Combination Of Catalyst Research Articles

Optimization and kinetics of the desulfurization of diesel fuel via high shear mixing oxidation assisted by adsorption of sulfones onto chitosan-coated bentonite

ABSTRACTRapid increase in the worldwide consumption of fuel has resulted in environmental and health hazards arising from elevated concentrations of sulfur dioxide and sulfate particulate matter in the atmosphere. In this study, the reduction of the sulfur content in commercial diesel with an initial concentration of 1428 ppm was carried out via oxidative desulfurization (ODS) assisted by high shear mixing using hydrogen peroxide as oxidant and phosphotungstic acid as catalyst in combination with the fixed-bed adsorption of sulfur compounds onto chitosan-coated bentonite (CCB) and activated carbon (AC). The effects of mixing speed (8,000–12,000 rpm), oxidation temperature (60–80ºC), and oxidation time (20–40 min) on sulfur removal were analyzed using the response surface methodology based on the Box–Behnken Design. Results show that the maximum sulfur removal of 81.97% could be attained at the following optimum conditions: 12,000 rpm, 80°C, and 34 min. Fixed-bed studies illustrated that CCB (0.2 mm) has higher adsorption efficiency of 82.66% than AC of 63.24% in the removal of sulfones from diesel.

Organocatalytic Asymmetric Cascade Reaction between o‐Hydroxycinnamaldehydes and γ/δ‐Hydroxyenones: A Route to Tetrahydrofuran/Tetrahydropyran‐Fused 3,4‐Dihydrocoumarins

AbstractThe first organocatalytic asymmetric synthesis of tetrahydrofuran/tetrahydropyran‐fused 3,4‐dihydrocoumarin has been developed via a cascade reaction between 2‐hydroxy cinnamaldehydes and γ/δ‐hydroxy enones followed by pyridinium chlorochromate oxidation. Diphenylprolinol silyl ether catalyst in combination with acetic acid was found to be the most effective for the cascade reaction. With 10 mol% of the catalyst and the additive, the desired products were obtained in high enantio‐ and diastereoselectivities.magnified image

Obtaining formaldehyde on a new catalytic system

Formaldehyde is widely used in many fields of industry. The increase in the need for formaldehyde led to an increase in scientific research, the purpose of which is to obtain the greatest yield of the product (formaldehyde) with minimal costs for raw materials, catalyst and its regeneration, energy carriers, etc. At industrial plants for the production of formaldehyde by oxidative dehydrogenation of methanol on the silver on pumice catalyst, the process temperature is maintained at 600 ° C. The process of obtaining formaldehyde by oxidation of methanol with air oxygen at the combination of catalysts "silver" and "silver on pumice" in the temperature range of 250–450 °C is investigated. The results showed the possibility of practical application of the combined catalyst. Chemical and technological parameters of the process with the use of a new catalyst are slightly lower than production indicators, however, the temperature of the pilot process is 2 times lower - this will reduce not only the energy costs, but also increase the life of the catalyst and the cost of its regeneration.

Catalytic Effect of a Combined Silver and Surfactant Catalyst on Cobalt Ore Bioleaching

The effects of Ag+, surfactants, and their combination on cobalt ore bioleaching were investigated in this article. Ag+ ions and surfactants, either individually or in combination, can significantly accelerate mineral dissolution and increase metal leaching efficiencies. When 20 mg L−1 Ag+ was added, the cobalt and copper leaching efficiencies increased from 67.8% and 58.5% to 94.3% and 80.7%, respectively. In addition, in the presence of 150 mg L−1 Tween-20, the cobalt and copper leaching efficiencies increased by more than 25% and 11%, respectively. A similar trend was observed with Tween-60 and Tween-80. When a combined catalyst of Ag+ ions and surfactant was employed, the cobalt and copper leaching efficiencies increased by more than 23% and 10%, respectively. Moreover, the leaching time decreased by one quarter. The catalytic effect of the combined catalyst was more significant than that of a single catalyst.

