Ultrasound-assisted synthesis and catalytic activity of mesostructured FeOx/SBA-15 and FeOx/Zr-SBA-15 catalysts for the oxidative desulfurization of model diesel

Zirconium-Based Catalysts in Organic Synthesis

Zirconium is a silvery-white malleable and ductile metal at room temperature with a crustal abundance of 162 ppm. Its compounds, showing Lewis acidic behavior and high catalytic performance, have been recognized as a relatively cheap, low-toxicity, stable, green, and efficient catalysts for various important organic transformations. Commercially available inorganic zirconium chloride was widely applied as a catalyst to accelerate amination, Michael addition, and oxidation reactions. Well-designed zirconocene perfluorosulfonates can be applied in allylation, acylation, esterification, etc. N-Chelating oganozirconium complexes accelerate polymerization, hydroaminoalkylation, and CO₂ fixation efficiently. In this review, the applications of both commercially available and synthesized zirconium catalysts in organic reactions in the last 5 years are highlighted. Firstly, the properties and application of zirconium and its compounds are simply introduced. After presenting the superiority of zirconium compounds, their applications as catalysts to accelerate organic transformations are classified and presented in detail. On the basis of different kinds of zirconium catalysts, organic reactions accelerated by inorganic zirconium catalysts, zirconium catalysts bearing Cp, and organozirconium catalysts without Cp are summarized, and the plausible reaction mechanisms are presented if available.

Cavitation based cleaner technologies for biodiesel production and processing of hydrocarbon streams: A perspective on key fundamentals, missing process data and economic feasibility - A review

The present review emphasizes the role of hydrodynamic cavitation (HC) and acoustic cavitation in clean and green technologies for selected fuels (of hydrocarbon origins such as gasoline, naphtha, diesel, heavy oil, and crude oil) processing applications including biodiesel production. Herein, the role of cavitation reactors, their geometrical parameters, physicochemical properties of liquid media, liquid oxidants, catalyst loading, reactive oxygen species, and different types of emulsification and formation of radicals, formation as well as extraction of formed by-products are systematically reviewed. Among all types of HC reactors, vortex diode and single hole orifices revealed more than 95 % desulfurization yield and a 20 % viscosity reduction in heavy oil upgrading, while multi-hole orifice (100 holes) and slit Venturi allowed obtaining the best biodiesel production processes in terms of high (%) yield, low cost of treatment, and short processing time (5 min; 99 % biodiesel; 4.80 USD/m³). On the other hand, the acoustic cavitation devices are likely to be the most effective in biodiesel production based on ultrasonic bath (90 min; 95 %; 6.7 $/m³) and desulfurization treatment based on ultrasonic transducers (15 min; 98.3 % desulfurization; 10.8 $/m³). The implementation of HC-based processes reveals to be the most cost-effective method over acoustic cavitation-based devices. Finally, by reviewing the ongoing applications and development works, the limitations and challenges for further research are addressed emphasizing the cleaner production and guidelines for future scientists to assure obtaining comprehensive data useful for the research community.

Catalytic pyrolysis of coconut oil with Ni/SBA-15 for the production of bio jet fuel

Catalytic pyrolysis of vegetable oil is one of the potential routes to convert oil to drop-in biofuels, known as renewable hydrocarbons. In this paper, we explored catalytic pyrolysis of coconut oil using SBA-15 impregnated with Ni in proportions of 1% to 5% to produce sustainable aviation fuel. The catalysts were synthesized, calcined and then characterized by XRD, FTIR, SEM, and EDS. In order to better understand the behavior of this process, thermal and kinetic studies were carried out by thermogravimetry. The TG curves of vegetable oil with (10%) and without catalysts were obtained at heating rates of 5, 15 and 20 °C min-1, in the temperature range between 30 and 600 °C. The kinetic parameters were calculated by the Ozawa-Flynn-Wall (OFW) and Kissinger-Akahira-Sunose (KAS) methods. In the kinetic study, lower heat rates promoted higher conversions and the KAS model suits the process. The results calculated for the OC sample using the two kinetic models showed an increase in the E a energy as the conversion progressed to a certain point. Catalytic pyrolysis experiments were performed in a one-stage tubular reactor at 500 °C with a catalyst loading of 10 wt% on the basis of mass of oil. The catalyst with 5% Ni showed greater presence of hydrocarbons and greater formation of water, indicating that the deoxygenation process occurred through decarbonylation. With this, the present study was successful in the development of methodologies for obtaining hydrocarbons with a composition close to that of drop-in fuels, compared to the process carried out with vegetable oil in the absence of catalysts.

Catalytic oxidative desulfurisation over Co/Fe-γAl2O3 catalyst: performance, characterisation and computational study

The world faces the challenge to produce ultra-low sulfur diesel with low-cost technology. Therefore, this research emphasised on production of low sulfur fuel utilising nanoparticle catalyst under mild condition. A small amount of cobalt oxide (10-30 wt%) was introduced into the Fe/Al₂O₃ catalyst through the wet impregnation method. Cobalt modification induces a positive effect on the performance of the iron catalyst. Hence, the insertion of cobalt species into Fe/Al₂O₃ led to the formation of lattice fringes in all directions which resulted in the formation of Co₃O₄ and Fe₃O₄ species. The optimised catalyst, Co/Fe-Al₂O₃, calcined at 400 °C with a dopant ratio of 10:90 indicating the highest desulfurisation activity by removing 96% of thiophene, 100% of dibenzothiophene (DBT) and 92% of 4,6-dimethyl dibenzothiophene (4,6-DMDBT). Based on the density functional theory (DFT) on Co/Fe-Al₂O₃, two pathways with the overall energy of -40.78 eV were suggested for the complete oxidation of DBT.

