Adsorption Of Thiophene Research Articles

Density functional theory screening of thiophene adsorbents and study of adsorption mechanism

Sulfides, widely found in fossil fuels, not only corrode equipment but also pollute the atmosphere. Adsorption desulphurization can not only remove sulfide effectively, but also reduce energy consumption, it is very necessary to develop desulphurization adsorbent. Metal-organic framework materials (MOFs) have great potential in adsorption desulfurization due to the unique structural properties. However, selecting high-performance adsorbents in the growing sea of MOFs by experiment still needs theoretical guidance. Therefore, the screening method based on density functional theory was adopted to develop the thiophene adsorbents and explore the overall picture of thiophene adsorption. Through applying a three-step screening strategy which involves, we evaluated adsorption performance of 12,020 computationally-ready experimental MOFs candidates. Three adsorbents were found the best activity with adsorption energy <-1.21 eV. According to the classification and electronic structure analysis, it is found that different combinations of ligand atoms and open metal site can induce different strength of d-band center movement during the adsorption process. The high-performance adsorbents are those d-band center of metal sites remain unchanged in the adsorption of thiophene. These results emphasize the importance of the structure-performance relationship of potential MOFs in adsorption desulfurization.

Competitive adsorption mechanism of thiophene with diethyl sulfide in Y zeolite: Displacement and migration

In order to study the competitive adsorption relationship between sulfides in the adsorption desulfurization (ADS) process, as the loads increase gradually to saturation adsorption, the competitive adsorption mechanism of thiophene /diethyl sulfide on the all-silicon Y zeolite was investigated by GCMC simulation for the first time. A two-stage loads dependence adsorption mechanism was acquired which can be named ‘‘optimization-displacement adsorption” and “relocation-displacement adsorption” with an inflection point of 36 molecule/UC. At the ‘‘optimization-displacement adsorption” stage, both thiophene and diethyl sulfide molecules could occupy the optimization adsorption site ideally in the initial phase and the thiophene molecules on the S sites (refers to other sites except for W sites in the supercages) would be displaced by the diethyl sulfide ones and migrated to the W (refers to the 12-members ring connecting the supercages site) when the total loads approached the inflection point. At “relocation-displacement adsorption”, the thiophene molecules on the S site would be displaced by the diethyl sulfide ones and migrated to the W sites sequentially. Meanwhile, more and more proportions of the latter diethyl sulfide molecules are adsorbed away from the center of the supercage. This transformation of the competitive adsorption mechanism was proved to be related to the interaction energy. Besides, three more realistic factors on the adsorption behavior were investigated respectively. It was concluded that high temperature is conducive to enhancing the selectivity of thiophene adsorption, but lower temperature can remove the sulfide more completely. Cations may improve the selectivity of sulfide ether. Besides, mercaptan has a great effect on the adsorption of other sulfides.

Beneficial effect of Au and Pt doping of the Ag-(100) surface for thiophene and pyridine adsorption from density functional theory calculations

We use density functional theory including van der Waals (vdW) interactions to investigate the adsorption of thiophene (C 4 H 4 S) and pyridine (C 5 H 5 N) on the Ag-(100) surface doped by Pt, Au, Pt 2 , Au 2 , PtAu, Pt 4 and Au 4 atoms. Our calculated adsorption energies show that the dopant atoms enhance significantly the binding of the C 4 H 4 S and C 5 H 5 N molecules. More precisely, the thiophene and the pyridine molecules present a larger interaction with the surface when it is doped with Pt atoms, indicating that Pt atoms have an extremely strong adsorption capacity for both molecules. In addition, the adsorption height of the different configurations shows that the Pt dopant atoms enhance the S-Pt and N-Pt bonds strength, while the C S and C N bond distances are elongated in the presence of Pt atoms. The effect of Au atoms is similar to the ones of Pt, albeit the adsorption is weaker. The Bader analysis reveals that charge transfer almost occurs from the thiophene and pyridine molecules to the studied surfaces, with a modest increase in charge transfer in certain cases, while, the charge density difference (CDD) results supported the adsorption behaviour of both molecules. Overall, it is expected that doping the Ag-(100) surface with either Pt or Au atoms will have a significant effect on the reactivity of thiophene and pyridine.

