Preparation method and application of modified red mud catalyst

Abstract

The invention discloses a preparation method and application of a modified red mud catalyst, and belongs to the technical field of resource recovery. The method comprises the following steps: drying, grinding and screening a large amount of solid waste red mud, preparing an acid solution with a certain concentration by using citric acid, pickling, titrating red mud slurry until the pH is 8-10 by using ammonia water after pickling, washing and drying the titrated slurry, and loading nickel by using an impregnation method, roasting the metal-loaded red mud in air at a certain temperature to complete the preparation of the modified red mud catalyst; the prepared red mud catalyst is used for producing synthesis gas through catalytic pyrolysis of solid waste, the yield of the synthesis gas can be remarkably increased, and meanwhile the recycling way of industrial solid waste red mud is widened.

Description

Technical Field

[0001] The invention relates to a preparation method and application of a modified red mud catalyst, belonging to the technical field of resource recovery. Background Art

[0002] Syngas is a raw gas with hydrogen and carbon monoxide as the main components, used for chemical synthesis. It can be produced in many ways, such as partial oxidation of coal or natural gas, steam reforming or pyrolysis of biomass. The composition of syngas can vary greatly, usually including H2, CO, CO2, CH4 and N2. At present, the main methods for preparing syngas include coal gasification, natural gas reforming and heavy oil catalytic cracking. However, these methods all face the problems of serious environmental pollution and high production costs.

[0003] At present, a widely used method for preparing synthesis gas is catalytic pyrolysis of organic solid waste, which can realize the resource utilization of organic solid waste. The selection of catalyst is very important for catalytic pyrolysis. Catalysts such as metal salts, metal oxides, molecular sieve catalysts, and low-cost waste catalysts have been widely used in catalytic pyrolysis. However, the preparation of industrial catalysts is usually complicated, and the separation and regeneration of these catalysts require additional technology, which increases the cost of pyrolysis technology. Therefore, it is very necessary to develop catalysts that are easy to prepare, low-cost, efficient, and clean.

[0004] A large amount of solid waste - red mud - is generated during the production of alumina. Red mud contains a variety of minerals, such as hematite, quartz, calcite, ilmenite, goethite, calcium nepheline, etc., and its chemical components include oxides such as Fe2O3, Al2O3, SiO2, CaO, and TiO2. Due to the high content of alkaline metal oxides, red mud can accelerate the decomposition of acidic substances and has a great catalytic effect on improving the quality of biomass pyrolysis products. As a bulk industrial solid waste, red mud has the advantages of being cheap and easy to obtain; combined with the above characteristics, it lays the foundation for its use as a pyrolysis catalyst. Summary of the invention

[0005] In order to provide a method for preparing synthesis gas, one of the objects of the present invention is to provide a method for preparing a modified red mud catalyst, comprising the following steps:

[0006] (1) The original red mud is dried, ground, and sieved for later use.

[0007] (2) The red mud treated in step (1) is mixed with the citric acid solution and stirred to obtain a red mud slurry.

[0008] (3) The red mud slurry obtained in step (2) is titrated with aqueous ammonia to alkaline, the titrated slurry is washed with water to neutrality, and then filtered and dried to obtain acid-washed red mud.

[0009] (4) After completely dissolving Ni(NO3)2·6H2O in anhydrous ethanol, add the acid-washed red mud obtained in step (3), stir and dry to obtain Ni-loaded red mud.

[0010] (5) The Ni-loaded red mud obtained in step (4) is placed in a muffle furnace and calcined at high temperature to obtain a modified red mud catalyst.

[0011] Preferably, in step (1), the drying temperature is 60-80°C, and the sieve is 60-100 mesh. The concentration of the citric acid solution is prepared.

[0012] Preferably, in step (2), the solid-liquid ratio of red mud to citric acid solution is 1:6-12, expressed in g:ml; and the molar concentration of the citric acid solution is 2-6 mol / L.

[0013] Preferably, in step (2), the stirring conditions are: stirring at 65-85° C. for 2-4 hours.

[0014] Preferably, in step (3), the alkaline pH value is 8 to 10, and the drying temperature is 100 to 120°C.

