Research

17 pages, 5197 KiB

Open AccessArticle

Okra Micro-Cellulose Crystal (MCC) and Micro-Clay Composites for the Remediation of Copper, Nickel, and Dye (Basic Yellow II) from Wastewater

by Anika Amir Mohana, Md. Aminur Rahman, Md. Hafezur Rahaman, Mohd. Maniruzzaman, S. M. Farhad, Md Meftaul Islam, Md. Sirajul Islam Khan and Md. Zahid Parvez

Reactions 2023, 4(3), 342-358; https://doi.org/10.3390/reactions4030021 - 04 Jul 2023

Cited by 2 | Viewed by 1194

Abstract

Water pollution by contaminants such as toxic metals and dyes is now a major concern due to their high toxicity and persistence in the environment. Advances in nanotechnology have enabled the use of micro/nanomaterials to treat and purify water in various industries. In [...] Read more.

Water pollution by contaminants such as toxic metals and dyes is now a major concern due to their high toxicity and persistence in the environment. Advances in nanotechnology have enabled the use of micro/nanomaterials to treat and purify water in various industries. In this study, Bijoypur clay was modified with ethyldiamine and incorporated into an okra fiber (Abelmoschus esculentus) micro-cellulose crystal (MCC) to produce a composite that could absorb copper (Cu), nickel (Ni), and dyes like basic yellow (II) from industrial wastewater. Composites were prepared using different percentages of MCC and clay. Atomic absorption spectroscopy (AAS) was used to determine the concentrations of Cu and Ni whereas a UV–Visible spectrophotometer measured the absorbance of basic yellow (II). The synthesized composites were extensively characterized using a range of techniques including thermogravimetry (TG) and differential thermogravimetry (DTG), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). Results show that both the MCC and clay could absorb Cu, Ni, and basic yellow (II) from the contaminated wastewater. The MCC and clay composite showed the maximum efficiency of metals removal, which was up to 95% (24 mg/g) for Cu at pH 6, 20 min contact time, 2 g/L adsorbent dose, and 100% (31 mg/g) for Ni at pH 8, 60 min contact time, and 2 g/L adsorbent dose, respectively, at the initial concentration of 50 mg/L. The maximum dye uptake capacity of 85% (19 mg/g) was observed by the MCC and clay composite under optimized conditions at the initial concentration of 50 mg/L, pH 8, 30 min contact time, and 1 g/L adsorbent dose compared to the pure clay, which had an efficiency up to 26% for Cu and 24% for dye removal. All of the results indicate that incorporating clay into MCC increases the absorption capacity of contaminants from wastewater, which could be more effective for environmental applications compared to untreated cellulose. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2022)

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8 pages, 1638 KiB

Open AccessArticle

Enhancing Photon Transfer Efficiency in Photocatalysis Using Suspended LED Lights for Water Treatment

by Samira Mosalaei Rad, Ajay K. Ray and Shahzad Barghi

Reactions 2023, 4(2), 246-253; https://doi.org/10.3390/reactions4020014 - 18 Apr 2023

Viewed by 956

Abstract

Photocatalysis application in water treatment has been the object of many researchers worldwide in recent decades. However, there are limited commercial applications due to low photon transfer efficiency, which create barriers leading to challenges in making the process efficient and economically feasible. Fixed [...] Read more.

Photocatalysis application in water treatment has been the object of many researchers worldwide in recent decades. However, there are limited commercial applications due to low photon transfer efficiency, which create barriers leading to challenges in making the process efficient and economically feasible. Fixed UV/visible light sources, which are generally located outside the reactor or encapsulated in quartz tube inside the reactor are the source of energy to activate photocatalyst generating powerful oxidants such as electrons and holes. Suspended waterproof LED visible lights were employed to enhance photon transfer efficiency. Consequently, the required energy was lower resulting in negligible temperature increase and eliminated the need for an external cooler, no need for quartz (UV transparent) or treated glass reactors, enhanced mixing due to continuous movement of light bulbs by convective currents, and minimum/no attenuation. Direct Blue 15 (DB15) dye was used as model compound and the photocatalyst was P25 TiO₂ (Average particle: 30 nm, Surface area: 50 m² g⁻¹). The samples taken at different time intervals were analyzed by UV-Vis. spectrophotometer (UV-3600), and TOC-V CPN total organic carbon analyzer (both from Shimadzu). It was found that for the same level of degradation, the degradation rate increased by about 50% compared to conventional fixed light photoreactor. Overall, the cost of the operation can be reduced substantially, paving the road for feasible commercialization of the process. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2022)