Evaluation of the effectiveness of red mud-supported catalysts in combination with ozone and TiO2 in the treatment of solution containing benzene, toluene, and xylene.

Ozone and a Fe2+/TiO2-based catalyst were examined in the degradation of a synthetic solution of benzene toluene and xylene (BTX) in an advanced oxidation process (AOP). The catalyst beads were made from the slurry waste of aluminum production process, by inserting the TiO2 content and subsequent calcination. The reduction of the BTX concentration load was monitored by the reduction of chemical oxygen demand (COD) and BTX concentration. Different levels were used on factors: pH, time of treatment, initial concentration of BTX, and percentage of TiO2. The process was conducted in a bubble column reactor with the insertion of catalyst beads. A response surface methodology technique (CCD) was used to build a model based on COD reduction results. The model was optimized using the normal-boundary intersection (NBI) algorithm to maximize COD reduction and minimize the variance attributed to the process. Optimization led to COD reductions of 80% in 2h of experiment. Correlation analysis of coefficient models from experimental data R2adj was 0.9966, showing a good fit of model data. In the optimized conditions, the possible increase of the biodegradability ratio of the BTX solution, through the biochemical oxygen demand (BOD) and COD, was also analyzed. Under pre-treatment conditions, the BOD/COD ratio was 0.13. After the treatment, it increased to 0.56. Graphical abstract ᅟ.

Synthesis of poly(methyl methacrylate) via ARGET ATRP and study of the effect of solvents and temperatures on its polymerization kinetics

AbstractThis investigation reports the synthesis of poly(methyl methacrylate) via activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) and studies the effect of solvents and temperature on its polymerization kinetics. ARGET ATRP of methyl methacrylate (MMA) was carried out in different solvents and at different temperatures using CuBr2 as catalyst in combination with N,N,N′,N″,N″‐pentamethyldiethylenetriamine as a ligand. Methyl 2‐chloro propionate was used as ATRP initiator and ascorbic acid was used as a reducing agent in the ARGET ATRP of MMA. The conversion was measured gravimetrically. The semilogarithmic plot of monomer conversion versus time was found to be linear, indicating that the polymerization follows first‐order kinetics. The linear polymerization kinetic plot also indicates the controlled nature of the polymerization. N,N‐Dimethylformamide (DMF), tetrahydrofuran (THF), toluene, and methyl ethyl ketone were used as solvents to study the effect on the polymerization kinetics. The effect of temperature on the kinetics of the polymerization was also studied at various temperatures. It has been observed that polymerization followed first‐order kinetics in every case. The rate of polymerization was found to be highest (kapp = 6.94 × 10−3 min−1) at a fixed temperature when DMF was used as solvent. Activation energies for ARGET ATRP of MMA were also calculated using the Arrhenius equation.

Organic Catalysis: Synthesis of Propylene Carbonate by the Carboxylation of Propylene Oxide in the Presence of Phenols and Fluorinated Alcohols

Phenol, polyphenols, as well as fluorinated alcohols actively catalyze the carboxylation of propylene oxide to form propylene carbonate in mild conditions (60°С, 7 at). The highest catalytic activity is characteristic of polyhydric phenols having neighbouring OH groups and alcohols with an enhanced acidity of OH protons. These catalysts in combination with tetrabutyammonium iodide exhibit activity at low concentrations (0.25 mol %) and ensure almost quantitative yields of propylene carbonate. The activity of the catalysts much increases with increasing ammonium salt amount (TOF up to 260), as well as temperature and initial СО2 pressure (TON up to 370).

