Effective Zinc-Substituted Keggin Composite To Catalyze the Removal of Sulfur from Real Diesels under a Solvent-Free System

Iron(III) Arylhydrazone Complexes Immobilized on Amine-Functionalized Mesoporous Silica: Catalysts for the Valorization of Biomass-Derived Furfuryl Alcohol

The aquasoluble Fe^III complexes [Fe(H₂ O)₃ (L¹ )] ⋅ 4H₂ O (Fe1) and [Fe(H₂ O)₃ (L² )] ⋅ 3H₂ O (Fe2), bearing the basic forms of 5-chloro-3-(2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl)-2-hydroxy-benzenesulfonic acid (H₃ L¹ ) and 3-(2-(2,4-dioxopentan-3-ylidene)hydrazinyl)-2-hydroxy-5-nitrobenzenesulfonic acid (H₃ L² ), were incorporated for the first time into amine-functionalized SBA-15 support via an impregnation method. The successful preparation of the composites was confirmed by Fourier-Transform Infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), scanning electron microscope (SEM/EDS), transmission electron microscopy (TEM), elemental analysis, and nitrogen adsorption-desorption isotherms. The resulting Fe1@aptesSBA-15 and Fe2@aptesSBA-15 composites were tested as the first SBA-15-based heterogeneous catalysts for the conversion of furfuryl alcohol under mild reaction conditions (80 to 100 °C) and with an environmentally friendly oxidant (TBHP, 70 % aq. sol. with 1 : 1 oxidant/substrate molar ratio). The influence of various factors, such as reaction time, amounts of oxidant and catalyst, was investigated. The reaction time can be fairly reduced by adopting a microwave-assisted method allowing it to reach complete conversion after 0.25 h, in the absence of any added solvent or additive. Under these conditions, a vigorous furfuryl alcohol polymerization process occurred, with furfural as a by-product. Recycling studies were carried out for Fe2@aptesSBA-15 and after four consecutive runs, the overall conversion of furfuryl alcohol remained high (≥99 %), without an appreciable change in the obtained yield.

Biogenic Amine Sensing Based on Rosamine a N-Methylpyridinium Derivative Supported on Silica Materials from Rice Husk

In this work new rosamine-silica composites were prepared and their sensing ability towards different amines was assessed. Rice husk wastes were used as a biogenic silica source. Silica was extracted by thermal treatment, before rice husk ash and after acid leaching with citric acid-treated rice husk ash. Mesoporous material (SBA-15) was also prepared using the extracted silica. The prepared materials were characterized by several techniques such as FTIR, XRD, SEM and N₂ adsorption. The materials were then used as adsorbents of the chromophore N-methylpyridinium rosamine (Ros4PyMe). The obtained loaded composites were tested in solution for amines sensing (n-butylamine, aniline, putrescine and cadaverine). The detection studies were analyzed by fluorescence and revealed 40% and 48% quenching in fluorescence intensity for the composite Ros4PyMe@SBA in the presence of the biogenic amines cadaverine and putrescine, respectively. The composite was also sensitive in the powder form, changing the color from violet to pale pink in the presence of putrescine vapors with a fast response (around 2 min), the process being reversible by exposure to air.

Lindqvist@Nanoporous MOF-Based Catalyst for Effective Desulfurization of Fuels

An effective and sustainable oxidative desulfurization process for treating a multicomponent model fuel was successfully developed using as a heterogeneous catalyst a composite material containing as an active center the europium Lindqvist [Eu(W5O18)2]9- (abbreviated as EuW10) encapsulated into the nanoporous ZIF-8 (zeolitic imidazolate framework) support. The EuW10@ZIF-8 composite was obtained through an impregnation procedure, and its successful preparation was confirmed by various characterization techniques (FT-IR, XRD, SEM/EDS, ICP-OES). The catalytic activity of the composite and the isolated EuW10 was evaluated in the desulfurization of a multicomponent model fuel containing dibenzothiophene derivatives (DBT, 4-MDBT and 4,6-DMDBT) with a total sulfur concentration of 1500 ppm. Oxidative desulfurization was performed using an ionic liquid as extraction solvent and aqueous hydrogen peroxide as oxidant. The catalytic results showed a remarkable desulfurization performance, with 99.5 and 94.7% sulfur removal in the first 180 min, for the homogeneous active center EuW10 and the heterogeneous EuW10@ZIF-8 catalysts, respectively. Furthermore, the stability of the nanocomposite catalyst was investigated by reusing and recycling processes. A superior retention of catalyst activity in consecutive desulfurization cycles was observed in the recycling studies when compared with the reusing experiments. Nevertheless, the nanostructure of ZIF-8 incorporating the active POM (polyoxometalate) was shown to be highly suitable for guaranteeing the absence of POM leaching, although structural modification was found for ZIF-8 after catalytic use that did not influenced catalytic performance.

Two POM-based compounds containing Zn-capped Keggin anions as decent heterogeneous catalysts for sulfur oxidation and cycloaddition of CO2 reactions

Carbon dioxide (CO2) and the combustion of sulfide in gasoline are the main causes of air pollution. Great deal of attention has been committed to solving the problem and the...

Solvent-Free Desulfurization System to Produce Low-Sulfur Diesel Using Hybrid Monovacant Keggin-Type Catalyst

Two quaternary ammonium catalysts based on the monovacant polyoxotungstate ([PW₁₁O₃₉]⁷⁻, abbreviated as PW₁₁) were prepared and characterized. The desulfurization performances of the PW₁₁-based hybrids (of tetrabutylammonium and trimethyloctadecylammonium, abbreviated as TBA[PW₁₁] and ODA[PW₁₁], respectively), the corresponding potassium salt (K₇PW₁₁O₃₉, abbreviated as KPW₁₁) and the peroxo-compound (TBA-PO₄[WO(O₂)₂], abbreviated as TBA[PW₄]) were compared as catalysts for the oxidative desulfurization of a multicomponent model diesel (2000 ppm S). The oxidative desulfurization studies (ODS) were performed using solvent-free systems and aqueous H₂O₂ as oxidant. The nature of the cation in the PW₁₁ catalyst showed to have an important influence on the catalytic performance. In fact, the PW₁₁-hybrid catalysts showed higher catalytic efficiency than the peroxo-compound TBA[PW₄], known as Venturello compound. TBA[PW₁₁] revealed a remarkable desulfurization performance with 96.5% of sulfur compounds removed in the first 130 min. The reusability and stability of the catalyst were also investigated for ten consecutive ODS cycles without loss of activity. A treated clean diesel could be recovered without sulfur compounds by performing a final liquid/liquid extraction diesel/EtOH:H₂O mixture (1:1) after the catalytic oxidative step.