Preparation method of carbon-based desulfurizing agent

Abstract

The invention relates to a preparation method of a carbon-based desulfurizer, which comprises the following steps: (1) placing biomass in an acid solution, and carrying out microwave hydrothermal reaction to obtain a mixture; and (2) cooling the mixture, carrying out suction filtration, recovering the acid solution, and drying, carbonizing and activating a solid sample in the residual mixture to obtain the metal-loaded carbon-based desulfurizing agent. The preparation method is simple in technological process, mild in condition and environmentally friendly, a raw material serving as an acid medium can be recycled, biomass is a renewable resource, low in price and easy to obtain, and the prepared carbon-based desulfurizing agent has the advantages of being good in desulfurizing effect, low in production cost and the like.

Description

Technical Field

[0001] The invention relates to the technical field of desulfurizing agents, and in particular to a method for preparing a carbon-based desulfurizing agent. Background Art

[0002] Carbon materials are widely used in gas purification, catalysis and other fields. For example, activated carbon materials can be used to adsorb sulfur-containing substances such as H2S in coal gas, thereby purifying coal gas. Metal-loaded carbon-based desulfurizers will further improve their performance. Therefore, a method for preparing a carbon-based desulfurizer with simple process, low cost and high reaction activity should be sought.

[0003] CN114192114A provides a method for preparing a desulfurizing agent by modifying activated carbon with metal ions. The method comprises the following steps: subjecting the activated carbon to a thermochemical reaction with water, dripping a concentrated ammonia solution containing metals into the dried activated carbon, and calcining the activated carbon in a tubular furnace. The metal ion component can effectively improve the pore structure and activity of the activated carbon during the preparation process of the activated carbon.

[0004] CN117643867A provides a preparation method and application of an activated carbon desulfurizer. The method prepares activated carbon with H2S removal ability by immersing the activated carbon in a nitric acid solution and drying and calcining. The surface of the activated desulfurizer prepared by acidification and calcination contains oxygen-containing functional groups and nitrogen-containing substances, wherein the oxygen-containing functional groups can provide an oxygen source for H2S oxidation, and the nitrogen-containing substances can provide alkaline sites to promote H2S dissociation, so that the carbon material has better desulfurization performance.

[0005] CN104028218B places bituminous coal in a carbonization furnace, heats it to 500-700°C under N2 protection, and carbonizes it for 0.5-2 h to obtain bituminous coal charcoal. Pyrolusite and bituminous coal charcoal are crushed into powder respectively, the pyrolusite powder is added to the carbonization material and mixed evenly, water and coal tar are added, and the mixture is fully kneaded at 30-60°C, and the fully kneaded material is extruded and dried. The dried shaped material is placed in an activation furnace, heated to 750-950°C under N2 protection and water vapor, and activated for 0.5-2 h to prepare catalytic desulfurization activated coke.

[0006] CN107051378A uses straw biomass to prepare biochar and modifies it in an alkaline environment. Afterwards, the biochar is immersed in an aqueous solution containing metal ions and roasted in an N2 atmosphere to obtain modified biochar loaded with metal particles, which is used as a biogas desulfurizer. However, this method requires the addition of a solution containing metal ions during the preparation of metal-loaded carbon materials, which is very costly.

[0007] CN113289583A provides a method for preparing an activated carbon desulfurizer loaded with metal oxides using blue charcoal. The method is characterized in that the blue charcoal after pickling and drying is used as a carrier to dissolve the iron precursor and the copper precursor in deionized water, and then loaded on the carrier by impregnation and roasting. The addition of iron and copper precursors can increase the sulfur capacity and the number of times the blue charcoal raw materials are used, but the preparation process has a large demand for iron and copper.

