The effect of low-concentration SO2 on the adsorption of NO from gas over activated carbon (original) (raw)
Related papers
Adsorption of SO2 on Activated Carbons: The Effect of Nitrogen Functionality and Pore Sizes
Langmuir, 2002
Activated carbons of different origins were studied as sulfur dioxide adsorbents. The materials were characterized using adsorption of nitrogen, titration, X-ray photoelectron spectroscopy, and thermal analysis. The investigation was focused on the role of nitrogen functionality and pore sizes in the process of SO2 adsorption/oxidation. The results showed that quaternary and pyridinic type nitrogen significantly enhance the adsorption capacity. It happens when catalytic centers are located in the small pores, which is likely to help in achieving high dispersion of these centers. Besides an oxidation effect due to the formation of active oxygen radicals, the nitrogen-containing centers attract the SO4 2ions causing the gradual pore filling which is the most effective usage of the carbon pore space.
Effect of Pressure on NO x Adsorption by Activated Carbons
Energy & Fuels, 1996
Exposing activated carbons to nitric oxide and oxygen at temperatures between 295 and 400 K leads to the conversion of the NO to NO 2 at the carbon surface and the adsorption of NO 2 . In the current study, the conversion and adsorption kinetics of the NO to NO 2 reaction were examined at total pressures between 1 and 28 bar using a commercially available activated carbon. Up to 144 mg of NO 2 /g of carbon was adsorbed at 28 bar and 343 K, of which 115 mg of NO 2 /g of carbon was reversibly adsorbed-desorbed during repeated pressurization-depressurization cycles. The amount of NO 2 adsorbed at 17 bar and 373 K was similar to the amount adsorbed at 1 bar and 343 K, whereas it was 3-4 times greater than the amount adsorbed at 1 bar and 373 K. Analysis of the adsorption isotherm suggested the mechanism of NO 2 uptake was associated with micropore filling with a monolayer of adsorbed NO 2 formed at a total gas pressure near 10 bar. Time profiles for the desorption of NO 2 , CO 2 , and O 2 during pressure release and temperature-induced desorption suggested the influence of critical temperatures and pressures of the adsorbed gases and that van der Waals adsorption forces are important during adsorption and condensation within the pores of the carbon.
Adsorption Science & Technology, 2017
Activated carbons modified with ammonia were used as sorbents of SO 2. The SO 2 uptake was dependent on both texture and type of surface groups introduced onto the studied materials. The most important parameter was the size of micropores, which positively influenced the amount adsorbed. Differing chemical properties had a mixed influence. The oxygen-containing groups negatively affected SO 2 amount adsorbed. N-containing moieties had a positive influence, while the amount of introduced nitrogen was not the major parameter where SO 2 uptake was concerned, possibly due to the differences in the type of introduced surface species.
Study of NO adsorption on activated carbons
Applied Catalysis B: Environmental, 2008
Activated carbons (ACs) with varied porous textures and surface chemistry were studied for NO removal under different test conditions at temperatures below 100 8C. When oxygen is absent, there is almost no NO removal. When oxygen is present ACs act both as a catalyst for NO oxidation and as an adsorbent for NO adsorption. NO conversion is correlated with the presence of narrow micropores and is independent of surface area. ACs with an average micropore size around 7 Å exhibit the best NO removal capacity. NO rather than NO 2 was observed to be the main adsorbed species during the initial period of adsorption. NO 2 adsorption and NO 2 gas release start only after the carbon surface was rapidly oxidized during the early stage of adsorption. The decomposition of NO 2 formed through NO oxidation was believed to be responsible for the rapid carbon surface oxidation and NO chemisorption.
Carbon, 2004
In this work, peat was used as a precursor to produce activated carbons, through pyrolysis at 800 °C, followed by activation with steam at 800 °C. The carbons produced were characterized and used for NO adsorption in the absence of oxygen, and the results were compared with those on a commercial activated carbon. The adsorptive and kinetic behavior patterns of NO on different carbons were investigated using the breakthrough curve method for temperatures in the range between 45 °C and 85 °C. The equilibrium adsorption of NO was described according to a linear model for NO concentrations up to 5%. The NO adsorption capacity depended indirectly on both the BET surface area and oxygen functional group content of the carbon, and increased as the oxygen content increased. The adsorption was reversible and the enthalpy of adsorption was lower than 10 kJ mol−1. The linear driving force model was used to describe the breakthrough curves and the results showed that this model was suitable to describe the adsorption of NO on activated carbons in a fixed-bed.
Noxious gases can be reduced through activated carbon; nevertheless, this process is very complex due to the changing parameters. Nitrogen dioxides take place in the so-called reactive gases. The nitrogen dioxide concentration existing in the environment can be harmful, in particular for asthmatics and it also has the potential to bring about other serious diseases. For instance, interior diseases are often caused by nitrogen oxide gases. Through this study, we have observed the nitrogen dioxide adsorption on the active carbon for varying air temperatures, gas concentrations and air relative humidities. In this context, it has been examined the effect of all three parameters. While conducting this project, we have used parameters between 1ppm and 30ppm (for NO2 concentration), 23°C and 33°C (for air temperature), 30% and 90% (for air relative humidity). In order to understand this process, breakthrough curves of NO2evaluated from experiments have been used in the present study. Results show that the humidity has not a remarkable effect on the adsorption of NO2; however, increasing relative humidity causes to a decrease in the capacity of the activated carbon for NO2 adsorption. Additionally, NO2 adsorption is exothermic, therefore it increases the air temperature.
