Molecules

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13 pages, 1864 KiB

Open AccessArticle

Investigating the Sole Olefin-Based Cycle in Small-Cage MCM-35-Catalyzed Methanol-to-Olefins Reactions

by Zhaohui Liu, Min Mao, Ruixue Yangcheng and Shuang Lv

Molecules 2024, 29(9), 2037; https://doi.org/10.3390/molecules29092037 - 28 Apr 2024

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Small-pore zeolites catalyze the methanol-to-olefins (MTO) reaction via a dual-cycle mechanism, encompassing both olefin- and aromatic-based cycles. Zeolite topology is crucial in determining both the catalytic pathway and the product selectivity of the MTO reaction. Herein, we investigate the mechanistic influence of MCM-35 [...] Read more.

Small-pore zeolites catalyze the methanol-to-olefins (MTO) reaction via a dual-cycle mechanism, encompassing both olefin- and aromatic-based cycles. Zeolite topology is crucial in determining both the catalytic pathway and the product selectivity of the MTO reaction. Herein, we investigate the mechanistic influence of MCM-35 zeolite on the MTO process. The structural properties of the as-synthesized MCM-35 catalyst, including its confined cages (6.19 Å), were characterized, confirming them as the catalytic centers. Then, the MTO reactions were systematically performed and investigated over a MCM-35 catalyst. Feeding pure methanol to the reactor yielded minimal MTO activity despite the formation of some aromatic species within the zeolite. The results suggest that the aromatic-based cycle is entirely suppressed in MCM-35, preventing the simultaneous occurrence of the olefin-based cycle. However, cofeeding a small amount of propene in methanol can obviously enhance the methanol conversion under the same studied reaction conditions. Thus, the exclusive operation of the olefin-based cycle in the MTO reaction, independent of the aromatic-based cycle, was demonstrated in MCM-35 zeolite. Full article

(This article belongs to the Special Issue Functional Nanomaterials in Green Chemistry)

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20 pages, 5301 KiB

Open AccessArticle

Adsorption Behavior of a Ternary Covalent Organic Polymer Anchored with SO₃H for Ciprofloxacin

by Zhuoran Wang, Chuanyu Qin, Dongyu Zhao, Ziheng Wang and Dongpeng Mao

Molecules 2023, 28(19), 6941; https://doi.org/10.3390/molecules28196941 - 5 Oct 2023

Viewed by 872

Abstract

Owing to the poor treatment efficiency of wastewater containing fluoroquinolones (FQs), effective removal of such pollutants has become a significant issue in waste management. In this study, a ternary covalent organic polymer anchored with SO₃H (COP-SO₃H) was designed using [...] Read more.

Owing to the poor treatment efficiency of wastewater containing fluoroquinolones (FQs), effective removal of such pollutants has become a significant issue in waste management. In this study, a ternary covalent organic polymer anchored with SO₃H (COP-SO₃H) was designed using the Schiff reaction and a multicomponent solvent thermal method. The synthesized COP-SO₃H polymer possesses multiple functional binding sites, including amide groups, sulfonic groups, and aromatic frameworks, enabling it to effectively adsorb ciprofloxacin (which belongs to FQs) through mechanisms such as pore-filling effects, electrostatic interactions, hydrogen bonding, π-π electron donor–acceptor (EDA) interactions, and hydrophilic–lipophilic balance. COP-SO₃H demonstrated outstanding adsorption performance for ciprofloxacin, exhibiting a high adsorption capacity, broad pH stability, strong resistance to ionic interference, and good regenerability. Moreover, it displayed preferential selectivity toward fluoroquinolone antibiotics. The present study not only investigates the intricate structural and functional design of COP-SO₃H materials but also presents potential applications for the efficient adsorption of specific antibiotics. Full article

(This article belongs to the Special Issue Functional Nanomaterials in Green Chemistry)

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15 pages, 5169 KiB

Open AccessArticle

Stable Loading of TiO₂ Catalysts on the Surface of Metal Substrate for Enhanced Photocatalytic Toluene Oxidation

by Le Xu, Jiateng Chen, Pengcheng Zhao, Boxiong Shen, Zijian Zhou and Zhuozhi Wang

Molecules 2023, 28(17), 6187; https://doi.org/10.3390/molecules28176187 - 22 Aug 2023

Viewed by 772

Abstract

To promote the practical application of TiO₂ in photocatalytic toluene oxidation, the honeycomb aluminum plates were selected as the metal substrate for the loading of TiO₂ powder. Surface-etching treatment was performed and titanium tetrachloride was selected as the binder to strengthen [...] Read more.

