Research

15 pages, 4379 KiB

Open AccessArticle

Surface Modification of Zinc Ferrite with Titanium to Be a Photo-Active Catalyst in Commercial LED Light

by Doaa F. Baamer and Islam Hamdy Abd El Maksod

Catalysts 2023, 13(7), 1082; https://doi.org/10.3390/catal13071082 - 10 Jul 2023

Cited by 2 | Viewed by 927

Titanium-doped zinc ferrite was used as a photo catalyst for breaking down C-C and C-H bonds of methylene blue dye as a model for the decomposition of organic pollutants. Different concentrations of Ti were used to impede into the spinel structure of zinc [...] Read more.

Titanium-doped zinc ferrite was used as a photo catalyst for breaking down C-C and C-H bonds of methylene blue dye as a model for the decomposition of organic pollutants. Different concentrations of Ti were used to impede into the spinel structure of zinc ferrite by in situ addition during the preparation. Different characterization techniques were used to characterize the prepared materials including the deep analysis of the electronic spectra, which proved the surface modification of ferrite due to the Ti doping. In addition, we make a comparison study of photo degradation using ordinary UV irradiation and commercial LED light irradiation, which gives very promising results. A correlation between the structure and the photo catalytic behavior of the materials is assigned. Full article

(This article belongs to the Special Issue The Role of Catalysts in Functionalization of C-H and C-C Bonds II)

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16 pages, 9034 KiB

Open AccessArticle

Conversion of Dimeric Diaryl Ethers over SiO₂- and HZSM5-Supported Pd and Ru Catalysts: A Focus on the Role of the Metal and Acidity

by Raphaela Azevedo Rafael, Fabio Bellot Noronha, Eric Marceau and Robert Wojcieszak

Catalysts 2023, 13(4), 783; https://doi.org/10.3390/catal13040783 - 21 Apr 2023

Cited by 1 | Viewed by 1807

Abstract

The effect of metal and support acidity on the hydroconversion of dimeric aryl ethers, used as model molecules for lignin, is still under debate, both in terms of hydrogenolysis (cleavage of the ether bond) and formation of by-products (coupling of aromatic monomers to [...] Read more.

The effect of metal and support acidity on the hydroconversion of dimeric aryl ethers, used as model molecules for lignin, is still under debate, both in terms of hydrogenolysis (cleavage of the ether bond) and formation of by-products (coupling of aromatic monomers to dimers by alkylation reaction). Their role is investigated here in the conversion of three typical molecules representative of the α-O-4, β-O-4, and 4-O-5 ether linkages of lignin, respectively, benzyl phenyl ether (BPE), phenethoxybenzene (PEB), and diphenyl ether (DPE), at 503 K, under 18 bar of H₂ in decalin. Ru- and Pd-based catalysts were synthesized on non-acidic SiO₂ and on acidic HZSM5. Under these reaction conditions, the conversion of the ethers over the bare supports was observed in the presence of acidic sites; the effect decreased as the ether bond strength increased. The results also suggest that the product distribution is directly affected both by the support acidity and by the oxophilicity of Ru. Alkylated products from isomerization reactions, which are reported to be formed only over acidic sites, were also produced on the surface of the Ru nanoparticles. Full article

(This article belongs to the Special Issue The Role of Catalysts in Functionalization of C-H and C-C Bonds II)

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23 pages, 24048 KiB

Open AccessArticle

Air-Stable Efficient Nickel Catalyst for Hydrogenation of Organic Compounds

by Vladyslav V. Subotin, Mykyta O. Ivanytsya, Anastasiya V. Terebilenko, Pavel S. Yaremov, Olena O. Pariiska, Yuri M. Akimov, Igor E. Kotenko, Tomash M. Sabov, Mykhailo M. Kurmach, Sergey V. Ryabukhin, Dmitriy M. Volochnyuk and Sergey V. Kolotilov

Catalysts 2023, 13(4), 706; https://doi.org/10.3390/catal13040706 - 06 Apr 2023

Cited by 3 | Viewed by 2758

Abstract

A series of composites containing nanoparticles of NiO (from 1 to 10% by weight per Ni), deposited on NORIT charcoal, was prepared by the decomposition of the Ni⁰ complex Ni(cod)₂ (cod = cis,cis-1,5-cyclooctadiene). Ni content in the composites [...] Read more.