Materials
The textural properties and surface chemistry of different activated carbons, prepared by the chemical activation of olive stones, have been investigated in order to gain insight on the NO 2 adsorption mechanism. The parent chemical activated carbon was prepared by the impregnation of olive stones in phosphoric acid followed by thermal carbonization. Then, the textural properties and surface chemistry were modified by chemical treatments including nitric acid, sodium hydroxide and/or a thermal treatment at 900 • C. The main properties of the parent and modified activated carbons were analyzed by N 2-adsorption, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) techniques, in order to enlighten the modifications issued from the chemical and thermal treatments. The NO 2 adsorption capacities of the different activated carbons were measured in fixed bed experiments under 500 ppmv NO 2 concentrations at room temperature. Temperature programmed desorption (TPD) was applied after adsorption tests in order to quantify the amount of the physisorbed and chemisorbed NO 2. The obtained results showed that the development of microporosity, the presence of oxygen-free sites, and the presence of basic surface groups are key factors for the efficient adsorption of NO 2 .
Low Temperature Catalytic Adsorption of SO 2 on Activated Carbon
The Journal of Physical Chemistry C, 2008
Catalytic adsorption of SO 2 on activated carbon materials provides an appropriate alternative for the control of low concentration emissions of this air pollutant. The surface complexes formed upon SO 2 adsorption at 30°C were studied by X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD). The effect of the addition of O 2 and the presence of copper as catalyst were studied. Copper assisted the oxygen transfer to the carbon matrix. For the Cu-impregnated carbon sample, the presence of O 2 favored SO 2 adsorption by increasing the breakthrough time, the adsorption capacity and the formation of sulfur and oxygen complexes of higher thermal stabilities, which mainly desorb as SO 2 and CO 2 .
E3S web of conferences, 2022
In today's technologies of gas purification systems, adsorption processes offer more advantages than traditional processes (amine absorption and cryogenic distillation). Thanks to advantages such as high efficiency, low energy consumption and ease of operation, the adsorption process plays an important role in today's natural gas purification and carbon capturing processes. In order to bring natural gas to the usage standards and to ensure carbon capture in the emission sources (coal mines, landfills, agricultural activities, etc.) that emit CO2-CH4 as a result of human activities, it is extremely important to purify impurities such as CO2 and N2, which are highly present in the gas mixture. In the study, the adsorption of N2 and CO2 gases on activated carbon and the effect of pressure and temperature on adsorption were examined. The operating conditions pressure range was 1-6 bar and temperatures below room temperature. Experimental studies were carried out in laboratory scale adsorption cell system. As a result of the studies, it was determined that the adsorption capacity of activated carbon N2 and CO2 increased with pressure. N2 adsorption capacities were determined between 0.4-7.8 mmol/g and CO2 adsorption capacities were determined in the range of 2.7-7.4 mmol/g. In addition, Langmuir and Freundlich isotherm models were created, model parameters were examined and the adsorption behaviour of activated carbon for CO2 and N2 gases was obtained.
2022
A volumetric system was used to assess carbon-based adsorbents for evaluation of the gas separation, equilibrium, and kinetics of oxygen (O 2), nitrogen (N 2), and carbon dioxide (CO 2) adsorption on granular activated carbon (GAC) and functionalized GAC at 298, 308, and 318 K under pressures up to 10 bar. The effects of ZnCl 2 , pH, arrangement of the pores, and heat-treatment temperature on the adsorptive capabilities of O 2 , N 2 , and CO 2 were evaluated. High-performance O 2 adsorption resulted with a fine sample (GAC-10-500) generated with a 0.1 wt % loading of ZnCl 2. The optimal sample structure and morphology were characterized by field-emission scanning electron microscopy, Fourier transform infrared spectroscopy, and powder X-ray diffraction. On the basis of the adsorption−desorption results, the fine GAC provides a surface area of 719 m 2 /g. Moreover, it possessed an average pore diameter of 1.69 nm and a micropore volume of 0.27 m 3 /g. At 298 K, the adsorption capacity of the GAC-10-500 adsorbent improved by 19.75% for O 2 but was not significantly increased for N 2 and CO 2. Isotherm and kinetic adsorption models were applied to select the model best matching the studied O 2 , N 2 , and CO 2 gas uptake on GAC-10-500 adsorbent. At 298 K and 10 bar, the sip isotherm model with the highest potential adsorption difference sequence and gas adsorption difference compared with pure GAC adsorbent as O 2 > N 2 > CO 2 follows well for GAC-10-500. Eventually, the optimal sample is more effective for O 2 adsorption than other gases.