparation method and application thereof. The method uses coal gasification slag as a raw material, and performs acetic acid modification treatment to expose internal active components, thereby generating activity for directly catalyzing and decomposing NO at medium temperature, thereby preparing a coal gasification slag denitration catalyst, namely an acetic acid-modified coal gasification slag denitration catalyst (hereinafter referred to as HAc-modified coal gasification coarse / fine slag denitration catalyst), wherein the carbon content is 20%-50%, the iron content is 3%-10%, and the aluminosilicate content is 30%-50%.

[0026] Specifically, the method for preparing the coal gasification slag denitration catalyst disclosed in the present invention comprises the following steps: Step 1, mixing coal gasification slag with acetic acid solution to obtain a mixed system, heating and drying the mixed system after standing for aging to obtain a coal gasification slag acetic acid modified product; Step 2, grinding and sieving the coal gasification slag acetic acid modified product to obtain coal gasification slag acetic acid modified powder; Step 3: calcining the coal gasification slag acetic acid modified powder to obtain an acetic acid modified coal gasification slag denitration catalyst, namely, a HAc modified coal gasification slag denitration catalyst.

[0027] In step 1 of the present invention, the coal gasification slag modification process adopts acid treatment (such as acetic acid, HCl, HNO3, etc.), which is not only conducive to increasing the pore structure of the surface of the glassy spherical shell of the coal gasification slag, but also can further destroy its aluminosilicate shell structure to melt out the internal active Fe. However, acidic substances with different pH values ​​have different corrosiveness to the structure of coal gasification slag. Excessive corrosion will cause its original structure to be destroyed, resulting in the metal compound generated after calcination being wrapped inside, and unable to form fully exposed catalytic active sites.

[0028] Preferably, the concentration selected in the present invention is 0.5~3 mol·L -1 of acetic acid aqueous solution.

[0029] Specifically, the laboratory preparation process includes: Step 1: weigh the coal gasification slag, place it in an oven to fully dry, put it in a beaker, and drop 0.5-3 mol·L -1 The acetic acid solution is added until the liquid just covers all the coal gasification slag, and the mixture is stirred to be fully mixed to obtain a mixed system; the mixed system is fully aged for 4 to 6 hours, and is placed in an oven at 60 to 80 ° C for 10 to 12 hours and fully dried to obtain a coal gasification slag acetic acid modified product; Preferably, in this process, when the coal gasification slag is a coarse coal gasification slag with a low carbon content, the concentration of the acetic acid solution is 3 mol·L -1 When the best.

[0030] Step 2, grinding and sieving the coal gasification slag acetic acid modified product to obtain coal gasification slag acetic acid modified powder; Step 3, placing the coal gasification slag acetic acid modified powder into a vacuum tube furnace, heating to 500-600°C for calcination for 4-6 hours in an argon or nitrogen atmosphere, and obtaining a HAc modified coal gasification slag denitration catalyst after cooling.

[0031] The HAc modified coal gasification slag denitration catalyst prepared above was tested in a denitration catalytic reaction. The specific experimental operation method includes: Step 1, weigh 0.3-0.4 g of HAc modified coal gasification slag denitrification catalyst, put it into the middle part of a corundum tube with a diameter of 100-1000 mm, and fix both ends of the solid powder with quartz wool.

[0032] Step 2: Heat the alumina tube to 50-600 °C, introduce 300 ppm NO gas into the tube, use Ar gas as carrier gas, and the gas flow rate is 60-100 mL min -1 , the exhaust gas outlet is connected to the flue gas analyzer.

[0033] The present invention will be further described below in conjunction with embodiments, but the present invention is not limited to the following embodiments: Example 1 1mol·L -1 Preparation of HAc modified coal gasification crude slag denitrification catalyst: Weigh 10 g of crude coal gasification slag, put it into a beaker, and add 1 mol·L -1Acetic acid solution was added until the liquid surface just covered all the solids. The magnetic stirrer was set to 400 rpm and stirred for 40 min. The mixture was allowed to stand at room temperature for 4 h and dried at 70 °C for 11 h. The dried product was placed in a quartz crucible and placed in a vacuum tube furnace. Ar was introduced at 600 °C and calcined for 4 h. The solid was then cooled to room temperature under an Ar environment. The solid was collected after passing through a 100-mesh sieve and named 1 mol·L -1 HAc modified coal gasification slag denitrification catalyst.

