Adsorptive desulfurization of model diesel fuel over mono-functionalized nickel/γ-alumina and bi-functionalized nickel/cerium/γ-alumina adsorbents

Dual rare earth-doped Pt-Sn/Al2O3 catalysts with synergistic Ce and Sm effects on high-efficiency aromatization and coke suppression in naphtha reforming

In the present study, the effect of rare earth (RE) metals of Ce and Sm on the naphtha reforming process catalyst, i.e., Pt-Sn/γ-Al2O3, is investigated. Two-, three-, and four-metal catalysts were synthesized through the successive wet impregnation of the support, employing various concentrations of cerium at 0.17 and 0.47 wt% and samarium at 0.33, 0.51, and 0.87 wt%. The corresponding catalytic activity on the naphtha reforming reactions was conducted in a reactor at 5 bar, 500 ℃, and WHSV = 2 h- 1. FESEM, BET, NH3-TPD, and H2-TPR were employed to scrutinize the physicochemical and active site properties of the developed catalysts. Besides, TGA was used to determine the deactivation rate of the developed catalysts. It is shown that adding a suitable amount of RE metals can reduce the Pt particle agglomeration and promote the distribution of the metal particles. Catalytic testing demonstrated that Ce and Sm-containing catalysts, especially SPC(0.47)S(0.33), exhibited superior aromatization activity, producing high levels of C8 and C9 aromatics, which are valuable for gasoline blending. Such catalysts also showed reduced cracking and paraffin production, which was attributed to the optimal balance of metallic and acidic properties resulting from the REMs. In addition, such RE dopants could diminish the degree of graphitization, resulting in decreased coke content and a lower combustion temperature, facilitating the catalyst regeneration process. Moreover, incorporating RE metals could inhibit the reduction of tin oxides, enhancing platinum's role as the promoter. Besides, the catalysts containing 0.47 wt% cerium, 0.33 wt% samarium and a combination of both RE metals exhibited superior activity in producing reformate with a high-octane number.

Fabrication of a chitosan-grafted-4‑vinylpyridine/thiol-amine-HZSM-5 nanocomposite via casting method in adsorption of heavy cations from water systems: an evaluation of adsorption mechanism

This study presents the synthesis of low-silica HZSM-5 zeolite through a hydrothermal process. Subsequently, chitosan-grafted-4‑vinylpyridine/thiol-amine-HZSM-5 nanocomposites were fabricated using casting method for the effective removal of copper (Cu2+) and zinc (Zn2+) cations from aqueous systems. The fabricated cast nanocomposites were characterized using XRD, BET, XPS, FESEM, EDX, CHNS, FTIR, and TGA analyses. The simultaneous roles of amine (-NH2) and thiol (-SH) groups in enhancing the adsorption efficiency of Cu2+ and Zn2+ were thoroughly investigated. Additionally, the influence of key factors, including solution pH, contact time, adsorption temperature, and cation concentration, was systematically assessed. Equilibrium data fitting revealed the dominance of monolayer adsorption, as evidenced by the excellent fit of the Redlich-Peterson (R-P) and Langmuir isotherm models for both Cu2+ and Zn2+ cations. Examination of the kinetic experimental data indicated a close correspondence with the double-exponential model. The maximum adsorption capacity of the fabricated cast nanocomposite was determined to be 328.05 mg/g for Cu2+ and 107.96 mg/g for Zn2+ cations. Additionally, the fabricated cast nanocomposite demonstrated satisfactory regeneration capabilities after 9 cycles of desorption. In both synthetic binary and ternary systems, as well as in real wastewater, the adsorption process exhibited antagonistic behavior, indicating that the presence of one type of cation interfered with the adsorption of the other. The nanocomposite displayed a higher affinity for Cu2⁺ compared to Zn2⁺ cations, in both synthetic and real systems, demonstrating its potential for selective heavy metal removal.

A review on the role of nanocomposites for desulfurization of liquid transportation fuels

Stringent sulfur removal regulations from transportation fuels from typical levels of 500 ppm to ultra-low levels of 10 ppm (BS-6 standard) present a critical challenge for the crude processing industry. This research thoroughly investigates emerging desulfurization technologies, with a focus on nanocomposite (NC) materials that exhibit exceptional sulfur removal efficiency. Advanced nanocomposite catalysts, such as (TBA)4PW11Fe@TiO2@PVA, have near-complete removal rates of 96-99% for complicated sulfur compounds like dibenzothiophene (DBT) and derivatives. The performance spectrum spans from basic materials with 20-38% removal to advanced nanocomposite systems with up to 99% desulfurization efficiency. By synthesizing current strategies involving transition metal-based, polyoxometalate, and hybrid nanocomposite materials, this study highlights transformative approaches to meeting increasingly stringent environmental regulations in fuel processing, with selective removal techniques targeting specific sulfur molecular structures.