Synthesis and characterization of a novel composites derived from SBA-15 mesoporous silica and iron pentacarbonyl

HYPOTHESIS

Fe(CO)₅ was deposited on SBA-15 from gaseous phase and the adsorbed iron precursor was oxidized and hydrolyzed. We hypothesize that a novel method produces composites of unique and useful properties. The absence of sulfur and halides in the composites is of special importance with respect of their potential application as catalysts and catalyst supports.

EXPERIMENTS

We obtained composites containing 1.3-157.5% of iron oxide with respect to silica (counted as 100%). The new materials were characterized by specific surface area, XRD (X-ray diffraction), Mossbauer spectroscopy, electron microscopy coupled with EDS (energy dispersive X-Ray spectroscopy), and microelectrophoresis.

FINDINGS

In the composites low in iron (<57% of iron oxide) the Mossbauer spectra showed only doublets, which were interpreted as tiny nanoparticles of Fe(III) oxide in the pores of SBA-15. In the composites high in iron (>65%) the Mossbauer spectra showed doublets and sextets. The later were interpreted as larger nanocrystals of hematite, and the presence of such nanocrystals was confirmed by XRD. EDS confirmed that in the composites low in iron, iron oxide was evenly distributed in the entire volume of pores of SBA-15.

Ultrasound-Assisted Hydrothermal Synthesis of V2O5/Zr-SBA-15 Catalysts for Production of Ultralow Sulfur Fuel

This work reports the results of the ultrasound-assisted hydrothermal synthesis of two sets of V2O5 dispersed on SBA-15 and Zr doped SBA-15 catalysts used for the oxidation of dibenzothiophene (DBT) in a model diesel via the combination of oxidation, catalysis, and extraction technical route. These catalysts contained Lewis acidity as major and Brønsted acidity as minor. The amount of acidity varied with the content of vanadia and zirconium doping. It was found that DBT conversion is very sensitive to the Lewis acidity. DBT conversion increased by increasing the vanadium content and correlated well with the amount of surface Lewis acidity. Under the optimal experimental condition (Reaction temperature: 60 °C, reaction time 40 min, catalyst concentration: 1 g/L oil; H2O2/DBT mole ratio = 10), the 30% V2O5/SBA-15 and 30% V2O5/Zr-SBA-15 catalysts could convert more than 99% of DBT. Two reaction pathways of DBT oxidation involving vanadia surface structure, Lewis acidity, and peroxometallic complexes were proposed. When the vanadia loading V2O5 ≤ 10 wt%, the oxidative desulfurization (ODS) went through the Pathway I; in the catalysts with moderate vanadia content (V2O5 = 20–30 wt%), ODS proceeded via the Pathways II or/and the Pathway I.

SBA-15 Anchored Metal Containing Catalysts in the Oxidative Desulfurization Process

Recalcitrant sulfur compounds are common impurities in crude oil. During combustion they produce SOx derivatives that are able to affect the atmospheric ozone layer, increasing the formation of acid rains, and reducing the life of the engine due to corrosion. In the last twenty years, many efforts have been devoted to develop conventional hydrodesulfurization (HDS) procedures, as well as alternative methods, such as selective adsorption, bio-desulfurization, oxidative desulfurization (ODS) under extractive conditions (ECODS), and others. Among them, the oxidative procedures have been usually accomplished by the use of toxic stoichiometric oxidants, namely potassium permanganate, sodium bromate and carboxylic and sulfonic peracids. As an alternative, increasing interest is devoted to selective and economical procedures based upon catalytic methods. Heterogeneous catalysis is of relevance in industrial ODS processes, since it reduces the leaching of active species and favors the recovery and reuse of the catalyst for successive transformations. The heterogenization of different types of high-valent metal transition-based organometallic complexes, able to promote the activation of stoichiometric benign oxidants like peroxides, can be achieved using various solid supports. Many successful cases have been frequently associated with the use of mesoporous silicas that have the advantage of easy surface modification by reaction with organosilanes, facilitating the immobilization of homogeneous catalysts. In this manuscript the application of SBA-15 as efficient support for different active metal species, able to promote the catalytic ODS of either model or real fuels is reviewed, highlighting its beneficial properties such as high surface area, narrow pore size distribution and tunable pore diameter dimensions. Related to this topic, the most relevant advances recently published, will be discussed and critically described.

Continuous Hydrogenation of Ethyl Levulinate to 1,4-Pentanediol over 2.8Cu-3.5Fe/SBA-15 Catalyst at Low Loading: The Effect of Fe Doping

Bimetallic Cu-Fe catalysts with low loading were prepared for hydrogenation of ethyl levulinate (EL) to 1,4-pentanediol (1,4-PDO). Among them, 2.8Cu-3.5Fe/SBA-15 (Cu/Fe molar ratio of 1:1.5) performed best, capable of converting EL to the key intermediate γ-valerolactone (GVL) at 140 °C with 97 % yield. It can also be used to hydrogenate GVL to 1,4-PDO with 92.6 % selectivity or convert EL to 1,4-PDO in one pot. The high activity of the catalyst at such a low loading was attributed to the highly dispersed metal species and the Fe doping effect. Various characterization methods indicated that Fe acted as both structural and electronic modifier to promote the chemical properties of the Cu species. Besides, the incorporation of Fe provided abundant Lewis acid sites and accelerated the reaction process. CuFeO₂ was detected by energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and XRD. On the basis of a combination of characterization and reaction kinetics, synergistic catalysis by Cu⁰ and CuFeO₂ is considered to be responsible for the excellent performance of the Cu-Fe catalysts.