Combination Of Catalyst Research Articles

New Type of Catalyst for Efficient Aerobic Oxidative Desulfurization Based On Tungsten Carbide Synthesized by the Microwave Method.

Herein, we present a new type of high-performance catalyst for aerobic oxidation of organosulfur compounds based on tungsten carbide. The synthesis of tungsten carbide was performed via microwave irradiation of the precursors, which makes it possible to obtain a catalyst in just 15 min. The synthesized catalyst was investigated by a variety of physicochemical methods: X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, electron microscopy, and N2 adsorption/desorption. It was shown that active centers containing tungsten in the transition oxidation state (+4) play a key role in the activation of oxygen. The main factors influencing the conversion of dibenzothiophene (DBT) were investigated. It should be noted that 100% conversion of DBT can be achieved under relatively mild conditions: 120 °C, 3 h, 6 bar, and 0.5% wt catalyst. The catalyst retained its activity for at least six oxidation/regeneration cycles. The simplicity and speed of synthesis of the proposed catalyst in combination with its high activity and stability open broad prospects for its further use both for oxidative desulfurization and for other reactions of aerobic oxidation of organic substrates.

Fenton-like degradation of carmine dyes based on artificial intelligence modeling and optimization of reduced graphene oxide loaded iron-cobalt-nickel trimetallic nanocomposites

In this experiment, reduced graphene oxide loaded iron-cobalt-nickel trimetallic nano compounds were prepared by co-precipitation method and coadministered with oxidant hydrogen peroxide to form Fenton-like reagents. The degradation of carmine dye simulated industrial wastewater by this type of fenton catalyst in combination with ultrasound was investigated and it can be identified that ultrasound is synergistic when combined with this type of fenton process. In this experiment, the synthesized nanocomposites were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, fourier transform infrared spectroscopy, raman spectroscopy, N2 adsorption, and superconducting quantum interferometry, and the results demonstrated that the materials have a typical graphite porous structure and excellent magnetic properties. The influences of four factors (V(H2O2), reaction time, initial concentration and catalyst dosage) on the degradation of carmine dye were further analyzed. The experiment was then modeled and optimized with response surfaces and artificial intelligence. Through the comparative analysis of the experimental value and the predicted value, it is found that the absolute error of the artificial neural network-particle swarm optimization model is the smallest, which indicates that the model makes a better prediction of the experimental results. The importance of influencing factors in the dye removal process was ranked according to F-test, random forest and Garson's formula, and it was discovered that V(H2O2) played the most dominant role. Finally, by a simple magnetic separation, the rGO/Fe/Co/Ni trimetallic nano compound was still retained 47% of its catalytic capacity after five consecutive recoveries using this catalyst and applying it to the next degradation experiment, which indicates its excellent reusability and reflects the outstanding degradation ability of this compounds.

Effect of flue gas impurities in carbon dioxide from power plants in the synthesis of isopropyl N-phenylcarbamate from CO2, aniline, and 2-propanol using CeO2 and 2-cyanopyridine

Current CO2 utilization technologies generally start with purification of CO2, which requires considerable energy input. Using CO2-containing flue gases as a feedstock in chemical conversions of CO2 can help simplify pre-treatment of CO2 and reduce the carbon footprint of the process, however, study of the effects of other components in the flue gases in chemical reactions using CO2 is limited. Our previous study demonstrated that the combination catalyst system of CeO2 and 2-cyanopyridine was effective for the reaction of pure CO2, aniline, and 2-propanol to afford isopropyl N-phenylcarbamate, which is a promising precursor for polyurethane, in over 90% yield. In this study, the addition effect of other components in CO2-containing flue gases namely N2, O2, SO2 (ppm-order) and NO2 (ppm-order) on the reaction was investigated. The addition of N2 and NO2 had almost no influence on the catalytic performance, however, that of O2 and SO2 had some negative effects. The addition of O2 decreased the selectivity and yield to the target carbamate due to the formation of aniline-derived byproducts such as aniline-coupling products and aniline-oligomers. The increase of the amount of 2-cyanopyridine and 2-propanol was effective for the suppression of the aniline-derived byproducts, providing a similar yield of the isopropyl N-phenylcarbamate to the case without any additives. The catalyst system was strongly poisoned by addition of SO2, and the activity of CeO2 was not recovered even by calcination treatment.

