CN112266000B - Method for preparing molecular sieve by using gasified slag - Google Patents
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- CN112266000B CN112266000B CN202011022615.6A CN202011022615A CN112266000B CN 112266000 B CN112266000 B CN 112266000B CN 202011022615 A CN202011022615 A CN 202011022615A CN 112266000 B CN112266000 B CN 112266000B
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- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B39/00—Compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites; Their preparation; After-treatment, e.g. ion-exchange or dealumination
- C01B39/02—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof; Direct preparation thereof; Preparation thereof starting from a reaction mixture containing a crystalline zeolite of another type, or from preformed reactants; After-treatment thereof
- C01B39/36—Pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11
- C01B39/38—Type ZSM-5
- C01B39/40—Type ZSM-5 using at least one organic template directing agent
Abstract
The invention discloses a method for preparing a molecular sieve by utilizing gasified slag, which comprises the following steps: (1) pretreating gasified slag; (2) carrying out hydrothermal reaction on the gasified slag treated in the step (1) by using an alkali solution to obtain a filtrate or a supernatant; (3) mixing the filtrate or supernatant obtained in the step (2) with a template agent, and carrying out crystallization reaction on the obtained mixed solution; (4) and (4) carrying out solid-liquid separation, drying and roasting on the crystallized product obtained in the step (3) to obtain a molecular sieve product. The method of the invention uses rich silicon dioxide in the coal gasification slag as a silicon source, reduces the synthesis cost of the molecular sieve, effectively improves the economic utilization value of the coal gasification slag, and simultaneously provides a new synthesis scheme of the coal gasification fine slag-based molecular sieve.
Description
Technical Field
The invention belongs to the technical field of solid waste recycling treatment and molecular sieve preparation, and particularly relates to a method for preparing a molecular sieve by utilizing gasified slag.
Background
The coal gasification slag is the residue generated in the coal gasification process, and according to statistics, the million ton grade coal indirect oil preparation process can generate 90 million tons of coal gasification slag every year. At present, coal gasification slag is more used as a low-value utilization way such as building materials, structural backfill and the like, but complex chemical components of the coal gasification slag are not fully treated and are put into use, and potential biological toxicity and environmental hazard exist in natural environment. With the continuous promotion of an environment management system and a series of environmental protection policies in China, the research on the value-added utilization of the gasified slag gradually becomes a hot research hotspot.
The gasified slag can be divided into coarse slag and fine slag according to the source. The coarse slag and the fine slag contain rich silicon dioxide, aluminum oxide and iron oxide, the sum of the contents of the silicon dioxide, the aluminum oxide and the iron oxide can reach more than 70 percent at most, and the volcanic ash has certain volcanic ash activity. These characteristics provide an important material basis for preparing the molecular sieve from the coal gasification slag.
However, compared with the raw materials for preparing the molecular sieve from coal-based solid waste fly ash, coal gangue and the like, the research for preparing the molecular sieve by taking gasified slag as a silica-aluminum source at home and abroad is less. Firstly, because the coal gasification process is complex, the physical and chemical properties of the gasified slag of coal produced in various places are various, and a completely universal treatment method is difficult to find; secondly, the gasified slag contains a lot of carbon residues, so that the treatment difficulty is high; thirdly, the starting time of the coal gasification industry is not long, and people pay attention to the treatment problem of coal gasification slag. Chinese patent CN108817030A "a method for activation treatment of coal gasification fine slag" provides a method for rapidly converting a silicon-aluminum compound in coal gasification fine slag into an active phase at a low external temperature. Chinese patent CN107855104A, "method for preparing composite mesoporous material from coal gasification coarse slag and prepared mesoporous material", proposes that coal gasification coarse slag is used as carbon and silicon source, and carbon/silicon composite mesoporous material is prepared by acid dissolution, high temperature to water quenching and quenching. With the change of coal utilization technology, the discharge amount of gasified slag is expanding day by day, and the treatment method thereof will also get attention.
Disclosure of Invention
The invention aims to provide a method for preparing a molecular sieve by utilizing coal gasification fine slag, which improves the resource utilization efficiency of coal gasification slag, has low cost and provides a new product path for value-added utilization of the coal gasification slag.
