High performance sorbents for diesel oil desulfurization

Catalytic-oxidative/adsorptive denitrogenation of model hydrocarbon fuels under ultrasonic field using magnetic reduced graphene oxide-based phosphomolybdic acid (PMo-Fe3O4/rGO)

In this work, the effect of ultrasound irradiation on the catalytic oxidative/adsorptive denitrogenation (COADN) of model hydrocarbon fuels (composed of pyrroleor indoleas an organonitrogen compounds dissolved in n-nonane) has been investigated using magnetic reduced graphene oxide supported with phosphomolybdic acid (PMo-Fe₃O₄/rGO) as a heterogeneous catalyst/adsorbent and hydrogen peroxide as an oxidant. The synthesized PMo-Fe₃O₄/rGO nanocomposite was characterized by XRD, FE-SEM, VSM and BET surface area analysis methods. Moreover, different experimental variables including catalyst dose, initial pyrrole/indoleconcentration, H₂O₂ to pyrrole/indole molar ratio, ultrasound power and sonication time have been studied on the COADN process. The regeneration/recyclability of PMo-Fe₃O₄/rGO catalyst was also examined. Experimental results revealed that, the ultrasound treatment significantly improved the adsorption process of organonitrogen compounds from model fuels (q_e increased by 50.3% for pyrrole and 18% for indole). Furthermore, high ultrasound-aided catalytic oxidative denitrogenation efficiency (85.6% for pyrrole and 90% for indole) has been attained under optimal conditions (ultrasonic power = 200 W, sonication time = 240 min, catalyst dose = 2 g/L, and H₂O₂:pyrrole/indole molar ratio = 5). The recyclability of catalyst displayed that the prepared catalyst can be reused five times without any significant reduction in its performance.

Adsorption desulphurisation of dimethyl sulphide using nickel-based Y zeolites pretreated by hydrogen reduction

A series of nickel-modified Y zeolites were prepared for the adsorption of dimethyl sulphide (DMS) in liquid hydrocarbon streams. The adsorption desulphurisation performance was investigated under ambient conditions of nickel-based adsorbents developed by the liquid-phase ion exchange (LPIE) method and the incipient wetness impregnation (IWI) method with and without the ultrasonic aid technique. It was found that the nickel-modified Y zeolite prepared by the IWI method with the ultrasonic aid technique with hydrogen reduction demonstrated a high sulphur capacity of 69.9 mg of S per g of sorbent at a break-through sulphur level of 10 μg g

Solvent desulfurization regeneration process and analysis of activated carbon for low-sulfur real diesel

The adsorption desulfurization process of diesel fuel is suffering from adsorbent regeneration limitation.

Removal of organic sulfur compounds from diesel by adsorption on carbon materials

Removal of organic sulfur compounds from diesel by adsorption on different carbon materials, including activated carbons (ACs), carbon aerogels, carbon nanotubes, and AC cloths, was reviewed. The effect of the textural and surface chemistry property of carbon on desulfurization performance, carbon surface modification, adsorption mechanism, and adsorbent regeneration and the effect of other components, including aromatics, additives, nitrogen compounds, and moisture, on adsorptive desulfurization of diesel fuel were also discussed in detail. Carbon materials showed very high selectivity for removing the dibenzothiophenes, especially for 4,6-dimethyldibenzothiophene, which is very difficult with hydrodesulfurization and other adsorbents. Both the textural and chemical properties of AC have an important impact on the adsorption of DBTs. Adsorption selectivity and capacity can be enhanced further by carbon surface modification. Considering the effect of diffusion hindrance and regeneration, mesoporous carbon is more suitable than microporous carbon with pore size <2 nm. It is necessary to eliminate the inhibiting effect of fuel additive and nitrogen compounds on the DBTs before carbon materials are used for desulfurization of real diesel fuel. In the end, some useful suggestions are also made.

