SO2 Adsorption Capacity Research Articles

Heteroatom-Doped Porous Carbons as Effective Adsorbers for Toxic Industrial Gasses.

Ammonia (NH3), often stored in large quantities before being used in the production of fertilizer, and sulfur dioxide (SO2), a byproduct of fossil fuel consumption, particularly the burning of coal, are highly toxic and corrosive gases that pose a significant danger to humans if accidentally released. Therefore, developing advanced materials to enable their effective capture and safe storage is highly desired. Herein, advanced benzimidazole-derived carbons (BIDCs) with an exceptional capacity for NH3 and SO2 have been designed and tested. These heteroatom-doped porous carbon adsorbents were synthesized by thermolysis of imidazolate-potassium salts affording high surface area and controlled heteroatom content to optimize for rapid NH3 and SO2 gas uptake and release under practical conditions. According to gas uptake measurements, these nitrogen-doped carbons exhibit exceptional gas adsorption capacity, with BIDC-3-800 adsorbing 21.42 mmol/g SO2 at 298 K and 1 bar, exceeding most reported porous materials and BIDC-2-700 adsorbing 14.26 mmol/g NH3 under the same conditions. The NH3 uptake of BIDC-2-700 surpassed reported activated carbons and is among the best adsorbents including metal organic frameworks (MOFs). Our synthetic method allows for control over both textural and chemical properties of the carbon and enables heteroatom functionality to be incorporated directly into the carbon framework without the need for postsynthetic modification. These materials were also tested for recyclability; all adsorbents showed almost complete retention of their initial gas uptake capacity during recyclability studies and maintained their structural integrity and their previous adsorption capacity of both NH3 and SO2, highlighting their potential for practical application.

Pebax-based membrane filled with photo-responsive Azo@NH2-MIL-53 nanoparticles for efficient SO2/N2 separation

The preparation of mixed matrix membranes (MMMs) using metal–organic framework (MOF) as fillers is one of the simple and effective methods to improve the gas permeability and selectivity of membranes, and it has an attractive prospect to achieve controllable gas separation process. Herein, NH2-MIL-53 nanoparticles are synthesized by hydrothermal method and modified by aminoazobenzene (Azo) by decompression loading technology. The multifunctional Azo@NH2-MIL-53 nanoparticles are incorporated into the Pebax matrix to fabricate MMMs for efficient and controllable SO2 separation. Pebax/Azo@NH2-MIL-53–20% membrane exhibits the maximum SO2 permeability of 2570 Barrer with a SO2/N2 selectivity of 717 and the separation process of SO2/N2 has dynamic photo-responsive characteristics under different light conditions, which is attributed to the incorporation of the Azo@NH2-MIL-53. First, the NH2-MIL-53 nanoparticles with high specific surface area of 637 m2.g−1 and pore size of 1.50 nm are introduced into MMMs to construct rich SO2 transport channels, increasing the diffusivity selectivity. Second, the inherent –NH2 groups and introduced -N = N- groups in Azo@NH2-MIL-53 increase the affinity of SO2, enhancing the solubility selectivity. Third, by artificially changing the light conditions to accurately control the conformation of Azo and the pore structure of NH2-MIL-53 is changed, which significantly changes the SO2 adsorption capacity of NH2-MIL-53. Due to light is available in abundance in the form of sunlight, the mixed matrix membrane coupled with photo-responsive MOF can achieve more efficient and energy-saving gas separation process.

Adsorption and Sensing for SF6 Decomposition Products by Ru–MoTe2 Monolayer

In this work, the adsorption of SF6 decomposition products (SO2, SOF2, and SO2F2) on Ru–MoTe2 monolayer is investigated based on density‐functional theory (DFT) calculations. The doping structure, band structure, adsorption structure, adsorption energy, charge transfer, density of states (DOS), and molecular orbital are analyzed to better analyze the interaction mechanism between gas molecules and Ru–MoTe2 system. In the results, it is shown that the conductivity of MoTe2 monolayer can be greatly increased by doping Ru atom. Pristine MoTe2 shows a weak adsorption capacity for SO2, SOF2, and SO2F2 gases, which belongs to physical adsorption. When Ru atom is doped on MoTe2, the adsorption capacity of the doping system for these three gases is obviously improved. The adsorption capacity of Ru–MoTe2 monolayer to the gases is ranked as SO2F2 > SOF2 > SO2. Moreover, the strong interaction between gas molecules and Ru–MoTe2 surfaces leads to the rise of the conductivity of all adsorption systems to varying degrees, and the degree of the rise of conductivity influenced by gas molecules is ranked as SO2F2 > SO2 > SOF2. Herein, a theoretical basis for the preparation of gas sensors or adsorbers based on Ru–MoTe2 is provided for detecting and absorbing SF6 decomposition products.

