Simulated Gasoline Research Articles

The introduction of nitrogen-containing heterocyclic compounds (NHC) and Cu2+ in Co-MOF further improves the removal of dibenzothiophene from model fuels

NHC/Co-MOF-Cu2+ composite adsorbent materials were prepared through the in-situ synthesis of nitrogenous heterocyclic compounds (NHC) on Co-containing metal–organic framework (Co-MOF) using terephthalaldehyde (C8H6O2) and p-Phenylenediamine (C6H8N2) at room temperature. Subsequently, further modification with Cu2+ was carried out. These materials were then utilized for the removal of dibenzothiophene (DBT) from simulated gasoline. The samples were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and other methods. The results indicated the uniform attachment of NHC and Cu2+ metal particles onto Co-MOF, confirming the successful synthesis of NHC/Co-MOF-Cu2+ adsorption materials. The introduction of Cu2+ enhanced the π-complexation between NHC/Co-MOF-Cu2+ and DBT. The introduction of NHC brought heteroatoms and ring structures to the composite, increasing the electron cloud density of the NHC/Co-MOF-Cu2+ composite and thereby amplifying the π-complexation with DBT. The adsorption capacity of NHC/Co-MOF-Cu2+ for DBT (150.4 mg/g) is significantly larger than that of Co-MOF (102.5 mg/g). The adsorption process of NHC/Co-MOF-Cu2+ for DBT followed the pseudo-second-order kinetic model and Langmuir model. Additionally, the adsorption process was found to be spontaneous and exothermic. Over five consecutive adsorption–desorption cycles, the efficiency of NHC/Co-MOF-Cu2+ decreased by only 10 %, indicating its excellent regeneration performance.

Electrochemical Determination of Thiophene by Dicyandiamide/Graphene Oxide/Modified Graphite Electrode in Gasoline by Square Wave Voltammetry (SWV)

An efficient stable electrochemical method for the determination of thiophene as a sulfur model compound in gasoline has been investigated based on the electrodeposition of graphene oxide and dicyandiamide on graphite electrode by cyclic voltammetry. The electroactive layer performance was considered by linear sweep voltammetry and square wave voltammetry by examining scan rates and their relevant equations to evaluate the electrochemical parameters. This modified electrode has high electrocatalytic characteristics to irreversible electrooxidation of thiophene. The electron transfer coefficient (α) was equal to 0.78, the electron transfer rate constant (log KS) was 3.2 s−1, and the saturated adsorptive capacity of the electroactive substance at the electrode surface (Γmax) was 1.14 × 10−8 mol cm−2 at pH 8 at low working potential of 0.5 V versus Ag/AgCl reference electrode. Scanning electron microscopy of the surface revealed the nanostructure of electrodeposited films and the morphology. This sensor is capable of electrochemical response to thiophene over the concentration range from 25 to 250 nmol L−1 with a detection limit of 8.31 nmol L−1, and a quantification limit of 25.18 nmol L−1. The method’s reliability was checked regarding the simulated gasoline samples and the desired response and sensitivity were provided. The wide dynamic range, low detection limit, favorable precision and accuracy, and fast response with no interferences confirm the ability of this sensor for thiophene determination. This nano-sensor can be used for electrochemical in-situ direct monitoring of liquid fuel desulfurization processes.

Screening Ba0.9A0.1MnO3 and Ba0.9A0.1Mn0.7Cu0.3O3 (A = Mg, Ca, Sr, Ce, La) Sol-Gel Synthesised Perovskites as GPF Catalysts.