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16 pages, 6954 KiB

Open AccessArticle

Behavior of Premixed Sooting Flame in a High-Pressure Burner

by Ahmad Saylam

Reactions 2023, 4(1), 155-170; https://doi.org/10.3390/reactions4010009 - 02 Feb 2023

Viewed by 1336

Abstract

The second-order factor effect of burner optical ports and edge inter-matrices (EIM) and the first-order factor of pressure on the soot formation process and behavior of premixed sooting flames in a high-pressure burner are numerically investigated here. Three-dimensional computational fluid dynamics (CFD) simulations [...] Read more.

The second-order factor effect of burner optical ports and edge inter-matrices (EIM) and the first-order factor of pressure on the soot formation process and behavior of premixed sooting flames in a high-pressure burner are numerically investigated here. Three-dimensional computational fluid dynamics (CFD) simulations of a premixed flame C₂H₄/air at p = 1.01 and 10 bar using a one-step chemistry approach are first performed to justify the satisfied predictability of the prospective axisymmetric two-dimensional (2D) and one-dimensional (1D) simulations. The justified 2D simulation approach shows the generation of an axial vorticity around the EIM and axial multi-vorticities due to the high expansion rate of burnt gases at the high pressure of 10 bar. This leads to the development of axial multi-sooting zones, which are manifested experimentally by visible luminous soot streaks, and to the boosting of soot formation conditions of a relatively low-temperature field, <1800 K, and a high mixing rate of gases in combustion around and above the EIM location. Nevertheless, a tolerable effect on the centerline soot volume fraction (f_V) profile, f_V < 3%, is manifested only at high heights above the burner of the atmospheric sooting flame C₂H₄/air ϕ = 2.1, and early at the high pressure of 10 bar of this flame, f_V < 10%. Enhancing the combustion process reactivity by decreasing the rich equivalence ratio of the fuel/air mixture and/or rising the pressure results in the prior formation of soot precursors, which shifts the sooting zone upstream. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2022)

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7 pages, 766 KiB

Open AccessArticle

A Simple Way to Obtain a Decachloro Derivative of Cobalt Bis(dicarbollide)

by Sergey A. Anufriev, Marina Yu. Stogniy and Igor B. Sivaev

Reactions 2023, 4(1), 148-154; https://doi.org/10.3390/reactions4010008 - 01 Feb 2023

Cited by 1 | Viewed by 1297

Abstract

A simple synthetic way to obtain a decachloro derivative of cobalt bis(dicarbollide) has been found. The reaction of cesium salt of cobalt bis(dicarbollide) anion with aluminum chloride in chloroform under reflux conditions results in Cs[3,3′-Co(4,7,8,9,12-Cl₅-1,2-C₂B₉H₆)₂] of high purity and good yield. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2022)

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9 pages, 1018 KiB

Open AccessArticle

Employing Molecular Docking Calculations for the Design of Alkyl (2-Alcoxy-2-Hydroxypropanoyl)-L-Tryptophanate Derivatives as Potential Inhibitors of 11β-Hydroxysteroid Dehydrogenase Type 1 (11β-HSD1)

by Diego Quiroga

Reactions 2023, 4(1), 108-116; https://doi.org/10.3390/reactions4010006 - 19 Jan 2023

Cited by 1 | Viewed by 1249

Abstract

In this paper, we presented the design by computational tools of novel alkyl (2-alcoxy-2-hydroxypropanoyl)-L-tryptophanate derivatives, which can be potential inhibitors of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). The molecular structure optimization of a group of 36 compounds was performed employing DFT-B3LYP calculations [...] Read more.