Anatase Nanocrystals Covalently Functionalized with EDTA-diol: Interaction with Aromatic Sulfur.

The current study addresses the generation of surface-modified nanograined anatase (5 nm) by a single-step in situ process. The EDTA-diol (ester) functionality existing on the surface of anatase nanoparticles was proved with the help of a battery of physicochemical techniques, including FTIR, XPS, and NMR spectral measurements. The sample showed excellent dispersity in ethanol. The anatase lattice showed disorder and had oxygen vacancies. From the XPS analysis, the existence of 14% of Ti3+ was established. The functionalized sample remained thermally stable up to 250 °C, beyond which it transformed into a graphite-titania nanocomposite. The interfacial ligand (ester) to metal (Ti) charge transfer (LMCT) transitions were present in the UV-visible spectrum of the sample and indicated the functionalization to be covalent. Unsaturated OH-groups on the surface yielded a ζ-potential value of -39.8 mV. The covalently functionalized nanotitania was exploited in the adsorptive desulfurization of thiophene, an aromatic sulfur model compound. The consequences of surface adsorption of thiophene were analyzed with the help of UV-visible, FTIR, and 1H and 13C NMR spectra and EDS and XPS measurements. The adsorption data, derived from the batch process, were fitted successfully to pseudo-second-order kinetics and the Temkin model. The adsorption capacity of covalently functionalized titania was compared with several other high surface area adsorbents containing thiophilic metal ions.

Adsorption desulfurization performance of PdO/SiO2@graphene oxide hybrid aerogel: Influence of graphene oxide

Preparation of PdO/SiO2@graphene oxide (GO) hybrid aerogels were carried out sol-gel method combined with atmospheric drying technology to study their adsorption performance for thiophenics and compared with PdO/SiO2. Scanning electron microscope (SEM), N2 adsorption-desorption isotherms, X-ray diffraction (XRD) analysis, X-ray photoelectron spectroscopy (XPS), and fourier transformation infrared spectroscopy (FT-IR) for samples were performed. The adsorption performance of PdO/SiO2@GO for thiophene were better than that of PdO/SiO2, attributed to that incorporation of GO increased the specific surface area and the Pd incorporation rate, where Pd2+ ions acted as the π-complexation and sulfur-metal (SM) bond adsorption active centers, as well as GO adsorbed thiophene by the π-π stacking effect. The adsorption capacities of PdO/SiO2@GO-1.0 for thiophene (TH), benzothiophene (BT) and dibenzothiophene (DBT) were 8.89, 9.3 and 12.6 mg-S/gads, respectively. The addition of GO in aerogels could improve the inhibition effect of toluene, cyclohexene and pyridine while decreased the inhibition effect of MTBE and H2O for the adsorption of thiophene, due to the π-π stacking effect and the hydrophobicity of GO, respectively. The adsorption process was spontaneous and exothermic, be well fitted by the apparent second-order kinetic model and dominated by chemical interaction. Pd/SiO2@GO-1.0 had a good solvent elution regeneration performance.

Enhanced desulfurization performance of polyethylene glycol membrane by incorporating metal organic framework MOF-505

• MOF-505/PEG mixed matrix membranes were prepared. • The filled MOF-505 provided extra free volume for the membranes. • The active metal sites of MOF-505 have selective adsorption for thiophene. • Both permeability and selectivity of the MOF-505/PEG MMMs were increased. The metal–organic framework MOF-505 particles were synthesized and incorporated into the polyethylene glycol (PEG) matrix to prepare mixed matrix membranes. A series of methods were used to characterize the structure and morphology of MOF-505 particles and membranes. The prepared MOF-505 had a well-developed pore structure, a large number of metal sites for selective adsorption of thiophene and good compatibility with polymer matrix. Accordingly, the desulfurization performance of the membrane was improved effectively. The effects of the content of MOF-505, operating temperature and feed sulfur content on membrane performance were investigated by pervaporation experiments. The membrane with 3 wt% MOF-505 showed the optimal desulfurization performance with a permeation flux of 2.66 kg/(m 2 ·h) and an enrichment sulfur factor of 8.15, which were increased by 158% and 25% versus pristine membrane, respectively.