Biomass and Coal Modification to Prepare Activated Coke for Desulfurization and Denitrification

SO2 and NOx in flue gas are serious environmental pollutants. As an excellent adsorbent, activated coke has good application potential in flue gas desulfurization and denitrification. In this study, different concentrations of NH3 and K2CO3 solutions were used to modify the activated coke made from biomass and coal, and then separate and coordinated desulfurization and denitrification experiments were carried out. The adsorption efficiency of activated coke and the adsorption capacity of SO2 and NO were compared, and the adsorption relationship between SO2 and NO was clarified. The changes of the surface functional groups of activated coke before and after adsorption and the forms of SO2 and NO after adsorption were analyzed by Fourier transform infrared spectrometer and X-ray diffractometer patterns. Results show that K2CO3 and NH3 modification can promote the adsorption of SO2 and NO in activated coke, and K2CO3 modification is more significant for improving the denitrification and desulfurization capacity. When the unmodified activated coke synergistically adsorbs SO2 and NO, there is a competitive adsorption between NO and SO2. However, when the activated coke modified with K2CO3 solution and NH3 synergistically adsorbs SO2 and NO, both have a promoting effect. After the adsorption of NH3-modified activated coke, CaSO4 and Na2SO4 crystals will appear. K2SO4 will exist after the adsorption of activated coke modified with K2CO3 solution.

Preparation of activated coke by carbonization, activation, ammonization and thermal treatment of sewage sludge and waste biomass for SO2 absorption applications

Flue gas desulfurization of coal-burning power plants is imperative to mitigate pollution and acid rain. Use of activated coke as a sulfur dioxide adsorbent is a promising technology, particularly since activated coke can also effectively remove other emissions, such as mercury. In this manuscript, a modified method of ammonia water was used to prepare activated coke for flue gas desulfurization. The feedstock is a blend of sewage sludge and waste biomass, at a mass ratio of 2:1. This material was carbonized prior to activation and ammonization; in some cases, additional thermal treatment was applied. The products were successfully tested for sulfur dioxide adsorption. A graphene model incorporating nitrogen-containing functional groups was used to simulate the sulfur dioxide adsorption process. Thereby, the effects of different ammonia modification concentrations on the physical and chemical properties of activated coke were studied, and the sulfur dioxide adsorption process of nitrogen-containing functional groups (such as pyridine and pyrrole) in activated coke, during flue gas desulfurization, was simulated. This study confirmed that the method of ammonization and heating can introduce nitrogen-containing functional groups on the surface of the activated coke. This greatly improves its chemical properties and, as a result, it markedly improves its SO2 adsorption capacity. It was found through simulation that the doping of nitrogen atoms changes the uniform electrostatic potential distribution and changes the surface polarity. H2O, pyridine functional groups and pyrrole functional groups can promote the adsorption of SO2 on the graphene surface. The pyrrole functional group showed selective adsorption for both SO2 and H2O, but it was predicted to be more effective in adsorbing SO2 than in adsorbing H2O. The pyridine functional group showed no selective adsorption for SO2 and H2O, and it was predicted to be more active in adsorbing SO2 when compared with the pyrrole functional group. The O2 had no effect on the physical adsorption of SO2 on the graphene.

Adsorption and gas-sensing properties of Aun (n = 1–3) cluster doped MoTe2 for NH3, NO2, and SO2 gas molecules

In this study, density functional theory calculations were adopted to investigate the adsorption of toxic gases (NH3, NO2, and SO2) on Aun (n = 1–3) doped MoTe2 monolayer. The adsorption structure, band structure, charge transfer, density of states, and molecular orbit were analyzed to better understand the interaction between the gases and the substrates. The results show that the conductivity of MoTe2 monolayer is improved after doping Au atoms. And pristine MoTe2 has poor adsorption capacity for NH3, NO2, and SO2, which belongs to physical adsorption. Compared to pristine MoTe2, the adsorption capacity of these three gases on Aun-MoTe2 is obviously improved. Moreover, Au3-MoTe2 monolayer has strong stability, and its structure hardly deforms after adsorbing gas. In addition, DOS analysis results show that Aun-MoTe2 has the strongest interaction with NO2, while the interaction with NH3 is the weakest. Molecular orbital analysis shows that the conductivity of the systems affected by gas molecules is in order of NO2 > SO2 > NH3 for Au-MoTe2 and Au2-MoTe2, and SO2 > NO2 > NH3 for Au3-MoTe2. These results provide a theoretical basis for the preparation of gas sensors based on Aun-MoTe2 used in industrial toxic gases detection.