In this paper, we presented the design by computational tools of novel alkyl (2-alcoxy-2-hydroxypropanoyl)-L-tryptophanate derivatives, which can be potential inhibitors of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). The molecular structure optimization of a group of 36 compounds was performed employing DFT-B3LYP calculations at the level 6-311G(d,p). Then, molecular docking calculations were performed using Autodock tools software, employing the Lamarckian genetic algorithm (LGA). Four parameters (binding, intermolecular and Van Der Waals hydrogen bonding desolvation energies, and HOMO-LUMO gap) were used to evaluate the potential as 11β-HSD1 inhibitors, which nominate L-tryptophan derivatives as the most promissory molecules. Finally, these molecules were obtained starting from the amino acid and pyruvic acid in a convergent methodology with moderate to low yields. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2022)

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14 pages, 1896 KiB

Open AccessArticle

Determination of Kinetic Parameters of Fischer–Tropsch Synthesis in the Presence of a Granular Cobalt Catalyst

by Lilia Sineva, Kirill Gryaznov, Victor De, Andrei Gorshkov and Vladimir Mordkovich

Reactions 2023, 4(1), 92-105; https://doi.org/10.3390/reactions4010004 - 11 Jan 2023

Viewed by 1342

Abstract

Some kinetic parameters of Fischer–Tropsch synthesis (FTS) were determined in the presence of a granular cobalt/zeolite catalyst. Usually, kinetic studies of granular catalysts are considered to be complicated by external and internal diffusion. We managed to obtain a catalyst with a special structure [...] Read more.

Some kinetic parameters of Fischer–Tropsch synthesis (FTS) were determined in the presence of a granular cobalt/zeolite catalyst. Usually, kinetic studies of granular catalysts are considered to be complicated by external and internal diffusion. We managed to obtain a catalyst with a special structure of the active surface, where sites active in FTS are isolated from each other due to the environment of inactive spinel CoAl₂O₄ and inter-site transport is provided by an extensive intragranular graphitic network serving simultaneously as a heat-conductive medium. As a result, FTS proceeded in the kinetic region. It was found that the reaction kinetics obey the Arrhenius law; whereas, the activation energy is different in different temperature ranges, i.e., 118.2 kJ/mol in the range of 180–210 °C, and 173.6 kJ/mol in the range of 232–243 °C. This behavior is determined by the presence of zeolite, which becomes active in the secondary transformations of FTS products at temperatures beyond 210 °C. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2022)

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16 pages, 5113 KiB

Open AccessArticle

Greener and Efficient Epoxidation of 1,5-Hexadiene with tert-Butyl Hydroperoxide (TBHP) as an Oxidising Reagent in the Presence of Polybenzimidazole Supported Mo(VI) Catalyst

by Md Masud Rana Bhuiyan, Misbahu Ladan Mohammed and Basudeb Saha

Reactions 2022, 3(4), 537-552; https://doi.org/10.3390/reactions3040036 - 21 Oct 2022

Cited by 1 | Viewed by 1594

Abstract

Alkene epoxidation with TBHP as an oxidising reagent using heterogeneous Mo(VI) catalyst is an environmentally friendly process since it eliminates acid waste and chlorinated by-products often associated with the conventional industrial method that uses stoichiometric peracid such as peracetic acid and m-chloroperbenzoic acid. [...] Read more.

Alkene epoxidation with TBHP as an oxidising reagent using heterogeneous Mo(VI) catalyst is an environmentally friendly process since it eliminates acid waste and chlorinated by-products often associated with the conventional industrial method that uses stoichiometric peracid such as peracetic acid and m-chloroperbenzoic acid. Polybenzimidazole supported Mo(VI) complex, i.e., PBI.Mo has been successfully prepared, characterised and assessed for the epoxidation of 1,5-hexadiene in the presence of tert-butyl hydroperoxide (TBHP) as an oxidising reagent. A quadratic polynomial model has been developed, demonstrating the yield of 1,2-epoxy-5-hexene in four independent variables. The effects of different parameters such as reaction temperature, feed mole ratio of 1,5-hexadiene to TBHP, catalyst loading, and reaction time were studied. Response surface methodology (RSM) using Box-Behnken Design (BBD) was employed to study the interaction effect of different variables on the reaction response. This study presents the optimization of 1,5-hexadiene epoxidation in a batch reactor using TBHP as an oxidant and a polymer-supported Mo(VI) catalyst. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2022)

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22 pages, 4527 KiB

Open AccessArticle

Chemical Conversion of Fischer–Tropsch Waxes and Plastic Waste Pyrolysis Condensate to Lubricating Oil and Potential Steam Cracker Feedstocks

by Philipp Neuner, David Graf, Niklas Netsch, Michael Zeller, Tom-Carlo Herrmann, Dieter Stapf and Reinhard Rauch

Reactions 2022, 3(3), 352-373; https://doi.org/10.3390/reactions3030026 - 06 Jul 2022

Cited by 5 | Viewed by 2409

Abstract

The global economy and its production chains must move away from petroleum-based products, to achieve this goal, alternative carbon feedstocks need to be established. One area of concern is sustainable production of synthetic lubricants. A lubricating oil can be described as a high [...] Read more.