Activity and sulfur resistance of co-impregnated bimetallic PdNi/γ-Al2O3 catalysts during hydrogenation of styrene

Pyrolysis gasoline (PyGas) is an unstable byproduct of the pyrolysis of naphtha and other hydrocarbons for the production of olefins. PyGas is stabilized by hydrogenation at mild conditions. The hydrogenation of styrene to ethylbenzene is considered a model test reaction for studying the selectivity of the catalysts because it has the slowest rate of conversion. The catalytic activity and selectivity of two bimetallic co-impregnated Pd–Ni catalysts supported on γ-alumina were assessed and compared to those of a commercial monometallic Pd catalyst (AXENS LD265). The laboratory-prepared catalysts had different metal content and Pd:Ni atomic ratios (1:1 and 1:7). Catalytic tests of selective hydrogenation of styrene to ethylbenzene were made in a batch stirred tank reactor and in a continuous fixed bed trickle bed reactor. The sulfur resistance of the bimetallic catalysts in semicontinuous condition, was assessed by means of the same operational conditions using thiophene as a model poison compound. The support, Pd–Ni co-impregnated catalysts and LD265 commercial catalysts were further characterized by N2 chemisorption, EPMA, OM, ICP elemental analysis, temperature programmed reduction, XPS and X-Ray diffraction. The results indicated the presence of different metal species: Pd0, Pdδ+, Ni0 and NiO. The lab-prepared bimetallic catalysts were found to be active for the selective hydrogenation of styrene (both in the batch and continuous system). During the continuous evaluations, the commercial LD265 catalyst had an intermediate activity level that lied between the values corresponding to the Pd–Ni bimetallic catalysts: PdNi(1:1) $$ \gg $$ LD265 > PdNi(1:7). During the poison free semicontinuous evaluations, the pattern of conversion as a function of contact time of co-impregnated Pd–Ni catalysts are quite similar to that of commercial LD265 catalyst, though the catalytic activity is slightly better for PdNi(1:1). After 90 min of contact time the order of conversion was: PdNi(1:1) > LD265 > PdNi(1:7). On the other hand, during the poison semicontinuous tests (with 300 pp of thiophene), the initial reaction rates of the co-impregnated catalysts decreased, pointing a poisoning of the active sites by thiophene. PdNi(1:1) had higher initial reaction rate than PdNi(1:7) during poison free or poisoned in both conditions. PdNi(1:7) was more sulfur resistant than PdNi(1:1). The higher activity of the PdNi(1:1) catalyst was attributed to the presence of Pd0 and Pdn+/Nim+ species that favored respectively, the homolytic cleavage of the H–H bond and the adsorption of styrene. The higher sulfur resistance of the PdNi(1:7) catalyst would be associated with the higher Cl/Al surface atomic ratio in this catalyst (electronic effect) and the presence of electrodeficient species of Pd (Pdxδ+OyClz) that prevented the adsorption of thiophene by steric hindrance (geometrical effect of the large species) or by electronic effects.

Describing adsorption of benzene, thiophene, and xenon on coinage metals by using the Zaremba-Kohn theory-based model.