Ba0.9A0.1MnO3 (BM-A) and Ba0.9A0.1Mn0.7Cu0.3O3 (BMC-A) (A = Mg, Ca, Sr, Ce, La) perovskite-type mixed oxides were synthesised, characterised, and used for soot oxidation in simulated Gasoline Direct Injection (GDI) engine exhaust conditions. The samples have been obtained by the sol-gel method in an aqueous medium and deeply characterised. The characterization results indicate that the partial substitution of Ba by A metal in BaMnO3 (BM) and BaMn0.7Cu0.3O3 (BMC) perovskites: (i) favours the hexagonal structure of perovskite; (ii) improves the reducibility and the oxygen desorption during Temperature-Programmed Desorption (O2-TPD) tests and, consequently, the oxygen mobility; (iii) mantains the amount of oxygen vacancies and of Mn(IV) and Mn(III) oxidation states, being Mn(IV) the main one; and (iv) for Ba0.9A0.1Mn0.7Cu0.3O3 (BMC-A) series, copper is partially incorporated into the structure. The soot conversion data reveal that Ba0.9La0.1Mn0.7Cu0.3O3 (BMC-La) is the most active catalyst in an inert (100% He) reaction atmosphere, as it presents the highest amount of copper on the surface, and that Ba0.9Ce0.1MnO3 (BM-Ce) is the best one if a low amount of O2 (1% O2 in He) is present, as it combines the highest emission of oxygen with the good redox properties of Ce(IV)/Ce(III) and Mn(IV)/Mn(III) pairs.

Evaluation of Pr2Zr2−xCexO7±δ pyrochlores as a potential Cu support catalysts for CO oxidation in simulated GDI conditions

This study evaluates the catalytic activity, both as bulk catalysts and as supports for copper catalysts for CO oxidation in a simulated Gasoline Direct Injection Engine (GDI) of two pyrochlores: Pr2Zr2O7 (PZ) and Pr2Zr1.9Ce0.1O7±δ (PZC). These pyrochlores were synthesized by the solvothermal method. XRD, FE-SEM, HR-TEM, XPS, H2-TPR, and O2-TPD characterization techniques were employed to determine the structural, microstructural, and redox properties of the samples. All materials exhibited high catalytic activity for CO oxidation, with Cu-PZC showing the best performance, which is comparable to that of a 1% Pt/Al2O3 commercial catalyst used as a reference. Thus, the synthesized solids could be a promising and cost-effective alternative to noble metal-based catalysts used to control GDI exhaust gas composition.

Deep oxidative desulfurization of simulated and real gas oils by NiFe2O4@SiO2-DETA@POM as a retrievable hybrid nanocatalyst

Magnetic nanoparticles surrounded with a silica shell are useful materials to immobilize active agents on their surface. Here, a heteropolyacid-functionalized hybrid nanomaterial (NiFe2O4@SiO2-DETA@POM) was prepared and characterized by X-ray powder diffraction patterns (XRD), Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA/DTG), vibrating sample magnetometer (VSM), the field emission scanning electron microscopy (FE-SEM), and the electron-dispersive X-ray spectroscopy (EDS). The synthesized hybrid nanostructure was used as a solid nanocatalyst in oxidative desulfurization (ODS) of real fuel and simulated gasoline samples. The ODS process of benzothiophene (BT) and dibenzothiophene (DBT) as model compounds in the presence of NiFe2O4@SiO2-DETA@POM and by using urea-hydrogen peroxide/acetic acid as a safer oxidizing agent was investigated. A good result was obtained by removing 97% of benzothiophene and 98% of dibenzothiophene. Also, 96% of the sulfur compounds were eliminated when the ODS process was tested on a real crude oil sample (600ppm) under an optimized dosage of nanocatalyst, urea-hydrogen peroxide/acetic acid (0.1g, 1g/4ml) at 50 ºC for 60min. NiFe2O4@SiO2-DETA@POM could be recycled for five consecutive oxidation runs without significant deterioration in its catalytic activity. The UHP's safety and efficiency as an oxidant, high removal efficacy, short transformation times, easy workup procedure, catalyst reusability, simple separation of nanocatalyst, green conditions, and environmental compatibility and sustainability. The obtained results prove that NiFe2O4@SiO2-DETA@POM is a suitable and efficient hybrid catalyst for the oxidative desulfurization of simulated and real fuels.

