Adsorptive removal of nitrogen-containing compounds from a model fuel using a metal–organic framework having a free carboxylic acid group
Graphical abstract
Introduction
With increasing population and development worldwide, the demand for energy is increasing continuously. To date, fossil fuel has been one of the most important sources for global energy. However, utilization of fossil fuel without adequate pre-treatment causes a serious problem, including emission of SOx and NOx, which are derived from burning of sulfur- and nitrogen-containing compounds (SCCs and NCCs, respectively) in the fuel [1], [2], [3], [4], [5], [6]. SOx and NOx can be easily converted into acid rain, which has a negative effect on the environment, forests, and man-made structures. Therefore, the removal of SCCs and NCCs from fuel is very important [1], [2], [3], [4], [5], [6].
SCCs in fuel have been removed mainly by a hydrodesulfurization (HDS) process which has been developed during the past few decades [1], [2], [3], [4]. During HDS, sulfur in the SCCs is converted into gaseous H2S by hydrogenation of the SCCs at high temperature in the presence of a suitable catalyst. Removal of NCCs have started to attract attention only recently, owing to the increased NCC content in nonconventional or newly developed fuels and the enforcement of stricter environmental policies throughout the world [5], [6]. Additionally, NCCs should be removed because NCCs and SCCs compete for the active sites of HDS catalysts, and NCCs generally reduce the efficiency of these catalysts [5], [6]. Similar to SCCs, NCCs can be removed by hydrodenitrogenation (HDN) at high temperature in the presence of an appropriate catalyst and hydrogen. However, the efficiency of HDN is generally lower than that of HDS because successful HDN requires the destruction of the cyclic rings of NCCs. Moreover, HDN usually requires higher temperatures and pressures than HDS because of its lower reaction rate. Therefore, it is important to find a new and efficient process to remove NCCs from fuel. Recently, a technique called adsorptive denitrogenation (ADN) [5], [6] has been developed to replace conventional HDN. ADN does not require the usage of hydrogen and a catalyst. Moreover, ADN can be carried out under ambient conditions if suitable adsorbents are available [5], [6]. Several adsorbents such as activated carbon [5], [7], Ti-HMS [8], silica–zirconia [9], ion exchange resins [10], and mesoporous silica [11] have been employed to this end.
There have been remarkable developments to porous materials in recent days thanks to the emergence of new advanced materials such as metal–organic frameworks (MOFs) [11], [12], [13], [14], [15], [16], [17], [18], [19] and other functional materials [20], [21]. In particular, MOFs are very attractive materials for adsorption because of their high porosity, designable pore structure, ease of modification, and various pore sizes (ranging from microporous to mesoporous) [22], [23], [24], [25], [26]. Various MOFs have been employed in both ADS [27], [28], [29], [30], [31], [32], [33], [34], [35] and ADN [36], [37], [38], [39] mainly due to the high hydrophilicity shown by MOFs and their ability to be readily modified. Not only pristine MOFs but also functionalized MOFs (such as composites [40]) have been used for both processes to obtain clean fuel.
NCCs can generally be removed by adsorbents having high porosity because of common interaction of van der Waals force [38]. Π-complexation has been also reported as an effective mechanism to adsorb NCCs having π-electrons [41], [42]. The removal of basic NCCs such as quinolone (QUI), in which the formation of acid–base interactions is expected to play an important role, has also been described [43], [44]. However, neutral NCCs such as indole (IND) do not have active functionalities for adsorption; therefore, the efficiency of adsorption of neutral NCCs is generally lower than that of basic NCCs. Recently, H-bond formation has been suggested as a way to adsorb neutral NCCs in cases where there is a hydrogen atom bound to a nitrogen atom in the NCC structure [45]. In this study, we investigated the adsorptive removal of NCCs from a model fuel by using functionalized MOFs that contain, in particular, a free carboxylic acid in their structure (UiO-66-COOH) [46], as –COOH groups may be effective in adsorption because of their acidity or polarity. Both neutral and basic NCCs (such as IND and QUI, respectively) were adsorbed over UiO-66-COOH and pristine UiO-66 in order to understand the factors influencing the selectivity of the adsorption. Moreover, the adsorption of similar NCCs such as pyrrole (PYR), methylpyrrole (MPYR), and pyridine (PY) was studied in order to understand the plausible mechanism of adsorption of NCCs. Additionally, the reusability of UiO-66-COOH was evaluated after washing the used adsorbents with simple solvents.
