Processes

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3 pages, 176 KiB

Open AccessEditorial

Special Issue “Metal Nanoparticles as Catalysts for Green Applications”

by Michela Signoretto and Federica Menegazzo

Processes 2021, 9(6), 1015; https://doi.org/10.3390/pr9061015 - 9 Jun 2021

Viewed by 1805

Abstract

This Special Issue of Processes on “Metal Nanoparticles as Catalysts for Green Applications” collects recent works of researchers on metal nanoparticles as catalysts for green applications [...] Full article

(This article belongs to the Special Issue Metal Nanoparticles as Catalysts for Green Applications)

Research

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10 pages, 1823 KiB

Open AccessArticle

Hydrodeoxygenation of Guaiacol over Pd–Co and Pd–Fe Catalysts: Deactivation and Regeneration

by Nga Tran, Yoshimitsu Uemura, Thanh Trinh and Anita Ramli

Processes 2021, 9(3), 430; https://doi.org/10.3390/pr9030430 - 27 Feb 2021

Cited by 16 | Viewed by 2783

Abstract

In bio-oil upgrading, the activity and stability of the catalyst are of great importance for the catalytic hydrodeoxygenation (HDO) process. The vapor-phase HDO of guaiacol was investigated to clarify the activity, stability, and regeneration ability of Al-MCM-41 supported Pd, Co, and Fe catalysts [...] Read more.

In bio-oil upgrading, the activity and stability of the catalyst are of great importance for the catalytic hydrodeoxygenation (HDO) process. The vapor-phase HDO of guaiacol was investigated to clarify the activity, stability, and regeneration ability of Al-MCM-41 supported Pd, Co, and Fe catalysts in a fixed-bed reactor. The HDO experiment was conducted at 400 °C and 1 atm, while the regeneration of the catalyst was performed with an air flow at 500 °C for 240 min. TGA and XPS techniques were applied to study the coke deposit and metal oxide bond energy of the catalysts before and after HDO reaction. The Co and Pd–Co simultaneously catalyzed the C_ArO–CH₃, C_Ar–OH, and multiple C–C hydrogenolyses, while the Fe and Pd–Fe principally catalyzed the C_Ar–OCH₃ hydrogenolysis. The bimetallic Pd–Co and Pd–Fe showed a higher HDO yield and stability than monometallic Co and Fe, since the coke formation was reduced. The Pd–Fe catalyst presented a higher stability and regeneration ability than the Pd–Co catalyst, with consistent activity during three HDO cycles. Full article

(This article belongs to the Special Issue Metal Nanoparticles as Catalysts for Green Applications)

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13 pages, 5083 KiB

Open AccessArticle

Microemulsion vs. Precipitation: Which Is the Best Synthesis of Nickel–Ceria Catalysts for Ethanol Steam Reforming?

by Cristina Pizzolitto, Federica Menegazzo, Elena Ghedini, Arturo Martínez Arias, Vicente Cortés Corberán and Michela Signoretto

Processes 2021, 9(1), 77; https://doi.org/10.3390/pr9010077 - 31 Dec 2020

Cited by 6 | Viewed by 2112

Abstract

Ethanol steam reforming is one of the most promising ways to produce hydrogen from biomass, and the goal of this research is to investigate robust, selective and active catalysts for this reaction. In particular, this work is focused on the effect of the [...] Read more.

Ethanol steam reforming is one of the most promising ways to produce hydrogen from biomass, and the goal of this research is to investigate robust, selective and active catalysts for this reaction. In particular, this work is focused on the effect of the different ceria support preparation methods on the Ni active phase stabilization. Two synthetic approaches were evaluated: precipitation (with urea) and microemulsion. The effects of lanthanum doping were investigated too. All catalysts were characterized using N₂-physisorption, temperature programmed reduction (TPR), XRD and SEM, to understand the influence of the synthetic approach on the morphological and structural features and their relationship with catalytic properties. Two synthesis methods gave strongly different features. Catalysts prepared by precipitation showed higher reducibility (which involves higher oxygen mobility) and a more homogeneous Ni particle size distribution. Catalytic tests (at 500 °C for 5 h using severe Gas Hourly Space Velocity conditions) revealed also different behaviors. Though the initial conversion (near complete) and H₂ yield (60%, i.e., 3.6 mol H₂/mol ethanol) were the same, the catalyst prepared by microemulsion was deactivated much faster. Similar trends were found for La-promoted supports. Catalyst deactivation was mainly related to coke deposition as was shown by SEM of the used samples. Higher reducibility of the catalysts prepared by the precipitation method led to a decrease in coke deposition rate by facilitating the removal of coke precursors, which made them the more stable catalysts of the reaction. Full article

