A method for low-temperature, high-selectivity catalytic oxidation of H2S to sulfur using carbon-based catalysts with hierarchical pore function.
By using carbon-based catalysts with hierarchical pore functionalization, the problem of synergistic catalytic reaction kinetics and sulfur capacity in the low-temperature oxidation of H2S by carbon-based catalysts has been solved, thereby improving catalytic oxidation performance and adaptability and achieving efficient sulfur recovery.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HARBIN INST OF TECH
- Filing Date
- 2023-11-09
- Publication Date
- 2026-08-04
AI Technical Summary
Existing carbon-based catalysts have difficulty coordinating catalytic reaction kinetics and sulfur capacity during the low-temperature oxidation of H2S, and are also difficult to adapt to complex and humid flue gas environments, resulting in poor catalytic oxidation performance.
A carbon-based catalyst with hierarchical pore functionalization is employed. By introducing polar oxygen- and nitrogen-containing functional groups into micropores and micropores, and non-polar graphitic nitrogen functional groups into mesopores/meso-macropores, a highly adaptable catalyst structure is constructed, which regulates the adsorption and mass transfer channels of water molecules.
This study achieved a synergistic improvement in the kinetics of H2S catalytic oxidation reaction and the sulfur generation capacity, avoided the poisoning effect of water on the catalytic process, and realized the efficient and low-energy recovery of sulfur.
Abstract
Description
Technical Field
[0001] This invention relates to a method for purifying H2S-containing waste gas, specifically to a method for producing sulfur from H2S by low-temperature, high-selectivity catalytic oxidation of carbon-based catalysts with hierarchical pore functionalization. Background Technology
[0002] Sulfur and hydrogen are fundamental elements in nature, and the gas they form, H2S, is widely present in industrial gases such as petroleum cracking gas, natural gas, biogas, blast furnace gas, coke oven gas, and converter gas. H2S is highly toxic and corrosive, posing a serious threat not only to human health and the ecological environment but also severely corroding production equipment and gas transmission pipelines. With rapid industrial development and increasingly stringent environmental standards, the development of efficient hydrogen sulfide removal technologies has gradually become an important issue of concern in the energy and environmental fields.
[0003] The Claus process is currently the most commonly used and classic process for H2S removal and resource recovery (H2S + SO2 → S). x (+H2O). However, this process is only suitable for treating high-concentration H2S gas, and is limited by thermodynamic equilibrium. Even after a three-stage Claus reaction, only 90-95% of the H2S gas in the waste gas can be converted. The remaining low-concentration H2S requires a complex and expensive incineration-chemical absorption process to meet ultra-low emission requirements. To achieve efficient removal of low-concentration H2S, catalytic oxidation processes using O2 as an oxidant have gradually attracted attention. Unlike the Claus reaction, catalytic oxidation theoretically allows for complete H2S conversion by controlling the physicochemical structure of the catalyst. Among various catalyst materials, porous carbon materials have gradually become a focus of attention in the field due to their advantages of low preparation cost, wide availability of raw materials, good structural tunability, and excellent low-temperature catalytic activity.
[0004] The catalytic performance of porous carbon-based catalysts is closely related to their physicochemical structure, and current research and patents mainly focus on regulating their surface chemical structure. CN106582598A reports that the catalytic oxidation activity of carbon materials is enhanced by introducing basic groups into porous carbon, and CN110026228B applies nitrogen-containing porous carbon to the field of H2S catalytic oxidation, achieving rapid catalytic reaction kinetics. In addition to surface chemical structure, the catalytic activity of porous carbon-based catalysts also depends on their pore grouping structure. Carbon-based catalysts rich in micropores and micropores have excellent reaction kinetics, but micropores and micropores are difficult to store sulfur products in large quantities, limiting their sulfur capacity and long-term stability (ACS Catalysis 2021, 11, 5974-5983; ACS Catalysis 2013, 3, 862-870); carbon-based catalysts dominated by mesopores and macropores can store sulfur products in high quantities, but their reaction kinetics are limited. Currently, carbon-based catalysts for H2S catalytic oxidation reported in literature and patents have simple pore grouping structures, which leads to a contradiction between fast reaction kinetics and difficulty in synergistically balancing sulfur capacity.