Combination of Pt@CeO2/MCM-56 and CeO2-CuO/MCM-56 to purify the exhaust emissions from diesel vehicles

Pt@CeO2/MCM-56 (PCM) and CeO2-CuO (9:1)/MCM-56 (CCM) were combined to purify the exhaust emissions from diesel vehicles in three configuration statuses, defined as configuration A—where CCM stays above PCM, configuration B—where PCM stays above CCM, and configuration C—where CCM mixes with PCM homogeneously in loose contact. Among these combined catalysts, the configuration A is most favorable for the selective catalytic reduction (SCR) reaction, with >80% NOx conversion obtained at the temperature range of 150–550 °C and gas hourly space velocity (GHSV) of 240,000 ml g−1 h−1. NH3-TPD, H2-TPR and NH3 conversion measurements demonstrated that NH3 can be selectively used to reduce NOx in the configuration A but is over-oxidized if the reaction is operated in configuration B or configuration C status, deteriorating the deNOx activity at temperature above 250 °C. Hence, configuration A not only takes advantage but also overcomes the shortcomings of PCM and CCM, leading to high NOx conversion and N2 selectivity. A significant decrease in the onset temperature of soot combustion was also observed in this research.

Development of a Kalman filter estimator for simulation and control of particulate matter distribution of a diesel catalyzed particulate filter

The knowledge of the temperature and particulate matter mass distribution is essential for monitoring the performance and durability of a catalyzed particulate filter. A catalyzed particulate filter model was developed, and it showed capability to accurately predict temperature and particulate matter mass distribution and pressure drop across the catalyzed particulate filter. However, the high-fidelity model is computationally demanding. Therefore, a reduced order multi-zone particulate filter model was developed to reduce computational complexity with an acceptable level of accuracy. In order to develop a reduced order model, a parametric study was carried out to determine the number of zones necessary for aftertreatment control applications. The catalyzed particulate filter model was further reduced by carrying out a sensitivity study of the selected model assumptions. The reduced order multi-zone particulate filter model with 5 × 5 zones was selected to develop a catalyzed particulate filter state estimator considering its computational time and accuracy. Next, a Kalman filter–based catalyzed particulate filter estimator was developed to estimate unknown states of the catalyzed particulate filter such as temperature and particulate matter mass distribution and pressure drop (Δ P) using the sensor inputs to the engine electronic control unit and the reduced order multi-zone particulate filter model. A diesel oxidation catalyst estimator was also integrated with the catalyzed particulate filter estimator in order to provide estimates of diesel oxidation catalyst outlet concentrations of NO2and hydrocarbons and inlet temperature for the catalyzed particulate filter estimator. The combined diesel oxidation catalyst–catalyzed particulate filter estimator was validated for an active regeneration experiment. The validation results for catalyzed particulate filter temperature distribution showed that the root mean square temperature error by using the diesel oxidation catalyst–catalyzed particulate filter estimator is within 3.2 °C compared to the experimental data. Similarly, the Δ P estimator closely simulated the measured total Δ P and the estimated cake pressure drop error is within 0.2 kPa compared to the high-fidelity catalyzed particulate filter model.

Mixed Copper States in Anodized Cu Electrocatalyst for Stable and Selective Ethylene Production from CO2 Reduction.

Oxygen-Cu (O-Cu) combination catalysts have recently achieved highly improved selectivity for ethylene production from the electrochemical CO2 reduction reaction (CO2RR). In this study, we developed anodized copper (AN-Cu) Cu(OH)2 catalysts by a simple electrochemical synthesis method and achieved ∼40% Faradaic efficiency for ethylene production, and high stability over 40 h. Notably, the initial reduction conditions applied to AN-Cu were critical to achieving selective and stable ethylene production activity from the CO2RR, as the initial reduction condition affects the structures and chemical states, crucial for highly selective and stable ethylene production over methane. A highly negative reduction potential produced a catalyst maintaining long-term stability for the selective production of ethylene over methane, and a small amount of Cu(OH)2 was still observed on the catalyst surface. Meanwhile, when a mild reduction condition was applied to the AN-Cu, the Cu(OH)2 crystal structure and mixed states disappeared on the catalyst, becoming more favorable to methane production after few hours. These results show the selectivity of ethylene to methane in O-Cu combination catalysts is influenced by the electrochemical reduction environment related to the mixed valences. This will provide new strategies to improve durability of O-Cu combination catalysts for C-C coupling products from electrochemical CO2 conversion.