A series of composites containing nanoparticles of NiO (from 1 to 10% by weight per Ni), deposited on NORIT charcoal, was prepared by the decomposition of the Ni⁰ complex Ni(cod)₂ (cod = cis,cis-1,5-cyclooctadiene). Ni content in the composites was set by loading the appropriate quantities of the Ni(cod)₂ precursor. The catalytic activity of the composites was associated with the in situ generation of active sites due to a reduction in NiO, hence the composites could be stored in air without a loss in their catalytic performance. The composites were analyzed by powder XRD, TEM, XPS, and adsorption methods. The hydrogenation of quinoline was used as a reference reaction for studies of the influence of temperature, P(H₂), catalyst loading on the product yield, and for the selection of the composite possessing the highest performance. It was found that 3% Ni loading was the most optimal. This composite was used as an efficient catalyst for the hydrogenation of compounds with ethylene and acetylene bonds, nitro- and keto- groups as well as a series of substituted quinolines and analogs. The studied composites can be proposed as air-stable and efficient catalysts for the hydrogenation of a wide range of organic compounds. Full article

(This article belongs to the Special Issue The Role of Catalysts in Functionalization of C-H and C-C Bonds II)

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12 pages, 2497 KiB

Open AccessArticle

Asymmetric Synthesis of trans-3-Alkoxyamino-4-Oxygenated-2-Piperidones Mediated by Transition-Metal-Free Dual C-H Oxidation and Its CAL-B-Assisted Enzymatic Resolution

by Julio Romero-Ibañez, Marina A. Ortega-Rojas, Jonathan R. Valdéz-Camacho, Luis G. Hernández-Vázquez, Fernando Sartillo-Piscil and Jaime Escalante

Catalysts 2023, 13(4), 703; https://doi.org/10.3390/catal13040703 - 06 Apr 2023

Viewed by 1287

Abstract

A general chemo-enzymatic approach to synthesize both enantioenriched trans-3-alkoxyamino-4-oxy-2-piperidones, which are important scaffold for various naturally occurring alkaloids, is reported. To this end, a selective transition-metal-free dual C−H oxidation of piperidines mediated by the TEMPO oxoammonium cation (TEMPO+) was used, followed by [...] Read more.

A general chemo-enzymatic approach to synthesize both enantioenriched trans-3-alkoxyamino-4-oxy-2-piperidones, which are important scaffold for various naturally occurring alkaloids, is reported. To this end, a selective transition-metal-free dual C−H oxidation of piperidines mediated by the TEMPO oxoammonium cation (TEMPO+) was used, followed by enzymatic resolution of the corresponding alkoxyamino-2-piperidones with Candida antarctica lipase (CAL-B), to yield the title compounds in high enantiomeric excess (ee). The absolute configuration of both enantioenriched compounds was determined using chemical correlation and circular dichroism (CD) spectroscopy. The former method highlights the oxidative ring contraction of the trans-alkoxyamine-2-piperidone ring into its corresponding 2-pyrrolidinone. Full article

(This article belongs to the Special Issue The Role of Catalysts in Functionalization of C-H and C-C Bonds II)

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12 pages, 10086 KiB

Open AccessArticle

Manganese Salan Complexes as Catalysts for Hydrosilylation of Aldehydes and Ketones

by Nora Almutairi, Srikanth Vijjamarri and Guodong Du

Catalysts 2023, 13(4), 665; https://doi.org/10.3390/catal13040665 - 29 Mar 2023

Cited by 1 | Viewed by 1512

Abstract

Manganese has attracted significant recent attention due to its abundance, low toxicity, and versatility in catalysis. In the present study, a series of manganese (III) complexes supported by salan ligands have been synthesized and characterized, and their activity as catalysts in the hydrosilylation [...] Read more.

Manganese has attracted significant recent attention due to its abundance, low toxicity, and versatility in catalysis. In the present study, a series of manganese (III) complexes supported by salan ligands have been synthesized and characterized, and their activity as catalysts in the hydrosilylation of carbonyl compounds was examined. While manganese (III) chloride complexes exhibited minimal catalytic efficacy without activation of silver perchlorate, manganese (III) azide complexes showed good activity in the hydrosilylation of carbonyl compounds. Under optimized reaction conditions, several types of aldehydes and ketones could be reduced with good yields and tolerance to a variety of functional groups. The possible mechanisms of silane activation and hydrosilylation were discussed in light of relevant experimental observations. Full article

(This article belongs to the Special Issue The Role of Catalysts in Functionalization of C-H and C-C Bonds II)

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17 pages, 3492 KiB

Open AccessArticle

Ultrasound-Assisted 1,3-Dipolar Cycloadditions Reaction Utilizing Ni-Mg-Fe LDH: A Green and Sustainable Perspective

by Mohamed Abdel Salam, Eman Saleem Imdadulhaq, Abeer Nasser Al-Romaizan, Tamer S. Saleh and Mohamed Mokhtar M. Mostafa

Catalysts 2023, 13(4), 650; https://doi.org/10.3390/catal13040650 - 25 Mar 2023

Cited by 1 | Viewed by 1333

Abstract

Ultrasound-assisted synthesis of novel pyrazoles using Ni-Mg-Fe LDH as a catalyst in cyclopentyl methyl ether (CPME) is introduced. Different LDHs were tested as a catalyst for the synthesis of pyrazoles via a 1,3-dipolar cycloaddition reaction. Among them, Ni-Mg-Fe LDH was the superior catalyst [...] Read more.