[0005] Furthermore, water vapor is commonly present in exhaust gases. Related studies have shown that water vapor in flue gas has a complex impact on the catalytic oxidation of H2S within porous carbon materials: a small amount of water forms a water film on the carbon-based surface, enhancing proton transfer and thus promoting the decomposition and catalytic oxidation of H2S; however, excessive adsorbed water can clog mass transfer channels, compete for adsorption sites, and create storage sites for sulfur products. Therefore, modifying the physicochemical structure of carbon materials to regulate the adsorption amount and location of water within carbon-based catalysts is crucial for improving their catalytic oxidation performance under actual operating conditions. However, there are currently no reports on research and patents related to carbon-based catalytic oxidation catalysts, making it difficult for currently prepared carbon-based catalysts to adapt to the complex flue gas environment. Summary of the Invention
[0006] To address the challenge of synergistic effects between catalytic reaction kinetics and sulfur capacity in low-temperature H2S oxidation processes, this invention provides a method for the low-temperature, highly selective catalytic oxidation of H2S to sulfur using a carbon-based catalyst with hierarchical pore functionalization. Compared to current carbon-based catalyst-based H2S catalytic oxidation technologies, this method synergistically enhances both H2S catalytic oxidation reaction kinetics and sulfur storage capacity, avoids the poisoning effect of water in flue gas on the catalytic oxidation process, and improves the applicability of H2S catalytic oxidation technology in complex and humid waste gases.
[0007] The objective of this invention is achieved through the following technical solution:
[0008] A method for low-temperature, high-selectivity catalytic oxidation of H2S to sulfur using a carbon-based catalyst with hierarchical pore functionalization includes the following steps:
[0009] Step 1: After uniformly mixing the pore-hierarchical functionalized carbon-based catalyst with quartz sand, place the mixture in an adiabatic reactor and control the temperature. The mass ratio of the pore-hierarchical functionalized carbon-based catalyst to quartz sand is 1:1 to 1:2. In the pore-hierarchical functionalized carbon-based catalyst, the pore volume ratio of micropores with a pore size less than 0.7 nm is not less than 25%, and the pore volume ratio of mesopores with a pore size greater than 2 nm is 40-60%. The micropores with a pore size less than 0.7 nm contain polar oxygen-containing and polar nitrogen-containing functional groups, while the mesopores with a pore size greater than 2 nm contain graphitic nitrogen functional groups and polar oxygen-containing functional groups. The content of functional groups is 5-15%, with polar nitrogen-containing functional groups accounting for no less than 8% and graphite nitrogen-containing functional groups accounting for no less than 3%. The polar oxygen-containing functional groups are one or more combinations of carboxyl, hydroxyl, and carbonyl groups, and the polar nitrogen-containing functional groups are one or more combinations of pyridine nitrogen, pyrrole nitrogen, and amino groups. The pore-hierarchical carbon-based catalyst that meets the above requirements can be obtained by the hierarchical porous zeolite template method. By controlling the pore size and corresponding functional groups of the zeolite template, the proportion of micropores, mesopores, and macropores and the types of functional groups distributed therein can be controlled. The temperature of the adiabatic reactor is in the range of 20-190℃.
[0010] Step 2: Low-concentration humid or dry waste gas containing H2S is introduced into an adiabatic reactor containing a carbon-based catalyst with hierarchical functionalization for catalytic oxidation. The humid waste gas has an H2S concentration not exceeding 3%, an O2 concentration not less than 5%, and an H2O concentration not exceeding 20%. The dry waste gas has an H2S concentration not exceeding 3% and an O2 concentration not less than 5%. The temperature range for the catalytic oxidation reaction is 20–190℃.
[0011] Step 3: After the catalyst reaches saturation, the catalyst is cleaned with an organic solvent to recover sulfur. The organic solvent is one or a combination of benzene, acetone, and carbon tetrachloride. When the catalytic oxidation reaction temperature is 160℃ or above, sulfur can be recovered by direct condensation.
[0012] In this invention, the micropores of the carbon-based catalyst with hierarchical functionalization are rich in polar oxygen functional groups and polar nitrogen functional groups, which simultaneously enhance H2S adsorption and enrichment, O2 activation and H2O-guided H2S dissociation; the mesopores and macropores are rich in non-polar graphitic nitrogen functional groups, which enhance mass transfer and guide high-capacity sulfur storage.