Section snippets
Chemicals and synthesis of adsorbents
Zirconium chloride (ZrCl4, 99.5%), IND (98.0%) and QUI (98.0%) were purchased from Sigma–Aldrich Co. Terephthalic acid (TPA, 99.0%) and PY (95.0%) were procured from Junsei Chemical Company and Duksan Pure Chemicals Co. Ltd., respectively. Dimethylformamide (DMF, 99.0%) and hydrochloric acid (HCl, 35.0%) were obtained from OCI Company Ltd. PYR (99.0%) and MPYR (99.0%) were purchased from Alfa Aesar. n-Octane (C8H14, 97%) and oxalic acid (99.0%) were obtained from Yakuri Pure Chemicals Co. Ltd.
Characterization of the adsorbents
Fig. 1(a) shows the XRD patterns of pristine UiO-66 and UiO-66-COOH. The XRD patterns for the synthesized UiO-66s, such as UiO-66 and UiO-66-COOH, are very similar to each other and agree with the pattern calculated for UiO-66 (Fig. 1(a), bottom), showing that the two MOFs have the crystal structure of UiO-66. However, the relatively low intensity of UiO-66-COOH suggests that the functionalized MOF has lower crystallinity than the pristine UiO-66. Fig. 1(b) presents the N2 adsorption isotherms
Conclusion
An MOF having the functional group –COOH (UiO-66-COOH) was prepared in order to mainly remove neutral NCCs for the application in ADN. The presence of this functional group, –COOH, increased the adsorption capacity for IND and PYR remarkably, though the porosity of the MOF was decreased. UiO-66-COOH was also effective for the adsorption of basic NCCs such as QUI and PY; however, the efficiency for basic NCCs was relatively low. An adsorption mechanism was suggested based on the adsorption
Acknowledgements
This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) Grant funded by the Korea government (MSIP) (grant number: 2013R1A2A2A01007176).
References (50)
- et al.
Recent advances in the science and technology of ultra low sulfur diesel (ULSD) production
Catal. Today
(2010) - et al.
Denitrogenation of middle distillates using adsorbent materials towards ULSD production: a review
Fuel Process. Technol.
(2013) - et al.
Adsorptive desulfurization and denitrogenation using metal–organic frameworks
J. Hazardous Mater.
(2016) - et al.
Removal of hazardous organics from water using metal–organic frameworks (MOFs): plausible mechanisms for selective adsorptions
J. Hazardous Mater.
(2015) - et al.
Adsorptive removal of hazardous materials using metal–organic frameworks (MOFs): a review
J. Hazardous Mater.
(2013) - et al.
Adsorptive denitrogenation of model fuels with porous metal–organic frameworks (MOFs): effect of acidity and basicity of MOFs
Appl. Catal. B: Environ.
(2013) - et al.
Composites of metal–organic frameworks: preparation and application in adsorption
Mater. Today
(2014) - et al.
Adsorptive denitrogenation of model fuel with CuCl-loaded metal–organic frameworks (MOFs)
Chem. Eng. J.
(2014) - et al.
Remarkable improvement in adsorptive denitrogenation of model fossil fuels with CuCl/activated carbon, prepared under ambient condition
Chem. Eng. J.
(2015) - et al.