[0015] Preferably, in step (4), the amount of Ni(NO3)2·6H2O used is 5% to 15% of the mass of the pickled red mud, and the solid-liquid ratio of the pickled red mud to anhydrous ethanol is 1:6, expressed in g:ml.

[0016] Preferably, in step (4), the stirring conditions are 40-60°C for 8-12h, and the drying temperature is 100-120°C.

[0017] Preferably, in step (5), the heating rate of calcination is 2-6°C / min, the calcination temperature is 450-700°C, and the calcination time is 4-6h.

[0018] Another object of the present invention is to provide a modified red mud catalyst, which can catalyze organic solid waste to produce synthesis gas.

[0019] Synthesis gas is mainly composed of carbon monoxide and hydrogen.

[0020] Beneficial effects of the present invention

[0021] (1) The present invention uses citric acid to pickle red mud, thereby effectively improving the efficiency of red mud catalyzing organic solid waste to produce synthesis gas.

[0022] (2) The present invention can effectively utilize red mud and organic solid waste at the same time, reducing resource waste and achieving the purpose of turning waste into treasure

[0023] (3) The yields of H2 and CO in the synthesis gas prepared by the present invention reached 675 mL / g raw material and 225 mL / g raw material, respectively, accounting for 61.1% and 20.3%. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention is a flow chart for preparing the modified red mud catalyst.

[0025] Figure 2 : XRD diagram of original red mud and modified red mud in Example 4.

[0026] Figure 3 : BET diagram of original red mud and modified red mud in Example 4. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. However, the following embodiments are only simple examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0028] The red mud used in the examples and comparative examples of the present invention is produced by an aluminum company in Wenshan Prefecture, Yunnan Province, and the remaining chemicals are all conventional commercially available analytical grade.

[0029] Example 1

[0030] A method for preparing a modified red mud catalyst for catalytic pyrolysis, the process is as follows Figure 1 As shown, the following steps are included:

[0031] (1) The raw red mud was dried in an electric constant temperature forced air drying oven at 60°C for 12 h, and ground with an agate mortar and sieved through a 60-mesh sieve to obtain red mud powder for later use.

[0032] (2) Red mud powder and a citric acid solution with a molar concentration of 2 mol / L were stirred at 65° C. for 2 h to be evenly mixed to form a red mud slurry, wherein the solid-liquid ratio of the red mud powder to the citric acid solution was 1:6, in units of g:ml.

[0033] (3) The red mud slurry is titrated with ammonia water to pH=8, the titrated slurry is washed with water to neutrality, and then placed in an electric constant temperature forced air drying oven and dried at 100°C for 12 hours to obtain acid-washed red mud.

[0034] (4) After completely dissolving Ni(NO3)2·6H2O in anhydrous ethanol, the mixture was evenly mixed with the acid-washed red mud and stirred at 40°C for 8 h. The mixture was then placed in an electric constant temperature forced air drying oven and dried at 100°C for 12 h to obtain Ni-loaded red mud, wherein the amount of Ni(NO3)2·6H2O was 5% of the mass of the acid-washed red mud.

[0035] (5) The Ni-loaded red mud was heated to 450°C in a muffle furnace at a heating rate of 2°C / min and calcined for 4 h to obtain a modified red mud catalyst.

[0036] The modified red mud catalyst prepared in this embodiment is used for catalyzing the co-pyrolysis of tobacco straw and LPDE (low-density polyethylene) waste plastic to produce synthesis gas. 0.1g of tobacco straw powder and 0.9g of LDPE powder are mixed evenly and put into a silo, 1g of the modified red mud catalyst prepared by the present invention is put into an automatic temperature-controlled tubular furnace, N2 is introduced into the automatic temperature-controlled tubular furnace at a flow rate of 30mL / min to exclude air, the tubular furnace is set to heat up to 750℃ at 10℃ / min, the silo is opened to allow the reaction raw materials to enter the tubular furnace to start the pyrolysis reaction, and the generated synthesis gas is collected by an air bag. The reaction process lasts for 30min, and the composition of the prepared synthesis gas is shown in Table 1.

[0037] Example 2

[0038] A method for preparing a modified red mud catalyst for catalytic pyrolysis, the process is as follows Figure 1 As shown, the following steps are included:

[0039] (1) The raw red mud was dried in an electric constant temperature forced air drying oven at 80°C for 12 h, and ground with an agate mortar and sieved through an 80-mesh sieve to obtain red mud powder for later use.