Semilocal (SL) density functional approximations (DFAs) are widely applied but have limitations due to their inability to incorporate long-range van der Waals (vdW) interaction. Non-local functionals (vdW-DF, VV10, and rVV10) or empirical methods (DFT+D, DFT+vdW, and DFT+MBD) are used with SL-DFAs to account for such missing interaction. The physisorption of a molecule on the surface of the coinage metals (Cu, Ag, and Au) is a typical example of systems where vdW interaction is significant. However, it is difficult to find a general method that reasonably describes both adsorption energy and geometry of even the simple prototypes of cyclic and heterocyclic aromatic molecules such as benzene (C6H6) and thiophene (C4H4S), respectively, with reasonable accuracy. In this work, we present an alternative scheme based on Zaremba-Kohn theory, called DFT+vdW-dZK. We show that unlike other popular methods, DFT+vdW-dZK and particularly SCAN+vdW-dZK give an accurate description of the physisorption of a rare-gas atom (xenon) and two small albeit diverse prototype organic molecules on the (111) surfaces of the coinage metals.

Molecular simulation on mechanism of thiophene hydrodesulfurization on surface of Ni2P

Hydrodesulfurization reaction, as the last step of hydrothermal cracking reaction, is of great significance for the reduction of viscosity and desulfurization of heavy oil. Based on Density Functional Theory and using Dmol3 module of Materials Studio, this research simulated the adsorption and hydrodesulfurization of thiophene on Ni2P (001) surface, and discussed the hydrodesulfurization reaction mechanism of thiophene on Ni2P (001) surface. It was found that the direct hydrodesulfurization of thiophene had more advantages than the indirect hydrodesulfurization of thiophene. Finally, the optimal reaction path was determined: C4H4S+H2→C4H6.

Interaction mechanism of calcite and four representative organic molecules: Experiments and DFT study

Calcite crystal-organic molecule interaction governs the wettability formation and alteration of carbonate reservoirs, and influences the oil recovery. However, its in-depth interaction mechanism in atomic scale have not been classified clearly. Regarding this, this study combines the atomic force microscopy (AFM), fourier transform infrared spectrometer (FTIR), X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) to systemically investigate the adsorption regularities and mechanisms of four representative organic molecules of crude oil on calcite surface. AFM results illustrated that the adsorption amount of the four organic molecules on calcite surface is in the order of benzoic acid>pyridine>thiophene>toluene. FTIR and XPS results explicated that the COOR and OH functional groups are formed in the benzoic acid adsorption; the Ca of calcite surface and N of pyridine are involved in the interaction, and OH functional groups are also formed in pyridine adsorption; only the OH bond is formed in thiophene adsorption, and no bond is formed in toluene adsorption. DFT results verified the experiments results and further revealed the interaction mechanism in atomic scale. Firstly, DFT results showed that the adsorption energies of benzoic acid, pyridine, thiophene and toluene on calcite surface are −1.39 eV, −0.97 eV, −0.49 eV and −0.31 eV, respectively. Secondly, DFT results explicated that the Ca-O ionic bond and HO covalent bond are formed in benzoic acid-calcite interaction; the Ca-N ionic bond and HO hydrogen bond are formed in calcite-pyridine interaction; only the HO hydrogen bond is formed in calcite-thiophene interaction; No chemical bond is formed in calcite-toluene interaction.

Zeolite catalyst containing metals.

Adsorption desulfurization is one of the most promising ways to reduce the sulfur content of gasoline at deeper level. In this work, thiophene (TP) adsorption capacity in cyclohexane onto [Cu3(BTC)2(H2O)3] (HKUST-1) was measured by batch method, and the effect of cyclohexene and toluene on sulfur capacity was investigated. Adsorption isotherms of TP, cyclohexene, and toluene in cyclohexane onto HKUST-1 were conducted at 298.15–313.15 K to explicate the different extent of influence by cyclohexene or toluene addition. The results showed that, compared with cyclohexene, the addition of toluene in model gasoline led to a moderate decline in sulfur capacity of HKUST-1. The isotherm data of TP adsorption were well-correlated using Langmuir equation, while those of cyclohexene or toluene adsorption fitted Freundlich model, indicating different adsorption mechanisms between TP and competitors. The adsorption capacities followed the order of toluene < cyclohexene ≪TP at the same equilibrium concentrations, implying the order of the adsorption affinities, which is in good agreement with the different extent of influence by cyclohexene and toluene. The excellent regeneration performance of HKUST-1 in TP adsorption benefits from the physical adsorption mechanism, which was hinted by the enthalpy of TP adsorption (−37.31 ± 2.04 kJ mol−1) and no detection of new sulfur species.

