Biomass-derived modified nitrogen-rich carbon catalyst as well as preparation method and application thereof

Abstract

The invention discloses a biomass-derived modified nitrogen-rich carbon catalyst as well as a preparation method and application thereof. The preparation method comprises the steps of pretreatment, activation and nitrogen doping, washing and preparation of the modified nitrogen-rich carbon catalyst. The application is the application of the modified nitrogen-rich carbon catalyst in one-step catalytic hydrolysis of carbonyl sulfide to produce sulfur. The modified nitrogen-rich carbon catalyst disclosed by the invention has good catalytic hydrolysis oxidation performance, COS can be hydrolyzed into H2S by utilizing trace H2O and active components, and the generated H2S further reacts with O2 to generate sulfur and water. Compared with the prior art, the method has the advantages of high efficiency, low cost, high stability and the like, toxic sulfur-containing gas can be changed into elemental sulfur, waste is turned into wealth, and resource utilization of waste biomass is realized; in addition, the method is simple and suitable for large-scale industrial production, has both technical feasibility and industrial application prospects, and provides important technical support for the research field of COS catalytic hydrolysis.

Description

Technical Field

[0001] This invention belongs to the field of organic solid waste resource utilization technology, specifically relating to a biomass-derived modified nitrogen-rich carbon catalyst, its preparation method, and its application. Background Technology

[0002] The use of fossil fuels such as coal, oil, and natural gas is always accompanied by the emission of sulfur compounds. These sulfur compounds, once released into the atmosphere, undergo transformations or reactions with other atmospheric substances through physical, chemical, or biological processes, generating a series of secondary pollutants that contaminate the atmospheric environment. Carbonyl sulfide (COS) is one of the major sulfur compounds, and studies have shown that long-term exposure to COS poses a threat to human health, leading to respiratory and cardiovascular diseases. The presence of COS in the atmosphere also has a serious impact on ecosystems, forming sulfate aerosol particles in the troposphere and stratosphere, adversely affecting atmospheric radiation intensity, ozone depletion, and global climate change, thus polluting the atmospheric environment. Even small amounts of COS in industrial production processes can cause catalyst deactivation, corrosion and damage to pipeline equipment, and reduced quality of industrial products. Direct emission or combustion of exhaust gases results in severe resource waste and environmental pollution. Therefore, developing effective technologies to reduce COS levels in the air and improve air quality has become a global priority.

[0003] Domestic and international COS removal technologies are mainly divided into two categories: wet and dry methods. Wet methods have a large processing capacity but insufficient precision, and are suitable for coarse desulfurization; dry methods have high precision and low pollution, and mainly include adsorption, hydroconversion, and hydrolysis. Adsorption methods are prone to saturation; hydroconversion requires high temperature and pressure and is prone to side reactions; catalytic hydrolysis is widely used due to its mild reaction conditions, few byproducts, and low cost. However, impurities such as SO2 and O2 in the feed gas compete for adsorption, which can poison the active sites of the catalyst, resulting in a short service life.

[0004] In recent years, biochar has received widespread attention due to its extensive applications in agriculture, environment, and energy. Biochar boasts significant advantages such as a wide range of raw material sources, low production costs, ecological safety, no pollution, and the potential for large-scale promotion. Derived from biomass, biochar can generally be categorized into fruit shell biochar and wood biochar. Yunnan Province, with its diverse topography, climate, and ecology, coupled with its rich endemic species and strategic resource status, possesses abundant biomass resources, including coconut shells, walnut shells, peanut shells, sugarcane bagasse, coffee grounds, and discarded cigarette butts. Every year, a large amount of waste biomass is discarded and burned, resulting not only in resource waste but also in disposal challenges and environmental pollution. However, this waste biomass possesses high carbon content and good mechanical strength, making it highly valuable for development and utilization. Therefore, using inexpensive biomass as a raw material to prepare biochar not only solves the waste disposal problem but also offers high resource recovery value, improving resource utilization.

[0005] Therefore, this invention proposes a green, efficient, and low-cost biomass-derived modified nitrogen-rich carbon catalyst and its application in one-step catalytic hydrolysis of carbonyl sulfur to produce sulfur. Summary of the Invention

[0006] To address the aforementioned technical problems, the primary objective of this invention is to provide a method for preparing a biomass-derived modified nitrogen-rich carbon catalyst, which effectively solves the environmental problems caused by the accumulation of waste biomass, realizes the resource utilization of waste, and reduces production costs and environmental impact.