Analysis of Unregulated VOCs Downstream a Three-Way Catalyst in a Simulated Gasoline Engine Exhaust under Non-Optimum Conditions

Urban air pollution is partly due to exhaust emissions from road transport. Vehicle emissions have been regulated for more than 30 years in many countries around the world. Each motor type is equipped with a specific emission control system. In gasoline vehicles, a three-way catalytic converter (TWC) is implemented to remove at the same time hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). However, TWCs are only efficient above 200 °C and at a stoichiometric air-to-fuel ratio in the exhaust. However, deviations from stoichiometry occur during fast accelerations and decelerations. This study reports the analysis of unregulated VOCs commercial mini-TWC fed by model gasoline gas mixtures. A synthetic gas bench was used to control the model exhaust containing two model hydrocarbons (propene and propane) to identify the conditions at which VOCs are created under non-optimal conditions. Most of the pollutants such as N2O and VOCs were emitted between 220 and 500 °C with a peak at around 280 °C, temperature which corresponds to the tipping point of the TWC activity. The combination of different mass spectrometric analysis (online and offline) allowed to identify many different VOCs: carbonated (acetone, acetaldehyde, acroleine), nitrile (acetonitrile, propanenitrile, acrylonitrile, cyanopropene) and aromatic (benzene, toluene) compounds. Growth mechanisms from propene and to a lesser extend propane are responsible for the formation of these higher aromatic compounds that could lead to the formation of secondary organic aerosol in a near-field area.

Enhanced oxygenates production from plasma catalytic partial oxidation of n-pentane over Fe/Al2O3 catalyst

Plasma technology is promising in partial oxidation of liquid fuel to oxygenates for cleaner combustion, but its efficiency requires improvement. Here, we demonstrate that the partial oxidation of n-C5H12 (a simulated gasoline fuel) by a dielectric barrier discharge (DBD) combined with Fe/Al2O3 catalysts could efficiently improve the oxygenates selectivity up to 53.1% with good stability at room temperature and atmospheric pressure. In comparison, the oxygenates selectivity for plasma only condition was 24.8%. However, a high background temperature and specific energy input had negative effect on the oxygenates selectivity. Plasma-added in situ diffuse reflectance infrared Fourier transform spectroscopy revealed that the n-C5H12 conversion was due to the electron-impact disassociation in the gas phase, and following plasma produced O-containing (O and OH) and CxHy active species could be adsorbed and then react with each other on the catalyst, improving the oxygenates production. Our results can guide the design of plasma-catalysis approach for fossil liquid fuel to oxygenates.

Highly Efficient Catalytic Oxidative Desulfurization of Gasoline Using PMnW11@PANI@CS as a New Inorganic–Organic Hybrid Nanocatalyst

In this manuscript, to obtain a high-purity fuel, a new inorganic–organic hybrid (IOH) nanocomposite (PMnW11@PANI@CS) based on mono-supplanted heteropolyanion (PMnW11), polyaniline (PANI), and chitosan (CS) was synthesized successfully. The synthesized nanocomposite (PMnW11@PANI@CS) was employed as a nanocatalyst in the nanocatalytic oxidative desulfurization (NODS) process. PMnW11@PANI@CS was confirmed by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), UV–vis, Fourier transform infrared spectroscopy (FT-IR), and energy-dispersive X-ray spectroscopy (EDX) analysis. The elimination of hazardous molecules containing sulfur from real and simulated gasoline was done according to the NODS process. The sulfur compounds in gasoline were oxidized and disengaged effectively under a mild reaction. PMnW11@PANI@CS with nanocatalytic activity was used as a recyclable nanocatalyst in this process. PMnW11@PANI@CS was evaluated in the NODS process using a combination of CH3COOH and H2O2 in a 1:2 volume ratio as an oxidant system. The results were compared with the obtained results of a simulated gasoline oxidation process under the same conditions. Furthermore, the effect of the nanocatalyst, types of oxidation system, dosage of the nanocatalyst, temperature, and reaction time on the NODS efficiency were investigated. Experimental results show that owing to the excellent efficiency of the PMnW11@PANI@CS NODS system, it can be a promising method to attain super clean gasoline.