The Reversible Removal of SO2 by Amino Functionalized ZIF8 with 5-Aminotetrazole via Post-Synthesis Modification

The post-synthesis modification is a highly efficient method for the modification of Metal-organic framework (MOF) materials, which has been used to synthesize MOF materials purposefully that cannot be prepared by direct synthesis and impregnation method. In this work, amino modified ZIF8 with 5-aminotetrazole was prepared by the post synthesis modification method and was employed to reversibly remove SO2 from flue gas. Based on the characterization and analysis of X-ray diffraction (XRD), Scanning Electron Microscope (SEM), and Brunner Emmet Teller (BET), it was found that the functionalized ZIF8 (Zn(5-ATZ)1.5) was a microporous material with a two-dimensional nano-layered structure. According to the SO2 adsorption experiments, the adsorption capacity of SO2 at the concentration of 1.6% vol can reach to 122 mg/g under the optimal conditions (25 °C, 2865 h−1). Five successive adsorption-desorption experiments exhibited that Zn(5-ATZ)1.5 had excellent regeneration performance. The characterization results of Raman Spectra (Raman) and X-ray photoelectron spectroscopy (XPS) as well as the DFT simulation calculations revealed that SO2 mainly interacted with Zn(5-ATZ)1.5 by hydrogen bonds between O of SO2 and amino H in the Zn(5-ATZ)1.5, and the interaction of SO2 with amino N and 5-aminotetrazole N by forming a non-covalent charge transfer complex. This work suggested that Zn(5-ATZ)1.5 is an excellent potential sorbent for SO2 removal.

Ultralow loading of Cu2O/CuO nanoparticles on metal-organic framework-derived carbon octahedra and activated semi-coke for highly efficient SO2 removal

A highly efficient desulfurizer is derived from a sacrificial Cu-based metal-organic framework (MOF) template, which is loaded on low-cost activated semi-cokes. The carbonized composite possesses highly-dispersed copper oxide nanoparticles (Cu2O/CuO) as active sites, which are distributed on MOF-derived carbon octahedra and activated semi-cokes. With an ultralow surface loading of 0.19 at% Cu and a high proportion of Cu+, the optimized sample shows an excellent breakthrough time of 822 min and SO2 adsorption capacity of 233.11 mg/g with a steady SO2 removal efficiency of 100%, which is superior to previously reported coke-base desulfurizers in literature. Meanwhile, the best-performed sample shows stability and reversibility for SO2 removal during 10 desulfurization−regeneration cycles. The excellent SO2 removal performance can be attributed to a well-developed porous structure and highly-dispersed copper oxide active sites due to the utilization of both sacrificial MOF template and activated semi-coke.

Structural control for inhibiting SO2 adsorption in porous MnCe nanowire aerogel catalysts for low-temperature NH3-SCR

The presence of SO2 in industrial flue gases will cause permanent deactivation of the catalyst active centre. Therefore, an effective method to improve the SO2 resistance of manganese-based catalysts at low temperatures is urgently needed. In this work, a hierarchical porous nanowire structure catalyst was designed by the in situ self-assembly method to inhibit SO2 adsorption. This hierarchical porous nanowire aerogel catalyst with great BET surface area and surface acidity exhibited NOx conversion above 90% at 100–400 °C. Notably, the NOx conversion of the MnCe-N catalyst was almost not inhibited by SO2 (250 ppm) compared to the 33% decrease of the MnCe-P catalyst. On the MnCe-P catalyst, SO2 has strong competitive adsorption with NH3 and NO, and the stronger adsorption capacity of SO2 inhibits the adsorption activation of the reaction gas and hinders the reaction proceeding through the L-H mechanism. Meanwhile, a large quantity of sulfate is formed on the catalyst surface, which prevents the active centre to participate in the redox reaction. The structure of nanowires enhances the number of acid sites, facilitates the adsorption and activation of NH3, and effectively inhibits the adsorption of SO2 on the MnCe-N catalyst. Fewer sulfate species are generated and difficult to deposit and aggregate on the catalyst surface, as a result, the active centre is less affected by sulfate species. The stable adsorption of NH3-related species ensures reliable reaction on MnCe-N through the E-R mechanism. This work emphasizes the importance of hierarchically porous structures in improving the NH3-SCR performance and SO2 resistance of monolithic catalysts, and provides new insights into the design of highly efficient and stable catalytic materials.