Air-Tolerant Nickel-Catalyzed Cyanation of (Hetero)aryl Halides Enabled by Polymethylhydrosiloxane, a Green Reductant.

An air-tolerant nickel-catalyzed cyanation of aryl bromides is reported. The reaction uses a NiCl2/Xantphos catalyst in combination with substoichiometric quantities of zinc cyanide and polymethylhydrosiloxane. This silane is a green, homogeneous alternative to the traditional, insoluble solid reductant zinc and renders the reaction tolerant to air. The reaction can be performed under an air atmosphere, obviating the need for degassing, a glovebox, or Schlenk techniques. The reaction scope is broad, proceeding in good yields with a variety of (hetero)arenes.

Aerobic Oxidation of Dihydroxyarenes Substrates Catalyzed by Polymer-Supported RuII-Pheox/Silica-Gel: A Beneficial Route for Purification of Industrial Water

Abstract: A broad class of dihydroxyarenes were easily oxidized by aerobic oxygen to quinone products in excellent yields under the catalytic effect of polymer-supported RuII-Pheox/silica-gel catalyst. By using this combined catalyst, hydroquinone and catechol derivatives with electron-donating groups were easily oxidized by molecular oxygen to quinone products in 90% to >99% yield, while in the case of electron-withdrawing group, only 70% was obtained. The biologically useful 1,4-Naphthoqinone products were obtained in 83% to 90%. The catalyst was easily obtained and reused many times without a significant decrease in reactivity. Interestingly, a sample of industrial water contaminated with phenolic compounds was subjected to aerobic oxidation by using this catalyst, and the resultant quinones were detected within one day and the catalyst was removed and reused several times with different contaminating samples with the same efficiency. Other catalytic oxidations by using this promising catalyst were investigated.

Enantioselective Synthesis of Tertiary β‐Boryl Amides by Conjunctive Cross‐Coupling of Alkenyl Boronates and Carbamoyl Chlorides

Synthesis of versatile β tert-boryl amides is accomplished by conjunctive cross-coupling of α-substituted alkenyl boron “ate” complexes and carbamoyl chloride electrophiles. This reaction can be accomplished in an enantioselective fashion using a palladium catalyst in combination with MandyPhos. The addition of water results in enhanced chemoselectivity for the conjunctive coupling product relative to the Suzuki–Miyaura cross-coupling product. Transformations of the reaction products were examined as well as application to the synthesis of (+)-adalinine.

Enantioselective Synthesis of Tertiary β-Boryl Amides by Conjunctive Cross-Coupling of Alkenyl Boronates and Carbamoyl Chlorides.

Synthesis of versatile β tert-boryl amides is accomplished by conjunctive cross-coupling of α-substituted alkenyl boron "ate" complexes and carbamoyl chloride electrophiles. This reaction can be accomplished in an enantioselective fashion using a palladium catalyst in combination with MandyPhos. The addition of water results in enhanced chemoselectivity for the conjunctive coupling product relative to the Suzuki-Miyaura cross-coupling product. Transformations of the reaction products were examined as well as application to the synthesis of (+)-adalinine.

Bifunctional catalysts with versatile zeolites enable unprecedented para-xylene productivity for syngas conversion under mild conditions

