Adsorption Of Nitrogen-containing Compounds Research Articles

Assessment of physicochemical properties of sorbent materials in passive and active sampling systems towards gaseous nitrogen-containing compounds

The adsorption and desorption behavior of volatile nitrogen-containing compounds in vapor phase by solid-phase microextraction Arrow (SPME-Arrow) and in-tube extraction (ITEX) sampling systems, were investigated experimentally using gas chromatography-mass spectrometry. Three different SPME-Arrow coating materials, DVB/PDMS, MCM-41, and MCM-41-TP and two ITEX adsorbents, TENAX-GR and MCM-41-TP were compared to clarify the selectivity of the sorbents towards nitrogen-containing compounds. In addition, saturated vapor pressures for these compounds were estimated, both experimentally and theoretically. In this study, the adsorption of nitrogen-containing compounds on various adsorbents followed the Elovich model well, while a pseudo-first-order kinetics model best described the desorption kinetics. Pore volume and pore sizes of the coating sorbents were essential parameters for the determination of the adsorption performance for the SPME-Arrow sampling system. MCM-41-TP coating with the smallest pore size gave the slowest adsorption rate compared to that of DVB/PDMS and MCM-41 in the SPME-Arrow sampling system. Both adsorbent and adsorbate properties, such as hydrophobicity and basicity, affected the adsorption and desorption kinetics in SPME-Arrow system. The adsorption and desorption rates of studied C6H15N isomers in the MCM-41 and MCM-41-TP sorbent materials of SPME-Arrow system were higher for dipropylamine and triethylamine (branched amines) than for hexylamine (linear chain amines). DVB/PDMS-SPME-Arrow gave fast adsorption rates for the aromatic-ringed pyridine and o-toluidine. All studied nitrogen-containing compounds demonstrated high desorption rates with DVB/PDMS-SPME-Arrow. Chemisorption and physisorption were the sorption mechanisms in MCM-41- and MCM-41-TP- SPME-Arrow, but additional experiments are needed to confirm this. An active sampling technique ITEX gave comparable adsorption and desorption rates on the selective MCM-41-TP and universal TENAX-GR sorbent materials for all the compounds studied. Vapor pressures of nitrogen-containing compounds were experimentally estimated by using retention index approach and these values were compared with the theoretical ones, calculated using the COnductor-like Screening MOdel for Real Solvent (COSMO-RS) model. Both values agreed well with those found in the literature proving that these methods can be successfully used in predicting VOC's vapor pressures, e.g. for the formation of secondary organic aerosols.

A potential material for removal of nitrogen compounds in petroleum and petrochemical derivates

Activated carbon from coconut shell (Elaeis guineensis), in both crude and chemically modified forms, was evaluated as an adsorbent for removing nitrogen compounds of samples from synthetic and real fuel. The preliminary adsorption tests showed that 97.95 of indoline was removed by sulfuric acid-treated activated carbon (SAAC). The optimum conditions toward adsorption of nitrogen-containing compounds in crude oil (54 °C, 150 rpm and 1.104 g of adsorbent) was evaluated according to the design of experiments (DOE) technique associated with Differential Evolution optimization algorithm and an effective removal of 30.37% of basic nitrogenous compounds present in crude oil was achieved. For comparative effect, the tests were carried out using the previously optimized condition with the vacuum residue, diesel S-500, and diesel S-10, obtaining the removal of 21.56%, 44.44%, and 62.09%, respectively. Complementing the quantitative analysis, the analysis of mass spectrometry confirmed that coconut shell is a potential material for selective adsorption of nitrogenous compounds.

Impact of linker functionalization on the adsorption of nitrogen-containing compounds in HKUST-1.

Functionalization of metal-organic framework (MOF) ligands can tune the adsorption properties of MOFs. The adsorptions of NO, NO2, NH3, C5H5N, C4H5N, and C4H4O on pristine and five X-functionalized HKUST-1, i.e. Cu3(BTC)2 (BTC = 1,3,5-benzenetricarboxylate) (X = CH3, CH3O, NH2, NO2, and Br) are evaluated by van der Waals corrected density functional theory calculations. Despite the fact that the open metal center is the energetically preferred adsorption site for most of them, the functional group site can yield a comparable adsorption ability with the open metal center. This is particularly true for pyrrole C4H5N adsorption on CH3O-functionalized HKUST-1 where the functional group site shows stronger adsorption stability than the open metal center site, probably due to the formed hydrogen bond between pyrrole and the CH3O functional group. While the CH3- or CH3O-functionalized organic linker in these MOFs strengthens the adsorption of all the considered species, that of NO2-, Br-, or NH2-functional groups reduces, which is associated with their topologies. Among them, only CH3- or CH3O-functionalized HKUST-1 presents the fmj (orthorhombic crystal system) topology while all the others are isostructural to the pristine HKUST-1 with the tbo (twisted boracite-type, cubic) topological structure. Among six adsorbates, two basic adsorbates, C5H5N and NH3, always yield the strongest bonding strength upon adsorption on the pristine and five functionalized HKUST-1. Electronic properties including the Bader charges, electron density differences, and electron localization function were investigated to comprehend their adsorption behaviors. This work provides guidance for the proper functionalization of HKUST-1 with improved adsorption properties for specific adsorbates.