[0013] Compared with current H2S catalytic oxidation technologies based on carbon-based catalysts, this invention has the following advantages:
[0014] (1) This invention achieves a synergistic effect between rapid H2S catalytic oxidation reaction kinetics and high sulfur production capacity: Low-temperature catalytic oxidation of H2S requires both high-density, highly active catalytic sites and a large-capacity sulfur storage space. Currently, carbon-based catalysts dominated by micropores or mesopores are difficult to achieve a synergistic effect between catalytic oxidation reaction kinetics and sulfur production capacity due to their simple pore grouping. This invention, based on a carbon-based catalyst with hierarchical pore functionalization, achieves a synergistic improvement in reaction kinetics and sulfur capacity: Polar nitrogen- and oxygen-containing functional groups in micropores and micropores enhance the adsorption and enrichment of H2S and the activation of O2 molecules, thereby improving the catalytic oxidation reaction kinetics; Non-polar graphitic nitrogen in mesopores / meso-macropores guides the directional migration of non-polar sulfur products and provides space for sulfur storage.
[0015] (2) This invention avoids the poisoning effect of water in the waste gas on the catalytic oxidation process: Water in actual H2S-containing waste gas will hinder mass transfer channels and compete for sulfur storage sites, making it difficult for current carbon-based catalyst-based H2S catalytic oxidation technology to adapt to complex flue gas environments. This invention proposes to construct hydrophilic polar oxygen- and nitrogen-containing functional groups in micropores and micropores through pore hierarchical functionalization, guiding water molecule adsorption and enrichment to provide proton transfer channels for catalytic oxidation, thereby promoting the kinetics of catalytic oxidation reaction: Hydrophobic nonpolar graphitic nitrogen functional groups are constructed in the mesopore / mesopore mass transfer channels to avoid water blocking the mesopore / mesopore mass transfer channels and the storage space of sulfur.
[0016] (3) This invention enables efficient and low-energy-consumption recovery of sulfur as a product: In the low-temperature catalytic oxidation technology of H2S based on carbon-based catalysts, the sulfur product is stored within the porous structure of the catalyst and requires desorption and regeneration for recovery. Commonly used microporous-dominated carbon-based catalysts have high mass transfer resistance, making it difficult to achieve efficient recovery of sulfur as a product. The method of constructing a pore-hierarchical carbon-based catalyst proposed in this invention can effectively reduce the resistance to sulfur desorption by constructing mesoporous / meso-macroporous mass transfer channels, thereby achieving efficient and low-energy-consumption recovery of sulfur as a product. Detailed Implementation
[0017] The technical solution of the present invention will be further described below with reference to the embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.
[0018] Example 1:
[0019] Step 1: Prepare a carbon-based catalyst with hierarchically functionalized pores using a hierarchical porous zeolite template method. By controlling the pore size and functional groups of the selected zeolite template, the prepared hierarchical porous carbon catalyst has a pore volume ratio of 30% for micropores smaller than 0.7 nm and 50% for mesopores and macropores larger than 2 nm. The micropores and micropores contain 8% hydroxyl and carbonyl functional groups and 10% pyridine and pyrrole nitrogen functional groups, while the mesopores and macropores contain 5% graphitic nitrogen functional groups.
[0020] Step 2: Place the carbon-based catalyst with hierarchical pore function prepared in Step 1 into a fixed-bed adiabatic reactor and introduce humid waste gas with H2S concentration of 3000ppm, O2 concentration of 20%, and H2O concentration of 10%, and carry out a catalytic oxidation reaction at 25℃.
[0021] Step 3: After the reaction reaches saturation, the sulfur is recovered by washing with acetone.
[0022] Experiments showed that this system could maintain a nearly 100% H2S conversion rate for almost 70 hours, with a cumulative sulfur capacity of up to 4.8 g. -1 .
[0023] Example 2:
[0024] The feed gas introduced in Example 1 was replaced with dry waste gas with an H2S concentration of 3000 ppm and an O2 concentration of 20%, while other conditions remained the same as in Example 1. Experiments showed that this system could maintain nearly 100% H2S conversion rate for approximately 60 hours, with a cumulative sulfur capacity as high as 3.2 g. -1 .
[0025] Example 3:
[0026] The catalytic oxidation reaction temperature in Example 1 was replaced with 160°C, and the generated sulfur vapor was directly recovered by condensation. Other conditions remained the same as in Example 1. Experiments showed that this system could maintain a sulfur recovery rate of 99.8% for an extended period.
[0027] Comparative Example 1:
[0028] The carbon-based catalyst used in Example 1 was replaced with a microporous carbon catalyst with a micropore volume ratio of 80%, an oxygen content of 8%, and a nitrogen content of 10%, while other conditions remained the same as in Example 1. Experiments showed that this system rapidly reached saturation after maintaining a near 100% H2S conversion rate for 20 hours, with a sulfur capacity of 1.6 g / L. -1 .
