Catalysts Based on Porous Polyaromatic Frameworks for Deep Oxidative Desulfurization of Model Fuel in Biphasic Conditions

HPW/PAM Catalyst for Oxidative Desulfurization-Synthesis, Characterization and Mechanism Study

In this work, polyacrylamide (PAM) was first used in the loading of heteropoly acids, and then the HPM/PAM-n catalyst was synthesized by simple reaction. The FTIR and SEM measurements showed that the HPM/PAM-n (n = 10,000, 20,000, 30,000) was successfully synthesized. In addition, the HPM/PAM-n effect on desulfurization was measured, which showed the optimal desulfurization efficiency. The optimal process condition for HPM/PAM-10000 desulfurization was optimized by a single-factor experiment. The optimal condition was as follows: The temperature was 60 °C, the amount of the catalyst was 0.2 g, the oxygen to sulfur ratio was 16, and the reaction time is 100 min. The catalyst was suitable for recycled use, and the desulfurization efficiency was high after 10 times. In the end, the oxidative desulfurization mechanism was put forward.

Heteroatom Bridging Strategy in Carbon-Based Catalysts for Enhanced Oxidative Desulfurization Performance

Carbon-based catalysts are found to be promising metal-free species for aerobic oxidative desulfurization of fuel oil. Thus, a proper approach to promote their catalytic performances is very much in demand. In this contribution, a heteroatom bridging strategy is proposed to enhance the catalytic activities of carbon-based catalysts. As proof of the strategy, a series of boron (B)-doped graphite catalysts were synthesized. Detailed characterizations showed that the hetero-B atoms were uniformly dispersed in graphite. More importantly, it was found that the doped B atoms functioned as a bridge for electron transfer. With the existence of the heteroatom bridge, the activation of oxygen by graphite during the catalytic oxidation process was enhanced remarkably, leading to an ultradeep oxidative desulfurization performance. Moreover, the catalyst can be readily recycled five times without a significant decrease in desulfurization performance.

Model Fuel Oxidation in the Presence of Molybdenum-Containing Catalysts Based on SBA-15 with Hydrophobic Properties

We have studied for the first time the role of hydrophobicity of the mesoporous silicate SBA-15 on the activity and the service life of a catalyst in the peroxide oxidation of sulfur-containing compounds. Immobilization of the molybdate anion on the SBA-15 support via ionic bonding with triethylammonium groups allows us not only to decrease the reaction temperature to a relatively low value of 60 °C without a drop in the dibenzothiophene conversion degree but also to increase the service life of the catalyst to many times that of the known analogs. The support and catalyst structures were investigated by low-temperature nitrogen adsorption/desorption, Fourier-transform infrared spectroscopy, X-ray fluorescence analysis, and transmission electron microscopy. Immobilization of the molybdate anion on the SBA-15 support, modified with ammonium species, prevents the leaching of active sites. However, only alkyl-substituted ammonium species minimize DBT sulfone adsorption, which significantly increases the catalyst's service life. The synthesized catalyst Mo/Et₃N-SBA-15 with hydrophobic properties is not sensitive to the initial sulfur content and hydrogen peroxide amount and retains its activity for at least six cycles of oxidation without regeneration. These catalysts can be efficiently used for clean fuel production.

Natural clay nanotube supported Mo and W catalysts for exhaustive oxidative desulfurization of model fuels

Oxidative desulfurization is a promising way to produce, under mild conditions, clean ecological fuels with ultra-low sulfur content. Herein, we present for the first time heterogeneous catalysts based on natural aluminosilicate nanotubes (halloysite) loaded with transition metal oxides for oxidative sulfur removal using hydrogen peroxide as environmentally safe oxidant. The halloysite nanotubes (HNTs) provide acid sites for C–S bond scission, while the Mo and W oxides act as hydrogen peroxide activators. The structure and acidity of both the clay support and catalysts were investigated by low-temperature nitrogen adsorption/desorption, Fourier-transform infrared spectroscopy, X-ray fluorescence analysis, and transmission electron microscopy techniques. These clay-based catalysts revealed the high activity in the oxidation of various classes of sulfur-containing compounds (sulfides, heteroatomic sulfur compounds) under mild reaction conditions. The conversion of various substrates decreases in the following trend: MeSPh > Bn2S > DBT > 4-MeDBT > BT, which deals with substrate electron density and steric hindrance. The influence of the temperature, oxidant to sulfur molar ratio, and reaction time on catalytic behavior was evaluated for Mo- and W-containing systems with various metal content. The complete oxidation of the most intractable dibenzothiophene to the corresponding sulfone was achieved at 80 °C and H2O2:S = 6:1 (molar) for 2 h both for Mo- and W-containing systems. These transition metal oxides HNTs supported catalysts are stable for 10 cycles of dibenzothiophene oxidation, which makes them promising systems for clean fuel production.

Formation and use of anaerobic consortia for the biotransformation of sulfur-containing extracts from pre-oxidized crude oil and oil fractions

A new solution for fossil raw materials desulfurization based on a hybrid chemical-biocatalytic scheme with biogas and sulfide production is proposed.·H₂O₂, formic acid and Na₂MoO₄ were used for petroleum or oil fractions pre-oxidation. Ethanol or dimethylformamide was used as extractant to remove sulfur-contained compounds from pre-oxidized straight-run diesel oil fraction, non-hydro treated vacuum gas oil, gas condensate or crude oil. Compositions of cells (anaerobic sludge, Desulfovibrio vulgaris, Clostridium acetobutilycum, Rhodococcus ruber, Rhodococcus erythropolis) were specially developed, immobilized in poly(vinyl alcohol) cryogel and used for methanogenic treatment of sulfur-containing extracts, diluted with phosphate buffer (pH 7.2) and hydrolysates of renewable raw materials. The sulfur coming into the reactor with the extracts was 100% converted to inorganic sulfide or cell biomass. The ratio of methane in the biogas was 68-76%. Bioluminescent express-methods were used to control the possible toxicity of media and metabolic activity of cells used as biocatalysts.

Allylic hydrocarbon polymers complexed with Fe(II)(salen) as a ultrahigh oxygen-scavenging and active packaging film

Macromolecular metal complexes provide a molecular-based synergy function of organic polymers and combined metal complexes. A new category of macromolecular complexes includes catalytically active metal complexes immobilized by organic polymers containing reactive substrate moieties in their repeating units. Here, we describe the extremely efficient oxidation of allylic hydrocarbon polymers with the attached iron complex catalyst, as well as the efficient oxygen-consumption or oxygen-scavenging function of the matrix polymer film. The less toxic N,N´-di(salicylaldehyde)ethylenediiminatoiron(II) complex was combined with or fixed onto a series of allylic hydrocarbon polymers as both the oxidative substrate and the film matrix, i.e. poly(1,2-butadiene), polynorbornene, poly(5-vinyl-2-norbornene), poly(2,5-norboenadiene), poly(dicyclopentadiene), and poly(5-ethylidene-2-norbornene). Ultra-high oxygen-scavenging capacity up to 300 mL (oxygen gas at STP)/g(film) was achieved, based on the oxidative consumption of the allylic bond (particularly of poly(5-ethylidene-2-norbornene)), which was more than three times that of the previously reported highest oxygen-scavenging polymers. These oxygen-scavenging films are based on the high reactivity of polymer-metal complexes that provides an innovative development in the area of active packaging polymer films that facilitate cost-effective performance, safety, and sustainability.