Ab initio screening of zeolite Y formulations for efficient adsorption of thiophene in presence of benzene

In the context of deep desulfurization of transport fuels, the present work aimed at identifying a suitable material for the selective removal of thiophene from fuels. Dispersion corrected density functional theory (DFT) calculations have been carried out in order to investigate the adsorption of benzene and thiophene in various faujasite zeolite formulations including DAY, HY, LiY, NaY, KY, CsY, Cu(I)Y, Cu(II)Y, Ag(I)Y, Zn(II)Y, and FAU containing Lewis acid sites (LAS) (defect or extra-framework). Bearing-LAS FAU, Cu(I)Y, Cu(II)Y, Zn(II)Y, CsY, and HY showed a higher affinity towards thiophene adsorption. In particular, thiophene is more adsorbed on defect LAS than benzene by 17.7 kJ/mol, suggesting that this zeolite could be chosen as a suitable candidate for the optimal selective adsorption of thiophene in the presence of benzene. In terms of regenerability, all formulations can be safely used (except the one containing extra-framework Lewis acid sites) as they can limit the activation of the C-S bond of thiophene. Considering both adsorption selectivity and sorbent regenerability criteria, faujasites containing defect Lewis acid sites could be chosen as a good compromise to perform a selective adsorption of thiophene in presence of benzene.

Enhanced Adsorption Desulfurization Performance over CuCeY Zeolites Prepared by Low‐Temperature Calcination under H2 Atmosphere

AbstractIn order to optimize the location and valence state of metal ions in the Y‐type zeolite, the bimetallic (cerium and copper) modified NaY (CuCeY) zeolites with different Cu/Ce ratios were prepared by calcination at 180 °C under H2 atmosphere. Their adsorptive capacity and selectivity for thiophene were preliminarily explored. Furthermore, the CuCeY zeolites were characterized by various techniques for explaining their adsorption behaviors. The obtained results show that the breakthrough adsorption sulfur capacity (Q) of CuCeY zeolites from model oil contains thiophene (TMO) shows a volcanic tendency with the increase of Cu ion contents in zeolites. This is because more metal ions, especially Cu+ ions, are distributed to the supercages of Y zeolites. When 1‐hexene coexists with thiophene in model oil (TOMO), the Q of CuCeY zeolites increase firstly and then remain almost unchanged as Cu ion contents in zeolites increases. It is related to competitive adsorption, alkylation and oligomerization of thiophene and 1‐hexene. When benzene coexists with thiophene in model oil (TAMO), the Q of CuCeY zeolites are linear with Cu ion contents in zeolites. This is possible because the competitive adsorption between olefins and sulfur compounds on Cu ions or weak Brönsted(B) acid centers are stronger than that between aromatics and sulfur compounds on the same adsorption sites. It′s worth mentioning that the Q values of CuCeY zeolites are larger than that of bimetallic modified CuCeY zeolites and that of most of monometallic modified Y zeolites reported in the references.

Design of novel conjugated microporous polymers for efficient adsorptive desulfurization of small aromatic sulfur molecules

This paper presents a computational study of the adsorptive desulfurization of small aromatic sulfur compounds by conjugated microporous polymers (CMPs). The density-functional tight-binding method augmented with an R−6 dispersion correction is employed to investigate the physisorption binding mechanism and electronic properties of the CMP-aromatic sulfur complexes. We show that the widely extended π conjugation in the CMP skeletons is favorable for the non-covalent adsorption of aromatic thiophene and dibenzothiophene via π–π, H–π, and S–π interactions. The average binding energies are calculated to be −6.2 ∼ −15.2 kcal/mol for CMP- thiophene/dibenzothiophene systems. For the dibenzothiophene molecule with larger size and more extended conjugation, it binds more than twice stronger to CMP than the thiophene molecule. We show that the replacement of quinoline unit to the phenylene group in the network linker effectively enhances the average binding capacities by around 0.8–1.8 kcal/mol. Our calculations theoretically demonstrate that CMPs materials are kind of promising candidates for the adsorptive desulfurization of small aromatic sulfur compounds. This paper provides useful theoretical guidance for design of novel carbon-based adsorbents for adsorptive desulfurization.