[0040] (2) Red mud powder and a citric acid solution with a molar concentration of 4 mol / L were stirred at 75° C. for 3 h to be evenly mixed to form a red mud slurry, wherein the solid-liquid ratio of the red mud powder to the citric acid solution was 1:9, expressed in g:ml.

[0041] (3) The red mud slurry is titrated with ammonia water to pH = 9, the titrated slurry is washed with water to neutrality, and then placed in an electric constant temperature forced air drying oven and dried at 100° C. for 12 h to obtain acid-washed red mud.

[0042] (4) After completely dissolving Ni(NO3)2·6H2O in anhydrous ethanol, the mixture was evenly mixed with the acid-washed red mud and stirred at 50°C for 10 h. The mixture was then placed in an electric constant temperature forced air drying oven and dried at 100°C for 12 h to obtain Ni-loaded red mud, wherein the amount of Ni(NO3)2·6H2O was 10% of the mass of the acid-washed red mud.

[0043] (5) The Ni-loaded red mud was heated to 600°C in a muffle furnace at a heating rate of 4°C / min and calcined for 5 h to obtain a modified red mud catalyst.

[0044] The modified red mud catalyst prepared in this embodiment is used for catalyzing the co-pyrolysis of tobacco straw and LPDE waste plastic to produce synthesis gas. 0.1g of tobacco straw powder and 0.9g of LDPE powder are mixed evenly and put into a silo, 1g of the modified red mud catalyst prepared by the present invention is put into an automatic temperature-controlled tubular furnace, N2 is introduced into the automatic temperature-controlled tubular furnace at a flow rate of 30mL / min to exclude air, the tubular furnace is set to heat up to 750℃ at 10℃ / min, the silo is opened to allow the reaction raw materials to enter the tubular furnace to start the pyrolysis reaction, and the generated synthesis gas is collected by an air bag. The reaction process lasts for 30min, and the composition of the prepared synthesis gas is shown in Table 1.

[0045] Example 3

[0046] A method for preparing a modified red mud catalyst for catalytic pyrolysis, the process is as follows Figure 1 As shown, the following steps are included:

[0047] (1) The raw red mud was dried in an electric constant temperature forced air drying oven at 80°C for 12 h, and ground with an agate mortar and sieved through a 100-mesh sieve to obtain red mud powder for later use.

[0048] (2) Red mud powder and a citric acid solution with a molar concentration of 6 mol / L were stirred at 85° C. for 4 h to be evenly mixed to form a red mud slurry, wherein the solid-liquid ratio of the red mud powder to the citric acid solution was 1:12, in units of g:ml.

[0049] (3) The red mud slurry is titrated with ammonia water to pH = 10, the titrated slurry is washed with water to neutrality and then placed in an electric constant temperature forced air drying oven to dry at 105° C. for 12 h to obtain acid washed red mud.

[0050] (4) After completely dissolving Ni(NO3)2·6H2O in anhydrous ethanol, the mixture was evenly mixed with the pickled red mud and stirred at 60°C for 8 h. The mixture was then placed in an electric constant temperature forced air drying oven and dried at 120°C for 12 h to obtain Ni-loaded red mud, wherein the amount of Ni(NO3)2·6H2O was 15% of the mass of the pickled red mud.

[0051] (5) The Ni-loaded red mud was heated to 750°C in a muffle furnace at a heating rate of 6°C / min and calcined for 6 h to obtain a modified red mud catalyst.

[0052] The modified red mud catalyst prepared in this embodiment is used for catalyzing the co-pyrolysis of tobacco straw and LPDE waste plastic to produce synthesis gas. 0.1g of tobacco straw powder and 0.9g of LDPE powder are mixed evenly and put into a silo, 1g of the modified red mud catalyst prepared by the present invention is put into an automatic temperature-controlled tubular furnace, N2 is introduced into the automatic temperature-controlled tubular furnace at a flow rate of 30mL / min to exclude air, the tubular furnace is set to heat up to 750℃ at 10℃ / min, the silo is opened to allow the reaction raw materials to enter the tubular furnace to start the pyrolysis reaction, and the generated synthesis gas is collected by an air bag. The reaction process lasts for 30min, and the composition of the prepared synthesis gas is shown in Table 1.