Evaluation of NOx emissions of a retrofitted Euro 5 passenger car for the Horizon prize “Engine retrofit”

The Horizon 2020 prize for the “Engine Retrofit for Clean Air” aims at reducing the pollution in cities by spurring the development of retrofit technology for diesel engines. A Euro 5 passenger car was retrofitted with an under-floor SCR (Selective Catalytic Reduction) for NOx catalyst in combination with a solid ammonia based dosing system as the NOx reductant. The vehicle was tested both on the road and on the chassis dynamometer under various test cycles and ambient temperatures. The NOx emissions were reduced by 350–1100 mg/km (60–85%) in the laboratory depending on the test cycle and engine conditions (cold or hot start), except at type approval conditions. The reduction for cold start urban cycles was < 75 mg/km (< 15%). The on road and laboratory tests were inline. In some high speed conditions significant increase of ammonia (NH3) and nitrous oxide (N2O) were measured. No effect was seen on other pollutants (hydrocarbons, carbon monoxide and particles). The results of the present study show that retrofitting high emitting vehicles can significantly reduce vehicle NOx emissions and ultimately pollution in cities.

Promoting Intermolecular C-N Bond Formation under the Auspices of Iodine(III).

The quest for the development of new protocols that provide general conditions for oxidative carbon-nitrogen bond formation has grown over recent years. Within this context, due to feasibility and benignity considerations in biochemical sciences, reactions that rely on main group oxidants as the only promoters have received particular interest. We have recently found that simple protonolysis events enable the incorporation of nitrogenated groups of the bissulfonimide family into the coordination sphere of common iodine(III) complexes such as diacetoxy iodobenzene. The products of the type ArI(OAc)(NTs2) represent rare examples of iodine(III) compounds displaying reactive iodine-nitrogen single bonds. Further protonolysis furnishes the corresponding iodine(III) compounds ArI(NTs2)2 containing two defined iodine-nitrogen single bonds for unprecedented dual transfer of both nitrogenated groups. It is of great synthetic importance that these new compounds contain iodine-nitrogen entities, which upon dissociation in solution lead to electrophilic iodine centers and nucleophilic nitrogen groups. This has enabled the development of a body of conceptually new amination reactions, which do not rely on conventional electrophilic nitrogen reagents but rather employ iodine(III) as an electrophilic activator and bissulfonimides as the source of subsequent nucleophilic amination. Additional diversification arises from the ambident nature of bissulfonimines enabling oxygenation pathways. The exciting chemistry covered in this Account comprises structural features of the reagents (including X-ray analysis), scope and limitation in synthetic amination of different hydrocarbons (including sp-, sp2-, and sp3-hybridized centers as in acetylenes, alkenes, enols, butadienes, allenes, arenes, and alkylketones), and physical-organic and theoretical analysis of the underlying reaction mechanisms. The oxidative transformations with all their rich diversifications originate from the versatile redox chemistry of the iodine(III) and iodine(I) pair, which shares several aspects of transition metal high oxidation state chemistry. For the present aryliodine(III) reagents, steric and electronic fine-tuning is possible through accurate engineering of the arene substituent. In addition to the general reactivity of the I-N bond, chiral aryliodine(III) reagents with defined stereochemical information in the aryl backbone are conceptually compatible with this approach. Thus, the development of enantioselective amination reactions with up to 99% ee was also successful. Several of the active enantioselective reagents have been isolated and structurally characterized. Following this approach for the important class of chiral vicinal diamines, an unprecedented direct diamination of alkenes could be conducted in an enantioselective catalytic manner under full intermolecular reaction control. This latter reaction is based on the precise engineering of a chiral aryliodine(III) catalyst in combination with bismesylimide as nitrogen source. It is the consequence of the precise understanding of the reaction behavior of structurally defined bisimidoiodine(III) reagents.

Extending the Scope of Parahydrogen-Based Hyperpolarization Methods

In this issue of Chem, Zhao et al. present a tailored heterogeneous catalyst in combination with parahydrogen to overcome the sensitivity challenge of water in nuclear magnetic resonance via effective hyperpolarization, paving the way for unprecedented applications in this important and versatile technique.