Adsorption of SO2 on ZnO Nanowires Using Activated Carbon by Langmuir Adsorption Isotherm

Sulphur dioxide (SO2) is one of the contaminants present in the environment. They are the by-product of combustion, industrial pollution, generation of electricity, etc. After some reactions in the atmosphere, SO2 changes its form and produces acid rain. The presence of SO2 needs to be detected to combat its effect. Many nanosensors are designed to detect the presence of SO2 in the environment. Zinc oxide (ZnO) nanowire sensor is one of those sensors used for SO2 detection. The size, structure, cost-effectiveness, and unique properties made it a choice for sensing purposes. Activated carbon is another compound that has porous substances that helps the adsorbate to settle down on the large surface area of its adsorbent surfaces. Combining the nature of ZnO nanowire and activated carbon, the adsorption of SO2 can be increased. This paper proposes a novel technique involving the activated carbon in the ZnO nanowire sensor to increase its SO2 adsorption capacity and rate. The Langmuir adsorption isotherm is used to find the adsorption efficiency between the solid adsorbent and gaseous adsorbate. MATLAB simulation was carried out for the proposed work in which it is seen that the novel method shows 33.34% efficiency in terms of SO2 adsorption capacity. The response of the proposed sensor shows 23% efficiency over time. The analysis shows that the usage of the activated carbon increases the adsorbent site for SO2 adsorbate to adsorb on the surfaces. According to the adsorption quantity, SO2 level has been obtained in the environment.

Light-responsive metal-organic framework sheets constructed smart membranes with tunable transport channels for efficient gas separation.

Exploring a new type of smart membrane with tunable separation performance is a promising area of research. In this study, new light-responsive metal–organic framework [Co(azpy)] sheets were prepared by a facile microwave method for the first time, and were then incorporated into a polymer matrix to fabricate smart mixed matrix membranes (MMMs) applied for flue gas desulfurization and decarburization. The smart MMMs exhibited significantly elevated SO2(CO2)/N2 selectivity by 184(166)% in comparison with an unfilled polymer membrane. The light-responsive characteristic of the smart MMMs was investigated, and the permeability and selectivity of the Co(azpy) sheets-loaded smart MMMs were able to respond to external light stimuli. In particular, the selectivity of the smart MMM at the Co(azpy) content of 20% for the SO2/N2 system could be switched between 341 and 211 in situ irradiated with Vis and UV light, while the SO2 permeability switched between 58 Barrer and 36 Barrer, respectively. This switching influence was mainly ascribed to the increased SO2 adsorption capacity in the visible light condition, as verified by adsorption test. The CO2 permeability and CO2/N2 selectivity of MMMs in the humidified state could achieve 248 Barrer and 103.2, surpassing the Robeson's upper bound reported in 2019.

Selective catalytic reductive removal of NOx with decreased interference from SO2 and H2O by use of Sm-modified SmxCo0.05-xCe0.05Ti0.9Oy catalysts

This work presents a novel and highly efficient NH3-SCR catalyst, Sm-modified CoCeTiOx, synthesized by a simple one-step sol–gel method. The optimum Sm0.03Co0.02Ce0.05Ti0.9Ox catalyst with a high BET surface area shows more than 90% NO conversion and nearly 100 % N2 selectivity at 180–440 °C. We investigated the relationship between Sm content and surface reactivity using NH3-TPD, H2-TPR, XPS, and in-situ DRIFTS. It demonstrated that the Sm-doping could precisely regulate the acidity and redox ability of the SmaCo0.05-aCe0.05Ti0.9Ox catalyst. Sm helped develop paths for fast electron transport, in which a charge transfer bridge was built between the Ce and Co, largely favoring the redox cycle. The nature of the acid sites, NOx adsorption, and the reactivity of surface adsorption species was characterized via in-situ DRIFTS. Moreover, the addition of Sm weakened the adsorption capacity of SO2 on the catalyst surface. We found that the electron transfer between SO2 and the activity sites was hindered on the modified catalyst.