In order to achieve the purpose, the invention provides the following technical scheme:
a method for preparing a molecular sieve by utilizing gasified slag comprises the following steps:
(1) pretreating the gasified slag;
(2) carrying out hydrothermal reaction on the gasification slag treated in the step (1) by using an alkali solution to obtain a filtrate or a supernatant;
(3) mixing the filtrate or supernatant obtained in the step (2) with a template agent, and carrying out crystallization reaction on the obtained mixed solution;
(4) and (4) carrying out solid-liquid separation, drying and roasting on the crystallized product obtained in the step (3) to obtain a molecular sieve product.
According to some embodiments of the above method, the molecular sieve is a ZSM-5 molecular sieve.
According to some embodiments of the above method, in step (1), the pre-treating comprises: and sequentially carrying out primary drying, acid leaching, washing and secondary drying on the gasified slag.
According to some embodiments of the above method, in the acid leaching step (1), the acid leaching agent is hydrochloric acid. Preferably, the hydrochloric acid concentration is 10% to 25%. According to some embodiments of the above method, the ratio of gasified sludge to hydrochloric acid is 1: 5 to 20 (g/mL). According to some embodiments of the method, the acid leaching temperature is 15-40 ℃ and the acid leaching time is 4-8 hours.
According to some embodiments of the above method, the washing in step (1) comprises washing the acid-leached coal gasification slag with deionized water to a filtrate pH of 6.0 to 8.0.
According to some embodiments of the above method, the templating agent is tetrapropylammonium hydroxide (TPAOH).
According to some embodiments of the above method, in the step (2), the alkali solution is sodium hydroxide solution, preferably, the concentration of sodium hydroxide is 1 to 5mol/L, and more preferably, the concentration of sodium hydroxide is 1.5 to 3 mol/L.
According to some embodiments of the above method, the ratio of the gasified slag and the alkali solution after the treatment in the step (1) is 1: 5 to 20 (g/mL).
According to some embodiments of the above method, the hydrothermal reaction temperature is 60 to 100 ℃ and the reaction time is 3 to 7 hours.
According to some embodiments of the method, in the crystallization reaction in step (3), the crystallization temperature is 150 to 200 ℃ and the crystallization time is 36 to 48 hours.
According to some embodiments of the method, in the step (4), the roasting temperature is 400-600 ℃, the roasting time is 3-10 hours, and the temperature rise rate is 0.5-3 ℃/min.
According to some embodiments of the above method, in the step (2), if centrifugation is adopted, the centrifuged supernatant may be filtered again to remove residues.
According to some embodiments of the above method, the SiO in step (3)2：TPAOH：H2The molar ratio of O is 1: (0.20-0.35): (40-80).
The invention also provides application of the method in the field of molecular sieve preparation or the field of coal gasification slag treatment.
The invention has the following beneficial effects:
(1) according to the method for preparing the ZSM-5 molecular sieve from the coal gasification fine slag, provided by the invention, the abundant silicon dioxide in the coal gasification fine slag is used as a silicon source, so that the synthesis cost of the molecular sieve is reduced, the economic utilization value of the coal gasification fine slag is effectively improved, and meanwhile, a new synthesis scheme of the coal gasification fine slag-based molecular sieve is provided.
(2) The ZSM-5 molecular sieve synthesized by the preparation process for preparing the ZSM-5 molecular sieve by using the coal gasification fine slag provided by the invention is good in crystallization and wider in preparation conditions.
Drawings
FIG. 1 is an XRD diffraction pattern of a ZSM-5 molecular sieve prepared by coal gasification fine slag in example 1 of the invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The examples are intended to be illustrative of the invention and not limiting.
In some embodiments of the invention, the method comprises:
(1) pretreating the coal gasification fine slag, which comprises drying, acid leaching, washing and drying the raw materials again in sequence;
(2) and (3) carrying out alkali treatment on the pretreated coal gasification fine slag, carrying out hydro-thermal treatment at a certain temperature, and carrying out vacuum filtration to collect filtrate or carrying out centrifugal treatment to obtain supernatant.
