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Open AccessArticle

Sodium Methoxide/Zeolite-Supported Catalyst for Transesterification of Soybean Waste Cooking Oil for Biodiesel Production

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Kidist Argaw Shiferaw

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Inorganics 2023, 11(4), 163; https://doi.org/10.3390/inorganics11040163 - 12 Apr 2023

Viewed by 1232

Abstract

This study aims to prepare a supported catalyst based on zeolite Y doped with NaOMe (sodium methoxide) for the transesterification of waste cooking oil (WCO). The catalytic screening data showed that NaOMe/zeolite is a prominent catalyst for the transesterification of WCO prepared by [...] Read more.

This study aims to prepare a supported catalyst based on zeolite Y doped with NaOMe (sodium methoxide) for the transesterification of waste cooking oil (WCO). The catalytic screening data showed that NaOMe/zeolite is a prominent catalyst for the transesterification of WCO prepared by a solvent-free, ball-milling process. We initially tested 5–20% of sodium methoxide loading onto zeolite Y and found that 20% is the optimum loading for the reaction. The transesterification reaction required a comparatively lower methanol-to-oil mole ratio of 16:1 with the reaction temperature as 60 °C. The ball-milled NaOMe/zeolite catalyst was characterized by BET surface area analysis, FE-SEM, TEM, FT–IR, and XRD. The BET surface analysis revealed that the surface area for zeolite Y was substantially decreased in the NaOMe/zeolite catalyst. The ball-milling process dropped the crystallinity of zeolite Y, which can be seen from the XRD and FE-SEM images of both zeolite Y and the NaOMe/zeolite catalyst. Finally, the transesterification reaction product was fully characterized by

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H-NMR and viscosity analysis for biodiesel, glycerol, and the WCO. The chemical shifts for the biodiesel and glycerol are found accordingly. This is also supported by the FT–IR characterization of biodiesel, glycerol, and WCO. It is noteworthy that a very high mass ratio of 250 g oil/g NaOMe is obtained when converting WCO to biodiesel, indicating very high catalytic activity for the aforementioned catalyst. Full article

(This article belongs to the Special Issue Inorganics for Catalysts: Design, Synthesis and Applications)

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Open AccessArticle

Simulation of Sorption-Enhanced Steam Methane Reforming over Ni-Based Catalyst in a Pressurized Dual Fluidized Bed Reactor

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Inorganics 2023, 11(3), 107; https://doi.org/10.3390/inorganics11030107 - 05 Mar 2023

Viewed by 834

Abstract

Steam methane reforming is a major method of hydrogen production. However, this method usually suffers from low energy efficiency and high carbon-emission intensity. To solve this issue, a novel steam-methane-reforming process over a Ni-based catalyst in a pressurized dual fluidized bed reactor is [...] Read more.

Steam methane reforming is a major method of hydrogen production. However, this method usually suffers from low energy efficiency and high carbon-emission intensity. To solve this issue, a novel steam-methane-reforming process over a Ni-based catalyst in a pressurized dual fluidized bed reactor is proposed in this work. A three-dimensional computational fluid dynamics (CFD) model for the complex physicochemical process was built to study the reforming characteristics. The model was first validated against the reported data in terms of hydrodynamics and reaction kinetics. Next, the performance of the proposed methane-steam-reforming process was predicted. It was found that the methane-conversion ratio was close to 100%. The mole fraction of H₂ in the dry-yield syngas reached 98.8%, the cold gas efficiency reached 98.5%, and the carbon-capture rate reached 96.4%. It is believed that the proposed method can be used for methane reforming with high efficiency and low carbon intensity. Full article

(This article belongs to the Special Issue Inorganics for Catalysts: Design, Synthesis and Applications)

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Open AccessArticle

Defect Structure of Nanocrystalline NiO Oxide Stabilized by SiO₂

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Maxim D. Mikhnenko

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Svetlana V. Cherepanova

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Evgeny Yu Gerasimov

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Alena A. Pochtar

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Maria V. Alekseeva (Bykova)

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Roman G. Kukushkin

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Vadim A. Yakovlev

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Olga A. Bulavchenko

Inorganics 2023, 11(3), 97; https://doi.org/10.3390/inorganics11030097 - 27 Feb 2023

Viewed by 743

Abstract

In this paper, structural features of the NiO-SiO₂ nanocrystalline catalyst synthesized by the sol-gel method were studied by X-ray diffraction (XRD), high-resolution transmission electron microscopy (TEM), and differential dissolution (DD). The XRD pattern of NiO-SiO₂ significantly differs from the “ideal” NiO [...] Read more.