Prediction of secondary organic aerosol from the multiphase reaction of gasoline vapor by using volatility–reactivity base lumping

Abstract. Heterogeneous chemistry of oxidized carbons in aerosol phase is known to significantly contribute to secondary organic aerosol (SOA) burdens. The UNIfied Partitioning Aerosol phase Reaction (UNIPAR) model was developed to process the multiphase chemistry of various oxygenated organics into SOA mass predictions in the presence of salted aqueous phase. In this study, the UNIPAR model simulated the SOA formation from gasoline fuel, which is a major contributor to the observed concentration of SOA in urban areas. The oxygenated products, predicted by the explicit mechanism, were lumped according to their volatility and reactivity and linked to stoichiometric coefficients which were dynamically constructed by predetermined mathematical equations at different NOx levels and degrees of gas aging. To improve the model feasibility in regional scales, the UNIPAR model was coupled with the Carbon Bond 6 (CB6r3) mechanism. CB6r3 estimated the hydrocarbon consumption and the concentration of radicals (i.e., RO2 and HO2) to process atmospheric aging of gas products. The organic species concentrations, estimated by stoichiometric coefficient array and the consumption of hydrocarbons, were applied to form gasoline SOA via multiphase partitioning and aerosol-phase reactions. To improve the gasoline SOA potential in ambient air, model parameters were also corrected for gas–wall partitioning (GWP). The simulated gasoline SOA mass was evaluated against observed data obtained in the University of Florida Atmospheric PHotochemical Outdoor Reactor (UF-APHOR) chamber under varying sunlight, NOx levels, aerosol acidity, humidity, temperature, and concentrations of aqueous salts and gasoline vapor. Overall, gasoline SOA was dominantly produced via aerosol-phase reaction, regardless of the seed conditions owing to heterogeneous reactions of reactive multifunctional organic products. Both the measured and simulated gasoline SOA was sensitive to seed conditions showing a significant increase in SOA mass with increasing aerosol acidity and water content. A considerable difference in SOA mass appeared between two inorganic aerosol states (dry aerosol vs. wet aerosol) suggesting a large difference in SOA formation potential between arid (western United States) and humid regions (eastern United States). Additionally, aqueous reactions of organic products increased the sensitivity of gasoline SOA formation to NOx levels as well as temperature. The impact of the chamber wall on SOA formation was generally significant, and it appeared to be higher in the absence of wet salts. Based on the evaluation of UNIPAR against chamber data from 10 aromatic hydrocarbons and gasoline fuel, we conclude that the UNIPAR model with both heterogeneous reactions and the model parameters corrected for GWP can improve the ability to accurately estimate SOA mass in regional scales.

A facile fabrication of highly dispersed CeO2/SiO2 aerogel composites with high adsorption desulfurization performance