(This article belongs to the Special Issue Metal Nanoparticles as Catalysts for Green Applications)

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12 pages, 3025 KiB

Open AccessCommunication

Remediation of Lead and Nickel Contaminated Soil Using Nanoscale Zero-Valent Iron (nZVI) Particles Synthesized Using Green Leaves: First Results

by Nimita Francy, Subramanian Shanthakumar, Fulvia Chiampo and Yendaluru Raja Sekhar

Processes 2020, 8(11), 1453; https://doi.org/10.3390/pr8111453 - 13 Nov 2020

Cited by 17 | Viewed by 2933

Abstract

Nanoscale zero-valent iron (nZVI) particles have proved to be effective in the remediation of chlorinated compounds and heavy metals from contaminated soil. The present study aimed to analyze the performance of nanoparticles synthesized from low-cost biomass (green leaves) as chemical precursors, namely Azadirachta [...] Read more.

Nanoscale zero-valent iron (nZVI) particles have proved to be effective in the remediation of chlorinated compounds and heavy metals from contaminated soil. The present study aimed to analyze the performance of nanoparticles synthesized from low-cost biomass (green leaves) as chemical precursors, namely Azadirachta indica (neem) and Mentha longifolia (mint) leaves. These leaves were chosen because huge amounts of them are present in the region of Vellore. These nanoparticles were used to remove lead and nickel from contaminated soil. Characterization of nZVI particles was conducted using the Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), and Brunauer–Emmett–Teller isotherm (BET) techniques. Remediation was performed on two different soil samples, polluted with lead or nickel at an initial metal concentration around 250 mg/kg of soil. The results revealed that after 30 days, the lead removal efficiency with 0.1 g of nZVI particles/kg of soil was 26.9% by particles synthesized using neem leaves and 62.3% by particles synthesized using mint leaves. Similarly, nickel removal efficiency with 0.1 g of particles/kg of soil was 33.2% and 50.6%, respectively, by particles using neem and mint leaves. When the nanoparticle concentration was doubled, Pb and Ni removal improved, with similar trends obtained at a lower dosage (0.1 g of particles/kg of soil). These first results evidenced that: (1) the nZVI particles synthesized using green leaves had the potential to remove Pb and Ni from contaminated soil; (2) the neem-derived particles gave better Ni removal efficiency than Pb one; (3) the mint-derived particles showed better Pb removal efficiency than Ni one; (4) the highest removal efficiency for both metals was achieved with the mint-derived particles; (5) double higher dosage did not greatly improve the results. Full article

(This article belongs to the Special Issue Metal Nanoparticles as Catalysts for Green Applications)

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16 pages, 2440 KiB

Open AccessFeature PaperArticle

MCM-41 Supported Co-Based Bimetallic Catalysts for Aqueous Phase Transformation of Glucose to Biochemicals

by Somayeh Taghavi, Elena Ghedini, Federica Menegazzo, Michela Signoretto, Delia Gazzoli, Daniela Pietrogiacomi, Aisha Matayeva, Andrea Fasolini, Angelo Vaccari, Francesco Basile and Giuseppe Fornasari

Processes 2020, 8(7), 843; https://doi.org/10.3390/pr8070843 - 15 Jul 2020

Cited by 9 | Viewed by 2952

Abstract

The transformation of glucose into valuable biochemicals was carried out on different MCM-41-supported metallic and bimetallic (Co, Co-Fe, Co-Mn, Co-Mo) catalysts and under different reaction conditions (150 °C, 3 h; 200 °C, 0.5 h; 250 °C, 0.5 h). All catalysts were characterized using [...] Read more.

The transformation of glucose into valuable biochemicals was carried out on different MCM-41-supported metallic and bimetallic (Co, Co-Fe, Co-Mn, Co-Mo) catalysts and under different reaction conditions (150 °C, 3 h; 200 °C, 0.5 h; 250 °C, 0.5 h). All catalysts were characterized using N₂ physisorption, Temperature Programmed Reduction (TPR), Raman, X-ray Diffraction (XRD) and Temperature Programmed Desorption (TPD) techniques. According to the N₂-physisorption results, a high surface area and mesoporous structure of the support were appropriate for metal dispersion, reactant diffusion and the formation of bioproducts. Reaction conditions, bimetals synergetic effects and the amount and strength of catalyst acid sites were the key factors affecting the catalytic activity and biochemical selectivity. Sever reaction conditions including high temperature and high catalyst acidity led to the formation mainly of solid humins. The NH₃-TPD results demonstrated the alteration of acidity in different bimetallic catalysts. The 10Fe10CoSiO₂ catalyst (MCM-41 supported 10 wt.%Fe, 10 wt.%Co) possessing weak acid sites displayed the best catalytic activity with the highest carbon balance and desired product selectivity in mild reaction condition. Valuable biochemicals such as fructose, levulinic acid, ethanol and hydroxyacetone were formed over this catalyst. Full article