In this paper, structural features of the NiO-SiO₂ nanocrystalline catalyst synthesized by the sol-gel method were studied by X-ray diffraction (XRD), high-resolution transmission electron microscopy (TEM), and differential dissolution (DD). The XRD pattern of NiO-SiO₂ significantly differs from the “ideal” NiO pattern: the peaks of the NiO-like phase are asymmetric, especially the 111 diffraction peak. The NiO-SiO₂ nanocrystalline catalyst was investigated by means of XRD simulations based on two approaches: conventional Rietveld analysis and statistical models of 1D disordered crystals. Through a direct simulation of XRD profiles, structural information is extracted from both the Bragg and diffuse scattering. XRD simulations showed that the asymmetry of all the diffraction peaks is due to the presence of two NiO-like oxides with different lattice constants and different average sizes: ~90 wt% of mixed Ni-Si oxide (Ni:Si = 0.14:0.86) with average crystallite sizes (D ~ 27.5 Å) and ~10 wt% of pure NiO (D ~ 50 Å). The high asymmetry of the 111 diffraction peak is due to the appearance of diffuse scattering caused by the inclusion of tetrahedral SiO₂ layers between octahedral NiO layers. Such methods as TEM and DD were applied as independent criteria to prove the structural model, and the results obtained confirm the formation of mixed Ni-Si oxide. Full article

(This article belongs to the Special Issue Inorganics for Catalysts: Design, Synthesis and Applications)

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Open AccessArticle

Optimal Choice of the Preparation Procedure and Precursor Composition for a Bulk Ni–Mo–W Catalyst

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Evgeniy Yu. Gerasimov

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Inorganics 2023, 11(2), 89; https://doi.org/10.3390/inorganics11020089 - 20 Feb 2023

Cited by 1 | Viewed by 906

Abstract

Among the known synthesis procedures and reagents for unsupported Ni–Mo–W catalysts, there is no consensus about optimal preparation conditions of their precursors. In the present work, Ni–Mo–W precursors were prepared via three preparation techniques—hydrothermal synthesis, precipitation method and spray drying—after the synthesis of [...] Read more.

Among the known synthesis procedures and reagents for unsupported Ni–Mo–W catalysts, there is no consensus about optimal preparation conditions of their precursors. In the present work, Ni–Mo–W precursors were prepared via three preparation techniques—hydrothermal synthesis, precipitation method and spray drying—after the synthesis of complex compounds in solution. Ni–Mo–W precursors were studied by the XRD analysis, SEM methods, Raman and UV-vis spectroscopies and XPS measurements and used for the hydrotreatment of straight-run gasoil. Precursors prepared by hydrothermal synthesis contain particles with stacked plate shapes, while other methods provide spherical particles. The formation of different amounts of individual molybdates, tungstates or mixed phases such as W_1−xMo_xO₃ possibly doped by Ni was detected. The precipitation technique results in the formation of spheres, with W located at the center and is unavailable for catalysis. The catalytic activity increased when all active metals are available for the feedstock, and a more mixed phase containing Ni, Mo and W is formed. This mixed phase is realized when the synthesis of the Ni–Mo–W precursors is carried out in solution followed by spray drying. The resulting catalyst has 1.2–4 times higher activity than catalysts prepared by other methods. Full article

(This article belongs to the Special Issue Inorganics for Catalysts: Design, Synthesis and Applications)

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Open AccessArticle

Preparing a Ca-Bi-O System by the Precipitation Method and Studying Its Intermediate Structural Properties for Applications in Water Treatment

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Inorganics 2023, 11(2), 79; https://doi.org/10.3390/inorganics11020079 - 09 Feb 2023

Viewed by 794

Abstract

This study focuses on the development of a Ca-Bi-O system (CBO) with efficiency in the degradation of Rhodamine B, which is extremely toxic to many organisms and can have long-term negative consequences if not safely removed from the water. The conventional precipitation method [...] Read more.

This study focuses on the development of a Ca-Bi-O system (CBO) with efficiency in the degradation of Rhodamine B, which is extremely toxic to many organisms and can have long-term negative consequences if not safely removed from the water. The conventional precipitation method was used to create a stable phase of Ca₂Bi₂O₅ with a stoichiometric 1:1 molar ratio of Ca:Bi. Before obtaining the pure phase, the details of the reaction processes were investigated and the various intermediate products were identified using X-ray diffraction followed by Fourier transform infrared, UV-Vis, and Raman spectroscopy. An ab initio calculation evaluated with the HSE06 functional yields a band gap of 3.5 eV, similar to the band gap obtained by diffuse reflectance recorded on Ca₂Bi₂O₅. This newly synthesized compound is addressed to the environmental application by investigating the photocatalytic properties of CBO materials obtained at different calcination temperatures. The investigation of pure Ca₂B_i2O₅, with characterization techniques and complemented by new first-principles calculations to investigate the photocatalysis provide valuable new insights for this scarcely studied yet potentially interesting compound. Full article

