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Open AccessEditorial

The Merit and the Context of Hydrogen Production from Water and Its Effect on Global CO₂ Emission

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Hicham Idriss

Catalysts 2022, 12(2), 231; https://doi.org/10.3390/catal12020231 - 18 Feb 2022

Viewed by 1451

Abstract

For a green economy to be possible in the near future, hydrogen production from water is a sought-after alternative to fossil fuels [...] Full article

(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members (EBMs) of Catalysts)

Research

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Open AccessCommunication

Depolymerization of Polyesters by Transesterification with Ethanol Using (Cyclopentadienyl)titanium Trichlorides

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Yuriko Ohki

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Yohei Ogiwara

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Kotohiro Nomura

Catalysts 2023, 13(2), 421; https://doi.org/10.3390/catal13020421 - 16 Feb 2023

Cited by 2 | Viewed by 1515

Abstract

Exclusive chemical conversions of polyesters [poly(ethylene adipate) (PEA), poly(butylene adipate) (PBA), poly(ethylene terephthalate) (PET), poly(butylene terephthalate) (PBT)] to the corresponding monomers (diethyl adipate, diethyl terephthalate, ethylene glycol, 1,4-butane diol) by transesterification with ethanol using Cp’TiCl₃ (Cp’ = Cp, Cp*) catalyst have been [...] Read more.

Exclusive chemical conversions of polyesters [poly(ethylene adipate) (PEA), poly(butylene adipate) (PBA), poly(ethylene terephthalate) (PET), poly(butylene terephthalate) (PBT)] to the corresponding monomers (diethyl adipate, diethyl terephthalate, ethylene glycol, 1,4-butane diol) by transesterification with ethanol using Cp’TiCl₃ (Cp’ = Cp, Cp*) catalyst have been demonstrated. The present acid-base-free depolymerizations by Cp’TiCl₃ exhibited completed conversions (>99%) of PET, PBT to afford diethyl terephthalate and ethylene glycol or 1,4-butane diol exclusively (selectivity >99%) without formation of any other by-products in the NMR spectra (150–170 °C, Ti 1.0, or 2.0 mol%). The resultant reaction mixture after the depolymerization of PBA with ethanol via the CpTiCl₃ catalyst (1.0 mol%, 150 °C, 3 h), consisting of diethyl adipate and 1,4-butane diol, was heated at 150 °C in vacuo for 24 h to afford high molecular weight recycled PBA with unimodal molecular weight distribution (M_n = 11,800, M_w/M_n = 1.6), strongly demonstrating a possibility of one-pot (acid-base-free) closed-loop chemical recycling. Full article

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Cobalt-Copper Oxide Catalysts for VOC Abatement: Effect of Co:Cu Ratio on Performance in Ethanol Oxidation

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Jean-Francois Lamonier

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Jaroslav Maixner

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František Kovanda

Catalysts 2023, 13(1), 107; https://doi.org/10.3390/catal13010107 - 03 Jan 2023

Cited by 4 | Viewed by 1227

Abstract

The effect of the Co-Cu oxide catalysts composition on their physicochemical properties and performance in the deep oxidation of ethanol was studied. The catalysts with Co:Cu molar ratios of 4:1, 1:1, and 1:4 were obtained by calcination (4 h at 500 °C in [...] Read more.

The effect of the Co-Cu oxide catalysts composition on their physicochemical properties and performance in the deep oxidation of ethanol was studied. The catalysts with Co:Cu molar ratios of 4:1, 1:1, and 1:4 were obtained by calcination (4 h at 500 °C in air) of the coprecipitated precursors and characterized in detail using powder XRD, Raman spectroscopy, N₂ physisorption, H₂-TPR, and XPS. The powder XRD and Raman spectroscopy indicated the formation of Co₃O₄ and CuO mixtures rather than Co-Cu mixed oxides. The CuO promoted the Co₃O₄ reduction; the Co-Cu catalysts were reduced more easily than the single-component Co and Cu oxides and the main reduction maxima were shifted to lower temperatures with increasing cobalt content in the catalysts. The Co-Cu oxide catalyst with a Co:Cu molar ratio of 4:1 exhibited the best performance in ethanol gas-phase oxidation, showing the lowest T₅₀ (91 °C) and T₉₀(CO₂) (159 °C) temperatures needed for 50% ethanol conversion and 90% conversion to CO₂, respectively. The excellent catalytic properties of this Co-Cu oxide catalyst were ascribed to the synergistic effect of Co and Cu components. The high activity and selectivity of the Co-Cu catalyst was attributed to the presence of finely dispersed CuO particles on the surface of Co₃O₄. Full article