A novel stiffener skeleton strategy in catalytic carbonization system with enhanced carbon layer structure and improved fire retardancy

Catalyzing carbonization of polymer itself to form a protective carbonaceous layer has been proven to be an effective way to improve polymer's flame retardancy, but there is still a great challenge to achieve synchronous enhancement in traditional test standards (such as LOI and UL-94 testing). In this study, a stiffener skeleton strategy combined with catalyzing carbonization was proposed to improve the flame retardancy of polycarbonate (PC). The synergistic effect of nanosized carbon black (CB)/Ni2O3 on carbon yield and combustion properties of PC were investigated. An improvement with 31.4% in LOI, V0 in UL-94, and 50% reduction for PHRR in cone calorimeter test was achieved. According to char morphology and structure analysis, the flame retardancy mechanism was attributed to the enhanced barrier effect of carbon layer with interconnected structure and self-supporting capacity, which was promoted by the formation of carbon skeleton framework from PC and the catalytic carbonization from combined catalysts.

The sulfation and combination of MnO&amp;lt;sub&amp;gt;&amp;lt;italic&amp;gt;x&amp;lt;/italic&amp;gt;&amp;lt;/sub&amp;gt; and Fe&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt; catalysts forNH&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;-SCR denitration reaction

Firstly, the metal oxide catalysts of MnO x and Fe2O3 were prepared by precipitation method. Thereafter, SO42−/ MnO x and SO42−/Fe2O3 were prepared by acidification with sulfuric acid in the synthesis step. After investigating their activities for selective catalytic reduction of NO x with NH3 (NH3-SCR) in turn, it was found that the denitrification of the sulfating SO42−/MnO x and SO42−/Fe2O3 were greatly improved. The characterization results showed that the introduction of SO42− suppressed the redox activity of MnO x and restrained ammonia oxidative reaction in high temperature; SO42− and Fe2O3 can form solid super acid to greatly improve the acidity of Fe2O3 and in favor of adsorbing and stabilizing alkaline reducing agent. Finally, the denitrification properties of MnO x and Fe2O3 were developed. In this paper, the modified SO42−/MnO x and SO42−/Fe2O3 were combined to form three combined catalysts. After combination, the two catalysts produced a good synergistic effect, exhibited respective advantages at both low temperatures and high temperatures, and displayed wider high activity-temperature window (200–450 °C; NO conversion >90%), lower yield of the by-product and higher nitrogen selectivity. It was also realized that the combining way, which put the high temperature activity SO42−/Fe2O3 in the first half unit and put the low temperature activity SO42−/MnO x in the second half unit could achieve the best denitrification effect with higher N2 yield (>80%, 100–450 °C) . It is effective to optimize the nitrogen selectivity of the manganese-based catalyst and the board activity-temperature window of the iron-based catalyst.

Functional Polyesters with Pendant Double Bonds Prepared by Coordination–Insertion and Cationic Ring-Opening Copolymerizations of ε-Caprolactone with Renewable Tulipalin A

The synthesis of functional copolyesters that contain pendant double bonds in their structures is reported by ring-opening copolymerization of renewable monomer Tulipalin A (α-methylene-γ-butyrolactone, MBL) and e-caprolactone (CL) using either coordination–insertion or monomer activated mechanisms. Aluminum tris(isopropoxide) (Al(OiPr)3) was successfully used as a cheap and commonly available catalyst for the coordination–insertion ring-opening copolymerization, and functional copolyesters with dispersities below 1.2 and with contents of MBL units in the copolymer up to 25 mol % were prepared. In addition, linear or multiarm copolymers of MBL with CL were synthesized by cationic ring-opening copolymerization that was conducted using protic acid as a “metal-free” catalyst in combination with mono- or multihydroxyl alcohols as initiators. The molecular characteristics and composition of the functional copolyesters were determined by GPC, NMR, two-dimensional NMR, and MALDI-TOF spectroscopy. The effect of M...