A flexible N-doped carbon-nanofiber film reinforced by halloysite nanotubes(HNTs) for adsorptive desulfurization

This report introduced the facile synthesis of the carbon-nanofiber films reinforced by halloysite nanotubes (HNTs) via electrospinning. The HNTs-reinforced N-doped carbon-nanofiber films (PAN/HNTs-CNFs) possessed the higher strength and toughness while keeping the prospective adsorption capability for different sulfur compounds in oil due to the higher N doping content. The PAN/HNTs-CNFs were produced by firstly electrospinning for the HNTs-filled polyacrylonitrile (PAN) nanofiber films, followed by the high-temperature carbonization for the conversion of the polymer films into the carbon-nanofiber films with the N doping. The characterizations testified that the HNTs were capable of fulfilling the uniform and disordered dispersion in the carbon-nanofibers. For overcoming the toughness of the carbon-nanofiber film, the HNTs filling the obviously improved the mechanical performance of the carbon-nanofiber films by the pulling-out and bridging effect. Due to accessing the lipophilic and acid surface, abundant hierarchical pore structure and highly N-doping content, the PAN/HNTs-CNFs exhibited the remarkable adsorption performances for thiophene, benzothiophene, and dibenzothiophene (46.73 mg S/g, 38.4 mg S/g and 35.03 mg S/g for 800 ppm sulfur model oil), especially being suitable to the adsorption of thiophene. Furthermore, the study on the adsorption kinetics, equilibrium isotherms, and thermodynamics of thiophene over the PAN/HNTs-CNFs were conducted to discuss the adsorption mechanism.

Site-dependent reactivity of MoS2 nanoparticles in hydrodesulfurization of thiophene

The catalytically active site for the removal of S from organosulfur compounds in catalytic hydrodesulfurization has been attributed to a generic site at an S-vacancy on the edge of MoS2 particles. However, steric constraints in adsorption and variations in S-coordination means that not all S-vacancy sites should be considered equally active. Here, we use a combination of atom-resolved scanning probe microscopy and density functional theory to reveal how the generation of S-vacancies within MoS2 nanoparticles and the subsequent adsorption of thiophene (C4H4S) depends strongly on the location on the edge of MoS2. Thiophene adsorbs directly at open corner vacancy sites, however, we find that its adsorption at S-vacancy sites away from the MoS2 particle corners leads to an activated and concerted displacement of neighboring edge S. This mechanism allows the reactant to self-generate a double CUS site that reduces steric effects in more constrained sites along the edge.

Adsorptive desulfurization of thiophene over Ti0.9Ce0.1O2 mixed oxide: A mechanistic study on the basis of XPS, in-situ FT-IR and TPD characterizations

The adsorption of thiophenic compounds over Ti0.9Ce0.1O2, an oxidatively regenerable sulfur adsorbent, was studied by XPS, DRIFT, and TPD-MS. Effect of the oxidative pretreatment on thiophene adsorption over Ti0.9Ce0.1O2 adsorbent, the adsorption site for thiophenic compound, and the role of surface Ce and Ti cations in the adsorptive desulfurization (ADS) were investigated. The results suggest that the surface oxygen plays an essential role in ADS and is a major active site for chemical adsorption of the thiophenic compounds. The surface Ce and Ti were further oxidized by the surface oxygen in the oxidative pretreatment, and then reduced during the adsorption of thiophenic compounds. This phenomenon is attributed to an electron transfer from the adsorbates to the surface Ce and Ti. It appears that the role of the surface Ce and Ti can accept electrons from adsorbate, and also contributes to producing the active oxygen to oxidize the sulfur atom of thiophenic compounds. An oxidative pretreatment, including oxidative regeneration, activates the surface oxygen to forms active oxygen species and oxidizes the surface Ce and Ti. Based on the results obtained, a possible mechanism was proposed for the chemical adsorption, dissociation and surface reaction of thiophene on Ti0.9Ce0.1O2 mixed metal oxide adsorbent.