[0008] The current method for preparing carbon-based desulfurizers is cumbersome and consumes non-renewable resources such as coal. In addition, metal solutions need to be added. Due to the high price of metals, the cost of the prepared metal-loaded carbon-based desulfurizer is high, which causes waste of metal resources. Biomass, as a renewable resource, has the advantages of wide sources and huge output. It contains metals such as K, Na, Ca, Mg and Fe. Biomass carbon has rich active sites and many functional groups that can be used for metal exchange. If the two can be used synergistically, metal-loaded carbon-based desulfurizers can be prepared to achieve efficient utilization of biomass resources and efficient removal of H2S in coal gas. Summary of the invention

[0009] In order to solve the above technical problems, the present invention provides a method for preparing a carbon-based desulfurizer. The method utilizes the metals, carbon active sites and functional groups in biomass to prepare a metal-loaded carbon-based desulfurizer, thereby obtaining a metal-self-loaded carbon-based desulfurizer while efficiently utilizing biomass, a renewable energy source.

[0010] The present invention solves the above technical problems through the following technical solutions: A method for preparing a carbon-based desulfurizer, the method comprising the following steps: (1) placing the biomass in an acid solution and performing a microwave hydrothermal reaction to obtain a mixture; (2) After the mixture is cooled, filtered, and the acid solution is recovered, the solid sample in the remaining mixture is dried, carbonized, and activated to prepare a metal-loaded carbon-based desulfurizer.

[0011] In the present invention, the carbon-containing matrix in the biomass itself is used as the carbon material matrix, and the metal in the biomass itself is the active metal source. The carbon-based desulfurizer prepared after the above treatment contains micropores and mesopores, forming a multi-level pore structure. The active metals include metal components such as K, Na, Ca, Mg and Fe existing in the biomass, which are converted into a composite of various metals and carbon materials after being compounded, carbonized and activated with the carbon material, and its composition includes a mixture of multiple components and forms such as the above metals and their metal oxides. As a preferred technical solution of the present invention, the biomass particle size described in step (1) is 0.3-0.6 mm.

[0012] As a preferred technical solution of the present invention, the biomass includes wax gourd peel powder, sawdust, corn cob powder and tobacco stems.

[0013] As a preferred technical solution of the present invention, the acid solution is nitric acid, hydrochloric acid or phosphoric acid solution.

[0014] As a preferred technical solution of the present invention, the concentration of the acid solution is 8 to 15 mol / L.

[0015] As a preferred technical solution of the present invention, the mass fraction of the biomass sample added to the acid solution in step (1) is 5-10%.

[0016] As a preferred technical solution of the present invention, the conditions of the microwave hydrothermal reaction are: heating temperature is between 80 and 120° C., and the temperature is kept constant for 0.5 to 3 hours.

[0017] As a preferred technical solution of the present invention, the solid sample in step (2) is dried at 90°C to 110°C, and carbonized and activated at 700°C to 850°C in a CO2 atmosphere.

[0018] Furthermore, the carbonization and activation time is 1 to 5 hours.

[0019] Compared with the prior art, the present invention has the following advantages: 1. The present invention provides a method for preparing a carbon-based desulfurizer. For renewable energy biomass, an acid solution is used to activate metals, carbon sites and functional groups in the biomass, and the activated metals are exchanged with carbon active sites, functional groups and the like in situ to form an active metal-loaded carbon-based desulfurizer. At the same time, the acid will expand the pores of the carbon material to form a multi-level pore structure to prepare a metal-loaded carbon-based desulfurizer.

[0020] 2. The present invention provides a method for preparing a carbon-based desulfurizer. The prepared carbon-based desulfurizer has a rich pore structure, synergistic effects can be exerted between metals and carbon materials, and between alkali metals, alkaline earth metals and transition metals, and has excellent desulfurization performance.