Investigating the Effect of the Presence and Arrangement of Functional Groups at the Carbon Sorbent Surface on Adsorption of Nitrogen-Containing Compounds

Investigation of the physical chemistry of adsorption by carbon sorbents is a very important task from both theoretical and practical points of view. The thermodynamics of adsorption is affected by defects on the sorbent surface, including oxygen-containing functional groups. In this work, adsorption of a series of aromatic and aliphatic amines and nitriles by the surface of graphitized thermal carbon black is simulated using the Monte Carlo method. The results of calculations are compared to the experimental data. The cases of isolated and paired arrangement of functional groups are considered, and regularities of interaction between different classes of nitrogen-containing compounds and such defects are revealed. On the basis of comparison with the experimental data, assumptions about the presence and distribution of hydroxyls on the surface of graphitized thermal carbon black are made.

Adsorption of nitrogen-containing compounds on hydroxylated α-quartz surfaces.

Adsorption energies of various nitrogen-containing compounds (specifically, 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT), 2,4-dinitroanisole (DNAn), and 3-nitro-1,2,4-triazole-5-one (NTO)) on the hydroxylated (001) and (100) α-quartz surfaces are computed. Different density functionals are utilized and both periodic as well as cluster approaches are applied. From the adsorption energies, partition coefficients on the considered α-quartz surfaces are derived. While TNT and DNT are preferably adsorbed on the (001) surface of α-quartz, NTO is rather located on both α-quartz surfaces.

Physicochemical Studies of Adsorptive Denitrogenation by Oxidized Activated Carbons

A commercially available activated carbon was oxidized by concentrated sulfuric acid, saturated ammonium persulfate solution, and mixed sulfuric acid and ammonium persulfate, respectively. The original carbon and the modified carbons were evaluated by batch adsorption using model diesel fuels. The pore structure and surface chemistry of adsorbents were characterized with N2 adsorption/desorption, Fourier transform infrared spectroscopy, and Boehm’s titration. Both physical and chemical aspects of the selectively adsorptive denitrogenation of oxidized activated carbons were investigated. Appropriate oxidation can promote the carbon’s ability to adsorb nitrogen-containing compounds. The effect of the density of acidic oxygen-functional groups on the adsorption of nitrogen-containing compounds was demonstrated by the regression method and quantum chemistry calculations. The capacities due to physisorption were also estimated. The behaviors of N-containing compounds in a competitive adsorption system were dep...

Adsorption of Nitrogen-Containing Compounds from Model Fuel over Sulfonated Metal–Organic Framework: Contribution of Hydrogen-Bonding and Acid–Base Interactions in Adsorption

Adsorptive denitrogenation (ADN) was carried out by adsorption of indole (IND) and quinoline (QUI) over metal–organic frameworks (MOFs) including acidic UiO-66—SO3H for the first time. The adsorbed amount of IND increased with increasing content of —SO3H in UiO-66. The favorable effect of the —SO3H group on the adsorptive removal of IND could be explained by hydrogen bonding between the O of —SO3H and the H of IND, which was firmly supported by the adsorption of pyrrole and methylpyrrole and by theoretical calculations. The application of an —SO3H group in the adsorptive removal of neutral IND is meaningful since neutral nitrogen-containing compounds are not easy to remove and since UiO-66—SO3H is reusable after simple washing with ethanol. The expected increase in QUI adsorption (due to acid–base interaction) with acidic —SO3H was observed when QUI was present at low concentrations (<∼400 ppmw). This favorable contribution of acidic —SO3H to the adsorption of basic QUI was also supported by calculations ...

Theoretical study of adsorption of nitrogen-containing environmental contaminants on kaolinite surfaces.

The adsorption of nitrogen-containing compounds (NCCs) including 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT), 2,4-dinitroanisole (DNAN), and 3-nitro-1,2,4-triazol-5-one (NTO) on kaolinite surfaces was investigated. The M06-2X and M06-2X-D3 density functionals were applied with the cluster approximation. Several different positions of NCCs relative to the adsorption sites of kaolinite were examined, including NCCs in perpendicular and parallel orientation toward both surface models of kaolinite. The binding between the target molecules and kaolinite surfaces was analyzed and bond energies were calculated applying the atoms in molecules (AIM) method. All NCCs were found to prefer a parallel orientation toward both kaolinite surfaces, and were bound more strongly to the octahedral than to the tetrahedral site. TNT exhibited the strongest interaction with the octahedral surface and DNAN with the tetrahedral surface of kaolinite. Hydrogen bonding was shown to be the dominant non-covalent interaction for NCCs interacting with the octahedral surface of kaolinite with a small stabilizing effect of dispersion interactions. In the case of adsorption on the tetrahedral surface, kaolonite-NCC binding was shown to be governed by the balance between hydrogen bonds and dispersion forces. The presence of water as a solvent leads to a significant decrease in the adsorption strength for all studied NCCs interacting with both kaolinite surfaces.

