Research

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11 pages, 3295 KiB

Open AccessArticle

Surfactant- and Ligand-Free Synthesis of Platinum Nanoparticles in Aqueous Solution for Catalytic Applications

by Rashmi P. Charde, Brian van Devener and Michael M. Nigra

Catalysts 2023, 13(2), 246; https://doi.org/10.3390/catal13020246 - 21 Jan 2023

Cited by 1 | Viewed by 1893

The synthesis of surfactant-free and organic ligand-free metallic nanoparticles in solution remains challenging due to the nanoparticles’ tendency to aggregate. Surfactant- and ligand-free nanoparticles are particularly desirable in catalytic applications as surfactants, and ligands can block access to the nanoparticles’ surfaces. In this [...] Read more.

The synthesis of surfactant-free and organic ligand-free metallic nanoparticles in solution remains challenging due to the nanoparticles’ tendency to aggregate. Surfactant- and ligand-free nanoparticles are particularly desirable in catalytic applications as surfactants, and ligands can block access to the nanoparticles’ surfaces. In this contribution, platinum nanoparticles are synthesized in aqueous solution without surfactants or bound organic ligands. Pt is reduced by sodium borohydride, and the borohydride has a dual role of reducing agent and weakly interacting stabilizer. The 5.3 nm Pt nanoparticles are characterized using UV-visible spectroscopy and transmission electron microscopy. The Pt nanoparticles are then applied as catalysts in two different reactions: the redox reaction of hexacyanoferrate(III) and thiosulfate ions, and H₂O₂ decomposition. Catalytic activity is observed for both reactions, and the Pt nanoparticles show up to an order of magnitude greater activity over the most active catalysts reported in the literature for hexacyanoferrate(III)/thiosulfate redox reactions. It is hypothesized that this enhanced catalytic activity is due to the increased electron density that the surrounding borohydride ions give to the Pt nanoparticle surface, as well as the absence of surfactants or organic ligands blocking surface sites. Full article

(This article belongs to the Special Issue Catalytic Reaction Engineering for the Sustainability of the Environment)

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14 pages, 1276 KiB

Open AccessArticle

Impact of Design on the Activity of ZrO₂ Catalysts in Cellulose Hydrolysis-Dehydration to Glucose and 5-Hydroxymethylfurfural

by Tatiana B. Medvedeva, Olga L. Ogorodnikova, Irina S. Yakovleva, Lyubov A. Isupova, Oxana P. Taran, Nikolay V. Gromov and Valentin N. Parmon

Catalysts 2021, 11(11), 1359; https://doi.org/10.3390/catal11111359 - 12 Nov 2021

Cited by 5 | Viewed by 1448

Abstract

The one-pot hydrolysis-dehydration of activated microcrystalline cellulose was studied in pure hydrothermal water at 453 K over ZrO₂ catalysts produced by thermodegradation, microwave treatment, mechanical activation, and sol–gel methods and spent without any co-catalyst. ZrO₂ prepared by microwave treatment was more [...] Read more.

The one-pot hydrolysis-dehydration of activated microcrystalline cellulose was studied in pure hydrothermal water at 453 K over ZrO₂ catalysts produced by thermodegradation, microwave treatment, mechanical activation, and sol–gel methods and spent without any co-catalyst. ZrO₂ prepared by microwave treatment was more active compared to ones derived by other methods. The catalyst calcination temperature also impacted reactivity. The cellulose conversion increased simultaneously with acidity and S_BET, which in turn were set by the preparation method and calcination temperature. Phase composition did not affect the activity. Yields of glucose and 5-HMF reaching 18 and 15%, respectively, were over the most promising ZrO₂ prepared by microwave treatment at 593 K. To our knowledge, this ZrO₂ sample provided the highest activity in terms of TOF values (15.1 mmol g⁻¹ h⁻¹) compared to the pure ZrO₂ systems reported elsewhere. High stability of ZrO₂ derived by microwave irradiation was shown in five reaction runs. Full article

(This article belongs to the Special Issue Catalytic Reaction Engineering for the Sustainability of the Environment)

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Review

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17 pages, 1501 KiB

Open AccessReview

Low-Temperature SCR Catalyst Development and Industrial Applications in China

by Hongtai Zhu, Liyun Song, Kai Li, Rui Wu, Wenge Qiu and Hong He

Catalysts 2022, 12(3), 341; https://doi.org/10.3390/catal12030341 - 17 Mar 2022

Cited by 15 | Viewed by 4368

Abstract

In recent years, low-temperature SCR (Selective Catalytic Reduction) denitrification technology has been popularized in non-power industries and has played an important role in the control of industrial flue gas NO_x emissions in China. Currently, the most commonly used catalysts in industry are [...] Read more.

In recent years, low-temperature SCR (Selective Catalytic Reduction) denitrification technology has been popularized in non-power industries and has played an important role in the control of industrial flue gas NO_x emissions in China. Currently, the most commonly used catalysts in industry are V₂O₅-WO₃(MoO₃)/TiO₂, MnO₂-based catalysts, CeO₂-based catalysts, MnO₂-CeO₂ catalysts and zeolite SCR catalysts. The flue gas emitted during industrial combustion usually contains SO₂, moisture and alkali metals, which can affect the service life of SCR catalysts. This paper summarizes the mechanism of catalyst poisoning and aims to reduce the negative effect of NH₄HSO₄ on the activity of the SCR catalyst at low temperatures in industrial applications. It also presents the outstanding achievements of domestic companies in denitrification in the non-power industry in recent years. Much progress has been made in the research and application of low-temperature NH₃-SCR, and with the renewed demand for deeper NO_x treatments, new technologies with lower energy consumption and more functions need to be developed. Full article

(This article belongs to the Special Issue Catalytic Reaction Engineering for the Sustainability of the Environment)

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