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Open AccessArticle

Interface Engineering of SRu-mC₃N₄ Heterostructures for Enhanced Electrochemical Hydrazine Oxidation Reactions

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Catalysts 2022, 12(12), 1560; https://doi.org/10.3390/catal12121560 - 02 Dec 2022

Cited by 2 | Viewed by 1097

Abstract

Hydrazine oxidation in single-atom catalysts (SACs) could exploit the efficiency of metal atom utilization, which is a substitution for noble metal-based electrolysers that results in reduced overall cost. A well-established ruthenium single atom over mesoporous carbon nitride (SRu-mC₃N₄) catalyst [...] Read more.

Hydrazine oxidation in single-atom catalysts (SACs) could exploit the efficiency of metal atom utilization, which is a substitution for noble metal-based electrolysers that results in reduced overall cost. A well-established ruthenium single atom over mesoporous carbon nitride (SRu-mC₃N₄) catalyst is explored for the electro-oxidation of hydrazine as one of the model reactions for direct fuel cell reactions. The electrochemical activity observed with linear sweep voltammetry (LSV) confirmed that SRu-mC₃N₄ shows an ultra-low onset potential of 0.88 V vs. RHE, and with a current density of 10 mA/cm² the observed potential was 1.19 V vs. RHE, compared with mesoporous carbon nitride (mC₃N₄) (1.77 V vs. RHE). Electrochemical impedance spectroscopy (EIS) and chronoamperometry (i-t) studies on SRu-mC₃N₄ show a smaller charge-transfer resistance (R_Ct) of 2950 Ω and long-term potential, as well as current stability of 50 h and 20 mA/cm², respectively. Herein, an efficient and enhanced activity toward HzOR was demonstrated on SRu-mC₃N₄ from its synergistic platform over highly porous C₃N₄, possessing large and independent active sites, and improving the subsequent large-scale reaction. Full article

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Open AccessArticle

Bioenergy Generation and Wastewater Purification with Li_0.95Ta_0.76Nb_0.19Mg_0.15O₃ as New Air-Photocathode for MFCs

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Leonarda Francesca Liotta

Catalysts 2022, 12(11), 1424; https://doi.org/10.3390/catal12111424 - 13 Nov 2022

Cited by 1 | Viewed by 880

Abstract

MFC is a promising technology that can be used for simultaneous electricity generation and wastewater treatment. Power energy generation of a ferroelectric cathodic ceramic, Li_0.95Ta_0.76Nb_0.19Mg_0.15O₃ (LTNMg), has been measured in microbial fuel cells, integrating [...] Read more.

MFC is a promising technology that can be used for simultaneous electricity generation and wastewater treatment. Power energy generation of a ferroelectric cathodic ceramic, Li_0.95Ta_0.76Nb_0.19Mg_0.15O₃ (LTNMg), has been measured in microbial fuel cells, integrating a single chamber fed by industrial wastewater (COD_initial = 471 mg L⁻¹, and pH_initial = 7.24 at T = 27 °C). In this process, the mixed multicomponent oxide material has been prepared and characterized by XRD, PSD, TEM, and UV-Vis spectroscopy. The catalytic activity has been investigated by COD determination, analysis of heavy metals, and polarization measurement. The results show a high COD reduction efficiency, which reaches 95.70% after a working time of 168 h with a maximal power density of 228 mW m⁻². In addition, the maximum value of generated voltage in the open-circuit potential (OCP) of this MFC configuration has been increased from 340 mV in the absence of a light source to 470 mV under irradiation, indicating the presence of a promoting photocatalytic effect of LTNMg, which improved the process of the cathodic electron transfer inside the MFC device. Full article

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Facile Preparation and Promising Hydrothermal Stability of Spherical γ-Alumina Support with High Specific Surface Area

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Catalysts 2022, 12(11), 1416; https://doi.org/10.3390/catal12111416 - 11 Nov 2022

Viewed by 904

Abstract

It is of great importance to develop a spherical γ-alumina support with high hydrothermal stability to be used in platinum reforming catalyst processes. The porous pseudo-boehmite powder with a high surface area was first synthesized via a simple separate nucleation and aging steps [...] Read more.