The direct conversion of syngas to aromatics has received considerable attention. The development of a highly active and stable catalyst with tunable selectivity for the synthesis of aromatics remains a great challenge, notwithstanding the understanding of the reaction mechanism. In this study, we fabricated a series of high-performance bifunctional catalysts comprising CoMnAl catalysts, which contain Co 2 C nanoprisms as the active phase, and versatile HZSM-5@silicalite-1 zeolites, with a hollow nanostructure and a scaly shell, for the transformation of syngas into aromatics. The catalysts achieve a CO conversion >70% under mild reaction conditions (280°C, 2 MPa), with ultrahigh stability. The selectivity toward aromatics is higher than 63% with <2.9% selectivity toward CH 4 , and the para -xylene (PX) fraction of the aromatics produced reaches 34.7%, leading to unprecedentedly high space-time yield of PX. Furthermore, the reaction pathway and the intermediates involved in the formation of the aromatic products are also determined. • ZSM-5@silicalite-1 zeolite with a hollow nanostructure and a scaly shell is prepared • CoMnAl/HZSM-5@S1 composite catalyst shows high activity, selectivity, and stability • Versatile HZSM-5 zeolite enables unprecedentedly high yield of para -xylene at 280°C • Oxygen-containing aromatic compounds play a crucial role in aromatics formation The direct transformation of syngas to aromatics, especially para -xylene (PX), has received considerable attention and can be achieved using tandem catalysts through methanol or olefin intermediates. However, it remains a great challenge to develop efficient catalysts with high catalytic activity, selectivity, and stability. We fabricated nanosized HZSM-5 with a hollow structure to enhance the diffusion of the intermediates and products, improving both the CO conversion and the aromatic selectivity. The addition of a scaly silicalite-1 layer grown epitaxially on the HZSM-5 crystals effectively inhibits side reactions from occurring without affecting the diffusion property of the zeolites; thus, the conversion of syngas to PX is improved, and catalyst shows ultrahigh stability. In addition to the development of a high-performing catalyst with industrial application potential, this work significantly improves our understanding of the complex reaction network of syngas to aromatics. To develop a highly active and stable catalyst with tunable selectivity for syngas to aromatics, especially para -xylene, versatile zeolites with a hollow nanostructure and a scaly shell were fabricated and combined with CoMnAl catalysts, with Co carbide nanoprisms as the active phase. The combined catalyst exhibited ultrahigh catalytic activity, selectivity, and stability under mild reaction conditions. Oxygen-containing aromatic compounds produced through the coupling of CO with olefins or higher oxygenates play a crucial role in the formation of aromatics.

Engineering Catalyst-Electrolyte Microenvironments to Optimize the Activity and Selectivity for the Electrochemical Reduction of CO2 on Cu and Ag.

The electrochemical reduction of carbon dioxide (CO2R) driven by renewably generated electricity (e.g., solar and wind) offers a promising means for reusing the CO2 released during the production of cement, steel, and aluminum as well as the production of ammonia and methanol. If CO2 could be removed from the atmosphere at acceptable costs (i.e., <$100/t of CO2), then CO2R could be used to produce carbon-containing chemicals and fuels in a fully sustainable manner. Economic considerations dictate that CO2R current densities must be in the range of 0.1 to 1 A/cm2 and selectivity toward the targeted product must be high in order to minimize separation costs. Industrially relevant operating conditions can be achieved by using gas diffusion electrodes (GDEs) to maximize the transport of species to and from the cathode and combining such electrodes with a solid-electrolyte membrane by eliminating the ohmic losses associated with liquid electrolytes. Additionally, high product selectivity can be attained by careful tuning of the microenvironment near the catalyst surface (e.g., the pH, the concentrations of CO2 and H2O, and the identities of the cations in the double layer adjacent to the catalyst surface).We begin this Account with a discussion of our experimental and theoretical work aimed at optimizing catalyst microenvironments for CO2R. We first examine the effects of catalyst morphology on the production of multicarbon (C2+) products over Cu-based catalysts and then explore the role of mass transfer combined with the kinetics of buffer reactions in the local concentration of CO2 and pH at the catalyst surface. This is followed by a discussion of the dependence of the local CO2 concentration and pH on the dynamics of CO2R and the formation of specific products over both Cu and Ag catalysts. Next, we explore the impact of electrolyte cation identity on the rate of CO2R and the distribution of products. Subsequently, we look at utilizing pulsed electrolysis to tune the local pH and CO2 concentration at the catalyst surface. The last part of the discussion demonstrates that ionomer-coated catalysts in combination with pulsed electrolysis can enable the attainment of very high (>90%) selectivity to C2+ products over Cu in an aqueous electrolyte. This part of the Account is then extended to consider the difference in the catalyst-nanoparticle microenvironment, present in the catalyst layer of a membrane electrode assembly (MEA), with respect to that of a planar electrode immersed in an aqueous electrolyte.