Zwitterionic Covalent Organic Frameworks: Attractive Porous Host for Gas Separation and Anhydrous Proton Conduction

Ionic covalent organic frameworks (COFs) consisting of an anionic or cationic skeleton and corresponding counterions have demonstrated great potential in many application fields such as ion conduction, molecular separation, and catalysis. However, arranging anionic and cationic groups into the same COF to form zwitterionic materials is still unexplored. Herein we design the synthesis of three zwitterionic COFs as attractive porous hosts for SO2/CO2 separation and anhydrous proton conduction. The separated cationic and anionic groups in zwitterionic COFs' channels can act as two different polar sites for SO2 adsorption, allowing zwitterionic COFs to achieve a high SO2 adsorption capacity (216 mL/g, 298 K) and impressive SO2/CO2 selectivity (118, 298 K). Furthermore, after loading with triazole/imidazole, the zwitterionic groups in COFs' channels can induce complete proton carrier deprotonation, producing more freely migrating protons. The free protons migrate along a continuous hydrogen-bonding network in zwitterionic COFs' channels, leading to outstanding anhydrous proton conductivity up to 4.38 × 10-2 S/cm, which is much higher than other N-heterocyclic-doped porous materials under anhydrous conditions. Proton dissociation energy calculations combined with frequency-dependent dielectric analysis give insight into the role of zwitterionic COFs for proton conductivity. Our work provides the possibility to design well-defined zwitterionic frameworks for gas separation and ion conduction.

Study on Photocatalytic Desulfurization and Denitrification Performance of Cu- and Cr-Modified MWCNT

Carbon nanotubes are a promising adsorbent for desulfurization and denitrification. In this paper, Cu- and Cr-doped TiO2 supported by multi-walled carbon nanotubes (MWCNTs/Cu-Cr-TiO2) were synthesized by the sol-gel method. Characterizations of the samples were performed by TEM, XPS, XRD, DRS, and BET. The experiments of simultaneous desulfurization and denitrification were conducted in a fixed-bed reactor. The results showed that the adsorbent with a Cu to Cr molar ratio of 3 displays excellent adsorption property. The SO2 and NO adsorption capacity of MWCNTs/Cu-Cr-TiO2 (Cu/Cr = 3) were 36.83 and 12.34 mg/g under the optimal experimental operating parameters (SO2 content: 1575 mg/m3, NO content 736 mg/m3, O2 content 8%, H2O content 5%, and space velocity 1003 h−1). The adsorption capacity of MWCNTs/Cu-Cr-TiO2 was significantly better than that of the adsorbent doped with Cu or Cr alone (MWCNTs/Cu-TiO2 and MWCNTs/Cr-TiO2). Compared with single metal doping, bimetallic multivalent states accelerate the electron migration and separation from holes, which increase the number of oxygen vacancies and enhance the adsorption of SO2 and NO. The kinetic models and the reaction mechanism of the desulfurization and denitrification were also analyzed in this work.

Evaluation of oil palm fiber biochar and activated biochar for sulphur dioxide adsorption

The emission of sulphur dioxide (SO2) gas from power plants and factories to the atmosphere has been an environmental challenge globally. Thus, there is a great interest to control the SO2 gas emission economically and effectively. This study aims to use and convert abundantly available oil palm fiber (OPF) biomass into an adsorbent to adsorb SO2 gas. The preparation of OPF biochar and activated biochar was optimised using the Response Surface Methodology (RSM) based on selected parameters (i.e., pyrolysis temperature, heating rate, holding time, activation temperature, activation time and CO2 flowrate). The best adsorbent was found to be the OPF activated biochar (OPFAB) compared to OPF biochar. OPFAB prepared at 753 °C for 73 min of activation time with 497 ml/min of CO2 flow yields the best adsorption capacity (33.09 mg/g) of SO2. Meanwhile, OPF pyrolysed at 450 °C of heating temperature, 12 °C/min of heating rate and 98 min of holding time yield adsorption capacity at 18.62 mg/g. Various characterisations were performed to investigate the properties and mechanism of the SO2 adsorption process. Thermal regeneration shows the possibilities for the spent adsorbent to be recycled. The findings imply OPFAB as a promising adsorbent for SO2 adsorption.