A simple, low energy consumption and environment-friendly strategy was used to prepare highly dispersed CeO2/SiO2 aerogel composites with different molar ratio of Si/Ce via sol-gel method and subsequently drying under the ambient pressure, in which the oxidation of Ce3+ species into Ce4+ species could be achieved by adding H2O2. The structural and surface properties of adsorbents were analyzed by XPS, XRD, FT-IR, Py-IR, SEM, XRF and N2 adsorption-desorption isotherm. The adsorption desulfurization performances of CeO2/SiO2 for thiophenic compounds from simulated gasoline and model aromatic products were investigated and compared by the breakthrough and batch adsorption experiments. As a result, the weak Lewis acid centers appeared on the surface of CeO2/SiO2. Among them, CeO2/SiO2 with a Si/Ce of 25 performed best, the adsd by Duanpacity for TP from simulated gasoline (n-heptane) was 10.9 mg-S/gads, followed by model aromatic products (benzene, 10.6 mg-S/gads; p-xylene, 10.1 mg-S/gads), however, the difference between them was slight, attributed to the formation of S-Ce bonding instead of C-Ce bonding. The very weak competitive adsorption of benzene and p-xylene with thiophene originated from the weak Lewis acid-base interaction. After the fourth solvent washing regeneration, the breakthrough adsorption capacity of regenerated CeO2/SiO2-25 still remained 60% of the fresh one. The equilibrium adsorption data of CeO2/SiO2-25 for thiophene were well fitted by Langmuir and Freundlich model, and the adsorption for TP was more favorable at the higher temperature. The adsorption process of CeO2/SiO2-25 was well fitted by pseudo-second-order kinetic model, which was spontaneous, endothermic and the freedom degree increased. The solvent (n-heptane, benzene, p-xylene) hardly influence the adsorption behavior of TP on CeO2/SiO2.

Partial oxidation of n-pentane to syngas and oxygenates in a dielectric barrier discharge reactor

Nonthermal plasma has a great potential for the partial oxidation of gasoline to form cleaner fuels. However, the formation of deep oxidation products and cracking products makes plasma environmentally unfriendly. This paper reports the partial oxidation of simulated gasoline (n-C5H12) to syngas and oxygenated products. For this purpose, a dielectric barrier discharge reactor was used in which the background temperature and gas pressure could be individually controlled. We found that the conversion of n-C5H12 increased with increasing background temperature until 498 K, then reduced at 523 K because of the resistive loss of discharge power. In contrast, the selectivity of oxygenates and the H2/CO value monotonously decreased with increasing background temperature. It was inferred that the conversion of n-C5H12 depends on both the thermo-chemistry and the electron-induced chemistry, and their contribution to this process was almost the same at 498 K. In contrast, the mechanism of product formation was mainly controlled by thermo-chemistry. The benefits of using cold plasma to simultaneously produce syngas and oxygenates were highlighted. Our results may be used to develop a new concept for designing an environmentally friendly plasma reformer.

A study on thiophene removals from model oils with different molecular compositions using an inexpensive N-methylpyrrolidone-FeCl3 ionic liquid

Extraction desulfurization technology (EDS) has been widely concerned because of its mild process conditions and low loss of octane number. At present, most of researches on EDS reported in literature mainly adopt single chain alkane as model oil. However, the chemical composition of fluid catalytic crack (FCC) gasoline is quite different from that of single chain alkane. Therefore, in this paper, the removal of thiophene from model oils containing different molecular compositions, such as n-octane, cyclohexane, 1-octene, cyclohexene and toluene, was systematically studied, using NMP + nFeCl3 (n = 0, 5 wt%, 10 wt%, 20 wt%) as extractants. The effects of different molecular compositions on desulfurization rate and the selectivity of extractants were systematically investigated, and their interaction mechanisms were discussed. The experimental results showed that the effects of different molecular compositions on desulfurization rate and selectivity were quite different, with the order of toluene > cyclohexene >1-octene > cyclohexane > n-octane. The higher the π electron cloud densities of the investigated molecular compositions or the more similar their chemical structures to extractants, the lower the desulfurization rates and selectivities. Moreover, the CH⋯π interaction between the investigated molecular composition and the extractant had a greater influence on desulfurization rate and selectivity than ring structure. The desulfurization results of simulated FCC gasoline showed that the selectivity and desulfurization rate of simulated gasoline containing olefins and aromatics were far lower than those of n-octane reported in the literature. The desulfurization results of real gasoline showed that the desulfurization rate and selectivity of real gasoline were also significantly lower than those of n-octane model oil.