The global economy and its production chains must move away from petroleum-based products, to achieve this goal, alternative carbon feedstocks need to be established. One area of concern is sustainable production of synthetic lubricants. A lubricating oil can be described as a high boiling point (>340 °C) liquid with solidification at least below room temperature. Historically, many lubricants have been produced from petroleum waxes via solvent or catalytic dewaxing. In this study, catalytic dewaxing was applied to potential climate neutral feedstocks. One lubricant was produced via Fischer–Tropsch (FT) synthesis and the other lubricant resulted from low temperature pyrolysis of agricultural waste plastics. The waxes were chosen because they each represented a sustainable alternative towards petroleum, i.e., FT waxes are contrivable from biomass and CO₂ by means of gasification and Power-to-X technology. The pyrolysis of plastic is a promising process to complement existing recycling processes and to reduce environmental pollution. Changes in cloud point, viscosity, and yield were investigated. A bifunctional zeolite catalyst (SAPO-11) loaded with 0.3 wt% platinum was used. The plastic waste lubricants showed lower cloud points and increased temperature stability as compared with lubricants from FT waxes. There was a special focus on the composition of the naphtha, which accumulated during cracking. While the plastic waste produced higher amounts of naphtha, its composition was quite similar to those from FT waxes, with the notable exception of a higher naphthene content. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2022)

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19 pages, 7041 KiB

Open AccessArticle

Dry Reforming of Methane on Ni/Nanorod-CeO₂ Catalysts Prepared by One-Pot Hydrothermal Synthesis: The Effect of Ni Content on Structure, Activity, and Stability

by Simonetta Tuti, Igor Luisetto, Umberto Pasqual Laverdura and Eleonora Marconi

Reactions 2022, 3(3), 333-351; https://doi.org/10.3390/reactions3030025 - 30 Jun 2022

Cited by 8 | Viewed by 1837

Abstract

The nanorod morphology of the CeO₂ support has been recognized as more beneficial than other morphologies for catalytic activity in the dry reforming of methane. Ni/nanorod-CeO₂ catalysts with different Ni contents were prepared by one-pot hydrothermal synthesis. Samples were characterized by [...] Read more.

The nanorod morphology of the CeO₂ support has been recognized as more beneficial than other morphologies for catalytic activity in the dry reforming of methane. Ni/nanorod-CeO₂ catalysts with different Ni contents were prepared by one-pot hydrothermal synthesis. Samples were characterized by X-ray diffraction (XRD), H₂-temperature-programmed reduction (H₂-TPR), H₂-temperature-programmed desorption (H₂-TPD), field emission scanning electron microscopy/energy dispersive spectroscopy (FE-SEM/EDS), Brunauer–Emmet–Teller (BET) and Barrett–Joyner–Halenda (BHJ) analysis. The effect of Ni content on the size and the intrinsic strain of ceria was analyzed by the Size–Strain plot and Williamson–Hall plot of XRD data. The average Ni particle size and Ni dispersion were determined by H₂-TPD. XRD and H₂-TPR analysis revealed a strong Ni–support interaction that limited nickel sintering. The activity for the dry reforming of methane was tested with the stoichiometric mixture CO₂:CH₄:N₂:He = 20:20:20:140, gas hourly space velocity (GHSV) = 300 L g⁻¹ h⁻¹, and temperatures in the range of 545–800 °C. The turnover frequency (TOF) value increased linearly with the average Ni particle size in the range of 5.5–33 nm, suggesting the structure sensitivity of the reaction. Samples with Ni loading of 4–12 wt.% showed high H₂/CO selectivity and stability over time on stream, whereas the sample with a Ni loading of 2 wt.% was less selective and underwent rapid deactivation. Only a small amount of nanotubular carbon was observed by FE-SEM after the time-on-stream experiment. Deactivation of the low-Ni-content sample is ascribed to the easier oxidation of the small Ni particles. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2022)