[0007] The second objective of this invention is to provide a biomass-derived modified nitrogen-rich carbon catalyst, which has excellent catalytic hydrolysis performance and can be used for the green and efficient purification and resource utilization of COS in various systems.

[0008] The third objective of this invention is to provide a new application of a biomass-derived modified nitrogen-rich carbon catalyst, offering an economical and environmentally friendly new approach to sulfur production.

[0009] The first objective of this invention is achieved by the following steps: (1) Dry the coffee grounds to completely remove moisture. First wash the coffee grounds with ethanol, then wash the coffee grounds with distilled water, and then dry the coffee grounds. The coffee grounds are pretreated to provide pure and structurally stable raw materials for subsequent activation and nitrogen doping, which is conducive to the formation of abundant active sites. (2) KOH is selected as the activator and urea as the nitrogen source. The coffee grounds treated in step (1) are mixed evenly with KOH and urea, ultrasonically treated and dried. The material is transferred to a tube furnace for calcination and cooled to obtain the calcined product. (3) Wash the calcined product with distilled water until the pH of the washing solution is neutral to remove residual potassium ions, ammonium ions and other impurities, and ensure chemical purity to obtain a nitrogen-rich carbon catalyst. (4) Add KOH and 18-crown ether-6 to ethanol and deionized water and stir. The molar ratio of KOH to 18-crown ether-6 is 1:1 and the volume ratio of ethanol to deionized water is 1:1. Then add nitrogen-rich carbon catalyst. Nitrogen-rich carbon catalyst mass Calculate using the following formula; ; In the formula, m p M represents the mass of the active metal potassium precursor KOH, in grams. K Represents the relative atomic mass of the active metal K, in g·mol⁻¹ -1 M P Represents the relative atomic mass of the active metal K precursor, in g·mol⁻¹ -1 The loading amount refers to the loading amount of active metal potassium, which is calculated using the following formula. ; In the formula, This represents the mass of nitrogen-rich carbon catalyst, in grams (g); m K This represents the mass of the active metal K, expressed in grams. Heating and stirring until completely evaporated, the precursor solvent was collected; the dried solid was ground into powder and calcined under N2 atmosphere to obtain KOH-modified nitrogen-rich carbon catalyst.

[0010] Preferably, in step (2), the mass ratio of coffee grounds, KOH, and urea is 1:0.5:2 to ensure the nitrogen content of the prepared nitrogen-enriched carbon catalyst and to increase the alkalinity of the catalyst surface to promote the catalytic hydrolysis of COS.

[0011] Preferably, the ultrasonic time in step (2) is 1 hour, and the calcination conditions are: heating to 500°C~800°C at a heating rate of 10°C / min under N2 atmosphere and maintaining activation for 2 hours~4 hours, followed by cooling to room temperature at a cooling rate of 10°C / min, which helps to increase the specific surface area and yield of the nitrogen-rich carbon catalyst.

[0012] Preferably, the active component potassium loading in the modified nitrogen-rich carbon catalyst described in step (4) is 10% to 20%, which improves the catalytic hydrolysis efficiency of the catalyst.

[0013] Preferably, the calcination conditions in step (4) are as follows: under N2 atmosphere, the temperature is heated to 600℃~800℃ at a heating rate of 10℃ / min and kept activated for 2h~4h, and then cooled to room temperature at a cooling rate of 10℃ / min.

[0014] The second objective of this invention is achieved by preparing the modified nitrogen-rich carbon catalyst according to the method for preparing the biomass-derived modified nitrogen-rich carbon catalyst described above.

[0015] The third objective of this invention is achieved by the application of a modified nitrogen-rich carbon catalyst in the one-step catalytic hydrolysis of carbonyl sulfur to produce sulfur.

[0016] Preferably, the feed gas containing COS, H2S, and O2, along with H2O and a modified nitrogen-rich carbon catalyst, are reacted. COS is first hydrolyzed to H2S, and the generated H2S further reacts with O2 to produce sulfur (S) and water (Formulas 1 and 2). .