[0034] Example 2 0.5 mol·L -1 Preparation of HAc modified coal gasification crude slag denitrification catalyst: Weigh 12 g of crude coal gasification slag, put it into a beaker, and add 0.5 mol·L -1 Acetic acid solution was added until the liquid surface just covered all the solids. The magnetic stirrer was set to 500 rpm and stirred for 35 min. The mixture was allowed to stand at room temperature for 5 h and dried at 60 °C for 12 h. The dried product was placed in a quartz crucible and placed in a vacuum tube furnace. N2 was introduced at 600 °C and calcined for 4 h. The solid was then cooled to room temperature under a N2 environment. The solid was collected after passing through a 100-mesh sieve and named 0.5 mol·L -1 HAc modified coal gasification slag denitrification catalyst.

[0035] Example 3 2 mol·L -1 Preparation of HAc modified coal gasification crude slag denitrification catalyst: Weigh 15 g of crude coal gasification residue, put it into a beaker, and add 2 mol·L -1 Acetic acid solution was added until the liquid surface just covered all the solids. The magnetic stirrer was set to 600 rpm and stirred for 30 min. The mixture was allowed to stand at room temperature for 4 h and dried at 80 °C for 10 h. The dried product was placed in a quartz crucible and placed in a vacuum tube furnace. Ar was introduced at 500 °C and calcined for 6 h. The solid was then cooled to room temperature under an Ar environment and collected after being sieved through an 80-mesh sieve. It was named 2 mol·L -1 HAc modified coal gasification slag denitrification catalyst.

[0036] Example 4 3 mol·L -1 Preparation of HAc modified coal gasification crude slag denitrification catalyst: Weigh 10 g of crude coal gasification slag, put it into a beaker, and add 3 mol·L -1Acetic acid solution was added until the liquid surface just covered all the solids. The magnetic stirrer was set to 500 rpm and stirred for 40 min. The mixture was allowed to stand at room temperature for 6 h and dried at 60 °C for 12 h. The dried product was placed in a quartz crucible and placed in a vacuum tube furnace. Ar was introduced at 600 °C and calcined for 5 h. The solid was then cooled to room temperature under an Ar environment. The solid was collected after passing through a 100-mesh sieve and named 3 mol·L -1 HAc modified coal gasification slag denitrification catalyst.

[0037] Example 5 1 mol·L -1 Preparation of HAc modified coal gasification fine slag denitrification catalyst: Weigh 15 g of coal gasification slag, put it into a beaker, and add 1 mol·L -1 The acetic acid solution was added until the liquid surface just covered all the solids. The magnetic stirrer was set to 600 rpm and stirred for 30 min. The mixture was allowed to stand at room temperature for 5 h and dried at 60 °C for 10 h. The dried product was placed in a quartz crucible and placed in a vacuum tube furnace. N2 was introduced at 600 °C and calcined for 4 h. The solid was then cooled to room temperature under a N2 environment. The solid was collected after passing through a 90-mesh sieve and named 1 mol·L -1 HAc modified coal gasification fine slag denitrification catalyst.

[0038] Described below is a comparative example of preparing an unmodified coal gasification slag denitration catalyst.

[0039] Comparative Example 1 Preparation of unmodified coal gasification slag denitrification catalyst 4 g of coal gasification crude slag was weighed and placed in a quartz crucible, which was then put into a vacuum tube furnace. Ar was introduced at 500 °C and calcined for 5 h. The resulting solid was then collected after being sieved through a 100-mesh sieve and named as unmodified coal gasification crude slag denitrification catalyst.

[0040] Comparative Example 2 Preparation of unmodified coal gasification slag denitrification catalyst 4 g of crude coal gasification slag was weighed and placed in a quartz crucible, which was then put into a vacuum tube furnace. N2 was introduced at 500 °C and calcined for 6 h. The resulting solid was then collected after being sieved through a 100-mesh sieve and named as unmodified coal gasification fine slag denitrification catalyst.

[0041] Taking the unmodified coal gasification crude slag denitration catalyst prepared in the above comparative example 1 as an example, the pore size distribution test was carried out with the acetic acid modified coal gasification crude slag denitration catalyst prepared in the embodiment of the present invention. The results are shown in the following Table 1: Table 1

[0042] It can be seen that with the increase of acetic acid concentration, the specific surface area, average pore size and pore volume of coal gasification slag all increase, indicating that after the surface is etched by acetic acid, new pore structures are formed, which are conducive to the escape of metal substances, the formation of active sites and the adsorption of more gases.

[0043] Figure 1 3 mol·L -1 The N2 adsorption and desorption isotherms and pore size distribution curves of the HAc modified coal gasification crude slag denitrification catalyst show that the N2 adsorption and desorption isotherms are S-shaped curves. When P / P0>0.43, there is a hysteresis loop, which belongs to the Ⅱ / Ⅳ mixed adsorption isotherm, indicating that there are both macropores and mesopores in the modified coal gasification slag.