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Graphical abstract

11 pages, 2114 KiB

Open AccessArticle

Regioselective Bond-Forming and Hydrolysis Reactions of Doubly Charged Vanadium Oxide Anions in the Gas Phase

by Chiara Salvitti, Federico Pepi, Anna Troiani and Giulia de Petris

Reactions 2022, 3(2), 254-264; https://doi.org/10.3390/reactions3020019 - 05 Apr 2022

Cited by 1 | Viewed by 1837

Abstract

The gas-phase reactivity of vanadium-containing dianions, NaV₃O₉²⁻ and its hydrated form H₂NaV₃O₁₀²⁻, were probed towards sulphur dioxide at room temperature by ion-molecule reaction (IMR) experiments in the collision cell of an ion [...] Read more.

The gas-phase reactivity of vanadium-containing dianions, NaV₃O₉²⁻ and its hydrated form H₂NaV₃O₁₀²⁻, were probed towards sulphur dioxide at room temperature by ion-molecule reaction (IMR) experiments in the collision cell of an ion trap mass spectrometer. The sequential addition of two SO₂ molecules to the NaV₃O₉²⁻ dianion leads to the breakage of the stable V₃O₉ backbone, resulting in a charge separation process with the formation of new V-O and S-O bonds. On the contrary, the H₂NaV₃O₁₀²⁻ hydroxide species reacts with SO₂, promoting regioselective hydrolysis and bond-forming processes, the latter similar to that observed for the NaV₃O₉²⁻ reactant anion. Kinetic analysis shows that these reactions are fast and efficient with rate constants of the 10⁻⁹ (±30) cm³ s⁻¹ molecule⁻¹ order of magnitude. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2022)

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Review

Jump to: Research, Other

42 pages, 15158 KiB

Open AccessReview

Visible Light Induced C-H/N-H and C-X Bonds Reactions

by Muhammad Siddique Ahmad, Po-Han Lin, Qing Zhang, Bing Zeng, Qifeng Wang and Kamel Meguellati

Reactions 2023, 4(1), 189-230; https://doi.org/10.3390/reactions4010012 - 02 Mar 2023

Viewed by 2658

Abstract

Herein, we report efficient visible light-induced photoredox reactions of C–H/N–H and C–X Bonds. These methods have provided access to varied portfolio of synthetically important γ-ketoesters, azaspirocyclic cyclohexadienones spirocyclohexadienones, multisubstituted benzimidazole derivatives, substituted N,2-diarylacetamide, 2-arylpyridines and 2-arylquinolines in good yields and under mild conditions. [...] Read more.

Herein, we report efficient visible light-induced photoredox reactions of C–H/N–H and C–X Bonds. These methods have provided access to varied portfolio of synthetically important γ-ketoesters, azaspirocyclic cyclohexadienones spirocyclohexadienones, multisubstituted benzimidazole derivatives, substituted N,2-diarylacetamide, 2-arylpyridines and 2-arylquinolines in good yields and under mild conditions. Moreover, we have successfully discussed the construction through visible light-induction by an intermolecular radical addition, dearomative cyclization, aryl migration and desulfonylation. Similarly, we also spotlight the visible light-catalyzed aerobic C–N bond activation from well-known building blocks through cyclization, elimination and aromatization. The potential use of a wide portfolio of simple ketones and available primary amines has made this transformation very attractive. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2022)

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26 pages, 12139 KiB

Open AccessReview

A Critical Review of Sustainable Vanillin-modified Vitrimers: Synthesis, Challenge and Prospects

by Muhammad Abdur Rashid, Md. Nabiul Hasan, Md. Anisur Rahman Dayan, Mohammad Salman Ibna Jamal and Mohammed Kayes Patoary

Reactions 2023, 4(1), 66-91; https://doi.org/10.3390/reactions4010003 - 02 Jan 2023

Cited by 15 | Viewed by 4563

Abstract

Nearly 90% of thermosets are produced from petroleum resources, they have remarkable mechanical characteristics, are chemically durable, and dimensionally stable. However, they can contribute to global warming, depletion of petroleum reserves, and environmental contamination during manufacture, use, and disposal. Using renewable resources to [...] Read more.