The role of chitosan grafted copolymer/zeolite Schiff base nanofiber in adsorption of copper and zinc cations from aqueous media

The objective of this research was to develop and assess chitosan-grafted copolymer/HZSM5 zeolite Schiff base nanofibers for Cu2+ and Zn2+ adsorption from aqueous media. Nanofibers were prepared via electrospinning and characterized using XRD, FTIR, 1H NMR, FESEM, TGA, BET, and XPS. The study evaluated the effect of unmodified HZSM5 and Schiff base functionalization on adsorption capacities. Incorporating 10.0 wt% zeolite Schiff base as the optimum content into the chitosan-grafted copolymer significantly enhanced adsorption, achieving increases of 98.2 % for Zn2+ and 42.2 % for Cu2+. Specifically, Zn2+ adsorption increased from 27.6 to 54.7 mg/g, and Cu2+ from 67.1 to 95.4 mg/g. Factors such as temperature, pH, adsorption time, and initial cation concentration were analyzed. Kinetic studies revealed a double-exponential model, and isotherm analysis indicated a good fit with the Redlich-Peterson model, showing maximum monolayer capacities of 310.1 mg/g for Cu2+ and 97.8 mg/g for Zn2+ (pH 6.0, 240 min, 45 °C). The adsorption thermodynamics indicated a spontaneous and endothermic adsorption. Reusability tests showed minimal capacity loss (4.91 % for Cu2+ and 5.59 % for Zn2+) after five cycles. The nanofiber displayed greater selectivity for Cu2+ over Zn2+ in multi-ion systems and real electroplating wastewater, highlighting its potential for targeted heavy metal removal.

Deep desulfurization of alkylated oil by alumina adsorbents: characteristics and mechanism study

Deep desulfurization of alkylated oil is the primary problem that has long plagued the petroleum refining industry. In this study, alkaline alumina adsorbent microspheres were synthesized by carbonization - hot oil column pelletization method. The adsorption desulfurization performance of as-synthesized adsorbent and three commercial alumina-based adsorbents were systematically evaluated and compared. The results showed that alkaline alumina adsorbent had the optimal adsorption performance with a saturated adsorption capacity of 8.604 mg·g^-1. Meanwhile, FTIR and sulfur speciation analysis indicated that the alkaline alumina adsorbent could deeply remove various sulfides (methyl mercaptan, dimethyl disulfide, hexacarbon sulfide, dibenzothiophene, <i>etc.</i>) from alkylated oil. Furthermore, the adsorption kinetics study manifested that the adsorption of sulfide was dominated by chemical adsorption, supplemented by physical adsorption, and accompanied by competitive adsorption among different sulfides. In addition, the regeneration experiment showed that nitrogen (90 °C) could realize the stable regeneration of the alkaline alumina adsorbent. To ensure stable regeneration performance in industry, it is recommended that the alkaline alumina adsorbent be regenerated once with nitrogen at 90 °C. This study will provide theoretical support for the process optimization of deep desulfurization of alkylated oil and contribute to the high-quality production of clean fuels worldwide.

Reduction of sulfur oxides emissions via adsorptive desulfurization of transportation fuels using novel silica-based adsorbent

Transportation fuels with high sulfur content are one of the primary contributors to air pollution because they emit massive quantities of sulfur oxides upon combustion. The emitted sulfur oxides undoubtedly contribute to global warming and climate change. Therefore, they should be minimized. The current study accurately describes a novel and direct synthetic pathway for the incorporation of sulfonic acid groups (-SO₃H) into mesoporous silica surface. The structure of the prepared materials was confirmed using FTIR, SEM, BET, SA-XRD, TEM, and TGA techniques. The batch adsorption technique was used to carefully evaluate the adsorption efficiency of the prepared adsorbent towards dibenzothiophene (DBT). At optimal adsorption conditions, a maximum adsorption capacity of 75-mg DBT/g adsorbent was achieved. The desulfurization process fitted well to Langmuir and pseudo-second-order models. In addition, the desulfurization process was found to be a spontaneous and exothermic process. As a final point, the practical applicability of the prepared adsorbent, as well as its reusability, was properly investigated, and the results were promising.