Express-method for Estimation of Electrocatalytic Activity of Oxide Films toward Oxygen Transfer Reactions

Oxidation catalysis of organic substances has attracted special attention in recent years due to of their high industrial significance in green and energy chemistry. The implementation of a transition metal-based catalyst in combination with oxygen is an alternative to the traditional procedures. This study justifies the application of amperometric response 'in situ' for estimation of the electrocatalytic activity of metal oxide films, which are known to be promising for oxygen transfer processes. The reaction of electrooxidation of Mn2+ ions may be termed as a 'marker' for oxygen transfer reactions due to its kinetic features, such as proportionality between the current density and the surface concentration of •OH-radicals. The relative parameter, kox, has been offered for estimation of the oxidizing capacity of an anode material toward oxygen transfer reaction in reference to platinum oxidizing capacity. kox value is automatically calculated exactly during electroplating of MnOx as a ratio of the current density of Mn2+ + 2H2O – 2e→MnO2+4H+ reaction on the tested surface to the current density of this reaction on Pt surface. The developed method was tested during the investigation of catalytic activity of MnOx films for electrooxidation of glucose. The parameter kox was calculated for other anode materials and was analyzed. The application of the new method allows estimating and comparing the catalytic performance toward oxygen transfer reactions of anode materials or of the same material in different modifications, such as nano particles, composites, different compositions etc. The pre-test reduces manifold the time spent for determination of oxidizing capacity of oxides.

Glycosyloxymethylfurfural (GMF) in Multicomponent Aza-Morita-Baylis-Hillman Reaction: Rapid Access to Highly Functionalized Carbohydrate Scaffolds

Aim and Objective: The use of glycosyloxymethylfurfural (GMF), the dehydration product of isomaltulose, in the one-step multicomponent aza-Morita-Baylis-Hillman (aza-MBH) reaction, was studied. Materials and Methods: The reaction conditions and scope were investigated with respect to solvent, combinations of catalysts (Lewis acids and nucleophilic base), and the nature of the amine and the acrylic partners. Results: The three-components one step aza-MBH reaction using GMF, sulfonamides and a Michael acceptor provides carbohydrate-based a-methylene-b-amino carbonyl derivatives in moderate to good yields. Optimized conditions are the use of La(OTf)3 and 3-HQD in methanol. The use of diphenylphosphinamide, though requiring the use of a protected GMF and a two-step protocol, offers alternatives in the type of activated imine involved the classical sulfonyl substitution. Conclusion: A wide structural range of adducts were obtained in fair to good yields, showing the synthetic efficiency of the strategy able to provide highly functionalized carbohydrate-containing new molecules in an unique step from very available starting materials. These explorations show that GMF can be transformed in very short sequences to rather elaborated new compounds using the MBH and aza-MBH strategy.

Irradiation-Induced Palladium-Catalyzed Direct C–H Alkylation of Heteroarenes with Tertiary and Secondary Alkyl Bromides

A palladium catalyst in combination with two types of phosphine ligands efficiently catalyzes direct C–H alkylation of heteroarenes with secondary and tertiary alkyl bromides under irradiation conditions. Irradiation of blue light-emitting diodes (blue LEDs) effectively excites phosphine-ligated palladium catalyst to facilitate oxidative addition with alkyl bromides, and also excites the alkylpalladium species to enable the generation of alkyl radicals to react with heteroarenes.

Cis-Selective Decarboxylative Alkenylation of Aliphatic Carboxylic Acids with Vinyl Arenes Enabled by Photoredox/Palladium/Uphill Triple Catalysis.

An iridium photoredox catalyst in combination with phenanthroline-supported palladium catalyst catalyzes decarboxylative alkenylation of tertiary and secondary aliphatic carboxylic acids with vinyl arenes to deliver β-alkylated styrenes with Z-selectivity. A broad scope of aliphatic carboxylic acids, including amino acids, exhibit as amenable substrates, and external oxidant is not required. The reaction proceeds by synergistic utilization of both energy-transfer and electron-transfer reactivity of iridium photoredox catalyst merging with palladium-catalyzed hydride elimination and insertion.