Nearly 90% of thermosets are produced from petroleum resources, they have remarkable mechanical characteristics, are chemically durable, and dimensionally stable. However, they can contribute to global warming, depletion of petroleum reserves, and environmental contamination during manufacture, use, and disposal. Using renewable resources to form thermosetting materials is one of the most crucial aspects of addressing the aforementioned issues. Vanillin-based raw materials have been used in the industrial manufacturing of polymer materials because they are simple to modify structurally. Conversely, traditional thermosetting materials as a broad class of high-molecular-weight molecules are challenging to heal, decompose and recover owing to their permanent 3-D crosslinking network. Once the products are damaged, recycling issues could arise, causing resource loss and environmental impact. It could be solved by inserting dynamic covalent adaptable networks (DCANs) into the polymer chains, increasing product longevity, and minimizing waste. It also improves the attractiveness of these products in the prospective field. Moreover, it is essential to underline that increasing product lifespan and reducing waste is equivalent to reducing the expense of consuming resources. The detailed synthesis, reprocessing, thermal, and mechanical characteristics of partly and entirely biomass thermosetting polymers made from vanillin-modified monomers are covered in the current work. Finally, the review highlights the benefits, difficulties, and application of these emerging vanillin-modified vitrimers as a potential replacement for conventional non-recyclable thermosets. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2022)

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25 pages, 21843 KiB

Open AccessReview

Hydrothermal Synthesis of Vanadium Oxide Microstructures with Mixed Oxidation States

by Daniel Navas

Reactions 2023, 4(1), 1-25; https://doi.org/10.3390/reactions4010001 - 28 Dec 2022

Cited by 2 | Viewed by 2594

Abstract

This review is based on hydrothermal synthetic procedures that generate different vanadium oxide microstructures with mixed oxidation states, where different vanadium (V⁵⁺) precursors (vanadate, vanadium oxide, vanadium alkoxide, etc.,) are used to obtain various types of morphologies and shapes, such as [...] Read more.

This review is based on hydrothermal synthetic procedures that generate different vanadium oxide microstructures with mixed oxidation states, where different vanadium (V⁵⁺) precursors (vanadate, vanadium oxide, vanadium alkoxide, etc.,) are used to obtain various types of morphologies and shapes, such as sea urchins, cogs, stars, squares, etc., depending on the amphiphilic molecules (usually surfactants) exhibiting a structural director role containing an organic functional group such as primary amines and thiols, respectively. The performance of sol–gel methodology, where intercalation processes sometimes take place, is crucial prior to the hydrothermal treatment stage to control the V⁴⁺/V⁵⁺. In every synthesis, many physical and chemical parameters, such as temperature, pH, reaction time., etc., are responsible for influencing the reactions in order to obtain different products; the final material usually corresponds to a mixed oxidation state structure with different content rates. This feature has been used in many technological applications, and some researchers have enhanced it by functionalizing the products to enhance their electrochemical and magnetic properties. Although some results have been auspicious, there are a number of projects underway to improve the synthesis in many ways, including yield, secondary products, size distribution, oxidation state ratio, etc., to achieve the best benefits from these microstructures in the large number of technological, catalytic, and magnetic devices, among other applications. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2022)

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48 pages, 15797 KiB

Open AccessReview

Advances for Biorefineries: Glycerol Hydrogenolysis to 1,3-Propylene Glycol

by Martin Nicolás Gatti, Nora Nancy Nichio and Francisco Pompeo

Reactions 2022, 3(3), 451-498; https://doi.org/10.3390/reactions3030032 - 19 Sep 2022

Cited by 8 | Viewed by 2566

Abstract

Humanity’s growing dependence on non-renewable resources and the ensuing environmental impact thus generated have spurred the search for alternatives to replace chemicals and energy obtained from petroleum derivatives. Within the group of biofuels, biodiesel has managed to expand worldwide at considerable levels, going [...] Read more.

Humanity’s growing dependence on non-renewable resources and the ensuing environmental impact thus generated have spurred the search for alternatives to replace chemicals and energy obtained from petroleum derivatives. Within the group of biofuels, biodiesel has managed to expand worldwide at considerable levels, going from 20 million tn/year in 2010 to 47 million tn/year in 2022, boosting the supply of glycerol, a by-product of its synthesis that can be easily used as a renewable, clean, low-cost raw material for the manufacture of products for the chemical industry. The hydrogenolysis of glycerol leads to the production of glycols, 1,2-propylene glycol (1,2-PG) and 1,3-propylene glycol (1,3-PG). In particular, 1,3-PG has the highest added value and has multiple uses including its application as an additive in the polymer industry, the manufacture of cosmetics, cleaning products, cooling liquids, etc. This review focuses on the study of the hydrogenolysis of glycerol for the production of 1,3-PG, presenting the main reaction mechanisms and the catalysts employed, both in liquid and vapor phase. Engineering aspects and the effect of the operating variables to achieve maximum yields are discussed. Finally, studies related to the stability and the main deactivation mechanisms of catalytic systems are presented. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2022)