To promote the practical application of TiO₂ in photocatalytic toluene oxidation, the honeycomb aluminum plates were selected as the metal substrate for the loading of TiO₂ powder. Surface-etching treatment was performed and titanium tetrachloride was selected as the binder to strengthen the loading stability. The loading stability and photocatalytic activity of the monolithic catalyst were further investigated, and the optimal surface treatment scheme (acid etching with 15.0 wt.% HNO₃ solution for 15 min impregnation) was proposed. Therein, the optimal monolithic catalyst could achieve the loading efficiency of 42.4% and toluene degradation efficiencies of 76.2%. The mechanism for the stable loading of TiO₂ was revealed by experiment and DFT calculation. The high surface roughness of metal substrate and the strong chemisorption between TiO₂ and TiCl₄ accounted for the high loading efficiency and photocatalytic activity. This work provides the pioneering exploration for the practical application of TiO₂ catalysts loaded on the surface of metal substrate for VOCs removal, which is of significance for the large-scaled application of photocatalytic technology. Full article

(This article belongs to the Special Issue Functional Nanomaterials in Green Chemistry)

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11 pages, 3307 KiB

Open AccessArticle

Enabling High Activity Catalyst Co₃O₄@CeO₂ for Propane Catalytic Oxidation via Inverse Loading

by Xuan Wang, Wei Liang, Changqing Lin, Tie Zhang, Jing Zhang, Nan Sheng, Zhaoning Song, Jie Jiang, Bing Sun and Wei Xu

Molecules 2023, 28(15), 5930; https://doi.org/10.3390/molecules28155930 - 7 Aug 2023

Viewed by 981

Abstract

Propane catalytic oxidation is an important industrial chemical process. However, poor activity is frequently observed for stable C–H bonds, especially for non-noble catalysts in low temperature. Herein, we reported a controlled synthesis of catalyst Co₃O₄@CeO₂–IE via inverse [...] Read more.

Propane catalytic oxidation is an important industrial chemical process. However, poor activity is frequently observed for stable C–H bonds, especially for non-noble catalysts in low temperature. Herein, we reported a controlled synthesis of catalyst Co₃O₄@CeO₂–IE via inverse loading and proposed a strategy of oxygen vacancy for its high catalytic oxidation activity, achieving better performance than traditional supported catalyst Co₃O₄/CeO₂–IM, i.e., the T₅₀ (temperature at 50% propane conversion) of 217 °C vs. 235 °C and T₉₀ (temperature at 90% propane conversion) of 268 °C vs. 348 °C at the propane space velocity of 60,000 mL g⁻¹ h⁻¹. Further investigations indicate that there are more enriched oxygen vacancies in Co₃O₄@CeO₂–IE due to the unique preparation method. This work provides an element doping strategy to effectively boost the propane catalytic oxidation performance as well as a bright outlook for efficient environmental catalysts. Full article

(This article belongs to the Special Issue Functional Nanomaterials in Green Chemistry)

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12 pages, 4343 KiB

Open AccessArticle

Dark–Light Tandem Catalytic Oxidation of Formaldehyde over SrBi₂Ta₂O₉ Nanosheets

by Weimin Ma, Qing Liu, Yuhan Lin and Yingxuan Li

Molecules 2023, 28(15), 5691; https://doi.org/10.3390/molecules28155691 - 27 Jul 2023

Cited by 1 | Viewed by 1080

Abstract

Formaldehyde (HCHO), as one of the main indoor toxic pollutions, presents a great threat to human health. Hence, it is imperative to efficiently remove HCHO and create a good indoor living environment for people. Herein, a layered perovskite material SrBi₂Ta₂ [...] Read more.

Formaldehyde (HCHO), as one of the main indoor toxic pollutions, presents a great threat to human health. Hence, it is imperative to efficiently remove HCHO and create a good indoor living environment for people. Herein, a layered perovskite material SrBi₂Ta₂O₉ (SBT), was studied for the first time and exhibited superior photocatalytic efficiency and stability compared to commercial TiO₂ (P25). Furthermore, a unique dark–light tandem catalytic mechanism was constructed. In the dark reaction stage, HCHO (Lewis base) site was adsorbed on the terminal (Bi₂O₂)²⁺ layer (Lewis acid) site of SBT in the form of Lewis acid-base complexation and was gradually oxidized to CO₃²⁻ intermediate (HCHO → DOM (dioxymethylene) → HCOO⁻ → CO₃²⁻). Then, in the light reaction stage, CO₃²⁻ was completely converted into CO₂ and H₂O (CO₃²⁻ → CO₂). Our study contributes to a thorough comprehension of the photocatalytic oxidation of HCHO and points out its potential for day–night continuous work applications in a natural environment. Full article