[0017] Preferably, the feed gas contains 150 ppm COS, 100 ppm H2S, 0 vol%~0.2 vol% O2, 5 vol%~10 vol% H2O, and N2 in equilibrium; the feed gas is at atmospheric pressure; the reaction temperature is 50℃~150℃; and the space velocity is 30000 h⁻¹. -1 More preferably, the reaction temperature is 60℃~120℃, and the O2 concentration is 0.1 vol% O2, so as to improve the efficiency of the catalyst in one-step catalytic hydrolysis of carbonyl sulfur to produce sulfur.

[0018] The beneficial effects of this invention are: 1. The preparation method of this invention reduces the accumulation of waste biomass and lowers environmental pollution. By optimizing the catalyst preparation conditions, the yield of sulfur is increased and the production cost is reduced. In addition, the preparation process of this invention is simple and suitable for large-scale industrial production. 2. This invention provides a simple, feasible, efficient, and rapid technology for removing COS and utilizing waste biomass resources. Compared with traditional COS hydrolysis catalysts, this invention can synthesize the required catalyst under mild conditions. Thanks to the easily modifiable surface chemistry and hierarchical pore structure of biomass, the prepared catalyst has high COS removal efficiency and strong catalytic oxidation ability for H2S at low temperature (80℃), and can successfully recover elemental sulfur, which is not only environmentally friendly but also economically feasible. 3. The catalyst of this invention is applied to the one-step catalytic hydrolysis of carbonyl sulfur to produce sulfur, and a carbonyl sulfur catalytic hydrolysis-sulfur production synergistic preparation technology system is constructed. Compared with the existing technology, the one-step catalytic hydrolysis of COS to produce sulfur technology of this invention has the advantages of high efficiency, low cost and strong stability, and can turn toxic sulfur-containing gas into elemental sulfur to turn waste into treasure. Attached Figure Description

[0019] Figure 1This is a schematic diagram of the process for preparing a nitrogen-rich carbon catalyst derived from coffee grounds and for one-step catalytic hydrolysis of carbonyl sulfide to produce sulfur according to the present invention. Figure 2 XRD comparison diagrams of the original NC, NC-KOH, and NC-K2CO3 catalysts; Figure 3 The graph shows the COS catalytic hydrolysis removal efficiency of NC-KOH and NC-K2CO3 catalysts. Figure 4 The graph shows the COS catalytic hydrolysis removal efficiency of NC-KOH catalyst at different temperatures. Figure 5 The graph shows the H2S removal efficiency of the NC-KOH catalyst at different temperatures. Detailed Implementation

[0020] The present invention will be further described below with reference to embodiments, but this is not intended to limit the present invention in any way. Any modifications or substitutions made based on the teachings of the present invention shall fall within the protection scope of the present invention.

[0021] Example 1 As attached Figure 1 As shown, the preparation method of the biomass-derived modified nitrogen-rich carbon catalyst in this embodiment includes the following steps: (1) Dry the coffee grounds in an oven at 100 ℃ for 8 hours to completely remove moisture. Transfer the dried coffee grounds to a container and wash them with an appropriate amount of ethanol. Repeat this process 3 times to initially remove impurities such as oil and pigments. Then wash the coffee grounds with distilled water. Repeat this process 3 times to further purify them. Finally, dry them in an oven at 80 ℃ for 12 hours for later use. (2) KOH was selected as the activator and urea as the nitrogen source. The coffee grounds treated in step (1) were mixed with KOH and urea at a mass ratio of 1:0.5:2. After ultrasonic treatment for 1 hour, the mixture was dried. The material was transferred to a tube furnace and calcined. The calcination was carried out at a heating rate of 10℃ / min to 700℃ and kept activated for 2 hours. Then the temperature was lowered to room temperature at a cooling rate of 10℃ / min. After cooling, the calcined product was obtained. (3) Wash the calcined product with distilled water until the pH of the washing liquid is 7 to remove residual potassium ions, ammonium ions and other impurities, and obtain a nitrogen-rich carbon catalyst, denoted as NC; (4) Add 1 mmol KOH and 1 mmol 18-crown ether-6 to 20 ml ethanol and 20 ml deionized water and stir. Then add 2 g NC, heat and stir at 60 °C until completely evaporated, and collect the precursor solvent. Grind the dried solid into powder, heat to 700 °C at a heating rate of 10 °C / min and keep it activated for 2 h. Then cool to room temperature at a cooling rate of 10 °C / min to obtain KOH modified nitrogen-rich carbon catalyst with a potassium loading of 6%.