Polyethylene glycol-based RAFT agent cum ATRP macroinitiator initiated block copolymerization of methyl methacrylate

PMMA-b-PEG-b-PMMA block copolymer has been synthesized by the activators regenerated by electron transfer atom transfer radical polymerization (ARGET-ATRP) of methyl methacrylate (MMA) using modified polyethylene glycol (PEG) as initiator. PEG is chemically modified by CS2 followed by an esterification to incorporate initiating sites for ATRP as well as for RAFT polymerization. The prepared macroinitiator has been characterized by FT-IR and NMR analyses for its structural validation. FT-IR and NMR analyses confirmed the successful synthesis of the macro initiator. This macro initiator has been used to prepare ABA type triblock copolymer with MMA via ARGET-ATRP. The polymerization reaction is carried out using cupric bromide (CuBr2) as catalyst in combination with N,N,N′,N″,N″-pentamethyl diethylenetriamine (PMDETA) as ligand in N, N dimethyl formamide (DMF) at 70C. Ascorbic acid is used as reducing agent. The conversion of the monomer was calculated gravimetrically. The successful preparation of the block copolymer is confirmed by FT-IR, 1H NMR and 13C NMR analyses. The MALDI-TOF mass analysis of the block copolymers also confirm the presence of monomer MMA, dithionate and PEG parts in the block copolymer. The purified block copolymer is analyzed by TGA, and SEM analyses. TGA analysis shows that the prepared block copolymer has better (Tmax = 366C) thermal stability than the PMMA (Tmax = 349C) homopolymer.

NbCl5+AgClO4 AS A VERSATILE COMBINED CATALYST SYSTEM FOR AN ACCELERATED SYNTHESIS OF 1, 4- DIHYDROPYRIDINE SCAFFOLDS

Herein presented work describes the catalytic potential of NbCl5+AgClO4 as a combined and convenient catalyst system for a straightforward, safe, quick, and single-pot synthesis of 1, 4-dihydropyridine (DHP) scaffolds. It was investigated that a small amount of NbCl5+AgClO4 is sufficient and potential enough to bring out the solvent-free synthesis of 1, 4-dihydropyridine scaffolds from a three-components, the cyclic reaction between substituted aldehyde(s), ethyl-3-oxobutanoate, and ammonium ethanoate. It is noteworthy to mention that good to excellent yields of DHPs were achieved by developing an environmentally compatible, sustainable, mild, and simple synthetic protocol. A range of differently substituted aldehydes was observed to undergo herein developed catalytic protocol smoothly to offer good yields of DHPs in 3 to 5 h at room temperature. Representative DHPs are characterized by adequate analytical techniques such as FTIR, 1HNMR, 13CNMR, and mass spectrometric techniques

Alcoholysis kinetics and mechanism studies of ethyl levulinate production from ball milled corn stover.

Alcoholysis of ball-milled biomass over catalysts with Brønsted and Lewis acid sites provides an efficient and sustainable scheme to produce versatile biobased chemicals under mild conditions; however, optimizing the process parameters is challenged by the complexity of reaction pathways and the multiplicity of ball milling and combination catalyst gains. To address these challenges, we present kinetic analysis of ethyl levulinate (EL) production from ball-milled corn stover catalyzed by Brønsted (B) acidic ionic liquid [Bmim-SO3H][HSO4] (SO3H-IL) and Lewis (L) acidic Al2(SO4)3. Product analysis shows that cellulosic substrates can form EL either through the intermediate ethyl-d-glycopyranoside (EDGP) or levoglucosenone (LGO), with the former leading the alcoholysis reaction. Kinetics results reveal that ball milling accelerates the reaction rate by promoting the formation of EDGP and LGO from cellulose. Pure SO3H-IL gives high selectivity towards EDGP from ball-milled corn stover and promotes the LGO production, whereas addition of Al2(SO4)3 substantially facilitates their further conversion to EL. Our findings contribute to the rational design of efficient catalytic strategies for sustainable and profitable biorefinery.