It is of great importance to develop a spherical γ-alumina support with high hydrothermal stability to be used in platinum reforming catalyst processes. The porous pseudo-boehmite powder with a high surface area was first synthesized via a simple separate nucleation and aging steps method, and was then used as a precursor to produce a spherical γ-Al₂O₃ support via an oil–ammonia column method. The as-synthesized pseudo-boehmite has a substantially greater specific surface area of 336.0 m²·g⁻¹ in comparison with the commercial Sasol boehmite powder (293.0 m²·g⁻¹) from Sasol Chemicals. In addition, the as-prepared spherical γ-Al₂O₃ support derived from the as-synthesized pseudo-boehmite also possesses a higher specific surface area of 280.0 m²·g⁻¹ compared to the corresponding Sasol sample. Moreover, the as-prepared spherical γ-Al₂O₃ balls demonstrate a much higher specific surface area of 185.0 m²·g⁻¹ compared with the Sasol sample of 142.0 m²·g⁻¹ after hydrothermal tests at 600 °C, suggesting its promising application in the chemical industry. Full article

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A Study of Support Effects for the Water-Gas-Shift Reaction over Cu

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Catalysts 2022, 12(11), 1364; https://doi.org/10.3390/catal12111364 - 04 Nov 2022

Cited by 1 | Viewed by 1017

Abstract

The water–gas-shift (WGS) reaction was studied on a series of supported Cu catalysts in which the MgAl₂O₄ (MAO) support was modified by depositing ZnO, CeO₂, Mn₂O₃ and CoO using Atomic Layer Deposition (ALD). Addition of [...] Read more.

The water–gas-shift (WGS) reaction was studied on a series of supported Cu catalysts in which the MgAl₂O₄ (MAO) support was modified by depositing ZnO, CeO₂, Mn₂O₃ and CoO using Atomic Layer Deposition (ALD). Addition of Cu by one ALD cycle gave rise to catalysts with nominally 1-wt% Cu. A 1.1-wt% Cu/MAO catalyst prepared by ALD exhibited twice the dispersion but ten times the WGS activity of a 1-wt% Cu/MAO catalyst prepared by impregnation, implying that the reaction is structure sensitive. However, Cu catalysts prepared with the ZnO, CeO₂, and Mn₂O₃ films showed negligible differences from that of the Cu/MAO catalyst, implying that these oxides did not promote the reaction. Cu catalysts prepared on the CoO film showed a slightly lower activity, possibly due to alloy formation. The implications of these results for the development of better WGS catalysts is discussed. Full article

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Efficient Removal of Organic Dye from Aqueous Solution Using Hierarchical Zeolite-Based Biomembrane: Isotherm, Kinetics, Thermodynamics and Recycling Studies

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Jyotishkumar Parameswaranpillai

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Bishweshwar Pant

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Suchart Siengchin

Catalysts 2022, 12(8), 886; https://doi.org/10.3390/catal12080886 - 12 Aug 2022

Cited by 5 | Viewed by 1658

Abstract

Bio adsorbents have received tremendous attention due to their eco-friendly, cheap and non-toxic nature. Recently, bio-adsorbent-based membranes have been frequently employed for water treatment. The work reports the preparation of a novel adsorbent membrane from hierarchical zeolite, polyvinyl alcohol, carboxymethyl cellulose and agar. [...] Read more.