Adsorptive denitrogenation of model fuel with CuCl-loaded metal–organic frameworks (MOFs)

CuCl impregnated MIL-100(Cr) was prepared with a facile method and then utilized for the adsorptive denitrogenation of model fossil fuels. CuCl was produced from CuCl2 solution at ambient temperature and pressure by reduction of CuCl2 using sodium sulfite as a mild reducing agent. Although the porosity of the adsorbent was reduced after impregnation, the adsorption of nitrogen-containing compounds (NCCs) increased. However, the adsorption of NCCs over CuCl2/MIL-100(Cr), which was produced in a similar manner but in the absence of Na2SO3, was decreased as a result of the reduced porosity. The maximum adsorption capacities of CuCl/MIL-100(Cr) as compared to pristine MIL-100(Cr) for quinoline (QUI) and indole (IND) were improved by 9% and 15%, respectively, which may be attributed to the π-complexation effect of the Cu+ sites of CuCl.

Adsorption of Nitrogen-Containing Compounds on the (100) α-Quartz Surface: Ab Initio Cluster Approach

A cluster approach extended to the ONIOM methodology has been applied using several density functionals and Moller–Plesset perturbation theory (MP2) to simulate the adsorption of selected nitrogen-containing compounds [NCCs, 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT), 2,4-dinitroanisole (DNAN), and 3-nitro-1,2,4-triazole-5-one (NTO)] on the hydroxyated (100) surface of α-quartz. The structural properties were calculated using the M06-2X functional and 6-31G(d,p) basis set. The M06-2X-D3, PBE-D3, and MP2 methods were used to calculate the adsorption energies. Results have been compared with the data from other studies of adsorption of compounds of similar nature on silica. Effect of deformation of the silica surface and adsorbates on the binding energy values was also studied. The atoms in molecules (AIM) analysis was employed to characterize the adsorbate–adsorbent binding and to calculate the bond energies. The silica surface shows different sorption affinity toward the chemicals considered de...

Adsorptive Removal of Nitrogen-Containing Compounds from Fuel

The feasibility of using microporous and mesoporous materials as adsorbents to remove nitrogen-containing compounds (NCCs) in fuel, such as pyridine, quinoline, pyrrole, and indole, was explored. A mesoporous molecular sieve Ti−HMS was chosen as the optimum adsorbent for the adsorptive denitrogenation (ADN) of fuel. Effect of adsorption time, temperature, and ratio of adsorbent to oil (A/O) on the removal of NCCs was investigated. Meanwhile, the adsorption isotherms and adsorption thermodynamics were studied. The thermodynamic functions show that the adsorption of NCCs on Ti−HMS is an exothermic, irregularity decreased, spontaneous physical process. Furthermore, the adsorption process primarily occurs in the pores of Ti−HMS, which is confirmed by comparing the adsorptive denitrogenation performance of Ti−HMS with uncalcined Ti−HMS.

Adsorptive denitrogenation of light gas oil by silica‐zirconia cogel

AbstractThe characteristics of adsorption and desorption of nitrogen‐containing compounds (NCCs) on the SiZr cogel were studied with regard to denitrogenation of light gas oil (LGO) through batch and dynamic experiments. The SiZr cogel adsorbent showed a high selectivity of NCCs due to the role of the zirconia on the cogel, regardless of the amount and types of sulfur‐containing compounds (SCCs) in the LGO. When the temperature increased from 283 to 323 K, the adsorbed amount of NCCs increased and the time taken to reach the adsorption equilibrium grew shorter. On the other hand, the adsorbent regeneration by the solvent grew worse at higher temperatures when the desorption temperature was applied to the adsorbent used at the corresponding adsorption temperature. At 283 and 303 K, the methyl isobutyl ketone (MIBK) with higher polarity showed a better desorption of NCCs, while the degree of regeneration by methyl tertiary butyl ether (MTBE) at 323 K was the best. The adsorption of NCCs on the cogel was significantly affected by the presence of water in the LGO. While MTBE and MIBK effectively desorbed the adsorbed water with NCCs from the cogel, methyl phenyl ether (Anisole) with aromatic ring was not effective in treating the water. Since the adsorbent could select only the NCCs with high capacity from the LGO at mild temperature and ambient pressure, success in the adsorption technology process would lead to major advances in petroleum refining by facilitating the improvement of HDS as well as fuel cell applications by offering greater protection of the nitrogen‐selective adsorbent. © 2005 American Institute of Chemical Engineers AIChE J, 2006