Solar-driven aromatic aldehydes: green production from mandelic acid derivatives by a Co(ii)/C3N4 combined catalyst in aqueous media.

According to the requirements for sustainable development, reclaiming fine chemicals from wastewater under mild conditions is an extremely significant line of research. A low-cost and high-efficiency polydentate chelate- and polymeric Co(ii)-based complex (Co-L)-loaded C3N4 photocatalyst (Co-L/C3N4) was constructed and used to convert aromatic mandelic acids in wastewater at room temperature. The BET specific surface area increased from 28 m2 g−1 to 68 m2 g−1, indicating its excellent absorptive character. The light absorption range of Co-L/C3N4 reached 650 nm, while the band energy reduced to 2.30 eV, which caused a significant enhancement in photocatalytic activity. The conversion of substituted mandelic acids was more than 90% due to the photoactivity of Co-L/C3N4. Time-resolved PL spectra indicated the remarkable separation of the photogenerated electron–hole pairs in Co-L/C3N4. Furthermore, the UV-vis and in situ FTIR spectra indicated the formation of aldehyde groups in the selective oxidation process, which provided support for the plausible catalytic mechanism.

9-BBN and chloride catalyzed reduction of chlorophosphines to phosphines and diphosphines.

The commercially available Lewis acid, 9-BBN and Lewis basic [Et4N]Cl are used as catalysts for the reduction of chlorophosphines R2PCl in the presence of phenylsilane. Aryl-chlorophosphines afford primarily diphosphines (P2R4) while secondary phosphines predominate for alkyl-substituted precursors. Use of the combined catalysts leads to reduced reaction time and temperature, providing a rapid, scalable, and facile protocol for the preparation of diphosphines or secondary phosphines.

Bronsted acidic surfactants: efficient organocatalysts for diverse organic transformations

Abstract Organic transformations using efficient, atom-economical, cost-effective and environmentally benign strategies for the construction of diversified molecules have attracted synthetic chemists worldwide in recent years. These processes often minimize the waste production and avoid the use of hazardous flammable organic solvents. Among various green protocols, the procedures using surfactant-based catalytic systems have received a considerable attention in organic synthesis. In this context, Bronsted acidic surfactants have emerged as efficient catalysts for various C–C, C–O, C–N and C–S bond forming reactions. Many of these reactions occur in water, as Bronsted acidic surfactants have a unique ability of creating hydrophobic pocket through micelle formation in aqueous medium and the substrate molecules react efficiently to afford the targeted products in good yields. In the past, Bronsted acidic surfactant combined catalysts successfully displayed their potential to accelerate the reaction rates of diverse organic transformations. This chapter presents a complete overview on Bronsted acidic surfactants catalyzed organic reactions to construct a variety of aromatic and heteroaromatic molecular frameworks.

Organophotoredox Catalyzed Stereoselective Nitration of Olefins with tert‐Butyl Nitrite under Air

AbstractAn efficient method for the E‐selective synthesis of nitroolefins is developed by employing DDQ as the organophotoredox catalyst in combination with tert‐BuONO (TBN) as a nitrating agent under visible‐light irradiation. This green transition metal‐free approach utilizes aerial oxygen as the terminal oxidant and occurs at room temperature. Following the established protocol, 41 different olefines containing broad diversity of substituents were nitrated in good to excellent yields. Mechanistic experiments and photophysical studies revealed the probable mechanism.

Synthesis of a Magnetic Co@C Material via the Design of a MOF Precursor for Efficient and Selective Adsorption of Water Pollutants