[0021] 3. The present invention provides a method for preparing a carbon-based desulfurizer. The preparation method has a simple process, mild conditions, and is green and environmentally friendly. The raw material of the acid medium can be reused. Biomass is a renewable resource, low in price, and easy to obtain. The prepared carbon-based desulfurizer has the advantages of low production cost and the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The conversion effect of the carbon-based desulfurizer prepared in Examples 1-6 of the present invention. DETAILED DESCRIPTION

[0023] The present invention is to grind and screen biomass to obtain a sample with a particle size range of about 0.3 to 0.6 mm, add 8 to 15 mol / L of an acid solution such as nitric acid, hydrochloric acid or phosphoric acid, mix the biomass with the acid solution and place it in a microwave hydrothermal kettle to heat it to between 80 and 120°C and keep the temperature constant, so as to promote the acid solution to activate metals, carbon active sites and functional groups in the biomass, strengthen the in-situ ion exchange between active metals and carbon active sites, functional groups, etc., form an active carbon-based desulfurizer precursor, and at the same time expand the pores of the carbon-based desulfurizer to form a multi-level pore structure. The mixed liquid is then cooled, filtered, and the acid solution is recovered. The carbon-based desulfurizer precursor is dried, in-situ carbonized, and activated at 700-850 °C under a CO2 atmosphere to obtain a carbon-based desulfurizer. The rich pore structure of the carbon-based desulfurizer further enhances the adsorption of H2S. Active metals such as K in the desulfurizer strengthen its adsorption of H2S in coal gas, while transition metals such as Fe can react the adsorbed H2S with O to form elemental S, achieving a synergistic effect between the metals.

[0024] Specifically, the preparation method of a carbon-based desulfurizer described in the present invention uses biomass as a source of metals such as K, Na, Ca, Mg and a source of carbon material carriers, but the metals contained in the biomass itself are in an inert state, and an acid solution such as nitric acid, hydrochloric acid or phosphoric acid is used to activate and exchange metal ions in situ under microwave hydrothermal conditions. After sufficient reaction, a precursor of an active metal-loaded carbon-based desulfurizer is formed. At the same time, the acid solution dissolves part of the metal in the biomass to further form mesopores, thereby enhancing the pore structure distribution of the carbon-based material. After cooling, filtering, and recovering the acid solution, the precursor is dried, and carbonized and activated under a CO2 atmosphere at 700-850 °C to obtain a metal-loaded carbon-based desulfurizer.

[0025] The carbon-based desulfurizer prepared by the present invention uses the carbon-containing matrix in the biomass as the carbon material matrix, and the metal in the biomass itself as the active metal source. The carbon-based desulfurizer prepared after the above treatment contains micropores and mesopores, forming a multi-level pore structure. The active metals include metal components such as K, Na, Ca, Mg and Fe existing in the biomass, which are converted into a complex of various metals and carbon materials after being compounded, carbonized and activated with the carbon material, and its composition form includes a mixture of multiple components and forms such as the above metals and their metal oxides. The active metals such as K, Na, Ca, Mg in the desulfurizer strengthen its adsorption of H2S in coal gas, while transition metals such as Fe can react the adsorbed H2S with O to form elemental S, enhance sulfur capacity, and further release the metal active sites. The reaction cycle is carried out, and the carbon-based desulfurizer prepared after acid oxidation and activation has a rich pore structure, which can further serve as an active center to enhance the adsorption of H2S.

[0026] The ratio and composition of active metals and carbon materials in carbon-based desulfurizers prepared from different biomass will vary. Generally, the carbon content in biomass is generally 40-50 wt%, the ash content in biomass ranges from 0-20%, and the ash contains different proportions of K2O, Na2O, CaO, MgO and Fe2O3. The differences between biomass will affect the content of active metals and carbon materials. The method of the present invention can be used to treat biomass from different sources to obtain a carbon-based desulfurizer with certain performance. The active metals such as K, Na, Ca, Mg and Fe in the metal-loaded carbon-based desulfurizer prepared by the method of the present invention account for 0.1-5%. The ratio between active metals and carbon materials is related to the metal content, carbon content and preparation conditions of the biomass itself.

[0027] In the examples of the present invention, different biomasses such as wax gourd peel powder, sawdust, corn cob powder and tobacco stems were selected. The results showed that the prepared carbon-based desulfurizers all had a multi-level pore structure and loaded with metals, and had good performance.