(3) The concentration of elemental silicon in the filtrate (or supernatant) was measured. If the silicon element in the supernatant is too low, the filtrate (or supernatant) can be placed in an oven at 60 ℃ to reduce the water content. Uniformly mixing the filtrate (or supernatant), TPAOH and a proper amount of deionized water according to a certain proportion, and adding concentrated sulfuric acid to adjust the pH to 9.5-11. And (3) carrying out crystallization reaction on the mixed solution, carrying out solid-liquid separation, grinding to obtain a white solid powder material, and drying.
(4) And (4) roasting the white powder material prepared in the step (3) to obtain the ZSM-5 molecular sieve material.
Preferably, in the acid leaching process in the step (1), the acid leaching agent is hydrochloric acid, the concentration of the hydrochloric acid is 10% -25%, and the ratio of the coal gasification fine slag to the hydrochloric acid is 1: 5-20 (g/mL), room temperature, and 4-8 hours.
Preferably, the washing in the step (1) includes washing the acid-leached raw material with deionized water until the pH of the filtrate is 6.0-8.0.
Preferably, in the step (2), the alkaline agent is sodium hydroxide, the concentration of the sodium hydroxide is 1-5 mol/L, and the ratio of the pretreated raw material to the sodium hydroxide is 1: 5-20 (g/mL), hydrothermal reaction temperature of 60-100 ℃, and reaction time of 3-7 hours.
Preferably, in the step (2), if centrifugation is performed, the centrifuged supernatant may be filtered again to remove residues.
Preferably, SiO in the step (3)2：TPAOH：H2The molar ratio of O is 1: (0.20-0.35): (40-80).
Preferably, in the crystallization reaction in the step (3), the crystallization temperature is 150-200 ℃, and the reaction time is 36-48 hours.
Preferably, in the step (4), the roasting temperature is 400-600 ℃, the roasting time is 3-10 hours, and the heating rate is 0.5-3 ℃/min.
Example 1
The coal gasification fine slag-based ZSM-5 molecular sieve is prepared by adjusting the proportion of all substances in gel through evaporating water (xerogel method), and the preparation method comprises the following steps:
(1) 5g of gasified slag from Ningxia Ningning coal is taken and put into an oven to be dried for 10 hours at the temperature of 80 ℃, 50mL of 20% hydrochloric acid is taken to be fully mixed with the gasified slag, and the mixture is stirred for 5 hours at room temperature. The solution was filtered with suction and the filter cake was rinsed with deionized water until the filtrate had a pH of 7. And (3) putting the treated coal gasification fine slag into an oven to be dried for 10 hours at the temperature of 80 ℃. (2) Taking 4g of pretreated coal gasification fine slag, adding 40mL of 3M NaOH solution, uniformly mixing, and carrying out reflux stirring at the hydrothermal reaction temperature of 70 ℃ for 4 hours. The solution was centrifuged and the supernatant collected and filtered to remove solid impurities. (3) The supernatant was put into an oven and water was evaporated at 60 ℃ to turn the supernatant into a gel state. 2.01g of the gel were transferred to a reaction vessel, to which 0.7375mmol of TPAOH (25% strength in water), 177mmol of H were added2And O, performing ultrasonic treatment for 15 minutes until the solution is uniformly mixed. Sulfuric acid was carefully added dropwise, the pH was adjusted to 11, and the mixture was stirred at room temperature for 30 minutes. Transferring into a drying oven, aging at 170 ℃ for 48 hours, performing solid-liquid separation, drying at 80 ℃, and grinding to obtain a white powder material. (4) Roasting the white powder material by using a muffle furnace, wherein the heating rate is 3Roasting at 550 ℃ for 6 hours at a temperature of 550 ℃ for a min, and naturally cooling to obtain the ZSM-5 molecular sieve.
The final product ZSM-5 molecular sieve was subjected to XRD (Smartlab (9), Japan Co., Ltd.) and the test results are shown in FIG. 1. As can be seen from FIG. 1, the final product is ZSM-5 molecular sieve material.