Post modification of Oxo-clusters in robust Zirconium-Based metal organic framework for durable SO2 capture from flue gas

The efficient capture of SO2 after the combustion of fossil fuels is of great challenge as the low SO2 concentration (<500 ppm) and coexisting with CO2, water, O2 in flue gas. Robust zirconium-based MOFs possessing accessible polar sites usually have high SO2 adsorption capacity but poor durably in adsorption desulfurization due to the acidic sulfate deposition on the Zr-O cluster. Herein, a Zr-O cluster post-modification method was introduced in a Zr-MOF (MOF-808) to form EDTA-MOF-808 (EDTA, ethylene diaminetetraacetic acid) for selective and durable removal of SO2. The introduction of EDTA not only improve their SO2 adsorption capacity, but also sharply increase their SO2/CO2 selectivity (57.2 vs 8.9) and SO2/N2 selectivity (1915.8 vs 292.7) at low SO2 partial pressure. Moreover, the synergistic effects of dipole and hydrogen bonding interaction between SO2 and EDTA in EDTA-MOF-808 make the capture of SO2 in a reversible manner, which can prevent the formation of S(VI) species in Zr-MOF. DFT calculation confirmed that SO2 was interacted with EDTA through moderate dipole–dipole interaction (S(SO2) with N(EDTA)) and hydrogen bonds (H(–COOH) with O(SO2)). Systematic investigations including thermodynamic SO2 adsorption, dynamic breakthrough experiments, stability tests and DFT-calculations in both MOF-808 and EDTA-MOF-808 confirmed the efficient performance of post modification of Zr-O clusters with EDTA in Zr-MOFs for durable SO2 capture.

Influence of the water vapor on the activity of CuO/SBA-15 SOx adsorbents

Both the performance and regenerability of SO2 adsorbents made of CuO supported on SBA-15 ordered mesoporous silica were studied for a cyclic DeSOx process under wet and dry conditions. H2O vapor decreases the performance of a 16 wt% loading CuO/SBA-15 (16CuO/SBA-15) adsorbent along the adsorption/regeneration cycles performed at 400 °C. Indeed, the SO2 breakthrough adsorption capacity of this adsorbent after ten adsorption- regeneration cycles under wet conditions (5 vol% of H2O) decreases of 61% compared to the SO2 performance obtained under dry conditions. The impact of the temperature as well as the CuO loading on the performance and regenerability of CuO/SBA-15 sorbents were also investigated under dry and wet conditions. XRD, TEM/EDX, N2 physisorption characterizations of the adsorbents were performed after the last cycle to correlate the structural and textural properties of the adsorbents and therefore the copper species, with the performance of the adsorbents. Increasing the temperature up to 450 °C with or without water increases the SO2 adsorption capacity of the 16CuO/SBA-15 adsorbent with higher SO2 adsorption capacity at 450 °C with water than without water. In the presence of water vapor, the 8CuO/SBA-15 adsorbent presents the highest average loss of SO2 adsorption capacity at the breakthrough of around 71% when expressed in mgSO2/gCuO, compared to the ones obtained with the 16CuO/SBA-15 and the 26CuO/SBA-15 adsorbents. The increase of the CuO loading up to 26 wt%, shows that the contribution of the surface copper active phase highlighted by the desorption curves, decreases significantly for the highest CuO loading under wet conditions. Moreover, with or without water, the highest total SO2 adsorption capacities obtained after the tenth cycle are observed for the lowest CuO loading (8 wt% of CuO: 547 and 495 mgSO2/gCuO without and with H2O, respectively). These higher total SO2 adsorption capacities could be explained by a better CuO phase dispersion on the SBA-15 support, which makes the copper active species more reactive especially with H2O.

First-Principles Study of Au-Doped InN Monolayer as Adsorbent and Gas Sensing Material for SF6 Decomposed Species.