(This article belongs to the Special Issue Metal Nanoparticles as Catalysts for Green Applications)

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15 pages, 6289 KiB

Open AccessFeature PaperArticle

Pd/Au Based Catalyst Immobilization in Polymeric Nanofibrous Membranes via Electrospinning for the Selective Oxidation of 5-Hydroxymethylfurfural

by Danilo Bonincontro, Francesco Fraschetti, Claire Squarzoni, Laura Mazzocchetti, Emanuele Maccaferri, Loris Giorgini, Andrea Zucchelli, Chiara Gualandi, Maria Letizia Focarete and Stefania Albonetti

Processes 2020, 8(1), 45; https://doi.org/10.3390/pr8010045 - 1 Jan 2020

Cited by 17 | Viewed by 3211

Abstract

Innovative nanofibrous membranes based on Pd/Au catalysts immobilized via electrospinning onto different polymers were engineered and tested in the selective oxidation of 5-(hydroxymethyl)furfural in an aqueous phase. The type of polymer and the method used to insert the active phases in the membrane [...] Read more.

Innovative nanofibrous membranes based on Pd/Au catalysts immobilized via electrospinning onto different polymers were engineered and tested in the selective oxidation of 5-(hydroxymethyl)furfural in an aqueous phase. The type of polymer and the method used to insert the active phases in the membrane were demonstrated to have a significant effect on catalytic performance. The hydrophilicity and the glass transition temperature of the polymeric component are key factors for producing active and selective materials. Nylon-based membranes loaded with unsupported metal nanoparticles were demonstrated to be more efficient than polyacrylonitrile-based membranes, displaying good stability and leading to high yield in 2,5-furandicarboxylic acid. These results underline the promising potential of large-scale applications of electrospinning for the preparation of catalytic nanofibrous membranes to be used in processes for the conversion of renewable molecules. Full article

(This article belongs to the Special Issue Metal Nanoparticles as Catalysts for Green Applications)

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13 pages, 4732 KiB

Open AccessArticle

The Synthesis of N-(Pyridin-2-yl)-Benzamides from Aminopyridine and Trans-Beta-Nitrostyrene by Fe₂Ni-BDC Bimetallic Metal–Organic Frameworks

by Trinh Duy Nguyen, Oanh Kim Thi Nguyen, Thuan Van Tran, Vinh Huu Nguyen, Long Giang Bach, Nhan Viet Tran, Dai-Viet N. Vo, Tuyen Van Nguyen, Seong-Soo Hong and Sy Trung Do

Processes 2019, 7(11), 789; https://doi.org/10.3390/pr7110789 - 1 Nov 2019

Cited by 9 | Viewed by 5352

Abstract

A bimetallic metal–organic framework material, which was generated by bridging iron (III) cations and nickel (II) cations with 1,4-Benzenedicarboxylic anions (Fe₂Ni-BDC), was synthesized by a solvothermal approach using nickel (II) nitrate hexahydrate and iron (III) chloride hexahydrate as the mixed metal [...] Read more.

A bimetallic metal–organic framework material, which was generated by bridging iron (III) cations and nickel (II) cations with 1,4-Benzenedicarboxylic anions (Fe₂Ni-BDC), was synthesized by a solvothermal approach using nickel (II) nitrate hexahydrate and iron (III) chloride hexahydrate as the mixed metal source and 1,4-Benzenedicarboxylic acid (H₂BDC) as the organic ligand source. The structure of samples was determined by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, and nitrogen physisorption measurements. The catalytic activity and recyclability of the Fe₂Ni-BDC catalyst for the Michael addition amidation reaction of 2-aminopyridine and nitroolefins were estimated. The results illustrated that the Fe₂Ni-BDC catalyst demonstrated good efficiency in the reaction under optimal conditions. Based on these results, a reaction mechanism was proposed. When the molar ratio of 2-aminopyridine and trans-β-nitrostyrene was 1:1, and the solvent was dichloromethane, the isolated yield of pyridyl benzamide reached 82%; at 80 °C over 24 h. The catalyst can be reused without a substantial reduction in catalytic activity with 77% yield after six times of reuse. Full article

(This article belongs to the Special Issue Metal Nanoparticles as Catalysts for Green Applications)