[0028] The mixed solution can be cooled and filtered to recover the acid solution for recycling to save resources. The separated solid precursor is dried to obtain a carbon-based desulfurization agent precursor. The carbon-based desulfurization agent precursor is carbonized and activated under a CO2 atmosphere, and forms a multi-level pore structure and a rich specific surface area under the action of metal. It is a metal-supported carbon-based desulfurization agent with a carbon structure as the main component and coordinated modification of active metals such as K, Na, Ca, Mg and Fe.

[0029] Furthermore, the biomass particle size is 0.3-0.6 mm, and the prepared nitric acid, hydrochloric acid or phosphoric acid solution has an acid solution concentration of 8-15 mol / L.

[0030] Furthermore, the biomass sample is added to the above solution, stirred and mixed evenly, and transferred to a hydrothermal reactor with microwave function for sealed heating. Microwaves can enhance the contact and activation between the acid and the metals, carbon materials, and functional groups in the biomass. The mass fraction of the biomass sample is required to be 5-10%, the heating temperature is between 80-120 °C, and the temperature is kept constant for 0.5-3h.

[0031] In the present invention, after the substances in the microwave hydrothermal reactor react fully, the cooled solution is filtered and separated, the acid solution is recycled, and the solid precursor is dried at 90°C to 110°C.

[0032] The present invention carries out in-situ carbonization and activation under the condition of 700-850°C in CO2 atmosphere, and the reaction time is 1-5h.

[0033] The present invention controls the combination form and ratio of metal and carbon materials by adjusting the type and concentration of acid solution, the mixing ratio of acid and biomass, microwave hydrothermal conditions, and carbonization / activation conditions, thereby achieving synergy between the two in the coal gas desulfurization function.

[0034] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Example 1 (1) Winter melon peel powder was selected as the biomass raw material and ground in a grinder. The sample particle size was selected to be 0.3-0.5 mm. Then, it was dried to constant weight at 105 °C to obtain a dry biomass sample, which was sealed and stored. A nitric acid solution with a concentration of 10 mol / L was prepared and mixed with 10 g of the biomass sample and stirred evenly. The mass of the biomass was 10% of the total mass of the acid and the biomass.

[0036] Pour it into a 500 ml high-pressure transparent quartz tank, stir and mix it evenly with a glass rod, and react it in a microwave hydrothermal reactor at a temperature of 100 °C for 2 h to obtain a mixture.

[0037] (2) After the reaction is completely completed and cooled, the mixture is filtered and separated, the residual acid solution is reused, and the solid matter is dried at 105 °C.

[0038] The metal-loaded carbon-based desulfurizer was prepared by in-situ carbonization, calcination and activation in a fixed bed reactor at 800 °C in a CO2 atmosphere for 2 h.

[0039] Example 2 (1) In the experiment, sawdust was selected as the biomass raw material and ground in a pulverizer. The sample particle size was 0.3-0.6 mm. Then, it was dried at 105 °C to a constant weight to obtain a dry biomass sample, which was sealed and stored. A hydrochloric acid solution with a concentration of 10 mol / L was prepared, poured into a beaker, and 5 g of the biomass sample was added to mix and stir evenly. The mass of the biomass was 5% of the total mass of the acid and the biomass.

[0040] Pour it into a 500 ml high-pressure transparent quartz tank, stir and mix it evenly with a glass rod, and carry out the reaction in a microwave hydrothermal reactor at a reaction temperature of 80 °C for 3 h to obtain a mixture.

[0041] (2) After the reaction is completely completed and cooled, a small amount of gas is discharged to the outside, the mixture is filtered, and the solid matter is dried at 90°C to constant weight and sealed for storage, and the residual acid solution is reused.

[0042] Finally, the samples were calcined and activated at 720 °C in a fixed bed reactor in a CO2 atmosphere for 5 h and then dried and stored.