[0022] Example 2 The preparation method of the biomass-derived modified nitrogen-rich carbon catalyst in this embodiment is the same as in Example 1, except that the KOH in steps (1) and (4) is replaced with K2CO3 solution and 1 mmol of K2CO3 is used.

[0023] Example 3 The preparation method of the biomass-derived modified nitrogen-rich carbon catalyst in this embodiment is the same as that in Example 1, except that the calcination temperature in step (2) is 800°C.

[0024] Example 4 The preparation method of the biomass-derived modified nitrogen-rich carbon catalyst in this embodiment is the same as that in Example 1, except that the potassium loading is 10%.

[0025] Example 5 The preparation method of the biomass-derived modified nitrogen-rich carbon catalyst in this embodiment is the same as that in Example 1, except that the potassium loading is 15%.

[0026] Example 6 The preparation method of the biomass-derived modified nitrogen-rich carbon catalyst in this embodiment is the same as that in Example 1, except that the potassium loading is 20%.

[0027] Example 7 The modified nitrogen-rich carbon catalyst prepared according to the preparation method of the biomass-derived modified nitrogen-rich carbon catalyst in Example 1 is denoted as NC-KOH.

[0028] Example 8 The modified nitrogen-rich carbon catalyst prepared according to the preparation method of biomass-derived modified nitrogen-rich carbon catalyst in Example 2 is denoted as NC-K2CO3. The catalyst NC-K2CO3 of Example 8 and the catalyst NC-KOH of Example 7 were compared by XRD. The results are shown in the appendix. Figure 2 As shown, attached Figure 2 The original NC in the middle was prepared in step (3) of Example 1, and was obtained from the attached Figure 2 It can be seen that three typical characteristic peaks of carbon materials are displayed at 2θ of 25.6℃ and 44℃, corresponding to the (002) and (101) crystal planes of graphitic carbon, respectively. Compared with the original NC catalyst, the main carbon peaks of the two samples, NC-KOH catalyst and NC-K2CO3 catalyst, did not change significantly, indicating that K is uniformly dispersed on the surface of the original NC catalyst. (Appendix) Figure 3The graphs show the COS removal efficiency of NC-KOH and NC-K2CO3 catalysts. The results show that the COS removal rate of the NC-KOH modified catalyst is 100% throughout 300 min, while the COS removal rate of the NC-K2CO3 modified catalyst reaches 100% only within 150 min. Therefore, the KOH modified catalyst is superior to the K2CO3 modified catalyst.

[0029] Example 9 The biomass-derived modified nitrogen-rich carbon catalyst of Example 7 was applied to the one-step catalytic hydrolysis of carbonyl sulfide to produce sulfur. Specifically, a feed gas containing 150 ppm COS, 100 ppm H2S, 0.1 vol% O2, and equilibrium nitrogen was reacted with 5 vol% H2O and 0.2 g of the modified nitrogen-rich carbon catalyst. The H2O was provided using a saturator system, and the water content was expressed as relative humidity (RH). A flow controller was used to control the flow rate of the feed gas into the fixed-bed reactor to 100 mL / min. The modified nitrogen-rich carbon catalyst was loaded into the fixed-bed reactor, and the reaction temperature was controlled at 80°C with a space velocity of 30,000 h⁻¹. -1 ; The results showed that the removal rate of COS by the potassium-modified nitrogen-rich carbon catalyst in this embodiment remained at 100% within 300 min, and the removal rate of H2S remained at 100% within 300 min, indicating that the hydrogen sulfide produced by COS hydrolysis was oxidized into elemental sulfur to generate sulfur.

[0030] Comparative experiment The comparative examples are based on Example 9. To further understand the effect of reaction temperature on performance, two additional reaction temperature cases were set in Example 9, namely 60°C and 100°C. The performance comparison results are shown in the appendix. Figure 4 Appendix Figure 5 ;; From the appendix Figure 4 It can be seen that within the range of 60℃ to 100℃, the COS-catalyzed hydrolysis to produce sulfur is most effective when the reaction temperature is 80℃. From the appendix Figure 5 It can be seen that both catalysts have a 100% catalytic oxidation capacity for H2S within 6 hours, indicating that both have strong H2S catalytic oxidation performance.