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16 pages, 4535 KiB

Open AccessArticle

Highly Selective Syngas/H₂ Production via Partial Oxidation of CH₄ Using (Ni, Co and Ni–Co)/ZrO₂–Al₂O₃ Catalysts: Influence of Calcination Temperature

by Anis Hamza Fakeeha, Yasir Arafat, Ahmed Aidid Ibrahim, Hamid Shaikh, Hanan Atia, Ahmed Elhag Abasaeed, Udo Armbruster and Ahmed Sadeq Al-Fatesh

Processes 2019, 7(3), 141; https://doi.org/10.3390/pr7030141 - 6 Mar 2019

Cited by 29 | Viewed by 4247

Abstract

In this study, Ni, Co and Ni–Co catalysts supported on binary oxide ZrO₂–Al₂O₃ were synthesized by sol-gel method and characterized by means of various analytical techniques such as XRD, BET, TPR, TPD, TGA, SEM, and TEM. This catalytic [...] Read more.

In this study, Ni, Co and Ni–Co catalysts supported on binary oxide ZrO₂–Al₂O₃ were synthesized by sol-gel method and characterized by means of various analytical techniques such as XRD, BET, TPR, TPD, TGA, SEM, and TEM. This catalytic system was then tested for syngas respective H₂ production via partial oxidation of methane at 700 °C and 800 °C. The influence of calcination temperatures was studied and their impact on catalytic activity and stability was evaluated. It was observed that increasing the calcination temperature from 550 °C to 800 °C and addition of ZrO₂ to Al₂O₃ enhances Ni metal-support interaction. This increases the catalytic activity and sintering resistance. Furthermore, ZrO₂ provides higher oxygen storage capacity and stronger Lewis basicity which contributed to coke suppression, eventually leading to a more stable catalyst. It was also observed that, contrary to bimetallic catalysts, monometallic catalysts exhibit higher activity with higher calcination temperature. At the same time, Co and Ni–Co-based catalysts exhibit higher activity than Ni-based catalysts which was not expected. The Co-based catalyst calcined at 800 °C demonstrated excellent stability over 24 h on stream. In general, all catalysts demonstrated high CH₄ conversion and exceptionally high selectivity to H₂ (~98%) at 700 °C. Full article

(This article belongs to the Special Issue Metal Nanoparticles as Catalysts for Green Applications)

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22 pages, 4822 KiB

Open AccessArticle

An Experimental Approach on Industrial Pd-Ag Supported α-Al₂O₃ Catalyst Used in Acetylene Hydrogenation Process: Mechanism, Kinetic and Catalyst Decay

by Ourmazd Dehghani, Mohammad Reza Rahimpour and Alireza Shariati

Processes 2019, 7(3), 136; https://doi.org/10.3390/pr7030136 - 5 Mar 2019

Cited by 22 | Viewed by 6022

Abstract

The current research presents an experimental approach on the mechanism, kinetic and decay of industrial Pd-Ag supported α-Al₂O₃ catalyst used in the acetylene hydrogenation process. In the first step, the fresh and deactivated hydrogenation catalysts are characterized by XRD, BET [...] Read more.

The current research presents an experimental approach on the mechanism, kinetic and decay of industrial Pd-Ag supported α-Al₂O₃ catalyst used in the acetylene hydrogenation process. In the first step, the fresh and deactivated hydrogenation catalysts are characterized by XRD, BET (Brunauer–Emmett–Teller), SEM, TEM, and DTG analyses. The XRD results show that the dispersed palladium particles on the support surface experience an agglomeration during the reaction run time and mean particle size approaches from 6.2 nm to 11.5 nm. In the second step, the performance of Pd-Ag supported α-Al₂O₃ catalyst is investigated in a differential reactor in a wide range of hydrogen to acetylene ratio, temperature, gas hourly space velocity and pressure. The full factorial design method is used to determine the experiments. Based on the experimental results ethylene, ethane, butene, and 1,3-butadiene are produced through the acetylene hydrogenation. In the third step, a detailed reaction network is proposed based on the measured compounds in the product and the corresponding kinetic model is developed, based on the Langmuir-Hinshelwood-Hougen-Watson approach. The coefficients of the proposed kinetic model are calculated based on experimental data. Finally, based on the developed kinetic model and plant data, a decay model is proposed to predict catalyst activity and the parameters of the activity model are calculated. The results show that the coke build-up and condensation of heavy compounds on the surface cause catalyst deactivation at low temperature. Full article

(This article belongs to the Special Issue Metal Nanoparticles as Catalysts for Green Applications)

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