[0053] Example 4

[0054] A method for preparing a modified red mud catalyst for catalytic pyrolysis, the process is as follows Figure 1 As shown, the following steps are included:

[0055] (1) The raw red mud was dried in an electric constant temperature forced air drying oven at 80°C for 12 h, and ground with an agate mortar and sieved through a 100-mesh sieve to obtain red mud powder for later use.

[0056] (2) Red mud powder and a citric acid solution with a molar concentration of 4 mol / L were stirred at 85° C. for 4 h to be evenly mixed to form a red mud slurry, wherein the solid-liquid ratio of the red mud powder to the citric acid solution was 1:6, expressed in g:ml.

[0057] (3) The red mud slurry is titrated with ammonia water to pH=8, the titrated slurry is washed with water to neutrality and then placed in an electric constant temperature forced air drying oven to dry at 105°C for 12 hours to obtain acid washed red mud.

[0058] (4) After completely dissolving Ni(NO3)2·6H2O in anhydrous ethanol, the mixture was evenly mixed with the pickled red mud and stirred at 60°C for 10 h. The mixture was then placed in an electric constant temperature forced air drying oven and dried at 105°C for 12 h to obtain Ni-loaded red mud, wherein the amount of Ni(NO3)2·6H2O was 10% of the mass of the pickled red mud.

[0059] (5) The Ni-loaded red mud was heated to 600°C in a muffle furnace at a heating rate of 2°C / min and calcined for 4 h to obtain a modified red mud catalyst.

[0060] The modified red mud catalyst prepared in this embodiment is used for catalyzing the co-pyrolysis of tobacco straw and LPDE waste plastic to produce synthesis gas. 0.1g of tobacco straw powder and 0.9g of LDPE powder are mixed evenly and put into a silo, 1g of the modified red mud catalyst prepared by the present invention is put into an automatic temperature-controlled tubular furnace, N2 is introduced into the automatic temperature-controlled tubular furnace at a flow rate of 30mL / min to exclude air, the tubular furnace is set to heat up to 750℃ at 10℃ / min, the silo is opened to allow the reaction raw materials to enter the tubular furnace to start the pyrolysis reaction, and the generated synthesis gas is collected by an air bag. The reaction process lasts for 30min, and the composition of the prepared synthesis gas is shown in Table 1.

[0061] Comparative Example 1

[0062] As a comparison, the difference between this comparative example and Example 2 is that the pickling solution used is hydrochloric acid, and the preparation method comprises the following steps:

[0063] (1) The raw red mud was dried in an electric constant temperature forced air drying oven at 80°C for 12 h, and ground with an agate mortar and sieved through an 80-mesh sieve to obtain red mud powder for later use.

[0064] (2) Red mud powder and a hydrochloric acid solution with a molar concentration of 4 mol / L were stirred at 75° C. for 3 h to be evenly mixed to form a red mud slurry, wherein the solid-liquid ratio of the red mud powder to the citric acid solution was 1:9, in units of g:ml.

[0065] (3) The red mud slurry is titrated with ammonia water to pH = 9, the titrated slurry is washed with water to neutrality, and then placed in an electric constant temperature forced air drying oven and dried at 100° C. for 12 h to obtain acid-washed red mud.

[0066] (4) After completely dissolving Ni(NO3)2·6H2O in anhydrous ethanol, the mixture was evenly mixed with the acid-washed red mud and stirred at 50°C for 10 h. The mixture was then placed in an electric constant temperature forced air drying oven and dried at 100°C for 12 h to obtain Ni-loaded red mud, wherein the amount of Ni(NO3)2·6H2O was 10% of the mass of the acid-washed red mud.

[0067] (5) The Ni-loaded red mud was heated to 600°C in a muffle furnace at a heating rate of 4°C / min and calcined for 5 h to obtain a modified red mud catalyst.