(This article belongs to the Special Issue Inorganics for Catalysts: Design, Synthesis and Applications)

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Open AccessArticle

C-TiO₂+Ni and ZnO+Ni Magnetic Photocatalyst Powder Synthesis by Reactive Magnetron Sputtering Technique and Their Application for Bacteria Inactivation

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Rimantas Daugelavicius

Inorganics 2023, 11(2), 59; https://doi.org/10.3390/inorganics11020059 - 26 Jan 2023

Viewed by 889

Abstract

In the current study, a bi-layered magnetic photocatalyst powder consisting of a Ni layer on one side and carbon-doped TiO₂ or ZnO photocatalyst layers on the other side was synthesized by magnetron sputtering technique. SEM, XRD, and XPS analysis of powders revealed [...] Read more.

In the current study, a bi-layered magnetic photocatalyst powder consisting of a Ni layer on one side and carbon-doped TiO₂ or ZnO photocatalyst layers on the other side was synthesized by magnetron sputtering technique. SEM, XRD, and XPS analysis of powders revealed that the photocatalytic TiO₂ layer had a mixed anatase-rutile structure, was doped by carbon to approximately 3 at. % and had a fraction of Ti(III) oxide. Meanwhile, the ZnO layer was crystalized in a wurtzite structure and had a considerable number of intrinsic defects, which are useful for visible light photocatalysis. The activity of magnetic photocatalyst powder was tested by photocatalytic bleaching of dyes, as well as performing photocatalytic inactivation of Salmonella bacteria under UV and visible light irradiation. It was observed, that C-TiO₂+Ni magnetic photocatalyst had relatively high and stable activity under both light sources (for five consecutive cycles dye degradation reached approximately 95%), but ZnO+Ni was generally lacking in activity and stability (over five cycles under UV and visible light, dye degradation fell from approximately 60% to 55% and from 90% to 70%, respectively). Photocatalytic treatment of bacteria also provided mixed results. On one hand, in all tests bacteria were not inactivated completely. However, on the other hand, their susceptibility to antibiotics increased significantly. Full article

(This article belongs to the Special Issue Inorganics for Catalysts: Design, Synthesis and Applications)

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Open AccessArticle

Cryogels with Noble Metal Nanoparticles as Catalyst for “Green” Decomposition of Chlorophenols

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Dmitriy A. Berillo

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Irina N. Savina

Inorganics 2023, 11(1), 23; https://doi.org/10.3390/inorganics11010023 - 02 Jan 2023

Cited by 3 | Viewed by 1097

Abstract

Pollution of the aquatic environment by halogen derivatives widely used as antiseptic compounds, as well as chemicals for various industrial purposes, is significant. Existing systems of bioremediation poorly solve the problem of eliminating pollution. This paper discusses the preparation of novel macroporous chitosan-based [...] Read more.

Pollution of the aquatic environment by halogen derivatives widely used as antiseptic compounds, as well as chemicals for various industrial purposes, is significant. Existing systems of bioremediation poorly solve the problem of eliminating pollution. This paper discusses the preparation of novel macroporous chitosan-based cryogels with in situ-immobilized Pd or Pt nanoparticles as a catalyst for dichlorination reactions. The formation mechanism of metal coordinated chitosan gels using Medusa software modelling and rheology (G’ and G’’) is discussed. Metal coordinated chitosan gels were subsequently converted into covalently cross-linked macroporous cryogels with in situ-immobilized Pd or Pt nanoparticles using the redox potentials difference of the reaction mixture. Noble metal nanoparticles of average size, 2.4 nm, were evenly distributed in the cryogel structure. The effectiveness of these gels as a catalyst for the decomposition of chloro-compounds o-chlorophenol, p-chlorophenol and 2,4-dichlorophenol was tested. The catalytic hydrogenation reaction was carried out using the “green reducing agent” formic acid. Increasing the excess of formic acid with heating increases the degree of conversion up to 80–90%. The CHI-GA-PdNPs cryogel at pH 6 showed better efficiency in the hydrogenation process compared to the CHI-GA-PtNPs cryogel; however, no significant difference in the degree of conversion at pH 3 was observed. The termination of a catalytic reaction in a batch mode have been studied. Several control tests were carried out to elucidate the mechanism of catalyst poisoning. The presented catalytic system may be of interest for studying reactions in a flow through mode, including the reactions for obtaining valuable chemicals. Full article

(This article belongs to the Special Issue Inorganics for Catalysts: Design, Synthesis and Applications)

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Open AccessArticle

Spontaneous Release of Metalloradicals and Coordinatively Unsaturated Species in Asymmetric Iridium Dimers to Promote C-N Bond Formation

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Inorganics 2022, 10(12), 237; https://doi.org/10.3390/inorganics10120237 - 02 Dec 2022

Viewed by 823

Abstract

An unusual iridium dimer 1, [(4-cpbo)Ir(μ-Cl)(μ-O)Ir(4-cpbo)] (4-cpbo = 4-chlorophenylbenzoxazolato-N,C²), was obtained by the oxidative addition of oxygen and reductive elimination of chlorine from a precursor [(4-cpbo)₂Ir(μ-Cl)]₂. This iridium dimer 1 has a metastable structure with an [...] Read more.