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17 pages, 1561 KiB

Open AccessReview

Application of Mixed Potential Theory to Leaching of Mineral Phases

by César A. C. Sequeira

Reactions 2022, 3(2), 312-328; https://doi.org/10.3390/reactions3020023 - 18 Jun 2022

Viewed by 2020

Abstract

Leaching is a central unit operation in the hydrometallurgical processing of minerals, which often occurs by means of electrochemical reactions. Application of mixed potential theory to explain the kinetics of oxidative and reductive leaching processes is a useful concept in explaining observed results. [...] Read more.

Leaching is a central unit operation in the hydrometallurgical processing of minerals, which often occurs by means of electrochemical reactions. Application of mixed potential theory to explain the kinetics of oxidative and reductive leaching processes is a useful concept in explaining observed results. Native metals, selected oxides, and most base metal sulfides are electron-conducting phases. For these minerals, leaching may take place by normal corrosion, passivation or galvanic couple mechanisms, which provide individual electrode kinetics enabling the calculation of mixed potentials and overall reaction kinetics. Examples of the electrochemical nature of selected leaching processes are presented and include the effect of mixed potentials, geometry, and associated kinetic reactions. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2022)

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21 pages, 6076 KiB

Open AccessReview

Recent Progresses in the Preparation of Chlorinated Molecules: Electrocatalysis and Photoredox Catalysis in the Spotlight

by Stefano Parisotto, Emanuele Azzi, Alberto Lanfranco, Polyssena Renzi and Annamaria Deagostino

Reactions 2022, 3(2), 233-253; https://doi.org/10.3390/reactions3020018 - 03 Apr 2022

Cited by 5 | Viewed by 5858

Abstract

Among halogenated molecules, those containing chlorine atoms are fundamental in many areas such as pharmaceuticals, polymers, agrochemicals and natural metabolites. Despite the fact that many reactions have been developed to install chlorine on organic molecules, most of them rely on toxic and hazardous [...] Read more.

Among halogenated molecules, those containing chlorine atoms are fundamental in many areas such as pharmaceuticals, polymers, agrochemicals and natural metabolites. Despite the fact that many reactions have been developed to install chlorine on organic molecules, most of them rely on toxic and hazardous chlorinating reagents as well as harsh conditions. In an attempt to move towards more sustainable approaches, photoredox catalysis and electrocatalysis have emerged as powerful alternatives to traditional methods. In this review, we collect the most recent and significant examples of visible-light- or current-mediated chlorination published in the last five years. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2022)

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Other

Jump to: Research, Review

5 pages, 195 KiB

Open AccessViewpoint

Initial Steps in the Reaction of H₂O₂ with Fe²⁺ and Fe³⁺ Ions: Inconsistency in the Free Radical Theory

by Mordechai L. Kremer

Reactions 2023, 4(1), 171-175; https://doi.org/10.3390/reactions4010010 - 20 Feb 2023

Cited by 1 | Viewed by 3152

Abstract

Consideration of the changes in free energy shows that the assumed initial steps in reactions of H₂O₂ with Fe²⁺ and Fe³⁺ in the free radical theory are not consistent. The free radical theory is unable to account for [...] Read more.

Consideration of the changes in free energy shows that the assumed initial steps in reactions of H₂O₂ with Fe²⁺ and Fe³⁺ in the free radical theory are not consistent. The free radical theory is unable to account for the Fe³⁺-initiated decomposition of H₂O₂ or for oxidations by it. In reactions with Fe²⁺ ions at high [H₂O₂], where O₂ evolution reaches a limit, such limit is not foreseen by the free radical model. At lower [H₂O₂], because of a disallowed substitution in the equation used, the interpretation is not valid. It appears, therefore, that free radicals derived from H₂O₂ do not provide a suitable basis for constructing models for these reactions. Non-radical models are more successful in interpreting experimental results. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2022)

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