Bio adsorbents have received tremendous attention due to their eco-friendly, cheap and non-toxic nature. Recently, bio-adsorbent-based membranes have been frequently employed for water treatment. The work reports the preparation of a novel adsorbent membrane from hierarchical zeolite, polyvinyl alcohol, carboxymethyl cellulose and agar. The fabricated membrane was characterized spectroscopically and microscopically with several techniques such as XRD, UTM, TGA, optical microscopy and FT-IR, as well as contact-angle studies. The result showed that the hierarchical-zeolite-loaded membrane is superior in terms of thermal stability, mechanical properties and surface roughness. The fabricated membrane was investigated for its efficiency in the removal of Congo red dye in aqueous conditions. The influence of pH, temperature, contact period and the initial concentration of dye and zeolite loading on the adsorption process are also explored. The adsorption results highlighted the maximum sorption property of Congo red on agar/zeolite/carboxymethyl cellulose/polymer biomembrane was found to be higher (15.30 mg/g) than that of zeolite powder (6.4 mg/g). The adsorption isotherms and kinetic parameters were investigated via Langmuir, Freundlich and pseudo-first order, pseudo-second order and the intraparticle diffusion model, respectively. The adsorption isotherms fitted well for both considered isotherms, whereas pseudo-second order fitted well for kinetics. The thermodynamic parameter, ΔG at 303 K, 313 K and 323 K was −9.12, −3.16 and −0.49 KJ/mol, respectively. The work further explores the antibacterial efficacy of the prepared membrane and its reusability. Full article

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Open AccessCommunication

Iridium(triNHC)-Catalyzed Transfer Hydrogenation of Glycerol Carbonate without Exogenous Reductants

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Catalysts 2022, 12(6), 656; https://doi.org/10.3390/catal12060656 - 15 Jun 2022

Cited by 2 | Viewed by 1437

Abstract

The iridium(Ir) (triNHC = tri-N-heterocyclic carbene)-catalyzed transfer hydrogenation of glycerol carbonate (GC) is described in the absence of additional hydride sources. The described reduction provides a sustainable route to produce industrially-valuable formate and lactate with high turnover numbers (TONs). The bimetallic [...] Read more.

The iridium(Ir) (triNHC = tri-N-heterocyclic carbene)-catalyzed transfer hydrogenation of glycerol carbonate (GC) is described in the absence of additional hydride sources. The described reduction provides a sustainable route to produce industrially-valuable formate and lactate with high turnover numbers (TONs). The bimetallic Ir(I) involving triNHC carbene ligands exhibits high TONs, and the reaction mechanism, including the bimetallic Ir(triNHC) catalyst, is proposed based on mechanistic studies. Full article

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Partial Hydrogenation of Soybean and Waste Cooking Oil Biodiesel over Recyclable-Polymer-Supported Pd and Ni Nanoparticles

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Maria Michela Dell’Anna

Catalysts 2022, 12(5), 506; https://doi.org/10.3390/catal12050506 - 30 Apr 2022

Cited by 2 | Viewed by 1658

Abstract

Biodiesel obtained through the transesterification in methanol of vegetable oils, such as soybean oil (SO) and waste cooking oil (WCO), cannot be used as a biofuel for automotive applications due to the presence of polyunsaturated fatty esters, which have a detrimental effect on [...] Read more.

Biodiesel obtained through the transesterification in methanol of vegetable oils, such as soybean oil (SO) and waste cooking oil (WCO), cannot be used as a biofuel for automotive applications due to the presence of polyunsaturated fatty esters, which have a detrimental effect on oxidation stability (OS). A method of upgrading this material is the catalytic partial hydrogenation of the fatty acid methyl ester (FAME) mixture. The target molecule of the partial hydrogenation reaction is monounsaturated methyl oleate (C18:1), which represents a good compromise between OS and the cold filter plugging point (CFPP) value, which becomes too high if the biodiesel consists of unsaturated fatty esters only. In the present work, polymer-supported palladium (Pd-pol) and nickel (Ni-pol) nanoparticles were separately tested as catalysts for upgrading SO and WCO biodiesels under mild conditions (room temperature for Pd-pol and T = 100 °C for Ni-pol) using dihydrogen (p = 10 bar) as the reductant. Both catalysts were obtained through co-polymerization of the metal containing monomer M(AAEMA)₂ (M = Pd, Ni; AEEMA⁻ = deprotonated form of 2-(acetoacetoxy)ethyl methacrylate)) with co-monomers (ethyl methacrylate for Pd and N,N-dimethylacrilamide for Ni) and cross-linkers (ethylene glycol dimethacrylate for Pd and N,N’-methylene bis-acrylamide for Ni), followed by reduction. The Pd-pol system became very active in the hydrogenation of C=C double bonds, but poorly selective towards the desirable C18:1 product. The Ni-pol catalyst was less active than Pd-pol, but very selective towards the mono-unsaturated product. Recyclability tests demonstrated that the Ni-based system retained its activity and selectivity with both the SO and WCO substrates for at least five subsequent runs, thus representing an opportunity for waste biomass valorization. Full article

