Mechanistic Study on Adsorption Desulfurization Using Modified Graphene

Synthesis, characterization and application of organoclays for adsorptive desulfurization of fuel oil

The present study encompasses the application of cost effective, organo-modified bentonite material for efficient desulfurization of model oil and real fuel. For the adsorptive desulfurization of oil, dibenzothiophene (DBT) was used as model compound. Various experimental parameters (time, temperature, adsorbent-amount and DBT concentration) were thoroughly investigated. The synthesized material was characterized via X-ray diffraction (XRD), X-ray Fluorescence (XRF), Scanning electron microscopy (SEM), Energy dispersive x-ray (EDX), Thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FT-IR). The modification exhibits the increase in interlayer spacing of clay as confirmed from XRD and modified material shows interesting morphology as compared to unmodified bentonite. The results showed that > 90% of DBT removal was achieved under optimized conditions for B-BTC, B-BTB and B-DSS and > 80% for B-BEHA, for model fuel oil which are greater than unmodified clay (< 45%). Additionally, the findings from desulfurization of real fuel oil declare that 96.76% and 95.83% removal efficiency was achieved for kerosene and diesel oil respectively, at optimized conditions and fuel properties follow ASTM specifications. The obtained findings well fitted with thermodynamic, isothermal (Langmuir) with adsorption capacity (70.8 (B-BTC), 66 (B-BTB), 61.2 (B-DSS) and 55.2 (B-BEHA) in mg/g) and pseudo-second-order kinetics. In thermodynamic studies, negative sign ([Formula: see text] specifies the spontaneity whereas, [Formula: see text] endothermic and positive sign [Formula: see text] show randomness after DBT adsorption onto organoclay.

Hierarchical-pore UiO-66 modified with Ag+ for π-complexation adsorption desulfurization

Adsorption desulfurization represents an alternative technology for the effective removal of thiophenic compounds from fuels. Metal-organic frameworks have been the ideal candidates for the adsorptive desulfurization of fuel due to the high surface areas. Pristine UiO-66 is thought to be appropriate for the removal of small thiophenic compounds. This work developed a new type of hierarchical-pore (micro and mesopores) UiO-66 with a higher specific surface area and porosity for the removal of larger adsorbates using MOF-5 as the template. To enhance adsorption desulfurization performance, the Ag⁺-exchanged hierarchical-pore UiO-66 (HP-UiO-66-SO₃Ag) with π-complexation was synthesized by the ion-exchange method. The HP-UiO-66-SO₃Ag samples were characterized by FTIR, XRD, SEM, TEM, and N₂ adsorption-desorption isotherms. Compared with the original UiO-66, the HP-UiO-66-SO₃Ag has a higher specific surface area, pore volume, and pore size. The static adsorption experiments showed that HP-UiO-66-SO₃Ag had a high adsorption capacity for thiophene and benzothiophene. Moreover, the HP-UiO-66-SO₃Ag sample still exhibits high adsorptive performance in the presence of toluene. The regeneration results show that about 90% of the initial adsorption capacity of HP-UiO-66-SO₃Ag can be regenerated after four cycles.

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.

Heteroatom-doped highly porous carbons prepared by in situ activation for efficient adsorptive removal of sulfamethoxazole

Porous carbons obtained by in situ activation of organic salts for highly efficient sulfamethoxazole adsorption.