[0029] Comparative Example 2:
[0030] The carbon-based catalyst used in Example 1 was replaced with a mesoporous carbon catalyst with a mesoporous-macropore volume ratio of approximately 90% and a graphitic nitrogen content of 5%, while other conditions remained the same as in Example 1. Experiments showed that this system could maintain an 80% H2S conversion rate for approximately 70 hours, with a sulfur capacity of 2 g / g. -1 .
[0031] Comparative Example 3:
[0032] The reaction temperature in Comparative Example 1 was adjusted to 160℃, and sulfur was recovered by condensing and desorbing sulfur vapor, with other conditions remaining the same as in Comparative Example 1. Experiments showed that the sulfur recovery rate of this system was 60%, reaching saturation after 50 hours.
Claims
1. A method for the low-temperature, high-selectivity catalytic oxidation of H2S to sulfur using a carbon-based catalyst with hierarchical pore functionalization, characterized in that... The method includes the following steps: Step 1: The carbon-based catalyst with hierarchical functionalization is mixed evenly with quartz sand and placed in an adiabatic reactor under controlled temperature. The mass ratio of the carbon-based catalyst with hierarchical functionalization to quartz sand is 1:1 to 1:
2. In the carbon-based catalyst with hierarchical functionalization, the pore volume ratio of micropores with a pore size less than 0.7 nm is not less than 25%, and the pore volume ratio of mesopores with a pore size greater than 2 nm is 40-60%. The micropores with a pore size less than 0.7 nm are distributed with polar oxygen-containing functional groups and polar nitrogen-containing functional groups, while the mesopores with a pore size greater than 2 nm are distributed with graphitic nitrogen functional groups. The content of the polar oxygen-containing functional groups is 5-15%, the content of the polar nitrogen-containing functional groups is not less than 8%, the content of the graphitic nitrogen functional groups is not less than 3%, and the polar nitrogen-containing functional groups are one or more combinations of pyridine nitrogen, pyrrole nitrogen, and amino groups. Step 2: Low-concentration humid or dry waste gas containing H2S is introduced into an adiabatic reactor containing a carbon-based catalyst with graded pores for catalytic oxidation. Step 3: After the catalyst reaches saturation, the catalyst is cleaned with an organic solvent to recover sulfur.
2. The method for low-temperature, high-selectivity catalytic oxidation of H2S to sulfur using a carbon-based catalyst with hierarchical pore functionalization according to claim 1, characterized in that... The polar oxygen-containing functional group is one or a combination of carboxyl, hydroxyl, and carbonyl groups.
3. The method for low-temperature, high-selectivity catalytic oxidation of H2S to sulfur using a carbon-based catalyst with hierarchical pore functionalization according to claim 1, characterized in that... The temperature of the adiabatic reactor is in the range of 20~190 ℃.
4. The method for low-temperature, high-selectivity catalytic oxidation of H2S to sulfur using a carbon-based catalyst with hierarchical pore functionalization according to claim 1, characterized in that... In the humid exhaust gas, the H2S concentration does not exceed 3%, the O2 concentration is not less than 5%, and the H2O concentration does not exceed 20%.
5. The method for low-temperature, high-selectivity catalytic oxidation of H2S to sulfur using a carbon-based catalyst with hierarchical pore functionalization according to claim 1, characterized in that... The concentration of H2S in the dried exhaust gas does not exceed 3%, and the concentration of O2 is not less than 5%.
6. The method for low-temperature, high-selectivity catalytic oxidation of H2S to sulfur using a carbon-based catalyst with hierarchical pore functionalization according to claim 1, characterized in that... The temperature range for the catalytic oxidation reaction is 20~190 ℃.
7. The method for low-temperature, high-selectivity catalytic oxidation of H2S to sulfur using a carbon-based catalyst with hierarchical pore functionalization according to claim 1, characterized in that... The organic solvent is one or a combination of benzene, acetone, and carbon tetrachloride.
8. The method for low-temperature, high-selectivity catalytic oxidation of H2S to sulfur using a carbon-based catalyst with hierarchical pore functionalization according to claim 1, characterized in that... Step 3 is replaced by: after the catalyst reaches saturation, when the catalytic oxidation reaction temperature is 160 °C or above, sulfur is recovered by direct condensation.