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Dimethyl Ether Hydrolysis over WO₃/γ-Al₂O₃ Supported Catalysts

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Maria Smyrnioti

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Theophilos Ioannides

Catalysts 2022, 12(4), 396; https://doi.org/10.3390/catal12040396 - 01 Apr 2022

Cited by 7 | Viewed by 1871

Abstract

Dimethyl ether (DME) is considered an alternative hydrogen carrier with potential use in fuel cells and automotive and domestic applications. Dimethyl ether hydrolysis to methanol is a thermodynamically limited reaction catalyzed by solid-acid catalysts, mainly Al₂O₃ and zeolites. Moreover, it [...] Read more.

Dimethyl ether (DME) is considered an alternative hydrogen carrier with potential use in fuel cells and automotive and domestic applications. Dimethyl ether hydrolysis to methanol is a thermodynamically limited reaction catalyzed by solid-acid catalysts, mainly Al₂O₃ and zeolites. Moreover, it is the rate-limiting step of the DME steam reforming reaction, which is employed for the production of hydrogen fuel for fuel cell feeding. In the present study, the performance of WO₃/Al₂O₃ catalysts (0–44% wt. WO₃) was tested in DME hydrolysis reaction. The catalysts were characterized by means of N₂-physisorption, XRD, Raman spectroscopy, XPS, NH₃-TPD and 2,6-di-tert-butylpyridine adsorption experiments. The reaction rate of DME hydrolysis exhibited a volcanic trend as a function of tungsten surface density, while the best-performing catalyst was 37WO₃/Al₂O₃, with a tungsten surface density of 7.4 W/nm², noting that the theoretical monolayer coverage for the specific system is 4–5 W/nm². Brønsted acidity was directly associated with the catalytic activity, following the same volcanic trend as a function of tungsten surface density. Blocking of Brønsted acid sites with 2,6-di-tert-butylpyridine led to a dramatic decrease in hydrolysis rates by 40 times, proving that Brønsted acid sites are primarily responsible for the catalytic activity. Thus, the type and strength rather than the concentration of acid sites are the key factors influencing the catalytic activity. Full article

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Lignin as a Bio-Sourced Secondary Template for ZSM-5 Zeolite Synthesis

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Camila Gomes Flores

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Helena Schneider

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Benoit Louis

Catalysts 2022, 12(4), 368; https://doi.org/10.3390/catal12040368 - 24 Mar 2022

Viewed by 1590

Abstract

The aim of this study was to investigate the effect of the addition of lignin as a sacrificial agent in ZSM-5 zeolite synthesis. Peculiar growths of ZSM-5 crystals leading to various textural properties were observed. Hence, the behavior in acid-catalyzed conversion of methanol [...] Read more.

The aim of this study was to investigate the effect of the addition of lignin as a sacrificial agent in ZSM-5 zeolite synthesis. Peculiar growths of ZSM-5 crystals leading to various textural properties were observed. Hence, the behavior in acid-catalyzed conversion of methanol into hydrocarbons (MTH) shifted from high selectivity toward olefins (>55%) to the sole formation of dimethyl ether (DME). Lignin acted as a bio-sourced secondary template (BSST), impacting the zeolite crystals’ shape and, thus, their physicochemical properties. Full article

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Open AccessArticle

Efficient Synthesis of Dihydropyrimidines Using a Highly Ordered Mesoporous Functionalized Pyridinium Organosilica

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Catalysts 2022, 12(3), 350; https://doi.org/10.3390/catal12030350 - 21 Mar 2022

Cited by 1 | Viewed by 2344 | Correction

Abstract

A Brönsted acidic ionic solid pyridinium-functionalized organosilica network (PMO-Py-IL) was demonstrated to efficiently catalyse one-pot Biginelli condensation reaction. The green synthesis of 3,4-dihydro-2(H)-pyrimidinones (DHPMs) with high yield was carried out via one-pot three component condensation of β- dicarbonyls, aldehydes, and urea in the [...] Read more.