[0068] The modified red mud catalyst prepared in this comparative example is used to catalyze the co-pyrolysis of tobacco straw and LPDE waste plastic to produce synthesis gas. 0.1g of tobacco straw powder and 0.9g of LDPE powder are mixed evenly and put into a silo, 1g of the modified red mud catalyst prepared by the present invention is put into an automatic temperature-controlled tubular furnace, N2 is introduced into the automatic temperature-controlled tubular furnace at a flow rate of 30mL / min to exclude air, the tubular furnace is set to heat up to 750℃ at 10℃ / min, the silo is opened to allow the reaction raw materials to enter the tubular furnace to start the pyrolysis reaction, and the generated synthesis gas is collected by an air bag. The reaction process lasts for 30min, and the composition of the prepared synthesis gas is shown in Table 1.

[0069] Comparative Example 2

[0070] As a comparison, the difference between this comparative example and Example 2 is that the pickling solution used is sulfuric acid, and the preparation method comprises the following steps:

[0071] A method for preparing a modified red mud catalyst for catalytic pyrolysis, such as Figure 1 As shown, the following steps are included:

[0072] (1) The raw red mud was dried in an electric constant temperature forced air drying oven at 80°C for 12 h, and ground with an agate mortar and sieved through an 80-mesh sieve to obtain red mud powder for later use.

[0073] (2) Red mud powder and a sulfuric acid solution with a molar concentration of 4 mol / L were stirred at 75° C. for 3 h to form a red mud slurry, wherein the solid-liquid ratio of the red mud powder to the citric acid solution was 1:9, in units of g:ml.

[0074] (3) The red mud slurry is titrated with ammonia water to pH = 9, the titrated slurry is washed with water to neutrality, and then placed in an electric constant temperature forced air drying oven and dried at 100° C. for 12 h to obtain acid-washed red mud.

[0075] (4) After completely dissolving Ni(NO3)2·6H2O in anhydrous ethanol, the mixture was evenly mixed with the acid-washed red mud and stirred at 50°C for 10 h. The mixture was then placed in an electric constant temperature forced air drying oven and dried at 100°C for 12 h to obtain Ni-loaded red mud, wherein the amount of Ni(NO3)2·6H2O was 10% of the mass of the acid-washed red mud.

[0076] (5) The Ni-loaded red mud was heated to 600°C in a muffle furnace at a heating rate of 4°C / min and calcined for 5 h to obtain a modified red mud catalyst.

[0077] The modified red mud catalyst prepared in this comparative example is used to catalyze the co-pyrolysis of tobacco straw and LPDE waste plastic to produce synthesis gas. 0.1g of tobacco straw powder and 0.9g of LDPE powder are mixed evenly and put into a silo, 1g of the modified red mud catalyst prepared by the present invention is put into an automatic temperature-controlled tubular furnace, N2 is introduced into the automatic temperature-controlled tubular furnace at a flow rate of 30mL / min to exclude air, the tubular furnace is set to heat up to 750℃ at 10℃ / min, the silo is opened to allow the reaction raw materials to enter the tubular furnace to start the pyrolysis reaction, and the generated synthesis gas is collected by an air bag. The reaction process lasts for 30min, and the composition of the prepared synthesis gas is shown in Table 1.

[0078] Comparative Example 3

[0079] As a comparison, the difference between this comparative example and Example 2 is that the loaded metal ion is Fe, and the preparation method comprises the following steps:

[0080] (1) The raw red mud was dried in an electric constant temperature forced air drying oven at 80°C for 12 h, and ground with an agate mortar and sieved through an 80-mesh sieve to obtain red mud powder for later use.

[0081] (2) Red mud powder and a sulfuric acid solution with a molar concentration of 4 mol / L were stirred at 75° C. for 3 h to form a red mud slurry, wherein the solid-liquid ratio of the red mud powder to the citric acid solution was 1:9, in units of g:ml.

[0082] (3) The red mud slurry is titrated with ammonia water to pH = 9, the titrated slurry is washed with water to neutrality, and then placed in an electric constant temperature forced air drying oven and dried at 100° C. for 12 h to obtain acid-washed red mud.

[0083] (4) After completely dissolving Ni(NO3)2·6H2O in anhydrous ethanol, the mixture was evenly mixed with the pickled red mud and stirred at 50°C for 10 h. The mixture was then placed in an electric constant temperature forced air drying oven and dried at 100°C for 12 h to obtain Fe-loaded red mud, wherein the amount of Fe(NO3)3·9H2O was 10% of the mass of the pickled red mud.