[0031] As can be seen from the above examples and comparative examples, the waste biomass-derived nitrogen-rich carbon-based catalyst provided by the present invention is applied to the one-step catalytic hydrolysis of carbonyl sulfur to produce sulfur. The catalyst has both high efficiency in catalytic hydrolysis of COS and catalytic oxidation of H2S. Compared with the prior art, the present invention can achieve efficient and stable treatment of toxic and harmful gases COS and H2S under low temperature and low oxygen conditions and realize the recovery of sulfur resources, turning waste into treasure. It is beneficial to solve the emission problems of various industrial tail gases containing COS and the treatment problems of a large amount of waste biomass generated every year.

Claims

1. A method for preparing a biomass-derived modified nitrogen-rich carbon catalyst, characterized in that... Includes the following steps: (1) Dry the coffee grounds to remove moisture completely. First wash the coffee grounds with ethanol, then wash them with distilled water, and then dry the coffee grounds. (2) KOH is selected as the activator and urea as the nitrogen source. The coffee grounds treated in step (1) are mixed evenly with KOH and urea, ultrasonically treated and dried. The material is transferred to a tube furnace for calcination and cooled to obtain the calcined product. (3) Wash the calcined product with distilled water until the pH of the washing solution is neutral to obtain a nitrogen-rich carbon catalyst. (4) Add KOH and 18-crown ether-6 to ethanol and deionized water and stir. The molar ratio of KOH to 18-crown ether-6 is 1:1 and the volume ratio of ethanol to deionized water is 1:

1. Then add nitrogen-rich carbon catalyst. Nitrogen-rich carbon catalyst mass Calculate using the following formula; ； In the formula, m p M represents the mass of the active metal K precursor KOH; K M represents the relative atomic mass of the active metal K; P The relative atomic mass represents the active metal K precursor; the loading refers to the active metal potassium loading, which is calculated by the following formula. ； In the formula, m s Represents the mass of nitrogen-rich carbon catalyst; m K Represents the mass of the active metal K; Heating and stirring until completely evaporated, the precursor solvent was collected; the dried solid was ground into powder and calcined under N2 atmosphere to obtain KOH-modified nitrogen-rich carbon catalyst.

2. The method for preparing the biomass-derived modified nitrogen-rich carbon catalyst according to claim 1, characterized in that... In step (2), the mass ratio of coffee grounds, KOH, and urea is 1:0.5:

2.

3. The method for preparing the biomass-derived modified nitrogen-rich carbon catalyst according to claim 1, characterized in that... Step (2) The ultrasonic time is 1 hour. The calcination conditions are: heating to 500℃~800℃ at a heating rate of 10℃ / min under N2 atmosphere and maintaining activation for 2h~4h, followed by cooling to room temperature at a cooling rate of 10℃ / min.

4. The method for preparing the biomass-derived modified nitrogen-rich carbon catalyst according to claim 1, characterized in that... The active component potassium loading in the modified nitrogen-rich carbon catalyst described in step (4) is 10%~20%.

5. The method for preparing the biomass-derived modified nitrogen-rich carbon catalyst according to claim 1, characterized in that... Step (4) The calcination conditions are as follows: under N2 atmosphere, heat to 600℃~800℃ at a heating rate of 10℃ / min and maintain activation for 2h~4h, then cool down to room temperature at a cooling rate of 10℃ / min.

6. A modified nitrogen-rich carbon catalyst prepared by a method according to any one of claims 1 to 5.

7. The application of the modified nitrogen-rich carbon catalyst according to claim 6 in one-step catalytic hydrolysis of carbonyl sulfur to produce sulfur.

8. The application according to claim 7, characterized in that... The feed gas containing COS, H2S, and O2, along with H2O and a modified nitrogen-rich carbon catalyst, are reacted. COS is first hydrolyzed into H2S, and the generated H2S further reacts with O2 to produce sulfur (S) and water.

9. The method for one-step catalytic hydrolysis of carbonyl sulfide to produce sulfur using a modified biomass-derived nitrogen-rich carbon catalyst according to claim 8, characterized in that... The feed gas consists of 150 ppm COS, 100 ppm H2S, 0 vol%~0.2 vol% O2, 5 vol%~10 vol% H2O, and N2 in equilibrium. The feed gas is at atmospheric pressure. The reaction temperature is 50℃~150℃, and the space velocity is 30000 h⁻¹. -1 .

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