Example 2
The method for preparing the coal gasification fine slag-based ZSM-5 molecular sieve by directly using the supernatant comprises the following steps:
(1) 5g of gasified slag from Ningxia Ningning coal is taken and put into an oven to be dried for 10 hours at the temperature of 80 ℃, 50mL of 15% hydrochloric acid is taken to be fully mixed with the gasified slag, and the mixture is stirred for 5 hours at room temperature. The solution was filtered with suction and the filter cake was rinsed with deionized water until the filtrate had a pH of 7. And (4) putting the treated coal gasification fine slag into an oven to be dried for 10 hours at the temperature of 80 ℃. (2) And 4g of pretreated coal gasification fine slag is taken, 40mL of 2M NaOH solution is added to be uniformly mixed, the hydrothermal reaction temperature is 80 ℃, reflux stirring is carried out, and the reaction time is 4 hours. Vacuum filtering, and collecting filtrate. (3) 15mL of the filtrate was transferred to a reaction kettle, 2.24g of TPAOH (25% aqueous solution) was added and sonicated for 15 minutes until the solution was mixed well. Sulfuric acid was carefully added dropwise, the pH was adjusted to 11, and the mixture was stirred at room temperature for 30 minutes. Transferring into a drying oven, aging at 170 ℃ for 48 hours, performing solid-liquid separation, drying at 80 ℃, and grinding to obtain a white powder material. (4) And roasting the white powder material by using a muffle furnace, wherein the heating rate is 3 ℃/min, roasting is carried out for 6 hours at 550 ℃, and natural cooling is carried out to obtain the ZSM-5 molecular sieve.
Examples 3 to 6
The reaction procedure is the same as in example 2, the reaction conditions are shown in Table 1, and the reaction conditions not shown in Table 1 are the same as in example 2.
XRD tests were performed on the final products of examples 2-6, and the results are shown in Table 1.
TABLE 1 reaction conditions and products of examples 1-6
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.
Claims (7)
1. A method for preparing a molecular sieve by utilizing gasified slag, wherein the gasified slag is gasified fine slag, and the molecular sieve is a ZSM-5 molecular sieve, and the method comprises the following steps:
(1) pretreating the coal gasification slag, wherein the pretreatment comprises the following steps: sequentially carrying out primary drying, acid leaching, washing and secondary drying on the gasified slag;
(2) carrying out hydrothermal reaction on the coal gasification slag treated in the step (1) by using an alkali solution to obtain a filtrate or a supernatant, wherein the alkali solution is a sodium hydroxide solution, and the concentration of the sodium hydroxide solution is 1.5-2 mol/L; the temperature of the hydrothermal reaction is 60-100 ℃;
(3) mixing the filtrate or supernatant obtained in the step (2) with a template agent, and carrying out crystallization reaction on the obtained mixed solution, wherein the template agent is tetrapropylammonium hydroxide;
(4) and (4) carrying out solid-liquid separation, drying and roasting on the crystallized product obtained in the step (3) to obtain a molecular sieve product.
2. The method of claim 1, wherein in the acid leaching process in the step (1), the acid leaching agent is hydrochloric acid, the concentration of the hydrochloric acid is 10% -25%, and the ratio of the gasified slag to the hydrochloric acid is 1 g: 5-20 mL, the acid leaching temperature is 15-40 ℃, and the acid leaching time is 4-8 hours.
3. The method of claim 1, wherein the washing in step (1) comprises washing the acid-leached coal gas slag with deionized water to a filtrate pH of 6.0 to 8.0.
4. The method according to any one of claims 1 to 3, wherein in the step (2), the ratio of the gasified slag to the alkali solution after the treatment in the step (1) is 1 g: 5-20 mL.
5. The method according to any one of claims 1 to 3, wherein the hydrothermal reaction is carried out for 3 to 7 hours.
6. The method as set forth in any one of claims 1 to 3, wherein the crystallization reaction in the step (3) is carried out at a crystallization temperature of 150 to 200 ℃ for a crystallization time of 36 to 48 hours.
7. Use of the process according to any one of claims 1 to 6 in the field of molecular sieve preparation or in the field of coal gasification slag treatment.
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