3D metal–organic frameworks (MOFs) can be appropriate templates for the fabrication of nanomaterials due to they have active sites exposed on the channel or surface, which thus provide them with improved catalytic performance. In this study, a 3D cobalt-based MOF [Co(H2bpta)]n (Co-MOF), where H4bpta denotes 2,2′,4,4′-biphenyltetracarboxylic acid, has been constructed with the use of a ligand with a high carbon content. On this basis, a 2D magnetic carbon-coated cobalt nanoparticle composite (Co@C) was prepared by using the title MOF under different temperatures. Magnetic Co@C can readily absorb dye from the solution and can thus act as an inexpensive and fast-acting adsorbent. Moreover, we have explored the adsorption isotherms, kinetics and thermodynamics of the anion dyes in detail. The adsorption capacity of the Co@C-800 for investigated methyl orange (MO) and congo red (CR) dyes were 773.48 and 495.66 mg g−1, respectively. It is noteworthy that MO adsorption is higher in existing materials. Thermodynamic studies suggest that the adsorption processes are spontaneous and exothermic. This study opens a new insight into the synthesis and application of carbon-based materials that enable the selective removal of organic dyes.Graphical AbstractA Co-MOF has been solvothermal synthesized and structurally characterized, which was used as a combined catalyst and carbon source for the synthesis of magnetic Co@C. Interestingly, the as-grown Co@C-800 exhibits high-performance selective adsorption of anionic dyes (MO and CR) with high adsorption capacities.

Conversion of glucose to 5-hydroxymethyl furfural in water-acetonitrile-dimethyl sulfoxide solvent with aluminum on activated carbon and maleic acid

The development of sustainable, efficient routes for conversion of glucose in biomass to 5-hydroxymethylfurfural (HMF), an important green intermediate in the production of value-added chemicals and fuels, has emerged due to the need to replace depletion of non-renewable fossil sources and climate change caused by their use. In this study, we describe a highly efficient reaction system for the production of HMF with a combination of homogeneous catalyst and heterogeneous catalyst in a polar cosolvent. The catalyst system consists of activated carbon (AC) supported aluminum (AC-Al) and maleic acid (MA) dissolved in a mixture of water, acetonitrile (ACN) and dimethyl sulfoxide (DMSO). Kinetic analysis of HMF production from glucose shows that carbon supported aluminum catalyst in combination with homogeneous maleic acid favored fructose dehydration to HMF instead of the formation of insoluble humins when compared to dissolved aluminum chloride and maleic acid in the same solvent. In addition, the rate constant of HMF hydrolysis to levulinic and formic acid was lower for AC-Al compared to dissolved Al. Response surface methodology (RSM), with central composite rotatable design (CCRD), identified the optimum conditions for glucose conversion to HMF as 168 °C for 11 min with a predicted molar yield of 50.3 mol%, which compared well to the experimentally verified yield of 45.8 mol% for these reaction conditions. To test the influence of glucose concentration on HMF yield, a range of initial glucose concentrations were examined. Results showed that the HMF yield increased with the decrease of weight percentage of glucose, suggesting that second order reactions result in humins formation.

NO reduction by semi-coke and tailing combined catalyst

The combined catalyst of semi-coke and tailing were used to study the NO reduction rate and CO production in the laboratory fixed-bed reactor. The experimental results indicate that the combined denitration method of semi-coke and tailing has significantly better NO conversion rate, CO production, and N2 selectivity than denitration of semi-coke alone. The increase in reaction temperature and the introduction of O2, CO2, and SO2 increased the effect of the combined coke-tailing catalytic denitration to varying degrees. The combined catalytic denitration effect of semi-coke and magnetic separation tailing was superior to the combined catalytic denitration effect of semi-coke and rare-earth tailing.

Ni-hydrotalcite loading on carbon as co-catalyst for fermentative hydrogen production

The influence of Ni-hydrotalcite (HT) loading on the activity and stability of Ni-HT supported on activated carbon (Ni-HT/AC) was investigated for fermentative hydrogen production. The basic sites of Ni-HT loading on AC support significantly boosted the catalytic performance with the initial faster rate. The combined function catalyst of Ni-HT/AC facilitates the rapid decomposition of saccharides and high selectivity to fructose that attained the maximum hydrogen production within 24 h. The optimum dose of Ni-HT/AC at 8.33 g/L showed a 25.84% increment over the control. In addition, shortening the lagging phase time at 1.50 h was achieved. The high adsorption capacity of lactic acid was induced with the basic sites of Ni-HT/AC. However, a deactivation of the Ni-HT/AC during prolonged fermentation was associated with metabolites formation, causing the leaching of Mg2+ ions from the surface of AC supported Ni-HT and reducing surface basicity of Ni-HT/AC.