Rh- and Rh–Ni–MgO-based structured catalysts for on-board syngas production via gasoline processing

Rh/Ce0.75Zr0.25O2-δ-ƞ-Al2O3/FeCrAl and Rh/Ni–MgO/Ce0.75Zr0.25O2-δ-ƞ-Al2O3/FeCrAl FeCrAlloy wire mesh supported catalysts were prepared via multistep procedure. They were characterized by XRD, SEM and TEM techniques. A comparative study of autothermal reforming (ATR) of isooctane and simulated gasoline (blends of isooctane, ortho-xylene and naphthalene) over Rh/Ce0.75Zr0.25O2-δ-ƞ-Al2O3/FeCrAl and Rh/Ni–MgO/Ce0.75Zr0.25O2-δ-ƞ-Al2O3/FeCrAl was performed. Both catalysts showed excellent performance in ATR of isooctane at molar ratios of O2:C = 0.51 and H2O:C = 2.59, T = 750°С and GHSV = 10000 h−1. In the ATR of isooctane – o-xylene blend in presence of Rh–Ni-containing catalyst carbon formation was observed. Rh-containing catalyst demonstrated rather good activity and stability even in the case of isooctane – o-xylene – naphthalene blend.

Synthesis and non‐parametric evaluation studies on high performance of catalytic oxidation‐extraction desulfurization of gasoline using the novel TBAPW11Zn@TiO2@PAni nanocomposite

In this work, the new catalyst (assigned as TBAPW11Zn@TiO2@PAni) was successfully designed and synthesized on the basis of quaternary ammonium salt of zinc monosubstituted phosphotungstate [(n‐C4H9)4N][PW11ZnO39] (TBAPW11Zn), titanium dioxide (TiO2), and polyaniline (PAni). This study reports the catalytic oxidation‐extraction desulfurization (ECODS) of sulfur‐containing molecules from real and the simulated (Th, BT, and DBT) gasoline using new organic–inorganic hybrid catalyst (TBAPW11Zn@TiO2@PAni). The ECODS results were shown that the concentration of sulfur compounds (SCs) of real gasoline was lowered from 0.4992 to 0.0122 wt.% with 97% efficiency at 35 °C after 1 h. Furthermore, the synthesized heterogeneous nanocatalyst showed high stability and reusability after five times without significant loss of activity. The high performance of TBAPW11Zn@TiO2@PAni/H2O2/CH3CO2H system can be a promising route with a superb potential in the generation of ultra‐low‐sulfur gasoline. Also the Mann–Whitney U‐test results show that there is not a significant difference between the mean of sulfur percentage for DBT & BT, BT & Th and DBT & Th in the presence of the catalyst. Based on the Kruskal–Wallis test results, we can conclude that the temperature, time and amount of catalyst have a significant effect on ECODS efficiency of TBAPW11Zn@TiO2@PAni nanocomposite.

Plasma reforming of n-pentane as a simulated gasoline to hydrogen and cleaner carbon-based fuels

Nonthermal plasma is a promising technology for the on-board reforming of gasoline or diesel fuels into cleaner fuels. However, the formation of deep cracking products, such as carbon particulates, discourages the development of an environmentally friendly process. The authors report the reformation of n-pentane (C5H12) using methane (CH4) or carbon dioxide (CO2) in a temperature-controlled dielectric barrier discharge reactor to produce the H2 and carbon-based clean products. A mechanistic study suggests that electron-induced chemistry dominates C5H12 and the added gas conversion, whereas the thermochemistry controls the product distribution. On this basis, the product distribution is varied by the enriched CH3 and H, or the enriched O by adding CH4 or CO2. When increasing CH4 percentage from 0 to 75%, the production of short-chain alkanes (C1–C4 alkanes) and H2 were increased by around 29% and 45%, respectively. The increase in CO2 (0–75%) percentage resulted in the increased production of oxygenated fuels (0–9%). Our results emphasize the advantages of using low-temperature plasma for the co-production of H2 and clean carbon-based fuels (chemical intermediates), which may offer a new concept for the design of a practical on-board plasma reformer.