[0044] Described below are the methods and results of testing the denitration performance of the acetic acid-modified coal gasification slag denitration catalyst prepared in the examples of the present invention and the coal gasification slag denitration catalyst not modified with acetic acid in the comparative example.

[0045] 1. Test conditions are as follows: Coal gasification slag denitrification catalyst dosage: 0.3g; particle size: 80~100 mesh; flue gas concentration: NO 300 ppm; carrier gas: Ar; gas velocity: 80mL·min -1 ; Airspeed: 30000h -1 .

[0046] 2. Performance test results The denitrification activity test results of Comparative Example 1 and Comparative Example 2 are as follows: Figure 2 As shown. Figure 2 It can be seen that the denitration activity of the unmodified coal gasification crude slag denitration catalyst without modification is low. Specifically, the denitration rate of the unmodified coal gasification fine slag denitration catalyst is 21.4% at a catalytic reaction temperature of 500 ℃, 31.5% at a catalytic reaction temperature of 550 ℃, and 34.8% at a catalytic reaction temperature of 600 ℃; the denitration rate of the unmodified coal gasification crude slag denitration catalyst is 22.9% at a catalytic reaction temperature of 500 ℃, 26.5% at a reaction temperature of 550 ℃, and 33.1% at a reaction temperature of 600 ℃, indicating that the unmodified coal gasification slag denitration catalyst has a certain denitration activity, but cannot meet the requirement of complete denitration.

[0047] The denitration activity test results of Example 1 and Comparative Example 1 are as follows: Figure 3 As shown. Figure 3 It can be seen that 1 mol·L -1The HAc modified coal gasification slag denitrification catalyst greatly improved the denitrification activity of coal gasification slag. -1 When the reaction temperature of HAc modified coal gasification crude slag denitrification catalyst reaches 500 ℃, the denitrification rate can reach 92.3%, when the reaction temperature reaches 550 ℃, the denitrification rate can reach 99.99%, and when the temperature reaches 600 ℃, the denitrification rate is 99.99%.

[0048] The XPS (X-ray photoelectron spectroscopy) spectra before and after modification and after denitrification reaction are as follows: Figure 4 XPS is a highly sensitive ultra-trace surface element composition analysis technique. According to the area integral ratio of the XPS surface photoelectron spectrum, the content of Fe element on the modified surface can be determined to be 2~10At%.

[0049] like Figure 4 As shown in a), b) and c), it can be seen that after acid treatment modification, the Fe2p response peak appears at the binding energy of 706.7 eV, which proves that Fe element appears on the surface of the denitrification catalyst after acid treatment. After the denitrification reaction, the intensity of the Fe peak weakens, which proves that the Fe element can participate in the redox process of NO. This shows that the Fe element melts out of the surface and participates in the denitrification reaction, which is the reason for the improvement of denitrification activity after acetic acid modification.

[0050] The denitration activity test results of Example 1, Example 2, Example 3 and Example 4 are as follows: Figure 5 As shown. Figure 5 It can be seen that as the concentration of acetic acid added to treat coal gasification slag increases, 3 mol·L -1 The activity of modified coal gasification slag denitrification catalyst at 500 ℃ is comparable to that of 2 mol·L -1 HAc modified coal gasification slag denitrification catalyst, 1 mol·L -1 The denitrification activity of the HAc modified coal gasification crude slag denitrification catalyst was significantly improved. At a reaction temperature of 500 °C, the denitrification rate reached 99.9%, proving that high-concentration acetic acid treatment can better etch the outer shell of the glassy gasified coal slag, exposing the active components inside, and has better denitrification activity at high reaction temperatures. However, too high a concentration of acetic acid treatment will increase costs and equipment requirements, so taking an appropriate acetic acid concentration is more beneficial to the reaction.

[0051] The denitrification activity test results of Example 1 and Example 5 are as follows: Figure 6 As shown. Figure 6 It can be seen that when using coarse gasification slag and fine gasification slag with different carbon contents as raw materials for acid treatment, the denitrification activity of coarse gasification slag with lower carbon content after acetic acid treatment is greater than that of fine gasification slag with higher carbon content. -1 The denitration rate of HAcHAc modified coal gasification crude slag denitration catalyst was 92.3%, while 1 mol·L -1 The denitration catalytic rate of the HAc modified coal gasification fine slag denitration catalyst is 57.8%, which proves that the coal gasification coarse slag with a lower carbon content is more conducive to the direct catalytic denitration reaction. It also shows that the coal gasification slag denitration catalyst of the present invention can be prepared industrially and used as a denitration catalyst to catalyze the removal of nitrogen oxides in flue gas.