A Brönsted acidic ionic solid pyridinium-functionalized organosilica network (PMO-Py-IL) was demonstrated to efficiently catalyse one-pot Biginelli condensation reaction. The green synthesis of 3,4-dihydro-2(H)-pyrimidinones (DHPMs) with high yield was carried out via one-pot three component condensation of β- dicarbonyls, aldehydes, and urea in the presence of a catalytic amount of PMO-Py-IL nanomaterial as an efficient nanocatalyst under solvent free conditions. Furthermore, the catalyst showed outstanding stability and could be easily separated and reused for at least ten reaction runs without significant loss of activity and product selectivity. The green protocol features simple set-up, cost-effectiveness, easy work-up, eco-friendly and mild reaction conditions. Full article

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Polyaromatic Carboxylate Ligands Based Zn(II) Coordination Polymers for Ultrasound-Assisted One-Pot Tandem Deacetalization–Knoevenagel Reactions

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Anirban Karmakar

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Mohamed M. A. Soliman

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Elisabete C. B. A. Alegria

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Maria Fátima C. Guedes da Silva

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Armando J. L. Pombeiro

Catalysts 2022, 12(3), 294; https://doi.org/10.3390/catal12030294 - 04 Mar 2022

Cited by 3 | Viewed by 2166

Abstract

Solvothermal reactions between the polyaromatic group containing carboxylic acid pro-ligands 5-{(pyren-1-ylmethyl)amino}isophthalic acid (H₂L1) and 5-{(anthracen-9-ylmethyl)amino}isophthalic acid (H₂L2) with Zn(NO₃)₂·6H₂O led to the formation of the new 1D coordination polymer [...] Read more.

Solvothermal reactions between the polyaromatic group containing carboxylic acid pro-ligands 5-{(pyren-1-ylmethyl)amino}isophthalic acid (H₂L1) and 5-{(anthracen-9-ylmethyl)amino}isophthalic acid (H₂L2) with Zn(NO₃)₂·6H₂O led to the formation of the new 1D coordination polymer [Zn(L1)(NMF)]_n (1) and four other coordination polymers, [Zn(L1)(DMF)]_n (2), [Zn(L1)(4,4′-Bipy)]_n (3), [Zn(L2)(DMF)(H₂O)₂]_n·n(H₂O) (4) and [Zn₂(L2)₂(DMF)(CH₃OH)]_n (5), which were previously reported by our group. Single crystal X-ray diffraction analyses revealed that the CP 1 has a one-dimensional (1D) double-chain-type structure similar to that of CP 2. For CP 3, the assembly of the Zn(II) ion with a deprotonated L1²⁻ ligand and 4,4′-bipyridine produces a 3D network. CP 4 and 5 exhibit 1D linear and 2D layered-type structures. The ultrasound-assisted tandem reactions promoted by CPs have not yet been well studied. Thus, in the present work, we have investigated the catalytic activities of the newly synthesized CP 1, as well as of the other CPs 2–5, towards the tandem deacetalization–Knoevenagel condensation reactions of various acetals under ultrasonic irradiation. They proved to be highly efficient, with special emphasis on catalyst 1, which completely converted the substrate (benzaldehyde dimethyl acetal) into the desired product (2-benzylidenemalononitrile) after 2 h. The stability of the catalysts, namely regarding the action of ultrasonic radiation, was demonstrated by their reuse, where only a slight loss of activity was observed after four cycles. Heterogeneity was also demonstrated, and no leaching was detected over the various cycles. Full article

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Identification of New Dioxygenases Able to Recognize Polycyclic Aromatic Hydrocarbons with High Aromaticity

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Apolonia Rodríguez

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Sandra G. Zárate

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Agatha Bastida

Catalysts 2022, 12(3), 279; https://doi.org/10.3390/catal12030279 - 02 Mar 2022

Cited by 2 | Viewed by 2008

Abstract

Polycyclic aromatic hydrocarbons (PAHs), products from the incomplete combustion of crude oil, are pollutants present in nature. Ring hydroxylating dioxygenase enzymes are able to catalyze polycyclic aromatic hydrocarbons in the biodegradation process with a high degree of stereo-, regio-, and enantiospecificity. In this [...] Read more.