Ultrasound-assisted synthesis of novel pyrazoles using Ni-Mg-Fe LDH as a catalyst in cyclopentyl methyl ether (CPME) is introduced. Different LDHs were tested as a catalyst for the synthesis of pyrazoles via a 1,3-dipolar cycloaddition reaction. Among them, Ni-Mg-Fe LDH was the superior catalyst for this reaction. This protocol offered high yields, a short reaction time, and a green solvent, and with the reuse of this catalyst six times with the same activity, it could be regarded as an ecofriendly, greener process. The NiMgFe LDH catalyst with the smallest particle size (29 nm) and largest surface area showed its superior efficacy for the 1,3 dipolar cycloaddition rection and can be successfully used in up to six catalytic cycles with little loss of catalytic activity. A plausible mechanism for this reaction over the Ni-Mg-Fe LDH is proposed. Full article

(This article belongs to the Special Issue The Role of Catalysts in Functionalization of C-H and C-C Bonds II)

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11 pages, 4508 KiB

Open AccessEditor’s ChoiceArticle

Methane Activation and Coupling Pathways on Ni₂P Catalyst

by Abdulrahman Almithn, Salem N. Alghanim, Abdullah A. Mohammed, Abdullah K. Alghawinim, Mazen A. Alomaireen, Zaid Alhulaybi and SK Safdar Hossain

Catalysts 2023, 13(3), 531; https://doi.org/10.3390/catal13030531 - 06 Mar 2023

Cited by 2 | Viewed by 1512

Abstract

The direct catalytic conversion of methane (CH₄) to higher hydrocarbons has attracted considerable attention in recent years because of the increasing supply of natural gas. Efficient and selective catalytic conversion of methane to value-added products, however, remains a major challenge. Recent [...] Read more.

The direct catalytic conversion of methane (CH₄) to higher hydrocarbons has attracted considerable attention in recent years because of the increasing supply of natural gas. Efficient and selective catalytic conversion of methane to value-added products, however, remains a major challenge. Recent studies have shown that the incorporation of phosphorus atoms in transition metals improves their selectivity and resistance to coke formation for many catalytic reactions. In this work, we report a density function theory-based investigation of methane activation and C₂ product formation on Ni₂P(001). Our results indicate that, despite the lower reactivity of Ni₂P relative to Ni, the addition of phosphorus atoms hinders excessive dehydrogenation of methane to CH* and C* species, thus reducing carbon deposition on the surface. CH₃* and CH₂* moieties, instead, are more likely to be the most abundant surface intermediates once the initial C–H bond in methane is activated with a barrier of 246 kJ mol⁻¹. The formation of ethylene from 2CH₂* on Ni₂P is facile with a barrier of 56 kJ mol⁻¹, which is consistent with prior experimental studies. Collectively, these findings suggest that Ni₂P may be an attractive catalyst for selective methane conversion to ethylene. Full article

(This article belongs to the Special Issue The Role of Catalysts in Functionalization of C-H and C-C Bonds II)

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14 pages, 5603 KiB

Open AccessEditor’s ChoiceArticle

Effect of Alkoxy Substituents on the Regioselectivity of Catalytic C-H Activation in Benzoic Acids: Experimental and DFT Study

by Vladimir B. Kharitonov, Dmitry V. Muratov, Yulia V. Nelyubina and Dmitry A. Loginov

Catalysts 2023, 13(2), 389; https://doi.org/10.3390/catal13020389 - 10 Feb 2023

Cited by 3 | Viewed by 1316

Abstract

This work demonstrates the influence of the catalyst and alkyne nature on the regioselectivity of rhodium-catalyzed annulation of alkoxy-substituted benzoic acids (such as 3-methoxybenzoic, 3,4-dimethoxybenzoic, and piperonylic acids) with alkynes. Here, X-ray diffraction and DFT calculation data gave evidence that the observed regioselectivity [...] Read more.

This work demonstrates the influence of the catalyst and alkyne nature on the regioselectivity of rhodium-catalyzed annulation of alkoxy-substituted benzoic acids (such as 3-methoxybenzoic, 3,4-dimethoxybenzoic, and piperonylic acids) with alkynes. Here, X-ray diffraction and DFT calculation data gave evidence that the observed regioselectivity is provided by both steric and coordination effects of methoxy groups. The latter is the result of weak non-covalent C–H⋯O interactions with the supporting ligand rather than with the rhodium atom. We believe that these results are also valid for other reactions of the C-H activation of methoxy-substituted arene compounds. Full article

(This article belongs to the Special Issue The Role of Catalysts in Functionalization of C-H and C-C Bonds II)

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