[0052] Example 4 prepared 3 mol·L -1 The reaction activity of HAc modified coal gasification slag denitrification catalyst at 500 ℃ for a long time is as follows Figure 7 As shown. Figure 7 It can be seen that when the temperature is maintained at 500 °C, 3 mol·L -1 The denitrification activity of the HAc modified coal gasification crude slag denitrification catalyst showed a relatively slow downward trend with the extension of time. At 12 h of reaction, the denitrification activity of the catalyst still reached 90%, and it could still maintain efficient denitrification, indicating that it has excellent stability.

[0053] In summary, the present invention utilizes the unique silicon-aluminum-based glassy spherical shell structure of coal gasification slag and the characteristics of partial iron melting, and uses acetic acid of different concentrations for etching, which can produce more pore structures on the surface of coal gasification slag, so that the internal iron active components are exposed, thereby generating more catalytic active centers. The coal gasification slag denitrification catalyst modified by this method can directly catalyze the decomposition of nitrogen oxides into non-toxic nitrogen and oxygen under reaction conditions without using ammonia as a reducing agent. This modification method is green and environmentally friendly, and the modification process is simple. It can not only transform "solid waste" into a high-value catalyst, but can also be used to treat atmospheric pollutants.

[0054] The innovative points of the present invention are explained from the perspective of principle and summarized as follows: the present invention uses acetic acid to acid-etch the surface of the coal gasification slag to produce more pore structures, and during the acid etching, Fe2O3 in the structure of the coal gasification slag is dissolved from the inside of the glassy spherical shell to the surface of the catalyst to form Fe 3+ ions. Due to the weak acid corrosion of acetic acid, the structure of the gasification slag is etched, so that the specific surface area of ​​the gasification slag becomes larger after modification, and more pore structures are produced, which is conducive to the adsorption of more nitrogen oxides. After calcination at 500~600℃ in an argon / nitrogen environment, the residual carbon in the gasification slag will react with Fe 3+ A carbothermal reaction occurs to form a stable ion pair Fe 3+ / Fe 2+, as the denitration active center, undergoes redox reaction with NO, thereby improving the denitration activity and long-term denitration stability. The coal gasification slag denitration catalyst prepared by the present invention can maintain a denitration efficiency of not less than 90% for 12 hours at 500-600°C, and has long-term denitration stability.

[0055] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

[0056] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a coal gasification slag denitration catalyst, characterized in that: The following steps are involved: Step 1, mixing coal gasification slag with acetic acid solution to obtain a mixed system, heating and drying the mixed system after standing for aging to obtain a coal gasification slag acetic acid modified product; Step 2, grinding and sieving the coal gasification slag acetic acid modified product to obtain coal gasification slag acetic acid modified powder; Step 3: calcining the coal gasification slag acetic acid modified powder to obtain the acetic acid modified coal gasification slag denitration catalyst.

2. The method for preparing a coal gasification slag denitration catalyst according to claim 1, characterized in that: In step 1, the acetic acid solution has a concentration of 0.5~3 mol·L -1 of acetic acid aqueous solution.

3. The method for preparing a coal gasification slag denitration catalyst according to claim 1, characterized in that: In step 1, the coal gasification slag is coarse coal gasification slag or fine coal gasification slag; wherein the carbon content of the coarse coal gasification slag is 20% to 25%, and the carbon content of the fine coal gasification slag is 40% to 45%.

4. The method for preparing a coal gasification slag denitration catalyst according to claim 1, characterized in that: In step 1, the ratio of coal gasification slag to acetic acid solution is (2-3) g: (3-4) mL.

5. The method for preparing a coal gasification slag denitration catalyst according to claim 1, characterized in that: In step 1, the standing aging time is 4 to 6 hours, the heating and drying temperature is 60 to 80°C, and the heating and drying time is 10 to 12 hours.

6. The method for preparing a coal gasification slag denitration catalyst according to claim 1, characterized in that: In step 2, the screen size used for the sieving process is 80-100 mesh.

7. The method for preparing a coal gasification slag denitration catalyst according to claim 1, characterized in that: In step 3, the calcination atmosphere is argon or nitrogen, the calcination temperature is 500-600°C, and the calcination time is 4-6 hours.

8. A coal gasification slag denitration catalyst prepared by the method for preparing a coal gasification slag denitration catalyst according to any one of claims 1 to 7.

9. The coal gasification slag denitration catalyst according to claim 8, characterized in that The coal gasification slag denitrification catalyst has a porous structure and a specific surface area of ​​234.73~291.47S BET (m 2 / g), the active component Fe element is precipitated on the surface of the porous structure, and the atomic percentage of the active component Fe element is 2%~10%.

10. Use of the coal gasification slag denitration catalyst according to claim 8 or 9 in catalytic denitration.

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