[0084] (5) The Fe-loaded red mud was heated to 600°C in a muffle furnace at a heating rate of 4°C / min and calcined for 5 h to obtain a modified red mud catalyst.

[0085] The modified red mud catalyst prepared in this comparative example is used to catalyze the co-pyrolysis of tobacco straw and LPDE waste plastic to produce synthesis gas. 0.1g of tobacco straw powder and 0.9g of LDPE powder are mixed evenly and put into a silo, 1g of the modified red mud catalyst prepared by the present invention is put into an automatic temperature-controlled tubular furnace, N2 is introduced into the automatic temperature-controlled tubular furnace at a flow rate of 30mL / min to exclude air, the tubular furnace is set to heat up to 750℃ at 10℃ / min, the silo is opened to allow the reaction raw materials to enter the tubular furnace to start the pyrolysis reaction, and the generated synthesis gas is collected by an air bag. The reaction process lasts for 30min, and the composition of the prepared synthesis gas is shown in Table 1.

[0086] Comparative Example 4

[0087] As a comparison, the difference between this comparative example and Example 2 is that the loaded metal ion is Cu, and the preparation method comprises the following steps:

[0088] (1) The raw red mud was dried in an electric constant temperature forced air drying oven at 80°C for 12 h, and ground with an agate mortar and sieved through an 80-mesh sieve to obtain red mud powder for later use.

[0089] (2) Red mud powder and a citric acid solution with a molar concentration of 4 mol / L were stirred at 75° C. for 3 h to be evenly mixed to form a red mud slurry, wherein the solid-liquid ratio of the red mud powder to the citric acid solution was 1:9, expressed in g:ml.

[0090] (3) The red mud slurry is titrated with ammonia water to pH = 9, the titrated slurry is washed with water to neutrality, and then placed in an electric constant temperature forced air drying oven and dried at 100° C. for 12 h to obtain acid-washed red mud.

[0091] (4) After completely dissolving Cu(NO3)2·3H2O in anhydrous ethanol, the mixture was evenly mixed with the acid-washed red mud and stirred at 50°C for 10 h. The mixture was then placed in an electric constant temperature forced air drying oven and dried at 100°C for 12 h to obtain Cu-loaded red mud, wherein the amount of Cu(NO3)2·3H2O was 10% of the mass of the acid-washed red mud.

[0092] (5) The Cu-loaded red mud was heated to 600°C in a muffle furnace at a heating rate of 4°C / min and calcined for 5 h to obtain a modified red mud catalyst.

[0093] The modified red mud catalyst prepared in this comparative example is used to catalyze the co-pyrolysis of tobacco straw and LPDE waste plastic to produce synthesis gas. 0.1g of tobacco straw powder and 0.9g of LDPE powder are mixed evenly and put into a silo, 1g of the modified red mud catalyst prepared by the present invention is put into an automatic temperature-controlled tubular furnace, N2 is introduced into the automatic temperature-controlled tubular furnace at a flow rate of 30mL / min to exclude air, the tubular furnace is set to heat up to 750℃ at 10℃ / min, the silo is opened to allow the reaction raw materials to enter the tubular furnace to start the pyrolysis reaction, and the generated synthesis gas is collected by an air bag. The reaction process lasts for 30min, and the composition of the prepared synthesis gas is shown in Table 1.

[0094] Figure 2 : The XRD diagram of the original red mud and the modified red mud in Example 4. It can be seen from the figure that the original red mud contains active components such as Fe2O3, Al2O3, Ca2CO3, etc. After modification, Ni is successfully loaded on the red mud in the form of NiO.

[0095] Figure 3 The BET diagram of the original red mud and the modified red mud in Example 4 shows that the specific surface area of ​​the red mud catalyst after modification is increased from 9.39 m 2 / g increased to 117.87m 2 / g.