(This article belongs to the Special Issue Functional Nanomaterials in Green Chemistry)

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13 pages, 3639 KiB

Open AccessArticle

Highly Selective and Stable Cu Catalysts Based on Ni–Al Catalytic Systems for Bioethanol Upgrading to n-Butanol

by Yan Xiao, Nannan Zhan, Jie Li, Yuan Tan and Yunjie Ding

Molecules 2023, 28(15), 5683; https://doi.org/10.3390/molecules28155683 - 27 Jul 2023

Cited by 1 | Viewed by 998

Abstract

The catalytic upgrading of ethanol into butanol through the Guerbet coupling reaction has received increasing attention recently due to the sufficient supply of bioethanol and the versatile applications of butanol. In this work, four different supported Cu catalysts, i.e., Cu/Al₂O₃ [...] Read more.

The catalytic upgrading of ethanol into butanol through the Guerbet coupling reaction has received increasing attention recently due to the sufficient supply of bioethanol and the versatile applications of butanol. In this work, four different supported Cu catalysts, i.e., Cu/Al₂O₃, Cu/NiO, Cu/Ni₃AlO_x, and Cu/Ni₁AlO_x (Ni²⁺/Al³⁺ molar ratios of 3 and 1), were applied to investigate the catalytic performances for ethanol conversion. From the results, Ni-containing catalysts exhibit better reactivity; Al-containing catalysts exhibit better stability; but in terms of ethanol conversion, butanol selectivity, and catalyst stability, a corporative effect between Ni–Al catalytic systems can be clearly observed. Combined characterizations such as XRD, TEM, XPS, H₂-TPR, and CO₂/NH₃-TPD were applied to analyze the properties of different catalysts. Based on the results, Cu species provide the active sites for ethanol dehydrogenation/hydrogenation, and the support derived from Ni–Al–LDH supplies appropriate acid–base sites for the aldol condensation, contributing to the high butanol selectivity. In addition, catalysts with strong reducibility (i.e., Cu/NiO) may be easily deconstructed during catalysis, leading to fast deactivation of the catalysts in the Guerbet coupling process. Full article

(This article belongs to the Special Issue Functional Nanomaterials in Green Chemistry)

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16 pages, 2251 KiB

Open AccessArticle

Conversion of Methanol to Para-Xylene over ZSM-5 Zeolites Modified by Zinc and Phosphorus

by Yang Bai, Xianjun Niu, Yi-En Du and Yongqiang Chen

Molecules 2023, 28(13), 4890; https://doi.org/10.3390/molecules28134890 - 21 Jun 2023

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Abstract

In this work, the influence of different phosphorus sources and the modification of zinc and phosphorus on the performance of the conversion of methanol to aromatics (MTA) was investigated. The results showed that the phosphorus source had a significant impact on the selectivity [...] Read more.

In this work, the influence of different phosphorus sources and the modification of zinc and phosphorus on the performance of the conversion of methanol to aromatics (MTA) was investigated. The results showed that the phosphorus source had a significant impact on the selectivity of para-xylene (PX) in xylene and catalyst stability. The introduction of P resulted in the covering of the active acid sites and the narrowing of the pore of the ZSM-5 zeolite, which improved the shape-selectivity for PX in the methanol conversion reaction. Compared with the modifiers of H₃PO₄ and (NH₄)₃PO₄, the ZSM-5 zeolite modified by (NH₄)₂HPO₄ exhibited better catalyst stability and PX-selectivity due to its larger specific surface area, pore volume and suitable acidity. When the ZSM-5 zeolite was modified by Zn and P, the effect of Zn and P on the selectivity to aromatics and PX in xylene was almost opposite. With the increase in P-loading, the selectivity of PX in xylene gradually increased but at the cost of decreasing the aromatic-selectivity. On the other hand, the loading of Zn introduced Zn-Lewis acid sites to provide aromatization active centers and improved the aromatic-selectivity. However, excessive Zn reduced the selectivity of PX in xylene. The catalyst activity and aromatic-selectivity could be improved to some extent with an appropriate ratio of Zn and P, while maintaining or increasing the para-selectivity of xylene. Compared with 5% P/ZSM-5 catalyst modified with only (NH₄)₂HPO₄, the PX selectivity in xylene over the Zn-P/ZSM-5 catalyst modified with 5% Zn and 1% P improved from 86.6% to 90.1%, and the PX yield increased by 59%. Full article

(This article belongs to the Special Issue Functional Nanomaterials in Green Chemistry)