Polycyclic aromatic hydrocarbons (PAHs), products from the incomplete combustion of crude oil, are pollutants present in nature. Ring hydroxylating dioxygenase enzymes are able to catalyze polycyclic aromatic hydrocarbons in the biodegradation process with a high degree of stereo-, regio-, and enantiospecificity. In this work, we present the first approximation of the binding modes of 9 PAHs with high aromaticity in the catalytic sites of biphenyl or naphthalene dioxygenases from four microorganisms usually used in bio-remediation processes: Sphingobium yanoikuyae, Rhodococcus jostii RHA1, Pseudomonas sp. C18, and Paraburkholderia xenovorans. Molecular modeling studies of two biphenyl dioxygenases from Sphingobium yanoikuyae and Paraburkholderia xenovorans showed good binding affinity for PAHs with 2–4 benzene rings (fluoranthene, pyrene, and chrysene), and both enzymes had a similar amount of substrate binding. Molecular docking studies using naphthalene dioxygenase from Pseudomonas sp. C18 showed that the enzyme is able to accommodate PAHs with high aromaticity (benzo(a)pyrene, indeno(1,2,3-cd)pyrene), with good docking scores. This study provides important insight into the utility of naphthalene dioxygenases in the degradation of HAPs with high aromaticity. Full article

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H₂O₂-Based Selective Oxidations Catalyzed by Supported Polyoxometalates: Recent Advances

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Nataliya V. Maksimchuk

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Oxana A. Kholdeeva

Catalysts 2023, 13(2), 360; https://doi.org/10.3390/catal13020360 - 06 Feb 2023

Cited by 2 | Viewed by 1351

Abstract

Polyoxometalates (POMs) are transition metal oxygen anionic clusters that are oxidatively and thermally robust due to their inorganic, metal oxide-like nature. The versatility of their structures and compositions ensures tunable acid and redox properties, solubility, and functionality. The potential of POMs as homogeneous [...] Read more.

Polyoxometalates (POMs) are transition metal oxygen anionic clusters that are oxidatively and thermally robust due to their inorganic, metal oxide-like nature. The versatility of their structures and compositions ensures tunable acid and redox properties, solubility, and functionality. The potential of POMs as homogeneous catalysts and building blocks for the construction of heterogeneous selective oxidations catalysts is being intensively investigated. POM catalysts immobilized on solid supports have the clear advantages of easy separation and reuse and, thus, better meet the requests of sustainable chemistry, provided that they are leaching-resistant under the reaction conditions. Here, we give a brief overview of recent advances in the field of liquid-phase selective oxidation of organic compounds using supported POMs and the green oxidant–hydrogen peroxide, with a focus on the critical issues of the catalyst stability and reusability. The scope and limitations of various approaches to POM immobilization are discussed. Full article

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Open AccessCorrection

Correction: Rajabi et al. Efficient Synthesis of Dihydropyrimidines Using a Highly Ordered Mesoporous Functionalized Pyridinium Organosilica. Catalysts 2022, 12, 350

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Catalysts 2023, 13(8), 1153; https://doi.org/10.3390/catal13081153 - 26 Jul 2023

Viewed by 287

Abstract

In the original publication [...] Full article

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Open AccessPerspective

Phenyl Formate as a CO Surrogate for the Reductive Cyclization of Organic Nitro Compounds to Yield Different N-Heterocycles: No Need for Autoclaves and Pressurized Carbon Monoxide

by

Fabio Ragaini

,

Francesco Ferretti

and

Manar Ahmed Fouad

Catalysts 2023, 13(2), 224; https://doi.org/10.3390/catal13020224 - 18 Jan 2023

Cited by 2 | Viewed by 973

Abstract

The reductive cyclization of different organic nitro compounds by carbon monoxide, catalyzed by transition metal complexes, is a very efficient and clean strategy for the synthesis of many N-heterocycles. However, its use requires the use of autoclaves and pressurized CO lines. In [...] Read more.

The reductive cyclization of different organic nitro compounds by carbon monoxide, catalyzed by transition metal complexes, is a very efficient and clean strategy for the synthesis of many N-heterocycles. However, its use requires the use of autoclaves and pressurized CO lines. In this perspective, the authors will present the results obtained in their laboratories on the use of phenyl formate as a convenient CO surrogate, able to liberate carbon monoxide under the reaction conditions and allowing the use of a cheap glass pressure tube as a reaction vessel. In most cases, yields were better than those previously reported by the use of pressurized CO, proving that the use of CO surrogates can be a viable alternative to the gaseous reagent. Full article

(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members (EBMs) of Catalysts)

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