Ultra-deep adsorptive desulfurization of a model diesel fuel on regenerable Ni-Cu/γ-Al₂O₃ at low temperatures in absence of hydrogen

A model diesel fuel containing 250 ppmw sulfur (as dibenzothiophene) in n-hexadecane was desulfurized at low temperatures in absence of hydrogen, down to about zero ppmwS on a novel adsorbent of well dispersed 3-12 nm Nix-Cu10-x (x=Ni wt%) nanoparticles formed by impregnation on γ-Al2O3 and reduced in H2 at 275 or 450°C. The sorbents were characterized by XRD, TEM-EDX, FESEM-EDS, H2-TPR, TPO, BJH and BET surface area measurement techniques. Effects of various parameters comprising Cu content, reduction and desulfurization temperatures, inhibition by naphthalene, and regeneration of spent sorbents were investigated. As copper is added to nickel: (a) the sorbent reduction temperature shifts to dramatically lower values, (b) sulfur adsorption capacity of the sorbents at lower reduction and desulfurization temperatures is significantly improved, and when 14 wt% Ni5Cu5 sorbent is added to the fuel, the sulfur content reduces from 250 ppmwS to about zero in less than 1 min, (c) loss of adsorption capacity after the regeneration of the spent sorbent reduced at 275°C is significantly diminished, and (d) the selectivity of the sorbents to dibenzothiophene in the presence of naphthalene is improved. A higher reduction temperature tends to agglomerate nickel nanoparticles and reduce the sulfur adsorption capacity.

The enhanced adsorption of sulfur compounds onto mesoporous Ni-AlKIT-6 sorbent, equilibrium and kinetic analysis

High performance nickel supported on mesoporous AlKIT-6 (Si/Al=15, 25, 50, 100) sorbents were prepared by incipient wetness impregnation (IWI) with ultrasonic aid for adsorptive desulfurization of commercial diesel and simulated fuels. The sorbents were characterized by N2 adsorption-desorption, XRD, NH3-TPD, Py-FT-IR, HRTEM, SEM and atomic absorption spectroscopy techniques. The analysis results confirmed that Aluminum atoms entered the framework and 20%Ni-AlKIT-6(15) can still retain three dimensional structure of AlKIT-6(15) and Ni is highly dispersed in the support. The kinetic pseudo second-order model and Langmuir isotherm are shown to exhibits the best fits of experimental data for the adsorption of thiophene (T), benzothiophene (BT) and dibenzothiophene (DBT) over AlKIT-6 and 5-30%Ni-AlKIT-6. Intraparticle diffusion and steric hindrance were the rate controlling step of the adsorption of T and DBT over AlKIT-6(15) and 20%Ni-AlKIT-6(15) as verified through the intraparticle diffusion model. The characterization of regenerated 20%Ni-AlKIT-6(15) revealed that three-dimensional cubic Ia3d symmetric structure was maintained in the sorbent after 6 successive desulfurization-regeneration cycles.

Effect of central metal ions of analogous metal-organic frameworks on the adsorptive removal of benzothiophene from a model fuel

Liquid phase adsorption of benzothiophene (BT) has been studied over CuCl₂-loaded analogous metal-organic frameworks (MOFs), metal-benzenedicarboxylates (Me-BDCs, Me: Al, Cr and V), to understand the effect of central metal ions on the adsorptive removal of BT from a model fuel. Among the central metal ions (Al(3+), Cr(3+) and V(3+)) of the Me-BDCs only V(3+) was oxidized by the loaded CuCl₂ (or Cu(2+)) at ambient condition resulting in V(4+) and Cu(+) species. Different from the CuCl₂-loaded Al- and Cr-BDCs, the CuCl₂/V-BDC adsorbed BT remarkably well compared to the virgin V-BDCs which suggests a specific favorable interaction (π-complexation) between the obtained Cu(+) in the CuCl₂/V-BDC and BT.

Low-temperature loading of Cu+ species over porous metal-organic frameworks (MOFs) and adsorptive desulfurization with Cu+-loaded MOFs

Porous metal-organic frameworks (MOFs, MIL-100-Fe, iron-benzenetricarboxylate) supported with Cu(+) species were obtained for the first time under mild condition without high temperature calcinations. The Cu(+)-loaded MOFs were evaluated as efficient adsorbents for the liquid-phase adsorption of benzothiophene (BT). The effect of Cu(+) loading on the adsorption kinetics and maximum adsorption capacity (Q(0)) for the adsorption of BT was also studied. Q(0) increased with increasing copper loading up to a Cu/Fe (wt./wt.) ratio of 0.07 in Cu(+)-loaded-MIL-100-Fe, resulting in an increase in the Q(0) by 14% compared with the virgin MIL-100-Fe without Cu(+) ions. Since the surface area and pore volume decrease with the loading of copper, the increased Q(0) over the Cu(+)-loaded MIL-100-Fe adsorbents suggests specific favorable interactions (probably by π-complexation) between Cu(+) and BT.