Synthesis and Adsorption Desulfurization Performance of Modified Mesoporous Silica Materials M-MCM-41 (M = Fe, Co, Zn)

AbstractAdsorption desulfurization is a potential new method for deep desulfurization of fuel oil. The development of adsorbents with high adsorption capacity and selectivity is the core of deep adsorption desulfurization. The adsorption behavior of thiophene in MCM-41 mesoporous materials modified by various metal ions was studied in order to understand the adsorption desulfurization process of molecular sieves. The Fe-, Co-, and Zn-modified MCM-41 materials were prepared using a one-step in situ hydrothermal synthesis method. The modified MCM-41 molecular sieves maintained the mesoporous structure, and the metal ions had specific dispersion on the surface of the molecular sieves. Adsorption of thiophene on the surfaces of molecular sieves had both physical and chemical characteristics. The adsorption desulfurization performance of the modified molecular sieve was superior to that of the pure silica molecular sieve. In the simulated gasoline with sulfur content of 220 μg/g, when the amount of adsorbent used was 100 mg, the adsorptive desulfurization performance tended to be in equilibrium, and the optimum adsorption temperature was 30°C. Fe-MCM-41 and MCM-41 molecular sieves reached adsorption equilibrium after ~60 min, but the desulfurization rate of Co-MCM-41 and Zn-MCM-41 still increased slightly. The kinetic simulation results indicated that the pseudo-second-order kinetics adsorption model described well the adsorption process of thiophene on molecular sieves. The molecular sieve Fe-MCM-41 had the best desulfurization performance with an equilibrium adsorption capacity of 14.02 mg/g and the desulfurization rate was ~90%.

Facile and Scalable Coating of Metal-Organic Frameworks on Fibrous Substrates by a Coordination Replication Method at Room Temperature.

Coating of metal-organic frameworks (MOFs) on flexible substrates is a crucial technology for applications such as purification/separation, sensing, and catalysis. In this work, a facile coordination replication strategy was developed to coat various MOFs onto flexible fibrous materials where a dense layer of an insoluble precursor template, such as a layered hydroxide salt, was first deposited onto a fiber substrate via a mild interfacial reaction and then rapidly transformed into a MOF coating in a ligand solution at room temperature. Spatiotemporal harmonization of solid precursor dissolution and MOF crystallization enabled precise replication of the precursor layer morphology to form a continuous MOF coating composed of intergrown crystals. The resulting flexible, highly robust, and processable fibrous MOF/textile composites demonstrated tremendous potential for industrially relevant applications such as continuous removal of the organosulfur compound dibenzothiophene from simulated gasoline and ammonia capture. This rapid, versatile, eco-friendly, and scalable MOF coating process at room temperature gives rise to new possibilities for preparing MOF-coated functional materials.