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17 pages, 8741 KiB

Open AccessArticle

Preparation of Fe/Ni-MOFs for the Adsorption of Ciprofloxacin from Wastewater

by Fuhua Wei, Kui Wang, Wenxiu Li, Qinhui Ren, Lan Qin, Mengjie Yu, Zhao Liang, Meng Nie and Siyuan Wang

Molecules 2023, 28(11), 4411; https://doi.org/10.3390/molecules28114411 - 29 May 2023

Cited by 7 | Viewed by 1791

Abstract

This work studies the use of Fe/Ni-MOFs for the removal of ciprofloxacin (CIP) in wastewater. Fe/Ni-MOFs are prepared by the solvothermal method and characterized by X-ray diffraction (XRD), a scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), and a thermal gravimetric analyzer [...] Read more.

This work studies the use of Fe/Ni-MOFs for the removal of ciprofloxacin (CIP) in wastewater. Fe/Ni-MOFs are prepared by the solvothermal method and characterized by X-ray diffraction (XRD), a scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), and a thermal gravimetric analyzer (TG). Under the conditions of the concentration of 50 ppm, a mass of 30 mg, and a temperature of 30 °C, the maximum adsorption capacity of ciprofloxacin removal within 5 h was 232.1 mg/g. The maximum removal rate was 94.8% when 40 mg of the Fe/Ni-MOFs was added to the solution of 10 ppm ciprofloxacin. According to the pseudo-second-order (PSO) kinetic model, the R² values were all greater than 0.99, which proved that the adsorption theory of ciprofloxacin by Fe/Ni-MOFs was consistent with the practice. The adsorption results were mainly affected by solution pH and static electricity, as well as other factors. The Freundlich isotherm model characterized the adsorption of ciprofloxacin by Fe/Ni-MOFs as multilayer adsorption. The above results indicated that Fe/Ni-MOFs were effective in the practical application of ciprofloxacin removal. Full article

(This article belongs to the Special Issue Functional Nanomaterials in Green Chemistry)

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16 pages, 4467 KiB

Open AccessArticle

Citrous Lime—A Functional Reductive Booster for Oil-Mediated Green Synthesis of Bioactive Silver Nanospheres for Healthcare Clothing Applications and Their Eco-Mapping with SDGs

by Nasir Sarwar, Muhammad Shahzad Zafar, Usama Bin Humayoun, Suhyeon Kim, Syed Waqas Ahmad, Yong Ho Kim and Dae Ho Yoon

Molecules 2023, 28(6), 2802; https://doi.org/10.3390/molecules28062802 - 20 Mar 2023

Viewed by 1884

Abstract

Silver nanoparticles (Ag-NPs) are most effective against pathogens and have widely been studied as antibacterial agents in commodity clothing, medical textile, and other hygiene products. However, prolonged utilization of silver and rapid mutation in bacterium stains has made them resistant to conventional silver [...] Read more.

Silver nanoparticles (Ag-NPs) are most effective against pathogens and have widely been studied as antibacterial agents in commodity clothing, medical textile, and other hygiene products. However, prolonged utilization of silver and rapid mutation in bacterium stains has made them resistant to conventional silver agents. On the other hand, strict compliance against excessive utilization of toxic reagents and the current sustainability drive is forcing material synthesis toward green routes with extended functionality. In this study, we proposed an unprecedented chemical-free green synthesis of bioactive Ag-NPs without the incorporation of any chemicals. Cinnamon essential oil (ECO) was used as a bio-reducing agent with and without the mediation of lime extract. A rapid reaction completion with better shape and size control was observed in the vicinity of lime extract when incorporated into the reaction medium. The interaction of natural metabolites and citrus compounds with nanoparticles was established using Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. The application of as-prepared nanoparticles on textiles encompasses extended bioactivity to treated fabric with infused easy-care performance. To the best of our knowledge, this is the first reported instance of utilizing bioactive silver nanoparticles as a functional finish, both as an antimicrobial and as for easy care in the absolute absence of toxic chemicals. The easy-care performance of fabric treated with lime-mediated nanoparticles was found to be 141^O, which is around 26% better than bare cotton without any significant loss in fabric strength. Furthermore, to enlighten the sustainability of the process, the development traits were mapped with the United Nations Sustainable Development Goals (SDGs), which show significant influence on SDGs 3, 8, 9, and 14. With the effective suspension of microorganisms, added functionality, and eco-mapping with SDGs with the chemical-free synthesis of nanoparticles, widespread utilization can be found in various healthcare and hygiene products along with the fulfillment of sustainability needs. Full article

(This article belongs to the Special Issue Functional Nanomaterials in Green Chemistry)

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