[0043] Example 3 (1) Corn cob powder was used as raw material in the experiment. It was ground in a pulverizer. The sample particle size was selected to be 0.4-0.6 mm. It was then dried at 105 °C to a constant weight to obtain a dry biomass sample, which was sealed and stored. A phosphoric acid solution with a concentration of 13 mol / L was prepared, poured into a beaker, and 8 g of the biomass sample was added to mix and stir evenly. The mass of the biomass was 8% of the total mass of the acid and the biomass.

[0044] Pour it into a 500 ml high-pressure transparent quartz tank, stir and mix it evenly with a glass rod, and carry out the reaction in a microwave hydrothermal reactor at a temperature of 110 °C for 1 h to obtain a mixture.

[0045] (2) After the reaction is completely completed and cooled, a small amount of gas is discharged to the outside, the mixture in the quartz container is filtered, and the solid matter is dried at 100 °C to constant weight and sealed for storage, and the residual acid solution is reused.

[0046] Finally, the product was calcined and activated at 850 °C in a fixed bed reactor under CO2 atmosphere for 1.5 h and then dried and stored.

[0047] Example 4 (1) The test selected tobacco stems as raw materials, ground them in a pulverizer, and selected sample particles with a size of 0.3-0.6 mm. Then, they were dried at 105 °C to a constant weight to obtain dry biomass samples, which were sealed and stored. A phosphoric acid solution with a concentration of 15 mol / L was prepared, poured into a beaker, and 7 g of biomass sample was added to mix and stir evenly. The mass of biomass was 7% of the total mass of acid and biomass.

[0048] Pour it into a 500 ml high-pressure transparent quartz tank, stir and mix it evenly with a glass rod, and carry out the reaction in a microwave hydrothermal reactor at a temperature of 110 °C for 4 h to obtain a mixture.

[0049] (2) After the reaction is completely completed and cooled, a small amount of gas is discharged to the outside, the mixture in the quartz container is filtered, and the solid matter is dried at 100 °C to constant weight and sealed for storage, and the residual acid solution is reused.

[0050] Finally, it was calcined and activated at 850 °C in a reactor under CO2 atmosphere for 3 h and then dried and stored.

[0051] Example 5 (1) Rice husk was selected as the raw material for the experiment. It was ground in a pulverizer. The sample particle size was selected to be 0.3-0.6 mm. It was then dried at 105 °C to a constant weight to obtain a dry biomass sample, which was sealed and stored. A hydrochloric acid solution with a concentration of 8 mol / L was prepared, poured into a beaker, and 5 g of the biomass sample was added to mix and stir evenly. The mass of the biomass was 10% of the total mass of the acid and the biomass.

[0052] Pour it into a 500 ml high-pressure transparent quartz tank, stir and mix it evenly with a glass rod, and carry out a microwave hydrothermal reaction in a microwave hydrothermal reactor at a temperature of 100 °C for 2 h to obtain a mixture.

[0053] (2) After the reaction is completely completed and cooled, a small amount of gas is discharged to the outside, the mixture in the quartz container is filtered, and the solid matter is dried at 100 °C to constant weight and sealed for storage, and the residual acid solution is reused.

[0054] Finally, it was calcined and activated at 850 °C in a reactor under CO2 atmosphere for 3 h and then dried and stored.

[0055] Example 6 (1) Corn cob powder was used as raw material in the experiment. It was ground in a pulverizer. The sample particle size was selected to be 0.3-0.6 mm. It was then dried at 105 °C to a constant weight. The dried sample was sealed and stored. A hydrochloric acid solution with a concentration of 8 mol / L was prepared. The solution was poured into a beaker. 5 g of biomass sample was added and mixed and stirred evenly. The mass of biomass was 5% of the total mass of acid and biomass.

[0056] Pour it into a 500ml high-pressure transparent quartz tank, stir and mix it evenly with a glass rod, and carry out the reaction in a microwave hydrothermal reactor at a temperature of 120 °C for 2 h to obtain a mixture. After the reaction is completely completed and cooled, the fixed substance is separated.