CuO/La0.5Sr0.5CoO3 nanocomposites in TWC

In this contribution several La0.5Sr0.5CoO3 based nanocomposites have been prepared and tested for application as Three-Ways Catalysts (TWC), aiming to develop Platinum Group Metal (PGM)-free catalysts. To reach this objective we designed and realized nanocomposites in which active CuO nanoparticles are deposited on La0.5Sr0.5CoO3. This perovskite is active in oxidation and is characterized by high oxygen anion mobility; copper is active in reduction: catalytic bifunctionality is thus built-in via a tailor-made and controlled nano-composition. The supporting perovskite was prepared following the “citrate” route. The deposition was carried out by means of the Ammonium-Driving-Deposition precipitation (ADP) to highly disperse CuO on La0.5Sr0.5CoO3. In a precedent paper we focused on nanocomposites obtained using LaCoO3 as a support because this perovskite is active in oxidation. Sr-doped LaCoO3, in addition, is characterized by a more relevant presence of oxygen vacancies and mobility and the desire of comparing these systems is to better investigate the different role played by all these aspects on the interaction between highly dispersed CuO nanoparticles and perovskite and on the catalytic activity.The copper amount on the nanocomposite surface does not increase linearly with the nominal composition reaching a plateau: migration below the surface is observed for the nanocomposite with 30 wt.% of Cu.The surface composition of the perovskite is modified by the copper deposition which causes the decrease of A-cations surface segregation and enhances the presence of cobalt suggesting a certain synergy; the reducibility of the perovskite is also greatly favored by deposition.Both model reactions (CO oxidation and CO assisted NO reduction) and reactions with a synthetic automotive exhaust mixture, including 10% steam, and oxygen, were carried out. We compared the results with the ones obtained in similar reactions with CuO/LaCoO3. Different interaction and synergy were observed with respect to CuO/ La0.5Sr0.5CoO3. Sr-doping, in fact, enhances oxygen mobility affecting the reducing character of the nanodispersed CuO and thus the reactivity under different conditions.The deposition of copper oxide significantly increases the activity of the nanocomposites in CO oxidation (about 100% conversion at 200 °C) and in CO + NO (50% conversion at 250 °C, more than 80% at 400 °C) reactions. When compared with the corresponding CuO/LaCoO3, the more significant difference has been observed in nanocomposites poorer in CuO, which became highly active at lower temperature. On simulated gasoline engine exhaust the nanocomposites always improve the oxidation activity compared to the parent perovskite, while the NO reduction is quantitative in the absence of O2.The activity on a mixture simulating actual gasoline-engine exhaust proves that ADP synthesis provides materials with a higher activity compared to wet impregnation (WI), thanks to a higher dispersion of copper. NO reduction in fuel-rich conditions is activated at approx. 300 °C, (400 °C on WI sample), when significant amount of O2 is still in the mixture. This feature completes the good performance in absence of noble critical metals that are promising facts to develop PGM-free catalysts for the automotive industry.

Upconversion nanocomposite CeO2:Tm3+/attapulgite intermediated by carbon quantum dots for photocatalytic desulfurization

Upconversion CeO2:Tm3+/attapulgite (ATP) nanocomposites intermediated by carbon quantum dots (CQDs) were synthesized by a facile deposition method using hexamethylenetetramine as precipitator. The products were characterized by various techniques. The photocatalytic degradation of dibenzothiophene (DBT) in simulated gasoline was conducted under visible light irradiation by taking advantage of CeO2:Tm3+/CQDs/ATP nanocomposites as catalyst. The influence of Tm3+ doping amount and the mass fraction of CeO2 to ATP on the desulfurization performance were investigated. Results indicated that the CeO2:Tm3+ nanoparticles were coupled uniformly on the CQDs/ATP surface. The desulfurization rate of DBT reached the highest 96% when the molar fraction of Tm3+ in CeO2 was 2% and the mass fraction of CeO2 to ATP was 20 wt%. The enhanced photocatalytic oxidative desulfurization was attributed to the upconversion property of CeO2:Tm3+ which transformed visible light into ultraviolet light increasing the utilization of solar energy, while CeO2:Tm3+ built indirect Z-scheme heterojunction with modified ATP mediated by CQDs, both favored the separation of the charges carriers and benefits the redox potentials.

Evaluation of perovskite catalysts prepared by flame spray pyrolysis for three-way catalyst activity under simulated gasoline exhaust feeds

We have used liquid-feed Flame Spray Pyrolysis (FSP) to prepare a series of high surface area, nanocrystalline perovskites of general formula AA’BB’O3 (A = La, A’ = Ca, Sr, Y, Ce; B = B’ = Mn, Fe, Co, Ni). Use of the FSP method has allowed the systematic investigation of changing both A site dopant and B site cation while maintaining high surface areas. The resulting perovskites have been evaluated for their CO, HC and NO (three-way catalyst (TWC)) activity under simulated gasoline exhaust feeds, their oxygen storage properties and their stability to high temperature redox conditions. The activity of the perovskites has been compared to a low loaded commercial PdRh TWC and were found to be significantly poorer after mild calcination and very significantly deactivated after high temperature hydrothermal redox ageing.