An unusual iridium dimer 1, [(4-cpbo)Ir(μ-Cl)(μ-O)Ir(4-cpbo)] (4-cpbo = 4-chlorophenylbenzoxazolato-N,C²), was obtained by the oxidative addition of oxygen and reductive elimination of chlorine from a precursor [(4-cpbo)₂Ir(μ-Cl)]₂. This iridium dimer 1 has a metastable structure with an asymmetric bridge, can spontaneously release metalloradicals and coordinatively unsaturated species in solution at room temperature, and exhibits high catalytic ability for synthetic applications. Full article

(This article belongs to the Special Issue Inorganics for Catalysts: Design, Synthesis and Applications)

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Review

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Open AccessReview

Layered Double Hydroxide Materials: A Review on Their Preparation, Characterization, and Applications

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Inorganics 2023, 11(3), 121; https://doi.org/10.3390/inorganics11030121 - 14 Mar 2023

Cited by 4 | Viewed by 2947

Abstract

Layered double hydroxides (LDHs), a type of synthetic clay with assorted potential applications, are deliberated upon in view of their specific properties, such as adsorbent-specific behavior, biocompatibility, fire-retardant capacity, and catalytic and anion exchange properties, among others. LDHs are materials with two-dimensional morphology, [...] Read more.

Layered double hydroxides (LDHs), a type of synthetic clay with assorted potential applications, are deliberated upon in view of their specific properties, such as adsorbent-specific behavior, biocompatibility, fire-retardant capacity, and catalytic and anion exchange properties, among others. LDHs are materials with two-dimensional morphology, high porosity, and exceptionally tunable and exchangeable anionic particles with sensible interlayer spaces. The remarkable feature of LDHs is their flexibility in maintaining the interlayer spaces endowing them with the capacity to accommodate a variety of ionic species, suitable for many applications. Herein, some synthetic methodologies, general characterizations, and applications of LDHs are summarized, encompassing their broader appliances as a remarkable material to serve society and address several problems viz. removal of pollutants and fabrication of sensors and materials with multifaceted useful applications in the medical, electrochemical, catalytic, and agricultural fields, among others. Full article

(This article belongs to the Special Issue Inorganics for Catalysts: Design, Synthesis and Applications)

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Open AccessReview

Green Energy by Hydrogen Production from Water Splitting, Water Oxidation Catalysis and Acceptorless Dehydrogenative Coupling

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Jesús Antonio Luque-Urrutia

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Thalía Ortiz-García

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Miquel Solà

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Albert Poater

Inorganics 2023, 11(2), 88; https://doi.org/10.3390/inorganics11020088 - 20 Feb 2023

Cited by 3 | Viewed by 1738

Abstract

In this review, we want to explain how the burning of fossil fuels is pushing us towards green energy. Actually, for a long time, we have believed that everything is profitable, that resources are unlimited and there are no consequences. However, the reality [...] Read more.

In this review, we want to explain how the burning of fossil fuels is pushing us towards green energy. Actually, for a long time, we have believed that everything is profitable, that resources are unlimited and there are no consequences. However, the reality is often disappointing. The use of non-renewable resources, the excessive waste production and the abandonment of the task of recycling has created a fragile thread that, once broken, may never restore itself. Metaphors aside, we are talking about our planet, the Earth, and its unique ability to host life, including ourselves. Our world has its balance; when the wind erodes a mountain, a beach appears, or when a fire devastates an area, eventually new life emerges from the ashes. However, humans have been distorting this balance for decades. Our evolving way of living has increased the number of resources that each person consumes, whether food, shelter, or energy; we have overworked everything to exhaustion. Scientists worldwide have already said actively and passively that we are facing one of the biggest problems ever: climate change. This is unsustainable and we must try to revert it, or, if we are too late, slow it down as much as possible. To make this happen, there are many possible methods. In this review, we investigate catalysts for using water as an energy source, or, instead of water, alcohols. On the other hand, the recycling of gases such as CO₂ and N₂O is also addressed, but we also observe non-catalytic means of generating energy through solar cell production. Full article

(This article belongs to the Special Issue Inorganics for Catalysts: Design, Synthesis and Applications)

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