[0096] Table 1 Contents of synthesis gas components in Examples 1 to 4 and Comparative Examples 1 to 4

[0097] material) <![CDATA[H2 (mL / g feedstock)]]> CO (mL / g raw material) <![CDATA[CH4 (mL / g feedstock)]]> <![CDATA[CO2 (mL / g raw material)]]> Example 1 236.46 217.96 79.01 39.76 Example 2 326.17 229.25 78.85 27.63 Example 3 317.77 239.74 68.41 29.53 Example 4 385.36 254.75 86.52 29.53 Comparative Example 1 167.39 144.49 61.57 20.73 Comparative Example 2 138.43 138.82 63.64 17.59 Comparative Example 3 211.68 41.25 153.38 39.83 Comparative Example 4 159.64 40.29 79.58 14.29

[0098] It can be seen from Examples 1-4 in Table 1 that when the citric acid concentration increases from 2 mol / L to 6 mol / L, the production of synthesis gas first increases and then decreases. This is because too little citric acid will lead to incomplete removal of Na in the red mud, and too much will lead to the removal of some active components (Fe2O3, Al2O3). In addition, when the Ni loading increases from 5% to 10%, the H2 yield in the synthesis gas increases significantly, but when the Ni loading further increases to 15%, the synthesis gas output does not increase significantly. This is because the loading of metal Ni has reached saturation. The calcination temperature has a huge impact on the catalytic activity of red mud. Too low or too high a temperature will significantly reduce the catalytic activity of red mud. At a calcination temperature of 400°C, the mass loss of the original red mud is mainly due to the evaporation of free water from the surface, but its mineral phase has not changed. When it is higher than 750°C, the minerals in the red mud will undergo sintering, resulting in a decrease in catalytic activity;

[0099] According to Example 2 and Comparative Examples 1-2 in Table 1, the catalytic effect of red mud treated with hydrochloric acid and sulfuric acid is reduced. This is because hydrochloric acid and sulfuric acid remove some of the active components (Fe2O3) in the red mud, resulting in a decrease in catalytic performance. According to Example 2 and Comparative Examples 3-4 in Table 1, by comparison, the metal Ni loaded on red mud has a significant improvement in the yield of H2 and CO, while Fe can effectively promote the yield of CH4. However, the loading of Cu leads to a decrease in the catalytic activity of red mud, and its gas production rate is lower than that without a catalyst.

[0100] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing a modified red mud catalyst, characterized in that: The following steps are involved: (1) drying, grinding, and screening the raw red mud for later use; (2) mixing the red mud treated in step (1) with the citric acid solution and stirring the mixture to obtain a red mud slurry; (3) titrating the red mud slurry obtained in step (2) with aqueous ammonia to alkalinity, washing the titrated slurry with water to neutrality, and then filtering and drying to obtain acid-washed red mud; (4) dissolving Ni(NO3)2·6H2O in anhydrous ethanol and adding the acid-washed red mud obtained in step (3) to obtain Ni-loaded red mud after stirring and drying; (5) The Ni-loaded red mud obtained in step (4) is placed in a muffle furnace and calcined at high temperature to obtain a modified red mud catalyst.

2. The method for preparing the modified red mud catalyst according to claim 1, characterized in that: In the step (1), the drying temperature is 60-80° C., and the sieve is 60-100 mesh.

3. The method for preparing the modified red mud catalyst according to claim 1, characterized in that: In the step (2), the solid-liquid ratio of red mud to citric acid solution is 1:6 to 1:12, expressed in g:ml; and the molar concentration of the citric acid solution is 2 to 6 mol / L.

4. The method for preparing the modified red mud catalyst according to claim 1, characterized in that: In the step (2), the stirring conditions are: stirring at 65-85° C. for 2-4 hours.

5. The method for preparing the modified red mud catalyst according to claim 1, characterized in that: In the step (3), the alkaline pH value is 8 to 10, and the drying temperature is 100 to 120°C.

6. The method for preparing the modified red mud catalyst according to claim 1, characterized in that: In the step (4), the amount of Ni(NO3)2·6H2O used is 5% to 15% of the mass of the pickled red mud.

7. The method for preparing the modified red mud catalyst according to claim 1, characterized in that: In the step (4), the stirring condition is 40-60°C for 8-12 hours, and the drying temperature is 100-120°C.

8. The method for preparing the modified red mud catalyst according to claim 1, characterized in that: In the step (5), the heating rate of the calcination is 2 to 6°C / min, the calcination temperature is 450 to 700°C, and the calcination time is 4 to 6 hours.

9. Use of the modified red mud catalyst prepared by the method of claim 1 in catalyzing organic solid waste to produce synthesis gas.

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