As an insulating medium, sulfur hexafluoride (SF6) is extensively applied to electrical insulation equipment to ensure its normal operation. However, both partial discharge and overheating may cause SF6 to decompose, and then the insulation strength of electrical equipment will be reduced. The adsorption properties and sensing mechanisms of four SF6 decomposed components (HF, SO2, SOF2 and SO2F2) upon an Au-modified InN (Au-InN) monolayer were studied in this work based on first-principles theory. Meanwhile, the adsorption energy (Ead), charge transfer (QT), deformation charge density (DCD), density of states (DOS), frontier molecular orbital and recovery property were calculated. It can be observed that the structures of the SO2, SOF2 and SO2F2 molecules changed significantly after being adsorbed. Meanwhile, the Ead and QT of these three adsorption systems are relatively large, while that of the HF adsorption system is the opposite. These phenomena indicate that Au-InN monolayer has strong adsorption capacity for SO2, SOF2 and SO2F2, and the adsorption can be identified as chemisorption. In addition, through the analysis of frontier molecular orbital, it is found that the conductivity of Au-InN changed significantly after adsorbing SO2, SOF2 and SO2F2. Combined with the analysis of the recovery properties, since the recovery time of SO2 and SO2F2 removal from Au-InN monolayer is still very long at 418 K, Au-InN is more suitable as a scavenger for these two gases rather than as a gas sensor. Since the recovery time of the SOF2 adsorption system is short at 418 K, and the conductivity of the system before and after adsorption changes significantly, Au-InN is an ideal SOF2 gas-sensing material. These results show that Au-InN has broad application prospects as an SO2, SOF2 and SO2F2 scavenger and as a resistive SOF2 sensor, which is of extraordinary meaning to ensure the safe operation of power systems. Our calculations can offer a theoretical basis for further exploration of gas adsorbent and resistive sensors prepared by Au-InN.

Simultaneous removal of SO2 and NOx from flue gas by low-temperature adsorption over activated carbon

An exceptional phenomenon has been observed that SO2 and NOx in flue gas can be effectively adsorbed over activated carbon with a surprising capacity at cold temperatures with the presence of oxygen. In this study, the adsorption characteristics of NO and SO2 over activated carbon at 80, 20, 0, and − 20 is experimentally investigated. Without the presence of oxygen, adsorption of NO is negligible. In the presence of oxygen, NO can be oxidized to NO2 over activated carbon which leads to the co-adsorption of NO/NO2 within the adsorption bed. Catalytic oxidation of NO over activated carbon can be significantly enhanced at cold temperatures, leading to an extraordinary increase of adsorption capacity of NO. With an initial concentration of NO = 200 ppmv and a space velocity of 5000 h−1, the average specific capacity increases from 3.8 to 169.1 mg/g when the temperature decreases from 80 to – 20 ℃. For NO–O2 co-adsorption, the specific capacity increases along the adsorption bed due to the increasing NO2 concentrations. The adsorption capacity of SO2 is also significantly enhanced at cold temperatures. With an initial concentration of SO2 = 1000 ppmv, the specific capacity increases from 12.9 to 123.1 mg/g when the temperature decreases from 80 to – 20 ℃. A novel low-temperature adsorption (LAS) process is developed to simultaneously remove SO2 and NOx from flue gas with a target of near-zero emission. A pilot-scale testing platform with a flue gas flowrate of 3600 Nm3/h is developed and tested. Emission of both SO2 and NOx is less than 1 ppmv, and the predicted energy penalty is about 3% of the net generation.

A Series of new Urea‐MOFs Obtained via Post‐synthetic Modification of NH2‐MIL‐101(Cr): SO2, CO2 and H2O Sorption

AbstractThe amino group in the MOF NH2‐MIL‐101(Cr) was post‐synthetically converted into urea‐groups partially using either ethyl isocyanatoacetate, furfuryl isocyanate, p‐toluenesulfonyl isocyanate or 3‐(triethoxysilyl)propyl isocyanate in acetonitrile. The derived four novel urea‐MOFs exhibit the expected lower BET surface areas and pore volumes than MIL‐101(Cr) and NH2‐MIL‐101(Cr) MOFs but the partially p‐toluenesulfonyl‐urea‐modified MOF exhibits an outstanding SO2 adsorption capacity of 823 cm3 g−1 (corresponding to 36.7 mmol g−1 or 70 wt.% at T=0 °C and 0.9 bar), which is the second highest SO2 uptake of any known material today – surprisingly even better than for highly porous MIL‐101(Cr) with an uptake of 645 cm3 g−1 SO2 under the same conditions. The high uptake is linked to the favorable dipole interactions of SO2 with the sulfonyl group of the p‐toluenesulfonyl‐modified MOF.