[0057] After testing, the prepared carbon-based desulfurizer contains active metals such as K, Na, Ca, Mg and Fe. According to ICP testing, the above active metals account for 2.1% in the sample prepared in Example 1; 0.3% in the sample prepared in Example 2; 0.7% in the sample prepared in Example 3; and 4.1% in the sample prepared in Example 4. The above active metals account for 0.08% in the sample prepared in Example 5, while the above active metals account for 1.1% in the sample prepared in Comparative Example 6. The specific ICP detection method is: the metal content in the sample is determined by an inductively coupled plasma emission spectrometer (AGILENT ICPOES720). The sample needs to be hydrothermally digested before testing, and the specific steps are as follows: weigh 0.1 g of the sample in a 50 ml test tube with an electronic analytical balance; add 20 ml of aqua regia, cover the stopper and place it in a graphite heater to heat until the sample is completely dissolved; then transfer the cooled solution to a 100 ml volumetric flask and make up to volume with deionized water. The instrument first prepares a calibration curve for the standard solution, inputs the sample mass and volume, then tests the digestion solutions in sequence, and finally determines the final content of the metal measured in the sample through the spectrum.

[0058] The desulfurization performance of the carbon-based desulfurizer was evaluated. The obtained material was subjected to a fixed bed to evaluate the desulfurization performance of H2S gas at 60°C. 4 g of the carbon-based desulfurizer sample prepared in Example 1-6 was placed, and the H2S concentration was 300 ppm. The specific test results are shown in the attached Figure 1 shown.

[0059] The carbon-based desulfurizer has good desulfurization performance for H2S. For example, the H2S conversion rate of the carbon-based desulfurizer prepared in Example 1 and Example 4 is above 99% before 75 minutes and 86 minutes respectively. The desulfurization performance of the carbon materials prepared in Example 5 and Example 6 is significantly lower than that of the carbon-based desulfurizer prepared in the examples within the scope of this patent, indicating that the selected biomass materials and the corresponding carbonization and activation operations have a relatively important influence on the desulfurization effect of the desulfurizer finally prepared.

Claims

1. A method for preparing a carbon-based desulfurizer, characterized in that: The preparation method comprises the following steps: (1) placing the biomass in an acid solution and performing a microwave hydrothermal reaction to obtain a mixture; (2) After the mixture is cooled, filtered, and the acid solution is recovered, the solid sample in the remaining mixture is dried, carbonized, and activated to prepare a metal-loaded carbon-based desulfurizer.

2. The method for preparing a carbon-based desulfurizing agent according to claim 1, characterized in that: The biomass in step (1) includes wax gourd peel powder, sawdust, corn cob powder and tobacco stems.

3. The method for preparing a carbon-based desulfurizing agent according to claim 2, characterized in that: The biomass particle size is between 0.3 and 0.6 mm.

4. The method for preparing a carbon-based desulfurizing agent according to claim 1, characterized in that: The acid solution is nitric acid, hydrochloric acid or phosphoric acid solution.

5. The method for preparing a carbon-based desulfurizing agent according to claim 4, characterized in that: The acid solution has a concentration of 8 to 15 mol / L.

6. The method for preparing a carbon-based desulfurizing agent according to claim 1, characterized in that: The mass fraction of the biomass sample added with the acid solution in step (1) is 5-10%.

7. The method for preparing a carbon-based desulfurizing agent according to claim 1, characterized in that: The conditions of the microwave hydrothermal reaction are: heating temperature between 80 and 120° C., and constant temperature for 0.5 to 3 hours.

8. The method for preparing a carbon-based desulfurizing agent according to claim 1, characterized in that: The solid sample in step (2) is dried at 90°C to 110°C, and carbonized and activated at 700°C to 850°C in a CO2 atmosphere.

9. The method for preparing a carbon-based desulfurizing agent according to claim 8, characterized in that: The carbonization and activation time is 1 to 5 hours.

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