Adsorptive denitrogenation of model fuels with porous metal–organic framework (MOF) MIL-101 impregnated with phosphotungstic acid: effect of acid site inclusion
J. Hazardous Mater.
(2013)
Adsorptive denitrogenation of model fossil fuels with Lewis acid-loaded metal–organic frameworks (MOFs)
Chem. Eng. J.
Effective adsorptive removal of indole from model fuel using a metal–organic framework functionalized with amino groups
J. Hazardous Mater.
Adsorptive removal of naproxen and clofibric acid from water using metal–organic frameworks
J. Hazardous Mater.
An evaluation of desulfurization technologies for sulfur removal from liquid fuels
RSC Adv.
Review of experimental characterization of active sites and determination of molecular mechanisms of adsorption, desorption and regeneration of the deep and ultra deep desulfurization sorbents for liquid fuels
Catal. Rev. Sci. Eng.
Removal of organic sulfur compounds from diesel by adsorption on carbon materials
Rev. Chem. Eng.
Selective adsorption for removal of nitrogen compounds from liquid hydrocarbon streams over carbon- and alumina-based adsorbents
Ind. Eng. Chem. Res.
Role of surface oxygen-containing functional groups in liquid-phase adsorption of nitrogen compounds on carbon-based adsorbents
Energy Fuels
Adsorptive removal of nitrogen-containing compounds from fuel
J. Chem. Eng. Data
Adsorptive denitrogenation of light gas oil by silica–zirconia cogel
AIChE J.
Selective adsorption of neutral nitrogen compounds from fuel using ion-exchange resins
J. Chem. Eng. Data
Denitrogenation of raw diesel fuel by lithium-modified mesoporous silica
Chem. Eng. J.
The chemistry and applications of metal–organic frameworks
Science
Development of computational methodologies for metal–organic frameworks and their application in gas separations
Chem. Rev.
Metal–organic frameworks for separations
Chem. Rev.
Cited by (68)
Engineering functionalized Zr-MOFs as facile removal of indole: Experimental studies and first-principles modeling
2024, Journal of Science: Advanced Materials and DevicesHydroxyl modified nano calcium phosphate, a novel adsorbent for denitrogenation of fuel: Synthesis, characterization and adsorptive performance for quinoline
2023, Journal of Environmental Chemical EngineeringAre complete metal-organic frameworks really responsible for improving the performance of high-temperature proton exchange membranes?
2023, Materials Today ChemistryCitation Excerpt :Are complete MOFs really responsible for improving the performance of HTPEMs? Aiming at this issue, a series of MOFs (UIO-66 [23,24], UIO-66-COOH [25,26], UIO-66-NH2 [27,28], UIO-66-SO3H [29,30], MIL-101(Cr) [31–33], and MIL-53(Al) [34–36]), which were widely used in HTPEMs, were selected to investigate their stability via simulating the operating environment for the first time. Composite membranes based on these MOFs were prepared to explore the influence of the MOFs stability and state on HTPEMs properties.
Towards high-quality petrochemical feedstocks from mixed plastic packaging waste via advanced recycling: The past, present and future
2022, Fuel Processing TechnologyCitation Excerpt :Typical nitrogen compounds found in plastic waste pyrolysis oils are anilines, porphyrines, quinolines and their derivatives which are mostly aromatic structures that require more severe conditions than linear nitrogen compounds such as amines [33,176,222,236–238]. Consequently, higher temperatures and pressures are needed for HDN compared to other hydrotreatment processes [239]. In conclusion, it can be stated that the biggest obstacle when hydrotreating plastic waste pyrolysis oils is the co-existence of a large range of heteroatomic compounds which all influence the individual hydrotreatment steps and hence make the application of hydrotreatment processes for the selective removal of certain contaminants difficult [32,33,176,237].
Optimized synthesis of molecularly imprinted polymers coated magnetic UIO-66 MOFs for simultaneous specific removal and determination of multi types of macrolide antibiotics in water
2022, Journal of Environmental Chemical Engineering