Monte Carlo Simulations of Adsorption of Thiophene/Benzene in NaX and NaY Zeolites from Model Fuel

The process of adsorptive desulfurization requires sorbents to have high adsorption capacity and selectivity for thiophene in contrast to aromatics or alkanes. We investigated the adsorption of thiophene, benzene, and their mixtures in the presence of n-octane by the sodium-exchanged FAU zeolite using the grand canonical Monte Carlo simulations. The adsorption isotherms were computed and compared with available experimental data. The simulation results show that the change in the Si/Al ratio of zeolite may cause significant differences in adsorption selectivity, which was also observed by experiments. The NaX zeolite shows a higher adsorption selectivity than the NaY zeolite. The location of cations in the zeolites results in a change of pore size and creates an additional type of adsorption site, which subsequently results in different adsorption selectivities between thiophene and benzene in model fuel.

Adsorption behavior of thiophene on MoS2 under a microwave electric field via DFT and MD studies

The adsorption behavior of sulfide over catalyst is the key to determine the desulfurization efficiency and its proceeding route. Molecular dynamics and density functional theory calculations were performed to provide theoretical insight into the effect of microwave electric field on the adsorption of thiophene over different MoS2 nanocrystallites, and investigate the electronic distribution. The adsorption position and configuration were significantly affected by microwave field, and the polarities of thiophene molecule and MoS2 were strengthened, which is beneficial to the cleavage of the thiophene C–S bond. Mo atoms lose charge in a large area and have a strong electrophilic effect after the generation of S vacancy, inducing S component adsorption on active sites. The hydrodesulfurization (HDS) selectivity is modified by affecting the priority of potential adsorption. Thiophene favors to η5 adsorption over multilayer dispersed MoS2 clusters under microwave field, inducing the HDS reactions to proceed along the hydrogenation route.

Facile fabrication of a superior Cu(I)-NH4Y zeolite adsorbent for improving thiophene adsorption selectivity in the presence of aromatics or olefins

Cu modified Y zeolite adsorbents have performed excellent adsorption desulfurization performance. Adsorption selectivity of thiophenic sulfur compounds, however, still remained a lower level in the presence of aromatics and olefins. In this work, we aim to address the above challenge, using Cu(I)-NH4Y zeolites obtained by liquid phase ion-exchanged method. Based on the coordination chemistry theory, the new adsorption active sites ([Cu+···NH3···H+] species) can be facilely fabricated at lower temperature (ca. 150 °C) and under H2 atmosphere. The desulfurization experimental results indicate that the outstanding breakthrough sulfur capacity (ca. 31.0 mg (S) · g−1) can be achieved by the Cu(I)0.10-NH4Y adsorbent, which is about 2.3 folds as high as the best one reported. After regeneration with three cycles, the adsorbent still remains a high sulfur capacity. Importantly, the thiophene adsorption selectivities of adsorbent have been improved in the presence of aromatics or olefins, which are about 44.5% and 6.3%, respectively. Meanwhile, the direct “S-M” bonding mechanism between thiophene and [Cu+···NH3···H+] species can be really proposed. Besides, the alkylation reaction between thiophene and olefins is significantly attenuated, mainly ascribed to the majority of strong Brønsted acid sites being masked. The new design idea of effective active sites in the zeolite adsorbents breaks out the traditional high-temperature preparation concept of excellent desulfurization adsorbents and can provide a new direction in the future.